Abstract:
A non-invasive blood component measuring device comprising: a light source section for irradiating a light to a blood vessel through a skin; an imaging section for imaging the irradiated blood vessel through the skin; and a controller, including a memory under control of a processor, the memory storing instructions enabling the processor to carry out operations, comprising: creating a concentration profile based on an image obtained by imaging the blood vessel with the imaging section; calculating a blood component concentration based on the concentration profile; acquiring a shape feature of the concentration profile; and correcting the blood component concentration based on the shape feature of the concentration profile is disclosed. A non-invasive blood component measuring method is also disclosed.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. JP2007-171875 filed Jun. 29, 2007, the entire content of which is hereby incorporated by reference. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to a non-invasive blood component measuring device and a non-invasive blood component measuring method for percutaneously measuring a blood component to be measured without drawing blood from a living body. 
       BACKGROUND 
       [0003]    A method and a device for non-invasively measuring hemoglobin concentration without drawing blood from a subject have been conventionally proposed. U.S. Pat. No. 6,061,583 Publication discloses a device for illuminating a living body tissue including blood vessels with a light source and imaging a transmitted light image, extracting an image concentration distribution distributed across the blood vessel from the imaged image as a concentration profile of the image, cutting out a portion corresponding to the blood vessel from the extracted concentration profile at a baseline, and measuring the blood component based on the cutout profile as a “non-invasive blood examination device”. 
         [0004]    The hemoglobin concentration is calculated using a peak height of the concentration profile as a ratio between a portion where blood exists and a portion where blood does not exist, and a distribution width (half-value width) of the concentration profile at the height of 50% of the peak as the width of the blood vessel. That is, if the cross section of a blood vessel is a perfect circle, the blood vessel diameter in the imaging direction and the blood vessel diameter in a direction orthogonal to the imaging direction become equal. Therefore, the hemoglobin concentration can be calculated by substituting the half-value width reflecting the blood vessel diameter in the direction orthogonal to the imaging direction with a distance the illumination light has moved through the blood, and performing a calculation process assuming the Law of Beer is approximately satisfied. 
         [0005]    However, the cross section of the blood vessel is not necessarily always a perfect circle, and sometimes deforms due to various reasons. For instance, if blood is not sufficiently flowing through the blood vessel, the pressure of the blood flow weakens and the blood vessel constricts, whereby the cross section of the blood vessel becomes an ellipse rather than a perfect circle. If the external temperature is low or depending on the bend of the wrist in time of measurement, or if the peripheral blood vessel has disability, the blood flow volume tends to become insufficient, whereby the blood vessel constricts and the cross section of the blood vessel deforms. 
         [0006]    In the invention disclosed in U.S. Pat. No. 6,061,583, the hemoglobin concentration is measured on the assumption that the cross section of the blood vessel is a perfect circle, and thus a correct measurement cannot be made if the cross section of the blood vessel deforms and a measurement error creates with the actual measurement value. 
       SUMMARY OF THE INVENTION 
       [0007]    The scope of the present invention is defined solely by the appended claims, and is not affected to any degree by the statements within this summary. 
         [0008]    A first aspect of the present invention is, a non-invasive blood component measuring device comprising: a light source section for irradiating a light to a blood vessel through a skin; an imaging section for imaging the irradiated blood vessel through the skin; and a controller, including a memory under control of a processor, the memory storing instructions enabling the processor to carry out operations, comprising: creating a concentration profile based on an image obtained by imaging the blood vessel with the imaging section; calculating a blood component concentration based on the concentration profile; acquiring a shape feature of the concentration profile; and correcting the blood component concentration based on the shape feature of the concentration profile. 
         [0009]    A second aspect of the present invention is, a non-invasive blood component measuring device comprising: a light source section for irradiating a light to a blood vessel through a skin; an imaging section for imaging the irradiated blood vessel through the skin; and a controller, including a memory under control of a processor, the memory storing instructions enabling the processor to carry out operations, comprising: creating a concentration profile based on an image obtained by imaging the blood vessel with the imaging section; and calculating a blood component concentration based on a peak height of the concentration profile, and a shape feature of the concentration profile. 
         [0010]    A third aspect of the present invention is, a non-invasive blood component measuring method comprising the steps of: irradiating a light to a blood vessel through a skin and imaging the irradiated blood vessel through the skin; creating a concentration profile distributed across the blood vessel based on an image obtained by imaging the blood vessel; calculating a blood component concentration based on the concentration profile; acquiring a shape feature of the concentration profile; and correcting the blood component concentration based on the shape feature of the concentration profile. 
         [0011]    A fourth aspect of the present invention is, a non-invasive blood component measuring method comprising the steps of: irradiating a light to a blood vessel through a skin and imaging the irradiated blood vessel through the skin; creating a concentration profile distributed across the blood vessel based on an image obtained by imaging the blood vessel; and calculating a blood component concentration based on a peak height of the concentration profile and a shape feature of the concentration profile. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  shows a schematic structure of a non-invasive blood component measuring device according to an embodiment; 
           [0013]      FIG. 2  is a cross sectional explanatory view showing the non-invasive blood component measuring device shown in  FIG. 1 ; 
           [0014]      FIG. 3  is a top view showing the structure of the light source; 
           [0015]      FIG. 4  shows a positional relationship of light emitting diodes arranged on a holding plate; 
           [0016]      FIG. 5  is a block diagram showing a structure of a measurement unit; 
           [0017]      FIG. 6  shows an example of a screen displayed when the non-invasive blood component measuring device is in a standby state; 
           [0018]      FIG. 7  shows an example of a screen displayed when the non-invasive blood component measuring device is aligned with a blood vessel position; 
           [0019]      FIG. 8  shows an example of a screen displayed when the non-invasive blood component measuring device completes a measurement; 
           [0020]      FIG. 9  is a flowchart showing a measurement operation by the non-invasive blood component measuring device; 
           [0021]      FIG. 10  is a view in which a rectangular region including an imaging region CR is coordinate divided into two-dimensional coordinates of x, y in a range of 0≦x≦640, 0≦y≦480; 
           [0022]      FIG. 11  shows an example of a luminance profile (luminance profile PF) of pixels in the x direction at the predetermined y coordinate; 
           [0023]      FIG. 12  illustrates a method for determining the position of a blood vessel; 
           [0024]      FIG. 13  is a flowchart showing details of a measuring process of a hemoglobin concentration executed in step S 11  of the flowchart shown in  FIG. 9 ; 
           [0025]      FIG. 14  shows a distribution of concentration D with respect to position X; 
           [0026]      FIG. 15  shows a distribution of luminance B with respect to position X; 
           [0027]      FIG. 16  shows a distribution of concentration D with respect to position X; 
           [0028]      FIG. 17  shows explanatory view showing the calculation process of a distribution width at a cutout height H; 
           [0029]      FIG. 18  shows a graph plotting the relationship between the kurtosis of the concentration profile and the distribution width when the flatness degree of the cross section of the blood vessel is changed step-wise; 
           [0030]      FIG. 19  shows a graph plotting the actually measured value obtained from the blood cell counting device and the calculated value by the non-invasive blood component measuring device according to the present embodiment for the hemoglobin concentration of a plurality of subjects; 
           [0031]      FIG. 20  shows the result of measuring the error between the hemoglobin concentration calculated by the non-invasive blood component measuring device according to the present embodiment while changing the bend of the wrist and the actually measured value obtained from the blood cell counting device for the hemoglobin concentration of a plurality of subjects; and 
           [0032]      FIG. 21  is a flowchart showing details of a measuring process of a hemoglobin concentration according to another embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0033]    The preferred embodiments of the present invention are described hereinafter with reference to the drawings. 
         [0034]    An embodiment of a non-invasive blood component measuring device of the present invention will now be described in detail with reference to the accompanying drawings. 
         [0035]      FIG. 1  shows a schematic configuration of a non-invasive blood component measuring device  1  according to a first embodiment of the present invention. The non-invasive blood component measuring device  1  is a wrist watch type device and includes a device body  3  and a holder  4 . The device body  3  is attached to the wrist of a human by means of the holder  4 . The device body  3  is attached in a position adjustable manner in a peripheral direction of the wrist by means of the holder  4 . A power/execute key  38  and a menu key  39  for enabling the user to operate the non-invasive blood component measuring device  1  are arranged on the side face of the device body  3 . A pressurization band  2  (cuff) is attached to the arm of the user closer to the heart than the wrist. The pressurization band  2  pressurizes the arm of the user at a predetermined pressure to inhibit the blood flow near the wrist, thereby dilating the blood vessel (vein) of the wrist. Thus, the imaging of the blood vessel is facilitated by making the measurement with the wrist being pressurized with the pressurization band  2 . 
         [0036]      FIG. 2  shows a cross sectional explanatory view showing a configuration of the non-invasive blood component measuring device  1 . The device body  3  includes an outer case  35 , a back lid  37  arranged on the back side of the outer case  35 , and an engagement member  41  attached to the lower part of the back lid  37 . A cylindrical unit holding part  35   a  for accommodating a measurement unit  5 , to be hereinafter described, is formed at the center of the outer case  35 . A space part for receiving the unit holding part  35   a  is formed at the center of the back lid  37  and the engagement member  41 . A pair of projections  35   c ,  35   d  are extending horizontally from an intermediate part of an outer wall of the unit holding part  35   a . Compression springs  37   a ,  37   b  are connected between the projection  35   c  and the back lid  37 , and between the projection  35   d  and the back lid  37 , respectively. The outer case  35  is biased towards the back lid  37  by the compression springs  37   a ,  37   b . An engagement part  41   a  depressed to a concave shape is formed at the side face of the engagement member  41  so as to be able to engage with an inner projection  42   a  of a supporting board  42  to be hereinafter described. 
         [0037]    The holder  4  is configured by the supporting board  42  and a wrist band  43 . The supporting board  42  has an upper surface shape of a rectangle, and has a circular opening to be fitted with the engagement member  41  of the device body  3  formed at a central part. The engagement part  42   a  to be rotatable engaged by the engagement member  41  about an axis AZ is formed at the edge of the opening. A stretchable rubber wrist band  43  is attached to the supporting board  42 . The outer case  35  and the back lid  37  are made of material that does not transmit light. 
         [0038]    The measurement unit  5  is supported by the unit holding part  35   a . The measurement unit  5  is configured by a light source section  51 , an imaging section  52 , a controller  53 , and a display section  54 , wherein the light source section  51 , the imaging section  52 , the display section  54 , and the controller  53  are connected by a wiring code, a flat cable (not shown), or the like so that electric signals can be mutually exchanged. 
         [0039]    The light source section  51  will now be described.  FIG. 3  is a top view showing the structure of the light source  51 . The light source section  51  is configured by a circular plate shaped holding plate  51   a , and four light emitting diodes R 1 , R 2 , L 1 , and L 2  held by the holding plate  51   a . A circular opening  51   b  for passing a light entering the imaging section  52  is formed at the center of the holding plate  51   a , and the light emitting diodes are arranged along the periphery of the opening  51   b.    
         [0040]      FIG. 4  shows a position relationship of the four light emitting diodes arranged on the holding plate  51   a . The light emitting diodes R 1 , R 2 , L 1 , and L 2  are arranged so as to be symmetric to a first axis AY and a second axis AX passing through the center of the opening  51   b  and being orthogonal to each other. In a state the non-invasive blood component measuring device  1  is attached to the wrist, an imaging region CR of the wrist surface is a region imaged by the imaging section  52 , and displayed on the display section  54 . A region  62   c  between an index line  62   a  on the light emitting diodes L 1  and L 2  (second light source section) side and an index line  62   b  on the light emitting diodes R 1  and R 2  (first light source section) side is the region suited for imaging by the imaging section  52 , that is, the region where the blood vessel is to be positioned in time of imaging. The index lines  62   a  and  62   b  are displayed on the display section  54  by the controller  53 . When analyzing the blood component, the attachment position of the device body  3  is adjusted so that an arbitrary blood vessel of the wrist is positioned within the region  62   c . The blood vessel is illuminated with a near-infrared ray (center wavelength=805 nm) from both sides by the light emitting diodes R 1 , R 2 , L 1 , and L 2 . 
         [0041]    The configuration of the imaging section  52  will now be described. As shown in  FIG. 2 , the imaging section  52  is configured by a lens  52   a  for narrowing the focus of a reflected light, a lens barrel  52   b  for fixing the lens  52   a , and a CCD camera  52   c  for imaging, and is able to capture the image of the imaging region CR. The lens  52   a  and the lens barrel  52   b  are inserted to a cylindrical light shield tube  52   d  having a black interior portion. The Imaging section  52   c  capture the image, and transmits the same to the controller  53  as an image signal. 
         [0042]    The configuration of the controller  53  will be described. The controller  53  is arranged on the upper part of the Imaging section  52   c .  FIG. 5  is a block diagram showing a configuration of the measurement unit  5 . The controller  53  includes a CPU  53   a , a main memory  53   b , a flash memory card reader  53   c , a light source section input/output interface  53   d , a frame memory  53   e , an image input interface  53   f , an input interface  53   g , a communication interface  53   h , and an image output interface  53   i . The CPU  53   a , the main memory  53   b , the flash memory card reader  53   c , the light source section input/output interface  53   d , the frame memory  53   e , the image input interface  53   f , the input interface  53   g , the communication interface  53   h , and the image output interface  53   i  are connected by way of a data transmission line so as to be able to mutually transmit data. According to such configuration, the CPU  53   a  can readout and write data with respect to the main memory  53   b , the flash memory card reader  53   c , and the frame memory  53   e , and transmit/receive data with respect to the light source section input/output interface  53   d , the image input interface  53   f , the input interface  53   g , the image output interface  53   i , and the communication interface  53   h.    
         [0043]    The CPU  53   a  is capable of executing the computer program loaded in the main memory  53   b . The present device functions as the non-invasive blood component measuring device when the computer program, as hereinafter described, is executed by the CPU  53   a.    
         [0044]    The main memory  53   b  is configured by SRAM, DRAM, or the like. The main memory  53   b  is used to read out the computer program stored in the flash memory card  53   j . The main memory is also used as a work region of the CPU  53   a  when executing the computer programs. 
         [0045]    The flash memory card reader  53   c  is used to read out the data stored in the flash memory card  53   j . The flash memory card  53   j  includes a flash memory (not shown), and is able to hold the data without being supplied with power from the outside. The computer program executed by the CPU  53   a , the data used for the same, and the like are stored in the flash memory card  53   j.    
         [0046]    An operating system complying with TRON specification is installed in the flash memory card  53   j . The operating system is not limited thereto, and may be operating system providing graphical user interface environment such as Windows (registered trademark) manufactured and sold by US Microsoft Corp. In the following description, the computer program according to the present embodiment is assumed to operate on the operating system. 
         [0047]    The light source section input/output interface  53   d  is configured by an analog interface including D/A converter, A/D converter, and the like. The light source section input/output interface  53   d  can be electrically connected with the four light emitting diodes R 1 , R 2 , L 1 , and L 2  arranged in the light source section  51  by the respective electrical signal lines to perform the operation control of the relevant light emitting diode. The relevant light source section input/output interface  53   d  controls the current to be applied to the light emitting diodes R 1 , R 2 , L 1 , and L 2  based on the computer program to be hereinafter described. 
         [0048]    The frame memory  53   e  is configured by SRAM, DRAM, or the like. The frame memory  53   e  is used to store data when the image input interface  53   f  to be hereinafter described executes image processing. 
         [0049]    The image input interface  53   f  includes a video digitize circuit (not shown) with an A/D converter. The image input interface  53   f  is electrically connected to the Imaging section  52   c  by an electrical signal line, so that image signals are input from the Imaging section  52   c . The image signal input from the Imaging section  52   c  is A/D converted in the image input interface  53   f . The image data digital converted as above is stored in the frame memory  53   e.    
         [0050]    The input interface  53   g  is configured by an analog interface including A/D converter. The power/execute key  38  and the menu key  39  are electrically connected to the input interface  53   g . According to such configuration, the user can use the menu key  39  to select the operation item of the device, and use the power/execute key  38  to cause the device to turn ON/OFF the power of the device and to execute the operation selected by the menu key  39 . 
         [0051]    The communication interface  53   h  is configured by serial interface such as USB, IEEE1394, RS-232C; or parallel interface such as SCSI. The controller  53  can transmit and receive data with an external connection equipment such as mobile computer and portable telephone by using a predetermined communication protocol through the communication interface  53   h . Thus, the controller  53  transmits measurement result data to the external connection equipment through the relevant communication interface  53   h.    
         [0052]    The image output interface  53   i  is electrically connected to the display section  54 , and outputs the image signal based on the image data provided from the CPU  53   a  to the display section  54 . 
         [0053]    The display section  54  will now be described. As shown in  FIG. 2 , the display section  54  is arranged at the upper part of the measurement unit  5 , and is supported by the outer case  35 . The display section  54  is configured by a liquid crystal display, and performs a screen display according to the image signal input from the image output interface  53   i . The screen display is switched according to the state of the non-invasive blood component measuring device  1 , and for example, a screen corresponding to a measurement end state is displayed on the display section  54  in standby state, or in time of blood vessel alignment. 
         [0054]      FIG. 6  shows one example of a screen displayed when the non-invasive blood component measuring device  1  is in the standby state. If the non-invasive blood component measuring device  1  is in the standby state, the date and the time are displayed at the center of the screen of the display section  54 . A menu display region  54   a  is provided at the lower right of the screen of the display section  54 , wherein the operation of the non-invasive blood component measuring device  1  of when the power/execute key  38  is pushed is displayed, and “measure” is displayed in the standby state. 
         [0055]      FIG. 7  shows an example of a screen displayed when the non-invasive blood component measuring device is aligned with a blood vessel position. The non-invasive blood component measuring device  1  according to the present embodiment is configured so that an index indicating a region suited for imaging by the imaging section  52  is displayed on the display section  54  and whether or not the blood vessel image is positioned within the region suited for imaging is determined. When aligning the blood vessel, a blood vessel pattern  61  formed as hereinafter described, and index lines  62   a ,  62   b  are displayed along with the image. 
         [0056]    The index lines  62   a  and the index line  62   b  are displayed in red if the blood vessel pattern  61  is not positioned within the region  62   c  (see  FIG. 4 ), and the index lines  62   a  and the index line  62   b  are displayed in blue if the blood vessel pattern  61  is positioned within the region  62   c . The user then can easily understand whether or not the blood vessel pattern  61  is positioned within the region  62   c.    
         [0057]    According to such display, the user performs position adjustment by moving or rotating the device body  3  so that the blood vessel pattern  61  is within the region  62   c.    
         [0058]    In time of such blood vessel alignment, “continue” is displayed in the menu display region  54   a , wherein when the blood pattern  61  is positioned within the region  62   c , the index lines  62   a ,  62   b  are displayed in blue, the power/execute key  38  is validated, and the measurement is continued when the user pushes the power/key key  38 . 
         [0059]      FIG. 8  shows an example of a screen displayed when the non-invasive blood component measuring device completes a measurement. The measurement result of hemoglobin concentration or blood component is displayed on the display section  54  in a digital representation as “15.6 g/dl” so as to be easily viewed by the user. “Confirm” is displayed on the menu display region  54   a  in this case. 
         [0060]    The measurement operation of the non-invasive blood component measuring device  1  will now be described.  FIG. 9  is a flowchart showing the measurement operation by the non-invasive blood component measuring device  1 . First, the pressurization band  2  is attached to the arm of the user, and the non-invasive blood component measuring device  1  is attached to the wrist (see  FIG. 1 ). In this case, the arm of the user is pressurized with a predetermined pressure by the pressurization band  2 , so that the blood flow near the wrist is inhibited and the blood vessels of the wrist are dilated. The user then pushes the power/execute key  38  arranged in the non-invasive blood component measuring device  1  to turn ON the power of the non-invasive blood component measuring device  1 , so that initialization of the software is performed and the operation check of each unit is performed (step S 1 ), whereby the device is in the standby state, and the standby screen (see  FIG. 6 ) of the standby state is displayed on the display section  54  (step S 2 ). 
         [0061]    When the user pushes the power/execute key  38  while the screen of the standby state is being displayed on the display section  54  (Yes in step S 3 ), the process proceeds to step S 4 . 
         [0062]    The CPU  53   a  then lights the light emitting diodes R 1 , R 2 , L 1 , and L 2  arranged in the light source section  61  respectively at a predetermined light quantity, illuminates the imaging region CR (see  FIG. 4 ), and executes the process of capturing the image of the illuminated imaging region CR with an imaging section  52  (step S 4 ). The captured image is stored in the frame memory  100   e.    
         [0063]      FIG. 10  is a view in which a rectangular region including the imaging region CR is coordinate divided into two-dimensional coordinates of x, y in a range of 0≦x≦640, 0≦y≦480. The CPU  53   a  coordinate divides the region A into two-dimensional coordinates of x, y with the coordinate of the most upper left pixel of the rectangular region A including the image of the imaging region CR as (0, 0), selects four points of (240, 60), (400, 60), (240, 420), (400, 420) from the coordinate divided points, and obtains an average luminance of a region B surrounded by the four points (step S 5 ). The points of the region B for obtaining the average luminance are not limited thereto, and may be obviously other coordinates. The region B may be a polygon other than a square, or a circle. 
         [0064]    The CPU  53   a  then determines whether or not the luminance of the region B is within a target range (step S 6 ). If the luminance of the region B is outside the target range, the current amount flowing to the light emitting diodes R 1 , R 2 , L 1 , and L 2  is adjusted using the light source section input/output interfaced  53   d , the light quantity adjustment thereof is performed (Step S 7 ), and the process returns to step S 4 . If the luminance of the region B is within the target range (Yes in step S 6 ), the CPU  53   a  sets a y coordinate value to be calculated of the luminance profile to be hereinafter described to an initial value (40) (step S 8 ). The luminance of the pixels from one end to another end of the x coordinate at the set y coordinate value (40) is obtained to create a luminance profile (step S 9 ). 
         [0065]      FIG. 11  shows one example of the luminance profile (luminance profile PF) of the pixel in the x direction at the predetermined y coordinate. When the luminance is obtained from the processes, the luminance profile (luminance profile PF) of the pixel in the x direction at the predetermined y coordinate is obtained. The CPU  53   a  then determines whether or not the set y coordinate value is an end value (440) (step S 10 ). If the y coordinate value is not the end value (440) (No in step S 10 ), the CPU  53   a  increments the y coordinate value by a predetermined value (20) (step S 11 ), and returns the process to step S 9 . If the y coordinate value is the end value (440) (Yes in step S 10 ), the CPU  53   a  extracts a point where the luminance is the lowest (hereinafter referred to as “luminance lowest point”) in each extracted luminance profile, and stores the same in the frame memory  53   e  (step S 12 ). 
         [0066]      FIG. 12  illustrates a method for determining the position of a blood vessel. In order to obtain the position of the blood vessel, the CPU  53   a  connects the luminance lowest point (a1, b1) near the center of the image of the imaging region CR and the luminance lowest points (a2, b2) and (a3, b3) adjacent in the vertical direction of the luminance lowest point (a1, b1). The CPU  53   a  connects the luminance lowest point (a2, b2) and the point adjacent in the vertical direction, and connects the luminance lowest point (a3, b3) and the point adjacent in the vertical direction. The CPU  53   a  repeats this operation over the entire region of the image, extracts the blood vessel as a line segment column, and forms the blood vessel pattern  61  (step S 13 ). The CPU  53   a  executes a process of displaying the image of the imaging region CR retrieved in step S 4 , the blood vessel pattern  61  formed in step S 5 , and the index line  62   a  and the index line  62   b  stored in the flash memory card  100   j  on the display section  54  (step S 14 ). The CPU  53   a  determines whether or not the blood vessel pattern  61  is positioned in the region  62   c  (see  FIG. 4 ) (step S 15 ). If the blood vessel pattern  61  is not positioned within the region  62   c  (No in step S 15 ), the COU  53   a  executes a process of instructing which direction the user should move the device body  3  (step S 16 ). After the process of step S 16  is terminated, the CPU  53   a  returns the process to step S 4 , and the CPU  53   a  again retrieves the captured image of the imaging region CR, and executes the processes of step S 4  to S 15 . From the retrieval of the captured image of the imaging region CR in step S 4  to the determination process of step S 15  are performed on 1/100 seconds, and the display of the display section  54  is updated on 1/100 seconds scale. These processes are repeatedly executed while position adjustment is being carried out by the user, wherein the user adjusts the attachment position of the device while checking the display of the display section  54  that is updated as needed. The processes of steps S 4  to S 16  are repeated from when the position adjustment is carried out by the user until determined that the blood vessel pattern  61  is positioned within the region  62   c  by the CPU  53   a.    
         [0067]    When the CPU  53   a  determines that the blood vessel pattern  61  is positioned within the region  61   c  as a result of position adjustment by the user (Yes in step S 15 ), the CPU  53   a  validates the power/execute key  38 , and enables the measurement to continue (step S 17 ). The CPU  53   a  then determines whether or not the power/execute key  38  is pushed by the user (step S 18 ). If determined that the power/execute key  38  is not pushed, the CPU  53   a  returns the process to step S 4 , executes the processes of steps S 4  to S 14 , and again determines whether or not the blood vessel pattern  61  is positioned within the region  61   c  in the process of step S 15 . 
         [0068]    In the process of step S 19 , when the CPU  53   a  determines that the power/execute key  38  is pushed (Yes in step S 18 ), the CPU  53   a  executes a process of hemoglobin concentration measurement (step S 19 ). Once the measurement is terminated, the CPU  53   a  displays a measurement result display screen as shown in  FIG. 8  on the display section  54  (step S 20 ) and terminates the process. 
         [0069]      FIG. 13  is a flowchart showing details of the measuring process of hemoglobin concentration executed in step S 19  of the flowchart shown in  FIG. 9 . When the power/execute key  38  is pushed, the CPU  53   a  controls the light source section input/output interface  53   d , illuminates the living body containing the blood vessel at an appropriate light quantity by the light emitting diodes R 1 , R 2  (first light source section), which is one of the light sources arranged on both sides with the blood vessel in between, (step S 101 ), and captures an image of the same in the imaging section  52  (step S 102 ). The CPU  53   a  determines whether or not the average luminance of the region B exceeds 100 (step S 103 ), adjusts the current amount flowing to the light emitting diodes R 1 , R 2  by using the light source section input/output interface  53   d  if the luminance does not exceed 100, and performs the light quantity adjustment thereof (step S 104 ), and returns the process to step S 102 . 
         [0070]    The value of luminance referred to herein is the digital conversion value (changes between 0 and 255) of the A/D converter of eight bits of the image input interface  53   f  being used in the present embodiment. This is because the luminance of the image and the magnitude of the image signal input from the Imaging section  52   c  are proportional, and thus the A/D conversion value (0 to 255) of the image signal is assumed as the value of luminance. 
         [0071]    If the average luminance of the region B exceeds 100 (Yes in step S 103 ), the CPU  53   a  obtains the luminance profile PF 1  and the concentration profile NP 1  non-dependent on the incident light quantity for the image obtained in step S 102  (step S 105 ). Furthermore, the CPU  53   a  controls the light source section input/output interface  53   d , illuminates the living body containing the blood vessel at an appropriate light quantity by the light emitting diodes L 1 , L 2  (second light source section), which is the other of the light sources arranged on both sides with the blood vessel in between, (step S 106 ), and captures an image of the same in the imaging section  52  (step S 107 ). The CPU  53   a  determines whether or not the average luminance of the region B exceeds 100 (step S 108 ) and increases the current amount flowing to the light emitting diodes L 1 , L 2  by using the light source section input/output interface  53   d  if the luminance does not exceed 100, performs the light quantity adjustment thereof (step S 109 ), and returns the process to step S 107 . 
         [0072]    If the average luminance of the region B exceeds 100 (Yes in step S 108 ), the CPU  53   a  performs a process similar to step S 105  for the image obtained in step S 107 , and obtains the luminance profile PF 2  and the concentration profile NP 2  non-dependent on the incident light quantity (step S 10 ). 
         [0073]      FIG. 15  shows a distribution of the luminance B with respect to the position X, wherein the luminance profile PF 1  is formed by step S 105  and the luminance profile PF 2  is formed by step S 110 .  FIG. 16  shows a distribution of the concentration D with respect to the position X, wherein the concentration profile NP 1  is formed by step S 105  and the concentration profile NP 2  is formed by step S 110 . 
         [0074]    The CPU  53   a  derives the peak value h 1  and the barycentric coordinate cg 1  from the concentration profile NP 1  obtained by step S 105 , and the peak value h 2  and the baryceritric coordinate gc 2  from the concentration profile NP 2  obtained by step S 110 , and calculates a blood vessel depth index S by using the above with the following calculation formula (1). Furthermore, the CPU  53   a  stores the calculation result in the frame memory  53   e  (step S 111 ). 
         [0000]        S =( cg 2 −cg 1)/{( h 1 +h 2)/2}  (1) 
         [0075]    The CPU  53   a  calculates the light quantity ratio of the left and right light sources (light emitting diodes R 1 , R 2  and light emitting diodes L 1 , L 2 ) of the blood vessel, and the light quantity based on the luminance profile PF 1  obtained by step S 105  and the luminance profile PF 2  obtained by step S 110  (step S 112 ), and performs light quantity adjustment of both light sources based on the obtained result (step S 113 ). 
         [0076]    The CPU  53   a  then controls the light source section input/output interface  53   d , illuminates the imaging region CR (see  FIG. 4 ) with the light quantity adjusted light emitting diodes R 1 , R 2 , L 1 , and L 2 , and captures an image of the same in the imaging section  52  (step S 114 ). The CPU  53   a  then obtains the average luminance of the region B shown in  FIG. 10 , and determines whether or not the obtained average luminance of the region B exceeds 150 (step S 115 ). An error display is made if the luminance does not exceed 150 (step S 116 ). 
         [0077]    If the average luminance of the region B exceeds 150 (Yes in step S 115 ), the CPU  53   a  creates a luminance profile (distribution of luminance B with respect to position X) PF (see  FIG. 11 ) showing a first luminance distribution with respect to an axis AX in the imaging region CR (see  FIG. 4 ), and reduces the noise by using methods such as fast Fourier transformation. The CPU  53   a  also standardizes the luminance profile PF with base line BL. The base line BL is obtained based on the shape of the luminance profile of the absorption portion by the blood vessel. The concentration profile (distribution of concentration D with respect to position X) NP non-dependent on the incidence light quantity is thereby created (step S 117 ).  FIG. 14  shows a distribution of the concentration D with respect to the position X, and the concentration profile NP as shown in the figure is created. 
         [0078]    The CPU  53   a  calculates a half-value width was the distribution width corresponding to the peak height h and the blood vessel diameter based on the created concentration profile NP (step S 118 ). The half-value width w is the distribution width at 50% of the peak height of the concentration profile NP. The peak height h represents the ratio of the light intensity absorbed by the blood vessel (blood) to be measured and the light intensity passed through the tissue portion, and the half-value width w represents the length corresponding to the blood vessel diameter in the direction orthogonal to the imaging direction. The CPU  53   a  then calculates a non-corrected hemoglobin concentration D with the following formula (2), and stores the result in the frame memory  53   e  (step S 119 ). 
         [0000]        D=h/w   n   (2) 
         [0079]    Here, n is a constant representing non-linearity of the spread of the half-value width due to scattering. If there is not light scattering, n=1, and if there is scattering, n&gt;1. 
         [0080]    The CPU  53   a  calculates a tissue blood amount index M representing the blood amount contained in the peripheral tissue based on the blood vessel peripheral tissue image in the image of the living body obtained in step S 101  (step S 120 ). Specifically, a second luminance distribution distributed along the blood vessel image is extracted based on the blood vessel peripheral tissue image in the image of the living body at a predetermined distance (e.g., 2.5 mm) from the blood vessel image in the image of the living body. The portion that seems to be saturated of the second luminance distribution is eliminated, and only the portion that can be substantially assumed as a parabola is remained. The tissue blood amount index M including the attenuation rate of the light is obtained based on the following formula with y0 as the luminance of the end portion of the remaining portion, y1 as the luminance at the point of lowest luminance, and was the distance from one end to the other end. 
         [0000]    
       
         
           
             
               ( 
               
                 
                   
                     y 
                      
                     
                         
                     
                      
                     0 
                   
                   - 
                   
                     
                       
                         y 
                          
                         
                             
                         
                          
                         
                           0 
                           · 
                           y 
                         
                          
                         
                             
                         
                          
                         0 
                       
                       - 
                       
                         y 
                          
                         
                             
                         
                          
                         
                           1 
                           · 
                           y 
                         
                          
                         
                             
                         
                          
                         1 
                       
                     
                   
                 
                 
                   y 
                    
                   
                       
                   
                    
                   1 
                 
               
               ) 
             
             
               2 
               W 
             
           
         
       
     
         [0081]    The CPU  53   a  stores the obtained tissue blood amount index M in the frame memory  53   e.    
         [0082]    The CPU  53   a  then analyzes the hill shaped concentration profile NP created in step S 117  (step S 121 ), calculates a blood vessel cross sectional shape index N (step S 122 ), and stores the calculation result in the frame memory  53   e.    
         [0083]    The is calculated in the following manner. First, a cutout height H is set with respect to the concentration profile NP obtained in step S 117 , the concentration profile NP in the cutout range is assumed as a distribution density function of a probability variable, and a kurtosis (k) in the function and a distribution width (dw) at the cutout height H are calculated.  FIG. 17  shows explanatory view showing the calculation process of a distribution width (dw) at a cutout height H. The cutout height H is a percentage of the peak height h which determines the range of analyzing respect to the concentration profile NP for calculating the blood vessel cross sectional shape index N, as shown in the figure. The kurtosis (k) is obtained from the concentration profile NP existing above the cutout height H, and the distribution width (dw) is obtained from the distribution width (length of bottom) of the concentration profile NP in the cutout range. The cutout height H=0.01% is preferable. 
         [0084]    The values of the kurtosis (k) and the distribution width (dw) obtained as above are substituted to the following formula (3) to obtain the blood vessel cross sectional shape index N. 
         [0000]        N ={(k+α)/dw β }/(π· w   2 /4)  (3) 
         [0085]    Here, α and β are constants determined experimentally, and π is the circumference ratio. The blood vessel cross sectional shape index N and the formula (3) will be hereinafter described. 
         [0086]    The CPU  53   a  obtains a correction coefficient fs based on the blood vessel depth index S calculated in step S 111 , a correction coefficient fm based on the tissue blood amount index M calculated in step S 120 , and a correction coefficient fn based on the blood vessel cross sectional shape index N calculated in step S 122 . The CPU  53   a  calculates the corrected hemoglobin concentration D 0  based on the following formula (4) by using such correction coefficients (step S 123 ). 
         [0000]        D   0   =D×fs×fm×fn   (4) 
         [0087]    The CPU  53   a  stores the calculation result in step S 123  in the frame memory  53   e  (step S 124 ), executes the process of displaying the measurement result on the display section  54  as shown in  FIG. 8  (step S 125 ), and returns the process to the main routine. 
         [0088]    In the present embodiment, the blood vessel depth index S, the tissue blood amount index M, and the blood vessel cross sectional shape index N are sequentially calculated, and the non-corrected hemoglobin concentration D is corrected at the point all the correction coefficients are calculated, but the configuration of the present invention is not limited thereto. For instance, a primary correction may be performed at the point the blood vessel depth index S is calculated, and the secondary correction may be performed at the point the tissue blood amount index M is calculated. 
         [0089]    In the hemoglobin concentration measuring process according to the present embodiment, the kurtosis (k) and the distribution width (dw) are calculated after the non-corrected hemoglobin concentration D is calculated, but the order is not limited thereto. For instance, the non-corrected hemoglobin concentration D may be calculated after the kurtosis (k) and the distribution width (dw) are calculated. 
         [0090]    The blood vessel cross sectional shape index N and the formula (3) will be described below. The blood vessel cross sectional shape index N is the index that indicates the shape of the blood vessel cross section. Here, the blood vessel cross sectional shape index N is defined as the ellipticity (ratio of diameter of minor axis with respect to diameter of major axis of an ellipse) of the blood vessel cross section under the assumption the blood vessel cross section is an ellipse. The blood vessel cross sectional shape index N is expressed by the following formula (5) where 2a is the blood vessel diameter in the imaging direction (direction of axis AZ in  FIG. 2 ), and 2b is the blood vessel diameter in the direction orthogonal to the imaging direction (direction orthogonal to AZ axis in plan view in  FIG. 2 ). 
         [0000]        N= 2 a/ 2 b=a/b   (5) 
         [0091]    The formula (3) for calculating the blood vessel cross sectional shape index N will now be described. 
         [0092]      FIG. 18  is a graph plotting the relationship between the kurtosis (k) of the concentration profile NP and the distribution width (dw) at the cutout height H when the flatness degree of the blood vessel cross section is changed gradually with the cutout height H as 0.01% with respect to the concentration profile NP extracted based on three types of blood vessels having different cross sectional areas. The vertical axis is the kurtosis (k), the horizontal axis is the distribution width (dw), and the data related to the same cross sectional area is indicated with the same symbol. 
         [0093]    As apparent from the figure, the kurtosis (k) and the distribution width (dw) change with drawing a constant correlation curve, unless the cross sectional area is changed, even if the flatness degree of the blood vessel cross section is changed. This means that, once the kurtosis (k) and the distribution width (dw) at the cutout height H are obtained, the cross sectional area Sa of the blood vessel to be measured can be estimated using the kurtosis (k) and the distribution width (dw) as indices. 
         [0094]    Focusing on such aspects, in the present embodiment, the approximation formula based-on the correlation between the kurotsis k and the distribution width (dw) at the cutout height H is obtained as the following formula (6). 
         [0000]        Sa =(k+α)/dw β   (6) 
         [0095]    Here, α and β are constants determined experimentally. 
         [0096]    From a different viewpoint, the area Sa of the blood vessel cross section of when the cross sectional shape of the blood vessel is an ellipse is obtained with the following formula (7). 
         [0000]        Sa=π·a·b   (7) 
         [0097]    Thus, according to formula (6) and formula (7), the following formula (8) is obtained. 
         [0000]      π· a·b =(k+α)/dw β   (8) 
         [0098]    Solving the formula (8) so that the left side becomes a/b, the following formula (9) is obtained. 
         [0000]        a/b ={(k+α)/dw β }/(π· b   2 )  (9) 
         [0099]    According to formula (5) and formula (9), the following formula (10) is obtained. 
         [0000]        N=a/b ={(k+α)/dw β }(π· b   2 )  (10) 
         [0100]    Furthermore, in formula (10), the value b is the blood vessel radius in the direction orthogonal to the imaging direction, and the value b can be substituted by ½ of the half-value width w of the concentration profile NP. Therefore, following formula (11) is obtained. 
         [0000]        N=a/b ={(k+α)/dw 2 }/(π· w   2 /4)  (11) 
         [0101]    Then, that is proved that formula (3) is logical. 
         [0102]      FIG. 19  is a graph plotting the actually measured value obtained from the blood cell counting device, and the calculated value by the non-invasive blood component measuring device  1  according to the embodiment of the present invention for the hemoglobin concentration of a plurality of subjects. As shown in the figure, the actually measured value and the calculated value by the non-invasive blood component measuring device  1  exist in the vicinity of a region surrounded by a line having a slope  1 , and the actually measured value and the calculated value are not deviated. Then, it can be seen that the non-invasive blood component measuring device  1  can accurately measure the hemoglobin concentration. 
         [0103]      FIG. 20  shows the result of measuring the error between the hemoglobin concentration calculated by the non-invasive blood component measuring device  1  according to the present embodiment while changing the bend of the wrist in three ways (inward, horizontal, outward) and the hemoglobin concentration calculated by the conventional device. The shaded bar graph shows the result obtained by measuring with the non-invasive blood component measuring device of the present embodiment, and the outlined bar graph shows the result obtained by measuring with the conventional device. As apparent from the figure, the error with the actually measured value is suppressed within 1 g/dl even if the bend of the wrist is changed in various ways, and a measurement result without variation of measurement value is obtained even if the bend of the wrist is different. Therefore, it is verified that according to the non-invasive living body component measuring device of the present embodiment, an accurate and stable hemoglobin concentration measurement can be made even if the dilate state of the blood vessel is changed due to external factors. 
         [0104]      FIG. 21  is a flowchart showing the details of a measuring process of the hemoglobin concentration by a non-invasive blood component measuring device according to another embodiment. The processes of steps S 101  to S 118  in the flowchart are the same as the processes of steps S 101  to S 118  in the flowchart of  FIG. 13 , and thus the description on the portion redundant with the description in the flowchart of  FIG. 13  will be omitted. The process after step S 119  will be described below. 
         [0105]    In the process of step S 119 , the CPU  53   a  analyzes the concentration profile NP created in step S 117 , and calculates the kurtosis (k) and the distribution width (dw) of the concentration profile NP. 
         [0106]    The process then proceeds to step S 120 , and the CPU  53   a  calculates the non-corrected hemoglobin concentration D 0 ′ by the following formula (12), and stores the result in the frame memory  53   a.    
         [0000]        D   0   ′=h/[ 2{(k+α)/dw β }/(π· w/ 2)] n   (12) 
         [0107]    The formula (12) is a formula for calculating the hemoglobin concentration non-dependent on the change in the blood vessel cross sectional shape, wherein an accurate hemoglobin concentration, taking the change in the blood vessel cross sectional shape into consideration, can be calculated without carrying out the step of obtaining the blood vessel cross sectional index N by using the formula (12). The formula (12) will be hereinafter described. 
         [0108]    The CPU  53   a  calculates the tissue blood amount index M based on the blood vessel peripheral tissue in the image of the living body (step S 121 ), calculates the corrected hemoglobin concentration D 0  based on the blood vessel depth index S and the tissue blood amount index M (step S 122 ), records the measurement result (step S 123 ), displays the result (step S 124 ), and returns the process to the main routine. 
         [0109]    The formula (12) will be described below. 
         [0110]    In the first embodiment, the hemoglobin concentration is calculated with the half-value width w reflecting the blood vessel diameter in the direction orthogonal to the imaging direction replaced with the blood vessel diameter in the imaging direction under the assumption that the blood vessel cross section is a perfect circuit. If the hemoglobin concentration is calculated in this manner, the blood vessel diameter in the imaging direction and the blood vessel diameter in the direction orthogonal to the imaging direction do not match due to change in the blood vessel cross sectional shape, and the calculated hemoglobin concentration and the actual hemoglobin concentration sometimes deviate. In order to solve such problem, the first embodiment proposes a configuration of calculating the blood vessel cross sectional shape index N and correcting the hemoglobin concentration. 
         [0111]    Therefore, if the hemoglobin concentration is calculated using the blood vessel diameter in the imaging direction in place of the half-value width w, the problem will not arise, and thus an accurate hemoglobin concentration non-dependent on the change in the blood vessel cross sectional shape can be calculated without carrying out the correction process. Assuming that the blood vessel diameter in the imaging direction is  2   a , the hemoglobin concentration D 0 ′ based on the blood vessel diameter in the imaging direction is given by the following formula (13). 
         [0000]        D   0   ′=h /(2 a ) n   (13) 
         [0112]    Solving formula (10), following formula (14) is obtained. 
         [0000]        a ={(k+α)/dw β }/(π· w/ 2)  (14) 
         [0113]    Thus, according to formula (13) and formula (14), following formula (14) is obtained. 
         [0000]        D   0   ′=h/[ 2{(k+α)/dw β }/(π· w/ 2)] n   (15) 
         [0114]    Then, that is proved that formula (12) is logical. 
         [0115]    From a different viewpoint, a different formula may be used as an formula for calculating the hemoglobin concentration. 
         [0116]    The height h x  of the concentration profile NP at position X reflects the distance the light reaching position X has moved in the blood vessel, such that the peak height h of the concentration profile NP reflects the portion where the light entering the target blood vessel moves the longest distance, that is, the blood vessel diameter in the imaging direction. Similarly in the entire region of the distribution width of the concentration profile NP, the sum of the height h x of the concentration profile NP corresponds to the sum of the distance the light moved in the blood vessel. The sum of the height h x  is equal to the area of the concentration profile NP, and the sum of the distance the light moved in the blood vessel is equal to the cross sectional area of the blood vessel. Therefore, the formula (13) consisting of the ratio between the peak height of the concentration profile NP and the blood vessel diameter in the imaging direction can be replaced with the following formula. 
         [0000]        D   0   ′=A /( Sa ) n   (16) 
         [0000]    (In the formula, A is the area of the concentration profile NP) 
         [0117]    The cross sectional area Sa of the blood vessel is obtained by formula (6). Therefore, following formula (17) is obtained by formula (16) and formula (6). 
         [0000]        D   0   ′=A /[(k+α)/dw β ] n   (17) 
         [0118]    If formula (17) is used, the hemoglobin concentration D 0 ′ is given based on the cross sectional area of the blood vessel. Since the cross sectional area of the blood vessel is always constant even if the shape of the blood vessel changes, an accurate hemoglobin concentration non-dependent on the change in the blood vessel cross sectional shape can be calculated. As a still variant of the second embodiment, the formula (17) may be used in step S 118  of the flowchart shown in  FIG. 21 .