Pulse wave estimating device and pulse wave estimation method

1 . A pulse wave estimating device mounted on a vehicle, the pulse wave estimating device comprising:

processing circuitry configured to acquire a captured image of a human that is a driver of the vehicle;

detect a skin region of the human on the captured image;

set, as a plurality of measurement regions for extracting luminance signals representing luminance changes, regions formed by dividing the skin region on the captured image in a predetermined manner;

perform measurement region resetting on the plurality of measurement regions, when a ratio of measurement regions, in which a number of pixels is equal to or greater than a preset reference value among the set plurality of measurement regions, is lower than a threshold, in such a manner as to make the ratio of measurement regions equal to or higher than the threshold;

extract the luminance signals on a basis of the luminance changes in the set measurement regions or the reset measurement regions on the captured image; and

estimate a pulse wave of the human on a basis of luminance signal segment information from the extracted luminance signals according to the set plurality of measurement regions or the reset plurality of measurement regions, wherein the estimated pulse wave based on the set plurality of measurement regions or the reset plurality of measurement regions suppresses deterioration of accuracy of the estimated pulse wave caused by movement of the human.

2 . The pulse wave estimating device according to claim 1 , wherein the processing circuitry performs the measurement region resetting by reducing the number of divisions of the skin region on the captured image in a case where the ratio is lower than the threshold.

3 . The pulse wave estimating device according to claim 1 , wherein the processing circuitry performs the measurement region resetting by setting at least one new measurement region extending over a predetermined number of adjacent measurement regions in the set plurality of measurement regions in a case where the ratio is lower than the threshold.

4 . The pulse wave estimating device according to claim 3 , wherein the at least one new measurement region includes a plurality of new measurement regions which can be overlapped with each other.

5 . The pulse wave estimating device according to claim 1 , wherein the processing circuitry performs the measurement region resetting by reducing the number of divisions of the skin region on the captured image, and also setting at least one new measurement region extending over a predetermined number of adjacent measurement regions in the plurality of measurement regions obtained by reducing the number of divisions, in a case where the ratio is lower than the threshold.

6 . The pulse wave estimating device according to claim 1 , wherein the processing circuitry makes the number of pixels per measurement region after the resetting greater than the number of pixels per measurement region before the resetting.

7 . The pulse wave estimating device according to claim 1 ,

wherein the processing circuitry is configured to select a luminance signal to be used for the estimation of the pulse wave of the human from among the extracted luminance signals, and estimate the pulse wave of the human on a basis of the selected luminance signal.

8 . The pulse wave estimating device according to claim 7 , wherein the processing circuitry selects, as the luminance signal to be used for the estimation of the pulse wave of the human, a luminance signal, from among the extracted luminance signals, which has been extracted when a deviation between an orientation of a face of the human and a preset reference face orientation is within a predetermined range.

9 . A pulse wave estimation method performed by a pulse wave estimating device mounted on a vehicle, the pulse wave estimation method comprising:

acquiring a captured image of a human that is a driver of the vehicle;

detecting a skin region of the human on the captured image; setting regions formed by dividing the skin region on the captured image in a predetermined manner, as a plurality of measurement regions for extracting luminance signals representing luminance changes;

performing measurement region resetting on the plurality of measurement regions, when a ratio of measurement regions, in which a number of pixels is equal to or greater than a preset reference value among the set plurality of measurement regions, is lower than a threshold, in such a manner as to make the ratio of measurement regions equal to or higher than the threshold;

extracting the luminance signals on a basis of the luminance changes in the set measurement regions or the reset measurement regions on the captured image; and

estimating a pulse wave of the human on a basis of luminance signal segment information from the extracted luminance signals according to the set plurality of measurement regions or the reset plurality of measurement regions, wherein the estimated pulse wave based on the set plurality of measurement regions or the reset plurality of measurement regions suppresses deterioration of accuracy of the estimated pulse wave caused by movement of the human.