Fast Three-Dimensional Image Reconstruction of Targets Under the Illumination of Terahertz Gaussian Beams With Enhanced Phase-Shift Migration to Improve Computation Efficiency

In this paper, an enhanced phase-shift migration-based image reconstruction (EPSM-IR) algorithm was investigated to improve the computation efficiency for three-dimensional (3-D) terahertz (THz) holographic imaging. In the proposed algorithm, an appropriate decomposition of the phase-shift operator was performed and a fast algorithm based on FFT was introduced to solve the integral transformation which is the most time-consuming step in the conventional phase-shift migration. The analytical expression of the reconstructed 3-D point-spread function (PSF) was derived based on the EPSM-IR algorithm. The reduction of the computation cost was evaluated quantitatively as compared with the conventional phase-shift migration. Simulation results with fairly good agreement were given to verify the proposed algorithm. Finally, a monostatic prototype imager with a Gaussian beam transceiver was designed for the proof-of-principle experiments in the 0.2-THz band. The 3-D image results of a target with metal strips and a mannequin with concealed threat objects were given to demonstrate the effectiveness and the efficiency of the 3-D EPSM-IR algorithm.