Interferometer for observing the interference pattern of a surface under test utilizing an adjustable aperture stop

摘要

An interferometer is used for observing the shape of a surface to be detected with the desired spatial resolution. A variable aperture stop is arranged at a Fourier transform image plane of the surface to be detected within an imaging optical system for forming an interference pattern of a reference light and a measuring light. The aperture diameter of the variable aperture stop is adjusted by a control in accordance with the desired spatial resolution.