WO2006102846A1

WO2006102846A1 - High efficient light coupling of solid-state light source into etendue maintained optical waveguide/fiber

Info

Publication number: WO2006102846A1
Application number: PCT/CN2006/000552
Authority: WO
Inventors: Yi Li; Li Xu
Original assignee: Yi Li; Li Xu
Priority date: 2005-04-01
Filing date: 2006-03-30
Publication date: 2006-10-05
Also published as: CN1847898A; CN100501476C

Abstract

A brightness maintaining low loss fiber delivering light system includes solid-state light emitting device, such as but not limited to LED; mounting base assembly for the light emitting device; a low loss light collecting assembly, structure integration assembly; optical waveguide such as fiber; and a fiber combiner in the system with multiple light emitting devices. The light emitting device, light collecting assembly and fiber are bonded directly to each other or by optically index matching transparent material. The etendue of the light emitting device and the fiber are selected so that the light brightness through the system is maintained or even increased. The light collecting assembly may use a high reflective coating surface or the total internal reflection at an interface. The system of multiple fibered light emitting devices output includes each individual brightness maintaining low loss fiber delivering light unit and the combiner of multiple fibers. This combiner can be fibers bundled together or fused together. The fiber core bundle or fused fiber core bundle includes a light concentration assembly as an alternative.

Description

High Efficient Light Coupling of Solid-state Light Source into Etendue Maintained Optical Waveguide/Fiber

Field of Invention

This patent application relates to lighting devices, systems, and techniques.

Background Art One of the most import applications for light sources is to provide high brightness and high power output at the same time. One example is the light source for image projection such as a rear projection TV (RPTV) or front projector. Another example is the headlights or illumination lights for transportation vehicles such as automobiles, motorcycles, boats and airplanes. Currently, the light sources for these and other applications are still dominated by traditional arc lamps such as high-pressure mercury lamps, Xenon lamps or metal halide lamps. However, many arc lamps exhibit certain technical limitations in applications, e.g., relatively short lifetimes, difficulty in control and maintenance of the light color, instablility.especially when operating in the pulsed mode. For many applications, especially in the environment where the heat or electricity is forbidden, the light coupling from the light source coupling into optical fiber or waveguide is required. However, the coupling from the arc lamp into fiber can becostly, bulky, inefficient and unstable due to, e.g., the change of discharge arc itself from time to time. In many cases, the arc lamp also potentially interferes with other components in the system.

Solid state light sources, especially light-emitting diodes (LEDs), exhibit the longer lifetimes, lower power consumption, manageable wavelengths and other benefits in comparison with the above and other traditional light sources.

Therefore, these solid-state light sources increasingly, become the alternative or even preferred choice of light sources for a variety of applications. However, there are a number of LED perfoπnance parameters that need to be improved so that LEDs can further broaden their applications. Currently, the LED light sources can offer two potential solutions for high brightness and high power applications. For example, the performance of an individual LED chip may be improved by increasing the chip dimension and improving it's the LED chip quality. However, this approach is limited by the total output of one individual chip and many, currently available LED chips are limited in their output in tens of lumens in the visible wavelength region. Going to larger area chips and higher driving currents may increase the total output but can compromise the device lifetime and brightness due to various technical issues in such LED chips including chip un-uniformity and the problem of thermal dissipation of large LED chips. One alternative approach to LEDs with high brightness and high power output is to package many LED chips together in an array structure to obtain high total output, e.g., up to hundreds even thousands lumens in some LED array chips in existence today. The brightness of light directly from LED array is significantly lower than that of a single LED since the array brightness is limited by the relatively low package density of LEDs in the array. The major challenge of high-density LED packaging is the thermal management of the high power operation of LEDs since the LEDs interferes each other thermally when located too close to each other on a common chip. For the above and other reasons, many existing LED light sources are not suitable for applications demanding high brightness and high power at the same time, and traditional light sources such as high pressure mercury lamp or metal halide lamp are still the choice for such applications.

It is known to optically couple an LED into fiber and optical waveguide by abutting the end of fiber or waveguide against the LED. However, in most of cases when the acceptance angle of fiber or waveguide is small comparing to the large LED emission angel, the coupling efficiency is very low practically even when the etendue of light source such as LED is matched with the fiber or waveguide. It is also well known to optically couple LED into fiber and optical waveguide by lenses and reflectors with high efficiency. However, the alignment of lenses and reflector with fiber is difficult and therefore expensive especially when array of LEDs involved. In addition, the brightness of light decreases significantly due to the etendue mismatch of LED and fiber. Furthermore, the light emission devices usually have rectangular shape and fiber or waveguide have circular shape in reality. This shape miss match can further reduce the coupling efficiency and light brightness.

Thus, there is a need for one single light source with high brightness and high power output with low power consumption, long lifetime, cost effective, compact, stable and well controlled in color, continuous wave (CW) or pulsed and other operating performances. Another need is to couple light emitting device into fiber, fiber bundles and waveguide to achieve the features that is desired by fibered light source. Another need is to coupling light from light emitting device(s) into fiber or waveguide with high efficiency and little loss in brightness.

Summary

This application describes, among others, designs and techniques for highly efficient light coupling from one or more solid state light sources into etendue matched optical waveguide/fiber. For example, a device is described to include a solid-state light source to emit light; an optic fiber having an optic etendue smaller than or equal to an optic etendue of the light source; and a light collecting assembly engaged between the light source and the optic fiber and operable to collect and couple the emitted light into the optic fiber. In this device, the light collecting assembly is formed of a material having a refractive index between refractive indices of the light source and the optic fiber. In some implementations of the described designs, a LED or multiple LEDs may be packaged into one single light output that offers the best combination of small etendue, high brightness, large flux, stability and reliability that is allowed by principles of optics. The designs and techniques described here may be used to provide one single light output with low loss of brightness and flux from one or multiple light emitting devices by optically coupling of one or multiple light emitting devices such as LED(s) into single or multiple fiber or waveguide. This high brightness light system includes light-emitting device such as but not limited to LED chip, LED chip mount assembly, light collecting and collimation assembly, structure integration assembly and optical waveguide or fiber. One aspect of some described examples is the high brightness and high power light system includes multiple high brightness devices mentioned above and the fiber combiner which combines the multiple light output into single one with little loss in brightness and power. In this regard, the described designs and techniques may be used to provide a low cost, high efficient and brightness maintaining light source with easy beam delivering that can be mass produced by means of micro-replication or injection molding and standard fiber coupling.

For case of one light emitting device such as but not limited to LED coupling into fiber, the etendue of light emitting device and the etendue of the normal surface of fiber should be closely matched so that the brightness of light can be maintained. The size and geometry of light emitting device are significantly different from fiber: rectangular vs. circular in most cases. In order to obtain high efficiency coupling into fiber, a light collecting and collimating assembly is required. One side of this assembly is attached to the light emitting device directly through index match epoxy or gel. Other side of the assembly is bonded directly to the etendue matched fiber or waveguide mentioned above or bonded through index match material such as epoxy or gel. Most of the light will be confined inside the assembly through reflection of high reflection surface coating or total internal reflection. To obtain high coupling efficiency from light emitting device to fiber or waveguide, one should choose the material with optimized index of refraction: between that of light emitting device and fiber or waveguide. This assembly can be a solid transparent material on the wavelength of the light from light emitting device. When the light emitting device is LED, LED chip mount assembly can be provided for heat dissipation, electric wiring/contact and even electronics. To achieve mechanical and environmental stability and durability, an integrating assembly can be used to structurally hold all above components together. The separation between adjacent LED chips can be kept sufficiently large to avoid thermal interaction between adjacent LED chips.

When multiple emitting devices are used, one single light output can be achieved by integrating the single light emitting device fiber output mentioned above together through the fiber combiner to combine output beams from different light emitting devices. The individual light emitting devices can be separate so that they are thermally independent to each other. Due to the flexibility of fiber, the combinercan be a simple fiber bundle by directly packing the fiber together. The output surface is a polished surface of condensed packed fibers. Due to the finite size of cladding layer of fiber, the etendue of the total output from fiber bundle increases comparing to the sum of each individual fiber output. To overcome this, the present invention suggests using fiber core bundle by removing individual fiber's cladding layer. The lights propagating in each fiber from different LED is coupled to adjacent fibers since the cladding layers are removed. With appropriate length of propagation in this fiber core bundle, the unevenness of light intensity due to output power and distribution is significantly reduced. To achieve better spatial uniform light output in shorter distance, optically transparent material with matched index of refraction can be used to fill the gaps among the fiber core. An alternative method to achieve the similar result is to fuse all these fiber cores or fibers together so that no gaps exist. Furthermore, the shape of the output fiber bundle, core bundle or fused core bundle can be shaped to the desired geometry such as but not limited to rectangular, triangle, oval, etc. When the fiber cladding layer removed, the etendue of the each fiber increased. However, the brightness of each fiber output does not change significantly. Therefore, an optical component such as but not limited to solid compound parabolic concentrator (CPC) using an optical material that is optically transparent and index matching to fiber core can be used to increase intensity at output surface of single fiber or fiber core bundle by directly contacting fiber core to the lager aperture side of the CPC. When the power loss of whole system is low, the brightness of light output from the combiner is maintained at the same level as single light emitting device.

One implementation of the described designs and techniques provides coupling one light emitting device into the multiple fibers or waveguides through a coupling assembly that maintains the brightness with high coupling efficiency. The etendue of light emitting device and the etendue of the normal surface of multiple fibers should be closely matched so that the brightness of light can be maintained. One side of this coupling assembly is attached to the light emitting device directly through index match epoxy or gel. Other side of the assembly is bonded directly to the etendue matched fiber bundle or its variations such as bundled fiber core, bundled fiber core filled with index matching epoxy or fused fiber cores that is mentioned above. Most of the light will be confined inside the coupling assembly through reflection of high reflection surface coating or total internal reflection. To obtain high coupling efficiency from light emitting device to fibers or waveguides, the material can be selected to have an optimized index of refraction which is between the index of the light emitting device and the index of the fiber or waveguide. This coupling assembly can be a solid transparent material on the wavelength of the light from light emitting device. When the light emitting device is LED, LED chip mount assembly can be used for heat dissipation, electric wiring/contacts and even electronics. For the other side of the multiple fibers, it can be fiber bundle with cladding or its variations such as bundled fiber core, bundled fiber core filled with index matching epoxy or fused fiber cores fiber core bundle. When multiple of light emitting devices are required in this case, the multiple fiber bundles or it variations can be further combined through putting all these bundles together repeatedly through simple fiber bundle with claddings or its variations such as bundled fiber core, bundled fiber core filled with index matching epoxy or fused fiber cores.

Brief Description of Drawings FIG. 1 is a longitudinal section schematic view of the apparatus of a light emitting device coupled into an optic fiber

FIG. 2 is a longitudinal section schematic view of an alternate embodiment of the invention shown in with supporting structure

FIG. 3 is a longitudinal section schematic view of another alternate embodiment of the invention shown in with integrating structure where the light is collected by high reflective surface

FIG. 4 is a longitudinal section diagram of the apparatus of multiple light emitting devices coupled into multiple optic fiber

FIG. 5 is a longitudinal section diagram of an alternate embodiment of the apparatus of multiple light emitting devices coupled into multiple optic fiber with cooling tunnel

FIG. 6 The schematic of the light source with multiple light emitting devices

FIG. 7A is the cross section of densely packed optical fibers FIG. 7B is the cross section of densely packed optical fiber cores

FIG. 8A is the cross section diagram of densely packed fiber cores with index matched transparent material filled in the gaps

FIG. 8B is the cross section diagram of fused fiber core bundle FIG. 9 is a longitudinal section schematic view of an alternative embodiment of the invention showing the apparatus of a light emitting device coupled into multiple optic fibers FIG. 10 is a schematic view of the light source shown in FIG. 9 with multiple light emitting devices

FIG. 11 is a longitudinal section schematic view of the light source with array of embodiment shown in FIG. 9 FIG. 12 is the schematic longitudinal section of waveguide bundle with low loss CPC to reduce the output aperture size and increase light intensity. Active material can be located at this high intensity area for light generation of different wavelengths.

FIG. 13 is the apparatus for light collimating or collection of the light generated from active material.

FIG 14 is the circuit schematics of LED light source

FIG. 15 is a schematic diagram of one embodiment of a projection system with single light modulator.

FIG. 16 is a schematic diagram of one embodiment of a projection system with multiple light modulators

FIG. 17 is a schematic diagram of one embodiment of headlights or illumination system for transportation vehicle.

Drawings - Reference Numerals 100. Base plate for light emitting device

102. Light emitting device such as LED chip

103. Lead wires for providing electric power to light emitting device

104. Light collecting assembly 105. Electrical contact on base plate

106. Index-matched and optically transparent material 108. Optic fiber 110. Reflector connector 112. Supporting structure 114. Bonding material between base plate 100 and supporting structure 112 116. Core of optical fiber 108

118. Cladding layer of optical fiber 108

120. Reflector body

122. Reflector surface with high reflection to the light from light emitting device

124. Tunnel for cooling flow

150. Individual fibered light emitting device

154. Fiber bundle

160. Light beam emitted from 102 162. Light beam emitted from 102

170. Output port of fiber bundle 154

171. Input port of fiber bundle 154 205. Fiber bundle with claddings 210. Fiber core bundle 220. Fiber core bundle with index matching material 106 in the gap

230. Fused fiber core output

151 The coupling assembly that collect and re-direct the light from one LED into multiple fibers or waveguides

260. The optical assembly that increase output light intensity from 154 by reducing the aperture size

262. Active material such as phosphor or quantum dots material

264. Optical filter that pass the light from the light emission devices but reflects the light generated by 262.

268. An optical assembly providing a light collection or collimated beam for the light generated from 262.

300. Light source with multiple light emitting devices such as

LED.

302. LED array

304. Light sensor

306. Temperature sensor

308. The driving circuit of LED arrays 310. Signal feedback loop from light sensor 304 to driving circuit 308

312. Signal feedback loop from temperature sensor 306 to driving circuit 308 320. Heat dissipation and cooling system

400. The signal processor that receiving image signal, provide commands to light sources and micro-display devices

402. Driving signal connection from processor 400 to Light sources

404. Feed back signal connection from light source to processor 400 406. Signal connection between signal processor and micro-display

410. Field lens

420. Dichoric cross prism

430. Light modulator

440. Projection lens 450. Light controller

460. Optics assembly collecting and redirecting the light output from 154 into desired pattern

Detailed Description of Exemplary Implementations

Various implementations of designs and techniques are described as examples to illustrate various features of the designs and techniques. It is understood that elements not specifically shown or described may take various forms, for example, certain designs that may be well known to those skilled in the art.

FIG. 1 illustrates an apparatus of a light emitting device coupled into an optic fiber. The apparatus comprises a light emitting device such as LED 102, a base plate for light emitting device 100, lead wires for providing electric power to light emitting device 103, a light collecting assembly 104, an optic fiber 108, and index-matched and optically transparent material 106. Light emitting device 102 is bonded to base plate 100. Base Plate 100 serves as either anode or cathode to provide electric power to light emitting device 102 through electrical contact 105. Lead wire 103 , serving as cathode or anode, is connected to light emitting device 102 on one side. The other side of 103 is bonded to electrical contact 105. Light emitting device 102 emits light when it is electrified by the current provided by base plate 100 and lead wire 103. The light emitting device 102 directly converts electric energy into light energy, and, at the same, also generates heat energy. Base plate 100 may be used as a primary source to dissipate the heat generated from light emitting device 102. In some implementations, the base plate 100 may be a high thermal-conductive material to dissipate the generated heat, such as aluminum, copper, thermal conductive ceramics including alumina nitride. To improve the brightness of light emitting device 102, the reflective property of base plate 100 should be considered. A gold and silver plating can be applied to base plate 100. To reduce the cost, base plate 100 can be made in array forms.

Light rays 160 emitted from light emitting device 102 can be directly coupled to optic fiber 108, by transmitting through index-matched media 106. Index-matched media 106 can be used to efficiently reduce Fresnel loss occurring at joins with an air gap. The index of index-matched media 106 should be closely matched to the index of optic fiber 108. The value of its index may range from 1.3 to 1.7 in some implementation. Index-matched material can be made of an optic transparent material, such as optic plastic or glass. A thermal curing or UV curing or thermal-UV combined curing adhesive can be chosen as the index-matched material 106 as well. Light 162 emitted from light emitting device 102 can be directly coupled to optic fiber 108without the light collecting assembly 104. In absence of the light collecting assembly 104 however, the coupling tends to be inefficient and thus a significant amount of the light 162 can be lost. Light collecting assembly 104 is designed to reduce or minimize the optical coupling loss and can be implemented in various configurations. The surface shape has smooth curvature such as but not limited to compound parabolic. Three examples of such configurations are : 1) a monolithic solid piece using index matched transparent material with polished surface; 2) a monolithic solid piece using index matched transparent material with polished surface and reflective coating such as silver, gold, or aluminum coating on the side surface; 3) a reflective cup, made of metal or plastic with the reflective coating such as silver, gold, or aluminum coating on the inner surface, while the cup is filled with index matched transparent material. Light 162 is reflected by the reflective layer at the side surface of 104 (variations 2 and 3) or by the total internal reflection at the side surface of 104 (vairationl), and then coupled into optic fiber 108. Notably, the light coupling assembly 104 is structured and designed to closely match the etendue of optic fiber 108 to the etendue of light emitting device 102 . This may be achieved by , e.g., selecting the suitable numerical aperture (NA) and core size of optic fiber 108 because the etendue for an optical device is the product of the numerical aperture and the aperture dimension or spot size of the optical device which is 108 or 102. Optic fiber 108 can be made of optic glass such as quartz or optic plastics or polymer. Optic fiber 108 can have a cladding- surrounding core or simply just have core material without cladding.

In some implementations, the etendue of optic fiber 108 may be less than the etendue of light emitting device 102 to improve the brightness at the end surface of optic fiber 108. Since the light emission pattern of light emitting device 102 can be non-uniform and at certain emitting angle the radiation intensity is greater than at other angles, a smaller etendue optic fiber 108 can effectively collect the lights at the angle where the radiation intensity is greater. As a result, the brightness at the end surface of optic fiber 108 can be greater than the averaged brightness of light emitting device 102. The positions of optic fiber 108 and light collecting assembly 104 need to be adjusted to obtain the maximum light output of light emitting device 102 into optic fiber 108. In another embodiment illustrated in FIG. 2, a supporting structure 112 is bonded to base plate 100 with bonding material 114. Bonding material 114 adheres supporting structure 112 to base plate 100 and dissipates the heat from base plate 100 to supporting structure 112. In this embodiment, optic fiber 108 has a cladding layer 118 surrounding the core layer 116. As a result, optic fiber 108 can be in direct contact to supporting structure 112. To further hold optic fiber 108 more stable, additional adhesive can be applied between supporting structure 112 and 118. A reflector connector 110 is inserted between light collecting assembly 104 and supporting structure 112 to hold light collecting assembly 104 with respect to supporting structure 112. The supporting structure 112 will serve as a register to light collecting assembly 104 and optic fiber 108. The out-diameters of light collecting assembly 104 and optic fiber 108 should match well to the inner-diameter of supporting structure 112. As a result, the assembly process of the whole package can be automated.

FIG. 3 shows another embodiment of the device illustrated in FIG. 2. A reflector 120 can be made of metal or plastic with a high reflective surface 122 inside. The high reflective surface 122 is shaped to reflect lights out of light emitting device 102 into optic fiber core 116. In one embodiment, the light emitting device 102 can be LED whose electrical connection is not through conducting wire but via a direct contact to the electrical contact 105 on the substrate. In one embodiment of the LED substrate is the printed circuit board with high heat dissipation or low thermal resistance. In one embodiment of the LED without wire-bonding is the thin-film type LED or OLED. The registration step is constructed so that the end surface of 108 can be aligned to the end surface of 122. Reflector 120 can be bonded to base plate 100 with a thermal-conductive material which facilitates the dissipation oflthe heat from base plate 100. In this particular design, the reflector 120 functions as a light collecting assembly, a supporting structure, and a heat sink. The reflector 120 may be designed part of the pre-assemble substrate PCB for volume production.

FIG. 4 shows another embodiment of the device illustrated in FIG. 3. Multiple light emitting devices are bonded on base plate 100. Reflector 120 has the corresponding number of multiple high-reflective surfaces 122 and optic fiber 108. Therefore an array of light emitting devices can be packaged with one reflector 120. The spacing between two adjacent light emitting devices 102 can be large enough so that the heat generated from individual light emitting device 102 will effectively dissipate to base plate 100 and will not be transferred to the adjacent light emitting devices. In other words, the packaging density of light emitting device should be small enough to avoid thermal interference.

FIG. 5 illustrates another embodiment of the device shown in FIG. 4. A cavity or tunnel 124 is inserted in reflector body 120 between two reflective surfaces 122. Tunnel 124 can be applied with a forced cooling flow such as air or a coolant. As a result, the heat generated form light emitting device can be effectively dissipated and carried away by the cooling flow. Thermal interference among light emitting devices can be further reduced.

FIG. 6 illustrates another embodiment of a light coupling device for coupling light from different LEDs. The output end of multiple optic fibers 108 are closed packaged together into a fiber bundle 154 and to direct the light to the output port 170. The various configurations of the output port 170 of fiber bundle 154 are illustrated in FIG. 7A, 7B, 8A, and 8B. FIG. 7A shows a cross section of densely packed optical fibers 108 with core 116 and cladding layer 118. FIG. 7B shows the cross section of densely packed optical fiber bundle 210. Within the bundle 210, cladding layers of optic fiber 108 are removed to reduce the size of the fiber bundle. Moreover the shape of output port 210 can be any shape such as circle, rectangular, etc. FIG. 8A shows the cross section diagram of densely packed fiber bundle 220. Within fiber bundle 220, cladding layers of optic fiber 108 are removed and index matched transparent material 106 are filled in the gaps among fiber cores 116. As a result the lights can transverse from one fiber to other fibers. The output port of fiber bundle can function as a light integrator to provide a uniformed light output across the output surface. Moreover the shape of output port 230 can be any shape such as circle, rectangular, etc. FIG. 8B shows the cross section diagram of fused fiber core bundle 230 by fusing multiple bare fiber cores 116 together. By fusing the fibers together, the fibers are maximum densely package together. Moreover the shape of output port 230 can be any shape such as circle, rectangular, etc.

FIG. 9 illustrates another embodiment of an LED device with one light emitting device coupled to multiple fibers or waveguides. This device is similarly constructed as the devices described in FIG. 1, 2, 3, 4 and 5 except that the light is coupled into multiple fibers. The coupling assembly 104 can be one of the coupling assemblies described in FIG. 1, 2, 3, 4 and 5. Coupling assembly 104 collects and re-directs the light into fiber bundle 154 through 171. FIG. 10 is another embodiment for the light source which includes multiple devices described in FIG. 9. The fiber bundle from each LED is combined into a larger bundle. The output of this large bundle is in form of 170. FIG. 11 is a longitudinal section schematic view of the light source with array of embodiment shown in FIG. 9.

FIG. 12 illustrates another example of a device. The particular geometry of the light coupling assembly 260 is designed to further reduce the output aperture size. The output port of fiber bundle 154 can be in a shape of spherical, aspherical and free form. The material of the assembly 260 may be the same as fiber core or other optically transparent material with matched index of refraction as fiber core. Moreover, an active material 262 such as a phosphor and quantum dots can be filled in the output port 260. When the light emitting devices emits blue or UV lights, the phosphor or quantum dots within output port 260 absorb the lights from the light emitting devices and emit lights in other wavelengths. An optical filter 264 is place before the active material 262to transmit the light from light emission devices (e.g., blue or UV wavelength) and to reflect the light generated from active material 262. the filter 264 can prevent the generated light propagating back to the fiber and increase light generating efficiency.

FIG. 13 is another embodiment. An optic reflector 268 is attached to the active material 262. Optic reflector 268 collects the lights generated from 262 and redirects the lights to a collimated beam or projected to a specified object.

FIG. 14 illustrates a light source assembly including one LED 102 or LED array 302 of multiple individual LEDs, light sensors 304 for monitoring lights emitted from LED 102 or LED array 302, and temperature sensor 306, electric driving circuit 308, and heat dissipation/cooling assembly 320. For system with multiple LEDs, the individual LED 102 is electrically connected in parallel or serial or parallel-serial configuration. When the separation among individual LED is large enough, the forced cooling is not required. Light sensor 304 is placed inside the light source assembly to monitor the wavelength and intensity of the lights emitted from the LED. Multiple light sensors can be applied to monitor different wavelengths of lights emitted from LED array 302. A typical light sensor can be silicon photodiodes with color filters such as Red, Green or Blue filter. The photo diodes with color filters can monitor the light intensity of various color LED such Red, Green, or Blue LED. By feeding back the intensity of the emitted lights at certain color through the feed back loop 310, the electrical driving circuit can adjust the input current to the corresponding color LEDs. Therefore the close-loop feed back system can adjust color temperature of the lights emitted from LED array. Another function of the feed back system consisting of 302 and 310 is to maintain a constant light intensity of the emitted light. When the monitored light signal is decreased due to various reason including thermal, aging, etc, electrical driving circuit 308 will increase the input current of 102 or 302 to compensate the light decrease. Temperature sensor 306 is also placed on the LED base-plate, monitoring the temperature of the LED base-plate and providing driving circuit the feedback signal through the feed back loop 312. With the feedback, electrical deriving circuit 308 will change the setting of heat dissipation/cooling assembly 320. As a result, the temperature of 102 or 302 can be maintained as constant. The electrical driving circuit can provide constant or pulsed electric output for specific applications.

FIG. 15 is a schematic view of a projection system using a LED light source. The projection system can have three LED light sources 300 for Red, Green, and Blue. Lights emitted from 300 are directed to field lens 410 via fiber bundle 154. The flexibility of fiber bundle 154 offers an easy packaging layout for the projection system. Dichoric cross-prism 420 directs the red, green, and blue light to light modulator 430. Light modulator can be of a MEMS (micro electronic mechanical system) device (for example DLP from Texas Instrument) or liquid crystal device (LCD or LCoS). Signal process 400 will synchronize light source 300 and light modulator 430 through connect loop 406. For example, Signal process 400 will send the red image data to light modulator 430 when the red light source 300 is turned on and emitting red light. Similarly, signal process 400 will send the green and blue image data to light modulator 430 when the green and blue light source 300 is turned on and emitting green/blue light, respectively. If all red, green and blue light source 300 is turned on, a gray image data is sent to light modulator 430. As illustrated in the invention shown in FIG. 14, the feed back loop 402 and 404 can maintain the color and brightness stability and adjust the color temperature of projected images. FIG. 16 is a schematic view of another projection system using a LED light source. The projection system can have three LED light sources 300 for Red, Green, and Blue. Lights emitted from 300 are directed to field lens 410 via fiber bundle 154. The flexibility of fiber bundle 154 offers an easy packaging layout for the projection system. Three light modulator 430 are place to the three input sides of dichoric cross prism 420. Light modulator can be of a MEMS (micro electronic mechanical system) device (for example DLP from Texas Instrument) or liquid crystal device (LCD or LCoS). Red, green, and blue light emitted from fiber bundle 154 will be modulated by 430 will be either reflected by or transmit through 420 and be directed to projection lens 440. As illustrated in the invention shown in FIG. 13, the feed back loop 402 and 404 can maintain the color and brightness stability and adjust the color temperature of projected images.

FIG. 17 is a schematic view of another application of the invented LED light source. An illumination system for transportation vehicle is based on the current light source invention. This white light generated from invention 154 is collected and re-shaped by optics 460 to generate the desired illumination distributions. The light control 450 receives and processes the command signal from external source, and then provides the driving electrical power to the light source 300. A feedback signal from light source goes into light control for best performance and life-time of the system.

The above described devices and techniques may be implemented to achieve certain advantages. For example, some implementations of the packaging of LED offer efficient coupling of lights out of LED or LEDs into optic fiber or fibers while maintain the etendue. As another example, a low cost and easy-scalable manufacturing process may be devised based on the described designs and techniques. As yet another example, the described packaging of LED may be used to provide efficient thermal conductibility from LED chips to the base plate to dissipate the heat generated by the LED While this specification contains many specifics, these should not be construed as limitations on the scope of an invention or of what may be claimed, but rather as descriptions of features specific to particular embodiments of the invention. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or a variation of a subcombination. Only a few implementations are described, other variations, enhancements, and modifications may be made based on what is described here.

Claims

1.A device, comprising: a solid-state light source to emit light; an optic fiber; and a light collecting assembly engaged between the light source and the optic fiber and operable to collect and couple the emitted light into the optic fiber, wherein the light collecting assembly is formed of a material having a retractive index between refractive indices of the light source and the optic fiber.; In this device, the optic fiber has an optic etendue smaller than or equal to the optic etendue of the light source.

2.A device as in claim 1 wherein the light source is a semiconductor light source.

3. A device as in claim 2, wherein the light source comprises a light-emitting diode.

4.A device as in claim 1 wherein the optic fiber is a multimode optic fiber.

5.A device as in claim 1 wherein the light collecting assembly has an input port engaged to an output port of the light source, wherein the input port of the light collecting has a geometry that matches the output port of the light source.

6.A device as in claim 1 wherein the light source, the optic fiber and the light collecting assembly directly contact with one another, wherein the light collecting assembly has an output port with a geometry that matches the input port of the fiber whose geometry can be not limited to circular.

7.A device as in claim 1 wherein the light collecting assembly has a smooth curvature surface such as but not limited to solid compound parabolic.

8. A device as in claim I₅ wherein each interface between the light source and the optic fiber and berween the light collecting assembly and the optical fiber is bonded by a thin layer index-matched transparent material.

9. A device, comprising: an array of solid-state light sources; an optic fiber bundle comprising a plurality of optic fibers; and an array of light collecting assembly units engaged between the fiber bundle and the array to couple light from the light sources to the optic fibers, respectively.

10. A device as in claim 9 wherein each light source is a light-emitting diode.

11. A device as in claim 9 wherein the optic fiber bundle has an interfacing section in which optic fibers are fused together.

12. A device as in claim 9, wherein the optic fiber bundle has an interfacing section in which cores of the optic fibers are densely packed together, and wherein the interfacing section comprises an index matching material filled in gaps between the optic fibers.

13. A device as in claim 11 or 12, further comprising: a light concentrator directly connected to an output of the fiber bundle with the concentrator's input aperture size larger than the concentrator's output aperture size so that light intensity will be increased.

14. A device as in claim 13, further comprising: an active material positioned to receive light from the light concentrator and operable to absorb at least a portion of the received light and to emit light at a wavelength different from a wavelength of the received light.

15. A device as in claim9, 10, 11 or 12, further comprising: an active material positioned to receive light from the optic fiber bundle and operable to absorb at least a portion of the received light and to emit light at a wavelength different from a wavelength of the received light.

16. A device as in claim 14 or 15, wherein the active material comprises at least one phosphor material or quantum dots.

17. A device as in claim 15, further comprising an optical filter located between the fiber bundle and the active material and operable to transmit light from the fiber bundle and reflect the light generated by the active material.

18. A device as in claim 14, further comprising an optical filter located between the light concentrator and the fiber bundle and operable to transmit light from the fiber bundle and reflect the light generated by the active material.

19. A device, comprising: a substrate; a solid-state light emitting device formed on the substrate, an optic fiber bundle formed of a plurality of optic fibers having an input end wherein the optic fibers are fused together into a contiguous section which receives light from the light emitting device; and a light collecting assembly unit engaged between the input end of the fiber bundle and the light emitting device to couple light from the light emitting device to the optic fiber bundle.

20. The device as in claim 19, wherein the solid-state light emitting device is a single light-emitting diode with a large light-emitting surface

21. A display system, comprising: a red light source operable to produce a red light beam and comprising (1) an array of red solid-state light sources to emit red light, (2) an optic fiber bundle formed of a plurality of optic fibers, and (3) an array of light collecting assembly units engaged between the fiber bundle and the array to couple red light from the red light sources to the optical fibers, respectively; a green light source operable to produce a green light beam and comprising (1) an array of green solid-state light sources to emit green light, (2) an optic fiber bundle formed of a plurality of optic fibers, and (3) an array of light collecting assembly units engaged between the fiber bundle and the array to couple green light from the green light sources to the optical fibers, respectively; a blue light source operable to produce a blue light beam and comprising

(1) an array of blue solid-state light sources to emit blue light, (2) an optic fiber bundle formed of a plurality of optic fibers, and (3) an array of light collecting assembly units engaged between the fiber bundle and the array to couple blue light from the blue light sources to the optical fibers, respectively; a display modulation mechanism to modulate the red, green, and blue light beams to carry color images; and an optical projection module to project the modulated red, green and blue light beams to a screen to form images.

22. A lighting system for a vehicle, comprising: an array of solid-state light sources producing light from driving currents; a control circuit to supply the driving currents to the light sources and responsive to a control command in controlling the driving currents; an optic fiber bundle formed of a plurality of optic fibers to receive light beams from the light sources; an array of light collecting assembly units engaged between the fiber bundle and the array to couple light from the light sources to the optical fibers, respectively; an active material positioned to receive light from the optic fiber bundle and to emit light at a wavelength different the received light; an optical filter located between the fiber bundle and the active material and operable to transmit light from the fiber bundle and reflect the light generated by the active material; and an optical reflector located near the active material to reflect the emitted light from the active material.

23. A device, comprising: a base plate; a plurality of light-emitting diodes arranged in an array and fixed on the base plate; a plurality of optic fibers coupled to receive light from the light-emitting diodes, respectively; and a reflector body formed over the base plate between the optic fibers and the light-emitting diodes, the reflector body comprising a plurality of reflectors and each reflector positioned between a light-emitting diode and a respective optic fiber to direct light to the respective optical fiber, wherein the reflector body further comprises a plurality of hollow cooling channels to dissipate heat generated by the light-emitting diodes and wherein each hollow cooling channel is positioned between two adjacent reflectors corresponding to two adjacent light-emitting diodes.

24. A device as in claim 23, further comprising a mechanism to supply a cooling air flow or a cooling fluid through the hollow cooling channels in the reflector body to cool the device.