Measurement Principle - Optical Transmission-Type Linear Encoders
The gage heads mainly use optical transmission-type linear encoders. In this type, the light source (LED) and the detector element (photodiode) face each other with the main scale and index scale (20µm pitch) positioned between them. As the scale moves with respect to the detector, the intensity of the light passing through the window in the index scale varies constantly. At this time, two synchronized sine-wave signals having a relative 90-degree phase difference are output. These signals are then amplified and split electrically (with additional waveforms inserted) and output as 0.1µm, 0.5µm, or 1µm square-wave signals.