Mech - User contributions [en]

https://hades.mech.northwestern.edu//api.php?action=feedcontributions&feedformat=atom&user=EricN Mech - User contributions [en] 2026-04-22T21:57:47Z User contributions MediaWiki 1.35.9 https://hades.mech.northwestern.edu//index.php?title=Optical_Locating&diff=9660 Optical Locating 2009-01-07T03:13:48Z

<p>EricN: /* Phase-Sensitive Detection Circuit */</p> <hr /> <div>[[Category:Sensors]]<br /> <br /> ===Overview===<br /> <b> This page still needs more revision and completeness, but the individual technologies are fully developed </b><br /> <br /> Many tracking applications require that the system identify the location of information within a visual field. This could be seeking a color, or a shape, or just the centroid of light intensity. This page discusses the use of a duo-lateral photodiode to sense the centroid of light within its field of view. The documented method uses a passive [[Sensing optical tape|retro-reflective]] target and [[Optics|optics]]. <br /> <br /> ===System Design===<br /> The system is designed to obtain the location of a reflective target within its visual field and track it at high speeds. Figure 1 is a system diagram showing the functional blocks of the system. The system needs to be able to obtain the position of the target relative to the current direction the "eye" is facing, which requires that it be able to distinguish between the target signal and potential ambient light, and then produce a signal which the microcontroller can utillize to drive motors which orient the eye toward the target.<br /> <br /> The system contains the following elements: <br /> <br /> * Eye structure on a 2-DoF gimbal<br /> * [[Lateral-Effect Photodiode|Position-sensing detector]]<br /> * [[IR Target Illumination|Target illumination circuit]]<br /> * [[Optics]]<br /> * [[Phase-Sensitive Detection|Phase-sensitive detection circuit]]<br /> * Microcontroller<br /> <br /> ==Position-Sensing Detector==<br /> The position sensing detector used in this system is a DLS-4, a [[Lateral-Effect Photodiode|two-dimensional lateral-effect position-sensing device]] from OSI Optoelectronics. This sensor (as shown in the image at right) has a 4mm x 4mm sensing area and has four output leads, one pair for each axis of measurement. Each output lead acts as a current source (due to photoelectric effect) either sourcing or sinking current based on the intensity of the light it is receiving and the distance from the centroid of the light spot from the terminal corresponding to the lead. One pair of leads corresponding to a direction pair (left-right or up-down) will be sourcing current while the other sinks current. For further details see the [[Lateral-Effect Photodiode|lateral-effect photodiode]].<br /> <br /> <br /> <br /> ==Target Illumination==<br /> Illuminating the target was achieved via eight TSHF 5210 [[IR Target Illumination|infrared-emitting diodes]] (IRED's)(http://www.vishay.com/docs/81303/tshf5410.pdf). These were arranged into two parallel groups of four which were each soldered together as part of the "eye"structure. The [[IR Target Illumination|IRED]] illumination circuit was pulsed synchronously with the [[Phase-Sensitive Detection|phase-sensitive detector]] switch at 20 kHz. The target was a 1.5" diameter sphere covered with retroreflective tape, providing a decent brightness spot even at distances beyond one meter.<br /> <br /> ==Optics==<br /> If light is directed at the sensor in a parallel beam (such as from a flashlight or laser, or potentially the reflection from a distant target), the light available from the field of view can be overshadowed by the intensity of the light in the beam, resulting in uniform distribution of the light on the sensing surface until the light source becomes occluded by the edge of the case or structure, resulting in a shadow. In theory, if the beam were narrow with respect to the size of the sensing area, the placement of the beam on the sensing area should produce output currents which are representative of the proximity of the "dot" to each edge of the sensor. The sensing area is only 4mm square, and even the "dot" produced by a laser pointer is 2mm in diameter with additional scatter, so the dot is anything but "small". To reduce this "large-dot" problem, an [[Optics|optical lens]] (salvaged from a laser pointer) and infrared filter (http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productID=1918) were used.<br /> <br /> ==Phase-Sensitive Detection Circuit==<br /> The most difficult part of trying to identify a target which could be buried within background ambient light is differentiating between the ambient signal and the target signal. The method of achieving that separation that this system uses is called [[Phase-Sensitive Detection|phase-sensitive-detection]]. The phase sensitive detection starts with modulating the signal voltage at a certain frequency. It is then multiplied by a reference signal at the same frequency. The multiplication can be carried out in a sectional called mixer, or in other ways. The phase sensitive detection ends with a low pass filter, which demodulates the signal voltage and outputs a DC value.</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Phase-Sensitive_Detection&diff=9657 Phase-Sensitive Detection 2009-01-07T01:59:29Z

<p>EricN: /* '''Example Circuit''' */</p> <hr /> <div>== '''Overview''' ==<br /> <br /> One effective way to recover the small signal buried by large ambient noise is to use the so called phase sensitive detector, or lock-in amplifier. A phase sensitive detector achieves narrow bandwidth amplification by reducing the noise content at falling outside the interested bandwidth.<br /> <br /> When the noise is white in nature, we can reduce its level of magnitude dramatically by limiting the bandwidth of detection, which includes the frequency occurring to the signal while excludes the frequencies occurring to the noise. Phase sensitive detection enables extremely narrow bandwidth detection (0.001Hz is normal). Typical application scenario is using electric transducers where the amplitude of noise is in mili volts and the signal falls into nano volt region. Sophisticated phase sensitive detector can extract signals buried in noise that is <math>10^7</math> times larger in magnitude. <br /> <br /> In this article, we focus on a quick and easy method of building a phase sensitive detector from op-amps and analog switches.<br /> <br /> == '''Mathematical model''' ==<br /> <br /> <br /> Consider two signals, <math>f_1</math> and <math>f_2</math>, where <math>f_1=Asin\omega_1 t</math> , <math>f_2=Bsin(\omega_2 t + \phi)</math><br /> <br /> Then, the product of <math>f_1</math> and <math>f_2</math> is:<br /> <br /> <br /> <math>f_1\times f_2 = ABsin\omega_1 tsin(\omega_2 t + \phi) </math><br /> <math>= -\frac{AB}{2} \times {cos[(\omega_1 + \omega_2 )t+\phi ]-cos[(\omega_1 - \omega_2 )t-\phi ]}</math><br /> <br /> Let’s integrate the product over time <math>[0, T)</math>:<br /> <br /> <math>\frac{1}{T} \int_{0}^{T}f_1\times f_2\, dt</math><br /> <math>=\frac{1}{T} \int_{0}^{T}-\frac{AB}{2} \times \{ cos[(\omega_1 + \omega_2 )t+\phi ]-cos[(\omega_1 - \omega_2 )t-\phi ]\} \, dt</math><br /> <math>= -\frac{AB}{2T} \int_{0}^{T} cos[(\omega_1 + \omega_2 )t+\phi ] \,dt + \frac{AB}{2T} \int_{0}^{T} cos[(\omega_1 - \omega_2 )t-\phi ] \,dt </math><br /> <br /> When <math> T \to \infty </math> , both parts are equal to 0, except when <math>\omega_1 = \omega_2 </math> and <math>\phi = 0</math>, the integration result is equal to <math>\frac{AB}{2}</math> .<br /> <br /> <br /> As can be observed, only signals in phase, in other words, sharing the same frequency and phase angle, will result in a non-zero value after multiplication and integration. This indicates a way to recover the signal from noise: by modulating the interesting signal and doing the maths.This is the mathematical foundation of phase sensitive detection, because all signals can be broken down in to several harmonic components.<br /> <br /> <br /> <br /> == '''Method''' ==<br /> <br /> <br /> A phase sensitive detection can be split into 6 stages:<br /> <br /> '''1.''' Modulation: Modulate the signal at a certain frequency.<br /> <br /> '''2.''' Pre-amplification: A high-speed amplifier required to amplify the signal (along with the noise) to a suitable level for succeeding circuit. We can also stick in a high pass filter (can be a capacitor) after amplification, just to eliminate the DC portion of the noise.<br /> <br /> '''3.''' Reference circuit: Usually a pulse wave at the modulating frequency, which can be from a function generator, or a 555 timer, or PIC, etc.<br /> <br /> '''4.''' Multiplier: At this stage, we multiply the pre-amplified signal (along with the noise) with the reference signal. One easy way to do multiplication is suggested here: we use the reference signal to turn on and off an analog switch periodically, and let the modulated input signal pass the analog switch. So when the switch is ON (meaning connected to the input pin of the integrator), the output is ‘<math>input \times 1</math>’, and when the switch is OFF (meaning connected to the ground), the output is ‘<math>input \times 0</math>’. <br /> <br /> '''5.''' Integrator (demodulation): Let the multiplied signal pass through an integrator. The multiplied signal can have a lot of components – almost all of them will become zero after integration (see explanation in the mathematical model), but the one which is the product of the modulated signal and the reference signal will remain, because they are at the same frequency and the same phase angle. This is the essence of phase sensitive detection – only the product of the two signals that are ‘in phase’ will remain after integration. ‘In phase’ means the two signals share common frequency and phase angle. We can also do amplification at the integration stage by sticking in a feedback resistor (see the example circuit diagram), just for convenience.<br /> <br /> '''6.''' Low pass filter: After integration, the signal is recovered and demodulated to a DC output. However, it may not be a perfect DC voltage due to high frequency spikes that still exist. That’s why the low pass filter come into play.<br /> <br /> == '''Example Circuit''' ==<br /> [[Image:phase_sensitive_detection_ckt.jpg|right|Circuit diagram of the phase sensitive detector]|thumb|350px]]<br /> <br /> The concept of phase sensitive detection has been proved effective in optical tracking with lateral effect photodiode. The following circuit picks up the difference of the two corresponding output pins of the photodiode, in order to tell the position of the centroid of IR light on the photodiode sensing surface. The connection for the Y+ and Y- pins of the photodiode is exactly the same with what’s shown here for X+ and X-. The timer is realized by a 555 chip, and the chip for analog switch is Max4526.<br /> <br /> <br /> Here is an illustration of the working principle of the example circuit.<br /> <br /> [[Image:Illustration of the example PSD circuit.jpg|right|Working principle of the phase sensitive detection circuit]|thumb|350px]]<br /> <br /> (1)The magnified signal from the X+ and X- pins of the photodiode.<br /> <br /> (2)Signals after high pass filter.<br /> <br /> (3)Reference signals for X+ and X- respectively.<br /> <br /> (4)Signals after multiplying with reference signals.<br /> <br /> (5)Signals before and after integration.<br /> <br /> == '''Commercial phase sensitive detectors''' ==<br /> <br /> This link below provides some useful information on commercially available phase sensitive detectors, or lock-in amplifiers.<br /> <br /> [http://www.thinksrs.com/products/SR810830.htm]SRS series Lock-in amplifiers: http://www.thinksrs.com/products/SR810830.htm</div>

EricN https://hades.mech.northwestern.edu//index.php?title=File:Phase_sensitive_detection_ckt.jpg&diff=9656 File:Phase sensitive detection ckt.jpg 2009-01-07T01:57:40Z

<p>EricN: Circuit diagram of the phase sensitive detector</p> <hr /> <div>Circuit diagram of the phase sensitive detector</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Phase-Sensitive_Detection&diff=9655 Phase-Sensitive Detection 2009-01-07T01:57:02Z

<p>EricN: /* '''Example Circuit''' */</p> <hr /> <div>== '''Overview''' ==<br /> <br /> One effective way to recover the small signal buried by large ambient noise is to use the so called phase sensitive detector, or lock-in amplifier. A phase sensitive detector achieves narrow bandwidth amplification by reducing the noise content at falling outside the interested bandwidth.<br /> <br /> When the noise is white in nature, we can reduce its level of magnitude dramatically by limiting the bandwidth of detection, which includes the frequency occurring to the signal while excludes the frequencies occurring to the noise. Phase sensitive detection enables extremely narrow bandwidth detection (0.001Hz is normal). Typical application scenario is using electric transducers where the amplitude of noise is in mili volts and the signal falls into nano volt region. Sophisticated phase sensitive detector can extract signals buried in noise that is <math>10^7</math> times larger in magnitude. <br /> <br /> In this article, we focus on a quick and easy method of building a phase sensitive detector from op-amps and analog switches.<br /> <br /> == '''Mathematical model''' ==<br /> <br /> <br /> Consider two signals, <math>f_1</math> and <math>f_2</math>, where <math>f_1=Asin\omega_1 t</math> , <math>f_2=Bsin(\omega_2 t + \phi)</math><br /> <br /> Then, the product of <math>f_1</math> and <math>f_2</math> is:<br /> <br /> <br /> <math>f_1\times f_2 = ABsin\omega_1 tsin(\omega_2 t + \phi) </math><br /> <math>= -\frac{AB}{2} \times {cos[(\omega_1 + \omega_2 )t+\phi ]-cos[(\omega_1 - \omega_2 )t-\phi ]}</math><br /> <br /> Let’s integrate the product over time <math>[0, T)</math>:<br /> <br /> <math>\frac{1}{T} \int_{0}^{T}f_1\times f_2\, dt</math><br /> <math>=\frac{1}{T} \int_{0}^{T}-\frac{AB}{2} \times \{ cos[(\omega_1 + \omega_2 )t+\phi ]-cos[(\omega_1 - \omega_2 )t-\phi ]\} \, dt</math><br /> <math>= -\frac{AB}{2T} \int_{0}^{T} cos[(\omega_1 + \omega_2 )t+\phi ] \,dt + \frac{AB}{2T} \int_{0}^{T} cos[(\omega_1 - \omega_2 )t-\phi ] \,dt </math><br /> <br /> When <math> T \to \infty </math> , both parts are equal to 0, except when <math>\omega_1 = \omega_2 </math> and <math>\phi = 0</math>, the integration result is equal to <math>\frac{AB}{2}</math> .<br /> <br /> <br /> As can be observed, only signals in phase, in other words, sharing the same frequency and phase angle, will result in a non-zero value after multiplication and integration. This indicates a way to recover the signal from noise: by modulating the interesting signal and doing the maths.This is the mathematical foundation of phase sensitive detection, because all signals can be broken down in to several harmonic components.<br /> <br /> <br /> <br /> == '''Method''' ==<br /> <br /> <br /> A phase sensitive detection can be split into 6 stages:<br /> <br /> '''1.''' Modulation: Modulate the signal at a certain frequency.<br /> <br /> '''2.''' Pre-amplification: A high-speed amplifier required to amplify the signal (along with the noise) to a suitable level for succeeding circuit. We can also stick in a high pass filter (can be a capacitor) after amplification, just to eliminate the DC portion of the noise.<br /> <br /> '''3.''' Reference circuit: Usually a pulse wave at the modulating frequency, which can be from a function generator, or a 555 timer, or PIC, etc.<br /> <br /> '''4.''' Multiplier: At this stage, we multiply the pre-amplified signal (along with the noise) with the reference signal. One easy way to do multiplication is suggested here: we use the reference signal to turn on and off an analog switch periodically, and let the modulated input signal pass the analog switch. So when the switch is ON (meaning connected to the input pin of the integrator), the output is ‘<math>input \times 1</math>’, and when the switch is OFF (meaning connected to the ground), the output is ‘<math>input \times 0</math>’. <br /> <br /> '''5.''' Integrator (demodulation): Let the multiplied signal pass through an integrator. The multiplied signal can have a lot of components – almost all of them will become zero after integration (see explanation in the mathematical model), but the one which is the product of the modulated signal and the reference signal will remain, because they are at the same frequency and the same phase angle. This is the essence of phase sensitive detection – only the product of the two signals that are ‘in phase’ will remain after integration. ‘In phase’ means the two signals share common frequency and phase angle. We can also do amplification at the integration stage by sticking in a feedback resistor (see the example circuit diagram), just for convenience.<br /> <br /> '''6.''' Low pass filter: After integration, the signal is recovered and demodulated to a DC output. However, it may not be a perfect DC voltage due to high frequency spikes that still exist. That’s why the low pass filter come into play.<br /> <br /> == '''Example Circuit''' ==<br /> <br /> The concept of phase sensitive detection has been proved effective in optical tracking with lateral effect photodiode. The following circuit picks up the difference of the two corresponding output pins of the photodiode, in order to tell the position of the centroid of IR light on the photodiode sensing surface. The connection for the Y+ and Y- pins of the photodiode is exactly the same with what’s shown here for X+ and X-. The timer is realized by a 555 chip, and the chip for analog switch is Max4526.<br /> <br /> <br /> [[Image:phase_sensitive_detection_ckt.jpg|right|Circuit diagram of the phase sensitive detector]|thumb|350px]]<br /> <br /> Here is an illustration of the working principle of the example circuit.<br /> <br /> [[Image:Illustration of the example PSD circuit.jpg]]<br /> <br /> (1)The magnified signal from the X+ and X- pins of the photodiode.<br /> <br /> (2)Signals after high pass filter.<br /> <br /> (3)Reference signals for X+ and X- respectively.<br /> <br /> (4)Signals after multiplying with reference signals.<br /> <br /> (5)Signals before and after integration.<br /> <br /> == '''Commercial phase sensitive detectors''' ==<br /> <br /> This link below provides some useful information on commercially available phase sensitive detectors, or lock-in amplifiers.<br /> <br /> [http://www.thinksrs.com/products/SR810830.htm]SRS series Lock-in amplifiers: http://www.thinksrs.com/products/SR810830.htm</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Phase-Sensitive_Detection&diff=9654 Phase-Sensitive Detection 2009-01-07T01:56:30Z

<p>EricN: /* '''Example Circuit''' */</p> <hr /> <div>== '''Overview''' ==<br /> <br /> One effective way to recover the small signal buried by large ambient noise is to use the so called phase sensitive detector, or lock-in amplifier. A phase sensitive detector achieves narrow bandwidth amplification by reducing the noise content at falling outside the interested bandwidth.<br /> <br /> When the noise is white in nature, we can reduce its level of magnitude dramatically by limiting the bandwidth of detection, which includes the frequency occurring to the signal while excludes the frequencies occurring to the noise. Phase sensitive detection enables extremely narrow bandwidth detection (0.001Hz is normal). Typical application scenario is using electric transducers where the amplitude of noise is in mili volts and the signal falls into nano volt region. Sophisticated phase sensitive detector can extract signals buried in noise that is <math>10^7</math> times larger in magnitude. <br /> <br /> In this article, we focus on a quick and easy method of building a phase sensitive detector from op-amps and analog switches.<br /> <br /> == '''Mathematical model''' ==<br /> <br /> <br /> Consider two signals, <math>f_1</math> and <math>f_2</math>, where <math>f_1=Asin\omega_1 t</math> , <math>f_2=Bsin(\omega_2 t + \phi)</math><br /> <br /> Then, the product of <math>f_1</math> and <math>f_2</math> is:<br /> <br /> <br /> <math>f_1\times f_2 = ABsin\omega_1 tsin(\omega_2 t + \phi) </math><br /> <math>= -\frac{AB}{2} \times {cos[(\omega_1 + \omega_2 )t+\phi ]-cos[(\omega_1 - \omega_2 )t-\phi ]}</math><br /> <br /> Let’s integrate the product over time <math>[0, T)</math>:<br /> <br /> <math>\frac{1}{T} \int_{0}^{T}f_1\times f_2\, dt</math><br /> <math>=\frac{1}{T} \int_{0}^{T}-\frac{AB}{2} \times \{ cos[(\omega_1 + \omega_2 )t+\phi ]-cos[(\omega_1 - \omega_2 )t-\phi ]\} \, dt</math><br /> <math>= -\frac{AB}{2T} \int_{0}^{T} cos[(\omega_1 + \omega_2 )t+\phi ] \,dt + \frac{AB}{2T} \int_{0}^{T} cos[(\omega_1 - \omega_2 )t-\phi ] \,dt </math><br /> <br /> When <math> T \to \infty </math> , both parts are equal to 0, except when <math>\omega_1 = \omega_2 </math> and <math>\phi = 0</math>, the integration result is equal to <math>\frac{AB}{2}</math> .<br /> <br /> <br /> As can be observed, only signals in phase, in other words, sharing the same frequency and phase angle, will result in a non-zero value after multiplication and integration. This indicates a way to recover the signal from noise: by modulating the interesting signal and doing the maths.This is the mathematical foundation of phase sensitive detection, because all signals can be broken down in to several harmonic components.<br /> <br /> <br /> <br /> == '''Method''' ==<br /> <br /> <br /> A phase sensitive detection can be split into 6 stages:<br /> <br /> '''1.''' Modulation: Modulate the signal at a certain frequency.<br /> <br /> '''2.''' Pre-amplification: A high-speed amplifier required to amplify the signal (along with the noise) to a suitable level for succeeding circuit. We can also stick in a high pass filter (can be a capacitor) after amplification, just to eliminate the DC portion of the noise.<br /> <br /> '''3.''' Reference circuit: Usually a pulse wave at the modulating frequency, which can be from a function generator, or a 555 timer, or PIC, etc.<br /> <br /> '''4.''' Multiplier: At this stage, we multiply the pre-amplified signal (along with the noise) with the reference signal. One easy way to do multiplication is suggested here: we use the reference signal to turn on and off an analog switch periodically, and let the modulated input signal pass the analog switch. So when the switch is ON (meaning connected to the input pin of the integrator), the output is ‘<math>input \times 1</math>’, and when the switch is OFF (meaning connected to the ground), the output is ‘<math>input \times 0</math>’. <br /> <br /> '''5.''' Integrator (demodulation): Let the multiplied signal pass through an integrator. The multiplied signal can have a lot of components – almost all of them will become zero after integration (see explanation in the mathematical model), but the one which is the product of the modulated signal and the reference signal will remain, because they are at the same frequency and the same phase angle. This is the essence of phase sensitive detection – only the product of the two signals that are ‘in phase’ will remain after integration. ‘In phase’ means the two signals share common frequency and phase angle. We can also do amplification at the integration stage by sticking in a feedback resistor (see the example circuit diagram), just for convenience.<br /> <br /> '''6.''' Low pass filter: After integration, the signal is recovered and demodulated to a DC output. However, it may not be a perfect DC voltage due to high frequency spikes that still exist. That’s why the low pass filter come into play.<br /> <br /> == '''Example Circuit''' ==<br /> <br /> The concept of phase sensitive detection has been proved effective in optical tracking with lateral effect photodiode. The following circuit picks up the difference of the two corresponding output pins of the photodiode, in order to tell the position of the centroid of IR light on the photodiode sensing surface. The connection for the Y+ and Y- pins of the photodiode is exactly the same with what’s shown here for X+ and X-. The timer is realized by a 555 chip, and the chip for analog switch is Max4526.<br /> <br /> <br /> [[Image:phase_sensitive_detection_ckt|right|Circuit diagram of the phase sensitive detector]|thumb|350px]]<br /> <br /> Here is an illustration of the working principle of the example circuit.<br /> <br /> [[Image:Illustration of the example PSD circuit.jpg]]<br /> <br /> (1)The magnified signal from the X+ and X- pins of the photodiode.<br /> <br /> (2)Signals after high pass filter.<br /> <br /> (3)Reference signals for X+ and X- respectively.<br /> <br /> (4)Signals after multiplying with reference signals.<br /> <br /> (5)Signals before and after integration.<br /> <br /> == '''Commercial phase sensitive detectors''' ==<br /> <br /> This link below provides some useful information on commercially available phase sensitive detectors, or lock-in amplifiers.<br /> <br /> [http://www.thinksrs.com/products/SR810830.htm]SRS series Lock-in amplifiers: http://www.thinksrs.com/products/SR810830.htm</div>

EricN https://hades.mech.northwestern.edu//index.php?title=IR_Target_Illumination&diff=9381 IR Target Illumination 2008-12-13T03:54:11Z

<p>EricN: </p> <hr /> <div>===Overview===<br /> <br /> The TSHF 5210 is a high radiant power, 890 nm emitting, GaAlAs, high-speed infrared emitting diode. They can be used to illuminate a target in the infrared range or they can be used as active signals to other devices for line-of-sight signal transfer.<br /> <br /> ==Summary==<br /> <br /> * 100 mA DC <br /> * ~200 mA AC (duty cycle ~50%, >10 kHz)<br /> * ~1 A AC (duty cycle ~5%, >10 kHz)<br /> * +/- 10 degrees - angle of half intensity<br /> * ~1.4 V (forward voltage at 100 mA)<br /> * ~2.3 V (forward voltage at 1 A)<br /> * ~50 mW radiant power (at 100 mA)<br /> * 12 MHz cutoff frequency (70 mA DC + 30 mA P-P)<br /> <br /> This IRED is good for high intensity IR illumination with reasonable half intensity angles and fairly high radiant power.<br /> <br /> ==Test Circuit==</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Main_Page&diff=9380 Main Page 2008-12-13T03:32:21Z

<p>EricN: </p> <hr /> <div>The Northwestern University mechatronics design wiki provides reference material on the theory and applications of electronics, sensors, actuators, etc., for use in mechatronics-related research and projects. Practical applications often refer to equipment and supplies available in the [http://mechatronics.mech.northwestern.edu/ Northwestern Mechatronics Design Lab].<br /> <br /> Important: Please be sure to read the [http://mechatronics.mech.northwestern.edu/mech-rules.pdf Rules for Using the Mechatronics Design Lab].<br /> <br /> <br /> __TOC__<br /> <br /> <br /> <br /> <br /> <h3>Design Competition 2008</h3><br /> <br /> Wiki pages on sensors, actuators, programming, and microcontrollers: use pages below<br /> <br><br /> * [http://www.mech.northwestern.edu/courses/433/Writeups/QuickStart/ Parts in the DC2008 quick start pack]<br /> * [http://peshkin.mech.northwestern.edu/pic/info/piccintro_2008-01-24.pdf PIC C intro slides, as presented 2008/01/24 (pdf)]<br /> * [http://peshkin.mech.northwestern.edu/pic/info/picinterfacing_2008-01-28.pdf PIC interfacing slides, as presented 2008/01/28 (pdf)]<br /> <br><br /> <br /> <h3>Sensors and actuators for DC</h3><br /> * [[Using Solderless Breadboard|Solderless Breadboard & wiring that works]]<br /> * [[Using LEDs & IREDs]]<br /> * [[Using a laser]]<br /> * [[Sensing optical tape|Infrared reflectivity]]<br /> ** Using phototransistors<br /> ** Sensing optical tape<br /> * [[Comparators | Comparators : the analog digital interface]]<br /> * [[Driving a DC Motor using PWM]]<br /> * [http://www.robotroom.com/FaulhaberGearmotor.html Faulhaber MiniMotor SA gearmotor with encoder], as well as [[Actuators_Available_in_the_Mechatronics_Lab#Faulhaber_1524E006S_motor_with_141:1_gearhead_and_HES164A_magnetic_quadrature_encoder|the local wiki page]]<br /> * [[Adding a magnetic encoder to a GM3 Gearmotor]]<br /> ** Using magnetic switches (Hall Effect)<br /> * [[Driving using a single MOSFET | Driving a DC motor using a single MOSFET]]<br /> * [[High-current devices|Driving high-current devices: several options]]<br /> * [[Driving a Stepper Motor]]<br /> * [[Driving an RC Servo]]<br /> * [[Accelerometers]]<br /> * [[Strain gauges]]<br /> * [[Using the Basic Stamp Microcontroller|Basic Stamp Microcontroller]] <b>Not recommended for DC2008</b><br /> * [http://www.mech.northwestern.edu/courses/433/Writeups/Battery_NiMH/ NiMH rechargable batteries and chargers]<br /> <br /> <h3> [http://peshkin.mech.northwestern.edu/datasheets Prof. Peshkin's favorite datasheets]</h3><br /> <br><br /> <br /> <h3>PIC 18F4520 prototyping board </h3><br /> *[[4520 Board intro|Prototyping board intro]]<br /> *[[4520 Board construction|Assembling the 18F4520 prototyping board, circuit, parts]]<br /> *[[4520 Board use|Using the 18F4520 prototyping board]]<br /> <br><br /> <br /> <h3>Programming with CCS C </h3><br /> *[[C language|The C language]]<br /> *[[CCS C|CCS C, specifically for the 18F4520]]<br /> *[[Embedded Programming Tips for CCS C]]<br /> *[[CCS IDE|Using the CCS development environment]]<br /> *[[Debugging C on a PIC]]<br /> *[[More debugging tips]]<br /> *[http://www.ccsinfo.com/forum/ CCS user forum]<br /> <br><br /> <br /> <h3>Interfacing and skeleton code for the PIC 18F4520</h3><br><br /> <b>These topics have wiki pages <i>and</i> sample code available</b><br><br /> <b>[http://peshkin.mech.northwestern.edu/pic/code Link to all sample code here.]</b><br /> <br><br /> * [[Digital inputs & outputs]] (filename: DigitalIO)<br /> * [[Analog Input]] (filename: AnalogInput)<br /> ** reading a trimpot<br /> ** reading a phototransistor<br /> ** amplified phototransistor, and IRED strobing<br /> ** using an instrumentation amp (example: for a strain gauge)<br /> * [[Analog Output|Analog Output, and the I2C bus]] (filename: AnalogOutput)<br /> * [[Waveform Generation with AD9833, and SPI]] (filename: AD9833)<br /> *[[Pulse width modulation|Pulse width modulation (PWM) for driving motors or other high current devices]] (filename: MotorPWM)<br /> ** using H-bridges<br /> * [[Interrupts]]<br /> * [[Quadrature decoding in software]] (filename: QuadratureSoft)<br /> * [[Quadrature decoding in hardware, or just counters]] (filename: QuadratureHard)<br /> * [[Running RC servos]] (filename: RCservoSoft & RCservoHard)<br /> * [[Watchdog timer]] (filename: Watchdog)<br /> * [[PIC RS232|RS-232 serial communication between a PC and a PIC]] (filename: RS232)<br /> * [[C Example: Serial LCD|Text output to a serial LCD display]]<br /> * [[C Example: Parallel Interfacing with LCDs|Text output to a parallel LCD display]]<br /> * [[Servo skeleton with fast & slow interrupts]]<br /> * [[XBee radio communication between PICs]] (and between a PC and a PIC)<br /> * [[I2C communication between PICs]]<br /> * [[Serial communication with Matlab]]<br /> * [[SPI communication between PICs]] <b> (Note: this function has not been successfully tested)</b><br /> * [[Microphones]]<br /> * [[Ambient light color sensing]]<br /> * [[Controlling a seven segment display]]<br /> * [[Storing constant data in program memory]]<br /> * [[PIC computation time benchmarks]]<br /> * [[Stepper motor control with the PIC]]<br /> * [[Global Positioning System]]<br /> * [[IR communication between PICs]] <b> (Note: this function has not been successfully tested) </b><br /> * [[Interfacing to External EEPROM]]<br /> * [[I2C Motor Controller]]<br /> * [[Interfacing with a Photodiode Array]]<br /> <br /> <br><br /> <b>These topics have sample code available, but no wiki pages yet</b><br><br /> <b>[http://peshkin.mech.northwestern.edu/pic/code Link to all sample code here.]</b><br /> <br /> * Counter0 - Counting pulses with Timer0]<br /> * Counter1 - Counting pulses with Timer1]<br /> * Interrupt0 - Periodic servo cycles using interrupt routines, 10mS & slower; Timer 0]<br /> * Interrupt2 - Periodic servo cycles using interrupt routines; 10mS & faster; Timer 2]<br /> * InterruptExternal - Interrupts generated by an external pulse]<br /> <br /> <br><br /> <b>These topics need more development</b><br><br /> <b>[http://peshkin.mech.northwestern.edu/pic/code Link to all sample code here.]</b><br><br /> * AnalogOutputParallel - Analog output using 8 digital lines]<br /> * PIC-to-PIC communication <br /> * Zigbee radio communication<br /> * Modulated IR communication<br /> * Strobing LEDs or IREDs for better range and immunity to background light<br /> * I2C communication <br /> * CAN bus<br /> * Capturing data to Matlab<br /> * Running stepper motors<br /> <br><br /> <br /> <h3>PIC Microcontrollers</h3><br /> * [[PIC Microcontrollers with CCS Compiler]], for DC, 333, etc, using the CCS ICD-U40 device <b>[this section has been replaced by the material above]</b><br /> * [[PIC Microcontrollers with C18 Compiler]], for e-puck, or using the Microchip ICD device or<br /> <br><br /> <br /> <h3>e-puck Mobile Robot</h3><br /> * [[e-puck Mobile Robot]]<br /> <br><br /> <br /> <h3>[[Printing Circuit Boards]]</h3><br /> <br /> <h3> Electronics </h3><br /> * [http://hades.mech.northwestern.edu/wiki/index.php/Category:Electronics Electronics]<br /> * [[Phase-Sensitive Detection]]<br /> * [http://en.wikipedia.org/wiki/Operational_amplifier_applications Op-Amp Applications]<br /> <br><br /> <br /> <h3>Analog and Digital chips</h3><br /> * [[Comparators | Comparators: the analog to digital interface]]<br /> * [[Filtering with the LMF100 | Filtering with the LMF100]]<br /> * [http://en.wikipedia.org/wiki/Operational_amplifier_applications Opamps : building blocks of analog computation]<br /> * [http://www.mech.northwestern.edu/courses/433/Writeups/InstAmp/instamp.htm Instrumentation amps, and NU circuit board for them]<br /> <br /> <br clear=all/><br /> <br /> <h3>[[:Category:Sensors|Sensors]]</h3><br /> <br /> * [[Potentiometers|Angle, Linear Position: Potentiometers]]<br /> * [[Optointerrupter|Beam Breaker: Optointerrupter]]<br /> * [[Optoreflector|Proximity: Optoreflector]]<br /> * [[Sensing optical tape|Infrared reflectivity : Sensing optical tape]]<br /> * [[Reed Switch|Proximity: Reed Switch]]<br /> * [[Hall Effect Sensor|Proximity, Angle: Hall Effect Sensor]]<br /> * [[Rotary Encoder|Angle: Rotary Encoder]]<br /> * Angular Velocity: Tachometer<br /> * [[Photodiodes and Phototransistors|Light: Photodiodes and Phototransistors]]<br /> * [[Photocell|Ambient Light: Photocell]]<br /> * [[Thermistor|Temperature: Thermistor]]<br /> * Temperature: Thermotransistor IC<br /> * Audio: [[Microphones]]<br /> * [[Accelerometers|Tilt, Acceleration: Accelerometers]]<br /> * [[Strain Gauge|Force: Strain Gauge]]<br /> * Current: Current Sense Resistor<br /> * [[Limit Switch|Contact: Microswitch (Limit Switch)]]<br /> * [[Ambient light color sensing]]<br /> * [[Global Positioning System]]<br /> * [[Optics]]<br /> * [[Optical Locating]]<br /> * [[Lateral-Effect Photodiode]]<br /> * [[IR Target Illumination|IRED's]]<br /> <br /> <br clear=all/><br /> <br /> <h3>[[:Category:Actuators|Actuators]]</h3><br /> [[image:All-actuators-captions-small.jpg|thumb|300px|[[Actuators Available in the Mechatronics Lab|Available Actuators]]|right]]<br /> <br /> * [[Brushed DC Motor Theory|Brushed DC Motors]]<br /> ** [[Choosing a Motor and Gearing Combination|Choosing a Motor and Gearing Combination]]<br /> ** [[Linear Amplifier Motor Driver|Driving Using a Linear Amplifier]]<br /> ** [[Driving using a single MOSFET|Driving using a single MOSFET]]<br /> ** [[Pulse Width Modulation|Driving Using Pulse Width Modulation]]<br /> ** [[PIC PWM Motor Driver]]<br /> ** [[Gear Motor]]<br /> *** [http://www.mech.northwestern.edu/courses/433/Writeups/AddEncoderHobbyEngGearMotor Adding a rotation encoder to a gearmotor]<br /> * [[Brushless DC Motors]]<br /> ** [[Driving Brushless DC Motors]]<br /> * [[Stepper Motor Theory|Stepper Motors]]<br /> ** [[Stepper Motor Circuits|Driving Stepper Motors]]<br /> ** [[Unipolar Stepper Motor Driver Circuit]]<br /> ** [[Bipolar Stepper Motor Driver Circuit]]<br /> * [[RC Servo Theory|RC Servos]]<br /> ** [[555 Servo Circuit|Driving Your Servo Using a 555 Timer]]<br /> * [[Solenoid Theory|Solenoids]]<br /> ** Practice: Driving Your Solenoid<br /> * AC Motors<br /> ** [[Using the Yaskawa Motors]]<br /> * [[Actuators Available in the Mechatronics Lab]]<br /> <br clear=all/><br /> <br /> <h3>Mechanical Design</h3><br /> *Mechanics of Materials<br /> **Beam Mechanics<br /> **[[Mohr's Circle]]<br /> *Failure Theories<br /> **Static Loading<br /> **Variable Loading and Fatigue<br /> *Fastening<br /> **Nuts and Bolts<br /> **Keys and Keyways<br /> **Press-fits<br /> **Set Screws<br /> *Support<br /> **Housings<br /> **Shafts<br /> **[[Bearings]]<br /> *Transmission<br /> **Rigid: [[Gears]]<br /> **Flexible: Belts, Chains<br /> **Motion Connection/Separation: Clutches, Brakes, Couplings<br /> *Linkages<br /> **Serial Chains<br /> **Parallel and Closed-Loop Chains<br /> *Other: springs/dampers, cams, etc.<br /> <br /> <br clear=all/><br /> <br /> <h3>The PC/104 Stack</h3><br /> [[Image:Img0174.jpg|thumb|300px|[[PC104 Overview|The PC104 Stack]]|right]]<br /> * [[PC104 Overview|Overview]]<br /> * [[The PC/104 Lab Kit]]<br /> * Hardware:<br /> ** [[Advantech CPU Card]]<br /> ** [[Sensoray 526 Data Aquisition Card]]<br /> <br /> ** [http://www.mech.northwestern.edu/courses/433/Writeups/PC104BoB/stack.htm#power[Power Components]]<br /> ** [http://www.mech.northwestern.edu/courses/433/Writeups/PC104BoB/stack.htm#electrical[I/O Electronics: Analog I/O, Digital I/O, Encoder Connections]]<br /> * Advanced: Creating a Working Stack from Parts<br /> ** [http://www.mech.northwestern.edu/courses/433/Writeups/PC104BoB/stack.htm [Building the Breakout Board]]<br /> ** [http://www.mech.northwestern.edu/courses/433/Writeups/PC104BoB/stack.htm#ribboncables[Breakout Board Ribbon Cables]]<br /> ** [http://www.mech.northwestern.edu/courses/433/Writeups/PC104BoB/stack.htm#mechanical[Assembling the PC104 Stack]]<br /> ** '''[[Creating an xPC Flash Boot Disk]]''' <- when new version of MATLAB<br /> * Custom Boards<br /> ** Dual PWM Motor Controller<br /> ** Dual Linear Amplifier Motor Controller<br /> <br clear=all/><br /> <br /> <h3>xPC Target Real-Time Operating System</h3><br /> <br /> * [[xPC Overview|Overview of Real-Time Programming with Simulink and xPC Target]]<br /> * [[Configuring xPC Target PC|Configuring xPC Host/Target PC]]<br /> * [[Creating a Simple xPC Program|'''Quickstart''':Creating a simple xPC Program]]<br /> * [[Common xPC Blocks|Commonly Used Blocks]]<br /> * [[Using the Host Scope]]<br /> *Advanced<br /> ** Model Properties<br /> ** [[XPC M-file Communication|M-file communication]]<br /> ** Using outside of the lab<br /> ** [[media:standalone.pdf|Standalone Mode]]<br /> ** Stateflow<br /> * Code Examples<br /> ** [[Controlling a DC Motor with an Encoder]]<br /> ** Something With State Machine<br /> ** [[Using RS-232 and Printing to LCD]]<br /> **[[UDP Communications between Target and Host PC]]<br /> ** M-functions and S-functions<br /> ** [[xPC Code From Student Projects]]<br /> <br clear=all/><br /> <br /> <h3>QNX Real-Time Operating System</h3><br /> *[[media:qnxtemplate.zip|QNX Control Program with Interrupts]]<br /> <br /> <br clear=all/><br /> <br /> <h3>Lab Supplies and Data Sheets</h3><br /> <br /> * [http://spreadsheets.google.com/pub?key=pa_bNAhFF-OvvxpSje1KDYg&output=html&gid=0&single=true Generally stocked lab inventory ]<br /> <br /> <br clear=all><br /> <br /> <h3>[[Vendors]]</h3><br /> <br /> <br clear=all><br /> <br /> <h3>Other Software</h3><br /> *[[List of Useful Software for Download]]<br /> *Circuit Schematics and PCB Layout<br /> *LaTex Document Preparation<br /> ** [http://meta.wikimedia.org/wiki/Help:Formula Mathematical Formulae]<br /> ** Document Formatting<br /> ** [[LaTeX Software Setup|Software Setup]]<br /> ** IEEE Styles<br /> <br /> <br clear=all><br /> <br /> <h3>[[Other Lab Equipment]]</h3><br /> * Prototyping Tools<br /> ** [[Tektronix TDS220 Oscilloscope]]<br /> ** [[Tektronix CFG253 Function Generator]]<br /> ** [[media:Mastech_power_supply_manual.pdf|Mastech Power Supply]]<br /> ** Fluke III Multimeter<br /> ** Benchtop Multimeter<br /> ** Powered Breadboard<br /> ** Soldering Iron<br /> * [http://ediacaran.mech.northwestern.edu/neuromech/index.php/Lab_Equipment High Performance Neuromechatronics Benches]<br /> * The Sensoray 626 DAQ Card<br /> <br /> <br clear=all><br /> <br /> <h3>Course Material</h3><br /> * [[ME 224 Experimental Engineering]]<br /> * [http://lims.mech.northwestern.edu/~lynch/courses/ME333/2008/index.html ME 333 Introduction to Mechatronics]<br /> ** [[Lab 5]]<br /> ** [[Suggested final projects]]<br /> ** [[ME 333 final projects]]<br /> <br /> * [http://www.mech.northwestern.edu/courses/433/ ME 433 Advanced Mechatronics] <br /> <br /> <br clear=all><br /> <br /> <h3>Miscellaneous</h3><br /> * [[Swarm Robot Project]]<br /> ** [[Swarm Robot Project Links]]<br /> <br /> * [[Indoor Localization System]]<br /> * [[Robot Helicopter Project]]<br /> * [[E-Puck Color Sensing Project]]<br /> * [[Guitar Tunning Project]]</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9379 Lateral-Effect Photodiode 2008-12-13T03:30:52Z

<p>EricN: /* Position Sensing Devices */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device sensing a single axis in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.jpg|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> <br /> The duo-lateral position sensing device functions as a current source/sink, where the amount of current sourced/sunk is proportional to the total intensity of light incident on the sensing area. At the P-N junction, light forces current to flow though the photo-electric effect, and since the junction only allows current to flow one way, the net function is as a current source.<br /> <br /> <br /> The device has four leads, two of which source current and two of which sink current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> <br clear=all><br /> [[Image:XY_position.jpg|right|description|thumb|350px]]<br /> <br /> The layers themselves act as resistors, where the resistance is proportional to the distance between the centroid of the incident light spot and the terminals, essentially resulting in a current divider. The position can be calculated precisely using the following formula:<br /> <br /> <br /> <math> X = \frac {i_{out2} - i_{out1}}{i_{out2} + i_{out1}} </math><br /> <br /> <br /> <math> Y = \frac {i_{in2} - i_{in1}}{i_{in2} + i_{in1}} </math><br /> <br /> <br /> <br /> This makes the center of each axis zero and makes the right side and the upper side positive in their respective directions. In the example diagram, the resulting X coordinate would be negative and the Y coordinate would be positive. Both calculations are scaled such that the range of position values for each axis are:<br /> <br /> <br /> -0.5 < X < 0.5<br /> <br /> <br /> -0.5 < Y < 0.5<br /> <br /> <br /> <br clear=all><br /> <br /> ==Application==<br /> <br /> For some applications, it may not be possible to filter the incoming light such that the desired signal is significantly stronger than the ambient light, resulting in little control over the location of the centroid. For cases such as these, alternative methods of computing the location of the desired signal may be necessary. One of these alternative methods is called [[Phase-Sensitive Detection| phase-sensitive detection]]. This utilizes the fact that a pulsing target would alter the centroid location in a periodic manner, so phase-locking the detector circuitry to add when the pulse is high then subtract when it is low would filter out the ambient signal and provide a good appriximation of the actual location of the desired incident signal.</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Photodiodes_and_Phototransistors&diff=9378 Photodiodes and Phototransistors 2008-12-13T03:29:53Z

<p>EricN: /* Applications */</p> <hr /> <div>==Phototransistors==<br /> [[image:phototransistor.jpg|left|150px]]<br /> [[image:phototransistor amplifiers.png|right]]<br /> Phototransistors are transistors with the base terminal exposed. Instead of applying a voltage to the base, the photons from striking light activate the transistor. Other than that, the phototransistor behaves just like a normal transistor. Two common configurations are shown on the right.<br /> <br /> *'''Common-Emitter Amplifier''' - goes from "high" to "low" with light.<br /> <br /> *'''Commond-Collector Amplifier''' - goes from "low" to "high" with light.<br /> <br /> The phototransistor can be used in two different modes: 1) active & 2) switch. These modes are controlled by changing the value of the resistor. The equations are:<br /> <br /> [[image:phototransistor modes.png]]<br /> <br /> ''Fairchild recommends a 5kohm resistor or greater to use as a switch''<br /> <br /> *'''Switch Mode''' - when operating as a switch, the transistor can be switched between the cut-off ("off") and saturated ("on") states. This means that when light strikes the phototransistor, it will conduct. Otherwise, it will insulate.<br /> <br /> *'''Active Mode''' - In active mode, the output of the transistor is proportional to the intensity of the light.<br /> <br /> ==Photodiodes==<br /> <br /> Photodiodes are semiconductors that produce current flow when they absorb light. In application, there are two types of photodiodes: 1) photovoltaics and 2) photoconductors.<br /> <br /> * '''Photovoltaics'''<br /> *: Photovoltaics work like solar cells (in fact they are the same). When light shines on the photodiode, a voltage is created across it, causing current to flow.<br /> <br /> * '''Photoconductors'''<br /> *: Photoconductors are reverse-biased photodiodes. When light shines on the photodiode, the resistance to the reverse-bias decreases. By measuring the current through the photodiode, you can detect the intensity of light.<br /> <br /> [[image:photo comparison.png|center]]<br /> <br /> ==Comparison==<br /> <br /> * '''Frequency Response'''<br /> *: Photodiodes are much faster than phototransistors (nanoseconds vs. microseconds)<br /> <br /> * '''Gain'''<br /> *: Phototransistors have a higher gain. Photodiodes require an amplifier to use.<br /> <br /> * '''Temperature Response'''<br /> *: Photodiodes vary ''less'' with temperature<br /> <br /> ==Applications==<br /> <br /> * '''Optocoupler'''<br /> *: Optocouplers are used in electronics-sensitive applications. For example, you may use this in a mobile robot application to separate the microcontroller circuitry (low voltage/power) from the motor driver circuitry (high voltage/power).<br /> <br /> [[image:optocoupler.png|center]]<br /> <br /> <br clear=all><br /> * [[Lateral-Effect Photodiode|Position-sensitive detector]]<br /> <br /> ==References==<br /> <br /> * [http://www.fairchildsemi.com Fairchild Semiconductor], "Design Fundamentals for Phototransistor Circuits," [[media:phototransistors.pdf|PDF]],</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Photodiodes_and_Phototransistors&diff=9377 Photodiodes and Phototransistors 2008-12-13T03:29:03Z

<p>EricN: /* Applications */</p> <hr /> <div>==Phototransistors==<br /> [[image:phototransistor.jpg|left|150px]]<br /> [[image:phototransistor amplifiers.png|right]]<br /> Phototransistors are transistors with the base terminal exposed. Instead of applying a voltage to the base, the photons from striking light activate the transistor. Other than that, the phototransistor behaves just like a normal transistor. Two common configurations are shown on the right.<br /> <br /> *'''Common-Emitter Amplifier''' - goes from "high" to "low" with light.<br /> <br /> *'''Commond-Collector Amplifier''' - goes from "low" to "high" with light.<br /> <br /> The phototransistor can be used in two different modes: 1) active & 2) switch. These modes are controlled by changing the value of the resistor. The equations are:<br /> <br /> [[image:phototransistor modes.png]]<br /> <br /> ''Fairchild recommends a 5kohm resistor or greater to use as a switch''<br /> <br /> *'''Switch Mode''' - when operating as a switch, the transistor can be switched between the cut-off ("off") and saturated ("on") states. This means that when light strikes the phototransistor, it will conduct. Otherwise, it will insulate.<br /> <br /> *'''Active Mode''' - In active mode, the output of the transistor is proportional to the intensity of the light.<br /> <br /> ==Photodiodes==<br /> <br /> Photodiodes are semiconductors that produce current flow when they absorb light. In application, there are two types of photodiodes: 1) photovoltaics and 2) photoconductors.<br /> <br /> * '''Photovoltaics'''<br /> *: Photovoltaics work like solar cells (in fact they are the same). When light shines on the photodiode, a voltage is created across it, causing current to flow.<br /> <br /> * '''Photoconductors'''<br /> *: Photoconductors are reverse-biased photodiodes. When light shines on the photodiode, the resistance to the reverse-bias decreases. By measuring the current through the photodiode, you can detect the intensity of light.<br /> <br /> [[image:photo comparison.png|center]]<br /> <br /> ==Comparison==<br /> <br /> * '''Frequency Response'''<br /> *: Photodiodes are much faster than phototransistors (nanoseconds vs. microseconds)<br /> <br /> * '''Gain'''<br /> *: Phototransistors have a higher gain. Photodiodes require an amplifier to use.<br /> <br /> * '''Temperature Response'''<br /> *: Photodiodes vary ''less'' with temperature<br /> <br /> ==Applications==<br /> <br /> * '''Optocoupler'''<br /> *: Optocouplers are used in electronics-sensitive applications. For example, you may use this in a mobile robot application to separate the microcontroller circuitry (low voltage/power) from the motor driver circuitry (high voltage/power).<br /> <br /> [[image:optocoupler.png|center]]<br /> <br /> <br clear=all><br /> * [[Position-Sensitive Detection|Position-sensitive detector]]<br /> <br /> ==References==<br /> <br /> * [http://www.fairchildsemi.com Fairchild Semiconductor], "Design Fundamentals for Phototransistor Circuits," [[media:phototransistors.pdf|PDF]],</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Photodiodes_and_Phototransistors&diff=9376 Photodiodes and Phototransistors 2008-12-13T03:28:41Z

<p>EricN: /* Applications */</p> <hr /> <div>==Phototransistors==<br /> [[image:phototransistor.jpg|left|150px]]<br /> [[image:phototransistor amplifiers.png|right]]<br /> Phototransistors are transistors with the base terminal exposed. Instead of applying a voltage to the base, the photons from striking light activate the transistor. Other than that, the phototransistor behaves just like a normal transistor. Two common configurations are shown on the right.<br /> <br /> *'''Common-Emitter Amplifier''' - goes from "high" to "low" with light.<br /> <br /> *'''Commond-Collector Amplifier''' - goes from "low" to "high" with light.<br /> <br /> The phototransistor can be used in two different modes: 1) active & 2) switch. These modes are controlled by changing the value of the resistor. The equations are:<br /> <br /> [[image:phototransistor modes.png]]<br /> <br /> ''Fairchild recommends a 5kohm resistor or greater to use as a switch''<br /> <br /> *'''Switch Mode''' - when operating as a switch, the transistor can be switched between the cut-off ("off") and saturated ("on") states. This means that when light strikes the phototransistor, it will conduct. Otherwise, it will insulate.<br /> <br /> *'''Active Mode''' - In active mode, the output of the transistor is proportional to the intensity of the light.<br /> <br /> ==Photodiodes==<br /> <br /> Photodiodes are semiconductors that produce current flow when they absorb light. In application, there are two types of photodiodes: 1) photovoltaics and 2) photoconductors.<br /> <br /> * '''Photovoltaics'''<br /> *: Photovoltaics work like solar cells (in fact they are the same). When light shines on the photodiode, a voltage is created across it, causing current to flow.<br /> <br /> * '''Photoconductors'''<br /> *: Photoconductors are reverse-biased photodiodes. When light shines on the photodiode, the resistance to the reverse-bias decreases. By measuring the current through the photodiode, you can detect the intensity of light.<br /> <br /> [[image:photo comparison.png|center]]<br /> <br /> ==Comparison==<br /> <br /> * '''Frequency Response'''<br /> *: Photodiodes are much faster than phototransistors (nanoseconds vs. microseconds)<br /> <br /> * '''Gain'''<br /> *: Phototransistors have a higher gain. Photodiodes require an amplifier to use.<br /> <br /> * '''Temperature Response'''<br /> *: Photodiodes vary ''less'' with temperature<br /> <br /> ==Applications==<br /> <br /> * '''Optocoupler'''<br /> *: Optocouplers are used in electronics-sensitive applications. For example, you may use this in a mobile robot application to separate the microcontroller circuitry (low voltage/power) from the motor driver circuitry (high voltage/power).<br /> <br /> [[image:optocoupler.png|center]]<br /> <br /> <br clear=all><br /> * [[Position-Sensitive Detector|Position-sensitive detector]]<br /> <br /> ==References==<br /> <br /> * [http://www.fairchildsemi.com Fairchild Semiconductor], "Design Fundamentals for Phototransistor Circuits," [[media:phototransistors.pdf|PDF]],</div>

EricN https://hades.mech.northwestern.edu//index.php?title=IR_Target_Illumination&diff=9375 IR Target Illumination 2008-12-13T03:26:19Z

<p>EricN: </p> <hr /> <div>===Overview===<br /> <br /> The TSHF 5210 is a high radiant power, 890 nm emitting, GaAlAs, high-speed infrared emitting diode.<br /> <br /> ==Summary==<br /> <br /> ==Test Circuit==</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9374 Lateral-Effect Photodiode 2008-12-13T03:03:49Z

<p>EricN: /* Output */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.jpg|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> <br /> The duo-lateral position sensing device functions as a current source/sink, where the amount of current sourced/sunk is proportional to the total intensity of light incident on the sensing area. At the P-N junction, light forces current to flow though the photo-electric effect, and since the junction only allows current to flow one way, the net function is as a current source.<br /> <br /> <br /> The device has four leads, two of which source current and two of which sink current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> <br clear=all><br /> [[Image:XY_position.jpg|right|description|thumb|350px]]<br /> <br /> The layers themselves act as resistors, where the resistance is proportional to the distance between the centroid of the incident light spot and the terminals, essentially resulting in a current divider. The position can be calculated precisely using the following formula:<br /> <br /> <br /> <math> X = \frac {i_{out2} - i_{out1}}{i_{out2} + i_{out1}} </math><br /> <br /> <br /> <math> Y = \frac {i_{in2} - i_{in1}}{i_{in2} + i_{in1}} </math><br /> <br /> <br /> <br /> This makes the center of each axis zero and makes the right side and the upper side positive in their respective directions. In the example diagram, the resulting X coordinate would be negative and the Y coordinate would be positive. Both calculations are scaled such that the range of position values for each axis are:<br /> <br /> <br /> -0.5 < X < 0.5<br /> <br /> <br /> -0.5 < Y < 0.5<br /> <br /> <br /> <br clear=all><br /> <br /> ==Application==<br /> <br /> For some applications, it may not be possible to filter the incoming light such that the desired signal is significantly stronger than the ambient light, resulting in little control over the location of the centroid. For cases such as these, alternative methods of computing the location of the desired signal may be necessary. One of these alternative methods is called [[Phase-Sensitive Detection| phase-sensitive detection]]. This utilizes the fact that a pulsing target would alter the centroid location in a periodic manner, so phase-locking the detector circuitry to add when the pulse is high then subtract when it is low would filter out the ambient signal and provide a good appriximation of the actual location of the desired incident signal.</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9373 Lateral-Effect Photodiode 2008-12-13T03:03:36Z

<p>EricN: /* Output */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.jpg|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> <br /> The duo-lateral position sensing device functions as a current source/sink, where the amount of current sourced/sunk is proportional to the total intensity of light incident on the sensing area. At the P-N junction, light forces current to flow though the photo-electric effect, and since the junction only allows current to flow one way, the net function is as a current source.<br /> <br /> <br /> The device has four leads, two of which source current and two of which sink current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> <br clear=all><br /> [[Image:XY_position.jpg|right|description|thumb|350px]]<br /> <br /> The layers themselves act as resistors, where the resistance is proportional to the distance between the centroid of the incident light spot and the terminals, essentially resulting in a current divider. The position can be calculated precisely using the following formula:<br /> <br /> <br /> <math> X = \frac {i_{out2} - i_{out1}}{i_{out2} + i_{out1}} </math><br /> <br /> <br /> <math> Y = \frac {i_{in2} - i_{in1}}{i_{in2} + i_{in1}} </math><br /> <br /> <br /> <br /> This makes the center of each axis zero and makes the right side and the upper side positive in their respective directions. In the example diagram, the resulting X coordinate would be negative and the Y coordinate would be positive. Both calculations are scaled such that the range of position values for each axis are:<br /> <br /> -0.5 < X < 0.5<br /> <br /> <br /> -0.5 < Y < 0.5<br /> <br /> <br /> <br clear=all><br /> <br /> ==Application==<br /> <br /> For some applications, it may not be possible to filter the incoming light such that the desired signal is significantly stronger than the ambient light, resulting in little control over the location of the centroid. For cases such as these, alternative methods of computing the location of the desired signal may be necessary. One of these alternative methods is called [[Phase-Sensitive Detection| phase-sensitive detection]]. This utilizes the fact that a pulsing target would alter the centroid location in a periodic manner, so phase-locking the detector circuitry to add when the pulse is high then subtract when it is low would filter out the ambient signal and provide a good appriximation of the actual location of the desired incident signal.</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9372 Lateral-Effect Photodiode 2008-12-13T03:03:15Z

<p>EricN: /* Output */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.jpg|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> <br /> The duo-lateral position sensing device functions as a current source/sink, where the amount of current sourced/sunk is proportional to the total intensity of light incident on the sensing area. At the P-N junction, light forces current to flow though the photo-electric effect, and since the junction only allows current to flow one way, the net function is as a current source.<br /> <br /> <br /> The device has four leads, two of which source current and two of which sink current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> <br clear=all><br /> [[Image:XY_position.jpg|right|description|thumb|350px]]<br /> <br /> The layers themselves act as resistors, where the resistance is proportional to the distance between the centroid of the incident light spot and the terminals, essentially resulting in a current divider. The position can be calculated precisely using the following formula:<br /> <br /> <br /> <math> X = \frac {i_{out2} - i_{out1}}{i_{out2} + i_{out1}} </math><br /> <br /> <br /> <math> Y = \frac {i_{in2} - i_{in1}}{i_{in2} + i_{in1}} </math><br /> <br /> <br /> <br /> This makes the center of each axis zero and makes the right side and the upper side positive in their respective directions. In the example diagram, the resulting X coordinate would be negative and the Y coordinate would be positive. Both calculations are scaled such that the range of position values for each axis are:<br /> <br /> <math> -0.5 \< X \< 0.5<br /> <br /> <br /> -0.5 \< Y \< 0.5 </math><br /> <br /> <br /> <br clear=all><br /> <br /> ==Application==<br /> <br /> For some applications, it may not be possible to filter the incoming light such that the desired signal is significantly stronger than the ambient light, resulting in little control over the location of the centroid. For cases such as these, alternative methods of computing the location of the desired signal may be necessary. One of these alternative methods is called [[Phase-Sensitive Detection| phase-sensitive detection]]. This utilizes the fact that a pulsing target would alter the centroid location in a periodic manner, so phase-locking the detector circuitry to add when the pulse is high then subtract when it is low would filter out the ambient signal and provide a good appriximation of the actual location of the desired incident signal.</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9371 Lateral-Effect Photodiode 2008-12-13T03:02:35Z

<p>EricN: /* Output */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.jpg|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> <br /> The duo-lateral position sensing device functions as a current source/sink, where the amount of current sourced/sunk is proportional to the total intensity of light incident on the sensing area. At the P-N junction, light forces current to flow though the photo-electric effect, and since the junction only allows current to flow one way, the net function is as a current source.<br /> <br /> <br /> The device has four leads, two of which source current and two of which sink current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> <br clear=all><br /> [[Image:XY_position.jpg|right|description|thumb|350px]]<br /> <br /> The layers themselves act as resistors, where the resistance is proportional to the distance between the centroid of the incident light spot and the terminals, essentially resulting in a current divider. The position can be calculated precisely using the following formula:<br /> <br /> <br /> <math> X = \frac {i_{out2} - i_{out1}}{i_{out2} + i_{out1}} </math><br /> <br /> <br /> <math> Y = \frac {i_{in2} - i_{in1}}{i_{in2} + i_{in1}} </math><br /> <br /> <br /> <br /> This makes the center of each axis zero and makes the right side and the upper side positive in their respective directions. In the example diagram, the resulting X coordinate would be negative and the Y coordinate would be positive. Both calculations are scaled such that the range of position values for each axis are:<br /> <br /> <math> -0.5 < X < 0.5<br /> <br /> -0.5 < Y < 0.5 </math><br /> <br /> <br /> <br clear=all><br /> <br /> ==Application==<br /> <br /> For some applications, it may not be possible to filter the incoming light such that the desired signal is significantly stronger than the ambient light, resulting in little control over the location of the centroid. For cases such as these, alternative methods of computing the location of the desired signal may be necessary. One of these alternative methods is called [[Phase-Sensitive Detection| phase-sensitive detection]]. This utilizes the fact that a pulsing target would alter the centroid location in a periodic manner, so phase-locking the detector circuitry to add when the pulse is high then subtract when it is low would filter out the ambient signal and provide a good appriximation of the actual location of the desired incident signal.</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9370 Lateral-Effect Photodiode 2008-12-13T03:00:42Z

<p>EricN: /* Output */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.jpg|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> <br /> The duo-lateral position sensing device functions as a current source/sink, where the amount of current sourced/sunk is proportional to the total intensity of light incident on the sensing area. At the P-N junction, light forces current to flow though the photo-electric effect, and since the junction only allows current to flow one way, the net function is as a current source.<br /> <br /> <br /> The device has four leads, two of which source current and two of which sink current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> <br clear=all><br /> [[Image:XY_position.jpg|right|description|thumb|350px]]<br /> <br /> The layers themselves act as resistors, where the resistance is proportional to the distance between the centroid of the incident light spot and the terminals, essentially resulting in a current divider. The position can be calculated precisely using the following formula:<br /> <br /> <br /> <math> X = \frac {i_{out2} - i_{out1}}{i_{out2} + i_{out1}} </math><br /> <br /> <br /> <math> Y = \frac {i_{in2} - i_{in1}}{i_{in2} + i_{in1}} </math><br /> <br /> <br /> <br /> This makes the center of each axis zero and makes the right side and the upper side positive in their respective directions. In the example diagram, the resulting X coordinate would be negative and the Y coordinate would be positive. Both calculations are scaled such that the range of position values for each axis are:<br /> <br /> <math> -0.5 < X < 0.5<br /> <br /> -0.5 < Y < 0.5 </math><br /> <br /> <br /> <br clear=all><br /> <br /> ==Application==<br /> <br /> For some applications, it may not be possible to filter the incoming light such that the desired signal is significantly stronger than the ambient light, resulting in little control over the location of the centroid. For cases such as these, alternative methods of computing the location of the desired signal may be necessary. One of these alternative methods is called [[Phase-Sensitive Detection| phase-sensitive detection]]. This utilizes the fact that a pulsing target would alter the centroid location in a periodic manner, so phase-locking the detector circuitry to add when the pulse is high then subtract when it is low would filter out the ambient signal and provide a good appriximation of the actual location of the desired incident signal.</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9369 Lateral-Effect Photodiode 2008-12-13T03:00:09Z

<p>EricN: /* Output */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.jpg|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> <br /> The duo-lateral position sensing device functions as a current source/sink, where the amount of current sourced/sunk is proportional to the total intensity of light incident on the sensing area. At the P-N junction, light forces current to flow though the photo-electric effect, and since the junction only allows current to flow one way, the net function is as a current source.<br /> <br /> <br /> The device has four leads, two of which source current and two of which sink current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> <br clear=all><br /> [[Image:XY_position.jpg|right|description|thumb|350px]]<br /> <br /> The layers themselves act as resistors, where the resistance is proportional to the distance between the centroid of the incident light spot and the terminals, essentially resulting in a current divider. The position can be calculated precisely using the following formula:<br /> <br /> <br /> <math> X = \frac {i_{out2} - i_{out1}}{i_{out2} + i_{out1}} </math><br /> <br /> <br /> <math> Y = \frac {i_{in2} - i_{in1}}{i_{in2} + i_{in1}} </math><br /> <br /> <br /> <br /> This makes the center of each axis zero and makes the right side and the upper side positive in their respective directions. In the example diagram, the resulting X coordinate would be negative and the Y coordinate would be positive. Both calculations are scaled such that the range of position values for each axis is <math> -0.5 < X < 0.5 </math> and <math> -0.5 < Y < 0.5 </math><br /> <br /> <br /> <br clear=all><br /> <br /> ==Application==<br /> <br /> For some applications, it may not be possible to filter the incoming light such that the desired signal is significantly stronger than the ambient light, resulting in little control over the location of the centroid. For cases such as these, alternative methods of computing the location of the desired signal may be necessary. One of these alternative methods is called [[Phase-Sensitive Detection| phase-sensitive detection]]. This utilizes the fact that a pulsing target would alter the centroid location in a periodic manner, so phase-locking the detector circuitry to add when the pulse is high then subtract when it is low would filter out the ambient signal and provide a good appriximation of the actual location of the desired incident signal.</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9368 Lateral-Effect Photodiode 2008-12-13T02:55:42Z

<p>EricN: /* Output */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.jpg|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> <br /> The duo-lateral position sensing device functions as a current source/sink, where the amount of current sourced/sunk is proportional to the total intensity of light incident on the sensing area. At the P-N junction, light forces current to flow though the photo-electric effect, and since the junction only allows current to flow one way, the net function is as a current source.<br /> <br /> <br /> The device has four leads, two of which source current and two of which sink current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> <br clear=all><br /> [[Image:XY_position.jpg|right|description|thumb|350px]]<br /> <br /> The layers themselves act as resistors, where the resistance is proportional to the distance between the centroid of the incident light spot and the terminals, essentially resulting in a current divider. The position can be calculated precisely using the following formula:<br /> <br /> <br /> <math> X = \frac {i_{x2} - i_{x1}}{i_{x2} + i_{x1}} </math><br /> <br /> <br /> <math> Y = \frac {i_{y2} - i_{y1}}{i_{y2} + i_{y1}} </math><br /> <br /> <br /> <br /> This makes the center of each axis zero and makes the right side and the upper side positive in their respective directions.<br /> <br /> <br /> <br clear=all><br /> <br /> ==Application==<br /> <br /> For some applications, it may not be possible to filter the incoming light such that the desired signal is significantly stronger than the ambient light, resulting in little control over the location of the centroid. For cases such as these, alternative methods of computing the location of the desired signal may be necessary. One of these alternative methods is called [[Phase-Sensitive Detection| phase-sensitive detection]]. This utilizes the fact that a pulsing target would alter the centroid location in a periodic manner, so phase-locking the detector circuitry to add when the pulse is high then subtract when it is low would filter out the ambient signal and provide a good appriximation of the actual location of the desired incident signal.</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9367 Lateral-Effect Photodiode 2008-12-13T02:55:20Z

<p>EricN: /* Output */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.jpg|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> <br /> The duo-lateral position sensing device functions as a current source/sink, where the amount of current sourced/sunk is proportional to the total intensity of light incident on the sensing area. At the P-N junction, light forces current to flow though the photo-electric effect, and since the junction only allows current to flow one way, the net function is as a current source.<br /> <br /> <br /> The device has four leads, two of which source current and two of which sink current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> <br clear=all><br /> [[Image:XY_position.jpg|right|description|thumb|350px]]<br /> <br /> The layers themselves act as resistors, where the resistance is proportional to the distance between the centroid of the incident light spot and the terminals, essentially resulting in a current divider. The position can be calculated precisely using the following formula:<br /> <br /> <br /> <math> X = \frac {i_{x2} - i_{x1}}{i_{x2} + i_{x1}} </math> \n<br /> <br /> <math> Y = \frac {i_{y2} - i_{y1}}{i_{y2} + i_{y1}} </math> \n<br /> <br /> <br /> <br /> This makes the center of each axis zero and makes the right side and the upper side positive in their respective directions.<br /> <br /> <br /> <br clear=all><br /> <br /> ==Application==<br /> <br /> For some applications, it may not be possible to filter the incoming light such that the desired signal is significantly stronger than the ambient light, resulting in little control over the location of the centroid. For cases such as these, alternative methods of computing the location of the desired signal may be necessary. One of these alternative methods is called [[Phase-Sensitive Detection| phase-sensitive detection]]. This utilizes the fact that a pulsing target would alter the centroid location in a periodic manner, so phase-locking the detector circuitry to add when the pulse is high then subtract when it is low would filter out the ambient signal and provide a good appriximation of the actual location of the desired incident signal.</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9366 Lateral-Effect Photodiode 2008-12-13T02:54:32Z

<p>EricN: /* Output */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.jpg|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> <br /> The duo-lateral position sensing device functions as a current source/sink, where the amount of current sourced/sunk is proportional to the total intensity of light incident on the sensing area. At the P-N junction, light forces current to flow though the photo-electric effect, and since the junction only allows current to flow one way, the net function is as a current source.<br /> <br /> <br /> The device has four leads, two of which source current and two of which sink current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> <br clear=all><br /> [[Image:XY_position.jpg|right|description|thumb|350px]]<br /> <br /> The layers themselves act as resistors, where the resistance is proportional to the distance between the centroid of the incident light spot and the terminals, essentially resulting in a current divider. The position can be calculated precisely using the following formula:<br /> <br /> <br /> <math><br /> <br /> X = \frac {i_{x2} - i_{x1}}{i_{x2} + i_{x1}} \n<br /> <br /> Y = \frac {i_{y2} - i_{y1}}{i_{y2} + i_{y1}} \n<br /> <br /> </math><br /> <br /> This makes the center of each axis zero and makes the right side and the upper side positive in their respective directions.<br /> <br /> <br /> <br clear=all><br /> <br /> ==Application==<br /> <br /> For some applications, it may not be possible to filter the incoming light such that the desired signal is significantly stronger than the ambient light, resulting in little control over the location of the centroid. For cases such as these, alternative methods of computing the location of the desired signal may be necessary. One of these alternative methods is called [[Phase-Sensitive Detection| phase-sensitive detection]]. This utilizes the fact that a pulsing target would alter the centroid location in a periodic manner, so phase-locking the detector circuitry to add when the pulse is high then subtract when it is low would filter out the ambient signal and provide a good appriximation of the actual location of the desired incident signal.</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9365 Lateral-Effect Photodiode 2008-12-13T02:54:14Z

<p>EricN: /* Output */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.jpg|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> <br /> The duo-lateral position sensing device functions as a current source/sink, where the amount of current sourced/sunk is proportional to the total intensity of light incident on the sensing area. At the P-N junction, light forces current to flow though the photo-electric effect, and since the junction only allows current to flow one way, the net function is as a current source.<br /> <br /> <br /> The device has four leads, two of which source current and two of which sink current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> <br clear=all><br /> [[Image:XY_position.jpg|right|description|thumb|350px]]<br /> <br /> The layers themselves act as resistors, where the resistance is proportional to the distance between the centroid of the incident light spot and the terminals, essentially resulting in a current divider. The position can be calculated precisely using the following formula:<br /> <br /> <br /> <math><br /> \begin{align}<br /> X & = \frac {i_{x2} - i_{x1}}{i_{x2} + i_{x1}} \\<br /> <br /> Y & = \frac {i_{y2} - i_{y1}}{i_{y2} + i_{y1}} \\<br /> \end{align}<br /> </math><br /> <br /> This makes the center of each axis zero and makes the right side and the upper side positive in their respective directions.<br /> <br /> <br /> <br clear=all><br /> <br /> ==Application==<br /> <br /> For some applications, it may not be possible to filter the incoming light such that the desired signal is significantly stronger than the ambient light, resulting in little control over the location of the centroid. For cases such as these, alternative methods of computing the location of the desired signal may be necessary. One of these alternative methods is called [[Phase-Sensitive Detection| phase-sensitive detection]]. This utilizes the fact that a pulsing target would alter the centroid location in a periodic manner, so phase-locking the detector circuitry to add when the pulse is high then subtract when it is low would filter out the ambient signal and provide a good appriximation of the actual location of the desired incident signal.</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9364 Lateral-Effect Photodiode 2008-12-13T02:53:15Z

<p>EricN: /* Output */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.jpg|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> <br /> The duo-lateral position sensing device functions as a current source/sink, where the amount of current sourced/sunk is proportional to the total intensity of light incident on the sensing area. At the P-N junction, light forces current to flow though the photo-electric effect, and since the junction only allows current to flow one way, the net function is as a current source.<br /> <br /> <br /> The device has four leads, two of which source current and two of which sink current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> <br clear=all><br /> [[Image:XY_position.jpg|right|description|thumb|350px]]<br /> <br /> The layers themselves act as resistors, where the resistance is proportional to the distance between the centroid of the incident light spot and the terminals, essentially resulting in a current divider. The position can be calculated precisely using the following formula:<br /> <br /> <br /> <math><br /> \begin {alignat}{2}<br /> X &= \frac {i_{x2} - i_{x1}}{i_{x2} + i_{x1}} \\<br /> <br /> Y &= \frac {i_{y2} - i_{y1}}{i_{y2} + i_{y1}} \\<br /> \end {alignat}<br /> </math><br /> <br /> This makes the center of each axis zero and makes the right side and the upper side positive in their respective directions.<br /> <br /> <br /> <br clear=all><br /> <br /> ==Application==<br /> <br /> For some applications, it may not be possible to filter the incoming light such that the desired signal is significantly stronger than the ambient light, resulting in little control over the location of the centroid. For cases such as these, alternative methods of computing the location of the desired signal may be necessary. One of these alternative methods is called [[Phase-Sensitive Detection| phase-sensitive detection]]. This utilizes the fact that a pulsing target would alter the centroid location in a periodic manner, so phase-locking the detector circuitry to add when the pulse is high then subtract when it is low would filter out the ambient signal and provide a good appriximation of the actual location of the desired incident signal.</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9363 Lateral-Effect Photodiode 2008-12-13T02:52:11Z

<p>EricN: /* Output */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.jpg|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> <br /> The duo-lateral position sensing device functions as a current source/sink, where the amount of current sourced/sunk is proportional to the total intensity of light incident on the sensing area. At the P-N junction, light forces current to flow though the photo-electric effect, and since the junction only allows current to flow one way, the net function is as a current source.<br /> <br /> <br /> The device has four leads, two of which source current and two of which sink current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> <br clear=all><br /> [[Image:XY_position.jpg|right|description|thumb|350px]]<br /> <br /> The layers themselves act as resistors, where the resistance is proportional to the distance between the centroid of the incident light spot and the terminals, essentially resulting in a current divider. The position can be calculated precisely using the following formula:<br /> <br /> <br /> <math><br /> \begin {array}{1cr}<br /> X &= \frac {i_{x2} - i_{x1}}{i_{x2} + i_{x1}} \\<br /> <br /> Y &= \frac {i_{y2} - i_{y1}}{i_{y2} + i_{y1}} \\<br /> \end {array}{1cr}<br /> </math><br /> <br /> This makes the center of each axis zero and makes the right side and the upper side positive in their respective directions.<br /> <br /> <br /> <br clear=all><br /> <br /> ==Application==<br /> <br /> For some applications, it may not be possible to filter the incoming light such that the desired signal is significantly stronger than the ambient light, resulting in little control over the location of the centroid. For cases such as these, alternative methods of computing the location of the desired signal may be necessary. One of these alternative methods is called [[Phase-Sensitive Detection| phase-sensitive detection]]. This utilizes the fact that a pulsing target would alter the centroid location in a periodic manner, so phase-locking the detector circuitry to add when the pulse is high then subtract when it is low would filter out the ambient signal and provide a good appriximation of the actual location of the desired incident signal.</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9362 Lateral-Effect Photodiode 2008-12-13T02:51:47Z

<p>EricN: /* Output */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.jpg|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> <br /> The duo-lateral position sensing device functions as a current source/sink, where the amount of current sourced/sunk is proportional to the total intensity of light incident on the sensing area. At the P-N junction, light forces current to flow though the photo-electric effect, and since the junction only allows current to flow one way, the net function is as a current source.<br /> <br /> <br /> The device has four leads, two of which source current and two of which sink current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> <br clear=all><br /> [[Image:XY_position.jpg|right|description|thumb|350px]]<br /> <br /> The layers themselves act as resistors, where the resistance is proportional to the distance between the centroid of the incident light spot and the terminals, essentially resulting in a current divider. The position can be calculated precisely using the following formula:<br /> <br /> <br /> <math><br /> /begin{array}{1cr}<br /> X &= \frac {i_{x2} - i_{x1}}{i_{x2} + i_{x1}} \\<br /> <br /> Y &= \frac {i_{y2} - i_{y1}}{i_{y2} + i_{y1}} \\<br /> \end{array}{1cr}<br /> </math><br /> <br /> This makes the center of each axis zero and makes the right side and the upper side positive in their respective directions.<br /> <br /> <br /> <br clear=all><br /> <br /> ==Application==<br /> <br /> For some applications, it may not be possible to filter the incoming light such that the desired signal is significantly stronger than the ambient light, resulting in little control over the location of the centroid. For cases such as these, alternative methods of computing the location of the desired signal may be necessary. One of these alternative methods is called [[Phase-Sensitive Detection| phase-sensitive detection]]. This utilizes the fact that a pulsing target would alter the centroid location in a periodic manner, so phase-locking the detector circuitry to add when the pulse is high then subtract when it is low would filter out the ambient signal and provide a good appriximation of the actual location of the desired incident signal.</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9361 Lateral-Effect Photodiode 2008-12-13T02:51:33Z

<p>EricN: /* Output */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.jpg|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> <br /> The duo-lateral position sensing device functions as a current source/sink, where the amount of current sourced/sunk is proportional to the total intensity of light incident on the sensing area. At the P-N junction, light forces current to flow though the photo-electric effect, and since the junction only allows current to flow one way, the net function is as a current source.<br /> <br /> <br /> The device has four leads, two of which source current and two of which sink current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> <br clear=all><br /> [[Image:XY_position.jpg|right|description|thumb|350px]]<br /> <br /> The layers themselves act as resistors, where the resistance is proportional to the distance between the centroid of the incident light spot and the terminals, essentially resulting in a current divider. The position can be calculated precisely using the following formula:<br /> <br /> <br /> <math><br /> \begin{array}{1cr}<br /> X &= \frac {i_{x2} - i_{x1}}{i_{x2} + i_{x1}} \\<br /> <br /> Y &= \frac {i_{y2} - i_{y1}}{i_{y2} + i_{y1}} \\<br /> \end{array}{1cr}<br /> </math><br /> <br /> This makes the center of each axis zero and makes the right side and the upper side positive in their respective directions.<br /> <br /> <br /> <br clear=all><br /> <br /> ==Application==<br /> <br /> For some applications, it may not be possible to filter the incoming light such that the desired signal is significantly stronger than the ambient light, resulting in little control over the location of the centroid. For cases such as these, alternative methods of computing the location of the desired signal may be necessary. One of these alternative methods is called [[Phase-Sensitive Detection| phase-sensitive detection]]. This utilizes the fact that a pulsing target would alter the centroid location in a periodic manner, so phase-locking the detector circuitry to add when the pulse is high then subtract when it is low would filter out the ambient signal and provide a good appriximation of the actual location of the desired incident signal.</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9360 Lateral-Effect Photodiode 2008-12-13T02:49:34Z

<p>EricN: /* Output */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.jpg|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> <br /> The duo-lateral position sensing device functions as a current source/sink, where the amount of current sourced/sunk is proportional to the total intensity of light incident on the sensing area. At the P-N junction, light forces current to flow though the photo-electric effect, and since the junction only allows current to flow one way, the net function is as a current source.<br /> <br /> <br /> The device has four leads, two of which source current and two of which sink current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> <br clear=all><br /> [[Image:XY_position.jpg|right|description|thumb|350px]]<br /> <br /> The layers themselves act as resistors, where the resistance is proportional to the distance between the centroid of the incident light spot and the terminals, essentially resulting in a current divider. The position can be calculated precisely using the following formula:<br /> <br /> <br /> <math><br /> \begin{align}<br /> X &= \frac {i_{x2} - i_{x1}}{i_{x2} + i_{x1}} \\<br /> <br /> &= \frac {i_{y2} - i_{y1}}{i_{y2} + i_{y1}} \\<br /> \end{align}<br /> </math><br /> <br /> This makes the center of each axis zero and makes the right side and the upper side positive in their respective directions.<br /> <br /> <br /> <br clear=all><br /> <br /> ==Application==<br /> <br /> For some applications, it may not be possible to filter the incoming light such that the desired signal is significantly stronger than the ambient light, resulting in little control over the location of the centroid. For cases such as these, alternative methods of computing the location of the desired signal may be necessary. One of these alternative methods is called [[Phase-Sensitive Detection| phase-sensitive detection]]. This utilizes the fact that a pulsing target would alter the centroid location in a periodic manner, so phase-locking the detector circuitry to add when the pulse is high then subtract when it is low would filter out the ambient signal and provide a good appriximation of the actual location of the desired incident signal.</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9359 Lateral-Effect Photodiode 2008-12-13T02:49:23Z

<p>EricN: /* Output */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.jpg|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> <br /> The duo-lateral position sensing device functions as a current source/sink, where the amount of current sourced/sunk is proportional to the total intensity of light incident on the sensing area. At the P-N junction, light forces current to flow though the photo-electric effect, and since the junction only allows current to flow one way, the net function is as a current source.<br /> <br /> <br /> The device has four leads, two of which source current and two of which sink current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> <br clear=all><br /> [[Image:XY_position.jpg|right|description|thumb|350px]]<br /> <br /> The layers themselves act as resistors, where the resistance is proportional to the distance between the centroid of the incident light spot and the terminals, essentially resulting in a current divider. The position can be calculated precisely using the following formula:<br /> <br /> <br /> <math><br /> \begin{align}<br /> X &= \frac {i_{x2} - i_{x1}}{i_{x2} + i_{x1}} \\<br /> <br /> Y &= \frac {i_{y2} - i_{y1}}{i_{y2} + i_{y1}} \\<br /> \end{align}<br /> </math><br /> <br /> This makes the center of each axis zero and makes the right side and the upper side positive in their respective directions.<br /> <br /> <br /> <br clear=all><br /> <br /> ==Application==<br /> <br /> For some applications, it may not be possible to filter the incoming light such that the desired signal is significantly stronger than the ambient light, resulting in little control over the location of the centroid. For cases such as these, alternative methods of computing the location of the desired signal may be necessary. One of these alternative methods is called [[Phase-Sensitive Detection| phase-sensitive detection]]. This utilizes the fact that a pulsing target would alter the centroid location in a periodic manner, so phase-locking the detector circuitry to add when the pulse is high then subtract when it is low would filter out the ambient signal and provide a good appriximation of the actual location of the desired incident signal.</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9358 Lateral-Effect Photodiode 2008-12-13T02:49:05Z

<p>EricN: /* Output */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.jpg|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> <br /> The duo-lateral position sensing device functions as a current source/sink, where the amount of current sourced/sunk is proportional to the total intensity of light incident on the sensing area. At the P-N junction, light forces current to flow though the photo-electric effect, and since the junction only allows current to flow one way, the net function is as a current source.<br /> <br /> <br /> The device has four leads, two of which source current and two of which sink current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> <br clear=all><br /> [[Image:XY_position.jpg|right|description|thumb|350px]]<br /> <br /> The layers themselves act as resistors, where the resistance is proportional to the distance between the centroid of the incident light spot and the terminals, essentially resulting in a current divider. The position can be calculated precisely using the following formula:<br /> <br /> <br /> <math><br /> \begin{align}<br /> X = \frac {i_{x2} - i_{x1}}{i_{x2} + i_{x1}} \\<br /> <br /> Y = \frac {i_{y2} - i_{y1}}{i_{y2} + i_{y1}} \\<br /> \end{align}<br /> </math><br /> <br /> This makes the center of each axis zero and makes the right side and the upper side positive in their respective directions.<br /> <br /> <br /> <br clear=all><br /> <br /> ==Application==<br /> <br /> For some applications, it may not be possible to filter the incoming light such that the desired signal is significantly stronger than the ambient light, resulting in little control over the location of the centroid. For cases such as these, alternative methods of computing the location of the desired signal may be necessary. One of these alternative methods is called [[Phase-Sensitive Detection| phase-sensitive detection]]. This utilizes the fact that a pulsing target would alter the centroid location in a periodic manner, so phase-locking the detector circuitry to add when the pulse is high then subtract when it is low would filter out the ambient signal and provide a good appriximation of the actual location of the desired incident signal.</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9357 Lateral-Effect Photodiode 2008-12-13T02:48:46Z

<p>EricN: /* Output */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.jpg|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> <br /> The duo-lateral position sensing device functions as a current source/sink, where the amount of current sourced/sunk is proportional to the total intensity of light incident on the sensing area. At the P-N junction, light forces current to flow though the photo-electric effect, and since the junction only allows current to flow one way, the net function is as a current source.<br /> <br /> <br /> The device has four leads, two of which source current and two of which sink current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> <br clear=all><br /> [[Image:XY_position.jpg|right|description|thumb|350px]]<br /> <br /> The layers themselves act as resistors, where the resistance is proportional to the distance between the centroid of the incident light spot and the terminals, essentially resulting in a current divider. The position can be calculated precisely using the following formula:<br /> <br /> <br /> <math><br /> \begin{align}<br /> X=\frac {i_{x2} - i_{x1}}{i_{x2} + i_{x1}} \\<br /> <br /> Y=\frac {i_{y2} - i_{y1}}{i_{y2} + i_{y1}} \\<br /> \end{align}<br /> </math><br /> <br /> This makes the center of each axis zero and makes the right side and the upper side positive in their respective directions.<br /> <br /> <br /> <br clear=all><br /> <br /> ==Application==<br /> <br /> For some applications, it may not be possible to filter the incoming light such that the desired signal is significantly stronger than the ambient light, resulting in little control over the location of the centroid. For cases such as these, alternative methods of computing the location of the desired signal may be necessary. One of these alternative methods is called [[Phase-Sensitive Detection| phase-sensitive detection]]. This utilizes the fact that a pulsing target would alter the centroid location in a periodic manner, so phase-locking the detector circuitry to add when the pulse is high then subtract when it is low would filter out the ambient signal and provide a good appriximation of the actual location of the desired incident signal.</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9356 Lateral-Effect Photodiode 2008-12-13T02:48:11Z

<p>EricN: /* Output */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.jpg|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> <br /> The duo-lateral position sensing device functions as a current source/sink, where the amount of current sourced/sunk is proportional to the total intensity of light incident on the sensing area. At the P-N junction, light forces current to flow though the photo-electric effect, and since the junction only allows current to flow one way, the net function is as a current source.<br /> <br /> <br /> The device has four leads, two of which source current and two of which sink current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> <br clear=all><br /> [[Image:XY_position.jpg|right|description|thumb|350px]]<br /> <br /> The layers themselves act as resistors, where the resistance is proportional to the distance between the centroid of the incident light spot and the terminals, essentially resulting in a current divider. The position can be calculated precisely using the following formula:<br /> <br /> <br /> <math><br /> \begin{align}<br /> X=\frac {i_{x2} - i_{x1}}{i_{x2} + i_{x1}}<br /> <br /> Y=\frac {i_{y2} - i_{y1}}{i_{y2} + i_{y1}} <br /> \end{align}<br /> </math><br /> <br /> This makes the center of each axis zero and makes the right side and the upper side positive in their respective directions.<br /> <br /> <br /> <br clear=all><br /> <br /> ==Application==<br /> <br /> For some applications, it may not be possible to filter the incoming light such that the desired signal is significantly stronger than the ambient light, resulting in little control over the location of the centroid. For cases such as these, alternative methods of computing the location of the desired signal may be necessary. One of these alternative methods is called [[Phase-Sensitive Detection| phase-sensitive detection]]. This utilizes the fact that a pulsing target would alter the centroid location in a periodic manner, so phase-locking the detector circuitry to add when the pulse is high then subtract when it is low would filter out the ambient signal and provide a good appriximation of the actual location of the desired incident signal.</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9355 Lateral-Effect Photodiode 2008-12-13T02:47:49Z

<p>EricN: /* Output */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.jpg|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> <br /> The duo-lateral position sensing device functions as a current source/sink, where the amount of current sourced/sunk is proportional to the total intensity of light incident on the sensing area. At the P-N junction, light forces current to flow though the photo-electric effect, and since the junction only allows current to flow one way, the net function is as a current source.<br /> <br /> <br /> The device has four leads, two of which source current and two of which sink current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> <br clear=all><br /> [[Image:XY_position.jpg|right|description|thumb|350px]]<br /> <br /> The layers themselves act as resistors, where the resistance is proportional to the distance between the centroid of the incident light spot and the terminals, essentially resulting in a current divider. The position can be calculated precisely using the following formula:<br /> <br /> <br /> <math><br /> \begin{align}<br /> X=\frac {i_{x2} - i_{x1}}{i_{x2} + i_{x1}}<br /> <br /> Y=\frac {i_{y2} - i_{y1}}{i_{y2} + i_{y1}}</math><br /> \end{align}<br /> <br /> <br /> This makes the center of each axis zero and makes the right side and the upper side positive in their respective directions.<br /> <br /> <br /> <br clear=all><br /> <br /> ==Application==<br /> <br /> For some applications, it may not be possible to filter the incoming light such that the desired signal is significantly stronger than the ambient light, resulting in little control over the location of the centroid. For cases such as these, alternative methods of computing the location of the desired signal may be necessary. One of these alternative methods is called [[Phase-Sensitive Detection| phase-sensitive detection]]. This utilizes the fact that a pulsing target would alter the centroid location in a periodic manner, so phase-locking the detector circuitry to add when the pulse is high then subtract when it is low would filter out the ambient signal and provide a good appriximation of the actual location of the desired incident signal.</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9354 Lateral-Effect Photodiode 2008-12-13T02:41:18Z

<p>EricN: /* Output */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.jpg|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> <br /> The duo-lateral position sensing device functions as a current source/sink, where the amount of current sourced/sunk is proportional to the total intensity of light incident on the sensing area. At the P-N junction, light forces current to flow though the photo-electric effect, and since the junction only allows current to flow one way, the net function is as a current source.<br /> <br /> <br /> The device has four leads, two of which source current and two of which sink current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> <br clear=all><br /> [[Image:XY_position.jpg|right|description|thumb|350px]]<br /> <br /> The layers themselves act as resistors, where the resistance is proportional to the distance between the centroid of the incident light spot and the terminals, essentially resulting in a current divider. The position can be calculated precisely using the following formula:<br /> <br /> <br /> <math>X=\frac {i_{x2} - i_{x1}}{i_{x2} + i_{x1}}<br /> <br /> Y=\frac {i_{y2} - i_{y1}}{i_{y2} + i_{y1}}</math><br /> <br /> <br /> This makes the center of each axis zero and makes the right side and the upper side positive in their respective directions.<br /> <br /> <br /> <br clear=all><br /> <br /> ==Application==<br /> <br /> For some applications, it may not be possible to filter the incoming light such that the desired signal is significantly stronger than the ambient light, resulting in little control over the location of the centroid. For cases such as these, alternative methods of computing the location of the desired signal may be necessary. One of these alternative methods is called [[Phase-Sensitive Detection| phase-sensitive detection]]. This utilizes the fact that a pulsing target would alter the centroid location in a periodic manner, so phase-locking the detector circuitry to add when the pulse is high then subtract when it is low would filter out the ambient signal and provide a good appriximation of the actual location of the desired incident signal.</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9353 Lateral-Effect Photodiode 2008-12-13T02:39:21Z

<p>EricN: /* Output */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.jpg|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> <br /> The duo-lateral position sensing device functions as a current source/sink, where the amount of current sourced/sunk is proportional to the total intensity of light incident on the sensing area. At the P-N junction, light forces current to flow though the photo-electric effect, and since the junction only allows current to flow one way, the net function is as a current source.<br /> <br /> <br /> The device has four leads, two of which source current and two of which sink current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> <br clear=all><br /> [[Image:XY_position.jpg|right|description|thumb|350px]]<br /> <br /> The layers themselves act as resistors, where the resistance is proportional to the distance between the centroid of the incident light spot and the terminals, essentially resulting in a current divider. The position can be calculated precisely using the following formula:<br /> <br /> <br /> <math>X=\frac {i_x2 - i_x1}{i_x2 + i_x1}<br /> <br /> Y=\frac {i_y_2 - i_y_1}{i_y_2 + i_y_1}</math><br /> <br /> <br /> This makes the center of each axis zero and makes the right side and the upper side positive in their respective directions.<br /> <br /> <br /> <br clear=all><br /> <br /> ==Application==<br /> <br /> For some applications, it may not be possible to filter the incoming light such that the desired signal is significantly stronger than the ambient light, resulting in little control over the location of the centroid. For cases such as these, alternative methods of computing the location of the desired signal may be necessary. One of these alternative methods is called [[Phase-Sensitive Detection| phase-sensitive detection]]. This utilizes the fact that a pulsing target would alter the centroid location in a periodic manner, so phase-locking the detector circuitry to add when the pulse is high then subtract when it is low would filter out the ambient signal and provide a good appriximation of the actual location of the desired incident signal.</div>

EricN https://hades.mech.northwestern.edu//index.php?title=File:XY_position.jpg&diff=9352 File:XY position.jpg 2008-12-13T02:37:15Z

<p>EricN: Shows currents and distances for calculating position using a duo-lateral position sensing device</p> <hr /> <div>Shows currents and distances for calculating position using a duo-lateral position sensing device</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9351 Lateral-Effect Photodiode 2008-12-13T02:36:36Z

<p>EricN: /* Output */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.jpg|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> <br /> The duo-lateral position sensing device functions as a current source/sink, where the amount of current sourced/sunk is proportional to the total intensity of light incident on the sensing area. At the P-N junction, light forces current to flow though the photo-electric effect, and since the junction only allows current to flow one way, the net function is as a current source.<br /> <br /> <br /> The device has four leads, two of which source current and two of which sink current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> <br clear=all><br /> [[Image:XY_position.jpg|right|description|thumb|350px]]<br /> <br /> The layers themselves act as resistors, where the resistance is proportional to the distance between the centroid of the incident light spot and the terminals, essentially resulting in a current divider. The position can be calculated precisely using the following formula:<br /> <br /> <br /> <math>X=\frac {i_x2 - i_x1}{i_x2 + i_x1}<br /> <br /> Y=\frac {i_y2 - i_y1}{i_y2 + i_y1}</math><br /> <br /> <br /> This makes the center of each axis zero and makes the right side and the upper side positive in their respective directions.<br /> <br /> <br /> <br clear=all><br /> <br /> ==Application==<br /> <br /> For some applications, it may not be possible to filter the incoming light such that the desired signal is significantly stronger than the ambient light, resulting in little control over the location of the centroid. For cases such as these, alternative methods of computing the location of the desired signal may be necessary. One of these alternative methods is called [[Phase-Sensitive Detection| phase-sensitive detection]]. This utilizes the fact that a pulsing target would alter the centroid location in a periodic manner, so phase-locking the detector circuitry to add when the pulse is high then subtract when it is low would filter out the ambient signal and provide a good appriximation of the actual location of the desired incident signal.</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9350 Lateral-Effect Photodiode 2008-12-13T02:35:18Z

<p>EricN: /* Application */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.jpg|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> <br /> The duo-lateral position sensing device functions as a current source/sink, where the amount of current sourced/sunk is proportional to the total intensity of light incident on the sensing area. At the P-N junction, light forces current to flow though the photo-electric effect, and since the junction only allows current to flow one way, the net function is as a current source.<br /> <br /> <br /> The device has four leads, two of which source current and two of which sink current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> The layers themselves act as resistors, where the resistance is proportional to the distance between the centroid of the incident light spot and the terminals, essentially resulting in a current divider. The position can be calculated precisely using the following formula:<br /> <br /> <br /> <math>X=\frac {i_x2 - i_x1}{i_x2 + i_x1}<br /> <br /> Y=\frac {i_y2 - i_y1}{i_y2 + i_y1}</math><br /> <br /> <br /> This makes the center of each axis zero and makes the right side and the upper side positive in their respective directions.<br /> <br /> <br /> <br clear=all><br /> <br /> ==Application==<br /> <br /> For some applications, it may not be possible to filter the incoming light such that the desired signal is significantly stronger than the ambient light, resulting in little control over the location of the centroid. For cases such as these, alternative methods of computing the location of the desired signal may be necessary. One of these alternative methods is called [[Phase-Sensitive Detection| phase-sensitive detection]]. This utilizes the fact that a pulsing target would alter the centroid location in a periodic manner, so phase-locking the detector circuitry to add when the pulse is high then subtract when it is low would filter out the ambient signal and provide a good appriximation of the actual location of the desired incident signal.</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9349 Lateral-Effect Photodiode 2008-12-13T02:30:16Z

<p>EricN: /* Output */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.jpg|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> <br /> The duo-lateral position sensing device functions as a current source/sink, where the amount of current sourced/sunk is proportional to the total intensity of light incident on the sensing area. At the P-N junction, light forces current to flow though the photo-electric effect, and since the junction only allows current to flow one way, the net function is as a current source.<br /> <br /> <br /> The device has four leads, two of which source current and two of which sink current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> The layers themselves act as resistors, where the resistance is proportional to the distance between the centroid of the incident light spot and the terminals, essentially resulting in a current divider. The position can be calculated precisely using the following formula:<br /> <br /> <br /> <math>X=\frac {i_x2 - i_x1}{i_x2 + i_x1}<br /> <br /> Y=\frac {i_y2 - i_y1}{i_y2 + i_y1}</math><br /> <br /> <br /> This makes the center of each axis zero and makes the right side and the upper side positive in their respective directions.<br /> <br /> <br /> <br clear=all><br /> <br /> ==Application==</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9348 Lateral-Effect Photodiode 2008-12-13T01:57:12Z

<p>EricN: /* Output */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.jpg|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> The output of a duo-lateral position sensing device is two leads with a positive current and two leads with a negative current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> <br clear=all><br /> <br /> ==Application==</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9347 Lateral-Effect Photodiode 2008-12-13T01:56:09Z

<p>EricN: /* Output */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.jpg|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> The output of a duo-lateral position sensing device is two leads with a positive current and two leads with a negative current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> ==Application==</div>

EricN https://hades.mech.northwestern.edu//index.php?title=File:Lateral_effect_psd.jpg&diff=9346 File:Lateral effect psd.jpg 2008-12-13T01:55:39Z

<p>EricN: Duo-lateral position sensitive detector currents</p> <hr /> <div>Duo-lateral position sensitive detector currents</div>

EricN https://hades.mech.northwestern.edu//index.php?title=File:Lateral_effect_psd.gif&diff=9345 File:Lateral effect psd.gif 2008-12-13T01:53:45Z

<p>EricN: Currents in a duo-lateral position sensing device.</p> <hr /> <div>Currents in a duo-lateral position sensing device.</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9344 Lateral-Effect Photodiode 2008-12-13T01:53:16Z

<p>EricN: /* Output */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> [[Image:lateral_effect_psd.gif|right|Duo-lateral PSD - Two leads allow current to enter opposing ends of one layer while two other leads allow current to exit through opposing ends of another layer which is rotated 90 degrees. The sums of the currents entering and exiting the device will be equal.]|thumb|350px]]<br /> The output of a duo-lateral position sensing device is two leads with a positive current and two leads with a negative current. Since the P-N junction only works one way, the two negative currents enter on the same layer and are thus representative of one axis while the two positive currents leave on the other layer, representing the other axis, provided that the leads on each layer are opposing each other, as in the image at right.<br /> <br /> ==Application==</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9343 Lateral-Effect Photodiode 2008-12-13T00:40:06Z

<p>EricN: /* Duo-Lateral Photodiode */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> <b>In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.</b><br /> <br /> ==Output==<br /> <br /> ==Application==</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9342 Lateral-Effect Photodiode 2008-12-13T00:39:31Z

<p>EricN: /* Duo-Lateral Photodiode */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.<br /> <br /> ==Output==<br /> <br /> ==Application==</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9341 Lateral-Effect Photodiode 2008-12-13T00:39:13Z

<p>EricN: /* Duo-Lateral Photodiode */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf|PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.<br /> <br /> ==Output==<br /> <br /> ==Application==</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9340 Lateral-Effect Photodiode 2008-12-13T00:39:00Z

<p>EricN: /* Duo-Lateral Photodiode */</p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.<br /> <br /> ==Output==<br /> <br /> ==Application==</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9339 Lateral-Effect Photodiode 2008-12-13T00:38:13Z

<p>EricN: </p> <hr /> <div>===Overview===<br /> <br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device, a tetra-lateral device in this case]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> <br clear=all><br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> There is a good description of this, but I cannot access the website because either it is having difficulties or my internet line is having issues. This should explain it in better detail:<br /> <br /> [http://www.centrovision.com/application-notes/AN-Position-Sensing-Photodiodes.pdf |PSD pdf file]<br /> <br /> We also need a pic of the photodiode here, but anything relating to this has been difficult to work with all day, so I think they may be having some kind of server issues or something, and I can make the wiki complete later, but you might want to try the link, Jon. I have a section of the text below, but in html version I cannot see the images and the pdf won't download for me.<br /> <br /> In duo-lateral PSD’s, there are two resistive layers, one at the top and the other at the bottom of the photodiode. The photocurrent is divided into two parts in each layer. This structure type can resolve light spot movements of less that 0.5 µm and have very small position detection error all the way almost to the edge of the active area. They also exhibit excellent position linearity over the entire active area.<br /> <br /> The tetra-lateral PSD’s, own a single resistive layer, in which the photocurrent is divided into two or four parts for one or two dimensional sensing respectively. These devices exhibit more position non linearity at distances far away from the center, as well as larger position detection errors compared to duo-lateral types.<br /> <br /> ==Output==<br /> <br /> ==Application==</div>

EricN https://hades.mech.northwestern.edu//index.php?title=File:Photoelectric_effect.gif&diff=9338 File:Photoelectric effect.gif 2008-12-12T22:55:41Z

<p>EricN: The photoelectric effect causes current to flow as light strikes the sensing area, with output currents proportional to the proximity between the terminal and the light centroid</p> <hr /> <div>The photoelectric effect causes current to flow as light strikes the sensing area, with output currents proportional to the proximity between the terminal and the light centroid</div>

EricN https://hades.mech.northwestern.edu//index.php?title=Lateral-Effect_Photodiode&diff=9337 Lateral-Effect Photodiode 2008-12-12T22:54:51Z

<p>EricN: /* Position Sensing Devices */</p> <hr /> <div>===Overview===<br /> <br /> ==Position Sensing Devices==<br /> [[Image:photoelectric_effect.gif|right|Photoelectric effect drives current in a position sensing device]|thumb|350px]]<br /> <br /> <br /> A position-sensing device (PSD) is a photosensor (photodiode or phototransistor) which is able to differentiate between the position where incident light strikes the sensing surface. There are uniaxial sensors which are only able to distinguish position along a single axis, and duo-lateral or tetra-lateral sensors which are able to distinguish position along two axes. All of these sensors provide currents on the output leads which is proportional to the overall intensity of light striking the sensing surface as well as to the distance between the output terminal and the location where the light struck the sensor. The sensors act as current sources, because the photoelectric effect dislodges electrons, which drives a current, so more light produces more current. The distance from the output terminal to the incident point is proportional to the resistance the current experiences, resulting in different currents at different distances.<br /> <br /> ==Duo-Lateral Photodiode==<br /> <br /> ==Output==<br /> <br /> ==Application==</div>

EricN