High-accuracy mirror surface measurement using three scanning interferometric displacement sensors, with motion error calibrated, is proposed for X-ray mirror metrology. The motion error of the scanning displacement stage significantly affects the high-accuracy measurement of mirror surfaces during scanning. The influence of motion errors on surface height measurements is studied. After eliminating motion errors with a system comprising three scanning interferometric displacement sensors, the mirror surface can be obtained. The formula for the surface height solution is derived, and the residual error terms are analyzed. A method of error reduction using three reference mirrors to calibrate distance is proposed. The calibration and test experiments are conducted. Experimental results demonstrate the effectiveness of calibration, and the measurement repeatability is 7.39 nm.
There is an urgent demand of novel X-ray optics for high heat load and radiation damage resistance for the new light source development. The compound refractive lens (CRL) is a good choice for the photon beam manipulation. Diamond, SiC and sapphire have been proved to be the preferred materials for CRL. However, on account of these materials are hard, brittle and difficult to process, conventional preparation prevents highly precise removal of materials. Meanwhile, CRL achieves X-ray focusing by stacking multiple lens units, which requires efficient and precise processing method to ensure that the error of each single lens is within an acceptable range. This paper uses scanning confocal laser microscopy and synchrotron X-ray computed tomography (CT) techniques to detect the manufacturing errors of bi-paraboloidal 2D focusing X-ray lenses of curvature radius R=1000 μm and aperture D=2000 μm produced via femtosecond laser ablation. Point cloud processing method is introduced to accurately characterize the relative position of two paraboloids deviation. The results showed that the local micro-roughness of lens surface is about 400 nm Sq. Relative transverse offsets of the front and back surfaces can be controlled within 35 μm and the axis deflection angle of the front and back paraboloid is between 20 and 40 mrad. Using the aforementioned methods, the manufacturing errors of bi-concave lenses can be effectively obtained, providing feedback for the optimization and improvement of process parameters.
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.
Conference Committee Involvement (2)
Optical Metrology and Inspection for Industrial Applications XII
11 October 2025 | Beijing, China
Optical Metrology and Inspection for Industrial Applications XI
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