Complex-Product Oriented Industrial CT Image Reconstruction & Analysis

In virtue of 2D and 3D image reconstruction from X-ray projections, people can get the interior information of an object in a non-destructive way and carry out the inner structure interpretation and analysis. Appeared firstly in the medicine field, 2D and 3D image reconstruction technology is the basic of the modern instruments such as CT and MRI and is widely applied in various domains including reverse engineering, non-destructive test, geology exploration and archaeology.However, there are still many key problems unsolved, especially in the ICT based industrial image reconstruction aspect because of some characteristic of industrial products such as the complex part structure, huge volume and multiple styles etc. Aiming at the non-destructive test and reverse engineering on complex assemblies and huge products in the field of aviation and astronomy, this thesis discusses some key and difficult issuses in 2D and 3D image reconstruction process to promote the development of CT technology. The main research contents and contributions in the thesis are as follows:Projection simulation for assembly products: Simulation technology is introduced to the image reconstruction and an assembly-oriented projection simulation system is developed to provide abundant research data for following image reconstruction. Different from traditional ICT simulation systems which are single part oriented, we studied the characteristics of multi-part and multi-material case for ICT simulation of assembly product, and realize system modeling by using objected-oriented modeling method. At last, the assembly is well modeled and the simulation system is realized for assemblies, projection data can be got by arbitrary scan style and in arbitrary projection angle.Slice image reconstruction from incomplete projections: Slice reconstruction theory is analyzed firstly, and three kinds of incomplete projection, hollow in center region and sparse viewing angle and limited projection angle range, are considered respectively according to the projection style. The projection rays supplement approach, joint two-grade neural network approach and genetic reconstruction algorithm are proposed respectively for above three cases to realize slice reconstruction from incomplete projections. The reconstruction effect and efficiency are analyzed, and the reconstruction for compound incomplete projection case is also studied.Parts-oriented decomposing and assembly relation recognition for assemblies: 3D reconstruction from slices for an assembly is a difficult task because the parts in it interfere with each other and the contours in adjacent slices can't bematched and tiled directly. This thesis studies this issues in detail. Firstly the contour tree with gray level for a slice and the contour forest for whole slices are established, and then based of them, all the parts are decomposed and contour forests for each part are set up to prepare for part reconstruction, at last the assembly relations between parts are recognized through contour tree and constructional relation figure is generated.> Part's 3D surface reconstruction from slices based on the part slice tree: Aiming at the matching problem caused by multi-branch, distortion or high complexity of the industrial product, we proposed a series of algorithms including global matching using ellipse parameter, local matching for contour segment, branch disposal through slice projection and post-matching based on area relations to implement matching between slices and part's 3D reconstruction.> Knowledge based 3D-feture recognition and representation: one of the differences between industrial part and human organ is that the former often contains a lot of 3D geometry features and could be described in total. So some common features and their corresponding slice contour as well as contour series are summarized as knowledge in the thesis, and a knowledge base is set up. By knowledge-based feature recognition, the relationships among all features are analyzed and a feature tree for the part is formed. To facilitate the data exchange among different applying systems, XML is utilized to represent parts instead of traditional triangle surface representation method.> Prototype system design for 2D and 3D industrial image reconstruction and analyze: By using dynamic library technology and VTK (visualization tool kit), a prototype system named ICT-SliceVolume is designed and implanted, the system integrates not only most research results but also some necessary algorithms for industrial image reconstruction to validate the key technologies proposed in this thesis.This research work is sponsored by the two funds of China Aeronautical Foundation Science Funds& Astronautical Innovation Funds (99H53111 and 2001 [181]), and it reflects the author's main research results since Mar. 2000.