Patent attributes
A displacement detection apparatus (100) includes a main scale (110) and a detection head (120). The detection head (120) includes a light emission/reception unit (130) and an optical device unit (140). The optical device unit (140) has a first diffraction scale (141) and a second diffraction scale (143). The first diffraction scale (141) has a transmission type first diffraction grating (142). The second diffraction scale (143) has a diffraction grating. The second diffraction scale (143) has a transmission type second diffraction grating (144) on both sides of a metal film (146). Furthermore, the metal film (146) configures a reflection type third diffraction grating (145) when the second diffraction scale (143) is viewed from the side of the main scale (110).
