Patent ID: 8085650

Claim:
An optical encoder comprising: an optical encoding disc comprising: a first annular track comprising a plurality of first coding units periodically arranged along a circumferential direction thereof, an angular period of the first encoding units being θ T1 , each first coding unit comprising a first light converging portion and a first light diverging portion, the light converging portions and the light diverging portions being arranged alternately along a circumferential direction of the optical encoding disc; and a second annular track, the first track and the second track being concentric, the second track comprising a plurality of second coding units periodically arranged along a circumferential direction thereof, an angular period of the second encoding units being θ T2 , wherein θ T2 =2*θ T1 , each second coding unit comprises a second light converging portion and a second light diverging portion, the light converging portions and the light diverging portions being arranged alternately along a circumferential direction of the optical encoding disc an interface between the first light converging portion and the first light diverging portion is aligned with a middle line of the second light converging portion or the second light diverging portion; a light source module configured for emitting a light beam towards the optical encoding disc; a motor coupled with the optical encoding disc and configured for driving the optical encoding disc to rotate; and an optical detection system comprising a plurality of photo-detectors arranged in a line parallel to a radius of the optical encoding disc, each photo-detector being corresponding to each track of the optical encoding disc respectively, each photo-detector being configured for receiving the light beam transmitted through the corresponding track, and generating a voltage according to an intensity of the received light beam.