Interpretation of dark-field contrast and particle-size selectivity in grating interferometers.
Interpretation of dark-field contrast and particle-size selectivity in grating interferometers.
复制标题
在光栅干涉仪中的暗场对比度和粒度选择性的解释。
DOI：
10.1364/ao.50.004310
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发表时间：
2011-08-01
期刊：
影响因子：
1.9
通讯作者：
Wen HH
中科院分区：
文献类型：
--
作者：
Lynch SK;Pai V;Auxier J;Stein AF;Bennett EE;Kemble CK;Xiao X;Lee WK;Morgan NY;Wen HH
在基于光栅的X射线相敏成像中，暗场对比度是指由于小角度散射而导致的干涉条纹的消光。对于其中样品被放置在分束器光栅之前的配置，暗场对比度已经用理论波传播模型量化。然而，当光栅被放置在样品之前，暗场对比度仅在几何光学制度中被建模。在这里，我们试图量化的暗场效应的光栅前样品的几何形状与第一性原理波计算和理解相关的颗粒尺寸的选择性。我们得到了一个表达式的暗场效应的样品材料的复折射率，这可以通过实验验证，而无需拟合参数。暗场计算机断层扫描实验表明，颗粒尺寸的选择性可以用来区分相同的X射线吸收的材料。
In grating-based x-ray phase sensitive imaging, dark-field contrast refers to the extinction of the interference fringes due to small-angle scattering. For configurations where the sample is placed before the beamsplitter grating, the dark-field contrast has been quantified with theoretical wave propagation models. Yet when the grating is placed before the sample, the dark-field contrast has only been modeled in the geometric optics regime. Here we attempt to quantify the dark-field effect in the grating-before-sample geometry with first-principle wave calculations and understand the associated particle-size selectivity. We obtain an expression for the dark-field effect in terms of the sample material’s complex refractive index, which can be verified experimentally without fitting parameters. A dark-field computed tomography experiment shows that the particle-size selectivity can be used to differentiate materials of identical x-ray absorption.