Patent ID: 7391011
Filing Date: 2008-06-24
Classification: G01D

Abstract:
1. An optical encoder for detecting relative movement of a scale to output two phase signals related to the detected relative movement, the optical encoder comprising: the scale having an optical grating formed therein; a holding member having a surface with a plurality of reflecting regions each having different reflectance, facing the scale and being rotatable around a shaft together with the scale; a light receiving portion having a plurality of photodiodes adapted to move relative to the scale and disposed so as to be associated with a pitch of the optical grating; and a light emitting portion for radiating light to the light receiving portion through the scale, wherein the optical encoder obtains a relative positional signal of the scale and the light receiving portion and a positional signal from a region corresponding to the reflecting region on the holding member having the different reflectance on the basis of signals generated from the light beam emitted from the photodiode and reflected by the optical grating of the scale and a signal generated from the light beam which is transmitted through the scale, reflected by the surface of the holding member, again transmitted through the scale, and received by the light receiving portion.