Abstract: A photosensitive composition and A photosensitive medium for volume hologram recording comprises a photopolymerization reactive compound (a monomer) and any one of the following binder: (a) an organic-inorganic hybrid polymer obtainable by copolymerizing an organometallic compound of the formula 1 “R1m M1 (OR2)” and an ethylenic monomer and/or its hydrolyzed polycondensate; (b) an organic-inorganic hybrid polymer obtainable by copolymerizing an organometallic compound of the formula 3 “R4m Si (OR5)n” and an ethylenic monomer and/or its hydrolyzed polycondensate; and (c) a binder resin bonded to a metal or a combination use of a binder resin containing a hydroxyl group and/or carboxyl group and a metal chelate compound.

Abstract: The present invention relates to a volume hologram laminate with low generation of spotty hologram flaws in the volume hologram layer even when kept under pressurized conditions during storage, and to a volume hologram laminate-fabricating label. The volume hologram laminate 1 of the invention has a first adhesive layer 3, a volume hologram layer 5, a second adhesive layer 4 and a surface protective film 6 formed in that order on a substrate 1, wherein the volume hologram layer is a hologram recording in a recording material comprising a matrix polymer and a photopolymerizable compound, having a glass transition point of 30° C.-70° C. and a dynamic storage elastic modulus of 5×105 Pa-5×107 Pa at 50° C. when measured at 6.28 rad/s, and the second adhesive layer has a dynamic storage elastic modulus of no greater than 5×104 Pa or at least 2.5×105 Pa at 50° C. when measured at 6.28 rad/s.

Abstract: A method of fabricating a hologram screen having a large visual range and a hologram imaging apparatus used for the particular method of fabricating the hologram screen are disclosed. A plurality of mirrors (3) extended toward a plurality of photosensitive members (5) are arranged at a plurality of end portions (21), respectively, of a light diffuser (2). At least a reference beam (41) and object beams (42) passed through the light diffuser (2) are radiated on a plurality of the photosensitive members (5) individually thereby to form a plurality of holograms. These holograms are integrated with each other by being arranged two-dimensionally thereby to fabricate a hologram screen. Among the mirrors (3), a reference beam-side mirror (31) arranged nearer to the light source of the reference beams (41) is extended from the light diffuser (2) by a length varied with the position of the photosensitive member (5) to be exposed.

Abstract: Disclosed is a storage medium which comprises strontium barium niobate single crystal containing europium and cerium as impurities. The material may be used in which the strontium barium niobate has a chemical formula: SrxBa1-xNb2O6 where x satisfies 0.25≦x≦0.75. Further, small amounts of cerium and europium are added to a main component comprised by strontium, barium, niobate and oxygen. The optical material can be used in various optical devices such as a holographic storage medium, a phase conjugate mirror and an optical amplifier.

Abstract: The invention relates to improvements in security features in paper and other substrates and in particular to an activatable feature to warn of tampering. The invention further relates to a security feature for a security document comprising at least one activatable layer and at least one visually apparent masking layer, said at least one activatable layer comprising a composition which is generally non-mobile but which becomes mobile when wetted with a liquid, said composition further including at least one detectable component, in which under dry conditions said at least one masking layer wholly covers the activatable layer and renders it non-detectable.

Abstract: A method for impressing holographic images or holograms in the surface of metal objects such as aluminum cans, sheet metal or metal foil. The surfaces of metal shims and print rolls bearing holograms are hardened as by coating them with thin amorphous diamond coatings or diamond like coatings so the holograms can be embossed into many thousands of metal objects with clarity and consistency.

Abstract: Multi-domain, phase-compensated, differential-coherence detection of photonic signals for interferometric processes and devices may be manufactured holographically and developed in situ or with an automatic registration between holograms and photonic sources in a single frame. Photonic or electronic post processing may include outputs from a cycling or rotation between differently phased complementary outputs of constructive and destructive interference. A hyper-selective, direct-conversion, expanded-bandpass filter may rely on an expanded bandpass for ease of filtering, with no dead zones for zero beat frequency cases. A hyper-heterodyning, expanded bandpass system may also provide improved filtering and signal-to-noise ratios. An ultra-high-resolution, broadband spectrum analyzer may operate in multiple domains, including complex “fingerprints” of phase, frequency, and other parameters.

Abstract: A method and apparatus is disclosed for creating a structure, such as a grating (45) in a photosensitive material (40). The method and apparatus relies upon creating at least two coherent beams of light (33, 38) and reflecting them, in a counter propagating manner, around a series of reflective elements (35, 37) along substantially equivalent paths so that the coherent beams interfere at a structure staging area (45). The structure staging area can then be utilized to create grating structures or the like having improved qualities.

Abstract: A method for fabricating an error-free linear position encoder incorporates the generation of fringes on a holographic plate by the interference of light from two point sources. The fringes are projected onto a curved holographic plate without intervening optical elements, the curve being such that the fringes have a constant pitch along the surface of the plate. A methodology for generating such a curve includes the creation of a graphic representation of the hyperbolic fringes generated by the interference between two coherent point sources, which would fall on an appropriately curved holographic plate. A numerical technique derived from the graphic representation produces a “constant-pitch” curve such that all of the fringes projected onto the curve are equidistant. The holographic plate, coated with a photosensitive material, is fabricated or formed in the shape of the constant-pitch curve.

Abstract: An optical information recording and reproducing apparatus, which detachably supports a holographic memory formed of a photorefractive crystal, includes a portion for supplying a coherent reference light beam at a first wavelength into the holographic memory; a portion for supplying a coherent signal light beam at the first wavelength, modulated in accordance with image data, into the memory to produce an optical interference pattern with the reference light within the memory; a portion for supplying a gate light beam at a second wavelength into the memory for activating or deactivating an index grating in accordance with the presence or absence of the optical interference pattern to enhance a photo-sensitivity of the memory; a detector for detecting diffraction light from the index grating of the memory by the irradiation of the reference light beam; and a portion for changing and regulating a light intensity of the gate light beam.

Abstract: New photosensitive acrylic material compositions for fabrication of holographic recording materials (HRMs) are provided. These compositions are comprised of polymerizable acrylic monomers and light absorbing dyes, and when polymerized they are thermally stable, light sensitive, hard and inert to common chemicals. Methods of fabricating HRMs with symmetric concentration distribution of the dye are also provided.

Abstract: The invention provides a partial metallic hologram wherein a light reflecting layer is formed easily at a low price and the light reflecting layer and the hologram region are formed in a pattern having an arbitrary shape, and a method of producing the same. A metallic hologram comprises a light reflecting layer, wherein the light reflecting layer is formed by coating or printing with a high brightness coating agent.

Abstract: Disclosed is a holographic recording medium. The novel holographic recording mediums disclosed herein comprises: a) at least one polyfunctional epoxide monomer or oligomer which undergoes acid initiated cationic polymerization. Each epoxide in the monomer or oligomer is linked by group comprising a siloxane to a silicon atom and each monomer or oligomer has an epoxy equivalent weight of greater than about 300 grams/mole epoxide; b) a binder which is capable of supporting cationic polymerization; c) an acid generator capable of producing an acid upon exposure to actinic radiation; and optionally d) a sensitizer.

Abstract: A method for making wire grid optical elements by preferentially depositing material on a substrate is disclosed. Material can be preferentially deposited by directing an electromagnetic interference pattern on to a substrate to selectively heat areas of the substrate coincident with the interference pattern maxima. The substrate can then be exposed to gas phase material that is capable of preferentially accumulating on surfaces based on surface temperature.

Abstract: The invention relates to a liquid crystal display device which enables a visual field range to be made wide and luminance drops to be reduced, so that bright displayed images can be presented, and provides a liquid crystal display device comprising, in order from a side of backlight 11, backlight 11, scatter plate 12, and liquid crystal element 20, wherein a transmission type of hologram scatter plate 13 is located in front of a display surface of liquid crystal display element 20. Hologram scatter plate 13, because of having been fabricated by means of single-step or two-step exposure, enables light more or less scattered through scatter plate 12 to be limitedly scattered within a given wide visual field range, so that bright displayed images can be presented over a wide visual field range yet with a reduced luminance drop. Scatter plate 12 may be omitted.

Abstract: It has been found that holographic images can be formed on the surfaces of plastic products or the plastic packaging for products. The elastic preferably is a thermoplastic that can flow into the narrow spacings that form the holographic image. The holographic image is formed while the product or packaging is being formed. These can be formed by injection molding, blowmolding, injection stretch blowmolding and thermoforming. A shim bearing the image of the hologram is placed in the mold and the plastic injected or otherwise flowed or placed in the mold. Upon the plastic under pressure being in contact with the shin in the mold, the shin will impart a holographic image into the plastic. The product or package is cooled and then is in a form for use.

Abstract: The invention relates to novel monodisperse or polydisperse compounds, in general named DNO (diamino acid N&agr;-substituted oligopeptides), preferably low molecular weight polypeptides, e.g., based on ornithine, lysine, diaminobutyric acid, diaminopropionic acid, aminoethylglycine or other amino acids or peptides having azobenzenes or other physicially functional groups, e.g., photoresponsive groups, as side chains. These compounds may be synthesized using solid phase peptide synthesis techniques. Materials, e.g., thin films, comprising such compounds may be used for optical storage of information (holographic data storage), nonlinear optics (NLO), as photoconductors, photonic band-gap materials, electrically conducting materials, electroluminescent materials, piezo-electric materials, pyroelectric materials, magnetic materials, ferromagnetic materials, ferroelectric materials, photorefractive materials, or materials in which light-induced conformational changes can be produced.

Abstract: Polymer techniques are used to reduce the feature size in electrical or mechanical processes. A first embodiment uses a light sensitive polymer. A first illumination forms a lens structure. A second illumination is focused by that lens structure to form a final feature. The lens can then be removed. A second embodiment uses holographic techniques to pattern polymers and form consistent pores within the polymers.

Abstract: Novel volume holographic elements were made from Bragg diffractive gratings in photo-thermo-refractive (PTR) glass with absolute diffraction efficiency ranging from greater than approximately 50% up to greater than approximately 93% and total losses below 5%. Both transmitting and reflecting volume diffractive elements were done from PTR glasses because of high spatial resolution enabling recording spatial frequencies up to 10000 mm−1. The use of such diffractive elements as angular selector, spatial filter, attenuator, switcher, modulator, beam splitter, beam sampler, beam deflectors controlled by positioning of grating matrix, by a small-angle master deflector or by spectral scanning, selector of particular wavelengths (notch filter, add/drop element, spectral shape former (gain equalizer), spectral sensor (wavelength meter/wavelocker), angular sensor (pointing locker), Bragg spectrometer (spectral analyzer), transversal and longitudinal mode selector in laser resonator were described.

Abstract: The present invention relates to compositions useful for optically recording or storing data by stimulating a composition having a refraction modulating composition, where a stimulated region of the composition represents one kind of data and a non-stimulated region of the composition represents another kind of data. The present invention also relates to methods of optically recording data utilizing the compositions of the present invention, as well as to optical data storage devices and optical data storage elements which utilize the optical data storage compositions of the invention.

Abstract: A multilevel diffractive optical element comprising a base and a plurality of phase zones having phase levels of a substantially identical height h, each phase zone being defined by a local modulation depth d and a local number of phase levels &xgr;=d/h, the local number of phase levels &xgr; per phase zone being a real number, an integer of which defines the number of complete levels in the phase zone, which complete levels have identical widths, and a fraction of which, in at least one phase zone, defines an incomplete level which is narrower than the complete levels, said local number of phase levels &xgr;=&xgr;(x, y) varying among different phase zones so as to provide corresponding variation of said local modulation depth d=d(x, y) whereby local diffraction efficiencies and consequently an overall diffraction efficiency of the optical element is arbitrarily controlled.

Abstract: A system and method of preparing artwork for a laser foil die implement prism lines designed to interact with the diffraction grating on a layer of laser hot foil. Artwork may be selectively segmented into discrete regions; prism lines may be created by assigning a halftone value, a frequency value, and an angle for each region of the artwork. A system and method of creating a laser foil die transfer such artwork and prism lines to a blank die; when created in accordance with the present invention, a die may transfer prism lines to a layer of laser foil applied to a substrate.

Abstract: Disclosed is an improvement in an optical information recording method by utilizing a unique phenomenon in which, when a thin film of a polymeric compound having a structure of azobenzene is irradiated spotwise with a light beam of a specified wavelength, a pattern of rugged surface with recesses and raises is resulted by the migration of the polymer molecules from the strongly irradiated area to the weakly irradiated area. The improvement has an object to increase the photosensitivity of this phenomenon by simultaneously irradiating the polymeric thin film with a second or bias light beam of a larger cross section to envelop the irradiation spot by the first or writing light beam.

Abstract: The photonic crystal material has a 3-D periodic structure with a periodicity that varies on a length scale comparable to the wavelength of electromagnetic radiation. The 3-D periodic structure is produced by irradiating photosensitive material with electromagnetic radiation such that interference between radiation propagating in different directions within the sample gives rise to a 3-D periodic variation in intensity within the sample. Thereafter the irradiated material is developed to remove the less or more irradiated regions of the material to produce a structure having 3-D periodicity in the refractive index of the composite material. 3-D photonic material is particularly suited to use as low-loss waveguides and as a control with lasers to limit the number of modes into which a laser may emit radiation.

Abstract: The present invention provides a volume hologram laminate by which a desirable reproduced wavelength is controlled and set optionally. The laminate has a first adhesive layer 3, a volume hologram layer 5, a second adhesive layer 4 and a surface protecting film 6 formed on a substrate 2 in the described order, wherein a substance for shifting a recorded wavelength to the volume hologram layer is contained in the first and/or the second adhesive layer(s) and a reproduced wavelength of hologram recorded in the volume hologram layer is controlled with shifting the substance between the layers.

Abstract: The invention provides a hologram transfer foil comprising a substrate and a transfer layer laminated thereon, said transfer layer comprising a surface protective layer, a thermoplastic resin layer, a hologram layer and a heat seal layer in this order. The hologram transfer foil is applied on the heat seal layet side to an application member. In this case, a peel force between the substrate and the surface protective layer is smaller than that between adjacent layers in other layers. This hologram transfer foil enables a hologram image, etc. to be reconstructed in an uninterrupted manner, and is improved in terms of transferability and productivity.

Abstract: A multilayer polymer film has an optical stack including a plurality of alternating polymer layers with skin layers having mechanical, optical, or chemical properties differing from those of the layers in the optical stack. In one embodiment, the multilayer polymeric film has one or more holograms that provide attractive and useful optical effects.

Abstract: New photosensitive acrylic material compositions for fabrication of holographic recording materials (HRMs) are provided. These compositions are comprised of polymerizable acrylic monomers and light absorbing dyes, and when polymerized they are thermally stable, light sensitive, hard and inert to common chemicals. Methods of fabricating HRMs with symmetric concentration distribution of the dye are also provided.

Abstract: The hologram recording sheet according to the invention is made up of a base film and hologram sensitive materials sensitive to different wavelength regions formed therein in a desired pattern, or a film and at least two hologram recording sensitive materials sensitive to different wavelength regions laminated on the film with a transparent plastic spacer layer located therebetween, thereby enabling the required diffraction light wavelengths to be recorded on the required sites without producing unnecessary interference fringes. At least two hologram recording sensitive materials sensitive to different wavelength regions are formed on different sites on a film in dotted or striped configuration, the size of which is up to 200 mm or at least twice as large as the thickness of the sensitive material layers, thereby enabling regions diffracting light of different wavelengths to be formed in the form of independent sets of interference fringes.

Abstract: There are disclosed the following three types of optical recording film:

Abstract: A method for fabricating a capacitor electrode on a semiconductor substrate includes the steps of: forming a conducting layer over the semiconductor substrate; forming a photoresist layer over the conducting layer; pattering the photoresist layer through an interfering exposure step; and pattering the conducting layer using the patterned photoresist layer as a mask, thereby forming a capacitor electrode.

Abstract: A holographic information storage and retrieval system provides an all-optical reversible method to fix information in doped or undoped photorefractive materials. The fixed information is sufficiently stable to provide long term archival storage over a period of decades or more and can be read out non-destructively by a coherent reference beam. Holograms recorded in a photorefractive material are fixed when the material is irradiated with incoherent ultraviolet light. Hence, the holograms are preserved indefinitely against erasure by a coherent beam and against dissipation in dark storage. Holograms, which are fixed in the photorefractive material with incoherent ultraviolet light, are also erased with incoherent ultraviolet light, thus making the process reversible.

Abstract: The invention provides an optical lens having a combination volume holographic optical element that provides a diffractive optical power. The optical lens has a programmed activating angle in which the holographic optical element provides a diffractive optical power. The invention also provides a method for producing a multilayer holographic element suitable for the optical lens.

Abstract: Lithography processes that use multiple layers require registration between layers. The accuracy requirement depends on the application of the lithograph. For microlithography, the registration requirement could be less than one micron. Systems that use lenses for imaging such as optical steppers can image conventional alignment marks through those lenses. A unique microlithography system that employs holograms has properties that are not compatible with known alignment techniques. The present invention is a new system for alignment of holographic microlithography elements.

Abstract: A pattern formation method wherein a very small pattern composed of a desired element (atoms) is formed directly on a substrate by using atomic beam hologram technology. Quantum coherent reflection of an atomic wave is utilized. A coherent atomic beam is irradiated as a material wave, for example, upon a hologram of the transmission type to modulate the atomic beam with pattern information included in the hologram. The atomic beam having passed through and diffracted by the hologram is introduced to a reflecting plane so that the atomic beam may be quantum coherent reflected by the reflecting plane, and the atomic beam thus reflected is introduced into a substrate. A binary (two-value) hologram produced by computer synthesis is used suitably as the hologram. A hologram of the potential control type may be also used.

Abstract: A thickness of each hologram lens for forming a hologram color filter is set so as to be smaller as the wavelength of light to be diffracted by each hologram lens is shorter. A thin plate glass layer is bonded to a surface of the hologram color filter such that it is in a firm contact therewith by adhesive agent and a sum of the thickness of the thin plate glass layer and thickness of the adhesive agent is smaller than the shortest focal length of the focal lengths in glass of a plurality of the hologram lenses. As a result, light diffracted and divided by the hologram color filter is focused on a picture element electrode of a corresponding color properly thereby eliminating deterioration of color reproduction due to mixing of colors. Further, upon production of the hologram color filter from hologram recording material, an influence of a fringe rotation is compensated.

Abstract: The invention provides a hologram transfer foil 1 comprising, in order from top to bottom, a substrate 7, a volume hologram layer 2 releasably stacked on substrate 7 and comprising a volume hologram in a cured resin layer, a first heat seal layer 3 and a second heat seal layer 4. In use, the hologram transfer foil 1 is applied on the second heat seal layer 4 side over an application member. The adhesion force of volume hologram layer 2 to the application member is larger than a material fracture force for the volume hologram layer or the application member, so that the hologram transfer layer can be applied by thermo-compression to the application member. This hologram transfer foil is useful for illegal copying of the hologram layer because when the volume hologram is forcibly peeled from the application, a material fracture of the volume hologram layer or application member occurs.

Abstract: A photoactive medium has a complex format grating written thereon, the complex format grating including at least three component gratings, each of the component gratings characterized by a unique grating vector. Methods for writing the complex format grating include the steps of providing a photoactive medium; and focussing a plurality of pairs of mutually coherent light beams into a focal plane in the medium.

Abstract: The present invention comprises an optical data storage system utilizing a host material and molecules that exhibit non-linear absorption dissolved therein. The non-linear absorbing molecules allow for energy in the form of heat to be generated during the optical data storage process. This heat provides for localized alterations to occur in the pre-formatted holographic grating. The non-linear feature of these molecules allow for alterations to occur at specific depths and locations within the storage medium while limiting the secondary effects on other locations within the storage medium. The molecules exhibiting non-linear absorption may be selected from the group of molecules exhibiting two-photon absorption or reverse saturable absorption. The invention also comprises a method for preparing the optical storage medium, an optical data storage device comprising the optical data storage medium and having a format hologram stored within the medium.

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 method for patterning a layer on a substrate can include projecting coherent radiation toward a reflector surface so that the coherent radiation is reflected off the reflector surface to provide a holographic projection of a desired image wherein the reflector surface includes information that corresponds to an inverse of the holographic projection of the desired image. The substrate including the layer can be maintained in the path of the reflected radiation so that the holographic projection is projected onto the layer. Related systems are also discussed.

Abstract: The invention provides a hologram-recording subject plate comprising a block and a variety of subjects fixedly contained therein, which ensures easy, stable yet continuous recording of a multiplicity of identical holograms or different holograms reconstructible by illuminating light as is the case with a hologram-replicating method, a hologram-making method using the same, and a hologram-recorded article. The subject plate comprises a transparent solid block 5 and a hologram-recording subject S contained therein. A photosensitive material film 1 is applied directly onto one surface of the subject plate, and the subject plate is then irradiated with laser light 7 through the photosensitive material film 1. Such simple operation enables a multiplicity of identical holograms to be recorded in an easy, stable yet continuous manner.

Abstract: Transmission and reflection type holograms may be formed utilizing a novel polymer-dispersed liquid crystal (PDLC) material and its unique switching characteristics to form optical elements. Applications for these switchable holograms include communications switches and switchable transmission, and reflection red, green, and blue lenses. The PDLC material of the present invention offers all of the features of holographic photopolymers with the added advantage that the hologram can be switched on and off with the application of an electric field. The material is a mixture of a polymerizable monomer and liquid crystal, along with other ingredients, including a photoinitiator dye. Upon irradiation, the liquid crystal separates as a distinct phase of nanometer-size droplets aligned in periodic channels forming the hologram. The material is called a holographic polymer-dispersed liquid crystal (H-PDLC).

Abstract: An optical data storage system and method comprising a photopolymer medium having generally a polymerizable monomer, an active binder, a first, hologram recording polymerization initiator, and a second, data writing polymerization initiator. The monomer is preferably a cationic ring-opening monomer. The hologram recording polymerization initiator preferably comprises a sensitizer and photoacid generator which initiate a first polymerization in the medium which defines a format hologram. The format hologram recording is carried out via interference of a signal and reference beam, with the sensitizer being specific for the wavelength(s) of the signal and reference beams. The hologram recording polymerization is only partial and does not consume all of the monomer present in the photopolymer medium.

Abstract: The stamp (10) for a lithographic process, such as patterning a surface layer, of the invention has a stamp body (5) with at least a first recess (11) formed therein, which recess defines a first aperture (15) in the printing face (3) of the stamp (10). The first recess (11) narrows with increasing distance to the printing face, while any cross-section of the first recess, when perpendicularly projected on the printing face (3), will lie within the aperture (15). The printing face may comprise small (11, 12) and large apertures (13) as well as small surfaces (14) in between apertures, while it is nevertheless able to produce prints which are accurate replicas of the printing face. Even details on a submicron scale can be adequately printed. The stamp (10) can be manufactured by a method which comprises anisotropic etching of a first body to make a mold and replicating the mold in the printing face (3) of the stamp (10).

Abstract: A transfer foil for use in a safety document includes a multilayer structure having a carrier layer and a plastic layer in which diffraction structures, for example holographic structures, are embossed in the form of a relief structure and which is combined with a reflective layer. The plastic layer includes a reaction lacquer layer selected from the group consisting of cationical curing lacquers, blue light-curing lacquers and chemical curing multicomponent lacquers.

Abstract: A duplicating photosensitive material film is brought into close contact with an ND glass reduced in thickness so as to become flexible or a flexible sheet or an ND glass coated with a cushioning layer through an optical contacting liquid containing a surface active agent. In addition, a spacer is interposed between a hologram original plate and a duplicating photosensitive material, and a space defined by the spacer is filled with an optical contacting liquid, thereby regulating the thickness of the optical contacting liquid layer with the spacer. Therefore, when pressure is applied, the optical contacting liquid is uniformly pressed, so that it can be made uniform and thin in thickness. Accordingly, it is possible to prevent a failure of duplication of a hologram image due to undesirable flow of the optical contacting liquid.

Abstract: A simplified method is provided for recording identification information, such as a serial number or the like, in a hologram-recorded film simultaneously with hologram duplication. The method includes the steps of coupling a hologram recording film with a master hologram plate having a master hologram, the master hologram plate having a reflective area adjacent the master hologram; and directing laser beams towards the master hologram plate to induce interference between incident laser light and diffraction laser light from the master hologram in the recording film, at least some of the laser beams radiating the reflective area through a transmission type controllable display device to record a pattern in the hologram recording film corresponding to a pattern displayed at the transmission type controllable display device.

Abstract: A positive unit magnification reflective head is used to back-reflect a primary light beam, for storing reflection microholograms at the coincident foci of the primary and reflected beams. Imaging the primary beam focus onto itself at positive unit magnification allows increasing system tolerance to tilts and transverse misalignments between the primary and reflective heads. Holograms are stored at multiple depths in a holographic storage medium. Tunable-focus primary and reflective heads are positioned on opposite sides of the storage medium. The reflective head images each storage location onto itself at positive unit magnification. Suitable reflective heads include: two lenses in an f-2f-f configuration and a planar mirror; a lens and a corner cube; a thin lens and a thick lens with a coated reflective back surface; and a thin lens and a back-coated gradient-index (GRIN) lens.

Abstract: Method for the preparation of holographic diffusers where the holographic diffuser is designed through iterative calculations according to the Fraunhofer theory of diffraction and some constrain conditions. In the iterative calculation some constrain conditions that can change the magnitude of the light passing through the diffuser are used to design the diffuser. A novel iterative calculation is disclosed such that uniformed mixing of colors and high light utilization efficiency of the diffuser may be provided.