Apparatus for optically detecting displacement of an object using a synthesizing means utilizing a substrate with two diffraction gratings thereon

摘要

A displacement detection apparatus includes a light source (1), a first diffraction grating (G1) which is arranged on the same substrate as a second diffraction grating (G2) so as to diffract and split light emitted from the light source and to irradiate +/-1st-order diffracted light beams onto the second diffraction grating (G2), a third diffraction grating (G3) for synthesizing a +1st-order reflectively diffracted light beam generated by reflectively diffracting the +1st-order diffracted light beam by the second diffraction grating, and a -1st-order reflectively diffracted light beam generated by reflectively diffracting the +1st-order diffracted light beam by the second diffraction grating to form interference light, and a light-receiving element (3) for converting the interference light into a signal representing a displacement of the substrate.