United States Patent
`Turnbull et al.
`
`11»
`
`[54]
`
`[75]
`
`LED ASSEMBLY
`
`Inventors: Robert R. Turnbull, Holland; Robert
`C. Knapp, Coloma; John K. Roberts,
`Holland, all of Mich.
`
`[73]
`
`Assignee: Gentex Corporation, Zeeland, Mich.
`
`|*]
`
`Notice:
`
`This patent is subject to a terminal dis-
`claimer.
`
`[21]
`
`[22]
`
`[63]
`
`[51]
`[52]
`
`[58]
`
`Appl. No.: 09/148,375
`
`Filed:
`
`Sep. 4, 1998
`
`Related U.S. Application Data
`
`Continuation of application No. 08/664,055, Jun. 13, L996,
`Pal. No. 5,803,579.
`
`Bish Cah? sccescsassraortetiaiguiciibsnartneanniysgpn: Bodog 1/00
`Ds ile! oopctittyios iA peas 362/494; 362/800; 362/545;
`362/490; 362/293; 362/231; 362/230
`Field of Search ..........cccccccceeee 362/516, 230,
`362/231, 293, 800, 494, 490, 135
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`3.875.456
`4,211,955
`4.208.869
`4.377.768
`4.450512
`4,580,196
`4.646.210
`4,733,336
`4,807,096
`4,882,565
`4.929.866
`4.947.291
`4,992,704
`5,008,595
`5,083,192
`5,136,483
`5,143,433
`5,255,171
`5,303,037
`5,325,271
`5,371,659
`
`4/1975 Kano eb al. ccc J13/S01
`
`7/1980 Ray......
`.. 315/53
`11/1981 Okuno .......
`340/782
`3/1983 Gallaro et al.
`313/467
`
`5/1984 Kristofek ......
`362/276
`
`4/1986 Task ec
`362/62
`2/1987 Skogler et al,
`362/142
`
`...
`we 362/142
`3/1988 Skogler et al.
`
`2/1989 Skogler et al,
`wee 362/142
`11/1989 Gallmeyer .....
`. 340/461
`
`5/1900 Murata et al.
`313/300
`...
`8/1990 McDermott
`« 362/19
`
`2/1991 Stinson .....
`315/312
`4/1991 Kayar ........
`315/178
`...
`1/1992 Reeznik etal.
`3357/74
`8/1992) Schoniger et al.
`362/61
`9/1992 Farrell
`.......
`362/29
`Loy19a3
`362/231
`4/1994
`356/406
`6/1994 Hutchissen....
`« 362/32
`12/1994 Pastrick ct al. sissies 302/83,1
`
`
`
`
`
`US006132072A
`(11) Patent Number:
`[45] Date of Patent:
`
`6,132,072
`*Oct. 17, 2000
`
`S,384,519
` T/L99IS Gotoh wisscisscscsstescccseeterttecterreeee SL /924
`
`5,477,436
`« 362/231
`12/1995 Bertling et al.
`.
`
`5,497,305
`. 362/83.1
`3/1996 Pastrick et al.
`.
`5,613,751
`we 362/31
`3/1997 Parker el al.
`...
`
`5,699,044
`12/1997 Van Lente et al,
`. 340/525
`
`5,895,115
`we 362/31
`4/1999 Parker el al.
`...
`5,971,652 F909 Parker ebal. sce
`escseseeneens 362/31
`
`FOREIGN PATENT DOCUMENTS
`
`0625 793 A2
`11/1994
`European Pat. OF ....... HOW 61/4
`0689 000 Al
`12/1995
`European Pat. OM 2.2... F2LO 1/00
`
`S9LGSTSAL
`-» B6OOQ 1/26
`12/1990 Germany ssc
`
`62-018775
`» HOLL 33/00
`1/1987
`Japan ...
`§2-235787 LO/L9BT Sapa vase HOLL 33/00
`
`OTHER PUBLICATIONS
`
`R. W..G. Hunt, Measuring Colour, reprinted in 1992 by Ellis
`Horwood Limited, pp. 38-79 and 124-133.
`SAE J578, Surface Vehicle Standard—Color Specification,
`revised Jun., 1995.
`
`English Translation “LED-Baulement™ of 2087 Elektronie,
`vol. 44, No. 15, Jul. 25, 1995, p. 134.
`JL. Schnapf, et al, “Spectral sensitivity of human cone
`photoreceptors”, Nature, vol, 325, Jan. 29, 1987, pp,
`439-441,
`
`David H. Brainard, Colorimetry, XP 002040706, Chapter
`26, p. 26.1-26.53.
`
`Primary Examiner—Thomas M, Sember
`Atorney, Agent, or Firm—Brian J. Rees; Price, Heneveld,
`Cooper, DeWitt & Litton
`
`[57]
`
`ABSTRACT
`
`An illuminator assembly, having # plurality of LEDs on a
`vehicular support member im a manner such thal, when all of
`the LEDs are energized,
`illumination exhibiting a first
`perceived hue, ¢.g., blue-green, and projected from at least
`one of the LEDs overlaps and mixes with illumination
`exhibiling a second perceived hue, e.g., amber, which is
`distinct from said first perceived hue and whichis projected
`from at least one of the remaining LEDs in such a manner
`that
`this overlapped and mixed illumination forms a
`metameric while color and has sufficient intensity and color
`rendering qualities to be an ellective illuminator.
`
`45 Claims, 20 Drawing Sheets
`
`Circuit
`
`
`
`
`
`
`
`Electronic
`
`VWGOoA EX1057
`VWGOAv. Spero
`IPR2023-00318
`
`VWGoA EX1057
`VWGoA v. Spero
`IPR2023-00318
`
`

`

`U.S. Patent
`
`Oct. 17, 2000
`
`Sheet 1 of 20
`
`6,132,072
`
`Le
`
`6!
`
`=Cee
`
`
`
`a5glTeujPEal9esJaeP|92
`
`JYINGAVEcee’TES9aWUE
`
`ce|afddAl
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`UOIAF
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`JININD
`WotAAXs
`
`Lo
`
`O8e
`
`62
`
`61
`
`
`
`

`

`U.S. Patent
`
`Oct. 17, 2000
`
`Sheet 2 of 20
`
`6,132,072
`
`
`Pea|PE
`GESE
`
`wz5°4¢So82
`
`=e
`
`CEyino4rD
`
`2UONI3/F
`
`TEINaySeNY
`
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`
`61
`
`
`
`
`

`

`U.S. Patent
`
`Oct. 17, 2000
`
`Sheet 3 of 20
`
`6,132,072
`
`_
`
`“
`
`pe
`
`
`
`
`
`RelativeSpectralPower
`
`
`
`RelativeSpectral
`
`Power
`
`SEO
`
`4.30
`
`480
`
`530
`
`580
`
`630
`
`680
`
`730
`
`780
`
`JE0
`
`4350
`
`480
`
`530
`
`SSE. S.A.
`
`~=680
`630
`580
`Wavelength (nm)
`
`730
`
`780
`
`Spectra Of erates Light Sources
`Zor /Hurninant 8a:
`Fi :
`
`
` -
`
`
`Muminant C
`
`Muminant A4
`
`|||
`
`||
`
`

`

`U.S.
`
`Patent
`
`Oct. 17, 2000
`
`Sheet 4 of 20
`
`6,132,072
`
`90
`en
`
`Reflective Properties For A
`50% Neutral Gray Target
`
`70
`
`
`
`
`
`SpectralReflectance(%)
`
`JO 430
`
`480
`
`630
`580
`550
`Wavelength (nm)
`Es, 22,
`
`680
`
`730
`
`780
`
`R (A)
`
`09
`08
`
`07
`
`06
`
`05
`
`0.4
`
`0.3
`
`02
`
`0.1
`
`
`
`
`
`felativeSpectralPower
`
`460
`
`Resultant Reflected Light
`Spectral Power Distribution
`P(A) = S(A)*R(A)
`
`
`
`480
`
`430
`
`530 580630
`Wavelength (nm)
`Ses eet
`
`680
`
`730
`
`780
`
`

`

`U.S. Patent
`
`Oct. 17, 2000
`
`Sheet 5 of 20
`
`6,132,072
`
`Spectral Luminous Efficiency Functions
`
` —— V (Photopic Response)
`
`——-— V(Scotopic Response)
`Estimated Typical
`Mesopic Response
`
`
`
`RelativeSensitivity
`
`JI0
`
`400
`
`450
`
`500
`
`650
`600
`550
`Wavelength (nm)
`
`700
`
`750
`
`800
`
`srs |S,
`
`CIE Color Matching Functions
`
`
`
`RelativeResponse S Q
`
`500 550
`450
`400
`Wavelength (nm)
`—Pa
`
`750 800
`
`J50
`
`600
`
`650 700
`
`

`

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`Oct. 17, 2000
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`Sheet 6 of 20
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`6,132,072
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`U.S. Patent
`
`Oct. 17, 2000
`
`Sheet 7 of 20
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`

`U.S. Patent
`
`Oct. 17, 2000
`
`Sheet 8 of 20
`
`6,132,072
`
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`Oct. 17, 2000
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`Sheet 9 of 20
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`6,132,072
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`6,132,072
`
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`

`U.S. Patent
`
`Oct. 17, 2000
`
`Sheet 11 of 20
`
`6,132,072
`
`
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`

`U.S. Patent
`
`Oct. 17, 2000
`
`ZeH
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`
`Sheet 12 of 20
`
`
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`

`

`U.S. Patent
`
`Oct. 17, 2000
`
`Sheet 13 of 20
`
`6,132,072
`
`134
`
`Electrochromic
`
`
`Glass FEPE
`
`Media
`
` fre|ferOPeeeeePeeeaOEee
`Cf7eeLOLS
`KASSANOS
`DeePletee
`
`
`138 Reflecting Loyer
`
`rear
`
`FKeflective
`Layer
`
`SESS, AOel
`Conductive Layers
`
`Z|
`
`
`

`

`U.S. Patent
`
`Oct. 17, 2000
`
`Sheet 14 of20
`
`6,132,072
`
`MIRROR WITH INTEGRAL LAMP ONLY
`
`Passenger Side
`
`178.0 mm Dia.
`(Typical)
`
`305.0 mm Dra.
`(Typical)
`
`Target Point
`For Illumination
`
`450.0 mm Dia.
`(Typical)
`
`
`
`

`

`
`
`

`

`U.S. Patent
`
`Oct. 17, 2000
`
`Sheet 16 of 20
`
`6,132,072
`
`Binary-Complementary Metameric—White LED Map Light For Interior
`Electrchomic Mirror
`
`(cd)
`
`ltensity(cd)
`
`Initial Intensity Distribution Intensity
`
`
`¢AngularDeflection(Degrees)
`
`Binary—Complementary Metameric—White LED Map Light For Interior
`Electrochromic Mirror
`Initial Intensity Distribution
`
`20
`
`15
`
`~S
`
`i
`
`/so-Inlensit‘y| Contours
`(cd)
`
`paasFeet =F Q Angulor Deflection (Degrees)
`
`-JO -28 —20'-95 -i08
`
`-3
`
`DOD
`
`FF
`
`10
`
`IS 2
`
`

`

`U.S. Patent
`
`Oct. 17, 2000
`
`Sheet 17 of 20
`
`6,132,072
`
`
`
`
`
`(sayouj)22U0)SIg/042}07
`
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`riesg-
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`Oct. 17, 2000
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`Sheet 18 of 20
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`6,132,072
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`U.S. Patent
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`Oct. 17, 2000
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`Sheet 19 of 20
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`6,132,072
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`U.S. Patent
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`Oct. 17, 2000
`
`Sheet 20 of 20
`
`6,132,072
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`6,132,072
`
`1
`LED ASSEMBLY
`
`This is aconlinualion of application Ser. No. 08/664,055,
`filed Jun. 13, 1996, U.S. Pat. No. 5,803,579,
`The present invention relates to an illuminator assembly
`incorporating light emitting diodes, and more particularly to
`vehicular, portable and olher specialty white light illumina-
`lion systems utilizing lighi emitting diodes having comple-
`mentary hues.
`
`BACKGROUND OF THE INVENTION
`
`Due to limitations in human vision in low light level
`environments, while light
`illuminator systems have long
`been used to produce artificial
`illumination and enhance
`visibility during nighttime or overcast conditions or within
`interior quarters obscured from the reach ofsolar ilumina-
`tion. [lluminators are therefore generally designed to mimic
`or reproduce daytime lighting conditions,
`to the extent
`possible, so that illuminated subjects of interest are bright
`cnough to be seen and have sufficient visual qualities such
`as color and contrast to be readily identifiable.
`A diversity of illuminator systems such as stationary
`lamps in buildings, portable Hashlights, and vehicular head-
`lamps and courtesy lights have evolved throughout history
`and have traditionally produced white light for general, spot
`or flood illumination, using a variety of sources such as
`candles, oil, kerosene and gas burning elements, incandes-
`cent and halogen bulbs, and fluorescent and other are-
`discharge lamps. White light is critical in such uses because
`of ils unique ability to properly render colored objects or
`printed images relative to one another and its similarly
`umque ability to preserve luminance and color contrast
`between adjacent objects or printed images having different
`colors. For instance, a blue photographic image of an ocean
`panorama will be readily distinguished by an unaided
`observer from black photographic images of volcanic rocks
`when the photograph containing these images is illuminated
`by white lighi, The two images would, however, be virtually
`indistinguishable from one another if illuminated with a
`deeply red colored illuminator. Anciher example arises [rom
`the need to properly identify differenily-colored regions on
`conventional acronautical or automotive maps. On an auto-
`motive map, white light illuminators make it easy to discern
`the difference between the yellow markings for urban
`regions and the surrounding white rural areas. A deeply
`yellow colored illuminator would make this distinction
`virtually impossible, On an aeronautical chart, white light
`illuminators make it possible to discern the difference
`between the characteristic blue markings for certain types of
`controlled airspace and the green pattern of underlying
`lerrain, whereas a deeply red colored ilwminator would
`make this distinction virtually impossible.
`Furthermore,
`these issues of color discrimination and
`contrast go beyond the simple need for accurate identifica-
`tion. It is, for example, a well known fact that high contrast
`is critical for avoiding severe operator eye fatigue and
`discomfort during prolonged visual tasks, whether the sub-
`ject of study is a book, magazine, newspaper or a map.
`White light
`iluminators provide more universally high
`contrast and good color discrimination,
`thereby avoiding
`these annoying and dangerous physiological side elfeets.
`The extensive evolution and widespread use of white light
`Uhiminators, along with rapidly advancing technology and a
`phenomenon known as color constancy, have fostered
`acceptance of a rather broad range of unsaturated colors as
`“white”. Color constancy refers to the well-known fact that
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`the level and color of slightly unsaturated or near-white
`illumination over an area can vary moderately without
`substantially altering the perceived colors of objects in thal
`selling relative to one another. An example ofthis is the
`appearance of an outdoor scene to an observer wearing
`slightly amber or green sunglasses, After a brief moment of
`adaptation upon donning the sunglasses, an observer
`becomes unaware that the scene is being passed through a
`slightly colored filter. Another example is the tacit accep-
`tance of a wide variety of “white” illuminators in residential,
`commercial, and public illumination. The bluish or cool
`white from various fluorescent lamps is virtually universal in
`office buildings, whereas the yellowish or warn white of
`incandescent lamps ts dominant in residential lighting. The
`brilliant bluish-whiie of mercury vapor and metal halide
`lamps is commonplace in factory assembly lines, whereas
`the bronze-white emission ofthe high pressure sodium lamp
`dominates highway overhead lighting in urban areas.
`Despite the discernible tint of each of these sources which
`would be evident if they were compared side by side, they
`are generally accepted as white illuminators because their
`emissions are close enough to an unsaturated white to
`substantially preserve relative color constancy in the objects
`they illuminate. In other words, they render objects in a
`manner that is relatively faithful to their apparent “true”
`colors under conditions of natural illumination.
`There are limits to the adaptability of human color vision,
`however, and color constancy does not hold if highly chro-
`matic illuminators are used or if the white illumination
`observed in a setting is altered by a strongly colored filter,
`A good example of this limitation can be experienced by
`peering through a deeply colored pair of novelty sunglasses
`If these glasses are red, for instance, then it will be nearly
`impossible to discern a line of red ink on white paper, even
`though the line would stand ont quite plainly in normal room
`ilumination if the glasses are removed. Another illustration
`of this effect
`is the low-pressure sodium lamp used for
`certain outdoor urban illumination tasks. This type of lamp
`emils a highly saturated yellow light which makes detection
`and or identification of certain objects or printed images
`very difficult
`if not
`impossible, and, consequently their
`commercial use has been very limited. As will be discussed
`later, a similar problemarises [rom prior-art attempts to use
`high intensity red or amber light emitting diodes (LEDs)as
`illuminators since they, like the low-pressure sodium lamp,
`emit narrow-band radiation without regard for rendering
`quality.
`In order to improve the effectiveness of white light
`illumination systems, various support structures are Lypi-
`cally employed to contain the assembly and provide energy
`or fuel to the incorporated light source therein. Furthermore,
`these systems typically incorporate an assortment of optical
`components to direct, project, intensify, filter or diffuse the
`light they produce. A modern vehicle headlamp assembly,
`for
`instance, commonly includes sealed electrical
`connectors, sophisticated injection-molded lenses and
`molded, metal-coated reflectors which work in concert to
`collimate and distribute white light from an incandescent,
`halogen, or are-discharge source. A backlight illuminator for
`an instrument panel in a vehicle or control booth typically
`contains elaborate light pipes or guides, light diffusers and
`extractors.
`
`Of course, traditional white light sources which generate
`light direetly by fel combustion are no longer suitable for
`most vehicular, watercrafi, airerafl, and portable and certain
`other applications where an open flame is unsafe or unde-
`sirable, These therefore have been almost universally super-
`
`

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`6,132,072
`
`3
`seded by electrically-powered, white light sources.
`Furthermore, many modern electric light sources are rela-
`tively inefficient, ¢.g., conventional
`tungsten incandescent
`lamps, or require high voltages to operate, e.g., fluorescent
`andthe gas discharge lamps, and therefore aren’! optimal for
`vehicular, portable, and other unique illuminators used
`where only limited poweris available, only low voltage is
`available or where high voltage is unacceptable for safety
`reasons.
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`and significant vibration ducing driving conditions which
`can cause damage to incandescent lamps, particularly the
`filaments from which their light emissions originate. This is
`an especially severe problem for lamps mounted on or near
`the engine hood, trunk lid, passenger doors, exterior mirrors,
`aod rear hatch or gate, all of which periodically gencrate
`tremendous shocks upon closing. Aircraft and portable illu-
`minators experience similar environments, and therefore
`another source of white light would be highly beneficial to
`decrease the time and cost associated with replacing lamps
`therein on a regular interval.
`Incandescent lamps can also be easily destroyed by expo-
`sure to liquid moisture due to the thermo-mechanical stress
`associated with contact between the hoi glass bulb wall and
`the room-temperature fluid.
`Incandescent
`lamps are also
`easily damagedby flying stones andthe like. ‘Thus, it is very
`diflicult to incorporate an incandescent light on an exterior
`minor without going to extreme measures to protect
`the
`light bulb from shock, vibration, moisture and fying objects
`while still allowing for removal of the light fixture when it
`either bums out or is otherwise permanently damaged,
`Incandescent lighis also exhibit certain electrical charac-
`teristics which make them inherently difficult to incorporate
`in vehicles, such as an automobile. For instance, when an
`incandescent
`light source is first energized by « vollage
`source, there is an initial surge of current which Hows into
`the filament. This inrush current, which is typically 12 to 20
`times ihe normal operating current, limits the lifetime of the
`lamp thus further amplifying the need for an illuminator
`siructure which allows for frequent
`replacement.
`Inrush
`current also necessitates uousual consideration when design-
`ing supporting electrical circuits which contain them, Fuses,
`relays, mechanical or electronic switches, wire harnesses,
`aod connectors electrically connected io such lamps must be
`capable of repeatedly carrying this extreme transient.
`In addition,
`the voltage-current (V-I) characteristic of
`incandescent lamps is notoriously noo-linear, as are cach of
`the relationships between light output and voltage, current,
`or power. The luminous inlensily, color temperature, and
`service life of incandescent lamps varies exponentially as a
`function applied current or voltage. This sensitivity to power
`source variation makes electronic control of incandescent
`lamps a particularly diffieult problem, They are further
`susceptible io significant reliability and field service life
`degradation when subjected continuously to DC electrical
`power, pulse-width modulated DC power, simple on/off
`switching of any Sort, or any over-vollage conditions, how-
`ever minor.
`Incandescent
`lamps also possess significant
`inductance which, when combined with their relatively high
`current load, complicates electronic switching and control
`greaily due to inductive resonant vollage transients. A typi-
`cal square wave, DCpulse modulation circuit for a 0.5 amp,
`12.8 volt incandescent lamp might produce brief transients
`as high as 30 volts, for inslance, depending on the switching
`time, the lamp involved, and the inductance, capacitance,
`aod resistance of the remainder ofthe circuil.
`
`Incandescent lamps also suffer from poor etliciency in
`converting electrical power into radiated visible white light,
`Most of the electrical energy they consume is wasted in the
`form of heat energy while less than 7% of the energy they
`consume is typically radiated as visible light. This has severe
`negalive consequences for vehicular, aerospace, watercraft,
`aod portable illuminator applications where the amount of
`power available for lighting systems is limited. In these
`applications, electrical power is provided by batteries which
`are periodically recharged by a generator on a ship or
`aircraft, an alternator in an automobile, by solar cells in the
`
`Because no viable alternatives have been available,
`however,
`illuminators for
`these overland vehicles,
`watereralt, aircraft and ihe other fields mentioned have used
`low-voliage incandescent white-light illuminators for quite
`some lime to assist
`their operators, occupants, or other
`observers in low light Jevel situations.
`[n automobiles,
`trucks, vans andthe like, white light illuminators are used as
`domelights, map lights. vanity mirror lights, courtesy lighis,
`headlamps, back-up lights and illuminators for the trunk and
`engine compartments and license plate. In such vehicles,
`white light illuminators are also used to backlight translu-
`cent screen-printed indicia such as those found in an instru-
`ment cluster panel, door panel, or heater and ventilation
`control panel. Similar uses of white light
`incandescent
`Uluminators are found on motorcycles, bicycles, electric
`vehicles and other overland craft. In aircraft, white-light
`Uluminators are used in the passenger compartment as
`reading lamps,
`to illuminate the Moor and exits during
`boarding, disembarking, and emergencies, to illuminate por-
`tions of the cockpil, and to back-light or edge-light circuit
`breaker panels and control panels. In watercraft such as
`ships, boats and submarines, white-light illuminators are
`used to illuminate the bridge, the decks, cabins and engi-
`neering spaces.
`In portable and specialty lighling
`applications, low-voltage while light illuminators are used
`as hand-held, battery-powered flashlighis, as helmet- ,
`mounted or head-mounted lamps for mountaineering or
`mining, as automatically-activated emergency lighting for
`commercial buildings, as task lighling in volatile
`environments, and as illuminators in a wide variety ofother
`situations where extreme reliability, low voltage, efficiency
`and compaciness are important.
`illuminators rely
`These aforementioned white-light
`almost exclusively upon incandescent lamps.as light sources
`because incandescent bulbs are inexpensive to produce in a
`wide variely of forms and, more importantly, they produce
`copious quantities of white light. Despite this, incandescent
`lamps possess a number of shortcomings which must be
`laken into accounl when designing an illuminator assembly.
`Incandescent lamps are fragile and have a short life even
`in stable environments and consequently must be replaced
`frequently al great inconvenience, hazard, and/or expense.
`This need for replacement has complicated designs for all
`manner of illuminators, but especially for vehicles. For
`example, in U.S. Pat. No, 4,087,096, Skogler et al. disclose
`a carrier module for supporting lamps for Uluminating a
`portion of a vehicle interior. The carrier module has a rigid
`body and a pair of mounting projections for removably
`mounting the carrier module in a rearview mirror. The
`design even has an opening specifically designed to allow
`insertion of a tool for releasing the module from the rearview
`mirror. This carrier module is an excellent example of the
`Herculean design efforts taken by mirror manufactures to
`ensure incandescent
`lamps can be easily removed and
`replaced by a vehicle owner.
`incandescent
`life,
`In addition to their inherently short
`lamps are very suscepuble to damage [rom mechanical
`shock and vibration. Automobiles experience severe shocks
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`6,132,072
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`5
`case of some remole or aerospace applications, or are
`otherwise periodically replaced or recharged with an AC/DC
`adapter such as in the case of a flashlight. Because these
`mechanisms for
`restoring battery charge are inherently
`bulky, heavy, and/or expensive, it is severely detrimental for
`an illuminator to possess poor power-conversion efficiency
`in generating visible light. An acule example of the impor-
`lance in illuminator efficiency is the electric vehicle. For
`electric bicycles, mopeds, motorcycles, automobiles, golf
`carts, or passenger or cargo transfer carts, white-light illu-
`minators in the form of electric headlamps, backup lamps,
`elc. consume an unusually large portion of the vehicle's
`limited power budget; hence they would benefit greatest
`from high-efficiency white-light
`illuminators. If a more
`efficient white-light source was available, much less power
`would be required to energize the illuminator and more
`power would be available for other systems. Alternatively,
`the power savings from an improved illuminator would
`allow for improved power supplies and energy storage or
`energy replacement mechanisms.
`Another result of poor efficiency associated with incan-
`descent lamps ts that they generate large amounts of heat for
`an equivalent amount of generated light as compared to
`other sources. This results in very high bulb-wall tempera-
`tures typically in excess of 250 degrees C. and large heat
`accumulations which must be dissipated properly by
`radiation, convection, or conduction to prevent damage or
`destruction to the illuminator support members, enclosure,
`optics or to other nearby vehicle components. This high heat
`signature of common incandescent light sources in illumi-
`nators has a particularly notable impact on the specialized
`reflector and lens designs and materials used to collimate
`and direet the light. Design efforts to dissipate the heat while
`retaining optical effectiveness further add requirements for
`space and weight
`to the illuminator assembly, a severe,
`disadvantage for vehicular, watercratt, aircraft and portable
`applications which are inherently sensitive to weight and
`space requirements.
`Portable illuminators such as hand-held flashlights and
`head-mounted lamps experience similar problems stemming
`from incandescent while-light sources and would derive the
`same benefits from an improved system.
`Physical mechanisms for generating, white-light radiation
`other
`than incandescence and pyroluminescence are
`available,
`including various gas discharges,
`electroluminescence,
`photoluminescence,
`calhodoluminescence, chemiluminescence and thermolumi-
`nescence. The output of sources using these phenomena can
`be tailored to meet
`the requirements of specific systems;
`however, they have had limited use in vehicular, watercraft,
`aircraft or portable illuminators because of a combination of
`low intensity, poor efficiency, high voliage requirements,
`limited environmental resilience, high weight, complexity,
`high cost, poor reliability, or short service life.
`More recently, great interest has been shownin the use of
`electroluminescent semi-conductor devices such as light
`emitting diodes (LEDs) as the light source for iuminator
`systems. Due to their strong, coloration and relatively low
`luminous output as compared to incandescent lamps, carly
`generations of LEDs found most of their utility as display
`devices, e.g., on/off and matrix-addressed indicators, etc,
`These uses still dominate the LED market today, however
`recent advances in LED materials, design and manufactur-
`ing have resulted in significant increases in LED luminous
`efficacy and, in their most recent commercial forms, exhibit
`a higher luminous efficacy than incandescent
`lights. But
`even the latest LEDs emit highly-saturated, narrow-
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`bandwidth, distinctively non-white light of various hues. As
`discussed above, while light in one of ils various maniles-
`lations is essential for most illuminator systems.
`they offer
`Despite the inherent colorfulness of LEDs,
`many potential advantages as compared to other conven-
`tional
`low vollage light sources for vehicles, watererafi,
`aircraft and portable illuminators. LEDs are highly shock
`resistant and therefore provide significant advantages over
`incandescent and fluorescent bulbs which can shatter when
`subjected to mechanical or thermal shock. LEDs possess
`operating lifetimes from 200,000 hours to 1,000,000 hours,
`as compared to the typical 1,000 to 2,000 hours for incan-
`descent lamps or 5,000-10,000 hours for fluorescent lamps
`It has been known that
`the narrow-band spectral emis-
`sions of several saturated light sources having different
`apparent colors can be combined to produce an additive
`color mixture having an apparent color which is different
`than that of any ofils constituents. The basics of additive
`color are evident, for instance, in the observation that white
`sunlight decomposes into ils constituent spectra when
`refracted by a prism or dispersions of walter droplets such as
`occurs in a typical rainbow, The visible white light of the sun
`can therefore be considered an additive color mixture of all
`of the hues associated with its radiation in the visible
`spectrum having wavelengths from 380 to 780 nanometers.
`An important and common example of additive color
`mixtures is the technique used in most color display screens
`possessing a cathode ray tube (CRT) or a liquid crystal
`display (LCD) element. These displays consist of address-
`able arrays of pixels, cach of which contains sub-pixels
`having the hues red, green and blue which can be energized
`alone or in combinations. In the case of the CRT, each
`sub-pixel
`is a dot of inorganic phosphor which can be
`excited via calhodoluminescence by a steered electron
`beam. In the case of the LCD, each sub-pixel is a dot of
`colored dye in regisiry with a swilehable liquid erystal
`shutter, the combination of which acts as a reconfigurable