Interferometric instrument provided with an arrangement for producing a frequency shift between two interfering beam components

摘要

An interferometric instrument for sensing the surfaces of a test object includes a radiation generating unit for emitting briefly coherent radiation and a first beam splitter for producing a first and second beam component. One beam component is aimed at the surface to be sensed and the other beam component is aimed at a device with a reflective element for periodically changing the light path. The instrument also has an interference element which causes the radiation coming from the surface and the radiation coming from the reflecting device to interfere with one another and a photodetector which receives the radiation. A simple design is used to achieve a highly accurate measurement by providing an arrangement which produces a frequency shift between the two interfering beam components in the optical path of the first beam component and/or in the optical path of the second beam component.