Physics-Guided Terahertz Computational Imaging: A tutorial on state-of-the-art techniques

Visualizing information inside objects is an everlasting need to bridge the world from physics, chemistry, and biology to computation. Among all tomographic techniques, terahertz (THz) computational imaging has demonstrated its unique sensing features to digitalize multidimensional object information in a nondestructive, nonionizing, and noninvasive way. Applying modern signal processing and physics-guided modalities, THz computational imaging systems have now been launched in various application fields in industrial inspection, security screening, chemical inspection, and nondestructive evaluation. In this article, we review recent advances in THz computational imaging modalities in the aspects of system configuration; wave propagation and interaction models; and physics-guided algorithms for digitalizing interior information of imaged objects. Several image restoration and reconstruction issues based on multidimensional THz signals are further discussed, which provides a crosslink among material digitalization, functional property extraction, and multidimensional imager utilization from a signal processing perspective.