WO2013023663A1

WO2013023663A1 - Illumination device with converting material dispersed in cooling fluid

Info

Publication number: WO2013023663A1
Application number: PCT/DK2012/050292
Authority: WO
Inventors: Dennis Jørgensen
Original assignee: Martin Professional A/S
Priority date: 2011-08-17
Filing date: 2012-08-10
Publication date: 2013-02-21

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; at least one flow channel wherein a cooling fluid flows, said flow channel comprises at least one pumping window transparent to said pumping light and at least one emitting window transparent to said converted light and said cooling fluid comprises said converting material. The present invention relates also to a method of creating illumination using such illumination device.

Description

ILLUMINATION DEVICE WITH CONVERTING MATERIAL DISPERSED IN COOLING FLUID

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 light converting material can also be quantum dots.

It is common knowledge to use LEDs as pumping light sources and provide phosphor based LEDs where a layer 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.

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. 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.

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.

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-4d 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. 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. The pumping light source is adapted to illuminate a converting material 107 (illustrated as small dots) 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 LED 1 03 mounted on a Printed circuits board (PCB) 1 1 1 as known in the art of LEDs. The illumination device comprises a cooling arrangement 1 13 comprising at least one flow channel 1 15 wherein a cooling fluid can flow as illustrated by flow arrows 1 17. The cooling fluid comprises the converting material and the flow channel comprises a pumping window 1 18 and an emitting window 120 and a converting area 122 is formed between the pumping window and the emitting window. The pumping window 1 18 is transparent to the pumping light 105 and at least a part of the pumping light can as a consequence enter the converting area 122 and be converted into converted light 109 by the converting material flowing with the cooling fluid. The emitting window 1 20 is transparent to the converted light 109 and at least a part of the converted light can as a consequence exit the flow channel 1 15 through the emitting window and can be used for illumination purposes. The converting material 1 07 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' for instance due the scattering within the converting material or because the converting material decay directly back to the ground state instead of stepwise decaying. This illumination device makes is possible to avoided over heating of the converting material as heat generated during the converting process will be removed by the cooling fluid flowing in the flow channel 1 15. Further as the converting material are a part of the cooling fluid heated converting material will also be removed from the area where the pumping light illuminated the converting material and replaced by cool converting material flowing with the cooling fluid. The converting material used for converting the pump light 1 09 into converted light 109 can as a consequence be keep at low and stable temperature where by the crated illumination can be keep at a high lumens output at without drifting in colors, color temperature or CRI.

That the pumping window 1 18 is transparent to the pumping light 105 means that at least 50% of the pumping light will be able to pass through the pumping window 1 18 and into the cooling fluid comprising the converting material. The skilled person will realize that the more pumping light that pass through the pumping window the more efficiency the illumination device become as the more pumping light can be converted by the converting material. In many practical situations at least 80% of the pumping light will pass through the pumping window. However it is also possible to provide solutions where at least 95% of the pumping light will pass through the pumping window. The transmission of pumping light through the pumping window can be increased by applying anti-reflective coating on the pumping window. The pumping window can be made by any material which is transparent to the pumping light for instance transparent ceramic materials or transparent polymers. 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 pumping window.

That the emitting window 120 is transparent to the converted light 109 means that at least 50% of the converted light hitting the emitting window will be able to pass through the emitting window 120. The skilled person will realize that the more converted light 109 that pass through the emitting window 120 the more efficiency the illumination device become as the more converted light can be used for illumination purposes. In many practical situations at least 80% of the converted light hitting the emitting window will pass through the emitting window. However it is also possible to provide solutions where at least 95% of the converted light hitting the emitting window will pass through the pumping window. The transmission of converted light through the emitting window can be increased by applying anti-reflective coating on the emitting window or by providing index- matching material between emitting window 120 and the cooling fluid. The emitting window can be made by any material which is transparent to the converted light for instance transparent ceramic materials or transparent polymers. The choice of material depends on choice converting material and pumping light as the converted light at least depends on these.

It is to be noted the pumping window and emitting windows can be embodied of different material or as the same material as long as the above requirements are met. Further the remaining parts of the flow channel may be embodied in a third material or in as the same material at either the pumping window or the emitting window.

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 and which can be dispersed by cooling fluid. The converting material can for instance be phosphor materials dispersed in a light transmissive liquid or gas material as described in US 201 1 /0127555 incorporated herein by reference. Other phosphor types may also be dispersed in cooling fluid and con for instance be some 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. The converting material can also be Quantum dots dispersed in liquid for instance as described in US 2009/0296368. Further 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. The cooling fluid can be any fluid comprising the converting material and capable of flown in the flow channel. Further the cooling fluid can be capable of absorbing heat and the converting material can be dissolved or mixed with the cooling fluid. However the cooling fluid may also act as converting material which is capable of converting the pumping light into converted light. The cooling fluid is chosen based in the spectral components of the pumping light and the converted light as the pumping light need to be able to enter the cooling fluid in order to be converted by the converting material and the converted light need to be able of exiting the cooling fluid. The cooling fluid can for instance be 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. Further converted light within the visible region is also able to pass through water (at least for relatively thin amounts of water e.g. with thickness below 25cm). 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.

Fig. 2 illustrates a structural diagram of the illumination device 101 in fig. 1 where the flow channel 1 15 is connected with a pump 202 and a heat exchanger 204. The pump 204 is adapted to force the cooling fluid from the pumping window 1 1 8 and the emitting window 120 to the heat exchanger 204 and the heat exchanger 204 is adapted to remove heat from the cooling fluid. In this embodiment a number of tubes 206 connect the flow channel 1 15 with the heat exchanger 204 and the pump 207. In this embodiment the cooling fluid is a cooling liquid and the pump 202 is adapted to pump the cooling liquid through the tubes 206, flow channel 1 15 and the heat exchanger 204 as illustrated by flow arrows 21 7. 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 206 and be feed into the flow channel 1 15 where the cooling fluid and the converting material passes the pumping window 1 18 and the emitting window 120. Heat generated by the converting material during to light converting process will be removed from the converting area by cooling fluid and heated converting material will also be removed from the converting area 122. The removed cooling fluid and converting material will be replaced with cold cooling liquid and cold converting material. As a consequence the converting material poisoned in the converting area 122 can be keep at low and stable temperature and it is thus possible to pump the converted material very intense with pumping light. The heated cooling liquid and heated converting material then flow to the heat exchanger 206 where the heat is removed from the cooling liquid and the cooled cooling liquid is then feed back into the flow channel 1 15 and the converting area 122. 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.

In this embodiment the pump 202 is adapted to run continuously and the cooling fluid and converting material situated at the converting area as this constantly replaced with cold cooling fluid android converting material. The flow rate of the cooling fluid and converting material through the converting area are regulated by the pumping rate of the pump 202 and are adapted to flow at a rate allowing the converting material to convert the pump light into converted light at least one time while passing the the emitting window 120.. Most converting material is able to convert the pumping light within micro seconds and it is thus possible to arrange the emitting window above the pumping window as the converting light converts the pump light into converted nearly instantly. However it is noted that the converting material having relatively long converting time may also be used and that in this case the emitting window and pumping window are displaced in relation to each other such that the emitting window is positioned down stream of the flow direction. The amount of displacement depends on the flow rate and the conversion time of the converting material and can be determined according to this. It is further noted that the pump also can be adapted to work in predetermined intervals such that in a first interval the pump is active whereby cooling fluid and converting material is pump into the converting area and in a second interval the pump is stooped whereby the cooling fluid and converting material are keep inside the pumping area. The first and second interval can then be repeated a number of times. During the second interval the cooling fluid and converting material are heated due to the converting process and the length of the second interval can be adapted in order to achieve maximum illumination for instance by activating the pump when the converting material becomes hot, whereby heated converting material is replaced with cold converting material. The length of the second interval can be predetermined and set to a fixed time for instance based on the expected time it take the converting material to reach an unacceptable temperature. However it is also possible to provide an adaptive adjustment. For instance the length of the second interval can be regulated based on the temperature of the converted material within the converting area. A temperature sensor can measure the temperature of the converting material within the converting area and the pump can be activated when a certain temperature have be archived. Alternatively the adaptive adjustment the interval length can be based on light sensor measuring the intensity of the converted light and the pump can for instance be activated when the light intensity drops.

Alternatively the cooling fluid may also be a cooling gas which is blown through the flow channel by a blower (not shown) and where heat is removed from the converting area in a similar way. It is also possible to use the cooling fluid to cool the pumping light sources for instance by mounting the pumping light sources on a heat sink comprising a source flow channel and then integrating this heat sink into the liquid cooling system shown in fig. 2. An additional loop comprising the source flow channel of the heat sink whereon the pump light source is mounted and followed by an additional heat exchanger can be included in the cooling system. This loop can be included between the heat exchanger 204 and the flow channel 1 15. Heat will then dissipate from the pump light source to the cooling fluid when the cooling fluid flows through the source flow channel and the heat can then be removed from the cooling fluid by the additional heat exchanger prior flowing into the flow channel 1 1 5.

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 1 07 (illustrated as small dots) dispersed in a cooling fluid and adapted to convert 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 illumination device comprises a cooling arrangement 313 comprising at least one flow channel 1 1 5 wherein a cooling fluid can flow as illustrated by flow arrows 1 1 7. The cooling fluid and converting material flow in a flow channel 1 15 comprising a pumping window 31 8 and an emitting window 320 where a converting area 322 is formed between the pumping window and the emitting window. The pumping window 31 8 is transparent to the pumping light 105 and at least a part of the pumping light can as a consequence enter the converting area 322 and be converted into converted light 109 by the converting material flowing with the cooling fluid. The pumping window 318 is further adapted to reflect the converted light 109 and backward emitted converted light (like 1 09") will thus be reflected forwardly by the pumping window. This can for instance be archived by embodying the pumping window as a dichroic filter or by arranging a dichroic filter at the inside or outside of the pumping window. It is to be understood that the dichroic filter must be transparent to the pumping light and reflecting the converted light. The emitting window 320 is transparent to the converted light 109 and at least a part of the converted light can as a consequence exit the flow channel 1 1 5 through the emitting window and can be used for illumination purposes. Further the emitting window 320 is adapted to reflect pumping light and pumping light 105' not which passes through the converting material as described above will be reflected back into the converting material where it can be converted into converted light. However it is noted that the emitting window 318 also can be transparent the pumping light if the some of the pumping light is wanted in the outgoing illumination.

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 1 5 and converting area 322 is formed between the upper and lower surfaces of the hollow dish and the cooling fluid is let into the flow channel 1 1 5 through the inlet 323 and let out through the outlet 325. The bottom surface of the hollow disc constitutes the pumping window 318 and the top surface constitutes the emitting window 320.

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. The edges of the hollow disc do also act as pumping windows 318 and a part of the pumping light 305 from the edge pumping light sources 303 will be transmitted through pumping window at the edge to the converting material 107 and be converted into converted light. This embodiment makes it possible to illuminate the converting material with pumping light usingmany pumping 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.

Fig. 4a-d illustrate another embodiment of an illumination device 401 according of the present invention, where fig. 4a is a top view, fig. 4b is a top view with converted light collector 429 removed, fig. 4c is a cross sectional view through line C-C in fig. 4a and fig. 4d is a cross sectional view through line D-D in fig. 4a. This illumination device 401 is similar to the illumination decide 301 illustrated in fig. 3a- 3c and like elements are illustrated with the same reference numbers in fig. 3a-3c. Like the illumination device in fig. 3a-3c a number of pumping light sources 403 arranged on PCB 41 1 are adapted to emit pumping light 105 into the converting area 322 inside the hollow disc through pumping windows 318 at the bottom side and edged of the hollow disc. Pumping light collectors 427 are further arranged above the pumping light sources and adapted to collect pumping light form the pumping sources and to concentrate the collected light into the converting area 322. The pumping light collectors makes it possible to collect more light from the pumping light sources whereby more light can be coupled into the converting area and be converted by the converting material. The pumping light collectors can be any optical means, like TIR lenses, reflectors, color mixers, optical lenses etc. capable of collecting pumping light and deflecting the pumping light in a predetermined manner in order to couple more pumping light into the converting area 322. In the illustrated embodiment the pumping light collectors are embodied as a number of TIR lenses arranged above a number of pumping LEDs 403. The TIR lenses may be identical or individually designed in order to adapt the lenses to the individual pumping light soruces. Further a converted light collector 429 have be arranged above the emitting window 320 and it adapted to collect the converted light emitted through the emitting window and convert the collected converted light into a light beam having a predetermined diverges and beam width. The converted light collector can be embodied as any optical means capable of collecting the converted light and transforming the converted light into a light beam and can for instance be optical lenses, TIR lenses, light mixers such as light rods etc. In the illustrated embodiment the collected light collector is embodied as a light rod embodied of a solid transparent material and the converted light will be transmitted through the light rod and be mixed into a homogeneous and uniform light beam.

Fig. 5 illustrates another embodiment of the illumination device 501 according of the present invention. In this embodiment flow channel 515 is formed as a u- shaped channel 515 where the cooling fluid comprising the converting material 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. The flow channel 515 enters an elliptic or parabolic dichroic reflector 531 and the pumping window 518, emitting window 520 and converting area 522 are situated inside the dichroic reflector. 522. The dichroic reflector is adapted to reflect converted 509 light and to transmit pumping light 505. In this embodiment the pumping window 518 and emitting window 520 constitute the same part of the flow channel and this part is thus transparent to both the pump light and the converted light. The pump light sources 503 are positioned outside the dichroic reflector 531 and adapted to illuminate the light converting material through the dichroic reflector 531 and the pumping window 51 8. The pumping light will be converted into converted light 509 inside the flow channel and the converted light will be emitted through the emitting window 520. 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 531 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. 6 illustrates another embodiment of the illumination device 601 according of the present invention. In this embodiment flow channel 615 is formed as a u- shaped channel 615 where the cooling fluid comprising the converting material 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 617. A TIR lens 633 is arranged above the u-shaped flow channel such a part of the u-shaped flow channel is positioned inside a cavity 635 delimited by a central part 637 and a surrounding part 639 of the TIR lens. A pumping source 603 is positioned below the u-shaped flow channel and adapted to emit pumping light 605 into the u-shaped flow channel through a pumping window 61 8. The pumping light is converted into converted light 609 inside the converting area 622 and emitted into the TIR lens through a emitting window 620. The TIR lens will collect most of the converted light as it surrounds the emitting window and is also able to collect converted light emitted sideways through the emitting window. The light source can be covered by a dichroic filter which is adapted to transmit pumping light and reflecting converted light, whereby backward emitted converted light is reflect forwardly ad can be collected by the TIR lens 633.

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 further comprising at least one flow channel wherein a cooling fluid flows, said flow channel comprises at least one pumping window transparent to said pumping light and at least one emitting window transparent to said converted light and said cooling fluid comprises said converting material.

2. An illumination device according to claim 1 characterized in that said flow channel is connected with a heat exchanger and a pump, and that said pump is adapted to force said cooling fluid from said pumping window and said emitting window to said heat exchanger and said heat exchanger is adapted to remove heat from said cooling fluid.

3. An illumination device according to claims 1 -2 characterized in that at least a part of said converting material is mixed with said cooling fluid.

4. An illumination device according to claims 1 -3 characterized in that at least a part of said converting material is dissolved in said cooling fluid.

5. An illumination device according to claims 1 -4 characterized in that said converting material is a phosphor material.

6 An illumination device according to claim 1 -4 characterized in that said converting material comprises quantum dots.

7. 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:

• dispersing said converting material in a cooling fluid;

• forcing said cooling fluid through a flow channel comprises at least one pumping window transparent to said pumping light and at least one emitting window transparent to said converted light;

· transmitting at least a part of said pumping light through said pumping window and to said converting material; and

• transmitting at least a part of said converted light through said emitting window.

8. A method according to claim 7 characterized in that said step forcing said cooling fluid through 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 back to said flow channel.