Matched amplification and switch joint transform correlator

Details Matched amplification and switch joint transform correlator Matched amplification and switch joint transform correlator

2001-10-09

2003-10-07

Epps, Georgia (Department: 2873)

Optical: systems and elements

Holographic system or element

Fourier transform holography

C359S559000, C359S561000

Reexamination Certificate

active

06631017

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to the field of optical correlator and image clean up and devices. Correlators have been under extensive study for more than a decade, due to their significance in various applications of science and technology. They have been proposed for use in a variety of application such as security, finger print identification and machine vision (H. Rajbenbach, S. Bonn, P. Refregier, P. Joffre, J. P. Huignard, H. S. Jensen and E. Rasumussen, “
Compact photorefractive correlator for robotics applications,” Appl. Opt
. 31, 5666-5647 (1992) and tracking(Allen Pu, Robert Denkewalter and Demetri Psaltis “
Real
-
time vehicle navigation using holographic memory,” Opt. Eng
10, 2737-2746, (1997). K. Curtis and D. Psaltis, “3-
dimensional disk based optical correlator,” Opt. Eng
. 33, 4051-4054 (1994).
So far, to my knowledge, three successful optical correlators have been built for this tracking purpose, The first is the TOPS one
TOPS optical correlation programLindell
, Scott D.; AA(Martin Marietta Astronautics Group) Publication:
Proc. SPIE Vol
. 1958, p. 7-18
, Transition of Optical Processors into Systems
1993, David P. Casasent; Ed. The size of this correlator is less than a one cubic foot, and manages to correlate 800 correlation per/sec. For this correlation the binary phase-only filter was used in the correlation plane. This correlator proved its success in tracking. A more compact correlator was built by Cortec, Inc(11) at Burlington Mass. For this correlator quantum well photorefractive materials with response time of less than &mgr;sec time were used. The size of this correlator was the size of a hand and managed to correlate nearly 10,000 correlations per sec. A group in Caltech demonstrated an opto-electronic correlator which can correlate 30,000 correlation per/sec(K. Curtis and D. Psaltis, “3-
dimensional disk based optical correlator,” Opt. Eng
. 33, 4051-4054 (1994) This correlation system has been successful in real-time vehicle navigation. This correlation system uses a holographic data base of correlation filter stored on a DuPont HRF-150 photo polymer.
In accordance of the present invention, a design of a compact optical correlator with operating speed exceeds 1,000,000 correlation/sec is illustrated. Correlator with this massive capability can be used in variety of application involved a large data base for comparing such as finger print identification, information search on the Internet, DNA sequence codes. Templates for machine vision.
BRIEF SUMMARY OF THE INVENTION
A matched amplification correlator of
FIG. 3
a
for correlating a noisy cluttered weak signal image with a strong reference image is provided in a first embodiment of the invention, wherein Fourier transforms of these images produce a real time hologram upon a photorefractive holographic storage device and a spatial light modulator, optically coupled to the storage device, modulates the hologram with a correlation filter, and the modulated signal is Fourier transformed to produce an output correlation signal.
In a second, presently most preferred embodiment of
FIG. 3
b
, overlapping Fourier transforms of beams bearing the signals to be correlated are projected upon a controlled absorption modulator having beam control III-V family semiconductor layers for selectively switching the Fourier transform of the noisy cluttered image through the device, and a spatial light modulator, optically coupled to the storage device, modulates the hologram with a correlation filter, and the resulting modulated signal is Fourier transformed to produce an output correlation signal. This embodiment can operate at extremely high speeds. As explained in the
FIG. 1
description, assuming that 100 images are fed simultaneously from image input multiplexer
103
of FIG.
1
through an image rotator
113
into the compact correlator
123
, it should be possible to achieve nearly one hundred million correlations per second (0.1 Ghz) if correlator
123
has a
FIG. 3
b
configuration. The image cleaning processors of FIGS.
2
(
b
) and
2
(
d
) are useful standing alone for cleaning noisy cluttered images, and are advantageously used as front end apparatus' in connection with the inventive correlators of FIGS.
3
(
a
) and
3
(
b
) respectively.


REFERENCES:
patent: 5376807 (1994-12-01), Liu et al.
patent: 5598485 (1997-01-01), Kobayashi et al.
patent: 5619596 (1997-04-01), Iwaki et al.

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