Methods, systems and devices for measuring fingertip heart rate

• US 9,039,614 B2
• Filed: 06/11/2014
• Issued: 05/26/2015
• Est. Priority Date: 01/15/2013
• Status: Active Grant

• Current Assignee: Fitbit, Inc. (Alphabet Inc.)
• Original Assignee: Fitbit, Inc. (Alphabet Inc.)
• Inventors: Yuen, Shelten, Venkatraman, Subramaniam, Albert, Eric Van, Park, James
• Primary Examiner(s): Thomson, William
• Assistant Examiner(s): SORIANO, BOBBY GILES
• Application Number:
  US14/302,360
• Publication Number:
  US 20140296658A1
• Time in Patent Office: 349 Days
• Field of Search: None
• US Class Current: 600/301
• CPC Class Codes: A61B 2503/10 Athletes
• CPC Class Codes: A61B 5/0022 Monitoring a patient using a global network, e.g. telephone networks, internet
• CPC Class Codes: A61B 5/0075 by spectroscopy, i.e. measuring spectra, e.g. Raman spectroscopy, infrared absorption spectroscopy A61B5/0071 takes precedence
• CPC Class Codes: A61B 5/0082 adapted for particular medical purposes
• 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 5/02433 for infrared radiation
• CPC Class Codes: A61B 5/1112 Global tracking of patients, e.g. by using GPS
• CPC Class Codes: A61B 5/1118 Determining activity level
• CPC Class Codes: A61B 5/681 Wristwatch-type devices
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6843 Monitoring or controlling sensor contact pressure
• CPC Class Codes: A61B 5/6885 Monitoring or controlling sensor contact pressure
• CPC Class Codes: A61B 5/721 using a separate sensor to detect motion or using motion information derived from signals other than the physiological signal to be measured
• CPC Class Codes: A61B 5/7271 Specific aspects of physiological measurement analysis A61B5/316, A61B5/349 and A61B5/374 take precedence
• CPC Class Codes: A61B 5/742 using visual displays A61B5/339 takes precedence
• CPC Class Codes: A61B 5/743 Displaying an image simultaneously with additional graphical information, e.g. symbols, charts, function plots
• CPC Class Codes: G16H 40/67 for remote operation
• CPC Class Codes: G16Z 99/00 Subject matter not provided for in other main groups of this subclass

Abstract

A system and method of tracking activity includes a motion sensor, a light source and a light detector. The light detector is configured to capture an amount of the light that is reflected back to the light detector, at least a first portion of the light reflected back to the light detector is reflected from a blood vessel disposed under a skin of a user when the user places the skin over the heart rate monitor location on the housing. A processor is in communication with the motion sensor and the light detector and can process the reflected light to identify heart beats of the user and produce an indication of a heart rate. The indication of the heart rate can be displayed on the display screen as an option, in addition to the metrics that quantify the motion data.

Claims

1. An activity tracking device, comprising,

a housing, the housing including:

a motion sensor and a processor, the processor configured for processing motion data produced by the motion sensor;

a display screen integrated with the housing to display metrics that quantify the motion data produced by the motion sensor;

a light source integrated within the housing to enable light to be directed out of the housing at a heart rate monitor location on the housing; and

a light detector integrated within the housing, the light detector configured to capture an amount of the light that is reflected back to the light detector, at least a first portion of the light reflected back to the light detector is reflected from a blood vessel under a skin of a user when the user places the skin over the heart rate monitor location on the housing, the processor further being in communication with the light detector to enable processing of the reflected light, the processing configured to identify heart beats of the user and produce an indication of a heart rate, the indication of the heart rate being displayable on the display screen as an option, in addition to the metrics that quantify the motion data, the processor including computer executable instructions for measuring a baseline reflectance signal of the light reflected from the blood vessel between each one of a plurality of heart beats and for detecting a second reflectance signal corresponding to at least one heart beat in the blood vessel, the second reflectance signal being less than the baseline reflectance signal, where the blood vessel scatters more of the light during the at least one heart beat than between each one of the plurality of heart beats, wherein the heart rate monitor location includes a button and the button has an infrared (IR) light transmitting structure, the light source and the light detector are disposed substantially below the button.

2. The activity tracking device of claim 1, wherein the motion sensor is one of or includes an accelerometer, or a global positioning sensor, or a magnetometer, or a gyroscope, or a rotary encoder, or a calorie measurement sensor, or a moisture measurement sensor, or a displacement sensor, or an ultrasonic sensor, or a pedometer, or an altimeter, or a linear motion sensor, or an angular motion sensor, or a multi-axis motion sensor, or a combination of two or more thereof.

3. The activity tracking device of claim 1, further comprising:

a communication transceiver configured for communicating via at least one a wireless network;

an ambient light sensor; and

an indicator for visually identifying the heart rate monitor location on the housing.

4. The activity tracking device of claim 1, further comprising, at least one infrared (IR) proximity sensor associated with the light source and light detector, the IR proximity sensor configured to activate the light source and light detector upon detecting presence of the skin of the user, wherein detecting presence of the skin of the user further functions to navigate to one or more metrics of the display screen.

5. The activity tracking device of claim 1, further comprising,

a pressure detecting system configured for detecting a pressure applied to the heart rate monitor location on the housing with the skin of the user during the identification of heart beats;

and

the activity tracking device outputs at least one a feedback signal regarding the detected pressure applied to the heart rate monitor location, the feedback indication being indicative of more or less pressure desired to produce the heart rate, the feedback signal including at least one of a visual signal, a graphic signal, a tactile signal, and an audible signal.

6. The activity tracking device of claim 5, wherein the pressure detecting system includes at least one of a group consisting of:

processing of the reflected light, the processing configured to identify one of an excess pressure, an insufficient pressure or an acceptable pressure from the detected heart beats of the user;

or

a pressure sensor disposed near light source and the light detector.

7. The activity tracking device of claim 1, further comprising, the display screen including one or both of waveform data or numerical data when the skin of the user is over the heart rate monitor location and the heart beats are being identified over a sampling time period;

and

upon concluding the sampling time period, displaying the heart rate on the display screen.

8. The activity tracking device of claim 7, further comprising, at least one recalled heart rate displayed on the display screen.

9. The activity tracking device of claim 1, wherein the light detector is disposed next to the light source.

11. The activity tracking device of claim 1, further comprising, two proximity sensors at least one of the two proximity sensors including the light source and light detector.

12. The activity tracking device of claim 1, wherein the light source and the reflected light detector can be selected for any suitable wavelength or suitable band of wavelengths of light ranging from between infrared wavelengths through a human visible spectrum to ultraviolet wavelengths.

13. The activity tracking device of claim 1, wherein the light source includes at least one of:

an infrared (IR) light source, wherein the IR light emitted from the light source produces a deadfront at the heart rate monitor location of the housing;

or

a green light source and the heart rate monitor location includes a translucent green window.

14. The activity tracking device of claim 1, wherein the heart rate monitor location includes a cover that enables infrared (IR) light of the light source to pass while blocking substantially all light in a human visible spectrum.

15. The activity tracking device of claim 1, wherein the light source and light detector additionally function as a proximity sensor to activate the display screen.

16. The activity tracking device of claim 1, wherein the button further functions to navigate to one or more metrics of the display screen and, wherein the functions to navigate are enabled while the heart beats are measured.

17. The activity tracking device of claim 1, wherein the skin is of a finger of a user.

18. The activity tracking device of claim 1, wherein the button includes a pressure sensor configured for detecting a pressure applied to the button, the pressure sensor consisting of at least one of a strain gauge, a push resistance, or a force sensitive film.

19. The activity tracking device of claim 1, wherein the processing configured to identify heart beats of the user can also include processing for determining a stress level of the user corresponding to at least one of a detected heart rate or a heart rate variation as compared to previously determined heart rate.

20. The activity tracking device of claim 1, wherein the processing configured to identify heart beats of the user can also include processing for determining a number of stairs the user has ascended and/or descended and/or determining a user'"'"'s change in altitude.

21. The activity tracking device of claim 1, the processing configured to identify heart beats of the user can also include processing for determining active minutes of the user.

22. The activity tracking device of claim 1, further comprising at least one marking on the housing to identify a location of the heart rate monitor on the housing.

10. An activity tracking device, comprising:

a housing, the housing including;

a motion sensor and a processor, the processor configured for processing motion data produced by the motion sensor;

a display screen integrated with the housing to display metrics that quantify the motion data produced by the motion sensor;

a light source integrated within the housing to enable light to be directed out of the housing at a heart rate monitor location on the housing; and

a light detector integrated within the housing, the light detector configured to capture an amount of the light that is reflected back to the light detector, at least a first portion of the light reflected back to the light detector is reflected from a blood vessel under a skin of a user when the user places the skin over the heart rate monitor location on the housing, the processor further being in communication with the light detector to enable processing of the reflected light, the processing configured to identify heart beats of the user and produce an indication of a heart rate, the indication of the heart rate being displayable on the display screen as an option, in addition to the metrics that quantify the motion data, the processor including computer executable instructions for measuring a baseline reflectance signal of the light reflected from the blood vessel between each one of a plurality of heart beats and for detecting a second reflectance signal corresponding to at least one heart beat in the blood vessel, the second reflectance signal being less than the baseline reflectance signal, where the blood vessel scatters more of the light during the at least one heart beat than between each one of the plurality of heart beats, wherein the heart rate is calculated based on an algorithm that;

detects the plurality of heart beats in the light received in the light detector within a sampling time period;

measures a first time interval between a first beat of the detected plurality of heart beats and a second beat of the detected plurality of heart beats;

divides the sample time interval by the first time interval to determine a first estimate of heart beats detected within the sampling time period;

extrapolates the first estimate of heart beats within the sampling time period to a first estimated heart beats per minute;

outputs the first estimate heart beats per minute to the display screen

adds at least one beat to the first estimate of heart beats to produce a second estimate of heart beats;

subtracts at least one beat from the first estimate of beats to produce a third estimate of heart beats;

scores the first estimate of heart beats, the second estimate of heart beats and the third estimate of heart beats;

selects a highest scoring of the first estimate of heart beats, the second estimate of heart beats and the third estimate of heart beats; and

outputs the selected estimated heart beats per minute to the display screen.