ORIGIN DETECTING DEVICE FOR ROTARY ENCODER AND MEASUREMENT DEVICE FOR ROTATION INFORMATION

摘要

PROBLEM TO BE SOLVED: To provide a small detection system for an origin position having high accuracy that enables origin detection at both sides of a rotary disk together with a detection optical system for incremental signal. SOLUTION: A monochromatic luminous flux is radiated from a light source to then be converted into a parallel luminous flux with a collimator lens and thereafter divided into two parallel luminous fluxes where an optical axis is parallelly shifted with a diffraction grating plate. This parallel luminous flux is individually divided into two parts and then taken out by each of polarized light components. Each of fluxes from the polarized light components is lighted to a point symmetrical position to the rotating axis of a diffraction grating track in a detection system for a rotation quantity, and then diffraction beams of mutually different orders generated in the diffraction grating track are taken out to be interfered by superimposing wave surfaces, and then a cycle signal accompanied with the rotation movement of a disk is generated. Each of other fluxes from polarized light components is lighted to a point symmetrical position to the rotating axis of a origin track, and then two fluxes modulated with a origin pattern are detected with each of photodetectors and then an origin signal is generated in a detection system for a origin position.