EP2607776A2 - Lighting device for a motor vehicle with a light guide structure - Google Patents

Abstract

The device (1) has a light conductor structure (12) including a linking region (14) and a planar light conductor region (16) that includes narrow sides (24, 26) lying between first and second edges (18.1, 20.1). One of the narrow sides includes a set of parallelized sub-regions (28, 30), where one of the sub-regions is movably arranged opposite to the other sub-region and stepped toward an interior region of the planar light conductor region. The former sub-region is limited by the edges, and the latter sub-region is limited by the second edge.

Description

The present invention relates to a lighting device for a motor vehicle according to the preamble of claim 1.

Such a lighting device is from the DE 10 2008 048 765 A1 , there in particular Fig. 5 and Fig. 6 , known. The known illumination device has a light guide structure which has a plurality of coupling-in areas and a planar light guide area. The latter has a first wide side and a second wide side. The first page is bounded by a first edge and the second page is bounded by a second edge. The second broad side is opposite to the first broad side equidistant. Narrow sides lying between the first edge and the second edge connect the first wide side to the second wide side. Second narrow sides are shaped as parabolic sections and thus set up from a first narrow side to direct light incident on the second narrow side of a light source onto a third narrow side which serves as a light exit surface.

With respect to the light exit surface of this optical waveguide structure, there is the property that only such curvatures can be realized that correspond to the edge curve of a correspondingly cut planar board on which laterally emitting light-emitting diodes (LEDs) are arranged as light sources. LEDs emitting laterally to their mounting surface are not as widely available on the market as standard LEDs which radiate parallel or antiparallel to the surface normal of their mounting surface. Compared to the standard LEDs, there are only a few choices for laterally emitting LEDs. In addition, they provide a lower luminous flux, which, when summed over several LEDs requires a certain luminous flux, requires more LEDs, which in turn leads to higher costs and a higher probability of failure.

From the Figures 5 and 6 of the DE 10 2008 048 765 A1 It can be seen that in each case only a very limited portion of the luminous flux emitted by an LED impinges on a parabolic surface and is thereby deflected in the desired direction. As a result, the light exit surface appears unevenly bright, since light hits at each point, which comes directly from the LED without a light directing reflection on a parabolic surface. The non-aligned rays all have a different direction. At the points that lie in front of the parabolic surfaces, this adds up to a strong, parallel light bundle, which leads to the overall undesirable inhomogeneous appearance.

Against this background, the object of the invention in the specification of a lighting device of the type mentioned, which does not have these disadvantages or at best in a reduced form.

This object is achieved with the features of claim 1. From the above-mentioned prior art, the present invention differs in that the second narrow side has a first partial surface and a second partial surface, wherein the second partial surface is staggered relative to the first partial surface toward the interior of the planar optical fiber region.

The second narrow side has a homogenizing effect on a part of the light. These effects are achieved by the said subdivision of the second narrow side into a first subarea and a second subarea which is staggered in relation to the first parallelizing subarea toward the interior of the planar lightguide region.

As a result of the subdivision of the second narrow side, the light incident on the second narrow side is subdivided into sub-beams, which permit an individual alignment of the light bundles. Each sub-area generates its own light distribution, which in sum give a different light distribution than if the second sub-area were not present. This makes it possible, in particular, to block light from the light bundle reflected by the first subarea through the second subarea. In particular, it is possible to block out a part of the light of this light bundle, which, without this measure, makes an already sufficiently bright first subregion of the light distribution generated by the first subarea even brighter would illuminate. Moreover, the invention further allows to direct the light hidden from the first light bundle into a second subarea of the light distribution generated by the first subarea, which without this measure would be comparatively darker than other subareas of the first light distribution.

As a result, the homogeneity of the overall resulting light beam is significantly improved. The resulting light beam is coupled out via the third narrow side. The third narrow side then appears to the viewer with the light source switched on homogeneously, ie as a narrow band of light shining with uniformly distributed brightness. Such appearance is desired.

A preferred embodiment is characterized in that the second narrow side is adapted to parallelize light incident on the second narrow side from the first narrow side and to direct it to the third narrow side, wherein the first partial surface is a parallelizing partial surface and wherein also the second partial surface is a parallelizing partial surface.

As a result, the light exit surface from the interior of the light guide structure is illuminated with parallel light.

A further preferred refinement is characterized in that the first narrow side forms a transition of a coupling region having a light entry surface and materially connected to the planar region to the planar region, which coupling region is adapted to parallelize light of a light source coupled via its light entry surface and the parallelized light on the second narrow side to direct that the first partial area (unless it is shaded by the second partial area) and the second partial area of the second narrow side is illuminated.

The illumination of the first partial area not shaded by the second partial area and of the second partial area avoids dark areas on the light exit area which could occur if only a part of the sum of the first partial area and the second partial area were illuminated. It is also preferred that exactly the first partial area, insofar as it is not shaded by the second partial area, and the second partial area of the second narrow side be illuminated.

The light coupled in via the coupling-in region is thus used completely for the illumination of the two partial surfaces mentioned. As a result, all coupled light is ultimately directed to the light exit surface, thus optimizing the efficiency that can be defined as the ratio of coupled light to coupled light.

It is also preferable that the width of the second partial area decreases with increasing distance from the first narrow side.

This offers another possibility for homogenizing the brightness distribution. Due to the decreasing with increasing distance from the first narrow side width of the second partial surface results in a sense below the second partial surface an expanding light guide cross-section, which ensures a desired further parallelization.
It is further preferred that the second partial surface has a trapezoidal or triangular contour.

It is also preferable that the second partial surface is arranged closer to the first narrow side than to the third narrow side.

It is further preferred that the second narrow side is divided into more than two partial surfaces.

A further preferred embodiment is characterized in that a part of the surface located further in the interior has a smaller focal length than a part of the surface lying further outside.

It is also preferable that the second narrow side has a parabolic shape. This means that the edges with which the second narrow side meets the first side and the second side are parabolas.

It is further preferred that the second narrow side comprises a series of adjacent surface segments, wherein edges with which the surface segments abut the first broad side and the second broad side have a parabola as an envelope.

A further preferred refinement is characterized in that the optical waveguide structure has a plurality of surface-connected optical waveguide regions and coupling regions, the coupling-in regions being curved so that their light entry surfaces lie in one plane.

Furthermore, it is preferred that the optical waveguide structure has an area which serves to produce a luminous light exit surface and which is a cohesive component of the optical waveguide structure and that in the optical path lies behind the parallelizing partial surfaces of the second narrow side.

Furthermore, it is preferred that the third narrow side is divided into stepwise offset partial surfaces. As a result, a curvature of a light exit surface can be reproduced with discrete steps without triggering an undesirable occurrence of internal total reflections. Internal total reflections are known to occur when the angle of incidence of the light on the curved light exit surface due to their curvature exceeds the critical angle of total reflection.

It is also preferred that the step-like offset partial surfaces are arranged, as it were, offset stepwise in the direction of a surface normal of the broad sides. By means of this configuration, a curvature can also be generated in a further spatial direction, so that the possibility arises of providing luminous light exit surfaces which appear three-dimensionally curved.

Further, it is preferable that the wide sides are flat parallel surfaces. As a result, a plate-shaped optical waveguide structure is provided which is suitable in particular for stacking. An alternative embodiment is characterized in that the broad sides are surfaces which are curved in space. This is advantageous for achieving three-dimensionally curved light exit surfaces in space.
Further advantages will become apparent from subclaims, the description and the accompanying figures.

It is understood that the features mentioned above and those yet to be explained not only in the each combination specified, but also in other combinations or alone, without departing from the scope of the present invention.

drawings

Fig. 1

ein Ausführungsbeispiel einer erfindungsgemäßen Beleuchtungseinrichtung für ein Kraftfahrzeug;

Fig. 2

verschiedene Ansichten eines Einkoppelbereichs einer Lichtleiterstruktur aus der Fig. 1;

Fig. 3

einen Einkoppelbereich und einen flächigen Lichtleiterbereich zusammen mit exemplarisch herausgegriffenen Strahlen eines Lichtbündels;

Fig. 4

verschiedene Ansichten eines flächigen Lichtleiterbereichs, dessen winkelverändernde zweite schmale Seite noch nicht in eine erste und zweite Teilfläche aufgeteilt ist;

Fig. 5

eine Draufsicht auf einen solchen flächigen Lichtleiterbereich zusammen mit einer resultierenden Helligkeitsverteilung;

Fig. 6

eine Draufsicht auf einen flächigen Lichtleiterbereich, dessen zweite schmale Seite in zwei Teilflächen unterteilt ist;

Fig. 7

einen Schnitt durch den Gegenstand der Fig. 6;

Fig. 8

eine Draufsicht auf einen gestuft unterteilten flächigen Lichtleiterbereich zur Veranschaulichung einer Abschattungswirkung;

Fig. 9

eine Draufsicht auf einen solchen flächigen Lichtleiterbereich zusammen mit einer resultierenden Helligkeitsverteilung;

Fig. 10

eine weitere Ausgestaltung einer Lichtleiterstruktur einer erfindungsgemäßen Beleuchtungseinrichtung in einer Schrägansicht;

Fig. 11

den Gegenstand der Fig. 10 in einer Draufsicht;

Fig. 12

eine bevorzugte Ausgestaltung, bei sich die Breite der zweiten Teilfläche mit zunehmendem Abstand von der ersten Schmalseite verringert;

Fig. 13

einen Verbund aus mehreren stoffschlüssig zusammenhängenden Lichtleiterstrukturen;

Fig. 14

eine Ausgestaltung, die sich zur Verwendung in Verbindung mit einer ebenen Platine eignet;

Fig. 15

eine erste Möglichkeit, eine dreidimensional gekrümmte leuchtende Kurve zur erzeugen;

Fig. 16

eine zweite Möglichkeit, eine dreidimensional gekrümmte leuchtende Kurve zu erzeugen;

Fig. 17

eine Möglichkeit, mehrere Lichtleiterstrukturen zu stapeln um komplexe Lichtaustrittsflächen aus einzelnen Lichtleiterstrukturen zu erhalten; und

Fig. 18

eine Ausgestaltung, bei der die winkelverändernde Fläche durch ebene Flächensegmente verwirklicht wird.

Embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description. In each case, in schematic form:

Fig. 1

an embodiment of a lighting device according to the invention for a motor vehicle;

Fig. 2

different views of a coupling region of a light guide structure of the Fig. 1 ;

Fig. 3

a coupling-in area and a planar light guide area together with exemplarily selected rays of a light bundle;

Fig. 4

different views of a planar light guide region, the angle-changing second narrow side is not yet divided into a first and second partial surface;

Fig. 5

a plan view of such a planar light guide area together with a resulting brightness distribution;

Fig. 6

a plan view of a planar light guide region, the second narrow side is divided into two sub-areas;

Fig. 7

a section through the object of Fig. 6 ;

Fig. 8

a plan view of a stepped divided planar light guide region to illustrate a shading effect;

Fig. 9

a plan view of such a planar light guide area together with a resulting brightness distribution;

Fig. 10

a further embodiment of a light guide structure of a lighting device according to the invention in an oblique view;

Fig. 11

the object of Fig. 10 in a plan view;

Fig. 12

a preferred embodiment, in which the width of the second partial area decreases with increasing distance from the first narrow side;

Fig. 13

a composite of several cohesively connected fiber optic structures;

Fig. 14

an embodiment suitable for use in conjunction with a planar board;

Fig. 15

a first possibility to generate a three-dimensionally curved luminous curve;

Fig. 16

a second way to create a three-dimensionally curved luminous curve;

Fig. 17

a possibility of stacking several optical waveguide structures in order to obtain complex light exit surfaces from individual optical waveguide structures; and

Fig. 18

an embodiment in which the angle-changing surface is realized by planar surface segments.

In this case, the same reference numerals in the various figures denote the same or at least functionally identical elements.

In detail, the shows FIG. 1 an illumination device 1 for a motor vehicle with a light guide structure 12. The light guide structure 12 is arranged in a housing 2 of the illumination device. The housing 2 has a light exit opening, which is covered by a transparent cover.

The light guide structure 12 has a coupling-in region 14 and at least one planar light guide region 16. The planar light guide region 16 has a first broad side 18, which is bounded by a first edge 18.1. In addition, the planar light guide region 16 has a second broad side which lies equidistantly opposite the first broad side and which is delimited by a second edge 20.1. In the Fig. 1 the second broad side is obscured by the volume of the planar light guide region 16. Narrow sides lie between the first edge 18.1 and the second edge 20.1 and connect the first wide side 18 to the second wide side.
A first narrow side, of which in the Fig. 1 only one edge 22.1 is shown delimits the planar light guide region 16 against the coupling region 14.

A second narrow side 24 is configured to parallelize light incident on a second narrow side 24 from a first narrow side and to direct it to a third narrow side 26. The third narrow Page 26 illustrates a light exit surface of the light guide structure 12.

The second narrow side 24 has a first parallelizing partial surface 28 and a second parallelizing partial surface 30. The second parallelizing partial surface 30 is staggered relative to the first parallelizing partial surface 28 in the direction of the interior of the planar optical fiber region 16. In this case, the first partial area is bounded by the first edge 18.1 and the second edge 20.1, and the second partial area is delimited by the second edge 20.1, but not by the first edge 18.1.

The coupling region 14 has a first end facing away from the planar light guide region and a second end facing the planar light guide region.

A light source 32 is arranged at the first end such that the light emitted by it is coupled into the end of the coupling region 14 facing away from the planar light guide region 16. The light source 32 is preferably a semiconductor light source, in particular a single light-emitting diode or laser diode, or a spatial combination of a plurality of such diodes. For vehicle lighting devices, and so also preferred here, light-emitting diodes are usually used, which have a quadrangular, planar light exit surface with an edge length of 0.3 mm to about 2mm. The arrangement is such that the distance between the light exit surface of the semiconductor light source and the light entry surface of the coupling region is less than 1 mm.

It is an objective to illuminate a long and narrow light exit surface of the light guide structure 12 homogeneously with parallel light from the interior of the light guide structure 12. The lighting should be as efficient as possible, ie with the highest possible proportion of the coupled-in light.

With respect to the third narrow side 26 serving as the light exit surface of the light guide structure 12 and the planar light guide section 16 in the light direction, the x direction becomes a direction of a depth of the sheet light guide section, the y direction a direction of a width of the sheet light guide section and the light exit surface and defines the z-direction as the thickness of the planar light guide region and the height of the light exit surface.

From a viewing direction opposite to the indicated x-direction, the luminous area in the embodiment shown in FIG Fig. 1 is shown, a rectangle of the height delta z and the width delta y. In the following, the x - y plane is considered as a horizontal plane and the x - z plane as a vertical plane. It is understood, however, that this consideration refers only to the explanation of the illustrated embodiments and thus defined in some way an entrained coordinate system. This is not intended to limit the possible orientations of the illumination device in a vehicle or even the possible orientations of light guide structures 12 within a lighting device 1. As far as horizontal angles are concerned in the following, these should lie in the x - y plane, while vertical angles should lie in the x - z plane.

The indication of these directions in the various figures therefore establishes a relationship between the orientations of the objects represented in each case. The light source 32 is located at the origin of the illustrated coordinate system.

A main propagation direction of the light runs in the planar light guide region 16 from the first narrow side 22, which serves as the light entry surface of the planar light guide region 16, to the third narrow side 26, which serves as light exit surface.

The first partial surface 28 and the second partial surface 30 are arranged such that the second partial surface 30 is arranged staggered in a stepwise manner relative to the first partial surface 28 in a cross-section lying transversely to the main propagation direction of the light in the planar light-guide region. A thickness of the planar light guide region 16 measured in the z direction is reduced in a transition region 29 lying between the first partial region 28 and the second partial region 30 in relation to the distance d present outside this transition region. The second partial surface 30 extends over the entire length of the second narrow side 24 lying between the first narrow side 22 and the third narrow side 26. The first partial surface 28 adjoins the first narrow side 22 and extends from there over only one Part of the length of the second narrow side 24 between the first narrow side 22 and the third narrow side 26.

In preferred embodiments, the length of the third narrow side 26 serving as the light exit surface is greater in the y-direction than its fourfold width in the z-direction, in particular greater than its sixfold width and particularly preferably greater than eightfold its width. These data refer to one Fiber optic volume that is illuminated by a light source, be it a single semiconductor light source or a spatially combined array of multiple semiconductor light sources. If several spatially separate light sources are used, a light guide volume is assigned to each light source, such an arrangement being considered as a unit cell. The depth of the planar light guide region is preferably a multiple, in particular at least four times its thickness, which justifies the designation as a planar light guide.

Modern automotive lighting devices provide signal light distribution and / or headlight distribution. A signal light distribution is used to indicate the presence of a motor vehicle and / or the intentions of his driver to other road users. Headlight light distributions, on the other hand, should illuminate objects in the travel path of the motor vehicle and thus make them perceptible to the driver. The generation of a light distribution is also called a light function. Frequently, a lighting device fulfills a plurality of light functions with the aid of one or more light modules, which are arranged in such a lighting device.

The invention presented here preferably fulfills signal light functions, in particular a daytime running light function, a flashing light function, a position light function, a taillight function or a brake light function. In an interconnection of multiple optical fiber structures and headlight lighting functions can be realized. It does not matter whether lighting devices 1 according to the invention in addition to a by the invention fulfilled light function fulfill other lighting functions, for which they may have other light modules. Therefore, embodiments of lighting devices according to the invention can be, in particular, separate front lights for flashing or daytime running light lighting functions, or they can be front lights or rear lights that fulfill a plurality of light functions.

Details of elements and / or configurations of optical waveguide structures 12 of lighting devices according to the invention are explained below. Here, the optical waveguide structure is first based on a planar design, as they are also in the Fig. 1 is illustrated explained. Below also three-dimensionally curved configurations are presented.

In principle, an elementary cell of an optical waveguide structure 12 of an embodiment of a lighting device according to the invention is composed of the coupling region 14, the planar optical waveguide region 16 and optionally a further region which serves to produce a predetermined contour of the light exit surface and which will be discussed in more detail below.

The FIG. 2 shows in its part a) an oblique view and in its part b) a plan view of the coupling region 14. By the light source 32 facing light entrance surface light enters the coupling region 14 and propagates within the light-conducting material of the coupling region 14 to an end surface 34th There begins in the Fig. 2 not shown area 16 of the optical waveguide structure 12. The coupling region 14 has a first region 14.1 and a Transition area 14.2 on. In the first region 14. 1, the cross-section of the coupling-in region 14 widens continuously, starting from the light entry surface until the beginning of the transitional section 14. 2. In this case, the widening in the xy plane may not be identical to widening in the z direction. When passing through the first region 14.1 of the coupling-in region 14, a large proportion of the coupled-in light undergoes internal total reflections once or several times on the longitudinal surfaces of the first region 14.1. As a result, the light experiences a parallelization there. In this case, a parallelization is understood to mean a narrowing of the opening angle of the light cone, which, however, does not yet merge into bundling with a focusing effect, that is to say the light propagating in parallel at maximum bundle constriction has the result.

With regard to the vertical direction, the light continues to move only between the surfaces perpendicular to the z-direction, except for special cases to be described below. It thus moves between the first surface 18 of the Fig. 1 , which is also referred to below as a lid, and the opposite surface of the lid, which is also referred to below as the bottom. This means that the distribution of the vertical angles of the light passing through the end surface 34 into the planar light guide region 16 is preserved when passing through the planar light guide region 16 and the associated light rays are exposed at the third narrow side of the planar light guide region 16 serving as the light exit side exit angle-increasing refraction. This in turn means that at the end of the coupling-in region 12, the vertical desired angle distribution must be present except for the angle-increasing exit refraction. It is therefore preferable in that the coupling-in region is just designed such that it generates a predetermined angular distribution in the vertical direction.

With respect to the horizontal direction applies that the horizontal angular distribution in the planar light guide region 16 is still selectively changed. The change is effected by the parallelizing effect of the second narrow side 24 of the planar light guide region 16.

In one embodiment, the coupling-in region 14 has a curved shape. Such a bent Einkoppellichtleiter has only two flat surfaces. In such a configuration, it is preferred that the coupling-in section has a rectangular cross-section and that this cross-section grows between the coupling-in surface and the transitional region in the form of the first narrow side 22 of the planar section 16 of the optical waveguide structure with a quadratic dependence on the length of the coupling-in region.

In a preferred embodiment, the coupling-in area is set up in such a way that it parallelizes the light of the light source 32 so far that the parallelized light beam that passes from the coupling region 12 into the planar light guide region 16 illuminates the entire angle-changing surface of the planar light guide region 16. The light beam should not illuminate more than this area in order to avoid otherwise occurring loss of efficiency. But it should illuminate not less than this area, otherwise dark areas on the serving as a light exit side third narrow side 26 may occur.

This is an independent aspect which, even without the step in the angle-changing surface, already gives a fairly good homogeneity and, above all, the same effectiveness.

In view of this aspect, the following combination of features is considered as an independent, solving the above-mentioned problem teaching: Lighting device 1 for a motor vehicle with a light guide structure 12 having at least one coupling region 14 and at least one planar light guide region 16, the first broad 18, which is bounded by a first edge 18.1 and which has a second broad side 20 which is equidistant from the first broad side and which is bounded by a second edge 20.1, and narrow sides 22, 24, 26, 28, which lie between the first edge 18.1 and the second edge 20.1 and which connect the first wide side to the second wide side, wherein a second narrow side 24 is arranged to incident from a first narrow side 22 ago on the second narrow side To direct light on a third narrow side 26, characterized in that the second narrow e page 24 is adapted to parallelize from the first narrow side 22 ago on the second narrow side 24 incident light and to judge the third narrow side 26, wherein the first narrow side a transition of a light entry surface having and cohesively with the planar Forming area coupling coupling portion 14 to the planar light guide portion 16 is formed, which Einkoppelbereich is adapted to parallelize via its light entrance surface coupled light of a light source 32 and to direct the parallelized light on the second narrow side so that only the second narrow side is illuminated.

FIG. 3 shows the coupling region 12 and the planar light guide region 16 together with exemplarily selected rays of a light bundle 36, which illuminates exactly the second narrow side 24 of the planar Lichtleiterbreichs 16 serving as angle-changing surface of the planar Lichtleiterbreichs 16 in this sense.

In a preferred embodiment, the coupling-in region 12 is cohesively connected to the planar light-conducting region 16, so that the first narrow side 22 of the planar light-guide region coincides with the end surface 34 of the coupling-in region 12. The optical waveguide structure preferably consists of a conventional optical waveguide material such as polycarbonate (PC) or polymethyl methacrylate (PMMA) or another crystal-clear material such as glass or silicone.

The Fig. 3 shows in particular an embodiment in which the first narrow side 22 of the planar light guide region 16 forms a transition of a coupling surface 14 having a light entry surface and cohesively connected to the planar light guide region 16 to the planar light guide region, which coupling region 14 is adapted to coupled via its light entrance surface Parallelize light of a light source 32 and direct the parallelized light on the second narrow side 24 of the planar light guide region that the angle-changing surface of the planar light guide region, ie in particular the first partial surface 28 and the second partial surface 30 of the second narrow side 24 of the planar light guide region 16 illuminated becomes.

If it is not possible to exactly illuminate the angle-changing surface 24 in the planar optical waveguide region 16 by changing the angle of attack with which the side surfaces of the coupling region 14 expand, rotation of the coupling region 16 by an angle α can be helpful. The fulcrum lies approximately in the middle 38 of the end face 34 of the coupling-in region 12. If this does not lead to the goal, the width delta y of the third narrow side of the planar light guide region 16 must be adapted in the design of the light guide structure 12.

The angle-changing side 24 opposite fourth narrow side 40 of the planar light guide region 26 has no optical function in the embodiments presented here. Analogous to this area is also the portion 35, between the coupling region 14 and the second narrow side 24 without optical function.

These sections are in preferred embodiments for the attachment of connecting and fastening elements such as the webs between the light guides according to the invention in the Fig. 13 and 14 used. Alternatively or additionally, it is preferred that the injection area required for the plastic injection molding is positioned there.

FIG. 4 shows in its part a) an oblique view and in its part b) a plan view of a planar light guide region 16, in which the angle-changing second narrow side 24 is not yet divided into a first and second partial surface. The angle-changing surface is obtained in a preferred embodiment by extruding a lying in the x-y plane parabola in the z direction.

The Fig. 5 shows a plan view of a planar light guide region 16, the angle-changing surface 24 is not yet divided into a first and second partial surface, together with a resulting distribution of the brightness H of the third narrow side 26 exiting light across the width delta y of the third narrow side 26th
The distribution is shown very schematically. The angle-changing surface here has a parabolic shape. It is essential that a fourth portion of the light exit surface 26 closer to the angle-changing side 24 is significantly brighter than the average of the other portions, while an eighth portion farther from the angle-changing side 24 appears significantly less bright than the average of the other portions. Overall, the brightness distribution thus has a pronounced and disturbing inhomogeneity.

FIG. 6 again shows a plan view of a planar light guide region 16. This differs from the planar light guide region of the Fig. 5 in that the second narrow side has a first parallelizing partial surface 28 and a second parallel partial surface 30, wherein the second parallelizing partial surface 30 is staggered relative to the first parallelizing partial surface 28 toward the interior of the planar optical fiber region 16.

In a preferred embodiment, both partial surfaces 28, 30 are parabolic, with the two parabolas having the same focal point and the same direction. It is also preferred that the parabola of the stepped inwardly offset partial surface 30 has a smaller focal length compared to the focal length of the outer partial surface 28. A beam 42 whose vertical angle distribution corresponds to that at the end of the coupling-in area becomes a portion 42b on the second partial surface 30 is reflected, the remainder 42a is reflected on the first partial surface 28. Overall, therefore, a splitting into two bundles 42a and 42b results, which leave the planar light guide region 16 at two different y-locations.

FIG. 7 shows a section through the subject of Fig. 6 along the line VII-VII. The flat optical waveguide region 16 shown there has a thickness d in the z-direction. In this z-direction, the first partial surface 28 has a thickness or width a, and the second partial surface 30 has a thickness or width b. The ratio a to b controls approximately the amount of light in the bundles 42a and 42b. In the case shown, where a = b, the two resulting bundles are about the same light.

Another consequence of the reduction of the layer thickness in the light path behind the classified second sub-area 42b is in FIG FIG. 8 shown. The first partial area 28 is illuminated in the area shown hatched only by half the amount of light, in which case a = b is assumed. Not only is it limited to two partial surfaces 28, 30, but moreover permits more classified partial surfaces, the overall result is a very effective method for homogeneously illuminating the exit surface over the entire width delta y.

Fig. 9 illustrates the effect of the division of the angle-changing surface on the two stepwise offset partial surfaces. How actually already that Fig. 6 shows, a sub-beam 42b of the light beam 42, which would be without a subdivision of the angle-changing surface 24 in the beam path of the sub-beam 42a, inwardly offset. This means that a luminous flux is shifted to the right against the y-direction. In comparison with the FIG. 5 this is reflected in the Fig. 9 in that the intensity distribution in the object of Fig. 9 is more homogeneous than at the subject of Fig. 5 , The excess luminous flux from the middle area in Fig. 5 has been moved into the too dimly lit right area.

The Fig. 10 shows a further embodiment of a light guide structure 12 of a lighting device according to the invention in an oblique view. The Fig. 11 shows the subject of the Fig. 10 in a top view. The optical waveguide structure 12 according to 10 and 11 has a contour generating region 44, which serves to generate a luminous light exit surface, preferably a cohesive component of the light guide structure 12, and which lies in the light path behind the parallelizing partial surfaces 28, 30 of the second narrow side 24. As the FIGS. 10 and 11 show, the third narrow side 26 is divided in this embodiment in stepwise offset faces.

As a result, a curved light exit surface can be reproduced with discrete steps, without triggering an undesired occurrence of total internal reflections, as occurs on actually curved surfaces, when the angle of incidence of the light on the curved light exit surface exceeds the critical angle of total reflection due to its curvature.

The light exit surfaces of the individual stages are configured in a preferred embodiment as light in predetermined directions refractive surfaces, for example as cylindrical surfaces.

The Fig. 10 shows an embodiment in which the second partial surface 30 has a constant width in the z-direction over its entire length.

The Fig. 12 on the other hand shows a preferred embodiment, in which the width of the second partial area decreases with increasing distance from the first narrow side.

This offers another possibility for homogenizing the brightness distribution. Due to the increasing with increasing distance from the first narrow side, that is from the coupling region 14, decreasing width of the second partial surface 30 results in a sense in the z-direction below the second partial surface 30, a widening optical fiber cross-section, which ensures a further desired parallelization.

It is further preferred that the second partial surface has a trapezoidal or triangular contour.

It is also preferable that the second partial surface is arranged closer to the first narrow side than to the third narrow side, or, which is the same, that the second partial surface 30 is arranged closer to the coupling region 14 than to the light exit surface 26.

FIG. 14 shows how a plurality of, here five, preferably cohesively coherent light guide structures 12.1, 12.2, 12.3, 12.4, 12.5, a headlamp light function can be realized. The areas for coupling light and parallelizing the light are each identical in this example, only the contour generating areas vary in length (parallel to x). The contour is formed by steps whose steps are parallel and perpendicular to x.

This is necessary so that the light can leave the light guide parallel to x. If one waived the steps, the light would remain due to total reflections on the then curved surface in the light guide.

The steps of the steps lying perpendicular to the x-direction are curved, in this case convex, in order to break the light incident parallel to the x-direction from the light guide interior into a desired light distribution.

The in the FIG. 13 arrangement shown still has the disadvantage that the light sources can not be arranged on a flat board. Level boards are above all cheaper than flexible boards, so that a use of planar and rigid boards is advantageous.

FIG. 14 1 shows an embodiment in which the example of the first coupling-in region 14.1 shows how the connection to a planar printed circuit board or to a standard LED mounted on a planar printed circuit board can be realized as a light source 32 by means of a corresponding curvature thereof. A standard LED is characterized in that its light-emitting surface is opposite to its mounting surface, with which it is fastened to a circuit board 46.

Of course, this curvature of the coupling-in region 14.1 can also be extended to the planar light guide region 16 and / or the contour generating region 44. Up to this point, it has merely been shown how a plane luminous curve can be generated with the aid of the contour generation area 44.

FIG. 15 shows a first way to get from a flat curve to a three-dimensional curved luminous curve. For this purpose, the contour generating area 46 is divided into individual bars, which are subsequently curved in such a way that the light exit area 26 also follows the desired curve in the z direction. The restriction of the curvature to the contour generating area 46 was made in the Fig. 15 just for the sake of simplicity. Alternatively or additionally, those regions of the planar light guide region 16 in which exclusively already parallelized light propagates can also be deformed in this way.

A second way to produce a three-dimensionally curved luminous curve is in the three views of a three-dimensionally curved contour generating area 46 of FIG FIG. 16 shown. Fig. 16 a) shows an oblique view, Fig. 16b shows a view from the direction of the coupling region, and Fig. 16c shows a plan view of such contour generating area. Again, for simplicity of illustration, a limitation is imposed on contour generating area 46. Instead of dividing the area into bars, as in the subject matter of FIGS FIG. 15 is the case, and then bend the bars in the design of the light guide structure according to the contour to be achieved, is the subject of the Fig. 16 the entire surface of the contour generating portion 46 is curved. This unfortunately has the consequence that the light propagating therein receives horizontal components in reflections on the lid and / or on the floor. As an undesirable consequence, the parallelism generated by the parabolic angle-changing reflection surface is lost. If the number of reflections on the lid and on the bottom is identical, these horizontal components cancel each other out. Those rays in which this favorable case does not apply, receive a horizontal component, which is at least maintained even after leaving the light guide through the outlet opening or even increased by refraction. This must be taken into account in the definition of the refractive surface on the exit surfaces in the design of the light guide structure in order to avoid an undesirably large horizontal scattering effect.

FIG. 17 FIG. 2 shows a possibility of stacking a plurality of optical waveguide structures 12 in order to obtain complex light exit surfaces of individual optical waveguide structures 12 serving as elementary cells. By combinations of superimpositions, side-by-side arrangements and arrangements of such unit cells or also different configurations of optical waveguide structures 12, further possibilities are obtained. If the individual optical waveguide structures 12 are at an angle in the space, which can be achieved, for example, by tilting the left upper end of the in FIG. 18 As shown downward arrangement, lying on the individual stages of the tilted light exit surface scattering elements (for example, cylinder) must be tilted in the opposite design, continue to obtain a purely horizontal scattering.

FIG. 18 shows a possibility that allows a further improvement of the uniformly bright appearance of the luminous and optionally three-dimensionally curved light exit surface. For this purpose, the angle-changing second narrow side is not realized as a real parabola, but such a parabola is approximated by straight line sections or by plane surface segments. FIG. 18 a) shows once again an embodiment of a planar light guide region 16, which is limited by a real parabola 52. One from the Bundle 48 entering bundle region 48 is parallelized on the parabola and illuminates exactly one refractive exit element 50 FIG. 18 b) the same bundle 48 strikes a flat area segment 54 drawn for illustrative purposes with thick line width. This has the consequence that the bundle 48 is not parallelized, but is deflected while maintaining its opening angle and therefore not as in the case of Fig. 18 a) Exactly one exit element 50 meets, but on an approximately two exit elements wide area of the light exit surface 26. Since the same applies to the two adjacent bundles, not shown, the exit element 50 is illuminated here by three superimposed bundles. As a result, otherwise possibly visible dark stripes between the images of adjacent exit elements are blurred in the resulting light distribution. This must be taken into account when designing the refracting surfaces on the exit surfaces in order to reduce otherwise threatening horizontal dispersion.

Claims (10)

Lighting device (1) for a motor vehicle with a light guide structure (12) having at least one coupling region (14) and at least one planar light guide region (16) having a first broad side (18) bounded by a first edge (18.1) and having a second broad side (20) equidistant from the first broad side and bounded by a second edge (20.1), and narrow sides (22, 24, 26, 28) extending between the first and second sides the first edge (18.1) and the second edge (20.1) and connecting the first broad side with the second broad side, wherein a second narrow side (24) is adapted to from a first narrow side (22) ago on the second narrow light incident on a third narrow side (26), characterized in that the second narrow side has a first partial surface (28) and a second partial surface (30), wherein the second partial surface (30) opposite the first partial surface is staggered in the direction towards the interior of the planar light guide region. Lighting device (1) according to claim 1, characterized characterized in that the second narrow side (24) is arranged to parallelize light incident on the second narrow side (24) from the first narrow side (22) and to direct it to the third narrow side (26), the first one Partial surface (28) is a parallelizing partial surface and wherein also the second partial surface (30) is a parallelizing partial surface. Lighting device (1) according to claim 1 or 2, characterized in that the first narrow side forms a transition of a light entry surface and cohesively connected to the planar area coupling region (14) to the planar light guide region (16), which coupling region is adapted to to parallelize light of a light source (32) which has been coupled in via its light entry surface and to direct the parallelized light onto the second narrow side in such a way that the first partial surface and the second partial surface of the second narrow side are illuminated. Lighting device (1) according to one of the preceding claims, characterized in that the second partial surface has a constant width or that the width of the second partial surface decreases with increasing distance from the first narrow side. Lighting device (1) according to claim 4, characterized in that the second partial surface has a rectangular, trapezoidal or triangular contour. Lighting device according to (1) one of the preceding claims, characterized in that the second partial surface is arranged closer to the first narrow side than on the third narrow side. Lighting device (1) according to one of the preceding claims, characterized in that the second narrow side is divided into more than two partial surfaces. Lighting device (1) according to one of the preceding claims, characterized in that a further inner partial surface has a smaller focal length than a further outer partial surface. Lighting device (1) according to one of the preceding claims, characterized in that the second narrow side has a parabolic shape. Lighting device (1) according to one of the preceding claims, characterized in that the second narrow side has a series of adjacent surface segments, wherein edges, with which the surface segments abut the first broad side and the second broad side, have a parabola as an envelope ,

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