Interferometric method of measuring external cylindricalsurfaces

A new method of measuring external cylindrical surfaces is proposed, making use of a ring beam transform unit. The unit is composed of three cone mirrors, with which a parallel beam can be transformed into annular and convergent beams. The method has advantages over classic methods: It avoids physical contact with the cylinder surface and is fast and stitching-free. In experiments using a dynamic interferometer to demonstrate the feasibility of the method, the RMS difference of the axis contour from results using a Luphoscan is 0.0282 µm, while the roundness difference of the circumferential contour is 0.0962 µm.