Cone beam CL (Computed Laminography) geometric full-parameter iterative correction method

Abstract

The invention discloses a cone beam CL (Computed Laminography) geometric full-parameter iterative correction method, which overcomes a defect that a CL geometric correction method in the prior art only corrects part of geometric parameters. The method disclosed by the invention comprises the steps of determining sensitive parameters for a CT (Computed Tomography) geometric parameter correction method in geometric parameters of a CL system; enabling the sensitive parameters to act as variables to be solved, and rebuilding an objective function containing the sensitive parameters according to a geometric error between an actual system and an ideal system of CL; and performing iterative solving on the objective function by using a Gauss-Newton algorithm. The sensitive parameters are radiation source focus coordinates S (sx, sy, sz), radiation source focus projection coordinates P (px, 0, pz), a spindle rotation angle eta and a geometric magnification ratio t. The invention further provides a geometric calibration algorithm suitable for the cone beam CL, which can solve all geometric parameters of the system. Simulation experiment results show that the convergence speed is high and the calculation accuracy is high. The accuracy for solving the radiation source focus projection longitudinal coordinate, the radiation source focus coordinates and the geometric amplification ratio is improved.

Description

technical field [0001] The invention relates to a method for correcting geometric parameters of a cone-beam CL, in particular to a method for iteratively correcting geometric parameters of a cone-beam CL. Background technique [0002] Computed Tomography (CT) technology can obtain the three-dimensional structure information inside the detected object without damage, and reconstruct the three-dimensional image of the object, which is widely used in non-destructive testing, medical diagnosis and other fields. However, in practical applications, when encountering flat objects such as integrated circuits and printed circuit boards, due to the limitation of detection space and ray energy, the CT imaging effect is not ideal. In order to avoid this limitation, computer tomography (Computed Laminography, CL) technology has been developed, which has unique advantages for the detection of flat objects. When the structure of the CL system is imaged, the light source and the detector d...

AI Technical Summary

Problems solved by technology

Among the traditional CT geometric correction algorithms, one type usually ignores the detector pitch angle and can only solve some geometric parameters; while the other type can solve all geometric parameters but usually requires complex calibration phantoms

In 2013, Zhang proposed an iterative cone-beam CT circular trajectory geometric calibration algorithm based on a double-sphere calibration phantom. The calibration phantom used in this algorithm is simple and can solve all geometric parameters, but it cannot be directly used for CL. Because the algorithm is greatly affected by the inclination angle of the rotating shaft in CL, the solution accuracy of some parameters is inaccurate, which affects the quality of the reconstructed image

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