Lighting device comprising multiple light sources and multiple light guide elements
The lighting device uses multiple recessed reflective surfaces in a light guide element to address inefficiencies and depth issues, ensuring effective light distribution and reduced glare in vehicle lighting systems.
Patent Information
- Authority / Receiving Office
- DE · DE
- Patent Type
- Patents
- Current Assignee / Owner
- MARELLI GERMANY GMBH
- Filing Date
- 2015-04-29
- Publication Date
- 2026-06-11
Smart Images
Figure 00000000_0000_ABST
Abstract
Description
[0001] The present invention relates to a lighting device comprising several light sources and several light guide elements. A plate-shaped light guide element is used in the lighting device of a motor vehicle. The light guide element comprises a light entry area through which light from a light source couples into the light guide element, a light exit area through which light couples out of the light guide element, and a reflection area that deflects the coupled-in light towards the light exit area.
[0002] Plate-shaped light guide elements in various embodiments are known from the prior art. For example, EP 2 778 512 A1 discloses a light guide element of the type mentioned above for use in a lighting device of a motor vehicle. When installed in the lighting device, the light guide element has a surface extending in the vertical direction and serves to generate a light distribution with a horizontal light-dark boundary, e.g., dipped beam or fog light, which complies with the legal requirements applicable in the respective country for the corresponding light distribution. The known light guide element has a light entry area in the form of a light entry surface with a substantially horizontal surface extension and a light exit area extending substantially perpendicular to it.Light coupled in through the light entry surface is reflected via a reflection zone towards the light exit zone. The reflection zone comprises a reflective surface formed by one or more interfaces of the optical fiber element. In a vertical section parallel to the surface area of the optical fiber element, the reflective surface has a slightly deviated shape from a parabola. This deviation of the reflective surface from a parabola achieves the desired vertical scattering of the reflected light. A lens element is arranged in the light exit zone, which causes horizontal scattering of the light exiting the optical fiber element.
[0003] A disadvantage of the known light guide element is the relatively small ratio of its height to its depth (length of the light-emitting area / length of the light-entry area), which means that for a given height, the light guide element requires a relatively large depth. Furthermore, the vertically oriented light-emitting area cannot be adequately adapted to the angled shape of a slanted lens in a vehicle lighting system. Such an angled shape is common, for example, in modern streamlined vehicles. In these cases, the lens can be recessed from a lower inner front edge of the lighting system (oriented towards the vehicle's longitudinal axis) either outwards (towards the vehicle's exterior) or upwards and rearwards (against the direction of travel and the direction of light emission).Adapting to the sloping shape of a cover plate is limited with the known light guide element to repositioning the light guide element in the lighting device, which, however, requires additional installation depth so that the front light exit area of the light guide element does not touch the cover plate at the top.
[0004] Furthermore, the lens element has a relatively large thickness (perpendicular to its surface area) in the light exit region and is therefore poorly suited for injection molding. Additionally, the efficiency of the known light guide element is not optimal.
[0005] Finally, the parabolic or parabolic-like reflective surface has a section located near the vertex of the parabola (the so-called no-TIR zone) where the light rays incident after coupling do not meet the condition for total internal reflection. To prevent the loss of light rays incident on this section, it can be coated with a reflective layer, but this entails additional manufacturing effort. Alternatively, it would be conceivable to rotate the entrance area, including the light source, around an imaginary horizontal axis (perpendicular to the surface area of the light guide element) in the direction of the light exit area, i.e., away from the no-TIR zone and into a light exit direction, until all coupled light rays meet the condition for total internal reflection upon striking the reflective surface.However, this has the disadvantage that either some of the coupled rays hit the light exit area directly, or the light guide element must have a very large installation depth.
[0006] US 2009 / 0091944A1 discloses a lighting device for motor vehicles, comprising an optical axis and at least one light source. A light guide is arranged between the light source and an exit surface.
[0007] US 2006 / 0268564A1 discloses a lighting device for a motor vehicle, comprising a light source and a light guide. Light rays emanating from the light source enter the light guide through an entry surface and propagate within the light guide, exiting it substantially parallel.
[0008] DE 10 2010 046 022 A1 relates to a motor vehicle lighting device with a light guide which has a light-guiding volume that lies between a light entry surface and a light exit surface of the light guide.
[0009] DE 102 31 326 A1 relates to a lighting unit for motor vehicles, comprising a plurality of lighting elements arranged at a distance from each other, each of which is assigned a light guide element.
[0010] DE 10 2011 000 038 A1 relates to a lighting device for vehicles with a planar light guide element, which has a light coupling surface for coupling in light, a light coupling surface for coupling out light and two opposite flat sides between which the coupled light is totally reflectable.
[0011] DE 10 2011 089 481 A1 discloses a motor vehicle lighting device with a long and flat luminous surface.
[0012] DE 10 2014 211 874 A1 relates to a lighting device for a motor vehicle. This device comprises a light source for emitting light and at least one plate-shaped light guide designed as a block optic. This light guide includes two opposing, spaced-apart interfaces, a totally reflective side surface formed between the interfaces, and a light-emitting surface also formed between the interfaces. A coupling section is formed on at least one of the interfaces. In addition to the at least one block optic, the lighting device has at least one substantially rod-shaped light guide with a light-emitting surface extending along the longitudinal extent of the light guide.
[0013] DE 10 2013 212 352 A1 discloses a motor vehicle lighting device with a coupling optic and a transport and forming optic.
[0014] Based on the prior art described above, the present invention aims to propose an alternative lighting device. In particular, the proposed lighting device is intended to overcome at least some of the disadvantages of the prior art mentioned above.
[0015] To solve this problem, it is proposed, starting from the lighting device of the type mentioned above, that the reflection area comprises several reflective surfaces, at least one of which is formed by a recess in the interior of the light guide element, wherein the reflective surfaces are designed and arranged taking into account the design and arrangement of the light entry and light exit areas of the light guide element such that, assuming a point light source, light coupled in via the light entry area, reflected at the reflective surfaces and exiting via the light exit area comprises light rays running parallel to each other.Through the recesses of the light guide elements and through channels of the light guide elements, which separate adjacent light emission surfaces of the light guide elements from each other, further light guides, electrical conductors and / or optical components of the lighting device run.
[0016] A lighting device with multiple light guide elements is proposed, arranged parallel to each other within the lighting device, employing plate-shaped light guide elements. Instead of a single, approximately parabolic reflective surface, a reflection area comprises several separate, spaced-apart parabolic or parabolic-like reflective surfaces, which together form the reflection area of the light guide element. This allows for a significant reduction in the depth of the light guide element. The reflective surfaces preferably have the same focal point and the same parabolic axis, or closely spaced parabolic axes, but different focal lengths. The reflective surfaces are preferably arranged such that all light rays originating from a light source and coupled in via the light entry area strike one of the reflective surfaces.
[0017] The reflective surfaces reflect the incident light rays by means of total internal reflection, preferably parallel to the parabolic axis. These reflective surfaces are formed by interfaces of recesses located within the optical fiber element. Each recess is bounded by an interface facing the light entry area and by further boundary surfaces.
[0018] The plate-shaped light guide element, in its operational state during intended use, is preferably positioned vertically within the housing of a motor vehicle lighting device. The light rays coupled out of the light guide element via the light output area serve, for example, to generate a dimmed light distribution with a horizontal cut-off line, such as a low beam or fog light, which meets the legal requirements for the respective light distribution in the respective country or region. One challenge, therefore, is ensuring that the light coupled out from the light output area, with its essentially vertical longitudinal extent, achieves the necessary horizontal dispersion to realize the desired light distribution and meet the corresponding legal requirements for luminous intensity distribution.A single light guide element can achieve the desired light distribution, or partial light distributions from several light guide elements according to the invention can complement or superimpose to create the desired light distribution. For example, it would be conceivable that a first light guide element could generate a focused low-beam spot in the center of the low beam, and another light guide element could generate a broadly diffused low-beam base light distribution.
[0019] According to an advantageous embodiment of the invention, it is proposed that the at least one recess is arranged and oriented in the light guide element such that each of the reflective surfaces reflects light from a defined angular range of a light beam coupled into the light guide element. Accordingly, the recesses, and thus the interfaces forming the reflective surfaces, are arranged such that all light rays coupled into the light guide element in a light beam with a specific opening angle strike one of the reflective surfaces. It is provided that each reflective surface receives light rays from a specific, defined angular range of the coupled light beam. If coupled light rays no longer strike a particular reflective surface but pass laterally by it, they strike an adjacent reflective surface.Preferably, none of the coupled light rays pass between two adjacent reflective surfaces and thus avoid being deflected towards the light emission area. Therefore, no coupled light rays are lost. The reflective surfaces are preferably designed and arranged in the light guide element such that as many, ideally all, coupled light rays as possible fulfill the condition for total internal reflection upon striking one of the reflective surfaces.
[0020] According to a preferred embodiment of the invention, it is proposed that the at least one recess be bounded not only by the interface but also by boundary surfaces that do not constitute the interface, and be arranged and oriented in the light guide element such that the light of the coupled light beam does not encounter boundary surfaces of the at least one recess on its way to the reflective surfaces. Otherwise, the light rays would be reflected from the boundary surfaces in undesired directions, where they could not contribute to generating the desired light distribution. This would result in low efficiency of the light guide element. Furthermore, uncontrolled reflected light rays could enter undesired areas of the light distribution, e.g., above the light-dark boundary, and cause glare for other road users.In this embodiment, the recesses in a vertical section parallel to the surface area of the plate-shaped light guide have, for example, a triangular shape, such that they each have two further boundary surfaces in addition to the interface surface. The interface surfaces of the recesses are preferably directed towards the light entry area or run obliquely to it. At least one of the boundary surfaces of a recess preferably runs parallel to the light rays passing by it, which were, for example, coupled into the light guide element via the entry area.
[0021] Furthermore, it is proposed that the at least one recess be bounded not only by the interface but also by boundary surfaces that do not constitute the interface, and be arranged and oriented in the light guide element such that the reflective surfaces reflect the light of the coupled light beam in such a way that it does not encounter a boundary surface of a recess on its way to the light exit area. According to this embodiment, the recesses in the vertical section parallel to the surface area of the plate-shaped light guide have, for example, a triangular shape, so that they each have two further boundary surfaces in addition to the interface. The interface surfaces of the recesses are preferably directed towards the light entry area or run obliquely to it. At least one of the boundary surfaces of a recess preferably runs parallel to the light rays passing by it, which, for example,were reflected by a neighboring reflective surface, which may be the boundary surface of a neighboring recess.
[0022] It is particularly preferred if the reflective surfaces, viewed in a vertical section through the light guide element, each form a segment of a parabolic or parabolic-like surface. The boundary surface of a recess forming one of the reflective surfaces is preferably curved in the direction of the recess in a parabolic segment or a parabolic-segment-like manner. Thus, instead of a single approximately parabolic reflective surface, the reflective area of the light guide element has several separate parabolic or parabolic-like segments as reflective surfaces. Assuming a point light source positioned exactly at the focal point of the reflective surfaces, parabolic reflective surfaces would deflect the incident light into parallel light rays, which, for example, run parallel to a parabolic axis.The light exiting the optical element's light-emitting surface would consist almost entirely of light rays that contribute to generating the dimmed light distribution, particularly the formation of the light-dark boundary. Virtually no light rays would be directed into an area above the light-dark boundary and cause glare for other road users.
[0023] This differs from a real light source with a finite extent of the light-emitting area (e.g., the filament of an incandescent lamp, the arc of a gas discharge lamp, the light-emitting chip area of an LED). Furthermore, the light-emitting area of a light guide element cannot be positioned exactly at the focal point, as this lies within the light guide element or on or near the light-entry surface. To ensure that as large a proportion as possible of the emitted light rays coupled into the light guide element contributes to generating the light distribution, while simultaneously minimizing the reflection of light rays into an area above a light-dark boundary of the light distribution, the reflective surfaces in this case are not perfectly parabolic but only approximately so.In the design of the light guide element, the deviations of the reflective surfaces from the parabolic shape can be determined and adjusted on a case-by-case basis, depending on the desired light distribution to be achieved.
[0024] In particular, it is proposed that the composite surface, viewed in a vertical section parallel to its extent, follows the shape of a parabola in a central section, has a flatter profile than the parabola in a section located near a vertex, and a steeper profile than the parabola in a section facing away from the vertex. Such a composite reflective surface offers a good compromise between maximizing efficiency on the one hand and minimizing the amount of light rays reflected into an undesired area of the light distribution, for example, an area above the light-dark boundary, on the other.According to the invention, a reflective surface designed in this way is subdivided into several internal reflective surfaces, at least one of which is formed by an interface that defines a recess inside the light guide element.
[0025] To ensure that, as far as possible, all light rays coupled into the light guide element via the light entry area fulfill the condition for total internal reflection upon striking one of the reflective surfaces, it is proposed that the light entry area have a light entry surface that is inclined when viewed in a vertical section through the light guide element. The light entry surface, together with the light source, is thus rotated about a horizontal imaginary axis (perpendicular to the surface area of the light guide element) in the direction of the light exit area until all coupled light rays fulfill the condition for total internal reflection upon striking the reflective surfaces. This prevents the formation of a no-TIR zone, such as that present in the light guide element known from EP 2 778 512 A1. Metallization of such no-TIR zones on the reflective surfaces can therefore be omitted.Furthermore, this can increase the efficiency of the light guide element.
[0026] According to another advantageous embodiment of the present invention, it is proposed that the light emission area comprises several separate light emission surfaces running parallel to one another when viewed in a vertical section through the light guide element parallel to the surface extent. Advantageously, the light emission surfaces are arranged offset from one another in the direction of light emission. In the vertically oriented light guide element, the upper light emission surfaces are preferably set back relative to the light emission surfaces arranged below them.
[0027] In this way, the light emission area can follow the angled contour of the vehicle's lighting system's cover lens. A light emission area of a light guide element that follows the angled contour of the cover lens allows the light guide element to be positioned close to the inside of the cover lens, thus particularly well meeting the requirements for the lateral visibility of the light emitted from the light guide element and its light emission surfaces. For certain lighting functions, the emitted light must be clearly visible not only against the direction of travel but also at relatively large angles from the side. Furthermore, positioning the light guide element closer to the inside of the cover lens reduces the overall depth of the lighting system in which the light guide element is located.
[0028] According to a preferred embodiment of the invention, it is proposed that adjacent light-emitting surfaces are separated from one another by channels leading outwards from one of the at least one recesses inside the light guide element in the direction of light emission. This measure significantly simplifies the manufacture of the light guide element. The channels between the light-emitting surfaces avoid edges that would have to be formed in a tool with a finite radius. Light rays striking these rounded edges would be deflected in undesirable directions, at best reducing efficiency and at worst causing glare for other road users.
[0029] According to another advantageous embodiment of the present invention, it is proposed that the light-emitting region, viewed in a section perpendicular to a vertical section (parallel to the surface extent) through the light guide element and parallel to a light emission direction, has an increasing thickness from the reflective surfaces to the light-emitting surfaces. This allows the light propagated from the reflective surfaces to the corresponding light-emitting surfaces to be focused in the aforementioned section plane. Thus, with a light guide element oriented vertically in the operating state, the horizontal scattering and therefore the width of the resulting light distribution can be varied or adjusted to desired values. The region of the light guide element from the light-intake area to the reflective surfaces preferably has a constant thickness.
[0030] Alternatively, it is also conceivable that the light guide element, viewed in a section perpendicular to a vertical section (parallel to the surface extent) through the light guide element and parallel to a light emission direction, exhibits an increasing thickness from the light entry area to the reflection area and / or from the reflection area to the light emission area. This allows the light to be focused in the aforementioned section plane even in these areas of increasing thickness.
[0031] The light guide element is used in a motor vehicle lighting system comprising a light source and the plate-shaped light guide element. It is proposed that the lighting system have multiple light sources and multiple light guide elements according to the invention, wherein the light guide elements are arranged parallel to each other in the lighting system. Preferably, at least one light source is always assigned to one of the light guide elements and couples light into the assigned light guide element. The various light guide elements of a lighting system can serve to implement light distributions for different lamp or headlight functions.Alternatively, several of the light guide elements can jointly generate a specific luminaire or headlight function by having the partial light distributions of the individual light guide elements complement or superimpose to form the resulting overall light distribution of the luminaire or headlight function.
[0032] Further features and advantages of the present invention are explained in more detail below with reference to the figures. They show: Fig. 1 a fiber optic element known from the prior art in a vertical section; Fig. 2 a light guide element according to the invention in a preferred embodiment in a vertical section; Fig. 3 the optical fiber element according to the invention made of Fig. 2 with enlarged light entry area and enlarged light exit area in the cutout; Fig. 4 the optical fiber element according to the invention made of Fig. 2 with exemplary drawn light ray paths; Fig. 5 the optical fiber element according to the invention made from the Fig. 2 and Fig. 4 in a perspective view; Fig. 6 a comparison of a known light guide element and a light guide element according to the invention, each in a top view with exemplary light ray paths shown; Fig. 7 a comparison of the luminous intensity profiles in a horizontal section at a vertical angle of zero degrees through the light distributions of a known light guide element and a light guide element according to the invention; Fig. 8 different views of a light guide element according to the invention in a further preferred embodiment; Fig. 9 the optical fiber element according to the invention made of Fig. 8 in a perspective view; Fig. 10 a vertical section through a reflector with a parabolic mirror surface and an exemplary arrangement of a light source; Fig. 11 a vertical section through the reflector made of Fig. 10 with two light sources arranged at an exemplary distance from the focal point; Fig. 12 a vertical section through a plate-shaped light guide element with a parabolic reflecting surface formed by a totally reflecting interface of the light guide element, with an exemplary arrangement of a light source; Fig. 13 a vertical section through a plate-shaped light guide element similar to the light guide element made of Fig. 12, wherein the reflecting surface has a shape that deviates from the parabolic shape; Fig. 14 a light guide element according to the invention in a further preferred embodiment in a vertical section; Fig. 15 two light guide elements arranged by way of example in a lighting device of a motor vehicle according to the invention; Fig. 16 the optical fiber element according to the invention made of Fig. 2 with exemplary drawn light ray paths and an imaginary division into areas a, b, c; Fig. 17a a perspective view of area b of the optical fiber element according to the invention; and Fig. 17b a longitudinal section through area b of the light guide element made of Fig. 17a.
[0033] In Fig. Figure 1 shows a light guide element known from the prior art. Such a light guide element is known, for example, from EP 2 778 512 A1. The light guide element as a whole is designated by reference numeral 1. It is plate-shaped and has in the Fig. The vertical section shown in Figure 1 (YZ plane) has a relatively large surface area. The light guide element 1 is intended for use in a motor vehicle lighting system. In its installed, operational state, it has a surface area in the vertical direction (YZ plane) and serves to generate a light distribution with a horizontal cut-off line, for example, low beam or fog light, which complies with the legal requirements applicable in the respective country for the corresponding light distribution.
[0034] The known optical fiber element 1 has on its underside a light-entry surface 2 oriented substantially horizontally (in the XZ plane) and a light-emission area 3 oriented substantially perpendicular to it (in the XY plane). Light coupled in via the light-entry surface 2 is reflected by a reflective surface 4 in the direction of the light-emission area 3. In the illustrated vertical section parallel to the surface area of the optical fiber element 1, the reflective surface 4 has a shape that deviates slightly from a parabola. This deviation of the reflective surface 4 from a parabola achieves the desired vertical scattering of the resulting light distribution. Preferably, the reflective surface 4 is shaped such that light rays emitted from a light source 10 with finite dimensions are reflected in the vertical section as parallel rays in the direction of the light-emission area 3.
[0035] The light source 10 preferably comprises one or more semiconductor light sources, in particular light-emitting diodes (LEDs). The LED 10 is preferably arranged with its light-emitting surface facing the light-entry surface 2, such that a main emission direction 11 of the LED 10 is substantially perpendicular to the light-entry surface 2.
[0036] In the light exit area 3 there is a lens element 5 (see figure). Fig. 6a) arranged to cause horizontal scattering of the light exiting the light guide element 1. The light exit area 3, or the lens element 5 provided therein, has a vertical extent (in the Y direction) of height h. The light entry surface 2 of the light guide element 1 has a length L in a light exit direction 6 (in the Z direction) that corresponds to the installation depth of the light guide element 1.
[0037] The disadvantages of the optical fiber element 1 known from the prior art are: - The ratio of height h to installation depth L is relatively small, which means that the light guide element 1 requires a relatively large installation depth L for a given height h. - The vertical light emission area 3 cannot be adequately adapted to the inclined cover lens of modern taillights or vehicle headlights and therefore must be moved further into the vehicle interior. This requires additional installation depth. - Fig. Figure 6a shows a top view of the light guide element 1. Fig. 1. The thickened area in the X-direction of lens element 5 at the light exit area 3 of the light guide element 1 is clearly visible. The focusing area of lens element 5 is so thick that it is very difficult to manufacture using an injection molding process. Finally, the efficiency of the known optical fiber element 1 is relatively poor. This results from the fact that the light rays 7 coupled into the optical fiber element 1 (cf. Fig. 1) Only a portion 4a of the reflective surface 4 fulfills the condition for total internal reflection and is totally reflected in the direction of the light exit area 3 (light rays 8). A portion of the coupled light rays 7 strikes another area 4b of the reflective surface 4, thereby violating the condition for total internal reflection. Therefore, these light rays are coupled out of the light guide element 1 as light rays 9 in an uncontrolled manner. This light cannot contribute to generating the desired light distribution of the light guide element 1 and is lost.
[0038] Area 4a of the reflective surface 4 is also referred to as the so-called TIR (Total Internal Reflection) zone, and area 4b as the No-TIR zone. The boundary between the two areas 4a and 4b is only valid for light rays directed towards the two lateral cover surfaces 1a and 1b (see figure). Fig. 6a) run parallel. As the angle of the rays to surfaces 1a, 1b increases, area 4a enlarges at the expense of 4b, since the angle of the rays to the normal of the reflecting surface increases. The two opposite lateral end faces 1a, 1b of the light guide element 1 are bounded by the parabolic or parabolic-like reflecting surface 4 and the two straight lines of the light entry surface 2 and the light exit area 3 or the lens element 5. The end faces 1a, 1b preferably run parallel to the Fig. 1 vertical section shown. Light rays that run parallel or at a small angle to these cover surfaces 1a, 1b may, upon striking the reflective surface 4, violate the condition for total internal reflection and emerge from the light guide element 1 undesirably and thus with loss of efficiency.
[0039] Since the axis of the parabola, its focal point (corresponding approximately to the location of the light-emitting surface of the LED 10), and the opening angle of the beam cone after refraction at the light-entry surface 2 are fixed, this deficiency cannot be easily remedied by changing the parabolic focal length of the reflecting surface 4 or by scaling it while preserving the angles. Instead, the horizontally oriented light-entry surface 2, along with the light source 10, must be rotated counterclockwise until the right edge ray of the light beam cone also meets the condition for total internal reflection. However, this results in light rays on the left side of the beam cone no longer striking the reflecting surface 4, but instead striking the vertically oriented, flat light-exit area 3 directly. Consequently, these rays exit the light guide element 1 in an incorrect or undesired direction and do not contribute to efficiency.
[0040] In Fig. Figure 2 shows a preferred embodiment of a light guide element 20 according to the invention. The light guide element 20 preferably consists of a transparent material, e.g., glass or plastic. In the light guide element 20, the reflection area comprises not just one, but several reflective surfaces 21, at least one of which is formed by a totally reflective interface that delimits a recess 22 inside the light guide element 20. In the illustrated embodiment, three recesses 22a to 22c are provided inside the light guide element 20, each having an interface 21a to 21c that delimits the recesses 22a to 22c. The reflective surface 21d is formed by an outer interface of the light guide element 20.
[0041] The reflective surfaces 21a to 21d are designed and arranged, taking into account the arrangement of a light entry area 23 and a light exit area 24 of the light guide element 20, such that, assuming a point light source 25, light coupled in via the light entry area 23, reflected at the reflective surfaces 21a to 21d and exited via the light exit area 24 are parallel light rays (cf. Fig. 4) includes.
[0042] The four reflective surfaces 21a to 21d are located in the Fig. The vertical section shown in Figure 2 is preferably parabolic. It preferably has the same focal point and the same parabolic axis (the dashed line indicating the axis on the underside of the light guide element 20, which passes approximately through the light source 25), but different focal lengths. The Fig. The recesses 22 shown in Figure 2 preferably have a triangular shape and are bounded by two boundary surfaces 27', 27'' in addition to a boundary surface 21a to 21c. Alternatively, the recesses 22 can also be located within the recesses shown in Figure 2. Fig. The triangles 21, 27', 27'' shown in the diagram are arranged in such a way that the reflective surfaces 21a - 21c remain unchanged. The light rays reflected from a reflective surface 21a, 21b, 21d do not strike any of the boundary surfaces 27b'', 27c'', 27a''. In particular, the light rays reflected from reflective surface 21d run parallel to the boundary surface 27a''. Likewise, the light rays reflected from reflective surface 21a run parallel to the boundary surface 27b'', and the light rays reflected from reflective surface 21b run parallel to the boundary surface 27c''. The reflective surfaces 21 are preferably designed and arranged in the light guide element 20 such that, if possible, all coupled light rays strike one of the reflective surfaces 21 and contribute to generating the desired light distribution.
[0043] In Fig. Figure 2 shows the position of a light cone emitted by the light source 25 and coupled in via the light entry area 23, indicated by a dashed line. A central ray 28a is perpendicular to a light entry surface of the light entry area 23 and thus also perpendicular to a light-emitting chip surface of a light source 25 designed as an LED. The central ray 28a is approximately coincident with the main emission direction of light from the chip surface of the LED 25. The marginal rays of the beam cone are designated with the reference symbol 28b. The opening angle of the beam cone corresponds to twice the critical angle for total internal reflection. The light entry surface 23, together with the light source 25, was rotated counterclockwise about an axis perpendicular to the plane of the drawing until total internal reflection occurs at the reflecting surface 21d for the right marginal ray 28b in the vertical section shown. An enlarged section showing the LED 25 is shown in Figure 2. Fig. 3b shown.
[0044] The light-entry surface 23, the reflection surfaces 21a, 21b, 21c, and 21d, and the light-emission surfaces 24a to 24d are all formed on one narrow side of the plate-shaped light guide element 20. The light guide element 20 can be used to generate any desired light distribution. The invention is not limited to vehicle functions that exhibit a light distribution with a light-dark boundary. By appropriately arranging the light source 25, any light distribution that occurs in vehicle lights can be generated. In the headlight area, for example, daytime running lights or turn signals can be generated; in the rear light area, for example, taillights, turn signals, brake lights, fog lights, or reversing lights can be generated. Therefore, the invention can generate all light distributions, even those with a very difficult-to-produce light-dark boundary.The light source 25 preferably does not illuminate in such a way that an edge of the luminous surface lies at the focal point and is thus sharply imaged. Rather, preferably the center of the luminous surface lies at the focal point, so that light is emitted above and below the vertical = 0° direction.
[0045] The flat vertical light emission surface in the state of the art (cf. Fig. 1) was in the Fig. In the embodiment of the invention shown in Figure 2, the light emission surfaces are divided into four flat surfaces 24a to 24d. These surfaces are stepped to the right, i.e., recessed, when viewed from bottom to top, allowing the light guide element 20 to adapt to an inclined cover plate of a lighting device. The light guide element 20 can be positioned closer to the inside of the cover plate. This improves the lateral visibility of the light emitted from the light guide element 20 and reduces the installation depth L.
[0046] Furthermore, the light-emitting surfaces 24a to 24d are not vertical, but rather at a small angle to the vertical 24'. In order for the light to assume precisely this desired direction 26 upon exiting the light guide element 20 after refraction at the slightly inclined light-emitting surfaces 24a to 24d, it must have a slight downward direction before refraction (in the light guide element 20) (cf. Fig. 3a using the example of light beam 29).
[0047] Boundary surfaces 30 between the individual light emission surfaces 24a to 24d run parallel to the light rays in the material, for example the light ray 29 in Fig. 3. This ensures that the emitted light rays 26 do not fall grazingly onto the boundary surfaces 30 and either re-enter the light guide element 20 (which would lead to a loss of efficiency) or are deflected by Fresnel reflection in a direction above the light-dark boundary (which would lead to glare for other road users).
[0048] Fig. Figure 4 shows the optical fiber element 20 according to the invention. Fig. Figure 2 shows exemplary light ray paths. The straight boundary surfaces 27', 27" of the three recesses 22a to 22c can have any orientation instead of being parallel to the light rays propagating in the light guide element 20, provided that they lie within the triangles of the recesses 22a to 22c shown.
[0049] Fig. Figure 5 shows a perspective view of the light guide element 20 according to the preferred embodiment of the Fig. 2, Fig. 3 to Fig. 4. The optical axis of the light guide element 20 is designated by the reference numeral 26. The axis 26 is not the parabolic axis.
[0050] The optical fiber element 20 according to the invention has, in particular, the following advantages over the known prior art: - In the prior art, the ratio of height h to installation depth L is approximately 10 / 12.5 = 0.8. However, the area of height h actually penetrated by light (area 4a of the reflective surface 4) is 5.5. Therefore, in the prior art, the effective ratio h / L is 5.5 / 12.5 = 0.44. In the optical fiber element 20 according to the embodiment of the invention, Fig. 2, Fig. 3, Fig. 4 to Fig. In 5, the corresponding ratio is approximately 0.85, since the light guide element 20 is completely irradiated over its entire height h. - In combination with the stepping of the light emission surfaces 24a to 24d following an inclined end plate of a lighting device, the light guide element 20 according to the invention results in a significant reduction in the installation depth L compared to the known light guide element 1. - From a comparison of Fig. 1 and Fig. 4 shows that in the optical fiber element 20 according to the invention, no light rays escape from the optical fiber element 20 in an undesired manner.
[0051] Fig. Figure 6a shows a light beam path through a light guide element 1 known from the prior art. Fig. Figure 6b shows the corresponding light beam path through a light guide element 20 according to the invention, as is used, for example, in the Fig. 2, Fig. 3, Fig. 4 to Fig. Figure 5 shows that in both cases, metallization or mirroring of specific areas (e.g., area 4b in Figure 5) was avoided. Fig. 1) The reflection surface 4 or the reflection surfaces 21 are omitted, since only the influence of a horizontal focusing of the light rays is to be considered here. In the case of the light guide element 1 known from the prior art made of Fig. 6a The light is guided, for example, through a square (e.g., 5 mm x 5 mm) light entry area 2 of the light guide element 1 and then strikes a beam-narrowing region (the lens element 5), which has a cross-sectional area of 5 mm x 20 mm at its widest point. A vertical section through the resulting light distribution exiting the known light guide element 1 at horizontal = 0° is shown in Fig. Figure 7a shows that approximately 83% of the luminous flux emitted by the light source 10 emerges from the light guide element 1.
[0052] Fig. Figure 6b shows the beam path of the optical fiber element 20 according to the invention. The light entry area 23 of the optical fiber element 20 has been reduced to 3 mm x 5 mm. In the direction of the light rays inside the optical fiber element 20, the cross-section increases to 5.5 mm x 5 mm. This results in an approximately identical beam narrowing as in the known optical fiber element 1. Fig. Figure 7b shows a vertical section through the light distribution emerging from this light guide element 20 at horizontal = 0°. The slight reduction in efficiency from 83% to 81% is caused by the reduction in the entrance area 23.
[0053] Fig. Figure 8 shows a further embodiment of a light guide element according to the invention in a side view or a vertical section ( Fig. 8a) as well as in a top view ( Fig. 8b). In the case of the light guide element 40 made of Fig. 8 the wall thickness increases within the dotted light emission area 41 (cf. Fig. 8b), so that the opening angle of a light beam passing through this area 41 after light exit under refraction compared to the embodiment from Fig. 5 is reduced. The thickening of the lens element 5 in the light exit area 3 of the light guide 1, which is present in the known light guide element 1, is thus avoided, so that the light guide element 20, 40 according to the invention is significantly better suited for production by injection molding. Fig. Figure 9 shows a perspective view of the light guide element 40. Fig. 8.
[0054] The light guide element 40 from the Fig. 8 and Fig. 9. The thickness of the optical fiber increases in the light exit area 41, which is only penetrated by light rays that are parallel when viewed in vertical section (see areas a in Fig. 16). This defines the direction (parallel to the light rays) in which the thickening should occur. The light guide thickening can additionally or alternatively also be located between the light entry area 23 and an area c (see Figure 16). Fig. 16) occur, in which light rays cross (see area b in Fig. 16). With reference to Fig. Therefore, thickening the optical fiber element 40 is only useful in areas a and b. Area c (see...) Fig. 16), where the light rays intersect (before and after reflection at the reflective surfaces 21), is not very suitable for thickening the light guide element 40, since there is no clear direction in which the thickening should occur, and light rays traveling at an angle to the thickening are subject to a (in this case undesirable) change in direction. The thickening must always be identical for adjacent light rays, otherwise the thickening will be perpendicular to the direction of light, leading to a change in the direction of the rays.
[0055] The large reflective light guide surfaces (cover surfaces 1a, 1b) are in this case - as can be seen from the Fig. 17a and Fig. 17b can be seen where the area b of a light guide element 40 is made of Fig. Figure 16 shows surfaces of revolution formed by rotating a cross-section around a plane passing through the light-emitting diode 25 and perpendicular to the drawing plane. Fig. 4 perpendicular rotation axis 31 can be generated. One can in the Fig. 17a, Fig. Figure 17b clearly shows the cover surfaces 1a, 1b diverging from the entrance surface 23. Area b seamlessly transitions into area c of the light guide element 40. Likewise, area c then seamlessly transitions into area a. Thus, areas a, b, c of the light guide element 40 are formed as a single piece.
[0056] The increase in thickness of the light guide element 40 can be seen in a horizontal section (see the Fig. 8b or Fig. 17) be designed to be straight or curved parallel to the direction of light. For example, it would be conceivable that the light emission areas 41 to the light emission surfaces 24a to 24d are arranged in the horizontal section instead of along straight lines (cf. Fig. 8b of the Fig. 17) thicken over hyperbolic side faces.
[0057] Different opening angles of the emitted light beam can be generated by the length of the region 41 in which the thickness increase takes place, and by the ratio of the thickness at the beginning and end of the thickness increase. Naturally, in addition to the thickness increase, a [missing information] can be [missing information] compared to the prior art. Fig. 1 (cf. lens element 5 in the light exit area) significantly reduced light exit area 24a to 24d are used.
[0058] In the preceding embodiments, the reflective surfaces 21 were always described as parabolic. However, parabolic reflective surfaces 21 only provide good results with theoretical point light sources 25. The following describes how the reflective surfaces 21 must be deformed when a real light source of finite size couples light into the light guide element 20, 40 and a predetermined light distribution is to be generated. This is based on an example restricting the description to light functions that have a sharp horizontal light-dark boundary, where no light is present above vertical = 0°, a great deal of light is present at vertical = 0°, and then less light is present as the angle decreases towards negative vertical angles.
[0059] Fig. Figure 10 shows a parabolic reflector 50 (in air) at whose focal point 51 lies an edge 52 of a light-emitting surface 53 of a semiconductor light source (light-emitting diode, LED) 54. The second edge 55 of the light-emitting surface 53 of the LED 54 lies outside the focal length of the parabolic reflecting surface 50, i.e., it is further away from a vertex 56 of the parabola 50. Furthermore, a parabolic axis is shown with a dashed line and labeled with the reference symbol 57. At two example points A and B on the parabola 50, the light rays emitted from the edges 52 and 55 of the light-emitting surface 50 of the LED 54 and the corresponding reflected light rays are shown. Light rays 58 originating from the edge 52 at the focal point 51 are reflected parallel to the parabolic axis 57 (light rays 59). When the parabolic axis 57 is directed towards the horizon, these light rays 59 illuminate the horizon.Light rays 60, originating from the other edge 55 of the light-emitting surface 53, are reflected below the horizon (light rays 61). The opening angle of the reflected light rays 59, 61 varies from point to point on the parabola 50. Since all points on the parabola project one edge 52 of the light-emitting surface 53 of the light source 54 onto the horizon, a sharp light-dark boundary is formed there. Due to the different opening angles of the reflected light beams, a sharp image is not produced from the second edge 55.
[0060] Fig. 11 shows the same parabolic reflector 50 as Fig. 10. In the case of an optical fiber, the light source 54 cannot be positioned directly at the focal point 51 due to the risk of heat damage, as this point is usually located in, on, or near the light-entry surface of the optical fiber. Instead, the light source 54 must be positioned as close as possible to the focal point 51 and thus to the light-entry surface below the parabolic axis 57. Fig. Figure 11 shows two possible positions for the arrangement of a light-emitting diode 54 on a light guide element. A first light-emitting diode 54.1 is positioned with an edge 52.1 of the light-emitting surface 53.1 on the extension of the light ray 58 from the focal point 51 to the reflector point B. Thus, a light ray emanating from this edge 52.1 is reflected horizontally at the reflector point B, parallel to the axis 57, and therefore contributes to the generation of the light-dark boundary (light ray 59). However, the same edge 52.1 is reflected upwards beyond the light-dark boundary at another reflector point A (light rays 74, 75), which leads to glare for other road users. Therefore, an arrangement of the light-emitting diode 54.1 at the position shown is not practical. Another light-emitting diode 54.2 is positioned with an edge 52.2 of a light-emitting surface 53.2 is arranged on an extension of the light ray 58 from the focal point 51 of the reflector 50 to the reflector point A. Thus, a light ray 58 originating from this edge 52.2 is reflected at reflector point A horizontally and parallel to the parabolic axis 57, thereby contributing to the formation of the light-dark boundary (light ray 59). However, the same edge 52.2 is reflected below the light-dark boundary at the other reflector point B (see light rays 76, 77) and therefore does not contribute to the formation of the light-dark boundary. Overall, it is therefore not possible to image a light-emitting diode 54, which is arranged below the parabolic axis 57, using a parabola 50 in such a way that, firstly, no glare occurs for other road users, and secondly, every point on the parabola contributes to the formation of the light-dark boundary.
[0061] Fig. Figure 12 shows a light guide element 70 with a horizontal light entry surface 72, a parabolic reflection surface 71, and a light exit surface 78 that is essentially perpendicular to the light entry surface 72. In this example, the entry surface 72 lies on an axis of the parabola 71. A focal point 73 of the parabola 71 is marked with a circle. The light-emitting surface 53 of a light-emitting diode is represented symbolically as a horizontal line and positioned such that the chip edge 52 closest to the parabola vertex 79 lies perpendicular to the light entry surface 72 and below the parabola's focal point 73. A vertical light ray 80 enters the light guide element 70 without changing direction and is reflected horizontally, i.e., parallel to the parabolic axis, since it passes through the focal point 73 (light ray 81). A light ray 82, which is in Fig. Light ray 82, originating from chip edge 52 and running to the left of the vertical, is refracted at the entrance surface 72, changes direction, strikes the reflecting surface 71 at reflector point A, and is reflected across the horizontal (light ray 83), causing glare for other road users. A point 84 below focal point 73 is also shown, indicating the apparent origin of light ray 82 when tracing it back after refraction.
[0062] For comparison, another theoretical light ray 85 is shown, which is reflected at the same point A as light ray 82 and travels without refraction at the entrance surface 72 (as in air). It is clearly visible that both light rays 82 and 85 are reflected across the horizontal (light rays 83 and 86), with the angle to the horizontal being significantly larger for light ray 83 than for light ray 86. The refraction at the entrance surface 72 therefore has a clearly negative effect on the direction of the rays.
[0063] Another light ray 87, which runs to the right of the vertical light ray 80, and a corresponding theoretical comparison ray 88 show the same result: Again, the light ray 87 refracted at the entrance surface 72 exhibits a significantly larger angle to the horizontal (this time below the horizontal) than the unrefracted comparison ray 88. Overall, this implies that the reflecting surface 71 in the light guide element 70 must deviate even more from a parabola than is expected by Fig. 11 is suggested in air if it is to generate horizontal light rays.
[0064] Fig. Figure 13 shows another light guide element 90 with a reflective surface 91 and a light-emitting diode 54, which is arranged relative to the light guide element 90 such that the light-emitting surface 53 is in the position as shown in Figure 13. Fig. As shown in Figure 12, the reflector is positioned as follows. In particular, the edge 52 closest to the reflector lies vertically below the focal point 73 of the dotted parabola 71. All light rays, shown as dashed lines, emanating from the edge 52 of the light-emitting surface 53 of the LED 54, propagate horizontally within the light guide element 90 after reflection at the varied reflective surface 91. Thus, the entire reflective surface 91 contributes to the formation of the luminous intensity maximum at 0° vertical. This cannot be improved further.
[0065] Light rays that do not originate from the chip edge 52, but from a point further to the right on the light-emitting surface 53, and that strike the same point on the reflective surface 91 like an edge ray, travel above the edge ray before reflection and therefore always below the edge ray after reflection. This creates an optimal light-dark boundary that cannot be further improved by varying the reflective surface 91. Below the light-dark boundary, the luminous intensity decreases continuously with increasing negative angle. The lower limit of the light distribution is defined by the largest existing helical images (images of the light-emitting surface 53).
[0066] The exact shape of the smooth reflective surface 91 can be calculated experimentally or using suitable simulation software. The varied surface 91 conforms to the parabola 71 above the chip edge 52. To the left of it (towards the vertex), the reflective surface 91 is flatter, and to the right (away from the vertex), it is steeper than the parabola 71. The position of the chip edge 52 below the parabola's focal point 73 is not mandatory but was chosen to illustrate the degree of curvature of the parabola 71. The parabola 71 is not required for the actual construction. Of course, the reflective surface 91 can also be calculated if the entrance surface 72 is shaped as shown in the Fig. 2, Fig. 3 to Fig. 4 shows that the reflecting surface 91 is inclined relative to the direction of radiation 6. Likewise, the reflecting surface 91 can be, as shown with Fig. 2 shown, can be decomposed into several reflection surfaces 21a to 21d and scaled, thus replacing the non-optimal parabola 71. Alternatively, the reflection surfaces 21a to 21d can also be used for each of the light emission areas 41 (see Figure 2). Fig. 8 and Fig. 9) be determined separately.
[0067] If the lower edge of the light distribution is to lie lower than the lower edge of the largest helical images (images of the light-emitting surface 53), it is necessary to partially deviate from the in Fig. The ideal reflection surface 91 shown in Figure 13 may deviate, which can lead to a slight reduction in the contrast of the light-dark boundary. Similarly, the light-exit surface 78 of the light guide element 90 can be deformed to lower the lower edge of the light distribution, which also results in a light-dark boundary with reduced contrast.
[0068] In the Fig. 10, Fig. 11, Fig. 12 to Fig. Figure 13 shows reflectors or light guide elements with a single reflective surface. This serves only to illustrate the shape of the reflective surface. This does not change the fact that, according to the invention, the reflective surface of the light guide element is divided into several surfaces, at least one of which is designed as an interface that defines a recess formed inside the light guide element. If the surface profiles of the various reflective surfaces of the light guide element according to the invention were placed side by side to form a single reflective surface, the reflective surface 91 of the light guide element 90 would preferably be obtained. Fig. 13.
[0069] Fig. Figure 14 shows a beam path through another embodiment of a light guide element 100 according to the invention. Just as in the embodiment of the Fig. 8 and Fig. 9 The reflective surfaces 21a to 21c define a recess 22a to 22c inside the light guide element 100. Additionally, the recesses 22a to 22c extend outwards in the light exit direction 6 via channels 101. This avoids edges 102 that would otherwise form between the four arms 41 of the light exit area due to the different thicknesses (see the areas 41 in Fig. 9) arise and must be executed in the tool with a finite radius. Light rays striking these rounded edges 102 would be deflected in undesired directions, leading at best to a loss of efficiency and at worst to glare for other road users.
[0070] In the described embodiments, four light-flooded branches 41 of the light-emitting area of the light guide elements 20, 40, 100 were always shown. Of course, it is also conceivable to implement fewer or more branches 41. Any number n of branches 41 is conceivable, where n > 2. The light-emitting surfaces 41a to 41d can be slightly rounded horizontally, which increases the homogeneity of the emitted light beam.
[0071] In a motor vehicle lighting device, which can be designed as a headlight or as a rear light of a motor vehicle, several identical or differently designed light guide elements 20, 40, 100 according to the invention can be arranged next to and / or above each other. Fig.Figure 15 shows an example of a lighting device 120 with two vertically oriented light guide elements 20, 40, 100 arranged side by side. Of course, the lighting device 120 can also have only one light guide element 20, 40, 100 or more than the two light guide elements 20, 40, 100 shown.
[0072] Each of the light guide elements 20, 40, 100 can generate a single light function, or several light guide elements 20, 40, 100 can work together to generate a specific light function of the lighting device 120. Additional rod-shaped or planar light guides, symbolically represented by planar or cylindrical elements 121, can be guided through the openings (recesses 22 and channels 101) in the light guide element 20, 40, 100. This can lead to increased design freedom. Care should be taken to ensure that the light guides passing through the openings 22, 101 do not touch the branches 41 of the light guide elements 20, 40, 100 to avoid disrupting the light transmission. The elements 121 could also represent electrical conductors or other optically effective elements of the vehicle lighting device that can be guided through the openings 22, 101.
Claims
[1] Lighting device (120) comprising several light sources (25) and several light guide elements (20, 40, 100), wherein the light guide elements (20, 40, 100) are arranged parallel to each other in their surface extent in the lighting device (120), wherein the light guide elements (20, 40, 100) are plate-shaped light guide elements (20, 40, 100) used in the lighting device (120) of a motor vehicle, each light guide element (20, 40, 100) comprising a light entry area (23) through which light from a light source (25) couples into the light guide element (20, 40, 100), a light exit area (24) through which light is coupled out of the light guide element (20, 40, 100), and a reflection area (21) of the coupled light in the direction of the light exit area (24) deflects, wherein the reflection area (21) comprises several reflection surfaces (21a, 21b, 21c, 21d), at least one of which is formed by a recess (22a, 22b,22c) a boundary surface (21a, 21b, 21c) is formed inside the light guide element (20, 40, 100), wherein the reflection surfaces (21a, 21b, 21c, 21d) are designed and arranged taking into account the design and arrangement of the light entry and light exit regions (23, 24) of the light guide element (20, 40, 100) such that, assuming a point light source (25), light coupled in via the light entry region (23), reflected at the reflection surfaces (21a, 21b, 21c, 21d) and exiting via the light exit region (24) comprises light rays running parallel to each other, wherein the recesses (22) of the light guide elements (20, 40, 100) and the channels (101) of the light guide elements (20, 40, 100), separating the adjacent light-emitting surfaces (24a, 24b; 24b, 24c; 24c, 24d) of the optical fiber elements (20, 40, 100) from each other, further optical fibers (121),electrical lines and / or optical components of the lighting device (120) run. [2] Lighting device (120) according to claim 1, characterized by , that the at least one recess (22a, 22b, 22c) is arranged and aligned in the light guide element (20, 40, 100) such that each of the reflective surfaces (21a, 21b, 21c, 21d) reflects light from a defined angular range of a light beam (28a, 28b) coupled into the light guide element (20, 40, 100). [3] Lighting device (120) according to claim 1 or 2, characterized by, that the at least one recess (22a, 22b, 22c) is bounded not only by the interface (21a, 21b, 21c) but also by boundary surfaces (27a', 27a''; 27b', 27b''; 27c', 27c'') which do not constitute the interface (21a, 21b, 21c) and is arranged and oriented in the light guide element (20, 40, 100) in such a way that the light of the coupled light beam (28a, 28b) on its way to the reflection surfaces (21a, 21b, 21c, 21d) does not encounter boundary surfaces (27a', 27a''; 27b', 27b''; 27c', 27c'') of the at least one recess (22a, 22b, 22c) hits. [4] Lighting device (120) according to one of claims 1 to 3, characterized by, that the at least one recess (22a, 22b, 22c) is bounded not only by the interface (21a, 21b, 21c) but also by boundary surfaces (27a', 27a''; 27b', 27b''; 27c', 27c'') which do not constitute the interface (21a, 21b, 21c) and is arranged and oriented in the light guide element (20, 40, 100) such that the reflective surfaces (21a, 21b, 21c, 21d) reflect the light of the coupled light beam (28a, 28b) in such a way that it does not strike a boundary surface (27a', 27a''; 27b', 27b''; 27c', 27c'') of a recess on its way to the light exit area (24). (22a, 22b, 22c) applies. [5] Lighting device (120) according to any one of claims 1 to 4, characterized by , that the reflective surfaces (21a, 21b, 21c, 21d) viewed in a vertical section through the light guide element (20, 40, 100) each form a section of a parabolic or parabolic-like surface. [6] Lighting device (120) according to claim 5, characterized by , that a surface (91) composed of the reflecting surfaces (21a, 21b, 21c, 21d) follows the course of a parabola (71) in a middle section, has a flatter course than the parabola (71) in a section located close to a vertex and has a steeper course than the parabola (71) in a section away from the vertex. [7] Lighting device (120) according to any one of claims 1 to 6, characterized by , that the light entry area (23) has a light entry surface that is inclined when viewed in a vertical section through the light guide element (20, 40, 100). [8] Lighting device (120) according to any one of claims 1 to 7, characterized by , that the light emission area (24) has several separate light emission surfaces (24a, 24b, 24c, 24d) which run parallel to each other when viewed in a vertical section through the light guide element (20, 40, 100). [9] Lighting device (120) according to claim 8, characterized by , that the light emission surfaces (24a, 24b, 24c, 24d) are arranged offset from each other in the direction of light emission (6). [10] Lighting device (120) according to claim 8 or 9, characterized by , that adjacent light emission surfaces (24a, 24b; 24b, 24c; 24c, 24d) are separated from each other by channels (101) which lead outwards from one of the at least one recess (22a, 22b, 22c) inside the light guide element (20, 40, 100) in the direction of light emission (6). [11] Lighting device (120) according to one of claims 8 to 10, characterized by , that the light exit area (24) in a section perpendicular to a vertical section through the light guide element (20, 40, 100) and parallel to a light exit direction (6) viewed from the reflection surfaces (21a, 21b, 21c, 21d) to the light exit surfaces (24a, 24b, 24c, 24d) has an increasing thickness. [12] Lighting device (120) according to any one of claims 1 to 10, characterized by , that the light guide element (20, 40, 100) in a section perpendicular to a vertical section through the light guide element (20, 40, 100) and parallel to a light exit direction (6) viewed from the light entry area (23) to the reflection area (21) and / or from the reflection area (21) to the light exit area (24) has an increasing thickness.