Phase-shifting interferometer for monitoring flat and spherical optical components

This paper discusses an automatic interferometer that makes it possible to measure the surface profile of flat and spherical (with a large radius of curvature) optical items. The interferometer’s field of view is as much as 30 mm in diameter. The vertical configuration of the main optical elements of the interferometer allowed it to be made compact and insensitive to vibrations. The surface profile is automatically measured by means of a nine-step phase-shift method. The results of experimental testing of the interferometer and its technical characteristics are presented.