摘要 |
In general, in one aspect, the invention features methods that include locating a plurality of alignment marks on a moveable stage, interferometrically measuring a position of a measurement object along an interferometer axis for each of the alignment mark locations, and using the interferometric position measurements to derive information about a surface figure of the measurement object. The position of the measurement object is measured using an interferometry assembly and either the measurement object or the interferometry assembly are attached to the stage.
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