SYSTEM AND METHOD FOR GENERATING A PPG SIGNAL

• US 20170105638A1
• Filed: 10/18/2016
• Published: 04/20/2017
• Est. Priority Date: 10/19/2015
• Status: Active Grant

• Current Assignee: Garmin Switzerland GmbH (Garmin Limited)
• Original Assignee: Garmin Switzerland GmbH (Garmin Limited)
• Inventors: Kulach, Christopher J.
• Granted Patent: US 9,717,424 B2
• Time in Patent Office: Days
• CPC Class Codes: A61B 2562/0219 Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches
• CPC Class Codes: A61B 5/02405 Determining heart rate variability
• 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 5/02438 with portable devices, e.g. worn by the patient
• CPC Class Codes: A61B 5/0833 Measuring rate of oxygen consumption
• 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 5/165 Evaluating the state of mind, e.g. depression, anxiety
• CPC Class Codes: A61B 5/4815 Sleep quality
• CPC Class Codes: A61B 5/486 Bio-feedback A61B5/375 takes precedence
• CPC Class Codes: A61B 5/681 Wristwatch-type devices
• 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 5/725 using specific filters therefor, e.g. Kalman or adaptive filters A61B5/316 take precedence
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence
• CPC Class Codes: A61B 5/7285 for synchronising or triggering a physiological measurement or image acquisition with a physiological event or waveform, e.g. an ECG signal A61B6/5205, A61B6/541, A61B8/5207, A61B8/543 take precedence

Abstract

Characterization of a fitness monitor based on its operation enables a processor to account for variations in device operating modes and biometric characteristics of the user. The fitness monitor includes an emitter (e.g., LED) for transmitting light toward skin of the user, a receiver (e.g., photodiode) for receiving a reflection of the transmitted light, a photometric front end for generating a photoplethysmogram (PPG) signal based on the received reflection, and a processor configured to select an intensity level for the emitter based on a comparison of a determined component of the PPG signal and a reference value. The reference value, which may characterize the fitness monitor based on a determined variability or range of the PPG signal, may be utilized by the processor to improve or maintain the signal quality of the PPG signal to enable determination of a cardiac component and/or reduction of power consumption by the fitness device.

Claims

1. A fitness monitor for monitoring a cardiac signal of a user, the device comprising:

an emitter configured to output light toward skin of the user;

an emitter driver configured to cause the emitter to output light at one of a plurality of intensity levels;

a receiver configured to receive a reflection of the transmitted light and generate a light intensity signal based on the received reflection;

a photometric front end configured to receive the light intensity signal and generate a photoplethysmogram (PPG) signal based on the light intensity signal, the PPG signal including a cardiac signal;

a memory device configured to store a reference value based on the variability of the PPG signal output from the photometric front end during idle operation; and

a processor communicatively coupled to the emitter, the receiver, photometric front end and the memory device, the processor configured to;

select a first intensity level for the emitter to output light,

transmit a first output control signal including the selected first intensity level to the emitter driver causing the emitter to output light at the selected first intensity level,

determine a DC component of the PPG signal,

select a second intensity level based on a comparison of the determined DC component of the PPG signal with the stored reference value,

transmit a second output control signal including the selected second intensity level to the emitter driver causing the emitter to output light at the selected second intensity level, and

identify the cardiac component in the PPG signal.

2. The fitness monitor of claim 1, wherein the emitter driver is integrated within the photometric front end.

3. The fitness monitor of claim 1, wherein the photometric front end is integrated within the processor.

4. The fitness monitor of claim 1, wherein the emitter is a LED and the receiver is a photodiode.

5. The fitness monitor of claim 1, wherein the processor is further configured to transmit a receiver control signal to the receiver causing the receiver to generate the light intensity signal.

6. The fitness monitor of claim 1, wherein the processor is further configured to transmit a receive timing signal to the photometric front end causing the photometric front end to receive the light intensity signal from the receiver.

7. The fitness monitor of claim 6, wherein the processor is further configured to cause the photometric front end to receive the light intensity signal in a first time period and a second time period based on the receive timing signal.

8. The fitness monitor of claim 1, wherein the first output control signal causes the emitter to output light in the first time period and the second output control signal causes the emitter to output light in the second time period.

9. The fitness monitor of claim 1, wherein the variability of the PPG signal output from the photometric front end during idle operation is determined when the receiver does not receive a reflection of the transmitted light.

10. The fitness monitor of claim 1, wherein the variability of the PPG signal output from the photometric front end during idle operation is a measurement uncertainty of the PPG signal.

11. The fitness monitor of claim 1, wherein the reference value is determined when the fitness monitor is not proximate to the skin of the user.

12. The fitness monitor of claim 1, further comprising an inertial sensor configured to provide a motion signal based on sensed movement of the fitness monitor, wherein the processor is further configured to transmit the second output control signal when the motion signal is below a predetermined motion level.

13. A fitness monitor for monitoring a cardiac signal of a user, the device comprising:

an emitter configured to output light toward skin of the user;

an emitter driver configured to cause the emitter to output light at one of a plurality of intensity levels;

a receiver configured to receive a reflection of the transmitted light and generate a light intensity signal based on the received reflection;

a photometric front end configured to receive the light intensity signal and generate a photoplethysmogram (PPG) signal based on the light intensity signal, the PPG signal including a cardiac signal;

a reference value based on the variability of the PPG signal output from the photometric front end when the fitness monitor is not proximate to the skin of the user;

a memory device configured to store the reference value; and

a processor communicatively coupled to the emitter, the receiver, photometric front end and the memory device, the processor configured to;

select a first intensity level for the emitter to output light,

transmit a first output control signal including the selected first intensity level to the emitter driver causing the emitter to output light at the selected first intensity level,

determine a DC component of the PPG signal,

select a second intensity level based on a comparison of the determined DC component of the PPG signal with the stored reference value,

transmit a second output control signal including the selected second intensity level to the emitter driver causing the emitter to output light at the selected second intensity level, and

identify the cardiac component in the PPG signal.

14. The fitness monitor of claim 13, wherein the emitter driver is integrated within the photometric front end.

15. The fitness monitor of claim 13, wherein the photometric front end is integrated within the processor.

16. The fitness monitor of claim 13, wherein the emitter is a LED and the receiver is a photodiode.

17. The fitness monitor of claim 13, wherein the processor is further configured to transmit a receiver control signal to the receiver causing the receiver to generate the light intensity signal.

18. The fitness monitor of claim 13, wherein the processor is further configured to transmit a receive timing signal to the photometric front end causing the photometric front end to receive the light intensity signal from the receiver.

19. The fitness monitor of claim 18, wherein the processor is further configured to cause the photometric front end to receive the light intensity signal in a first time period and a second time period based on the receive timing signal.

20. A fitness monitor for monitoring a cardiac signal of a user comprising an emitter configured to output light toward skin of the user, an emitter driver configured to cause the emitter to output light at one of a plurality of intensity levels, a receiver configured to receive a reflection of the transmitted light and generate a light intensity signal based on the received reflection, a photometric front end configured to receive the light intensity signal and generate a photoplethysmogram (PPG) signal based on the light intensity signal and representing the cardiac signal, and a tangible non-transitory computer-readable medium storing instructions and a reference value based on the variability of the PPG signal output from the photometric front end during idle operation, wherein the instructions, when executed by one or more processors, cause the fitness monitor to:

select a first intensity level for the emitter to output light,

transmit a first output control signal including the selected first intensity level to the emitter driver causing the emitter to output light at the selected first intensity level,

determine a DC component of the PPG signal,

select a second intensity level based on a comparison of the determined DC component of the PPG signal with the stored reference value,

transmit a second output control signal including the selected second intensity level to the emitter driver causing the emitter to output light at the selected second intensity level, and

identify the cardiac component in the PPG signal.