Research On Multiple Dielectric Objects Hybrid Electromagnetic Inverse Scattering Imaging Algorithm

The inverse scattering of electromagnetic field has the ability to infer features and properties of unknown targets.In recent years,it has been widely used in various fields of society,such as geophysics,medical diagnosis,nondestructive testing,biological research and scientific exploration,such as geophysics and medicine.diagnosis,nondestructive testing,biological research and scientific exploration.Due to the multiple scattering effects and the interaction of the incident electromagnetic wave with the medium target,the received electric field parameters(dielectric constant and conductivity)of the scattered field and the medium target are nonlinear,and the dimension of the measured scattering field is usually much smaller than the dimensions of the parameters unknown and to be estimated make the electromagnetic field integral equation inherently nonlinear and ill-conditioned.For the nonlinear problem of the integral equation of electromagnetic field,mainly from the following two aspects,First,linear measurement model,such as direct sampling method(Direct Sampling Methods,DSM),the algorithm can be quickly and qualitatively reconstruction,the calculation cost is low,but There are great limitations,and it is impossible to quantitatively reconstruct the electrical performance parameters.Second,nonlinear measurement models such as Contrast Source Inversion(CSI),Subspace Optimization Method(SOM).This type of algorithm can solve the shortcomings of the direct sampling method that cannot reconstruct the electrical performance parameters,but the computational cost is much higher.In view of this,for high-contrast media scatters,this paper proposes a hybrid algorithm that combines the ideas of DSM algorithm and SOM algorithm,inherits the advantages of each method,first using the DSM algorithm to quickly reconstruct the prior information of the target position,shape size and number,and then based on the SOM algorithm combined with the prior information to reconstruct the spatial distribution of the permittivity and conductivity,and finally the measured data provided by the Fresnel laboratory the results obtained from the inversion are verified.It can be seen that the hybrid algorithm can significantly reduce the computational complexity while keeping the imaging accuracy similar.For the ill-posed problem of the electromagnetic field integral equation,the regularization method is mainly used to obtain the solution of the equation in the sparse domain.In this paper,two nonlinear inverse scattering algorithms based on sparse constraints are proposed,and truncation and iteration are used to achieve sparseness of the solution.Finally,the contrast source inversion algorithm is deduced from 2D to 3D.The reconstruction results show the effectiveness of the 3D inverse scattering imaging algorithm based on the contrast source inversion method.