Light concentrator module with high refractive index interconnect

Abstract

The invention provides a lighting device (1) comprising: —one or more light sources (10) configured to provide light source light (11); —a luminescent element (5) comprising an elongated light transmissive body (100); the elongated light transmissive body (100) comprising a luminescent material (120) configured to convert at least part of light source light (11) received at one or more radiation input faces (111) into luminescent material light (8), and the luminescent element (5) configured to couple at least part of the luminescent material light (8) out at the first radiation exit window (112) as converter light (101); wherein the light transmissive body (100) has a first index of refraction n1; —a beam shaping optical element (224) optically coupled with the first radiation exit window (112), the beam shaping optical element comprising a radiation entrance window (211) configured to receive at least part of the converter light (101); wherein the beam shaping optical element (224) has a second index of refraction n2; wherein: −0.75≤n1/n2≤1.25; 15 —the beam shaping optical element (224) or an optical connector (300) configured between the elongated light transmissive body (100) and the beam shaping optical element (224) comprise a glass material (310), wherein the glass material (310) is based on at least one or more of bismuth oxide, boron oxide, potassium oxide, lithium oxide, phosphorus oxide, lead oxide, tin oxide, antimony oxide, tellurium oxide, silicon dioxide, and vanadium oxide.

Claims

1. A lighting device comprising: one or more light sources configured to provide light source light; a luminescent element comprising an elongated light transmissive body having a first face and a second face defining a length (L) of the light transmissive body, the light transmissive body comprising one or more radiation input faces and a first radiation exit window, wherein the second face comprises the first radiation exit window; the elongated light transmissive body comprising a luminescent material configured to convert at least part of light source light received at one or more radiation input faces into luminescent material light, and the luminescent element configured to couple at least part of the luminescent material light out at the first radiation exit window as converter light; wherein the light transmissive body has a first index of refraction n1; a beam shaping optical element optically coupled with the first radiation exit window, the beam shaping optical element comprising a radiation entrance window configured to receive at least part of the converter light; wherein the beam shaping optical element has a second index of refraction n2; wherein: 0.75≤/n2≤1.25; an optical connector configured between the elongated light transmissive body and the beam shaping optical element, the optical connector comprising a glass material, wherein the glass material has a composition selected from a range defined in the ternary B.sub.2O.sub.3—Bi.sub.2O.sub.3—ZnO diagram by the following compositions indicating the quadrilateral corner points of the range: TABLE-US-00004 mol % B.sub.2O.sub.3 mol % Bi.sub.2O.sub.3 mol % ZnO 25 mol % 7.5 mol % 67.5 mol % 80 mol % 20 mol % 0 mol % 65 mol % 35 mol % 0 mol % 22.5 mol % 20 mol % 57.5 mol % and wherein the beam shaping optical element comprises an optical element material (240) different from the glass material.

2. The lighting device according to claim 1, wherein the elongated light transmissive body comprises a garnet material.

3. The lighting device according to claim 1, wherein the optical connector comprises a glass frit connection.

4. The lighting device according to claim 1, wherein the elongated light transmissive body and the beam shaping optical element are associated to each other via the optical connector, wherein (i) the elongated light transmissive body and the optical connector are associated to each other with a glass frit connection and (ii) the optical connector and the beam shaping optical element are associated to each other with a glass frit connection, and wherein the beam shaping optical element comprises an optical element material different from the glass material.

5. The lighting device according to claim 4, wherein the one or more light sources are operated in a pulsed operation with a duty cycle selected from the range of 10-80%.

6. The lighting device according to claim 1, wherein the beam shaping optical element comprises a compound parabolic concentrator and a mirror partially covering the light exit face of the compound parabolic concentrator.

7. The lighting device according to claim 1, wherein the light transmissive body has a first coefficient of linear thermal expansion, wherein the beam shaping optical element has a second coefficient of linear thermal expansion, and wherein the optical connector has a third coefficient of linear thermal expansion, wherein a difference between the first coefficient of linear thermal expansion and the second coefficient is at most ±1 ppm/K, wherein a difference between the first coefficient of linear thermal expansion and the third coefficient is at most ±1 ppm/K, and wherein a difference between the second coefficient of linear thermal expansion and the third coefficient is at most ±1 ppm/K.

8. The lighting device according to claim 1, wherein the glass material (310) has a third index of refraction n3, wherein if n2<n1, then n3>n2, wherein if n2≥n1, then n3≥n1, and wherein one or more of 0.75≤n1/n3≤1.25 applies.

9. The lighting device according to claim 1, wherein the beam shaping optical element comprises a light concentrator, and wherein the light transmissive body has a bar-like shape having a width (W) and a high (H), wherein the width (W) is equal to or smaller than 1.7 mm, and wherein the height (H) is equal to or smaller than 1.1 mm.

10. A method of producing the lighting device according to claim 1, the method comprising (i) providing the elongated light transmissive body, the beam shaping optical element, and the optical connector, (ii) melting at least part of the glass material, and associating the elongated light transmissive body and the beam shaping optical element with the optical connector in between, (iii) providing one or more light sources at one or more radiation input faces.

11. An image projection system comprising one or more lighting devices according to claim 1.

12. A luminaire comprising one or more lighting devices according to claim 1.

13. A headlight or a taillight of a motor vehicle comprising one or more lighting devices according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

(2) FIGS. 1a-1e schematically depict some aspects of the invention; and

(3) FIGS. 2a-2c schematically depict some embodiments.

(4) FIG. 3 depicts a ternary diagram defining a composition of the invention.

(5) The schematic drawings are not necessarily on scale.

(6) The schematic drawings are not necessarily on scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(7) A light emitting device according to the invention may be used in applications including but not being limited to a lamp, a light module, a luminaire, a spot light, a flash light, a projector, a (digital) projection device, automotive lighting such as e.g. a headlight or a taillight of a motor vehicle, arena lighting, theater lighting and architectural lighting.

(8) Light sources which are part of the embodiments according to the invention as set forth below, may be adapted for, in operation, emitting light with a first spectral distribution. This light is subsequently coupled into a light guide or waveguide; here the light transmissive body. The light guide or waveguide may convert the light of the first spectral distribution to another spectral distribution and guides the light to an exit surface.

(9) An embodiment of the lighting device as defined herein is schematically depicted in FIG. 1a. FIG. 1a schematically depicts a lighting device 1 comprising a plurality of solid state light sources 10 and a luminescent concentrator 5 comprising an elongated light transmissive body 100 having a first face 141 and a second face 142 defining a length L of the elongated light transmissive body 100. The elongated light transmissive body 100 comprising one or more radiation input faces 111, here by way of example two oppositely arranged faces, indicated with references 143 and 144 (which define e.g. the width W), which are herein also indicated as edge faces or edge sides 147. Further the light transmissive body 100 comprises a radiation exit window 112, wherein the second face 142 comprises the radiation exit window 112. The entire second face 142 may be used or configured as radiation exit window. The plurality of solid state light sources 10 are configured to provide (blue) light source light 11 to the one or more radiation input faces 111. As indicated above, they especially are configured to provide to at least one of the radiation input faces 111 a blue power W.sub.opt of in average at least 0.067 Watt/mm.sup.2. Reference BA indicates a body axis, which will in cuboid embodiments be substantially parallel to the edge sides 147. Reference 140 refers to side faces or edge faces in general.

(10) The elongated light transmissive body 100 may comprise a ceramic material 120 configured to wavelength convert at least part of the (blue) light source light 11 into converter light 101, such as at least one or more of green and red converter light 101. As indicated above the ceramic material 120 comprises an A.sub.3B.sub.5O.sub.12:Ce.sup.3+ ceramic material, wherein A comprises e.g. one or more of yttrium (Y), gadolinium (Gd) and lutetium (Lu), and wherein B comprises e.g. aluminum (Al). References 20 and 21 indicate an optical filter and a reflector, respectively. The former may reduce e.g. non-green light when green light is desired or may reduce non-red light when red light is desired. The latter may be used to reflect light back into the light transmissive body or waveguide, thereby improving the efficiency. Note that more reflectors than the schematically depicted reflector may be used. Note that the light transmissive body may also essentially consist of a single crystal, which may in embodiments also be A.sub.3B.sub.5O.sub.12:Ce.sup.3+.

(11) The light sources may in principle be any type of light source, but is in an embodiment a solid state light source such as a Light Emitting Diode (LED), a Laser Diode or Organic Light Emitting Diode (OLED), a plurality of LEDs or Laser Diodes or OLEDs or an array of LEDs or Laser Diodes or OLEDs, or a combination of any of these. The LED may in principle be an LED of any color, or a combination of these, but is in an embodiment a blue light source producing light source light in the UV and/or blue color-range which is defined as a wavelength range of between 380 nm and 490 nm. In another embodiment, the light source is an UV or violet light source, i.e. emitting in a wavelength range of below 420 nm. In case of a plurality or an array of LEDs or Laser Diodes or OLEDs, the LEDs or Laser Diodes or OLEDs may in principle be LEDs or Laser Diodes or OLEDs of two or more different colors, such as, but not limited to, UV, blue, green, yellow or red.

(12) The light sources 10 are configured to provide light source light 11, which is used as pump radiation 7. The luminescent material 120 converts the light source light into luminescent material light 8 (see also FIG. 1e). Light escaping at the light exit window is indicated as converter light 101, and will include luminescent material light 8. Note that due to reabsorption part of the luminescent material light 8 within the luminescent concentrator 5 may be reabsorbed. Hence, the spectral distribution may be redshifted relative e.g. a low doped system and/or a powder of the same material. The lighting device 1 may be used as luminescent concentrator to pump another luminescent concentrator.

(13) FIGS. 1a-1b schematically depict similar embodiments of the lighting device. Further, the lighting device may include further optical elements, either separate from the waveguide and/or integrated in the waveguide, like e.g. a light concentrating element, such as a compound parabolic light concentrating element (CPC). The lighting devices 1 in FIG. 1b further comprise a collimator 24, such as a CPC.

(14) As shown in FIGS. 1a-1b and other Figures, the light guide has at least two ends, and extends in an axial direction between a first base surface (also indicated as first face 141) at one of the ends of the light guide and a second base surface (also indicated as second face 142) at another end of the light guide.

(15) FIG. 1c schematically depicts some embodiments of possible ceramic bodies or crystals as waveguides or luminescent concentrators. The faces are indicated with references 141-146. The first variant, a plate-like or beam-like light transmissive body has the faces 141-146. Light sources, which are not shown, may be arranged at one or more of the faces 143-146 (general indication of the edge faces is reference 147). The second variant is a tubular rod, with first and second faces 141 and 142, and a circumferential face 143. Light sources, not shown, may be arranged at one or more positions around the light transmissive body. Such light transmissive body will have a (substantially) circular or round cross-section. The third variant is substantially a combination of the two former variants, with two curved and two flat side faces.

(16) In the context of the present application, a lateral surface of the light guide should be understood as the outer surface or face of the light guide along the extension thereof. For example, in case the light guide would be in form of a cylinder, with the first base surface at one of the ends of the light guide being constituted by the bottom surface of the cylinder and the second base surface at the other end of the light guide being constituted by the top surface of the cylinder, the lateral surface is the side surface of the cylinder. Herein, a lateral surface is also indicated with the term edge faces or side 140.

(17) The variants shown in FIG. 1c are not limitative. More shapes are possible; i.e. for instance referred to WO2006/054203, which is incorporated herein by reference. WO2006/054203, for instance, describes a light emitting device comprising at least one LED which emits light in the wavelength range of >220 nm to <550 nm and at least one conversion structure placed towards the at least one LED without optical contact, which converts at least partly the light from the at least one LED to light in the wavelength range of >300 nm to ≤1000 nm, characterized in that the at least one conversion structure has a refractive index n of >1.5 and <3 and the ratio A:E is >2:1 and <50000:1, where A and E are defined as follows: the at least one conversion structure comprises at least one entrance surface, where light emitted by the at least one LED can enter the conversion structure and at least one exit surface, where light can exit the at least one conversion structure, each of the at least one entrance surfaces having an entrance surface area, the entrance surface area(s) being numbered A.sub.1 . . . A.sub.n and each of the at least one exit surface(s) having an exit surface area, the exit surface area(s) being numbered E.sub.1 . . . E.sub.n and the sum of each of the at least one entrance surface(s) area(s) A being A=A.sub.1+A.sub.2 . . . +A.sub.n and the sum of each of the at least one exit surface(s) area(s) E being E=E.sub.1+E.sub.2 . . . +E.sub.n.

(18) The ceramic bodies or crystals, which are used as light guides, generally may be rod shaped or bar shaped light guides comprising a height H, a width W, and a length L extending in mutually perpendicular directions and are in embodiments transparent, or transparent and luminescent. The light is guided generally in the length L direction. The height H is in embodiments <10 mm, in other embodiments <5 mm, in yet other embodiments <2 mm. The width W is in embodiments <10 mm, in other embodiments <5 mm, in yet embodiments <2 mm. The length L is in embodiments larger than the width W and the height H, in other embodiments at least 2 times the width W or 2 times the height H, in yet other embodiments at least 3 times the width W or 3 times the height H. Hence, the aspect ratio (of length/width) is especially larger than 1, such as equal to or larger than 2, such as at least 5, like even more especially in the range of 10-300, such as 10-100, like 10-60, like 10-20. Unless indicated otherwise, the term “aspect ratio” refers to the ratio length/width. FIG. 1c schematically depicts an embodiment with four long side faces, of which e.g. two or four may be irradiated with light source light.

(19) The aspect ratio of the height H:width W is typically 1:1 (for e.g. general light source applications) or 1:2, 1:3 or 1:4 (for e.g. special light source applications such as headlamps) or 4:3, 16:10, 16:9 or 256:135 (for e.g. display applications). The light guides generally comprise a light input surface and a light exit surface which are not arranged in parallel planes, and in embodiments the light input surface is perpendicular to the light exit surface. In order to achieve a high brightness, concentrated, light output, the area of light exit surface may be smaller than the area of the light input surface. The light exit surface can have any shape, but is in an embodiment shaped as a square, rectangle, round, oval, triangle, pentagon, or hexagon.

(20) Note that in all embodiments schematically depicted herein, the radiation exit window is especially configured perpendicular to the radiation input face(s). Hence, in embodiments the radiation exit window and radiation input face(s) are configured perpendicular. In yet other embodiments, the radiation exit window may be configured relative to one or more radiation input faces with an angle smaller or larger than 90°.

(21) Note that, in particular for embodiments using a laser light source to provide light source light, the radiation exit window might be configured opposite to the radiation input face(s), while the mirror 21 may consist of a mirror having a hole to allow the laser light to pass the mirror while converted light has a high probability to reflect at mirror 21. Alternatively or additionally, a mirror may comprise a dichroic mirror.

(22) FIG. 1d very schematically depicts a projector or projector device 2 comprising the lighting device 1 as defined herein. By way of example, here the projector 2 comprises at least two lighting devices 1, wherein a first lighting device (1a) is configured to provide e.g. green light 101 and wherein a second lighting device (1b) is configured to provide e.g. red light 101. Light source 10 is e.g. configured to provide blue light. These light sources may be used to provide the projection (light) 3. Note that the additional light source 10, configured to provide light source light 11, is not necessarily the same light source as used for pumping the luminescent concentrator(s). Further, here the term “light source” may also refer to a plurality of different light sources. The projector device 2 is an example of a lighting system 1000, which lighting system is especially configured to provide lighting system light 1001, which will especially include lighting device light 101.

(23) High brightness light sources are interesting for various applications including spots, stage-lighting, headlamps and digital light projection.

(24) For this purpose, it is possible to make use of so-called luminescent concentrators where shorter wavelength light is converted to longer wavelengths in a highly transparent luminescent material. A rod of such a transparent luminescent material can be used and then it is illuminated by LEDs to produce longer wavelengths within the rod. Converted light which will stay in the luminescent material such as a doped garnet in the waveguide mode and can then be extracted from one of the surfaces leading to an intensity gain (FIG. 1e).

(25) High-brightness LED-based light source for beamer applications appear to be of relevance. For instance, the high brightness may be achieved by pumping a luminescent concentrator rod by a discrete set of external blue LEDs, whereupon the phosphor that is contained in the luminescent rod subsequently converts the blue photons into green or red photons. Due to the high refractive index of the luminescent rod host material (typically ˜1.8) the converted green or red photons are almost completely trapped inside the rod due to total internal reflection. At the exit face of the rod the photons are extracted from the rod by means of some extraction optics, e.g. a compound parabolic concentrator (CPC), or a micro-refractive structure (micro-spheres or pyramidal structures). As a result the high luminescent power that is generated inside the rod can be extracted at a relatively small exit face, giving rise to a high source brightness, enabling (1) smaller optical projection architectures and (2) lower cost of the various components because these can be made smaller (in particular the, relatively expensive, projection display panel).

(26) In the current solutions the optical efficiency may be limited due to the large difference in refractive index of the high index luminescent rod materials and the relatively low refractive index interconnect interface and CPC. If the refractive index of the interconnect interface and CPC could be increased towards the level of the luminescent element, it is predicted that 22-26% more light could be extracted which also results in a 22-26% increase of efficiency. Furthermore, in the current solution the coefficient of linear thermal expansion (CTE) of the glass CPC does not match to the CTE of the luminescent element. Upon heating-up and cooling down this leads to stresses on the interconnect interface and could lead to reliability issues. A silicone interface material can fortunately deform relatively easily to accommodate for most of these thermally induced stresses. Hence, it is a desire to overcome said optical losses associated to the current extraction optic solution while simultaneously ensuring a high reliability related to thermo-mechanical aspects.

(27) It appeared not to be easy to find proper material combination that allows a reliable light extraction functionality for a luminescent element with a relatively high refractive index.

(28) Amongst others, it is proposed to attach a glass or ceramic CPC, having preferable a relatively high refractive index, to the luminescent element material by means of a glass frit material consisting of especially (at least) three components: boron oxide B.sub.2O.sub.3, bismuth oxide Bi.sub.2O.sub.3 and zinc oxide ZnO. Such a frit consists of powdered glass compositions formed by the three mentioned components. The glass powder may be applied in the form of a paste e.g. by dispensing on the nose of the rod or by pressing into a small platelet and positioned on the nose of the rod (see more details in the process flow shown in the detailed section).

(29) With the proper window of compositional ranges of these components this will ensure an improved optical efficiency as well as a good thermo-mechanical functionality:

(30) High refractive index interconnect interface to extract virtually all light from the luminescent element and transfer this to the high refractive index CPC, by which it is extracted towards the ambient.

(31) Close CTE matching with both the luminescent element and the high refractive index CPC to ensure an interconnect with low stress levels, both during the high temperature bonding process of the CPC to the luminescent element as well as during operating conditions of the lighting device.

(32) High optical transparency of the interconnect interface: low absorption and scatter.

(33) A sufficiently low softening point of the glass frit mixture in order for the frit to flow to form the interconnect interface while not deforming the high refractive index CPC.

(34) A number of materials have been found that comply with one or more of the following conditions:

(35) TABLE-US-00003 Refractive index 1.7 < n.sub.525 nm < 3.5 Linear thermal expansion 7.0 < α.sub.100° C. < 8.0 8.0 < α.sub.300° C. < 9.0 ppm/K Softening point 375 < T.sub.10.sub.7.Math.6 .sub.dPas < 550° C. Water resistance RW = 1 Transparency T > 95% at 50 μm thickness

(36) Specific embodiments of the garnet-CPC bonding use a low-melting B.sub.2O.sub.3—Bi.sub.2O.sub.3—ZnO glass with composition indicated in green in the ternary diagram in mol. % below with quadrilateral corner points:

(37) 25 mol % B.sub.2O.sub.3 7.5 mol % Bi.sub.2O.sub.3 67.5 mol % ZnO

(38) 80 mol % B.sub.2O.sub.3 20 mol % Bi.sub.2O.sub.3 0 mol % ZnO

(39) 65 mol % B.sub.2O.sub.3 35 mol % Bi.sub.2O.sub.3 0 mol % ZnO

(40) 22.5 mol % B.sub.2O.sub.3 20 mol % Bi.sub.2O.sub.3 57.5 mol % ZnO.

(41) This is also schematically depicted in FIG. 3; note that this ternary diagram, as well as the above indicated in mol % and not in wt. %.

(42) In addition, low levels of other atoms may be present in the glass frit layer after processing due to possible ion exchange with the rod and/or CPC material. For instance, some Al and Lu or Y could be detected in the glass frit without significantly changing its properties. Alternatively, small amounts of other atoms may be applied with little influence on the properties. For instance, small levels of Li.sub.2O could be added or exchanged with ZnO to lower the softening T of the glass. Therefore, we could define a compositional range window of the 3 main components, where the wt. % levels do not add-up to 100% but, e.g. 95%, as the remainder could be composed of other material types.

(43) A number of glass materials were made, amongst others with 22 wt. %, 73 wt. % and 5 wt. % of boron oxide, bismuth oxide and zinc oxide, respectively, and with 21 wt. %, 68 wt. % and 11 wt. % of boron oxide, bismuth oxide and zinc oxide, respectively.

(44) A basic process was executed wherein the oxides as powder were combined with a liquid and a binder to create a suspension, which was provided as suspension on the radiation exit window of an elongated body. The body was heated to bake out the binder and then heated to form a molten frit droplet (molten connector). In a furnace at elevated temperature the elongated body and beam shaping element were joined together with the molten interconnect in between, after which cooling provided the desired assembly.

(45) As an alternative embodiment of frit bonding, direct garnet-glass bonding could potentially be possible above the softening point of the glass CPC.

(46) Other alternative materials compositions that meet our requirements for bonding with proper optical and thermo-mechanical properties may exist. For instance, a mixture of ZnO—Bi.sub.2O.sub.3—P.sub.2O.sub.5 could be used. Being relatively sensitive to water this mixture is less preferred over the B.sub.2O.sub.3—Bi.sub.2O.sub.3—ZnO system.

(47) Various materials can be identified as candidates to attach the CPC to the Luminescent element with the proposed glass frit solution: high index glass CPC, high index ceramic materials such as: YAG, Y.sub.2O.sub.3, Spinel, materials similar to the Luminescent element: LuAG, LuYAG, YAG, GdYAG, etc.

(48) When ceramic CPCs are used, as described above, a much wider range of frit materials may be used for interconnect as there is no softening point of the CPC to consider. As such, there is no strict need for a low softening temperature of the frit.

(49) Especially, n1/n2≤1.1, such as more especially n1/n2≤1.08. Further, especially, 0.9≤n1/n2≤1.1, even more especially 0.95≤n1/n2≤1.08, such as 0.95≤n1/n2≤1.05. The index of refraction of the elongated body 100 is indicated with n1 and the index of refraction of the beam shaping optical element 224 is indicated with n2.

(50) FIG. 2a schematically depicts part of the lighting device 1, but yet without the beam shaping element 224 connected to the elongated body 100. An optical connector 300, comprising glass material 310 is depicted with dashed lines, indicating that this connector is optional.

(51) The beam shaping optical element 224 or an optical connector 300 configured between the elongated light transmissive body 100 and the beam shaping optical element 224 comprise glass material 310, wherein especially the glass material 310 is based on at least Bi.sub.2O.sub.3 and for instance one or more of ZnO, B.sub.2O.sub.3, and P.sub.2O.sub.5 (see also above).

(52) When heating the glass material 310 above the softening point, the glass material can be used to adhere the beam shaping element to the elongated body 100 via the connector, see FIG. 2b. When the beam shaping optical element 224 comprises the glass material 310, then the beam shaping optical element can be adhered to the elongated body 100 directly. Frit connections, i.e. the interfaces between the materials are indicated with reference 324.

(53) The beam shaping optical element 224 is thus optically coupled with the radiation exit window 112. The beam shaping element may be a light transmissive body, indicated with reference 225. The beam shaping optical element 224 comprises a radiation entrance window 211 configured to receive at least part of the converter light and a radiation exit window 212. The distance between the radiation entrance window 211 and the radiation exit window 212 defines a length of a light transmissive body 225 of the beam shaping optical element 224. Especially, the beam shaping optical element 224 comprises a light transmissive body where the radiation exit window 212 has a larger cross section than the radiation entrance window 211. Hence, the beam shaping optical element may tapers from the radiation exit window 212 to the radiation entrance window 211.

(54) The beam shaping optical element 224 comprises a light transmissive body 225 with a radiation entrance window 211 which may have an area and cross section which may be essentially the same as the area and cross-section of the radiation exit window 112 of the elongated body 100. When the connector 300 is configured in between the elongated body 100 and the beam shaping element 224, then the connector has also essentially the same area and cross-section as the radiation exit window 112 and the radiation entrance window 211.

(55) FIG. 2b schematically depicts a second assembly 1002 comprising the elongated light transmissive body 100, the beam shaping optical element 224 optically coupled with the first radiation exit window 112, the beam shaping optical element comprising a radiation entrance window 211 configured to receive at least part of the converter light 101, and the optical connector 300 configured between the elongated light transmissive body 100 and the beam shaping optical element 224 comprising a glass material 310. The elongated light transmissive body 100 and the beam shaping optical element 224 are associated to each other via the optical connector 300, wherein the beam shaping optical element 224 comprises an optical element material 240 different from the glass material 310.

(56) FIG. 2c schematically depicts an embodiment of a first assembly 1001 comprising the elongated light transmissive body 100, the beam shaping optical element 224 optically coupled with the first radiation exit window 112, the beam shaping optical element comprising a radiation entrance window 211 configured to receive at least part of the converter light 101; wherein the beam shaping optical element 224 has a second index of refraction n2. The beam shaping optical element 224 comprises a glass material 310. The elongated light transmissive body 100 and the beam shaping optical element 224 are associated to each other with a glass frit connection 324.

(57) The term “substantially” herein, such as in “substantially all light” or in “substantially consists”, will be understood by the person skilled in the art. The term “substantially” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective substantially may also be removed. Where applicable, the term “substantially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. Where stated that an absorption, a reflection or a transmission should be a certain value or within a range of certain values these values are valid for the intended range of wavelengths. Such, if stated that the transmission of an elongated luminescent light transmissive body is above 99%/cm, that value of 99%/cm is valid for the converted light rays within the desired range of wavelengths emitted by the lighting device 1, while it would be clear to the person skilled in the art that the transmission of an elongated luminescent light transmissive body will be well below 99%/cm for the range of wavelengths emitted by the light sources 10, since the source light 11 is intended to excite the phosphor material in the elongated luminescent light transmissive bodies such that all the source light 11 preferably is absorbed by the elongated luminescent light transmissive bodies instead of highly transmitted.

(58) The term “comprise” includes also embodiments wherein the term “comprises” means “consists of”. The term “and/or” especially relates to one or more of the items mentioned before and after “and/or”. For instance, a phrase “item 1 and/or item 2” and similar phrases may relate to one or more of item 1 and item 2. The term “comprising” may in an embodiment refer to “consisting of” but may in another embodiment also refer to “containing at least the defined species and optionally one or more other species”.

(59) Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

(60) The devices herein are amongst others described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation or devices in operation.

(61) It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb “to comprise” and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”. The article “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

(62) Practical designs may be further optimized the person skilled in the art using optical ray trace programs, such particular angles and sizes of microstructures (reflective microstructures or refractive microstructures) may be optimized depending on particular dimensions, compositions and positioning of the one or more elongated light transmissive bodies.

(63) The invention further applies to a device comprising one or more of the characterizing features described in the description and/or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterizing features described in the description and/or shown in the attached drawings.

(64) The various aspects discussed in this patent can be combined in order to provide additional advantages. Further, the person skilled in the art will understand that embodiments can be combined, and that also more than two embodiments can be combined. Furthermore, some of the features can form the basis for one or more divisional applications.