Photorefractive two-beam coupling nonlinear joint transform correlator
AssigneeThe United States of America as represented by the Secretary of the Air Force
InventorsJehad Khoury, Charles L. Woods, Peter D. Gianino, Mark Cronin-Golomb
Life of this patent
Estimating the term…
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.
Claims16
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.
A two beam coupling joint transform correlator comprising:
- (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.
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;
- (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.
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;
- (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.
Dependencies are inferred from the claim text.