Sunday, November 17, 2013

TeTech blog-Terahertz Standoff Detection Systems for Security Applications





Benefiting from unique characteristics, THz technology has demonstrated a great potential to address many of the challenges facing modern security and surveillance systems. Therefore, THz technology has drawn a lot of attentions and received huge investments.  Some major factors are contributing in capability of THz technology to address the existing problems in security applications. The ability of “seeing through” concealing barriers might be the most fascinating aspect of THz technology as the THz waves can readily transmit through the most conventionally opaque materials such as cloth, paper, wood, and plastic. As opposed to the x-ray package inspection systems which raise health concerns, THz radiation is safe and non-invasive due to its low energy photons. THz imaging systems therefor has been applied in different locations such as airports to provide standoff accurate detection for packaged contraband. To this end, the systems usually work in single point reflection mode measurements where the high power THz signal is focused on the object under inspection, and the reflected signal which depends on the characteristics of the object, is detected. The whole image of object can be created through raster scanning. Recently, the New York police department has also employed the THz technology for detecting firearms concealed under cloth.
Additionally, many chemical materials of interest can be identified using THz spectroscopy due to their distinctive finger prints in THz range of frequency. Most of the explosives (TNT, RDX, HMX...) molecules show unique spectral feature in THz range as a consequence of being organics compounds. Other existing explosives detection technologies such as X-ray imaging, nuclear detection and infrared imaging cannot identify the type of explosives. They are also either harmful for human or blind to the opaque packages. THz technology is also able to detect much greater amount (in range of milligrams) of energetic materials. The reflection scheme is applied for explosives inspection too where the received signal is compared with the library of the fingerprints to identify the explosive type.
Through improvement of THz radiation efficiency and also development of the THz scanners in array configuration (THz camera), a high speed and high performance THz security system can be realized. The system would be an excellent candidate to eliminate the aforementioned problems in other technologies and be widely used for security purposes.

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