Method of removing spurious responses from optical joint transform correlators
First Claim
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1. A joint transform correlator for producing a plurality of joint transform image cross-correlation signals comprising:
- (a) joint image production means for producing a joint image of a reference image at a reference image plane and an input image at an input image plane;
(b) first Fourier transform means for producing an interference pattern between Fourier transforms of said reference image and said input image;
(c) detector means for detecting said interference pattern and for outputting a Fourier transform interference intensity distribution signal;
(d) a second Fourier transform means for inverse Fourier transforming said interference intensity distribution signal;
(e) and further including optical path length adjustment means for causing a first optical path length between said reference image plane and said first Fourier transform means to differ from a second optical path length between said input image plane and said first Fourier transform means by an amount whereby said second Fourier transform means produces a first off-axis cross-correlation function signal in a first plane and a second off-axis cross-correlation function signal in a second plane separated from said first plane.
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Abstract
A joint transform optical correlator is disclosed having an optical path length adjustment technique for causing a first optical path length between the reference image plane and the first Fourier transform lens to differ from a second optical path length between the input image plane and the first Fourier transform lens by an amount whereby the second Fourier transform lens separates the desired cross-correlation signals from the undesired signals to enhance the performance and reliability of the correlator.
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Citations
22 Claims
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1. A joint transform correlator for producing a plurality of joint transform image cross-correlation signals comprising:
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(a) joint image production means for producing a joint image of a reference image at a reference image plane and an input image at an input image plane; (b) first Fourier transform means for producing an interference pattern between Fourier transforms of said reference image and said input image; (c) detector means for detecting said interference pattern and for outputting a Fourier transform interference intensity distribution signal; (d) a second Fourier transform means for inverse Fourier transforming said interference intensity distribution signal; (e) and further including optical path length adjustment means for causing a first optical path length between said reference image plane and said first Fourier transform means to differ from a second optical path length between said input image plane and said first Fourier transform means by an amount whereby said second Fourier transform means produces a first off-axis cross-correlation function signal in a first plane and a second off-axis cross-correlation function signal in a second plane separated from said first plane. - View Dependent Claims (2, 3, 4, 5, 6, 19, 20)
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7. A joint transform correlator for producing a plurality of joint transform image cross-correlation signals comprising:
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(a) joint image production means for producing a joint image of a reference image at a reference input plane and an input image at an input image plane; (b) a first Fourier transform lens means for producing an interference pattern between Fourier transforms of said reference image and said input image; (c) an image energy detector located at a Fourier plane for receiving said interference pattern and for outputting a light pattern comprising a Fourier transform interference intensity signal; (d) a second Fourier transform lens means for receiving said light pattern from said image energy detector and for inverse Fourier transforming said light pattern; (e) and further including optical path length adjustment means for causing a first optical path length between a reference image plane and said first Fourier transform lens means to differ from a second optical path length between an input image plane and said first Fourier transform lens means by an amount whereby said second Fourier transform lens means focuses a first off-axis cross-correlation function signal in a first plane and a second off-axis cross-correlation function signal in a second plane separated from said first plane. - View Dependent Claims (8, 9, 10, 11, 12)
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13. A joint transform correlator for producing a plurality of joint transform image cross-correlation signals comprising:
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(a) joint image production means for producing a joint image of a reference image at a reference input plane and an input image at an input image plane; (b) a first Fourier transform lens means for producing an interference pattern between Fourier transforms of said reference image and said input image; (c) a nonlinear thresholded image detector for receiving said interference pattern and for outputting a binary Fourier transform interference intensity distribution signal; (d) a second Fourier transform lens means for inverse Fourier transforming said binary Fourier transform interference intensity distribution signal; (e) and further including optical path length adjustment means for causing a first optical path length between a reference image plane and said first Fourier transform lens means to differ from a second optical path length between an input image plane and said first Fourier transform lens means by an amount whereby said second Fourier transform lens means focuses a first off-axis cross-correlation peak signal in a first plane and a second off-axis cross-correlation peak signal in a second plane separated from said first plane. - View Dependent Claims (14, 15, 16, 17, 18, 21, 22)
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Specification