8 September 2016 Subaperture stitching interferometry with reduced reference errors for ultrasmooth surfaces
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Abstract
Low-roughness ultrasmooth surfaces are under increasing demand in short-wavelength optical systems. Substitching interferometry has been used to measure the profiles of surfaces used in X-ray beam. To validate the stitching accuracy of our optical profiler, a comparison of stitching surfaces using a 10X objective and those directly measured using a 2.5X objective is performed with a resolution of 1 μm. By studying the multiple measurements and defocussing errors, the reference surface error is measured in various regions of a standard flat surface with random positions and rotation angles. In the final experiment, 25 subapertures measured using a 10X objective with reduced reference surface error are stitched to a 2.54 X 1.90 mm area. The comparison is between the stitching and the same area measured directly using the 2.5X objective, and the results show that a root-mean-square accuracy of <0.2 nm can be achieved.
Conference Presentation
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Xudong Xu, Qiushi Huang, Zhengxiang Shen, Zhanshan Wang, "Subaperture stitching interferometry with reduced reference errors for ultrasmooth surfaces", Proc. SPIE 9962, Advances in Metrology for X-Ray and EUV Optics VI, 996208 (8 September 2016); doi: 10.1117/12.2236629; https://doi.org/10.1117/12.2236629
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