Grating interferometer for flatness testing

Abstract

Two diffraction gratings placed in front of a flat surface generate an interference pattern representing the surface deformations. The interference pattern is achromatic and has an equivalent wavelength between 4 and 40 μm, depending on the grating frequencies and the viewing angle. Using phase-shifting techniques, the grating interferometer provides high-precision profile measurements of both smooth and rough surfaces.

© 1996 Optical Society of America

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