WEAPON DETECTOR UTILIZING THE PULSED FIELD TECHNIQUE TO DETECT WEAPONS ON THE BASIS OF WEAPONS THICKNESS

• US 3,707,672 A
• Filed: 06/02/1971
• Issued: 12/26/1972
• Est. Priority Date: 06/02/1971
• Status: Expired due to Term

• Current Assignee: George T. Mallick Jr, Robert C. Miller, Walter J. Carr Jr
• Original Assignee: George T. Mallick Jr, Robert C. Miller, Walter J. Carr Jr
• Inventors: Miller, Robert C., Carr, Walter J. Jr., Mallick, George T. Jr.
• Primary Examiner(s): Corcoran, Robert J.
• Application Number:
  US05/149,226
• Time in Patent Office: 573 Days
• Field of Search: 324/41,40,3,4,7 340/258G,258C
• US Class Current: 324/239
• CPC Class Codes: G01V 3/10 using induction coils

Abstract

This invention is a metal detector which utilizes pulsed field techniques in order to detect the presence of metal objects and to provide discrimination between metal objects based on characteristics such as thickness, size and shape. An object to be monitored for metal content is subjected to pulsating magnetic fields. The rate of change of the magnetic field occurring at either the initiation or termination of magnetizing pulses is interpreted to identify the metal object in terms of thickness.

Claims

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.

2. Apparatus as claimed in claim 1 wherein said first means subjects said subject to a pulsed magnetic field changing from a first predetermined value to a second predetermined value.

3. Apparatus as claimed in claim 2 wherein said first and second predetermined values correspond tO steady state magnetic flux conditions within said subject.

4. Apparatus as claimed in claim 1 wherein said weapon is a hand gun and said reference signal is a value corresponding substantially to the thickness of a hand gun such that the output signals from said means for comparing identifies the presence of a hand gun within said subject.