IDENTIFICATION OF POTENTIAL THREAT MATERIALS USING ACTIVE ELECTROMAGNETIC WAVES
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Abstract
Electrical properties of concealed dielectric objects, such as the dielectric permittivity, can be deduced from incident, reflected, and transmitted electromagnetic waves in an imaging system. In a confocal arrangement a horn illuminates a reflect array and the reflect array is configured to focus the radiation at an element in the scan volume. The reflections are in turn refocused by a reflect array at the horn aperture. The reflect array is electronically configured to scan the focal point throughout the scan volume in a systematic way. Knowledge of the horn pattern and the scan strategy allows the system to compute the geometry associated with each volume element. Amplitude and phase variations between the object and the surrounding volume and the computed geometry are used to estimate the relative permittivity and thus facilitate categorization of the object using a database of material relative permittivities.
41 Citations
35 Claims
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1-19. -19. (canceled)
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20. An imaging system comprising
a transmitter for directing radiation at a scan volume in which there is a target; -
a receiver for receiving scattered radiation from the volume; and a reflect array for focusing incident beam radiation; a processor for processing the scattered radiation to generate an image according to amplitude and phase of the received radiation; a display coupled to the processor, for generating an image display; wherein the transmitter is adapted to transmit the incident radiation with a substantially single frequency; wherein the system is adapted to identify a concealed material; wherein the processor is adapted to classify a concealed dielectric material according to permittivity relative to that of the human body, said relative permittivity being deduced from amplitude and phase information in the received radiation; wherein the processor is adapted to measure phase and amplitude of scattered radiation both near the concealed material and at the concealed material, that near the concealed material providing a reference; and wherein the system is adapted to detect radiation from two or more volume elements, a volume element providing reference data if it does not include the concealed material. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
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Specification