ce
`a
`[11] Patent Number:
`5,758,644
`United States Patent ou
`Diab et al.
`[45] Date of Patent:
`Jun. 2, 1998
`
`
`CxX-1702
`
`[54] MANUAL AND AUTOMATIC PROBE
`CALIBRATION
`
`[75]
`
`Inventors: Mohamed Kheir Diab, Mission Viejo;
`Massi E. Kiani. Laguna Niguel;
`Charles Robert Ragsdale, Newport
`Beach; James M. Lepper, Jn. Trabuco
`Canyon,all of Calif.
`
`[73] Assignee: Masime Corporation, Irvine, Calif.
`
`{21] Appl. No.: 478,493
`
`[22] Filed:
`Jun. 7, 1995
`
`2] »oe _ “enOleaLaelcoa,teeas
`
`6
`
`
`
`,
`
`356/41
`[58] Field of Search 0... 128/633, 634,
`128/664, 665; 356/39, 41; 315/151, 307.
`310, 311; 250/552, 214 R
`References Cited
`US. PATENT DOCUMENTS
`
`[56]
`
`|i
`
`|
`|
`|
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`DISPLAY
`
`i
`SBE -
`_t
`RECENWING AND
`CONDITIONING
`
`PAGE 1 OF 36
`
`APL_MAS_ITC_00302640
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`MASIMO2026
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`IPR2022-01300
`
`
`8/1992 Biegel wu.
`was BIS/BLO
`5,140,228
`5,267,562 12/1993 Ukawaet al.
`128/633
`
`21994 Vester et ab rssescsscsrsnserseeeres 128/633
`5,287,853
`FOREIGN PATENT DOCUMENTS
`019478 14/1980 European Pat. Off.
`.
`5275746 10/1993
`Japan.
`88/10452 12/1988 WIPO.
`OTHER PUBLICATIONS
`
`Reynolds, K.J., et al. “Temperature Dependence of LED and
`its Theoretical Effect on Pulse Oximetry”. Brisish Journal of
`Anaesthesia, 1991, vol. 67, pp. 638-643.
`de Kock, LP. et al. “The Effect of Varying LED Intensity on
`Pulse Oximeter Accuracy”. Journal ofMedical Engineering
`&Technology, vol. 15, No. 3, May/Jun. 1991, pp. 111-116.
`
`Primary Examiner—Jennifer Bahr
`Assistant Examiner—Bric F Winakur
`Attormey, Agent, or Firm—Knobbe, Martens. Olsen & Bear
`[57]
`ABSTRACT
`The method and apparatus ofthe present invention provides
`a system wherein light-emitting diodes (LEDs) can be tuned
`within a given range byselecting their operating drive
`current in order to obtain a precise wavelength. The present
`invention further provides a manner in which to calibrate
`and utilize an LED probe. such that the shift in wavelength
`for a known change in drive current is a known quantity. In
`general, the principle of wavelength shift for current drive
`Changes for LEDs is utilized in order to allow better cali-
`bration and added flexibility in the use of LED sensors,
`particularly in applications when the precise wavelength is
`needed in order to obtain accurate measurements. The
`present invention also provides a system in whichit is not
`necessary to know precise wavelengths of LEDs where
`precise wavelengths were needed in the past. Finally. the
`present
`invention provides a method and apparatus for
`determining the operating wavelength of a light emitting
`element such as a light emitting diode.
`
`26 Claims, 20 Drawing Sheets
`
`bE
`
`8/1969 Harte .
`3,463,142
`3/1972 Lavallee .
`3,647,299
`.
`6/1973 Kaglin ef al.
`3.740570
`3/1974 Vurek .
`3,799,672
`5/1978 Kofsky etal. .
`4,086,915
`4,169,976 10/1979 Cirn .
`4,182,977
`1/1980 Stricklin, Ft. eeccessssncsnen 315/151
`4,346,590
`8/1982 Brown .
`4,407,290 10/1983 Wilber .
`4,449,821
`5/1984 Lee.
`.
`4,621,643
`11/1986 New, Ir. et al.
`4,653,498
`3/1987 New,Ir. et al. .
`4,700,708 10/1987 New,Jn. et al. .
`4,770,179
`9/1988 New, Ir. et al.
`.
`4,848,901
`7/1989 Hood, Ir.
`.
`4,913,150
`4/1990 Cheung etal. .
`4,942,877
`7/1990 Sakai et al.
`5,058,588 10/1991 Kaestle .
`5,113,862
`5/1992 Mortazavi
`
`
`
`_ 128/634
`128/633
`.. 128/633
`
`...
`
`190°
`CONTROLLER
`
`-
`
`182 ~,
`*
`
`LED DRIVER
`
`
`
`|
`{
`{
`|
`|
`{
`|
`{
`I
`|
`|
`\
`i
`
`po 92
`
`
`
`MASIMO 2026
`Apple v. Masimo
`IPR2022-01300
`
`

`

`US. Patent
`
`Jun, 2, 1998
`
`Sheet 1 of 20
`
`5,758,644
`
`CX-1702
`
`coJOF
`
`
`—>
`
`=
`JO?YS
`
`ill
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`ee
`
`
`il Ct
`
`300
`
`FIG. | rior arr
`
`PAGE 2 OF 36
`
`APL_MAS_ITC_00302641
`
`MASIMO2026
`Apple v. Masimo
`IPR2022-01300
`
`MASIMO 2026
`Apple v. Masimo
`IPR2022-01300
`
`

`

`
`
`907)3‘IN3IDI44309NOILONILXS
`
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`
`CX-1702
`
`U.S.Patent
`
`Jun.2,1998
`Sheet2of20
`
`5,758,644
`
`760
`
`800
`
`840
`
`WAVELENGTH, A (nm)
`
`1000
`
`PAGE 3 OF 36
`
`APL_MAS_ITC_00302642
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`MASIMO2026
`Apple v. Masimo
`IPR2022-01300
`
`MASIMO 2026
`Apple v. Masimo
`IPR2022-01300
`
`
`

`

`U.S. Patent
`
`Jun. 2, 1998
`
`Sheet 3 of 20
`
`5,758,044
`
`CX-1702
`
`ow
`
`LEDCURRENT(I)
`(A)
`WAVELENGTH
`
`FIG.3A
`
`LED VOLTAGE (V)
`
`675nm
`
`660nm
`
`50ma
`
`100ma
`
`FIG. 3B
`
`LED CURRENT (1)
`
`PAGE 4 OF 36
`
`APL_MAS_ITC_00302643
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`MASIMO2026
`Apple v. Masimo
`IPR2022-01300
`
`MASIMO 2026
`Apple v. Masimo
`IPR2022-01300
`
`

`

`U.S. Patent
`
`Jun. 2, 1998
`
`Sheet 4 of 20
`
`5,758,644
`
`CX-1702
`
`eranTS I
`490
`VG?
`
`CONTROLLER
`
`DISPLAY
`
`
`CONDITIONING
`
`182
`
`LED DRIVER
`
`RECEIVING AND
`
`PAGE 5 OF 36
`
`APL_MAS_ITC_00302644
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`MASIMO2026
`Apple v. Masimo
`IPR2022-01300
`
`MASIMO 2026
`Apple v. Masimo
`IPR2022-01300
`
`

`

`U.S. Patent
`
`Jun. 2, 1998
`
`Sheet 5 of 20
`
`5,758,644
`
`CX-1702
`
`462
`
`432
`
`
`OXIMETER
`SYSTEM
`
`PHOTO-
`DETECTOR
`
`FIG.AB
`
`PAGE 6 OF 36
`
`APL_MAS_ITC_00302645
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`MASIMO2026
`Apple v. Masimo
`IPR2022-01300
`
`MASIMO 2026
`Apple v. Masimo
`IPR2022-01300
`
`

`

`U.S. Patent
`
`Jun. 2, 1998
`
`Sheet 6 of 20
`
`CX-1702
`
`5,758,644
`
`go?
`
`FIG. 5B
`
`PAGE 7 OF 36
`
`APL_MAS_ITC_00302646
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`Apple v. Masimo
`IPR2022-01300
`
`MASIMO 2026
`Apple v. Masimo
`IPR2022-01300
`
`

`

`U.S. Patent
`
`Jun. 2, 1998
`
`Sheet 7 of 20
`
`5,758,644
`
`CX-1702
`
`950nm
`
`FIG.6
`
`PAGE 8 OF 36
`
`APL_MAS_ITC_00302647
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`MASIMO2026
`Apple v. Masimo
`IPR2022-01300
`
`MASIMO 2026
`Apple v. Masimo
`IPR2022-01300
`
`

`

`U.S. Patent
`
`Jun. 2, 1998
`
`Sheet 8 of 20
`
`5,758,644
`
`CX-1702
`
`eers a
`- L64
`266
`
`CONTROLLER
`
`tt|
`
`ho
`--4-I
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`|
`|
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`ua!
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`DISPLAY ee i
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`i14i}}jj !
`
`!
`|
`268-.
`pearo
`| WAVELENGTH!
`|
`DETECTOR
`=!
`
`PAGE 9 OF 36
`
`APL_MAS_ITC_00302648
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`MASIMO2026
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`IPR2022-01300
`
`{|
`
`220 ~~
`
`272
`
`MASIMO 2026
`Apple v. Masimo
`IPR2022-01300
`
`

`

`U.S. Patent
`
`Jun, 2, 1998
`
`Sheet 9 of 20
`
`5,758,644
`
`CX-1702
`
`FIG. 8
`
`OXIMETER SYSTEM
`
`IFO
`
`
`
`
`CONNECTOR
`
`JZ0
`
`ISL
`
`FIO
`
`SIO
`
`PAGE 10 OF 36
`
`APL_MAS_ITC_00302649
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`MASIMO2026
`Apple v. Masimo
`IPR2022-01300
`
`MASIMO 2026
`Apple v. Masimo
`IPR2022-01300
`
`

`

`U.S. Patent
`
`Jun.2, 1998
`
`Sheet 10 of 20
`
`5,758,644
`
`CX-1702
`
`FIG. BA
`
`OXIMETER SYSTEM
`
`
`
`FIP
`
`PAGE 11 OF 36
`
`APL_MAS_ITC_00302650
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`MASIMO2026
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`IPR2022-01300
`
`MASIMO 2026
`Apple v. Masimo
`IPR2022-01300
`
`

`

`U.S. Patent
`
`Jun. 2, 1998
`
`Sheet 11 of 20
`
`5,758,644
`
`CX-1702
`
`ACO
`oo 5
`
`
`
`AIS
`
`7
`|
`PHOTO
`_|
`_|DETECTOR
`3
`
`
`
`——
`
`402
`
`id74
`a
`
`(ls
`~
`
`_
`
`PAGE 12 OF 36
`
`APL_MAS_ITC_00302651
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`MASIMO2026
`Apple v. Masimo
`IPR2022-01300
`
`MASIMO 2026
`Apple v. Masimo
`IPR2022-01300
`
`

`

`U.S. Patent
`
`Jun.2, 1998
`
`Sheet 12 of 20
`
`5,758,644
`
`CX-1702
`
`FIG.IOA
`
`|
`
`TA)
`LED EMISSION
`' Le-4404
` »
`
`Ao,
`
`FILTER RESPONSE
`450
`
`| |
`
`|
`
`| |
`
`At
`
`og
`
`re
`
`A
`
`F1IG./0B
`
`F(A)
`
`FIG.10C
`
`NORMALIZED EMISSION AND FILTER RESPONSE
`
`
`
`PAGE 13 OF 36
`
`APL_MAS_ITC_00302652
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`MASIMO2026
`Apple v. Masimo
`IPR2022-01300
`
`MASIMO 2026
`Apple v. Masimo
`IPR2022-01300
`
`

`

`CX-1702
`
`5,758,644
`
`U.S. Patent
`
`Jun. 2, 1998
`
`Sheet 13 of 20
`
`
`
`
`
`
`
`
`
`
`
`
`dol“914
`
`0'l
`
`60
`
`8°0
`
`£0
`
`9°0
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`"0
`
`¥°0
`
`£0
`
`7
`
`PAGE 14 OF 36
`
`APL_MAS_ITC_00302653
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`MASIMO2026
`Apple v. Masimo
`IPR2022-01300
`
`MASIMO 2026
`Apple v. Masimo
`IPR2022-01300
`
`

`

`CX-1702
`
`=A =
`
`)
`
`a& f
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`eo=
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`=
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`Soe
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`on
`e
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`.oS
`
`RC645
`
`RG69S
`
`FIG. Il
`
`TRANSMITTANCE
`
`1.0
`
`0.9
`0.8
`0.7
`0.6
`
`0.5
`0.4
`0.3
`0.2
`0.1
`
`0.0
`620 720#730630 640 650 660 670 680 690 700 710
`
`
`
`
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`shea
`
`APL_MAS.ITC_00302654
`
`MASIMO2026
`Apple v. Masimo
`IPR2022-01300
`
`(nm)
`
`PAGE 15 OF 36
`
`MASIMO 2026
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`IPR2022-01300
`
`

`

`FIG. LIA
`
`1.0
`
`0.9
`
`TRANSMITTANCE
`
`0.0
`
`0.8
`
`0.7
`
`0.6
`
`0.5
`
`0.4
`
`0.3
`
`0.2
`
`0.1
`
`CX-1702
`
`ued“Sn
`Seer‘Z“UNE
`07JOSTWANS
`
`pr9'SsL's
`
`APL_MAS.ITC_00302655
`
`MASIMO2026
`Apple v. Masimo
`IPR2022-01300
`
`(nm)
`
`PAGE 16 OF 36
`
`MASIMO 2026
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`IPR2022-01300
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`

`

`U.S. Patent
`
`Jun. 2, 1998
`
` 510.509
`
`506
`
`CX-1702
`
`Sheet 16 of 20
`
`5,758,644
`
`
`
`PAGE 17 OF 36
`
`APL_MAS_ITC_00302656
`
`MASIMO2026
`Apple v. Masimo
`IPR2022-01300
`
`MASIMO 2026
`Apple v. Masimo
`IPR2022-01300
`
`

`

`U.S. Patent
`
`Jun.2, 1998
`
`Sheet 17 of 20
`
`CX-1702
`
`5,758,644
`
`
`
`PAGE 18 OF 36
`
`APL_MAS_ITC_00302657
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`MASIMO2026
`Apple v. Masimo
`IPR2022-01300
`
`MASIMO 2026
`Apple v. Masimo
`IPR2022-01300
`
`

`

`U.S, Patent
`
`Jun. 2, 1998
`
`Sheet 18 of 20
`
`5,758,644
`
`CX-1702
`
`SIE
`
`3IL
`
`5d
`
`
`ae
`
`Big 13
`
`IIE
`
`ISO
`
`PAGE 19 OF 36
`
`APL_MAS_ITC_00302658
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`MASIMO2026
`Apple v. Masimo
`IPR2022-01300
`
`MASIMO 2026
`Apple v. Masimo
`IPR2022-01300
`
`

`

`
`
`
`615A 673BR
`
`CX-1702
`
`
`
`g66r“uneyuszeg“Sn
`
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`
`Pr9'SsL‘s
`
`PAGE 20 OF 36
`
`APL_MAS.ITC_00302659
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`MASIMO2026
`Apple v. Masimo
`IPR2022-01300
`
`MASIMO 2026
`Apple v. Masimo
`IPR2022-01300
`
`

`

`U.S. Patent
`
`Jun. 2, 1998
`
`Sheet 20 of 20
`
`5,758,644
`
`CX-1702
`
`Big 15C 602
`
`Wig, L5D
`
`602
`
`624
`
`622
`
`PAGE 21 OF 36
`
`APL_MAS_ITC_00302660
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`MASIMO2026
`Apple v. Masimo
`IPR2022-01300
`
`MASIMO 2026
`Apple v. Masimo
`IPR2022-01300
`
`

`

`CX-1702
`
`5,758,644
`
`1
`MANUAL AND AUTOMATIC PROBE
`CALIBRATION
`
`BACKGROUNDOF THE INVENTION
`1. Field of the Invention
`
`The present invention relates generally to more effective
`calibration and use of light-emitting diodes. More
`particularly, the present invention relates to an apparatus and
`method of calibrating and using light-emitting diodes in a
`sensor for use with an oximeter system.
`2. Description of the Related Art
`Light-emitting diodes (LEDs) are used in many applica-
`tions. In certain applications, knowledge of the particular
`wavelength of operation of the LED is required to obtain
`accurate measurements. One such application is noninvasive
`oximeters conventionally used to monitor arterial oxygen
`saturation.
`
`In conventional oximetry procedures to determine arterial
`oxygen saturation, light energy is transmitted from LEDs.
`each having a respective wavelength, through human tissue
`carrying blood. Generally, the LEDs are part of a sensor
`attached to an oximeter system.
`In common usage,
`the
`sensor is attached to a finger or an earlobe. The light energy,
`which is attenuated by the blood, is detected with a photo-
`detector and analyzed to determine the oxygen saturation.
`Additional constituents and characteristics of the blood,
`such as the saturation of carboxyhemoglobin and scattering
`can be monitored by utilizing additional LEDs with addi-
`tional wavelengths.
`U.S. Pat. No. 4.653.498 to New, Jr., et al, discloses a
`pulse oximeter that utilizes two LEDs to provide incident
`light energy of two different, but carefully selected. wave-
`lengths.
`In conventional oximeters, the wavelength of each LED
`in a sensor must be precisely known in order to calculate
`accurately the oxygen saturation. However, the sensors are
`detachable from the oximeter system to allow for replace-
`ment or disinfection.
`‘When a sensor is replaced, the LEDs of the new sensor
`may have a slightly different wavelength for the predeter-
`mined LED drive current due to manufacturing tolerances.
`Accordingly, conventional oximeters provide for indicating
`to the oximeter the particular wavelength of the LEDs for a
`given sensor. In one known system. a resistor is used to code
`each transmission LEDs. The resistor is selected to have a
`value indicative of the wavelength of the LED. The oximeter
`reads the resistor value on the sensor and utilizes the value
`of the resistor to determine the actual wavelength of the
`LEDs. This calibration procedure is described in U.S. Pat.
`No. 4.621.643, assigned to Nellcor, Inc. Such a prior art
`sensor is depicted in FIG. 1.
`SUMMARY OF THE INVENTION
`
`In conventional oximeters which provide an indication of
`the operational wavelength of cach LED for each sensor, the
`oximeter systems are programmed to perform the desired
`calculations for various wavelengths. This complicates the
`design of the oximeter system, and therefore, adds expense
`to the oximeter system. Accordingly, it would be advanta-
`geous to provide sensors which exhibit the same wavelength
`characteristics from sensor to sensor.
`
`25
`
`30
`
`33
`
`45
`
`55
`
`In addition. conventional sensors require an additional
`LED for each additional wavelength desired. For replace-
`able sensors, each LED can add significanttotal additional
`cost because of the large number of sensors that are used in
`
`65
`
`2
`hospitals and the like. Therefore, it would be desirable to
`provide a sensor which provides more than one wavelength
`from a single LED.
`Many LEDsare observed to exhibit a wavelength shift in
`response to a change in drive current. drive voltage.
`temperature, or other taming parameters such as light
`directed on the LED. The prcscat invention involves an
`improved method and apparatus to calibrate LEDs by uti-
`lizing this wavelength shift. In addition, the present iaven-
`tion involves utilizing the wavelength shift to allow a single
`LEDto provide more than one operating wavelength. The
`addition of a wavelength provides the ability to monitor
`addidonal parameters in a medium under test without adding
`an LED. In oximetry. this allows monitoring of additional
`constituents in the blood without adding additional LEDs to
`the oximeter sensor.
`
`The present invention also involves an application of the
`waveicngth shift
`in LEDs to obtain physiological data
`regarding the oxygen saturation of blood without knowing
`the precise operational wavelength of an LED in the sensor.
`One aspect of the present invention provides a tuned light
`transmission network for transmitting light energy at a
`preselected wavelength. The network has a current source
`configured to provide a preselected source current with a
`light emitting diode coupled to the current source. The light
`emitting diode is of the type that exhibits a shift in wave-
`length with a shift
`in a selected tuning parameter.
`Advantageously,
`the tuning parameter is drive current or
`drive voltage. A tuning resistor connected in parallel with the
`light emitting diode has a value selected to drawat least a
`first portion of the preselected source current such that a
`second portion of the preselected source current passes
`through the light emitting diode. The second portion ofthe
`preselected source current is selected to cause the light
`emitting diode to generate light energy of a preselected
`wavelength.
`In the present embodiment; the tuned light transmission
`network also comprises a detector responsive to light energy
`from the light emitting diode to generate an output signal
`indicative of the intemsity of the light energy.
`Anotheraspect of the present invention involves a method
`for precalibrating a light generating sensor. The method
`involves a number of steps. A first level of current passing
`through a light source as required to operate the light source
`at a preselected wavelength is determined. A secondlevel of
`currentis then defined. The second level of current is higher
`than the first level of current. The second level of current
`forms a drive current. A resistor is then selected which when
`coupled in parallel with the light source forms a tuned light
`source network. The resistor is selected such that whenit is
`connected in parallel with the light source. it draws a
`sufficient amountof the drive current such that the first level
`of current passes through the light source.
`Another aspect of the present invention is a method of
`providing two wavelengths from a single light emitting
`diode. A light emitting diode is selected of the type that
`exhibits a wavelength shift with a change in drive current
`through the light emitting diode for a rangeof drive currents.
`A source of electrical energy is coupled to the light emitting
`diode to provide the drive currents. The light emitting diode
`is driven with a first level of drive current within the range
`of drive current to cause the light emitting diode to become
`active and operate at a first wavelength in response to the
`first level of drive currents. The light emitting diode is then
`driven with a second level of drive current within the range
`of drive current and different from the first level of drive
`
`PAGE 22 OF 36
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`APL_MAS_ITC_00302661
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`MASIMO2026
`Apple v. Masimo
`IPR2022-01300
`
`MASIMO 2026
`Apple v. Masimo
`IPR2022-01300
`
`

`

`CX-1702
`
`5,758,644
`
`3
`current to cause the light emitting diode to becomeactive
`and operate at a second wavelength in responseto the second
`level of drive current.
`
`In an embodiment where the light emitting diode is
`configured to transmit light energy to a medium under test.
`the method comprises further steps. While the light emitting
`diode is operating at the first wavelengths light is transmitted
`as a first light energy at the first wavelength through the
`medium under test. The first wavelength is chosen fora first
`predetermined attenuation characteristic of the light energy
`as it propagates through the medium undertest. The attenu-
`ated light energy is measured from the light emitting diode
`with a photodetector. In addition. while the light emitting
`diode is operating at the second wavelength, light energy is
`transmitted at the second wavelength through the medium
`under test. The second wavelength is chosen for a second
`predetermined attenuation characteristic of the light energy
`as it propagates through the medium undertest. The atienu-
`ated light energy is measured at the second wavelength from
`the light emitting diode.
`In one advantageous embodiment. the method is used to
`determine the oxygen saturation of blood, and the medium
`under test comprises a portion of the human body having
`flowing blood.
`In this embodiment,
`the method further
`involves coupling the source of energy to a second light
`emitting diode which operates at a third wavelength distinct
`from the first and the second wavelengths. Further,
`the
`change in wavelength between the first and second wave-
`lengths has a preselected value. Third light energy is trans-
`mitted at the third wavelength through the medium under
`test, and the third light energy is measured after propagation
`through the medium under test. Based upon the
`measurements, the oxygen saturation of the blood is deter-
`mined.
`In one embodiment, parameters in addition to oxygen
`saturation may also be determinedrelating to the medium
`under test when the first wavelength has a known valuc, and
`the change in wavelength between the first and the second
`wavelengths has a preselected value, In this embodiment,
`value of the second wavelength is determined, and another
`parameter is calculated relating to the blood.
`In one
`embodiment,
`the another parameter is the saturation of
`carboxyhemoglobin. Alternatively. another parameter is
`scattering. Yet another parameter is Methhemoglobin.
`Advantageously. using the apparatus described above for
`tuning, the first light emitting diode is adjusted with an
`adjusting resistor such that the change in wavelength for an
`incremental change in current matches a presclected wave-
`length change. Preferably, adjusting involves placing the
`adjusting resistor in parallel with the first light emitting
`diode, and selecting the value of the adjusting resistor to
`cause the first light emitting diode to exhibit the preselected
`change for the incremental change in current.
`Yet a further aspect of the present invention provides an
`oximeter sensor having a first light emitting device config-
`ured to generate a light at a first known wavelength with a
`resistor in parallel with the first
`light emitting device.
`Preferably, the light emitting device comprises a light emit-
`ting diode. In one ernbodiment, the resistor comprises an
`encoding resistor having a value indicative of the first
`known wavelength value. The value of the encoding resistor
`is sufficiently high such that the encoding resistor draws
`effectively insignificant current during active operation of
`the first light emitting device.
`In another embodiment. the resistor comprises a security
`resistor having a value indicative that the oximeter sensor is
`
`4
`of a predetermined type. In addition, the value of the security
`resistor is sufficiently high such that the security resistor
`drawseffectively insignificant current during active opera-
`tion of the first light emitting device.
`Still a further aspect of the present invention involves a
`method of tuning a light emitting diode to operate at a
`preselected wavelength within a range of wavelengths. The
`method involves selecting a light emitting diode that exhib-
`its a wavelength shift in response to a changein drive current
`within a range of drive current and driving the light emitting
`diode with a first drive current. The wavelength of the light
`emitting diode during operation at the first drive current is
`measured,and, if the light emitting diode is not operating at
`the preselected wavelength, the drive current is adjusted
`within the range of drive current to a second drive current
`such that the light emitting diode operates at the preselected
`wavelength.
`Another aspect of the present invention involves a sensor
`configured to transmit and detect light. The sensor has at
`least one light emitting element, the light emitting element
`having an emission with a centroid transmission wave-
`length. The sensor further has first and second photodetec-
`tors. The emission of the light emitting element being within
`the response of the first and second photodetectors. A light
`directing member is configured to direct light from the at
`least one light emitting element to the first and second
`photodetectors. A filter positioned between the second pho-
`todetector and the at least one light eraitting element has a
`transition band selected to encompass the centroid transmis-
`sion wavelength.
`In one embodiment. the sensor comprises an oximeter
`sensor, and the at least one light emitting clement comprises
`first and second light emitting diodes. Advantageously, the
`first light emitting diode has a centroid wavelength in the red
`Tange and the second light emitting diode has a centroid
`wavelength in the infrared range. Advantageously, the filter
`has a (ansition band which encompasses the centroid wave-
`length of the first light emitting diode.
`the light directing
`In one advantageous embodiment,
`member comprises an integrating optical sphere having the
`first and second photodetectors positioned about the sphere
`so as to receive substantially equivalent portions of light
`from the at least one light emitting element.
`In another embodiment, light directing member comprises
`a beam splitting member positioned to substantially equally
`divide light from the at least one light emitting member and
`to direct substantially equal portions of the light to the first
`and the second photodetectors.
`Still another aspect of the present invention involves a
`method of determining the centroid wavelength of a light
`emitting clement The method involves providing a set of a
`plurality of predetermined ratios, each of the plurality of
`predetermined ratios corresponding to an associated cen-
`troid wavelength. Light is transmitted from the light emit-
`ting elementto a first light detecting element to obtain a first
`intensity, and light is transmitted from the light emitting
`element through a filter which attenuates the light to a
`second light detecting element to obtain a second intensity.
`A ratio of the second intensity to the first intensity is then
`calculated. Theratio is compared to the set of predetermined
`ratios to reference the centroid wavelength of the light
`emitting element.
`In one embodiment, the first and second light detecting
`elements comprise the same light detecting element.
`
`20.
`
`35
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`PAGE 23 OF 36
`
`APL_MAS_ITC_00302662
`
`MASIMO2026
`Apple v. Masimo
`IPR2022-01300
`
`MASIMO 2026
`Apple v. Masimo
`IPR2022-01300
`
`

`

`CX-1702
`
`5,758,644
`
`5
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 represents a calibrated prior art oximeter probe;
`FIG. 2 depicts a representational graph illustrating the
`relationship between the extinction coefficients of three
`constituents of blood with respect to the transmission wave-
`length of light transmitted through the blood;
`FIGS. 3A and 3B depict exemplary LED characteristics;
`FIG. 4A depicts a representation of a tuned oximeter
`sensor according to one aspect of the present invention;
`FIG. 4B depicts an oximeter system with a digit for
`monitoring;
`FIGS. 5A and 5B depict a representational diagram of one
`embodiment of a resistor for use in accordance with the
`present invention;
`FIG. 6 depicts the averaging effect in the wavelength of
`two simultaneously active LEDs with close transmission
`wavelengths;
`FIG. 7 depicts an embodiment of an oximeter sensor
`according to another aspect of the present invention; and
`FIGS. 8 and 8A depict exemplary embodiments of
`improved calibrated oximeter sensors;
`FIGS. SA and 9B depict alternative embodiments sensors
`in accordance with of one aspect of the present invention
`relating to detecting the wavelength of light emitting diodes;
`FIGS, 1A. 10B. 10C. and 10D depict graphs relating to
`the wavelength detection aspect of the present invention;
`and
`
`FIGS. 11 and HA depict graphs offilter response curves
`for various filters in accordance with the wavelength detec-
`tion aspect of the present invention.
`FIGS. 12. 12A-12C, 13, 14, 15, and ISA~15D depict four
`different probe configurations for use with the present iaven-
`tion.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`
`invention has applicability to the use of
`The present
`medical probes and LEDs in general. However, an under-
`standing is facilitated with the following description of the
`application of the principles of the present invention to
`oximetry.
`The advantages of noninvasive techniques in monitoring
`the arterial oxygen (or other constituents) saturation of a
`patient are well-known. In oximetry.
`light of a known
`wavelength is transmitted through a medium (e.g., a human
`digit such as a finger) under test. The light energy is partially
`absorbed and scattered by the constituents that make up the
`medium as the light propagates through the medium. The
`absorption and scattering of the light energy by any given
`constituent depends upon the wavelength of the light passing
`through the constituent, as well as several other parameters.
`The absorption by a constituent is characterized with whatis
`known as the extinction coefficient.
`FIG. 2 represents an exemplary graph 160 of the rela-
`tionship between the extinction coefficient of three possible
`constituents of blood with respect to the wavelength of light.
`Specifically, a first curve 102 illustrates the relationship
`between the extinction coefficient of oxyhemoglobin
`(oxygenated hemoglobin) with respect to the transmission
`wavelength; a second curve 104 illustrates the relationship
`between the extinction coefficient of reduced hemoglobin
`with respect to the transmission wavelength; and a third
`curve 106 illustrates the relationship between the extinction
`coefficient of carboxyhemoglobin (hemoglobin containing
`
`20
`
`30
`
`40
`
`45
`
`50
`
`35
`
`60
`
`6ca
`
`6
`carbon monoxide) with respect to the transmission wave-
`length. This relationship is well understood in the art.
`One wavelength is required for each separate constituent
`in the medium. The wavelengths used for oximetry are
`chosen to maximize sensitivity of the measurement (ie..
`oxygen saturation, etc.). These principles are well under-
`stood in the art.
`The amplitude of the energy incident on a homogencaus
`media having at least one constituent under test is approxi-
`mately related to the amplitude of the cnergy transmitted
`through the media as follows:
`
`a
`
`x
`j= Len
`where I, is the energy incident on the medium, I is the
`attenuated signal, d, is the thickness of the i,, constituent
`through which light energy passes, e, is the extinction (or
`absorption) coefficient of the iy, constituent through which
`the light energy passes (the optical path length of the i,,
`constituent), and c, is the concentration of the i,, constituent
`in thickness d;. As well-understood in the art. this basic
`relationship is utilized to obtain oxygen saturation using
`conventional oximetry techniques.
`It should be understood that the above equation is sim-
`plified for discussion purposes. Other factors such as mul-
`tiple scattering alse contribute to the resulting attenuation of
`the light energy. Multiple scattering is discussed in a paper
`by Joseph M. Schmitt entitled, “Simple Photon Diffusion
`Analysis of the Effects of Multiple Scattering on Pulse
`Oximetry,” JEEE Transactions on Biomedical Engineering,
`vol. 38, no. 12, December 1991.
`However, for further discussion purposes, the simplified
`equation (1) will be utilized. In procedures based on oxim-
`etry technology. the accuracy of the physiological measure-
`ment is impacted by the accuracy of the wavelength of the
`transmission LEDs because, as depicted in FIG. 2,
`the
`extinction coefficient is dependent upon the wavelength of
`the transmission LED. In order to obtain oxygen saturation.
`two LEDs. one in the red wavelength range and one in the
`infrared wavelength range, are typically utilized in order to
`obtain the saturation measurementfor a patient. Further, as
`set forth in Equation (1), the extinction coefficient
`is a
`critical variable in the equation. Accordingly.it is important
`that the oximeter be provided with information as to the
`specific wavelength of the transmission LEDs for the sensor.
`However, the wavelength of different LEDs. although manu-
`factured for a specified wavelength. varies for the same drive
`current from LED to LED due to manufacturing tolerances
`Wavelength Tuned LEDs
`:
`One aspect of the present invention provides an apparatus
`and method for tuning each LED in a sensor such that the
`operating wavelengths for LEDs do not vary significantly
`from sensor to sensor. The tuning is performed by utilizing
`the wavelength shift exhibited in many LEDs in response to
`a change in drive current. FIGS. 3A and 3B illustrate this
`wavelength shift principle in two graphs. The graph 110 of
`FIG. 3A depicts (with a curve 112) current in the vertical
`axis versus voltage in the horizontal axis for a typical LED.
`The graph 110 of FIG. 3A is well-understood in the art. In
`the area referenced between the axis indicated A and B, just
`beyond the shoulder of the curve 112, the wavelength of
`certain LEDs shifts in a substantially linear fashion in
`response to a corresponding change in drive current or
`voltage. The amount of wavelength shift per incremental
`change in drive current typically differs for cach LED
`(designed for the same wavelength). just as the operating
`wavelength for LEDs (designed for a specific wavelength)
`varies for the same drive current from LED to LED.
`
`PAGE 24 OF 36
`
`APL_MAS_ITC_00302663
`
`MASIMO2026
`Apple v. Masimo
`IPR2022-01300
`
`MASIMO 2026
`Apple v. Masimo
`IPR2022-01300
`
`

`

`CX-1702
`
`5,758,644
`
`7
`FIG. 3B depicts an exemplary graph 120 of the wave-
`length of an LED in response to the drive currentin the area
`of the shoulder depicted in FIG. 3A. This graph depicts in a
`curve 122 an exemplary wavelength shift for an LIED in the
`red range in response to drive current changes. The slope of
`the curve 122 depicted in FIG. 3B varies from LED to LED.
`as docs the wavelength range. However, for conventional
`LEDsused in blood oximetry, an incremental shift in drive
`current through the LEDs causes some incremental shift in
`the wavelength. Because this relationship is substantially
`linear in the area just beyond the shoulder of the curve 112
`depicted in FIG. 3A, in one preferred embodiment, the shift
`is obtained in the area beyond the shoulder. The graph of
`FIG. 3B is not meant to represent all LEDs, but merely to
`represent one possible wavelength shift corresponding to a
`particular change in drive current.
`Accordingly, one way to obtain a selected wavelength is
`to drive the LEDs with the current necessary to obtain the
`wavelength. However, such embodiment would require an
`oximeter design which varies the LED drive current for each
`sensor.
`
`In one advantageous embodiment. in order to avoid the
`added complexity of oximeter system design. a resistor is
`placed ia parallel with an LED in order to adjust the drive
`current through the LED to a level which will result in a
`selected wavelength. In such embodiment.
`the oximeter
`systera is designed to operate at the selected wavelength for
`each LEDin the sensor. And. the oximeter need only provide
`a fixed drive current. Accordingly, in one embodiment, the
`design of the oximeter is simpler in that it need not take into
`account variations of wavelength from sensor to sensor. The
`oximeter can siroply be designed to operate at the selected
`wavelengths and have a fixed drive current.
`Each LED sensor manufactured for the oximeteris tuned.
`using the wavelength shift, such that the LEDs in the sensor
`generate light at the selected wavelengths for the oximeter.
`FIG. 4 depicts one embodiment of a tuned sensor 15@.
`connected to an exemplary oximeter system 152, according
`to the LED tuning aspect of the present invention
`The sensor 150is illustrated with a first light source 166
`and a second light source 17. typically LEDs.A first tuning
`resistor 162 connected in parallel with the first LED 166
`forms a first tuned LED network 164, Similarly, a second
`tuning resistor 172 is connected in parallel with the second
`LED 170 to form a second tuned LED network 174, The
`sensor 150 further comprises a photodetector 180.