Angle encoder has laser source split into three beams and focussed on reflecting coding disc with quarter wave deep impressed pattern on marking rings

摘要

An angle encoder has a (2) laser source (1) split into three beams by a diffraction grating (2) and focussed (6) on a reflecting coding disc (7) with concentric marking ring tracks with regular quarter wave raised and sunk parts and three photo detectors (A, E, F) for the reflected part beams with processor to calculate the rotation angle. Independent claims are included for procedures using the encoder to measure angular rotation.