Lighting equipment for a motor vehicle

Abstract

Lighting device for a motor vehicle, comprising a light guide (1) for totally reflecting light along a direction of light propagation, wherein the light originates from at least one light source (2) and can be coupled in via at least one coupling surface (3) at an end face of the light guide (1), with an output coupling surface (4) arranged along the direction of light propagation for coupling out light, which exits the light guide (1) at an exit surface (5) arranged along the direction of light propagation, thereby overcoming the total internal reflection condition, wherein the at least one light source (2), whose light can be coupled in via the at least one coupling surface (3), is a laser light source, characterized in that a converter device is provided for converting the light from the laser light source (2) into a point light source, which has a maximum dimension of 500 µm or less in plan view.wherein the converter device comprises a phosphor conversion layer which generates a point-like white light source or a point-like light source with a wavelength other than the laser light from monochromatic laser light, wherein the phosphor conversion layer is configured such that it is arranged in front of the end face of the optical fiber (1) and / or is placed in a recess of the optical fiber (1).

Description

[0001] The invention relates to a lighting device for a motor vehicle.

[0002] Nowadays, LED lighting systems are increasingly used in motor vehicles to generate suitable light distributions for the vehicle's signal lights or headlights.

[0003] LEDs are also used in motor vehicles in combination with light guides, into which the light from the LEDs is coupled and guided through the light guide. A coupling surface is formed along the length of the light guide, which deflects the light within the light guide so that it exits via an exit surface. German patent application DE 103 17 062 A1 shows an LED lighting device with a light guide, in which the coupling surface coincides with the light-exit surface. This lighting device can generate a light distribution extending along the length of the light guide. However, due to the low luminance of the LEDs used for light generation, only light guides with limited length and / or a minimal cross-sectional area can be used.

[0004] The publication DE 198 12 794 B4 shows a lighting device for a motor vehicle according to the preamble of claim 1.

[0005] From publication JP 2009-289 976 A, a light emission device is known which comprises a laser light source in the form of a semiconductor laser element and a conversion element, wherein the conversion element converts the light of the laser light source into light of a different wavelength and emits the converted light.

[0006] The object of the invention is to create a lighting device for a motor vehicle with which a light distribution can be efficiently generated using a light guide.

[0007] This problem is solved by the lighting device according to claim 1. Further developments of the invention are defined in the dependent claims.

[0008] The lighting device according to the invention is intended for a motor vehicle, in particular for a passenger car and optionally also for a truck. The device comprises a light guide for the totally internal reflection of light along a direction of light propagation, wherein the light originates from at least one light source that is part of the lighting device. The light is coupled in via at least one coupling surface on an end face of the light guide, wherein the light guide further comprises an output coupling surface arranged along the direction of light propagation for coupling light out of the light guide, so that the coupled-out light exits the light guide at an exit surface arranged along the direction of light propagation, thereby breaking the total internal reflection condition. The output coupling surface and the exit surface thus also have an extension transverse to the direction of light propagation. The light guide is preferably elongated and optionallyThe optical fiber is designed in a rod shape, with the longitudinal direction of the light guide corresponding to the direction of light propagation. The lighting device according to the invention is characterized in that at least one light source, whose light can be coupled in via the at least one coupling surface, is a laser light source. This laser light source preferably produces monochromatic light.

[0009] The use of a laser light source in combination with optical fibers offers the significant advantage that, due to the high luminance of the laser light source, the light can be coupled out with sufficient intensity over long distances within the fiber. Furthermore, optical fibers with a small cross-section can be used in the lighting device.

[0010] The light guide of the lighting device according to the invention can be designed in various ways. In particular, the light guide can be designed in the same way as in the lighting device of publication DE 103 17 062 A1. The entire disclosure content of that publication is made available by reference to the content of the present application.

[0011] In a particularly preferred embodiment, the laser light source of the illumination device is a point light source and / or a converter device is provided for converting the light from the laser light source into a point light source, wherein the converter device particularly comprises an optic and / or a phosphor conversion layer which generates a point white light source or a point light source with a wavelength other than the laser light from monochromatic laser light. Phosphor conversion layers are known per se from the prior art. For example, in the case of a blue laser light source with an emission wavelength of 450 nm, a phosphor conversion layer made of Ce:YAG phosphorus can be used to generate white light.For violet laser light with a wavelength of 405 nm, a phosphor conversion layer made of cerium-doped nitride phosphorus or cerium-doped o-xinitride phosphorus is used in particular.

[0012] A point light source within the meaning of the invention is understood to be a light source with a very small radiating area, which, with respect to the dimensions of the lighting device, can be considered to be point-like to a very good degree, such that all rays of the light source originate from a single point. The maximum extent of the point light source in plan view, i.e., viewed in the main beam direction with the greatest intensity of the light source, is, in a particularly preferred embodiment, 500 µm or less, preferably 100 µm or less, and particularly preferably 20 µm or less. Furthermore, the point light source preferably has an emitting area of ​​0.5 mm² in plan view. 2or less, especially from 0.01 mm 2 or less and particularly preferably of 0.0002 mm 2 or less. The point light source comprises, in particular, an emissive rectangular surface, the edges of which each have a length of 500 µm or less, and preferably 20 µm or less. However, the point light source may also comprise a circular emissive surface. The point light source with the dimensions just described is preferably configured to generate a luminous flux of 100 lm or more, and in particular 200 lm or more, and / or a radiant power of 1 watt or more, and / or a luminance of at least 10 8 Cd / m 2 and especially of 10 9 Cd / m 2 or more. Such point-like light sources can only be achieved with laser light, e.g. using laser diodes.

[0013] In a particularly preferred embodiment, the light from the laser light source, and especially from the point light source, is converted into a collimated light beam at the at least one coupling surface of the optical fiber by a collimator. The collimator can be formed by a curved end face at which the light from the point laser light source is diffracted or reflected. The curved end face can form a transmitting lens onto which the light from a laser light source located outside the optical fiber falls. Alternatively, the laser light source can be arranged within the optical fiber, for example, in a recess at the coupling surface, and radiate towards the interface formed by the coupling surface between the optical fiber and the surrounding medium, with the light being reflected at this interface and guided back into the optical fiber as a collimated light beam.

[0014] In a further embodiment, the lighting device according to the invention is designed such that a collimated laser beam is generated from the light of the laser light source via an attachment optic. The laser light source and the attachment optic can optionally form a single unit for generating the laser beam, which is conventionally also referred to as a laser. The collimated laser beam is coupled into the optical fiber via the preferably flat coupling surface, with the laser beam preferably being guided to the coupling surface by means of beam deflection. In this way, the light from a laser light source can be coupled into the optical fiber from various positions with great flexibility. This allows for efficient use of available installation space in the vehicle.Furthermore, the laser light generates a beam with high luminance, which can also be coupled into light guides with compact dimensions and especially with small cross-sections, and guided over long distances.

[0015] In a further, particularly preferred embodiment, the laser light source, and in particular the point-like light source, is a laser diode. Preferably, the laser light source is a monochromatic light source whose light is converted into white light or into light with a different wavelength than the light of the monochromatic light source by a phosphor conversion layer, wherein the phosphor conversion layer is arranged, in particular, in front of the end face of the optical fiber and / or is placed in a recess of the optical fiber and / or is formed on the output coupling surface of the optical fiber. The phosphor conversion layer can optionally also form the output coupling surface and / or be placed outside the optical fiber downstream of the output coupling surface.

[0016] In a further, particularly preferred embodiment, the output surface has a deflecting means and, in particular, a prism arrangement or a roughened surface, by which light incident on the output surface is deflected in the optical fiber to the exit surface. The roughened surface can be designed analogously to the optical fiber of German patent DE 103 17 062 A1.

[0017] In a particularly preferred embodiment, the deflecting means is designed such that the intensity of the light exiting via the exit surface remains essentially constant along the direction of light propagation or longitudinal direction of the light guide, which can be achieved, for example, by a continuous widening of the extent of the prism arrangement or the roughened surface transverse to the direction of light propagation with increasing distance from the coupling surface.

[0018] In a further preferred embodiment of the lighting device according to the invention, the exit surface of the light guide is curved such that collimated light emerges from the exit surface. However, an (additional) deflection arrangement, in particular in the form of a reflector and / or a lens, can also be provided, which generates collimated light from the light emerging from the exit surface. In particular, the deflection arrangement described in German publication DE 103 17 062 A1 can be used.

[0019] Depending on the design, the lighting device can have a light guide with a rectangular or circular cross-section. Preferably, the maximum cross-sectional area is 10 mm or less. However, the light guide can also be designed such that one edge in the rectangular cross-section has a length of 10 mm or more, while the other edge has a length of 4 mm or less, thus forming a planar light guide. The light emission occurs, in particular, essentially perpendicular to the longer edge and essentially parallel to the shorter edge. This allows for the use of particularly flat light guides in the lighting device according to the invention.

[0020] The lighting device according to the invention can be configured to generate any desired light distribution. Preferably, the lighting device is used as a signal light, such as daytime running lights, marker lights, cornering lights, turn signals, rear lights, and / or brake lights. However, the lighting device can also optionally function as a headlight for actively illuminating the vehicle's surroundings, such as a low beam or high beam.

[0021] In another variant of the lighting device according to the invention, the coupling surface and the exit surface are identical, as is also the case in the lighting device of DE 103 17 062 A1.

[0022] In addition to the lighting device described above, the invention further relates to a motor vehicle which includes one or more of the lighting devices according to the invention.

[0023] Exemplary embodiments of the invention are described in detail below with reference to the accompanying figures.

[0024] They show: Fig. 1 a schematic side view of an embodiment of a lighting device according to the invention with laser diode and light guide; Fig. 2 an enlarged side view of a modification of the embodiment of Fig. 1 in the area of ​​the coupling surface; Fig. 3 a cross-sectional view of the in Fig. 1 of the light guide shown; and Fig. 4 a cross-sectional view of a modification of the in Fig. 1 of the light guide shown.

[0025] An embodiment of the lighting device according to the invention, based on a light guide 1 with a rectangular cross-section, is described below. This light guide is Fig. Figure 1 shows a side view. The optical fiber consists of a transmissive material, e.g., polycarbonate or Plexiglas, in a manner known per se, and comprises two end faces 3 and 3', respectively, with end face 3 serving as the coupling surface through which the light from a laser diode 2 is guided into the optical fiber. The essential feature of the invention is that laser light is used for coupling into the optical fiber. This makes it possible to integrate light sources with very high luminance into the lighting device, thereby creating a compact lighting device with high luminous efficiency. Compared to the dimensions and, in particular, the cross-section of the optical fiber, the laser diode 2 can be considered essentially point-like; that is, the radiation emitted from the light source originates, to a very good approximation, from a single point. The coupling surface 3, due to its curved shape, forms a lens, at the focal point of which the laser diode 2 is arranged.As a result, a collimated laser beam is introduced into the optical fiber. The collimation of the beam is very high due to the small size of the laser diode. This small size of the light source minimizes coupling losses, especially with flat cross-sectional areas.

[0026] In the embodiment of the Fig. In the figure 1, an arrangement of multiple prisms 401 is provided on the underside 4 of the optical fiber 1, whereas the opposite surface 5 of the optical fiber is planar. Surface 4 forms an output coupling surface for the laser light, which exits the optical fiber via the exit surface 5. In conventional optical fibers, where surface 4 is also planar, light is guided through the optical fiber, e.g., for data transmission, via total internal reflection at surfaces 4 or 5. In contrast, the prism arrangement 401 deflects the rays grazing the prisms towards the exit surface 5. The angle at which the deflected radiation strikes the exit surface 5 is smaller than the angle of total internal reflection, so that the radiation exits the optical fiber via the exit surface 5.

[0027] The arrangement of the prisms 401 is designed such that the percentage of the coupled-out light increases from the coupling surface 3 towards the opposite end face 3' such that the absolute coupled-out fraction remains constant, and thus light of constant intensity emerges along the longitudinal direction of the waveguide. The increasing percentage of coupled-out light takes into account the fact that the light intensity decreases along the longitudinal direction of the waveguide due to the progressive coupling through the prisms, so that an ever-increasing percentage of the light must be coupled out to achieve the same intensity. To achieve an increase in the percentage of coupled-out light, the extent of the prisms perpendicular to the plane of the sheet can, for example, be increased. Fig. 3. The angle increases with increasing distance from the coupling surface. Similarly, the sides of the prisms can increase in a suitable manner.

[0028] The extraction of light via prisms is merely one possible variant. In particular, the surface of the extraction area 4 can also be roughened and its surface area can increase with increasing distance from the input area, as described in German publication DE 103 17 062 A1. The optical fiber in that publication differs from the optical fiber described here in that the extraction area and the exit surface coincide and are located on the top surface of the optical fiber. This design can optionally also be implemented in the optical fiber according to the invention.

[0029] In the embodiment of the Fig. 1. The coupled light exits in different directions via the exit surface 5, which in Fig. Figure 3 again shows a cross-sectional view as seen from the end face 3'. The cross-section was formed in an area near the coupling surface 3, which is evident from the fact that the horizontal extent of the prisms 401 on the coupling surface 4 is relatively small in this area. Furthermore, it can be seen that both the coupling surface 4 and the exit surface 5 are planar. This results in radiation reflected from the prisms exiting the optical fiber in different directions via the exit surface 5, which is shown by the beam path S' in Fig. Figure 3 is shown by way of example. In order to generate a collimated light beam from this emerging light, a reflector with a curvature profile that is at least partially parabolic is used in a particularly preferred embodiment, in whose focal line the light guide 1 is placed. The reflector shown in German publication DE 103 17 062 A1 can be used for this purpose.

[0030] As demonstrated by Fig. As explained in section 1, the light from the laser diode 2 falls from the outside onto the outside of the curved coupling surface 3, which generates a parallel beam of light due to the curvature. Fig. Figure 2 shows a modification of this embodiment. In this figure, the coupling area 3 is shown in an enlarged side view. In contrast to Fig. 1. The laser diode 2 is now positioned in a central bore in the light guide 1 and emits light in comparison to Fig. 1 in the opposite direction. The light from the laser diode is reflected on the inside of the coupling surface 3, analogous to the embodiment of the Fig. 1 in turn a parallel beam of rays is generated, which is represented by the beam path S.

[0031] Fig. 4 shows a view analogous to Fig. 3 of an alternative embodiment of the optical fiber according to the invention. The optical fiber differs from the conductor of the Fig. 3 in that the light-emitting surface 5 is now curved, thereby forming a lens. The coupling surface 4 is located in the focal plane of this lens, which results in the radiation emerging from surface 5 forming a collimated beam, as indicated by the beam path S''. In this embodiment of the invention, an additional reflector for collimating the emerging radiation can be omitted, thus reducing the installation space required for the lighting device in the vehicle.

[0032] Depending on the application, the spatial extent of the optical fiber can vary. Fig. 1. They can be different. Due to the use of a laser light source, particularly long optical fibers of 50 cm and more can be created. Likewise, the cross-section of the optical fiber can be made very small. Both rectangular and round cross-sections are possible. In the Fig. 3 or Fig. In the fourth variant of the optical fiber shown, it can have a height of 8 mm or less and a width of approximately 3 mm or less, for example, 2 mm. In contrast, the radiating surface of the laser diode has a cross-sectional area of ​​only about 0.0002 mm². 2 on.

[0033] The lighting device described above can perform various functions in a motor vehicle. It can be used as a signal light to signal other road users or, if necessary, as a headlight to actively illuminate the vehicle's surroundings. However, its preferred use is as a signal light. Preferably, monochromatic light, e.g., red light, is generated by the laser light source or laser diode and then exits the light guide in this color via its exit surface. Optionally, the monochromatic light from the laser light source can also be converted into another color or into white light via a suitable phosphor conversion layer. The phosphor conversion layer can, for example, be positioned in front of the coupling surface.The light from the laser diode strikes the phosphor conversion layer via a focusing optic, thereby generating a point light source on this layer, the light from which then enters the optical fiber. Optionally, the output coupling surface 4 can also contain the phosphor conversion layer, so that the conversion of the monochromatic light to white light or to light with a different wavelength occurs upon reflection at the output coupling surface.

[0034] In one embodiment of the lighting device according to the invention, the beam of a laser can also fall onto the coupling surface. The laser beam generated by the laser can optionally be directed onto the coupling surface via suitable deflection optics, so that the laser can be flexibly arranged in different positions and does not have to be positioned directly on the coupling surface. This allows the installation space for the lighting device to be used more effectively, depending on the application.

[0035] The embodiments of the invention described above offer a number of advantages. In particular, significantly higher efficiencies can be achieved in the coupling area into the optical fiber due to the high luminance of a laser light source, and the light propagation in the optical fiber can be better controlled. The output coupling in the optical fiber can be specifically influenced by appropriate surface design of the output coupling surface, thereby achieving a homogeneous light emission from the output surface of the optical fiber. Furthermore, the color of the light produced by the illumination device can be easily controlled by the targeted positioning of phosphor conversion material, for example, on the output coupling surface.Furthermore, due to the high luminance of the emitted laser light, it is possible to realize significantly longer light guides with sufficient beam intensity than is possible with an LED light source.

Claims

[1] Lighting device for a motor vehicle, comprising a light guide (1) for totally reflecting light along a direction of light propagation, wherein the light originates from at least one light source (2) and can be coupled in via at least one coupling surface (3) at an end face of the light guide (1), with an output coupling surface (4) arranged along the direction of light propagation for coupling out light, which exits the light guide (1) at an exit surface (5) arranged along the direction of light propagation, thereby overcoming the total internal reflection condition, wherein the at least one light source (2), whose light can be coupled in via the at least one coupling surface (3), is a laser light source, characterized by, that a converter device is provided for converting the light from the laser light source (2) into a point light source which has a maximum dimension of 500 µm or less in plan view, wherein the converter device comprises a phosphor conversion layer which generates a point white light source or a point light source with a wavelength other than the laser light from monochromatic laser light, wherein the phosphor conversion layer is configured such that it is arranged in front of the end face of the light guide (1) and / or is placed in a recess of the light guide (1). [2] Lighting device according to claim 1, characterized by that the converter device includes a front-mounted optic. [3] Lighting device according to claim 1 or 2, characterized by , that the point light source (2) has an emitting area of ​​0.01 mm in plan view 2or less and particularly preferably of 0.0002 mm 2 or less. [4] Lighting device according to any of the preceding claims, characterized by , that the point light source (2) has, in plan view, an emitting angular surface, the edges of which each have a length of 500 µm or less and preferably of 20 µm or less. [5] Lighting device according to any of the preceding claims, characterized by , that the point light source (2) is designed such that it generates a luminous flux of 100 lm or more and in particular of 200 lm or more and / or a radiant power of 1 watt or more and / or a luminance of at least 10 8 Cd / m 2 and especially of 10 9 Cd / m 2 and more. [6] Lighting device according to any of the preceding claims, characterized by, that the light from the laser light source (2) is converted into a collimated light beam at the at least one coupling surface (3) of the light guide (1) with a collimator. [7] Lighting device according to claim 6, characterized by , that the collimator is formed by a curved end face (3) of the light guide (1) at which the light from the laser light source (2) is diffracted or reflected. [8] Lighting device according to any of the preceding claims, characterized by , that the lighting device is designed such that a collimated laser beam is generated from the light of the laser light source (2) via an attachment optic, which is coupled into the light guide (1) via the preferably planar coupling surface (3), wherein the laser beam is preferably guided into the light guide (1) via a beam deflection. [9] Lighting device according to any of the preceding claims, characterized by, that the laser light source (2) comprises a laser diode. [10] Lighting device according to any of the preceding claims, characterized by , that the output coupling surface (4) has a deflecting means (401) and in particular a prism arrangement or a roughened surface, via which light incident on the output coupling surface (4) is deflected in the light guide (1) to the exit surface (5). [11] Lighting device according to claim 10, characterized by , that the deflecting means is designed in such a way that the intensity of the light exiting via the exit surface (5) remains essentially constant along the direction of light propagation of the optical fiber (1). [12] Lighting device according to any of the preceding claims, characterized by , that the exit surface (5) of the light guide (1) is curved in such a way that collimated light exits from the exit surface. [13] Lighting device according to any of the preceding claims, characterized by , that a deflection arrangement, in particular a reflector and / or a lens, is provided which produces collimated light from the light exiting from the exit surface (5). [14] Lighting device according to any of the preceding claims, characterized by that the optical fiber (1) has a rectangular or round cross-section, wherein the maximum extent of the cross-section is preferably 10 mm or less, or wherein the optical fiber (1) is preferably designed such that one edge in the rectangular cross-section of the optical fiber (1) has a length of 10 mm or more, whereas the other edge has a length of 4 mm or less. [15] Lighting device according to any of the preceding claims, characterized by , that the coupling surface (4) and the exit surface (5) are identical. [16] Lighting device according to any of the preceding claims, characterized bythat the lighting device includes a signal light and / or a spotlight. [17] Motor vehicle comprising one or more lighting devices according to any of the preceding claims.

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