Patent ID: 6201239
Filing Date: 2001-03-13
Classification: G01D

Abstract:
An optical encoder comprising a movable scale movable relative to a surface emitting laser light source, the surface emitting laser light source for illuminating part of the movable scale, and a photodetector for receiving a light beam which has been reflected by or passed through the movable scale,wherein in a case where a distance between the movable scale and a light beam emission plane of the surface emitting laser light source along a center axis of the light beam is L, a wavelength of the light beam is .lambda., a scale pitch of the movable scale is p, an angle between a pitch direction of the movable scale and a plane perpendicular to the center axis of the light beam is .theta., and an opening width of the surface emitting laser light source along a direction in which the pitch direction of the movable scale is projected on the plane perpendicular to the center axis of the light beam is a, a relationship, p.cos .theta.<a, is satisfied when L.ltoreq.1.0a.sup.2 /.lambda..