Patent ID: 7592584

Claim:
An optical encoder, comprising: a main scale on which at least two displacement-measuring optical gratings are arranged in a predetermined direction; a single detector head movable in the predetermined direction relative to the main scale; at least two light-emitting elements that emit light respectively to the optical gratings provided on the main scale; and at least two photo detectors respectively provided for the optical gratings on the detector head, the photo detectors receiving the light transmitted through or reflected by the optical gratings, wherein the light-emitting elements emit light having a different wavelength to the respective optical gratings provided on the main scale, the photo detectors receive the light having a predetermined wavelength that has been transmitted through or reflected by the respective optical gratings, a filter is provided on an optical path of the light from the light-emitting elements to the photo detectors on at least one of a light-incident surface or a light-emitting surface of the optical gratings, the filter transmitting light that is emitted from the light-emitting elements and is provided with a predetermined wavelength while shielding light having a wavelength other than the predetermined wavelength, the at least two optical gratings being provided in parallel on the main scale adjacently with each other, and the at least two light-emitting elements and the at least two photo detectors being provided on the single detector head adjacently with each other corresponding to the optical gratings.