Evaluation of partial coherence correction in X-ray ptychography
Evaluation of partial coherence correction in X-ray ptychography
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DOI：
10.1364/oe.23.005452
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发表时间：
2015-03-09
期刊：
影响因子：
3.8
通讯作者：
Robinson, Ian K.
中科院分区：
文献类型：
--
作者：
Burdet, Nicolas;Shi, Xiaowen;Robinson, Ian K.
相干X射线衍射成像(CDI)和X射线层析成像都严重依赖于X射线照明的高度空间相干性，以获得足够的实验数据质量以实现重建收敛。然而，大多数可用的同步辐射波荡器源具有有限程度的部分相干，导致数据质量降低，相干衍射图中的散斑对比度较低。实验者是否应该妥协X射线源的相干性以换取样品中更高的通量密度，这仍然是一个悬而未决的问题，特别是当一些科学感兴趣的材料是相对较弱的散射体时。以前的一项研究表明，在CDI中，研究强相物体的最佳策略是保持照明X射线的高度相干性，因为强相结构导致了解空间的拓宽。在这篇文章中，我们首次系统地分析了部分相干校正在层析成像中的有效性，它是相干特性、照明的复杂程度(探头的相位分集程度)和样品的相位复杂程度的函数。我们还分析了在重建开始时，对于无噪声的模拟数据，在实值对象和高度复杂的对象的情况下，当这些变量未知时，层析算法精炼X射线探针和复相干函数的效果如何。(C)2015年美国光学学会
Coherent X-ray Diffraction Imaging (CDI) and X-ray ptychography both heavily rely on the high degree of spatial coherence of the X-ray illumination for sufficient experimental data quality for reconstruction convergence. Nevertheless, the majority of the available synchrotron undulator sources have a limited degree of partial coherence, leading to reduced data quality and a lower speckle contrast in the coherent diffraction patterns. It is still an open question whether experimentalists should compromise the coherence properties of an X-ray source in exchange for a higher flux density at a sample, especially when some materials of scientific interest are relatively weak scatterers. A previous study has suggested that in CDI, the best strategy for the study of strong phase objects is to maintain a high degree of coherence of the illuminating X-rays because of the broadening of solution space resulting from the strong phase structures. In this article, we demonstrate the first systematic analysis of the effectiveness of partial coherence correction in ptychography as a function of the coherence properties, degree of complexity of illumination (degree of phase diversity of the probe) and sample phase complexity. We have also performed analysis of how well ptychographic algorithms refine X-ray probe and complex coherence functions when those variables are unknown at the start of reconstructions, for noise-free simulated data, in the case of both real-valued and highly-complex objects. (C) 2015 Optical Society of America