Research On 3-Dimensional Image Reconstruction For Electrical Capacitance Tomography

It is important measuring the parameters of two-phase flow measurement for industrial and scientific research. Electrical capacitance tomography (ECT) is one of Process tomography (PT) technique which is based on capacitance sensor, it can provide interior behavior 2/3 dimension visualizing information in process equipment such as closed pipe, vessels and so on in real time. ECT has the advantage of being non-intrusive, fast in response, simple in structure ,high safety and low in cost, so it is one technique which has great developing potential in field of petroleum ,chemical engineering and so on. This dissertation investigates the method of reconstructing 3D surface for ECT which is based on the research of 2D image reconstruction algorithm for ECT , the technique charaters of ECT and the method of 3D reconstruction applications in medicine. A visual reconstruct experimental soft system based on PC and Windows OS platform is designed which supplies the users with an inter-communicating tool in real time, and it is applied to the visualzation experiment.The main contributions and works are as follows:1. The ECT basic principle,system structure,technique characters,researches on application statue ,future development prospect and so on are synthesized summarized.2. Some existence typical 2D reconstruct algorithms of ECT are analyzed and compared in this article. An optimized interative image reconstruction algorithm is adopted to reconstructed images which are the base of the research on 3D image reconstruction.3. The basic principle and some algorithms used wildly of 3D image reconstruction are analyzed. The development and application status of 3D image reconstruction are summarized. We do some research elementarily in 3D reconstruction algorithms based on 2D cross sections. A method of reconstructing 3D surface for ECT which speed is fast is proposed: Firstly, the pre-processing includes extracting, thinning , and trailing the contours .Secondly, contour correspondence is operated for each contours on two adjcent cross sections , an algorithm based on equal-longitude position adjusted profile weighted averaging to generate matching outline is adopted. Finaily,the method of short-diagonal is used to reconstructingtriangle surface between two adjacent contours. The simulate experiment result shows the method can reconstruct 3-D surface of object efficiently,and the speed of reconstruction is fast.4. We design and implement a experimental soft system of 3D image recontruction for ECT by Visual C++6.0 and OpenGL. The system supplies the users with an inter-communicating tool in real time,and it supplies the operation of move,zoom in,zoom out,circumrotate and so on. It is easily to measure the volume of the discrete-phase in two-phase flow in a pipe based on the 3D reconstruction image.The 3D reconstrution images and the result of volume indicate the more sections interpolated,the better the 3D reconstruct image will be,but not the less the volume error will be.