as United States
`a2) Patent Application Publication co) Pub. No.: US 2001/0056243 A1
`
` Ohsaki et al. (43) Pub. Date: Dec. 27, 2001
`
`
`US 20010056243A1
`
`(54) WRISTWATCH-TYPE HUMAN PULSE WAVE
`SENSOR ATTACHED ON BACKSIDE OF
`USER’S WRIST
`
`(76)
`
`Inventors: Rie Ohsaki, Anjo-city JP); Teiyuu
`Kimura, Nagoya-city (JP); Naoki
`Fukaya, Obu-city (1P)
`Correspondence Address:
`LAW OFFICE OF DAVID G POSZ
`2000 L STREET. N.W.
`SUITE 200
`,
`WASHINGTON, DC 20036 (US)
`(21) Appl. No.:
`09/852,698
`
`(22)
`
`Filed:
`
`May11, 2001
`
`(30)
`
`Foreign Application Priority Data
`
`Jun. 14, 2000
`
`(IP) cee eecesseceeenseseeeseneenees 2000-177999
`
`Publication Classification
`
`Inte C17 caccccscssssessessstsssseessseesetntn AGB 5/02
`(51)
`(52) WS. Ch.
`caccscssssssssstessstntntesene 600/503; 600/500
`
`ABSTRACT
`(57)
`A pulse wave sensor includes a detecting element and a
`sensor body. The pulse wave sensor is worn on the back side
`of a user’s wrist corresponding to the back of the user’s
`hand. The detecting element includes a translucent member
`on its top, and the translucent memberhas a convex surface.
`The detecting element is attached on the back side of the
`user’s wrist by a dedicated belt so that the convex surface of
`the translucent member is in intimate contact with the
`surface of the user’s skin. The sensor bodyis attached on the
`back side of the user’s wrist by another dedicated belt so that
`it is arranged on the detecting element. A cushionis arranged
`between the sensor body and the detecting element. The
`pulse wave sensor can stably detect the pulse wave without
`being affected by the movementof the user’s wrist.
`
` 11
`
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`
`APPLE 1008
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`

`

`Patent Application Publication Dec. 27,2001 Sheet 1 of 2
`
`US 2001/0056243 Al
`
`FIG.
`
`|
`
`MICRO-
`COMPUTER
`
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`

`

`Patent Application Publication Dec. 27, 2001 Sheet 2 of 2
`
`US 2001/0056243 Al
`
`BACK SIDE
`
`IN MOTION
`|
`c———__—_—_>
`!
`|
`!
`|
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`|
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`
`FIG. 3A = 4000
`t 3500
`~ 3000
`2500
`2000
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`
`
`
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`
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`
`;
`t(s)
`FRONT SIDE |
`IN MOTION
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`FIG. 3B _4000 !
`= 3500
`3000 }
`
`2500
`
`2000
`
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`
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`
`4
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`6
`
`t (s)
`
`IN MOTION
`
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`

`

`US 2001/0056243 Al
`
`Dec. 27, 2001
`
`WRISTWATCH-TYPE HUMAN PULSE WAVE
`SENSOR ATTACHED ON BACKSIDE OF USER’S
`WRIST
`
`CROSS REFERENCE TO RELATED
`APPLICATION
`
`{0001] This application is based on and incorporates
`herein by reference Japanese Patent Application No.2000-
`177999 filed on Jun. 14, 2000.
`
`detecting element so that it is arranged on the detecting
`element. A cushionis arranged between the sensor body and
`the detecting element.
`
`[0010] According to this construction, the user does not
`feel uncomfortable when the pulse wave sensor is worn on
`the user’s wrist. Furthermore the detecting elementis fixed
`on the user’s wrist withoutslippingoff the detection position
`of the user’s wrist, even if the user is in motion. Accordingly
`the pulse wave sensorcan stably detect the pulse waveofthe
`user.
`
`BACKGROUND OF THE INVENTION
`
`BRILI DESCRIPTION OP THE DRAWINGS
`
`[0002]
`
`1. Field of the Invention
`
`[0003] The present invention relates to an optical sensor
`for detecting the pulse wave of a human body.
`
`[0004]
`
`2. Related Art
`
`JP-A-11-70087 proposes a wristwatch-type device
`[0005]
`for detecting the pulse wave of a human body. This detecting
`device is worn on the user’s wrist. The device includes a
`detecting element for detecting a pulse wave and a sensor
`body including a display. The detecting elementis fixed on
`the front side of the user’s wrist corresponding to the palm
`of the user’s hand by a band attachedto the sensor body. The
`information of pulse wave detected by the detecting element
`is displayed on the display of the sensor body fixed on the
`back side of the user’s wrist.
`
`[0006] Thc two bones (the radius and the ulna) pass
`through the front side of the user’s wrist. Therefore the
`detecting element has a tendency to slip off the detection
`position of the user’s wrist, since the skin surface of the front
`side of the user’s wrist greatly moves as the user’s wrist
`moves. Furthermore, the user feels uncomfortable since the
`radius and the ulna are pressed. As a result, the user further
`moves his/her wrist unconsciously and it becomes further
`difficult to detect the pulse wave stably.
`
`SUMMARYOF THE INVENTION
`
`[0007] The present invention overcomes the above draw-
`backs, and has an object to provide a human pulse wave
`sensor which is capable of detecting the pulse wave of a
`human body stably and has high detection probability.
`
`[0008] The pulse wave sensor according to the present
`invention includes a detecting element and a sensor body.
`The pulse wave sensor is worn on the back side ofthe user’s
`wrist corresponding to the back of the user’s hand for
`detecting the pulse wave of the user. The detecting clement
`includes a light emitting element and a light receiving
`element. The sensor body is connected to the detecting
`element by a signal line.
`
`[0009] Preferably, a translucent member is arranged on the
`light emitting element and the light receiving element. The
`translucent member has a convex surface. The detecting
`elementis attached on the back side of the user’s wrist by a
`dedicated belt so that the convex surface of the translucent
`memberis in intimate contact with the surface of the user’s
`
`skin. The light emitting element and the light receiving
`element are arranged in the longitudinal direction of the
`user’s arm. The sensor bodyis attached on the back side of
`the user’s wrist by a dedicated belt other than the belt of the
`
`[0011] The above and other objects, features and advan-
`tages of the present invention will become more apparent
`from the following detailed description made with reference
`to the accompanying drawings. In the drawings:
`
`[0012] FIG. 1 is a cross-sectional view of a pulse wave
`sensor attached on the user’s wrist;
`
`[0013] FIG. 2 is a schematic diagram of a mechanismfor
`detecting a pulse wave;
`
`[0014] FIGS. 3A and 3B are graphs of the pulse wave
`detected by a pulse wave sensor attached on the back side of
`the user’s wrist and the pulse wave detected by a pulse wave
`sensor attached on the front side of the user’s wrist, respec-
`tively; and
`
`[0015] FIGS. 4A and 4B are graphs of the pulse wave
`detected by a pulse wave sensor including a convex detect-
`ing surface and the pulse wave detected by a pulse wave
`sensor including a flat detecting surface, respectively.
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`
`[0016] Referring to FIG. 1, a pulse wave sensor 1 includes
`a detecting element 2 and a sensor body 3. The pulse wave
`sensor 1 is worn on the back side of the user’s wrist 4
`corresponding to the back of the user’s hand in the similar
`manner as a wristwatch is normally worn. This sensor 1 is
`used for detecting the pulse wave of the user’s bodyfor a
`medical diagnosis, a physical check up, and thelike.
`
`[0017] Referring to FIG.2, the detecting element 2 com-
`prises a package 5, a light emitting element 6 (e.g., LED), a
`light receiving element7 (e.g., PD), and a translucent board
`8. The package 5 has an opening and includesa circuit board
`9 therein. The light emitting clement 6 and light recciving
`element7 are included in the package 5 and arranged on the
`circuit board 9. The translucent board 8 is a glass board
`whichis transparentto light, and attached to the opening of
`the package 5. A convex surface is formed onthe top of the
`translucent board 8 as shown in FIG.2.
`
`[0018] The detecting element 2 is fixed on the user’s wrist
`4 by a dedicated belt 10 attached to the detecting element 2
`as shown in FIG. 1. The belt 10 may be made from elastic
`material so that regular pressure is applied to the user’s wrist
`4. In this case,
`it is prevented that light reflected by the
`surface of the skin or disturbance light from the outside
`penetrates the translucent board 8, since the surface of the
`translucent board 8 is in intimate contact with the surface of
`the user’s skin. However the user feels uncomfortable if the
`pressure applied to the user’s wrist 4 is too high. Therefore
`it is desirable that the pressure applied to the user’s wrist 4
`is limited to 5-15 mmHg.
`
`4
`
`

`

`US 2001/0056243 Al
`
`Dec. 27, 2001
`
`[0019] The light emitting element 6 andthe light receiving
`element 7 are arranged side by side as shown in FIG.2.
`Accordingly the length of the detecting element 2 from the
`right side to the left side in FIG. 2 is longer than the length
`from the upper side to the lower side. If the detecting
`element2 is arrangedso thatits longitudinal direction (from
`the right side to the left side in FIG. 2) agrees with the
`circumferential direction of the user’s wrist 4,
`it has a
`tendency to slip off. Therefore it
`is desirable that
`the
`detecting element 2 is arranged so that
`its longitudinal
`direction agrees with the longitudinal direction of the user’s
`arm. The dedicated belt 10 is attached to the detecting
`element 2 so that it can fix the detecting element 2 on the
`user’s wrist 4 in this way.
`
`[0020] The sensor body 3 is connected to the detecting
`element2 by a signal line 13, and includes, as shownin FIG.
`2, a drive circuit 11, a microcomputer 12, and a monitor
`display (not shown). The drive circuit 11 drives the light
`emitting element 6 to emit light toward the wrist 4. The
`microcomputer 12 calculates the pulse rate from the
`reflected light received by the detecting element 2. This
`reflected light varies with the user’s pulsation. The monitor
`display shows the calculated pulse rate and the like.
`
`[0021] The sensor body3 is arranged on the top of the
`detecting element 2, and fixed on the user’s wrist 4 by a
`dedicated belt 14 attached to the sensor body 3. A cushion
`15 such as a spongeor a gelis inserted betweenthe detecting
`element 2 and the sensor body 3 so that
`the detecting
`element 2 does not directly contact the sensor body 3.
`
`[0022] The pulse wave sensor 1 detects the pulse wave of
`the user’s body as follows. The light emitting element 6
`emits light toward the user’s wrist 4, a portion of the emitted
`light penetrates the capillary arteriole 16 in the inside of the
`user’s wrist 4 and is absorbed by the haemoglobin in the
`blood. Therest of the emitted light is reflected and scattered
`by the capillary arteriole 16, and partly reaches the light
`emitting element 7. As the amountof the haemoglobinin the
`blood varics in waves duc to the pulsation of the uscr’s
`blood, the amountof the light absorbed by the haemoglobin
`also varies in waves. As a result, the amount of the light
`whichis reflected by the capillary arteriole 16 and reaches
`the light receiving element 7 varies in waves. This variation
`in the amount of the light received by the light receiving
`element 7 is detected as the pulse wave information.
`
`If the detecting element 2 is arranged on the front
`[0023]
`side of the user’s wrist 4, the amountof the light received the
`light receiving element 7 is larger. That is, the intensity of
`the signal received bythe light receiving element7 is higher.
`However, the detecting element 2 has a tendencyto slip off
`the detecting position of the user’s wrist 4 as the user moves
`his/herwrist, and therefore the intensity of the light received
`by the light receiving element7 largely varies depending on
`the shift amount of the detecting element 2. As shown in
`FIG.3B, in the case that the detecting element2 is arranged
`onthe front side of the user’s wrist 4, the pulse wave can be
`detected well if the user is at rest. However, when the user
`is in motion, the detected pulse waveis adversely affected by
`the movement of the user’s wrist 4.
`
`In contrast to this, if the detecting element 2 is
`[0024]
`arranged on the back side of the user’s wrist 4, the user will
`not move his/her wrist unconsciously since the radius and
`the ulna inside the user’s wrist 4 are not pressed and
`
`consequently the user does not feel so uncomfortable. Fur-
`ther, the detecting element 2 will not shift so widely even if
`the user’s wrist moves. Therefore the detecting element2 is
`stably fixed to the detecting position ofthe user’s wrist 4. As
`a result,
`the pulse wave is detected stably without being
`affected by the movementof the user’s wrist 4 as shown in
`FIG.3A.
`
`[0025] The detecting element 2 is arranged on the user’s
`wrist 4 so that the convex surface of the translucent board 8
`is in intimate contact with the surface of the user’s skin.
`
`Thereby it is prevented that the detecting element 2 slips off
`the detecting position of the user’s wrist 4. If the translucent
`board 8 has a flat surface,
`the detected pulse wave is
`adversely affected by the movementof the user’s wrist 4 as
`shown in FIG. 4B. However,in the case that the translucent
`board 8 has a convex surface like the present embodiment,
`the variation of the amount of the reflected light which is
`emitted from the light emitting element 6 and reaches the
`light receiving element7 by being reflected by the surface of
`the user’s skin is suppressed. It is also prevented that noise
`such as disturbance light from the outside penetrates the
`translucent board 8. Therefore the pulse wave can be
`detected without being affected by the movement of the
`user’s wrist 4 as shown in FIG. 4A.
`
`[0026] The detecting element 2 and the sensor body 3 is
`attached to theuser’s wrist 4 by the dedicated belts10 and 14,
`respectively. That is, the detecting element 2 and the sensor
`body 3 are allowed to moverelatively. Further the cushion
`15 is arranged between the detecting element 2 and the
`sensor body 3. Therefore, if force is applied to the sensor
`body 3 or the sensor body 3 moves, the force applied to the
`sensor body3 or the movementof the sensor body 3 cannot
`be transmitted to the detecting element 2 easily.
`
`[0027] Accordingly the detecting element2 is stably fixed
`to the user’s wrist 4. As a result, the pulse wave sensor can
`detect the pulse wave at a high S/N ratio, that is, it can
`provide high detection probability, not only whenthe user is
`at rest but also when the uscr is taking light exercise.
`
`[0028] Modifications
`
`In the above embodiment, the sensor body 3 need
`[0029]
`not include the microcomputer 12 if it includes a transmitter
`instead. In this case, the pulse wave information detected by
`the detecting element 2 is transmitted to a receiver by the
`transmitter. The sensor body 3 can be downsizedandlight in
`weight in this case and consequently the force applied to the
`sensor body 3 or the movementof the sensor body 3 cannot
`be transmitted to the detecting element 2 easily.
`
`In the above embodiment, the detecting element 2
`[0030]
`and the sensor body 3 may be worn on the backside of the
`user’s forearm.
`
`Whatis claimedis:
`1. A pulse wave sensor for detecting a pulse wave of a
`human body comprising:
`
`a detecting elementincludinga light emitting element and
`a light receiving element; and
`
`a sensor body including a circuit connected to the detect-
`ing element via a signal line,
`
`wherein the detecting element is constructed to be worn
`on a backside of a user’s wrist or a user’s forearm.
`
`5
`
`

`

`US 2001/0056243 Al
`
`Dec. 27, 2001
`
`2. A pulse wave sensor as set forth in claim 1, wherein:
`
`includes a translucent member
`the detecting element
`whichis transparent to light and arranged on the light
`emitting element and the light receiving element;
`
`the translucent member has a convex surface; and
`
`the translucent memberis arranged on the back side of the
`user’s wrist or the user’s forearm so thal the convex
`surface of the translucent memberis in intimate contact
`with a surface of the user’s skin.
`
`3. A pulse wave sensor for detecting a pulse wave of a
`human body comprising:
`
`a detecting elementincludinga light emitting element and
`a light receiving element; and
`
`a sensor body including a circuit connected to the detect-
`ing element via a signal line,
`
`wherein the detecting clement is constructed to be worn
`on a user’s wrist or a user’s forearm,
`
`the pulse wave sensor further comprising:
`
`a first belt for fixing the detecting element to the user’s
`wrist or the user’s forearm; and
`
`a second belt for fixing the sensor bodyto the user’s wrist
`or the user’s forearm.
`
`4. A pulse wave sensor for detecting a pulse wave of a
`human body comprising:
`
`a detecting elementincludinga light emitting element and
`a light receiving element; and
`
`a sensor body including a circuit connected to the detect-
`ing element via a signal line,
`
`wherein the detecting element is constructed to be worn
`on a user’s wrist or a user’s forearm,
`
`wherein the sensor body is arranged on the detecting
`element, and
`
`wherein a cushion is arranged between the detecting
`element and the sensor body.
`5. A pulse wave sensor for detecting a pulse wave of a
`human body comprising:
`
`a detecting elementincluding a light emitting element and
`a light receiving element; and
`
`a sensor body including a circuit connected to the detect-
`ing element via a signal line,
`
`wherein the detecting element is constructed to be worn
`on a user’s wrist or a user’s forearm,
`
`wherein the light emitting element andthe light receiving
`element are arranged side by side in a longitudinal
`direction of the user’s arm.
`
`6. A pulse wave sensor as set forth in claim 5, wherein:
`
`translucent member
`includes a
`the detecting element
`whichis transparent to light and arranged on the light
`emitting element and the light receiving element;
`the translucent memberhas a convex surface; and
`
`the translucent memberis arranged on the user’s wrist or
`the user’s forearm so that the convex surface of the
`translucent memberis in intimate contact with a surface
`of the user’s skin.
`
`7. A pulse wave sensor as set forth in claim 6 further
`comprising:
`
`a first belt for fixing the detecting element to the user ’s
`wrist or the user’s forearm; and
`
`a second belt for fixing the sensor body to the user’s wrist
`or the user’s forearm.
`
`8. A pulse wave sensor as set forth in claim 7, wherein:
`
`the sensor body is arranged on the detecting element; and
`
`a cushion is arranged between the detecting clement and
`the sensor body.
`
`6
`
`