Optical path length determining method, involves arranging reference surface in-front of surface of object such that portion, which is reflected by reference surface, forms interference pattern with another portion

摘要

The method involves aligning a coherent electromagnetic wave front at a surface of an object (O), and arranging a reference surface (RF) in-front of the surface in such a manner that a portion reflected by the reference surface, forms a interference pattern with another portion reflected by the surface of the object. Interference pattern in a detection device (K) is detected by separating differently polarized radiation portions between the reference surface and the surface of the object and adjusting relative intensities of the radiation portions by an adjustable polarization filter. An independent claim is also included for an interferometer arrangement with a coherent radiation source.