Headlight assembly comprising light-conducting rods for a headlight

Abstract

The invention relates to a lamp unit (1) for a headlight, in particular a motor vehicle headlight, the lamp unit (1) comprising multiple light sources (2), a light guide unit (3), and a downstream projector lens (4), the light guide unit (3) having multiple light guides (30), each light guide (30) having one light decoupling surface (30a) and one light coupling surface (30b), and each light source (2) coupling light exactly into a light guide (30) assigned to it through a light coupling surface (30b). The invention provides that the light sources (2) and the light coupling surfaces (30b) of the light guides (30) have light conducting rods (10) arranged between them, which are joined into at least one light conducting rod bundle (100), each light source (2) coupling light essentially exclusively into the light conducting rod coupling areas (10a) of the light conducting rods (10) assigned to the respective light source (2), the light of an assigned light source (2) that exits from the light conducting rod decoupling areas (10b) being coupled essentially exclusively into the light coupling surface (30b) of the light guide (30) assigned to the respective light source (2).

Claims

1. A lamp unit for a headlight, the lamp unit comprising: multiple light sources; a light guide unit; and a downstream projector lens, wherein the light guide unit has multiple light guides, each light guide having one light decoupling surface and one light coupling surface, and each light source coupling light into exactly one light guide assigned to it through one light coupling surface, wherein the light sources and the light coupling surfaces of the light guides have light conducting rods arranged between them, which are joined into at least one light conducting rod bundle, each light source having a plurality of light conducting rods assigned to it, and each light source coupling light essentially exclusively into the light conducting rod coupling areas of light conducting rods assigned to the respective light source, and the light of an assigned light source that exits from the light conducting rod decoupling areas being coupled essentially exclusively into the light coupling surface of the light guide assigned to the respective light source to reduce crosstalk.

2. The lamp unit of claim 1, wherein a number of the light conducting rods are joined into a fiber rod, and the at least one light conducting rod bundle consists of a number of such fiber rods, so that each light source couples light into a number of such fiber rods.

3. The lamp unit of claim 2, wherein the fiber rods have a square hexagonal cross section.

4. The lamp unit of claim 2, wherein the light conducting rods of a fiber rod are surrounded by a glass covering or other covering.

5. The lamp unit of claim 2, wherein the light conducting rods of a fiber rod are fused together or otherwise connected together.

6. The lamp unit of claim 2, wherein the fiber rods of a fiber rod bundle are fused together or otherwise connected together.

7. The lamp unit of claim 2, wherein the fiber rods of a fiber rod bundle run parallel to one another.

8. The lamp unit of claim 1, wherein the light conducting rods are joined into precisely one light conducting rod bundle.

9. The lamp unit of claim 1, wherein the light conducting rods have a square or hexagonal cross section.

10. The lamp unit of claim 1, wherein the light conducting rods are made in the form of glass rod/tube systems, with a cladding glass as a tube and a core glass as a rod, the core glass being surrounded by the cladding glass.

11. The lamp unit of claim 10, wherein the core glass has a refractive index that is greater than that of the cladding glass.

12. The lamp unit of claim 1, wherein the light conducting rods of a light conducting rod bundle are fused together or otherwise connected together.

13. The lamp unit of claim 1, wherein the light conducting rods of a light conducting rod bundle run parallel to one another.

14. The lamp unit of claim 1, wherein the at least one light conducting rod bundle is arranged at a light source distance from the light sources.

15. The lamp unit of claim 14, wherein the light source distance approaches zero or is zero.

16. The lamp unit of claim 1, wherein the at least one light conducting rod bundle is arranged at a light guide unit distance from the light coupling surfaces of the light guide unit.

17. The lamp unit of claim 1, wherein the thickness of the at least one light conducting rod bundle, which is the distance between the surface of the light conducting rod bundle facing the light sources and the surface of the light conducting rod bundle facing the light guide unit, has or exceeds a defined minimum value, which is selected so that light exiting from the side of a light conducting rod assigned to a light source at most gets into allowable light conducting rods.

18. The lamp unit of claim 17, wherein two or more light conducting rod bundles are arranged directly adjacent to one another, one after the other in the light exit direction.

19. The lamp unit of claim 1, wherein the at least one light conducting rod bundle is plate-shaped.

20. The lamp unit of claim 1, wherein the light conducting rods are gradient-index rods.

21. The lamp unit of claim 1, wherein at least one light conducting rod bundle consists of a plurality of light conducting rods.

22. The lamp unit of claim 1, wherein each light source has 10 or more light conducting rods assigned to it.

23. The lamp unit of claim 22, which has from 50 to 100 light conducting rods per light source.

24. The lamp unit of claim 1, wherein each light source has 100 or more of the light conducting rods assigned to it.

25. The lamp unit of claim 24, which has from 5,000 to 10,000 light conducting rods per light source.

26. The lamp unit of claim 1, wherein the light sources are LEDs, each LED light source comprising at least one light-emitting diode.

27. The lamp unit of claim 26, wherein each LED light source is separately controllable, allowing it to be turned on or off and/or dimmed separately.

28. The lamp unit of claim 27, wherein each light-emitting diode of the LED light source is separately controllable, allowing it to be turned on or off and/or dimmed separately.

29. A vehicle headlight with at least one lamp unit of claim 1.

30. The lamp unit of claim 1, wherein the at least one light conducting rod bundle is the same distance to all assigned light sources.

Description

(1) The invention is explained in detail below using the drawing, which shows a sample embodiment of it. The figures are as follows:

(2) FIG. 1 shows a schematic perspective exploded view of an inventive lamp unit;

(3) FIG. 2 shows a schematic exploded view of an inventive lamp unit in the area of a light conducting rod bundle;

(4) FIG. 3 shows a detail view of a fiber rod with several light conducting rods;

(5) FIG. 4 shows a light source with a schematic depiction of its emission pattern; and

(6) FIG. 5 shows two light sources with an upstream light conducting rod bundle.

(7) FIG. 1 shows an inventive lamp unit 1 for a motor vehicle headlight consisting of multiple light sources 2, a light guide unit 3 with multiple light guides 30, and a downstream projector lens 4. Each light guide 30 has a light decoupling surface 30a, and each light source 2 couples light through a light coupling surface 30b exactly into the light guide 30 assigned to it (concerning this see especially FIG. 2). The light sources 2 are arranged on a common carrier 5, for example a heat sink.

(8) Light sources 2 are LEDs, each LED light source 2 comprising at least one or—as in this example—exactly one light-emitting diode. Such a light-emitting diode 2 has a light exit surface 2a. Preferably, each LED light source 2 is separately controllable, allowing it to be turned on or off and/or dimmed separately.

(9) The light guides 30 in light guide unit 3 are next to one another, and in the example shown in FIG. 1, arranged in three rows lying on top of one other. These light guides 30 are oriented essentially in the direction of an optical axis x belonging to projector lens 4.

(10) In the embodiment shown in FIG. 1, the light guides 30 are designed as reflectors, so they form a hollow tube, so to speak, and have light decoupling surfaces that are set up to radiate the light in the direction of downstream projector lens 4. Thus, the light decoupling surfaces, like the light coupling surfaces, are limited openings in light guide unit 3.

(11) By contrast, the light guides in FIG. 2 are in the form of totally reflecting optical elements, e.g., plastic or glass bodies, into which light exiting from the light exit surfaces 2a of the light-emitting diode 2 assigned to each of them is coupled into the light coupling surfaces 30b, propagates by total reflection in the optical elements (light guides) 30, and exits through light exit surfaces 30a, and is radiated into an area in front of the lamp unit by means of lens 4.

(12) The selection of different embodiments of the light guides in FIG. 1 and FIG. 2 is intended to express, on the one hand, that the form of the light guides is unimportant for the invention, and, on the other hand the embodiment in FIG. 2 allows clearer discussion of the invention.

(13) To prevent easy damage to or destruction of the light guide units 30 shown as examples in FIGS. 1 and 2, due to the thermal and optical loads produced by the radiation and heat from the light sources, especially in the light coupling areas of the light guides, an optical element 100 is provided between the light sources 2 and the light coupling surfaces 30b of the light guides 30. As can easily be seen by comparing FIG. 2 and FIG. 3, this optical element 100 is a so-called light conducting rod bundle 100, which consists of several or many light conducting rods 10 (FIG. 3) that are joined together into light conducting rod bundle 100. This light conducting rod bundle 100 is, for example, a plate-shaped element as shown.

(14) In the embodiment shown in FIG. 2, the bundle 100 consists of a number of fiber rods 11, each fiber rod 11 in turn consisting of a number of light conducting rods 10, as shown in FIG. 3. Thus, in every case a number of light conducting rods 10 is joined into a fiber rod 11, and several or many fiber rods 11 form the light conducting rod bundle 100 (also referred to as the fiber rod bundle, also referred to below simply as the “bundle”).

(15) The number of light conducting rods arranged in a fiber rod is typically 7, 19, 37, 61, 91, etc.

(16) To allow the light conducting rods 10 to be packed as densely as possible, light conducting rods 10 have a hexagonal cross section. In the same way, it is preferable for fiber rods 11 to have a hexagonal cross section.

(17) However, in theory it is also possible for bundle 100 to be manufactured not by first joining the light conducting rods into fiber rods, but rather by making bundle 100 directly from light conducting rods. However, for reasons having to do with production engineering and mechanical stability, it can be advantageous for the light conducting rods 10 first to be joined into fiber rods 11, as shown in FIG. 3.

(18) The embodiment shown in FIG. 3 also provides that the light conducting rods 10 of a fiber rod 11 are surrounded by a covering 12, preferably a glass covering. Such a glass covering can be provided to hold together the light conducting rods 10 while the fiber rods are being manufactured, and then become a component of the fiber bundle 11, as described in DE 10 2010 052 479 A1.

(19) To achieve optimal total reflecting properties in the light conducting rods 10, the light conducting rods 10 are, for example, made in the form of glass rod/tube systems, with a cladding glass 10′ as a tube and a core glass 10″ as a rod, the core glass 10″ being surrounded by the cladding glass 10′. In this case, the refractive index of core glass 10″ is greater than that of cladding glass 10′. This allows the transmission of light as a consequence of reflection at the interface of the inner and outer glass in a light conducting rod 10.

(20) To make the bundle mechanically stable, it is advantageous for the light conducting rods 10 of a fiber rod 11 to be connected together, preferably fused together. It is also advantageous for the fiber rods 11 of a fiber rod bundle 100 to be connected together, preferably fused together. This produces mechanically homogeneous fiber rods 11 or mechanically homogeneous fiber rod bundles.

(21) The light conducting rods 10 or fiber rods 11 of a light conducting rod bundle 100 run parallel to one another, as can easily be seen in FIG. 2. This results in a bundle 100 with a thickness d.

(22) The interposition of the optical element in the form of a light conducting rod bundle 100 between light sources 2 and light guide unit 30 can thermally decouple light guide unit 30 from light sources 2, so that light guide unit 30 experiences no thermal interference due to light sources 2.

(23) The inventive structure of the interposed element in the form of a light conducting rod bundle 100, consisting of multiple light conducting rods 10, in which the input light propagates by means of total reflection, allows a light source 2 to be projected onto the coupling area 30b of the light guide 30 assigned to it as exactly as possible, preventing a light source 2 from coupling light into another light guide than the one assigned to it.

(24) The smaller the cross section of these individual light conducting rods 10, i.e., the more light conducting rods 10 are used to project a light source 2 (i.e., its light exit surface 2a) onto the assigned coupling area 30b of light guide 30, the more exactly the light exit surface 2a is projected onto coupling area 30b.

(25) The fact that light sources 2 or their light exit surfaces 2a do not, as a rule, lie directly against one another, but rather are a certain distance away one another, as can be seen in FIG. 2, also reliably ensures, if light conducting rods 10 have a correspondingly small diameter, that a light source 2 does not, not even to a small extent (or only to an irrelevant extent), couple light into a light guide 30 not assigned to it.

(26) Here it should also be taken into consideration that light guides 30 taper, as a rule in the direction toward light sources 2, as can be seen in FIG. 2, i.e., the light coupling surface 30b of a light guide is smaller than its light decoupling surface 30a. Therefore, the light coupling surfaces 30b or light coupling areas 30b of adjacent light guides are separated from one another.

(27) Of course it is also possible for there to be light guides that do not taper, however adjacent light coupling areas are separated by a certain distance.

(28) Now every light source 2 couples light essentially exclusively or actually exclusively into light conducting rod coupling areas 10a of [the] light conducting rods 10 assigned to the respective light source 2, and couples, essentially exclusively or actually exclusively, the light of an assigned light source 2 exiting from the light conducting rod decoupling areas 10b into the light coupling surface 30b of the light guide 30 assigned to the respective light source 2.

(29) As is shown in a rough schematic manner in FIG. 2, every light exit surface couples light into light conducting rods 10 that lie within an (imaginary) rectangle 200. The light coupling surfaces 30b are usually larger than the light exit surfaces 2a; examples of typical values are for the light exit surfaces 2a are about 0.7 mm×0.7 mm, and those for a light coupling surface 30b are about 1 mm×1 mm, so that the light is usually coupled into the assigned light coupling surface 30b, even in the case that light is coupled from a light exit surface 2a into a light conducting rod that no longer lies opposite the light exit surface 2a, or does so only partially.

(30) Moreover, since the light coupling surfaces 30b are separated from one another, if the number of light conducting rods is sufficiently large, that is, if the resolution is high, it can be ensured that light of a light source does not get into a light guide that is not assigned to it, even if some light conducting rods do not couple light into the assigned light guide, or do so only partially.

(31) Thus, the term “a light conducting rod assigned to a light source” is understood to mean a light conducting rod that couples light completely into the assigned to light guide. The term can also be understood to mean light conducting rods that do not couple light into the assigned light guide, or do so only partially, but without coupling light into an unassigned to light guide (“allowable” light conducting rods). The larger the number of light conducting rods per unit area, the fewer “allowable” light conducting rods there are, and the more light from the light source gets into the assigned light guide.

(32) It is also provided that light conducting rod bundle 100 is arranged at a light source distance from light sources 2, the light conducting rod bundle 100 preferably having the same distance from all assigned to light sources 2, that is lying parallel to the plane of the light exit surfaces 2a.

(33) This light source distance is the normal distance from the light exit surface 2a of light source 2 to the light coupling surface of light conducting rod bundle 100; this light coupling surface of light conducting rod bundle 100 is formed by the light coupling surfaces 10a of the light conducting rods.

(34) It is especially advantageous for the light source distance to approach zero or preferably be zero, as is shown in FIG. 5. The reason why is that a light-emitting diode 2 has a spatial radiation behavior, as is common knowledge; this is shown in a rough schematic manner in FIG. 4. Arranging surface 2a as close as possible to the light conducting rods, as illustrated in FIG. 5, can have the result that light is only actually coupled into the assigned light conducting rods 10, or at most that it is additionally coupled into “allowable” ones.

(35) It is also provided that the light conducting rod bundle 100 is arranged so that the distance from the light guide unit to the light coupling surfaces 30b of the light guide unit 3 is preferably zero.

(36) In the light conducting rods 10, light propagates as a consequence of total reflection, as is shown in FIG. 5. Here it should be pointed out that to make the schematic beam paths in FIG. 5 easier to see, the light conducting rods 10 not are not true to scale, and have a (substantially) larger diameter than in reality. (The diameter of a light conducting rod 10 in FIG. 5 is about that of a fiber rod 11 in FIG. 2.). The cladding and core structure of the light conducting rods shown in FIG. 3, is also not shown in FIG. 5, to make the portrayal clearer.

(37) Light beams that do not meet the total reflection condition, that is, that impinge on the cladding of light conducting rod 10 at an angle smaller than the critical angle for total reflection, exit from the light conducting rod 10 into which they were coupled. To prevent these light beams from coupling into an unassigned light guide, it is also preferable that the thickness d of the light conducting rod bundle 100, i.e., the distance between the surface of the light conducting rod bundle 100 facing light sources 2 and the surface of the light conducting rod bundle 100 facing the light guide unit 3, has or exceeds a defined minimum value, which is selected so that light that exits from the side of a light conducting rod assigned to a light source at most gets into allowable light conducting rods. This corresponds to light conducting rods having a diameter of about 100 μm.

(38) In this regard, a higher number (greater density) of light conducting rods is also advantageous—the more light conducting rods that must be traversed by a light beam that enters them because it does not meet the total reflection condition, the weaker it becomes. If a light beam is sufficiently weakened in this way before it enters an unassigned light guide, then it is already weak enough that its intensity is negligible.

(39) The thickness d must also be selected in such a way that the light guides are sufficiently thermally decoupled from the light sources. Thus, the thickness d is also dependent on the material used in the light conducting rod bundle, that is, its thermal conductivity. Typically, the thickness d is on the order of a few millimeters.

(40) In theory, the light exit surfaces 2a of a light-emitting diode can be of any shape. However, typical shapes are rectangular or square. For example, a typically used LED chip of the type Osram Compact LED chip has a light exit surface (luminous surface) 2a that is square (one corner being rounded off toward the inside), and side lengths of about 0.7 mm. In a specific arrangement of such LED chips, these are arranged in 3 rows and several gaps, and adjacent LED chips in a row are spaced about 2 mm apart from one another. The rows themselves are also spaced apart from one another by 2 mm (top and middle row) or 2.5 mm (middle and lower row). The distance is always measured as the center-to-center distance of two adjacent LED chips, the center being the midpoint of the square bordering the light exit surfaces. The above-mentioned measurements are typical values of a specific application and serve here to illustrate the dimensions with an example. In the above-mentioned example, the resulting light exit surface is about 0.49 mm.sup.2.

(41) In a well-functioning embodiment, about 50-100 light conducting rods are provided for one light exit surface. This corresponds to light conducting rods having a diameter of about 100 μm. (To simplify the calculation, if we assume that the light conducting rods have circular cross sections whose surfaces ideally completely cover the light exit surfaces, then given a light exit surface of 0.49 mm.sup.2 and a light conducting rod diameter of 100 μm, this gives about 62 light conducting rods for this light exit surface.)

(42) Theoretically, it is also conceivable for there to be fewer light conducting rods; in particular, it is also possible for there to be exactly one light conducting rod per light exit surface. However, this light conducting rod must then be shaped as exactly as possible to match the shape of the light exit surface, and must also be positioned very exactly, which has the disadvantage that manufacturing and assembly tolerances once again become important, and assembly requires more effort.

(43) Thus, it is fundamentally advantageous to use a large number of light conducting rods per light source. Thus, it is advantageous for every light source 2 to have many light conducting rods 10 assigned to it. If these light conducting rods are joined into one (or more) light conducting rod bundles, the bundle (or each of the bundles) also consists of many light conducting rods.

(44) It is especially advantageous if the number of light conducting rods per light exit surface/light source is ≧10. For example, having 50-100 light conducting rods per light exit surface has turned out to be expedient.

(45) The light exit surface can be projected onto the assigned to light guide even better if the number of light conducting rods is ≧100, preferably 1,000; about 5,000-10,000 light conducting rods per light exit surface has proved to be a good number. (In the above example, for a light conducting rod with [a diameter of] 10 μm the result is about 6,242 light conducting rods for the light exit surface.)

(46) Joining light conducting rods 10 in a light conducting rod bundle 100 or fiber rods 11 in a single fiber rod bundle 100 has the advantage that when the inventive lamp unit is assembled, tolerances and inaccuracies do not have to be taken into consideration, or have to be taken into consideration only to a small extent, other than would be the case if, for example, only a single totally reflecting light conducting body were arranged between each light source and each light coupling area of a light guide.

(47) This has the advantage that the light sources and the light guide unit only need to have a single additional optical element incorporated between them, whose lateral slippage in directions perpendicular to a normal to the light exit surfaces of the light sources is completely insignificant, as long as the number of light conducting rods is sufficiently large, since if the resolution is high enough (i.e., if the number of light conducting rods is sufficiently large) the light exit surface is projected almost 1:1 onto the light coupling area of the assigned light guide, and only small quantities of light get into adjacent light conducting rods that do not couple light into the assigned light coupling area. In addition, this light does not, for the most part, or even at all, get into unassigned light guides, so that there also cannot be detrimental optical effects.

(48) Thus, the invention allows optimal thermal decoupling of the light guides or light guide unit from the light sources, as described above. Therefore, it is advantageous if a material with low thermal conductivity is used for the light conducting rods, and thus for a light conducting rod or fiber rod bundle, in which light can propagate by means of total reflection. As was already mentioned above, glass is an example of a material that is very suitable for this.