PULSE DETECTOR

• US 20120215115A1
• Filed: 02/09/2012
• Published: 08/23/2012
• Est. Priority Date: 02/23/2011
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: TAKAHASHI, Yusuke
• Granted Patent: US 9,402,551 B2
• Time in Patent Office: Days
• US Class Current: 600/483
• 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 5/1118 Determining activity level
• 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

Abstract

To detect whether the pulse detector is in an unworn state, the pulse detector is provided for detecting a pulse signal that originates in the pulse of a subject has a pulse wave sensor, a pulse wave sensor sensitivity adjustment section that adjusts the sensitivity of the pulse wave sensor, a body movement sensor, and an unworn-state detector that detects that the pulse detector has been removed from the subject and is in an unworn state, on the basis of the sensitivity of the pulse wave sensor sensitivity adjustment section and a body movement sensor signal outputted from the body movement sensor.

Claims

1. A pulse detector that detects a pulse signal originating from a pulse of a subject, the pulse detector, comprising:

a pulse wave sensor for outputting a pulse wave signal possibly including the pulse signal;

a pulse wave sensor sensitivity adjustment section that adjusts the sensitivity of the pulse wave sensor on the basis of an input signal to the pulse wave sensor or the intensity of the pulse wave signal;

a body movement sensor that detects body movement of the subject and outputting a body movement sensor signal originating from the body movement; and

an unworn-state detector that detects an unworn state in which the pulse detector has been removed from the subject, on the basis of the sensitivity of the pulse wave sensor adjusted by the pulse wave sensor sensitivity adjustment section and the body movement sensor signal outputted from the body movement sensor.

2. The pulse detector according to claim 1, further comprising

a frequency analyzer that performs frequency analysis at predetermined time intervals on the basis of the pulse wave signal or a filtered signal obtained by subjecting the pulse wave signal to filtering for suppressing noise included in the pulse wave signal, wherein

the unworn-state detector detects the unworn state on the basis of the sensitivity of the pulse wave sensor adjusted by the pulse wave sensor sensitivity adjustment section, the body movement sensor signal outputted from the body movement sensor, and the result of the frequency analysis of the pulse wave signal performed by the frequency analyzer.

3. The pulse detector according to claim 2, wherein the unworn-state detector judges the unworn state to be in effect in the case that

the sensitivity of the pulse wave sensor adjusted by the pulse wave sensor sensitivity adjustment section is out of a range permitted when the pulse signal is detected;

the level of the body movement sensor signal outputted from the body movement sensor is within a range judged to be devoid of body movement of the subject; and

the frequency spectrum obtained as a result of frequency analysis of the pulse wave signal does not include a spectrum equal to or greater than a first threshold value.

4. The pulse detector according to claim 2, wherein the unworn-state detector judges the unworn state to be in effect in the case that

the sensitivity of the pulse wave sensor adjusted by the pulse wave sensor sensitivity adjustment section is out of a range permitted when the pulse signal is detected;

the level of the body movement sensor signal outputted from the body movement sensor is within a range judged to be devoid of body movement of the subject;

the frequency spectrum obtained as a result of frequency analysis of the pulse wave signal does not contain a spectrum equal to or greater than a first threshold value; and

an amount of noise included in the pulse wave signal is judged to be equal to or greater than a predetermined amount on the basis of the frequency spectrum.

5. The pulse detector according to claim 3, wherein

the unworn-state detector performs a detection of the unworn state at predetermined time intervals, and, when the unworn-state detector has judged the unworn state not to be in effect and has judged the unworn state to be in effect prior to a predetermined length of time, a judgment that the unworn state is not in effect is made in the case that the frequency spectrum includes a spectrum equal to or greater than a second threshold value, and a judgment that the unworn state is in effect is made in the case that the frequency spectrum does not include a spectrum equal to or greater than a second threshold value.

6. The pulse detector according to claim 1, wherein

the unworn-state detector performs a detection of the unworn state at predetermined time intervals and, when the unworn state is judged to be in effect, discards at least one among the frequency analysis results of the pulse wave signal in advance of a predetermined time, and information showing a trend of the frequency of the pulse signal used in the frequency analysis of the pulse wave signal.

7. The pulse detector according to claim 1, wherein

the pulse detector has a subject information acquisition section that acquires at least one of biological information of the subject and accompanying information related to activity by the subject;

and

the unworn-state detector stops operation of the subject information acquisition section when the unworn state has been detected.

8. The pulse detector according to claim 1, wherein

the unworn-state detector stops the frequency analysis operation carried out by the frequency analyzer when the unworn state has been detected.