CN117916792A - Head-up display with reduced shadowing - Google Patents

Abstract

The present invention relates to a method, a computer program comprising instructions and an apparatus for reducing virtual image occlusion of a head-up display of a vehicle. The invention further relates to a head-up display for a vehicle using such a method or such a device. In a first step, a horizon is determined (S1). Thereafter, the image to be displayed is subdivided (S2) into a plurality of partial areas. In this case, the partial areas are rectangular, and the vertical extent of the partial areas differs depending on the area of the image to be displayed. For each partial region, a mask region is determined (S3) and a check is performed (S4) to determine whether the determined mask region exceeds an allowable size of at least one of the partial regions. If the allowable size is exceeded, a warning signal is output (S5). Finally, at least one measure for reducing shadowing is implemented (S6) in response to the warning signal.

Description

Head-up display with reduced shadowing

Technical Field

The present invention relates to a method, a computer program comprising instructions and an apparatus for reducing virtual image occlusion of a head-up display of a vehicle. The invention further relates to a head-up display for a vehicle using such a method or such a device.

Background

Head-up displays (also known as HUDs) are understood as the following display systems: in this display system, the viewer can maintain his viewing direction because the content to be presented is inserted into his field of view. While such systems were primarily used primarily in the aeronautical field due to their complexity and cost, they are now also used in the automotive field for mass production.

Head-up displays are generally composed of an image generator, an optical unit and a mirror unit. The image generator generates an image. The optical unit directs the image onto the mirror unit. The image generator is also commonly referred to as an imaging unit or PGU (Picture Generating Unit, picture generation unit). The mirror unit is a partially reflective light transmissive pane. Thus, the viewer sees what the image generator presents as a virtual image, and at the same time sees the real world behind the pane. In the automotive field, windshields are often used as mirror units and the curved shape of the windshield must be considered when presenting. Due to the interaction between the optical unit and the mirror unit, the virtual image is an enlarged representation of the image generated by the image generator.

For head-up displays, liquid crystal displays (LCD: liquid CRYSTAL DISPLAY) having a backlight for an imaging unit are currently generally used. Displays based on OLED technology (OLED: organic LIGHT EMITTING diode, organic light emitting diode) and DMD technology (Digital Micromirror Device ) are also used.

Against this background, DE 10 2015 215 180 A1 describes a head-up display for a vehicle. The head-up display includes a display device for emitting light having an image generating unit, and an image control unit for controlling the image generating unit. In this case, the reduced brightness is set according to the viewing direction of the user in the area of the display device. This makes it possible to reduce the power consumption during image generation. However, if the surrounding brightness is low and the area of the display device is set to be too bright without being reduced in its brightness, the user's glare cannot be prevented.

In the case of a large bright head-up display covering a large driver's field of view, problems of shading may occur in addition to the glare problem. It is necessary to avoid the situation: related objects (such as cyclists, pedestrians, animals, or soccer balls rolling onto the road) may be obscured by bright areas in the virtual image of the heads-up display and thus may not be perceived by the driver.

A general approach to solving this problem involves avoiding the appearance of a relatively large area on the LCD display where the entire area is bright, and preferentially selecting virtual images constructed from thin lines rather than using padding areas.

To monitor whether bright areas would lead to shadows, the virtual image may be broken up into small rectangles (so-called tiles), each of which is checked for transparency. In this case, the transparency is used as a measure of the mask area of the drawing block. The examination should take into account the following facts: the size of the allowed transparency is only a quarter of the transparency of the maximum allowed masking zone. This takes into account the fact that: in the worst case, the regional bright region may be divided into four tiles.

Disclosure of Invention

It is an object of the present invention to provide an improved solution for reducing the virtual image occlusion of a head-up display.

This object is achieved by a method having the features of claim 1, by a computer program comprising instructions having the features of claim 9 and by an apparatus having the features of claim 10. The dependent claims relate to preferred embodiments of the invention.

According to a first aspect of the invention, a method for reducing virtual image occlusion of a head-up display of a vehicle comprises the steps of:

-subdividing the image to be displayed into a plurality of partial areas, wherein the partial areas are rectangular and the vertical extent of the partial areas differs from area to area of the image to be displayed;

-determining masking zones of the respective partial zones; and

-Outputting a warning signal if the determined screening zone exceeds the allowed size of at least one of the partial zones.

According to another aspect of the invention, a computer program comprises instructions which, when executed by a computer, cause the computer to perform the following steps for reducing virtual image occlusion of a heads-up display of a vehicle:

-subdividing the image to be displayed into a plurality of partial areas, wherein the partial areas are rectangular and the vertical extent of the partial areas differs from area to area of the image to be displayed;

-determining masking zones of the respective partial zones; and

-Outputting a warning signal if the determined screening zone exceeds the allowed size of at least one of the partial zones.

In this case, the term "computer" should be understood in a broad sense. In particular, the computer also includes a control unit, a controller, an embedded system, and other processor-based data processing devices.

For example, a computer program may be provided for electronic retrieval or may be stored on a computer readable storage medium.

According to another aspect of the invention, an apparatus for reducing virtual image obscuration of a head-up display of a vehicle comprises:

-a subdivision module for subdividing an image to be displayed into a plurality of partial areas, wherein the partial areas are rectangular and the vertical extent of the partial areas differs from area to area of the image to be displayed;

-a processing module for determining masking zones of the respective partial zones; and

-A warning module for outputting a warning signal if the determined screening zone exceeds the allowable size of at least one of the partial zones.

In the case of the solution according to the invention, the image to be displayed is decomposed into rectangular tiles, the vertical extent of which varies within the image. The smaller the object perceived by the viewer to be covered by the image to be displayed, the smaller the tiles in the corresponding area. Since perceived object size varies with object distance, tiles in those areas of the image that cover distant objects are smaller. At the upper and lower edges of the image, perceived objects (such as a vehicle directly in front of the lower edge of the image or in front of an adjacent lane, or such as a hanging branch at the upper edge of the image) are closer together; thus, tiles in these areas may also be larger. The difference compared to subdividing the image to be displayed into rectangles of the same size is that the maximum size of the bright areas that is still permissible is different in size in the different image areas. The subdivision axes pass horizontally and vertically through the field of view, but at different distances from each other. The subdivision depends on the distance from the horizon and thus corresponds approximately to the size proportion of the perceived image. Rectangular areas are easy to process and calculate because image data is typically provided in a manner that is divided into rows and columns (i.e., according to a rectangular scheme). If only the vertical extent of the partial areas is different, during the processing, in each case a different number of rows can be combined for the same type of joint processing, while the number of columns of the partial areas is unchanged. The inventors of the present invention have found that the size of the adjustment section in terms of height is sufficient to achieve a safe shielding reduction. In this case, finer division is provided in the area of the horizon, since this area has been found to be the most critical area for safe driving in terms of masking. For example, the warning signal may be an optical or acoustic warning. Preferably, the warning signal is used to turn off the image output of the heads-up display. In this regard, the display element is switched entirely to "opaque" and/or the backlight of the display element is turned off entirely. This increases security.

According to one aspect of the invention, when determining the occlusion, the transparency of the partial region is taken as a measure of the occlusion. Transparency is an easily determinable measure of the percentage share size of the obscured area within the corresponding partial area.

According to an aspect of the present invention, before outputting the warning signal, a check is performed to determine whether the determined masking zone exceeds the allowable size of two or more adjacent partial zones. In the worst case, the regional bright areas that lead to shading are distributed over four partial areas. The allowable size of the masking zone within a portion of the zone is selected to take this into account. However, if the examination of the adjacent partial areas indicates that the permissible size of the masking zone is not exceeded and that there is an acceptable masking in general, the output of the warning signal may be omitted.

According to one aspect of the invention, the partial areas have a decreasing vertical extent from the upper edge area and/or the lower edge area of the image to be displayed to the horizon. The size of the image perceived by the observer follows the horizon, i.e. the closer the object is located to the horizon, the smaller the perceived object, and the higher or lower the object is located to the horizon, the larger the perceived object. Thus, the closer to the horizon the position is, the smaller the vertical extent of the rectangular part-area is. The further the object is located below the horizon, the closer to the vehicle. Thus, these objects are perceived to be larger than objects located near the horizon. Objects located above the horizon are either very far from the vehicle and appear so small that they are often difficult to perceive or cannot be perceived at all. Or, objects located above the horizon are closer to the horizon, such as birds flying in front of the vehicle, hanging branches, signs or other vehicles located immediately in front of or in adjacent lanes. Also, these objects are perceived to be larger than objects located near the horizon. Thus, the present invention provides that the vertical extent of the partial areas both below and above the horizon increases with increasing distance from the horizon.

According to one aspect of the invention, the horizon is determined by determining the inclination of the vehicle. The position of the horizon can easily be determined from the inclination of the vehicle, which inclination can be detected, for example, by means of a gyroscopic sensor.

According to one aspect of the invention, it is assumed that the horizon is a fixed predefined horizon of the image data of the image to be displayed and that the vertical displacement of the entire image content to be presented is performed in accordance with the detected vertical eye position of the user. This simplifies the method steps to be performed, since a fixed predefined grid is always employed. This eliminates: for example, determination of a current horizon in image data of an image to be displayed, determination or movement of a horizontal boundary of a partial region in a vertical direction correspondingly in a manner suitable for the position of the current horizon, and the like. Adaptation of the horizon to the vertical eye position of the observer is achieved by moving the entire presented image up or down, with the result that the image line fixedly predefined as the horizon corresponds to the actual horizon. For example, the eye position of the observer is detected by an internal camera. In any case, such an internal camera and its evaluation unit are present in many vehicles. Thus, little or no additional cost is required to use the information determined by these cameras. There are also actuators for adjusting the vertical position of the presented image.

According to one aspect of the invention, at least one measure for reducing shadowing is implemented in response to the warning signal. For example, at least one image element causing a mask may be moved. By moving the picture elements to a partial region located somewhat further in the direction of the image edge it is achieved that the resulting occlusion region no longer exceeds the allowed size. Alternatively or additionally, the area obscured by the image element may be reduced. For this purpose, for example, the picture elements may be constructed from thin lines or simply represented as contours.

According to one aspect of the invention, display of image elements in the region of the horizon is prevented. To further increase the security it is advantageous if the horizon itself is omitted entirely from the display of the picture elements. Especially in high speed situations, for example the end of a congestion may look very small and be easily obscured.

Preferably, the method according to the invention or the device according to the invention is used in a head-up display for a vehicle, for example for a motor vehicle. The advantage of such a head-up display is that the safety of the driver is improved, since the shielding of relevant objects in the driver's field of view is reduced or completely avoided.

According to one aspect of the invention, the device according to the invention is arranged on a substrate of a display element. The space available in this place is generally small, and it is impossible to arrange therein components requiring a relatively large number of calculation operations due to the difficulty of heat dissipation conditions. However, the method according to the invention now requires only a few and uncomplicated method steps, so that the method not only requires little space to implement, but also generates little process heat and does not require heat dissipation. Thus, the present invention makes it possible to realize mask recognition and reduction in the vicinity of the image generating element, that is, on the substrate of the display element for the first time. Thus, a shorter conduction path can be achieved, which reduces negative effects caused by external interference effects.

Drawings

Further features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.

Fig. 1 schematically shows a head-up display for a motor vehicle according to the prior art;

FIG. 2 shows the subdivision of an image to be displayed into rectangular partial areas;

FIG. 3 shows the subdivision of an image to be displayed into rectangular partial areas with different vertical extent;

FIG. 4 schematically illustrates a method for reducing virtual image obscuration of a head-up display of a vehicle;

fig. 5 schematically shows a first embodiment of an apparatus for reducing the virtual image occlusion of a head-up display of a vehicle;

fig. 6 schematically shows a second embodiment of an apparatus for reducing the virtual image occlusion of a head-up display of a vehicle; and

Fig. 7 shows an arrangement of means for reducing the shadowing of a virtual image of a head-up display of a vehicle on its display element.

Detailed Description

For a better understanding of the principles of the present invention, embodiments of the invention are explained in more detail below with reference to the drawings. In the drawings, the same reference numerals are used for the same or functionally identical elements and need not be described again for each drawing. It goes without saying that the invention is not limited to the embodiments shown and that the described features can also be combined or modified without departing from the scope of protection of the invention as defined in the appended claims.

Fig. 1 shows a schematic diagram of a head-up display for a motor vehicle. The head-up display has a display device 1 having an imaging unit 10 and an optical unit 14. The beam SB1 emerges from the display element 11 and is reflected by the refractive mirror 21 onto a curved mirror 22, which reflects said beam in the direction of the mirror unit 2. The mirror unit 2 is shown here as a windshield 20 of a motor vehicle. From there, beam SB2 travels in the direction of the eyes of observer 3.

The observer 3 sees a virtual image VB outside the motor vehicle, above the hood or even in front of the motor vehicle. The virtual image VB is an enlarged representation of the image displayed by the display element 11 due to the interaction between the optical unit 14 and the mirror unit 2. Here, a speed limit, a current vehicle speed, and a navigation instruction are symbolically presented. All elements of the virtual image VB are visible to the observer 3 as long as the eye of the observer 3 is located within the eyebox (Eyebox) 4 indicated by the rectangle. If the eyes of the observer 3 are located outside the eyebox 4, the virtual image VB is only partially visible or not visible at all to the observer 3. The larger the moving bezel 4, the less restrictive the observer is in selecting his seating position.

The curvature of the curved mirror 22 adapts to the curvature of the windscreen 20 and ensures that the image distortion is stable across the moving frame 4. The curved mirror 22 is rotatably mounted by means of a support 221. The rotation of the curved mirror 22 thus allowed makes it possible to move the eyebox 4 and thus adapt the position of the eyebox 4 to the position of the observer 3. The refractive mirror 21 serves to ensure a long path for the beam SB1 to travel between the display element 11 and the curved mirror 22, while nevertheless ensuring a compact optical unit 14. The imaging unit 10 and the optical unit 14 are separated from the environment by a housing 15 having a transparent cover plate 23. The optical elements of the optical unit 14 are thus protected, for example from dust in the vehicle interior. In addition, an optical film or polarizer 24 may be located on the cover plate 23. The display element 11 is typically polarized and the mirror unit 2 functions like an analyzer. The purpose of polarizer 24 is therefore to affect polarization in order to achieve uniform visibility of the useful light. The cover assembly 25 disposed on the cover plate 23 serves to reliably absorb light reflected via the boundary surface of the cover plate 23 so that an observer is not dazzled. In addition to sunlight SL, light from another stray light source 5 may also reach the display element 11. In combination with the polarizing filter, the polarizer 24 may additionally be used to reduce the incident sunlight SL.

Fig. 2 shows the subdivision of the image to be displayed into rectangular partial areas K. The illustration shows the resulting virtual image VB and partial region K from the perspective of the driver of the vehicle 50. The partial region K is a rectangle having a uniform size. It is easy to see that the partial region K in the area of the vanishing point FP or the horizon H covers a larger surrounding perceived area than the partial region K at the edge of the image. For example, the partial areas K at the vanishing points FP extend over the entire width of the road, whereas the partial areas K at the lower edges each cover only a small part of the road.

Fig. 3 shows the subdivision of the image to be displayed into rectangular partial areas K, KO-KO 5, KU1-KU3 with different vertical ranges. The illustration again shows the resulting virtual image VB and partial areas K, KO, KU1-KU3 from the perspective of the driver of vehicle 50. From the upper edge of the image to the horizon H, the partial areas KO5, KO4, KO3, KO2, KO1 have decreasing heights. Thus, the vertical extent of these partial areas decreases, seen from top to bottom. From the lower edge of the image towards the horizon H, the partial areas KU3, KU2, KU1 have decreasing heights. Thus, the vertical extent of these partial areas increases, seen from top to bottom. Since the perceived object size varies with the distance of the object, the partial areas K, KO-KO 5, KU1-KU3 in those areas of the image that cover distant objects are smaller. In the upper and lower regions of the image, the perceived object is closer; thus, the upper-most and lower-most partial regions KO5 and KU3, respectively, may also be larger than the partial regions KO4-KO1 and KU2-KU1, respectively, which are closer to the horizon H. Furthermore, in an alternative variant, the regions immediately surrounding the horizon (here the partial regions KO1 and KU 1) are omitted entirely from the display of the image elements. The partial region kon (where n=1 …) and the partial region kun (where n=1 … 3) have rectangular shapes, and partial regions adjacent to each other in the horizontal direction (i.e., partial regions having the same n value) have the same width and height. The partial region KO6 at the upper edge of the image has an approximately square shape and is the partial region with the largest area in this presentation. According to a variant not shown here, at least the partial regions K at the leftmost and rightmost edges additionally have a greater horizontal extent than the partial regions located further inwards. Here, it is also preferable to dispense with a complex determination of the exact position of the vanishing point FP and a variable masking determination in connection therewith.

Fig. 4 schematically illustrates a method for reducing virtual image obscuration of a head-up display of a vehicle. In a first step, the S1 horizon is determined. In order to determine the S1 horizon, the inclination of the vehicle may be predetermined. Alternatively, on the other hand, the vertical eye position of the observer may be determined. The vertical position of the entire image to be displayed is adjusted according to the determined horizon, preferably by tilting the curved mirror 22 around its support 221. Thereafter, the image to be displayed is subdivided S2 into a plurality of partial areas. In this case, the partial areas are rectangular, and the vertical extent of the partial areas differs depending on the area of the image to be displayed. These partial areas have a decreasing vertical extent from the upper edge area or the lower edge area of the image to be displayed towards the horizon. Preferably, a fixedly predefined line of image data of the image to be displayed is used as the horizon. The masking zones are determined S3 for the respective partial zones. In this case, for example, the transparency of a partial region can be regarded as a measure of the mask region. Finally, a check S4 is performed to determine whether the determined occlusion area exceeds the allowable size of at least one of the partial areas. And if the allowable size is exceeded, outputting an S5 warning signal. Before outputting the warning signal, a check may optionally be performed to determine whether the determined occlusion area exceeds the allowable size of two or more adjacent partial areas. Finally, at least one measure for reducing shadowing is implemented S6 in response to the warning signal. Preferably, in this case, the display of the image element in the area of the horizon is prohibited.

Fig. 5 shows a simplified schematic diagram of a first embodiment of an apparatus 30 for reducing the virtual image occlusion of a head-up display of a vehicle. The device 30 has an input 31 via which an image B to be displayed is received. Information N, BR may also be received via input 31 from which evaluation module 32 may determine the horizon. For determining the horizon, for example, the inclination N of the vehicle can be evaluated. To determine the horizon, the vertical eye position BR of the observer can also be evaluated. The subdivision module 33 is arranged to subdivide the image B to be displayed into a plurality of partial areas. In this case, the partial areas are rectangular, and the vertical extent of the partial areas differs depending on the area of the image B to be displayed. Preferably, these partial areas have decreasing sizes from the upper edge area and/or the lower edge area of the image B to be displayed to the horizon. The processing module 34 is arranged to determine the masking zone of the respective partial zone. In this case, processing module 34 may consider, for example, the transparency of a portion of the area as a measure of the obscured area. The processing module 34 is further arranged to check whether the determined screening zone exceeds the allowable size of at least one of the partial zones. If the allowable size is exceeded, the warning module 35 is arranged to output a warning signal W. The processing module 34 may optionally check whether the determined masking zone exceeds the allowable size of two or more adjacent partial zones before outputting the warning signal W. The warning signal W can be output via the output 38 of the device 30, for example for activating at least one measure for reducing shadowing. Preferably, in this case, the display of the image element in the area of the horizon is prohibited.

The evaluation module 32, the subdivision module 33, the processing module 34 and the warning module 35 may be controlled by a control module 36. The settings of the evaluation module 32, the subdivision module 33, the processing module 34, the warning module 35 or the control module 36 may be changed via the user interface 39, if appropriate. If desired, the data accumulated in the device 30 may be stored in a memory 37 of the device 30, for example for later evaluation or for use by components of the device 30. The evaluation module 32, the subdivision module 33, the processing module 34, the warning module 35 and the control module 36 may be implemented as dedicated hardware, such as an integrated circuit. However, these modules may of course also be implemented in partial or complete combination or as software running on a suitable processor (e.g. on a GPU or CPU). The input 31 and the output 38 may be implemented as separate interfaces or as a combined interface.

Fig. 6 shows a simplified schematic diagram of a second embodiment of an apparatus 40 for reducing the virtual image occlusion of a head-up display of a vehicle. The device 40 has a processor 42 and a memory 41. For example, the device 40 is a controller or an embedded system. Stored in memory 41 are instructions that, when executed by processor 42, cause apparatus 40 to perform steps according to one of the methods described. Thus, the instructions stored in the memory 41 embody a program executable by the processor 42 and embodying the method according to the invention. The device 40 has an input 43 for receiving information. The data generated by the processor 42 is provided via an output 44. In addition, the data may be stored in the memory 41. The input 43 and output 44 may combine to form a bi-directional interface.

The processor 42 may include one or more processor units, such as a microprocessor, digital signal processor, or a combination thereof.

The memories 37, 41 of the described devices may have volatile memory areas and nonvolatile memory areas, and may include a variety of memory devices and storage media, such as hard disks, optical storage media, or semiconductor memories.

Fig. 7 shows an arrangement of the means 30, 40 for reducing the shadowing of a virtual image VB of a head-up display of a vehicle on its display element 11. Shown is a perspective view of an embodiment of a display device 1 of a head-up display according to the invention having a plurality of electronic components 112, one of which is a driver 12. The heat conducting element 114 is arranged above the electronic component 112. An exploded perspective view of the display device 1 is shown. These electronic components 112 in this exemplary embodiment are the image brightness monitoring unit 16, the driver 12 for the display element 11, and the device 30, 40 according to the invention, all of which are arranged on the substrate 115 of the display element 11 in such a way that they adjoin the active area 113, which is shown here with dashed lines. A cover 126 is located over the active area 113, the design and function of which cover depends on the type of display. In the case of a liquid crystal display, the cover 126 is, for example, a color filter glass, in contrast to the cover glass required for encapsulation in the case of an OLED display. Active region 113 is typically slightly smaller than cap 126. A cover glass 111 is provided above the display element 11. Here, the heat conducting element 114 extends over the entire width of the display element 11 and thus over all three components 112. As a result of the planar application of the heat-conducting element 114, which is composed of a suitable material with high thermal conductivity, the heat input of these components 112 is distributed uniformly and thus the temperature is reduced. The method according to the invention makes it possible to perform the mask recognition and the mask reduction with few method steps, so that the mask recognition and the mask reduction can be performed without problems on one of the electronic components 112 arranged directly on the substrate 115 of the display element 11. Although the means 30, 40 provided as one of the components 112 is here indicated as a separate component 112, it is preferably implemented in a single component 112 in combination with the image brightness monitoring unit 16.

In the case of a large bright head-up display covering a large driver's field of view, problems of shading may occur in addition to the glare problem. What is important here is how this can be avoided: important objects (such as cyclists, pedestrians, animals, soccer balls rolling onto the road, etc.) are obscured by bright light emitting areas (especially white areas) in the virtual image of the heads-up display and may therefore not be perceived by the driver. A general approach is to avoid a relatively large area on the LC display that emits light over the whole area. In the case where such a region that emits light over the entire region occurs, the LC display is transparent in the corresponding region, and thus light from its backlight is allowed to pass through. Instead of using a padding region, the virtual image VB is preferably constructed of thin lines. Thus reducing possible shadowing.

To monitor the occlusion, the virtual image VB is broken up into small rectangles, also called tiles, and the transparency of these tiles is then checked. This should take into account the following facts: the size of the transparency that is allowed to be checked in this way is only a quarter of the transparency of the maximum allowed masking area, since in the worst case the regional white (light-emitting) area can be divided precisely into four rectangles adjacent to each other. In order to implement occlusion avoidance for functional safety purposes in heads-up displays, it is necessary to monitor the image transparency. Such monitoring is typically implemented in a chip on the transmission path upstream of the display. Faults may also occur at the interface of the display controller or in the input area of the display controller. Furthermore, tracking the position of the eyes of an observer (so-called eye tracking) to identify the viewing direction is technically demanding.

One configuration of the invention provides for arranging the shadowing monitoring as far back as possible in the transmission chain and/or simplifies the concept of the shadowing monitoring to such an extent that the shadowing monitoring can be implemented without problems on components located near the LC display. It is proposed to change the heights of tiles within the area of the image to be presented, i.e. to change the extent of these tiles in the vertical direction. It is also proposed to implement masking monitoring in a display controller, i.e. on a component (display glass) arranged on the substrate 115. In this case, the determination of complex eye tracking or vanishing points is replaced by the assumption of a fixed horizon height. This is advantageously extended by the height information as a result of the eyebox adjustment (i.e. a vertical adaptation of the presentation of the virtual image to the height of the eye position of the observer 3). In any case, such a function is provided for a head-up display and is achieved, for example, by mechanically adjusting the curved mirror 22 by means of its support 221. In future vehicles with controllers for highly automated driving, it is expected that the vertical position of the horizon will be determined by means of image processing for highly automated driving. Thus, mechanical eyebox adjustment may particularly well adapt the presentation of the virtual image to the actual horizon. Thus, the tile size is only a function of the vertical distance to the horizon. This simplifies implementation on components arranged near the active area 113 of the LC display, for example on a display timing controller (control unit which controls, inter alia, the time sequence of pixels presented on the LC display). Preferably, the masking monitor is arranged as far back as possible in the processing chain of the display controller. This ensures that as much of the potential effects that may lead to undesired masking as possible are covered, including for example those that occur only in processing steps upstream of the display timing controller. Regardless of these effects, the effects that may cause undesirable masking and occur on the interface between the graphics chip providing the image B to be displayed and the display controller controlling the active area 113 of the LC display are monitored and identified. Thus increasing the safety during operation of the head-up display.

List of reference numerals:

1. Display device

2. Mirror unit

3. Observer(s)

4. Eye movement frame

5. Stray light source

10. Image forming unit

11. Display element

111. Cover glass

112. Electronic component

113. Active region

114. Heat conducting element

115. Substrate board

12. Driver(s)

126. Covering material

14. Optical unit

15. Shell body

16. Image brightness monitoring unit

20. Windshield glass

21. Refractive reflector

22. Curved mirror

221. Support member

23. Cover plate

24. Optical film/polarizer

25. Cap assembly

30. Device and method for controlling the same

31. Input terminal

32. Evaluation module

33. Subdivision module

34. Processing module

35. Warning module

36. Control module

37. Memory device

38. An output terminal

39. User interface

40. Device and method for controlling the same

41. Memory device

42. Processor and method for controlling the same

43. Input terminal

44. An output terminal

50. Transport means

B image to be displayed

BR vertical eye position

FP vanishing point

H horizon

K. KO1 … KO5, KU1 … KU3 partial region

Inclination of N

SB1, SB2 beam

SL sunlight

VB virtual image

W warning signal

S1 determining horizon

S2 subdividing the image to be displayed into partial areas

S3 determining the shielding area

S4 checking the shielding area

S5 outputting a warning signal

S6 implementing measures for reducing shading

Claims (12)

1. A method for reducing the obscuration of a virtual image (VB) of a head-up display of a vehicle (50), the method comprising the steps of:

-subdividing (S2) the image to be displayed into a plurality of partial areas (K, KO1 … KO5, KU1 … KU 3), wherein the partial areas (K, KO1 … KO5, KU1 … KU 3) are rectangular and the vertical extent of the partial areas differs from area to area of the image to be displayed;

-determining (S3) masking regions of the respective partial regions (K, KO1 … KO5, KU1 … KU 3); and

-Outputting (S5) a warning signal (W) if the determined masking zone exceeds the allowable size of at least one of the partial zones (K, KO1 … KO5, KU1 … KU 3).

2. The method according to claim 1, characterized in that when determining (S3) the mask areas, the transparency of the partial areas (K, KO1 … KO5, KU1 … KU 3) is taken as a measure of the mask area.

3. The method according to claim 1 or 2, characterized in that before outputting (S5) the warning signal (W), a check (S4) is performed to determine whether the determined shadowed area exceeds the allowed size of two or more adjacent partial areas (K, KO1 … KO5, KU1 … KU 3).

4. Method according to any of the preceding claims, characterized in that the partial areas (K, KO1 … KO5, KU1 … KU 3) have a decreasing vertical extent from the edge area of the image to be displayed to the horizon (H).

5. Method according to claim 4, characterized in that the horizon (H) is determined (S1) by determining the inclination (N) of the vehicle (50).

6. Method according to claim 4, characterized in that the horizon (H) is a fixedly predefined horizon of the image data of the image (B) to be displayed and that the vertical displacement of the entire image content to be presented is performed in accordance with the detected vertical eye position (BR) of the observer (3).

7. Method according to any one of the preceding claims, characterized in that at least one measure for reducing the shading is implemented (S6) in response to the warning signal (W).

8. A method according to claim 7, characterized in that the display of picture elements in the area of the horizon (H) is inhibited.

9. A computer program comprising instructions which, when executed by a computer, cause the computer to perform the steps of the method for reducing the occlusion of a virtual image (VB) of a heads-up display of a vehicle (50) according to any one of claims 1 to 8.

10. An apparatus (30, 40) for reducing shadowing of a virtual image (VB) of a head-up display of a vehicle (50), the apparatus comprising:

-a subdivision module (33, 42) for subdividing (S2) an image to be displayed into a plurality of partial areas (K, KO1 … KO5, KU1 … KU 3), wherein the partial areas (K, KO1 … KO5, KU1 … KU 3) are rectangular and the vertical extent of the partial areas differs from area to area of the image to be displayed;

-a processing module (34, 42) for determining (S3) a masking zone of the respective partial zones (K, KO1 … KO5, KU1 … KU 3); and

-A warning module (35, 42) for outputting (S5) a warning signal (W) if the determined masking zone exceeds the allowable size of at least one of the partial zones (K, KO1 … KO5, KU1 … KU 3).

11. Head-up display for a vehicle (50), wherein the head-up display has an apparatus (30, 40) according to claim 10 or is configured to perform the method for reducing the occlusion of a virtual image (VB) of the head-up display according to any one of claims 1 to 8.

12. Head-up display according to claim 11, characterized in that the device (30, 40) is arranged on a substrate (115) of the display element (11).