Test sample's e.g. concave test sample, optically smooth surface e.g. free form surface, laminar measurement method, involves filtering object waves, which are reflected from surface, by aperture stop in Fourier plane of imaging lens

摘要

The method involves illuminating an optically smooth surface (33) with discrete object waves (32). The object waves, which are reflected by the optically smooth surface, are super imposed with a reference wave (42) on a detector (38) for an interferogram. The surface is illuminated synchronously with multiple switchable object waves. The object waves, which are reflected from the surface, are filtered by an aperture stop (40) that is arranged in an optical path before the detector, where the aperture stop is provided in a Fourier plane of an imaging lens (36). An independent claim is also included for a measuring device for measuring an optically smooth surface.