United States Patent (19)
`Turnbull et al.
`
`54). ILLUMINATOR ASSEMBLY
`NCORPORATING LIGHT EMITTING
`DODES
`
`(75) Inventors: Robert R. Turnbull, Holland; Robert
`C. Knapp, Coloma; John K. Roberts,
`Holland, all of Mich.
`73 Assignee: Gentex Corporation, Zeeland, Mich.
`
`Appl. No.: 664,055
`21
`22 Filed:
`Jun. 13, 1996
`6
`51) Int. Cl. ....................................................... B60Q100
`52 U.S. Cl. ......................... 362/83.1; 362/800; 362/293;
`362/230; 362/231
`58 Field of Search ..................................... 362/293, 800,
`362/231, 83.1, 61,230
`
`56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`3,875,456 4/1975 Kano et al. ............................. 313/5O1
`4,211.955 7/1980 Ray ........................................... 315/53
`4,298,869 11/1981. Okuno ..................................... 340/782
`4,377,768 3/1983 Gallaro et al. .......................... 313/467
`4,450,512 5/1984 Kristofek ......
`... 362/147
`4,580,196 4/1986 Task ..............
`36262
`4,646.210 2/1987 Skogler et al. ...
`... 362/142
`4,733,336 3/1988 SE et al.
`362/142
`4,807.096 2/1989 Skogler et al. ......................... 362/142
`4,882.565 11/1989 Gallmeyer .........
`... 340/.461
`4,929,866 5/1990 Murata et al.
`... 313/500
`4,947,291 8/1990 McDermott ............................... 362/19
`4,992,704 2/1991 Stinson .....
`... 315/312
`5,008,595
`4/1991 Kazar ...
`... 315/178
`5,083,192
`1/1992 Rzeznik ........
`5,136,483 8/1992 Schoniger et al. ........................ 362/61
`5,143,433 9/1992 Farrell ....................................... 362/29
`5.255,171 10/1993 Clark .........
`... 362/231
`5,303,037 4/1994 Taranowski ...
`... 356/406
`5,325,271 6/1994 Hutchisson ................................ 362/32
`5,371,659 12/1994 Pastrick et al. ........................ 362/83.1
`
`- - - - - - 357/74
`
`
`
`USOO5803579A
`Patent Number:
`11
`(45) Date of Patent:
`
`5,803,579
`Sep. 8, 1998
`
`1/1995 Gotoh ...................................... 362/231
`5,384,519
`5,477,436 12/1995 Bertling et al. ......................... 362/231
`5,497,305 3/1996 Pastricket al. .....
`... 362/83.1
`5,699,044 12/1997 Van Lente et al. .................... 362/83.1
`FOREIGN PATENT DOCUMENTS
`
`O 625 793 A2 11/1994 European Pat. Off..
`O 689 000 A1 12/1995 European Pat. Off..
`3916875A1 12/1990 Germany.
`62-018775 1/1987 Japan.
`62-235787 10/1987 Japan.
`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 of 2087 ELEKTRONIC, vol. 44, No.
`15, Jul. 25, 1995, p. 134, “LED-Bauelement”.
`J.L. 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, pp. 26.1-26.53.
`Primary Examiner Thomas M. Sember
`Attorney, Agent, or Firm Brian J. Rees
`(57
`ABSTRACT
`An illuminator assembly, having a plurality of LEDs on a
`vehicular Support member in a manner Such that, when all of
`the LEDs are energized, illumination exhibiting a first
`perceived hue, e.g., blue-green, and projected from at least
`one of the LEDs overlaps and mixes with illumination
`exhibiting a Second perceived hue, e.g., amber, which is
`distinct from Said first perceived hue and which is projected
`from at least one of the remaining LEDs in Such a manner
`that this overlapped and mixed illumination forms a
`metameric white color and has Sufficient intensity and color
`rendering qualities to be an effective illuminator.
`
`39 Claims, 20 Drawing Sheets
`
`21
`
`f7
`
`17
`
`77
`
`77
`
`
`
`Afactoric
`Circliff
`22
`
`VWGoA EX1021
`U.S. Patent No. 9,955,551
`
`

`

`U.S. Patent
`
`Sep. 8, 1998
`
`Sheet 1 of 20
`
`5,803,579
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`Sep. 8, 1998
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`Sheet 2 of 20
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`U.S. Patent
`
`Sep. 8, 1998
`
`Sheet 3 of 20
`
`5,803,579
`
`Spectra Of Selected light Sources
`
`- 1
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`w n
`By
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`

`

`U.S. Patent
`
`Sep. 8, 1998
`
`Sheet 4 of 20
`
`5,803,579
`
`90
`30
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`feffective Aroperties for A
`50% Weutra/ Gray Jorget
`
`380
`
`430
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`450
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`560
`550
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`Spectral Power Distribution
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`550
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`El. 1-C.
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`660
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`7.30
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`7.30
`
`

`

`U.S. Patent
`
`Sep. 8, 1998
`
`Sheet 5 of 20
`
`5,803,579
`
`Spectral Zurminous Efficiency functions
`
`O3
`Sa
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`- - - V (Scotopic fresponse)
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`
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`Wavelength (nm)
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`350 400 450 500 550 600 650 700 750 800
`Wave/ength (nm)
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`s El C. E.
`
`

`

`U.S. Patent
`
`Sep. 8, 1998
`
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`U.S. Patent
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`Sep. 8, 1998
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`5,803,579
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`U.S. Patent
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`Sep. 8, 1998
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`Sheet 9 of 20
`
`5,803,579
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`Sheet 10 0f 20
`Sheet 10 of 20
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`U.S. Patent
`U.S. Patent
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`U.S. Patent
`U.S. Patent
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`Sep. 8, 1998
`Sep. 8, 1998
`
`Sheet 11 of 20
`Sheet 11 of 20
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`5,803,579
`5,803,579
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`

`U.S. Patent
`
`Sep. 8, 1998
`
`Sheet 13 0f 20
`
`5,803,579
`
`
`
`136 Aeffecting layer
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`152d
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`
`

`

`U.S. Patent
`
`Sep. 8, 1998
`
`Sheet 14 of 20
`
`5,803,579
`
`M/APROF WIH /W7E GAAI (AMA OWLY
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`

`U.S. Patent
`Sep. 8, 1998
`Sheet 16 of 20
`5,803,579
`Binary-Complementary Metomeric-White LEL) Map Light for interior
`Afectrichonic Mirror
`finitial /ntensity Distribution
`
`Binary-Complementary Metameric-White ZEZ Map light for interior
`Efectrochromic Mirror
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`
`

`

`U.S. Patent
`U.S. Patent
`
`Sep. 8, 1998
`Sep. 8, 1998
`
`Sheet 17 Of 20
`Sheet 17 of 20
`
`5,803,579
`5,803,579
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`

`U.S. Patent
`
`Sep. 8, 1998
`
`Sheet 18 of 20
`
`5,803,579
`
`
`
`longitudinal Distance (inches)
`
`

`

`U.S. Patent
`U.S. Patent
`
`
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`Sep. 8, 1998
`Sep. 8, 1998
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`5,803,579
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`U.S. Patent
`
`Sep. 8, 1998
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`Sheet 20 0f 20
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`5,803,579
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`LED Current (mA)
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`1
`ILLUMINATOR ASSEMBLY
`INCORPORATING LIGHT EMITTING
`DODES
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`The present invention relates to an illuminator assembly
`incorporating light emitting diodes, and more particularly to
`vehicular, portable and other specialty white light illumina
`tion Systems utilizing light emitting diodes having comple
`mentary hues.
`
`BACKGROUND OF THE INVENTION
`Due to limitations in human vision in low light level
`environments, white 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 of Solar illumina
`tion. Illuminators are therefore generally designed to mimic
`or reproduce daytime lighting conditions, to the extent
`possible, So that illuminated Subjects of interest are bright
`enough 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 flashlights, 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 arc
`discharge lamps. White light is critical in Such uses because
`of its unique ability to properly render colored objects or
`printed images relative to one another and its similarly
`unique 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 light. The two images would, however, be virtually
`indistinguishable from one another if illuminated with a
`deeply red colored illuminator. Another example arises from
`the need to properly identify differently-colored regions on
`conventional aeronautical 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
`terrain, whereas a deeply red colored illuminator 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 illuminators provide more universally high
`contrast and good color discrimination, thereby avoiding
`these annoying and dangerous physiological side effects.
`The extensive evolution and widespread use of white light
`illuminators, 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 that
`Setting relative to one another. An example of this 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 warm white of
`incandescent lamps is dominant in residential lighting. The
`brilliant bluish-white of mercury vapor and metal halide
`lamps is commonplace in factory assembly lines, whereas
`the bronze-white emission of the 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 Sun
`glasses. 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 out quite plainly in normal
`room illumination 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 emits 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 problem arises from 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 typi
`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 arc-discharge Source. Abacklight 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 directly by fuel combustion are no longer Suitable for
`most vehicular, watercraft, aircraft, and portable and certain
`other applications where an open flame is unsafe or unde
`sirable. These have therefore have been almost universally
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`Superseded by electrically-powered, white light Sources.
`Furthermore, many modem electric light Sources are rela
`tively inefficient, e.g., conventional tungsten incandescent
`lamps, or require high Voltages to operate, e.g., fluorescent
`and the gas discharge lamps, and therefore arent optimal for
`vehicular, portable, and other unique illuminators used
`where only limited power is available, only low Voltage is
`available or where high Voltage is unacceptable for Safety
`CaSOS.
`Because no viable alternatives have been available,
`however, illuminators for these overland vehicles,
`watercraft, aircraft and the other fields mentioned have used
`low-voltage incandescent white-light illuminators for quite
`Some time to assist their operators, occupants, or other
`observers in low light level Situations. In automobiles,
`trucks, vans and the like, white light illuminators are used as
`dome lights, map lights, Vanity mirror lights, courtesy lights,
`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
`illuminators are found on motorcycles, bicycles, electric
`vehicles and other overland craft. In aircraft, white-light
`illuminators are used in the passenger compartment as
`reading lamps, to illuminate the floor and exits during
`boarding, disembarking, and emergencies, to illuminate por
`tions of the cockpit, and to back-light or edge-light circuit
`breaker panels and control panels. In water-craft 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 lighting
`applications, low-voltage white light illuminators are used
`as hand-held, battery-powered flashlights, as helmet
`mounted or head-mounted lamps for mountaineering or
`mining, as automatically-activated emergency lighting for
`commercial buildings, as task lighting in volatile
`environments, and as illuminators in a wide variety of other
`Situations where extreme reliability, low Voltage, efficiency
`and compactness are important.
`These aforementioned white-light illuminators rely
`almost exclusively upon incandescent lamps as light Sources
`because incandescent bulbs are inexpensive to produce in a
`wide variety of forms and, more importantly, they produce
`copious quantities of white light. Despite this, incandescent
`lamps possess a number of Shortcomings which must be
`taken into account when designing an illuminator assembly.
`Incandescent lamps are fragile and have a short life even
`in Stable environments and consequently must be replaced
`frequently at 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 illuminating 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.
`In addition to their inherently short life, incandescent
`lamps are very Susceptible to damage from mechanical
`Shock and vibration. Automobiles experience Severe shockS
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`and Significant vibration during 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,
`and rear hatch or gate, all of which periodically generate
`tremendous shockS periodically upon closing. Aircraft and
`portable illuminators 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 hot glass bulb wall and
`the room-temperature fluid. Incandescent lamps are also
`easily damaged by flying Stones and the like. Thus, it is very
`difficult to incorporate an incandescent light on an exterior
`mirror without going to extreme measures to protect the
`light bulb from Shock, Vibration, moisture and flying objects
`while still allowing for removal of the light fixture when it
`either burns, out or is otherwise permanently damaged.
`Incandescent lights 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 a Voltage
`Source, there is an initial Surge of current which flows into
`the filament. This in-rush current, which is typically 12 to 20
`times the normal operating current, limits the lifetime of the
`lamp thus further amplifying the need for a illuminator
`Structure which allows for frequent replacement. Inrush
`current also necessitates unusual consideration when design
`ing Supporting electrical circuits which contain them. Fuses,
`relays, mechanical or electronic Switches, wire harnesses,
`and connectors electrically connected to Such lamps must be
`capable of repeatedly carrying this extreme transient.
`In addition, the voltage-current (V-I) characteristic of
`incandescent lamps is notoriously non-linear, as are each of
`the relationships between light output and Voltage, current,
`or power. The luminous intensity, 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 difficult problem. They are further
`Susceptible to 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-Voltage conditions, how
`ever minor. Incandescent lamps also possess significant
`inductance which, when combined with their relatively high
`current load, complicates electronic Switching and control
`greatly due to inductive resonant Voltage transients. A typi
`cal Square wave, DC pulse modulation circuit for a 0.5 amp,
`12.8 volt incandescent lamp might produce brief transients
`as high as 30 volts, for instance, depending on the Switching
`time, the lamp involved, and the inductance, capacitance,
`and resistance of the remainder of the circuit.
`Incandescent lamps also Suffer from poor efficiency 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
`negative consequences for vehicular, aerospace, watercraft,
`and 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
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`case of Some remote 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 acute example of the impor
`tance 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,
`etc. 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 resultant of poor efficiency associated with
`incandescent lamps is that they generate large amounts of
`heat for an equivalent amount of generated light as com
`pared to other sources. This results in very high bulb-wall
`temperatures 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 direct 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, watercraft, 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, Stem
`ming from incandescent white-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 discharge S,
`electrol u mine Scence, photo lumine Scence,
`cathodoluminescence, 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 Voltage requirements,
`limited environmental resilience, high weight, complexity,
`high cost, poor reliability, or short Service life.
`More recently, great interest has been shown in the use of
`electroluminescent Semi-conductor devices Such as light
`emitting diodes (LEDs) as the light Source for illuminator
`Systems. Due to their Strong coloration and relatively low
`luminous output as compared to incandescent lamps, early
`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, white light in one of its various manifes
`tations is essential for most illuminator Systems.
`Despite the inherent colorfulness of LEDs, they offer
`many potential advantages as compared to other conven
`tional low voltage light Sources for Vehicles, watercraft,
`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.
`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 of its constituents. The basics of additive
`color are evident, for instance, in the observation that white
`Sunlight decomposes into its constituent spectra when
`refracted by a prism or dispersions of water 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, each 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 cathodoluminescence by a steered e