| 摘要 |
PROBLEM TO BE SOLVED: To remove such a defect that many errors are generated in measurement of a fine angle on the grounds that an angle is measured by a measuring device shifted from a standard of the angle such as a rotary encoder and that only 90 degrees, 60 degrees or the like can be used as the standard of the angle, in conventional high-accuracy angle measurement. SOLUTION: A plane mirror 1 is mounted on an angle measuring object (not illustrated), and the plane mirror 1 is mounted displaceably against a standard plane 4 together with the angle measuring object about a rotation center 2. A slit or a pinhole 6 is formed on the standard plane 4, and a displacement meter 3 having a laser emitting hole formed oppositely to the slit or the pinhole 6 so that a laser enters the slit or the pinhole 6 is arranged. When the angle of the plane mirror 1 against the standard plane 4 is measured, a laser beam 7 is emitted from the displacement meter 3 into the slit or the pinhole 6, to obtain the distance between reference plane mirror 1.
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