MEASUREMENT DEVICE, MEASUREMENT METHOD, AND STORAGE MEDIUM

A measurement device includes the following: an imaging unit configured to image a living organism to acquire an image; a determination-index calculating unit configured to calculate, for a region of interest included in the image, a determination index relating to a pixel count of a target pixel having a pixel value equal to or greater than a predetermined lower limit and equal to or smaller than a predetermined upper limit; and a biological-information calculating unit configured to calculate biological information from the pixel value of a pixel included in a region of interest with the determination index being equal to or greater than a threshold.

BACKGROUND

Field of the Disclosure

The present disclosure relates to a measurement device, a measurement method, and a program. The present application claims priority from Japanese Application No. JP2022-104103, filed on Jun. 29, 2022, the content of which is hereby incorporated by reference into this application.

Description of the Related Art

Japanese Unexamined Patent Application Publication No. 2016-190022 discloses a technique of calculating the difference between luminance information about a video signal in a skin region indicating the face of a target person and luminance information about a video signal in a skin region indicating parts of the target person other than the face at the same time as the video signal of the face, and measuring fluctuations in the blood pressure of the target person corresponding to increase or decrease in the calculated difference.

SUMMARY

One method is calculating biological information by imaging skin to acquire information about the skin surface, the skin inner blood vessels and other things. For instance, the technique disclosed in Japanese Unexamined Patent Application Publication No. 2016-190022 includes extracting pixels of luminance information corresponding to skin color from a region of interest set manually, to set a region including the extracted pixels as a skin region. However, the biological information cannot be calculated accurately in some cases in the technique disclosed in Japanese Unexamined Patent Application Publication No. 2016-190022 when the skin region includes inappropriate pixels containing information irrelevant to the blood vessels, such as a blocked-up shadow image, caused by excessively dark surroundings, a spot image, a wrinkle image and other things. The reason is that such an inappropriate pixel containing information unnecessary for the calculation of biological information calculation cannot reflect the biological information correctly; thus, it is difficult to calculate the biological information accurately when an image includes many inappropriate pixels like this. Examples of the inappropriate pixel include a pixel with a blocked-up shadow, caused by excessively dark surroundings as described above, a pixel darkened due to, but not limited to, a spot, a wrinkle, a moles or a face shadow, and a pixel with an image showing blown-out highlights due to excessively intensive illumination or sunlight.

Accordingly, one aspect of the present disclosure aims to provide a measurement device, a measurement method, and a recording medium that can calculate biological information accurately by using an appropriate pixel.

A measurement device according to one aspect of the present disclosure includes the following: an imaging unit configured to image a living organism to acquire an image; a determination-index calculating unit configured to calculate, for a region of interest included in the image, a determination index relating to a pixel count of a target pixel having a pixel value equal to or greater than a predetermined lower limit and equal to or smaller than a predetermined upper limit; and a biological-information calculating unit configured to calculate biological information from the pixel value of a pixel included in a region of interest with the determination index being equal to or greater than a threshold.

A measurement method according to one aspect of the present disclosure includes the following steps: imaging a living organism to acquire an image; calculating, for a region of interest included in the image, a determination index relating to a pixel count of a target pixel having a pixel value equal to or greater than a predetermined lower limit and equal to or smaller than a predetermined upper limit; and calculating biological information from the pixel value of a pixel included in a region of interest with the determination index being equal to or greater than a threshold.

A computer-readable recording medium according to one aspect of the present disclosure records a program that is executed by a computer. The program includes the following functions: imaging a living organism to acquire an image; calculating, for a region of interest included in the image, a determination index relating to a pixel count of a target pixel having a pixel value equal to or greater than a predetermined lower limit and equal to or smaller than a predetermined upper limit; and calculating biological information from the pixel value of a pixel included in a region of interest with the determination index being equal to or greater than a threshold.

DETAILED DESCRIPTION OF THE DISCLOSURE

First Preferred Embodiment

A first preferred embodiment will be described with reference toFIG.1toFIG.6. It is noted that identical or equivalent components in the drawings will be denoted by the same signs, and that the description of redundancies will be omitted.

FIG.1illustrates an example aspect of use of a measurement device100. As illustrated inFIG.1, the measurement device100includes an imaging unit101.

The measurement device100measures time-series changes in the skin's surface and inside of a living organism102from an image acquired by the imaging unit101, to acquire biological information. Examples of the measurement device100include a personal computer (PC), a smartphone, a tablet terminal, a terminal dedicated for biological-information measurement, and a monitoring robot provided with the imaging unit101. Examples of the biological information include blood pressure, pulse, breathing rate, and blood oxygen saturation.

The imaging unit101images the living organism102to acquire an image. In the present disclosure, still and moving images cut out of a continuous or discontinuous live-action record indicating volume changes in a blood vessel of the living organism102imaged by the imaging unit101are referred to as images.

The imaging unit101is placed in a location where the imaging unit101can image a portion where the body surface of the living organism102is exposed. Examples of the portion where the body surface of the living organism102is exposed include the forehead, cheek, fingertips, wrists and palms of the living organism102. The imaging unit101is placed in, but not limited to, a PC, a display, a mirror, and a washstand.

The imaging unit101is a camera that includes a charged-coupled-device (CCD) image sensor or complementary-metal-oxide-semiconductor (CMOS) image sensor, and a lens. The imaging unit101may be composed of a camera image sensor including an RGB filter. The imaging unit101includes, for instance, a color filter of RGB Bayer arrangement in order to detect a small change in the skin color of the living organism102. Alternatively, the imaging unit101may include a color filter of RGBCy, RGBIR or other things. The color filter of RGBCy, RGBIR or other things is suitable for observing increase and decrease in blood volume indicated by reflected light of light passed through the skin's inside.

FIG.2is a block diagram illustrating an example configuration of the measurement device100. The measurement device100includes the imaging unit101, an input unit201, an output unit202, a storage unit203, a control unit204, a determination-index calculating unit205, a biological-information calculating unit206, and other components. The imaging unit101, the input unit201, the output unit202and the storage unit203are electrically connected to the control unit204.

The imaging unit101images the living organism102to acquire an image211and sends the acquired image211to the control unit204. The imaging unit101images the living organism102at, for instance, 30 to 60 frames per second (fps) to acquire the image211. The image211includes an image of the body surface of the living organism102.

The input unit201receives an input of information necessary for the measurement device100. Examples of the input unit201include a keyboard, a mouse, and a touch panel.

The output unit202outputs the image211, biological information212, a message to the living organism102, date and time, and other things. The output unit202is composed of, but not limited to, a display and a loudspeaker.

The storage unit203is a recording medium that can record various data pieces, various programs, and other things and is composed of, but not limited to, a hard disk, a solid-state drive (SSD), and a semiconductor memory. The storage unit203stores a predetermined lower limit213, a predetermined upper limit214, a threshold215, information related to the biological information212, time changes in the biological information212, and other things. The information relating to the biological information212is the type of the biological information212, logs of the biological information212(e.g., changes on a day-to-day basis), data for correcting information already stored in the storage unit203, or other things.

The control unit204executes various processes in accordance with programs and data stored in the storage unit203. The control unit204is composed of a processor, such as a central processing unit (CPU) or a graphic processing unit (GPU).

The control unit204includes the determination-index calculating unit205, the biological-information calculating unit206, and other components.

The determination-index calculating unit205calculates, for a region of interest included in the image211, a determination index216relating to the number of target pixels TP having a pixel value equal to or greater than the predetermined lower limit213and equal to or smaller than the predetermined upper limit214. A pixel value in the present disclosure is information indicating the brightness of a pixel included in the image211; examples include the pixel value of a subpixel of each of red (R), green (G) and blue (B) in an RGB color space, the luminance value of a pixel in the RGB color space, and the values of hue (H), saturation (S) and value (V) calculated from the pixel values of the R-, G- and B-subpixels in an HSV color space.

The biological-information calculating unit206calculates the biological information212from the pixel value of a pixel included in a region of interest with the determination index216being equal to or greater than the threshold215. To be specific, the biological-information calculating unit206calculates the biological information212from the pixel values of the target pixels TP included in the region of interest with the determination index216being equal to or greater than the threshold215.

FIG.3is a flowchart illustrating an example operation of the measurement device100according to this preferred embodiment.

In Step S301, the imaging unit101images the living organism102to acquire the image211. When the output unit202is implemented by a display, the control unit204controls the display to show the acquired image211.

In Step S302, the determination-index calculating unit205identifies a region of interest including a body surface image from the acquired image211. For instance, the determination-index calculating unit205detects a facial region of the living organism102from the acquired image211. To be specific, the determination-index calculating unit205detects characteristics, such as the eyes, the nose and the mouth, from the image211and detects the facial region on the basis of the detected characteristics. The determination-index calculating unit205then identifies a region of interest including an image of the forehead or cheek of the living organism102from the detected facial region.

In Step S303, the determination-index calculating unit205identifies a single target pixel TP or two or more target pixels TP included in the identified region of interest and having a pixel value equal to or greater than the predetermined lower limit213and equal to or smaller than the predetermined upper limit214.

For instance, the determination-index calculating unit205determines whether the pixel values of the R-, G- and B-subpixels constituting a pixel included in the region of interest is equal to or greater than the predetermined lower limit213and equal to or smaller than the predetermined upper limit214. The determination-index calculating unit205then identifies, as a target pixel TP, a pixel with the pixel values of the R-, G- and B-subpixels being all equal to or greater than the predetermined lower limit213and equal to or smaller than the predetermined upper limit214.

For instance, the predetermined lower limit213has a value corresponding to the lower limit of a dynamic range of the image211, and the predetermined upper limit214has a value corresponding to the upper limit of the dynamic range of the image211. To be specific, the predetermined lower limit213has a larger value than the lower limit of the dynamic range, and the predetermined upper limit214has a smaller value than the upper limit of the dynamic range.

For instance, let the predetermined lower limit213stand at one, and let the predetermined upper limit214stand at254when the lower limit, which is a pixel value corresponding to the lower limit of an RGB dynamic range, stands at zero, and when the upper limit, which is a pixel value corresponding to the upper limit of the RGB dynamic range, stands at255. The determination-index calculating unit205in this case identifies, as target pixels TP, pixels included in the region of interest and having a pixel value of 1 to 254 inclusive. The determination-index calculating unit205can accordingly exclude a blocked-up shadow pixel having a pixel value of zero, and a blown-out highlight pixel having a pixel value of 255 from the target pixels TP. Alternatively, the predetermined lower limit213may have a larger value than the lower limit of the dynamic range by a predetermined value, and the predetermined upper limit214may be a smaller value than the upper limit of the dynamic range by a predetermined value. For instance, when the lower limit of the RGB dynamic range stands at zero, and when the upper limit of the RGB dynamic range stands at255, the predetermined lower limit may stand at10, and the predetermined upper limit may stand at244. It is noted that the upper and lower limits of the dynamic range will be hereinafter indicated by corresponding pixel values, and that a grayscale, such as 12-bit, may be used other than a 256-level grayscale.

In Step S304, the determination-index calculating unit205calculates the determination index216relating to the number of target pixels TP identified in Step S303. For instance, the determination-index calculating unit205calculates the ratio of the target pixels TP to all the pixels in the region of interest as the determination index216. For instance, let the region of interest include 100 pixels in total, and let 80 pixels have a pixel value equal to or greater than the predetermined lower limit213and equal to or smaller than the predetermined upper limit214. The determination index216in this case stands at 80%. Alternatively, the determination-index calculating unit205may calculate the number of target pixels TP as the determination index216. In Step S305, the biological-information calculating unit206determines whether the determination index216calculated in Step S304is equal to or greater than the threshold215. For instance, when the determination index216indicates the ratio of the target pixels TP to all the pixels in the region of interest, and when the threshold215stands at 60%, the biological-information calculating unit206determines whether the ratio of the target pixels TP indicated by the determination index216is equal to or greater than 60%.

If the determination index216is equal to or greater than the threshold215in Step S305, the control unit204moves the process to Step S307. In contrast, if the determination index216is lower than the threshold215in Step S305, the biological-information calculating unit206registers the image211including the region of interest with the determination index216being lower than the threshold215into the storage unit203as an out-of-condition image. For instance, the determination-index calculating unit205registers the identification information of the image211including the region of interest with the determination index216being lower than the threshold215into the storage unit203as the identification information of the out-of-condition image. An example of the identification information of the image211is a frame number. The control unit204then moves the process to Step S307.

In Step S307, the biological-information calculating unit206determines whether the image211has been acquired for a predetermined time or a predetermined number of frames. The predetermined time or the predetermined number of frames is the time or the number of frames necessary for calculating the biological information212. The predetermined time or the predetermined number of frames may be different from type to type of the biological information212.

If the image211has not been acquired for the predetermined time or the predetermined number of frames in Step S307, the control unit204moves the process back to Step S301. In contrast, if the image211has been acquired for the predetermined time or the predetermined number of frames in Step S307, the control unit204moves the process to Step S401, which is illustrated inFIG.4.

The operation of the measurement device100according to this preferred embodiment will be still described with reference toFIG.4.

In Step S401, the biological-information calculating unit206determines whether an out-of-condition image has been registered. For instance, the biological-information calculating unit206determines whether the identification information of the out-of-condition image has been registered in the storage unit203. If the identification information of the out-of-condition image has not been registered in the storage unit203, the control unit204moves the process to Step S403. In contrast, if the identification information of the out-of-condition image has been registered in the storage unit203, the biological-information calculating unit206in Step S402excludes, among a plurality of images or images in a predetermined number of frames acquired by imaging the living organism102for a predetermined time, an out-of-condition image with identification information registered in the storage unit203being assigned thereto from the process of calculating the biological information212. Alternatively, the biological-information calculating unit206may exclude a moving image including the out-of-condition image with the identification information registered in the storage unit203being assigned thereto from the process of calculating the biological information212. That is, the biological-information calculating unit206determines an out-of-condition image including a region of interest with the determination index216being lower than the threshold215, or a moving image including the out-of-condition image as an imaging failure and then excludes the out-of-condition image, or the moving image including the out-of-condition image from the process of calculating the biological information212.

In Step S403, the biological-information calculating unit206calculates a pulse wave signal indicating a pulse wave from time changes in the pixel value of a pixel included in a region of interest with the determination index216being equal to or greater than the threshold215. A pulse wave in the present disclosure is a time-series signal that indicates blood-vessel volumetric change, and that is calculated from a time-series signal indicating the pixel value of a pixel included in the image211.

For instance, the biological-information calculating unit206calculates a representative value of pixel values of the pixels included in the region of interest with the determination index216being equal to or greater than the threshold215. The biological-information calculating unit206then calculates the pulse wave signal from time changes in a value calculated by substituting the extracted pixel values, or the representative value of these pixel values into a predetermined mathematical expression. Alternatively, the biological-information calculating unit206may calculate, through independent component analysis, pigment composition separation or other methods, the pulse wave signal from time changes in the pixel value of the pixel included in the region of interest with the determination index216being equal to or greater than the threshold215.

In Step S404, the biological-information calculating unit206calculates the biological information212corresponding to the type of the biological information212, which is a calculation target, from the pulse wave signal calculated in Step S403. For instance, when the type of the calculation target, i.e., the biological information212, is pulse rate, the biological-information calculating unit206calculates the pulse rate on the basis of the time required for a single beat of the pulse wave indicated by the pulse wave signal. Further for instance, when the type of the calculation target, i.e., the biological information212, is blood pressure, the biological-information calculating unit206estimates the blood pressure from the shape of the pulse wave signal.

In Step S405, the biological-information calculating unit206controls the output unit202to output the biological information212calculated in Step S404.

For instance, when the output unit202is composed of a display, the biological-information calculating unit206controls the display to show characters, a graph or other things indicating the pulse rate, blood pressure or other things indicated by the biological information212. Furthermore, when the output unit202is composed of a display, the biological-information calculating unit106may control the display to show a message to the living organism102, date and time, and other things. An example message to the living organism102indicates whether the pulse rate, blood pressure or other things indicated by the biological information212falls within a predetermined range; a message saying, “a normal measurement” is an example of such a message. Alternatively, when the output unit202is composed of a loudspeaker for instance, sounds indicating, but not limited to, a message to the living organism102, such as the pulse rate, blood pressure or other things indicated by the biological information212, and date and time may be output from the loudspeaker.

FIG.5illustrates example target pixels TP and example non-target pixels NTP included in a region of interest501. The non-target pixels NTP are pixels having a pixel value smaller than the predetermined lower limit213or greater than the predetermined upper limit214.

The region of interest501includes 64 pixels in total, among which 34 pixels are the target pixels TP. Thus, the determination-index calculating unit205calculates the determination index216as standing at 53.125% (=34/64) when, for instance, calculating the ratio of the target pixels TP to all the pixels in the region of interest as the determination index216.

FIG.6illustrates the threshold215, and a graph601showing example time changes in the determination index216. The lateral axis inFIG.6indicates time, and the longitudinal axis in the same indicates the determination index. Individual points shown in the graph601indicate the determination index216about regions of interest included in the images211acquired at mutually different time points. The determination index216in the regions of interest included in the images211acquired from a time point t611to a time point t612and on or after a time point t613is equal to or greater than the threshold215. Thus, the biological-information calculating unit206calculates the biological information212from the pixel values of pixels included in the images211acquired from the time point t611to the time point t612and on or after the time point t613.

It is noted that a relatively lower threshold215possibly involves more inappropriate pixels. In contrast, a relatively higher threshold215is less likely to involve the determination index216equal to or greater than the threshold215, thus possibly increasing the time required from the start of the imaging of the living organism102to the output of the biological information212. Hence, the threshold215is preferably set in accordance with pixel quality allowable for the biological information212, and latency time allowable by the living organism102.

As described above, the measurement device100according to this preferred embodiment calculates the biological information212from time changes in a pixel value that is included in a region of interest included in the image211acquired by imaging the living organism102, and that falls within a previously set range. The measurement device100according to this preferred embodiment can thus calculate the biological information212while preventing the accuracy of biological information calculation from lowering due to an adverse effect of an inappropriate pixel having a pixel value that is off from the previously set range.

First Modification of First Preferred Embodiment

In a first modification of the measurement device100according to this preferred embodiment, the biological-information calculating unit206does not have to calculate the biological information212until the determination index216is kept equal to or greater than the threshold215during a predetermined time or a predetermined number of frames. Furthermore, the imaging unit101in this modification may image the living organism102until the determination index216becomes equal to or greater than the threshold215. The biological-information calculating unit206in this case does not use the image211including a region of interest with the determination index216being lower than the threshold215in the process of calculating the biological information212. The biological-information calculating unit206can thus calculate the biological information212from time changes in the pixel value of a pixel included in a region of interest with the determination index216being equal to or greater than the threshold215. Biological information is reflected to the wave shape of a pulse wave; thus, using a temporally continuous wave shape in its entirety can calculate biological information more accurately than using a discontinuous wave shape.

For instance, let time changes in the determination index216be indicated by the graph601, illustrated inFIG.6. Furthermore, let the determination index216be kept equal to or greater than the threshold215during a predetermined number of frames on or after the time point t613. The biological-information calculating unit206in this modification in this case excludes the images211acquired from the time point t611to the time point t612from the process of calculating the biological information212. The biological-information calculating unit206in contrast calculates the biological information212from the pixel values of pixels included in regions of interest included in the images211acquired at time points on or after the time point t613. The biological-information calculating unit206can consequently use the continuously acquired images211in the process of calculating the biological information212. It is noted that whether to use the measurement device100according to this modification may be determined in accordance with latency time allowable by the living organism102.

Second Modification of First Preferred Embodiment

In a second modification of the measurement device100according to this preferred embodiment, the determination-index calculating unit205may calculate the determination index216by using the average, variance, standard deviation or other things of the pixel values of the target pixels TP included in a region of interest. For instance, the determination-index calculating unit205may calculate the determination index216on the basis of the average, variance, standard deviation or other things of the pixel values of the target pixels TP included in the region of interest, and on the basis of the number of target pixels TP included in the region of interest.

Second Preferred Embodiment

A second preferred embodiment will be described. It is noted that identical or equivalent components in the drawings will be denoted by the same signs, and that the description of redundancies will be omitted. Configurations and processes having functions common substantially with those in the other preferred embodiments will be referred to with common symbols, and their description will be thus omitted; in addition, differences between this preferred embodiment and the other preferred embodiments will be described.

The predetermined lower limit213and predetermined upper limit214according to this preferred embodiment are set on the basis of at least one of an RGB color space and an HSV color space. To be specific, the predetermined lower limit213has a value based on at least one of the RGB color space and HSV color space. Likewise, the predetermined upper limit214has a value based on at least one of the RGB color space and HSV color space.

For instance, when the predetermined lower limit213is set on the basis of the RGB color space, a predetermined lower limit r1for the pixel value of an R-subpixel, a predetermined lower limit g1for the pixel value of a G-subpixel, and a predetermined lower limit b1for the pixel value of a B-subpixel are set. That is, when the predetermined lower limit213is set on the basis of the RGB color space, the predetermined lower limit213is set for each of the R-, G- and B-subpixels.

When a region of interest includes an image of a spot, wrinkle, mole or other things of the living organism102, an image of a blood vessel included in the region of interest is possibly mixed with the image of the spot, wrinkle, mole or other things of the living organism102. The biological information212in this case cannot be possibly calculated appropriately from time changes in the pixel value of a pixel included in the region of interest. However, when a pixel value lower than the predetermined lower limit r1, predetermined lower limit g2and predetermined lower limit b3is a value indicating the color of the image of the spot, wrinkle, mole or other things of the living organism102, the determination-index calculating unit205can exclude, from the target pixels TP, pixels included in the image of the spot, wrinkle, mole or other things of the living organism102included in the region of interest. The biological-information calculating unit206can consequently prevent the accuracy of calculation of the biological information212from degradation caused by an inappropriate pixel.

Alternatively, the predetermined lower limit213, when set on the basis of the RGB color space, may be set using the pixel value of a subpixel of one color and the pixel value of a subpixel of another color. For |PixR(x,y)−PixG(x,y)|>m4for instance, the determination-index calculating unit205determines a pixel including PixR(x,y), which is an R-subpixel, and PixG(x,y), which is a G-subpixel, as a target pixel TP. PixR(x,y) denotes the R-subpixel having x and y coordinates, PixG(x,y) denotes the G-subpixel having x and y coordinates, and m4denotes the predetermined lower limit213.

It is noted that the predetermined lower limit213and the predetermined upper limit214may be different between the R-, G- and B-subpixels.

Further, the pixel values of R, G and B indicated by the RGB color space are different greatly in some cases, depending on surrounding brightness at the time of imaging even when objects of the same color undergo imaging. In contrast to this, hue, saturation and value indicated by the HSV color space are less likely to be affected by the surrounding brightness at the time of imaging than the pixel values of R, G and B indicated by the RGB color space; thus, the determination-index calculating unit205may determine the target pixels TP on the basis of the hue, saturation and value indicated by the HSV color space when the surrounding brightness at the time of imaging is susceptible to fluctuations. For instance, the predetermined lower limit213and the predetermined upper limit214are set on the basis of the HSV color space, a predetermined lower limit h1and a predetermined upper limit h2both for the hue, a predetermined lower limit s1and a predetermined upper limit s2both for the saturation, and a predetermined lower limit b1and a predetermined upper limit b2both for the value are set.

The determination-index calculating unit205converts the pixel value of each pixel included in the region of interest from a value in the RGB color space into a value in the HSV color space when the predetermined lower limit213and the predetermined upper limit214are set on the basis of the HSV color space. The determination-index calculating unit205then determines whether the pixel value indicating the converted value in the HSV color space is equal to or greater than the predetermined lower limit213and equal to or smaller than the predetermined upper limit214.

Determining the target pixels TP on the basis of the hue, saturation and value indicated by the HSV color space enables the determination-index calculating unit205to calculate the determination index216while preventing an effect caused by fluctuations in the surrounding brightness at the time of imaging.

Alternatively, the determination-index calculating unit205may determine the target pixels TP having a pixel value that is equal to or greater than the predetermined lower limit213corresponding to the RGB color space and is equal to or smaller than the predetermined upper limit214corresponding to the RGB color space, and that is equal to or greater than the predetermined lower limit213corresponding to the HSV color space and is equal to or smaller than the predetermined upper limit214corresponding to the HSV color space. It is noted that the predetermined lower limit213and predetermined upper limit214at this time are values corresponding to a color space; thus in some cases, a value corresponding to the RGB color space is different from a value corresponding to the HSV color space. The determination-index calculating unit205may then calculate the determination index216relating to the number of determined target pixels TP. The predetermined lower limit213and the predetermined upper limit214have their values based on the RGB color space and HSV color space, thus enabling the determination-index calculating unit205to select the target pixels TP having necessary information more accurately than it does in the case where the predetermined lower limit213and the predetermined upper limit214have their values based on a single color space.

It is noted that the color of a blood vessel image that is imaged by the imaging unit101is affected by the performance of a camera and the illumination level of the surrounding environment in some cases. Hence, the range of the pixel values of the target pixels TP based on at least one of the RGB color space and HSV color space may be set in accordance with the performance of the camera and the illumination level of the surrounding environment.

Third Preferred Embodiment

A third preferred embodiment will be described with reference toFIG.7toFIG.9. It is noted that identical or equivalent components in the drawings will be denoted by the same signs, and that the description of redundancies will be omitted. Configurations and processes having functions common substantially with those in the other preferred embodiments will be referred to with common symbols, and their description will be thus omitted; in addition, differences between this preferred embodiment and the other preferred embodiments will be described.

The configuration of the measurement device100according to this preferred embodiment is illustrated inFIG.1. The biological-information calculating unit206according to this preferred embodiment calculates the biological information212from the pixel values of all the pixels included in a region of interest with the determination index216being equal to or greater than a total-use threshold exceeding the threshold215.

FIG.7is a flowchart illustrating an example operation of the measurement device100according to this preferred embodiment. The process steps in Steps S701through S706illustrated inFIG.7, which are similar to those in Steps S301through S306illustrated inFIG.3, will not be detailed.

In Step S707, the determination-index calculating unit205determines whether the determination index216is equal to or greater than the total-use threshold. If the determination index216is not equal to or greater than the total-use threshold in Step S707, the control unit204moves the process to Step S709. In contrast, if the determination index216is equal to or greater than the total-use threshold in Step S707, the determination-index calculating unit205in Step S708registers the identification information of the image211including a determination-target region of interest into the storage unit203as the identification information of a total-use region of interest. The control unit204then moves the process to Step S709.

In Step S709, the biological-information calculating unit206determines whether the image211has been acquired for a predetermined time or a predetermined number of frames. The process step in Step S709, which is similar to that in Step S307illustrated inFIG.3, will not be detailed.

If the image211has not been acquired for the predetermined time or the predetermined number of frames in Step S709, the control unit204moves the process back to Step S701. In contrast, if the image211has been acquired for the predetermined time or the predetermined number of frames in Step S709, the control unit204moves the process to Step S801illustrated inFIG.8.

Next, the operation of the measurement device100according to this preferred embodiment will be still described with reference toFIG.8. The process steps in Steps S801through S802, which are similar to those in Steps S401through S402illustrated inFIG.4, will not be detailed.

In Step S803, the biological-information calculating unit206calculates a pulse wave signal from time changes in the pixel values of all the pixels included in the total-use region of interest, and from time changes in the pixel values of the target pixels TP included in a region of interest with the determination index216being lower than the total-use threshold and equal to or greater than the threshold215. The total-use region of interest is a region of interest included in the image211indicated by the identification information of the total-use region of interest registered in Step S708illustrated inFIG.7and is a region of interest with the determination index216being equal to or greater than the total-use threshold. The control unit204then moves the process to Step S804. The process steps in Steps S804through S805, which are similar to those in Steps S404through S405illustrated inFIG.4, will not be detailed.

For instance, let the threshold215stand at 60%, and let the total-use threshold stand at 70%. The biological-information calculating unit206in this case uses, in the process of calculating the biological information212, the pixel values of all the pixels included in a region of interest with the determination index216standing at 70% or greater. The biological-information calculating unit206also uses, in the process of calculating the biological information212, the pixel values of the target pixels TP included in a region of interest with the determination index216standing at 60% or greater and less than 70%.

Although the numeric value 70% is non-limiting, it is preferable to set a numeric value such that a merit rather than an adverse effect that is exerted on measurement using a few inappropriate pixels is achieved greatly thanks to many pixels that are used. For instance, in using the average of the pixel values of pixels within a region of interest or other things to calculate biological information, using many appropriate pixels can achieve a signal quality improvement such as an improvement in signal noise ratio, thus improving the accuracy of biological information calculation in some cases even when data acquired by an image sensor constituting the imaging unit101includes inappropriate pixels.

FIG.9illustrates a threshold, a total-use threshold, and a graph901showing example time changes in the determination index216. The lateral axis inFIG.9indicates time, and the longitudinal axis in the same indicates the determination index. Individual points shown in the graph901indicate the determination index216about regions of interest included in the respective images211. In response to the determination index216calculated as indicated by the graph901, the biological-information calculating unit206uses, in the process of calculating the biological information212, time changes in the pixel values of all the pixels in a region of interest included in each of the images211acquired at a time point t915to a time point t916and a time point t919to a time point t920. For instance, the biological-information calculating unit206uses, in the process of calculating a pulse wave signal, time changes in the pixel values of all the pixels in the region of interest included in each of the images211acquired at the time point t915to the time point t916and the time point t919to the time point t920.

Furthermore, in response to the determination index216calculated as illustrated in the graph901, the biological-information calculating unit206uses, in the process of calculating the biological information212, time changes in the pixel values of the target pixels TP included in regions of interest of the images211acquired at a time point t911to a time point t912, a time point t913to a time point t914and a time point t917to a time point t918. For instance, the biological-information calculating unit206uses, in the process of calculating the pulse wave signal, time changes in the pixel values of the target pixels TP included in the regions of interest of the images211acquired at the time point t911to the time point t912, the time point t913to the time point t914and the time point t917to the time point t918.

As such, the biological-information calculating unit206uses, in the process of calculating the biological information212, the pixel values of all the pixels included in a region of interest with the determination index216being equal to or greater than the total-use threshold. There are at this time fewer inappropriate pixels than appropriate pixels to such a degree that the determination index216satisfies the total-use threshold, thus predominating improvement in calculation accuracy resulting from use of many appropriate pixels for calculation over accuracy degradation resulting from use of inappropriate pixels. The measurement device100according to this preferred embodiment can consequently calculate the biological information212by using the pixel values of many appropriate pixels and can thus improve the accuracy of calculation of the biological information212.

Fourth Preferred Embodiment

A fourth preferred embodiment will be described with reference toFIG.10. It is noted that identical or equivalent components in the drawings will be denoted by the same signs, and that the description of redundancies will be omitted. Configurations and processes having functions common substantially with those in the other preferred embodiments will be referred to with common symbols, and their description will be thus omitted; in addition, differences between this preferred embodiment and the other preferred embodiments will be described.

The configuration of the measurement device100according to this preferred embodiment is illustrated inFIG.1.

The determination-index calculating unit205according to this preferred embodiment calculates the determination index216for each of a plurality of regions of interest included in the image211.

The biological-information calculating unit206according to this preferred embodiment calculates the biological information212from the pixel value of a pixel included in a region of interest with the determination index216being equal to or greater than the threshold215among the plurality of regions of interest included in the image211. To be specific, the biological-information calculating unit206calculates the biological information212from the pixel values of the target pixels TP included in a region of interest with the determination index216being equal to or greater than the threshold215among the plurality of regions of interest included in the image211.

Alternatively, the biological-information calculating unit206may calculate the biological information212from the pixel values of the target pixels TP included in a region of interest with the determination index216being the largest of the plurality of regions of interest included in the image211.

Alternatively, the biological-information calculating unit206may calculate the biological information212from the pixel values of all the pixels included in a region of interest with the determination index216being equal to or greater than a total-use threshold among the plurality of regions of interest included in the image211.

FIG.10illustrates a plurality of example regions of interest included in the image211. Let pixels constituting a region1011included in a region of interest1001, pixels constituting a region1012included in a region of interest1002, pixels constituting a region1013included in the region of interest1002, and pixels constituting a region1014included in a region of interest1003be defined as non-target pixels NTP. Moreover, let the determination index216in the region of interest1001and the determination index216in the region of interest1003be equal to or greater than the threshold215. Further, let the determination index216in the region of interest1002be lower than the threshold215. The biological-information calculating unit206in this case calculates the biological information212from the pixel values of the pixels included in the region of interest1001and the region of interest1003. The biological-information calculating unit206herein excludes the pixels constituting the region1011and the pixels constituting the region1014from the process of calculating the biological information212and then calculates the biological information212. It is noted that in an image211different from the image211illustrated inFIG.10, the biological-information calculating unit206excludes this different image211from the process of calculating the biological information212when the determination index216is lower than the threshold215in any of the regions of interest1001to1003.

As described above, the measurement device100according to this preferred embodiment can calculate the biological information212from the pixel values of the target pixels TP included in a region of interest suitable for calculating the biological information212among the plurality of regions of interest.

Modification of Fourth Preferred Embodiment

In a modification of the measurement device100according to this preferred embodiment, a region of interest may include a plurality of divided regions of interest.

FIG.11illustrates a plurality of example regions of interest included in a region of interest. A region of interest1101illustrated inFIG.11includes a region of interest1111to a region of interest1114. The region of interest1111to the region of interest1114are regions with the region of interest1101divided. Furthermore, the region of interest1114includes a region of interest1121to a region of interest1124. The region of interest1121to the region of interest1124are regions with the region of interest1114divided.

When the determination index216is lower than the threshold215in a region of interest that is a determination target, the determination-index calculating unit205according to this modification calculates the determination index216for a plurality of regions of interest composed of this determination-target region of interest divided. For instance, when the determination index216is lower than the threshold215in the region of interest1101, the determination-index calculating unit205calculates the determination index216for each of the regions of interest1111to1114.

Furthermore for instance, when the determination index216is lower than the threshold215in the regions of interest1111to1114, the determination-index calculating unit205calculates the determination index216for each of a plurality of regions of interest with the regions of interest1111to1114divided. For instance, the determination-index calculating unit205calculates the determination index216for each of the regions of interest1121to1124. As described above, the determination-index calculating unit205calculates the determination index216for a divided determination-target region of interest until the determination index216becomes equal to or greater than the threshold215in the determination-target region of interest having a predetermined size or larger size.

The biological-information calculating unit206then calculates the biological information212from the pixel value of a pixels included in the divided determination-target region of interest when the calculated determination index216is equal to or greater than the threshold215in the divided determination-target region of interest. That is, the biological-information calculating unit206calculates the biological information212from the pixel value of a pixel included in a region of interest having a predetermined minimum size or larger size and with the determination index216being equal to or greater than the threshold215. For instance, when the region of interest1124has a predetermined size or larger size, and when the determination index216in the region of interest1124is equal to or greater than the threshold215, the biological-information calculating unit206calculates the biological information212from the pixel value of a pixel included in the region of interest1124.

As such, even when the determination index216in a relatively large region of interest is lower than the threshold215, the biological-information calculating unit206according to this modification calculates the biological information212from the pixel value of a pixel included in a region of interest included in the relatively large region of interest and with the determination index216being equal to or greater than the threshold215.

As described above, the measurement device100according to this modification can calculate the biological information212from the pixel value of a target pixel included in a region of interest where the biological information212can be calculated accurately within a relatively large region of interest even when the determination index216in the relatively large region of interest is lower than the threshold215.

Fifth Preferred Embodiment

A fifth preferred embodiment will be described. It is noted that identical or equivalent components in the drawings will be denoted by the same signs, and that the description of redundancies will be omitted. Configurations and processes having functions common substantially with those in the other preferred embodiments will be referred to with common symbols, and their description will be thus omitted; in addition, differences between this preferred embodiment and the other preferred embodiments will be described.

In the measurement device100according to this preferred embodiment, at least any selected from the group consisting of the predetermined lower limit213, predetermined upper limit214and threshold215has a value corresponding to the type of the biological information212that is a calculation target.

The predetermined lower limit213, predetermined upper limit214and threshold215associated with the type of this calculation-target biological information212are stored in the storage unit203according to this preferred embodiment.

For instance, for pulse calculation in the biological-information calculating unit206, the reliability of the calculated biological information212tends to be able to be satisfied even when pixels within a region of interest include relatively many pixels containing unnecessary information other than blood vessels when compared with an instance of blood pressure calculation. That is, when the type of the biological information212is pulse, there is a tendency where the difference between the predetermined upper limit214and predetermined lower limit213may be relatively large when compared with an instance where the type of the biological information212is blood pressure. Likewise, when the type of the biological information212is pulse, there is a tendency where the threshold215may be relatively low when compared with the instance where the type of the biological information212is blood pressure. That is, the range of a pixel value that is required, and the determination index216that is needed vary in accordance with the type of biological information that is a calculation target.

However, the predetermined lower limit213and predetermined upper limit214varying from type to type of the biological information212that is a calculation target are stored in the storage unit203, thereby enabling the determination index216to be calculated based on a criterion corresponding to the type of the biological information212. Furthermore, the threshold215varying from type to type of the biological information212is stored in the storage unit203, thereby enabling the biological-information calculating unit206to determine, on the basis of the threshold215corresponding to the type of the biological information212, a region of interest and the image211that are used for calculating the biological information212. The measurement device100can consequently calculate the biological information212from the pixel value of a pixel included in a region of interest, on the basis of a criterion corresponding to the type of the biological information212.

Sixth Preferred Embodiment

A sixth preferred embodiment will be described. It is noted that identical or equivalent components in the drawings will be denoted by the same signs, and that the description of redundancies will be omitted. Configurations and processes having functions common substantially with those in the other preferred embodiments will be referred to with common symbols, and their description will be thus omitted; in addition, differences between this preferred embodiment and the other preferred embodiments will be described.

In the measurement device100according to this preferred embodiment, at least one selected from the group consisting of the predetermined lower limit213and predetermined upper limit214has a value corresponding to a body surface color associated with a type to which the living organism102belongs. Examples of the type to which the living organism102belongs include the age and race of the living organism102.

For instance, the color, saturation, value and other things of an image of an imaged blood vessel tend to vary in accordance with age, such as childhood, adolescence, the age of maturity and old age. However, the predetermined lower limit213and predetermined upper limit214corresponding to the age are associated and stored in the storage unit203, thereby enabling the determination-index calculating unit205to calculate the determination index216appropriately in accordance with the age of the living organism102.

As described above, the measurement device100can determine the target pixels TP on the basis of the type to which the living organism102belongs by storing the predetermined lower limit213and predetermined upper limit214, varying from type to type to which the living organism102belongs, in the storage unit203. The measurement device100according to this preferred embodiment can consequently calculate the biological information212from the pixel values of the target pixels TP corresponding to the age, race and other things of the living organism102.

Modification of Sixth Preferred Embodiment

In a modification of the measurement device100according to this preferred embodiment, at least one selected from the group consisting of the predetermined lower limit213and predetermined upper limit214may have a value corresponding to a body surface color associated with the type to which the living organism102belongs, and the threshold215may have a value corresponding to the type of the biological information212that is a calculation target. The measurement device100according to this modification in this case can determine the target pixels TP on the basis of a criterion corresponding to the type to which the living organism102belongs and can calculate the determination index216on the basis of a criterion corresponding to the type of this calculation-target biological information212. The measurement device100according to this modification can consequently calculate the biological information212from the pixel value of a pixel included in a region of interest, on the basis of a criterion corresponding to the type to which the living organism102belongs, and corresponding to the type of the calculation-target biological information212.

The individual processes that are executed in the foregoing preferred embodiments are not limited to the process aspects illustrated in the respective preferred embodiments. The foregoing function blocks may be implemented with either a logic circuit (hardware) formed in, but not limited to, an integrated circuit or software using a CPU. The individual processes that are executed in the foregoing preferred embodiments may be executed by a plurality of computers. For instance, some of the processes that are executed in the respective function blocks of the control unit204of the measurement device100may be executed by another computer, or all of the processes may be shared among the plurality of computers.

The present disclosure is not limited to the foregoing individual preferred embodiments. Various modifications can be devised with the scope of the claims. A preferred embodiment that is obtained in combination, as appropriate, with the technical means disclosed in the respective preferred embodiments is also included in the technical scope of the present disclosure. Furthermore, combining the technical means disclosed in the respective preferred embodiments can form a new technical feature.