Abstract: A unipolar terminal-attractor based neural associative memory (TABAM) system with adaptive threshold for perfect convergence is presented. By adaptively setting the threshold values for the dynamic iteration for the unipolar binary neuron states with terminal-attractors for the purpose of reducing the spurious states in a Hopfield neural network for associative memory and using the inner-product approach, perfect convergence and correct retrieval is achieved. Simulation is completed with a small number of stored states (M) and a small number of neurons (N) but a large M/N ratio. An experiment with optical exclusive-OR logic operation using LCTV SLMs shows the feasibility of optoelectronic implementation of the models. A complete inner-product TABAM is implemented using a PC for calculation of adaptive threshold values to achieve a unipolar TABAM (UIT) in the case where there is no crosstalk, and a crosstalk model (CRIT) in the case where crosstalk corrupts the desired state.

Abstract: A system for optically providing one-to-many irregular interconnections, and strength-adjustable many-to-many irregular interconnections which may be provided with strengths (weights) w.sub.ij using multiple laser beams which address multiple holograms and means for combining the beams modified by the holograms to form multiple interconnections, such as a cross-bar switching network. The optical means for interconnection is based on entering a series of complex computer-generated holograms on an electrically addressed spatial light modulator for real-time reconfigurations, thus providing flexibility for interconnection networks for large-scale practical use. By employing multiple sources and holograms, the number of interconnection patterns achieved is increased greatly.

Abstract: An optical implementation of an inner-product neural associative memory is realized with a first spatial light modulator for entering an initial two-dimensional N-tuple vector and for entering a thresholded output vector image after each iteration until convergence is reached, and a second spatial light modulator for entering M weighted vectors of inner-product scalars multiplied with each of the M stored vectors, where the inner-product scalars are produced by multiplication of the initial input vector in the first iterative cycle (and thresholded vectors in subsequent iterative cycles) with each of the M stored vectors, and the weighted vectors are produced by multiplication of the scalars with corresponding ones of the stored vectors. A Hughes liquid crystal light valve is used for the dual function of summing the weighted vectors and thresholding the sum vector.

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: An inner-product array processor is provided with thresholding of the inner product during each iteration to make more significant the inner product employed in estimating a vector to be used as the input vector for the next iteration. While stored vectors and estimated vectors are represented in bipolar binary (1,-1), only those elements of an initial partial input vector that are believed to be common with those of a stored vector are represented in bipolar binary; the remaining elements of a partial input vector are set to 0. This mode of representation, in which the known elements of a partial input vector are in bipolar binary form and the remaining elements are set equal to 0, is referred to as trinary representation. The initial inner products corresponding to the partial input vector will then be equal to the number of known elements. Inner-product thresholding is applied to accelerate convergence and to avoid convergence to a negative input product.

Abstract: A relatively small and low-cost system is provided for projecting a large and bright television image onto a screen. A minature liquid crystal array is driven by video circuitry to produce a pattern of transparencies in the array corresponding to a television image. Light is directed against the rear surface of the array to illuminate it, while a projection lens lies in front of the array to project the image of the array onto a large screen. Grid lines in the liquid crystal array are eliminated by a spacial filter which comprises a negative of the Fourier transform of the grid.

Abstract: A real-time, pre-detection optical dynamic range compression system uses a photorefractive crystal, such as BaTiO.sub.3 or LiNbO.sub.3, in which light induced scattering from crystal inhomogeneities of the optical input occurs as a nonlinear function of the input intensity. The greater the intensity, the faster random interference gratings are created to scatter the incident light. The unscattered portion of the optical signal is therefore reduced in dynamic range over time. The amount or range of dynamic range compression may be controlled by adjusting the time of application of the unscattered crystal output to the photodetector with regard to the time of application of the optical input to the crystal.

Abstract: A method and apparatus are disclosed for real-time optical broadband pseudocolor encoding of an image. A light polarization spatial modulator is utilized to density encode an incident beam of plane-polarized light; the beam is dispersed into its primary colors; the polarizations of the dispersed beams are analyzed to produce positive, negative, and bidirectionally modualated images which are each separately encoded with a primary color; and the primary-color encoded beams are combined to produce a pseudocolored image. In a preferred embodiment the pseudocolor encoding apparatus comprises a compact white-light projection system and a liquid-crystal television spatial light polarization modulator. The invention makes possible the large-screen display of broadband pseudocolor images from real-world input scenes from a television camera.

Abstract: A method and apparatus for generation of second-rank tensors using a photorefractive crystal to perform the outer-product between two vectors via four-wave mixing, thereby taking 2n input data to a control n.sup.2 output data points. Two orthogonal amplitude modulated coherent vector beams x and y are expanded and then collimated before directing them onto two opposing parallel sides of the photorefractive crystal in exact opposition. A beamsplitter is used to direct a coherent pumping beam onto the crystal at an appropriate angle so as to produce a conjugate beam that is the matrix product of the vector beams x and y, and to separate the resulting conjugate beam that propagates in the exact opposite direction from the pumping beam. The conjugate beam thus separated is the tensor output xy.sup.T.

Abstract: System for optically recognizing and tracking a plurality of objects within a field of vision. Laser (46) produces a coherent beam (48). Beam splitter (24) splits the beam into object (26) and reference (28) beams. Beam expanders (50) and collimators (52) transform the beams (26, 28) into coherent collimated light beams (26', 28'). A two-dimensional SLM (54), disposed in the object beam (26'), modulates the object beam with optical information as a function of signals from a first camera (16) which develops X and Y signals reflecting the contents of its field of vision. A hololens (38), positioned in the object beam (26') subsequent to the modulator (54), focuses the object beam at a plurality of focal points (42). A planar transparency-forming film (32), disposed with the focal points on an exposable surface, forms a multiple position interference filter (62) upon exposure of the surface and development processing of the film (32).

Abstract: An image difference detection system is described, of the type wherein two created image representations such as transparencies representing the images to be compared lie coplanar, while light passes through the two transparencies and is formed into coincident images at the image plane for comparison. The two transparencies are formed by portions of a polarization rotation spacial light modulator display such as a multi-pixel liquid crystal display or a magneto optical rotation type. In a system where light passing through the two transparencies is polarized in transverse directions to enable the use of a Wollaston prism to bring the images into coincidence, a liquid crystal display can be used which is devoid of polarizing sheets that would interfere with transverse polarizing of the light passing through the two transparencies.

Abstract: Apparatus is provided which greatly reduces the intensity of bright portions of an image while only moderately reducing the brightness of dimmer portions of the image, to thereby compress the range of light intensities to facilitate detection of the image. The apparatus includes a light detector device formed by a chip of photorefractive material. A two-dimensional array of light beams from an object to be detected, passes through a beam splitter to form two arrays of light beams. The two arrays of light beams are directed at different angles against a surface of the chip of photorefractive material, the two arrays of light beams forming coincident images on the surface. One of the two-dimensional arrays of beams emerging from an opposite surface of the chip has a lower range of intensities, to facilitate detection of the object despite very bright spots on its image. The other array of light beams energing from the chip has a greater range of intensities than the unprocessed image of the object.

Abstract: An optical processor is provided which facilitates selection of any of a variety of patterns or images which are to be compared with a Fourier transform of a template image, wherein the processor can be constructed at low cost. One of the two images that are to be compared is formed by generating video signals representing the image and using those signals to drive a liquid crystal array through which light passes.

Abstract: An improved halftone dot screen for use in reproduction of continuous-tone graphic images is disclosed. The screen comprises a two-dimensional matrix of cells (dots) each cell having a common pattern of transmittance to radiation utilized in the reproduction process. The common pattern of transmittance for each cell is characterized by a finite number of different discrete transmittance level patterns. In a preferred embodiment, these patterns include portions arranged along the respective sides of a parallelogram. In one preferred embodiment, the discrete transmittance level patterns comprise an array of concentric parallelograms. Each parallelogram has a plurality of dot portions arranged along the sides of the parallelogram. The sides of the parallelogram patterns are preferably disposed at a substantial angle to the horizontal to reduce moire and rosette pattern effects and to simplify the reproduction process.

Abstract: A method of making a halftone contact screen having a plurality of discrete different optical transmittance levels by making multiple relative translations of light-sensitive material under and in close contact with a ruling mask while exposures to light through the ruling mask are made between the translations. The mask comprises a thin flat plate having an array of parallel periodic equal width opaque straight bars separated by an array of parallel equal width transparent bars. In a first process, translations are normally made perpendicular to the parallel of the bars. Two-dimensional or dot halftone contact screens are made by repeating the process wherein the light-sensitive material is rotated relative to the ruling mask, in its own plane, at an angle greater than zero to the direction of the ruling bars during the first process. Using the single process creates a line halftone contact screen; adding the second process creates a dot halftone contact screen.

Abstract: A method of making multilevel equidensity contour mappings and pseudo-colored versions of a photograph. First a half-tone transparency of the photograph is made by the method described in copending patent application entitled "Method of Making Half-Tone Screens", Ser. No. 708,539 filed 26 July, 1976 by Liu, now abandoned. The half-tone photograph transparency is placed at the object plane of a first lens. A spatially filtered collimated light beam is directed through the transparency and the lens such that a multitude of diffraction orders appear in the focal plane of the lens. A particular non-zero order of diffraction is singled out by placing a thin slit spatial filter at the Fourier plane of the lens. Reimaging of the diffraction order by another lens produces a filtered image which contains multilevel equidensity contours of the original photographic image. In one embodiment the light beam is generated by lasers of different wavelengths.

Abstract: An improved halftone dot screen for use in reproduction of continuous-tone graphic images is disclosed. The screen comprises a two-dimensional matrix of cells (dots) each cell having a common pattern of transmittance to radiation utilized in the reproduction process. The common pattern of transmittance for each cell is characterized by a finite number of different discrete transmittance level patterns. In a preferred embodiment, these patterns include portions arranged along the respective sides of a parallelogram. In one preferred embodiment, the discrete transmittance level patterns comprise an array of concentric parallelograms. Each parallelogram has a plurality of dot portions arranged along the sides of the parallelogram. The sides of the parallelogram patterns are preferably disposed at a substantial angle to the horizontal to reduce moire and rosette pattern effects and to simplify the reproduction process.