USA As Represented by Secretary of the Navy

US Government As Represented by the Secretary of the Army

Other

John N Lee

Ray B Brown, Jr

Robert L Denningham

Irwin J Abramovitz

Norman J Berg

Michael W Casseday

Ravindra A Athale

Robert B Oswald, Jr

Anthony E Spezio

Edward M Alexander

Carl M Verber

Arthur D Fisher

Peter B Rolsma

A light beam encoded with data simultaneously reads out data stored in tracks on an optical disk and produces a reflected beam directed to a detector array. The data stored on the optical disk and the encoded data may be components of vector arrays. As the light beam illuminates the rotating optical disk, the data stored on the disk is multiplied by the encoded data. The products of the multiplication are encoded in the reflected beam. A multiplicity of data is read out in parallel from the optical disk and simultaneously correlated with the encoded data. This comparison or correlation operation is performed on digitally encoded data utilizing convolution, or with analog encoding. The present invention can be utilized in pattern matching.

Method and apparatus for parallel readout and correlation of data on optical disks

A apparatus and method for coherently stretching or compressing signals of nterest, i.e. without loss of information. A first, or tapping, Bragg cell has an acoustic signal launched in it which is modulated onto a laser carrier. The signal of interest is launched into a second, or signal, Bragg cell, and is similarly modulated onto the carrier exiting the first Bragg cell. Upon demodulation, the resultant signal, is the convolution of the two acoustic signals in the respective Bragg cells, but whose duration is either stretched or compressed according to the relative velocity between the acoustic signals in the two Bragg cells, and by the magnification of optics between the two cells. If the signal in the first Bragg cell is of such a short duration that it is effectively an impulse, the resultant signal is a coherently stretched or compressed replica of the signal launched into the second Bragg cell, i.e. the signal of interest.

Apparatus and method for coherent acousto-optic signal width modification

A common-path interferometric acoustic-optic heterodyne spectrum analyzer ving high immunity to ambient vibration uses two, counter-propagating beams, two Bragg cells for beam diffraction, a series of waveplates and a birefringent quartz wedge. Proper light polarization with the waveplates and Bragg cell geometry allows one Bragg cell to diffract primarily the clockwise beam and the other Bragg cell to diffract the counterclockwise beam. The birefringent quartz wedge shifts the diffracted beams to provide a heterodyne signal with a non-zero IF carrier frequency. The analyzer is highly angle compensated and alignment stable when components are disturbed in position or orientation.

Optically stable, large time bandwidth acousto-optic heterodyne spectrum

An improved compact optical and rugged laser-driven RF spectrum analyzer ng made up of slab-like waveguide means. The waveguide means has at one end enhanced surface diffraction grating means for intercepting and selectively diffracting a laser source beam so that the diffracted laser beam is deflected, expanded and focussed to converge toward the other end and in relation to both a surface acoustic wave (SAW) and detector array means. The waveguide means includes novel combined signal detection and arcuate-shaped transducer (CSD/AT) means between its ends for forming and directing the SAW in response to a detected RF (microwave) signal to be analyzed such that the SAW optically intercepts, interacts and further diffracts in Bragg-Cell-like fashion that converging beam so as to deflect same relative to detector array means at the other end of the waveguide means. The detector array means normally analyzes a series of differently deflected beams so as to provide frequency distribution and intensity of one or more detected signals. A second surface diffraction grating means can be provided on the waveguide means and interposed between the first surface diffraction grating means and the CSD/AT means so as to compensate for aberrations in the converging beam that might otherwise interfere with the detector array means analysis of an optically diffracted source beams.

Compact optical RF spectrum analyzer

Disclosed as a beamforming system, particularly useful for seismic exploration or undersea surveillance, in which data processing of the system is done optically. Sensor outputs are subjected to plural sets of time delays, and the system beams formed optically. Four embodiments are presented of the optical processing hardware.

Optical beamformers

Correlation is used to enhance the temporal resolution capability of incident energy detectors for high bandwidth signals. Such enhanced resolution is attained by using a primary response of the detectors, which may be weak but which accurately replicates the temporal waveshape of the incident energy pulse. A secondary response of the detectors, which is delayed from and more powerful than the primary response, but does not track the incident energy pulse as well as the primary, is correlated with the primary response. The secondary response is preferably passed through an inverse matched filter to provide a pulse more faithfully following the incident energy pulse prior to correlation with the primary response. Circuitry is provided for performing the enhancement, and a modulating device is used to permit the detector to respond to long-duration incident energy.

Method and apparatus for enhancement of primary pyroelectric response

A triple matrix product processor for optically multiplying three matrices U. G, and V, comprising a matrix-vector processor for sequentially multiplying each column of an M.times.N matrix G by at least a row of a P.times.M matrix U so that the 1.sup.th column of G is multiplied by the at least a row of matrix U producing at least the il.sup.th element of an intermediate result. The triple matrix product processor further includes an outer product processor for multiplying at least the il.sup.th element of the intermediate result with the 1.sup.th row of an N.times.Q matrix V producing at least a row of an N.times.N outer product matrix in a first plane, and a time-integrating optical detector array for summing the light impinging on the first plane from the outer product processor to produce all or a portion of a P.times. triple matrix product after all of the N columns of the matrix G and all of the N rows of the matrix V have been cycled through the processors.

Triple matrix product optical processors using combined time-and-space

An integrated optical signal processor device. The device includes a thin film of yttrium iron garnet ferrite material formed on a gadolinium gallium garnet substrate. A guided optical beam in a first polarization mode is directed through the thin film. A stripline antenna formed on the surface of the thin film is coupled to receive a microwave RF input signal. Under the influence of a bias magnetic field, the RF input signal excites a magnetostatic wave in the thin film. By means of Bragg diffraction, the magnetostatic wave diffracts the guided optical beam and thereby converts a portion of the beam into a second orthogonal polarization mode in response to the RF input signal. The guided optical beam is thereby modulated by the RF input signal. A preferred embodiment is disclosed which can be configured to form a spectrum analyzer, a time integrating correlator, and a space integrating convolver.

Integrated optical signal processor using diffraction of light by

A signal processor for generating the ambiguity integral using a modulatable, broadband, incoherent light source, a multiplicity of acousto-optic cells and diffraction gratings, and a two-dimensional time-integrating photodetector array. The various colors of the source spectrum are shifted by differing radio frequencies. These modified spectral components are also modulated by an input signal and serve as input sources for performing a multiplicity of correlations using an acousto-optic cell with an unknown Doppler-shifted signal. The answer is displayed on a two-dimensional time-integrating photodetector array where the spectral components are dispersed within the columns. The row corresponding to the color that has been properly frequency-compensated will contain the correlation or ambiguity peak, thereby identifying the Doppler component. Position within the row determines range.

Polychromatic time-integrating optical processor for high-speed

An acousto-optic time integrating two-dimensional frequency scanning correlator for cross-correlating signals which are separated in frequency. Two coherent light beams which are derived from the same laser are fed across respective Bragg cells, one cell having the signal A(t) cos .omega..sub.A t propagating thereacross and the other cell having the signal B(t) cos .omega..sub.B t propagating thereacross. The respective output beams are comprised in the x direction and expanded in the y direction and are made incident on an acousto-optical correlator device having chirp signals counter-propagating thereacross. The optical output is fed to a time-integrating photodiode array which provides an output signal corresponding to the cross-correlation of A(t) and B(t). In a further embodiment, the two Bragg cells are replaced by a single Bragg cell and beams having different polarizations are fed thereacross. In a still further embodiment, only a single crystal is used which has the A(t) and B(t) signals, as well as the chirp signals, counter-propagating thereacross.

Acousto-optic time integrating frequency scanning correlator

A highly efficient time integrating acousto-optic correlator which determs the time difference of arrival of the signals being correlated as well as the center frequency and bandwidth of the signals. A surface acoustic wave delay line is provided with two counter-propagating surface acoustic waves with wavefronts tilted with respect to each other. Two laser beams are directed across the propagating waves with an angle of 4.theta..sub..beta. between them where .theta..sub..beta. is the Bragg angle, so that one beam interacts primarily with one propagating wave while the other beam interacts primarily with the other wave. The modulated optical beams are directed to a time-integrating photodetector means which provides a signal output corresponding to the correlation function.

Acousto-optic time integrating correlator

A method for producing durable optical baffling materials comprising poling to a mirror finish the surface of a starting material, preferably having a very fine-grained structure, and then bombarding the surface of the starting material with low energy (0 to 50 keV) pulsed electrodes at a pulse length of about 0.1 microseconds. A fluence of 0.5 cal/cm.sup.2 renders the surface completely black in appearance, retaining none of its initial mirror-like properties.

Method for producing optical baffling material using pulsed electron

A method and an apparatus for controlling the angle of incidence of low-egy, high current density electron beams are disclosed. The apparatus includes a current generating diode arrangement with a mesh anode for producing a drifting electron beam. An auxiliary grounded screen electrode is placed between the anode and a target for controlling the average angle of incidence of electrons in the drifting electron beam. According to the method of the present invention, movement of the auxiliary screen electrode relative to the target and the anode permits reliable and reproducible adjustment of the average angle of incidence of the electrons in low energy, high current density relativistic electron beams.

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Silver Spring, MD, United States of America

John N Lee