Lighting element

Abstract

Lighting element in particular for an automobile, comprising a mixing box comprising a backwall and sidewalls extending from the backwall, at least one light emitting element, extending through an opening of the backwall, and a diffusor connected to the mixing box opposite to the backwall and having a front face facing away from the backwall and an opposite back face facing in the direction of the backwall, wherein the diffusor receives light from the at least one light emitting element via its back face and emits light via its front face, wherein the back face of the diffusor extends towards the backwall of the mixing box, wherein the extension of the back face is asymmetrical along at least one lateral direction and the back face is distant of the backwall.

Claims

1. A lighting element for an automobile, the lighting element comprising: a mixing box comprising a backwall and sidewalls extending from the backwall; at least one light emitting element, extending through an opening of the backwall; and a diffusor connected to the mixing box opposite to the backwall and having a front face facing away from the backwall and an opposite back face facing in the direction of the backwall, wherein the diffusor receives light from the at least one light emitting element via its back face and emits light via its front face, wherein the back face of the diffusor extends towards the backwall of the mixing box, and wherein the light emitted via the front face of the diffusor is non-symmetric.

2. The lighting element according to claim 1, wherein the back face is distant of the backwall.

3. The lighting element according to claim 1, wherein two or more light emitting elements are present, wherein at least two light emitting elements emit light with a different color.

4. The lighting element according to claim 1, wherein the front face of the diffusor is flat.

5. The lighting element according to claim 1, wherein the diffusor comprises a stub extending from the back face towards the at least one light emitting element.

6. The lighting element according to claim 5, wherein the stub has a rectangular shape.

7. The lighting element according to claim 5, wherein a shape of the stub corresponds to the shape of the light emitting surface of the at least one light emitting element.

8. The lighting element according to claim 5, wherein the cross-sectional area of the stub is between 0.8 to 1.5 times the area of the light emitting surface of the at least one light emitting element.

9. The lighting element according to claim 8, wherein the cross-sectional area of the stub is between 1 and 1.2 times the area of the light emitting surface of the at least one light emitting element.

10. The lighting element according to claim 5, wherein the stub has a recess directly above the light emitting surface of the at least one light emitting element.

11. The lighting element according to claim 1, wherein the height of the lighting element is smaller than 10 mm.

12. The lighting element according to claim 11, wherein the height of the lighting element is smaller than 5 mm.

13. The lighting element according claim 1, wherein the backwall of the mixing box is reflective.

14. The lighting element according to claim 1, wherein the diffusor comprises a diagonal mirror plane, and the extension of the back face of the diffusor is symmetric along the diagonal mirror plane.

15. The lighting element according to claim 1, wherein at least one of the extension of the back face is asymmetrical along two or more lateral directions or the extension of the back face is symmetric along only one lateral direction.

16. The lighting element according to claim 1, wherein the extension of the back face is defined by one or more splines.

17. The lighting element according to claim 16, wherein the one or more splines comprises five splines or eight splines.

Description

(1) The figures show:

(2) FIG. 1 a lighting element according to the present invention,

(3) FIG. 2 an exploded view of the lighting element of FIG. 1 in a first perspective and

(4) FIG. 3 an exploded view of the lighting element of FIG. 1 in a second perspective,

(5) FIG. 4 back face of the diffusor according to the present invention,

(6) FIG. 5 another embodiment of the present invention,

(7) FIG. 6 an emission of the lighting element and

(8) FIG. 7 an emission of the lighting element.

(9) The lighting element 10 according to the present invention as shown in FIGS. 1 to 3 comprises a mixing box 12, as well as a diffusor 14. Therein, the diffusor 14 is connected to the mixing box 12. The diffusor 14 has a flat front face and a complex shaped back face as shown for example in FIGS. 2 and 4 and described in more detail below. The mixing box 12 comprises side walls 24 extending from a backwall 22. Therein, the backwall 22 is complex shaped in order to support the light distribution and homogenization of the light in order to create a uniform luminance appearance of the lighting element. Thus, backwall 22 and/or sidewalls 24 may be reflective. A light emitting element 18 is extending through an opening 20 in the backwall 22 of the mixing box 12 into the volume created by the mixing box 12 and the diffusor 14. The lighting element 18 may be arranged on an interposer 16 or PCB. Light from the light emitting element 18 is emitted in a direction towards the front face of the diffusor 14. Light scattered back from the diffusor 14 may be reflected at the backwall 22 and/or sidewalls 24 of the mixing box.

(10) In the following it is referred to FIG. 4 showing the back face of the diffusor 14. The diffusor 14 has a stub 28, wherein the end face of the stub 28 is placed directly above the at least one light emitting element 18. Therein, the area of the stub 28 is preferably larger than a light emitting surface of the at least one light emitting element 18. By the stub 28, more material of the diffusor 14 including scatterers is present in the main direction of emission of the at least one light emitting element 18. Hence, sufficient distribution of this light in the main direction of emission is feasible by the additional material of the stub 28 in order to avoid bright spots at the front face of the diffusor 14 directly above the light emitting element 18. Therein, the cross-sectional shape of the stub 28 may correspond to the shape of the light emitting surface of the at least one light emitting element 18. If more than one light emitting elements 18 are implemented in the lighting element, the shape of the stub 28 can be adapted correspondingly.

(11) The back face of the diffusor 14 is built as freeform surface. Therein, the extension of the back face of the diffusor 14 may be asymmetrical along at least one lateral direction. Therein, the lateral direction is parallel to the front face of the diffusor 14. As shown in FIG. 4, the extension of the back face of the diffusor 14 is shaped by five indicated splines 26. Further, the shape of the extension of the back face is symmetric along a diagonal mirror plane 27. Hence, the back face of the diffusor 14 is described by five splines in the example of FIG. 4. However, other descriptions are also possible, i.e. use of eight splines 26 to describe the extension of the back face of the diffusor 14. Therein, the shape of the splines 26 may be determined by an iterative optimization process in order to optimize the emitted uniform luminance appearance at the front face of the diffusor. Therein, each spline 26 in the example of FIG. 4 may be different and describe a different shape determining the extension of the back face of the diffusor 14. The emission of the lighting element is exemplified in FIGS. 6 and 7. FIG. 6 shows an emission spectrum having a slight asymmetry in the distribution as indicated by the arrows. However, it was found by the inventors of the present invention that a slight asymmetry will be perceived by the observer as a more uniform luminance appearance. Contrary, FIG. 7 shows a symmetric emission. As the human eye is trained and sensitive for repetitive or periodic patterns, the symmetry of FIG. 7 might be perceived by an observer and inhomogeneity of the luminance noticed due to the pattern recognition of the human eye. Contrary, in the inhomogeneous luminance as shown in FIG. 6, due to the asymmetry of the light distribution, the emission of the lighting element will be perceived as uniform luminance despite their slight imperfections. Hence, even with variation of the luminance in the range of 15% or less and preferably 10% or less, the emission will be recognized as uniform luminance due to the induced asymmetry. Thus, light homogeneity of the emissions of the lighting element are acceptable and do not disturb the appearance of the light emission. Thus, the lighting element can be built compact, and increasing the height H of the lighting element for a more homogeneous luminance can be prevented. Thus, a very compact lighting element with small building height H less than 10 mm and preferably less than 5 mm can be achieved still providing uniform luminance appearance.

(12) Referring to FIG. 5 showing a dual color lighting element 10. Therein, same or similar elements are indicated by the same reference number. The dual color lighting element 10 comprises a first lighting element 18A and a second lighting element 18B. Therein, the first lighting element 18A and the second lighting element 18B may emit light with a different color. Similar to the embodiments described before, the diffusor 14 may comprise a stub 28. However, in the embodiment of FIG. 5, the stub 28 may comprise a recess 30. Therein, the recess 30 coincides with the combined or cumulative area of the light emitting surfaces of the light emitting elements 18A, 18B. Thus, by the stub 28 and the recess 30, extensions 32 are built which serve as mixing extensions and mix the light of the individual light emitting elements 18A, 18B and suppress bright spots at the front face of the diffusor 14 irrespective of the origin of the light.

(13) Hence, by the present invention a compact lighting element is provided providing a uniform luminance appearance at its front face at same small building height. The lighting element can be used in a versatile manner providing automotive manufacturer sufficient degree of freedom to create their signature illumination at the front grill of the automobiles despite the limited building space.