Metal detection system

A metal detection system, comprising:

• an oscillator;
• a field generation coil connected to and excited by the oscillator to generate an electromagnetic field disrupted by the presence of a metal object therein;
• a plurality of receiver coils for receiving the generated electromagnetic field;
• a plurality of detector circuits, each of said detector circuits connected in one-to-one correspondence to each of said receiver coils, each detector circuit including means for detecting the disruption of the electromagnetic field received by the corresponding receiver coil and outputting a detection signal indicative thereof, and wherein each detector circuit comprises a balun connected to the corresponding receiver coil, a preamp connected to the balun, a quadrature detector connected to the pre-amp and outputting coupled phase and amplitude signals, a summer for adding the phase and amplitude signals, a low pass filter connected to the summer, and a dual rate high pass filter connected to the low pass filter to output the detection signal;
• means for receiving and processing the detection signals output from the detector circuits to generate a mass signal indicative of the total metal mass of the metal object disrupting the electromagnetic field;
• means for comparing the mass signal to a threshold signal;
• and
• means for outputting an alarm indication when the mass signal exceeds the threshold signal.

A metal detection system, comprising:

• an oscillator;
• a field generation coil connected to and excited by the oscillator to generate an electromagnetic field disrupted by the presence of metal objects therein;
• a plurality of first receiver coils positioned on one side of a passageway through which metal objects pass for receiving the generated electromagnetic field;
• a plurality of second receiver coils positioned on another side of the passageway for receiving the generated electromagnetic field;
• a plurality of detector circuits connected in one-to-one correspondence to each of said first and second plurality of receiver coils, each detector circuit including means for detecting the disruption of the electromagnetic field received by the corresponding receiver coil and outputting a detection signal indicative thereof;
• means for receiving and processing the detection signals output from the detector circuits to generate a mass signal indicative of the metal mass of each individual metal object detected disrupting the electromagnetic field;
• means for comparing each generated mass signal to a threshold signal;
• means for outputting an alarm indication when any individual mass signal exceeds the threshold signal;
• means for processing the detection signals output from the detector circuits to generate a digitized image of each individual metal object detected disrupting the electromagnetic field;
• and
• means for displaying the digitized image to display the approximate location of each individual metal object detected disrupting the electromagnetic field.

A metal detection system, comprising:

• an oscillator;
• a field generation coil connected to and excited by the oscillator to generate an electromagnetic field disrupted by the presence of metal objects therein;
• a plurality of first receiver coils positioned on one side of a passageway through which individual metal objects pass for receiving the generated electromagnetic field;
• a plurality of second receiver coils positioned on another side of the passageway for receiving the generated electromagnetic field;
• a plurality of detector circuits connected in one-to-one correspondence to each of said first and second plurality of receiver coils, each detector circuit including means for detecting the disruption of the electromagnetic field received by the corresponding receiver coil and outputting a detection signal indicative thereof;
• means for receiving and processing the detection signals output from the detector circuits to generate an individual mass signal indicative of the metal mass of each individual metal object detected disrupting the electromagnetic field;
• means for comparing each generated individual mass signal to an individual object threshold signal;
• means for outputting an alarm indication when any individual mass signal exceeds the compared individual object threshold signal;
• means for storing metal mass data of each individual metal object detected disrupting the electromagnetic field for a person or article;
• means for linking the stored metal mass data with an identification number for the person or article;
• means for scanning a person or article passing through the passageway for the assigned identification number;
• means for retrieving the stored metal mass data linked to the scanned identification number;
• and
• means for comparing the retrieved metal mass data with the individual mass signal indicative of each individual metal object detected disrupting the electromagnetic field.