A profilometer for in situ measurement of the topography of aspheric mirrors called the Swing arm Optical CMM (SOC) was built, and has been used for measuring the figure of 1.4 m convex aspheric mirrors with a performance rivaling full aperture interferometric tests. Errors in the SOC that have odd symmetry are self-calibrated due to the test geometry. Even errors are calibrated against a full aperture interferometric test.
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Su et al. (2009) studied this question.
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