Abstract: A holographic imaging apparatus having a pulsed laser light source for generating an object beam and a reference beam whereby an object, obscured by a diffusing medium, is illuminated by the object beam. A real time interferogram recording medium is exposed to the coincidence of light reflected from the object and the reference beam to record an interferogram. A holographic image is then reconstructed from the interferogram and may be viewed and recorded. The pulsed laser light source generates a beam which is divided by a conventional beam splitter device into an object beam and a reference beam. The object beam is then diverged by a lens which forms a diverging object beam to illuminate the object. The reference beam is diverged through another lens to form a diverging reference beam which is directed so that it illuminates a photoreactive crystal.

Abstract: Substantial improvements in photorefractive device lifetimes are provided by control of electron migration which results in the decay of gratings in photorefractive materials due to diffusion and other effects. A new class of photorefractive devices using compensating electronic and ionic gratings having relatively low efficiency but nonetheless usable gratings is provided by arranging the gratings to be reflective in a wavelength band outside the photo-excitation band of the photorefractive material, as by using an infrared operating wavelength. Longer lifetimes in high efficiency gratings are achieved by constant or periodic illumination of photorefractive materials to assure uniform charged distribution of electrons and maintenance of the ionic backbone grating.

Abstract: A plurality of holograms are simultaneously angularly and spatially multiplexed within a storage medium by writing the holograms at different locations within the storage medium using reference and object beams directed thereto via cooperating reference beam and object beam scanners, respectively. The simultaneously angular and spatially multiplexed holograms are subsequently read-out by directing a reference beam through a desired location within the storage medium using the reference beam scanner. The reference beam is directed from the storage medium to a phase conjugator which conjugates the phase of the reference beam and directs the phase conjugated reference beam back to the same desired location within the storage medium so as to excite a corresponding conjugate object beam which is then directed onto a detector array.

Abstract: A method of holographic recording in a photorefractive medium wherein stored holograms may be retrieved with maximum signal-to noise ratio (SNR) is disclosed. A plurality of servo blocks containing position feedback information is recorded in the crystal and made non-erasable by heating the crystal. The servo blocks are recorded at specific increments, either angular or frequency, depending whether wavelength or angular multiplexing is applied, and each servo block is defined by one of five patterns. Data pages are then recorded at positions or wavelengths enabling each data page to be subsequently reconstructed with servo patterns which provide position feedback information. The method of recording data pages and servo blocks is consistent with conventional practices. In addition, the recording system also includes components (e.g.

Abstract: A method and apparatus for producing images in which phase variation introduced by reflections from a transparent phase object are represented in interference generated phase contrast, and in which gradients in phase introduced by transmission through the phase modulating object or plate are represented in phase gradient contrast. Combination interference generated phase contrast-phase gradient contrast images are also produced. A laser beam is directed by a beam splitter through the transparent phase and falls onto a photorefractive crystal where a temporary hologram forms. The hologram generates the phase conjugate of the transmitted beam which moves back through the plate, so the phase distortions introduced by the transparent phase object are removed in the back propagating beam. This beam interferes with a specularly reflected beam from the transparent phase object.

Abstract: Apparatus for the simultaneous parallel recording of holograms on a dynamic volume medium. Directed along a recording axis is a polychromatic source image which has multiple component images to be recorded in the dynamic volume medium. Each component image of the polychromatic source image has a separate frequency. Directed along a reference axis is a polychromatic reference beam having a plurality of monochromatic reference components with each reference component having a separate wavelength. Positioned upstream from the volume on the reference axis is a prism which angularly multiplexes the reference components to provide a plurality of monochromatic reference beams which are directed at angular offsets from the reference axis to the medium. Each of the reference beams has a wavelength which is identical to the wavelength of only one of the monochromatic component images of the polychromatic source image.

Abstract: A two-photon process for writing to a holographic recording medium comprising a photorefractive material doped with an excitation dopant selected from rare earth ions and an ionization dopant selected from transition metal ions or rare earth ions.

Abstract: Ionic and impurity concentrations in a photorefractive holographic storage medium are optimized such that electronic and ionic Debye numbers match an expected grating wave number K, at fixing and recording temperatures, respectively. Simultaneous and sequential recording and fixing are evaluated. The photovoltaic effect is reduced, subject to response time and absorption constraints, by matching reduced and oxidized impurity concentrations.

Abstract: A method and system are disclosed for dynamically refreshing angle-multiplexed holograms stored in a photorefractive medium. In accordance with the invention the photorefractive medium is simultaneously exposed to a plurality of reference beams. Each reference beam is oriented at an angle corresponding to an angle at which a hologram was previously stored within the photorefractive medium. The frequency and duration of the reference beams are regulated such that each reference beam enhances the diffraction efficiency of an associated hologram, stored at the angle corresponding to the angle of the reference beam. Each reference beam is preferably at a frequency different from the frequency of the other reference beams so as to avoid the generation of plane-wave holograms due to interference between the multiple reference beams.

Abstract: A multiphoton photorefractive holographic recording material includes an electro-optic host material doped with at least one lanthanide.

Abstract: Ferroelectric materials are disclosed as reversible holographic recording media (25) for use in two-photon recording systems. The ferroelectric materials disclosed herein provide long-lived electronic states intermediate the ferroelectric material's valence and conduction bands. These intermediate states have a sufficiently long life (on the order of 1 to 100 milliseconds) that low-power continuous wave ("cw") lasers (1) can be used to record interference patterns on them. Thus, two-photon holographic recording systems are also disclosed which do not require high-power, short pulse length, mode-locked or Q-switched lasers. Rather, the disclosed holographic recording systems employ visible and near IR cw lasers such as diode lasers.The disclosed two-photon holographic recording systems provide for absorption of a first photon which excites electrons of holographic recording media to an intermediate state.

Abstract: A method and apparatus for fixing images, holograms and domain gratings in crystals by application of an electric field on a crystal and simultaneous illumination of it with a light pattern. The fixing procedure is based on a screening effect. The modulation of the domains may be perpendicular to the c-axis. Another application of the method is in frequency mixing such as second harmonic generation and parametric processes, by overcoming the problem of phase matching using the domain gratings. Thus, it is possible to obtain controllable broadband mixing and tailored quasi-phase matching for several wavelengths or for prespecified wavelength tuning ranges and frequency widths.

Abstract: A new type of holographic recording in photorefractive crystals is disclosed, termed orthogonal data storage, in which counterpropagating, reflection mode holograms are wavelength multiplexed to form gratings lying along a common axis. It is shown that this configuration provides substantial improvements in data storage capacity in comparison to prior art systems and that higher coupling coefficients are achieved. In consequence, not only storage of data but a wide range of other devices including wavelength selective filters, lenses and optical correlation systems are disclosed. Further, methods of writing and processing metastable images are disclosed which substantially improve the strength of the gratings that are permanently developed in the medium. These methods include advantageous use of electrical potentials and photovoltaic properties, together with different interrelationships during processing.

Abstract: A hologram with a dynamically controlled diffraction efficiency and enhanced signal-to-noise ratio is recorded in ferroelectric photorefractive materials, such as strontium barium niobate (Sr.sub.x Ba.sub.1-x Nb.sub.2 O.sub.6) (SBN), BSTN, SCNN, PBN, BSKNN, BaTiO.sub.3, LiNbO.sub.3, KNbO.sub.3, KTN, PLZT and the tungsten bronze family. The diffraction efficiency of the hologram is dynamically controlled by applying an electric field along the polar axis of the ferroelectric photorefractive recording medium. Electrically controlled diffraction is used in conjunction with hologram fixing and operation of the material at a temperature in the vicinity of or above its Curie temperature to additionally provide prolonged, low-noise readout. The general methods for recording and reconstructing a hologram (or a set of multiplexed holograms) using these techniques is disclosed.

Abstract: Rare earth doped ferroelectric materials are disclosed as reversible holographic recording medium (25) for use in two-photon recording systems. Such rare earth elements provide long-lived electronic states intermediate the ferroelectric material's valence and conduction bands. In some cases, these rare earth intermediate states have a sufficiently long life that low-power continuous wave ("cw") lasers (1) can be used to record interference patterns on them. Thus, two-photon holographic recording systems are also disclosed which do not require high-power, short pulse length, mode-locked or Q-switched lasers. Rather, the disclosed holographic recording systems employ cw lasers such as diode lasers. The rare earth dopants include praseodymium, neodymium, dysprosium, holmium, erbium, and thulium. These dopants provide ions having 4f excited states that give rise to absorptions in the near infra-red and visible spectral regions and typically have lifetimes on the order of 0.1 to 1 milliseconds.

Abstract: A method and read/write memory based thereon for storing phase holograms in a photorefractive crystalline material in which electric-field-mobile positive ions are associated with certain sites within the material broadly characterized by first forming a halogram (light interference pattern) in the material in order to redistribute the electrons therein to cause variations of the electric fields which variations represent the halogram, and then illuminating the material with light of a frequency in an absorption band of the ionic bond and having sufficient energy to cause the positive ions to be redistributed to neutralize the electric field variations caused by the electrons, whereat said positive ions remain fixed. As applied to a specific crystalline material, Fe:LiNbO.sub.3, having protons held in OH.sup.- bonds, a crystal of Fe:LiNbO.sub.

Abstract: In a method for mitigating cross-talk in high-efficiency, angle-multiplexed holograms stored in photorefractive media, a plurality of uniformly low-efficiency holograms are first stored within a common holographic storage medium and then simultaneously exposed to a like plurality of mutually incoherent reference beams. Each reference beam effects enhancement of its corresponding hologram so as to increase the level thereof while also minimizing cross-talk between holograms.

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.

Abstract: An adaptive optics imaging system uses a double pumped phase conjugate mirror (DPCM) to compensate for phase, amplitude or polarization aberrations imposed upon a multi-pixel object beam. A remote reference beam is used to sample an aberrating medium through which the object beam is transmitted, and forms a shared hologram in a two-beam coupling medium with a local reference beam having known phase characteristics, generally plane-wave. An output beam is produced in the phase conjugate direction of the local reference beam, with the pixelized difference in phase characteristics between the output and local reference beams corresponding to the pixelized difference in phase characteristics between the object and remote reference beams; the remote reference beam is also preferably planar.

Abstract: A photorefractive apparatus is exposed to a write beam or radiation for creating a system of interference fringes in the apparatus, as well as to a read beam or radiation which diffracts the system created and includes at least one elementary pattern (1) having an electrooptical material (6) with a high electrooptical coefficient with respect to the read radiation, which is transparent to the read radiation and which is surrounded by photoconductive materials (2, 4). The photoconductive materials are transparent to the read radiation and under the effect of the write radiation are able to respectively produce electrons and holes having a high mobility. Application to the optical processing of signals.

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.

Abstract: An electrically addressable wavefront-modulation device has a thin film of transparent conductive material finely patterned as a hologram in which individual fringe elements need not have electrical continuity with each other or with external electrodes. The holographic pattern is covered with a transparent dielectric whose refractive index preferably matches that of the patterned material. An electro-optic layer varies in refractive index depending on application of a voltage to transparent conductive electrodes, one on each side of the device area to be addressed. The hologram's diffraction efficiency may be varied at high frequency. Thus the electrohologram is addressed by area or field rather than by element or matrix addressing. The electro-optic layer may be liquid crystal material. Preferred embodiments have T-shaped structures formed by subetching under each fringe element.

Abstract: A light responsive device (10) has a body (12) that includes a matrix comprised of Group III-V material, the matrix having inclusions (14) comprised of a Group V material contained therein. The body is responsive to a presence of a light beam that has a spatially varying intensity for modifying in a corresponding spatially varying manner a distribution of trapped photoexcited charge carriers within the body. The distribution of trapped charge carriers induces a corresponding spatial variation in at least one optical property of the Group III-V material, such as the index of refraction of the Group III-V material and/or an absorption coefficient of the Group III-V material. The Group III-V material is comprised of LTG GaAs:As or LTG AlGaAs:As.

Abstract: A passive broadband sensor protection and enhancement system and technique. ncident light is focused with a cylindrical lens on the optical axis into an intense light strip onto the input face of a photorefractive crystal which may include optional anti-reflection coatings on the input and output face. A broadband high reflection coating proximate to the input face reflects all radiation from approximately 0.68 out to at least 1.5 micrometers wavelength and light exiting includes a transmitted beam and beam fan. A weak holographic grating is used to seed the beam fan, such that is fanned out of the optical path in a direction determined by the c-axis, dominant electro-optic coefficient, and charge carriers participating in the photorefractive process. The transmitted beam contains only incoherent radiation as input to a sensitive detector resulting in broadband multiline protection from the visible spectrum for substantially all pulsewidths and cw lasers, with enhanced time response and interaction length.

Abstract: Multiple bits of information are stored in the frequency domain in a bulk glass using optically encoded .chi..sup.(2) gratings. The information is read out by measuring a second harmonic generation (SHG) from the encoded glass as a function of wavelength. Information storage densities in excess of 10.sup.8 bits/cm.sup.2 are readily achievable. The stored information is stable under readout conditions, and the information can be erased and rewritten.

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.

Abstract: A method of writing plane holographic gratings Bragg-matched for reflection in the infrared in a photorefractive material using shorter wavelength light through a face perpendicular to the grating planes. The writing beam wavelength is selected to be within the photorefractive sensitivity range of the crystal and the angles are chosen relative to the wavelength to define a reflection grating with a period such that counter-propagating reflection occurs at the desired IR wavelength. For reflection gratings at different wavelengths, either the transmission or the reflection mode geometry may be used. In the transmission mode, the writing beams are incident on the same side face while in the reflection made the writing is on opposite faces in an off-axis (non-counter-propagating) configuration. Anti-reflection coatings of the appropriate wavelengths are used on the crystal surfaces to reduce reflection losses and improve the diffraction efficiency of the grating.

Abstract: A new type of holographic recording in photorefractive crystals is disclosed, termed orthogonal data storage, in which counterpropagating, reflection mode holograms are wavelength multiplexed to form gratings lying along a common axis. It is shown that this configuration provides substantial improvements in data storage capacity in comparison to prior art systems and that higher coupling coefficients are achieved. In consequence, not only storage of data but a wide range of other devices including wavelength selective filters, lenses and optical correlation systems are disclosed. Further, methods of writing and processing metastable images are disclosed which substantially improve the strength of the gratings that are permanently developed in the medium. These methods include advantageous use of electrical potentials and photovoltaic properties, together with different interrelationships during processing.

Abstract: There is described a semiconductor microcrystallite doped glass that exhibits SHG, and a method of preparing, or encoding, a semiconductor microcrystallite doped glass by the simultaneous injection of fundamental and second harmonic fields, such as 1.06 .mu.m and 532 nm. More specifically, the disclosure pertains to a structure that exhibits SHG, the structure being comprised of, by example, borosilicate glass that contains CdS.sub.x Se.sub.1-x microcrystallites. Also disclosed are embodiments of devices having an optical waveguide structure formed within a glass substrate that contains semiconductor microcrystallites. The optical waveguide structure guides and contains injected radiation and also converts a portion thereof to the second harmonic. Also disclosed are optoelectronic devices that include frequency doublers, self-doubling lasant material, bichromatic optical switches, and a volume holographic medium, all of which include a glass host having semiconductor microcrystallites embedded within.

Abstract: The present invention relates to an improved process for producing photorefractive net gain two beam coupling utilizing polymeric materials.

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.

Abstract: An improved method for storing permanent holographic gratings in photorefractive materials for use in narrow band filters such as the H.sub.60 filter, as well as the filters themselves. The invention also provides an improved method of controlling the electric field and the nature of the photorefraction to minimize wavelength shifts and band broadening at a minimal reduction of diffraction efficiency.

Abstract: A 2D/3D optically controlled spatial and angular electromagnetic wave modulator is disclosed. The modulator of the present invention modulates the amplitude and direction of an electromagnetic wave such as millimeter microwaves or infrared waves by diffracting or scattering the electromagnetic wave from a semiconductor material upon which is incident a controlling lightwave. The lightwave incident upon the semiconductor is of varying intensity, and may be time varying, and changes the complex refractive permittivity of the semiconductor material. The electromagnetic wave is thus modulated in accordance with the controlling lightwave.

Abstract: Holographic apparatus and methods are provided for generating high resolution telescopic images using low cost, small aperture lenses. Holographic media, such as photorefractive crystals, are used in conjunction with multiple and/or synthetic aperture techniques. In a multiple aperture system, a thin nonlinear holographic medium is used with a plurality of small optical lenses to compensate for the inherent piston and tilt errors of the lenses, thereby providing higher resolution. In another embodiment, synthetic aperture techniques are accomplished by illuminating a far field object with coherent light, deriving a reference beam from the coherent light, and changing the position of the reference beam in accordance with a computational formula. A hologram is formed from a sequence of image exposures in the holographic media, each made at different positions with respect to the image.

Abstract: A self amplifying optical pattern recognizer includes a geometric system configuration similar to that of a Vander Lugt holographic matched filter configuration with a photorefractive crystal specifically oriented with respect to the input beams. An extraordinarily polarized, spherically converging object image beam is formed by laser illumination of an input object image and applied through a photorefractive crystal, such as a barium titanite (BaTiO.sub.3) crystal. A volume or thin-film difORIGIN OF THE INVENTIONThe invention described herein was made in the performance of work under a NASA contract, and is subject to the provisions of Public Law 96-517 (35 USC 202) in which the Contractor has elected to retain title.

Abstract: A pattern recognition apparatus and a method for operating same. The apparatus includes a volume holographic medium (4) having a plurality of Fourier-space volume holograms representing pattern templates stored within. The apparatus further includes a spatial light modulator (1) and a phase encoder (2). The phase encoder has an output optically coupled to the medium by a first Fourier transform lens (3). The spatial light modulator spatially modulates a spatially uniform laser beam (7) in accordance with an unknown pattern. The two-dimensional phase encoder causes the spatially modulated laser beam to be spatially distributed prior to application to the medium. The apparatus further includes a detector (6, 11) having an input optically coupled by a second Fourier transform lens (5) means to an angular spectrum of plane waves generated by the medium in response to the output of the spatial modulator, phase encoder, and first Fourier lens.

Abstract: Composite holograms are disclosed wherein microvoids between the holographic interference fringes are filled with a liquid crystal. The diffraction efficiency and other holographic properties of such composite holograms may be varied by external stimuli, e.g., application of an electric field of thermal energy.

Abstract: An apparatus for displaying a three-dimensional image of a plurality of tomographic images by storing pictorial information of a tomographic image in an image convering element, forming interference fringes between a reading light beam which is transmitted through the image converting element and is modulated in accordance with the pictorial information stored therein and a reference light beam, and recording the interference fringes on a photographic plate. A three-dimensional image is reproduced by projecting the reference light beam onto the thus developed photographic plate. The image converting element is formed by a Pockels readout optical modulator. An intensity and position of a coherent light beam is modulated in accordance with the pictorial information of the tomographic image, and the thus modulated coherent reading light beam is made incident upon the Pockels readout optical modulator.

Abstract: A photorefractive device is provided for converting an image-bearing incoherent input beam to a high contrast coherent output beam the intensity of which varies as the square of the input intensity pattern. The device uses an incoherent image beam to write a holographic grating directly in a photorefractive medium. In one embodiment, a parallel, laterally displaced, telecentric system of lenses is used to split a quasi-monochromatic, incoherent image-bearing beam into two equal components. The two components are superimposed at the surface of the photorefractive medium to produce the hologram. In a second embodiment, the incoherent input beam is directed through a physically translating external grating to write the hologram in the photorefractive medium. The moving grating improves the diffraction efficiency of the hologram under the influence of an applied electric field and stabilizes the temporal response characteristics for signal processing.

Abstract: An adaptive filter having a correlation weighting structue having a single Bragg cell, acting as a tapped delay line and having an input and an output, the Bragg cell intensity modulating a write laser beam for computing correlation values, and modulating a read laser field strength for multiplying the correlation values by delayed signal values. A photorefractive element is arranged such that substantial portions of diffracted and undiffracted light components from the single Bragg cell overlap within the photorefractive element. A write laser is intensity modulated by an error signal to produce an optical write signal that is received at the photorefractive element input and which writes correlation coefficients in the photorefractive element. A read laser produces a light signal, a portion of which is diffracted by the single Bragg cell, the portion of the light signal that is not diffracted by the single Bragg cell being partially diffracted by the photorefractive element.

Abstract: A polarization independent energy exchanger transfers optical energy from a first coherent beam of optical energy to a second coherent beam of optical energy where the second beam is coherent with respect to the first beam, the second beam is counterpropagating with respect to the first beam, and the second beam possesses substantially the same polarization as the first beam. The energy exchanger includes a nonlinear optical uniaxial crystal having electro-optic coefficients r.sub.13 and r.sub.23 of equal magnitude and having a sufficiently large photorefractive charge density to achieve efficient contradirectional two-beam coupling, independent of the polarization states of the first and second beams. The crystal is oriented to receive the first and second beams therein such that the optic axis of the crystal is aligned parallel to the propagation directions of the first and second beams.

Abstract: An optical correlator according to the present invention generates a cross-correlation peak of two patterns of pictorial information to be compared. It generates pictorial patterns of a sum of the two patterns of pictorial information and of a difference between the two patterns of pictorial information by a phase conjugate waveform, transforms the pictorial patterns into first Fourier transform images, generates a pictorial pattern of a difference between an intensity distribution of the first Fourier transform images by the phase conjugate waveform, and transforms the pictorial pattern of a difference between an intensity distribution of the first Fourier transform images into second Fourier transform images. The optical correlator detects a cross-correlation peak of the two patterns of pictorial information for comparison at a high S/N ratio.

Abstract: Edge enhancement of an input image by four-wave mixing a first write beam with a second write beam in a photorefractive crystal, e.g., GaAs, achieved for VanderLugt optical correlation with an edge enhanced reference image by optimizing the power ratio of a second write beam to the first write beam, e.g., 70:1, and optimizing the power ratio of a read beam, which carries the reference image to the first write beam, e.g., 100:701. Liquid crystal TV panels are employed as spatial light modulators in order to change the input and reference images in real time.

Abstract: A holographic apparatus has an inferometer for concurrently irradiating an image recording medium by a writing reference light of spherical or plane wave form and a signal light containing image information which interfere with each other to form a hologram, and means for irradiating the hologram by a reading reference light in the opposite direction of the reference light to thereby reconstruct the image information. The image recording medium is comprised of a photoconductive layer, an optical reflective layer, a pair of liquid crystal alignment layers, a ferroelectric liquid crystal layer having bistable memory characteristic between its optical reflectivity and an applied voltage, means for applying the voltage and a pair of transparent substrates.

Abstract: A method is provided for reconstructing an image transmitted through a thick distorting medium. A remote source provides coherent light at the object plane, and a local source, typically derived from the remote source, provides corresponding light that is coherent with respect to the remote source. Light from the remote source is directed through the thick aberrator and into a holographic medium, such as a photorefractive crystal, to interact with corresponding light from the local source and produce a volume hologram. An angularly multiplexed volume hologram, which covers the entire object field, is written into the holographic medium by successive exposures of light from the remote and local sources for successive pixels of the object plane. Light from an object, which comprises two-dimensional information from the object plane, can be reconstructed by the volume hologram after being distorted by the thick aberrator.

Abstract: A holographic learning machine comprising a volume holographic recording medium, 2N photo-detectors receiving light diffracted from the medium, and N electrical circuits subtracting respective pairs of outputs of the photo-detectors, thresholding the differences and comparing them to target values. During training, a coherent image beam shines on the recording medium and corresponding target values are supplied to the circuits. Depending on whether the comparison between the thresholded difference and the target is positive or negative, a positive error or negative error amplitude modulator in a 2N array is turned on to transmit to the recording medium light coherent with the image beam. Thereby, the full bipolar perceptron algorithm is implemented. The implementation may be integrated into a rugged, integral unit.

Abstract: The present invention relates to a novel architecture and associated apparatus for the development of highly multiplexed photonic interconnection networks and holographic optical elements with maximum optical throughput efficiency and minimum interchannel crosstalk, based on parallel incoherent/coherent holographic recording and readout principles. This scheme further provides for arbitrarily weighted and independent interconnections, which are of potential importance in the development of neuro-optical computers, as well as photonic interconnection networks and multiplexed holographic optical elements. In addition, the extremely difficult problem of copying the contents of a three-dimensional holographic storage device in one step is soluble by utilization of the architectural principles and specified apparatus that are key features of this invention.

Abstract: New methods for producing computer generated holograms to be used for a liquid crystal spacial light modulator having a plurality of pixels, wherein the amplitude component of a coherent wave disturbance is corrected by taking into account the phase distortion due to the twist of liquid crystal molecules of the liquid crystal spacial light modulator.

Abstract: A holographic television apparatus is disclosed for detecting and displaying three-dimensional holographic information corresponding to a holographic optical interference pattern. The apparatus includes an image detecting device for successively detecting two-dimensional slices of the three-dimensional holographic optical interference pattern, an image reproduction device for successively reproducing two-dimensional slices of the three-dimensional holographic optical interference pattern, a transmission means connecting the image detection device to the image reproduction device, and an actuation unit for moving the image detection device at predetermined regular intervals in an depth direction normal to the two-dimensional image portions to obtain information with respect to the three-dimensional optical interference pattern at unformly spaced two-dimensional layers thereof corresponding to the displacement intervals.