Optical position transmitter having a movable code element with optical path difference generating structure which is greater than the coherence length of the source

摘要

An optical position transmitter comprises a movable code element (36). A light beam (44) is directed onto the code element. The coding of the code element (36) generates in the reflected light beam (44) sub-light beams having different optical path differences. This may be effected by stepped surface portions on the surface of the code element (36). The optical path differences are greater than the coherency length of the light of the light source (62). The reflected light beam is directed through a beam splitter (42) onto an interferometer for detection of the optical path differences. Interferences between sub-light beams are permitted by well-defined quick changes in the interferometer with determined path differences. Position signals can be obtained from the thus obtained "interference peaks".