Pandeshwar Amogha, Kagias Matias, Wang Zhentian, Stampanoni Marco
Opt Express. 2020 Jun 22;28(13):19187-19204. doi: 10.1364/OE.395237.
X-ray grating interferometry (XGI) can provide access to unresolved sub-pixel information by utilizing the so-called dark-field or visibility reduction contrast. A recently developed variant of conventional XGI named dual-phase grating interferometer, based only on phase-shifting structures, has allowed for straightforward micro-structural investigations over multiple length scales with conventional X-ray sources. Nonetheless, the theoretical framework of the image formation for the dark-field signal has not been fully developed yet, thus hindering the quantification of unresolved micro-structures. In this work, we expand the current theoretical formulation of dual-phase grating interferometers taking into account polychromatic sources and beam hardening effects. We propose a model that considers the contribution of beam hardening to the visibility reduction and accounts for it. Finally, the method is applied to previously acquired and new experimental data showing that discrimination between actual micro-structures and beam hardening effects can be achieved.
X射线光栅干涉测量法（XGI）可以通过利用所谓的暗场或可见度降低对比度来获取未解析的亚像素信息。最近开发的一种传统XGI的变体，称为双相光栅干涉仪，仅基于相移结构，使得使用传统X射线源能够在多个长度尺度上直接进行微观结构研究。尽管如此，暗场信号成像的理论框架尚未完全建立，从而阻碍了对未解析微观结构的量化。在这项工作中，我们扩展了双相光栅干涉仪的当前理论公式，考虑了多色源和束硬化效应。我们提出了一个模型，该模型考虑了束硬化对可见度降低的贡献并对其进行了说明。最后，该方法应用于先前获取的和新的实验数据，结果表明可以实现实际微观结构与束硬化效应之间的区分。
