EMBody - Next generation electromagnetic walk by body scanners

该项目由三个相辅相成、相互依存的方面构成，平衡了发展和战略研究工作，并有相应的短期/长期目标。这三个方面中的每一个都有明确的工作方案。第一个方面是使用层析成像通过利用阵列中多个线圈组合之间的耦合来增强WTMD的性能。目前的系统通常只使用专用线圈对之间的耦合，而忽略来自其他线圈组合的信息。因此，探测器的灵敏度分布不均匀，通常在入口的中心具有最低的响应。这限制了他们的辨别力和定位威胁对象的能力。通过使用从多线圈组合获得的信息，使用为电磁层析成像开创的技术，预计可以增强对多个威胁对象的辨别和定位。第二个方面是将视频作为探测器操作的组成部分。当然，视频可以简单地用来为安全人员提供更有效的视觉反馈。然而，这方面是更基本的，因为视频数据将被处理以确定在通过探测器时对象的位置，并考虑说话步态。然后，时间排序的3D数据可以被用作先验信息，使用我们在早期试点研究中设计的算法来反转来自EM断层成像传感器的数据。简而言之，当受试者通过门户时的信号配置文件包含关于威胁对象的性质和位置的大量当前未使用的信息。预计改进的性能将有助于从根本上提高可检测性和对象定位，并减少误报(例如忽略皮带扣等)，从而显著减少操作员的时间。还将研究新的探测器配置，这是通过综合层析/视频技术实现的。这些配置将与现有的建筑家具/固定装置兼容，因此不像现有的穿过门户的通道那么显眼。人们希望这些探测器可以很容易地伪装起来，用于公共场所。在视频中突出显示的是，在受试者不知情的情况下对重要金属物体进行筛查的能力，可能会为执法当局提供一种强大的工具，以应对日益增长的社会问题，如枪支和持刀犯罪。第三个方面是射频和微波频率的使用，以及超宽带技术。在低频下(小于100 kHz)，金属物体的响应占主导地位，是当前WTMD的基础。在1 MHz以上的频率下，由于感应涡流的缘故，可以检测到导电的身体组织。这些电流倾向于在身体表面附近流动，随着频率的增加，响应变得由表层的电导率主导。在100兆赫以上，电磁波长变得与身体的尺寸相当，随着频率的进一步增加，波长变得与给出相应光谱特征的隐蔽物体的尺寸相当。低GHz频率可以用来分析接近毫米分辨率的物体，同时不受衣服的影响。

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.