Eyewear display system for displaying a virtual image in a field of view of a user, comprising invisible micromirror elements

Abstract

The invention relates to an eyewear display system (1) for displaying a virtual image in a field of view of a user, the eyewear display system comprising: a display unit (14) for emitting light (163", 161'', 162'') as computer-generated image information in an emission direction; a deflection unit (17) for deflecting the light (163", 161'', 162'') emitted by the display unit (14) as computer-generated image information into an eye (10) of the user; and a plurality of micromirror elements (12, 12', 12"), each of which can be tilted in a support structure (200) and each of which has a reflective surface (25) for deflecting the light (163", 161", 162") emitted by the display unit (14) as computer-generated image information; wherein the micromirror elements (12, 12', 12'') and the support structure (200) are arranged in a sealed housing element (17a) of the deflection unit (17), said housing element being filled with a liquid (23), in order to provide an eyewear display system (1) which offers improved immersion.

Description

[0001] title

[0002] Glasses display system for displaying a virtual image in a user's field of view using invisible micro-mirror elements

[0003] This application claims the priority of DE 10 2024 101 597.7, filed on January 19, 2024, and the priority of DE 10 2024 101 596.9, filed on January 19, 2024, the disclosures of which are hereby incorporated in their entirety by reference.

[0004] Scope of the invention

[0005] The disclosure relates to a spectacle display system for displaying a virtual image in a field of vision of a user, comprising a display unit for emitting a light as computer-generated image information in an emission direction and comprising a deflection unit for deflecting the light emitted by the display unit as computer-generated image information into an eye of the user, comprising a plurality of micro-mirror elements, each tiltable in a support structure, which each have a reflection surface for deflecting the light emitted by the display unit as computer-generated image information.

[0006] background

[0007] Glasses display systems for displaying a virtual image in a user's field of vision, "augmented reality glasses" or "AR glasses" for short, are able to overlay virtual objects in the form of virtual images onto the natural environment in the user's field of vision, thus virtually supplementing the field of vision. By displaying stereo images, these virtual objects can be placed freely in space. For this reason, it is advantageous to enable the largest possible virtually supplementable field of vision and a display with high (angular) resolution in order to create an immersive feeling through permanent visibility and spatially consistent positioning of the virtual objects, namely the feeling that the virtual objects are physical objects. The weight of such glasses in particular contributes to the immersive feeling, which can lead to an unnatural feeling for the user, especially when moving the head. The so-calledVergence accommodation problem is also a well-known effect that detracts from the immersive feeling.

[0008] The vergence accommodation problem exists in all 3D displays that show 3D objects using two stereo images. The 3D information, i.e. the distance of the object from the eye, is given by the shifted stereo images. This distance conflicts with the distance at which the eye is focused in order to see a sharp image. A related problem arises in AR applications where virtual 3D objects are integrated into a real 3D environment. If the focus distance of the stereo image does not match the focus distance for the real environment, both scenes, the real and the virtual, cannot be viewed simultaneously, even though they are spatially fixed at the same location in the environment. Various optical methods are known in the state of the art for projecting a virtual image into the field of view of the natural environment.However, it remains a technically unsolved problem to make the necessary optics small enough to achieve the form factor and weight of regular glasses. Glasses that are too large represent a technical limitation on possible applications, as, for example, a large product would not be acceptable on the face in every everyday situation. Excessive weight means that AR glasses can only be worn for a limited time. Exemplary solutions are described in DE 10 2020 206 392 A1 and DE 10 2023 101 777 A1.

[0009] US Patent No. 10,623,707 B2 describes AR glasses with a high-resolution image for the central field of vision (fovea centralis) and a lower-resolution image area projected into the peripheral field of vision. For this purpose, the eye's gaze direction is measured using an eye-tracking sensor, and the projection optics are adjusted accordingly.

[0010] The publications US 2020 0186761 A1 and US 11422 274 B2 present AR glasses that allow the focal length of the AR optics to be adjusted to display objects at different distances. Thus, a technical solution to the vergence accommodation problem is disclosed. US 20200186761 A1 also includes an eye-tracking module for measuring the vergence eye parameters. Furthermore, it is proposed to use these measured values ​​to track the eye with optics to enable eye tracking for different eye positions.

[0011] The technical task is therefore to provide a glasses display system with improved immersion, in particular with minimized weight and the largest possible virtually augmentable field of view, as well as the possibility of addressing problems typical for AR glasses such as the vergence accommodation problem and / or the problem of visual acuity correction.

[0012] overview

[0013] This problem is solved by the subject matter of the independent claim. Advantageous embodiments emerge from the dependent claims, the description, and the figures.

[0014] One aspect relates to a spectacle display system for displaying a virtual image in a user's field of vision, comprising a display unit for emitting light as computer-generated image information in a radiation direction and a deflection unit for deflecting the light emitted by the display unit as computer-generated image information into an eye of the user. The radiation direction preferably runs at least substantially in the direction of the user's field of vision (forward, so the light is emitted into the field of vision). The deflection unit, with at least the micro-mirror elements mentioned below, is arranged in the user's field of vision (in front of the user's eye(s)) and serves to deflect the light back (backward) into the user's eye(s).The deflection unit has a plurality of tiltable micro-mirror elements, each arranged in a support structure, which each have a reflective surface for deflecting the light emitted by the display unit as computer-generated image information into the user's eye. The reflective surface is permeable to ambient light emitted from the environment in front of the user in their field of vision towards the eye. The reflective surfaces can therefore be regarded as semi-transparent mirror surfaces. Accordingly, a micro-mirror element can also have multiple mirror surfaces. This is the case, for example, when the micro-mirror elements each have a substrate, in particular a glass substrate, with a coating. One side of the substrate can be coated and an opposite side of the substrate can be uncoated, for example.Accordingly, two reflections can occur, with one side as a reflection surface and the opposite side as another reflection surface.

[0015] The reflection on the coated side can be adjusted (technologically) as desired using a suitable coating (designed to achieve a desired optical effect). The reflection on the uncoated side is then based on a Fresnel reflection resulting from the change in the refractive index of the substrate and the surroundings (e.g., the liquid of the housing element mentioned below). For micromirror elements stored in liquid, the latter reflection is typically very low, since typical glass substrates and liquids have very similar refractive indices. Alternatively, the opposite side of the substrate can also be coated.For example, this can be a counterforce coating which, in contrast to a coating designed for optical effect, is designed to compensate for stresses that occur between the substrate and its coating on the one hand and that can lead to a curvature of the substrate. The reflective surface, which is technologically adjusted, can also be located within the volume of the micro-mirror element, so that a total of three reflective surfaces can then be present. In this case, two further reflections are present at the interfaces between the micro-mirror element and the environment (ideally the liquid). The further reflections can be of a subordinate nature, i.e. significantly weaker than the (main) reflection at the technologically adjusted reflective surface. For example, the further reflections can be one or more orders of magnitude weaker than the main reflection.It is also possible to apply a coating to one side and the opposite side designed to achieve a desired optical effect. This allows, for example, the (main) reflections on the front and back of the substrate to be technologically adjusted, i.e., their optical properties can be adjusted. Multiple coatings on one side of the substrate are also possible; accordingly, the micromirror elements can each have a multitude of reflective surfaces.

[0016] A multitude of micromirrors can be understood here, for example, as at least 20, at least one hundred, or at least one thousand micromirrors. The reflecting surfaces are small, as is typical for micromirrors, for example, <100 mm. 2 or <20mm 2Since the micromirrors are movably mounted in the support structure, the reflective surfaces can each be aligned with their angular orientation in two dimensions. This means that the light emitted by the display unit, the light from the display unit, can be redirected into the eye or pupil for different orientations and / or positions of the eye. Since the deflection unit is at least partially (i.e. partially or completely), in particular with the micromirror elements, arranged in an optical path of ambient light from the user's field of vision into the user's eye, the virtual image corresponding to the computer-generated image information in the user's field of vision can be overlaid with real objects in the environment, since the micromirror elements are at least partially transparent to light from the environment (ambient light) (as required for AR glasses).For a better immersive feeling with virtual images that are as large as possible and as free of artifacts as possible, the deflection unit and / or the display unit are controlled depending on the orientation of the eye(s), for example with the control unit described below.

[0017] Advantageously, all or at least a large portion (preferably almost all) of the micro-mirror elements (in particular always and / or predominantly) are angularly aligned, at least in a standard operating mode of the spectacle display system, such that only light from the display unit can be directed into the user's eye. In the standard operating mode, this angular alignment can be provided regardless of whether the micro-mirror element(s) are illuminated by the display unit or not. This has the advantage that no light source placed elsewhere leads to a visible reflection in the eye. This avoids annoying light reflections visible as ghost images. This is particularly advantageous for applications in outdoor environments, where the sun, as a very bright light source, can lead to otherwise unpleasant stray light reflections.A resulting further advantage is that a high reflectance, for example a semi-transparent coating, can be selected for the reflection surfaces of the micro-mirror elements, since even with high reflectance, unwanted light reflections in the eye cannot be amplified.

[0018] In addition, a power-saving operating mode of the spectacle display system can be provided, in which (in particular only) micro-mirror elements not illuminated by the display unit are brought into a predetermined resting orientation. In the resting orientation, an actuator with the actuator element(s) mentioned below can then be fully or partially deactivated. For example, the micro-mirror elements can be brought into the resting orientation when no virtual image is displayed or the virtual image has large / prolonged black areas. Preferably, the micro-mirror elements are only moved again when they are illuminated again by the display unit. The resting orientation of the micro-mirror elements can be predetermined such that they correspond to a resting position of the respectively assigned eye.In the resting orientation of the micro-mirror elements, essentially only light from the display unit is directed into the user's eye when the eye is in its resting position. In this case, however, the reflection condition is not met and disruptive reflections of light coupled in from behind can occur. Undesired reflections of ambient light can therefore sometimes cause visual artifacts, but it has been shown that people predominantly keep their eyes in the aforementioned resting or neutral gaze position, so that the likelihood of artifacts occurring is minimized. Overall, it is therefore advantageous to select the resting orientation of the micro-mirror elements according to the resting position of the eye, so that the reflection condition into the exit aperture of the projector is met most of the time, even when the actuators are switched off.Alternatively or additionally, a high-quality operating mode can also be provided in which the angular alignment of the micro-mirror elements is continuously adjusted, i.e., the micro-mirror elements are constantly tracked by the eye movements (e.g., even when no virtual image is displayed or the virtual image has large / prolonged black areas). It can also be provided that the glasses display system has a sensor device (e.g., a camera sensor device) that detects and / or evaluates the environment, for example, with regard to prevailing lighting conditions, as well as an automatic switching device that is designed to automatically switch back and forth between different operating modes based on one or more predefined switching criteria.For example, the switching criterion can be based on the probability of bright light spots (which can easily lead to distracting reflections) evaluated by the sensor device, so that power-saving mode is activated with a lower probability and high-quality operating mode with a higher probability. The environment can also be recorded and analyzed for location data; for example, bright light spots are more likely to occur when the glasses display system is used outdoors than indoors. By specifying an appropriate control scheme, power consumption and immersion can be optimized.

[0019] The display unit can have one or more preferably flat screen elements ("displays") for generating the light, but also one or more (laser) projector elements. In particular, the display unit can be a stereo display unit which is suitable for generating a virtual stereo image in the field of vision. For this purpose, the stereo display unit can have two screen elements or two (laser) projector elements, each of which is assigned to one of the two eyes of the user. For example, the screen elements or

[0020] (Laser) projector elements are each arranged on a temple unit of the spectacle display system, located to the side of the user. Ideally, the light from a light-generating pixel element of the display unit should only fall on one micro-mirror element and not be visible simultaneously via one or more neighboring micro-mirror elements. In the latter case, the same pixel information would be perceived from two different spatial directions, i.e., as two different virtual pixels (image points of the virtual image), since neighboring micro-mirror elements are generally tilted relative to one another at an angle other than zero, i.e., are aligned differently.

[0021] In one embodiment, it can be provided that the display unit has a light-generating display, in particular a so-called "microdisplay," as well as a microlens arrangement, a so-called "microlens array." The microlens arrangement has a plurality of microlens elements arranged parallel (as opposed to serially) in the beam path from the light-generating display of the display unit to the exit aperture of the display unit. Such microlens elements can, for example, have a diameter of less than 1000 μm, preferably less than 500 μm, and / or greater than 50 μm. The display unit preferably also has a (particularly achromatic) projector optics with a plurality of optical lenses. The projector optics are arranged in the beam path between the microlens arrangement and the exit aperture.In particular, the projector optics are designed to direct light exclusively from one microlens element of the microlens array to a micromirror element. Each microlens element used in the operation of the glasses display system can therefore be assigned exactly one micromirror element. The optical imaging realized by the projector optics thus ensures that light leaving a microlens element is only visible or perceivable via exactly one micromirror. This has the advantage that no multiplexing (or, when using the adjustable aperture unit described below, only a less pronounced multiplexing) is necessary, i.e., all (or, when using the adjustable aperture unit, many of) the micromirror elements can display virtual pixels simultaneously.In contrast to a multiplexing approach, lower light intensities of the light-generating pixel elements are sufficient because the pixel elements can be switched on / activated for the entire time of a single image ("frame") and not just a (very short) fraction of an individual image. Accordingly, less bright display technologies such as organic light-emitting diodes (OLEDs) can be used.

[0022] If the projector optics are achromatic, the associated optical image is achromatic, so that the respective images from microlens element to micromirror element are at least essentially wavelength-independent for the primary colors of the display unit. The primary colors are typically red, green, and blue. The technical goal is to ensure that the field of view resulting from each micromirror element is limited to only one microlens element, so that no crosstalk of image content can occur.

[0023] Preferably, each microlens element is assigned its own pixel element area on the light-generating display. Light from the light-generating pixel elements of this pixel element area is imaged via only one microlens element. The microlens elements and the projector optics can be adapted to one another in such a way that, in addition to the image of the plane of the microlens elements onto the plane of the micromirror elements, a sharp image of the light-generating pixel elements is also generated in the user's eye or the "eyebox" associated with the position of the eye. The planes can also be curved planes or other two-dimensional manifolds of three-dimensional space. Preferably, the aforementioned adaptation takes place under the boundary condition that maximum image sharpness of the virtual image is achieved when the eye is directed centrally onto the respective micromirror element.In this orientation, the eye views the respective micro-mirror element with its maximum imaging performance. Since the eye's imaging performance drops rapidly and sharply towards the sides, the resulting poorer image quality for micro-mirror elements to the side of the central viewing direction is unproblematic. If the display unit is arranged in or on a temple of the spectacle display system, the plane of the micro-lens elements and the plane of the micro-mirror elements are tilted relative to each other. Accordingly, a Scheimpflug optic can be selected for the projector optics. In principle, however, the optics can be adapted to alternative geometric arrangements of the display unit relative to the deflection unit.

[0024] In a further embodiment, the microlens array is arranged so as to be movable, in particular displaceable, relative to the light-generating display by means of a focus actuator. This is particularly advantageous because the focal length of the microlens array is comparatively small, for example, less than 2 mm, preferably less than 1 mm. As a result, only a small mobility / displaceability of, for example, less than 2 mm, preferably less than 1 mm, is required for a virtual image that is improved in terms of improved focusing. For example, the focal plane can be quickly shifted when the user's eye jumps from one virtual object to another. This can mitigate the vergence accommodation problem, leading to improved immersion.

[0025] In another embodiment, it is provided that not all micro-mirror elements are assigned to a micro-lens element. There can therefore be more micro-mirror elements than micro-lens elements. Accordingly, the micro-mirror elements that are not assigned to a micro-lens element are then imaged directly onto the light-generating display via the projector optics, or the corresponding pixel element regions of the light-generating display are imaged onto the micro-mirror elements to which no micro-lens element is assigned. Preferably, the micro-mirror elements that are not assigned to a micro-lens element are arranged closer to an outer edge of a field of view, i.e., closer to the respective nearest temple of the spectacle display system, than the micro-mirror elements that are assigned to a micro-lens element.This is advantageous because in the nose region of the field of view, the angular distance between one micro-mirror element and the next typically decreases, increasing the risk of unwanted crosstalk from one micro-mirror element to the next. This is because the distance between the micro-mirror elements and the display unit is significantly greater in the bracket region than in the bracket region. The angular distance results from the difference in the tilt angles of the next-to-nearest micro-mirror elements.

[0026] In a further embodiment, the microlens array is configured to correct and / or compensate for dispersion in the light emitted by the light-generating display. This can be achieved, for example, by an additional diffractive structure as part of the microlens array and / or by (outer) boundary surfaces that are inclined relative to one another. Such boundary surfaces that are inclined relative to one another can compensate for dispersion, analogous to the prism effect. This improves image quality, leading to improved immersion.

[0027] In one embodiment, it can be provided that the micro-mirror elements and the support structure are arranged in a sealed housing element of the deflection unit that is filled with a liquid. The housing element can be arranged in front of the user's eyes, similar to the lenses of conventional eyeglasses. Accordingly, the liquid, the micro-mirror elements, and the support structure are arranged in an interior of the housing element such that the micro-mirror elements and the support structure are surrounded by the liquid. The housing element is accordingly oil-tight and / or waterproof and is made of or with a material that is (at least substantially) transparent to the ambient light and the light of the display unit, as is the case with conventional eyeglass lenses. The micro-mirror elements and the support structure are also advantageously made of a transparent material, as will be explained again below.

[0028] The liquid bath of micro-mirror elements and support structure has a damping effect, suppressing vibrations and thus unwanted small, rapid changes in the angular alignment of the reflecting surfaces. This is advantageous because the eye performs sudden movements of up to 1000° per second and then rests. Furthermore, the liquid reduces a difference in refractive index at the material transition, i.e., the interface between the liquid and the micro-mirror or support structure. This reduces Fresnel reflections on the one hand, and other refractive effects on the other. Both the reduction of reflections and effects reduces the visibility of the elements or structures in the liquid bath, as is known, for example, from glass components immersed in water.This avoids artifacts in the field of view that would detract from the user's immersive experience, and makes the use of the micro-mirror element arrangement ("micro-mirror array") directly in front of the user's eyes in their field of view possible in the first place. However, the micro-mirror array enables the large-area virtual extension of the field of view with greater (angular) resolution for the virtual image and is thus a prerequisite for an immersive glasses display system with dimensions similar to those of commercially available glasses.

[0029] In a further embodiment, it is provided that the micro-mirror elements and / or the support structure and / or further components which are surrounded by the liquid or border the liquid (such as a side of the housing element facing the interior) are each (at least substantially) transparent to the ambient light from the user's field of vision, as also described above for the housing element. The micro-mirror elements and / or the support structure and / or further components are accordingly made from or with a respective transparent material with a first refractive index. In particular, the housing element and / or the micro-mirror elements and / or the support structure and / or the further components can be made from the same material, which facilitates the adaptation of the optical properties to one another.

[0030] The liquid is also (at least substantially) transparent to ambient light and has a second refractive index adapted to the first refractive index in order to minimize the deviation. In particular, the second refractive index (at a defined temperature value, which preferably lies in the temperature range specified below) can be equal to the first refractive index for at least one wavelength of a green wavelength range. Accordingly, the liquid must be selected such that the second refractive index does not deviate from the first refractive index by more than a predetermined limit value of, for example, 0.005 over a predetermined wavelength range of, for example, 400 nm–700 nm and / or a predetermined temperature range of, for example, 0°–30°.The liquid can also be optimized for one or more sub-ranges of the respective ranges, for example, in the wavelength range of 540nm + / - 30nm and / or in the temperature range of 21° + / - 2°, it can have a second refractive index that is particularly similar to the first refractive index. The similarity in the green wavelength range (520nm-565nm) is particularly advantageous because it has been shown that artifacts in the green wavelength range are perceived by humans with a higher resolution than in the red or blue wavelength ranges. In this sub-range, in particular the green wavelength range, a smaller maximum limit for the deviation can be specified, for example 0.002. The refractive index curves of the liquid and the first material plotted against the wavelength preferably intersect in the green wavelength range.Such liquids, called "refractive index matching liquids," are commercially available with desired properties. Accordingly, it may be advantageous to actively control the temperature of the micro-mirror array, i.e., to measure it and set a target temperature or target temperature range by heating or cooling. A temperature control device for the liquid may therefore be provided. The temperature control device may comprise a sensor unit for measuring the temperature of the liquid and a temperature control unit for adjusting the temperature of the liquid to a predetermined temperature value, i.e., depending on the measured value and the predetermined temperature, either for heating or cooling. Thus, temperature-dependent deviations can be avoided or at least reduced.

[0031] This means that the ambient light is refracted so little as it passes through the deflection unit that any change in the ambient light, particularly at least in the wavelength range of the ambient light and / or at least in an angular range of the ambient light and / or at least in the temperature range, is below the user's perception threshold. As a result, the material transitions and thus the micro-mirror elements and / or the support structure and / or other components surrounded by the liquid become virtually invisible to the user. Thus, the micro-mirror elements can be arranged over a large area in front of the user's eyes without disrupting their perception of the environment and thus of the virtual image, significantly improving the immersive experience when using the glasses display system.

[0032] In another embodiment, the micro-mirror elements are mechanically coupled to a common actuator element, in particular by means of a two-dimensional guide matrix structure. The guide matrix structure can be mechanically scanned by the support structure in order to realize individual tilts (the angular orientations) of the micro-mirror elements. Alternatively, it can be provided that the micro-mirror elements are each coupled to an individual actuator element. In both cases, the angular orientation of the micro-mirror elements can be controlled according to a stored specification via the common actuator element or the individual actuator elements, once in the form of a mechanical guide slot and once in the form of, for example, a lookup table.The common or individual actuator elements can be designed to move at least some of the micro-mirror elements, in particular most and / or all of the micro-mirror elements, differently from one another and / or non-linearly. The angular orientations of the reflection surfaces can therefore be specified individually and / or non-linearly, for example by the guide matrix structure and / or an actuator control specification. Through this individual and / or non-linear adjustment, it can be ensured that the deflected light always reaches the eye and that larger, coherent virtual images are created there. The common actuator element reduces the number of required components of the deflection unit that are arranged in the user's field of vision. This contributes to the weak visibility of the structures in the user's field of vision and thus improves the immersive feeling.

[0033] The micro-mirror elements can each be equipped with an individual angle sensor for measuring the respective angular orientation. This allows for the comparison of the nominal and actual angular orientation of the respective reflection surface, thus helping to reduce unwanted shifts of virtual pixels in the virtual image. With such angle sensors, small deviations from the nominal in the order of 1 / 120° can be compensated for using a corresponding control signal for the actuator element(s) (and thus via software).

[0034] In one embodiment, the reflection surfaces are each hexagonal, and in particular the respective micro-mirror element has a coating on its reflection surface. The reflection surfaces can have a diameter, in particular an overall height and / or width, of at least 1 mm, in particular at least 2 mm, and / or at most 10 mm, in particular at most 4 mm. The hexagonal shape allows a particularly dense arrangement of the micro-mirror elements and a correspondingly flat representation of the virtual image in high resolution, which, due to the reduced visibility of the micro-mirror elements and connected components, also occurs with minimal artifacts without diminishing the immersive feeling. If polarized light is used for the virtual image, it is advantageous to select a coating with increased reflection for the polarization used. For example, a reflection factor of 20% can be selected.The reflectance can be largely wavelength-independent, i.e., across the range of relevant (visible) wavelengths, it can vary by less than 10% (and thus lie between 10% and 30%), preferably less than 5% (and thus lie between 15% and 25%). This is because when viewing the natural environment through the partially mirrored reflective surfaces, both polarization states are present in the natural ambient light, and the effective transparency of the micromirror coating is thus higher. The coating also allows the definition of desired reflection properties without negatively affecting the visibility of the micromirror elements, which is otherwise determined (for example, by the geometry of the micromirror elements).

[0035] Particularly advantageous is a coating whose reflection properties are adapted to the emission spectrum of the display unit, in particular to maxima in the emission spectrum. Typically, the display unit has several spectral maxima ("peaks"), generally for red, green, and blue. Accordingly, it is advantageous to select a higher reflectance for the partial wavelength ranges located around these maxima and the lowest possible reflectance in the remaining wavelength ranges, preferably a reflectance of at least essentially zero. The partial wavelength ranges located around the maxima are separated by intermediate wavelength ranges. The partial wavelength ranges located around the maxima can, for example, have a width of 40 nm, in particular 30 nm, preferably 20 nm, and particularly preferably 5 nm. This has the advantage that more natural ambient light, which is typically spectrally broader, reaches the eye.In effect, this increases transparency without compromising the system's efficiency. The maximum reflectance can be designed to reach 100% without significantly reducing the average transmission, for example, achieving an average transmission of 90%.

[0036] Accordingly, it is particularly advantageous to combine the described higher reflectance with narrow spectral maxima of the primary colors of the display unit (such as the aforementioned red, green, and blue). For example, the emission spectrum of the display unit can be selected such that the maxima have a full width half maximum (FWHM) of at most 40 nm, in particular at most 20 nm, preferably at most 10 nm, and particularly preferably at most 2 nm. Ideally, the display unit (or the light of the display unit used for the virtual image) has no more than three maxima.In addition to further increasing transparency for natural ambient light, this spectral restriction has the advantage that the chromatic correction of dispersion is significantly simplified because it does not have to be carried out for a broad wavelength range, but only for (for example three) small ranges in the (especially blue, green and red) wavelength range.

[0037] For example, when a micro-mirror element is arranged in a medium such as a liquid, light dispersion occurs due to the wavelength-dependent change in the refractive index. Light from the display unit hits the air-liquid interface at one angle, is then reflected by the micro-mirror element, and generally reflects at a new angle. At this new angle, the light re-enters the liquid-air interface and leaves it at a different, third angle. This is known from a dispersion prism, where a splitting of the light wavelengths occurs. This splitting must be corrected in the optics of the spectacle display system. It is particularly advantageous if the spectral range to be corrected is as small as possible, which is why it is particularly desirable for the micro-mirror elements to reflect only small spectral peaks or only around small spectral peaks.This allows high system efficiency, high system transparency and high image quality to be achieved through simplified dispersion correction.

[0038] In a further embodiment, it is provided that the reflective surfaces have at least partially different sizes, i.e., different widths and / or different heights. In particular, one or more reflective surfaces that are closer to a central viewing axis of the user in a forward-facing neutral position of the eye can be smaller than one or more reflective surfaces that are arranged further from the user's central viewing axis. In order for the virtual image to be visible to the eye, the light from an exit aperture of the display unit must be redirected into the pupil of the eye via the respective micro-mirror element. This results in a relationship between the maximum size of the respective micro-mirror elements and a diameter of the exit aperture of the display unit.In an advantageous embodiment, the respective reflection surfaces can be selected as close as possible to or equal to the maximum size. The maximum size is smaller near the central viewing axis than further from the central viewing axis. This takes advantage of the fact that this results in fewer mirror transitions at which each virtual partial image that can be seen via only one micro-mirror element must connect to the adjacent partial image. This partial image must be calculated for each transition to avoid artifacts. A smaller number of micro-mirror elements thus reduces this computational effort. Diffraction effects that occur in the edge region of each micro-mirror element due to the cropping of the beam when it only partially strikes the micro-mirror are also minimized.The design with fewer micro-mirror elements thus minimizes these diffraction artifacts and enables an improved display of a virtual image and thus improved immersion.

[0039] In another embodiment, the reflection surfaces are concave reflection surfaces. Alternatively or additionally, the reflection surfaces can be flat reflection surfaces. The concave reflection surfaces enable particularly high light efficiency. This makes it possible to achieve a situation where the light from only one physical pixel of the display unit is imaged onto a respective micromirror, which then redirects it to the location in the user's eye intended for the virtual image. Accordingly, no multiplexing is required in this case. The concave reflection surfaces can also be selected to focus directly onto the display unit. This eliminates the need for additional optical elements, but all micromirror elements simultaneously image the display unit.As a result, a multiplexing process must be used to map pixel information (the light of a physical pixel of the display unit) unambiguously in one viewing direction.

[0040] Flat reflective surfaces are particularly advantageous if an additional focusing unit is provided in the optical path between the display unit and the deflection unit, for example, to resolve the vergence accommodation problem and / or to compensate for the user's visual impairment. The additional focusing unit allows the focus of the virtual image to always be adjusted to the position of the current viewing direction. For this purpose, information on the orientation of the eye ("eye tracking") can be used, as described further below. Preferably, the focus is changed uniformly for the entire virtual image, for example, by using an electrically adjustable liquid lens. However, other optical approaches are also possible, for example, by stacking several transparent displays.With flat reflection surfaces, any focal distance of the display unit can be displayed without causing imaging errors - other known beam splitter technologies such as the so-called "waveguides", on the other hand, must be designed for a fixed predetermined focal distance.

[0041] With the additional focusing unit, particularly the fluid-controlled lens, a user's visual impairment can be dynamically compensated (i.e., individually for different users) regardless of the resolution of the vergence accommodation problem. In this case, an additional lens element must be placed in an optical path of the ambient light from the field of vision to the eye, between the environment and the deflection unit. For example, it is conceivable for the user to wear their conventional glasses for visual acuity correction over the AR glasses or use a corresponding attachment. Visual acuity correction can be further refined with additional lens elements between the display unit and the deflection unit.

[0042] In one embodiment, the support structure and / or the micro-mirror elements and / or other components surrounded by the liquid are shaped such that the ambient light from the user's field of vision passes through interfaces between transparent material and liquid and / or between liquid and transparent material at least predominantly, for example from a predetermined sub-region of the field of vision, at small angles, in particular at least predominantly at angles of less than 45°. The ambient light should therefore strike the aforementioned interfaces very flatly in as few places as possible, ideally nowhere, and steeply in as many places as possible, ideally everywhere.Since ambient light hits the aforementioned interfaces from different areas of the field of view at different angles, particularly important parts can be selected for the given sub-area, for example, an area surrounding the user's central line of sight. This allows a geometry to be selected for the support structure and / or micro-mirror elements and / or other components that minimizes perceptible refraction and diffraction effects, thus further reducing the visibility of the aforementioned components, with the aforementioned effects.

[0043] In a further embodiment, the reflective surfaces of at least some micro-mirror elements, in particular most of the micro-mirror elements, overlap in an orthogonal projection onto a plane running perpendicular to the user's central line of sight. This applies if the micro-mirror elements or the reflective surfaces are oriented parallel (in the case of physical contact: as parallel as possible). With the overlapping micro-mirror elements, diffraction effects can be reduced and the resolution increased. Preferably, the micro-mirror elements only overlap in areas in which the micro-mirror elements are sufficiently tilted during intended use (for example, in the range of angular orientations used specified by the actuator element(s)) so that no physical contact can occur during operation.In particular, it can be provided that the reflective surfaces do not overlap in areas in which, during intended use, they are at least at one point in time perpendicular to the central viewing axis.

[0044] It can be provided that the reflective surfaces of the micro-mirror elements overlap in the orthogonal projection in a region surrounding the user's central line of sight. This design is advantageous because, in typical positions of the display unit on the side of a pair of glasses, the micro-mirrors visible when looking straight ahead are tilted sufficiently to mechanically enable overlap. Towards the side of the pair of glasses, there is then an area where overlap is not possible. This overlap, and thus reduced diffraction effects, allows for higher resolution in the straight-ahead viewing area, which is advantageous for use in AR glasses.In addition, people tend to turn their heads in the medium term when looking sideways, in combination with looking in the central line of sight ("straight-ahead line of sight"), rather than looking sideways with their eyes rolled, so the increased resolution improves immersion, especially in the area of ​​the central line of sight ("straight-ahead line of sight").

[0045] In one embodiment, the micro-mirror elements are arranged in a one- or two-dimensional curved surface. The curved surface can be defined as a two-dimensional manifold in three-dimensional space. The micro-mirror elements are thus arranged at least partially offset from one another in the direction of the central viewing axis. This is particularly advantageous in conjunction with the overlapping micro-mirror elements described above, since it allows for an overlap (with the described advantages) to be realized in more areas, i.e., for more micro-mirror elements.

[0046] In a further embodiment, the housing element has an anti-reflective coating on a side facing the display unit, in particular an anti-reflective coating with locally varying anti-reflective properties. Since the light from the display unit is generally coupled laterally from the temple side into the deflection unit and then reflected by the micro-mirror elements, reflection also occurs at the interface between the air and the transparent material of the housing element. This reflection is visible to the eye at different positions depending on the pupil position and is undesirable, but can be sufficiently reduced by the anti-reflective coating. This also reduces artifacts and thus increases immersion.

[0047] In an advantageous variant, the display unit can emit polarized light, in particular linearly polarized light, so that unwanted reflection can be further reduced by means of the matching anti-reflective coating. It is also advantageous to align the polarization direction accordingly for minimal reflection. If the direction of radiation of the light relative to the side of the housing element facing the display unit is selected as close as possible to the Brewster angle, depending on the overall geometry of the spectacle display system, unwanted reflection can be almost completely avoided. Anti-reflective coatings are also typically applied to the coating of conventional spectacle lenses to provide a view of the natural surroundings.For the spectacle display system, it is therefore advantageous to choose a coating that enables both low reflection under normal viewing conditions and low reflection of the light emitted by the display unit. Since the reflection of the light emitted by the display unit can only be seen in a narrow area, locally variable coatings are advantageous. These eliminate the reflection of the light emitted by the display unit in the area of ​​the virtually complete field of view and particularly improve visibility in the remaining area.

[0048] In one embodiment, the glasses display system comprises an eye-tracking device ("eye tracking") for determining the orientation of the user's eye, as well as a control unit for controlling the deflection unit depending on the result of determining the eye's orientation. This allows the light to be directed specifically into the pupil of the eye, increasing light efficiency and avoiding undesirable effects such as "eye glow," in which third parties see reflections of the deflected light in the user's eye. Due to the improved energy efficiency, the weight of, for example, a battery, as well as the required size of, for example, the display unit, can be reduced, which also leads to improved immersion.

[0049] It can be provided that the control unit is also designed to control the display unit according to an assignment rule stored in the control unit. In this case, the assignment rule can specify an assignment of the respective virtual pixels of the virtual image to a respective physical pixel of the display unit that changes depending on the orientation of the eye. The content of a virtual pixel is thus specified by different physical pixels for different orientations of the eye (and thus at different times). This is because, when the micro-mirror elements move, the assignments of physical pixels of the display unit to virtual pixels of the virtual image are always changed, and in a different way for each pixel combination.This non-linear change is compensated for by the assignment rule, so that the virtual pixels retain their desired position within the virtual image. This increases image quality and enables particularly large virtual images. In one embodiment, an aperture unit that can be adjusted by means of a control signal is arranged in an optical path of the light between the display unit and the tiltable micro-mirror elements or within the display unit. The adjustable aperture unit is designed to adjust at least one beam position and / or at least one beam width assigned to the respective beam position for the light deflected at the reflection surfaces of the tiltable micro-mirror elements in accordance with the control signal.The adjustable aperture unit can thus be used to determine, via the adjustable beam position, a location of the light striking the deflection unit or other optics such as a microlens arrangement, for example of the display unit, and thus which micro-mirror elements the light strikes and / or, via the adjustable beam width, a size of an area on the deflection unit onto which the light strikes, whereby certain micro-mirror elements among the micro-mirror elements near the beam position can be excluded from being irradiated by the light, for example micro-mirror elements which would only be irradiated with light to a small extent if the beam were larger (as explained in more detail below).

[0050] This has the effect that, with the control signal and the adjustable aperture unit (which can also be referred to as an adaptive aperture), an exit aperture of the display unit can be dynamically adjusted, i.e., temporally varying, via a control signal. Even when using a display unit that, as described above, has a light-generating display with a downstream microlens array, multiplexing can thus be implemented with the corresponding advantage of increased spatial resolution. This combines the advantages of different technological approaches.

[0051] In general (i.e., when viewed without an aperture unit), the exit aperture of the display unit is visible to the eye as a mirror image via each micro-mirror element. If the exit aperture is chosen to be very large, any necessary multiplexing, for example, becomes more complex, and the weight of the AR glasses increases without any added value. When designing the exit aperture (i.e., its diameter), it is therefore desirable to achieve the smallest possible diameter. If the exit aperture of the display unit is too small, then a virtual image cannot be projected for every direction the user is looking in, and the virtually augmentable field of view is therefore relatively small.

[0052] The exit aperture of the display unit therefore requires a certain minimum size to enable a light path from the display unit to the micro-mirror element and from the micro-mirror element to the eye for all AR viewing angles, i.e., the largest possible virtually complete field of view. A pixel image information is thus projected as a beam of rays with the diameter of the display unit's exit aperture onto the deflection unit, onto the micro-mirror elements (the "micro-mirror array" as a whole). A typical diameter of an exit aperture, for example, is 8 mm. A typical diameter for micro-mirror elements or their reflective surfaces is 2-4 mm. Thus, the beam of rays from a pixel image information falls on several neighboring micro-mirror elements simultaneously.Since each micro-mirror element is ideally aligned, depending on the current orientation of the eye, so that the central visual ray from the pupil is projected into the center of the exit aperture of the display unit, it can happen that light from a pixel image information incident on two neighboring micro-mirror elements simultaneously can also be seen in the eye simultaneously. However, because neighboring micro-mirror elements are aligned differently, the same pixel image information is perceived from two different reflected directions, resulting in one or more virtual ghost images.

[0053] The adjustable aperture unit ensures that only a cropped beam of rays is projected onto the different micro-mirror elements or the different micro-lenses of the micro-lens array for each pixel of image information, so that as little light as possible falls on the (nearest) neighboring micro-mirror elements or micro-lenses, or only light that does not hit the pupil and is therefore not visible.

[0054] It is therefore advantageous to design the adjustable aperture unit in such a way that for each micro-mirror element only viewing directions for the virtual image are provided in which the light striking the respective micro-mirror element takes up a larger area than on other, (nearest) neighboring micro-mirror elements. Extreme viewing directions which primarily (i.e. at least predominantly) strike a neighboring micro-mirror element and in doing so only hit the respective micro-mirror element being viewed (at a particular point in time) to a very small extent, for example just barely grazing it, should accordingly no longer hit the exit aperture of the display unit. Accordingly, a small exit aperture of the display unit can be selected for each micro-mirror element being viewed at a particular point in time, for example as part of a time-multiplexing process, in order to improve the image quality.This is achieved with the adjustable aperture unit and / or the microlens array.

[0055] This has the advantage that diffraction effects during image construction are minimized and maximum sharpness of the virtual image can be achieved. This is because a micro-mirror element, which only redirects a small portion of the total beam originally emitted by the display unit into the eye, acts as an aperture. This means that the beam can be clipped if it is only partially reflected. It is known from optics that if the aperture is chosen to be small, diffraction increases. Therefore, it is advantageous to position the beam on the micro-mirror element using the adjustable aperture unit in such a way that it is not, or almost not, clipped by the micro-mirror element.

[0056] In another embodiment, it is provided that the adjustable aperture unit is designed to adapt the beam position by adapting at least one position of at least one transparent partial aperture region, i.e. one switched transparent by means of the control signal, within an overall aperture region that can be switched transparent or opaque by the control signal. A remaining region of the overall aperture region that is complementary to the at least one partial region is opaque, i.e. switched opaque by means of the control signal. Thus, one or more partial aperture regions can be switched transparent, so that only these partial aperture regions are permeable to light from one or more pieces of pixel image information assigned to the respective partial aperture region, and other pieces of pixel image information do not reach the deflection unit.As described below, the location of the transparent sub-area(s) can vary over time, for example, to implement a time-division multiplexing process. This has the advantage of avoiding or at least reducing crosstalk between pixel image information, which can cause, for example, the aforementioned ghosting. This improves image quality even for large fields of view and increases the immersion of the system.

[0057] The described features and feature combinations, including those in the general introduction, as well as the features and feature combinations disclosed in the description of the figures or the figures alone, can be used not only alone or in the described combination, but also with other features or without some of the disclosed features, without departing from the scope of the invention. Consequently, embodiments that are not explicitly illustrated and described in the figures, but that can be created by separately combining the individual features disclosed in the figures, are also part of the invention. Therefore, embodiments and feature combinations that do not encompass all features of an originally formulated independent claim are also to be considered disclosed.Furthermore, embodiments and combinations of features are to be considered as disclosed which deviate from the combinations of features or go beyond those described in the dependencies of the claims.

[0058] In the context of this disclosure, "transverse / alongitudinal" can be understood as "at least substantially perpendicular / parallel", i.e., "vertical / parallel" or "substantially perpendicular / parallel", i.e., perpendicular / parallel except for a predetermined deviation. The predetermined deviation can, for example, be at most 15°, preferably at most 5°, particularly preferably at most 3°. Accordingly, "oppositely oriented" in the context of this disclosure can be understood as "at least substantially oppositely oriented", i.e., "at least substantially antiparallel oriented". The restriction "substantially" can also refer to a maximum permissible deviation specified as a percentage, for example, at most 15%, preferably at most 5%, particularly preferably at most 3%.

[0059] Detailed description

[0060] Exemplary embodiments are described in more detail below with reference to schematic drawings.

[0061] Fig. 1 is a plan view of an exemplary embodiment of a spectacle display system;

[0062] Fig. 2 is a plan view of an exemplary embodiment of a spectacle display system with offset and overlapping micro-mirror units;

[0063] Fig. 3 an illustration of the optimization of the geometry of the micro-mirror units with regard to reduced visibility;

[0064] Fig. 4 is a plan view of an exemplary embodiment of a spectacle display system with additional focusing unit and prescription correction;

[0065] Fig. 5 shows exemplary refractive indices of liquid and transparent material as a function of wavelength; Fig. 6 shows fractional Fresnel reflections as a function of the angle of incidence for an exemplary wavelength.

[0066] Fig. 7 wavelength-dependent refraction effects as a function of the angle of incidence and the wavelength;

[0067] Fig. 8 is a plan view of an exemplary embodiment of a spectacle display system with concave reflective surfaces;

[0068] Fig. 9 is a plan view of another exemplary embodiment of a spectacle display system with concave reflective surfaces; and

[0069] Fig. 10 an illustration of the deflection of the micro-mirror units by means of a guide matrix structure; and

[0070] Fig. 11 is a front view and interior view of another exemplary embodiment of a glasses display system.

[0071] In the figures, identical or functionally equivalent features are provided with the same reference numerals.

[0072] Figure 1 shows a plan view of an exemplary embodiment of a spectacle display system, illustrating one half, i.e., one eye. The system can be expanded accordingly to accommodate two eyes.

[0073] Fig. 1a shows one half of the spectacle display system 1, for example the left half from above or the right half from below. Light 163", 161", 162" is emitted by a display unit 14 (here arranged laterally), which in the present case is imaged by an optics 13 such that this light 163", 161", 162" is reflected by micro-mirror elements such as 12, 12', 12" of a deflection unit 17 (part I) and strikes the pupil 11 of the eye 10. The optics 13 can comprise one or more lenses and / or mirrors and / or other optical components such as one or more aperture units (also adaptive, i.e., adjustable with a control signal). The optics 13 can also comprise or be a microlens array with a plurality of microlens elements and / or a projector optics as explained by way of example in the general description.

[0074] The eye is oriented in a central viewing direction B (here parallel to the y-direction). If the micro-mirror elements 12, 12', 12" (for example, with typical dimensions of approximately 2 mm) are designed to be at least substantially transparent to ambient light, then both a viewing of the natural environment 100 according to light rays such as 161', 162', 163' is possible, and a virtual image with light rays 161", 162", 163" can be superimposed on the light rays 161', 162', 163' of an ambient light. The optics 13 can be designed such that the virtual image can be viewed sharply at a finite or infinite distance. The micro-mirror elements 12, 12', 12" are mounted so that they can be tilted so that their angular orientation can be adjusted in two dimensions. The micro-mirror elements 12, 12', 12" and a support structure 200 (Fig.10) for the micro-mirror elements 12, 12', 12" are arranged in a sealed housing element 17a filled with a liquid 23. The liquid 23 is selected in this case such that the refractive index between the micro-mirror element material(s) and the liquid is as identical as possible. It is known that glass components become invisible when they are placed in a liquid that has a nearly identical refractive index. Two effects occur. Firstly, the Fresnel reflection that occurs when transitioning from one medium to another with a different refractive index disappears. Secondly, light rays are not refracted at the material transition. However, even with very small differences, the possibility of partial reflection and total internal reflection still exists if the angles impinge on the interface at a very flat angle. This is shown and explained in more detail in Fig. 6.

[0075] In the present case, in conjunction with determining the orientation of the eyes 10 and thus the position of the pupils 11 by means of an eye tracking device 15, it is possible to direct the light 163", 161", 162" of the optics 13 very specifically into the pupil 11 of the eye 10. In the event of an eye movement, for example a lateral eye movement as shown in Fig. 1b, with a changed position of the pupil 11, the micro-mirror elements 12, 12', 12" are aligned accordingly so that the light 163", 161", 162" of the optics 13 again hits the pupil 11 precisely.In addition to the support structure for the micro-mirror elements 12, 12', 12", the micro-mirror elements 12, 12', 12" are also equipped with one or more actuator elements (not shown for reasons of clarity) for adjusting the angular orientation and thus the respective reflection angles, and in the present case additionally with an individual angle sensor (also not shown here) for measuring the current angular orientation.

[0076] This enables a control loop for tracking the micro-mirror elements 12, 12', 12", so that the light 163", 161", 162" of the optics 13 hits the pupil 11 of the eye 10. For this purpose, the position of the pupil 11 is measured with the eye tracking device 15, and the target angular orientation of the micro-mirror elements 12, 12', 12" is calculated by a control unit and subsequently compared with the actual position of the micro-mirror elements 12, 12', 12". The actuator element(s) then regulates the difference between the actual and target positions, aiming for a sufficiently high speed so that the eye 10 can perceive the virtual image stably even when moving. Speeds of 1000% are known as the maximum eye speed, from which a minimum processing speed can be derived.

[0077] When the angular orientation of the micro-mirror elements 12, 12', 12" changes, the viewing direction also changes with the new orientation of the eye 10, which now deviates from the central viewing direction B. Comparing Fig. 1a and 1b, it is noticeable that the light 161" is reflected as light 161 in Fig. 1a and as light 161b in Fig. 1b, with the lights 161b and 161 differing in their direction. This results in the assignment of the respective virtual pixels of the virtual image to a respective physical pixel of the display unit 14 changing, and the image information emitted in direction 161" by the display unit 14 must be adapted to the changed angular orientation. Thus, in the event of an eye movement, not only the orientation of the micro-mirror elements 12, 12', 12" should be adjusted, but also the pixel light image information generated on the display unit 14.However, since the geometric arrangement of projector to micromirror is known, the laws of optics can be used to calculate which new image information must be displayed so that the human observer at a given location of the pupil (given "eyebox") has the impression that the virtual image has not shifted, and a corresponding assignment rule can be stored in a control unit of the display unit 14.

[0078] The control of the micro-mirror elements 12, 12', 12" is preferably carried out in such a way that the central viewing beam, i.e. the viewing beam that starts from the center of the pupil and hits the associated micro-mirror element in the center, is deflected, for example, along light 163b in Fig. 1b, to the center of the optics 13. Since a change in the inclination of the micro-mirror elements 12, 12', 12" changes the angle at which a pixel image information is seen by the display unit 14, as explained, it may be advantageous not to continuously adjust the micro-mirror elements 12, 12', 12", but rather in steps based on a limit value that specifies how off-center the light 163b may hit the pupil 11 of the eye 10. It is advantageous that the eye makes micro-movements that do not need to be corrected as a result.It is also advantageous that the micro-mirror elements 12, 12', 12" are embedded in the liquid 23, which has a damping effect and suppresses vibrations (i.e. small, rapid angular movements).

[0079] The micro-mirror elements 12, 12', 12" are drawn in a plane in Fig. 1. As shown in Fig. 2, however, they can also be arranged on a one- or two-dimensionally curved surface. The micro-mirror elements 12, 12', 12" are accordingly arranged offset from one another in the central viewing direction running transversely to a main extension plane of the deflection unit 17 (here the xz plane), for example, two, several or all of the nearest adjacent micro-mirror elements 12, 12', 12" are arranged offset from one another. This is advantageous because spectacle lenses typically have curved surfaces, the so-called base curves, and thus the spectacle display system 1 can be designed more similarly to conventional spectacles. Furthermore, more of the micro-mirror elements 12, 12', 12" can be designed with mutual overlap and / or the extent of the overlap of respective adjacent micro- Mirror elements 12, 12', 12" can be increased.

[0080] Fig. 3a shows different geometries of the micro-mirror elements and their consequences for undesirable refraction and reflection effects. Due to the liquid 23, which has a nearly identical refractive index to the material of the micro-mirror elements 12, 12', the Fresnel reflection that occurs when passing from one medium to another with a different refractive index disappears, and the light rays 21, 21', 22, 22' are not refracted.

[0081] However, even with very small differences, the possibility of partial reflection and total internal reflection still exists if the light rays impinge very flatly on the respective interfaces. For example, light beam 22" is shown as such a partially reflected light beam. Accordingly, two micro-mirror elements 12 and 12' with different geometries are shown in Fig. 3a. Both micro-mirror elements 12 and 12' realize a semi-transparent reflection surface 25, e.g. by applying a thin metal coating to the micro-mirror elements 12, 12'. The micro-mirror elements 12, 12' themselves are made, for example, from a plastic or glass with a first refractive index that matches as closely as possible to the second refractive index of the surrounding liquid 23.

[0082] The difference between the two exemplary micro-mirror elements 12, 12' in Fig. 3a lies in their geometric construction, with micro-mirror element 12' creating interfaces at which the visible rays of the human eye 10 corresponding to the light beam 22 strike the optical interface at a shallow angle. In this case, depending on the actual angle, total reflection or partial reflection can occur. These reflections cloud the transparency of the deflection unit 17 by superimposing ghost images on the partial reflections. Thus, it is advantageous for the mechanical structures of the micro-mirror element to be designed so that visible rays pass through interfaces with refractive index transitions as orthogonally as possible. Thus, the geometry of micro-mirror elements 12 with a rounded back is preferable to the rectangular geometry of micro-mirror elements 12'.

[0083] Accordingly, another geometry of a micro-mirror element 12" is shown in Fig. 3b. There, the micro-mirror element 12" has a trapezoidal geometry in the cross-section shown, with the long side of the trapezoid corresponding to the reflection surface 25. The light beam 23 passing through the two parallel base sides of the trapezoid runs parallel before and after the micro-mirror element 12" as well as before and after the deflection unit. The light beam 23' passing only through the long base side of the trapezoid and one of the legs, however, does not, since the interface at the leg is traversed at too shallow an angle. The trapezoidal geometry of micro-mirror elements 12" is therefore preferable to the rectangular geometry of micro-mirror elements 12' but not to the geometry of micro-mirror elements 12 with a rounded back.

[0084] Fig. 4 shows a plan view of one plane of an exemplary embodiment of a spectacle display system with an additional focusing unit and, in this case, also vision correction. The additional focusing unit 13" as adaptive optics is adjusted in its focus by a control unit 110. For example, the focus of the virtual image can be set either to infinity (ray path / light beam 112) or to finite (ray path / light beam 111). This solves the vergence accommodation problem. If the focus can be adjusted faster than a frame rate, different focal planes can even be set within a virtual image.

[0085] With an additional lens element 13'" between the deflection unit 17 and the environment 100, a visual acuity correction can be integrated without great effort. Its properties are then to be taken into account accordingly by the control unit 110.

[0086] Figure 5 shows exemplary refractive indices of a liquid, here an oil, and a transparent material, here quartz glass, as a function of wavelengths (wavelength in nm) from 400 nm to 700 nm at an exemplary temperature. Curve 80 corresponds to the first refractive index of the liquid 23, and curve 81 to the second refractive index of the material of the micro-mirror elements 12, 12', 12". It should be noted that the maximum difference between the first and second refractive indices is reached here at 400 nm and does not exceed the relatively small amount of 0.004. It is particularly advantageous if the two curves 80, 81 have an intersection point in the green wavelength range (520 nm-565 nm), since it has been found that artifacts in the green wavelength range are perceived by humans with higher resolution than in the red and blue ranges. For these refractive indices, the values ​​shown in Figs.Figures 6 and 7 illustrate values ​​for Fresnel reflections and refraction effects, which lead to largely invisible material transitions and thus largely invisible micro-mirror elements 12, 12', 12" and a largely invisible support structure or largely invisible housing element 17a. It should also be noted at this point that reflections can also occur as a boundary layer on an inner side 17b (Fig. 1) of the housing element 17a facing the user and display unit 14. These reflections are disruptive due to the offset of the inner side 17b in the y-direction relative to the micro-mirror elements 12, 12', 12". These disruptive reflections can be reduced or eliminated with an anti-reflective coating, as is essentially known from conventional eyeglasses.

[0087] In Fig. 6a, curve 82 shows the Fresnel reflection as a percentage of the total intensity versus the angle of incidence in degrees for the combination of the two refractive indices from Fig. 4 for a wavelength of 450 nm. The difference in the refractive indices here is approximately 0.002. An exponential increase in the proportion of reflected intensity resulting from this effect is evident. The reflection is close to zero up to an angle of incidence above 80° and increases to 100% within a few degrees at 90°, i.e., when the light falls flatly, almost grazing, onto the interface. (The angle of incidence is measured relative to a normal to the interface.)

[0088] Fig. 6b shows that the reflected light fraction is below 0.01% up to approximately 70°, meaning that Fresnel reflection plays no role below this angle of incidence. Fig. 6b plots the Fresnel reflection as a percentage of the total intensity ("reflection in % (100% max)") versus the angle of incidence in degrees ("angle of incidence in degrees") for the combination of the two refractive indices from Fig. 4 for a wavelength of 450 nm from 0° to 70°. Curve 82a shows the curve for s-polarized light, curve 82b for p-polarized light.

[0089] In addition to the Fresnel reflections in Fig. 6, refraction effects must also be taken into account, which also depend on the angle of incidence and wavelength. Accordingly, Fig. 7 shows the wavelength-dependent refraction effect, a deflection in degrees ("change in direction in degree") as a function of the angle of incidence ("angle of incidence in degree") and the wavelength from 400 nm to 700 nm. Temperature and refractive indices here again correspond to the temperature and refractive indices in Figs. 4 and 5. The solid curves 83a, 83i, 83z describe the deflection upon light incidence from the optically denser medium into the optically rarer medium for the wavelengths from 400 nm (curve 83a) to 700 nm (curve 83z). The dashed curves 84a, 84i. ,84z describe the deflection when light falls from the optically thinner medium into the optically denser medium for the wavelengths from 400nm (curve 84a) to 700nm (curve 84z).

[0090] Deflections in a core area W around 0 degrees are not perceived by the user due to the angular resolution of the human eye being limited to approximately 1 / 60° = 0.0167 and are therefore not critical. Thus, for example, curves 83i, 84i show that angles of incidence of up to approximately 38° for wavelengths above 550 nm cannot be perceived by the user and are therefore not critical. From such representations, an optimized geometry for the micro-mirror elements 12, 12', 12" can be derived depending on the overall geometry of the spectacle display system 1.

[0091] Figure 8 shows a plan view of an exemplary embodiment of a spectacle display system with concave reflection surfaces. The principle shown allows for the elimination of multiplexing.

[0092] This approach is particularly light-efficient because all of the light 163", 161", 162" is directed into the pupil 10 of the eye 11. For this purpose, the optics 13' are designed such that the light from the display unit 14 is imaged onto an intermediate image 101. However, the intermediate image 101 does not have to be sharply imaged. For example, it may be advantageous to compensate for imaging errors that occur due to the subsequent reflection at a curved micro-mirror element 12, 12', 12" at this point. The intermediate image 101 is selected such that the intermediate image 101 is imaged into the pupil 11 of the eye 10 by a curved micro-mirror element 12, 12', 12". Due to the geometric constellation of pupil position to micro-mirror element 12, 12', 12" and the diameter of pupil 11 and micro-mirror elements 12, 12', 12", a field of view 102 or 103 results which is imaged by a micro-mirror element 12 or

[0093] 12'. The intermediate image 101 is positioned such that adjacent viewing areas 102 and 103 do not overlap. Thus, the light 163", 161", 162" of a physical pixel of the display unit 14 is imaged onto only one micro-mirror element 12, 12', 12", and no further multiplexing process is necessary.

[0094] In the embodiment shown in Fig. 8, each light beam 104, 105 has its own intermediate focus 106, 107, which is imaged with its own physical pixel on the display unit 14. Because such light beams 105 not only strike one micro-mirror element 12, but also another micro-mirror element 12', which in turn is imaged onto a separate physical pixel on the display unit 14, redundant physical pixels are necessary, i.e., more physical pixels than virtual pixels displayed in the virtual image.

[0095] In one variant, the intermediate image 101 can also be designed so that adjacent viewing areas 102, 103 overlap. The corresponding micro-mirror elements 12, 12' are then designed so that the same intermediate focus 107 is used for the same viewing angles that impinge on the pupil 11, thus requiring only one physical pixel per viewing direction. This design is optically more demanding because the micro-mirror elements 12, 12', 12" not only have to produce a sharp image, but also the distortion must be controlled so that adjacent and differently tilted micro-mirror elements 12, 12', 12'" must form a common intermediate image 101. In the design of the optics 13', it can be exploited that the maximum sharpness only needs to be achieved for a central area, the so-called "foveated area", i.e. when the eye 10 is precisely aligned with the respective micro-mirror element 12, 12', 12'".When the eye 10 turns away, human imaging performance drops rapidly and sharply, so that image errors are usually not perceived in this case. Fig. 9 shows a plan view of a further exemplary embodiment of a spectacle display system with concave reflection surfaces, which is similar to that of Fig. 8, but optionally does not include the optics 13'.

[0096] The micro-mirror elements 12, 12', 12'" are designed so that they focus directly onto the display unit 14. In addition, further optical elements 13'" can be inserted to improve the image quality. Thus, all micro-mirror elements 12, 12', 12'" simultaneously image the display unit 14. In order to clearly image pixel information in one viewing direction, a multiplexing process must be used. A multiplexing process based on a switchable, adjustable aperture unit is suitable for this purpose, so that unwanted micro-mirror elements 12, 12', 12" are masked out at a time and the aperture unit is only transparent for desired micro-mirror elements. Such a switchable, adjustable aperture unit can be implemented, for example, using a liquid crystal shutter.

[0097] In different embodiments, the focus of the micro-mirror elements 12, 12', 12'" can thus be at different distances. Figure 8 shows an example in which the focus 101 is in front of the display unit 14. In Figure 9, the focus is on the display. The focus can also be behind the display unit 14 at infinity. The focal plane can therefore be freely selected in front of, on, or behind the display unit 14. If pixel information is projected onto several micro-mirror elements 12, 12', 12'" simultaneously, a multiplexing method such as the one described in the last paragraph is necessary to clearly display pixel information in one image direction.

[0098] Fig. 10 shows an illustration of the deflection of the micro-mirror units using a guide matrix structure.

[0099] Figure 10a shows, by way of example, a micro-mirror unit 12, which is arranged on a support structure 200 so as to be tiltable about two tilt axes K1, K2. A two-dimensional guide matrix structure 202 with respective guide surfaces 203a, 203a', 203b, 203c, 203d is formed on a common actuator element 201 (Fig. 10b). The respective micro-mirror units 12, 12', 12" in the present case scan the guide matrix structure 202 in the form of the associated guide surfaces 203a, 203a', 203b, 203c, 203d with respective sensors 204a, 204a', 204b, 204c, 204d, one sensor per tilt axis K1, K2, so that upon a displacement of the actuator element 201, the respective micro-mirror units 12, 12', 12" can be tilted non-linearly by the displacement of the actuator element 201 in a manner different from one another, in accordance with the spatial shape of the guide surfaces 203a, 203a', 203b, 203c, 203d.

[0100] This is illustrated in Fig. 10b in a sectional view for one dimension of tilting. For example, two micro-mirror units 12, 12" are tilted counterclockwise when the actuator element 201 is moved in the negative x-direction, while another micro-mirror unit 12' is tilted clockwise.

[0101] Fig. 11 shows another exemplary embodiment of a spectacle display system. As can be seen from Fig. 11a, the spectacle display system 1 in this example has a deflection unit 17 with a plurality of micro-mirror units 12, 12', 12", which are arranged over a large area in a field of view corresponding to that of conventional spectacles. Fig. 11b shows an interior view of the deflection unit 17 with the many micro-mirror units 12, 12', 12". Adjacent micro-mirror units 12, 12' are shown here as examples, which partially overlap. In the example shown, the micro-mirror units 12, 12', 12" are arranged offset in the y-direction and are also of different sizes. Micro-mirror unit 12" has a larger reflection surface than micro-mirror unit 12', and micro-mirror unit 12' has a larger reflection surface than micro-mirror unit 12.

Claims

Claims 1. Glasses display system (1) for displaying a virtual image in a field of vision of a user, with - a display unit (14) for emitting a light (163", 161", 162") as computer-generated image information in a radiation direction; - a deflection unit (17) for deflecting the light (163", 161", 162") emitted by the display unit (14) as computer-generated image information into an eye (10) of the user, with a plurality of micro-mirror elements (12, 12', 12"), each tiltable in a support structure (200), which each have at least one reflection surface (25) for deflecting the light (163", 161", 162") emitted by the display unit (14) as computer-generated image information; characterized in that the micro-mirror elements (12, 12', 12") and the support structure (200) are arranged in a sealed housing element (17a) of the deflection unit (17) filled with a liquid (23).

2. Glasses display system (1) according to the preceding claim, characterized in that - the micro-mirror elements (12, 12', 12") and / or the support structure (200) are each at least substantially transparent to ambient light from the field of vision of the user, in particular invisible to the user in at least one wavelength range and / or at least one angular range of the ambient light, made of or with a respective transparent material having a first refractive index; and - the liquid (23) is also at least substantially transparent to the ambient light and has a second refractive index adapted to the first refractive index in the sense of a deviation as small as possible, which second refractive index is equal to the first refractive index in particular for at least one wavelength of a green wavelength range.

3. Spectacle display system (1) according to one of the preceding claims, characterized in that the micro-mirror elements (12, 12', 12") are mechanically coupled to a common actuator element (201), in particular by means of a two-dimensional guide matrix structure (202).

4. Spectacle display system (1) according to the preceding claim, characterized in that the actuator element (201) is designed to move at least some of the micro-mirror elements (12, 12', 12"), in particular most of the micro-mirror elements (12, 12', 12"), differently from one another and / or non-linearly.

5. Spectacle display system (1) according to one of the preceding claims, characterized in that the respective micro-mirror element (12, 12', 12") has a coating on its reflection surface (25) whose reflection properties are adapted to a emission spectrum of the display unit, in particular to maxima in the emission spectrum.

6. Spectacle display system (1) according to one of the preceding claims, characterized in that the reflection surfaces (25) have at least partially different sizes, in particular one or more reflection surfaces (25) closer to a central viewing axis (B) of the user have a smaller size than one or more reflection surfaces (25) further away from the central viewing axis (B) of the user.

7. Spectacle display system (1) according to one of the preceding claims, characterized in that the display unit (14) comprises a microlens arrangement with a plurality of microlens elements, each microlens element being assigned exactly one micromirror element (12, 12', 12").

8. Spectacle display system (1) according to one of the preceding claims, characterized in that the support structure (200) and / or the micro-mirror elements (12, 12', 12") are shaped such that the ambient light from the field of vision of the user passes through interfaces between transparent material and liquid (23) and / or between liquid (23) and transparent material at least predominantly at small angles, in particular at least predominantly at angles of less than 45°.

9. Spectacle display system (1) according to one of the preceding claims, characterized in that the reflection surfaces (25) of at least some micro-mirror elements (12, 12', 12") overlap in an orthogonal projection onto a plane extending transversely to the central viewing axis (B) of the user.

10. Spectacle display system (1) according to the preceding claim, characterized in that the reflection surfaces (25) of the micro-mirror elements (12, 12', 12") overlap in an area surrounding the central viewing axis (B) of the user in the orthogonal projection.

11. Spectacle display system (1) according to one of the preceding claims, characterized in that the micro-mirror elements (12, 12', 12") are arranged in a one- or two-dimensionally curved surface.

12. Spectacle display system (1) according to one of the preceding claims, characterized in that the housing element (17a) has an anti-reflective coating on a side (17b) facing the display unit (14), in particular an anti-reflective coating which locally varies in its anti-reflective properties and / or an anti-reflective coating which is applied to a Anti-reflective coating tailored to the polarized light of the display unit.

13. Glasses display system (1) according to one of the preceding claims, characterized by - an eye tracking device (15) for determining an orientation of the eye (10) of the user, and - a control unit for controlling the deflection unit (17) depending on a result of determining the orientation of the eye (10).

14. Spectacle display system (1) according to the preceding claim, characterized in that the control unit is also designed to control the display unit (14) according to an assignment rule stored in the control unit, wherein the assignment rule prescribes an assignment of the respective virtual pixels of the virtual image to a respective physical pixel of the display unit (14), which assignment changes depending on the orientation of the eye (10).

15. Glasses display system (1) according to one of the two preceding claims, characterized in that - in a standard operating mode, at least almost all micro-mirror elements (12, 12', 12") are aligned with their angular orientation of the spectacle display system (1) in such a way that only light from the display unit (14) is directed into the eye (10) of the user by the respective micro-mirror element (12, 12', 12"), and / or - in a power-saving operating mode of the spectacle display system (1), micro-mirror elements (12, 12', 12") not irradiated by the display unit (14) are brought into a predetermined rest orientation, in which rest orientation essentially only light from the display unit (14) is directed into the eye (10) of the user when the eye (10) is in its rest position, in particular when the actuator element (201) is deactivated.

Images