Continuous-wave terahertz diffraction tomography based on digital holography

In this paper, we implemented diffraction tomography (DT) by using a continuous-wave (CW) terahertz (THz) source. An off-axis digital holographic interferometry was built to measure the complex amplitude distributions of the sample at various rotational angles. Based on the Rytov approximation, the three dimensional (3D) refractive index (RI) distribution of the polystyrene (PS) foam spheres was reconstructed by the filtered backpropagation (FBPP) algorithm. For enhancing the quality of the reconstructed RI tomograms, the auto-focusing algorithm was applied to correct the decentered error of the sample when placed on the rotation configuration. This study demonstrated that THz-DT can be applied to reconstruct the high-precision 3D RI distribution, which has extensive application prospects in 3D imaging and nondestructive testing.