The name is absent

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2.1.4 Terahertz imaging applications

The idea of using terahertz radiation for imaging and sensing, in analogy to the many
similar applications of both optical and microwave radiation, has been discussed for at
least several decades. Early researchers speculated on the use of sub-millimeter waves
for seeing through fog or haze with reduced scattering losses, locating objects hidden
in camouflage, and detecting defects in optically opaque materials, in addition to other
research areas such as high bandwidth communications and metrology. More recently,
this list of promising applications has grown to include security screening such as
weapon detection [48,49], quality control such as accurate measurement of paint
thickness [50], non-destructive testing such as detection of defects inside spacecraft
foam insulation [51], and spectroscopic characterization of materials such as illict
drug detection [52]. Many of these ideas exploit the unique properties of terahertz
radiation which include the transparency of common packaging materials such as
cardboard and plastics, the submillimeter wavelength which permits imaging with a
diffraction-limited resolution similar to that of the human eye, and the fact that many
interesting materials exhibit unique spectral fingerprints in the terahertz range which
can be used for identification and chemical analysis. Due to its non-invasive nature,
THz imaging research have also expanded into the fields of medical diagnosis [53] and
the study of historical art such as mural paintings [54].

2.2 Compressive sensing (CS)

2.2.1 CS background

Traditionally, digital signal processing involves first uniformly sampling a signal and
then processing it in some way that enhances it and/or prepares it for storage or

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