INTERFEROMETRISK MAETANORDNING MED GEMENSAM OPTISK BANA.

摘要

An interferometric measurement arrangement with a common optical path comprises an optical beam 14 that is divided into two beams. Both beams are modulated and recombined after the length difference between the optical paths has been made larger than the coherent length of the optical source 12. The combined beam is controlled along a common optical path 46 and then divided into reference and measurement beams. The measurement beam is controlled along an optical measurement path that contains a surface 60 of a moving workpiece. Both beams are recombined after a length difference between the optical paths has been established between them to reproduce coherence between portions of them to form the optical interference that indicates movement in surface 60.