WITH SUCH A LIGHT GUIDE

Description

The present invention concerns a light guide for a lighting device of a vehicle accord ing to the preamble of claim 1 as well as a lighting device with such a light guide.

A light guide and a lighting device of the above mentioned type are known from DE 10 2012 108855 A1. The lighting device described therein comprises a light guide with an entrance surface at the front, into which the light of a light source can enter. The light guide further comprises a plurality of prism-shaped coupling-out elements oppo site an exit surface through which a portion of the light entering can exit laterally. The end section of the light guide facing away from the frontal entrance surface is not dis closed in detail in DE 102012 108855 A1.

Such an end region 2 of a light guide 1 , for example, has a flat surface 3 as shown in Fig. 5. With the light guide shown in Fig. 5 the light 4 can exit the light guide 1 through an exit surface 5 located on the right hand outer side. This exit surface 5 points, for example, in the forward direction of travel of the vehicle indicated by the arrow 6.

Reflections of light 4 from the flat surface 3 prove to be problematic in such a design, Fig. 5 shows some examples of light beams 7 that are reflected by the flat surface 3 and then emerge laterally from the light guide 1 in the end region 2. These light beams 7 run in unwanted directions and therefore prove to be disturbing. They also impair the appearance of the lighting device, for example by creating so-called hot spots, be cause the end area appears as a bright light spot. The problem underlying the present invention is the creation of a light guide and a lighting device of the type mentioned above, in which the portion of light escaping un- wantedly from the end area is reduced.

According to the invention, this is achieved by a light guide of the type mentioned above with the characteristic features of claim 1 and by an lighting device of the type mentioned above with the characteristic features of claim 7. The dependent claims concern preferred embodiments of the invention.

According to Claim 1 , the end region is structured and/or shaped in such a way that the portion of light which laterally emerges from the region adjacent to the end region after reflection at or in the end region is reduced or minimised. By an appropriate de sign, disturbing light beams and an impairment of the appearance of the lighting de vice can be largely avoided.

It may be provided that the end region is structured at least in sections. A suitable structure can be used to reduce the portion of light reflected back which is disturbingly emitted laterally.

There is the possibility that the end region is at least in sections conical orfrustoconi- cal in shape, in particular wherein the base of the cone or the frustum of a cone faces the light guide. For example, the light guide has a conical tip in the end region. In this tapered geometry, a large portion of the light is transmitted into the tip, where a large part of it exits from the tip in a widely scattered form. A possibly back-reflected part is mostly reflected back into the light guide out of the end area and is only very unlikely to exit laterally in the end area. In this way, the disturbing light rays exiting laterally are almost completely avoided.

It may be provided that the end region comprises a plurality of conical or frustoconical sections which are in particular arranged next to one another. This plurality of conical or frustoconical sections also makes it possible to largely avoid the disturbing light rays emerging laterally. However, a plurality of conical or truncated conical sections can be more space-saving than a single large conical or frustoconical end section.

It is possible that the end region has a plurality of circumferential structures, in particu lar coaxially circumferential structures. These structures may be similar to Fresnel lenses, for example. These structures can also largely avoid the disturbing light rays that emerge sideways and at the same time be more space-saving than a single large conical or frustoconical end region.

It may be provided that the entrance surface is arranged at the end of the light guide remote from the end region. In general, it has been found to be practicable to couple the light into the light guide at the front end, as in the state of the art. However, later ally arranged entrance surfaces are also possible.

According to claim 7, it is intended that the lighting device comprises a light guide ac cording to the invention.

It is possible that the light guide is arranged in the lighting device in such a way that, when the lighting device is installed in a vehicle, the light emerging from the at least one lateral exit surface can exit the vehicle, preferably at least partially forwards in the longitudinal direction of the vehicle.

It may be provided that an absorption device is arranged in front of the end region of the light guide, which can at least partially absorb the light emerging from the end of the light guide. In this way the light emerging from the end of the light guide can be prevented from propagating in undesirable directions.

Alternatively, it may be provided that a reflection device is arranged in front of the end region of the light guide, which can at least partially reflect back the light emerging from the end of the light guide, preferably reflect it back in a broadly scattered manner. The proportion of light propagating in unwanted directions can also be significantly re duced by, for example, uniform scattering in many different directions.

On the basis of the attached drawings, the invention is explained in more detail below. Thereby shows:

Fig. 1 a schematic side view of a detail of a first embodiment of a lighting device according to the invention with a first embodiment of a light guide according to the invention and sketched light beams;

Fig. 2 a schematic side view of a detail of a second embodiment of a lighting de vice according to the invention with a second embodiment of a light guide according to the invention and sketched light beams;

Fig. 3 a schematic side view of a detail of a third embodiment of a light guide ac cording to the invention with sketched light beams;

Fig. 4 a schematic side view of a detail of a fourth embodiment of a light guide according to the invention;

Fig. 5 a schematic side view of a detail of an embodiment of a light guide according to the state of the art with sketched light beams.

In the figures, identical or functionally identical parts are marked with identical refer ence signs.

The lighting device shown in Fig. 1 comprises a light guide 10 with an entrance sur face not shown, into which light 11 can enter. The entrance surface can be located in particular at the front end of the light guide 10 not shown in the illustration. Further more the light guide 10 comprises an exit surface 12 through which the light 11 can exit laterally. On the side of the light guide 10 opposite the exit surface 12, a non-im- aged plurality of, for example, prism-shaped coupling-out elements can be arranged which deflect the light 11 in the direction of the exit surface 12.

In particular, the illuminating device may be fitted to a vehicle in such a way that the exit surface 12 faces forward in the direction of travel of the vehicle indicated by the arrow 16.

The light guide 10 shown in Fig. 1 also includes an end region 13, which is conical in shape so that a large portion of the light 11 is transmitted in this conical geometry to the tip 14 of the end section 13. There the light 11 is distributed over a large solid an gle range. Any reflected light is substantially reflected back out of the end region 13 into the light guide and is only very unlikely to exit laterally in the end region 13. In this way, the disturbing light rays emitted laterally are largely avoided.

The illuminating device further comprises an absorption device 15 placed in front of the tip 14 of the light guide 10 and capable of absorbing the light 11 emerging from the tip 14. The absorption device 15, for example, is designed as a housing open on one side into which the light 11 can enter. The inner surfaces of the housing may be coated with absorbing materials, for example blackened.

In the version shown in Fig. 2, instead of the absorption device 15, a reflection device 17 is arranged, which can at least partially reflect back the light 11 emerging from the tip 14 of the light guide 10. The reflection device 17 can, for example, be designed as barrel optics. By means of the reflection device 17, the light 11 can, in particular, be distributed comparatively evenly over a large solid angle range, so that an impairment of the appearance of the illumination device can also be largely avoided by this meas ure. The design of a light guide 10 shown in Fig. 3 has a number of separate cones in the end section 13 instead of a single cone. Through each of the tips 14 the light 11 emerges into a large spatial angle range, so that overall a comparatively even distribu tion over a large solid angle range is achieved. In particular, a portion 18 of light 11 emerging in the direction of travel 16 can make a positive contribution to the light dis tribution produced by the lighting device.

The design of a light guide 10 shown in Fig. 4 has a plurality of coaxially circumferen tial structures 19 in the end region 13 instead of a plurality of separate cones. These structures 19 can be similar to Fresnel lenses, for example. These structures 19 can also largely avoid the disturbing light rays emerging laterally and at the same time be more space-saving than a single large conical or frustoconical end region 13.

List of reference signs

1 light guide

2 end region of the light guide 1

3 plane surface of the end region 2

4 light entering the entrance surface of light guide 1

5 exit surface of the light guide 1

6 direction of travel

7 light beam that emerges laterally from the light guide 1 in the end region 2

10 light guide

11 light entering the entrance surface of the light guide 10

12 exit surface of the light guide 10

13 end region of the light guide 10

14 tip 14 of the end region 13

15 absorption device

16 direction of travel

17 reflection device

18 light emitted in direction of travel 16

19 circumferential structure in the end region 13