Heart rate detection module, and detection and denoising method thereof

• US 9,974,487 B2
• Filed: 06/05/2015
• Issued: 05/22/2018
• 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
• Primary Examiner(s): NGUYEN, HIEN NGOC
• Application Number:
  US14/731,711
• Publication Number:
  US 20160089086A1
• Time in Patent Office: 1,082 Days
• 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;

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

a processing unit comprising a conversion module, a peak value extraction module and a calculation module,

the conversion module configured to respectively convert the PPG signal and the acceleration signal to

first frequency domain information, which comprises a first frequency index set and a first spectrum value set associated with the first frequency index set, and

second frequency domain information, which comprises a second frequency index set and a second spectrum value set associated with the second frequency index set,

the peak value extraction module configured to identify a plurality of frequency indexes corresponding to a plurality of spectrum peak values in the first frequency domain information and the second frequency domain information,

the calculation module configured to determine a reference index as a denoising parameter according to a frequency index corresponding to a maximum spectrum peak value of the second frequency domain information to denoise the first frequency domain information, wherein, to denoise the first frequency domain information, the calculation module is configured to remove spectrum values, which correspond to frequency indexes of the denoising parameter, from the first frequency domain information, and

the calculation module further configured to determine a heart rate index according to a denoised maximum spectrum peak value of the denoised first frequency domain information, and calculate a heart rate according to the heart rate index.

2. The heart rate detection module as claimed in claim 1, wherein the

conversion module is configured to

convert the PPG signal to a frequency domain PPG signal,

generate the first frequency domain information according to the frequency domain PPG signal,

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

generate the second frequency domain information according to the frequency domain acceleration signal.

3. The heart rate detection module as claimed in claim 1, 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 1, wherein the

calculation module is further configured to 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 1, 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.

6. 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.

11. The heart rate detection module as claimed in claim 1, wherein a passband of the band pass filter is from 0.45 Hz to 4.5 Hz.

7. A heart rate detection method of a heart rate detection module, the heart rate detection module comprising a PPG measuring device, a motion sensor, a band pass filter 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;

filtering, by the band pass filter, the PPG signal and the acceleration signal;

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

respectively converting, by the processing unit, the PPG signal and the acceleration signal to

first frequency domain information, which comprises a first frequency index set and a first spectrum value set associated with the first frequency index set, and

second frequency domain information, which comprises a second frequency index set and a second spectrum value set associated with the second frequency index set;

identifying, by the processing unit, a plurality of frequency indexes corresponding to a plurality of spectrum peak values in the first frequency domain information and the second frequency domain information;

determining, by the processing unit, a reference index as a denoising parameter according to a frequency index corresponding to a maximum spectrum peak value of the second frequency domain information to denoise the first frequency domain information, wherein denoising the first frequency domain information comprises removing spectrum values, which correspond to frequency indexes of the denoising parameter, from the first frequency domain information; and

determining, by the processing unit, a heart rate index according to a denoised maximum spectrum peak value of the denoised first frequency domain information, and calculating a heart rate according to the heart rate index.

8. The heart rate detection method as claimed in claim 7, wherein the respectively converting comprises:

converting, by the processing unit, the PPG signal to a frequency domain PPG signal and generating the first frequency domain information according to the frequency domain PPG signal; and

converting, by the processing unit, the acceleration signal to a frequency domain acceleration signal and generating the second frequency domain information according to the frequency domain acceleration signal.

9. The heart rate detection method as claimed in claim 7, further comprising:

calculating, by the processing unit, multiples of the reference index; and

taking, by the processing unit, the reference index and at least one of the multiples of the reference index as the denoising parameter.

10. The heart rate detection method as claimed in claim 7, wherein the calculating further comprises:

calculating, by the processing unit, the heart rate according to the heart rate index and frequency indexes adjacent to the heart rate index.

12. The heart rate detection method as claimed in claim 8, wherein the frequency domain PPG signal and the frequency domain acceleration signal are converted by Fast Fourier Transform or Discrete Fourier Transform.

13. The heart rate detection method as claimed in claim 7, wherein a passband of the band pass filter is from 0.45 Hz to 4.5 Hz.