| 摘要 |
PROBLEM TO BE SOLVED: To measure an angle of rotation with high precision independently of mechanical precision of a rotary body like a worm gear. SOLUTION: This angle gauge is equipped with an interferometer 142 which changes an optical path length X1 to be inspected in accordance with the rotation of a rotary body 138 and obtains the interference light L4 of light L3 to be inspected and reference light L2, a photo detector 144 photoelectrically converting the intensity change of the interference light L4, a calculating means 146 obtaining the variation information of the optical length X1 in accordance with the angle of rotation of the rotary body 138, from the intensity change of the interference light L4 obtained by the photo detector 144, and a converting means 148 obtaining the angle of rotation of the rotary body 138, from the variation information of the optical length X1.
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