Display device for a motor vehicle, in particular head-up display

Description

[0001] The invention lies in the field of electronics and is particularly advantageous for use in automotive engineering. More specifically, the invention lies in the field of display devices, which, especially in automotive engineering but also in other applications, serve, among other things, to present information clearly.

[0002] For a universally applicable and user-friendly display, it is possible, for example, to represent a display area within a physical or virtual screen on which pictorial representations of instrument gauges can be shown. It is already known, for instance, to display an analog speedometer with an analogously movable pointer on a screen. This typically requires the area-based control of screen segments, especially screen pixels.

[0003] A common technique of this type involves the use of TFT displays equipped with suitable backlighting. If appropriate light sources, such as LEDs with a collimation device, are used for backlighting, such TFT displays can also be used to create so-called head-up displays. In these displays, a message is projected onto a vehicle's windshield or reflected into the driver's field of vision via the windshield or an additional reflective lens (combiner lens).

[0004] For such an application, as well as for a TFT display intended for direct viewing, relatively high luminance levels are necessary, meaning high power dissipation from the light sources used, such as LEDs. Especially when used in a vehicle, the power consumption must be minimized, particularly given that only a small portion of the produced light is perceptible to the viewer when a specific image is transmitted. For example, certain polarizations are partially filtered out from the light path, and the backlit TFT display typically blocks out most of the dark image areas.

[0005] Besides energy consumption, heat generation also plays an important role, as the temperature of the relevant components of the display unit must be limited. Particularly in the automotive sector, temperature conditions can already vary considerably, so that especially at high ambient temperatures, limits are quickly reached that may necessitate a reduction in lighting output.

[0006] So far, it is known from the state of the art to use the most efficient light-emitting diodes possible for backlighting, to optimize the use of the various polarization components, and to regulate the brightness of the backlighting depending on the ambient light, various system temperatures, and individual user settings.

[0007] A display device according to the preamble of claim 1 is known from DE 102 12 600 B4.

[0008] Against the background of the prior art, the present invention is based on the objective of creating a display device, for example for a motor vehicle, which allows the most efficient and energy-efficient use of lighting elements for illuminating a screen matrix.

[0009] The problem is solved by the features of the invention according to claim 1. Subclaims 2 to 6 specify advantageous embodiments of the invention. Method claims 7 and 8 describe solutions according to the invention within the framework of operational processes.

[0010] The invention thus relates specifically to a display device for a motor vehicle, in particular a head-up display, with a screen matrix and a lighting matrix comprising a plurality of lighting elements for at least partial illumination of the screen matrix and with a control device for the lighting matrix.

[0011] The problem is solved according to the invention by one or more lighting patterns stored in a storage device for selectively and differently controlling the lighting elements depending on classes of images to be displayed.

[0012] The invention is based on the understanding that many images displayed within a display device exhibit relatively large dark areas and that the displayed images can be divided into groups or so-called classes, with the images within a class differing only slightly. For example, when displaying a speedometer in a head-up display, the speed scale can remain the same when showing different speeds, with only the pointer position changing from image to image within that class. Many areas, for example, on a circular speedometer display, both inside and outside the speed scale, can remain dark, and the actual display within the class changes only through the position of the speedometer needle, i.e., the speed indicator.The corresponding displays can thus be grouped into a class of images to be displayed, whereby the illuminance distribution of the illumination matrix, also referred to as the illumination pattern in this text, can be the same for each such class. This illuminance distribution stipulates that certain lighting elements of the illumination matrix remain dark where dark areas are required in the displayed image. Specific image areas of the illumination matrix are uniquely assigned to corresponding areas of the screen matrix. A differentiation can be made between light and dark areas or light and black areas; however, more than two brightness levels can also be considered when controlling the individual lighting elements.In this context, it is important that for each class of display images, an illuminance distribution, i.e., an illumination pattern or a control pattern of the individual lighting elements, is provided and stored and can be retrieved by the control unit of the lighting matrix.

[0013] A displayed image can also include more than one display element. The display unit can generally allow various display options, enabling a user to switch between different display images, for example, when the measured quantities need to be displayed in different units of measurement, such as when switching a speedometer from kilometers per hour to miles per hour. Furthermore, switching to other displayed measured quantities, such as engine speed or temperature in a motor vehicle, is also generally possible. When such a display switch occurs, the control unit checks which class of displayed images the image belongs to and retrieves and applies the corresponding illumination pattern for the lighting elements from the memory unit.

[0014] This allows the luminous intensity of the individual lighting elements of the screen matrix to be reduced to the minimum necessary for a specific class, thus limiting both power consumption and the contribution to temperature increase. This is made possible in particular by the fact that the lighting matrix is ​​composed of individually controllable lighting elements.

[0015] According to the invention, a current measuring device connected to the control unit of the lighting matrix is ​​provided for recording the power consumption of the lighting matrix of the display device, wherein the control unit is designed as an adjustable current source with individual control channels for each light source in the lighting matrix. According to the invention, depending on the need to save electrical power, the energy supply and energy consumption of the lighting matrix are reduced by reducing the absolute illuminance or the number of operated lighting elements. This application, as well as the consideration of the ambient temperature, is particularly useful and important when using the invention in the context of motor vehicles.

[0016] Advantageously, the classes of images are divided in such a way that each class of images has essentially the same black areas or dark areas.

[0017] Furthermore, it can be advantageously provided that within a class of images, at least 70%, and in particular 90%, of the black areas between different images are congruent. This ensures that when transitioning from one image to another of the same class, no additional black areas, or only a few in exceptional cases, need to be displayed. For these areas, the light generated by the illumination matrix can be easily blocked by the screen matrix without generating excessive heat or power loss. With a high degree of congruence of the black areas, the number of lighting elements required can be significantly reduced, or the illuminance can be sufficiently reduced for a large number of lighting elements to limit heat input and power consumption.

[0018] For example, in a class of images depicting a display instrument with a movable pointer, the area that the moving pointer can sweep across can be backlit. Within this area, light is then only transmitted through the screen matrix in the region where the pointer is currently being indicated, while in the other areas where the pointer / indicator needle could potentially move, the light generated by the backlight matrix is ​​blocked by the screen matrix.

[0019] Advantageously, in the embodiment of the invention, it may be provided that a plurality of applications are provided, each corresponding to the representation of different display instruments or combinations of display instruments.

[0020] Each class of images can be assigned to a specific application of the display device, for example, the application to display a speedometer. Different speedometer readings, typically represented by different positions of a pointer needle on a scale, usually require a colored display in the same image area, where the scale itself remains constant and only the position of the pointer needle changes. The illumination matrix can then be controlled such that the area of ​​the image containing the scale and the area swept by the pointer needle is illuminated in the corresponding area of ​​the screen matrix, while other areas of the display remain dark. These dark areas of the display are then not illuminated by the illumination matrix.

[0021] Instead of a speedometer, another display instrument, such as an analog clock, can also be shown. In this case, too, the areas of the display that correspond to the clock scale and the area swept by the hour and minute hands are illuminated by the lighting matrix. Ultimately, several display instruments can be shown simultaneously in the display unit. In this case, the lighting pattern of the lighting matrix is ​​correspondingly more complex.

[0022] The lighting patterns of the lighting matrix, which are assigned to the individual applications or application images, can be calculated in advance, assigned to the individual applications and stored in a storage device.

[0023] However, it is also possible to calculate the required distribution of illuminance on the screen matrix for an application in real time from pre-calculated and saved partial images and apply it accordingly.

[0024] This is particularly advantageous if the arrangement of advertisements on the display device can be customized to some extent by the user, for example by enlarging certain advertisements or by making a selection when arranging different displays on a screen.

[0025] In this case, the screen matrix pattern can be used to calculate the required illuminance and, consequently, the distribution of the lighting elements to be controlled within the lighting matrix. Since the corresponding application images do not change rapidly, this calculation can be performed once during the display's operation and then applied. During the period between commissioning the display and calculating the required lighting patterns, the display can be operated with the lighting matrix fully illuminated.

[0026] An advantageous embodiment of the invention provides for a temperature measuring device connected to the control unit of the lighting matrix. In this case, the design of the lighting patterns used for specific application images can be made dependent on the ambient temperature and / or the temperature of the lighting matrix. This ensures that, under certain temperature conditions, for example, and particularly at high ambient temperatures, the pattern of the operating lighting elements of the lighting matrix is ​​minimized and / or the lighting intensity of the corresponding lighting elements is reduced to a minimum.

[0027] For example, the control unit for the lighting matrix can switch to energy-saving modes with progressively reduced illuminance and reduced lighting patterns when certain temperature thresholds are exceeded. Certain parts of the displayed image on the display unit can also be switched off by turning off the corresponding lighting elements, provided that the respective displays can be considered dispensable.

[0028] This could, for example, lead to the speedometer continuing to display at high ambient temperatures, while a tachometer or fuel gauge in the display unit would be switched off by turning off certain lighting elements.

[0029] The invention relates not only to a display device of the type described above, but also to a method for controlling a display device. According to the invention, the control device for the illumination matrix assigns an illumination pattern to the class of images to be displayed and controls the illumination matrix according to this illumination pattern.

[0030] Furthermore, it can be advantageous to take into account the temperature detected by the temperature measuring device when controlling the lighting matrix.

[0031] According to the invention, it is provided that when controlling the lighting matrix, the power consumption of the display device, in particular the lighting matrix, as detected by the current measuring device, is taken into account.

[0032] The invention is shown below with reference to exemplary embodiments in the figures of a drawing and subsequently explained. The figures show: Fig. 1 schematically shows a vehicle in a side view with a driver and a schematically represented head-up display; Fig. 2 a screen display with a speedometer, a thermometer and a fuel gauge; Fig. 3 a screen display as in Figure 2 with a different displayed speed value, Fig. 4 a real application image of a screen display, Fig. 5 in a perspective view the application image from Figure 4 and the necessary luminance distribution as well as the necessary illumination pattern of the illumination matrix and Fig. 6 schematically the technical structure of the head-up display.

[0033] Figure 1Figure 1 shows a side view of a motor vehicle 1 with a driver 2 looking in the direction of travel 3 and looking through a windshield 4. In addition to his surroundings, the driver 2 also sees an image projected onto the windshield 4 by a display device 5 in the form of a head-up display, as indicated by arrow 6. The driver 2 sees a virtual image in the image plane 7, which, from his perspective, lies behind the windshield above the vehicle's hood. This image plane can also be located in front of the windshield from the driver's point of view. The virtual image in image plane 7 thus superimposes itself on the images the driver perceives of his surroundings through the windshield.

[0034] In order to project an image across the windshield 4 towards the driver 2, the display device 5 has a projector-like device that directs light beams from a light source towards the windshield. The design of the projector-like device is shown in Figure 6 shown in more detail and explained further below.

[0035] A head-up display, as schematically illustrated by the Figure 1 As described, it allows the driver of a motor vehicle to simultaneously take in information provided to him via the head-up display in the same direction of view, without taking his eyes off the surroundings in the direction of travel.

[0036] In Figure 2Figure 1 shows an example of the screen content of a display device according to the invention, wherein the screen is bounded by a dashed line 8. Within the screen are arranged a speedometer display 9, a thermometer display 10 for displaying, for example, the temperature of engine oil, and a fuel gauge 11 with three illuminated fields 11a, 11b, 11c. The instruments 9, 10, 11 shown are illuminated against a dark background and are displayed in one or more colors.

[0037] In Figure 3 The same display elements are arranged on a screen in the same way as already shown in Figure 2, however, the displayed speed of the speedometer 9 is different, so that the pointer 9a is in a different position than in Figure 2. Figure 2 The position that pointer 9a reaches in Figure 2 has taken is in Figure 3 Shown as dashed lines.

[0038] The lighting of the image should be designed in such a way that the speed indicator 9a is visible both in the Figure 2 position shown as well as in the Figure 3 The position shown should be well illuminated. For example, to illuminate the three display elements from the Figures 2 and 3 To be able to display this information, it makes sense that the areas of a screen matrix defined by the scales are generously illuminated by a lighting matrix. Other areas, such as those in Figure 3 The area shown below the speedometer 9 with a dash, 12, can remain unlit, since in no variant of images of this class does an image element need to be displayed by illumination.

[0039] Figure 4As an example, it shows realistic screen content in the form of a combined analog and digital speedometer, where a scale, a pointer, and a digital number display in the form of light text on a dark background are shown, as well as a display field whose background is light and where text is displayed in black against the light background, and a text field (in Figure 4 (labeled with the word "Testtext"), in which text can be displayed in light text on a dark background.

[0040] Figure 5Figure 13 shows, in three perspective layers, the actual screen display 13, below which is the appropriate distribution of the screen illumination 14, which enables sufficient illumination of the corresponding segments of the screen matrix representing the image information, and finally, in the layer below the screen illumination 14, the illumination matrix 15, in which fifteen individual illumination elements 16, 17, 18 are shown, each providing different illumination intensities. For example, a first illumination element 16 is operated at medium illuminance, a second illumination element 17 at high illuminance, and a third illumination element 18 remains dark. Overall, the pattern of the fifteen exemplary illumination elements of the illumination matrix 15, when illuminating the screen matrix, results in the illuminance distribution 14 shown in the middle layer.The lighting elements 16, 17, 18 can be individually controlled within the lighting matrix by a control device.

[0041] Figure 6 The figure schematically shows a head-up display in which light from individual lighting elements 16, 17, 18 in the form of light-emitting diodes is guided through a collimator unit 19 to a frosted screen 20 and from there illuminates or shines through elements of a screen matrix 21 to a greater or lesser degree. The optical image information is projected from the screen matrix 21 to an optional mirror system 22 and from there reflected to an imaging optic 23, which may include a windshield 4, and from there reflected to the eye 24 of the driver 2.

[0042] The collimator 19 has collimation optics that essentially focus the divergent beams emitted by the individual LEDs 16, 17, 18 into bundled light beams, which are then directed to the frosted screen 20. Segments of a screen matrix 21 are backlit and illuminated through the frosted screen 20. The individual segments of the screen matrix are transparent, optionally colored, screen pixels or display segments, through which only light of a desired color is transmitted. This creates the desired image pattern and thus the image display. Areas that are to remain dark during the image display are controlled with the color information "black" in the screen matrix 21, i.e., the incident light is blocked. Therefore, within the scope of the invention, it is advantageous not to unnecessarily illuminate the black screen areas in the region of the screen matrix 21 with light from the LEDs 16, 17, 18.

[0043] The screen matrix 21 is controlled segment by segment or pixel by pixel by the screen control unit 24, which receives the information to be displayed from sensors 25 or an image generation unit. The type of display can be customized by the user via an interface 26, for example by selecting colors, switching display content on or off, or enlarging, reducing, or rearranging it.

[0044] The screen control device 24 provides information about the necessary illuminance distribution or basic information about the nature of the image to be displayed to the control device 27, which, for example, has a storage device 28 containing pre-stored lighting patterns corresponding to the screen content used, which can be retrieved and passed on to the lighting matrix 15 for its control.

[0045] The control unit 27 for the lighting matrix also receives information from a temperature sensor 29 and from a current sensor 30, wherein the temperature sensor 29 detects the ambient temperature of the lighting matrix and the current sensor 30 detects the current consumption by the lighting elements 16, 17, 18. The current sensor 30 is inserted into the supply line of the lighting elements for this purpose.

[0046] The design of the display device and its operating method according to the invention allows for reliable operation of a head-up display even under adverse temperature conditions and with the lowest possible electrical energy consumption.

Claims

1. A display apparatus (5) for a motor vehicle (1) with a screen matrix (21), which can be backlit and is configured to allow light through or to block it, and with a screen control apparatus (24) for the screen matrix (21), and an illumination matrix (15) having a plurality of luminous elements (16, 17, 18) for the at least partial transillumination of the screen matrix (21) and with a control apparatus (27) for the illumination matrix (15), having a storage apparatus (28) in which one or more illumination patterns are stored, wherein the screen control apparatus (24) is configured to pass on information about a necessary illumination pattern or fundamental information about the nature of the image to be displayed to the control apparatus (27), and wherein the control apparatus (27) is configured to, in accordance with said information, retrieve illumination patterns from the storage apparatus (28) and control the luminous elements (16, 17, 18) of the illumination matrix (15) selectively and differently as a function of classes of images to be displayed, characterised in that an illumination pattern is assigned to the class of the images to be displayed in the control apparatus for the illumination matrix and the illumination matrix is controlled according to the illumination pattern, and in that a current measuring apparatus (30) connected to the control apparatus (27) of the illumination matrix (15) is present for detecting the power consumption of the illumination matrix (15) of the display apparatus (5), wherein the control apparatus is designed as a controllable current source with individual control channels for each luminous means in the illumination matrix (15), and wherein the control apparatus is configured, depending on the necessity to save electrical power, to reduce the energy supply and the energy consumption of the illumination matrix, by the absolute illumination intensity or the number of operated illumination elements being reduced.

2. The display apparatus according to claim 1, characterised in that a class of images in each case has essentially the same dark and / or black image regions (12).

3. The display apparatus according to claim 2, characterised in that within a class of images at least 70 %, in particular 90 % of the black areas between different images are congruent.

4. The display apparatus according to claim 1 or one of the following, characterised in that in each case a class of images is assigned to an application of the display apparatus.

5. The display apparatus according to claim 4, characterised in that a plurality of applications is provided, which in each case correspond to the representation of different display instruments (9, 10, 11) or combinations of display instruments (9, 10, 11).

6. The display apparatus according to claim 1 or one of the following, characterised by a temperature measuring apparatus (29) which is connected to the control apparatus (27) of the illumination matrix (15).

7. A method for controlling a display apparatus according to claim 1 or one of the following, characterised in that an illumination pattern is assigned to the class of the images to be displayed in the control apparatus (27) of the illumination matrix (15) and the illumination matrix is controlled according to the illumination pattern, and in that the power consumption of the illumination matrix (15) of the display apparatus (5) detected by the current measuring apparatus (30) is taken into account during the control of the illumination matrix (15).

8. The method according to claim 7, characterised in that the temperature detected by the temperature measuring apparatus (29) is taken into account during the control of the illumination matrix (15).