Wearable heart rate monitor

• US 8,920,332 B2
• Filed: 06/03/2014
• Issued: 12/30/2014
• Est. Priority Date: 06/22/2012
• Status: Active Grant

• Current Assignee: Fitbit, Inc. (Alphabet Inc.)
• Original Assignee: Fitbit, Inc. (Alphabet Inc.)
• Inventors: Hong, Jung Ook, Yuen, Shelten Gee Jao
• Primary Examiner(s): D'ANGELO, MICHAEL J
• Application Number:
  US14/295,144
• Publication Number:
  US 20140288390A1
• Time in Patent Office: 210 Days
• Field of Search: 600/301, 600/310, 600/481, 600/483, 600/500, 600/502, 600/503
• US Class Current: 600/500
• CPC Class Codes: A61B 2562/0233 Special features of optical sensors or probes classified in A61B5/00
• CPC Class Codes: A61B 5/0002 Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network A61B5/07 takes precedence; transmission systems for measured values G08C; transmission H04B; transmission of digital information H04L; wireless communication networks H04W
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/02427 Details of sensor
• CPC Class Codes: A61B 5/02433 for infrared radiation
• CPC Class Codes: A61B 5/02438 with portable devices, e.g. worn by the patient
• CPC Class Codes: A61B 5/11 Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb for measuring pulse A61B5/02 ;A61B5/1038 takes precedence; motion detection to correct for motion artifacts in physiological signals A61B5/721
• CPC Class Codes: A61B 5/1118 Determining activity level
• CPC Class Codes: A61B 5/1123 Discriminating type of movement, e.g. walking or running A61B5/1116, A61B5/112 take precedence
• CPC Class Codes: A61B 5/4812 Detecting sleep stages or cycles
• CPC Class Codes: A61B 5/681 Wristwatch-type devices
• CPC Class Codes: A61B 5/6843 Monitoring or controlling sensor contact pressure
• CPC Class Codes: A61B 5/6844 Monitoring or controlling distance between sensor and tissue
• CPC Class Codes: A61B 5/6886 Monitoring or controlling distance between sensor and tissue
• CPC Class Codes: A61B 5/7235 Details of waveform analysis A61B5/349 takes precedence
• CPC Class Codes: H04L 67/12 specially adapted for proprietary or special-purpose networking environments, e.g. medical networks, sensor networks, networks in vehicles or remote metering networks
• CPC Class Codes: H04W 4/027 using movement velocity, acceleration information
• CPC Class Codes: H04W 4/08 User group management
• CPC Class Codes: H04W 4/80 Services using short range communication, e.g. near-field communication [NFC], radio-frequency identification [RFID] or low energy communication
• CPC Class Codes: Y02D 30/70 : in wireless communication networks

Abstract

Some embodiments provide a wearable fitness monitoring device including a motion sensor and a photoplethysmographic (PPG) sensor. The PPG sensor includes (i) a periodic light source, (ii) a photo detector, and (iii) circuitry determining a user'"'"'s heart rate from an output of the photo detector. Some embodiments provide methods for operating a heart rate monitor of a wearable fitness monitoring device to measure one or more characteristics of a heartbeat waveform. Some embodiments provide methods for operating the wearable fitness monitoring device in a low power state when the device determines that the device is not worn by a user. Some embodiments provide methods for operating the wearable fitness monitoring device in a normal power state when the device determines that the device is worn by a user.

Claims

1. A method of operating a heart rate monitor of a wearable fitness monitoring device comprising a plurality of sensors including the heart rate monitor and a motion detecting sensor, the method comprising:

(a) detecting motion of the wearable fitness monitoring device using the motion detecting sensor;

(b) in response to detecting the motion in (a), operating the heart rate monitor in a worn detection mode configured to detect near proximity of the wearable fitness monitoring device to a user'"'"'s skin; and

(c) upon determining via the worn detection mode that the wearable fitness monitoring device is proximate to the user'"'"'s skin, operating the heart rate monitor in a first mode configured to determine one or more characteristics of the user'"'"'s heartbeat waveform, and wherein operations (b) and (c) are carried out by a processor.

2. The method of claim 1, wherein the heart rate monitor comprises an optical heart rate monitor.

3. The method of claim 2, wherein the heart rate monitory comprises a photoplethysmographic sensor.

4. The method of claim 1, wherein the one or more characteristics of the user'"'"'s heartbeat waveform comprises the user'"'"'s heart rate.

5. The method of claim 1, wherein (b) comprises operating the heart rate monitor in the worn detection mode occurs no more than about 50% of the time.

6. The method of claim 1, wherein

operating the heart rate monitor in the worn detection mode comprises pulsing a light source in the heart rate monitor at a worn detection mode frequency and detecting light from the light source at the worn detection mode frequency;

and

operating the heart rate monitor in the first mode comprises pulsing the light source in the heart rate monitor at a first mode frequency and detecting light from the light source at the first mode frequency.

7. The method of claim 6, wherein the worn detection mode frequency is greater than the first mode frequency.

8. The method of claim 1, wherein operating the heart rate monitor in the worn detection mode comprises:

emitting light pulses from a light source in the heart rate monitor having a second frequency and/or phase;

detecting light from the light source at the second frequency and/or phase; and

determining whether the light detected at the second frequency and/or phase has an intensity and/or pattern indicating that the light from the light source has interacted with the user'"'"'s skin.

9. The method of claim 8, wherein the emitting light pulses from the light source comprises emitting a succession of light pulses having variable intensity.

10. The method of claim 9, wherein a first one of the succession of light pulses has an intensity at least 5 times greater than a second one of the succession of light pulses.

11. The method of claim 9, wherein the succession of light pulses comprises a first set of pulses having an intensity providing variable response when interacting with light skin, and wherein the succession of light pulses comprises a second set of pulses having an intensity providing a variable response when interacting with dark skin.

12. The method of claim 1, wherein operating the heart rate monitor in the worn detection mode comprises:

emitting a succession of light pulses of variable intensity; and

determining whether detected light corresponding to the succession of light pulses has a variable response corresponding to the variable intensity of the light pulses.

13. The method of claim 1, wherein the motion detecting sensor comprises an accelerometer, a magnetometer, an altimeter, a GPS detector, gyroscope, or a combination of any of these.

14. The method of claim 1, further comprising:

determining from information output by the motion detecting sensor that the wearable fitness monitoring device has been still for at least a defined period; and

in response to detecting that the wearable fitness monitoring device has been still for at least the defined period, powering down the device.

15. The method of claim 1, wherein (a) is performed when the heart rate monitor is not operating or is operating in a low power mode.

16. The method of claim 15, wherein (a) comprises detecting an output from the motion detecting sensor, wherein the output exceeds a defined threshold.

17. The method of claim 15, further comprising prior to (a):

(i) operating the heart rate monitor in the first mode while also operating in a second mode configured to detect near proximity of the wearable fitness monitoring device to a user'"'"'s skin;

(ii) from information collected in the second mode, determining that the heart rate monitor is not proximate to the user'"'"'s skin; and

(iii) in response to determining that the heart rate monitor is not proximate to the user'"'"'s skin, ending operating the heart rate monitor in the first mode.

18. A wearable fitness monitoring device comprising:

a motion sensor configured to provide output corresponding to motion by a user wearing the fitness monitoring device;

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 a user'"'"'s skin, and (iii) circuitry determining a user'"'"'s heart rate from an output of the photo detector; and

control logic configured to;

(a) detect motion of the wearable fitness monitoring device using the motion detecting sensor;

(b) in response to detecting the motion in (a), operate the heart rate monitor in a worn detection mode configured to detect near proximity of the wearable fitness monitoring device to a user'"'"'s skin; and

(c) upon determining via the worn detection mode that the wearable fitness monitoring device is proximate to the user'"'"'s skin, operate the heart rate monitor in a first mode configured to determine one or more characteristics of the user'"'"'s heartbeat waveform.

19. The wearable fitness monitoring device of claim 18, wherein the one or more characteristics of the user'"'"'s heartbeat waveform comprises the user'"'"'s heart rate.

20. The wearable fitness monitoring device of claim 18, wherein operating the heart rate monitor in the worn detection mode occurs no more than about 50% of the time.

21. The wearable fitness monitoring device of claim 18, wherein

operating the heart rate monitor in the worn detection mode comprises pulsing a light source in the heart rate monitor at a worn detection mode frequency and detecting light from the light source at the worn detection mode frequency;

and

operating the heart rate monitor in the first mode comprises pulsing the light source in the heart rate monitor at a first mode frequency and detecting light from the light source at the first mode frequency.

22. The wearable fitness monitoring device of claim 21, wherein the worn detection mode frequency is greater than the first mode frequency.

23. The wearable fitness monitoring device of claim 18, wherein operating the heart rate monitor in the worn detection mode comprises:

emitting light pulses from a light source in the heart rate monitor having a second frequency and/or phase;

detecting light from the light source at the second frequency and/or phase; and

determining whether the light detected at the second frequency and/or phase has an intensity and/or pattern indicating that the light from the light source has interacted with the user'"'"'s skin.

24. The wearable fitness monitoring device of claim 23, wherein the emitting light pulses from the light source comprises emitting a succession of light pulses having variable intensity.

25. The wearable fitness monitoring device of claim 24, wherein a first one of the succession of light pulses has an intensity at least 5 times greater than a second one of the succession of light pulses.

26. The wearable fitness monitoring device of claim 24, wherein the succession of light pulses comprises a first set of pulses having an intensity providing variable response when interacting with light skin, and wherein the succession of light pulses comprises a second set of pulses having an intensity providing a variable response when interacting with dark skin.

27. The wearable fitness monitoring device of claim 18, further comprising:

determining from information output by the motion detecting sensor that the wearable fitness monitoring device has been still for at least a defined period; and

in response to detecting that the wearable fitness monitoring device has been still for at least the defined period, powering down the device.

28. The wearable fitness monitoring device of claim 18, wherein (a) is performed when the heart rate monitor is not operating or is operating in a low power mode.

29. The wearable fitness monitoring device of claim 28, wherein (a) comprises detecting an output from the motion detecting sensor, wherein the output exceeds a defined threshold.

30. The wearable fitness monitoring device of claim 28, wherein the control logic is further configured, prior to (a), to:

(i) operate the heart rate monitor in the first mode while also operating in a second mode configured to detect near proximity of the wearable fitness monitoring device to a user'"'"'s skin;

(ii) from information collected in the second mode, determine that the heart rate monitor is not proximate to the user'"'"'s skin; and

(iii) in response to determining that the heart rate monitor is not proximate to the user'"'"'s skin, end operating the heart rate monitor in the first mode.