Limited angle phase-contrast Terahertz tomography

Terahertz (THz) computed tomography is a powerful modality for the non-destructive inspection of low loss dielectric materials. However, in practice physical constraints can limit the available angular range. This restricted sampling results in severe artifacts such as elongation and blurring when using standard reconstruction techniques. In this study we propose a limited angle THz phase-contrast tomography approach to enhance 2D image fidelity under restricted sampling conditions. Utilizing a frequency-modulated continuous-wave (FMCW) radar system operating from 230 to 320 GHz, we retrieve the phase shift induced by the sample’s refractive index. To address experimental challenges, we developed a preprocessing pipeline incorporating 2D phase unwrapping and automated center of rotation correction via entropy minimization. We evaluate the performance of filtered back projection (FBP) against total variation (TV) regularization using a heart-shaped polyurethane foam phantom. The results demonstrate that while FBP suffers from significant distortion at a 90° angular range, TV regularization successfully recovers sharp material boundaries and maintains geometric integrity. To our knowledge, this is the first demonstration of limited angle reconstruction specifically for THz phase-contrast tomography. This technique facilitates a significant reduction in measurement time without compromising spatial resolution, offering a robust solution for high-throughput 3D THz inspection in constrained environments.