Phase shifting interferometric method, interferometer apparatus and method of manufacturing an optical element

摘要

A phase shifting interferometric method and apparatus comprises generating at least four different phase shifts and recording interferograms corresponding to the different phase settings and recording interferograms corresponding to the different phase settings. In the analysis of the recorded interferograms the generated phase shifts between the at least four different phase settings are determined from the measurement, i.e. from the recorded interferograms. A model simulating the interferogram intensities may be used for determining the phase shifts. The phase shifts are free adaptable parameters of the model.