United States Patent
`US 7,088,040 B1
`(10) Patent No.:
`(12)
`Ducharmeet al.
`(45) Date of Patent:
`Aug. 8, 2006
`
`
`US007088040B1
`
`(75)
`
`(54) LIGHT SOURCE USING EMITTING
`PARTICLES TO PROVIDE VISIBLE LIGHT
`Inventors: Alfred D. Ducharme, Orlando, FL
`(US); Michael Bass, Orlando, FL (US);
`Alexandra Rapaport, Orlando, FL
`(US)
`.
`.
`:
`.
`(73) Assignee: University of Central Florida
`Research Foundation, Inc., Orlando,
`FL (US)
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 301 days.
`(21) Appl. No.: 10/606,551
`
`(*) Notice:
`
`9/1993 McFarlane 0... 372/69
`5,245,623 A
`
`.. 359/326
`LL/1997 Downing.......
`5,684,621 A
`
`ee 435/6
`5,698,397 A * 12/1997 Zarli
`tal.
`5,764,403 A
`6/1998 Downing :veeee
`... 359/326
`5,914,807 A
`6/1999 Downing...
`.. 359/326
`5,943,160 A
`8/1999 Downing...
`w+. 359/326
`5,956,172 A
`9/1999 Downing ...
`... 359/326
`6,327,074 Bl
`12/2001 Bass.............
`... 359/326
`6,812,500 BL* 11/2004 Rechet al.
`ecccsssssssssee 257/98
`
`
`
`* cited by examiner
`Primary Examiner—Joseph Williams
`(74) Attorney, Agent, or Firm—Brian S. Steinberger; Law
`Office of Brian S. Steinberger
`
`(22)
`
`Filed:
`
`Jun. 26, 2003
`
`67)
`
`ABSTRACT
`
`(51)
`
`Related U.S. Application Data
`.
`.
`(60) Provisional application No. 60/392,131, filed on Jun.
`27, 2002.
`Int. Cl.
`(2006.01)
`HOW V2
`(2006.01)
`HOSB 33/00
`(52) US. C0.
`eecseeeesssssstesseessseeseessseeeeeeees 313/512; 445/23
`(58) Field of Classification Search ............ 313/512;
`257/98-100 103
`See application file for complete search history.
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`Upconversion methods and devices that converts near-in-
`frared light to the visible spectrum using a rare-earth-doped
`crystalline host for use as general and decorative lighting.
`The pseudo-monochromatic output of the processes can be
`specified by altering the amount and type of rare-earth
`material used and by selection of an appropriate host. Using
`rare-earth materials such as ytterbium-erbium or ytterbium-
`thulium can producered, green and blue emissions, where
`the additive mixture of these colors yields a high-quality
`white light. The materials can be adjusted to achieve white
`light with any color temperature and high color-rendering
`index (CRI) for any general and decorative lighting appli-
`cations both indoors and outdoors.
`
`5,003,179 A
`
`3/1991 Pollack wo... eee 250/483.1
`
`29 Claims, 11 Drawing Sheets
`
`ISO
`
` “ee
`
`APPLE 1009
`
`APPLE 1009
`
`1
`
`

`

`U.S. Patent
`
`Aug.8, 2006
`
`Sheet 1 of 11
`
`US 7,088,040 B1
`
`
`
`2
`
`

`

`U.S. Patent
`
`Aug.8, 2006
`
`Sheet 2 of 11
`
`US 7,088,040 B1
`
` 9\
`
`n
`
`3
`
`

`

`U.S. Patent
`
`Aug.8, 2006
`
`Sheet 3 of 11
`
`US 7,088,040 B1
`
`ov
`
`oT?
`
`(i
`
`}1oO
`
`4
`
`

`

`U.S. Patent
`
`Aug.8, 2006
`
`Sheet 4 of 11
`
`US 7,088,040 B1
`
` a
`
`[+
`
`5
`
`

`

`U.S. Patent
`
`Aug.8, 2006
`
`Sheet 5 of 11
`
`US 7,088,040 B1
`
`Wavelength {nm]
`
`iv
`
`o 3o
`
`Qo.
`ao
`2a
`aL
`
`® O
`
`o
`
`Uy
`%
`SZ
`MT
`Bh
`Th
`Ke
`wD
`O5
`oC
`% 0% "0 OD OOD DD
`
`Figures. Emission from YF3:Yb,Er with continuous 980nm pump.
`
`6
`
`

`

`U.S. Patent
`
`Aug.8, 2006
`
`Sheet 6 of 11
`
`US 7,088,040 B1
`
`_ ao x 2t
`
`H
`
`Wavelength [nm]
`
`Figure. Emission from LiYFy: Th, Yb with continuous 980 pump.
`
`
`
`hk
`
`o 3°a ® 2—
`
`7
`
`

`

`U.S. Patent
`
`Aug.8, 2006
`
`Sheet 7 of 11
`
`US 7,088,040 B1
`
`Power
`Relative
`
`p >
`
`de
`
`So Wo Ya.
`By “Op
`*2p
`"Ox
`
`Ot
`% Ts
`“Gy Op “RL
`
`Wavelength [nm]
`Figureg. Additive mixture of emissions from YF3:Yb,Er and LiYFy:Th,Yb.
`
`8
`
`

`

`U.S. Patent
`
`Aug.8, 2006
`
`Sheet 8 of 11
`
`US 7,088,040 B1
`
`8
`
`x!
`> &
`3oO
`= 4
`
`e3
`
`—- 3
`
`Incident Power [mW]
`
`ow
`
`o 22
`© |
`
`0
`
`FigureB Optical efficiency of the YF;:Yb,Er material scaled to the absorbed power.
`
`9
`
`

`

`U.S. Patent
`
`Aug.8, 2006
`
`Sheet 9 of 11
`
`US 7,088,040 B1
`
`+
`/
`/
`
`at
`
`ae
`
`ca
`:
`
`+
`
`~—~+— CW
`+ +Pulse 5 ms
`—+— Pulse 1.4ms
`
`3.5
`
`3.0
`x 2.5
`>
`=
`20
`
`9&u
`
`i
`
`Incident Pump Power (mW)
`
`Figure 9: Efficiency of YLiF4:Yb,Tm for different pulse lengths
`
`10
`
`

`

`U.S. Patent
`
`Aug. 8, 2006
`
`Sheet 10 of 11
`
`US 7,088,040 B1
`
`p50
`
`Fy
`
`10
`
`222.0
`
`Pool or Spa
`
`
`
`Fiber Optic
`ae
`
`
`Laser Source
`2/0
`
`Reflector Cup with upconversion material
`230
`
`Pool or Spa Lighting — Colored light and white light applications.
`
`Lens or Diffuser
`
`Ps. |
`
`23S
`230
`
`
`a
`ao
`
`
`
`240
`Upconversion Material &
`
`Fiber Optic
`
`a20
`
`Laser Source
`
`2/0
`
`
`
`11
`
`

`

`U.S. Patent
`
`Aug. 8, 2006
`
`Sheet 11 of 11
`
`US 7,088,040 B1
`
`Ore
`
`ol
`oy
`
`yBnosy10Bue
`
`[EM Buny6rq
`wbeqe1B9U0DS
`
`
`$}4617umogJodoiq
`
`OK
`
`orcs
`
`O7€
`
`12
`
`12
`
`
`

`

`US 7,088,040 B1
`
`1
`LIGHT SOURCE USING EMITTING
`PARTICLES TO PROVIDE VISIBLE LIGHT
`
`This invention claims the benefit of U.S. Provisional
`Patent Application 60/392,131 filed Jun. 27, 2002.
`FIELD OF INVENTION
`
`This invention relates to visible light sources, and in
`particular to methods and devices for forming visible light
`sources, such as wall and ceiling lights using upconversion
`of near infrared light with rare earth type particles. This
`invention relates to U.S. Pat. No. 6,327,074 to Bass et al., by
`the same assignee as the subject invention, and to US.
`patent application Ser. No. 09/919,131 filed Jul. 31, 2001, to
`Bass et al. by the same assignee of the subject invention
`which are both incorporated by reference.
`BACKGROUND AND PRIOR ART
`
`light sources have been
`Incandescent and fluorescent
`knownto be the most popular sources of visible whitelight.
`However, these traditional light sources have been known to
`use electrical energy supplies and give off undesirable
`amounts of heat when being used.
`The Secretary of Energy, Spencer Abraham, at the 13th
`Annual Energy Efficiency Forum (Jun. 12, 2002) referred to
`solid-state lighting as an “area of exciting possibilities.” He
`went on to say, “The time has come to take the next step
`toward solid state lighting” and he used the organic light-
`emitting diode (OLED) andthe light-emitting diode (LED)
`as examples of solid-state lighting technologies. These
`devices utilize one of two approaches for generating visible
`white light. The first approach is to use the additive com-
`bination of several wavelengths generated by LEDssuch as
`red, green, and blue to produce white light. The secondis to
`use either ultra-violet (UV) or blue light from an LED to
`pump a phosphor material to down-convert the light to the
`visible spectrum, where careful selections of phosphors are
`required in order to yield white light.
`In the solid-state lighting field LEDs and OLEDsare well
`known sources of providing white visible light for general
`illumination and as decorative light sources. The highest
`efficacy LED with the greatest
`luminous output
`is the
`LumiLeds 5 W Luxeon. This LED emits 120 lumens with a
`5 W electrical input or 24 lumens/watt. This LED has been
`in development for 5 years and has had the benefit of
`millions of dollars of development as general illumination
`and decorative light sources.
`USS. Pat. No. 6,327,074 to Bass et al., by the same
`assignee, the University of Central Florida, as the subject
`invention, describes the use of upconversion materials that
`can be used in a “Display medium using emitting particles
`dispersed in a transparent host”, where the display mediums
`are limited to two dimensional and three dimensional dis-
`
`play devices. The generation of white light using upconver-
`sion materials encapsulated in p-PMMA is also described by
`the same assignee in a related application, U.S. Ser. No.
`09/919,131 to Bass et al. filed Jul. 31, 2001, by the same
`assignee as that of the subject application and is also limited
`to being used only in display mediumssuch as two and three
`dimensional displays.
`To the inventors knowledge, no one uses upconversion
`materials such as those disclosed in the patents and patent
`applications of the subject assignee for the generation of
`white light or colored lights as a visible light source that can
`be used in general illumination lights sources and/or for
`decorative light sources.
`
`2
`SUMMARY OF THE INVENTION
`
`The first objective of the present invention is to provide
`solid state lighting using up-conversion that utilizes a 980
`nm laser diode used in telecommunications systems.
`The second objective of the present invention is to pro-
`vide solid state lighting that can use approximately 980 nm
`laser diodes have an up to approximately 50% or more
`electrical-to-optical conversion efficiency.
`The third objective of the present invention is to provide
`solid state lighting having a long-life based on semiconduc-
`tor lasers.
`
`The fourth objective of this invention is to provide solid
`state lighting that uses low heat based on higherefficiency.
`The fifth objective of the present invention is to provide
`solid state lighting that has overall efficiencies already at
`20%.
`
`The sixth objective of the present invention is to provide
`solid state lighting that uses upconversion materials that can
`be easily and inexpensively manufactured.
`invention is to
`The seventh objective of the present
`provide solid state lighting that has little waste in the
`manufacturing process.
`The eighth objective of the present invention is to provide
`solid state lighting that can be molded into any shape.
`The ninth objective of the present invention is to provide
`solid state lighting that uses true point source emitters so that
`all generated light is useful.
`The tenth objective of the present invention is to provide
`solid state lighting that is a more efficient alternative to
`incandescent and fluorescent
`lighting instead of using
`OLEDs and LEDs.
`
`invention is to
`The eleventh objective of the present
`provide up conversion materials that can be used as general
`illumination and decorative light sources.
`This invention shows that there is another viable solid-
`
`state lighting technology using the up-conversion oflight to
`those ofthe prior art. These results show that in the race for
`more efficient alternatives to incandescent and fluorescent
`lighting, up-conversion is a strong competitor to typical
`OLEDs and LEDs.
`
`The subject invention includes photonics called upcon-
`version. The upconversion process converts near-infrared
`light to the visible spectrum using a rare-earth-doped crys-
`talline host. The pseudo-monochromatic output of the pro-
`cess can be specified by altering the amount and type of
`rare-earth material used and by selection of an appropriate
`host. Using rare-earth materials such as ytterbium-erbium or
`ytterbium-thulium can produce red, green and blue emis-
`sions. The inventors can use a specific recipe of materials to
`produce red, green, and blue light from infrared light using
`an upconversion process, where the additive mixture of
`these colors yields a high-quality white light. The recipe can
`be adjusted to achieve white light with any color tempera-
`ture and high color-rendering index (CRI).
`Embodiments of the invention can use the visible light
`source emissions for general and decorative lighting appli-
`cations. The visible light emissions can be used on portable
`lamps such as table and floor lamps, ceiling drop directed
`light sources, ceiling surface mounted light sources, wall
`type sconcelights, as well as other application such as those
`used in pools and spas.
`Further objects and advantages of this invention will be
`apparent from the following detailed description of presently
`preferred embodiments which are illustrated schematically
`in the accompanying drawings.
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`13
`
`13
`
`

`

`US 7,088,040 B1
`
`3
`BRIEF DESCRIPTION OF THE FIGURES
`
`FIG. 1 shows an upconversion embodimentof the inven-
`tion with conical reflector.
`FIG. 2 shows another upconversion embodiment with a
`reflector cup.
`FIG. 3 shows the output of a diode laser coupled to a
`waveguide.
`FIG. 4 shows another upconversion embodiment with a
`reflector lens.
`
`FIG. 5 shows emission from YF3:Yb,Er with continuous
`980 nm pump.
`FIG. 6 shows emission from the output of LIYF,:Yb,Tm
`with continuous 980 pump.
`FIG. 7 shows the additive mixture of emissions from
`YF,:Yb,Er and LiYF,:Yb,Tm.
`FIG. 8 showsoptical efficiency of the YF;:Yb,Er material
`scaled to the absorbed power.
`FIG.9 showsefficiency increase with shortening of pulse
`length.
`FIG. 10 shows a pool/spa embodimentthat can use the
`novel upconversion visible light sources.
`FIG. 11 is an enlarged view of the unconversion light
`source used in FIG. 10.
`
`FIG. 12 shows a room using the novel upconversion
`visible lights for applications as general lighting and deco-
`rative lighting sources.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`20
`
`25
`
`30
`
`4
`can be coupled into a waveguide 120, such as a planer(e.g.,
`flat glass), optical fiber, and the like. The waveguide 120
`delivers the near-infrared pump light to the upconversion
`particles that are in the mixture 140 of the upconversion
`particles encapsulated in p-PMMA.The upconversion par-
`ticles then emit a second wavelength dependant on the type
`of particles used. The light of the second wavelength is then
`reflected and directed by a reflector 130 such as a parabolic,
`compound parabolic concentrator (CPC), or reflector cup,
`and thelike.
`
`FIG. 4 shows another upconversion embodiment 150 with
`a reflector 190. An approximately 970 to approximately 980
`nm diode laser 160 can be used to pump the upconversion
`particles within a mixture 180 of the upconversion particles
`encapsulated in p-PMMA.The upconversion particles then
`emit a second wavelength dependant on the type of material
`used. The light of the second wavelength is then reflected by
`a reflector 175, such as a conicalreflector, reflector cup, and
`the like, within a sample holder 170 and directed towards the
`outer reflector 190. The outer reflector 190 can be a para-
`bolic, compoundparabolic concentrator (CPC), and the like.
`The shapeofthe outer reflector 190 can focus the light of the
`second wavelength in the desired beam angle.
`An aspect of the invention has been in the encapsulation
`of the upconversion materials in a manufacturable form. The
`crystal materials once doped are crushed and then milled
`into a fine powder consisting of particles in the approxi-
`mately 10 to approximately 50 micron size range. The index
`of refraction of these particles is approximately 1.45 and
`therefore reflects much of the incident pumplight in air. In
`addition, the jagged surface features decrease the overall
`efficiency since this contributes to the amountoflightthat is
`reflected.
`
`Before explaining the disclosed embodiments of the
`present invention in detail it is to be understood that the
`invention is notlimited in its application to the details of the
`particular arrangement shownsince the invention is capable
`of other embodiments. Also, the terminology used herein is
`for the purpose of description and not of limitation.
`FIG. 1 shows an upconversion embodiment 1 of the
`invention with conical reflector 25. An approximately 970 to
`approximately 980 nm diode laser 40 can be used to pump
`the upconversion material particles (to be described later)
`26 Lm/w
`10% — 40% Yb
`0.5% += 5% Er
`NaYF,
`green
`within a mixture 30 of the upconversion particles that are
`3 Lm/w
`10% — 40% Yb
`0.5% += 5% Er
`YF;
`red
`encapsulated
`in
`p-PMMA(phosphorylated
`—polym-
`
`
`
`blue 0.2% = 3% Tm=10% — 40% YbYLiFy 3 Lm/w
`ethymethacrylate). The upconversion particles then emit a
`YF; 0.2% = 3% Tm=10% — 40% Yb
`
`45
`second wavelength dependant on the type of material used.
`The light of the second wavelength is then reflected by
`conical reflector 25 such as an aluminum, metal conical
`reflector and the like, within sample holder 20 and can be
`directed towards a lens 10 such as an acrylic lens, polycar-
`bonate lens, and the like. The shape of the lens 10 focuses
`the light of the second wavelength in a selected beam angle.
`FIG. 2 shows another upconversion embodiment 50 with
`a reflector cup 85. An approximately 970 to approximately
`980 nm light-emitting diode (LED) 60 can be used to pump
`the upconversion particles that are part of a mixture 70 of the
`upconversion particles that are encapsulated in p-PMMA.
`The upconversion particles then emit a second wavelength
`dependant on the type of material used. The light of the
`second wavelength can then bereflected by a reflector cup
`85 such as a aluminum,metalreflector cup, and the like, and
`are directed towards the lens 90 such as an acrylic lens,
`polycarbonate lens, and the like. Similar to the lens in FIG.
`1, the shape of the lens 90 in FIG. 2 can focus the light of
`the second wavelength in the desired beam angle.
`FIG. 3 shows an embodiment 100 of the output of a diode
`laser 110 coupled to a waveguide 120. The output of an
`approximately 970 to approximately 980 nm diode laser 110
`
`35
`
`Table 1 showsa preferred list of upconversion particles
`that include host materials with dopant concentrations, that
`can be used for generating various visible light emissions.
`
`TABLE 1
`
`40
`
`Emitted Host
`color
`material
`
`Dopant concentrations
`
`Known
`efficiency
`
`The upconversion particles of Table 1 can be mixed with
`encapsulation materials, such as p-PMMA(phosphorylated
`polymethymethacrylate), index matched PMMAderivative,
`phosphorylated-PMMA and index-matchedversion, solgels,
`and thelike.
`
`The encapsulation materials can be injection molded into
`any shape using conventional plastic molding techniques.
`The p-PMMA,for example, can have an index of refraction
`that can be adjusted to optimally match the index of the
`crystal particles. This increases the absorbed pumplight and
`subsequently increases the overall optical-to-optical effi-
`ciency of the materials.
`The exact concentration of rare-earth to host materials can
`
`be optimized as needed. A preferred example can use a host
`of yttrium fluoride (YF,) doped with a large amount of
`ytterbium (Yb) and a small amount of erbium (Er) to yield
`an emission with peaks at approximately 540 nm and
`approximately 660 nm. The output of this material with a
`pump laser at approximately 980 nm is shown in FIG. 5
`which shows emissions from YF3:Rb,Er with continuous
`approximately 980 nm pump.
`
`50
`
`55
`
`60
`
`65
`
`14
`
`14
`
`

`

`US 7,088,040 B1
`
`5
`This upconversion material can provide emissions at both
`the red and green wavelengths. The human eye perceives the
`combined output of these peaks as an orange light. White
`light can be obtained by adding blue to the mixture using
`another upconversion material. The blue emission can be
`generated using a host of lithtum yttrium fluoride (LiYF,
`also referred to as YLF) with a doping of thulium (Tm) and
`ytterbium (Yb). The output of LiYF, is shown in FIG. 6
`which shows emissions with continuous approximately 980
`nm pump.
`The combination of YF3:Yb,Er and LiYF,: Yb,Tm with
`an appropriate ratio will yield a white light emission. FIG.
`7 showsthe additive mixture of emissions from YF: Yb,Er
`and LiYF,: Yb,Tm. The spectrum shown in FIG. 7 can be
`perceived as white light with an approximate color tempera-
`ture of approximately 6000K.
`An important factor for determining the technical feasi-
`bility of any lighting technology isits efficiency. Efficiency
`can be described in many waysbutin the lighting world one
`definition is widely accepted and that
`is efficacy. This
`quantity can be defined as the luminousoutput divided by
`the electrical power used, or lumensper watt. FIG. 7 shows
`that
`in fact
`the upconversion materials can be used to
`generate white light but it doesn’t show how efficient the
`process is. For this discussion a few more concepts must be
`understood regarding the characteristics of the upconversion
`material.
`The first is that the upconversion materials emit more
`light as the pump intensity increases. In fact, the emitted
`power increases as the square of the intensity. This occurs
`until the material is saturated. Therefore, the efficiency of the
`material plateaus or saturates a measurable intensity. Pump-
`ing the materialpast the saturation intensity is simply wasted
`power.
`The secondinteresting characteristic of these materials is
`that they continue to emit
`light once the pump light is
`discontinued. This persistence allows the material
`to be
`pumpedup to the saturation point and then allowed torelax.
`Once the light output drops to a noticeable level the pump
`can be turned back on. This pulsing ability will be discussed
`in more detail
`later as a potential means of increasing
`efficacy.
`Thethird characteristic that needs to be understood is that
`
`becausethe particles reflect light much of the incident pump
`poweris not utilized. Presently this hinders our measure-
`ments since we can only measure the efficiency with respect
`to the incident power. Next, there will be discussion on how
`this unused pump power can be recycled and used to
`increase efficiency.
`The data plotted in FIG. 8 showsthe efficiency of the
`YF;:Yb,Er material defined as the optical output divided by
`the absorbed optical input power.
`From this plot we can calculate the efficacy of the overall
`system based on an approximate 7% optical efficiency. A
`standard approximately 980 nm laser diode has an electrical-
`to-optical efficiency of approximately 50%. An optical pump
`equivalent to approximately 25 watts can be generated from
`an approximately 50 watt electrical power consumption by
`a laser diode (actually an array for this level of power).
`Approximately, 120 lumensoflight is generated based on
`the optical efficiency of approximately 7%. This equates to
`approximately 120 lumensfor an electrical input of approxi-
`mately 50 watts or approximately 2.4 lumens/watt. How-
`ever, only approximately 50% of the pump light is used in
`the measurement shownin FIG. 8 meaningthat if the unused
`pump could be recycled an overall efficacy of approximately
`5 lumens/watt could be achieved.
`
`6
`The subject invention optimizesthe efficacy of the upcon-
`version materials. We have three main objectives: optimi-
`zation of rare-earth-doping, increasing the amount of pump
`light utilized, and the investigation of pulsing effects.
`
`Optimization of Concentrations
`Table 1 above showsvarious upconversion materials that
`have been demonstrated to emit different visible light emis-
`sions. Further optimization can establish green/red upcon-
`version material and a blue upconversion material that yield
`the highest possible efficiency.
`
`Pump Light Usage
`Several optical configurations can be used for pumping
`the upconversion materials referenced above. Optical ray-
`trace software such as ASAP can be used to further narrow
`the possible numberof configurations which can be further
`tested for efficiency.
`
`Pulsing Effects
`An experiment was performed to show that pulsing of the
`pump power can dramatically increase the overall efficiency
`of the upconversion materials. Our initial tests for the blue
`material show that an increase of a factor of approximately
`4(four) in efficacy is possible with short duration pulsing on
`the order of several milli-seconds. This equates to an efficacy
`of approximately 3 lumens/watt in the blue and red, and 26
`lumens/watt in the green for our technology at this time.
`We have performed an experiment to show that pulsing
`can increase the efficiency of the blue emitting material. The
`experiment showed that using continuous wave pumping
`(no pulsing) the YLiF,:Yb, Tm sample provides approxi-
`mately 0.9% efficiency in the blue portion of the spectrum.
`The pump laser was then pulsed at approximately 33 Hz
`with an approximately 1.4 ms pulse. The efficiency
`increased by a factor of approximately 4 to approximately
`3.6%. Simulations show that that this factor increases as the
`
`pulse length is shortened until a pulse length of about 700
`microsecond. Whenthe pulse is shortened below 700 micro-
`second, the efficiency does not improve any further. The
`results of this experiment are plotted in FIG. 9 for various
`pulse lengths. These results are in good agreement with the
`numerical simulations performed.
`
`Energy Benefits
`The installed unit for the invention is initially approxi-
`mately 10% ofthe total lighting market. The total consump-
`tion of electricity by lighting in the United States was
`approximately 600 million kWhr in year 2001. Initially, the
`cost of the invention can be higher when compared to
`incandescent and fluorescentlighting. As a result, the upcon-
`version white light will begin to penetrate the lighting
`market in niche sectors where long-life and high efficiency
`will make it acceptable despite the high initial cost. We
`estimate 5% market penetration within 5 years of its intro-
`duction. This equates to approximately 30 million kWhr of
`the total 600 Million kWhrs used for lighting. The expected
`efficiency is approximately two timeshigher than traditional
`light sources. Therefore, approximately 15 Million kWhr of
`electricity will be saved using the upconversion technology.
`This is equals a savings of 50 Trillion BTUs peryear.
`FIG. 10 showsa pool/spa embodiment 200 that can use
`the novel upconversion visible light sources for either or
`both general
`lighting sources and decorative lighting
`sources. FIG. 11 is an enlarged view of the unconversion
`light source used in FIG. 10. Referring to FIGS. 10-11, a
`pool/spa enclosure 250 can use the novel light sources that
`can emit visible white light and/or colored light through the
`sidewalls 255 of the pool/spa enclosure 250. A laser source
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`15
`
`15
`
`

`

`US 7,088,040 B1
`
`7
`210, such as a laser diode previously described, can emit
`through a waveguide 220 such as an optical fiber which
`passes the light into a mixture 240 of upconversion mate-
`rials/particles
`and encapsulation material,
`previously
`described. Visible light can be reflected from a reflector 230
`such as a parabolic reflector, and the like, out through a
`transmission medium 235, such as a lens, diffuser, and the
`like,
`into the pool/spa enclosure 250. As previously
`described, visible light can be visible white light, colored
`light, various mixes, andthe like.
`FIG. 12 shows a room embodiment 300 using the novel
`upconversion visible lights for applications as general light-
`ing and decorative lighting sources. Here, the novel upcon-
`version visible
`emission lighting devices previously
`described can be used indoors suspended from a ceiling in
`drop or down lights housed in downwardly directed enclo-
`sures 310, on ceiling surface or in ceiling trough lighting
`320, as visible lighting in wall sconces 330, andalsoin table
`lighting applications 340, such as in a portable table lamp,
`floor lamp, and the like, where a typical shade can be used.
`The novel invention has a wide variety of applications in
`residential and commercial uses for applications as general
`lighting sources, decorative lighting sources, and the like,
`and can be used in outdooras well as any indoor applications
`as needed.
`Other applications for the invention can be for use in
`automotive headlights, where the infrared generated visible
`source light can be used to flood a selected area in front of
`or behind a vehicle. An onboard infrared camera can then be
`aided by the infrared generated visible source light. The
`generated visible light can be reflected and/or focused away
`from the vehicle for enhanced vision when driving during
`night-time, or storm or fog or smoke or haze conditions.
`The invention can have other applications where the user
`would want visible light unless they were wearing night-
`vision goggles. In this case the user would see a display with
`the un-aided eye and the infrared source light using their
`night vision goggles.
`While the invention has been described, disclosed, illus-
`trated and shownin various terms of certain embodiments or
`
`modifications which it has presumed in practice, the scope
`of the invention is not intended to be, nor should it be
`deemed to be, limited thereby and such other modifications
`or embodiments as may be suggested by the teachings herein
`are particularly reserved especially as they fall within the
`breadth and scope of the claims here appended.
`We claim:
`
`1. A method of forming visible light sources with up
`conversion materials, comprising the steps of:
`generating near infrared light from a source;
`upconverting the near infrared light through a an encap-
`sulated mixture of upconversion materials located in a
`sample holder having a reflective surface into a visible
`light emission dependant on the type of upconversion
`material used, wherein the near infrared light is uncon-
`verted to the visible light emission;
`reflecting the visible light emission off the reflective
`surface; and
`applying the reflected visible light emission to a light
`fixture for at least one of a general lighting source or a
`decorative lighting source.
`2. The method of claim 1, wherein the generated near
`infrared light is emitted from a diode laser.
`3. The method of claim 2, wherein the diode laser includes
`an approximately 970 to approximately 980 nm diode laser
`source.
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`16
`
`8
`4. The method of claim 1, wherein the upconversion
`materials are encapsulated in p-PMMA.
`5. The method of claim 1, wherein the visible
`emission includes: red light.
`6. The method of claim 1, wherein the visible
`emission includes: green light.
`7. The method of claim 1, wherein the visible
`emission includes: blue light.
`8. The method of claim 1, wherein the visible
`emission includes: white light.
`9. The methodof claim 1, wherein the mixture of upcon-
`version materials includes:
`
`light
`
`light
`
`light
`
`light
`
`of
`
`of
`
`of
`
`yttrium fluoride (YF;) doped with ytterbium (Yb) and
`erbium (Er).
`10. The method of claim 1, wherein the mixture of
`upconversion materials yields emissions with peaks at
`approximately 540 nm and approximately 660 nm.
`11. The method of claim 1, wherein the mixture
`upconversion materials includes: rare-earth material.
`12. The method of claim 1, wherein the mixture
`upconversion materials includes:
`ytterbium-erbium.
`13. The method of claim 1, wherein the mixture
`upconversion materials includes:
`ytterbium-thulium.
`14. A method of forming visible light using upconversion
`comprising the steps:
`providing near-infrared light; and
`upconverting the near-infrared light with a rare-earth-
`doped crystalline host as upconversion particles to
`produce a visible light;
`reflecting the visible light from a reflector onto a lens,
`wherein a shapeof the lens focuses the reflected visible
`light in a beam angle; and
`applying the reflected visible light to a light fixture as a
`general lighting source or decorative lighting source,
`wherein the near infrared light is unconverted to the
`visible light emission.
`15. The method of claim 14, wherein the visible light
`includes: visible red light.
`16. The method of claim 14, wherein the visible light
`includes: visible green light.
`17. The method of claim 14, wherein the visible light
`includes: visible blue light.
`18. The method of claim 14, wherein the visible light
`includes: visible white light.
`19. The method of claim 14, wherein the rare earth doped
`crystalline host includes: NaYF, doped with Er and Yb.
`20. The method of claim 14, wherein the rare earth doped
`crystalline host includes: YF, doped with Er and Yb.
`21. The method of claim 14, wherein the rare earth doped
`crystalline host includes: YLiF, doped with Tm and Yb.
`22. The method of claim 14, wherein the rare earth doped
`crystalline host includes: YF, doped with Tm and Yb.
`23. An upconversion visible light source for general and
`decorative lighting, comprising:
`means for generating near infrared light from a source;
`upconversion materials for upconverting the near infrared
`light into a visible light emission;
`a reflector for reflecting the visible light emission; and
`a meansfor focusingthe visible light emission into a light
`fixture as at least one of a general lighting source or a
`decorative lighting source.
`24. The upconversion visible light source of claim 23,
`wherein the generating means includes: a laser diode.
`
`16
`
`

`

`US 7,088,040 B1
`
`9
`25. The upconversion visible light source of claim 23,
`wherein the upconversion materials include:
`rare earth
`dopedcrystalline host particles mixed within encapsulation
`materials.
`26. The upconversion visible light source of claim 25,
`wherein the visible light emission includes: visible white
`light.
`27. The upconversion visible light source of claim 25,
`wherein thevisible light omission includes: visible red light.
`
`10
`28. The upconversion visible light source of claim 25,
`wherein the visible light emission includes: visible green
`light.
`29. The upconversion visible light source of claim 25,
`wherein the visible light emission includes: visible blue
`light.
`
`17
`
`17
`
`