Patent ID: 6610975
Filing Date: 2003-08-26
Classification: G01D

Abstract:
An optical encoder, including a light source, a reflective grating of a predetermined form and a fixed pitch, a light transmitting grating of a predetermined form and a fixed pitch, and photodetectors with light receiving surfaces of predetermined form and a predetermined pitch that receive a reflected image produced by light from the light source that has passed through the light transmitting grating and been reflected by the reflective grating, the optical encoder detecting at least a speed of relative movement of the reflective grating and the light transmitting grating, based on detection signals produced by the photodetectors,the optical encoder comprising: a reflective grating plate in which the reflective grating is formed; and a semiconductor substrate in which the light transmitting grating and the photodetectors are formed, the light transmitting grating being one of slits for transmitting light that are formed in the semiconductor substrate and thin-film parts for transmitting light that are formed in the semiconductor substrate, a first region, in which the photodetectors and parts of the light transmitting grating are alternately arranged, and a second region, in which the photodetectors and parts of the light transmitting grating are alternately arranged, being formed in the semiconductor substrate, and a detection signal obtained from the photodetectors in the first region having a phase difference of 90Â° with a detection signal obtained from the photodetectors in the second region.