USOO7060963B2
`
`(12) United States Patent
`Maegawa et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 7,060,963 B2
`Jun. 13, 2006
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`(54) ORGANISM INFORMATION MEASURING
`DEVICE AND ORGANISM INFORMATION
`MEASURING METHOD
`
`(75) Inventors: Kazuya Maegawa, Chiba (JP); Takashi
`Nakamura, Chiba (JP): Koichi
`Moriya, Chiba (JP); Shinichiro
`Miyahara, Chiba (JP)
`
`(73) Assignee: Seiko Instruments Inc., Chiba (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.: 11/121,320
`(22) Filed:
`May 3, 2005
`
`(65)
`
`Prior Publication Data
`US 2005/0253047 A1
`Nov. 17, 2005
`Foreign Application Priority Data
`(30)
`May 17, 2004 (JP)
`............................. 2004-146O77
`
`(51) Int. Cl.
`(2006.01)
`A6 IB 5/02
`(52) U.S. Cl. ....................... 250/221; 600/323; 600/500
`(58) Field of Classification Search ................ 250/221;
`600/500, 502,310,323
`See application file for complete search history.
`
`
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`6,198.951 B1* 3/2001 Kosuda et al. .............. 600,323
`FOREIGN PATENT DOCUMENTS
`
`3, 2001
`
`JP
`O1078973
`* cited by examiner
`Primary Examiner Kevin Pyo
`(74) Attorney, Agent, or Firm—Adams & Wilks
`(57)
`ABSTRACT
`
`An organism information measuring device has two light
`irradiating parts that irradiate light of short and long wave
`length, respectively, toward an organism, and two light
`receiving parts that receive backward Scattered light from
`the organism and produce organism information signals
`according to the quantity of received light. A data processor
`determines organism information indicative of a condition
`of the organism based on the organism information signals.
`The two light irradiating parts may be combined into a single
`light irradiating part, with one of the light receiving parts
`disposed farther from the light irradiating part than the other
`and having a light receiving area larger in size than that of
`the other and proportional to the distance thereof from the
`light irradiating part.
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`11 Claims, 7 Drawing Sheets
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`APPLE 1011
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`1.
`ORGANISM INFORMATION MEASURING
`DEVICE AND ORGANISM INFORMATION
`MEASURING METHOD
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`BACKGROUND OF THE INVENTION
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`1. Field of the Invention
`The present invention relates to an organism information
`measuring device capable of measuring an organism infor
`mation Such as pulse rate under a state of being mounted to
`a wrist (arm), and an organism information measuring
`method.
`2. Description of the Prior Art
`Due to an increase in concern for health care in recent
`years, various kinds of organism information measuring
`devices, which can measure various organism information
`Such as pulse rate while being mounted to the wrist (arm)
`and the like intact, have been proposed. See, for example,
`Japanese Published Patent Application No. 2001-078973
`(Patent Document 1).
`In the organism information measuring device described
`in Patent Document 1, under the state of being mounted to
`the wrist, a light is irradiated from an LED toward an
`organism. Backward scattered light from blood in a blood
`vessel is received by a photodiode, and the pulse rate is
`calculated by extracting a pulse signal from the backward
`scattered light. Especially, since a measurement of the pulse
`rate can be easily performed while being mounted to the
`wrist intact, it is simply used by a user.
`By the way, in the organism information terminal device
`described in the above Patent Document 1, there has been a
`fear that, in addition to the fact that the light containing a
`pulse information is received when receiving the backward
`scattered light from the organism by the photodiode, there is
`received a light containing no pulse information, for
`example, a light directly entering from the LED, a light
`reflected by an organism Surface, or a light reflected by a
`transparent glass disposed above the LED. By this, in the
`photodiode, a noise (electrical disturbance) increases, and a
`reduction in S/N ratio has occurred. Accordingly, there has
`been a possibility that an accurate organism information
`cannot be measured.
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`SUMMARY OF THE INVENTION
`
`The present invention is one made in view of such
`circumstances, and its object is to provide an organism
`information measuring device and an organism information
`measuring method, in each of which it is possible to improve
`the S/N ratio and increase a measurement accuracy of the
`organism information.
`In order to solve the above problems, the present inven
`tion provides means mentioned below.
`An organism information measuring device of the present
`invention is one characterized by possessing a main body
`disposed under a state that its lower face has contacted with
`an organism Surface, a light irradiating part which is dis
`posed in the lower face of the main body and irradiates a
`light toward an organism, a 1st light receiving part which is
`disposed in the lower face of the main body and near the
`light irradiating part, receives a backward Scattered light
`from the organism and generates an organism information
`signal complying with a received light quantity, a 2nd light
`receiving part which is disposed in the lower face of the
`main body and in a position spaced from the light irradiating
`part more than a distance between the 1st light receiving part
`and the light irradiating part, receives a backward Scattered
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`light from the organism and generates an organism infor
`mation signal complying with a received light quantity, and
`an organism information operating part which calculates an
`organism information on the basis of the organism informa
`tion signals having been generated by the 1st light receiving
`part and the 2nd light receiving part.
`In this organism information measuring device concern
`ing the invention, after the lower face of the main body has
`been contacted with the organism Surface, a light is irradi
`ated from the light irradiating part toward the organism. The
`irradiated light is absorbed and scattered in the organism by
`tissue. Such as fat and muscle, and the blood, and one part
`of the irradiated light is received as the backward scattered
`light by the 1st light receiving part and the 2nd light
`receiving part. This received light fluctuates with a change
`in blood quantity by a pulsation. The 1st light receiving part
`and the 2nd light receiving part receive this backward
`scattered light and generate pulse signals (organism infor
`mation signals) in accordance with a change in the received
`light quantity.
`On this occasion, since the 1st light receiving part is
`disposed near the light irradiating part, it receives the light
`depending on the light irradiating part. That is, it receives the
`light containing no organism information. On the other
`hand, since the 2nd light receiving part is disposed in a
`position spaced farther from the light irradiating part than
`the 1st light receiving part, it receives the backward scat
`tered light from the organism in addition to receiving the
`light depending on the light irradiating part.
`On the basis of the organism information signal generated
`by the 1st light receiving part and the organism information
`signal generated by the 2nd light receiving part, i.e., by
`taking the organism information signal generated by the 1st
`light receiving part into consideration, the organism infor
`mation operating part can remove as far as possible the light
`containing no organism information, i.e., noise (electrical
`disturbance), from the organism information signal gener
`ated by the 2nd light receiving part. By this, it is possible to
`improve S/N ratio, and it is possible to perform a more
`accurate calculation of the organism information.
`Further, an organism information measuring device of the
`present invention is one characterized in that, in the above
`organism information measuring device of the present
`invention, the light irradiating part possesses a 1st light
`irradiating part for detecting a noise and a 2nd light irradi
`ating part for detecting an organism information, each of
`which irradiates a light different in wavelength, and,
`between both the light irradiating parts, the 1st light irradi
`ating part utilizes a light whose wavelength is short and the
`2nd light irradiating part utilizes a light whose wavelength
`is long.
`In this organism information measuring device concern
`ing the invention, since it possesses the 1st light irradiating
`part and the 2nd light irradiating part, the 1st light receiving
`part receives much more light containing no organism
`information (much in noise component), and the 2nd light
`receiving part receives much more backward scattered light
`from the organism. Accordingly, it is possible to additionally
`improve S/N ratio, and it is possible to perform the more
`accurate calculation of the organism information. Especially,
`since the 2nd light irradiating part utilizes the light whose
`wavelength is long, it is easy to obtain the backward
`scattered light from the organism.
`Further, an organism information measuring device of the
`present invention is one characterized in that, in the above
`organism information measuring device of the present
`invention, the 2nd light receiving part is disposed at a
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`distance in which the light irradiated from the 1st light
`irradiating part does not directly enter.
`In this organism information measuring device concern
`ing the invention, since the 2nd light receiving part is
`disposed at the distance in which the light irradiated from the
`1st light irradiating part does not directly enter, it collec
`tively receives the backward scattered light without under
`going an influence from the 1st light irradiating part.
`Accordingly, it is possible to accurately calculate the organ
`ism information.
`Further, an organism information measuring device of the
`present invention is one characterized in that, in any of the
`above organism information measuring devices of the
`present invention, the 2nd light receiving part is set Such that
`a light receiving area increases in compliance with a dis
`tance spacing from the light irradiating part.
`In this organism information measuring device concern
`ing the invention, since the 2nd light receiving part is set
`Such that the light receiving area increases in compliance
`with the distance spacing from the light irradiating part, it
`receives much more backward scattered light which has
`attenuated. By this, the 2nd light receiving part can increase
`the received light quantity.
`Accordingly, the organism information operating part can
`more Surely remove the light containing no organism infor
`mation, i.e., noise component, and thus can more accurately
`perform the calculation of the organism information.
`Further, an organism information measuring device of the
`present invention is one characterized in that, in any of the
`above organism information measuring devices of the
`present invention, the 1st light receiving part is provided in
`plural pieces, and the organism information operating part
`utilizes any one or an average value of the organism infor
`mation signals having been generated by the plural 1st light
`receiving parts.
`In this organism information measuring device concern
`ing the invention, since it has the plural 1st light receiving
`parts, the light containing no organism information, i.e., a
`noise component, can be Surely received irrespective of the
`position where the 1st light receiving part is disposed. And,
`by utilizing any one or the average value of the organism
`information signals having been generated by the plural 1st
`light receiving parts, the organism information operating
`part can additionally accurately perform the calculation of
`45
`the organism information.
`Further, an organism information measuring method con
`cerning the present invention is an organism information
`measuring method in which a light is irradiated from a light
`irradiating part toward an organism, a backward Scattered
`light from the organism is received in two places of a 1st
`light receiving part disposed near the light irradiating part
`and a 2nd light receiving part spaced from the light irradi
`ating part more than a distance between the 1st light receiv
`ing part and the light irradiating part, and an organism
`information is measured on the basis of the results of
`received light of both the light receiving parts, characterized
`by possessing a transformation process in which, from the
`backward scattered light received by the 1st light receiving
`part and the 2nd light receiving part, organism information
`signals complying with a received light quantity are respec
`tively generated and the organism information signals are
`high-speed-Fourier-transformation-processed, and an opera
`tion process in which values transformed by the transfor
`mation process are normalized by a power spectrum of
`optional frequency and the organism information is operated
`by mutually subtracting the normalized values.
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`In this organism information measuring method concern
`ing the invention, the light irradiated from the light irradi
`ating part toward the organism is absorbed and Scattered in
`the organism by the tissue, such as fat and muscle, and the
`blood, and one part of the irradiated light is received as the
`backward Scattered light by the 1st light receiving part and
`the 2nd light receiving part. This received light fluctuates
`with the change in blood quantity by the pulsation.
`And, by the transformation process, the 1st light receiving
`part and the 2nd light receiving part receive this backward
`scattered light and generate pulse signals (organism infor
`mation signals) complying with a change in the received
`light quantity, and the pulse signals are high-speed-Fourier
`transformation-processed. On this occasion, since the 1st
`light receiving part is disposed near the light irradiating part,
`it receives more light depending on the light irradiating part.
`That is, it is receiving much light containing no organism
`information. On the other hand, since the 2nd light receiving
`part is disposed in the position spaced from the light
`irradiating part more than the 1st light receiving part, it is
`receiving more backward scattered light from the organism
`in addition to receiving the light depending on the light
`irradiating part.
`And, by the operation process, by normalizing the high
`speed-Fourier-transformation-processed values by the
`power spectrum of optional frequency and mutually Sub
`tracting the normalized values, it is possible to remove as far
`as possible the noise (electrical disturbance) from the organ
`ism information signal generated by the 2nd light receiving
`part.
`Accordingly, it is possible to improve S/N ratio, and it is
`possible to perform the accurate calculation of the organism
`information.
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`BRIEF DESCRIPTION OF THE DRAWINGS
`
`A preferred form of the present invention is illustrated in
`the accompanying drawings in which:
`FIG. 1 is a front view showing one embodiment of an
`organism information measuring device concerning the
`present invention;
`FIG. 2 is a side view showing a state that the organism
`information measuring device shown in FIG. 1 has been
`mounted to a wrist;
`FIG. 3 is a side view showing the state that the organism
`information measuring device shown in FIG. 1 has been
`mounted to the wrist, and is a view seen from a direction
`opposite to a direction shown in FIG. 2;
`FIG. 4 is a sectional view of the organism information
`measuring device shown in FIG. 1, which is seen from an
`arrow line 4–4;
`FIG. 5 is a sectional view of the organism information
`measuring device shown in FIG. 1, which is seen from an
`arrow line 5–5;
`FIG. 6 is a perspective view showing the organism
`information measuring device shown in FIG. 1 under a state
`of being obliquely seen from below:
`FIG. 7 is a view showing a positional relation between an
`LED and both PDs, as viewed from above a cover glass;
`FIG. 8 is a diagram showing a state that a data processing
`part has calculated a pulse rate on the basis of pulse signals
`generated by a 1st PD and a 2nd PD; and
`FIG. 9 is a view showing a positional relation between
`two LEDs and two PDs in a modified arrangement, as
`viewed from above a cover glass.
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`DETAILED DESCRIPTION OF THE
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`each button 20 mentioned later. Additionally, the data pro
`cessing part 9 has a function of synthetically controlling
`other constituent articles as well.
`The above display part 11 is a liquid crystal display such
`as LCD (Liquid Crystal Display), and has a time display
`function which displays, besides the above-mentioned pulse
`rate, the current time counted by, e.g., a quartz oscillator not
`shown in the drawing, and a function of displaying other
`various information. It is adapted so as to be capable of
`displaying, e.g., the current time, a date, a day of week, a
`remaining electric power quantity of the storage battery 13,
`and the like.
`Further, as shown in FIG. 1 to FIG. 3, in the housing 2.
`there are provided plural buttons 20, for example, three
`buttons 20 existing in the upper face 2b of the housing 2 and
`disposed in an underside of the display part 11, and one
`button 20 disposed in a side face of the housing 2. It is
`adapted Such that, by pressing down each of these buttons
`20, various operations can be performed. It is adapted so as
`to be capable of performing Such operations as, e.g., a
`measurement commencement of the pulse rate, a measure
`ment stop, a display changeover between the pulse rate and
`the current time, and a data transmission of the pulse rate
`data recorded in the memory 14 to an external equipment.
`Additionally, in the side face of the housing 2, there is
`provided an external connection terminal 21 for charging the
`above storage battery 13 by Supplying an electric power
`from an outside Such as battery charger. Incidentally, the
`external connection terminal 21 may be protected by attach
`ing a cover etc. So as to cover the external connection
`terminal 21. By so doing, it becomes possible to protect the
`external connection terminal 21 from waterdrop, dust and
`the like, so that it is more appropriate. Further, not limited
`to the external connection terminal 21, it may be constituted
`Such that a transformer and the like for respectively supply
`ing the electric power are provided in the battery charger and
`the housing 2, and a charging of the storage battery 13 is
`performed under a non-contact state.
`As shown in FIG. 6, the above protrusion part 4 is formed
`in a shape in which three circles have been combined in a
`shape, i.e., a keyhole-like shape in which, to a center circle,
`there have been connected two circles each having a diam
`eter smaller than the former circle so as to interpose it from
`left and right.
`As shown in FIG. 5, in a center of the lowerface 4a of this
`protrusion part 4, there is formed a through-hole 22 causing
`an inside of the housing 2 to communicate with an outside,
`and a cover glass 23 is fixed to the housing 2 so as to close
`the through-hole 22 concerned. And, the above LED 5 and
`both the PDs 6, 7 are disposed so as to contact with an inside
`of the cover glass 23.
`As shown in FIG. 6 and FIG. 7, out of both the PDs 6, 7,
`the 1st PD 6 is disposed near the LED 5, and the 2nd PD 7
`is disposed in a position spaced from the LED 5 more than
`a distance between the 1st PD 6 and the LED5. Further, the
`2nd PD 7 has a light receiving area that is proportional to and
`increases in accordance with a distance spacing from the
`LED5. In other words, the 2nd PD 7 is set such that the light
`receiving area is larger than the 1st PD 6.
`It is adapted Such that the pulse signals from both these
`PDs 6, 7 are sent to the above data processing part 9 through
`a flexible substrate 24, the sub-substrate 15 and the main
`substrate 12.
`The above one pair of electrodes 8 are disposed in the
`lower face 4a of the protrusion part 4 under a state that the
`LED 5 and both the PDs 6, 7 have been interposed between
`them. That is, one pair of electrodes 8, the LED 5 and both
`
`Hereunder, one embodiment of each of an organism
`information measuring device and an organism information
`measuring method, which concern the present invention, is
`explained by referring to FIG. 1 to FIG. 8.
`As shown in FIG. 1 to FIG. 6, an organism information
`measuring device 1 of the present embodiment is a wrist
`watch type, and one calculating the pulse rate that is the
`organism information under the state of being mounted to a
`wrist (arm) A.
`This organism information measuring device 1 accom
`modates therein various electrical components and elec
`tronic components, and comprises a housing (main body) 2
`disposed under a state that its lower face 2a contacts with an
`organism Surface B, and fixing means 3 which mounts the
`housing 2 to the wrist A. Further, a protrusion part 4
`protruding from the lower face 2a is formed in the lower
`face 2a of the housing 2.
`As shown in FIG. 6 and FIG. 7, in a lower face 4a of this
`protrusion part 4, i.e., the lower face 2a of the housing 2.
`there are disposed an LED (Light Emitting Diode) (light
`irradiating part) 5 which irradiates the light toward the
`organism under the state of contacting with the organism
`surface B, a 1st PD (Photo Diode) (1st light receiving part)
`6 and a 2nd PD (2nd light receiving part) 7, each of which
`receives the backward Scattered light from the organism
`within the light irradiated by the LED 5 and generates a
`pulse signal (organism information signal) complying with
`a received light quantity, and one pair of electrodes 8 which
`detect whether or not the above LED and both the PDs 6, 7
`contact with the organism surface B. As the LED 5, there is
`used an LED whose wavelength is 530 nm for instance. As
`the 1st PD and the 2nd PD, there is used a PD whose
`sensitivity in long wavelength of wavelength 600 nm or
`longer for instance has been cut.
`Further, in the housing 2, there is provided a data pro
`cessing part (organism information operating part) 9 which
`calculates the pulse rate on the basis of the pulse signals
`generated by both the PDs 6, 7.
`The above housing 2 comprises a plastic or a metal
`material Such as aluminum, and is formed, e.g., in an
`approximately rectangular shape when seen from above
`while having a predetermined thickness. An approximately
`square shape cover glass 10 is fitted to a center portion of an
`upper face 2b of the housing 2 and, inside the cover glass 10,
`there is disposed a display part 11 which displays the above
`calculated pulse rate and other various information.
`Further, as shown in FIGS. 3-5, in the housing 2, there is
`provided a main substrate 12 and, to the main substrate 12,
`there are mounted or electrically connected by a wiring, etc.
`the above data processing part 9, the above display part 11,
`a storage battery 13 capable of being charged, a memory 14
`for recording the pulse rate, a sub-substrate 15, and other
`various electronic components.
`The above data processing part 9 is one containing an IC
`component such as CPU, and is adapted Such that, after the
`pulse signals generated by both PDs 6, 7 have been once
`amplified by an amplifier and the like, it performs a prede
`termined processing Such as high-speed Fourier transforma
`tion processing (FFT processing) and calculates the pulse
`rate by comparing results of both processings. As to this
`calculation of the pulse rate, it is detailedly explained later.
`Further, the data processing part 9 is adapted such that it
`records the calculated pulse rate to the memory 14 and
`displays it to the display part 11 on the basis of an input from
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`the PD 6, 7 are disposed so as to be arranged in one row in
`a direction perpendicular to a longitudinal direction of the
`housing 2. Further, one pair of electrodes 8 are provided
`such that their tips somewhat protrude from the lower face
`4a of the protrusion part 4, and their base end sides are 5
`electrically connected to the sub-substrate 15.
`These one pair of electrodes 8 have a function of detect
`ing, on the basis of a potential difference between the
`electrodes, whether or not they contact with the organism
`Surface B. The data processing part 9 is set so as to control, 10
`when this detected result has been received and it has been
`detected that they contact with the organism surface B for
`instance, an operation of the LED 5 such that the light is
`irradiated from the LED 5. Incidentally, not limited only to
`this case, it may be set such that, when the fact has been 15
`detected that they don’t contact with the organism surface B
`for instance, the FFT processing is not performed.
`As shown in FIG. 1, the above fixing means 3 has a 1st
`band 30 and a 2nd band 31, whose base end sides are
`attached to the housing 2 and which can be mounted to the 20
`wrist A. The 1st band 30 and the 2nd band 31 are provided
`in the longitudinal direction of the housing 2 so as to be
`opposed while interposing the housing 2.
`A buckle 30a and a tongue 30b are attached to the above
`1st band 30 in its tip. Further, in the 2nd band 31, there are 25
`formed plural insertion holes 31a into which the above
`tongue 30b is inserted along the longitudinal direction of the
`2nd band 31 concerned. By this, it is adapted such that
`lengths of the 1st band 30 and the 2nd band 31 can be
`adjusted in compliance with a thickness of the wrist A of a 30
`USC.
`It is explained hereunder about an organism information
`measuring method in which the pulse rate is calculated by
`the organism information measuring device 1 constituted
`like this under the state of being attached to the wrist A.
`The organism information measuring method of the
`present embodiment has a transformation process in which,
`from the backward scattered light received by the 1st PD 6
`and the 2nd PD 7, pulse signals complying with the received
`light quantity are respectively generated and the pulse 40
`signals concerned are FFT-processed, and an operation
`process in which values transformed by the transformation
`process concerned are normalized by a power spectrum of
`optional frequency and the pulse information is operated by
`mutually subtracting the normalized values. It is detailedly 45
`explained below about each of these processes.
`First, as shown in FIG. 2 and FIG. 3, both the bands 30,
`31 are wound so as to encircle the wrist A of the user, and
`the tongue 30b of the 1st band 30 is inserted into the
`insertion hole 31a of the 2nd band 31 in compliance with a 50
`size of the wrist A, thereby mounting the housing 2 to the
`wrist A. When the housing 2 is mounted to the wrist A, since
`the protrusion part 4 protrudes than the lower face 2a of the
`housing 2, the organism surface B and the lower face 4a of
`the protrusion part 4 become a closely contacted State. 55
`Accordingly, it is unnecessary to mount the housing 2 so as
`to fasten the wrist A, and it suffices to adjust the lengths of
`both the bands 30, 31 such that they are tightened by a
`predetermined force.
`If the organism surface B and the lower face 4a of the 60
`protrusion part 4 come into a closely contacted State, i.e.,
`when the organism surface B contacts with the lower face 4a
`of the protrusion part 4, one pair of electrodes 8 contact with
`the organism surface B. Especially, since one pair of elec
`trodes 8 are disposed so as to somewhat protrude from the 65
`lower face 4a of the protrusion part 4, they are liable to
`contact with the organism surface B. If one pair of electrodes
`
`35
`
`US 7,060,963 B2
`
`8
`8 contact with the organism surface B, a discharge is
`performed through the organism surface B, so that a Voltage
`between both the electrodes 8 decreases. By receiving this
`Voltage drop (for example, a drop to lower than a certain
`threshold value), the data processing part 9 performs a
`detection of the fact that one pair of electrodes 8 are surely
`contacting with the organism Surface B. That is, the fact is
`detected that the LED 5 and both the PDs 6, 7 are surely
`contacting with the organism surface B. Especially, since
`one pair of electrodes 8 are disposed with the LED 5 and
`both the PDs 6, 7 being interposed between them, it is
`possible to accurately detect whether or not the LED 5 and
`both the PDs 6, 7 are contacting with the organism surface
`B.
`If the fact is detected that the LED 5 and both the PDs 6,
`7 are contacting with the organism Surface B, the data
`processing part 9 irradiates the light from the LED 5 toward
`the organism. The irradiated light is absorbed and scattered
`in the organism by the tissues, such as fat and muscle, and
`the blood, and one part of the irradiated light is received by
`both the PDs 6, 7 as the backward scattered light. This
`received light fluctuates with the change in blood quantity
`by the pulsation. Both the PDs 6, 7 receive this backward
`scattered light and generate the pulse signal complying with
`the change in the received light quantity, thereby outputting
`it to the data processing part 9. In other words, since a light
`quantity of the backward scattered light of the light irradi
`ated from the LED 5 fluctuates in compliance with a blood
`flow fluctuation in an artery and an arteriole inside the wrist
`A, both the PDs 6, 7 can perform a reception of the pulsation
`of the artery, i.e., the backward Scattered light complying
`with a pulse wave. By this, both the PDs 6, 7 can perform
`a generation of the pulse signal.
`On this occasion, since the 1st PD 6 is disposed near the
`LED 5, it receives the light depending on the LED 5 more
`than the backward Scattered light from the organism. That is,
`it receives much light containing no pulse signal, e.g., the
`light directly entering from the LED 5, the light reflected by
`the organism surface B, and the light reflected by the cover
`glass 23. On the other hand, since the 2nd PD 7 is disposed
`in the position spaced from the LED 5, it receives much
`backward Scattered light from the organism in addition to the
`light depending on the LED 5.
`The data processing part 9 performs the FFT processing
`after amplifying the pulse signal sent from both the PDs 6,
`7. That is, the process till this FFT processing is the above
`transformation process.
`After the transformation process, the operation process is
`performed. In other words, the data processing part 9 can
`accurately detect only the pulse signal by normalizing the
`FFT-processed values by the power spectrum of optional
`frequency and mutually subtracting the normalized values
`(mutual FFT results), i.e., as shown in FIG. 8, removing
`(subtracting) the pulse signal generated by the 1st PD 6 from
`the pulse signal generated by the 2nd PD7. By performing
`this operation process, it is possible to remove as far as
`possible the noise (electrical disturbance) containing no
`organism information from the pulse signal generated by the
`2nd PD 7. Accordingly, it is possible to improve in S/N ratio,
`and it is possible to perform the more accurate calculation of
`the pulse rate.
`And, the data processing part 9 records the calculated