Patent ID: 7820957

Claim:
An optical encoder comprising: a light emitting section; and a light receiving section having a plurality of light receiving elements placed so as to be aligned in one direction in an area where a light beam from the light emitting section reaches, for detecting movement of a moving object which is composed of a light-ON section for enabling the light beam to come incident into the light receiving element when the moving object passes through a predetermined position corresponding to the light receiving element, and a light-OFF section for disabling the light beam from coming incident into the light receiving element when the moving object passes through a predetermined position corresponding to the light receiving element the light-ON section and the light-OFF section alternately passing through the predetermined position when the moving object moves in the one direction, the optical encoder further comprising a light receiving signal processing section for receiving inputs of a plurality of light receiving signals with different phases from a plurality of the light receiving elements, performing signal processing including at least one signal processing among a logical operation processing, an addition processing and a subtraction processing on a plurality of the light receiving signals, and outputting an output signal containing a plurality of signal components which are different in phase and different in signal level with respect to a predetermined threshold level, wherein the light receiving signal processing section comprises: an exclusive OR circuit for calculating exclusive OR of first and second signals, which are obtained from a plurality of the light receiving signals and which are different in phase from each other by 90 degrees, and outputting a third signal; an AND circuit for calculating a logical AND of the third signal outputted from the exclusive OR circuit and one signal out of the first and second signals, and outputting a fourth signal; and a subtraction circuit for subtracting the fourth signal outputted from the AND circuit from the other signal out of the first and second signals, and outputting a fifth signal.