Patent Publication Number: US-2016228011-A1

Title: Bio-information acquiring device and bio-information acquiring method

Description:
TECHNICAL FIELD 
     The present invention relates to a bio-information acquiring device acquiring a pulse wave. 
     BACKGROUND ART 
     A technique is widely used in which a pulse wave is detected by referring to a moving image obtained by imaging a living body (for example, the human body). Here, the “pulse wave” indicates that the pulsation of blood vessels due to ejecting of blood in the heart is expressed as a waveform. Particularly, a pulse wave in which a pressure change of blood vessels is expressed as a waveform is referred to as a “pressure pulse wave”, and a pulse wave in which a volume change of blood vessels is expressed as a waveform is referred to as a “volume pulse wave”. 
     PTL 1 discloses a method of detecting a volume pulse wave from a face image obtained by imaging the face. In the method disclosed in PTL 1, the volume pulse wave is detected by using a phenomenon in which a person&#39;s complexion changes according to a volume change of blood vessels. 
     In the method disclosed in PTL 1, a dedicated image capturing apparatus is not necessary, and a dedicated illumination device for illuminating a subject (that is, the face of a person to be measured) is not also necessary. Therefore, it is possible to detect pulse waves of a person to be measured by using a general video camera. In the method disclosed in PTL 1, a person to be measured is required to direct his or her face toward a camera, but it is not necessary to restrict body parts (for example, the fingers) of the person to be measured. 
     Bio-information (an index indicating a physiological condition of a living body) which can be derived from a pulse wave may include pulse wave velocity. Here, the “pulse wave velocity” indicates velocity at which a pulse wave propagates through a blood vessel. The pulse wave velocity may be calculated by dividing the length of a blood vessel between two parts of the living body by a phase difference (difference in arrival time) of pulse waves in the two parts. A pulse wave has the property that propagation velocity thereof increases as a blood vessel is hardened, and thus the pulse wave velocity is used as a useful index for finding cardiovascular diseases such as arteriosclerosis. 
     PTL 2 discloses an apparatus which calculates a pulse wave velocity on the basis of pulse waves in the base and the tip of the finger. In the apparatus disclosed in PTL 2, pulse waves in the base and the tip of the finger are detected by referring to a finger image obtained by imaging the finger. 
     In the apparatus disclosed in PTL 2, the finger image is captured by detecting light which is applied from a light source and is transmitted through the finger, by a camera disposed on an opposite side to the light source with respect to the finger. In this case, the finger of a person to be measured is fixed to a predetermined position between the light source and the camera so that images of the base and the tip of the finger are formed in two predefined regions on the finger image (this fixation is realized, for example, by inserting the finger into an insertion hole). 
     The pulse waves in the base and the tip of the finger are detected as temporal changes in luminance values in the above-described two regions (regions in which the images of the base and tip of the finger are formed) on the finger image. Here, a phenomenon is used in which, if the artery expands, the intensity of light passing through the finger is reduced. The pulse wave velocity is calculated by dividing the length from the base of the finger to the tip thereof by a difference between time points at which a luminance value becomes the minimum in the above-described two regions on the finger image. 
     CITATION LIST 
     Patent Literature 
     PTL 1: U.S. Patent No. US2011/0251593A1 (published on Oct. 13, 2011) 
     PTL 2: Japanese Unexamined Patent Application Publication No. 2008-301915 (published on Dec. 18, 2008) 
     SUMMARY OF INVENTION 
     Technical Problem 
     Various bio-information pieces can be derived by using a phase difference of pulse waves in different parts of a living body (for example, the human body). The above-described pulse wave velocity is an example of such bio-information. 
     However, in a case where a phase difference of pulse waves is calculated by using the apparatus disclosed in PTL 2, it is necessary to form images of two predefined parts (for example, the base and tip of the finger) of a person to be measured in two predefined regions on an image. For this reason, there is a problem in that the living body is required to be restricted so that the parts are fixed to predetermined positions between the light source and the camera. 
     In the method disclosed in PTL 1, a volume pulse wave is calculated by using a change in a color which is averaged over the entire face of the person to be measured. In other words, the method disclosed in PTL 1 can be said to be a method of detecting a pulse wave in only a single region. Therefore, there is a problem in that an influence of the occurrence of difference in the arrival time of a pulse wave according to each position on the face is not taken into consideration, and a highly accurate measurement result of a pulse wave cannot be obtained. 
     The present invention has been made in order to solve the above-described problems, and an object thereof is to implement a bio-information acquiring device which can calculate a phase difference of pulse waves in different parts of a living body without restricting the living body, and can derive various bio-information pieces from the phase difference. 
     Solution to Problem 
     In order to solve the problems, according to an aspect of the present invention, there is provided a bio-information acquiring device which derives bio-information from a moving image obtained by imaging a living body, the device including region specifying means for specifying, through image processing, regions respectively corresponding to at least two parts of the living body in frame images forming the moving image; pulse wave detection means for detecting pulse waves in the at least two parts by referring to the regions specified by the region specifying means; and phase difference calculation means for calculating a phase difference between the pulse waves in the at least two parts, detected by the pulse wave detection means. 
     Advantageous Effects of Invention 
     According to the bio-information acquiring device related to an aspect of the present invention, it is possible to achieve an effect in which a phase difference between pulse waves in different parts of a living body can be calculated without restricting the living body. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a functional block diagram illustrating a configuration of a bio-information acquiring device according to Embodiment 1 of the present invention. 
         FIG. 2  Part (a) of  FIG. 2  is a diagram illustrating a state in which an imaging section images the face of a person to be measured in Embodiment 1 of the present invention. Part (b) of  FIG. 2  is a diagram exemplifying one of a plurality of frame images obtained under an imaging environment illustrated in the part (a) of  FIG. 2 . 
         FIG. 3  Part (a) of  FIG. 3  is a diagram exemplifying a skin color region extracted from a face region in Embodiment 1 of the present invention. Part (b) of  FIG. 3  is a diagram exemplifying two measurement regions in the face region. 
         FIG. 4  is a flowchart exemplifying a flow of processes of calculating pulse wave velocity in the bio-information acquiring device according to Embodiment 1 of the present invention. 
         FIG. 5  is a functional block diagram illustrating a configuration of a bio-information acquiring device according to Embodiment 2 of the present invention. 
         FIG. 6  Part (a) of  FIG. 6  is a diagram exemplifying a frame image including a hand region in Embodiment 2 of the present invention. Part (b) of  FIG. 6  is a diagram exemplifying two measurement regions in the hand region. 
         FIG. 7  is a diagram exemplifying calculation points M(i), M(i−1) and M(i+1), vectors u(i) and v(i), and an angle θ in Embodiment 2 of the present invention. 
         FIG. 8  is a functional block diagram illustrating a configuration of a bio-information acquiring device according to Embodiment 3 of the present invention. 
         FIG. 9  is a functional block diagram illustrating a configuration of a bio-information acquiring device according to Embodiment 4 of the present invention. 
         FIG. 10  is a functional block diagram illustrating a configuration of a bio-information acquiring device according to Embodiment 5 of the present invention. 
         FIG. 11  is a functional block diagram illustrating a configuration of a bio-information acquiring device according to Embodiment 6 of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention will be described with reference to the drawings. In the following respective embodiments, a description will be made of a bio-information acquiring device which derives bio-information of a person from a moving image obtained by imaging the person, but the present invention is not limited thereto. In other words, the category of the present invention also includes a bio-information acquiring device which derives bio-information of a living body from a moving image obtained by imaging the living body (any living body having a heart) which is not a person. 
     Embodiment 1 
     Embodiment 1 of the present invention will be described with reference to  FIGS. 1 to 4 . 
     (Bio-Information Acquiring Device  1 ) 
       FIG. 1  is a functional block diagram illustrating a configuration of a bio-information acquiring device  1  according to the present embodiment. The bio-information acquiring device  1  includes an imaging section  11 , a display section  19 , a storage section  90 , and a main control section  10 . 
     (Imaging Section  11 ) 
     The imaging section  11  generates a moving image by imaging a subject (that is, a person to be measured  121 ) and sends the generated moving image to an image acquisition unit  12  included in the main control section  10 . 
     Imaging of a subject in the imaging section  11  is performed for a preset measurement time period (for example, 30 seconds). The imaging section  11  may accumulate the moving image for the entire measurement time period and may send the moving image to the image acquisition unit  12 , or may divide the moving image at intervals of predetermined time and may sequentially send the moving image to the image acquisition unit  12  in the middle of the measurement time period. 
     Outputting of the moving image from the imaging section  11  to the image acquisition unit  12  may be performed in a wired manner by using a cable or the like, or may be performed in a wireless manner. The imaging section  11  may record the moving image on a recording medium (for example, a semiconductor memory) provided therein, and the image acquisition unit  12  may read the moving image. 
     Part (a) of  FIG. 2  is a diagram exemplifying a state in which the imaging section  11  images the face of the person to be measured  121 . The part (a) of  FIG. 2  illustrates a situation in which the imaging section  11  images the person to be measured  121  reading a book, sitting in front of a desk  122 . The imaging section  11  is provided on the desk  122  so as to image the face of the person to be measured  121 . 
     As illustrated in the part (a) of  FIG. 2 , the imaging section  11  can image a body part of the person to be measured  121  without restricting the person to be measured  121 . A body part of the person to be measured  121  imaged by the imaging section  11  is not limited to the face. For example, as will be described in Embodiment 2 later, the hand may be imaged as a body part of the person to be measured  121 . A luminaire or the like may be provided, and, for example, in relation to a thin part such as the finger, transmitted light from the luminaire or the like may be imaged. 
     (Display Section  19 ) 
     The display section  19  is a display device such as a liquid crystal display. The display section  19  may display the pulse wave velocity calculated by the main control section  10  as data such as image data or text data. Details of an operation of the display section  19  will be described later. 
     (Storage Section  90 ) 
     The storage section  90  is a storage device which stores various programs executed by the main control section  10 , and data used by the programs. 
     (Main Control Section  10 ) 
     The main control section  10  generally controls operations of the imaging section  11  and the display section  19 . A function of the main control section  10  may be realized by a CPU (central processing unit) executing the programs stored in the storage section  90 . 
     In the present embodiment, the main control section  10  functions as the image acquisition unit  12 , a measurement region setting unit  13  (region specifying means), a pulse wave calculation unit  14  (pulse wave detection means), a difference calculation unit  15  (phase difference calculation means), a distance calculation unit  16  (distance calculation means), a pulse wave velocity calculation unit  17  (velocity calculation means), and an output unit  18 . 
     (Image Acquisition Unit  12 ) 
     The image acquisition unit  12  decomposes a moving image sent from the imaging section  11  into frames so as to generate frame images. In a case where the generated frame images are coded, the image acquisition unit  12  decodes the frame images. The image acquisition unit  12  sends the frame images to the measurement region setting unit  13 . 
     In a case where the frame images are sent from the imaging section  11  in the unit of a single frame, the process of decomposing a moving image into frames in the image acquisition unit  12  is not necessary. 
     (Measurement Region Setting Unit  13 ) 
     The measurement region setting unit  13  reads the frame images sent from the image acquisition unit  12  and sets a measurement region therein. The measurement region is a region in a frame image, corresponding to a part as a target for detecting a pulse wave among body parts of the person to be measured. 
     The measurement region is required to be selected from a region in which the skin of the person to be measured is imaged in the frame image. This is because a pulse wave is detected by using temporal changes in a skin color of the person to be measured. The present invention is aimed to measure a pulse wave in a plurality of parts, and thus the measurement region setting unit  13  sets at least two measurement regions. 
     A pulse wave is generated due to ejecting of blood from the heart, and propagates to a peripheral part along the artery. For this reason, there is the occurrence of difference between times when a pulse wave arrives at the measurement regions whose distances from the heart are different from each other. Therefore, the measurement region setting unit  13  sets a plurality of measurement regions corresponding to a plurality of parts whose distances from the heart are different from each other. 
     Hereinafter, a description will be made of a case where the measurement region setting unit  13  sets measurement regions in an image of the face of the person to be measured  121 . Part (b) of  FIG. 2  is a diagram exemplifying one of a plurality of frame images obtained under the imaging environment illustrated in the part (a) of  FIG. 2 . In the part (b) of  FIG. 2 , a frame image  111  indicates one of a plurality of frame images. 
     The measurement region setting unit  13  performs a face detection process on the frame image. The face detection process may be performed according to an appropriate well-known method. As illustrated in the part (b) of  FIG. 2 , a face region  131  detected through the face detection process is set in an internal region of the frame image  111  including the entire face of the person to be measured  121 . The face region  131  has, for example, a rectangular shape including the entire face image of the person to be measured  121 . 
     Next, the measurement region setting unit  13  extracts a skin color region  141  from the face region  131 . In other words, the measurement region setting unit  13  converts a color space of the face region  131  (or the frame image  111 ) into a color space of HSV (hue, saturation, and value). The measurement region setting unit  13  extracts pixels in which values of H (hue), S (saturation), and V (value) are respectively included in predetermined ranges, as the skin color region  141 . 
     Color spaces other than the HSV color space may be used to extract the skin color region  141 . Part (a) of  FIG. 3  is a diagram exemplifying the skin color region  141  extracted from the face region  131 . 
     Next, the measurement region setting unit  13  sets two regions including a measurement region  154  (first region) and a measurement region  155  (second region) in the skin color region  141 . Here, with reference to the part (b) of  FIG. 3 , a description will be made of a case where the measurement region  154  corresponding to an upper facial part (a first part, that is, a part which is more distant from the heart of the person to be measured  121 ) and the measurement region  155  corresponding to a lower facial part (a second part, that is, a position which is closer to the heart of the person to be measured  121 ) are set. 
     Part (b) of  FIG. 3  is a diagram exemplifying the two measurement regions  154  and  155  in the face region  131 . In the part (b) of  FIG. 3 , a vertical positional relationship is defined by setting a side (that is, a portion close to the head) on which the upper facial part is present as an upper side, and a side (that is, a portion distant from the head) on which the lower facial part is present as a lower side. A direction from the lower side to the upper side (or from the upper side to the lower side) is referred to as a vertical direction. 
     The measurement region setting unit  13  calculates a skin color region height p. The skin color region height p is an amount obtained as a value of a difference between (i) a coordinate in the vertical direction of a pixel located at an upper end of the skin color region  141  and (ii) a coordinate in the vertical direction of a pixel located at a lower end of the skin color region  141 . 
     Next, the measurement region setting unit  13  calculates a measurement region height c×p by using the skin color region height p and a preset constant c (where 0&lt;c&lt;1). 
     The measurement region setting unit  13  sets, as the measurement region  154 , a portion included in the lower side range from the upper end of the skin color region  141  to c×p in the skin color region  141 . The measurement region setting unit  13  sets, as the measurement region  155 , a portion included in the upper side range from the lower end of the skin color region  141  to c×p in the skin color region  141 . 
     The measurement region setting unit  13  sends the frame image, the face region  131 , and the measurement regions  154  and  155  to the pulse wave calculation unit  14  and the distance calculation unit  16 , respectively. 
     In the measurement region setting unit  13 , the constant c used to set the measurement region  154  (first region) and the constant c used to set the measurement region  155  (second region) may be different values. 
     A method of setting a measurement region in the measurement region setting unit  13  is not limited to the above-described method. For example, a method of detecting the eye and the mouth through a well-known facial organ detection process may be used. In this case, in a frame image, a portion above the eye in the skin color region  141  may be set as the measurement region  154 , and a portion under the mouth in the skin color region  141  may be set as the measurement region  155 . Even in a case where the face is obliquely imaged, a direction of the face may be further detected in order to appropriately select the vertical direction of the face. 
     In a frame image, not only upper and lower portions of the face, but also other portions such as left and right portions of the face may be set as measurement regions. The number of measurement regions is not necessarily limited to two, as long as a plurality of measurement regions are set. For example, a portion near the nose detected through a facial organ detection process may be further set as a measurement region. Therefore, the measurement region setting unit  13  may set N (where N is an integer of 2 or greater) measurement regions. 
     In the present embodiment, a case where a measurement region is selected in each frame is exemplified. On the other hand, a measurement region may be set in an initial frame, and the measurement region set in the initial frame may be used without being changed in subsequent frames. For example, a measurement region may be selected at a constant frame interval such as five frames, and the measurement region set in the previous frame may be used without being changed in other frames. 
     As another example, a measurement region may be set in an initial frame, and a region corresponding to the measurement region in the previous frame may be set as a measurement region by performing a motion detection process on the previous frame and the present frame in subsequent frames. 
     (Pulse Wave Calculation Unit  14 ) 
     The pulse wave calculation unit  14  detects a pulse wave in each of the measurement regions  154  and  155  set by the measurement region setting unit  13 . Computation of a pulse wave in the pulse wave calculation unit  14  is performed by using temporal changes in G (green) values of a color space of RGB (red, green, and blue). 
     Such a computation method is focused on a property of hemoglobin in blood absorbing green light. Therefore, a pulse wave is computed by approximately regarding a temporal change in a color of a skin surface due to blood flow as a volume pulse wave. 
     The pulse wave calculation unit  14  calculates an average value of G values of respective pixels inside each measurement region (that is, each of the measurement regions  154  and  155 ) in each frame image. In a case where a color space of each frame image is not the RGB color space, the pulse wave calculation unit  14  performs conversion into the RGB color space on each frame image in advance. 
     The pulse wave calculation unit  14  performs a smoothing process using a low-pass filter in a time direction on the average value of the G values so as to remove noise. A frequency characteristic of the low-pass filter is selected so that a frequency of a pulse wave is included in a passband. Therefore, for example, a low-pass filter having a frequency of 4 Hz or lower as a passband is used. 
     The pulse wave calculation unit  14  performs a normalization process so that a pulse wave has a maximum value of 1 and a minimum value of −1. The normalization process is performed, for example, according to the following Equation (1). 
     
       
         
           
             
               
                 
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     Here, f(t) on the right side of Equation (1) indicates an average value of G values of the measurement region  154  or  155  after the smoothing process using a low-pass filter is performed. Here, t indicates a frame number. In addition, max indicates the maximum value of f(t) for a measurement time period, and min indicates the minimum value of f(t) for the measurement time period. Further, g(t) on the left side of Equation (1) indicates a pulse wave in the measurement region  154  or  155 , obtained through the normalization process. 
     As a result of a series of processes in the pulse wave calculation unit  14 , a pulse wave g 1 ( t ) (first pulse wave) in the measurement region  154  and a pulse wave g 2 ( t ) (second pulse wave) in the measurement region  155  are detected. The pulse wave calculation unit  14  sends the pulse wave g 1 ( t ) and the pulse wave g 2 ( t ) to the difference calculation unit  15 . 
     In the pulse wave calculation unit  14 , prior to the normalization process, a detrending process for removing a smooth temporal variation may be further performed. An amount used to detect a pulse wave is not limited to a G value. For example, a pulse wave may be detected by performing the same process on luminance of a pixel. Also in a case where the number of measurement regions is three or larger, a pulse wave may be detected in each measurement region in the same manner as in a case of two measurement regions. 
     (Difference Calculation Unit  15 ) 
     The difference calculation unit  15  calculates temporal difference between the pulse wave g 1 ( t ) and the pulse wave g 2 ( t ), that is, a phase difference between the pulse wave g 1 ( t ) and the pulse wave g 2 ( t ). The phase difference is calculated by calculating a cross correlation function z(T) between the two pulse wave g 1 ( t ) and pulse wave g 2 ( t ). Here, τ indicates a shift amount. A shift amount which causes a value of cross correlation function z(T) to become the minimum is calculated as the phase difference. 
     The cross correlation function z(T) for the pulse wave g 1 ( t ) and the pulse wave g 2 ( t ) is represented by the following Equation (2). T indicates the number of frames included for a measurement time period. 
     
       
         
           
             
               
                 
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     The difference calculation unit  15  calculates a value of z(τ) in a range of −α≦τ≦α by using a preset constant α. Here, α is the expected maximum value of a phase difference. 
     The difference calculation unit  15  calculates a value τ=τmin of τ which causes a value of z(τ) to become the minimum in the range of −α≦τ≦α. Here, τmin (frame) indicates a phase difference between the pulse wave g 1 ( t ) and the pulse wave g 2 ( t ). The difference calculation unit  15  sends a value of the phase difference τmin to the pulse wave velocity calculation unit  17 . 
     The difference calculation unit  15  may calculate the phase difference τmin with decimal pixel accuracy by performing parabola fitting or spline interpolation by using τmin and a value of the cross correlation function z(τ) in the vicinity thereof. 
     In a case where imaging is performed by an image sensor using a rolling shutter in the imaging section  11 , the imaging is performed so that a pixel value of a pixel in a frame image is obtained in a delayed manner as the pixel is located on a lower side therein. In this case, the difference calculation unit  15  may add (q 2 −q 1 )×γ×r/n to the phase difference τmin so as to perform correction of an imaging time difference caused by the rolling shutter on the phase difference τmin. 
     Here, q 1  and q 2  respectively indicate average values of coordinates in the vertical direction of pixels included in a first region (for example, the measurement region  154 ) and a second region (for example, the measurement region  155 ). γ(s) indicates a difference between an imaging time of a pixel in the uppermost row of an image and an imaging time of a pixel in the lowermost row. In addition, r(frame/s) indicates a frame rate of the moving image sent to the image acquisition unit  12 . Further, n indicates the number of pixels of the frame image in the vertical direction. 
     In a case where the number of measurement regions is three or greater, each phase difference τmin may be calculated with respect to two combinations taken from a plurality of measurement regions in the same manner as in a case of two measurement regions. The phase difference τmin may also be referred to as difference τmin. 
     (Distance Calculation Unit  16 ) 
     The distance calculation unit  16  calculates a distance d (pixel) between the measurement regions  154  and  155  in the face region  131  as d=p−2×c×p with respect to an initial frame. The distance calculation unit  16  calculates a height h (pixel) of the face region  131  by using a value of a difference between an upper end coordinate and a lower end coordinate in the vertical direction of the face region  131 . The part (b) of  FIG. 3  exemplifies d and h. 
     The distance calculation unit  16  calculates an inter-part distance D (mm) which is a distance between the part corresponding to the measurement region  154  and the part corresponding to the measurement region  155  as D=H×d/h. The distance calculation unit  16  sends a value of the inter-part distance D to the pulse wave velocity calculation unit  17 . 
     H (mm) is a height of the face of the person to be measured  121 , measured in advance, or an average height of a person&#39;s face. A value of H is recorded in the storage section  90  in advance, and is read by the distance calculation unit  16  as appropriate. 
     In the present embodiment, the shortest distance between the measurement regions  154  and  155  is used as the distance d, but a method of calculating the distance d is not limited thereto. For example, the longest distance between the measurement regions  154  and  155  may be used as the distance d. A distance between a central point of the measurement region  154  and a central point of the measurement region  155  may be used as the distance d. 
     An example of obtaining the inter-part distance D in the initial frame has been described, but the present invention is not limited thereto, and the inter-part distance D may be calculated in the last frame or an intermediate frame. The distance d may be calculated in each frame, and the inter-part distance D may be calculated by using an average value thereof. A conversion expression for obtaining the length of a blood vessel from the inter-part distance D may be prepared in advance, and a value of the length of a blood vessel obtained according to the conversion expression may be used as the inter-part distance D. 
     In a case where the number of measurement regions is three or greater, the inter-part distance D may be calculated in each of two combinations taken from a plurality of measurement regions. 
     (Pulse Wave Velocity Calculation Unit  17 ) 
     The pulse wave velocity calculation unit  17  calculates pulse wave velocity V (mm/s) by using the phase difference τmin calculated in the difference calculation unit  15  and the inter-part distance D calculated in the distance calculation unit  16 . 
     In other words, the pulse wave velocity calculation unit  17  calculates the pulse wave velocity V according to V=D×r/τmin. Here, r (frame/s) is a frame rate of the moving image sent to the image acquisition unit  12 . The pulse wave velocity calculation unit  17  sends a value of the pulse wave velocity V to the output unit  18 . 
     In a case where the number of measurement regions is three or greater, the pulse wave velocity V may be calculated in each of two combinations taken from a plurality of measurement regions. 
     (Output Unit  18 ) 
     The output unit  18  outputs the pulse wave velocity V to a device provided outside the main control section  10 . For example, the output unit  18  may output the pulse wave velocity V to the display section  19 . The output unit  18  may output the pulse wave velocity V to the storage section  90 . 
     The output unit  18  may convert the pulse wave velocity V as appropriate so that the pulse wave velocity is easily processed in an output target device. For example, in a case where the output unit  18  outputs the pulse wave velocity V to the display section  19 , the output unit  18  may convert the pulse wave velocity V from numerical value data into text data or image data. 
     (Flow of Processes of Calculating Pulse Wave Velocity in Bio-Information Acquiring Device  1 ) 
     Hereinafter, with reference to  FIG. 4 , a description will be made of a flow of processes of calculating pulse wave velocity in the bio-information acquiring device  1 .  FIG. 4  is a flowchart exemplifying a flow of processes of calculating pulse wave velocity in the bio-information acquiring device  1 . 
     First, the image acquisition unit  12  decomposes a moving image sent from the imaging section  11  into frames so as to generate frame images (process S 1 ) (frame image generation step). 
     The measurement region setting unit  13  sets the two measurement regions  154  and  155  in the frame image (process S 2 ) (region specifying step). The pulse wave calculation unit  14  detects the pulse wave g 1 ( t ) in the measurement region  154  and the pulse wave g 2 ( t ) in the measurement region  155  (process S 3 ) (pulse wave detection step). 
     The difference calculation unit  15  calculates the phase difference τmin which is an amount indicating temporal difference between the pulse wave g 1 ( t ) and the pulse wave g 2 ( t ) (process S 4 ) (phase difference calculation step). The distance calculation unit  16  calculates a distance between a part corresponding to the measurement region  154  and a part corresponding to the measurement region  155 , that is, the inter-part distance D (process S 5 ) (distance calculation step). 
     The pulse wave velocity calculation unit  17  calculates pulse wave velocity V by using the phase difference τmin and the inter-part distance D (process S 6 ) (velocity calculation step). The output unit  18  outputs the pulse wave velocity V to a device (for example, the display section  19  or the storage section  90 ) provided outside the main control section  10  (process S 7 ) (pulse wave velocity output step). 
     The pulse wave velocity V is obtained in the bio-information acquiring device  1  through the above-described the processes S 1  to S 7 . 
     In the above-described example, the pulse wave velocity is output once by using the moving image obtained for a preset measurement time period (for example, 30 seconds), but the present invention is not limited thereto, and the pulse wave velocity may be output at a preset measurement interval (for example, 3 seconds). In this case, a measurement time period and a measurement interval are set in advance, and the pulse wave velocity V is calculated and is output for each measurement interval by using the moving image between a certain time point and a time point before the certain time point by the measurement time period. 
     (Effects of Bio-Information Acquiring Device  1 ) 
     According to the bio-information acquiring device  1 , a plurality of measurement regions corresponding to a plurality of parts as pulse wave detection targets can be automatically set through an image recognition process in each frame image of a moving image obtained by imaging the human body of the person to be measured  121 . 
     Even if the person to be measured  121  moves during measurement, regions on the frame image corresponding to a plurality of parts, that is, regions on the frame image which are referred to in order to detect a pulse wave are specified through image processing. 
     In other words, the bio-information acquiring device  1  can detect the pulse wave g 1 ( t ) and the pulse wave g 2 ( t ) in the plurality of parts respectively corresponding to the plurality of measurement regions (that is, the measurement regions  154  and  155 ) even by using images captured without restricting the person to be measured  121 . 
     Therefore, according to the bio-information acquiring device  1 , it is possible to achieve an effect in which a plurality of regions for measuring a pulse wave can be set in a captured image of a person to be measured in a simple manner. 
     According to the bio-information acquiring device  1 , it is possible to achieve an effect in which the pulse wave velocity V can be calculated by using the pulse waves g 1 ( t ) and g 2 ( t ). 
     Embodiment 2 
     Embodiment 2 of the present invention will be described with reference to  FIGS. 5 to 7 . For convenience of description, members having the same functions as those of the members described in the above embodiment are given the same reference numerals, and description thereof will be omitted. 
     (Bio-Information Acquiring Device  2 ) 
       FIG. 5  is a functional block diagram illustrating a configuration of a bio-information acquiring device  2  of the present embodiment. The bio-information acquiring device  2  of the present embodiment has a configuration in which (i) the main control section  10  of the bio-information acquiring device  1  of Embodiment 1 is replaced with a main control section  20 , and (ii) the measurement region setting unit  13  of the main control section  10  of Embodiment 1 is replaced with a measurement region setting unit  23  (measurement region setting means). 
     Remaining members of the bio-information acquiring device  2  of the present embodiment are the same as the members of the bio-information acquiring device  1  of Embodiment 1 and are thus given the same reference numerals, and description thereof will be omitted. 
     (Measurement Region Setting Unit  23 ) 
     The measurement region setting unit  23  sets a plurality of measurement regions in the hand of the person to be measured  121 . From this viewpoint, the measurement region setting unit  23  of the present embodiment is different from the measurement region setting unit  13  of Embodiment 1 in that a plurality of measurement regions are set in the face of the person to be measured  121 . 
     As illustrated in the part (a) of  FIG. 2 , the imaging section  11  is provided on the desk  122  so as to image the hand of the person to be measured  121 . A frame image obtained by imaging the hand of the person to be measured  121  is sent to the measurement region setting unit  23 . Part (a) of  FIG. 6  is a diagram exemplifying one of a plurality of frame images obtained under the imaging environment illustrated in the part (a) of  FIG. 2 . In the part (a) of  FIG. 6 , a frame image  211  indicates one of a plurality of frame images. 
     The measurement region setting unit  23  performs a hand region detection process on the frame image. The hand region detection process may be performed according to an appropriate well-known method such as extracting a skin color region. A hand region  271  illustrated in the part (a) of  FIG. 6  is an example of a region obtained through the hand region detection process. 
     Next, the measurement region setting unit  23  sets two regions including a measurement region  274  (first region) and a measurement region  275  (second region) in the hand region  271 . For example, as illustrated in the part (b) of  FIG. 6 , a region (that is, a region corresponding to a first part as a part which is more distant from the heart) including the fingertips is set as the measurement region  274 , and a region (that is, a region corresponding to a second part as a part which is closer to the heart) including the wrist is set as the measurement region  275 . 
     The part (b) of  FIG. 6  is a diagram exemplifying two measurement regions  274  and  275  in the hand region  271 . The measurement region  274  is also referred to as a tip side region. The measurement region  275  is also referred to as a root side region. 
     The measurement region setting unit  23  performs a finger recognition process in order to set the measurement region  274 . The finger recognition process may be performed by using an appropriate well-known method but is performed, for example, by using the following method. 
     In other words, the measurement region setting unit  23  detects, as a tip point, a point which is convex and at which a curved degree of a curve is the maximum in the curve forming a contour of the hand region  271 . The tip point may be regarded as a point indicating a fingertip. Hereinafter, a description will be made of an example of a specific process in the measurement region setting unit  23 . 
     First, the measurement region setting unit  23  performs a process of extracting a contour of the hand region  271  and further smoothing a contour shape. Next, the measurement region setting unit  23  sequentially sets a calculation point M(i) (where i=1, 2, . . . ) at a constant interval in a clockwise direction in a curve forming the contour. 
     Next, the measurement region setting unit  23  calculates a vector u(i) directed from the calculation point M(i) toward a calculation point M(i+1), and a vector v(i) directed from the calculation point M(i) toward a calculation point M(i−1). 
     The measurement region setting unit  23  calculates an angle θ (where) 0≦θ&lt;360° formed between the vectors u(i) and v(i). If 0≦θ&lt;180°, the calculation point M(i) is located at a convex shape. If 180°&lt;θ&lt;360°, the calculation point M(i) is located at a concave shape. 
     The measurement region setting unit  23  detects the calculation point M(i) in which a value of the angle θ is the minimum, and specifies the calculation point M(i) as a tip point.  FIG. 7  exemplifies the calculation points M(i), M(i−1) and M(i+1), the vectors u(i) and v(i), and the angle θ. 
     As illustrated in the part (b) of  FIG. 6 , the measurement region setting unit  23  detects a tip point  272  in the hand region  271  as a result of the above-described finger recognition process. The measurement region setting unit  23  detects a point which is longest from the tip point  272  as a root point  273  in the hand region  271 . 
     Successively, the measurement region setting unit  23  sets a region located within a range of a predetermined constant distance from the tip point  272  as the measurement region  274  (that is, a tip side region). The measurement region setting unit  23  sets a region located within a range of a predetermined constant distance from the root point  273  as the measurement region  275  (that is, a root side region). 
     The measurement region setting unit  23  sends the frame images, the hand region  271 , and the measurement regions  274  and  275  to the pulse wave calculation unit  14  and the distance calculation unit  16 . Then, in the same manner as in Embodiment 1, the pulse waves g 1 ( t ) and g 2 ( t ), and the pulse wave velocity V are calculated in the bio-information acquiring device  2 . 
     In a case where the number of measurement regions is three or greater in the measurement region setting unit  23 , appropriate regions located in the middle of the measurement region  274  and the measurement region  275  may be added as third and subsequent measurement regions. 
     The root point  273  is not limited to a point which is most distant from the tip point  272 , and may be a point which is separated from the tip point  272  by a predetermined distance or longer. 
     As a value of H used in the distance calculation unit  16 , a size of the hand of the person to be measured  121  measured in advance, or a numerical value indicating an average size of a person&#39;s hand (for example, a length from the wrist to a tip of the middle finger) may be used. 
     As another example of the present embodiment, the imaging section  11  may simultaneously measure both of the face and the hand of the person to be measured  121 , the measurement region setting unit  23  may set one or more measurement regions in each of the face and the hand. The difference calculation unit  15  may calculate a phase difference between a pulse wave in the measurement region set in the face and a pulse wave in the measurement region set in the hand. The distance calculation unit  16  may calculate an inter-part distance between the measurement region set in the face and the measurement region set in the hand by using a length between the face and the hand of the person to be measured  121  measured in advance. 
     The pulse wave velocity calculation unit  17  may calculate pulse wave velocity by using (i) the phase difference between the pulse wave in the measurement region set in the face and the pulse wave in the measurement region set in the hand, and (ii) the inter-part distance between the measurement region set in the face and the measurement region set in the hand. 
     (Effects of Bio-Information Acquiring Device  2 ) 
     According to the bio-information acquiring device  2 , a plurality of measurement regions (that is, the measurement regions  274  and  275 ) can be set in each frame image of a moving image obtained by imaging the hand of the person to be measured  121 . 
     Therefore, also in the bio-information acquiring device  2  of the present embodiment, it is possible to achieve an effect in which the pulse waves g 1 ( t ) and g 2 ( t ), and the pulse wave velocity V can be calculated without restricting the person to be measured  121  in the same manner as in the bio-information acquiring device  1  of Embodiment 1. 
     Embodiment 3 
     A description will be made of still another embodiment of the present invention with reference to  FIG. 8 . For convenience of description, members having the same functions as those of the members described in the above embodiments are given the same reference numerals, and description thereof will be omitted. 
     (Bio-Information Acquiring Device  3 ) 
       FIG. 8  is a functional block diagram illustrating a configuration of a bio-information acquiring device  3  of the present embodiment. The bio-information acquiring device  3  of the present embodiment has a configuration in which the main control section  10  of the bio-information acquiring device  1  of Embodiment 1 is replaced with a main control section  30 . 
     Remaining members of the bio-information acquiring device  3  of the present embodiment are the same as the members of the bio-information acquiring device  1  of Embodiment 1 and are thus given the same reference numerals, and description thereof will be omitted. 
     (Main Control Section  30 ) 
     The main control section  30  functions as an image acquisition unit  12 , a measurement region setting unit  13 , a pulse wave calculation unit  14 , a difference calculation unit  15 , a pulse wave post-processing unit  37  (pulse wave accuracy increasing means), and an output unit  18 . 
     Therefore, the main control section  30  of the present embodiment has a configuration in which (i) the distance calculation unit  16  is omitted from the main control section  10  of Embodiment 1, and (ii) the pulse wave velocity calculation unit  17  is replaced with the pulse wave post-processing unit  37 . 
     The main control section  30  of the present embodiment is configured to detect a pulse wave with higher accuracy. Therefore, the main control section  30  of the present embodiment is not configured for the purpose of calculating pulse wave velocity unlike the main control section  10  of Embodiment 1. 
     (Pulse Wave Post-Processing Unit  37 ) 
     The pulse wave post-processing unit  37  receives N (where N is an integer of 2 or greater) pulse waves detected in the pulse wave calculation unit  14 . Hereinafter, the N pulse waves will be referred to as a pulse wave g 1 ( t ) (first pulse wave), a pulse wave g 2 ( t ) (second pulse wave), . . . , and a pulse wave gN(t) (N-th pulse wave). N measurement regions set by the measurement region setting unit  13  will be referred to as a measurement region  1 A, a measurement region  2 A, . . . , and a measurement region NA. 
     The pulse wave g 1 ( t ) indicates a pulse wave calculated in a part corresponding to the measurement region  1 A; the pulse wave g 2 ( t ) indicates a pulse wave calculated in a part corresponding to the measurement region  2 A; and the pulse wave gN(t) indicates a pulse wave calculated in a part corresponding to the measurement region NA. 
     The pulse wave post-processing unit  37  receives (N−1) phase differences between the measurement region  1 A and the remaining measurement regions, calculated in the difference calculation unit  15 . Hereinafter, the (N−1) phase differences will be referred to as a phase difference τmin 2 , a phase difference τmin 3 , . . . , and a phase difference τminN. 
     The phase difference τmin 2  indicates a phase difference between the pulse wave g 1 ( t ) and the pulse wave g 2 ( t ); the phase difference τmin 3  indicates a phase difference between the pulse wave g 1 ( t ) and the pulse wave g 3 ( t ); and the phase difference τminN indicates a phase difference between the pulse wave g 1 ( t ) and the pulse wave gN(t). Therefore, the phase differences τmin 2  to τminN can be said to be respectively phase differences between the pulse wave g 1 ( t ) and the pulse waves g 2 ( t ) to gN(t). 
     The pulse wave post-processing unit  37  computes a post-processed pulse wave g(t) according to the following Equation (3). 
     
       
         
           
             
               
                 
                   
                       
                   
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     The post-processed pulse wave g(t) can be said to be an averaged pulse wave obtained by removing the phase differences between the N pulse waves g 1 ( t ) to gN(t). It is possible to obtain the post-processed pulse wave g(t) in which an influence of noise components included in the pulse waves g 1 ( t ) to gN(t) is reduced by using Equation (3). 
     A method of computing the post-processed pulse wave g(t) is not limited to Equation (3). For example, phase differences between the N pulse waves g 1 ( t ) to gN(t) may be removed, and an average value other than the arithmetic mean (that is, the right side of Equation (3)), such as the weighted mean or the geometric mean may be calculated and be used as the post-processed pulse wave g(t). In addition, phase differences between the N pulse waves g 1 ( t ) to gN(t) may be removed, and a statistical value such as a median or a mode may be calculated and be used as the post-processed pulse wave g(t). Further, phase differences between the N pulse waves g 1 ( t ) to gN(t) may be removed, and then a component obtained by performing multivariate analysis such as principal component analysis or independent component analysis may be used as the post-processed pulse wave g(t). 
     The pulse wave post-processing unit  37  sends a value of the post-processed pulse wave g(t) to the output unit  18 . The post-processed pulse wave g(t) is output from the output unit  18  to a device provided outside the main control section  30 . The same distance calculation unit and pulse wave velocity calculation unit as in Embodiment 1 may be additionally provided, and pulse wave velocity may be further calculated. 
     (Effect of Bio-Information Acquiring Device  3 ) 
     According to the bio-information acquiring device  3 , it is possible to achieve an effect in which the post-processed pulse wave g(t) which is a more highly accurate pulse wave can be obtained by respectively detecting the pulse waves g 1 ( t ) to gN(t) in a plurality of measurement regions  1 A to NA. 
     Embodiment 4 
     A description will be made of still another embodiment of the present invention with reference to  FIG. 9 . For convenience of description, members having the same functions as those of the members described in the above embodiments are given the same reference numerals, and description thereof will be omitted. 
     (Bio-Information Acquiring Device  4 ) 
       FIG. 9  is a functional block diagram illustrating a configuration of a bio-information acquiring device  4  of the present embodiment. The bio-information acquiring device  4  of the present embodiment has a configuration in which the main control section  10  of the bio-information acquiring device  1  of Embodiment 1 is replaced with a main control section  40 . 
     Remaining members of the bio-information acquiring device  4  of the present embodiment are the same as the members of the bio-information acquiring device  1  of Embodiment 1 and are thus given the same reference numerals, and description thereof will be omitted. 
     (Main Control Section  40 ) 
     The main control section  40  includes an image acquisition unit  12 , a measurement region setting unit  13 , a pulse wave calculation unit  44  (pulse wave detection means), a difference calculation unit  15 , a distance calculation unit  16 , a pulse wave velocity calculation unit  17 , a correction value calculation unit  49  (correction value calculation means), and an output unit  18 . Therefore, the main control section  40  of the present embodiment has a configuration in which (i) the pulse wave calculation unit  14  of the main control section  10  of Embodiment 1 is replaced with the pulse wave calculation unit  44 , and (ii) the correction value calculation unit  49  is additionally provided in the main control section  10  of Embodiment 1. 
     The main control section  40  of the present embodiment is configured for the purpose of handling a situation in which the imaging section  11  is provided near the display section  19 . 
     For example, a case is assumed in which the face of the person to be measured  121  is directed toward the display section  19 . In this case, the face of the person to be measured  121  is irradiated with light emitted from the display section  19 . The light emitted from the display section  19  temporally changes according to data (for example, a moving image) displayed on the display section  19 . Therefore, a color of a face image of the person to be measured  121  captured by the imaging section  11  temporally changes due to the light emitted from the display section  19  regardless of a blood flow. 
     Therefore, the main control section  40  of the present embodiment is configured for the purpose of correcting the temporal change in a color of the face image of the person to be measured  121 , caused by the light emitted from the display section  19 . 
     (Display Section  19  and Imaging Section  11  of Present Embodiment) 
     In the present embodiment, the display section  19  outputs a display image to the correction value calculation unit  49  at a predetermined time interval set in advance. 
     In the present embodiment, the imaging section  11  is disposed on an upper surface of the display section  19 , a lower surface of the display section  19 , or a side surface of the display section  19 . In other words, the imaging section  11  can be said to be disposed near the display section  19 . An operation of the imaging section  11  is the same as in Embodiment 1. 
     (Correction Value Calculation Unit  49 ) 
     The correction value calculation unit  49  receives a display image from the display section  19 . The correction value calculation unit  49  calculates an average value of G values of respective pixels included in the display image. The average value of the G values may be calculated in the entire display image, and may be calculated in a partial region of the display image. The partial region of the display image is set in advance in the correction value calculation unit  49  prior to calculation of G values. 
     The correction value calculation unit  49  calculates a correction value by multiplying the average value of the G values by a predetermined constant. The constant for calculating the correction value is set in advance in the correction value calculation unit  49 . 
     The correction value calculated by the correction value calculation unit  49  can be said to be a value for canceling out an influence of light emitted from the display section  19  on a temporal change in a color of a face image of the person to be measured  121 . The correction value may be calculated by performing the same process on an average value of luminance of the respective pixels instead of the average value of the G values of the respective pixels. 
     The correction value calculation unit  49  calculates the above-described correction value in each display image which is sent from the display section  19  at a predetermined time interval. The correction value calculation unit  49  records the correction value calculated at the predetermined time interval in the storage section  90 . As a result, time series data of the correction values calculated at the predetermined time interval is obtained. 
     Successively, the correction value calculation unit  49  performs a process of correcting the time interval of the time series data of the correction values to a time interval at which the imaging section  11  captures a moving image. For example, spline interpolation is used for the correction process. 
     As a result, the correction value calculation unit  49  calculates a correction value corresponding to each frame image output from the measurement region setting unit  13 . The correction value calculation unit  49  sends the correction value corresponding to each frame image to the pulse wave calculation unit  44 . 
     The calculation of the correction value corresponding to each frame image in the correction value calculation unit  49  may be collectively performed after all display images are sent to the correction value calculation unit  49 , or may be sequentially performed whenever each display image is sent to the correction value calculation unit  49 . 
     (Pulse Wave Calculation Unit  44 ) 
     In the same manner as the pulse wave calculation unit  14  of Embodiment 1, the pulse wave calculation unit  44  calculates an average value of G values of respective pixels inside a measurement region in each frame image. The pulse wave calculation unit  44  calculates a corrected average value of the G values by subtracting the correction value corresponding to each frame image from the average value of the G values of the respective pixels inside the measurement region in each frame image. 
     The pulse wave calculation unit  44  performs a smoothing process and a normalization process on the corrected average value of the G values so as to detect the pulse waves g 1 ( t ) and g 2 ( t ) in the same manner as the pulse wave calculation unit  14  of Embodiment 1. 
     In a case where a correction value is calculated on the basis of an average value of luminance of the respective pixels in the correction value calculation unit  49 , the pulse wave calculation unit  44  may detect the pulse waves g 1 ( t ) and g 2 ( t ) by using the average value of the luminance of the respective pixels inside a measurement region in each frame image. 
     In the present embodiment, a configuration is exemplified in which the display section  19  is provided alone, but a plurality of display sections may be provided. Therefore, a display section as an output target of the output unit  18  and a display section which sends a display image to the correction value calculation unit  49  may be different from each other. 
     (Effects of Bio-Information Acquiring Device  4 ) 
     According to the bio-information acquiring device  4 , it is possible to remove an influence of a temporal change in a color of a face image of the person to be measured  121 , caused by light emitted from the display section  19 , through correction using a display image which is being displayed on the display section  19 . 
     Therefore, it is possible to achieve an effect in which deterioration in accuracy of a detected pulse wave can be suppressed even in a case where a portion (for example, the face) of the person to be measured  121  which is a target for measuring a pulse wave is irradiated with the light emitted from the display section  19 . 
     In the same manner as the bio-information acquiring device  1  of Embodiment 1, the bio-information acquiring device  4  of the present embodiment is exemplified to have a configuration of calculating the pulse wave velocity V. However, a configuration of the bio-information acquiring device  4  of the present embodiment is not limited thereto, and there may be a configuration in which the post-processed pulse wave g(t) is detected in the same manner as in the bio-information acquiring device  3  of Embodiment 3. 
     The bio-information acquiring device  4  of the present embodiment may have a configuration in which the hand of the person to be measured  121  is a target part for detecting a pulse wave in the same manner as the bio-information acquiring device  2  of Embodiment 2. 
     Embodiment 5 
     A description will be made of still another embodiment of the present invention with reference to  FIG. 10 . For convenience of description, members having the same functions as those of the members described in the above embodiments are given the same reference numerals, and description thereof will be omitted. 
     (Bio-Information Acquiring Device  5 ) 
       FIG. 10  is a functional block diagram illustrating a configuration of a bio-information acquiring device  5  of the present embodiment. The bio-information acquiring device  5  of the present embodiment has a configuration in which (i) the imaging section  11  of the bio-information acquiring device  1  of Embodiment 1 is replaced with a stereo camera  51  (imaging section), and (ii) the main control section  10  of the bio-information acquiring device  1  of Embodiment 1 is replaced with a main control section  50 . 
     Remaining members of the bio-information acquiring device  5  of the present embodiment are the same as the members of the bio-information acquiring device  1  of Embodiment 1 and are thus given the same reference numerals, and description thereof will be omitted. 
     (Stereo Camera  51 ) 
     The stereo camera  51  is a camera provided with two lenses including a left eye lens and a right eye lens. The stereo camera  51  images a subject by using the left eye lens and the right eye lens so as to generate a moving image. 
     Hereinafter, a description will be made of a case where the stereo camera  51  sends a moving image generated by imaging the face of the person to be measured  121  to an image acquisition unit  52  in the same manner as the imaging section  11  of Embodiment 1. The stereo camera  51  may measure parts other than the face of the person to be measured  121 , and may image, for example, the hand of the person to be measured  121  in the same manner as the imaging section  11  of Embodiment 2. 
     (Main Control Section  50 ) 
     The main control section  50  includes the image acquisition unit  52 , a measurement region setting unit  53  (measurement region setting means), a pulse wave calculation unit  14 , a difference calculation unit  15 , a distance calculation unit  56  (distance calculation means), a pulse wave velocity calculation unit  17 , and an output unit  18 . Therefore, the main control section  50  of the present embodiment has a configuration in which the image acquisition unit  12 , the measurement region setting unit  13 , and the distance calculation unit  16  of the main control section  10  of Embodiment 1 are respectively replaced with the image acquisition unit  52 , the measurement region setting unit  53 , and the distance calculation unit  56 . 
     (Image Acquisition Unit  52 ) 
     The image acquisition unit  52  decomposes a moving image sent from the stereo camera  51  into frames so as to generate a left eye frame image and a right eye frame image. The image acquisition unit  12  sends the left eye frame image and the right eye frame image to the measurement region setting unit  53 . 
     (Measurement Region Setting Unit  53 ) 
     The measurement region setting unit  53  reads the left eye frame image and the right eye frame image sent from the image acquisition unit  52 . The measurement region setting unit  53  sets a measurement region in one of the left eye frame image (left eye image) and the right eye frame image (right eye image) in the same manner as the measurement region setting unit  13 . 
     Hereinafter, a description will be made of a case where the measurement region setting unit  53  sets two regions including a measurement region  554  (first region) and a measurement region  555  (second region) in the left eye frame image. The measurement region  554  is an upper side region of the face of the person to be measured  121  in the same as the measurement region  154 . The measurement region  555  is a lower side region of the face of the person to be measured  121  in the same manner as the measurement region  155 . 
     The measurement region setting unit  53  sends the left eye frame image and the right eye frame image, and the measurement regions  554  and  555  to the pulse wave calculation unit  14  and the distance calculation unit  56 . 
     Operations of the pulse wave calculation unit  14 , the difference calculation unit  15 , the pulse wave velocity calculation unit  17 , and the output unit  18  are the same as those in Embodiment 1, and thus description thereof will be omitted. Hereinafter, a description will be made of an operation of the distance calculation unit  56 . 
     (Distance Calculation Unit  56 ) 
     The distance calculation unit  56  calculates disparity (positional difference of each pixel, occurring between the left eye frame image and the right eye frame image) of each of pixels included in the measurement regions  554  and  555  in the left eye frame image by using both of the left eye frame image and the right eye frame image. A method of estimating disparity may employ an appropriate well-known method. 
     The distance calculation unit  56  calculates an average value of the disparities of the respective pixels included in the measurement region  554  as average disparity δ 1  (pixel). The distance calculation unit  56  calculates an average value of the disparities of the respective pixels included in the measurement region  555  as average disparity  62  (pixel). 
     The distance calculation unit  56  calculates an actual distance K1 (mm) from the subject included in the measurement region  554  to the camera and an actual distance K2 (mm) from the subject included in the measurement region  555  to the camera by using K1=(B×F)/(α×δ 1 ) and K2=(B×F)/(α×δ 2 ), respectively. 
     Here, B (mm) indicates a base line length of the stereo camera  51 , F (mm) indicates a focal length of the stereo camera  51 , and α (mm/pixel) indicates a pixel pitch (a horizontal width of one pixel) of the stereo camera  51  in the horizontal direction. 
     Next, the distance calculation unit  56  calculates an inter-part distance D (mm) which is a distance between a part corresponding to the measurement region  554  and a part corresponding to the measurement region  555  according to the following Equation (4). 
       [Equation 4] 
         D =√{square root over (( X   1   −X   2 ) 2 +( Y   1   −Y   2 ) 2 +( K   1   −K   2 ) 2 )}  (4)
 
     Here, X1, X2, Y1, and Y2 are expressed by the following Equation (5). 
     
       
         
           
             
               
                 
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     β (mm/pixel) indicates a pixel pitch (a vertical width of one pixel) of the left eye frame image in the vertical direction. In addition, m indicates the number of pixels of the left eye frame image in the horizontal direction, and n indicates the number of pixels of the left eye frame image in the vertical direction. (x1,y1) are coordinates indicating a lower end point of the measurement region  554 , and (x2,y2) are coordinates indicating an upper end point of the measurement region  555 . The coordinates (x1,y1) and (x2,y2) may be calculated in the same manner as in the distance calculation unit  16  of Embodiment 1. 
     The inter-part distance D calculated by the distance calculation unit  56  of the present embodiment is an amount obtained by taking into consideration a disparity difference (depth difference) between the measurement region  554  and the measurement region  555 , and can be said to be an amount which is higher in accuracy than the inter-part distance D calculated by the distance calculation unit  16  of Embodiment 1. 
     The distance calculation unit  56  sends a value of the inter-part distance D to the pulse wave velocity calculation unit  17 . The pulse wave velocity calculation unit  17  can calculate the pulse wave velocity V with higher accuracy by using the value of the inter-part distance D calculated by the distance calculation unit  56  than in Embodiment 1. 
     The inter-part distance D may not necessarily be calculated by using Equation (4). For example, the inter-part distance D may be calculated by correcting rotation of the stereo camera  51  or an influence of characteristics of the lenses provided in the stereo camera  51 . 
     In a case where the number of measurement regions is three or greater, the inter-part distance D may be calculated in each of two combinations of the measurement regions taken from a plurality of measurement regions. 
     (Effects of Bio-Information Acquiring Device  5 ) 
     According to the bio-information acquiring device  5 , it is also possible to calculate the inter-part distance D corresponding to each measurement region in consideration of a disparity difference between the respective measurement regions and by using a moving image captured by the stereo camera  51 . Therefore, it is possible to achieve an effect in which the pulse wave velocity V can also be calculated with higher accuracy. 
     In the same manner as the bio-information acquiring device  1  of Embodiment 1, the bio-information acquiring device  5  of the present embodiment is exemplified to have a configuration in which the hand of the person to be measured  121  is a measurement target. However, a configuration of the bio-information acquiring device  5  of the present embodiment is not limited thereto, and there may be a configuration in which the hand of the person to be measured  121  is a measurement target in the same manner as in the bio-information acquiring device  2  of Embodiment 2. 
     Embodiment 6 
     A description will be made of still another embodiment of the present invention with reference to  FIG. 11 . For convenience of description, members having the same functions as those of the members described in the above embodiments are given the same reference numerals, and description thereof will be omitted. 
     (Bio-Information Acquiring Device  6 ) 
       FIG. 11  is a functional block diagram illustrating a configuration of a bio-information acquiring device  6  of the present embodiment. The bio-information acquiring device  6  of the present embodiment has a configuration in which (i) the imaging section  11  of the bio-information acquiring device  1  of Embodiment 1 is replaced with a first imaging section  61   a  (imaging section) and a second imaging section  61   b  (imaging section). 
     Remaining members of the bio-information acquiring device  6  of the present embodiment are the same as the members of the bio-information acquiring device  1  of Embodiment 1 and are thus given the same reference numerals, and description thereof will be omitted. 
     A schematic configuration of the bio-information acquiring device  6  of the present embodiment is different from that of the bio-information acquiring device  1  of Embodiment 1 in that a plurality of imaging sections are provided. In the present embodiment, the bio-information acquiring device  6  is exemplified to have a configuration in which the two imaging sections (the first imaging section  61   a  and the second imaging section  61   b ) are provided, but the number of imaging sections is not limited to two and may be three or greater. 
     The first imaging section  61   a  and the second imaging section  61   b  respectively image different parts of the person to be measured  121 . For example, the first imaging section  61   a  images the face of the person to be measured  121 , and the second imaging section  61   b  images the fingers of the person to be measured  121 . 
     The first imaging section  61   a  and the second imaging section  61   b  output generated moving images to the image acquisition unit  12 . The imaging in the first imaging section  61   a  and the second imaging section  61   b  are preferably performed in synchronization with each other. 
     The image acquisition unit  12  decomposes each of the plurality of moving images output from the first imaging section  61   a  and the second imaging section  61   b  into frame images. 
     The measurement region setting unit  13  sets a measurement region in the frame image. As in the present embodiment, in an example in which each of the first imaging section  61   a  and the second imaging section  61   b  images the face and the fingers, the measurement region is set in a specific region inside a face region in a frame image of a moving image obtained by imaging the face in the same manner as in Embodiment 1. One or a plurality of measurement regions may be set in the face region. 
     One or more measurement regions are also set in a frame image of a moving image obtained by imaging the fingers. For example, in a case where the entire image is obtained as a region of the fingers through close imaging, the entire image may be set as a single measurement region. In the above-described manner, in relation to a plurality of moving images, one or more measurement regions are set in each frame image. 
     The pulse wave calculation unit  14  calculates a pulse wave in each measurement region in the same manner as in Embodiment 1. The difference calculation unit  15  calculates a phase difference between pulse waves calculated in the respective measurement regions for each combination of two measurement regions which can be taken in the same manner as in Embodiment 1. In a case where a plurality of imaging sections are not synchronized with each other, the difference calculation unit  15  also corrects difference between imaging timings. 
     The distance calculation unit  16  calculates an inter-part distance for each combination of two measurement regions which can be taken by using the respective pulse waves calculated in the measurement regions. In a case where two measurement regions are imaged by different imaging sections, a length of a part of the body of the person to be measured, measured in advance, may be used to calculate an inter-part distance without being changed. 
     The pulse wave velocity calculation unit  17  calculates pulse wave velocity by using the pulse waves, the phase differences, and the inter-part distance in the same manner as in Embodiment 1. In the same manner as in Embodiment 3, a pulse wave post-processing unit may be provided, and accuracy of a pulse wave may be increased instead of calculating pulse wave velocity. 
     (Effects of Bio-Information Acquiring Device  6 ) 
     According to the bio-information acquiring device  6 , it is possible to achieve an effect in which a phase difference between pulse waves can be calculated even in a plurality of parts which are hardly imaged by a single camera. For example, as the first imaging section  61   a , an in-camera of a smart phone (that is, a camera mounted on a surface of a side on which a display section of the smart phone is disposed) may be used, and, as the second imaging section  61   b , an out-camera of the smart phone (that is, a camera mounted on a surface of the opposite side to the surface on which the in-camera is provided) may be used. 
     Modification Example 
     In the above-described Embodiments 1 to 6, a description has been made of a case where the face or the hand of the person to be measured  121  is a measurement target, but a measurement target is not limited thereto. A measurement target for detecting a pulse wave may be a part in which the skin is exposed among predetermined parts of the body of the person to be measured  121 , and may be, for example, the arm, the leg, or the abdomen of the person to be measured  121 . 
     [Implementations Using Software] 
     The control blocks (especially, the main control sections  10 ,  20 ,  30 ,  40  and  50 ) of the bio-information acquiring devices  1 ,  2 ,  3 ,  4 ,  5  and  6  may be implemented by a logic circuit (hardware) formed on an integrated circuit (IC chip) or the like, and may be implemented by software by using a CPU. 
     In the latter case, each of the bio-information acquiring devices  1 ,  2 ,  3 ,  4 ,  5  and  6  includes a CPU executing a command of a program which is software realizing each function, a ROM (read only memory) or a storage device (this is referred to as a “recording medium”) in which the program or various data items are recorded in a computer (or the CPU) readable manner, a RAM (random access memory) in which the program is developed, and the like. The computer (or the CPU) reads the program from the recording medium and executes the program, and thus the object of the present invention is achieved. As the recording medium, a “non-transitory tangible medium”, for example, a tape, a disk, a card, a semiconductor memory, or a programmable logic circuit may be used. The program may be supplied to the computer via any transmission medium (a communication network, a broadcast wave, or the like) which can transmit the program. The present invention can also be implemented in the form of a data signal which is embodied through electronic transmission of the program and is embedded in a carrier. 
     CONCLUSION 
     A bio-information acquiring device ( 1 ) related to Aspect 1 of the present invention derives bio-information from a moving image obtained by imaging a living body (for example, the person to be measured  121 ), and includes region specifying means (measurement region setting unit  13 ) for specifying, through image processing, regions (for example, the measurement regions  154  and  155 ) respectively corresponding to at least two parts of the living body in frame images forming the moving image; pulse wave detection means (pulse wave calculation unit  14 ) for detecting pulse waves (for example, the pulse waves g 1 ( t ) and g 2 ( t )) in the at least two parts by referring to the regions specified by the region specifying means; and phase difference calculation means (difference calculation unit  15 ) for calculating a phase difference (τmin) between the pulse waves in the at least two parts, detected by the pulse wave detection means. 
     According to the configuration, even if a living body moves during measurement, regions on a frame image corresponding to at least two parts of the living body, that is, regions on the frame image referred to for detecting pulse waves are specified through image processing. Therefore, according to the configuration, it is possible to achieve an effect in which a phase difference between the pulse waves in the at least two parts can be calculated without restricting the living body during measurement. 
     In the above Aspect 1, the bio-information acquiring device related to Aspect 2 of the present invention may further include distance calculation means (distance calculation unit  16 ) for calculating an inter-part distance (D) which is a distance between the at least two parts by using a distance (d) between the regions specified by the region specifying means; and velocity calculation means (pulse wave velocity calculation unit  17 ) for calculating pulse wave velocity (V) by using the phase difference calculated by the phase difference calculation means and the inter-part distance calculated by the distance calculation means. 
     According to the configuration, it is possible to achieve an effect in which the pulse wave velocity can be calculated without restricting a living body during measurement. 
     In the above Aspect 1 or 2, the bio-information acquiring device related to Aspect 3 of the present invention may further include pulse wave accuracy increasing means (pulse wave post-processing unit  37 ) for calculating a statistical value (for example, the post-processed pulse wave g(t)) excluding the phase difference calculated by the phase difference calculation means in at least two pulse waves detected by the pulse wave detection means. 
     According to the configuration, it is possible to achieve an effect in which a pulse wave with noise reduced and with higher accuracy than in the related art can be calculated without restricting a living body during measurement. 
     According to the bio-information acquiring device related to Aspect 4 of the present invention, in any one of the above Aspects 1 to 3, the moving image may be obtained as a result of being captured by a plurality of cameras (for example, the first imaging section  61   a  and the second imaging section  61   b ). 
     According to the configuration, it is possible to achieve an effect in which a phase difference between pulse waves can be calculated even in a plurality of parts which are hardly imaged by a single camera. 
     According to the bio-information acquiring device related to Aspect 5 of the present invention, in any one of the above Aspects 1 to 4, the living body may be a person, the moving image may be obtained by imaging at least one of the face and the hand of the person, and the region specifying means may specify, through image processing, regions (for example, the measurement regions  154  and  155 , and the measurement regions  274  and  275 ) respectively corresponding to at least two parts included in at least one of the face and the hand. 
     According to the configuration, it is possible to achieve an effect in which accurate pulse wave velocity can be calculated without restricting a living body during measurement by using at least one of, for example, a well-known face detection process and a well-known hand region detection process. 
     According to the bio-information acquiring device related to Aspect 6 of the present invention, in any one of the above Aspects 1 to 5, the at least two parts may be parts whose distances from the heart of the living body are different from each other. 
     According to the configuration, it is possible to achieve an effect in which a part suitable for calculating a phase difference between pulse waves can be selected. 
     In any one of the above Aspects 1 to 6, the bio-information acquiring device related to Aspect 7 of the present invention may further include correction value calculation means (correction value calculation unit  49 ) for calculating a correction value for canceling out an influence of light emitted from a display section on detection of a pulse wave by referring to an image displayed on the display section ( 19 ), and the pulse wave detection means may detect the pulse wave by further using the correction value. 
     According to the configuration, it is possible to achieve an effect in which a phase difference between pulse waves can be calculated more accurately. 
     According to the bio-information acquiring device related to Aspect 8 of the present invention, in the above Aspect 2, the moving image may include a left eye image (left eye frame image) and a right eye image (right eye frame image) obtained by imaging the living body with a stereo camera ( 51 ), and the distance calculation means may calculate the inter-part distance by further using average disparity (δ 1  and δ 2 ) which is calculated by using the left eye image and the right eye image. 
     According to the configuration, it is possible to achieve an effect in which pulse wave velocity can be calculated more accurately. 
     In a bio-information acquiring method related to Aspect 9 of the present invention of deriving bio-information from a moving image obtained by imaging a living body, the method includes a region specifying step of specifying, through image processing, regions respectively corresponding to at least two parts of the living body in frame images forming the moving image; a pulse wave detection step of detecting pulse waves in the at least two parts by referring to the regions specified in the region specifying step; and a phase difference calculation step of calculating a phase difference between the pulse waves in the at least two parts, detected in the pulse wave detection step. 
     According to the configuration, it is possible to achieve an effect in which a phase difference between the pulse waves in the at least two parts can be calculated without restricting the living body during measurement in the same manner as in the bio-information acquiring device related to Aspect 1. 
     The bio-information acquiring device related to each aspect of the present invention may be implemented by a computer. In this case, the category of the present invention also includes a control program for the bio-information acquiring device which causes the bio-information acquiring device to be implemented by the computer by causing the computer to be operated as each piece of means included in the bio-information acquiring device, and a computer readable recording medium recording the program thereon. 
     APPENDIXES 
     The present invention is not limited to the respective above-described embodiments and may be variously modified within the scope disclosed in the claims, and embodiments obtained by combining the disclosed technical means with other embodiments as appropriate are also included in the technical scope of the present invention. A new technical feature may be formed by combining the pieces of technical means disclosed in the respective embodiments with each other. 
     The present invention may also be expressed as follows. 
     In other words, a bio-information acquiring device related to an aspect of the present invention calculates a pulse wave from an image, and includes measurement region setting means for setting at least two measurement regions for calculating the pulse wave; pulse wave detection means for calculating a pulse wave in each measurement region; and difference calculation means for calculating difference between the pulse waves obtained by the pulse wave detection means. 
     The bio-information acquiring device related to the aspect of the present invention further includes distance calculation means for calculating a distance between the measurement regions; and pulse wave velocity calculation means for calculating pulse wave velocity on the basis of the difference and the distance between the measurement regions. 
     In the bio-information acquiring device related to the aspect of the present invention, the image includes a face image of a person in whom a pulse wave is measured, and an entire measurement region setting unit sets at least two regions among regions of the face image of the person to be measured as the measurement regions. 
     In the bio-information acquiring device related to the aspect of the present invention, the image includes a hand image of a person in whom a pulse wave is measured, and an entire measurement region setting unit sets at least two regions among regions of the hand image of the person to be measured as the measurement regions. 
     The bio-information acquiring device related to the aspect of the present invention further includes pulse wave post-processing means for improving accuracy of the pulse waves by using difference between the pulse waves. 
     The bio-information acquiring device related to the aspect of the present invention further includes display means for displaying an image, and correction value calculation means for calculating a correction value on the basis of the image displayed by the display means, and the pulse wave detection means calculates the pulse wave by using the correction value. 
     In the bio-information acquiring device related to the aspect of the present invention, the image obtained by imaging the person to be measured is captured by a stereo camera, and the distance calculation means calculates the distance between the measurement regions by using a depth difference between the measurement regions. 
     INDUSTRIAL APPLICABILITY 
     The present invention may be used for a bio-information acquiring device, particularly, a device measuring a pulse wave. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1 ,  2 ,  3 ,  4 ,  5 ,  6  BIO-INFORMATION ACQUIRING DEVICE 
               11  IMAGING SECTION 
               13 ,  23 ,  53  MEASUREMENT REGION SETTING UNIT (REGION SPECIFYING MEANS) 
               14 ,  44  PULSE WAVE CALCULATION UNIT (PULSE WAVE DETECTION MEANS) 
               15  DIFFERENCE CALCULATION UNIT (PHASE DIFFERENCE CALCULATION MEANS) 
               16 ,  56  DISTANCE CALCULATION UNIT (DISTANCE CALCULATION MEANS) 
               17  PULSE WAVE VELOCITY CALCULATION UNIT (VELOCITY CALCULATION MEANS) 
               19  DISPLAY SECTION 
               37  PULSE WAVE POST-PROCESSING UNIT (PULSE WAVE ACCURACY INCREASING MEANS) 
               49  CORRECTION VALUE CALCULATION UNIT (CORRECTION VALUE CALCULATION MEANS) 
               51  STEREO CAMERA (IMAGING SECTION) 
               61   a  FIRST IMAGING SECTION (IMAGING SECTION) 
               61   b  SECOND IMAGING SECTION (IMAGING SECTION) 
               121  PERSON TO BE MEASURED 
               154 ,  155 ,  274 ,  275 ,  554 ,  555  MEASUREMENT REGION 
             D INTER-PART DISTANCE 
             N INTEGER (INTEGER INDICATING NUMBER OF MEASUREMENT REGIONS) 
               1 A TO NA MEASUREMENT REGION 
             g 1 ( t ) TO gN(t) PULSE WAVE 
             g(t) POST-PROCESSED PULSE WAVE (STATISTICAL VALUE OF PULSE WAVE) 
             τmin, τmin 2  TO τminN PHASE DIFFERENCE 
             δ 1 , δ 2  AVERAGE DISPARITY 
             V PULSE WAVE VELOCITY