Fingertip laser light sensor

Original Assignment

I will provide you with a laser that emits a sheet of laser light and a phototransistor for detecting this light. You will investigate their use in developing a fingertip position sensor that senses distance to the finger based on reflected laser light. Your job is to design a sensor circuit and determine the analog voltage readings you get as a function of (1) your finger position and (2) the sensor's location relative to the emitter. You will likely display your results by communicating with a PC or by writing to an LCD (see, e.g., C Example: Serial LCD or C Example: Parallel Interfacing with LCDs).

Overview

A laser that emits a sheet of laser light and phototransistor for detecting this light were the main components of this lab. Their use in developing a fingertip position sensor that senses distance to the finger based on reflected laser light was investigated. A sensor circuit was designed and analog voltage readings as a function of (1) finger position and (2) the sensor's location relative to the emitter were taken. The results were displayed by communicating with a PC.

Data from several situations involving different positionings of the laser, phototransistor, and fingertip was taken.

Data

Finger in front of the laser and phototransistor (Resistors and Y distance from finger to laser/transistor varied)

Transistor in front of the laser (Y distance from transistor and laser varied)

Transistor next to laser (For certain Y distances, X coordinates varied)

Transistor next to laser (For certain X coordinates, Y distance varied)