Micro-stitching interferometry at the ESRF

The ESRF metrology laboratory has recently acquired a new optical micro-interferometer optimised for micro-roughness measurement of X-ray mirrors. The fully integrated system offers a wide range of measurement capabilities adapted for both very rough surfaces and super smooth surfaces (<1 A rms). The high level of automation of the instrument permits a great deal of flexibility in performing pre-defined measurement sequences and, in particular, by using measurement of overlapping fields includes a stitching measurement option. First we give an overview of the performance of the instrument in terms of accuracy and repeatability. Subsequently we present the stitching option, how to handle it to improve accuracy, indicating some limits and approaches to overcome difficulties. Finally, we compare profiles obtained by micro-stitching interferometry with those measured using a long trace profiler.