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 quantum well infrared photodetector and modulator are monolithically integrated to one another. The infrared scene impinges on an infrared receiving element such as a phase grating, which couples it to a modulator. The modulator includes asymmetric quantum wells which are shifted by an applied bias. By appropriately adjusting the bias, the modulator can pass a maximum amount of the input information or can pass less. The photodetector and modulator both use the same kinds of materials, preferably GaAs and Al.sub.x Ga.sub.1-x As, so they essentially become a single unit, obtaining better noise and operating characteristics from the combination.

Abstract: Photorefractive crystals having the formula K.sub.1-y Li.sub.y Ta.sub.1-x Nb.sub.x O.sub.3 wherein x is between 0 and 1 and y is between 0.0001 and 0.15. The crystals are useful as a photorefractive material for use in optical systems. The crystals may be doped with various first transition elements and lanthanides including copper, vanadium, chromium, iron, and manganese, nickel, europium and cerium.

Abstract: A method and apparatus is described for refreshing the analog content of a analog memory having a volatile storage device. An analog value stored on a volatile storage device is iteratively adjusted to maintain the analog value in proximity to one of a set of predetermined discrete analog memory levels. Binary quantization of the stored value, yielding one bit of information corresponding to the analog value stored, determines whether to increase or decrease the stored value by a given small amount. In essence, the bit obtained by binary quantization encodes the direction toward the nearest discrete level. Memory retention achieved by periodic iteration of the method is robust to noise and random errors in the quantization, over a wide range of operating conditions.

Abstract: Noise and distortion due to scattering and reflection in a fiber-optic communications system are suppressed by modulating the optical frequency of (chirping) a laser light source to broaden the spectrum of the laser light output. The broader spectrum spreads the noise produced by an unchirped source over a broader band. A noise and distortion suppression system includes a chirp signal generator coupled to the signal path of an RF input signal carrying information to modulate the laser optical output. In some cases, the frequency of the chirp generating signal may result in second-order intermodulation products falling within the information band. In such cases, the RF input signal is predistorted to offset the expected distortion products.

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: Noise and distortion due to scattering and reflection in a fiber-optic communications system are suppressed by modulating the optical frequency of (chirping) a laser light source to broaden the spectrum of the laser light output. The broader spectrum spreads the noise produced by an unchirped source over a broader band. A noise and distortion suppression system includes a chirp signal generator coupled to the signal path of an RF input signal carrying information to modulate the laser optical output. In some cases, the frequency of the chirp generating signal may result in second-order intermodulation products falling within the information band. In such cases, the RF input signal is predistorted to offset the expected distortion products.

Abstract: New methods are presented for multiplexing volume holograms in electrooptic materials. Multiple volume holograms can be superimposed in a medium and be individually addressed by tuning the underlying refractive index of the medium or the crystal parameters, while keeping the external parameters (wavelength, angles) fixed. According to the presented methods, the refractive index and crystal parameters of the material can be varied via the electrooptic, elastooptic or piezoelectric effects, alone or in combination with each other, by tuning the value of an applied electric field, or by tuning an applied mechanical stress, or by changing the material temperature. Volume holograms that have been multiplexed by either wavelength or angle or electric field or mechanical stress or temperature can be individually addressed by any one of the same five parameters. Additionally, selective, updatable fixing and erasing of volume holograms in photorefractive media is described.

Abstract: A fully parallel CCD memory chip of N address lines which detects in just one clock cycle, a perfect match between an input pattern and any of a plurality of stored patterns and also detects in less than (N+1)-comparison cycles and still just one XOR operation, the best matching in case a perfect one does not exist. The chip disclosed herein has a fully parallel architecture in which an input word is compared to all stored words at one time. A preferred embodiment of the invention uses a four phase CCD, wherein each stored word occupies one row of the CCD and each such bit of each such word occupies two cells. Where perfect matches exist, only one comparison clock cycle is needed to compare the input word with all stored words and where there is no perfect match, the best match will be detected on a subsequent comparison pulse. Charge packets represent binary words generated by external pulses that are applied to the chip through data input lines and then are compared to the data applied to the address lines.

Abstract: A synapse for neural network applications providing four quadrant feed-forward and feed-back modes in addition to an outer-product learning capability allowing learning in-situ. The invention, in its preferred embodiment, utilizes a novel two-transistor implementation which permits each synapse to be built in an integrated circuit chip surface area of only 20 by 20 micrometers. One of the two transistors at each synapse of the present invention comprises a floating gate structure composed of a floating gate electrode and a control electrode which permits learning upon application of incident ultraviolet light. During ultraviolet light application, a floating gate electrode voltage may be altered to modify the weight of each synapse in accordance with preselected criteria, based upon the input and output weight change vector elements corresponding to that particular matrix element.

Abstract: An all-optical, self-aligning, holographic phase modulation and motion sensing apparatus includes a crystal exhibiting a zero electric field photorefractive effect, a phase modulation or vibration source or mechanism, a source of coherent optical radiation, beam splitting and directing optics, and at least one optical radiation detector. The output from the optical radiation source is split into separate beams, one or all of which are phase modulated. The beams are directed through the crystal exhibiting a zero electric field photorefractive effect, and the resultant transmitted beams are detected by an optical radiation detector to provide a measurement of the phase modulation of the beams. The sensor functions in the absence of an electric field because of the unique characteristic of the crystal exhibiting the zero electric field photorefractive effect whereby if either the phase of the crystal's index grating or of the interfering beams is modulated with a phase change very much less than .pi.

Abstract: An adjustable CCD gate structure utilizing ultra-violet light activated floating gates, wherein a floating polysilicon gate is used between a CCD electrode and the underlying substrate to provide a fixed voltage bias to the CCD gate during the manufacturing process thereof The floating gate is programmed with a desired voltage bias during the application of ultra-violet light and is thereafter fixed at that adjusted level, upon the removal of the ultra-violet light.

Abstract: The present invention provides a compact and robust architecture and a corresponding method to implement a monotonic algorithmic D/A converter that processes the bits of the digital input in the order from MSB to LSB, and a successive approximation A/D converter employing the intermediate conversion results of this D/A converter. The invention is aimed at applications requiring a dense integration in general VLSI technologies of multiple D/A and A/D converters, where individual trimming of components to compensate for component offsets and mismatches is virtually impossible. The architecture comprises four charge holding components, one switch for charge sharing, two bi-directional replication elements for charge storage and recall, and one comparator. Also described is an efficient way of performing pseudo-logarithmic compression of conversion values merely by adjusting the relative sizes of two of the charge holding components.

Abstract: A charge domain bit serial vector matrix multiplier for real time signal processing of mixed digital/analog signals for implementing opto-electronic neural networks and other signal processing functions. A combination of CCD and DCSD arrays permits vector/matrix multiplication with better than 10.sup.11 multiply accumulates per second on a one square centimeter chip. The CCD array portion of the invention is used to load and move charge packets into the DCSD array for processing therein. The CCD array is also used to empty the matrix of unwanted charge. The DCSD array is designed to store a plurality of charge packets representing the respective matrix values such as the synaptic interaction matrix of a neural network. The vector multiplicand may be applied in bit serial format. The row or sensor lines of the DCSD array are used to accumulate the results of the multiply operation.

Abstract: A novel display screen structure and method of manufacturing such screens for use, for example, in large screen television displays. The process of the present invention is one which can be accomplished with no new materials, no critical geometric requirements such as critical separations and alignments and only low voltage drivers. The combination of these features results in a technology which can be easily scaled to large sizes to provide relatively low-cost large screens for televisions. An important step in a first embodiment of the present invention is the alignment of a large plurality of columnar-shaped light emitting diode slivers in an uncured optical epoxy by applying an electric field through a mixture of such slivers and epoxy and then curing the epoxy to effectively fix the light emitting diode slivers in that aligned configuration. In a second embodiment, the LED slivers are mixed with molten glass which is formed into elongated glass fibers.

Abstract: A novel display screen structure and method of manufacturing such screens for use, for example, in large screen television displays. The process of the present invention is one which can be accomplished with no new materials, no critical geometric requirements such as critical separations and alignments and only low voltage drivers. The combination of these features results in a technology which can be easily scaled to large sizes to provide relatively low-cost large screens for televisions. An important step in the disclosed embodiment of the present invention is the alignment of a large plurality of columnar-shaped light emitting diode slivers in an uncured optical epoxy by applying an electric field through a mixture of such slivers and epoxy and then curing the epoxy to effectively fix the light emitting diode slivers in that aligned configuration.

Abstract: An optically-coupled high frequency amplifier is disclosed herein. The ampliifer of the present invention includes a laser and a receiver coupled by an optical beam. The amplifier further includes a modulator responsive to an input signal for modulating the optical beam generated by the laser. The receiver produces an output signal in response to the modulated optical beam. A specific embodiment of the present invention further includes impedance matching means for increasing the maximum operating frequency of the laser and the receiver.

Abstract: A non-destructive charge domain multiplier and process thereof wherein the unique characteristics of the charge coupled device permits sensing the size of the charge packet as it moves past an electrode and creating a new charge packet proportional to the product of the original packet and an externally applied value. The device non-destructively senses the size of the charge packet and multiplies it with another value using a multiple metering gate variation of the "Fill and Spill" technique. The present invention therefore constitutes a unique CCD configuration which creates as an output, a charge packet proportional to the product of the charge in an input packet and an externally applied value. Thus, the present invention enables the performance of non-linear operations by CCD integrated circuits.

Abstract: Several embodiments of neural processors implemented on a VLSI circuit chip are disclosed, all of which are capable of entering a matrix T into an array of photosensitive devices which may be charge coupled or charge injection devices (CCD or CID). Using CCD's to receive and store the synapses of the matrix T from a spatial light modulator, or other optical means of projecting an array of pixels, semiparallel synchronous operation is achieved. Using CID's, full parallel synchronous operation is achieved. And using phototransistors to receive the array of pixels, full parallel and asynchronous operation is achieved. In the latter case, the source of the pixel matrix must provide the memory necessary for the matrix T. In the other cases, the source of the pixel matrix may be turned off after the matrix T has been entered and stored by the CCD's or CID's.

Abstract: Coherent coupling of a plurality of reflection type optical gain elements with a seeding laser is provided by illuminating the optical gain elements with fanned laser light scattered from a photorefractive medium. The reflection type optical gain elements have an anti-reflective end nearer the photorefractive medium and a reflective opposite end. The optical gain elements also illuminate the photorefractive medium. The resultant amplified and coherent light beam has its wavefront cleaned up with a photorefractive oscillator to provide a diffraction limited or nearly diffraction limited beam.