throbber
(12) United States Patent
`Beeson et al.
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`US 6,960,872 B2
`Nov. 1, 2005
`
`US006960872B2
`
`(54) ILLUMINATION SYSTEMS UTILIZING
`LIGHT EMITTING DIODES AND LIGHT
`RECYCLING TO ENHANCE OUTPUT
`RADIANCE
`
`(75) Inventors: Karl W. Beeson, Princeton, NJ (US);
`Scott M. Zimmerman, Baskin Ridge,
`NJ (US)
`
`(73) Assignee: Goldeneye, Inc., Carlsbad, CA (US)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 64 days.
`
`(21) Appl. No.: 10/814,043
`(22) Filed:
`Mar. 30, 2004
`
`(65)
`
`Prior Publication Data
`
`US 2004/0232812 A1 Nov. 25, 2004
`
`Related US. Application Data
`
`63 C '
`'
`' p
`f ppl'
`' N 10/445 136 ?l d
`e on
`,
`,
`ication o.
`ontmuation-m- arto a
`May 23, 2003, now Pat. No. 6,869,206.
`
`(51) Int. c1.7 .......................... .. F21V 7/00; H01L 33/00
`(52) US. Cl. ..................... .. 313/113; 313/498; 362/247;
`362/545
`
`(58) Field of Search ....................... .. 313/110, 112—113,
`313/498—512; 362/247, 310, 240, 544—545,
`555, 800, 347, 31, 217, 26
`References Cited
`U.S. PATENT DOCUMENTS
`
`(56)
`
`4/1995 Murase et al.
`5,410,454 A
`6,144,536 A 11/2000 Zimmerman et al.
`6,185,357 B1
`2/2001 Zou et al.
`6,186,649 B1
`2/2001 Zou et al.
`6,280,054 B1 * 8/2001 Cassarly et al. .......... .. 362/231
`6,488,389 B2 * 12/2002 Cassarly et al. .......... .. 362/231
`6,550,942 B1
`4/2003 Zou et al.
`
`* cited by examiner
`Primary Examiner—Karabi Guharay
`(74) Attorney, Agent, or Firm—William Propp, Esq.
`(57)
`ABSTRACT
`
`An illumination system has a light source that is at least
`partially enclosed Within a light-recycling envelope. The
`light source is a light-emitting diode that emits light, and a
`fraction of that light Will exit the light-recycling envelope
`through an aperture. The light-recycling envelope recycles
`part of the light emitted by the light source back to the light
`source in order to enhance the output radiance of the light
`exiting the illumination system.
`
`38 Claims, 16 Drawing Sheets
`
`104
`
`110 108
`
`100
`
`114
`
`W
`
`116
`
`118
`
`Energetiq Ex. 2080, page 1 - IPR2015-01377
`
`

`
`U.S. Patent
`
`Nov. 1,2005
`
`Sheet 1 0f 16
`
`US 6,960,872 B2
`
`FIG. 1A
`(Prior Art)
`
`FIG. 1B
`(Prior Art)
`
`,4
`27 j
`
`29
`
`28
`
`21
`
`20
`
`/
`
`26
`/
`
`Qout
`
`22
`Area“,
`
`23
`
`Lens
`
`25
`
`Energetiq Ex. 2080, page 2 - IPR2015-01377
`
`

`
`U.S. Patent
`
`Nov. 1,2005
`
`Sheet 2 0f 16
`
`US 6,960,872 B2
`
`FIG. 2A
`(Prior Art)
`
`32
`
`36
`
`3O /
`
`34
`
`FIG. 2B
`(Prior Art)
`
`40
`
`43
`
`y
`
`WNW“
`
`V
`,,,,,\\”__’J
`
`ll \
`
`,
`
`IINIIHHHIIWHIH
`
`Energetiq Ex. 2080, page 3 - IPR2015-01377
`
`

`
`U.S. Patent
`
`Nov. 1, 2005
`
`Sheet 3 0f 16
`
`US 6,960,872 B2
`
`FIG. 3A
`
`WWII/WWW
`
`100
`
`108
`
`lzggzéégzééé ¢/////////////////////////////////////////AV////////?///////////
`
`102
`
`102
`
`FIG. 3C
`
`100
`
`110
`
`108 K 104 /
`
`WWW/kw,
`
`'
`

`
`4//////J/////////////////,
`V///////////////[///////////////////////,
`
`106
`
`1 12
`
`102
`
`4////////////4////é//////7///4»///V/Zr///?/////////7//177/
`
`Energetiq Ex. 2080, page 4 - IPR2015-01377
`
`

`
`U.S. Patent
`
`Nov. 1,2005
`
`Sheet 4 0f 16
`
`US 6,960,872 B2
`
`FIG. 3D
`
`100
`
`114 /
`
`104
`
`\T/)
`W
`
`118
`
`FIG. 3E
`
`100
`
`120
`
`2
`
`106
`
`112
`
`102
`
`Energetiq Ex. 2080, page 5 - IPR2015-01377
`
`

`
`U.S. Patent
`
`Nov. 1,2005
`
`Sheet 5 0f 16
`
`US 6,960,872 B2
`
`130
`
`132
`
`FIG. 4
`
`110
`
`108 K 104
`
`
`
`mm\\\\\\\\\\ gamma
`
`106
`
`112
`
`102
`
`Energetiq Ex. 2080, page 6 - IPR2015-01377
`
`

`
`U.S. Patent
`
`Nov. 1,2005
`
`Sheet 6 6f 16
`
`US 6,960,872 B2
`
`FIG. 5
`
`140
`
`108
`
`110
`
`5
`
`Energetiq Ex. 2080, page 7 - IPR2015-01377
`
`

`
`U.S. Patent
`
`Nov. 1,2005
`
`Sheet 7 0f 16
`
`US 6,960,872 B2
`
`FIG. 6A
`
`160
`
`a“ 168
`
`162
`
`168
`
`108
`
`110
`
`Wiggly/“ZZZ? 1.
`
`169
`
`7//////////////////////
`
`112
`
`4%
`.? w l i i y M W w ,4 l i K % i 4., i % % i i W vb M M w % A M
`
`Energetiq Ex. 2080, page 8 - IPR2015-01377
`
`

`
`U.S. Patent
`
`Nov. 1,2005
`
`Sheet 8 of 16
`
`US 6,960,872 B2
`
`FIG. 6B
`
`170
`
`172
`
`176
`
`
`N$\\\
`
`176
`
`64’
`
`
`
`
`102
`
`112
`
`Energetiq Ex. 2080, page 9 - |PR2015-01377
`
`
`
`108
`
`110
`
`Energetiq Ex. 2080, page 9 - IPR2015-01377
`
`

`
`U.S. Patent
`
`Nov. 1,2005
`
`Sheet 9 0f 16
`
`US 6,960,872 B2
`
`FIG. 6C
`
`180
`
`188
`
`190
`
`186
`
`‘"182
`
`184
`
`/--—104
`
`192\\
`
`190
`
`108
`
`110
`
`192
`
`106
`
`112
`
`102
`
`Energetiq Ex. 2080, page 10 - IPR2015-01377
`
`

`
`U.S. Patent
`
`Nov. 1,2005
`
`Sheet 10 0f 16
`
`US 6,960,872 B2
`
`FIG. 7A
`
`200
`
`220
`
`\W///////////////////%7///%
`
`224
`
`w\\\\\\\\\\
`
`106
`
`112
`
`102
`
`222
`
`Energetiq Ex. 2080, page 11 - IPR2015-01377
`
`

`
`U.S. Patent
`
`Nov. 1,2005
`
`Sheet 11 0f 16
`
`US 6,960,872 B2
`
`FIG. 7B
`
`256
`
`272
`
`260
`
`108
`
`110
`
`104
`
`A
`
`258
`
`106
`
`112
`
`102
`
`Energetiq Ex. 2080, page 12 - IPR2015-01377
`
`

`
`U.S. Patent
`
`Nov. 1,2005
`
`Sheet 12 0f 16
`
`US 6,960,872 B2
`
`FIG. 8
`
`600
`
`638
`
`642
`
`630
`
`254
`
`\
`
`l
`
`.> 1
`
`634
`
`652
`
`636
`
`274
`
`620
`
`642
`
`272 v/‘\'
`
`252
`
`162
`652
`
`604
`
`104
`
`270
`
`608
`
`610
`
`10s \
`
`110
`
`602
`
`106
`
`Energetiq Ex. 2080, page 13 - IPR2015-01377
`
`

`
`U.S. Patent
`
`Nov. 1,2005
`
`Sheet 13 0f 16
`
`US 6,960,872 B2
`
`310
`
`\\/////////¢
`
`2 \1
`
`FIG. 9A
`
`300
`
`/ W W i w 1 1 / w W w
`
`2222/62/42??? ,
`
`FIG. 9B
`
`300
`
`320 330
`
`Energetiq Ex. 2080, page 14 - IPR2015-01377
`
`

`
`U.S. Patent
`
`Nov. 1,2005
`
`Sheet 14 0f 16
`
`US 6,960,872 B2
`
`FIG. 10A
`
`FIG. 10B
`
`.400
`
`400
`
`é ¢///////////////,// K a
`
`0 4
`
`7
`?//////////////////////////////////////,
`
`402
`
`J______%"— 406b
`K402
`
`FIG. 10C
`
`408b
`
`l 4
`
`
`
`7/1. /////A
`
`b M V4
`
`% m
`
`2
`
`27/176 /
`
`406a
`
`418
`
`Energetiq Ex. 2080, page 15 - IPR2015-01377
`
`

`
`U.S. Patent
`
`Nov. 1,2005
`
`Sheet 15 0f 16
`
`US 6,960,872 B2
`
`FIG. 11A
`
`FIG. 11B
`
`510a
`
`500
`
`50621
`/
`
`2
`?
`
`/////////// //////////////////////////////»7
`
`508C
`
`5106:
`
`502
`
`5060
`
`‘Ill
`
`11
`
`506d *'
`
`51:11:13:
`
`__4___J____L____.
`
`506c
`
`FIG. 11C
`
`504
`
`508d
`
`500
`
`508b
`
`506d
`
`512d
`
`502
`
`Energetiq Ex. 2080, page 16 - IPR2015-01377
`
`

`
`U.S. Patent
`
`V.
`
`10.1
`
`awnu4ow4as
`
`a1
`
`«Ana4
`
`11MnnaaaooovaM.mM.mS11
`0agMaaaeaevxsuw
`
`§ m%¢ wA\\\\\\\\\\.
`
`7/////////
`
`Onunuc7mm,m7
`6/;n
`a:nuw7c77nu
`
`0D017
`
`00O7
`
`Ob
`
`DD607
`
`k607
`
`710k
`
`708k
`
`I/////////.
`
`.////////A
`w\\\\\\\\\;‘
`
`7////////////////////////////,.,/////,.,
`
`/.
`awaazzzmawazwaamwwzag
`
`702
`
`Energetiq Ex. 2080, page 17 - |PR2015-01377
`
`0a
`
`IImupH;MMWAwM0“n.Wzzaavzza
`«Aan/oevxxssxsur
`1’7///«/:7/////////////////////////7;7///////.~
`
`0N
`
`MaH7m
`
`7am07
`
`708e
`
`710e
`
`7066
`
`706i
`
`710i
`
`708i
`
`nooeuvxssu
`22499255
`
`
`
`\\\\\\\\\\kI7/////////////////////////fl7/;7////r////////////////////////7/////
`
`Energetiq Ex. 2080, page 17 - IPR2015-01377
`
`
`

`
`US 6,960,872 B2
`
`1
`ILLUMINATION SYSTEMS UTILIZING
`LIGHT EMITTING DIODES AND LIGHT
`RECYCLING TO ENHANCE OUTPUT
`RADIANCE
`
`CROSS REFERENCE TO RELATED
`APPLICATION
`
`10
`
`This application is a continuation-in-part of US. patent
`application Ser. No. 10/445,136 ?led on May 23,2003, now
`US. Pat. No. 6,869,206, entitled “ILLUMINATION SYS
`TEMS UTILIZING HIGHLY REFLECTIVE LIGHT
`EMITTING DIODES AND LIGHT RECYCLING TO
`ENHANCE BRIGHTNESS,” Which is herein incorporated
`by reference. This application is also related to US. patent
`application Ser. No. 10/814,044 entitled “ILLUMINATION
`SYSTEMS UTILIZING MULTIPLE WAVELENGTH
`LIGHT RECYCLING” and to US. patent application Ser.
`No. 10/815,005 entitled “PROJECTION DISPLAY SYS
`TEMS UTILIZING LIGHT EMITTING DIODES AND
`20
`LIGHT RECYCLING,” both of Which are ?led concurrently
`With this application and Which are herein incorporated by
`reference.
`
`15
`
`TECHNICAL FIELD
`
`This invention relates to illumination systems incorporat
`ing light-emitting diodes (LEDs). Light-emitting diodes
`include inorganic light-emitting diodes and organic light
`emitting diodes (OLEDs).
`
`BACKGROUND OF THE INVENTION
`
`Illumination systems are used as either stand-alone light
`sources or as internal light sources for more complex optical
`systems. Examples of optical systems that utiliZe or incor
`porate illumination systems include projection displays,
`?at-panel displays, avionics displays, automotive lighting,
`residential lighting, commercial lighting and industrial light
`ing applications.
`Many applications require illumination systems With high
`brightness and a small effective emitting area. An example
`of a conventional light source With high brightness and a
`small effective emitting area is an arc lamp source, such as
`a xenon arc lamp or a mercury arc lamp. Arc lamp sources
`may have emitting areas as small as a feW square millime
`ters. An example of a complex optical system that can utiliZe
`an illumination system With high brightness and a small
`effective source area is a projection television display.
`Current projection television displays typically project the
`combined images of three small red, green and blue cathode
`ray-tube (CRT) devices onto a vieWing screen using projec
`tion lenses. More recent designs sometimes use a small-area
`arc lamp source to project images from a liquid crystal
`display (LCD), a liquid-crystal-on-silicon (LCOS) device or
`a digital light processor (DLP) device onto a vieWing screen.
`Light sources such as LEDs are currently not used for
`projection television displays because LED sources do not
`have sufficient output brightness.
`The technical term brightness can be de?ned either in
`radiometric units or photometric units. In the radiometric
`system of units, the unit of light ?ux or radiant ?ux is
`expressed in Watts and the unit for brightness is called
`radiance, Which is de?ned as Watts per square meter per
`steradian (Where steradian is the unit of solid angle). The
`human eye, hoWever, is more sensitive to some Wavelengths
`of light (for example, green light) than it is to other Wave
`lengths (for example, blue or red light). The photometric
`
`2
`system is designed to take the human eye response into
`account and therefore brightness in the photometric system
`is brightness as observed by the human eye. In the photo
`metric system, the unit of light ?ux as perceived by the
`human eye is called luminous ?ux and is expressed in units
`of lumens. The unit for brightness is called luminance,
`Which is de?ned as lumens per square meter per steradian.
`The human eye is only sensitive to light in the Wavelength
`range from approximately 400 nanometers to approximately
`700 nanometers. Light having Wavelengths less than about
`400 nanometers or greater than about 700 nanometers has
`Zero luminance, irrespective of the radiance values.
`In US. patent application Ser. No. 10/445,136, brightness
`enhancement referred to luminance enhancement only.
`Since luminance is non-Zero only for the visible Wavelength
`range of 400 to 700 nanometers, US. patent application Ser.
`No. 10/445,136 is operative only in the 400- to 700
`nanometer Wavelength range. In the present application,
`hoWever, brightness enhancement refers to radiance
`enhancement and is valid for any Wavelength throughout the
`optical spectrum.
`In a conventional optical system that transports light from
`an input source at one location to an output image at a
`second location, one cannot produce an optical output image
`Whose radiance is higher than the radiance of the light
`source. A conventional optical system 10 of the prior art is
`illustrated in cross-section in FIG. 1A. In FIG. 1A, light rays
`18 from an input light source 12 are focused by a convex
`lens 14 to an output image 16. The conventional optical
`system 10 in FIG. 1A can also be illustrated in a different
`manner as optical system 20 shoWn in cross-section in FIG.
`1B. For simplicity, the input source 22, the lens 24 and the
`output image 26 are all assumed to be round. In FIG. 1B, the
`input source 22 has area, Areal-n. The light rays from input
`source 22 ?ll a truncated cone having edges 21 and 23. The
`cone, Which is shoWn in cross-section in FIG. 1B, extends
`over solid angle 27. The magnitude of solid angle 27 is QM.
`Lens 24 focuses the light rays to image 26 having area,
`Areaom. The light rays forming the image 26 ?ll a truncated
`cone having edges 25 and 29. The cone, Which is shoWn in
`cross-section, extends over solid angle 28. The magnitude of
`solid angle 28 is 90,”.
`If the optical system 20 has no losses, the light input ?ux
`at the input source 22,
`
`[Equation 1]
`<I>,-,,=(Radiance,-,,) (AreamXQm),
`equals the light output ?ux at the output image 26,
`
`25
`
`30
`
`35
`
`40
`
`45
`
`<I>out=(RadianceUM) (AreaUMXQUM).
`
`[Equation 2]
`
`In these equations, “Radiancein” is the radiance at the input
`source 22, “Radianceom” is the radiance at the output image
`26, “Areal-n” is the area of the input source 22 and “Areaom”
`is the area of the output image 26. The quantities QM and
`Q0,” are, respectively, the projected solid angles subtended
`by the input source and output image light cones. In such a
`lossless system, it can be shoWn that
`
`55
`
`Radiancem=RadianceoM
`
`[Equation 3]
`
`60
`
`and
`
`(Aream)(§2m)=(AreaW)(90M)
`
`[Equation 4]
`
`If the index of refraction of the optical transmission medium
`is different at the input source and output image positions,
`the equality in Equation 4 is modi?ed to become
`
`65
`
`("l-n2)(Afeam)(QMFWMZ)(AreaWXQWL
`
`[Equation 5]
`
`Energetiq Ex. 2080, page 18 - IPR2015-01377
`
`

`
`US 6,960,872 B2
`
`3
`Where nm is the index of refraction at the input position and
`no,” is the index of refraction at the output position. The
`quantity (n2)(Area)(Q) is variously called the “etendue” or
`“optical extent” or “throughput” of the optical system. In a
`conventional lossless optical system, the quantity (n2)(Area)
`(Q) is conserved.
`In US. Pat. No. 6,144,536, herein incorporated by
`reference, Zimmerman et al demonstrated that for the special
`case of a source that has a re?ecting emitting surface, an
`optical system can be designed that recycles a portion of the
`light emitted by the source back to the source and transmits
`the remainder of the light to an output position. Under
`certain conditions utiliZing such light recycling, the effective
`luminance of the source as Well as the output luminance of
`the optical system can be higher than the intrinsic luminance
`of the source in the absence of recycling, a result that is not
`predicted by the standard etendue equations. In US. Pat. No.
`6,144,536, the term “luminance” is used for brightness. As
`previously stated, the term “luminance” is only useful for
`visible optical Wavelengths betWeen 400 and 700 nanom
`eters. Therefore US. Pat. No. 6,144,536 is operative only in
`that spectral region.
`An example of a light source With a re?ecting emitting
`surface is a conventional ?uorescent lamp. A cross-section
`of a conventional ?uorescent lamp 30 is shoWn in FIG. 2A.
`The ?uorescent lamp 30 has a glass envelope 32 enclosing
`a holloW interior 36. The holloW interior 36 is ?lled With a
`gas that can emit ultraviolet light When a high voltage is
`applied. The ultraviolet light excites a phosphor coating 34
`on the inside surface of the glass envelope, causing the
`phosphor to emit visible light through the phosphor coating
`34. The phosphor coating 34 is a partially re?ecting surface
`in addition to being a light emitter. Therefore, it is possible
`to design an optical system that recycles a portion of the
`visible light generated by the phosphor coating 34 back to
`the coating 34 and thereby cause an increase in the effective
`brightness of the conventional ?uorescent lamp.
`The disclosures on light recycling in US. Pat. No. 6,144,
`536 relate to linear light sources that have long emitting
`apertures With aperture areas greater than 100 square milli
`meters
`Such con?gurations, Which typically use
`?uorescent lamps as light sources, are not suitable for many
`applications such as illumination systems for large projec
`tion displays. At the application date for US. Pat. No.
`6,144,536, a typical LED had an output of only 1 lumen per
`square millimeter (mm2) and a light re?ectivity of less than
`20%. To make an illumination system that produces 1000
`lumens output for a projection display Would require at least
`1000 LEDs having a total LED surface area of 1000 mm2.
`If 1000 loW-re?ectivity, loW-output LEDs are placed on the
`inside surface of a light-recycling envelope that has a 10
`mm2 output aperture and that has a total inside area of 1010
`mm2 (including the area of the output aperture), the overall
`output e?iciency Will be less than 2%. Less than 20 lumens
`from the original 1000 lumens Will exit the light-recycling
`envelope. Such an illumination system is not very practical.
`Recently, highly re?ective green, blue and ultraviolet
`LEDs and diode lasers based on gallium nitride (GaN),
`indium gallium nitride (InGaN) and aluminum gallium
`nitride (AlGaN) semiconductor materials have been devel
`oped. Some of these LED devices have high light output,
`high radiance and have a light-re?ecting surface that can
`re?ect at least 50% of the light incident upon the device. The
`re?ective surface of the LED can be a specular re?ector or
`a diffuse re?ector. Typically, the re?ective surface of the
`LED is a specular re?ector. Radiance outputs close to 7000
`Watts per square meter per steradian and total outputs of
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`4
`approximately 0.18 Watt from a single packaged device are
`possible. Light outputs per unit area can exceed 0.045
`Watt/mm2. As such, several neW applications relating to
`illumination systems have become possible. Advantages
`such as spectral purity, reduced heat, and fast sWitching
`speed all provide motivation to use LEDs and semiconduc
`tor lasers to replace ?uorescent, incandescent and arc lamp
`sources.
`FIG. 2B illustrates a cross-sectional vieW of a recently
`developed type of LED 40 that has an emitting layer 46
`located beloW both a transparent top electrode 43 and a
`second transparent layer 44. Emitting layer 46 emits light
`rays 45 When an electric current is passed through the device
`40. BeloW the emitting layer 46 is a re?ecting layer 47 that
`also serves as a portion of the bottom electrode. Electrical
`contacts 41 and 42 provide a pathWay for electrical current
`to ?oW through the device 40. It is a recent neW concept to
`have both electrical contacts 41 and 42 on the backside of
`the LED opposite the emitting surface. Typical prior LED
`designs placed one electrode on top of the device, Which
`interfered With the light output from the top surface and
`resulted in devices With loW re?ectivity. The re?ecting layer
`47 alloWs the LED to be both a light emitter and a light
`re?ector. Lumileds Lighting LLC, for example, produces
`highly re?ective green, blue and ultraviolet LED devices of
`this type. It is expected that highly re?ective red and infrared
`LEDs With high outputs and high radiance Will also even
`tually be developed. HoWever, even the neW green, blue and
`ultraviolet gallium nitride, indium gallium nitride and alu
`minum gallium nitride LEDs do not have sufficient radiance
`for many applications.
`LEDs, including inorganic light-emitting diodes and
`organic light-emitting diodes, emit incoherent light. On the
`other hand, semiconductor laser light sources, such as edge
`emitting laser diodes and vertical cavity surface emitting
`lasers, generally emit coherent light. Coherent semiconduc
`tor laser light sources typically have higher brightness than
`incoherent light sources, but semiconductor laser light
`sources are not suitable for many applications such as
`displays due to the formation of undesirable speckle light
`patterns that result from the coherent nature of the light.
`It Would be highly desirable to develop incoherent illu
`mination systems based on LEDs that utiliZe light recycling
`to increase the illumination system output radiance. Possible
`applications include projection displays, ?at-panel displays,
`avionics displays, automotive lighting, residential lighting,
`commercial lighting and industrial lighting.
`
`SUMMARY OF THE INVENTION
`This invention is an illumination system that is comprised
`of a light source, a light-recycling envelope and at least one
`light output aperture. The light source is at least one light
`emitting diode that emits light. The at least one light
`emitting diode is further comprised of an emitting layer that
`emits light and a re?ecting layer that has re?ectivity RS and
`that re?ects light. The total light-emitting area of the light
`source is area AS and the light emitted by the light source has
`a maximum intrinsic source radiance.
`The light-recycling envelope at least partially encloses the
`light source and has re?ectivity RE. The light-recycling
`envelope re?ects and recycles part of the light emitted by the
`emitting layer back to the re?ecting layer of the light
`emitting diode.
`The at least one light output aperture is located in a
`surface of the light-recycling envelope. The total light output
`aperture area is area A0 and areaAO is less than area AS. The
`light source and the light-recycling envelope direct at least
`
`Energetiq Ex. 2080, page 19 - IPR2015-01377
`
`

`
`US 6,960,872 B2
`
`5
`a fraction of the light out of the light-recycling envelope
`through the at least one light output aperture. The fraction of
`the light that exits the at least one light output aperture exits
`as incoherent light having a maximum exiting radiance.
`Under some conditions utiliZing light recycling, the maxi
`mum exiting radiance is greater than the maximum intrinsic
`source radiance of the light source.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`A more complete understanding of the present invention,
`as Well as other objects and advantages thereof not enumer
`ated herein, Will become apparent upon consideration of the
`folloWing detailed description and accompanying draWings,
`Wherein:
`FIGS. 1A and 1B are cross-sectional side vieWs of con
`ventional optical systems of the prior art.
`FIGS. 2A and 2B are cross-sectional vieWs of prior art
`light sources that have both emitting and re?ecting surfaces.
`FIGS. 3A, 3B, 3C, 3D and 3E illustrate an embodiment of
`this invention that has one light-emitting diode.
`FIG. 4 is an embodiment of this invention in Which the
`light-recycling envelope is partially ?lled With a light
`transmitting solid.
`FIG. 5 is an embodiment of this invention that further
`comprises a planar re?ecting polariZer.
`FIGS. 6A, 6B and 6C are embodiments of this invention
`that further comprise light-collimating elements.
`FIG. 7A is an embodiment of this invention that further
`comprises both a light-collimating element and a planar
`re?ective polariZer.
`FIG. 7B is an embodiment of this invention that further
`comprises both a light-collimating element and a beam
`splitting prism polariZer.
`FIG. 8 is an embodiment of this invention that comprises
`tWo light sources, tWo light-recycling envelopes, tWo light
`collimating elements and a beam-splitting prism polariZer.
`FIGS. 9A and 9B illustrate an embodiment of this inven
`tion that further comprises a light guide.
`FIGS. 10A, 10B and 10C illustrate an embodiment of this
`invention that has tWo light-emitting diodes.
`FIGS. 11A, 11B and 11C illustrate an embodiment of this
`invention that has four light-emitting diodes.
`FIGS. 12A and 12B illustrate an embodiment of this
`invention that has tWelve light-emitting diodes.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`The preferred embodiments of the present invention Will
`be better understood by those skilled in the art by reference
`to the above FIGURES. The preferred embodiments of this
`invention illustrated in the FIGURES are not intended to be
`exhaustive or to limit the invention to the precise form
`disclosed. The FIGURES are chosen to describe or to best
`explain the principles of the invention and its applicable and
`practical use to thereby enable others skilled in the art to best
`utiliZe the invention.
`The embodiments of this invention are comprised of at
`least a light source, a light-recycling envelope and a light
`output aperture located in the surface of the light-recycling
`envelope.
`The preferred light source of this invention comprises at
`least one light-emitting diode (LED). Preferred LEDs are
`inorganic light-emitting diodes and organic light-emitting
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`6
`diodes (OLEDs) that both emit light and re?ect light. More
`preferred LEDs are inorganic light-emitting diodes due to
`their higher light output brightness. The light emitted by the
`light source is preferably greater that 200 nanometers in
`Wavelength and less than 3000 nanometers in Wavelength.
`Various illumination systems that utiliZe LEDs are illus
`trated in FIGS. 3—12. An LED depicted in FIGS. 3—12 may
`be any LED that both emits light and re?ects light. Examples
`of LEDs that both emit and re?ect light include inorganic
`light-emitting diodes and OLEDs. Inorganic light-emitting
`diodes can be fabricated from materials containing gallium
`nitride, aluminum gallium nitride, indium gallium nitride,
`aluminum nitride, aluminum indium gallium phosphide,
`gallium arsenide, indium gallium arsenide or indium gallium
`arsenide phosphide, for example, but are not limited to such
`materials. OLEDs may be constructed from a variety of
`light-emitting organic small molecules or polymers. Appro
`priate small molecules include, for example, tris
`(8-hydroxyquinoline) aluminum(III), Which can be abbrevi
`ated as Alq3, and certain types of chelates, oxadiaZoles,
`imidaZoles, benZidines and triarylamines, but are not limited
`to such materials. Appropriate polymers include, for
`example, poly(ethylene dioxythiophene) and poly(styrene
`sulfonate).
`For purposes of simplifying the FIGURES, each LED in
`FIGS. 3—12 is illustrated in an identical manner and each
`LED is shoWn as being comprised of tWo elements, an
`emitting layer that emits light and a re?ecting layer that
`re?ects light. Note that typical LEDs are normally con
`structed With more than tWo elements, but for the purposes
`of simplifying the FIGS. 3—12, the additional elements are
`not shoWn. Some of the embodiments of this invention may
`contain tWo or more LEDs. Although each LED in FIGS.
`3—12 is illustrated in an identical manner, it is Within the
`scope of this invention that multiple LEDs in an embodi
`ment may not all be identical. For example, if an embodi
`ment of this invention has a plurality of LEDs, it is Within
`the scope of this invention that some of the LEDs may be
`inorganic light-emitting diodes and some of the LEDs may
`be OLEDs. As a further example of an illumination system
`having multiple LEDs, if an embodiment of this invention
`has a plurality of LEDs, it is also Within the scope of this
`invention that some of the LEDs may emit different colors
`of light. Example LED colors include, but are not limited to,
`Wavelengths in the infrared, visible and ultraviolet regions
`of the optical spectrum. For example, one or more of the
`LEDs in a light-recycling envelope may be a red LED, one
`or more of the LEDs may be a green LED and one or more
`of the LEDs may be a blue LED. If an embodiment, for
`example, contains red, green and blue LEDS, then the red,
`green and blue LEDs may be poWered concurrently to
`produce a single composite output color such as White light.
`Alternatively, the red, green and blue LEDs in this example
`may each be poWered at different times to produce different
`colors in different time periods.
`Preferred LEDs have at least one re?ecting layer that
`re?ects light incident upon the LED. The re?ecting layer of
`the LED may be either a specular re?ector or a diffuse
`re?ector. Typically, the re?ecting layer is a specular re?ec
`tor. Preferably the re?ectivity R S of the re?ecting layer of the
`LED is at least 50%. More preferably, the re?ectivity R5 is
`at least 70%. Most preferably, the re?ectivity R5 is at least
`90%.
`Each LED in FIGS. 3—8 and 10—12 is illustrated With an
`emitting layer facing the interior of the light-recycling
`envelope and a re?ecting layer positioned behind the emit
`ting layer and adjacent to the inside surface of the light
`
`Energetiq Ex. 2080, page 20 - IPR2015-01377
`
`

`
`US 6,960,872 B2
`
`7
`recycling envelope. In this configuration, light can be emit-
`ted from all surfaces of the emitting layer that are not in
`contact with the reflecting layer. It is also within the scope
`of this invention that a second reflecting layer can be placed
`on the surface of the emitting layer facing the interior of the
`light-recycling envelope. In the latter example, light can be
`emitted from the side surfaces of the emitting layer that do
`not contact either reflecting layer. A second reflecting layer
`is especially important for some types of LEDs that have an
`electrical connection on the top surface of the emitting layer
`since the second reflecting layer can improve the overall
`reflectivity of the LED.
`The total light-emitting area of the light source is area As.
`If there is more than one LED within a single light-recycling
`envelope, the total light-emitting area As of the light source
`is the total
`light-emitting area of all
`the LEDs in the
`light-recycling envelope.
`Alight source, whether comprising one LED or a plurality
`of LEDs, has a maximum intrinsic source radiance that
`depends on the light source design and the driving electrical
`power applied to the light source. The maximum intrinsic
`source radiance is determined in the following manner. First,
`the radiance is measured for each LED in the light source
`when the light-recycling envelope is not present and when
`no other LED is directing light to the LED under measure-
`ment. The measurements are done with each LED powered
`at the same level as in the illumination system and are done
`as a function of emitting angle. From these radiance
`measurements, a maximum radiance value can be deter-
`mined for all the LEDs. This maximum value is defined as
`the maximum intrinsic source radiance.
`
`The light-recycling envelope of this invention is a light-
`reflecting element that at least partially encloses the light
`source. The light-recycling envelope may be any three-
`dimensional surface that encloses an interior volume. For
`
`example, the surface of the light-recycling envelope may be
`in the shape of a cube, a rectangular three-dimensional
`surface, a sphere, a spheroid, an ellipsoid, an arbitrary
`three-dimensional facetted surface or an arbitrary three-
`dimensional curved surface. Preferably the three-
`dimensional shape of the light-recycling envelope is a
`facetted surface with flat sides in order to facilitate the
`
`attachment of LEDs to the inside surfaces of the envelope.
`Preferable three-dimensional shapes have a cross-section
`that is a square, a rectangle or a polygon.
`The light-recycling envelope reflects and recycles part of
`the light emitted by the light source back to the light source.
`Preferably the reflectivity RE of the inside surfaces of the
`light-recycling envelope is at least 50%. More preferably,
`the reflectivity RE is at least 70%. Most preferably,
`the
`reflectivity RE is at least 90%. Ideally, the reflectivity RE
`should be as close to 100% as possible in order to maximize
`the efficiency and the maximum exiting radiance of the
`illumination system.
`The light-recycling envelope may be fabricated from a
`bulk material that is intrinsically reflective. A bulk material
`that is intrinsically reflective may be a diffuse reflector or a
`specular reflector. Preferably a bulk material that is intrin-
`sically reflective is a diffuse reflector. Diffuse reflectors
`reflect light rays in random directions and prevent reflected
`light from being trapped in cyclically repeating pathways.
`Specular reflectors reflect light rays such that the angle of
`reflection is equal to the angle of incidence.
`Alternatively, if the light-recycling envelope is not fabri-
`cated from an intrinsically reflective material, the interior
`surfaces of the light-recycling envelope must be covered
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`8
`with a reflective coating. The reflective coating may be a
`specular reflector, a diffuse reflector or a diffuse reflector that
`is backed with a specular reflecting layer. Diffuse reflectors
`typically need to be relatively thick (a few millimeters) in
`order to achieve high reflectivity. The thickness of a diffuse
`reflector needed to achieve high reflectivity can be reduced
`if a specular reflector is used as a backing to the diffuse
`reflector.
`
`Diffuse reflectors can be made that have very high reflec-
`tivity (for example, greater than 95% or greater than 98%).
`However, diffuse reflectors with high reflectivity are gener-
`ally quite thick. For example, diffuse reflectors with reflec-
`tivity greater than 98% are typically several millimeters
`thick. Examples of diffuse reflectors include, but

This document is available on Docket Alarm but you must sign up to view it.


Or .

Accessing this document will incur an additional charge of $.

After purchase, you can access this document again without charge.

Accept $ Charge
throbber

Still Working On It

This document is taking longer than usual to download. This can happen if we need to contact the court directly to obtain the document and their servers are running slowly.

Give it another minute or two to complete, and then try the refresh button.

throbber

A few More Minutes ... Still Working

It can take up to 5 minutes for us to download a document if the court servers are running slowly.

Thank you for your continued patience.

This document could not be displayed.

We could not find this document within its docket. Please go back to the docket page and check the link. If that does not work, go back to the docket and refresh it to pull the newest information.

Your account does not support viewing this document.

You need a Paid Account to view this document. Click here to change your account type.

Your account does not support viewing this document.

Set your membership status to view this document.

With a Docket Alarm membership, you'll get a whole lot more, including:

  • Up-to-date information for this case.
  • Email alerts whenever there is an update.
  • Full text search for other cases.
  • Get email alerts whenever a new case matches your search.

Become a Member

One Moment Please

The filing “” is large (MB) and is being downloaded.

Please refresh this page in a few minutes to see if the filing has been downloaded. The filing will also be emailed to you when the download completes.

Your document is on its way!

If you do not receive the document in five minutes, contact support at support@docketalarm.com.

Sealed Document

We are unable to display this document, it may be under a court ordered seal.

If you have proper credentials to access the file, you may proceed directly to the court's system using your government issued username and password.


Access Government Site

We are redirecting you
to a mobile optimized page.





Document Unreadable or Corrupt

Refresh this Document
Go to the Docket

We are unable to display this document.

Refresh this Document
Go to the Docket