Millimeter-wave imaging system
First Claim
1. A millimeter-wave imaging system, comprising:
- an array of detector elements, each element generating a signal responsive to detected millimeter wave radiation, said elements being spaced apart a distance Δ
X;
means for imaging millimeter-wave radiation from a field of view onto said array;
means mounted in the path of radiation from the imaging means to the array of detector elements for redirecting radiation incident thereon so as to shift the point at which such radiation is incident on the detector array in a first direction a distance that is less than Δ
X;
means for rotating the redirecting means in the path of radiation so as to rotate the first direction in which the radiation is shifted; and
means for forming an image from the signals generated by the detector elements that is responsive to radiation received from the field of view wherein each pixel of the image is responsive to radiation detected by a particular element of the array from the portion of its field of view corresponding to a particular angle of orientation of said redirecting means.
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Accused Products
Abstract
An improved millimeter imaging system is disclosed which generates high quality images from the field of view. Such system can be employed in a variety of application ranging from providing an aircraft pilot with an image of the landing field in fog, rain, snow, blowing sand, etc. to detection of concealed non-metallic contraband. The system elements, in which different elements detect signals from different portions of the field of view, so that images of the entire field of view are generated in real time, without using electrical or mechanical scanning. The outputs of the array elements are mapped to display pixels. The resolution of such images has previously been limited by the response characteristics of array elements to energy from only a portion of the corresponding field of view. One aspect of the invention is a significant improvement in image resolution. In the preferred embodiment, a radiation redirecting element redirects incident radiation toward the centerline of each element, so that the elements are uniformly exposed to different portions of the corresponding field of view. As a result, a plurality of display pixels corresponding to different portion of the field of view of each array element are generated, thus significantly increasing display resolution. Another aspect of the invention relates to a novel way of periodically illuminating the imaging array with background noise signal, which is then subtracted from the field of view signal, in order to reduce signal-to-noise ratio. In the preferred embodiment, an optical arrangement of a reflector/load element and a rotating polarization rotation element supplies background signal synchronously with generation of the field of view images, without utilizing electronic switching devices or special "noise" power illuminators.
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Citations
36 Claims
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1. A millimeter-wave imaging system, comprising:
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an array of detector elements, each element generating a signal responsive to detected millimeter wave radiation, said elements being spaced apart a distance Δ
X;means for imaging millimeter-wave radiation from a field of view onto said array; means mounted in the path of radiation from the imaging means to the array of detector elements for redirecting radiation incident thereon so as to shift the point at which such radiation is incident on the detector array in a first direction a distance that is less than Δ
X;means for rotating the redirecting means in the path of radiation so as to rotate the first direction in which the radiation is shifted; and means for forming an image from the signals generated by the detector elements that is responsive to radiation received from the field of view wherein each pixel of the image is responsive to radiation detected by a particular element of the array from the portion of its field of view corresponding to a particular angle of orientation of said redirecting means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A millimeter-wave imaging system comprising:
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an array of detector elements, each having an effective aperture, each element generating a signal responsive to detected millimeter wave radiation from a field of view; means for focusing millimeter-wave radiation from said field of view onto said array, such that each portion of the field of view is mapped to a specific element of the detector array; wherein said elements are spaced apart by a spacing Δ
x, and wherein the signal response of each element to the signal received from the corresponding portion of the field of view effectively varies across its aperture from a maximum value centered on each element;a refractive element mounted in said optical axis for rotation, whereby the radiation from a peripheral portion of the field of view of a detector element is redirected toward the center of the detector element, such that as the refractive element is rotated through 370°
each element of the array detects radiation from 360°
of the peripheral portion of the field of view of the detector element; andmeans for forming an image from the signals generated by the detector elements that is responsive to radiation received from the field of view wherein each pixel of the image is responsive to radiation detected by a particular element of the array from the portion of its field of view corresponding to a particular angular rotation of said refractive element. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. A millimeter-wave imaging system, comprising:
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an array of detector elements; means for focusing millimeter wave radiation from a field of view onto said array; background source means for providing a comparison load signal to said array of detector elements; a polarization rotating means mounted in the path of radiation from said field of view and said background source means to the array for alternately directing the signal from the field of view and from the background source means onto the array of detector elements; means for subtracting the signal detected by the elements of the array while the signal from the background source means is directed onto the elements of the array from that detected by the elements of the array when the signal from the field of view is directed thereon to yield an enhanced image signal having an increased signal-to-noise ratio; and means for forming an image of the field of view responsive to the enhanced image signal detected by the array of elements. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36)
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Specification