Contactless interferometric incremental measurement technique

This paper presents a measurement technique which makes it possible to scan varying interference patterns by using the incremental procedure (forward-backward counting method). The essence of this procedure is that the primary interference pattern is scanned point-shaped (with a very small detector area) and in a locally identical way. The quarter-wave phase shift is realised by polarisation-optical means. By using this measurement procedure one may use plane measuring mirrors without being forced to guide them strictly in parallel. Besides, the contactless scanning of plane and curved surfaces will be possible.