OPTICAL ROTARY ENCODER AND CORRECTION METHOD THEREOF

PROBLEM TO BE SOLVED: To allow the detection of variation of a distance between a rotating body and a light receiving part.SOLUTION: A reflective diffraction grating 12-1 is formed on a scale 12. A light receiving part 14 includes a plurality of photo diodes which output output signals corresponding to amounts of received light. A light reception signal shaper 15 combines outputs from the plurality of photo diodes receiving light which is emitted from a laser diode 11 and is reflected by the diffraction grating 12-1, to obtain a signal indicative of a stripe pattern component with a prescribed period included in the reflected light. A sensor distance variation direction and distance estimator 17 detects a direction of variation of a distance between the scale 12 and the light receiving part 14. This detection is performed on the basis of a first signal indicative of a stripe pattern component with a period shorter than that of interference fringes which the diffraction grating 12-1 generates in light reception positions of the plurality of photo diodes, and a second signal indicative of a stripe pattern component with a period longer than that of the interference fringes.