(12) United States Patent
`KOSuda et al.
`
`USOO61989.51B1
`(10) Patent No.:
`US 6, 198,951 B1
`(45) Date of Patent:
`Mar. 6, 2001
`
`(54) REFLECTION PHOTODETECTOR AND
`BIOLOGICAL INFORMATION MEASURING
`INSTRUMENT
`
`(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)
`(*) Notice:
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`(21) Appl. No.:
`09/297,438
`(22) PCT Filed:
`Sep. 4, 1998
`(86) PCT No.:
`PCT/JP98/03972
`S371 Date:
`Apr. 30, 1999
`S 102(e) Date: Apr. 30, 1999
`(87) PCT Pub. No.: WO99/12469
`PCT Pub. Date: Mar. 18, 1999
`Foreign Application Priority Data
`(30)
`Sep. 5, 1997 (JP).
`Nov. 11, 1997
`(JP) ................................................... 9-3O8913
`(51) Int. Cl." .................................................... A61B 5/00
`(52) U.S. Cl. .............................................................. 600/323
`(58) Field of Search ..................................... 600/322, 323,
`600/336,310,316, 330, 340, 344
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`7/1995 Matthews ............................. 600/323
`5.431,170
`5,524,617 * 6/1996 Mannheimer ...
`... 600/323
`5,645,060 * 7/1997 Yorkey ........
`... 600/323
`5.830,137
`11/1998 Scharf .................................. 600/323
`
`FOREIGN PATENT DOCUMENTS
`50-16180
`12/1975 (JP).
`60-135029
`7/1985 (JP).
`3-1291.07
`12/1991 (JP).
`5-506802
`10/1993 (JP).
`7-88092
`4/1995 (JP).
`7-155312
`6/1995 (JP).
`7-308299
`11/1995 (JP).
`9-114955
`5/1997 (JP).
`9-2993.42
`11/1997 (JP).
`
`* cited by examiner
`
`Primary Examiner John P. Lacyk
`(74) Attorney, Agent, or Firm Michael T. Gabrik
`(57)
`ABSTRACT
`When emitted light from LED 31 is incident on photodiodes
`32 and 33 with luminance Pa and Pb, currents ia and ib are
`generated according to luminance Pa and Pb. When outside
`light is incident through the finger tissueS on photodiodes 32
`and 33 with luminance Pc, current ic is produced. The
`current i1 (=ia+ic) generated by photodiode 32, and the
`current i2 (=-ib-ic) generated by photodiode 33, are added
`at node X, and the current ic corresponding to outside light
`is thus cancelled. In addition, photodiodes 32 and 33 are
`disposed at different distances from LED 31. As a result, the
`current flowing to opamp 34 is 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.
`
`5,285,784
`
`2/1994 Secker .................................. 600/323
`
`19 Claims, 27 Drawing Sheets
`
`
`
`1
`
`APPLE 1010
`
`

`

`U.S. Patent
`
`Mar. 6, 2001
`
`Sheet 1 of 27
`
`US 6,198,951 B1
`
`4O
`
`3O
`
`FIG. 1
`
`40
`ZZZZZZZZZZZZZZZZZZZZZZZZZZ
`4-6-4
`
`Finger
`
`
`
`
`
`ZZZZZZZZZZZZZZZZZZZZZZZX22
`
`31
`
`52
`
`J5
`
`40
`
`FIG 2
`
`2
`
`

`

`U.S. Patent
`
`Mar. 6, 2001
`
`Sheet 2 of 27
`
`US 6,198,951 B1
`
`
`
`J2: Photodiode
`31. LED
`
`2O: Cable
`
`J7: Transparent Glass
`
`
`
`to
`
`55. Circuit Eferent
`
`3. Photodiode
`
`35
`
`34: Op Amp
`36. Circuit Boord
`
`31. LED
`36. Circuit BoGrod
`2O: Cable
`
`N
`YNYYNNYSNYNYYYYYYYYYYYYYN
`J4: Op Amp
`J9. Bottorn Case
`J2: Photodiode
`
`
`
`J7: Transparent Glass
`33: Top Case
`earAaaaaaaaaaZZYZZY
`35. Photodiode
`Z/Yazawa 227axaaZazaaaaaa2
`Y
`
`
`
`FIG. 4
`
`30
`
`To Cable
`2O
`
`3
`
`

`

`U.S. Patent
`
`Mar. 6, 2001
`
`Sheet 3 of 27
`
`US 6,198,951 B1
`
`O. 6
`
`O.5
`
`O. 4
`
`O.3
`
`O.2
`
`O. 1
`
`O
`O 2004OO 600 800 1000 1200
`
`FIG. 6
`
`1OO
`
`5 O
`
`400
`
`450
`
`5OO
`
`650
`6OO
`55O
`Wavelength (nm)
`FIG. 7
`
`700
`
`750
`
`4
`
`

`

`U.S. Patent
`
`Mar. 6, 2001
`
`Sheet 4 of 27
`
`US 6,198,951 B1
`
`Current
`Luminance Increases
`
`Voltage
`
`FIG. 8
`
`Luminance Increases
`
`PG-Pb
`
`FIG. 9
`
`
`
`N
`Noise Y-1N, -7
`3O
`Source Nu-1TYa
`3.O y
`Comparative
`Sensor Unit
`
`A
`W
`Amplifier
`
`
`
`O
`
`S
`Frequency
`Analyzer
`
`FIG. 12
`
`5
`
`

`

`U.S. Patent
`
`Mar. 6, 2001
`
`Sheet S of 27
`
`US 6,198,951 B1
`
`
`
`Fror 3O
`Vr
`Pulse Wave
`Signal Converter
`MD
`
`
`
`
`
`
`
`
`
`Pulse Wave
`Frequency Analyzer
`MKD
`
`Fror 60
`
`Body Movement
`Signal Converter
`TD
`
`53
`
`Body movement
`Frequency Analyzer
`TKD
`
`
`
`
`
`Pulse Wave
`Component Extractor
`MKD'
`Pulse Rate
`Calculator
`HR
`
`56
`
`57
`
`FIG 10
`
`|- V
`
`- V
`
`* - In
`
`351
`
`re
`
`Vrr
`
`34 C-
`- V
`FIG 11
`
`6
`
`

`

`U.S. Patent
`
`Mar. 6, 2001
`
`Sheet 6 of 27
`
`US 6,198,951 B1
`
`SSSSSSSSSSSSSSSSSSSSSSSSSSSS
`sess SSSS N N - N - , cays. NNSNSSNs
`FIG. 13 Frequency (Hz)
`
`O QN) loco ) No O N N lo) o O N
`
`go
`
`*N.
`
`
`
`7
`
`

`

`U.S. Patent
`
`Mar. 6, 2001
`
`Sheet 7 of 27
`
`US 6,198,951 B1
`
`o Comparative Sensor Unit
`Sensor Unit
`
`(2)
`1OO
`s
`Q
`90
`C
`S C 80
`
`S. S 70
`60
`(S
`3.
`50
`O
`2.
`4O
`3O
`2O
`
`
`
`O
`
`1
`
`7
`6
`5
`4
`J
`2
`Outside Light Noise Power
`(Luminance Difference)
`FIG 16
`
`Qy
`
`10
`9
`3
`(10,000 lux)
`
`S1
`
`Generate Pulse Wave Data
`
`S2
`
`Generate Body Movement Data
`
`S3
`
`Store Pulse Wave Data and Body Movement Data
`
`S4
`
`Genergte Pu?se Wave Dotd
`
`S5
`
`Generate Body Movement Data
`
`S6
`
`Extract Pulse Wave Component
`
`S7
`
`Calculate Pulse Rote
`
`Erd
`
`FIG 16
`
`8
`
`

`

`U.S. Patent
`
`Mar. 6, 2001
`
`Sheet 8 of 27
`
`US 6,198,951 B1
`
`
`
`4. O
`3O20-AH-H -
`II
`II
`L.,,,,,,,,,,,,,,,,, TV, In, , , , , , , In, , ,,,,,,,,
`Q to
`to Q to
`no
`to
`v-
`CN
`NS
`QS
`Frequency (Hz)
`FIG. 17A
`
`N. S
`Q
`Q
`S
`S
`
`(S-
`
`s to
`Q
`
`to
`n
`
`no
`to Q to
`Vs
`CN
`Frequency (Hz)
`FIG. 17E9
`
`100
`
`60
`5 O
`
`9 t 6 O
`3O t :
`
`1 O
`
`
`
`C)
`NS
`
`v-
`F1 c\,
`Frequency (Hz)
`FIG. 17C
`
`9
`
`

`

`U.S. Patent
`
`Mar. 6, 2001
`
`Sheet 9 of 27
`
`US 6,198,951 B1
`
`-0
`
`34: Op Amp
`
`FIG. 18
`
`J2: Photodiode
`
`2O: Cable
`
`To The Main Unit
`
`J7: Transparent Glass
`31. LED
`
`
`
`-- V
`
`31
`
`351
`
`
`
`A 1
`Light Emitting
`Means
`
`
`
`B1
`Photodetection
`Means
`
`T1
`
`
`
`C1
`
`FIG. 20
`
`10
`
`

`

`U.S. Patent
`
`Mar. 6, 2001
`
`Sheet 10 of 27
`
`US 6,198,951 B1
`
`
`
`S.
`S
`S.
`3
`r
`
`I4: Arterial Blood Absorption
`Component
`
`Z
`
`A
`
`SS
`I3: Venous Blood Absorption
`Component
`2 I2. Tissue Absorption
`Component
`
`Tirne
`
`Q
`.S.
`s
`S
`
`h
`N
`
`
`
`(f
`
`C)
`S
`3 N Q
`S
`O o
`
`(i)
`
`S
`S O)
`CO
`S. S
`.S
`S Q
`S
`S S S S S S
`
`O
`-u
`
`s
`
`N
`N
`
`t
`
`r
`
`Q
`
`N
`N
`R
`
`C/S
`
`Ci
`
`Qy
`
`N
`
`:
`
`(Dotted Lines Indicate
`Average)
`
`FIG. 22
`
`11
`
`

`

`U.S. Patent
`
`Mar. 6, 2001
`
`Sheet 11 of 27
`
`US 6,198,951 B1
`
`2OO
`
`
`
`1N 100
`N
`
`SS S. S SN 10
`SS
`SS
`SS SS
`S &
`
`O. 1
`O. O5
`3OO 4OO 5OO 6OO 7OO 3OO 900 1 OOO
`Wave Length (nm)
`FIG. 23
`
`1.2
`
`1
`
`O.8
`
`O. 6
`0.4
`O.2
`
`N S.
`O
`Q
`S.
`$
`Q
`
`O
`55O 6OO 650 7OO 75O 3OO
`Wave Length (nm)
`FIG. 24
`
`12
`
`

`

`U.S. Patent
`
`Mar. 6, 2001
`
`Sheet 12 of 27
`
`US 6,198,951 B1
`
`- Vt l? 300
`
`To Cable
`2O
`
`V
`t
`
`- V
`
`GND
`
`Fror 3OO
`
`. 5OO
`
`540
`
`Pitch CO/CLI/dtor
`
`541
`
`Signal Specifier
`
`542
`
`First Wolve Identifier
`
`
`
`545
`
`Second Wolve Identifier
`
`544
`
`Signal Discriminator
`
`FIG. 26
`
`13
`
`

`

`U.S. Patent
`
`Mar. 6, 2001
`
`Sheet 13 of 27
`
`US 6,198,951 B1
`
`N S.
`O
`Q
`
`s
`O
`Q
`
`SA2
`
`SA 1
`
`6O
`
`12O
`
`18O
`
`FIG 27A
`
`Frequency
`(Times/Minute)
`
`SB1
`
`SB3
`
`SE2
`
`6O
`
`12O
`
`18O
`
`FIG. 27E9
`
`Frequency
`(Times/Minute)
`
`1.2
`
`1
`
`O. 3
`
`h
`S
`O
`
`O.6
`S.
`5 0.4
`Q)
`Q
`O.2
`
`O
`4OO 45O 5OO 550 600 650
`Wave Length (nm)
`FIG. 28
`
`14
`
`

`

`U.S. Patent
`
`Mar. 6, 2001
`
`Sheet 14 of 27
`
`US 6,198,951 B1
`
`O
`
`TIME (SECONDS)
`3
`
`12
`
`4.
`
`16
`
`( S
`
`Q
`Q
`
`WF1
`
`O
`
`1
`
`2
`FIG. 29
`
`3.
`4
`FREQUENCY (Hz)
`
`O
`
`
`
`TIME (SECONDS)
`5
`
`12
`
`4.
`
`16
`
`C S
`
`Q
`Q
`
`O
`
`1
`
`2
`FIG. 3O
`
`3.
`4.
`FREQUENCY (Hz)
`
`15
`
`

`

`U.S. Patent
`
`Mar. 6, 2001
`
`Sheet 15 of 27
`
`US 6,198,951 B1
`
`DETERMINE
`HIGHEST LEVEL
`SIGNAL
`
`SIGNAL FREQUENCY
`100 TIMES/
`MINUTE?
`
`
`
`
`
`ST1
`
`YES
`
`
`
`
`
`
`
`
`
`
`
`
`
`IS THERE A SIGNAL
`WITH A FREQUENCY
`1/3 THE FREQUENCY
`OF THIS REFERENCE WAVE
`AND AN AMPLITUDE
`A T LEAST 1/2 THE
`AMPLITUDE OF THE
`REFERENCE WAVE2
`
`
`
`
`
`
`
`
`
`
`
`
`
`DETERMINE NEXT
`LOWEST - LEVEL
`SIGNAL
`
`ST4
`
`CANDIDATE
`
`LAST MEASURED
`AITCH -
`CURRENT PITCH
`
`
`
`ST5
`
`FIRST
`-,
`-- WAVE
`IDENTIFIER
`
`
`
`
`
`- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
`
`SECOND
`
`
`
`Is THERE A SIGNAL \ }
`WITH A FREQUENCY
`2/3 THE FREQUENCY
`OF THIS REFERENCE WAVE
`AND AN AMPLITUDE
`AT LEAST 1/2 THE
`AMPLITUDE OF THE
`REFERENCE WAVE?
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`--- WAVE
`- IDENTIFIER
`
`
`
`SIGNAL
`SFECIFIER
`
`
`
`FREQUENCY OF
`REFERENCE WAVE 150
`TIMES/MINUTE?
`
`
`
`CALCULATE 2/3
`REFERENCE WAVE
`FREOUENCY
`
`16
`
`

`

`U.S. Patent
`
`Mar. 6, 2001
`
`Sheet 16 0f 27
`
`US 6,198,951 B1
`
`
`
`
`
`No.Z.
`
`
`
`|?ZZX ZZZZZZZZZZZZZZZZZ?
`
`[09]
`
`
`
`
`
`
`
`
`
`
`
`17
`
`

`

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

`

`U.S. Patent
`US. Patent
`
`Mar. 6, 2001
`Ddar.6,2001
`
`Sheet 18 of 27
`Sheet18 0f27
`
`US 6,198,951 B1
`US 6,198,951 B1
`
`EM,
`
`ME«Emod
`
`Flut+§nyt
`
`«£1anqu
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`
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`99 "59/-/
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`
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`
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`0[9]
`EM
`
`19
`
`19
`
`
`
`
`

`

`U.S. Patent
`US. Patent
`
`Mar. 6, 2001
`Mar. 6, 2001
`
`Sheet 19 of 27
`Sheet 19 0f 27
`
`US 6,198,951 B1
`US 6,198,951 B1
`
`
`
`FIG.36
`
`N
`vr
`f)
`"3
`~ n
`S
`307
`
`E
`c
`"3
`N
`
`20
`
`20
`
`

`

`U.S. Patent
`
`Mar. 6, 2001
`
`Sheet 20 of 27
`
`US 6,198,951 B1
`
`5O1
`
`.
`
`
`
`
`
`5O2
`
`
`
`
`
`
`
`
`
`FROM 301
`Vrn
`
`MD
`
`MD
`
`MKD
`
`HR
`
`FIG. 37
`
`FROM 301
`Vrn
`
`MD
`
`MD
`
`MD
`
`MKD K
`
`PULSE RATE CALCULATOR
`HR
`
`FIG. 4O
`
`
`
`
`
`
`
`
`
`51
`
`53
`
`54
`
`57
`
`51
`
`53
`
`58
`
`54
`
`57
`
`21
`
`

`

`U.S. Patent
`US. Patent
`
`Mar. 6, 2001
`Mar. 6, 2001
`
`Sheet 21 of 27
`Sheet 21 0f 27
`
`US 6,198,951 B1
`US 6,198,951 B1
`
`
`357’f
`
`312
`372
`
`
`
`-- V
`+V
`
`FIG. 47
`
`22
`
`22
`
`

`

`U.S. Patent
`
`Mar. 6, 2001
`
`Sheet 22 of 27
`
`US 6,198,951 B1
`
`TIME (SECONDS)
`4.
`
`O
`
`
`
`8
`
`12
`
`16
`
`WF4
`
`Q S
`
`Q
`Q
`
`Q S
`
`Q
`Q
`
`FREQUENCY (Hz)
`
`FIG. 4f
`
`O
`
`TIME (SECONDS)
`3
`
`4.
`
`12
`
`16
`
`O
`
`1
`
`2
`3.
`4.
`FIG. 42 FREQUENCY (Hz)
`
`23
`
`

`

`U.S. Patent
`
`Mar. 6, 2001
`
`Sheet 23 of 27
`
`US 6,198,951 B1
`
`O
`
`
`
`TIME (SECONDS)
`8
`
`4.
`
`12
`
`16
`
`WF6
`
`WF7
`
`S
`Q
`Q
`
`O
`
`1
`
`2
`FIG 43
`
`4.
`3.
`FREQUENCY (HZ
`(Hz)
`
`O
`
`TIME (SECONDS)
`8
`
`4.
`
`12
`
`16
`
`Q N
`
`Q
`Q
`
`Sr.
`
`O
`
`1
`
`2
`3.
`4
`FIG. 44 FREQUENCY (Hz)
`
`24
`
`

`

`U.S. Patent
`
`Mar. 6, 2001
`
`Sheet 24 of 27
`
`US 6,198,951 B1
`
`50.3
`y
`
`51
`
`Vrr
`
`PULSE WAVE
`SIGNAL CONVERTER
`
`Vt
`
`BODY MOVEMENT
`SIGNAL CONVERTER
`
`52
`
`MD
`
`TD
`
`58
`
`CTI AUTO CORRELATION
`OPERATOR
`
`54
`
`6
`
`MD-
`SW
`O
`
`PULSE WAVE
`FREQUENCY ANALYZER
`
`MD
`
`CTL
`
`MEMORY
`TD
`
`53
`
`55
`
`BODY MOVEMENT
`FREQUENCY ANALYZER
`
`MKD
`
`S/N RATIO
`EVALUATION MEANS
`
`ThkD
`
`540
`
`PULSE RATE
`CAL CULATOR
`
`59
`
`57
`
`HR
`
`PITCH
`CAL CULATOR
`
`P
`
`FIG. 45
`
`25
`
`

`

`U.S. Patent
`
`Mar. 6, 2001
`
`Sheet 25 Of 27
`
`US 6,198,951 B1
`
`N,
`ZZZZZZ
`
`Ø
`Ø
`
`ZZZ 2% Ø
`
`
`
`
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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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`US 6,198,951 B1
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`U.S. Patent
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`Mar. 6, 2001
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`Sheet 27 of 27
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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
`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 pulse wave, pulse, the pitch of body movement or other
`biological information.
`2. Description of Related Art
`Devices for measuring biological information Such as the
`pulse and body motion include electronic devices for opti
`cally detecting a change in blood Volume to display biologi
`cal information based on the detected result. This type of
`optical pulse wave measuring device (biological information
`measuring apparatus) emits light from an LED (light emit
`ting diode) or other light emitting element to the finger tip,
`for example, and detects light reflected from the body (blood
`vessel) by means of a photodiode or other light detecting
`element. It is therefore possible to detect a change in blood
`flow produced by the blood pulse wave as a change in the
`amount of detected light. The change in the pulse rate or
`pulse wave is then displayed based on the pulse wave signal
`thus obtained. Infrared light is conventionally used as the
`light emitted from the light emitting element.
`It should be noted here that when outside light such as
`natural light or fluorescent light is incident on the
`photodetector, the amount of detected light fluctuates with
`the variation in the incidence of outside light. More
`Specifically, the fingertip or other detected part is typically
`covered by a light Shield in a conventional biological
`information measuring apparatus to SuppreSS the effects of
`outside light because this outside light is noise (external
`disturbance) to the pulse wave signal to be detected.
`The luminance of natural light is, however, Significantly
`greater than the luminance of light emitted from the light
`emitting element when directly exposed to natural light,
`Such as when outdoors. A problem with a conventional
`biological information measuring apparatus is, therefore,
`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 light is
`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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`There are, however, individual differences in the trans
`mission of outside light, and it 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 providing a filter with constant transmission
`characteristics.
`A conventional device for detecting the pitch of body
`movement typically uses a built-in acceleration detector to
`detect movement of the body, and determines the pitch of
`body movement from the body movement Signal. A
`pedometer, for example, uses a piezoelectric element PZT as
`a compact acceleration detector, and detects the Speed at
`which the user is moving by applying wave shaping to the
`detected body movement Signal.
`Devices combining the above-noted acceleration detector
`and an optical pulse wave Sensor are also available as
`portable pulsimeters capable of measuring the pulse while
`the user is exercising. Such portable pulsimeters apply a fast
`Fourier transform process (FFT) to the body movement
`Signal detected by the acceleration detector and the pulse
`wave signal detected by the optical pulse wave Sensor to
`Separately detect a body movement spectrum indicative of
`the body movement signal and a pulse wave spectrum
`indicative of the pulse wave signal. The pulse wave Spec
`trum and body movement spectrum are then compared, the
`frequency component corresponding to the body movement
`spectrum is removed from the pulse wave spectrum, and the
`frequency with the greatest Spectrum power is then removed
`from the remaining Spectrum to determine the fundamental
`frequency of the pulse wave Signal. The pulse rate is then
`calculated based on the fundamental frequency of the pulse
`wave signal. A conventional pulsimeter therefore applies
`two FFT operations, and calculates the pulse rate based on
`the results of these FFT operations.
`The present inventors have also proposed in Japanese
`Patent Application H5-241731 (1993-241731) a device
`enabling pulse rate detection while the user is exercising
`using only an optical pulse wave Sensor and not using an
`acceleration detector. This device focuses on the difference
`in the absorption characteristics of oxygenated hemoglobin
`in arterial blood and reduced hemoglobin in venous blood.
`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 makes it difficult to reduce
`the size.
`A further problem with the above-described pulsimeters
`that use an acceleration detector is that it is not possible to
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`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.
`
`SUMMARY OF 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 element is 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 emits light 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 element to 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 means of a first photoelectric conver
`Sion element; a step for generating a Second Signal by
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`detecting and photoelectrically converting outside light by
`means of the Second photoelectric conversion element; and
`a step for detecting the intensity of the reflected light by
`calculating the difference between the 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 comprises a light emitting means for emitting light
`to a detection Site of a body, and a photodetection means for
`detecting light emitted by the light emitting means into the
`body and generating a body movement Signal according to
`the detected light quantity, and measuring movement of 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 measurement in 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 movement signal 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 provides a 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 means into 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 movement signal 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
`movement Signal from the pulse wave signal, and output the
`difference Signal.
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`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 on this
`pulse wave analysis data.
`Furthermore, the biological information generating means
`can apply an autocorrelation function to 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 movement signal, and deter
`mine whether to perform an autocorrelation operation based
`on the result 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 means in 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 embodiment of 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 according to 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 shows the relationship between voltage and current
`at node X when the 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 shows the 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, (b) 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. 28 is 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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`FIG. 32 is a section view of a biological information
`measuring apparatus according to a third embodime