Device for exposure of a master hologram to a freeform wave

Abstract

The invention relates to a device for replicating a holograms from a master hologram. The device preferably comprises an intensity-modulating unit and a beam-shaping unit, wherein the intensity-modulating unit is configured for adjusting an intensity distribution of a light wave with which the beam-shaping unit is subsequently irradiated. The beam-shaping unit is configured for generating a free-form wave having a spatially variable angular distribution for exposure of the master hologram, wherein the angular distribution of the free-form wave can be specified by the intensity distribution of the light wave from the intensity-modulating unit, which is incident on the beam-shaping unit.

Description

[0001] DEVICE FOR EXPOSURE A MASTER HOLOGRAM WITH A FREEFORM SHAFT

[0002] DESCRIPTION

[0003] The invention relates to a device for replicating a hologram from a master hologram. The device preferably comprises an intensity-modulating unit and a beam-shaping unit, wherein the intensity-modulating unit is configured for setting the intensity distribution of a light wave with which the beam-shaping unit is subsequently irradiated. The beam-shaping unit is configured for generating a free-form wave with a spatially varying angular distribution for illuminating the master hologram, wherein the angular distribution of the free-form wave can be predetermined by the intensity distribution of the light wave from the intensity-modulating unit incident on the beam-shaping unit.

[0004] Background and state of the art

[0005] The invention relates to the field of hologram replication.

[0006] 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 any substrate. The holographic properties preferably exploit the wave nature of light, particularly coherence and interference effects. Both the intensity and phase of the light are taken into account.

[0007] 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).

[0008] 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.The master element is illuminated with a coherent light source to replicate the image from the master hologram into a photosensitive composite. For mass production, the photosensitive composite can be provided in the form of a movable photosensitive web comprising a photosensitive material and one or more support or protective layers. The photosensitive web is preferably transported through various workstations to produce the HOEs.

[0009] During exposure, the composite path is placed on a surface of the master element. To create a reflection hologram, the coherent light can traverse the composite path before reaching the master hologram, from which it is reflected back into the composite path. The object and reference rays interfere with each other in the photosensitive material and form the replicated hologram. The replication process is sensitive to changes in the exposure angle, intensity, wavelength, etc., which must be adjusted according to the optical function of the master hologram. Therefore, the exposure of the master holograms must be carried out with specific wavelengths and angles of incidence, depending on the optical function of the master holograms.

[0010] German patent application DE 10 2022 115 595 A1 discloses a replication method for producing a hologram copy and a corresponding exposure device. For this purpose, a master hologram is irradiated with radiation. The illuminated master hologram forms a light field. A copy carrier is irradiated by the light field and may comprise a glass plate. The glass plate can be used to hold the copy carrier. The glass plate can also be used as a beam trap. A reference beam is used to expose the copy carrier. To enable the reference beam to penetrate the copy carrier without reflections, the copy carrier is in contact with a contact element. Due to the elasticity of the contact element, adhesion occurs between the contact element and the copy carrier as the contact element moves towards the copy carrier.

[0011] Especially for the replication of master holograms with more complex optical functions, it may be necessary to reconstruct different positions of the HOE with an exposure beam from different angles.

[0012] For this purpose, it may therefore be necessary to expose the master hologram to radiation using a free-form wave. Such a free-form wave can direct the radiation to different locations on the master hologram at different angles, so that a local angular distribution of a reconstruction wave can be provided, depending on the optical function of the master hologram.

[0013] Such a local angular distribution of a reconstruction wave could be generated mechanically by physically moving an exposure source and / or an optical element. However, this requires a high degree of synchronization between the light source and the master hologram, as well as tight mechanical tolerances.

[0014] The configured freeform waveform, which is mechanically implemented, is typically adapted to a theoretical optical function of the master hologram and the HOE to be produced. If the actual optical properties of the master hologram deviate from the theoretical optical function, the defined freeform waveform will not be able to efficiently replicate all areas of the master hologram, which can lead to quality defects in the produced HOE.

[0015] A deviation in the optical function of the master hologram from its intended properties can occur for various reasons. In particular, the manufacturing of the master hologram, up to its use in replication, involves a number of process steps that can alter the optical function of the originally produced master. For example, the polymerization of a photopolymer during the creation of the master hologram can be accompanied by shrinkage in local areas. The shrinkage of the photosensitive material, e.g., due to partial drying and an increase in its density as a result of polymerization, can reduce the wavelength required to generate an interference pattern recorded within it. Further deviations in the properties of the master hologram can occur due to temperature fluctuations during the manufacturing process or during the bonding or embedding of the master hologram into a master element.Similarly, over time, the master element may degrade, which can also alter its optical function.

[0016] Adapting the freeform waveform to the changing actual properties of the master hologram is complex using mechanical freeform waveform generation methods and often requires hardware configuration changes, thus interrupting the replication process. Furthermore, considering the potential use of the same exposure module to produce different HOEs using different master holograms, a simpler method for modifying the freeform waveform would be desirable.

[0017] Therefore, there is a need for a device for the rapid and precise adjustment of a freeform waveform for the exposure of a master element in a replication process. Furthermore, there is a need for a device for the rapid and precise modification of a freeform waveform for the exposure of different master elements in an exposure module, preferably with a reduction in the required mechanical interventions within the exposure module.

[0018] Object of the invention

[0019] The object of the invention is to provide a device that enables the rapid and precise adaptation of a freeform wave to the current properties of a master hologram for the exposure of a master element. Preferably, the device allows the adaptation of the freeform wave without replacing the components of an exposure module. A further object of the invention is to provide a device that enables the rapid modification of the freeform wave for the exposure of different master elements, preferably without replacing the components of the exposure module.

[0020] Summary of the invention

[0021] The problem is solved by the features of the independent claim. Advantageous embodiments of the invention are described in the dependent claims.

[0022] In a first aspect, the invention relates to a device for replicating a hologram in a replication assembly with an exposure module, wherein the exposure module comprises at least one light source and a support means for receiving a master element comprising a master hologram to be replicated. The exposure module is configured to bring the replication assembly into optical contact with the master element, while the light source exposes the master hologram to a region of the replication assembly in order to obtain a replicated hologram.

[0023] The exposure module is designed for exposing the master hologram with a free-form wave exhibiting a spatially varying angular distribution. For this purpose, the exposure module preferably comprises an intensity-modulating unit and a beam-shaping unit. The intensity-modulating unit is configured to adjust the intensity distribution of a light wave from the light source illuminating the beam-shaping unit. The beam-shaping unit is configured to generate the free-form wave with the spatially varying angular distribution, the angular distribution being predetermined by the intensity distribution of the light wave incident on the beam-shaping unit.

[0024] The invention utilizes the fact that combining an intensity-modulating unit with a beam-shaping unit generates a precise, rapidly adaptable, and modifiable freeform wave. Furthermore, the freeform wave is generated in a compact manner with as few moving components as possible. By reducing the number of moving parts that would need to be synchronized, the exposure module becomes less prone to errors and can be used for the same replication series or for different replication series without exchanging optical or mechanical components. This ensures an efficient replication process with high flexibility and reduced downtime.

[0025] The use of an intensity modulation unit, which selectively directs exposure beams from the light source through the beam-shaping unit toward the master hologram, enables the targeted spatial distribution of light. This spatial distribution can encompass areas with varying light intensities, including dark areas. By using an intensity modulation unit to generate a spatial distribution, there is no need to move one or more light sources to the different areas of the master hologram that require illumination at different angles or intensities. Simultaneously, such an intensity modulation unit can be easily controlled electronically to vary the generated light distribution without moving or replacing the unit itself.This can advantageously be done without any time delay or interruption, and without the need to reposition mechanical or optical components, which can lead to positioning errors. In this way, potentially complex mechanical light manipulation techniques for generating a free-form waveform can be replaced by fast and reliable digital exposure adjustment. In particular, this makes it possible to adjust the free-form waveform used to expose the master hologram as needed.

[0026] Simultaneously, the use of an intensity-modulating unit in combination with the beam-shaping unit allows different areas of the master hologram to be illuminated with light at different angles of incidence without having to reposition or rotate the light source(s) or intermediate optical components. This is because the beam-shaping unit can be configured to transmit the light rays with or without deflection, depending on the position of the light rays transmitted from the intensity-modulating unit to the beam-shaping unit. In other words, the beam-shaping unit can translate the position of an incoming light ray into the angle of an outgoing light ray.

[0027] This can advantageously be achieved mechanically in a static manner, i.e., without moving the optical components of the beam-shaping unit. For example, the shape of one or more lenses of the beam-shaping unit can determine the relationship between the position of a light beam entering the one or more lenses and the angle at which the same light beam exits the one or more lenses. This known relationship allows the light distribution via the intensity-modulating unit to be adjusted accordingly, e.g., to adapt the free-form waveform to the actual properties of a changing mast element (e.g., due to external influences or degradation) or to adapt the free-form waveform for illuminating a new mast element with different reconstruction requirements.

[0028] With the aid of the device according to the invention, the beam-shaping unit and the intensity-modulating unit in the exposure module can be used for the replication of a multitude of different series of master holograms without requiring complex repositioning or changes to the hardware configuration. In particular, no adjustment of the position of the beam-shaping unit and the intensity-modulating unit relative to each other or relative to the master hologram is required to change the free-form wave. Positioning errors are inherently avoided.

[0029] A further advantage of the invention is that the combination of the intensity-modulating unit and the beam-shaping unit can accelerate the exposure and processing time for the individual holograms. Unlike known methods where a light source or one or more optical components move to generate the freeform wave, in preferred versions the entire freeform wave can be generated simultaneously for the entire hologram or larger sections thereof. For this purpose, the intensity-modulating unit can preferably be illuminated over a large area to generate a desired intensity and angular distribution.

[0030] The device according to the invention thus enables the rapid and reliable generation of a free-form wave that is quickly adaptable, preferably digitally.

[0031] For the purposes of this invention, the term "light wave" preferably refers to the electromagnetic rays emitted with an electromagnetic wavefront from one or more light sources. The electromagnetic rays of the light wave may also be referred to herein as "light rays" or "exposure rays," regardless of whether they have a wavelength in the visible range.

[0032] 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 pm, 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 pm, preferably in the near-infrared range, i.e., preferably from 780 nm to 3000 nm, particularly from 780 nm to 1400 nm.

[0033] 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.

[0034] 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. Examples include ruby ​​lasers, He-Ne lasers, Ar lasers, and others. + - Lasers, Kr^-lasers, He-Cd lasers and / or Nd 3+:YAG lasers can be used. These or other laser types can be combined with an optical parametric oscillator to generate coherent beams of different wavelengths. Lasers with different wavelengths can also be combined, for example, to provide an RGB laser.

[0035] 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 + fjdler) can preferably be employed. By changing the frequency f_signal and / or fjdler, 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 can also be changed in order to adjust the input frequency f_pumpe as well.

[0036] In the context of the invention, a wide variety of light sources, preferably coherent, can be used. Narrowband light sources are preferred, preferably monochromatic light sources, which can include lasers as well as light-emitting diodes (LEDs), optionally in combination with monochromators.

[0037] In the context of the invention, a "free-form wave" is preferably an electromagnetic wavefront comprising electromagnetic rays for the exposure of a master hologram, wherein different rays or sections of the wavefront form different angles of incidence onto the master hologram. Such different angles of incidence preferably comprise a difference of at least 1°, more preferably at least 2°, more preferably at least 5°, and more preferably at least 10°. Different rays or sections of the wavefront may also have different intensities or wavelengths.

[0038] It may be preferred that the freeform wave, upon striking the master hologram, comprises a spatial distribution of angles, intensities, and / or wavelengths that is irregular and / or asymmetrical, such that it cannot be generated by a single regular optical component such as a point light source, a regular concave mirror, or a parabolic mirror. The freeform wave thus preferably differs from collimated, diverging, or random illumination. The freeform wave for illuminating the master hologram can be generated simultaneously over a large area, section by section, or by scanning.

[0039] For the purposes of the invention, an "intensity-modulating unit" is preferably a unit for selectively changing the local intensity of exposure beams passing through it, particularly to generate a spatial intensity distribution. Preferably, the intensity-modulating unit has a shape adapted to the shape of the exposed surface of the mast element. Preferably, the intensity-modulating unit has a planar, preferably flat, shape with a significantly larger width or length (area) than thickness (depth), for example by a factor of 5, 10, 20, 100 or more.

[0040] The surface area of ​​the intensity-modulating unit can preferably correspond to the surface area of ​​the master hologram. However, it may also be preferred to choose a smaller or larger surface area for the intensity-modulating unit. The intensity-modulating unit can preferably be a light-modulating surface or screen, in particular a light-modulating pixel array. Preferably, the intensity-modulating unit generates an intensity distribution of the exposure radiation in a surface or an image that includes darker and lighter areas and, in combination with a downstream beam-shaping unit, as explained in more detail herein, can be used to generate the free-form wave.

[0041] For the purposes of the invention, a "beam-shaping unit" is preferably a unit for selectively changing the angles of exposure beams to generate a free-form wave for illuminating a master hologram. The beam-shaping unit is preferably configured to receive intensity-modulated exposure beams from the intensity-modulating unit and redirect them toward the master element. Preferably, the beam-shaping unit comprises one or more optical components that redirect electromagnetic beams depending on their point of impact on the optical components. For example, the beam-shaping unit can comprise a functional hologram and / or an array of (micro)lenses. Preferably, the beam-shaping unit also has a shape adapted to the shape of the exposed surface of the mast element.Preferably, the beam-shaping unit has a planar, preferably flat, shape, with a significantly larger dimension in width or length (area) than thickness (depth), for example by a factor of 5, 10, 20, 100 or more.

[0042] The surface area of ​​the beam-shaping unit can preferably correspond to the surface area of ​​the master hologram. However, it may also be preferred to choose a smaller or larger surface area for the beam-shaping unit. The beam-shaping unit preferably has a planar shape analogous to a screen and is preferably arranged between the intensity-modulating unit and the support element of the master element, wherein the beam-shaping unit is preferably oriented parallel to the intensity-modulating unit.

[0043] For the purposes of the invention, an "exposure module" is preferably a section of a device for replicating holograms, wherein the exposure module comprises at least one light source for exposing a master hologram and a carrier for receiving a master element. The master element is preferably interchangeable so that the exposure module can be used for different replication series. Furthermore, the exposure module preferably comprises an input and an output for a replication network, wherein the input and output are preferably located in a light-tight housing.

[0044] A "master element" is preferably a three-dimensional unit that comprises or carries at least one master hologram in a mold. A master element can also comprise a plurality of master holograms, for example, 2, 3, 5, or more. Preferably, the master element has a length and a width that are at least equal to the length and width of the master hologram. Preferably, the master element is at least twice, more preferably five times, and particularly preferably at least twenty times as high as the master hologram.

[0045] The master element preferably comprises a substrate body that either encloses or carries the at least one master hologram. In embodiments, the master element can, for example, include a transparent top cover to protect a master hologram located between the cover and the substrate body. Preferably, the top cover is also transparent. The top cover can, for example, be a transparent film or a layer of glass.

[0046] The master element preferably has the form of a cuboid block, a plate, 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), for example by a factor of 2, 5, 10, or more.

[0047] In some embodiments, the master element or its substrate body can also have the shape of a general cylinder, i.e., it has a constant cross-section of any shape, e.g., square, polygonal, elliptical, or circular. The ends of the substrate body, which have the shape of the cross-section, can be referred to as the "base." The elongated surface of the substrate body, i.e., in particular the surface along a longitudinal side located between the two ends, can be referred to as the "shell surface." In some embodiments, the shape of an axially rotatable circular cylinder is preferred. For the purposes of the invention, the shape of a rotatable cylindrical substrate body or master element, preferably a vertical cylinder, can also be referred to as a "cylinder."It may be preferred that the master element be designed to be axially rotatable as a roller, with exposure during replication preferably occurring along a line scan, as explained in more detail below. Preferably, the substrate body of the master element may be made of a material that is an optical polymer, preferably selected from the group consisting of polymethyl methacrylate (PMMA), polycarbonate (PC), cycloolefin polymers (COP), and cycloolefin copolymers (COC), and / or an optical glass, preferably selected from the group consisting of borosilicate glass, fused silica, B270, N-BK7, N-SF2, P-SF68, P-SK57Q1, P-SK58A, and P-BK7.

[0048] Preferably, both the substrate body and any covering of the master element have a refractive index between 1.4 and 1.6.

[0049] The choice of material for the substrate body may depend on the desired angle of exposure or refractive index.

[0050] It may be preferred that the surface or covering of the master element comprises glass, PC, TAC, or PMMA. The surface material may be in the form of a film or sheet to protect the master hologram. However, the surface or covering material may also be the material of the substrate body itself and, for example, have a cuboid or cylindrical shape.

[0051] A “substrate body” within the meaning of the invention is preferably a three-dimensional block of material that carries or encloses the master hologram. Preferably, the substrate body is transparent. In some embodiments, the substrate body has several surfaces, including a flat surface that may be horizontally oriented. In some embodiments, the substrate body is prismatic, i.e., it has a constant cross-section of any shape, e.g., square or polygonal.

[0052] For the purposes of the invention, the term "transparent" or "transparency" preferably refers to a property of a material that makes it essentially permeable to light. Preferably, a transparent material within the meaning of the invention is transmissive for at least a portion of the electromagnetic spectrum, preferably with a wavelength between 200 nm and 25 pm, and particularly preferably between 400 nm and 780 nm. Particularly preferably, a transparent material, for example, a transparent substrate, is permeable to light within a wavelength range used to illuminate the master hologram. A transparent material can also be colored to selectively transmit light of one or more specific wavelengths.

[0053] 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 more wavelengths. 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, e.g., in the form of a local difference in the refractive index. Such a master hologram is considered a so-called "volume hologram." The light transmitted by a DOE can be transformed into almost any desired distribution by diffraction and subsequent propagation.This could be, for example, an image, a logo, a text, an interference pattern, or something similar.

[0054] 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.

[0055] A "light-sensitive 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 pm. The composite web comprises a light-sensitive material. Preferably, the composite web encloses the light-sensitive material between two transparent carrier films that have a similar refractive index to the light-sensitive material. Preferably, the refractive index of the carrier films and the light-sensitive material is between 1.4 and 1.6. The light-sensitive material can, for example, be a light-sensitive photopolymer or a dichroic gelatin.The photosensitive material can be photosensitive across the entire visible spectrum or wavelength-selective.

[0056] 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 or even total internal reflection. Direct, material-bonded contact between the process components is possible, but not necessary. To mediate an optical contact between the master element and the replication composite, in particular the composite web, an optical adhesive film or an optical liquid can, for example, be provided. If a gap exists between the surfaces of the components, it is preferably smaller than half a wavelength of the light used for illuminating 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 a preferred embodiment of the invention, the device is configured so that the intensity-modulating unit is coherently irradiated with the light wave. The use of a coherent light wave is particularly advantageous for generating holographic diffraction patterns through the interference of object and reference beams in the replication system, since electromagnetic waves have a fixed phase relationship. The holographic diffraction patterns therefore take into account the wavelength, angle of incidence, and phase of the light.

[0057] Coherence preferably refers to the property of optical waves whereby a fixed phase relationship exists between two wave trains. As a consequence of this fixed phase relationship, spatially stable interference patterns can arise. With regard to coherence, a distinction can be made between temporal and spatial coherence. Spatial coherence preferably represents a measure of a fixed phase relationship between wave trains perpendicular to the direction of propagation and is present, for example, for parallel light rays. Temporal coherence preferably represents a fixed phase relationship between wave trains along the direction of propagation and is present, in particular, for narrowband, preferably monochromatic, light rays.

[0058] The coherence length preferably refers to 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 refers to the time the light takes to travel a coherence length.

[0059] In a further preferred embodiment of the invention, the device is configured such that the intensity-modulating unit is irradiated with the light wave, wherein the light wave has a maximum divergence of up to 3°, preferably up to 1°, and particularly preferably up to 0.5°. The light wave for irradiating the intensity-modulating unit is preferably collimated.

[0060] The use of collimated beams, particularly as a collimated wavefront, allows for precise control of the angle of incidence of the exposure beams on the master hologram. The collimated beams emitted by the light source preferably all have essentially the same direction or angle. When such collimated beams pass through the intensity-modulating unit, they preferably maintain this direction. Thus, the collimated beams exiting the intensity-modulating unit are preferably guided to the beam-shaping unit with known incidence positions and angles. This allows for a particularly precise determination of how (e.g., with what degree of deflection) intensity-modulated collimated beams are manipulated by the beam-shaping unit.This allows the required intensity-modulating function of the intensity-modulating unit to be specifically determined and adjusted, particularly with regard to a desired free-form wave, taking into account the intensity distribution required to generate such a free-form wave using the beam-shaping unit.

[0061] In a further preferred embodiment of the invention, the light wave is directed substantially orthogonally onto the intensity-modulating unit. An orthogonal direction of the electromagnetic rays of the light wave onto the intensity-modulating unit at a substantially orthogonal angle of incidence preferably leads to a substantially orthogonal exit of the intensity-modulated rays from the intensity-modulating unit. If the beam-shaping unit is aligned parallel to the intensity-modulating unit, a correspondingly orthogonal angle of incidence of the intensity-modulated rays onto the beam-shaping unit can be ensured. Firstly, with an orthogonal angle of incidence, the intensity-modulating unit can modulate the intensity of the exposure rays particularly effectively.Secondly, essentially orthogonal angles of incidence of the intensity-modulated beams onto the beam-shaping unit allow for a particularly wide range of angles that can be generated by the beam-shaping unit. This is especially true when the beam-shaping unit is formed by an array of lenses.

[0062] In other embodiments, it may also be preferred to irradiate the intensity-modulating unit non-orthogonally, preferably, however, at a constant angle of incidence across the surface of the intensity-modulating unit. Such irradiation can be particularly advantageous if a downstream beam-shaping unit comprises a diffractive element or hologram, for example, to provide a lens function. Often, diffractive elements or holograms, as beam-deflectoring components of a beam-shaping unit, do not require orthogonal angles of incidence, but rather hologram-specific angles of incidence, depending on the requirements, for example, from 20° to 70°, preferably from 30° to 60°.In these cases, it may be preferable to irradiate the intensity-modulating unit at such a non-orthogonal angle, with the beam-shaping unit preferably being parallel to the intensity-modulating unit.

[0063] In other embodiments, it may also be preferred to direct the light wave substantially orthogonally onto the intensity-modulating unit, wherein, however, the intensity-modulating unit is not aligned parallel to the beam-shaping unit, or an optical arrangement between the intensity-modulating unit and the beam-shaping unit provides light deflection at a constant angle. Such an embodiment may be particularly preferred if a downstream beam-shaping unit requires a non-orthogonal angle of incidence. Advantageously, however, an orthogonal passage of the light wave through the intensity-modulating unit with corresponding orthogonal angles of entry and exit can still be ensured for increased effectiveness of the intensity modulation.The required non-orthogonal angle of incidence on the beam-shaping unit can instead be determined by an angle between the intensity-modulating unit and the beam-shaping unit, or by an additional optical arrangement. In a further preferred embodiment of the invention, the device comprises a control unit configured to drive the intensity-modulating unit to generate an intensity distribution of the light wave according to a desired spatially varying angular distribution of the free-form wave. In this way, the free-form wave can be easily adapted to changes in the properties of a mast element or to a replacement of the mast element, with the adaptation being possible directly and without the need to replace any optical or mechanical components.

[0064] The term "control unit" preferably refers to any computing unit comprising a processor, processor chip, microprocessor, or microcontroller that enables automatic control of the device's components, e.g., the voltage across a pixel or subpixel of the intensity-modulating unit, the distance between the beam-shaping unit and the master element, the movement of a scan mirror, the switching on / off of a light source, or the temporal modulation of a light source, etc. The control unit's components may be conventionally configured or individually tailored for the specific implementation. Preferably, the control unit includes a processor, memory, and computer code (software / firmware) for controlling the device's components.

[0065] The control unit may also include a programmable circuit board, a microcontroller, or other device for receiving and processing data signals from the device components, for example, from sensors relating to the intensity distribution on the intensity-modulating unit, the free-form wave, and other relevant 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 components may be written in any programming language or model-based development environment, such as C / C++, C#, Objective-C, Java, Basic / VisualBasic, MATLAB, Python, Simulink, StateFlow, LabView, or Assembler, or others.

[0066] The term "control unit is configured to" perform a specific operation, such as setting an intensity distribution of the intensity modulating unit, may include custom or standard software installed on the control unit that initiates and regulates these operational steps.

[0067] Preferably, the control unit sets local transmission and / or reflection via the intensity-modulating unit. For reflection, it is preferred to be able to set pixel-wise reflection between at least two states, reflection onto the master hologram to be illuminated, or reflection onto a position outside the master hologram, e.g., onto an absorber. Preferably, the transmission can be set between at least two values, e.g., 0% and 100%, and it is preferred that intermediate transmission values ​​can also be set by the control unit. In this way, the device according to the invention can not only set the angles of the free-form wave by specifying the positions at which exposure rays strike the beam-shaping unit, but also their intensity on the master hologram.

[0068] In a further preferred embodiment of the invention, the intensity-modulating unit comprises a light-modulating pixel array. Preferably, the individual pixels of the pixel array are electronically controllable to adjust the intensity distribution of the light wave. Such a pixel array can advantageously generate any image from a collimated wavefront and can be provided with any suitable image resolution. Furthermore, a pixel array is particularly suitable for electronic or digital control. In this way, highly complex freeform waves can be generated to expose a master hologram. The resulting replicated hologram can be reconstructed using a complex wavefront. Preferably, the light-modulating pixel array can have a plurality of pixels, for example, 100, 500, 1000, 5000, 10000, 100000, 1,000,000 or more pixels.

[0069] In a further preferred embodiment of the invention, the intensity-modulating unit configured as a pixel array has a pixel pitch no greater than 500 pm, preferably no greater than 250 pm, more preferably no greater than 100 pm, and even more preferably no greater than 75 pm. Such a pixel pitch enables the production of high-quality, high-resolution holograms. This is because the smaller pixel pitch increases the resolution of the free-form wave. As a result, the electromagnetic beams strike the master hologram at a local angle that more precisely corresponds to the angle at which the master hologram most efficiently diffractes the radiation. The master hologram generates a more strongly diffracted object beam, thus improving the efficiency of the diffraction pattern that arises in the replication network through interference of the reference beam with the object beam.

[0070] For the purposes of the invention, a “pixel pitch” is preferably the distance between the center of a pixel and the center of a nearest pixel in a pixel array.

[0071] In a further preferred embodiment of the invention, the light-modulating pixel array is selected from the following group: LCD (liquid crystal display), micromirror array, preferably DMD, LCoS, and an aperture array. Such pixel array devices are particularly compact and configurable for control by the control unit, so that their intensity modulation functions can be varied quickly and precisely as required.

[0072] In general, liquid crystal displays (LCDs) are based on the fact that liquid crystals can influence the polarization direction of light depending on an applied voltage. By modulating the crystal orientation pixel by pixel, polarized illumination radiation can be transmitted or absorbed pixel by pixel to create a desired intensity distribution or image. For example, the polarized light can be rotated by 90 degrees in one state of the liquid crystal and not rotated in another. To create an LCD with an absorbing state or a transmitting state, a polarizer can be placed on each side of the liquid crystal so that the polarization angles of the polarizers are offset by 90 degrees.

[0073] An "LCD" (liquid-crystal display) can, for example, comprise a transparent electrode installed on the inner surfaces of two substrates in different display modes, e.g., in a twist-nematic (TN) display mode, in which liquid crystal molecules with positive (+) dielectric isotropy are arranged parallel to the substrates and twisted with an angular difference of almost 90 degrees between the substrates, or in a supertwisted nematic (STN) display mode, in which the liquid crystal molecules are arranged similarly to a TN display mode but twisted with an angular difference of 180 to 270 degrees between the substrates. Other display types, such as triple super-twisted nematic, etc., are also conceivable. According to the invention, a variety of different liquid crystal displays can be used.

[0074] An LCD can be preferred for use as a light-modulating pixel array because the intensity modulation of individual pixels can be adjusted by setting the voltage supplied to each pixel. This can be easily accomplished using known electronic or digital control methods and can provide intermediate values ​​for the transmission of the light wave, i.e., switching transmission on or off (0% or 100%), as well as defining values ​​between 0 and 100% based on the applied voltage. Furthermore, LCD screens do not suffer from the image persistence problem that occurs with some types of displays (e.g., CRTs) and allow for rapid switching of the intensity modulation function.

[0075] A micromirror array is preferably a microelectromechanical system (MEMS) comprising a plurality of micromirrors for the dynamic modulation of light. In a (tilting) mirror matrix or a micromirror array, preferably a DMD (Digital Micromirror Device), the pixels are formed by the individual (micro)mirrors, which can preferably assume discrete deflections. The individual micromirrors of the (tilting) mirror matrix can preferably be controlled electrostatically and, in particular, switch between at least two (tilting) states, wherein preferably one state causes the illumination radiation to be deflected to a pixel on the image to be generated or, in this case, to the beam-shaping unit, and another state causes the illumination radiation to be deflected outside the image to be generated or outside the beam-shaping unit, for example, to an absorber.

[0076] Micromirror arrays, or DMDs, can be constructed in various ways. For example, the mirrors can be connected to an underlying yoke, which in turn is connected via two thin, mechanically compliant torsion hinges to support posts mounted on the underlying substrate. Electrostatic fields generated between an underlying memory cell (e.g., SRAM), the yoke, and the mirror can cause a positive or negative tilting direction.

[0077] A DMD may also be preferred for use as an intensity-modulating pixel array, as these allow for particularly fast adjustment of light intensity in a robust manner. However, DMDs typically switch between two states (i.e., preferably an intensity modulation of 0% or 100%) and often do not produce grayscale levels or intermediate values.

[0078] An LCoS screen may also be preferred for use as an intensity-modulating pixel array because the intensity modulation function can be changed quickly, usually faster than with an LCD.

[0079] An “LCoS screen” (liquid crystal on silicon screen) according to the invention is preferably a screen in which each pixel comprises a liquid crystal layer on a silicon back wall. The silicon back wall preferably acts as a mirror, while the liquid crystal layer responds to a change in voltage by changing its refractive index and optical path length. This allows the intensity of the light reflected from the silicon back wall to be varied.

[0080] An aperture array can also be preferred for use as an intensity-modulating pixel array due to its simple fabrication and ease of replacement. Such an aperture array can have a static light modulation function and is extremely compact and economical to use.

[0081] An “aperture array” within the meaning of the invention is preferably a matrix arrangement of light-filtering or light-blocking components which may be static or variable in their intensity-modulating function.

[0082] Other spatial light modulators (SLMs) can also be used in preferred forms as intensity-modulating pixel arrays.

[0083] In a further preferred embodiment of the invention, each pixel of the intensity-modulating unit comprises at least two, preferably at least three, subpixels. Preferably, the subpixels comprise different color filters, in particular RGB filters. This makes it possible to generate different freeform waves with different colors or wavelength ranges using the same exposure setup. For example, different freeform waves for red, green, and blue light can be generated simultaneously or sequentially. This can be particularly useful when different color channels or parts of a hologram are to be viewed from different angles in the final product. For example, a hologram can include various security features that are visible when a card is tilted at different angles.Additionally or alternatively, subpixels with different color filters can be used to create a full-color image that is reconstructed using only light corresponding to the wavelengths of the color filters.

[0084] In a preferred embodiment of the invention, a red filter selectively transmits electromagnetic radiation with wavelengths between 590 and 750 nm, preferably between 620 and 700 nm, and preferably absorbs or reflects all other wavelengths. A green filter preferably selectively transmits electromagnetic radiation with wavelengths between 490 and 590 nm, preferably 500 and 560 nm, while preferably absorbing or reflecting all other wavelengths. A blue filter preferably selectively transmits electromagnetic radiation with wavelengths between 380 and 490 nm, preferably 420 and 475 nm, while preferably absorbing or reflecting all other wavelengths. Electromagnetic radiation of a particular wavelength is preferably considered to be transmitted if its absorption by the filter is less than 30%.The filter for a particular color may also have a transmission peak (preferably of at least 70%) or an absorption low (preferably of less than 30%) within the relevant wavelength range for that color.

[0085] 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), wherein an intensity 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, and red light a central wavelength of approximately 630 nm.

[0086] When filters for red, green, and / or blue light are used, it is preferred that there is essentially no overlap between the wavelength ranges selectively transmitted by filters for different colors. In particular, this makes it possible to simultaneously irradiate the intensity-modulating unit with multiple wavelengths (e.g., using an RGB laser) in a broadband manner, in order to expose the master hologram with different wavelengths at the same time.

[0087] If some overlap is unavoidable, potential cross-talk caused by overlap can be prevented by pulsing the light wave between different wavelengths, as described below.

[0088] In a further preferred embodiment of the invention, the subpixels of the intensity-modulating unit have a pixel pitch of no more than 180 pm, preferably no more than 90 pm, and even more preferably no more than 30 pm.

[0089] In a further aspect of the invention, a device according to the invention can have a plurality of light sources, wherein the device is configured to specify a desired intensity distribution of a light wave from the plurality of light sources. Instead of providing at least one light source whose light wave can be modulated with an intensity-modulating unit, preferably in the form of a pixel array, it may therefore also be preferred to provide a plurality, preferably an array, of light sources, wherein the emission of the individual light sources is preferably separately controllable.

[0090] In a further aspect, the invention therefore relates to a device for replicating a hologram into a replication assembly with an exposure module, wherein the exposure module has at least one light source and a carrier means for receiving a master element comprising a master hologram to be replicated, and the exposure module is configured to bring the replication assembly into optical contact with the master element, while the at least one light source exposes the master hologram to obtain a replicated hologram onto an area of ​​the replication assembly, wherein the exposure module is designed for exposing the master hologram with a free-form wave with a spatially varying angular distribution and for this purpose the device comprises a plurality of light sources and a beam-shaping unit.wherein the device is configured for adjusting an intensity distribution of a light wave from the plurality of light sources with which the beam-shaping unit is illuminated, and the beam-shaping unit is configured for generating the free-form wave with the spatially varying angular distribution, wherein the angular distribution can be predetermined by the intensity distribution of the light wave incident on the beam-shaping unit.

[0091] In this embodiment as well, the inventive adjustment of an intensity distribution of a light wave with which the beam-shaping unit is irradiated is thus carried out by means of the device, wherein the beam-shaping unit is configured for the generation of the free-form wave with the spatially varying angular distribution and wherein the angular distribution can further be predetermined by the intensity distribution of the light wave which is incident on the beam-shaping unit.

[0092] For this purpose, however, in the preferred embodiment, the device does not necessarily have a separate intensity-modulating unit with which the light wave from the at least one light source is preferably guided onto the beam-shaping unit with a desired intensity distribution. Instead, the device can comprise a plurality of light sources, for example in the form of an array, which together generate a light wave whose intensity distribution can be adjusted as desired upon incidence onto the beam-shaping unit.

[0093] Preferably, the plurality of light sources can be controlled separately for this purpose, for example by means of a suitable control device. Alternatively, an intensity-modulating unit (not necessarily in the form of a contiguous pixel array) can also be provided. Subunits or pixels of the intensity-modulating unit can each be provided for adjusting the emission of radiation from the respective light sources. Those skilled in the art understand that preferred embodiments disclosed with regard to providing a light-modulating unit for adjusting a desired intensity distribution of the light wave upon incidence on the beam-shaping unit apply mutatis mutandis to embodiments in which the device has a plurality of light sources with the aid of which a light wave with a desired intensity distribution can be provided.

[0094] For example, it is disclosed elsewhere herein that it may be preferred for the light-modulating unit to have a plurality of pixels, such as 100, 500, 1000, 5000, 10000, 100000, 1,000,000 or more pixels, as a pixel array. The person skilled in the art understands that it may be equally preferred, and thus, with regard to providing a device with a plurality of light sources for adjusting a light wave with a desired intensity distribution, to provide a plurality of light sources, such as 100, 500, 1000, 5000, 10000, 100000, 1,000,000 or more light sources.

[0095] Furthermore, it is disclosed elsewhere herein that it may be preferred to assign at least 3, 6, 10, 20, 30, or more pixels of an intensity-modulating unit to each pixel of a beam-shaping unit. The person skilled in the art understands that, therefore, with regard to providing a device with a plurality of light sources for adjusting a light wave with a desired intensity distribution, it may also be preferred that, corresponding to each pixel of a beam-shaping unit, at least 3, 6, 10, 20, 30, or more light sources can be assigned, the emission of which is preferably separately controllable.

[0096] Other preferred parameters, particularly with regard to preferred embodiments of an intensity-modulating unit as a pixel array, also preferably apply to a preferred array comprising a plurality of light sources. This includes, without limitation, for example, a pixel pitch or the distance between adjacent light sources on an array, or the preferred provision of two or three subpixels with different color filters, or the provision of two or three different colored light sources.

[0097] In a further preferred embodiment of the invention, the beam-shaping unit is configured as a pixel array. By configuring the beam-shaping unit as a pixel array, each pixel of the beam-shaping unit can generate a (preferably identical) range of emission angles. This allows one or more different beam angles to be emitted from different points of the beam-shaping unit, enabling the generation of a complex free-form wave. Simultaneously, the pixel array configuration allows for simplified tracing of the desired free-form wave back to a required intensity distribution, which is to be provided by the intensity-modulating unit.

[0098] Preferably, each pixel of the beam-shaping unit comprises a light-deflectoring optical component whose light-deflectoring optical function depends on the incident position of a light beam. This allows a relationship to be established between the position of the light beams emitted by the intensity-modulating unit and the angle of the light beams emitted by the beam-shaping unit. In this way, the intensity distribution generated by the intensity-modulating unit can be adapted to the desired free-form wave according to the known relationship. Preferably, the beam-shaping unit can be configured as a pixel array comprising a plurality of pixels, for example, 10, 50, 100, 500, 10,000, 100,000, or more pixels.

[0099] For the purposes of the invention, a "light-deflectoring optical component" is preferably an optical component that can change the direction of electromagnetic radiation. The change in the direction of the radiation can be achieved by refraction, diffraction, or reflection. For example, the light-deflectoring component comprises a lens or a functional hologram, preferably with an optical lens function.

[0100] In a further preferred embodiment of the invention, each pixel of the beam-shaping unit is assigned to a section of the intensity-modulating unit, which can have several spatially distributed intensities (see Fig. 3). Preferably, each pixel of the beam-shaping unit covers several pixels of the intensity-modulating unit. This preferably means that the light emitted by several pixels of the intensity-modulating unit is configured to fall on a single pixel of the beam-shaping unit. By assigning several pixels of the intensity-modulating unit to each pixel of the beam-shaping unit, an intensity distribution can be generated for each pixel of the beam-shaping unit.

[0101] In other words, the intensity-modulating unit can advantageously provide an intensity distribution for each pixel of the beam-shaping unit. Specifically, each pixel of the beam-shaping unit can receive intensity-modulated beams at different positions within the same pixel, depending on which pixels of the light-modulating unit transmit or block the illumination beams. For example, some pixels of the beam-shaping unit can be illuminated only from their center, their right edge, or their left edge. It is also possible for pixels of the beam-shaping unit to be illuminated across their entire area, but with different intensities in the center, at the right edge, and at the left edge. This takes advantage of the position-dependent light-deflection function of the pixels of the beam-shaping unit.This allows different pixels of the beam-shaping unit to independently emit electromagnetic beams at different exit angles. In this way, a free-form wave can be generated that illuminates different parts of a master hologram from different angles and, optionally, with different intensities.

[0102] Preferably, the pixel pitch of the beam-shaping unit, which is configured as a pixel array, is at least 200 pm, more preferably at least 500 pm, and even more preferably at least 1000 pm. In a preferred embodiment of the invention, each pixel of the beam-shaping unit is assigned several pixels of the intensity-modulating unit. This makes it possible to supply each pixel of the beam-shaping unit with a variable intensity distribution. Preferably, each pixel of the beam-shaping unit is assigned at least 3, preferably at least 6, more preferably at least 10, more preferably at least 20, and even more preferably at least 30, or more pixels of the intensity-modulating unit. This preferably also applies to all subpixels of the intensity-modulating unit, taking into account the preferred number of subpixels per pixel in the intensity-modulating unit.For RGB subpixels, it is preferred that each pixel of the beam-shaping unit is assigned at least 9, preferably at least 18, more preferably at least 30, more preferably at least 60, more preferably at least 90 or more subpixels of the intensity-modulating unit. This can be achieved by selecting a smaller pixel pitch in the intensity-modulating unit than in the beam-shaping unit, relative to the number of pixels (or subpixels) of the intensity-modulating unit that each pixel of the beam-shaping unit is intended to illuminate. This is particularly preferred if the beam-shaping unit has substantially the same modulation area as the intensity-modulating unit.

[0103] An alternative is to vary the modulation area of ​​the intensity-modulating unit to support a desired resolution, whereby each pixel of the beam-shaping unit can be illuminated by a desired number of pixels of the intensity-modulating unit. The discrepancy between the modulation area of ​​the intensity-modulating unit and the modulation area of ​​the beam-shaping unit can be resolved by using an intermediate optical magnification or reduction arrangement. This is explained in more detail elsewhere (see also Fig. 8).

[0104] In a further preferred embodiment of the invention, the pixel array of the beam-shaping unit is a lens array or a diffractive optical element functioning as a lens array. Preferably, the lens array is a microlens array, preferably with a pixel pitch of less than 5 mm, more preferably less than 2 mm, and most preferably less than 1 mm. A lens array can advantageously transmit electromagnetic beams across a broad spectrum of different angles, depending on the position at which each lens of the lens array is irradiated with intensity-modulated light. Depending on the shape of the lens, orthogonal intensity-modulated beams (angle of incidence approximately 90°) could be deflected in an angular range of essentially 0° to 180° in each of two perpendicular planes (e.g., an x-z ​​and a yz plane).In this way, a freeform wave can be produced that exposes different positions of a master hologram at the required angle of incidence. Simultaneously, the lenses can be manufactured in a compact manner with a high optical standard.

[0105] Preferably, each pixel of the lens array has an identical focal length, with the beam-shaping unit preferably defining a focal plane located between the beam-shaping unit and the master hologram. Providing lenses with the same focal length simplifies the relationship between the angle of incidence of the electromagnetic beams at different positions of the master hologram, the angles of exit of the electromagnetic beams from the lenses, and, in turn, the required intensity distribution to generate the desired free-form wave. By positioning the beam-shaping unit such that the focal plane lies between the beam-shaping unit and the master hologram, the light beams can diverge from the beam-shaping unit before reaching the master hologram.This allows for an increase in the areas of the master hologram that can be illuminated by each pixel of the beam-shaping unit, compared to the case where the focal plane is located behind the master hologram in the direction of radiation.

[0106] In a further preferred embodiment of the invention, the shape or size of the individual optical elements of the beam-shaping unit and / or the distance between this beam-shaping unit and the master hologram are adjusted so that light beams from the beam-shaping unit can cover all areas of the master hologram without gaps.

[0107] In a further preferred embodiment of the invention, the beam-shaping unit is positioned at a distance d from the master hologram. The distance d is preferably at least twice the distance between the beam-shaping unit and a focal plane of the beam-shaping unit. This is particularly preferred when the beam-shaping unit and the master hologram have essentially the same surface area. Such an arrangement ensures that each lens illuminates an area of ​​the master hologram that is essentially the size of the lens. Thus, the entire master hologram can be illuminated with all lenses. This ensures that all areas of the master hologram can be illuminated by the beam-shaping unit at the desired angles of incidence.

[0108] Due to potential inefficiencies at the edges of the lenses, it is particularly preferred that the distance d between the beam-shaping unit and the master hologram be at least 2.5 times the focal length, preferably at least 3 times the focal length, more preferably at least 4 times the focal length, and even more preferably at least 5 times the focal length. This not only eliminates gaps or unexposed zones during the exposure of the master hologram, but also allows for the realization of a free-form wave with a wider range of angles. In particular, this embodiment makes it possible to expose a position on the master hologram with a large number of different lenses, thus providing greater flexibility in specifying the appropriate angle of incidence for that position on the master hologram.

[0109] In a further preferred embodiment of the invention, the beam-shaping unit is a (micro)lens array. The master hologram is preferably arranged parallel to the beam-shaping unit, so that the master hologram and the beam-shaping unit each define a parallel plane. The maximum angle a ma The angle x that can be emitted by the beam-shaping unit is determined by the diameter II and the focal length f of each lens. In the case of orthogonal illumination of the lens, the maximum angle is that which would be produced by light rays arriving at the circumference of the lens and passing through the focal point. The maximum angle can therefore be determined as follows:

[0110] The minimum angle is the negative of the maximum angle, assuming the lens is regular. Depending on the lens size and focal length, a range of values ​​for the angle of incidence onto the master hologram can therefore be determined. ma x to - a m in are generated.

[0111] In a further preferred embodiment of the invention, the distance d between the beam-shaping unit and the master hologram is at least equal to the focal length multiplied by the number of lenses or pixels over a length I of the beam-shaping unit plus the number of lenses or pixels of the beam-shaping unit that are covered by the length h of the master hologram:

[0112] This arrangement ensures that all lenses along the length of the beam-shaping unit can emit electromagnetic radiation to any position of the master hologram when the beam-shaping unit is illuminated orthogonally. This increases the range of angles that can be present in the free-form wave at the respective points of impact on the master hologram and expands the spectrum of master holograms that can be efficiently replicated by a device of the present invention.

[0113] In a further preferred embodiment of the invention, a modulation area of ​​the intensity-modulating unit is larger than a modulation area of ​​the beam-shaping unit. A (reducing) optical arrangement is preferably configured to generate a reduced image of the intensity-modulating unit on the beam-shaping unit. The reducing optical arrangement is preferably positioned between the intensity-modulating unit and the beam-shaping unit. The reducing optics can, for example, be a lens system that projects a reduced image of the intensity-modulating unit onto a beam-shaping unit (see Fig. 7).

[0114] In this way, a freeform wave can be created with virtually any resolution. The resolution of the intensity-modulating unit need not be limited by the size of its individual pixels or its overall size. This means that an intensity-modulating pixel that can only be manufactured in a relatively large dimension according to the desired optical standard can still be used to illuminate small pixels of the beam-shaping unit. The downscaling optical arrangement can ensure that a large section of the intensity-modulating unit, preferably comprising several pixels, illuminates a smaller section, preferably a single pixel, of the beam-shaping unit. Furthermore, any size difference between the intensity-modulating unit and the beam-shaping unit can be compensated for using static means.Advantageously, each pixel of the beam-shaping unit can be assigned to a multitude of pixels of an intensity-modulating unit. In this way, each pixel of the beam-shaping unit can be illuminated from a variety of different positions and, in turn, generate exposure beams from a multitude of angles.

[0115] In the context of the invention, the modulation surface is preferably the surface of the intensity-modulating unit or the beam-shaping unit that is actually usable for changing the intensity or direction of a wavefront. As such, the modulation surface preferably comprises all areas of the unit in question that are configured to influence or form a part of the free-form wave, while excluding areas that are inactive because they are switched off for the replication series or because they form a peripheral part of the unit in question, e.g., a frame.

[0116] In a further preferred embodiment of the invention, the modulation area of ​​the intensity-modulating unit is smaller than the modulation area of ​​the beam-shaping unit. A (magnifying) optical arrangement is preferably configured to generate a magnified image of the intensity-modulating unit on the beam-shaping unit. This can be useful, for example, if the intensity-modulating unit can be manufactured particularly compactly at the desired resolution, or if the beam-shaping unit has large dimensions due to the minimal size of its pixels. Thus, the device according to the invention can be implemented by selecting an intensity-modulating unit from a wide range of screen types, resolutions, and sizes, and combining it with a beam-shaping unit, which is also selected from a wide range of optically deflecting components (arrays) and sizes.

[0117] In a further preferred embodiment of the invention, a further optical arrangement, in particular an optical array, is provided between the intensity-modulating unit and the beam-shaping unit. Such an optical arrangement can fulfill any optical function, such as filtering one or more wavelength ranges, polarizing or deflecting light, particularly in a manner that is not independent of the point of incidence of the light rays on the optical arrangement.

[0118] In a further preferred embodiment of the invention, the intensity-modulating unit and the beam-shaping unit are arranged sequentially in the direction of radiation and are preferably aligned concentrically. To improve optical contact between the intensity-modulating unit and the beam-shaping unit, they can be in contact with each other, with the contact being mediated by an optical fluid or optical adhesive layer. However, it may be preferred that there be a lateral offset between the positions of the intensity-modulating unit and the beam-shaping unit, so that they are no longer concentric. In such a case, a prism array or blaze grating can preferably be provided in a plane between the intensity-modulating unit and the beam-shaping unit.Such a prism array or blaze grating preferably aligns the beams emitted by the intensity-modulating unit at a specific angle. Thus, an orthogonally illuminated intensity-modulating unit can be used to generate an oblique intensity-modulated light wavefront with the aid of the prism array or blaze grating. Therefore, the angles of incidence of the intensity-modulating light on the beam-shaping unit can be deliberately non-orthogonal according to the requirements of the master hologram.

[0119] In a further preferred embodiment of the invention, a blaze grating is provided between the intensity-modulating unit and the beam-shaping unit. This embodiment is particularly preferred in combination with a microlens array. The blaze grating preferably creates an angular offset, thereby preventing interruptions in the illumination of the master hologram, for example, due to unusable transition areas between the lenses. In a beam-shaping unit configured as a (micro)lens array, the edges of each lens, corresponding to a region of, for example, up to 10% of the radius, can deflect orthogonal light at such a large angle that it is reflected back from neighboring lenses of the array or does not strike the master hologram.The Blaze grid allows the angle of incidence of the intensity-modulating light onto the beam-shaping unit to be advantageously adjusted, so that such zones are avoided and optimal use of the beam-shaping unit is ensured.

[0120] In a further preferred embodiment of the invention, the device further comprises an optical path manipulator configured to direct a light wave from the at least one light source at a predetermined angle of incidence, preferably substantially orthogonal, and with substantially parallel light rays onto the intensity-modulating unit, wherein the optical path manipulator preferably comprises one or more optical components. The use of such an optical path manipulator preferably ensures that all areas, in particular pixels, of the intensity-modulating unit are irradiated at a known angle and optionally also at a known intensity. In this way, the relationship between the desired free-form wave and the intensity distribution to be set on the intensity-modulating unit can be reliably determined. The free-form wave can be generated repeatedly, e.g.,for a specific master hologram. Advantageously, the same optical path manipulator, which, for example, generates an orthogonal wavefront, can be used for all series. In a further preferred embodiment of the invention, the path manipulator is configured to direct a light wave from the at least one light source with a predetermined non-orthogonal angle of incidence onto the intensity-modulating unit, for example, with a constant non-orthogonal angle of incidence of 20° to 70°, preferably of 30° to 60°. This is particularly advantageous when the intensity-modulating unit and / or the beam-shaping unit are diffractive optical elements or holograms that require predetermined hologram-specific angles of incidence as needed, for example, of 20° to 70°, preferably of 30° to 60°.In some cases, a non-orthogonal angle, especially a Brewster angle, is advantageous to reduce optical losses due to reflections at the surface of the intensity-modulating unit and / or the beam-shaping unit.

[0121] In a further preferred embodiment of the invention, the at least one light source comprises one or more lasers. The optical path manipulator preferably comprises a scanning element and a light-collecting element, wherein the scanning element is preferably arranged at a focal point of the light-collecting element, so that light beams can be guided by means of the scanning element at a substantially constant angle of incidence over different positions of the intensity-modulating unit.

[0122] The scanning element can, for example, comprise a tiltable mirror or a prism. Particularly preferably, the scanning element comprises a scanning mirror, which is preferably tiltable about one or more axes. For example, the scanning element can comprise a first scanning mirror, wherein the first scanning mirror is tiltable about a first axis to guide the light rays on the intensity-modulating unit along a first direction (e.g., horizontally), and a second scanning mirror, which is tiltable about a second axis to guide the light rays on the pixel along a second direction (e.g., vertically). Preferably, the scanning mirror can be a galvanometer mirror (e.g., with a gimbal suspension) or a microelectromechanical mirror (MEMS). The element can be a single scanning mirror (with tilting in at least two axes) or a combination of two or more scanning mirrors.

[0123] The light-collecting element can preferably be a converging lens or a concave mirror, preferably a parabolic mirror. In a preferred embodiment, the scanning element directs collimated laser beams onto the concave surface of the mirror, so that the concave mirror reflects the collimated laser beams in the direction of the intensity-modulating unit. Such an arrangement can reliably provide a collimated wavefront at a desired angle, for example, orthogonal to the intensity-modulating unit, in a compact and efficient manner. Scanning the laser beams allows the use of lower-power lasers. Furthermore, as explained below, scanning the light source allows the intensity-modulating unit to be illuminated with different intensities depending on its position.The provision of a scanning unit also enables the master hologram to be exposed to different wavelength ranges sequentially or simultaneously without cross-talk.

[0124] In preferred embodiments, the device may for these purposes comprise a temporal modulation unit which can temporally modulate the intensity of the light wave with which the intensity-modulating unit is irradiated during a scanning process.

[0125] A temporal modulation unit, as defined in the invention, is preferably a component capable of changing or modulating the intensity of a light beam, preferably a laser beam, over time, preferably gradually, i.e., with intermediate values ​​between 0% (blocking) and 100% (transmitting). In preferred embodiments, the temporal modulation unit comprises an acousto-optic modulator (AOM) and / or an acousto-optically tunable filter (AOTF). Additionally or alternatively, an optical parametric oscillator can be used to change the wavelength of the light generated by a laser over time.

[0126] In a further preferred embodiment of the invention, the device is configured for large-area illumination of the intensity-modulating unit, wherein the device preferably comprises optical components for generating a substantially planar light wave. Such an arrangement enables particularly fast replication of the hologram using simple means and a reduced number of optical components. Large-area illumination of the intensity-modulating unit preferably means that a substantial area of ​​the intensity-modulating unit is illuminated simultaneously, for example, by at least 30%, 50%, 70%, 90% or more. This embodiment is particularly advantageous if the intensity-modulating unit can also generate intermediate values ​​between 0% and 100% in the transmission of the light wave.In this way, the large-area illumination of the intensity-modulating unit with a single intensity can still produce an intensity distribution with different transmission values.

[0127] In another preferred embodiment, the device is configured for line-by-line exposure of the master hologram, preferably by means of a line scan.

[0128] During exposure using a line scan, the master hologram is replicated, preferably section by section, and in particular successively. For this purpose, the master hologram can preferably be exposed in a line or stripe pattern. Thus, in the line scan, the master hologram is preferably not illuminated over a large area in a single exposure process, but successively, and in particular line by line (preferably row by row or column by column).

[0129] In this context, exposure can be achieved by a light beam or a light stripe extending across a line of the master hologram. The light stripe preferably corresponds to a scan line. This light stripe can be generated by appropriately designed intensity-modulating units, beam-shaping units, light sources, and / or additional optical components (e.g., lenses, mirrors, apertures, etc.).

[0130] In a preferred embodiment, the shape and / or size of the intensity-modulating unit and / or the beam-shaping unit can be adapted to the shape and / or size of the master hologram, so that simultaneous, large-area illumination of the intensity-modulating unit (as well as the beam-shaping unit and the master hologram) would be possible. However, instead of large-area illumination of the intensity-modulating unit, it may be preferred to illuminate the intensity-modulating unit with a line- or strip-shaped light beam from the light source, which is guided as a line or strip across the intensity-modulating unit (and preferably, therefore, the beam-shaping unit and the master hologram).

[0131] Similarly, the light source can illuminate the intensity-modulating unit with a point-shaped light beam, which is preferably guided point by point, line by line, across the intensity-modulating unit (and thus preferably also across the beam-shaping unit and the master hologram). While the point-shaped light beams preferably illuminate one or (a few) several pixels of the intensity-modulating unit simultaneously, a line- or strip-shaped illumination preferably refers to the illumination of an entire line (row or column) of an intensity-modulating unit.

[0132] The desired freeform wave for exposing the master hologram is generated line by line, as described in more detail elsewhere herein, by changing the local intensity of the exposure rays that can pass through or traverse the intensity-modulating unit in order to set an intensity distribution of the light wave that hits the beam-shaping unit.

[0133] In a further preferred embodiment of the invention, the shape and / or size of the intensity-modulating unit and / or the beam-shaping unit can be adapted to the shape and / or size of a light strip with which the master hologram is to be exposed line by line. For example, it may be preferred that the intensity-modulating unit and / or beam-shaping unit in the preferred embodiment is also designed in a linear or strip-shaped form. In this embodiment as well, it may be preferred to expose the intensity-modulating unit (and thus the beam-shaping unit) with a (substantially) point-shaped light beam, which is guided over the linear or strip-shaped intensity-modulating unit in order to adjust the intensity distribution of a light strip that strikes the beam-shaping unit.

[0134] The intensity-modulating unit and / or beam-shaping unit may preferably have a flat shape, preferably with a significantly larger width or length (area) than thickness (depth). The area of ​​the intensity-modulating unit and / or beam-shaping unit may, in preferred configurations, correspond to the area of ​​the light strip. However, it may also be preferred to choose a smaller or larger area for the intensity-modulating unit and / or beam-shaping unit. As explained in more detail elsewhere herein, appropriate optical magnification or reduction arrangements may preferably be incorporated to ensure imaging of the intensity-modulating unit onto the beam-shaping unit and from there onto the area of ​​the master hologram to be exposed.

[0135] To expose the complete master hologram, the line- or strip-shaped intensity-modulating unit and / or beam-shaping unit is preferably moved relative to the master hologram to expose it line by line. The desired freeform wave for exposing the master hologram is generated line by line, as described, by changing the local intensity of the exposure beams that can pass through or traverse the intensity-modulating unit. The line-by-line generation of the desired freeform wave can be performed independently for each line (row or column) of the master hologram by appropriately controlling the intensity-modulating unit (preferably a line- or strip-shaped pixel array). This advantageously allows the use of more compact line- or strip-shaped intensity-modulating and / or beam-shaping units.

[0136] Various operating modes for line scanning can be implemented, for example, continuous scanning or stepwise / intermittent scanning. In continuous line scanning, the light stripe of the freeform wave is preferably continuously scanned across the master hologram, preferably with permanent exposure. In stepwise / intermittent line scanning, the light stripe preferably lingers section by section over a line or stripe of the master hologram and is then scanned across the entire master hologram. It may be preferred that the scan passes over the master hologram multiple times, i.e., in particular, that multiple overlapping exposures occur, so that, for example, more complex superimpositions are possible.

[0137] In a preferred embodiment of the invention, the master element is mounted for axial rotation. In this embodiment, the master element preferably has the form of a roller. The roller shape, particularly in combination with the axial rotatability, enables synchronous movement between the master element and the replication assembly.

[0138] Depending on the materials used, a frictional force between the replication assembly and the master element may be sufficient to cause the master element to move. In this case, the master element advantageously does not require its own drive, and the movement is essentially passive, driven by the movement of the replication assembly. Alternatively or additionally, the rotational speed of the master element can be controlled separately via a (suitable) drive, which preferably ensures synchronous movement of the master element's surface with the replication assembly. For example, power transmission can be achieved via a functional roller, a flanged gear ring, a cardan drive, or a belt drive. The drive mechanism is preferably designed such that the surface of the master element is maximally accessible to an exposure beam.Preferably, the drive of the master element is controlled by a control unit according to preferred embodiments disclosed herein in order to maintain a desired circumferential speed of the lateral surface of the master element. In particular, the control unit can be configured to maintain a desired web tension in front of and / or behind the master element in the replication assembly.

[0139] Contact between the replication composite and the roller's outer surface can preferably be established continuously or incrementally by bringing the replication composite into circumferential contact with the roller, which facilitates the elimination of air gaps. This advantageously allows for good optical contact with little or no pressure. Furthermore, the axial rotatability of the master element enables synchronous rotation with the movement of a replication composite mounted on it. The master element can thus function mechanically similarly to a deflecting roller. This arrangement is therefore particularly suitable for a continuous process in which the replication composite is guided and exposed along a rotating roller.

[0140] The roller (as an embodiment of the master element) is preferably a cylindrical geometric shape with a circular or elliptical cross-section. Particularly preferred is a so-called vertical (or right) circular cylinder with a circular cross-sectional area. In other preferred embodiments, however, it can also be an oblique circular cylinder or a vertical cylinder with an elliptical cross-sectional area. It is also preferred that the roller has a polygonal cross-section, in particular with an obtuse angle between different flat sides.

[0141] In a preferred embodiment of the invention, the replication composite is guided along a lateral surface of the roller during exposure, preferably with a section of the replication composite adhering to or at least coming into contact with a section of the lateral surface of the roller.

[0142] Moving the replication composite along the cylindrical surface preferably means that the movement of the replication composite and the cylindrical surface is synchronous. Preferably, during this movement, the replication composite assumes a shape of the cylindrical surface of the roller in certain areas. For example, the section of the cylindrical surface of the roller to which the replication composite adheres or with which it at least comes into contact can have an opening angle α of at least 10°, preferably at least 20°, preferably at least 45°, preferably at least 60°, more preferably at least 90°, even more preferably at least 120°, and even more preferably at least 180°. In embodiments, this partial shaping can also include a substantially tangential contact. For example, a contact area can also be designed as a relatively thin or narrow contact line (e.g., with a contact line width between 0.5 and 10 mm).

[0143] In the preferred embodiment, where the master element is configured as a roller, it is particularly preferred that the master hologram be replicated by means of a line scan. In the line scan, it is preferred that the master hologram is exposed by means of a narrow line, row, or column along an area where the replication composite is in contact with the master element or master substrate. To provide the optical contact, the roller can preferably exert a uniform pressure so that the replication composite contacts the master element along a section of its surface.

[0144] Simultaneously or immediately thereafter, an exposure occurs as a narrow line, row, or column. This exposure can preferably be achieved with a (essentially) point-shaped beam guided across the narrow line, row, or column, or with a strip-shaped beam of light that preferably exposes the narrow line, row, or column simultaneously. The contact is then released, and the master element continues to move or rotate so that the next line (e.g., row or column) of the master hologram can be transferred or replicated onto the replication array.

[0145] This continuous, line-by-line replication creates a seamless image of the entire master hologram on the replication matrix. Replication is advantageously achieved with high reproduction accuracy. The use of the roller ensures uniform pressure distribution and enables high processing speeds, which is particularly beneficial in the production of large quantities.

[0146] For example, it may be preferred that the line scan is performed along the longitudinal side of the cylinder as the master element and that the light source is configured to illuminate the cylinder accordingly. The line scan can, for instance, be performed line by line along the longitudinal side of the cylinder to replicate the master hologram section by section or line by line onto the replication assembly. Thus, the light source can preferably illuminate the section of the cylindrical master element from the side that is partially contacted by the replication assembly.

[0147] In a further preferred embodiment of the invention, the shape and / or size of the beam-shaping unit and / or the intensity-modulating unit are adapted to the shape and size of the exposed surface of the mast element, which, in the case of a cylindrical master element, preferably corresponds to a contact area, preferably a narrow contact line, along the longitudinal side of the cylinder. For example, it may be preferred that the intensity-modulating unit and / or beam-shaping unit in the preferred embodiment is also designed in a linear or strip-like form.

[0148] The intensity-modulating unit and / or beam-shaping unit may preferably have a flat shape, with a significantly larger width or length (area) than thickness (depth). In preferred configurations, the area of ​​the intensity-modulating unit and / or beam-shaping unit may correspond to the area of ​​the contact region. However, it may also be preferred to choose a smaller or larger area for the intensity-modulating unit and / or beam-shaping unit. As explained in more detail elsewhere herein, suitable optical magnification or reduction arrangements may preferably be incorporated to ensure imaging of the intensity-modulating unit onto the beam-shaping unit and from there onto the area of ​​the master hologram to be exposed.

[0149] Preferably, the device according to the invention is configured to carry out a method for replicating a hologram in a replication assembly with an exposure module, wherein the exposure module has at least one light source and a master element comprising a master hologram to be replicated, and is configured to bring the replication assembly into optical contact with the master element, while the light source illuminates a region of the replication assembly to obtain a replicated hologram. The method comprises the following steps:

[0150] Provision of an intensity-modulating unit and a beam-shaping unit;

[0151] Direction of a light wave from the light source towards the intensity-modulating unit;

[0152] Setting the intensity distribution of the light wave with which the beam-shaping unit is irradiated, by means of the intensity-modulating unit and

[0153] Generation of a free-form wave using the beam-shaping unit with a spatially varying angular distribution, wherein the angular distribution is determined by the intensity distribution of the light wave.

[0154] This method enables the compact and efficient fabrication of a freeform wave for replicating a master hologram in a replication array. Since the intensity-modulating unit and the beam-shaping unit can be kept essentially stationary within the exposure module, they are not subject to the mechanical tolerances of previous technical solutions for generating a freeform wave. The replication process is therefore highly repeatable and carries a lower risk of downtime.

[0155] Furthermore, the use of an intensity-modulating unit allows for essentially immediate adjustment or modification of the freeform waveform by changing the intensity distribution generated by the unit. This is primarily because the intensity-modulating unit can be configured particularly well as an array and controlled electronically or digitally. Thus, the freeform waveform can be directly adapted to the current properties of a master hologram being replicated or to a change in the master element, such as when producing multiple hologram series in the same exposure module. The freeform waveform and the generated holograms can therefore be modified without replacing the intensity-modulating unit or the beam-shaping unit.This eliminates a potential source of error in the replication of holograms and enables a high replication speed, as in the case of a continuous or intermittent process.

[0156] Preferred features and advantages of the device according to the invention also apply mutatis mutandis to the replication method and vice versa.

[0157] Preferably, the intensity distribution of the light wave with which the beam-shaping unit is irradiated can also be specified using a plurality of light sources. Instead of providing at least one light source whose light wave can be modulated with an intensity-modulating unit, preferably in the form of a pixel array, it may therefore also be preferred to provide a plurality, preferably an array, of light sources, wherein the light emission of the individual light sources is preferably separately controllable.

[0158] The method is preferably also suitable for replicating a hologram in a replication assembly with an exposure module, wherein the exposure module comprises at least one light source and a master element comprising a master hologram to be replicated, and is configured to bring the replication assembly into optical contact with the master element, while the at least one light source illuminates a region of the replication assembly to obtain a replicated hologram. The method comprises the following steps:

[0159] Provision of a variety of light sources

[0160] Direction of emission from the plurality of light sources onto the beam-shaping unit, wherein an intensity distribution of the light wave from the plurality of light sources is set with which the beam-shaping unit is irradiated and

[0161] Generation of a free-form wave using the beam-shaping unit with a spatially varying angular distribution, wherein the angular distribution is determined by the intensity distribution of the light wave.

[0162] In this embodiment, the preferred setting of an intensity distribution of a light wave with which the beam-shaping unit is irradiated is also carried out, wherein the beam-shaping unit is configured for generating the free-form wave with the spatially varying angular distribution and wherein, furthermore, the angular distribution can be predetermined by the intensity distribution of the light wave incident on the beam-shaping unit.

[0163] However, a separate intensity-modulating unit is not necessarily required, preferably to guide the light wave from the at least one light source with a desired intensity distribution onto the beam-shaping unit. Instead, a plurality of light sources can be provided, which together generate a light wave whose intensity distribution can be adjusted as desired upon incidence onto the beam-shaping unit.

[0164] Preferably, the multiple light sources can be controlled separately for this purpose, for example by means of a suitable control device. Alternatively, an intensity-modulating unit (not necessarily in the form of a contiguous pixel array) can also be provided. Subunits or pixels of the intensity-modulating unit can each be used to adjust the emission of radiation from the respective light sources.

[0165] The "direction of a light wave from the light source towards the intensity-modulating unit" preferably refers to the irradiation of the intensity-modulating unit with electromagnetic radiation from the light source, such that the light wave can leave the intensity-modulating unit with a modified intensity distribution in a predetermined direction. Intensity modulation can be achieved, for example, by reflective, refractive, or diffractive means, whereby any of the aforementioned technical means of intensity modulation, such as LCDs or DMDs, can be used.

[0166] It may be preferred that the direction of the light wave towards the intensity-modulating unit includes directing the electromagnetic beams towards a side of the intensity-modulating unit facing away from the master element, so that the electromagnetic beams emerge from a side of the intensity-modulating unit facing the master element. In this case, the electromagnetic beams pass through the intensity-modulating unit, and, as explained above, the intensity distribution can preferably be adjusted, for example, by means of a liquid crystal.

[0167] It may be preferred, particularly when intensity modulation is achieved by reflection, that the direction of the light wave towards the intensity-modulating unit includes directing the electromagnetic beams to one side of the intensity-modulating unit, so that the electromagnetic beams are selectively or intensity-modulated emitted from the same side of the intensity-modulating unit. This is particularly preferred for an intensity-modulating unit as a micromirror array (DMD). The "adjustment of an intensity distribution of the light wave by means of the intensity-modulating unit" preferably refers to at least a region-specific change in the intensity of the electromagnetic beams of the light wave, wherein this change is achieved through the optical interaction of the electromagnetic beams with the intensity-modulating unit.Additional modulation of the intensity distribution of the light wave before reaching the intensity-modulating unit, e.g. at the light source or by means of a temporal modulation unit (e.g. by an AOM or AOTF), is not excluded.

[0168] It may be preferred that a light-deflectoring optical function of the beam-shaping unit depends on the point of impact of a light beam from the light wave. The intensity distribution of the light wave illuminating the beam-shaping unit is preferably adjusted to generate a free-form wave with a desired varying angular distribution for the exposure of the master hologram. This can be achieved based on a known relationship between the intensity distribution of the light exiting the light-modulating unit and the angular and intensity distribution of the light in the free-form wave. A change in the position of a bright spot in the intensity-modulating unit can thus lead to a predetermined change in the direction of a correspondingly bright beam exiting the beam-shaping unit. The free-form wave can therefore be precisely adjusted and modified as required.

[0169] It may be preferable that the light wave with which the intensity-modulating unit is irradiated is generated by the following steps:

[0170] Provision of the light source, preferably comprising one or more lasers, and of an optical path manipulator comprising a scanning element and a light-collecting element, wherein the scanning element is preferably arranged in a focal point of the light-collecting element;

[0171] Guiding light beams by means of the scanning element over different positions of a modulation surface of the intensity-modulating unit, preferably at a substantially constant angle of incidence, particularly preferably at a substantially orthogonal angle of incidence.

[0172] The scanning element is preferably a galvo scanner, while the light-collecting element is preferably a parabolic mirror. Preferably, the scanning element directs the laser beams onto the elliptical concave mirror so that they are reflected at a desired angle to the intensity-modulating unit. In this way, the master hologram can be illuminated with intensity-modulated and shaped beams that scan the master hologram according to the function of the freeform wave.

[0173] Scanning the master hologram in this way allows not only for different areas of the master hologram to be illuminated by electromagnetic beams at different angles, but also for these electromagnetic beams to be modulated in intensity and / or wavelength. This is because the scanning technique enables additional temporal modulation of the exposure beams before they reach the intensity-modulating unit. For example, the exposure beams of the light wave can be modulated at the light source, which emits electromagnetic beams of different wavelength ranges and / or different intensities during scanning. Alternatively or additionally, a temporal modulation unit (e.g., an AOM or AOTF) can be used to perform temporal intensity adjustment.

[0174] Advantageously, temporal modulation can compensate for any limitations of the intensity-modulating unit or prevent crosstalk between different wavelength ranges. For example, temporal modulation can generate intermediate intensity values ​​even if the intensity-modulating unit is configured only for pixel-by-pixel changes between two states (e.g., between 0% and 100% transmission or reflection onto the master hologram or an absorber). Furthermore, the dependence on wavelength filters of the intensity-modulating unit can be avoided by varying the wavelength of the light at the source. This prevents reproduction errors, especially in multiplex holograms, where holographic patterns in one color channel can be reproduced as shadows in another.This can occur, for example, if a filter for one color channel in the intensity modulation unit allows a residual amount of light from another color channel to pass through. This leads to crosstalk between the color channels, which can reduce the quality of the replicated hologram. Such crosstalk can advantageously be avoided by varying the wavelength of the light wave at the source, particularly using an AOM or AOTF, to selectively direct exposure beams of different color channels to the beam-shaping unit without relying on inaccurate color filters.

[0175] This increases flexibility in the exposure of the master hologram and enables the production of more complex holograms in high quality. For example, the color balance between different color channels can be finely adjusted during the scanning process.

[0176] It may be preferred that the intensity of the light wave with which the intensity-modulating unit is irradiated is temporally modulated during a scanning process, wherein the temporal modulation of the intensity of the light wave is preferably configured so that the intensity-modulating unit is illuminated with different intensities depending on its position.

[0177] In an embodiment comprising a scanning mirror and a parabolic mirror, the intensity of a light beam passing over the parabolic mirror to direct collimated light onto the intensity-modulating unit can be varied before it reaches the parabolic mirror. In this way, different positions of the parabolic mirror are illuminated with different light intensities. Light beams reflected from the parabolic mirror to the intensity-modulating unit can therefore have different intensities. These light beams are subject to the additional intensity-modulating function of the unit, which can block (e.g., absorb or reflect) some light beams to prevent them from reaching the beam-shaping unit.In this way, a light wave with a more complex intensity distribution function can be supplied to the beam-shaping unit than can be generated by the intensity-modulating unit alone.

[0178] Such temporal modulation allows for the generation of intermediate radiation intensity values ​​before it strikes a beam-shaping unit, even if the intensity-modulating unit does not inherently support this, for example, if it is a micromirror array capable of representing only two states. Furthermore, temporal modulation enables the exposure of different color channels with known wavelengths without relying on imprecise color filters in the pixels or subpixels of the intensity-modulating unit. This allows for the creation of a freeform wave with more finely tuned properties, thus improving the quality of the resulting holograms.

[0179] It may be preferable for the light wave to be generated by lasers of different wavelength ranges and / or by an RGB laser. The laser(s) are preferably pulsed between the different wavelength ranges. This avoids crosstalk between different color channels, which improves the quality of the generated hologram.

[0180] Pulsing the laser(s) between different wavelength ranges preferably means that at any given time only light from one wavelength range is used to illuminate the intensity-modulating unit. Simultaneous illumination of the intensity-modulating unit with multiple wavelength ranges can preferably be avoided.

[0181] Preferably, when pulsing between different color channels, the intensity-modulating unit is first illuminated with a single color to selectively illuminate specific areas of the unit, e.g., those corresponding to green subpixels. The unit can then be illuminated with a different color to illuminate specific areas, e.g., those corresponding to red subpixels. This process can be repeated to prevent the light of one color from being directed onto the subpixel or position of another color. This ensures that the intensity distributions or freeform waves of the different color channels are generated with pure color purity. By illuminating different color channels of the master hologram not simultaneously, but sequentially, e.g.,By pulsing, the dependence on color filters in the intensity-modulating unit (IMU), which provide the freeform waves for the various color channels, can be reduced or eliminated. Color filters, for example, in the subpixels of a pixel array of the IMU, can be configured to transmit the light of a single color channel. In practice, however, a small dose of light corresponding to one or more other color channels is often also transmitted, which can result in a holographic pattern of the wrong color channel being written to the replication array at the same location. This can appear as a shadow during the reconstruction of the replicated hologram and degrade the color quality of the final reproduced hologram.Especially when different color channels are to be reconstructed from different angles, unwanted shadows can impair the display of holographic information at each angle. This problem, known as "cross-talk," can be avoided by illuminating each color channel with a monochromatic light wave.

[0182] It is preferred that the intensity-modulating unit is electronically controlled. The electronic control is preferably configured to generate a free-form wave for illuminating the master hologram with a desired angular distribution of local angles of incidence. Preferably, the required exit angles from the beam-shaping unit are calculated to obtain the desired angular distribution. Preferably, the required exit positions from the beam-shaping unit are also calculated, which serve to illuminate the master hologram with the necessary local angles of incidence. Preferably, the distribution of the light rays exiting the beam-shaping unit and their respective exit angles are specified. This can be carried out by a person skilled in the art using known geometric and / or mathematical techniques.Optionally, additional parameters of the light rays, such as their wavelength and / or intensity, can be calculated.

[0183] In the case of a beam-shaping unit with a pixel array configuration, the size of each pixel can represent the lowest resolution for identifying the exit position of a light beam from the beam-shaping unit. Therefore, the calculation of the exit position can be approximated to the nearest pixel of the beam-shaping unit.

[0184] Based on the calculated required exit angles and, optionally, the required exit positions, the required impact positions of light rays of the light wave on the beam-shaping unit are preferably calculated. This is preferably done by backward ray tracing in order to determine an intensity-position matrix for the electronic control of the intensity-modulating unit based on the required impact positions on the beam-shaping unit. A "backward ray tracing" in the sense of the preferred methods is preferably a mathematical method for determining a required intensity distribution of an intensity-modulating unit with regard to a desired free-form wave upon impact on a master hologram, taking into account a known light-deflection function of the beam-shaping unit.In particular, backward ray tracing relates the desired freeform wave to the required exit positions of rays from the beam-shaping unit (see Fig. 12A).

[0185] In another preferred embodiment of the invention, in backward ray tracing, a desired freeform wave is guided back from a master hologram plane onto a plane of the beam-shaping unit. Here, the precise target positions on the beam-shaping unit are determined from which the rays of the freeform wave would have to be emitted to generate the freeform wave. However, irradiating the master hologram with the target angles of incidence from the determined target positions of the beam-shaping unit may not be feasible under certain circumstances due to the design of the beam-shaping unit. This could be the case, for example, if a desired ray would not pass through a focal point of the relevant lens of the beam-shaping unit.

[0186] Should this lack of feasibility of some beams be disregarded and the intensity distribution of the intensity-modulating unit be set according to the target positions, the free-form wave would not be reproduced or meaningfully approximated.

[0187] To bring the achievable distribution as close as possible to the desired distribution, the rays should be directed through the focal points. Two approaches are generally conceivable for this purpose. Firstly, the angles of the rays originating from the master hologram can be adjusted or repositioned so that the rays now pass through the focal points. Secondly, the positions of the rays on the master hologram can be adjusted or repositioned so that the rays now pass through the focal points.

[0188] To approximate the freeform wave as accurately as possible, it is preferred to adjust the angle of the unrealizable rays from the master hologram plane so that the rays pass through a focal point of the beam-shaping unit.

[0189] The angle can be increased or decreased. Increasing the angle can cause the light beam to pass through the focal point of a lens that is not associated with the relevant position or section of the master hologram. In such a case, the angle is decreased instead until it passes through the focal point of the relevant lens.

[0190] As an additional means of approximating the freeform wave with the beam-shaping unit, the rays of the freeform wave can also be shifted until they pass through a relevant focal point. However, this shift is limited by the different angular requirements of adjacent positions in the master hologram. Therefore, approximating the freeform wave by primarily shifting the angle rather than the position of individual rays is preferred, as this tends to lead to greater replication efficiency.

[0191] This approximation process is preferably carried out using a suitable algorithm.

[0192] It may be preferable to change the master element for hologram replication in the replication assembly within the exposure module between replication series. When changing the master element, the intensity-modulating unit for generating a different intensity distribution is preferably electronically controlled. This has the advantage that a change of the freeform wave is possible without having to mechanically reposition or replace the components of the exposure module. The change between different series can therefore be carried out quickly and with minimal interruption or setup time. This makes the method particularly well-suited for producing short-series holograms in high quality and economically.

[0193] It may be preferable for the intensity-modulating unit to be designed and / or controlled to compensate for aberrations of the beamforming unit. Examples of such aberrations include chromatic aberration, which results from the wavelength-dependent refractive properties of lenses and can cause electromagnetic beams of different wavelengths to be deflected slightly differently by the beamforming unit. An aberration can cause distortion in the actually generated freeform wave from an intensity distribution compared to a theoretically generated freeform wave. In particular, aberrations can cause pixels of the beamforming unit to distort areas of the master element or illuminate them with unwanted overlap.Instead of forming illuminated areas on the master hologram that are uniformly sized and seamlessly arranged next to each other, the beam-shaping unit can, due to aberration, produce overlapping illuminated areas or irregular shapes such as trapezoids, while gaps between the illuminated areas of the master hologram remain unexposed (see Fig. 9A). The aberration can be compensated for by counter-distortion of the intensity distribution in the light modulation unit, thus eliminating the aberration (see Fig. 9B).

[0194] Various types of counter-distortion are known for this purpose, e.g., from image processing such as pre-warping. Preferably, when counter-distorting the intensity distribution at the intensity-modulating unit, the Gaussian intensity distributions of the illuminated areas are taken into account in order to achieve complete exposure of the master hologram.

[0195] The type and degree of counter-distortion can be determined based on a quantification of the aberration produced by the beam-shaping unit. This can be quantified by simulation or experiment. Methods are known to those skilled in the art for analyzing the beam-shaping unit and / or its individual components and quantifying the degree and type of deviation.

[0196] The device can also preferably be used in a method for determining the intensity distribution of a light wave, which is to be set by an intensity-modulating unit of a device according to the invention in order to expose a master hologram with a desired free-form wave. The determination method preferably comprises the following steps:

[0197] Determination of a desired freeform wave for the exposure of the master hologram, with a desired angular distribution of local angles of incidence on the master hologram;

[0198] Calculation of the required exit angles from a beam-shaping unit to obtain the desired free-form wave;

[0199] Calculation of the required impact positions of light rays of the light wave on the beam-shaping unit, which generate the desired free-form wave, in order to determine the intensity distribution of the light wave, which is to be set by the intensity-modulating unit, based on the required impact positions on the beam-shaping unit, wherein a backward ray tracing is preferably used to calculate the required exit angles from a beam-shaping unit and / or the required impact positions of light rays of the light wave on the beam-shaping unit.

[0200] Such a determination method allows the adjustment of an intensity distribution of an intensity-modulating unit to generate a desired free-form wave from a beam-shaping unit. This enables the digital adaptation of the same combination of optical units, in particular the intensity-modulating unit and the beam-shaping unit, to the requirements of essentially arbitrary reproduction series.

[0201] In particular, the detection method utilizes the optical properties of a preferably static beam-shaping unit to generate virtually any desired free-form wave for the exposure of a master hologram and its replication in a replication network.

[0202] This can advantageously be achieved without any mechanical intervention in the structure and components of an exposure module. Since no mechanical restructuring of the exposure module is required between production runs, this detection method can make the production of short series of holograms very economical.

[0203] It may be preferred that an intensity-modulating unit be used to expose a master hologram with a desired freeform waveform in a replication process. The intensity-modulating unit is configured to generate an intensity distribution of the light wave for illuminating the beamforming unit, which was determined using the specified method. Such an intensity-modulating unit can have a fixed intensity distribution that is specifically manufactured for a particular master hologram or a particular replication series. Such an intensity-modulating unit generates the required freeform waveform for the replication of a specific master hologram when illuminated in combination with a suitable beamforming unit, in particular a lens array.

[0204] It may be preferred that the intensity-modulating unit is configured to produce an intensity distribution adapted to the exposure of a particular master hologram, preferably taking into account the light-deflectoring function of a particular beam shape of the unit.

[0205] Preferably, the properties of the intensity-modulating unit that generates the intensity distribution are determined by an iterative application of the determination method. It may be preferable to first determine an intensity distribution achievable by the intensity-modulating unit using backward ray tracing with respect to a desired free-form wave and an existing beam-shaping unit. A digitally or electronically controllable intensity-modulating unit can preferably be controlled such that a light-modulating function is provided which implements the desired intensity distribution.

[0206] The intensity-modulating unit can be tested for its effectiveness in generating a desired freeform wave using the configured light-modulating function (e.g., a control pattern for the pixels of a pixel array). For example, the quality of a hologram generated with the intensity-modulating unit can be compared to a tolerance range of a specific quality parameter such as efficiency.

[0207] If the quality is deemed unacceptable, the backward ray tracing can be adjusted and repeated to set a new light-modulating function on the digitally or electronically controlled intensity-modulating unit. This light-modulating function can also be tested again until the quality of the freeform wave or replicated hologram is deemed acceptable.

[0208] Based on the determined light-modulating function (e.g., a control pattern for the pixels of a pixel array), a static intensity-modulating unit in the form of an aperture or mask can preferably be manufactured, which ensures the required intensity distribution of a light wave for illuminating the beam-shaping unit. An intensity-modulating unit manufactured in this way differs from simple masks or apertures in that it can provide a complex intensity distribution optimized in combination with the beam-shaping unit to generate a replication hologram of excellent quality. It may be preferred that the intensity-modulating unit be supplied in conjunction with the master hologram for whose exposure it was optimized, particularly as a kit.In this way, a specific intensity-modulating unit can be provided for a specific master hologram.

[0209] It may be preferred that the intensity-modulating unit according to the invention is provided in conjunction with a master hologram and with a beam-shaping unit with which it is to be used, particularly as a kit. As explained above, providing an intensity-modulating unit together with the beam-shaping unit advantageously ensures a particularly reliable free-form waveform, which guarantees optimal exposure of the master hologram.

[0210] It may be preferred that a preferred intensity-modulating unit is used for the replication of a master hologram into a replication network.

[0211] The use of such an intensity-modulating unit surprisingly enables the compact and efficient adjustment of a freeform waveform, essentially without the need for synchronous moving optical components. A master hologram can be exposed at different positions with varying angles of incidence and / or intensities using the freeform waveform. This allows the reproduced holograms to be reconstructed under specific and potentially complex optical conditions or to fulfill an optical function. The use of the intensity-modulating unit enables the simple, rapid, and cost-effective generation of a freeform waveform of virtually any complexity for replicating such holograms.

[0212] 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.

[0213] The average person skilled in the art recognizes that technical features, definitions and advantages of preferred embodiments of the device according to the invention also apply to the replication method, the detection method, the intensity-modulating unit or the use, and vice versa.

[0214] Detailed description

[0215] The invention will be explained in more detail below using examples and illustrations, without being limited to these.

[0216] Brief description of the illustrations

[0217] Fig. 1 is a schematic representation of a free-form wave, which is required for the efficient replication of a master hologram. Fig. 2 is a schematic representation of a device for replicating a hologram with a free-form wave according to a preferred embodiment of the present invention.

[0218] Fig. 3 is a schematic representation of a use of a device according to a preferred embodiment of the invention in a replication process comprising the generation of a free-form wave.

[0219] Fig. 4 is a schematic representation of a use of a device according to a preferred embodiment of the invention in a replication process comprising the generation of a free-form wave using a time-modulated scanning light source.

[0220] Fig. 5 is a schematic representation of the generation of the free-form wave according to Fig. 4 using a device according to a preferred embodiment of the invention comprising an optical path manipulator.

[0221] Fig. 6 is a schematic representation of a use of a device according to a preferred embodiment of the invention in a replication process comprising the generation of a free-form wave using an intensity-modulating unit and a beam-shaping unit with a different modulation surface and orientation.

[0222] Fig. 7 is a schematic representation of a cross-section through a single pixel of a beam-shaping unit and several associated pixels of the intensity-modulating unit.

[0223] Fig. 8 is a schematic representation of an optical arrangement for adapting the image size of an intensity-modulating unit to the modulation area of ​​a beam-shaping unit.

[0224] Figs. 9A and 9B schematically show a counter-distortion of the intensity distribution of the intensity-modulating unit to compensate for an optical aberration.

[0225] Fig. 10 schematically shows the maximum angle of incidence on a master hologram that can be produced by a lens of a beam-shaping unit.

[0226] Fig. 11 schematically shows a setup in which all positions along a master hologram can be exposed from all positions along a beam-shaping unit.

[0227] Figs. 12A and 12B schematically show a technique of backwards ray tracing and freeform wave approximation according to a preferred embodiment of the invention.

[0228] Detailed description of the illustrations

[0229] Figure 1 schematically shows the exposure of a master hologram 2 with a freeform wave 12.

[0230] As shown in Fig. 1, the master hologram 2 is located on a master substrate 4 to form a master element 6. The master element 6 can be held by a support (not shown). In this example, the master hologram 2 is a reflection hologram. A replication assembly 8 is located on a surface of the master element 6, which faces the freeform wave 12. The rays of the freeform wave 12 arrive at different positions on the master element 6, or master hologram 2, at different angles of incidence. Individual rays of the freeform wave 12 serve as reference rays. These traverse the replication assembly 8 before reaching the master hologram 2, where they are diffracted and form object rays (not shown). The object rays interfere with the reference rays in the photosensitive layer of the replication assembly 8 and form a holographic pattern.A hologram generated in this way can preferably be reconstructed at the same angles of the reference rays 10 of the freeform wave 12.

[0231] In the prior art, it is known to provide a free-form wave 12 by mechanically moving an optical component (e.g., an exposure source and / or a mirror from which the exposure takes place) along a complex motion path. The present invention reduces the optical-mechanical complexity by providing an intensity-modulating unit 16 and a beam-shaping unit 18 in an exposure module.

[0232] As explained in more detail below with reference to Fig. 2 and Fig. 3, a freeform wave 12 can advantageously be provided without movement of optical components, and preferably this can also be easily changed by digital control of the intensity-modulating unit.

[0233] Fig. 2 shows parts of an exposure module according to a preferred embodiment of the invention. A light source (not shown) is used to generate a light wave 14. The light wave 14 is collimated and directed at an orthogonal angle onto an intensity-modulating unit 16, illuminating the side facing away from the master element 6. The intensity-modulating unit 16 is configured as a light-modulating pixel array (e.g., an LCD). Depending on the control of the intensity-modulating unit 16, different pixels of the pixel array either allow the light of the light wave 14 to pass through or block it. In this way, an intensity distribution can be defined with which a beam-shaping unit 18 downstream in the beam path is illuminated.

[0234] The beam-shaping unit 18 is positioned between the master element 6 and the intensity-modulating unit 16, with the three components arranged in parallel planes. The beam-shaping unit 18 is also configured as a pixel array (e.g., as an array of microlenses).

[0235] However, the resolution of the beam-shaping unit 18 is lower than that of the intensity-modulating unit 16; that is, the pixel pitch of the beam-shaping unit 18 is larger than the pixel pitch of the intensity-modulating unit 16, so that multiple pixels of the intensity-modulating unit 16 provide intensity-modulated light for each individual pixel 24 of the beam-shaping unit 18. For example, 5, 10, 20, 30, 40, or more pixels of the intensity-modulating unit 16 can be used to illuminate a single pixel of the beam-shaping unit 18. Since the intensity-modulating unit 16 and the beam-shaping unit 18 are essentially the same size in this embodiment, and no image enlargement / reduction arrangement is provided between them, this requires that the pixel pitch of the intensity-modulating unit 16 be smaller than the pixel pitch of the beam-shaping unit 18 by a corresponding factor.

[0236] This allows the intensity-modulating unit 16 to advantageously provide an intensity distribution for each pixel 24 of the beam-shaping unit 18. The pixels 24 of the beam-shaping unit 18 are each light-deflectoring components 20, in this case lenses. Each lens 20 deflects the light to produce a beam with an exit angle that depends on the position at which the lens 20 is illuminated. The intensity distribution supplied to each lens 20 thus determines the directions of the reference beams 10, which form part of the free-form wave. By illuminating all pixels of the intensity-modulating unit 16, and thus of the beam-shaping unit 18, a desired free-form wave can be generated to expose the entire master hologram 2.

[0237] Fig. 3 schematically shows a representation of the generation of a free-form wave using the setup of Fig. 2. As can be seen in the figure, the intensity-modulating unit 16, with appropriate electronic control, ensures an intensity distribution. In this case, the intensity distribution is achieved by switching pixels 22 on or off by varying the transmission of the respective pixels between two states, 0 and 100%, and the pixels either transmit light from the light wave 14 or block the light. As explained in more detail elsewhere, it may also be preferable to set intermediate values, so that a switched-on pixel can also adjust the intensity of the beams by selecting a transmission coefficient greater than 0% but less than 100%. In the schematic illustration, however, the switched-on and switched-off pixels are represented as a black-and-white intensity distribution.Such a black-and-white (or also black-grey-white with intermediate values) intensity distribution can be provided, for example, by configuring the intensity-modulating unit 16 as an LCD.

[0238] By switching off various pixels 22 of the intensity-modulating unit 16, only some of the pixels 22 allow light to pass to the beam-shaping unit 18. Consequently, each light-deflectoring component 20 of the beam-shaping unit 18 receives electromagnetic rays from different positions in the plane of the intensity-modulating unit 16. In this example, all light rays from the intensity-modulating unit 16 arrive orthogonally at the side of the beam-shaping unit 18 facing away from the master element before being deflected by the light-deflectoring components 20. The individual light-deflectoring components 20 (here: lenses) are identical in this case.Each light-deflectoring component 20 (here: lens) therefore has an identical focal point and an identical focal length, so that the focal points of all light-deflectoring components 20 of the beam-shaping unit 18 form a focal plane 28 between the beam-shaping unit 18 and the master element 6.

[0239] Intensity-modulated light rays from the intensity-modulating unit 16 are refracted differently by each lens 20, depending on their point of incidence along a diameter of the lens 20. All intensity-modulated light rays striking the beam-shaping unit 18 are deflected so that they pass through a focal point of the same lens 20 onto which they were directed. Depending on their point of incidence on the respective lens 20, i.e., depending on which pixel 22 of the intensity-modulating unit 16 the light rays were emitted from, the light rays will pass through the focal point at different angles and form the free-form wave 12. This determines the angles of incidence at which the free-form wave 12 can strike the master hologram 2.

[0240] The ratio of the focal length f to the size of the respective lenses (II) defines the range of possible angles that can be generated by each pixel 24 of the beam-shaping unit 18 (see Fig. 10). This also determines the range of angles of incidence at which the free-form wave 12 can strike the master hologram 2.

[0241] Due to the limitation of the angular range that can be emitted by each pixel 24 of the beam-shaping unit 18, in particular by each lens 20, each pixel 24 of the beam-shaping unit 18 can only expose a limited section of the master hologram 2. The size of this section is further determined by the distance d between the plane of the master hologram 2 and the plane occupied by the beam-shaping unit 18.

[0242] To ensure that the beam-shaping unit 18, and thus the free-form wave 12, can expose the entire master hologram without gaps, the distance d between the beam-shaping unit 18 and the master hologram 2 is preferably at least twice as large as the distance between the focal plane 28 and the beam-shaping unit 18. However, a larger distance d is preferable.

[0243] Figure 4 schematically shows the preferred generation of a free-form wave using a preferred device according to the invention comprising a time-modulated scanning light source. A light source 15 comprises a plurality of lasers that generate light in different wavelength ranges. The light from all lasers is fed to a time-modulation unit 52, which may include, for example, an acousto-optic modulator (AOM) and / or an acousto-optically tunable filter (AOTF). The time-modulating unit 52 adjusts the intensities of the color channels from the lasers while the wavefront 14 is generated, so that the balance of the different color channels as well as the total light intensity can be adjusted differently at different positions on a side of the intensity-modulating unit 16 facing away from the master element.An optical path manipulator 31 is provided to direct a time-modulated light beam from the time-modulating unit 52 to different positions of an intensity-modulating unit 16. In contrast to three-dimensional scanning with movement of various optical components, which would be necessary for the direct generation of a free-form wave 12, the scanning of the intensity-modulating unit 16 can advantageously be performed in a regular manner, e.g., line by line, and with a constant angle of incidence onto the intensity-modulating unit 16. Furthermore, the same optical path manipulator 31 with the same settings can be used to generate different free-form waves for corresponding replication series, regardless of any changes to the master element 6 or its replacement.

[0244] In this way, a wavefront 14 can be generated not only with a varying color balance but also with a varying intensity distribution on the side of the intensity-modulating unit 16 facing away from the master element. Even if, for example, an intensity-modulating unit 16 is provided in which the pixels 22 of the intensity-modulating unit 16 can only be switched between two possible transmission values ​​(0 or 100), an intensity distribution with intermediate intensity values ​​can advantageously be generated at the beam-shaping unit 18. The free-form wave 12 can therefore comprise not only electromagnetic beams 10 with different angles but also with different intensities and different colors. The embodiment is thus also suitable for the replication of master holograms 2 into a replication array 8 with virtually arbitrarily complex optical functions.

[0245] Fig. 5 shows further details for the preferred generation of a free-form wave using a preferred device according to the invention comprising an optical path manipulator. The optical path manipulator receives a modulated light beam from the temporal modulation unit 52. A tiltable scan element 30 is also provided, as is a stationary parabolic mirror 32, which can also be referred to as a collimation mirror. The collimated beams are directed by the scan element 30 onto the parabolic mirror 32 so that they are reflected at an orthogonal angle of incidence onto the intensity-modulating unit 16. While a beam is reflected from the parabolic mirror 32 towards the intensity-modulating unit 16, the intensity and / or wavelength properties of the beam can simultaneously be changed by means of the temporal modulation unit 52 according to the requirements of the master hologram 2.Optionally, temporal modulation of the scanning beam can also include counter-distortion, particularly to counteract the effects of optical aberration in the beam-shaping unit. This is explained in more detail in connection with Figures 9A and 9B.

[0246] Fig. 6 shows a schematic representation of a replication method using a preferred device according to the invention, comprising the generation of a free-form wave by means of an intensity-modulating unit 16 and a beam-shaping unit 18 with a different modulation area and orientation. In this case, the intensity-modulating unit 16 comprises a micromirror array (DMD). For this reason, the light beams from the parabolic mirror arrive at one side of the intensity-modulating unit 16 and are reflected from the same side towards the mirror 54a. Collimated electromagnetic beams from several lasers with different wavelength ranges are fed via a combiner 50 to a temporal modulation unit 52, which modifies the intensities of the different wavelength ranges over time.Simultaneously, a scanning element 30 directs the time-modulated combined beam onto a parabolic mirror 32. The parabolic mirror 32 reflects the time-modulated combined beam towards an intensity-modulating unit 16 with an orthogonal angle of incidence. In this embodiment of the invention, the intensity-modulating unit 16 is not parallel, but perpendicular to the beam-shaping unit 18. Furthermore, the intensity-modulating unit 16 has a smaller modulating area than the beam-shaping unit 18. Therefore, various optical components are arranged between the intensity-modulating unit 16 and the beam-shaping unit 18 to utilize the intensity distribution of the intensity-modulating unit 16 for the complete illumination of the beam-shaping unit 18.

[0247] A pair of mirrors 54 is provided to receive the wavefront from the intensity-modulating unit 16 and redirect it into a vertical wavefront. A set of lenses 34 acts as an image magnification arrangement, enlarging the vertical wavefront to match the modulation area of ​​the beam-shaping unit 18. A reverse configuration of an image magnification arrangement would also be conceivable.

[0248] The embodiment allows for a particularly compact design and precise alignment of an intensity-modulated light wave 14 onto a modulation surface of the beam-shaping unit 18.

[0249] For this purpose, the lenses of the image magnification unit 34 and, optionally, a mirror 54b of the pair can preferably be moved together along an axis, for example, by means of an actuator. This is indicated by a horizontal double arrow. The beam-shaping unit 18 is preferably also arranged to be displaceable along an axis orthogonal to it, e.g., by means of an actuator (indicated by a double arrow in the image plane). This enables perfect alignment between an intensity-modulated wavefront 14, which is emitted by the intensity-modulating unit 16, and the modulation surface of the beam-shaping unit 18, so that a precise mapping between pixels of the intensity-modulating unit 16 and the beam-shaping unit 18 can be ensured.

[0250] Fig. 7 is a schematic representation of a cross-section through a single pixel 24 of a beam-shaping unit 18 and several associated pixels 22 of the intensity-modulating unit 16. The single pixel 24 of the beam-shaping unit 18 has the shape of a lens with a single focal point. The diameter of the lens is, for example, about 300 pm in the case shown, which also corresponds to the pixel pitch of the beam-shaping unit 18. The lens is located over a section of the intensity-modulating unit 16 that comprises six pixels 22. The pixels 22 of the intensity-modulating unit 16 are smaller and may, for example, have a pixel pitch of about 50 pm. Each pixel 22 comprises three subpixels 26, which have an R, G, and B color filter. The subpixels 26 may, for example, have a pixel pitch of about 17 pm.

[0251] The intensity-modulating unit 16 preferably modulates the intensity of the light falling on each subpixel 26 independently of the other subpixels 26. Thus, each pixel 22 of the intensity-modulating unit 16 can transmit red, green, and blue light from a wavefront 14 to varying degrees. The light rays are then deflected by the lens 24 depending on the position of the point of incidence and form part of a free-form wave 12 comprising rays of different color channels. Advantageously, this embodiment allows multiple angular distributions for different wavelengths to be generated simultaneously.

[0252] Fig. 8 schematically shows another embodiment of the invention in which each pixel 24 of the beam-shaping unit 18 is assigned a larger number of pixels 22 and subpixels 26 of the intensity-modulating unit 16. In the embodiment shown, the intensity-modulating unit 16 has a significantly higher resolution than the beam-shaping unit 18. Due to possible limitations regarding the minimum size of the pixels 22 and subpixels 26 of the intensity-modulating unit 16, it may be preferable to configure the modulation area of ​​the intensity-modulating unit 16 such that it is significantly larger (e.g., by a factor of 2, 3, or more) than the modulation area of ​​the beam-shaping unit 18.To ensure the mapping of the pixels of the intensity-modulating unit 18 to the pixels of the beam-shaping unit 16, an image reduction unit 34 is provided, which reduces the size of the intensity-modulated wavefront 14 of the intensity-modulating unit 16 so that it corresponds exactly to the modulation area of ​​the beam-shaping unit 18. This is achieved using a set of lenses, which are preferably adjustable in their position and orientation. This embodiment thus makes it possible to map a plurality of pixels 24, preferably RGB pixels 22 with subpixels 26, onto one pixel (e.g., a light-deflectoring component such as a lens 20) of the beam-shaping unit 16. For example, it may be preferred to map 6, 10, 20, 30, 40, 50, 100 or more pixels (e.g., pixels 24 or RGB pixels 22 (with subpixels 26)) onto each lens.This allows the angles of incidence for illuminating the master hologram to be adjusted with particularly high resolution, preferably simultaneously for different colors.

[0253] Figures 9A and 9B schematically show a counter-distortion of the intensity distribution of the intensity-modulating unit 16 to compensate for an optical aberration. Figure 9A shows an exemplary input intensity distribution 36 to the beam-shaping unit 16 and the optical image 38 that, starting from this input intensity distribution 36 and deflected by the beam-shaping unit 18, is projected onto a master hologram 2.

[0254] As can be seen in the figure, rectangular illuminated areas, e.g., pixel 22, of the intensity-modulating unit 16 are distorted when they arrive at the master hologram 2, so that they take on different shapes and partially overlap, but also form unexposed gaps. This distortion can be caused by an optical aberration between the intensity-modulating unit 16 and the master hologram 2 and would be undesirable. Advantageously, however, this aberration can be minimized or eliminated by adjusting the spatial intensity modulation performed by the intensity-modulating unit 16 and / or the temporal intensity modulation of the wavefront 14 to correct the distortion of the intensity-modulated wavefront fed to the beamforming unit 18.This counter-distortion can cancel the effect of an optical aberration in the optical arrangement between the intensity-modulating unit 16 and the master hologram 2. The counter-distorted intensity distribution 40 is shown schematically in Fig. 9B, as is the aberration-free image 42 projected onto the master hologram 2.

[0255] Fig. 10 schematically shows the maximum angle of incidence onto a master hologram 2 that can be generated by a lens 20 of a beam-shaping unit 18. The master hologram 2 is arranged parallel to the beam-shaping unit 18, so that the master hologram 2 and the beam-shaping unit 18 each define a parallel plane. The maximum angle a mThe axis that can be emitted by the beam-shaping unit is determined by the diameter II and the focal length f of each lens. In the case of orthogonal illumination of the lens, the maximum angle is that which would be produced by light rays arriving at the circumference of the lens and passing through the focal point. The maximum angle can be determined as follows:

[0256] The minimum angle is the negative of the maximum angle, assuming the lens is regular.

[0257] Depending on the choice of lens size and its focal length, value ranges for the angles of incidence onto the master hologram 2 of a can thus be determined. ma x to - a m in are generated.

[0258] Fig. 11 schematically shows a setup in which every position along a master hologram 2 can be illuminated from any position along a beam-shaping unit 18. Analogous to Fig. 10, the beam-shaping unit 18 is arranged parallel to a master hologram 2. One end (e.g., bottom) of the beam-shaping unit 18 forms a diagonal to an opposite end (e.g., top) of the master hologram 2. This diagonal should pass through a focal point of a lens 20 to represent a realizable exposure beam of the free-form wave. The diagonal formed between the end of the beam-shaping unit 18 and the opposite end of the master hologram 2 preferably defines a maximum angle of incidence β. max at the extreme end of the master hologram 2. Starting from this required angle βmax, the diameter II and the focal length f of a lens 20 of the beam-shaping unit 18 can be adjusted such that C( max — βmax - Alternatively, the distance d between the beam-shaping unit 18 and the master hologram 2 can be adjusted so that βmax — Clmax-

[0259] In the case that the beam-shaping unit 18 is dimensioned and positioned so far from the master hologram 2 that the entire length of the master hologram 2 can be exposed by the entire length of the beam-shaping unit 18, the maximum and minimum angles of incidence on the master hologram can be calculated as follows:

[0260] Here, d denotes the distance between beam-shaping unit 18 and master hologram 2, I denotes the length of the beam-shaping unit 18, while x denotes the position on the master hologram 2.

[0261] Figures 12A and 12B schematically illustrate a technique for backward ray tracing and freeform wave approximation according to a preferred embodiment of the invention. Here, the precise target positions on the beam-shaping unit 18 are determined, from which the rays of the freeform wave 12 would have to be emitted to generate the freeform wave 12. However, irradiating the master hologram 2 with the target angles of incidence from the determined target positions of the beam-shaping unit 18 is not always directly feasible due to the design of the beam-shaping unit 18. This can be the case, for example, because a desired ray 10 would not pass through a focal point of the relevant lens of the beam-shaping unit 18, which would be necessary to irradiate the target position. This is shown schematically on the left in Figure 12A.

[0262] To bring the achievable distribution as close as possible to the desired distribution, the rays should be directed through the focal points. Two methods are generally conceivable for this purpose.

[0263] Firstly, the angles of the rays can be adjusted or reversed starting from the master hologram so that the rays now pass through the focal points (see Fig. 12B left).

[0264] On the other hand, the positions of the rays on the master hologram can be adjusted or repositioned so that the rays now pass through the focal points (see Fig. 12B right)).

[0265] In the case of an angular shift, an angular inaccuracy results on the master hologram, but the position distribution remains unchanged. With a positional shift, theoretically the angular distribution on the hologram is preserved, but the positions themselves change. However, this shift is limited by the different angular requirements of adjacent positions in master hologram 2, ensuring that all positions of master hologram 2 can be replicated with sufficient efficiency.

[0266] Preferably, an angular displacement is performed (see Fig. 12A, right). However, combinations of both variants (angular and / or positional displacement) are also conceivable. An approximation process is preferably carried out by a suitable algorithm.

[0267] REFERENCE MARK

[0268] 2 Master holograms

[0269] 4 Master substrate

[0270] 6 Master Element

[0271] 8 Replication network

[0272] 10 Reference beam

[0273] 12 Freeform wave

[0274] 14 Light wave

[0275] 15 light sources

[0276] 16 intensity-modulating units

[0277] 18 beam-shaping units

[0278] 20 light-deflectoring component of the beam-shaping unit

[0279] 22 pixels of the intensity-modulating unit

[0280] 24 pixels of the beam-shaping unit

[0281] 26 subpixels of the intensity-modulating unit

[0282] 28 Focal plane

[0283] 30 scan elements

[0284] 31 Optical path manipulator

[0285] 32 Light-collecting element, preferably a collimating mirror

[0286] 34 optical arrangement for reducing or enlarging an image

[0287] 36 Input intensity distribution at beam-shaping unit

[0288] 38 Distorted intensity distribution on the master hologram

[0289] 40 Pre-compensated input intensity distribution at beam-shaping unit

[0290] 42 Correct intensity distribution on the master hologram

[0291] 44 Master hologram level

[0292] 46 Plane of the beam-shaping unit

[0293] 48 Focus

[0294] 50 Combiner

[0295] 52 Temporal modulation unit, preferably AOM or AOTF

[0296] 54 Mirror d Distance between intensity-modulating unit and master hologram f Focal length

[0297] BP Hotspot

[0298] 11 Lens diameter h Length of the master hologram x Position on the length of the master hologram

Claims

PATENT CLAIMS 1. Device for replicating a hologram into a replication assembly (8) with an exposure module, wherein the exposure module comprises at least one light source (15) and a carrier means for receiving a master element (6) comprising a master hologram (2) to be replicated, and the exposure module is configured to bring the replication assembly (8) into optical contact with the master element (6), while the at least one light source (15) exposes the master hologram (2) to obtain a replicated hologram onto an area of ​​the replication assembly (8), characterized in that the exposure module is designed for exposing the master hologram (2) with a free-form wave (12) with a spatially varying angular distribution and, for this purpose, comprises a beam-shaping unit (18), wherein the device is configured for adjusting an intensity distribution of a light wave (14) of the at least one light source (15).with which the beam-shaping unit (18) is irradiated and the beam-shaping unit (18) is configured for generating the free-form wave (12) with the spatially varying angular distribution, wherein the angular distribution can be predetermined by the intensity distribution of the light wave (14) incident on the beam-shaping unit (18).

2. Device according to the previous claim characterized in that the device for adjusting the intensity distribution of the light wave (14) of the at least one light source (15) comprises an intensity-modulating unit (16) which is configured for adjusting the intensity distribution of the light wave (14) of the at least one light source (15) with which the beam-shaping unit (18) is irradiated.

3. Device according to the previous claim characterized in that the device is configured to irradiate the intensity-modulating unit (16) coherently with the light wave (14) and / or the intensity-modulating unit (16) is irradiated with the light wave (14), wherein the light wave (14) has a maximum divergence of up to 3°, preferably up to 1°, particularly preferably up to 0.5° and / or is directed substantially orthogonally to the intensity-modulating unit (16).

4. Device according to one of the preceding claims 2 or 3, characterized in that The device comprises a control unit configured to control the intensity modulating unit (16) to generate an intensity distribution of the light wave (14) according to a desired spatially varying angular distribution of the free-form wave (12), wherein the control unit preferably sets a local transmission and / or reflection via the intensity modulating unit (16).

5. Device according to one of the preceding claims 2-4 characterized in that the intensity-modulating unit (16) comprises a light-modulating pixel array, wherein individual pixels (22) of the pixel array are preferably electronically controllable to adjust the intensity distribution of the light wave (14).

6. Device according to the previous claim characterized in that the light-modulating pixel array is selected from the following group: LCD, DMD, Leos and an aperture array.

7. Device according to one of the preceding claims 5 or 6 characterized in that each pixel (22) of the intensity-modulating unit (16) comprises at least two, preferably at least three, subpixels (26), wherein the subpixels (26) comprise different color filters, in particular RGB filters.

8. Device according to one of the preceding claims characterized in that the beam-shaping unit (18) is configured as a pixel array, wherein each pixel of the beam-shaping unit (18) comprises a light-deflectoring optical component (20) whose light-deflectoring optical function depends on an incident position of a light beam, and wherein preferably each pixel (24) of the beam-shaping unit (18) is assigned to a section of the intensity-modulating unit (16) which may have several spatially distributed intensities, wherein particularly preferably each pixel (24) of the beam-shaping unit (18) covers several pixels (22) of the intensity-modulating unit (16).

9. Device according to the previous claim, characterized in that the pixel array of the beam-shaping unit (18) is a lens array or a diffractive optical element (DOE) functioning as a lens array, wherein preferably each pixel (24) of the pixel array has an identical focal length (28), wherein preferably the beam-shaping unit (18) defines a focal plane (28) which lies between the beam-shaping unit (18) and the master hologram (2).

10. Device according to one of the preceding claims characterized in that the beam-shaping unit (18) is positioned at a distance (d) from the master hologram (2), wherein the distance (d) is at least twice the distance between the beam-shaping unit (18) and a focal plane (28) of the beam-shaping unit (18).

11. Device according to one of the preceding claims, provided that it is dependent on claim 2, characterized in that a modulation area of ​​the intensity-modulating unit (16) is larger than a modulation area of ​​the beam-shaping unit (18) and an optical arrangement (34) is configured to generate a reduced image of the intensity-modulating unit (16) on the beam-shaping unit (18).

12. Device according to one of the preceding claims, provided that it is dependent on claim 2, characterized in that a modulation area of ​​the intensity-modulating unit (16) is smaller than a modulation area of ​​the beam-shaping unit (18) and an optical arrangement (34) is configured to generate an enlarged image of the intensity-modulating unit (16) on the beam-shaping unit (18).

13. Device according to one of the preceding claims, if dependent on claim 2, characterized in that the device further comprises an optical path manipulator configured to direct a light wave (14) from the at least one light source (15) with a predetermined angle of incidence, preferably substantially orthogonal, and with substantially parallel light rays onto the intensity-modulating unit (16), wherein the optical path manipulator preferably comprises one or more optical components.

14. Device according to the previous claim characterized in that the at least one light source (15) comprises one or more lasers and the optical path manipulator comprises a scanning element (30) and a light-collecting element (32), wherein preferably the scanning element (30) is located at a focal point of the light-collecting element The element (32) is arranged such that light beams can be guided over different positions of the intensity-modulating unit (18) by means of the scanning element (30) at a substantially constant angle of incidence.

15. Device according to one of the preceding claims, if dependent on claim 2, characterized in that the device is configured for large-area illumination of the intensity-modulating unit (18), the device preferably comprising optical components for generating a substantially planar light wave (14).

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