Abstract: The Holographic Beam Combiner, (HBC), is used to combine the output from many lasers into a single-aperture, diffraction-limited beam. The HBC is based on the storage of multiple holographic gratings in the same spatial location. By using a photopolymer material such as quinone-doped polymethyl methacrylate (PMMA) that uses a novel principle of “polymer with diffusion amplification” (PDA), it is possible to combine a large number (N) of diode lasers, with an output intensity and brightness 0.9 N times as much as those of the combined outputs of individual N lasers. The HBC will be a small, inexpensive to manufacture, and lightweight optical element.

Abstract: A method of establishing transmission of light through a chirped Bragg-reflector, a method of analyzing the power spectrum of a light signal using a chirped Bragg-reflector, and an arrangement for analyzing the power spectrum of a light signal. The Bragg-reflector reflects, in an unperturbed state, essentially all incident light within a predefined wavelength range. The methods include the steps of directing the light to be analyzed into an input end of a light-guiding structure, such as an optical fiber, which light-guiding structure is provided with a Bragg-reflector, and sending an acoustic pulse along the light-guiding structure, thereby effectively lowering the reflectance of the Bragg-reflector for a certain wavelength at a certain time. By monitoring the light thus transmitted through the Bragg-reflector, a power spectrum analysis of the incident light is obtained.

Abstract: A system for converting an image into a hologram formed from diffraction gratings includes obtaining image data for each pixel in an image to be converted, putting it into digital form and using the image data to control portions of a laser beam split into a reference beam and at least one object beam. The diffraction gratings are formed by an interference pattern of a reference beam and at least one object beam intersecting on the surface of a photoresist material on a pixel-by-pixel basis. Modulation of at least one object beam and adjustment of the angle at which that beam interferes with the reference beam on the photoresist material is used to reflect image data for each pixel of the image being converted into a hologram consisting of diffraction gratings.

Abstract: Holographic printers for producing simultaneous and near real time white light viewable holographic imagery are disclosed. Such printers include fiber optics for dividing the reference beam into a plurality of identical reference beams each intersecting the object beam path at the recording medium. In one embodiment, the recording medium is simultaneously exposed to both the object beam and the plurality of reference beams. An alternate embodiment is provided for sequentially opening each of the reference beam shutters with the opening of the object beam shutter. Preferably, the printer includes a liquid crystal panel and a computer for supplying images in the liquid crystal panel between each sequential opening of the shutters. For the formation of integral holograms, fiber optics are provided for dividing the object beam.

Abstract: A hologram having a covert image is made by recording on the hologram an object beam that will reconstruct an unrecognizable, scrambled image. The scrambled image can be modified to form a recognizable image by passing the scrambled image through a plate overlying the hologram.

Abstract: Disclosed is a hologram recording method using a beam with a very large incident angle, a hologram reproduction apparatus using a holographic reflector, a hologram reproduction method using the same and a flat display element apparatus using a holographic reflector. The hologram recording method using a beam with a very large incident angle comprises the steps of generating a sheet beam as the reference beam, and introducing the reference beam into the recording medium at an incident angle of at least 70°. The hologram reproduction apparatus using a holographic reflector comprises a light, a holographic reflector, an adjustor, and a hologram.

Abstract: An optical beam steerer includes one or more layers of electro-optically active material in which is formed a chirped distributed Bragg reflector. An electric field generated across the electro-optically active material in the direction of propagation of the chirped distributed Bragg reflector causes the index of refraction within the material to change. The electric field varies in a direction normal to the direction of propagation of the chirped distributed Bragg reflector which causes a variation in the local index of refraction proportional to the strength of the electric field. Changes in the index of refraction cause the wavefront of the incident optical beam to experience different delays such that the incident optical beam is reflected out of the beam steerer at an angle that is tangential to the direction of variation of the applied electric field. Two dimensional beam steering is provided by the creation of two electric fields that are orthogonal to each other.

Abstract: A holographic microscope is described along with a method for numerically reconstructing a holographic image. The method uses a coordinate transformation of the Kirchhoff-Helmholtz equation to remove the non-linear component from the phase factor. The intensity distribution in the transformed coordinate system is then interpolated on an equidistant point grid and Fast-Fourier-Transforms are used to compute the result.

Abstract: An apparatus for use in contoured architectural milieus includes a contoured large screen display having a mounting means to which modular flat display tiles including, tiles of diverse or non-standard shapes and sizes are attached, each display tile having a plurality of optical fibers affixed behind the tile and communicating with a front surface of the tile.

Abstract: The first reading beam identical to the first reference beam and the second reading beam conjugate to the second reference beam are simultaneously applied to a hologram recording medium 1, on which holograms 2 and 3 have been recorded. A hologram is formed by interference between the first beam reproduced from the first reading beam and the second reading beam. Another hologram is formed by interference between the second beam reproduced from the second reading beam and the first reading beam. These holograms are recorded and superposed on the original holograms 2 and 3, thereby reproducing the original holograms 2 and 3.

Abstract: An illumination panel for illuminating an object, comprising a substrate, a light diffractive grating and a light source. The substrate is made from an optically transparent material having first and second areal surfaces disposed substantially parallel to each other and a light input surface for conducting a light beam into the substrate. The light diffractive grating is mounted to the first areal surface and has a slanted fringe structure embodied therein for diffracting the light beam falling incident thereto, along a first diffractive order of the slanted fringe structure. The light source produces a light beam for transmission through the input surface and direct passage through the substrate to the slanted fringe structure so as to produce an output light beam of areal extent that emerges from either the first or second areal surface along the first diffractive order, for use in illuminating an object.

Abstract: A reference beam telescope, which is also referred to as a relay imaging system for a reference beam, using reflection optics is disclosed. The relay imaging system according to the present invention comprises at least one concave mirror and one convex mirror. A reference beam is reflected at least twice by the concave mirror and once by the convex mirror. The output reference beam is collimated if the input reference beam is collimated. This relay imaging system is used in a holographic storage system to deliver the reference beam to the holographic storage medium. In particular, this system can be used for angular multiplexing in a holographic storage system.

Abstract: The present invention concerns methods and devices for creating and printing variable size and variable resolution holographic stereograms and holographic optical elements using computer rendered images of three-dimensional computer models or using computer processed images. The present invention is an apparatus and method for printing one-step, full-color, full-parallax holographic stereograms utilizing a reference beam-steering system that allows a reference beam to expose a holographic recording material from different angles. More particularly, a coherent beam is split into object and reference beams. The object beam passes through an object beam unit in which a rendered image is displayed, while the reference beam passes through the reference beam-steering system. The object and reference beams interfere with each other at an elemental hologram on a holographic recording material.

Abstract: High storage densities using a holographic system are achievable using a stratified medium while maintaining a relatively high selectivity upon reconstruction of the stored images. Such combination of high density and high selectivity is achievable by employing a stratified medium and a recording process where selectivity does not vary with recording thickness.

Abstract: A self-routing switch such as a Banyan switch has a controller which recognizes incoming routing requests which would give rise to blocking in the switch and makes and optimum selection of queued requests which can be handled without blocking. The controller is implemented by means of an optical neural network having a light source array to illuminate a photodetector array through a mask, there being a light source array element and a photodetector element for each possible path through the switch. The assignment of paths to array locations is such that, for the path corresponding to any light source array element, the photodetector array element positions corresponding to the paths blocked thereby form a pattern which is a shifted version of the pattern formed by the photodetector array elements corresponding to the paths blocked by a path corresponding to any other light source array element, whereby a single mask may be employed.

Abstract: A fiber optic display apparatus consists of a plurality of optical fibers which convey a projected image from an input, or first surface, to a display, or second surface, whose area is greater than or equal to that of the first surface, such that any image projected on to the first surface appears enlarged on the second surface. The second surface is comprised of tiles which attach to adjoining tiles by means of flexible tabs and pliable locator rods in such a fashion as to allow the second surface to follow general contours (e.g. concave or convex), while the optical fiber bundles from each tile are collected into a fixture to form the first planar surface. Because of the modular design of the display it can be assembled or disassembled rapidly.

Abstract: An optical add/drop filter is formed using a hologram which is tuned to a wavelength in an optical signal. The diffraction condition of the hologram may be varied to vary the in add or drop content.

Abstract: The invention provides a hologram recording or replicating optical system wherein a misalignment-with-time of the center of a laser generated beam is automatically corrected so that the color balance in a color hologram surface, for instance, can be well maintained with no disturbance. In the hologram recording or replicating optical system for irradiating a photosensitive material 20 with a beam from a laser 31 through a pinhole 10, a beam position correcting mechanism 32 and a beam splitter 33 are located in an optical path between the laser 31 and the pinhole 10, and a laser beam position detector 35 is located at a position in an optical path split by the beam splitter 33 and conjugate to the pinhole 10, so that the beam position correcting mechanism 32 can be operated on the basis of a beam position error signal obtained from the laser beam position detector 35 to keep the position of the beam incident on the pinhole 10 always constant.

Abstract: A method and an apparatus capable of filtering based on desired spatial frequency characteristics without loss of Fourier spectrum frequency components, and of matched filtering of high recognition capability without losing functions of data recording and reconstruction as well as high-speed transmission and retrieval features and mass storage capacity characteristic of a holographic memory. Fourier transformed object light with 0° polarization of a target image is stored as a hologram using reference light having a spatial polarization distribution such that a daughter wavelet on scale m has 90° polarization. The hologram is retrieved using the Fourier transformed object light with 0° polarization. The hologram yields diffracted light in the form of a spatial frequency component which corresponds to scale m and is polarized 90° with respect to the other spatial frequency components. A polarizing element is used to extract only the spatial frequency component corresponding to scale m.

Abstract: Device, method, and system for recording diffractive high resolution text, pictorial, and/or other graphical information is provided which is particularly suited to recording information that would be difficult to reproduce by typical counterfeiting methods. The information recorded may be used to authenticate the recorded item, or indirectly, an item to which the recording is attached. Such items may include legal, financial and commercial instruments, credit cards, and packaging for such items as software, art, and other items where forgery of the item may be a concern. In one embodiment of the invention light is selectively passed by a shutter, and a spatial filter then cleans the beam to remove undesirable frequency components.

Abstract: A method for suppressing image speckles in a holographic screen is provided in which the screen is illuminated in the hologram in a plurality of individual steps, changing the recording parameters at each step. As a result, a holographic screen is obtained that produces a speckle-free image from a hologram recorded with lasers and then illuminated by a laser. Depending on the application, the object screen can be recorded as a reflection or transmission hologram.

Abstract: A method for the numerical reconstruction of digital holograms which allows simultaneously amplitude and quantitative phase contrast imaging. The reconstruction method computes the propagation of the field that would be diffracted by the hologram during a standard hologram reconstruction. The method requires the adjustment of several reconstruction parameters for the definition of a digital replica of the reference wave. When the set-up used for the hologram creation produces phase aberrations, the method includes a digital method for the correction of the phase aberrations. The phase contrast image is quantitative, meaning that the reconstructed phase distribution can be used for quantitative measurements. The method can be used to reconstruct a set of holograms taken in different conditions. The method can be used to reconstruct several images from a single hologram taken with more than one reference waves and/or more than one object waves.

Abstract: Three separate input beams of light can be combined in a photorefractive material and outputs one signal. Each of the three input beams can carry information, for example, by passing each input beam through a glass slide with opaque lettering. The message may be segmented and a portion of it placed in each input beam for security reasons. Only the output beam contains the full message. Further, the invention can be used as an all-optical three-input AND gate. A signal is only produced when all three beams of light are present.

Abstract: An apparatus for making a high quality reflection type holographic optical element (HOE) using a single input laser beam, including a reflective mirror, a holographic photoplate having a photo emulsion layer on a surface nearest the reflective mirror, a cassette for retaining the reflective mirror and the holographic photoplate, and a refractive index matching fluid containing a light absorbent dye for absorbing an input laser beam. The cassette is immersed in the fluid so that fluid is retained between the photo emulsion layer of the holographic photoplate and a reflective surface of the reflective mirror. Parasitic interference patterns are suppressed by heating the refractive index matching fluid with the input laser beam, which causes a shift of the phase of the parasitic beams with respect to the phase of the beams responsible for recording the HOE. If the photo emulsion layer of the holographic photoplate consists of a dichromated gelatin (DCG), then a photo sensitizer agent (e.g.

Abstract: A user is able to interact with and modify an electronic holographic image using a force-feedback (or haptic) device, which is capable of sensing and reporting the 3D position of its hand-held stylus and “displaying” appropriate forces to the user. Thus, a user can feel and modify specified shapes in the haptic workspace. The haptic workspace is precisely registered with the free-standing, spatial image displayed by a holographic video (holovideo) system. In the coincident visuo-haptic workspace, a user can see, feel, and interact with synthetic objects that exhibit many of the properties one expects of real ones, and the spatial display enables synthetic objects to become a part of the user's manipulatory space.

Abstract: An improved process for holography is provided, in which the reference beam used for storage and readout has a correlated phase content. In particular, it was found that reference beams having random phase content limited the attainable storage density and the accuracy of readout of stored holograms due to uncontrolled fluctuations in the correlation selectivity. By contrast, a reference beam having correlated phase content provides accurate shift selectivity, the ability to tailor the reference beam spectrum to minimize crosstalk between neighboring holograms, and mitigation of limitations inherent in the holographic system or holographic medium. Improved storage density and readout accuracy are thereby attained.

Abstract: A system and method for controlling the selectivity function in a holographic memory system that permits more rapid location and retrieval of holographically stored data. The system and method direct a reference beam through a filter such as, for example, an aperture, to bandwidth limit the beam before the beam illuminates a holographic optical element having stored therein a hologram of a reference beam.

Abstract: An optical interface of a holographic memory system electrically selects one of several optical pathways to store or retrieve an image from a holographic memory by activating liquid crystal polarization rotators and novel liquid crystal gratings. In a preferred embodiment a spatial light modulator, a pixelized readout device (i.e., focal-plane array), a series of polarizing optical components, liquid-crystal polarization rotators, liquid-crystal beam-steering devices, and interconnecting and imaging optics are provided. The parallel interconnection accepts a laser-beam input, divides the beam among multiple paths, imparts a data-bearing spatial signature on a signal beam by means of a spatial light modulator, steers a reference beam by means of liquid-crystal beam-steering devices, and directs the appropriate beams into the recording medium.

Abstract: Holographic memory including a beam source for emitting a beam, a beam splitter for splitting the beam into a reference beam and an object beam, a hologram memory unit for recording information designated to a cell when the reference beam and the object beam are incident thereto at a time, and reproducing the information recorded before when only the reference beam is incident thereto, a first optical path changing unit for directing the reference beam to be incident to the hologram memory unit at an arbitrary angle for recording and reproduction of the information, including a first deflector for deflecting the reference beam to an arbitrary angle, a second deflector for re-deflecting the reference beam deflected at the first deflector in a vertical direction, and a telescope having at least one composite HOE(Holographic Optical Element) for directing the reference beam re-deflected at the second deflector to be incident to the hologram memory unit, and a second optical path changing unit for adjusting an op

Abstract: We disclose apparatus for holographic recording of information. The apparatus includes a lens or lens system, referred to here as the "FT lens," situated in such a way that light from an object beam enters the FT lens after passing through an object, and light leaving the FT lens impinges on a recording medium situated at a Fourier transform plane of the object with respect to the FT lens. In certain aspects of the invention, the apparatus includes a phase element effectively juxtaposed with the object, the phase element is effective for redistributing object-beam intensity in the Fourier transform plane, and the phase element has a correlation length greater than a maximum pixel side length associated with the object. In certain other aspects of the invention, the apparatus includes an optical element or optical system, referred to here as a "power optic," that adds convergence or divergence to the object beam before the object beam enters the FT lens.

Abstract: A method of making a holographic device comprising sensitizing a plurality of layers and stacking the layers to form a composite structure. Each layer is sensitized to at least one color wavelength. The method further includes directing at least two laser beams at the composite structure. Each of the laser beams is oriented at an angle with respect to an incident surface of the composite structure such that the laser beams intersect one another within one of the layers of the composite structure. The laser beams are moved along the layer to create interference patterns in the sensitized layer.

Abstract: A holographic memory device includes: a hologram memory part for information recording by using a reference beam and an object beam, the hologram memory part having a plurality of cells; a first optical path modifying part having a fine adjustment element that adjusts the reference beam's path so as to be incident on the hologram memory part at a specific angle for information recording and reconstructing, and that adjusts the reference beam's path so as to be incident on the hologram memory part at a desired angle for information reconstructing when an angle of incidence of reference beam for information reconstructing doesn't coincide with that of reference beam for information recording; and a second optical path modifying part that adjusts the object beam's path so as to be incident on the hologram memory part for information recording.

Abstract: A generator of energy-depleted radiation and various methods and applications using the energy-depleted radiation. Various embodiments are disclosed of the energy-depleted radiation generator and an energy-restored radiation generator, which permits detection of wave properties of the radiation without regard to the depletion of its energy. The energy-depleted radiation generator functions in one embodiment by selective transmission of destructively interfering radiation. Other embodiments use two-beam coupling or directional coupling to achieve energy depletion. Restoring energy to an energy-depleted radiation beam is accomplished by transferring energy to it from a reference beam, in a beam-to-beam transfer or in an optical amplifier. The invention has important applications in fields such as communications, specimen analysis, photorefractive recording, holography, and other fields in which the reduction of energy content in the associated radiation is advantageous.

Abstract: A method for coded-wavelength multiplexing according to which a signal waves S.sub.i (r) is recorded in a holographic medium in a counter-propagating geometry using corresponding writing reference waves R.sub.i (r). The method involves selecting discrete wavelengths .lambda. and encoding reference wave vectors .rho..sub.l which make up writing reference waves R.sub.i (r) such that the writing reference waves R.sub.i (r) at each wavelength .lambda. are orthogonal. The stored signal waves S.sub.i (r) are reconstructed in the form of reconstruction waves A.sub.c (.sigma.) with reconstruction reference waves R.sub.c (r) selected from among the writing reference waves R.sub.i (r). In the event of angular multiplexing of the reference wave vectors .rho..sub.l, it is possible to use one reference wave to produce a number of reconstruction waves A.sub.c (.sigma.) and generate a mosaic of desired holographic pages.

Abstract: The invention features methods and systems for thermally fixing or erasing a laser-induced hologram in a photorefractive material, for example, by directing laser radiation having a wavelength through a thickness of the photorefractive material containing the hologram, wherein the wavelength is selected such that the photorefractive material absorbs a portion of the laser radiation and transmits another portion of the laser radiation. The transmitted laser radiation can be redirected back through the hologram, wherein both the laser radiation directed and redirected to the hologram are sufficiently absorbed by the photorefractive material to thermally fix or erase the hologram.

Abstract: A method and an apparatus for increasing detection signal-to-noise ratio, while reading out a hologram from a holographic storage medium, are disclosed. The hologram is written by interfering a write reference beam with an object beam. The method comprises the steps of (1) effecting multiple sequential hologram-read operations using multiple read reference beams separated from each other by a separation angle; (2) shifting the detector array contents in between hologram-read operations such that the data signal patterns incident on the detector array are approximately identical but the incident scatter noise patterns are uncorrelated; and (3) integrating the multiple hologram readouts electronically on the detector array. The apparatus comprises a laser source, a beamsteerer, a detector array and a shifting device.

Abstract: Apparatus for and a method of optical inspection in a total internal reflection holographic imaging system. Multi wavelength laser beams are directed onto a prism supporting a first substrate containing pre-recorded hologram which is to be imaged onto a recording medium of a second substrate, the multi wavelength beams being normal to both substrates. The distance between the two substrates is measured by interferometric techniques. Actuators are provided for adjusting the distance between the two substrates, these actuators being energized to cause minute adjustments of the spacing during a scanning operation whereby the imaging of the pre-recorded hologram is ensured at the correct focus throughout the scanning operation.

Abstract: The invention relates to a sensor (9) comprising a hologram (17) supported on or within a holographic support medium (10).A species to be detected is reactive with a substance disposed throughout, the sensor (9). Optionally, a chemical reactive with a species to be detected or a specific binding conjugate of a species to be detected is disposed throughout part of or all of the sensor (9).The resulting reaction(s) cause(s) variation(s) in the hologram (17) or holographic support medium (10) which in turn varies one or more optical characteristic(s) of the hologram (17).The variation in the optical characteristic(s) of the hologram (17) and/or the holographic support medium (10), preferably give(s) rise to a wavelength shift in incident radiation. The variation of the optical parameter is related to the species to be detected.The advantages of the sensor are that it is cheap, easy to manufacture and, once calibrated, reliable and robust.

Abstract: Device, method, and system for recording diffractive high resolution text, pictorial, and/or other graphical information is provided which is particularly suited to recording information that would be difficult to reproduce by typical counterfeiting methods. The information recorded may be used to authenticate the recorded item, or indirectly, an item to which the recording is attached. Such items may include legal, financial and commercial instruments, credit cards, and packaging for such items as software, art, and other items where forgery of the item may be a concern. In one embodiment of the invention light is selectively passed by a shutter, and a spatial filter then cleans the beam to remove undesirable frequency components.

Abstract: The present invention is a holographic reconstruction device for reconstructing successive holograms previously recorded by a recording reference beam in a recording medium, each previously recorded successive hologram being spaced apart a recording displacement. The recording reference beam has a recording wavelength in the range where the recording medium is photosensitive and a recording propagation angle. The device comprises a reconstruction mechanism having a reconstruction reference beam with a reconstruction wavelength in the range where the recording medium is relatively photo-insensitive and a reconstruction propagation angle. The reconstruction reference beam is provided onto the recording medium. Also, a succession of relative displacements in the recording medium is produced and each of the displacements are equal to the distance of the recording displacements with which the holograms were previously recorded.

Abstract: A method and an apparatus for increasing detection signal-to-noise ratio of a holographic image by compensating for noise characteristics of a holographic storage medium are disclosed.

Abstract: An architecture for holographic data storage and processing integrates multifunctional silicon-based optoelectronic devices, rewritable holographic material, optical devices and other electro-optical elements in compact and high-performance systems. A dynamic hologram refresher based on optoelectronic integrated circuits has a smart pixel structure including an electrically addressed SLM to write a new data page, a thresholding detector array for readout, and a memory to latch the data from the detector to the modulator in each pixel. In particular, conjugate reconstruction is used in combination with the dynamic hologram refresher to retrieve data from volume multiplexed holograms in the rewritable holographic material.

Abstract: The invention is embodied in a method of recording successive holograms in a recording medium, using at least a fan of M waves along at least a first axis with a separation angle between adjacent waves and directing the fan of M waves as a reference beam along a reference beam path onto the recording medium, successively modulating a wave with a succession of images to produce a succession of signal beams along a signal beam path lying at a propagation angle relative to the reference beam path so that the signal and reference beams intersect at abeam intersection lying within the medium, the beam intersection having a size corresponding to beam areas of the reference and signal beams, producing a succession of relative displacements in a direction parallel to the first axis between the recording medium and the beam intersection of the signal and reference beam paths in synchronism with the succession of signal beams, each of the displacements being less than the size of the intersection whereby to record succ

Abstract: Fast speed hologram memory device, including a first holographic optical element array for directing a reference beam to a desired hologram memory cell directly and a second holographic optical element array for directing an objective beam to a desired hologram memory cell directly, both having a plurality of holographic optical elements one to one matched to a plurality of the hologram memory cells.

Abstract: A polarisation independent optical switch is constituted by a light input (6), a diffractive and re-configurable liquid crystal device (8), a collimating lens (7) for distributing the input light over the liquid crystal device (8), a transform lens (9) receiving light from the liquid crystal device (8) and light output (6), wherein no polarisers are present between the light input and output. The diffractive and re-configurable liquid crystal device (8) may be formed as a liquid crystal spatial light modulator configured as a binary phase computer generated hologram with the holograms required to form broadcast, individual or multicast switching being re-generated using an iterative algorithm and then being recalled on demand. In one embodiment the switch has a folded configuration and includes a reflector (10) so that the light input and output are both on the same side of the liquid crystal device (8).

Abstract: Feedback is employed in a holographic memory system to facilitate rapid access to information in a stored data page. This feedback technique provides compensation for thermal, optical and/or mechanical variations in the system components that tend to interrupt the projection of a data page image on a sensor array. A page indicator or mark is stored in a holographic storage medium with a page of data such that, during playback, a quality, e.g., intensity, of its projected image is indicative of the quality of the corresponding projected data page image. A corresponding page indicator sensor is employed with the associated sensor array to detect the quality of a projected page indicator image. The projected data page image can then be read by sensor elements of the detector based on the detected quality of the page indicator image. Such a detector can be implemented in an active pixel sensor (APS) array with the page indicator sensor being implemented as a region of the APS array.

Abstract: A holographic recording apparatus includes first and second light sources for respectively generating first and second light beams. A mask is located in front of a hologram recording material and has an aperture. Interference fringes are recorded in a hologram cell on the hologram recording material corresponding to the aperture. A movement mechanism supports the hologram recording material masked by the mask and relatively moves the hologram recording material with respect to the mask in predetermined directions so that an interference pattern is formed in an area on the hologram recording material. A spatial frequency changing mechanism changes incident angles of the first and second light beams with respect to the mask.

Abstract: An optical interconnection network in which more than one communication can ccur at any give time is disclosed. The interconnection network can form part of a parallel computer, a fiber optic switching network, a massive video or data server or an asynchronous transfer mode (ATM) network. The network includes transmission network elements, reception network elements and a holographic storage element. The holographic storage element is located equidistant form all the transmission and reception network elements and stores therein a multiplicity of holograms. Each volume hologram is responsive to a different angle of incidence of wavelength.

Abstract: A video image F?k! is identified as a basis image and stored as a basis page S?k! in a holographic storage medium. A subsequent image F?k+n! is stored by recording in the medium a page S?k+n!=F?k+n!-a?k!F?k!, where a?k!.noteq.0 and preferably a?k!=1. The page S?k! is recorded with a reference beam R?k!, while S?k+n! is recorded with a reference beam R?k+n! orthogonal to R?k!. The basis page is reset whenever the average intensity of a page to be stored exceeds a predetermined threshold. An image F'?k! is retrieved by reading basis page S?k! and letting F'?k!=S?k!. Subsequent images F'?k+n! are retrieved as S?k+n!+b?k!S?k!, where b?k!.noteq.0 and preferably b?k!=a?k!=1. The page addition step is performed coherently, i.e. by accessing the medium with a reference wave function R?k+n!+b?k!R?k!.

Abstract: A holographic planar concentrator (HPC) for collecting and concentrating optical radiation is provided. The holographic planar concentrator comprises a planar highly transparent plate and at least one multiplexed holographic optical film mounted on a surface thereof. The multiplexed holographic optical film has recorded therein a plurality of diffractive structures having one or more regions which are angularly and spectrally multiplexed. Two or more of the regions may be configured to provide spatial multiplexing. The HPC is fabricated by: (a) recording the plurality of diffractive structures in the multiplexed holographic optical film employing angular, spectral, and, optionally, spatial multiplexing techniques; and (b) mounting the multiplexed holographic optical film on one surface of the highly transparent plate. The recording of the plurality of diffractive structures is tailored to the intended orientation of the holographic planar concentrator to solar energy.