Patent ID: 9625283
Date: 2017-04-18
CPC Classifications: G01D

Claim:
1. An encoder comprising: a track having optical effecters which are arranged to have an absolute pattern along a measurement direction and configured to reflect or transmit light; a point light source configured to emit diffusion light to the track; and a light receiving array having light receiving elements arranged along the measurement direction, and configured to receive light reflected or transmitted at the track, the light receiving elements falling within an area which is positioned corresponding to an area between the optical effecters and to which light reflected or transmitted at the track does not reach, wherein a width of an emitting surface of the point light source in the measurement direction and a width of the light receiving elements in the measurement direction are set, so that the light receiving elements fall within the area which is positioned corresponding to the area between the optical effecters and to which light reflected or transmitted at the track does not reach, and wherein when the width of the emitting surface in the measurement direction is φ, a minimum width of the optical effecters in the measurement direction is y, the width of the light receiving elements in the measurement direction is x, a distance from the emitting surface to the optical effecters is u, and a distance from the optical effecters to the light receiving elements is v, the following relation is satisfied: and wherein when the distance from the emitting surface to the optical effecters u is equal to the distance from the optical effecters to the light receiving elements y, the following is satisfied: