arrangement for light emission

Abstract

arrangement for light emission with • a light guide (10) extending along a first direction (L), which has a first side (15) and a second side (20) opposite the first side (15), · an LED light source (50) which is arranged at an end region (11) of the light guide (10) facing the first side (15), such that an end region (16) of the first side (15) forms a light entry surface for the light emitted by the LED light source (50), wherein the second side (20) in the end region (11) of the light guide (10) has a non-planar configuration such that light rays entering via the light entry surface are totally reflected at the second side (20), and wherein the arrangement for light emission has several light guides (10) which extend in different directions from a common intersection point (5), wherein the LED light source (50) is arranged at the intersection point (5), characterized by that a partially reflective hollow body (30) is arranged at the common intersection (5) of the light guides (10), wherein light rays emitted from the LED light source (50) first enter the hollow body (30) and, after leaving the hollow body (30), are coupled into the light guides (10) via its circumferential wall (31).

Description

[0001] The present invention relates to an arrangement for light emission, which has a light guide extending along a first direction and an associated LED light source, the light of which is coupled into the light guide.

[0002] Optical fibers are typically used in lighting technology when light needs to be emitted as uniformly as possible over a larger area compared to the surface of the actual light source. The optical fibers used are usually plate-shaped, with light emission occurring from one or possibly both sides of the fiber. Light is coupled in, however, usually via a narrow side of the optical fiber, with the light sources positioned to the side of the fiber. While elongated light sources in the form of fluorescent lamps or gas discharge lamps were used in the past, LED-based light sources are now commonly employed. For example, elongated LED boards are positioned to the side of a plate-shaped optical fiber instead of fluorescent lamps.

[0003] This lateral coupling of light, i.e., via a surface that is essentially perpendicular to the light-emitting surface of the optical fiber, generally represents the most efficient solution for coupling light into an optical fiber and then emitting it as uniformly as possible across its beam surface. However, in certain situations, such an arrangement of the light sources is not possible. This can be the case, for example, if the optical fiber is not to be laterally framed by other components or if a lateral arrangement of the light sources is actually impossible due to the design of the optical fiber.

[0004] US 2013 / 0 163 283 A1 shows an LCD backlight in which light is coupled into grid-like arranged, rod-like light guides by means of total internal reflection on a non-planar surface.

[0005] The CN 1 02 261 602 A and CN 1 03 486 494 A also show grid-like arranged, rod-like light guides with similar coupling by means of total internal reflection of light from LEDs.

[0006] The present invention is therefore based on the objective of providing a way to achieve the most uniform possible light emission via a light guide, even in the situations described above.

[0007] The problem is solved by a light-emitting arrangement having the features of claim 1. Advantageous embodiments of the invention are the subject of the dependent claims.

[0008] The solution according to the invention is particularly suitable for use with elongated or rod-shaped optical fibers. However, the concept can also be applied to plate-shaped optical fibers. It is provided that an LED light source is arranged on one side of the optical fiber, more precisely at a corresponding end region of the optical fiber facing the first side, so that this first side forms a light-entry surface for the light emitted by the LED light source in the end region of the optical fiber. A second side of the optical fiber, opposite the first side, is then designed in the end region such that it has a non-planar configuration, such that light rays entering via the light-entry surface are totally reflected at this non-planar area.

[0009] Previously, there was often a risk that when light was coupled in via one side of the light guide, a large portion of the light would exit the light guide again in the area opposite the coupling point on the other side, and consequently this area of ​​the light guide would appear significantly brighter than other areas. However, according to the invention, by designing the light guide to achieve total internal reflection of the light rays, the light is influenced in such a way that it can be distributed more efficiently and thus more uniformly across the entire light guide. Despite the less than optimal positioning of the LED light source, this achieves a coupling efficiency into the light guide that is approximately equivalent to the coupling efficiency achieved with an end-face or side-mounted arrangement of the LED(s).In particular, this also prevents those areas of the light guide in which the light sources are positioned from appearing as clearly perceptible brighter areas.

[0010] According to the invention, an arrangement for light emission is proposed which has a light guide extending along a first direction, which has a first side and a second side opposite the first side, wherein furthermore an LED light source is provided which is arranged at an end region of the light guide facing the first side, so that the first side in the end region forms a light entry surface for the light emitted by the LED light source, and wherein the second side in the end region of the light guide has a non-planar configuration such that light rays entering via the light entry surface are totally reflected.The arrangement for light emission has several light guides which extend in different directions from a common intersection point, wherein the LED light source is arranged at the intersection point and wherein a partially reflective hollow body is arranged at the common intersection point of the light guides, wherein light rays emitted from the LED light source first enter the hollow body and, after leaving the hollow body, are coupled into the light guides via its circumferential wall.

[0011] The above-described measure according to the invention thus ensures that light rays coupled into the optical fiber do not immediately leave it again, but instead are distributed evenly over the optical fiber in a known manner due to total internal reflections.

[0012] The concept according to the invention utilizes rod-shaped optical fibers, and the arrangement comprises several optical fibers extending in different directions from a common intersection point. The light source is positioned at this intersection point, so that the light emitted by it is coupled essentially uniformly into all optical fibers and transmitted there in the manner described above. This allows for the assembly of a large number of such optical fibers into a grid-like or lattice-like structure. The advantages of the solution according to the invention are particularly evident here, since such a grid-like structure ideally requires a distributed positioning of the light sources, while the optical fiber grid should nevertheless appear as uniformly bright as possible.This objective can be achieved with the aid of the measures according to the invention, whereby in particular the LED light sources are not perceived as individual bright points. In the hollow body provided in the intersection area of ​​the light guides, which serves as a so-called mixing chamber, the rays emitted by the light source are first partially reflected before they leave the hollow body and are coupled into the light guide(s) in the manner described above.

[0013] This hollow body can be designed, for example, as a hemispherical or semi-spherical shape, and due to partial reflections of the light, it causes a certain mixing and thus a more uniform distribution of the light rays emitted by the LED light source before they finally enter the light guides. This has the advantageous effect of compensating for any color variations in the light emitted from the LED light source in different directions. This problem is well known, for example, with white LEDs, since the light rays emitted at a sharp angle usually have a slightly different hue than the light rays emitted directly in the direction of emission. The mixing chamber described above can compensate for this effect.

[0014] Because the light source is located at the end of the light guide, the light emitted from the second side has a certain preferred direction. To achieve a more uniform light emission, it is preferable for this second side to have at least a slight light-scattering effect. Appropriate light-scattering structures can therefore be provided on this surface, for example, by roughening the surface or by arranging suitable scattering structures such as prisms or the like.

[0015] To extract the light via the second side, a preferred embodiment provides that the first side adjacent to the light entry area has structures that are preferably oriented transversely to the longitudinal direction of the light guide and are particularly implemented in the form of flank sections oriented such that light rays are reflected at these flank sections, allowing the light to exit the light guide via the second side. Furthermore, the first side can also be configured such that a certain proportion of the light is emitted via the first side, so that this proportion can be used, for example, for indirect lighting or to create other lighting effects.

[0016] In the case of a grid-like arrangement of the light guides as described above, it is further possible that they do not run entirely in one plane, but instead are oriented at an angle to the main emission direction of the LED light source. This results in a wave-like structure, which gives the light guide arrangement a particularly appealing appearance, while still achieving very uniform light emission across the entire arrangement.

[0017] According to an unclaimed example, a light emission arrangement is proposed with rod-shaped light guides forming a grid-like light guide structure, and light sources arranged at the end faces of the light guides, the light from which is coupled into the light guides. Light coupling structures are provided on one side of the light guides opposite the side intended for light emission. In this example as well, a grid-like structure can be realized through which light is emitted in a substantially homogeneous manner.

[0018] The invention will now be explained in more detail with reference to the accompanying drawings. These show: Fig. 1 a view of a fiber optic arrangement according to the invention, in which the concept according to the invention is used for coupling light; Fig. 2 and Fig. 3 different perspective partial views of the light guide arrangement of Fig. 1; Fig. 4 a sectional view of a section of the fiber optic arrangement; Fig. 5 the cross-section of a rod-shaped light guide; Fig. 6 and Fig. 7. Descriptions of the mode of action of the various measures according to the invention Fig. 8 an advantageous further development of the area for light coupling and Fig. 9 and Fig. 10 views of an unclaimed example of a grid-like optical fiber arrangement.

[0019] Fig. Figure 1 shows a top view of a light guide arrangement 100 in which the concept of light coupling and light extraction according to the invention is used.

[0020] As in Fig. As shown in Figure 1, the optical fibers together form a lattice structure consisting of diagonally oriented individual optical fibers 10. The exact structure is shown in more detail in Figure 1. Fig. 2, Fig. 3 to Fig. 4 removable, each individual optical fiber 10 having an elongated shape, but being approximately wedge-shaped at both ends with a termination angle of 90°. This means that the individual optical fibers 10 can be assembled to form the grid-like structure, with four optical fibers 10 always joining together at the intersection points.

[0021] A special feature of the depicted optical fiber structure 100 is that the individual optical fibers 10 do not run in a common plane, but are instead inclined. This results in the wave-like three-dimensional structure visible in the figures, with first intersection points 5 arranged in a first, higher plane, and second intersection points 7 positioned alternately in a second, lower plane. LED light sources 50 are positioned at the center of each of the higher intersection points 5. These LED light sources can be LED boards with a single LED or, if applicable, an LED cluster. No further light sources are provided at the intersection points 7 of the lower plane.

[0022] In the illustrated light guide arrangement 100, light is coupled in evenly distributed across the entire arrangement; however, the coupling only occurs at specific points at the higher interfaces 5 of four adjacent light guides 10. Since, however, a uniform light emission, especially across the undersides of the individual light guides 10, is desired, and the occurrence of local high brightness in the area of ​​the intersection points 5, where the LED light sources 50 are positioned, is to be avoided, the individual light guides 10 are designed in a special way, as shown below, to achieve optimized light emission.

[0023] The inventive design of a single optical fiber 10 can be particularly illustrated by the sectional view of Fig. 5 can be taken from, with particular the end area facing the intersection or crossing point 5, where the LED light source 50 is positioned, being shown here.

[0024] Each individual light guide 10 is thus designed as shown in a rod-shaped form and extends along a longitudinal direction L, which encloses an angle of less than 90°, preferably in the range of about 75°, with the vertical main emission direction A of the LED light source 50, so that the inclined orientation of the light guide 10 shown here results, which ultimately leads to the above-mentioned wave-like three-dimensional structure of the overall arrangement 100.

[0025] The optical fiber 10 has an upper (flat) side 15 and an opposing lower (flat) side 20, which run essentially parallel to each other along the entire length of the optical fiber 10. However, in the end region 11 facing the LED light source 50, they are designed in a special way. For this purpose, the end region 16 of the upper surface 15 is slightly convex, so that, in conjunction with the end regions of the other optical fibers 10, a slight, approximately pyramid-shaped depression is formed at the joints, in which the LED light source 50 is positioned or protrudes. The surface of this end region 16 of the upper surface 15 is smooth and forms the entry surface for the light into the optical fiber 10. Light rays striking this surface 16 are intended to be refracted, if at all, but not reflected.In particular, it is provided that all light rays from the LED light source that strike this surface 16 can enter the light guide 10 almost unhindered.

[0026] A key function with regard to light coupling is fulfilled by the end region 21 of the underside 20, which is opposite the light coupling area 16. As can be seen, this end region is also convex, and its shape is chosen such that light rays entering via the light entry surface 16 are totally reflected at this curved end region 21 and therefore cannot exit the optical fiber 10 via this region 21. The immediate re-egress of such light rays has previously posed a significant problem when coupling light into an optical fiber via one side, as this led, on the one hand, to high local brightness and, on the other hand, to reduced efficiency in terms of light emission.However, the portion entering the optical fiber 10 is now at least once totally reflected at the surface 21 and thereby forwarded in the longitudinal direction L of the optical fiber 10, so that the rays can subsequently be distributed by further reflections until they are finally coupled out in the manner described in more detail below.

[0027] For light extraction, a structure 17 located on the upper surface 15 of the light guide 10, adjacent to the light entry area 16, is responsible. As can be seen, this structure 17 consists of triangular prism structures extending transversely to the longitudinal direction L. Each prism consists of a first, shorter flank 18 and a subsequent longer flank 19, which forms an angle of approximately 90° with the first flank 18, resulting in the recognizable sawtooth-like structure with successive right-angled triangles in cross-section. The angle enclosed between the longer flank 19 and the main emission direction A of the LED light source 50 is approximately 52°.

[0028] As demonstrated by the simulated ray path of Fig. As can be seen in Figure 6, light rays reflected from the underside 20, particularly in area 21, are primarily reflected at the longer inclined flanks 19, where they are deflected so that they can then exit the light guide 10 on the opposite underside 20. The inclination of the flanks 19 can be adjusted as desired so that the light exiting the underside is emitted within a specific preferred angular range. In particular, the angle can be chosen so that the emitted light is emitted at angles that do not cause glare for an observer of the arrangement. A symmetrical distribution is not strictly necessary, as the grid-like arrangement of the individual light guides 10 already results in an overall symmetrical light emission.In principle, however, the inclination angle for the light-emitting structures 17 on the upper surface 15 of the light guide 10 is preferably selected such that even an individual light guide achieves the most uniform light emission possible. As already mentioned, the concept according to the invention is not necessarily limited to the illustrated grid-like light guide structure, but can also be used with individual light guides in which light is coupled in only on one side.

[0029] Accordingly, a uniform light emission is also desirable in a transverse direction with respect to the light guide 10. It is therefore preferred that the surface 22 of the underside 20 of the light guide 10 adjoining the area responsible for total internal reflection 21 is designed to be slightly light-scattering. This also results in a symmetrical and thus uniform distribution of the light emission, as shown by the ray path of the Fig. 7 shows.

[0030] Ultimately, the interaction of three measures leads to a particularly optimized light coupling and emission despite the difficult conditions regarding light coupling. Firstly, the totally reflective end region 21 of the flat or underside 20 intended for light emission ensures efficient overall light coupling and prevents the occurrence of local brightnesses below the LED light sources 50.

[0031] With the help of the light extraction structures 17 provided on the top side, the light extraction can be carried out in the desired way without glare, whereby a uniform and homogeneous light emission is additionally achieved by the light-scattering property of the light emission surface 22 on the underside 20 of the light guide.

[0032] Another special feature of the invention is in Fig. Figure 8 shows the joint where the four rod-shaped light guides 10 meet. A hemispherical hollow body 30, serving as a mixing chamber, is now provided in this intersection area. Light from the LED light source 50 is first directed into this hollow body 30 and can be reflected once or possibly several times at its side walls 31 before exiting the hollow body 30 and being coupled into the light guides 10 as described above. The multiple reflections of the light beforehand compensate for any color differences between individual light rays and achieve a homogenization of the light.This problem is known with white LEDs, as light rays emitted at shallow angles often exhibit a slightly yellowish tint. Without additional measures, this could ultimately lead to the arrangement 100, or a surface illuminated by the arrangement 100, not appearing with the same hue or color temperature. However, with the help of the upstream mixing chamber 30, this effect can be eliminated, resulting in an even more uniform light output with respect to color and color temperature.

[0033] The Fig. 9 and Fig. Figure 10 finally shows an example of a fiber optic arrangement 200, which is not the subject of the claimed invention. Again, fiber optics are used as in the variant in Fig. 1 arranged in a grid-like manner, although no wave-like three-dimensional structure is provided, but rather all light guides 210 are arranged according to the representation of Fig. 10 extend in a plane.

[0034] In this case, as is already known, light coupling is provided at the end faces 211 of the elongated rod-like light guides 210, as shown in Fig. Figure 9 shows that the special measures regarding total internal reflection of incoming light rays in the end region, as described in the first embodiment, are therefore not required here, and the coupling of the light emitted by the light sources 250 is relatively straightforward. On the other hand, this has the disadvantage that light can only be coupled in within the circumference of the entire arrangement 200. Accordingly, care must be taken during light coupling to ensure that the coupling is as uniform as possible across the entire arrangement.

[0035] For this purpose, 200 are located on the top of the arrangement. Fig.Ten identifiable output coupling structures 220 are responsible for deflecting incident light rays in a known manner so that they can now exit the light guide arrangement 200 at its underside. By modifying the density or size of these output coupling structures 220 depending on their position within the overall structure 200, it can be taken into account that areas further away from the input regions can utilize fewer light rays for output coupling. Therefore, the density or size of the output coupling structures 220 is increased in these areas to compensate for the reduced amount of available light.

[0036] Even within this example, a grid-like light guide structure can be implemented, through which light is emitted as uniformly as possible. Nevertheless, the embodiment according to the invention offers certain advantages, since it allows the use of a greater number of light sources and, consequently, a larger quantity of light can be emitted overall, while maintaining high quality.

Claims

[1] Arrangement for light emission with • a light guide (10) extending along a first direction (L), which has a first side (15) and a second side (20) opposite the first side (15), · an LED light source (50) which is arranged at an end region (11) of the light guide (10) facing the first side (15), such that an end region (16) of the first side (15) forms a light entry surface for the light emitted by the LED light source (50), wherein the second side (20) in the end region (11) of the light guide (10) has a non-planar configuration such that light rays entering via the light entry surface are totally reflected at the second side (20), and wherein the arrangement for light emission has several light guides (10) which extend in different directions from a common intersection point (5), wherein the LED light source (50) is arranged at the intersection point (5), characterized by , that a partially reflective hollow body (30) is arranged at the common intersection (5) of the light guides (10), wherein light rays emitted from the LED light source (50) first enter the hollow body (30) and, after leaving the hollow body (30), are coupled into the light guides (10) via its circumferential wall (31). [2] Arrangement according to claim 1, characterized by , that the first side (15) adjacent to the light entry area has structures (17) for coupling out the light via the second side (20). [3] Arrangement according to claim 2, characterized by , that the structures (17) are aligned transversely to the longitudinal direction (L) of the optical fiber (10). [4] Arrangement according to claim 3, characterized by , that the structures (17) are formed by alternating inclined flanks (18, 19). [5] Arrangement according to any one of claims 2 to 4, characterized by , that the structures (17) enable the emission of part of the light via the first side (15) of the optical fiber. [6] Arrangement according to any one of the preceding claims, characterized by , that the second side (20) has a light-scattering structure in an area intended for light emission (22). [7] Arrangement according to any one of the preceding claims, characterized by that the light guide (10) is aligned at an angle other than 90°, preferably at an angle of about 75°, relative to a direction of emission (A) of the LED light source (50). [8] Arrangement according to any one of the preceding claims, characterized by , that the optical fibers (10) together form a grid-like structure. [9] Arrangement according to any one of the preceding claims, characterized by, that the hollow body (30) is approximately hemispherical in shape.

Images