Interference grid reduction in hologram replication through polarization manipulation

Abstract

The invention relates to a method for replicating a hologram. The method comprises the following steps: providing a master element comprising a substrate body and at least one master hologram; providing a replication assembly comprising at least one photosensitive layer on a front side of the master element; and exposing the front side of the master element comprising the master hologram by means of a replication beam from a light source in order to replicate the hologram into the photosensitive layer. At least one polarization-sensitive element is mounted on a rear side of the substrate body of the master element. In a further aspect, the invention relates to a master element for carrying out a method according to the invention and to a device for replicating a hologram by means of a method according to the invention.

Description

The invention relates to a method for replicating a hologram. The method comprises the following steps: providing a master element comprising a substrate body and at least one master hologram; providing a replication assembly comprising at least one photosensitive layer on a front side of the master element; and illuminating the front side of the master element comprising the master hologram by means of a replication beam from a light source in order to replicate the hologram into the photosensitive layer. At least one polarization-sensitive element is mounted on a rear side of the substrate body of the master element. In a further aspect, the invention relates to a master element for carrying out a method according to the invention as well as a device for replicating a hologram by means of a method according to the invention. Background and state of the art The invention relates to the field of hologram replication. HOEs (Holographic Optical Elements) are typically optical components that utilize holographic properties to achieve a specific light path, such as transmission, reflection, diffraction, scattering, and / or deflection. This allows desired optical functionalities to be implemented compactly in arbitrary substrates. 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. Such holographic elements are used in many areas, such as transparent displays (e.g., in shop windows, refrigerated display cases, vehicle windows), for lighting applications, such as indicator or warning signals in glass surfaces, and light-sensitive detection systems, for example, for interior monitoring (eye tracking in vehicles or presence status tracking of people indoors). Holograms are created by the interference of a reference beam with light reflected or diffracted from the surface of an object (object beams). Traditionally, three-dimensional objects were used to produce unique, custom-made holograms. Commercially available HOEs, however, are often mass-produced using duplication processes. Such duplication processes typically use a master hologram containing the image to be copied. The master holograms used are often stored in a substrate body that carries 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 and the substrate body forms a master element. To replicate the image from the master hologram into a light-sensitive replication array, the master element is exposed to a coherent light source. A reflection hologram, acting as the master hologram, is preferably located on the front face of the substrate body of the master element. During the replication of a reflection hologram, the replication assembly is preferably brought into optical contact with the master hologram on the front face of the substrate body and illuminated from this front. The beam penetrates the photosensitive assembly and is partially diffracted by the reflection hologram to generate the desired interference pattern within the replication assembly. However, an undiffracted portion of the light can pass through the reflection hologram and enter the substrate body. At the interface on the rear face of the substrate body, the light can be reflected back into the replication assembly and interfere with the original replication beam or the object beam diffracted by the reflection hologram. This interference between the light reflected from the back of the substrate and the replication beam or the object beam diffracted by the reflection hologram leads to the formation of unwanted interference gratings. These gratings can adversely affect the actual interference pattern of the hologram and impair image quality. Therefore, there is a need for a method and a device for the replication of holograms that ensures a reduced formation of unwanted interference grids in the replication network. Object of the invention One object of the invention is to provide a method and a device which ensure a reduced formation of interference grids in the replication of holograms and which are preferably characterized at the same time by simple handling, compact design and easy integration into a replication process. Summary of the invention The problem is solved by the features of the independent claims. Advantageous embodiments of the invention are described in the dependent claims. In a first aspect, the invention relates to a method for replicating a hologram comprising the following steps: a. providing a master element comprising a substrate body and at least one master hologram, b. providing a replication assembly comprising at least one photosensitive layer on a front side of the master element, c. exposing the front side of the master element comprising the master hologram by means of a replication beam from a light source in order to replicate the hologram into the photosensitive layer, wherein at least one polarization-sensitive element is provided on a back side of the substrate body of the master element. The method according to the invention advantageously enables interference-reduced replication of a master hologram into a replication assembly by advantageously having at least one polarization-sensitive element attached to the back of the substrate body of the master element. The polarization-sensitive element is preferably an optical component that influences the polarization of an incident light or exhibits different optical behavior depending on the polarization of an incident light. Typical examples of polarization-sensitive elements are polarizers; they only allow light with a specific polarization to pass through and block other polarizations. Polarizers thus exhibit a different degree of transmission depending on the polarization. Another typical example of polarization-sensitive elements are wave delayers. They change the polarization of passing light by delaying the phase of the light in a specific polarization component differently than in another, preferably orthogonal, polarization component. For example, a linear polarization of light is decomposed into two orthogonal components aligned parallel to the fast and slow axes of the wave delayer. These two components are delayed differently, resulting in a phase shift and thus changing the polarization. In this context, polarization preferably refers, in a known manner, to the orientation of the electric field vector of an electromagnetic wave, such as light, as it propagates through space. In electromagnetic waves, the electric and magnetic fields oscillate perpendicular to the direction of wave propagation and to each other. Polarization preferably refers to the direction of oscillation of the electric field. There are preferably several types of polarization. In linear polarization, the electric field vector oscillates in a constant direction that is perpendicular to the direction of wave propagation. This fixed direction lies in a plane, preferably called the polarization plane. In circular polarization, the electric field vector rotates continuously as it propagates, describing a circular motion. Depending on the direction of rotation, a distinction is made between left- and right-circular polarization. A generalization of circular polarization is elliptical polarization, in which the electric field vector describes an ellipse instead of a circle. In both circular and elliptical polarization, the polarization plane changes continuously because the electric field vector rotates in space. When polarized light passes through polarization-sensitive elements such as wave retarders, the polarization of the light is decomposed into orthogonal components. These are two electric field components that are perpendicular to each other with respect to the principal axes of the wave retarder (the fast and slow axes). Although the original light is linearly polarized, for example, these two components can experience different phase velocities depending on how they travel through the birefringent material of the wave retarder. This phase shift causes the direction of the electric field vector to change as the light propagates, which can lead to a change in polarization, such as from linear to circular polarization or a rotation of the plane of polarization. When linearly polarized light is polarized at an angle of 45° to the principal axes of the wave delayer, it can be decomposed into equal components along the fast and slow axes. The 45° angle is therefore particularly advantageous because, in this orientation, both components of the electric field have the same magnitude and couple equally strongly into the wave delayer material. This maximizes the phase shift between the two components. In a λ / 4 plate, this causes the two orthogonal components to be phase-shifted by 90°, resulting in circular polarization. In a λ / 2 plate, the 180° phase shift causes a 90° rotation of the polarization plane, rotating the linear polarization into an orthogonal direction. By using polarization-sensitive elements on the back side of the substrate body, the Fresnel reflection on the back side of the substrate body and the resulting reflection beam are advantageously modified or reduced in such a way that there is little or preferably no interference between the replication beam and the reflection beam in the replication system. This advantageously reduces or avoids the formation of undesired interference patterns in the replication system. For example, it may be advantageous to provide a polarization-sensitive element that reduces the proportion of light reflected from the back of the substrate body, thus minimizing the amount of reflected light available for interference with the replication beam in the replication assembly. For instance, the polarization-sensitive element may include a polarizer designed to absorb electromagnetic radiation polarized with the same polarization as the replication beam, thereby reducing the proportion of reflected light. It is also preferable for the polarization-sensitive element to influence the polarization of the light component reflected from the back of the substrate (reflection beam) such that the reflection beam and replication beam are essentially orthogonally polarized to each other. Preferably, this means that their polarization planes are perpendicular to each other in the photosensitive layer of the replication assembly. If the polarization planes of the beams are perpendicular to each other, these beams advantageously cannot interfere with each other. Interference patterns occur instead if the electric field vectors of the light waves have a component in the same direction and can therefore effectively superimpose.When polarization planes are perpendicular to each other, the oscillation directions of the electric fields are oriented differently, so that no direct superposition of the fields takes place and thus no - in this case different - interference patterns are generated. Such preferred conditions, in which the interference of the reflection beam and the replication beam is reduced or preferably completely avoided, can be advantageously realized by providing one or more polarization-sensitive elements on the back of the substrate body of the master element using simple means. In contrast to alternative solutions for reducing the formation of unwanted interference grids, the introduction of one or more polarization-sensitive elements on the back of the substrate body also offers a number of process-related advantages. As an alternative solution for reducing Fresnel reflections, a non-planar design of the substrate's back surface or the application of an absorbing black coating could be considered. A non-planar back surface leads to divergent reflection at the substrate's rear, thus reducing interference between reflected light and the replication beam or the object beam diffracted by the reflection hologram. The application of an absorbing black coating can decrease the intensity of a back-reflected light beam and also reduce the occurrence of interference gratings.However, these measures negatively impair exposure from the back through the substrate body, which is advantageous, for example, if further optical functionalizations, such as holographic markings, are to be incorporated into the replication assembly, or if pre-bleaching of the replication assembly is to be carried out from the back of the master element. A black coating on the back of the substrate body can prevent further illumination of the replication assembly from the back through the substrate body, whereas a non-planar back of the substrate can lead to aberrations. Conversely, by providing a polarization-sensitive element, optical functionalization, such as holographic labeling, can be advantageously incorporated into the replication assembly without the polarization element, used to reduce interference grating, impairing the quality of the backside illumination. The invention thus advantageously enables the replication of holograms with high quality while avoiding detrimental interference grids, and at the same time maintains a high degree of flexibility with regard to further process steps. Furthermore, the integration of a polarization-sensitive element can be advantageously achieved in a compact manner using simple means, for example by attaching a polarizer and / or wave retarder in the form of a film to the back of the substrate. Therefore, it is advantageous to dispense with elaborate devices for reducing interference grids during the replication of holograms. The invention thus provides a cost-effective and economical way to produce high-quality holograms with significantly reduced interference grids. Advantageously, the method according to the invention can be easily implemented in a mass-production replication series, preferably without the need for further, complex adaptation of established processes or devices. For the purposes of the invention, a "method for replication of 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 into a photosensitive material. This includes at least one exposure of the respective master hologram, but may also include further preferred steps such as fixing, cutting, or trimming. In the context of the invention, "exposure" preferably refers to the targeted guidance of electromagnetic beams onto a suitably sensitive surface, preferably for the formation of a hologram. Various methods for exposing a hologram are known, including transmissive or reflective techniques for producing three-dimensional holograms. A "light source" within the meaning of the invention is preferably a device configured to emit electromagnetic radiation with a wavelength between 200 nm and 25 µm, particularly between 400 and 780 nm. The electromagnetic radiation may 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 of 200 nm to 400 nm, particularly preferably 300 nm to 400 nm. Visible radiation particularly means electromagnetic radiation in the range of 400 to 780 nm. Infrared radiation preferably means a range from 780 nm to 25 µm, preferably in the near-infrared range, i.e., preferably from 780 nm to 3000 nm, particularly from 780 nm to 1400 nm.The use of the term "light" in reference to a light source, an exposure, or light rays does not therefore imply a restriction to electromagnetic radiation in the visible range. Instead, the term "light" also includes electromagnetic radiation in the UV or infrared range, preferably in the range of 200 nm to 3000 nm. For the purposes of this invention, the terms "light wave" or "light rays" preferably refer to the electromagnetic rays emitted with an electromagnetic wavefront from one or more light sources. These electromagnetic rays may also be referred to as "light rays" or "exposure rays" regardless of whether they have a wavelength in the visible range. The light source may include or be associated with light-deflectoring devices such as lenses. The light source may preferably emit collimated beams, particularly with a specific width and direction. It is also preferred that the beams emitted by the light source exhibit a desired divergence at a specific exposure point. Preferably, the light source is configured to emit a coherent light wave. In the context of the invention, various, preferably coherent, light sources can be used. Narrowband light sources are preferred, preferably monochromatic light sources, which, in addition to lasers, can also include light-emitting diodes (LEDs), optionally in combination with monochromators. The front side is illuminated by the light source, preferably by means of a coherent light wave. Coherence preferably refers to the property of optical waves according to which there is a fixed phase relationship between two wave trains. As a consequence 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 propagation and is given, for example, for parallel light rays.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 rays. The coherence length preferably denotes the maximum path length or travel time difference that two light beams from a starting point have, such that their superposition still results in a (spatially and temporally) stable interference pattern. The coherence time preferably denotes the time the light requires to travel a coherence length. Since sufficiently large coherence lengths are preferred for the replication of holograms, it may be preferable for the coherence length to be greater than or equal to the thickness of the substrate. However, particularly in the latter cases, undesirable interference patterns resulting from the reflection of undiffracted light beams at the back of the substrate can also be favored, as explained. 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. For this purpose, for example, several holograms, each diffracting light of a single wavelength, and / or multiplex holograms, diffracting light of multiple wavelengths, can be arranged as hologram stacks. 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 within the volume of the element in the form of a local difference in the refractive index.Through diffraction, for example at a DOE or volume hologram, light can be advantageously converted into almost any desired distribution. This can be an image, a logo, text, a refraction pattern, or something similar. Furthermore, the master hologram can be a technical hologram, such as a Bragg mirror, a diffuser, or a hologram functioning as a lens. A "master element" is preferably a three-dimensional unit comprising a master hologram in a form that facilitates its handling and movement. The master hologram is particularly fixed in position within the master element such that a movement of the master element directly results in a corresponding movement of the master hologram. Preferably, the master element has a length and width approximately equal to those of the master hologram. Preferably, the master element is at least twice, more preferably five times, and most preferably at least twenty times as high as the master hologram. The master element can preferably have the form of a cuboid block, a plate, a parallelepiped, a pyramid, or a prism. The substrate body can be shaped accordingly. Particularly preferably, the master element is plate-shaped, i.e., cuboid-shaped with a depth or thickness less than its width / length (area). The master element preferably comprises a substrate body that either encloses or carries the master hologram. In preferred embodiments, the master element can comprise two, three, or more master holograms arranged in a layered structure. In preferred embodiments, the master hologram is located on a front surface of the substrate body. In embodiments, the master element can, for example, comprise a transparent top cover to protect a master hologram located between the cover and the substrate body. Preferably, the top cover has a refractive index selected such that light is transmitted through it, the master hologram, and the substrate body without significant reflection at the interfaces between the substrate body, master hologram, or cover. The top cover can, for example, be a transparent film or a glass layer. Preferably, the materials of the substrate body, the master hologram, and the cover are selected such that the differences in refractive index between the individual layers are small. This helps to avoid internal reflections. A “substrate body” within the meaning of the invention is preferably a three-dimensional block of material that carries or encloses the master hologram. The substrate body can be monolithic or non-monolithic. The substrate body is preferably rigid. This preferably means that the material exhibits no or only very slight mechanical deformation when external forces act upon it. It remains unchanged in its shape and structure, without flexibility or bending. Preferably, the substrate body is transparent. In some embodiments, the substrate body has several surfaces, including a front flat surface (front side) and a rear flat surface (back side). The front side preferably refers to the surface of the substrate or master element on which the master hologram is attached or implemented and which is preferably exposed. The back side is preferably the surface opposite the front side.The front and back sides are preferably arranged essentially parallel to each other. The master hologram is preferably aligned essentially parallel to the front side of the substrate. The preferred substantially parallel arrangement of the front and back surfaces preferably means that a surface normal of the front surface is also a surface normal of the back surface. Conversely, the preferably substantially parallel arrangement of the master hologram to the front surface of the substrate means that a surface normal of the master hologram is also a surface normal of the front surface of the substrate. Preferably, the master hologram is thus arranged substantially perpendicular to the surface normal of the front surface of the substrate. Those skilled in the art know that parallelism can refer not only to planar but also to curved surfaces. Curved surfaces are particularly parallel if they are curved in the same way and do not intersect, or would not intersect if they were arbitrarily enlarged, or would only intersect at infinity.In the case of a curved plane, the surface normal is preferably a surface normal of the tangent plane at the geometric centroid of the plane. For the purposes of the invention, the term “transparent” or “transparency” preferably refers to a property of a material which makes it essentially permeable to light. Preferably, a transparent material according to the invention is transmittable for at least part of the electromagnetic spectrum, preferably with a wavelength between 200 nm and 25 µm, more preferably between 200 nm and 3 µm, and particularly preferably between 400 nm and 780 nm. Particularly preferred is a transparent material, for example, a transparent substrate, that is transparent to light of a wavelength range used to illuminate the master hologram. A transparent material can also be colored such that it selectively emits light of one or more specific wavelengths. A "replication composite" within the meaning of the invention is preferably a multilayer material comprising at least one photosensitive layer, wherein the photosensitive layer comprises a photosensitive material, e.g., a photopolymer. The replication composite preferably also comprises one or more carrier films and / or protective films. Preferably, the replication composite is in the form of a photosensitive composite web. This is particularly suitable for a continuous replication process. A "photosensitive 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 provide a degree of flexibility, allowing it, for example, to be partially wound around a roller. 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, for example, be a photosensitive photopolymer or a dichroic gelatin.The photosensitive material can be photosensitive across the entire visible spectrum or wavelength-selective. The fact that the at least one polarization-sensitive element is located on the back side of the substrate preferably means that there is optical contact between the back side of the substrate and the polarization-sensitive element. Likewise, there is preferably optical contact between the individual polarization-sensitive elements in cases where more than one polarization-sensitive element is present. Similarly, there is preferably optical contact between the replication assembly and the front side of the master element. The front side of the master element preferably refers to the surface of the master element onto which an exposure is directed. In embodiments in which the master hologram comprises a transparent cover to protect it, the cover forms the front side. The fact that there is optical contact between the replication composite and the front side of the master element can therefore preferably also mean that the replication composite is located, for example, on the cover of the master element. In preferred embodiments in which the master hologram is applied, for example, as a master composite or master film to a substrate body, for example, by lamination, the front side of the master element can be formed by an outer layer or film of the master composite or film. In the latter case, optical contact is preferably formed between the master film and the replication composite. An “optical contact” within the meaning of the invention is preferably a relationship between components, wherein a beam of light is transmitted between the components without experiencing significant reflections, in particular without total internal reflection. Direct contact between the process components is possible, but not necessary. For example, an optical adhesive film or an optical liquid can be provided to mediate optical contact between the master element and the replication assembly or the polarization-sensitive element. If a gap exists between the surfaces of the components, it is preferably smaller than half a wavelength of the light used to illuminate the master hologram, so that no interference fields form at the interface between the surfaces.Preferably, neither reflection (especially total internal reflection) nor scattering occurs at the interface between the surfaces. In preferred embodiments, the optical contact is mediated by a detachable connection, which can be released, in particular, after exposure to light. The "front of the master element" preferably refers to the side of a master element with which the replication assembly is brought into optical contact and which contains the recorded interference pattern. In the replication of reflection holograms, this side is preferably illuminated directly from the front. In edge-lit holograms, the light is preferably directed onto the master hologram by means of a coupling element. Here, the light preferably first passes through a coupling element before striking the front of the master element. In both cases, the front of the master element is preferably the optically active surface responsible for generating the hologram. For the purposes of the invention, a "coupling element" is preferably a three-dimensional block of transparent material with a refractive index and dimensions configured to direct the exposure rays onto and / or away from the master holograms. The coupling element can preferably have any three-dimensional shape, in particular a cuboid, a wedge, a cylindrical, a prismatic, and / or a prismatic shape with a semicircular or semi-elliptical cross-section. The coupling element can preferably have various optically accessible surfaces. Preferably, at least one side surface or base surface and one underside or lateral surface of the coupling element are optically accessible. Preferably, an optically accessible surface of the coupling element is also low-reflective.It may be preferred that the optically accessible surface has a reflectance for visible light at a normal angle of incidence of less than 50%, preferably less than 40%, less than 30%, less than 20%, or less than 10%. In some preferred embodiments, an optically accessible surface has an antireflective coating (AR coating). This can increase the utilization of the incident light for illuminating the composite web. The "back side of the master element" preferably refers to the surface of the substrate body opposite the front side, which is preferably substantially parallel to the front side. However, the back side need not necessarily be a directly parallel surface, but can also be any opposite surface that forms an angle with a front side and represents a potential source of light reflections. However, it is preferable for the front and back surfaces to be parallel to each other. When replicating holograms, part of the light beam passing through the substrate can strike this opposite surface and be reflected. These reflections can cause interference effects in the photosensitive layer, which impair the quality of the hologram. The term "front-facing exposure" refers to the process by which light reaches the side of a master element where the replication composite is applied and the interference pattern is generated. In reflection holograms, the light typically falls directly onto this surface, while in edge-lit holograms, the light is directed to the front via a coupling element. Regardless of whether the light reaches the master element directly or via a coupling element, this side is preferably referred to as the "front" because it is the active optical surface on which the hologram is located, for example, laminated onto the substrate or protected by a cover. The term "front-side exposure" is therefore preferably applicable to both reflection holograms and edge-lit holograms, because it refers to the function of the front surface of the master element, which is crucial for capturing the interference pattern. Front-side exposure thus preferably describes the process of light acting on the functional layer of the hologram, regardless of whether the light strikes this surface directly or is coupled in via a coupling element. The term "replication beam" primarily refers to the light beam used in the replication of a reflection hologram to transfer the optical information stored in the master hologram to a new medium. This beam illuminates the master hologram, thereby copying the interference patterns contained within it onto the replication system. Part of the replication beam is diffracted by the master hologram, resulting in the reconstruction of the interference patterns stored in the master hologram and their transfer to the replication system. Simultaneously, another part of the replication beam passes through the substrate of the master hologram. The term "reflection beam" or "back-reflection beam" refers to the light beam that is reflected at the rear of the substrate after passing through it. The light thus first enters the transparent substrate, passes through it, and is reflected at the interface between the rear of the substrate and the surrounding air. This portion of the replication beam reflected at the rear of the substrate is preferably called a reflection beam or back-reflection beam. A "polarization-sensitive element" preferably refers to an optical component that influences the polarization properties of an incident light or exhibits different optical behavior depending on the polarization of the incident light. Light is an electromagnetic wave in which the electric and magnetic fields oscillate perpendicular to each other and to the direction of propagation. Polarization is known to preferably describe the orientation of the electric field relative to the direction of propagation of the wave. Polarization-sensitive elements are preferably characterized by exhibiting different optical behavior or modifying the oscillation direction of the electric field vector depending on its direction of oscillation. Polarization-sensitive elements can preferably be divided into two main categories: selecting and modifying elements. Selective elements are preferably used to select the polarization state of light. They function by transmitting or blocking light to varying degrees depending on its polarization direction. This is preferably achieved by the interaction of the oscillation direction of the electric field with the optical properties of the element, thereby allowing certain polarization planes to pass through while attenuating or completely eliminating others. The function of these elements is preferably based on their selective response to the orientation of the electric field vector. Examples of selecting elements are polarizers. A polarizer is preferably an optical element that selectively transmits light based on its polarization direction. A polarizer absorbs light waves whose electric field does not oscillate in the preferred polarization plane, while transmitting those whose polarization plane coincides with the polarizer's orientation. The operating principle of a polarizer is based on the interaction between the electric field of the light and the material structure of the polarizer. This interaction preferably results in only light waves with a specific electric field orientation being able to pass through. Modifying elements are preferably capable of selectively changing the polarization state of the light, preferably without significantly affecting the overall intensity of the light. Modifying elements preferably act by changing the phase relationship between the orthogonal components of the electric field. By modifying the phase relationships, the polarization properties of the light can be advantageously controlled. The function of modifying elements is preferably based on controlling the phase relationships between the electric field components, thereby allowing the polarization plane to be selectively rotated or the polarization properties of the light to be changed. Examples of modifying elements are wave delayers, for example λ / 2 wave delayers and / or λ / 4 wave delayers. A λ / 2 wave delay plate (also called a λ / 2 wave plate) preferably refers to an optical element that changes the polarization state of light by a phase shift of half a wavelength (180°) between two orthogonal components of the electric field. This phase shift preferably causes the direction of oscillation of the electric field vector to rotate, resulting in a rotation of the polarization plane. For linearly polarized light, this means that the polarization plane is rotated by a fixed angle, the magnitude of which depends on the orientation of the incident light relative to the optical axis of the plate. In a half-wave plate, the polarization state—that is, whether the light is linearly, circularly, or elliptically polarized—remains unchanged, while the direction of the polarization plane is altered. A λ / 4 wave delayer (λ / 4 wave plate), on the other hand, preferably generates a phase shift of one quarter of the wavelength (90°) between the orthogonal components of the electric field. This phase shift preferably converts linearly polarized light into circularly or elliptically polarized light, or circularly polarized light into linearly polarized light. The operation of the quarter-wave plate is preferably based on the delay of one of the two components of the electric field, thus changing the phase relationship between the orthogonal components. This can cause the electric field vector to either rotate continuously around the propagation axis (circular polarization) or to exhibit an elliptical oscillation (elliptical polarization).As in the case of the λ / 2 wave delayer, the exact effect depends on the relative alignment of the incident light to the optical axis of the wave delayer. If the linearly polarized light is polarized at an angle of 45° to the principal axes of the wave delay, this means that it can preferably be decomposed into equal components along the fast and slow axes. The 45° angle is therefore particularly preferred because, in this orientation, both components of the electric field have the same magnitude and couple equally strongly into the wave delay material. This results in the phase shift between the two components being maximally effective. However, if the angle deviates from 45°, the contributions of the electric field along the fast and slow axes are no longer equal. With a λ / 4 wavelength retarder, this can lead to the resulting components having different amplitudes and no longer summing completely to circular polarization—resulting in elliptically polarized light. With a λ / 2 wavelength retarder, the light preferably remains essentially linearly polarized, although the plane of polarization rotates. The further one moves away from an angle of 45°, the less evenly the two polarization components are distributed along the fast and slow axes, which changes the nature and extent of the polarization effects. At 0° or 90°, one of the two axes dominates, and the wavelength retarder has hardly any effect on the polarization. In preferred embodiments, the polarization-sensitive element can comprise one or more selecting or modifying elements. In a preferred embodiment of the invention, the at least one polarization-sensitive element is designed to prevent or reduce the formation of a grating in the photosensitive layer, wherein the grating may result from interference of a part of the replication beam reflected at the rear of the substrate body with the replication beam or the object beam diffracted by the reflection hologram. In a further preferred embodiment, the at least one polarization-sensitive element is designed to prevent or reduce the formation of a grating by influencing the polarization state of a portion of the replication beam reflected from the rear of the substrate body and / or by reducing the intensity of a portion of the replication beam reflected from the rear of the substrate body with respect to a polarization state. The influencing or reduction of the intensity of a portion of the replication beam reflected from the rear of the substrate body preferably relates to a case in which no polarization-sensitive element is present and a portion of the replication beam reflected from the rear of the substrate body could lead to a grating.For this purpose, the polarization-sensitive element can preferably influence or reduce both the portions of the replication beam that pass through the substrate body and could be reflected at its rear side, both on the path to the rear side and on the path back from the rear side of the substrate body. A grating preferably refers to an undesired interference pattern that can arise during the replication of holograms and can impair the quality of the resulting hologram. Gritting occurs, for example, when unwanted interference effects arise in addition to the desired interference pattern. In particular, reflections or scattering of light at interfaces of the substrate material, such as the rear side of the substrate body, can lead to such undesired interference patterns in the photosensitive layer.The unwanted reflections lead, for example, to phase shifts and superposition of the light waves, resulting in an additional interference pattern that can overlay and distort the actual hologram. Undesired reflections occur particularly when the replication beam passes through the substrate and Fresnel reflections occur at the rear of the substrate during the phase transition from the substrate material to the surrounding material (e.g., air). These reflected light components can again penetrate the photosensitive layer and interfere with the incident light within the photosensitive layer, potentially leading to an additional grating pattern that is not part of the intended hologram. A Fresnel reflection (or Fresnel refraction) is the reflection of a light beam at the interface between two media with different refractive indices, based on Fresnel's equations. When a replication beam passes through a transparent substrate, the Fresnel reflection occurs at the interface between the transparent material and the surrounding medium (e.g., air). It is therefore the partial reflection of a light beam at the interface between the transparent material and the surrounding medium after the light has passed through the substrate. This phenomenon is caused by the differences in the optical properties of the two media and, due to interference between the incident and reflected components of the replication beam, can lead to the formation of gratings in the photosensitive material. Interference grids are problematic because they can significantly degrade the optical quality of the replicated hologram. They impair the image sharpness and brightness of the hologram and can make the reconstructed image appear blurry or distorted. Furthermore, interference grids can also be reconstructed by other light sources not intended for hologram reconstruction (such as sunlight or room lighting). In such cases, disturbing rainbow-like effects can occur, for example, which impair the appearance of the hologram. To avoid the formation of interference grids, the at least one polarization-sensitive element on the back side of the substrate body is advantageously designed to reduce or prevent the formation of interference grids in the photosensitive layer. The reduction of interference grid formation is preferably achieved by the polarization element on the back side of the substrate body acting on the portion of the replication beam passing through the substrate body and / or the portion of the replication beam reflected from the back side of the substrate body. Preferably, the polarization-sensitive element can, for this purpose, comprise a selective element, for example, a polarizer, which reduces the intensity of light rays that are reflected back from the back side of the substrate body and could reach the photosensitive layer. In a further preferred embodiment, the polarization-sensitive element is formed by a polarizer, preferably a linear polarizer, wherein the polarizer is preferably configured to absorb electromagnetic radiation with a polarization of the replication beam. The term "formed" can preferably mean both "consisting of" and "comprising." That is, in preferred forms, the polarization-sensitive element can comprise a polarizer (and optionally further components to fulfill the desired function) or consist essentially of such a polarizer (without any further components being necessary to fulfill the desired function). Polarizers preferably filter light waves based on the direction of oscillation of the electric field. A linear polarizer, for example, preferably transmits the portion of light whose electric field oscillates parallel to the polarization axis and attenuates portions that oscillate at an angle to the axis. The transmitted portion of the electric field is preferably proportional to the cosine of the angle between the direction of oscillation of the electric field and the polarization axis. Light whose electric field oscillates perpendicular to the polarization axis is preferably completely absorbed. When interacting with unpolarized light, a linear polarizer preferentially filters out only those light waves whose electric field oscillates parallel to the polarization axis. The light transmitted through the polarizer is then linearly polarized, with the planes of oscillation that do not correspond to this orientation being absorbed by the polarizer. When polarized light strikes a linear polarizer, the result preferably depends on the relative orientation of the light's plane of polarization to the polarizer's axis of polarization: 1. Parallel alignment: Light already polarized in the same plane as the polarizer's axis of polarization is preferably transmitted substantially completely. 2. Perpendicular alignment: Light polarized perpendicular to the axis of polarization is preferably blocked substantially completely. 3. Angled alignment: Light polarized at any other angle is preferably partially transmitted, the intensity of the transmitted light depending on the square of the cosine of the angle between the light's polarization and the axis of polarization, according to Malus's formula I = I0cos2θ, where I is the intensity of the light after passing through the polarizer, I0 being the initials. intensity of the incident polarized light, and θ is the angle between the polarization plane of the incident light and the polarization axis of the polarizer. In order for a linear polarizer to preferably absorb all or almost all of the incident light of the replication beam, it is therefore preferred that the replication beam has a polarization that is oriented perpendicular to the polarization axis of the polarizer. Even an essentially perpendicular alignment of the replication beam's polarization to the polarization axis of the polarizer can still lead to high absorption. For example, the aforementioned Malus formula shows that with a deviation of 12.9° from a precise 90° orientation between the polarization of the replication beam and the polarization axis of the polarizer, an absorption of 95% is still achieved. It is advantageous if as high a proportion as possible of the incident replication beam is absorbed by the polarizer at the rear of the substrate body, as this minimizes the reflection of the portion of the replication beam passing through the substrate body from the rear of the substrate body. The portion of the replication beam that passes through the substrate body strikes the polarizer at the rear of the substrate body, and the replication beam preferably has a polarization that leads to absorption of the light by the polarizer. Because the polarizer is in optical contact with the rear of the substrate body, there is preferably no or hardly any (Fresnel) reflection at the interface between the rear of the substrate body and the polarizer.Instead, the portion of the replication beam passing through the substrate body is preferably absorbed essentially completely by the polarizer. Light reflected from the back of the substrate could cause interference with the incident replication beam in the photosensitive layer, leading to the formation of gratings during hologram replication. Therefore, it is preferable to minimize these reflections through absorption. The use of a polarizer, preferably a linear polarizer, on the back of the substrate is suitable for this purpose. Unlike, for example, a black, absorbing coating on the back of the substrate, a polarizer is also able to transmit light striking the substrate from the back. This can be desirable, for example, when a functionalization beam is to be applied from the back of the master element to introduce additional functionalities, such as holographic markings, into the photosensitive layer. Preferably, the functionalization beam has a substantially parallel polarization with respect to the polarization axis of the polarizer. Furthermore, this advantageously allows for possible pre-bleaching or pre-fixing of the replication composite from the back of the master element in order to stabilize the replicated hologram in the replication composite for the subsequent process steps. In a further preferred embodiment, the polarization-sensitive element is formed by a wave delay, which is preferably designed to influence, preferably rotate, the polarization of a part of the replication beam that is incident on the back of the substrate body and reflected from the back of the substrate body. Rotating the polarization plane of the portion of the replication beam reflected from the back of the substrate is advantageous because it also reduces or eliminates interference between the replication beam and the portion reflected from the back of the substrate within the photosensitive layer. Specifically, rotating the polarization plane of the portion reflected from the back of the substrate preferably results in the replication beam and its reflected portion no longer having the same orientation of their polarization planes, thereby reducing the formation and inscription of a (disturbing) interference pattern into the photosensitive composite. Interference between the replication beam and a light beam reflected from the back of the substrate would preferably be maximal if the polarization planes of the two interfering light waves are parallel to each other. This preferably means that the angle between their polarization planes is 0°. In this configuration, the electric field vectors are collinear, which preferably means that they oscillate in the same plane and direction. This configuration is preferably avoided by rotating the polarization of the portion of the replication beam reflected from the back of the substrate. When replicating holograms, it is desirable to preserve the original hologram's interference pattern in order to reconstruct a precise image of the original object. Interference between the reflected portion of the replication beam and the replication beam itself, or between the object beam diffracted by the reflected hologram and the resulting grating, can disrupt the finely tuned pattern. Partial interference, where the polarization planes are neither parallel nor perpendicular to each other, can also cause disruptive effects. At an angle of 90° between the polarization plane of the replication beam and the polarization plane of the light beam reflected from the back, interference between the two beams is preferably not possible. In such a case, no interference would occur between the two beams, regardless of their intensity. This configuration is particularly preferred. In another preferred embodiment, the polarization-sensitive element is formed by a wave delay, which essentially functions as a λ / 4 wave delay. (See Fig. 3) The term "formed" can preferably mean both "consisting of" and "comprising." That is, in preferred forms, the polarization-sensitive element can comprise a wave delay (and optionally further components to fulfill the desired function) or essentially consist of such a wave delay (without any further components being necessary to fulfill the desired function). A wave delay is an optical element used to shift the phase of a wave. A λ / 4 wave delay results in a phase shift of one quarter of the wavelength (λ / 4) between two orthogonal polarization components. Polarization components preferably refer to the components of the electric field vector of a light beam that are aligned along two orthogonal directions. When light strikes an anisotropic material, it can be decomposed into two independent polarization directions. These are often called ordinary and extraordinary rays. These components oscillate in perpendicular planes and are affected differently by the material, resulting in different phase velocities. The phase shift between these two components is crucial for changing the polarization state of the light, for example, from linear to circular polarization. The optical axis preferably denotes a characteristic direction in an anisotropic material along which light propagates without birefringence. In crystals, the optical axis is determined by the symmetrical arrangement of atoms and influences how light interacts within the crystal. Light incident parallel to the optical axis does not split into ordinary and extraordinary rays. In polymers, the optical axis can arise from the alignment of the polymer chains. When polymers are aligned through processes such as stretching, they develop anisotropic optical properties. The optical axis then lies along the alignment direction, and the material exhibits different refractive indices for light polarized parallel or perpendicular to this axis. A wave delay typically consists of a birefringent material. This means that light travels through the material at different speeds depending on the orientation of the polarization plane. In particular, the polarization components of a polarized incident light wave can exhibit a path difference due to different refractive indices and, consequently, different propagation speeds, depending on the polarization direction. The different propagation speeds for components of the light with a polarization parallel or perpendicular to an optical axis of the wave delay cause a phase shift between the two polarization components. The required thickness of a film or plate to function, for example, as a λ / 4 wave delay, depends on the difference between the two refractive indices (Δn) and the wavelength used (λ). The phase difference between the two polarization components after passing through the material is given by: For a λ / 4 wave delay, the phase difference should be [value]. From this it follows that... Rearranging the equation yields the above equation for a preferred material thickness for a λ / 4 wave delay. For a λ / 2 wave delay, the equation is correspondingly... A λ / 4 wave delay can convert linearly polarized light into circularly polarized light if the light is polarized at an angle of ±45° to the optical axis of the wave delay. Incident angles of linearly polarized light at +45° to the optical axis result in right-hand circular polarization, and incident angles of -45° result in left-hand circular polarization. If the light is already circularly polarized, it is converted into linearly polarized light. For polarization angles other than 45° to the optical axis of the wave delay, linearly polarized light can be converted into elliptically polarized light.At angles close to 0° or 90°, it is possible for the light to remain linearly polarized, but to undergo a phase shift. The delay of a wave delay depends not only on the material properties and thickness, but also on the wavelength of the light and the angle of incidence. The phase shift is preferably given by: where Δϕ is the phase shift, Δn is the difference in refractive indices for the two polarizations, d is the thickness of the material, and λ is the wavelength of the light. Preferably, for the same material thickness d, the phase shift is greater the shorter the wavelength. Conversely, for longer wavelengths, the delay preferably decreases. When light strikes a wave delay at an angle of incidence, the optical paths for the two polarizations are affected differently. Firstly, the effective refractive index changes with the angle of incidence according to the laws of anisotropy in birefringent media. This preferentially leads to a change in the phase difference depending on the angle of incidence. Secondly, the geometric path that the light travels through the wave delay also changes and becomes longer if the light does not strike the wave delay perpendicularly. This means that the effective thickness of the wave delay increases when the angle of incidence is greater than 0°. Therefore, the phase shift is generally altered when the light strikes at an angle, since the light ray travels a longer optical path in the material and the effective birefringence also depends on the angle of incidence. It may be preferred that the wave delay is designed to be optimized for an angle of incidence other than 0°. The design of a wave delay can preferably be adapted to the desired angle of incidence and the specific wavelength of the incident light, so that the wave delay also produces the desired phase shift even with a defined oblique incidence of the light. It may also be preferred to use a wave delay optimized for a wavelength Z and an angle of incidence of 0° for a different wavelength X at an oblique angle of incidence. In such a case, it is preferred that the following relationship is satisfied: where θ is the angle of incidence. Oblique incidence at an angle of incidence θ greater than 0° increases the optical path through the material, which compensates for the difference in wavelength and allows for an approximately constant phase shift. The angle of incidence (or angle of incidence) with respect to a plane, for example, the surface of a master element, preferably denotes the angle between the direction of propagation of an incident light ray and the surface normal of the plane or surface at the point of incidence. The surface normal corresponds to a normal vector that is perpendicular (90°) to the surface at the point of incidence, or, in the case of a curved plane, perpendicular to the tangent plane at the point of incidence. For example, if a light ray strikes the surface perpendicularly, the angle of incidence is therefore 0°. As the angle of incidence increases, the incident light ray approaches the surface, with an angle of incidence of 90° meaning that the incident ray strikes the surface tangentially. A function “essentially a λ / 4 wave delay” preferably describes such that, under realistic operating conditions for replication using the exposure beam, the λ / 4 wave delay causes a phase shift of approximately λ / 4 (90°) between the two orthogonal polarization components of a light beam. This can apply to a specific wavelength and a defined angle of incidence, or to a range of wavelengths, with the wave delay preferably being optimized for a mean wavelength in the latter case. Minor deviations in wavelength or angle of incidence can still lead to an approximate λ / 4 delay, as long as the deviations do not significantly impair the desired effect. When using a wave delay, the input parameters such as wavelength of the light, orientation of the polarization plane and angle of incidence can preferably be selected within certain tolerance ranges to ensure that the resulting phase shift remains within ±20%, preferably ±10%, of the ideal phase shift. Regarding wavelength, deviations of ±20% around the optimal wavelength are preferably acceptable to maintain the phase shift within the desired range. For example, a retarder optimized for 550 nm will provide a phase shift within ±20% in the wavelength range of 440 nm to 660 nm. With tighter tolerances of ±10%, the acceptable range is between 495 nm and 605 nm. The polarization plane is preferably oriented as close as possible to the ideal angle of 45° to the optical axis of the wave delay. A deviation of ±10° (for ±20% phase shift) or ±5° to ±6° (for ±10% phase shift) is preferably tolerable. The range for ±20% is preferably 35° to 55°, while the range for ±10% is preferably 40.5° to 49.5°. The angle of incidence of the light lies within a tolerance range in preferred designs. Although a theoretical calculation based solely on the path length would allow for larger deviations, it may be preferable to keep the angle of incidence within ±5° to ±20°, preferably ±10°, for retarders optimized for perpendicular incidence. For retarders optimized for an oblique angle of incidence (e.g., 30°), it may be preferable to allow smaller deviations, preferably not exceeding ±5° to ±10°, preferably not exceeding ±7°. A λ / 4 wave delay applied to the back of the substrate preferably converts an incident linearly polarized replication beam (i.e., the portion of the replication beam that passes through the master hologram undiffracted) into elliptically or, preferably, circularly polarized light, depending on the orientation of the polarization plane relative to the optical axis of the wave delay. Upon reflection of the light at the back of the master element, the direction of polarization is preferably reversed, meaning that circularly right-polarized light becomes circularly left-polarized light after reflection (or vice versa). When this reflected beam then passes through the λ / 4 wave delay again, it is once more converted back to linearly polarized light.Since the phase shift due to the two passages through the λ / 4 wave delayer is a total of 180° (i.e., λ / 2), the polarization plane of the resulting linearly polarized light is rotated by 90° relative to the original polarization plane. A 90° rotation of the polarization plane of the reflected portion of the replication beam preferably results in the polarization planes of the replication beam and the light beam reflected back from the substrate being rotated 90° relative to each other. This orientation of the polarization planes advantageously prevents the formation of interference gratings in the photosensitive layer. As explained above, deviations in wavelength or angle of incidence that lead to an approximate λ / 4 delay can further advantageously reduce the formation of interference gratings.Even if the reflected portion of the light and the original replication beam exhibit a rotation of the polarization planes of only essentially 90°, for example 80° or 100°, the efficiency of the interference and thus the formation of interference gratings is still reduced, albeit to a lesser extent than with a rotation of the polarization planes by exactly 90°: Depending on the (expected) intensity of the back reflection, conditions can be chosen that take into account the quality requirements for the holograms. In another preferred embodiment, the wave delay is essentially an achromatic λ / 4 wave delay. An achromatic wave delay is preferably an element that generates a constant phase shift between two orthogonal components of the electric field of a light beam over a wide range of wavelengths. In contrast to non-achromatic wave delays, whose delay depends on the wavelength of the incident light, an achromatic wave delay is preferably designed to provide a nearly constant delay independent of the wavelength. This is achieved, for example, by combining different materials or by using multiple wave delays of varying thicknesses. The use of an achromatic wave delay on the back of the substrate may be advantageous when replicating a hologram with more than one wavelength. An achromatic wave delay allows the desired polarization change to occur for several or all of the wavelengths used. In contrast, with a non-achromatic wave delay, the polarization change would differ for each wavelength. In particular, the use of an achromatic wave delay may be preferred for the replication of polychromatic holograms where exposure is carried out using different wavelengths, preferably for a red, green, or blue color (RGB). The wavelengths for exposure in the red, green, blue, or red color range may preferably be in the range of approximately 440 to 660 nm, such that an achromatic wave delay preferably has a substantially constant phase shift over a wavelength range of approximately 440 to 660 nm. Substantially constant preferably means a phase shift within a tolerance range of ± 20%, preferably ± 10% or less. Even when replication with only one wavelength is intended, it can be advantageous to use an achromatic wave delay, as these can, for example, better tolerate small angular deviations in the beam path if the beam does not strike the image at the angle for which the wave delay is optimized. Since achromatic delays consist of multiple materials, the angular dependence of the phase shift can often be compensated for more effectively than with simple delays. Furthermore, achromatic delays are preferably optimized to minimize dispersion effects, which leads to more consistent results even with slight deviations in the angle of incidence, even with a single wavelength. In a further preferred embodiment, the replication beam is linearly polarized, and the polarization-sensitive element is formed by a wave delay, preferably a substantially λ / 4 wave delay. This causes a portion of the replication beam reflected from the back of the substrate body to exhibit a polarization after passing through the wave delay, which is at an angle of substantially 90° to the polarization of the replication beam. Linearly polarized light is preferred for hologram replication because it produces stable and consistent interference patterns. Since the replication beam and the object beam originate from the same exposure beam, they essentially have the same polarization, resulting in optimal superposition and a clear interference pattern in the photosensitive layer. Linearly polarized light also has a fixed oscillation direction of the electric field, which means that the interference patterns are consistent. The use of linearly polarized light is also preferred to reduce or avoid the formation of interference gratings during hologram replication. Both the replication beam and the reflected portion of the replication beam have a defined plane of polarization. By using linearly polarized light and a λ / 4 wave delay on the back of the substrate, it is advantageously possible to rotate the plane of polarization of the portion of the replication beam reflected from the back of the substrate by 90° relative to the incident replication beam. This advantageously reduces or avoids the formation of unwanted interference patterns (interference gratings) caused by the reflection of the replication beam from the back of the substrate in the photosensitive layer, since light waves cannot interfere with each other when polarized at 90° to each other. This 90° orientation of the polarization planes of the incident, linearly polarized replication beam and the reflected beam is preferably achieved by using the λ / 4 wave delay on the back side of the substrate body. The portion of the replication beam that passes through the substrate body passes through the λ / 4 wave delay, which converts it into preferably circularly polarized light. After reflection at the back side of the master element, the now circularly polarized reflected portion of the replication beam again passes through the λ / 4 wave delay, where it is converted back into linearly polarized light, but with a polarization plane rotated by 90° relative to the replication beam. In a further preferred embodiment, the polarization-sensitive element comprises a polarizer, preferably a linear polarizer, and a wave delay, preferably a λ / 4 wave delay. The polarization-sensitive element is arranged on the rear side of the master element such that a replication beam first passes through the polarizer, preferably the linear polarizer, before entering the wave delay, preferably a substantially λ / 4 wave delay (see Fig. 4). Preferably, the replication beam is linearly polarized and the polarizer is formed by a linear polarizer which is configured to transmit electromagnetic radiation with a polarization of the replication beam. This arrangement advantageously allows the portion of the linearly polarized replication beam that passes through the substrate and remains undiffracted by the master hologram to first enter the polarizer. Downstream of the polarizer, the replication beam is converted into preferably circularly polarized light by the λ / 4 wave delayer. After reflection at the rear of the master element, the (back-)reflected portion of the replication beam (back reflection) passes through the λ / 4 wave delayer again, where it is converted back into linearly polarized light, but with a polarization plane rotated by 90° relative to the replication beam. The (back-)reflected portion of the light cannot pass further through the polarizer but is absorbed by it. This results in a back reflection.The amount of light reflected from the back of the master element that reaches the photosensitive layer is greatly reduced, or preferably completely avoided. Thus, advantageously, no or only very minimal unwanted interference from the reflected part of the replication beam can occur in the photosensitive layer. The combination of a polarizer and a λ / 4 wave delay advantageously also results in the polarizer absorbing any incorrectly polarized light from the replication beam. This embodiment thus advantageously avoids the formation of interference gratings essentially independent of the polarization of the replication beam. Components of the replication beam whose polarization is aligned parallel to the polarizer's transmission direction can pass through it. However, if reflected back from the substrate, they undergo a phase shift, as explained by the λ / 4 wave delay, which prevents interference with the replication beam in the photosensitive assembly. Components of the replication beam that are not aligned parallel to the polarizer are absorbed by it. Additionally, any scattered light, which might occur particularly at transitions, for example, at the interface between the wave delay and the surroundings, can also be absorbed by the polarizer. The combination of a linear polarizer, which is transparent to the polarization of the replication beam, and a λ / 4 wave delayer thus ensures a particularly efficient reduction, preferably prevention, of unwanted interference by the reflected part of the replication beam in the photosensitive layer. Another advantage of the combination of a linear polarizer and a λ / 4 wave delayer, for example compared to the exclusive use of a polarizer as a polarization-sensitive element on the back of the substrate body, is that this arrangement provides that the linear polarizer is transparent to the polarization of the replication beam. If only a polarizer were used as the polarization-sensitive element on the back side of the master element, the polarizer would not be transparent to the polarization of the replication beam. However, if the polarizer is transparent to the polarization of the replication beam, this advantageously allows additional optical functions, which are introduced into the photosensitive layer from the back side of the master element via a functionalization beam, to be implemented with the same polarization as the hologram replication. It may therefore be particularly preferred that the preferably linear polarization of the functionalization beam and the preferably linear polarization of the original replication beam are the same. In a further preferred embodiment, the polarization-sensitive element is designed as one or more films, preferably polymer films. The one or more films, preferably the one or more polymer films, are preferably applied directly to a back side of the substrate of the master element. Polarization-sensitive elements can comprise or consist of films or polymer films. For the purposes of the invention, films preferably refer to thin, flexible layers made of one or more materials. They can be designed to manipulate light. Examples include crystalline materials such as quartz or calcite, which are often used as wave retarders due to their natural birefringence. Nanostructured materials such as metals or dielectrics can also be used to achieve polarization changes or other optical effects. For example, thin-film polarizers based on such materials function by blocking or transmitting specific wavelengths of light through interference mechanisms. Polymer films preferably comprise plastic materials and are particularly advantageous due to their flexibility, low cost, and ease of processing. Polarizers can preferably be made from polyvinyl alcohol (PVA). In polarizing films, PVA molecules are preferably stretched and aligned in a specific direction and optionally colored, for example, with iodine or other dichroic substances, so that only light of a defined polarization direction is transmitted. Polycarbonate (PC) or polyethylene terephthalate (PET) are preferably used for wave retarders. These polymers are preferably processed to exhibit anisotropic properties, such as birefringence, and thus preferably to alter the phase of the light. Cellulose acetate can also be used advantageously in some cases. Polarization-sensitive elements consisting of foils typically have a small thickness of less than 1 mm, preferably less than 500 µm, and most preferably 50 - 300 µm. The use of films is advantageous because they offer low weight and high flexibility. Compared to solid optical components, they are easier to handle and often less expensive to manufacture. Their thin structure makes them ideal for simple application to the master element without significantly increasing its weight or volume. Polymer films offer additional advantages. They are particularly flexible, lightweight, and robust, making them more resistant to damage. Their production is especially cost-effective and can be carried out in large quantities. Therefore, they are also well-suited for mass-produced goods. Polymer films can also be easily coated to further improve properties such as polarization performance or scratch resistance. Another advantage of using films is that they can provide a particularly homogeneous optical contact with the substrate, preferably without additional adhesives, for example by means of lamination. In comparison, rigid polarization-sensitive elements are less easy to apply to the substrate in a surface-conforming manner and often require the application of buffer or adhesive layers. The films can preferably be laminated directly onto the back of the substrate body, preferably establishing optical contact between the two elements. A "lamination" within the meaning of the invention is preferably a method for joining two process components. For embodiments of the lamination, one of the two components (e.g., a substrate body of the master element) can preferably comprise a rigid, flat surface and preferably be fixed in place, while another of the two components (here preferably the film) is preferably flexible and can be moved or applied over the rigid, flat surface for the purpose of lamination. Optionally, the films are laminated onto a flat surface using a laminating roller, which preferably can exert pressure. Lamination can be carried out at room temperature (20°C). Optionally, the laminating roller can also be heated to a lamination temperature above room temperature, for example, selected from a range of 20°C to 200°C, preferably 20°C to 100°C. The lamination process (e.g., lamination pressure or lamination temperature) is preferably designed to ensure a gap-free bond between the film and the substrate. Additionally or alternatively, it is also possible to use an adhesive, preferably an Optically Clear Adhesive (OCA), to bond the film to the back of the substrate body, whereby, again preferably, an optical contact is established between the film and the substrate body by means of the OCA. By laminating the film and / or gluing the film to the substrate body, a homogeneous optical contact is preferably provided in such a way that back reflection at an interface between the substrate body and the polarization-sensitive element is avoided. It may also be preferred that the polarization-sensitive element is not in the form of a polymer film, but rather, for example, as a glass plate or disc, whose polarization-specific properties are realized, for example, by coatings with dichroic materials, by utilizing the intrinsic or induced birefringent properties of the glass, or by the precise joining of birefringent crystals. Such glass plates are preferably bonded or cemented onto the substrate body. In another preferred embodiment, the replication beam is linearly polarized, preferably s-polarized. S-polarized light (perpendicularly polarized light) preferably refers to a form of polarized light that is defined solely in connection with reflection or refraction at interfaces. In this case, the electric field of the light ray oscillates perpendicular to the plane of incidence. The plane of incidence is defined by the direction of propagation of the light ray and the normal to the surface upon which the light strikes. For S-polarized light, the direction of oscillation of the electric field is preferably parallel to the surface upon which the light strikes (for example, the front face of the master element). S-polarized light can generally be used for the replication of holograms, especially reflection holograms, because it exhibits a higher diffraction efficiency compared to p-polarized light (where the electric field oscillates parallel to the plane of incidence). S-polarized light preferably shows stronger diffraction over a wide range of incidence angles. This preferably leads to a stronger interference signal and thus to a more precise interference pattern in hologram replication. In a further preferred embodiment, the light source comprises one or more lasers, preferably one or more monochromatic lasers with a wavelength in the infrared, visible, and / or ultraviolet range. In preferred embodiments, the master element is exposed to electromagnetic radiation with a wavelength in one or more wavelength ranges, preferably a red, green, and / or blue wavelength range. The light source can be, for example, 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. For example, ruby ​​lasers, He-Ne lasers, Ar+ lasers, Kr+ lasers, He-Cd lasers, and / or Nd3+: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 provide an RGB laser.Various laser types, particularly solid-state lasers, can also 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 a nonlinear optical crystal. Preferably, an optical parametric oscillator with a selection of converter crystals, particularly nonlinear optical crystals, can be used for fine-tuning the wavelength. A three-wave mixture (f_pumpe = f_signal + f_idler) can preferably be employed. By changing the frequency f_signal and / or f_idler, laser wavelengths can be generated over a very broad wavelength range. This includes, in particular, the entire visible and infrared regions of the electromagnetic spectrum.To fine-tune the generated wavelength, the optical path length of the resonator in the optical parametric oscillator (OPO) can also be changed to adjust the input frequency f_pumpe. In preferred embodiments, an OPO can first generate light in the infrared range, which can then be converted, for example, by second harmonic generation (SHG) into light in the desired visible range (VIS). In preferred embodiments, the front face of the master element is illuminated with light of two or more colors to replicate a polychromatic master hologram. A “polychromatic hologram” is preferably a hologram configured to diffract electromagnetic beams of different wavelengths, the different wavelengths preferably differing 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 can comprise a plurality of channels, each channel corresponding to a different wavelength and / or a different range of wavelengths. Each channel can be the result of replicating a master hologram configured for the respective wavelength or range of wavelengths. For example, the channels can correspond to different colors, such as red, green, and blue light.For the purposes of the invention, a color preferably refers to 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, wherein a maximum or peak is present at a central wavelength characteristic of the color. For blue light, for example, the central wavelength may be approximately 460 nm, while green light may have a central wavelength of approximately 530 nm, or red light a central wavelength of approximately 630 nm. When exposing the master element with two or more colors, it is preferred to use an achromatic polarization-sensitive element. Alternatively, it may be preferable to design the polarization-sensitive element for a mid-wavelength within the wavelength range of the exposure. For example, in the case of RGB exposure with blue (approx. 460 nm), green (approx. 530 nm), or red (approx. 630 nm), the polarization-sensitive element (e.g., a wavelength retarder) may be designed for a wavelength between 500 nm and 550 nm, preferably approx. 530 nm. In another preferred embodiment, the front and back sides of the substrate body are essentially parallel planes. The substrate body preferably has the shape of a disk and / or a cuboid. If the front and back of the substrate body are essentially parallel planes, the use of a polarization-sensitive element on the back of the substrate body is particularly advantageous. With an essentially parallel orientation of the front and back of the substrate body, a back reflection of the replication beam can disadvantageously occur at the back of the substrate body, which can interfere with the replication beam in the photosensitive layer in the region of the hologram to be replicated with particularly high efficiency. This would result in particularly pronounced interference gratings, which, however, can be effectively avoided or reduced by using a polarization-sensitive element. In a further preferred embodiment, the substrate body is formed from a material that is transparent to a wavelength range used for illuminating the master element. The material is preferably an optical polymer, preferably selected from the group comprising polymethyl methacrylate (PMMA), polycarbonate (PC), cycloolefin polymers (COP), cycloolefin copolymers (COC), and / or an optical glass, preferably selected from the group comprising borosilicate glass, fused silica, B270, N-BK7, N-SF2, P-SF68, P-SK57Q1, P-SK58A, and / or P-BK7. Preferably, the substrate body of the master element can be formed from a material which is an optical plastic, preferably selected from the group: polymethyl methacrylate (PMMA), polycarbonate (PC), cycloolefin polymers (COP) and cycloolefin copolymers (COC) and / or is 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. Preferably, both the substrate body and any covering of the master element have a refractive index between 1.4 and 1.7. Preferably, the photosensitive composite 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 of the replication composite is also between 1.4 and 1.7. In preferred embodiments, the polarization-sensitive element also preferably has a refractive index between 1.4 and 1.7. If the polarization-sensitive element is an anisotropic material, preferably with different refractive indices along orthogonal axes, it is preferred that at least one of the refractive indices, preferably both refractive indices or an average of the refractive indices, lies in the range between 1.4 and 1.7. In a further preferred embodiment of the invention, the refractive index difference between the polarization-sensitive element and the substrate body, preferably the rear surface of the substrate body, is no more than 0.2, more preferably no more than 0.1, and more preferably no more than 0.05. These low refractive index differences provide a particularly smooth optical transition between the components and prevent or minimize Fresnel reflection at the interface between the substrate body and the polarization-sensitive element. If the polarization-sensitive element comprises two or more components or layers, it is preferred that the aforementioned small tolerances for a refractive index difference between the layer or component of the polarization-sensitive element facing the rear surface of the substrate body and the rear surface of the substrate body are maintained. If the polarization-sensitive element comprises an anisotropic material with different refractive indices along orthogonal axes, particularly adjacent to the rear substrate body, it is preferred that the aforementioned small tolerance ranges for a refractive index difference apply for at least one refractive index along an axis of the anisotropic material or for an average of the refractive indices of the anisotropic material. If optical contact between the polarization-sensitive element and the substrate body is mediated by an optical adhesive film, the above-mentioned preferred tolerance range applies to the refractive indices for the transition from the substrate body to the optical adhesive film and / or for the transition from the optical adhesive film to the polarization-sensitive element. In another preferred embodiment, the master hologram is a reflection hologram. Reflection holograms preferably refer to reflective holograms that diffract light arriving from the light source. Preferably, the direction of incidence of the replication beam (preferably an incident light beam from the light source) and the object (in this case, the master hologram) can be arranged on opposite sides of the replication assembly. A replication beam penetrates the replication assembly and is then diffracted by the master hologram back into the photosensitive layer of the replication assembly (object beam). In the photosensitive layer of the replication assembly, the replication beam and object beam thus superimpose to generate the replicated hologram. The master hologram can preferably be applied to a surface of the master element or be integrated into the substrate. The light source for a reflection hologram can be arranged such that the replication beam strikes the replication assembly in a desired direction, preferably in a direction required for subsequent reconstruction. In a preferred embodiment, the light source is oriented with respect to the master element such that the replication assembly is located between the light source and the master element. For example, the light source can be aligned with respect to the master element such that the replication beam strikes the replication assembly in a predetermined direction. The replication beam is preferably at least partially diffracted back into the replication assembly by the master element in the form of an object beam. Thus, the replication beam and the object beam enter the replication assembly from opposite sides and interfere in its light-sensitive layer to replicate the hologram. In a further preferred embodiment, before, during, or after exposure of the master element for replication of the master hologram into the photosensitive layer, a rear side of the substrate body is exposed with a functionalization beam. This introduces a further optical function into the photosensitive layer, for example, a holographic inscription. A functionalization beam preferably refers to an additional light beam that strikes the replication assembly from the back of the substrate body (i.e., through the transparent material). This beam could be used before, during, or after the replication process to introduce additional information, such as security features or additional details like markings. Advantages of a functionalization beam coming from the rear include, for example, the avoidance of interference with the main image. The term "main image" preferably refers to the hologram replicated from the master hologram into the replication network. Instead, additional information, such as holographic labels, can be precisely integrated into the hologram. Furthermore, this approach allows for the independent editing of different layers of the hologram. This separation of layers can advantageously increase the hologram's complexity and make counterfeiting more difficult. Security features, such as hidden or hard-to-detect details, can be placed so deeply within the hologram that they are only visible under specific conditions, thus improving protection against tampering and counterfeiting. In a further preferred embodiment, the functionalization beam, upon incidence into the photosensitive layer, exhibits a polarization, preferably a linear polarization, which corresponds to the polarization, preferably the linear polarization, of the replication beam. It is advantageous that the linear polarization of the functionalization beam matches the polarization of the original replication beam. This ensures that the main image and the elements added by the functionalization beam appear uniform in the finished hologram under the same lighting conditions. Differences in representation, diffraction, or color reproduction are thus avoided, resulting in a coherent and harmonious hologram. In a further preferred embodiment, at least one additional wave delay, preferably a substantially λ / 4 wave delay and / or a substantially λ / 2 wave delay, is located at a distance from the rear of the substrate body.In this process, the back side of the substrate body is preferably exposed to a linearly polarized functionalization beam, which passes through the additional wave delay before entering the substrate body via the rear-side polarization-sensitive element. By means of an additional wave delay mounted at a distance from the back of the substrate body, such as an essentially λ / 4 wave delay, and / or an essentially λ / 2 wave delay, a functionalization beam introduced from the back of the master element can be influenced before entering the master element. For example, it may be preferred that the functionalization beam passes through a λ / 4 plate before entering the master element (see Fig. 5). This is preferred if the functionalization beam is linearly polarized. The linearly polarized light is converted into circularly polarized light by the λ / 4 wave delay, which is spaced from the back of the master element. This is advantageous, for example, if a λ / 4 wave delay is mounted on the back of the master element as a polarization-sensitive element. Upon passing through the λ / 4 wave delay, the circularly polarized functionalization beam is converted back into a linearly polarized functionalization beam. If the polarization-sensitive element has a linear polarizer between the substrate body and the λ / 4 wave delay, in addition to the λ / 4 wave delay, the resulting linear polarization of the functionalization beam is preferably directed towards it in such a way that it can pass through the polarizer. Other arrangements may also be preferred to allow the functionalization beam to pass through the arrangement of polarization-sensitive elements attached to the back of the master element. In cases where, for example, the polarization of the functionalization beam is oriented parallel to a polarizer mounted on the back side of the substrate body of the master element, it may be preferred for the functionalization beam to pass through a λ / 2 wave delayer and a λ / 4 wave delayer. In such a case, the λ / 2 wave delayer would preferably rotate the plane of polarization by 90°, and the λ / 4 wave delayer would convert the linearly polarized light into circularly polarized light. Upon entering the back side of the master element, the now circularly polarized light would pass through another λ / 4 wave delayer, which would convert the functionalization beam back into linearly polarized light. The plane of polarization is preferably rotated such that the functionalization beam can pass through the polarizer on the back side of the master element. In a further aspect, the invention relates to a master element for carrying out a method according to the invention for replicating a hologram. The master element comprises a substrate body and at least one master hologram, which is located on the front side of the master element, wherein at least one polarization-sensitive element is mounted on a rear side of the substrate body of the master element. In a further aspect, the invention relates to a device for replicating a hologram by means of a method according to the invention, wherein the device has an exposure module comprising the following elements: • a master element comprising a substrate body and at least one master hologram, • a light source for exposing the master element, wherein the exposure module is configured to bring a replication compound into optical contact with a front face of the master element and is further configured to irradiate the master element from the front face by means of the light source in order to replicate the master hologram in a photosensitive layer of a replication compound. A polarization-sensitive element is provided on a rear face of the substrate body of the master element. A person skilled in the art will recognize that all embodiments and all advantages disclosed with respect to the method according to the invention also apply to the master element or the device. For example, it has been disclosed for the method that the polarization-sensitive element preferably comprises a selecting element (e.g., a polarizer) and / or a modifying element (e.g., a wave delay). A person skilled in the art will recognize that it is therefore also preferred for the master element and the device according to the invention to provide such polarization-sensitive elements, thereby achieving the same advantages with regard to the avoidance or reduction of interference grids. The device for replicating a hologram by means of a method according to the invention preferably has an exposure module comprising a master element, a substrate body and at least one master hologram, as well as a light source for exposing the master element. The exposure module is configured to bring a replication assembly into optical contact with a front face of the master element and is further configured to irradiate the master element from the front face using the light source in order to replicate the master hologram into a light-sensitive layer of a replication assembly, wherein a polarization-sensitive element is mounted on a rear face of the substrate body of the master element. In a preferred embodiment of the invention, the exposure module comprises a light source. It is preferable for the device to further include a lamination module. A lamination module preferably brings the photosensitive material into mechanical contact with the master element and ensures sufficient optical contact with the master holograms. By laminating, rather than simply placing the photosensitive material onto the master elements, a particularly homogeneous contact between the master element and the photosensitive material can be achieved, effectively preventing bubbles or wrinkles. Using a composite web of the photosensitive material allows this to be repeated efficiently, so that the composite web flows while the master element preferably remains stationary. In particular, a removable lamination makes it possible to remove the replication composite without damage or residue and to continue the process through further stations in a production line. It may be preferred that the composite liner or replication liner be an adhesive composite liner, meaning that it has an adhesive surface on at least one side. The exposure module may be designed to apply the adhesive composite liner to the master element. Preferably, applying an adhesive composite layer to the surface of another optical component means that at least a section of the adhesive composite layer assumes the shape of the surface onto which it is applied. For example, if the adhesive composite layer is applied to a flat optical component, the adhesive composite layer will preferably assume the shape of the flat surface. It is further preferred that applying an adhesive composite layer to the surface of an optical component creates a continuous contact between the optical adhesive layer or the photosensitive composite layer and the surface or a section thereof, which may require section-by-section deformation of the optical adhesive layer or the photosensitive composite layer. For this purpose, pressure can be exerted on the adhesive composite layer in preferred embodiments. The exposure module can preferably direct light onto the composite web and / or master elements to replicate a master hologram in the master element into the composite web. The exposure module can also include one or more actuators or motors configured to adjust the angle of the light source and / or move the light source along a path. The light source can be configured, for example, as a scanning light source. The light source can also be equipped with an axis along which it can slide. The exposure module can also include one or more mirrors, the position of which can also be adjustable, to direct the path of a light beam onto the master elements and / or the composite track. The exposure module can also include one or more lenses, for example, a diverging lens, to widen a light beam onto the master element. It can also be advantageous if the exposure module is equipped with means to adjust the intensity of the light falling from the light source onto the master elements and / or the composite track. In preferred embodiments, the device according to the invention further comprises a fixation module configured to cure the replicated hologram within the replication composite. The fixation module preferably allows the replication composite to be transferred quickly and with minimal deflection from the exposure module. The fixation module may preferably include a light source emitting wavelengths in the visible or ultraviolet range and / or a heat treatment source. In the case of fixation with a UV lamp (also referred to as a "UV emitter" within the meaning of the invention), the lamp is preferably adjusted to emit intense UV radiation between 315 and 400 nm onto the photopolymer layer. In the case of fixation with a visible light source, the lamp is preferably adjusted to emit intense radiation between 380 and 750 nm onto the photopolymer layer. The fixing module can be located in the same housing as the exposure module or in a separate housing. The device preferably also includes a control unit, which is preferably configured for controlling the components of the device for carrying out the method according to the invention, for example the alignment and / or control of the wavelength and / or alignment of a light source for exposing the master element, the control of one or more actuators to bring the master element into contact with the replication assembly, or the control of unwinding or winding and / or transport rollers to guide the replication assembly through the exposure module for repeated replication of a master hologram. The term "control unit" preferably refers to any computing unit with a processor, processor chip, microprocessor, or microcontroller that enables automatic control of the device's components, e.g., the rotational speed of an unwinding roller, winding roller, laminating roller, transport roller, or master element, or the adjustment of a photopolymer composition, coating thickness, lamination temperature, lamination pressure, lamination pressure force, orientation and / or scanning speed of a light source, fixation intensity, etc. The control unit components can be conventionally configured or individually tailored for the specific implementation. Preferably, the control unit comprises a processor, memory, and computer code (software / firmware) for controlling the device's components. The term "control unit" preferably refers to any computing unit with a processor, processor chip, microprocessor, or microcontroller that enables automatic control of the device's components, e.g., movement of the light source, control of different wavelengths, control of one or more actuators to bring the master element into contact with the replication assembly, or control of unwinding, rewinding, and / or transport rollers to guide the replication assembly through the exposure module for repeated replication of a master hologram, lamination temperature or pressure, fixation intensity, etc. The control unit components can be configured conventionally or individually for the specific implementation.Preferably, the control unit comprises a processor, a memory and a computer code (software / firmware) for controlling the components of the device. The control unit may also include a programmable circuit board, a microcontroller, or other device for receiving and processing data signals from the device's components, such as sensor information related to light intensity, angle of incidence, or other sensory information. The control unit preferably further includes a computer-usable or computer-readable medium, such as a hard drive, 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 device's components may be written in any programming language or model-based development environment, such as, but not limited to, C / C++, C#, Objective-C, Java, Basic / VisualBasic, MATLAB, Python, Simulink, StateFlow, LabVIEW, or Assembler. The term "control unit is configured to" perform a specific operation, such as adjusting the angle of incidence, for example by moving optical elements such as mirrors, prisms, or lenses, may include custom or standard software installed on the control unit that initiates and regulates the operational steps. In preferred embodiments, the device can include sensors, for example goniometers, for measuring the angle of incidence of the replication beam. In these cases, the control unit is preferably configured to receive data from the sensors, for example goniometers, and optionally evaluate it, for example, to compare the measured values ​​with reference values. The control unit can also preferably be configured to adjust process parameters, for example, the position of optical elements, based on an evaluation of the data. Terms such as essentially, approximately, about, about, nearly, almost, etc. preferably describe a tolerance range of less than ± 20%, preferably less than ± 10%, particularly preferably less than ± 5% and particularly less than ± 1%, and include the exact value. Detailed description The invention will be explained in more detail below using examples and illustrations, without being limited to these. Brief description of the images Fig. 1 Schematic representation of the occurrence of interference gratings due to the Fresnel reflection on the back side of the master hologram in the prior art. Fig. 2 Schematic representation of possible functions, such as pre-bleaching or other optical functionalization, which are performed from the back side of the master element in the prior art. Fig. 3 Schematic representation of the method according to the invention according to a preferred embodiment in which a λ / 4 wave delay is mounted on the back side of the master element and forms a polarization-sensitive element. Fig. 4 Schematic representation of the method according to the invention according to a further preferred embodiment in which a polarizer and a λ / 4 wave delay form a polarization-sensitive element and are mounted on the back side of the master element.5 Schematic representation of the method according to the invention in a further preferred embodiment, in which a polarizer and a λ / 4 wave delay form a polarization-sensitive element and are located on the back side of the master element. Furthermore, a λ / 4 wave delay is located spaced from the back side of the master element, through which an additional functionalization beam passes. Detailed description of the illustrations Figure 1 schematically shows a representation of the Fresnel reflection that can occur during the replication of holograms on the back side of a master element in the prior art. The master element comprises a substrate body 5 and, on the front side, the master hologram 6, which can, for example, be laminated directly onto the substrate body 5 or protected by a cover glass 4. Also located on the front side of the master element is the replication assembly 3, which is preferably in optical contact with the front side of the master element. The replication beam 1 strikes the front side of the master element. It passes through the replication assembly 3 and the cover glass 4 and strikes the master hologram 6, where it is diffracted into the replication assembly 3 according to the diffraction conditions.In the light-sensitive replication assembly 3, the optical information of the master hologram 6 is recorded as an interference pattern through the interference of the replication beam 1 and the object beam diffracted by the master hologram 6. These patterns form the basis for the resulting replica, which, under appropriate illumination, can reconstruct the stored image in the application. However, an undiffracted portion of the replication beam 1 can pass through the master hologram 6 and also through the rest of the substrate body 5. At the rear of the substrate body 5, a Fresnel reflection occurs at the interface with the surroundings. A Fresnel reflection (or Fresnel refraction) preferably refers to the reflection of a light beam at the interface between two media with different refractive indices, based on Fresnel's laws.When the replication beam 1 passes through the transparent substrate body 5, the Fresnel reflection occurs at the interface between the transparent material and the surrounding medium (e.g., air). The beam 2 reflected from the rear of the substrate body 5, which can also be called the back reflection, passes through the substrate body 5 again and can interfere with the replication beam 1 or the object beam diffracted by the reflection hologram in the photosensitive layer of the replication assembly 3. This can lead to the formation of unwanted interference gratings 14. Interference gratings 14 are problematic because they can significantly degrade the optical quality of the replicated hologram. They can impair the image sharpness and brightness of the hologram, as well as lead to unwanted diffraction properties, and can make the reconstructed image appear blurry or distorted. Figure 2 schematically shows the introduction of additional functionalization beams 12 or pre-bleaching beams 13 from the back side of the master element. Backward irradiation with functionalization beams 12 may be preferred, for example, to introduce holographic markings into the replication assembly 12. Pre-bleaching the photosensitive material immediately following exposure can be advantageous to avoid distortions of the holographic pattern when the lamination is removed or during further transport of the replication assembly 3 to a fixing station. For example, applying an absorbing black coating to the back of the device to prevent a Fresnel effect would be disadvantageous for both the rear application of functionalization beams 12 or beams for pre-bleaching 13. Applying an absorbing black coating can reduce the intensity of a reflected light beam and also reduce the appearance of interference gratings. However, this measure disadvantageously prevents rear exposure for additional functionalization or pre-bleaching. Figure 3 schematically shows a preferred embodiment of a method according to the invention. The structure of the master element corresponds to that in Figure 1, except that a polarization-sensitive element 11, in this case formed by a λ / 4 wave delay 8, is additionally attached to the rear side of the master element. The replication beam 1 entering the master element has an s-polarization 15 and passes through the replication assembly 3 and the cover glass 4 onto the master hologram 6. The portion of the replication beam 1 not diffracted by the master hologram 6 passes through the substrate body 5 and exits the rear side of the substrate body 5 through a λ / 4 wave delay 8 and is reflected at the interface between the master element and the environment. A λ / 4 wave delay 8, applied to the back of the substrate body 5, preferably converts the incident linearly polarized replication beam 1 (i.e., the portion of the replication beam that passes through the master hologram undiffracted) into elliptically or, preferably, circularly polarized light, depending on the orientation of the polarization plane relative to the optical axis of the wave delay. Upon reflection of the light at the back of the substrate body 5, the direction of polarization is preferably reversed, meaning that circularly right-polarized light becomes circularly left-polarized light after reflection (or vice versa). When this reflected beam then passes through the λ / 4 wave delay 8 again, it is once more converted back to linearly polarized light.Since the phase shift caused by the two passages through the λ / 4 wave delayer 8 is a total of 180° (i.e., λ / 2), the polarization plane of the resulting linearly polarized light is rotated by 90° relative to the original polarization plane. Therefore, after passing through the λ / 4 wave delayer 8 twice, the reflected part 2 of the replication beam 1 exhibits a p-polarization 16 in this exemplary case. The polarization planes of replication beam 1 and the reflected part 2 of the replication beam 1 are thus essentially perpendicular to each other. Advantageously, beams polarized by 90° relative to each other cannot form interference patterns with each other in the replication system 3. This advantageously reduces or avoids the formation of interference gratings. Figure 4 schematically shows a preferred embodiment of a method according to the invention. The structure of the master element corresponds to that shown in Figure 3, except that a polarizer 7 is additionally arranged between the substrate body 5 and the λ / 4 wave delayer 8. In the preferred embodiment, the polarization-sensitive element thus comprises a polarizer 7 and a λ / 4 wave delayer 8. The polarization-sensitive element is arranged on the rear side of the master element 10 such that a replication beam 1 first passes through the polarizer 7 before entering the λ / 4 wave delayer 8. The replication beam 1 entering the master element 10 passes through the replication assembly 3 and the cover glass 4 onto the master hologram 6. The portion of the replication beam 1 not diffracted by the master hologram 6 passes through the substrate body 5 and first emerges from the rear of the substrate body 5 through the polarizer 7. The polarization of the replication beam 1 (here: an s-polarization 15) is chosen such that the replication beam 1 can pass through the polarizer 7. Downstream of the polarizer 7, the replication beam 1 is converted into preferably circularly polarized light by the λ / 4 wave delayer 8. After reflection at the back of the master element 10, the reflected part of the replication beam (back reflection) 2 passes through the λ / 4 wave delayer 8 again, which converts it back into linearly polarized light, but with a polarization plane rotated by 90° to the replication beam 1 (here p-polarization 16). The polarizer 7, which is optimized for the polarization axis of the replication beam 1 (here: s-polarization 15), preferably absorbs the reflected portion of the replication beam 2 completely, since its polarization plane, after passing through the λ / 4 wave delayer 8 twice, is now perpendicular to the polarization plane of the polarizer 7 (here: p-polarization 16). This significantly reduces, or preferably completely eliminates, back reflection or the amount of light 2 reflected from the rear of the master element that reaches the photosensitive layer. Thus, advantageously, no or only very minimal unwanted interference from the reflected portion of the replication beam can occur in the photosensitive layer. Furthermore, the combination of polarizer 7 and λ / 4 wave delayer 8 advantageously also absorbs any incorrectly polarized light from the replication beam 1 directly from the polarizer 7.The embodiment shown can thus advantageously avoid the need for interference grids essentially independently of the polarization of the replication beam 1. Figure 5 schematically shows a preferred embodiment of a method according to the invention. The setup corresponds to that of Figure 4, except that an additional λ / 4 wave delayer 8 is provided, spaced apart from the rear of the master element. This additional λ / 4 wave delayer 8, located at a distance from the rear of the master element, can convert a linearly polarized exposure beam 18 (e.g., a functionalization beam) into a circularly polarized exposure beam 17 (e.g., a functionalization beam). Since another λ / 4 wave delayer 8 is provided on the rear of the master element, the circularly polarized exposure beam 17 is converted back into a linearly polarized exposure beam 18 (e.g., a functionalization beam) upon entering the master element.The linear polarization 18 of the functionalization beam 12 preferentially matches the polarization direction of the polarizer that the functionalization beam 12 next passes through. The functionalization beam 12 thus preferentially passes through the substrate body 5 and reaches the replication assembly 3, so that it can advantageously introduce further optical functions, such as markings, into the replication assembly 3. Reference symbol list 1 Replication beam 2 Back-reflected part of the replication beam (back reflection) 3 Replication assembly 4 Cover glass 5 Substrate body 6 Master hologram 7 Polarizer 8 λ / 4 wave delayer 9 λ / 2 wave delayer 10 Master element 11 Polarization-sensitive element 12 Functionalization beam 13 Pre-bleaching irradiation 14 Interference grating 15 s-polarization 16 p-polarization 17 Circular polarization 18 Linear polarization

Claims

A method for replicating a hologram comprising the following steps: a. providing a master element comprising a substrate body (5) and at least one master hologram (6), b. providing a replication assembly (3) comprising at least one photosensitive layer on a front side of the master element, c. exposing the front side of the master element comprising the master hologram (6) by means of a replication beam (1) of a light source to replicate the hologram into the photosensitive layer, characterized in that at least one polarization-sensitive element (11) is provided on a back side of the substrate body (5) of the master element. Method according to the previous claim characterized in that the at least one polarization-sensitive element (11) is designed to prevent or reduce the formation of a grating (14) in the photosensitive layer, wherein the grating (14) may result from interference of a part (2) of the replication beam (1) reflected at the rear of the substrate body (5) with the replication beam (1). Method according to one or more of the preceding claims, characterized in that the at least one polarization-sensitive element (11) is designed to prevent or reduce the formation of a disturbance grating (14) in order to influence a polarization state of a part (2) of the replication beam (1) reflected from the back of the substrate body (5) and / or to reduce an intensity of a part (2) of the replication beam (1) reflected from the back of the substrate body (5) with respect to a polarization state. Method according to one or more of the preceding claims characterized in that the polarization-sensitive element (11) is formed by a polarizer (7), preferably by a linear polarizer, wherein the polarizer (7) is preferably configured to absorb electromagnetic radiation with a polarization of the replication beam (1). Method according to one or more of the preceding claims characterized in that the polarization-sensitive element (11) is formed by a wave delay (8, 9) which is preferably designed to influence, preferably rotate, the polarization of a part of the replication beam incident on the back of the substrate body and reflected from the back of the substrate body (5). Method according to one or more of the preceding claims characterized in that the polarization-sensitive element (11) is formed by a wave delay (8, 9) which essentially functions as a λ / 4 wave delay (8). Method according to the preceding claim characterized in that the wave delay is essentially an achromatic λ / 4 wave delay (8). Method according to one of the preceding claims characterized in that the replication beam (1) is linearly polarized (18) and the polarization-sensitive element (11) is formed by a wave delay (8, 9), preferably a substantially λ / 4 wave delay (8), causing a part (2) of the replication beam (1) reflected from the back of the substrate body (5) to have a polarization which is rotated by an angle of substantially 90° relative to the polarization of the replication beam (1). Method according to one or more of the preceding claims, characterized in that the polarization-sensitive element (11) comprises a polarizer (7), preferably a linear polarizer, and a wave delayer (8, 9), preferably substantially a λ / 4 wave delayer (8), wherein the polarization-sensitive element (11) is arranged on the rear side of the master element such that a replication beam (1) first passes through the polarizer (7), preferably the linear polarizer, before the replication beam (1) enters the wave delayer (8, 9), preferably substantially a λ / 4 wave delayer (8). Method according to the preceding claim characterized in that the replication beam (1) is linearly polarized (18) and the polarizer (7) is formed by a linear polarizer which is configured to transmit electromagnetic radiation with a polarization of the replication beam (1). Method according to one or more of the preceding claims characterized in that the polarization-sensitive element (11) is designed as one or more films, preferably polymer films, wherein the one or more films, preferably the one or more polymer films, are preferably applied directly to a back side of the substrate (5) of the master element. Method according to one or more of the preceding claims characterized in that the replication beam (1) is linearly polarized (18), preferably s-polarized (15). Method according to one or more of the preceding claims characterized in that the light source comprises one or more lasers, preferably one or more monochromatic lasers with a wavelength in the infrared, visible and / or UV range and / or exposure of the master element with electromagnetic radiation with a wavelength in one or more wavelength ranges, preferably a red, green and / or blue wavelength range. Method according to one or more of the preceding claims characterized in that the front and back of the substrate body (5) are parallel planes, wherein the substrate body (5) preferably has the shape of a disk and / or a cuboid. A method according to one or more of the preceding claims, characterized in that the substrate body (5) is formed from a material which is transparent for a wavelength range with which exposure of the master element is carried out, wherein the material is preferably an optical plastic, preferably selected from a group comprising polymethyl methacrylate (PMMA), polycarbonate (PC), cycloolefin polymers (COP), cycloolefin copolymers (COC) and / or an optical glass, preferably selected from the group comprising borosilicate glass, quartz glass, B270, N-BK7, N-SF2, P-SF68, P-SK57Q1, P-SK58A and / or P-BK7. Method according to one or more of the preceding claims characterized in that the master hologram (6) is a reflection hologram. Method according to one or more of the preceding claims characterized in that, before, during or after exposure of the master element for replication of the master hologram (6) into the photosensitive layer, a back side of the substrate body (5) is exposed with a functionalization beam (12) which introduces a further optical function into the photosensitive layer, for example a holographic inscription. Method according to the previous claim characterized in that the functionalization beam (12) has, upon incidence into the photosensitive layer, a polarization, preferably a linear polarization, which corresponds to the polarization, preferably the linear polarization, of the replication beam (1). Method according to one of the two preceding claims characterized in that at least one additional wave delay (8, 9), preferably a substantially λ / 4 wave delay (8) and / or a substantially λ / 2 wave delay (9), is spaced apart from the back of the substrate body (5), wherein the back of the substrate body (5) is exposed with a preferably linearly polarized functionalization beam (12), which passes through the additional wave delay (8, 9) before entering the substrate body (5) via the rear polarization-sensitive element (11). Master element for an implementation of the method for replicating a hologram according to one of the preceding claims, wherein the master element comprises a substrate body (5) and at least one master hologram (6) which is located on a front side of the master element, characterized in that at least one polarization-sensitive element (11) is provided on a back side of the substrate body (5) of the master element. Device for replicating a hologram by means of a method according to any one of the preceding claims 1-19, wherein the device comprises an exposure module comprising: • a master element comprising a substrate body (5) and at least one master hologram (6), • a light source for exposing the master element, wherein the exposure module is configured to bring a replication assembly (3) into optical contact with a front face of the master element and is further configured to irradiate the master element from the front face by means of the light source in order to replicate the master hologram (6) into a photosensitive layer of a replication assembly, characterized in that a polarization-sensitive element (11) is provided on a rear face of the substrate body (5) of the master element.

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