Transmissive Encoders

The Transmissive Encoder is an emitter/detector module. Coupled with a code wheel, this transmissive encoder translates rotary motion of a shaft into digital output. The transmissive encoder contains a single Light Emitting Diode (LED) as its light source. The light is collimated into a parallel beam by means of a single polycarbonate lens located directly over the LED. Opposite the emitter is the integrated detector circuit.

This IC consists of multiple sets of photodetectors and the signal processing circuitry necessary to produce the digital waveforms. The code wheel rotates between the emitter and detector of the transmissive encoder, causing the light beam to be interrupted by the pattern of spaces and bars on the codewheel. The photodiodes which detects these interruptions are arranged in a pattern that corresponds to the radius and design of the code wheel. These detectors are also spaced such that a light period on one pair of detectors corresponds to a dark period on the adjacent pair of detectors. Broadcom offers an extensive range of transmissive encoders to meet the different needs of a wide variety of applications.