| 摘要 |
PURPOSE:To measure an angle of rotation and an arc with high precision by forming a reflecting mirror cylindrically and irradiating it with laser light at a specific angle of incidence, and measuring a frequency difference by the Doppler effect between the irradiation light and reflected light. CONSTITUTION:The laser light of frequency f1 is made incident to a cylindrical mirror 21 which has a radius (r) and moves at an angular speed omega at an angle theta to the radius direction. The frequency f1 becomes f1+DELTAf after reflection owing to an optical path component vf with a peripheral speed (v). Then, DELTAf is extracted by the Doppler effect between the frequencies f1, DELTAf, and the optical path component vf is calculated therefrom. Further, when the angle theta of incidence is fixed, the peripheral speed (v) is vf/sintheta, the angular speed omega is v/r, and the movement extent L on the circumference is integral vdt, so that the angle phi of rotation is calculated from phi=integral omegadt.
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