Analyze Of Sensitivity Field Characteristics And Image Reconstruction For Electromagnetic Tomography

Electromagnetic tomography is a new process tomography which is based on the principle of electromagnetic induction. This paper will explore the sensitive features in different excitation mode as well as the image reconstruction algorithm of electromagnetic tomography. According to the principle of electromagnetic, when conductive material is being excited by Alternating magnetic from different directions, it will induce eddy current and in turn to change the electromagnetic characteristics of the original object space. The data from the detector coils around the object space will be used to reconstruct the conductive material distribution images.Through the theoretical study of electromagnetic tomography, this paper analysis the forward and inverse problems, and simulate the sensitivity characteristics of both parallel and single excitation coils mode with16exciting16detecting directions using the Finite element simulation software Ansys. Besides, the Landweber algorithm improved with regularization method is applied to the electromagnetic tomography. This paper has done the following work:1. Combined with home and abroad research of electromagnetic tomography, the forward and inverse problem has been researched based on the Maxwell equations group.2. The finite element simulation software Ansys has been used to solve the forward problem of electromagnetic. In order to get the forward problem solution, the extreme problem of Quadratic function is transformed to the common extreme problem of multivariate quadratic function with the help of finite subdivision method provided by Ansys.3. The sensitivity distribution of the modal with16exciting and16detecting direction has been calculated and compared in both parallel and single coil mode using Ansys.4. Analyzed some common image reconstruction algorithms of the EMT system, including linear back-projection method (LBP), Tikhonov regularization method, the neural network method, algebra ART and Landweber iterative method, Combined with finite element simulation software to get the prior condition, then with VC plus plus to simulate the LBP, Tikhonov regularization algorithms, and the Landweber algorithm is improved, the initial value which is calculated by LBP was instead by Tikhonov reconstruction, at last analyzed regularization factors and iteration step to the influence of Landweber algorithm based on reconstruction.