A Hierarchical Subspace-Based Optimization Method for Reconstruction of 2-D Uniaxial Anisotropic Scatterers Using Multi-Frequency Data

In this article, a hierarchical subspace-based optimization method (HSOM), which combines the subspace-based optimization method (SOM) and hierarchical strategy using multi-frequency data, is proposed to reconstruct 2-D uniaxial anisotropic scatterers. The hierarchical strategy utilizes the results obtained at lower frequencies to provide initial information for higher frequency inversion. The domain of scatterers is extracted from the domain of interest at lower frequencies according to the range-constrained Otsu thresholding method. Then, the inversion at higher a frequency only executes in the domain of scatterers. Compared with the frequency-hopping approach, this method can obtain higher quality reconstruction images with much lower computation loads. Numerical examples validate the efficacy of the proposed method.