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