METHOD AND APPARATUS FOR OFF-BODY DETECTION FOR WEARABLE DEVICE

• US 20160154952A1
• Filed: 02/01/2016
• Published: 06/02/2016
• Est. Priority Date: 02/01/2016
• Status: Active Grant

• Current Assignee: Fitbit, Inc. (Alphabet Inc.)
• Original Assignee: Fitbit, Inc. (Alphabet Inc.)
• Inventors: Venkatraman, Subramaniam, Weekly, Kevin Pu, Yuen, Shelten Gee Jao
• Granted Patent: US 10,181,021 B2
• Time in Patent Office: Days
• CPC Class Codes: G06F 21/32 using biometric data, e.g. fingerprints, iris scans or voiceprints
• CPC Class Codes: G06F 21/35 communicating wirelessly
• CPC Class Codes: G06Q 20/321 using wearable devices
• CPC Class Codes: G06Q 20/3278 RFID or NFC payments by means of M-devices
• CPC Class Codes: G06Q 20/354 Card activation or deactivation
• CPC Class Codes: G06Q 20/40145 Biometric identity checks
• CPC Class Codes: G16H 40/63 for local operation
• CPC Class Codes: G16Z 99/00 Subject matter not provided for in other main groups of this subclass
• CPC Class Codes: H04L 63/0492 by using a location-limited connection, e.g. near-field communication or limited proximity of entities
• CPC Class Codes: H04L 63/0861 using biometrical features, e.g. fingerprint, retina-scan cryptographic mechanisms or cryptographic arrangements for entity authentication using biological data H04L9/3231
• 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

Abstract

A method and apparatus for capacitive off-wrist detection for wearable device are disclosed. In one aspect, the wearable device includes one or more biometric sensors including a capacitive sensor. The method may involve measuring, based on output of the capacitive sensor, a capacitance value indicative of proximity of the wearable device to a user. The method may also involve detecting a change in the capacitance value within a defined time interval, the change being greater than or equal to a threshold change indicative of the wearable device not being proximate to the user'"'"'s skin. The method may further involve determining that the wearable device has been removed from the user in response to detecting that the change in the capacitance value within the defined time interval is greater than or equal to the threshold change.

Claims

1. A method of operating a wearable device, the wearable device comprising one or more biometric sensors including a capacitive sensor, the method comprising:

measuring, based on output of the capacitive sensor, a capacitance value indicative of proximity of the wearable device to a user;

detecting a change in the capacitance value within a defined time interval, the change being greater than or equal to a threshold change indicative of the wearable device not being proximate to the user'"'"'s skin;

determining that the wearable device has been removed from the user in response to detecting that the change in the capacitance value within the defined time interval is greater than or equal to the threshold change; and

de-authenticating the user from the wearable device in response to determining that the wearable device has been removed from the user.

2. The method of claim 1, wherein the de-authenticating of the user from the wearable device comprises de-authorizing mobile payment with the wearable device.

3. The method of claim 1, wherein the de-authenticating of the user from the wearable device comprises de-authorizing at least one of:

automated teller machine (ATM) transactions;

keyless entry into a vehicle;

keyless starting of a vehicle;

keyless entry through a door;

opening of a lock;

execution of an electronic signature;

unlocking of a computer;

automatic logging into a website;

exchange of social network information;

exchange of contact information;

disarming of a security system;

automatic upload of biometric data to an online user account associated with the user; and

altering of preferences of a thermostat.

4. The method of claim 1, wherein the wearable device further comprises an optical sensor, the method further comprising:

monitoring, based on output of the optical sensor, at least one characteristic of the user'"'"'s heartbeat waveform.

5. The method of claim 4, further comprising:

determining a first on-wrist confidence metric based on the output of the capacitive sensor;

determining a second on-wrist confidence metric based on the output of the optical sensor;

classifying one of the first on-wrist confidence metric and the second on-wrist confidence metric as a greater value confidence metric; and

selecting one of the capacitive sensor and the optical sensor associated with the greater confidence metric,

wherein the determining that the wearable device has been removed from the user is performed based on the output of the selected sensor.

6. The method of claim 4, further comprising:

determining that the at least one characteristic of the user'"'"'s heartbeat waveform is not representative of a cardiac signal,

wherein the determining that the wearable device has been removed from the user is further in response to determining that the at least one characteristic of the user'"'"'s heartbeat waveform is not representative of a cardiac signal.

7. The method of claim 6, wherein the determining that the at least one characteristic of the user'"'"'s heartbeat waveform is not representative of a cardiac signal is performed in response to determining that the change in the capacitance value within the defined time interval is greater than or equal to the threshold change.

8. The method of claim 6, wherein the determining that the change in the capacitance value within the defined time interval is greater than or equal to the threshold change is performed in response to determining that the at least one characteristic of the user'"'"'s heartbeat waveform is not representative of a cardiac signal.

9. The method of claim 4, further comprising:

determining, based on the output of the optical sensor, at least one characteristic of the user'"'"'s skin; and

calibrating, based on the determined at least one characteristic of the user'"'"'s skin, an expected amount of light to be received by the optical sensor during the operating of the optical sensor,

wherein the monitoring of the at least one characteristic of the user'"'"'s heartbeat waveform is performed in response to the calibrating.

10. The method of claim 4, wherein the optical sensor comprises a photoplethysmographic (PPG) sensor.

11. The method of claim 1, wherein the wearable device further comprises an optical sensor, the method further comprising:

detecting that an output signal of the optical sensor falls to or below an optical threshold indicative of the wearable device not being proximate to the user'"'"'s skin,

wherein the determining that the wearable device has been removed from the user is further in response to detecting that the output signal of the optical sensor has fallen to or below the optical threshold.

12. The method of claim 1, further comprising authenticating the user with the wearable device in response to receiving from the user at least one of:

a personal identification number (PIN);

a fingerprint;

biometric data;

facial recognition;

a password; and

a pattern match.

13. The method of claim 1, further comprising ending one or more operations of the wearable device in response to determining that the wearable device has been removed from the user.

14. The method of claim 13, wherein the ending of the one or more operations comprises ending operation of at least one of the one or more biometric sensors of the wearable device.

15. The method of claim 1, further comprising setting a flag associated with output received from at least one of the one or more biometric sensors in response to determining that the wearable device has been removed from the user, the flag indicating that the received output should be verified for accuracy.

16. The method of claim 1, further comprising:

tracking a moving baseline capacitance value based on the output of the capacitive sensor; and

setting an on-wrist baseline value and an off-wrist baseline value relative to the moving baseline capacitance value.

17. The method of claim 16, further comprising:

determining that the moving baseline capacitance value is closer to the off-wrist baseline value than the on-wrist baseline value,

wherein the determining that the wearable device has been removed from the user is further in response to determining that the moving baseline capacitance value is closer to the off-wrist baseline value than the on-wrist baseline value.

18. The method of claim 16, further comprising:

determining that the moving baseline capacitance value is closer to the on-wrist baseline value than the off-wrist baseline value; and

determining that the wearable device is being worn by the user in response to determining that the moving baseline capacitance value is closer to the on-wrist baseline value than the off-wrist baseline value.

19. The method of claim 16, further comprising:

determining that the moving baseline capacitance value has deviated from the on-wrist baseline value by more than a defined percentage; and

wherein the determining that the wearable device has been removed from the user is further in response to determining that the moving baseline capacitance value has deviated from the on-wrist baseline value by more than the defined percentage.

20. The method of claim 16, further comprising:

determining that the moving baseline capacitance value has deviated from the off-wrist baseline value by more than a defined percentage; and

determining that the wearable device is being worn by the user in response to determining that the moving baseline capacitance value has deviated from the off-wrist baseline value by more than a defined percentage.

21. The method of claim 1, wherein the determining that the wearable device has been removed from the user is further in response to output received from at least one of:

a skin temperature thermometer;

a galvanic skin response sensor;

an electromyographic sensor; and

an accelerometer.

22. The method of claim 1, wherein the change in the capacitance value comprises a change in a magnitude of the capacitance value within the defined time interval.

23. The method of claim 1, wherein:

the capacitive sensor comprises a capacitive sensor electrode;

the wearable device further comprises (i) a ground plane that shields the capacitive sensor electrode from other circuitry of the wearable device and (ii) an active shield interposed between the capacitive sensor electrode and the ground plane; and

the method further comprises driving the active shield and the capacitive sensor electrode at the same potential.

24. A method of operating a wearable device, the wearable device comprising one or more biometric sensors including an optical sensor and a capacitive sensor, the method comprising:

detecting that an output signal of the optical sensor falls to or below an optical threshold indicative of the wearable device not being proximate to the user'"'"'s skin;

measuring, based on output of the capacitive sensor, a capacitance value indicative of proximity of the wearable device to the user;

detecting that a change in the capacitance value within a defined time interval is greater than or equal to a threshold change indicative of the wearable device not being proximate to the user'"'"'s skin;

determining that the wearable device has been removed from the user in response to at least one of (i) detecting that the output signal of the optical sensor has fallen to or below the optical threshold and (ii) detecting that the change in the capacitance value within the defined time interval is greater than or equal to the threshold change; and

de-authenticating the user from the wearable device in response to determining that the wearable device has been removed from the user.

25. The method of claim 24, further comprising:

determining a first on-wrist confidence metric based on the output of the capacitive sensor;

determining a second on-wrist confidence metric based on the output of the optical sensor;

classifying one of the first on-wrist confidence metric and the second on-wrist confidence metric as a greater value confidence metric; and

selecting one of the capacitive sensor and the optical sensor associated with the greater confidence metric,

wherein the determining that the wearable device has been removed from the user is performed based on the output of the selected sensor.

26. The method of claim 24, wherein the de-authenticating of the user from the wearable device comprises de-authorizing mobile payment with the wearable device.

27. A wearable device, comprising:

a capacitive sensor configured to measure a capacitance value indicative of proximity of the wearable device to a user;

at least one processor; and

a memory storing computer-executable instructions for controlling the at least one processor to;

detect that a change in the capacitance value within a defined time interval is greater than or equal to a threshold change indicative of the wearable device not being proximate to the user'"'"'s skin;

determine that the wearable device has been removed from the user in response to detecting that the change in the capacitance value within the defined time interval is greater than or equal to the threshold change; and

de-authenticate the user from the wearable device in response to determining that the wearable device has been removed from the user.

28. The device of claim 27, further comprising an optical sensor configured to monitor at least one characteristic of the user'"'"'s heartbeat waveform, wherein the memory further comprises computer-executable instructions for controlling the at least one processor to:

determine that the at least one characteristic of the user'"'"'s heartbeat waveform is not representative of a cardiac signal,

wherein the determining that the wearable device has been removed from the user is further in response to determining that the at least one characteristic of the user'"'"'s heartbeat waveform is not representative of a cardiac signal.

29. The device of claim 27, wherein the memory further comprises computer-executable instructions for controlling the at least one processor to perform the de-authenticating of the user from the wearable device via de-authorizing mobile payment with the wearable device.

30. A wearable device, comprising:

an optical sensor;

a capacitive sensor configured to measure a capacitance value indicative of proximity of the wearable device to a user;

at least one processor; and

a memory storing computer-executable instructions for controlling the at least one processor to;

detect that an output signal of the optical sensor falls to or below an optical threshold indicative of the wearable device not being proximate to the user'"'"'s skin;

detect that a change in the capacitance value within a defined time interval is greater than or equal to a threshold change indicative of the wearable device not being proximate to the user'"'"'s skin;

determine that the wearable device has been removed from the user in response to at least one of (i) detecting that the output signal of the optical sensor has fallen to or below the optical threshold and (ii) detecting that the change in the capacitance value within the defined time interval is greater than or equal to the threshold change; and

de-authenticate the user from the wearable device in response to determining that the wearable device has been removed from the user.