Hidden object detection: security applications of terahertz technology

Abstract

Recent events have led to dramatic changes to the methods employed in security screening. For example, following the failed shoe bombing, it is now common for shoes to be removed and X-rayed at airport checkpoints. There is therefore an increasing focus on new technologies that can be applied to security screening, either to simplify or speed up the checking process, or to provide additional functionality. Terahertz (THz) technology is a promising, emerging candidate. In previous publications we have shown how our THz pulsed imaging systems can be used to image threat items, and have demonstrated that explosive materials have characteristic THz spectra.1 We have also demonstrated that nonmetallic weaponry can be imaged when concealed beneath clothing. In this work we examine more closely the properties of barrier and potential confusion materials. We demonstrate that barrier materials have smooth spectra with relatively low attenuation. We further demonstrate that the terahertz spectra of several common chemicals and medicines are distinct from those of threat materials.

Terahertz spectroscopy of explosive materials

“…Subsequently, measurements by other groups [2][3][4] have validated these results and, below, we report measurements carried out by several different techniques and on different samples -providing further validation.…”

New frontiers for infrared

“…or even high, performances sources and sensors have made the previously un−used terahertz frequency bands accessible for spectros− copy analysis and even for imaging systems. Nowadays, applications include detection of biological and chemical hazardous agents, explosive detection, applications in build− ing and airport security weapons concealed underneath clothing (airports), environmental monitoring and control, product inspection (industry), spectroscopy (chemistry, as− tronomy and space research), material characterization (physics) to biomedicine diagnostics (new detection sys− tems for cancer pathologies) and wide bands secure point to point TLC and high definition SAR [79][80][81][82]. THz transmission properties have open new applications thanks to the fact that THz waves can penetrate through materials opaque to other parts of the EM spectrum.…”

Terahertz Frequency Domain Spectroscopy Identification System Based on Decision Trees

“…But, the reliance on human input is questionable because of few reasons [1]. The most important is, that for large data sets, the manual process can be slow.…”

“…The societal, economic, and political sphere are interested in having all technological options exhausted to prevent such attacks. So far, no stand-o detection devices are available that will detect potential assassins from a safe distance [1]. In the eld, well-trained snier dogs are the best alternative for sensing explosives remotely, albeit at distances of no more than a few meters.…”