Figure 4 Reconstruction of lossless cylinder with a contrast of 13.5. ลฝ . ลฝ . ลฝ . a True profile of the permittivity. b แ h Results of the permittivity derived from the first, fifth, tenth, fifteenth, seventeenth, eighteenth, and nineteenth iterations ลฝ . butions. The real profile is shown in Figure 3 a , and the reconstructed parameter profiles are plotted in Figures ลฝ . ลฝ . 4 b แ4 l . For the second numerical experiment, we choose a lossless cylindrical object with a peak permittivity contrast of ลฝ . 13.5. Figure 4 a shows the real parameter profile of the ลฝ . ลฝ . object, and Figures 4 b แ4
l exhibit the first, fifth, tenth, seventeenth, eighteenth, and nineteenth iterated parameter profiles reconstructed by the use of the present method. The results show that the method is able to handle, with relative ease, high-contrast profiles that would be difficult to treat with the use of the Born or the Born-iterative methods.
V. CONCLUSIONS
An effective nonlinear optimization scheme for reconstructing strongly scattering dielectric objects has been presented in this article. Future work will be directed toward the derivation of nonlinear objective functions that are simpler to work with than the one employed in the present approach.