| 摘要 |
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 ).
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