Motor vehicle headlights for producing a dimmed light distribution

Abstract

Motor vehicle headlight (101) for generating a dipped light distribution (13), comprising a housing (102) and a light module (105) arranged therein for generating the dipped light distribution (13), the light module (105) comprising a light source (11) for emitting light and a reflector (10) with microfacets for focusing the emitted light and for generating the dipped light distribution (13), wherein the reflector (10) comprises a base surface (10b) in the form of an unfaceted freeform surface suitable for generating the dimmed light distribution (13) and microfacets applied at least partially thereon, wherein the microfacets are divided into several groups (6), each of the groups (6) having several microfacets which together generate a partial light distribution corresponding to the dimmed light distribution (13) with a lower intensity than the dimmed light distribution (13), and the dimmed light distribution (13) of the headlight (101) results from a superposition of the partial light distributions of the microfacet groups (6), characterized by the fact that Each microfacet is tilted downwards relative to a surface normal (15) of the base surface (10b) so that the light reflected by the microfacet enters an area below a horizontal light-dark boundary (17) of the blocked light distribution (13).

Description

[0001] The present invention relates to a motor vehicle headlight for generating a dipped light distribution according to the preamble of claim 1. The headlight comprises a housing and a light module arranged therein for generating the dipped light distribution. The light module comprises a light source for emitting light and a reflector with microfacets for focusing the emitted light and for generating the dipped light distribution.

[0002] Such vehicle headlights are known in various designs from the prior art. For example, WO 2015 / 031 925 A1 discloses an optical structure for a reflector of a headlight for motor vehicles with microfaceting for smoothing or homogenizing the light distribution.

[0003] Furthermore, a motor vehicle headlight with a faceted reflector is known from DE 10 2007 063 569 A1. Reflectors that produce a complete light distribution are usually designed as free-form reflectors with multiple facets, whereby each facet typically generates a specific sub-area of ​​the headlight's light distribution, and the headlight's light distribution results from the superposition or complementation of the sub-areas illuminated by the facets. The light distribution areas generated by the individual facets can overlap or even be nearly identical. However, steps or edges often occur at the facet transitions, which complicate the manufacturing of the reflector and therefore consume valuable, unusable reflective surface area.Furthermore, the steps or edges of the facet transitions often generate scattered light that is very difficult to control and cannot be used effectively to create the light distribution of the headlight. This problem can be partially solved by using microfacets on the reflector's reflective surface instead of conventional facets.

[0004] Microfacets are defined and deliberately designed structures on the reflective surface to create a specific light distribution. They are not randomly formed reflective elements arranged on the reflector's base surface. Microfacets are characterized by their reflective surfaces deviating from the reflector's base surface by micrometers. For example, the reflective surfaces of the microfacets can deviate from the base surface by up to approximately 500 µm. Preferably, the deviations are in the range of 20–100 µm. The dimensions of the microstructure in a top view of the reflective surface are in the range of up to a few millimeters, preferably less than 1 mm, particularly preferably between 0.4 and 1.0 mm, and most preferably between 0.2 and 0.6 mm.

[0005] Finally, a motor vehicle headlight is known from the subsequently published DE 10 2020 102 135 A1, the reflector of which comprises a base surface, preferably in the form of an unfaceted freeform surface suitable for generating a dipped light distribution, and microfacets applied at least partially thereon. The microfacets are divided into several groups, each group having several microfacets which together generate a partial light distribution corresponding to the dipped light distribution with a lower intensity than the dipped light distribution of the headlight, and the dipped light distribution of the headlight results from a superposition of the partial light distributions of the microfacet groups.

[0006] Based on the described prior art, the present invention aims to design and further develop a known headlight with a microfaceted reflector in such a way that it can produce a dimmed light distribution.

[0007] To solve this problem, a motor vehicle headlight with the features of claim 1 is proposed. In particular, starting from the headlight of the type mentioned at the outset, it is proposed that each microfacet is tilted downwards relative to a surface normal of the base surface to such an extent that the light reflected by the microfacet enters an area below a horizontal light-dark boundary of the dimmed light distribution.

[0008] The dipped beam light distribution preferably has a substantially horizontal cut-off line. This cut-off line can be either symmetrical (with a purely horizontal extent) or asymmetrical (with a partially horizontal extent and an incline, e.g., a 15° slope). Such a headlight can be used, for example, to generate dipped beam, fog light, or parts thereof. The dipped beam light distribution could also have a vertical cut-off line.

[0009] The unfaceted base surface, which is designed, for example, as a freeform surface, creates the light-dark boundary. The microfacets are applied to this base surface. The reflective surfaces of the individual microfacets are designed and / or oriented such that the light-dark boundary created by the microfaceted reflector is maintained. For example, the light reflected from the reflective surfaces of the microfacets can be directed below a horizontal light-dark boundary or, on the illuminated side, next to a vertical light-dark boundary. In this sense, the invention proposes that each microfacet be tilted downwards relative to the surface normal of the base surface to such an extent that the light reflected from the microfacet falls into an area below a horizontal light-dark boundary of the blocked light distribution.It is particularly advantageous if each microfacet is tilted downwards by half its scattering angle relative to the surface normal of the base surface. Of course, it would also be conceivable for a small portion of the light reflected by the reflector or by one or more microfacets to be reflected into an overhead area above a horizontal luminance boundary in order to achieve the prescribed minimum intensities in the overhead area of ​​a dimmed light distribution. The legally mandated measurement points in this area extend up to 4° above the horizon and are characterized by minimum and maximum values, as well as so-called sum values, for the illuminance at each measurement point.

[0010] According to an advantageous embodiment of the invention, it is proposed that several microfacet groups be arranged distributed over a reflective surface of the reflector. It is possible to provide only a portion of the reflector's reflective surface with microfacet groups. However, it is particularly preferred if microfacet groups are arranged over the entire reflective surface of the reflector.

[0011] The microfacet groups distributed across the reflective surface can have the same or different compositions of microfacets. According to a preferred embodiment of the invention, it is proposed that each microfacet group comprises several classes of microfacets, each microfacet class having at least one microfacet and being configured to illuminate a specific area of ​​the partial light distribution generated by the microfacet group, and wherein the partial light distribution of the microfacet group results from a superposition of the different areas illuminated by the microfacet classes. For example, it is conceivable that a microfacet group comprises ten microfacets of a first class, five microfacets of a second class, three microfacets of a third class, and one microfacet of a fourth class. The different microfacet classes can, for example, be configured as follows:The microfacet classes differ from one another by their main reflection direction (orientation of the surface normals), their scattering angle in the horizontal and / or vertical direction, the shape of the area of ​​the partial light distribution illuminated by the microfacet classes, their shape and / or area dimensions, or by other optical or structural parameters. It is particularly preferred if the areas of the partial light distribution illuminated by the different microfacet classes differ from one another by the luminous flux in the respective area.

[0012] The number, arrangement, orientation, and design of the microfacet classes are selected such that the microfacet group generates the desired partial light distribution, its extent and relative intensity distribution corresponding to the resulting light distribution of the headlight, albeit with a lower absolute intensity. A superposition of the partial light distributions then forms the resulting light distribution of the headlight. Advantageously, the number of microfacets of a specific microfacet class per microfacet group is selected based on the luminous flux in the area of ​​the partial light distribution illuminated by that microfacet class. This means that a microfacet group contains more microfacets of a specific class the higher the luminous flux in the area illuminated by the microfacets of the corresponding class.Therefore, a larger number of microfacets are provided in a microfacet group for illuminating brighter areas of the partial light distribution.

[0013] Preferably, the number of individual microfacet classes per microfacet group is determined for the entire reflector and remains constant across the entire reflective surface, regardless of the design of the reflector's base. Within the different microfacet groups, the number of individual microfacet classes is preferably also the same. However, it is also conceivable that the number of individual microfacet classes within the different microfacet groups differs. In this case, the ratio of the microfacet classes to each other preferably remains constant across the entire reflective surface. It is also conceivable that the reflector's base is divided into several sub-areas, with the microfacet groups in the different sub-areas of the reflector differing from one another in terms of the number, design, and / or arrangement of the microfacets or microfacet classes.

[0014] The light source of the headlight according to the invention preferably comprises a white semiconductor light source, preferably a white high-power LED, or a laser light source, in particular a semiconductor laser light source, which emits white light. In this sense, the light source comprises one or more semiconductor light sources that emit light of a first wavelength (e.g., blue light) onto a converter material, which is partially converted by the converter material into light of a second wavelength (e.g., yellow light). A superposition of the unconverted and converted light of the two wavelengths then produces the desired white light of the light source. One or more semiconductor light sources and the converter material can be combined in a single semiconductor chip. The light reflected by the reflector is then...The luminous surface of the light source shown is therefore preferably formed by the surface of the converter material, which has a square or rectangular shape.

[0015] Regarding the shape of the reflector's base surface, it is proposed that the base surface be parabolic or elliptical in both horizontal and vertical sections. Starting with a parabolic or elliptical base surface, a freeform reflector can be generated by selectively varying the reflective surface or by varying it across a range of areas. This freeform reflector produces a desired diffused light distribution with a defined light-dark boundary. Preferably, the base surface is parabolic or elliptical in the horizontal direction and more preferably follows a freeform shape in the vertical direction.

[0016] According to another advantageous embodiment of the invention, it is proposed that at least one of the microfacet classes generates images of the light source or its illuminating surface rotated by 15° to the horizontal, which serve to illuminate an area below a 15° rise of a horizontal light-dark boundary of the partial light distribution or the resulting light distribution of the headlight.

[0017] Further features and advantages of the present invention are explained in more detail below with reference to the figures. The individual features described below and shown in the figures can be implemented in any combination, even if they are described or shown in other combinations. The figures show: Fig. 1 a motor vehicle headlight according to the invention in a preferred embodiment; Fig.2. An exemplary high beam spot distribution divided into different areas using standard Isolux lines; Fig. 3. An exemplary high beam spot distribution divided into different areas using Isolux contour lines; Fig. 4 one based on the subdivision of the high beam spot distribution from Fig. 3 high beam spot distribution divided into different areas based on Isolux contour lines; Fig. 5 an example of a group of several microfacets that are assigned to different microfacet classes; Fig. 6 a base surface of a reflector of the headlight according to the invention in a perspective view; Fig. 7 a base surface of the reflector made of Fig. 6 with applied microfacets in a top view against a direction of light emission; Fig.8 a light distribution achieved with the headlight according to the invention with a reflector with the proposed microfaceted reflective surface; Fig. 9 a base surface of a reflector of the headlight according to the invention; Fig. 10 through the base area made of Fig. 9 produced exemplary drawn images of a luminous surface of the light source of the headlight as part of a dimmed light distribution with a symmetrical light-dark boundary; Fig. 11 one based on the Fig. 4 described subdivision of a dimmed light distribution with symmetrical light-dark boundary into several areas; Fig. 12 a schematic view of a headlight according to the invention in a vertical section; Fig. 13 a subdivision of a dimmed light distribution with an asymmetrical light-dark boundary into several areas; and Fig.14 a base surface of a reflector of a headlight according to the invention in a top view opposite a direction of light emission.

[0018] In Fig.1 is a headlight according to the invention for motor vehicles, designated in its entirety by reference numeral 101. The headlight 101 comprises a housing 102, which is preferably made of plastic. In a light emission direction 103, the headlight housing 102 has a light emission opening which is closed by a transparent cover lens 104. The cover lens 104 is made of colorless plastic or glass. The lens 104 can be designed without optically effective profiles as a so-called clear lens. Alternatively, the lens 104 can be provided, at least in some areas, with optically effective profiles (e.g., cylindrical lenses or prisms) that cause the transmitted light to be scattered, preferably in a horizontal direction. The headlight 101 is intended for installation on a mounting side of a motor vehicle.Two of the headlights 101 shown, which are arranged on different sides of the motor vehicle, form a motor vehicle lighting device. The headlights 101 installed on different sides are preferably designed to be mirror-symmetrical with respect to a vertical plane through a longitudinal axis of the motor vehicle with respect to their general geometric external appearance.

[0019] Inside the headlight housing 102, two light modules 105, 106 are arranged in the illustrated example. The light modules 105, 106 are arranged either fixedly or movable relative to the housing 102. A dynamic cornering light function or an adaptive light distribution (e.g., partial, continuous, or glare-free high beam; spot or marker light) can be implemented by moving the light modules 105, 106 relative to the housing 102 in a horizontal direction. Moving the light modules 105, 106 about a horizontal axis, i.e., in a vertical direction, allows for headlight range control or an adaptive light distribution. Of course, the headlight housing 102 can also contain more or fewer than the two light modules 105, 106 shown. One or more of the light modules 105, 106 of the headlight 101 can be designed as a reflection module within the meaning of the present invention.The invention is described below by way of example using the light module 105.

[0020] The light module 105 is designed to generate a dipped light distribution with a horizontal and / or vertical cut-off line. The horizontal cut-off line of a dipped light distribution can be symmetrical (strictly horizontal) or asymmetrical (with a slope, e.g., a step or a 15° slope on the side of the vehicle facing the road). The dipped light distribution can be, for example, a dipped beam, a fog light, or a part thereof. It is conceivable that the light distributions of the headlights 101 on different sides of the vehicle combine to form the resulting dipped light distribution of the headlight 101.

[0021] A control unit 107 is arranged in a control unit housing 108 on the outside of the headlight housing 102. Of course, the control unit 107 can also be arranged at any other location on the headlight 101.

[0022] In particular, a separate control unit can be provided for each of the light modules 105, 106, whereby the control units can be an integral part of the light modules 105, 106. Of course, the control unit 107 can also be located remotely from the headlight 101, e.g., in the engine compartment of the vehicle. The control unit 107 serves to control and / or regulate the light modules 105, 106 or subcomponents of the light modules 105, 106, such as light and / or radiation sources, movable shutters, stepper motors, actuating magnets, etc. of the light modules 105, 106. The control of the light modules 105, 106 or the subcomponents by the control unit 107 is effected via connecting lines 110, which are located in Fig. The lines 110 are represented symbolically by a dashed line. The lines 110 can also supply electrical energy to the light modules 105, 106 and their subcomponents. The lines 110 run from inside the headlight 101 through an opening in the headlight housing 102 into the control unit housing 108 and are connected there to the circuit of the control unit 107. If control units are provided as an integral part of the light modules 105, 106, the lines 110 and the opening in the headlight housing 102 can be omitted. The control unit 107 includes a connector 109 for connecting a cable to a higher-level control unit (e.g., a body controller unit) and / or a power source (e.g., a vehicle battery).

[0023] Although the present invention is directed towards headlights for generating a dimmed light distribution, the invention and in particular the design of the reflective surface with the microfacets will below be described with reference to the Fig. Sections 2 to 8 are first explained using the design of the microfacets on the reflective surface of a headlight reflector to generate a high beam distribution. Subsequently, with reference to the Fig. Sections 9 to 14 explain in more detail the special features relating to a headlight for producing a dimmed light distribution.

[0024] The light module 105 of the headlight 101 according to the invention comprises a reflective surface which is provided with microfacets, at least in certain areas. Preferably, various microfacets, each with its own partial light distribution (illuminating different areas 4 of the partial light distribution), are grouped together, and this group is then arranged repeatedly, at least in certain areas, on the reflective surface. The groups each generate the light distribution intended for the overall reflector or the light module 105, only in a dimmed form, i.e., with lower illuminance or intensity.

[0025] Such microfacets can be produced on a base surface with a continuous transition, meaning the reflector no longer has any steps or edges, thus reducing stray light and increasing the efficiency of the light module 105 or the headlight 101. Furthermore, local defects in the reflector are less significant and do not affect only a specific area of ​​the light distribution, since each microfacet group generates the entire light distribution, thereby mitigating the effects of the defects.

[0026] In particular, the invention differs from the prior art in that it proposes a special arrangement of microfacets on the reflector, which is applicable to a general reflector and improves its manufacturability and efficiency. The special arrangement of the microfacets does not primarily aim to produce a particularly high C6 value or a specific light pattern on a projection lens or a cover plate.

[0027] In conventional light modules or spotlights, the reflector's base surface typically consists of a freeform shape with several conventional facets. Each facet generates a predefined individual light distribution, which usually does not correspond to the overall light distribution of the spotlight, but only to a sub-area of ​​it. The resulting overall light distribution arises from the superposition or combination of the individual light distributions of the facets. The facets are usually arranged horizontally next to each other and extend vertically along the reflector, with a predominantly vertical dividing line between them.

[0028] The separation between the facets becomes more pronounced the more different the vertical orientation and thus the individual light distributions are in the vertical direction. The shape of a facet approximately follows an ellipsoidal surface.

[0029] The invention proposes modulating an unfaceted base surface with a specific arrangement of microfacets, wherein several microfacets are grouped together to generate a partial light distribution that—except for the lower intensity (illuminance)—corresponds to the resulting overall light distribution of the headlight. The overall light distribution is generated by superimposing the partial light distributions of the microfacet groups. For a light module or headlight used to generate a high beam distribution, the reflector base surface is preferably an ellipsoid, but can also be an unfaceted freeform surface or a paraboloid.

[0030] For the design and arrangement of the microfacets on the base surface, the following method is proposed, for example: A light distribution 2 (cf. e.g. a high beam spot distribution from the Fig.2 to 4) is subdivided into different areas 4. The Isolux contour lines of the light distribution serve, for example, as the basis for areas 4. In Fig. 2 is the standard Isollux representation and in Fig. Figure 3 shows the isolux representation with the isolux contour lines 3, where contour line 3a = 10 ×, contour line 3b = 50 ×, contour line 3c = 100 ×, and contour line 3d = 140 ×. The light distribution 2 is then decomposed into corresponding regions 4 based on the contour lines 3, where region 4a approximates contour line 3a, region 4b approximates contour line 3b, region 4c approximates contour line 3c, and region 4d approximates contour line 3d. In the example shown, it would be advantageous to choose the contour lines 3 as regions 4, but this is generally not necessary. Likewise, the regions 4 do not have to be rectangular but can have almost any shape.

[0031] For each area 4, a horizontal and vertical extent as well as the luminous flux within the area are defined. In this example, the following results: Area Horizontal Vertical Luminous flux 10 Ix ± 2,8° ± 2,0° 196 In 50 Ix ± 1,6° ± 1,0° 93 In 100 Ix ± 0,8° ± 0,6° 42 In 140 Ix ± 0,3° ± 0,3° 10 In

[0032] For each region 4a to 4d, a class 5a to 5d of microfacets is defined, which generates the respective light distribution of region 4. In this example, class 5b, for instance, produces a scattering width of ± 1.6° horizontally and ± 1.0° vertically. The different microfacet classes 5 are shown in the following table: Nr. Number Height Min. / max. horizontal angle Min. / max. vertical angle Rmin 1 5470 14,381 µm -0,98° / 0,98° -0,64° / 0,64° 7,144 mm 2 2742 7,407 µm -0,54° / 0,54° -0,30° / 0,30° 13.00 mm 3 1371 1,948 µm -0,20° / 0,20° -0,02° / 0,02° 35.79 mm 4 457 0,000 µm 0,00° / 0,00° 0,00° / 0,00° >100 mm

[0033] The “number” refers to the number of microfacet class across the entire reflective surface and not within the microfacet group.

[0034] Next, a group 6 of microfacets is defined. As a first step, the relative number of classes 5 in group 6 is determined from the luminous flux values ​​in areas 4: In area 4d, class 5d must "generate" 10 Im of light. Since area 4d lies within area 4c, class 5c only needs to generate the luminous flux that is still missing in area 4c after subtracting the luminous flux of class 5d, i.e., in this case, 42 Im - 10 Im = 32 Im, and so on. This is illustrated in the following table. Class 5a 5b 5c 5d Luminous flux 196 - 93 Im = 103 Im 93 - 42 = 51 In 42 - 10 = 32 In 10 In

[0035] Rounded, this results in a ratio of microfacet classes 5 to: 5a : 5b : 5c : 5d = 100 : 50 : 32 : 10 or 10 : 5 : 3 : 1

[0036] In this example, a group 6 therefore comprises 10 microfacets of class 5a, 5 microfacets of class 5b, 3 microfacets of class 5ca, and 1 microfacet of class 5d. This totals 19 microfacets. An example of a corresponding group 6 is shown in Fig. Figure 5 shows that in this example, the edge lengths a and b of a facet are 1.0 mm. It is understood that the number, arrangement, shape, and / or dimensions of the individual microfacets within a group may differ from the example shown, depending on the requirements for light distribution or the wishes of the customer (vehicle manufacturer).

[0037] Group 6 already generates the entire resulting light distribution of the headlight 101 (with respect to extent and relative intensity distribution), albeit with a lower absolute intensity. By repeatedly arranging the microfacet group 6 in several areas, preferably on the entire reflector, the resulting light distribution with the desired intensity is obtained. A corresponding reflector 1 is in Fig. 7 shown in a top view opposite the direction of light emission 103. Fig. Figure 6 shows the corresponding base surface 1b. The microfacets of the distributed groups 6 are modulated onto this base surface 1b. The black border in Fig. Figure 7 forms the reflector contour. Of course, the contour can deviate from the rectangular shape shown if desired or necessary due to space constraints inside housing 102.

[0038] Reflector 1 generates the light distribution of the light module 105 or the headlight 101 as defined by the microfacet groups 6. Since the light distribution is created by each group 6 distributed across the reflective surface, the susceptibility to errors is greatly reduced. Likewise, the tolerance behavior of reflector 1 is significantly improved; the light distribution is less distorted and remains much more stable in its shape and luminous intensity.

[0039] In Fig. Figure 4 shows a target light distribution 2 of a high beam / spotlight achieved with a conventional reflector known from the prior art, and in Fig. Figure 8 shows, for comparison, a light distribution 2 of a high beam / spotlight produced with the microfacet reflector 1 described above.

[0040] Depending on the light distribution, the areas 4 can be contiguous, overlapping areas or separate areas. Furthermore, the areas 4 do not have to be square or rectangular; they can also have other shapes.

[0041] The division of the light distribution into the areas 4 can be carried out essentially from two perspectives: The areas 4 should be selected such that the characteristics of the resulting overall light distribution are reflected in the partial light distributions of the areas 4, and that the partial light distribution of an area 4 can be generated by the microfacets of area 4. Since the microfacets should ideally have a continuous transition to one another, the dispersion width that can be generated with a single microfacet may be limited.

[0042] Microfacets are defined structures deliberately formed on the base surface 1b of the reflector 1 to create a specific light distribution. They are not randomly formed reflective elements arranged on the base surface 1b of the reflector 1. Microfacets are characterized by their reflective surfaces deviating from the base surface 1b of the reflector 1 in the micrometer range. For example, the reflective surfaces of the microfacets can deviate from the base surface 1b by up to approximately 500 µm. Preferably, the deviations are in the range of 20–100 µm. A microfacet can have dimensions in plan view ranging from approximately 0.5 mm x 0.5 mm to approximately 5 mm x 5 mm. These dimensions need not be square, but can also be rectangular or other shapes, such as round, oval, triangular, or polygonal.

[0043] In general terms, the relative number of microfacet classes 5 in a group 6 to each other results from the ratio of the luminous fluxes of the assigned areas 4 of the light distribution 2 to each other, minus the luminous flux that is already generated in an area 4 by an overlapping or other microfacet class 5 located in that area.

[0044] In reality, it is rarely possible to achieve the exact ratio of classes 5 within a group 6. In the example described above, group 6 has 4 x 5 = 20 group elements available, but only 19 elements are needed based on the relative ratio. This problem can be mitigated by giving the extra element in the group a slightly larger spread compared to the originally specified target value of range 4.

[0045] It is conceivable to combine a reflector having several conventional facets with the described method for microfaceting by, for example, only one or some conventional facets being designed with microfacets according to the invention.

[0046] The arrangement of classes 5 within group 6 should preferably be as varied as possible. The microfacets can also be statistically distributed across the entire reflector; however, a repeating arrangement of groups 6 is easier to construct. Furthermore, the classes 5 within group 6 can be arranged not only as rectangles or squares, but also in rows or columns.

[0047] It may be useful to increase the edge length of class 5 towards the edge of reflector 1, so that each microfacet receives the same luminous flux, even if it is not in the direct beam cone of the light source, but laterally at the edge.

[0048] With the present invention (see Fig. 9 to 14) the microfaceted reflector 1 described above for generating a high beam distribution 2 is improved by the measures described below, so that the reflector 10 of the headlight 101 according to the invention for generating a low beam distribution (cf. Fig. 11 and Fig. 13) is suitable.

[0049] The reflector 10 of the invention is based on a base surface which is designed to produce a dimmed light distribution 13 (cf. Fig. 11) to create a light-dark boundary 17. The light-dark boundary 17 can be symmetrical (see below). Fig. 11), in which case it exhibits an essentially continuous horizontal course. It would also be conceivable that the light-dark boundary 17 is asymmetrically formed (cf. Fig.13), wherein it then has an essentially horizontal course 17a on the opposite side of the road and an ascending course 17b on the own side of the road.

[0050] The base surface 10b is preferably a freeform surface. It can be provided with conventional facets or be unfaceted. The microfacets are applied to this base surface 10b in such a way that the light-dark boundary 17 is maintained for the microfaceted reflector 10. In this sense, the microfacets are aligned with respect to the surface normal 15 of the base surface 10b (cf. Fig. 12) tilted downwards. Preferably, the microfacets are tilted downwards by half their scattering angle relative to the surface normal 15.

[0051] The microfacet reflector 10 for generating the low beam distribution 13 is constructed according to the same scheme as the microfacet reflector 1 described above for generating the high beam distribution 2. For a conventional low beam reflector, it is important that it can generate the light-dark boundary 17 on its own. In the prior art, this is usually achieved by the reflector having conventional facets whose reflective surfaces are designed, arranged and / or aligned such that the upper edges of images 12 of the light source 11 of the light module 105 overlap (cf. Fig. 9) and thus form the light-dark boundary 17 (cf. Fig. 10) Preferably, the reflective surfaces of such conventional facets are freeform surfaces. Such a conventional reflector can be used as a base surface 10b for the microfaceted reflector 10.

[0052] The microfacets are applied to the base surface 10b. The representation of the light source images 12 of the light distribution of such a base surface 10b is shown in Fig. Figure 10 shows that the light source 11 has a rectangular luminous surface, formed, for example, by the converter material of a semiconductor light source. Of course, the luminous surface of the light source 11 can also have a different shape, which can be reflected in a corresponding shape of the light source images 12. The light source images 12 are generally representations of an arbitrarily designed and shaped luminous surface of the light source 11.

[0053] The base surface 10b is preferably parabolic or elliptical in the horizontal direction. Therefore, in Fig.10 all light source images 12 are horizontally centered. In the vertical direction, the base surface 10b preferably follows a freeform surface, such that all upper edges of the light source images 12 lie at the light-dark boundary 17. Subsequently, the number of required microfacet classes 5 per microfacet group 6 and the required number of microfacets per class 5 or the ratio of the number of microfacets per class 5 to each other are determined analogously to the high beam reflector 1.

[0054] For this purpose, the light distribution 13, which is in Fig.The low beam distribution 11 is configured as a symmetrical low beam distribution, subdivided into several areas 4, here in the example into areas 4a to 4d, and the number of microfacets for each class 5 of a microfacet group 6 is calculated according to the luminous flux in areas 4. Each area 4x (x = a...d) is assigned a corresponding class 5x of microfacets. Each group 6 with the classes 5 of microfacets is configured to generate a partial light distribution that corresponds to the resulting light distribution of the light module 105, except that it has a lower intensity. A superposition of the partial light distributions formed by the groups 6 yields the resulting light distribution of the light module 105 or the headlight 101.

[0055] The groups 6 with the classes 5 of microfacets are then arranged distributed across the base surface 10b. Preferably, the entire base surface 10b is covered with the microfacets. Due to the vertical dispersion of a microfacet class 5x, the light source images 12 can be directed across the light-dark boundary 17, thus softening it. This is generally undesirable. To counteract this effect, an angle 13 (see figure) is used for each microfacet class 5x (x = a...d). Fig.12) determines how far a scattering cone 16 would shift the light source images 12 beyond the light-dark boundary 17. Each microfacet of this class 5x is then modulated onto the base surface 10b by this angle 13 or a part thereof, e.g., by half the angle 13, relative to the surface normal 15. With a symmetrical scattering width of the microfacets, the angle 13 can be determined relatively easily, as it is exactly half the total opening angle of the scattering cone 16. Although this procedure can create edges at the microfacet transitions, their effect on the resulting light distribution 13 is negligible.

[0056] In a further education course, 18 sub-areas can be defined on the basic area 10b (see below). Fig.14), e.g., into sub-areas that generate light source images 12 with a similar orientation. For each sub-area 18 of the reflector 10, a separate composition of microfacet classes 5 is determined. However, the total frequency of the microfacets of each class 5 is determined for the entire reflector 10 as before and remains unchanged overall. Thus, for example, for a low beam distribution 12 with a 15° slope, it may be advantageous to preferentially use the light source images 12 of class 5c, which have a rotation of approximately 15° with respect to the horizontal, to generate this part 17b of the light-dark boundary 17. By way of example, in such a case, a division into microfacet classes 5a ... 5d with the in Fig. The 13 partial light distributions shown are shown.

[0057] If, for the entire reflector 10, the ratio of the frequencies of the microfacet classes 5 to each other is, for example, 5a : 5b : 5c : 5d = 10 : 5 : 3 : 1, then in this variant it is advantageous to change the ratio in the regions 18a ... 18d to, for example, 5a : 5b : 5c : 5d = 10 : 5 : 10 : 1, so that this part 17b of the light-dark boundary 17 utilizes disproportionately strongly favorably oriented light source images 12 from the microfacets of class 5c. This makes it easier to generate a maximum, or rather, the sharpness of the light-dark boundary 17 is improved.

[0058] In another advanced training, microfacet classes 5 can also be designed with asymmetrical scattering angles, so that the tilt angle for the microfacets can be taken into account during the design phase. By smoothing the transitions between the microfacets, the transitions between them can be made seamless (without kinks and / or steps). However, in this variant, the seamless transition always results in a portion of light that is necessarily directed across the light-dark boundary 17. This portion can, however, be advantageously used selectively to illuminate an overhead area of ​​the light distribution 13 above the light-dark boundary 17.

[0059] In summary, the invention proposes a method for designing a microfaceted reflector 10 for generating a low-beam light distribution 13, as well as a reflector 10 produced according to the method, a light module 105 with such a reflector 10, and a headlight 101 with such a reflector 10. The method preferably uses a freeform surface as the base surface 10b, which generates a low-beam light distribution 13 from a single facet and onto which the microfacets are modulated. Such a reflector 10 is sensitive to mechanical tolerances and contamination. To reduce this disadvantage, the invention proposes applying microstructures to the reflector 10, which broaden the light source patterns 12 and smooth the light distribution 13.If the light distribution 13 is also broadened in the vertical direction, it should be lowered by tilting the microfacets in order not to exceed the light-dark boundary 17.

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