Indicator device with defect detection for anti-reflective louvers

Description

[0001] The present invention relates to a defect detection system for anti-reflective lamellae of a display device comprising an imaging unit with a display element for displaying an image and an optical unit for projecting the image onto a projection surface.

[0002] Such display devices can be used, for example, for a head-up display in a vehicle. A head-up display, also known as a HUD, is a display system that allows the viewer to maintain their line of sight, as the displayed content is projected into their field of vision. While such systems were originally used primarily in aviation due to their complexity and cost, they are now also being mass-produced in the automotive industry.

[0003] Head-up displays generally consist of an image generator, an optical unit, and a mirror unit. The image generator creates the image. The optical unit projects the image onto the mirror unit. The image generator is often also referred to as the image-generating unit or PGU (Picture Generating Unit). The mirror unit is a partially reflective, translucent panel. The viewer thus sees the content displayed by the image generator as a virtual image while simultaneously seeing the real world behind the panel. In automotive applications, the windshield often serves as the mirror unit, and its curved shape must be taken into account during the projection process. Through the interaction of the optical unit and the mirror unit, the virtual image is a magnified representation of the image generated by the image generator.

[0004] The viewer can only see the virtual image from within the so-called eyebox. The eyebox is defined as an area whose height and width correspond to a theoretical viewing window. As long as the viewer's eye is within the eyebox, all elements of the virtual image are visible. If the eye is outside the eyebox, however, the virtual image is only partially visible or not visible at all. Therefore, the larger the eyebox, the less restricted the viewer is in their choice of seating position.

[0005] The eyebox size of conventional head-up displays is limited by the size of the optical unit. One approach to increasing the eyebox size is to couple the light from the imaging unit into an optical fiber. The light coupled into the optical fiber undergoes total internal reflection at its interfaces and is thus guided within the fiber. Additionally, a portion of the light is coupled out at numerous positions along the direction of propagation. This process dilates the exit pupil. The effective exit pupil is composed of images of the aperture of the imaging system.

[0006] Against this background, US 2016 / 0124223 A1 describes a display device for virtual images. The display device comprises an optical waveguide that causes light arriving from an imaging unit and incident through a first light-incident surface to undergo repeated internal reflections in order to propagate away from the first light-incident surface in a first direction. The optical waveguide also causes a portion of the light guided in the optical waveguide to exit through regions of a first light-exit surface extending in the first direction. The display device further comprises a first light-incident-side diffraction grating that diffracts incident light to cause the diffracted light to enter the optical waveguide, and a first light-exiting diffraction grating that diffractes light incident from the optical waveguide.US 2012 / 0224062 A1 also shows a display device for virtual images using an optical fiber.

[0007] In the currently known design of such a device, where the optical waveguide consists of glass plates containing diffraction gratings or holograms, a problem arises if external light enters the device. Reflections of this external light can cause stray light to enter the user's eye. Furthermore, the contrast of the virtual image perceived by the user is reduced.

[0008] In conventional devices, reflective components are therefore sometimes tilted and combined with beam traps so that reflections do not reach the area where the driver's eye is expected. Alternatively, anti-reflective coatings are used and structural roughness is employed to reduce the reflection intensity.

[0009] Tilting the components significantly reduces installation space, which is limited in automobiles. Furthermore, component performance is generally reduced when installed at an angle. Layers and structures decrease the achievable intensity, while reflections typically remain clearly visible and considerably reduce contrast.

[0010] From DE 10 2018 213 061 A1, a device for generating a virtual image is known, comprising a display element for generating an image, an optical fiber for dilating an exit pupil, and a glare protection element downstream of the optical fiber in the beam path, which is designed as a louvered blind. From JP 2017-165 163 A, a head-up display is known that also uses fixed louvers during operation.

[0011] A device according to the preamble of claim 1 is known from DE 10 2015 224 939 A1. It is known from JP H09 21278 A to detect defective components of a device by means of an interrupted electrical circuit.

[0012] It is an object of the present invention to propose an improved device for generating a virtual image in which the influence of stray light is reduced.

[0013] This problem is solved by a device having the features of claim 1. Preferred embodiments of the invention are the subject of the dependent claims.

[0014] A device according to the invention for generating a virtual image has the following features: A display element for generating an image; and a glare protection element designed as a louvered blind, wherein the louvers are clamped in a tensioning device outside the device's field of view and bear against a contacting element under tension. This has the advantage that defect detection of a louver is possible via the contacting element. A defective louver, which is partially or completely torn, exhibits no tension and thus loses contact with the contacting element. A lack of contact indicates a defect, while existing contact indicates an intact louver. Advantageously, the tensioning device and contacting element are arranged outside the device's field of view, which prevents these elements from interfering with the beam path and thus the virtual image.

[0015] The contacting element is an electrically conductive spring that, in its compressed state and at rest, is electrically connected to a stop pole, and in its other state, electrically disconnected from the stop pole. The spring can be made of metal or a non-conductive or poorly conductive material with an electrically conductive layer or area. An advantage of this solution is that defect detection is not performed directly via the lamella, but rather by a separate element actuated by the lamella's preload. Therefore, no special design or material selection measures for the lamella are required.

[0016] Advantageously, the device features a fiber optic cable for dilating the exit pupil, to which the glare protection element is subordinate.

[0017] Advantageously, the lamella is electrically conductive at least in a portion located outside the viewing area of ​​the device. This has the advantage that the lamella itself establishes an electrical contact, preferably between the pre-tensioning device and the contacting element. The lamella can be electrically conductive along its entire length. For example, the lamella can be made of an electrically conductive material, such as an electrically conductive plastic, a metal foil, or another suitable electrically conductive material. Alternatively, the lamella can be coated with a suitably conductive material. Preferably, the lamella is electrically conductive only in the portion located outside the viewing area of ​​the device. In this case, no interference with the beam path caused by electrical conductivity occurs within the viewing area.Such an impairment could occur, for example, when using a metallic coating, which can lead to unwanted reflections if it is in the field of vision.

[0018] Advantageously, the lamella is electrically insulating on the side facing away from the contact element. Even if a lamella breaks off and comes into contact with a neighboring contact element, no electrical contact is made in this case, thus preventing a faulty signal.

[0019] Advantageously, the preloading device and contacting element are arranged offset in a direction perpendicular to the longest dimension of a lamella. The lamella is thus also preloaded in a direction perpendicular to the preload generated by the preloading device. This increases the contact pressure of the lamella against the contacting element, which improves the reliability of the electrical contact and thus the defect detection. Furthermore, the preload exerted by the preloading device can be very low, so that the actual preload applied during operation in the direction of the lamella's longest dimension is determined by the stress generated by the offset arrangement of the preloading device and contacting element. In this case, the preloading device acts purely as a holding device, which itself does not exert any specific preload.

[0020] The contact element is advantageously an adjustment mechanism for changing the angle of the slats. This has the advantage that a separate contact element is not required, as its function is taken over by an adjustment mechanism that is already present in many cases. The number of components required is thus reduced.

[0021] An inventive device advantageously comprises an electrical evaluation circuit with which several lamellae are monitored simultaneously. This has the advantage of keeping the circuit complexity low.

[0022] It is advantageous to provide the pre-tensioning device and / or the contacting element with an electrically conductive adhesive. This allows for easy establishment of electrical contact with the lamella or a contact point.

[0023] Further features of the present invention will become apparent from the following description and the attached claims in conjunction with the figures. Figure overview

[0024] Fig. 1 schematically shows a prior art head-up display for a motor vehicle; Fig. 2 shows an optical fiber with two-dimensional magnification; Fig. 3 schematically shows a head-up display with an optical fiber; Fig. 4 schematically shows a head-up display with an optical fiber in a motor vehicle; Fig. 5 schematically shows a head-up display with an optical fiber and an anti-reflective coating as a glare protection element; Fig. 6 shows an alternative optical fiber with two-dimensional magnification; Fig. 7 schematically shows a device for generating a virtual image; Fig. 8 shows a louver and a magnified section thereof; Fig. 9 shows a sectional view of the glare protection element in top view; Fig. 10 shows a solution for defect detection of louvers that does not fall under the definition of claim 1. Fig. 11 shows an adjustment mechanism; Fig. 12 shows the solution from Figur 10 in top view; Fig. 13 shows a solution according to the invention with a spring; Fig. 14 shows a solution according to the invention with a spring; Fig. 15 shows an electrical evaluation circuit; Fig. 16 shows a glare protection element in top view; Fig. 17 shows a glare protection element; Fig. 18 shows a schematic spatial representation of a pretensioning device; Fig. 19 shows a pretensioning device designed as a spring; Fig. 20 shows embodiment variants; Fig. 21 shows a further embodiment variant. Character description

[0025] To better understand the principles of the present invention, embodiments of the invention are explained in more detail below with reference to the figures. The same reference numerals are used in the figures for identical or equivalently acting elements and are not necessarily described again for each figure. It is understood that the invention is not limited to the embodiments shown and that the described features can also be combined or modified without departing from the scope of protection of the invention as defined in the appended claims.

[0026] First, we will use the following as a starting point Figuren 1 bis 4 The basic concept of a head-up display using fiber optics will be explained.

[0027] Fig. 1 Figure 1 shows a schematic diagram of a state-of-the-art head-up display for a motor vehicle. The head-up display comprises an image generator 1, an optical unit 2, and a mirror unit 3. A beam of light SB1 originates from a display element 11 and is reflected by a folding mirror 21 onto a curved mirror 22, which reflects it towards the mirror unit 3. The mirror unit 3 is represented here as the windshield 31 of a motor vehicle. From there, the beam of light SB2 travels towards the eye 61 of a viewer.

[0028] The viewer sees a virtual image VB, which is located outside the vehicle, above the hood or even in front of the vehicle. Through the interaction of optical unit 2 and mirror unit 3, the virtual image VB is a magnified representation of the image displayed by display element 11. Here, a speed limit, the current vehicle speed, and navigation instructions are symbolically represented. 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 visible or not visible at all. The larger the eyebox 62, the less restricted the viewer is in choosing their seating position.

[0029] The curvature of the curved mirror 22 serves two purposes: firstly, to reshape the beam path, thus providing a larger image and a larger eyebox 62; and secondly, to compensate for the curvature of the windshield 31, so that the virtual image VB corresponds to a magnified reproduction of the image displayed by the display element 11. The curved mirror 22 is rotatably mounted by means of a bearing 221. This rotation of the curved mirror 22 allows the eyebox 62 to be moved, thereby adjusting its position to that of the eye 61. The folding mirror 21 ensures that the path traveled by the beam SB1 between the display element 11 and the curved mirror 22 is long, while simultaneously maintaining the compact size of the optical unit 2. The optical unit 2 is separated from its surroundings by a transparent cover 23.The optical elements of the optical unit 2 are thus protected, for example, against dust present in the vehicle's interior. Furthermore, the cover 23 has an optical film 24 or a coating designed to prevent incident sunlight SL from reaching the display element 11 via the mirrors 21, 22. Otherwise, the display element 11 could be temporarily or permanently damaged by the resulting heat generation. To prevent this, for example, the infrared component of the sunlight SL is filtered out by the optical film 24. A glare shield 25 serves to block light incident from the front, preventing it from being reflected by the cover 23 towards the windshield 31, which could cause glare for the viewer. In addition to sunlight SL, light from another interfering light source 64 can also reach the display element 11.

[0030] Fig. 2 Figure 5 shows a schematic spatial representation of an optical waveguide 5 with two-dimensional magnification. In the lower left area, a coupling hologram 53 can be seen, by means of which light L1 coming from an imaging unit (not shown) is coupled into the optical waveguide 5. Within the waveguide, the light propagates upwards and to the right in the drawing, corresponding to arrow L2. In this area of ​​the optical waveguide 5, there is a folded hologram 51, which acts similarly to many semi-transparent mirrors arranged one behind the other and generates a beam of light that is broadened in the Y-direction and propagates in the X-direction. This is indicated by three arrows L3.In the right-hand portion of the optical waveguide 5 shown in the figure, there is an output coupling hologram 52, which also functions similarly to many semi-transparent mirrors arranged one behind the other, and couples light upwards out of the optical waveguide 5 in the Z-direction, as indicated by arrows L4. This results in a broadening in the X-direction, so that the original incident light beam L1 exits the optical waveguide 5 as a light beam L4 enlarged in two dimensions.

[0031] Fig. 6 shows in schematic representation a to Fig.2 Alternative optical waveguides with two-dimensional magnification. Here, the output hologram 52 is designed such that it couples light out not perpendicular to the surface of the optical waveguide 5, but at an angle to the Z-direction, as shown by the arrows L4. This allows the optical waveguide 5 to be arranged according to the available installation space without having to take into account a perpendicular exit of the light beam magnified in two dimensions.

[0032] Fig. 3 The figure shows a three-dimensional representation of a head-up display with three optical fibers 5R, 5G, 5B, arranged one above the other, each representing one of the primary colors: red, green, and blue. Together, they form optical fiber 5. The holograms 51, 52, 53 contained within optical fiber 5 are wavelength-dependent, so that one optical fiber 5R, 5G, 5B is used for each of the primary colors. Above optical fiber 5, an image generator 1 and an optical unit 2 are shown. The optical unit 2 has a mirror 20, by means of which the light generated by the image generator 1 and shaped by the optical unit 2 is deflected towards the respective coupling hologram 53. The image generator 1 has three light sources 14R, 14G, 14B for the three primary colors. It can be seen that the entire depicted unit has a low overall height compared to its light-emitting surface.

[0033] Fig. 4 A head-up display in a motor vehicle shows something similar to Fig. 1 Here, however, the system is shown in a three-dimensional representation and with an optical waveguide 5. The schematically indicated image generator 1 is visible, which produces a parallel beam of light SB1 that is coupled into the optical waveguide 5 via the mirror plane 523. The optical unit is not shown for the sake of simplicity. Several mirror planes 522 each reflect a portion of the incident light towards the windshield 31, the mirror unit 3. From there, the light is reflected towards the eye 61. The viewer sees a virtual image VB above the hood or, at a greater distance, in front of the vehicle.

[0034] Fig. 5 Figure 1 schematically shows a head-up display with a fiber optic cable 5 and an anti-reflective coating as a glare protection element 81, a windshield 31, and a viewer with an eye 61. The fiber optic cable 5 is arranged directly on the glare protection element 81.

[0035] Fig.7 shows a device in which an optical fiber 5 is used accordingly Fig.6 The image generator 1 with display element 11 and the optical fiber 5 are visible. Light L4 emerges from the optical fiber 5 at an angle α to the normal N, where the angle α is greater than 0°. The emerging light L4 strikes the light-intake surface 85 of a louver 83, whose slats 82 are arranged parallel to the emerging light L4, allowing it to pass unhindered through the spaces 84 between the slats 82. The light L6 emerging from the louver 83 strikes the windshield 31 at an angle β and is reflected by it, reaching the eye 61 of a vehicle occupant, in this case the driver, as light L8. The driver thus sees a virtual image VB. In this embodiment, the louver 83 forms the cover of the optical unit; a separate cover element is not provided.The blind 83 can therefore come into direct contact with objects or people inside the vehicle. Damage to the blind 83 is thus possible. The blind 83 is therefore designed to be removable, so that it can be easily dismantled and replaced with a new or repaired blind 83 if necessary.

[0036] Fig.8 Figure 83 shows the blind 83 and a close-up detail 830. The slats 82 are visible, allowing light L5, which originates from the optical fiber 5 and travels essentially parallel to the slats 82, to pass through. Stray light SL, which does not travel parallel to the slats 82, is blocked by the slats 82. The slats 82 are spaced AL apart and are inclined at an angle α relative to the normal NJ to the light-intake surface 85 of the blind 83. The slats have a height HL and a thickness DL, where the height HL is a multiple of the thickness DL. The angle α corresponds to that of the light exiting the optical fiber 5 when its light-exit surface 54 and the light-intake surface 85 of the blind 83 are parallel to each other. For non-parallel arrangements, these angles must be adjusted accordingly. The angle α depends, among other things, on the driver's position and viewing angle.For different vehicle types or different windshield 31 inclinations, the distance AL must be adjusted, among other things. The louvers 82 are preferably designed to be non-reflective, i.e., essentially black. If the louvers are arranged to be tiltable, meaning that the angle α is variably adjustable during operation, they can be set to different positions of the eyebox or to different positions of the eye 61 within the eyebox. This requires that the light coming from the optical fiber 5 covers a certain angular range, so that for each set angle α, light rays parallel to the louvers also reach them and thus pass through them.

[0037] Fig.9 Figure 1 shows a cross-sectional view of a glare protection element 81 in top view. The louvers 82 run parallel to each other through the viewing area 860, through which the light L5 coming from the optical fiber 5 passes through the glare protection element 81. The louvers 82 are attached at both ends in the x-direction in a mounting area 861 located outside the viewing area 860. The mounting area 861 is shown here only schematically as a black area; details of the attachment of the louvers 82 in this area are described below.

[0038] Fig.10 Figure 1 shows a solution for the defect detection of slats that does not fall under the definition of claim 1. A slat 82 of the blind 83 is attached to a tensioning device 831, which serves as a holding mechanism for the slat 82. In the figure, the slat 82 extends to the right, runs along an adjustment mechanism 92, and then exits the mounting area 861 into the viewing area 860 of the device. On the opposite side, the slat is also attached to a corresponding holding mechanism outside the viewing area 860, which is not shown here for clarity. In this embodiment, the adjustment mechanism 92 also serves as a contacting element 90. It is in contact with an electrically conductive coating of the slat 82, which is arranged in the slat area 825 on the side facing away from the viewer and facing a contact surface 921 of the adjustment mechanism.The pre-tensioning device 831 and the adjusting mechanism 92 are electrically conductive or equipped with corresponding electrically conductive elements, which are not shown here for the sake of simplicity. Both are electrically connected to an evaluation circuit 94. This is indicated schematically by electrical leads 941, a battery 942, and a lamp 943. As long as the lamella 82 is under mechanical tension and thus in contact with the contact surface 921, the electrical circuit is closed, and the lamp 943 illuminates. If the lamella 82 breaks, it loses mechanical tension, no longer in contact with the contact surface 921, and the electrical circuit is no longer closed. A non-illuminated lamp 943 indicates the detected defect. The contact surface 921 is shown vertically in the figure.It is intended that it can also be tilted using the adjustment mechanism, which also changes the angle of attack of the lamella 82 accordingly.

[0039] Fig.11 Figure 1 shows a schematic side view of an adjustment mechanism 92. The contact surface 921 is visible, against which the lamella 82 rests with its electrically conductive coating 823, located on the side facing the contact surface 921. In this representation, the contact surface 921 is in contact with a sliding surface 922 on its underside. The sliding surface 922 can be moved. A movement to the left is shown with a dashed line. During this movement, the lower end of the contact surface 921 also moves to the left, while its upper end remains unchanged. The contact surface 921 now exhibits a tilt by an angle α to the vertical. The lamella 82, which rests against it, is also tilted by an angle α due to its contact with the contact surface 921, as shown in the dashed line.

[0040] Fig.12 shows the solution of Fig.10 In a top view, it can be seen that the pretensioning device 831 and the adjusting mechanism 92 are arranged slightly offset from each other. The lamella 82 thus has an offset in its lamella region 825. The electrically conductive coating 823, located on the side facing the pretensioning device 831, can be seen in this lamella region 825.

[0041] Fig.13 Figure 1 shows a solution according to the invention with a spring 91 as a contacting element 90. The spring 91 is provided with an electrically conductive layer 911, which is connected on one side to a first electrical contact and on the other side, when in contact with an electrically conductive stop pole 914, with a second contact 913. In this figure, the spring 91 is subjected to a contact force FA by the lamella 82 in contact with it, which is greater than the spring force FF, thereby pressing the spring 91 against the stop pole 914.

[0042] Fig.14 Figure 1 shows the solution according to the invention with a spring 91 from the preceding figure, but here with a lamella 82 that is torn at a point not shown and is therefore no longer under preload. It is therefore no longer in contact with the spring 91, which is in its relaxed state, in which it is separated from the stop pole 914. The electrical circuit is thus open.

[0043] According to a first embodiment, the electrical switch formed by the spring 91 and the stop pole 914 is arranged between a preloading device 831 and an adjusting mechanism 92. In comparison to the one in Fig.10 In the illustrated embodiment, the evaluation circuit 94 is then to be connected accordingly to spring 91 and stop pole 914; electrical conductivity of the lamella 82 is not required in this case. The lamella 82 rests against the spring 91 in its lamella area 825.

[0044] In another variant, the lamella 82 is tensioned by means of the switch. In this case, the spring 91 serves as a pre-tensioning device. If the lamella 82 breaks, the switch closes again.

[0045] Fig.20 This schematically illustrates these design variants. The right-hand section shows a top view of the lamella 82 attached to the pre-tensioning device 831, which rests against the spring 91. The spring 91 extends essentially perpendicular to the plane of the drawing, but its portions above and below the plane are also indicated. The spring exerts a spring force FF1 on the lamella 82. The electrical switch is held open by the tensioned lamella 82. The tension of the spring 91 is applied via the lamella 82, and the lamella 82 is not, or only minimally, tensioned from a straight line. The intended top view of the lamella 82 is a straight line. If any deviation occurs at all, it is minimal, as exaggerated here, whereas in the left-hand variant, the deviation is utilized and increased. In the left part of the Fig.20 A holding device 832 is arranged instead of the previously described pre-tensioning device 831. The pre-tensioning is provided by the spring 91, which exerts a greater spring force FF2 on the lamella 82, indicated here by a longer arrow. This force serves to tension the lamella 82. The lamella 82 is thus tensioned by means of the switch. The tensioning is applied via the switch, and the lamella 82 is thereby deliberately tensioned or pulled out of a straight line. The intended top view of the lamella 82 is therefore not a straight line.

[0046] Fig.21 Figure 1 shows another embodiment in schematic representation. The lamellae 82 and the springs 91 attached to them are visible. The springs 91 are preferably made of metal and are connected to a common base 910. The base 910 is connected to an evaluation circuit 94. Stop poles 914 are connected to a common contact 913 of the evaluation circuit. The three lamellae 82 shown on the left are intact; they exert a force on the corresponding springs 91 sufficient to keep each spring away from its associated stop pole 914. The switches formed by each spring 91 and its associated stop pole 914 are thus open. The rightmost lamella 82 is defective; it cannot exert a sufficient force on the corresponding spring 91, causing it to contact the associated stop pole 914 and close the circuit. This is indicated by a stylized lightning bolt BS.

[0047] Fig.15 Figure 1 schematically shows an electrical evaluation circuit 94 in two variants. A battery 942 is electrically connected to the pre-tensioning device 831 by means of an electrical line 941. The pre-tensioning device 831 is itself electrically conductive or has electrical connections to the lamellae 82 and their electrically conductive coating 823. The coatings 823 of four lamellae 82 (not shown here) are shown schematically. The corresponding contact elements 90 are represented as electrical switches. In the first variant, each of the contact elements 90 is connected to a lamp 943. A defect in each individual lamellae can thus be detected. The right part of the figure shows an alternative variant in which all contact elements 90 are connected to a single measuring device 944.If one or more of the contact elements 90 are open because the corresponding slat 82 is torn, the current flow through the measuring device 944 changes, and a defect is detected. Even if this variant does not detect which slat 82 is torn, the defect detection still serves to replace the entire blind 83 with one with intact slats 82, if necessary.

[0048] In other words, the invention relates to the following: Anti-reflective coating in head-up displays is achieved via a so-called glare trap (glare protection element 81) with a curved film. This design results in a minimum installation depth corresponding to the film curvature. Anti-reflective coating of head-up displays that use the windshield 31 as a mirror element or projection surface is achieved by means of louvers 82 or a grid structure as a final assembly, see for example [reference]. Fig.5 A solution for anti-reflective coating is particularly needed for head-up displays with fiber optics 5 in flat installations, as flat glass components directly under the windshield 31 are especially susceptible to disruptive reflections. This solution is preferably angle-adjustable to reduce shadowing in the eyebox 62. Anti-reflective louvers 82 are provided. Such a solution requires louver crack detection to protect the driver from reflections.

[0049] For safety reasons, any potential damage to one or more louvers 82 must be detected by the vehicle both before and during driving and reported back to the driver to protect them from potential reflections. Currently, there is no reliable solution for detecting a louver tear. The louvers 82 are installed directly behind the windshield 31, meaning they can be subjected to high thermal stresses, such as those caused by sunlight. The assembly containing the louvers 82 is within the driver's reach and is also exposed to cleaning and / or other cleaning activities. Therefore, damage to the louvers, which could lead to a louver breaking off, cannot be ruled out with sufficient certainty. Detection and warning are thus necessary for safety reasons.

[0050] According to at least one embodiment of the invention, slats 82 are each fastened to the pretensioning device 831 by retaining mechanisms and clamped between the retaining mechanisms. Adjustment mechanisms 92 are inserted between the retaining mechanisms to ensure the angular adjustability of the slats 82.

[0051] As holding mechanisms, for example, the preload devices 7, 7' described in the following figures can be used in one embodiment. This embodiment combines the holding of the lamellae 82, the preloading of the lamellae 82, and the adjustment of the angle of attack α of the lamellae 82 in a single component. For defect detection, the embodiment of the contacting element 90 described above is used as a spring 91.

[0052] Fig. 16 Figure 1 shows a top view of a glare protection element 81, with force applied in the lower part of the figure and without in the upper part. The glare protection element 81 has a spring-type pretensioning device 7 on the left and a corresponding pretensioning device 7' on the right. These have first planes 71, 71' and second planes 72, 72'. Slats 82 are tensioned between the pretensioning devices 7, 7'. In the embodiment shown, the slats 82 are attached at their ends to transition ramps 73, which are therefore not visible in the figure. In the upper part of the figure, it can be seen that the planes 71, 71' and 72, 72' are not displaced relative to each other. In the lower part of the figure, a force F acts on the planes 72, 72', causing them to be displaced relative to the first planes 71, 71'. The transition ramps 73 change their angle, and thus the slats 82 also change.

[0053] Fig. 17 Figure 1 shows a schematic three-dimensional view of a glare protection element 81 as shown in the preceding figure. Two pretensioning devices 7, 7', stylized only by lines, with their transition slopes 73 to which the louvers 82 are attached, can be seen. The angle of attack α is also shown.

[0054] Fig.18 Figure 1 shows a schematic spatial representation of a prestressing device 7, as shown in the two preceding figures, in its three-dimensional form. The spatially separated planes 71 and 72 are visible. The first plane 71 is located above the second plane 72. The transition slopes 73 run obliquely from the upper left to the lower right. At their upper end, they are connected by webs 711, and at their lower end by webs 721. A perforation 731, 732 is located in the transition area between webs 711 and 721 and the transition area 73. If the upper plane 71 is displaced to the left by the application of a force, the angle of attack α decreases, the transition slope 73 is less inclined, and consequently, so is the respective lamella in contact with it (not shown here). If the upper plane 71 is displaced to the right by the application of a force, the angle of attack α increases, the transition slopes 73 become steeper, and consequently, so do the corresponding lamellae.The one-piece design of the spring 7 ensures that the transition slopes 73 are always parallel to each other in this case, i.e., they have the same angle of attack α.

[0055] According to one embodiment, an electrically conductive coating 823 is applied exclusively to the back of the lamella 82, i.e., on its side facing the adjustment mechanism 92. The coating 823 is thus located outside the field of vision 860 of the device, which is designed, in particular, as a waveguide head-up display. This ensures an electrically conductive connection between the preloading device 831,7, acting as a holding mechanism, and the contacting element 90, designed as the adjustment mechanism 92 or as a spring 91. This electrically conductive connection can be monitored from the vehicle. Depending on the evaluation circuit 94 used, the lamellae 82 are monitored individually or in groups for lamella cracks. Either a complete break or a partial change in resistance is detected.

[0056] In the event of a lamella tear, contact between the lamella 82 and the contacting element 90, which is designed, for example, as a spring 91 or an adjusting mechanism 92, is lost. This loss of contact can be accelerated by a slight displacement of the retaining mechanism, for example, the preload device 831, 7, relative to the contacting element 90, such as the spring 91 or adjusting mechanism 92. To mitigate the loss of contact in the event of a lamella tear, the geometric properties can be adapted, for example, by appropriately arranged grooves.

[0057] In another embodiment, both the holding mechanism and the contacting element 90, i.e., spring 91 or adjusting mechanism 92, can be partially insulated. This can be achieved, for example, by applying an insulating layer in combination with partially damaging the insulating coating.

[0058] The electrical contact in the holding mechanism can, for example, be used as described in the article. Fig. 19 As described, this can be achieved by using a partially applied electrically conductive adhesive 751, 752. A corresponding adhesive can also advantageously be provided for the contacting element 90.

[0059] Fig. 19Figure 1 shows a spring-shaped preload device 7 in a top view. The preload device 7 is shown here in its two-dimensional form, as it appears before being formed into its three-dimensional shape during production. The first plane 71 and the second plane 72 are visible; in the two-dimensional form, they both lie in the same plane, here the plane of the drawing. Webs 711 extend from the first plane 71 towards the second plane 72. Webs 721 extend from the second plane 72 towards the first plane 71. Transition ramps 73 connect each web 711 to a web 721. A perforation 731 is arranged at the transition between a web 711 of the first plane 71 and the transition ramp 73. A perforation 732 is arranged at the transition between a web 721 of the second plane 72 and the transition ramp 73.A kink forms at this perforation 731, 732 when the spring 7 is transferred from its illustrated two-dimensional shape to its three-dimensional shape. The transition chamfer 73 then stands at an angle to the planes 71, 72 and forms a substantially planar surface between the perforations 731, 732. For the manufacture of the spring of the preloading device 7, preferably a thin, rectangular sheet or a corresponding foil is used, which is cut, punched, or otherwise suitable processed according to a cutting contour 70. The left part of the figure shows, by way of example, a groove 734, which is provided either instead of or in addition to the perforation 731. Edge recesses 735 are also shown as an alternative to the perforation 731. It is understood that normally only either perforations 731, grooves 734, or edge recesses 735 are provided in a preloading device 7.However, a combination of two or three of these elements can also be a sensible design option.

[0060] Two variants of a partially applied electrically conductive adhesive 751, 752 are shown as examples. In a first variant, a strip of electrically conductive adhesive 751 is applied to each transition slope 73, with this strip extending from the transition slope 73 into the region of the first plane 71. In the region of the transition slope 73, the adhesive 751 is then in electrical contact with a lamella 82 (not shown here), and in the region of the plane 71 with a contact point (not shown here). Advantageously, the lamella 82 and / or the contact point are attached to the prestressing device 7 by means of the adhesive. The adhesive 751 can be applied to the two-dimensional shape of the prestressing device 7 shown here, i.e., before it is folded three-dimensionally, and then connected to the lamella 82 or the contact point.After the adhesive 751 has cured, the conductive track formed by it, which connects the lamella 82 to the contact, is also cured, thus preventing unwanted adhesion to other components. The electrically conductive adhesive 751 can also be applied shortly before the lamella 82 and / or the contact is attached. This has the advantage that a fast-drying adhesive can be used as the adhesive 751, and that handling during assembly is not complicated by unintentional adhesion of the already applied but not yet cured adhesive. In a second variant, a strip of electrically conductive adhesive 752 is provided, which extends over a longer section of the first layer 71 and has several branches, each ending on a transition chamfer 73. In this way, several lamellae 82 in the assembly can be detected for lamella cracks.

[0061] Contact between the upper surface of the lamella and a subsequently arranged element of the adjustment mechanism 92 is prevented by coating the lamella 82 on one side with an electrically conductive coating 823.

[0062] One variant provides that the lamella 82, in its assembled state, depresses a spring 91, and the contact pressure ensures that a stop pole 914 makes contact with the spring 91. The springs 91 are therefore not rigidly connected to the stop pole 914. In the event of a lamella breakage, the spring 91 returns to its uncompressed starting position due to the lack of contact pressure. The spring 91 and the stop pole 914 are no longer in contact.

[0063] Another variant provides that the switch, implemented for example by means of the spring 91, closes when a lamella 82 tears without the preload of the lamella, and is opened by the lamella tension. As soon as a lamella 82 tears, the contact closes and the event is detected.

[0064] The necessary conductive coating 823 of the louvers 82 is applied outside the visible area 860 of the glare protection element 81. Therefore, the coating 823 does not need to fulfill any special optical properties. The necessary properties for glare prevention and increased conductivity, including conductivity stability over different temperature ranges, are thus spatially separated.

[0065] In the event of a lamella tear, the lamella 82 loses contact with the contacting element 90, for example the spring 91 or the adjustment mechanism 92. This allows a clear digital on / off signal to be detected, and not a potentially ambiguous change in a signal, as is the case with other solutions.

[0066] The relevant electrical resistance of the louver area 825 is low and significantly lower than the resistance of an entire louver over its full length without an additional coating to increase conductivity. A further advantage of the variant in which an electrically conductive coating 823 is arranged in the louver area 825, i.e., outside the visible area 860, is that temperature changes caused by solar radiation, which can affect electrical conductivity, or other conductivity changes caused by light, have no or only a minor influence on the electrical conductivity of an electrical conductor arranged exclusively in the mounting area 861, regardless of whether this conductor is an electrically conductive coating 823, electrically conductive material of the louver 82, or another type of electrical conductor.

[0067] The solution according to the invention can also be applied in conventional head-up displays (for example, mirror-based ones). Here, the glare protection element 81 is preferably used as a final assembly. The solution according to the invention can also be used as an adjustable anti-reflective coating within assemblies. The glare protection element 81 is then integrated into the assembly.

Claims

1. A device for generating a virtual image (VB), having: - a display element (11) for generating an image; and - an antiglare element (81), which is configured as a shutter (83) comprising lamellae (82), wherein - the lamellae (82) are braced in a pretensioning device (831) outside of a visible region (860) of the device, characterized in that the lamellae (82) bear under prestress against a contacting element (90,91,92), and - the contacting element (90,91,92) is connected to an evaluation circuit (94), which detects a defect of a lamella (82), and the contacting element (90) is a spring (91) with an electrically conductive embodiment, which is electrically connected to a stop terminal (914) in a tensioned state or in a rest state and which is electrically separated from the stop terminal (914) in the corresponding other state.

2. The device as claimed in claim 1, having an optical waveguide (5, 510, 520) for expanding an exit pupil, wherein the anti-glare element (81) is arranged downstream of the optical waveguide (5) in the beam path.

3. The device as claimed in claim 1 or 2, wherein the lamella (82) has an electrically conductive embodiment, at least in a lamella region (825) situated outside of the visible region (860) of the device.

4. The device as claimed in claim 3, wherein the lamella (82) has an electrically insulating embodiment on its side facing away from the contacting element (90,92).

5. The device as claimed in any of the preceding claims, wherein the pretensioning device (831,7) and contacting element (90,92) are arranged offset from one another in a direction (x) perpendicular to the longest extent of a lamella (82).

6. The device as claimed in any of the preceding claims, wherein the contacting element (90) is an adjustment mechanism (92) for changing the angle of incidence (α).

7. The device as claimed in any of the preceding claims, wherein an electrical evaluation circuit (94) is provided, by means of which multiple lamellae (82) are jointly monitored.

8. The device as claimed in any of the preceding claims, wherein the pretensioning equipment (823,7) and / or the contacting element (90,91,92) are / is provided with an electrically conductive adhesive (751,752).