Lighting device for vehicle

Abstract

The invention relates to a lighting device for a vehicle, comprising: a housing (1); a cover plate (2, 2 ') covering the opening of the housing (1); a light module (4) comprising a plurality of light sources (5) and comprising an optical unit (6) for generating a predetermined light distribution, the optical unit (6) having a light guide (7) with a light-in surface (12) and a light-out surface (23); wherein the light guide (7) is connected to the cover plate (2, 2 '); a first section (16) of the light guide (7) facing the light source (5) protrudes from an inner side (17) of the cover plate (2, 2 '), or a light coupling-in surface (12) of the light guide (7) extends flush with the inner side (17) of the cover plate (2, 2'); a second section (18) of the light guide (7) facing away from the light source (5) protrudes from an outer side (19) of the cover plate (2, 2 '), or a light coupling-out surface (23) of the light guide (7) extends flush with the outer side (19) of the cover plate (2, 2').

Description

Field of the Invention

[0001] The present invention relates to a lighting device for a vehicle, the lighting device having a housing, a cover plate covering an opening of the housing, an optical module including a plurality of light sources, and an optical unit for generating a predetermined light distribution, wherein the optical unit has an optical waveguide with a light coupling-in surface and a light coupling-out surface. Background Art

[0002] A lighting device for a vehicle is known from DE102012112072A1, which has an optical module including a light source and an optical element for generating a predetermined light distribution. The optical module is arranged in an interior space of the lighting device, wherein the interior space is defined by a housing and a light-transmissive cover plate covering an opening of the housing. An optical unit arranged in front of the light source along a main radiation direction includes a light plate extending substantially parallel to the cover plate, the light plate having regional grooves for receiving an optical waveguide and a light-shielding member. The optical waveguide extends substantially perpendicular to the cover plate and is configured as a flat optical waveguide having a narrow-side light coupling-in surface and a narrow-side light coupling-out surface. Parallel flat sides extend between the light coupling-in surface and the light coupling-out surface, and the coupled-in light is totally reflected at the flat sides. The light coupling-out surface of the optical waveguide is arranged at a small distance from the inner side of the cover plate. If the lighting device is arranged in an opening of a vehicle body at a strong grazing angle, wherein the cover plate extends at a sharp grazing angle relative to the main radiation direction of the lighting device, total reflection may occur at the inner side of the cover plate, so that the light emitted from the light coupling-out surface of the optical waveguide causes damage to the light distribution. In addition, the light reflected at the cover plate may cause further retro-reflection at an adjacent light-shielding member, which has an interfering effect on the desired predetermined lighting signature. It is therefore desirable to generate a clear and distinct light signature.

[0003] A lighting device for a vehicle is known from EP3201523B1, which is arranged beside a radiator grille of a vehicle. The interior space of the lighting device is formed by a housing and a light-transmissive cover plate covering an opening of the housing. A light source is arranged in the interior space of the lighting device, and a reflector is provided as an optical unit to generate a predetermined driving direction indication function. Additionally, the cover plate has corresponding formed optical slats in extensions of the slats of the radiator grille, the optical slats protruding from an outer surface of the cover plate. Thereby, the front side of the vehicle has a uniform shape feature, which includes the radiator grille and the lighting device. Not only the optical slats but also adjacent surface regions of the cover plate are used for transmitting light generated by the same light source to generate the same light function. Summary of the Invention

[0004] It is an object of the present invention to further improve a lighting device for a vehicle having an optical waveguide, such that a light function is provided in a simple and cost-effective manner, wherein in particular light losses are avoided.

[0005] To achieve the above object, the present invention is characterized in combination with the preamble of claim 1 in that the light guide is connected to the cover plate, wherein a first section of the light guide facing the light source projects from the inner side of the cover plate, or the light coupling-in surface of the light guide extends flush with the inner side of the cover plate, and wherein a second section of the light guide facing away from the light source projects from the outer side of the cover plate, or the light coupling-out surface of the light guide extends flush with the outer side of the cover plate.

[0006] According to the present invention, the light guide is integrally provided in the cover plate of the lighting device. Therefore, the light transmitted by the light guide is directly emitted or coupled out into the surrounding environment of the lighting device or the vehicle, thereby providing an effective light function or signal function. Thereby, disturbing retroreflection on the cover plate is avoided because the light coupling-out surface is provided on the outer side of the cover plate. Thereby, light loss can be reduced. Since only a part of the light guide is provided in the internal space of the lighting device or no part of the light guide is provided in the internal space of the lighting device, the lighting device can have a smaller structural depth. Since the light is directly emitted from the light guide into the surrounding environment, a clear and interference-free light signature can be generated. This is determined only by the light coupling-out surface of the light guide.

[0007] According to a further improvement of the present invention, the light guide is integrally connected to the cover plate. Advantageously, these two components can be manufactured in a single manufacturing step, for example, by injection molding. Thereby, components and tools can be advantageously saved. The assembly cost is reduced.

[0008] According to a further improvement of the present invention, a coupling-in optical device is provided upstream of the light flow of the light guide. The coupling-in optical device is arranged between the light source and the light coupling-in surface of the light guide and enables targeted coupling of the light generated by the light source into the light guide. Thereby, disturbing scattered light radiating past beside the light guide is avoided.

[0009] According to a further improvement of the present invention, the light coupling-out surface of the light guide has a scattering optical device or an optical structure. Advantageously, in this way, legal requirements regarding the horizontal illumination width of the light function can be met.

[0010] According to a further improvement of the present invention, the light coupling-out surface of the light guide has a plurality of micro-optical device elements as the scattering optical device, and the size of the micro-optical device elements is in the millimeter range. For example, the micro-optical device elements can have a width and / or height of less than 1 mm, preferably less than 0.5 mm. Thereby, scattering, especially horizontal scattering, is advantageously achieved, and the observer cannot perceive the scattering structure from the outside, and more precisely, especially in the non-operating state of the lighting device, the observer cannot perceive the scattering structure from the outside. Instead of the micro-optical device elements, the desired light scattering can also be achieved by means of a diffused structure implemented as an etched structure, a corrosion structure or a laser structure.

[0011] According to a further improvement of the present invention, the cover plate and the light guide are manufactured by two-component injection molding, wherein the back side of the cover plate is at least partially formed by a black or light-impermeable material component. This black or light-impermeable material component extends particularly in the peripheral region of the light guide, and the light guide itself is composed of a transparent material. Thereby, it is advantageously ensured that the adjacent sections of the light guide and the cover plate are optically separated. Thereby, it is also possible to advantageously prevent the light source of other light modules within the lighting device from having an undesired scattering effect on the light guide.

[0012] According to a further improvement of the present invention, the cover plate and the light guide have a common intersection section, and the cover plate and the light guide intersect in this intersection section. The intersection section extends in the first surface area of the cover plate and is made of a transparent material. In addition, the cover plate has a second surface area configured to be transparent, and the second surface area is spaced apart from the first surface area by a distance, so that the light of another second light module provided within the lighting device can be transmitted through the second surface area. Therefore, the cover plate has respective window-shaped surface areas for the light to pass through for different light functions.

[0013] According to a further improvement of the present invention, the light guide is designed as a flat light guide, and the flat light guide has a narrow-side light coupling-in surface and a narrow-side light coupling-out surface. Advantageously, the flat light guide can be integrated into the cover plate in a space-saving manner for generating, for example, a signal light function.

[0014] According to a further improvement of the present invention, at least a part of the flat side of the light guide extending outside the lighting device is provided with scattering optical devices, so that additional lateral light radiation can be achieved. This lateral light radiation can be used, for example, to generate a lateral marking light function. The light coupling-out surface configured on the narrow side is used to generate a main signal light function, such as a daytime running light function or a tail light function.

[0015] According to a further improvement of the present invention, the outer surface of the cover plate is provided with scattering optical devices. Advantageously, the light functions generated by the second light module can undergo predetermined scattering. Description of the Drawings

[0016] The embodiments of the present invention will be described in more detail with reference to the accompanying drawings. In the drawings:

[0017] Figure 1 A schematic top view of the lighting device is shown,

[0018] Figure 2 A perspective view of the cover plate of the lighting device with an integrated light guide, viewed obliquely from the front, is shown,

[0019] Figure 3 shows a front view of a cover plate according to Figure 2 ,

[0020] Figure 4 shows a side view of the cover plate according to Figure 3 in the direction X according to Figure 2 ,

[0021] Figure 5 shows an enlarged view in the light guide area of the lighting device as viewed from above,

[0022] Figure 6 shows a perspective rear view of a cover plate - light guide - structural unit according to another embodiment, wherein the structural unit consists of two different material parts,

[0023] Figure 7 shows a perspective front view of the cover plate - light guide - structural unit, wherein for the sake of simplicity of the view, a black material part and a transparent material part arranged in front of it in the main radiation direction are shown,

[0024] Figure 8 shows an enlarged view of the upper region of the light guide integrated in the cover plate according to another embodiment according to Figure 2 , wherein an optical structure is provided on the light coupling out surface of the front side of the light plate,

[0025] Figure 9 shows another embodiment of the light guide, wherein in addition to the optical structure on the front light coupling out surface, an optical structure is also provided on the side surface of the light guide,

[0026] Figure 10 shows a rear view of the lighting device according to another embodiment, wherein light is coupled into the coupling optical device not along the main radiation direction but along the lateral direction of the main radiation direction, and

[0027] Figure 11 shows an enlarged view of the cover plate according to Figure 10 as viewed from the rear. Detailed Description

[0028] The lighting device for a vehicle can be arranged in the front area or the rear area of the vehicle. In the present embodiment according to Figure 1 , the lighting device has a housing 1 and a cover plate 2 covering the opening of the housing 1, wherein the housing 1 and the cover plate 2 define an internal space 3.

[0029] To generate a preferred signal light function, such as a driving direction indicator light function or a daytime running light function, a first light module 4 having a light source 5 and an optical unit 6 is provided for generating a predetermined light distribution for the signal light function. The optical unit 6 includes an optical waveguide 7 and an input coupling optical device 8 disposed upstream of the light flow of the optical waveguide 7. The optical waveguide 7 is configured as a flat optical waveguide extending in an extending plane E. In the present embodiment, the extending plane E extends in the vertical direction.

[0030] The input coupling optical device 8 is arranged behind the optical waveguide 7 along the main radiation direction H of the lighting device. As can be seen from Figure 5 it, the input coupling optical device 8 has a tapered widening section 9 on the side facing the light source 5 and an adaptation section 10 connected in the light flow direction, wherein the adaptation section 10 has a light exit surface 11, which in the present embodiment corresponds to the light input surface 12 of the narrow side of the optical waveguide 7. This ensures that all the light emitted by the light source 5 irradiates onto the light input surface 12 of the optical waveguide 7. The light source 5 is linearly arranged on the circuit board 13 corresponding to the shape of the light input surface 12 of the optical waveguide 7 and is arranged in a row. Therefore, the light source 5 and the input coupling optical device 8 follow the profile of the light input surface 12 of the optical waveguide 7. If the optical waveguide 7 is not configured to be flat but is arcuately configured with an arcuate light input surface 12, the orientation of the input coupling optical device 8 and the light source 5 will also be arcuate accordingly.

[0031] As can be seen from Figure 1 it, the lighting device is arranged at a grazing angle, wherein the cover plate 2 extends arcuately from the edge 14 facing the vehicle center plane to the outer edge 15, and wherein the side body part of the vehicle is joined to the outer edge 15.

[0032] According to the present invention, the optical waveguide 7 is integrated in the cover plate 2. In the present embodiment, the optical waveguide 7 is integrally connected to the cover plate 2 and is preferably made of a transparent or colored material by single-component injection molding. The optical waveguide 7 intersects the cover plate 2 at an acute angle The main radiation direction H of the lighting device extends within the extending plane E of the optical waveguide 7. The cover plate 2 and the optical waveguide 7 form a cover plate - optical waveguide - structural unit, which can be simply manufactured in manufacturing technology.

[0033] The light guide 7 has a first section 16 that projects from the inner side 17 of the cover plate 2, where the first section extends substantially in the interior space 3 of the lighting device. In addition, the light guide 7 includes a second section 18 that projects from the outer side 19 of the cover plate 2 and is arranged substantially in the surroundings 20 of the lighting device, i.e., not in the external space 20. Furthermore, if the light guide 7 is not integrated in the cover plate 2, the light guide 7 includes an intersection section 21 that corresponds to the continuous profile of the inner side 17 and the outer side 19 of the cover plate 2. Since the cover plate 2 is integrally connected to the light guide 7, the intersection section 21 does not have an optical function. It does not form an optical interface, so that the optical function of the light guide 7 is substantially achieved by the first section 16 and the second section 18.

[0034] The light guide 7 has opposite flat sides 22 that extend in the first section 16 and the second section 18 of the light guide 7 and are used for total reflection of the light coupled into the light guide 7. Since the wall thickness d of the cover plate 2 is relatively small, the undesired scattering fraction of the light leaving the intersection section 21 of the light guide 7 is relatively small.

[0035] The light-incoupling surface 12 of the light guide 7 forms the free end of the first section 16 of the light guide 7 that extends in the interior space 3. The free end of the second section 18 of the light guide 7 forms the light-outcoupling surface 23 of the light guide 7. Since the light guide 7 extends flatly, the light-incoupling surface 12 and the light-outcoupling surface 23 of the light guide 7 extend parallel to each other. The light-incoupling surface 12 and the light-outcoupling surface 23 of the light guide 7 are both configured as narrow sides in this embodiment, and the area enclosed by the narrow sides is significantly smaller than the flat sides 22 of the light guide 7.

[0036] The light-outcoupling surface 23 of the light guide 7 preferably extends perpendicular to the main radiation direction (H). For example, the light-outcoupling surface 23 of the light guide 7 can extend horizontally and / or be angled or arcuate with respect to the main radiation direction (H).

[0037] In this embodiment according to Figures 1 to 5 the light guide 7, the light-incoupling optical device 8, and the plurality of light sources 5 are arranged in a common extension plane E. The light-incoupling optical device 8 is arranged between the light source 5 and the light guide 7.

[0038] The first light module 4, including the light guide 7, extends in the portion of the lighting device facing away from the vehicle's longitudinal plane and oriented toward the vehicle's side sections. A second light module 24 is arranged in the region oriented toward the vehicle's longitudinal center plane. This second light module serves as both the light source 5 and the optical unit 6 for generating a further predetermined light function, such as a low-beam and / or high-beam function, if the lighting device is a headlight. The light generated by the first light module 4 passes through a first surface area of the cover plate 2, corresponding to the intersection section 21 of the light guide 7, while the light generated by the second light module 24 passes through a second surface area 25 of the cover plate 2, which is spaced apart from the first surface area 21. The light emitted by the first light module 4 and the second light module 24 do not overlap at the cover plate 2.

[0039] In order to ensure an optimal realization of the signal function, in particular a good perceptibility of the light-emitting surface of the light guide 7, the Figure 8 In another embodiment, the light outcoupling surface of the light guide 7 is provided with a scattering optical element 26. The scattering optical element 26 can be designed, for example, as a micro-optical element having a plurality of micro-optical elements that protrude protruding from the surface of the light guide 7 or extend flat on the surface of the light guide. The dimensions of the micro-optical elements can be in the millimeter range, for example, less than 1 mm, preferably less than 0.5 mm.

[0040] According to an alternative embodiment of the invention (not shown), the light coupling-in surface 12 of the light guide 7 can be provided with scattering optics.

[0041] According to the light guide 7 Figure 9 In another embodiment, in addition to the diffuser optics 26 on the light coupling-out surface 23 , the flat side 22 of the outer section 18 of the light guide 7 may also have diffuser optics 27 . The diffuser optics 27 may be configured, for example, as grooved optics having groove elements extending along the extension direction E. Preferably, the diffuser optics 27 are located on the side of the light guide 7 facing away from the longitudinal center plane of the vehicle, so that the light emitted via the diffuser optics 27 on the outer flat side 22 can function as a side marker light. This ensures the function of an additional signal light.

[0042] According to the lighting device or cover Figure 6 and Figure 7In an alternative embodiment, a cover plate 2' is provided, and the cover plate 2' is manufactured by a two-component injection molding process with an integrated light guide 7. The cover plate 2' has a transparent and / or light-transmissive material component 28 on the one hand and an opaque and / or black material component 29 on the other hand. The black material component 29 extends substantially on the back side 30 of the cover plate 2' and forms windows to a certain extent for the first surface area 21' and the second surface area 25' of the cover plate 2' for the light of the first optical module 4 or the second optical module 24 to pass through. Thus, a first window 31 and a second window 32 are formed from the back side 30 of the cover plate 2', and the first window and the second window each have a transparent material 28 and are surrounded by the black material component 29 on the peripheral side. Thereby, the undesired scattered radiation from the light guide 7 can be advantageously reduced in the intersection section 21'. In addition, a dark appearance of the cover plate 2' is produced in the non-operating state of the lighting device.

[0043] In an alternative embodiment (not shown) according to the invention, the light guide 7 can only have an external second section 18, wherein the light coupling-in surface 12 of the light guide 7 extends flush with the inner side 17 of the cover plate 2. Advantageously, the coupling-in optical device 8 or the light source 5 can thereby be arranged closer to the cover plate 2, which reduces the structural depth of the lighting device.

[0044] In another alternative embodiment (not shown) according to the invention, the light guide 7 can only have an internal first section 16, wherein the light coupling-out surface 23 of the light guide 7 extends flush with the outer side 19 of the cover plate 2. Advantageously, in this embodiment, the cover plate 2 has a uniform and continuous arcuate or planar run on the outer side 19.

[0045] In an alternative embodiment (not shown) according to the invention, the coupling-in optical device 8 can not - as Figure 5 shown - be formed by an additional light guide, but instead be formed by a lens or a reflector.

[0046] Figure 1 As shown, the cover plate 2 extends arcuately from the inner edge 14 to the outer edge 15 in a plane extending perpendicular to the extension plane E of the light guide 7. The edges 14, 15 or their edges enclose an angle α in the range of 30° to 90°. Thus, a grazing angle lighting device is involved, in which most of the area of the cover plate 2 forms an acute grazing angle with the main radiation direction H of the lighting device. extends.

[0047] According to the present invention Figure 10 and Figure 11Another embodiment differs from the previous embodiment in that a different coupling-in optical device 8' is provided for the light guide 7. The coupling-in optical device 8' has a deflection section 33, by means of which the light coupled into the light guide 8' is deflected by 90° in the direction of the light coupling-in surface 12 of the light guide 7. Advantageously, the light source 5 can be arranged laterally to the light guide 7 instead of being arranged in an extension of the light guide. In this embodiment, the optical axis of the light source 5 extends perpendicularly to the extension plane E of the light guide 7 or perpendicularly to the main radiation direction H, and according to Figures 1 to 9 The optical axis of the light source 5 of the embodiment of FIG. 1 extends in the extension plane E and in the direction of the main radiation direction H. Upstream of the light flow of the deflection section 33, the coupling-in optical system 8 ′ has an input section 34, by means of which the light from the light source 5 is coupled into the coupling-in optical system 8 ′. Downstream of the light flow of the deflection section 33, the coupling-in optical system 8 ′ has an output section 35, from which the light is transferred to the light coupling-in surface 12 of the light guide 7.

[0048] According to another embodiment of the invention (not shown), the outer side 19 of the cover plate 2, 2' can be provided with an optical structure, preferably a micro-optical structure, in order to ensure the desired scattering effect or light deflection. If the dimensions of the micro-optical elements of the scattering optical system are sufficiently small, preferably having dimensions of less than 1 mm or less than 0.5 mm, they are not perceptible to the human eye and are therefore not disruptive.

[0049] Reference Signs List

[0050] 1 shell

[0051] 2. 2' cover

[0052] 3. Internal Space

[0053] 4First optical module

[0054] 5 light sources

[0055] 6 optical units

[0056] 7 Light Guide

[0057] 8. 8' coupling optics

[0058] 9 widening section

[0059] 10 Adaptation section

[0060] 11 Light exit surface

[0061] 12 Optical coupling surface

[0062] 13 Circuit Board

[0063] 14 Edge

[0064] 15 Edge

[0065] 16 First section

[0066] 17 Inner side

[0067] 18 Second section

[0068] 19 Outer side

[0069] 20 Surrounding environment

[0070] 21, 21' Intersection section

[0071] 22 Flat side

[0072] 23 Opto-coupler exit surface

[0073] 24 Second optical module

[0074] 25, 25' Second surface area 26 Scattering optical device 27 Scattering optical device 28 Transparent material component 29 Black material component 30 Back side

[0075] 31 First window

[0076] 32 Second window

[0077] 33 Deflection section 34 Input section E Extension plane H Main radiation direction d Wall thickness α Angle Acute angle

Claims

1. A lighting device for a vehicle, comprising: a housing (1), a cover plate (2, 2'), which covers an opening of the housing (1), a light module (4), which includes a plurality of light sources (5) and an optical unit (6) for generating a predetermined light distribution, the optical unit (6) having an optical waveguide (7) with a light coupling-in surface (12) and a light coupling-out surface (23), It is characterized in that the optical waveguide (7) is connected to the cover plate (2, 2'), a first section (16) of the optical waveguide (7) facing the light source (5) extends from the inner side (17) of the cover plate (2, 2'), or the light coupling-in surface (12) of the optical waveguide (7) extends flush with the inner side (17) of the cover plate (2, 2'), and a second section (18) of the optical waveguide (7) facing away from the light source (5) extends from the outer side (19) of the cover plate (2, 2'), or the light coupling-out surface (23) of the optical waveguide (7) extends flush with the outer side (19) of the cover plate (2, 2').

2. The lighting device according to claim 1, characterized in that, The light coupling-in surface (12) of the optical waveguide (7) is formed by the free end of the optical waveguide (7) or the free end of the first section (16) of the optical waveguide (7), and the light coupling-out surface (23) of the optical waveguide (7) is formed by the free end of the optical waveguide (7) or the free end of the second section (18) of the optical waveguide (7).

3. The lighting device according to claim 1 or 2, characterized in that, The optical waveguide (7) is integrally connected to the cover plate (2, 2').

4. The lighting device according to one of claims 1 to 3, characterized in that Coupling-in optical devices (8, 8') are connected upstream of the light flow of the optical waveguide (7).

5. The lighting device according to claim 4, characterized in that, The coupling-in optical devices (8, 8') are configured as an optical waveguide or as a lens or as a reflector.

6. The lighting device according to any one of claims 1 to 5, characterized in that, The plurality of light sources (5) are arranged upstream of the light flow of the coupling-in optical device (8).

7. The lighting device according to any one of claims 1 to 6, characterized in that, The light coupling-out surface (23) of the optical waveguide (7) has a scattering optical device (26) or an optical structure.

8. The lighting device according to any one of claims 1 to 7, characterized in that, The cover plate (2, 2') and the optical waveguide (7) are made by injection molding from a single transparent or colored material.

9. The lighting device according to one of claims 1 to 7, characterized in that, The cover plate (2, 2') and the optical waveguide (7) are made by two-component injection molding, wherein the back side (30) of the cover plate (2, 2') has an opaque material part (29) at least in the peripheral region of the optical waveguide (7).

10. The lighting device according to claim 9, characterized in that, The cover plate (2, 2') has a first light-transmissive surface area (21) from which the optical waveguide (7) extends, and the cover plate (2, 2') has a second light-transmissive surface area (25) for light of a second light module (24) to pass through, the second light module (24) being arranged within an internal space (3) of the lighting device defined by the cover plate (2, 2') and the housing (1).

11. The lighting device according to any one of claims 1 to 10, characterized in that, The optical waveguide (7) is configured as a flat optical waveguide (7) having opposite flat sides (22), light coupled into the flat optical waveguide (7) is totally reflected at the flat sides, and the light coupling-in surface (12) and the light coupling-out surface (23) of the flat optical waveguide (7) are respectively configured as linear narrow sides.

12. The lighting device according to any one of claims 1 to 11, characterized in that, The cover plate (2, 2') extends arcuately in a plane transverse to the extension plane (E) of the optical waveguide (7), and the edges (14, 15) of the cover plate (2, 2') enclose an angle (α) in the range of 40° to 90°.

13. The lighting device according to any one of claims 1 to 12, characterized in that, The light coupling out surface (23) of the light guide (7) extends perpendicularly, horizontally, at an angle or in an arc relative to the main radiation direction (H), and at least one flat side (22) of the light guide (7) that adjoins the light coupling out surface (23) is provided with a scattering optical device (27).

14. The lighting device according to any one of claims 1 to 13, characterized in that, The outer side (19) of the cover plate (2, 2') is provided with a scattering optical device.

15. The lighting device according to any one of claims 1 to 14, characterized in that, The scattering optical device (26) consists of a plurality of micro-optical device elements that protrudingly extend from the surface of the light guide (7) and / or the cover plate (2, 2') or extend planar on the surface; or an optical diffusion structure in the form of an etching structure, a corrosion structure or a laser structure is used for light scattering.

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