Configuration of a replication process of a master holographic optical element for variable intensity or polarisation

Abstract

The invention relates to techniques for producing a holographic optical element (HOE) by replication of a master HOE. In particular, the invention relates to techniques for flexibly adjusting the diffraction efficiency of the HOE. An adjustable optical element (54) can be used to modify the intensity and / or the polarisation of light during the exposure process.

Description

[0001] DESCRIPTION

[0002] CONFIGURATION OF A REPLICATION PROCESS OF A MASTER HOLOGRAPHIC OPTICAL ELEMENT FOR VARIABLE INTENSITY OR POLARI¬

[0003] SATION

[0004] TECHNICAL FIELD

[0005] Various examples concern techniques for producing a holographic optical element (HOE) by replicating a master HOE. In particular, various examples concern techniques for variably adjusting the illumination of the master HOE during replication.

[0006] BACKGROUND

[0007] HOEs are used in various applications. For example, HOEs can be used to implement a transparent screen. Applications include, for example, use in a head-up display in an automobile or the integration of a holographic optical element into a mirror. HOEs are used to generate holograms.

[0008] One technique for fabricating HOEs relies on the use of a master HOE, which is then used in an exposure process to form the HOE. An example of a master HOE is a reflection free-jet volume HOE.

[0009] During replication of the master HOE, the carrier layer (for example, a photopolymer arranged on a substrate) of the master HOE is arranged along the carrier layer of the HOE to be replicated (hereinafter simply "replicated HOE"). By exposure to light, the diffraction structure of the master HOE can then be replicated in the replicated HOE. Such manufacturing methods which use replication of the master HOE to produce the HOE can, for example, use a roll-to-roll process in which the master HOE and the HOE are arranged on a respective roll which is rotated in synchronization with one another so that a respective portion of the master HOE extends along a corresponding portion of the replicated HOE. Another technique is the flat board process; in this case, the master HOE and the replicated HOE are arranged on a respective flat orflat carrier so that the entire surface of the respective carrier layers extend along each other.

[0010] In such manufacturing processes, the diffraction efficiency of the replicated HOE may deviate from certain target specifications. This may reduce the quality of the hologram generated using the replicated HOE. Furthermore, in such manufacturing processes, deviations between the replicated HOE and the master HOE are not typically possible, for example, to allow for a different color distribution.

[0011] BRIEF DESCRIPTION OF THE INVENTION

[0012] Therefore, there is a need for improved manufacturing processes for HOEs. In particular, there is a need for improved manufacturing processes that enable high quality for the replicated HOE.

[0013] This problem is solved by the features of the independent patent claims. The features of the dependent patent claims define embodiments.

[0014] A control device for an exposure device is described. The exposure device serves to produce a HOE. The HOE is produced by replicating a master HOE during an exposure process performed by the exposure device. During the exposure process, a carrier layer of the master HOE is arranged along a carrier layer of the HOE. The control device comprises at least one processor and a memory. The at least one processor is configured to load program code from the memory and to execute the program code.

[0015] The at least one processor is further configured to control at least one light source of the exposure device based on the program code, such that the light source emits light having at least one wavelength along a beam path toward a surface of the carrier layer of the master HOE.

[0016] The at least one light source can, for example, emit light in the visible spectrum. Radiation could also be emitted in the ultraviolet or infrared range of the electromagnetic spectrum. The at least one light source can be a coherent laser light source. For example, multiple light sources could be used that emit light components at different wavelengths. For example, a light source could have three channels, such as red, green, and blue (multi-channel light source).

[0017] The at least one processor is further configured to control a beam movement unit of the exposure device based on the program code so that it moves the beam path with respect to the surface of the carrier layer of the master HOE during the exposure process.

[0018] For example, the angle of incidence could be tilted. A light spot could, for example, be moved across the surface of the carrier layer. A scanning movement could occur. Line scanning would be conceivable. It would be conceivable to use a galvo scanner that implements step operation, i.e. remains in one position and is then moved to the next stable position. It would be possible for the beam movement unit to scan a beam path of the light across the surface of the carrier layer of the master HOE. Alternatively or additionally, it would be conceivable for the beam movement unit to move a reference point arranged along the beam path and at a distance from the surface of the carrier layer on a curved trajectory with respect to the master HOE during the exposure process. The reference point could, for example, be arranged in a scanning mirror or a deflection mirror.This allows, in particular, the angle of incidence of the beam path onto the surface of the master HOE's carrier layer to be varied during the exposure process. The beam movement unit can be used to move a spot of light across the master HOE. This means that the master HOE is not illuminated over a large area, but rather gradually by moving the spot. This means that the HOE is not exposed in a single-shot process, but rather gradually.

[0019] Furthermore, the at least one processor is configured to control, based on the program code, at least one adjustable optical element of the exposure device, which is arranged in the beam path. As a result, the at least one adjustable optical element changes the intensity and / or polarization of the light over time during the exposure process. The at least one adjustable optical element can therefore be a filter that changes the intensity or changes the polarization.

[0020] The master HOE can be formed in a photopolymer that is part of the carrier layer. The carrier layer could also additionally comprise a substrate. The carrier layer could be film-based. A so-called volume HOE could be used.

[0021] The HOE can be formed in a photopolymer that is part of the corresponding carrier layer. The carrier layer could also additionally comprise a substrate. The carrier layer could be film-based. A so-called volume HOE could be used.

[0022] Through replication, a diffraction structure can be created in the HOE based on the diffraction structure in the master HOE. A copy can be made, but a 1:1 copy is not necessary. The diffraction structure corresponds to a local variation in the refractive index, for example, due to different chain lengths or a different degree of polymer interlinking in a corresponding layer.

[0023] By illuminating the master HOE, the replicated HOE can be exposed. A specific dose of light can thus create a diffraction efficiency in the replicated HOE. The diffraction structures are copied from the master HOE to the replicated HOE. The replication efficiency of the master HOE describes the ratio between ( / ) the diffraction efficiency in the replicated HOE and ( / 7) the amount of light (dose) used to expose the replicated HOE. This means: the smaller / larger the replication efficiency, the larger / lower the light dose required to achieve a specific diffraction efficiency.

[0024] Diffraction efficiency replicated HOE = Replication efficiency • Amount of light

[0025] (1)

[0026] In the above equation, it must be taken into account that the proportionality between the diffraction efficiency of the replicated HOE and the required amount of light is limited to a linear

[0027] The maximum achievable diffraction efficiency of the replicated HOE is typically in the range of 95% to 98% and is limited, for example, by the thickness of the HOE region (where the refractive index is modulated). Once this maximum diffraction efficiency is reached, further exposure does not result in a further increase in the diffraction efficiency. This is described by the so-called Kogelnik theory.

[0028] Replication efficiency can be influenced by several factors. Some examples are summarized in Table 1.

[0029]

[0030] TABLE 1: Various factors influencing replication efficiency. The diffraction efficiency is explained in more detail below. Microscopically, the diffraction efficiency can be explained by the amplitude of the refractive index variation, which can depend, for example, on the degree of polymer linkage. Macroscopically, the diffraction efficiency can be described by the proportion of diffracted light to the total incident (coherent) light.

[0031] Light can be defined: amount of light diffracted light

[0032] Diffraction efficiency = - - — : - total amount of light

[0033] The more polymers are linked, the higher the refractive index modulation, the higher the diffraction efficiency.

[0034] The dose of light used to expose the replicated HOE is influenced by the dwell time of a light spot at a particular location on the surface of the support layer, as well as the intensity of the light.

[0035] By providing at least one adjustable optical element, it is possible to flexibly vary the intensity and / or the polarization of the light during the exposure process, i.e. as a function of the position of the light spot on the surface of the carrier material of the master HOE. This could, for example, compensate for manufacturing variations that lead to a locally variable replication efficiency (cf. TABLE 1: Example II). Alternatively or additionally, it would be possible to compensate for a variation in the replication dose due to different angles of incidence and thus different angles between a polarization plane of the light with respect to the surface of the carrier layer of the master HOE (cf. TABLE 1: Example III). Alternatively or additionally, it would be conceivable to deliberately use different intensities in order to obtain different diffraction efficiencies for the HOE, in particular deviating from the diffraction efficiencies of the master HOE.Overall, such effects can ensure that the hologram generated by the HOE exhibits a particularly high quality, i.e., a specific diffraction efficiency that corresponds to a target specification. In particular, the diffraction efficiencies of different wavelength components can be achieved in a desired ratio to each other. Negative influences caused by replication can be reduced.

[0036] As a general rule, the intensity could be changed absolutely. This means that, for example, the intensity can be increased or decreased from a reference level to a certain absolute level. This can be done individually for several components of the light, which correspond to different wavelengths. However, it would also be conceivable for the intensity to be changed equally for all components of the light. As a further general rule, it would be conceivable for the intensity of the different wavelength components of the light to be adjusted relative to one another. For example, if the intensities for red-green-blue (RGB) components are 1:1:1 as a reference, an adjustment to, for example, 0.8:1 or 2:1 could be made.

[0037] For example, it would be conceivable for the at least one processor to be further configured based on the program code to load control data. The control data can, for example, indicate the change in polarization and / or intensity as a function of time. The control data can indicate a relationship between the movement of the beam path relative to the surface of the carrier layer, on the one hand, and the change in intensity and / or polarization of the light, on the other. The control of the beam movement unit and the control of the at least one adjustable optical element can then be synchronized based on the control data.

[0038] This means that, depending on the position of a corresponding light spot on the surface of the master HOE's carrier layer and / or the angle of incidence of the beam path onto the surface of the master HOE's carrier layer, a different intensity and / or polarization of the light can be set. This results in a change in intensity and / or polarization over time because the light spot is moved accordingly over time. This means that the position and / or angle of incidence of the beam path on the surface of the carrier layer changes as a function of time.

[0039] Such synchronization can be used to specifically compensate for undesired properties of the master HOE or the carrier layer at different positions on the surface of the carrier layer. A local deviation between the master HOE and the HOE could also be specifically provided.

[0040] For example, if the beam movement unit implements step-by-step operation, i.e., it remains in each position and moves step by step between these positions (as opposed to continuous movement, such as in a resonantly operated scanning mirror), the at least one adjustable optical element could be controlled to change the intensity and / or polarization in conjunction with a step of the step-by-step operation. For example, if a galvo scanner is moved, the intensity and / or polarization could be changed simultaneously.

[0041] For example, it would be conceivable for the at least one adjustable optical element and the beam movement unit to be controlled in such a way that the influence of the variation in structural properties of the master HOE on the diffraction efficiency (and thus on the replication efficiency, cf. TABLE 1: Example II) is reduced by changing the light intensity during the exposure process. This means that, for example, a change in the diffraction efficiency by a certain value between two points on the surface of the carrier layer of the master HOE is not replicated in the replicated HOE, or is replicated only to a lesser extent: If the diffraction efficiency varies between points A and B by 10 percentage points in the master HOE, the diffraction efficiency of the HOE between the corresponding points A and B could only vary by 5 percentage points.

[0042] For example, the diffraction efficiency could vary for different positions on the surface of the master HOE's carrier layer due to variable structural properties—e.g., caused by manufacturing variations, aging, or scratches. In practical terms, this means: If all positions on the surface of the master HOE's carrier layer were illuminated with the same light dose, i.e., if the same light intensity were used to illuminate all different positions on the surface of the master HOE's carrier layer (with the same dwell time of the light spot at the different positions on the surface), these different diffraction efficiencies of the master HOE would also result in correspondingly different diffraction efficiencies in the HOE (because the replication efficiency varies accordingly, see TABLE 1: Example 0).As a result, the hologram generated by the replicated HOE would, for example, exhibit varying brightnesses, blurriness, or color inhomogeneities such as color fringing. Such undesirable effects can be avoided by appropriately adjusting the light intensity during the exposure process to reduce or compensate for the variation in diffraction efficiency. The at least one adjustable optical element and the beam movement unit can thus be controlled such that the influence of the variation in structural properties of the master HOE on the diffraction efficiency is reduced by changing the light intensity during the exposure process. This allows imperfections in the master HOE to be compensated. A master HOE can be used for longer.

[0043] Another factor that influences the efficiency of replication is the orientation of the polarization plane of the light (for linearly polarized light) with respect to the surface of the carrier material of the master HOE, see TABLE 1: Example III. For example, s-polarization or p-polarization can be present, or a mixture. The orientation of the polarization plane is changed when the angle of incidence of the light on the master HOE changes. The angle of incidence, in turn, can change if the light spot is moved over the surface of the carrier layer of the master HOE during exposure. This has an influence on the replication efficiency. It is possible that the at least one adjustable optical element and the beam movement unit are controlled in such a way that the orientation of the polarization with respect to the surface of the carrier layer of the master HOE is stabilized.This means that the control can be configured in such a way that the influence of the beam path movement on a change in the orientation of the polarization of the light relative to the surface of the master HOE's support layer during the exposure process is reduced. In short, this reduces the influence of variable angles of incidence (due to the movement of the beam path) on replication efficiency.

[0044] This allows for more flexible beam path movements through the beam movement unit. This allows, for example, replication for curved master HOEs.

[0045] These and other effects are also achieved by means of other methods and devices:

[0046] A method for configuring a manufacturing process for producing an HOE by replicating a master HOE during an exposure process performed by an exposure device is disclosed. During the exposure process, a carrier layer of the master HOE is arranged along a carrier layer of the HOE. The method comprises generating control data for at least one adjustable optical element of the exposure device, which is arranged in a beam path of light used for replication. Using the control data, the at least one adjustable optical element can be controlled so that it changes at least one of an intensity and a polarization of the light over time during the exposure process.

[0047] A device comprises at least one processor and a memory. The at least one processor is configured to load and execute program code from the memory. The at least one processor is further configured to execute the method for configuring the manufacturing method based on the program code.

[0048] A method for controlling an exposure device for producing a HOE by replicating a master HOE is disclosed. The replication takes place within the framework of an exposure process performed by the exposure device. During the exposure process, a carrier layer of the master HOE is arranged along a carrier layer of the HOE. The method comprises controlling at least one light source of the exposure device such that, during the exposure process, it emits light with at least one wavelength along a beam path toward the surface of the carrier layer of the master HOE. The method also comprises controlling a beam movement unit of the exposure device such that it moves the beam path relative to the surface of the carrier layer of the master HOE during the exposure process.The method also comprises controlling at least one adjustable optical element of the exposure device, which is arranged in the beam path, so that the at least one adjustable optical element changes at least one of an intensity and a polarization of the light over time during the exposure process.

[0049] A control device for an exposure device for producing a holographic optical element (HOE) by replicating a master HOE during an exposure process performed by the exposure device is disclosed. The exposure process uses light emitted by at least one light source of the exposure device during the exposure process along a beam path toward a surface of the carrier layer of the master HOE. During the exposure process, a carrier layer of the master HOE is arranged along a carrier layer of the HOE. The control device comprises at least one processor and a memory, wherein the at least one processor is configured to load program code from the memory and to execute the program code.The at least one processor is configured to control a beam movement unit of the exposure device based on the program code, such that it moves the beam path relative to the surface of the carrier layer of the master HOE during the exposure process. The at least one processor is further configured to control at least one of an adjustable optical element of the exposure device arranged in the beam path, the at least one light source, or the beam movement unit, such that at least one of a dose and a polarization of the light is changed over time during the exposure process.

[0050] A corresponding method is also disclosed.

[0051] For example, a diode current through a laser diode could be varied to vary the intensity of the light.

[0052] For example, a scanning speed could be varied so that the dwell time of a light spot on the surface (for example, at the same intensity of the light) is varied, thus increasing or decreasing the dose.

[0053] The features set forth above and the features described below may be used not only in the corresponding explicitly set forth combinations, but also in further combinations or in isolation, without departing from the scope of the present invention. BRIEF DESCRIPTION OF THE FIGURES

[0054] FIG. 1 is a flow diagram of an exemplary method for manufacturing a HOE.

[0055] FIG. 2 schematically illustrates a system for exposing an HOE in the context of a replication of a master HOE according to various examples.

[0056] FIG. 3 is a flowchart of an exemplary method for generating

[0057] FIG. 4 schematically illustrates the illumination of a master HOE based on a corresponding map according to various examples.

[0058] FIG. 5 schematically illustrates the illumination of a master HOE based on a corresponding map according to various examples.

[0059] FIG. 6 is a flowchart of an exemplary method for creating an HOE by replicating a master HOE.

[0060] FIG. 7 schematically illustrates the illumination of a master HOE in a target surface shape according to various examples.

[0061] FIG. 8 schematically illustrates the illumination of the master HOE of FIG. 7 in an exposure surface shape that differs from the target surface shape, according to various examples.

[0062] FIG. 9 schematically illustrates the illumination of the master HOE of FIG. 7 in the exposure surface shape of FIG. 8, wherein a reference point of a beam of light moves along a trajectory.

[0063] FIG. 10 shows a roll-to-roll process.

[0064] FIG. 11 schematically illustrates a flatboard replication process for exposing an HOE by replicating a master HOE according to various examples.

[0065] FIG. 12 schematically illustrates the master HOE of FIG. 12 with a planar illumination surface shape according to various examples. FIG. 13 is a side view of the master HOE of FIG. 11.

[0066] FIG. 14 is another side view of the master HOE of FIG. 11 .

[0067] FIG. 15 illustrates aspects related to a beam moving unit according to various examples.

[0068] FIG. 16 schematically illustrates a p-polarization.

[0069] FIG. 17 schematically illustrates an s-polarization.

[0070] FIG. 18 schematically illustrates an exposure device according to various examples.

[0071] FIG. 19 schematically illustrates an exposure device according to various examples.

[0072] FIG. 20 schematically illustrates an exposure device according to various examples.

[0073] FIG. 21 schematically illustrates an exposure device with a sensor according to various examples.

[0074] FIG. 22 schematically illustrates an exposure device with a sensor according to various examples.

[0075] FIG. 23 schematically illustrates an exposure device with a sensor according to various examples.

[0076] FIG. 24 is a flow chart according to various examples, which enables intensity stabilization during the exposure process to, for example, a time-variable target intensity value.

[0077] DETAILED DESCRIPTION The above-described properties, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more clearly understood in connection with the following description of the embodiments, which are explained in more detail in connection with the drawings.

[0078] The present invention is explained in more detail below using preferred embodiments with reference to the drawings. In the figures, identical reference numerals designate identical or similar elements. The figures are schematic representations of various embodiments of the invention. Elements shown in the figures are not necessarily drawn to scale. Rather, the various elements shown in the figures are depicted in such a way that their function and general purpose will be understood by those skilled in the art. Connections and couplings between functional units and elements shown in the figures can also be implemented as an indirect connection or coupling. A connection or coupling can be implemented wired or wirelessly. Functional units can be implemented as hardware, software, or a combination of hardware and software.

[0079] Techniques for fabricating HOEs are described below. For example, bulk HOEs or surface HOEs can be fabricated using the techniques described herein.

[0080] The techniques described herein are based on the replication of a master HOE to produce a replicated HOE. A corresponding exposure process can be used to produce the master HOE. Various examples described herein specifically relate to the exposure of the replicated HOE by replicating the master HOE.

[0081] Replication can be achieved, for example, through a scanning process. A laser spot is formed into a line or other shape by a rapidly scanning element (such as a scanning mirror), which in turn is moved across the master HOE. In a snapshot, a laser spot thus moves across the master. More generally, the light beam path (which can contain multiple components corresponding to different wavelengths) is moved across the surface of the master HOE's substrate material by a beam movement unit during the exposure process. During the exposure process, different areas of the replicated HOE are thus gradually exposed by moving the light spot.Various examples described herein are based on the realization that, for various reasons, it may be desirable to vary the intensity and / or polarization of the light used for exposure during the exposure process using an adjustable optical element. Some scenarios are listed in Table 2.

[0082] TABLE 2: Several example scenarios for the change in intensity and / or polarization over time during the exposure process. In practical examples, the different scenarios can be combined. For example, it would be conceivable to combine the polarization adjustment from Scenario II for large angles of incidence with the local intensity adjustment according to Scenario III, so that Fresnel losses are additionally achieved by increasing the power at large angles of incidence.

[0083] From TABLE 2 it can be seen that, for example, a distinction must be made between the scenario in which an imperfect master HOE (e.g., inhomogeneity in the mixture of the RGB components of the light) is to be compensated - Scenario I - and the case in which a perfect master HOE is to be exposed differently for other reasons (spatially resolved), e.g., to compensate for inhomogeneities in the replication material and / or the subsequent illumination - Scenario V. A mixture of both cases is also conceivable. To change the intensity of the light during exposure, modulation frequencies in the kHz or MHz range can be used. These can be achieved, for example, by acousto-optical elements such as acousto-optical modulators (AOM) or acousto-optical filters (AOTF) as examples of adjustable optical elements for changing the intensity.Such a modulation frequency is sufficiently high to change the intensity quickly compared to the movement of the light spot across the surface of the master HOE's carrier material. Typically, the beam movement unit is controlled in the kHz range, e.g., at a few hundred Hz. As a general rule, the beam movement unit can be controlled with a smaller signal bandwidth than the signal bandwidth used to control the adjustable optical element—e.g., a factor of 3 to 4 can exist between the signal bandwidths. In summary, a corresponding signal bandwidth for controlling the adjustable optical element can be in the megahertz range, for example, if the beam movement unit is controlled with a signal bandwidth in the kilohertz range.

[0084] In some variants, it is conceivable that the intensity is varied during the exposure process using a control loop. This means that (using a suitable sensor, e.g., a photodiode) a measured value can be recorded that indicates the intensity of the light used to replicate the master HOE. This measured value can then be used to check whether the actual intensity of the light deviates from a target intensity. This target intensity can be varied during the exposure process, as described above. Such a control loop can be implemented in software and / or hardware. For example, the target intensity can be output as program output from a software program; and the control loop can then be implemented in hardware.

[0085] Modulation frequencies in the MHz range can also be used to change the polarization of the light during exposure, which can be achieved, for example, using a Pockels cell or a lambda / 2 plate that can be flexibly inserted into the beam path. As discussed above in connection with an intensity control loop, it is also conceivable, alternatively or additionally, to use a control loop to change the polarization during the exposure process.

[0086] FIG. 1 illustrates a method for manufacturing a replicated HOE according to various examples.

[0087] In Box 3005, a master HOE is created. For this purpose, a corresponding photopolymer located in or on a carrier layer of the master HOE is exposed. For exposure, an object beam and a reference beam of corresponding light, which are phase-coherent to each other, can be used. An analog exposure could be used, with the object generating the object beam. Digital exposure with a pixelated light modulator and a stitching process could also be used.

[0088] FIG. 1 shows that the master HOE (or more precisely, the carrier material of the master HOE) in box 3005, i.e., upon exposure of the master HOE, has the target surface shape 911. This target surface shape 911 is illustrated schematically and by way of example in FIG. 1 as curved, but could have any desired shape.

[0089] Then, in box 3010, the replicated HOE is exposed by replicating the master HOE. A roll-to-roll process or a flatbed copying process can be used.

[0090] In box 3010, the substrate material of the master HOE as well as the substrate material of the replicated HOE has an exposure surface shape 912; this is shown as flat in FIG. 1 for example, but could also have a curvature.

[0091] In some examples, the exposure surface shape 912 may differ from the target surface shape 911. This can be compensated by moving a reference point in the beam path along a curved trajectory during the exposure process. This can, in particular, achieve a variation in the angle of incidence of the beam path on the surface of the carrier material. After the exposure process, the replicated HOE is fixed again in the target surface shape 911 for the carrier layer, box 3015.

[0092] FIG. 2 illustrates aspects related to a system 50 that can be used to create a replicated HOE 96 by replicating a master HOE 92. Thus, the system 50 can be used particularly in conjunction with box 3010 according to the method of FIG. 1.

[0093] The system 50 includes an exposure device 59 and a control device 51 for the exposure device 59. The control device 51 (or controller 51 for short) includes a processor 191 and a memory 192. The processor 191 can load and execute program code from the memory 192 and then control the exposure device 59 based thereon.

[0094] The exposure device 59 comprises a light source 52, for example a laser.

[0095] The light source 52 emits light along a beam path 41. The exposure device 59 could, for example, comprise multiple light sources (not shown) for different components of the light associated with different wavelengths. The exposure device 59 could, for example, comprise three light sources 52 for RGB components of the light. The light source can emit coherent light. The light can be in the visible spectrum or adjacent wavelength ranges, for example, in the infrared or ultraviolet part of the electromagnetic spectrum.

[0096] The light illuminates a master HOE 92 to expose a replicated HOE 96. In FIG. 2, it is schematically indicated that the carrier layer of the master HOE 92 is arranged along the carrier layer of the HOE 96.

[0097] The exposure device 59 has an optical element 54 in the beam path. The optical element 54 can change the intensity and / or polarization of the light. The optical element is adjustable, meaning that the change in the intensity and / or polarization of the light can be adjusted, in particular, it can be varied over time during the exposure process. Examples of adjustable optical elements 54 are listed below in Table 3.

[0098] TABLE 3: Several examples of the implementation of the adjustable optical element 54. As a general rule, the exposure device 59 could also have several such adjustable optical elements, for example in a series connection in the beam path 41 (but this is not shown in FIG. 2).

[0099] In addition, the system 50 also includes a beam movement unit 55. This can include, for example, one or more motorized actuators and an optical element arranged in the beam path (e.g., a mirror, a prism, a lens, and / or a scanning mirror), which can be passive or active, i.e., adjustable or fixedly oriented. The motorized actuators can position the optical element according to multiple degrees of freedom. It may be possible to implement one or more translational degrees of freedom of movement. Alternatively or additionally, one or more rotational degrees of freedom of movement can be implemented. This allows the beam path of the light to be moved. The actuator could, for example, be implemented by a robot arm with multiple adjustable axes. Implementation by means of a multi-axis optical linear adjustment stage would also be conceivable.The actuator can be controlled by the controller 51. By means of the beam movement unit 55, it may be possible to move the beam path 41 during the exposure process with respect to the surface of the carrier layer of the master HOE 96. For example, by means of the beam movement unit 55, it may be possible to scan the beam path 41, which is represented by a corresponding exit angle or scan angle 85. Alternatively or additionally, it may be possible to move a reference point 84, which is arranged along the beam path 41, along a curved trajectory 61 (indicated by the dotted-dashed line), by means of the beam movement unit 55.

[0100] By moving the beam path 41, the position of a corresponding light spot 42 on the surface of the carrier layer of the master HOE 96 is changed during the exposure process. By moving the beam path 41 relative to the master HOE 96, the angle of incidence 89 of the beam path 41 onto the surface of the carrier layer of the master HOE 96 can be changed during the exposure process.

[0101] FIG. 2 also shows that a sensor 57 is present, which is configured to measure an intensity of the light in the region of the beam path 41. The sensor 57 is optional. The sensor 57 can be a photodiode, for example. The sensor 57 can output a signal indicative of the intensity of the light. The sensor 57 can therefore measure, for example, a luminous flux or light power. In the example in FIG. 2, the sensor 57 is connected to the controller 51. The sensor 57 could also be connected directly to the light source 52 and / or another adjustable element for adjusting the intensity (such as a Pockels cell or an AOTF). Based on a measurement signal from the sensor 57, it is possible to implement exposure monitoring. This means that, in particular, the light power for the exposure of the HOE 92 can be monitored.A closed control loop can be implemented that adjusts the control signals for an adjustable optical element to control the actual value of the light output at a target value of the light output.

[0102] To control the adjustable optical element 54 and / or the light source 52 and / or the beam movement unit 55, the controller can use control data 401. In particular, a (time-)synchronized control of the adjustable optical element 54 as well as the beam movement unit 55 and optionally the light source 52 can be carried out. This means that a time-correlated control takes place, so that, for example, depending on the position of a light spot on the surface of the carrier material of the master HOE, a different setting of the adjustable optical element 54 is selected. It is possible for this control data 401 to be specifically assigned to a particular master HOE 96. This means that different control data 401 can be used for different master HOEs. This is because the control data 401 can specifically compensate for specific properties of the master HOE.Details relating to the generation of control data 401 are described below. FIG. 3 is a flowchart of an exemplary method. FIG. 3 illustrates aspects relating to the configuration of a manufacturing method for producing an HOE by replicating a master HOE. FIG. 3 particularly illustrates aspects relating to the generation of control data for an exposure device, by means of which the master HOE can be replicated. The control data can be, for example, the control data 401 for the exposure device 59. In particular, reference is made below to the generation of control data 401, which enable control of at least one adjustable optical element (cf. TABLE 3). By generating control data 401, the intensity and / or polarization of light used by the exposure device to expose the master HOE for replication can be changed.This can occur due to one or more scenarios, such as those listed in TABLE 2.

[0103] It is particularly possible for the control data to couple the control of the beam movement unit and the at least one adjustable optical element, ie for the light spot to be moved over the surface of the carrier layer of the master HOE and for the polarization and / or intensity to be changed in correlation thereto.

[0104] First, one or more input data items are received in box 3805. Based on the input data, the control data can then be generated in box 3810. The control data contains instructions for the at least adjustable optical element, so that it changes the intensity and / or polarization of the light over time during the exposure process to replicate the master HOE.

[0105] Different types of input data are conceivable for determining the control data. In particular, different input data can be considered depending on the scenario from TABLE 2. Table 4 below describes some examples of the input data to be considered that can be obtained in Box 3805.

[0106]

[0107] TABLE 4: Various examples of input data that can be used to generate control data for an adjustable optical element. The various examples can also be combined.

[0108] As a general rule, the control data in box 3810 can be determined at different phases. This is described in Table 5.

[0109] TABLE 5: Different variants for phases in which the control data for a tailored diffraction efficiency of the replicated HOE can be generated. Such variants can also be combined with each other. In particular, a distinction can be made between a case in which measurements are carried out at the manufacturer of the master HOE to characterize the master HOE in order to

[0110] to generate control data that is delivered, for example, together with the master HOE (cf. Example I in TABLE 5); and a case in which the control data is generated after delivery of the master HOE to a user, either in advance or together with the production of the replicated HOE (cf. Examples II and II in TABLE 5). These cases can also be combined, for example, to address different scenarios according to TABLE 2. Using the techniques described in FIG. 4, it is possible to generate the control data in an optimized manner. If, for example, an excessively high dose is exposed to a poor master HOE and the resulting poor interference contrast (due to an excessively high intensity selection or incorrect change in polarization), the opposite effect can occur locally and the diffraction efficiency in the replicated HOE can be reduced, as the refractive index modulation of the material is "exposed out" again.This can be avoided by appropriately determining the tax data.

[0111] Once the control data has been determined, the HOE can then be exposed by replicating the master HOE. This is disclosed in connection with FIG. 6.

[0112] FIG. 6 illustrates an exemplary method. The method of FIG. 6 is for creating a replicated HOE. In particular, the method of FIG. 6 relates to the replication process, see FIG. 1: box 3010. For example, the method of FIG. 6 could be implemented by a controller, such as controller 51 of system 50 of FIG. 2. For example, the processor could load and execute program code 191 from memory 192 to perform the method of FIG. 6.

[0113] In box 3105, a light source, such as a laser, is controlled to emit light along a beam path to a master HOE. For example, the light source could be controlled to continuously emit light at a specific luminous intensity during an exposure process. The light source could also be switched on and off alternately. This can be useful, for example, when stepping the beam path across the surface of the carrier layer—in this example, moving the light spot between two different positions or two scan lines.

[0114] In box 3110, a beam movement unit (see beam movement unit 55) can be controlled to move a beam path relative to the surface of the master HOE's carrier layer. For example, the angle of incidence could be changed along with the position when a scan line is traced by a scanning mirror. A more complex movement could also occur, in which a reference point is moved along a curved trajectory. A robot arm could be controlled for this purpose, for example.

[0115] In box 3115, the adjustable optical element can be controlled to change the intensity and / or polarization of the light. For example, the intensity and / or polarization could be changed between two finite values ​​that are >0. A stepped change could occur whenever the light source is turned off and / or the beam path is or has been moved (see box 3105). Boxes 3105, 3110, and 3115 can therefore be performed synchronously.

[0116] To adjust the intensity, it would be conceivable to adjust a target specification for the intensity, which is taken into account within the framework of a control loop. However, it is not necessary to use a control loop in all variants: a non-controlled change in the intensity is also conceivable. Aspects relating to a variant with a control loop will be described later in connection with FIG. 24. Aspects relating to the beam movement unit are explained below. In some examples, the beam movement unit can generate a curved trajectory 61 for the reference point 84 (cf. FIG. 2; Box 3110). The curved trajectory 61 can vary depending on the master HOE 92. This changes in particular the angle of incidence 89, but also, for example, the position of the light spot on the surface of the carrier material of the master HOE.The reason for this dependence of the curved trajectories 61 on the master HOE used is that, depending on the master HOE 92, different target surface shapes 911 can be used (whereby the exposure process for replication can take place in the same exposure surface shape 912 because this exposure surface shape 912 is dictated by the replication process used). Accordingly, a different compensation is provided by the curved trajectory 61. This is explained below in connection with FIG. 7, FIG. 8, and FIG. 9. FIG. 7 illustrates aspects relating to the target surface shape 911. FIG. 7 illustrates master HOE 92 on the corresponding carrier layer 91, which has the target surface shape 91.

[0117] In the example shown in FIG. 7, the master HOE 92 implements the optical functionality of an off-axis paraboloidal mirror illuminated by a point light source. An incident divergent beam 81 is converted into a parallel beam 82. This is only one example of an optical functionality, and a wide range of different optical functionalities is conceivable.

[0118] In any case, the replicated HOE 96 shall implement the corresponding optical functionality if the replicated HOE 96 has the same target surface shape 911.

[0119] However, upon exposure of the replicated HOE 96 (see FIG. 1: box 3010), the replicated HOE 96 and the master HOE 92 have the exposure surface shape 912. This is shown in FIG. 8.

[0120] The transformation between the target surface shape 911 and the exposure surface shape 912 causes a change in the diffraction structure of the master HOE 92; this change in the diffraction structure can be translated accordingly into a change in the rays of the incident beam 81# and the rays of the outgoing beam 82#: These beams 81# and 82# are "drawn up" in the drawing plane, just like the diffraction structure.

[0121] Various examples are based on the realization that, to produce the replicated HOE 96 using the exposure surface shape 912, the beam path 41 of the light used for exposure should replicate the rays of the adapted beam bundle of the 81# (see FIG. 8) in order to ensure the optical functionality of the replicated HOE 96 according to FIG. 7 (shown there for the master HOE 92) in the presence of the target surface shape 911. This is shown in FIG. 9.

[0122] FIG. 9 illustrates aspects related to a flatbed replication process for replicating the master HOE 92 and exposing the replicated HOE 96. FIG. 9 shows that the support layer 91 of the master HOE 92 extends parallel to the support layer 95 of the replicated HOE 96 during exposure of the replicated HOE 96. To expose the replicated HOE 96, the master HOE 92 is illuminated with light along rays 81#; from FIG. 9 it can be seen that the angle of incidence 89 of these rays 81# varies as a function of the position of the corresponding light spot on the master HOE 92, which is achieved by using the curved trajectory 61 of the reference point 84 along the beam path 41 and optionally by changing the exit angle of the light from the reference point 84 (for example, by using a scanning mirror).When the replicated HOE 96 is then in use and has the target surface shape 911, illumination with other beams (shown in FIG. 9 with the dashed arrows) can again take place, as already described above in conjunction with FIGS. 7 and 8.

[0123] FIG. 10 illustrates aspects related to a roll-to-roll replication process for replicating the master HOE 92, i.e., for exposing the replicated HOE 96. In FIG. 10, a section through the master HOE 92 is shown on the left when it has the target surface shape 911, i.e., when it is manufactured (cf. box 3005 in FIG. 1). Also shown are the corresponding rays 81-1 - 81-4 of a beam used for exposure, which is later used when applying the replicated HOE 96 to illuminate the replicated HOE 96.

[0124] In the roll-to-roll replication process (see box 3010 in FIG. 1), the master HOE 92 is applied to a roller 71, and the corresponding rays 81 #-1 - 81 #-4 of the light beam path 41, which are used to illuminate the master HOE 92, are reached with increasing rotation of the roller 71 by a movement 21 of the reference point 84 and a correspondingly changed exit angle 85 of the light from the reference point 84 (e.g., achieved by tilting 22 a corresponding mirror arranged at the reference point 84). As a result, during the exposure process of the replicated HOE (which is applied to another roller 72 and is not shown in FIG. 10 for reasons of clarity), the curvature of the carrier material 91 of the master HOE 92 is compensated for by the curved trajectory. Techniques related to the movement of the reference point 84 were explained above.It was also explained how the exit angle 89 can be changed. It is optionally possible to synchronize the movement of the reference point 84 along the curved path 61 with a scan of the light beam 41. In contrast to a change in the exit angle 89, as discussed above, the scanning of the light beam 41 can be implemented by a periodic scanning movement.

[0125] For example, the reference point 84 could mark a center point of the scanning movement 53. Aspects related to scanning are illustrated below in connection with FIG. 11 and FIG. 12.

[0126] FIG. 11 shows a master HOE 92 that implements the optical functionality of an off-axis parabolic mirror by way of example. FIG. 11 shows the master HOE 92 in the target surface shape 911; FIG. 12 shows the same master HOE 92 in the exposure surface shape 912. From FIG. 11, it can be seen that the master HOE 92 in the target surface shape 911 has a one-dimensional curvature along a curvature axis 199.

[0127] This means that the target surface shape 911 and the exposure surface shape 912 can be mediated by a one-dimensional curvature operation along the curvature axis 199 (a curvature perpendicular to the curvature axis 199 is not changed). The same applies (inversely) to the example in FIG. 8. Generally speaking, a transition occurs between a one-dimensional curvature of the carrier layer 91 of the master HOE and a planar configuration of the carrier layer 91 of the master HOE 92.

[0128] The scanning direction 36 of the scanning movement 53 of a scanned light spot 49 on the master HOE 92 by means of the scanning mirror is oriented perpendicular to the curvature axis 199, see FIG. 12. This is because no displacement of the origin of the scanning movement 53 is necessary perpendicular to the curvature axis 199, because there is no transformation of the curvature of the corresponding surface in this direction 36. The example in FIG. 12 therefore corresponds to a line scanner.

[0129] Superimposed on the scanning movement 53 along the scanning direction 36, the movement of the reference point 84 takes place along the curved trajectory 61. This shifts the light spot 49 along the direction 37. The corresponding movement 21 has a component along an axis 37 which is oriented perpendicular to the scanning direction 36 (and thus parallel to the curvature axis 199) along the direction 37.

[0130] FIG. 12 also shows the (non-scanned) change in the exit angle 85 by correspondingly controlling the beam movement unit. In some examples, a two-dimensional scanning mirror could be used to implement both the scanning (i.e., a periodic movement around a scan center point) along the scanning direction 36, as well as the non-scanned change in the exit angle 85, for example, by a corresponding tilt 22 in the reference point 84. A corresponding scenario was discussed in connection with FIG. 2; the scanning mirror can then be arranged at the reference point 84.

[0131] In the example of FIG. 12, scanning could be performed with a fixed scanning frequency and a fixed scanning amplitude, so that the entire area between the two edges of the master HOE 92 is covered by the light spot 49. In such an example, a resonantly driven scanning mirror could be used.

[0132] It is not necessary to implement scanning movement 53 in all examples. For example, at least one optical element could be arranged at reference point 84, which causes the light spot 49# of the light on the master HOE 92 to be expanded along direction 36 (compare light spot 49 with light spot 49#). Then, the lines that would otherwise be scanned are exposed in an integrated manner.

[0133] FIG. 13 and FIG. 14 are side views from perpendicular perspectives for the scenario of FIG. 10.

[0134] FIG. 15 shows an exemplary implementation of the beam movement unit 55. The beam movement unit 55 comprises a robot arm 231. A fiber optic cable 212 guides the light from the laser 52 to the moving end of the robot arm 231. There, the light is output by an output unit 281, which may, for example, comprise a corresponding lens (GRIN lens), etc. The output unit 281 may be polarization-maintaining. Furthermore, a two-dimensional galvo scanner 261 is arranged at the moving end of the robot arm 231; this implements both the tilt 22 for non-scanningly changing the exit angle 85 at which the light leaves the reference point 84, as well as the scanning movement.

[0135] FIG. 15 also shows how the angle of incidence 89 can change during the exposure process because the beam path 41 is moved by the beam movement unit 55 across the surface of the carrier layer of the master HOE. This can change the orientation of the polarization 641 of the light with respect to the surface of the carrier layer of the master HOE 92. For example, instead of s-polarization, p-polarization could occur, compare FIG. 16 and FIG. 17 (if the beam path is rotated about a rotation axis that is not coincident with the polarization direction, the angle of the polarization direction changes with respect to the surface normal of the surface of the carrier layer of the master HOE). This would influence the replication efficiency and can be compensated for by adjusting the polarization and / or the intensity, as described above.

[0136] FIG. 18 is a schematic illustration of the exposure device 59 according to various examples. In the illustrated example, the exposure device 59 comprises a plurality of lasers 311-313 for different wavelength components of the light. The lasers 311-313 implement a multicolor light source. Corresponding components of the light are guided via optical fibers to a beam combining element 331, which then combines the corresponding partial beam paths.

[0137] An A-OTF 332, which implements an adjustable optical element, is arranged in the beam path downstream of the beam combining element 331. A Pockels cell 333, which also implements an adjustable optical element, is also arranged. This allows the intensity or polarization of the light to be adjusted. A wave plate 334 is also provided, followed by the scanning mirror 261 and deflection mirrors 336, 337. (For example, a robot arm, if used, is not shown in FIG. 17).

[0138] The AOTF 332 filters light using sound waves. This occurs through the process of acousto-optic interaction in a suitable medium, often a crystal. As a sound wave propagates through the crystal, it induces periodic density changes in the material. These density changes lead to a periodic change in the refractive index of the medium. When light passes through the crystal with the periodically changing refractive indices, it is diffracted, similar to light passing through a grating. This creates several components of the light; these correspond to the different orders of diffraction, specifically the 0th order of diffraction and the 1st order of diffraction. Typically, only the 1st order of diffraction is used to replicate the master HOE.

[0139] Instead of a single Pockels cell 333 as shown in the example of Fig. 18, it would be conceivable to provide multiple Pockels cells, e.g., one for each part of the beam path between the beam combining element 331 and the light sources 311-313. Then, the polarization for the different wavelength components of the light can be adjusted separately.

[0140] FIG. 19 shows a variation of the exposure device 59 from FIG. 18. Instead of the A-OTF 332, AOMs 341, 342, 343 are now used. These are arranged upstream of the beam combining element 331 and are respectively assigned to the lasers 311-313 (in FIG. 20, the AOMs 341, 342, 343 are integrated into the lasers 311-313).

[0141] While no Pockels cell is shown in FIG. 19 and FIG. 20, a Pockels cell could also be used.

[0142] Aspects related to power monitoring are described below. Power monitoring can ensure that the light intensity during the exposure process corresponds to a specified value. The light intensity can be changed according to a time-variable target value. Light intensity control is possible. To ensure correct light intensity adjustment, the light intensity can be checked during the replication / exposure process.

[0143] Various examples are based on the realization that measuring the effective beam during the exposure process is not easily possible: conventional sensors block the beam during the measurement. To still enable the measurement of the light intensity, various variants exist.

[0144] In one variant, a portion of the power of the useful beam is diverted using a beam splitter, e.g., a 90:10 beam splitter, or other optics, and used for measurement. A corresponding sensor (see FIG. 1: sensor 57) is then arranged in the diverted partial beam. However, this results in power being lost from the useful beam.

[0145] It may be desirable to measure the intensity of the useful beam indirectly. This avoids reducing the power of the useful beam (that is, the portion of the light used to replicate the master HOE). Such variants are shown below.

[0146] A variant of the exposure device 59 is shown in FIG. 21. FIG. 21 basically corresponds to FIG. 18 (elements that have already been explained with reference to FIG. 18 will not be explained again). In the AOTF 332, the incident superimposed beams are split into a 0th diffraction order 800 and a 1st diffraction order 801 (the reference numerals 800, 801 denote the corresponding beam paths). The 1st diffraction order 801 is the set desired power, and the remaining power is located in the 0th diffraction order 800. Depending on the type and design, the AOTF 332 can be set up so that, for example, the 1st diffraction order 801 (i.e., the useful beam) is dispersion-corrected. This means that all wavelengths of the 1st diffraction order 801 exit the AOTF 332 at the same angle. The 0th diffraction order 800 contains the residual power, where the angles of the wavelengths are slightly different.Another property of the filters is the polarization state of the two diffraction orders 800, 801, which are linearly polarized at 90° to each other. In the example shown in FIG. 21, the first diffraction order 801 is p-polarized with respect to the window, while the zero order is s-polarized.

[0147] One way to monitor the power without interfering with the useful beam - i.e., the first diffraction order 801 - is to measure the light of the 0th diffraction order 800 during the exposure process. Since the power in the 1st diffraction order 801 is missing from the 0th diffraction order 800, there is an inversely proportional relationship between the useful power and the measured value of the sensor 57 of the 0th diffraction order 800. By adjusting (calibrating) the two diffraction orders 800, 801, the 1st diffraction order 801 can be controlled based on the measurement of the 0th diffraction order 800. An indirect measurement of the intensity of the useful beam (1st diffraction order 801) is therefore used.

[0148] However, due to the small angular difference between the 0th diffraction order 800 and the 1st diffraction order 801 (possibly a few degrees), a long beam path is required to sufficiently separate the beams. This is evident in FIG. 21, where sensor 57 is arranged at a large distance from AOTF 332, allowing the light of the 1st diffraction order 801 to pass by sensor 57.

[0149] In FIG. 21, further optical elements (arranged downstream in the beam path of the first-order diffraction light 801), such as a Pockels cell or a deflection mirror (cf. FIG. 18: Pockels cell 333, deflection mirror 261, etc.), are not shown. The various further optical elements can be implemented according to the various variants described herein.

[0150] A more compact variant than in FIG. 21 with sensor 57 of the exposure device 59 is shown in FIG. 22. FIG. 22 basically corresponds to FIG. 21. In FIG. 22, a polarizing beam splitter 820 is present along the beam path of the light behind the AOTF 332. The AOTF 332 is oriented such that the 1st diffraction order 801 is vertically polarized. The light of the 1st diffraction order 801 is thereby deflected and coupled into the rest of the optical system (as not shown in FIG. 21, but variably configurable according to the rest of the disclosure), whereas the 0th diffraction order 800 passes straight through the polarizing beam splitter 820 to a power measuring head of the sensor 57. It can therefore be used without intervention in the 1st Diffraction order 801, the intensity of the light of the 1st diffraction order can be determined during the exposure process by measuring the intensity of the light of the 0th diffraction order 800 (again an indirect measurement).The disadvantage of this variant of FIG. 22 arises at particularly high laser powers, e.g., greater than a few 100 mW: It may be necessary to use a sensor 57 that determines the intensity thermally; the measurement frequency is then very low. In certain circumstances, a neutral density filter or similar may be used, which could either lead to back reflections or, in the case of absorptive filters, could be destroyed. To mitigate or eliminate these disadvantages, the variant in FIG. 23 can be used.

[0151] The variant of FIG. 23 basically corresponds to the variant of FIG. 21 or the variant of FIG. 22.

[0152] An optical plate 811 (i.e., a window made of, for example, bk7, quartz glass, etc.) is positioned at an angle along the light beam path behind the AOTF 332 so that the 1st order of diffraction 801, p-polarized, strikes the optical plate at the Brewster angle (approximately 57° for bk7). As a result, the 1st order of diffraction passes through the window with virtually no reflection losses (as indicated by the crossed reflection beam 815). The 0th order of diffraction 800, on the other hand, exhibits no Brewster effect due to its polarization and the changed angle and is reflected according to the usual Fresnel equations. The approximately 5-15% reflection can be detected with sensor 57, as it is only a fraction of the high laser power. Fast sensors are therefore available. The remaining power passes through the window and can be safely directed into a designated beam trap / absorber 812.If necessary, the angle between the 0th diffraction order 800 and the 1st diffraction order 801 can be increased by a wedge-shaped design of the optical plate 811 in order to achieve a faster separation of the beams.

[0153] Above, various aspects related to implementing the adjustable element using an AOTF 332 were described. However, it would also be conceivable for the adjustable element to be implemented using an AOM. Here, too, different diffraction orders occur, which, as described above, can be used once for replication and once for measuring the intensity.

[0154] FIG. 24 shows a flowchart of an exemplary method. The method in FIG. 24 is used to control the light intensity during an exposure process used to replicate a master HOE. The method of FIG. 24 may therefore be part of box 3010 of FIG. 1.

[0155] For example, the method of FIG. 24 can be executed by a controller. For example, the method of FIG. 24 can be implemented by the controller 51 of FIG. 2. It is conceivable that the method of FIG. 24 is implemented partially in software and partially in hardware, or only in software or only in hardware. For example, a hardware implementation can be used if particularly fast control of the light intensity during the exposure process is desired.

[0156] The exposure process is started in box 5005. This means that a light source (see, for example, FIG. 2: light source 52) is controlled to emit light. A beam movement unit and / or at least one optical element can also be controlled. Corresponding aspects were explained above in connection with the method according to FIG. 6.

[0157] A current target intensity value is received in box 5010. For example, the corresponding target intensity value for control data can be displayed. Various aspects related to control data 401 have been described above.

[0158] In box 5015, the actual intensity value of the light used to replicate the master HOE is measured. For this purpose, corresponding measured values ​​can be obtained from a sensor, e.g., a photodiode. The sensor is preferably arranged near the HOE to be illuminated. Aspects related to a corresponding sensor 57 were described above in connection with FIG. 2 and the variants of FIG. 21, FIG. 22, and FIG. 23. In box 5020, a control signal can then be set based on a deviation between the target intensity value of the current iteration of box 5010 and the actual intensity value of the current iteration of box 5015. In particular, the control signal can be adjusted to reduce the deviation. For example, a PID controller can be used to determine the control signal. The control signal can be used in various ways to control the intensity.For example, a Pockels cell could be controlled. Alternatively or additionally, it is also conceivable that the light source itself is controlled. An AOTF (see FIG. 21, FIG. 22, FIG. 3: AOTF 332) or an AO M could also be controlled.

[0159] Box 5025 checks whether the exposure process is complete. If the exposure process is not yet complete, another iteration 5026 is performed. In another iteration 5026 of box 5010, another target intensity value is obtained, and so on. When the exposure process is complete in box 5025, the process ends in box 5030.

[0160] In summary, the following EXAMPLES were described in particular:

[0161] EXAMPLE 1. A control device (51) for an exposure device (59) for producing a holographic optical element, HOE, (96) by replicating a master HOE (92) as part of an exposure process carried out by the exposure device (59), wherein the exposure process uses light emitted by at least one light source (52) of the exposure device during the exposure process along a beam path (41) toward a surface of the carrier layer of the master HOE (92), wherein during the exposure process a carrier layer of the master HOE (92) is arranged along a carrier layer of the HOE, wherein the control device (51) comprises at least one processor (191) and a memory (192), wherein the at least one processor (191) is configured to load program code from the memory (192) and to execute the program code, wherein the at least one processor (191) is configured,to carry out the following steps based on the program code: - controlling a beam movement unit (55) of the exposure device (59) so that it moves the beam path (41) during the exposure process with respect to the surface of the carrier layer of the master HOE (92), and,

[0162] - controlling at least one adjustable optical element (54) of the exposure device (59) which is arranged in the beam path (41) such that the at least one adjustable optical element (54) changes at least one of an intensity and a polarization of the light over time during the exposure process.

[0163] EXAMPLE 2. Control device (51) according to EXAMPLE 1, wherein the at least one processor (191) is further configured to perform the following step based on the program code:

[0164] - Loading control data (401) indicating a relationship between the movement of the beam path (41) with respect to the surface of the carrier layer and the change in at least one of the intensity and the polarization of the light, wherein the control of the beam movement unit (55) and the control of the at least one adjustable optical element (54) are synchronized based on the control data (401).

[0165] EXAMPLE 3. The control device (51) according to EXAMPLE 1 or 2, wherein the at least one adjustable optical element (54) changes the intensity of the light, wherein the at least one adjustable optical element (54) and the beam movement unit (55) are controlled such that an influence of a variation of structural properties of the master HOE (92) on an efficiency of replication of the master HOE is reduced by the change in the intensity of the light during the exposure process.

[0166] EXAMPLE 4. The control device (51) according to EXAMPLE 3, wherein the at least one adjustable element (54) and the beam movement unit are controlled such that an influence of the variation of structural properties of the master HOE (92) on a diffraction efficiency of the master HOE is reduced by changing the intensity of the light during the exposure process.

[0167] EXAMPLE 5. Control device (51) according to one of the preceding EXAMPLES, wherein the at least one adjustable optical element (54) changes the polarization of the light, wherein the at least one adjustable optical element (54) and the beam movement unit (55) are controlled such that an influence of the movement of the beam path (41) on a change in an orientation of the polarization of the light with respect to the surface of the carrier layer of the master HOE during the exposure process is reduced.

[0168] EXAMPLE 6. Control device (51) according to one of the preceding EXAMPLES, wherein the at least one adjustable optical element (54) changes the polarization of the light, wherein the at least one adjustable optical element (54) is controlled such that an influence of a changing angle of incidence of the beam path (41) by the movement of the beam path (41) on a change in an efficiency of the replication during the exposure process is compensated.

[0169] EXAMPLE 7. The control device (51) according to any one of the preceding EXAMPLES, wherein the at least one wavelength comprises a plurality of wavelengths, wherein the at least one adjustable optical element (54) is controlled such that it changes the intensity of components of the light corresponding to the plurality of wavelengths relative to one another during the exposure process.

[0170] EXAMPLE 8. The control device (51) according to any one of the preceding EXAMPLES, wherein the beam movement unit (55) is controlled with a first signal bandwidth in the kilohertz range, wherein the adjustable optical element (54) is controlled with a second signal bandwidth that is greater than the first signal bandwidth. EXAMPLE 9. The control device (51) according to any one of the preceding EXAMPLES, wherein the beam movement unit (55) is controlled to move the beam path in a step-by-step operation, wherein the at least one adjustable optical element (54) is controlled to change the at least one of the intensity and the polarization in connection with a step of the step-by-step operation.

[0171] EXAMPLE 10. Control device (51) according to any one of the preceding EXAMPLES, wherein the control device (51) is further configured to vary the intensity of the light by means of a control loop over time during the exposure process.

[0172] EXAMPLE 11 . System (50) comprising:

[0173] - the control device (51) according to one of the preceding EXAMPLES, and

[0174] - the exposure device (59).

[0175] EXAMPLE 12. The system (50) of EXAMPLE 11, wherein the at least one adjustable optical element (54) comprises at least one acousto-optic modulator for changing the intensity of the light by adjusting a transmittance.

[0176] EXAMPLE 13. The system (50) of EXAMPLE 12, wherein the at least one wavelength comprises a plurality of wavelengths, wherein the at least one tunable optical element (54) comprises an acousto-optic modulator for each of the plurality of wavelengths.

[0177] EXAMPLE 14. The system (50) of EXAMPLE 13, wherein the control device is further configured to wherein the at least one light source (52) comprises a plurality of light sources for components of the light corresponding to the plurality of wavelengths, wherein the exposure device (59) further comprises a beam combining element which combines partial beam paths of the plurality of light sources for the components of the light corresponding to the plurality of wavelengths, wherein the acousto-optical modulators are arranged upstream of the beam combining element along the partial beam paths.

[0178] EXAMPLE 15. The system (50) of any one of EXAMPLES 11 to 14, wherein the at least one adjustable optical element (54) comprises an acousto-optic multi-channel filter for varying the intensity of the light by adjusting a transmittance.

[0179] EXAMPLE 16. The system (50) of EXAMPLE 15, wherein the at least one wavelength comprises a plurality of wavelengths, wherein a filter curve of the acousto-optic filter can be individually adjusted for each of the plurality of wavelengths.

[0180] EXAMPLE 17. The system (50) of EXAMPLE 16, wherein the at least one light source (52) comprises a plurality of light sources for components of the light corresponding to the plurality of wavelengths, wherein the exposure device (59) further comprises a beam combining element which combines partial beam paths of the plurality of light sources for the components of the light corresponding to the plurality of wavelengths, wherein the acousto-optic filter is arranged downstream of the beam along the partial beam paths from the beam combining element.

[0181] EXAMPLE 18. The system (50) of any one of EXAMPLES 11 to 17, wherein the at least one adjustable optical element splits the light into at least a first component (800) and a second component (801), the system (50) comprising a sensor (57) configured to measure an intensity of the first component, the exposure device (59) configured to implement the exposure process with the second component. EXAMPLE 19. The system (50) of EXAMPLE 18, wherein the first component corresponds to a diffraction order with a first polarization, the second component corresponds to another diffraction order with a second polarization, the diffraction order being different from the another diffraction order, the first polarization optionally being different from the second polarization.

[0182] EXAMPLE 20. System (50) according to EXAMPLE 18 or 19, further comprising:

[0183] - a polarizing beam splitter (820) arranged in the beam path of the first component and in the beam path of the second component.

[0184] EXAMPLE 21. System (50) according to EXAMPLE 17 or 18, further comprising:

[0185] - an optical plate (811) arranged in the beam path of the first component (800) and in the beam path of the second component (801), wherein the optical plate is arranged tilted relative to the beam path of the second component (801) in such a way that the latter is incident on the optical plate at the Brewster angle.

[0186] EXAMPLE 22. The system (50) of any one of EXAMPLES 11 to 21, wherein the at least one adjustable optical element (54) comprises a Pockels cell for changing polarization by rotating a plane of polarization.

[0187] EXAMPLE 23. System (50) according to any one of EXAMPLES 11 to 22, wherein the at least one adjustable optical element (54) comprises one or more lambda / 2 plates which can be alternately introduced into the beam path (41) by means of a motor.

[0188] EXAMPLE 24. A method for controlling an exposure device (59) for producing a holographic optical element, HOE, (96) by replicating a master HOE (92) during an exposure process carried out by the exposure device (59), wherein the exposure process uses light emitted by at least one light source (52) of the exposure device during the exposure process along a beam path (41) toward a surface of the carrier layer of the master HOE (92), wherein a carrier layer of the master HOE (92) is arranged along a carrier layer of the HOE (96) during the exposure process, the method comprising:

[0189] - controlling a beam movement unit (55) of the exposure device (59) so that it moves the beam path (41) during the exposure process with respect to the surface of the carrier layer of the master HOE (92), and

[0190] - controlling at least one adjustable optical element (54) of the exposure device (59) which is arranged in the beam path (41) such that the at least adjustable optical element (54) changes at least one of an intensity and a polarization of the light over time during the exposure process.

[0191] EXAMPLE 25. The method of EXAMPLE 24, wherein at least the controlling of the at least one adjustable optical element (54) and / or the beam movement unit (55) is carried out based on control data.

[0192] EXAMPLE 26. The method of EXAMPLE 24 or 25, wherein the at least one adjustable optical element (54) is controlled based on a closed control loop that minimizes a deviation between a desired intensity and an actual intensity of the light.

[0193] EXAMPLE 27. Method according to one of EXAMPLES 24 to 26, wherein the method is carried out by the control device (51) according to one of EXAMPLES

[0194] GAMES 1 to 10 are executed.

[0195] EXAMPLE 28. A method for configuring a manufacturing process for producing a holographic optical element, HOE, by replicating a master HOE (92) during an exposure process carried out by an exposure device (59), wherein during the exposure process a carrier layer of the master HOE (92) is arranged along a carrier layer of the HOE (96), the method comprising the following step:

[0196] - generating (3810) control data (401) for at least one adjustable optical element (54) of the exposure device (59) which is arranged in a beam path (41) of light used for replication, wherein the at least one adjustable optical element (54) can be controlled by means of the control data (401) so that it changes at least one of an intensity and a polarization of the light over time during the exposure process.

[0197] EXAMPLE 29. The process of EXAMPLE 28, further comprising:

[0198] - Obtaining a map (799) of the master HOE (92), the map (799) indicating a diffraction efficiency as a function of a position on a surface of the carrier layer of the master HOE (92), wherein the control data (401) is determined based on the map (799).

[0199] EXAMPLE 30. The method of EXAMPLE 29, wherein the control data (401) is determined using a predetermined transfer function based on the map (799), wherein the predetermined transfer function assigns a comparatively greater intensity of light to first regions (701, 702, 703) on the surface of the carrier layer having a comparatively low diffraction efficiency, wherein the predetermined transfer function assigns a comparatively lower intensity of light to second regions (701, 702, 703) on the surface of the carrier layer having a comparatively high diffraction efficiency.

[0200] EXAMPLE 31. The method of any one of EXAMPLES 28 to 30, wherein the method further comprises: - obtaining exposure configuration data describing a movement of the beam path (41) during the exposure process with respect to the surface of the carrier layer of the master HOE (92), wherein the control data (401) is generated based on the exposure configuration data.

[0201] EXAMPLE 32. The method of EXAMPLE 31, wherein the exposure configuration data describes a change in an angle of incidence of the beam path (41) during the exposure process with respect to the surface of the carrier layer of the master HOE (92), wherein the control data (401) causes a rotation of a polarization plane to maintain an s-polarization or a p-polarization under the change in the angle of incidence of the beam path (41).

[0202] EXAMPLE 33. The method of any one of EXAMPLES 28 to 32, wherein the method further comprises:

[0203] - Obtaining a target specification for a diffraction efficiency of the HOE (96), wherein the control data (401) is generated based on the target specification for the diffraction efficiency of the HOE (96).

[0204] EXAMPLE 34. The method of EXAMPLE 33, wherein the target specification indicates a local variation of the diffraction efficiency of the HOE (96) relative to a local variation of a diffraction efficiency of the master HOE.

[0205] EXAMPLE 35. The method of any one of EXAMPLES 28 to 34, wherein the method further comprises:

[0206] - Obtaining in-line measurement data acquired in connection with the manufacture of the HOE (96), wherein the control data (401) is generated based on the in-line measurement data. EXAMPLE 36. The method of EXAMPLE 35, wherein the in-line measurement data describes a diffraction efficiency of a test instance of the HOE (96).

[0207] EXAMPLE 37. An apparatus comprising at least one processor and a memory, wherein the at least one processor is configured to load and execute program code from the memory, wherein the at least one processor is configured to perform a method according to any one of EXAMPLES 28 to 36 based on the program code.

[0208] Of course, the features of the previously described embodiments and aspects of the invention can be combined with one another. In particular, the features can be used not only in the described combinations, but also in other combinations or on their own, without departing from the scope of the invention.

[0209] For example, techniques were described above in which the light intensity is changed via an adjustable optical element arranged in the beam path. Similarly, a light source, such as a laser, could also be controlled to change the light intensity. For example, a supply current for a laser diode could be reduced to reduce the intensity. In such variants, it may sometimes be unnecessary to provide a separate adjustable optical element in the beam path.

[0210] Furthermore, techniques were described above in which the light intensity is changed via an adjustable optical element arranged in the beam path. This results in a change in the dose of light used for exposure. To change the dose, the dwell time of the light spot on the surface of the master HOE or the replicated HOE could alternatively or additionally be adjusted.

[0211] For example, techniques related to implementing a closed-loop control system for the light intensity during the exposure process were described above (see, for example, FIG. 24). Alternatively or in addition to such a closed-loop control system for the light intensity, a closed-loop control system for the light polarization can also be implemented.

[0212] While techniques have been described above that allow using a sensor value of intensity or polarization for a closed control loop, it would also be possible to use corresponding sensor values ​​to monitor whether the sensor values ​​lie within a specified range. If the tolerance range is exceeded, the replication process can be aborted.

Claims

PATENT CLAIMS 1. A method for configuring a manufacturing process for producing a holographic optical element, HOE, by replicating a master HOE (92) during an exposure process carried out by an exposure device (59), wherein during the exposure process a carrier layer of the master HOE (92) is arranged along a carrier layer of the HOE (96), the method comprising the following step: - generating (3810) control data (401) for at least one adjustable optical element (54) of the exposure device (59) which is arranged in a beam path (41) of light used for replication, wherein the at least one adjustable optical element (54) can be controlled by means of the control data (401) so that it changes at least one of an intensity and a polarization of the light over time during the exposure process.

2. The method of claim 1, wherein the method further comprises: - Obtaining a map (799) of the master HOE (92), the map (799) indicating a diffraction efficiency as a function of a position on a surface of the carrier layer of the master HOE (92), wherein the control data (401) is determined based on the map (799).

3. The method according to claim 2, wherein the control data (401) are determined using a predetermined transfer function based on the map (799), wherein the predetermined transfer function assigns a comparatively greater intensity of light to first regions (701, 702, 703) on the surface of the carrier layer with a comparatively low diffraction efficiency, wherein the predetermined transfer function assigns a comparatively lower intensity of light to second regions (701, 702, 703) on the surface of the carrier layer with a comparatively high diffraction efficiency.

4. A method according to any one of the preceding claims, wherein the method further comprises: - Obtaining exposure configuration data describing a movement of the beam path (41) during the exposure process with respect to the surface of the carrier layer of the master HOE (92), wherein the control data (401) is generated based on the exposure configuration data.

5. The method according to claim 4, wherein the exposure configuration data describe a change in an angle of incidence of the beam path (41) during the exposure process with respect to the surface of the carrier layer of the master HOE (92), wherein the control data (401) cause a rotation of a polarization plane to maintain an s-polarization or a p-polarization under the change in the angle of incidence of the beam path (41).

6. A method according to any one of the preceding claims, wherein the method further comprises: - Obtaining a target specification for a diffraction efficiency of the HOE (96), wherein the control data (401) is generated based on the target specification for the diffraction efficiency of the HOE (96).

7. The method of claim 6, wherein the target specification indicates a local variation of the diffraction efficiency of the HOE (96) relative to a local variation of a diffraction efficiency of the master HOE.

8. A method according to any one of the preceding claims, wherein the method further comprises: - Obtaining in-line measurement data recorded in connection with the manufacture of the HOE (96), wherein the control data (401) is generated based on the in-line measurement data.

9. The method of claim 8, wherein the in-line measurement data describe a diffraction efficiency of a test instance of the HOE (96).

10. Apparatus comprising at least one processor and a memory, wherein the at least one processor is configured to load and execute program code from the memory, wherein the at least one processor is configured to execute a method according to one of the preceding claims based on the program code.

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