14 February 1997 Concealed weapons detection using low-frequency magnetic imaging
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Proceedings Volume 2935, Surveillance and Assessment Technologies for Law Enforcement; (1997) https://doi.org/10.1117/12.266791
Event: Enabling Technologies for Law Enforcement and Security, 1996, Boston, MA, United States
Abstract
Military personnel, law-enforcement officers, and civilians face ever-increasing dangers from persons carrying concealed handguns and other weapons. In direct correspondence with this danger is a need for more sophisticated means of detecting concealed weapons. We have developed a novel concealed-weapons detector based on the principle of low- frequency magnetic imaging. The detector is configured as a portal, and constructs an image of electrically conductive objects transported through it with a potential spatial resolution of approximately 1 inch. Measurements on a breadboard version of the weapons detector have, to date, yielded a resolution of 2 inches. In operation, magnetic dipole radiation, emitted by transmitting antennas in the perimeter of the portal, is scattered from conductive objects and is picked up by receive antennas, also positioned around the portal. With sufficient measurements, each with a different geometry, a solution to the inverse scattering problem can be found. The result is an image of conductive objects in the detector. The detector is sensitive to all metals, semiconductors, and conductive composites. The measured conductivity image formed by the detector is combined with the video signal from a visible CCD camera to form a composite image of persons transiting the detector portal and the conductive objects they are carrying. Accompanying image recognition software could be used to determine the threat level of objects based upon shape, conductivity, and placement on the person of the carrier, and provide cueing, logging, or alarm functions to the operator if suspect weapons are identified. The low- power, low-frequency emissions from the detector are at levels considered safe to humans and medical implants..
© (1997) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Byron G. Zollars, Bradley Sallee, Michael G. Durrett, Clay Cruce, William Hallidy, "Concealed weapons detection using low-frequency magnetic imaging", Proc. SPIE 2935, Surveillance and Assessment Technologies for Law Enforcement, (14 February 1997); doi: 10.1117/12.266791; https://doi.org/10.1117/12.266791
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