Abstract
A device for generating a virtual image comprising a display element for generating an image, an optical waveguide for expanding an exit pupil, and an antiglare element, which is arranged after the optical waveguide in a beam path and is configured as a shutter comprising slats, wherein the slats are arranged variably in their setting angle during operation is disclosed.
Claims
1. A device for generating a virtual image, comprising: a display element for generating an image; an optical waveguide for expanding an exit pupil; and an antiglare element, which is arranged after the optical waveguide in a beam path and is configured as a shutter comprising slats, wherein the slats are arranged variably in their setting angle during operation.
2. The device as claimed in claim 1, comprising stabilization threads, which are in contact with the slats.
3. The device as claimed in claim 2, wherein the slats comprise openings through which the stabilization threads extend.
4. The device as claimed in claim 2, wherein slats and stabilization threads are connected to one another by glue points.
5. The device as claimed in claim 2, wherein the stabilization threads are coated with an adhesive material.
6. The device as claimed in claim 2, wherein the stabilization threads are arranged in a frame not parallel to a longitudinal direction of the slats.
7. The device as claimed in claim 2, wherein at least some of the stabilization threads are interwoven with one another.
8. The device as claimed in claim 1, wherein the slats are arranged on a spring element at end regions located in a longitudinal direction.
9. The device as claimed in claim 8, wherein a broad spring is the spring element and the end regions respectively of two slats at a fastening location of the broad spring are respectively arranged opposite one another in the direction of their width.
10. The device as claimed in one of claim 8, wherein the end regions respectively of two slats at the fastening location of the spring element are respectively arranged opposite one another, and at least one of the respective end regions is arranged by a spacer.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 schematically shows a head-up display according to the prior art for a motor vehicle;
[0026] FIG. 2 shows an optical waveguide with two-dimensional enlargement;
[0027] FIG. 3 schematically shows a head-up display with an optical waveguide;
[0028] FIG. 4 schematically shows a head-up display with an optical waveguide in a motor vehicle;
[0029] FIG. 5 schematically shows a head-up display with an optical waveguide and antireflection as an antiglare element;
[0030] FIG. 6 shows an alternative optical waveguide with two-dimensional enlargement;
[0031] FIG. 7 schematically shows a device according to the disclosure for generating a virtual image;
[0032] FIG. 8 shows a shutter and a detail enlargement thereof;
[0033] FIG. 9 shows an alternative embodiment with stabilization threads;
[0034] FIG. 10 shows an alternative embodiment with stabilization threads;
[0035] FIG. 11 shows an alternative embodiment with stabilization threads;
[0036] FIG. 12 shows an alternative embodiment with stabilization threads;
[0037] FIG. 13 shows a further alternative embodiment with stabilization threads;
[0038] FIG. 14 shows a further alternative embodiment with stabilization threads;
[0039] FIG. 15 shows a further alternative embodiment with stabilization threads;
[0040] FIG. 16 shows an alternative embodiment;
[0041] FIG. 17 shows the arrangement of slats in a frame;
[0042] FIG. 18 shows an alternative embodiment; and
[0043] FIG. 19 shows an alternative embodiment.
DETAILED DESCRIPTION
[0044] For a better understanding of the principles of the present disclosure, embodiments of the disclosure will be explained in more detail below with reference to the figures. The same references are used in the figures for identical or functionally identical elements and are not necessarily described again for each figure. It is to be understood that the disclosure is not restricted to the embodiments represented, and that the features described may also be combined or modified without departing from the scope of protection of the disclosure, as defined in the appended claims.
[0045] First, the basic concept of a head-up display with an optical waveguide will be explained with reference to FIGS. 1 to 4.
[0046] FIG. 1 shows a schematic diagram of a head-up display according to the prior art for a motor vehicle. The head-up display comprises an image generator 1, an optics unit 2, and a mirror unit 3. A beam of rays SB1 emanates from a display element 11 and is reflected by a folding mirror 21 onto a curved mirror 22, which reflects it in the direction of the mirror unit 3. The mirror unit 3 is represented here as a windshield 31 of a motor vehicle. From there, the beam of rays SB2 travels in the direction of an eye 61 of a viewer.
[0047] The viewer sees a virtual image VB that is located outside the motor vehicle, above the engine hood or even in front of the motor vehicle. Due to the interaction of the optics unit 2 and the mirror unit 3, the virtual image VB is an enlarged representation of the image displayed by the display element 11. A speed limit, the current vehicle speed, and navigation instructions are symbolically represented here. As long as the eye 61 is within the eyebox 62 indicated by a rectangle, all elements of the virtual image are visible to the eye 61. If the eye 61 is outside the eyebox 62, the virtual image VB is only partially or not at all visible to the viewer. The larger the eyebox 62 is, the less restricted the viewer is when choosing their seating position.
[0048] The curvature of the curved mirror 22 serves to condition the beam path and thus to ensure a larger image and a larger eyebox 62. In addition, the curvature compensates for a curvature of the windshield 31, with the result that the virtual image VB corresponds to an enlarged reproduction of the image represented by the display element 11. The curved mirror 22 is rotatably mounted by a bearing 221. The rotation of the curved mirror 22 that this allows makes it possible to displace the eyebox 62 and thus to adapt the position of the eyebox 62 to the position of the eye 61. The folding mirror 21 serves to ensure that the path traveled by the beam of rays SB1 between the display element 11 and the curved mirror 22 is long but, at the same time, that the optics unit 2 is nevertheless compact. The optics unit 2 is delimited from the environment by a transparent cover 23. The optical elements of the optics unit 2 are thus protected, for example, against dust located in the interior of the vehicle. An optical film 24 or a coating that is intended to prevent incident sunlight SL from reaching the display element 11 via the mirrors 21, 22 is furthermore situated on the cover 23. Said display element 11 could otherwise be temporarily or permanently damaged by the resulting development of heat. In order to prevent this, an infrared component of the sunlight SL is for example filtered out by means of the optical film 24. Antiglare protection 25 serves to shade light incident from the front, so that it is not reflected by the cover 23 in the direction of the windshield 31, which could cause the viewer to be dazzled. In addition to sunlight SL, the light from another stray light source 64 may also reach the display element 11.
[0049] FIG. 2 shows a schematic spatial representation of an optical waveguide 5 with two-dimensional enlargement. The lower left region shows an input coupling hologram 53, by means of which light L1 coming from a picture generating unit (not represented) is coupled into the optical waveguide 5. It propagates therein to the top right in the drawing, according to the arrow L2. In this region of the optical waveguide 5, there is a folding hologram 51 that acts similarly to many partially transmissive mirrors arranged one behind the other and produces a light beam that is broadened in the Y-direction and propagates in the X-direction. This is indicated by three arrows L3. In the part of the optical waveguide 5 that extends to the right in the figure, there is an output coupling hologram 52 that likewise acts similarly to many partially transmissive mirrors arranged one behind the other and couples out light, indicated by arrows L4, upward in the Z-direction out of the optical waveguide 5. In this case, broadening takes place in the X-direction, so that the original incident light beam L1 leaves the optical waveguide 5 as a light beam L4 that is enlarged in two dimensions.
[0050] FIG. 6 shows a schematic representation of an optical waveguide with two-dimensional enlargement, which is an alternative to FIG. 2. Here, the output coupling hologram 52 is configured in such a way that it couples light out not perpendicularly to the surface of the optical waveguide 5 but at an angle with respect to the Z-direction, as illustrated by the arrows L4. In this way, the optical waveguide 5 may be arranged according to the available installation space, without having to allow for perpendicular emergence of the light beam enlarged in two dimensions.
[0051] FIG. 3 shows a spatial representation of a head-up display with three optical waveguides 5R, 5G, 5B, which are arranged one above the other and each stand for an elementary color red, green, and blue. Together they form the optical waveguide 5. The holograms 51, 52, 53 present in the optical waveguide 5 are wavelength-dependent, so that one optical waveguide 5R, 5G, 5B is respectively used for one of the elementary colors. An image generator 1 and an optics unit 2 are represented above the optical waveguide 5. The optics unit 2 comprises a mirror 20, wherein the light produced by the image generator 1 and shaped by the optics unit 2 is deflected in the direction of the respective input coupling hologram 53. The image generator 1 comprises three light sources 14R, 14G, 14B for the three elementary colors. It can be seen that the entire unit shown has a small overall height compared to its light-emitting surface.
[0052] FIG. 4 shows a head-up display in a motor vehicle similarly to in FIG. 1, but here in a spatial representation and with an optical waveguide 5. It shows the schematically indicated image generator 1, which produces a parallel beam of rays SB1 that is coupled into the optical waveguide 5 by the mirror plane 523. The optics unit is not represented for the sake of simplicity. A plurality of mirror planes 522 each reflect a portion of the light incident on them in the direction of the windshield 31, the mirror unit 3. The light is reflected thereby in the direction of the eye 61. The viewer sees a virtual image VB above the engine hood or at an even farther distance in front of the motor vehicle.
[0053] FIG. 5 schematically shows a head-up display with an optical waveguide 5 and antireflection as an antiglare element 81, a windshield 31 and a viewer with an eye 61. The optical waveguide 5 is in this case arranged directly on the antiglare element 81.
[0054] FIG. 7 shows a device according to the disclosure, in which an optical waveguide 5 is used in a manner corresponding to FIG. 6. It shows the image generator 1 with a display element 11 and the optical waveguide 5, from which light L4 emerges at an angle α with respect to the normal N to the light exit surface 54 of the optical waveguide 5, the angle α being greater than 0°. The emerging light L4 impinges on the light entry surface 85 of the shutter 83, the slats 82 of which are arranged parallel to the emerging light L4, so that it may pass unimpeded through the intermediate spaces 84 between the slats 82. The light L6 emerging from the shutter 83 impinges on the windshield 31 at an angle β and is reflected thereby, and enters the eye 61 of a vehicle occupant, here the driver, as light L8. The latter therefore sees a virtual image VB. In this exemplary embodiment, the shutter 83 forms the cover of the optics unit, and a separate cover element is not provided. The shutter 83 may therefore even come in direct contact with objects or persons located in the interior of the vehicle. Damage to the shutter 83 is therefore not precluded. The shutter 83 is therefore arranged releasably so that, if need be, it is removed without great effort and replaceable with a new or repaired shutter 83.
[0055] FIG. 8 shows the shutter 83 and a detail enlargement 830. It shows the slats 82, which let through light L5 that emanates from the optical waveguide 5 and travels substantially parallel to the slats 82. Stray light SL that does not travel parallel to the slats 82 is blocked by the slats 82. The slats 82 have a spacing AL from one another and are inclined by an angle α with respect to the normal NJ to the light entry surface 85 of the shutter 83. The slats have a height HL and a thickness DL, the height HL being a multiple of the thickness DL. The angle α corresponds to that of the light emergence from the optical waveguide 5 when the light exit surface 54 of the latter and the light entry surface 85 of the shutter 83 are arranged parallel to one another. In the case of a non-parallel arrangement, these angles are to be converted accordingly. The angle α depends, inter alia, on the position of the driver and their angle of view. For different types of vehicle or different inclinations of the windshield 31, inter alia the spacing AL needs to be adapted. The slats 82 are for example configured to be nonreflective, that is to say substantially black and opaque. If the slats are arranged so as to be tiltable, that is to say the angle α is variably adjustable during operation, they may be adjusted to different positions of the eyebox, or to different positions of the eye 61 inside the eyebox. This assumes that the light emanating from the optical waveguide 5 covers a certain angle range so that, for each angle α set, light rays that are aligned parallel to the slats arrive on the latter and therefore pass through them.
[0056] FIG. 9 shows an alternative embodiment with stabilization threads 87. The slats 82 are fixed in position by a plurality of stabilization threads 87 over their length, the extent in the x-direction. Oscillation/vibration of the slats 82 is thus prevented. The slats 82 are fixed in both the x- and z-direction. If the spacing of the stabilization threads 87 with respect to one another is selected to be sufficiently small, the possibility of displacing the slats 82 in the y-direction is also minimized. The stabilization threads 87 may, in one alternative embodiment, be fastened on a frame 86 of the antireflection unit, the antiglare element 81. The diameter of the stabilization threads 87 is selected to be as small as possible in the μm range, so that the stabilization threads 87 interfere with the beam path little or almost not at all, and are therefore not visible in the virtual image VB. Relatively large-area gaps 871 remain, through which light emanating from the optical waveguide 5 may pass unimpeded.
[0057] FIG. 10 shows a further alternative embodiment with stabilization threads 87, in which the position of the stabilization threads 87 in relation to the slat height HL varies over the width BL of the slat 82. The stabilization threads 87 may therefore be arranged in one, two or more planes. Openings 88, which are represented here as round holes, through which the stabilization threads 87 extend are furthermore shown. The stabilization threads 87 bear at least pointwise on the edge of the holes, and are therefore in contact with the openings 88.
[0058] FIG. 11 shows an alternative embodiment with stabilization threads 87, together with fixing and adjustment. If the stabilization threads 87 are also meant to be used for fixing and adjustment, the position of the slats 82 is also fixed in the y-direction. Additionally, in this case noise due to movement of the slats 82 is minimized. In one alternative embodiment, the stabilization threads 87 are fastened on the slats 82 with an adhesive material at glue points 882. In this case, the fixing points 881 are configured in such a way that they are not visible in the virtual image, for example by a minimal amount of glue at the glue points 882. In this regard, see the upper part A of the figure. In a further alternative embodiment, the stabilization threads 87 are provided with an adhesive material 872. The visibility of the fixing points 881 in the virtual image is thus minimized. In this regard, see the lower part B of the figure. The fixing points 881 are located in the region of the gaps 871.
[0059] FIG. 12 shows an alternative embodiment with stabilization threads 87. Here, the stabilization threads are used in combination with adhesive material 872 for adjusting the setting angle γ of the slats 82. In this case, the upper side 821 of the slats 82 is displaced in the negative y-direction (arrows P1) and the lower side 822 of the slats 82 is displaced in the positive y-direction (arrows P2). The adjustment of the threads in the upper and lower part of the slats 82 may take place separately, see the left of the figure, or together, see the right of the figure. Return rollers 875, by means of which the coordinated movement of the stabilization threads 87 and therefore the variation of the setting angle γ are achieved, are schematically indicated on the right in the figure.
[0060] FIG. 13 shows a further alternative embodiment with stabilization threads 87. Here, the stabilization threads 87 are fastened with adhesive material 872 (not represented here) or with an adhesive coating 873 on the lower edge 8221 and the upper edge 8211 of the slats 82 at fixing points 881, without holes or other openings 88 for passage being needed in the slats 82.
[0061] FIG. 14 shows a further alternative embodiment with stabilization threads 87. Here, the stabilization threads 87 extend diagonally with respect to the slats 82 and therefore themselves form a grid. In this alternative embodiment as well, it is possible to arrange the stabilization threads in one, two or more planes. The gaps 871 have an irregular instead of rectangular shape here. It may be seen that the stabilization threads 87 are arranged in a frame 86. In the embodiment represented, the frame 86 is arranged on the antiglare element 81.
[0062] FIG. 15 shows a further alternative embodiment with stabilization threads 87. Here, the stabilization threads 87 are interwoven with one another. The figure shows an exemplary variant of the interweaving of the stabilization threads 87. In this case, an arbitrary stabilization thread 87 is interwoven with its two neighboring stabilization threads 87.
[0063] FIG. 16 shows an alternative embodiment with slats 82 arranged on a spring as a spring element 89. End regions 824 of the slats 82 are fixed on spring elements 89—predominantly compression springs—that have a particular inclination angle. This inclination angle may—if necessary—be varied by changing the diameter of the spring element 89 over the length. In the coil spring schematically represented here, the spacing PI (pitch) between two turns of the spring element 89 is constant. In the case of contraction of the compression springs by a pressure force FD (elongation in the case of extension springs), the inclination angle is varied equally over the entire length of the spring element 89 for all slats 82, and therefore so is their setting angle γ. The functional principle of the invention is shown here.
[0064] FIG. 17 shows the arrangement of slats 82 in a frame 86. The spring elements 89 are guided through a housing 891 in order to define their position over the entire length. In the design of the slats 82, it is taken into account that the slat spacing varies with the setting angle γ. Very precise adjustment of the angle is ensured (intended/actual deviation of the angle as minimal as possible) since springs may be manufactured precisely even in mass production. Very uniform adjustment of the setting angle γ for all slats 82 is highly advantageous particularly when being used for head-up displays (spring characteristic: equal angle in all turns).
[0065] FIG. 18 shows an alternative embodiment with an increased number of slats 82 per spring turn. The slat spacing is halved by placing slats 82 at a fastening location 893 on the upper and lower side of the spring turns. Here, a broad spring with a spring width BF is provided as the spring element 89.
[0066] FIG. 19 shows an alternative embodiment with spacers 892. In the exemplary embodiment represented here, a spacer 892 is provided, which is fastened on a fastening location 893 and on which the end region 824 of a slat 82 bears, while another slat 82 is fastened with its end region 824 directly on the fastening location 893. The use of spacers 892 allows the use of a less broad spring 89. Depending on the spring configuration, different adaptations are therefore provided.
[0067] In other words, the disclosure relates to the following: Antireflection is carried out in head-up displays by a so-called glare trap as an antiglare element 81 with a curved film. This design has a minimum installation depth corresponding to the film curvature as a consequence. Antireflection of head-up displays which use the windshield 31 as a mirror element, or projection surface, is carried out by slats 82 or a grid structure as a terminating module, see for example FIG. 5. Particularly for head-up displays with optical waveguides 5 in flat fitting, an antireflection solution is needed since flat glass components directly under the windshield 31 are particularly susceptible to perturbing reflections. This solution is preferably angle-adjustable in order to reduce shading in the eyebox 62. Slats 82 secured in a frame 86 are for example provided for the antireflection.
[0068] According to the disclosure, different setting angles γ of the slats 82 are made possible for different eyebox positions. This helps to avoid undesired shading. The disclosure proposes a secured solution for allowing the angle adjustment of the slats 82.
[0069] In head-up displays with optical waveguides 5 in flat fitting, an important module is fitted directly behind the windshield 31, so that high thermal stresses may occur, for example due to sunlight.
[0070] According to the disclosure, possible vibration of the slats 82 is reduced. Vibration may lead to distortion/curvature of the slats 82. This would lead to shading in the virtual image VB of the head-up display.
[0071] According to the disclosure, automobile-compatible angle adjustment, which is distinguished by thermal stability and longterm stability, is proposed for slats 82. Slats 82 without stabilization according to the disclosure are prone to oscillations (distortion/curvature) in the vehicle during driving. Advantages of the solutions according to the disclosure are, inter alia: thermal strength since stabilization threads 87 with a stable, temperature-independent behavior are used, or metal springs with a stable temperature-independent behavior as spring elements 89. Longterm stability: no relevant material aging takes place in stabilization threads 87, or in metal springs as a spring element 89. Uniform angle adjustment of all slats 82 in the component after setting up has been carried out. Only a single element is needed for the angle adjustment—each slat 82 does not need to be adjusted or controlled individually.
[0072] The solution according to the disclosure may also be employed in conventional head-up displays (for example based on mirrors). Here, the antiglare element 81 is preferably used as a terminating module. The solution according to the disclosure may also be used as adjustable antireflection inside modules. The antiglare element 81 is then integrated into the module. The solution according to the disclosure may also be used as privacy protection for displays (privacy filter) as an adaptive solution. The solution according to the disclosure may also be used as privacy protection for windows/domelight windows (smartwindows) for brightness adjustment. The solution according to the disclosure is also usable for military applications (reflection avoidance for telescopic sights) or for reflection avoidance for cameras and surveillance cameras.
