Abstract: An improved non-obtrusive weapon detection system and method used in discriminating between a concealed weapon made of a ferromagnetic material. The system provides a high probability of detection of hand guns and other types of weapons with a low false alarm rate. The detection of the weapon is accomplished by measuring a total electromagnetic field. The total field being the sum of an incident electromagnetic field and an electromaetic field scattered from the object. The system uses a magnetic field transmitter, which transmits a low intensity electromagnetic signal. The electromagnetic signal illuminates a volume wherein the weapon, called a target, may or may not be carried by a person. The electromagnetic signal is in a form of a sudden steplike change in a constant magnetic field, called a “time-domain” excitation. The waveform or step pulse of the time-domain excitation is called a Heaviside step pulse.

Abstract: A non-obtrusive, non-threatening weapon detection system for discriminating between a concealed weapon and other metal objects. The system is designed for a high probability of detection with a low false alarm rate. When the subject system is in use, a person under surveillance need not be aware that he or she is being monitored nor is the person's privacy invaded. The system includes the use of a magnetic field generator for transmitting low intensity electromagnetic step pulses causing eddy currents to flow in any metal object carried by the person. The eddy currents scatter a signal that is detected by one or more fast response magnetic field sensors. The eddy currents excited in the metal body, which may be called a target, by the leading edges of the transmitted step pulses take the form of an exponentially decaying transient immediately following the step pulses abrupt initial rise. This "decay curve" provides a basic observable, namely, a time constant of the current decay.