DE102020209030A1 - Display device for displaying a symbol on a window of a vehicle and method for operating a display device - Google Patents

Abstract

The invention relates to a display device (100) for displaying a symbol on a window (110) of a vehicle (105). The display device (100) has a projection unit (115) for outputting a light beam (120) with a lens unit (130) and a light source unit (125) connected to the lens unit (130), the lens unit (130) in the area of a roof pillar ( 135) of the vehicle (105) is arranged or can be arranged. Furthermore, the display device (100) comprises a reflection element (140) designed to reflect the light beam (120) as a reflected light beam (145), and a holographic projection surface (150) designed to display the symbol in a display area (155) using the reflected light beam (145), wherein the projection surface (150) is formed as at least a portion of the window (110).

Description

State of the art

The invention is based on a display device or a method according to the generic type of the independent claims. The subject matter of the present invention is also a computer program.

In vehicles, for example, projection systems are known, by means of which information can be displayed on transparent vehicle windows. the U.S. 7,258,450 B2 describes a plurality of red, green and blue light-emitting diodes arranged two-dimensionally on a substrate.

Disclosure of Invention

Against this background, with the approach presented here, an improved display device for displaying a symbol on a window of a vehicle and an improved method for operating a display device, an improved control unit that uses this method, and finally a corresponding computer program according to the main claims are presented. Advantageous developments and improvements of the device specified in the independent claim are possible as a result of the measures listed in the dependent claims.

The approach presented here presents a possibility for not dazzling a vehicle occupant and also for reducing a risk of injury for the vehicle occupant due to a position of the display device. Furthermore, such a display device is advantageously implemented or can be implemented in different vehicle models.

A display device for displaying a symbol on a window of a vehicle is presented, the display device having a projection unit for outputting a light beam with a lens unit and a light source unit connected to the lens unit. The lens unit is arranged or can be arranged in the area of a roof pillar of the vehicle. Furthermore, the display device has a reflection element which is designed to reflect the light beam as a reflected light beam. Furthermore, the display device comprises a holographic projection surface which is designed to display the symbol in a display area using the reflected light beam, the projection surface being formed as at least a partial area of the window.

The display device can be arranged in a vehicle which is implemented, for example, as a motor vehicle, in particular as a land vehicle, for example as a passenger car or as a commercial vehicle. The window can be designed, for example, as a side window or windshield or as a rear window. The projection unit can also be referred to as a projector, for example, which can be designed to project the symbol or an image, for example. The symbol can, for example, include or contain vehicle information, such as speed information or information about the surroundings of the vehicle. The light beam can, for example, have one or more colors, thus for example one or more wavelengths. In this case, the objective unit can comprise at least one lens, such as can also be implemented in image acquisition devices, for example. The reflection element can, for example, be in the form of a mirror, for example a micromechanical mirror. In this case, for example, the reflection element and additionally or alternatively the projection unit can be set in such a way that a beam direction of the light beam and additionally or alternatively of the reflected light beam can be varied, for example. Advantageously, the display area can be arranged at head height of a vehicle occupant. The projection surface can be arranged, for example, on or in the window, in particular on or in the side window. Advantageously, the projection surface is transparent.

According to one embodiment, the projection surface can be formed as a reflection hologram, in which case the light source unit can additionally or alternatively be arranged in the area of a roof pillar. As a result, the light source unit is advantageously arranged above the projection surface, ie outside of an impact area, so that the vehicle occupant advantageously does not injure himself in the area of his head in a dangerous situation, for example.

According to one embodiment, the projection unit can be thermally connected to the vehicle by means of a heat conductor in order to enable heat to be dissipated. Advantageously, overheating of the projection unit and thus, for example, a malfunction can be avoided as a result.

The heat conductor can be formed as a metal-core printed circuit board, an aluminum plate or a copper plate, in particular with the heat conductor being able to be arranged between the projection unit and the roof rail of the vehicle. Advantageously, by means of Wärmelei ters, the heat can be dissipated better than if the projection unit rests directly on the roof rail.

According to one embodiment, the display device can have at least one heat sink connected to the projection unit, which is designed to cool the projection unit. In particular, the at least one heat sink can have a plurality of cooling fins. Advantageously, the heat can be actively dissipated by means of the heat sink, so that the projection unit advantageously does not overheat.

According to one embodiment, the projection unit and the reflection element can be arranged such that the reflected light beam is emitted at an acute angle between the light beam and the reflected light beam of at least 50 degrees, at least 60 degrees or at least 70 degrees. Advantageously, an unwanted reflection, which can be unavoidable, for example, can hit a merely diffusely scattering interior surface of the vehicle, so that the vehicle occupant is not dazzled. Advantageously, this is all the more possible the more steeply the reflected light beam hits the projection surface.

The projection unit can have at least one light source for outputting a partial beam of the light beam. Furthermore, the projection unit can have at least one further light source for emitting a further partial beam of the light beam, it being possible for the light source and the further light source to be arranged adjacent to one another. In particular, the light source and additionally or alternatively the further light source can be in the form of a light-emitting diode or a laser diode. The light-emitting diode can also be referred to as an LED, for example. The light source and the further light source can advantageously be arranged at a distance from one another on the roof rail along a longitudinal axis of the vehicle, so that the light sources are advantageously arranged next to one another. As a result, the light sources can advantageously be realized in a space-saving manner in the vehicle.

According to one embodiment, the light source unit can have the light source and additionally or alternatively the further light source. Additionally or alternatively, the light source and additionally or alternatively the further light source can be designed to be operated color sequentially. This means that the light source and additionally or alternatively the further light source advantageously have different wavelengths and additionally or alternatively different colors.

Furthermore, the projection unit can have a housing in which the lens unit and the light source unit are arranged. This means that the lens unit and the light source unit are advantageously arranged in a common housing. As a result, the projection unit can advantageously be implemented in a compact manner.

According to one embodiment, the lens unit and the light source unit can be arranged or can be arranged in housings that are spatially separate from one another in the vehicle, it being possible for the lens unit and the light source unit to be connected to one another by means of a light guide. For example, the lens unit can be designed to hold a plurality of lenses. The light source unit can advantageously be arranged in a trunk of the vehicle due to the spatial separation of the lens unit and the light source unit, so that waste heat from the light source unit and additionally or alternatively, for example, background noise caused by a heat sink, do not affect the vehicle occupants. This can, for example, increase customer satisfaction.

According to one specific embodiment, the projection unit can be or can be connected to a vehicle body by means of a fastening element. The fastening element can be implemented, for example, as a screw and additionally or alternatively as a nut. As a result, the projection unit can advantageously be attached rigidly to the vehicle body, more precisely to the roof pillar, so that advantageously vibrations and additional or alternative movements of the symbol are avoided.

Furthermore, a method for operating a display device is presented in an aforementioned variant, the method comprising a step of emitting a light beam by means of the projection unit onto the reflection element in such a way that a representation of a symbol on a holographic projection surface in a display area using the reflected light beam is shown.

The display device can advantageously be operated by the method. In this way, for example, safety-relevant information can advantageously be transmitted to the vehicle occupants.

This method can be implemented, for example, in software or hardware or in a mixed form of software and hardware, for example in a control unit.

The approach presented here also creates a control device that is designed to carry out, control or implement the steps of a variant of a method presented here in corresponding devices. The object on which the invention is based can also be achieved quickly and efficiently by this embodiment variant of the invention in the form of a control unit.

For this purpose, the control unit can have at least one computing unit for processing signals or data, at least one memory unit for storing signals or data, at least one interface to a sensor or an actuator for reading in sensor signals from the sensor or for outputting control signals to the actuator and/or or have at least one communication interface for reading in or outputting data that are embedded in a communication protocol. The arithmetic unit can be, for example, a signal processor, a microcontroller or the like, with the memory unit being able to be a flash memory, an EEPROM or a magnetic memory unit. The communication interface can be designed to read in or output data wirelessly and/or by wire, wherein a communication interface that can read in or output wire-bound data can, for example, read this data electrically or optically from a corresponding data transmission line or can output it to a corresponding data transmission line.

In the present case, a control device can be understood to mean an electrical device that processes sensor signals and outputs control and/or data signals as a function thereof. The control unit can have an interface that can be designed in terms of hardware and/or software. In the case of a hardware design, the interfaces can be part of what is known as a system ASIC, for example, which contains a wide variety of functions of the control device. However, it is also possible for the interfaces to be separate integrated circuits or to consist at least partially of discrete components. In the case of a software design, the interfaces can be software modules which are present, for example, on a microcontroller alongside other software modules.

A computer program product or computer program with program code, which can be stored on a machine-readable carrier or storage medium such as a semiconductor memory, a hard disk memory or an optical memory and for carrying out, implementing and/or controlling the steps of the method according to one of the embodiments described above, is also advantageous used, especially when the program product or program is run on a computer or device.

• 1 eine schematische Darstellung einer Anzeigeeinrichtung gemäß einem Ausführungsbeispiel;
• 2 eine schematische Darstellung einer Anzeigeeinrichtung gemäß einem Ausführungsbeispiel;
• 3 eine schematische Querschnittsdarstellung einer Anzeigeeinrichtung gemäß einem Ausführungsbeispiel;
• 4 eine schematische Querschnittsdarstellung einer Anzeigeeinrichtung gemäß einem Ausführungsbeispiel;
• 5 eine schematische Querschnittsdarstellung einer Anzeigeeinrichtung gemäß einem Ausführungsbeispiel;
• 6 eine schematische Querschnittsdarstellung einer Anzeigeeinrichtung gemäß einem Ausführungsbeispiel; und
• 7 ein Ablaufdiagramm eines Verfahrens zum Betreiben einer Anzeigeeinrichtung gemäß einem Ausführungsbeispiel.

Exemplary embodiments of the approach presented here are shown in the drawings and explained in more detail in the following description. It shows:

• 1 a schematic representation of a display device according to an embodiment;
• 2 a schematic representation of a display device according to an embodiment;
• 3 a schematic cross-sectional view of a display device according to an embodiment;
• 4 a schematic cross-sectional view of a display device according to an embodiment;
• 5 a schematic cross-sectional view of a display device according to an embodiment;
• 6 a schematic cross-sectional view of a display device according to an embodiment; and
• 7 a flowchart of a method for operating a display device according to an embodiment.

In the following description of favorable exemplary embodiments of the present invention, the same or similar reference symbols are used for the elements which are shown in the various figures and have a similar effect, with a repeated description of these elements being dispensed with.

1 shows a schematic representation of a display device 100 according to an embodiment. According to this exemplary embodiment, a cross-sectional area of a vehicle 105 is depicted, which is realized, for example, as a passenger car or alternatively as a commercial vehicle. In this case, the display device 100 is arranged in a lateral interior area of a vehicle cabin of the vehicle 105 . Display device 100 is designed to display a symbol on a side window 110 of vehicle 105 . This means that projection onto scattering surfaces in side window 110 of vehicle 105 is made possible, with the image being optionally visible from inside and/or outside vehicle 105 . In this advantageous embodiment, the symbol can be displayed on a side window 110 of vehicle 105 . Alternatively or in addition the symbol can also be displayed on another window in the vehicle 105, for example on a windshield or on a rear window.

For this purpose, the display device 100 has a projection unit 115 which is designed to emit a light beam 120 . The projection unit 115 also has a lens unit 130 and a light source unit 125 connected to the lens unit 130 . The lens unit 130 is arranged or can be arranged in the area of a roof pillar 135 of the vehicle 105 . The display device 100 also has a reflection element 140 which is designed to reflect the light beam 120 as a reflected light beam 145 . The display device 100 also has a holographic projection surface 150 which is designed to display the symbol in a display area 155 using the reflected light beam 145 , the projection surface 150 being formed as at least a partial area of the side window 110 . According to this exemplary embodiment, the display area 155 is arranged or can be arranged at the level of a head position of a head of the vehicle occupant. A position of the display area 155 is also related to an orientation of the projection unit 115 and/or the reflection element 140, for example.

According to this exemplary embodiment, the projection surface 150 is formed as a reflection hologram, so that the reflected light beam 145 is reflected into the display area 155, for example. In addition or as an alternative to this, the light source unit 125 according to this exemplary embodiment is also arranged in a roof area 157 . More precisely, according to this exemplary embodiment, the projection unit 115 is arranged between the roof pillar 135 and, for example, an optional sunroof rail 160 . That is, the projection unit 115 according to this embodiment is connectable or connected to a vehicle body by means of a fastener such as a screw. This rigid connection avoids vibrations and/or movements of the image. The projection unit 115 is optionally arranged outside a headspace of the vehicle occupant, so that the vehicle occupant does not hit the projection unit 115 .

According to this exemplary embodiment, the reflection element 140 is arranged on the sunroof rail 160 . Optionally, the reflection element 140 is implemented or can be implemented as a micromechanical mirror which is formed in a curved manner. In this case, the reflection element 140 is optionally set in such a way that a direction of the reflected light beam 145 can be set. According to this exemplary embodiment, the projection unit 115 and the reflection element 140 are arranged in such a way that the reflected light beam 145 is emitted at an acute angle of, for example, at least 50°, at least 55° or at least 60°. This means that the reflected light beam 145 falls so steeply on the projection surface 150 that unwanted reflections, such as a Fresnel reflection, are reflected in an area that is not critical for the vehicle occupants. This prevents the vehicle occupant from being blinded, for example. Instead, the unwanted reflection falls on, for example, a diffusely scattering interior surface.

The approach presented here describes the display device 100, also referred to as a projection system, which is designed to display information on the transparent side window 110 in the vehicle 105. According to this exemplary embodiment, the projection unit 115 is installed in the roof area 157, which is referred to here as a digital projector and which has the lens unit 130, which can be referred to as an electro-optical subsystem or as an “optical engine”.

Furthermore, the display device 100 has the holographic projection surface 150 . According to this exemplary embodiment, the projection unit 115 with the lens unit 130 records a symbol or image similar to a cinema screen on the projection surface 150, which can be described as a hologram. The projection surface 150 acts as a scattering surface with a specific emission characteristic. The projection surface 150 is designed as a volume hologram, for example, at least for multicolored representations. The advantages of such a holographic scattering surface are, for example, that the light emitted by the projection unit 115 is only scattered in a defined angular range and therefore has a particularly light-efficient effect. Also optionally, the projection surface 150 only scatters certain wavelengths of light from certain directions and is therefore largely transparent to light from the vehicle environment, for example. Optionally, an optical scattering function also varies across the projection surface 150, so that efficiency and image performance can be further optimized. According to this exemplary embodiment, the projection unit 115 has different or different types of image generators, which are not shown here, however. For example, the imaging device is designed as a so-called DMD system (Digital Mirror Display) or as a DLP chip (Digital Light Processor). Furthermore, the image generator is formed, for example, as an LCOS image generator (Liquid Crystal On Silicon) or as an image generator based on transparent LCDs, such as active matrix displays in HTPS or LTPS technology.

In summary, the approach presented here makes it possible for neither vehicle occupants nor passers-by to look directly into the light beam 120 of the projection unit 115 under normal conditions, with the projection unit 115 being arranged above a height of the projected image or symbol. Furthermore, due to the approach, only an intended reflection of the projection surface 150 reaches the eyes of the vehicle occupants, but not the undesired Fresnel reflection on a window surface, for example. According to this exemplary embodiment, the Fresnel reflection and possibly other parasitic luminous fluxes do not have a disruptive effect, but strike, for example, diffusely scattering surfaces in the usual field of vision of the vehicle occupants. According to this exemplary embodiment, the projection unit 115 is arranged in the vehicle in such a way that an injury to the head of the vehicle occupant is avoided in the event of an accident (head crash safety). The projection unit 115 is also positioned in the vehicle 105 in an area that is available in all vehicles of a series. In this case, the projection unit 115 has a rigid connection to the body structure of the vehicle 105, since even very small tilting vibrations of the projection unit 115 become visible in the projected image with a high amplitude. According to this exemplary embodiment, this connection is advantageous in order to avoid a complex supply of electrical lines, some of which have a high bandwidth, such as in doors. With regard to heat management, it makes sense to consider that, for example, when the projection unit 115 is attached in the roof area 157, very high ambient temperatures occur, which can exceed 100° C., for example. It can be avoided that vehicle components are thermally damaged by the waste heat of the projection unit 115 . For this purpose, for example, a fan, a heat conductor and/or a heat sink is used, as is described in more detail in one of the following figures and which advantageously cannot be perceived as disturbing by the vehicle occupant(s).

2 shows a schematic representation of a display device 100 according to an embodiment. The display device 100 shown here can be the one shown in 1 correspond to or at least resemble the display device 100 described. According to this exemplary embodiment, the only difference is the perspective from which the display device 100 is depicted. According to this exemplary embodiment, the display device 100 is shown from the vehicle interior. In this case, the vehicle occupant 200 is arranged between a B pillar 205 and a C pillar 210 of the vehicle 105 . According to this exemplary embodiment, it is clear that the projection surface 150 covers or occupies only a partial area of the side window 110 . According to this exemplary embodiment, the reflection element 140 is shown only in outline in order to clarify a positioning of the same. According to this exemplary embodiment, the projection unit 115 is arranged adjacent to a handle 215 of the vehicle 105 which, like the projection unit 115 , is also arranged on the roof rail 135 .

3 FIG. 1 shows a schematic cross-sectional representation of a display device 100 according to an embodiment. The display device 100 shown here shows an embodiment of a display device 100, as in one of 1 or 2 was described. In addition to the display device 100 described above, the display device 100 shown here has a heat conductor 300 which is arranged between the projection unit 115, more precisely the light source unit 125, and the vehicle in order to allow heat to be dissipated to the vehicle. According to this exemplary embodiment, a heat sink 302 is also arranged between the heat conductor 300 and the roof rail 135 . The heat is generated, for example, by operating at least one light source 305 which, according to this exemplary embodiment, is formed as part of the light source unit 125. This protects the projection unit 115 from overheating. Optionally, the thermal conductor 300 is formed as a metal-core circuit board, an aluminum plate, or a copper plate, for example. Also optionally, the light source unit 125 and the lens unit 130 according to this exemplary embodiment are arranged in a housing, not shown here. According to this exemplary embodiment, at one end of the objective unit 130 it has only optionally a projection objective 307 at which, according to this exemplary embodiment, the light beam 120 exits the projection unit 115 before the light beam 120 strikes the reflection element 140 .

The light source 305 is designed to emit a partial beam 308 of the light beam 120 . Furthermore, the light source unit 125 according to this exemplary embodiment has at least one further light source 310 which is designed to emit a further partial beam 309 of the light beam 120 . According to this exemplary embodiment, the two light sources 305, 310 are arranged adjacent to one another and are in the form of light-emitting diodes or laser diodes, for example. According to this exemplary embodiment, the light sources 305, 310 are furthermore arranged at a distance from one another along a longitudinal axis of the vehicle. According to this exemplary embodiment, the light source 305 and/or the further light source 310 is/are designed to be operated color-sequentially. Only optionally has the light sources Unit 125 has an additional light source 315, which is designed, for example, in the same way as light source 305 and/or the additional light source 310 and/or differs only in terms of its color.

Furthermore, the display device 100 according to this exemplary embodiment has at least one heat sink 320 which is connected to the projection unit 115 . The heat sink 320 is designed to cool the projection unit 115 and according to this exemplary embodiment only optionally has a plurality of cooling ribs 325 . According to this exemplary embodiment, the heat sink 320 is arranged on an image generator 330, which is also referred to as a DLP chip (Digital Light Processing).

According to this exemplary embodiment, the projection unit 115 is shaped in such a way that the lens unit 130 has two kinks or kinks or, to put it another way, is shaped with two kinks. According to this exemplary embodiment, the individual partial beams of the light sources 305, 310, 315 are directed in a first of the two kinks as a combined light beam to the image generator 330. Proceeding from the image generator 330, the combined light beam is reflected in such a way that it passes through the projection objective 307 and, when the projection objective 307 exits, is emitted as a scattered light beam 120 to the reflection element 140. According to this exemplary embodiment, the imaging device 330 is arranged on the second of the two kinks of the objective unit 130 .

In other words, according to this exemplary embodiment, a thermal connection of the projection unit 115 to the body, that is to say to the roof rail 135, is shown. As in the previously described figures, the projection unit 115 has the objective unit 130 and the light source unit 125 which comprises light sources 305 , 310 , 315 in the form of LEDs, the projection objective 307 and the image generator 330 . Furthermore, the display device 100 includes a housing, not shown here, which is connected to the heat sink 320, and a control unit, not shown here, but which is described in more detail in one of the following figures.

According to this exemplary embodiment, the projection unit 115 is attached to the roof rail 135 in a mechanically rigid manner. For example, nuts for a screw connection are attached, as well as a pin or the like for precise positioning. According to this exemplary embodiment, the light sources 305, 310, 315 are also thermally conductively connected to a respective heat conductor 300, for example as part of the projection unit 115, which in turn is pressed onto the roof rail 135 when it is screwed on or can be adjusted. The heat conductor 300 is formed, for example, as a metal-core printed circuit board onto which the light source is soldered, or an additional aluminum or copper plate. To compensate for tolerances with good heat transfer at the same time, a thermally conductive pad or thermally conductive paste or the like, referred to here as a heat sink 302, is arranged between the thermal conductor 300 and the roof rail 135, for example. The light sources 305 , 310 , 315 in red, green and blue that are required, for example, for a color display are advantageously arranged in a row in the longitudinal direction of the vehicle parallel to the roof rail 135 .

According to this exemplary embodiment, the imaging device 330 is either cooled with its own heat sink 320 or optionally thermally connected to the roof pillar 135 (not shown). If necessary, a Peltier element is additionally interposed or can be switched on (not shown) in order to cool the imaging device 330 below this temperature when the roof spar 135 is very hot. The Peltier element can also be used at low temperatures, for example, in order to quickly heat up the imaging device 330 to temperatures above 0°C. Alternatively, instead of the light sources 305, 310, 315, semiconductor lasers in the colors red, green and blue can also be used. These have the advantage that they can emit collimated and spectrally narrow-band light. The collimation allows a compact construction of the lens unit 130 with a greater depth of field of the projection at the same time. An almost linear spectrum of the light sources 305, 310, 315 also results in a higher diffraction efficiency for the holographic projection surface 150 and also reduces light that is parasitically transmitted to the outside.

According to this exemplary embodiment, the lens unit 130 with the reflection element 140, which is also implemented as a folding mirror or mirror, forms, for example, a so-called ultra short throw projector—ie a projection unit 115 with an extremely short distance from the plane of the projected image. For this purpose, the reflection element 140 is embodied as a free-form mirror, for example, which simultaneously widens the beam path from the lens unit 130 and, in conjunction with the projection lens 307, brings the focal plane of the image into the projection surface 150 as precisely as possible.

4 FIG. 1 shows a schematic cross-sectional representation of a display device 100 according to an embodiment. The display device 100 shown here is similar to the display device 100, as in one of 1 until 3 was described. The only difference is the shape of the projection unit 115, more precisely the shape of the lens unit 130, which according to this Embodiment is realized L-shaped. According to this exemplary embodiment, an air duct 400 is also arranged between the projection unit 115 and the roof pillar 135 of the vehicle, through which an air flow 405 flows, for example. According to this exemplary embodiment, the heat sink 320 is arranged between the light sources 305 , 310 , 315 and the roof pillar 135 , and has a cooling element 410 for each light source 305 , 310 , 315 and/or image generator 330 , for example. The cooling elements 410 are arranged in such a way that they protrude into the air duct 400 . As a result, for example, any heat that is generated is actively carried away by the air flow 405 .

• Bildgeber 330 (thermisch am kritischsten, wenig Verlustleistung);
• Lichtquelle 305 (Rote LED mit mittlerer Verlustleistung, thermisch auch kritisch);
• Lichtquelle 310 (Grüne LED mit hoher Verlustleistung, thermisch moderat empfindlich);
• Lichtquelle 315 (Blaue LED mit mittlerer Verlustleistung, thermisch moderat empfindlich).

In other words, instead of being thermally connected to the roof rail 135, the light sources 305, 310, 315 and the imaging device 330 are each connected to cooling elements 410, which have cooling fins, for example. The cooling fins are oriented in the direction of airflow 405, so they are not shown. The airflow 405 , also referred to as cooling air, flows through the air duct 400 and past the cooling elements 410 . Taking into account the power loss and thermal properties of the components, the following sequence is particularly advantageous according to this exemplary embodiment:

• Imager 330 (most thermally critical, low power dissipation);
• Light Source 305 (Red LED with medium power dissipation, also thermally critical);
• Light source 310 (Green LED with high power dissipation, moderately thermally sensitive);
• Light source 315 (blue LED with medium power dissipation, thermally moderately sensitive).

The air flow 405 can be sucked in, for example, through a barely visible gap in the area of a transition from the roof rail 135 to a vehicle door. An exhaust air is preferably discharged through the covered air duct 400 into an area where neither the air flow 405 nor the waste heat can be felt by the vehicle occupants, such as into the trunk of the vehicle. A fan, not shown, is attached, for example, to an outlet of the air flow 405 from the projection unit 115, which is formed, for example, as a simple electrical connection and is dampened by the fan noise, for example, or to an outlet of the air duct 400, for example in the trunk for optimal noise damping.

5 FIG. 1 shows a schematic cross-sectional representation of a display device 100 according to an embodiment. The display device 100 can, for example, correspond to the display device 100 or at least be similar to that in one of 1 until 4 was described. According to this exemplary embodiment, the projection unit 115 corresponds to that in 4 described projection unit 115. In this case, the display device 100 shows, in addition to the projection unit 115, a control unit 500 which is designed, for example, to operate the projection unit 115. For this purpose, control unit 500 is energized via an energization input 502, for example. According to this exemplary embodiment, the projection unit 115 and the control unit 500 are arranged together in a housing 505 .

According to this exemplary embodiment, control unit 500 has a transducer or converter 510, which is also referred to as a converter. The converter 510 is accordingly designed to convert a video signal 515 into a modulation signal 520, which is also referred to as a TTL-RGB signal. Furthermore, control unit 500 has a so-called DLP chip set 525, which controls image generator 330, for example, by means of a control signal 530. Furthermore, the DLP chip set 525 is designed to control at least one light source driver 535, which is connected to the at least one light source 305, 310, 315. According to this exemplary embodiment, each individual light source 305, 310, 315 therefore has a light source driver 535, which is controlled, for example, by means of at least one light signal 537. Also optionally, according to this exemplary embodiment, the projection unit 115 has a light sensor 540 which is designed to provide a feedback signal 545 to the control unit 500, by means of which a luminous flux and a white color point of the lens unit 130 are or can be regulated.

According to this exemplary embodiment, the video signal 515 is generated by a head unit (not shown here), for example, and is fed into the projection unit 115 only optionally as an LVDS video signal. Alternatively, it is conceivable that, for example, a microcontroller with a graphics unit is integrated, which directly generates the video signal 515 in the projection unit 115 . The converter 510 converts the video signal 515 into the modulation signal 520 according to this embodiment. The DLP chip set 525 drives the imager 330 according to this exemplary embodiment and via the light source drivers 535, also referred to as high-current drivers. The light sensor 540 optionally supplies the internal feedback signal 545 for controlling (closed loop control) the luminous flux and white color point of the lens unit 130.

6 FIG. 1 shows a schematic cross-sectional representation of a display device 100 according to an embodiment. functionally equivalent the display device 100 shown here in one of 1 until 5 described display device 100. Only their shape differs from the previously described display devices 100 in that, according to this exemplary embodiment, the lens unit 130 and the light source unit 125 are arranged or can be arranged in housings 505 that are spatially separate from one another in the vehicle. According to this exemplary embodiment, the lens unit 130 and the light source unit 125 are connected to one another by means of a light guide 600 . Furthermore, the at least one light source driver 535 is also arranged in the housing 505 in which the light source unit 125 is arranged. This can be arranged, for example, in a trunk of the vehicle. Optionally, for example, at least one heat sink (not shown here) is or can be arranged in the same housing 505 .

According to this exemplary embodiment, the lens unit 130 and the control unit 500 are arranged or can be arranged in a common housing 505 . The control unit 500 corresponds, for example, to that in 5 described control unit 500.

In other words, the components of the projection unit 115 are divided into two separate units. The light source unit 125 is arranged, for example, in the trunk and contains the light sources 305, 310, 315 with the light source drivers 535 and a cooling system (not shown). According to this exemplary embodiment, the light source unit 125 has optics for combining the beam and coupling optics into the optical fibers of the light guide 600 . Projection unit 115 on the roof rail includes optics unit 130, which, according to this exemplary embodiment, is reduced to illumination optics for image generator 330 and imaging optics, as well as another part of control unit 500.

The main advantage of this arrangement is that there are only components with low power loss in the thermally critical roof area. The light sources 305, 310, 315 together with the light source drivers 535, on the other hand, are installed in a thermally non-critical area of the vehicle, for example in the area of the trunk or in an underbody of the vehicle. There they can be cooled more easily, for example either by means of heat sinks and free convection, optionally with an additional fan, or by thermal connection to metal body elements. If a fan is used, impairments for the vehicle occupants due to noise or air flow can advantageously be easily avoided. A further advantage is that high and at times extremely short current pulses for the light sources 305, 310, 315, which therefore contain a high potential for electromagnetic interference, are efficiently shielded in a completely closed housing 505.

Furthermore, the installation space required on the roof rail is reduced by the approach of the projection unit 115 presented here, since the light source unit 125 takes up less space in comparison to a projection unit 115 comprising the light sources. This makes it easier to integrate on the roof rail. An advantageous division of the electronics is, for example, such that assemblies with a high signal bandwidth are attached in the area of the projection unit 115, assemblies with high power loss, especially light sources 305, 310, 315 and light source driver 535 in the area of the light source unit 125. The assembly in the lens unit 130 according to this exemplary embodiment, therefore only optionally comprises a microcontroller with a graphics unit and/or a video signal input for reading the video signal 515 into the converter 510. The video signal 515 is implemented, for example, as an LVDS signal (low voltage differential signaling). Connected to this is the chip set for the image generator 330, referred to as the DLP chip set 525, and the image generator 330 itself. This is done, for example, either electrically, for example as a current loop via a so-called twisted pair line, or (not shown) via the optical fiber in the opposite direction to visible light, for example in the form of infrared light pulses. According to this exemplary embodiment, the optical connection between light source unit 125 and lens unit 130 is made by means of light guide 600. In the case of LEDs as light sources 305, 310, 315, this is advantageously a fiber bundle, in the case of laser light sources 305, 310, 315 a single one Multi-mode plastic fiber.

7 shows a flowchart of a method 700 for operating a display device according to an embodiment. The method 700 is carried out, for example, by a control unit, as is the case, for example, in one of 5 or 6 was described. The method 700 includes a step 705 of emitting a light beam by means of the projection unit onto the reflection element in such a way that a representation of a symbol is displayed via a holographic projection surface in a display area using the reflected light beam. According to this exemplary embodiment, step 705 of outputting is controlled, for example, by means of a light signal.

If an embodiment includes an "and/or" link between a first feature and a second feature, this should be read in such a way that the embodiment according to one embodiment includes both the first feature and the second feature and according to a further embodiment either only that having the first feature or only the second feature.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• US7258450B2 [0002]

Claims (15)

Display device (100) for displaying a symbol on a window (110) of a vehicle (105), the display device (100) having the following features: - a projection unit (115) for outputting a light beam (120) with a lens unit (130) and a light source unit (125) connected to the lens unit (130), the lens unit (130) being in the area of a roof pillar (135) of the vehicle (105 ) is arranged or arrangeable; - A reflection element (140) which is designed to reflect the light beam (120) as a reflected light beam (145); - a holographic projection surface (150) configured to display the symbol in a display area (155) using the reflected light beam (145), the projection surface (150) being formed as at least a portion of the window (110). Display device (100) according to claim 1 , wherein the projection surface (150) is formed as a reflection hologram, and/or wherein the light source unit (125) is arranged in the area of a roof pillar (135). A display device (100) according to any one of the preceding claims, wherein the projection unit (115) is thermally connected to the vehicle (105) by means of a heat conductor (300) to enable dissipation of heat. Display device (100) according to claim 3 , wherein the heat conductor (300) is formed as a metal core circuit board, an aluminum plate or as a copper plate, in particular wherein the heat conductor (300) is arranged between the projection unit (115) and the roof rail (135) of the vehicle (105). Display device (100) according to one of the preceding claims, having at least one cooling body (320) connected to the projection unit (115) and designed to cool the projection unit (115), in particular wherein the at least one cooling body (320) has a plurality of Having cooling fins (325). Display device (100) according to one of the preceding claims, wherein the projection unit (115) and the reflection element (140) are arranged such that the reflected light beam (145) at an acute angle between the light beam (120) and the reflected light beam (145) of at least 50 degrees, at least 60 degrees or at least 70 degrees. Display device (100) according to one of the preceding claims, wherein the projection unit (115) has at least one light source (305) for emitting a partial beam (308) of the light beam (120), wherein the projection unit (115) has at least one further light source (310) for outputting a further partial beam (309) of the light beam (120), and wherein the light source (305) and the further light source (310) are arranged adjacent to one another, in particular wherein the light source (305) and/or the further light source (310) as a light-emitting diode or a laser diode is or are formed. Display device (100) according to claim 7 , wherein the light source unit (125) has the light source (305) and/or the further light source (310), and/or wherein the light source (305) and/or the further light source (310) is or are designed to be operated color sequentially will. Display device (100) according to one of the preceding claims, wherein the projection unit (115) has a housing (505) in which the lens unit (130) and the light source unit (125) are arranged. Display device (100) according to one of Claims 1 until 8th , wherein the lens unit (130) and the light source unit (125) are arranged or can be arranged in separate housings (505) in the vehicle (105), wherein the lens unit (130) and the light source unit (125) are connected by means of a light guide (600) are connected to each other. Display device (100) according to one of the preceding claims, wherein the projection unit (115) can be connected or is connected to a vehicle body by means of a fastening element. Method (700) for operating a display device (100) according to one of the preceding claims, the method (700) comprising the following step: - Outputting (705) a light beam (120) by means of the projection unit (115) onto the reflection element (140) in such a way that a representation of a symbol via a holographic projection surface (150) in a display area (155) using the reflected light beam (145) is shown. Control unit (500), which is set up to step (705) of the method (700) according to claim 12 to be executed and/or controlled in at least one corresponding unit. Computer program that is set up to step (705) of the method (700) according to claim 12 execute and/or control. Machine-readable storage medium on which the computer program Claim 14 is saved.

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