Method for actively optimizing a playback configuration of a virtual retinal display, holographic recording material, holographic combiner and data glasses

Abstract

The invention relates to a method for actively optimizing a playback configuration of a virtual retinal display (16a-d) comprising a light projector (10a-d) and a holographic combiner (12a-d) with at least one holographic-optical element (14a-d). It is proposed that in at least one process step (52a-d) of the process, one or more beam parameters of a light signal (18a-d) emitted by the light projector (10a-d) and / or one or more holographic reconstruction parameters of the holographic combiner (12a-d), in particular during operation of the virtual retinal display (16a-d), are actively modified with the aim of optimizing a hologram efficiency of the holographic-optical element (14a-d), in particular optimizing a hologram-side angular and / or wavelength bandwidth with which a hologram target efficiency can be achieved.

Description

State of the art

[0001] Methods for optimizing playback configurations of light projectors and a holographic combiner with virtual retinal displays comprising at least one holographic-optical element have already been proposed. These methods involve complex manual selection processes to identify individually suitable pairs of light projectors and holographic combiners, where, in particular, the reconstruction wavelength of the hologram and the laser emission wavelength of the light projector are compatible.

[0002] Holograms produced by holographic combiners typically possess a limited bandwidth across wavelengths and angles. The wavefront transformations performed by these holograms, as well as characteristic properties such as hologram bandwidth in terms of angle and wavelength, are determined by the initial hologram capture configuration. For a given wavelength, a volume hologram has a specific angle of incidence range within which diffraction is efficient. The greater the deviation from an ideal angle of incidence within this range, the lower the hologram's diffraction efficiency. Changing the optical properties of a hologram is typically impossible after the hologram capture is complete. Therefore, manufacturing tolerances in hologram production, laser manufacturing, and the combination of combiner and light projector are critical.

[0003] Undesirable effects can also occur during the operation of a virtual retinal display, influencing the behavior of the combiner or light projector, for example, due to temperature-related drift or mechanical misalignment. Known virtual retinal displays lack the capability to counteract these undesirable effects. Disclosure of the invention

[0004] The invention relates to a method for optimizing a playback configuration of a virtual retinal display comprising a light projector and a holographic combiner with at least one holographic optical element (HOE).

[0005] It is proposed that the method incorporates active optimization, whereby one or more beam parameters of a light signal emitted by the light projector and / or one or more holographic reconstruction parameters of the holographic combiner are actively modified, particularly during operation of the virtual retinal display, with the aim of optimizing the hologram efficiency of the holographic-optical element, specifically optimizing a hologram-side angular and / or wavelength bandwidth, with which a (preferably definable / defined) target hologram efficiency can be achieved. This advantageously improves the robustness of the virtual retinal display, particularly in field applications. Furthermore, it advantageously enables the most optimal, and in particular error-free, operation of the virtual retinal display in a wide variety of scenarios and environments.Advantageously, the invention ensures that the combiner's hologram is always reconstructed close to its optimal operating point, thus consistently exhibiting the best possible diffraction efficiency. This has the beneficial effect of reducing the laser power required for operating the virtual retinal display, which in turn has a positive impact on the overall system's energy consumption. Furthermore, reducing the laser power allows for greater compliance with eye safety requirements, particularly since holograms currently used in smart glasses exhibit a diffraction efficiency of only a few percent for most reconstruction angles. This results in a large portion of the laser power being transmitted through the hologram and emitted on the world-facing side of the lens.By reducing this transmitted portion, a laser with lower power can be advantageously used. Furthermore, well-known, proven, and inexpensive photopolymer or silver halide materials can be used to record the holographic optical functions of the holographic combiner.

[0006] In particular, the virtual retinal display is part of smart glasses. "Smart glasses" refers specifically to a wearable device (head-mounted display) that adds information to a user's field of vision. Preferably, smart glasses enable augmented reality, virtual reality, and / or mixed reality applications. They are also commonly referred to as smart glasses, VR glasses, or AR glasses. The virtual retinal display is also called a retinal scan display or laser beam scanning (LSB) display. The virtual retinal display is specifically designed to scan an image content sequentially by deflecting at least one visible light signal, especially a laser beam, from at least one time-modulated light source, such as one or more (RGB) laser diodes or superluminescent (RGB) LEDs (SL-LEDs) of a light projector.The virtual retinal display is projected onto the user's retina via a MEMS micromirror system and optical elements. This projection typically relies on at least one holographic combiner. The combiner transmits ambient light to the eye (real image) and simultaneously overlays / combines this transmitted ambient light with artificially generated image content (augmented image / scanned image) from the virtual retinal display's light projector. A well-known type of holographic combiner is the free-space combiner. The free-space combiner can be integrated into a lens of the smart glasses. Alternatively, it can also be a separate optical element, distinct from the lens.The free-space combiner overlays / combines the augmented / scanned image of the virtual retinal display with the surrounding image by acting as a reflective or diffracting surface for the image content (the scanned image) projected by the virtual retinal display's light projector. Other wavelengths, predominantly contained within the surrounding image, pass through the free-space combiner essentially unimpeded. This reflection or diffraction is primarily generated by reflection off one or more holograms. For example, the holographic optical element (HOE) can be integrated into the spectacle lens as a free-space combiner. HOEs possess high angular and wavelength selectivity.

[0007] Beam parameters of the light signal include, in particular, beam shape, propagation direction, propagation angle, divergence / convergence, wavelength spectrum, etc. Reconstruction parameters of the holographic combiner include, in particular, playback angle, playback wavelength / spectrum, etc. Specifically, "active modification" of a parameter refers to a modification of the parameter during operation, for example, during image output by the data glasses with the virtual retinal display. Specifically, active modification allows direct, adjustable intervention in the playback configuration of the virtual retinal display. Specifically, active modification allows a change to at least one of the beam parameters and / or at least one of the reconstruction parameters through a software and / or hardware setting change of the virtual retinal display.In particular, active modification aims to optimize the hologram's angular and / or wavelength bandwidth so that a defined target hologram efficiency is exceeded for the widest possible range of angles and wavelengths at any given time. Specifically, active modification aims to maximize the hologram efficiency achievable in any given situation. Hologram efficiency is higher the greater the relative proportion of the light signal initially emitted by the projector that is deflected towards the eye of the user of the smart glasses. Specifically, the hologram's angular and / or wavelength bandwidth is determined by the individual Bragg characteristic of the respective hologram, derived from the Bragg equation.

[0008] Furthermore, it is proposed that at least one of the (actively modifiable) holographic reconstruction parameters of the holographic combiner be actively modified by, in particular, targeted heating of the holographic combiner, especially the holographic-optical element. This advantageously allows for influencing the temperature drift of the holographic combiner, especially the HOE. Advantageously, the temperature drift of the HOE can be adjusted / aligned with the temperature drift of the light projector, especially a laser diode or an SL-LED of the light projector. Advantageously, a good and efficient display of the artificial image content output by the virtual retinal display can be achieved independently of any heating of the smart glasses, e.g., due to an ambient temperature (e.g., during a change from indoor to outdoor use), solar radiation, and / or operating temperature.In particular, the emission wavelength of a laser diode and / or an SL-LED typically drifts more than the HOE playback wavelength. Therefore, heating the holographic combiner is preferably intended to amplify the thermal drift of the HOE playback wavelength. Specifically, heating the holographic combiner is intended to generate thermal expansion of the holographic material and thereby adjust the optical function imprinted into the hologram material, especially the playback wavelength and / or the playback angle of the hologram. In this case, the holographic reconstruction parameter can be the playback wavelength of the hologram, especially the HOE. However, the playback angle / incidence angle of the hologram, especially the HOE, could also be changed in the same way.In particular, a change in the temperature of a hologram can lead to a stretching or compression of the grating constants of underlying diffraction gratings (especially in the case of a homogeneously distributed temperature change) and thus, in particular, to a change in the playback wavelength and / or to a change in the tilt angle of individual grating planes (especially in the case of a localized temperature change) and thus, in particular, to a change in the playback angle / deflection angle of the hologram.

[0009] The terms "intended" and / or "configured" should be understood to mean, in particular, specifically programmed, designed, and / or equipped. The fact that an object is intended and / or configured for a specific function should be understood to mean, in particular, that the object fulfills and / or performs this specific function in at least one application and / or operating state. Advantageously, heating the holographic combiner can also compensate for manufacturing tolerances in a peak wavelength of the light projector, especially of the respective laser diode and / or the respective SL-LED, and in particular for tuning differences (wavelength and / or angle) between the hologram and the light projector. Advantageously, heating the holographic combiner can also compensate for other drift effects, such as aging drift, e.g., of the light projector.

[0010] If the holographic combiner, in particular the holographic-optical element, is heated by an oscillating field, especially an oscillating magnetic field, which excites nanoparticles embedded in the holographic combiner, especially in the holographic-optical element, to oscillate, a targeted active modification of the reconstruction parameter(s) can advantageously be achieved, e.g., by adjusting the oscillation frequency or amplitude. Advantageously, the oscillation of the nanoparticles and the resulting heat input provide a means of tuning the grating constant of the holographic diffraction grating of the HOE. Preferably, the nanoparticles are excited to resonant oscillation. In particular, the embedded nanoparticles are excited to oscillate by an oscillating alternating magnetic field.In particular, the oscillating alternating magnetic field is generated by a controllable magnetic coil. The magnetic coil can be integrated into the smart glasses, for example, into the frame, and / or controlled by a control unit of the smart glasses. A "control unit" is understood to be, in particular, a unit with at least one control electronics module. "Control electronics" is understood to be, in particular, a unit with a processor, a memory unit, and an operating program stored in the memory unit. The oscillating nanoparticles generate, in particular, a homogeneous heat source integrated into the HOE. Through heating, the nanoparticles can cause a controlled expansion and / or deformation of the HOE, especially of the diffraction grating of the HOE, and thus of the optical function of the HOE.It is conceivable that several different types and / or sizes of nanoparticles, particularly those with different resonant frequencies, are embedded in the HOE. This could allow for more precise control options. Furthermore, it is conceivable that different nanoparticles or nanoparticle densities are arranged in different regions of the HOE, for example, at different depths. This could generate spatially differentiated heating effects. Additionally, the nanoparticles could be homogeneously distributed, arranged in a linear pattern, concentrically, and / or with a concentrically increasing or decreasing density distribution. In particular, the HOE is made of an established holographic recording material, such as a photopolymer or a silver halide. The nanoparticles could be silver nanoparticles.

[0011] Alternatively or additionally, it is proposed that at least one of the (actively modifiable) beam parameters of the light signal is a spectral emission bandwidth of the light projector emitting the light signal, in particular a laser projector, which is actively modified by a high-frequency modulation of an operating parameter of the light projector, in particular an operating current of the light projector, preferably a pump medium of a laser emitter of the laser projector. This advantageously increases the interaction overlap between the light signal and the hologram. Advantageously, an optimal hologram efficiency range can be achieved through the wavelength spectrum of the light signal in many different scenarios and environments. High-frequency modulation is understood to mean, in particular, modulation with frequencies in the megahertz range. The laser emitter of the laser projector is preferably a diode laser.a laser diode. In particular, the high-frequency modulation is selected such that the spectral emission bandwidth of the light signal is increased by at least 50%, preferably by at least 100%, and preferably by at least 200%. For example, the spectral bandwidth can be increased from 0.5 nm to 2 nm by the high-frequency modulation. Preferably, the increased spectral bandwidth is still always below an upper limit of 5 nm. This allows high image quality (especially image sharpness) to be maintained, particularly in flying-spot projectors.

[0012] Furthermore, it is proposed that at least one of the emission parameters of the light projector be actively modified by an acousto-optic modulator, an electro-optic modulator, or variable spectral filters, particularly in combination with spectrally broad light sources. This advantageously increases the interaction overlap between the light signal and the hologram. It also advantageously allows for the achievement of an optimal hologram efficiency range through the wavelength spectrum of the light signal in many different scenarios and environments. In particular, the acousto-optic modulator and / or the electro-optic modulator increases the spectral emission bandwidth (similar to the modulation of the pump medium). Specifically, the variable spectral filter shifts the output spectral bandwidth of the light signal.In particular, the acousto-optic modulator is a Bragg cell or an acousto-optically tunable filter (ATOF). In particular, the electro-optic modulator is a Pockels cell or an electro-optic polarization modulator. In particular, the acousto-optic modulator and / or the electro-optic modulator is arranged in a beam path of the light projector, in particular upstream of the MEMS micromirror system.

[0013] As an alternative to increasing the spectral emission bandwidth of a laser signal, an already spectrally broader signal from a superluminescent LED could also be used to generate a light signal.

[0014] Additionally, it is proposed that the variable spectral filter be designed as an actively tiltable spectral filter, which is configured to extract a spectrally narrower spectrum from the emission spectrum of a spectrally broader light emitter of the light projector, e.g., an LED or a superluminescent LED. This narrower spectrum must be matched to the instantaneous playback wavelength of the holographic combiner, in particular the HOE. Advantageously, this provides a simple mechanical means for actively modifying the beam parameter. The spectral filter is preferably a bandpass filter. The spectral filter can be designed as a line filter or as an interference filter. The spectral filter is preferably mechanically tiltable. The spectral filter is preferably tiltable by an electronic actuator. The spectral filter is particularly tiltable and arranged in the beam path of the light signal.Depending on the tilt angle, a different part of the wider spectrum is allowed through the spectral filter, while the rest of the wider spectrum is blocked.

[0015] Furthermore, it is proposed that at least one of the beam parameters of the light signal is an angle of incidence at which the light signal, in particular a wavefront of the light signal, strikes the holographic combiner. This angle is actively modified by an adaptive beam guidance unit of the virtual retinal display. This advantageously increases the interaction overlap between the light signal and the hologram. Furthermore, it is advantageous to actively correct a mismatch between the HOE and the light emitter caused by drift or mechanical adjustment of the HOE and / or light emitter by selectively playing the HOE under a modified angular configuration that also corresponds to the Bragg condition, but in which the HOE again exhibits its optimal diffraction efficiency.In particular, a hologram can be reconstructed with high efficiency even in a configuration that differs from the recording configuration, provided that the playback angle and playback wavelength are adjusted according to the Bragg equation.

[0016] If the adaptive beam guidance unit actively modifies the angle of incidence of the light signal using a 2D tilting mirror, a targeted and easily adjustable modification of the playback configuration can advantageously be achieved. Hologram efficiency can also be advantageously modified. Preferably, in addition to the 2D tilting mirror, a tunable lens is used, which advantageously prevents a loss of focus due to changes in the angle of incidence or the path length to the eye. In particular, the frequency and / or the emission spectrum of the light signal can also be modified simultaneously, so that the Bragg condition is still optimally fulfilled.

[0017] Furthermore, a holographic recording material, in particular a heated holographic recording material, intended at least for use in the aforementioned method, is proposed. This holographic recording material comprises a multitude of embedded nanoparticles that can be excited to oscillation, particularly resonant oscillation, in oscillating physical fields, especially oscillating magnetic fields. This advantageously enables internal and, in particular, wireless, easily controllable heating of holograms. This also advantageously improves the robustness of the virtual retinal display, especially in field applications. Furthermore, it advantageously enables the most optimal, and in particular error-free, operation of the virtual retinal display in a wide variety of scenarios and environments.Advantageously, the nanoparticles are embedded in a matrix of an established holographic recording material, such as a photopolymer or a silver halide.

[0018] If the nanoparticles are smaller than 20 nm, any negative impact of the particles introduced into the holographic recording material to achieve the heating function on the optical function and / or the optical transparency of the HOE, e.g., through light scattering, can be advantageously minimized. The nanoparticles can, for example, consist of silver ions. Furthermore, a resonant vibration of the nanoparticles can be achieved within readily accessible frequency ranges.

[0019] If the nanoparticles are silver nanoparticles, good compatibility with established holographic imaging materials such as silver halide can be advantageously achieved. Furthermore, good interaction of the nanoparticles with external oscillating magnetic fields can be advantageously achieved.

[0020] Furthermore, the holographic combiner, in particular the holographic optical element, comprising an exposed holographic recording material, is proposed. This advantageously allows for internal and, in particular, wireless and easily controllable heating of the holographic combiner for the active modification of the optical functions of the holograms of the holographic combiner. In particular, the exposure defines an optical output function of the holographic combiner, which can then be actively modified by the method to optimize a playback configuration.

[0021] Furthermore, the data glasses, in particular an AR headset, are proposed to be combined with the virtual retinal display, comprising at least the light projector and the holographic combiner with at least the holographic-optical element, wherein the virtual retinal display is preferably intended for carrying out the aforementioned method for actively optimizing the playback configuration, wherein the virtual retinal display is configured to actively modify one or more beam parameters of the light signal emitted by the light projector and / or one or more holographic reconstruction parameters of the holographic combiner, in particular during operation, with the aim of optimizing the hologram efficiency of the holographic-optical element, in particular optimizing a hologram-side angular and / or wavelength bandwidth with which a hologram target efficiency can be achieved.This can advantageously improve the robustness of the smart glasses, especially in field use. It can also enable the most optimal, and in particular error-free, operation of the smart glasses in a wide variety of scenarios and environments. AR headsets are primarily head-worn smart devices that project artificially generated images into the user's field of vision.

[0022] The inventive method, the inventive holographic recording material, the inventive holographic combiner, and the inventive data glasses are not to be limited to the application and embodiment described above. In particular, the inventive method, the inventive holographic recording material, the inventive holographic combiner, and the inventive data glasses may, to achieve a functionality described herein, comprise a different number of individual elements, components, units, and process steps than those specified herein. Furthermore, values ​​within the specified limits of this disclosure are also to be considered disclosed and freely usable.

[0023] It is conceivable that several of the methods listed herein for the active modification of beam parameters of the light signal and / or of holographic reconstruction parameters of the holographic combiner can be combined. drawing

[0024] Further advantages become apparent from the following description of the drawings. The drawings illustrate four exemplary embodiments of the invention. The drawings, the descriptions, and the claims contain numerous features in combination. It is advantageous for those skilled in the art to also consider the features individually and combine them into meaningful further combinations.

[0025] They show: Fig. 1 a schematic representation of part of a pair of data glasses with a virtual retinal display, Fig. 2 a schematic sectional view of part of a holographic combiner of the data glasses with an exposed holographic recording material, Fig. 3 a schematic flowchart of a procedure for the active optimization of a playback configuration of the virtual retinal display, Fig. 4 An exemplary efficiency curve of a maximum efficiency of a holographic-optical element of the holographic combiner, plotted against a wavelength of a light signal, Fig. 5 Another exemplary efficiency curve of the maximum efficiency of the holographic-optical element of the holographic combiner, plotted against an angle of incidence at which the light signal hits the holographic-optical element, Fig. 6 a combined representation of the two efficiency curves for different wavelengths and different angles of incidence, Fig. 7 a schematic representation of part of a data glasses with a first alternative virtual retinal display, Fig. 8 a schematic representation of part of a data glasses with a second alternative virtual retinal display and Fig. 9 a schematic representation of part of a data glasses with a third alternative virtual retinal display. Description of the exemplary implementations

[0026] The Fig. Figure 1 schematically shows a part of a pair of smart glasses 36a. The smart glasses 36a form an AR headset. The AR headset is configured to overlay artificial image content in the field of vision of one eye 42a of a user with real image content. The smart glasses 36a comprise a frame 38a. The smart glasses 36a comprise a lens 40a. The smart glasses 36a comprise a virtual retinal display 16a. The virtual retinal display 16a is configured to generate and output the artificially generated images. The virtual retinal display 16a comprises a control unit 44a. The control unit 44a is shown integrated into the frame 38a as an example. Alternatively, the control unit 44a could also be at least partially externalized, e.g., to a mobile device, a cloud, or the like. The virtual retinal display 16a comprises a light projector 10a.The control unit 44a digitally generates the artificially created images and controls the light projector 10a accordingly, so that it outputs the images in the form of scanned light beams. The light projector 10a comprises at least one light emitter 46a. The light emitter 46a is, by way of example, configured as a laser diode. Alternatively, the light emitter 46a could also be an LED, in particular a superluminescent LED. Preferably, the light projector 10a has several light emitters 46a of different light colors, so that any color can be represented in the artificially generated output image by mixing the different light colors. The light projector 10a comprises a MEMS micromirror system (not shown). The MEMS micromirror system is designed to scan an output (color-modulated) light signal 18a and thereby generate a two-dimensional image.

[0027] The virtual retinal display 16a comprises a holographic combiner 12a. The holographic combiner 12a has a holographic-optical element 14a. The holographic combiner 12a is formed by the lens 40a of the smart glasses 36a. The holographic-optical element 14a is embedded in the lens 40a of the smart glasses 36a or applied to the lens 40a of the smart glasses 36a as a layer. The holographic-optical element 14a comprises an optical function 48a. In the exemplary embodiment of the Fig. 1 exemplified as an optical function 48a which reflects and focuses the light signal 18a.

[0028] The virtual retinal display 16a includes an adaptive beam guidance unit 32a. The adaptive beam guidance unit 32a is configured as a 2D tilting mirror. The adaptive beam guidance unit 32a is configured to actively modify the angle of incidence 30a at which the light signal 18a strikes the spectacle lens 40a, and in particular the holographic combiner 12a.

[0029] The holographic combiner 12a comprises a holographic recording material 34a. The holographic-optical element 14a comprises the holographic recording material 34a. In the Fig. Figure 2 schematically and exemplarily shows a section of the holographic recording material 34a. The holographic recording material 34a is intended for recording at least one hologram / one holographic optical function 48a by means of exposure. The one in the Fig. The holographic combiner 12a shown as an example is exposed. The optical function 48a of the in the Fig. In the example shown in Figure 2, the material is introduced into the holographic recording material 34a by means of exposure. During exposure of the holographic recording material 34a, a diffraction grating is formed within the holographic recording material 34a that is fixed for a fixed ambient temperature. The holographic recording material 34a is designed as a heatable holographic recording material 34a. The holographic recording material 34a comprises a multitude of nanoparticles 22a. The nanoparticles 22a are smaller than 20 nm. The nanoparticles 22a are silver nanoparticles. However, other types of nanoparticles 22a are also conceivable. The nanoparticles 22a are embedded in the holographic recording material 34a.The nanoparticles 22a are embedded in the holographic recording material 34a in such a way that they can be excited to a (resonant) oscillation in oscillating physical fields 20a, in particular in oscillating magnetic fields, which leads to heat input into the holographic-optical element 14a and / or to a targeted heating of the holographic-optical element 14a. The data glasses 36a have a magnetic field generation unit 50a (e.g., a magnetic coil). The magnetic field generation unit 50a can be integrated into the data glasses 36a, e.g., into the frame 38a. The magnetic field generation unit 50a is intended for generating the oscillating field 20a.

[0030] The virtual retinal display 16a is configured to carry out a method for actively optimizing a playback configuration of the virtual retinal display 16a, in particular of the holographic-optical element 14a of the virtual retinal display 16a. The holographic recording material 34a is intended for use in the method for actively optimizing the playback configuration. Fig. Figure 3 shows a schematic flowchart of the procedure for actively optimizing the playback configuration.

[0031] In at least one process step 52a of the process, one or more beam parameters of the light signal 18a emitted by the light projector 10a and / or one or more holographic reconstruction parameters of the holographic combiner 12a are actively modified during operation of the virtual retinal display 16a with the aim of optimizing the hologram efficiency of the holographic-optical element 14a, in particular optimizing a hologram-side angular and / or wavelength bandwidth with which a target hologram efficiency can be achieved. In at least one sub-step 54a of process step 52a, at least one of the holographic reconstruction parameters of the holographic combiner 12a is actively modified by selectively heating the holographic combiner 12a, in particular the holographic-optical element 14a.In step 54a, the holographic combiner 12a, in particular the holographic-optical element 14a, is heated by means of the oscillating field 20a. The oscillating field 20a excites the nanoparticles 22a, which are embedded in the holographic combiner 12a, in particular in the holographic-optical element 14a, to vibrate. The vibrations of the nanoparticles 22a generate heat in the holographic combiner 12a.

[0032] In at least one sub-step 56a of process step 52a, which can be performed alternatively or additionally to sub-step 54a, at least one spectral emission bandwidth of the light projector 10a emitting the light signal 18a is actively modified by a high-frequency modulation of an operating parameter of the light projector 10a. In this case, the operating parameter is exemplified as an operating current of the light projector 10a and / or as an operating current of a pump medium of a laser emitter of the light projector 10a.

[0033] Alternatively or additionally, in an alternative or additional sub-step 56b of process step 52a, the spectral emission bandwidth of the light signal 18a is adjusted by an acousto-optic modulator 24b (see also Fig. 7) actively modified. In this process, the light signal 18a passes through the acousto-optic modulator 24b at least once on its way to the holographic combiner 12a. Alternatively or additionally, in an alternative or additional sub-step 56c of process step 52a, the spectral emission bandwidth of the light signal 18a is modified by an electro-optic modulator 26c (see also Fig. 8) actively modified. In this process, the light signal 18a passes through the electro-optic modulator 26c at least once on its way to the holographic combiner 12a. Alternatively or additionally, in an alternative or additional sub-step 56d of process step 52a, the spectral emission bandwidth of the light signal 18a is modified by a variable spectral filter 28d (see also Fig. 9) actively modified. In this process, the light signal 18a passes through the filter 28d at least once on its way to the holographic combiner 12a. The variable spectral filter 28d can be designed as an actively tiltable spectral filter, which extracts a spectrally narrower spectrum from the spectrally broader light emitter 46a of the light projector 10d, a spectrum that matches a current playback wavelength of the holographic combiner 12d, in particular of the holographic-optical element 14d.

[0034] In at least one sub-step 58a of process step 52a, which can be performed alternatively or additionally to sub-steps 54a and 56a, at least one angle of incidence 30a, at which the light signal 18a, in particular a wavefront of the light signal 18a, strikes the holographic combiner 12a, is actively modified by the adaptive beam guidance unit 32a of the virtual retinal display 16a. The angle of incidence 30a of the light signal 18a is changed by means of the 2D tilting mirror. Several of the sub-steps 54a, 56a, 56b, 56c, 56d, 58a can be implemented simultaneously or sequentially in a data spectacle 36a, or only a single sub-step 54a, 56a, 56b, 56c, 56d, 58a.

[0035] In the Fig. To facilitate understanding, an exemplary efficiency curve 60a, expressed as a percentage of the maximum efficiency of a holographic-optical element 14a, is shown in Figure 4, plotted against a wavelength of the light signal 18a. The holographic-optical element 14a has a narrow wavelength range within which the hologram can be played back efficiently. Fig. To facilitate understanding, an exemplary efficiency curve 62a, normalized to the maximum efficiency of a holographic-optical element 14a, is shown in Figure 5. This curve is plotted against an angle of incidence 30a at which the light signal 18a strikes the holographic-optical element 14a. The holographic-optical element 14a has a narrow angular range within which the hologram can be played back efficiently. Fig. Figure 6 combines the two efficiency curves 60a and 62a in a two-dimensional contour plot 64a. In the two-dimensional contour plot 64a, the hologram efficiency is plotted against a playback wavelength (x-axis) and a playback incidence angle (y-axis). This clearly illustrates the relationship between the playback wavelength and the playback angle of a hologram, according to the Bragg equation, which allows a hologram to be reconstructed with relatively high efficiency even in configurations that deviate from the recording configuration of the hologram.

[0036] In the Fig. Figures 7 to 9 show three further embodiments of the invention. The following descriptions and drawings are essentially limited to the differences between the embodiments, whereby, with regard to identically designated components, in particular components with the same reference numerals, reference is also generally made to the drawings and / or the description of the other embodiments, in particular the Fig. 1 to 6, reference can be made. To distinguish the embodiments, the letter a is the reference numeral of the embodiment in the Fig. 1 to 6 are appended. In the exemplary embodiments of the Fig. In letters 7 to 9, the letter a is replaced by the letters b to d.

[0037] The Fig. Figure 7 schematically shows a portion of a data glasses 36b with a first alternative virtual retinal display 16b. The virtual retinal display 16b comprises a light projector 10b. The virtual retinal display 16b is configured for the active optimization of a playback configuration of the virtual retinal display 16b, in particular of a holographic-optical element 14b of the virtual retinal display 16b. The light projector 10b comprises an acousto-optic modulator 24b. The acousto-optic modulator 24b is designed to actively modify an emission parameter, in particular an emission bandwidth, of the light projector 10b to optimize the playback configuration of the virtual retinal display 16b.

[0038] The Fig. Figure 8 schematically shows a portion of a data glasses 36c with a second alternative virtual retinal display 16c. The virtual retinal display 16c comprises a light projector 10c. The virtual retinal display 16c is configured for the active optimization of a playback configuration of the virtual retinal display 16c, in particular of a holographic-optical element 14c of the virtual retinal display 16c. The light projector 10c comprises an electro-optic modulator 26c. The electro-optic modulator 26c is designed to actively modify an emission parameter, in particular an emission bandwidth, of the light projector 10c to optimize the playback configuration of the virtual retinal display 16c.

[0039] The Fig.Figure 9 schematically shows a portion of a data glasses 36d with a third alternative virtual retinal display 16d. The virtual retinal display 16d comprises a light projector 10d. The virtual retinal display 16d is configured for the active optimization of a playback configuration of the virtual retinal display 16d, in particular of a holographic-optical element 14d of the virtual retinal display 16d. The light projector 10d comprises a variable spectral filter 28d. The variable spectral filter 28d is designed to actively modify an emission parameter, in particular a spectral emission band, of the light projector 10d to optimize the playback configuration of the virtual retinal display 16d. The variable spectral filter 28d is configured as an actively tiltable spectral filter. The variable spectral filter 28d is designed to extract from an emission spectrum of a spectrally broader light emitter 46d of the light projector 10d, e.g.to cut out a spectrally narrower and reduced spectrum matching a momentary playback wavelength of the holographic-optical element 14d of a holographic combiner 12d of the data glasses 36d from an LED or a superluminescent LED.

Claims

[1] Method for actively optimizing a playback configuration of a virtual retinal display (16a-d) comprising a light projector (10a-d) and a holographic combiner (12a-d) with at least one holographic-optical element (14a-d), characterized by , that one or more beam parameters of a light signal (18a-d) emitted by the light projector (10a-d) and / or one or more holographic reconstruction parameters of the holographic combiner (12a-d), in particular during operation of the virtual retinal display (16a-d), are actively modified with the aim of optimizing the hologram efficiency of the holographic-optical element (14a-d), in particular optimizing a hologram-side angular and / or wavelength bandwidth with which a hologram target efficiency can be achieved. [2] Method according to claim 1, characterized by, that at least one of the holographic reconstruction parameters of the holographic combiner (12a-d) is actively modified by heating the holographic combiner (12a-d), in particular the holographic-optical element (14a-d), especially in a targeted manner. [3] Method according to claim 2, characterized by , that the holographic combiner (12a-d), in particular the holographic-optical element (14a-d), is heated by means of an oscillating field (20a-d), in particular an oscillating magnetic field, which excites nanoparticles (22a-d) embedded in the holographic combiner (12a-d), in particular in the holographic-optical element (14a-d), to oscillate. [4] Method according to any one of the preceding claims, characterized by, that at least one of the beam parameters of the light signal (18a-d) is a spectral emission bandwidth of the light projector (10a-d), in particular a laser projector, emitting the light signal (18a-d), which is actively modified by a high-frequency modulation of an operating parameter of the light projector (10a-d), in particular an operating current of the light projector (10a-d), preferably a pump medium of a laser emitter of the laser projector. [5] Method according to any one of the preceding claims, characterized by , that at least one of the emission parameters of the light projector (10a-d) is actively modified by an acousto-optic modulator (24b), by an electro-optic modulator (26c) or by at least one variable spectral filter (28d). [6] Method according to claim 5, characterized by, that the variable spectral filter (28d) is formed by an actively tiltable spectral filter, which is designed to cut out a spectrally narrower spectrum from an emission spectrum of a spectrally broader light emitter (46d) of the light projector (10d), e.g. an LED or a superluminescent LED, and which is suitable for an instantaneous playback wavelength of the holographic combiner (12d), in particular the holographic-optical element (14d). [7] Method according to any one of the preceding claims, characterized by , that at least one of the beam parameters of the light signal (18a-d) is an angle of incidence (30a-d) with which the light signal (18a-d), in particular a wavefront of the light signal (18a-d), hits the holographic combiner (12a-d), which is actively modified by an adaptive beam guidance unit (32a-d) of the virtual retinal display (16a-d). [8] Method according to claim 7, characterized by, that the adaptive beam guidance unit (32a-d) actively modifies the angle of incidence (30a-d) of the light signal (18a-d) by means of a 2D tilting mirror. [9] Holographic recording material (34a-d), in particular heated holographic recording material (34a-d), which is intended in particular at least for use in a method according to one of claims 2 or 3, characterized by a variety of embedded nanoparticles that can be excited to oscillation, especially resonant oscillation, in oscillating physical fields (20a-d), in particular in oscillating magnetic fields (22a-d) [10] Holographic recording material (34a-d) according to claim 9, characterized by , that the nanoparticles (22a-d) are smaller than 20 nm. [11] Holographic recording material (34a-d) according to claim 9 or 10, characterized by that the nanoparticles (22a-d) are silver nanoparticles. [12] Holographic combiner (12a-d), in particular holographic-optical element (14a-d), comprising an exposed holographic recording material (34a-d) according to any one of claims 9 to 11. [13] Data glasses (36a-d), in particular AR headset, with a virtual retinal display (16a-d), comprising at least a light projector (10a-d) and a holographic combiner (12a-d) with at least one holographic-optical element (14a-d), wherein the virtual retinal display (16a-d) is preferably configured to carry out a method according to one of claims 1 to 8, characterized by, that the virtual retinal display (16a-d) is configured to actively modify one or more beam parameters of a light signal (18a-d) emitted by the light projector (10a-d) and / or one or more holographic reconstruction parameters of the holographic combiner (12a-d), particularly during operation, with the aim of optimizing a hologram efficiency of the holographic-optical element (14a-d), in particular optimizing a hologram-side angular and / or wavelength bandwidth with which a hologram target efficiency can be achieved.

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