Patent ID: 9605982
Date: 2017-03-28
CPC Classifications: G01D

Claim:
1. A rotary encoder comprising a rotary disk which has a rotation axis, and a light emitting part which emits light toward said rotary disk, wherein said rotary disk has a plurality of tracks which extend concentrically about said rotation axis, each of said plurality of tracks has light transmitting parts which transmit incident light to said rotary disk and non-transmitting parts which do not transmit incident light to said rotary disk, said light transmitting parts and said non-transmitting parts being arranged alternately in a circumferential direction about said rotation axis, said non-transmitting parts have pluralities of projecting parts which are arranged along said circumferential direction of said rotary disk, each of said plurality of projecting parts having a pair of reflecting surfaces which retro reflect incident light to said rotary disk toward said light emitting part, said plurality of tracks include a periodic track where said light transmitting parts and said non-transmitting parts are arranged in said circumferential direction with a periodic pattern and a non-periodic track where said light transmitting parts and said non-transmitting parts are arranged in said circumferential direction with a non-periodic pattern, said periodic track and said non-periodic track are arranged in a radial direction of said rotary disk at positions where further reflected light at said light emitting part after retro reflection at said reflecting surfaces of said non-periodic track will not enter said periodic track, said plurality of tracks further include a second non-periodic track where said light transmitting parts and said non-transmitting parts are arranged in said circumferential direction with a non-periodic pattern, said periodic track is arranged in said radial direction between said non-periodic track and said second non-periodic track, and said periodic track and said second non-periodic track are arranged in said radial direction at positions where further reflected light at said light emitting part after retro reflection at said reflecting surfaces of said second non-periodic track will not enter said periodic track.