Product Cad Model Of The Ct Slice Model Registration

There are some position and orientation problems when a 3D CT equipment undertakes nondestructive testing to industrial products. So product's CT slice model and its CAD model should be registered. Registration is an important problem in the field of graph and image processing. Now in our country a large amount of study is about planar registration study, three-dimensional registration study is few in industry field. For the registration of model, this paper takes into account gray information and image contour respectively. Registration method based on gray's deviation square sum and registration method based on inertia ellipse are put forward. In Microsoft Visual C++ and VTK's environment, the programming verifies the two algorithms by simulation experiment. Then evaluating registration parameters and theory values are compared, satisfactory results are received. The detail research works are as follows:· spatial transformation and re-sampling in registration. Spatial transform and re-sampling are carried out in three-dimensional model registration. Spatial transformation from skew CT slice model to its CAD model is established by transfer matrix and rotation matrix. In model's registration, image should re-sample to get transformed CT slice. This paper adopts bilinear interpolation and tri-linear interpolation to re-sample.· algorithm based on gray's deviation square sum. First the method proceeds to match gray centroid using one-order moment of image model. Then deviation square sum between product's image model and CAD model is defined as optimized object function. We search the minimum by the golden section method and make use of specified structure character to get the position and orientation registration parameters of spatial transformation. Finally spatial transformation from product's CT slice model to its CAD model is established according to registration parameters.· registration by ellipse matching and gray centroid. First this method extracts the contour points of CT slice images, then chooses extracted contour points as object. We can build up the inertia ellipses with the help of the moment of inertia and match these ellipses to obtain the parameters of the required spatial transformation. Thus registration between product's CT model and theory model is realized.· verifying two kinds of algorithms above by simulation experiments. For the registration of three-dimensional model, the programming realizes the two algorithms above in the environment of Microsoft Visual C++ and VTK. Then XY section image and YZ section image between registered three-dimensional CT model and CAD model are compared to verify validity and feasibility of algorithms.