Charles Morgan Woods

US Patent:

53371801, Aug 9, 1994

Filed:

Jul 29, 1992

Appl. No.:

7/921542

Inventors:

Charles L. Woods - Stow MA
Jihad Khoury - Arlington VA

Assignee:

The United States of America as represented by the Secretary of the Air
Force - Washington DC

International Classification:

G02B 2746
G02B 523

US Classification:

359568

Abstract:

Spatially variable nonlinear optical thresholding in the Fourier plane reduces signal-dependent noise, such as scalar multiplicative noise. Coherent artifact noise reduction by a factor of four is attained using deamplifying photorefractive two-beam coupling. A variable light transmittance threshold across a spatially thresholded light modulating element such as a photorefractive crystal is utilized for this purpose.

US Patent:

56046340, Feb 18, 1997

Filed:

Sep 20, 1993

Appl. No.:

8/300692

Inventors:

Jihad Khoury - Arlington MA
Charles L. Woods - Stow MA

Assignee:

The United States of America as represented by the Secretary of the Air
Force - Washington DC

International Classification:

G02B 2746
G03H 102
G03H 116

US Classification:

359559

Abstract:

A fully parallel, self-aligning, nonlinear and all optical joint transform correlator utilizes a photorefractive four wave mixer positioned to record the joint transform spectrum interfering with a reference beam together with a phase conjugator which directs a readout beam at the four wave mixer. The signal readout of the mixer is Fourier transformed and can be recorded upon an image sensor to detect the correlation spots indicating the degree of similarity of the two input images.

US Patent:

55350240, Jul 9, 1996

Filed:

May 6, 1992

Appl. No.:

7/879658

Inventors:

Jihad Khoury - Somerville MA
Charles L. Woods - Stow MA

Assignee:

The United States of America as represented by the Secretary of the Air
Force - Washington DC

International Classification:

G03H 102

US Classification:

359 7

Abstract:

A novelty filter utilizes self-nulling and self-aligning of reflection and transmission phase conjugate beams. A photorefractive crystal is arranged so that the contributions to the phase conjugate are equal and opposite in the steady state to produce destructive interference when the input image is stationary, and thus no output image is displayed. If the image moves, then the gratings will rewrite and erase themselves, each with their own response times, total destructive interference will not occur, and transient enhancement and surpression of the phase conjugate output signal will indicate the direction of motion of the input image.

US Patent:

53371704, Aug 9, 1994

Filed:

Jul 29, 1992

Appl. No.:

7/921541

Inventors:

Jihad Khoury - Arlington MA
Charles L. Woods - Stow MA

Assignee:

The United States of America as represented by the Secretary of the Air
Force - Washington DC

International Classification:

G03H 102

US Classification:

359 7

Abstract:

A degenerate four-wave mixing arrangement employs a photorefractive crystal as a real time holographic recording medium to record a hologram of the noisy optical signal. The signal passes through the crystal and is phase conjugated by a self pumped barium titanate phase conjugator, and the resulting phase conjugate beam reads out the hologram and multiplicative noise is substantially reduced in the optical output signal.

US Patent:

53612221, Nov 1, 1994

Filed:

Jun 30, 1992

Appl. No.:

7/906987

Inventors:

Jihad A. Khoury - Somerville MA
Jonathan S. Kane - Wayland MA
Philip R. Hemmer - Fitchbury MA
Charles L. Woods - Stow MA

Assignee:

The United States of America as represented by the Secretary of the Air
Force - Washington DC

International Classification:

G06K 976
G11C 1304

US Classification:

365 49

Abstract:

An associative memory apparatus having a 2f Fourier transform optical correlation configuration wherein the correlation spots produced in the correlation plane are projected back by a mirror through the inverse Fourier transform lens and a phase correction reference image filter to produce the output image representing the best match between the input image and the associative memory reference images. A 4f Fourier transform embodiment projects the correlation spots forward through a second filter and transform means and the output image can be fed back to the input image display SLM to enhance the output image.

US Patent:

55110193, Apr 23, 1996

Filed:

Apr 26, 1994

Appl. No.:

8/234523

Inventors:

Thomas J. Grycewicz - Belmont MA
Jehad Khoury - Arlington MA
Charles L. Woods - Stow MA

Assignee:

The United States of America as represented by the Secretary of the Air
Force - Washington DC

International Classification:

G06E 300
G02B 2746
G06F 15336

US Classification:

364822

Abstract:

A joint transform correlator has modulators for temporally modulating a first optical input signal at a first frequency and a second optical input signal at a second frequency. An image sensor in the Fourier plane forms a product signal modulated by temporal sum and difference frequencies of the first and second frequencies. The product signal is thereafter demodulated at the temporal sum or difference frequency and the resulting optical signal is inverse Fourier transformed to recover the desired cross correlation signals.

US Patent:

55945864, Jan 14, 1997

Filed:

May 2, 1994

Appl. No.:

8/236936

Inventors:

Jehad Khoury - Arlington MA
Charles L. Woods - Stow MA
Mark Cronin-Golomb - Reading MA
Jack Fu - Brighton MA

Assignee:

The United States of America as represented by the Secretary of the Air
Force - Washington DC

International Classification:

G02B 2746
G02B 523

US Classification:

359559

Abstract:

Limiting quadratic processing and compansion in photorefractive two beam coupling is disclosed. Two-beam coupling in photorefractive barium titanate employs the imaged intensity of the signal to amplify the reference beam while maintaining the phase of the reference beam. The phase distorted signal beam is converted to that of the controlled phase of the reference beam. The high pump limit of amplification in this two-beam coupling device produces an amplitude compressed output to reduce multiplicative noise. Lost contrast of the image is thereafter restored. Beam clean-up of a non-intelligence bearing beam can be carried out by a similar process; a low pass filter consisting of a pinhole plate can be used in place of the second photorefractive crystal in the Fourier plane and only the planar wavefront portion will pass through the pinhole and may be collimated by a lens to provide a cleaned planar output beam.

US Patent:

54934443, Feb 20, 1996

Filed:

Apr 28, 1994

Appl. No.:

8/238032

Inventors:

Jehad Khoury - Arlington MA
Charles L. Woods - Stow MA
Peter D. Gianino - Melrose MA
Mark Cronin-Golomb - Reading MA

Assignee:

The United States of America as represented by the Secretary of the Air
Force - Washington DC

International Classification:

G02B 2742
G02B 2746
G06E 300
G06K 976

US Classification:

359559

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.