Table-topX光强度关联衍射成像系统研究
文献类型：学位论文
| 作者 | 谈志杰 |
| 文献子类 | 硕士 |
| 导师 | 喻虹 |
| 关键词 | X光成像 x-ray imaging 关联成像 ghost imaging X光显微 x-ray microscopy 角谱 angular spectrum 部分相干 partially coherent |
| 其他题名 | Study on Table-top X-ray Intensity Correlated Diffraction Imaging System |
| 英文摘要 | X光显微成像技术是探究生物细胞内部微细结构和研究材料性质的重要工具。基于吸收的X光成像技术往往是在实空间成像，其分辨率受限于探测器像素尺寸，而傅里叶空间衍射成像可以突破这一限制，实现高分辨。但是现有的傅里叶空间衍射成像技术对光源空间相干性要求较高，在一定程度上限制了X光显微技术的广泛应用。关联成像是上世纪九十年代研究量子信息时提出的一种成像方法，通过测量辐射场的空间关联得到物体的图像信息，由于其特殊的成像性质，已广泛应用于遥感探测、多光谱成像等领域。 本文充分进行了X光成像技术调研，在关联成像理论研究和X光傅里叶变换关联成像原理演示实验的基础上，提出Table-top X光强度关联衍射成像系统，该成像系统使用小型化的实验室X光源，有望实现纳米级的X光显微。本文以成像系统的设计为主要目标，完成的工作主要有以下几个方面： 1. 采用角谱衍射理论，从频谱空间推导光源有限大小情况下的关联成像公式，澄清了关联成像中谱分辨率会受到参考臂散斑尺度的影响，参考臂散斑尺度决定探测臂上一点接收到的谱的宽度。同时讨论了点探测器位置的影响，当光源较小，点探测器位置在探测臂将会给成像结果带来误差。 2. 采用高斯谢尔模型，理论分析了入射光的部分相干性对赝热X光二阶关联函数的影响，结果表明部分相干性将会降低关联成像的可见度和分辨率。同时提出在散射屏前置尺寸与X光横向相干尺寸相当的针孔可以抑制部分相干性的影响，提高关联成像的可见度。并在此基础上，提出使用针孔阵列来增大视场，根据入射光相干尺寸和散斑场的发散角来确定针孔阵列的针孔间隔。 3. 结合具体的实验设备，对Table-top X光强度关联衍射成像系统的光路进行了初步的设计。同时针对成像参数优化问题，提出了可见光波长独立实验方案，并对针孔宽度与针孔间隔进行了初步的实验研究，实验结果与理论分析相符。; X-ray microscopic technology is an important tool in exploring and analyzing the microstructure of cells and materials. Most of the x-ray imaging methods based on x-ray absorption are realized in real space, where the resolution is usually limited by the pixel size of the detector. While Fourier-transform diffraction imaging can break such restriction and achieve higher resolution. However, to perform Fourier-transform diffraction imaging, it requires x-ray source with high spatial coherence, which to a certain extent, restricts its potential applications. Correlated imaging, known as ghost imaging, is a relatively novel imaging method that was discovered during the quantum information study in 1990s. In correlated imaging, the image information of samples are obtained by measuring the correlation between light fields. Because of this special characteristic, correlated imaging has been widely used in remote sensing, multi-spectral imaging and other fields. In this paper, we carried out the research on an x-ray microscopy method, based on the relevant theory of correlated imaging and the corresponding demonstration experiment of x-ray Fourier-transform ghost imaging. We propose a table-top x-ray intensity correlated diffraction imaging system, where a miniaturized laboratory X-ray source is used and nanoscale microscopy can be expected. With the goal of the imaging system design, this thesis mainly achieved the following results: 1. The diffraction theory of angular spectrum was used to derive the ghost imaging formula in the spectral space when the light source is size-limited. It was clarified that the spectral resolution in a ghost imaging system is affected by the speckle size at the reference arm, and the speckle size decides the spectral width detected in the testing arm. The influence of the position of the point detector was also discussed, and point detector in testing arm will introduce image distortion in the case of small size light source. 2. By using the Gaussian Schell model, the influence of the x-ray partial coherence on the second-order correlation function was analyzed theoretically. The results shows that the partial coherence will reduce the visibility and resolution of ghost imaging. The method to place a pinhole in front of the diffuser was proposed to improve the visibility of x-ray Fourier-transform ghost imaging, where the pinhole size should be equal to the transverse coherence size of the incident x rays. A pinhole array method was also proposed to increase the field of view. By means of theoretical derivation and simulation, we analyzed that the interval between pinholes on the pinhole array should be designed according to the incident light coherence size and the divergence angle of the speckle fields. 3. The optical setup of the table-top x-ray intensity correlated diffraction imaging system was designed. Aiming at the imaging parameter optimization, an independent experimental scheme of visible light was propose. Preliminary experimental studies were performed, and the results are consistent with the theory. |
| 学科主题 | 光学工程 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/30913]  |
| 专题 | 中国科学院上海光学精密机械研究所 |
| 作者单位 | 中国科学院上海光学精密机械研究所 |
| 推荐引用方式 GB/T 7714 | 谈志杰. Table-topX光强度关联衍射成像系统研究[D]. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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