Research On Simulation And Imaging Method Of Computed Laminography

Industrial computed tomography(CT)is widely used in the field of nondestructive testing because it can detect the internal details of the object.However,CT has limitations on the detection of flat or shell plane objects.For example,the imaging field can not meet the requirements,and ray penetration difference is too large,etc.Computer laminography(CL)provides a better solution,which has attracted more and more attention.However,CL detection range is relatively narrow and not mature enough,so this paper studies a number of issues about CL,the main work is as follows:1.Introduce the research background and development of CL,compare the similarities and differences between CT and CL,and describe the basic principles of CL imaging system,components,as well as the functions of each component.The basic principle of the iterative reconstruction algorithm is introduced in detail,and the basic knowledge of the CL simulation system is briefly introduced as well.2.Based on the C programming language,CT/CL simulation program is written,which provides accurate projection data for the research of CL imaging technology in the following chapters.The simplified model of the scanning mechanism,the mathematical model of the X ray source,the sample and the flat panel detector are established,and the interaction process between the ray and the sample is simulated.Finally,CT simulation program is completed.According to the similarities and differences between the CT and CL scanning mechanism model,the CL simulation is based on the CT simulation by making some modifications to generate CL images.The reliability of the simulation is verified by the simulation modules of CT and CL,respectively.3.Some problems in CL reconstruction are studied.The ART algorithm is applied to CL reconstruction,and its implementation process is programmed based on the C programming language.The simulation model is reconstructed by using ART algorithm.In view of the large storage space of the projection coefficient,here proposes a new method,which can effectively reduce the storage space and improve the computed efficiency of reconstruction process.For the “adhesion” artifacts caused by the ART algorithm,total variation(TV)minimization is applied to CL reconstruction to remove the artifacts.To verify this method,some experiments are made.4.Design a new scanning method by combining limited-angle and CL imaging method,and the corresponding research is carried out.Here introduces the basic concept of data correlation,analyzes the influence of different inclination angles on the reconstruction results.Because of data truncation problem in CL imaging process,here combines limited-angle and CL.The corresponding experimental results demonstrate the validity of this method.