US Patent 7710580 Vibration resistant interferometry

In general, in one aspect, the invention features a method including providing scanning interferometry data for a test object using phase shifting interferometry, the data including intensity values for each of multiple scan positions for different spatial locations of the test object, the intensity values for each spatial location defining an interference signal for the spatial location, the intensity values for a common scan position defining a data set for that scan position. The method also includes temporally transforming at least some of the interference signals into a first frequency domain signal, determining an estimated phase profile of the test object based on the first frequency domain signal, determining phase shifts at multiple scan positions based on the estimated phase profile, and determining a more accurate phase profile of the test object based on the estimated phase profile and the phase shifts.