| 摘要 |
PROBLEM TO BE SOLVED: To enhance the sensitivity of measurement of a travel of a moving substance by reflecting leser beams split into two, by two reflecting means from reverse directions, and returning them to the same direction respectively and causing them to interfere with each other. SOLUTION: A polarizing beam splitter 3 splits a laser beam 2 into first (s-polarized) and second (p-polarized) laser beams. The first laser beam is reflected by rectangular prisms 41, 42, and is emitted in parallel with the direction of movement of a moving substance 90 and in the right direction, and enters a corner cube 31. This reflected beam proceeds in a direction reverse to the incidence, is reflected by the polarizing beam splitter 3, passes a polarizing plate 6 thereafter, and enters a photodetector 7. The second laser beam is reflected by rectangular prisms 43-45, and enters a corner cube 32 from the right direction. The reflected beam strikes the photodetector 7 and both laser beams interfere with each other. In this case the corner cubes 31, 32 move byΔL byΔL movement of the moving substance 90 also. The optical path length of the first (second) laser beam becomes shorter (longer) by 2ΔL, and an optical path length difference of 4ΔL is generated and the sensitivity becomes twice as high as in the condentional art.
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