| X射线菲涅耳波带板成像和投影式相衬成像的数值模拟比较 |
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| 引用本文： | 袁亚运,王晓方.X射线菲涅耳波带板成像和投影式相衬成像的数值模拟比较[J].强激光与粒子束,2016,28(10):102001. |
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| 作者姓名： | 袁亚运 王晓方 |
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| 作者单位： | 1.中国科学技术大学 近代物理系, 合肥 230026 |
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| 摘 要： | 通过解析分析和数值模拟，比较了钛K线（4.5 keV）与铜K线（8.0 keV）等X射线源背光透视物体情况下，菲涅耳波带板直接成像与投影式相衬成像对被透视物体的空间分辨能力。结果表明，波带板成像可实现优于1 m的高空间分辨能力，而且使用较大尺度背光源更有利于成像。对于高透射或弱吸收的透视物体，波带板难以成像，可采用投影式相衬成像实现m级空间分辨。计入了以前文献没有考虑到的更高阶影响后，解析给出了点光源照射下相衬像的强度分布与对比度。模拟了微焦点X射线源照射存在厚度起伏的薄膜靶以及密度空间调制靶的相衬成像，点光源情况下模拟结果和解析结果相符。讨论了光源大小、成像距离等参数对相衬成像对比度和空间分辨能力的影响，结果表明，通过减小光源尺度和调节物体到探测面的距离，空间分辨能力可优化到1～4 m。
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| 关 键 词： | X射线成像 菲涅耳波带板 相衬成像 |
| 收稿时间： | 2015-12-21 |
Comparison between X-ray imaging by Fresnel zone plate and projection-type phase contrast imaging by numerical simulations |
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| Affiliation: | 1.Department of Modern Physics,University of Science and Technology of China,Hefei 230026,China |
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| Abstract: | X-ray diffraction imaging is capable of realizing near-diffraction-limited spatial resolution. This paper uses analytical and numerical approaches to study and compare Fresnel zone plate (FZP) imaging and projection-type phase contrast imaging of an object backlit by an X-ray source. The energy of X-rays is the Ti K line (4.5 keV) or Cu K line (8 keV). The results show that the spatial resolution of FZP imaging is better than 1 m, and it is beneficial to use a backlighting source of larger size. For high transmission or weak absorption object, FZP imaging does not work well due to poor contrast. In this case, projection-type phase contrast imaging may be applied to achieve a spatial resolution of a few microns. By including higher-order effect that was not considered before, analytical formulae for image intensity and contrast are given. Numerical approaches are also used to study the phase contrast imaging of thin film target with thickness fluctuations or spatial density modulations illuminated by a microfocus X-ray source. In the case of a point source the theoretical contrast of images coincides well with simulation result. The influence of X-ray source size and imaging distance on the images contrast and spatial resolution is discussed. It is indicated that by controlling the source size and changing the distance between the object and the detector, the spatial resolution could be optimized to 1-4 m. |
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