Multi-channel photoplethysmography sensor

• US 10,433,739 B2
• Filed: 04/28/2017
• Issued: 10/08/2019
• Est. Priority Date: 04/29/2016
• Status: Active Grant

• Current Assignee: Fitbit, Inc. (Alphabet Inc.)
• Original Assignee: Fitbit, Inc. (Alphabet Inc.)
• Inventors: Weekly, Kevin Pu, Venkatraman, Subramaniam, Axley, Andrew Larsen, Freschl, Daniel J., Richards, Peter W., Sarantos, Chris H.
• Primary Examiner(s): Cox, Thaddeus B
• Application Number:
  US15/582,240
• Publication Number:
  US 20170311825A1
• Time in Patent Office: 893 Days
• 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 5/681 Wristwatch-type devices
• CPC Class Codes: A61B 5/6814 Head
• CPC Class Codes: A61B 5/6815 Ear
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence

Abstract

In one embodiment, a data processing method comprises obtaining one or more first photoplethysmography (PPG) signals based on one or more first light sources that are configured to emit light having a first light wavelength corresponding to a green light wavelength; obtaining one or more second PPG signals based on one or more second light sources that are configured to emit light having a second light wavelength corresponding to a red light wavelength, one or more of the first light sources and one or more of the second light sources being co-located; generating an estimated heart rate value based on one or more of the first PPG signals and the second PPG signals; and causing the estimated heart rate value to be displayed via a user interface on a client device.

Claims

1. An activity monitoring apparatus comprising:

one or more first light sources that are configured to emit light having a first light wavelength corresponding to a green light wavelength;

one or more second light sources that are configured to emit light having a second light wavelength corresponding to a red light wavelength, wherein one or more of the one or more first light sources and one or more of the one or more second light sources are co-located;

one or more processors;

a non-transitory computer-readable storage medium coupled to the one or more processors and storing one or more sequences of instructions which, when executed using the one or more processors, cause the one or more processors to;

obtain one or more first photoplethysmography (PPG) signals based on light emitted from the one or more first light sources;

obtain one or more second PPG signals based on light emitted from the one or more second light sources;

determine a first quality metric based on the one or more first PPG signals;

determine a second quality metric based on the one or more second PPG signals;

compare the first quality metric to the second quality metric and select either the first quality metric or the second quality metric as a greater quality metric; and

generate an estimated heart rate value based on the one or more first PPG signals or the one or more second PPG signals that corresponds to the greater quality metric; and

cause the estimated heart rate value to be displayed via a user interface on a client device.

2. The activity monitoring apparatus of claim 1, further comprising:

a first detector; and

a second detector, wherein;

the first detector and the second detector are located at different locations having different light paths with respect to at least one of the one or more first light sources and with respect to at least one of the one or more second light sources, and

the non-transitory computer-readable storage medium further stores one or more sequences of instructions which, when executed using the one or more processors, further cause the one or more processors to;

obtain at least one PPG signal selected from the group consisting of;

the one or more first PPG signals and the one or more second PPG signals using the first detector; and

obtain at least one PPG signal selected from the group consisting of;

the one or more first PPG signals and the one or more second PPG signals using the second detector.

3. The activity monitoring apparatus of claim 1, wherein at least one of the one or more first light sources and at least one of the one or more second light sources comprise discrete light-emitting diode (LED) emitters.

4. The activity monitoring apparatus of claim 1, wherein one or more of the one or more first light sources and one or more of the one or more second light sources collectively comprise a single multi-color light-emitting diode (LED).

5. The activity monitoring apparatus of claim 4, wherein the single multi-color LED is a red-green-infrared LED.

6. The activity monitoring apparatus of claim 1, wherein:

the activity monitoring apparatus is configured to align the one or more first light sources adjacent to blood vessels of a human when worn on a body location of the human selected from the group consisting of;

a wrist, an ear, and the head, and

the non-transitory computer-readable storage medium further stores one or more additional sequences of instructions which, when executed using the one or more processors, further cause the one or more processors to obtain the first PPG signals based on light from the one or more first light sources when the activity monitoring apparatus is worn on the body location.

7. The activity monitoring apparatus of claim 1, further comprising a first detector having a first side and a second side opposite the first side, wherein:

the one or more first light sources include a first green light source and a second green light source,

the one or more second light sources include a first red light source and a second red light source,

the first green light source and the first red light source are at the first side of the first detector,

the second green light source and the second red light source are at the second side of the first detector, and

the non-transitory computer-readable storage medium further stores one or more additional sequences of instructions which, when executed using the one or more processors, further cause the one or more processors to;

obtain the one or more first PPG signals based on emission of green light from the first green light source and the second green light source; and

obtain the one or more second PPG signals based on emission of red light from the first red light source and the second red light source.

8. The activity monitoring apparatus of claim 7, wherein at least the first green light source and the first red light source are co-located so as to emit light on a common light path toward the first detector.

9. The activity monitoring apparatus of claim 7, wherein both the first green light source and the first red light source are in a common light source package.

10. The activity monitoring apparatus of claim 7, wherein a diffusion layer is positioned over at least the first green light source and the first red light source.

11. The activity monitoring apparatus of claim 7, wherein the first detector is one of a plurality of discrete detectors that are configured to detect light emitted from the first green light source, the second green light source, the first red light source, and the second red light source.

12. The activity monitoring apparatus of claim 1, wherein the non-transitory computer-readable storage medium further stores one or more additional sequences of instructions which, when executed using the one or more processors, further cause the one or more processors to:

selectively activate at least one of the one or more first light sources and at least one of the one or more second light sources at different times.

13. The activity monitoring apparatus of claim 1, wherein the non-transitory computer-readable storage medium further stores one or more additional sequences of instructions which, when executed using the one or more processors, further cause the one or more processors to:

determine the first quality metric by determining a first confidence value associated with the one or more first PPG signals, the first confidence value indicating a quality of a first preliminary estimated heart rate value generated based on the one or more first PPG signals, and

determine the second quality metric by determining a second confidence value associated with the one or more second PPG signals, the second confidence value indicating a quality of a second preliminary estimated heart rate value generated based on the one or more second PPG signals.

14. The activity monitoring apparatus of claim 13, further comprising a motion sensor that is proximate to the one or more first light sources and the one or more second light sources, wherein the non-transitory computer-readable storage medium further stores one or more additional sequences of instructions which, when executed using the one or more processors, further cause the one or more processors to:

determine that motion data from the motion sensor indicates that a user of the activity monitoring apparatus is performing exercise; and

select, responsive to determining that the motion data indicates that the user of the activity monitoring apparatus is performing the exercise, a higher heart rate value from among the first preliminary estimated heart rate value and the second preliminary estimated heart rate value for use in generating the heart rate value.

15. The activity monitoring apparatus of claim 1, wherein the non-transitory computer-readable storage medium further stores one or more additional sequences of instructions which, when executed using the one or more processors, further cause the one or more processors to:

obtain one or more third PPG signals based on light emitted from one or more third light sources that are configured to emit light having a third light wavelength, wherein the third light wavelength is an infrared wavelength; and

modify the estimated heart rate value based on data obtained from the one or more third PPG signals.

16. An activity monitoring apparatus comprising:

one or more first light sources that are configured to emit light having a first light wavelength corresponding to a green light wavelength;

one or more second light sources that are configured to emit light having a second light wavelength corresponding to a red light wavelength, wherein one or more of the one or more first light sources and one or more of the one or more second light sources are co-located;

one or more processors;

a non-transitory computer-readable storage medium coupled to the one or more processors and storing one or more sequences of instructions which, when executed using the one or more processors, cause the one or more processors to;

obtain one or more first photoplethysmography (PPG) signals based on light emitted from the one or more first light sources;

obtain one or more second PPG signals based on light emitted from the one or more second light sources;

determine that a majority of the one or more second PPG signals are comprised of cardiac signals;

generate, responsive to determining that the majority of the one or more second PPG signals are comprised of cardiac signals, an estimated heart rate value based on only the one or more first PPG signals; and

cause the estimated heart rate value to be displayed via a user interface on a client device.

17. An activity monitoring apparatus comprising:

one or more first light sources that are configured to emit light having a first light wavelength corresponding to a green light wavelength;

one or more second light sources that are configured to emit light having a second light wavelength corresponding to a red light wavelength, wherein one or more of the one or more first light sources and one or more of the one or more second light sources are co-located;

one or more processors;

a non-transitory computer-readable storage medium coupled to the one or more processors and storing one or more sequences of instructions which, when executed using the one or more processors, cause the one or more processors to;

obtain one or more first photoplethysmography (PPG) signals based on light emitted from the one or more first light sources;

obtain one or more second PPG signals based on light emitted from the one or more second light sources;

determine that a majority of the second PPG signals are comprised of motion signals;

remove, responsive to determining that the majority of the one or more second PPG signals are comprised of motion signals, corresponding motion signals from the one or more first PPG signals;

generate an estimated heart rate value based on only the first PPG signals after the corresponding motion signals have been removed from the one or more first PPG signals; and

cause the estimated heart rate value to be displayed via a user interface on a client device.

18. The activity monitoring apparatus of claim 17, wherein the non-transitory computer-readable storage medium further stores one or more additional sequences of instructions which, when executed using the one or more processors, further cause the one or more processors to remove the corresponding motion signals from the one or more first PPG signals by:

transforming the second PPG signals based on an optical linear transform, and

subtracting the transformed second PPG signals from the first PPG signals.