Microstitching interferometry for x-ray reflective optics

A new stitching interferometry based on a microscopic interferometer having peak-to-valley height accuracy of subnanometer order and lateral resolution higher than 20 μm was developed to measure surface figures of large-size x-ray mirror optics. Cumulative errors of the stitching angle in a long spatial wavelength range were effectively reduced to be 1×10−7 rad levels using another interferometer having a large cross section in the optical cavity. Some optical performances of ultraprecise x-ray mirrors, such as submicrofocused beam profile, were wave optically calculated from the measured surface figure profiles and observed at the 1 km long beamline (BL29XUL) of SPring-8. Observed and wave optically calculated results were in good agreement with a high degree of accuracy.