| 摘要 |
PROBLEM TO BE SOLVED: To relaize deflection measurement with high resolution and high accuracy by sending laser light having two frequencies to a deflection sensing head from a light source through an optical fiber and adopting the optical heterodyne interferometry which is symmetrical complementarily. SOLUTION: A light beam passing through a fiber F is collimated by a lens L, and it is sent to the following routes. A polarization beam splitter P2 divides the light into two frequency elements through polarization. A mirror reflects the beam toward a non-polarization beam splitter N, and the beam arrives at a return reflector R1 or R2. Polarization analysers A1 and A2 before optical detectors D1 and D2 are arranged orthogonally in the same manner as typical heterodyne interferometer, and they send about half of respective polarization element of incident beam. The beam has two frequency elements, and since they are in the same polarization condition, they are subject to optical interference. The inter-ferometer processes electrically two interference phases which are changed due to deflection, and the quantity to be processed thereby is the same as that of heterodyne interferometer excluding their phase difference.
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