Light guide arrangement and motor vehicle lighting device with such a light guide arrangement

Abstract

Light guide arrangement (10) for use in a motor vehicle lighting device (1), comprising a planar light disk (11) made of a solid transparent material, with an upper cover surface (18, 20), a lower base surface (19, 21) parallel to the cover surface (18, 20), and an edge surface connecting the cover surface (18, 20) to the base surface (19, 21), wherein a portion of the edge surface is a light entry surface (13) of the light disk, through which light (14) can be coupled into the light disk (11), so that the light (16) propagates in the light disk (11) by means of total internal reflection at the cover surface (18, 20) and the base surface (19, 21) in a principal propagation direction (z), and at least portions of the cover surface (18, 20) and / or the base surface (19, 21) form a light exit surface (17) of the form a light disk (11) through which propagating light (24) in the light disk (11) exits the light disk (11),wherein the exit surface (17) is associated with coupling elements (22) which direct incident light rays (24) from the light disk (11) via the exit surface (17).

Description

The present invention relates to a light guide arrangement for use in a motor vehicle lighting system. A light guide arrangement according to the preamble of claim 1 is already known from JP H03-121 942 A. DE 10 2006 032 373 A1 discloses a motor vehicle rear light with a light source that emits light when switched on. The light can be coupled into a transparent light-guiding element. The light-guiding element comprises photometrically effective light-emitting surfaces and separate luminous, non-illuminating design surfaces. DE 10 2011 076 621 A1 discloses a lighting device for use in a motor vehicle. The lighting device comprises a light source for emitting light. A light guide element has a light entry surface for coupling in the emitted light. A light exit surface is provided for coupling out the coupled light. DE 10 2015 210 372 A1 discloses a signal light module for a motor vehicle, which has a light guide, a light source and a coupling optic. DE 10 2011 018 508 A1 relates to a light guide element arrangement for use in a light module of a motor vehicle lighting device. Furthermore, the invention relates to a motor vehicle lighting device comprising a housing with a light emission opening directed in the direction of light emission, which is closed by a transparent cover plate, and a lighting module arranged inside the housing for generating a predetermined lighting function, in particular a daytime running light or a flashing light. When designing headlights, lighting functions (e.g., turn signals, position lights, daytime running lights, taillights, brake lights, etc.) are usually considered design elements that, in addition to complying with the respective legal requirements, should also create a distinctive signature. This often leads to a desire for illuminated freeform surfaces. However, current technology generally requires that, for high-intensity lighting functions such as turn signals and daytime running lights, the design elements be separated from the optical components necessary to meet legal requirements.For the actual lighting function, reflectors, optics (transparent solid bodies with a light-entry surface, a light-emission surface, and interfaces in between, whereby light is focused by refraction at the entry and exit surfaces as well as by total internal reflection at the interfaces), light guides, or so-called slit lights (see, for example, US 2012 / 0075876A1) are usually used. In contrast, for illuminated freeform surfaces, concepts are employed that produce a less directional light distribution and are therefore best suited for low-intensity lighting functions, such as position lights or side marker lights, or as support for other functions. For this purpose, so-called light curtains or frosted panels are often used, which are either illuminated through or into which light is directly coupled. The present invention is based on the objective of realizing lighting functions with high optical efficiency from extended freeform surfaces. In this way, even high-intensity functions such as daytime running lights and flashing lights should be able to be implemented with acceptable electrical power consumption. To solve this problem, it is proposed, starting from the optical fiber arrangement of the type mentioned above, that an input coupling section of the optical disk, encompassing the light entry surface, is bent relative to the remaining part of the optical disk, which forms an output coupling section, by an angle (α) that is smaller than the critical angle of total internal reflection in the material of the optical disk, so that largely parallel light rays coupled into the input coupling section, which propagate parallel to the top and bottom surfaces of the input coupling section, meet the top or bottom surface of the output coupling section adjacent to the input coupling section over a length (l) in the main propagation direction, such that the output coupling elements have an extent (a) in the main propagation direction, such that there are as many output coupling elements arranged in the output coupling section asthat the sum of the extent of all coupling elements in the main propagation direction is greater than or equal to the length (l), wherein coupling elements which are downstream of other coupling elements in the main propagation direction are arranged such that they are not in the shadow of preceding coupling elements, and that the light coupled out of the light disk via the exit surface alone generates a luminaire function of the lighting device. Further preferred embodiments of the invention can be found in the dependent subclaims. One aspect of the present invention is the controlled coupling of largely parallel light beams into and out of a transparent disk whose main plane of extension is curved or domed and follows a freeform surface. When the light is coupled out, a light distribution in accordance with the legal requirements for the respective luminaire is to be achieved. The starting point for the light guide arrangement is a largely parallel beam of light, which can be generated, for example, by a front optic or a slit light and propagated in a transparent optical medium. According to an advantageous embodiment of the invention, it is proposed that the coupling elements are arranged on the base or top surface opposite the respective sub-areas and are designed such that the coupling elements deflect at least a portion of the incident light rays by means of total internal reflection in such a way that, upon striking the opposite top or base surface, the conditions for total internal reflection are no longer met for these light rays and they exit the light disk. Alternatively, it is also conceivable that the coupling elements are arranged in the sub-areas of the base or top surface forming the exit surface and are designed such that, at least for a portion of the incident light rays, the conditions for total internal reflection are no longer met and these light rays exit the light disk upon striking the coupling elements.The angle (α) by which the coupling section of the light disk is angled relative to the coupling section is preferably less than 45°, particularly preferably less than 10°. Further features and advantages of the present invention are explained in more detail below with reference to the figures. Figure 1 shows a motor vehicle lighting device according to a preferred embodiment; Figure 2 shows a light guide arrangement according to the invention, but without coupling elements; Figure 3 shows a light guide arrangement according to a first preferred embodiment; and Figure 4 shows a light guide arrangement according to a further preferred embodiment. Figure 1 shows a headlight 1 as an example of a lighting device according to the invention. This headlight primarily serves to generate a predetermined light distribution. The light distribution can be any headlight function, e.g., low beam, high beam, fog light, or any adaptive light distribution (e.g., partial high beam, marker light). In the case of so-called partial high beam, the vehicle, preferably outside built-up areas, drives with continuous high beam, whereby those areas of the light distribution in which other road users are located are isolated, shaded, or dimmed to prevent dazzling other road users. The other road users can be detected, for example, by means of a camera in the front area of ​​the vehicle. In the case of so-calledMarker lights are permanently activated with a dimmed light distribution and a horizontal light-dark boundary, whereby those areas above the light-dark boundary in which objects (pedestrians, cyclists, wild animals, etc.) have been detected are selectively illuminated in isolation to draw the driver's attention to these objects. The headlight 1 comprises a housing 2, preferably made of an opaque material, in particular plastic. The headlight 1 is arranged at an arbitrary location on the outside, preferably in the front area of ​​the vehicle, in a corresponding mounting opening. In a light emission direction 3, the housing 2 has a light emission opening 4, which is closed by a cover lens 5. The cover lens 5 preferably consists of a transparent material, e.g., glass or plastic. In this example, the cover lens 5 is designed without optically effective elements (e.g., prisms or cylindrical lenses). However, it would also be conceivable for the cover lens 5 to be provided with optically effective elements, at least in some areas. One or more light modules 6, shown here only schematically, are arranged at an arbitrary position inside the housing 2.These modules, either individually or together, serve to generate the light distribution of the headlight 1 or a part thereof. In addition to the light modules 6, a lighting module 7 is also arranged in the housing 2. This module is designed to implement any desired lighting function (e.g., turn signal, daytime running light, parking light, or position light) and is explained in more detail below. Of course, the lighting module 7 can also be arranged in the housing 2 of a lighting device 1 without one or more light modules 6. Furthermore, the lighting device 1 can also be designed as a vehicle light. The lighting module 7 comprises a light guide arrangement 10 according to the invention, as explained in more detail below with reference to Fig. 2, Fig. 3 to Fig. 4. The light guide arrangement 10 comprises a planar light disk 11 made of a solid transparent material, preferably plastic (e.g., PC or PMMA). Figures 2, 3 to 4 show a cross-sectional view of the light disk 11. The surface area of ​​the light disk 11 extends perpendicular to the plane of the drawing. The light disk 11 is divided into a light-input section 12, which includes a light-entry surface 13 through which largely parallel light 14 is coupled into the light disk 11, and a light-output section 15, in which the coupled light rays 16 propagate by means of total internal reflection at interfaces of the output section 15 and are coupled out of the light disk 11 via at least one light-exit surface 17. The coupling section 12 has an upper cover surface 18 and a lower base surface 19. Similarly, the coupling section 15 has an upper cover surface 20 and a lower base surface 21. The cover surfaces 18, 20 and the base surfaces 19, 21 of each section 12, 15 are parallel to each other and form interfaces of the light disk 11. A circumferential edge surface connects the interfaces 18-21. The light entry surface 13 of the coupling section 12 is part of the edge surface. The light exit surface 17 of the coupling section 15 is formed by one or more of the interfaces 20, 21. The coupling section 12 and the coupling section 15 each have a surface extent that is both perpendicular to the drawing plane and parallel to the interfaces 18-21. The exit surface 17 is associated with coupling elements 22, which couple incident light rays 23 out of the light disk 11 via the exit surface 17. The coupling elements 22 can be designed, for example, as prisms or wedges. The coupling elements 22 can be arranged on the interface 20, 21 opposite the exit surface 17 and be designed such that the coupling elements 22 deflect (reflect) at least a portion of the incident light rays 24 by means of total internal reflection, such that the conditions for total internal reflection are no longer met for these light rays 24 upon striking the opposite interface 20, 21, and they exit the light disk 11 as light rays 23. This is shown in Fig. 3.Alternatively, the output coupling elements 22 can be arranged on the interface 20, 21 forming the exit surface 17 and designed such that, at least for some of the light rays 24 incident on the output coupling elements 22, the conditions for total internal reflection are no longer met, and these light rays 24 exit the light disk 11 as light rays 23 upon striking the output coupling elements 22. This is shown in Fig. 4. According to the invention, the light disc 11 is specially designed to improve the efficiency of the extraction of light from the light disc 11, so that even high-intensity lighting functions (e.g. daytime running lights or flashing lights) can be generated solely by the light extracted from the light disc 11. In this sense, for example, the coupling section 12 and the coupling section 15, or rather their surface extensions, are inclined to each other at an angle α. Unlike what is usually done in optics, the angle α is not measured here with respect to the normal. The angle α is smaller than a critical angle for total internal reflection for the material used for the light disk 11. Preferably, the angle α is < 45°, and most preferably < 10°. The angle α between the coupling section 12 and the coupling section 15 of the light disk 11 results in largely parallel light rays 14 coupled into the coupling section 12, which propagate parallel to the top surface 18 and the bottom surface 19 of the coupling section 12, meeting the interface 20, 21 of the coupling section 15 adjacent to the coupling section 12 in the main propagation direction (in the z-direction) over a length l (see Fig. 2).In other words, l is the path along the light disk 11 after which a light ray again strikes the corresponding surface 20, 21. The coupling elements 22 have a dimension a in the main propagation direction z. In the coupling section 15, enough coupling elements 22 are arranged such that the sum of the dimensions a of all coupling elements 22 in the main propagation direction z is greater than or equal to the length l. Coupling elements 22 that are downstream of other coupling elements 22 in the main propagation direction z are arranged such that they are not in the shadow of preceding coupling elements 22. The light coupled out of the light disk 11 via the exit surface 17 alone generates the luminaire function of the lighting device 1. In the illustrated embodiment, the distance b between the cover surface 18 and the base surface 19 of the coupling section 12 of the light disk 11 is greater than the distance d between the cover surface 20 and the base surface 21 of the coupling section 15 of the light disk 11. A kink 25 runs between the cover surface 18 of the coupling section 12 and the cover surface 20 of the coupling section 15. Correspondingly, a kink 26 runs between the base surface 19 of the coupling section 12 and the base surface 21 of the coupling section 15. In particular, the light disk 11 is designed such that the distance b between the cover surface 18 and the base surface 19 of the coupling section 12 of the light disk 11 is selected such that the kink 25 of the cover surfaces 18, 20 is located exactly opposite halfway along the length l, i.e., at l / 2, on the base surface 21 of the coupling section 15. is arranged (see Fig. 1) The following relationships apply in the fiber optic arrangement 10: The coupling elements 22 are preferably all arranged either on the upper cover surface 20 or on the lower bottom surface 21 of the coupling section 15 of the light disk 11. It is conceivable that the coupling section 15 of the light disk 11 is curved, with a section of the cover surface 20 or the bottom surface 21 existing at each point of the curved coupling section, which runs along a straight line. In this case, the coupling section 15 would thus be curved about a straight line perpendicular to the plane of the drawing. To generate the parallel light 14 that enters the coupling section 12 of the light disk 11 via the light entry surface 13, the light guide arrangement 10 can include a focusing optical element (not shown) designed to largely collimate the light rays 14 emitted by at least one light source and coupled into the coupling section 12 of the light disk 11 via the light entry surface 13. The focusing element can be, for example, a front-mounted optic or a so-called slit light. A front-mounted optic is a transparent, solid body made of glass or plastic (e.g., PC or PMMA) with a light entry surface, a light exit surface, and interfaces in between, whereby the front-mounted optic achieves a focusing of light by refraction at the light entry and exit surfaces as well as by total internal reflection at the interfaces. A slit light is, for example,The focusing optical element is known from US 2012 / 0 075 876 ​​A1 and is described there in detail with regard to its structure and function. Reference is made to the corresponding passages of this publication. Preferably, the focusing optical element is formed in a component with the light disk 11. It is conceivable that the coupling elements 22 are oriented and / or shaped differently in order to specifically tailor the luminaire function with regard to legal requirements and customer-specific wishes. Furthermore, it is conceivable that coupling elements 22 located downstream of other coupling elements 22 in the main propagation direction are larger than preceding coupling elements 22. In this way, the downstream coupling element 22 can extend partially over a shaded area. In this case, it becomes more likely that the desired amount of light will still reach the coupling element 22 and be coupled out of the light disk 11, even with small angular deviations (e.g., due to non-parallel light 14; unevenness on the interfaces 20, 21; variation in the thicknesses b, d of the light disk 11, etc.). Finally, it is also conceivable that the coupling elements 22 are arranged in such a way that the light 23 coupled out by the coupling elements 22 selectively creates a luminous pattern. The cross-section of the light beam coupled into the coupling section 12, consisting of parallel light rays 14, has an extent b in a plane perpendicular to the top and bottom surfaces 18, 19 (corresponding to surfaces F1, F2 in Figs. 2-4). The rays 14 of the beam strike the interface F1 at an angle α, where they are reflected by total internal reflection. Due to the oblique angle α, the rays 14 of the beam strike surface F1 along a length l. The second interface F2 of the disk 11 begins (at the bend 25) at a distance l / 2 from the first point of impact of the beam (at the bend 26) along the z-direction at a distance d from surface F1. If the disk 11 is constructed as shown in Fig. 2-4, it is ensured that the initially parallel light rays 16 of the beam are guided between the two surfaces F1 and F2 by total internal reflection and that at each point on the surfaces F1 and F2 a light ray 16 falls on the surfaces at an angle α. Due to the extraction of light at the extraction elements 22, a light ray 16 no longer falls on surfaces F1 and F2 at every point along the further course of the light disk 11 (in the main propagation direction z). If an extraction element 22 has a dimension a along a main propagation direction z of the light disk 11 in the z-direction, the component a / l is missing from the light beam further along. If several extraction elements are now introduced along the longitudinal extent of the light disk 11 in the z-direction, the extraction elements 22 can extract the entire light beam in a controlled manner, as long as the total dimension of all extraction elements 22 in the z-direction is greater than or equal to the length l and the extraction elements 22 are not in the "shadow" of preceding extraction elements 22. Furthermore, it should be avoided that the extraction elements 22 are arranged at a distance l from each other or an integer multiple thereof, e.g., with respect tothe center of the coupling elements 22. The coupling elements 22 do not need to have a uniform size or a specific shape. They can be individually designed and arranged on one or both surfaces F1 and F2 to create the specified light distribution of the luminaire function. The coupling elements 22 can be distributed statistically across the disk 11 in virtually any way, provided that one coupling element 22 is not in the shadow of another. It is also conceivable that the coupling elements 22 or their reflective or refracting surfaces are oriented differently, so that a light distribution of the luminaire function is generated not only by the scattering of a single coupling element 22, but by the sum of the light coupled out by individual coupling elements 22. Slight deviations from the specified straight profile of the light disk 11 can, in principle, be tolerated. Thus, a differential dependency of surfaces F1 and F2 ensures that light strikes each point on surfaces F1 and F2 at a defined angle of incidence. At shallow impact angles α, high demands are placed on the quality of surfaces F1 and F2; therefore, strong variations in the layer thickness b, d of the disk 11 should be avoided if possible. To improve the tolerance situation in the light disk 11, the light rays 14 of the initially coupled light beam can also be slightly divergent. Furthermore, to improve the tolerance situation, the coupling elements 22 located further back in the beam path can be made larger than those located further forward. In this way, the coupling element 22 located further back can extend partially over shadowed areas onto which no light falls, since this light has already been coupled out of the light disk by preceding coupling elements. In this case, it becomes more likely that the desired amount of light will still reach the coupling element even with small angular deviations.

Claims

Light guide arrangement (10) for use in a motor vehicle lighting device (1), comprising a planar light disk (11) made of a solid transparent material, with an upper cover surface (18, 20), a lower base surface (19, 21) parallel to the cover surface (18, 20), and an edge surface connecting the cover surface (18, 20) to the base surface (19, 21), wherein a portion of the edge surface is a light entry surface (13) of the light disk, through which light (14) can be coupled into the light disk (11), so that the light (16) propagates in the light disk (11) by means of total internal reflection at the cover surface (18, 20) and the base surface (19, 21) in a principal propagation direction (z), and at least portions of the cover surface (18, 20) and / or the base surface (19, 21) form a light exit surface (17) of the form a light disk (11) through which propagating light (24) in the light disk (11) exits the light disk (11),wherein the exit surface (17) is associated with coupling elements (22) which couple incident light rays (24) out of the light disk (11) via the exit surface (17), and that the light (23) coupled out of the light disk (11) via the exit surface (22) alone generates a luminaire function of the lighting device (1), characterized in that an input coupling section (12) of the light disk (11) comprising the light input surface (13) is bent relative to the remaining part of the light disk (11), which forms an output coupling section (15) of the light disk (11), by an angle (α) that is smaller than the critical angle of total internal reflection in the material of the light disk (11), such that largely parallel light rays (16) coupled into the input coupling section (12), which are parallel to the top surface (18) and the bottom surface (19) of the input coupling section (12) in this propagatein the main propagation direction (z) over a length (l) onto the top surface (20) or bottom surface (21) of the output coupling section (15) adjacent to the coupling section (12), such that the output coupling elements (22) have an extent (a) in the main propagation direction (z), such that there are so many output coupling elements (22) arranged in the output coupling section (15) that the sum of the extent of all output coupling elements (22) in the main propagation direction (z) is greater than or equal to the length (l), wherein output coupling elements (22) that are downstream of other output coupling elements (22) in the main propagation direction (z) are arranged such that they are not in the shadow of preceding output coupling elements (22), and that a distance (b) between the top surface (18) and the bottom surface (19) of the coupling section (12) of the light disk (11) is greater than a distance (d) between the cover surface (20) and the base surface (21) of the coupling section (15) of the light disk (11)., Light guide arrangement (10) according to claim 1, characterized in that the coupling elements (22) are arranged on the bottom surface (21) or top surface (20) opposite the exit surface (17) and are designed such that the coupling elements (22) deflect at least a part of the incident light rays (24) by means of total internal reflection such that the conditions for total internal reflection are no longer met for these light rays (24) when they hit the opposite top surface (20) or bottom surface (21) and they exit the light disk (11). Light guide arrangement (10) according to claim 1, characterized in that the output coupling elements (22) are arranged on the exit surface (17) and are designed such that at least for a part of the light rays (24) incident on the output coupling elements (22) the conditions for total internal reflection are no longer met and these light rays (24) exit the light disk (11) when they incident on the output coupling elements (22). Optical fiber arrangement (10) according to one of claims 1 to 3, characterized in that the angle (α) is less than 45°, preferably less than 10°. Light guide arrangement (10) according to claim 1, characterized in that a bend (25, 26) runs between the cover surface (18) of the coupling section (12) and the cover surface (20) of the coupling section (15) and between the bottom surface (19) of the coupling section (12) and the bottom surface (21) of the coupling section (15), wherein the distance (b) between the cover surface (18) and the bottom surface (19) of the coupling section (12) of the light disk (11) is selected such that the bend (25) of the cover surfaces (18, 20) is arranged exactly opposite half the length (l) on the bottom surface (21) of the coupling section (15). Optical fiber arrangement (10) according to one of the preceding claims, characterized in that the following relationships apply in the optical fiber arrangement (10): b = 2 ⋅ d / cos ( α ) , 1 = 2 ⋅ d / tan ( α ) . Light guide arrangement (10) according to one of claims 1 to 6, characterized in that the coupling elements (22) are all arranged either on the upper cover surface (20) or on the lower bottom surface (21) of the coupling section (15) of the light disk (11). Light guide arrangement (10) according to one of claims 1 to 7, characterized in that the coupling section (15) of the light disk (11) is curved, wherein at each point of the curved coupling section (15) there exists a section of the top surface (20) or the bottom surface (21) which runs along a straight line. Light guide arrangement (10) according to one of claims 1 to 8, characterized in that the light guide arrangement (10) has a focusing optical element which is configured to largely collimate the light rays emitted by at least one light source and coupled into the coupling section (12) of the light disk (11) via the light entry surface (13). Light guide arrangement (10) according to claim 9, characterized in that the focusing optical element is formed in a component with the light disk (11). Optical fiber arrangement (10) according to one of claims 1 to 10, characterized in that the coupling elements (22) are designed as prisms or wedges. Light guide arrangement (10) according to one of claims 1 to 11, characterized in that the coupling elements (22) are oriented differently and / or shaped in order to specifically shape the lighting function with regard to legal requirements and customer-specific wishes. Optical fiber arrangement (10) according to one of claims 1 to 12, characterized in that coupling elements (22) which are arranged downstream of other coupling elements (22) in the main propagation direction (z) are larger than preceding coupling elements (22). Light guide arrangement (10) according to one of claims 1 to 13, characterized in that the coupling elements (22) are arranged such that the light coupled out by the coupling elements (22) selectively produces a luminous pattern. Motor vehicle lighting device (1) comprising a housing (2) with a light emission opening (4) directed in the direction of light emission (3) which is closed by a transparent cover plate (5) and a lighting module (7) arranged inside the housing (2) for generating a predetermined lighting function, in particular a daytime running light or a flashing light, characterized in that the lighting module (7) has a light guide arrangement (10) according to one of the preceding claims.

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