Identification of hidden objects by terahertz heterodyne laser imaging
First Claim
Patent Images
1. A method of inspecting an object concealed in a package;
- recording a plurality of images of the package and the object therein by detecting THz-radiation transmitted through the package, at least two of the images being recorded at different frequencies of said THz-radiation and at least two of the images being recorded at different transmission directions of the THz radiation; and
estimating the absorption coefficient of object at the different frequencies from the recorded images.
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Abstract
A method for inspecting a package to identify an object concealed in the package includes passing two beams of THz-radiation through the package. The frequency of THz radiation in one beam is different from that in the other, and the beams are at an angle to each other. Each of the transmitted beams is used to form an image of the package and the object. The absorption coefficient of the object is determined from the two images. The material of the object is determined from the absorption coefficients at the two frequencies. The method is useful for detecting explosive material concealed in baggage.
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Citations
20 Claims
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1. A method of inspecting an object concealed in a package;
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recording a plurality of images of the package and the object therein by detecting THz-radiation transmitted through the package, at least two of the images being recorded at different frequencies of said THz-radiation and at least two of the images being recorded at different transmission directions of the THz radiation; and
estimating the absorption coefficient of object at the different frequencies from the recorded images. - View Dependent Claims (2, 3, 4, 5, 6, 7, 14)
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8. Apparatus for inspecting a package, comprising:
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first and second sources of THz-radiation, said first and second sources delivering said THz-radiation at respectively first and second frequencies;
first and second optical arrangements for transmitting said THz radiation from respectively said first and second sources thereof through the package;
first and second THz-radiation receivers;
third and fourth optical arrangement optical arrangements for collecting THz radiation transmitted through the package from respectively said first and second sources of THz-radiation, and delivering said collected radiation to respectively said first and second receivers; and
electronic circuitry cooperative with said first and second THz-radiation receivers for recording electronic images of the package at each of said first and second frequencies and arranged to estimate from said images the absorption coefficient at each of said first and second frequencies of any object contained in the package. - View Dependent Claims (9, 10, 11, 12, 13)
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15. A method of inspecting a package comprising the steps of:
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scanning the package with a first beam of terahertz radiation at a first frequency;
scanning the package with a second beam of terahertz radiation at a second frequency, with the direction of the scanning of the second beam being different from the direction of scanning of the first beam;
detecting the first and second beams after transmission through the sample and generating output signals in response thereto; and
processing the output signals to estimate the absorption coefficient of material inside the package. - View Dependent Claims (16, 19)
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17. A method of inspecting a package comprising the steps of:
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scanning the package with a first beam of terahertz radiation at a first frequency from a first terahertz source;
scanning the package with a second beam of terahertz radiation at a second frequency from a second terahertz source with the direction of the scanning of the second beam being different from the direction of scanning of the first beam;
rotating the package with respect to the propagation direction of first and second beams;
detecting the first and second beams after transmission through the sample and generating output signals in response thereto; and
processing the output signals to estimate the absorption coefficient of material inside the package. - View Dependent Claims (18, 20)
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Specification