Metal Detection System and Method

Abstract

This application describes a system for contraband and weapons detection. The system comprises a coplanar sensor array, electronic drive circuitry, a data acquisition circuit, a video frame grabber, a video camera, and a computer control unit with a control module installed. Properly constructed and aligned, the system allows for the detection of very small magnetic moments, which surround ferromagnetic materials. This ferromagnetic detection allows users to screen personnel for contraband electronic devices and concealed weapons.

1 . A metal detection system comprising:
 a sensor array comprising a plurality of magnetic field fluxgate sensors mounted on a support structure, the sensors being arranged to define a sensing region within the sensor array;   electronic drive circuitry in communication with each magnetic field fluxgate sensor, the electronic drive circuitry comprising one or more filtering digital mixers and a frequency-to-voltage converter;   data acquisition circuitry in communication with the electronic drive circuitry of each magnetic field fluxgate sensor;   a video camera aimed at the sensing region of the sensor array;   a video frame grabber in communication with the video camera; and   a computer control unit comprising a control module and a user interface, the computer control unit in communication with the data acquisition circuitry and the video frame grabber.   
   
   
       2 . The metal detection system of  claim 1 , wherein the support structure comprises a frame constructed of wood, plastic, or aluminum. 
   
   
       3 . The metal detection system of  claim 1 , wherein the support structure comprises decor, landscaping concrete, or doorway moldings. 
   
   
       4 . The metal detection system of  claim 1 , comprising eight magnetic field fluxgate sensors arranged in two columns of four sensors each, wherein the sensors in each column are spaced approximately 16 inches apart, and wherein the lower most sensors in each column are located approximately 9 inches off the ground. 
   
   
       5 . The metal detection system of  claim 1 , wherein each magnetic field fluxgate sensor comprises a drive coil wound around a magnetically permeable core material, and a sensing coil wound perpendicularly around the drive coil and the core material. 
   
   
       6 . The metal detection system of  claim 1 , wherein each magnetic field fluxgate sensor is configured to detect magnetic fields in the range of about ±50 micro-tesla. 
   
   
       7 . The metal detection system of  claim 1 , wherein each magnetic field fluxgate sensor exhibits a sensitive radius region of about 20 inches. 
   
   
       8 . The metal detection system of  claim 1 , wherein the electronic drive circuitry is integrated into body of each magnetic field fluxgate sensor. 
   
   
       9 . The metal detection system of  claim 1 , wherein the electronic drive circuitry is constructed using stand-alone electronic wiring boards, printed circuit cards, or electronic bread boards. 
   
   
       10 . The metal detection system of  claim 1 , wherein the digital mixers comprise D-type flip-flop bistable circuits. 
   
   
       11 . The metal detection system of  claim 1 , wherein the video camera comprises an analog video camera, digital video camera, USB camera, Firewire camera, or wireless network camera. 
   
   
       12 . The metal detection system of  claim 1 , wherein the video frame grabber is installed on the computer control unit. 
   
   
       13 . The metal detection system of  claim 1 , wherein the control module allows a user to customize alarm set points and colors. 
   
   
       14 . The metal detection system of  claim 1 , wherein the magnetic field fluxgate sensors, electronic drive circuitry, data acquisition circuitry, and computer control unit are coupled together via twisted pair wiring or shielded coaxial cable. 
   
   
       15 . The metal detection system of  claim 1 , wherein a Field Programmable Gate Array electronic device is utilized for signal conditioning and routing of the output data from the sensor array. 
   
   
       16 . The metal detection system of  claim 1 , further comprising a plurality of buffers configured to condition the output signals generated by the magnetic field fluxgate sensors. 
   
   
       17 . The metal detection system of  claim 1 , further comprising a plurality of capacitors, wherein each capacitor is connected between an output terminal of a corresponding frequency-to-voltage converter and electrical ground. 
   
   
       18 . The metal detection system of  claim 17 , wherein the capacitors comprise aluminum capacitors, each having a capacitance of about 100 μF. 
   
   
       19 . The metal detection system of  claim 1 , further comprising a plurality of double-regulated power supply circuits, wherein each double-regulated power supply circuit is coupled to a corresponding magnetic field fluxgate sensor. 
   
   
       20 . The metal detection system of  claim 19 , wherein each double-regulated power supply circuit comprises a plurality of voltage regulators and a plurality of capacitors connected between electrical ground and the voltage input and output pins of each voltage regulator. 
   
   
       21 . The metal detection system of  claim 19 , wherein each double-regulated power supply circuit comprises a capacitor connected between the input and ground terminals of the corresponding magnetic field fluxgate sensor, and an inductor connected in series with the input terminal of each magnetic field fluxgate sensor. 
   
   
       22 . The metal detection system of  claim 1 , further comprising a self-contained power system. 
   
   
       23 . The metal detection system of  claim 22 , wherein the self-contained power system comprises a solar power system, fuel cell, battery, gas operated generator, or air operated generator. 
   
   
       24 . A metal detection system comprising:
 an array of magnetic field sensors mounted on a support structure, each sensor being configured to generate an output signal having a frequency that is substantially proportional to a magnetic field detected by the sensor;   means for physically aligning the magnetic field sensors;   means for electronically tuning the magnetic field sensors;   electronic drive circuitry in communication with each magnetic field sensor; and   data acquisition circuitry in communication with the electronic drive circuitry of each magnetic field sensor,   wherein the data acquisition circuitry is configured to communicate with a computer via cabling.   
   
   
       25 . The metal detection system of  claim 24 , wherein the magnetic field sensors comprise magnetic field fluxgate sensors. 
   
   
       26 . The metal detection system of  claim 24 , wherein the magnetic field sensors comprise magneto-resistive effect type magnetic field sensors. 
   
   
       27 . The metal detection system of  claim 24 , wherein the means for physically aligning each magnetic field sensor comprises a ball and socket joint configured to enable angular adjustment of the corresponding sensor. 
   
   
       28 . The metal detection system of  claim 27 , wherein the ball and socket joint enables about 6 degrees of angular adjustment to the corresponding sensor. 
   
   
       29 . The metal detection system of  claim 24 , wherein the means for physically aligning each magnetic field sensor comprises an electromechanical device and a feedback system. 
   
   
       30 . The metal detection system of  claim 29 , wherein the electromechanical device comprises a motor, linear positional device, or an electronic muscle wire. 
   
   
       31 . The metal detection system of  claim 24 , wherein the means for electronically tuning each magnetic field sensor comprises a digital mixer.