Photorefractive two-beam coupling nonlinear joint transform correlator
First Claim
Patent Images
1. A two beam coupling joint transform correlator comprising:
- (a) a nonlinear photorefractive medium;
(b) image producing means for producing a signal beam including a pair of images to be correlated with each other;
(c) first Fourier transform means for simultaneously Fourier transforming said pair of images and directing the resulting joint spectra upon said nonlinear photorefractive medium;
(d) reference beam generating means for writing an interference pattern between the joint spectra and the reference beam upon the nonlinear photorefractive medium with a reference beam coherent with said signal beam; and
(e) second Fourier transform means for inverse transforming the resulting signal formed upon the nonlinear photorefractive medium to produce an output correlation signal beam.
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Abstract
An all-optical nonlinear joint transform correlator has been implemented for the first time without using a spatial light modulator and digital processing in the Fourier plane. The correlator utilizes energy transfer from two-beam coupling in the Fourier plane. A compressional nonlinearity in the hard-clipped regime is implemented by pumping a weak plane wave with the intense joint spectrum of the reference and signal images. Operation of this device rivals or exceeds that of the phase-only filter for detecting objects in cluttered noise. Experimental results are compared with both plane wave and beam propagation simulations.
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Citations
16 Claims
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1. A two beam coupling joint transform correlator comprising:
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(a) a nonlinear photorefractive medium; (b) image producing means for producing a signal beam including a pair of images to be correlated with each other; (c) first Fourier transform means for simultaneously Fourier transforming said pair of images and directing the resulting joint spectra upon said nonlinear photorefractive medium; (d) reference beam generating means for writing an interference pattern between the joint spectra and the reference beam upon the nonlinear photorefractive medium with a reference beam coherent with said signal beam; and (e) second Fourier transform means for inverse transforming the resulting signal formed upon the nonlinear photorefractive medium to produce an output correlation signal beam. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A two beam coupling joint transform correlator comprising:
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(a) a nonlinear two beam coupling medium; (b) image producing means for producing a signal beam including a pair of images to be correlated with each other; (c) first Fourier transform means for simultaneously Fourier transforming said pair of images and directing the resulting joint spectra upon said nonlinear two beam coupling medium; (d) reference beam generating means for writing an interference pattern between the joint spectra and the reference beam upon the nonlinear two beam coupling medium with a reference beam coherent with said signal beam; and (e) second Fourier transform means for inverse transforming the resulting signal formed upon the nonlinear two beam coupling medium to produce an output correlation signal beam. - View Dependent Claims (11, 12, 13)
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14. A two beam coupling joint transform correlator comprising:
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(a) a nonlinear photorefractive medium; (b) image producing means for producing a signal beam including a pair of images to be correlated with each other; (c) first Fourier transform means for simultaneously Fourier transforming said pair of images and directing the resulting joint spectra upon said nonlinear photorefractive medium; (c) reference beam generating means for illuminating he joint spectra upon the nonlinear photorefractive medium with a reference beam coherent with said signal beam; (e) second Fourier transform means for inverse transforming the resulting signal formed upon the nonlinear photorefractive medium to produce an output correlation signal beam; and (f) wherein the reference beam is a clean beam having a substantially lesser intensity than the signal beam. - View Dependent Claims (15)
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16. A two beam coupling joint transform correlator comprising:
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(a) a nonlinear photorefractive medium; (b) image producing means for producing a signal beam including a pair of images to be correlated with each other; (c) first Fourier transform means for simultaneously Fourier transforming said pair of images and directing the resulting joint spectra upon said nonlinear photorefractive medium; (c) reference beam generating means for illuminating the joint spectra upon the nonlinear photorefractive medium with a reference beam coherent with said signal beam; (e) second Fourier transform means for inverse transforming the resulting signal formed upon the nonlinear photorefractive medium to produce an output correlation signal beam; and (f) means for adjusting the beam intensity ratios.
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Specification