High performance Fizeau and scanning white-light interferometers for mid-spatial frequency optical testing of free-form optics

摘要

Two specially-designed visible-wavelength interferometers meet demanding performance requirements in the mid-spatial frequency regime for current and next generation free-form x-ray and EUV optics. A Fizeau phase shifting interferometer measures waviness in the spatial frequency range from 0.5 to 10 mm~(-1) and an interferometric microscope measures finer-scale deviations from 1 to 1000 mm~(-1). Uncertainty analysis and experimental work demonstrate < 1-nm system error after calibration and 0.05-nm repeatability for both instruments working in a clean-room environment.