| 摘要 |
PROBLEM TO BE SOLVED: To realize an optical path deviation detecting device detecting the deviation of an optical path to be detected by dividing it to shift/tilt. SOLUTION: This device is equipped with branching means (51 and 52) picking up light from the optical path to be detected and branching the picked-up light at least to two optical paths, and light detection means (26, 53, 54 and 55) respectively detecting a light receiving position on a light receiving surface by respectively arranging the light receiving surface at optical path length different from each other at the branching edges of the branching means. The tilt of the optical path to be detected is detected from the difference of the light receiving positions respectively detected by the light detection means, and the shift of the optical path to be detected is detected from the commonness of the light receiving position after removing the difference. Stray light generated in the branching means (for example, half mirror) is surely reduced by doubly providing an incidence restricting means and a reflection restricting means. As a result, the detecting accuracy of the optical path deviation detecting device is enhanced.
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