阅读说明：本技术 侧面发射的光导体及其制造方法 (Side-emitting optical waveguide and method for producing the same ) 是由 M·卡佩尔 L·威尔姆斯 H·拉瑟特 B·霍普 于 2020-09-03 设计创作，主要内容包括：本发明的目的是提供具有线形外观的光源,该光源具有柔性的光导体,该光导体具有包括高的光密度的、均匀的光辐射。为此提出一种侧面发射的光导体(1),光导体包括：-至少一个构造成侧面发射的纤维的光导纤维(7),使得在纤维(7)中传导的光沿着纵向方向分布地散射出来,以及-包围纤维(7)的套管(3),其中-套管(3)构造成散射光的且半透明的,使得纤维(7)输出的光在散射的情况下能穿过套管(3),其中-套管(3)被套罩物(5)包围,并且其中套管(3)和套罩物(5)由塑料制成。(It is an object of the invention to provide a light source with a linear appearance having a flexible light conductor with a homogeneous light radiation comprising a high optical density. For this purpose, a side-emitting optical waveguide (1) is proposed, comprising: -at least one optical fiber (7) configured as a side-emitting fiber, such that light conducted in the fiber (7) scatters out distributively in the longitudinal direction, and-a sleeve (3) surrounding the fiber (7), wherein-the sleeve (3) is configured to scatter light and to be translucent, such that light output by the fiber (7) can pass through the sleeve (3) in the event of scattering, wherein-the sleeve (3) is surrounded by a shroud (5), and wherein the sleeve (3) and the shroud (5) are made of plastic.)

1. A side-emitting optical waveguide (1), comprising:

-at least one optical fiber (7) configured as a side-emitting fiber, such that light conducted in said fiber (7) is scattered out distributed along a longitudinal direction,

and

-a sleeve (3) surrounding the fibres (7), wherein

-the sleeve (3) is configured to be light-scattering and translucent such that light output by the fibers (7) can pass through the sleeve (3) in a scattered manner, wherein

-the cannula (3) is surrounded by a shroud (5), and wherein the cannula (3) and the shroud (5) are made of plastic.

2. The side-emitting optical waveguide (1) according to claim 1, wherein a fiber bundle (8) with a plurality of optical fibers (7) is guided in the sleeve (3).

3. The side-emitting optical waveguide (1) according to any of claims 1 to 2, characterized in that the at least one fiber (7) or the fiber bundle (8) is guided loosely in the sleeve (3).

4. A side-emitting optical waveguide (1) according to any one of claims 1 to 3, wherein the sleeve (3) has a wall thickness which is at least five times smaller than the outer diameter of the transparent shroud (5), wherein the diameter of the transparent shroud is at least 1mm, preferably at least 2 mm.

5. The side-emitting optical waveguide (1) according to any of claims 1 to 4, wherein the wall thickness of the sleeve (3) is less than 200 μm.

6. A side-emitting optical waveguide (1) according to any of claims 1 to 5, characterized by at least one of the following features:

-the ratio of the diameter of the shroud (5) to the diameter of the casing (3) is at least 1.5/1,

-the ratio of the cross-sectional area of the cross-section enclosed by the outer contour of the shroud (5) to the cross-sectional area of the face enclosed by the outer contour of the sleeve (3) is at least 2.25/1,

-the fiber bundle (8) has a diameter in the range of 0.5mm to 5mm, preferably in the range of 1mm to 3mm,

-the at least one optical fiber (7) is a side-emitting glass fiber,

-the at least one optical fiber (7) has a diameter in the range of 10 to 250 μm, preferably 20 μm to 100 μm, preferably 30 μm to 70 μm,

-the cross-sectional area of the fiber bundle (8) is 0.19mm²To 19.7mm²In the range of (1), preferably in the range of 0.78mm²To 7.1mm²In the range of (1).

7. The side-emitting light guide (1) according to any one of claims 1 to 6, wherein the light guide fiber (7) has a fiber core (72) surrounded by a fiber sheath (70), wherein the fiber core (72) has a higher refractive index than the fiber sheath (70), characterized in that the light guide fiber comprises at least one of the following features:

-in the fiber core (72) at least one light-scattering core (74) extends in the longitudinal direction of the optical fiber (7),

-there is a light scattering element (75) at the interface (73) between the fiber core (72) and the fiber sheath (70),

-at least partially or locally at an interface (73) between the fiber core (72) and the fiber sheath (70) there is at least one scattering region comprising scattering centers,

-elements scattering light are distributed in the fiber core (72) and/or the fiber sheath (70).

8. The side-emitting optical waveguide (1) according to any one of claims 1 to 7, characterized in that the sleeve (3) is configured as a plastic sleeve (30) which is shrunk at least partially or at least partially around the fiber bundle (8).

9. The side-emitting optical conductor (1) according to any of claims 1 to 8, characterized in that the plastic of the jacket (5) comprises a polymer blend,

preferably, the light conductor has at least one of the following features:

-at least one polymer of the polymer blend is an aliphatic polyurethane,

-at least one polymer of the polymer blend forms a thermoplastic elastomer,

-one polymer of the polymer blend is polymethyl methacrylate,

-one polymer of the polymer blend is a polycarbonate.

10. The side-emitting optical waveguide (1) according to claim 9, characterized in that the polymer blend comprises polymethyl methacrylate and thermoplastic polyurethane.

11. The side-emitting light guide (1) according to any one of claims 1 to 10, characterised in that the plastic of the encasement (5) comprises at least one filler, in particular a UV stabilizer, an impact modifier or a flame retardant.

12. A side-emitting optical waveguide (1) according to any of claims 1 to 11, characterized by at least one of the following features:

-the light loss due to the bending of the light guide (1) is less than 0.1 times the total light intensity guided in the light guide per winding of the light guide (1) at a bending radius of the light guide (1) of 21mm,

-the light loss due to the bending of the light guide (1) is less than 0.3 times the total light intensity guided in the light guide per winding of the light guide (1) at a bending radius of the light guide (1) of 12 mm.

13. Side-emitting light guide (1) according to one of claims 1 to 12, characterised in that the light guide (1) has an angular distribution of the emitted light in which the light intensity I for the light emitted at an angle of 45 ° to the light guide direction_45°Light intensity I of light emitted at an angle of 135 DEG with respect to the light guide direction_135°Is (I)_45°-I_135°)/(I_45°+I_135°) A is < 0.1, preferably A < 0.05.

14. The side-emitting light guide (1) according to any one of claims 1 to 13, characterised in that the shroud (5) has fastening elements (14) in the form of ribs (24) or grooves (25) extending axially along the light guide (1).

15. The side-emitting optical waveguide (1) according to one of claims 1 to 14, characterized in that the jacket (5) has at least one channel (15) extending in the axial direction, in particular in the form of a cavity (16).

16. A side-emitting optical waveguide (1) according to any of claims 1 to 15, characterized by at least one of the following features:

the light guide (1) comprises an elongate optical effect section (19) which is connected to the jacket (5), in particular is embedded in the jacket (5), extends in the longitudinal direction of the light guide (1), the texture of which influences the color, brightness or emission direction of the light emitted by the sleeve (3),

the light guide (1) is designed to change the spectrum of the emitted light relative to the spectrum of the coupled-in light,

-the sleeve (3) contains pigment or coloured scattering particles,

-at least one of the plastics of the core (6) and the cover (5) is dyed,

-the light conductor (1) comprises a photoluminescent material.

17. The side-emitting optical waveguide (1) according to any one of claims 1 to 16, characterized in that a fluid-filled, in particular gas-filled, gap is present between the jacket (3) and the jacket (9).

18. Side-emitting optical waveguide (1), in particular according to any of claims 1 to 17, having an elongate inner section (6) and a jacket (5) surrounding the inner section, wherein in the inner section (6) the light is guided by coupling-in at one of the ends (10, 11) of the optical waveguide (1), said light being gradually deflected laterally from the inner section (6) through the jacket (5) outwards by scattering or refraction, so that the inner section (6) appears as an elongate, in particular linear or fiber-like, light-emitting element, as seen from the jacket (5), wherein a layer (9) surrounding the inner section is present between the inner section (6) and the jacket (5), said layer having a refractive index which is lower than the refractive index of the jacket (5),

preferably, the layer (9) comprises a gas layer.

19. Side emitting light guide (1) according to claim 18,

-the diameter D of the inner part (6)₆With the diameter D of the layer (9)₉The proportion of (A) is as follows: 1-Or

-is:wherein A is₆Is the area enclosed by the outer envelope curve of the cross section of the inner part (6) and A₉Is an outer envelope curve of a cross section of the layer (9)The area of the enclosure.

20. Side-emitting optical waveguide (1) according to any of claims 18 to 19, characterized in that the interface (18) between the jacket (5) and the layer (9) forms a concave refraction surface.

21. A method for producing a side-emitting optical waveguide (1) according to one of claims 1 to 20, wherein at least one side-emitting optical fiber (7) is arranged in a light-scattering and translucent sleeve (3) made of plastic, and wherein the sleeve (3) with the at least one optical fiber contained therein is surrounded by a jacket (5) made of plastic.

22. Method according to claim 21, characterized in that the shroud (5) is shaped around the sleeve (3) by extrusion.

23. A light source (2) with an optical conductor (1) according to any one of claims 1 to 20 and at least one light emitter (4) which is optically coupled at one end (10, 11) with a fiber (7) of the fiber bundle (8) for coupling light into the optical fiber (7).

24. The light source (2) according to claim 23, wherein the side-emitting light guide (1) is connected to a further flexible light guide (21), and wherein the light emitter (4), the laser (40), is coupled to the further flexible light guide (21) such that light of the light emitter (4) is coupled into the side-emitting light guide (1) via the further light guide (21) and is emitted along the side-emitting light guide (1).

25. Use of the light guide (1) according to any one of claims 1 to 20 or the light source (2) according to any one of claims 23 to 24 as contour or accent lighting or in a medical device.

Technical Field

The present invention relates generally to the field of light emitting elements. The invention relates in particular to the use of light guides in lighting or display devices.

Background

It may be desirable to use a line-shaped light source for illumination or display purposes. As such a light source, a light emitter with a side-emitting optical waveguide coupled thereto may be used. Such an assembly is advantageous over an assembly consisting of a plurality of small emitters (for example LED chains) arranged side by side, in particular with regard to a space-saving construction and high robustness. In such a chain, a large number of components can quickly lead to failure of a single led, thereby immediately drawing attention.

Another solution for providing a line light source is a side-emitting optical conductor. In the light guide, light emitters are connected at one or both ends, which light emitters couple the light into the light guide. A scattering element is distributed in the light guide, and the scattering element scatters the light scattering element conducted in the light guide. The light source provides very uniform illumination. The overall light flow is however limited by the intensity provided by the light emitters.

Even if the light guide emits light uniformly to the naked eye, a problem may occur when the light guide is bent. If the light guide is bent, for example when fastened to a base by means of clips (clips), the scattering coating lying only loosely on the core can flake off or can elongate at the outer region by bending and then become thinner and contract within the bend, so that wrinkles can occur. Here, an air gap is created between the scattering cladding and the light-guiding core, which air gap remains even after realignment. This air gap then leads to locally different outcoupling of light and to inhomogeneous light intensity.

Disclosure of Invention

It is therefore an object of the present invention to provide a light source with a linear appearance having a flexible light conductor with uniform light radiation with a high optical density. This object is achieved by the subject matter of the independent claims. Advantageous embodiments are given in the dependent claims. A light source having a linear appearance is understood to be a light source which is seen by the naked eye of an observer at normal viewing distances as a luminous line without significant lateral stretching. The line need not be a straight line, but may also extend in a curved manner. The invention therefore proposes a side-emitting optical waveguide comprising at least one optical fiber designed as a side-emitting fiber, so that light guided in the fiber is scattered distributed in the longitudinal direction, and a sleeve surrounding the fiber, wherein the sleeve is designed to be translucent and preferably to scatter light, so that the light output by the fiber can pass through the sleeve in the event of scattering, wherein the sleeve is surrounded by a transparent covering. The sleeve and the casing are made of plastic.

Preferably, not only a single optical fiber but also a fiber bundle with a plurality of optical fibers is guided in the sleeve. The division into a plurality of fibers is advantageous in order to keep the light conductor as flexible as possible.

It is also particularly advantageous for the flexibility of the light guide that at least one fiber or fiber bundle is guided loosely in the sleeve 3. Thus, there is no connection between the sleeve and the adjoining fiber or fibers. The fibers are thereby movable within the sleeve in particular in the longitudinal direction, which facilitates bending and avoids stresses on the fibers during bending.

In this case, at least one fiber, preferably a plurality of optical fibers in the form of a fiber bundle, is arranged in the interior of the sleeve, wherein each optical fiber is configured to be side-emitting in each case, so that light coupled into the respective fiber is gradually scattered out along the longitudinal extent of the optical fiber, passes through the sleeve in the case of further scattering and emerges out through the jacket. The light guide thus has an at least double-shelled structure with an outer transparent jacket and a jacket forming an inner jacket. Since the sleeve is light-scattering, the angular distribution of the light emitted by the fibers is further homogenized, so that in a preferred embodiment the deviation of the radiation intensity in the angular range of +45 ° to-45 ° in any spatial direction compared to 0 ° (perpendicular) is less than 55%, particularly preferably less than 30%, and most preferably less than 20%. This applies in particular and also in the bending region of the light guide according to the invention.

The light guide can be produced by a method in which at least one side-emitting light guide fiber is arranged in a translucent sleeve made of plastic and designed to scatter light, wherein the sleeve with the at least one light guide fiber contained therein is surrounded by a transparent jacket made of plastic.

The problem of air gaps after bending is also avoided with the light guide described here. Even if an air gap is formed locally between the shroud and the sleeve, this air gap no longer influences the light outcoupling and thus the local scattering effect, since the scattering and outcoupling of light takes place in the individual optical fibers in the interior of the sleeve.

Drawings

The invention is described in more detail below and with reference to the accompanying drawings.

Fig. 1 shows a light source with a side-emitting optical waveguide.

Fig. 2, 3 and 4 show cross-sectional views of a side-emitting fiber.

Fig. 5 shows a cross-sectional view of a light guide.

Fig. 6 shows a variant with a single optical fibre.

Fig. 7 shows a variant of the example of fig. 5 with an effect section.

Fig. 8, 9 and 10 show cross-sectional views of variants of light guides with fastening elements.

Fig. 11 shows an example of a light guide with additional channels in the longitudinal direction.

Fig. 12 and 13 show graphs of the measured values of the luminous flux of the light guide before and after bending.

Fig. 14 shows the angle-dependent luminance of two light conductors.

Fig. 15 shows the optical density in relation to the longitudinal position along the two light conductors.

Fig. 16 shows a light guide with a region of low refractive index surrounding the sleeve.

Fig. 17 shows the light path on the optical waveguide.

Fig. 18 shows a simulation of the light emission of a light guide with and without an air gap between the shroud and the part of the luminous interior.

Fig. 19 shows a graph in which the apparent width of the portion of the inside that emits light is correlated with the width of the air gap.

Fig. 20 shows a light source in which light is coupled into a side-emitting light guide via a further light guide.

Detailed Description

Fig. 1 schematically shows a light source 2 according to the disclosure having a side-emitting optical waveguide 1. The light source 2 comprises a light emitter 4 which is optically coupled to at least one optical fiber 7, preferably to an optical fiber 7 of a fiber bundle 8, at an end 10 of the optical conductor 1, in order to couple light into the fiber or fibers 7. Generally, without being limited to the shown embodiment, it is preferred that a semiconductor light emitter is used for the light source 2. The semiconductor light emitter may comprise a light emitting diode or a semiconductor laser. In this way, a plurality of light emitters with different colors can also be coupled in order to obtain a light color-adjustable illumination. In contrast to the illustration in fig. 1, light emitters 4 can also be arranged at both ends 10, 11 of the optical waveguide 1 in order to couple light into the fibers 7.

Typically, the fiber bundle 8 runs in the sleeve 3. The sleeve is in turn surrounded by a cover 5. Both the sleeve 3 and the shroud 5 are made of plastic. This gives the light guide 1 a high flexibility, so that the light guide can be provided with the bend 12 and fixed in a simple manner. In the example shown, the light guide 1 is provided, for example, with a bend 12 which is offset by 90 °.

Typically, side-emitting light conductors differ from data-carrying light conductors by a smaller set length, since the light density decreases with increasing length given the brightness of the coupled light emitter. Without being limited to a specific embodiment, for this purpose, in a development of the invention, the light guide 1 has a length in the range from 0.5 to 100 meters, preferably to 50 meters. The large length is particularly suitable for cooperating with a laser group as a light emitter. For decorative lighting and other light technology applications, small lengths of up to 105 meters, preferably 2.5 to 5 meters, are particularly suitable. In the medical field, in particular as a component for single-or multi-use in devices for diagnostic and therapeutic treatment, a length of less than 0.5m, preferably less than 0.1 m, particularly preferably from 0.01 to 0.05 m, applies to the diameters of the light conductors 1 of about 1mm and less, which are preferred here.

Fig. 2 shows a cross-sectional view of an embodiment of a side-emitting fiber 7 of a light guide. A fiber bundle 8 for an optical fiber can be produced by combining a plurality of such fibers 7. Without being limited to the example shown, the fiber 7 generally comprises a fiber core 72 surrounded by a fiber sheath 70, wherein the fiber core 72 has a higher refractive index than the fiber sheath 70, so that light can be guided in the fiber core 72 to the fiber sheath 70 in the usual manner by total reflection at the interface 73. In the fiber core 72, a light-scattering core 74 extends in the longitudinal direction of the optical fiber 7. The core partially scatters the light guided in the fiber core 72 so that the light can be emitted from the fiber 7. Light is continuously scattered along the fibre 7 in this way.

Fig. 3 shows an example of another embodiment of an optical fiber 7. As in the fiber of fig. 3, the fiber 7 has a fiber core 72 surrounded by a fiber sheath 70 of lower refractive index. This embodiment is based on the fact that at the interface 73 between the fiber core 72 and the fiber sheath 70, there are light-scattering elements 75. The light-scattering element changes the direction of the light that would otherwise be reflected at the interface 73 by scattering, so that the light is partially scattered out. Typically, the light scattering elements may also be in the fiber sheath 70. In particular, light scattering elements located in the vicinity of or at the interface scatter the light. Fig. 4 shows a further embodiment in which the light-scattering elements 75 are distributed in the fiber core 72. In general, the light-scattering fiber 7 according to one embodiment has a fiber core 72 and a fiber sheath 70 having a lower refractive index than the fiber core 72, wherein at least one light-scattering element 74, 75 is arranged in the fiber 7 such that the light guided in the fiber core 72 is gradually scattered out in the longitudinal direction of the fiber 7. In the case of fig. 2, the individual light-scattering elements are arranged in the form of a mandrel 74 extending in the longitudinal direction of the fiber 7. A plurality of cores 74 may be present. All embodiments shown can also be combined with each other. The embodiment according to fig. 2 may thus also have an additional light-scattering element 75 at the interface 73 or in the fiber core 72. The at least one fibre 7 may be made of glass or of plastic. Preferably, the optical fiber 7 is a side-emitting glass fiber. This embodiment is advantageous because the high transparency of glass is utilized over a long distance and a flexible light guide 1 can be provided because of the use of a fiber bundle with a plurality of fine fibers.

Fig. 5 shows a cross section of a side-emitting optical waveguide 1. The optical waveguide 1 comprises a fiber bundle 8 with a plurality of laterally emitting optical fibers 7, which scatter light out of the fibers 7 and thus out of the optical waveguide 1 in a distributed manner in the longitudinal direction, so that a thin, longitudinal or linear illumination is provided. The fiber bundle 8 is surrounded by the sleeve 3. The sleeve is light scattering and translucent. The light thus output through the fibers 7 of the fiber bundle 8 passes through the sleeve 3, wherein the light is usually scattered at least partially in the wall of the sleeve 3. The cannula 3 is further surrounded by a transparent shroud 5. The sleeve 3 and the shroud 5 are made of plastic. This provides a flexibly laid optical waveguide 1 which is particularly flexible.

The sleeve 3 is preferably generally thin-walled. The diameter of the assembly of fiber bundle 8 and jacket 3 is thereby kept as small as possible. This advantageously achieves a high optical density. The wall thickness of the jacket tube and the diameter of the optical fiber 1 or the jacket 5 should therefore also differ as significantly as possible. The large ratio of the outer diameter and the wall thickness of the jacket tube 3 also reduces the bending radius which is obtained at the jacket tube and in the fiber bundle 8 during bending and in this way prevents the fibers 7 in the fiber bundle 8 from breaking when the optical fiber 1 is bent too much. Without being limited to the particular example shown, for this purpose in one development the sleeve 3 has a wall thickness which is at least 5 times smaller than the outer diameter of the transparent casing 5. It is also preferred for this purpose that the diameter of the transparent covering is at least 1mm, preferably at least 2mm, in order to limit the bending radius in the fiber bundle 8.

It is generally also preferred that the wall thickness of the sleeve 3 is up to 200 micrometers, in particular up to 100 micrometers. This results in a high flexibility of the part of the interior of the light guide having the sleeve 3 and the fiber bundle 8 accommodated therein. In particular when interacting with the use of scattering particles whose diameter is more than 100 times smaller, particularly preferably more than 150 times smaller, and very particularly preferably more than 200 times smaller than the wall thickness of the jacket tube 3, a high optical density of the light guide and a uniform angular distribution of the side-emitted light are simultaneously achieved. Since scattering particles having a size distribution are generally involved, the diameters of the scattering particles are directed to the average value (also referred to as D50).

The ratio of the diameter of the jacket 5 to the diameter of the jacket 3 is preferably at least 1.5/1, in order to achieve a high optical density and to avoid too narrow a bending radius of the fiber bundle 8 given the diameter of the optical waveguide 1. Unlike that shown in fig. 5, the shroud 5 need not have a right circular cross-section. The same applies to the sleeve 3. In the example shown, the sleeve 3 has already matched the shape of the fiber bundle 8 and the cross section of the sleeve is thus not exactly perfectly circular. In this case, the average diameter of the shroud 5 and sleeve 8 may be set to the ratio of 1.5 to 1 given above. But may equally well relate to cross-sectional area. It is generally preferred here that the ratio of the cross-sectional area of the face enclosed by the outer contour of the shroud 5 to the cross-sectional area enclosed by the outer contour of the sleeve 3 is at least 2.25/1. In the case of a very thin wall thickness of the sleeve 3, the cross-sectional area enclosed by the outer contour of the sleeve corresponds approximately to the cross-sectional area of the fiber bundle 8.

According to a preferred embodiment, the fiber bundle 8 has a diameter in the range of 0.5mm to 5mm, preferably 1mm to 3 mm. Accordingly, for non-circular geometries, the cross-sectional area of the fiber bundle is 0.19mm²To 19.7mm²Preferably 0.78mm²To 7.1mm²。

It has been found to be particularly suitable for the optical and mechanical properties of the light guide 1 that the sleeve 3 is designed as a plastic sleeve which is shrunk around the fiber bundle 8. A good form-fit of the sleeve 3 to the contour of the fiber bundle 8 can be achieved by shrinking without the fiber bundle 8 having to be compressed too strongly. Furthermore, such a shrink sleeve with a wall thickness of 30 μm or less can be used, which further increases the optical density of the light guide. If necessary, the plastic sleeve can also be shrunk only partially or partially around the fiber bundle. It is often advantageous if the fibers are also loosely integrated in the jacket 3 or are guided loosely, without material or form-locking connection, in the jacket 3. This prevents tensile stresses on the individual fibers 7 and the associated fiber breakage when the light guide 1 is bent.

Suitable for the optical fiber 7 is a diameter in the range of 10 to 250 μm, preferably 20 μm to 100 μm, preferably 30 μm to 70 μm, to achieve good flexibility of the fiber bundle 8.

Polyester is particularly suitable as material for the sleeve 3. In order to provide the sleeve 3 with light-scattering properties, light-scattering particles can be included as additives in the plastic. According to one embodiment, the plastic comprises oxide particles. Particularly highly refractive oxides, such as titanium oxide, are suitable. In one embodiment, the sleeve 3 is therefore provided in the form of a polyester sleeve with oxide particles, in particular titanium oxide particles. In this case, more than 50% of the scattering particles embedded in the sleeve 3 preferably have a diameter of less than 1 μm in order to increase the radiation homogeneity.

Polymer blends have been found to be particularly suitable as plastics for the shroud 5. The properties of high transparency and high flexibility can be matched by means of the polymer blends. Preferably, aliphatic polyurethanes can be used as a component or as a polymer in a polymer blend. This component is in particular elastic and can be combined with other plastics to form highly transparent polymer blends. In particular, such aliphatic polyurethanes can also be thermoplastic elastomers. Alternatively or additionally, as a component, another thermoplastic elastomer may also be an integral part of the polymer blend. Thus, according to another embodiment, one of the polymers in the polymer blend forms a thermoplastic elastomer.

In another embodiment one of the polymers of the polymer blend is a polycarbonate. Polycarbonate is advantageous for transparency of the encasement. PMMA is also suitable. Thus according to another alternative or additional embodiment, one of the polymers of the polymer blend is polymethyl methacrylate.

One particularly suitable combination is a polymer blend that typically includes polymethyl methacrylate and a thermoplastic polyurethane. The two components can in particular form a polymer blend individually or, in the case of the presence of further components, can be present in the mixture of the blend in two largest portions.

According to a further refinement, at least one of the plastics of the sleeve 3 and the shroud 5 comprises polymer particles. The particles may further improve mechanical properties. The polymer particles are therefore known as additives for increasing the impact strength. According to an advantageous development, a transparent and at the same time impact-resistant and abrasion-resistant and scratch-resistant plastic can be obtained when at least one of the plastics of the shroud 5 and of the sleeve 3 comprises polymer particles with crosslinked PMMA. This embodiment is more particularly suitable here for combination with polymer blends comprising PMMA. According to a further development of the invention, a polymer blend is provided which comprises PMMA as a constituent and additionally polymer particles with crosslinked PMMA.

With the described configuration of the light guide 1, it is also possible to add, instead of or in addition to the impact modifier, other fillers which are otherwise disadvantageous for the optical properties. It is particularly contemplated to use at least one filler in shroud 5, which may be a flame retardant or a UV stabilizer. The optical properties of the light guide 1 are hardly influenced by the filler in the jacket 5, since the transmission of the light guide fibers is not disturbed and the light propagates only for a short distance in the jacket 5 after passing through the jacket 3.

Fig. 6 shows a variant of the example of fig. 5. Instead of the fiber bundle 8, this variant has a single side-emitting optical fiber 7. The fibers 7 may, as shown, be thicker than the fibers of the fiber bundle to be able to couple in as much light as possible. On the other hand, however, the cross section of the light guide 1 is generally smaller than in the embodiment with fiber bundles. As shown, the individual fibers 7 can also be guided loosely in the jacket 3 or not connected to the jacket 3, in order to facilitate the bending of the optical fiber 1 and also to avoid irreversible changes after the bending process. In the example shown, the fibers correspond to the configuration according to fig. 2.

In one embodiment of the optical waveguide 1, the optical waveguide 1 comprises an elongate optical effect section 19 which is connected to the jacket 5, in particular is embedded in the jacket 5, extends in the longitudinal direction of the optical waveguide 1, and whose texture influences the color, brightness or emission direction of the light emitted by the sleeve 3. An example of this is the variant of fig. 7. In this example, effect sections 19 in the form of diffusely reflecting stripes are arranged in the shroud. This effect section changes the spatial emission of light, so that the angular region around the light guide 1 is shaded and the brightness in the remaining angular region is increased. The color of the emitted light can also be influenced by suitable coloring or pigment-dyeing of the effect section. This makes it possible to provide a light guide 1 whose jacket 3 with fibre bundles 8 appears as a bright line of a first colour against which light is reflected diffusely in effect segments of other colours.

In general, without being limited to the example shown, according to a further embodiment, functional elements running in the longitudinal direction of the optical fibre 1 are guided in a sleeve together with at least one optical fibre 7. Such functional elements may be in particular electrical conductors 27 or reinforcing elements 28. Metal wires or plastic wires or core wires are considered as reinforcing elements 28. The electrical conductor 27 can also simultaneously have the function of a stiffening element 28 which improves the stability. It is also conceivable to arrange such functional elements in the shroud 5 outside the sleeve 3.

The embodiment of the light guide 1 with the jacket 5 made of plastic makes it possible to realize this in a strand forming method, for example by extrusion. More complex geometries can also be realized in a very simple manner by this method. In one embodiment, the shroud 5 has fastening elements 14 in the form of springs or ribs 24 extending axially along the light guide 1. To this end, fig. 8 shows an example in which two such ribs 24 are formed in the shroud 5. Unlike the illustration, the fastening element can also be a separate element, which is anchored in the shroud 5. An example of such an implementation is shown in fig. 9. The ribs 24 may be, for example, prefabricated elements or metal elements made of a different plastic than the material of the shroud 5. The rib 24 in the form of a separate element can be anchored in the shroud 5, for example, as the sleeve 3 is extruded. For mounting the light guide 1, the light guide with the ribs 24 can be inserted into corresponding recesses of the component to be provided with the light guide 1.

Fig. 10 is an example of another embodiment. In this embodiment, a fastening element 14 in the form of a groove 25 is provided which extends axially along the light guide 1. The groove 25 may be directly engaged into the shroud 5 as shown or may be formed by the shape of the shroud 5. In the example shown so far, the sleeve 3 with the fiber bundle 8 is arranged substantially centrally in the cross section of the mantle. An example of fig. 10 also shows that an eccentric arrangement is also possible.

According to a further embodiment, the shroud 5 may have at least one channel 15 extending in the axial direction, in particular in the form of a cavity 16. An example of such an implementation is shown in fig. 11. In this example, there are three channels 15, each forming a cavity 16. Instead of being shown, the channel 15 can also be filled, for example, with a cable, a wire or a filling material. Fig. 11 is an example of a cross section of the bushing 3 with the fiber bundle 8 accommodated therein, which cross section need not be circular. With this arrangement, a plurality of variants with regard to the cross-sectional shape are possible. In the example, the sleeve has the cross-sectional shape of a circular ring segment, as do two laterally adjoining channels 15.

In general, the light guide 1 described here is characterized by a high resistance to changes in optical properties after bending of the light guide. This is because the light radiation characteristics are substantially determined by the sleeve 3 and the fibres 7 guided therein. In particular, according to one embodiment, the additional light loss due to the bending of the optical waveguide 1 is less than 0.1 times the total light intensity guided in the optical waveguide per winding of the optical waveguide 1 at a bending radius of 21mm of the optical waveguide 1. In addition, the additional light loss due to the bending of the optical waveguide 1 is less than 0.3 times the total light intensity guided in the optical waveguide per winding of the optical waveguide 1 at a bending radius of 12mm of the optical waveguide 1. These properties are used in particular for light conductors 1 having an outer diameter or a diameter of the jacket of 3mm or less, in particular for light conductors having a diameter in the range from 1 to 3 mm. The additional light losses (i.e. in addition to the light losses caused anyway by the exit of the side-emitting light conductor) are shown as brighter segments than in the adjacent regions. Thus, light emission occurs non-uniformly along the light conductor, which has one or more brighter light emitting areas. In addition, the absence of additional outcoupled light in the further extension of the light guide makes the light guide overall darker. Fig. 12 and 13 show for this purpose the measurement of the luminous flux before and after winding the optical conductor with a winding of one or more turns. Fig. 12 shows the flux with a bending radius of 21mm in the initial state and after winding one and two turns of the winding.

Fig. 13 shows a similar graph with measured values after winding a winding of one to three turns and with a bending radius of 12 mm. Curve (a) shows the measured values of the light guide 1 described here in two graphs. For comparison, curves (b) and (c) show measured values for conventional side-emitting polymer photoconductors. The measured values were respectively normalized to values without a bend. As can be seen, the large degree of curvature in the light guide body described here does not substantially affect the emission intensity. After winding three turns of the winding with a bending radius of 12mm, the flux was above 70% of the original value (fig. 13). In contrast, it is shown in the prior art optical waveguides (curves (b) and (c)) that the flux is reduced by almost half after winding a winding with a bending radius of 12mm for two turns (fig. 12) and by about 2/3 when winding a winding with a bending radius of 12mm for three turns (fig. 13).

A particularly high homogeneity of the emitted light is also achieved by the light guide described here. This is achieved in particular by homogenizing the angular distribution of the light emitted from the individual optical fibers 7, again by scattering in the wall of the sleeve 3. In one embodiment, the light guide 1 has an angular distribution of the emitted light in which the light intensity I for the light emitted at an angle of 45 ° to the light guide direction_45°Light intensity I of light emitted at an angle of 135 DEG with respect to the light guide direction_135°Is (I)_45°-I_135°)/(I_45°+I_135°) A is < 0.1, preferably A < 0.05. This asymmetry is manifested as a difference between the light emission having a directional component in the forward direction and the light emission having a directional component in the backward direction (i.e. the direction opposite to the light guide). The small asymmetry in the emission is clearly shown in fig. 14. Fig. 14 shows two curves (a) and (b) with measured values of the angle-dependent luminance for two light conductors. Curve (a) shows a curve forMeasurement of the photoconductor of 2mm in diameter of the present disclosure. Curve (b) shows the light guide with the fiber bundle, but without the translucent scattered-light sleeve 3, for comparison. It can be seen that in the light guide according to the disclosure, the light is emitted almost perfectly uniformly or independent of the angle. In contrast, significant forward scattering is shown in curve (b). The emission with a directional component in the direction of the light guide is significantly more intense than the emission against the direction of the light guide.

The arrangement according to the disclosure also produces a significantly higher optical density than the side-emitting polymer photoconductors to date. This is shown in the example of fig. 15. In the diagram shown here, the optical density is measured as a function of the longitudinal position on the optical waveguide 1. As the light is gradually scattered out of the light guide 1, the light density decreases as the distance between the end of the light guide and the light emitter increases. Compared to light guides in which the fibers are guided in a simple transparent jacket tube (curve (b)), a higher optical density and a higher visible brightness are achieved by combining the fibers with the jacket tube in a compact bundle having a very small diameter (curve (a)).

The factor that affects optical density is the refractive index at the outer surface of the shroud 5. In a light guide 1 with a circular cross section, the outer surface of the jacket acts like a cylindrical lens. The cylindrical lens enlarges the actively emitting part of the light guide 1, i.e. has a sleeve 3 in which the fiber bundle 8 is guided. But the optical density is correspondingly reduced by this optical amplification. Even if this effect does not directly affect the total luminous flux emitted, the actively emitting part appears larger, but correspondingly darker. This effect is disadvantageous when the light guide is used as a design element to provide a visual accent in the form of a luminous line. At low optical densities, the light guide can, for example, be optically unnoticeable in bright surroundings, so that the light guide loses its visually emphasized function. It is therefore desirable to design a light guide 1, which light guide 1 has an inner, laterally emitting, in particular strip-shaped or elongate inner portion and a jacket surrounding this portion, such that the optical amplification effect at the outer surface of the jacket 5 caused by refraction at the outer surface is at least reduced. This object is generally achieved by an elongated side-emitting optical waveguide 1 having an inner, elongated inner portion, also referred to as core, in which light can be conducted by coupling-in at one of the ends 10, 11 of the optical waveguide 1, and a jacket 5 surrounding the inner portion, wherein the light is gradually deflected laterally from the inner portion through the jacket 5 outwards by scattering or refraction, so that the inner portion, viewed from the jacket 5, exhibits elongated, in particular linear or fiber-like, light-emitting elements, wherein a layer surrounding the inner portion is present between the inner portion and the jacket 5, which layer has a lower refractive index than the refractive index of the jacket 5.

In a further development of the preceding embodiment, the inner part is formed by the sleeve 3 with the fiber bundles 8 contained therein, since the sleeve 3 is part of the light source of the light guide 1 which appears to be linear or fiber-shaped. Fig. 16 shows an example of such an embodiment, namely a light guide 1 with a layer 9 of lower refractive index surrounding the jacket 3. As mentioned, the sleeve 3 with the fiber bundles 8 forms the inner part 6 surrounded by the layer 9. In the simplest case, in which the optical effect is particularly effective, a gap or spacing is present between the jacket 5 and the inner part 6, so that the layer 9 is formed by a fluid layer, in particular an air layer, or in general a gas layer. In a further development of the embodiment described so far, a fluid-filled, in particular gas-filled, particularly preferably air-filled gap is present between the sleeve 3 and the casing 9.

In another embodiment, however, the inner part 6 can also be formed by a single side-emitting fiber. Here, the inner portion 6 generally represents the portion that behaves as a light-emitting element. Typically, the light-emitting element is defined by a scattering element that appears to emit light, which is the output point of the emitted light to the viewer.

If there is a fixed connection between the white luminous core or inner part and the transparent covering, the light emitted from the inner part is then guided through the transparent covering 5 in a uniformly distributed manner at all angles and is guided outwards on its surface 50 according to the law of refraction. It is to be noted here that the observer can perceive with the naked eye only the beam emerging substantially parallel to the covering at an observation distance which is many times greater than the cable diameter (which is usually the case in practice). All of the different angles of the beam emerging from the surface of the outer skin are not projected onto the retina of the eye and are therefore not perceived. The sketch of fig. 17 shows the light path on which this is based. The limit case can be determined by the law of refraction and the outermost parallel beam, which can also be perceived with the naked eye, is located at the position of the limit case, the parallel beam then forming the perceived diameter of the light. According to the law of refraction, the angles α, β for the beam 20 correspond to:

(1)by passingAndfor appreciable diameter D is obtained_vis：

(2)D_vis＝2*r*n_{Outer skin}。

This diameter corresponds to twice the distance b according to fig. 17. The refractive index of the transparent outer layer is about n_{Covering article}1.5 and the diameter 2 r of the white core or inner part 6 is d_{Core part}Diameter D at 2.1mm giving appreciable luminescence_visIs 3.2 mm. This corresponds to the outer diameter of the transparent shroud 5. This does not result in the desired increase in optical density through a smaller sensing area, even if a light emitting core is used that is smaller than the outer diameter.

At a smaller diameter of the inner part, for example 0.3mm, the light emission diameter is in this case perceived as 0.45mm, which is much smaller than the outer diameter of the light guide 1 of 3.2mm, thus leading to the desired increase in the light density.

However, if a layer 9 with a lower refractive index, in particular an air gap, is present between the luminescent core or inner part 6 and the transparent covering 5, additional refraction occurs at the inner surface of the transparent outer skin, i.e. at the interface between the covering 5 and the layer 9, so that a new proportion of the perceived luminescent diameter occurs. However, this can no longer be calculated analytically, but can be derived digitally or graphically via simulation. It has surprisingly been found that a perceived light emitting diameter even slightly smaller than the diameter of the white light emitting core or inner portion 6 can be achieved. The effect of increasing the optical density caused by the layer 9 is produced here in particular by the shape of the interface between the layer 9 and the covering. Typically, the interface 18 forms a refractive surface that is substantially or at least partially or partially concavely shaped. According to a preferred development, the interface 18 between the jacket 5 and the layer 9 is thus formed as a concave refractive surface, so that this refractive surface acts as a refractive surface for the emitting lens or the defocused optical element in a plane perpendicular to the longitudinal direction of the optical waveguide 1.

In view of the foregoing, it is generally preferred in a development of the invention for the inner portion 6 to have a diameter of at least 0.75 mm. Although there is this effect below this diameter, it is less noticeable because the diameter is already small.

Fig. 18 shows in sub-diagrams (a) and (b) two simulations of the light path for a light conductor 1 with an air gap (sub-diagram (a)) and without an air gap (sub-diagram (b)). The air gap is not indicated in sub-diagram (a) for simplicity.

It is clearly apparent that the apparent diameter D1 of the luminous inner part 6 is significantly smaller for the observer in this embodiment with an air gap than the diameter D2 in the embodiment without an air gap (sub-diagram (b)). It is even possible that the apparent diameter is smaller than the actual diameter. Whereby the air gap or generally the layer 9 with the lower refractive index effectively increases the optical density.

The thickness of the layer 9, preferably the thickness of the air gap, is generally of less importance. This is shown in the graph of fig. 19. Half the apparent width b in the graph (as constructed in fig. 17) is a function of the width of the air gap. Half the apparent width b corresponds to half the apparent diameter or apparent radius of the inner part 6. As can be seen from the graph, the effect of the width of the air gap on the apparent width of the inner portion 6 is minimal. Thus, the layer 9 can be kept very thin. Generally, without being limited to the example shown, for this purpose in one embodiment the ratio of the diameter D6 of the inner part 6 to the diameter D9 of the layer 9 applies:

(3)

as mentioned, the light guide 1 does not necessarily have a perfectly circular cross section. The above-mentioned relation (3) can be listed here accordingly for the cross-sectional area of the envelope curves of the inner part 6 and the layer 9. In this case, according to a further embodiment:

(4)

where A is₆Is the area enclosed by the outer envelope curve of the cross section of the inner part 6 and A₉Is the area enclosed by the outer envelope curve of the cross section of the layer 9.

It is generally sufficient to prevent or eliminate the connection from the surface of the sleeve 3 or the inner part 6 to the shroud 5. The gas-filled gap, in particular an air gap of sufficient width, is then maintained by the surface roughness of the surface. This also applies when the light guide is bent with an approximately arbitrary bending radius. There may also be a coating with particles on the sleeve 3 or generally the inner part 6, wherein the particles keep the surfaces of the shroud 5 and the inner part apart and provide a gap. In the air-filled gap, preferably a dry gaseous medium with a dew point of at most-20 ℃ is used to avoid deposits in the gap. Suitable are, for example, dry air or inert gas for filling.

The light guide 1 is, as described herein, particularly suitable for contour lighting or in general for decorative lighting and also as a design element for interior spaces of buildings and vehicles. Light guides can be used as such a design element for such lighting devices in the interior of buildings and in their installations, for example in indoor installations, or on or in instruments and machines, and in the outer regions of buildings, for example on facades of buildings, and for interior or exterior illumination of vehicles. The vehicles may be vehicles, ships and airplanes associated with wheels and rails.

In particular in vehicles, such as automobiles, aircraft, ships and/or trains, the light guide can be used as part of the interior of the vehicle. In the area of interior installations, the light guide can be part of a piece of furniture, in particular a vehicle seat, a living space and/or a galley. Other applications are

-as a component of a headlamp (40), in particular of a vehicle headlamp,

-lighting means for the landing track of the aircraft,

together with further light conductors and/or further side-emitting step-index fibers for forming a planar pattern, which itself may form the illuminating body,

-a background illumination of the display,

use as atmosphere or demarcation lighting in vehicles, boats, airplanes, buildings, streets, road signs, guideboards, textiles,

safety lighting with self-luminescent phosphorescent additives.

Another application is in or on medical devices, for example as accent or contour or safety lighting thereon. The light guide 1 or the light source 2 is also used as a device or at least a component of a device for medical treatment methods, especially photodynamic therapy (PDT) for tumor treatment, intravenous laser therapy (EVLT) for varicose veins treatment, for laser-induced interstitial thermotherapy (LITT), or in the field of ophthalmology, dentistry and dermatology. In particular the latter, also for assisting wound healing. Also advantageous in connection with the use in a medical environment is that the one plastic used, the plastics used (i.e. the polymer blend) preferably comprise biocompatible plastic materials, listed for example according to the standard EN ISO 10993-1:2018 or EN ISO 10993-5:2009 or USP class VI. Furthermore, the materials used are selected to be sterilizable, in particular ethylene oxide sterilizable (EO), since this sterilization method is particularly suitable for disposable applications (disposable or single-use applications) in the field of medical technology, as described in ISO 11135: 2014. Chlorine-free materials are particularly conceivable here, since otherwise chlorine compounds may be generated during the EO process, which on the one hand may be toxic and on the other hand can only be removed incompletely after the sterilization process.

Fig. 20 shows an embodiment of a light guide 2 which is particularly and particularly also suitable for medical applications. In this embodiment, the light of the light emitter 4 is coupled into a further light guide 21, which is optically connected to one end 10 of the side-emitting light guide 1. This embodiment is particularly advantageous in this case if the further light guide 21 is flexible. Preferably, short sections are used here for the side-emitting light conductors. In a further development of this embodiment, it is thus conceivable to use light guides with a length in the range from 5mm to 50 mm. The light guide 1 serves here as a diffuser for the light fed into the further light guide 21. For medical applications, the diffuser may be guided at a predetermined position on or in the body of a patient requiring treatment and the light is emitted there via the light guide 1. The further light guide 21 can be fused to the light guide 1 for optical coupling or can be glued to the light guide 1. For high light intensities, a laser 40 is generally suitable here as light emitter 4.

In summary, the light source 2 is provided without being limited to the specific example shown, wherein the side-emitting optical waveguide 1 is connected to a further flexible optical waveguide 21, and wherein the light emitter 4, preferably the laser 40, is coupled to the further flexible optical waveguide 21, so that light of the light emitter 4 is coupled into the side-emitting optical waveguide 1 via the further optical waveguide 21 and emerges along the side-emitting optical waveguide 1. The light source 2 may be used in particular for the medical applications described above.

The basic function of the side-emitting optical waveguide 1 is achieved by light scattering in the sleeve 3 or on the sleeve 3. In addition to the scattering properties, however, the light guide body 1 can also have, as a rule, a filter property or a spectral change of the outgoing light with respect to the incoming light. In this way a variety of light effects can be achieved. According to one embodiment, the sleeve 3 contains pigment or other colored scattering particles. The scattering particles absorb part of the light according to wavelength, so that the reflected or scattered light is spectrally different from the light guided in the core and has a color. According to another alternative or additional embodiment, at least one of the plastic of the sleeve 3 and the shroud 5 is coloured. The colorant generally does not enhance scattering so that the plastic remains transparent. The coloring agent according to this embodiment is therefore not a pigment. The spectral distribution of the light passing through the plastic is changed by the partial spectral absorption of the dye. The colorant is provided by the polymer or polymer component used itself if necessary, in contrast to the alternative of colorant molecules dissolved in the polymer matrix.

Another solution for the spectral influence of light is the conversion into other wavelengths, i.e. light of one wavelength is converted into light of at least one other wavelength by means of a suitable conversion material. This is advantageous so that spectral variations of the emitted light lose less intensity. This conversion is achieved in particular by the light conductor 1 containing a photoluminescent material. Photoluminescence can be fluorescence as well as phosphorescence. The photoluminescent material may be contained in one or more components of the light conductor which is in contact with the light, particularly in the core 3 and the shroud 5. For example, the sleeve 3 may contain photoluminescent particles 30. For example, blue light can thereby be fed in and scattered at the sleeve 3 and partially converted into yellow light in order to emit white light by mixing these components. However, it is also possible to include a photoluminescent material, for example in the shroud, to convert at least a portion of the intensity as light emitted from the sleeve 3 passes through it. The different optical effects achievable here are also significant. In the case of a dyed covering 5, the color impression of the brightly luminous sleeve 3 to the observer is changed. In the presence of the photoluminescent dye in the shroud 5, a light ray is generated around the brightly luminous sleeve 3, wherein the light ray has a different color than the light directly emerging from the sleeve 3.

In the case of phosphorescent additives, the afterglow effect of the light conductor can be produced even if the light source of the light conductor is switched off. Thereby, a safe illumination can be achieved, for example for use in hospitals, vehicles or in the aircraft field. Furthermore, the phosphorescent particles in the light guide bodies can also be acted upon by external light, so that these light guide bodies can also be used as passive safety lighting or passive accent lighting.

One application of the light guide according to the invention is particularly advantageous in photobioreactors or any other type of photobiological process, since it is not easily bendable. The light guide can be installed both from the outside on the (transparent) reactor and in the interior of such a reactor independently of the transparency of the reactor wall, since the light guide is liquid-impermeable and chemically resistant.

All the variants described above can also be integrated or applied only locally in the light guide, while the other parts do not have these functions. Thereby achieving various effects. The property of locally no side-emitting light is also possible, whereby light can be transmitted at a more remote location with low losses.

Depending on the fiber material used and the desired application, a radiation source can generally be used for the light guide in the wavelength range from 150nm to 15 μm. Any type of laser source, LED, arc lamp, light bulb, or any other type of suitable radiation source is contemplated herein.

List of reference numerals

1	Optical conductor
		2	Light source
3	Sleeve pipe
		4	Light emitter
5	Covering article
		6	1 inner part
7	Fiber
		8	Fiber bundle
9	Layer(s)
		10、11	1 end of
12	1 in the bending section
		13	Gap
14	Fastening element
		15	Channel
16	Hollow cavity
		18	Interface between 5 and 9
19	Optical effect zone
		20	Light beam
21	Another light conductor
		24	Rib
25	Groove
		27	Electrical conductor
28	Reinforcing element
		40	Laser device
50	5 outer surface of
		70	Fiber sheath
72	Fiber core
		73	Interface between 70, 72
74	Mold core
		75	Light scattering element