| 摘要 |
PROBLEM TO BE SOLVED: To calibrate the alignment error correction required for measuring the surface accuracy of a test surface by constituting an aspherical prototype with a first face being a nonspherical surface having a nonspherical surface axis to be a reference of a rotary asymmetric shape and a second face being a composite surface composed of a plane and spherical surface. SOLUTION: A plane wave 5a from an interferometer is incident on a first wave front conversion element 2 to convert into a desired null wave front 2a. The opposite side of an aspherical prototype 1 is a composite surface composed of a plane 1b and spherical surface 1c. A plane wave 5b is incident on a second wave front conversion element 3 to create a desired plane wave 3a and spherical wave 3b, the coincidence of the alignment deviation obtd. by the alignment error correction at the aspherical surface with the alignment deviation obtd. by the alignment error correction at the composite surface is utilized, an interference fringe formed with the planes 1b, 3c shows two shifts, and an interference fringe formed with the spherical surfaces 1c, 3d shows two alignment deviations formed by two shifts and two tilts in directions X, Y and the focus.
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