Patent ID: 7045770
Filing Date: 2006-05-16
Classification: G01D

Abstract:
1. An optical encoder comprising: a light source; a scale having a reflecting portion that is arranged so as to oppose the light source; and a light-receiving element that receives a reflected light beam from the scale, wherein the reflecting portion of the scale has an optical characteristic such that a divergent light beam from the light source is divided into a plurality of wavefronts after a plurality of reflections, and respective light beams obtained as a result of the division are made to overlap each other at an predetermined position, wherein an air conversion optical path length from a light-receiving surface position of the light-receiving element to a reflecting surface of the scale is referred to as gP, a pitch of the scale is referred to as P gap is set at gP which is determined so that the following relations are satisfied within a range of n<0.5