We review recent progress in the field of terahertz "T-ray" imaging. This r
elatively new imaging technique, based on terahertz time-domain spectroscop
y, has the potential to be the first portable far-infrared imaging spectrom
eter. We give several examples which illustrate the possible applications o
f this technology, using both the amplitude and phase information contained
in the THz waveforms. We describe the latest results in tomographic imagin
g, in which waveforms reflected from an object can be used to form a three-
dimensional representation. Advanced signal processing tools are exploited
for the purposes of extracting tomographic results, including spectroscopic
information about each reflecting layer of a sample. We also describe the
application of optical near-field techniques to the THz imaging system. Sub
stantial improvements in the spatial resolution are demonstrated.