LIGHTING SYSTEM FOR VEHICLES

Description

[0001] The present application relates to lighting devices for vehicles, in particular lighting devices which can be used as signal lights such as direction indicators (turn signals) or brake lights or also as taillights (rear lights).

[0002] Lighting devices are used in vehicles to illuminate the vehicle's surroundings, enabling the driver to see even in darkness, and to draw the attention of other people or vehicles to the vehicle equipped with the lighting device. Examples of such lighting devices include headlights, taillights, brake lights, and turn signals.

[0003] Besides their technical function, such lighting devices are increasingly used to give vehicles of a particular brand a distinctive appearance. The external shape of these devices is primarily used as a design element. The lighting signature of these devices is also increasingly being designed to be characteristic. For example, distinctive lighting signatures are used in vehicle taillights. At the same time, there are increasingly strict constraints regarding installation space and placement on the vehicle, for example, to maximize the use of cargo space width. To circumvent the limitations mentioned in the examples, or to meet the constraints required by law and vehicle design, highly adapted optical concepts are often necessary.Traditionally, mirrors, prisms and macroscopic scattering structures are used to create the desired lighting devices.

[0004] German patent application DE 10 2016 117 969.8 describes devices for generating luminous signatures using holograms, particularly volume holograms. This application describes the use of both reflection and transmission holograms. In transmission holograms, the hologram is illuminated from one half of the hologram (i.e., from one side of the hologram) and viewed from the other half (from the opposite side of the hologram). In contrast, reflection holograms are illuminated from the same side as the viewing side. This can be difficult to implement when space is limited, especially if the hologram has to be positioned near the outside of the vehicle, as a light source for illuminating the hologram would then have to be located outside the vehicle.On the other hand, reflection holograms have the advantage of generally being more wavelength-selective than transmission holograms; that is, only light within a narrow wavelength range is projected as a luminous signature. This means that even when using a relatively broadband light source such as a red LED, the generated luminous signature always appears to have essentially the same wavelength. This is desirable because, due to slight variations in the spectral sensitivity of red and green color receptors in the eye, even small wavelength changes between approximately 550 nm and 640 nm result in a significant spatial shift in the perceived color.Furthermore, transmission volume holograms can experience the problem of so-called overmodulation, which essentially means that the optimal layer thickness of the transmission hologram, given its geometry and refractive index modulation, depends on the wavelength, which can lead to color shifts.

[0005] Another lighting device is known from document JP H08 108793 A.

[0006] It is therefore an object of the present invention to provide lighting devices which can operate on the basis of reflection holograms and which nevertheless have a compact design.

[0007] In this regard, a lighting device according to claim 1 is provided. The dependent claims define further embodiments.

[0008] According to the invention, a lighting device for a vehicle is provided, comprising: a light source arrangement which is arranged to emit light in the direction of a first hemisphere, a reflection hologram which is arranged to produce a luminous signature when illuminated from a direction which points in a hemisphere opposite to the first hemisphere, and a light guide with a beam deflection section which is arranged to direct the light from the light source arrangement in the direction of the second hemisphere onto the hologram.

[0009] By using the light guide, the light source device can be positioned next to the hologram or on the side opposite the side of the hologram that is ultimately illuminated, which facilitates installation in vehicles.

[0010] The beam deflection section can be designed to direct light emanating from the light source arrangement as a spherical wave onto the hologram as a plane wave. In other words, the spherical wave can be collimated.

[0011] By using an approximately plane wave (plane wave), a hologram can be illuminated evenly at a constant angle. Furthermore, a plane wave is technically easy to test. Slight decentering of the hologram during installation, as well as a slight tilt, does not result in irregular distortion of the generated light signature when using a plane wave.

[0012] The beam deflection section can include a curved mirror, in particular a section of a paraboloid mirror, where the mirror can be configured as an off-axis mirror. This allows the light to be easily directed onto the hologram.

[0013] Alternatively, the beam deflection section can include a transmittive or reflective diffractive element, such as another hologram. The light source arrangement can include multiple light sources, with the beam deflection section comprising separate sections for these multiple light sources. These sections can be configured so that the light from all sections is directed onto the hologram from the same direction. This allows for the illumination of larger holograms and / or the achievement of higher luminance levels.

[0014] The multiple sections can also be configured to direct light onto the hologram at different angles to selectively create various lighting signatures. In this way, different lighting functions can be integrated.

[0015] The beam deflection section can be configured to direct at least part of the light from the light source arrangement to the hologram via a reflection at one side of the light guide body.

[0016] The side can include a side of the light guide opposite the hologram.

[0017] The hologram may have a section of reduced efficiency, wherein the light guide is configured to direct non-diffracted light from the section of reduced efficiency to another section of the hologram.

[0018] This allows larger holograms to be illuminated with comparatively thin optical fibers. In this way, the thickness of the optical fiber can be reduced.

[0019] The light guide can have a curved light coupling surface for coupling light from the light source, with the center of curvature of the light coupling surface located at the position of a light source in the light source arrangement. In this way, refraction effects during light coupling are minimized, since light rays from the light source strike the light coupling surface essentially perpendicularly.

[0020] The light guide can also have a curved light coupling surface for coupling light from the light source. A combination of the curved light coupling surface and the beam deflection section is designed to direct light emanating from the light source arrangement as a spherical wave onto the hologram as a plane wave. A collimation function can thus be "distributed" across both the light coupling surface and the beam deflection section, allowing for greater design freedom.

[0021] The optical fiber can have a refractive index of approximately 1 in its light-guiding core, i.e., the region where the light is guided within the optical fiber, particularly if it is filled with air. However, the refractive index can also be non-1 if the light-guiding core is filled with a material other than air.

[0022] The light source arrangement can consist of one or more approximately point light sources. This can improve the collimation of the light through the beam deflection area or other components and / or achieve a better quality of the luminous signature generated by the hologram (e.g., less "smearing").

[0023] The invention is explained in more detail below with reference to exemplary embodiments and the accompanying drawing. The drawing shows: Fig. 1 a sectional view of a lighting device according to an exemplary embodiment, Fig. 2A und 2B Sectional views of a lighting device according to further embodiments, Fig. 3A and 3B possible views of the lighting system Fig. 2A from another direction, Fig. 4 a sectional view of a lighting device according to a further embodiment, Fig. 5 a sectional view of a lighting device according to a further embodiment, Fig. 6 a sectional view of a lighting device according to a further embodiment, Fig. 7A-7C Views of a lighting device according to a further embodiment, Fig. 8 a view of a lighting device according to a further embodiment, Fig. 9 a sectional view of a lighting device according to a further embodiment, and Fig. 10 a sectional view of a lighting device according to a further embodiment.

[0024] The following section explains various embodiments with reference to the accompanying drawing. It should be noted that these embodiments serve only for illustration and are not to be interpreted as limiting. Elements from different embodiments can also be combined to form further embodiments. Variations, modifications, and details described for components of one embodiment are also applicable to corresponding components of other embodiments.

[0025] Fig. 1 shows a sectional view of a lighting device according to an exemplary embodiment. The lighting device of the Fig. 1 The device comprises a light source arrangement 4, which may, for example, include one or more light-emitting diodes. Furthermore, the device includes Fig. 1 a reflection hologram 2 which, when illuminated by light from the light source arrangement 4, produces a luminous signature, i.e., it bends or scatters the light in a directed manner to create a desired luminous impression.

[0026] In the exemplary embodiment of the Fig. 1 Beams 6 from the light source arrangement 4 enter a light guide 1, which has a beam deflection region 3. In the beam deflection region 3, the beams 6 are deflected in such a way that they illuminate the reflection hologram. An image is then formed on the same side, i.e., in the same hemisphere from which the illumination originates. Fig. 1 that is, on the left side of the reflection hologram 2. The light source arrangement 4 can be arranged in this way, pointing towards a Fig. 1 to radiate into the left-hand hemisphere, and through the light guide 1 with the beam deflection area 3, the hologram is nevertheless projected at a suitable angle in the direction of the Fig. 1 The light source illuminates the right-hand half-space. This allows the lighting device to be positioned on the outside of a vehicle. Preferably, the refractive index of the light guide 1 is as close as possible to the refractive index of the hologram 2 and any carrier or adhesive layers present, in order to minimize reflection losses at internal interfaces.

[0027] The beam deflection area 3 is preferably designed such that the light from the light source device 4, which in the illustrated example essentially corresponds to a beam 6 from a point light source, is converted into a plane wave (plane wave) that strikes the reflection hologram 2 at an angle. The reflection hologram 2 has a corresponding acceptance range such that the light striking the reflection hologram 2 at this angle produces a corresponding image. This can be achieved, for example, by also using this angle for exposure during the production of the hologram.

[0028] The use of at least approximately plane waves for illuminating hologram 2 offers several advantages. Since the angle of incidence remains identical across the entire surface of a planar hologram 2, there is no decrease in local illuminance on hologram 2 due to the projection of light from the light source arrangement 4 onto the hologram's surface. Furthermore, slight decentering of the hologram during installation or a slight tilt does not result in irregular distortion of the signal generated by the hologram, i.e., the luminous signature. Finally, a plane wave is technically easy to test, thus defining a clear interface between the light guide 1 and the hologram 2, which could, for example, be a film.

[0029] A potential problem with plane wave illumination lies in the residual divergence of the approximately collimated plane wave emanating from the beam deflection region 3. This divergence results from the finite focal length of the beam deflection region 3 and the finitely small illuminating area of ​​the light source device 4. In other words, the light source device 4 has a certain volume from which light is emitted, corresponding to a illuminating area "seen" by the beam deflection region. The use of more extended light source devices 4, such as the tungsten filament of a halogen lamp, results in a blurring of the scattering function stored in the hologram. Therefore, within the scope of this application, the use of light source devices that approximate point light sources is preferred.In this application, approximately point light sources, or simply point light sources, are understood to be light sources whose luminous area is less than 4 mm², in particular less than 2 mm², preferably less than 1.1 mm², and especially less than 0.3 mm². The luminous area is the area from which the approximately point light source emits light in the direction of the light guide 1, e.g., as seen from the beam deflection area 3. Examples of such approximately point light sources are commercially available light-emitting diodes (LEDs), in which the light emission is generated in a small region of a pn junction.

[0030] The beam deflection area 3 can therefore serve in particular as one or more collimators to image light from one or more light sources as a plane wave, i.e. to infinity.

[0031] The beam deflection area 3 can be designed as a mirror, in particular as an off-axis mirror (i.e., the axis of symmetry of the illumination does not coincide with the axis of symmetry of the mirror), for example, an off-axis paraboloid mirror. However, other types of mirrors, such as ellipsoidal mirrors, are also possible. In addition, an aperture 9 can be provided for beam narrowing. The use of off-axis mirrors has the advantage that the light sources of the light source arrangement can be better cooled by large heat sinks, which is often necessary for high-power LEDs used in the automotive sector. With an on-axis paraboloid mirror segment, such a heat sink would clip the collimated beam.

[0032] At one end of the light guide 1, a surface 5 is provided which absorbs incoming light in order to prevent or at least minimize uncontrolled light emission and unwanted stray light effects caused by multiple reflections within the light guide 1. Surface 5 represents only one example of a light absorber arrangement. A light absorber can, for example, also be arranged at an angle other than 90° to a surface of the hologram 2 in order to prevent residual reflections from an absorbing coating from being directed towards the exterior of the vehicle. The light guide can also be provided with an absorber layer at other interfaces not required for its optical function.

[0033] The exemplary embodiment of the Fig. 1 This serves as the basis for further examples of implementation, which describe variations and modifications. Identical elements are designated with the same reference symbols to avoid repetition.

[0034] When using an off-axis paraboloid mirror as the beam deflection region 3, the space between the light source arrangement 4 and the beam deflection region 3 is preferably made of a medium (material) with a homogeneous refractive index corresponding to the refractive index of the light guide. As in Fig. 2A As has been clarified, deviations from this are possible, for example, to save installation space or weight. Fig. 2A The first part of the path from the light source arrangement 4 to the beam deflection area 3 is filled with a first medium, which can be, for example, air with a refractive index n=1.0, and a second part of the path with the medium of the light guide. The latter can, without loss of generality, be, for example, a plastic with a refractive index n≈1.5, but other materials with different refractive indices are also possible.

[0035] In order for the wave illuminating hologram 2 to remain a plane wave, the beam deflection area 3 and / or the coupling surface of light from the light source arrangement 4 into the light guide body 1, which is designated by reference numeral 7, must be in comparison to Fig. 1 can be modified. The coupling surface 7 is in Fig. 2A The coupling surface 7 is designed as a planar surface, with its surface normal perpendicular to the main beam of the beam emitted from the light source arrangement 4 onto the beam deflection area 3. Due to the refraction of the beams originating from the light source arrangement 4 at the coupling surface 7, spherical aberration occurs. Therefore, the use of an off-axis paraboloid in the beam deflection area 3 does not result in a plane wave in the direction of the hologram 2, but rather a plane wave with spherical aberration. If the spherical aberration is sufficiently large, this can lead to a distortion of the luminous signature stored in the hologram and reproduced upon illumination.

[0036] This problem can occur in Fig. 2A On the one hand, this can be solved by replacing the mirror in the beam deflection area with a freeform mirror that deviates slightly from the shape of an off-axis paraboloid mirror in order to correct the wavefront error. Furthermore, if the coupling surface 7 is tilted relative to the main beam of the beam emitted from the light source arrangement 4 onto the beam deflection area 3, additional wavefront aberrations such as coma and astigmatism arise, which can also be corrected by a suitable freeform mirror in the beam deflection arrangement 3.

[0037] Another correction option for minimizing spherical aberration and other wavefront errors caused by refraction at the coupling point 7 is to lower the refractive index of the optical fiber 1. Fig. 2A , which in the limiting case can reach n=1.0, corresponding to a hollow body filled with air. A disadvantage of this solution is the limited material selection for the hologram substrate, for which only a few commercially available materials exist, often possessing a refractive index around n=1.5 or n=1.6. If the refractive index of the optical fiber 1 deviates significantly from that of the hologram material 2, a considerable amount of light is lost due to Fresnel losses at the interface between the optical fiber 1 and the hologram 2.

[0038] The Fig. 2B Figure 1 shows an alternative embodiment that compensates for the wavefront error caused by the light source arrangement 4 and the beam deflection arrangement 3 traveling through a medium with a different refractive index than that of the optical fiber 1A by adapting the coupling surface 7b. Here, surface 7b is concentric with the light source 4, meaning that the center of curvature of 7b lies within the light source 4. Each beam propagating from the light source 4, which can be considered approximately as a point light source, to the beam deflection area 3 strikes the coupling surface 7b perpendicularly, thus preventing aberrations caused by the transition from the surrounding medium, such as air, into the optical fiber 1A. The shape of the coupling surface therefore represents a degree of freedom in the design, which, in the case of the coupling surface 7b, is used to compensate for wavefront errors.

[0039] This degree of freedom can also be used in other ways to distribute the collimation function for collimating the light emitted from the light source 4 essentially arbitrarily between the coupling surface 7b and the beam deflection area 3. One possibility is to design the coupling surface 7b as a convex lens surface and thus perform the collimation on this surface, which would give the beam deflection area 3 an infinite radius of curvature, corresponding to a plane mirror. The division between the two surfaces can also be made for different directions of the spherical wave emitted by the light source 4, so that, for example, the coupling surface has a convex cylindrical surface that performs the collimation in a first direction (a first cut), and the beam deflection area 3 has a cylindrical shape that performs collimation in a second direction (a second cut).The first direction and the second direction can be approximately perpendicular to each other (e.g. 90° + / - 5° or + / - 1°), which implies that the cylinder axes of the coupling surface and the beam deflection section are also approximately perpendicular to each other.

[0040] Furthermore, the exit surface, designated 13, through which light diffracted by the hologram leaves the luminaire, is modified. The exit surface 13 can be, as in Fig. 2B The exit surface 13 is shown as flat and inclined towards the hologram 2. However, other shapes are also possible, in particular spheres, cylinders, or toroidal surfaces. These shapes increase the efficiency of coupling the radiation outwards after diffraction at the hologram 2 towards the vehicle exterior. If the exit surface 13 is designed as a cylinder whose axis points upwards in the installed vehicle, for example, it is preferred to also curve the surface of the hologram 2 in the same way in order to keep the material thickness of the optical fiber constant. Furthermore, if this approach is combined with the one described in Fig. 6 In the combined configuration shown, the shape of the exit surface 13 can be coupled with the shape of the surface of the hologram 2, which simultaneously forms the rear boundary of the light guide. In the case of, for example, a cylindrical exit surface 13 with, for example, a vertically oriented cylinder axis, the surface of the hologram 2 can also be designed as a cylindrical surface in such an embodiment, wherein, in such an embodiment, the cylinder axes of the exit surface 13 and the surface of the hologram 2 preferably lie one above the other.

[0041] In other embodiments, the light guide body 1 can be an air-filled hollow body. In this case, a light-guiding core of the light guide body 1 thus has a refractive index of 1. In the case of such an air-filled hollow body, the output surface for the light signal, through which light diffracted by the hologram is emitted towards the outside of the vehicle, is [see 13 in ]. Fig. 2B ), non-functional. Thus, these and other interfaces of the light guide body, which do not fulfill an optical function, can be omitted or, for example, in the case of the output coupling surface 13 in Fig. 2B This can be implemented in the form of an outer light disk separated from the actual light guide body. Only optical functional surfaces such as the beam deflection arrangement 3, the absorber 5, or the hologram 2 must be present in such an air-filled hollow body, which then allows the body to have several openings to the outside.

[0042] As mentioned, the light source arrangement 4 can include one or more light sources. This will now be discussed with reference to the Fig. 3A and 3B Illustrated. The Fig. 3A and 3B These show top views of the device of Fig. 1 oder 2A in the direction of an arrow 12 of the Fig. 1 .

[0043] The Fig. 3A shows an arrangement with a single light source 4, which is located in the beam deflection region 3 as in Fig. 3A schematically shown (see also Fig. 1, 2A ). The Fig. 3B In contrast, it shows three light sources 4a, 4b, 4c arranged next to each other, which are reflected in different sections 3a, 3b, 3c of the beam deflection area.

[0044] It should be noted that the number of three light sources 4a-4c in Fig. 3B This is only to be understood as an example, and only two or more than three light sources can be used. The light sources 4a-4c and the associated beam deflection sections 3a-3c are shown in Fig. 3B arranged in a line. In the case of an arrangement on a cylindrically curved waveguide, the light sources 4a-4c and the beam deflection sections 3a-3c are aligned radially around the center of the cylinder. Various arrangements are therefore possible.

[0045] In the Fig. 3B Are the light sources 4a-4c shown in the view of the Fig. 1 oder 2 Arranged one behind the other. Further possibilities for arranging multiple light sources are now discussed with reference to the Fig. 4-6 explained.

[0046] In Fig. 4 is a sectional view of a lighting device according to an exemplary embodiment corresponding to the view of the Fig. 1 und 2 shown. In the exemplary embodiment of the Fig. 4 The light source arrangement 4 comprises two light sources 4a, 4b, whose light rays are deflected as beams 6a, 6b by respective associated parts 3a, 3b of the beam deflection area 3. In particular, the areas 3a, 3b can each be off-axis mirrors such as off-axis paraboloid mirrors. However, as shown in Fig. 2B As shown, combinations of refractive and reflective elements are possible. Accordingly, Fig. 4 , each light source has its own refractive coupling surface, but they can also have a common coupling surface.

[0047] Using multiple light sources allows for a higher overall luminous intensity. Furthermore, the total beam area of ​​the light source arrangement can be increased while maintaining the same focal length for each individual beam deflection area. This enables even larger holograms to be fully illuminated within a relatively small installation space. Additionally, a higher luminance can be achieved, for example, for use as a brake light.

[0048] Even in the exemplary embodiment of the Fig. 4 The number of two light sources 4a, 4b is only to be understood as an example, and more light sources may be provided.

[0049] The Fig. 5 shows another embodiment. In the embodiment of Fig. 5 The light source arrangement comprises two light sources 4d and 4e. Light rays from light sources 4d and 4e are reflected by respective sections 3d and 3e of the beam deflection section 3. Sections 3d and 3e can each be off-axis mirrors. The beams 6e emanating from light source 4e are reflected by section 3e to a front face, i.e., a side opposite hologram 2, of the light guide 1, reflected again at this front face, and then reach hologram 2. Beams 6d from light source 4d are reflected directly to hologram 2 from section 3d. The reflection at the front face of the light guide 1 places corresponding cleanliness and scratch-free requirements on this surface, but can help to reduce the thickness of the light guide 1 while simultaneously illuminating a comparatively large hologram 2.Again, the number of two light sources 4d, 4e is only meant as an example, and more than two light sources or even a single light source are also possible.

[0050] Another embodiment is shown in Fig. 6 shown, which is based on the exemplary embodiment of the Fig. 5 based on and extending this. The illumination by means of two light sources 4d, 4e and correspondingly two sections 3d, 3e of the beam deflection area corresponds to that of the Fig. 5 .

[0051] In the embodiment of the Fig. 6 Thus, beams 6d and 6e also fall on the hologram. In contrast to the Fig. 5 The hologram 2, where the beams 6d, 6e strike, is designed such that it has an efficiency significantly less than 100%, for example, on the order of 50%, e.g., between 45% and 55%, for example, approximately 49%. Thus, only a portion of the beams 6d, 6e is diffracted by the hologram 2 to generate the luminous signature. The remaining portion of the beams 6d, 6e is diffracted on the back side of the light guide 1 (the right side in Fig. 6 ) as beams 6f, 6g totally reflected and again totally reflected at the front to form another part of the hologram 2 (in the representation of the Fig. 6 to illuminate the lower part. This further part then preferably has a higher efficiency, for example at or near 100%, in order to utilize the beam bundles 6f and 6g, i.e. the initially reflected part of the radiation (for example approximately 50% of the original radiation), as completely as possible.

[0052] With the arrangement of Fig. 6 Even larger holograms 2 can be illuminated with comparatively thin light guides 1. The disadvantage is that the hologram 2 is typically located in the area of ​​lower efficiency (in the upper part of the Fig. 6 ) exhibits a wavelength-dependent and a diffraction-angle-dependent efficiency profile. This can lead to the reproduction of the luminous signature by the upper area of ​​the hologram differing in color impression from the reproduction of the luminous signature by the lower area (illuminated by beams 6f and 6g). The principle of Fig. 6 can also be used with the one from Fig. 3B The system can be combined in such a way that the illuminated wave is provided by only one light source (4a, ...) instead of by the two light sources 4d and 4e (with their respective associated beam deflection regions 3d and 3e). With the beam cross-section remaining the same, the beam deflection region 3a can then be made wider. The narrowing to the desired thin light guide in the area of ​​the hologram 2 can then occur at the point where the rays 6d make their final contact with the output coupling surface 13.

[0053] The reference to Figuren 1-5 The illustrated embodiments can also be combined in other ways. For example, light sources can illuminate corresponding areas of the beam deflection section 3 (e.g., facets of a paraboloid mirror) both in the view of the Fig. 4 side by side as well as in top view as in Fig. 3B They should be arranged side by side, resulting in a two-dimensional array of light sources.

[0054] In the Figuren 1-5 The images show lighting devices that can perform a function in a motor vehicle, for example, as a taillight, brake light, or turn signal. Modern taillights often integrate several functions, such as a rear light, brake light, and turn signal. Such integration is also desirable in taillights that use holograms for image generation, particularly reflective holograms, as described in the... Figuren 1-5 explained, use. Corresponding examples of implementation are now given with reference to the Figuren 7 and 8 explained.

[0055] The Fig. 7A shows a side view of a lighting device according to the view of the Fig. 1 , the Fig. 7B shows a view from the direction of arrow 13 of the Fig. 7A on the lighting device of the Fig. 7A , and the Fig. 7C shows a sectional view along a line AA of the Fig. 7A . The Figuren 7A-7C are summarized below as Fig. 7 designated.

[0056] In this embodiment, a hologram 2 is provided which contains several holographic structures, each of which diffracts efficiently, i.e., produces a luminescent signature, only when the incident radiation comes from a specific direction of incidence. Here, the angular selectivity of holograms is exploited.

[0057] In the Fig. 7 , as especially in the Fig. 7A As can be seen, light from a light source 4a is directed through a beam deflection section 3a into Fig. 7A directed at an angle from above onto hologram 2. The beam deflection section 3a can include an off-axis mirror as a collimator, as already explained. This illumination essentially corresponds to that in Fig. 1 und 2 The lighting is shown. Instead of a single light source 4a, several light sources 4a arranged side by side can also be used, as in the Fig. 3B shown to be used.

[0058] Furthermore, in the exemplary embodiment of the Fig. 7 Several light sources 4b are provided, which illuminate the hologram from a second direction via a beam deflection section 3b, which in turn may have one or more off-axis paraboloid mirrors as collimators, as is shown in particular in Fig. 7C This is evident. Light source 4a illuminates at a different angle than light source 4b. Due to the angular selectivity of holograms, different holographic structures in hologram 2 can be addressed by the different illuminations, thus generating different signatures. The illuminance on the hologram, i.e., the luminance, can be varied by the focal lengths of the beam deflection sections 3a and 3b used as collimators, as well as by the number of light sources 4a and 4b used and by the emitted radiant intensity of the light sources 4a and 4b. For example, a higher luminance can be provided for a brake light function than for a tail light, since regulations require a higher luminance for a brake light.

[0059] The separate hologram functions can be integrated into a single hologram layer (for example, by sequential exposure from different directions during hologram production), at least if they operate at the same wavelength (e.g., red light) and high efficiency of the reflection holograms is desired. However, two holograms in two separate layers for each hologram function can also be used; these are then stacked as Hologram 2.

[0060] The Fig. 8 shows an extension of the exemplary embodiment of the Fig. 6 to include a third light source and a third beam deflection section, and shows a view corresponding to the view of the Fig. 7B Here, a third light source 4c, together with a beam deflection section 3c (for example, another off-axis parabolic mirror as a collimator), is provided to illuminate the hologram 2 from a third direction. In this process, Fig. 8 Only a portion of hologram 2 is illuminated; the marginal rays are labeled 7c. The light source 4c could, for example, be a yellow light source for a turn signal function. Accordingly, a holographic structure for this function only needs to be provided in the illuminated strips of the hologram (bounded by the marginal rays 7c). If, as in the example with brake lights, taillights, and turn signals, a different wavelength is used for the indicator, another hologram layer can be used for this additional wavelength. This layer could be located a short distance from hologram 2 or applied to it. However, the hologram functions can also be written within a single hologram layer.

[0061] In the above embodiments, a curved mirror surface, in particular an off-axis paraboloid mirror, was used for beam deflection in a beam deflection region. Now, with reference to the Figuren 8 und 9 Alternatives to this are explained. Figuren 8 und 9 Each shows a cross-sectional view corresponding to the view of the Figuren 1 und 2 .

[0062] In the Fig. 9 A diffractive off-axis reflection lens 8 is provided as a beam deflection section, for example, a hologram, which can also provide individual facets or individual areas for different light sources 4. Light rays 6a from the light source 4 are directed by the reflection lens 8 as a plane wave 6b to the hologram 2. Other diffractive elements besides holograms can also be used. Since the deflection of the light from the spherical wave (6a) emanating from the light source 4 to the plane wave 6b occurs here via a diffractive (diffractive) interaction mechanism, both the deflection angle and the efficiency depend on the wavelength. The former, i.e., the dependence of the deflection angle, can at least partially compensate for a dispersion of the hologram 2, at least for the one described in Fig. 9 The displayed central ray 6a, which emanates from the light source 4. Compared to embodiments with mirrors as in Fig. 1 However, a larger installation space may be required, at least if the diffractive reflecting lens 8 is planar and parallel to the hologram 2.

[0063] One variant of this is in Fig. 10 The diagram shows a diffractive element 8', for example a transmission hologram, used instead of a reflecting lens 8. This element deflects light rays 6a from the light source 4, for example a spherical wave, into a plane wave, which is reflected at the front of the optical fiber 1 and directed towards the hologram 2. This allows the thickness of the optical fiber 1 to be reduced. Furthermore, the diffractive element 8' can be arranged together with the hologram 2, for example, on a common film. A disadvantage is that, as a transmitting element, the efficiency of element 8' is typically wavelength-dependent.

[0064] Such diffractive elements 8, 8' can also be used in other illustrated embodiments, for example in Fig. 5, Fig. 6 or Fig. 7 be used.

[0065] From the above description of various variations and modifications, it is evident that the exemplary embodiments serve only for illustration and are not to be interpreted as restrictive.

Claims

1. Light-emitting device for a vehicle, comprising: a light source arrangement (4), which is arranged to emit light in the direction of a first half-space, a reflection hologram (2), which is configured to produce a light-emission signature during illumination in a direction that faces in a half-space that it located opposite the first half-space, and a one-piece light-guiding body (1) with a beam deflection portion (3), which is configured to direct the light from the light source arrangement (4) in the direction of the second half-space onto the hologram (2), wherein the beam deflection portion (3) comprises a curved mirror formed by a curved surface of the light-guiding body (1), wherein the beam deflection portion (3) is designed to direct light coming from the light source arrangement (4) as a spherical wave onto the hologram (2) as a plane wave.

2. Light-emitting device according to Claim 1, wherein the mirror comprises a portion of a parabolic mirror.

3. Light-emitting device according to either of Claims 1 or 2, wherein the light source arrangement comprises a plurality of light sources, wherein the beam deflection portion comprises separate portions for the plurality of light sources.

4. Light-emitting device according to Claim 3, wherein the plurality of portions are configured to direct light at different angles onto the hologram (2) for selectively producing different light-emission signatures.

5. Light-emitting device according to any of Claims 1-4, wherein the beam deflection portion (3; 8) is configured to direct at least one part of the light from the light source arrangement (4) to the hologram via a reflection at one side of the light-guiding body (1).

6. Light-emitting device according to Claim 5, wherein the side comprises a side of the light-guiding body located opposite the hologram.

7. Light-emitting device according to Claim 5 or 6, wherein the hologram (2) has a portion with an efficiency of between 45% and 55%, wherein the light-guiding body (1) is configured to direct non-diffracted light from the portion with the efficiency of between 45% and 55% to a further portion of the hologram (2).

8. Light-emitting device according to any of Claims 1-7, wherein the light-guiding body (1) has a curved light input coupling face (7b) for coupling in light from the light source, wherein a centre of curvature of the light input coupling face (7b) is located at the location of a light source of the light source arrangement (4).

9. Light-emitting device according to any of Claims 1-8, wherein the light-guiding body (1) has a curved light input coupling face (7b) for coupling in light from the light source, wherein a combination of the curved light input coupling face (7b) and the beam deflection portion (3) is designed to direct light coming from the light source arrangement (4) as a spherical wave onto the hologram (2) as a plane wave.

10. Light-emitting device according to any of Claims 1-9, wherein the light source arrangement (4) is formed by one or more approximate point light sources.

11. Light-emitting device according to any of Claims 1 to 10, wherein the light-guiding body (1) is produced from a plastic having a refractive index of approximately 1.5.