Patent ID: 8735801

Claim:
An optical encoder comprising: a light source, a displacement scale including a scale track having a transmittance distribution or a reflectance distribution including position information, and a light receiving element array configured to receive a light flux emitted from the light source and transmitted or reflected by the displacement scale, wherein the scale track includes a first part having a first modulation period and a second part having a second modulation period in a scale displacement direction of the displacement scale, wherein the light receiving element array is formed of a plurality of light receiving elements one-dimensionally arranged in the scale displacement direction of the displacement scale, the light receiving elements each configured to receive both light from the first part and light from the second part, wherein the light receiving element array is arranged to detect a first signal group including two-phase signals, relative phases of which are reversed, in the first modulation period and a second signal group including two-phase signals, relative phases of which are reversed, in the second modulation period, wherein first position information in the first modulation period is detected from the first signal group, and second position information in the second modulation period is detected from the second signal group, and wherein the second modulation period is an odd multiple of the first modulation period.