A surface‐profile measuring system for synchrotron radiation mirrors

The optical head for a new surface‐profile measuring system was constructed on the basis of the Twyman–Green interferometer with heterodyne phase detection method. Stability in optical path difference (OPD) was within 2 nm for a fixed point under the well shielded condition. The measured OPD map at the null fringe condition shows the possibility for direct or segment measurement method of aspheric and/or large size mirrors in SR optics. Based on experiments, a new surface‐profile measuring system by phase measurement interferometry and segment method is designed. Designed features of the system are briefly reported.