Motor vehicle lighting device for emitting a dimmed light distribution

Abstract

Motor vehicle lighting device (2) for emitting a dimmed light distribution (4) with a horizontal light-dark boundary (6), wherein the dimmed light distribution (4) comprises light of a first maximum illuminance below the light-dark boundary (6) and light of a second maximum illuminance in an overhead area (14) of the light distribution (4) above the light-dark boundary (6), wherein the lighting device (2) has at least one first light source (26) for emitting at least the light below the light-dark boundary (6), and at least one further light source (38) for emitting at least part of the light of the overhead area (14), characterized by the fact that which is designed and operated to emit light that renders an object (46) of a selected color located in the overhead area (14) of the light distribution (4) with a better color rendering according to CIE 1976 than would be possible with light from the at least one first light source, wherein at least one further light source (38) is configured to emit light whose color rendering value Ri for the selected color of the object according to CIE 1976 Ri > 80.

Description

[0001] The present invention relates to a motor vehicle lighting device, in particular a motor vehicle headlight, for emitting a dimmed light distribution with a horizontal light-dark boundary. The dimmed light distribution comprises light of a first maximum illuminance below the light-dark boundary and light of a second maximum illuminance in an overhead region of the light distribution above the light-dark boundary. The lighting device has at least one first light source for emitting at least the light below the light-dark boundary, and at least one further light source for emitting at least part of the light of the overhead region.

[0002] Such a lighting device is known from DE 10 2017 120 748 A1.

[0003] A dimmed light distribution is, for example, dipped beam or fog light. Especially with dipped beam, the emitted light distribution includes not only the light below the cut-off line, but also a small amount of light above the cut-off line to illuminate the so-called overhead area and any traffic signs, sign gantries, or other objects located there. The second maximum illuminance of the light in the overhead area is lower than the first maximum illuminance of the light below the cut-off line.

[0004] According to ECE Regulation No. 112, which applies to dipped beam headlights, a maximum illuminance of 0.4 lux is permitted at a point B50L for right-hand traffic or B50R for left-hand traffic in the overhead area on a measuring screen located 25 m from the headlight. Point B50L is located 1,500 mm to the left of a vertical plane vv on the measuring screen and 250 mm above a horizontal plane hh on the measuring screen, with a focal axis of the headlight passing through the intersection point HV of the two planes vv and hh. At the same time, according to ECE R112, the sum of the illuminance in the overhead area at three points: 1 (-3,500 mm / +1,750 mm), 2 (0 / +1,750 mm), and 3 (+3,500 mm / +1,750 mm) must be at least 0.3 lux, and at three other points: 4 (-1,750 mm / +875 mm), 5 (0 / +875 mm), and 6 (+1,750 mm / +875 mm) must be at least 0.6 lux. The coordinates of the points are each related to the intersection point HV.This also means that minimum values ​​for illuminance are prescribed for the overhead area.

[0005] The overhead area is usually illuminated by light from at least one light source to create the dimmed light distribution below the cut-off point. Either scattered light from the light source is used to illuminate the overhead area, or light from the light source is specifically directed into the overhead area. Furthermore, spotlights are known from the prior art that have an additional light source for illuminating the overhead area (e.g., DE 10 2013 207 850 A1).

[0006] Newer headlights in particular have standard light sources (e.g. LEDs, high-performance LEDs or laser diodes) which, at least for objects of certain colors, only have inadequate color rendering according to CIE 1976. The spectrum of such standard light sources has only a low intensity in the corresponding wavelength ranges. The color rendering index Ra = 1 / I x sum(Ri) with i=1...I and I corresponding to the number of colors i whose color rendering is being considered, for such standard light sources is in a range of only Ra = 60-70, with 100 being the maximum. This leads to illuminated objects being reproduced with insufficient color fastness and appearing pale. This particularly applies to objects of a color that is underrepresented in the spectrum of the aforementioned standard light sources (e.g. blue-green in the range of approx. 470 nm - 530 nm or red in the range of approx. 600 nm - 800 nm). This leads to, for example,Motorway signs in blue (in Germany, France) or green (in Italy, Switzerland, the USA) are only reproduced in a pale blue or pale green and are therefore very difficult for the driver of a motor vehicle to recognize.

[0007] Finally, DE 10 2013 001 259 A1 discloses a motor vehicle headlight in which the additional light source emits light of a selected color to illuminate the overhead area in order to improve the contrast of traffic signs located in the overhead area. For example, it is proposed to illuminate a traffic sign with white lettering on a blue background with yellow light. This makes the background of the traffic sign appear black, so that the white lettering stands out with particularly strong contrast. Similarly, it is proposed, for example, to illuminate a traffic sign with white lettering on a green background with magenta light, so that the background of the traffic sign appears black and the white lettering stands out with particularly strong contrast.

[0008] However, the colored illumination of the overhead area proposed in DE 10 2013 001 259 A1 distorts the color of the traffic sign or its background. This creates a synthetic impression that can be confusing for the driver of a motor vehicle equipped with the described headlights. For example, when looking for a motorway sign, the driver expects a traffic sign with a blue or green background, but in reality, they are only presented with traffic signs with a black background.

[0009] Despite the improved contrast of the illuminated traffic signs, it is therefore very difficult for the driver to recognize them. The driver's subjective expectation of a traffic sign with a certain background color conflicts with the objectively perceived color of the traffic sign. This increases stress for the driver, which can ultimately lead to distraction, inattention, and endangering other road users.

[0010] Based on the described prior art, the present invention is based on the object of designing and developing a motor vehicle lighting device, in particular a motor vehicle headlight, in such a way that it provides illumination of the overhead area which realizes a particularly color-true color reproduction of the illuminated objects.

[0011] To achieve this object, a motor vehicle lighting device having the features of claim 1 is proposed. In particular, starting from the motor vehicle lighting device of the type mentioned at the outset, it is proposed that the at least one further light source is designed and operated to emit light which reproduces an object of a selected color located in the overhead region of the light distribution with better color rendering according to CIE 1976 than would be possible with light from the at least one first light source, wherein the at least one further light source is designed to emit light whose color rendering value Ri for the selected color of the object is Ri > 80 according to CIE 1976.

[0012] In particular, the invention proposes that the at least one additional light source illuminating the overhead area compensates for the color rendering deficiencies of the at least one first light source, i.e., the inadequate rendering of objects in their actual color, with the light it emits. As a result, objects in the overhead area of ​​the light distribution are rendered both in their actual color and with high color saturation. In this way, the driver of a motor vehicle equipped with the lighting device according to the invention can recognize traffic signs more quickly and more reliably. This is beneficial to road safety.

[0013] Unlike the prior art, which aims to improve contrast in the overhead range, the invention is concerned with improving color rendering and color saturation. This is expressed by the color rendering value Ri or the color rendering index Ra, which is significantly higher than the corresponding value of the light emitted by the at least one first light source to generate the dimmed light distribution below the light-dark boundary.

[0014] Contrast is the difference between the brightest and darkest visible tonal values. Color rendering, on the other hand, is a quality characteristic of artificial light compared to natural sunlight, how the colors of illuminated objects are reproduced. A light source whose light contains all spectral colors - like sunlight - makes the colors of the illuminated objects appear natural - the color rendering is optimal. However, modern LEDs, high-power LEDs, and laser diodes do not reproduce all spectral colors equally well. Therefore, the invention proposes supplementing or implementing the illumination in the overhead area with light from an additional light source that reproduces objects of selected colors better than the light from the first light source can or could.

[0015] Light sources with particularly good color rendering, which can be used, for example, as at least one additional light source for illuminating the overhead area, often have a relatively low luminous flux. However, this is not critical for illuminating the overhead area, as high illuminance values ​​are not required there.

[0016] To determine the color rendering index, 14 reference colors were defined according to DIN 6169. The following are intended as reference colors: #1 Old pink #2 Mustard yellow #3 Yellow-green #4 Light green #5 Turquoise blue #6 Sky Blue #7 Aster Violet #8 Lilac Violet #9 Red saturated #10 Saturated Yellow #11 Saturated Green #12 Blue saturated #13 Pink (Skin Color) #14 Leaf Green

[0017] For these reference colors, the secondary spectra are measured using a reference light source (e.g., sunlight) and a test light source (e.g., the first or subsequent light source). The deviations result in 14 reference values ​​(Ri). To determine the general color rendering index Ra, the arithmetic mean of the first eight indices i = 1...8 is determined. The eight numerical Ri values ​​are added together and the result is divided by eight. Additional reference values ​​can be specified, for example, R9 for saturated red.

[0018] The number of reference colors included in the color rendering index Ra was initially expanded to 14 and later to 15. The more colors included in the calculation of the Ra index, the more accurately it describes the quality of the light. Since an average is determined from the various Ri values, even a high-quality light source can have weaknesses in the reproduction of individual colors. In the present invention, the at least one additional light source is designed to compensate for the weaknesses in the color rendering of the at least one first light source.

[0019] Advantageously, the at least one first light source is designed to emit light exclusively below the light-dark boundary. The overhead area is thus illuminated only by light from the at least one further light source. Of course, it would also be conceivable for a portion of the light emitted by the at least one first light source (e.g., scattered light or deliberately deflected light) to reach the overhead area. The color rendering in the overhead area would then result from a superposition of the light component of the at least one first light source and the light from the at least one further light source.

[0020] In a corresponding manner, it can be provided that the at least one further light source is designed to emit light exclusively into the overhead area. The area of ​​the light distribution below the light-dark boundary is therefore only illuminated by light from the at least one first light source. Of course, it would also be conceivable for a small proportion of the light emitted by the at least one further light source (e.g. scattered light) to also reach the area below the light-dark boundary. However, since the intensity of the light from the at least one further light source is relatively low, or in any case significantly lower, than the intensity of the light from the at least one first light source below the light-dark boundary, the (possibly colored) light from the at least one further light source would not disturb or impair the dimmed light distribution.

[0021] The light emitted by the at least one further light source should, for example, compensate for the low intensity of the light from the at least one first light source in a wavelength range of approximately 470 nm - 530 nm (blue-green) and / or 600 nm - 800 nm (red), so that blue or green motorway information signs or red warning / prohibition or other red signs are reproduced with better color, in particular with more saturated color. This can be achieved by designing the at least one further light source to emit light primarily in a spectral range of 470 nm - 530 nm and / or 600 nm - 800 nm. "Primarily" in this context means that the spectrum of the at least one further light source has a significantly greater intensity in one or more of the aforementioned wavelength ranges than the spectrum of the at least one first light source of conventional design.

[0022] When driving on German or French motorways, the light emitted by the at least one additional light source could be adjusted so that it better reproduces the color of blue objects (e.g. blue motorway signs). If, on the other hand, driving on Italian or Swiss motorways, the light emitted by the at least one additional light source could be adjusted so that it better reproduces the color of green objects (e.g. green motorway signs). The light emitted by the at least one additional light source can be adjusted with a view to improving the color reproduction of objects of a certain color, for example, depending on position information from a motor vehicle navigation system. The adjustment can even go so far as to distinguish whether the motor vehicle is driving on a motorway, on a country road, or in a built-up area.On rural roads in Germany, for example, the light emitted by at least one additional light source could be adjusted to better represent yellow objects (e.g., yellow rural road signs and signs at town entrances). Within built-up areas, for example, the light emitted by at least one additional light source could be adjusted to better represent red objects (e.g., stop signs, yield signs, and red borders around prohibition signs).

[0023] In particular, it is proposed that the at least one further light source is designed to emit light that reproduces an object located in the overhead region of the light distribution in a saturated red color with a color rendering according to CIE 1976 of R9 > 80. As a result, objects in red color are reproduced particularly well, ie particularly realistically.

[0024] It is further proposed that the at least one further light source be configured to emit light that renders an object located in the overhead region of the light distribution in a saturated yellow color with a color rendering according to CIE 1976 of R10 > 80. As a result, objects in yellow color are rendered particularly well, ie particularly realistically.

[0025] Furthermore, it is proposed that the at least one further light source is designed to emit light that reproduces an object located in the overhead area of ​​the light distribution in a saturated green color with a color rendering according to CIE 1976 of R11 > 80. As a result, objects in green color are reproduced particularly well, ie particularly realistically.

[0026] Finally, it is proposed that the at least one further light source is designed to emit light that reproduces an object located in the overhead area of ​​the light distribution in a saturated blue color with a color rendering according to CIE 1976 of R12 > 80. As a result, objects in blue color are reproduced particularly well, ie particularly realistically.

[0027] Of course, it is conceivable that the at least one further light source is designed to emit light that meets the requirements of several of the aforementioned reference values ​​R9 ... R12.

[0028] Alternatively or additionally, it is proposed that the at least one further light source be configured to emit light having a color rendering index Ra according to CIE 1976 of Ra > 80. The color rendering index is also referred to as the color rendering index (CRI). The color rendering index Ra is the arithmetic mean of the first eight indices i = 1...8 or the first 14 indices i = 1...14 or even the first 15 indices i = 1...15 of the reference values ​​Ri for the various reference colors.

[0029] According to an advantageous development of the invention, it is proposed that the at least one further light source comprises an RGB LED whose spectrum is adjusted such that the light emitted by the RGB LED reproduces an object located in the overhead range of the light distribution of a selected color with better color rendering according to CIE 1976 than would be possible with light from the at least one first light source. An RGB LED is a combination of three LEDs with different colors: a red LED, a green LED, and a blue LED, which are arranged in a common housing. An RGB LED can emit different colors by mixing the three primary colors red, green, and blue and, if necessary, also changing the intensity.The light spectrum emitted by the RGB LED can be adjusted by appropriately controlling the three colored LEDs so that the emitted light has a high intensity, particularly in the wavelength range where the spectrum of the at least one first light source for generating the dimmed light distribution has a deficit.

[0030] According to a preferred embodiment of the present invention, it is proposed that the or each first light source is designed as an LED or a laser diode for emitting white light with the aid of a conversion material. Such light sources initially emit blue or UV light, which strikes a conversion material (e.g. phosphor), which converts part of the incident light into yellow light. Superimposing the unconverted blue and converted yellow light produces the desired white light. However, this has a blue-green spectral range (approx. 470 nm - 530 nm) and a red spectral range (approx.600 nm - 800 nm) only has a relatively low intensity, so that a blue, green, or red object illuminated by the light emitted by the at least one first light source - if it reaches the overhead area - is only reproduced in an inadequate color (not very realistic, not very color-intensive, e.g., pale). This is to be compensated for by the present invention.

[0031] In this sense, it is proposed that the at least one further light source be configured to emit light in a spectral range of 470 nm - 530 nm and / or 600 nm - 800 nm with a higher intensity than a conventional LED (e.g., the at least one first light source). The intensity of the light is thus particularly high in one or both of the aforementioned spectral ranges, so that the deficiencies of the light emitted by the at least one first light source can be compensated.

[0032] Further features and advantages of the present invention are explained in more detail below with reference to the figures. Individual features of the exemplary embodiments may also be relevant to the invention individually or may be combined with one another in any desired combination, even if this combination is not explicitly shown and / or described. They show: Fig. 1 a schematic sectional view through a motor vehicle lighting device according to the invention; Fig. 2 Distributions of the relative intensity of a conventional LED and a light source with a high color rendering index Ra; Fig. 3 an example of a traffic situation in front of a motor vehicle with traffic signs in the overhead area of ​​a dimmed light distribution; Fig. 4 a dimmed light distribution on a vertical measuring screen arranged at a distance in front of the motor vehicle lighting device in accordance with ECE R112; and Fig. 5 measuring points above the horizontal plane hh on a vertical measuring screen arranged at a distance in front of the motor vehicle lighting device in accordance with ECE R112.

[0033] The present invention relates to a motor vehicle lighting device, in particular a motor vehicle headlight, which is Fig. 1 in a schematic sectional view and designated in its entirety by the reference numeral 2. The headlight is designed to emit a dimmed light distribution (cf. Fig. 4) with a horizontal light-dark boundary 6. The shielded light distribution 4 comprises light of a first maximum illuminance below the light-dark boundary 6 and light of a second maximum illuminance in an overhead region of the light distribution 4 above the light-dark boundary 6.

[0034] A dimmed light distribution 4 is, for example, dipped beam or fog light or a part thereof. Fig. 4 shows a dimmed light distribution 4 using the example of a dipped beam distribution on a measuring screen 8 arranged at a distance of 25 m in front of the motor vehicle or the motor vehicle lighting device, which is arranged perpendicular to an optical axis 10 of the headlight 2, in accordance with Annex 3 of ECE R112, for right-hand traffic. A horizontal plane hh and a vertical plane vv are recorded on the measuring screen 8. An intersection point HV of the two planes runs through the optical axis 10. For left-hand traffic, the light distribution 4 is mirrored on the vertical plane vv; a relevant measuring point in the overhead area is no longer B50L, but B50R. The invention is described below with reference to right-hand traffic, but the explanations also apply accordingly to left-hand traffic.

[0035] The low beam 4 in Fig. 4 is designed as a so-called asymmetrical dipped beam with a first horizontal section 6a of the light-dark boundary 6 on the oncoming traffic side and a second section 6b on the own traffic side, which rises diagonally upwards (e.g. at an angle of 45°) starting from the vertical plane vv. The rising section 6b can merge into a further section 6c on the own traffic side, which rises at a lower gradient, or into a horizontal section 6c', which runs above the horizontal section 6a, which is arranged on the oncoming traffic side. In particular, with the dipped beam 4, the emitted light distribution includes not only the light in an area 12 below the light-dark boundary 6, but also a small amount of light above the light-dark boundary 6 to illuminate the so-called overhead area 14 and any traffic signs, sign gantries, or other objects located there.

[0036] Fig. Figure 5 shows various measuring points above the horizontal plane hh for a dipped beam distribution 4 on the measuring screen 8 according to ECE R112 for right-hand traffic. For left-hand traffic, the measuring points 7 and 8 are mirrored on the vertical plane vv. According to ECE R112, a maximum illuminance of 0.4 lux is permitted on the measuring screen 8 at a point B50L for right-hand traffic or B50R for left-hand traffic in the overhead area 14. Point B50L is located 1,500 mm to the left of the vertical plane vv and 250 mm above the horizontal plane hh. At the same time, according to ECE R112, the overhead area (cf. Fig. 5) The sum of the illuminance at three points: 1 (-3,500 mm / +1,750 mm), 2 (0 / +1,750 mm), and 3 (+3,500 mm / +1,750 mm) must be at least 0.3 lux, and at three other points: 4 (-1,750 mm / +875 mm), 5 (0 / +875 mm), and 6 (+1,750 mm / +875 mm) must be at least 0.6 lux. The coordinates of the points are each related to the intersection point HV. Therefore, minimum illuminance values ​​are also prescribed for overhead area 14.

[0037] The headlight 2 is designed for installation in a corresponding installation opening on the front of a motor vehicle. The headlight 2 comprises a housing 16, which is preferably made of plastic. In a light exit direction 18, the housing 16 has a light exit opening 20, which is closed by a transparent cover plate 22. This is preferably made of plastic or glass. It can be designed with or without optically active elements (e.g., prisms or cylindrical lenses) for scattering the light passing through. A headlight module 24 is arranged inside the housing 16.

[0038] The headlight module 24 serves to generate the dimmed light distribution 4. For this purpose, the module 24 has at least one first light source 26, which comprises, for example, a semiconductor light source, in particular a light-emitting diode (LED), preferably a high-power LED, or a laser diode. The or each first light source 26 is preferably designed as an LED or a laser diode for emitting white light with the aid of a conversion material. Furthermore, the module 24 has a bundling or primary optics 28, which comprises, for example, a reflector and / or - as in Fig. 1 - may comprise a lens (so-called front optics). The module 24 may be designed as a reflection module or - as shown in Fig. 1 - be designed as a projection module.

[0039] To generate the light-dark boundary 6 of the dimmed light distribution 4, the headlight module 24 comprises Fig. 1 has a diaphragm of 30, which has a vertical or - as in Fig. 1 - may have a horizontal extension. An edge 32 of the aperture 30 - in the example from Fig. 1 a front edge 32 of the aperture 30 - is imaged by a projection or secondary optics 34 to generate the light-dark boundary 6 in front of the vehicle. A light distribution in an intermediate image plane 36 of the headlight module 24 is imaged by the projection optics 34 to generate the dimmed light distribution 4 in front of the vehicle. In this case, the image is preferably reversed (light above the optical axis 10 is imaged below the light-dark boundary 6 and light to the right or left of a vertical plane through the optical axis 10 is imaged left or right in the light distribution 4). The projection optics 34 can be designed as a reflector or - as in Fig. 1—may be designed as a projection lens. A focal point or focal point cloud of the projection optics 34 lies on or near the intermediate plane 36.

[0040] Furthermore, the headlight module 24 comprises at least one further light source 38, which is arranged below a horizontal plane through the optical axis 10. Light emitted by the at least one further light source 38 is projected by the projection optics 34 into the overhead area 14 of the dimmed light distribution 4 above the light-dark boundary 6. The at least one further light source 38 can be designed as desired, provided it emits light of a predetermined wavelength spectrum. Preferably, it comprises a semiconductor light source, in particular an LED with a specific color rendering value for specific colors and / or a specific color rendering index (so-called CRI value). It would also be conceivable for the light source 38 to comprise an RGB LED, each having at least one LED for emitting red, yellow, and blue light, wherein the RGB LEDs are integrated in a common LED housing.

[0041] The overhead area 14 of the dimmed light distribution 4 can be illuminated by light from the at least one first light source 26 to generate the dimmed light distribution 4 below the light-dark boundary 6. Either scattered light from the light source 26 can be used to illuminate the overhead area 14, or a portion of the light from the light source 26 can be specifically directed into the overhead area 14. In the present invention, the at least one further light source 38 is provided to additionally illuminate the overhead area 14.

[0042] In particular, headlights 2 of newer designs have standard light sources 26 (e.g., LEDs, high-performance LEDs, or laser diodes), which, at least for objects 46 of certain colors in front of the motor vehicle, have only inadequate color rendering according to CIE 1976. The spectrum 40 of such standard light sources 26 (cf. Fig. 2) exhibits only a low intensity in the corresponding wavelength ranges 42, 44. The color rendering index Ra = 1 / I × sum(Ri) with i=1... I and I corresponding to the number of colors i whose color rendering value Ri is considered, lies in a range of only Ra = 60-70 for such standard light sources 26, with 100 being the maximum. This leads to illuminated objects 46 (cf. Fig. 3) are only reproduced with insufficient color fidelity and consequently appear pale. This particularly applies to objects 46 of a color that are underrepresented in the spectrum 40 of the aforementioned standard light sources 26 (e.g., blue-green in the range 42 from approximately 470 nm to 530 nm or red in the range 44 from approximately 600 nm to 800 nm). If such conventional light sources 26 are used to illuminate the overhead area 14, this results in, for example, motorway signs 46 in blue (in Germany, France) or green (in Italy, Switzerland, the USA) being reproduced only in a pale blue or pale green, respectively, and are thus very difficult for the driver of a motor vehicle to recognize. This also applies to headlights 2 in which the at least one further light source 38 for illuminating the overhead area 14 is designed as such a standard semiconductor light source.

[0043] Therefore, it is proposed according to the invention that the at least one further light source 38 is designed to emit light which illuminates an object 46 located in the overhead area 14 of the light distribution 4 (cf. Fig. 3) a selected color with a better color rendering according to CIE 1976 than would be possible with light from at least one first light source 26.

[0044] The at least one further light source 38, which illuminates the overhead area 14, can compensate for the color rendering deficiencies of the at least one first light source 26, i.e., the inadequate rendering of objects 46 in their actual color, with the light it emits. As a result, objects 46 in the overhead area 14 of the light distribution 4 are rendered both in their actual color and with high color saturation. In this way, the driver of a motor vehicle equipped with the lighting device 2 according to the invention can recognize traffic signs 46 more quickly and more reliably, which is greatly beneficial for road safety.

[0045] Unlike the prior art, where an improvement in contrast in the overhead area 14 is sought, which can lead to a reproduction of the color of objects 46 in an incorrect color or with low color saturation, the invention is concerned with an improvement in color reproduction and color saturation, in particular a strong reproduction of the objects in their actual color. This is expressed by the color rendering value Ri or the color rendering index Ra, which for the at least one further light source 38 is significantly higher than the corresponding value of the light emitted by the at least one first light source 26 to generate the dimmed light distribution 14 below the light-dark boundary 6.

[0046] To determine the color rendering index Ra, 14 reference colors were defined in accordance with DIN 6169. The number of reference colors can be fewer (e.g. eight reference colors) or more (e.g. 15 reference colors). For these reference colors, the secondary spectra are measured using a reference light source (e.g. sunlight) and a test light source (e.g. the first or further light source). The deviations result in 14 reference values ​​Ri. To determine the general color rendering index Ra (so-called CRI value), the arithmetic mean of the first eight indices i = 1...8 is determined. The eight numerical values ​​Ri are added together and the result is divided by eight. Further discrete reference values ​​can be specified, for example R9 for saturated red. It is also conceivable to determine the color rendering index Ra based on the arithmetic mean of a different number of reference values ​​Ri, e.g. based on the first 14 or the first 15 reference values ​​Ri.The more colors used to calculate the Ra index, the more accurately it describes the quality of the light.

[0047] Advantageously, the at least one first light source 26 is designed to emit light exclusively into the region 12 below the light-dark boundary 6. The overhead region 14 is thus illuminated only by light from the at least one further light source 38. Of course, it would also be conceivable for a portion of the light emitted by the at least one first light source 26 (e.g., scattered light or deliberately deflected light) to reach the overhead region 14. The color reproduction in the overhead region 14 would then result from a superposition of the light component of the at least one first light source 26 and the light from the at least one further light source 38.

[0048] In a corresponding manner, it can be provided that the at least one further light source 38 is designed to emit light exclusively into the overhead area 14. The area 12 of the light distribution 4 below the light-dark boundary 6 is therefore only illuminated by light from the at least one first light source 26. Of course, it would also be conceivable for a portion of the light emitted by the at least one further light source 38 (e.g. scattered light) to also reach the area 12 below the light-dark boundary 6. Since the intensity of the light from the at least one further light source 38 is relatively low, or in any case significantly lower, than the intensity of the light from the at least one first light source 26 below the light-dark boundary 6, the (possibly colored) light from the at least one further light source 38 would not disturb or impair the dimmed light distribution 4.

[0049] The at least one further light source 38 can be optimized with regard to the color rendering value Ri for one or more colors and / or with regard to the color rendering index Ra (CRI value). Therefore, the at least one further light source 38 is designed to emit light whose color rendering value Ri for the at least one selected color of the object is Ri > 80 according to CIE 1976. The light emitted by the at least one further light source 38 should, for example, compensate for the low intensity of the light from the at least one first light source 26 in a wavelength range 42 of approximately 470 nm - 530 nm (blue-green), so that blue or green highway signs 46 are reproduced with better color, in particular with more true color and color saturation.

[0050] If driving preferably on German or French motorways, the light emitted by the at least one further light source 38 could be adjusted so that it better reproduces, for example, objects 46 in blue (e.g., blue motorway signs). If, on the other hand, driving is on Italian, Swiss, or US motorways, the light emitted by the at least one further light source 38 could be adjusted so that it better reproduces, for example, objects 46 in green (e.g., green motorway signs). The light emitted by the at least one further light source 38 can be adjusted with a view to improved color reproduction of objects 46 of a specific color, for example, depending on position information from a navigation system of the motor vehicle.The adaptation can even go so far as to distinguish whether the motor vehicle is traveling on a motorway, a country road, or in a built-up area. On country roads in Germany, for example, the light emitted by the at least one additional light source 38 could be adjusted such that it better reproduces yellow objects 46 (e.g., yellow country road signs and signs at town entrances) in color. Within built-up areas, for example, the light emitted by the at least one additional light source could be adjusted such that it better reproduces red objects 46 (e.g., stop signs, yield signs, and red borders of prohibition signs).

[0051] In particular, it is proposed that the at least one further light source 38 is designed to emit light which reproduces an object 46 located in the overhead region 14 of the light distribution 4, which object has a saturated red color with a color rendering according to CIE 1976 of R9 > 80. As a result, objects 46 in red are reproduced particularly well, i.e. particularly realistically. Alternatively or additionally, it is proposed that the at least one further light source 38 is designed to emit light which reproduces an object 46 located in the overhead region 14 of the light distribution 4, which object has a saturated yellow color with a color rendering according to CIE 1976 of R10 > 80. As a result, objects 46 in yellow are reproduced particularly well, i.e. particularly realistically.Furthermore, it is alternatively or additionally proposed that the at least one further light source 38 is designed to emit light which reproduces an object 46 located in the overhead area 14 of the light distribution 4 of a saturated green color with a color rendering according to CIE 1976 of R11 > 80. As a result, objects 46 in green are reproduced particularly well, i.e. particularly realistically. Finally, it is alternatively or additionally proposed that the at least one further light source 38 is designed to emit light which reproduces an object 46 located in the overhead area 14 of the light distribution 4 of a saturated blue color with a color rendering according to CIE 1976 of R12 > 80. As a result, objects 46 in blue are reproduced particularly well, i.e. particularly realistically.

[0052] The at least one further light source 38 is designed to emit light that meets the requirements of only one or more of the reference values ​​R9 ... R12 mentioned.

[0053] Alternatively or additionally, it is proposed that the at least one further light source 38 is designed to emit light having a color rendering index Ra according to CIE 1976 of Ra > 80. The color rendering index Ra is the arithmetic mean of the first eight indices i = 1...8 or the first 14 indices i = 1...14 or even the first 15 indices i = 1...15 of the reference values ​​Ri for the various reference colors. The spectrum of such a further light source 38 is, for example, in Fig. 2 and designated by the reference numeral 48.

[0054] If the at least one further light source 38 comprises an RGB LED, its spectrum is preferably adjusted such that the light emitted by the RGB LED 38 reproduces an object 46 of a selected color located in the overhead area 14 of the light distribution 4 with better color rendering according to CIE 1976 than would be possible with light from the at least one first light source 26. An RGB LED 38 can emit different colors by mixing the three primary colors red, green, and blue and, if necessary, also changing the intensity. The light spectrum emitted by the RGB LED 38 can be adjusted by suitable control of the three colored LEDs so that the emitted light has a high intensity, particularly in the wavelength range 42, 44, where the spectrum 40 of the at least one first light source 26 for generating the dimmed light distribution 14 has a deficit.The spectrum of the at least one further light source 38 would then correspond approximately to the spectrum 40 of a conventional LED 26 with the exception that the relative intensity in the regions 42, 44 would be significantly higher, in particular > 0.3, preferably > 0.4, particularly preferably > 0.5, most particularly preferably > 0.6.

[0055] Most preferably, the at least one further light source 38 is designed to emit light in a spectral range 42 of 470 nm - 530 nm and / or in a spectral range 44 of 600 nm - 800 nm with a higher intensity than a conventional LED 26 (cf. the spectrum 40 in Fig. 2). The intensity of the light is therefore particularly high in one or both of the spectral ranges 42, 44 mentioned, so that the deficiencies of the light emitted by the at least one first light source 26 can be compensated.

[0056] If the intensity values ​​of the light in the overhead area 14 are already partially served by the at least one first light source 26, as in the example of Fig. 1 by branched light of the light source 26 (cf. exemplary light beam 50), at least one further light source 38 is sufficient, which fills the gaps in the spectrum 40 of the standard LED 40 only in the areas 42, 44, i.e. which essentially emits light in the spectral range 42 at approximately 470 nm - 530 nm and in the spectral range 44 at approximately 600 nm - 800 nm, possibly also with several color chips (RGB LED). The overall color and the CRI value in the overhead area 14 of the light distribution 4 then result from the superposition of the two light sources 26, 38.

[0057] If the intensity values ​​of the light in the overhead area 14 are controlled solely by the at least one additional light source 38, an LED 38 with a high CRI value is preferred. In this case, too, an RGB LED with the corresponding spectrum of the individual color chips can be used as at least one additional light source 38.

[0058] Particularly when using an RGB LED as at least one additional light source 38 with individually controllable chips, the color spectrum in the overhead area 14 can be adapted to the driving situation. Information about the driving situation can be position data / map data, camera data from an onboard camera or a navigation system. For example, when driving towards a motorway in Germany or France, the color spectrum in the overhead area 14 can be shifted towards blue in order to particularly highlight the motorway signs 46. When driving towards a motorway in Italy, Switzerland or the USA (cf. Fig. 3) the color spectrum in the overhead area 14 can be shifted to greenish in order to particularly highlight the motorway signs 46.

[0059] The abundance of signs here requires a driver to maintain a high level of attention and overview. For example, if the navigation system were to plan a route to Los Angeles via the freeway, it would be advantageous to place the focus of spectrum 48 of the intensity values ​​in the overhead range 14 in the greenish spectral range 42 (approximately 490 nm - 560 nm) to make the corresponding signs 46 particularly easy to recognize.

[0060] Furthermore, it would be conceivable to additionally reduce the proportion from other spectral ranges, for example in the Fig. 3, the bluish range (approx. 450 nm - 490 nm) is reduced. This makes blue signs appear less intense and paler. This further improves the driver's perception of the important green signs 46, allowing them to be recognized preferentially.

[0061] Furthermore, it would be conceivable to use several RGB LEDs as additional light sources 38 and create a matrix RGB overhead light 14. Thus, if necessary, different parts of the overhead area 14 can be illuminated with different spectra, e.g., to avoid a traffic light.

[0062] In particular, it is also conceivable to enrich the color spectrum in the high beam mode by means of at least one additional light source 38. However, due to the low intensity of the light from the at least one additional light source 38 compared to the light used to generate the high beam, this effect is relatively small. In this case, it would be advantageous to use several additional light sources 38, preferably with optics that operate dimmed in the low beam mode and undimmed in the high beam mode. This can improve the enrichment effect of the spectrum above the light-dark boundary 6 in the high beam mode.

[0063] It is also conceivable to temporarily switch the overhead light distribution 14 completely to a specific color or color range, e.g., to completely blue. This is particularly advantageous if game has been detected in front of the vehicle on the roadway or at the side of the road. Game reacts particularly to light from the blue color spectrum by fleeing.

[0064] In summary, the present invention thus proposes a headlight 2 that provides improved visibility of objects 46 in the overhead area 14. The improved visibility of colored objects 46, such as traffic signs, can be achieved by using at least one additional light source 38 with a high color rendering index Ra (CRI value). LEDs with a high luminous flux, such as those used for the at least one first light source 26 to generate the low beam, generally have a lower CRI value than LEDs with a low luminous flux, such as those that can be used for the at least one additional light source 38. Only a small luminous flux is necessary to illuminate the overhead area 14.

Claims

[1] Motor vehicle lighting device (2) for emitting a dimmed light distribution (4) with a horizontal light-dark boundary (6), wherein the dimmed light distribution (4) comprises light of a first maximum illuminance below the light-dark boundary (6) and light of a second maximum illuminance in an overhead region (14) of the light distribution (4) above the light-dark boundary (6), wherein the lighting device (2) has at least one first light source (26) for emitting at least the light below the light-dark boundary (6), and at least one further light source (38) for emitting at least part of the light of the overhead area (14), characterized by , that the at least one further light source (38) is designed and operated to emit light which reproduces an object (46) of a selected colour located in the overhead area (14) of the light distribution (4) with a better colour rendering according to CIE 1976 than would be possible with light from the at least one first light source, wherein the at least one further light source (38) is designed to emit light whose color rendering value Ri for the selected color of the object is Ri > 80 according to CIE 1976. [2] Motor vehicle lighting device (2) according to claim 1, characterized by that the at least one first light source (26) is designed to emit light exclusively below the light-dark boundary (6). [3] Motor vehicle lighting device (2) according to claim 1 or 2, characterized by that the at least one further light source (38) is designed to emit light exclusively into the overhead area (14). [4] Motor vehicle lighting device (2) according to one of the preceding claims, characterized by in that the at least one further light source (38) is designed to emit light which reproduces an object (46) located in the overhead area (14) of the light distribution (4) of a saturated red colour with a colour rendering according to CIE 1976 of R9 > 80. [5] Motor vehicle lighting device (2) according to one of the preceding claims, characterized by in that the at least one further light source (38) is designed to emit light which reproduces an object (46) located in the overhead area (14) of the light distribution (4) of a saturated yellow colour with a colour rendering according to CIE 1976 of R10 > 80. [6] Motor vehicle lighting device (2) according to one of the preceding claims, characterized byin that the at least one further light source (38) is designed to emit light which reproduces an object (46) located in the overhead area (14) of the light distribution (4) of a saturated green colour with a colour rendering according to CIE 1976 of R11 > 80. [7] Motor vehicle lighting device (2) according to one of the preceding claims, characterized by in that the at least one further light source (38) is designed to emit light which reproduces an object (46) located in the overhead area (14) of the light distribution (4) of a saturated blue colour with a colour rendering according to CIE 1976 of R12 > 80. [8] Motor vehicle lighting device (2) according to one of the preceding claims, characterized by that the at least one further light source (38) is designed to emit light having a color rendering index Ra according to CIE 1976 of Ra > 80. [9] Motor vehicle lighting device (2) according to one of the preceding claims, characterized by that the at least one further light source (38) comprises an RGB LED, the spectrum (48) of which is adjusted such that the light emitted by the RGB LED reproduces an object (46) of a selected colour located in the overhead area (14) of the light distribution (4) with better colour rendering according to CIE 1976 than would be possible with light from the at least one first light source (26). [10] Motor vehicle lighting device (2) according to one of the preceding claims, characterized by that the or each first light source (26) is designed as an LED or a laser diode for emitting white light with the aid of a conversion material. [11] Motor vehicle lighting device (2) according to one of the preceding claims, characterized bythat the at least one further light source (38) is designed to emit light mainly in a spectral range of 470 nm - 530 nm and / or 600 nm - 800 nm.

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