| 摘要 |
A differential plane mirror interferometer comprises a source (10) which emits a light beam containing two linear orthogonally polarized components; a beamsplitter/beam folder assembly (16, 16A) for converting the input beam into two separated, parallel, orthogonally polarized beams; a half-wave retardation plate (29A, 29) located in one of the separated beams to produce two separated parallel beams with the same polarization; means including a polarizing beamsplitter (44), for causing each of the separated parallel beams with the same polarization to be reflected twice by one of two plane mirrors (71, 70) to produce two parallel output beams with the same polarization; a half-wave retardation plate (29B, 29) located in one of the separated parallel output beams, with the beamsplitter/beam folder assembly (16, 16B) converting the two separated parallel orthogonally polarized output beams into a single output beam in which the phase difference between the two polarization components of the single output beam is directly proportional to the optical path length between the two plane mirrors (70, 71); a polarizer (81) for mixing the orthogonal components of the output beam; a photoelectric detector (83) to produce the measurement signal; and an electronic module (90) to indicate the phase difference which is directly proportional to the changes in the optical path length between the two plane mirrors.
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