Research On Inter-slice Aliasing Artifacts Removal Algorithm For CL Imaging Of Plate-like Objects

Computed Tomography(CT)is a well-established non-destructive testing technology,which has been widely used in medical diagnostics,aerospace,precision manufacturing,geology and archaeology.However,the combination of scanning characteristics and imaging principles make CT unsuitable for the testing and imaging for plate-like objects(PLO).In contrast,Computed Laminography(CL)has become a powerful tool for non-destructive testing of PLO due to its different scanning characteristics from CT.One of the serious challenges of current CL imaging is the inter-slice aliasing artifacts in the form of structural blurring in reconstruction images due to incomplete scan data.In this paper,an inter-slice aliasing artifacts removal algorithm for CL imaging of PLO is investigated,with the following main work:1.The history of the development of CL is introduced;the current domestic and international research trends in the field of CL imaging are investigated;the common scan trajectories,representative image reconstruction algorithms and deblurring algorithms in CL technology are described.2.The Automatic Focal Plane Identification Shift and Add(AFI SAA)algorithm is proposed to improve the reconstruction accuracy of SAA;based on the AFI SAA,an Iterative Difference Dealiasing(IDD)algorithm for linear CL system is proposed;a linear CL simulation system is established and several simulation phantoms are designed for simulation experiments;experimental phantoms with multi-layer structures are designed for real scanning experiments;the simulated and experimental data are reconstructed using the SAA and IDD algorithms respectively,and quantitative evaluation metrics are used to compare the reconstruction results;the comparison results showed that the IDD algorithm can effectively eliminate the inter-slice aliasing artifacts in reconstruction images and improve the quality of the reconstructed images;the same simulation phantom is reconstructed by filtering backprojection,algebraic reconstruction and IDD algorithm and the reconstruction results show that The IDD algorithm can recover the image details better with higher reconstruction efficiency;motion errors are added to the simulation system to evaluate the error resistance of the IDD algorithm,and the results show that the image reconstruction quality of the IDD algorithm is largely unaffected when the error is less than 100μm.3.The applications of the IDD algorithm are extended.The application of the AFI SAA in IDD algorithm is extended to the layer spacing measurements and the layer spacing of the seven-layer structural phantom in the simulation experiment is correctly measured;the application of the IDD algorithm is extended to the circular trajectory type CL scan mode,thus eliminating the structural artefacts parallel to the direction of motion(X direction);the effects of the number of samples,layer spacing,layer attenuation coefficient and the number of layers to be reconstructed on the reconstruction effect of the IDD algorithm are analyzed separately,demonstrating that the IDD algorithm can achieve clear reconstruction of PLO with multiple layers of internal structure with very sparse sampling,and the larger the layer spacing,the better the dealiasing effect.