Patent ID: 7969856

Claim:
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 θT 1 , 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 θT 2 , wherein θT 2 =2*θT 1 , 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.