WO2013023662A1

WO2013023662A1 - Illumination device with fluid cooled converting material

Info

Publication number: WO2013023662A1
Application number: PCT/DK2012/050291
Authority: WO
Inventors: Dennis Jørgensen
Original assignee: Martin Professional ApS
Current assignee: Harman Professional Denmark ApS
Priority date: 2011-08-17
Filing date: 2012-08-10
Publication date: 2013-02-21
Anticipated expiration: 2014-02-17

Abstract

The present invention relates to an illumination device comprising: at least one pumping light source emitting pumping light of at least a first wavelength; a converting material adapted to convert at least a part of the pumping light into converted light of at least a second first wavelength and to emit the converted light; and where the second wavelength is different from the first wavelength;null the converting material is further arranged at an cooling arrangement comprising at least one flow channel wherein a cooling fluid can flow, the flow channel and the cooling fluid are transparent to the pumping light and at least a part of the pumping light illuminating the converting material passes through the flow channel and the cooling fluid. The present invention relates also to a method creating illumination using such illumination device.

Description

ILLUMINATION DEVICE WITH FLUID COOLED CONVERTING MATERIAL

Field of the Invention

The present invention relates to an illumination device comprising a pumping light source adapted to illuminate a converting material with pumping light, where the converting material is adapted to convert the pumping light into converted light having wavelengths which are different from the wavelengths of the pumping light.

Background of the Invention

Light fixtures creating various effects are getting more and more used in the entertainment industry in order to create various light effects and mood lighting in connection with concerts, live shows, TV shows, sport events or as a part of an architectural installation. Typically entertainment light fixtures creates a light beam having a beam width and a divergence and can for instance be wash/flood fixtures creating a relatively wide light beam with a uniform light distribution or it can be profile fixtures adapted to project image onto a target surface.

Light emitting diodes (LED) are, due to their relatively low energy consumption or high efficiency, long lifetime, and capability of electronic dimming, becoming more and more used in connection with lighting applications. LEDs are used in lighting applications for general illumination such as wash/flood lights illuminating a wide area or for generating wide light beams e.g. for the entertainment industry and/or architectural installations. For instance like in products like MAC101™, MAC301™_; MAC401™, Stagebar2™, Easypix™, Extube™, Tripix™, Exterior 400™ series provided by the applicant, Martin Professional a/s. Further LEDs are also being integrated into projecting systems where an image is created and projected towards a target surface, for instance like in the product MAC 350 Entour™ provided by the applicant, Martin Professional a/s.

Illumination devices where pumping light from a number of pumping light sources are converted into light having other wavelengths are starting to be used more and more. Typically the pumping lights are converted by a converting material which is illuminated with pumping light form a number of pumping light sources. Generally the this technique is known as luminescence where the converting material is excited by photons from the pumping light and thereafter stepwise decay while emitting photons having other wavelengths. The converting material can be any material cable of being excited by electromagnetic radiation in the optical region including IR light, visible light and UV light. The light converting material can for instance be phosphor materials as known in the prior art and for instance as described in "Phosphor Handbook", second edition; edited by William M. Yen, Shigeo Shionoya, Hajime Yamamoto; CRC Press, Taylor & Francis Group 2007; ISBN: 0-8493-3564-7. The converting material can also be quantum dots.

It is known to use LEDs as pumping light sources and provide phosphor based LEDs where a layer of phosphor have been arranged above the LED die. The LED functions as pumping light source and the layer of phosphor acts as a converting material converting the light form the LED into other wavelengths. Light converting material is temperature dependent and its' properties depend on the temperature. For instance the efficiency of the converting material can decrease with increasing temperature and the optical properties of converted light changes also with the temperature. As a consequence the converting material need to be kept at low and constant temperature in order to provide an efficient and stable light source based on converting material. However it has turned out that this is difficult where the converting material are arranged above the LED die, as the LED die heats up converting material whereby the efficiency of the converting material decreases and/or the optical properties of the converted light may also change resulting in change in color temperature (in case of white light), color drift, change in color rendering etc. Both the efficacy and change in optical properties of the converted light is not accepted in entertainment lighting where efficient and stable light are needed.

Attempts to overcome the above issues have been tried by arranging the color converting material remote form the pumping light source. However sufficient cooling and stability of the temperature of the converting material have not yet been achieved, as the shift from short to longer wavelength yields a loss which is converted into heat in the converting material.

US 7,070,300 discloses an illumination device uses a wavelength converting element, such as a phosphor layer, that is physically separated from a light source, such as one or more light emitting diodes, a Xenon lamp or a Mercury lamp. The wavelength converting element is optically separated from the light source, so that the converted light emitted by the wavelength converting element is prevented from being incident on the light source. Accordingly, the temperature limitations of the wavelength converting element are removed, thereby permitting the light source to be driven with an increased current to produce a higher radiance. Moreover, by optically separating the wavelength converting element from the light source, the conversion and recycling efficiency of the device is improved, which also increases radiance.

US2008/0192458 discloses a lighting system for generating an illumination product comprises an excitation source, blue/UV LED, operable to generate excitation radiation and a remotely located phosphor, photo luminescent material. Excitation radiation is guided from the excitation source to the phosphor by a waveguiding medium, the waveguiding medium being configured such that the distance the radiation travels from the excitation source to the phosphor layer is at least one centimeter in length. The UV/blue excitation source provides excitation radiation to the phosphor(s), causing the phosphor(s) to photo luminesce, and it may also provide a component of the final illumination product.

WO091 15976A discloses an illumination system, with a light source emitting light of at least a first wavelength, and a luminescent element which is irradiated with the light emitted by the light source and which emits light of at least a second wavelength which is different from the first wavelength, wherein the luminescent element is comprised of a plurality of sub-elements which are each in heat- conducting contact with a heat sink. Each sub-element is surrounded by a heat- conducting material, e.g. a metal such as copper, gold, diamond, graphite, or ceramic that is heat-conducting and opaque or optically transparent. W010049875 discloses wavelength converter and a laser lighting device comprising such a wavelength converter. The wavelength converter converts laser light of a first wavelength to second light having a different wavelength by means of a wavelength converting material, wherein the surface of the wavelength converting material where the laser light enters the wavelength converting material is in good thermal contact with a transparent material. The transparent material on the other hand is in good thermal contact with a heat sink which has a window to let the laser light pass before the laser light enters the wavelength converting material. The wavelength converter is especially suited for remote laser lighting and particularly the high power densities of lasers and the related local heating of the wavelength converter.

US2010/295438 discloses a semiconductor light source, where the semiconductor light source having a primary radiation source which, when the semiconductor light source is operated, emits electromagnetic primary radiation in a first wavelength range, and having a luminescence conversion module into which primary radiation emitted by the primary radiation source is fed. The luminescence conversion module contains a luminescence conversion element which, by means of a luminescent material, absorbs primary radiation from the first wavelength range and emits electromagnetic secondary radiation in a second wavelength range. The luminescence conversion element is arranged on a heat sink at a distance from the primary radiation source. It has a reflector surface which reflects back into the luminescence conversion element primary radiation which passes through the luminescence conversion element and is not absorbed thereby and/or reflects secondary radiation in the direction of a light coupling-out surface of the luminescence conversion element.

WO2008/018002 discloses an illumination device including a light source, such as one or more light emitting diodes in an array, that produces light having a first wavelength range. A separated wavelength converting element is mounted to receive the light emitted by the light source. The wavelength converting element is physically separated from the light source along the beam path. The wavelength converting element converts the light having a first wavelength range into light having a second wavelength range. In one embodiment, a color separation element is directly coupled to the wavelength converting element. The color separation element is also physically separated from the light source. In another embodiment, the wavelength converting element is held by a heat sink by the sides.

WO2010/052640 relates to an illumination device, comprising: at least one LED having an emission maximum in a first wavelength range; at least one LED having an emission maximum in a second wavelength range; and a wavelength converting material arranged to receive light of at least said first light wavelength range and having an emission maximum in a third wavelength range which is between said first wavelength range and said second wavelength range. The illumination device according to the invention may provide white light of acceptable overall color rendering while producing particularly high saturation of selected colors.

WO201 1 /1 1 1223 discloses a lighting device comprising a solid state light emitter and a fan, the fan blowing fluid toward the emitter. A lighting device comprising a solid state light emitter and a baffle, the solid state light emitter being movable. A lighting device comprising a solid state light emitter, a substrate and a diaphragm, the diaphragm defining a chamber having a valve and being movable. A lighting device comprising a housing and a solid state light emitter within the housing, the solid state light emitter being movable. Also, methods of cooling a lighting device Description of the Invention

The object of the present invention is to reduce and/or solve the above described limitations related to prior art. This is achieved by an illumination device and method as described in the independent claims. The dependent claims describe possible embodiments of the present invention. The advantages and benefits of the present invention are described in the detailed description of the invention. Description of the Drawing

Fig. 1 illustrates an embodiment of an illumination device according to the present invention; fig. 2 illustrates a structural diagram of the illumination device of in fig. 1 integrated into a liquid cooling system; fig. 3a-3c illustrate another embodiment of an illumination device according to the present invention; fig. 4a-4c illustrate another embodiment of an illumination device according to the present invention; fig. 5 illustrates another embodiment of an illumination device according to the present invention; fig. 6 illustrates another embodiment of an illumination device according to the present invention; fig. 7 illustrates another embodiment of an illumination device according to the present invention; fig. 8a and 8b illustrate another embodiment of an illumination device according to the present invention; fig. 9 illustrates another embodiment of an illumination device according to the present invention.

Detailed Description of the Invention

The present invention is described in view of an illumination device comprising a number of LEDs that generate the pumping light. However the person skilled in the art realizes that any kind of light source such as discharge lamps, OLEDs, plasma sources, halogen sources, fluorescent light sources, lasers etc. can be used to generate the pumping light. Further it is to be understood that the illustrated embodiments only serve as illustrating examples illustrating the principles of the present invention and that the skilled person will be able to provide several embodiments within the scope of the claims. In the illustrated embodiments the illustrated light beams and optical means do only serve as to illustrate the principles of the invention rather than illustrating exact and precise light beams and optical means.

Fig. 1 illustrates a simplified cross-sectional view of an illumination device according of the present invention. The illumination device 101 comprises a pumping light source 1 03 emitting pumping light 105 (illustrated as solid lines) of at least a first wavelength. A converting material 107 adapted to convert at least a part of the pumping light 105 into converted light 109 (illustrated as dotted lines) of at least a second wavelength and to emit the converted light 109. The second wavelength is different from the first wavelength and the converted light can thus have a different color than the pumping light. In the illustrated embodied the pumping light source is a LED 103 mounted on a printed circuits board (PCB) 1 1 1 as known in the art of LEDs. The converting material is arranged on a cooling arrangement 1 13 comprising at least one flow channel 1 15 wherein a cooling fluid (not shown) can flow as illustrated by flow arrows 1 17. The flow channel 1 15 and the cooling fluid are transparent to the pumping light 103 and the pumping light passes through the flow channel and the cooling fluid before illuminating the converting material 107. The converting material 107 converts the pumping light and emits the converted light into a different directions as illustrated by the fact that the lines illustrating the converted light points in different directions. Typically the converting material will emit the converted light in a spherical pattern. However it is noted some of the pumping light may not be converted into other wavelength by the converting material as illustrated by 105' and due to scattering within the converting material or because the converting material decay directly back to the ground state instead of stepwise decaying.

The transparent flow channel 1 1 5 and transparent cooling fluid makes it possible to provide efficient cooling of the converting material as heat generate by the converting material during light conversion can dissipate to the cooling fluid and very effectively be removed. The transparent flow channel can cover the entire surface of the converting material whereby heat can be removed from the entire mounting surface of the converting material. Further the transparent flow channel makes it possible to illuminate the entire mounting surface of the converting material whereby more light can be converted. The transparent flow channel acts as a thermal insulator between the pumping light source and the converting material and prevents heat from dissipating from the pumping light source to the converting material 107 and visa versa. Heat form the pumping light source that eventually would dissipate into the cooling fluid will not dissipate to the converting material as the cooling fluid will flow through the cooling channel and removed from the light source and converting material.

The terms transparent flow channel 1 15 and transparent cooling fluid means that at least 50% of the pumping light will be able to pass through the flow channel 1 15 and the cooing fluid and hit the converting material 107. The skilled person will realize that the more light that pass through flow channel and the cooling fluid the more efficiency the illumination device become. In many practical situations at least 80% of the pumping will pass through the transparent flow channel and transparent cooling fluid. However it is also possible to provide solutions however where at least 90% of the pumping light will pass through the transparent flow channel and transparent cooling fluid. High transmission of pumping light through the transparent flow channel and the transparent cooling fluid results in a high pump efficiency. The transmission of pumping light can be increased by applying anti-reflective coating on the flow channel windows, where the pumping light hits the flow channel. Reflection losses at the flow channel can also be reduced by providing index-matching material between flow channel windows and cooling fluid, hence avoiding AR-coating on the side of the windows in contact with cooling fluid. Also the reflection losses between the pumping source and air and between air and flow channel window can be avoided if an index matching material is inserted between pumping source and flow cannel window, which can also improve cooling of the pump source 103 as heat from the pump source can be conduction into the flow channel and removed by the cooling fluid. The flow channel windows can be made of a material with both high heat conductivity and transmission such as sapphire substrate.

Typically the pumping light sources emits blue or UV light which is down converted into light having longer wavelengths, which typically are within the visible spectra. The converting material can be any material cable of converting light of a first wavelength into light of a second wavelength. The converting material can for instance be phosphor materials for instance any of those described in: "Phosphor Handbook", second edition; edited by William M. Yen, Shigeo Shionoya, Hajime Yamamoto; CRC Press, Taylor & Francis Group 2007; ISBN: 0-8493-3564-7. However it is noted that new converting material are continuously being developed and that these also can be used in the illustrated illumination device. In fact it may be possible to develop new kinds of converting material as more heat now can be removed from the converting material. The invention can also be used with converting materials converting the pump light into shorter wavelengths. Further the light converting material can be any composition comprising quantum dots which is capable of converting the pumping light into converted light comprising at least one wavelength different from the pumping light. The cooling fluid can be any fluid transparent to the pumping light and capable of absorbing heat and which can flow in the flow channel. The cooling fluid needs to be transparent to the pumping light and is chosen based on the spectral components of the pumping light and may be both gasses (e.g. air, hydrogen, inert gasses ect.) and liquids (water, oils, Freos, etc.).

In the case where pumping light source emits pumping light within the near UV, violet and blue regions of the optical spectra (200nm-475nm) the cooling fluid can comprise water, as water has a high transmission coefficient at these wavelengths and is further a good heat conductor. The water may be mixed with other components like corrosion inhibitors and antifreeze. Antifreeze, a solution of a suitable organic chemical (most often ethylene glycol, diethylene, glycol, or propylene glycol) in water, is used when the water-based coolant has to withstand temperatures below 0 °C, or when its boiling point has to be raised. Hereby it can be avoided that the liquid system can be destroyed due to low temperatures which for instance may occur during transportation and/or sorting of the illumination device. The flow channel can be constructed as a hollow channel where inside the cooling fluid can flow. The flow channel can be made by any material which is transparent to the pumping light source for instance transparent ceramic materials or transparent polymers. Advantageously the flow channel material may also be a good thermal conductor and can for instance be a sapphire substrate which is both transparent to optical light and also have relatively high thermal conductive properties. The choice of material depends on the choice of pumping light source as at least a part of the pumping light must be transmitted through the flow channel. Fig. 2 illustrates a structural diagram of the illumination device 101 in fig. 1 integrated into a liquid cooling system 200. The liquid cooling system 200 comprises a number of tubes 202 connecting the flow channel 1 15 to a heat exchanger 204 and a pump 206. In this embodiment the cooling fluid is a cooling liquid and the pump 206 is adapted to pump the cooling liquid through the tubes 202, flow channel 1 15 and the heat exchanger 204 as illustrated by flow arrows 1 17. The heat exchanger is adapted to remove heat from the cooling liquid flowing through the heat exchanger as known in that art of liquid cooling. The cooling liquid will thus circulate in the liquid cooling system through the tubes 202 and be feed into the flow channel 1 15 where it takes up heat generated by the converting material 1 07. The heated cooling liquid then flow to the heat exchanger where the heat is removed from the cooling liquid and the cooled cooling liquid is then feed back into the flow channel 1 15. The cooling system may comprise an expansion chamber 208 which allow the cooling liquid to expand and thereby prevent leakage of the cooling system. In the illustrated embodiment the expansion chamber is illustrated as a separate unit, however the expansion chamber may be provided by embodying the tubes 202 as flexible tubes which can expand for instance flexible polymers. Alternatively the cooling fluid may also be a cooling gas which is blown through the flow channel by a blower (not shown) and where the cooling gas obtain heat generated by the converting material 107. For instance the illumination device 101 may be embodied in housing where the blowing means is adapted to ventilate the flow channel with cold cooling air which is taken in from outside the housing and then exhaust the heated cooling gas into the surroundings.

Fig. 3a-3c illustrates another embodiment of an illumination device 301 according of the present invention, where fig. 3a is a top view, fig. 3b is a cross sectional view through line A-A in fig. 3a and 3c is a cross sectional view through line B-B in fig. 3a.

Like the illumination device 101 illustrated in fig. 1 this illumination device 301 comprises a pumping light source 103 arranged on PCB 1 1 1 , a converting material 107 adapted to convert at least a part of the pumping light 105 (in solid lines) into converted light 109 (illustrated as dotted lines) of at least a second wavelength and to emit the converted light 109. The converting material is also arranged on a cooling arrangement 313 comprising a flow channel 1 15 where though a cooling fluid can flow as illustrated by flow arrows 1 1 7. A dichroic filter 31 9 has been arranged between the cooling arrangement 313 and the light converting material 107. The dichroic filter 31 9 is adapted to reflect converted light 109 and passing pump light 1 05 and as a consequence backward emitted converted light (like 109") will be reflected forwardly. The efficiency of the illumination device is hereby improved. A light collector 321 have further been arranged to collect the converted light 1 09 and transform the collected light into a light beam. The light collector can be formed as any optical means capable of collecting the emitted converted light 109 and transforming the light into a light beam having a predefined beam width and divergence. In the illustrated embodiment the light collector 321 is embodied as a TIR lens having a central part surrounded by peripheral part. The central part collects a central part of the converted light 109 emitted by the converting material 1 07 and the peripheral part collects and reflects a peripheral part of the converted light emitted by the converting material. However it is to be understood that at other kinds of optical light collectors also can be used.

In this embodiment and as illustrated in fig. 3a the cooling arrangement 31 3 is formed as a hollow dish with an inlet 323 and an outlet 325 at opposite sides of the hollow disc. The flow channel 1 15 is formed between the upper and lower surfaces of the hollow dish and the cooling fluid is let into the flow channel 1 15 through the inlet 323 and let out through the outlet 325. A number of additional edged pumping light sources 303 on PCBs 31 1 are further arranged at the outer edge of the hollow disc and adapted to emit pumping light 305 into the hollow disc. As illustrated in fig. 3c a part of the pumping light 305 from the edge pumping light sources 303 will be transmitted through cooling arrangement and to the converting material 1 07 via a number of reflections. The transparent flow channel and cooling fluid act as a wave guide wherein the pumping light 305 is transmitted via a number of reflections. In this embodiment the reflection are based on total internal reflection due the difference in refractive index of the transparent flow channel and the surrounding air. The pumping light will be coupled out of the transparent cooling arrangement when it hit the upper surface at the center where the dichroic filter and converting material are arranged as the refractive index of the dichroic filter, converting material and transparent cooling arrangement are of the same magnitude resulting in the fact that the pumping light 305 do not experience total internal reflection. It is noted that there will be a deflection when the pumping light passes the surface between the cooling fluid and the transparent cooling arrangement, however this deflection is relatively small if the refractive index of the cooling fluid and the transparent are of the same magnitude, which typical would be the case when cooling liquids are used. However it is noted that the transparent cooling arrangement also can be provided with a reflective coating at the areas where there are no color converting material as an alternative to or in addition to the internal reflection.

This embodiment makes it possible to illuminate the converting material with pumping light form many light sources and at the same time keeping the temperature of the converting material stable and low as the cooling fluid removed the heat from the converting material as described above. The illumination device can further be very compact as the transparent cooling arrangement acts as both heat sink and waveguide. Alternatively the wall of the transparent cooling channel, where on the converting material is arranged, can be also used as wave guides if the refractive index of the wall has a higher refractive index than the cooling fluid. This is the typical case when the cooling fluid is a cooling gas. In this case the edge pumping light sources 303 will be adapted to emit pumping light into the wall where on the converting material is arranged and the pumping light will be transmitted through the wall to the converting material via a number of reflections.

Fig. 4a-c illustrate another embodiment of an illumination device 401 according of the present invention, where fig. 4a is a top view, fig. 4b is a cross sectional view through line C-C in fig. 4a and fig. 4c is a cross sectional view through line D-D in fig. 4a.

Like the illumination device illustrated in fig 3a-3c the transparent cooling arrangement is formed as a hollow disc wherein the cooling fluid can flow, however the inlet 423 and outlet 425 have been arranged at the bottom side of the hollow disc and at opposite sides of the center of the hollow disc. The cooling fluid will still flow through the transparent flow channel and remove heat generated by the light converting material 1 07. In this embodiment the light collector is embodied as a dichroic reflector 417 reflecting the converted light 109 and passing pump light. Light collectors 427 have also been provided at the edge pump sources 303 at the edge of the in order to control the divergence of the pump light 305 entering the cooling arrangement through the edges. Hereby more of the light emitted from the edge light sources can be transmitted to the converting martial as the outer light rays from the edged pump light sources 303 can be directed into the wave guide such they experience total internal reflection.

Further it can be seen that further pumping light sources 403 have been arranged above and below the cooling arrangement 413. The pump light source below the cooling arrangement will emit light to the converting material 107 through the transparent flow channel 415 and the transparent cooling fluid. The pump light sources 427 arranged above the cooling arrangement 413 will illuminate the converting material through the dichroitic reflector 417. Light collectors 427 are also provide above the pump light sources and light collectors 427 makes it possible to collect more light from the pump light sources and control the pump light. It is noted that the light collectors 427 does not need to be identical and that they can be designed differently in order to optimize how the pump light from the different pump light sources hits the converting material. Further it is noted that the pump light sources 1 03, 303, 403 can be both identical and/or different. It is also possible to adapt the shape of the flow channel window where through the pumping light enters the flow channel and thereby use the flow channel window as optical means focusing the pump light at the converting material. For instance the flow channel window can be formed as an optical lens adapted to concentrate the pump light onto the converting material.

The additional pump light sources can be provided around the light converting material in a spherical pattern both above and below the cooling arrangement 413 it thus possible to provide many pumping light sources where by more light can be converted. The cooling arrangement ensures that the converting material can be keep at a low and stable temperature.

Fig. 5 illustrates another embodiment of the illumination device 501 according of the present invention. In this embodiment the illumination device comprises a number of pumping light source 503 emitting pumping light 505 (in solid lines) of a first wavelength, a converting material 507 adapted to convert at least a part of the pumping light 505 into converted light 509 (in dotted lines) of at least a second wavelength to emit the converted light. In this embodiment the converting material 507 is positioned at the focal point of an elliptic or parabolic dichroic reflector 517 embodied as a light collector and adapted to reflect converted light and to transmit pumping light. The pump light sources are positioned outside the dichroic reflector and adapted to illuminate the light converting material through the dichroic reflector 517. The transparent flow channel is formed as a u-shaped transparent channel 515 where the converting material is positioned at the bottom part of the U-shaped flow channel and in thermal connection with the U-shaped flow channel. The cooling fluid is adapted to enter the U-shaped flow channel at one leg and leave the U-shaped flow channel through the other leg as illustrated by flow arrows 51 7. In this embodiment the flow channel is transparent to both the pump light and the converted light. The pump light will thus pass through the flow channel and cooling fluid before illuminating the converting material and a part of the converted light will be emitted through the flow channel and cooling fluid. The dichroic reflector can be designed to collect the converted light and transform the collected light into a light beam having a predefined divergence and beam width. The shape of the dichroic reflector 517 can be designed according to this for instance in order to create a wide and uniform light beam which can be used in a wash light or in order to concentrate the light at an imaging forming object crating an optical image, which can be projected to a target surface be a projecting system, as known in the art in projecting systems.

Fig. 9 illustrates a simplified cross-sectional view of an illumination device similar to the one illustrated in fig. 1 . However in this embodiment a number pumping light sources 903 emitting pumping light (illustrated as solid lines) are arranged on a PCB 91 1 . Light collectors 927 collimating the pumping light 905 from the pump light sources have been arranged above each pumping light source 903. The bottom side 91 5 of the transparent flow channel 1 1 5 have been shaped as an optical lens adapted to focus the collimate pumping light 905 onto the converting material 107 where it is converted into converted light 109 (illustrated as dotted lines) of at least a second wavelength and to emit the converted light 109. The second wavelength is different from the first wavelength and the converted light can thus have a different color than the pumping light. Further the top side of the flow channel have been embodied as a dichroic filter which is transparent to the pump light and reflecting converted light 109, as a consequence backward remitted converted light (like 109") is thus reflected forward by the top surface of the flow channel. Some of the pumping light may not be converted into other wavelength by the converting material as illustrated by 905' and due to scattering within the converting material or because the converting material decay directly back to the ground state instead of stepwise decaying.

Fig. 6 illustrates a simplified cross-sectional view of another embodiment of an illumination device 601 according of the present invention. The illumination device is similar to the illumination device illustrated in fig 1 , however there are some differences which will be described below. In this embodiment the pumping light source 1 03 has been arranged just below the flow channel 1 15 and is in thermal contact with the flow channel 1 15. As a consequence some of the heat generated by the pump light source 103 will be removed by the cooling fluid flowing in the flow channel 1 1 5. The cooling arrangement will thus remove heat from that the converting material 1 07 and the pump light source 1 03 can be kept a stable and low temperature. The heat form the pump light source will not dissipate to the converting material as it is removed by the cooling fluid.

Further a second transparent flow channel 615 have been provided above the light collecting material 107 and a second cooling fluid flows in the second flow channel 615 as illustrated by flow arrows 617. The second flow channel 615 and second cooling fluid is transparent to the converted light. As a consequence the converted light 109 can be emitted through the second flow channel 615 and second cooling fluid. In this embodiment the converting material 607 is sandwiched between the first 1 15 and second 615 flow channel and heat generated by the converting material 107 can dissipate through both the first flow channel 1 15 and the second flow channel and be removed by the first and second cooling fluid respectively. The converting material can as a consequence be cooled further and thus kept at a low and stable temperature. In the illustrated embodiment the first and second cooling fluid can flows in opposite directions whereby the temperature can be keep stable across the converting material. However it is also possible the let the first and second cooling fluid flow in the same direction or at directions angled in relation to each other.

The first flow channel and second flow channel can be provided of the same material however in this case the material need to be transparent to both the pump light and the converted light as both types of light need to pass through the material. Similar the first and second cooling fluid can be identical and be transparent to both the pump light and the converted light. However the first flow channel and second flow channel can also be embodied in different materials as long as the first flow channel is transparent to pump light and the second first flow channel is transparent to the converted light. Similar the first and second cooling fluid may be different. It is further possible to provide dichroic filters at the bottom of the converting material which is adapted to transmit pump light and reflect converted light whereby back emitted converted light can be reflected forwardly. A dichroic filter adapted to reflect pump light and transmit converted light can further be positioned above the converting material and as a consequence pump light passing through the converting material will be back reflected into the converting material where it can be converted in to converted light. Fig. 7 illustrates a simplified cross-sectional view of another embodiment of an illumination device 701 according of the present invention. The illumination device is similar to the illumination device illustrated in fig. 6; however there are some differences which will be described below. In this embodiment the illumination device comprises a third flow channel 71 5 which is in thermal contact with at least one pump light source 103 and heat generated by the pump light source 103 can be removed by a cooling fluid flowing in the third flow channel 715. In this embodiment the third flow channel need not the be transparent since no light need to pass through third cooling channel and the third cooling channel can thus be constructed as known in the art of fluid cooling light sources. However embodiments where the third flow channel and third cooling fluid need to be transparent to light may also be provided. For instance in embodiments where further pumping light sources emit pump light to the converting material through the third flow channel. This makes it possible to provide additional pumping light sources (not shown) below the illustrated pump light source 1 03 and at the same time efficiently cooling the pump light source 103.

It is to be understood that the pump light sources can be cooled using traditional heat sinks with cooling fins and eventual active cooling or fluid cooling. The multiple number of flow channels illustrated in fig. 6 and 7 may be integrated into a liquid cooling system similar to the one illustrated in fig. 2. For instance by providing separate cooling systems where each flow channel is connected to a number of tubes connecting each flow channel to a heat exchanger and a pump, which is adapted to pump cooling fluid from the flow channel to the heat exchanger. However the flow channels may also be integrated into the same cooling system where the flow channels are coupled in series or in parallel. Fig. 8a and 8b illustrate another embodiment of an illumination device 801 according of the present invention, where fig. 8a is a top view and fig. 8b is a cross sectional view through line E-E in fig. 8a. Like the illumination devices illustrated in the previous figures this illumination device 801 comprises a number of pumping light source 803 arranged on PCBs 81 1 and converting materials 807a-d adapted to convert at least a part of the pumping light 805 (in solid lines) into converted light 809a-d (in dotted, dashed, dotted-dashed, or dotted-dotted-dashed lines) having different wavelengths than the pumping light. The converting materials 807a-d are arranged on a cooling arrangement 813 formed as a hollow cuboid and the converting material is arranged at a top side of the hollow cuboid. The hollow cuboid comprise a number of inlets 823 and a number of outlets 825 at opposite sides at the cuboid and a flow channel 815 is formed between the top and bottom surfaces of the hollow cuboid. As a consequence cooling fluid can be let into the flow channel 815 through the inlets 823 and let out through the outlets 825. A part of the pumping light sources 803 are arranged below the hollow cuboid and adapted to illuminate the converting materials 807 through the bottom surface, flow channel, cooling fluid and top surface. Another part of the pumping light sources 803' are arranged to emit light into the sides of the hollow cubic and the emitted light will be transmitted through the hollow cuboid to the converting material via a number of reflections as described above in connection with fig. 3a- 3c. The converting material 807a-d comprises different types of converting material arranged in an array. The different types of converting material are adapted to convert the pumping light hitting the converting material into converted light having different wavelengths. In the illustrated embodiment the converting material comprises:

• a first converting material 807a adapted to convert the pumping light of at least a first wavelength into first converted light 809a (dotted line) of at least a second wavelength different form the first wavelength;

• a second converting material 807b adapted to convert the pumping light of at least a first wavelength into second converted light 809b (dashed line) of at least a third wavelength different form the first wavelength and the second wavelength;

• a third converting material 807c adapted to convert the pumping light of at least a first wavelength into third converted light 809c (dotted-dashed line) of at least a fourth wavelength different form the first wavelength, the second wavelength and the third wavelength;

• a fourth converting material 807d adapted to convert the pumping light of at least a first wavelength into fourth converted light 809d (dotted-dotted- dashed line) of at least a fifth wavelength different form the first wavelength, the second wavelength, the third wavelength and the fourth wavelength.

It is to be understood the any number of different converting material can be used and that the different converting material can be combined in any pattern for instance in order to create different visual effects or signs.

The illumination device illustrated in fig. 8a and fig. 8b can for instance be used as light sources in a mechanical color mixing system as described in the pending patent application titled "MECHANICAL COLOR MIXING DEVICE" having application number DK PA 201 1 70293 and filed 10^th of June 201 1 in Denmark by the applicant Martin Professional a/s or the pending patent application titled "MECHANICAL COLOR MIXING DEVICE" having application number PCT/DK2012/0501 98 and filed 8th of June 2012 in Denmark by the applicant Martin Professional a/s. Both applications are incorporate herein by reference.

The mechanical color mixing illumination device according to the patent applications tilted "MECHANICAL COLOR MIXING DEVICE" comprises:

• a number of light sources generating light; and

• a number of light collecting means adapted to collect the generated light and to convert the collected light into a number light beams propagating along an optical axis;

wherein the light sources are arranged in a first group of light sources and in a second group of light sources, where the first and second group of light sources emit light having different spectral distribution; and wherein the number of light sources and the light collecting means are displaceable in relation to each other and can be positioned in a number of mixing positions, where in the number of mixing positions the light collecting means are adapted to collect at least a part of said light emitted by said first group of light sources and at least a part of said light emitted by said second group of light sources and to convert said collected light into number of mixed light beams. The illumination device illustrated in fig. 8a and 8b can be integrated into the color mixing illumination device according by letting the different converting materials 807a-d act as the different groups of light sources and adapting the number of collecting means to collect converted light from different converting material 807a- d.

Claims

1 . An illumination device comprising:

• at least one pumping light source emitting pumping light of at least a first wavelength;

• a converting material adapted to convert at least a part of said pumping light into converted light of at least a second first wavelength and to emit said converted light; and where said second wavelength is different from said first wavelength;

characterized in that said converting material is arranged at an cooling arrangement comprising at least one flow channel wherein a cooling fluid can flow, said flow channel and said cooling fluid are transparent to said pumping light and at least a part of said pumping light illuminating said converting material passes through said flow channel and said cooling fluid.

2. An illumination device according to claim 1 characterized in that at least a part of said flow channel is adapted to transmit at least a part of said pumping light to said converting material through a number of reflections.

3. An illumination device according to claims 1 -2 characterized in that in said illumination device comprises light collecting means adapted to collect said converted light and to transform said converted light into a light beam.

4. An illumination device according to claims 1 -3 characterized in that at least one of said pumping light sources are in thermal contact with said flow channel.

5. An illumination device according to claims 1 -4 characterized in that said flow channel is integrated into a cooling system comprising:

• a heat exchanger adapted to remove heat from cooling fluid flowing through said heat exchanger;

• a number of tubes connecting said flow channel to a heat exchanger; and

• a pump adapted to pump said cooling fluid through said flow channel, said tubes and said heat exchanger.

6. An illumination device according to claims 1 -5 characterized in that said cooling arrangement comprises a second flow channel wherein a second cooling fluid can flow, said second flow channel and said second cooling fluid are transparent to said converted light, said converting material being in thermal contact with said second flow channel and at part of said converted light emitted by said converting material passes through said second flow channel and said second cooling fluid.

7. An illumination device according to claims 1 -6 characterized in that said cooling arrangement comprises a third flow channel wherein a third cooling fluid can flow and at least on of said pumping light sources are in thermal contact with said third flow channel.

8. An illumination device according to claims 1 -7 characterized in that in at least said first cooling fluid, said second cooling fluid and/or said third cooling fluid is a cooling liquid.

9. An illumination device according to claim 9 characterized in that said cooling liquid comprises water.

10. An illumination device according to claim 1 -9 characterized in that said pumping light is blue and/or UV light where said first spectra distribution comprises 95% light with a wavelength below 475nm.

1 1 . A method of creating illumination using an illumination device, said illumination device comprises:

· a converting material adapted to convert at least a part of said pumping light into converted light of at least a second wavelength and to emit said converted light; and where said second wavelength is different from said first wavelength; said method comprises the step of:

• arranging said converting material an cooling arrangement, where said cooling arrangement comprising at least one flow channel wherein a cooling fluid can flow, said flow channel and said cooling fluid are transparent to said pumping light;

• transmitting at least a part of said pumping light through said flow channel and said cooling fluid and to said converting material.

12. A method according to claim 1 1 characterized in that said step of transmitting said at least a part of said pumping light through said cooling arrangement comprises the step of reflecting said pumping light inside said cooling arrangement.

13. A method according to claims 1 1 -12 characterized in further comprising the step of arranging at least one of said pumping light sources in thermal contact with said flow channel and removing heat from said light source by forcing said cooling fluid through said flow channel.

14. A method according to claims 1 1 -13 characterized in comprising the step of removing heat from said converting material by forcing said cooling fluid through said flow channel.

15. A method according to claim 14 characterized in that said step of removing heat from said flow channel comprises the steps of:

• forcing said cooling fluid from said flow channel through a number of tubes and to a heat exchanger, said heat exchanger is adapted to remove heat from said cooling fluid; and thereafter

• forcing said cooling fluid from said heat exchanger and through a number of tubes and said flow channel.