Display device for a motor vehicle

Abstract

The present disclosure relates to a display device (2) for a motor vehicle (1) comprising at least a light guide assembly (20), a display element (23) and a light source (24). The light guide assembly (20) comprises a light output area (22) and a light input area (21). The display element (23) is arranged in relation to the light output area (22). The light output area (22) is configured to extract coupled light (11, 12) from the light guide assembly (20) to illuminate the display element (23). The light guide assembly (20) is configured to guide ambient light (11) coupled via the light coupling area (21) into the light coupling area (22) via a first lateral side. The light source (24) is arranged on the light guide assembly (20) such that the light guide assembly (20) is configured to guide artificial light (12) from the light source (24) into the light coupling area (22) via a second lateral side. The light guide assembly (20) includes a controllable light valve (30) which is arranged between the light coupling area (21) and the light coupling area (22).

Description

Technical area

[0001] The invention relates to a display device for a motor vehicle and a motor vehicle with a corresponding display device. State of the art

[0002] DE 100 26 892 A1 discloses an instrument cluster for a commercial vehicle or a bus, which includes a liquid crystal display (LCD). The instrument cluster further comprises a light guide plate with a structure for coupling out light, which structure is arranged in a light extraction region behind the liquid crystal display for background lighting. Light-emitting diodes can be arranged laterally on the light guide plate, with which artificial light can be coupled into the light guide plate and guided into the light extraction region. The light guide plate is furthermore guided out of the instrument cluster as a single-piece or multi-piece light guide system. The light guide plate leading out of the instrument cluster ends in the region of an opening in an instrument panel, which is arranged aligned with a windshield of a vehicle.Ambient light can be captured by the light guide plate through the opening and guided to the light extraction area so that the liquid crystal display can be backlit with ambient light.

[0003] A disadvantage of this state of the art is that the light guide system for the backlighting of a display device is not suitable for use in a passenger car simply by adjusting its dimensions. In particular, unwanted light reflections in the windshield, caused, for example, by the lighting during nighttime operation, cannot be effectively suppressed due to the geometric conditions of a car. Brief description of the invention

[0004] Against this background, the object of the invention is to further develop a display device with dual illumination, which can be operated with light from an environment and an artificial light source, in such a way that it can also be used for passenger cars.

[0005] Accordingly, a display device for a motor vehicle according to the main claim and a motor vehicle according to the secondary claim are proposed. Further embodiments are the subject of the respective dependent claims.

[0006] According to a first aspect of the invention, the object is achieved by a display device for a motor vehicle, which comprises at least one light guide assembly, a display element and a light source.

[0007] The motor vehicle is, in particular, a passenger car. The display can be a liquid crystal display or, in particular, a TFT screen for graphically displaying color image information.

[0008] The light-guiding assembly comprises a light output region and a light input region, with the display element being arranged aligned with the light output region. The light output region is designed to output coupled-in light from the light-guiding assembly to illuminate the display element.

[0009] The light guide assembly is designed to guide ambient light coupled via the light coupling region into the light coupling region via a first lateral side. The light source is arranged on the light guide assembly in such a way that the light guide assembly is designed to guide artificial light from the light source into the light coupling region via a second lateral side.

[0010] The light guide assembly further comprises a controllable light valve arranged between the light coupling region and the light coupling region.

[0011] The maximum brightness of a backlight for a display device is generally designed for sunlight or daylight conditions in order to ensure sufficiently good readability. The display device according to the invention makes it possible to use ambient light, i.e. sunlight or daylight, as a natural resource for background lighting in a car, so that the artificial light sources of a backlight unit can be smaller than in conventional display devices. While sunlight or daylight is in use, the backlight unit is switched off. The backlight unit is only required when the sunlight or daylight is no longer sufficient. The energy consumption of a display device according to the invention can therefore be reduced compared to conventional display devices.

[0012] With the controllable light valve of the display device according to the invention, stray light can be effectively suppressed, which would otherwise be guided from the background lighting unit via the light guide assembly out of the light coupling area.

[0013] The backlight unit is preferably automatically controllable by means of a controller and an associated brightness sensor. Furthermore, the controller is configured to close the controllable light valve as soon as the backlight unit is activated.

[0014] According to a further development of the display device, the controllable light valve can comprise a liquid crystal assembly which can be switched to be light-transparent or non-light-transparent depending on an applied voltage.

[0015] The liquid crystal assembly is preferably switched to opaque when a certain voltage level is applied. This allows the light sources of the backlight unit and the liquid crystal assembly to be switched using the same voltage signal.

[0016] According to a further development, the light guide assembly can comprise a first light guide plate and a second light guide plate, wherein the liquid crystal assembly is arranged between the first light guide plate and the second light guide plate.

[0017] Alternatively, the liquid crystal assembly may be arranged at the light coupling region of the light guide assembly.

[0018] Furthermore, an anti-reflective layer can be arranged on an upper side of the liquid crystal assembly.

[0019] According to an alternative development of the display device, the controllable light valve can have a mechanically adjustable closure element which is arranged on the light coupling region of the light guide assembly.

[0020] According to an alternative development of the display device, the controllable light valve can comprise a rotatable mirror element, wherein the light guide assembly further comprises a first light guide plate and a second light guide plate. The light coupling region is arranged on the first light guide plate, and the light coupling region is arranged on the second light guide plate. The rotatable mirror element has a first mirror surface and a second mirror surface and is adjustable about a rotation axis between a first position and a second position. The first light guide plate, the second light guide plate, and the rotatable mirror element are arranged aligned with one another such that, in the first position, ambient light coupled in from the first light guide plate is directed via the first mirror surface into the second light guide plate.In the second position, coupled artificial light is reflected back from the second light guide plate through the second mirror surface into the second light guide plate.

[0021] According to an alternative development of the display device, the controllable light valve can comprise a circular-cylindrical light guide, wherein a cylindrical shell of the circular-cylindrical light guide is divided circumferentially into two opaque regions and two translucent regions. The two opaque regions and the two translucent regions are each arranged opposite one another with respect to a cylinder axis. The circular-cylindrical light guide is rotatably adjustable around the cylinder axis between a closed position and an open position.

[0022] According to a further development, the display device can further comprise at least one optoelectronic sensor and an associated comparator circuit, wherein the comparator circuit is designed to compare an electrical signal from the optoelectronic sensor with a threshold value and to activate the light source and / or to close the controllable light valve when the signal falls below the threshold value.

[0023] The comparator circuit is designed to deactivate the light source and / or open the controllable light valve when a threshold value is exceeded.

[0024] When using ambient light as backlighting, the light source for coupling artificial light into the light guide assembly can be deactivated. The LED-based backlight unit is only required when the ambient light is no longer sufficient to backlight the display element.

[0025] The optoelectronic sensor and the associated comparator circuit enable automatic switching between ambient light operation (day mode) and artificial light operation (night mode) of the display device.

[0026] The optoelectronic sensor can preferably be arranged on the fiber optic assembly such that the light valve is not located in an optical path between the light coupling region and the optoelectronic sensor. Thus, ambient light coupled into the fiber optic assembly can be detected independently of the switching state of the light valve.

[0027] Preferably, the display device can further be assigned a second optoelectronic sensor with a second comparator circuit, wherein the second comparator circuit is designed to compare an electrical signal from the second optoelectronic sensor with a second threshold value and to output a signal for closing the controllable light valve when the second threshold value is undershot.

[0028] The two optoelectronic sensors and the associated comparator circuits enable automatic switching between ambient light operation (day mode), artificial light operation (night mode) and mixed operation with ambient and artificial light (mixed mode) of the display device.

[0029] The second optoelectronic sensor can be a light sensor for automatic control of vehicle lighting, preferably arranged in combination with a rain sensor on the windshield of a motor vehicle. Mixed operation with ambient and artificial light can be used in ambient light conditions that are no longer sufficient to backlight the display element, but are not yet so dark that light emerging from the light coupling area is perceived as stray light.

[0030] According to a second aspect of the invention, the object is achieved by a motor vehicle having a display device according to the first aspect of the invention and a dashboard, wherein the dashboard has a front opening and an upper opening. A display element of the display device is arranged in alignment with the front opening. A light coupling region of a light guide assembly is arranged in alignment with the upper opening of the display device.

[0031] The motor vehicle can, in particular, be a passenger car. Due to the typical dimensions of a passenger car, an upper side of the dashboard can be aligned essentially parallel to a horizontal plane of the vehicle. The upper opening can thus be aligned on the upper side of the dashboard toward a windshield. Short description of the drawing figures

[0032] Further features and details emerge from the following description, in which at least one exemplary embodiment is described in detail—possibly with reference to the drawing. Described and / or illustrated features constitute the subject matter, either individually or in any meaningful combination, possibly independently of the claims, and may, in particular, also be the subject of one or more separate applications. Identical, similar, and / or functionally identical parts are provided with the same reference numerals. Here, the following are shown: Fig. 1 shows a longitudinal section through a car with a dashboard and a display device; Fig. 2 shows a longitudinal section through a display device according to the prior art; Fig. 3 shows an operation of the display device in a day mode (a) and in a night mode (b); Fig. 4 shows a longitudinal section through a first embodiment of a light guide assembly of a display device according to the invention; Fig. 5 shows a longitudinal section through a second embodiment of a light guide assembly of a display device according to the invention; Fig. 6 shows an embodiment of a rotatable mirror element of the second embodiment of the light guide assembly; Fig. 7 shows a longitudinal section through a third embodiment of a light guide assembly of a display device according to the invention; Fig. 8 shows a longitudinal section through a fourth embodiment of a light guide assembly of a display device according to the invention; Fig. 9 shows an alternative embodiment of the fourth embodiment: Fig. 10 shows a circuit device for controlling a light source and a light valve of a display device according to the invention. Description of the execution types

[0033] The Fig. 1 shows a longitudinal section through a passenger car 1 (PKW) with a display device 2 for displaying vehicle operating information to a driver 3. The display device 2 is arranged in a dashboard 4 above a steering column 5 of the PKW 1. The display device 2 is adjacent to two openings in the dashboard 3. A display area of ​​the display device 2 is arranged at a front opening 41 of the dashboard 4 in a field of vision of the driver 3. An upper opening 42 is arranged on an upper side of the dashboard 3, oriented toward a windshield 8 of the PKW 1.

[0034] In the Fig. 2 shows a longitudinal section through a display device 2 for a motor vehicle for dual lighting by means of ambient and artificial light, which has been adapted to the geometric conditions of the passenger car 1 on the basis of DE 100 26 892 A1 already mentioned in the introduction.

[0035] The display device 2 has a liquid crystal screen 23, which is arranged, for example, as a driver information display above the steering column 5 in the dashboard 4 of the passenger car 1. The display device 2 further has a light guide assembly 20 with a first light guide plate 201 and a second light guide plate 202, which are optically connected to one another. The light guide assembly 20 can alternatively also be formed by a one-piece light guide plate.

[0036] A light coupling region 21 is formed on the first light guide plate 201 and is aligned with the upper opening 42 in the dashboard 4. The light coupling region 21 is essentially a surface through which ambient light 11 from the surroundings of the passenger vehicle 1 can couple into the first light guide plate 201. For improved light capture, an anti-reflective layer 28 can be arranged between the light coupling region 21 and the first light guide plate 201.

[0037] The second light guide plate 202 is arranged behind the liquid crystal screen 23, as viewed from the driver 3. A diffusing film 221 is arranged on a front side of the second light guide plate 21, via which an illumination light 13 can be coupled out of the light guide assembly and guided through the liquid crystal screen 23. A brightness enhancement film (BEF) 222 can also be arranged between the second light guide plate 202 and the liquid crystal screen 23. A surface of the diffusing film 221 defines a light coupling region 22 of the light guide assembly 20.

[0038] On a side of the second light guide plate 21 opposite the scattering film 221, a reflection film 27 (enhanced specular reflector film, ESR) is arranged, with which the reflection properties of the light guide plate 21 are increased.

[0039] In the Fig. 2, a light-emitting diode (LED) 24 is shown on a lower lateral side of the second light guide plate 202, representing an artificial light source for backlighting. A number of LEDs 24 arranged in a row form a backlight unit (BLU) that extends in a transverse direction of the vehicle.

[0040] An artificial light 12 emitted by the LED 24 is coupled into the second light guide plate 202 via the lower lateral side and guided through the second light guide plate 202 by means of total internal reflection. The coupled artificial light 12 is partially coupled out in the light coupling region 22 and shines through the liquid crystal display 23 as illumination light 13 for uniform backlighting.

[0041] The first light guide plate 201 is arranged in alignment on an upper lateral side of the second light guide plate 202, so that the two light guide plates are optically connected to each other. According to the present example, the first light guide plate 201 extends substantially orthogonally to the first second light guide plate 202.

[0042] The ambient light 11 captured by the first light guide plate 201 through its light coupling region 21 is guided by total internal reflection through the first and second light guide plates 201 and 202 into the light coupling region 22. The coupled ambient light 11 can be partially coupled out in the light coupling region 22 and shine through the liquid crystal display 23 as illumination light 13.

[0043] Since total reflection in a light guide always acts in both directions, light can also escape in all areas into which it is to be coupled into the light guide assembly 20. As with the Fig. 3, the effects described below occur.

[0044] In day mode ( Fig. 3a), ambient light 11, which is coupled into the light guide assembly 20 via the light coupling area 21, can exit again as leakage light 14 from the lower lateral side of the second light guide plate 202. By encapsulating a housing of the display device 2 (not shown in the figures), the leakage light 14 can be captured so that it is not disturbingly visible to a driver 3.

[0045] The problem is with a night mode ( Fig. 3b), i.e., when the LED 24 of a BLU is in operation, the coupled artificial light 12 is guided through the light guide assembly 20 to the light coupling area 21 on the first light guide plate 201. The light can partially exit the light guide assembly 20 via the light coupling area 21 as stray light 15, so that it is perceptible to a driver 3 as disturbing light spots on the dashboard 4 or as a disturbing reflection in the windshield 8.

[0046] To use night mode ( Fig. 3b) of the display device 3, the invention provides for the integration of a light valve 30 into the light guide assembly 20. A light valve 30 can be understood as a two-state optical switch that can allow or deny light to pass through a portion of the light guide assembly 20 depending on the switching state.

[0047] In the Fig. 4 to 8 show various exemplary designs of light guide assemblies 20 and light valves 30.

[0048] The Fig. Figure 4 shows a longitudinal section of a first embodiment of a light valve 30, which is arranged in an optical path between a light coupling region 21 and a light coupling region 22. The Fig. 4a shows a state with an open light valve 30 for a day mode. Fig. 4b shows a state with a closed light valve 30 for a night mode.

[0049] The light valve function is performed by a cylindrical light guide 31, the circumference of which corresponds approximately to four times the thickness of the (equal thickness) light guide plates 201 or 202.

[0050] A cylindrical shell of the cylindrical light guide 32 is divided in a circumferential direction by two opaque regions 32 and two translucent regions 33. The opaque regions 32 and the translucent regions 33 are arranged opposite one another with respect to a cylinder axis and measure approximately the thickness of a light guide plate 201 or 202 in the circumferential direction.

[0051] The cylindrical light guide can be rotated by 90° using an actuator 34. In day mode ( Fig. 4a), in a first position, coupled light is passed through the cylindrical light guide 33. In night mode ( Fig. 4b) the light valve 30 is blocked so that artificial light 12 cannot reach the light coupling area 21.

[0052] In the Fig. 5 shows a second embodiment of a light guide assembly 20 according to the invention with a controllable light valve 30 in longitudinal section. The light guide assembly 20 comprises, as in the previous figures, a first light guide plate 201 and a second light guide plate 202, which are each arranged adjacent to the light valve 30. The two light guide plates 201 and 202 are arranged at right angles to one another. The light valve 30 comprises a rotatable mirror element 35 with a mirror body 351. The mirror body 351 has the shape of a triangular prism, with at least two lateral surfaces each being mirrored. The base area of ​​the mirror body 351 is formed by a right-angled and isosceles triangle. The side length of both triangle legs (ie the short triangle sides) corresponds approximately to the thickness of a light guide plate 201 or 202. A long triangle side (iethe hypotenuse) is accordingly longer than the two triangle legs by a factor of √2.

[0053] In day mode ( Fig. 5a) is a large mirror surface 352, which is arranged on the long side of the triangle, each aligned at a 45° angle to the first and second light guide plates 201 and 202. Ambient light 11, which has been captured from the environment by the first light guide plate 201, is guided towards the light valve 30 by means of total internal reflection. The light exits a lateral side of the first light guide plate 201 and is reflected by the large mirror surface 352, thereby deflecting it towards the second light guide plate 202, so that the light is coupled into the second light guide plate 202 at an upper lateral side. The light guided through the second light guide plate 202 by means of total internal reflection is partially coupled out in the light output region 22 as illumination light 13 for transilluminating a liquid crystal display 23.

[0054] For a night mode ( Fig. 5b), ie when artificial light 12 from an artificial light source is coupled into the second light guide plate 202 from a lower lateral side, the mirror body 351 of the rotatable mirror element 35 is oriented rotated by 180° relative to its position in day mode.

[0055] A first small mirror surface 253, formed on a first of the two triangular legs, is aligned parallel to the upper lateral side of the second light guide plate 202. The artificial light 12, which is coupled into the second light guide plate 202 at the lower lateral side, is guided toward the upper lateral side by means of total internal reflection. In the light output region 22, the coupled-in light can be partially output as illumination light 13. A portion of the remaining light, which exits the second light guide plate 202 via the upper lateral side, is reflected by the first small mirror surface 253 and returned to the second light guide plate 202.

[0056] In the Fig. 6 shows an exemplary embodiment of the rotatable mirror element 35. The rotatable mirror element 35 shows a plan view in the longitudinal direction ( Fig. 6a) the mirror body 351, which extends between a right and left pivot bearing 356. On one of the pivot bearings, a receptacle 355 is provided for a drive (not shown in the figures) for adjusting the rotatable mirror element 35 ( Fig. 6b). In a longitudinal section ( Fig. 6c) Along a section line AA through the mirror body 351, the shape of a triangular prism can be seen. The mirror body 351 has a large mirror surface 352 and at least one small mirror surface 353. A third surface 354 can also be mirrored or coated with a light-absorbing material.

[0057] The Fig. Figure 7 shows a third embodiment of a light guide assembly 20 according to the invention with a controllable light valve 30. The light valve 30 is formed by a single-cell liquid crystal assembly 36, which blocks the passage of light when an electrical voltage is applied. If no voltage is applied to the liquid crystal assembly 36, the passage of light is correspondingly enabled.

[0058] In the Fig. Figure 8 shows an alternative of the third embodiment, wherein the single-cell liquid crystal assembly 36 is arranged between the first light guide plate 201 and a light coupling region 21. The light coupling region 21 of the light guide assembly 20 is defined, for example, by an upper side of the liquid crystal assembly 36. Additionally, an anti-reflective layer can be provided on an upper side of the liquid crystal assembly 36.

[0059] As in the Fig. As can be seen in Figure 9, instead of the liquid crystal assembly 36, a closure element 37 can also be used as the light valve 30. This closure element is arranged at the light coupling region 21 and is adjustable by means of an actuator. The closure element 37 can be, for example, an electrically driven roller blind. The light coupling region 21 is arranged above an adjustment region of the closure element 37.

[0060] The Fig.10 shows a circuit for controlling the LED 24 and the light valve 30. The BLU is always required when the ambient light 11 (i.e. sunlight or daylight) is no longer sufficient to illuminate a liquid crystal display 23 with sufficient brightness. The brightness of the ambient light 11 can be electronically detected by a suitable optoelectronic sensor 25 (e.g. a photodiode, a phototransistor, photoresistor, etc.) and compared with a predetermined threshold value by a comparator 26. If the threshold value is undershot, the comparator 26 outputs a signal S1 to control the LED 24. The signal S1 is received by an LED driver 51, which provides a constant current for the LED 24 when the signal S1 is present.The optoelectronic sensor 25 is arranged on the light guide assembly 20 and is optically connected, for example, to the first light guide plate 201, so that the brightness of a light coupled in from the environment can be detected by a sensor. According to a first alternative, the signal S1 can also be used to control the light valve 30. A circuit 53 closes the light valve 30 as soon as a signal S1 from the comparator 26 is present. The light valve 30 is opened as soon as the signal is no longer present.

[0061] Alternatively, a second signal S2 from a light sensor unit for automatically controlling vehicle lighting can be supplied to the circuit device, based on which signal the light valve 30 can be controlled. The light sensor unit comprises an optoelectronic sensor 25b arranged on the windshield 8 of a passenger car 1 and a comparator 26b for threshold value comparison. This alternative embodiment enables not only the day and night mode but also a mixed mode, in which the display device 2 can be operated simultaneously with ambient and artificial light.

[0062] Although the subject matter has been illustrated and explained in detail by means of exemplary embodiments, the invention is not limited by the disclosed examples, and other variations may be derived therefrom by those skilled in the art. It is therefore clear that a multitude of possible variations exist. It is also clear that the exemplary embodiments mentioned are merely examples and should not be construed as limiting the scope, possible applications, or configuration of the invention in any way.Rather, the preceding description and the description of the figures enable the person skilled in the art to implement the exemplary embodiments in concrete terms, whereby the person skilled in the art, with knowledge of the disclosed inventive concept, can make various changes, for example with regard to the function or the arrangement of individual elements mentioned in an exemplary embodiment, without departing from the scope of protection defined by the claims and their legal equivalents, such as further explanations in the description. List of reference symbols VB supply voltage GND Ground 1 passenger car (car) 2 Display device 3 drivers 4 Dashboard 5 Steering column 8 Windshield 11 Ambient light 12 Artificial light 13 Illumination light 14 Leakage light 20 Fiber optic assembly 21 Light coupling area 22 Light extraction area 23 Liquid crystal display 24 light-emitting diodes (LEDs) 25, 25b optoelectronic sensor 26, 26b Comparator 27 Reflective foil 28 Anti-reflective coating 30 Light valve 31 cylindrical light guide 32 opaque area 33 translucent area 34 Actuator 35 rotatable mirror element 36 Liquid crystal assembly 37 locking element 41 front opening 42 upper opening 51 LED drivers 52 circuit 201 first light guide plate 202 second light guide plate 221 scatter film 222 Brightness enhancement film 351 mirror bodies 352 large mirror surface 353 small mirror surface 354 third area 355 recording 356 pivot bearings QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 100 26 892 A1 [0002, 0034]

Claims

[1] Display device for a motor vehicle (1) comprising at least one light-guiding assembly (20), a display element (23) and a light source (24), wherein the light-guiding assembly (20) comprises a light output region (22) and a light input region (21), wherein the display element (23) is arranged aligned with the light output region (22) and wherein the light output region (22) is designed to output coupled-in light (11, 12) from the light-guiding assembly (20) for illuminating the display element (23), wherein the light-guiding assembly (20) is designed to guide ambient light (11) coupled in via the light input region (21) into the light output region (22) via a first lateral side, and wherein the light source (24) is arranged on the light-guiding assembly (20) in such a way that the light-guiding assembly (20) is designed,to guide artificial light (12) from the light source (24) via a second lateral side into the light coupling area (22), , characterized by that the light guide assembly (20) comprises a controllable light valve (30) which is arranged between the light coupling region (21) and the light coupling region (22). [2] Display device according to claim 1, wherein the controllable light valve (30) comprises a liquid crystal assembly (36) which can be switched to be light-transmissive or non-light-transmissive depending on an applied voltage. [3] A display device according to claim 2, wherein the light guide assembly (20) comprises a first light guide plate (201) and a second light guide plate (202), and wherein the liquid crystal assembly (36) is arranged between the first light guide plate (201) and the second light guide plate (202). [4] Display device according to claim 2, wherein the liquid crystal assembly (36) is arranged on the light coupling region (21) of the light guide assembly (20). [5] Display device according to claim 1, wherein the controllable light valve (30) has a mechanically adjustable closure element (37) which is arranged on the light coupling region (21) of the light guide assembly (20). [6] Display device according to claim 1, wherein the controllable light valve (30) comprises a rotatable mirror element (35) and wherein the light guide assembly (20) further comprises a first light guide plate (201) and a second light guide plate (202), wherein the light coupling region (21) is arranged on the first light guide plate (201) and wherein the light coupling region (22) is arranged on the second light guide plate (202), wherein the rotatable mirror element (35) has a first mirror surface (352) and a second mirror surface (353) and is adjustable about a rotation axis between a first position and a second position, wherein the first light guide plate (201), the second light guide plate (202) and the rotatable mirror element (35) are arranged aligned with one another in such a way,that ambient light (11) coupled in the first position is directed from the first light guide plate (201) via the first mirror surface (352) into the second light guide plate (202), and that artificial light (12) coupled in the second position is reflected back from the second light guide plate (202) through the second mirror surface (353) into the second light guide plate (202). [7] A display device according to claim 6, wherein the first light guide plate (201) and the second light guide plate (202) are each formed as a flat light guide plate and are arranged aligned at a right angle to each other, and wherein the rotatable mirror element (35) is arranged aligned to a lateral side of the first light guide plate (201) and to a lateral side of the second light guide plate (202). [8] Display device according to claim 1, wherein the controllable light valve (30) comprises a circular-cylindrical light guide (31), wherein a cylinder jacket of the circular-cylindrical light guide (31) is divided in the circumferential direction into two opaque regions (32) and two translucent regions (33), wherein the opaque regions (32) and the translucent regions (33) are each arranged opposite one another with respect to a cylinder axis, and wherein the circular-cylindrical light guide (31) is rotatably adjustable about the cylinder axis between a closed position and an open position. [9] Display device according to one of claims 1 to 8, further comprising an optoelectronic sensor (25) and a comparator circuit (25), wherein the comparator circuit (25) is designed to compare an electrical signal from the optoelectronic sensor (25) with a threshold value and to activate the light source (24) and to close the controllable light valve (30) when the signal falls below the threshold value. [10] Motor vehicle with a display device (2) according to one of the preceding claims 1 to 9 and a dashboard (4), wherein the dashboard (4) has a front opening (41) and an upper opening (42), wherein a display element (23) of the display device (2) is arranged aligned with the front opening (41), and wherein a light coupling region (21) of a light guide assembly (20) of the display device (2) is arranged aligned with the upper opening (42).

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