DE102011084062A1 - LED lighting device used in e.g. interior space of building, has intermediate portion whose length is selected so that brightness difference measured in intermediate portion center at specific distance is set about predefined percentage - Google Patents

Abstract

The device has two separate optical fibers (1) that are separated from each other by intermediate portion of length (A). The radiation (5) of LED (3) passing through optical waveguides is coupled into waveguides in operating state. The guided radiation is reflected into waveguides, so that radiation under passage through waveguide laterally from optical fibers is coupled out in operating state. The length is selected so that brightness difference measured in intermediate region center at distance of 10 mm is set about 25%, based on maximum value of brightness along axis of fibers.

Description

The invention relates to an LED lighting device and its applications. LEDs (Light Emitting Diodes) are becoming increasingly important as a light source, on the one hand because they are considered energy-efficient, on the other hand because they have a long service life and thus can be expected to require little maintenance.

An LED is an electronic semiconductor device. When supplied with electricity, it emits electromagnetic radiation whose wavelength can be in the infrared, visible and / or ultraviolet spectral range. The term LED used in the present specification includes no limitation to a particular wavelength of the emitted radiation.

It is also possible that a plurality of emitting active elements are arranged on a chip, which is also referred to as LED in the sense of the present description. Furthermore, no limitation of the coherence length of the emitted radiation is associated with the term LED used, so that laser diodes are likewise included therein.

A disadvantageous feature of LEDs for lighting applications, however, is that commercially available LEDs are provided in an encapsulation that includes a reflector and / or a lens that emits the radiation emitted by the LED forward at a relatively small opening angle. For the illumination of larger areas, therefore, fluorescent tubes are still popular. However, these have the disadvantage that they can break easily, which is particularly problematic in applications where strong vibrations or other mechanical stresses may occur, but also that they require a relatively high ignition voltage, which require correspondingly expensive electronic components in the power supply and can also emit electromagnetic interference. Another disadvantage of fluorescent tubes is that they emit heat and UV radiation at their luminous area.

In order to avoid the latter disadvantage in particular suggests the US 4,733,332 to couple the light emitted by an incandescent or gas discharge lamp light in the end face of a glass rod, which is provided with a line-shaped diffusion pattern on its lateral surface. The glass rod acts as a light guide for the coupled light, the diffusion pattern decouples it from the glass rod in such a way that it reflects the incident light into the glass rod, passes through it and can be coupled out laterally on the opposite side of the glass rod. In this way, a line-shaped lighting profile with an opening angle, which may correspond to a fluorescent tube with reflector, Apart from the usual disadvantages of the proposed light sources, the proposed device has the disadvantage that with her no arbitrarily long light sources in the form of light strips are to produce because as the length of the glass rods increases, the brightness decrease in the center of the glass rod would increase unacceptably.

Against this background, it is an object of the invention to provide an LED-based illumination device, with the aid of which an arbitrarily long light source with as few local differences in brightness along its longitudinal axis can be produced.

The object is achieved by the lighting device according to the main claim. Preferred embodiments and applications emerge from the dependent claims.

The LED lighting device according to the invention comprises at least two light guides. Each of these light guides has at least one end face. The light guides are arranged so that their respective facing end faces are at a distance A from one another. These end faces thus form an intermediate region of the length A. Preferably, the light guides are arranged so that they lie on the extension of their respective longitudinal axes. This results in a linear arrangement of the light guide, which appears to the user in the operating state as a light strip. But it is also an offset arrangement possible in which the end faces of the light guides are not directly opposite. Nevertheless, they are in the context of the invention facing each other. Preferably, the light guides are rigid, but the principle of the invention is also feasible with flexible light guides.

The intermediate region is used in the operating state to couple the radiation emitted by at least one LED into the end faces and thus into the light guides. In order for the radiation guided in the light guides to be used in the sense of a lighting device, the optical fibers have means for coupling radiation in the outer peripheral surface area. In the operating state, ie when electricity flows through the LED, the radiation emitted by the at least one LED radiation is radiated through the end face in the light guide and guided by this by total reflection. The means for decoupling the radiation ensure that the radiation impinging on them is reflected into the light guide and, while passing through the light guide laterally, ie laterally or at the exit from its outer peripheral surface, is coupled out of the light guide. The distance A and thus the length A of the intermediate region is selected such that in the operating state the resulting brightness difference ΔI in the middle of the intermediate region at a distance of 10 mm perpendicular to the axis of the light guides is at most 25%. This value is related to the maximum value of the brightness measured along the axis of the optical fibers at the same distance perpendicular to their axis. The measurement of the brightness along the axis of the light guides and in the intermediate area always takes place from the direction of the user, this means from the direction of the radiation emerging through the means for coupling the radiation out of the light guides.

At a distance of 20 mm perpendicular to the axis of the optical fibers, the brightness difference ΔI in the middle of the intermediate region is preferably at most 5% relative to the maximum value along the axis of the optical fibers.

In order to determine this value .DELTA.I, the intensity of the radiation emitted by the illumination device in the operating state and striking a ground glass is measured at a position in the middle of the intermediate region and at a distance of 10 mm perpendicular to the axis of the optical fibers. Thereupon, the difference between the maximum value of the intensity along the axis of the optical fibers and the value of the intensity in the middle of the intermediate area is formed. This difference value is then set in relation to the said maximum value of the intensity. So the following formula applies: ΔI = (Imax - Imine) / Imax

Imax stands for the described maximum value of the intensity and Imin for the value of the intensity in the middle of the intermediate range. The numerical value of ΔI is given in the sense of the description in percent, the amount of the difference of Imax and Imin is decisive.

If the measured values for Imax of the two light guides differ, the measured value corresponding to the highest measured intensity is used. As a rule, the brightest point is located near the respective end face. In this way, the value for the brightness decrease becomes a measure of the user perceivable brightness fluctuations along the axis of the lighting device. It is desired that these brightness variations are as low as possible. Since the human eye does not perceive differences in brightness in a linear manner but reacts approximately logarithmically to differences in brightness in the perception, a measured value of ΔI of 25% or less means a brightness difference barely perceptible to human observers.

The ground glass to be used for the measurement is mounted at the respective distance to the LED illumination device and the LED illumination device is put into the operating state. As a ground glass, for example, serve a sheet of paper, which is preferably applied to a support, for example a transparent glass pane. The focusing screen has a very large acceptance angle and thus makes the measurement comparable to the behavior of the human eye. The intensities of the radiation impinging on the ground glass can be measured by suitable measures, for example by recording with a digital camera from the back of the ground glass, wherein the local light values can subsequently be read out by an image processing program. Other suitable methods for measuring the intensity profile on the ground glass are also possible and known to the person skilled in the art.

The measurement can be repeated at other intervals, with the differences in brightness ΔI decreasing as the distance increases, due to the increasing over-radiation of the intermediate region as the distance increases. The measured values of ΔI thus depend significantly on the two parameters length A of the intermediate region and distance of the measurement perpendicular to the axis of the light guides. If different lighting devices are to be compared, this must be done at the same distance from the light guides.

It is possible and encompassed by the invention to arrange the LED outside the axis of the light guides. The radiation emitted by it can be coupled by means for beam deflection in the end faces of the light guides, for example by mirrors and / or by prisms. This makes it possible to couple the radiation emitted by an LED radiation into the two opposite end faces of the light guides.

The end faces of the light guides at the ends facing away from the intermediate region may be mirrored, which is preferred when the illumination device is designed with a single LED in the intermediate region. This can be advantageous in lighting devices with very limited lengths and / or very expensive LEDs. However, it is likewise possible for at least one further LED, which in turn can radiate radiation into the respective light guide, to be located on the end faces facing away from the intermediate region of the light guide.

Preferably, at least each adjacent to the intermediate region end face of the light guide is associated with at least one LED. The invention provides that the distance between the respective LED and the respective end face associated with it is selected to be as small as possible. This small distance makes it possible that there are no further optical devices in this preferred embodiment between the respective LED and the respective associated end face. In this case, further optical devices are understood to mean, in particular, beam-focusing and / or beam-deflecting optical devices, such as focusing lenses and / or collimator systems, which in principle must be used at longer distances in order to be able to couple sufficient radiation emitted by the LED into the optical fiber. However, it is of course possible and encompassed by this formulation that the LED itself may be encapsulated by optical devices or that may have the optical devices which are often present in the state of delivery. Due to the small distance so additional optical devices are made redundant and even the brightness difference .DELTA.I reduced.

In a particularly preferred embodiment, the distance between the respective LED and the respective end face of the light guide associated therewith is at most 3 mm, particularly preferably at most 1 mm. These distances are measured from the end of the respective LED housing to the end face of the respective light guide, it thus corresponds to the length of the free-jet area between the LED housing and the end face of the respective light guide.

In the intermediate region between the mutually facing end faces of the light guide are the LED or LEDs and, if necessary. at least one carrier element and / or electronic connection components of the LEDs. The length A of the intermediate region is preferably chosen as short as possible in accordance with the preceding embodiments. Preferably, the length A of the intermediate region is at most 15 mm, particularly preferably at most 12 mm or at most 10 mm, very particularly preferably at most 8 mm.

The light guides themselves may consist of any suitable materials, for example plastics and / or glass. However, it is preferred that the optical fibers preferably consist of a multi-component glass, at least in their core region. A multi-component glass, also called mineral glass, is melted from more than one raw material and contains the oxides of more than one chemical element. This differentiates it from a quartz glass, which consists only of SiO ₂ .

Preferably, the light guides consist at least in their core region of a glass containing: 70% -85% SiO ₂ , 8% -20% B ₂ O ₃ and individually or in total 2% -8% Na ₂ O and / or K ₂ O and / or Li ₂ O. This means that not every one of the alkali metals mentioned must be present in the glass, but at least one in said minimum amount. Further preferred optional components are up to 7% Al ₂ O ₃ and individually or in total up to 5% MgO and / or CaO and / or BaO and / or ZnO. All percentages in this specification are given in weight percent (wt.%) On an oxide basis. Preferably, the glass contains in total at most 50 ppm Fe ²⁺ and / or Fe ^3+, preferably at most 20 ppm, particularly preferably at most 10 ppm. Other components are optional, but the proportion of heavy metals such as Pb, Cd, Hg and Cr is preferably less than 100 ppm.

Such a glass is characterized by its excellent resistance to attack by water, acids and alkalis. In particular, it corresponds to a water resistance class HGB1 according to ISO 719 , an acid resistance class S1 after DIN 12116 and an alkali resistance class A2 ISO 695 , During operation of the lighting device, the light guides can very easily come into contact with water, acids or alkalis, for example in the form of atmospheric moisture, vapors of operating materials and / or solvents and / or cleaning agents. A lower resistance of the glass of the light guide could lead to blindness of the same, whereby the light guide could be limited in their function and at the end of the lighting device could be unusable. Therefore, the excellent durability of the preferred glass results in a long life expectancy of the lighting device, even under adverse circumstances.

Particularly preferably, the light guides consist at least in their core region of a glass containing: 75% -85% SiO ₂ , 8% -15% B ₂ O ₃ , individually or in total 2% -8% Na ₂ O and / or K. ₂ O and / or Li ₂ O, optionally 0% -5% Al ₂ O ₃ and optionally individually or in total 0% -2% MgO and / or CaO and / or BaO and / or ZnO. The aforementioned condition of the contents of Fe ²⁺ and / or Fe ^{3+ of} course also applies to these particularly preferred glasses.

The glass preferably has a modulus of elasticity E, also called Young's modulus, of at most 66 × 10 ³ N · mm ^-2 . The smaller the numerical value of E is, the lower is the rigidity of the relevant component, in this case of the particular rigid optical waveguide made of said glass. It has been found that the modulus of elasticity E correlates with the resistance of the glass to vibrations, in such a way that the less rigid the optical fiber is, the better it will withstand the vibrations. This means that the aim is that the value of the modulus of elasticity E of the glass of the light guides should be as low as possible in order to ensure good vibration resistance. Vibrations can damage a light guide made of glass in particular in that cracks form in it, which can lead to breakage of the light guide and / or to spalling of material. Both are undesirable and can lead to the failure of the lighting device. As compared to the above-mentioned value for the modulus of elasticity E of at most 66 · 10 ³ N · mm ^-2 , quartz glass has a modulus of elasticity E of 72.5 · 10 ³ N · mm, as is known for lighting devices of the prior art ^{. 2} on. As already described, it is much more brittle than the multicomponent glass according to the invention and can withstand vibration loads less well.

In a particularly preferred embodiment, the multicomponent glass contains at most 50 ppm (parts per million) Fe ²⁺ and / or Fe ³⁺ . In particular, with larger lengths of the light guide, the iron content of the glass may cause the light guide itself to shift the color spectrum of the radiation conducted in it, which would make emission of pure white radiation impossible. In other words, in the case of glass optical fibers containing a higher content of Fe ²⁺ and / or Fe ³⁺ than 50 ppm, if white light were passed in them, a color cast at the exit of the light would be observed for Lighting applications is undesirable or at least disadvantageous.

The Fe ²⁺ and / or Fe ³⁺ may be present in the glass in the form of ions, or else in the form of oxides, for example FeO and / or Fe ₂ O ₃ . Iron often gets into glass due to contamination of the raw materials used in melting the glass, but also through the use of steel components that come in conjunction with the molten glass. Therefore, particularly pure raw materials are preferably used in the production of the glass rods which are part of the lighting device according to the invention.

The use of glass as a material for the optical fibers has the advantage of a higher intrinsic transmission of the optical fibers and thus better light intensity of the illumination device compared to those made of plastics in the rule. In addition, a lighting device according to the invention with glass optical fibers is fireproof, d. H. It fulfills high requirements for fire safety, as required for example as approval regulations for various applications. This criterion is important for use in, for example, aerospace and / or laboratory environments and / or hot environments.

According to the invention, the means for decoupling the radiation are applied in the outer peripheral region of the light guides. If the light guides are formed as a glass rod, the radiation in the glass rod at the interface of the glass rod by total reflection against the surrounding medium, generally air, passed. In this simplest case, the means for decoupling the radiation are applied directly outside on the light guide and thus on its outer peripheral surface.

But it is also possible that the exemplary rod-shaped light guide consists of a core region of said glass, which is covered by another glass with a lower refractive index. The total reflection required for the light pipe then takes place at the interface between the core and the cladding glass with the lower refractive index. The means for decoupling the radiation may be mounted on the core glass and covered by the cladding glass, or with a suitable choice z. As the refractive indices of the glasses on the cladding glass itself. Compared to the core, the thickness of the or the surrounding shells but relatively low. For this reason, the term outer peripheral surface area in the sense of the invention means not only the outer peripheral surface of the optical fibers, but a surface which is located in the outer periphery of the optical fibers, that is also at a certain depth near the surface. Thus, it is also possible and encompassed by the invention that the means for decoupling the radiation and / or the light guides of at least one further layer, for. As a protective layer, are covered, regardless of whether the means for coupling the radiation directly on the core or on a him surrounding mantle. In this case, the invention may provide for the light guides to be designed as side-emitting light guides in which the means for coupling out the radiation are formed by scattering centers in the core-cladding interface. Such light guides are in the WO 2009/100834 A1 described.

In the simplest form, however, means for decoupling the radiation are printed on the lateral surface and / or glued and / or sprayed. You are then as a layer directly on the outer peripheral surface. But it is also possible to produce the means for coupling the radiation by structuring the lateral surface, for. B. by roughening. It is also possible to apply layers, for example, reflective layers, by physical vapor deposition (PVD), plasma-induced chemical vapor deposition (PICVD) and / or sputtering. The easiest way, however, is the printing or spraying of, for example, white color. Depending on the application, however, all conceivable other colors are possible. As a result of the preferably at most slight discoloration of the incident light by the light guide according to the invention, the color emitted by the illumination device can thus be adjusted simply by the color of the means for decoupling the radiation. Alternatively, a color filter can be introduced into the beam path.

The light guides preferably have at least one chamfer on at least one of their respective ends, following their end faces. The chamfer causes the cross-sectional area of the end face to be smaller than the cross-sectional area of the light guide in its center. The chamfer itself is preferably designed so that it has at least one substantially flat side surface. It has been found that such a chamfer does not appreciably worsen the coupling efficiency of the LEDs into the end surfaces. The chamfering is preferably used to ensure a defined installation position of the light guides, preferably with the aid of a mechanical stop as described below.

For fixing the LED lighting device to other objects, a mounting body is provided which performs this function. In a preferred embodiment, the mounting body is thermally conductively connected to at least one carrier element or carrier for short, on which the at least one LED is mounted in the above-described intermediate region. Preferably, the carrier and mounting element are integrally formed. The carrier may then be, for example, a strip which has been cut or punched out of the mounting element and bent over. The mounting element itself is preferably a profile made of sheet metal, the carrier element according to a metal strip.

The carrier and the heat-conducting connected to the carrier mounting member serve in this embodiment as a heat sink for the at least one LED. This counteracts the frequently occurring problem in the use of LEDs, in particular bright high-performance LEDs, the development of heat. If the LED is too hot, it can be destroyed in extreme cases or emit less useful radiation. Another effect due to the operating temperature is the so-called caloric shift, which means that the spectrum of the emitted radiation of the LED changes depending on the operating temperature.

For the purposes of the invention, all available LEDs, irrespective of whether individual LEDs or LED chips, are used as LEDs. This also encloses laser diodes when the application of the lighting device requires it. However, particularly preferred are LED chips in SMD construction, because they can be provided with these particularly cost-effective lighting devices for general lighting purposes. The LED is also preferably an LED chip, which in particular comprises an RGB, RGBA, RGBW or RGGB chip. Furthermore, this sensor may be associated with a sensor (and measures described below by way of example) for controlling the color locus and / or the brightness of the emitted radiation of the LED. It is possible that the sensor is located on the LED chip, or it may be integrated at another point in the beam path. It is also possible that the sensor is located at any point of the light guide. It is also possible that the sensor is the sensor above or below the light guide, preferably mounted on the mounting body. In this embodiment, it preferably detects light scattered by the light guide. Also possible is an arrangement behind the LEDs and / or behind the LED chip, if they are at least partially transmissive to radiation.

The LED and / or the chip is usually associated with an evaluation and control electronics, which determines the color location and / or the brightness, whereupon the LED or the LED chip is controlled so that certain operating states of the LED can be set. By targeted control of the elements of the chip is a color mixing of the emitted radiation. In this way, for example, light of any color can be emitted from the LED and thus the illumination device. As already with respect to the Colorshift described the color location, however, depending on the environmental conditions, in particular the temperature, but also on the age of the LED vary. This variation can not be determined, which is why the sensor should measure the intensity of the radiation and its color location. By taking these values into account when controlling the LED or LED chips, a reproducible and permanently stable color location as well as a reproducible and permanently stable intensity of the radiation emitted by the illumination device can be achieved.

The installation position of the light guides determined because of the means applied to them for decoupling the radiation the place of illumination during operation. In a particularly preferred embodiment, therefore, the carrier has at least one stop, which cooperates with the chamfering of the optical waveguides described above in such a way that a defined mounting position of the optical waveguides and thus the means for decoupling the radiation relative to the mounting body results. In simple terms, this means that the rotation of the light guide relative to the mounting body is prevented by the stop and / or the rotation of the light guide and thus its position relative to the mounting body is defined during installation.

The stop itself can be made in any suitable manner. It is preferably a mechanical stop, which is in contact with the chamfering of the light guides. For example, it may be designed as a pin which protrudes from the carrier in the direction of the light guide. Other shapes are also conceivable, for example the following structures, at least in sections of the shape of the chamfer.

The light guides themselves are not necessarily round, d. H. they do not necessarily have a circular cross-sectional area. You can, for example, have an oval cross-sectional area, or z. B. a cross-sectional area which is flattened on the side of the means for decoupling the radiation. Any suitable form is conceivable and encompassed by the invention. Likewise, the optical fibers in the context of the invention need not be straight. Any shape is possible and encompassed by the invention.

In order to produce the most homogeneous emission profile possible, the means for decoupling the radiation are formed by a coating applied at least in sections to the optical fibers, which is preferably formed by varying its density and / or structure and / or geometric pattern and / or composition such that in the operating state of the increasing with the distance to the LED drop in the intensity of the guided in the light guide radiation is at least partially balanced. Thus, the impression of a largely homogeneously radiating light source can be achieved for the user. All methods suitable for applying the coating are possible, but preference is given to printing methods, in particular screen or pad printing. A preferred geometric pattern for the means for coupling out the radiation is a sawtooth structure. The height and width of the individual teeth and their distance from each other can be adjusted in a suitable manner along the axis of the light guide according to the requirements in order to achieve the desired illumination profile, in particular the desired intensity distribution.

It is also possible and encompassed by the invention that several of the lighting devices according to the invention described are arranged side by side in extension of their respective longitudinal axes. Between each of the optical fibers used is then an intermediate region in which the radiation from at least one LED can be coupled in each case. This embodiment is preferred in order to produce particularly long illumination devices. The illumination device according to the invention thus preferably forms a module of a larger illumination arrangement in which the illumination device according to the invention repeats as often as desired. At the respective final end faces of the lighting arrangement are preferably at least one LED, which radiates radiation in the operating state of the final light guide.

As described, heat may be generated during operation of the LED lighting device, but it is also possible that the LED lighting device is in environments that may experience large temperature fluctuations. The components of the illumination device, in particular the light guides and their holding means generally have different thermal expansion coefficients. This has the consequence that the components mentioned can move against each other with temperature changes. If they collide, these components may be damaged and / or misaligned. Therefore, it is provided to form the holders, which connect the light guides in the illumination device, in such a way that an axial displacement of the light guides is possible. By this measure, it is also possible to compensate for manufacturing tolerances in particular with respect to the length of the light guide. Likewise, the assembly is facilitated.

Likewise, it is provided that the holders of the light guides are designed so that they can intercept vibrations of the light guide also in the direction perpendicular to its longitudinal axis. This can be achieved by at least some holding means are deflected substantially perpendicular to the longitudinal axis of the light guide and return to its original position after the deflection. In addition to the design of this holder, this can be made possible by a suitable choice of material, for example made of thermoplastic materials.

The lighting device according to the invention has the particular advantage that it can be coupled together in the intermediate region to an arbitrarily long chain of lighting devices due to the small perceived differences in brightness .DELTA.I, which has a largely homogeneous for the user lighting profile. In addition, flameproof materials can be used, in particular light guides made of glass. These are also vibration-resistant due to the preferred choice of the glass. This makes the lighting device particularly suitable for use in interiors of aircraft subject to special safety regulations. Particularly preferred applications are therefore carried out in aircraft cabins and / or aircraft cargo holds.

Their advantages are also useful in the interiors of other means of transport such as trains or automobiles (passenger cars as well as trucks).

Further advantageous and preferred uses are generally light elements of vehicles, preferably daytime running lights and / or position lights on the front of automobiles and / or as an element whose headlights, or as an element of the taillight of automobiles.

A further preferred use of the illumination device according to the invention takes place as an element of a designer lamp and / or household lamp and / or office lamp. Further preferred applications are shelf lighting, especially on store shelves, cabinets and other furniture, including kitchen appliances such as refrigerators and / or ovens or cold stores.

In general, the lighting device according to the invention can also be used for the illumination of external surfaces, such as squares or parking levels, streets, paths, platforms, stops, tunnels, etc. Facades or interiors of houses may also be preferred application areas.

The invention will be further clarified below with reference to the drawings. The drawings are schematic, the scales and dimensions do not have to match the actual objects. Show it:

1 : The longitudinal section through a described lighting device.

2 : The longitudinal section through another described illumination device.

3 : The longitudinal section through another described illumination device.

4 : The longitudinal section through another described illumination device.

5 : The principle of light extraction.

6 : The longitudinal section through a further described illumination device and the corresponding intensity profile.

7 : Intensity profiles of a lighting device according to 1 at different distances to the light guides.

8th : The longitudinal section through a lighting device with carrier and mounting body.

9 : The perspective view of a real existing lighting device.

10 : The longitudinal section of a light guide with chamfer and support with stop.

11 : The cross-section of a fiber optic with chamfer and support with stop.

12a : A described illumination device with a chain with curved light guides,

12b : A described lighting device with a chain with curved light guides.

12c : A described illumination device with a chain with curved light guides,

13 : An aircraft interior with a described illumination device.

1 shows the principle of the LED lighting device according to the invention in a schematic longitudinal section. In operation, radiation ( 5 ) from the LEDs ( 3 ) emitted. The LEDs ( 3 ) are in front of the respective end face ( 2 ) the light guide ( 1 ) and in the intermediate region between the opposing end faces ( 2 ) the light guide ( 1 ) arranged. The intermediate region has the length A, the distance A between these end faces ( 2 ) corresponds. For coupling the radiation ( 5 ) in the light guide no further optical devices are used. In the outer peripheral surface area of the optical fibers ( 1 ) are means for coupling the radiation ( 4 ), which in the operating state of the LED ( 3 ) is emitted. In the simplest case, these means for decoupling the radiation ( 4 ) as also already described on the outer peripheral surface of the optical fibers ( 1 ) or sprayed on, the light guides ( 1 ) are preferably rigid sheath-free rods of the described glass. Meets in the light guides ( 1 ) guided radiation on the means for decoupling ( 4 ), it is reflected into the optical fibers, passes through them and is laterally decoupled from these. The decoupled radiation ( 5 ) is the useful radiation or shortly the light that is provided to the user of the illumination device.

In 1 are the light guides ( 1 ) in extension of their longitudinal axes and arranged on these. Therefore, this arrangement is called a linear arrangement. However, the invention also includes the in 2 illustrated staggered arrangement in which the optical fibers ( 1 ) are arranged parallel to their longitudinal axes but offset from each other. Preferably lie the planes of the end faces ( 2 ) parallel to each other. In the space between the two light guides ( 1 ) are again the LEDs ( 3 ), the gap in turn has the length A. The length A of the intermediate region is in the staggered arrangement on the extension of a longitudinal axis of the light guides ( 1 ), so not on a diagonal, which the centers of the faces ( 2 ) would connect.

3 shows an embodiment with a linear arrangement, in which the in the optical fibers ( 1 ) through the end faces ( 2 ) coupled radiation ( 5 ) of only one LED ( 3 ). This is outside the axis of the light guides ( 1 ), the radiation emitted by it is irradiated by the optical element ( 10 ) and on the front surfaces ( 2 ) of the two light guides ( 1 ) steered. The optical element ( 10 ) may be a prism, which in particular may have mirrored side surfaces, or an angle mirror as in the 3 shown. Any other suitable optical element is also possible and encompassed by the invention.

In 3 is also shown that the intermediate area facing away from the end faces ( 2 ) the light guide ( 1 ) as already described need not necessarily be used for irradiation of radiation. According to the invention, it is only necessary to ensure that the end faces adjoining the intermediate region (FIG. 2 ) the light guide ( 1 ) at least one LED ( 3 ) assigned.

4 shows an example in turn a parallel to the longitudinal axes of the light guide ( 1 ) staggered arrangement in which areas of the optical fibers ( 1 ) overlap. The intermediate area also has a length A, which in this case is the length of the intersection of the light guides ( 1 ) corresponds. As can be seen from the drawings, it is also possible for the planes of the mutually adjacent end faces (FIGS. 2 ) lie in the staggered arrangement on each other, so that the length A of the intermediate region can assume the value 0.

An as homogeneous as possible intensity profile with the lowest possible difference in brightness ΔI is generally desired. This can be achieved by suitable arrangement and implementation of the means for decoupling the radiation ( 4 ) can be achieved in all embodiments.

The principle of operation of the LED lighting device according to the invention is based on 5 clarified. The operating state of the LED ( 3 ) emitted radiation ( 5 ) is determined by total reflection in the light guide ( 1 ) guided. Does the radiation hit the means for decoupling ( 4 ), which in the figure on the outer peripheral surface of the light guide ( 1 ) and thus located in the outer peripheral surface area, it is in the Lichtleier ( 1 ) is reflected in it. As a result, the reflected emitters pass through the light guide ( 1 ) and strike in a significant proportion at an angle to the wall of the light guide ( 1 ), which (measured from the tangent of the wall of the light guide ( 1 )) is greater than the angle of total reflection so that it passes through the wall of the light guide ( 1 ) and are thus available for lighting purposes. It may well be desirable that a certain proportion of the rays at an angle to the wall of the light guide ( 1 ), which is smaller than the angle of total reflection. This ensures that not all the radiation immediately from the light guide ( 1 ), but a lighting profile is achieved which corresponds to the shape of the means for decoupling ( 4 ), preferably a line-shaped (including curved lines) illumination profile. The illumination profile itself, ie the intensities of the radiation emitted by the illumination device ( 5 ) in certain places, can also be described as described by the design of the means for decoupling ( 4 ) of the radiation.

The LED illumination device according to the invention is intended to achieve the most homogeneous possible intensity profile with the lowest possible brightness difference ΔI. This manifests itself in that the intensity drop over the entire length of the lighting device should be as low as possible. A special problem area is the intermediate area, in which the intensity profile naturally drops. In 6 is an LED lighting device according to the invention according to the embodiment according to the 1 and above it the scheme of an intensity profile to be measured. This represents the measured intensity of the radiation emitted by the means for decoupling ( 4 ) from the light guides ( 1 ) directed radiation ( 5 ) along the longitudinal axis of the light guides ( 1 ), in the direction of the radiation coupled out laterally from the light guides and at a constant distance from the longitudinal axis of the light guides. In the area of the end faces ( 2 ) the light guide ( 1 ), the highest intensity is achieved with the value Imax. Because each face ( 2 ) an LED ( 3 ) are assigned at the same power of the LEDs ( 3 ) and the same configuration of the light guides ( 1 ) including the means for decoupling the radiation ( 4 ) in principle the same intensity values in the area of the end faces ( 2 ) reached. In the intermediate region with the length A, the intensity drops to the minimum value Imin. The absolute intensity values to be measured in the intermediate range also depend to a significant extent on the distance during the measurement perpendicular to the longitudinal axis of the light guides (FIG. 1 ) from and of the length A of the intermediate region. The brightness difference ΔI in the intermediate region is calculated as described by the formula given by the difference between Imax and Imin, which is set in relation to Imax and expressed as a percentage. The absolute values of the intensities and thus those of the LEDs ( 3 ) radiated power plays therefore for the indication of the brightness difference ΔI irrelevant.

7 shows the intensity profiles measured at a real existing illumination device at different distances to the longitudinal axis of the light guides (FIG. 1 ) and in arbitrary units. This measured illumination device corresponds to the embodiment according to 1 , but without the LEDs ( 3 ) at which the intermediate region opposite end faces ( 2 ) the light guide ( 3 ). Therefore, lower intensity values are achieved at the ends of the optical fibers than at the coupling-in points at the intermediate region.

The upper picture of the 7 represents the intensity profile at a distance of 10 mm measured perpendicular to the axis of the light guide, the middle figure the intensity profile at a distance of 15 mm and the lower figure the intensity profile at a distance of 20 mm. The length A of the intermediate area is of course identical. The values of the intensities are given in arbitrary units that do not have to match from picture to picture. As can be seen, the values of Imin increase with increasing distance of the measurement relative to Imax, so that the difference between Imax and Imin decreases with increasing distance. In arbitrary units, the values of Imax and Imin are 50 and 43 at a distance of 10 mm, which corresponds to a difference of 7 and thus to a value of ΔI of 14%. At a distance of 15 mm, Imax is also in arbitrary units 50, but Imin is at least 48. The difference of 2 leads to a value of ΔI of 4%. At a distance of 20 mm, the value Imax in arbitrary units is again 50, while Imin is already 49. The difference is 1, which corresponds to a ΔI of 2%.

At a distance of 20 mm, therefore, it is almost impossible to see any difference between these values and thus only an extremely small brightness difference ΔI. Taking into account that the distance of a user of a lighting device according to the invention is usually at least one meter and considerably more makes it apparent that the illumination device according to the invention has a remarkably homogeneous intensity profile despite the economical handling of the number of LEDs.

In 8th is the preferred assembly of a lighting device according to the embodiment according to 1 shown schematically. The LEDs ( 3 ) are on the carriers ( 40 ) appropriate. The carriers ( 40 ) are connected to the mounting body ( 50 ) connected. The compound is preferably carried out so that a heat conduction from the carriers ( 40 ) in the mounting body ( 50 ) is possible. The surfaces of the supports ( 40 ) and in particular the mounting body ( 50 ) can be used by the LEDs ( 3 ) Heat generated in the operating state as a heat sink record and in particular radiate over their surface again. Carrier ( 40 ) and mounting body ( 50 ) can serve as a heat sink.

The mounting body ( 50 ) and the carriers ( 40 ) are preferably formed in one piece as described. They are preferably made of a thermally conductive material, in particular a metal (including alloys of metals). Particularly preferred are aluminum and / or copper and / or brass and / or steel, in particular stainless steel. To enhance the cooling effect of the housing body may have measures to increase its surface, such as cooling fins. The mounting body ( 50 ) is again preferably attached to other objects.

In 9 is shown schematically and in perspective an advantageous embodiment of an LED lighting device according to the invention. This figure also represents the embodiment. This illumination device has five in the extension of their longitudinal axes arranged on this rigid rod-shaped light guide ( 1 ) from said glass. Between the light guides are four intermediate regions of length A, in the exemplary embodiment 14 mm, in which the carrier ( 40 ) are mounted. At the ends of the illumination device is again a carrier ( 40 ). On the carriers ( 40 ) are the LEDs, in such a way that each to end surface of the light guide ( 1 ) is assigned an LED. Carrier ( 40 ) and mounting body ( 50 ) are made in one piece. As you can see, the profile of the mounting body ( 50 ) has an asymmetrical shape, the light guides ( 1 ) and supports ( 40 ) are mounted on a surface of the L-shaped profile. On the back of the mounting body ( 50 ) are preferably mounted electronic components, which z. B. needed to operate the LEDs. The mounting body ( 50 ) also has holes to see, by means of which it can be bolted or riveted to other objects.

10 represents a light guide ( 1 ) of a lighting device according to the invention, each with a chamfer ( 25 ) at its ends in longitudinal section. The cross-sectional area of the end faces ( 2 ) have in this example the shape of a hexagon, the surface area of the end face is smaller than a cross-sectional area through the volume of the light guide ( 1 ). Therefore, the chamfer increases in the direction of the outer peripheral surface in the supervision. A stepped shape is also possible. The hexagonal shape creates 6 flat surfaces in the area of the chamfer. These could be used to adjust the installation position of the light guide ( 1 ) define. For this purpose, the carrier ( 40 ) a stop ( 45 ), which is in contact with a flat surface of the chamfer. This allows the light guide ( 1 ) no longer in relation to the carrier during operation and when strong vibrations occur ( 40 ) and thus not with respect to the mounting body ( 50 ) are twisted. Due to the hexagonal shape, individual discrete values of a possible rotation of the light guide ( 1 ), so that no further adjustment effort arises during installation. The rotation of the light guide ( 1 ) defines the position of the means for decoupling the radiation ( 4 ) and thus the place of illumination. The means for decoupling ( 4 ) are shown in the figure as a previously described sawtooth structure in which the spacing between the teeth is varied to set a desired intensity profile.

11 shows the light guide ( 1 ) with chamfering ( 25 ) and stop ( 45 ) according to 10 in cross-section at the level of the end face ( 2 ).

In the 12a to 12c Examples of LED lighting devices according to the invention with curved rigid rod-shaped optical fibers ( 1 ). The means for decoupling ( 4 ) of the LEDs ( 3 ) radiation emitted in the operating state ( 5 ) follow in the drawings the contour of the light guide ( 1 ). But it is also possible that they are in any shape on the light guide ( 1 ) are applied. As based on the 12c can be seen, the means for decoupling ( 4 ) of the radiation also in sections on the light guide ( 1 ) be applied. Any chains with arbitrary shapes and still low brightness differences ΔI can be generated in this way.

The in the 12a to 12c shown embodiments with the bent rigid optical fibers ( 1 ) are preferably used in decorative lighting. Also possible is the use as position lighting, especially in automobiles, trucks and / or trains. In these applications, the LED lighting devices and thus the light guides ( 1 ) preferably integrated in the headlights of the vehicles. The viewer sees in this case through the light guide ( 1 ) and sees the contour of the means for decoupling ( 4 ) in the operating state. So far, such shape profiles have been achieved by attaching a plurality of LEDs. This previous solution has the disadvantage that the probability of failure increases with the number of installed LEDs, as a failed LED has the consequence that the headlight must be replaced. In addition, the LEDs are perceived as individual points of light, which is why the LEDs must not differ greatly in their brightness and their color location. Therefore, the LEDs must be closely selected before their installation, which increases the manufacturing cost. As the number of LEDs increases the statistical meantime between failures (MTBF), since lighting equipment is generally considered to be defective if one single LED fails. The LED lighting device according to the invention comes with significantly fewer LEDs per headlamp, whereby the MTBF is significantly improved by the invention.

13 shows by way of example a particularly preferred field of application of the LED illumination device according to the invention, namely for illuminating the interior of an aircraft, in this case a passenger cabin. According to an embodiment, an LED lighting device has been designed according to FIG 9 installed instead of fluorescent tubes in the cabin. In addition to the advantages already described with respect to the insensitivity to vibration and the power savings, the LED lighting device according to the invention has the further advantage in this application that it can fulfill a dual function of general and ambient lighting, in particular if the LEDs ( 3 ) are executed in the form of LED chips, which make different colors and lighting scenarios possible by color mixing. Likewise, it is possible to install the LED lighting device according to the invention behind a fairing part to an indirect lighting, for. B. as grazing lighting the cabin ceiling to achieve.

The LED lighting devices presented have the advantage over the prior art that they make the advantages of LED technology available for panel lights. The inventive design and thus achieved low brightness differences ΔI in the intermediate areas, it is possible to provide a uniform intensity of illumination on larger areas and good energy efficiency. In particular, the LED lighting devices are also able to be used in environments in which strong vibrations can occur. With a suitable choice of material, they are also flameproof and allow use in environments with high fire protection requirements.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 4733332 [0005]
• WO 2009/100834 A1 [0030]

Cited non-patent literature

• ISO 719 [0023]
• DIN 12116 [0023]
• ISO 695 [0023]

Claims (10)

LED lighting device comprising two separate optical fibers ( 1 ), which are arranged so that in each case one end face ( 2 ) of a light guide ( 1 ) one end face each ( 2 ) of the other light guide ( 1 ), so that these two end faces ( 2 ) have the distance A and thus form an intermediate region of the length A, in which in the operating state, the radiation of at least one LED ( 3 ) by the adjacent to the intermediate region end faces ( 2 ) in the light guides ( 1 ) and in the light guides ( 1 ), wherein the outer peripheral surface areas of the optical fibers ( 1 ) Means for decoupling ( 4 ) of radiation ( 5 ), which in the optical fibers ( 1 ) guided radiation into the optical fibers ( 1 ), so that in the operating state the radiation ( 5 ) passing through the optical fibers ( 1 ) laterally out of the light guides ( 1 ) is selected, wherein the distance A is selected so that in the operating state, the brightness difference .DELTA.I measured perpendicular to the axis of the optical fibers ( 1 ) in the middle of the intermediate area at a distance of 10 mm perpendicular to the axis of the light guides ( 1 ) not more than 25% relative to the maximum value of the brightness along the axis of the optical fibers ( 1 ) is. LED lighting device according to the preceding claim, wherein each end face ( 2 ) the light guide ( 1 ) in the intermediate area at least one LED ( 3 ) and wherein between the respective LED ( 3 ) and the respective end face ( 2 ) are no further optical devices. LED lighting device according to claim 2, wherein the distance between the respective LED ( 3 ) and the respective end face ( 2 ) is at most 3 mm, preferably at most 1 mm. LED lighting device according to at least one of the preceding claims, wherein the length A of the intermediate region is at most 15 mm. LED lighting device according to at least one of the preceding claims, wherein the glass contains (in wt .-% based on oxide): SiO ₂ 70-85 ^B 2O3 8-20 Na ₂ O + K ₂ O + Li ₂ O 2-8 Al ₂ O ₃ 0-7 MgO + CaO + BaO + ZnO 0-5, the glass preferably contains in total at most 50 ppm Fe ²⁺ and / or Fe ³⁺ . LED lighting device according to at least one of the preceding claims, wherein the light guides ( 1 ) with a mounting body ( 50 ) are connected to fix the LED lighting device to other objects and the at least one LED ( 3 ) on a support ( 40 ) is attached, the heat-conducting with the mounting body ( 50 ) connected is; preferred are carriers ( 40 ) and mounting body ( 50 ) in one piece. LED lighting device according to claim 6, wherein each optical fiber ( 1 ) at least at one end a chamfering ( 25 ) and the carrier ( 40 ) at least one attack ( 45 ), which with the chamfer ( 25 ) the light guide ( 1 ) cooperates so that a defined mounting position of the means for decoupling ( 4 ) of radiation ( 5 ) relative to the mounting body ( 50 ) results. LED lighting device according to at least one of the preceding claims, wherein the LED ( 3 ) comprises a chip, in particular an RGB, an RGBA, an RGBW or an RGGB chip, to which a sensor and measures for controlling the color locus and / or the intensity are assigned. Lighting arrangement, comprising more than one LED lighting device according to at least one of the preceding claims, which are arranged so that the arrangement of the light guides ( 1 ) and the intermediate areas of the illumination device. Use of the LED lighting device according to at least one of the preceding claims for illuminating surfaces and / or rooms selected from the group - outer surfaces and / or - Roads and / or paths and / or - Façades and / or interiors of buildings and / or - Furniture and / or kitchen appliances and / or cold rooms and / or - Interiors of vehicles, preferably aircraft cabins or aircraft cargo holds or trains or automobiles, and / or - Contour lighting of vehicles.

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