Abstract: Holograms within an array are recorded and/or read out by use of a reference/read out beam produced by illumination of a phase mask.

Abstract: A system for high density holographic storage announced by Cal Tech is improved. The basic Cal Tech system records successive holograms by physically shifting the recording medium relative to the paired reference and signal beams. By depending on Bragg selectivity, successive holograms may be overlapped and still differentiated in the direction of overlap--in the "x-direction". The claimed system improves storage density by tilting the holographic plane to introduce a Bragg component in the y-direction, thereby enabling differentiation of overlapping holograms in that direction as well.

Abstract: A remote controlled locking system employing a holographic window display, particularly adapted for vehicle use. The system includes a remotely-operated transmitter for transmitting locking and unlocking signals, and a locking mechanism that is locked and unlocked in response to the transmitted signals. The locking mechanism outputs a status signal or status signals, corresponding to at least one of the locking and unlocking signals. Control electronics process the status signals from the locking mechanism to provide control signals that are coupled to first and second light emitting members, such as LED arrays. The light emitting members produce light output signals in response to the control signals. First and second prism couplers are attached to a surface of a window and are optically coupled to the first and second light emitting members. First and second hologram decals that comprise the holographic window display are attached to the surface of the window and are responsive to the light output signals.

Abstract: A holographic data storage system includes a laser (12) for generating both data and reference beams. The reference beam is deflected by an optic system such that the reference beam can be directed at the surface of a thin holographic storage media (10) to interfere with a data beam to store data in the form of an interference grating. For each Bragg angle associated with a reference beam and a data beam, multiple pages of information are stored in the storage media (10). Each page of information stored at a given Bragg angle is associated with a different Bragg plane. Upon reconstruction of the data, a given reference beam at a given Bragg angle will reconstruct the data in the associated Bragg plane on a detector (42) and will reconstruct data for the same Bragg angle but a different Bragg plane in an off-image plane (88) or (90). This, therefore, allows multiple pages of information to be stored for the same Bragg angle in the same storage region (54).

Abstract: A holographic optical system includes volume hologram configurations providing a waveplate for, e.g. an optical storage device, and an aliasing suppression filter. The waveplate has diffraction characteristics adapted to impart a propagation delay for selected polarization directions. By controlling the propagation delay and the angle of an incident light beam, an output beam having altered polarization characteristics can be produced. Quarter waveplates for reflective optical storage systems and half waveplates for magneto-optical storage systems are disclosed. The holographic aliasing suppression filter divides an input optical beam into spatially separated components and may be configured to be polarization insensitive or color selective.

Abstract: A holographic optical device includes a light-transmissive substrate, a first holographic optical element, and a second holographic optical element that is laterally disposed on the substrate from the first holographic optical element. At least one of the holographic optical elements is a complex diffraction grating that can handle a multiplicity of plane and/or spherical waves arriving from a range of angles, and having a range of wavelengths. Applications for the device include a wavelength division multiplexer/demultiplexer, an image reconstructor, a beam expander/compressor, and a visor/head-up display.

Abstract: A hologram forming system for forming holograms on multiple exposures is provided. In this system, a holographic recording medium is exposed to light beams at least twice at incident angles different between exposures. The incident angle during each exposure process is determined in a given relation to the thickness of the holographic recording medium which tends to vary as the exposure process is repeated so that the reconstruction wavelengths match with target values without shifting between image colors during reconstruction of the hologram.

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 a beam 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 suc

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: A hologram of a virtual object or an object which actually exists is formed and a solid image is displayed. 3-dimensional information of the object to be displayed is divided into regions in the depth direction. Depth images are formed as 2-dimensional images where are seen from a plurality of points which are obtained by finely dividing the hologram forming surface for every region. A phase distribution at the hologram forming surface is calculated from the depth images and displayed on a liquid crystal display or the like as an electronic hologram. A reference light is irradiated onto the display and is converted into an optical wave front, thereby displaying a solid image. When forming a hologram recording medium, a zone image corresponding to each of the finely divided exposure regions of a dry plate is exposed multiple times.

Abstract: A hologram for security markings is provided by a laser transmission hologram (1-4) formed as a surface relief pattern and a coating of a thin metallic layer (5) on the surface relief pattern whereby the hologram is capable of reflecting light from a laser (10). The metallic layer is, preferably, about 500 angstroms thick and the hologram may be mounted on a substrate (7) of an item required to bear the security marking defined by the hologram. In a feature of the invention an apparatus is provided for reading light reflected from the hologram comprising a laser (10) for projecting a beam (9) onto the hologram to be read and a detector (31) and associated logic devices for recognizing a real image of the hologram. The apparatus has the advantage that the laser (10) and detector (31) are both located on the same side of the hologram to be read.

Abstract: An apparatus for positioning a data and reference beam onto the surface of a holographic storage media (10) includes a laser (16) for generating the reference beam, and a first reflecting surface (18) for positioning the output of the laser (16) along the y-axis. The beam is split into a data beam and a reference beam by a beam splitter (24) with the data beam directed toward an SLM (36) and the reference beam (26) directed toward an angle multiplexing reflective surface (40). The data beam during a record operation is reflected from the surface of the SLM (36) to a transform lens (34) and then to a column (35) on the surface of a holographic storage media (10). The reference beam is reflected from a reflective surface (40) at a predetermined angle determined by the position of the reflective surface (40) to an HOE (46) for redirection to the surface of the storage media (10) to interfere with the data beam. During a data reconstruction operation, only the reference beam is generated.

Abstract: A process for making a multilayer photopolymer hologram structure without intervening adhesive layers between component photopolymer layers.

Abstract: A hologram system is comprised of two identical volume holograms. Both holograms have Bragg planes oriented perpendicular to the surface of the hologram. The first volume hologram separates a single beam into two orthogonal polarization component beams. The second volume hologram diffracts one of the polarization component beams such that a desired separation angle is achieved between the two beams. This separation angle may be precisely adjusted during manufacture by orienting the Bragg planes of the second volume hologram at a rotational angle with respect to the Bragg planes of the first volume hologram.

Abstract: A method and apparatus for making holograms includes a technique for exposing a film substrate or other light-sensitive medium to consecutive two-dimensional images, together representative of a physical three-dimensional system, to generate a three-dimensional hologram of the physical system. Low beam ratios are employed to superimpose multiple (20-300) images on the substrate. Each image is relatively weak, but the combination of the series of weak images ultimately appears as a single clearly defined hologram.

Abstract: The invention provides an optical device with high light utilization efficiency that is capable of scribing patterns on curved surfaces, as well as flat surfaces, using a liquid crystal spatial light modulator. The invention offers an optical device with high light utilization efficiency and that is capable of three-dimensional formation of curved surfaces using a liquid crystal spatial light modulator. Additionally, the invention offers a widely applicable optical processing system that mounts these optical devices on robots. The invention includes at least a coherent light source, a liquid crystal spatial light modulator for controlling the wavefront of the light from the coherent light source, and a means that records the complex amplitude distribution on the liquid crystal spatial light modulator.

Abstract: A hologram of a virtual object or an object which actually exists is formed and a solid image is displayed. 3-dimensional information of the object to be displayed is divided into regions in the depth direction. Depth images are formed as 2-dimensional images where are seen from a plurality of points which are obtained by finely dividing the hologram forming surface for every region. A phase distribution at the hologram forming surface is calculated from the depth images and displayed on a liquid crystal display or the like as an electronic hologram. A reference light is irradiated onto the display and is converted into an optical wave front, thereby displaying a solid image. When forming a hologram recording medium, a zone image corresponding to each of the finely divided exposure regions of a dry plate is exposed multiple times.

Abstract: The position of a solid image which changes with the elapse of time is detected. The position of a virtual screen is set so that a distance from an object enters an allowable range such as to reduce a fatigue of an observer. A 2-dimensional image is formed at the set virtual screen position. A phase distribution is calculated at the hologram forming surface, thereby displaying a solid image. Even when the position of a solid image changes with the elapse of time, the fatigue of the eyes can be minimized.

Abstract: A holographic particle image velocimeter employs stereoscopic recording of particle images, taken from two different perspectives and at two distinct points in time for each perspective, on a single holographic film plate. The different perspectives are provided by two optical assemblies, each including a collecting lens, a prism and a focusing lens. Collimated laser energy is pulsed through a fluid stream, with elements carried in the stream scattering light, some of which is collected by each collecting lens. The respective focusing lenses are configured to form images of the scattered light near the holographic plate. The particle images stored on the plate are reconstructed using the same optical assemblies employed in recording, by transferring the film plate and optical assemblies as a single integral unit to a reconstruction site.

Abstract: Holographic images are constructed in a recording material in accordance with a temporal interleaving technique in which a first set of images is constructed for a predetermined first imaging time with a predetermined first time gap being defined between each of the images. Thereafter, in accordance with a subsequent predetermined sequence a subsequent set of images is constructed into the same predetermined location. The image sets have at least one member in common. In one aspect all of the images are constructed into the same predetermined defined region of the holographic recording material (an angle hologram). In another aspect the predetermined defined region into which each of the images is constructed is separate from all other regions of the holographic recording material (a spatial hologram).

Abstract: A holographic filter for protection from radiation, notably laser radiation. At least one support is covered with at least two holograms. Each hologram is constituted by a stack of strata. The holograms are fixed to each other by an optical bonder associated with a selective absorbent material.

Abstract: An exposure apparatus is used for reproducing a mask pattern of a semiconductor device or the like onto a photosensitive substrate using a holography. The holography is utilized also in a process for alignment between a mask pattern hologram and an exposure region of the substrate. The pattern hologram is recorded to a recording medium by interference between an object wave from the pattern and a reference wave, and a second hologram is formed to the medium by diffraction light from an alignment mark formed on the mask. Prior to reconstruction of the pattern image, reconstruction light from the second hologram, illuminated with a reconstruction wave, is irradiated onto the substrate arranged in place of the mask. A reproduction image of the alignment mark on the substrate surface illuminated with the reconstruction light is measured, and relative displacement between the medium and the substrate is detected from a result of the measurement.

Abstract: A hologram copying system that includes a first reconstruction beam, a second reconstruction beam that is incoherent with respect to the first reconstruction beam, a first master hologram responsive to the first reconstruction beam for producing a first diffracted beam, a second master hologram responsive to the second reconstruction beam for producing a second diffracted beam, and a holographic recording layer responsive to the first and second reconstruction beams and the first and second diffracted beams, whereby a first hologram is formed by interference of the first reconstruction beam and the first diffracted beam, and a second hologram is formed by interference of the second reconstruction beam and the second diffracted beam.

Abstract: An encoded hologram that produces a first image and a second image pursuant to playback illumination, wherein the first image is resolvable by human vision while the second image is not resolvable by human vision when the playback illumination comprises non-coherent broad band illumination, and wherein the second image is machine readable when the hologram is illuminated with playback illumination that is based on the original reference beam.

Abstract: A monochromatic-light reproduction type hologram having a hologram recorded area provided with interference fringes that form a hologram image, the hologram image being reproducible by irradiating the hologram recorded area with monochromatic light at a given angle. A plurality of hologram images different from each other in the directionality of interference fringes are multiple-recorded in the hologram recorded area. Alternatively, the hologram recorded area is divided into a plurality of regions so that a plurality of hologram images different from each other in the directionality of interference fringes are separately recorded in the divided regions. The recorded area is successively or simultaneously irradiated with monochromatic light rays at given angles corresponding to the directionality of interference fringes of the respective hologram images, to reproduce the hologram images as a plurality of information patterns or a single information pattern.

Abstract: A security device includes first and second diffractive structures contained within a surface relief structure. The structures are such that the device responds to illumination at a first, visible wavelength to generate a first, visible pattern while any pattern generated by the second structure is not substantially visible at that wavelength, and the device responds to illumination at a second wavelength substantially different from the first wavelength to generate a second pattern suitable for machine reading while any pattern generated by the first structure is substantially suppressed relative to the machine readable pattern at that wavelength.

Abstract: A color image reading apparatus includes a multiple-line sensor in which a plurality of one-dimensional sensor arrays are arranged on a single substrate, a projection optical system for projecting a subject on the sensor, and a color separator disposed in an optical path between the projection optical system and the sensor, for color-separating light from the subject into a plurality of color beams. The color separator includes a volume hologram and an optical interference film.

Abstract: An achromatic hologram optical system for converting a wave front A into a wave front B. Two holograms (H.sub.1 and H.sub.2) are provided. The length of an optical path from an equiphase front of the wave front A to an equiphase front of the wave front B is constant, and each of the two holograms has a curved surface shape.

Abstract: A hologram structure including a plurality of holograms having substantially identical reconstruction characteristics disposed on a substrate for rotation about a rotation axis and containing segments of a composite image. The holograms are angularly offset relative to each other about a rotation axis such that the composite image is visible over at least one narrow solid angular region pursuant to rotation of the holograms about the rotation axis and illumination of the holograms with a reconstruction beam.

Abstract: A portable holographic display system emboding holographic plates which are disposed upon a plurality of thin film holographic emulsions coupled to multiple channel Kerr units that generate a series of multi-colored holographic images. The holographic images generated by transmission thin film emulsions are based on the number and order that multiple light channels, fiber optics elements and thin film holographic emulsions are illuminated. The process of illumination depends directly on the activation sequence of lens elements or cells, which contain an optically active medium controlled by command signals from a central control means coupled to a source of electrical power.

Abstract: A hologram system comprises two volume holograms on two separate substrates which are cemented together with an optical cement. The two volume holograms are manufactured with identical Bragg planes. The two volume holograms are oriented with respect to one another such that the Bragg planes are optically aligned. The result is that the two volume holograms operate as a single thicker volume hologram wherein the Bragg angle sensitivity is greatly increased.

Abstract: A hologram exposure system for simultaneously exposing a plurality of holograms in a holographic recording layer, including first optical elements for providing a first reference beam and a first object beam that interfere in the holographic recording layer and are coherently matched relative to each other, and second optical elements for providing a second reference beam and a second object beam that interfere in the holographic recording layer and are coherently matched relative to each other but are coherently mismatched relative to the first reference and object beams, whereby the crosstalk holograms formed by interference of (1) the first reference beam with the second object beam, (2) the first object beam with the second reference beam, (3) the first object beam with the second object beam, and (4) the first reference beam with the second reference have reduced efficiencies.

Abstract: A hologram containing information recorded such a manner that it is difficult to read. A Lippmann hologram (10) contains photoelectrically readable information (13) recorded so as to be reconstructible only with a specific invisible wavelength (6) in the infrared or ultraviolet region. It is difficult to read the information recorded on the hologram unless information about the wavelength of diffracted light (14) for reconstruction is given. The hologram is also difficult to forge and hence suitable for security purposes.

Abstract: Scanner optics, usable for example in a bar code reader, generate a multitude of Gaussian beams derived from a common light source to produce a beam with extended working range. In the preferred embodiment, a 360 degree fan of Gaussian beams is generated by passing a laser beam through at least one diffractive element, e.g., computer generated holographic (CGH) plate, computed to perform the transformation of the illuminating beam into the desired output beam. The beam thus produced, having a small diameter over a large longitudinal distance, is useful for long range scanning.

Abstract: An improved method for forming a Bragg grating in a photosensitive, optical waveguiding medium by exposure to an interference pattern formed by overlapping beams of actinic radiation. When Bragg gratings are formed according to methods of the prior art, these gratings tend to exhibit reflectivity spectra having, in addition to a central peak, a generally undesirable series of subsidiary peaks. These subsidiary peaks are caused by a wave interference effect. The inventive method modifies or eliminates the subsidiary peaks by spatially modulating the average refractive index of the grating, or by spatially modulating the grating period.

Abstract: A three-dimensional optical recording medium is made of a photo-induced refractive index-changing material or two-photons absorbing material, which is based on photo-dissociation or photopolymerization. An optical information recording apparatus comprises a device for loading a three dimensional recording medium; a device for generating a high coherent optical pulse or a train of partially-coherent optical waves; a device for splitting the optical pulse into two pulse components and causing the two pulse components to propagate in the recording medium from opposite directions to meet at a predetermined three-dimensional position; a device for converging a light beam in the recording medium into a parallel beam; and a device for discretely scanning the meeting position of the pulse components to ensure three-dimensional recording in accordance with information to be recorded.

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: Multiple layers or holographic exposures and methods for preparing multiple layers of holographic exposures are described. The multiple layers of holographic exposure combine to form holographic stacks and are fabricated from layers of exposed and processed photosensitive recording films, each of which has at least one independently recorded hologram. The holographic stacks are useful for providing wide bandwidth holograms and holograms having superimposed images.

Abstract: The present invention concerns an optical system for the reproduction of color video images, comprising a source of illumination (1), an electro-optical modulator (3) formed from pixels associated with the colors red, green, and blue respectively, and optical collimation means (2) used to illuminate the entirety of the modulator. This system further comprises a series of wavelength-selective holographic lenses (6) making it possible to focus the light of each red, green, or blue component on the associated pixels of the modulator. Applications to videoprojectors and direct viewing.

Abstract: A holographic display system is disclosed. Utilization of holographic elements provides good transmissivity with respect to both outside stimulus and the superimposed display information. Full color display is enabled by a composite spherical lens and the efficient optical coupling of the display information and the pupil allows the weight of the helmet with the display system to be kept to a minimum.

Abstract: A guard hologram blocks ambient turn-on of an image hologram. In a center high-mounted rearview stoplight assembly, a guard hologram is used to prevent ambient turn-on by the sun and still allow optical transparency of the image hologram. The guard hologram preferred is optically mounted to the lamp side of the image hologram and includes two 0-degree reflection holograms separated by a halfwave film.

Abstract: A method and apparatus for the collation or fine comparison of closely related images made with coherent light, such as those that may arise in holographic interferometry, in holo-photoelasticity, or in speckle interferometry.

Abstract: A holographic head-up display having first and second superimposed reflection holograms supported by a vehicle windshield, and first and second playback sources respectively associated with the first and second reflection holograms and positioned such that reflection by the windshield of playback illumination from one playback source is toward the other playback source. In particular, the first and second playback sources are configured such that the centerlines of the playback beams provided by the first and second playback sources are coplanar in a common plane that is substantially normal to the holograms, with the centerlines intersecting generally in the hologram layers and having substantially the same angle of incidence on the hologram layers as measured relative to normal in the common plane.

Abstract: A heads-up display including a holographic optical element which reflects only at least one specific wavelength and allows a background light of other wavelengths to pass therethrough, an information source which emits information light having the specific wavelength, and a device for removing a wavelength of light corresponding to a complementary color of the specific wavelength.

Abstract: The present invention is a technique for construction of a laser protection window providing broadened angular protection. Plural modulated index of refraction filter elements are constructed to reflect incident light at a predetermined laser threat wavelength over a cone of protection. The plurality of modulated index of refraction filter elements are disposed in tandem at angles to a direction of primary view through the laser protection window which are symmetrical with respect to the direction of primary view. In a first embodiment, a first optional modulated index of refraction filter element is disposed perpendicular to the direction of primary view; the other modulated index of refraction filter elements are disposed in pairs at opposing angles to the direction of primary view. In an alternative embodiment, the angled modulated index of refraction filter element plates are formed of angled segments.

Abstract: An optical system which contains multiple images comprised of two or more images at varying focal distances, which when viewed consecutively and in repetition will exercise the ciliary muscle of the eyes. The optical system may have its own power to illuminate said images. The shifting of conditions of the viewer to alternate the viewing of one image and then the other, may involve the physical movement of the user's head, the system may contain a motor coupled to rotate said system, or the configuration of the lighting source(s) shall illuminate one image and then another. The system may include a clock-timer and control of the variable speed of illumination between one optical image to another. The system may include a sound alarm to remind the viewer to utilize the holographic system.

Abstract: A holographic objective system (3) produces an intermediate real image (4) of information displayed on an electrically addressable spatial light modulator or SLM (1), the real image (4) being collimated by a powered holographic reflector (5) constructed as part of the visor of a helmet worn by the viewer (9). The SLM (1) is illuminated by laser light from a remote laser (8) via a single optical fibre (6) and beam splitter (2). A diffuser (7) is provided either between the laser and the beam splitter or in the plane of the intermediate image (4). The objective system (3) may alternatively include, or consist entirely of, conventional optical elements.

Abstract: A method is disclosed for forming a multi-layer holographic device 22. A first hologram is formed on a major surface of a substrate 14. The first hologram is desensitized to prevent interaction with a second subsequently formed hologram. The second hologram is formed conterminous with said first hologram.

Abstract: A disk cover is provided with a reflection-type hologram assembly having multiple exposure images therein. The sun or an artificial light source illuminates the hologram assembly as it rotates as a result of the body moving. The exposure images are successively reconstructed to produce a single image that may be remotely positioned from and stationary relative to the rotating disk cover.

Abstract: The invention relates to a holographic display element which includes a reflection hologram and is attached to, for example, an automobile windshield so as to project light rays carrying images of display information onto the display element from a luminous source in the car. When external light such as sunlight coming is diffracted by the reflection hologram there is a possibility that visible light ranging from 570 nm (greenish yellow) to 780 nm (red) is diffracted into a certain range of angles in a horizontal plane and makes a strange impression on persons viewing the windshield from the outside. According to the invention another reflection hologram having different diffraction characteristics is superposed on the first hologram on the outer side in order that diffraction of visible light into the aforementioned range of angles may become inconspicuous.