Automated system for measuring the surface shape of large-size flat and cylindrical mirrors on a Fizeau interferometer

An automated system is described for measuring the surface shape of mirrors larger than the aperture of a Fizeau interferometer and cylindrical mirrors using a Fizeau interferometer. The system is based on a Zygo Verifire interferometer with a 100 mm aperture. The sample is mounted on a motorized motion system that performs linear movement along the interferometer aperture and tilts around axes perpendicular to the optical axis of the interferometer, providing the movements required for measurements by the subaperture stitching method. Stitching is carried out at the end of measurements using the overlap matrix method. The system allows determination of systematic measurement errors, including reference errors, using the unilateral multiple shift method and accounts for them in the measurements, as well as performing measurements with repeatability at the 15 pm level and accuracy at the subnanometer level.