Method for operating a headlight device for a vehicle and motor vehicle with a headlight device

Abstract

Method for operating a headlight device (100) for a vehicle (1) by performing the following process steps: a) Providing multiple light sources, each of which is configured to emit monochromatic light (10) of a predetermined wavelength, wherein the wavelengths of the light sources are different, b) Emitting monochromatic light (10b to 10r) at a multitude of the several specified wavelengths, c) Determine the backscattered amount of light and / or luminance with respect to the respective emitted wavelength, d) Determining those wavelengths of monochromatic light of several different wavelengths (10b to 10y) which fall below a specified level of backscattered light quantity and / or luminance and e) Operating the headlight device (100) exclusively with that monochromatic light (10b, 10ir) which has the determined wavelengths.

Description

[0001] The invention relates to a method for operating a headlight device for a vehicle, a computer program product for this method and a motor vehicle with a headlight device.

[0002] Motor vehicles use fog light bulbs that emit a broad light spectrum. Although this light spectrum is multi-colored, it appears to the human eye as white light due to the overlap of the colors. Other fog light bulbs emit a constant monochromatic light. In fog or heavy rain, the light can be scattered by the water droplets, causing a large proportion of the light to be reflected back diffusely. A driver can therefore often be blinded by their own fog light. In particularly thick fog, glare can also occur when the high beam is used. Currently, this problem is addressed by adjusting the luminous intensity and / or geometry of the fog light based on the reflected light intensity.In this case, the corresponding light source is automatically switched off if it causes glare to the driver. Another approach is to adjust the intensity depending on the amount of light reflected back.

[0003] In this context, published patent application DE 10 2011 077 282 A1 describes a spectral control system for lighting devices. It describes a lighting system for a motor vehicle that includes a lighting device and a control device connected to it.

[0004] Using a position detection device, the position of the motor vehicle can be detected, and information about a predominant color spectrum in the environment around the detected position can be read out via a map memory. The control device is configured to control the color spectrum of the emitted light depending on the predominant color spectrum of the environment.

[0005] While a possible reduction in the illuminance or luminance of the fog lights, or even their deactivation, can reduce the amount of reflected light and thus protect the driver from unnecessary glare, this light may then be missing from the illumination of the surroundings. In this case, the driver's field of vision would continue to be significantly restricted by adverse weather conditions such as fog or heavy rain. The same can apply to the sensors of autonomous driving functions. For example, a vehicle's front camera may no longer be able to record usable images or videos in such a situation. In this case, the driver is usually forced to adapt their driving style accordingly. In this case, the vehicle's speed is usually reduced.

[0006] DE 10 2019 214 319 A1 describes a method for improved detection of the surroundings of a vehicle using a corresponding sensor. Illumination is provided by a lighting device comprising a headlight, a fog light, an infrared light source, and / or an additional light source attached to the vehicle. The additional light source can be a light source configured to emit light at a selectable frequency, whereby the specific frequency can be used to highlight certain objects with known reflection characteristics in the detected surroundings.

[0007] US 2013 / 0128603 A1 describes a vehicle headlight that reliably emits light at a desired color temperature and intensity, allowing the lighting conditions of the vehicle headlight to be adapted to different weather conditions. For this purpose, a control device is provided that allows the brightness of the vehicle headlight to be specifically adjusted by switching individual light sources on or off.

[0008] One task can be seen in being able to operate a headlight device even in adverse weather conditions, whereby glare for a driver and / or sensors is reduced.

[0009] A first aspect of the invention therefore provides a method for operating a headlight device for a vehicle. The following method steps are preferably carried out. In a first step a, a plurality of light sources are provided, each of these multiple light sources being designed to emit monochromatic light at predetermined, different wavelengths. This means in particular that although the plurality of light sources can generate different light in the form of different wavelengths, they can simultaneously generate and / or emit light with a predetermined wavelength, i.e., monochromatic light, during an emission process. For example, up to 100 different wavelengths can be provided for the respective monochromatic light. Starting from 300 nm, for example, different light could be emitted by the light sources at intervals of 10 nm.This preferably occurs step by step, i.e., successively. The light sources can comprise one or more LEDs. Each individual LED or light source can emit monochromatic light with one or more predetermined wavelengths. Light can be described, in particular, by photons, each with a specific frequency. Light can also be an electromagnetic wave. Within the framework of the wave-particle duality known from quantum physics, light can be a particle and / or a wave. The light or light rays can exhibit properties of a particle and / or properties of an electromagnetic wave.

[0010] In monochromatic light, the corresponding photons have the same frequency. Monochromatic light can be described as single-color light. Monochromatic light is, in particular, electromagnetic radiation or a wave with a precisely defined frequency or a fixed vacuum wavelength. As a rule, it is difficult to provide perfectly monochromatic light, but it is sufficient if the monochromatic light only fluctuates slightly around a given frequency or wavelength. In this case, a tolerance range of 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 nanometers around the defined wavelength can still be considered monochromatic light. Light that fluctuates by up to 10 percent around the given wavelength can be considered monochromatic light. The tolerance range can be up to 10 percent around the given wavelength.Monochromatic light can be characterized either by its corresponding wavelength or by its frequency. The term "light" can mean the same as "light rays." Using the relationship f = c / λ, the frequency of monochromatic light can be converted into a wavelength and vice versa. f represents the frequency, c represents the speed of light in a vacuum, and λ represents the wavelength.

[0011] In a further step b of the method, monochromatic light or monochromatic light rays are emitted at a plurality of the plurality of predetermined wavelengths. In particular, a plurality of test rays of different colors can be emitted. The different light rays are preferably emitted one after the other by the light sources. A light spectrum of monochromatic light, i.e. light with predetermined wavelengths, can be emitted one after the other, i.e. successively, whereby at a certain point in time only light of the predetermined wavelength can be emitted. For example, the light source can emit light only at a first wavelength at a first point in time and only at a second wavelength at a later point in time. Each different color is preferably represented by corresponding monochromatic light rays.In particular, a given light spectrum can be emitted successively. For example, monochromatic light can be emitted starting at 300 nanometers, and then monochromatic light with a wavelength of 350, 400, or 1,200 nanometers can be emitted. The wavelength of the monochromatic light can be up to 2 millimeters. Thus, a given set of monochromatic light rays can be emitted or transmitted successively.

[0012] In a further step c, in particular, a backscattered light quantity and / or backscattered luminance can be determined with respect to the respective emitted wavelength. For this purpose, the backscattered light quantity can be measured, for example, using a light sensor. The light quantity can be measured using a light sensor or a spectral sensor. An "active pixel sensor," for example, can be used as a light sensor. An active pixel sensor is, in particular, a semiconductor detector for measuring light. The active pixel sensor is often referred to as a CMOS sensor. A backscattered light intensity and / or a backscattered luminance can be measured using the light sensor and / or the CMOS sensor.

[0013] In a further step d, in particular those wavelengths of the monochromatic light of the several different wavelengths are determined which fall below a predetermined level of backscattered light quantity. In this step, in particular, it can be determined which wavelength and / or frequency of the corresponding monochromatic light causes a minimum of backscattering. It can thus be determined at which frequency the backscattered light intensity or luminance is minimal. However, it is usually sufficient if the predetermined level of backscattering is not exceeded. The luminance of a surface determines, in particular, the surface brightness with which a surface is perceived. The unit of luminance is candela per square meter (cd / m 2). Luminance is defined in particular as the quotient of luminous intensity and the luminous area. Luminous intensity, on the other hand, is a basic quantity of the International System of Units and is given in candelas (cd). Candela is preferably defined using a radiation source. One candela is the luminous intensity of a radiation source that emits monochromatic light at a frequency of 540 terahertz with a radiant intensity of 1 / 683 watts / sr (sr = steradian) in a specific direction. The amount of light reflected back can refer to the luminous intensity or the luminance, depending on the context. Luminous intensity therefore provides information in particular about how much light is emitted in a specific direction, while luminance standardizes the luminous intensity to a given area.

[0014] In contrast, the term illuminance refers to the luminous flux, which is standardized with respect to a given area. The luminous flux is represented by the product of the luminous intensity and the solid angle of the light transmitted. The unit of luminous flux is preferably given in lumens, while the unit of illuminance is preferably given in lux (lumens per square meter). The amount of backscattered light can be specified or measured based on the luminous intensity, luminance, luminous flux, and / or illuminance. Depending on the headlight device, a quantity or unit that is easier to measure can be used. The term luminous intensity can mean luminous intensity, luminance, illuminance, and / or luminous flux. In particular, the luminance can be measured and used for the method.

[0015] In a further step e, the headlight device is preferably operated exclusively with that monochromatic light which has the determined wavelengths. This means in particular that the headlight device emits only that monochromatic light which has low backscattering, i.e. which falls below the predetermined level of backscattered light quantity. Thus, in particular, a part of the light spectrum is not emitted by the headlight device. The headlight device can then be adjusted accordingly so that only that monochromatic light with precisely this particularly low-scattering light color is emitted. This allows, for example, a fog light or a high beam to be operated despite adverse weather conditions without dazzling the driver or the vehicle sensor.This allows visibility for the driver or the vehicle sensor to be maintained or increased, resulting in a significant increase in road safety.

[0016] Visibility, or visibility, is generally defined as the maximum horizontal distance that just barely allows a dark object near the ground to be seen against a light background. Visibility can be estimated visually or measured instrumentally. For example, visibility sensors can measure light scattering by particles in the atmosphere and use this to determine visibility. A forward-scattering method can be used to measure visibility. Visibility sensors are well known and regularly used in traffic engineering and / or meteorological engineering. Accordingly, those skilled in the art will be familiar with corresponding visibility sensors, for example, from meteorological engineering.

[0017] An additional or alternative embodiment provides that steps b, c and / or d are executed again at predetermined time intervals. This embodiment is preferably carried out with a moving vehicle. This allows the headlight device to optimally adjust to changing ambient conditions. For example, the weather conditions around the vehicle may change, which may correspondingly lead to a change in the amount of backscattered light for corresponding monochromatic wavelengths. In this case, it may be necessary to use other monochromatic light beams to operate the headlight device. By repeating the aforementioned method steps, it is possible to respond flexibly to new ambient conditions around the vehicle.

[0018] Additionally or alternatively, steps b, c and / or d can be carried out again depending on an environmental parameter. The environmental parameter can be, for example, a fog density, an ambient atmosphere of the headlight device and / or a visibility range in the area of ​​the headlight device. The ambient atmosphere of the headlight device can, for example, comprise a brightness, a temperature and / or a humidity of an environment of the vehicle. The fog density can, in particular, be described on the basis of a visual impairment of an observer looking in the azimuth direction. Thus, instead of the fog density, a derived variable of the visibility range can be used for the fog density. The environmental parameter can be selected such that changing weather conditions can be detected quickly.This allows the light frequency or wavelength to be determined for operating the headlight device that exhibits the least scattering or at least does not exceed a specified level of backscattering. This allows the area around the vehicle or headlight device to be better illuminated, and the driving functions or an autonomous driving function can be operated more effectively due to a greater visibility. This allows for better contrast, and surrounding objects around the headlight device can be detected earlier, which benefits road safety. Under certain circumstances, even higher driving speeds may be possible without compromising driving safety.

[0019] The selected or determined light frequency or wavelength for the monochromatic light can be adjusted dynamically or at high frequencies. If, for example, weather conditions change abruptly, for example, due to reduced visibility or sudden onset of heavy rain, a rapid response can be achieved by adapting the monochromatic light beams accordingly by changing the light frequency. In particular, the execution of steps b, c and / or c can depend on a rate of change or a gradient relating to the environmental parameter. The rate of change or the gradient can influence a repetition frequency.

[0020] An additional or alternative embodiment provides that the headlight device is operated with regard to the monochromatic light with a first wavelength in a range visible to a person and with a second wavelength in a range invisible to a person. The first wavelength is in particular a value from the range 380 nm to 800 nm. It is assumed that the person can see light in the range 380 nm to 800 nm. The range from 380 nm to 800 nm can be regarded as the visible range. The second wavelength is in particular defined between 900 nm and 2 millimeters. The person can be regarded as a standard person or average person with average vision. In the case of ametropia, it is assumed that the person wears a visual aid such as glasses or contact lenses. It is assumed that the person cannot see light of the second wavelength.Wavelengths with the second wavelength can therefore be assigned to a non-visible range. It is possible, in particular, to operate the headlight device using only light of these two wavelengths. The headlight device can only emit light of the first and / or second wavelength. The second wavelength is used, in particular, to operate a vehicle sensor. Dynamic switching between these two wavelengths is preferably carried out at a frequency of at least 60 hertz.

[0021] The visible range can in particular extend in a wavelength range from 380 to 780 nanometers. The second wavelength can in particular be in a wavelength range from 850 nanometers to 1 millimeter. The visible range corresponds in particular to a frequency of 380 to 700 THz. The second wavelength preferably corresponds to a frequency range between 300 gigahertz and 375 THz. The visible range corresponds in particular to light that a human eye can register, while the second wavelength is located in particular in the range of thermal radiation or infrared radiation. In particular, light of the first wavelength serves to illuminate the surroundings of the vehicle for a human driver, while the second wavelength can be designed for a camera, in particular an infrared camera.Thus, the first wavelength can represent the most suitable light frequency for the human eye, while the second wavelength can represent the best light frequency for an imaging sensor such as a camera.

[0022] The camera is, in particular, a vehicle sensor. This can be particularly advantageous because, for example, very little light is reflected by water in the near infrared range. In terms of reflection technology, the second wavelength makes sense for an infrared camera. However, the second wavelength in the infrared range is not suitable for illuminating the vehicle's surroundings for a driver. This allows the area around the headlight device or the vehicle to be optimally illuminated for both the human eye and the vehicle sensor, in particular the camera. If the switching between these two wavelengths or frequencies is sufficiently fast, i.e. switching back and forth, the headlight device optimally appears as a homogeneous light source. Good illumination of the vehicle's surroundings can thus be achieved for both the driver and the vehicle sensor.With a sufficiently high switching frequency of 60 Hertz or more, a human driver, the person, ideally does not even notice this switching.

[0023] An additional or alternative embodiment provides that the vehicle sensor is a camera, and an image or a video sequence comprising multiple images is taken precisely when the second wavelength is emitted or reflected back. The video sequence can be viewed as a sequence of multiple images at different times. The camera can be an infrared camera. The vehicle sensor or camera is preferably activated precisely when the non-visible light, i.e., the second light wavelength, is emitted. Alternatively, the camera can always be activated precisely when the non-visible light is scattered back. The determination of the ideal monochromatic light beams can also be used taking other materials, such as dust or sand, into account. This allows the headlight device to be flexibly operated optimally under various environmental scenarios.It is possible to adapt the headlight device to new situations.

[0024] An additional or alternative embodiment provides that light with exactly the first wavelength and light with exactly the second wavelength are detected. The light can be emitted in the form of light rays with the first and / or second wavelength. The light with the first and second wavelengths has the lowest amount of backscattered light and / or luminance in their respective ranges. When the headlight device is operated, dynamic switching occurs between these two wavelengths. Preferably, switching back and forth between these two wavelengths occurs at a frequency of at least 60 Hertz. A frequency of 80, 90, 100, or 1,000 Hertz can be used for switching. This makes it possible to achieve the best possible illumination of the surroundings for both the driver and for an autonomous driving function, i.e. for the vehicle sensor.Dynamic switching between these two wavelengths is particularly advantageous because both the vehicle sensor and the driver benefit from good illumination. Thanks to the switching, the vehicle sensor can still operate optimally thanks to the optimal illumination in the second wavelength range.

[0025] An additional or alternative embodiment provides, in particular, that light with wavelengths that, upon backscattering, exceed a predetermined limit value regarding the backscattered light quantity and / or backscattered luminance is excluded for a predetermined time interval during operation of the headlight device while emitting the respective monochromatic light beams at the plurality of predetermined different wavelengths (step b). In the step of determining the wavelengths that fall below a predetermined level of backscattered light quantity (step d), it can additionally be determined which wavelengths cause a high level of backscattered light quantity.

[0026] Thus, a resonance effect during backscattering can be detected for certain wavelengths. In order to reliably exclude strong glare effects during further operation of the headlight device, this embodiment provides that these wavelengths, which generate a high degree of backscattering, are not used during operation of the headlight device, i.e., are excluded. This exclusion can refer to a predetermined time interval. Preferably, the exclusion refers to the emission of the monochromatic light, which precedes the determination of the amount of backscattered light. This can prevent brief glare effects from occurring even when the monochromatic light beams are emitted to determine the respective amount of backscattered light.For example, if it is known that a certain wavelength causes high glare in a very foggy environment, this wavelength can be excluded when determining the amount of backscattered light, since it is already known that glare would be caused in this case. This also allows unwanted glare to be reliably avoided during the step of determining those wavelengths (step d).

[0027] An additional or alternative embodiment can provide that, during operation of the vehicle's headlight device, a visibility range is determined and a speed of the motor vehicle is adjusted depending on the visibility range. This embodiment can be used for autonomously driving vehicles or semi-autonomously driving vehicles. In particular, the speed of the vehicle is reduced accordingly when the visibility range is lower. The term visibility range can refer to the first wavelength or the second wavelength. Thus, the visibility range can represent the visibility of the human eye as well as the visibility range of the vehicle sensor. If, for example, there is no reduction in visibility for the human driver, but there is for the vehicle sensor, the speed of the vehicle can still be reduced in this case.This allows autonomous driving functions to automatically adjust to reduced visibility. Alternatively or additionally, reduced visibility in the visible range, i.e., in the first wavelength range, can also result in a reduction in vehicle speed. In this case, a control unit of the motor vehicle can generate a corresponding control signal for the motor vehicle. Ideally, the new method for operating the headlight device can reduce or prevent a reduction in visibility. This can reduce or, in the best case, even eliminate the need to reduce vehicle speed.

[0028] A second aspect of this invention relates to a headlight device for a vehicle. The headlight device preferably has one or more light sources. The light source is particularly designed to emit monochromatic light of several predetermined different wavelengths. Each individual light source of the plurality of light sources can emit monochromatic light at the predetermined different light sources. The light source can be a light bar, a plurality of LED elements, a halogen lamp, and / or a gas discharge lamp. The light source can also be implemented in the form of a pixel light headlight. All of these light sources are particularly designed to emit predetermined monochromatic light wavelengths. The headlight device further comprises a light sensor for measuring a backscattered light quantity and / or luminance. The headlight device can comprise a control unit.The control unit is particularly configured to emit monochromatic light beams at a plurality of the plurality of predetermined wavelengths by means of the light source. The control unit, particularly in conjunction with the light sensor, can determine a backscattered light quantity and / or luminance for each emitted wavelength of the monochromatic light. Furthermore, the control unit can determine each wavelength of the monochromatic light that falls below a predetermined level of backscattered light quantity. The predetermined level can be 1, 2, 3, 4, or 5 percent of the emitted luminous intensity or luminous flux, or a measured backscattered luminance can be converted into the luminous flux or luminous intensity quantities to determine the predetermined level.In addition, the control unit can control the headlight device in such a way that the headlight device is operated exclusively with the monochromatic light which has the determined wavelengths.

[0029] A third aspect of the invention relates to a computer program product. The computer program product comprises, in particular, instructions that cause the control unit of the headlight device to execute each described embodiment. Thus, the control unit can comprise instructions that can implement each described embodiment.

[0030] A fourth aspect of the invention relates to a vehicle with a headlight device and / or with a computer program product. The computer program product can be integrated into the control unit.

[0031] The features presented in connection with the method according to the first aspect of the invention, as well as their advantages, apply accordingly to the headlight device according to the second aspect of the invention, the computer program [product] according to the third aspect of the invention, and the vehicle according to the fourth aspect of the invention, and vice versa. This means that device features can be interpreted as method features, and vice versa.

[0032] The vehicle may include a computer program product containing instructions that cause each embodiment of the method to be executed. The computer program product may be stored on a computer-readable medium.

[0033] The invention also includes the control unit for the vehicle. The control unit can have a data processing device or a processor device configured to carry out an embodiment of the method according to the invention. For this purpose, the processor device can have at least one microprocessor and / or at least one microcontroller and / or at least one FPGA (Field Programmable Gate Array) and / or at least one DSP (Digital Signal Processor). Furthermore, the processor device can have program code configured to carry out the embodiment of the method according to the invention when executed by the processor device. The program code can be stored in a data memory of the processor device.

[0034] The invention also includes further developments of the method according to the invention that have features already described in connection with the further developments of the vehicle according to the invention. For this reason, the corresponding further developments of the method according to the invention are not described again here.

[0035] The vehicle is preferably designed as a motor vehicle, a motor vehicle, in particular a passenger car or a truck, or as a passenger bus or motorcycle. The vehicle can be an aircraft or aeroplane.

[0036] The invention also encompasses combinations of the features of the described embodiments. The invention therefore also encompasses implementations that each comprise a combination of the features of several of the described embodiments, unless the embodiments are described as mutually exclusive.

[0037] Exemplary embodiments of the invention are described below. Shown are:

[0038] The invention will now be explained in more detail with reference to the accompanying drawings. It should be noted that the drawings merely indicate exemplary embodiments of the invention. In no case should the drawings be considered as limiting or even exclusive possibilities. They show: Fig. 1 is a schematic side view of a vehicle with a headlight device; Fig. 2 a schematic sketch of the headlight device.

[0039] The exemplary embodiments explained below are preferred embodiments of the invention. In the exemplary embodiments, the described components of the embodiments each represent individual features of the invention that can be considered independently of one another, each of which also develops the invention independently of one another. Therefore, the disclosure is intended to encompass combinations of the features of the embodiments other than those shown. Furthermore, the described embodiments can also be supplemented by further features of the invention already described.

[0040] In the figures, the same reference symbols designate elements with the same function.

[0041] Fig. 1 shows, for example, a vehicle 1 with a headlight device 100. The headlight device 100 includes, in particular, a left headlight 2, a right headlight 3, an image sensor 4, a control unit 6, and a vehicle sensor 7. The headlights 2, 3 can each have one or more light sources or be designed as pixel light headlights. The headlight device can be part of the vehicle 1. The vehicle sensor 7 is designed as a camera. The vehicle sensor 7 can also be an ultrasonic sensor, radar sensor, and / or lidar sensor. A person 8 can be seen in the vehicle 1. The left headlight 2 and the right headlight 3 emit light 10. Using the example of Fig. 1 does not yet address the respective wavelengths or frequencies of light 10. Light 10 is often white light, which in typical headlights has a variety of different wavelengths. A type of cloud 9 is indicated in front of vehicle 1. Cloud 9 can represent, for example, fog, heavy rain, dust, and / or sand.

[0042] Scattering material 5 may be present in the cloud 9 and / or in the surroundings of the vehicle 1. The scattering material 5 may be in the form of water droplets, dust, and / or sand. The scattering material 5 may be considered scattering particles 5. Any material that can backscatter the emitted light 10 may be considered as scattering material 5. The headlights 2, 3 or headlight device 100 are used in particular to provide optimal illumination or a high visibility range for the driver 8 or the vehicle sensor 7.

[0043] However, the scattering particles 5 can lead to unpleasant backscattering, which can impair or even hinder the driver 8 or the vehicle sensor 7. The degree of backscattering, i.e., the amount of light scattered back, can depend on the frequency of the emitted light or the wavelength of the emitted light 10.

[0044] In Fig. 2, the headlight device 100 is indicated with the headlights 2, 3 as well as the vehicle sensor 7 and the image sensor 4 as well as the control unit 6. The image sensor 4 can be designed as a light sensor, CMOS sensor or active pixel sensor. The control unit 6 can contain a computer program product or be implemented as part of a computer program product. The headlights 2, 3 each have, in particular, at least one light source. This light source can, in particular, generate and emit different monochromatic light wavelengths. In the right-hand area of Fig. 2 shows different light rays 10b to 10y. 10b stands for blue, 10g for green, 10r for red, and 10y for yellow light. 10ir represents infrared light, which is invisible to humans. These different light rays 10b to 10y represent photons of different frequencies. Different light rays are often classified not by their wavelength or frequency, but by their color. Each color represents a corresponding frequency or wavelength of the corresponding light ray 10b to 10y.

[0045] Certain light rays are shown in dashed lines, with the reflected light beam 10br, 10rr pointing back to the headlight device 100. These light rays can be scattered back by the scattering particles 5. In the case of Fig. 2, this affects the light rays 10rr and 10br. This means that red light rays 10r and blue light rays 10b can be reflected back by the scattering particles 5.

[0046] When determining those monochromatic light rays that result in a minimum and / or maximum amount of backscattered light, the control unit 6 can emit a predetermined spectrum of light rays of different wavelengths based on a predetermined sequence. Using the light sensor 4, it is also possible to determine which wavelength results in a corresponding amount of backscattered light. The amount of light can be determined by measuring the luminous intensity, luminance, luminous flux, and / or illuminance. This means that a corresponding backscatter can be determined for each wavelength. In the example of Fig. 2, the red and blue light beams 10b, 10r lead to increased light backscattering (reflected light beams 10br, 10rr). In contrast, the yellow light beams 10y and the green light beams 10g show no backscattering. In addition, Fig. Two infrared light rays 10ir are shown. For example, infrared light rays 10ir have a wavelength of more than 1,000 nanometers. Infrared rays 10ir are invisible to the human eye. However, infrared rays 10ir may be optimal for vehicle sensor 7.

[0047] Based on the backscattering detected by the image sensor 4, the control unit 6 can evaluate or determine which light rays or their corresponding wavelengths result in minimal backscattering or determine which wavelengths do not exceed a predetermined level of backscattering. The optimal frequency or wavelength can be in the non-visible spectrum. In the case of Fig. 2, these would be the light rays of the infrared range 10ir. Even though the infrared rays 10ir have the lowest reflection, the infrared rays 10ir are not suitable for illuminating the surroundings of the vehicle 1 for the driver 8.

[0048] Therefore, it is provided that the control unit 6 determines another wavelength or frequency for the light, which lies in the visible range, i.e., in the wavelength range between 380 and 780 nanometers, and which also does not exceed the specified degree of backscattering. The specified degree of backscattering can be less than 10 percent of the emitted luminous intensity or luminous flux, in particular less than 5 percent, preferably less than 2 percent. In the following, it is assumed that the green light rays 10g exhibit the lowest backscattering in the visible range. In this case, the control unit can switch back and forth between the green light rays 10g and the infrared rays 10ir.

[0049] The control unit 6 can ensure that a switch is made between these two light beams 10g and 10ir in the visible and invisible spectrum. For this purpose, the control unit 6 can control the headlights 2, 3 accordingly. The vehicle sensor 7 is preferably always triggered precisely when the invisible light, i.e., the infrared rays 10ir, are emitted. The vehicle sensor 7 can, in particular, be a front camera that is only sensitive in the infrared range. This allows an environment for the infrared camera as the vehicle sensor 7 to be optimally illuminated. Due to the dynamic switching between the visible light (green light rays 10g) and the invisible light (infrared rays 10ir), optimal ambient illumination can be provided for both the driver 8 and the vehicle sensor 7. This can increase the visibility of both the driver 8 and the vehicle sensor 7, such as the infrared camera.

[0050] The headlight device 100 can be used not only in foggy environments or heavy rain. The headlight device 100 can also demonstrate its advantages in environments with dust or sand. In this case, the control unit 6 can determine the corresponding wavelengths at which the light 10 is reflected by the scattering particles 5. Accordingly, as previously described, those light rays that do not exceed the specified degree of backscattering can be determined, and the left headlight 2 and the right headlight 3 can be operated accordingly with the monochromatic light that has a low level of backscattering. Thus, even under changing ambient conditions, optimal illumination for the driver and the vehicle sensor 7 can always be achieved, which benefits road safety.

Claims

[1] Method for operating a headlight device (100) for a vehicle (1) by carrying out the following method steps: a) providing a plurality of light sources, each individual light source of said plurality of light sources being designed to emit monochromatic light (10) of a predetermined wavelength, the wavelengths of the light sources being different, b) emitting monochromatic light (10b to 10r) at a plurality of said plurality of predetermined wavelengths, c) Determining a quantity of backscattered light and / or luminance with respect to the respective emitted wavelength, d) Determining those wavelengths of the monochromatic light of the plurality of different wavelengths (10b to 10y) which fall below a predetermined level of backscattered light quantity and / or luminance and e) operating the headlight device (100) exclusively with that monochromatic light (10b, 10ir) which has the determined wavelengths. [2] Method according to claim 1, wherein steps b), c) and / or d) are carried out again at predetermined time intervals and / or depending on an environmental parameter, in particular a fog density (9), an ambient atmosphere (5) of the headlight device (100) and / or a visibility range in an environment of the headlight device (100), the steps b), c) and / or d) are carried out again. [3] Method according to one of the preceding claims, wherein the headlight device (100) is operated with respect to the monochromatic light (10b to 10y) at a first wavelength in a range between 380 nm and 800 nm and at a second wavelength in a range between 900 nm and two millimeters, wherein in particular the second wavelength is used for operation of a vehicle sensor (7), and switching is carried out dynamically between the two wavelengths, in particular at a frequency of at least 60 Hz. [4] Method according to claim 3, wherein the vehicle sensor (7) is a camera, in particular an infrared camera, and an image or a video sequence with several images is taken precisely when the second wavelength is emitted or backscattered. [5] Method according to one of claims 3 or 4, wherein exactly the first wavelength and exactly the second wavelength are determined which have the lowest backscattered light quantity and / or luminance in the respective areas and dynamic switching is carried out between these two wavelengths during operation of the headlight device (100). [6] Method according to one of the preceding claims, wherein light (10) with wavelengths which, during backscattering, exceeds a predetermined limit value relating to the quantity of light and / or luminance is excluded during operation of the headlight device (100) for a predetermined time interval during a respective repeated implementation of step b). [7] Method according to one of the preceding claims, wherein during operation of the headlight device (100) of the vehicle (1) a visibility range is determined and a speed of the vehicle (1) is set as a function of the visibility range. [8] Headlight device (100) for a vehicle (1) comprising: - a plurality of light sources, each individual light source of said plurality of light sources being designed to emit monochromatic light (10b - 10y) at predetermined different wavelengths, - a light sensor (4) for measuring a backscattered light quantity and / or luminance, - a control unit (6) which is arranged ◯ to emit monochromatic light (10b to 10y) at a plurality of the plurality of predetermined wavelengths by means of the light sources, ◯ to determine a backscattered light quantity and / or luminance with respect to each emitted wavelength by means of the light sensor (4), ◯ to determine those wavelengths of monochromatic light (10b to 10y) which fall below a given level of backscattered light and / or luminance, and ◯ to operate the headlight device (100) exclusively with that monochromatic light (10g, 10ir) which has the determined wavelengths. [9] Vehicle (1) with a headlight device (100) according to claim 8.

Images