The reverse projection protocol results in fast phase‐contrast imaging thanks to its compatibility with conventional computed‐tomography scanning. Many researchers have proposed variants. However, all these reverse projection methods in grating‐based phase‐contrast imaging are built on the hypothesis of the synchronous phase of reference shifting curves in the whole field of view. The hypothesis imposes uniformity and alignment requirements on the gratings, thus the field of view is generally limited. In this paper, a generalized reverse projection method is presented analytically for the case of non‐uniform reference in grating‐based phase tomography. The method is demonstrated by theoretical derivation, numerical simulations and synchrotron radiation experiments. The influence of imaging position to sensitivity, and the phase‐wrapping phenomenon are also discussed. The proposed method combines the advantages of the high efficiency of the reverse projection method and the universal applicability of the phase‐stepping method. The authors believe that the method would be used widely in fast and dose‐constrained imaging.

中文翻译：

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基于光栅的相位层析成像的广义反投影方法

反向投影协议与常规计算机断层扫描兼容，因此可以实现快速的相衬成像。许多研究人员提出了变体。但是，基于光栅的相衬成像中的所有这些反向投影方法都是基于在整个视场中参考偏移曲线的同步相位的假设而建立的。该假设对光栅施加了均匀性和对准要求，因此通常限制了视野。本文针对基于光栅的相位层析成像中非均匀参考的情况，分析性地提出了一种广义逆投影方法。通过理论推导，数值模拟和同步辐射实验证明了该方法。成像位置对灵敏度的影响，还讨论了相位包裹现象。所提出的方法结合了反向投影方法的高效率和相位步进方法的普遍适用性的优点。作者认为，该方法将广泛用于快速且剂量受限的成像中。