Device for detecting pulse waves

A pulse wave detection device capable of accurately detecting pulse waves without influence of noise caused by hand movement or the like has a main sensor disposed on a radial artery and having an emitter for emitting an ultrasonic signal toward the radial artery and a receiver for receiving a reflected ultrasonic signal, and an auxiliary sensor disposed on an ulnar artery and having an emitter for emitting an ultrasonic signal toward the ulnar artery and a receiver for receiving a reflected ultrasonic artery. If the amplitude of an ultrasonic signal received by the main sensor is not between two threshold values, it is determined that detection of pulse waves from the radial artery is difficult. Then detection of pulse waves from the ulnar artery is performed by using the auxiliary sensor. After the lapse of a predetermined period of time from the start of detection using the ulnar artery, the main sensor is again selected to be used. If detection with the main sensor is possible, detection with the main sensor is continued. If detection with the main sensor is difficult even after the predetermined time period, the auxiliary sensor is again selected. If detection with the auxiliary sensor is also difficult, a buzzer is caused to sound to inform the user of this condition.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS.

1(

a)-

1(

b) are a diagram showing the configuration of a pulse wave detection device which represents a first embodiment of the present invention;

FIGS.

2(

a) through

2(

d) are diagrams showing waveforms output from the essential components of the pulse wave detection device shown in FIG. 1;

FIGS.

3(

a) through

3(

c) are diagrams showing a state where pulse waves are detected by a pulse wave detection device incorporated in a watch according to the first embodiment;

FIGS.

4(

a) and

4(

b) are diagrams showing an external appearance of the pulse wave detection device (watch) shown in FIGS.

3(

a) through

3(

c);

FIG. 5 is a diagram for explaining the principle of changing arteries from which pulse waves are detected;

FIG. 6 is a flowchart showing the process performed by a signal intensity comparison section;

FIG. 7 is a diagram showing the configuration of a pulse wave detection device which represents a second embodiment of the present invention;

FIGS.

8(

a) and

8(

b) are diagrams showing examples of modification of sensors; and

FIGS.

9(

a) and

9(

b) are diagrams showing changes in the frequency of ultrasound by the Doppler effect.

1. A device for detecting pulse waves, comprising: a first sensor positionable on a user's wrist above the user's radial artery and having first emitting means for emitting an ultrasound signal toward the radial artery and first receiving means for receiving an ultrasound signal emitted from the first emitting means and reflected by blood flowing in the radial artery; a second sensor positionable on the user's wrist above the user's ulnar artery and having second emitting means for emitting an ultrasound signal toward the ulnar artery and second receiving means for receiving an ultrasound signal emitted from the second emitting means and reflected by blood flowing in the ulnar artery; pulse wave information acquisition means for acquiring pulse wave information based on pulse waves from the ultrasound signals received by one of the first receiving means and the second receiving means; and output means for outputting the pulse wave information acquired by the pulse wave information acquisition means; wherein the first and second sensors are adjacent each other along a line extending about a circumference of the user's wrist.

2. A device for detecting pulse waves according to claim 1; further comprising effectiveness determination means for determining whether the ultrasound signals received by the first receiving means and the second receiving means are effective for detecting the pulse wave information; and wherein the pulse wave information acquisition means acquires pulse wave information based on pulse waves detected from the ultrasound signal recognized as effective by the effectiveness determination means.

3. A device for detecting pulse waves according to claim 2; further comprising switching means for selecting one of the first sensor or the second sensor when the effectiveness determination means determines that the ultrasound signal received by the other one of the first receiving means and the second receiving means is ineffective.

4. A device for detecting pulse waves according to claim 3; wherein the switching means selects the first sensor after a lapse of a predetermined period of time from a time when the switching means has selected the second sensor.

5. A device for detecting pulse waves according to claim 2; further comprising indication means for indicating that the ultrasound signals received by the first receiving means and the second receiving means are ineffective when the effectiveness determination means has determined that the ultrasound signals received by the first receiving means and the second receiving means are ineffective.

6. A device for detecting pulse waves according to claim 3; further comprising indication means for indicating that the ultrasound signals received by the first receiving means and the second receiving means are ineffective when the effectiveness determination means has determined that the ultrasound signals received by the first receiving means and the second receiving means are ineffective.

7. A device for detecting pulse waves according to claim 4; further comprising indication means for indicating that the ultrasound signals received by the first receiving means and the second receiving means are ineffective when the effectiveness determination means has determined that the ultrasound signals received by the first receiving means and the second receiving means are ineffective.

8. A device for detecting pulse waves, comprising: a first sensor positionable on a user's wrist above the user's radial artery and having a first transmitter for transmitting ultrasound signals toward the user's radial artery and a first receiver for receiving ultrasound signals transmitted from the first transmitter and reflected by blood flowing in the radial artery; a second sensor positionable on the user's wrist above the user's radial artery and having a second transmitter for transmitting ultrasound signals toward the user's ulnar artery and a second receiver for receiving ultrasound signals transmitted from the second transmitter and reflected by blood flowing in the ulnar artery; a pulse wave information acquisition circuit for acquiring pulse wave information in accordance with pulse waves detected from the ultrasound signals received by one of the first receiver and the second receiver; and an output circuit for outputting the pulse wave information acquired by the pulse wave information acquisition circuit; wherein the first and second sensors are adjacent each other along a line extending about a circumference of the user's wrist.

9. A device for detecting pulse waves according to claim 1; wherein the first and second sensors are provided on an inner surface of a wriststrap of a wristwatch so as to be disposed against the user's wrist when the wristwatch is worn on the user's wrist.

10. A device for detecting pulse waves according to claim 1; wherein the pulse wave information acquired by the pulse wave information acquisition means comprises the user's pulse rate.

11. A device for detecting pulse waves according to claim 10; further comprising a display for displaying the pulse rate.

12. A device for detecting pulse waves according to claim 11; wherein the display provides a visual indication of which of the first and second sensors has been selected.

13. A device for detecting pulse waves according to claim 11; wherein the display provides a visual indication of a relative signal strength of the ultrasound signal received by the receiving means of the driven sensor.

14. A device for detecting pulse waves according to claim 1; further comprising a display for displaying the pulse wave information.

15. A device for detecting pulse waves according to claim 14; wherein the display provides a visual indication of which of the first and second sensors has been selected.

16. A device for detecting pulse waves according to claim 14; wherein the display provides a visual indication of a relative signal strength of the ultrasound signal received by the receiving means of the driven sensor.

17. A device for detecting pulse waves according to claim 1; wherein the first and second sensors comprise Doppler sensors.

18. A device for detecting pulse waves according to claim 1; further comprising a housing for containing the pulse wave information acquisition means and the output means, and having a wriststrap on which the first sensor and the second sensor are mounted.

19. A device for detecting pulse waves according to claim 18; further comprising a timepiece movement contained in the housing.

20. A device for detecting pulse waves according to claim 2; wherein the effectiveness determination means determines that a received ultrasonic signal is effective when a magnitude of the received ultrasonic signal is within a predetermined range.

21. A wrist-wearable pulse detector comprising: a housing; a wrist strap attached to the housing for removably attaching the housing to a user's wrist; a first sensor provided on the wrist strap so as to be positioned over the user's radial artery when the pulse detector is attached to the user's wrist, the first sensor having a first emitter for emitting an ultrasound signal toward the radial artery and a first receiver for receiving a first ultrasound signal emitted from the first emitter and reflected by blood flowing in the radial artery; a second sensor provided on the wrist strap so as to be positioned over the user's ulnar artery when the pulse detector is attached to the user's wrist, the second sensor having a second emitter for emitting an ultrasound signal toward the ulnar artery and a second receiver for receiving a second ultrasound signal emitted from the second emitter and reflected by blood flowing in the ulnar artery; and a control circuit for selectively driving one of the first and second sensors based on the relative strength of the received first and second ultrasound signals and calculating pulse information based on the ultrasound signal received by the driven sensor.

22. A wrist-wearable pulse detector according to claim 21; further comprising a display for displaying the calculated pulse information.

23. A wrist-wearable pulse detector according to claim 21; wherein the display provides a visual indication of which one of the first and second sensors is being driven.

24. A wrist-wearable pulse detector according to claim 21; wherein the display provides a visual indication of a relative signal strength of the ultrasound signal received by the receiver of the driven sensor.

25. A wrist-wearable pulse detector according to claim 21; wherein the control circuit determines whether the first and second ultrasound signals are effective for calculating the pulse information by determining whether the first and second ultrasonic signals are within a predetermined range, and preferentially drives the first sensor when the first ultrasound signal is effective for calculating the pulse information.

26. A wrist-wearable pulse detector according to claim 24; wherein the control circuit calculates the pulse information based on one of the first and second ultrasound signals recognized as effective by the effectiveness determining circuit.