HEART RATE DETECTION MODULE, AND DETECTION AND DENOISING METHOD THEREOF

• US 20160089086A1
• Filed: 06/05/2015
• Published: 03/31/2016
• Est. Priority Date: 09/26/2014
• Status: Active Grant

• Current Assignee: PixArt Imaging Incorporated
• Original Assignee: PixArt Imaging Incorporated
• Inventors: LIN, Chih-Hsin, GU, Ren-Hau
• Granted Patent: US 9,974,487 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/02438 with portable devices, e.g. worn by the patient
• 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 5/7257 using Fourier transforms

Abstract

A heart rate detection module including a PPG measuring device, a motion sensor and a processing unit is provided. The PPG measuring device is configured to detect a skin surface in a detection period to output a PPG signal. The motion sensor is configured to output an acceleration signal corresponding to the detection period. The processing unit is configured to respectively convert the PPG signal and the acceleration signal to first frequency domain information and second frequency domain information, determine a denoising parameter according to a maximum spectrum peak value of the second frequency domain information to denoise the first frequency domain information, and calculate a heart rate according to a maximum spectrum peak value of the denoised first frequency domain information.

Claims

1. A heart rate detection module comprising:

a PPG measuring device configured to detect a skin surface in a detection period to output a PPG signal;

a motion sensor configured to output an acceleration signal corresponding to the detection period; and

a processing unit configured to

respectively convert the PPG signal and the acceleration signal to first frequency domain information and second frequency domain information,

determine a denoising parameter according to a maximum spectrum peak value of the second frequency domain information to denoise the first frequency domain information, and

calculate a heart rate according to a maximum spectrum peak value of the denoised first frequency domain information.

2. The heart rate detection module as claimed in claim 1, wherein the processing unit comprises:

a conversion module configured to

convert the PPG signal to a frequency domain PPG signal,

generate a first frequency index set and a first spectrum value set associated therewith configured as the first frequency domain information,

convert the acceleration signal to a frequency domain acceleration signal, and

generate a second frequency index set and a second spectrum value set associated therewith configured as the second frequency domain information; and

a peak value extraction module configured to

identify a plurality of spectrum peak values in the first frequency domain information and the second frequency domain information, and

output frequency indexes corresponding to the plurality of spectrum peak values.

3. The heart rate detection module as claimed in claim 2, wherein the first frequency index set and the second frequency index set have an identical number of frequency indexes.

4. The heart rate detection module as claimed in claim 2, wherein the processing unit further comprises:

a calculation module configured to determine, according to a frequency index corresponding to the maximum spectrum peak value of the second frequency domain information, a reference index configured as the denoising parameter, and calculate a half of the reference index and a double of the reference index,

wherein the denoising parameter further comprises at least one of the half of the reference index and the double of the reference index.

5. The heart rate detection module as claimed in claim 4, wherein, to denoise the first frequency domain information, the calculation module is further configured to remove spectrum values in the first frequency domain information corresponding to frequency indexes of the denoising parameter.

6. The heart rate detection module as claimed in claim 4, wherein the processing unit further comprises:

a heart rate monitoring module configured to record a variation tendency of heart rates corresponding to a plurality of the detection periods,

wherein the calculation module is further configured to estimate a heart rate according to the variation tendency.

7. The heart rate detection module as claimed in claim 1, further comprising:

a band pass filter configured to filter the PPG signal and the acceleration signal.

8. The heart rate detection module as claimed in claim 1, wherein the heart rate detection module is integrated with a wearable device or a mobile device.

9. A heart rate detection method adapted to a heart rate detection module, the heart rate detection module comprising a PPG measuring device, a motion sensor and a processing unit, the heart rate detection method comprising:

detecting, by the PPG measuring device, a skin surface in a detection period to output a PPG signal;

outputting, by the motion sensor, an acceleration signal corresponding to the detection period;

receiving, by the processing unit, the PPG signal and the acceleration signal;

respectively converting the PPG signal and the acceleration signal to first frequency domain information and second frequency domain information;

determining a denoising parameter according to a maximum spectrum peak value of the second frequency domain information to denoise the first frequency domain information; and

calculating a heart rate according to a maximum spectrum peak value of the denoised first frequency domain information.

10. The heart rate detection method as claimed in claim 9, wherein the step of respectively converting the PPG signal and the acceleration signal to first frequency domain information and second frequency domain information further comprises:

converting the PPG signal to a frequency domain PPG signal and generating a first frequency index set and a first spectrum value set associated therewith configured as the first frequency domain information; and

converting the acceleration signal to a frequency domain acceleration signal and generating a second frequency index set and a second spectrum value set associated therewith configured as the second frequency domain information.

11. The heart rate detection method as claimed in claim 10, further comprising:

determining a reference index according to a frequency index corresponding to the maximum spectrum peak value of the second frequency domain information; and

taking the reference index and at least one of multiples of the reference index as the denoising parameter.

12. The heart rate detection method as claimed in claim 11, wherein the step of calculating a heart rate according to a maximum spectrum peak value of the denoised first frequency domain information further comprises:

determining a heart rate index according to the maximum spectrum peak value of the denoised first frequency domain information; and

calculating the heart rate according to the heart rate index.

13. The heart rate detection method as claimed in claim 11, wherein the step of calculating a heart rate according to a maximum spectrum peak value of the denoised first frequency domain information further comprises:

determining a heart rate index according to the maximum spectrum peak value of the denoised first frequency domain information; and

calculating the heart rate according to the heart rate index and frequency indexes adjacent to the heart rate index.

14. The heart rate detection method as claimed in claim 11, wherein to denoise the first frequency domain information is referred to remove spectrum values in the first frequency domain information corresponding to frequency indexes of the denoising parameter.

15. The heart rate detection method as claimed in claim 9, further comprising:

filtering, by a band pass filter, the PPG signal and the acceleration signal.

16. A denoising method of a heart rate detection module comprising:

receiving a PPG signal and an acceleration signal in a detection period;

converting the PPG signal to a frequency domain PPG signal and generating first frequency domain information comprising a first frequency index set and a first spectrum value set associated therewith;

converting the acceleration signal to a frequency domain acceleration signal and generating second frequency domain information comprising a second frequency index set and a second spectrum value set associated therewith;

identifying three frequency indexes corresponding to top three spectrum peak values in the first frequency domain information and a reference index corresponding to a maximum spectrum peak value in the second frequency domain information; and

denoising the first spectrum value set according to the three frequency indexes and the reference index.

17. The denoising method as claimed in claim 16, further comprising:

calculating a half of the reference index and a double of the reference index; and

determining a denoising range according to the reference index, the half of the reference index and the double of the reference index.

18. The denoising method as claimed in claim 17, further comprising:

determining a heart rate index and two residual indexes among the three frequency indexes according to the denoising range.

19. The denoising method as claimed in claim 18, further comprising:

estimating a heart rate according to a variation tendency of heart rate indexes of a plurality of detection periods when a difference value between the heart rate index and one of the residual indexes is smaller than a threshold.

20. The denoising method as claimed in claim 18, further comprising:

calculating a heart rate according to the heart rate index.