Surface measurements in oblique incidence for multiple elements piezoelectric x-ray bimorph mirror

Abstract

The oblique incidence is a crucial metrology method to realize the measurement demand for high aspect ratio multiple elements piezoelectric X-ray bimorph mirror surface by small-aperture Fizeau interferometers in one single shot. Due to the change of optical path difference in oblique incidence, we analyzed how different oblique incidence angles would affect the results of the surface height with numerical simulation and evaluated angular errors when curved mirrors are measured.Then we constructed an oblique incidence measurement system for measuring the 200 mm X-ray bimorph mirror with multiple elements piezoelectric by using a 100 mm clear aperture Fizeau interferometer and return reference mirror based on a preliminary determination of the angle of oblique incidence, and so the precise angle of oblique incidence is calculated from the actual measurement results. The oblique incidence can directly observe the dynamic effects of a high aspect ratio X-ray bimorph mirror surface in response to the applied voltages. With practical interferometric measurements of the multiple elements piezoelectric X-ray bimorph mirror by the constructed oblique incidence measurement system, and we obtained multiple sets of response functions and optimized surface at different voltages. Furthermore, the bimorph mirror surface optimized height profile was experimentally controlled and measured to be 17.13 nm PV (peak to valley) at the centerline, which can lay the foundation for measuring the X-ray bimorph mirror surface with extremely high aspect ratios.