  We present an implementation of the single-pixel imaging approach into a
terahertz (THz) time-domain spectroscopy (TDS) system. We demonstrate the
indirect coherent reconstruction of THz temporal waveforms at each spatial
position of an object, without the need of mechanical raster-scanning. First,
we exploit such temporal information to realize (far-field) time-of-flight
images. In addition, as a proof of concept, we apply a typical compressive
sensing algorithm to demonstrate image reconstruction with less than 50% of the
total required measurements. Finally, the access to frequency domain is also
demonstrated by reconstructing spectral images of an object featuring an
absorption line in the THz range. The combination of single-pixel imaging with
compressive sensing algorithms allows to reduce both complexity and acquisition
time of current THz-TDS imaging systems.
