CN114562707A

CN114562707A - Lighting device with optical waveguide and optical waveguide for a lighting device

Info

Publication number: CN114562707A
Application number: CN202111305360.9A
Authority: CN
Inventors: 迈克尔·里希特; 丹尼尔·吕尔克; 马蒂亚斯·格鲍尔; 佩特拉·弗兰克
Original assignee: Marelli Automotive Lighting Reutlingen Germany GmbH
Current assignee: Marelli Automotive Lighting Reutlingen Germany GmbH
Priority date: 2020-11-27
Filing date: 2021-11-05
Publication date: 2022-05-31
Also published as: DE102020131517A1

Abstract

A lighting device (20) having a light guide body (28) and a light source (26) for feeding light into the light guide body (28) through a light incoupling region (36) of the light guide body (28), wherein the light guide body (28) has an elongated shape extending between a first end (32) and a second end (34), the elongated shape having a light exit lens (44) and a prism rib (40), wherein the prism rib (40) is arranged to deflect light to the light exit lens (44) such that light exits the light guide body (28), wherein, in order to homogenize an angular distribution of the light propagating in the light guide body (28), an optical structure (50) is arranged in the light incoupling region (36) and on the prism rib (40); and a variation of the geometric design of the prisms (46) provided with the prism ribs (40) in order to locally influence the brightness on the light exit lens (44), such that at least two prisms (46) of the prism ribs (40) have a different geometric design from each other.

Description

Lighting device with optical waveguide and optical waveguide for a lighting device

Technical Field

The present invention relates to a lighting device. The invention also relates to a light guide.

Background

Such a lighting device comprises a light guide and a light source for feeding light into the light guide via a light incoupling region of the light guide. The light conductor 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 rear side having prism ribs. The prism ribs are typically arranged to deflect incident light to a light exit lens so that the light exits the light guide body through the light exit lens.

Such lighting devices and light guides are widely used on account of their small space requirement and their uniform appearance in the illuminated state, for example as motor vehicle lighting in the field of the signal light function of motor vehicle lighting. The light propagating in the light guide is not collimated but has a specific opening angle which is smaller than the total internal reflection angle. In order to obtain a uniform appearance in the illuminated state, it is necessary for the light propagating in the light guide to be distributed as uniformly as possible statistically. This means that the same uniform light distribution within the beam angle should start from every point located within the light guide body.

Light-emitting diodes, which are often used as light sources in motor vehicle lighting devices, have a specific angle-dependent emission characteristic, which does not change at all when coupled into the light guide, except for an angular offset caused by refraction. As a result, certain beam angles are disproportionately present in the light guide, while others do not occur at all. Without sufficient mixing, it is not possible to irradiate the photoconductor uniformly with such a beam distribution.

Thus, homogenization of the light from the light source propagating in the light guide is generally ensured by "mixing" the directional distribution of the light in the mixing region of the light guide with an ideally slightly curved course over a length of at least 100mm, measured from the light entry surface. The mixing is promoted by total internal reflection at the walls of the light guide.

If the distance between the visible irradiation region of the light guide and the light entry face has to be selected to be significantly smaller than 100mm due to requirements such as, for example, requirements resulting from a lack of available structural space, the following measures are used in the known solutions: in DE102012106481, an additional disk with micro-optics is arranged between the light source and the light conductor. Furthermore, it is described in US2012/0314448 to couple in a light guide shaped as a cylindrical lens in order to parallelize the light in one dimension.

In the case of the light guides known from the prior art, very bright spots, so-called "hot spots", which alternate with darker spots, undesirably appear on the lens in the viewing direction. These hot spots are produced by imaging a separate, particularly bright prism on the light exit lens.

Disclosure of Invention

It is therefore desirable to provide a lighting device that overcomes the various disadvantages known in the prior art.

This is achieved by a lighting device according to the invention. In order to homogenize the angular distribution of the light propagating in the light guide, it is therefore provided according to the invention that optical structures are provided on at least one surface of the light incoupling region and on at least one deflection surface of the prism rib; and a variation of the geometric design of the prisms provided with the prism ribs in order to locally influence the brightness on the light exit surface of the light exit lens, such that at least two prisms of the prism ribs have a geometric design different from each other.

Thus, according to the invention, a combination of measures for homogenizing the angular distribution of the light propagating in the light guide and for locally influencing the brightness on the light exit surface of the light exit lens is proposed. This allows, on the one hand, the illumination of the light guide to be homogenized and, on the other hand, undesired hot spots on the light exit surface to be specifically reduced or completely avoided.

By means of the optical structure on at least one surface of the light incoupling region, the uniformity of the illumination of the light guide is improved already at the incoupling-side end and thus also when the light is incoupled into the light guide.

By means of the optical structure on at least one deflection surface of the prism rib, the uniformity of the illumination of the light guide is further improved when the light incident on the prism rib is diverted to the light exit lens.

Finally, the brightness on the light exit surface of the light exit lens is locally influenced by a change in the geometric design of the prisms of the prism ribs by a targeted change in the geometric design of the prisms of the prism ribs.

By combining the measures mentioned, advantageously no or only a small region in the light guide is required for mixing. The invention represents a possibility of achieving, in the initial region of the first end of the light guide body, in the ideal case already at the time of light incidence, homogenization and thus mixing of the light beam in the light guide body and thus uniform illumination of the light guide body from the beginning, i.e. of the light exit lens directly after the light incoupling region.

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 optical waveguide from the first end to the second end. Thus, illumination of the light exit lens can be performed next to the light incoupling area.

The illumination device according to the invention is therefore particularly suitable as an illumination device in which the visible illumination surface of the light guide should start immediately after the light is incident into the light guide and/or in which only a few light-emitting diodes should be used as light sources, i.e. as an illumination device with a small space requirement.

According to one embodiment, it is provided that the optical structures in the light coupling-in region of the optical waveguide are formed on a light entry surface of the optical waveguide, which is located at the first end of the optical waveguide, transversely to the front side and transversely to the rear side, and/or the optical structures are formed on at least one deflection surface of the prism rib as scattering structures and/or extinction structures. Broadening of the beam profile emitted from the light source is achieved by optical structures on the light entrance surface. In particular, a flattening of the inherent lambertian emission characteristics of the LED can thereby be achieved. The widening can take place in one spatial direction, for example by means of scattering structures in the form of cylindrical structures. The widening can also take place in two spatial directions, for example by means of a light-extinction structure or a scattering structure in the form of a pillow structure. Since the illumination of the light exit lens is influenced in particular by whether the light from the light entry surface is uniformly distributed onto the prisms of the prism rib, it is advantageous to widen the angular distribution of the existing light beam in the surface extending from the center of the prism rib to the center of the light exit lens.

What is achieved by the optical structure on the deflection surface is that the direction of the light beam deflected at the prism rib is modulated at the respective deflection surface of the respective prism. On the one hand, therefore, the imaging of the respective prism on the light exit lens becomes blurred and thus a more uniform illumination is achieved. On the other hand, a statistically uniform light distribution within the light guide body is facilitated. The shaping of the scattering structure can take place, for example, in the form of longitudinal grooves along the elongate shape of the light conductor.

As an alternative or complement to the optical structure on the light entry surface of the light guide body located transversely to the front side and transversely to the rear side at the first end of the light guide body, it may be provided that the lighting device has a light incoupling contour which is arranged between the light source and the light entry surface of the light guide body located transversely to the front side and transversely to the rear side at the first end of the light guide body and which has a light incoupling surface on the light source side and a light outcoupling surface facing the light guide body, wherein the optical structure in the light incoupling region of the light guide body is formed on the light incoupling surface and/or the light outcoupling surface of the light incoupling contour.

By means of the light coupling-in profile, the uniformity of the illumination of the light guide at its coupling-in side end can be improved by achieving a significantly more favorable beam profile and thus an essentially improved appearance, compared to the case of direct coupling-in into the light guide, i.e. no light coupling-in profile.

It can be advantageously provided that the light incoupling contour is arranged, in particular fastened, at the light guide.

In addition, in the illumination device according to the invention, in order to locally influence the brightness on the light exit surface of the light exit lens, in particular to avoid or reduce hot spots, a change in the geometric design of the prisms provided with the prism ribs is made. In this case, it may prove advantageous to provide a change in the geometric design in the initial region at the first end of the light guide in the case of one or more prisms of the prism rib. In this way, hot spots, which occur in particular in the initial region of the light guide body, can be reduced or avoided if complete mixing has not been achieved by the measures set for homogenizing the angular distribution of the light propagating in the light guide body.

According to an advantageous embodiment, the variation of the geometric design comprises a convex and/or concave curvature of the deflection surface of the at least one prism. Thereby, the area where the light is deflected by the prism is widened and causes local defocusing. This results in a reduced brightness of the prism image on the light exit lens and a less bright image, especially viewed from the main focus direction of the photoconductor. In principle, the deflection surface may be convexly or concavely curved. For manufacturing reasons, a convex curvature may be more advantageous.

According to another advantageous embodiment, the variation of the geometric design of the prisms comprises a variation of the depth of at least one prism. Since the local brightness at the light exit lens of the light guide is determined by the amount of light falling on the respective prism, the brightness can be influenced locally by changing the depth of the prism rib. Prisms with a smaller depth are more exposed to light propagating in the light guide than prisms with a larger depth. Thus, more light is deflected from a prism having a smaller depth onto the light exit lens than a prism having a larger depth. Thus, especially when the statistically uniform distribution of the propagating light in the light conductor is not optimal, hot spots on the light exit lens can be reduced by increasing the depth of the respective prism. At the transition between smaller and larger depths, mutual shadowing of the prisms should be avoided as much as possible during the arrangement.

According to another advantageous embodiment, the change in geometrical design comprises a change in height of the at least one prism. In principle, the use of a prism with a larger height may widen the vertical focus of the light distribution compared to a prism with a smaller height. The undesired hot spots on the light exit lens typically have an at least approximately trapezoidal shape. By targeted local adaptation of the height of the prisms, the trapezoidal side surfaces can be flattened. For this reason, the prism that appears too small in the imaging on the light exit lens is shaped lower than the prism that does not appear too small in the imaging on the light exit lens. Thereby, the focus is improved and the imaging is larger. Similarly, prisms that appear too large in imaging on the light exit lens are shaped larger. Thereby, defocusing is achieved and imaging of the prism on the light exit surface of the light exit lens becomes small.

According to a further advantageous embodiment, it is provided that a further optical structure is provided on the upper side and/or the lower side of the light guide body, which extends between the first end and the second end transversely to the front side and the rear side, and/or on the side of the light guide body, which is arranged in particular parallel to the light entry surface at the second end. The optical structure is designed, for example, as a scattering structure. The light propagating in the light guide body is advantageously reflected at the upper side and/or the lower side of the light guide body and/or at a side of the light guide body arranged at the second end. By means of the optical structure, a further mixing can be achieved upon reflection and thus contribute to a statistically uniform light distribution within the light guide. The coupling-out of light should be avoided as far as possible at the upper and/or lower side of the light guide and/or at the side of the light guide arranged at the second end. Therefore, the scattering structure should be shaped only slightly.

According to a further advantageous embodiment, an optical structure is provided on the surface of the light exit lens. The optical structure is designed, for example, as a scattering structure, in particular corrugated. The light can be scattered out of the main focus direction using scattering structures. Thus, the light exit lens appears less bright as viewed from the main focus direction. Thus, undesired hot spots on the light exit lens may be avoided or reduced. However, optical structures on the light exit lens sometimes adversely affect the appearance and/or efficiency of the lighting device. It may therefore prove advantageous to arrange at least one further optical element behind the light guide, which further optical element at least partially obscures the field of view of the light exit lens. In addition, it may prove advantageous if the optical structure on the light exit lens is arranged only in an initial region at the first end of the light conductor. In this case, it can further be provided that the surface of the light exit lens, starting from the optical structure, gradually changes to a smooth surface without optical structures.

The measures described can advantageously be combined with one another in any desired manner. The lighting device according to the invention is preferably used, for example, for implementing a signaling light function by means of a light guide in a headlight or a tail light.

Another embodiment relates to a light guide according to the invention for a lighting device according to the embodiment.

According to the invention, it is provided that, for homogenizing the angular distribution of the light propagating in the light guide body, optical structures are arranged on at least one surface of the light coupling-in region and on at least one deflection surface of the prism rib; and a variation of the geometric design of the prisms provided with the prism ribs in order to locally influence the brightness on the light exit surface of the light exit lens, such that at least two prisms of the prism ribs have a geometric design different from each other.

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

Drawings

Further advantages are given from the description and the drawings. Embodiments of the invention are illustrated in the drawings and are described in more detail in the following description. The same reference numbers in different figures denote identical or at least functionally comparable elements, respectively, here. In describing a single figure, reference may also be made to elements in other figures as necessary. The figures are shown in schematic form:

fig. 1a and 1b schematically show a light guide known from the prior art;

fig. 2 shows the technical environment of the invention in the form of a lighting device for a motor vehicle according to one embodiment;

fig. 3 shows a section of a light guide according to a first embodiment of the invention;

fig. 4 shows a side view of a light guide according to a first embodiment of the invention;

fig. 5 shows a section of a light guide according to a further embodiment of the invention;

fig. 6 shows a light guide according to the invention in a plan view according to a further embodiment;

fig. 7 shows a section of a light guide according to a further embodiment of the invention;

fig. 8 shows a side view of a light guide according to another embodiment of the invention;

fig. 9 shows a side view of a light guide according to another embodiment of the invention;

fig. 10 shows a light guide according to the invention in a plan view according to a further embodiment;

fig. 11 shows a side view of a light guide body according to another embodiment of the invention;

fig. 12 shows a rear view of a light guide body according to another embodiment of the present invention;

fig. 13a shows the light distribution of a light guide known from the prior art;

fig. 13b shows the light distribution of a light guide body according to the invention;

fig. 14 shows a side view of a light guide body according to another embodiment of the invention; and

fig. 15a, 15b and 15c show different views of a light guide according to a further embodiment of the invention.

Detailed Description

Fig. 1a and 1b schematically show a light guide 10 known from the prior art. Fig. 1a shows a light guide 10 in a cross-sectional view. Fig. 1b shows the light guide 10 in a plan view. Light emitted by light source 12 is coupled into light guide 10 via coupling-in surface E of light guide 10. At the prism rib P, light incident on the prism rib P is deflected. Light exits the light guide 10 in a main emission direction 14 through a light exit lens L. The mixing region D is schematically shown in top view after the coupling-in surface E. No outcoupling has occurred in this region. Therefore, the prism rib P is not mounted in this region. In mixing region D, the mixing of the directional distribution of the light and thus the homogenization of the light propagating in light guide 10 is to be achieved by total reflection.

The illumination device according to the invention and the light guide according to the invention are described below with reference to fig. 2 to 15.

In detail, fig. 2 shows a lighting device 20 for a motor vehicle. The lighting device 20 has a housing 22 and a transparent cover 24, the transparent cover 24 covering the light exit opening of the housing 22. In the interior of the housing 22 there is a motor vehicle lamp which emits light in a regular signal light distribution for the motor vehicle lamp. The main emission direction of motor vehicle lamps is usually parallel to the longitudinal axis of the motor vehicle in which the lighting device and the motor vehicle lamp are used as intended.

For example, a regular signal light distribution is characterized by reaching a predetermined minimum brightness value in the horizontal direction H and in the vertical direction V at a predetermined distance in front of the motor vehicle lamp, wherein these directions are each defined as an angular deviation from the main emission direction.

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

The lighting device 20 has a light source 26 in the form of a light-emitting diode or a device composed of a plurality of light-emitting diodes and a light guide 28, the light guide 28 being fed with light 30 of the light source 26. Light conductor 28 has an elongated shape and extends between a first end 32 and a second end 34 of light conductor 28, in particular along a curve L curved in space. The illustrated light guide 28 is thus an elongated rod-shaped light guide which is curved in accordance with the curve L, but may also run straight. Curve L therefore also corresponds to the main light propagation direction of the light of light source 26 in light conductor 28. An elongated shape is understood to be a shape having a length that is at least 5 times greater than the width and height.

In the exemplary embodiment shown, light source 26 is arranged at a first end 32 of light guide body 18 in such a way that light 20 emitted therefrom is incident into light guide body 28 via a light coupling-in region 36 arranged at first end 32 transversely to length L. A part of light 30 undergoes total internal reflection at the boundary surface of light conductor 28 surrounding light conductor 28 and is thereby transmitted in the interior of light conductor 28 in a propagation direction that is scattered around curve L.

Light conductor 28 has a rear side 38, at which rear side 38 prism ribs 40 are arranged. In addition, a light exit lens 44 is provided at the front side 42 of the light guide. A portion of the light 20 undergoes total internal reflection at the prism ribs 40. The prism ribs 40 are arranged to deflect the light incident thereon so steeply to the light exit lens 44 that it exits there from the light exit lens 44.

Fig. 2 shows a section of an elongated light guide 28 in an oblique view, having a preferred cross-sectional shape, which is oriented perpendicular to the course of the light guide 28. The prism rib 40 at 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 deflecting surface 48.

In the x-direction, the cross section of the light guide preferably widens continuously to the height of the light exit lens 44. Thereby, the opening angle of light propagating in the x-z plane in light conductor 28 is reduced. The light exit lens 44 preferably has a convex shape as shown. The light exit lens 44 forms a converging lens in its convex shape. The focal length of the light exit lens 44 is preferably matched to the distance of the prism rib 40 from the light exit lens 44 and to the height of the prisms 46 of the prism rib 40 in such a way that the height of the prisms is optically increased to the height of the light exit lens 44 for the observer. This helps to obtain a desired uniform brightness over the height of the light exit lens 44.

In light guide body 28 according to the present invention, measures are provided for homogenizing the illumination of light guide body 28 and for specifically reducing or completely avoiding undesired hot spots on the light exit surface of the light exit lens.

These measures are explained below.

In order to homogenize the angular distribution of light 30 propagating in light guide body 28, an optical structure 50 is provided on at least one surface of light incoupling region 36.

According to one specific embodiment, optical structure 50 in light coupling region 36 of light guide 28 is arranged on a light entry surface 52 of light guide 28, which is located at first end 32 of light guide 28, transversely to front side 42 and transversely to rear side 38. This is illustrated in fig. 4 and 5 by way of example. The optical structure 50 is designed, for example, as a scattering structure and/or an extinction structure.

Broadening of the beam profile emitted from the light source 26 is achieved by the optical structure 50 on the light entrance surface 52. In particular, a flattening of the inherent lambertian emission characteristics of the LED can thereby be achieved. The widening can take place in one spatial direction, for example by means of scattering structures in the form of cylindrical structures. The widening can also take place in two spatial directions, for example by means of a light-extinction structure or a scattering structure in the form of a pillow structure. Since the illumination of the light exit lens 44 is influenced in particular by whether the light from the light entry surface 52 is uniformly distributed onto the prisms 46 of the prism rib 40, it is advantageous to widen the angular distribution of the existing light beam in the surface extending from the center of the prism rib 40 to the center of the light exit lens 44.

Fig. 4 shows a side view of light conductor 28 on light entry surface 52. An optical structure 50, which is composed of a section of a roll for scattering light incident on the light incidence surface, is schematically arranged on the light incidence surface 52. The optical structures can also be configured as sections of pellets or pillows.

Fig. 5 shows a section of light conductor 28 on light entry surface 52 in an oblique view.

The light entry surface 52 has an optical structure in the form of a cylindrical light entry optic 54. The respective light incidence optics 54 may, for example, be assigned to the respective LEDs of the light source 26. Two light entry optics 54 are illustratively shown. However, additional light entry optics 54 may also be provided.

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

According to the embodiment shown, the light incoupling contour 56 is fastened to the light guide 28. For this purpose, the light incoupling profile 56 has a collar 62 which projects beyond the light outcoupling surface 60 in the light propagation direction, which collar 62 surrounds the first end 32 of the light conductor 28 at least partially in a form-fitting and force-fitting manner. In the illustrated embodiment, collar 62 is also connected to light guide 28 by means of pins 64. Pin 64 projects through collar 62, i.e. through the side wall of light incoupling profile 56, into light guide 28.

The collar 62 is preferably interrupted in the region of the light exit lens 44 and/or the prism rib 44, and differently from the illustration in fig. 2.

According to the embodiment shown, the light of the light source 26 is not coupled directly from the light source 26 into the light guide 28, but rather is first coupled into a light incoupling contour 56, which light incoupling contour 56 is fastened to the light guide 28. The light incoupling profile 56 has a contact sub-region 66 and a light infeed sub-region 68. The basic idea here is that light emitted from the light source 26 is guided in a controlled manner to the light out-coupling surface 60 of the light in-coupling contour 56 and is scattered there.

The light outcoupling surface 60 of the light incoupling profile 56 is arranged opposite to the light entrance surface 52 of the light guide body 28. One of the last-mentioned two

surfaces

60, 52 is provided with an optical structure 50. The other of the two

surfaces

60, 52 is a smooth surface.

The optical structure 50 in one embodiment consists of pellets, sections of a roll or sections of a pillow.

Here, the contact region 66 of the light incoupling contour is shaped such that it at least partially surrounds the first end 32 of the light guide body 28 and can therefore be fastened thereto, for example by means of pins 64, which pins 64 project through the collar 62 and into recesses/holes in the light guide body 28 matching therewith.

The light feed sub-region 68 has a cross section 70 transverse to the main propagation direction of the light source 26 coupled into the light feed sub-region 68. These cross sections 70 become monotonically larger with increasing distance from the light incoupling surface 58.

As a result, a significantly more favorable light distribution and thus a fundamentally improved appearance are achieved by the light incoupling contour 56 in the light guide 28 and in particular for the illumination thereof at the first end 32 thereof, compared to the case of direct incoupling into the light guide 28.

According to the embodiment shown in fig. 4 to 6, the optical structures 50 in the light coupling-in region 36 of the light guide body 28 are formed on the light coupling-in surface 58 and/or the light coupling-out surface 60 of the light coupling contour 56.

By means of optical structures 50 on at least one surface of light coupling-in region 36, the illumination uniformity of light guide body 28 is already improved at coupling-in-side end 32 and thus also when light 30 is coupled into light guide body 28.

Furthermore, in order to homogenize the angular distribution of light 30 propagating in light guide body 28, an optical structure 50 is provided on at least one deflection surface 48 of prism rib 40. What is achieved by the optical structures 50 on the deflection surfaces 48 is that the direction of the light beam deflected at the prism rib 40 is modulated at the respective deflection surface 48 of the individual prism 46. Thus, on the one hand, the imaging of the respective prism 46 on the light exit lens 44 becomes blurred and thus a more uniform illumination is achieved. On the other hand, it contributes to forming a statistically uniform light distribution in light guide body 28. The shaping of the optical structure 50 may take place, for example, in the form of longitudinal grooves 72 along the elongate shape of the optical conductor. This is shown by way of example in fig. 7.

Fig. 7 shows an oblique view of the deflection surface 48 of the prism 46. A longitudinal groove 72 is provided on the deflecting surface 48. The improved illumination of the light exit lens 44 of the light guide 18 thus determined and mentioned above results from the fact that: longitudinal grooves 72 also scatter light incident thereon in the z-direction of light conductor 28, whereby the brightness inhomogeneities of the light incident on deflection surface 48, which existed before the light was incident on deflection surface 48, become blurred.

The prisms 46 on the prism ribs 40 may directly abut each other or be separated by surface sections between the prisms 46. The surfaces between the individual prisms 46 are preferably also provided with longitudinal grooves 72. In fig. 5, an embodiment is shown in which the prisms 46 on the prism rib 40 are separated by surface sections between the prisms. Light impinging on the surface sections between the prisms is not outcoupled but continues to be totally internally reflected. The surface sections advantageously become smaller and smaller in area towards the second end 34 of the light guide 28. This makes it possible to achieve that not too much light is coupled out of light guide 28 at the beginning of light guide 28. Meanwhile, the area of prism 46 becomes larger toward second end 34 along the route of light guide body 28. This is advantageous again because less light is available in light guide 28 towards second end 34, so a similar, almost uniform brightness can still be achieved along the course of light guide 28. When the grooves shown in fig. 7 also extend over the surface sections shown in fig. 5 between the prisms, the angular distribution of the light in light guide body 28 is thereby homogenized.

The optical structures 50 on the prismatic ribs 40 may also include a different design than that shown in fig. 7.

In addition, in light guide body 28 according to the present invention, in order to locally influence the brightness on the light exit surface of light exit lens 44, there is a change in the geometric design of prism 46 provided with prism rib 40. Here, at least two prisms 46 of the prism rib 40 have a different geometric design from each other.

By varying the geometric design of the prism 48, the brightness at the light exit surface of the light exit lens 44 is locally influenced by a targeted change of the geometric design of the prism 46. Thus, homogenization along light guide body 28 can be achieved.

Variations in the geometric design of the prisms 46 include, for example, the convex and/or concave curvature 74 of the deflection surface 48 of at least one, preferably cylindrical, prism 46. This is shown by way of example in fig. 8. Thereby, the surface through which the light is deflected by the prism 46 is widened. This causes local defocusing. This results in a reduced brightness of the image of prism 46 on light exit lens 44 and a less bright image, especially viewed from the main focus direction of light guide body 28. In principle, the deflection surface 48 may be convexly or concavely curved. The convex curvature 74 may be more advantageous for manufacturing reasons. In fig. 8, the curvature 74 is schematically illustrated in terms of a circle of radius r. The radius r is typically 5mm to 15 mm.

Variations in the geometric design of the prisms 46 include, for example, variations in the depth of at least one prism 46. This is illustrated by way of example in fig. 9 and 10. Since the local brightness at light exit lens 44 of light guide 28 is determined by the amount of light falling on the corresponding prism 46, the brightness can be locally influenced by changing the depth of prism rib 40. Prisms 46 having a smaller depth are more exposed to light propagating in light guide body 28 than prisms 46 having a larger depth. Therefore, more light is deflected onto the light exit lens 44 from the prism 46 having the smaller depth than the prism 46 having the larger depth. Thus, particularly when the statistically uniform distribution of the propagating light in light conductor 28 is not optimal, hot spots on light exit lens 44 may be reduced by increasing the depth of the respective prism 46. At the transition between smaller and larger depths, mutual shadowing of the prisms 46 should be avoided as much as possible during the arrangement. According to the embodiment shown in fig. 9 and 10, modulation is performed between the first depth T1 and the second depth T2 to make the corresponding area on the light exit lens 44 brighter or darker. Typical values for the depths T1 and T2 are in the range of 0mm to 5 mm.

The variation in the geometric design of the prisms 46 includes, for example, a variation in the height of at least one prism 46. This is illustrated by way of example in fig. 11 and 12. In principle, the use of prisms 46 having a greater height may broaden the vertical focus of the light distribution compared to prisms 46 having a smaller height. The undesired hot spots on the light exit lens 44 typically have an at least approximately trapezoidal shape. By targeted local adaptation of the height of the prisms 46, the trapezoidal shape of the side faces can be flattened. For this reason, the prisms 46 that appear too small in the imaging on the light exit lens are shaped lower than the prisms 46 that do not appear too small in the imaging on the light exit lens 44. Thereby, the focus is improved and the imaging is larger. Similarly, prisms 46 that appear too large in the image on light exit lens 44 are shaped larger. Thereby, defocusing is achieved and imaging becomes small. According to the embodiment shown in fig. 11 and 12, modulation is performed between a first height H1 and a second depth H2. Typical values for heights H1 and H2 are in the range of about 0.5mm to 2mm wide.

Fig. 13a schematically shows the light distribution of a light guide with an undesired hot spot 76. Fig. 13b schematically shows a light distribution, wherein undesired hot spots can be avoided by the measures described.

Although the individual measures are illustrated in the individual figures, the subject of the invention is a light guide 28 which comprises at least the following measures: the optical structure 50 is arranged on at least one surface of the light incoupling region 36 and on at least one deflection surface 46 of the prism rib 40, and is provided with a variation of the geometric design of the prisms 46 of the prism rib 40, so that at least two prisms 46 of the prism rib 44 have a different geometric design from each other.

By combining the measures mentioned, advantageously no or only a small region in the light conductor 28 is required for mixing. The present invention represents a possibility of achieving, in the initial region of first end 32 of light guide body 28, in the ideal case already at the time of light incidence, homogenization and thus mixing of the light beams in light guide body 28 and thus uniform illumination of light guide body 28 from the outset, i.e. illumination of light exit lens 44 directly after light incoupling region 36.

According to one specific embodiment, light exit lens 44, in particular the light exit surface of light exit lens 44, extends over the entire length of light guide body 28 from first end 32 to second end 34. Therefore, illumination of the light exit lens 44 can be performed next to the light incoupling region 36.

The illumination device 20 according to the invention is therefore particularly suitable as an illumination device 20 in which the visible illumination surface of the light guide 28 should start immediately after the light is incident into the light guide 28 and/or in which only a few light-emitting diodes should be used as light sources 26, i.e. as an illumination device 20 with a small space requirement.

Advantageously, further measures can be provided in the case of light conductors 28.

According to the embodiment shown in fig. 14, it is provided that a further optical structure 50 is provided on an upper side 78 and/or a lower side 80 of light guide body 28, which extends between first end 32 and second end 34 transversely to front side 42 and rear side 38. The optical structure 50 is configured, for example, as a preferably corrugated scattering structure. The light propagating in the light guide body 28 is advantageously reflected at the upper and/or

lower sides

78, 80 of the light guide body. By means of optical structure 50, a further mixing can be achieved upon reflection and thus contribute to a statistically uniform light distribution within light conductor 28. Light is to be prevented from being coupled out as far as possible at the upper and/or

lower sides

78, 80 of the light guide 28. Therefore, the scattering structure should be shaped only slightly.

These scattering structures allow light to be scattered in a targeted manner within light guide body 28 and in the course thereof, in order to obtain a statistically uniform light distribution within light guide body 28. Here, these scattering structures can be introduced on the

surfaces

78 and 80 in full length or in segments. The scattering structure 50 is preferably formed with a constant curvature and particularly preferably undulated. The scattering structures may grow out of the cross-section of light conductor 28 or sink into light conductor 28. The transition along the light guide body 28 between the section without scattering structures and the section with scattering structures is also designed with a constant curvature.

According to the embodiments shown in fig. 15a, 15b and 15c, an optical structure 50 is also provided on the surface of the light exit lens 44. The optical structure 50 is, for example, a wave-shaped scattering structure. The light can be scattered out of the main focus direction using scattering structures. Therefore, the light exit lens 44 appears less bright as viewed from the main focusing direction. Thus, undesired hot spots on the light exit lens 44 may be avoided or reduced. The optical structure 50 on the light exit lens 44 can sometimes adversely affect the appearance and/or efficiency of the illumination device 20. It may therefore prove advantageous to arrange at least one further optical element behind the light guide, which further optical element obscures the field of view of the light exit lens 44. In addition, it may prove advantageous for the optical structures on the light exit lens 44 to be arranged only in the initial region at the first end 32 of the light conductor body 28. In this case, it can further be provided that the surface of the light exit lens 44, starting from the optical structure 50, gradually changes to a smooth surface without optical structures. Fig. 15a shows a sectional view at a section a in the region of first end 32 of light conductor 28. Fig. 15B shows a cross-sectional view B. The transition region 82 between section a and section B is typically 50mm to 100mm long.

The scattering structures on the surface of light exit lens 44 in fig. 15b are suitable for influencing and obtaining a statistically uniform light distribution along the course of light guide 28, but also act on the light coupled out by prism 46, which limits the use of these structures. The scattering structure 50 is preferably formed with a constant curvature and particularly preferably undulated. The scattering structures may grow out of the cross-section of light conductor 28 or sink into light conductor 28. The transition along the light guide body 28 between the section without scattering structures and the section with scattering structures is also designed with a constant curvature. Likewise, transition region 82 may also be formed on the light exit side of light guide body 28. Alternatively, a light extinction structure may be used.

In principle, all described optical structures 50 can be designed as scattering structures and/or extinction structures. In principle, similar optical results can be obtained using a light-extinction structure, as with a specially designed scattering structure. Often in the case of a light extinction structure, the light loss is higher than in the case of a scattering structure, and therefore the overall efficiency is lower.

Claims

1. A lighting device (20) having a light guide body (28) and a light source (26) for feeding light into the light guide body (28) through a light incoupling region (36) of the light guide body (28), wherein the light guide body (28) has an elongated shape running between a first end (32) and a second end (34), the elongated shape having a front side (42) and a rear side (38), the front side (42) having a light exit lens (44), the rear side (38) having a prism rib (40), wherein the prism rib (40) is arranged to deflect incoming light to the light exit lens (44) such that the light exits the light guide body (28) through the light exit lens (44), characterized in that, for homogenizing an angular distribution of the light propagating in the light guide body (28), at least one surface of the light incoupling region (36) and at least one deflection surface (48) of the prism rib (40) is arranged Having an optical structure (50); and a variation of the geometric design of the prisms (46) provided with the prism ribs (40) in order to locally influence the brightness on the light exit surface of the light exit lens (44), such that at least two prisms (46) of the prism ribs (40) have a geometric design different from each other.

2. The lighting device (20) according to claim 1, wherein 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 conductor (28) from the first end (32) to the second end (34).

3. Illumination device (20) according to claim 1 or 2, characterized in that the optical structure (50) in the light incoupling region (36) of the light conductor (28) is formed on a light incidence surface of the light conductor (28) at the first end (32) of the light conductor (28) transversely to the front side (42) and transversely to the rear side (38) and/or as a scattering structure and/or a light extinction structure on the at least one deflection surface (48) of the prism rib (40).

4. A lighting device (20) as claimed in claim 1 or 2, characterized in that the lighting device (20) has a light incoupling contour (56), the light incoupling contour (56) being arranged between the light source (26) and a light entry surface (52) of the light guide body (28) at the first end (32) of the light guide body (28) transversely to the front side (42) and transversely to the rear side (38), and the light incoupling contour (52) having a light source-side light incoupling surface (58) and a light outcoupling surface (60) facing the light guide body (28), wherein the optical structures (50) in the light incoupling region (36) of the light guide body (28) are formed on the light incoupling surface (58) and/or the light outcoupling surface (60) of the light incoupling contour (56).

5. The lighting device (20) according to claim 4, characterized in that the light incoupling profile (56) is arranged at the light conductor (28), in particular fastened at the light conductor (28).

6. The illumination device (20) according to claim 1 or 2, characterized in that the change in geometrical design comprises a convex and/or concave curvature (74) of the deflection surface (48) of the at least one prism (46).

7. The lighting device (20) according to claim 1 or 2, wherein the variation in the geometric design of the prisms (46) comprises a variation in the depth of at least one prism (46).

8. The lighting device (20) according to claim 1 or 2, wherein the change in geometric design comprises a change in height of at least one prism (46).

9. The illumination device (20) according to claim 1 or 2, characterized in that a further optical structure is provided on an upper and/or lower side (78, 80) of the light guide extending transversely to the front side (42) and the rear side (38) between the first end (32) and the second end (34) and/or on a side of the light guide (28) arranged at the second end (34), in particular parallel to the light entry surface.

10. The lighting device (20) according to claim 1 or 2, characterized in that an optical structure is provided on the surface of the light exit lens (44).

11. Light conductor (28) for a lighting device (20) according to one of claims 1 to 10, wherein the light conductor (28) has an elongated shape running between a first end (32) and a second end (34), the shape having a front side (42) and a back side (38), the front side (42) having a light exit lens (44), the back side (38) having prism ribs (40), wherein the prism ribs (40) are arranged to deflect incident light to the light exit lens (44), so that light exits the light guide (28) through the light exit lens (44), characterized in that, in order to homogenize the angular distribution of the light propagating in said light-guide body (28), -providing an optical structure (50) on at least one surface of the light incoupling region (36) and on at least one deflection surface (48) of the prism rib (40); and a variation of the geometric design of the prisms (46) provided with the prism ribs (40) in order to locally influence the brightness on the light exit surface of the light exit lens (44), such that at least two prisms (46) of the prism ribs (40) have a geometric design different from each other.

12. Light guide (28) according to claim 11, characterised in that the light guide (28) has a light incoupling profile (56), the light incoupling profile (56) being arranged at a light entry surface (52) of the light guide (28) at the first end (32) of the light guide (28) transversely to the front side (42) and transversely to the rear side (38), and the light incoupling profile (52) having a light source-side light incoupling surface (58) and a light outcoupling surface (60) facing the light guide (28), wherein the optical structures (50) in the light incoupling region (36) of the light guide (28) are formed on the light incoupling surface (58) and/or the light outcoupling surface (60) of the light incoupling profile (56).