Automatic Characterization of Sub-nm Surface Height Errors of Aspherical Mirrors by 2D Data Reconstruction

Optical manufacturing is a multi-billion-dollar industry that is an indispensable part of modern technology and science. The performance of any optical manufacturing process directly depends on the ability of its integrated optical surface metrology method to provide trustworthy feedback. High-accuracy metrology is vitally essential in manufacturing ultra-high-quality free-form mirrors designed to manipulate X-ray light with nanometer-scale wavelengths. Due to the shorter wavelength, requirements for the surface figure and finish of X-ray mirrors are three orders of magnitude more stringent than for visible-light optics. Correspondingly, the metrology integrated into X-ray mirror manufacturing must ensure the accuracy of optical surface fabrication on the sub-nanometer level. Improvements are needed not only for the classical plane, spherical, and sagittal cylindrical X-ray mirrors, but even more urgently, for free-form aspherical X- ray mirrors with moderately and strongly curved shapes, such as paraboloids, ellipsoids, hyperbolas, diaboloids, etc. Availability of such mirrors on the market will directly advance the fundamental and applied research performed at the DOE X-ray light facilities. As an adage say, if you can't measure it, you cannot make it. We are developing a turn-key solution for surface metrology based on a thorough calibration of the Instrumental Transfer Function (ITF) of a metrology tool in the same experimental arrangement used for measurements with highly curved aspherical x-ray mirrors under fabrication. The developed technology will be integrated into the existing metrology systems. Our original product will provide a robust methodology to thoroughly characterize them and process the data to remove the effects of their imperfections. Metrology is used in virtually every industry where the manufacturers need to measure the surface roughness for quality assurance (e.g., mirrors, car parts, and foods). The world's top companies highly valued our results, requesting the test samples and software immediately after they become commercially available. The solution will improve reliability, exclude the "human factor," and simplify and expedite the calibration.