Computed Tomography for Refractive Index using an X-ray Shearing Interferometer

本研究的目的是证明所提出的剪切干涉仪的有效性，并将其应用于利用计算机断层扫描重建折射率分布。我们得到了以下结果：1。用自制的x射线剪切干涉仪测量了x射线穿透塑料制品的干涉强度分布和相位分布。在测量中，我们使用了点x射线源和闪烁计数器，并对物体进行了机械扫描。利用该系统可以检测到小至1 μm的厚度差异，灵敏度高于通常的强度检测。利用线x射线源和CCD相机构建了一套x射线剪切干涉仪系统。利用该系统无需机械扫描即可获得塑料物体的干涉x射线图像。在该系统中引入相移法，测量了x射线穿透由塑料制成的物体时的相位差分布。利用x射线动态衍射的球面波前理论对干涉仪的光束宽度进行了分析，表明剪切干涉仪可达到的球面分辨率为几微米。我们设计了分离式干涉仪，但由于硅晶体中残余应力的存在，干涉仪工作效果不佳。我们找到了另一种制作干涉仪的方法，正在制作中。本工程的相位差测量是用旧的干涉仪进行的。根据得到的相位分布编制了计算折射率分布的程序，并通过模拟研究了用自制的x射线剪切干涉仪重建CT的可能性。我们用光栅剪切干涉仪在可见光谱和CT算法中重建了流体流动剖面上的动态折射率分布，证明了剪切干涉仪的有效性。利用x射线剪切干涉仪的数据，得到了轴对称折射率分布

The object of the present investigation is to show the effectiveness of the proposed shearing interferometer and to apply it to the reconstruction of refractive index distribution using computed tomography. We obtain following results :1. We measured interferometric intensity distribution and phase distribution of the X-ray penetrated through objects made of plastics with the fabricated X-ray shearing interferometer. For the measurement, we used a point X-ray source and scintillation counter and scan the object mechanically. With this system, we can detect thickness difference as small as 1 μm, with sensitivity higher than the usual intensity detection.2. We constructed a X-ray shearing interferometer system with a line X-ray source and a CCD camera. With this system we obtain interferometric X-ray image of plastic object without mechanical scanning. By introducing phase shifting method to this system, we measured phase difference distribution of X-ray penetrated through objects made o … More f plastics.3. We analyzed the beam width in the interferometer with the spherical wave-front theory of X-ray dynamic diffraction and show that the attainable spherical resolution of the shearing interferometer is a few micron.4. We constructed interferometers which were planned to make separated type, but the interferometer did not work well perhaps because the residual stress in the Si crystal. We find another method of making the interferometer and are under way to make it. Phase difference measurements in this project are made with the old interferometer. .5. We made a program for calculating the refractive index distribution from the obtained phase distribution and investigate the possibility of CT reconstruction with the fabricated X-ray shearing interferometer by simulation.6. We showed effectiveness of the shearing interferometer by reconstructing dynamic refractive index distribution on a section of a fluid flow with a grating shearing interferometer in the visible spectrum and CT algorithm.7. We obtain axially symmetrical refractive index distribution from the data taken with the X-ray shearing interferometer Less