| 摘要 |
The optical system for measuring variations in distance with precision comprises three interferometers (16,30,44) connected in series. The first interferometer (16) is illuminated with polychromatic light and has a path difference representing the distance, L, to be measured. The second interferometer (30) has an optical path difference representing a fixed reference distance (L0). The third interferometer (44) has an optical path difference which is adjustable between a null value and the distance, E, which is the difference between the distance to be measured (L) and the reference distance (L0). A photosensitive detector (54) receives the output from the third interferometer. The third interferometer is illuminated by a stabilised source, such as a frequency stabilised laser.
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