Signal processing for object detection system
First Claim
1. A method of detecting an object, the method comprising the steps of:
- illuminating a target person with horizontally polarized radiation;
collecting radiation reflected from said target which has a polarization which is the same as the radiation used to illuminate said target;
collecting radiation reflected from said target which has a polarization that is orthogonal to that of said radiation which is used to illuminate said target;
calculating a difference between a collected radiation level of radiation reflected from said target which has a polarization that is orthogonal to that of said radiation which is used to illuminate said target and a predetermined average radiation level, which, if positive, indicates that the object is present; and
calculating one or more differences between collected radiation levels and predetermined average radiation levels, which, if positive, indicates that there is a false alarm.
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Accused Products
Abstract
Methods and apparatus for detecting objects are disclosed. In one embodiment of the invention, a person entering a secured or “Safe Zone™” is illuminated with low-power polarized radio waves. Differently polarized waves which are reflected back from the person are collected and measured. In a preferred embodiment of the invention, concealed weapons are detected by calculating the difference of a pair of differences between levels of different polarized reflected energy in the time domain, and by using signal processing methods and apparatus to improve the reliability of the detection process. Alternative embodiments of the invention may be used to detect a wide variety of objects other than concealed firearms. The invention may be used for inventory control or to thwart shoplifting.
107 Citations
20 Claims
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1. A method of detecting an object, the method comprising the steps of:
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illuminating a target person with horizontally polarized radiation;
collecting radiation reflected from said target which has a polarization which is the same as the radiation used to illuminate said target;
collecting radiation reflected from said target which has a polarization that is orthogonal to that of said radiation which is used to illuminate said target;
calculating a difference between a collected radiation level of radiation reflected from said target which has a polarization that is orthogonal to that of said radiation which is used to illuminate said target and a predetermined average radiation level, which, if positive, indicates that the object is present; and
calculating one or more differences between collected radiation levels and predetermined average radiation levels, which, if positive, indicates that there is a false alarm. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An apparatus for detecting an object, said apparatus comprising:
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means for illuminating a target person with horizontally polarized radiation;
means for collecting radiation reflected from said target which has a polarization which is the same as said radiation used to illuminate said target;
means for collecting radiation reflected from said target which has a polarization that is orthogonal to that of said radiation which is used to illuminate said target;
means for calculating a difference between a collected radiation level of radiation reflected from said target which has a polarization that is orthogonal to that of said radiation which is used to illuminate said target and a predetermined average radiation level, which, if positive, indicates that a weapon is present; and
means for calculating one or more differences between collected radiation levels and predetermined average radiation levels, which, if positive, indicates that there is a false alarm. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification