Headlights and methods for operating a headlight

Abstract

Headlights for a motor vehicle, with a first projection device (12) comprising several first light point sources (18) for illuminating an area (16), a second projection device (14) comprising several second light point sources (22) for illuminating the same area (16) and a computing unit for deactivating those first light point sources (18) and / or second light point sources (22) which, in the projected state on the surface, illuminate only one area of ​​the surface.

Description

[0001] The invention relates to a headlight and a method for operating a headlight, by means of which a graphically delimited symbol can be projected onto a surface in front of a motor vehicle.

[0002] From DE 10 2015 201 764 A1 a motor vehicle is known in which a headlight can display a symbol on a roadway by means of a correspondingly adapted light distribution.

[0003] From DE 10 2016 119 567 A1 a motor vehicle is known in which a movable symbol is projected into a lighting area of ​​a first headlight by a second headlight.

[0004] There is a constant need to be able to clearly recognize a symbol projected by a spotlight.

[0005] The object of the invention is to specify measures that enable good recognizability of a symbol projected by a headlight.

[0006] The problem is solved according to the invention by a headlight having the features of claim 1 and a method having the features of claim 9. Preferred embodiments of the invention are specified in the dependent claims and the following description, each of which can individually or in combination represent an aspect of the invention.

[0007] According to the invention, a headlight for a motor vehicle is provided with a first projection device comprising several first light sources for illuminating a surface, a second projection device comprising several second light sources for illuminating the same surface, and a processing unit for deactivating those first and / or second light sources that, in the projected state, illuminate only a portion of the surface. In particular, the processing unit is additionally configured to activate those first and / or second light sources that overlap in the projected state.

[0008] To ensure that a symbol projected by the spotlight is as clearly visible as possible, the highest possible light intensity is desirable. This intensity should be achieved within a defined, limited area so that the projected symbol stands out from the surrounding ambient light. For this purpose, more than one projection device is used. The projected images generated by different light sources are superimposed to project the desired symbol, allowing the light output of at least two projection devices to overlap. However, it is possible that the projected images will not be perfectly aligned, resulting in multiple images that are offset from one another. This is particularly true if the distance of the projected symbol and / or the relative position of the surface onto which the symbol is to be projected is variable.For example, a symbol might be projected closer to or farther away from the road surface depending on the vehicle's current speed. This results in a shorter or longer beam path for the projection equipment, which, due to a lateral offset of the projected symbols relative to each other, can lead to blurring at the edges of the graphically defined symbol. This blurring can make the symbol difficult to perceive, even with sufficient light intensity.

[0009] Since the respective projection device can have multiple light sources, especially LED elements, as its light source, illuminating, for example, a display projected by a lens, the multiple separately controllable light sources make it possible to deactivate precisely those individual light sources that illuminate only one pixel on the surface and do not overlap sufficiently with another projected pixel from a light source in a different projection device, or to at least partially overlap them with a pixel generated by an additionally activated light source.Assuming a flat surface defined by a road surface, and knowing the vertical distance of the projection device to the road surface, the projection direction of the projection devices, and the horizontal distance between the projection devices, the processing unit can calculate how the symbols projected by each projection device would superimpose on the surface for a specific desired distance of the projected symbol from the vehicle. Under these assumptions, the beam paths of the projection devices depend only on their position and orientation within the headlight and can therefore be known in advance, possibly after initialization.This allows the computer, knowing the determined relative position and the known beam paths of the projection devices, to calculate in advance how the projected images would appear on the surface and to determine which individual pixels would not result in a sufficiently overlapping pixel when the symbol is projected. The computer can then deactivate precisely these light sources, while activating those that would overlap sufficiently when the symbol is projected. This results in a symbol projected onto the surface that exhibits high brightness due to the superimposed light intensities of the projection devices and high sharpness, particularly edge sharpness, due to the deactivated, non-overlapping light sources.By deactivating non-overlapping light sources of the projection devices, high brightness and sharpness of the symbol projected onto the surface can be achieved, thus enabling good recognizability of a symbol projected by a spotlight.

[0010] The projection device can use LED elements, an LCD (liquid crystal display), and / or a DMD (dot matrix display) to generate the symbol. The DMD can provide multiple, individually controllable light sources for projecting the respective assigned pixel. The symbol projected by the headlight can, for example, be an area of ​​illumination for a motor vehicle, which can be both brightly lit and sharply defined to avoid dazzling oncoming traffic. Specifically, the symbol projected by the headlight can be a warning signal, an alphanumeric message, a graphic directional indicator, or something similar. This allows information to be projected onto the road surface for the driver of a motor vehicle without requiring them to take their eyes off the road to perceive the information.In particular, the processing unit is designed to assume predefined vehicle heights for different vehicle types, such as off-road vehicles and / or lowered vehicles, and / or standard suspension heights. Since the suspension height also influences the vertical distance between the projection devices, the relevant beam path of the projection devices can be easily determined based on the suspension height. For this purpose, corresponding values ​​for different suspension heights can be stored in a lookup table. Preferably, the processing unit can also take into account a pitch angle and / or roll angle and / or yaw angle of the vehicle, which is measured anyway for driver assistance systems and can be queried by the processing unit via a CAN bus.Deviations in the beam paths of the projection devices caused by one of these angles can be taken into account by the computing unit using a lookup table.

[0011] Preferably, an area detector is provided to detect the three-dimensional relative position of the area to the first and second projection devices. This enables a sharp-edged projection of the symbol even on an uneven surface, such as one that is angled and / or curved. Instead of assuming a flat surface, the actual three-dimensional position of the area in space can be taken into account by the processing unit. For example, if the area for the symbol is provided by the surface of a road, a shorter beam path and thus a shorter distance for the symbol to be projected may result on an uphill road than on a downhill road. For this purpose, the area detector, for example a radar sensor, can be used to determine the relative position of the area in three-dimensional space, and in particular the distance of the area to the projection devices.The area detector is specifically designed to measure the surface suitable for the projection device using non-contact measurement techniques. For this purpose, the distance between several measurement points on the surface lying in a precisely defined direction can be determined, and a three-dimensional compensating surface encompassing these measurement points can be calculated. The area can be scanned by the area detector using, for example, sound waves, radar waves, light waves, or similar methods. Preferably, those areas of the surface in which the edges of the symbol to be projected lie, according to the calculations of the computing device, are scanned by the area detector with a higher resolution than the other areas.

[0012] In particular, the processing unit is designed to deactivate a light source if the projected light source overlaps with another projected light source on the surface by less than 50%. This takes into account that a pixel projected by a given light source has a certain area, and that a perfectly centered overlap of two projected pixels is generally not possible, and that there is usually a partial overlap of pixels at the edges of the symbol to be projected. By deactivating light sources that selectively overlap with another pixel by less than 50%, brighter areas can be retained at the edges, and darker areas can be avoided, thus achieving a high brightness contrast at the edges of the projected symbol, resulting in a sharper appearance.

[0013] Preferably, the first and / or second light sources are arranged regularly, particularly at substantially identical intervals, in rows and columns. This makes it easier to deactivate and / or activate different light sources row by row and / or column by column for the projection of a specific geometrically defined symbol, so that it is not necessary to control all light sources individually. This allows for faster switching of the light sources.

[0014] The first projection device and the second projection device are particularly well-suited for projecting a two-dimensional symbol with at least partially straight edges. At least some of the straight edges of the symbol to be projected can follow the orientation of the columns and / or rows of the light sources, allowing the edges to be easily generated by activating and / or deactivating rows or columns of the light sources. Furthermore, the processing unit can calculate only the projected vertices of the symbol's edges and interpolate the pixels running from one vertex to the other along the edge. This simplifies and speeds up the calculation of which of the edge light sources should be activated or deactivated.

[0015] In particular, the processing unit features a lookup table containing optical offsets of the images projected by the first and second projection devices relative to each other for different relative orientations and / or different distances to a flat surface. Especially assuming a flat surface onto which the symbol is to be projected, this allows for very fast and accurate results with minimal computational effort. It is particularly useful to consider that there are certain threshold values ​​at which an offset corresponding to the extent of a light source, two adjacent light sources, or several light sources arranged in a row occurs. Therefore, it is sufficient to determine the range of values ​​within which the relative position of the surface falls with a specific offset of the projected images from the projection devices.

[0016] Preferably, the lookup table contains correction values ​​for the optical offset between the images projected by the first and second projection devices for different surface curvatures. Using these correction values, values ​​stored in the lookup table for flat surfaces can be converted into values ​​for curved surfaces. This allows for a high degree of sharpness for the symbol projected onto a curved surface with a reasonable computational effort.

[0017] The computing unit is preferably configured to completely deactivate at least one projection device when the surface is in at least one specific predefined relative position, particularly when positioned below a minimum distance and essentially vertically oriented. During the vehicle's journey, the symbol, especially for displaying driving-related information, is typically projected onto the road surface. The symbol is projected at a sufficiently large distance from the vehicle so that the driver can easily perceive it while looking at the road. However, it is also possible that the vehicle is not aligned with a road and, for example, is facing a vertical wall. A vertical wall directly in front of the vehicle implies a situation in which driving straight ahead is obviously impossible.Such a detected relative position of the surface for the projected symbol indicates an operating situation different from a typical driving situation, which may necessitate the display of different information than that shown while driving. For example, a vertical wall in front of the vehicle immediately after starting could indicate a garage wall, on which relevant information, such as an upcoming inspection appointment or the remaining range, could be displayed. Particularly when projecting the symbol onto a nearby vertical wall, a lower brightness level is sufficient for good visibility compared to a distant projection onto a road surface while driving.This allows the number of projection devices required for projecting the symbol to be reduced, for example, to just one, thereby significantly reducing the effort required to avoid blurring in the projected symbol. In particular, the number of projection devices involved in projecting the symbol depends on the detected distance of the surface.

[0018] In particular, the first projection device and the second projection device are arranged essentially vertically one above the other, wherein, in particular, a first output lens of the first projection device and a second output lens of the second projection device have an essentially constant relative position to each other. Preferably, the first output lens and the second output lens are arranged essentially directly adjacent to one another. This minimizes any offset of the images projected by the projection devices and limits it to a single coordinate direction. The computational effort required to compensate for the offset by deactivating light sources is thus kept low.

[0019] The invention further relates to a method for operating a spotlight, which can be designed and further developed in particular as described above, in which an image projected onto a surface by a first projection device having several first light sources and a projected image by a second projection device having several second light sources are brought to substantially complete overlap by deactivating a portion of the first light sources and / or the second light sources. The method can be further developed in particular as explained above with reference to the spotlight. By deactivating non-overlapping light sources of the projection devices, high brightness and high sharpness of the symbol projected onto the surface can be achieved, thus enabling good recognizability of a symbol projected by a spotlight.

[0020] Preferably, the relative position of the surface is determined, and any perspective blur caused by this relative position is compensated for by deactivating some of the first and / or second light sources. This easily compensates for any perspective distortion caused by the surface's relative position.

[0021] Areas of the surface in which, according to the calculations of the computing device, the edges of the symbol to be projected lie are particularly favored and are scanned by the area detector with a higher resolution than the other areas.

[0022] The invention is explained below by way of example with reference to the accompanying drawings and preferred embodiments, wherein the features shown below can represent an aspect of the invention, either individually or in combination. The drawings show: Fig. 1: A schematic perspective representation of the projection of a spotlight before correction and Fig. 2: a schematic perspective representation of the projection of the spotlight from Fig. 1 after a correction.

[0023] The in Fig. A headlight 10 of a motor vehicle, shown only in principle, has a first projection device 12 and a second projection device 14, which can illuminate a surface 16. In the illustrated embodiment, the surface 16 is a road surface. The first projection device 12 has several first light sources 18 arranged in rows and columns, designed as LED elements, which can optionally display one pixel each of a first image projected onto the surface 16 by means of a first lens 20 of the first projection device 12 via an interposed display. The shape of the projected first image can be adjusted by selecting the activated and deactivated first light sources 18.Accordingly, the second projection device 14 has several second light source elements 22 arranged in rows and columns, each designed as an LED element and capable of representing one pixel of a second image projected onto the surface 16 by means of a second lens 24 of the second projection device 14. The shape of the projected second image can be adjusted by selecting which second light source elements 22 are activated or deactivated. The first image projected by the first projection device 12 and the identical second image projected by the second projection device 14 are superimposed on the surface 16. However, the orientation, distance, and three-dimensional shape of the surface 16 are not always constant. Furthermore, the light paths of the projection devices 12 and 14 are offset from each other because the lenses 20 and 24 are arranged very close to each other but always with a minimum distance between them.This can result in an offset of the images projected by the projection devices 12, 14, which leads to poor edge sharpness of one of the symbols 26 projected jointly by both projection devices 12, 14, as in . Fig. 1 shown.

[0024] The geometric relative position of the projection devices 12, 14 to each other, and thus an offset and a path of the beams of the projection devices 12, 14, is known. The surface 16 can be assumed to be a flat plane, defined in particular by a road surface. It is also possible to determine the relative position of the surface 16 and / or the actual three-dimensional extent of the surface 16 using an area detector. With the aid of a processing unit, it can be calculated which pixels of the images of the projection devices 12, 14 projected onto the surface 16 overlap or do not overlap, given the assumed or detected relative position of the surface 16 to the projection devices 12, 14. Those light sources 18, 22 whose projected pixels do not overlap with a projected pixel of the other projection device 14, 12 can be deactivated by the processing unit, as shown in Fig.Figure 2 illustrates this. This allows for an essentially complete overlap of the corrected images projected by the projection devices 12 and 14 without offset, so that the symbol 26 projected jointly by both projection devices 12 and 14 has a high degree of edge sharpness. Alternatively, to increase the edge sharpness of the symbol 26, additional light point sources 18 and 22 can be activated so that those projected pixels that would otherwise not overlap with another projected pixel also overlap with another pixel.

Claims

[1] Headlights for a motor vehicle, with a first projection device (12) comprising several first light point sources (18) for illuminating an area (16), a second projection device (14) comprising several second light point sources (22) for illuminating the same area (16) and a computing unit for deactivating those first light point sources (18) and / or second light point sources (22) which, in the projected state on the surface, illuminate only one area of ​​the surface. [2] Headlights according to claim 1 characterized by , that an area detector is provided for detecting the three-dimensional relative position of the area (16) to the first projection device (12) and the second projection device (14). [3] Headlights according to claim 1 or 2 characterized by, that the computing unit is designed to deactivate a light point source (18, 22) if there is an overlap of less than 50% of the projected light point source (18, 22) with another projected light point source (22, 18) on the surface (16). [4] Headlight according to any one of claims 1 to 3 characterized by , that the first light sources (18) and / or the second light sources (22) are arranged regularly, in particular with substantially identical intervals, in rows and columns. [5] Headlight according to any one of claims 1 to 4 characterized by , that the first projection device (12) and the second projection device (14) are designed to project a planar symbol (26) with at least partial straight edges. [6] Headlight according to any one of claims 1 to 5 characterized by, that the computing unit has a conversion table with optical offsets of the images projected by the first projection device (12) and the second projection device (14) to each other for different relative orientations and / or different distances of a flat surface (16). [7] Headlight according to any one of claims 1 to 6 characterized by , that the computing unit is designed to completely deactivate at least one projection device (12, 14) when the surface (16) is in at least one specific predefined relative position, in particular when the surface (16) is positioned below a minimum distance and is essentially vertical. [8] Headlight according to any one of claims 1 to 7 characterized by, that the first projection device (12) and the second projection device (14) are arranged substantially vertically one above the other, wherein in particular a first output lens (20) of the first projection device (12) and a second output lens (24) of the second projection device (14) have a substantially unchanging relative position to each other. [9] Method for operating a spotlight (10) in which an image projected onto a surface (16) from a first projection device (12) having several first light sources (18) and a projected image from a second projection device (14) having several second light sources (22) is brought to substantially complete overlap by deactivating a part of the first light sources (18) and / or the second light sources (22). [10] Method according to claim 9, wherein the relative position of the surface (16) is determined and a perspective blur caused by the relative position of the surface (16) is compensated by deactivating a part of the first light point sources (18) and / or the second light point sources (22).

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