Title

Head up display projecting visual information onto a screen

Background The present invention relates to a head up display that projects visual information onto a screen.

Such head up displays are typically integrated into a vehicle dashboard and are intended to supply a passenger of the vehicle with information such as the current vehicle speed, the fuel gauge and/or warnings, for example. Typically, the visual information is projected onto a mirror or a combiner that is reversibly transformable between a usage position and a non-usage position.

In general, it is essential to realize a compact head up display due to the limited space in front of the passenger. It is therefore reliable to arrange the components of the head up display directly next to each other. As a consequence, the space between a kinematic device (for transforming the combiner between the usage and the non-usage position) and a liquid crystal device, such as a TFT-display, is limited. This space is, however, provided for a light source that generates the backlight for illuminating the TFT-display as it is needed for pro- jecting the visual information generated by the TFT-display onto the screen. Consequently, heat being generated by the light source of the operating head up display influences the TFT-display negatively and can even destroy it.

Summary

It is therefore the objective of the present invention to provide a head up display with a projector unit, wherein the heat of the operating projector unit is reduced without giving up the positive effect of arranging a heat generating light source and a liquid crystal device, which is affected by the heat, next to each other.

The problem of the present invention is solved by a head up display for projecting visual information onto a screen, wherein the head up display has a projector unit comprising a light source and a light modulation device for generating the visual information, wherein the projector unit has a global radiator for cooling the projector unit. Further it is provided that the projector unit is arranged immediately adjacent to a kinematic device and the global radiator comprises at least partially a material having a thermal conductivity greater than 100 W/(mK), preferably greater than 150 W/(mK) and more preferably greater than 200 W/(mK).

In contrast to the state of the art, it is herewith advantageously possible to reduce the heat of the projector unit by the global radiator such that a proper operating of the head up display is possible. Thus, a potential defect that can be otherwise caused by the heat originating from the light source can be avoided. Furthermore, it is possible to use such a powerful light source as a backlight for the light modulation device, that the screen is illuminated uniformly and reaches an illumination of at least 6000 Cd/m ² .

Preferably, it is provided that the light modulation device generates the visual information that is projected onto the screen by illuminating the light modulating device using the backlight of the light source. In particular, the light modulating device is at least partially transparent and the light from the light source, namely the backlight, passes the light modulation device at least partially. Preferably, at least a part of the light modulating device changes its transparency and/or color whenever the visual information has to be modified. Thus, the modulating device modulates the light of the light source corresponding to the visual information. Furthermore, it is provided that the global radiator device reduces the heat of at least two components of the projector unit by contacting them respectively.

According to another embodiment of the present invention, it is provided that

- the light modulation device comprises a lens and/or a liquid crystal display and/or

- the light source is integrated into a printed circuit board. By using the liquid crystal display such as a TFT (thin film transistor)-display a light modulation device is provided that can generate the visual information. In particular, it is provided that the global radiator guarantees that the temperature of the TFT-display is below 95° C and therefore a damage caused by the heat of the TFT-display may be avoided. Furthermore, it is provided that the light from the light source passes the liquid crystal display for projecting the visual information generated by the liquid crystal device onto the screen. In particular, it is possible to change the visual information rapidly by controlling the liquid crystal display. For this purpose, the liquid crystal display is preferably connected to a control unit that determinates the information that should be generated by the light modulation device. Furthermore, it is provided that the light modulation device comprises a component, such as a lens, an aperture or a lens system, that modifies the light emitted by the light source for a preferably uniform illumination of the screen. As a consequence, the quality of the projected visual information is further raised. Furthermore, it is provided that the light source is a LED that is preferably integrated into a printed circuit board. Such a light source is small sized and easy to handle advantageously. According to a preferred embodiment it is provided that the projecting device is at least partially framed by the global radiator. By framing the projecting device the global radiator is able to cool jointly several, in particular all, components of the projecting device that requires cooling. Preferably the global radiator extends at least partially along the periphery of the projecting device. It is also thinkable that the global radiator covers more than 15 %, prefera- bly more than 25 % and more preferably more than 40 % of the projecting device. In particular the projection device is almost completely framed by the global projecting device.

According to another embodiment of the present invention, it is provided that the screen is a combiner and/or a mirror. In particular, the screen is designed such that the projected visual information is at least partially reflected back to the passenger or at least partially transmitted to the passenger. Using a semi-transparent screen such as a combiner has the advantage that the field of view of the passenger is not restricted significantly.

According to another embodiment of the present invention, it is provided that the global radi- ator contacts both the light source and the light modulation component. In particular, the global radiator contacts the light source, the lens and the TFT-display in order to realize an effective cooling of all essential parts of the projector unit.

According to another embodiment of the present invention, it is provided that the screen is part of a windscreen and/or is reversibly transferable by a kinematic device between an usage position and a non-usage position. Thereby a space-saving head up display is realized advantageously. In particular, the kinematic device comprises a gearing mechanism and the screen is movably connected to a housing of the head up display. In particular, the screen is pivoted and/or shifted for transferring the screen between the usage position and the non- usage position.

According to another embodiment of the present invention, it is provided that the projector unit is arranged below the screen in the usage position. That provides a compact head up display.

According to another embodiment of the present invention, it is provided that the head up display has another mirror for forwarding the generated visual information from the projector unit to the screen. Thereby the projector unit can be located directly below the combiner and/or mirror.

According to another embodiment of the present invention, it is provided that the lens is ar- ranged between the light sources and the liquid crystal display, wherein the lens is arranged inside the global radiator. In particular, it is provided that the lens, the light source and the liquid crystal display are framed by the global radiator. It is herewith possible to generate a compact and robust projector unit. According to another embodiment of the present invention, it is provided that the global radiator has

— a ripped design and/or

— an additional fan. Such a configuration of the global radiator advantageously increases the capability of the global radiator for cooling the projector unit at least partially. The ripped design increases the surface that can emit the heat being collected by the global radiator.

Global radiators having a high thermal conductivity are preferably effective global radiators.

According to another embodiment of the present invention, it is provided that the global radi- ator comprises at least partially Aluminum. Aluminum has a high thermal conductivity. A radiator having Aluminum is therefore an effective global radiator.

According to another embodiment of the present invention, it is provided that the projector unit is arranged immediately adjacent to the screen in its non-usage position. It is herewith advantageously possible to realize a head up display that is designed such that it can be easily integrated into a vehicle. In such a case the global radiator allows using a powerful light source for a desired screen illumination without jeopardizing the liquid crystal device.

According to another embodiment of the present invention, it is provided that the head up display is part of a vehicle dashboard. Preferably, the head up display is arranged in front of the passenger. It is therefore advantageously possible to localize the combiner within the field of view of the passenger.

Another subject of the present invention is a vehicle dashboard having a head up display as it is described before. Another subject of the present invention is a vehicle having a head up display as it is described before.

These and other characteristics, features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. The description is given for the sake of example only, without limiting the scope of the invention. The reference figures quoted below refer to the attached drawings.

Brief description of the drawings

Figure 1 shows a head up display according to a first exemplary embodiment of the present invention in a perspective view.

Figure 2 shows the head up display according to the first exemplary embodiment of the present invention in a sectional view.

Detailed description

The present invention will be descripted with respect to particular embodiments and with the reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some elements may be exaggerated and not drawn on scale for illustrative purposes.

Where an indefinite or definite article is used when referring to a singular noun, e.g. "a", "an", "the", this includes a plural of the noun unless something else is specifically stated.

Furthermore, the terms first, second, third and the like in the description and in the claims are used to distinguish between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein. In figure 1 a head up display 1 according to a first exemplary embodiment of the present invention is illustrated in a perspective view. Such a head up display 1 is preferably integrated into a vehicle dashboard 10 and comprises a screen 4 for displaying visual information. In particular, the head up display 1 is arranged such that a passenger of the vehicle, in particular its driver, can take notice of the visual information without changing the head position and/or viewing direction. For example, such information is related to a current vehicle speed, fuel gauge and/or other parameters specifying the state of the vehicle and is displayed on the screen. It is also thinkable that warnings are displayed on the screen, too. Consequently, the head up display is used as a kind of prompter that supplies the passenger straightforward with information.

It is provided that the visual information is projected onto a screen 4. A mirror, a combiner or a windscreen may be used as a screen 4, for instance. In particular, it is provided that the combiner is reversibly transferable between a usage position and a non-usage position. Preferably, the combiner being in the usage position is arranged in a field of view of the passenger and the combiner being in the non-usage position forms a part of the vehicle dashboard 10.

In figure 2 a sectional view of the head up display 1 according to the first exemplary embodiment is illustrated. Herewith, it is provided that the head up display 1 has a projector unit 9 that generates the visual information. For generating the visual information, the projector unit 9 has a light source 2 as a backlight, such as a LED integrated in a printed circuit board, and a light modulation device for modulating the backlight such that a visual information is projected from the light modulation device to the screen 4. Preferably, the light modulation device comprises a lens 6 and/or a liquid crystal display 3, in particular a TFT (thin film transistor) display. In particular, it is provided that the liquid crystal display 3 generates the visual information that is projected onto the screen 4 by using the backlight of the light source 2. Preferably, the projector unit 9 is arranged immediately below the head up display 1. Therefore, another mirror 12 is needed for forwarding the visual information from the projector unit 9 to the screen 4 in the usage position. Preferably, another mirror 12 is integrated in a housing or part of the dashboard that accommodates also the projector unit 9. Furthermore, it is provided that the combiner is pivotally connected to the housing and/or can be moved trans- lationally. In particular, the combiner is pivoted and/or shifted by a kinematic device 7 between the usage position and the non-usage position, wherein the kinematic device 7 preferably comprises a gearing mechanism 8.

For adequately illuminating the screen 4 in such a head up display 1 , the backlight originating from the light source 2 has to be powerful. In particular, the light source 2 has to be so powerful that an illumination of 6000 Cd/m ² is realized on the combiner. As a consequence, a heat originating from the light source affects the liquid crystal display 3, in particular the TFT display, disadvantageously. The compact arrangement of the combiner, the kinematic device 7, the light source 2, the lens 6 and liquid crystal display 3 enhances the impairment of the liquid crystal display 3 by the heat of the light source 2. An increment of the heat of the liquid crystal display 3 may damage it or prevent it from being operable properly. Therefore, it is necessary to cool the projector unit 9 at least partially for guaranteeing a proper operating of the head up display 1. For this purpose, it is provided that the projector unit 9 comprises a global radiator 5 for cooling the head up display 1 without giving up the advantageous arrangement components that form the head up display 1. In particular, it is provided that the global radiator 5 maintains the light source 2, preferably the printed circuit board with the in- tegrated LED, the lens 6 and the liquid crystal display 3, in particular the TFT-display, and cool the liquid crystal display 3, preferably the TFT-display. In particular, the global radiator 5 has a ripped design and/or is at least partially made from a metal having a thermal conductivity greater than 100 W/(mK), preferably greater than 150 W/(mK) and more preferably greater than 200 W/(mK). Furthermore, it is provided that the global radiator 5 contacts the printed circuit board with the integrated LED, the lens 6 and the TFT-display. In particular, the lens 6 is framed by the global radiator 5. Furthermore, it is preferably provided that the printed circuit board with the integrated LED and/or the TFT-display are located at opposite regions of the global radiator 5 and determinate the ends of the global radiator. As a consequence, the global radiator 5 provides a compact projector unit 9 having components that are rigidly fixed to each other in well-defined distances by the framing global radiator 5.

Furthermore, it is provided that such a TFT-display is tilted with respect to a direction being perpendicular to a main propagation direction of the backlight in order to compensate aberrations on the screen 4. Preferably, the global radiator 5 is adapted to the tilted TFT-display and is designed asymmetrically.

Reference signs

1 head up display

2 light source

3 liquid crystal display

4 screen

5 global radiator

6 lens

7 kinematic device

8 gearing mechanism

9 projector unit

10 housing/dashboard

12 another mirror