Lighting device

Abstract

Lighting device (100) and automotive lighting comprising: a plurality of lighting elements (12), wherein a first group of lighting elements (12A) is arranged along a first direction (x) and a second group of lighting elements (12B) is arranged along the first direction (x) and arranged next to the first group of lighting elements (12A) along a second direction (y) perpendicular to the first direction (x), a single lens (14) in a distance from the first group of lighting elements (12A) and / or the second group of lighting elements (12B) to collimate light from the first group of lighting elements (12A) and the second group of lighting elements (12B), a cylindrically shaped optical element (10) extending along the first direction (x) placed between the plurality of lighting elements (12) and the lens (14), wherein the optical element (10) has a non-uniform shape.

Description

[0001] Lumileds...

[0002] Lighting device

[0003] The present invention relates to a lighting device in particular for an automotive lighting in order to implement a high beam and a low beam. Further, the present invention relates to an automotive lighting comprising such a lighting device.

[0004] In direct imaging adaptive driving beam (ADB) applications an image of the light source produces the individual pixels, i.e. the light source is imaged by a lens or other optical element into the far field. So, if a row of individually addressable LEDs is imaged, a row of controllable pixels is created. In case of an automotive beam, where one row of pixels may contribute to the low beam and one row of pixels to the high beam, different shape requirements exist for the different types of pixel. The high beam pixel needs to be spread in vertical direction to enable sufficient beam height with sufficient horizontal resolution. The low beam needs a sharp cutoff in the vertical direction; thus a vertical spread would destroy this cutoff. Typically, the aspect ratio of light sources corresponds or is equal to the aspect ratio of the pixels or image. With specifically shaped lenses the aspect ratio can be deformed by the lens in one direction. However, this kind of deformation would be applied on all pixels equally. Hence, in order to distinguish the light distribution of the high beam and the low beam complex optical elements need to be implemented in order to create a good vertical spread for the high beam and a sharp cutoff for the low beam in the vertical direction.

[0005] It is an object of the present invention to provide a lighting device with a simplified optical design.

[0006] The problem is solved by a lighting device according to claim 1 and an automotive lighting according to claim 15. The lighting device according to the present invention comprises a plurality of lighting elements. A first group of lighting elements of the plurality of lighting elements is arranged along a first direction and a second group of lighting elements is also arranged along the first direction. The first group of lighting elements and the second group of lighting elements are arranged next to each other along a second direction perpendicular to the first direction. The first direction may correspond in the mounted state to a horizontal direction, wherein the second direction may correspond in a mounted state to a vertical direction. Hence, by the plurality of lighting elements, an array of lighting elements is created having a first row provided by the first group of lighting elements and an adjacent second row provided by the second group of lighting elements. In particular, the lighting elements of the first group are independently addressable from the lighting elements of the second group. Furthermore, preferably the plurality of lighting elements are each individually addressable in order to provide an adaptive driving beam (ADB) such that the lighting elements can be individually addressed in order to shape the respective beam or light output.

[0007] According to the present invention, the lighting device comprises a single lens in a distance from the first group of lighting elements and / or the second group of lighting elements to collimate light from the first group of lighting elements and the second group of lighting elements. In particular, by the single lens light of the plurality of lighting elements is imaged into the far field, i. e. a distance of 25m or more. Therein, it is noted that the lighting device comprises only a single lens for the first group of lighting elements as well as the second group of lighting elements together. Further, the lighting device comprises a cylindrically shaped optical element extending along the first direction and placed between the plurality of lighting elements and the lens. Therein, the cylindrically shaped optical element may at least partially surround the first group of lighting elements and the second group of lighting elements. Light from either the first group of lighting elements or the second group of lighting elements passes through the cylindrically shaped optical element towards the lens of the lighting device. Therein, the optical element has a non-uniform shape. Since the optical properties of the single lens are applied to each of the plurality of lighting elements in the same manner, by the optical element and in particular due to the non-uniform shape of the optical element, the light distribution from the first group of lighting elements and / or the second group of lighting elements can be adapted so as to form a high beam and a low beam of an automotive lighting having the required vertical spread for the high beam and the vertical cut-off for the low beam. Hence, the optical design of the lighting device is simplified and a single lens can be used for both of the first group of lighting elements and the second group of lighting elements, wherein the specific and necessary light distribution of either the first group of lighting elements or the second group of lighting elements is shaped by the cylindrically shaped optical element.

[0008] Preferably, the lighting elements are light emitting diodes and in particular white light emitting LEDs.

[0009] Preferably, the distance between the lighting elements of the first group and the lighting elements of the second group along the second direction is smaller than 1mm, preferably smaller than 500pm and more preferably than 100pm. Therein, the gap is in particular determined between the light emitting area of the respective lighting elements.

[0010] Preferably, by the first group of lighting elements a high beam is provided. Alternatively or additionally, by the second group of lighting elements a low beam is provided. In particular, the high beam could also be provided by a super position of the light of the first group of lighting elements and the second group of lighting elements.

[0011] Preferably, the single lens is uniform along the first direction and the second direction. Thus, a simple lens design and shape can be used in order to image the individual lighting elements into the far field. Preferably, the lens is a cylindrical lens. Therein, the lens extends along the first direction.

[0012] Preferably, the plurality of lighting elements and the lens are arranged on and centered around a common optical axis.

[0013] Preferably, the distance between the lens and one or both of the first group of lighting elements and the second group of lighting elements corresponds to the focal length of the lens. Thus, the first group of lighting elements and / or the second group of lighting elements may be placed in the focus of the single lens.

[0014] Preferably, the first group and the second group of lighting elements each comprise at least one lighting element and preferably more than one lighting element. In particular, the first group of lighting elements comprises an equal number of lighting elements as the second group or a different number. Preferably, the number of lighting elements in each group may be adapted to the respective application.

[0015] Preferably, the first group of lighting elements and / or the second group of lighting elements comprise more than one row each arranged in the first direction. Hence, the first group of lighting elements may comprise more than one row of lighting elements in the first direction. Additionally, or alternatively the second group may comprise more than one row of lighting elements in the first direction.

[0016] Preferably, the light of the first group is directed by the optical element through the lens, wherein light of the second group of lighting element is directed by the optical element only partially through the lens. Hence, light of the first group of lighting element may be completely or at least substantially completely directed by the optical element through the lens and thus contributes to the light output of the lighting device. However, light of the second group of lighting elements only partially contributes to the light output of the lighting device in order to create a cutoff and provide a specifically shaped light distribution in the far filed. Remaining light of the second group of lighting elements may be absorbed or blocked inside the lighting device.

[0017] Preferably, light of the second group of lighting elements is partially directed by the optical element away from the lens. Hence, due to the non-uniform shape of the optical element, light of the second group of lighting elements is partially directed such that it misses the lens and cannot contribute to the light output of the lighting device. Light which misses the lens may be absorbed within the lighting device. Hence, shape of the light distribution of the lighting device is provided by distinguishing whether the light of the second group of lighting elements reaches the lens, passes through the lens and is imaged into the far field. Since the extension of the single lens is finite, a sharp cutoff is created in dependence on whether the light of the lighting elements misses the lens or is projected into the far field. Thus, contrary to other optical solutions to create the cutoff of an automotive low beam, by the present invention a sharp cutoff is created.

[0018] Preferably, the optical element is shaped as free-form.

[0019] Preferably, the optical element has a non-uniform shape along the second direction. As mentioned before, the second direction may correspond in the mounted condition to the vertical direction and consequently, by the optical element the non-uniform shape of the optical element may shape the light distribution or light spread in the vertical direction at least of light of the second group of lighting elements.

[0020] Preferably, the optical element has a uniform shape along the first direction. Thus, each lighting element of the first group may be subjected to the same refraction provided by the optical element. Similar, each lighting element of the second group may be subjected to the same refraction provided by the optical element which is, however, according to the present invention different to the refraction characteristics applied to light of the first group of lighting elements.

[0021] Preferably, the optical element is a single part. Thus, the optical design of the present lighting device is further simplified. Alternatively, the optical element may be built by a combination of more than one piece combinedly providing the optical element.

[0022] Preferably, the optical element is tube-shaped. Therein, the tube-shaped optical element may at least partially surround the plurality of lighting elements. Due to the tube-shaped optical element parameters such as the outer radius (the radius away from the plurality of lighting elements towards the lens) the inner radius (the diameter towards the plurality of lighting elements) or the thickness of the tube-shaped optical element are parameters, which can be adapted in order to form the non-uniform lighting element and specifically shape the light distribution of the plurality of lighting elements of the lighting device. In particular, the center of the tube-shaped optical element may be located in a plane of the first group of lighting elements and / or the second group of lighting elements.

[0023] Preferably, the optical element has a non-constant thickness along the second direction. Due to the increased thickness, light of either the second group or the first group of lighting elements is refracted by the optical elements, such that light of the first group of lighting elements and / or the second group of lighting elements misses the lens and does not contribute to the light output of the lighting device. Thus, light distribution of the lighting elements can be shaped by control of the thickness of the optical element. Preferably, the optical element has an increased thickness at an end of the optical element opposite to the second group of lighting elements along the second direction. Alternatively, or additionally, the optical element may have an increased thickness at an end of the optical element opposite to the first group of lighting elements along the second direction.

[0024] Preferably, the optical element has a non-constant radius along the second direction. Thus, the radius may change along the second direction and thus, by the non-constant radius control of the light distribution in the far field can be achieved. Therein, if the optical element is tube shaped, the inner radius and / or the outer radius of the optical element may change along the second direction.

[0025] Preferably, the optical element has a substantially straight section corresponding to a position of one or more of the first group of lighting elements and the second group of lighting elements along the second direction. The straight section may act as plane-parallel plate allow unrefracted transmission of light. Hence, the optical element may comprise a substantially straight section such that the light of either the first group of lighting elements or the second group of lighting elements close to an optical axis of the lighting device may travel undisturbed by the optical elements towards the lens to the far field.

[0026] Preferably, the optical element is substantially centered in the second direction around one or both of the first group of lighting elements and the second group of the lighting elements. In particular, the optical element is arranged on or centered with the optical axis connecting the plurality of lighting elements with the lens.

[0027] Preferably, the optical element is made of glass. Alternatively, the optical element is made of plastic and in particular PMMA or PC. Those materials provide a high transparency and sufficient good thermal properties. In particular, plastic can be shaped in a molding process with high accuracy and thus can be fabricated with low costs.

[0028] Preferably, a gap is present between a light emitting surface of the lighting elements of the first group and / or the second group and the optical element. In particular, if the optical element has a tube shape, the gap is provided by the inner radius of the optical element. Due to the gap, heat conduction from the lighting elements to the optical element is reduced. Further, due to the gap a larger difference in the refractive indices is created enhancing the refractive effect of the optical element. Consequently, the optical element can be built more compact.

[0029] Preferably, the lighting elements of the first group and the lighting elements of the second group are arranged in a common plane, wherein the optical element extends to the common plane. Hence, the cylindrically shaped optical element may extend to the common plane and thus surrounds the plurality of lighting elements in a semi-circle.

[0030] Preferably, the lighting device has a non-symmetrical light distribution in the far field along the second direction by the optical element, when only the second group of lighting elements are emitting light. Further, the lighting device has a symmetrical light distribution in the far field along the second direction by the optical element when one of the first group of lighting elements or both groups of lighting elements are emitting light. Thus, due to the non-uniform shape of the optical element mainly the light of the second group of lighting elements is affected in order to create a non-uniform light distribution in the far field. This in particular may correspond to a sharp cutoff in the vertical direction.

[0031] Preferably, the light distribution of the first group of lighting elements overlaps at least partially with the light distribution of the second group of lighting elements. Hence, the combination of the light of the first group of lighting elements together with the second group of lighting elements may also create a symmetric distribution. Thus, in the implementation as an automotive lighting, the high beam may either be provided by the first group of lighting elements or a combination of the first group of lighting elements with the second group of lighting elements.

[0032] In another aspect an automotive lighting is provided comprising a lighting device as described before. In particular, the first direction may correspond to a horizontal direction of the automotive beam, wherein the second direction corresponds to a vertical direction. Consequently, the first group of lighting elements may provide a high beam with a sufficient vertical spread in height and a good horizontal solution. Light of the second group of lighting elements may provide a low beam with a cutoff in the vertical direction.

[0033] The present invention is described in more detail with reference to the accompanying figures.

[0034] The figures show:

[0035] Figure 1 a front view of a lighting device according to the present invention,

[0036] Figure 2 a side view of a lighting device according to the present invention,

[0037] Figure 3 a representation of the light distribution of the lighting device according to the present invention and

[0038] Figures 4A-4E different embodiments of the optical element according to the present invention. Referring to Figure 1 showing a lighting device 100 according to the present invention. For sake representation the single lens 14 (see Figure 2) is omitted in Figure 1. The lighting device 100 comprises a first group 12A of lighting elements 12 arranged in or along a first direction corresponding to the x-direction in the figures. Further, the lighting device 100 comprises a second group 12B of lighting elements 12 also arranged along the x-direction, wherein the first group 12A and the second group 12B are arranged next to each other along a second direction corresponding to the y-direction in the figures. The x-direction may correspond in the mounted state to a horizontal direction, wherein the y-direc- tion may correspond in a mounted state to a vertical direction.

[0039] A small gap is present between the lighting elements 12 of the first group 12A and the second group 12B. In particular, the gap in the y-direction is smaller than 1mm, preferably smaller than 500pm and more preferably smaller than 100pm. Further, the lighting device 100 comprises an optical element 10 described in more detail with reference to Figure 2 and Figures 4A-4E.

[0040] In Figure 1 it is exemplified that the first group 12A and the second group 12B may comprise ten individual lighting elements 12. However, the present invention is not limited to the example of figures and in particular the lighting device 100 may have more than ten lighting elements or less. In particular, in the figures it is shown that the first group 12A and the second group 12B may have the same number of lighting elements 12. Of course, the present invention is not limited to this specific embodiment and the number of lighting elements 12 of the first group 12A or / and the second group 12B may differ. Further, in Figure 1 it is shown that the first group 12A as well as the second group 12B may comprise only a single row in the y-direction. However, also the first group 12A and / or the second 12B may comprise more than one row in the y-direction.

[0041] Referring to Figure 2, it is shown, that the first group 12A of lighting elements 12 and the second group 12B of lighting elements 12 arranged in a common plane 32. By the plane 32 an optical axis 30 is defined which may be perpendicular to the plane 32. The lighting device 100 comprises a single lens 14 which may be built as cylindrical lens extending in the x-direction. The single lens 14 is arranged on the optical axis 30, i. e. symmetrically to the optical axis 30. The lens 14 therein is symmetrically shaped in the x-direction and the y-direction. In particular, the length of the lens 14 as well as the length of the optical element 10 in the x-direction may correspond to the length of the row of lighting elements 12 of the first group 12A and / or the second group 12B.

[0042] In Figure 2 the optical element 12 is shown to be tube shaped. The shape is described in more detail with reference to Figures 4A to 4E. However, the cylindrically shaped optical element 10 has a non-uniform shape in particular in the y-direction. Preferably, the optical element 10 may have a uniform shape along the x-direction such that light of each of the lighting element 12 of either the first group 12A or the second group 12B along the respective rows are deformed in the same way. In Figure 2 two exemplified light paths 16, 18 are depicted. Light of a lighting element 12 of the second group 12B indicated by reference sign 18 may pass through the optical element 10 and is directed by the optical element 10 to the lens 14. Thus, the light passes through the lens 14 and is imaged into the far field of the lighting device 100. Contrary, the light path 16 is directed by the optical element 10 to miss the lens 14 and thus is not projected into the far field. The light of the light path 16 does not contribute to the light output of the lighting device 100. Thus, by the edge, and here in particular, the lower edge 14' of the lens 14 a sharp cutoff in the light distribution is created depending on whether the light passes through the lens 14 and thus contributes to the light output of the lighting device 100 or misses the lens.

[0043] Thus, according to the present invention, by the optical element a simplified optical design can achieved providing with a single lens individual adaptation of light at least in the y-direction for a first group 12A and a second group 12B of lighting elements 12. Figure 3 shows the light distribution of the lighting device for the first group 12A and the second group 12B in the same graph. Therein, only the left half of the light distribution is depicted in Figure 3 for the first group 12A and the right half is depicted in Figure 3 for the second group 12B. As shown in Figure 3, light distribution 20 of the light emitting elements 12 of the first group 12A is symmetric or substantially symmetric along the y-direction. Thus, the individual lighting elements 12 of the first group 12A are fully imaged into the far field by the combination of optical element 10 and the lens 14. Contrary, for the second group 12B, the light distribution 22 is non-uniform in the y-direction and comprises a sharp cutoff 24 at the upper edge. Light of the second group 12B of lighting elements 12 above the cutoff edge 24 misses the lens 14 and does not contribute anymore to the light output of the lighting device. Hence, by the second group 12B a low beam is created with a sufficient vertical cutoff, wherein by the first group 12A a high beam with a sufficient vertical spread is provided.

[0044] In the following it is referred to the specific embodiments of the optical element 10 according to Figures 4A-4E. Figure 4A shows an optical element having a tube shape centered around the optical axis 30. Therein, the center of the tubeshaped optical element may coincide with the crossing point of the optical axis 30 with plane 32. In particular, the optical element 10 may extend to the plane 32 for ease of fixturing. The optical element 10 of Figure 4A may have a constant thickness but a changing radius along the y-direction.

[0045] Referring to Figure 4B showing another embodiment of the optical element 10 according to the present invention. The optical element 10 may at least partially surround the light emitting elements 12. Therein, the optical element 10 of Figure 4B has an increased thickness section 26 opposite to the second group 12B. Thereby, light of the second group 12B is partially diverted away from a lens 14 such that this light does not contribute anymore to the light output of the lighting device. Figure 4C may have in addition a straight section 28 such that light from the lighting element 12 close to the optical axis 30 may pass through the straight section 28 undeflected.

[0046] In the embodiment of Figure 4D the lighting element 10 may have a second section of increased thickness 26' opposite to the first group 12A in order to control light appropriately.

[0047] Figure 4E has in addition to the second section of increased thickness 26' a straight section 28 is implemented similar to the embodiment of Figure 4C.

[0048] Although Figures 4A to 4E show different embodiments of the optical element 10, the present invention is not limited to a specific shape and the skilled person will be able to determine the exact shape of the optical element 10.

[0049] Thus, by the present invention a lighting device is provided which has a simplified optical design. In particular, a single lens can be used for the high beam and low beam applying different vertical spreads to different groups of lighting elements.

Claims

Claims1. Lighting device comprising: a plurality of lighting elements, wherein a first group of lighting elements is arranged along a first direction and a second group of lighting elements is arranged along the first direction and arranged next to the first group of lighting elements along a second direction perpendicular to the first direction, a single lens in a distance from the first group of lighting elements and / or the second group of lighting elements to collimate light from the first group of lighting elements and the second group of lighting elements, a cylindrically shaped optical element extending along the first direction placed between the plurality of lighting elements and the lens, wherein the optical element has a non-uniform shape.

2. Lighting device according to claim 1, wherein light of the first group of lighting elements is directed by the optical element through the lens, wherein light of the second group of lighting elements is directed by the optical element only partially through the lens.

3. Lighting device according to claim 1 or 2, wherein light of the second group of lighting elements is partially directed by the optical element away from the lens.

4. Lighting device according to any of claims 1 to 3, wherein the optical element has a non-uniform shape along the second direction and / orwherein the optical element is substantially uniform along the first direction.

5. Lighting device according to any of claims 1 to 4, wherein the optical element has a tube shape.

6. Lighting device according to any of claims 1 to 5, wherein the optical element has a non-constant thickness along the second direction.

7. Lighting device according to any of claims 1 to 6, wherein the optical element has an increased thickness at an end of the optical element opposite to the second group of lighting elements.

8. Lighting device according to any of claims 1 to 7, wherein the optical element has a non-constant radius along the second direction.

9. Lighting device according to any of claims 1 to 8, wherein the optical element has a substantially straight section corresponding to a position of one or both of the first group of lighting elements and the second group of lighting elements along the second direction.

10. Lighting device according to any of claims 1 to 9, wherein the optical element is substantially centered in the second direction around one or both of the first group of lighting elements and the second group of lighting elements.

11. Lighting device according to any of claims 1 to 10, wherein the optical element is made of glass or plastic in particular PMMA or PC.

12. Lighting device according to any of claims 1 to 11, wherein a gap is present between a light emitting surface of the lighting elements of the first group and / or second group optical element.

13. Lighting device according to any of claims 1 to 12, wherein the lighting elements of the first group and the lighting elements of the second group are arranged in a common plane, wherein the optical element extends to the common plane.

14. Lighting device according to any of claims 1 to 13, wherein the lighting device has a non-symmetric light distribution along the second direction by the optical element when only the second group of lighting elements are emitting light and has a symmetric light distribution along the second direction by the optical element when one of the first group of lighting elements or both groups of lighting elements are emitting light.

15. Automotive lighting comprising a lighting device according to any of claims 1 to 14.

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