Non-obtrusive weapon detection system and method for discriminating between a concealed weapon and other metal objects
First Claim
1. A non-obtrusive weapon detection system for detection of and discrimination between a concealed weapon and other metal objects, the system comprising:
- a transmitter for transmitting low intensity electromagnetic step pulses and causing eddy currents to flow in a metal object under observation, the eddy currents creating a plurality of scattered signals sufficient to accurately plot a "decay curve" due to the relaxation of the eddy currents;
a receiver for detecting the scattered signals from the eddy currents; and
data processing and computing equipment means connected to said receiver, said data processing and computing equipment means digitally processing the scattered signals for defining a time constant of the decay curve, the processed information of the time constant of the decay curve providing an accurate determination of a relationship to the conductive properties of the object under surveillance and the size and shape of the object using appropriate mathematical equations, the processed information allowing an observer to identify objects that are threatening or non-threatening.
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Accused Products
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. The decay curve is analyzed by an appropriate means such as a preprogrammed computer, to determine accurately the time constant of the decay curve. The processed information can then be compared with similar values of the time constant contained in a stored data base to predict the nature of the target. The analyzed information allows an observer to identify the target as being threatening or non-threatening.
91 Citations
21 Claims
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1. A non-obtrusive weapon detection system for detection of and discrimination between a concealed weapon and other metal objects, the system comprising:
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a transmitter for transmitting low intensity electromagnetic step pulses and causing eddy currents to flow in a metal object under observation, the eddy currents creating a plurality of scattered signals sufficient to accurately plot a "decay curve" due to the relaxation of the eddy currents; a receiver for detecting the scattered signals from the eddy currents; and data processing and computing equipment means connected to said receiver, said data processing and computing equipment means digitally processing the scattered signals for defining a time constant of the decay curve, the processed information of the time constant of the decay curve providing an accurate determination of a relationship to the conductive properties of the object under surveillance and the size and shape of the object using appropriate mathematical equations, the processed information allowing an observer to identify objects that are threatening or non-threatening. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A non-obtrusive weapon detection system for detection of and discrimination between a concealed weapon and other metal objects, the system comprising:
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a transmitter for transmitting low intensity electromagnetic step pulses and causing eddy currents to flow in a metal object under observation, the eddy currents excited by a transient associated with a rise-time of the step pulses and with the eddy currents relaxing as soon as excitation is over and creating scattered signals to plot accurately a "decay curve" of eddy current relaxation; a receiver for receiving the scattered signal from the eddy currents; and a computer connected to said receiver and used to digitally process scattered signals, the scattered signals synchronously stacked and replotted, ie. algebraically transformed, by using a logarithm of the scattered strength and creating an exponential decay curve as a line, with the Slope of the straight line being the time constant, the processed information of the time constant of the decay curve providing an accurate determination of a relationship to the conductive properties of the object under surveillance and the size and shape of the object using appropriate mathematical equations, the processed information allowing an observer to identify objects that are threatening or non-threatening. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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17. A method for observing and discriminating between a concealed weapon and other metal objects carried by a person or storied in various carriers such as luggage, boxes, and the like, the steps comprising:
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transmitting low intensity electromagnetic step pulses outwardly from a magnetic field generator and causing eddy currents to flow in the metal object creating a plurality of scattered signals; detecting the scattered signals from the eddy currents using a receiver, the leading edges of the transmitted step pulses taking the form of an exponentially decay curve with time constant which can be accurately plotted; and digitally processing with a preprogrammed computer the information of the time constant of the decay curve, the processed information providing an accurate relationship of the conductive properties of the object under surveillance and the size and shape of the object using appropriate mathematical equations, the analyzed information allows an observer to identify objects that are threatening or non-threatening. - View Dependent Claims (18, 19, 20, 21)
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Specification