Wu Xizeng, Liu Hong
Department of Radiology, University of Alabama at Birmingham, Birmingham, Alabama 35233, USA.
Appl Opt. 2008 Aug 1;47(22):E44-52. doi: 10.1364/ao.47.000e44.
X-ray coherence evolution in the imaging process plays a key role for x-ray phase-sensitive imaging. In this work we present a phase-space formulation for the phase-sensitive imaging. The theory is reformulated in terms of the cross-spectral density and associated Wigner distribution. The phase-space formulation enables an explicit and quantitative account of partial coherence effects on phase-sensitive imaging. The presented formulas for x-ray spectral density at the detector can be used for performing accurate phase retrieval and optimizing the phase-contrast visibility. The concept of phase-space shearing length derived from this phase-space formulation clarifies the spatial coherence requirement for phase-sensitive imaging with incoherent sources. The theory has been applied to x-ray Talbot interferometric imaging as well. The peak coherence condition derived reveals new insights into three-grating-based Talbot-interferometric imaging and gratings-based x-ray dark-field imaging.
成像过程中的X射线相干演化在X射线相敏成像中起着关键作用。在这项工作中，我们提出了一种用于相敏成像的相空间公式。该理论根据交叉谱密度和相关的维格纳分布进行了重新表述。相空间公式能够对相敏成像中的部分相干效应进行明确和定量的描述。所给出的探测器处X射线光谱密度公式可用于进行精确的相位检索和优化相衬可见度。从该相空间公式导出的相空间剪切长度概念阐明了使用非相干源进行相敏成像的空间相干要求。该理论也已应用于X射线塔尔博特干涉成像。导出的峰值相干条件为基于三光栅的塔尔博特干涉成像和基于光栅的X射线暗场成像提供了新的见解。
