USOO9119266B1
`
`(12) Unlted States Patent
`(10) Patent N0.:
`US 9,1 19,266 B1
`
`Lebens et al.
`(45) Date of Patent:
`Aug. 25, 2015
`
`(54) PULSED L.E.D. ILLUMINATION APPARATUS
`AND METHOD
`
`(71) Applicant: LED Tech Development, LLC,
`Burnsville, MN (US)
`
`(72)
`
`Inventors: Gary A. Lebens, Chaska, MN (US);
`Charles T. Bourn, Minnetonka, MN
`(US); Charles A. Lemaire, Apple Valley,
`MN (US)
`
`(2006.01)
`(2006.01)
`
`F21L 4/02
`F2] V 1/00
`(52) US. Cl.
`CPC ............ H05B 33/0869 (2013.01); F21L 4/027
`(2013.01); H05B 33/0815 (2013.01); H05B
`33/0851 (2013.01); H05B 33/0863 (2013.01);
`F211. 2001/00 (2013.01)
`(58) Field of Classification Search
`USPC ............. 315/1527159, 209 R, 225, 226, 291,
`315/307, 308, 362
`See application file for complete search history.
`
`(73) Assignee: LED Tech Development, LLC,
`Burnsville, MN (US)
`
`(56)
`
`References Cited
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`31:13 lfsi’glitg gyzdluswd under 35
`
`(21) APPI- N0-3 14/480,630
`
`(22)
`
`Filed:
`
`Sep. 8, 2014
`
`Related U-S- Application Data
`
`(60) Division of application No. 14/049,188, filed on Oct.
`8 2013 now Pat. No. 8 829 808 which is a division of
`application No. 13/736:865: filed on Jan. 8, 2013, now
`Pat. No. 8,643,305, which is a division of application
`No. 13/244,481, filed on Sep. 25, 2011, now Pat. No.
`8,362,712, which is a division of application No.
`12/820 139 filed on Jun. 22 2010 now Pat. No.
`8,159,146, awhich is a division of application No.
`12/166 315 filed on Jul.
`1
`2008 now Pat. No.
`7,740,571, awhich is a division of 5application No.
`11/674 143 filed on Feb. 12 2007 now Pat. No.
`’
`5
`5
`5
`
`(Continued)
`
`(51)
`
`Int. Cl-
`H05B 3 7/02
`H05B 33/08
`
`(2006.01)
`(2006.01)
`
`U'S' PATENT DOCUMENTS
`5,253,047 A * 10/1993 Machishima .............. 348/2241
`Primary Examiner 7 Jimmy Vu
`(74) Attorney, Agent,
`or Firm 7 Eduardo E. Drake;
`Fantastic lP Consulting, LLC; Charles A. Lemaire
`
`ABSTRACT
`(57)
`An illumination source for a camera includes one or more
`
`LEDs, and an electrical circuit that selectively appliespower
`from the DC voltage source to the LEDs, where1nthe111um1-
`nation source is suitable for handheld portable operation. In
`some embodiments, the electrical circuit further includes a
`control circuit for driving the LEDs with electrical pulses at a
`frequency h1gh enough that llght produced has an appearance
`to a human user of being cont1nuous rather than pulsed, the
`control circuit changing a pulse characteristic to adjust a
`proportion of light output having the first characteristic color
`spectrum output to that having the second characteristic color
`spectrum output. Some embodiments provideanillumination
`source including a housing including one or more LEDs and
`a control circuit that selectively applies power from a source
`of electric power to the LEDs, thus controlling a light output
`color spectrum of the LEDs.
`
`20 Claims, 11 Drawing Sheets
`
`AND CONTROL
`
`POWER SUPPLY
`
`HTC, Exhibit 1003
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`HTC, Exhibit 1003
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`

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`US 9,119,266 B1
`Page 2
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`Related US. Application Data
`.
`.
`.
`.
`.
`.
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`7’393’119’ Wthh IS a d1V151on Of apphcatlon NO’
`10/945,801, filed on $60 20, 2004, HOW Pat N0
`7,186,000, WhiCh is a diViSiOH 0f application NO-
`10/299,609, filed on Nov. 18, 2002, now Pat. No.
`
`6,808,287, which is a continuation of application No.
`09/978,760, filed on Oct. 16, 2001,now Pat. No. 6,488,
`390, whichisacontinuationofapplicationNo.09/627,
`268, filed on Jul. 28, 2000, now Pat. No. 6,305,818,
`whichisadiVisionofapplicationNo. 09/044,559, filed
`on Mar. 19, 1998, now Pat. No. 6,095,661.
`
`HTC, Exhibit 1003
`
`HTC, Exhibit 1003
`
`

`

`U.S. Patent
`
`Aug. 25, 2015
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`US 9,119,266 B1
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`HTC, Exhibit 1003
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`U.S. Patent
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`Aug. 25, 2015
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`U.S. Patent
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`Aug. 25, 2015
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`Sheet 3 of 11
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`US. Patent
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`Aug. 25, 2015
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`Sheet 5 of 11
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`HTC, Exhibit 1003
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`HTC, Exhibit 1003
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`

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`US. Patent
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`Aug. 25, 2015
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`Sheet 6 of 11
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`HTC, Exhibit 1003
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`HTC, Exhibit 1003
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`

`

`U.S. Patent
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`Aug. 25, 2015
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`US. Patent
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`Aug. 25, 2015
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`HTC, Exhibit 1003
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`HTC, Exhibit 1003
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`

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`U.S. Patent
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`Aug. 25, 2015
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`U.S. Patent
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`Aug. 25, 2015
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`US 9,119,266 B1
`
`1
`PULSED L.E.D. ILLUMINATION APPARATUS
`AND METHOD
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`This application is a divisional application of US. patent
`application Ser. No. 14/049,188 filed Oct. 8, 2013 (which
`issued as US. Pat. No. 8,829,808 on Sep. 9, 2014); which is
`a divisional application of US. patent application Ser. No.
`13/736,865 filed Jan. 8, 2013 (which issued as US. Pat. No.
`8,643,305 on Feb. 4, 2014); which was a divisional applica-
`tion ofU.S. patent application Ser. No. 13/244,481 filed Sep.
`25, 2011 (which issued as US. Pat. No. 8,362,712 on Jan. 29,
`2013); which was a divisional application of US. patent
`application Ser. No. 12/820,139 filed Jun. 22, 2010, (which
`issued as US. Pat. No. 8,159,146 on Apr. 17, 2012); which
`was a divisional application of US. patent application Ser.
`No. 12/166,315 filed Jul. 1, 2008 (which issued as US. Pat.
`No. 7,740,371 on Jun. 22, 2010); which was a divisional of
`US. patent application Ser. No. 11/674,143 filed Feb. 12,
`2007 (now US. Pat. No. 7,393,119); which was a divisional
`ofU.S. patent application Ser. No. 10/945,801 filed Sep. 20,
`2004 (now US. Pat. No. 7,186,000); which was a divisional
`ofU.S. patent application Ser. No. 10/299,609 filed Nov. 18,
`2002 (now US. Pat. No. 6,808,287); which was a continua-
`tion of US. patent application Ser. No. 09/978,760 filed Oct.
`16, 2001 (now US. Pat. No. 6,488,390); which was a con-
`tinuation of US. patent application Ser. No. 09/627,268 filed
`Jul. 28, 2000 (now US. Pat. No. 6,305,818); which was a
`divisional ofUS. patent application Ser. No. 09/044,559 filed
`Mar. 19, 1998 (now US. Pat. No. 6,095,661); each ofwhich
`applications is incorporated herein in its entirety 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 with-
`drawn 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 parameters
`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 corresponding
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`power loss in the resistor is dissipated as waste heat, which is
`ineflicient for a flashlight which should be designed to emit
`light.
`In addition, it is awkward or diflicult to determine the
`amount ofremaining charge in a battery cell, generally requir-
`ing 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 mar-
`ket. 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 flashlight in order to
`perform the measurement and ob serve the indication of
`remaining power.
`
`BRIEF SUMMARY OF THE INVENTION
`
`Some embodiments provide a method of providing
`changeable illumination of such compact size and low weight
`as to be suitable for single-handed portable operation by a
`user. The method includes providing one or more LEDs hav-
`ing a first characteristic color spectrum output and one or
`more LEDs having a second characteristic color spectrum
`output, wherein the first characteristic color spectrum output
`is different from the second characteristic color spectrum
`output, selectively applying pulsed power from a DC voltage
`source to the LEDs, wherein the pulses are of high-enough
`frequency such that the human eye does not perceive the
`pulses, and changing a pulse characteristic of the pulsed
`power in order to change a proportion of light output having
`the first characteristic color spectrum output to that having the
`second characteristic color spectrum output.
`Some embodiments provide a portable pulsed LED illumi-
`nation source of such compact size and low weight as to be
`suitable for single-handed portable operation by a user. The
`source include one or more LEDs having a first characteristic
`color spectrum output, one or more LEDs having a second
`characteristic color spectrum output, wherein the first char-
`acteristic color spectrum output different from the second
`characteristic color spectrum output, and a control circuit that
`controls a pulse characteristic to the one or more LEDs having
`a first characteristic color spectrum output in order to change
`a proportion of light output having the first characteristic
`color spectrum output to that having the second characteristic
`color spectrum output.
`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 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 illumination.
`In one embodiment, the LED optical axes of the first plu-
`rality of LED units in the flashlight are substantially parallel
`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 for-
`
`HTC, Exhibit 1003
`
`HTC, Exhibit 1003
`
`

`

`US 9,119,266 B1
`
`3
`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 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 for-
`wardly 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 fur-
`ther includes a control circuit for maintaining a predeter-
`mined light output level of the LED units as a charge on the
`battery cell varies. In one such embodiment, the control cir-
`cuit 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 out-
`put level of the LED units by measuring a battery voltage and
`adjusting a pulse width or a pulse frequency or both to main-
`tain the average light output at the predetermined level. In still
`another such embodiment, the control circuit maintains 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 predeter-
`mined 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 por-
`table operation by a user, the flashlight further having a pur-
`pose 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
`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 fur-
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`ther 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 por-
`table 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 forwardly there-
`from 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 substantially maintain-
`ing a light output characteristic ofthe LEDs as a voltage ofthe
`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 embodi-
`ment, the control circuit maintains an average predetermined
`light output level ofthe 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 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 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 bat-
`tery, 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 appearance 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
`
`HTC, Exhibit 1003
`
`HTC, Exhibit 1003
`
`

`

`US 9,119,266 B1
`
`5
`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 corresponding range for
`which light intensity is equally constant without the feedback
`circuit. In one such embodiment, the feedback circuit mea-
`sures 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 ofpulses 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 maintain-
`ing a predetermined light output color spectrum of the one or
`more LEDs as a voltage ofthe source of electric power varies.
`In one such embodiment, the one or more LEDs comprise one
`or more LEDs having a first characteristic color spectrum
`output and one or more LEDs having a second characteristic
`color spectrum output, the first characteristic color spectrum
`output different from the second characteristic color spec-
`trum output, and the control circuit controls a pulse charac-
`teristic in order to control the proportion of light output hav-
`ing 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 con-
`trols 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 cam-
`corder 500 of FIG. 5 or other devices such as machine-vision
`systems.
`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.
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`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.
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`FIG. 9 is a graph of color spectrum (photoluminescence)
`versus temperature for an LED to be used in one embodiment
`of the present invention.
`FIG. 10 is circuit block diagram ofa machine vision system
`using an LED illumination device according to the present
`invention.
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`FIG. 11 is circuit block diagram of an LED illumination
`device according to the present invention.
`
`DETAILED DESCRIPTION OF THE INVENTION
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`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 efliciency 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 inte-
`grated circuits and components, and the efliciency derived
`from switching the current to and limiting the duration of
`current to the LEDs to project light efliciently and with con-
`stant 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 ofthe LEDs. The present invention controls
`the current flow duration (pulse width) to limit power dissi-
`pation in the LEDs during the LEDs’ on state, and increasing
`the pulse width as the battery voltage decreases over time to
`maintain substantially constant perceived or average LED
`intensity over the course of the battery’s life. The invention
`controls the switching frequency ofthe pulse width to further
`control the LED intensity and power dissipation while main-
`taining 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, por-
`table light source, 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 inven-
`tion measures 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 regu-
`late 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 bright-
`ness is not required. In one such pulse-frequency embodi-
`ment, the apparent (visible) pulse frequency would provide a
`stroboscope effect for safety or entertainment. In this embodi-
`ment, the visibly interrupted or pulsed pulse train may include
`
`HTC, Exhibit 1003
`
`HTC, Exhibit 1003
`
`

`

`US 9,119,266 B1
`
`7
`repetitive pulses or a coded sequence as in Morse code “SOS”
`or a predetermined password or security string of pulses that
`may then be 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 understood that what appears to
`be a single Visible pulse may actually include a high-fre-
`quency 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-fre-
`quency embodiment of the invention, a variable or adjustable
`constant sequence pulse train is established for the accurate
`measurement of the velocity or frequency of an object in
`motion or vibration.
`
`Another embodiment of the present invention uses various
`colored LEDs for specialized purposes. In one such embodi-
`ment, 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 func-
`tionality is also useful for tropical aquarium owners who also
`wish to observe the nocturnal activities of the occupants of
`their aquariums. In another such embodiment, short-wave-
`lengthblue 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 ofElectronic Engineer—
`ing fimes, page 39), these could be used in place of the blue
`LEDs. In other embodiments, a suitable LED normally emit-
`ting in the blue spectrum, for example made from GaN (gal-
`lium nitride) or InGaN (indium gallium nitride), is pulsed by
`pulses of sufliciently 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 military or police use to enhance the
`usefulness of night-vision equipment and for friend-or-foe
`identification, multiple color LEDs to produce a white light
`source, and combinations of colored LEDs to enhance the
`ability of color-blind individuals to perceive colors. Other
`uses include LEDs chosen for use in photographic darkrooms
`wherein the LED wavelength 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
`
`Fresnel lens (or other lens or reflector arrangement) to pro-
`vide a focusable light source. Another embodiment uses
`polarizers to reduce specular reflections for enhanced view-
`ing or for use in machine-vision applications. Another
`embodiment utilizes quickly and easily pluggable/replace-
`able LED arrays or heads of various shapes, colors, and/or
`viewing angles for different applications.
`In yet another embodiment, the light output is momentarily
`interrupted repetitively, or strobed, to indicate low battery
`condition with some estimation oftime to battery failure, e.g.,
`the number of pulses could indicate the estimated number of
`minutes of battery time. As the estimation of time to battery
`failure changes,
`the repetition rate is varied to indicate
`impending battery failure. It is understood that this opera-
`tional mode is easily distinguished from other operational
`modes by the duration of on time versus off time. In strobe
`mode, low battery condition is indicated by dropping pulses;
`e.g., every fourth output pulse is dropped, or three of four
`pulses is dropped creating an easily distinguishable variance
`in visible output of the invention.
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`In another embodiment ofthe invention, a switch is utilized
`to control the functions (and/or brightness) ofthe invention. A
`variance of this embodiment uses a thumb-wheel, or rotary
`switch to vary the switching characteristics to produce a
`variable light output.
`In another embodiment, a programmable microprocessor
`is utilized to provide control functionality.
`FIG. 1 shows one embodiment of the present