US006198951B1
`(10) Patent No:
`a2) United States Patent
`US 6,198,951 B1
`Kosudaetal.
`(45) Date of Patent:
`Mar.6, 2001
`
`
`(54) REFLECTION PHOTODETECTOR AND
`BIOLOGICAL INFORMATION MEASURING
`INSTRUMENT
`
`5,431,170 *
`7/1995 Matthews .....ssesesccneceeees 600/323
`5,524,617 *
`w 600/323
`6/1996 Mannheimer .
`
`5,645,060 *
`w. 600/323
`7/1997 Yorkey ..........
`5,830,137 * 11/1998 Scharf wesc ceeeeeee 600/323
`
`(75)
`
`Inventors: Tsukasa Kosuda; Yutaka Kondo, both
`of Matsumoto; Hajime Kurihara;
`Norimitsu Baba, both of
`Shimosuwa-machi, all of (JP)
`;
`;
`(73) Assignee: Seiko Epson Corporation, Tokyo (JP)
`
`FOREIGN PATENT DOCUMENTS
`50-16180
`12/1975 (JP).
`60-135029
`7/1985 (IP) .
`3-129107
`12/1991 (JP).
`5-506802
`10/1993 (IP).
`7-88092
`4/1995 (JP).
`7-155312
`6/1995 (JP).
`Subject to any disclaimer, the term ofthis
`(*) Notice:
`
`patent is extended or adjusted under 35 7-308299=11/1995 (JP).
`U.S.C. 154(b) by 0 days.
`9-114955
`5/1997 (IP).
`9-299342
`11/1997 (JP).
`
`09/297,438
`(21) Appl. No.:
`(22) PCT Filed:—Sep. 4, 1998 * cited by examiner
`
`86)
`PCT No.:
`PCT/JP98/03972
`(86)
`°
`/SP98)
`Primary Examiner—John P. Lacyk
`§ 371 Date:
`Apr. 30, 1999
`(74) Attorney, Agent, or Firm—Michael T. Gabrik
`
`§ 102(e) Date: Apr. 30, 1999
`
`(57)
`
`ABSTRACT
`
`Whenemitted light from LED 31is incident on photodiodes
`(87) PCT Pub. No.: WO99/12469
`32 and 33 with luminance Pa and Pb, currents ia and ib are
`.
`generated according to luminance Pa and Pb. Whenoutside
`PCT Pub. Date: Mar. 18, 1999
`light is incident throughthe finger tissues on photodiodes 32
`Foreign Application Priority Data
`(30)
`and 33 with luminance Pc, current ic is produced. The
`9.241426
`5, 1997
`Sep.
`(IP)
`
`
`ep. 5,1997IP)crecccscssecssceteseseeecseseneeeeses - current il (=iatic) generated by photodiode 32, and the
`
`Nov. 11, 1997
`UP) cesssssssssssssssssssssssesscssssssseseeseeeeeeeee 9308913 (--ib-ic) generated by photodiode 33, are added
`CSL) Tt C0 eeeccccceeeecccsssssssnnnsecceessnnnnseecceesnnnnees A61B 5/00
`at node X, and the current ic corresponding to outside light
`
`(52) US. CM. ceeceecccccsssssssssssessensseseeseeseessensenseneerseneenees 600/323._is thus cancelled. In addition, photodiodes 32 and 33 are
`
`(58) Field of Search o....ccccccscsscssssseesssen 600/322, 323, disposedat different distances from LED31. Asaresult, the
`600/336, 310, 316, 330, 340, 344
`current flowing to opamp 34is current ia corresponding to
`luminance Pa because luminance Pb is extremely low. The
`opamp 34 then applies a current voltage conversion to
`generate pulse wave signal Vm.
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`(56)
`
`5,285,784 *
`
`2/1994 Secker w.ceececccsessceseeeeneeenees 600/323
`
`19 Claims, 27 Drawing Sheets
`
`
`
`APPLE 1058
`Apple v. Masimo
`IPR2020-01715
`
`APPLE 1058
`Apple v. Masimo
`IPR2020-01715
`
`

`

`40
`
`30
`
`U.S. Patent
`
`Mar.6, 2001
`
`Sheet 1 of 27
`
`US 6,198,951 B1
`
`40
`
`FIG.
`
`7
`
`Finger
`
`VLLLLRLLLLELLELLLLLLLLEALELE
`
`
`
`31
`
`32
`
`33
`
`“40
`
`FIG. 2
`
`2
`
`

`

`U.S. Patent
`
`Mar.6, 2001
`
`Sheet 2 of 27
`
`US 6,198,951 B1
`
`yo
`
`JT:
`
`
`
`“34: Op Amp
`36: Circuit Board
`
`
`
`37: Transparent Glass
`31; LED
`36: Circuit Boord~
`parhedemmpemrmnris~
`38: Top Case
`
`20; Cable SSCEES=
`55: Photodiode
`
`
`5
`LLL
`
`34 Op Amp Ug
`
`
`32: Photodiode
`
`
`
`aso
`
`FIG. 4
`
`20
`
`can
`
`To Cable
`
`3
`
`

`

`U.S. Patent
`
`Mar.6, 2001
`
`Sheet 3 of 27
`
`US 6,198,951 B1
`
`0.6
`
`0.5
`
`0.4
`
`0.3
`
`0.2
`
`0.7
`
`0
`
`0 200 400 600 800 1000 1200
`
`FIG. 6
`
`100
`
`50
`
`400
`
`450
`
`500
`
`600
`550
`Wavelength (nm)
`
`650
`
`700
`
`750
`
`FIG. 7
`
`
`
`
`
`RelativePower(%)
`
`4
`
`

`

`U.S. Patent
`
`Mar.6, 2001
`
`Sheet 4 of 27
`
`US 6,198,951 B1
`
`Current
`
`Luminance Increases |
`
`Voltage
`
`FIG. 8
`
`Luminance Increases
`
`
`
`
`Pa-—Pb
`
`FIG. 9
`
`N
`
`
`
`
`
`Frequency
`
`Noise\~~__4 30
`Amplifier
`30’.
`Source.“
`Analyzer
`
`
`
`Comparative
`Sensor Unit
`
`FIG. 12
`
`5
`
`

`

`U.S. Patent
`
`Mar.6, 2001
`
`Sheet 5 of 27
`
`US 6,198,951 B1
`
`From 60
`From 30
`J
`vm
`Vt
`
`
`
`
`Pulse Wave
`
`
`Signal Converter
`
`50
`
`MD
`
`
`
`
`
`
`Body movement
`Pulse Wave
`
`
`Frequency Analyzer
`Frequency Analyzer
`
`
`TKD
`
`MKD
`
` Pulse Wave
`
`Component Extractor
`MKD’
`
`
`
`Pulse Rate
`Calculator
`
`HR
`
`
`
`
`
`FIG. 10
`
`SINS We K-32
`
`4V
`
`4V
`351
`
`sr”
`
`GyA
`
`> um
`
`-V
`
`FIG.
`
`11
`
`6
`
`

`

`U.S. Patent
`
`Mar.6, 2001
`
`Sheet 6 of 27
`
`US 6,198,951 B1
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`SMOHDNOHNAD-HOHODOMHDANYNDHOHYHHOYMH DONO Y
`=NNGERD PNVHLOHD FNM GERD EAMG OND
`Sag r6csqG KKK KKK NNN NNN ONS OO
`FIG. 13
`Frequency (Hz)
`
`
`
`
`
`
`
`
`
`
`
`
`||
`
`eeeAl
`
`OHO DNMNDA™HHDHYMHODAHH DN HON DOM OB
`HANH GORD FRNH OND EmNY QOS m= NM pg CON 90
`FIG. 14
`Frequency (Hz)
`
`Sn (none)
`
`7
`
`

`

`U.S. Patent
`
`Mar.6, 2001
`
`Sheet 7 of 27
`
`US 6,198,951 B1
`
`Power/Pulse NoiseSpectrum
`NoiseSpectrumPower X100
`
`
`
`
`
`
`
`
`S
`
`—h
`
`« Comparative Sensor Unit
`" Sensor Unit
`
`2
`
`7
`6
`5
`4
`#3
`Outside Light Noise Power
`(Luminance Difference)
`FIG. 15
`
`10
`9
`8
`(10,000 lux)
`
`55
`
`5
`
`52
`
`sé
`
`55
`
`96
`
`57
`
`FIG. 16
`
`8
`
`

`

`U.S. Patent
`
`Mar.6, 2001
`
`Sheet 8 of 27
`
`US 6,198,951 B1
`
`
`
`SpectrumPower
`
`
`i
`
`20
`aig
`
`10 TTPpUT
`
`3.5
`
`QoQ
`
`iw
`CS
`
`=
`
`N
`
`DQ
`wy
`Oj
`.~
`Frequency (Hz)
`
`MS
`
`FIG. 17A
`
` Spectrum
`Power
`
`Ss
`
`mh
`S
`
`7
`
`N
`
`»
`OH
`~
`“
`Frequency (Hz)
`
`HM
`
`©
`ns
`
`FIG. 17B
`
`
`
`is
`
`FIN
`~
`Frequency (Hz)
`
`FIG. 17C
`
`S
`
`§ S &
`
`9
`
`

`

`U.S. Patent
`
`Mar.6, 2001
`
`Sheet 9 of 27
`
`US 6,198,951 B1
`
`Se
`
`Al
`Light Emitting
`
`B1
`
`Photodetection
`Means
`
`Means
`
`
`CT
`
`FIG. 20
`
`10
`
`10
`
`

`

`U.S. Patent
`
`Mar.6, 2001
`
`Sheet 10 of 27
`
`US 6,198,951 B1
`
`Absorption Tissue Absorption
`
`: Arterial Blood Absorption
`Component
`
`‘ Venous Blood Absorption
`Component
`
`Component
`
`n Bi S= o
`
`i)
`
`(Dotted Lines Indicate
`Average)
`
`Veins
`
`FIG. 22
`
`11
`
`9 &n
`
`a)
`
`LeftVentricle
`
`LargeVeins
`
`SmallVeins
`Pressure
`Blood
`
`UO
`
`t|I'5t!1 ||
`
`Aorta
`
`Artery
`
`11
`
`

`

`U.S. Patent
`
`Mar.6, 2001
`
`Sheet 11 of 27
`
`US 6,198,951 B1
`
`~ 100
`=
`c &
`
`Ss
`
`X 10
`
` 200
`
`5 S
`
`o
`3Sse
`SS
`
`0.1
`
`0.05
`300 400 500 600 700 800 900 1000
`Wave Length (nm)
`
`FIG. 23
`
`1.2
`
`1
`
`0.8
`
`0.6
`«OA
`
`0.2
`
`05
`
`50 600 650 700 750 800
`Wave Length (nm)
`
`FIG. 24
`
`i g
`
`S
`QO
`
`g
`=
`
`Oc
`
`12
`
`

`

`U.S. Patent
`
`Mar.6, 2001
`
`Sheet 12 of 27
`
`US 6,198,951 B1
`
` Mt S300
`
`V(
`
`—V
`
`GND
`
`To Cable
`20
`
`From 300
`
`Ss 500
`
`ID
`Body Movement Frequency Analyzer
`
`55
`
`540
`
`
`
`Pitch Calculator
`
`54]
`
`Signal Specifier
`
`52
`
`
`
`
`
`9
`
`54.
`
`543
`
`54
`
`4
`
`First Wave Identifier
`
`Second Wave Identifier
`
`
`Signal Discriminator
`
`P F
`
`IG. 26
`
`13
`
`13
`
`

`

`U.S. Patent
`
`Mar.6, 2001
`
`Sheet 13 of 27
`
`US 6,198,951 B1
`
`SAZ
`
`SA?
`
`60
`
`120
`
`180
`
`Frequency
`(Times/Minute)
`
`FIG. 27A
`
`SB3
`
`SBI
`
`SB2Z
`
`60
`
`120
`
`180
`
`FIG. 278
`
`Frequency
`(Times/Minute)
`
`12
`
`/
`
`0.8
`
`O.6
`
`04
`
`0.2
`
`0 4
`
`00 450 500 550 600 650
`Wave Length (nm)
`
`FIG. 28
`
`14
`
`Nw
`2
`9
`qa
`
`Xg
`
`So
`a
`
`©
`
`=9S
`
`=S
`
`o Q
`
`s
`e
`
`14
`
`

`

`U.S. Patent
`
`Mar.6, 2001
`
`Sheet 14 of 27
`
`US 6,198,951 B1
`
`0
`
`TIME (SECONDS)
`6
`
`12
`
`4
`
`WFT
`
`WF2
`
`|i |0
`
`0
`
`Ox
`
`=O
`
`o
`QO.
`
`Oe
`
`=g
`
`SO
`
`16
`
`
`
`1
`
`2
`
`FIG. 29
`
`4
`3
`FREQUENCY (Hz)
`
`TIME (SECONDS)
`8
`
`12
`
`4
`
`16
`
`4
`3
`FREQUENCY (Hz)
`
`1
`
`2
`
`FIG. 30
`
`15
`
`15
`
`

`

`U.S. Patent
`
`Mar.6, 2001
`
`Sheet 15 of 27
`
`US 6,198,951 B1
`
`STI
`
`CANDIDA TE
`
`
`
`ST4
`
`STS
`
`
`
`DETERMINE
`
`
`HIGHEST LEVEL
`
`DETERMINE NEXT
`SIGNAL
`
`LOWEST — LEVEL
`
`
`SIGNAL
`
`NEXT ,
`"ES
`100 TIMES/
`
`
`
`SIGNAL FREQUENCY
`
`
`MINUTE?
`
`
`
`
`
`LAST MEASURED
`
`
`
`IS THERE A SIGNAL
`PITCH =
`
`WITH A FREQUENCY
`
`CURRENT PITCH
`
`
`1/3 THE FREQUENCY
`
`
`OF THIS REFERENCE WAVE
`
`AND AN AMPLITUDE
`
`AT LEAST 1/2 THE
`
`
`
`~
`FIRST
`AMPLITUDE OF THE
`
`
`
`~-- WAVE
`REFERENCE WAVE?
`
`
`IDENTIFIER
`
`
`
`PomRTTTT SECOND
`
`
`
`IS THERE A SIGNAL
`v77 WAVE
`
`
`WITH A FREQUENCY
`- IDENTIFIER
`2/3 THE FREQUENCY
`
`
`OF THIS REFERENCE WAVE
`AND AN AMPLITUDE
`
`
`AT LEAST 1/2 THE
`SIGNAL
`
`AMPLITUDE OF THE
`SPECIFIER
`
`
`
`
`
`REFERENCE WAVE?
`\
`
`
`
`
`FREQUENCY OF
`
`
`REFERENCE WAVE 150
`TIMES/MINUTE?
`
`
`
`CALCULATE 2/3
`
`
`REFERENCE WAVE
`FREQUENCY
`
`
`
`16
`
`16
`
`

`

`U.S. Patent
`
`Mar.6, 2001
`
`Sheet 16 of 27
`
`US 6,198,951 B1
`
`CL
`
`\X2X
`
`9FGE
`
` Zel
`ileeoZ&ole
`
`17
`
`LOS
`
`c&OA
`
`17
`
`
`
`

`

`U.S. Patent
`
`Mar.6, 2001
`
`US 6,198,951 B1
`
`Sheet 17 of 27
`
`POWER
`
`0
`
`1
`
`2
`FIG. 38
`
`3
`4
`FREQUENCY (Hz)
`
`18
`
`18
`
`

`

`U.S. Patent
`
`Mar.6, 2001
`
`Sheet 18 of 27
`
`US 6,198,951 B1
`
`WA|FONFIMFLITG
`YOLVeFdO
`
`(O14,W4+Ul=)]]
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`
`
`Lig
`
`OLS
`
`19
`
`19
`
`
`

`

`U.S. Patent
`
`Mar.6, 2001
`
`Sheet 19 of 27
`
`US 6,198,951 B1
`
`+V
`
`Vm
`
`GND —V
`
`FIG.36
`
`~
`_ mS
`
`5
`
`307
`
`20
`
`20
`
`

`

`U.S. Patent
`
`Mar.6, 2001
`
`Sheet 20 of 27
`
`US 6,198,951 B1
`
`501
`
`G
`
`
`
`
`
`
`
`FROM 301
`
`
`
`
`
`
`
`
`
`
`
`
`HR
`
`FIG. 37
`
`502
`
`FROM 301
`
`
`
`
`
`
`
`PULSE WAVE SIGNAL CONVERTER
`
`
`MEMORY
`
`
`AUTOCORRELATION OPERATOR
`
`
`MD’
`
`
`
`
`
`
`
`PULSE WAVE FREQUENCY ANALYZER
`
`
`MKD
`
`PULSE RATE CALCULATOR
`
`HR
`
`FIG. 40
`
`21
`
`21
`
`

`

`U.S. Patent
`
`Mar.6, 2001
`
`Sheet 21 of 27
`
`US 6,198,951 B1
`
`
`357
`
`302
`
`+V
`
`312
`
`22
`
`22
`
`

`

`U.S. Patent
`
`Mar.6, 2001
`
`Sheet 22 of 27
`
`US 6,198,951 B1
`
`We4
`
`TIME (SECONDS)
`4
`
`0
`
`8
`
`12
`
`16
`
`Qe
`
`<9Q
`
`o.
`
`0
`
`1
`
`2
`
`4
`3
`FREQUENCY (Hz)
`
`FIG. 417
`
`TIME (SECONDS)
`8
`
`12
`
`16
`
`NW WF5
`
`0
`
`4
`
`VN
`
`0
`
`|
`
`|
`3
`4
`FREQUENCY(Hz)
`
`2
`FIG. 42
`
`23
`
`Ox
`
`=o
`
`S
`QO
`
`23
`
`

`

`U.S. Patent
`
`Mar.6, 2001
`
`Sheet 23 of 27
`
`US 6,198,951 B1
`
`TIME (SECONDS)
`8
`
`4
`
`12
`
`16 WEE
`
`0
`
`e ||
`Yo
`|
`S|
`
`|||||:0
`
`1
`
`2
`FIG. 43
`
`3
`
`FREQUENCY (Hz
`
`/ ,
`
`TIME (SECONDS)
`8
`
`.
`
`4
`
`a)
`
`on
`
`Or
`
`x1
`
`)
`Qa
`
`|
`
`12
`
`16
`
`.
`
`WE7
`
`Sm
`
`0
`
`1
`
`2
`
`FIG. 44
`
`24
`
`4
`3
`FREQUENCY (Hz)
`
`24
`
`

`

`U.S. Patent
`
`Mar.6, 2001
`
`Sheet 24 of 27
`
`US 6,198,951 B1
`
`vm
`
`PULSE WAVE
`SIGNAL CONVERTER
`
`503
`
`\
`51
`
`MD
`
`58
`
`Vt
`
`BODY MOVEMENT
`SIGNAL CONVERTER
`
`52
`
`TD
`
`c7t|AUTO CORRELATION o9
`
`
`OPERATOR
`MEMORY
`
`54
`
`MD”
`
`6
`
`&
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`
`C)
`
`MD
`
`1D
`
`55
`
`PULSE WAVE
`FREQUENCY ANALYZER
`
`TL
`
`C
`
`BODY MOVEMENT
`FREQUENCY ANALYZER
`
`MKD
`
`S/N RATIO
`EVALUATION MEANS
`
`TKD
`
`540
`
`59
`
`57
`
`PULSE RATE
`CALCULATOR
`
`HR
`
`PITCH
`CALCULATOR
`
`P
`
`FIG. 45
`
`25
`
`25
`
`

`

`U.S. Patent
`
`Mar.6, 2001
`
`Sheet 25 of 27
`
`US 6,198,951 B1
`
`Cl
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`
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`TtDebiieLE
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`U.S. Patent
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`Mar.6, 2001
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`Sheet 26 of 27
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`U.S. Patent
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`Mar.6, 2001
`
`Sheet 27 of 27
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`US 6,198,951 B1
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`US 6,198,951 B1
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`1
`REFLECTION PHOTODETECTOR AND
`BIOLOGICAL INFORMATION MEASURING
`INSTRUMENT
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`2
`There are, however, individual differences in the trans-
`mission of outside light, andit is therefore difficult using the
`above-noted technology to accurately compensate for an
`outside light component. Furthermore, the path of outside
`light to the pulse wave detector varies according to the
`relative positions of the pulse wave detector and the finger.
`That is, each time the detection device is used, the path
`length from the point of incidence of outside light on the
`tissue to the pulse wave detector changes.It is therefore not
`possible to accurately compensate for an outside light com-
`ponent even by providinga filter with constant transmission
`characteristics.
`
`in the absorption characteristics of oxygenated hemoglobin
`in arterial blood and reduced hemoglobin in venousblood.
`The operating principle of this device uses the long wave-
`length (e.g., 940 nm) of the absorption characteristic of
`oxygenated hemoglobin compared with the absorption char-
`acteristic of reduced hemoglobin, and the long wavelength
`(e.g., 660 nm) of the absorption characteristic of reduced
`hemoglobin compared with the absorption characteristic of
`oxygenated hemoglobin to detect pulse wave signals,
`applies a FFT operation to both pulse wave signals, and
`determines the fundamental frequency of the pulse wave
`signals by comparing the results of the FFT operations.
`Small, low cost acceleration detectors used in pedometers
`are sensitive in only one direction, therefore cannot detect
`movement
`in all directions, and thus cannot accurately
`detect body movement. This problem can be resolved using
`a acceleration detector with three axes, but this results in a
`more complex construction, and makesit difficult to reduce
`the size.
`
`A further problem with the above-described pulsimeters
`that use an acceleration detectoris that it is not possible to
`
`The present invention relates to a reflection type photo-
`detection apparatus suitable for detecting the intensity of the
`reflection of an emitted light reflected by a detected object
`without being affected by outside light, and relates further to
`a biological information measuring apparatus comprising
`this reflection type photodetection apparatus for measuring
`A conventional device for detecting the pitch of body
`a pulse wave, pulse, the pitch of body movement or other
`movement typically uses a built-in acceleration detector to
`biological information.
`detect movement of the body, and determines the pitch of
`2. Description of Related Art
`body movement from the body movement signal. A
`Devices for measuring biological information such as the
`pedometer, for example, uses a piezoelectric element PZT as
`pulse and body motion include electronic devices for opti-
`a compact acceleration detector, and detects the speed at
`cally detecting a change in blood volumeto display biologi-
`which the user is moving by applying wave shaping to the
`cal information based on the detected result. This type of
`detected body movementsignal.
`optical pulse wave measuring device (biological information
`Devices combining the above-noted acceleration detector
`measuring apparatus) emits light from an LED (light emit-
`and an optical pulse wave sensor are also available as
`ting diode) or other light emitting element to the fingertip,
`portable pulsimeters capable of measuring the pulse while
`for example, and detects light reflected from the body (blood
`the user is exercising. Such portable pulsimeters applyafast
`25
`vessel) by means of a photodiode or other light detecting
`Fourier transform process (FFT) to the body movement
`element. It is therefore possible to detect a change in blood
`signal detected by the acceleration detector and the pulse
`flow produced by the blood pulse wave as a change in the
`wave signal detected by the optical pulse wave sensor to
`amount of detected light. The change in the pulse rate or
`separately detect a body movement spectrum indicative of
`pulse waveis then displayed based on the pulse wave signal
`the body movement signal and a pulse wave spectrum
`thus obtained. Infrared light is conventionally used as the
`indicative of the pulse wave signal. The pulse wave spec-
`light emitted from the light emitting element.
`trum and body movement spectrum are then compared, the
`It should be noted here that when outside light such as
`frequency component corresponding to the body movement
`natural
`light or
`fluorescent
`light
`is incident on the
`spectrum is removed from the pulse wave spectrum, and the
`photodetector, the amount of detected light fluctuates with
`frequency with the greatest spectrum poweris then removed
`the variation in the incidence of outside light. More
`from the remaining spectrum to determine the fundamental
`specifically, the fingertip or other detected part is typically
`frequency of the pulse wave signal. The pulse rate is then
`covered by a light shield in a conventional biological
`calculated based on the fundamental frequency of the pulse
`information measuring apparatus to suppress the effects of
`wave signal. A conventional pulsimeter therefore applies
`outside light because this outside light is noise (external
`two FFToperations, and calculates the pulse rate based on
`disturbance) to the pulse wave signal to be detected.
`the results of these FFT operations.
`The luminance of natural light is, however, significantly
`The present inventors have also proposed in Japanese
`greater than the luminance of light emitted from the light
`Patent Application H5-241731 (1993-241731) a device
`emitting element when directly exposed to natural light,
`enabling pulse rate detection while the user is exercising
`such as when outdoors. A problem with a conventional
`using only an optical pulse wave sensor and not using an
`biological
`information measuring apparatus is,
`therefore,
`acceleration detector. This device focuses on the difference
`that when it is used where exposed to outside light, such as
`outdoors, some of the outside light inevitably passes though
`the finger tissues and reaches the photodetector no matter
`how large the light shield for blocking outside light is made,
`and pulse detection errors resulting from variations in the
`luminance of outside light occur easily. Such conventional
`biological information measuring apparatuses are therefore
`limited to use in places where they are not exposed to
`outside light, or where the luminance of any outside lightis
`constant. This limitation can be overcome by using an even
`larger light shield structure, but the size of the biological
`information measuring apparatus then cannot be reduced.
`To resolve this problem, Japan Unexamined Utility Model
`Application Publication (jikkai) S57-74009 (1982-74009)
`teaches a pulse wave sensor comprising, in addition to a
`pulse wave detector for detecting a pulse wave, an outside
`light detector for detecting outside light. This outside light
`detector is covered with a filter having the same transmis-
`sion characteristics as the body tissues so that the pulse wave
`sensor can compensate for the effects of outside light based
`on the result of outside light detection by the outside light
`detector.
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`US 6,198,951 B1
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`3
`continue detecting the pulse rate while exercising if the
`acceleration detector fails. In addition, whether or not an
`acceleration detector is used, conventional pulsimeters
`require two FFT operations, thereby resulting in a more
`complex configuration and requiring a further process to
`determine the fundamental frequency of the pulse wave
`signal from the frequency analysis result.
`
`SUMMARYOF THE INVENTION
`
`The present invention is therefore directed to resolving
`the aforementioned problems, and includes in its primary
`objects the following. That is, a first object of the present
`invention is to provide a reflection type photodetection
`apparatus of simple configuration for detecting the intensity
`of the reflection of emitted light reflected by a detected
`object without being affected by outside light. A second
`object of the present invention is to provide a biological
`information measuring apparatus of simple configuration for
`accurately measuring body movement with high reliability.
`A third object of the present
`invention is to provide a
`biological information measuring apparatus that is suitable
`for measuring a pulse wave, pulse, and other biological
`information using a reflection type photodetection appara-
`tus.
`
`The present invention is directed to resolving the afore-
`mentioned problems, and to achieve the above-noted first
`object provides a reflection type photodetection apparatus as
`follows. This reflection type photodetection apparatus has a
`light emitting element for emitting light to a detected object,
`and detects the intensity of reflected light, which is emitted
`light from this light emitting element reflected by the
`detected object. This reflection type photodetection appara-
`tus comprises: a first photoelectric conversion element for
`receiving and converting light
`to an electrical signal; a
`second photoelectric conversion element for receiving and
`converting light to an electrical signal; and a difference
`detection means for detecting and outputting the difference
`between an output signal of the first photoelectric conver-
`sion element and an output signal of the second photoelec-
`tric conversion element; wherein the first photoelectric con-
`version element, second photoelectric conversion element,
`and light emitting element are arranged so that the distance
`from the photodetection center of the second photoelectric
`conversion element to the light emitting center of the light
`emitting elementis different from the distance from the light
`emitting center of the light emitting element to the photo-
`detection center of the first photoelectric conversion
`element, and the first photoelectric conversion element and
`second photoelectric conversion element are positioned so
`that outside light reaches each with substantially equal
`intensity.
`This reflection type photodetection apparatus can be
`applied to a biological information measuring apparatus. In
`this case, the light emitting element emitslight to a detection
`site of the body,
`the difference detection means detects
`pulsation of the blood flow as the difference signal, and
`biological
`information indicative of a body condition is
`measured based on the detection result.
`
`This reflection type photodetection apparatus can also be
`expressed as a reflected light detection method. This aspect
`of the invention comprises: a step for emitting emitted light
`from a light emitting elementto a detected object; a step for
`generating a first signal by detecting and photoelectrically
`converting reflected light reflected by the detected object,
`and outside light, by meansofa first photoelectric conver-
`sion element; a step for generating a second signal by
`
`4
`detecting and photoelectrically converting outside light by
`meansof the second photoelectric conversion element; and
`a step for detecting the intensity of the reflected light by
`calculating the difference betweenthe first signal and second
`signal.
`To achieve the above-noted second object, the present
`invention also provides a biological information measuring
`apparatus as follows. This biological information measuring
`apparatus comprisesa light emitting meansfor emitting light
`to a detection site of a body, and a photodetection meansfor
`detecting light emitted by the light emitting means into the
`body and generating a body movementsignal according to
`the detected light quantity, and measuring movementof the
`body based on the body movement signal as biological
`information, and is characterized by generating the body
`movement signal based on the result of a measurementin a
`wavelength range of 600 nm and above. It should be noted
`that the invention of this biological information measuring
`apparatus can also be expressed as a biological information
`measurement method.
`
`It should be further noted that the wavelength of emitted
`light from the light emitting means can be 600 nm or above.
`In addition, a wavelength of light received by the photode-
`tection means from the light emitting means can be 600 nm
`or above.
`
`In addition, the biological information measuring appa-
`ratus can further comprise a frequency analysis means for
`frequency analyzing the body movementsignal measured by
`the photodetection means, and generating a body movement
`spectrum; and a pitch detection means for extracting a
`fundamental frequency based on the body movement spec-
`trum analyzed by the frequency analysis means, and detect-
`ing the pitch of body movement based on the extracted
`fundamental frequency.
`Furthermore, to achieve the above-noted third object, the
`present invention providesa biological information measur-
`ing apparatus as follows. This biological information mea-
`suring apparatus comprises: a light emitting means for
`emitting light to a detection site on the body, and a body
`movement detection means for detecting light emitted by
`this light emitting means into the body, and generating a
`body movement signal according to the amount of detected
`light; a light emitting means for emitting light to a detection
`site on the body, and a pulse wave detection means for
`detecting light emitted by this light emitting meansinto the
`body, and generating a pulse wave signal according to the
`amount of detected light; and a biological
`information
`generating means for generating biological
`information
`indicative of a body condition based on this body movement
`signal and pulse wave signal; wherein the body movement
`detection means generates the body movementsignal based
`on a measurement made in a wavelength range of 600 nm or
`greater, and the pulse wave detection means generates the
`pulse wave signal based on a measurement made in a
`wavelength range of 600 nm or below. It should be noted
`that the invention of this biological information measuring
`apparatus can also be expressed as a biological information
`measurement method.
`
`The biological information generating means in this case
`can comprise a comparison operator for comparing the body
`movement signal and pulse wave signal such that biological
`information is generated based on the result of this com-
`parison.
`In addition, the comparison operator can subtract the body
`movementsignal from the pulse wave signal, and output the
`difference signal.
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`US 6,198,951 B1
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`5
`Furthermore, the biological information generating means
`can frequency analyze the difference signal output by the
`comparison operator to generate pulse wave analysis data
`from which the body movement component is removed, and
`generate biological information for the body based onthis
`pulse wave analysis data.
`Furthermore, the biological information generating means
`can apply an autocorrelation functionto the difference signal
`output by the comparison operator to generate autocorre-
`lated pulse wave data, and generate biological information
`based on this autocorrelated pulse wave data.
`Furthermore, the biological information generating means
`can be comprised to detect a degree of irregularity in body
`movement based on the body movementsignal, and deter-
`mine whether to perform an autocorrelation operation based
`on theresult of this detection. If an autocorrelation operation
`is to be performed,it applies an autocorrelation function to
`the difference signal output by the comparison operator to
`generate autocorrelated pulse wave data and generates bio-
`logical information based on this autocorrelated pulse wave
`data. If an autocorrelation operation is not performed,it
`generates biological
`information based on the difference
`signal.
`Moreover, the photodetection means of the body move-
`ment detection means is preferably a first photodiode for
`outputting an electrical signal according to the amount of
`detected light; the photodetection means of the pulse wave
`detection means is a second photodiode for outputting an
`electrical signal according to the amount of detected light;
`and the comparison operator outputs the difference signal
`from a node connected in series with the first photodiode and
`second photodiode.
`In addition, to achieve the above-noted third object, the
`present
`invention provides in addition to the above-
`described biological information measuring apparatus a bio-
`logical information measuring apparatus as follows.
`This biological information measuring apparatus has a
`light emitting means for emitting light to a wrist or arm, and
`a photodetection means for detecting light emitted by the
`light emitting means into the body and generating a pulse
`wave signal according to the amount of detected light, and
`generates biological information indicative of a body con-
`dition based on a pulse wave signal measured in a 500 nm
`to 600 nm wavelength range.
`The primary wavelength of light emitted by the light
`emitting meansin this case is preferably 500 nm to 600 nm.
`In addition, the primary wavelength of light detected by the
`photodetection means is 500 nm to 600 nm.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is an external view of a biological information
`measuring apparatus according to a first embodimentof the
`present invention.
`FIG. 2 is a typical section view of a sensor unit 30
`according to this preferred embodiment when worn.
`FIG. 3 is a plan view of a sensor unit 30 accordingto this
`preferred embodiment.
`FIG. 4 is a section view of a sensor unit 30 according to
`this preferred embodiment.
`FIG. 5 is a circuit diagram showing the electrical con-
`figuration of a sensor unit 30 according to this preferred
`embodiment.
`
`FIG. 6 is a graph of the spectral sensitivity characteristic
`of photodiodes 32 and 33 according to this preferred
`embodiment.
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`FIG. 7 is a graph of the light emitting characteristic of an
`LED 31 according to this preferred embodiment.
`FIG. 8 showsthe relationship between voltage and current
`at node X whenthe circuit is interrupted at point Y in FIG.
`5.
`
`FIG. 9 is a graph showing the relationship between
`brightness Pa—Pb and a pulse wave signal according to this
`preferred embodiment.
`FIG. 10 is a function block diagram of data processing
`circuit 50 according to this preferred embodiment.
`FIG. 11 is a circuit diagram of a sensor unit 30' prepared
`for comparison.
`FIG. 12 is a block diagram of a comparison test system.
`FIG. 13 shows the results of an analysis of the output
`signal from comparative sensor unit 30".
`FIG. 14 showsthe results of an analysis of the output
`signal from sensor unit 30.
`FIG. 15 shows the results of noise spectrum power and
`pulse wave spectrum power measured for comparative sen-
`sor unit 30' and sensor unit 30 when the brightness of the
`light noise source was varied.
`FIG. 16 is a flow chart of the operation of data processing
`circuit 50 according to this preferred embodiment.
`FIG. 17(a) is an example of pulse wave analysis data
`MKD, (6) of body movement analysis data TKD, and (c) of
`pulse wave analysis data after body movement component
`removal MKD".
`
`FIG. 18 is a plan view of sensor unit 30 according to an
`alternative version of the first embodiment.
`
`FIG. 19 is a circuit diagram showing the electrical con-
`figuration of a sensor unit 30 according to this alternative
`version of the first embodiment.
`
`FIG. 20 is used to explain the principle of a reflected light
`optical sensor according to a second embodiment of the
`present invention.
`FIG. 21 is a graph showing the distribution of light
`absorption when the body is in a state of rest with no
`movement and light is emitted to the blood vessels of the
`body from an external source.
`FIG. 22 is a graph showing the change in blood pressure
`of blood pumped from the heart.
`FIG. 23 is a graph of the molecular extinction coefficient
`of reduced hemoglobin Hb and oxygenated hemoglobin
`HbO,.
`FIG. 24 is a graph of the light emitting characteristic of a
`LED 310 according to this second embodiment.
`FIG. 25 is a circuit diagram showing the electrical con-
`figuration of a sensor unit 300 according to this second
`embodiment.
`
`FIG. 26 is a function block diagram of data processing
`circuit 500 according to this second embodiment.
`FIG. 27(a) is a typical example of the body movement
`signal spectrum when running, and (b) is a typical example
`of the body movement signal spectrum when walking.
`FIG. 28is a graph of the light emitting characteristic of an
`LED 310' used in a comparative sensor unit 300’.
`FIG. 29 is a graph showing an example of output signal
`wave of comparative sensor unit 300' and the result of
`frequency analysis applied thereto.
`FIG. 30 is a graph showing an example of output signal
`wave of sensor unit 300 and the result of frequency analysis
`applied thereto.
`FIG. 31 is a flow chart of the pitch calculation process of
`pitch calculator 540 according to this second embodiment.
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`US 6,198,951 B1
`
`7
`FIG. 32 is a section view of a biological information
`measuring apparatus accordingto a third embodimentof the
`present invention.
`FIG. 33 is a plan view of the back of sensor unit 301
`according to a first version of this third embodiment.
`FIG. 34 is a block diagram showing the electrical con-
`figuration of sensor unit 301 according to a first version of
`this third embodiment.
`
`FIG. 35 is a circuit diagram of an exemplary difference
`operator 340 according to this preferred embodiment.
`FIG. 36 is a circuit diagram of sensor unit 301 according
`to a second version of this third embodiment.
`
`FIG. 37is a block diagram of a data processing circuit 501
`according to this preferred embodiment.
`FIG. 38is a graph of the signal waveform of a pulse wave
`signal and frequency analysis thereof according to this
`preferred embodiment.
`FIG. 39 is a plan view of a sensor unit 301 according to
`an alternative version of this third embodiment.
`
`FIG. 40 is a block diagram of a data processing circuit 502
`according to a fourth embodimentof the present invention.
`FIG. 41 is a graph of the output signal waveform mea-
`sured as a first comparison and frequency analysis thereof.
`FIG. 42 is a graph of the output signal waveform mea-
`sured as a second comparison and frequency analysis
`thereof.
`
`FIG. 43 is a graph of the output signal waveform mea-
`sured as a third comparison and frequencyanalysis thereof.
`FIG. 44 is a graph of the output signal waveform mea-
`sured in a preferred