Analysis And Experimental Research Of Geometric Errors Of A New-type Microscopic Computed Laminography System

As we all know,since the invention of X-ray computed tomography(X-CT or CT)in the last century,it has been widely used in medical,industrial and other fields,and the technology development is becoming more and more mature.However,due to the limitation of its geometric structure and scanning mode,it is difficult to obtain or provide high-precision and high contrast tomographic images for the nondestructive testing of large-scale plate structure objects.For this kind of non-destructive testing object,computed laminography(X-CL or CL)with oblique scanning mode will increasingly play its unique role.Because of its special scanning mode,CL technology can scan and imaging from the length or thickness direction of the plate object,so as to obtain the internal structure information of the object.On the other hand,for the limited-angle scanning situation,the imaging quality and accuracy of CL is significantly higher than that of CT.Because of these characteristics,CL technology has broad application prospects in printed circuit board(PCB),paleontological fossils,chips and so on.Based on the sub project of "X-ray three-dimensional laminography imager" of the national key scientific instrument and equipment R&D program of the Ministry of science and technology,"Research and development of X-ray 3D computed laminography",this paper carried out the research work based on a new-type micro CL(Micro-CL)system.Compared with the conventional CL system,the geometry of Micro-CL system is more complex,so its error calibration is more difficult.The main content of this paper is to carry out simulation and experimental research on geometric errors of the Micro-CL system.Through simulation and experiment,the influence of various errors on the imaging quality of the Micro-CL system is studied and analyzed,so as to guide the geometric error calibration of the actual system.This thesis firstly introduces and analyzes the basic principles and error classification of geometric errors of the radiographic imaging system in detail.Then the basic components and geometric structure of the Micro-CL are introduced in detail,and the types of geometric errors that may be generated by the imaging system in practical applications are discussed.In the part of mathematical modeling,this thesis coordinates the Micro-CL system,and analyzes the existing form and expression of geometric errors for each component.The complex geometry structure and multi-degree of freedom of the Micro-CL make the geometric errors of different parts have certain correlation.The analysis of single error often needs to consider the global impact,which is also a major difficulty of this study.In the simulation experiment,this thesis first classifies geometric errors of the system,and then simulates the errors under the condition of the same and different magnification of the system.For the processing of reconstruction results,the difference image and gray value curve are used to observe the influence of errors directly,and the normalized distance criterion and structural similarity are introduced to quantitatively analyze the scope of geometric errors.In addition to simulating the most commonly used synchronous circular trajectory rotation scanning mode of the Micro-CL system,this thesis also carries out simulation experiments on the geometric errors of object rotation mode and translation scanning mode,and then studies and analyzes the possible influence on the imaging quality.