Lighting device, in particular for a motor vehicle

Abstract

The invention relates to a lighting device (2), in particular for a motor vehicle, for the visible display of at least one decoration (4). The lighting device (2) comprises: a plurality of light sources (100) for generating light; and at least one outer light guide section (200), which is arranged outside a radar coupling-in surface (402) of the at least one radar transmission section (400) for coupling in a radar beam with respect to an optical axis (A) of the lighting device (2), the at least one outer light guide section (200) guides light generated by the light source (100) and coupled through the respective coupling-in surface (202) from the respective light coupling-in surface (202) into the at least one radar transmission section (400).

Description

Technical Field

[0001] The invention relates to a lighting device, in particular a lighting device for a motor vehicle. Background Art

[0002] The radome or cover of an automotive radar system installed in the radiator grille is arranged in the prior art behind the manufacturer's logo in the center of the vehicle in the radiator grille. Summary of the invention

[0003] The problems of the prior art are solved by the lighting device according to claim 1 .

[0004] One aspect of the present description relates to the following subject matter: a lighting device, in particular a lighting device for a motor vehicle, for the visible display of at least one decorative object, the lighting device comprising: a plurality of light sources for generating light; at least one external light guide segment, which is arranged relative to an optical axis of the lighting device outside a radar coupling-in surface of at least one radar transparent segment for coupling-in radar radiation, wherein the at least one external light guide segment guides light generated by the light sources and coupled-in via the respective coupling-in surface, starting from the respective light coupling-in surface, into the at least one radar transparent segment; and at least one radar transparent segment, which A method of manufacturing a decorative object comprising: providing a radar coupling-in surface for coupling in radar radiation and providing a coupling-out surface for coupling out the coupled-in radar radiation and for emitting a light distribution representing at least one decorative object in dependence on light introduced into an internal light-conducting section of a radar transparent section along an imaginary circular section by means of an external light-conducting section; wherein at least one adhesive connects a surface of the internal light-conducting section of the radar transparent section pointing toward the coupling-out surface with a surface of the remaining radar transparent section pointing away from the coupling-out surface, at least in sections, in a flat and material-fitting manner, and wherein a first optical refractive index of the internal light-conducting section is greater than a second optical refractive index of the at least one adhesive.

[0005] On the one hand, the use of adhesive between the inner light guide section and the remaining radar transparent section allows a decoupling of design and manufacturing technology. In other words, a degree of freedom is created in the design and manufacture of the lighting device. Thus, for example, the layer structure and possible coating of the remaining radar transparent section can be carried out independently of the light and radar transparent inner light guide section that is glued on later.

[0006] On the other hand, surface gluing with a selected refractive index jump achieves not only an increased strength but also a reduced color shift.The refractive index of the adhesive is selected to be lower than the refractive index of the substrate or the internal light guide section into which the light is guided.

[0007] If light beams from the inner light-conducting section now impinge on the glued surface with a flat angle of incidence, these light beams undergo total reflection in the visible spectrum which is almost independent of the wavelength.

[0008] A light beam impinging on the interface between the internal light-conducting section and the adhesive at an acute angle of incidence is not completely reflected at the refractive index jump between substrate and adhesive, but only experiences its reflection at another layer, such as a PVD coating, in the remaining radar-transparent section.

[0009] However, the proportion of the brightness of the flat reflected light beam is low in the case of a refractive index jump in the area farther from the light source. The intensity of the light beam with an acute angle of incidence in the area close to the light source in the outcoupling region is not significantly disturbed. The refractive index jump adjusted by the selection of the inner light guide segment and the adhesive therefore acts as a filter for the light beam guided in the inner light guide segment in dependence on the angle of incidence.

[0010] An advantageous example is characterized in that the or a further adhesive is arranged on a surface of the external light-conducting section, in particular oriented toward the light coupling-out surface.

[0011] Therefore, it has an optical advantage when the glue or adhesive, for example, overflows at the exit point and wets the part of the light guide that is coupled into the collar. Of course, the glue can also be arranged at this point in a dedicated manner. The adhesive with a lower refractive index does not refract the light beam and leave the light guide. Therefore, the loss of this beam component is reduced by the adhesive. More precisely, these light beams are already completely reflected in the coupling geometry and do not experience losses.

[0012] An advantageous example is characterized in that the layer comprising adhesive comprises a plurality of spacers which are dimensioned substantially identically for a layer thickness associated with the adhesive.

[0013] A uniform layer thickness is ensured by means of the spacers in order to keep the losses during radar transmission low. Therefore, it is proposed at this point to introduce the spacers into the light guides to be glued.

[0014] If adhesive is applied, it is pressed into the remaining free space between the inner light-conducting section and the remaining radar-transmissive section during pressing, for example until it exits laterally. The resulting layer thickness is defined by the height of the spacer.

[0015] An advantageous example is characterized in that the spacer or at least a part of the spacer is arranged in a lateral region of the radar transparent section or outside the radar transparent section.

[0016] Advantageously, the spacers are arranged on at least one of these surfaces in such a way that they are located outside the area to be illuminated and the radar area, so that neither the light function nor the radar function is negatively influenced.

[0017] An advantageous example is characterized in that the spacer or at least a part thereof protrudes as a projection from the surface of the inner light-conducting segment.

[0018] An advantageous example is characterized in that the spacer or at least a part thereof protrudes as a projection from the surface of the remaining radar-transparent section.

[0019] It is thereby particularly advantageous if the contact surface contacts an opposing surface of the inner light-conducting section, thereby reducing adverse optical influences of the spacer.

[0020] An advantageous example is characterized in that at least a portion of the plurality of spacer holders tapers distally, in particular tapers to a point.

[0021] Advantageously, the spacer is designed, for example, to be conical, so that the resting surface on the panel or the remaining radar-transparent area is reduced, but the function of the distance adjustment is still ensured.

[0022] An advantageous example is characterized in that at least a portion of the spacer has a second optical refractive index and / or a permeability such as an adhesive.

[0023] Advantageously, optical interference is reduced by the spacers and these spacers can also be used in the optically active area of ​​the layer with adhesive. The spacers are thus not only "invisible" to the wavelength of the radar but also to the human eye and can therefore also be arranged in a more central area of ​​the radar-transparent section.

[0024] An advantageous example is characterized in that the spacers are arranged prefabricated from a cured base material of the adhesive on one of the two surfaces before the adhesive is introduced while still in a liquid state.

[0025] Advantageously, further material selection with regard to the spacers can be omitted.

[0026] An advantageous example is characterized in that the further light-conducting section as part of the remaining radar-transmissive section provides a surface which points away from the outcoupling surface, wherein the projection projects from the further light-conducting section.

[0027] The further light-conducting section can be produced in a simple and cost-effective manner.

[0028] An advantageous example is characterized in that a further section, in particular a holding section or a distance section, is connected to the lighting device by means of a further adhesive and an associated spacer.

[0029] Advantageously, the light-conducting properties can therefore also be improved in the region of the other section. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In the attached picture:

[0031] Figure 1 A lighting device for a motor vehicle is shown in schematic cross section;

[0032] Figure 2 shows the effect of an adhesive in a schematic cross section of an example lighting device;

[0033] Figures 3 to 9 Shows something like Figure 1 Another example of a lighting device. DETAILED DESCRIPTION

[0034] Figure 1 A lighting device 2, in particular for motor vehicles, is shown schematically in section AA. The lighting device 2 comprises a plurality of light sources for emitting light and a light guide segment 200, which is arranged, for example, radially outside of a radar coupling surface 402 of a radar transparent segment 400 for coupling in radar radiation 6 relative to the optical axis A of the lighting device 2 and extends at least in sections along an imaginary circular segment 220, which is arranged at the transition from the segment 400 to the inner light guide segment 406. The imaginary circular segment 220 can be configured, for example, as a circle, a polygon or as an arbitrary line guide. Here, the circular segment 220 can be closed or opened in sections. In this example, the circular segment 220 is configured as a substantially circular and closed by itself. It can be provided that the circular segment 220 is adapted to a specified structural space for the lighting device 2. Thus, the light guide segment 200 is also adapted to or can be adapted to the structural space.

[0035] The light source 100 is in this example designed as a respective LED. It can be provided that a plurality of LEDs are arranged on one or more printed circuit boards 108 and form the light source 100. Furthermore, it can be provided that an LED strip provides the light source. LEDs with one or more selected colors or RGB LEDs can be used, wherein a single light source of the RGB LED can directly generate the colors or at least some of the colors are generated using a color converter / fluorescent dye pumped with blue or UV light.

[0036] It can be provided that the printed circuit board 108 is designed to be continuous or separate. Here, the LEDs arranged on the continuous and / or separate printed circuit board 108 can be arranged in groups of different numbers and with different or uniform spacings between the LEDs or groups.

[0037] In the example shown, the light sources 100 are arranged in a plane 110. It may be provided that the LEDs are arranged in different planes.

[0038] In another example, the light sources are arranged on four separate printed circuit boards, which are located in the plane 110 and rotated 45° clockwise adjacent to each other (the axis of rotation is the optical axis in the direction of travel). Here, each two circuit boards on opposite sides are jointly controlled by the corresponding control functions of at least one control device 500. Alternatively, the opposite circuit boards or printed circuit boards are operated by the corresponding assigned control devices. Thus, if one of the two sides fails, the proportion of the luminous flux conducted into the radome is halved, whereby although the division of the light sources is not performed geometrically in a mirror-symmetrical manner, homology of the position light with the overall panel behind can be achieved later.

[0039] The optical waveguide section 200 comprises at least one light coupling-in surface 202 for coupling-in light from the light sources 100, 100a, 100b, wherein the optical waveguide section 200 guides the coupled-in light 102 starting from the light coupling-in surface 202 to a light transition region 300 between the optical waveguide section 200 and the radar transparent section 400. Of course, the optical waveguide section 200 and the light transition region 300 may also be designed to be radar transparent.

[0040] Furthermore, the light guide section 200 facing the light transition region 300 has a light guide surface 208 which is formed by a convex outer contour 206 which is an imaginary extension facing away from the optical axis A of the lighting device 2 .

[0041] The curvature of the convex outer contour 206 can be adapted to a given construction space for the lighting device 2. Furthermore, it can be provided that the curvature of the convex outer contour 206 is different at corresponding points on the imaginary circumferential path section 220. In an exemplary embodiment, the light guide surface 208 is generated by rotating the convex outer contour 206 about the optical axis A.

[0042] The convex outer contour 206 can be designed in its basic form as an ellipse, which can be deformed into a freely deformable surface due to given conditions or the desired guidance of the light 102 .

[0043] The lighting device 2 also includes a radar-transparent inner section 400 having a radar coupling-in surface 402 for coupling-in radar radiation 6 and having a coupling-out surface 404 for coupling-out the coupled-in radar radiation 6 and for emitting a light distribution 106 as a function of light introduced into the radar-transparent inner section 400 by means of the optical waveguide section 200 .

[0044] At least one adhesive 600 connects a surface 406S of the inner light-conducting section 406 of the radar transparent section 400, which is arranged in the direction of the radar component 8 and points toward the coupling-out surface 404, to the remaining surface 400S of the radar transparent section 400, which extends in the direction of the coupling-out surface 404 and points away from the coupling-out surface 404, at least in sections in a planar and materially bonded manner. A first optical refractive index of the inner light-conducting section 406 is greater than a second optical refractive index of the at least one adhesive 600.

[0045] In this specification, the remaining radar transparent section 400 may be understood as a portion of the radar transparent region 400 located between the surface 400S and the outcoupling surface 404 .

[0046] Radar transparent section 400 is designed to couple incident radar radiation at radar coupling-in surface 402 into radar transparent section 400 and to couple this radar radiation out at coupling-out surface 404 .

[0047] In this example, radar radiation 6 is generated and / or processed by a radar device or component. Radar component 8 is therefore arranged relative to radar transparent section 400 in such a way that radar component 8 receives and / or transmits radar waves via radar transparent section 400 .

[0048] The radar component 8 receives and / or transmits radar waves having a magnetic field direction and a field direction of an electric field, wherein a preferred direction V of at least one heating wire 10 coincides with one of the magnetic field directions of the radar waves or encloses an angle with the magnetic field direction that is less than 15°, in particular less than 10°, in particular less than 5°.

[0049] Radar transparent section 400 comprises at least one, in particular a plurality of, heating elements or heating wires 10 .

[0050] The heating line 10 is shown in this example as a plurality of heating coils. The heating coils in this example consist of an electrically conductive material, in particular of a metal wire, for example a copper wire and / or a nickel wire.

[0051] In this example, the radar transparent section 400 and the light guide section 200 consist of at least a material that is transparent to visible light, such as PC, PU, ​​PUR, PMMA or silicone. Different materials may also be provided for the respective sections.

[0052] For example, it is provided that at least one heating wire 10 is guided at least in sections through the inner light-conducting section 406 of the radar-transparent section 400 .

[0053] Instead of using a low-refractive index adhesive, it is also possible to select a high-refractive index substrate for the light guide (Zeonex, polysulfone) and connect it with a "normal" adhesive with a refractive index close to that of PMMA / PC. Then, the physical basis of the described effect - the refractive index jump to a lower refractive index at the layer transition - would also be created.

[0054] The heating wire 10 is thus integrated into the radar-transparent section 400 and surrounded by a material that is transparent to visible light. Here, the structural height of the lighting device along the optical axis A is accordingly kept in the region of approximately multiples of λ / 2 of the radar radiation 6. In one example, the radar radiation has a frequency of 76.5 GHz, so that the structural height of the lighting device 2 is 1.4 mm when polycarbonate is used as the radar-transparent section 400. At multiples of this structural height, the transmittance of the radar radiation 6 decreases with increasing multiples.

[0055] It may be provided that the surface 12 of the heating wire 10 comprises white or a white tint, in particular in the form of a layer applied to the heating wire 10 .

[0056] In this example, the heating wire 10 has a wire diameter of 50 μm to 200 μm. The heating wire 10 is visible through the radar transparent section 400 when the light source 100, 100a, 100b is switched off without the application of the layer. When the light source 100, 100a, 100b is switched on, the shadow of the heating wire 10 is visible through the radar transparent section without the application of the layer. The applied layer makes the heating wire 10 less recognizable when the light source 100, 100a, 100b is switched off. When the light source is switched on, the applied layer causes the light irradiated onto the surface 12 of the heating wire 10 to be scattered in multiple directions, wherein the shadow of the heating wire 10, in particular parts of the heating wire, are less recognizable.

[0057] The light source 100 is operated by means of at least one control device 500 .

[0058] The radar transparent section 400 comprises light-transmitting openings 408a, 408b in a transmission-inhibiting layer 408 having a reduced degree of transmission to light. In this example, the transmission-inhibiting layer 408 is provided as a coating. Foil or other materials or intermediate layers are also conceivable. The transmission-inhibiting layer 408 can also be designed to be non-transparent.

[0059] By means of the light transmission openings 408a, 408b in the transmission-inhibiting layer 408, any pattern or logo 4 in the sense of a decoration 4 can be depicted, through which the light 102 introduced into the radar-transparent section 400 emerges. This results in an illumination of the decoration formed by the light transmission openings 408a, 408b, which is particularly recognizable in a top view of the lighting device 2.

[0060] It can be provided that the reflective section 410 of the radar transparent section 400, which is arranged in an orientation in the direction of the coupling-in surface 202 for coupling-in the radar radiation 6, comprises at least in sections reflective surfaces 412a, 412b which increase the scattering effect on the incident light. As a result, the light incident on the reflective surfaces 412a, 412b introduced into the radar transparent section 400 is scattered, whereby more light beams are deflected in the direction of the optical axis A and the light-through openings 408a, 408b. As a result, more light beams pass through the openings 408a, 408b. The area of ​​the reflective section is a reflection area for visible light, not for radar radiation.

[0061] It can be provided that the reflective surfaces 412a, 412b with increased scattering effect are arranged such that the reflected and scattered light passes through the respectively assigned light transmission openings 408a, 408b. In this example, the reflective surfaces 412a, 412b are aligned and arranged with the openings 408a, 408b.

[0062] It can be provided that a partially transparent layer 416, which appears chrome-like in optical appearance and has a higher degree of transmission than the transmission-inhibiting layer 408, at least partially closes the openings 408a, 408b. In this example, the partially transparent layer 416 is continuously formed through the lighting device 2. The partially transparent layer 416 can be arranged in front of or behind the transmission-inhibiting layer 408 in the light emission direction. Alternatively, other appearances of the partially transparent layer 416 can be conceived, such as a color filter. By means of the partially transparent layer 416, the pattern presented by the openings 408a, 408b is also affected in its appearance even when the light sources 100a, 100b are turned off.

[0063] It may be provided that the lighting device 2 is designed as part of a front grille for a motor vehicle or is integrated or integrable into this part.

[0064] It may be provided that at least one heating wire 10 is arranged between the associated light passage opening 408 a , 408 b and the reflective section 410 , in particular one of the reflective surfaces 412 a , 412 b which increase the scattering effect.

[0065] It is provided that the light-conducting region 406 is manufactured separately at least in sections, in particular as a heating section. Here, the light-conducting section 406 can include the heating element 10. Of course, the heating element 10 can also be manufactured separately from the inner light-conducting section 406.

[0066] In one example, the hardness of the adhesive 600 is at least Shore A5 but at most Shore A60 at a tensile strength of 0.5 to 5 MPa and a processing viscosity of 300 to 15000 mPas.

[0067] In another example, in the case of full-surface gluing, a very liquid glue with improved optical properties is used during processing. In the case of a liquid glue, air bubbles are avoided during curing, which leads to a reduction in the amount of losses during curing.

[0068] Figure 2 The effect of the adhesive 600 on the light coupled into the internal light guide section 406 is illustrated. Since a light beam incident evenly on the interface between the adhesive 600 and the internal light guide section 406 is totally reflected and thus guided further away from the region of the light coupling section 200, sufficient luminous flux can also be provided to the light-transmitting opening 408a for producing the decoration, which is located further away from the edge and in the middle of the decoration, to produce an apparently uniform luminous image of the decoration.

[0069] On the inside of the panel, along Figure 2 The direction of the radar component 6, not shown in the figure, partially follows a layer 408 in the form of a lacquer layer (black / car paint...), with which the panel is concealed so that only the areas that can then be illuminated are visible from the front side, i.e. all gaps remain black or are covered with a corresponding top print color.

[0070] The spaces to be illuminated that are not covered by the top printed color are additionally coated on the inside with a chrome design material (e.g. indium or silicon) or a material stack with radar transparent properties by a coating process (e.g. PVD coating: A side outward, B side inward) and have a chrome-like appearance on the A side outward, so that in the unilluminated state, these surfaces have a chrome appearance. Figure 1 Differently, the surface 400S is therefore provided by a coating having a first side 420 and a second side 430, for example a PVD coating. PVD stands for "Physical Vapor Deposition". Here, it is a vacuum coating process in which a thin film is applied to the corresponding surface by condensing a material from the gas phase. PVD processes also include: electron beam evaporation (E-Beam Evaporation), thermal evaporation, sputtering (atomization), arc evaporation. The advantages of PVD coatings also include: high hardness and wear resistance; good adhesion on the substrate; high corrosion resistance; thin and uniform coating; the possibility of coating a variety of materials; more environmentally friendly compared to some wet chemical processes.

[0071] In the optical structure, the internal light guide section 406 is glued over the entire surface to the underside of the panel on the built-in layer of the second side 430. For example, a highly transparent glue in the visible spectrum is used, such as an adhesive 600 with low absorption, which has a refractive index in the region of the substrate to be glued.

[0072] For a chrome optical appearance on the front side in the unilluminated case, i.e. a label design, a radar transparent coating is applied on the rear side in the direction of the side sections 420 and 430. Such a coating provides different optical properties on its upper side 420 and lower side 430, for example, depending on whether the reflection measurement is made from the upper and lower sides of the coating. Here, in the present case, the B side 430 of the PVD coating provides much lower reflection properties and a very large wavelength dependence. The result is a high color shift, especially in the case of multiple reflections. The light beam coupled into the light guide is now totally reflected across the visible spectral range almost without loss in the region of the coupling-in collar. Due to the matching of the refractive indices of the adhesive 600 and the light-transmitting section 406, the light beam strikes the B side 430 of the PVD coating with its full intensity, but is totally reflected already at the interface between the section 406 and the adhesive 600 at a flat illumination angle. As a result, the outcoupling region with a greater distance from the LED is preferably illuminated as brightly as the outcoupling region located near the LED, which leads to a significant improvement in the uniformity in the logo or decoration to be illuminated.

[0073] Figure 3 A further example of a lighting device 2 is shown in schematic cross section. The or a further adhesive 600 is arranged on a surface 200S of the outer light guide segment 200 , in particular oriented towards the light outcoupling surface 404 .

[0074] Figure 4 An example of lighting device 2 is shown in which uniform spacing of two surfaces surrounding adhesive 600 is improved. The layer including adhesive 600 includes a plurality of spacers 602a-b that are sized substantially the same for a layer thickness associated with adhesive 600.

[0075] The layer thickness is preferably adjusted by means of adhesive 600 in such a way that an optimal layer thickness for the radar wavelength of the radar component results from a multiple of λ / 2 for the overall structure of radar transparent section 400, wherein the dielectric constant of adhesive 600 is taken into account by a suitable choice of the layer thickness of adhesive 600. At the same time, it is thereby ensured that the entire upper side of inner light-conducting section 406 is completely covered with adhesive, so that a refractive index jump occurs at every location on the light-conducting surface.

[0076] The spacers 602 a - b or at least a portion of the spacers 602 a - b are arranged in a lateral region of the radar transparent section 400 or outside of the radar transparent section 400 relative to the optical axis A or the central axis.

[0077] The spacers 602a - b or at least a portion thereof protrude as a protrusion from the surface 406S of the inner light guide segment 406 .

[0078] Figure 5 Shows Figure 4An alternative embodiment of the example of . There, the spacers 602a-b are configured as cones or pyramids. At least a portion of the plurality of spacers 602a-b tapers in the distal direction, in particular gradually becomes pointed.

[0079] Figure 6 Another example of the lighting device 2 is shown. The spacers 602a - b or at least a part thereof protrude as a protrusion from the surface 400S of the remaining radar transparent section 400 .

[0080] Therefore, it is proposed to design the spacers 602a-b as conical and attach them to the underside of the panel or the remaining radar-transparent section 400 so that the contact surface on the inner light-conducting section 406 is as small as possible, but the function of the distance adjustment is still guaranteed. In addition, the tip of the spacer cone is thus rotated downward in the direction of the radar component 6. The area that rests on the inner light-conducting section 406 is now reduced or minimized, so that negative light effects such as hot spots or brightness efficiency losses no longer occur.

[0081] Figure 7 Another example of a lighting device 2 is shown in cross section. At least a portion of the spacers 602a - d has a second optical refractive index and / or permeability like the adhesive 600 .

[0082] The spacers 602 a - b are prefabricated from a cured base material of the adhesive 600 and are arranged on one of the two surfaces before the liquid adhesive 600 is introduced.

[0083] Figure 8 Another example of a lighting device 2 is shown. A further light-guiding section 407 as part of the remaining radar-transparent section 400 provides a surface 400S pointing away from the outcoupling surface 404 , wherein projections protrude from the further light-guiding section 407 .

[0084] Figure 7 and Figure 8 The difference between the lighting devices shown is that in Figure 7 In the case of a spacer, the spacer as a separate element must be separately mounted on the rear side of the panel, whereas in Figure 8 In the case of a panel, the spacers are an integral part of the panel.

[0085] Fig. 9 An additional example of a lighting device 2 is shown. A further section 900 , in particular a holding section or a distance section, is connected to the lighting device 2 by means of a further adhesive 902 and associated spacers 904a - b.

[0086] Of course, the shape of the spacer can also be different from that shown. For example, a mesh consisting of thin plates can be designed instead of a cone, so that it has sufficient stability through the interconnection of the individual webs and the spacing for the glue is specified by the height of the mesh.

[0087] The adhesive 600 in this specification is used in a viscous state, for example, during manufacture, so as to form part of the relevant layer after curing. Alternatively, a gluing film can also be used instead of a thin liquid glue for flat gluing. Here, the film substrate or the glue on the film has a lower refractive index. Advantageously, the film substrate ensures a constant thickness. Then, the spacer can also be omitted.

[0088] For example, the protective layer of this layer is used as a finishing layer for a PVD coating or an indium chromium look coating or a chrome look film. The effect also occurs when the protective layer has a lower refractive index than the light guide element. In the case of chrome design films and light guides made of PC, this effect can also be achieved by a film embedded in PMMA.

Claims

1. A lighting device (2), in particular a lighting device (2) for a motor vehicle, for visibly displaying at least one decorative object (4), the lighting device (2) comprising: a plurality of light sources (100) for generating light; at least one external light guide section (200), which is arranged, relative to an optical axis (A) of the lighting device (2), outside a radar coupling-in surface (402) of at least one radar transparent section (400) for coupling-in radar radiation, wherein the at least one external light guide section (200) guides light generated by the light source (100) and coupled-in via the corresponding coupling-in surface (202) starting from the corresponding light coupling-in surface (202) into the at least one radar transparent section (400); and the at least one radar transparent section (400), the radar transparent section (400) having the radar coupling-in surface (402) for coupling-in radar radiation and having a coupling-out surface (404) for coupling-out the coupled-in radar radiation and for emitting a light distribution representing the at least one decorative object (4) in dependence on light introduced into the inner light-conducting section (406) of the radar transparent section (400) along an imaginary circular path section (220) by means of the outer light-conducting section (200); wherein at least one adhesive (600) connects a surface (406S) of the internal light-conducting section (406) of the radar transparent section (400) pointing toward the coupling-out surface (404) at least in sections with a surface (400S) of the remaining radar transparent section (400) pointing away from the coupling-out surface (404) in a flat and materially compatible manner, and wherein a first optical refractive index of the internal light-conducting section (406) is greater than a second optical refractive index of the at least one adhesive (600).

2. The lighting device (2) according to claim 1, wherein: The or a further adhesive (600) is arranged on a surface (400S) of the external light-guiding section (200), in particular oriented toward the light-coupling surface (404).

3. The lighting device (2) according to claim 1 or 2, wherein: A layer comprising the adhesive (600) includes a plurality of spacers (602a-b) that are substantially equally sized for a layer thickness associated with the adhesive (600).

4. The lighting device (2) according to claim 3, wherein: The spacers (602a-b) or at least a portion of the spacers (602a-b) are arranged in a lateral region of the radar transparent section (400) or outside the radar transparent section (400).

5. The lighting device (2) according to claim 3 or 4, wherein: The spacers (602a-b) or at least a portion thereof protrude as a protrusion from the surface (406S) of the inner light guide segment (406).

6. The lighting device (2) according to any one of claims 3 to 5, wherein: The spacers (602a-b) or at least a portion thereof protrude as a protrusion from the surface (400S) of the rest of the radar transparent section (400).

7. The lighting device (2) according to any one of claims 3 to 6, wherein: At least a portion of the plurality of spacer holders (602a-b) tapers distally, in particular, tapers to a point.

8. The lighting device (2) according to any one of claims 3 to 7, wherein: At least a portion of the spacers (602a-d) has the second optical refractive index and / or permeability as the adhesive (600).

9. The lighting device (2) according to any one of claims 3 to 8, wherein: The spacers (602a-b) are prefabricatedly arranged on one of the two surfaces from a cured base material of the adhesive (600) before the adhesive (600) is introduced while still in a liquid state.

10. The lighting device (2) according to any one of claims 3 to 9, wherein: A further light-conducting section (407) as part of the remaining radar-transparent section (400) provides the surface pointing away from the outcoupling surface (404), and the projection protrudes from the further light-conducting section (407).

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