US4726639A
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Optically implemented memory correlator using a photorefractive crystal
Assignee: United States Department of the Army
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Filing: 1986-02-03
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Granted: 1988-02-23
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Expires: 2006-02-03
Abstract
Abstract An optically implemented technique which generates the correlation functionf two electrical signals. A reference signal is used in conjugation with an acousto-optic device to generate an optical field which is incident on a photorefractive crystal. This produces in the crystal a reflection phase conjugate wave front reconstructing volume hologram. A retropropagating reconstructed optical field passes back through the device which contains a second signal. This optical field is then focused onto a photodiode. The time varying component of the photodiode output is the correlation of the two signals.
Inventors
- 👤 Philip S. Brody
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 01:09
CPC Classifications
G; G03; G03H; G03H1/00; G03H1/02; G03H1/024; G03H1/0248; G06; G06E; G06E3/00; G06E3/001; G06E3/005
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
274 words
Apparatus for generating the correlation function of two signals comprising: a photorefractive crystal; a short pulse laser of first wavelength; a first beam splitter disposed between said photorefractive crystal and said short pulse laser; a second beam splitter disposed between said photorefractive crystal and said first beam splitter; an acousto-optic device disposed between said photorefractive crystal and said second beam splitter; means for introducing a first radio frequency signal of first duration into said acousto-optic device; means for triggering said short pulse laser when said first radio frequency signal is introduced into said acousto-optic device such that said short pulse laser first illuminates said acousto-optic device and then illuminates said photorefractive crystal to produce a phase conjugate generating volume phase hologram in the photorefractive crystal; means for introducing, after the duration of said first radio frequency signal, a second radio frequency signal into said acousto-optic device; a low intensity laser of first wavelength; means for triggering said low intensity laser when said second radio frequency signal is introduced into said acousto-optic device such that the laser beam is reflected off of said first beam splitter and through said second beam splitter to first illuminate said acousto-optic device and then said photorefractive crystal to produce a back propagating wave which then illuminates said acousto-optic device and is reflected off of said second beam splitter; photodiode detector means for detecting the correlation function of the first radio frequency signal and the second radio frequency signal from the back propagating beam reflected off of said second beam splitter; and means for focusing said back propagating beam reflected off of said second beam splitter onto said photodiode detector.
Claim 2
Dependent Claim
274 words
Apparatus for generating the correlation function of two signals comprising: a photorefractive crystal; a short pulse laser of first wavelength; a first beam splitter disposed between said photorefractive crystal and said short pulse laser; a second beam splitter disposed between said photorefractive crystal and said first beam splitter; an acousto-optic device disposed between said photorefractive crystal and said second beam splitter; means for introducing a first radio frequency signal of first duration into said acousto-optic device; means for triggering said short pulse laser when said first radio frequency signal is introduced into said acousto-optic device such that said short pulse laser first illuminates said acousto-optic device and then illuminates said photorefractive crystal to produce a phase conjugate generating volume phase hologram in the photorefractive crystal; means for introducing, after the duration of said first radio frequency signal, a second radio frequency signal into said acousto-optic device; a low intensity laser of first wavelength; means for triggering said low intensity laser when said second radio frequency signal is introduced into said acousto-optic device such that the laser beam is reflected off of said first beam splitter and through said second beam splitter to first illuminate said acousto-optic device and then said photorefractive crystal to produce a back propagating wave which then illuminates said acousto-optic device and is reflected off of said second beam splitter; photodiode detector means for detecting the correlation function of the first radio frequency signal and the second radio frequency signal from the back propagating beam reflected off of said second beam splitter; and means for focusing said back propagating beam reflected off of said second beam splitter onto said photodiode detector.
Claim 3
Dependent Claim
16 words
The device of claim 1, wherein said acousto-optic device comprises a surface acoustic wave delay line.
Claim 4
Dependent Claim
15 words
The device of claim 1, wherein said acousto-optic device comprises a bulk wave Bragg cell.
Claim 5
Dependent Claim
43 words
The device of claim 1, wherein the total optical energy incident on said photorefractive crystal by said low intensity laser of first wavelength is less than the total optical energy incident on said photorefractive crystal by said short pulse laser of first wavelength.
Claim 6
Dependent Claim
14 words
The device of claim 1 wherein said photorefractive crystal is comprised of barium titanate.
Claim 7
Dependent Claim
15 words
The device of claim 1 wherein said photorefractive crystal is comprised of barium strontium niobate.
Claim 8
Dependent Claim
12 words
The device of claim 1 wherein said low intensity laser is continuous.
Claim 9
Dependent Claim
12 words
The device of claim 1 wherein said low intensity laser is pulsed.
Claim 10
Dependent Claim
13 words
The device of claim 1 wherein said low intensity laser is repetitively pulsed.
Claim 11
Dependent Claim
184 words
Method for generating the correlation function of two signals comprising: introducing a first radio frequency signal of first duration into an acousto-optic device; triggering a short pulse laser of first wavelength when said first radio frequency signal is introduced into said acousto-optic device such that said short pulse laser first illuminates said acousto-optic device and then illuminates a photorefractive crystal to produce a saturation phase conjugate generating volume phase hologram in the photorefractive crystal; introducing, after the duration of said first radio frequency signal, a second radio frequency signal into said acousto-optic device; triggering a low intensity laser of first wavelength when said second radio frequency signal is introduced into said acousto-optic device such that said low intensity laser first illuminates said acousto-optic device and then illuminates said photorefractive crystal to produce a back propagating beam which illuminates said acousto-optic device; and directing said back propagating beam, after it has illuminated said acousto-optic device, through a lens so as to focus said back propagating beam onto means for detecting the correlation function of the first radio frequency signal and the second radio frequency signal.
Claim 12
Dependent Claim
184 words
Method for generating the correlation function of two signals comprising: introducing a first radio frequency signal of first duration into an acousto-optic device; triggering a short pulse laser of first wavelength when said first radio frequency signal is introduced into said acousto-optic device such that said short pulse laser first illuminates said acousto-optic device and then illuminates a photorefractive crystal to produce a saturation phase conjugate generating volume phase hologram in the photorefractive crystal; introducing, after the duration of said first radio frequency signal, a second radio frequency signal into said acousto-optic device; triggering a low intensity laser of first wavelength when said second radio frequency signal is introduced into said acousto-optic device such that said low intensity laser first illuminates said acousto-optic device and then illuminates said photorefractive crystal to produce a back propagating beam which illuminates said acousto-optic device; and directing said back propagating beam, after it has illuminated said acousto-optic device, through a lens so as to focus said back propagating beam onto means for detecting the correlation function of the first radio frequency signal and the second radio frequency signal.
Claim 13
Dependent Claim
16 words
The method of claim 10 wherein said acousto-optic device comprises a surface acoustic wave delay line.
Claim 14
Dependent Claim
16 words
The method of claim 10 wherein said said acousto-optic device comprises a bulk wave Bragg cell.
Claim 15
Dependent Claim
43 words
The method of claim 10 wherein the total optical energy incident on said photorefractive crystal by said low intensity laser of first wavelength is less than the total optical energy incident on said photorefractive crystal by said short pulse laser of first wavelength.
Claim 16
Dependent Claim
14 words
The method of claim 10 wherein said photorefractive crystal is comprised of barium titanate.
Claim 17
Dependent Claim
15 words
The method of claim 10 wherein said photorefractive crystal is comprised of barium strontium niobate.
Claim 18
Dependent Claim
12 words
The method of claim 10 wherein said low intensity laser is pulsed.
Claim 19
Dependent Claim
12 words
The method of claim 10 wherein said low intensity laser is continuous.
Claim 20
Dependent Claim
13 words
The method of claim 10 wherein said low intensity laser is repetitively pulsed.
References Cited (Backward Citations)
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