Image Reconstruction of the Buried Metallic Cylinder Using FDTD Method and Ssga

This paper presents an image reconstruction approach based on the time-domain and steady state genetic algorithm (SSGA) for a 2-D perfectly conducting cylinder buried in a half-space. The computational method combines the finite difference time domain (FDTD) method and the steady state genetic algorithms (SSGA) to determine the shape and location of the subsurface scatterer with arbitrary cross section. The subgirdding technique is implemented in the FDTD code for modeling the shape of the cylinder more closely. In order to describe a a unknown 2-D cylinder with arbitrary cross section more effectively, the shape function is expanded by closed cubic-spline function instead of frequently used trigonometric series. The inverse problem is reformulated into an optimization problem and the global searching scheme SSGA with closed cubic-spline is then employed to search the parameter space. Numerical results show that the shadowing effect for the inverse problem in a half space results in poor image reconstruction on the backside of the cylinder. We propose the two-step strategy to overcome the shadowing effect. It is found that good imaging quality could be attained based on the proposed strategy.