光学耦合CT系统几何位姿参数标定方法  

Geometric Parameters Calibration Method for Optically CCD-coupled CT System

作　　者：邹晶[1] 蒋一鸣 胡晓东[1] 赵金涛 ZOU Jing;JIANG Yiming;HU Xiaodong;ZHAO Jintao(School of Precision Instrument and Opto-electronics Engineering,Tianjin University,Tianjin 300072,China)

机构地区：[1]天津大学精密仪器与光电子工程学院,天津300072

出　　处：《光子学报》2022年第4期256-264,共9页Acta Photonica Sinica

基　　金：国家自然科学基金(No.61771328)。

摘　　要：利用光学耦合CT系统对样品进行高分辨清晰成像的前提是准确求取系统的几何位姿参数。为求取系统几何位姿参数,针对光学耦合CT系统,提出一种数学参数定标模型。该模型利用由两个微球组成的双微球模体,通过对模体进行圆周扫描成像,获取双微球投影构成的椭圆轨迹,建立椭圆方程与几何位姿参数之间的数学关系,从而求解几何位姿参数。实验结果表明,将利用该数学模型求解的几何位姿参数代入重建算法中,重构图像质量比代入前有明显提高,边缘重叠及模糊现象得到改善,校准后图像细节分辨更加清晰,重建效果更好。Micro-computed tomography is widely used for medical diagnosis and non-destructive testing since the 1970s. In three-dimensional micro-CT imaging,the quality of the reconstructed images depends highly on the precision of the geometric parameters of the system. Image quality could be severely degraded by misaligned parameters,resulting in artifacts,blur and lower resolution in images,especially for CCDcoupled CT system(CCT system). Therefore, high-precision methods for estimating CT system parameters are necessary. Different research groups have proposed various methods to estimate geometric parameters for fan-beam CT or cone-beam CT. In terms of data acquisition methods,the main methods can be categorized as multi-angles projection and single-angle projection. However,due to the narrow field of view caused by the ultra-high resolution of the CCD-coupled detector,neither of these two methods can be applied to CCT system directly. Generally,a CCT system consists of an X-ray source,a CCD-coupled detector,and a precision rotation stage for placing samples,in which the X-ray source and detector are distributed on both sides of the sample. During scanning,the sample rotates around the rotation axis,while the X-ray source and the detector remain stationary. In an ideal CCT system,strict geometric alignment must be satisfied. It can be summarized as follows:Firstly,the X-ray focal spot,the axis of the rotation,and the center of the detector should be in a plane;secondly,the straight line which passes the focal spot and the detector center,should be perpendicular to the axis of rotation and the detector;thirdly,the axis of the rotation should be parallel to the row of the detector. Basing on precious studies,there are five geometric parameters to be calibrated totally in a CCT system. We conclude all the calibrated parameters as follows:1)u0,v0are projection coordinate of the X-ray source spot on the detector;2)η is the angle of detector tilt around X axis;3) R is the distance between X-ray source and rotation axis;4) D

关 键 词：光学耦合CT系统 几何位姿参数 系统标定 微球模体 图像重建 

分 类 号：TH742[机械工程—光学工程]