Abstract: A holographic display apparatus has a display section including a back plate, on which a cold cathode device of the field emission type having a great number of fine emitter electrodes is arranged. The display section includes a transparent and conductive front plate, on which a great number of anode electrodes, which define pixels, are arranged respectively opposite the emitter electrodes. The emitter electrodes are selected so as to emit electrons by an input signal prepared in accordance with the interference pattern of a holographic diffraction figure. The anode electrodes are excited and induced by electron rays from the emitter electrodes to change their reflection coefficient. The interference pattern is displayed on the basis of the change in the reflection coefficient of the anode electrodes.

Abstract: A photorefractive device intended to be exposed to a marking radiation which is provided so as to create a grating of interference fringes in the device and to a reading radiation diffracted by the created grating. The device includes an electro-optical material having a quantum well structure (24) and formed in an intrinsic semi-conductor matrix (22, 24) and, on both sides of the material in the semi-conductor matrix, suitable means (28, 30) to trap, both parallel to the axis of the structure and perpendicular to this axis, free carriers generated by the marking radiation.

Abstract: A serial-to-parallel and parallel-to-serial conversion apparatus and method are disclosed to convert optical pulse data into temporally multiplexed ultra-fast optical pulses, and vice versa, using Fourier holographic transform techniques. In a first embodiment, optical pattern data is converted from a serial temporal-domain optical input signal to an output signal having parallel bits by recording a spectral hologram of the pulse data and reading it out with a continuous-wave (cw) laser. In a second embodiment, signals representing input bits in parallel may be optically multiplexed in the time domain, so that a single optical fiber may carry such signals without the electronic processing necessary in conventional switching multiplexers.

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

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.

Abstract: In a conventional hologram, a photographic film records the interference pattern of monochromatic light, scattered from an object (20) to be imaged, with a reference beam of unscattered light. Illumination of the developed film with a replica of the reference beam then creates a virtual image of the original object. Molecular resonance may be used to record an interference pattern between light signals that arrive at different times, and with this technique create a hologram (10') with time resolution. Using a time reference pulse (16) as a "light shutter", holographic images may be recorded selectively, according to the time taken by light travelling from the object to the hologram. This method may be used to image an object obscured by a light-scattering medium.

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 photosensitive element 46 absorbs at least a portion of an incident write beam 40, causing a spatially varying electric field to be applied across a layer of a ferroelectric liquid crystal (FLC) 48, thereby forming a pattern of local polarizations corresponding to the spatially varying electric field. In one embodiment, a signal beam is modulated with a phase variation characteristic of a particular aberrator. The signal beam is then combined with a substantially plane wave reference beam to form interference fringes. These interference fringes are directed as a write beam onto photosensitive layer 46, forming a hologram in FLC layer 48 which can be read optically. An incident beam of light can be diffracted by a hologram formed in the FLC layer, thereby modulating the incident beam of light with the phase variations comprising the hologram.

Abstract: A moving holographic image is projected into three space by producing a series of slides or fixed holographic images in quick succession in a process similar to a conventional motion picture All of the slides are produced on a single photochromic surface in succession by writing on the surface with UV light. Each slide consists of a set of identical strip holograms positioned on the photochromic surface as an array. Each strip hologram is produced by creating a series of traces arranged side by side. As the maxima traverse the surface, the UV source is turned on and off according to a program to produce a series of dots of either unchanged or darkened color on the photochromic surface. During the next scan a new set of unchanged or darkened dots are produced on each strip hologram, and so on until the slide is completed. After being illuminated the surface is quickly washed clean in preparation for the next slide by illuminating it with a burst of high intensity UV light.

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: The present invention relates to polymeric materials that exhibit an erasable photorefractive effect which can be fabricated into optical devices such as optical wave guides.