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
Original Manuscript: June 26, 1995
Published: February 1, 1996
Peter J. de Groot, "Grating interferometer for flatness testing," Opt. Lett. 21, 228-230 (1996)