Joint transform image correlation using a nonlinear spatial light modulator at the fourier plane
First Claim
1. A nonlinear joint transform image correlator comprising:
- a joint image production means for producing a collimated joint image of a reference image and an input image;
a first Fourier transform lens device disposed to receive said collimated joint image at an object plane thereof and to produce the interference between the Fourier transforms of said reference image and said input image at a Fourier plane thereof;
an image detector means located at said Fourier plane of said first Fourier transform lens device, said image detector means including a plurality of detection cells disposed in a planar array at said Fourier plane, each of said detection cells generating an indication of the light intensity of said interference of said Fourier transforms of said reference image and said input image at said detection cell;
a threshold device connected to each detection cell of said image detector means for determining if the light intensity detected by each detection cell is greater than a threshold value, thereby generating a thresholded indication of the light intensity of said interference of said Fourier transforms of said reference image and said input image at said detection cell; and
inverse Fourier transform means connected to said thresholding means for producing the inverse Fourier transform of said thresholded indication of the light intensity of said interference of said reference image and said input image, said inverse Fourier transform being the correlation between said reference image and said input image.
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Abstract
The present invention is a nonlinear joint transform image correlator which employs a spatial modulator operating in a binary mode at the Fourier plane. The reference and input images are illuminated by a coherent light at the object plane of a Fourier transform lens system. A image detection device, such as a charge coupled device, is disposed at the Fourier plane of this Fourier transform lens system. A thresholding network detects the median intensity level of the imaging cells of the charge coupled device at the Fourier plane and binarizes the Fourier transform interference intensity. The correlation output is formed by an inverse Fourier transform of this binarized Fourier transform interference intensity. In the preferred embodiment this is achieved via a second Fourier transform lens system. This binary data is then applied to spatial light modulator device operating in a binary mode located at the object plane of a second Fourier transform lens system. This binary mode spatial light modulator device is illuminated by coherent light producing the correlation output at the Fourier plane of the second Fourier transform lens system. The inverse Fourier transform may also be formed via a computer. In an alternative embodiment, the Fourier transform interference intensity is thresholded into one of three ranges. An inverse Fourier transform of this trinary Fourier transform interference intensity produces the correlation output.
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Citations
17 Claims
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1. A nonlinear joint transform image correlator comprising:
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a joint image production means for producing a collimated joint image of a reference image and an input image; a first Fourier transform lens device disposed to receive said collimated joint image at an object plane thereof and to produce the interference between the Fourier transforms of said reference image and said input image at a Fourier plane thereof; an image detector means located at said Fourier plane of said first Fourier transform lens device, said image detector means including a plurality of detection cells disposed in a planar array at said Fourier plane, each of said detection cells generating an indication of the light intensity of said interference of said Fourier transforms of said reference image and said input image at said detection cell; a threshold device connected to each detection cell of said image detector means for determining if the light intensity detected by each detection cell is greater than a threshold value, thereby generating a thresholded indication of the light intensity of said interference of said Fourier transforms of said reference image and said input image at said detection cell; and inverse Fourier transform means connected to said thresholding means for producing the inverse Fourier transform of said thresholded indication of the light intensity of said interference of said reference image and said input image, said inverse Fourier transform being the correlation between said reference image and said input image. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A nonlinear joint transform image correlator comprising:
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a joint image production means for producing a collimated joint image of a reference image and an input image; a first Fourier transform lens device disposed to receive said collimated joint image at an object plane thereof and to produce the interference between the Fourier transforms of said reference image and said input image at a Fourier plane thereof; an optically addressed spatial light modulator operating in the binary mode including a plurality of nonlinear light modulator cells of high contrast disposed at said Fourier plane of said first Fourier transform lens device, each light modulator cell having a first transparency state if the light intensity thereon is greater than a predetermined threshold value and having a second transparency state of the light intensity thereon is not greater than said predetermined threshold value, thereby transmitting light therethrough based upon the relation of the light intensity of said interference between the Fourier transforms of said reference image and said input image to said predetermined threshold value for each light modulator cell;
ana second Fourier transform lens device disposed to receive light transmitted from said optically addressed spatial light modulator at an object plane thereof, the correlation output of said nonlinear joint transform image correlator appearing at a Fourier plane thereof.
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14. A nonlinear joint transform image correlator comprising:
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a joint image production means for producing a collimated joint image of a reference image and an input image; a first Fourier transform lens device disposed to receive said collimated joint image at an object plane thereof and to produce the interference between the Fourier transforms of said reference image and said input image at a Fourier plane thereof; an image detector means located at said Fourier plane of said first Fourier transform lens device, said image detector means including a plurality of detection cells disposed in a planar array at said Fourier plane, each of said detection cells generating an indication of the light intensity of said interference of said Fourier transforms of said reference image and said input image at said detection cell; a threshold device connected to each detection cell of said image detector means for determining if the light intensity detected by each detection cell is within one of three intensity ranges, thereby generating a thresholded indication of the light intensity of said interference of said Fourier transforms of said reference image and said input image at said detection cell; and inverse Fourier transform means connected to said thresholding means for producing the inverse Fourier transform of said thresholded indication of the light intensity of said interference of said reference image and said input image, said inverse Fourier transform being the correlation between said reference image and said input image.
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15. A method of forming a nonlinear joint transform image correlation, comprising the steps of:
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producing a collimated joint image of a reference image and an input image; forming the Fourier transform of said collimated joint image using a first Fourier transform lens device disposed to receive said collimated joint image at an object plane thereof and to produce the interference between the Fourier transforms of said reference image and said input image at a Fourier plane thereof; detecting the Fourier transform interference intensity at said Fourier plane of said first Fourier transform lens device, including detection of the Fourier transform interference light intensity at a plurality of detection cells disposed in a planar array at said Fourier plane; determining if the detected light intensity of each cell is greater than a threshold value, thereby generating a thresholded indication of the light intensity of said interference of said Fourier transforms of said reference image and said input image at said detection cell; and forming the inverse Fourier transform of said thresholded indication of the light intensity of said interference of said reference image and said input image, said inverse Fourier transform being the correlation between said reference image and said input image. - View Dependent Claims (16)
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17. A method of forming a nonlinear joint transform image correlation, comprising the steps of:
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producing a collimated joint image of a reference image and an input image; forming the Fourier transform of said collimated joint image using a first Fourier transform lens device disposed to receive said collimated joint image at an object plane thereof and to produce the interference between the Fourier transforms of said reference image and said input image at a Fourier plane thereof; detecting the Fourier transform interference intensity a said Fourier plane of said first Fourier transform lens device, including detection of the Fourier transform interference light intensity at a plurality of detection cells disposed in a planar array at said Fourier plane; determining if the detected light intensity of each cell is within one of three intensity ranges, thereby generating a thresholded indication of the light intensity of said interference of said Fourier transforms of said reference image and said input image at said detection cell; and forming the inverse Fourier transform of said thresholded indication of the light intensity of said interference of said reference image and said input image, said inverse Fourier transform being the correlation between said reference image and said input image.
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Specification