EMBody - Next generation electromagnetic walk by body scanners

点击翻译按钮获取中文摘要

The project is structured with three complementary and interdependent aspects, balancing developmental and strategic research work, with corresponding short / long term goals. Each of the three aspects has clearly defined work packages. The first aspect is the use of tomography to enhance the performance of WTMD's by exploiting the coupling between multiple combinations of coils in the array. Present systems generally use only the coupling between dedicated coil pairs and ignore the information available from other coil combinations. Consequently, the detectors suffer from non-uniform sensitivity distribution, typically with the lowest response in the centre of the portal. This limits their discrimination and ability to locate threat objects. By using the information available from multiple coil combinations, using techniques pioneered for EM tomography, it is expected that both discrimination and location of multiple threat objects can be enhanced The second aspect is the incorporation of video as an integral part of the operation of the detector. Of course video could be simply used to provide security staff with more effective visual feedback. However, this aspect is more fundamental as the video data will be processed to determine the position of the subject during passage pass through the detector, talking gait into account. The time sequenced 3D data can then be used as a-priori information to invert the data from the EM tomography sensors using algorithms devised in our earlier pilot study. In simple terms, the signal profile as the subject passes through the portal contains a wealth of presently unused information on the nature and location of the threat object. It is expected that the improved performance will help to radically improve detectability and object location and reduce false positives (e.g. ignoring belt buckles etc.), significantly reducing operator time. New detector configurations will also be investigated, which are made possible by the integrated tomography / video techniques. These configurations will be compatible with existing building furniture/fixtures and so less conspicuous than existing walk through portals. It is hoped that these detectors can be readily disguised for use in public spaces. The ability to screen subjects, without their knowledge, for significant metal objects, whilst highlighted on video, may provide law enforcement authorities with a powerful tool to counter the growing societal problems such as gun and knife crime. The third aspect is the use of RF and microwave frequencies, with UWB techniques. At low frequencies (less than 100 kHz) the response of metallic objects dominates and is the basis of current WTMD's. At frequencies above 1 MHz, conductive body tissues become detectable by virtue of induced eddy currents. These currents tend to flow near the surface of the body and the response becomes dominated by the conductivity of surface layers as the frequency increases. Above 100 MHz, EM wavelengths become comparable to body dimensions and as the frequencies are increased further, wavelengths become comparable to the dimensions of concealed objects giving corresponding spectral signatures. Frequencies in the low GHz can be used to profile objects with near mm resolution whilst being unaffected by clothing.