US007744241B2
`
`(12) United States Patent
`Xu
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 7,744,241 B2
`Jun. 29, 2010
`
`(54) HIGH BRIGHTNESS LIGHT SOURCE USING
`LIGHT EMITTING DEVICES OF DIFFERENT
`WAVELENGTHS AND WAVELENGTH
`CONVERSION
`
`(75) Inventor: Li Xu, Saratoga, CA (US)
`
`(73) Assignee: YLX, Ltd. (KY)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 592 days.
`
`(21) App1.N0.: 11/762,581
`
`(22) Filed:
`
`Jun. 13, 2007
`
`(65)
`
`Prior Publication Data
`
`Us 2008/0310845 A1
`
`Dec‘ 18’ 2008
`
`(51) Int. Cl.
`
`F21V 9/16
`
`(2006.01)
`
`F21V 9/00
`(2006.01)
`(52) US. Cl. ....................... .. 362/231; 362/84; 362/235;
`362/583
`
`_
`_
`_
`(58) Field of Classi?cation Search ............... .. ~362/231,
`362/84’ 235’ 293’ 583’ 551’ 239’ 800’ 345/82’
`1_ f 341511831; 398/821’ f5’ 149k Eli/498’ 501
`S
`ee app 102‘ Ion e or Comp e e Seam 15 Dry‘
`References Cited
`
`(56)
`
`U.S. PATENT DOCUMENTS
`
`7,415,210 B2 *
`2007/0047608 A1 *
`
`8/2008 Gurevich et a1. ............ .. 398/86
`3/2007 Volodin et a1. ......... .. 372/5012
`
`FOREIGN PATENT DOCUMENTS
`
`WO
`
`2006/102846 A1
`
`10/2006
`
`* Cited by examiner
`
`Primary ExamineriBao Q Truong
`(74) Attorney, Agent, or Firm4Chen Yoshimura LLP
`
`(57)
`
`ABSTRACT
`
`A Wavelength division multiplexer and etendue conserved
`optics are used to combine multiple Wavelength LED lights
`into a combined light. The combined light, With higher inten
`sity and higher poWer than the light from an individual LED,
`.
`.
`.
`.
`is used to excite a Wavelength conversion material such as
`.
`.
`.
`.
`phosphors to generate a high brightness and high poWer light.
`.
`.
`Light generated by multiple LEDs of the same Wavelength
`b
`1 d- t
`t- l?b b d1 b f
`-
`tt-
`-t
`may e coup e in o a'op ica
`er‘ un e e ore inpu ingi
`into the Wavelength-division multiplexer, further increasing
`the brightness and pOWen The Wavelength Conversion mate_
`rial may generate light of three different color under excita
`tion by different LED lights, or a White light With higher
`brightness and higher poWer. Such a light source can be used
`in image display devices such as a projector or in illumination
`systems.
`
`7,070,300 B2
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`7/2006 Harbers et a1.
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`20 Claims, 3 Drawing Sheets
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`13
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`12-1
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`13-1
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`‘L
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`11-1
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`12-2
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`16
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`Will W
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`14
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`12-2
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`11-3
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`US. Patent
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`Jun. 29, 2010
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`Sheet 1 013
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`US 7,744,241 B2
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`12-1
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`\ 1:1
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`11-1
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`12-2
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`15
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`14
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`12-2
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`11-3
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`Fig. 1
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`12-1
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`13-1
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`w
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`11-1
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`12-2
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`14
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`12-2
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`11-2
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`11-3
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`Fig. 2
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`US. Patent
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`Jun. 29, 2010
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`Sheet 2 of3
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`US 7,744,241 B2
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`US. Patent
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`29, 2010
`Jun.
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`Sheet 3 0f 3
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`US 7,744,241 B2
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`Input Video
`Signal
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`300-1
`
`Light
`—P
`Source (1) ~
`
`Light
`Signal
`40 O\ processor —>
`Source (2)
`4—i
`Light
`Source (3)
`—>
`
`0
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`‘
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`WDM
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`300-3
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`/ Micro Display Driving Signal
`406
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`Fig. 4A
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`Command
`lnnut
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`410\
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`Control
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`3% Light‘
`>
`4—| /300
`Light
`> Source (2)
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`WDM
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`/
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`Light
`Source (3)
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`>
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`‘
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`00-3
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`Fig. 4B
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`US 7,744,241 B2
`
`1
`HIGH BRIGHTNESS LIGHT SOURCE USING
`LIGHT EMITTING DEVICES OF DIFFERENT
`WAVELENGTHS AND WAVELENGTH
`CONVERSION
`
`BACKGROUND OF THE INVENTION
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`tional light source such as high pressure mercury lamp or
`metal halide lamp are still the choice of applications.
`
`SUMMARY OF THE INVENTION
`
`The present invention is directed to a light source that
`substantially obviates one or more of the problems due to
`limitations and disadvantages of the related art.
`An object of the present invention is to provide a high
`brightness and high poWer light source.
`Additional features and advantages of the invention Will be
`set forth in the descriptions that folloW and in part Will be
`apparent from the description, or may be learned by practice
`of the invention. The objectives and other advantages of the
`invention Will be realiZed and attained by the structure par
`ticularly pointed out in the Written description and claims
`thereof as Well as the appended draWings.
`To achieve these and other advantages and in accordance
`With the purpose of the present invention, as embodied and
`broadly described, the present invention provides a light
`source, Which includes: tWo or more light emitting devices for
`generating light having respective spectra different from each
`other; a Wavelength-division multiplexer receiving the light
`from the tWo or more light emitting devices and combining
`them into a combined light Which exits an output end of the
`Wavelength-division multiplexer; and a Wavelength conver
`sion material disposed near the output end of the Wavelength
`division multiplexer, the Wavelength conversion material
`absorbing the combined light and emitting an output light
`having a spectrum different from the spectra of the light
`generated by the emitting devices.
`The light source preferably also includes tWo or more
`light-coupling devices each for coupling the light generated
`by a light emitting devices to the Wavelength-division multi
`plexer, a dichroic ?lter disposed betWeen the output end of the
`Wavelength-division multiplexer and the Wavelength conver
`sion material for transmitting the combined light from the
`Wavelength-division multiplexer and re?ecting light gener
`ated by the Wavelength conversion material, an output light
`coupling device disposedbetWeen the output end of the Wave
`length-division multiplexer and the Wavelength conversion
`material for coupling the combined light to the Wavelength
`conversion material.
`Practical applications of such a light source include illu
`mination systems and image display devices such as projec
`tors.
`It is to be understood that both the foregoing general
`description and the folloWing detailed description are exem
`plary and explanatory and are intended to provide further
`explanation of the invention as claimed.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`1. Field of the Invention
`This invention relates to lighting devices and systems, and
`in particular, it relates to high brightness light sources.
`2. Description of the Related Art
`Light sources are used in a Wide variety of application,
`including image projection such as rear projection TV
`(RPTV) or front projector, headlights or illumination lights
`for transportation vehicles such as automobiles, motorcycles,
`boats and airplanes, etc. One import requirement for a light
`source is to provide high brightness and high poWer output at
`the same time. Currently, light sources for these and other
`applications are still dominated by traditional light sources
`such as high-pressure mercury lamps, Xenon lamps or metal
`halide lamps. HoWever, the arc lamps have technical limita
`tions in many applications: relatively short lifetime, dif?culty
`to control and maintain its color, un-stability especially When
`operating in a pulsed mode. For many applications, especially
`in an environment Where heat generation is undesirable or
`When electricity is unavailable, light from the light source
`needs to be coupled into optical ?bers or Waveguide and
`directed to Where illumination is required. HoWever, the cou
`pling from the arc lamp into ?ber can be costly, bulky, inef
`?cient 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 a system.
`Solid state light sources, especially light emitting diodes
`(LEDs), exhibit longer lifetimes, loWer poWer consumption,
`manageable Wavelengths and other bene?ts in comparison
`With the above and other traditional light sources. Therefore,
`these solid-state light sources increasingly become the alter
`native or even preferred choice of light sources for a variety of
`applications. HoWever, there are many performance issues
`that need to be improved for LEDs so that their applications
`can be broadened. Currently, tWo potential solutions can be
`explored to achieve high brightness and high poWer LED light
`sources. The ?rst one is to further improve individual LED
`chip performance by increase chip dimension and improve its
`quality. HoWever, this approach is limited by the total output
`of one individual chip, currently in tens of lumen level in the
`visible Wavelength range. Going to larger area chips and
`higher driving currents can increase the total output but Will
`compromise the device lifetime and brightness. The chip
`uniformity and thermal dissipation of large LED chip are
`serious limitation for this approach. The second approach is
`to package many LED chips together in an array structure to
`obtain high total output, up to hundreds even thousands
`lumens currently. The brightness of light directly from an
`LED array is signi?cantly loWer than that of 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 LED interferes each
`other thermally if they are too close to each other. Due to the
`reasons discussed above, When the application demanding
`high brightness and high poWer at the same time, the tradi
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`FIG. 1 illustrates a light source device and system accord
`ing to an embodiment of the present invention.
`FIG. 2 illustrates a light source device and system accord
`ing to another embodiment of the present invention.
`FIG. 3 illustrates a structure for coupling the light from a
`light emitting diode into an optical ?ber.
`FIG. 4A illustrates a projection display system according
`to an embodiment of the present invention.
`
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`US 7,744,241 B2
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`3
`FIG. 4B illustrates an illumination system that generates
`light of various colors or color temperatures according to an
`embodiment of the present invention.
`
`DETAILED DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`Wavelength conversion using a light source, such as a light
`emitting diode (LED), and a Wavelength conversion material,
`such as phosphors, can produce high brightness light having
`a Wavelength different from the Wavelength of the LED light.
`Embodiments of the present invention utiliZe a Wavelength
`division multiplexer to combine light of different Wave
`lengths from a plurality of light sources such as LEDs to
`impinge on and excite a Wavelength conversion material to
`achieve a high brightness and high poWer light source. The
`light from the LED may be in the UV and blue area. The
`Wavelength conversion material may be phosphor materials
`or nano-material such as quantum dots. The absorption spec
`trum of the Wavelength conversion material preferably covers
`the Wavelengths of the multiple LEDs, and the emission spec
`trum of the Wavelength conversion material may be broad
`(eg a White light) or narroW (e.g., single color, such as red,
`green and blue). If the output spectra of the Wavelength con
`version material under multiple LED excitations are Well
`overlapped, the output from the Wavelength conversion mate
`rial can achieve a high brightness and high poWer light. By
`using a Wavelength-division multiplexer and etendue con
`served optics to combine LED outputs With different Wave
`lengths, the combined poWer outputted by the Wavelength
`conversion material is increased Without increasing the eten
`due.
`Wavelength-division multiplexers (WDMs) are Widely
`used in ?ber-optic communications to multiplex multiple
`optical carrier signals of different Wavelengths on a single
`optical ?ber to achieve a multiplication in signal carrying
`capacity. A Wavelength-division multiplexer is typically con
`structed using one or more ?lters (hereinafter referred to as
`WDM ?lters) that transmit light in certain Wavelength ranges
`and re?ect light in certain other Wavelength ranges.
`FIG. 1 illustrates a light source device and system accord
`ing to embodiments of the present invention. This system
`combines output light from a plurality of light emitting
`devices With different Wavelengths to achieve a high bright
`ness and high poWer light source. In the illustrated embodi
`ment, a Wavelength-division multiplexer 13 having tWo
`WDM ?lters 13-1 and 13-2 is used to combine the output light
`from three light emitting devices 11-1, 11-2 and 11-3. The
`light emitting devices may be light emitting diodes (LEDs),
`laser diodes, other solid-state light sources, or other suitable
`light sources. Light-coupling devices 12-1, 12-2 and 12-3 are
`used to couple the light from the light emitting devices to the
`Wavelength-division multiplexer 13. Each of the light-cou
`pling devices 12-1, 12-2 and 12-3 may have a structure simi
`lar to that shoWn in FIG. 3, described in more detail later.
`Although not shoWn in FIG. 1, an optical ?ber may be used to
`couple the light from each light emitting device to the Wave
`length-division multiplexer. If an optical ?ber is used, suit
`able light-coupling optics such as that shoWn in FIG. 3 may be
`used to couple the light from the light emitting devices to the
`optical ?ber. An optical ?ber together With the light-coupling
`optics may be generally referred to as a light-coupling device
`for coupling the light from the light emitting device to the
`Wavelength-division multiplexer.
`The Wavelength-division multiplexer 13 includes ?rst and
`second WDM ?lters 13-1 and 13-2 arranged successively
`along an optical path. The light from the ?rst light emitting
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`device 11-1, having a ?rst Wavelength, is transmitted through
`the ?rst and second WDM ?lters to reach an output light
`coupling device 14 at the output end of the Wavelength
`division multiplexer 13. The light from the second light emit
`ting device 11-2, having a second Wavelength different from
`the ?rst Wavelength, enters the Wavelength-division multi
`plexer 13 at an angle different from the angle at Which the
`light from the ?rst light emitting device 11-1 enters, and is
`re?ected by the ?rst WDM ?lter 13-1 and transmitted by the
`second WDM ?lter 13-2 to reach an output light coupling
`device 14. The light from the third light emitting device 11-3,
`having a third Wavelength different from the ?rst and second
`Wavelengths, enters the Wavelength-division multiplexer 13
`at an angle different from the angle at Which the light from the
`?rst light emitting device 11-1 enters, and is re?ected by the
`second WDM ?lter 13-2 to reach an output light coupling
`device 14. The ?rst WDM ?lter 13-1 is one that Will transmit
`light With the ?rst Wavelength and re?ect light With the sec
`ond Wavelength, and the second WDM ?lter 13-2 is one that
`Will transmit light With the ?rst and second Wavelengths and
`re?ect light With the third Wavelength. Although three light
`emitting devices are shoWn in FIG. 1, other numbers of light
`emitting devices may be used and the number of WDM ?lters
`Will change accordingly. The structure and construction of a
`free space Wavelength-division multiplexer for combining
`light from different sources are Well knoWn in the art, and
`many different structures may be used to form a Wavelength
`division multiplexer. Wavelength-division multiplexers in
`single ?bers have also been made, but they tend to be more
`expensive With current technologies and are therefore cur
`rently less preferred.
`The output light-coupling device 14 is located at the output
`end of the Wavelength-division multiplexer 13 and receives
`light from all three light emitting devices. The output light
`coupling device 14 shoWn in FIG. 1 is a loW loss compound
`parabolic concentrator (CPC) designed to reduce the output
`aperture siZe and increase light intensity, but a light-coupling
`device that does not reduce the output aperture siZe may also
`be used.
`A Wavelength conversion material 16, Which may be phos
`phor materials or nano-materials such as quantum dots, is
`provided at the output end of the light-coupling device 14.
`The Wavelength conversion material absorbs the light from
`the multiple light emitting devices after they are combined by
`the Wavelength-division multiplexer 13, and emits a light
`having different spectrum than the absorbed light. The light
`from the light emitting devices (referred to as the excitation
`light) is typically blue or UV light, and the light emitted by the
`Wavelength conversion material typically has longer Wave
`lengths than the excitation light. The absorption spectrum of
`the Wavelength conversion material 16 preferably covers the
`spectra of all of the multiple light emitting devices so the
`lights from all light emitting devices are absorbed and con
`verted. In one example, the lights from the three light emitting
`devices 11-1, 11-2 and 11-3 have Wavelengths of360 nm, 405
`nm and 420 nm, respectively. Thus, in such an example, the
`absorption spectrum of the Wavelength conversion material
`16 should cover all of these Wavelengths.
`Various types of Wavelength conversion materials have
`different absorption and emission characteristics. The
`absorption spectrum of a Wavelength conversion material
`typically depends on the material properties. For example,
`certain phosphors manufactured by Intematix, such as
`G3 161 ,Y4254, 05742, etc., have relatively broad absorption
`spectra. Some other Wavelength conversion materials, such as
`FL63/S-Dl, HPL63/F-Fl, QMK58/F-Ul, QUMK58/F-Dl,
`etc. manufactured by Phosphors Technology Ltd., have rela
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`US 7,744,241 B2
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`5
`tively narrow absorption spectra. The emission spectrum of a
`Wavelength conversion material such as phosphors is the
`intrinsic property of the material and is typically relatively
`independent of the Wavelength of the excitation light. The
`emission spectrum of a Wavelength conversion material may
`be broad (for example, a White light) or narroW (for example,
`being a single color such as red, blue or green). For example,
`the above mentioned phosphors made by Intematix have rela
`tively broad emission spectra. The Wavelength conversion
`material 16 may be a single active material that has an absorp
`tion spectrum covering the Wavelengths of multiple excita
`tion lights, or a composite material With different active mate
`rial components that absorb different Wavelength lights and
`emit lights having similar or different emission spectra. The
`choices of Wavelength conversion material 16 for the light
`source system should be made by considering the Wave
`lengths of the excitation lights, the type of application (i.e.
`What type of output light is desired), and other appropriate
`factors such as cost.
`In one type of application, the Wavelength conversion
`material 16 has a broad absorption spectrum. When such a
`material is excited by three lights having different Wavelength
`but all falling Within the absorption spectrum, the light emit
`ted by the Wavelength conversion material 1 6 Will be approxi
`mately three times brighter than When the Wavelength con
`version material is excited by one of the three lights.
`In another application, the Wavelength conversion material
`is a composite material including three components, each of
`Which absorbs one excitation light and emits one output light
`having a relatively narroW spectrum. If the emission spectra
`of the Wavelength conversion material 16 corresponding to
`the three excitation lights are suf?ciently separated, the light
`source system of FIG. 1 may be used to generate three colored
`lights, such as red, green and blue lights, from the same
`composite Wavelength conversion material. In such an appli
`cation, the three light emitting devices 11-1, 11-2 and 11-3
`may be driven to turn on/ off or turn on at different intensities
`to change the color of the light emitted by the Wavelength
`conversion material. One practical application of such a light
`source system is to construct image display devices such as
`projectors.
`FIG. 4A shoWs a projection display system using such a
`light source. The excitation lights from three light emitting
`devices 300-1, 300-2 and 300-3 are combined by the Wave
`length-division multiplexer 310 and focused by a light cou
`pling device (focusing optics) 320 to impinge on a Wave
`length conversion material 330. The light emitted by the
`Wavelength conversion material 330 is directed to a micro
`display device 430, and projected to a screen by appropriate
`optics. The three light emitting devices 300-1, 300-2 and
`300-3 are driven by a signal processor 400, Which also drives
`the micro-display device 430 in a synchronized fashion. The
`signal processor 400 may receive a video signal as input.
`In another practical application, the three light emitting
`devices may be selectively turned on/off or turned on at
`different intensities to generate White lights of different color
`temperatures, e.g., “cool White” or “Warm White” lights. Such
`light sources may be useful in various illumination systems,
`including but not limited to headlights or illumination lights
`for transportation vehicles such as automobiles, motorcycles,
`boats and airplanes. FIG. 4B illustrates such an illumination
`system, Where excitation lights from three light emitting
`devices 300-1, 300-2 and 300-3 are combined by the Wave
`length-division multiplexer 310 and focused by a light cou
`pling device (focusing optics) 320 to impinge on a Wave
`length conversion material 330.A control circuit 410 receives
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`an external command as input and controls the three light
`emitting devices 300-1, 300-2 and 300-3 accordingly.
`In the instant disclosure, the Wavelength-division multi
`plexer is said to “combine” the different input lights into a
`combined light, even through in systems such as those shoWn
`in FIGS. 4A and 4B, sometimes not all of the multiple input
`lights are present. Thus, the Word “combine” should be under
`stood to include the meaning of having the ability to direct
`multiple input lights to a common output, regardless of
`Whether the input lights are present at the same time. Simi
`larly, a “combined light” may have some but not all of the
`input lights, depending on hoW the light emitting devices are
`driven.
`In the embodiment shoWn in FIG. 1, a dichroic ?lter 15 is
`provided before the Wavelength conversion material 16 to
`pass the excitation light from the output light-coupling device
`14 and re?ect the light emitted by the Wavelength conversion
`material (typically of longer Wavelength than the excitation
`light). The ?lter 15 can prevent the light generated by the
`Wavelength conversion material from propagating back to the
`Wavelength-division multiplexer 13 and increase light gener
`ating e?iciency. In an alternative embodiment shoWn in FIG.
`2, the dichroic ?lter 15 is located betWeen the output end of
`the Wavelength-division multiplexer 13 and the light-cou
`pling device 14. The embodiment of FIG. 2 is otherWise
`similar to that of FIG. 1. As another alternative (not shoWn in
`the ?gures), the output light-coupling device 14 is omitted,
`and the dichroic ?lter 15 and the Wavelength conversion
`material 16 are directly provided at the output end of the
`Wavelength-division multiplexer 13.
`Although it is preferable that the light from each light
`emitting device 11-1 to 11-3 is monochromatic or near mono
`chromatic, each light emitting device may also emit a broad
`spectrum light.
`FIG. 3 shoWs a structure for coupling the light from a light
`emitting device such as a light emitting diode (LED) into an
`optical ?ber. Such a high e?iciency light coupling device for
`coupling solid-state light source into etendue maintained
`optical Waveguide/?ber is described in commonly-oWned
`international patent application publication WO 2006/
`102846, published Oct. 5, 2006. As shoWn in FIG. 3 (similar
`to FIG. 1 of the above-referenced publication), a light emit
`ting device 102 such as an LED is mounted on a base place
`100, and light rays 160 and 162 emitted from the LED 102 are
`coupled to an optic ?ber 108 by an index-matched media 106
`either directly or after being re?ected on the surface of the
`index-matched media (either by a re?ective coating or by
`total internal re?ection). The optical ?ber 108 can be
`designed to have a desired etendue by selecting the numerical
`aperture (NA) and the core siZe of optical ?ber 108 (etendue
`is the product of the numerical aperture and the aperture
`dimension or spot siZe of the ?ber 108 or the light emitting
`device 102).
`Although not shoWn in FIGS. 1 and 2, each light emitting
`device 11-1, 11-2 or 11-3 may be composed ofa plurality of
`physical devices that emit light at the same Wavelength, and
`each light-coupling device 12-1, 12-2 or 12-3 may include an
`optical ?ber bundle for coupling the light from the plurality of
`physical devices into the Wavelength-division multiplexer.
`The output ends of the optical ?bers in the bundle may be
`fused together. The above-referenced patent publication WO
`2006/ 102846 describes various structures for coupling light
`from multiple LEDs into a ?ber bundle. Using multiple physi
`cal devices for each light emitting device 11-1, 11-2 or 11-3
`increases the output poWer Within each Wavelength range and
`the total output poWer.
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`US 7,744,241 B2
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`7
`It Will be apparent to those skilled in the art that various
`modi?cation and variations can be made in the light source
`device and system of the present invention Without departing
`from the spirit or scope of the invention. Thus, it is intended
`that the present invention cover modi?cations and variations
`that come Within the scope of the appended claims and their
`equivalents.
`What is claimed is:
`1. A light source comprising:
`tWo or more light emitting devices for generating lights
`having respective spectra different from each other;
`a Wavelength-division multiplexer for receiving the light
`from the tWo or more light emitting devices and for
`combining them into a combined light Which exits an
`output end of the Wavelength-division multiplexer; and
`a Wavelength conversion material disposed near the output
`end of the Wavelength-division multiplexer, the Wave
`length conversion material absorbing the combined light
`and emitting an output light having a spectrum different
`from the spectra of the lights generated by the light
`emitting devices.
`2. The light source of claim 1, Wherein each light emitting
`device is a solid state light source.
`3. The light source of claim 1, Wherein each light emitting
`device is a light emitting diode.
`4. The light source of claim 1, further comprising:
`tWo or more light-coupling devices each for coupling the
`light generated by one of the light emitting devices to the
`Wavelength-division multiplexer.
`5. The light source of claim 4, Wherein each light-coupling
`device includes an optical ?ber.
`6. The light source of claim 1, Wherein the Wavelength
`division multiplexer comprises one or more Wavelength-di
`vision multiplexing ?lters, each Wavelength-division multi
`plexing ?lter transmitting light in a ?rst Wavelength range and
`re?ecting light in a second Wavelength range different from
`the ?rst Wavelength range.
`7. The light source of claim 1, further comprising:
`a dichroic ?lter disposed betWeen the output end of the
`Wavelength-division multiplexer and the Wavelength
`conversion material for transmitting the combined light
`from the Wavelength-division multiplexer and re?ecting
`the output light generated by the Wavelength conversion
`material.
`8. The light source of claim 1, further comprising:
`an output light-coupling device disposed betWeen the out
`put end of the Wavelength-division multiplexer and the
`Wavelength conversion material for coupling the com
`bined light to the Wavelength conversion material.
`9. The light source of claim 8, further comprising:
`a dichroic ?lter disposedbetWeen the output light-coupling
`device and the Wavelength conversion material, the dich
`roic ?lter transmitting the combined light from the out
`put light-coupling device and re?ecting the output light
`generated by the Wavelength conversion material.
`10. The light source of claim 8, further comprising:
`a dichroic ?lter disposed betWeen the output end of the
`Wavelength-division multiplexer and the output light
`coupling device, the dichroic ?lter transmitting the com
`bined light from the Wavelength-division multiplexer
`and re?ecting the output light generated by the Wave
`length conversion material.
`11. The light source of claim 1, Wherein each light emitting
`device comprises a plurality of light emitting diodes,
`the light source further comprising tWo or more light
`coupling devices each including an optical ?ber bundle
`having a plurality of optical ?bers, each optical ?ber
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`coupling the light generated by one of the light emitting
`diodes to the Wavelength-division multiplexer.
`12. The light source of claim 1, Wherein the tWo or more
`light emitting devices comprise three light emitting diodes
`emitting lights having Wavelengths of 360 nm, 405 nm and
`420 nm, respectively.
`13. The light source of claim 1, Wherein the Wavelength
`conversion material generates lights of different colors after
`absorbing lights generated by different ones of the tWo or
`more light emitting devices.
`14. The light source of claim 1, Wherein the tWo or more
`light emitting devices comprise ?rst, second and third light
`emitting devices, and Wherein the Wavelength conversion
`material generates red, green and blue lights, respectively,
`after absorbing lights generated by the ?rst, second and third
`light emitting devices, respectively.
`15. A display system comprising:
`tWo or more light emitting devices for generating lights
`having respective spectra different from each other;
`a Wavelength-division multiplexer for receiving the light
`from the tWo or more light emitting devices and for
`combining them into a combined light Which exits an
`output end of the Wavelength-division multiplexer;
`a Wavelength conversion material disposed near the output
`end of the Wavelength-division multiplexer to absorb the
`combined light and emit an output light, the Wavelength
`conversion material emitting lights of different colors
`When absorbing lights from different ones of the tWo or
`more light emitting devices;
`a micro-di splay device for directing the light emitted by the
`Wavelength conversion material to a screen; and
`a signal processor coupled to and controlling the tWo or
`more light emitting devices and the micro-display
`device.
`16. The display system of claim 15, further comprising:
`an output light-coupling device disposed betWeen the out
`put end of the Wavelength-division multiplexer and the
`Wavelength conversion material for coupling and focus
`ing the combined light to the Wavelength conversion
`material.
`17. The display system of claim 15, further comprising:
`a dichroic ?lter disposed betWeen the output end of the
`Wavelength-division multiplexer and the Wavelength
`conversion material for transmitting the combined light
`from the Wavelength-division multiplexer and re?ecting
`the output light generated by the Wavelength conversion
`material.
`18. An illumination system comprising:
`tWo or more light emitting devices for generating lights
`having respective spectra different from each other;
`a Wavelength-division multiplexer for receiving the light
`from the tWo or more light emitting devices and for
`combining them into a combined light Which exits an
`output end of the Wavelength-division multiplexer;
`a Wavelength conversion material disposed near the output
`end of the Wavelength-division multiplexer to absorb the
`combined light and emit an output light, the Wavelength
`conversion material emitting lights of different colors
`When absorbing lights from different ones of the tWo or
`more light emitting devices; and
`a control circuit coupled to and controlling the tWo or more
`light emitting devices.
`19. The illumination system of claim 18, further compris
`ing:
`an output light-coupling device disposed betWeen the out
`put end of the Wavelength-division multiplexer and the
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`Energetiq Ex. 2079, page 8 - IPR2015-01377
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`US 7,744,241 B2
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`Wavelength conversion material for coupling and focus
`ing the combined light to the Wavelength conversion
`material.
`20. The illumination system of claim 18, further compris
`m