| 摘要 |
A differential plane mirror interferometer system comprises a laser source (10) which emits an input beam (12) having two linear orthogonally polarized components, which may or may not be of the same optical frequency. A birefringent optical element (64) converts the input beam components (20,21) into two separated, parallel, orthogonally polarized beams (22,23). The birefringent element (64) together with a first quarter-wave phase retardation plate (66), a second quarter-wave phase retardation plate (62) with a pair of holes, and a retroreflector (60) with a pair of holes aligned with the holes in the second quarter-wave phase retardation plate (62), causes each of the separated, parallel, orthogonally polarized beams to be reflected twice by one of two plane mirrors (68,70), namely a first plane mirror (68) or a second plane mirror (70), respectively, to produce two separated, parallel, orthogonally polarized output beams (54, 55). The birefringent optical element (64) converts the two separated, parallel, orthogonally polarized outbeams (54, 55) into a single output beam (80) in which the phase difference between the two polarization components of the single output beam (80) is directly proportional to the optical path length between the two plane mirrors (b 68, 70). This phase difference is measured by passing the output beam (80) through a polarizer (81) which mixes the two orthogonally polarized components in beam (80) with the interference between these two components being detected by a photodector (83) which produces an electrical signal (85). An electronic module (80) extracts the phase variation from this signal (85).
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