DE102020131517A1 - Lighting device with a light guide and light guide for the lighting device - Google Patents

Abstract

Lighting device (20) with a light guide (28) and a light source (26) feeding light into the light guide (28) via a light coupling region (36) of the light guide (28), the light guide (28) having a light guide between a first end (32) and an elongate shape extending from a second end (34) having a light exit lens (44) and a prism rib (40), the prism rib (40) being adapted to redirect light to the light exit lens (44) so that the light exits the light guide (28), optical structures (50) being provided in the light coupling region (36) and on the prismatic rib (40) to homogenize an angular distribution of the light propagating in the light guide (28), and for locally influencing a luminance on the light exit lens (44 ) a variation of a geometric configuration of prisms (46) of the prismatic rib (40) is provided, so that at least two prisms (46) of the prismatic rib (40) one from the other have different geometric configurations.

Description

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

Furthermore, the present invention relates to an optical fiber according to the preamble of claim 11.

Such lighting devices include a light guide and a light source that feeds light into the light guide via a light coupling region of the light guide. The light guide has an elongated shape extending between a first end and a second end. The elongated shape has a front side having a light exit lens and a back side having a prismatic rib. The prismatic rib is usually set up to deflect incident light to the light exit lens, so that the light exits the light guide via the light exit lens.

Such lighting devices and light guides are used, for example, as motor vehicle lighting devices in the field of signal light functions of motor vehicle lighting devices due to their small space requirements and their homogeneous appearance when lit. The light propagating in the light guide is not collimated, but has a specific opening angle that is smaller than the angle of total internal reflection. For a homogeneous appearance in the illuminated state, it is imperative that the light propagating in the light guide is statistically distributed as evenly as possible. This means that the same uniform light distribution within the opening angle of the light beam should emanate from every point located within the light guide.

The light-emitting diodes frequently used as light sources in motor vehicle lighting devices have a specific angle-dependent radiation characteristic that does not change fundamentally when it is coupled into the light guide, apart from an angular offset due to refraction. As a result, certain light beam angles are disproportionately represented in the light guide and others do not occur at all. A homogeneous illumination of the light guide with such a beam distribution is not possible without sufficient mixing.

The homogenization of the light from the light source propagating in the light guide is therefore usually ensured by “mixing” the directional distribution of the light in a mixing area of the light guide with an ideally slightly curved course over a length of at least 100 mm, measured from the light entry surface. Mixing is promoted by total internal reflections that occur on the walls of the light guide.

If the distance between the visibly illuminated area of the light guide and the light entry surface has to be significantly smaller than 100 mm due to requirements, such as those resulting from a shortage of available installation space, the following means are used in known solutions: In the DE 10 2012 106 481 an additional pane with micro-optics is placed between the light source and the light guide. In the U.S. 2012/0 314 448 among other things, the shaping of the light guide coupling to a cylindrical lens is described in order to parallelize the light in one dimension.

In the case of the light guides known from the prior art, very bright areas, so-called “hot spots”, which alternate with darker areas, can occur in an undesirable manner on the lens in the viewing direction. These hot spots are created by imaging individual, particularly bright prisms on the light exit lens.

The aim is therefore to provide a lighting device which overcomes the various disadvantages known from the prior art.

This is achieved by an illumination device according to the characterizing features of claim 1. Accordingly, it is provided according to the invention that optical structures are provided on at least one surface of the light coupling area and on at least one deflection surface of the prismatic rib to homogenize an angular distribution of the light propagating in the light guide, and that locally influencing a luminance on a light exit surface of the light exit lens, a variation of a geometric configuration of prisms of the prismatic rib is provided, so that at least two prisms of the prismatic rib have a different geometric configuration from one another.

According to the invention, the combination of measures for homogenizing the angular distribution of the light propagating in the light guide and for locally influencing the luminance on the light exit surface of the light exit lens is proposed. In this way, on the one hand, the illumination of the light guide can be homogenized and, on the other hand, undesired hot spots on the light exit surface can be specifically weakened or avoided altogether.

The optical structures on at least one surface of the light coupling region already improve the homogeneity of the illumination of the light guide at the end on the coupling side, and thus when light is coupled into the light guide.

The optical structures on at least one deflection surface of the prismatic rib further improve the homogeneity of the illumination of the light guide when deflecting the light incident on the prismatic rib to the light exit lens.

Finally, by varying the geometric configuration of prisms of the prism rib, the luminance on the light exit surface of the light exit lens is locally influenced by specifically varying the geometric configuration of prisms of the prism rib.

As a result of the combination of the measures mentioned, no or only a small area in the light guide is advantageously required for mixing. The present invention represents a way of achieving the homogenization and thus the mixing of the light rays in the light guide in an initial area at the first end of the light guide, ideally directly when the light enters, and thus a homogeneous illumination of the light guide from the start, i.e. a homogeneous To enable illumination of the light exit lens directly after the light coupling area.

According to one embodiment it is provided that the light exit lens, in particular the light exit surface of the light exit lens, extends over the entire length of the light guide from the first end to the second end. It is thus possible to illuminate the light-emitting lens directly adjacent to the light-coupling region.

The lighting device according to the invention is therefore particularly suitable as a lighting device in which the visible luminous surface of the light guide is to begin immediately after light enters the light guide and/or in which only a few light-emitting diodes are to be used as the light source, i.e. as a lighting device with a low space requirement.

According to one embodiment, it is provided that the optical structures in the light coupling region of the light guide on a light entry surface of the light guide lying at the first end transversely to the front side and transversely to the rear side of the light guide and/or that the optical structures on the at least one deflection surface of the prismatic rib as scattering structures and/or or are designed as matting structures. An optical structure on the light-entry surface expands the beam profile emitted by the light source. In particular, a flattening of the LED-inherent Lambertian emission characteristic can be achieved as a result. The widening can take place in one spatial direction, for example by means of a scattering structure in the form of a cylindrical structure. The widening can also take place in two spatial directions, for example by means of a matting structure or a scattering structure in the form of a cushion structure. Since the illumination of the light exit lens is influenced, among other things, by whether the light from the light entry surface of the light guide is distributed evenly to the prisms of the prismatic rib, it is advantageous to check the angular distribution of the existing rays in the surface which extends from the center of the prismatic rib to the center of the exit lens extends to expand.

An optical structure on the deflection surface of the prismatic rib ensures that the direction of the beams, which are deflected at the prismatic rib, are modulated at the respective deflection surfaces of the individual prisms. On the one hand, an image of a respective prism on the light exit lens is washed out and more homogeneous illumination is thus achieved. On the other hand, a further contribution is made to the formation of the statistically homogeneous light distribution within the light guide. The scattering structure can be formed, for example, by longitudinal grooves along the elongated shape of the light guide.

As an alternative or in addition to the optical structures on the light entry surface of the light guide, which is located at the first end transversely to the front side and transversely to the rear side of the light guide, it can be provided that the lighting device has a light coupling profile that is positioned between the light source and a light source at the first end transversely to the front side and transversely on the rear side of the light guide and which has a light input surface on the light source side and a light output surface facing the light guide, with the optical structures being formed in the light input area of the light guide on the light input surface and/or the light output surface of the light input profile.

The light coupling profile can improve the homogeneity of the illumination of the light guide at its coupling-side end by achieving a much more advantageous distribution of rays and thus a fundamentally improved appearance than with direct coupling into the light guide, i.e. without a light coupling profile.

It can advantageously be provided that the light coupling profile on the light guide arranged, in particular attached to the light guide, is.

Furthermore, in the lighting device according to the invention, the variation of the geometric design of prisms of the prism rib is provided for locally influencing the luminance on the light exit surface of the light exit lens, in particular for avoiding or reducing hot spots. It can prove to be advantageous if the variation in the geometric configuration is provided for one or more prisms of the prismatic rib in the starting area at the first end of the light guide. In this way, if complete mixing has not yet been achieved by the measures provided for homogenizing the angular distribution of the light propagating in the light guide, hot spots occurring in particular in the initial area of the light guide can be reduced or avoided.

According to an advantageous embodiment, the variation in the geometric configuration includes a convex and/or concave curvature of a deflection surface of at least one prism. This widens the area over which light is redirected by the prism and causes local defocusing. The result of this is that the luminance of the image of the prism on the light exit lens is reduced and the image is less bright, particularly when viewed from a main focus direction of the light guide. In principle, the deflection surface can be convex or concave. A convex curvature can be more advantageous for manufacturing reasons.

According to a further advantageous embodiment, the variation in the geometric configuration of the prisms includes the variation in a depth of at least one prism. Since the local luminance on the light exit lens of the light guide is determined by the amount of light falling on the corresponding prism, the luminance can be influenced locally by varying the depth of the prism rib. A prism with a shallower depth is more exposed to the light propagating in the light guide compared to a prism with a greater depth. Accordingly, more light is deflected onto the light exit lens by a prism with a smaller depth compared to a prism with a greater depth. Thus, especially if the statistically homogeneous distribution of the propagating light in the light guide is not optimal, a hot spot on the light exit lens can be reduced by increasing the depth of the corresponding prism. When changing from a smaller to a larger depth, mutual shading of the prisms should advantageously be avoided as far as possible when arranging the prisms on the prism rib.

According to a further advantageous embodiment, the variation in the geometric configuration includes the variation in a height of at least one prism. In principle, a prism with a higher height can expand the vertical focus of the light distribution compared to a prism with a lower height. An undesired hot spot on the light exit lens usually has an at least approximately trapezoidal shape. The flanks of the trapezoidal shape can be flattened by targeted local adjustment of the height of the prisms. For this purpose, a prism that appears too small in the image on the light exit lens is formed lower than a prism that does not appear too small in the image on the light exit lens. This improves focus and enlarges the image. Analogously, a prism that appears too large in the image on the light exit lens is formed larger. This results in defocusing and the image of the prism on the light exit surface of the light exit lens becomes smaller.

According to a further advantageous embodiment, it is provided that on an upper and/or lower side of the light guide extending between the first and the second end transversely to the front and rear and/or on a side of the light guide arranged at the second end, in particular parallel to the light entry surface Light guide further optical structures are provided. The optical structures are designed as scattering structures, for example. The light propagating in the light guide is advantageously reflected on the top and/or underside of the light guide and/or on the side of the light guide arranged at the second end. Due to the optical structures, further mixing can be achieved during reflection and thus contribute to the formation of the statistically homogeneous light distribution within the light guide. On the upper and/or lower side of the light guide and/or on the side of the light guide arranged at the second end, coupling out of light should be avoided as far as possible. Accordingly, the scattering structures should only be slightly formed.

According to a further advantageous embodiment, an optical structure is provided on a surface of the light exit lens. The optical structure is designed, for example, as a scattering structure, in particular a wave-shaped one. With the scattering structure, light can be scattered out of the main focus direction. The light exit lens thus appears less bright when viewed from the main focus direction. Undesirable hot spots on the light exit lens can thus be avoided or reduced. However, optical structures on the light exit lens can sometimes have a negative effect on the appearance and/or the efficiency of the lighting device. Accordingly, it can prove to be advantageous to arrange at least one further optical element after the light guide, which at least partially blurs the view of the light exit lens. Furthermore, it can prove to be advantageous if the optical structure is provided on the light exit lens only in the initial area at the first end of the light guide. In this case, provision can also be made for the surface of the light exit lens, starting from the optical structures, to gradually transition into a smooth surface without optical structures.

Advantageously, the measures described can be combined with one another as desired.

The lighting device according to the invention is preferably used, for example, to implement signal light functions by means of a light guide in the front headlight or a rear light.

Further embodiments relate to a light guide for a lighting device according to the described embodiments according to the preamble of claim 11.

According to the invention, optical structures are provided for homogenizing an angular distribution of the light propagating in the light guide on at least one surface of the light coupling region and on at least one deflection surface of the prismatic rib, and for locally influencing a luminance on a light exit surface of the light exit lens, a variation of a geometric configuration of Prisms of the prismatic rib is provided, so that at least two prisms of the prismatic rib have a different geometric configuration.

According to an advantageous embodiment, it can further be provided that the light guide has a light coupling profile which is arranged on a light entry surface of the light guide lying at the first end transversely to the front side and transversely to the rear side of the light guide and which has a light coupling surface on the light source side and a light coupling surface facing the light guide. wherein the optical structures in the light coupling region of the light guide are formed on the light coupling surface and/or the light coupling surface of the light coupling profile.

• 1a und 1b schematisch einen aus dem Stand der Technik bekannten Lichtleiter;
• 2 das technische Umfeld der Erfindung in Form einer Beleuchtungseinrichtung für Kraftfahrzeuge gemäß einer Ausführungsform;
• 3 einen Abschnitt eines erfindungsgemäßen Lichtleiters gemäß einer ersten Ausführungsform;
• 4 eine Seitenansicht eines erfindungsgemäßen Lichtleiters gemäß einer ersten Ausführungsform;
• 5 einen Abschnitt eines erfindungsgemäßen Lichtleiters gemäß einer weiteren Ausführungsform;
• 6 einen erfindungsgemäßen Lichtleiter in einer Draufsicht gemäß einer weiteren Ausführungsform;
• 7 einen Abschnitt eines erfindungsgemäßen Lichtleiters gemäß einer weiteren Ausführungsform;
• 8 eine Seitenansicht eines erfindungsgemäßen Lichtleiters gemäß einer weiteren Ausführungsform;
• 9 eine Seitenansicht eines erfindungsgemäßen Lichtleiters gemäß einer weiteren Ausführungsform;
• 10 einen erfindungsgemäßen Lichtleiter in einer Draufsicht gemäß einer weiteren Ausführungsform;
• 11 eine Seitenansicht eines erfindungsgemäßen Lichtleiters gemäß einer weiteren Ausführungsform;
• 12 eine Rückansicht eines erfindungsgemäßen Lichtleiters gemäß einer weiteren Ausführungsform;
• 13a eine Lichtverteilung eines aus dem Stand der Technik bekannten Lichtleiters;
• 13b eine Lichtverteilung eines erfindungsgemäßen Lichtleiters;
• 14 eine Seitenansicht eines erfindungsgemäßen Lichtleiters gemäß einer weiteren Ausführungsform, und
• 15a, 15b und 15c verschiedene Ansichten eines erfindungsgemäßen Lichtleiters gemäß einer weiteren Ausführungsform.

Further advantages result from the description and the accompanying drawings. Embodiments of the invention are shown in the drawings and are explained in more detail in the following description. The same reference symbols in different figures denote the same elements or elements that are at least comparable in terms of their function. In the description of individual figures, reference is also made to elements from other figures where appropriate. They each show in schematic form:

• 1a and 1b schematically a light guide known from the prior art;
• 2 the technical environment of the invention in the form of a lighting device for motor vehicles according to one embodiment;
• 3 a section of a light guide according to the invention according to a first embodiment;
• 4 a side view of a light guide according to the invention according to a first embodiment;
• 5 a section of a light guide according to the invention according to a further embodiment;
• 6 a light guide according to the invention in a plan view according to a further embodiment;
• 7 a section of a light guide according to the invention according to a further embodiment;
• 8th a side view of a light guide according to the invention according to a further embodiment;
• 9 a side view of a light guide according to the invention according to a further embodiment;
• 10 a light guide according to the invention in a plan view according to a further embodiment;
• 11 a side view of a light guide according to the invention according to a further embodiment;
• 12 a rear view of a light guide according to the invention according to a further embodiment;
• 13a a light distribution of a light guide known from the prior art;
• 13b a light distribution of a light guide according to the invention;
• 14 a side view of a light guide according to the invention according to a further embodiment, and
• 15a , 15b and 15c different views of a light guide according to the invention according to a further embodiment.

1a and 1b show a schematic of a light guide 10 known from the prior art. 1a shows the light guide 10 in profile cross section. 1b shows the light guide 10 in plan view. Light emitted by a light source 12 is coupled into the light guide 10 via a coupling surface E of the light guide 10 . Light incident on the prism rib P is deflected at a prism rib P. The light exits the light guide 10 via the light exit lens L in a main emission direction 14 . In the top view, a mixing area D after the coupling surface E is marked schematically. No decoupling takes place in this area. Accordingly, no prism rib P is attached in this area. In the mixing area D, a mixing of the directional distribution of the light and thus a homogenization of the light propagating in the light guide 10 is to be achieved by total reflection.

Based on 2 until 15 a lighting device according to the invention and a light guide according to the invention are described below.

In detail shows 2 a lighting device 20 for a motor vehicle. The lighting device 20 has a housing 22 and a transparent cover plate 24 which covers a light exit opening of the housing 22 . A motor vehicle light is located inside the housing 22 and emits light in a signal light distribution for motor vehicle lights that conforms to the rules. A main emission direction of the motor vehicle light is generally parallel to a longitudinal axis of the motor vehicle in which the lighting device and the motor vehicle light are used as intended.

A rule-compliant signal light distribution is characterized, for example, by the fact that prescribed minimum brightness values in the horizontal direction H and in the vertical direction V are achieved at a specified distance in front of the motor vehicle light, with the directions being defined as angular deviations from the main emission direction.

In the example shown, the main emission direction is an x-direction of a right-angled and right-handed coordinate system, the z-direction of which is parallel to a vertical axis of the motor vehicle when the lighting device 20 is used as intended, and the y-direction of which is parallel to a transverse axis of the motor vehicle when it is used in this way.

The lighting device 20 has a light source 26 in the form of a light-emitting diode or an arrangement of several light-emitting diodes and a light guide 28 which is supplied with light 30 from the light source 26 . The light guide 28 has an elongate shape and extends in particular along a spatially curved curve L between a first end 32 and a second end 34 of the light guide 28. The light guide 28 shown is therefore an elongate and rod light guide which is Course L is bent accordingly, but can also be straight. The curve L thus also corresponds to the main light propagation direction of light from the light source 26 in the light guide 28. An elongate shape is understood to mean a shape in which a length is greater by at least a factor of 5 than a width and a height.

In the exemplary embodiment shown, the light source 26 is arranged at the first end 32 of the light guide 18 in such a way that light 20 emanating from it enters the light guide 28 via a light coupling region 36 arranged transversely to the length L at the first end 32 . A portion of the light 30 experiences total internal reflections at the boundary surface of the light guide 28 that encases the light guide and is thereby forwarded inside the light guide 28 with propagation directions that scatter around the curve L.

The light guide 28 has a rear side 38 on which a prismatic rib 40 is arranged. A light exit lens 44 is also provided on a front side 42 of the light guide. Part of the light 20 undergoes total internal reflection at the prismatic rib 40. The prismatic rib 40 is designed to deflect light incident on it so steeply to the light exit lens 44 that it exits the light exit lens 44 there.

2 shows a section of the elongated light guide 28 with a preferred cross-sectional shape, which is oriented perpendicular to the course of the light guide 28, in an oblique view. The prismatic rib 40 on the rear side 38 of the light guide 28 has a series of deflection elements in the form of individual prisms 46 . Each prism 46 has a deflection surface 48 .

In the x-direction, the cross section of the light guide preferably widens continuously to a height of the light exit lens 44. This reduces the aperture angle of the light propagating in the light guide 28 in the xz plane. The light exit lens 44 preferably has the illustrated convex shape. With its convex shape, the light exit lens 44 forms a converging lens. The focal length of the light exit lens 44 is preferably matched to the distance between the prismatic rib 40 and the light exit lens 44 and the height of the prisms 46 of the prismatic rib 40 such that the height of the prisms is optically enlarged to the height of the light exit lens 44 for an observer. This contributes to a homogeneous luminance that is desired at the height of the light exit lens 44 .

In the case of the light guide 28 according to the invention, measures are provided to homogenize the illumination of the light guide 28 and to selectively weaken or completely avoid unwanted hot spots on a light exit surface of the light exit lens.

These measures are explained below.

Optical structures 50 are provided on at least one surface of the light coupling region 36 in order to homogenize an angular distribution of the light 30 propagating in the light guide 28 .

According to one embodiment, the optical structures 50 are provided in the light coupling region 36 of the light guide 28 on a light entry surface 52 of the light guide 28 lying at the first end 32 transversely to the front side 42 and transversely to the rear side 38 of the light guide 28 . This is exemplified in the 4 and 5 shown. The optical structures 50 are designed, for example, as scattering structures and/or as matting structures.

An expansion of the beam profile emitted by the light source 26 is achieved by an optical structure 50 on the light entry surface 52 . In particular, a flattening of the LED-inherent Lambertian emission characteristic can be achieved as a result. The widening can take place in one spatial direction, for example by means of a scattering structure in the form of a cylindrical structure. The widening can also take place in two spatial directions, for example by means of a matting structure or a scattering structure in the form of a cushion structure. Since the illumination of the light exit lens 44 is influenced, among other things, by whether the light from the light entry surface 52 is distributed evenly onto the prisms 46 of the prismatic rib 40, it is advantageous to adjust the angular distribution of the rays present in the surface that extends from the center of the prismatic rib 40 extends to the center of the light exit lens 44 to widen.

4 shows a side view of the light guide 28 onto the light entry surface 52. On the light entry surface 52 there are schematically optical structures 50 made up of sections of rollers for scattering light impinging on the light entry surface. The optical structures can also be designed as a grain or as sections of cushions.

5 shows a section of a light guide 28 in an oblique view of the light entry surface 52.

The light entry surface 52 has optical structures in the form of cylindrical light entry optics 54 . A respective light entry optics 54 can be assigned to a respective LED of the light source 26, for example. Two light entry optics 54 are shown as an example. However, additional light entry optics 54 can also be provided.

6 shows a light guide 28 with a light coupling profile 56. The light coupling profile 56 is arranged between the light source 26 and the light entry surface 52 of the light guide 28, which is located at the first end 32 transversely to the front side 42 and transversely to the rear side 38 of the light guide 28. The light coupling profile 56 comprises a light coupling surface 58 on the light source side and a light coupling surface 60 facing the light guide 28.

According to the illustrated embodiment, the light coupling profile 56 is fastened to the light guide 28 . For this purpose, the light coupling profile 56 has a collar 62 which protrudes beyond the light coupling surface 60 in the light propagation direction and which surrounds the first end 32 of the light guide 28 at least partially in a positive and non-positive manner. In the embodiment shown, collar 62 is additionally connected to light guide 28 by pins 64 . The pins 64 protrude through the collar 62, ie through a side wall of the light coupling profile 56, into the light guide 28.

The collar 62 is preferred and differs from that shown in FIG 2 interrupted in the area of the light exit lens 44 and/or the prismatic rib 44 .

According to the illustrated embodiment, instead of being coupled directly from the light source 26 into the light guide 28 , light from the light source 26 is first coupled into the light coupling profile 56 which is fastened to the light guide 28 . The light coupling profile 56 has a partial contact area 66 and a partial light feed area 68 . The basic idea here is to guide the light emanating from the light source 26 in a controlled manner to the light coupling-out surface 60 of the light-coupling profile 56 and to scatter it there.

The light decoupling surface 60 of the light coupling profile 56 is arranged opposite the light entry surface 52 of the light guide 28 . One of the two surfaces 60 , 52 last mentioned is provided with an optical structure 50 . The other of these two surfaces 60, 52 is a smooth surface.

In one embodiment, the optical structures 50 consist of a grain, of sections of rollers or of sections of cushions.

The partial contact area 66 of the light coupling profile is shaped in such a way that it at least partially encompasses the first end 32 of the light guide 28 and can thus be attached to it, e.g. by pins 64 that protrude through the collar 62 and into matching recesses/holes in the Light guide 28 protrude.

The partial light-feeding area 68 has cross-sections 70 lying transversely to a main direction of propagation of the light from the light source 26 coupled into the partial light-feeding area 68 . These cross sections 70 increase monotonically as the distance from the light coupling surface 58 increases.

As a result, the light coupling profile 56 in the light guide 28 and in particular for its illumination at its first end 32 achieves a much more advantageous distribution of rays and thus a fundamentally improved appearance than when coupling takes place directly into the light guide 28 .

According to the in the 4 until 6 In the illustrated embodiments, the optical structures 50 are formed in the light coupling region 36 of the light guide 28 on the light coupling surface 58 and/or the light coupling surface 60 of the light coupling profile 56.

The optical structures 50 on at least one surface of the light coupling region 36 already improve the homogeneity of the illumination of the light guide 28 at the end 32 on the coupling side, and thus when light 30 is coupled into the light guide 28 .

Furthermore, optical structures 50 are provided on at least one deflection surface 48 of the prismatic rib 40 in order to homogenize the angular distribution of the light 30 propagating in the light guide 28 . An optical structure 50 on the deflection surface 48 ensures that the direction of the rays that are deflected at the prismatic rib 40 is modulated at the respective deflection surfaces 48 of the individual prisms 46 . On the one hand, an image of a respective prism 46 on the light exit lens 44 is washed out and more homogeneous illumination is thus achieved. On the other hand, it contributes to the formation of the statistically homogeneous light distribution within the light guide 28 . The optical structure 50 can be shaped, for example, in the form of longitudinal grooves 72 along the elongated shape of the light guide. This is an example in 7 shown.

7 shows an oblique view of a deflection surface 48 of a prism 46. Longitudinal grooves 72 are provided on the deflection surface 48. FIG. The resulting and above-mentioned improved illumination of the light exit lens 44 of the light guide 18 results from the fact that the longitudinal grooves 72 also scatter light impinging on them in the z-direction of the light guide 28, whereby an inhomogeneity in the luminance of the light density that existed before impinging on the deflection surface 48 on the deflection surface 48 incident light is blurred.

The prisms 46 on the prism rib 40 can directly adjoin one another or be separated by a surface section between the prisms 46 . The surface between the individual prisms 46 is preferably also provided with longitudinal grooves 72 . In 5 An embodiment is shown in which the prisms 46 on the prism rib 40 are separated by land portions between the prisms. Light that hits the surface sections between the prisms is not decoupled, but is totally reflected internally. The area of these surface sections advantageously becomes smaller and smaller towards the second end 34 of the light guide 28 . In this way it can be achieved that too much light is not coupled out of the light guide 28 at the beginning of the light guide 28 . At the same time, the area of the prisms 46 along the course of the light guide 28 increases towards the second end 34 . This in turn is advantageous since less light is available in the light guide 28 towards the second end 34 and a similar, almost homogeneous brightness can be achieved along the course of the light guide 28. When the in 7 shown grooves also have the in 5 shown surface sections extend between the prisms, the angular distribution of the light in the light guide 28 is thereby homogenized.

The optical structures 50 on the prismatic rib 40 can also be one of the 7 shown deviating configuration include.

Furthermore, in the light guide 28 according to the invention, a variation of a geometric configuration of prisms 46 of the prismatic rib 40 is provided for locally influencing a luminance on a light exit surface of the light exit lens 44 . At least two prisms 46 of the prismatic rib 40 have a different geometric configuration from one another.

By varying the geometric configuration of prisms 48, the luminance on the light exit surface of the light exit lens 44 is influenced locally, in which the geometric configuration is deliberately varied by prisms 46. In this way, homogenization along the light guide 28 can be achieved.

The variation in the geometric configuration of the prisms 46 includes, for example, a convex and/or concave curvature 74 of a deflection surface 48 of at least one preferably cylindrical prism 46. This is shown in FIG 8th shown. This widens the area over which light is redirected by the prism 46 . This causes local defocusing. As a result, the luminance of the image of the prism 46 on the light exit lens 44 is reduced and the image is less bright, particularly when viewed from a main focus direction of the light guide 28 . In principle, the deflection surface 48 can be convex or concave. A convex curvature 74 can be more advantageous for manufacturing reasons. In 8th the bulge 74 is illustrated schematically using a circle with the radius r. The radius r is typically 5 mm to 15 mm.

The variation of the geometric configuration of the prisms 46 includes, for example, the variation of a depth of at least one prism 46. This is an example in FIGS 9 and 10 shown. Since the local luminance on the light exit lens 44 of the light guide 28 is determined by the amount of light falling on the corresponding prism 46, the luminance can be influenced locally by varying the depth of the prism rib 40. A prism 46 with a shallower depth is more exposed to the light propagating in the light guide 28 compared to a prism 46 with a greater depth. Accordingly, more light is deflected onto the light exit lens 44 by a prism 46 with a smaller depth, compared to a prism 46 with a greater depth. Thus, especially when the statistically homogeneous distribution of the propagating light in the light guide 28 is not optimal, a hot spot on the light exit lens 44 can be reduced by reducing the depth of the corresponding prism 46 . When changing from a smaller to a larger depth, mutual shading of the prisms 46 should be avoided as far as possible in the arrangement. According to the 9 and 10 The embodiment illustrated is modulated between a first depth T1 and a second depth T2 in order to make the respective areas on the light exit lens 44 lighter or darker. Typical values of the depths T1 and T2 are in the range from 0 mm to 5 mm.

The variation of the geometric configuration of the prisms 46 includes, for example, the variation of a height of at least one prism 46. This is an example in FIGS 11 and 12 shown. In principle, the vertical focusing of the light distribution can be widened with a prism 46 with a greater height, compared with a prism 46 with a smaller height. An undesired hot spot on the light exit lens 44 usually has an at least approximately trapezoidal shape. Targeted local adjustment of the height of the prisms 46 allows the flanks of the trapezoidal shape to be flattened. For this purpose, a prism 46 that appears too small in the image on the light exit lens is formed lower than a prism 46 that does not appear too small in the image on the light exit lens 44 . This improves focus and enlarges the image. Analogously, a prism 46 that appears too large in the image on the light exit lens 44 is formed larger. This results in defocusing and the image becomes smaller. According to the 11 and 12 illustrated embodiment is modulated between a first height H1 and a second depth H2. Typical values of the heights H1 and H2 range from about 0.5 mm to 2 mm wide.

13a shows schematically a light distribution of a light guide with unwanted hot spots 76. 13b shows a schematic of a light distribution in which the undesired hotspots can be avoided by the measures described.

Although the individual measures are shown in separate figures, the subject matter of the invention is a light guide 28 which comprises at least the following measures: optical structures 50 on at least one surface of the light coupling region 36 and on at least one deflection surface 46 of the prismatic rib 40 and a variation of a geometric configuration of prisms 46 of the prismatic rib 40, so that at least two prisms 46 of the prismatic rib 44 have a different geometric configuration from one another.

As a result of the combination of the measures mentioned, no or only a small area in the light guide 28 is advantageously required for mixing. The present invention represents a way of achieving the homogenization and thus the mixing of the light beams in the light guide 28 already in a starting area at the first end 32 of the light guide 28, ideally directly when the light enters, and thus a homogeneous illumination of the light guide 28 from the start , so the illumination of the light exit lens 44 directly after the light coupling region 36 to allow.

According to one embodiment it is provided that the light exit lens 44, in particular the light exit surface of the light exit lens 44, over the entire length of the light guide 28 from the first end 32 to the second end 34 extends. It is thus possible to illuminate the light exit lens 44 directly adjacent to the light coupling region 36 .

The lighting device 20 according to the invention is therefore particularly suitable as a lighting device 20 in which the visibly luminous surface of the light guide 28 is to begin immediately after light enters the light guide 28 and/or in which only a few light-emitting diodes are to be used as the light source 26, i.e. as an illumination device 20 with a small space requirement.

Further measures can advantageously be provided for the light guide 28 .

According to the 14 The embodiment illustrated provides that further optical structures 50 are provided on an upper side 78 and underside 80 of the light guide 28 extending between the first end 32 and the second end 34 transversely to the front side 42 and rear side 38 . The optical structures 50 are designed, for example, as preferably wave-shaped scattering structures. The light propagating in the light guide 28 is advantageously reflected on the top and/or bottom side 78, 80 of the light guide. A further mixing can be achieved by the optical structures 50 during the reflection and thus contribute to the formation of the statistically homogeneous light distribution within the light guide 28 . On the top and/or bottom 78, 80 of the light guide 28, coupling out of light should be avoided as far as possible. Accordingly, the scattering structures should only be slightly formed.

These scatter structures allow the light to be scattered in a targeted manner within the light guide 28 and along its course in order to obtain the statistically homogeneous light distribution within the light guide 28 . In this case, these scattering structures can be applied to the surfaces 78 and 80 in their full length or in sections. The scattering structures 50 preferably have a constant curvature and are particularly preferably embodied in a wavy manner. The scattering structures can grow out of the cross section of the light guide 28 or can be sunk into the light guide 28 . The transition along the light guide 28 between a section without scattering structures and a section with scattering structures is also designed with a constant curvature.

According to the 15a , 15b and 15c embodiment shown, an optical structure 50 is also provided on the surface of the light exit lens 44 . The optical structure 50 is designed, for example, as a scattering structure, in particular a wave-shaped one. With the scattering structure, light can be scattered out of the main focus direction. The light exit lens 44 thus appears less bright when viewed from the main focus direction. Undesirable hot spots on the light exit lens 44 can thus be avoided or reduced. Optical structures 50 on the light exit lens 44 can sometimes have an adverse effect on the appearance and the efficiency of the lighting device 20 . Accordingly, it can prove to be advantageous to arrange at least one further optical element after the light guide, which blurs the view of the light exit lens 44 . Furthermore, it can prove to be advantageous if the optical structure on the light exit lens 44 is only provided in the initial area at the first end 32 of the light guide 28 . In this case, provision can also be made for the surface of the light exit lens 44 to gradually transition from the optical structures 50 into a smooth surface without optical structures. 15a shows a sectional view at section A in the area at the first end 32 of the light guide 28. 15b shows a sectional view B. A transition area 82 between section A and section B is typically 50 mm to 100 mm long.

The scattering structures in 15b on the surface of the light exit lens 44 are suitable for influencing and maintaining the statistically homogeneous light distribution along the course of the light guide 28, but the structures also have an effect on the light that is coupled out via the prisms 46, which limits the use of these structures. The scattering structures 50 preferably have a constant curvature and are particularly preferably embodied in a wavy manner. The scattering structures can grow out of the cross section of the light guide 28 or can be sunk into the light guide 28 . The transition along the light guide 28 between a section without scattering structures and a section with scattering structures is also designed with a constant curvature. The transition region 82 on the light exit side of the light guide 28 can also be designed in the same way. Alternatively, a matt finish can also be used.

In principle, all of the described optical structures 50 can be embodied as scattering structures and/or as matting structures. In principle, similar optical results can be achieved with a matting structure as with a specially designed diffusing structure. With a matting structure, the light losses tend to be higher and thus the overall efficiency lower than with scattering structures.

QUOTES INCLUDED IN DESCRIPTION

This list of the documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102012106481 [0007]
• US2012/0314448 [0007]

Claims (12)

Lighting device (20) with a light guide (28) and a light source (26) feeding light into the light guide (28) via a light coupling region (36) of the light guide (28), the light guide (28) having a light guide between a first end (32) and an elongated shape extending from a second end (34) having a front face (42) having a light exit lens (44) and a back face (38) having a prismatic rib (40), the prismatic rib (40) being adapted to block incident light to the light exit lens (44) so that the light exits the light guide (28) via the light exit lens (44), characterized in that to homogenize an angular distribution of the light propagating in the light guide (28) on at least one surface of the light coupling region (36) and optical structures (50) are provided on at least one deflection surface (48) of the prismatic rib (40), and that for locally influencing a luminance a A variation of a geometric configuration of prisms (46) of the prism rib (40) is provided on a light exit surface of the light exit lens (44), so that at least two prisms (46) of the prism rib (40) have different geometric configurations. Lighting device (20) after claim 1 , characterized in that the light exit lens (44), in particular the light exit surface of the light exit lens (44), extends over the entire length of the light guide (28) from the first end (32) to the second end (34). Lighting device (20) according to at least one of the preceding claims, characterized in that the optical structures (50) in the light coupling region (36) of the light guide (28) on a first end (32) transverse to the front (42) and transverse to the rear ( 38) of the light guide (28) and/or the optical structures on the at least one deflection surface (48) of the prismatic rib (40) are designed as scattering structures and/or as matting structures. Lighting device (20) according to at least one of the preceding claims, characterized in that the lighting device (20) has a light coupling profile (56) which extends between the light source (26) and at the first end (32) transversely to the front side (42) and transversely on the rear side (38) of the light guide (28) and which has a light input surface (58) on the light source side and a light output surface (60) facing the light guide (28), the optical structures (50 ) are formed in the light coupling region (36) of the light guide (28) on the light coupling surface (58) and/or the light coupling surface (60) of the light coupling profile (56). Lighting device (20) after claim 4 , characterized in that the light coupling profile (56) is arranged on the light guide (28), in particular attached to the light guide (28). Lighting device (20) according to at least one of the preceding claims, characterized in that the variation in the geometric configuration comprises a convex and/or concave curvature (74) of a deflection surface (48) of at least one prism (46). Lighting device (20) according to at least one of the preceding claims, characterized in that the variation in the geometric configuration of the prisms (46) includes the variation in the depth of at least one prism (46). Lighting device (20) according to at least one of the preceding claims, characterized in that the variation in the geometric configuration includes the variation in the height of at least one prism (46). Lighting device (20) according to at least one of the preceding claims, characterized in that on a top and/or bottom side extending between the first end (32) and the second end (34) transversely to the front side (42) and rear side (38). (78, 80) of the light guide and/or further optical structures are provided on a side of the light guide (28) arranged at the second end (34), in particular parallel to the light entry surface. Lighting device (20) according to at least one of the preceding claims, characterized in that an optical structure is provided on a surface of the light exit lens (44). Light guide (28) for an illumination device (20) according to one of Claims 1 until 10 , wherein the light guide (28) has an elongated shape running between a first end (32) and a second end (34), which has a front side (42) having a light exit lens (44) and a back side (38 ), wherein the prismatic rib (40) is set up to deflect incident light to the light exit lens (44), so that the light exits the light guide (28) via the light exit lens (44), characterized in that optical structures are provided to homogenize an angular distribution of the light propagating in the light guide on at least one surface of the light coupling region (36) and on at least one deflection surface (48) of the prismatic rib (40), and that for locally influencing a luminance on a light exit surface the light exit lens (44) a variation of a geometric configuration of prisms (46) of the prismatic rib (40) is provided, so that at least two prisms (46) of the prismatic rib (40) have a different geometric configuration from one another. Light guide (28) after claim 11 , characterized in that the light guide (28) has a light coupling profile (56) which, on a first end (32) lying transversely to the front side (42) and transversely to the rear side (38) of the light guide (28), is located on a light entry surface (52) of the light guide (28) and which has a light input surface (58) on the light source side and a light output surface (60) facing the light guide (28), the optical structures (50) in the light input area (36) of the light guide (28) on the light input surface (58 ) and/or the light coupling-out surface (60) of the light coupling-in profile (56).

Images