Wearable heart rate monitor
A biometric monitoring device is used to determine a user's heart rate by using a heartbeat waveform sensor and a motion detecting sensor. In some embodiments, the device collects output data from the heartbeat waveform sensor and output data from the motion detecting sensor, determines an expected heart rate range from the output data from the motion detecting sensor, and determines the user's heart rate within the expected heart rate range using the output data from the heartbeat waveform sensor.
1. A method of determining a user's heart rate using a wearable biometric monitoring device comprising a plurality of sensors including a heartbeat waveform sensor and a motion detecting sensor, wherein the heartbeat waveform sensor comprises at least one light source and at least one photodetector, the method comprising:
(a) pulsing the at least one light source to emit light pulses in a time period when the wearable biometric monitoring device is worn by the user;
(b) operating the at least one photodetector to detect the light pulses emitted by the at least one light source after the light pulses interact with the user's tissue, and obtaining, through the at least one photodetector, output data from the heartbeat waveform sensor, wherein the output data from the heartbeat waveform sensor contains information about the user's heart rate and is susceptible to motion artifacts;
(c) operating the motion detecting sensor in the time period when the wearable biometric monitoring device is worn by the user, and obtaining output data from the motion detecting sensor, wherein the output data from the motion detecting sensor provides information about the user's physical movements other than heartbeats;
(d) determining a range of expected heart rates using the output data from the motion detecting sensor;
(e) determining the user's heart rate from output data from the heartbeat waveform sensor or from data derived therefrom, wherein determining the user's heart rate comprises: (i) excluding from consideration one or more putative heart rates outside of the range of expected heart rates, and (ii) determining the user's heart rate within the range of expected heart rates; and
(f) presenting the user's heart rate.
2. The method of claim 1 , wherein determining the range of expected heart rates comprises:
(i) determining the user's stationary heart rate when another output data from the motion detecting sensor indicates that the user is substantially stationary;
(ii) determining the user's activity level and/or activity type from the output data from the motion detecting sensor; and
(iii) determining the range of expected heart rates from the user's stationary heart rate determined in (i) and the user's activity level and/or activity type determined in (ii).
3. The method of claim 2 , wherein a minimum expected heart rate in the range of expected heart rates is greater than the user's stationary heart rate determined in (i).
4. The method of claim 2 , wherein determining the user's activity type comprises inferring the activity type from information contained in the output data from the motion detecting sensor or detecting a manually entered selection of activity type.
5. The method of claim 1 , wherein determining the user's heart rate comprises, before excluding the one or more putative heart rates from consideration, transforming the output data from the motion detecting sensor into a frequency domain to obtain spectral representations of the putative heart rates.
6. The method of claim 1 , wherein the wearable biometric monitoring device further comprises one or more processors, and wherein (d)-(e) are performed by the one or more processors.
7. The method of claim 1 , wherein the wearable biometric monitoring device further comprises a display device, and wherein presenting the user's heart rate in (f) comprises visually displaying the user's heart rate on the display device.
8. The method of claim 1 , wherein determining the range of expected heart rates comprises determining the user's step rate from the output data from the motion detecting sensor.
9. The method of claim 1 , wherein determining the user's heart rate comprises calculating a spectral density of the output data from the heartbeat waveform sensor.
10. The method of claim 1 , wherein the user's physical movements other than heart beats comprise a wearer's limb movements.
11. The method of claim 1 , wherein the motion detecting sensor is an accelerometer, a gyroscope, or a GPS sensor.
12. The method of claim 1 , wherein pulsing the at least one light source comprises pulsing the at least one light source at a first frequency and operating the at least one photodetector comprises detecting light pulses at the first frequency.
13. The method of claim 12 , wherein pulsing the at least one light source at the first frequency comprises emitting a succession of light pulses of substantially constant intensity.
14. The method of claim 1 , wherein presenting the user's heart rate comprises presenting the heart rate on the wearable biometric monitoring device or on an external device that periodically communicates with the wearable biometric monitoring device.
15. The method of claim 1 , wherein determining a range of expected heart rates comprises: determining the user's activity type from the output data from the motion detecting sensor; and determining the range of expected heart rates based on the determined activity type.
16. The method of claim 1 , wherein the output data from the heartbeat waveform sensor in (e) are obtained by:
determining a periodic component of the output data from the motion detecting sensor; and
processing the output data from the heartbeat waveform sensor to remove the periodic component from the output data from the heartbeat waveform sensor.
17. A wearable biometric monitoring device comprising:
a motion sensor configured to provide output corresponding to motion by a user wearing the wearable biometric monitoring device;
a heartbeat waveform sensor comprising at least one light source and at least one photodetector; and
control logic comprising instructions for:
(a) pulsing the at least one light source to emit light pulses in a time period when the wearable biometric monitoring device is worn by the user;
(b) operating the at least one photodetector to detect the light pulses emitted by the at least one light source after the light pulses interact with the user's tissue, and obtaining, through the at least one photodetector, output data from the heartbeat waveform sensor, wherein the output data from the heartbeat waveform sensor contains information about the user's heart rate and is susceptible to motion artifacts;
(c) operating the motion detecting sensor in the time period when the wearable biometric monitoring device is worn by the user, and obtaining output data from the motion detecting sensor, wherein the output data from the motion detecting sensor provides information about the user's physical movements other than heartbeats;
(d) determining a range of expected heart rates using the output data from the motion detecting sensor;
(e) determining the user's heart rate from output data from the heartbeat waveform sensor or from data derived therefrom, wherein determining the user's heart rate comprises: (i) excluding from consideration one or more putative heart rates outside of the range of expected heart rates, and (ii) determining the user's heart rate within the range of expected heart rates; and
(f) presenting the user's heart rate.
18. The wearable biometric monitoring device of claim 17 , wherein the heartbeat waveform sensor is a photoplethysmographic sensor comprising (i) a periodic light source, (ii) a photo detector positioned to receive periodic light emitted by the periodic light source after interacting with the user's skin, and (iii) circuitry determining the user's heart rate from output of the photo detector.
19. The wearable biometric monitoring device of claim 17 , wherein the instructions for determining the range of expected heart rates comprise instructions for:
(i) determining the user's stationary heart rate when another output data from the motion detecting sensor indicates that the user is substantially stationary;
(ii) determining the user's activity level and/or activity type from the output data from the motion detecting sensor; and
(iii) determining the range of expected heart rates from the user's stationary heart rate determined in (i) and the user's activity level and/or activity type determined in (ii).
20. The wearable biometric monitoring device of claim 19 , wherein a minimum expected heart rate in the range of expected heart rates is greater than the user's stationary heart rate determined in (i).
21. The wearable biometric monitoring device of claim 19 , wherein the instructions for determining the user's activity type comprise instructions for inferring the activity type from information contained in the output data from the motion detecting sensor or detecting a manually entered selection of activity type.
22. The wearable biometric monitoring device of claim 17 , wherein the instructions for determining the range of expected heart rates comprise instructions for determining the user's step rate from the output data from the motion detecting sensor.
23. The wearable biometric monitoring device of claim 17 , wherein the instructions for determining the user's heart rate comprise the instructions for calculating a spectral density of the output data from the heartbeat waveform sensor.
24. The wearable biometric monitoring device of claim 17 , wherein the motion detecting sensor is an accelerometer, a gyroscope, or a GPS sensor.
25. The wearable biometric monitoring device of claim 17 , wherein the instructions for determining a range of expected heart rates comprises instructions for: determining the user's activity type from the output data from the motion detecting sensor; and determining the range of expected heart rates based on the determined activity type.
26. The wearable biometric monitoring device of claim 17 , wherein the instructions for determining the range of expected heart rates comprise instructions for:
(i) determining the user's stationary heart rate when another output data from the motion detecting sensor indicates that the user is substantially stationary;
(ii) determining the user's step rate from the output data from the motion detecting sensor; and
(iii) determining the range of expected heart rates from the user's stationary heart rate determined in (i) and the user's step rate determined in (ii).
27. The wearable biometric monitoring device of claim 17 , wherein determining the user's heart rate comprises, before excluding the one or more putative heart rates from consideration, transforming the output data from the motion detecting sensor into a frequency domain to obtain spectral representations of the putative heart rates.
28. The wearable biometric monitoring device of claim 17 , wherein the output data from the heartbeat waveform sensor in (e) are obtained by:
determining a periodic component of the output data from the motion detecting sensor; and
processing the output data from the heartbeat waveform sensor to remove the periodic component from the output data from the heartbeat waveform sensor.