Weapon detector utilizing the pulsed field technique to detect weapons on the basis of weapons thickness

Claim 1

Apparatus for monitoring a subject to detect the presence of a weapon on the basis of thickness comprising, first means for subjecting said subject to a rapidly changing magnetic field, second means for measuring a rate of change of magnetic flux within said subject immediately subsequent to the change in the magnetic field, said second means including a first integrator means for generating a first DC signal corresponding to said rate of change of magnetic flux during a first time interval and a second integrator means for generating a second DC signal corresponding to the rate of change of magnetic flux during a second time interval, and third means for evaluating said first and second DC signals to determine if said subject contains a weapon, said third means including means for determining the ratio of said first and second DC signals and producing an output signal indicative of the relative thickness of a metal object associated with said subject, means for providing a reference signal indicative of the thickness of a weapon, and means for comparing said output signal indicative of the thickness of the metal object associated with said subject to said reference signal, said means for comparing developing an output signal indicative of the presence of a weapon when a predetermined relationship exists between said output signal indicative of the thickness of the metal object associated with said subject and said reference signal.