Patent ID: 7223963

Claim:
An optical encoder which comprises a moving body wherein light transmission areas and non-light transmission areas are alternately formed along a moving direction, a light-emitting part for emitting lights toward the moving body, and a light-receiving part for receiving lights emitted from the light-emitting part and transmitted through the light transmission areas and outputting a plurality of independent movement information signals which represent the movement information of the moving body, wherein the light-receiving part which is arranged so as to face a plurality of the light transmission areas, outputs a plurality of the independent movement information signals and comprises photodiodes equal in number to a common multiplier of a number of the light transmission areas facing the light-receiving part and a number of the independent movement information signals; wherein the photodiodes include at least a first group of photodiodes and a second group of photodiodes, the photodiodes in the first and second groups being disposed for a plurality of the light transmission areas of the moving body, and wherein output terminals of the first group of photodiodes are connected so that a first of the plurality of movement information signals is obtained by adding output signals of the plurality of photodiodes in the first group, and wherein output terminals of the second group of photodiodes are connected so that a second of the plurality of movement information signals is obtained by adding output signals of the plurality of photodiodes in the second group; a number of the light transmission areas facing each of the light-receiving parts is three, a number of the independent movement information signals is four, and the light-receiving part comprises 12 photodiodes; when the moving direction of the moving body is considered as a longitudinal direction and an arrangement pitch in the light transmission area is considered as one pitch, the 12 photodiodes are arranged along the longitudinal direction, having a length equal to one-sixth of the pitch respectively; the light-receiving part comprises three photodiode groups, each of which is composed of the four photodiodes, distance between each of the photodiodes in each of the photodiode groups is 1/12 of the pitch, in two adjacent photodiode groups, a photodiode in one photodiode group closest to the other photodiode group and a photodiode in the other photodiode group closet to the one photodiode group are adjoined at a pitch 5/12 of the pitch; and four photodiodes in the photodiode groups respectively output output signals corresponding to four independent different movement information signals, and output one movement information signal by adding output signals of the three photodiodes corresponding to one movement information signal out of four movement information signals outputted from the three photodiode groups.