Patent Application
20250130506
Various examples concern techniques for producing a holographic optical element (HOE) by replicating a master HOE. Various examples concern in particular techniques for variably adapting the illumination of the master HOE during replication.
HOEs are used in various fields of application. For example, HOEs can be used to implement a transparent screen. Fields of application concern, for example, the use in a head-up dis-play in an automobile or the integration of a holographic optical element in a mirror. HOEs are used for generating holograms: the HOE is illuminated for this purpose; with the result that the hologram is reconstructed.
One technique for producing HOEs is based on the use of a master HOE, which is used in an exposure process of the HOE to form the HOE. In this case, the carrier layer (for example a photopolymer, which is arranged on a substrate) of the master HOE is arranged along the carrier layer of the HOE to be replicated (hereinafter simply “replicated HOE”). With exposure, the diffraction structure of the master HOE can then be replicated in the replicated HOE.
Such production methods which use replication of the master HOE for the production of the HOE can use a roll-to-roll process, for example, in which the master HOE and the HOE are arranged on a respective roll as fixing element, which rolls are rotated synchronously with one another, so that a partial region of the master HOE extends in each case along a corresponding partial region of the replicated HOE. Another technique is the flatbed process, in which the master HOE and the replicated HOE are fixed on a respective planar or flat carrier, so that the entire surfaces of the respective carrier layers extend along one another.
In such production methods, the surface shape of the carrier layer of the master HOE and of the HOE during the replication process is predefined by the technical boundary conditions of this process. By way of example, the master HOE is one-dimensionally curved in the roll-to-roll process; whereas the master HOE is arranged in planar fashion in the flatbed process. This pre-definition of the surface shape makes it more difficult to produce HOEs which are intended to be fixed after the exposure process upon application in arbitrary surface shapes, for example on account of boundary conditions of the field of application. Some fields of application may require the HOE to be integrated into curved surfaces, for example on account of the limited installation space, etc.
There is a need for improved production methods for HOEs. In particular, there is a need for improved production methods that enable a flexible surface shape of HOEs in the application. There is a need to produce HOEs with high quality.
A method for producing a replicated HOE by replicating a master HOE in the context of an exposure process is disclosed. During the exposure process, in this case, a carrier layer of the master HOE is arranged along a carrier layer of the replicated HOE. The method comprises controlling a radiation source in order to emit light onto the master HOE during the exposure process, with the result that the HOE is exposed. The master HOE is replicated. Moreover, the method comprises controlling a positioning module in order to move a reference point, which is arranged along a beam path of the light, in relation to the master HOE on a trajectory during the exposure process.
The trajectory thus denotes a path along which a point along the beam path of the light is moved. The beam path of the light can be fixed in relation to this reference point, i.e. can run through the reference point by provision of a corresponding optical element at the reference point. At different points in time, the reference point is situated at different positions along the trajectory.
A point light source can be arranged at the reference point. An emitter of the light source can be arranged at the reference point. Alternatively, the emitter of the light source can be arranged further upstream; and the light emitted by the emitter can be focused at the reference point, for example. The light emitted by the emitter can be collimated. The collimated beam path can run through the reference point.
The reference point can thus denote that point along the beam path at which the positioning module acts on the beam path of the light in a time-variant manner. The beam path is linked with the reference point and is guided and/or directed at the reference point. At the reference point, the positioning module can tilt and/or deflect and/or translationally offset and/or rotate the beam path in a time-variant manner, for example.
The reference point can be arranged downstream of the radiation source. However, the radiation source could also be arranged at the reference point; i.e. the reference point would be arranged right at the beginning of the beam path.
In addition, an optical element can be provided which acts on the beam path at the reference point in a time-invariant manner; for example, the beam path can be expanded or collimated.
The trajectory can be curved (i.e. in a global coordinate system of a corresponding appa-ratus). The trajectory can be straight.
The trajectory can extend within a plane. The trajectory can also extend in three-dimensional space.
The trajectory can comprise a component perpendicular to the carrier layer of the master HOE and to the carrier layer of the replicated HOE.
The radiation source can emit light in the visible spectrum, for example. Radiation in the ultraviolet or infrared range of the electromagnetic spectrum could also be emitted. The radiation source can be a coherent laser light source. By way of example, the radiation source could have one or more channels, at different wavelengths. For example, the radiation source could have 3 channels, for instance red-green-blue.
The radiation source can be embodied as a point source. That means that an emitter area is particularly small. Typical emitter areas can have edge dimensions of less than 1 mm or less than 100 μm or less than 50 μm.
A corresponding optical system can be used to form a light point of the light on the master HOE. That means that the master HOE is not illuminated over a large area, but rather is illuminated gradually by moving the light point. The movement of the light point is achieved in particular by the movement of the reference point on a trajectory.
The master HOE can be formed in a photopolymer which 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.
The HOE can be formed in a photopolymer which 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.
By replication, a diffraction structure of the master HOE can be copied in the HOE. The HOE is exposed for the purpose of replication. This typically causes chain formation of polymers. The diffraction structure corresponds to a local variation in the refractive index, for example due to different chain lengths or a different degree of chain formation of polymers in a corresponding layer. When the diffraction structure is illuminated, the hologram is reconstructed. Hereinafter, the terminology “exposure” or “expose” is used in connection with the replication of the master HOE during generation of the HOE; whereas the terminology “illumination” or “illuminate” is used in connection with the use of an already produced HOE for the reconstruction of a hologram.
The use of the positioning module can enable a variable angle of incidence of the light on the master HOE (and thus on the replicated HOE) during the exposure process. In particular, it is possible to vary the angle of incidence of the light as a function of the location of a corresponding light point of the light on the master HOE. That means that the positioning module is configured to move a light point of the light of the radiation source over the carrier layer of the HOE (or the master HOE). Different angles of incidence are realized for different positions of the light point. This is made possible for example by a suitable trajectory, for instance by a suitable curvature. Alternatively or additionally, suitable scanning patterns can be used. What is achieved by such techniques is compensation of a curvature of the carrier layer of the master HOE during the exposure process, which curvature is predefined on the basis of the production process and deviates from the surface shape in the intended field of application. To put it another way, it is thus possible to compensate for a curvature of the carrier material of the master HOE during the exposure process (where this curvature is defined e.g. in relation to a reference coordinate system defined by the shape of the carrier material of the master HOE during the production of the master HOE).
Use of the positioning module can enable in particular variable curved trajectories (“freeform trajectories”). That means that different curved trajectories can be implemented depending on the control of the positioning module. This is made possible by corresponding degrees of freedom of the movement of the positioning module. As a result, it is possible to compensate for different curvatures of the master HOE during the exposure process.
Different implementations for the reference point are conceivable depending on the implementation of the positioning module and associated optics. By way of example, the reference point could correspond to a focus point of the light along the beam path, that is to say that the light can have a smaller beam cross-section at the focus point compared with downstream or upstream along the beam path. Alternatively or additionally, the reference point could be coinci-dent with the arrangement of a lens element or a mirror which implements a last beam deflection before the light is incident on the master HOE.
In some examples, a beam deflection of the beam path at the reference point could also be set besides a movement of the reference point along the e.g. curved trajectory by means of the positioning module.
As a result, it is possible to achieve different scanning patterns for the movement of a light point for the exposure of the HOE.
In one example, this beam deflection can be set by the movement of the reference point; that means: by shifting the reference point with respect to the light source, it is possible to achieve a different beam deflection. That means, in other words, that the position of the reference point and the beam deflection cannot be set separately from one another.
In other examples, however, it would also be conceivable that the beam deflection can be set independently of the movement of the reference point. For this purpose, for example, an optical element such as, for example, a lens element or a deflection mirror or a prism can be arranged in a tiltable fashion at the reference point in order in this way to change the emergence angle of the beam path at the reference point along the curved trajectory in relation to the master HOE.
This additional degree of freedom concerning the orientation of the beam path in relation to the reference point makes it possible to further vary the angle of incidence of the light on the master HOE during the exposure process. Flexible scanning patterns can be implemented.
By way of example, such a variation of the emergence angle of the beam path at the reference point could be effected step by step by means of the positioning module. A mirror could be tilted step by step. The emergence angle of the beam path at the reference point could be changed by way of tilting using a corresponding motorized joint.
Such a variation of the emergence angle of the beam path at the reference point by means of the positioning module can be superimposed by a scanning movement of the beam path. The reference point could be defined for example as the center of the scanning movement. The scanning movement can correspond to a periodic movement around a scanning midpoint. The midpoint can correspond to the reference point. In connection with the scanning movement, it is thus possible to define a scanning frequency and a scanning amplitude.
By way of example, the method could furthermore comprise controlling a scanning mirror in order to scan the light in relation to the master HOE during the exposure process.
The use of the scanning mirror makes it possible to scan the light point over an extensive region of the master HOE in order in this way to illuminate all regions of the master HOE in the context of the exposure process. A scanning pattern is used for this purpose.
As a general rule, a local irradiance (expressed in watts per square meter, for example) integrated over the exposure process could vary as a function of the position on the master HOE by not more than plus minus 20 percent, optionally by not more than plus minus 5 percent. The same can correspondingly apply to the dose together with the residence duration of the light point on the different positions of the master HOE.
In particular, a scanning direction during the scanning of a light point of the light on the master HOE during the exposure process can have a component which is orthogonal to a movement direction of the light point of the light on the master HOE which is caused by the movement of the reference point along the curved trajectory.
In other words, the light point of the light on the master HOE as a result of the movement of the reference point along the e.g. curved trajectory could be moved principally from left to right (in an arbitrarily defined reference system); whereas the light point of the light on the master HOE as a result of the scanning is moved principally from top to bottom. As a result, a substantially homogeneous irradiation or exposure integrated over the exposure process can be attained; at the same time, however, a flexible compensation of different surface shapes of the carrier layer of the HOE during the exposure process and in the subsequent application can be made possible.
By means of the combination of the movement along the e.g. curved trajectory (and optionally a change of the emergence angle by means of the positioning module), firstly, and the scanning, secondly, the angle of incidence of the light on the master HOE can thus be varied flexibly. Moreover, it is possible to attain an integrated irradiation that is as homogeneous as possible in the different regions of the master HOE during the exposure process. Accordingly, it is possible to flexibly adapt the scanning amplitude and/or the scanning frequency. By way of example, the scanning amplitude could be adapted such that the light point of the light during the scanning moves in each case from edge to edge of the master HOE. This corresponds e.g. to a Cartesian scanning pattern with scan lines. Together with a variable scanning amplitude, the scanning frequency can be adapted so that the residence duration of the light point in the different regions along a scan line remains constant independently of the scanning amplitude; a homogeneous integrated irradiation in the different regions of the master HOE during the exposure process can be made possible as a result.
In one simple variant, it would be conceivable for the master HOE to be arranged during the exposure process such that the scanning frequency and optionally the scanning amplitude can remain constant during the exposure process. By way of example, the master HOE could be arranged with a specific fixed transverse extent such that this fixed transverse extent is swept over by the scanning of the light point with a fixed scanning amplitude and scanning frequency.
The scanning mirror could be arranged at the reference point. However, it would also be conceivable for the scanning mirror to be arranged offset with respect to the reference point, in particular upstream along the beam path. It would be conceivable for the scanning mirror to be arranged at a focus point of the beam path. If the scanning mirror is arranged at the focus point of the beam path, comparatively small mirror surfaces can be sufficient; this enables higher scanning frequencies because the moved mass and thus the required forces or dynamic deformations decrease.
Various implementations of the scanning mirror are conceivable. By way of example, a scanning mirror with a galvanometer drive could be used, i.e. a so-called galvanometer mirror. A mirror implemented in microelectromechanical form (MEMS) could also be used. A polygon scanning mirror could be used. An acousto-optic deflector could also be used.
The scanning mirror can have one or more degrees of freedom of the scanning movement. For example, one-dimensional or two-dimensional scanning could be made possible.
The scanning mirror could be a two-dimensionally tiltable scanning mirror of the positioning module. In such a scenario, the scanning mirror could be controlled in order—in a manner superimposed with the scanning—additionally to change the emergence angle of the beam path at the reference point in relation to the master HOE. Such a change of the emergence angle can take place particularly slowly in comparison with the scanning.
A description has been given above of techniques for exposing the HOE by illuminating the master HOE when the corresponding carrier materials are arranged next to one another.
In various examples, the method can also comprise producing the master HOE in a further (upstream) exposure process. In such a further exposure process for producing the master HOE, the carrier layer of the master HOE is typically fixed in a surface shape corresponding to the surface shape of the replicated HOE in the application situation. It is thus possible for the carrier layer of the master HOE during the further exposure process to have a first surface shape, which is different than a second surface shape of the carrier layer during the exposure process.
In this regard, it would be conceivable, for example, for the first surface shape (during exposure of the master HOE for producing the master HOE) to correspond to a one-dimensional curvature of the carrier layer; and the second surface shape (during illumination of the master HOE for exposure and production of the replicated HOE) to correspond to a planar embodiment of the carrier layer, that is to say without curvature, of the master HOE. This would be possible in particular for a flatbed replication process.
In another example, it would be conceivable for the first surface shape (during exposure of the master HOE for producing the master HOE) to be planar; and the second surface shape (during illumination of the master HOE for exposure and production of the replicated HOE) to correspond to a one-dimensional curvature of the carrier layer. That would be possible for example in a roll-to-roll replication process.
This means that only a one-dimensional change of the curvature of the carrier layer needs to be compensated for in such cases by a suitable choice of the e.g. curved trajectory and/or the angle of incidence of the light during the illumination of the master HOE for exposure and production of the replicated HOE.
In such an example, the scanning direction of the scanning movement caused by the scanning mirror can run perpendicular to the axis of the one-dimensional curvature.
As a general rule, it is not necessary in all variants to use a scanning mirror for scanning during the exposure process. By way of example, in some scenarios, it would be conceivable for one or more optical elements (e.g. lens elements and/or mirrors, for instance dichroic mirrors) to be arranged at the reference point along the beam path, which cause the light point of the light on the master HOE to be expanded (that is to say in relation to a case in which the at least one lens element were not present). By way of example, such an expansion could take place one-dimensionally along one axis—which would be scanned for example in another implementation scenario. By way of example, such an expansion of the light point could take place in such a way that the light point covers the entire transverse extent of the master HOE.
In some examples, a combination of at least one expanding optical element, as described above, with a scanning mirror would also be conceivable.
In principle, various implementations are conceivable for the positioning module. For example, the positioning module could comprise a robotic arm with a plurality of adjustable axes. It would also be conceivable for the positioning module to comprise a multi-axis optical linear adjustment table. An adjustment table could optionally also have a rotational degree of freedom. Generally, the positioning module can comprise one or more actuators which address different degrees of freedom of the adjustment of the positioning module in order in this way to enable the curved trajectory and/or a change of the emergence angle.
The positioning module can be controlled in a computer-implemented manner.
By way of example, the positioning module can be controlled on the basis of control data determining the e.g. curved trajectory and/or optionally also the emergence angle of the light at the reference point in relation to the master HOE.
With the aid of the control data, it is possible to determine the angle of incidence of the light on the master HOE.
With the aid of the control data, the scanning pattern or the angle of incidence of the light for replication of the master HOE during exposure of the HOE is determined as a function of the position of the light point on the carrier layer.
In some examples, it would also be conceivable for the control data to specify the angle of incidence of the light on the master HOE, i.e. as a function of the position of the light point on the carrier layer; the angle of incidence of the light on the master HOE may then be translated into a suitable movement of the positioning module by means of a corresponding logic—which typically depends on the architecture of the positioning module. That means, therefore, that the control data can specify/indicate the angle of incidence of the light on the master HOE.
In some examples, the method can also comprise calculating the control data. For example, the control data could be calculated on the basis of a first surface shape of the carrier material of the master HOE during the further exposure process for exposing the master HOE, and on the basis of a second surface shape of the carrier material of the master HOE during the exposure process (for exposing the replicated HOE), and further on the basis of the angle of incidence of light as a function of the location on the master HOE during the further exposure process.
When calculating the control data, it is also possible to take account of the emitter geometry of a light source which is used later when reconstructing the hologram by illumination of the HOE. In this way, for example, areal light sources for illuminating the HOE when reconstructing the hologram can also be made possible, whereas a non-areal light source (or generally a light source with a different emitter geometry) is used when replicating the master HOE.
When calculating the control data, it is possible to take account of a deformation of the diffraction structure of the master HOE on account of a change of the surface shape. A changed diffraction pattern results on account of the deformation of the diffraction structure. This changed diffraction structure of the master HOE during the exposure process for exposing the replicated HOE is copied to the replicated HOE. That means that if the replicated HOE is fixed after the exposure processes with respect to a different surface shape—typically the first surface shape present during exposure of the master HOE—the inverse change of the surface shape is present and so, too, is an inverse change of the diffraction pattern. The replicated HOE can then be illuminated in a flexible surface shape. It is possible to use various light sources for the illumination, e.g. including extensive light sources.
In order to compensate for this change of the surface shape (or the inverse change of the surface shape), the angle of incidence of the light can be correspondingly adapted during exposure of the replicated HOE. This is suitably stored in the control data.
Such a calculation of the control data can typically take place for example during production of the master HOE. The control data can then be stored in a corresponding database or lookup table.
It is possible to take account of various input variables in the calculation of the control data. By way of example, it is possible to take account of the surface shape of the HOE during exposure and the surface shape of the HOE during illumination for reconstructing the hologram. It is also possible to take account of the illumination geometry or emitter geometry during illumination. That means that an arrangement of the light source used for illumination when reconstructing the hologram with respect to the HOE can be taken into account; and so, too, can an extent of the light source. It is possible to anticipate and correct aberrations, for instance on account of material expansion, etc.
It would be conceivable for the control data to be selected from a control data lookup table, depending on the master HOE used. In this case, the control data lookup table can comprise a multiplicity of candidate control data associated with different master HOEs. In such a scenario, it is thus possible to use different control data depending on the master HOE—thus typically also depending on the intended surface shape for the replicated HOE.
Techniques for producing the replicated HOE have thus been described above. After the exposure process for replicating the master HOE, the carrier layer of the replicated HOE can then be fixed in a surface shape that is different than the surface shape of this carrier layer during the exposure process for the replicated HOE.
A computer program comprises program code that can be loaded and executed by a processor. When the processor executes the program code, this causes the processor to carry out a method for producing a HOE by replicating a master HOE in the context of an exposure process. During the exposure process, a carrier layer of the master HOE is arranged along a carrier layer of the HOE. The method comprises controlling a radiation source in order to emit light onto the master HOE during the exposure process, with the result that the HOE is exposed. Moreover, the method comprises controlling a positioning module in order to move a reference point, which is arranged along a beam path of the light, in relation to the master HOE on a curved trajectory during the exposure process.
A data processing unit comprises at least one processor and a memory. The at least one processor is configured to load and execute program code from the memory. This causes the at least one processor to carry out a method for producing a HOE by replicating a master HOE in the context of an exposure process. During the exposure process, a carrier layer of the master HOE is arranged along a carrier layer of the HOE. The method comprises controlling a radiation source in order to emit light onto the master HOE during the exposure process, with the result that the HOE is exposed. Moreover, the method comprises controlling a positioning module in order to move a reference point, which is arranged along a beam path of the light, in relation to the master HOE on a curved trajectory during the exposure process.
A device (can also be referred to as an exposure system) for producing a HOE comprises at least one fixing element on which a carrier layer of a master HOE and a carrier layer of the HOE can be arranged during an exposure process, with the result that these extend at least locally along one another. The device also comprises a radiation source configured to emit light onto the master HOE during the exposure process, with the result that the HOE is exposed. Moreover, the device also comprises a positioning module configured to move a beam path of the light during the exposure process relatively in relation to the carrier layer of the master HOE and the carrier layer of the HOE.
A data processing unit 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 also configured, on the basis of the program code, to calculate control data for the control of a device for replicating a master HOE or for exposing a HOE.
Corresponding program code that can be executed by at least one processor is also disclosed. When the at least one processor executes the program code, this causes the at least one processor to calculate control data for the control of a device for replicating a master HOE or for exposing a HOE.
The features set out above and features that are described hereinbelow can be used not only in the corresponding combinations explicitly set out, but also in further combinations or in isolation, without departing from the scope of protection of the present invention. By way of example, techniques in connection with a method for producing a HOE by replicating a master HOE have been described above. Corresponding methods and techniques can be implemented by a device or an exposure system, as described above. Moreover, techniques in connection with the use of control data for controlling one or more components of such a device have been described above. Corresponding techniques can be combined with a data processing unit configured for calculating corresponding control data.
The properties, features and advantages of this invention described above and the way in which they are achieved will become clearer and more clearly understood in association with the following description of the exemplary embodiments which are explained in greater detail in association with the drawings.
The present invention is explained in greater detail below on the basis of preferred embodiments with reference to the drawings. In the figures, identical reference signs denote identical or similar elements. The figures are schematic representations of various embodiments of the invention. Elements illustrated in the figures are not necessarily illustrated as true to scale. Rather, the various elements illustrated in the figures are rendered in such a way that their function and general purpose become comprehensible to a person skilled in the art. Connections and cou-plings between functional units and elements illustrated in the figures can also be implemented as an indirect connection or coupling. A connection or coupling can be implemented in a wired or wireless manner. Functional units can be implemented as hardware, software or a combination of hardware and software.
Techniques for producing HOEs are described below. For example, volume HOEs or surface HOEs can be produced by means of the techniques described herein.
The techniques described herein are based on replicating a master HOE to produce a replicated HOE. For the production of the master HOE, a corresponding exposure process can be used upstream thereof. Various examples described herein concern in particular the exposure of the replicated HOE by replicating the master HOE.
Various examples are based on the insight that different fields of application require the integration of HOEs in curved surfaces. That means that, depending on the field of application, a carrier layer of the replicated HOE is fixed in a curved surface shape. For this purpose, the carrier layer of the replicated HOE could be applied for example to a corresponding carrier produced for example in an injection molding method or by means of additive manufacturing. The corresponding curvature of the surface shape can be one-dimensional or two-dimensional.
In such a case, the master HOE can be exposed in a state in which the carrier layer of the master HOE has the same surface shape which the replicated HOE has in the application situation. This surface shape is called target surface shape hereinafter because it is the intended surface shape after the end of the production method for the replicated HOE.
During the production method for the replicated HOE, it may however be necessary on account of technical limitations to deviate from the target surface shape. In particular, it may be conceivable that the surface shape of the carrier material of the replicated HOE during replication, that is to say during exposure of the replicated HOE, deviates from the target surface shape. This surface shape of the carrier material of the replicated HOE during replication, that is to say during exposure of the replicated HOE, is referred to hereinafter as exposure surface shape.
By way of example, a roll-to-roll process or a flatbed copying method requires specific exposure surface shapes. That means that in the roll-to-roll process or in the flatbed copying method, for example, the exposure surface shape of the replicated HOE (and accordingly of the master HOE) can be predefined and can deviate in particular from the target surface shape.
Besides such a deviation—governed by the system integration of the HOE—between the surface shape during exposure and the surface shape during illumination for reconstructing the hologram, an illumination geometry or emitter geometry which is governed by the system integration and deviates from the illumination geometry or emitter geometry during exposure can alternatively or additionally also occur during illumination for reconstructing the hologram. By way of example, a point light source can be used during the exposure. A light point can be moved over the carrier material of the HOE for the exposure. An extensive light source can be used during illumination. That means that an emitter area of the light source during illumination is significantly larger than an emitter area of the radiation source during exposure. By way of example, the emitter area of the light source during illumination can be at least a factor of 1000 larger than the emitter area of the radiation source during exposure. The light source during illumination can also comprise an array of individual emitters, e.g. a light emitting diode panel (i.e. e.g. an array of light emitting diodes or more generally an arrangement of a plurality of light emitting diodes on a carrier). Such illumination geometries governed by the system integration of the HOE can also be taken into account in the exposure.
A master HOE was produced in box 3005. Forthis purpose, a corresponding photopolymer is exposed, which is located in or on a carrier layer of the master HOE. For the exposure, an object beam and a reference beam of corresponding light can be used, which are formed phase-coher-ently with respect to one another. An analogue exposure could be performed, in which the object generates the object beam. A digital exposure with a pixelated light modulator and a stitching method could also be used.
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.
In box 3010, a laser is typically used as radiation source. The laser beam can be scanned. A light point of the laser beam can be moved over the surface of the carrier layer in which the HOE is generated.
In box 3010, the carrier material of the master HOE and the carrier material of the replicated HOE have an exposure surface shape 912; this is illustrated as planar by way of example in
The exposure surface shape 912 is different than the target surface shape 911.
After the exposure process for the carrier layer, the replicated HOE is fixed again in the target surface shape 911, box 3015. A system integration is effected for a target application, for example in a motor vehicle. Afterward, the replicated HOE can be illuminated by a suitable light source, with the result that the hologram is reconstructed, box 3020.
The replicated HOE can then be illuminated in order to reconstruct a hologram. The illumination can be effected by an arbitrary light source, e.g. a point light source or an areal light source. Put generally, in certain examples the light source used for illumination deviates from the radiation source used for exposure.
The system 50 comprises a radiation source or light source 52, for example a laser, which emits coherent laser light along a beam path 41. The “light” can be in the visible spectrum or adjacent wavelength ranges, for example in the infrared or ultraviolet part of the electromagnetic spectrum. The light source 52 is controlled by a controller 51 (for example a processor which can load and execute program code from a memory; or an application-specific integrated circuit; or a field programmable array).
The light source 52 can be a point source. That means that an emitter area of the light source 52 is particularly small. By way of example, edge dimensions of the emitter area could be <1 mm or less than 100 μm or less than 20 μm. The light source 52 can comprise collimator optics that reduce the divergence of the beam path of the light.
A laser or a laser diode can be used as light source. A collimation along a “fast axis” and a “slow axis” can take place.
The light illuminates a master HOE 92 in order to expose a replicated HOE 96 in this way. A light point generated by the light source 52 can be moved over the carrier material of the HOE 96.
In addition, the system 50 also comprises a positioning module 56. The latter comprises one or more motorized actuators 55 and also at least one optical element 54 (which can be pas-sive or active, i.e. can be settable or fixedly oriented).
The motorized actuators 55 can position at least one optical element 54 in accordance with a plurality of degrees of freedom. It may be possible to implement one or more degrees of freedom of translational movement. Alternatively or additionally, one or more degrees of freedom of rotational movement can be implemented.
The actuator 55 could be implemented for example by a robotic arm with a plurality of adjustable axes. An implementation by means of a multi-axis optical linear adjustment table would also be conceivable. Corresponding examples will be described later in association with
The actuator 55 can be controlled by the controller 51.
As a general rule, the at least one optical element 54 can be implemented for example by a mirror or a prism. The at least one optical element 54 could alternatively or additionally comprise one or more lens elements.
An at least partly collimated beam can be generated by the at least one optical element 54.
In some examples, it would be conceivable for the at least one optical element to comprise a scanning mirror that can scan the beam path 41. In such a case, the scanning mirror can be controlled by the controller 51. Different scanning patterns can be used. In one example, a Cartesian scanning pattern is used. That means that lines are scanned successively. A spiral scanning pattern could also be used. A plurality of ellipses could be used (elliptic scanning pattern), which e.g. gradually become smaller or larger. Depending on the choice of scanning pattern, for example specific aberrations can be compensated for. By way of example, a spiral scanning pattern or an elliptic scanning pattern could be particularly suitable for correcting spherical aberrations.
It is not necessary in all scenarios for a scanning mirror—if present at all—to be integrated into the positioning module 56. By way of example,
By means of the positioning module 56, it is possible to move a reference point 84, which is arranged along the beam path 41 (here in the optical element 54), on a trajectory 61 (indicated by the dotted-dashed line). The trajectory 61 thus denotes the path along which the reference point 84 of the beam path moves while the master HOE 92 is being replicated. What can be achieved as a result is that the angle of incidence can be varied in a targeted manner as a function of the position of the light point on the master HOE 92.
The trajectory 61 can for example be curved (i.e. in a global coordinate system of the system 50, as shown in
In this case, the controller 51 can be configured to control the positioning module 56 during the exposure process (that is to say while the light source 52 is being controlled in order to emit the light along the beam path 41), with the result that the reference point 84 is moved in relation to the master HOE 92 on the curved trajectory 61.
The controller 51 can also be configured to vary the emergence angle 85 of the light from the reference point 84 during the exposure process. For example, for this purpose, a mirror of the at least one optical element 54 could be tilted in relation to the actuator 55 or a (rigid) mirror oriented fixedly in relation to the actuator 55 could be positioned differently with respect to the light source 52.
The controller 51 is correspondingly configured to vary the angle 89 of incidence of the light on the carrier layer of the master HOE 92 or of the HOE 96 during the exposure process.
By virtue of the movement along the trajectory 61 and/or by virtue of the variation of the emergence angle 85, an angle 89 of incidence of the light on the master HOE 92 is varied as a result.
For the purpose of controlling the positioning module 56 and optionally the scanning mir-ror 58, the controller 51 can load control data 401 specifying the movement of the actuator 55 and/or optionally of a settable optical element 54, from a corresponding control data lookup table 400. For example, the suitable control data can be selected depending on the master HOE used. That means that different curved trajectories 61 are used in each case for different master HOEs.
The control data 401 could be provided for example by a manufacturer of the master HOE. The control data 401 could be determined for example in connection with box 3005 from
This dependence of the curved trajectories 61 on the master HOE used stems from the fact that, depending on the master HOE 92, different target surface shapes 911 can be used (wherein the exposure process for replication can take place in each case in the same exposure surface shape 912 because this exposure surface shape 912 is dictated by the replication process used). Accordingly, a different compensation has to be effected by the curved trajectory 61. This is explained below in association with
In the example in
In any case, the replicated HOE 96 is intended to implement the corresponding optical functionality if the replicated HOE 96 has the same target surface shape 911.
During exposure of the replicated HOE 96 (cf.
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 correspondingly translated into a change in the rays of the incident beam 81 # and the rays of the reflected beam 82 #: These beams 81 # and 82 # are “drawn” in the drawing plane, just like the diffraction structure.
Various examples are based on the insight that in order to produce the replicated HOE 96 with the use of the exposure surface shape 912, the beam path 41 of the light used for exposure are intended to simulate the rays of the adapted beam 81 #(cf.
This is made possible by means of a method discussed below in association with
In box 3105, a light source, for example a laser, is controlled in order to emit light along a beam path onto a master HOE. For example, the light source could be controlled in such a way that it continuously emits light at a specific light intensity during an exposure process.
Optionally, subsequently in box 3110, a scanning mirror can be controlled in order to scan the light in relation to the master HOE during the exposure process. By way of example, a corresponding scanning mirror 58 was discussed in connection with the system 50 in the example in
In some examples, no scanning mirror at all is required. Accordingly, box 3110 is optional.
Afterward, in box 3115, the positioning module 56 is controlled in order to move a reference point along the beam path of the light in relation to the master HOE on an e.g. curved trajectory during the exposure process. Aspects in connection with the curved trajectory 61 have been discussed above in association with
Optionally, it would also be conceivable for the positioning module also to be controlled in box 3115 in order to change the emergence angle of the beam path at the reference point during movement of the reference point along the curved trajectory in relation to the master HOE. It is thus possible to effect a separate movement for changing the emergence angle and for movement along the curved trajectory.
By means of such techniques, it is possible to vary the angle of incidence of the light on the master HOE 92. For example, a flatbed replication process or a roll-to-roll replication process can benefit from this.
In the roll-to-roll replication process (cf. box 3010 in
Techniques in connection with the movement of the reference point 84 have been explained above. The way in which the emergence angle 85 can be changed has additionally been explained. It is optionally possible to synchronize the movement of the reference point 84 along the curved trajectory 61 with a scanning of the light beam 41 (cf.
For example, the reference point 84 could mark a midpoint of the scanning movement 53. Aspects in connection with the scanning are illustrated below in association with
That means that it is possible to mediate between the target surface shape 911 and the exposure surface shape 912 by way of a one-dimensional curvature operation along the axis 199 of curvature (a curvature perpendicular to the axis 199 of curvature is not changed). The same correspondingly applies (in inverse form) to the example in
The scanning direction 36 of the scanning movement 53 of a scanned light point 49 on the master HOE 92 by means of the scanning mirror is oriented perpendicular to the axis 199 of curvature, cf.
The example in
The movement of the reference point 84 along the curved trajectory 61 takes place in a manner superimposed with the scanning movement 53 along the scanning direction 36. This shifts the light point 49 along the direction 37. The corresponding movement 21 has a component along an axis 37 that is oriented perpendicular to the scanning direction 36 (and thus parallel to the axis 199 of curvature) along the direction 37.
In the example in
Not all examples require the implementation of the scanning movement 53. For example, at least one optical element could also be arranged at the reference point 84, which optical element causes the light point 49 # of the light on the master HOE 92 to be expanded along the direction 36 (compare light point 49 with light point 49 #). The otherwise scanned lines are then exposed in an integrated manner.
In the example in
That means, in other words, that reference points 84 are calculated which represent the lengthening of the spanned scan line 860 into an intersection point 859. The areal light source 851 can thus likewise be represented by a moved reference point.
Such techniques can be taken into account in the calculation of the control data 401. When calculating the control data, it is thus possible to take account of the geometry of the light source 851 which is used for reconstructing the hologram during illumination of the HOE. In particular, an areal extent of the light source 851 can be taken into account.
These techniques make it possible to use a point light source, for example at the reference point 84. Alternatively, the areal light source 851 during the illumination of the HOE for reconstructing the hologram could also be attained by the use of suitable optics for the light source during the exposure for the replication of the master HOE. By way of example, suitable optics enabling an areal exposure could be arranged at the reference point 84.
Other techniques can also be used instead of a robotic arm 231 for the implementation of the positioning module 56. One example is shown in
Various aspects have been disclosed above in connection with the production of a HOE which enables a flexible choice of the surface shape when replicating a master HOE. However, the techniques described herein do not just enable the flexible choice of the surface shape when replicating the master HOE. The disclosed techniques of flexibly moving the reference point along differently shaped trajectories make it possible to generate wavefronts for the replication process with a multiplicity of degrees of freedom. In this way, it is possible to take account of various influences during manufacturing (over and above specific surface shapes during replication). By way of example—as an alternative or in addition to a compensation of different surface shapes when replicating the master HOE and when generating the master HOE or during system integration of the replicated HOE—aberrations can be flexibly compensated for. This will be explained in greater detail with reference to the following figures.
The spherical aberration is caused by shrinkage of the carrier layer of the HOE 96; the shrinkage occurs perpendicular to the substrate (i.e. along the plane normals; that is shown by the dashed arrows in
The spherical aberration then occurs because the shrinkage has a varying effect on the different (optical) deflection angles. One example: A volume grating that deflects a beam by 30° is embossed in the polymer. Elsewhere there is a deflection by 50°. The structure which causes 50° deflection is then tilted by the “anisotropic” shrinkage to a greater extent than the structure with the 30°. As a result, e.g. a lens element function (radially different deflection angles) does not change uniformly over the carrier material layer, but rather locally differently—and the spherical aberration arises.
Such shrinkage or contraction of the carrier layer occurs for example if the carrier layer of the HOE 96 is integrated into a system and in the course of this is clamped into a frame or carrier or is adhesively bonded thereto, for example. Aberrations or imaging aberrations can alternatively or additionally occur during the replication process when the HOE is exposed. By way of example, such aberrations can occur on account of the fixing of the carrier layer of the HOE along the carrier layer of the master HOE. Aberrations can alternatively or additionally occur if the carrier layer of the HOE is integrated in a master plate with the master HOE. Alternatively or additionally, aberrations can also occur during the illumination process after system integration, i.e. when the HOE is being illuminated in order to reconstruct the hologram 859. The carrier layer of the HOE is integrated into a carrier in such a case. By way of example, material expansion can occur on account of temperature fluctuations.
In order to reconstruct the hologram 859 without corruption in the case of such a shrunk carrier layer of the HOE 96, wavefronts are generated in accordance with the spatially variable light source 851 (dashed line) shown in accordance with
Put more generally: An existing or anticipated aberration can be compensated for during the replication process (in addition or as an alternative to the compensation of different surface shapes and/or different illumination geometries or emitter geometries). This can be done as shown in
Analogously thereto, other aberrations can be generated (and thus proactively compen-sated for) by choosing a scanning pattern which matches the “symmetry” of the aberration. These can be described e.g. as Zernike polynomials. Such a combination of scanning pattern and movement of the reference point 84 on arbitrary trajectories 61 allows virtually arbitrary wavefronts to be generated for the replication.
Techniques such as have been described in association with
In summary, the following examples, in particular, have been described:
EXAMPLE 1. A device (50) for producing a holographic optical element, HOE, (96), wherein the device (50) comprises:
EXAMPLE 2. The device according to EXAMPLE 1,
EXAMPLE 3. The device according to EXAMPLE 1 or 2,
EXAMPLE 4. The device according to EXAMPLE 1 or 2,
EXAMPLE 5. The device according to any of the preceding EXAMPLES, furthermore comprising:
EXAMPLE 6. The device according to EXAMPLE 5,
EXAMPLE 7. The device according to EXAMPLE 5 or 6,
EXAMPLE 8. The device according to EXAMPLE 7,
EXAMPLE 9. The device according to EXAMPLE 7 or 8,
EXAMPLE 10. The device according to any of EXAMPLES 7 to 9,
EXAMPLE 11. The device according to any of EXAMPLES 5 to 10,
EXAMPLE 12. The device according to any of the preceding EXAMPLES, furthermore comprising:
EXAMPLE 13. The device according to EXAMPLE 12,
EXAMPLE 14. The device according to EXAMPLE 12 or 13, and according to any of EXAMPLES 7 to 11,
EXAMPLE 15. The device according to EXAMPLE 14,
EXAMPLE 16. The device according to any of EXAMPLES 12 to 15,
EXAMPLE 17. The device according to any of EXAMPLES 12 to 16,
EXAMPLE 18. The device according to any of the preceding EXAMPLES, furthermore comprising:
EXAMPLE 19. The device according to EXAMPLE 18, and according to any of EXAMPLES 7 to 11,
EXAMPLE 20. The device according to any of the preceding EXAMPLES,
EXAMPLE 21. A data processing unit (760) comprising at least one processor (761) and a
EXAMPLE 22. The data processing unit according to EXAMPLE 21,
EXAMPLE 23. The data processing unit according to EXAMPLE 21 or 22,
EXAMPLE 24. The data processing unit according to any of EXAMPLES 21 to 23, wherein
EXAMPLE 25. The data processing unit according to any of EXAMPLES 21 to 24, wherein
EXAMPLE 26. The data processing unit according to any of EXAMPLES 21 to 25, wherein
Besides such examples in connection with devices and data processing units, the following examples in connection with methods have also been described. The examples reproduced above can be combined with the examples reproduced below in order to form further examples.
EXAMPLE 1. A method for producing a holographic optical element, HOE, (96) by replicating (3010) a master HOE (92) in the context of an exposure process, wherein a carrier layer (91) of the master HOE (92) is arranged along a carrier layer (95) of the HOE (96) during the exposure process,
EXAMPLE 2. The method according to EXAMPLE 1,
EXAMPLE 3. The method according to EXAMPLE 1 or 2, wherein the method furthermore comprises:
EXAMPLE 4. The method according to EXAMPLE 3,
EXAMPLE 5. The method according to EXAMPLE 3 or 4,
EXAMPLE 6. The method according to any of EXAMPLES 3 to 5,
EXAMPLE 7. The method according to EXAMPLE 2, and according to any of EXAMPLES 3 to 6,
EXAMPLE 8. The method according to any of EXAMPLES 2 to 7,
EXAMPLE 9. The method according to any of the preceding EXAMPLES, wherein the method furthermore comprises:
EXAMPLE 10. The method according to EXAMPLE 9,
EXAMPLE 11. The method according to EXAMPLE 4 and according to EXAMPLE 10,
EXAMPLE 12. The method according to any of the preceding EXAMPLES,
EXAMPLE 13. The method according to any of the preceding EXAMPLES,
EXAMPLE 14. The method according to any of the preceding EXAMPLES,
EXAMPLE 15. The method according to any of the preceding EXAMPLES,
EXAMPLE 16. The method according to EXAMPLE 14,
EXAMPLE 17. The method according to EXAMPLE 16, wherein the method furthermore comprises:
EXAMPLE 18. The method according to EXAMPLE 16 or 17, wherein the method furthermore comprises:
EXAMPLE 19. The method according to any of EXAMPLES 16 to 18, wherein the method furthermore comprises:
EXAMPLE 20. The method according to any of EXAMPLES 15 to 19, wherein the method furthermore comprises:
EXAMPLE 21. The method according to any of the preceding EXAMPLES,
EXAMPLE 22. The method according to any of the preceding EXAMPLES,
EXAMPLE 23. A method for producing a holographic optical element, HOE, (96) by replicating (3010) a master HOE (92) in the context of an exposure process, wherein a carrier layer (91) of the master HOE (92) is arranged along a carrier layer (95) of the HOE (96) during the exposure process,
EXAMPLE 24. The method according to EXAMPLE 23,
EXAMPLE 25. The method according to EXAMPLE 24,
EXAMPLE 26. The method according to EXAMPLE 24 or 25,
EXAMPLE 27. The method according to any of EXAMPLES 24 to 26,
EXAMPLE 28. The method according to any of EXAMPLES 23 to 27, wherein the method furthermore comprises:
EXAMPLE 29. The method according to EXAMPLE 28,
EXAMPLE 30. The method according to EXAMPLE 28 or 29,
EXAMPLE 31. The method according to any of EXAMPLES 28 to 30,
EXAMPLE 32. The method according to any of EXAMPLES 28 to 31,
EXAMPLE 33. The method according to any of EXAMPLES 23 to 32, wherein the method furthermore comprises:
EXAMPLE 34. The method according to EXAMPLE 33,
EXAMPLE 35. The method according to any of EXAMPLES 23 to 34,
EXAMPLE 36. The method according to any of EXAMPLES 23 to 34,
EXAMPLE 37. The method according to any of EXAMPLES 23 to 36,
EXAMPLE 38. The method according to EXAMPLE 37,
EXAMPLE 39. The method according to EXAMPLE 37 or 38, wherein the method furthermore comprises:
EXAMPLE 40. The method according to any of EXAMPLES 37 to 39, wherein the method furthermore comprises:
EXAMPLE 41. The method according to any of EXAMPLES 37 to 40, wherein the method furthermore comprises:
EXAMPLE 42. The method according to any of EXAMPLES 37 to 41, wherein the method furthermore comprises:
EXAMPLE 43. The method according to any of EXAMPLES 23 to 42,
EXAMPLE 44. The method according to any of EXAMPLES 23 to 43,
EXAMPLE 45. The method according to any of EXAMPLES 23 to 44, wherein the method furthermore comprises:
EXAMPLE 46. The method according to EXAMPLE 45,
EXAMPLE 47. A computer program comprising program code which can be loaded and
EXAMPLE 48. A method, comprising:
EXAMPLE 49. The method according to EXAMPLE 48,
It goes without saying that the features of the embodiments and aspects of the invention described above can be combined with one another. In particular, the features can be used not only in the combinations described but also in other combinations or on their own, without departing from the scope of the invention.
By way of example, various aspects in connection with a curved trajectory have been described. The trajectory can have this curvature in a global coordinate system, i.e. can be curved as viewed from outside (not only relatively in relation to the surface shape of the carrier layers of the master HOE and of the replicated HOE during replication). Generally, however, it would also be conceivable to use a straight trajectory. By way of example, comparable effects can be achieved with a suitable variation of the angle of incidence of the light on the carrier layer of the replicated HOE. Comparable effects can be achieved by the use of suitable scanning patterns.
Influences of aberrations and techniques for compensating for such influences have been discussed above on the basis of the example of a spherical aberration. However, it is also possible to take account of other aberrations described by corresponding Zernike polynomials.
A description has been given above of how different influences—for example different surface shapes 911, 912 during production of the master HOE, replication and system integration; different illumination geometries during exposure and illumination; aberrations—on the replication process and the reconstruction process can be taken into account. The various examples can also be combined with one another, which is helpful in particular in scenarios where the various effects occur in a superimposed manner—i.e. e.g. there is a specific curvature during system integration, but also aberrations on account of material shrinkage for instance during fixing for replicating the master HOE.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2022 102 646.9 | Feb 2022 | DE | national |
The present application is a National Phase patent application of PCT Appl. No. PCT/EP2023/052825, filed on Feb. 6, 2023, which claims priority to German Patent Appl. No. DE102022102646.9, filed on Feb. 4, 2022, each of which is hereby fully incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2023/052825 | 2/6/2023 | WO |
