| 摘要 |
PROBLEM TO BE SOLVED: To provide a rotation angle measurement instrument capable of angle measurement at a low cost.SOLUTION: The rotation angle measurement instrument includes: a fixed part 8; a relatively rotating movable part 9; a light source 2 provided in either one of the fixed part and the movable part to emit detection light and reference position signal light; a polarizing plate 4 which polarizes the detection light into polarized light; a polarized light rotation part which rotates the polarized light around an optical axis 7 of the light source; the reference position signal light emitted at a reference rotation position of the polarized light; a stationary polarizing plate 5 which is provided in the other of the fixed part and the movable part and is stationary for rotation of the polarized light; a light receiving sensor 6 which is provided in the fixed part or the movable part to receive the polarized light transmitted through the stationary polarizing plate and the reference position signal light; and an arithmetic unit 10 which calculates a detection waveform of variation in quantity of light on the basis of a signal from the light receiving sensor and detects the reference position signal light and calculates a relative rotation angle between the fixed part and the movable part in accordance with a phase of the detection waveform at the time of detecting the reference position signal light and a prescribed detected reference phase. |
