(12) United States Patent
`(10) Patent No.:
`US 6,488,390 B1
`
`Lebens et al.
`(45) Date of Patent:
`*Dec. 3, 2002
`
`U5006488390B1
`
`(75)
`
`(54) COLOR-ADJUSTED CAMERA LIGHT AND
`METHOD
`Inventors: Gary A. Lebens, Chaska, MN (US);
`.
`Charles T- Bourm Mln?et0nka> MN
`(US); Charles A. Lemaire, Apple
`Valley, MN (Us)
`.
`_
`_
`.
`.
`(73) ASSignee: F551) V1510“: Inc., Eden Prairie, MN
`
`( * ) Notice:
`
`Subject. to any disclaimer, the term of this
`patent 15 extended or adjusted under 35
`U50 154(1)) by 0 days.
`.
`Th'
`.
`b'
`is patent is su Ject to a termina
`claimer.
`
`1 d'
`is-
`
`(21) APP1~N0~309/9783760
`(22)
`Filed:
`Oct. 16, 2001
`
`Related US. Application Data
`
`(60) Continuation of application No. 09/627,268, filed 011]u1.28,
`2009: “5"” Pat N°~ 673057818: Whieh is ‘1 diViSion 0f
`£113:116021932121): 09/044’559’ filed on Man 19’ 1998’ now Pat'
`7
`
`.................................................. F21V 9/00
`Int. Cl.
`(51)
`....................... 362/231; 362/184; 362/185;
`(52) US. Cl.
`362/208; 362/183; 362/800; 362/234; 362/11;
`362/13
`(58) Field of Search ................................. 362/157, 183,
`362/159, 184, 208, 800, 249, 11, 13, 234;
`315/224, 307, 291, 312, 360, 362
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`370697654 A
`3,663,752 A
`4’208’579 A
`4,212,073 A
`4,290,095 A
`4 346 329 A
`
`12/1962 HOUgh ~~~~~~~~~~~~~~~~~~~~ 340/1463
`5/1972 FIOSChle
`6/1980 Scrivo et al’ """""""" 250/227
`7/1980 Balasubramanian ........ 364/562
`
`9/1981 Schmidt
`..............
`362/191
`8/1982 Schmidt
`...................... 315/51
`
`EP
`{E50
`W0
`
`FOREIGN PATENT DOCUMENTS
`0356680
`3/1990
`901638801
`2/1995
`/06846
`5/1991
`98/02716
`1/1998
`
`""""" GOlN/21/88
`........... GOlB/11/03
`
`OTHER PUBLICATIONS
`“Copy of US. application Ser. No. 08/825,774 entitled High
`Speed Digital Video Serial Link”, 33 pgs., (Apr. 2, 1997).
`(List continued on next page.)
`Primary Examiner—Stephen Husar
`Assistant Examiner—Bertrand Zeade
`(74) Attorney, Agent, or Firm—Schwegman, Lundberg,
`Woessner & Kluth, RA.
`(57)
`ABSTRACT
`
`Improved method and apparatus for hand-held portable
`illumination. A flashlight and corresponding method are
`described. The flashlight includes a housing, a plurality of
`LEDs, and an electrical circuit that selectively applies power
`from the DC voltage source to the LED units, wherein the
`flashlight is suitable for handheld portable operation by a
`user. In one embodiment, the first electrical circuit further
`includes a control circuit for maintaining a predetermined
`light output level of the LED units as a charge on a battery
`varies. In another embodiment, the control c1rcuit maintains
`an average predetermined light output level of the LED units
`as the charge on the battery cell varies by changing a pulse
`width or frequency as the charge on the battery cell varies to
`maintain a given average light output. Another aspect pro-
`vides an illumination source that includes a light-emitting
`diode (LED) housing including one or more LEDs, and a
`control circuit that selectively applies power from a source
`of electric power to the LEDs, the control circuit substan-
`tially maintaining a light output characteristic of the LEDs
`as a voltage of the voltage source varies over a range that
`would otherwise vary the light output characteristic. Still
`another aspect provides an illumination source including a
`light-emitting diode (LED) housing including one or more
`LEDS’ and a control circuit that selectivel
`a
`lies ower
`’
`.
`y pp
`.p
`.
`from a source of electric power to the LEDs, thus maintain-
`mg or contmmng a light output C01“ SPelem 0f the LEDS~
`
`(List continued on next page.)
`
`40 Claims, 11 Drawing Sheets
`
`15m
`
`CONTROL cmcurr
`FOR LEDs
`
`
`
`
`
`V7301
`
`31%
`
`5W
`
`
`
`
`
`
`
`
`=T
`
`3“
`
`HTC, Exhibit 1002
`
`
`
`
`
`
`
`VIDEO [MAGER
`
`
`CIRCUIT
`
`
`
`
`I
`RECORDER
`
`
`
`
`
`
`HTC, Exhibit 1002
`
`

`

`US 6,488,390 B1
`
`Page 2
`
`US. PATENT DOCUMENTS
`
`4,509,266 A
`4,592,147 A
`4,639,139 A
`4,641,972 A
`4743773 A
`4,820,229 A
`4,831,504 A
`49877326 A
`4,882,498 A
`4,893,815 A
`4,914,289 A
`4,962,347 A
`4,964,023 A
`4,965,665 A
`4,967,284 A
`4,972,093 A
`4,974,138 A
`2231323 2
`,
`,
`5,015,918 A
`5,051,825 A
`5,058,982 A
`5,059,013 A
`5,060,065 A
`570657035 A
`5’072’127 A
`5,085,502 A
`5,172,005 A
`5,179,335 A
`5,179,474 A
`5,279,513 A
`52999227 A
`:733273; 2
`,
`,
`5,398,113 A
`5,424,927 A
`5,457,492 A
`5,465,152 A
`5,468,950 A
`5,546,189 A
`5,561,525 A
`5,604,550 A
`
`4/1985 Cusack ..................... 33/174 L
`6/1986 Herman .......... 33/366
`
`.....
`1/1987 Wyant et a1.
`356/359
`
`356/376
`2/1987 Halioua et a1.
`-
`250/566
`5/1988 Katana et a1~
`
`~~ 446/26
`4/1989 Spraggins ~~~~~
`
`
`5/1989 Nishizawa eta.
`..
`362/100
`10/1989 Chadwick 6t al~ ~~~~~~~~~~ 356/394
`11/1989 Cochran et a1~
`~~~~~~~~~~~~ 250/571
`1/1990 Rowan ........................ 273/84
`4/1990 Nguyen et a1.
`250/223 B
`
`........... 320/48
`10/1990 Burroughs et a1.
`10/1990 Nishizawa et al.
`......... 362/100
`10/1990 Amir ................
`358/101
`
`10/1990 YOShida 6t al~
`358/300
`
`............ 250/572
`11/1990 Cochran et a1.
`11/1990 Negrshi
`...................... 362/347
`1421/1990 Juengel ”
`’ 250551
`
`/1991 Garriss
`. 348/371
`5/1991 Copeland
`.. 315/76
`
`9/1991 Cochran eta.
`. 358/106
`
`10/1991 Katzir ............... 385/33
`10/1991 Jain ........................... 359/503
`10/1991 Wasserman ................. 358/106
`11/1991 Juengel """"
`250551
`
`12/1991 COChran et al'
`250572
`"
`2/1992 Womack et al.
`356/376
`.....
`12/1992 Cochran et al.
`..
`...... 250/57
`
`1/1993 Nor ................... 320/21
`............... 359/798
`1/1993 Bailey et al.
`1/1994 Connelly .................... 446/219
`3/1994 R056
`375/1
`
`13133: Eofismelt 1~
`~ 322731;;
`0 en e a.
`..
`.......
`3/1995 de Groot
`356/360
`
`6/1995 Schaller et a1.
`362/157
`10/1995 Sasakietal.
`............... 348/126
`11/1995 Bilodeau et al.
`............ 356/371
`11/1995 Hanson
`235/472
`
`8/1996 Svetkoff et al.
`............ 356/376
`10/1996 Toyonaga et a1.
`........... 356/360
`2/1997 White ........................ 396/429
`
`6/1997 Bieman et a1.
`............. 356/374
`5,636,025 A
`7/1997 Bieman ..........
`356/376
`5,646,733 A
`
`10/1997 Huber et al
`356/371
`5,680,215 A
`
`4/1998 Lebens ..
`348/370
`5,745,176 A
`
`......
`10/1998 Huber
`356/371
`5,825,495 A
`10/1998 King et a1.
`..
`...... 356/237
`5,828,449 A
`
`............. 340/815.45
`11/1998 Bladowski
`5,838,247 A
`4/1999 Abtahi et a1.
`............... 362/294
`5,890,794 A
`
`7/2000 Tonkin et a1.
`..
`248/212
`6,084,631 A
`.............. 362/184
`8/2000 Lebens et al.
`6,095,661 A
`6,305,818 B1 * 10/2001 Lebens et al.
`.............. 362/184
`
`OTHER PUBLICATIONS
`
`“Edmund Scientific Company 1993 Annual Referencing
`Catalog, Cylinder Lenses (CYL)”, catalog pg. 47.
`“Hewlett Packard Optotronics Designer’s Catalog, Techni-
`cal Data entitled High power AllnGalP Amber and Red-
`dish—Orange LampS”,PgS~ 3-24 through 3-29) 1993-
`Ballard, D.H., “Generalizing the Hough Transform to Detect
`.
`”
`.
`.
`Arbitrary Shapes , Pattern Recognition, Z3 (2), Pergamon
`Press, PP~ 183-194, (1981)
`Davies, E.R., Machine Vision: Theory, Algorithns, Practi-
`calities, 2nd Edition, Academic Press, San Diego, pp.
`195—210,(1997).
`Gennert, M.A., et al., “Uniform Fontal Illumination 0f
`Planar Surfaces: Where to place the lamps”, Optical Engi-
`.
`”6”?”5) VOL 32’ NO‘ 6’ pp‘ 1261—1271’ 01.1“; 199.3)
`.
`NOVIHI, A, “Fundamentals of maChlne VISIOH nghtlng”,
`Electra Conference Record, New York, NX pp. 435-443,
`(1993).
`Uber, G.T., “Illumination Methods for Machine Vision”,
`SPIE vol. 728 Optics, Illumination, and Image Sensing for
`-
`-
`MaChme Vlsmn’ pp; 93—102} (1.986)
`.
`.
`.
`Yang, HS, et al., Determination 0f.the Identity, Posrtron
`and Orlentatlon 0f the TOPHIOSt ObJect In a P1161 Some
`Further EXperimentS”, IEEE International Conference on
`Robotics and Automation, 1, San Francisco. CA, 293—298,
`(1986).
`
`* cited by examiner
`
`HTC, Exhibit 1002
`
`HTC, Exhibit 1002
`
`

`

`US. Patent
`
`Dec. 3, 2002
`
`Sheet 1 0f 11
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`US 6,488,390 B1
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`US. Patent
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`US. Patent
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`Dec. 3, 2002
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`Sheet 6 0f 11
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`US 6,488,390 B1
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`US. Patent
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`US 6,488,390 B1
`
`1
`COLOR-ADJUSTED CAMERA LIGHT AND
`METHOD
`
`This application is a continuation of US. application Ser.
`No. 09/627,268, filed Jul. 28, 2000 (US. Pat. No. 6,305,
`818), which is a divisional of US. application Ser. No.
`09/044,559, filed Mar. 19, 1998 (US. Pat. No. 6,095,661),
`which applications are incorporated herein by reference.
`
`FIELD OF THE INVENTION
`
`This invention relates to the field of lighting, and more
`specifically to a method and apparatus of controlling and
`powering a solid-state light source such as a light-emitting
`diode or LED, for a portable battery-powered flashlight.
`
`BACKGROUND OF THE INVENTION
`
`There is a widespread need for hand-held flashlights and
`lanterns. One common flashlight includes a two-cell battery
`for power, an incandescent lamp to emit light, and a simple
`single-pole switch to connect and disconnect the battery to
`the lamp. Other flashlights use other numbers of battery cells
`in order to provide a voltage suitable for various particular
`conditions. Lanterns often use a fluorescent tube to emit
`
`light. Certain keychain fobs use a pair of hearing-aid cells
`and a red-light
`light-emitting diode (LED) in order to
`provide short-range lighting such as might be needed to find
`a keyhole in the dark.
`Battery technology is such that as electrical power is
`withdrawn from a battery cell, the voltage available across
`a given current load will decrease. This decreased available
`voltage across the given load causes reduced light output,
`gradually dimming the light as the battery charge depletes.
`Further, LEDs have voltage, current, and power param-
`eters that must be controlled in order to maximize device
`
`life. Commonly, a current-limiting resistor is placed in series
`with an LED in order that only a portion of the voltage drop
`from the battery is across the LED and the rest of the voltage
`drop is across the resistor. This voltage drop and correspond-
`ing power loss in the resistor is dissipated as waste heat,
`which is inefficient for a flashlight which should be designed
`to emit light.
`it is awkward or difficult to determine the
`In addition,
`amount of remaining charge in a battery cell, generally
`requiring removal of the battery from the flashlight in order
`to measure the remaining charge. In addition, the cost of a
`separate measurement device can be a negative for this
`market. Some battery cells today include a built-in liquid-
`crystal indicator for the charge in the cell, but such a solution
`requires a separate measurement device/indicator for each
`battery, and requires removal of the battery from the flash-
`light in order to perform the measurement and observe the
`indication of remaining power.
`
`SUMMARY OF THE INVENTION
`
`The present invention provides a method and apparatus
`for an LED. flashlight or other LED illumination source. In
`one embodiment, a flashlight is described. The flashlight
`includes a flashlight housing suitable for receiving therein
`and/or mounting thereon at least one DC voltage source such
`as a battery. The flashlight also includes a light-emitting
`diode (LED) housing connected to the flashlight housing,
`the LED housing including a first plurality of LED units-
`that each emit light and have a reflector for collimating the
`emitted light forwardly therefrom generally along an LED
`optical axis, the first plurality of LED units including at least
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`seven individual LED units. The flashlight also includes a
`first electrical circuit that selectively applies power from the
`DC voltage source to the LED units, wherein the flashlight
`is of such compact size and low weight as to be suitable for
`single-handed portable operation by a user, the flashlight
`further having a purpose of providing general-purpose illu-
`mination.
`
`In one embodiment, the LED optical axes of the first
`plurality of LED units in the flashlight are substantially
`parallel to one another. In one such embodiment, the flash-
`light further includes a second plurality of LED units that
`each emit
`light and have a reflector for collimating the
`emitted light forwardly therefrom generally along an LED
`optical axis, wherein the LED optical axes of the second
`plurality of LED units converge or diverge from one another
`forwardly from the housing.
`In another embodiment, an optical spread angle of the first
`plurality of LED units in the flashlight are substantially
`equal to one another. In one such embodiment, the flashlight
`further includes a second plurality of LED units that each
`emit light and have a reflector for collimating the emitted
`light forwardly therefrom generally along an LED optical
`axis, wherein an optical spread angle of the second plurality
`of LED units are substantially equal to one another, and
`different than the optical spread angle of the first plurality of
`LED units.
`
`In yet another embodiment, the LED units are connected
`in a parallel-series configuration with at least two LED units
`coupled in parallel to one another and in series with at least
`one other LED unit, and the DC voltage source includes at
`least three battery cells connected in series.
`In still another embodiment,
`the first electrical circuit
`further includes a control circuit for maintaining a prede-
`termined light output level of the LED units as a charge on
`the battery cell varies. In one such embodiment, the control
`circuit maintains an average predetermined light output level
`of the LED units as the charge on the battery cell varies by
`increasing a pulse width or a pulse frequency as the charge
`on the battery cell decreases. In another such embodiment,
`the control circuit maintains an average predetermined light
`output level of the LED units by measuring a battery voltage
`and adjusting a pulse width or a pulse frequency or both to
`maintain the average light output at the predetermined level.
`In still another such embodiment, the control circuit main-
`tains an average predetermined light output level of the LED
`units by measuring an average light output and adjusting a
`pulse width or a pulse frequency or both to maintain the
`measured average light output at the predetermined level.
`Another aspect of the present invention provides a flash-
`light including: (a) a flashlight housing, the housing being
`suitable for at least one of receiving therein and mounting
`thereon at least one DC voltage source that includes at least
`one battery cell; (b) a light-emitting diode (LED) housing
`connected to the flashlight housing, the LED housing includ-
`ing one or more first LED units that each emit light and have
`a reflector for collimating the emitted light forwardly there-
`from generally along an LED optical axis; and (c) a first
`electrical circuit that selectively applies power from the DC
`voltage source to the LED units, the first electrical circuit
`further including a control circuit for maintaining a prede-
`termined light output level of the LED units as a charge on
`the battery cell varies; wherein the flashlight is of such
`compact size and low weight as to be suitable for single-
`handed portable operation by a user, the flashlight further
`having a purpose of providing general-purpose illumination.
`In one such embodiment, the first LED units being a first
`plurality of LED units, wherein the LED optical axes of the
`
`HTC, Exhibit 1002
`
`HTC, Exhibit 1002
`
`

`

`US 6,488,390 B1
`
`3
`first plurality of LED units are substantially parallel to one
`another. In another such embodiment, the flashlight-further
`includes a second plurality of LED units that each emit light
`and have a reflector for collimating the emitted light for-
`wardly therefrom generally along an LED optical axis,
`wherein the LED optical axes of the second plurality of LED
`units converge or diverge from one another forwardly from
`the housing.
`In another such embodiment, the first LED units are a first
`plurality of LED units, wherein an optical spread angle of
`the first plurality of LED units are substantially equal to one
`another.
`In yet another such embodiment,
`the flashlight
`further includes a second plurality of LED units that each
`emit light and have a reflector for collimating the emitted
`light forwardly therefrom generally along an LED optical
`axis, wherein an optical spread angle of the second plurality
`of LED units are substantially equal to one another, and
`different than the optical spread angle of the first plurality of
`LED units.
`
`Another aspect of the present invention provides a method
`of providing general-purpose illumination of such compact
`size and low weight as to be suitable for single-handed
`portable operation by a user,
`including the steps of: (a)
`providing one or more first LED units that each emit light
`and have a reflector for collimating the emitted light for-
`wardly therefrom generally along an LED optical axis; (b)
`selectively applying power from a DC voltage source to the
`LED units; and (c) maintaining a predetermined light output
`level of the LED units as a charge on the battery cell varies
`by controlling the step (b).
`In one embodiment, the step of maintaining maintains an
`average predetermined light output level of the LED units as
`the charge on the battery cell varies by increasing a pulse
`energy or a pulse frequency as the charge on the battery cell
`decreases. In another embodiment, the step of maintaining
`maintains an average predetermined light output level of the
`LED units by measuring a battery voltage and adjusting a
`pulse width or a pulse frequency or both to maintain the
`average light output at
`the predetermined level. In still
`another embodiment, the step of maintaining maintains an
`average predetermined light output level of the LED units by
`measuring a light output and adjusting a pulse energy or a
`pulse frequency or both to maintain an average light output
`at the predetermined level.
`Yet another aspect of the present invention provides an
`illumination source, that includes (a) a light-emitting diode
`(LED) housing including one or more LEDs; and (b) a
`control circuit that selectively applies power from a source
`of electric power to the LEDs, the control circuit substan-
`tially maintaining a light output characteristic of the LEDs
`as a voltage of the voltage source varies over a range that
`would otherwise vary the light output characteristic. In one
`such embodiment,
`the light output characteristic that
`is
`maintained is light output
`intensity.
`In another such
`embodiment, the control circuit maintains the light output
`intensity of the LED units as the voltage of the DC voltage
`source varies by increasing a pulse width, a pulse energy, or
`a pulse frequency as the voltage of the DC voltage source
`decreases. In another such embodiment, the control circuit
`maintains an average predetermined light output level of the
`LED units by measuring a voltage and adjusting a pulse
`energy or a pulse frequency or both to maintain the average
`light output at the predetermined level. In yet another such
`embodiment, the control circuit maintains an average pre-
`determined light output level of the LED units by measuring
`an average light output and adjusting a pulse width or a pulse
`frequency or both to maintain the measured average light
`output at the predetermined level.
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`invention provides a
`Another aspect of the present
`battery-powered portable flashlight (100) including: a casing
`(110) suitable to hold a battery; one or more light-emitting
`devices (LEDs) (150) mounted to the casing; a switch (140)
`mounted to the casing; and a control circuit (130) coupled to
`the battery, the LEDs, and the switch, wherein the control
`circuit drives the LEDs with electrical pulses at a frequency
`high enough that light produced by the LEDs has an appear-
`ance to a human user of being continuous rather than pulsed,
`and wherein the LEDs have proportion of on-time that
`increases as remaining battery power decreases. One such
`embodiment further includes a feedback circuit that controls
`
`the pulses so that light intensity produced by the LEDs, as
`perceived by the human user, is substantially constant across
`a greater range of battery power or voltage than a corre-
`sponding range for which light intensity is equally constant
`without the feedback circuit. In one such embodiment, the
`feedback circuit measures a light output of the LEDs.
`Another such embodiment further includes a battery-
`voltage-measuring circuit coupled to the control circuit.
`Yet another aspect of the present invention provides a
`method for driving battery-powered portable flashlight (100)
`having a casing (110), a DC power source mounted to the
`casing, one or more solid-state light-emitting device (LEDs)
`(150) mounted to the casing, the method including the steps
`of: receiving input from a user; and based on the received
`input, generating a series of pulses to drive the LEDs such
`that the LEDs have proportion of on-time that increases as
`remaining battery power decreases.
`Still another aspect of the present invention provides an
`illumination source including (a) a light-emitting diode
`(LED) housing including one or more LEDs; and (b) a
`control circuit that selectively applies power from a source
`of electric power to the one or more LEDs, the control circuit
`maintaining a predetermined light output color spectrum of
`the one or more LEDs as a voltage of the source of electric
`power varies. In one such embodiment, the one or more
`LEDs comprise one or more LEDs having a first character-
`istic color spectrum output and one or more LEDs having a
`second characteristic color spectrum output, the first char-
`acteristic color spectrum output different from the second
`characteristic color spectrum output, and the control circuit
`controls a pulse characteristic in order to control the pro-
`portion of light output having the first characteristic color
`spectrum output to that having the second characteristic
`color spectrum output. In another such embodiment, the one
`or more LEDs comprise one or more LEDs having a
`characteristic color spectrum output that varies based on
`applied current, and the control circuit controls a pulse
`current in order to control the characteristic color spectrum
`output.
`Yet another aspect of the present invention provides an
`illumination source that includes (a) a light-emitting diode
`(LED) housing including one or more LEDs; and (b) a
`control circuit that selectively applies power from a source
`of electric power to the LEDs to adjust a light output color
`spectrum of the one or more LEDs.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 shows one embodiment of the present invention, a
`schematic representation of a handheld LED flashlight 100.
`FIG. 2 is a circuit block diagram of an LED flashlight
`circuit 200, which circuit is used in some embodiments of
`LED flashlight 100 of FIG. 1 or LED light source in
`camcorder 500 of FIG. 5 or other devices such as machine-
`
`vision systems.
`
`HTC, Exhibit 1002
`
`HTC, Exhibit 1002
`
`

`

`US 6,488,390 B1
`
`5
`FIG. 3 a circuit block diagram of an LED flashlight circuit
`300, which circuit is used in some embodiments of LED
`flashlight 100 of FIG. 1 or LED light source in camcorder
`500 of FIG. 5 or other devices such as machine-vision
`systems.
`FIG. 4 a circuit block diagram of an LED flashlight circuit
`400, which circuit is used in some embodiments of LED
`flashlight 100 of FIG. 1 or LED light source in camcorder
`500 of FIG. 5 or other devices such as machine-vision
`systems.
`FIG. 5 is a diagram showing a controlled LED light
`source is integrated into a handheld camcorder 500.
`FIG. 6 is a graph of color spectrum versus current for an
`LED to be used in one embodiment of the present invention.
`FIG. 7 is circuit block diagram of an LED illumination
`device circuit 700, which circuit is used in some embodi-
`ments of LED flashlight 100 of FIG. 1 or LED light source
`in camcorder 500 of FIG. 5 or other devices such as
`
`machine-vision systems.
`FIG. 8 is circuit block diagram of an LED illumination
`device circuit 700 that uses a current mirror.
`
`FIG. 9 is a graph of color spectrum (photoluminescence)
`versus temperature for an LED to be used in one embodi-
`ment of the present invention.
`FIG. 10 is circuit block diagram of a machine vision
`system using an LED illumination device according to the
`present invention.
`FIG. 11 is circuit block diagram of an LED illumination
`device according to the present invention.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`
`In the following detailed description of the preferred
`embodiments, reference is made to the accompanying draw-
`ings that form a part hereof, and in which are shown by way
`of illustration specific embodiments in which the invention
`may be practiced. It is understood that other embodiments
`may be utilized and structural changes may be made without
`departing from the scope of the present invention.
`The present invention takes advantage of the efficiency of
`high-intensity, light-emitting diodes (LEDs) in the visible
`spectrum and/or infra-red (IR) or ultra-violet (UV), arranged
`in various patterns,
`the low-voltage properties of CMOS
`integrated circuits and components, and the efficiency
`derived from switching the current
`to and limiting the
`duration of current to the LEDs to project light efficiently
`and with constant brightness even as the battery supply
`voltage decays over time. The invention takes advantage of
`the dynamic impedance of the LEDs which causes the
`voltage across the LED to rise rapidly relative to the current
`flow through the LED to limit the initial current flow to the
`LED, when battery voltage is highest, to prevent wire bond
`heating from causing premature failure of the LEDs. The
`present invention controls the current flow duration (pulse
`width) to limit power dissipation in the LEDs during the
`LEDs’ on state, and increasing the pulse width as the battery
`voltage decreases over time to maintain substantially con-
`stant perceived or average LED intensity over the course of
`the battery’s life. The invention controls the switching
`frequency of the pulse width to further control the LED
`intensity and power dissipation while maintaining a constant
`light output from the LEDs as perceived or visible to the
`human eye, or a light-sensing device, e.g., camera, night-
`vision scope, CMOS and CCD sensor and pixel arrays. The
`present invention provides a compact, portable light source,
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`preferably sized to be readily hand-held, for illuminating an
`object, several objects, or areas for human use and/or
`machine operation. In one embodiment, the invention mea-
`sures battery voltage and in turn regulates the LED intensity.
`In another embodiment, the present invention uses a light-
`sensing device such as a light-sensing transistor or light-
`detecting diode (LDD) in proximity to the output LED(s) to
`measure the average brightness and further regulate the
`LEDs’ output.
`Another embodiment of the present invention provides
`operator-selectable control of the pulse frequency and/or the
`pulse width to provide a reduced apparent brightness in
`order to increase battery life in situations when maximum
`brightness is not required.
`In one such pulse-frequency
`embodiment, the apparent (visible) pulse frequency would
`provide a stroboscope effect for safety or entertainment. In
`this embodiment,
`the visibly interrupted or pulsed pulse
`train may include repetitive pulses or a coded sequence as in
`Morse code “SOS” or a predetermined password or security
`string of pulses that may then he used as a key or identifier.
`A further refinement of this embodiment would provide the
`user with a method for strobing out a message. It is under-
`stood that what appears to be a single visible pulse may
`actually include a high-frequency series of pulses in order to
`increase the apparent brightness of a single pulse while also
`protecting the LEDs from excessive power dissipation. In
`yet another pulse-frequency embodiment of the invention, a
`variable or adjustable constant sequence pulse train is estab-
`lished for the accurate measurement of the velocity or
`frequency of an object in motion or vibration.
`Another embodiment of the present invention uses vari-
`ous colored LEDs for specialized purposes. In one such
`embodiment, long-wavelength LEDs, 660 nm or longer, are
`used to provide underwater divers or aquarium enthusiasts a
`light source for observing undersea life at night without
`adversely affecting the nocturnal activities of such wildlife.
`This functionality is also useful for tropical aquarium own-
`ers who also wish to observe the nocturnal activities of the
`
`occupants of their aquariums. In another such embodiment,
`short-wavelength blue LEDs are used with a UV filter to
`view fluorescing materials,
`including but not limited to:
`taggants, stamps, security codes and security seals. As UV
`LEDs become readily available (such as those announced as
`made by IBM Corporation in the Mar. 9, 1998 issue of
`Electronic Engineering Times, page 39), these could be used
`in place of the blue LEDs. In other embodiments, a suitable
`LED normally emitting in the blue spectrum, for example
`made from GaN (gallium nitride) or InGaN (indium gallium
`nitride), is pulsed by pulses of sufficiently high current to
`blue-shift the output and sufficiently short duration to not
`destroy the LED in order to maintain a constant
`light
`intensity while shifting the color spectrum from blue to
`ultraviolet. Other embodiments include IR LEDs for mili-
`
`tary or police use to enhance the usefulness of night-vision
`equipment and for fiend-or-foe identification, multiple color
`LEDs to produce a white light source, and combinations of
`colored LEDs to enhance the ability of color-blind individu-
`als to perceive colors. Other uses include LEDs chosen for
`use in photographic darkrooms wherein the LED wave-
`length is chosen to prevent undesired exposure of light-
`sensitive materials.
`
`Another embodiment of the present invention uses LEDs
`of various “viewing” angles to achieve wide-angle viewing
`versus narrow-angle, long-range viewing and combinations
`thereof. A further refinement of this embodiment utilizes a
`
`lens (or other lens or reflector arrangement) to
`Fresnel
`provide a focusable light source. Another embodiment uses
`
`HTC, Exhibit 1002
`
`HTC, Exhibit 1002
`
`

`

`US 6,488,390 B1
`
`7
`polarizers to reduce specular reflections for enhanced view-
`ing or for use in machine-vision applications. Another
`embodiment utilizes quickly and easily pluggable/
`replaceable LED arrays or heads of various shapes, colors,
`and/or viewing angles for different applications.
`In yet another embodiment, the light output is momen-
`tarily interrupted repetitively, or strobed,
`to indicate low
`battery condition with some estimation of time