Light module for a vehicle lighting system

Abstract

Light module (10) for a lighting device for a motor vehicle (motor vehicle), with a light source arrangement (12) comprising a plurality of matrix-like arranged light emission surfaces (16) for emitting a source light distribution (20), wherein each adjacent light emission surfaces (16) have a distance from each other which is at most a maximum pixel distance (34) of the light source arrangement (12), and with a secondary optic (24) for projecting the source light distribution (20) into a beam light distribution (30) of the light module (10), characterized in that the secondary optic (24) has a characteristic resolution limit such that such areas of the source light distribution (20) which have an angular distance (α) less than the resolution limit with respect to the secondary optic (24) are assigned to such areas in the beam light distribution (30) that are no longer distinguishable, wherein the light source arrangement (12) is arranged relative to the secondary optics (24) such that the maximum pixel spacing (34) with respect to the secondary optics (24) corresponds to an angular spacing (α) below the resolution limit.

Description

[0001] The invention relates to a light module for a vehicle lighting device according to the preamble of claim 1.

[0002] In the field of automotive lighting systems, various types of emitted light distributions (beam distributions) are distinguished, the properties of which are partly regulated by law. For example, the front light distribution includes, for instance, a low beam distribution and a high beam distribution, as well as possibly other light distributions such as side illumination or fog lights.

[0003] The various light distributions are characterized by often complex intensity profiles. For example, the low beam light distribution exhibits a cut-off line that, at least in some sections, runs horizontally during normal operation of the lighting system. An illuminated area lies below this cut-off line, particularly in front of the vehicle. The cut-off line can also have several vertically offset sections connected by a diagonal section (so-called "z-shape"). In contrast, the high beam light distribution extends at least in some sections above the cut-off line and can therefore achieve a greater range. Finally, the side illumination illuminates an area offset laterally from the vehicle's longitudinal axis.

[0004] In automotive lighting technology, it is often desirable to be able to generate several different light distributions with a single, ideally compact, light module. Furthermore, so-called adaptive front lighting systems are increasingly used to prevent glare for other road users by selectively masking or dimming certain areas of the front light distribution.

[0005] Vehicle headlights with the features of the preamble of claim 1 are known from EP 2 752 615 A1 and DE 10 2009 053 581 B3. In such devices, a source light distribution with a desired intensity distribution can be generated using a plurality of matrix-arranged light sources. This source light distribution is projected onto the emitted light distribution by means of a projection lens. The numerous light sources are arranged side by side on a circuit board in a matrix or strip-like pattern. The problem here is that achieving sufficient homogeneity of the emitted light distribution often requires considerable technical effort. In particular, the light-emitting surfaces of the light sources are spaced apart from each other by gaps due to the design.These non-illuminated gaps can lead to darkened structures in the light distribution, which are perceived as unpleasant or tiring by the driver and other observers. A high-contrast grid pattern of dark lines can also impair the perception of the surroundings and therefore pose a safety risk.

[0006] To achieve the most homogeneous emitted light distribution possible, DE 10 2009 053 581 B3 describes, for example, that a primary optic with a plurality of light-guiding elements is arranged between the light sources and the projection lens, with each light-guiding element being assigned to a specific light source and the light-guiding elements converging in exit optics. Thus, in such devices, the primary optic must be manufactured separately and adjusted within the device. EP 2 752 615 A1 describes a different approach, in which the matrix-like light sources are arranged within the focal length of the projection lens, resulting in a blurred image of the source light distribution. However, this approach does not eliminate undesirable contrast fluctuations.

[0007] The present invention is based on the objective of enabling the emission of a light distribution perceived as homogeneous as possible with a compact design. In particular, light distributions with more complex or variably predefined intensity patterns, such as a dimmed light distribution, should be achievable.

[0008] This problem is solved by a light module for a lighting device for a motor vehicle (MV) according to claim 1. In this context, a light module is understood to be the component that emits the usable light distribution. Therefore, a light module can be part of an MV lighting device (e.g., a headlight). However, it is also conceivable that the lighting device comprises several light modules. Conversely, a compact lighting device can also comprise only a single light module.

[0009] The light module comprises a light source array with a multitude of matrix-like light-emitting surfaces arranged side-by-side to emit a source light distribution. Adjacent light-emitting surfaces are spaced apart, typically by design. This spacing is at most a defined maximum pixel pitch of the light source array. Therefore, the distance between the light-emitting surfaces is always less than or equal to the maximum pixel pitch of the light source unit. The light module also includes secondary optics for projecting the source light distribution onto a beam light distribution of the light module. The secondary optics are arranged such that the source light distribution is captured and projected onto the beam light distribution.

[0010] The secondary optics exhibit a characteristic resolution limit, such that areas of the source light distribution which have an angular separation smaller than the resolution limit relative to the secondary optics (i.e., viewed from the secondary optics) are no longer distinguishable in the emitted light distribution. This means that two different areas of the source light distribution, which illuminate the secondary optics at an angular separation smaller than the resolution limit, result in illuminated areas in the emitted light distribution that are no longer resolvable.

[0011] The light source arrangement is positioned relative to the secondary optics such that the maximum pixel spacing with respect to the secondary optics corresponds to an angular distance below the resolution limit. In other words, the maximum pixel spacing of the light source arrangement is smaller than the resolution limit; that is, the maximum pixel spacing, viewed from the secondary optics, covers an angle that is smaller than the resolution limit.

[0012] The resolving power is a physical property of the secondary optics, which depends in particular on the geometric dimensions and materials of the secondary optics, as well as, if applicable, on the wavelength or wavelength spectrum of the source light distribution. A fundamental limitation on the resolution limit arises from diffraction effects of the light from the source light distribution at the secondary optics (so-called diffraction limiting). Corresponding criteria for the diffraction limiting are known in microscopy as the Abbe criterion or Helmholtz criterion. In telescopes, corresponding criteria for the diffraction limiting of resolution are known. In reality, however, the resolution limit of the secondary optics can be higher than the diffraction limiting limit, since various aberrations of the secondary optics also contribute to the resolution limit.The resolution limit is also increased, for example, by aberrations, astigmatism, dichroism, dispersion errors or irregularities in the surface geometry of the secondary optics.

[0013] In this light module, the intensity pattern of the source light distribution can be projected or mapped onto the emitted light distribution using secondary optics. Since the resolution of the secondary optics is lower than the pixel spacing of the light-emitting surfaces, the distances between these surfaces do not result in perceptible dark areas in the emitted light distribution. This allows for the creation of an emitted light distribution that appears homogeneous to the viewer and is therefore perceived as comfortable.

[0014] The light source arrangement features a multitude of light-emitting surfaces arranged in a matrix-like manner, particularly in the form of an array, i.e., regularly and preferably in a plane. Therefore, the overall shape and intensity distribution of the source light distribution can be freely chosen, allowing the desired properties of the light distributions required in automotive lighting applications to be achieved. Due to the described coordination of the resolution limit and pixel spacing, even with a complex shape of the emitted light distribution, the illuminated areas of the source light distribution can exhibit a homogeneous intensity profile.

[0015] The light source arrangement and the secondary optics are specifically matched. Therefore, the design effort required to adapt other optical components can be reduced. The light module has a comparatively simple, compact, and robust design.

[0016] It is particularly advantageous if the secondary optics directly replicate the source light distribution present on the light-emitting surfaces, i.e., if no further intermediate optics are required between the light-emitting surfaces of the light source arrangement and the secondary optics. This allows for a simpler design. For example, complex primary optics for combining the light distributions of individual light sources are not strictly necessary. This avoids the dispersion effects or color aberrations that frequently occur with such primary optics. Furthermore, the design effort associated with mounting and adjusting primary optics in relation to the light source arrangement is eliminated.

[0017] The distance between adjacent light-emitting surfaces is defined, in particular, by the distance between the facing boundary edges of adjacent light-emitting surfaces. Specifically, the distance between two facing boundary edges of two adjacent light-emitting surfaces is at most as large as the pixel pitch. In other words, the aforementioned distance between two adjacent light-emitting surfaces is formed by a gap enclosed by the boundary edges. However, this gap is not resolved by the secondary optics because it is smaller than the resolution limit.

[0018] For further refinement, it can be provided that the light-emitting surfaces themselves have dimensions smaller than the pixel pitch. In particular, it is provided that opposing boundary edges of one and the same light-emitting surface have a distance of at most equal to the pixel pitch. In this configuration, neither the space between light-emitting surfaces nor the light-emitting surface itself is resolved by the secondary optics.

[0019] The secondary optics are, in particular, an optical element with which an optical imaging of the source light distribution can be achieved, for example, a converging lens. Specifically, the secondary optics are designed as a projection lens such that a focal area, for example, a focal point or focal line, is defined. Preferably, at least one of the light-emitting surfaces of the light source arrangement lies within this focal area. This allows the light emanating from the light-emitting surface located in the focal area to be transformed into parallel light beams of the emitted light distribution. The intensity pattern of the source light distribution generated on the matrix of the light-emitting surfaces can then be directly imaged as the emitted light distribution, whereby disturbing dark areas, which are attributable to the pixel spacing between the light-emitting surfaces, are not discernible in the emitted light distribution due to the resolution limit.

[0020] However, it is also conceivable that the light-emitting surfaces are arranged outside the focal area. This allows the source light distribution to be additionally blurred and projected onto the emitted light distribution, thereby further smoothing unwanted contrasts. In particular, it is possible to arrange the light-emitting surfaces within the focal length, i.e., between the focal area and the projection lens.

[0021] For further refinement, the secondary optics can have an optical axis, with the light-emitting surfaces running perpendicular to the optical axis. In particular, all light-emitting surfaces lie in a common plane. The optical axis preferably runs through the aforementioned focal area of ​​the secondary optics.

[0022] According to one aspect of the invention, a light-emitting surface is assigned to each individual light source, such that only the light from that individual light source exits through the assigned light-emitting surface. The light-emitting surface can, in particular, be an optically active surface of the light source (e.g., a semiconductor light source such as a light-emitting diode LED), or the surface of an attachment optic assigned to the individual light source.

[0023] For further development, the light source arrangement features a multitude of matrix-like light sources, with each individual light source being independently controllable, i.e., in particular, independently activatable and deactivatable, or independently variable in its emitted radiation intensity. This allows any desired intensity pattern to be specified as the source light distribution, which is then converted into the emitted light distribution without any disturbing dark areas appearing in the illuminated regions of the emitted light distribution.

[0024] For example, the light sources are designed as light-emitting diodes (LEDs), with the light-emitting surfaces being the optically active surfaces of the LEDs. Each light source is specifically assigned a light-emitting surface. In particular, the light source arrangement can comprise a 2D array of LEDs arranged and interconnected on a common chip.

[0025] For further refinement, the light source arrangement can include a secondary optic featuring matrix-like arrangements of light-emitting surfaces. Specifically, each light source within the arrangement is assigned its own light-emitting surface. It is conceivable that each light source has its own lens, which is assigned to an optically active surface of the light source, for example, fixed to that surface. The light source arrangement could, for instance, be an LED array with microlenses attached to each LED. Such configurations allow the emitted light from a single light source to be focused more effectively towards the secondary optic, thus increasing the optical efficiency of the system.

[0026] However, it is also conceivable that the matrix-like arrangement of light-emitting surfaces is not formed by physical components, but by real intermediate images of a light source following a prior optical imaging process. In this respect, the light module can be designed as a two-stage projection system.

[0027] For further refinement, the secondary optics can additionally incorporate so-called resolution limiting elements to increase the resolution limit. These resolution limiting elements can be designed, for example, as diffraction structures, image offset elements, facets, prism structures, and / or areas of the secondary optics with increased surface roughness. This allows for the deliberate introduction of aberrations by the secondary optics, thereby raising the resolution limit. In this way, the secondary optics can be adapted to the structurally predetermined dimensions of the light source arrangement and thus to its pixel pitch.

[0028] The secondary optics can have an anti-reflective coating on at least one of their surfaces, particularly on the surface facing the light-emitting surfaces. This reduces stray light and increases the optical efficiency of the light module.

[0029] The problem stated at the outset is also solved by the fact that, in a light module with light source arrangement and secondary optics of the type mentioned, the light source arrangement is arranged relative to the secondary optics in such a way that such areas of the emitted light distribution, which are assigned to each of two adjacent light emission surfaces of the light source arrangement, appear at an angle which is below the resolution limit of the human eye, in particular below an angle of 0.2° or preferably less than 0.1°.

[0030] It can be arranged that the light source arrangement is positioned relative to the secondary optics such that any two adjacent light-emitting surfaces appear, when viewed from the secondary optics, at an angle greater than the resolution limit, meaning that the secondary optics can, in principle, resolve the individual light-emitting surfaces. A homogeneous appearance is nevertheless achieved, since no individual structures are resolvable by the human eye in the emitted light distribution.

[0031] The invention will be explained in more detail below with reference to the figures.

[0032] They show: Fig. 1: Sketched representation of a light module; Fig. 2: Enlarged detail view of the light source arrangement according to Fig. 1; Fig. 3: Sketched representation of an intensity distribution of an exemplary source light distribution caused by individual light-emitting surfaces; Fig. 4: Sketched representation of the intensity distribution in the Fig. 3 assigned beam light distribution.

[0033] In the following description and in the figures, the same reference symbols are used for identical or corresponding features.

[0034] The Fig. Figure 1 shows a sketched representation of a light module 10 with a light source arrangement 12, which comprises a multitude of individual light sources 14 arranged in a matrix-like manner on a circuit board not shown in detail (see Figure 1). Fig. 2) comprises. The individual light sources 14 are, for example, light-emitting diodes (LEDs) with light-emitting surfaces 16. In this respect, the light-emitting surfaces 16 form a planar, matrix-like arrangement in the illustrated example. The light module 10 also includes a control unit 18, shown in sketch form, which is designed to control the light output of the individual light sources 14 independently of one another. This allows a light distribution 20 to be generated with the light source arrangement 12, which has a desired and, in particular, variable intensity profile.

[0035] The light module also includes a secondary optic 24, designed as a projection lens 22 in the example shown. The projection lens 22 has an optical axis 26 and defines, for example, a focal point 28 on its side facing the light source arrangement 12. Depending on the design, however, it can also be a more extended focal area.

[0036] In the illustrated example, the circuit board with the individual light sources 14, and thus the individual light-emitting surfaces 16, extends essentially perpendicular to the optical axis 26. In particular, the light-emitting surfaces 16 can all lie in one plane (e.g., on the aforementioned circuit board). In the illustrated example, the light source arrangement 12 is positioned such that the light-emitting surfaces are located between the focal point 28 and the projection lens 22. Therefore, the light-emitting surfaces 16 are arranged within the focal length of the projection lens 22.

[0037] However, it is also conceivable that the focal point 28 (or focal area) of the light module 10 lies in one of the light emission surfaces 16. In particular, it is then provided that all light emission surfaces 16 lie in a common plane, which extends perpendicular to the optical axis 26 at a distance equal to the focal length from the secondary optics 24.

[0038] The secondary optics 24 are designed such that the source light distribution 20, emanating from the light-emitting surfaces 16, can be projected onto a beam light distribution 30 of the light module. Due to the projection properties of the secondary optics 22, the beam light distribution 30 in turn exhibits an intensity distribution that essentially corresponds to the intensity distribution defined by the source light distribution 20. However, in the light module 10 according to the invention, the optical properties of the secondary optics (namely, the resolution limit) are adapted to the geometric design of the light source arrangement, as will be explained in more detail below.

[0039] The Fig. Figure 2 shows an enlarged view of a section II from the plane of the light source arrangement 12 containing the light-emitting surfaces 16. As illustrated by one of the light-emitting surfaces 16, the light-emitting surface 16 is bounded by boundary edges 32. In the example shown, the boundary edges 32 form a substantially square or rectangular shape. The light-emitting surfaces 16 of the light source arrangement 12 form a square or rectangular matrix in the example shown.

[0040] In the matrix-like arrangement, two adjacent light-emitting surfaces 16 have a defined distance from each other, which in the illustrated example corresponds to a maximum pixel spacing 34. It is also conceivable that the distances between different adjacent light-emitting surfaces 16 may differ, with the pixel spacing 34 forming an upper limit for the distance. The pixel spacing 34 is, for example, given by the distance between the facing boundary edges 32 of two adjacent light-emitting surfaces 16. In the illustrated example, the distances between the light-emitting surfaces are identical in the vertical and horizontal directions of the matrix-like arrangement. However, this is not mandatory. For example, in the matrix-like arrangement, the light-emitting surfaces may have a typical distance from each other in a row direction that differs from the distance in a column direction.

[0041] In the illustrated configuration, each of the light-emitting surfaces 16 also has a dimension defined between opposing boundary edges 32, which corresponds at most to the pixel pitch 34. However, it is also conceivable that the individual light-emitting surfaces 16 are larger than the pixel pitch 34.

[0042] By appropriately controlling the individual light sources 14 of the light source arrangement 12, a source light distribution 20 can be generated globally with the light source arrangement 12, which exhibits a desired and / or variable intensity profile. However, due to the spaces between the light-emitting surfaces 16, the source light distribution 20 also exhibits dark areas 38 between brightly illuminated areas 36 (see illustration of the Fig. 2) Due to the projecting properties of the secondary optics 24, the problem here is that the dark areas 38 can lead to an undesirable contrast and / or an undesirable intensity pattern in the emitted light distribution 30.

[0043] In the light module 10, the secondary optics 24 are assigned a resolution limit, which results from the geometric dimensions of the secondary optics 24, the lens material used for the secondary optics 24, and the spectral properties of the source light distribution 20 emitted by the light emission surfaces 16. The resolution limit manifests itself in the fact that light rays of the source light distribution 20, which strike the secondary optics 24 at an angular distance α (see sketched representation in Fig. 1) The secondary optics 24 transforms areas of the emitted light distribution 30 that are no longer distinguishable. In other words, those areas of the source light distribution 20 which, viewed from the secondary optics 24, appear at an angular distance α that is smaller than the resolution limit of the secondary optics 24, are transformed into indistinguishable areas of the emitted light distribution 30.

[0044] In the light module 10, the light source arrangement 12 is arranged relative to the secondary optics 24 such that, viewed from the secondary optics 24, the pixel spacing 34 covers an angle that is smaller than the resolution limit of the secondary optics 24. In other words, two adjacent light emission surfaces 16 appear, viewed from the secondary optics 24, at an angle that is smaller than the resolution limit of the secondary optics 24.

[0045] This leads to the dark areas 38 of the source light distribution 20 caused by the pixel spacing 34 (cf. Fig. 2) cannot be resolved by the secondary optics 24. As a result, no dark zones corresponding to the dark areas 38 are discernible in the source light distribution 30. Instead, the emitted light distribution is largely homogeneous, as shown in the sketched representation of the Fig. 4 illustrates this. The Fig.Figure 4 shows, for example, an intensity pattern of the emitted light distribution 30, which can be observed on a test screen spaced apart in the direction of emission (corresponding to the optical axis 26). Thus, it is possible to generate a desired intensity pattern as a source light distribution by selectively controlling the individual light sources 14 of the light source arrangement 12. However, this distribution exhibits dark areas 38 due to its design. By matching the secondary optics 24 to the light source arrangement 12, the source light distribution 30 does not exhibit any disturbing dark areas, but essentially shows a homogeneously illuminated emitted light distribution 30 with the properties defined by the source light distribution 20.

Claims

[1] Light module (10) for a lighting device for a motor vehicle (motor vehicle), with a light source arrangement (12) comprising a plurality of matrix-like arranged light emission surfaces (16) for emitting a source light distribution (20), wherein each adjacent light emission surfaces (16) have a distance from each other which is at most a maximum pixel distance (34) of the light source arrangement (12), and with a secondary optic (24) for projecting the source light distribution (20) into a radiated light distribution (30) of the light module (10), characterized by , that the secondary optics (24) has a characteristic resolution limit, such that such areas of the source light distribution (20) which have an angular distance (α) smaller than the resolution limit with respect to the secondary optics (24) are assigned to such areas in the emitted light distribution (30) which are no longer distinguishable, wherein the light source arrangement (12) is arranged relative to the secondary optics (24) such that the maximum pixel spacing (34) with respect to the secondary optics (24) corresponds to an angular spacing (α) below the resolution limit. [2] Light module (10) according to claim 1, characterized by , that the light emission surfaces (16) are bounded by boundary edges (32), wherein mutually facing boundary edges (32) of two adjacent light emission surfaces (16) each have a distance from each other corresponding to the maximum pixel spacing (34). [3] Light module (10) according to claim 1 or 2, characterized by , that opposite boundary edges (32) of each light emission surface (16) have a distance from each other corresponding to the maximum pixel spacing (34). [4] Light module (10) according to any of the preceding claims, characterized by, that the secondary optics (24) is designed as a projection lens (22) with an associated focal area (28) which lies in at least one light emission surface (16) of the light source arrangement (12). [5] Light module (10) according to any one of the preceding claims, characterized by , that the secondary optics (24) has an optical axis (26), wherein the light emission surfaces (16) are perpendicular to the optical axis (26). [6] Light module (10) according to any one of the preceding claims, characterized by , that the light source arrangement (12) has a plurality of matrix-like arranged light sources (14), wherein the individual light sources (14) can be controlled independently of each other. [7] Light module according to claim 6, characterized by , that the light source arrangement (12) comprises a front optic which has the matrix-like arranged light emission surfaces (16), wherein each light emission surface (16) is assigned to a light source (14). [8] Light module according to any of the preceding claims, characterized by , that the secondary optics (24) have resolution limiting elements to increase the resolution limit. [9] Light module according to any of the preceding claims, characterized by , that the secondary optics (24) has an anti-reflective coating on one of its surfaces, in particular on a surface facing the light emission surfaces (16). [10] Light module according to the preamble of claim 1, characterized by, that the secondary optics (24) has a characteristic resolution limit such that such areas of the source light distribution (20) which have an angular separation (α) smaller than the resolution limit with respect to the secondary optics (24) are assigned to such areas in the emitted light distribution (30) that are no longer distinguishable, wherein the light source arrangement (12) is arranged relative to the secondary optics (24) such that any two adjacent light emission surfaces (16) appear, viewed from the secondary optics (24), at an angular separation (α) which is greater than the resolution limit, but wherein such areas of the emitted light distribution (30) which are assigned to any two adjacent light emission surfaces (16) appear at an angle which is below the resolution limit of the human eye.

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