Hu Lingfei, Wang Hongchang, Sutter John P, Sawhney Kawal
Opt Express. 2021 Feb 1;29(3):4270-4286. doi: 10.1364/OE.417030.
X-ray beams reflected from a single layer or multilayer coating are widely used for X-ray tomography, holography, and X-ray phase contrast imaging. However, the observed irregular stripe patterns from either unfocused or defocused beams often cause disturbing artifacts and seriously deteriorate the image quality. In this work, we investigate the origin of these irregular fine structures using the wave optics theory. The connection to similar results obtained by the geometric optics theory is also presented. The proposed relation between the second derivative of the wavefront and the irregular structures was then verified by conducting at-wavelength metrology with the speckle-based wavefront sensing technique. This work will not only help to understand the formation of these irregular structures but also provide the basis for manufacturing future 'stripe-free' refection optics.
从单层或多层涂层反射的X射线束被广泛用于X射线断层扫描、全息术和X射线相衬成像。然而，从未聚焦或散焦光束中观察到的不规则条纹图案常常会导致干扰伪影，并严重降低图像质量。在这项工作中，我们使用波动光学理论研究这些不规则精细结构的起源。还介绍了与几何光学理论获得的类似结果的联系。然后，通过基于散斑的波前传感技术进行波长计量，验证了所提出的波前二阶导数与不规则结构之间的关系。这项工作不仅将有助于理解这些不规则结构的形成，还将为制造未来的“无条纹”反射光学器件提供基础。
