Patent ID: 7649168
Filing Date: 2010-01-19
Classification: G01D

Abstract:
1. An optical encoder comprising: a light source; a photodetector; a scale which is relatively displaceable with respect to the light source and the photodetector; a first grating which is interposed between the light source and the scale, and on which, an optical pattern of a first pitch p a second grating which is provided on the scale, and on which, an optical pattern of a second pitch p a third grating which is interposed between the scale and the photodetector, and on which, an optical pattern of a third pitch p light emerged from the light source travels via the first grating and the second grating, and forms an image on the third grating as a magnified scale-image pattern in which the optical pattern formed on the second grating is magnified at a predetermined magnification, and a periodic signal according to an amount of relative displacement of the scale is detected, and the first grating and the third grating are formed on separate members, and values of a first effective width W