Illumination device and method for manufacturing

Abstract

Illumination device, comprising an LED package (10) comprising one or more semiconductor portions (10a, 10g, 10b) and the package material surrounding the one or more semiconductor portions (10a, 10g, 10b) and forming the LED package (10), the LED package (10) having a light emitting area (12e); an elongated light guide (14, 14') being directly attached to said light emitting area (12e) of the LED package (10).

Description

[0001] Illumination Device and Method for Manufacturing

[0002] Description

[0003] Embodiments of the present invention refer to an illumination device, especially an illumination device having an elongated light guide. According to a first aspect the illuminated light guide is directly attached to a light emitting area of an LED package. According to a second aspect the elongated light guide forms a housing for semiconductor portions of an LED unit. According to a third aspect the elongated light guide comprises a core and at least a slit. According to another aspect a method for manufacturing an illumination device is provided.

[0004] In general, embodiments of the present invention are in the field of guiding lights, especially by use of a light guide or mixing system.

[0005] An LED package is typically formed by two or more LEDs. An example for an LED package is a RGB LED package comprising, for example, three LEDs of different color (red, green, blue). Depending on the controlling of the three LEDs of different color the RGB package can be illuminated having different spectra. Here, also a mixture of two colors may be generated, e.g., activating all colors so as to reproduce a mixed color, like white light. Starting from this and starting from the possibility that light intensity of each of the LEDs of the LED package can be varied almost all colors of the color space can be reproduced.

[0006] However, the LEDs of the LED package are typically arranged side by side. Due to this, the respective color of each LED element of the LED package is mixed. For this, so-called mixing systems, like light guides or light parts may be used.

[0007] Some of the mixing systems have the shape of a light pipe or the shape of a light pipe a diameter of which extends from the light source to the light emitting surface of the mixing system. Due to the this, the light pipe may have a cone shape. For some applications it might make sense to vary the geometry of the light pipe from the light receiving side ( collecting area) to the light emitting side of the light guide. For example, the light guide may have a triangle or rectangular shape at the light receiving side and a round shape at the light emitting side of the light pipe.

[0008] Final 5g24em01A combination of the LED package and the light guide should be designed so as to enable high efficient light extraction.

[0009] It is an objective of the present invention to provide a concept of high efficiency light extraction.

[0010] The objective is solved by the subject matter of the independent claims.

[0011] Embodiments of the present invention provide an illumination device comprising an LED package and an elongated light guide. The LED package comprises one or more semiconductor portions of the package material surrounding the one or more semiconductor portions and forming the LED package. The LED package has a light emitting area. The elongated light guide is directly attached to said light emitting area of the LED package.

[0012] According to embodiments an elongated light guard is directly attached to said light emitting area of the package by use of glue.

[0013] Embodiments of the first aspect of the present invention are based on the principle that a direct attachment or a glue enables to improve the coupling of the LED package to the light guide so that optical losses can be avoided or reduced. This beneficially enables that the LED unit can be formed without a glass window, also referred to as light emitting area of the package. Consequently, the efficiency is increased.

[0014] According to embodiments the light emitting area of the LED package and / or an area, also referred to as light collecting area of the elongated light guide attached to said light emitting area, comprises a surface tolerance below 0.5mm or preferably below 0.2mm or approximately 0.1mm.

[0015] According to embodiments, the light emitting area of the package is formed by a packaging material, like a glass window of the package material. The package material may, for example, be formed by a transparent material, like a transparent polymer.

[0016] Another embodiment provides an illumination device comprising an LED unit and an elongated light guide. The LED unit comprises a substrate and one or more semiconductor portions arranged on the substrate. The elongated light guide is attached to the substrate and forms a housing for the one or more semiconductor portions.

[0017] Final 5g24em01Embodiments of the present invention according to this second aspect beneficially enables to increase the light coupling efficiency due to the fact that a material junction between the glass window of the package and the light collecting area of the light guide is not used anymore.

[0018] According to embodiments, the elongated light guide is attached to the substrate via a spacer. In doing so, the spacer forms together with the elongated light guide a kind of cavity within which the one or more semiconductor portions are arranged. Due to the spacer it is beneficially possible to directly attach the elongated light guide so as to avoid the glass window.

[0019] According to embodiments, the elongated light guide comprises a cavity. According to further embodiments, the elongated light guide is attached to the substrate, wherein the one or more semiconductor portions are arranged within the cavity. Due to the cavity it is beneficially possible to directly attach the light part to the substrate so as to avoid the glass window.

[0020] The below embodiments are defined by optional aspects being applicable for the first and second aspect. According to embodiments, the one or more semiconductor portions may be LED elements (e.g. red, green, blue, ...). This enables beneficially to output light having variable spectrum. According to embodiments, one or more semiconductor portions form a PN junction.

[0021] According to further embodiments each of the one or more semiconductor devices or two semiconductor devices in combination are configured to emit light and / or to emit light having different color.

[0022] According to embodiments the LED unit comprises a PCB board as a substrate, wherein the one or more semiconductor portions are arranged on the substrate. Expressed in other words, the substrate is formed by a PCB board.

[0023] According to embodiments the light guide forms a light mixer. According to embodiments the elongated light guide has an aspect ratio of at least 5 to 1 (length to width) and / or has

[0024] Final 5g24em01a tube shape. The high aspect ratio is beneficial with regard to the mixing quality for mixing the light of the different colors. According to further embodiments the shape may be a cone shape. According to further embodiments the above discussed aspects with the different shape of the cross section of the elongated light guide may be used as well. Such a shape enables beneficially to improve the mixing.

[0025] Another embodiment provides a light fixture comprising the illumination device as defined by the first or second aspect.

[0026] Another embodiment provides an illumination device comprising an LED unit and an elongated light guide. The LED unit comprises one or more semiconductor portions. The elongated light guide is coupled to said LED unit, wherein the elongated light guide comprises an elongated core and an elongated outer holder structure, the elongated core and elongated outer holder structure being partially separated from each other by one or more slits.

[0027] Embodiments of this third aspect are based on the principle that an elongated light pipe may be formed by a transparent material block having a core and an outer holder structure, where in the core and the outer holder structure are separated by slits. The slits defined the optical properties of the core, wherein the holder structure enables the mechanical support. The elongated light guide may be used for the first and second aspect.

[0028] According to embodiments the elongated core is arranged along a light emitting direction of the illumination device. According to embodiments the slits are in parallel or substantially in parallel (less than ± 15° or 30°) to the light emitting direction. According to embodiments the slit extends along a length of 60% or 75% or 85% or even 90% of the entire length of the elongated light guide. According to embodiments it is possible to form a shape of a tube or a cone by the elongated core. For example, a cross shape of the elongated core extends along a light emitting direction, according to embodiments the elongated core has a round cross shape or square cross shape or polygonal cross shape or a cross shape varying along the light emitting direction. Such a shape enables beneficially to improve the mixing.

[0029] For example, for a square cross shape the elongated light guide comprises four slits provided side by side to each other and crossed by the two other slits. According to embodiments the usage of the slits and especially of the four slits improves the

[0030] Final 5g24em01manufacturing since by use of the slits the shape of the elongated core can be defined, wherein such slits are easily manufacturable.

[0031] In case the elongated core has a cone shape, the cross shape of the elongated core increases along the light emitting direction according to embodiments. For example, the elongated light guide may comprise a light collecting side and a light emitting side. According to embodiments, an elongated outer holder and the elongated core are coupled to each other on the light emitting side.

[0032] As mentioned above, the elongated light guide may, according to embodiments, comprise four slits, wherein two slits of the four slits cross the other two slits of the four slits or wherein the two slits of the four slits cross perpendicular to the other two slits of the four slits. According to further embodiments the elongated light guide comprises a three cross three surface portion at the light collecting side, wherein the central surface portion belongs to the elongated core and wherein the other surface portions belong to the elongated outer holder. According to embodiments the other surface portions are attached to or are in contact with the substrate. According to embodiments this means that the central surface portion is set back with respect to the other surface portions. This setting back enables to form the cavity.

[0033] It should be noted that according to embodiments the elongated core forms the light mixer. Beneficially the slits enable that the central core is optically separated from the outer elements so that the central core can be defined with regard to its shape in accordance to the required optical properties.

[0034] Regarding the elongated outer holder and the elongated core it should be noted that preferably both are formed by one element and / or comprise the same material. Examples for the material are polycarbonate, glass or acrylic. Other transparent materials are possible as well.

[0035] Another embodiment provides an illumination device as is defined above comprising the elongated light guide formed by use of the slits.

[0036] Another embodiment refers to a method for manufacturing (fourth aspect) the illumination device and / or the elongated light guide, wherein the slits are formed by a laser or laser cutting. Alternatively, the slits may be formed by different cutting technology like waterjet cutting. According to further embodiments the cutting comprises cutting in accordance with

[0037] Final 5g24em01a first 2D pattern on a first side and in accordance with a second 2D pattern on a second side, e.g., a perpendicular side of the entire element.

[0038] Embodiments will subsequently be discussed referring to the enclosed figures, wherein

[0039] Fig. 1 shows a schematic block diagram of a typical LED system including a light guide to discuss principles of the below embodiments;

[0040] Fig. 2 shows a schematic block diagram of an LED system for illustrating the connection of the light guide with the LED package window (aspect 1) according to embodiments;

[0041] Fig. 3 shows a schematic LED system for illustrating the connection of the LED package with the light guide without a window according to further embodiments (aspect 2 and 3);

[0042] Fig. 4 shows a schematic representation of an LED system for illustrating the connection of the LED package border with the light guide according to embodiments;

[0043] Fig. 5 shows a schematic block diagram of a light guide for illustrating embodiments according to aspect 3;

[0044] Figs. 6a and 6b show a schematic representation of cutting lines to be used for the application of a light guide according to embodiments (aspect 4);

[0045] Figs. 7a and 7b show a schematic representation for illustrating method steps for manufacturing a plurality of light pipes according to embodiments;

[0046] Figs. 8a and 8b show schematic 3D views of light pipes manufactured according to embodiments of aspect 3 for illustrating advantages of the manufacturing method of embodiments of aspect 4.

[0047] Below, embodiments of the present invention will subsequently be discussed referring to the enclosed figures, wherein identical reference numerals are provided to objects identical or similar function.

[0048] Final 5g24em01In the below discussion four aspects will be discussed, wherein the aspects 1 and 2 are quite comparable to each other and follow the same idea but have different implementations. Aspect 3 refers to a light guide manufactured in a manner different from the embodiments of aspect 1 and 2, wherein the elongated light pipe can be used for the aspects 1 and 2. Aspect 4 refers to the method for manufacturing the light pipe according to embodiments of aspect 3.

[0049] Before discussing the aspects the background for the four aspects will be discussed with respect to Fig. 1.

[0050] Fig. 1 shows a typical system configuration having a light source 10, a mixing system comprising a light guide 14 and an optional secondary optic 16. The light source may be an LED module having a substrate 10s and LED elements, here the LED elements 10r (red), 10g (yellow) and 10b (blue). The LED elements 10r, 10g and 10b may be arranged side by side on the substrate 10s and / or stacked on the substrate 10s. according to some embodiments the three LED elements (in general the LED elements) are packetized using a transparent material, like a polymer or a resin. The element 12 forms a kind of light emitting area 12e, also referred to as window. Here, the light generated by the elements 10r, 10g and 10b are emitted into the light emitting direction D. On top of the window 12e the light guide 14 is arranged such that the light emitting area 12 is coupled to the light collecting area 14c of the light guide 14. The light guide 14 comprises two sides along the longitudinal shape, namely the light collecting side 14c and on an opposite side the light emitting side 14e. The light emitted from the area 12e is guided from 14c to 14e through the light guide 14. The light guide may have, according to embodiments, a shape or optical property so as to perform a mixing of the light. The background thereof is that the LED elements, e.g., 10b, is arranged laterally displaced with respect to the LED element 10r. If red and blue light should be mixed so as to generate purple light, the light sources of the two lights should be superimposed or mixed. This is done by the elongated light guide 14.

[0051] The principle for mixing the light is based on the situation that light of different wavelengths is reflected at the outer walls of the light guide 14 by use of total internal reflection. However, the total internal reflection angle depends on the wavelengths and on the displacement of the light source from the center axis. Due to a plurality of total reflections along the guiding by the elongated light guide (cf. direction d) a plurality of total internal reflections are done so that the light is mixed. For the mixing it is beneficial that the geometry forms plain side

[0052] Final 5g24em01walls (the less the better) so the light collecting area might have a cross section of a triangle or rectangle (square) or other polygon. For emitting the light it might be beneficial that the light emitting area 14e has a round shape or similar. Starting from this some light guides might have a varying cross section from the side 12e to the side 14e.

[0053] The light is emitted by 14e and then further projected by the secondary optics 16. The secondary optics 16 might be a lens and is arranged when seen in the emission direction d at the end of the light guide 14 (cf. surface 14e).

[0054] The elements 10, 12, 14, 16 form an optical path of a fixture that utilizes a light source. The combination with the light guide 14 for mixing and a secondary optics 16, like a lens, is beneficial since it enables to provide a good projection of the light.

[0055] As discussed above, the light guide mixing system has room for improvement of the efficiency, compactness and the manufacturing process. These factors are addressed by the aspects 1 to 4. All aspects can be viewed either as a combined system or individually, as some technologies rely on others for full functionality. This is made possible by the availability of small energy chips enabling more compact and efficient designs.

[0056] Aspect 1 and aspect 2 are addressed to increase the efficiency between the junction of the areas 12e and 12c. As can be seen with respect to Fig. 1a, the junction between 12e and 14c, having two different components or even two different materials, is used. When a light passes such a junction the efficiency may be reduced.

[0057] To increase efficiency different options are available.

[0058] According to a first aspect the surface tolerances of the light emitting area 12e and / or of the light collecting area 14c are optimized so that it is possible to directly attach the area 14c of the elongated light pipe 14 directly to said light emitting area 12e. For example, the tolerances may be below 0.5mm or preferably below 0.2mm. A preferred variant is a tolerance of 0.1 mm. The result of this design is that the gap - whether air or glass - between the LED 12 and the light mixing system (light guide 14) is minimized, e.g., by virtually illuminating it. As shown by Fig. 2 this is accomplished by directly connecting the light pipe 14 to the LED package 12. According to further embodiments this may be done or further improved by gluing. This means that according to embodiments a glue is provided between the areas 12e and 14c. Preferably, the glue is a transparent glue provided as a thin layer.

[0059] Final 5g24em01A glue has the benefit that the material junction forms a kind of continuous transmission from one material to the other material without forming surfaces, like a glass window in between. Such a homogenous material junction is improved with respect to the light coupling efficiency.

[0060] In this design, the manufacturing tolerance for the gap is measured from the LED package itself, rather than from the PCB as in traditional designs, resulting in a significantly smaller tolerance. Another objective of the patent is to remove the typical glass window found in LEDs and replace it with the light guide, which also serves to protect the LEDs, making the glass window unnecessary.

[0061] • Minimizes Gap and Tolerances

[0062] • Improve Coupling Efficiency

[0063] • Improve Luminance Intensity

[0064] Below optional features of the embodiment of Fig. 2 will be discussed.

[0065] It should be noted that the packaging 12 of the LED device 10 might include a kind of cavity within which the elements 10r, 10g and 10b are arranged. A cavity is marked by 12k. Due to the cavity the surrounding of the element 12 is in touch and / or attached to the substrate 10s. According to embodiments the cavity 12k may be filled with a gas or another material, like the material of the element 12. According to embodiments the element 12 forms an even surface at the emitting area 12e. Here, tolerances, e.g., of 0.1mm may be used.

[0066] As discussed above, the element 14 may have a cone shape so that the size increases from the side of the collecting area 14c to the emitting area 14e, i.e. , in illumination direction d. According to embodiments the surface of the emitting area 14e might additionally be increased so that the light guide 14 has an elongated head forming the emitting area 14e. The head might be beneficial for the coupling to the secondary optics 16 (cf. Fig. 1).

[0067] Instead of direct coupling of the light pipe 14 to the light emitting area 12e of the package material 12 a direct coupling without package material may be used. This embodiment will be discussed in context with Fig. 3.

[0068] Fig. 3 shows the LED device 10 having the substrate 10s, the RBB elements 10r, 10g, 10b and a light pipe 14’. 14’ comprises a light pipe 14co’ which is directly, optically coupled to

[0069] Final 5g24em01the elements 10r, 10g and 10b without the element 12 in between. The light pipe 14co’ is surrounded by an outer portion 14op’. The outer portion maintains the distance between the elements 10r, 10g, 10b and the core 14co. For this, the outer portion may - according to embodiments - extend overly length of the core 14co, such that the outer portion 14op’ can be connected to the substrate 10s. Due to the setting back of the area 14c of the element 14co’ a kind of cavity 14k is formed. Within this cavity, the elements 10r, 10g and 10b are arranged.

[0070] According to embodiments the outer portion 14 op’ may be formed by the same material than the core 14co’ or another material surrounding the core 14co’. The outer portion 14op’, also referred to as outer holder structure 14op’ has the purpose to hold the light guide 14’ in its position. In this case the light guide can be formed without an additional holder. Possible materials are polycarbonate (PC), glass or acrylic or another transparent material. For example, 14op’ may be a kind of housing for the core 14co’. Due to the situation that the correcting area 14c receives the light emitted by the elements 10r, 10g and / or 10b directly, the optical efficiency is increased.

[0071] Fig. 4 shows an embodiment which is substantially equal to the embodiment of Fig. 3, wherein the core portion 14co is not set back with respect to the outer portion 14op’. Instead, a spacer 13 is arranged between the element 14’ and the substrate 10s’. This embodiment can, thus, refer to an LSD package border with the light guide. The spacer 13 surrounds the three elements 10r, 10g and 10b so as to ensure that the distance between the elements 10r, 10g and 10b and the surface of the collecting area 14c remains constant. Due to this a kind of cavity 13k is formed.

[0072] Again, the two elements 14op’ and 14co’ may be formed out of different material, wherein the optically used portion 14co’ comprises preferably a transparent and / or optical transparent and / or optical material while the requirements regarding the material of 14op’ are mainly set by the mechanics. According to a preferred variant the two elements 14co’ and 14op’ are separated from each other by a kind of slit as will be discussed with respect to Fig. 5.

[0073] Fig. 5 shows the light guide 14’ of Fig. 3. It comprises the core 14co’ and the outer portion 14op’. The core 14co’ and the outer portion 14op’ are separated by slits. This means that both are formed by the same material, e.g., a transparent material like glass or transparent polymer, wherein slits 14s’ are provided. Due to the slits 14s’ an outer surface of the core

[0074] Final 5g24em0114co’ is formed along the slits 14s’ so that the surfaces along the slits 14s’ are enabled to perform total reflection of light within the core 14co’.

[0075] Below, advantages of this embodiment will be discussed in other words: A typical lightguide system comprises a lightguide 14co’ and a holder 14op’ that secures it in place. It is crucial that the holder 14op’ does not interfere with the optical properties of the lightguide. This embodiment eliminates the need for a separate holder by introducing a design that integrates the lightguide and holder into a single component. An embodiment provides detailed instructions on the manufacturing process of this integrated lightguide. Since the lightguide is made from a single material, tighter tolerances are achievable due to consistent thermal expansion properties.

[0076] In the Fig. 5, the lightguide design separates the light path from the holding structure. The LED is positioned at the center of the bottom section, directing the light upward. The cuts in the material serve to isolate the light path from the holder, ensuring that the holding structure does not interfere with the light distribution.

[0077] It should be noted that according to embodiments the slits 14s’ are arranged along the length of the elongated element 14’ but not along the entire length. Preferably the slits 14s’ extend from the side 14c into the direction d up to 60% or 90% of the entire length so that a portion 14p’ connects 14op’ and 14co’. The 14p’ is arranged at the emitting side 14e. Such an embodiment is beneficial since the manufacturing has low complexity since just the slits 4s’ have to be provided. According to embodiments the plurality of slits are provided so that the core 14co’ is separated at four sides. This is illustrated by Figs. 8a and 8b. Here, the core is marked by the reference numeral 14co’, wherein the six outer portions are marked by the reference numeral 14op’1 to 14op’8. The structure surrounding 14co’ is also referred to as additional holder or elongated outer holder structure. These eight elements 14op’1 to 14op’8 surround the core 14co’. The total nine elements are formed due to the four slits 14s’1 to 14s’2 provided in a first direction and 14s’3 and 14s’4 provided in a second direction. The first and second direction cross each other, e.g., perpendicular. As can be seen, the slits 14s’1 and 14s’2 may, in this embodiment, be arranged not parallel to each other but tapered. The same holds true for slits 14s’3 and 14s’4 so that the element 14co’ comprises a cone shape. Due to the cone shape the area 14c’ is smaller than the area 14e’.

[0078] Fig. 6a and 6b show arrangements of the slits 14s1 and 14s2. As can be seen, they are arranged substantially in parallel to the direction d, but slightly angled, e.g., by 15° or in

[0079] Final 5g24em01general in a range between 1° and 30°. The pistols 14s’1 and 14s’2 are angled into different directions so as to obtain the tapering of the element 14co’.

[0080] The Figs. 7a and 7b show how a plurality of light guides 14’ can be produced in series. In a first step the slits 14s1’ and 14s2’ are provided (cf. Fig. 7a), wherein in a second step, which is shown by Fig. 7b, the elements 14’ are separated from each other by the additional slits 15s.

[0081] By doing so multiple light guides 14’, here four light guides, can be manufactured in series. The fabrication method employs a laser to cut precise lines completely through the material. The material is processed from both sides using a specified 2D pattern. For a single lightguide, the design is represented as follows, with black lines indicating complete cuts through the material. The first step involves making cuts from the top side, while the second step consists of cuts from the right side.

[0082] Providing the slits 14s’ and the slits 15s is done by cutting, e.g., by laser cutting or another cutting technology like waterjet cutting.

[0083] It should be noted that the above embodiments are mainly discussed in context of an apparatus, wherein also methods are in focus, like the method for manufacturing. Therefore, a description of a feature used for an apparatus can also be interpreted as a description of a feature used for one of the disclosed methods.

[0084] Final 5g24em01

Claims

Claims1. Illumination device, comprising:an LED package (10) comprising one or more semiconductor portions (10a, 10g, 10b) and the package material surrounding the one or more semiconductor portions (10a, 10g, 10b) and forming the LED package (10), the LED package (10) having a light emitting area (12e);an elongated light guide (14, 14’) being directly attached to said light emitting area (12e) of the LED package (10).

2. Illumination device according to claim 1, wherein the elongated light guide (14, 14’) is directly attached to said light emitting area (12e) of the package by use of glue.

3. Illumination device according to one of previous claims, wherein the light emitting area (12e) and / or an area of the elongated light guide (14, 14’) attached to said light emitting area (12e) comprise surface tolerances below 0.5mm, or preferably below 0.2mm or approximately 0.1 mm.

4. Illumination device, comprising:an LED unit comprising a substrate (10s) and one or more semiconductor portions (10a, 10g, 10b) arranged on the substrate (10s);an elongated light guide (14, 14’) being attached to the substrate (10s) and forming a housing for the one or more semiconductor portions (10a, 10g, 10b).

5. Illumination device according claim 4, wherein the LED unit is formed without glass window (light emitting area (12e) of the package).

6. Illumination device according to claim 4 or 5, wherein the elongated light guide (14, 14’) is attached to the substrate (10s) via a spacer.

7. Illumination device according to one of claims 4 to 6, wherein the elongated light guide (14, 14’) comprises a cavity (14k); and / orFinal 5g24em01wherein the elongated lightguide (14, 14’) is attached to the substrate (10s), wherein the one or more semiconductor portions (10a, 10g, 10b) are arranged within the cavity (14k).

8. Illumination device according to one of the previous claims, wherein each of the one or more semiconductor portions (10a, 10g, 10b) form a PN junction.

9. Illumination device according to one of the previous claims, wherein each of the one or more semiconductor devices or two semiconductor devices in combination are configured to emit light and / or to emit light having different colors.

10. Illumination device according to one of the previous claims, wherein the LED unit comprises a PCB board as substrate (10s) or wherein the substrate (10s) is formed by a PCB board.

11. Illumination device according to one of the previous claims, wherein the elongated light guide (14, 14’) forms a light mixer.

12. Illumination device according to one of the previous claims, wherein the elongated light guide (14, 14’) has an aspect ratio of at least 5 : 1 (length : width); and / or has a cone shape or tube shape.

13. Illumination fixture comprising a plurality of illumination devices according to one of the previous claims.

14. Illumination device comprising:an LED unit comprising one or more semiconductor portions (10a, 10g, 10b);an elongated light guide (14, 14’) being coupled to said LED unit, wherein the elongated light guide (14, 14’) comprises an elongated core (14co’) and an elongated outer holder structure (14op’), the elongated core (14co’) and the elongated outer holder being partially separated from each other by a slit (14s’, 14s’1 to 14s’4).Final 5g24em0115. Illumination device according to claim 14, wherein the elongated core (14co’) is arranged along a light emitting direction of the illumination device.

16. Illumination device according to claim 14 or 15, wherein the slit (14s’, 14s’1 to 14s’4) extends along a length of 60 % or 75 % or 85 % or even 90 % of the entire length of the elongated light guide (14, 14’).

17. Illumination device according to claims 14, 15 or 16, wherein the elongated core (14co’) has a shape of a tube or a cone; and / orwherein the cross shape of the elongated core (14co’) extends along a light emitting direction.

18. Illumination device according to one of claims 14 to 17, wherein the elongated core (14co’) has a round cross shape, square cross shape, polygonal cross shape, or a cross shape varying along the light emitting direction.

19. Illumination device according to claim 18, wherein an area of the cross shape increases along the light emitting direction.

20. Illumination device according to one of claims 14 to 19, wherein the elongated light guide (14, 14’) comprises a light collecting side (14c) and a light emitting side (14e).

21. Illumination device according to claim 20, wherein the elongated outer holder and the elongated core (14co’) are coupled to each other at the light emitting side (14e).

22. Illumination device according to claim 20 or 21, wherein the elongated light guide (14, 14’) comprises four slits (14s’, 14s’1 to 14s’4), wherein two slits (14s’, 14s’1 to 14s’4) of the four slits (14s’, 14s’1 to 14s’4) cross the other two slits (14s’, 14s’1 to 14s’4) of the four slits (14s’, 14s’1 to 14s’4) or wherein two slits (14s’, 14s’1 to 14s’4) of the four slits (14s’, 14s’1 to 14s’4) cross perpendicularly the other two slits (14s’, 14s’1 to 14s’4) of the four slits (14s’, 14s’1 to 14s’4).

23. Illumination device according to one of claims 20 to 22, wherein the elongated light guide (14, 14’) comprises a 3x3 surface portion at the light collecting side (14c),Final 5g24em01wherein the central surface portion (14co’) belongs to the elongated core (14co’) and wherein the other surface portions belong to the elongated outer holder; orwherein the elongated light guide (14, 14’) comprises a 3x3 surface portion at the light collecting side (14c), wherein the central surface portion (14co’) belongs to the elongated core (14co’) and wherein the other surface portions belong to the elongated outer holder, wherein the other surface portions are attached to a substrate (10s).

24. Illumination device according to claim 23, wherein the central surface portion (14co’) is set back with respect to the other surface portions.

25. Illumination device according to one of claims 14 to 24, wherein the elongated core (14co’) forms a light mixer.

26. Illumination device according to one of claims 14 to 24, wherein the elongated outer holder and the elongated core (14co’) are formed by one element and / or comprise the same material.

27. Illumination device according to one of claims 14 to 26, wherein the elongated light guide (14, 14’) is formed by polycarbonate, glass or acrylic.

28. Illumination device according to one of claims 14 to 27 forming the elongated light guide (14, 14’) according to one of claims 1 to 13.

29. Method for manufacturing an illumination device according to one of claims 14 to 27, wherein the slits (14s’, 14s’1 to 14s’4) are formed by a laser and / or by laser cutting; orwherein the slits (14s’, 14s’1 to 14s’4) are formed by a cutting, especially laser cutting and / or by waterjet cutting.

30. Method according to claim 29, wherein the cutting comprises cutting in accordance to a first 2D pattern on a first side and according to a second 2D pattern on a second side.Final 5g24em01

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