| 摘要 |
An interferometer for measuring a target surface 313 and in particular for measuring movement (e.g. vibration) of a target surface provides spaced beams, the spaced beams TEST 1-16 in a measurement arm 332 of the interferometer being passed to the target surface to provide a predetermined pattern of points across the target surface, and in a reference arm 331 said plurality of spaced beams REF 1-16 striking reference surface 309, means for combining the beams which have struck the target surface and struck the reference surface, the combined beams being divided into two channels A,B, means 315 to introduce a phase change in one of the channels and a first array of detectors 316 for detecting a set of beams in the first channel and second array of detectors 317 for detecting a set of beams in the second channel.
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