| 摘要 |
Interferometry system including a multiple-pass interferometer having reflectors to reflect at least two beams along multiple passes through the interferometer. The multiple passes include a first set of passes and a second set of passes. The reflectors have first alignments that are normal to the directions of the paths of the beams that are reflected by the reflectors. The two beams provide information about changes in a first location on one of the reflectors after the first set of passes, and provide information about changes in the first location and changes in a second location on the reflector after the second set of passes. The paths of the beams are sheared during the first set of passes and during the second set of passes if at least one of the reflectors has an alignment other than the first alignment. The interferometry system includes optics to redirect the beams after the first set of passes and before the second set of passes so that shear imparted during the second set of passes cancels shear imparted during the first set of passes.
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