【作者】 杜杨；

【导师】 牛憨笨；

【作者基本信息】 中国科学院研究生院（西安光学精密机械研究所） ， 物理电子学， 2013， 博士

【摘要】 X射线相衬成像技术是近几年来X射线成像领域的研究热点之一，它可以对传统吸收成像无法探测的轻元素构成的物质成像，因此在医学、生物学、材料科学以及无损检测等领域具有重大的应用价值。光栅微分干涉相衬成像方法可以在常规X射线源的条件下进行成像，可以同时得到物体的吸收、相衬和散射多元化信息，但由于使用了两个吸收光栅，不仅使制造难度和成本大增，还使其性能的改进受到限制。为此，本论文作者所在课题组首次提出采用结构阳极的X射线源和具有分析光栅功能转换屏来代替两个吸收光栅获得相衬图像，我们称此种相衬成像方法为无吸收光栅的微分干涉相衬成像方法。本论文正是基于此种相衬成像方法而展开的，主要取得如下进展：1、首次实现了无吸收光栅微分干涉相衬成像方法，在实验上获得了视场为55mm×55mm的相衬图像。该方法克服了吸收光栅带来的缺点，为相衬成像在医疗、工业探伤、科研等领域的应用奠定了理论和技术基础。2、基于菲涅尔衍射原理，在理论上详细分析了结构阳极的轴向扩展分布对成像视场的影响。更进一步，采用改进型结构阳极X射线源的方法可以扩大相衬成像视场，理论分析表明，在相同的辐射强度下，改进后的结构阳极X射线源可扩大成像视场4倍以上。3、发展了两步相移新算法，并在理论和实验上分别验证了这种算法的可行性。与其它两步相移算法相比较，其优点是算法简单，容易实现，大大降低了X射线源不稳定性的影响，更能准确恢复物体的相位信息。更多还原

【Abstract】 X-ray phase contrast imaging is an interesting technology in the field of X-rayimaging in recent years. It can detect the substance composed of light elements thatcan’t be detected by traditional X-ray absorption imaging. Thus, it has significantscientific value and wide application potential in the field of medicine, biology,materials science, and non-destructive testing. The approach based on gratinginterferometry can carry out at the traditional low-brilliance X-ray source and provideabsorption, differential phase contrast and dark-field signals simultaneously. However,because of using two absorption gratings, it not only makes the fabrication difficultyand high cost but also make the efficiency limited.To overcome this limitation, our research team firstly propose a method by usingmulti-line X-ray source and structured scintillator to replace two absorption grating inthe grating interferometry, which is called non-absorption grating approach for X-raydifferential phase contrast imaging. The thesis is based on such method to launchrelated research and mainly achieve the following progress:Firstly, we realize the non-absorption grating approach for X-ray differential phasecontrast imaging and acquire the large size of55mm×55mm phase contrast imagesexperimentally for the first time. The setup overcomes the limited of field of view bythe multi-line X-ray source and the limited of high photon-energy X-rays by theabsorption grating. It is more benefit for the future practical application in the field ofmedicine and industry, etc.Secondly, based on the Fresnel diffraction theory, we give a detailed analysis of thequantitative relation between the axis extension length and the imaging field of view.Furthermore, the field of view of phase contrast imaging can be widened by using animproved multi-line X-ray source. Compared with the multi-line X-ray source, it canexpand the imaging field of view of more than4times at the same radiation intensity.Thirdly, we have developed two-step phase-shifting algorithm to retrieve the objectphase information. According to the theoretical analysis and experimental verificationfor the feasibility of this algorithm, the advantage of the algorithm is simple and easyto implement, and it has a strong inhibition to the instability of X-ray source, and thusit can retrieve the phase information more accurately.更多还原