Optical Encoder Disks and Strips Information
Optical encoder disks and strips are used with rotary and linear encoders, respectively. They are usually made of metal, plastic, glass, or paper.
Typically, encoder disks and strips are made by cutting slots in the material, or by printing alternating dark and light areas. Optical encoder disks are paired with a light emitting diode (LED) and optical detector to "read" slot patterns as they pass in front of the optics. These are used to detect both the speed and direction that an encoder disk is turning. There are several patterns for rotary encoder disks and strips that are made by printing or cutting alternating dark and light areas. Quadrature, a common technique, offsets two sets a half line-width apart to produce four counts per line. Other types of patterns permit different types of output signals from the optical encoder. As a rule, the resolution or counter per revolution of an encoder disk or strip depend upon how closely the slot pattern is placed.
A typical rotary encoder disk.
Image credit: US Digital