Displacement detection apparatus

摘要

A displacement detection apparatus comprises a light source 1, a first diffraction grating including a blazed grating for diffracting and splitting light from the light source to irradiate a 0-order diffraction light and a +1-order diffraction light to a second diffraction grating, a third diffraction grating including a blazed grating for combining a +1-order reflected diffraction light produced by the reflection and diffraction of the 0-order diffraction light by the second diffraction grating and a -1-order reflected diffraction light produced by the diffraction of the +1-order diffraction light by the second diffraction grating to produce an interference light, and a photo-sensing element for converting the interference light to a signal representing a change in the second diffraction grating.