基于分析晶体成像投影偏移研究

投影偏移将严重影响基于分析晶体成像系统的信息提取精度和图像质量。从基于分析晶体成像系统的原理出发，建立了光路模型，分析了产生投影偏移的主要原因，计算机模拟研究了投影偏移对折射角信息提取的影响。结果表明，投影偏移主要由分析晶体本征摇摆曲线宽度和折射角所产生。本征摇摆曲线宽度将导致相邻像素之间的射线随分析晶体的摇摆相互偏移，当样品未被射线完全覆盖时，边界像素的摇摆曲线将出现形变，虚像素将出现计数并形成畸形摇摆曲线。折射角引起的投影偏移将使摇摆曲线形状和高度发生改变，随折射角增大，出现像素错位，其影响折射角信息提取的正确性。本征摇摆曲线宽度和折射角共同产生投影偏移并影响折射角信息的提取。

Study of Projection Offset in Analyzer-based Imaging

The projection offset significantly affects the extraction accuracy and image quality in analyzer-based imaging (ABI) system. Based on the principle of the ABI system, optical models were established to study the main causes of projection offset. The effect of projection offset on the extraction of refraction-angle was studied by computer simulation. The results show that the projection offset is mainly caused by the width of the intrinsic rocking curve and the refraction-angle. The width of the intrinsic rocking curve causes the crosstalk of X-ray between adjacent pixels with the rocking of the analyzer. The rocking curve of the boundary pixel deforms, and for the virtual pixel counts appear and abnormal rocking curve forms when samples are not completely covered with the beam. Both shape and height of the rocking curve change by the projection offset caused by refraction-angle, and pixel shifting occurs with the increase of refraction angle, further affecting the correct of the extraction of refraction-angle. The width of the intrinsic rocking curve and the refraction-angle together produce projection offset and affect the extraction of refraction-angle.