基于实验室光源的X射线相衬成像应用研究

发布时间：2017-12-31 03:17

本文关键词：基于实验室光源的X射线相衬成像应用研究　出处：《深圳大学》2017年硕士论文　论文类型：学位论文

【摘要】：X射线相衬成像技术是近年来X射线研究领域的一个热点,它通过探测X射线穿过物体后相位的改变来对物体成像,克服了传统吸收成像无法对弱吸收物体成像的缺点,因而在医学、无损检测和材料学方面有很高的应用价值。目前,比较成熟的相衬成像方法主要有:晶体干涉成像法、衍射增强法、同轴相衬成像法和基于光栅的相衬成像法。受到光源和晶体的限制,晶体干涉成像法和衍射增强法对设备的要求很高,适用性较差。相较而言,同轴相衬成像法和基于光栅的相衬成像方法,对光源和实验设备的要求较低,便于在实验室开展,所以本文将这两种方法作为研究的主要内容。同轴法相衬成像最初是在同步辐射源上开展的,但因为它对于光源的时间相干性要求不高,所以也可以在微焦斑X射线源下进行。微焦斑源的相干性较好,但因为焦斑太小,所以光通量很小。为了解决X射线成像中,光源光通量和相干性不可兼得的矛盾,我们使用了一种焦斑为线型的X射线源,间接的解决了这个问题。线焦斑源在线宽方向的相干性较好,但在线长方向不具有空间相干性,会丢失线长方向上的物体细节,所以我们采用旋转物体的方式,将多个方向的物体图像进行叠加,从而重构出能反应物体(芯片)细节的高分辨率图像。我们将此结果分别与微焦斑X射线源类同轴成像以及大焦斑源成像结果进行对比,给出了基于线焦斑源成像在相干性和通量方面具有优势的实验验证。基于光栅的相衬成像方法,发展至今有Talbot-Lau和逆Talbot-Lau方法,Talbot-Lau干涉仪法对光栅要求高,光栅制作较为困难;逆Talbot-Lau法受限于光源的相干长度,成像系统的距离很长,不利于实用。本文研究了光栅相衬成像方法中基于探测器积分效应的位移曲线在无分析光栅情况下的实验采集技术,通过对于Talbot-Lau干涉仪中分析光栅作用的分析,得出了分析光栅的主要作用是分割自成像条纹和选择积分区域,并由此得出在无分析光栅情况下,位移曲线产生的充分条件。通过实验验证了不同像素下位移曲线的存在性,在实测位移曲线的基础上,研究了像素优化读出方法,并成功的对聚乙烯棒进行了相位恢复。然后利用此方法对生物样品(鸡爪)进行了成像实验,最终获得了比以往所发表过的论文中成像衬度更清晰且结构信息更丰富的相衬图像。利用此方法可以极大的缩短成像系统的长度,具有一定的实用性。
[Abstract]:X-ray phase contrast imaging technology is a hot spot in the field of X-ray research in recent years. It detects the change of phase after X-ray passing through an object to image an object. It overcomes the shortcoming that traditional absorption imaging can not image weakly absorbing objects, so it has high application value in medicine, nondestructive testing and materials science. The relatively mature phase contrast imaging methods mainly include crystal interferometry, diffraction enhancement, coaxial phase contrast imaging and raster-based phase contrast imaging, which are limited by light source and crystal. The requirements of crystal interferometry and diffraction enhancement are very high and the applicability is poor. Compared with coaxial phase contrast imaging and grating based phase contrast imaging, the requirements of light source and experimental equipment are lower. Coaxial contrast imaging is initially carried out on synchrotron emitter, but the time coherence of light source is not high. So it can also be carried out under the micro-focal X-ray source. The micro-focal spot source has good coherence, but because the focal spot is too small, so the luminous flux is very small. In order to solve the X-ray imaging. Because of the contradiction between the luminous flux and coherence of the light source, we use a focal spot as a linear X-ray source, which indirectly solves this problem. The linear focal spot source has good coherence in the wide direction on line. But there is no spatial coherence in the long direction of the line, and the details of the object in the long direction of the line will be lost, so we use the method of rotating the object to superposition the image of the object in multiple directions. In order to reconstruct the high-resolution image which can reflect the details of the object (chip), we compared the results with the results of micro-focal X-ray source coaxial imaging and large focal spot source imaging. The experimental verification based on linear focal spot source imaging is given in terms of coherence and flux. The phase contrast imaging method based on grating is presented. Up to now, Talbot-Lau and inverse Talbot-Lau methods have been developed, which require the grating to be high, so it is difficult to fabricate the grating. The inverse Talbot-Lau method is limited by the coherent length of the light source and the distance of the imaging system is very long. This paper studies the experimental acquisition technology of the displacement curve based on the integral effect of the detector in the grating phase contrast imaging method without analyzing the grating. Through the analysis of the effect of grating in Talbot-Lau interferometer, it is concluded that the main function of the analysis grating is to divide the image fringes and select the integral region. The sufficient conditions for the generation of displacement curves without analyzing gratings are obtained. The existence of displacement curves in different pixels is verified by experiments, on the basis of the measured displacement curves. The pixel optimization readout method is studied and the phase recovery of polyethylene rod is successfully carried out. Then the imaging experiment of biological sample (chicken claw) is carried out by using this method. Finally, a phase contrast image with clearer contrast and more abundant structure information is obtained, which can greatly shorten the length of the imaging system and has certain practicability.
【学位授予单位】：深圳大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O434.1

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