EP-3949841-B1 - PULSE RATE DETECTION DEVICE AND PULSE RATE DETECTION PROGRAM

Inventors

• JONES MICHAEL

Dates

Publication Date

20260506

Application Date

20200327

Claims (4)

1. A pulse rate detection device (1) comprising: a moving image obtaining means (8) configured to obtain a moving image captured by photographing a body surface of a subject; a pulse rate obtaining means (2) configured to obtain a pulse rate of the subject on the basis of change of a pixel value of the body surface in the moving image; and a reliability obtaining means (2) configured to obtain reliability of the obtained pulse rate, wherein the pulse rate obtaining means (2) is configured: to obtain the pulse rate from a pulse rate peak in a frequency domain of the obtained moving image, and to obtain the disturbance peak in a frequency domain of a disturbance factor; and wherein the reliability obtaining means (2) is configured to obtain the reliability on the basis of a signal-to-noise ratio of the obtained pulse rate; characterized in that the device further comprises: a reducing means (2) configured to reduce the reliability if the disturbance peak in the frequency domain of a disturbance factor that reduces accuracy of the obtained pulse rate is equal to or closer than a predetermined amount to the obtained pulse rate peak, and an output means (5) configured to output the obtained pulse rate if the reliability thereof is equal to or greater than predetermined reliable criteria.
2. The pulse rate detection device (1) according to claim 1, wherein the disturbance factor is due to a movement of the body surface, and the reducing means (2) is configured to reduce the reliability if a movement peak in the frequency domain of the movement of the body surface is equal to or closer than the predetermined amount to the obtained pulse rate peak.
3. The pulse rate detection device according to claim 1 or 2, wherein the disturbance factor is due to variation of light illuminating the body surface, and the reducing means (2) is configured to reduce the reliability if a light peak in the frequency domain of the variation of light is equal to or closer than the predetermined amount to the obtained pulse rate peak.
4. A pulse rate detection program for causing a computer to realize: a moving image obtaining function for obtaining a moving image captured by photographing a body surface of a subject; a pulse rate obtaining function for obtaining a pulse rate of the subject on the basis of change of a pixel value of the body surface in the moving image; and a reliability obtaining function for obtaining reliability of the obtained pulse rate, wherein the pulse rate obtaining function obtains the pulse rate from a pulse rate peak in a frequency domain of the obtained moving image, and to obtain the disturbance peak in a frequency domain of a disturbance factor; and wherein the reliability obtaining function obtains the reliability on the basis of a signal-to-noise ratio of the obtained pulse rate; characterized in that the pulse rate detection program is further configured to cause a computer to realize: a reducing function for reducing the reliability if the disturbance peak in the frequency domain of a disturbance factor that reduces accuracy of the obtained pulse rate is equal to or closer than a predetermined amount to the obtained pulse rate peak, and an output function for outputting the obtained pulse rate if the reliability thereof is equal to or greater than predetermined reliable criteria.

Description

TECHNICAL FIELD The present invention relates to a pulse rate detection device and a pulse rate detection program, and relates to, for example, detection of a pulse rate by image processing. BACKGROUND ART It is important to detect a pulse rate in order to grasp a health condition and a physiological state of a subject. Usually, the pulse rate is detected by attaching an instrument to the subject, but there has been a high demand for easily detecting the pulse rate, and therefore technologies for detecting the pulse rate of the subject in a noncontact manner have been actively researched. This can monitor, for example, a pulse rate of a driver of a vehicle and thereby further promoting traffic safety. The article entitled "Non-contact monitoring techniques - Principles and applications" by D. Teichmann, C. Bruser, B. Eilebrecht, A. Abbas, N. Blanik, and S. Leonhardt (Con. Proc. IEEE Eng., Med. Biol. Soc. 34th Ann. Int. Conf., San Diego, CA, USA, 2012, pp. 1302-1305) discloses such a technology of detecting the pulse rate of the subject in such a noncontact manner. This technology photographs an arm of the subject with a camera, and obtains changes of skin color, brightness, or the like from a camera image to detect the pulse rate. Since the brightness and the color of a body surface change due to blood flow, the pulse rate can be detected by executing image processing of video. However, when the pulse rate is detected under an environment where there is a disturbance such as the subject moving or environmental light changing, there is a problem that degree of reliability (reliable accuracy) of the detected pulse rate is uncertain. For example, when a pulse rate is detected for a certain period, 86% of the detections are reliable and rest of the detections are not reliable due to a disturbance, it is uncertain which portion of the detections are reliable. Moreover, there is also another problem that even if the reliability of the detected value can be evaluated, a period during which the pulse rate can be detected becomes shorter as the evaluation is made more stringent. The document US 2017/238805 A1 discloses systems and methods for video-based monitoring of vital signs, such as the pulse rate, wherein images of a patient are captured, intensity signals are produced from the images, those signals to focus on a physiologic component are filtered, and a vital signal is measured from the filtered signals. The document US 2014/276099 A1 discloses a device and a method for determining vital signs of a subject. The document US 2016/015277 A1 discloses a device and a method for monitoring a baby and for interaction, including a method for video evaluation of the heart rate and/or respiration rate of a baby, in particular under dim or nocturnal conditions. Further related art is known from the document US 2015/302158 A1. SUMMARY OF INVENTION The object of the present invention is to output a pulse rate that is highly reliable. According to the present invention, in order to achieve the above object, there are provided a pulse rate detection device and a pulse rate detection program, as defined by the claims. The present disclosure can be summarized as follows. (1) A first aspect of the present disclosure provides a pulse rate detection device comprising: a moving image obtaining means configured to obtain a moving image captured by photographing a body surface of a subject; a pulse rate obtaining means configured to obtain a pulse rate of the subject on the basis of change of a pixel value of the body surface in the moving image; a reliability obtaining means configured to obtain reliability of the obtained pulse rate; and an output means configured to output the obtained pulse rate if the obtained reliability thereof is equal to or greater than predetermined reliable criteria.(2) A second aspect of the present disclosure provides the pulse rate detection device according to the first aspect, wherein the pulse rate obtaining means obtains the pulse rate from a pulse rate peak in a frequency domain of the obtained moving image, and the reliability obtaining means obtains the reliability on the basis of an SN ratio of the obtained pulse rate.(3) A third aspect of the present disclosure provides the pulse rate detection device according to the second aspect, further comprising a reducing means configured to reduce the reliability if a disturbance peak in the frequency domain of a disturbance factor that reduces accuracy of the obtained pulse rate is equal to or closer than a predetermined amount to the obtained pulse rate peak.(4) A fourth aspect of the present disclosure provides the pulse rate detection device according to the third aspect, wherein the disturbance factor is due to a movement of the body surface, and the reducing means reduces the reliability if a movement peak in the frequency domain of the movement of the body surface is equal to or closer than the predetermined amount to the obtained pulse rate p