Patent ID: 7348544

Claim:
An optical encoder comprising: a movable scale including an optical grating, the optical grating having a pitch and an optical discontinuous part; a plurality of light-receiving units each having the same number of light-receiving elements arranged in a relationship to the pitch of the optical grating, the light-receiving unit being disposed in a row in the moving direction of the scale; a light-emitting unit configured to apply a plurality of light beams via the scale to the plurality of light-receiving units at a predetermined interval corresponding to the pitch of the light-receiving units; a signal processing circuit processing signals obtained from the plurality of light-receiving units to generate two phased analog signals and two phased digital signals by combining the output signals from the light-receiving elements each located in the different light-receiving units and having the predetermined relation with each other, and obtaining an incremental signal from the two phased signals; and an origin-position detecting unit detecting an origin position of the optical encoder based on at least one of the two-phased analog signals and at least one of the digital signals, wherein the origin-position detecting unit detects a change in an output level of the at least one of the two phased analog signals obtained at an edge timing of at least one of the digital signals from the processing circuit when substantially no light beam is being applied to at least one of the light-receiving units due to the discontinuous part passing at a position having a relation with the light-receiving units and the light-emitting unit, and wherein the origin-position detecting unit detects the origin position by detecting a change in center voltage of the output of the signal processing circuit.