Pulse wave detecting apparatus and fourier transform process apparatus

• US 20040086060A1
• Filed: 09/10/2003
• Published: 05/06/2004
• Est. Priority Date: 10/04/2002
• Status: Active Grant

• Current Assignee: Seiko Instruments Incorporated (Seiko Group)
• Original Assignee: Seiko Instruments Incorporated (Seiko Group)
• Inventors: Tsubata, Keisuke
• Granted Patent: US 7,195,596 B2
• Time in Patent Office: Days
• US Class Current: 375/316
• CPC Class Codes: A61B 5/024 Detecting, measuring or recording pulse rate or heart rate A61B5/0205, A61B5/021 take precedence
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• 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 5/7257 using Fourier transforms
• CPC Class Codes: A61B 8/02 Measuring pulse or heart rate
• CPC Class Codes: A61B 8/5276 due to motion

Abstract

A pulse wave detecting apparatus is provided which is capable of measuring a pulse rate more accurately even with a calculation unit having low calculating capability. An A-D conversion circuit samples a pulse wave detected by a pulse wave sensor at 16 Hz to perform A-D conversion of the same and sequentially outputs resultant signals-to a modified moving average process circuit. The modified moving average process circuit sequentially averages every two of the signals from the A-D conversion circuit without duplication and outputs signals at 8 Hz, and an FFT circuit performs Fourier transform on signals obtained through the averaging. Another A-D conversion circuit samples kinetic noises detected by an acceleration sensor at 8 Hz to perform A-D conversion of the same and sequentially outputs resultant signals to another FFT circuit, and the FFT circuit performs Fourier transform on the input signals. A pulse rate calculation circuit obtains differences between the signals output by the FFT circuits to calculate a pulse rate. The pulse rate is displayed by a display section.

Claims

1. A Fourier transform processing apparatus, comprising:

a sampling process unit for sampling input signals at a first frequency and sequentially outputting resultant signals;

an averaging process unit for sequentially averaging every predetermined number of signals from the sampling process unit and sequentially outputting resultant signals at a second frequency; and

a Fourier transform process unit for performing a Fourier transform process on the signals from the averaging process unit.

2. A Fourier transform process apparatus according to claim 1, wherein the first frequency is n times (n is an integer equal to or greater than 2) the second frequency and wherein the averaging process unit averages every n signals from the sampling process unit in the order of input and sequentially outputs signals obtained through the averaging.

3. A Fourier transform process apparatus according to claim 1, wherein the second frequency is 2^m Hz (m is a positive integer).

4. A pulse wave detecting apparatus comprising:

a signal detecting unit for detecting a pulse wave and outputting pulse signals associated therewith;

a signal sampling process unit for sampling the pulse signals from the signal detecting unit at a first frequency and sequentially outputting resultant signals;

an averaging process unit for sequentially averaging every predetermined number of signals from the signal sampling process unit and sequentially outputting resultant signals at a second frequency;

a signal Fourier transform process unit for performing a Fourier transform process on the signals from the averaging process unit; and

a pulse rate calculation process unit for calculating a pulse rate based on the result of the process at the signal Fourier transform process unit.

5. A pulse wave detecting apparatus according to claim 4, further comprising;

a noise detecting unit for detecting kinetic noises and outputting noise signals associated therewith;

a noise sampling process unit for sampling the noise signals from the noise detecting unit at the second frequency and sequentially outputting resultant signals; and

a noise Fourier transform process unit for performing a Fourier transform process on the signals from the noise sampling process unit, wherein the pulse rate calculation process unit calculates a pulse rate based on signals output by the signal Fourier transform process unit and the noise Fourier transform process unit.

6. A pulse wave detecting apparatus according to claim 4, wherein the first frequency is n times (n is an integer equal to or greater than 2) the second frequency and wherein the averaging process unit averages every n signals from the signal sampling process unit in the order of input and sequentially outputs signals obtained through the averaging.

7. A pulse wave detecting apparatus according to claim 4, wherein the second frequency is 2^m Hz (m is a positive integer).