8 December 2004 Stand-off detection of hidden threat objects on personnel at checkpoints and in public areas using active millimetre-wave imaging
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The use of millimetre-wave imaging to identify threat objects such as guns and bomb material concealed on the person is well documented. However, the technology has been hindered by the performance and cost barriers typically associated with imaging at mm-wave frequencies. A novel scanning technique that minimises the receiver count while operating at very high efficiency levels has made it possible to build a cost-effective and high-performance mm-wave imager that can make security screening a commercial reality. The imager design allows for either passive or active operation and its compact form factor is suitable for practical installation in security channel situations. The uses of this technology include portal screening of personnel for high-resolution imaging of concealed threat objects or longer distance surveillance type monitoring of checkpoints and crowds. This presentation details the use of the imager in an active configuration to observe a checkpoint or crowd scene at stand-off distances of up to 50 metres. Target objects to be detected are the hidden metal components associated with suicide bomb constructions. A typical bomb consists of several explosive filled pipes strapped to the body or clusterings of small metallic objects embedded in explosives. Trials at 94GHz have yielded positive results by showing the presence of concealed metallic objects on people at distances of 25 metres. Objects detected have included simulated bomb constructions such as groups of metal pipes and clusters of nuts and bolts. These tests have been conducted using a Gunn based CW source and direct detect receiver unit. Further enhancement of the system includes the use of an FMCW front-end configuration.
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Rory S. Doyle, Brendan N. Lyons, Alan H. Lettington, Tony McEnroe, John Walshe, John McNaboe, Peter Curtin, Stan Bleszynski, "Stand-off detection of hidden threat objects on personnel at checkpoints and in public areas using active millimetre-wave imaging", Proc. SPIE 5619, Passive Millimetre-Wave and Terahertz Imaging and Technology, (8 December 2004); doi: 10.1117/12.578056; https://doi.org/10.1117/12.578056

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