Method for the replication of a polychromatic hologram, with alignment of a master stack

Abstract

The invention relates to a method for the replication of a polychromatic hologram. The method involves providing a master assembly, comprising a first master hologram and a second master hologram which are arranged in a layer structure. The method also involves providing a replication assembly and aligning the first master hologram in relation to the replication assembly by translation and / or by rotation of the master assembly. The first master hologram is exposed by means of electromagnetic radiation of a first wavelength range in order to obtain a first replicated hologram in the replication assembly. In addition, the method involves aligning the second master hologram in relation to the replication assembly by translation and / or by rotation of the master assembly. The second master hologram is exposed by means of electromagnetic radiation of a second wavelength range in order to obtain a second replicated hologram in the replication assembly. The invention also relates to a replication assembly that can be produced by means of the method according to the invention. In addition, the invention relates to a master element and a device for carrying out the method according to the invention.

Description

[0001] “METHOD FOR REPLICATION OF A POLYCHROMATIC HOLOGRAM UNDER MASTER STACK ALIGNMENT”

[0002] DESCRIPTION

[0003] The invention relates to a method for replicating a polychromatic hologram. The method comprises providing a master composite comprising a first master hologram and a second master hologram arranged in a layered structure and fixed in their relative position to one another, wherein the first master hologram is designed for a first wavelength range and the second master hologram is designed for a second wavelength range. Furthermore, the method comprises providing a replication composite and aligning the first master hologram with respect to the replication composite by translating the master composite in a longitudinal and / or transverse direction and / or by rotating the master composite. The first master hologram is exposed using electromagnetic radiation of the first wavelength range in order to obtain a first replicated hologram in the replication composite.The method further comprises aligning the second master hologram with respect to the replication composite by translating the master composite in a longitudinal and / or transverse direction and / or by rotating the master composite. The second master hologram is exposed to electromagnetic radiation of the second wavelength range to obtain a second replicated hologram in the replication composite.

[0004] The invention also relates to a replication composite comprising at least a first and a second replicated hologram, wherein the replication composite can be produced using the method according to the invention. Furthermore, the invention relates to a master element comprising a master composite and a base substrate for carrying out the method according to the invention. The master composite comprises a first and a second master hologram, which are mounted on the base substrate, wherein the master element comprises an alignment module configured for translation and / or rotation of the master composite relative to the base substrate.

[0005] The invention further relates to a device for replicating a polychromatic hologram, wherein the device has an exposure module. The exposure module comprises a master composite comprising a first master hologram and a second master hologram arranged in a layered structure and fixed in their relative position to one another, wherein the first master hologram is designed for a first wavelength range and the second master hologram is designed for a second wavelength range; one or more exposure sources configured to direct electromagnetic radiation of the first wavelength range and the second wavelength range onto the master composite in order to replicate the first master hologram and the second master hologram into a replication composite;and an alignment module configured to translate the master composite in a longitudinal and / or transverse direction and / or to rotate the master composite to individually align the first master hologram and the second master hologram with respect to the replication composite prior to exposure by the one or more exposure sources;

[0006] Background and state of the art

[0007] The invention relates to the field of hologram replication.

[0008] Holograms are created by the interference of a reference beam with light reflected or diffracted from the surface of an object (object rays). Traditionally, three-dimensional objects have been used to create unique, customized holograms. Commercially available holograms, however, are often mass-produced using duplication processes. Such duplication processes typically use a master hologram containing a diffraction pattern to be copied. The diffraction pattern can be configured to diffract radiation of a single wavelength (monochromatic) or multiple wavelengths (polychromatic). In the case of a polychromatic diffraction pattern, a master hologram is often created stepwise using lasers of different wavelengths.For this purpose, the diffraction pattern can be divided into color channels, which are recorded simultaneously in a single layer or each represent a separate layer of a multilayer stack. It is also possible for the color channels to form separate master holograms, which are not arranged as a stack but rather next to each other or at different workstations of a duplication process. The master holograms can be in the form of a thin film.

[0009] The master holograms used are often stored in or on a substrate body that bears the master hologram. The substrate body is preferably transparent and can have various shapes, such as a cuboid, a plate, or a cylinder. The combination of the master hologram (or master holograms) with the substrate body forms a master composite.

[0010] The master composite is exposed to a coherent light source to replicate the image from the master hologram into a photosensitive material, wherein the photosensitive material is provided, for example, in layered form, in particular as a composite with one or more carrier films. The photosensitive material can be sensitive to radiation within a specific wavelength range, for example, the wavelength range of a specific color (e.g., red, green, or blue). Photosensitive materials are also known that are sensitive to the entire visible spectrum. For mass production, the photosensitive composite can be provided in the form of a flowing web comprising a photosensitive material and one or more carrier or protective layers.For this purpose, the light-sensitive web is preferably transported through various workstations to produce the HOEs (Holographic Optical Elements). During exposure, the composite web is brought into optical contact with a surface of the master composite. "Optical contact" should preferably allow a ray of light to pass between process components without experiencing significant reflections or even total internal reflection. Direct, integral contact between the process components is possible but not necessary. Preferably, neither reflection (especially total internal reflection) nor scattering occurs at the interface between the surfaces of adjacent process components.

[0011] To create a reflection hologram, the coherent light can traverse the composite path before reaching the master hologram, which reflects it back into the composite path. The object and reference beams interfere with each other in the light-sensitive material, forming the replicated hologram. The replication process is sensitive to changes in exposure angle, intensity, wavelength, etc., which must be adjusted according to the optical function of the master hologram. Typically, the exposure for each master hologram is performed according to a set of preprogrammed parameters.

[0012] HOEs (holographic optical elements) typically refer to optical components in which holographic properties are used to achieve a specific light beam path, such as transmission, reflection, diffraction, scattering, and / or deflection, etc. This allows desired optical functionalities to be implemented compactly in any substrate. The holographic properties preferably exploit the wave nature of light, particularly coherence and interference effects. Both the intensity and phase of the light are taken into account.

[0013] For example, HOEs can be configured to perform the optical function of a classic optical component such as a lens or mirror. However, due to their thin construction, they can be much more compact than conventional optical components. They can also be designed to avoid the well-known optical errors of conventional optical components, such as spherical aberration and chromatic aberration. For example, HOEs can convert a plane wavefront into a spherical one and vice versa. They require very little space and can be easily integrated into a surface such as a window, eyeglasses, a card, or other product surfaces.

[0014] For some applications, it may be desirable for the HOEs to be exposed in multiple layers or with multiple superimposed patterns or wavelengths (e.g., color channels). In some cases, a hologram can contain a polychromatic diffraction pattern in the form of Bragg gratings at different frequencies in a single layer of material. Such a hologram can be recorded simultaneously at multiple wavelengths, for example, as an RGB or CMY hologram. The polychromatic hologram can be copied from a polychromatic RGB or CMY master hologram, which can be a single layer or a stack of holograms with different wavelengths. This would require the use of a light-sensitive material sensitive to all color channels used.However, such materials are often not equally sensitive to all wavelengths and may not offer the highest image resolution across the entire wavelength range.

[0015] A polychromatic holographic element can also comprise multiple holograms arranged one on top of the other in a stack. For example, a holographic element can comprise a plurality of superimposed monochromatic holograms that were recorded separately and combined into a stack. This allows the use of light-sensitive materials specifically designed for a particular wavelength or color channel, improving the quality of the hologram.

[0016] Such holographic elements are used in many areas, such as in transparent displays (e.g. in shop windows, refrigerated cabinets, vehicle windows), for lighting applications such as information or warning signals in glass surfaces, and light-sensitive detection systems, for example for interior surveillance (eye tracking in vehicles or presence status tracking of people indoors).

[0017] For example, DE102021116146A1 discloses a polychromatic hologram comprising six layers in a single stack. The layers are configured for different wavelengths. Three upper layers can form a first holographic element configured to convert an upward spherical wavefront into a downward plane wavefront by reflecting light from the blue, green, and red parts of the electromagnetic spectrum at predetermined angles. Three lower layers can form a second holographic element configured to reflect the downward plane wavefront back up to create a plane wavefront at a predetermined angle. In this way, the layers of the two holographic elements can function like a combination of a concave and a plane mirror.Advantageously, by arranging two holographic elements arranged directly one behind the other and at least partially reflective, a high refractive power can be achieved, while at the same time providing high image quality and a compact structure.

[0018] However, precise positioning of the holographic layers relative to each other is necessary to avoid unwanted filter effects and ensure the optical function.

[0019] With multilayer holograms, it is crucial for the quality of the produced HOE that the superimposed holograms of a stack are correctly positioned relative to one another. Depending on the complexity of the HOE, the number of layers in such a stack can increase, which presents a significant challenge during the alignment steps of its production. In an exemplary manufacturing process, a single multilayer, photosensitive composite web passes through various stations of a replication process, with replication for different master composites configured for a specific color channel taking place at each station. The composite web can comprise various wavelength-selecting photosensitive layers, into which a master hologram of a color channel is replicated at each station.To achieve perfect positioning of the holograms replicated in the various layers of the composite web, the flowing composite web must be braked at a precise position at each workstation. Due to the deformable nature of the composite webs, this is extremely difficult to achieve with a high degree of repeatability.

[0020] Alternatively, a multilayer composite web can also be exposed at a single workstation, where a master composite is provided. Exposure can be performed sequentially for each required wavelength. The flowing multilayer composite web only needs to be slowed down once during exposure, reducing the risk of errors due to inaccurate positioning and / or deformation. However, errors in the relative positioning of the layers of the master hologram are reproduced in the composite web. For example, the layers for a particular color channel in a master composite may exhibit a twist or offset due to the integration process, which adversely affects the optical function, particularly of complex HOEs.

[0021] Another alternative is to produce each layer of a HOE master composite in a separate composite web with a single layer of photosensitive material, and then combine the individual layers of the respective composite web into a stack. Due to technical limitations, the placement, lamination, and bonding of the layers is carried out within tolerances, which also accumulate when the steps are repeated to create a stack with two, three, four, or more layers.

[0022] JPH11272153A discloses the use of positioning marks to align different layers of a hologram stack. According to this document, a multilayer hologram is produced from a plurality of layers of light-sensitive material. Holograms with different properties are recorded in each layer of light-sensitive material, and positioning marks are holographically recorded in each of the multiple hologram layers. The positioning marks are then used to align the layers on a substrate and laminate them together.

[0023] This is not only time-consuming, but the process of laminating the layers itself can also lead to alignment errors, for example, due to varying degrees of deformation of the layers.

[0024] There is therefore a need for alternative methods with which polychromatic holograms can be produced with a high degree of positioning accuracy. DE 10 2010 014 305 A1 discloses a method for producing copies of a volume reflection hologram. For this purpose, a holographic film is laminated over a drum with at least two (polygon) master surfaces, onto which it is brought into contact with at least one master hologram and exposed. One or more master surfaces can be laser-exposed simultaneously. The drum is rotated uniformly or stepwise during exposure. This should enable an increase in productivity even in the production of large-area reflection holograms. A use of the method for the production of polychromatic holograms is not disclosed.

[0025] Object of the invention

[0026] The object of the invention is to provide a method that enables the replication of a polychromatic hologram without the disadvantages of the prior art. In particular, it was an object of the invention to provide a method for replicating a polychromatic hologram in which multiple color channels or patterns with different wavelengths can be positioned relative to one another in a holographic element using simple means, repeatably, and with high precision. Furthermore, it was an object of the invention to provide a replication method suitable for the continuous mass production of a polychromatic hologram of any degree of complexity, in particular for the production of a multilayer HOE.

[0027] Summary of the invention

[0028] The object is achieved by the features of the independent claims. Advantageous embodiments of the invention are described in the dependent claims.

[0029] In a first aspect, the invention relates to a method for replicating a polychromatic hologram. The method comprises the following steps: a) providing a master composite comprising a first master hologram and a second master hologram arranged in a layered structure and fixed in their relative position to one another, wherein the first master hologram is designed for a first wavelength range and the second master hologram is designed for a second wavelength range, b) providing a replication composite, c) aligning the first master hologram with respect to the replication composite by translating the master composite in a longitudinal and / or transverse direction and / or by rotating the master composite, d) exposing the first master hologram to electromagnetic radiation of the first wavelength range to obtain a first replicated hologram in the replication composite,e) aligning the second master hologram with respect to the replication composite by translating the master composite in a longitudinal and / or transverse direction and / or by rotating the master composite, f) exposing the second master hologram to electromagnetic radiation of the second wavelength range to obtain a second replicated hologram in the replication composite.

[0030] The replication composite can preferably be provided in roll form and continuously pass through the station(s) of a replication process, making the process particularly suitable for mass production. A particularly advantageous feature is that the replication composite itself does not need to be moved between replications of the first and second master holograms. By providing the first and second master holograms in the layer structure of a master composite, the exposure of a replication composite can advantageously be performed at a single workstation for the corresponding wavelengths. Transport-related deformations and positioning errors of the replication composite can be avoided.

[0031] The possibility of separately aligning the first and second master holograms with respect to the replication composite also advantageously makes it particularly easy to compensate for any positional variations between the holograms. Aligning the second master hologram with respect to the replication composite can, in particular, mean aligning the second master hologram with respect to a first replicated hologram present in the replication composite. Thus, the second master hologram can be positioned such that it exactly matches the position of the already exposed first hologram on the replication composite. This advantageously makes it possible to compensate for tolerances that may arise when integrating the first and second master holograms into a master composite. Likewise, differences in the positioning of the master holograms with respect to the replication composite can be avoided.

[0032] Furthermore, it is advantageous that the alignment of the second master hologram can be performed in the same way each time the replication process is repeated. This allows any submillimeter deviations that may occur during transport of the replication array and / or integration of the master holograms into a master array to be compensated for in a repeatable and highly accurate manner by appropriate adjustment of the master array.

[0033] By replicating the second master hologram into the replication composite, a polychromatic hologram with precisely aligned layers or channels can be created. Such a hologram is of particularly high quality, especially since undesirable filter effects between the layers can be avoided. Advantageously, any misalignments of the master holograms in the master composite are not replicated into the polychromatic hologram. Instead, the possibility of independently aligning the first and second master holograms allows for an optimized polychromatic hologram to be obtained, in which the replicated holograms are reliably aligned with each other with high precision.

[0034] Because the first and second holograms are present in a master composite, they are fixed relative to each other. The alignment of the master holograms can be performed in the same way for each replication of the polychromatic hologram. The first and second holograms cannot be freely translated or rotated relative to each other, preventing new positioning errors from occurring during the replication process that were not present during the master composite's production. Instead, the same sequence of alignment steps can be reliably repeated. The replication process can therefore be easily performed with a high degree of positioning accuracy.

[0035] By providing a replication composite, a light-sensitive material can be brought into optical contact with the master composite to create a volume hologram. Advantageously, multiple color channels or wavelength channels can be exposed in a single or different light-sensitive layers of the replication composite. The sequential exposure of the first and second master holograms can preferably also be performed in a single workstation, thereby improving the precision of the replication process. The replication composite preferably comprises different light-sensitive layers sensitive to specific wavelength ranges of the electromagnetic spectrum.

[0036] Replication preferably involves a step-by-step buildup of the polychromatic hologram within the replication system. For this purpose, the first and second master holograms are replicated into a replication stack with corresponding light-sensitive layers. The ability to align the master holograms before each replication step, as explained above, allows for high precision stack construction. This avoids the need for subsequent lamination of exposed layers to build a replication stack, as well as the associated alignment errors.

[0037] The replication composite can be supplied as a roll and provided with carrier and / or protective layers to protect the replicated hologram. Process components such as the master composite can also be protected from unwanted residues, such as photosensitive resins.

[0038] Aligning the first master hologram with respect to the replication composite ensures reliable repeatability of the process. For example, a previous replication can be completed by aligning the second (or nth) master hologram (and thus the entire master hologram) with the replication composite. The first master hologram is then returned to a standard position above the replication composite by appropriate alignment. In this way, the diffraction pattern of the first master hologram can always be replicated in a desired orientation and position on the replication composite.

[0039] Since the master composite preferably comprises a rigid master substrate on or in which the master holograms are mounted, it is preferably stiffer than a flowing replication composite in foil form. Thus, the positioning of the master holograms present on or in a master substrate can be achieved with a higher degree of repeatability than would be the case for replicated holograms in a replication composite in foil form.

[0040] In preferred embodiments, alignment of the master composite with respect to the replication composite can be ensured by providing a master element which, in addition to a master composite, comprises a separate base substrate, wherein the master composite and the base substrate are arranged so as to be movable relative to one another. During replication, a replication composite preferably contacts the base substrate of the master element, so that alignment of the separate master composite, preferably in the form of a master substrate comprising the master holograms, can take place without any movement occurring between the replication composite and the base substrate. The transfer of stresses or deformations into the replication composite due to alignment of the master holograms can advantageously be completely avoided, since no relative movement is necessary at the interface between the replication composite and the master element.

[0041] The advantageous contact between the base substrate and the replication composite can further stabilize the latter and ensure that the replication composite remains stationary during the exposure of the first and second master holograms. The process thus exhibits a particularly low susceptibility to the introduction of alignment errors in the replication composite, as it does not need to be aligned between exposure steps.

[0042] Furthermore, since the same master stack can be used for multiple iterations of a replication process, the master stack can be adjusted in the same way and to the same extent each time. This can be done more precisely than subsequently aligning and laminating several separately replicated holograms on top of each other to form a stack. In the latter case, each stack would have to be individually constructed outside the replication facility according to the replication process, for example, using positioning markers, which is very time-consuming. Instead, the required position adjustment of the first and second master holograms, once determined, can be performed in the same way for each copied polychromatic hologram, so that a correctly aligned polychromatic hologram is constructed while the replication process is being carried out in the replication facility.Advantageously, the alignment of the first master hologram and the second master hologram can be preprogrammed. A program for aligning the master holograms can be determined by measuring the position errors between the master holograms in the master array. This can be done in various ways, as explained below.

[0043] By exposing the first hologram in the replication array to a first wavelength, a first channel of a polychromatic hologram can be exposed at a desired position in the replication array. Due to its precise positioning and the lack of need to move the replication array to additional exposure stations to expose additional channels, additional channels can be reached by replication with additional wavelengths at exactly the desired position, thus compensating for alignment errors in the master array. The quality of the replicated polychromatic holograms can advantageously exceed the quality of the master array, since any positioning errors in the master holograms are compensated for during the replication process, as explained above.Compared to known state-of-the-art methods, significantly higher quality can be achieved with simple means in terms of positioning several color channels or several layers relative to each other.

[0044] For the purposes of the invention, a "method for replicating a hologram" or a "replication method" is preferably a method in which the diffraction pattern of an object, in particular a master hologram, is recorded in a light-sensitive material. This comprises at least one exposure of the respective master hologram, but may also include further preferred steps such as fixing, cutting, or trimming.

[0045] A "master hologram" within the meaning of the invention is preferably a holographic-optical element comprising at least one hologram to be replicated. The master hologram is designed for an optical function (e.g., diffraction, reflection, transmission, and / or refraction) for one or a plurality of wavelengths within a wavelength range. The master hologram can, for example, be a diffractive optical element (DOE). Diffractive optical elements (DOEs) utilize a surface relief profile with a microstructure for their optical function. Alternatively, the microstructure can also be present in the volume of the element in the form of a local difference in the refractive index. Such a master hologram is considered a so-called "volume hologram." The light transmitted by a DOE can be converted into almost any desired distribution through diffraction and subsequent propagation.This can be an image, a logo, text, a light refraction pattern, or something similar. The master hologram can also be a technical hologram, such as a Bragg mirror, a diffuser, or a hologram acting as a lens.

[0046] A "design of a master hologram for a wavelength range" preferably means that the diffraction pattern is configured for the diffraction of electromagnetic radiation with a wavelength in the wavelength range. In other words, the first master hologram is preferably wavelength-selective for a first wavelength range, while the second master hologram is wavelength-selective for a second wavelength range. Wavelength selectivity means, in particular, that the diffraction conditions provided by the first master hologram are preferably only for light of a first wavelength range. Light of other wavelengths is preferably not diffracted. The same applies to a wavelength selectivity of the second master hologram, according to which diffraction should occur selectively for light of a wavelength in the second wavelength range.

[0047] According to the invention, the first and second wavelength ranges are not identical. In preferred embodiments, the first and second wavelength ranges may represent disjoint ranges and have essentially no intersections. This may be the case, for example, if the first and second wavelength ranges correspond to different colors. For example, a first wavelength range may correspond to one color (e.g., blue, red, or green), while the second wavelength range corresponds to a different color.

[0048] For the purposes of the invention, a “wavelength range” may essentially comprise light of one wavelength, for example the wavelength emitted by a monochromatic laser.

[0049] In the case of a reflection hologram, the hologram can be configured such that electromagnetic rays in the wavelength range are diffracted, so that a first-order diffracted beam travels back into a replication compound. The first-order diffracted beam can interfere with the reference beam in the replication compound. Radiation with wavelengths outside the wavelength range can preferably be transmitted without diffraction. In the case of a transmission hologram, the hologram can be configured such that electromagnetic rays in the wavelength range are diffracted, so that a diffracted beam interferes with a reference beam in the replication compound. Electromagnetic rays with wavelengths outside the wavelength range can preferably be transmitted undiffracted. The master hologram thus preferably diffractes the radiation of the wavelength for which it is designed.

[0050] A "master composite" within the meaning of the invention is preferably a multilayer composite comprising at least one master hologram. The master composite preferably comprises at least a first master hologram and a second master hologram in a layered structure. The master composite can preferably comprise further layers, such as one or more covers and / or a master substrate, so that the master hologram (or master holograms) are preferably present between the master substrate and the cover. The master holograms are preferably laminated to a surface of the master substrate. The master composite is preferably rigid. The rigidity of the master composite can be ensured by a master substrate. Preferably, all layers of the master composite are firmly connected to one another. The "master composite" can be arranged in a master element, wherein in preferred forms the master element comprises the master composite and a base substrate.

[0051] A "layer structure" of a first and a second (or further) master holograms, within the meaning of the invention, preferably describes an arrangement of the master holograms on top of or above one another. The master holograms arranged one above the other are preferably present on one and the same surface of a master substrate. For example, a first master hologram can be laminated to a surface of a master substrate, while a second master hologram is applied to the first master hologram. In preferred embodiments, further layers are present on a layer structure consisting of two master holograms. A "master element" preferably comprises at least one master hologram and supports the creation of a mechanical and / or optical contact between the respective master hologram and a replication composite without damaging the master hologram.The master element preferably comprises a master substrate on or in which at least one master hologram is present. The master element preferably further comprises a base substrate, wherein the master substrate is movably mounted relative to the base substrate. The base substrate is preferably aligned for contact with the replication composite. The master element preferably further comprises an alignment module for moving the master substrate (and thus also the master hologram) relative to the base substrate.

[0052] The "master substrate" is preferably a three-dimensional unit comprising a master hologram in a shape that facilitates its handling and mobility. The master hologram is, in particular, fixedly positioned within the master substrate such that a movement of the master substrate directly leads to a corresponding movement of the master hologram. The master substrate preferably has a length and width that approximately correspond to that of the master hologram. The master substrate is preferably at least twice, preferably five times, and particularly preferably at least twenty times as high as the master hologram. The master substrate preferably has a regular shape that allows for a mosaic-like or linear arrangement.

[0053] The master substrate is preferably a transparent plate, preferably made of optical glass or plastic. The master holograms can be laminated to a surface of the master substrate to create a master composite. In some preferred embodiments, the master composite can further comprise a transparent top cover for protecting one or both master holograms, which is / are present between the cover and the master substrate. Preferably, the top cover is also transparent. The top cover can be, for example, a transparent film or a glass layer.

[0054] For the purposes of the invention, the term "transparent" or "transparency" preferably refers to a property of a material whereby it is substantially permeable to light. A transparent material within the meaning of the invention is preferably transmissive for at least part of the electromagnetic spectrum, preferably with a wavelength between 200 nm and 25 pm, particularly preferably between 400 nm and 780 nm. A transparent material, for example a transparent master substrate or a transparent cover, is particularly preferably permeable to light of a wavelength range with which the master hologram is exposed. A transparent material can also be colored in such a way that it selects the light radiation of one or more specific wavelengths.

[0055] It is preferred that the surface or cover of the master composite comprises glass, PC, TAC, or PMMA. The surface material can be in the form of a film or plate to protect the master hologram. However, the surface or cover material can also be the material of the master substrate itself and, for example, have a cuboid or cylindrical shape.

[0056] In preferred embodiments, the master element comprises a master composite and a base substrate, wherein the master composite and the base substrate are mounted so as to be movable relative to one another. This solution allows one substrate of the master element to be held stationary while another substrate is rotated or translated. Preferably, the base substrate is held stationary while the master substrate (and thus the master holograms) is moved. In this way, the replication composite can be brought into constant contact with a surface of the master element without frictional forces or deformation occurring between exposure steps due to relative movement at an interface. Direct contact of the replication composite with a movable mechanical part of the master element (the master composite) is avoided, thus also eliminating the risk of mechanical deformation of the replication composite.At the same time, the master assembly can be moved freely relative to the base substrate (and thus also the replication assembly) to compensate for any positioning error in the master assembly. Furthermore, the replication assembly does not need to be kept at a distance from the master element that could lead to a loss of efficiency in the exposure process. Instead, the mechanical contact between the replication assembly and the base substrate can ensure optimal optical contact, thus minimizing optical losses at the interface between the replication assembly and the master element.

[0057] A "base substrate" within the meaning of the invention is preferably a three-dimensional unit designed for mechanical contact with a replication composite. The base substrate is preferably rigid so that one or more layers can be laminated onto it. The base substrate is preferably mounted stationary, with a master composite preferably being mounted movably with respect to the base substrate. The base substrate preferably has analogous optical and mechanical properties to those of the master substrate. The base substrate is in particular transparent, preferably made of optical glass or plastic. The shape and dimensions of the base substrate can be analogous to those of the master composite and preferably exceed them, so that the master composite is still completely covered by the base substrate in all rotational and translational positions.For example, the length and / or width of the base substrate may be at least 110%, preferably at least 120%, more preferably at least 130% of the length and / or width of the master assembly.

[0058] A "replication composite" within the meaning of the invention is preferably a multilayer material comprising at least one photosensitive layer. The photosensitive layer preferably comprises a photosensitive material, such as a silver halide, a dichroic gelatin, a photoresist, a photopolymer, a photochromic material, a photothermoplastic, LiNbCh, Bii2SiO2O, CCD, or combinations thereof. The photosensitive layer can be sensitive to electromagnetic radiation in a broad wavelength range. For example, the photosensitive layer can be sensitive to electromagnetic radiation of both the first wavelength range and the second wavelength range.Alternatively, a first photosensitive layer may be sensitive exclusively to electromagnetic radiation in the first wavelength range, and a second photosensitive layer may be sensitive exclusively to electromagnetic radiation in the second wavelength range. Any number of photosensitive layers may be provided, for example, two, three, or more, with the sensitivities of the layers overlapping or not overlapping in the wavelength ranges as required.

[0059] The replication composite preferably comprises at least one, preferably two, outer carrier films, wherein the carrier films are preferably transparent to electromagnetic radiation of all wavelengths with which the replication composite is to be irradiated. The light-sensitive layers can be in the form of a composite web. In preferred forms, the replication composite can also be in the form of a composite web. The replication composite can comprise a replication substrate, which is preferably in contact with the light-sensitive layers directly or with other intermediate layers.

[0060] For the purposes of the invention, a "replication substrate" is a component which, during exposure, is preferably located between the one or more photosensitive layers and the master composite. The replication substrate preferably provides optical contact between the master composite and the photosensitive layers, wherein the replication substrate preferably also protects the photosensitive layers from mechanical damage. In a preferred embodiment of the invention, the replication substrate is a further film-like layer, such as a protective layer, flexible base, or carrier layer. It can be used in the handling of the replication composite, e.g., to bring it to a master element and integrate it into a final product, wherein the replication substrate can be removed during the integration process.In a further preferred embodiment of the invention, the replication substrate is rigid, wherein a section of a composite web comprising two or more photosensitive layers is laminated to the replication substrate to create a stable replication composite. Such a replication substrate can have similar properties to the master substrate and / or the base substrate and can serve as an alternative to the base substrate. An advantage of this embodiment is that a rigid replication substrate can be transported with the remaining parts of the replication composite to further processing stations of a manufacturing process. This may be preferred in cases where the production of a series of polychromatic holograms, each built on a rigid replication substrate, is desirable for the subsequent processing of the polychromatic hologram.For example, a rigid replication substrate can be used to mechanically precisely position multiple polychromatic holograms on top of each other and encapsulate them between the substrates.

[0061] A “composite web” within the meaning of the invention is preferably a composite material with a length that is at least twice, preferably at least five times, and even more preferably at least twenty times its width. The thickness of the composite web is preferably adjusted to have a certain flexibility so that it can be provided, for example, as a roll. Preferably, the composite web has a thickness of up to 300 μm. The composite web comprises a photosensitive material. Preferably, the composite web encloses the photosensitive material between two transparent carrier films that have a similar refractive index to the photosensitive material. Preferably, the refractive index of the carrier films and the photosensitive material is between 1.4 and 1.6. The photosensitive material can be, for example, a photosensitive photopolymer or a dichroic gelatin.The light-sensitive material can be light-sensitive to the entire visible spectrum or wavelength-selective.

[0062] In the context of the invention, "exposure" is preferably understood to mean the targeted directing of electromagnetic radiation onto a correspondingly sensitive surface, preferably to form a hologram. Various methods for exposing a hologram are known, including transmissive or reflective techniques for producing volume holograms.

[0063] A volume hologram is preferably written into a sensitive layer by the interference of two light beams (a so-called reference beam and an object beam). Preferably, a volume hologram is written into the replication composite. This can preferably be done using a transmission or reflection technique. Interference of object and reference beams within the hologram volume preferably creates a sequence of Bragg planes. A volume hologram therefore preferably has a non-negligible extension in the propagation direction of the light beams, whereby the Bragg condition applies during reconstruction on a volume hologram. For this reason, volume holograms exhibit wavelength and / or angular selectivity. The ability of volume holograms to store multiple images simultaneously enables, among other things, the production of colored holograms.Light sources that emit the three primary colors blue, green, and red can be used to record holograms. These three beams preferably simultaneously illuminate a portion of the replication composite at equal angles. After exposure, three holograms are stored simultaneously in the volume hologram. To reproduce the color hologram, one can take advantage of the fact that each partial hologram can be reconstructed using only the color with which it was recorded. Thus, the three reconstructed color separations overlap to create a color, true-to-original image, provided the color components are correctly weighted.

[0064] Exposure can preferably be carried out by an exposure module which has one or more exposure sources provided for this purpose. The exposure source(s) (also “light sources” within the meaning of the invention) preferably emit electromagnetic radiation in a first and / or second wavelength range for this purpose. The electromagnetic radiation can preferably comprise infrared, visible and / or ultraviolet radiation, with visible radiation being particularly preferred. In the context of the invention, UV radiation preferably means electromagnetic radiation in the range from 200 pm to 400 pm, particularly preferably 300 pm to 400 pm. Visible radiation means in particular electromagnetic radiation in the range from 400 - 780 nm and infrared radiation from 780 nm to 25 pm, preferably in the near infrared range, i.e. preferably from 780 nm to 3000 nm, in particular from 780 nm to 1400 nm.

[0065] Preferably, a coherent light beam is emitted from the light source. Coherence preferably refers to the property of optical waves according to which there is a fixed phase relationship between two wave trains. As a result of the fixed phase relationship between the two wave trains, spatially stable interference patterns can arise. With regard to coherence, a distinction can be made between temporal and spatial coherence. Spatial coherence preferably represents a measure of a fixed phase relationship between wave trains perpendicular to the direction of propagation and is given, for example, for parallel light beams. Temporal coherence preferably represents a fixed phase relationship between wave trains along the direction of propagation and is given in particular for narrowband, preferably monochromatic light beams.

[0066] The coherence length preferably refers to the maximum path length or travel time difference between two light beams from a starting point, so that a (spatially and temporally) stable interference pattern is still created when they superpose. The coherence time preferably refers to the time it takes for the light to travel a coherence length.

[0067] In preferred embodiments, the light source comprises a laser. Particularly preferably, it is a narrowband, preferably monochromatic laser with a preferred wavelength in the visible range (preferably 400 nm to 780 nm). Non-exhaustive examples include solid-state lasers, preferably semiconductor lasers or laser diodes, gas lasers, or dye lasers. Lasers can be selected to emit light of a specific wavelength or wavelength range. This can be achieved by selecting a laser made of a suitable material. Examples include ruby ​​lasers, He-Ne lasers, Ar + -Laser, Kr + -Laser, He-Cd laser and / or Nd 3+YAG lasers can be used. These or other laser types can be combined with an optical parametric oscillator to generate coherent beams of different wavelengths. Lasers with different wavelengths can also be combined, for example, to create an RGB laser.

[0068] Various laser types, particularly solid-state lasers, can be combined with an optical parametric oscillator to generate coherent beams of different wavelengths as a tunable system. The optical parametric oscillator preferably comprises an optical resonator and at least one nonlinear optical crystal. Systems with a plurality of converter crystals can be used, in particular, using three-wave mixing (f_pumpe = f_signal + f_dler). By varying the frequency of f_signal and / or f_dler, laser wavelengths can be generated in a very broad wavelength range. This includes, in particular, the entire visible and infrared ranges of the electromagnetic spectrum.

[0069] Other light sources, preferably coherent light sources, can also be used. Narrowband light sources, preferably monochromatic light sources, such as light-emitting diodes (LEDs), optionally in combination with monochromators, are preferred.

[0070] For replication with different wavelengths, in particular a first and second wavelength range, it is preferred to provide illumination radiation in the respective different wavelength ranges, e.g. in a red wavelength range (preferably 620 nm - 700 nm), a green wavelength range (preferably 500 nm - 560 nm) and / or a blue wavelength range (preferably 420 nm - 475 nm).

[0071] For example, a laser system with three monochromatic lasers or one polychromatic laser with a laser emission in the red, green or blue (RGB) range can be provided for this purpose.

[0072] In the context of the invention, "alignment of a master hologram" preferably means that the master hologram is moved from an actual position to a desired position. Preferably, the movement from the actual position to a desired position comprises a slight correction, in particular to compensate for a positioning error, and is therefore different from a step in which a master composite or master hologram is brought to a workstation. The alignment preferably comprises a translation in a transverse direction, a translation in a longitudinal direction, and / or a rotation in a plane comprising the transverse and longitudinal directions. The transverse and longitudinal directions are preferably orthogonal to one another in a plane comprising the master hologram and / or parallel to the replication composite. Preferably, the alignment movement is large enough to compensate for any errors in the positioning of the master hologram.For example, the translation in the longitudinal and / or transverse directions can be up to 1000 micrometers, preferably up to 100 micrometers, particularly preferably up to 20 micrometers, even more preferably up to 10 micrometers. The rotation is preferably up to 2°, preferably up to 1°, particularly preferably up to 0.5°. Alignment of a master hologram occurs in particular with respect to a replication composite and thus preferably in a plane parallel to the replication composite.

[0073] A "longitudinal direction" within the meaning of the invention is preferably any direction in the plane formed by a surface of the master hologram in question. This is preferably a substantially horizontal plane. The longitudinal direction particularly preferably coincides with a direction in which a replication composite moves to move into or out of an exposure station where exposure takes place.

[0074] A "transverse direction" within the meaning of the invention preferably runs orthogonally to the longitudinal direction in a plane formed by the surface of the master hologram in question. A "rotation" of the master hologram preferably also occurs in this plane.

[0075] For the purposes of the invention, a "polychromatic hologram" is preferably a hologram configured to diffract electromagnetic radiation of different wavelengths, wherein the different wavelengths preferably differ by at least 50 nm, more preferably by at least 100 nm, and even more preferably by at least 200 nm. Preferably, the polychromatic hologram may comprise a plurality of channels, each channel corresponding to a different wavelength and / or wavelength range. Each channel may be the result of replicating a master hologram configured for the respective wavelength or wavelength range. For example, the channels may correspond to different colors, such as red, green, and blue light.For the purposes of the invention, a color preferably means light of a specific wavelength range from the visible spectrum (380 nm to 780 nm) with a bandwidth of less than 50 nm, preferably less than 40 nm, less than 30 nm, or less, with a maximum or peak at a central wavelength characteristic of the color. For blue light, for example, the central wavelength can be approximately 460 nm, while green light can have a central wavelength of approximately 530 nm, or red light a central wavelength of approximately 630 nm.

[0076] It may also be preferred that one or more of the channels correspond to electromagnetic radiation outside the visible spectrum, such as UV radiation or IR radiation. The various channels can be present in a polychromatic hologram in the form of a diffraction pattern configured to diffract electromagnetic radiation of the respective wavelength or wavelength range. The diffraction patterns can be present in a single layer of the photosensitive material or in different layers. This means that while the master composite comprises several master holograms in different layers, these can all be replicated in the same photosensitive layer of the replication composite.However, the replication composite can also comprise several light-sensitive layers, which are preferably arranged one above the other in a layer structure and can preferably reflect the layer structure of the master composite.

[0077] A "light-sensitive material" within the meaning of the invention is a material that reacts to radiation from a region of the electromagnetic spectrum with which the master hologram is exposed. Preferably, the light-sensitive material reacts to light from the visible region of the electromagnetic spectrum. Particularly preferably, the light-sensitive material reacts to the radiation by producing a local change in its refractive index. This can occur, for example, through local polymerization of monomers or shorter polymer chains, as in a photopolymer.

[0078] In a preferred embodiment of the invention, a third master hologram is provided. The third master hologram can be part of the master composite comprising the first and second master holograms. For example, the third master hologram can be present in a layered structure with the first and second master holograms. The position of the third master hologram can be fixed relative to the first and second master holograms.

[0079] In this case, a polychromatic hologram can be produced with a third replicated hologram or a third (color) channel in the replication cluster without having to move the replication cluster to another exposure station.

[0080] In an alternative preferred embodiment of the invention, the third master hologram is provided separately from the master composite of the first and second master holograms. The third master hologram can, for example, be provided in a further master composite, wherein the further master composite preferably comprises a further master substrate such as a glass plate. The further master composite can optionally comprise further master holograms, such as a fourth, fifth and further master holograms. The further master composite can also be provided at the same exposure station as the first master composite, such that it is mounted rotatably and / or displaceably with respect to the first master composite. The further master composite can alternatively also be provided at a downstream exposure station.

[0081] Preferably, the method comprises the following further steps: g) aligning the third master hologram with respect to the replication composite by translating a master composite comprising the third master hologram in a longitudinal and / or transverse direction and / or by rotating a master composite comprising the third master hologram, h) exposing the third master hologram to electromagnetic radiation of a third wavelength range to obtain a third replicated hologram in the replication composite.

[0082] The master composite comprising the third master hologram can be the same master composite that comprises the first and second master holograms. Likewise, as explained above, it can be preferred for the third master hologram to be comprised of a separate, further master composite. By adjusting the position of the third master hologram with respect to the replication composite, its position with respect to the already exposed first and second master holograms can be corrected. A position error of the third master hologram in the first or further master composite or a position error of the first or further master composite in a workstation can thus be compensated. In this way, a polychromatic hologram with three (color) channels can be produced in which the three (color) channels are aligned with one another with extremely high precision.

[0083] If the third master hologram is included in the same master array as the first and second master holograms, its position can be adjusted by translating or rotating the master array. All three master holograms can be replicated at the same workstation using the same three position settings for each of the three master holograms. These settings can be repeated for each replication of the master array, making the process particularly easy to automate.

[0084] However, if the third master hologram is provided in a further master array at a further workstation, the replication array comprising the first and second holograms is preferably first positioned relative to the third master hologram before the third master hologram is aligned. The translational position of the third master hologram in the longitudinal direction may therefore need to be calculated or estimated individually for each replication. However, the alignment parameters for rotation and translation in the transverse direction may remain the same between replications. This is because a flowing array path forming or comprising the replication array typically moves only in the longitudinal direction, not in the transverse direction.

[0085] For some polychromatic HOEs, such as the wavefront manipulator shown in Fig. 11 of DE102021116146A1, it has been found that a larger tolerance for translational offset between the channels in a single axis, particularly the longitudinal axis, can be provided without significantly disrupting the optical function of the HOE. In this way, a polychromatic hologram already exposed with at least two wavelengths can be further built up step by step over several workstations. This offers several advantages, such as the possibility of continuously passing the replication composite through an intermediate processing station between exposures. The intermediate processing station can, for example, comprise a fixing module for fixing exposed holograms in the replication composite and / or a coating module for applying further light-sensitive material layers to the replication composite.The intermediate station can also be used to add or remove films from the replication array, for example, optical adhesive films, protective films, or wavelength filter films. This allows the replication array to be stabilized in separate intermediate stations before exposing additional holograms, reducing the risk of replication errors and eliminating the need to use wavelength-selective photosensitive materials for each channel.

[0086] In a further preferred embodiment of the invention, one of the first, second or third wavelength ranges corresponds to red light, wherein the wavelength range is preferably between 590 - 750 nm, particularly preferably between 620 - 700 nm. Preferably, one of the first, second or third wavelength ranges corresponds to green light, wherein the wavelength range is preferably between 490 - 590 nm, particularly preferably between 500

[0087] - 560 nm. Preferably, one of the first, second or third wavelength ranges corresponds to blue light, wherein the wavelength range is preferably between 380

[0088] - 490 m, particularly preferably between 420 - 475 nm.

[0089] In this way, a polychromatic RGB (red-green-blue) hologram can be created. Such a hologram can diffract light from essentially the entire visible spectrum, producing full-color holographic images with a high degree of sharpness. Such images can achieve very high visual quality due to the precise alignment of the channels. The polychromatic RGB hologram can also specifically redirect light from essentially all regions of the visible spectrum in a compact manner, which is particularly useful for HOEs integrated into car, aircraft, or other vehicle windows.

[0090] In a further preferred embodiment of the invention, the replication composite is provided in step b) of the process according to the invention as a first photosensitive layer. The first photosensitive layer (as well as any associated support or protective layers) is preferably temporarily releasably laminated to a base substrate. The base substrate preferably comprises a rigid transparent plate. For example, a section of a continuous composite web can be temporarily laminated by rolling to a surface of a base substrate. The lamination can be achieved by means of an optical adhesive film applied between the replication composite and the base substrate. This can stabilize the composite web for the duration of an exposure and / or a fixing step. The fixing step can be pre-fixing, step-fixing, or full fixation.

[0091] For the purposes of the invention, a "pre-fix" is preferably a treatment of a light-sensitive material to reduce its sensitivity to further exposure by further electromagnetic irradiation. A pre-fix can further be configured to adapt the material properties of the light-sensitive material, in particular by reducing its viscosity and / or by converting the material into a semi-solid or solid form. It can be preferred that a pre-fix is ​​used on an already exposed light-sensitive layer of a replication composite in order to stabilize the light-sensitive material and prevent further exposure of grids. The same means as for a full fix can be used for the pre-fix, in particular UV irradiation and heat treatment. It can be preferred that the process parameters used for the pre-fix, such asthe intensity of UV radiation or the temperature of a heater, can be adjusted to achieve the desired mechanical properties and / or the desired lower light sensitivity.

[0092] In preferred embodiments of the invention, each light-sensitive layer of the replication composite is pre-fixed after exposure. The pre-fixing preferably takes place in situ, without moving the replication composite. The pre-fixing can stabilize the exposed light-sensitive layer sufficiently to apply another light-sensitive layer thereto without affecting the already replicated hologram. It may also be preferred that the replicated polychromatic hologram comprising any desired number of layers is completely fixed after all exposure steps. The complete fixation can take place in situ, in particular in an exposure station, without moving the replicated polychromatic hologram. Alternatively or additionally, the complete fixation can take place in a downstream fixation station.Such fixation can be performed on a stationary, replicated polychromatic hologram or while the replicated polychromatic hologram is flowing through the fixation station. The latter can allow for uniform dosing of UV irradiation and / or heat across the replicated polychromatic hologram while using lower-power devices.

[0093] In the following preferred embodiments, "fixing" preferably refers to a complete fixation, a pre-fixation, or a final step of fixing a photosensitive material that has already been pre-fixed.

[0094] Preferably, after exposure in step d), the first replicated hologram is fixed in the first light-sensitive layer. Preferably, the fixing takes place without moving the first replicated hologram. This means that both the exposure and the fixing of the first hologram preferably take place in one workstation. The same workstation can preferably comprise an exposure module and a fixing module. Each module can be activated as needed for the respective process step, e.g., by switching on an exposure source, a UV lamp, a heating lamp, etc. In process steps where a module is not used, the module can be deactivated.

[0095] By fixing the first hologram in the first photosensitive layer, the risk of a subsequent exposure step affecting the first hologram is eliminated. This is particularly useful because the wavelength ranges of even wavelength-selective photosensitive materials often overlap. The first photosensitive layer can, advantageously but does not have to, exhibit wavelength selectivity.

[0096] It may be preferred that a second photosensitive layer is added to the replication composite after the first hologram has been fixed in the first photosensitive layer. The second photosensitive layer can, for example, be supplied as a roll and applied to a layer structure of the replication composite by lamination with a roller. The second hologram can then be exposed in the second photosensitive layer. In this way, the photosensitive layers do not have to be wavelength-selective and subsequent exposure steps do not interfere with the previous ones. At the same time, the various layers do not have to be aligned with one another in the conventional manner after parallel exposure and laminated to form a layer structure. Instead, the first and second holograms are already provided as a composite in precise alignment during exposure.As needed, additional layers can be added to the replication composite. This allows for the creation of a particularly flawless polychromatic hologram.

[0097] In a further preferred embodiment of the invention, fixation occurs after each exposure. Preferably, fixation is carried out by UV radiation, radiation in the visible range of the electromagnetic spectrum, and / or by heat treatment. Fixation can be carried out using a fixation module, wherein the fixation module is preferably located in the same workstation as an exposure module. In this way, both exposure and subsequent fixation can take place in the same workstation in which the hologram was exposed. As a result, a replication network is preferably constructed or provided at a single workstation, without the need for movement of the replicated holograms between process steps. This further prevents alignment errors.

[0098] By fixing the replicated holograms after exposure, they can be stabilized and rendered immune to defects caused by stray light or the exposure of additional layers. Furthermore, the fixed light-sensitive layers can be moved to additional workstations without distortion or shrinkage, for example, in soft resins.

[0099] It is particularly advantageous to fix each hologram immediately after exposure to obtain a finished, aligned polychromatic hologram stack without having to move the hologram stack from the workstation. This allows the precisely aligned holograms of the various layers to remain fixed in their relative positions in a replication stack. The resulting polychromatic holograms are therefore largely error-free. In preferred embodiments of the invention, a translation and / or rotation of the master stack is controlled by a control unit. This allows the translation and / or rotation to be carried out particularly precisely and repeatably.

[0100] The term "control unit" preferably refers to any computer unit comprising a processor, a processor chip, a microprocessor, or a microcontroller that enables automatic control of one or more actuators, e.g., a carriage, a motor, a brake, an electromagnet, etc. The components of the control unit can be conventional or individually configured for the respective implementation. Preferably, the control unit comprises a processor, a memory, and computer code (software / firmware) for controlling the components of the device.

[0101] The control unit may also comprise a programmable circuit board, a microcontroller, or other device for receiving and processing data signals from the components of the device, for example, from sensors relating to the speed of a composite web and / or the position of a master hologram, in particular the position of an alignment mark of the master hologram, as well as other relevant sensory information. The control unit preferably further comprises a computer-usable or computer-readable medium, such as a hard disk, random access memory (RAM), read-only memory (ROM), flash memory, etc., on which computer software or code is installed. The computer code or software for controlling the components of the device may be written in any programming language or model-based development environment, e.g.in C / C++, C#, Objective-C, Java, Basic / VisualBasic, MATLAB, Python, Simulink, StateFlow, Lab View or Assembler, but not only.

[0102] The term "control unit is configured to" perform a specific operation, such as translating and / or rotating the master assembly, may include custom or standard software installed on the control unit that initiates and controls these operational steps.

[0103] In a further preferred embodiment of the invention, reference values ​​for a degree and / or direction of a required translation and / or rotation of the first and second master holograms are stored in a memory. Preferably, the control unit is configured to control a translation and / or rotation of the master array (comprising the first and second master holograms) according to the reference values. In preferred embodiments, the reference values ​​are automatically provided to the control unit repeatedly for a series of replication arrays (or a series of sections of a continuously supplied replication array). By preloading reference values ​​into a memory, the alignment of the master holograms can be performed for repetitions of the same sequence of exposure steps without recalculating the required alignment.Time-consuming steps for converging to an alignment position of the master holograms can be skipped. This allows for very fast and automated processing of unexposed parts of a composite web or unexposed replication composites.

[0104] In some preferred embodiments of the invention, instructions for the alignment of the first and second master holograms are determined experimentally. For this purpose, the first and second holograms can be provided with alignment marks during their manufacture. The alignment marks of the holograms can be compared with an external alignment mark outside the master composite, which represents the target position of the holograms. For example, the external alignment mark can be present on the replication composite or on a base substrate. Alternatively, the external alignment mark can be present only in software, for example, as a predetermined image coordinate.

[0105] It may be preferred that the required alignment of a hologram is determined by translating and / or rotating the master composite until an alignment mark of each of the first and second holograms spatially coincides with the external alignment mark representing the desired position of the respective hologram. This can be performed by incremental translation and / or rotation of the respective hologram and an assessment of the correspondence of the respective alignment mark with the desired alignment mark. The evaluation can be performed using software, in particular using image analysis software. It may also be preferred that a degree and / or direction of a translation and / or rotation direction of the hologram, at which the best alignment or the best image quality was assessed, is stored in the memory.The selection of the translation and / or rotation positions to be tested can be performed repeatedly to converge on a position with the best alignment. Preferably, a converging function can be used to select the translation and / or rotation positions, i.e., preferably a mathematical or algorithmic process based on refining an estimated value until it is sufficiently accurate within defined limits or converges to an optimum. The converging function for selecting optimal translation and / or rotation positions can be based, for example, on an iterative or recursive algorithm.

[0106] As an alternative to using alignment marks, the holographic image or the optical function of each master hologram can be compared with a correctly aligned target function. This can be done by reconstructing the hologram, in particular the relevant wavelength channel, and evaluating the correspondence of all or part of the reconstructed hologram with the target function. This can also be done using software, in particular image analysis software. In a further preferred embodiment of the invention, to determine a degree and direction of a required translation and / or rotation of the first and / or second master hologram, the master composite is irradiated with collimated reconstruction light to generate a convergent point (e.g., a focus).This is particularly suitable for master holograms that have the optical function of a concave mirror or a light focusing lens.

[0107] Preferably, a degree and / or direction of a required translation and / or rotation of the first and / or second master hologram is selected such that a convergent point for reconstruction light of the first wavelength range coincides with a convergent point for reconstruction light of the second wavelength range. An external target point can be used as a reference for the position of the convergent point. Alternatively, the point at which either the first or the second master hologram actually converges the light can also be used.

[0108] In this way, the different wavelength channels can be exposed in such a way that all channels of the polychromatic hologram also focus a planar wavefront to a single point. This allows the polychromatic hologram to fulfill the optical function of a conventional optical element in a much more compact form without chromatic aberration.

[0109] In further preferred embodiments of the invention, additional or alternative alignment methods can be used to determine the required alignment of the individual master holograms in the master assembly. For example, each master hologram can be provided with a positioning mark. The master assembly can thus be gradually shifted until the position of the positioning mark coincides with a desired position. The positioning mark can take any form, such as an imprint, a notch, or a holographic element.

[0110] Preferably, a required translation and / or rotation to achieve the best alignment for a master hologram is captured as an instruction in memory. Preferably, the control unit is configured to signal an actuator to translate and / or rotate the master hologram according to the pre-captured instructions.

[0111] To perform the translation or rotation, it may be advantageous to provide an alignment module. This may comprise a gantry structure in which the master assembly is positioned. It may also be preferred for the master assembly to be positioned in or on a carriage that can be translated about two orthogonal axes, e.g., using pins, rails, or the like. It may be preferred for the carriage to be located on a rotatable support connected to a motor, e.g., a piezoelectric motor. Of course, additional pins, gears, or the like may be provided to finely adjust and / or limit the movement.In a further preferred embodiment of the invention, the first and second master holograms are arranged in or on a master substrate to form the first master composite, wherein the master substrate is preferably translated and / or rotated by an alignment module to perform an alignment.

[0112] The master substrate is preferably configured to support the layer structure of the first and second master holograms, and optionally third or further master holograms. The first and second master holograms are preferably laminated to a surface of the master substrate to create the layer structure. The master substrate is preferably rigid and transparent to the first and second wavelength ranges. The dimensions of the master substrate are preferably larger than those of the master hologram in all directions. The master substrate preferably has a thickness that is at least 5 times, preferably at least 10 times, and even more preferably at least 10 times the thickness of the first or second master hologram. The master substrate can preferably be in the form of a cuboid block, a plate, or a prism.At least one surface of the master substrate is preferably parallel to the master holograms and traverses the longitudinal and transverse directions.

[0113] Preferably, the master substrate can be formed from a material that is an optical plastic, preferably selected from the group: polymethyl methacrylate (PMMA), polycarbonate (PC), cycloolefin polymers (COP), and cycloolefin copolymers (COC), and / or an optical glass, preferably selected from the group: borosilicate glass, quartz glass, B270, N-BK7, N-SF2, P-SF68, P-SK57Q1, P-SK58A, and P-BK7. The master substrate preferably has a refractive index between 1.4 and 1.6.

[0114] By attaching the first and second master holograms to or integrating them into the master substrate, the master composite can be made extremely robust and protected against damage. Due to its larger dimensions and higher rigidity, it can also be translated and rotated more reproducibly without the risk of stretching, shrinking, or otherwise deforming. Furthermore, precise translation and / or rotation is facilitated.

[0115] The master substrate or a cover of the master substrate can provide a rigid surface to which an optical fluid can be applied to improve optical contact with the replication composite without the risk of residues remaining on the master holograms. In this way, a smooth optical transition of light rays between the master composite and the replication composite with minimal reflections and / or aberrations at interfaces can be ensured. Such unwanted reflections cause optical losses that reduce the efficiency of the replication process. In a further preferred embodiment of the invention, the master composite comprising the first and second master holograms is mounted on a base substrate, wherein a translation and / or rotation of the master composite relative to the base substrate preferably takes place to carry out an alignment.The master composite and base substrate are preferably parts of a master element within the meaning of the invention.

[0116] This enables the separation of functions between the master composite and the base substrate. The base substrate can be configured, in particular, for optical contact with the replication composite. This allows the base substrate to be advantageously held stationary during the various phases of exposure, while the master composite can be aligned for optimal replication, as described. Advantageously, this way, no stresses or deformations are introduced into the replication composite through translation and / or rotation. Friction between the master composite and the replication composite, which could occur during alignment, is avoided. Such friction can impair alignment, preventing it from being performed to the required extent.Instead, there is a stable mechanical contact between the base substrate and the replication compound, while a relative movement for the alignment of the master holograms occurs within a two-part master element, namely between a base substrate and a master compound.

[0117] The base substrate can preferably be mounted on a device that holds it securely. This serves to further improve the stability of the mechanical contact between the replication composite and the master element. By bringing the replication composite into contact with the base substrate and not with the master composite, the latter can be protected from friction, adhesive residue, and the like. The base substrate can thus be cleaned more easily, particularly by separating it from the master element and / or the holding device on which it is installed. The base substrate is also easier and more cost-effective to replace.

[0118] Furthermore, the base substrate allows for excellent optical contact between the replication composite and the master composite, while the master composite is spaced apart from the replication composite and remains freely movable. For this purpose, it may be preferred for the base substrate to comprise the same materials as the master composite, in particular a master substrate. The base substrate may additionally or alternatively comprise the same materials as an adjacent layer of the replication composite.

[0119] The base substrate is preferably configured such that the electromagnetic rays flow from the replication composite into the corresponding master hologram and back into the replication composite. The base substrate is preferably transparent to the wavelengths of the electromagnetic radiation with which the replication composite is to be irradiated at a corresponding workstation. The refractive index of the base substrate is preferably approximately equal to that of an adjacent layer of the replication composite, which can be a carrier layer or a replication substrate. The refractive index of the base substrate can preferably be between 1.4 and 1.6. This allows for very good optical contact between the replication composite and the base substrate, eliminating light loss due to total internal reflection at the interface between the replication composite and the base substrate.Such unwanted reflections can represent stray light that could impair the quality of the reproduced polychromatic hologram. This is advantageously prevented here.

[0120] In preferred embodiments of the invention, the optical contact between the replication composite and the base substrate is mediated by an intervening material. The material between the replication composite and the base substrate can be a solid, such as a film, in particular an adhesive film, or a deformable transparent element, e.g. made of silicone. The material can also comprise a semi-solid substance such as a gel or a fluid, such as an optical liquid. In preferred embodiments of the invention, the optical contact between the base substrate and the master composite is mediated by an intervening material. The material is preferably liquid so that it does not hinder the movement of the master composite relative to the base substrate.

[0121] During exposure, an optical fluid is preferably present between the master composite and the base substrate. Such an optical fluid preferably has a refractive index that corresponds to or is close to that of the base substrate, a master substrate, and / or the master holograms, improving the optical contact between them. An optical fluid advantageously achieves frictionless mobility of both components, while also enabling interference-free optical contact. The optical fluid can also absorb any vibrations that arise during exposure, particularly due to the movement of the master composite. The replication composite can thus be kept particularly stable during exposure.

[0122] To facilitate optical contact between the base substrate and the replication composite (in particular a replication substrate), some embodiments provide an optical adhesive film. Direct mechanical contact is preferably established between the optical adhesive film and the two adjacent substrates or between the base substrate and the replication composite. Should a gap be present between the surfaces of the optical adhesive film and adjacent substrates, it is preferably smaller than half a wavelength of the radiation used for exposure, so that no interference fields form at the interface between the surfaces. The optical adhesive film can thus improve the optical contact between the replication composite and the master element. It is particularly advantageous that the optical adhesive film need not be removed between exposure of the first and second master holograms into the replication composite.The optical adhesive film can also help stabilize the position of the replication composite relative to the master element, making the replication process particularly efficient.

[0123] In a further preferred embodiment of the invention, an optical fluid is introduced between the base substrate and the replication composite to establish optical contact. The optical fluid can advantageously be applied continuously, without a lamination step. On the one hand, this can be faster and more efficient than applying an optical adhesive film. At the same time, the risk of leaving adhesive residue on the base substrate can be avoided. Furthermore, the optical fluid can serve as a lubricant to protect the base substrate from surface damage.

[0124] The provision of a base substrate between the replication composite and the master composite, particularly by applying optical fluids and / or adhesive films at the interfaces, can also ensure particularly stable, vibration-free mechanical contact between the replication composite and the master composite. This significantly reduces the risk of unwanted displacement during the exposure process. Furthermore, the arrangement provides highly efficient optical contact, whereby the light rays used for exposure remain essentially unbroken on their path between a master hologram and a light-sensitive layer. The exposure process is thus highly efficient and produces sharp holographic images.

[0125] In preferred embodiments, the base substrate, the master composite, in particular the master substrate, and / or a replication substrate can be provided with an anti-reflection coating. Such a coating can contribute to further reducing efficiency losses due to reflections.

[0126] In a further preferred embodiment of the invention, the master composite can be used without a base substrate. In this case, it is preferred that the replication composite be placed at a predetermined distance from the master composite during exposure. The predetermined distance is preferably large enough to prevent unwanted mechanical contact between the master composite and the replication composite. The predetermined distance is also preferably small enough to be bridged by an optical fluid that is held stable by intermolecular forces. Preferably, an optical fluid is introduced between the master composite and the replication composite.

[0127] For the purposes of the invention, an "optical adhesive film" is preferably a transparent film with a refractive index close to the refractive index of the master substrate, the replication substrate, and / or the light-sensitive material. The optical adhesive film is preferably designed to improve optical contact between the base substrate and the replication composite, so that reflections at the interface between the base substrate and the replication substrate are reduced or eliminated.

[0128] Preferably, the materials used for the optical adhesive film have identical or similar optical properties to those used for the base substrate or the adjacent layer of the replication composite. These similar or identical properties preferably include transparency, haze, stress birefringence properties, and / or the refractive index. The use of identical or similar materials enables a very close adaptation of the refractive index of the optical adhesive film to the refractive indices of the adjacent base substrate and / or replication substrate, ensuring a transition between the adjacent refractive indices without refractive index jumps. Reflections at the interface between the master element, the optical adhesive film, and / or the replication composite are thereby largely eliminated or significantly minimized.

[0129] An "optical fluid" within the meaning of the invention is preferably a transparent fluid with similar or identical optical properties to the base substrate, master substrate, master composite, replication substrate, and / or replication composite. The similar or identical properties preferably include transparency, haze, stress birefringence properties, and / or the refractive index. The use of an optical fluid can prevent unwanted reflections at the interfaces between components.

[0130] In a further preferred embodiment of the invention, the base substrate comprises an optical glass and / or an optical plastic. The optical glass or optical plastic is preferably selected from the following group: polymethyl methacrylate (PMMA), polycarbonate (PC), cycloolefin polymers (COP), and cycloolefin copolymers (COC), and / or an optical glass is preferably selected from the group: borosilicate glass, quartz glass, B270, N-BK7, N-SF2, P-SF68, P-SK57Q1, P-SK58A, and P-BK7. The base substrate preferably has a refractive index between 1.4 and 1.6.

[0131] In a further preferred embodiment of the invention, the replication composite comprises a replication substrate. The replication substrate preferably serves to support the light-sensitive layers of the replication composite in order to improve its handling.

[0132] In a preferred embodiment of the invention, the replication substrate is a rigid component. A rigid replication substrate preferably has analogous properties and dimensions to the base substrate. The same materials can be used for this, and a similar refractive index is preferably selected, which is preferably between 1.4 and 1.6. In some embodiments, a rigid replication substrate can be used instead of the base substrate. In this way, the rigid replication substrate can be bonded to the other layers of the replication composite and further processed with them. In this way, the substrate is individual for each polychromatic hologram. In-situ lamination of an optical adhesive film to the base substrate can be omitted, so that exposure can be faster.The need to clean the base substrate can also be eliminated; instead, a polychromatic hologram can be built directly on the replication substrate and exhibit very good quality.

[0133] In some applications, the rigid replication substrate can form part of the final product, e.g., as a carrier layer for incorporating the polychromatic hologram into a final product. This is particularly advantageous when multiple polychromatic holograms are to be stacked on top of each other in a precise relative position. The use of rigid replication substrates for the various polychromatic holograms offers an alternative to roll-based stacking methods, which can lead to deformation of the replication composites. The replication substrates can include positioning marks. These can, for example, be used to precisely position two polychromatic holograms on top of each other, so that the two polychromatic holograms are encapsulated between the two replication substrates, with the respective positioning marks aligned.

[0134] In other cases, the exposed and preferably fixed polychromatic hologram can be delaminated from the rigid replication substrate to obtain a flexible polychromatic hologram. The rigid replication substrate can then be reused.

[0135] The replication substrate can ensure particularly good optical contact between the replication composite and the master composite. Similar to the base substrate, the replication substrate can be used in combination with an optical fluid or an optical adhesive film without the risk of leaving residues on the replicated hologram itself. In embodiments where the replication substrate is used instead of the base substrate, an optical fluid can be arranged between the replication substrate and the master composite. This would offer advantages analogous to those of applying an optical fluid between the base substrate and the master composite.

[0136] The replication substrate can impart sufficient rigidity to the replication composite so that it can be held particularly stable during multi-step exposure. Furthermore, the strength and rigidity of the replication substrate can enable the lamination of additional layers and / or the removal of layers from the replication composite between exposure steps without undesired deformation of the replication composite. This can support a step-by-step layer buildup of the replication composite, allowing light-sensitive layers to be exposed to the desired wavelength and fixed before additional light-sensitive layers are applied. The exposure of subsequent layers need not impair the optical function of the preceding layers, even if the layers are not wavelength-selective. A particularly stable and error-free replication process is thus provided.

[0137] In a further preferred embodiment of the invention, the replication substrate is in film form. Such a replication substrate can also carry the polychromatic hologram. Furthermore, it can comprise positioning marks that serve to stack multiple polychromatic holograms on top of one another, so that the positioning marks can later be cut away or the replication substrate can be removed from the final product. In such embodiments, the replication substrate can preferably be supplied in roll form so that it can be laminated to the rigid surface of a base substrate and easily transported to further workstations in a continuous process. In such an embodiment, the produced polychromatic hologram can advantageously be flexible, which facilitates its integration into a three-dimensional component such as a windshield.

[0138] In a further preferred embodiment of the invention, a layer structure of the replication composite is arranged mirror-symmetrically with respect to the layer structure of the master composite. The mirror symmetry here particularly applies to the light-sensitive layers of the replication composite. In this way, the optical function of the generated polychromatic hologram can correspond exactly to the optical function of the multilayer master hologram. When reversed, such a polychromatic hologram has the same layer structure as the master hologram. The arrangement of the layers can be configured, in particular, to minimize filter effects between the layers and to improve the efficiency of the optical function of the polychromatic hologram.

[0139] In a further preferred embodiment of the invention, the replication composite is in the form of a web of any desired length. This enables an efficient continuous replication process in which the web (also called a "composite web") is moved so that different sections are located at different workstations. In this way, an already exposed section of the composite web can be fixed while an upstream section of the composite web is still being exposed. The fixing can be performed using a fixing module in a fixing station, with the fixing station preferably located downstream of an exposure station. Such a composite web can also be provided in a compact and practical manner in the form of a roll, especially if the thickness and flexibility of the replication composite are suitable. This enables easy transport of the composite web through a replication process by unwinding and rewinding the composite web.In preferred embodiments of the invention, the exposure steps and one or more fixing steps can be performed using an exposure module and a fixing module within the same workstation. This arrangement can reduce the process time for producing the polychromatic hologram. In such an embodiment, the exposure and fixing steps can be performed not simultaneously, but intermittently, by activating the respective modules according to a process sequence. In such an embodiment, the replication assembly can also be provided in roll form, with further processes upstream or downstream of the workstation occurring continuously in time with the exposure and fixing.Such further processes may include removing protective films, cutting, and / or combining a finished polychromatic hologram with other polychromatic holograms to form an HOE. Such a process can be performed with high throughput and reliable control.

[0140] Alternatively or additionally, the replication composite or the replication substrate is transported on a flow track by means of transport rollers, whereby the replication process preferably takes place continuously.

[0141] In a preferred embodiment of the invention, the photosensitive layers are pre-fixed prior to exposure to increase their mechanical stability. Such pre-fixing may, for example, involve partial crosslinking of photopolymer molecules, thereby increasing the viscosity of a liquid layer while simultaneously maintaining sufficient photosensitivity.

[0142] In a further preferred embodiment of the invention, at least the first photosensitive layer is pre-fixed after exposure of the first hologram and before application of the second photosensitive layer. This can protect the first photosensitive layer from mechanical deformation, for example, during lamination of the second photosensitive layer. Furthermore, the first photosensitive layer can be protected from unwanted exposure. It may be preferred that such pre-fixing takes place after each exposure step.

[0143] In a further preferred embodiment of the invention, the replicated polychromatic hologram is completely fixed after exposure of all holograms contained therein. Complete fixation can also take place in the exposure module to avoid mechanical movement of the polychromatic hologram. Alternatively, complete fixation can take place in a separate workstation. This can reduce the process time, since an upstream section of the web-shaped replication composite can be exposed simultaneously in the exposure module.

[0144] In a preferred embodiment of the invention, the polychromatic hologram is configured to fulfill the optical function of an optical component such as a lens or a mirror. This optical function can be fulfilled by a particularly compact, particularly film-shaped component that can be discreetly integrated into a product.

[0145] In a further preferred embodiment of the invention, the above-described steps a) to f) of the method according to the invention are repeated analogously to replicate a second polychromatic hologram into a second replication composite using a second master composite. By performing steps a) to f) at least twice with a first and a second replication composite, a first polychromatic hologram and a second polychromatic hologram can be produced.

[0146] Preferably, one of the first and second replication composites is exposed using a planar wavefront. Preferably, the other of the first and second replication composites is exposed using a spherical wavefront. In this way, one of the two polychromatic holograms can be configured to convert a spherical wavefront into a planar wavefront, and the other of the two polychromatic holograms can be configured to reflect a planar waveform at a predetermined angle.

[0147] The polychromatic holograms can perform the function of a concave mirror or a planar mirror in a very compact manner without unwanted chromatic aberration. Since the polychromatic holograms can be manufactured from light-sensitive materials with thicknesses in the micrometer range, they can perform their respective optical functions with high efficiency across multiple wavelength ranges while requiring very little space. They can therefore be discreetly integrated into AR glasses, car windshields, aircraft windows, pilot training devices, and the like.

[0148] In a further preferred embodiment of the invention, the first and second polychromatic holograms are connected to one another, wherein the first and second polychromatic holograms are preferably arranged at a distance of less than 1 mm, preferably less than 0.5 mm, particularly preferably less than 0.1 mm. The first and second polychromatic holograms preferably have a layered structure, wherein a first layer corresponds to a first wavelength range and a second layer corresponds to a second wavelength range. The polychromatic holograms are preferably arranged such that their layers are mirror-symmetrical to one another - that is, the order of the layers corresponding to each wavelength range is preferably the same from the center line outwards.

[0149] In this way, a light-redirecting HOE can be manufactured with very tight tolerances, resulting in a very high efficiency. Since only the two polychromatic holograms could be applied and bonded together in a conventional manner, e.g., by lamination, only one alignment of the two generated polychromatic holograms is required. This is a significant improvement over the current state of the art, in which six layers must be aligned and laminated to create such a multilayer RGB hologram. The precision of the HOE can be drastically improved. The resulting polychromatic HOE can combine the functions of the concave mirror and the planar mirror to perform complex redirection of electromagnetic beams in a very compact manner.

[0150] In a further aspect, the invention relates to a replication composite comprising at least a first and a second replicated hologram producible by the method according to the invention. The first and the second replicated hologram can preferably be present in one or more layers of fixed light-sensitive material in order to provide a polychromatic hologram. The first hologram is preferably exposed to a wavelength from a first wavelength range, while the second hologram is preferably exposed to a different wavelength from a second wavelength range, so that the resulting replication composite can diffract radiation of both wavelengths. In addition, the replication composite can comprise further layers such as carrier films, protective layers and / or the replication substrate.

[0151] Such a replication array advantageously comprises diffraction patterns configured to diffract radiation at two or more different wavelengths. The diffraction patterns corresponding to the different wavelengths are advantageously precisely aligned with each other, ensuring the replication array is of high quality and performs its optical function very efficiently. Unwanted filtering of light due to incorrect alignment of the different wavelength channels is avoided.

[0152] In a further aspect, the invention relates to a master element comprising a master composite and a base substrate for carrying out the method according to the invention. The master composite comprises a first and a second master hologram, which are movably mounted on the base substrate.

[0153] Preferably, the master composite further comprises a master substrate on or in which the first and second master holograms are fixed.

[0154] Such a master element advantageously enables the movement of the master holograms relative to the base substrate, allowing the master holograms to be aligned even after optical contact has been established between the base substrate and a replication composite. The master holograms located in the master element can thus be adjusted in position before exposure, allowing any positioning error of the master holograms relative to each other or to a master substrate to be compensated for during exposure. Even if the master holograms of a multilayer master element have unacceptable positioning tolerances due to their manufacturing method, they can be used to produce a polychromatic hologram with significantly tighter tolerances. The base substrate can be configured, in particular, for optical contact with the replication composite.In contrast to master holograms, the base substrate can advantageously be kept stationary during various phases of exposure. This ensures stability in the replication process and prevents potential undesirable deformation of the light-sensitive layer of a replication composite.

[0155] Thus, during exposure, only the master composite needs to be moved to align the master holograms. The master composite can be particularly light while maintaining sufficient rigidity. If the replication composite is not laminated directly to the master composite, the master substrate can, in particular, have somewhat lower rigidity and mechanical strength than the base substrate and accordingly also be characterized by a lower thickness. Since the replication composite and / or an optical adhesive film as an intermediate layer are laminated to the base substrate instead of to the master composite, in this case only the base substrate needs to withstand lamination pressure. The master composite, preferably comprising a master substrate, can be made lighter and can therefore be moved particularly precisely by the alignment module, e.g., by a piezo motor, to perform the alignment.

[0156] Preferably, the thickness of the base substrate is selected to ensure sufficient mechanical stability during the application of a replication composite and / or photosensitive layers. The thickness of the base substrate is preferably limited to keep the optical path between each photosensitive layer and the corresponding master hologram sufficiently small. This way, unnecessary optical losses can be avoided.

[0157] The base substrate preferably has a length, a width, and a thickness. The length and width of the base substrate are preferably selected such that all used positions of the master composite are covered by the base substrate. In other words, it is advantageous if, when rotating or translating the master composite, no area of ​​the master composite lies outside the base substrate. Thus, the length and / or width of the base substrate can exceed the length and / or width of the master composite, with the excess being, for example, 1-3 mm.

[0158] The master element preferably further comprises an alignment module which is configured for translation and / or rotation of the first master assembly relative to the base substrate.

[0159] The alignment module preferably comprises a control unit, wherein the control unit is configured to automatically perform a predetermined translation and / or rotation of the first master array for each alignment step in a replication series. Automatic alignment with a control unit allows the known alignment parameters of the master array to be used for each repetition of a replication cycle without having to be recalculated. The control unit can also automatically adjust the pace of the alignment to the exposure steps. Thus, the translational or rotational movements required for the alignment of the first and second master holograms can be performed repeatedly in sync with other aspects of a replication process.For example, a cycle of preprogrammed movements of the master composite can coincide with the cycle time for bringing an unexposed replication composite into contact with the base substrate. This can provide a very fast and continuous replication process for the mass production of polychromatic holograms with very high quality.

[0160] Preferably, the translation and / or rotation can be performed with an accuracy of at least 10 pm and / or at least 0.1°. With such a movement precision, even small alignment errors of the master holograms can be effectively compensated, resulting in very high efficiency and sharpness of the resulting polychromatic holograms.

[0161] In a further aspect, the invention relates to a device for replicating a polychromatic hologram using a method according to the invention. The device comprises an exposure module comprising:

[0162] - a master composite comprising a first master hologram and a second master hologram which are arranged in a layer structure and fixed in their relative position to one another, wherein the first master hologram is designed for a first wavelength range and the second master hologram is designed for a second wavelength range;

[0163] - one or more exposure sources configured to direct electromagnetic radiation of the first wavelength range and the second wavelength range onto the master composite in order to replicate the first master hologram and the second master hologram into a replication composite; and

[0164] - an alignment module configured to translate the master composite in a longitudinal and / or transverse direction and / or to rotate the master composite in order to individually align the first master hologram and the second master hologram with respect to the replication composite prior to exposure by the one or more exposure sources.

[0165] For the purposes of the invention, a "module" preferably refers to a workstation in a continuous manufacturing process, which is preferably equipped with the necessary technical means to carry out the process step. Different modules can be separated from each other by a housing or a partition wall, but this is not necessary. In some embodiments of the invention, some modules are subunits of other modules.

[0166] The exposure module preferably comprises the master assembly, the exposure source(s), and the alignment module in a housing, wherein the housing is preferably opaque for the exposure used. The exposure module is preferably provided with an inlet and an outlet, which are provided for the entry and exit of the replication assembly into the exposure module, respectively. The device preferably also comprises a transport module for introducing the replication assembly into the exposure module and for transporting the polychromatic hologram out of the exposure module. Suitable embodiments of a transport module, such as transport rollers and / or a transport belt, are known to those skilled in the art.

[0167] An "exposure source" preferably includes any type of radiation source configured to emit electromagnetic wavelengths in the first and second wavelength ranges. Preferably, a coherent light source, such as a laser, is used as the exposure source. Analogously to the method according to the invention, the radiation from the exposure source can be adjusted by means of an optical parametric oscillator and / or directed by means of suitable light-deflecting components such as lenses, mirrors, prisms, and the like. Furthermore, the light-deflecting components can be equipped with controllable actuators to direct the radiation onto the master composite at a predetermined angle. Additionally or alternatively, the exposure source itself can be equipped with actuators to direct the radiation onto the master composite.Such an optical parametric oscillator, light-deflecting components and / or actuators may also preferably form part of the exposure module.

[0168] In a preferred embodiment of the invention, the device further comprises a control unit which is configured to carry out a predetermined translation and / or rotation of the master composite of the first master hologram and second master hologram in each case prior to exposure by the one or more exposure sources with respect to the replication composite by means of the alignment module, wherein the translation and / or rotation can preferably be carried out with an accuracy of at least 10 pm and / or at least 0.1 °.

[0169] In preferred embodiments of the invention, the control unit is a component of the alignment module; however, this does not mean that the device is preferably arranged within a housing of an alignment module and must be spatially arranged together with it. However, the control unit is preferably connected to the alignment module and / or an interface, in particular in a connection for exchanging data or control signals, although the connection may be wireless or wired. In a preferred embodiment of the device, the control unit is configured to control all steps of a replication method according to any embodiment of the invention.Such a control unit is preferably further connected to the exposure source and all associated actuators, the transport module, a lamination module, a coating module, a fixing module or any other actuatable component of the device.

[0170] In a further preferred embodiment of the invention, the device comprises any modules, components or computer program products that are configured or required to carry out a method step of a preferred embodiment of the replication method according to the invention.

[0171] In a preferred embodiment of the device, the master composite is present in a master element, wherein the master element comprises a base substrate. Preferably, the alignment module is configured to translate and / or rotate the master composite relative to the base substrate. Such a master element advantageously enables the movement of the master holograms relative to the base substrate, so that the master holograms can still be aligned even after optical contact has been established between the base substrate and a replication composite.

[0172] In a further preferred embodiment, the device comprises a lamination module, wherein the lamination module is preferably configured to laminate the replication composite to the base substrate. By laminating the replication composite to the base substrate, a mechanically stable and optically seamless contact can be established between the replication composite and the master element. This reduces the risk of defects penetrating the replication composite.

[0173] Alternatively or additionally, the lamination module is configured for applying additional light-sensitive layers to the replication composite. This is particularly preferred if the additional light-sensitive layers are provided in solid form or on a solid carrier film.

[0174] In a preferred embodiment of the invention, the device can comprise a coating module. Such a coating module is preferably configured to apply new layers of photosensitive material to a replication composite. The coating module is preferably located within the exposure module so that the replication composite does not have to be moved from its position to be coated. However, it can also be preferred for the coating module to be provided between exposure modules, in particular in order to apply a third or further layers of the photosensitive material to the replication composite. In a further preferred embodiment, the device further comprises a fixing module, wherein the fixing module is configured to fix at least one photosensitive layer of the replication composite and is preferably present in a housing of the exposure module.By inserting the fixation module into the exposure module housing, fixation or pre-fixation of the replication assembly or a portion of it can be performed in-situ. This prevents errors from being introduced into the replication process.

[0175] Preferably, the same fixation module can be adjusted in its operating parameters so that it can be used for both pre-fixation and full fixation. Alternatively, it may be preferred for the device to comprise multiple fixation modules, one or more of which are preferably positioned in the housing of the exposure module.

[0176] Terms such as substantially, approximately, about, approximately, nearly, etc. preferably describe a tolerance range of less than ± 20%, preferably less than ± 10%, more preferably less than ± 5% and especially less than ± 1% and include the exact value.

[0177] The average person skilled in the art recognizes that technical features, definitions and advantages of preferred embodiments of the method according to the invention also apply to the replication network according to the invention, the master element according to the invention and the device according to the invention, and vice versa.

[0178] Detailed description

[0179] In the following, the invention will be explained in more detail using examples and illustrations, without being limited to these.

[0180] Short description of the figures

[0181] Fig. 1 is a schematic representation of the structure of a master assembly comprising three master holograms.

[0182] Fig. 2A is a schematic representation of the alignment of the first master hologram so that its convergence point coincides with a reference point.

[0183] Fig. 2B is a schematic representation of the exposure of a first master hologram into a first photosensitive layer of a replication composite.

[0184] Fig. 3A is a schematic representation of the alignment of the second master hologram to coincide with the convergence point of the first master hologram.

[0185] Fig. 3B is a schematic representation of the exposure of a second master hologram into a second photosensitive layer of the replication composite. Fig. 4A is a schematic representation of the alignment of the third master hologram to coincide with the convergence point of the first and second master holograms.

[0186] Fig. 4B is a schematic representation of the exposure of a third master hologram into a third photosensitive layer of the replication composite.

[0187] Fig. 5 shows an exemplary replication composite comprising a polychromatic z-hologram, which was produced by the method according to the invention.

[0188] Detailed description of the illustrations

[0189] Fig. 1 schematically shows the structure of a master composite 2 with three master holograms, which correspond to the three wavelength channels, in particular RGB channels. The figure shows the master composite 2 in plan view at various stages of its production. The master composite 2 comprises a master substrate 10, which can be a glass plate, for example. A first master hologram 4 is laminated to a surface of the master substrate 10. The first hologram 4 is designed for a first wavelength range Ai, for example, a blue region of the visible spectrum. The master substrate 10 has a length and width that are greater than the length and width of the first master hologram 4. This can be seen in the first image of Figure 1.

[0190] A second master hologram 6 is laminated onto the composite comprising the master substrate 10 and the first master hologram 4. The second master hologram 6 is designed for a second wavelength range, in particular a green range of the visible spectrum. As illustrated in the second image of Fig. 1, a position shift between the second master hologram 6 and the first master hologram 4 can occur during lamination. This means that a longitudinal, transverse and / or rotational position of the second master hologram 6 may not exactly match the longitudinal, transverse and / or rotational position of the first master hologram 4. Furthermore, the positions of the first and second master holograms 4, 6 may not exactly match their target positions on the master substrate 10.

[0191] A third master hologram 8 is subsequently laminated onto the second master hologram 6 and forms part of the layer structure of the resulting master composite 2. The third master hologram 8 corresponds to a third wavelength range As, for example, a red region of the visible spectrum. Here, too, an offset occurs during lamination, so that the position of the third master hologram 8 does not exactly coincide with the position of the first master hologram 4 or the second master hologram 6. Optionally, the master composite 2 can be provided with a transparent cover (not shown) to protect the master holograms. In the exemplary embodiment, the three master holograms 4, 6, and 8 are reflection holograms and have an optical function for concentrating incident radiation.Due to the offset between the channels of the master composite 2, the quality of a holographic image generated by its reconstruction or its optical function may be limited. Color channels of the master composite 2 do not exactly match each other, so that areas of the master composite 2 may appear in the wrong color tone. Using the method according to the invention, a master composite 2 with high tolerances can nevertheless be used to produce a polychromatic hologram 20 with extremely tight tolerances.

[0192] The master assembly 2 is preferably arranged on a base substrate 42 and provided with an alignment module to form a master element 12. The alignment module can change the translational or rotational position of the master assembly 2 with respect to the base substrate 42. The base substrate 42 preferably comprises a transparent, rigid plate.

[0193] Figures 2A and 2B schematically show a replication of the first master hologram 4 of the master composite 2 from Fig. 1 into a light-sensitive layer 14 of a replication composite 44. The master composite 2 is part of a master element 12, which further comprises a base substrate 42, which is designed to be movable relative to the master composite 2. In a first exposure step, the replication composite 44 comprises a first light-sensitive layer 14 and protective layers located underneath and above it. The layer structure of the replication composite 44 is built up step by step by applying further light-sensitive layers. The advantage here is that the light-sensitive layers do not have to be wavelength-selective. The master holograms 4, 6, and 8 are preferably exposed in a mirrored order into the replication composite 44.Since in this case the first master hologram 4, which corresponds to blue light, is closest to the first light-sensitive layer 14 of the replication composite 44, the first exposure step is carried out with blue light, in particular with a blue laser.

[0194] A top side of the base substrate 42 and a bottom side of the master substrate 10 are arranged at a predetermined distance from each other and each provided with an anti-reflection layer so that no unwanted reflections occur on these sides. An optical fluid 30 is introduced between the top side of the base substrate 42 and the bottom side of the master substrate 10 so that a light beam can cross the distance between the base substrate 42 and the master substrate 10 essentially without diffraction. To further prevent unwanted reflections at the interface between the replication composite 44 and the base substrate 42, an optical adhesive film is inserted between these components for the duration of the steps shown in Figs. 2A-4B. This optical adhesive film is not shown in the figures.

[0195] Before exposure, the first master hologram 4 is first arranged such that it is in a desired position with respect to the replication composite 44. This is done by translating and / or rotating the master composite 2 comprising the first master hologram 4, as schematically shown in Fig. 2A. The base substrate 42 remains stationary. The position of the base substrate 42 is shown in dashed lines. As explained further below for Fig. 3A and Fig. 4A, this position remains unchanged during the three exposure steps. The translation and rotation of the master composite 2 are preferably carried out by an alignment module according to previously stored instructions. The desired position can be a position at which the blue light used to reconstruct the first master hologram 4 converges to a convergence point 40 corresponding to a predetermined coordinate.The position of the convergence point 40 can be stored in advance and compared with the data of a light detector monitoring the reconstruction of the first master hologram 4 to determine the alignment instructions.

[0196] The position of the master hologram 4 can also be adjusted relative to the position of an underlying base substrate 42. For example, the master hologram 4 can be centered directly above the base substrate 42 with a predetermined margin, as schematically illustrated in Fig. 2A.

[0197] To replicate the first master hologram 4, a planar wavefront comprising reference rays 26 of blue light is irradiated onto the first master hologram 4. This process is schematically illustrated in Fig. 2B. The reference rays 26 pass through the first photosensitive layer and are reflected by the first master hologram 4. A reflected object beam 28 interferes with the reference beam 26 in the first photosensitive layer 14, forming an interference pattern therein. A first hologram 140 (shown in the following figures) is generated in the photosensitive layer of the replication composite 44. The first hologram 140 can be reconstructed with blue light (or light comprising a blue region of the spectrum) and fulfills the optical function of converting a spherical wavefront into a planar wavefront.Optionally, the first hologram 140 can be fixed (not shown) before further exposure steps are performed. This can be done by activating a fixation module in the same workstation.

[0198] 3A and 3B schematically show the steps of replicating the second hologram corresponding to the green channel. The position of the replication composite 44 and the base substrate 42 preferably remains unchanged. As shown in Fig. 3A, the second master hologram 6 can be translated or rotated to bring it into a desired position. In addition, a second light-sensitive layer 16 can be applied to the replication composite 44 to further build up its layer structure. The second light-sensitive layer 16 can be applied, for example, by lamination from a roll. To perform such lamination, the base substrate 42 is preferably sufficiently rigid and stably mounted. Exposure can then be achieved by directing reference beams 26 of green light onto the second master hologram 6. A green laser can be used for this purpose.The reference beams 26 are reflected by the second master hologram 6 and form object beams 28, which converge to the convergence point 40. The absolute position of the convergence point 40 is the same as for the first master hologram 4. The reference beams 26 and the object beams 28 interfere in the light-sensitive material 16 of the replication composite and form the second hologram 160. This can be fixed before further exposure.

[0199] Analogously, the third master hologram 8 can be aligned according to predetermined instructions to bring it into a desired position, as shown in Fig. 4A. A third light-sensitive layer 18 can be added to the layer structure of the replication composite 44. A red laser can be used to direct reference beams 26 onto the third master hologram 8 and generate the third hologram 180 in the replication composite 44. The third hologram 180 can also be fixed before further processing. The replication composite 44 thus comprises a polychromatic RGB hologram. In this way, all three channels of the polychromatic hologram are precisely aligned with one another, as shown by the identical positions of the convergence points 40 during each exposure step. This is possible despite the alignment errors in the master composite 2 using the method according to the invention.

[0200] The exposed and preferably fixed polychromatic hologram can be delaminated from the rigid base substrate 42 to obtain a flexible polychromatic hologram, or the base substrate 42 can serve as a rigid replication substrate to obtain a stable polychromatic hologram. The rigid replication substrate can be positioned according to the substrate already used in an application and / or another polychromatic hologram can be positioned on top of one another to encapsulate the replicated holograms between two rigid replication substrates.

[0201] Fig. 5 shows a HOE comprising a first polychromatic hologram 20 and a second polychromatic hologram 22, each produced according to the method of the invention. Each of the two polychromatic holograms is an RGB hologram, with the RGB holograms attached to each other in a mirrored sequence. Thus, the z-hologram, for example, has a BGRRGB layer structure. While the first polychromatic hologram 20 was produced as shown in Figs. 2A-4B, the second polychromatic hologram 22 has a planar reflective optical function and is exposed with a planar wavefront.

[0202] The first polychromatic hologram 20 converts a spherical reconstruction wavefront 32 into a planar wavefront. A red component of the reconstruction wave from 32 is reflected by the third hologram 180 to form the red reflected rays 38. A green component of the reconstruction wave from 32 is reflected by the second hologram 160 to form the red reflected rays 36. Similarly, a blue component of the reconstruction wave from 32 is reflected by the first hologram 140 to form the red reflected rays 34.

[0203] The second polychromatic hologram 22 then reflects the light beams 38, 36, and 34 to create the planar deflected wavefront 46. The holograms 140, 160, and 180 of the second polychromatic hologram reflect the blue light beams 34, the green light beams 36, and the red light beams 38, respectively. Thus, the planar wavefront 46 can preferably appear white. It can also have a color determined by the intensities of the reflected beams. A complex light-deflecting function can thus be performed in a precise and compact manner.

[0204] List of reference symbols

[0205] 2 Master's network

[0206] 4 first master hologram

[0207] 6 second master hologram

[0208] 8 third master hologram

[0209] 10 Master substrate

[0210] 12 Master element

[0211] 14 first light-sensitive layer

[0212] 16 second light-sensitive layer

[0213] 18 third light-sensitive layer

[0214] 20 first polychromatic hologram

[0215] 22 second polychromatic hologram

[0216] 24 HOE

[0217] 26 Reference beam

[0218] 28 Object beam

[0219] 30 optical fluid

[0220] 32 Reconstruction wavefront

[0221] 34 reflected waves of the first wavelength range

[0222] 36 reflected wave of the second wavelength range

[0223] 38 reflected wave of the third wavelength range

[0224] 40 Convergence point

[0225] 42 Base substrate

[0226] 44 Replication network

[0227] 46 deflected wavefront

[0228] 140 first replicated hologram

[0229] 160 second replicated hologram

[0230] 180 third replicated hologram

Claims

PATENT CLAIMS 1 . Method for the replication of a polychromatic hologram (20) comprising the following steps: a) providing a master assembly (2) comprising a first master hologram (4) and a second master hologram (6) which are arranged in a layer structure and fixed in their relative position to one another, wherein the first master hologram (4) is designed for a first wavelength range (Ai) and the second master hologram (6) is designed for a second wavelength range (A2), b) providing a replication composite (44), c) aligning the first master hologram (4) with respect to the replication composite (44) by translating the master composite (2) in a longitudinal and / or transverse direction and / or by rotating the master composite (2), d) exposing the first master hologram (4) by means of electromagnetic radiation of the first wavelength range (Ai) to obtain a first replicated hologram (140) in the replication composite (44),e) aligning the second master hologram (6) with respect to the replication composite (44) by translating the master composite (2) in a longitudinal and / or transverse direction and / or by rotating the master composite (2), f) exposing the second master hologram (6) by means of electromagnetic radiation of the second wavelength range (λ2) to obtain a second replicated hologram (160) in the replication composite (44).

2. Method according to claim 1, characterized in that a third master hologram (8) is provided, wherein the third master hologram (8) is comprised by the master composite (2) comprising the first master hologram (4) and the second master hologram (6) or a further master composite, and the method comprises the following further steps: g) aligning the third master hologram (8) with respect to the replication composite (44) by translating the master composite (2) and / or the further master composite in a longitudinal and / or transverse direction and / or by rotation, h) exposing the third master hologram (8) to electromagnetic radiation of a third wavelength range (λ3) to obtain a third replicated hologram (180) in the replication composite (44).

3. Method according to the preceding claim, characterized in that one of the first (Ai), second (A2) or third (A3) wavelength ranges corresponds to red light, one of the first (Ai), second (A2) or third (A3) wavelength ranges corresponds to green light and one of the first (Ai), second (A2) or third (A3) wavelength ranges corresponds to blue light and / or the first (4), second (6) and third master hologram (8) is a reflective hologram.

4. Method according to one of the preceding claims, characterized in that the replication composite (44) is provided in step b) with a first light-sensitive layer (14) and after the exposure in step d) a fixing of the first replicated hologram (140) in the first light-sensitive layer (14) takes place.

5. Method according to one of the preceding claims, characterized in that after each exposure, fixation is carried out, preferably by UV radiation, radiation in the visible range of the electromagnetic spectrum and / or a heat treatment.

6. Method according to one of the preceding claims, characterized in that Reference values ​​for a degree and a direction of a required translation and / or rotation of the first (4) and second master hologram (6) are stored in a memory and are automatically provided repeatedly by a control unit for a series of replication networks (44).

7. Method according to the preceding claim, characterized in that in order to determine a degree and a direction of a required translation and / or rotation of the first (4) and / or second master hologram (6), the master composite (2) is irradiated with a collimated reconstruction radiation (32) to generate a convergent point (40), wherein a degree and / or a direction of a required translation and / or rotation of the first and / or second master hologram (2) is to be selected such that a convergent point (40) for reconstruction radiation (32) of the first wavelength range (Ai) coincides with a convergent point (40) for reconstruction radiation of the second wavelength range (A2).

8. Method according to one of the preceding claims, characterized in that the first (4) and second master hologram (6) are arranged in or on a master substrate (10) to form the master composite (2), wherein the master substrate (10) is translated and / or rotated by an alignment module to carry out an alignment.

9. Method according to one of the preceding claims, characterized in that the master composite (2) comprising the first (4) and second master hologram (6) is mounted on a base substrate (42), wherein a translation and / or rotation of the master composite (2) relative to the base substrate (42) takes place to carry out an alignment.

10. Method according to one of the preceding claims, characterized in that the master composite (2) comprising the first (4) and second master hologram (6) is mounted on a base substrate (42), wherein the base substrate (42) comprises an optical glass and / or an optical plastic.

11. Method according to one of the preceding claims, characterized in that the replication composite (44) comprises a replication substrate and the master composite (2) is mounted on a base substrate (42), wherein for exposure the replication substrate is positioned on the base substrate (42), wherein preferably an optical adhesive film or an optical liquid (30) is applied between the base substrate (42) and the replication substrate, wherein preferably the replication substrate and / or the base substrate (42) is provided with an anti-reflection coating.

12. Method according to one of the preceding claims, characterized in that during the exposure steps a layer structure of the replication composite (44) is arranged mirror-symmetrically with respect to the layer structure of the master composite (2).

13. Method according to one of the preceding claims, characterized in that the replication composite (44), light-sensitive layers and / or a replication substrate is in the form of a web of any length and / or on a Flow path is transported by means of transport rollers, whereby the replication process preferably takes place continuously.

14. Method according to one of the preceding claims, characterized in that by steps a) to f) a first polychromatic hologram (20) is produced in a first replication composite (44), steps a) to f) are repeated analogously in order to copy a second polychromatic hologram (22) into a second replication composite (44) using a second master composite (2), wherein preferably the exposure of one of the first or second replication composites (44) is carried out by means of a planar wavefront and the exposure of the other of the first or second replication composites (44) is carried out by means of a spherical wavefront.

15. Method according to the preceding claim, characterized in that the first (20) and second polychromatic holograms (22) are connected to one another, wherein the first (20) and second polychromatic holograms (22) are arranged at a distance of less than 1 mm, preferably less than 0.5 mm, particularly preferably less than 0.1 mm.

16. Replication composite (44) comprising at least a first (140) and a second replicated hologram (160) producible by a method according to one of the preceding claims.

17. Master element (12) comprising a master composite (2) and a base substrate (42) for carrying out a method according to one of the preceding claims 1-15, characterized in that the master composite (2) comprising a first (4) and a second master hologram (6) is mounted on the base substrate (42), wherein the master element (12) preferably comprises an alignment module which is configured for a translation and / or rotation of the master composite (2) relative to the base substrate (42).

18. Master element (12) according to the preceding claim, characterized in that the alignment module comprises a control unit, wherein the control unit is configured to automatically carry out a predetermined translation and / or rotation of the master assembly (2) for each alignment step in a replication series, wherein the translation and / or rotation can preferably be carried out with an accuracy of at least 10 pm and / or at least 0.1 °.

19. A device for replicating a polychromatic hologram (20) in a method according to any one of the preceding claims 1-15, wherein the device comprises an exposure module comprising: a master composite (2) comprising a first master hologram (4) and a second master hologram (6) arranged in a layered structure and fixed in their relative position to one another, wherein the first master hologram (4) is designed for a first wavelength range (Ai) and the second master hologram (6) is designed for a second wavelength range (A2); one or more exposure sources configured to direct electromagnetic radiation of the first wavelength range (Ai) and the second wavelength range (A2) onto the master composite in order to replicate the first master hologram (4) and the second master hologram (6) into a replication composite (44);and an alignment module configured to translate the master composite (2) in a longitudinal and / or transverse direction and / or to rotate the master composite (2) in order to align the first master hologram (4) and the second master hologram (6) with respect to the replication composite (44) prior to exposure by the one or more exposure sources; 20. Device for the replication of a polychromatic hologram (20) according to the preceding claim, characterized in that the device further comprises a control unit which is designed to carry out a predetermined translation and / or rotation of the master composite (2) of the first master hologram (4) and second master hologram (6) in each case before an exposure by the one or more exposure sources with respect to the replication composite (44) by means of the alignment module, wherein the translation and / or rotation can preferably be carried out with an accuracy of at least 10 pm and / or at least 0.1 °.

21. Device for the replication of a polychromatic hologram (20) according to one of the preceding claims 19 or 20, characterized in that the master composite (2) is present in a master element (12), wherein the master element (12) comprises a base substrate (42) and the alignment module is configured to translate and / or rotate the master assembly (2) relative to the base substrate (42).

22. Device for the replication of a polychromatic hologram (20) according to the preceding claim, characterized in that the device comprises a lamination module, wherein the lamination module is preferably configured to laminate the replication composite (44) to the base substrate.

23. Device for the replication of a polychromatic hologram (20) according to one of claims 19 - 22, characterized in that the device further comprises a fixing module, wherein the fixing module is configured for the fixing of at least one light-sensitive layer of the replication composite and is preferably present in a housing of the exposure module.

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