Patent ID: 7061624

Claim:
A grating interference type optical encoder comprising: a scale board with a diffraction grating located thereon; an illumination optical system for emitting coherent light fluxes to the diffraction grating on the scale board, that relatively moves, and for producing two diffraction light fluxes having different orders; an arc-shaped grating for re-emitting to the diffraction grating through deflection means the two diffraction light fluxes having different orders produced in the diffraction grating; light guiding means for superimposing a plurality of rediffraction limit fluxes produced by rediffracting the two diffraction light fluxes re-emitted to the diffraction grating and guiding the superimposed rediffraction light fluxes to a light receiving element; a phase graftings for dividing the rediffraction light fluxes superimposed between the diffraction grating and the light receiving element into a plurality of divided light fluxes; a linear deflection element having different deflection directions corresponding to the plurality of divided light fluxes divided by the phase grating; an origin detecting pattern formed near the diffraction grating on the scale board; a light flux separating clement for deflecting a part of the coherent light fluxes to guide the part of the coherent light fluxes deflected onto the origin detecting pattern; and origin signal detecting means for detecting only a reflection diffraction light flux optically modulated by the origin detecting pattern.