| 摘要 |
PROBLEM TO BE SOLVED: To measure a relative angular relation between illuminating light and an optical unit. SOLUTION: Since both states of interfering light at a first diffraction grating 127a and a second diffraction grating 127b of the optical unit 26 are varied in response to a relative variation in the angle between the illuminating light emitted by a light source and the optical unit 26 having the first diffraction grating 127a and the second diffraction grating 127b, the relative angular relation between the illuminating light and the optical unit can be measured by receiving the interfering light by using a light receiving element. COPYRIGHT: (C)2007,JPO&INPIT
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