Millimeter wave imaging sensors, sources and systems
First Claim
1. A millimeter wave imaging sensor, comprising:
- an array of sensing elements, each comprising an antenna element consisting of a pair of conductive elements, said conductive elements being adapted to detect millimeter wave radiation, and a nonlinear circuit element connected across each pair of conductive elements for rectifying millimeter wave radiation detected by said pair of conductive elements; and
means for focusing millimeter wave radiation from a field of view onto said array, said means for focusing being aligned along an optical axis with said array of sensing elements;
an oscillator for emitting linearly-polarized millimeter-wave radiation, disposed off said optical axis;
a polarizing grid on said optical axis for dividing said radiation emitted by said oscillator into major and minor components, and for directing said major component of said radiation into the field of view, said minor component of said radiation passing through said polarizing grid; and
means for rotating the polarization of said minor component and reflecting it onto said polarizing grid, whereby said polarizing grid reflects said minor component onto said array of sensing elements as a local oscillator signal.
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Abstract
A millimeter wave imaging system is disclosed which has wide applicability throughout transportation and related industries. For example, the system may be used to provide an aircraft pilot with an image of a landing field which is essentially unaffected by fog, rain, snow, blowing sand, etc. The system comprises an array of imaging elements as its fundamental component. Each of the imaging elements of the basic array comprises an antenna consisting of a pair of conductive elements and a non-linear circuit element connected thereacross. A image can then be formed responsive to millimeter-wave radiation without complex processing steps or any form of mechanical or electronic scanning.
To increase the sensitivity of the imaging array system, a local oscillator signal may be mixed with the energy received from the field of view in each of the imaging elements by the non-linear circuit element. The oscillator used to provide the local oscillator signal can also be used to illuminate the field of view. Coded beacons emitting encoded millimeter wave energy for detection by the imaging array may also be employed.
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Citations
19 Claims
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1. A millimeter wave imaging sensor, comprising:
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an array of sensing elements, each comprising an antenna element consisting of a pair of conductive elements, said conductive elements being adapted to detect millimeter wave radiation, and a nonlinear circuit element connected across each pair of conductive elements for rectifying millimeter wave radiation detected by said pair of conductive elements; and means for focusing millimeter wave radiation from a field of view onto said array, said means for focusing being aligned along an optical axis with said array of sensing elements; an oscillator for emitting linearly-polarized millimeter-wave radiation, disposed off said optical axis; a polarizing grid on said optical axis for dividing said radiation emitted by said oscillator into major and minor components, and for directing said major component of said radiation into the field of view, said minor component of said radiation passing through said polarizing grid; and means for rotating the polarization of said minor component and reflecting it onto said polarizing grid, whereby said polarizing grid reflects said minor component onto said array of sensing elements as a local oscillator signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method of generating a millimeter wave image of objects in a field of view, comprising the steps of:
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focusing millimeter wave energy emitted by or reflected from the objects in said field of view onto an array of imaging elements, each of said imaging elements comprising antenna means for detecting millimeter wave energy received from a corresponding portion of said field of view; simultaneously illuminating said imaging elements of said array with an array of sources of local oscillator signal to provide a local oscillator signal of substantially uniform amplitude over the array; mixing the energy received from the corresponding portion of the field of view with the local oscillator signal separately for each of the imaging elements; and forming an image, essentially in real time, each pixel of which corresponds to the millimeter wave energy detected by one of said imaging elements of said array. - View Dependent Claims (13)
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14. A system for providing a millimeter wave image of a field of view, comprising:
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a millimeter wave imaging sensor, comprising an imaging array of sensing elements, each comprising an antenna including a pair of conductive elements sensitive to millimeter-wave radiation, and a non-linear circuit element coupled thereacross, and means for focusing millimeter wave radiation reflected by or emitted from objects in the field of view onto said elements of said array; an array of sources of local oscillator signal for simultaneously illuminating said sensing elements of said imaging array with a local oscillator signal of substantially uniform amplitude over the array; and image signal processing means for generating an image, essentially in real time, responsive to millimeter wave energy detected by said imaging elements of said array, wherein each pixel of said image is responsive to the signal provided by one of the elements of said array. - View Dependent Claims (15, 16, 17, 18)
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19. A system for providing a millimeter wave image of a field of view, comprising:
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a millimeter wave imaging sensor, comprising an array of imaging elements, each comprising an antenna consisting of paired conductive elements having a non-linear circuit element coupled thereacross; means for focusing millimeter wave radiation reflected by or emitted from objects in the field of view onto said imaging elements of said array; an array of sources of local oscillator signal for simultaneously illuminating said imaging elements of said array with a local oscillator signal of substantially uniform amplitude over the array; image signal processing means for generating essentially in real time an image responsive to millimeter wave energy detected by said imaging elements of said array, wherein each pixel of said image is responsive to one of the elements of said array; and at least one millimeter wave radiation source illuminating a portion of said field of view, said source emitting radiation which varies according to a predetermined function of time; wherein said image signal processing means comprises means for detecting radiation from the field of view response to the illumination from said source.
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Specification