A dual-wavelength heterodyne differential interferometer was developed and tested together with scanning mechanics. To extend the range of unambiguity, two wavelengths were applied. This is important for measuring structures with surface discontinuities (reliefs, steps). The automatic adjustment of the interferometer with respect to the rotational symmetrical measuring surfaces (aspheres) is important. An adjustment is needed to scan the asphere through its vertex. Typical measurements on a sphere, an asphere, and steps are shown.
© 1996 Optical Society of America
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