基于轮廓先验约束的复杂异形工件CT成像方法研究

Research on CT Imaging Method of Complex Shaped Workpiece Based on Contour Prior Constraint

在X射线CT成像检测系统中,复杂异形工件由于结构复杂,散射、硬化等现象较严重,而且在部分投影角度上,由于在射线透照方向上的有效厚度差异大,固定能量的射线剂量与厚度不匹配,投影数据质量较差,传统的CT重建算法得到的重建图像质量低,边缘模糊,无法获取工件的完整轮廓信息.为此文章研究了一种基于轮廓先验约束的复杂异形工件CT成像方法.首先利用双目立体视觉技术获取工件的轮廓信息,根据双目坐标系与CT坐标系间的空间位置关系完成先验图像的配准;然后将轮廓先验纳入到CT重建过程中并结合TV正则化进行轮廓约束重建.实验结果表明,该方法能够有效地抑制伪影和噪声,保留重建图像的边缘,改善重建图像质量,有助于提高复杂异形工件缺陷检测的可靠性.

In the X-ray CT imaging inspection system,due to the complicated structure of complex shaped workpieces,scattering,hardening and other phenomena are more serious.At some projection angles,due to the large difference in effective thickness in the ray transillumination direction,the fixed energy ray dose does not match the thickness,the quality of the projection data is poor,the reconstructed image obtained by the traditional CT reconstruction algorithm is of low quality,the edges are blurred,and the complete contour information of the workpiece cannot be obtained.In this paper,a CT imaging method for complex shaped workpieces based on contour prior constraints is studied.Firstly,the binocular stereo vision technology is used to obtain the contour information of the workpiece,and the registration of the a priori image is completed according to the spatial positional relationship between the binocular coordinate system and the CT coordinate system.The contour prior is then incorporated into the CT reconstruction process and contour constrained reconstruction is performed in conjunction with TV(Total-variation)regularization.The experimental results show that the proposed method can effectively suppress artifacts and noise,preserve the edges of reconstructed images,improve the quality of reconstructed images,and improve the reliability of defect detection of complex shaped workpieces.