A new phase-shift microscope designed for high accuracy stitching interferometry

Characterizing nanofocusing X-ray mirrors for the soon coming nano-imaging beamlines of synchrotron light sources motivates the development of new instruments with improved performances. The sensitivity and accuracy goal is now fixed well under the nm level and, at the same time, the spatial frequency range of the measurement should be pushed toward 50 mm−1. SOLEIL synchrotron facility has therefore undertaken to equip with an interferential microscope suitable for stitching interferometry at this performance level. In order to keep control on the whole metrology chain it was decided to build a custom instrument in partnership with two small optics companies EOTECH and MBO.The new instrument is a Michelson micro-interferometer equipped with a custom-designed telecentric objective. It achieves the large depth of focus suitable for performing reliable calibrations and measurements. The concept has been validated with a predevelopment set-up, delivered in July 2010, which showed a static repeatability below 1 nm PV despite a non-thermally stabilized environment. The final instrument was delivered early this year and was installed inside SOLEIL's controlled environment facility, where thorough characterization tests are under way. Latest test results and first stitching measurements are presented.