Contrast Source Inversion-Based Multilayered Object Analysis for Terahertz Wave Imaging

A complex permittivity profile reconstruction for multilayered objects was presented in this study by incorporating compressed sensing (CS)-based thickness estimation with contrast source inversion (CSI) non-linear inverse scattering (IS) method using a terahertz (THz) frequency band. Several studies investigated permittivity estimation for multiple layers. However, they require a prior knowledge of the thickness of each layer. Moreover, a critical problem in this field is the simultaneous estimation of both the dielectric constant and the thickness of each layer. To address this, a super-resolution thickness estimator using a CS filter and the CSI-based dielectric profile reconstruction scheme was used. This problem was effectively solved by introducing the cost function estimated using the CSI scheme, where the number of layers is given. The finite-difference time-domain (FDTD) numerical test indicated that the proposed method provides an accurate estimation of the thickness and dielectric profile in double-layered objects.