直接衍射X射线位相成像技术研究
文献类型：学位论文
| 作者 | 喻虹 |
| 学位类别 | 硕士 |
| 答辩日期 | 2003 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 韩申生 |
| 关键词 | X射线 位相成像 部分相干 位相复原 |
| 其他题名 | Researches on Directly Diffractive X-ray Phase-contrast Imaging Technology |
| 中文摘要 | 现代成像技术已超出了常规光学的成像范围，而是以各种非常规光学的射线成像和纳米分辨的显微成像技术为主体，成像系统的极限分辨率取决于所使用的波长。而X射线的突出特点是其短波长和高穿透性，因此具有高分辨率显微成像的潜在优势。近年来，X射线位相成像技术引起了人们的极大关注，利用同步辐射光源和微聚焦X射线源取得了较多的研究成果。本文在充分进行了部分相干X射线位相成像理论研究的基础上，提出了一种基于通用X光机的直接衍射位相成像技术，并通过实验进行了进一步的研究。所进行的研究工作主要包括以下几个方面的内容：1、部分相干X射线位相成像理论从部分相干光成像的基本理论出发，进行了部分相干X射线直接衍射位相成像理论研究。借助于光学传递函数概念，分析了不同成像参数下的两种基本位相成像过程：微分位相成像和直接位相成像，以及两种成像过程中成像参数对成像对比度和分辨率的影响，并采用F畔算法编程模拟了成像过程。并且，详细讨论了不同波长所需的成像参数，空间相干性对成像质量的影响，以及光源非均匀分布对成像的影响，从实际条件出发论证了此类实验的可行性。 2、基于通用X光机的位相成像技术针刘现有硬X射线源进行X射线位相成像的不足之处，设计了一种新的基于普通x光机的高亮度空间相干x射线源，它具有亮度高、空间相干性好、成本低、体积小等优点。并且，采用这种新型X射线源进行了X射线直接衍射位相成像的实验研究，通过分析样品在不同实验参数的X射线位相成像图，验证了理论分析的结论，通过和传统的吸收成像进行比较，证明了基于通用X光机的位相成像技术能很好的提高成像对比度和分辨率，具有良好的应用前景。3、直接衍射X射线位相成像中的位相重建由直接衍射X射线位相成像中得到的图像进行位相重建，一直是本领域研究的热点之一。利用数字图像处理的优越性，考虑到直接衍射位相成像中光学传递函数的特点，可以利用不同成像参数获得不同频率的物体信息，提出了一种新的频域图像融合方法来复原物体位相分布，并通过模拟计算得到了良好的结果。直接衍射X射线位相成像技术有很高的应用价值，我们希望能在将来的研究工作中，进一步完善直接衍射X射线位相成像理论，使之于实验结论更为一致，并进一步改进成像X射线源，使之具有体积小、成本低、稳定性好、高亮度、空间相干性好等特点，真正应用到生物医学、材料学、工业检测和科研工作中。 |
| 英文摘要 | Beyond traditional optical imaging, modern imaging technology is dominated by many radial (x-ray, neutron and so on) imaging and nm resolution microscopy, and the ultimate resolution of an imaging system depends on the wavelength of the imaging light. Very short wavelength and powerful penetrability are the most important characteristics of x-ray, so x-ray imaging has notable potential advantages to obtain high resolution microscopic images. Recently, x-ray phase-contrast imaging has attracted much attention, and lots of researches have been done using synchrotron x-ray sources and microfocus x-ray tubes. In this paper, on the basis of theoretical researches of partially coherent x-ray phase-contrast imaging, a new directly diffractive x-ray phase-contrast imaging technology has been proposed, and experimental researches have been performed using a traditional x-ray tube. The researches include following contents: 1、Partially coherent x-ray phase-contrast theory. On the basis of imaging theory of partially coherent light, directly diffractive phase-contrast imaging, using partially coherent x-ray, is studied theoretically. Two basic imaging processes under different imaging parameters, differential phase-contrast imaging and direct phase-contrast imaging, are analyzed in terms of the optical transfer function (OTF), and simulated digitally using FFT algorithm. How the different imaging parameters influence the imaging contrast and resolution of the two imaging processes is also analyzed. The proper imaging parameters at different x-ray wavelength, the non-uniformity distribution of the x-ray source and the spatial coherence that influence imaging quality are detailed discussed. All above prove the feasibility of directly diffractive x-ray phase-contrast imaging. 2、Phase-contrast imaging technology based on traditional x-ray tube. Considering the defects of existing hard x-ray sources for phase-contrast imaging, a new low-cost room-size x-ray source based on x-ray tube, with high intensity and spatial coherence, is designed. And experimental study of directly diffractive x-ray phase-contrast imaging is performed using this new kind of x-ray source. Our theory above is proved by analyzing x-ray phase-contrast images under different experiment parameters. Compared with traditional absorption imaging, the technology of x-ray phase-contrast imaging can greatly improve the imaging contrast and resolution, and has many attracting applications. 3、Phase restoration of directly diffractive x-ray phase-contrast imaging. One of the hotspots in this field is phase reconstruction from the directly diffractive x-ray phase-contrast imaging. Take the characteristics of the imaging OTF into account, digital image processing methods can be introduced to the phase reconstruction. A new image fusion method in the frequency domain is proposed to restore the object phase distribution. And the object information at different spatial frequencies can be obtained by imaging under different experimental parameters. Good simulating results are showed in this paper. Directly diffractive x-ray phase-contrast imaging is a very valuable method. There are many tasks need to be fulfilled in the future researches. The theory of directly diffractive x-ray phase-contrast imaging is still not perfectly in accord with the experiment results, and the x-ray source needs further improvement to get small size, low cost, good stability, high intensity and spatial coherence. We hope it can be used in the biology, clinics, materials, industry inspection and scientific researches in the future. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/16470]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 喻虹. 直接衍射X射线位相成像技术研究[D]. 中国科学院上海光学精密机械研究所. 2003. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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