Signal processing for object detection system
First Claim
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1. A method of detecting an object comprising the steps of:
- illuminating a target with polarized radiation;
collecting first radiation reflected from said target which has a polarization which is the same as the radiation used to illuminate said target;
collecting second radiation reflected from said target which is oppositely polarized to that of said radiation which is used to illuminate said target; and
comparing a difference between amplitudes of said first and second radiation with a predetermined value representative of an expected difference were the object not present; and
wherein a single receiver channel is employed by the two collecting steps, which receiver channel is time multiplexed.
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Abstract
Methods and apparatus for detecting objects. In one embodiment, 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, concealed weapons are detected by calculating the difference of a pair of differences (Delta A and B) of different polarized reflected energy (upper and lower curves in the two graphs) in the time domain, and by using signal processing methods and apparatus to improve the reliability of the detection process.
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Citations
17 Claims
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1. A method of detecting an object comprising the steps of:
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illuminating a target with polarized radiation;
collecting first radiation reflected from said target which has a polarization which is the same as the radiation used to illuminate said target;
collecting second radiation reflected from said target which is oppositely polarized to that of said radiation which is used to illuminate said target; and
comparing a difference between amplitudes of said first and second radiation with a predetermined value representative of an expected difference were the object not present; and
wherein a single receiver channel is employed by the two collecting steps, which receiver channel is time multiplexed. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of detecting an object comprising the steps of:
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illuminating a target with polarized radiation;
collecting first radiation reflected from said target which has a polarization which is the same as the radiation used to illuminate said target;
collecting second radiation reflected from said target which is oppositely polarized to that of said radiation which is used to illuminate said target;
generating a reference signal from sampling transmit and local oscillators;
comparing a difference between amplitudes of said first and second radiation with a predetermined value representative of an expected difference were the object not present; and
using a Fast Fourier Transform to substantially discount the moving components of said target to improve the detection of unchanging components of said target. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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Specification