Abstract: Systems, devices, and methods for optical splitters are described. An optical splitter includes a transparent polygonal structure having an input side to receive light from a light source and an output side that is segmented into multiple facets. Each facet is engineered to provide a respective planar surface that is oriented at a different angle in each of at least two spatial dimensions relative to the other facets in order to refract and route a respective portion of the light along a respective set of optical paths. The input side may be faceted as well to further refine the optical paths. A particular application of the polygonal structure in an optical splitter providing eyebox expansion by exit pupil replication in a scanning laser-based wearable heads-up display is described in detail.

Abstract: The invention relates to a photopolymer formulation comprising specific aromatic glycol ethers as writing monomers, matrix polymers and a photoinitiator. The invention further provides an unexposed holographic medium obtainable using an inventive photopolymer formulation, and an exposed holographic medium obtainable by exposing a hologram into an inventive unexposed holographic medium. The invention likewise provides a visual display comprising an inventive exposed holographic medium, for the use of an inventive exposed holographic medium for production of chip cards, identification documents, 3D images, product protection labels, labels, banknotes or holographic optical elements, and specific aromatic glycol ethers.

Abstract: In the antireflection film, a hydrogenated carbon film as a first layer is formed on a surface of an optical substrate. A MgF2 film as a second layer having a lower refractive index than the first layer is formed on the first layer and functions as a low refractive index layer. The hydrogenated carbon film and the MgF2 film are formed using a RF magnetron sputtering equipment. During the formation of the hydrogenated carbon film, a mixed gas of argon and hydrogen is supplied to a vacuum chamber such that some of C—C bonds in the film are replaced with C—H bonds. Some of C—C bonds are cut by hydrogenation, and strains (stress) accumulating due to C—C bonds can be relaxed. As a result, the antireflection film which has excellent adhesiveness and is not broken is obtained.

Abstract: The invention relates to an assembly comprising a substrate and a photopolymer film, which are joined to one another partably at least in sections, the substrate comprising polyethylene terephthalate, and the photopolymer film comprising three-dimensionally crosslinked polyurethane matrix polymers, a writing monomer and a photoinitiator, characterized in that the substrate, after seven-day incubation at 23° C. in a 0.5 volume percent butyl acetate solution of the dye of formula (I) has an L value L1 and before the incubation an L value of L0, the L values being determined by CieLAB measurements, and the difference between the L values L1 and L0 satisfying the formula (II) L1?L0>?0.25??(formula II).

Abstract: In the specification and drawings, a collinear holographic storage medium is described and shown with a recording layer, wherein the lateral linear thermal expansion coefficient of the recording layer is substantially the same as the linear thermal expansion coefficient of the material of the recording layer.

Abstract: An apparatus for detecting a defect of an object may include a light emitter configured to emit straight polarized lights having different polarized directions, a spatial filter having openings through which the straight polarized lights selectively pass, an optical member configured to condense the straight polarized lights, which pass through the openings, on the object, and a light detector configured to detect lights reflected from the object. Thus, the defect may be accurately detected in a short time.

Abstract: A diffraction grating and a method for fabricating the diffraction grating. In one embodiment, a layer of photo-monomer is applied to a substrate and the photomonomer is exposed to a collimated beam of light to form the diffraction grating. The intensity of the collimated beam of light incident on the layer of photo-monomer may have substantially no spatial variation across the first collimated beam of light.

Abstract: Provided are an optically addressable spatial light modulator (OASLM) divided into a plurality of segments, and an apparatus and method for displaying a holographic three-dimensional (3D) image using the OASLM. The holographic 3D image display apparatus includes a first light source which emits a write beam, an electric addressable spatial light modulator (EASLM) which modulates the write beam emitted from the first light source according to hologram information regarding a 3D image, a second light source which emits a read beam, an OASLM which receives the write beam modulated by the EASLM and modulates the read beam emitted from the second light source according to hologram information included in the modulated write beam, a scanning optical unit which projects the write beam modulated by the EASLM onto the OASLM, and a Fourier lens which focuses the read beam modulated by the OASLM onto a predetermined space to form the 3D image.

Abstract: Although an organic resin substrate is highly effective at reducing the weight and improving the shock resistance of a display device, it is required to improve the moisture resistance of the organic resin substrate for the sake of maintaining the reliability of an EL element. Hard carbon films are formed to cover a surface of the organic resin substrate and outer surfaces of a sealing member. Typically, DLC (Diamond like Carbon) films are used as the carbon films. The DLC films have a construction where carbon atoms are bonded into an SP3 bond in terms of a short-distance order, although the films have an amorphous construction from a macroscopic viewpoint. The DLC films contain 95 to 70 atomic % carbon and 5 to 30 atomic % hydrogen, so that the DLC films are very hard and minute and have a superior gas barrier property and insulation performance.

Abstract: This invention relates to a holographic medium comprising a protective layer and a photopolymer film which is bonded to the protective layer and contains polyurethane matrix polymers, acrylate writing monomers and photoinitiators, wherein the protective layer is impermeable to the constituents of the photopolymer film, is optically clear and is transparent to electromagnetic radiation having a wavelength in the range of from 350 to 800 nm. The invention further provides the use of a holographic medium according to the invention in the production of holograms, and a process for the production of a holographic medium according to the invention.

Abstract: An integrated circuit includes a holographic recording material substantially filling a cavity in a semiconductor layer. During operation of the integrated circuit, a holographic pattern in the holographic recording is reconstructed and used to diffract an optical signal propagating in a plane of an optical waveguide, which is defined in the semiconductor layer out of the plane through the cavity. In this way, the holographic recording material may be used to couple the optical signal to an optical fiber or another integrated circuit.

Abstract: A method for the production of a holographic sensor which comprises a support medium supporting a reflection hologram wherein the support medium interacts with its physical or chemical environment to create an optical response which is a change in one or more optical properties of the hologram, the method comprising the steps of: a) introducing a colloidal dispersion of a recording material into the support medium; and b) ablating the colloidal particles of the recording material using a pulsed laser to form the holographic element in the support medium. The method of production can be used to introduce a reflection holographic grating into a hydrophobic support medium, in particular, polydimethylsiloxane (PDMS), which possesses an extraordinary ability to swell in the presence of both liquid and/or gaseous low molecular weight hydrocarbons and organic solvents and thus has many applications as a holographic sensor.

Abstract: The invention relates to a photopolymer formulation comprising matrix polymers, writing monomers, and photoinitiators, to the use of the photopolymer formulation for producing optical elements, in particular for producing holographic elements and images, to a method for illuminating holographic media made of the photopolymer formulation, and to special fluorourethanes.

Abstract: A hologram recording film manufacturing method includes the steps of obtaining a laminated structure by alternately laminating M (where M?2) photosensitive material precursor layers including a photosensitive material and at least one (M?1) resin layer on one another, obtaining M photosensitive material layers, where at least two interference fringes with a desired pitch and a desired slant angle are formed on each of the M photosensitive material layers, from the M photosensitive material precursor layers by irradiating the laminated structure with a reference laser light beam and an object laser light beam, and making the slant angles of the M photosensitive material layers different from each other while retaining the pitch value, which is defined on a face of the photosensitive material layer, by irradiating the laminated structure with an energy ray from the laminated structure's one face side, and heating the laminated structure.

Abstract: The invention provides a process capable of fabricating a cholesteric liquid crystal medium having a volume hologram with efficiency yet without recourse to complicated steps such as an alignment step. This is achievable as follows. A volume hologram layer is formed on a substrate, and a cholesteric liquid crystal layer is then formed on another substrate. The volume hologram layer and the cholesteric liquid crystal layer are laminated together via a bonding layer. Further, a bonding for lamination onto an application member is formed on either the volume hologram layer side or the cholesteric liquid crystal layer side to obtain a cholesteric liquid crystal medium having a volume hologram.

Abstract: A hologram-including medium is disclosed, which is an integrated medium on which at least two items of identification information are recorded, wherein one of the two items of identification information is holographic identification information which can be observed within a predetermined angle range when illuminated from a predetermined angle.

Abstract: A see-through display including a light source for emitting light, a projection optical system for projecting the light emitted by the light source, and a volume hologram for deflecting the light projected by the projection optical system. The volume hologram has a linear expansion coefficient of ? (/° C.) and interference fringes recorded with recording light having a wavelength of ? (nm). The wavelength of the light emitted by the light source has a temperature dependency of K (nm/° C.), and the wavelength ? (nm) and the temperature dependency K (nm/° C.) satisfy the relationship of 0?K/??2?.

Abstract: A method is provided for mastering optically variable devices (OVDs) used to authenticate optical discs. The method generally includes the steps of providing a laser beam recorder (LBR), introducing a substrate to the LBR, and exposing a portion of the substrate to the LBR. The mastering system thus includes the LBR, which has a laser that emits a beam, a processor or computer for programming or otherwise controlling the beam in order to expose the substrate and create the desired optical effect. Depending on the material used for the substrate, the exposure is then developed, if necessary, and processed to generate a master for the OVD. The OVD can then be replicated in order to provide authentic resultant products or articles, such as optical discs.

Abstract: The subject matter of the invention is a method for producing illuminated, holographic media comprising a photopolymer formulation having the adjustable mechanical modulus GUV. A further subject matter of the invention is an illuminated, holographic medium that can be obtained by means of the method according to the invention.

Abstract: The invention relates to optical device for illuminating a pixel matrix and/or a controllable spatial light modulator for a display, in particular a stereoscopic or holographic 3D display, wherein the optical device comprises a layer formed as a light waveguide, in which illumination light is guided in a light guiding layer, in particular according to the principle of total internal reflection, between two reflection layers lying opposite one another, wherein an extraction means for extracting illumination light from the light guiding layer is provided. The optical device is characterized in that the extraction means has different properties, in particular different optical properties, at a first extraction position than at another extraction position different to the first extraction position.

Abstract: A hologram recording material includes a polymerizable monomer (A) that is active in radical polymerization but is substantially inactive in cationic polymerization, a polymerizable monomer (B) that is active in cationic polymerization but is substantially inactive in radical polymerization, and an initiator system (C) that polymerizes at least one of the polymerizable monomer (A) and the polymerizable monomer (B) through irradiation with light. The polymerizable monomer (A) and the polymerizable monomer (B) each have, in its structure, a moiety selected from the group consisting of aromatic rings, halogen atoms other than a fluorine atom, and sulfur atoms not derived from a cyclic sulfide or a mercapto group. A hologram recording medium includes a recording layer composed of the hologram recording material.

Abstract: A Head Up Display can be utilized to find light from an energy source. The Head Up Display includes a first waveguide having a first input coupler and a first output coupler. The Head Up Display can also include a second waveguide having a second input coupler and a second output coupler. The first waveguide has a first major surface and the second waveguide has a second major surface, which are disposed approximately parallel to each other. The first waveguide and the second waveguide are positioned as a combiner and allowing viewing an outside feed and information from an image source. The first input coupler diffracts light in the first field of view into the first waveguide and light in a second field of view reaches the second input coupler and is diffracted into the second waveguide.

Abstract: The invention combines several techniques applying high-resolution photosensitive emulsions for the long-term, archival storage of data, images and text. Data is stored as vertical interference patterns of multiple frequencies in a photographic emulsion. Read-out of the stored data uses a precision mechanism to locate and decode stored data.

Abstract: The invention relates to a method for producing a holographic film, wherein a photopolymer formulation comprising matrix polymers, writing monomers, photoinitiator system, and optionally auxiliary materials and additives is provided, the photopolymer formulation is applied as a film to the surface of a substrate, and the film is dried, wherein a photopolymer formulation having a plateau module G0 of =0.03 MPa is used. The invention further relates to a holographic medium that can be obtained by means of the method according to the invention.

Abstract: The invention relates to a photopolymer formulation comprising matrix polymers, writing monomers, and photo initiators, comprising a combination of at least two different writing monomers. The invention further relates to the use of the photopolymer formulation for producing optical elements, in particular for producing holographic elements and images, to a method for producing the photopolymer formulation and to a method for illuminating holographic media made of the photopolymer formulation.

Abstract: The invention relates to a photopolymer formulation comprising matrix polymers, writing monomers and photo initiators, to a method for producing said photopolymer formulation, a photopolymer formulation obtained according to said method, a sheeting, a film, a layer, a layer structure or a moulded body made from said photopolymer formulation and to the use of said photopolymer formulation for producing optical elements, in particular for producing holographic elements and images.

Abstract: A package that has at least one hologram on its exterior surface is formed from a paper, paperboard or thermoplastic substrate material that has an inner surface and an outer surface. The outer surface has a radiation curable particulate metal containing coating. This coating is cured and zero to one or more ink containing coatings are applied to the radiation curable particulate metal containing coating in areas that are not to have a hologram. Each of these ink containing coatings are cured, and a substantially transparent radiation curable coating is applied to the areas deficient in the zero to one or more ink coatings. This substantially transparent radiation curable coating is contacted with a substantially transparent holographic shim in an area not having thereon ink containing coatings while curing radiation is applied to the substantially transparent radiation curable coating and the substantially transparent shim.

Abstract: This invention provides a volume hologram photosensitive composition, which can realize a hologram having an excellent brightness and, at the same time, having excellent heat resistance and mechanical strength, and a photosensitive medium for volume hologram recording using the volume hologram photosensitive composition. The volume hologram photosensitive composition comprises at least a photopolymerizable monomer, a photopolymerization initiator, a sensitizing dye for sensitizing the initiator, and a binder resin. The binder resin comprises a heat curing resin, and optionally a thermoplastic resin, and the thermoplastic resin is contained in an amount of 0 to 25% by weight based on the total solid content of the photosensitive composition.

Abstract: The present invention relates to a polyurethane composition comprising A) a polyisocyanate component comprising an exclusively diol-based NCO-terminated polyurethane prepolymer, wherein the NCO groups are bonded in a primary manner, B) an isocyanate-reactive polymer, C) a compound having groups which react by polymerizing with an ethylenically unsaturated compound under the action of actinic radiation (radiation-curing groups) wherein the compound is free of NCO groups, D) a free-radical stabilizer, E) a photoinitiator, F) optionally a catalyst, G) optionally assistants and additives.

Abstract: This invention relates to a holographic medium comprising a protective layer and a photopolymer film which is bonded to the protective layer and contains polyurethane matrix polymers, acrylate writing monomers and photoinitiators, wherein the protective layer is impermeable to the constituents of the photopolymer film, is optically clear and is transparent to electromagnetic radiation having a wavelength in the range of from 350 to 800 nm. The invention further provides the use of a holographic medium according to the invention in the production of holograms, and a process for the production of a holographic medium according to the invention.

Abstract: A method for storing data including: providing a first substrate having a plurality of micro-holograms therein, the micro-holograms being indicative of the data; providing a second hologram-supporting substrate; illuminating the plurality of micro-holograms in the first substrate through the second substrate, thereby producing a holographic pattern in the second substrate indicative of reflections of the plurality of micro-holograms in the first substrate; providing a third hologram-supporting substrate; and, illuminating the holographic pattern in the second substrate through the third substrate, thereby substantially replicating the plurality of micro-holograms in the first substrate in the third substrate.

Abstract: A component includes a micro-hologram layer, where the micro-hologram layer includes layers inert to light interleaved with layers of functional film. The functional film layers are made of a material that undergoes a change in its refractive index when illuminated by a light beam, yet undergoes no change in its refractive index when illuminated by a different light beam. The components may further include interleaved spacer films with multiple micro-hologram layers and other elements (e.g., servo layer, coatings, and the like) so as to comprise a data storage device. Methods of manufacturing the component and device are also disclosed.

Abstract: A main object of the present invention is to provide a method of producing a volume hologram laminate which can regenerate a hologram image in an arbitrary wavelength by a simple process. To attain the object, the present invention provides a method of producing a volume hologram laminate using a volume hologram forming substrate which comprises: a substrate, a volume hologram layer formed on the substrate and containing a photopolymerizable material, a resin layer, formed on the substrate so as to contact to the volume hologram layer, containing a resin and a polymerizable compound, characterized in that the producing method comprises processes of: a hologram recording process to record a volume hologram to the volume hologram layer, a substance transit process of transiting the polymerizable compound to the volume hologram layer, and an after-treatment process of polymerizing the polymerizable compound.

Abstract: A holographic film for recording multicolor volume holograms, especially full color volume reflection holograms, and/or manufacturing techniques for such film, and/or corresponding methods of recording multicolor and full-color volume, in particular volume reflection holograms. In one case, a holographic film for recording a multicolor volume hologram is set forth that includes: a carrier; a first photosensitive recording layer sensitive to one or both of red and green laser light; and a second photosensitive recording layer sensitive to blue laser light.

Abstract: This invention provides, for example, a highly stable and reliable volume hologram optical recording medium which can suppress an intensity variation, for example, in diffraction efficiency after signal recording and can stably develop a high S/N ratio. The volume hologram optical recording medium includes a recording layer containing at least one compound selected from compounds (A1) having a terpenoid structure, compounds (A2) represented by a formula (I), and cyclic or noncyclic compounds (A3) having at least two double bonds two of these double bonds are located at 1,4-position relatively, wherein R1 and R2 each independently represent an organic group having 1 to 20 carbon atoms, and R1 and R2 may combine to form a cyclic structure.

Abstract: A hologram recording film manufacturing method includes the steps of obtaining a laminated structure by alternately laminating M (where M?2) photosensitive material precursor layers including a photosensitive material and at least one (M?1) resin layer on one another, obtaining M photosensitive material layers, where at least two interference fringes with a desired pitch and a desired slant angle are formed on each of the M photosensitive material layers, from the M photosensitive material precursor layers by irradiating the laminated structure with a reference laser light beam and an object laser light beam, and making the slant angles of the M photosensitive material layers different from each other while retaining the pitch value, which is defined on a face of the photosensitive material layer, by irradiating the laminated structure with an energy ray from the laminated structure's one face side, and heating the laminated structure.

Abstract: The invention relates to novel specially substituted urethane acrylates based on tris(p-isocyanatophenyl)thiophosphate having a high refractive index and reduced double bond density, and to a method for the production and use thereof.

Abstract: A volume hologram layer (2) is formed on a substrate (1), and a cholesteric liquid crystal layer (3) is then formed on the hologram layer (2). After the substrate (1) is peeled off the volume hologram layer (2), an adhesive layer (4) is formed on the surface of the volume hologram layer (2) with the substrate (1) peeled off, and another substrate (5) is then formed on the adhesive layer (4). Finally, a label form of cholesteric liquid crystal medium having a volume hologram is shaped out of the resulting multilayer structure; it is thus possible to fabricate cholesteric liquid crystal media having a volume hologram with efficiency yet without recourse to any complicated steps such as an alignment step.

Abstract: A method for storing holographic data, said method comprising: step (A) providing an optically transparent substrate comprising a polymer composition and a light absorbing chromophore, said polymer composition comprising a continuous phase and a dispersed phase, said dispersed phase being less than about 200 nm in size; and step (B) irradiating a volume element of the optically transparent substrate with a holographic interference pattern, wherein the pattern has a first wavelength and an intensity both sufficient to cause a phase change in at least a portion of the dispersed phase within the volume element of the substrate to produce within the irradiated volume element refractive index variations corresponding to the holographic interference pattern, thereby producing an optically readable datum corresponding to the volume element.

Abstract: A substrate includes a diffracting structure providing a hologram (20, 6). The diffracting structure encodes a holographic image so that thatholographic image is produced in response to reference light being incident on a major surface of the substrate at an angle of incidence with respect to the said major surface of the substrate, wherein the angle of incidence is no more than 20°.

Abstract: Described are methods and apparatuses for manufacturing ultralong fiber Bragg gratings with arbitrary reflection wavelength. The method may include: generating two holographic beams entering a fiber with a certain intersection angle there-between from one side of the fiber and forming holographic interference fringes in the fiber, driving the two holographic beams to scan along the fiber by a motorized translation stage controlled by a computer; and adjusting the intersection angle between the two beams by motorized rotation stages or motorized mirror mounts controlled by the computer. The present disclosure can be applied in manufacturing ultralong fiber Bragg gratings with arbitrary reflection wavelength, such as narrow-reflection-band gratings, chirped gratings, and apodized gratings, etc.

Abstract: An optical data storage medium is provided. The optical data storage medium includes a polymer matrix; a reactant capable of undergoing a change upon triplet excitation, thereby causing a refractive index change; and a non-linear sensitizer capable of absorbing actinic radiation to cause upper triplet energy transfer to said reactant. The refractive index change capacity of the medium is at least about 0.005. The non-linear sensitizer comprises a triarylmethane dye.

Abstract: Encoding of quantum algorithm and devices therefrom are provided. The encoding includes receiving a unitary matrix operator representing the quantum algorithm, each row of the unitary matrix operator defining a superposition of basis state vectors for transforming input states to output states. The encoding also includes recording rows of the unitary matrix operator by applying, to a volume holographic element, a combination of an ith one of n reference waves and a superposition of n signal waves defined by the superposition defined in an ith row of the unitary matrix operator. The n signal waves are a first set of n plane waves lying on a first conical surface having a first half angle and the n reference waves are a second set of n plane waves lying on a second conical surface, concentric with the first conical surface, with a second half angle different that the first half angle.

Abstract: The invention relates to a method for producing holographic films, in which a photopolymer formulation is provided which comprises as constituents matrix polymers, writing monomers, a photoinitiatior system, optionally a non-photopolymerizable component and optionally catalysts, radical stabilizers, solvents, additives and other auxiliaries and/or additives. The photopolymer formulation is applied in a planar manner and in the form of a film on a support film and the photopolymer formulation is dried on the support film at a temperature 60<T<120 DEG C, wherein only compounds are selected as components for the photopolymer formulation, the TGA 95 values of which are >100 DEG C and are above the temperature T by at least 30 DEG C, and a photopolymer formulation having a plateau module of =0.030 MPa is used.

Abstract: The invention relates to a method for producing holographic media, wherein a photopolymer formulation comprising matrix polymers, writing monomers, a photoinitiator system, and optionally auxiliary materials and additives as components is provided, the photopolymer formulation is applied as a coating on the surface of a carrier film and the photopolymer formulation is dried on the carrier film at a temperature XX<T>YY DEG C, wherein only those compounds having TGA 95 values >100 DEG C. and at least 30 DEG C. above the temperature T are selected as components for the photopolymer formulation. The invention further relates to a holographic medium that can be obtained by means of the method according to the invention.

Abstract: A novel polymerizable high-refractive index compound which is useful as an optical material, and a holographic recording medium using the same, which has high diffraction efficiency, high light transmittance and small rate of shrinkage, are provided. A composition for forming a holographic recording layer containing a reactive compound represented by the following formula 1, a holograph recording material, and a holographic recording medium provided with a recording layer containing the same, are disclosed.

Abstract: Systems and methods for creating an autostereoscopic display include a holographic optical element (HOE) recorded using coherent light divided into diverging reference and object beams that illuminate the HOE from opposite sides. The object beam passes through first and second diffusers with one diffuser being a directional diffuser to more uniformly illuminate the HOE. Optic elements may be used to more closely match beam diameters and/or profiles of the recording wavelengths. Baffles may be positioned on opposite sides of the HOE with openings aligned proximate the reference beam and object beam paths, respectively, to reduce stray reflections and provide ambient air flow attenuation or damping. One or more edges of the HOE are masked to reduce or prevent stray light from entering and reflecting within the HOE during recording.

Abstract: Method of Fast Fourier Transform (FFT) Analysis for collecting waveforms and other vibrational intelligence and modulating or embedding same into one or more coherent reference beams of an n-dimensional holographic recording device for producing one or more holograms of objects, including singularity points in space. The result provides wholesale differentiation of waveforms distinguishable from others based on their spectral characteristics. When said holograms are presented with reference beams of vibrational waveforms having similar characteristics to those which were present during recording of the original objects, phantoms of the original objects or subjects will reconstruct themselves in space with an energy glow of intensity that varies thusly with the degree of similarity between the waveform modulations of the reconstructing wavefronts and those of that same which were used to originally record said objects. Said n-dimensional description space can be sampled of the said glowing phantoms.

Abstract: Articles for recording a holographic image are described. The articles include a holographic recording medium having a plurality of surfaces, having a transparent polymeric binder and a photochemically active dye, the holographic recording medium having a holographic image recorded therein formed by exposed areas of the photochemically active dye and unexposed areas of the photochemically active dye; and a first light-blocking layer or material over a first surface of the holographic recording medium from which surface the holographic image is viewed, the light blocking layer or material absorbing light in the wavelength range to which the photochemically active dye is sensitive and allowing transmission of light in a different wavelength range for viewing the holographic image.

Abstract: The layered generation of at least one volume grating in a recording medium by way of exposure, the recording medium having at least one photosensitive layer which is sensitised for a presettable wavelength oft the exposure light. Each volume grating is generated in the recording medium by at least two wave fronts of coherent light capable of generating interference, the wave fronts being superposed in the recording medium at a presettable depth, at a presettable angle and with a presettable interference contrast. The depth and the thickness of the refractive index modulation and/or transparency modulation of a volume grating in the recording medium is controlled by depth-specific control of the spatial and/or temporal degree of coherence of the interfering wave fronts in the direction of light propagation.