TECHNICAL FIELD

The present invention relates to a pulse wave detection device, a vehicle device, and a pulse wave detection program and relates to a method for detecting the pulse rate of a subject.

BACKGROUND ART

Detection of a pulse wave is important in order to grasp the health state or physiological state of a subject. Usually, a device is attached to a subject for detection of the pulse wave, but there is a high demand for simpler detection methods, and the art for detecting the pulse wave of a subject in a non-contact manner has been keenly studied.

As a result, traffic safety can be further promoted by monitoring pulse wave of a vehicle driver, for example.

The art for detecting the pulse wave in a non-contact manner as mentioned above includes an art in Non-Patent Literature 1. In this art, an arm of the subject is photographed by a camera, and the pulse wave is detected from images from the camera. Since the brightness or color of a body surface is changed by blood flow, the pulse can be detected by image processing of the images.

In the art in Patent Literature 1, when a detection region becomes smaller due to a change in the direction of the face to right or left, the pulse wave is estimated by changing the detection region to a portion in the face where the detection region can be taken relatively widely.

When the pulse wave of the subject is to be detected by a camera, an incident light source is needed, but if environmental lighting is not sufficient, illumination is needed.

If the position of the subject relative to the lighting is constant, the pulse wave can be detected, but if the subject moves, the brightness of the light reflected by the subject is greatly influenced, and the pulse wave cannot be measured anymore, which is a problem.

CITATION LIST

Patent Literature

Patent Literature 1: Japanese Patent Application Publication No. 2014-198201

Non-Patent Literature

Non-Patent Literature 1: “Non-contact Monitoring Techniques—Principles and Applications,” D. Teichmann, C. Bruser, B. Eilebrecht, A. Abbas, N. Blanik, and S. Leonhardt, Proc. IEEE Eng., Med. Biol. Soc. 34th Ann. Int. Conf., San Diego, Calif., USA, 2012, pp. 1302-1305.

DISCLOSURE OF INVENTION

Problem to be Solved by the Invention

The object of the present invention is to appropriately detect a pulse wave even if the brightness of a subject changes due to movement of the subject with respect to the lighting.

SUMMARY OF THE INVENTION(S)

(1) The invention described in claim1provides a pulse wave detection device, comprising: a video obtainment means for obtaining videos obtained by photographing a body surface of a subject; a region obtainment means for obtaining a region where the body surface is photographed from the obtained videos; a brightness obtainment means for obtaining brightness of the obtained region; a correction means for correcting the obtained brightness by using correlation between a relative rearward and forward position of the body surface and the brightness of the region; and a pulse wave obtainment means for obtaining a pulse wave of the subject on the basis of a change in the corrected brightness of the region.
(2) The invention described in claim2provides the pulse wave detection device according to claim1, wherein the body surface is a face, and the region obtainment means obtains a face region as the region.
(3) The invention described in claim3provides the pulse wave detection device according to claim2, comprising: an illumination means for illuminating the face with infrared light; and a video photographing means for photographing a video of the face illuminated by the infrared light, wherein the video obtainment means obtains the videos from the video photographing means.
(4) The invention described in claim4provides the pulse wave detection device according to claim2or3, wherein the correction means obtains the rearward and forward position of the face from the size of the face region.
(5) The invention described in claim5provides the pulse wave detection device according to claim2,3or4, comprising: a face detection region obtainment means for obtaining a face detection region larger than the face including the face, wherein the region obtainment means obtains the face region by using the brightness distribution in the obtained face detection region.
(6) The invention described in claim6provides the pulse wave detection device according to any one of claims2to5, wherein when the obtained face region has a closed region not included in the face region, the correction means includes the closed region when determining the size of the face region.
(7) The invention described in claim7provides the pulse wave detection device according to claim3, comprising: an environmental luminance obtainment means for obtaining environmental luminance; and an activation means for activating lighting by the illumination means and video photography by the video photographing means when the obtained environmental luminance falls below a predetermined value.
(8) The invention described in claim8provides the pulse wave detection device according to claim7, comprising: a second pulse wave obtainment means for obtaining the pulse wave when the environmental luminance is at a predetermined value or more, wherein the activation means activates lighting by the illumination means and photography of videos by the video photographing means after obtainment of the pulse wave by the second pulse wave obtainment means is stopped when the obtained environmental luminance falls below a predetermined value.
(9) The invention described in claim9provides a vehicle device comprising: the pulse wave detection device according to any one of claims1to8.
(10) The invention described in claim10provides a pulse wave detection program for causing a computer to realize: a video obtainment function for obtaining videos obtained by photographing a body surface of a subject; a region obtainment function for obtaining a region where the body surface is photographed from the obtained videos; a brightness obtainment function for obtaining brightness of the obtained region; a correction function for correcting the obtained brightness by using correlation between a relative rearward and forward position of the body surface and the brightness of the region; and a pulse wave obtainment function for obtaining a pulse wave of the subject on the basis of a change in the corrected brightness of the region.

EFFECT OF THE INVENTION(S)

According to the present invention, the pulse wave can be detected appropriately by correcting brightness in accordance with the position of the subject.

