Optical Locating

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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 retro-reflective target and optics.

System Design

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.

The system contains the following elements:

  • Eye structure on a 2-DoF gimbal
  • Position-sensing detector
  • Target illumination circuit
  • Optics
  • Phase-sensitive detection circuit
  • Microcontroller

Position-Sensing Detector

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Target Illumination

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Phase-Sensitive Detection Circuit

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Microcontroller Code

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