| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a device and method for performing displacement measurement using a laser beam without frequency measurement of the laser beam.SOLUTION: A controller 4 controls an optical frequency comb 1 and a frequency variable laser 2. A laser beam L22 from the frequency variable laser 2 impinges on a Fabry-Perot interferometer 5. A photodetector PD1 detects interference light L10. A photodetector PD2 detects a laser beam L23. A frequency measurement unit 3 detects a beat frequency ffrom a detection signal DET1 from the photodetector PD1. The controller 4 uses the beat frequency fto lock a frequency of the frequency variable laser 2 on the basis of a spectrum of the optical frequency comb 1 and varies the frequency of the frequency variable laser 2 and a repeat frequency fso as to fix a strength of the laser beam L23 and the beat frequency f, and calculates displacement of an interferometer length of the Fabry-Perot interferometer 5 on the basis of the variation of the repeat frequency f.</p> |
