RGB Interferometer Measures Diffractive Optical Elements

While white-light interferometry may be a standard tool for measurement of discontinuous profiles, it requires significant data collection and evaluation. Researchers at the University of Erlangen-Nuremberg in Germany offer a solution involving phase-shifting interferometry. The technique simultaneously records three interference patterns from a three-chip color CCD camera at red, green and blue wavelengths. Because it is possible to calculate the absolute profile height for each pixel or location in the exit pupil of the interferometer, the technique effectively resolves common problems of other phase-shifting devices; namely, limitations related to the requirement that the height difference between two neighboring pixels be smaller than one-quarter of the wavelength.