Patent Publication Number: US-2016242683-A1

Title: Information acquisition apparatus

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to an information acquisition apparatus. 
     2. Related Art 
     Apparatuses that acquire biological information of a subject in a noninvasive fashion are in use. Such apparatuses put a small burden on subjects, and have high safety. One such apparatus is disclosed in JP-A-11-323 as a noninvasive blood analyzing apparatus that acquires information of blood components using light. According to this publication, a sensor is brought into contact with the subject&#39;s skin surface, and measurement light is applied into the body of the subject. Hemoglobin in the blood absorbs light of specific wavelengths. The reflected light from the subject is analyzed to detect the proportion of the oxygenated form of hemoglobin. The apparatus also detects biological information such as information of blood components. 
     The apparatus described in the foregoing publication detects blood information from a blood vessel selected as a test object. The apparatus emits light from a light source unit, and an imaging section receives light. The light source unit and the imaging section are electronic components, and undergo changes over time. The quantity of light from the light source decreases, and the imaging section lowers its sensitivity to light. The accuracy of the detected light information thus decreases with time. There accordingly is a need for an information acquisition apparatus that can accurately detect the characteristics of reflected light from an object even when sensor sensitivity changes with time. 
     SUMMARY 
     An advantage of some aspects of the invention is to solve the problems described above, and the invention can be implemented as the following forms or application examples. 
     Application Example 1 
     An information acquisition apparatus according to this application example includes: a first unit including a photoreceiver that receives first reflected light reflected at an object, and that outputs a signal corresponding to light intensity of the first reflected light; and a second unit separately provided from the first unit, the second unit including a calibrator that has a stable reflectance and that outputs second reflected light to the photoreceiver, the second reflected light being used for comparing the light intensity of the first reflected light. 
     According to this application example, the information acquisition apparatus includes the first unit and the second unit. The first unit and the second unit are separable from each other. Upon receiving the first reflected light, the photoreceiver outputs a signal corresponding to the light intensity of the first reflected light reflected at the object. Upon reflecting light, the object absorbs light of a specific wavelength that varies with the component of the object. Information of the object can thus be acquired by analyzing the output light intensity of the first reflected light from the photoreceiver. 
     The second unit includes the calibrator that outputs to the photoreceiver the second reflected light used to compare the light intensity of the first reflected light. Upon receiving the second reflected light, the photoreceiver outputs a signal corresponding to the light intensity of the reflected light at the calibrator. The light source of the light applied to the calibrator and the object undergoes changes with time, and the rate at which the photoreceiver converts the reflected light into a signal also varies with time. On the other hand, the reflectance of the calibrator remains stable over extended time periods. The amount of change of the detected light intensity of the reflected light at the calibrator has a correlation with changes occurring in the light applied to the calibrator and the object, and changes occurring in the rate at which the photoreceiver converts the reflected light into a signal. The amount of change of the detected light intensity of the reflected light at the calibrator, and the detected light intensity of the reflected light at the object can thus be used to accurately detect the characteristics of the reflected light at the object. 
     Application Example 2 
     In the information acquisition apparatus according to the application example, the first unit and the second unit include locating sections with which the photoreceiver and the calibrator are installed face to face. 
     According to this application example, the first unit and the second unit have locating sections. The photoreceiver and the calibrator are installed face to face with the locating sections. This ensures that the photoreceiver receives the second reflected light from the calibrator. 
     Application Example 3 
     In the information acquisition apparatus according to the application example, the photoreceiver includes: a light-emitting device that emits light applied to the calibrator or the object; and a light-receiving device that receives the second reflected light or the first reflected light, the light-emitting device and the light-receiving device having optical axes in the same direction. 
     According to this application example, the photoreceiver includes the light-emitting device and the light-receiving device. The light-emitting device and the light-receiving device have optical axes in the same direction. The light-emitting device emits light in a predetermined directional characteristic. The direction with the highest light quantity in the light of this directional characteristic is the optical axis of the light-emitting device. The light-receiving device has a predetermined directional characteristic for the sensitivity of the light it receives. The direction with the highest sensitivity in the sensitivity directional characteristic is the optical axis of the light-receiving device. In the photoreceiver, the direction with a high emission quantity and the direction with the highest photoreception sensitivity are the same. 
     The photoreceiver can thus receive the second reflected light with good sensitivity with the calibrator installed in the direction of the optical axes of the light-emitting device and the light-receiving device. Likewise, the photoreceiver can receive the first reflected light with good sensitivity with the object placed in the direction of the optical axes of the light-emitting device and the light-receiving device. 
     Application Example 4 
     In the information acquisition apparatus according to the application example, the calibrator contains polytetrafluoroethylene. 
     According to this application example, the calibrator contains polytetrafluoroethylene. Polytetrafluoroethylene reflects near-infrared light without absorbing it. This makes it possible to efficiently obtain the second reflected light used for calibration. 
     Application Example 5 
     In the information acquisition apparatus according to the application example, the first unit includes: a glucose level arithmetic section that computes a glucose level using an output signal from the photoreceiver of which signal corresponds to light intensity of the first reflected light; a determining section that compares the glucose level with a determination value to determine whether the object is in an abnormal state; and a warning section that gives a warning when the object is in an abnormal state. 
     According to this application example, the information acquisition apparatus includes the glucose level arithmetic section, the determining section, and the warning section. The glucose level arithmetic section computes a glucose level using an output signal from the photoreceiver of which signal corresponds to light intensity of the first reflected light. The determining section compares the glucose level with a determination value to determine whether the object is in an abnormal state. The warning section gives a warning when it is determined that the object is in an abnormal state. This makes it possible to immediately notify the object of an abnormal state when the object is in an abnormal state. 
     Application Example 6 
     In the information acquisition apparatus according to the application example, the first unit includes a sending section that sends information of the glucose level, and the second unit includes a receiving section that receives information of the glucose level, and a storage section that stores information of the glucose level. 
     According to this application example, the first unit includes the sending section, and the second unit includes the receiving section. The first unit sends glucose level information to the second unit. The second unit includes the storage section, and the glucose level information is stored in the storage section. The storage section can store long-term information of glucose levels. This makes it possible to analyze the trend of glucose level changes over extended time periods. 
     Application Example 7 
     In the information acquisition apparatus according to the application example, the second unit includes an analysis arithmetic section that analyzes information of the glucose level. 
     According to this application example, the analysis arithmetic section analyzes information of glucose levels. The storage section of the second unit stores long-term information of glucose levels. The analysis arithmetic section can thus analyze long-term patterns of glucose levels, and long periodic changes of glucose levels. 
     Application Example 8 
     In the information acquisition apparatus according to the application example, the analysis arithmetic section selects a countermeasure for the object, and the second unit includes a display section that displays the countermeasure. 
     According to this application example, the analysis arithmetic section selects a countermeasure for the object. The display section displays the countermeasure. This makes it possible to present to the object ways to maintain normal glucose levels. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIG. 1A  is a schematic view explaining an installation example of a component measurement apparatus according to First Embodiment, and  FIGS. 1B and 1C  are schematic plan views representing the structure of a first unit. 
         FIG. 2  is an exploded perspective view representing the structure of the first unit. 
         FIG. 3A  is a schematic plan view representing the structure of a sensor module,  FIG. 3B  is a schematic side sectional view representing the structure of the sensor module, and  FIG. 3C  is a partial schematic side sectional view explaining an operation of the sensor module. 
         FIG. 4A  is a schematic perspective view representing the structure of a second unit,  FIG. 4B  is a schematic plan view representing the contacting structure of the first unit and the second unit, and  FIG. 4C  is a schematic side view representing a structure in which the first unit and the second unit are in contact with each other. 
         FIG. 5  is a block diagram representing the electrical control of the first unit. 
         FIG. 6  is a block diagram representing the electrical control of the second unit. 
         FIG. 7  is a flowchart of an information acquisition method. 
         FIG. 8  is a flowchart representing a maintenance step (step S 1 ) in detail. 
         FIG. 9  is a flowchart representing an object measurement step (step S 3 ) in detail. 
         FIGS. 10A to 10D  are schematic views explaining the biological information acquisition method. 
         FIGS. 11A to 11C  are schematic views explaining the biological information acquisition method. 
         FIGS. 12A to 12D  are schematic views explaining the biological information acquisition method. 
         FIGS. 13A to 13C  are schematic views explaining the biological information acquisition method. 
         FIGS. 14A to 14D  are schematic views explaining the biological information acquisition method. 
         FIG. 15A  is a block diagram representing a relevant portion of a sensor drive circuit according to Second Embodiment, and  FIG. 15B  is a flowchart representing a maintenance step (step S 1 ) in detail. 
         FIG. 16  is a flowchart representing an object measurement step (step S 3 ) in detail. 
         FIG. 17A  is a block diagram representing a relevant portion of a sensor drive circuit according to Third Embodiment, and  FIG. 17B  is a flowchart representing a maintenance step (step S 1 ) in detail. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Embodiments are described below with reference to the accompanying drawings. 
     Note that the members in the drawings are shown in sizes that make the members recognizable in the drawings, and are not to scale relative to actual size or each other. 
     First Embodiment 
     The present embodiment describes typical examples of a component measurement apparatus, and a component information acquisition method that analyzes blood components using the component measurement apparatus, with reference to the accompanying drawings. A component measurement apparatus according to First Embodiment is described with reference to  FIG. 1A  to  FIG. 6 .  FIG. 1A  is a schematic view explaining an installation example of the component measurement apparatus. As illustrated in  FIG. 1A , the component measurement apparatus  1  as an information acquisition apparatus is configured from a first unit  2  and a second unit  3 . The first unit  2  is installed on a wrist of a subject  4  (object). The second unit  3  is separately installed from the first unit  2 , and functions to assist the first unit  2 . The component measurement apparatus  1  is a medical device for measuring blood components of the subject  4  in a noninvasive fashion, and represents medical equipment. The component measurement apparatus  1  measures components of the blood flowing in the blood vessels in the wrist. In the present embodiment, for example, the blood component measured is glucose concentration. Glucose concentration measurement enables measuring glucose levels. 
       FIGS. 1B and 1C  are schematic plan views representing the structure of the first unit.  FIG. 1B  shows the top surface of the first unit  2 .  FIG. 1C  shows the back surface of the first unit  2 . As illustrated in  FIG. 1B , the first unit  2  has a shape similar to the shape of a wrist watch. The first unit  2  has a first exterior portion  5 . The first exterior portion  5  has a fixing band  6  on both sides (left and right in the figure). The fixing band  6  is used to fix the component measurement apparatus  1  to a measured portion such as the wrist and arm of the subject  4 . The fixing band  6  uses a Magic Tape®. In referring to the component measurement apparatus  1 , Y direction is the direction of extension of the fixing band  6 , and X direction in the direction of extension of the arm of the subject  4 . The direction in which the component measurement apparatus  1  faces the subject  4  is Z direction. X-, Y-, and Z-directions are orthogonal to each other. 
     The first exterior portion  5  has a surface  5   a  that faces outward upon mounting the first unit  2  on the subject  4 . On the surface  5   a  of the first exterior portion  5  are installed operation switches  7 , a touch panel  8 , and a speaker  9  (warning section). The subject  4  enters measurement start instructions through the operation switches  7  and the touch panel  8 . The touch panel  8  displays measurement result data. The component measurement apparatus  1  through the speaker  9  produces a warning sound to caution the subject  4 . 
     As shown in  FIG. 1C , a sensor module  10  is installed as a photoreceiver on the back surface  5   b  side of the first exterior portion  5 . When in use, the sensor module  10  is brought close to the skin of the subject  4 . The sensor module  10  applies measurement light to the skin of the subject  4 , and receives reflected light. The sensor module  10  is a thin image sensor with a built-in light source and photosensor array. A communication connector  11  for communicating with external devices is installed on the back surface  5   b  of the first exterior portion  5 . On the communication connector  11  are arranged contacts that contact and communicate with the second unit  3 . A power connector  12  used to charge a rechargeable battery (not illustrated) is also installed. The power connector  12  is a connector that contacts the second unit  3  to receive power. 
       FIG. 2  is an exploded perspective view illustrating the structure of the first unit. As illustrated in  FIG. 2 , the first unit  2  is configured from a caseback  13 , the sensor module  10 , a circuit unit  14 , a spacer  15 , the touch panel  8 , a vibrator (warning section)  16 , and a top case  17 , which are stacked in this order in Z direction. The caseback  13  and the top case  17  constitute the first exterior portion  5 . The sensor module  10 , the circuit unit  14 , the spacer  15 , the touch panel  8 , and the vibrator  16  are housed in the first exterior portion  5 . 
     The caseback  13  is a plate-shaped member that comes into contact with the subject  4 . The caseback  13  has a quadrangular first window portion  13   a  installed on X direction side. The first window portion  13   a  is where the sensor module  10  is exposed. A light transmissive plate such as glass may be disposed in the first window portion  13   a . This makes it possible to prevent entry of dust into the first exterior portion  5  through the first window portion  13   a . Such a plate also can prevent contamination of the sensor module  10 . The caseback  13  has a quadrangular second window portion  13   b  and third window portion  13   c  on −X direction side. The second window portion  13   b  is where the communication connector  11  is exposed. The third window portion  13   c  is where the power connector  12  is exposed. 
     The sensor module  10  is a sensor with light-emitting devices, light-receiving devices, and spectral devices installed in a grid. The sensor module  10  applies light to the subject  4 , and detects the intensity of reflected light of specific wavelengths. The circuit unit  14  has a circuit board  18 . On the circuit board  18  is installed an electrical circuit  21  that drives and controls the vibrator  16 , the sensor module  10 , and the touch panel  8 . The electrical circuit  21  is configured from a plurality of semiconductor chips. The operation switches  7 , the speaker  9 , the communication connector  11 , the power connector  12 , and a rechargeable battery  22  are also installed on the circuit board  18 . The rechargeable battery  22  is electrically connected to the power connector  12 , and is chargeable via the power connector  12 . 
     The spacer  15  is a structure installed between the circuit unit  14  and the touch panel  8 . With the plurality of devices installed on the surface of the circuit unit  14  on −Z direction side, the circuit unit  14  has irregularities on this surface. The spacer  15  is installed over the circuit board  18 , and provides a flat surface against the touch panel  8 . The spacer  15  has a plurality of holes  15   a , and the operation switches  7 , the speaker  9 , and the vibrator  16  penetrate through the holes  15   a.    
     The touch panel  8  is structured to include a first display section  23 , and an operation input section  24  installed on the first display section  23 . The first display section  23  is not particularly limited, as long as it can display electronic data in the form of an image. The first display section  23  may be, for example, a liquid crystal display device, or an OLED (organic light-emitting diode) display device. In the present embodiment, the first display section  23  uses, for example, OLED. 
     The operation input section  24  is an input section with transparent electrodes disposed in a grid on a surface of a transparent plate. Upon an operator touching the transparent electrodes, current passes across the crossing electrodes, and enables detection of the location touched by the operator. The transparent plate may be a resin sheet or a glass plate, as long as it is light transmissive. The transparent electrodes may be, for example, IGO (indium-gallium oxide), ITO (indium Tin Oxide), or ICO (indium-cerium oxide), as long as it is a light-transmissive conductive film. The first display section  23  displays information such as a measurement status, and measurement results. The operation switches  7  are switches used to operate the component measurement apparatus  1 , as is the operation input section  24 . An operator operates the operation input section  24  and the operation switches  7  to enter various instructions, such as an instruction for starting a measurement of glucose level, and measurement conditions. 
     The vibrator  16  is installed on +Z direction side of the top case  17 . The vibrator  16  is adapted to vibrate the first exterior portion  5 . The component measurement apparatus  1  can function to caution the subject  4  with the vibration of the first exterior portion  5 . The member used to constitute the vibrator  16  is not particularly limited, as long as it can vibrate the first exterior portion  5 . In the present embodiment, for example, the vibrator  16  is a piezoelectric element. 
     The top case  17  has a plurality of holes  17   a . The operation input section  24 , the operation switches  7 , and the speaker  9  are exposed through the holes  17   a . The components from the sensor module  10  to the touch panel  8  are housed between the caseback  13  and the top case  17 . 
       FIG. 3A  is a schematic plan view showing the structure of the sensor module  10 , as viewed from the back surface  5   b  side.  FIG. 3B  is a schematic side sectional view illustrating the structure of the sensor module.  FIG. 3C  is a partial schematic side sectional view explaining the operation of the sensor module. As illustrated in  FIG. 3A , the sensor module  10  has a two-dimensional array of light-emitting devices  25  in a grid. Between the adjacent light-emitting devices  25  are installed spectral devices  26 . 
     The arrayed directions of the light-emitting devices  25  and the spectral devices  26  are X and Y directions. The light-emitting devices  25  and the spectral devices  26  are disposed at the same intervals in X and Y directions. The light-emitting devices  25  and the spectral devices  26  are disposed in a staggered fashion in X and Y directions with a predetermined distance in between. Accordingly, the spectral devices  26  have wide non-overlapping portions with the light-emitting devices  25  as viewed from the back surface  5   b  side. This structure permits light propagating from the subject  4  side to reach the spectral devices  26 . 
     The light-emitting devices  25  are configured from imaging light-emitting devices  25   a  and measurement light-emitting devices  25   b . In the figure, the rows are in +Y direction from the bottom. The 1st, 3rd, 5th, 7th, and 9th rows are configured from the measurement light-emitting devices  25   b . The imaging light-emitting devices  25   a  and the measurement light-emitting devices  25   b  are alternately disposed in the 2nd, 4th, 6th, and 8th rows in the figure. The light-emitting devices  25  are installed in such a manner that four light-emitting devices  25  surround a single spectral device  26 . A unit of four light-emitting devices  25  includes one imaging light-emitting device  25   a , and three measurement light-emitting devices  25   b.    
     In capturing an image to detect locations of blood vessels, the imaging light-emitting devices  25   a  apply light to the subject  4 . The light applied by the imaging light-emitting devices  25   a  has a 700 nm to 900 nm wavelength range centered at 800 nm. Hemoglobin in the blood has high absorption of light at 800 nm wavelength. An image of blood vessel locations can thus be captured with light applied to the subject  4  by the imaging light-emitting devices  25   a.    
     In detecting blood glucose concentration, the measurement light-emitting devices  25   b  apply light to the subject  4 . The light applied by the measurement light-emitting devices  25   b  has a 900 nm to 2000 nm wavelength range centered at 1450 nm. Glucose in the blood has high absorption of light at 1200 nm, 1600 nm, and 2000 nm wavelengths. Blood glucose concentration can thus be detected with light applied to the subject  4  by the measurement light-emitting devices  25   b . Glucose is also called grape sugar. 
     For simplicity, the light-emitting devices  25  are shown as an array of 9 rows and 9 columns. The number of rows and the number of columns in the array of the light-emitting devices  25  and the spectral devices  26  are not particularly limited, and may be appropriately set. For example, the interval between these devices is preferably 1 to 1500 μm. Considering the balance between manufacturing cost and measurement accuracy, the interval is more preferably, for example, about 100 to 1500 μm. The light-emitting devices  25  and the spectral devices  26  are not limited to the layered configuration, and these may be disposed side by side on a plane. In the present embodiment, for example, 250 rows×250 columns of light-emitting devices  25  are installed. The interval between the light-emitting devices  25  is not particularly limited either. In the present embodiment, for example, the interval between the light-emitting devices  25  is 0.1 mm. The sensor module  10  can thus also function as an imaging device. 
     As illustrated in  FIG. 3B , the array of light-emitting devices  25  constitutes a light-emitting layer  27  (light source). The light-emitting devices  25  represent an irradiator that applies measurement light. The light-emitting devices  25  are not particularly limited, as long as it can emit near-infrared rays that can pass through the subcutaneous tissue. The light-emitting devices  25  may use, for example, LED (light emitting diode), or OLED (organic light-emitting diode). 
     A light-shielding layer  28  is installed over the light-emitting layer  27 . The measurement light  29  emitted by the light-emitting layer  27  toward the subject  4  is reflected at the subcutaneous tissue of the subject  4 , and becomes reflected light  30 . The light-shielding layer  28  passes light directed to the spectral devices  26 , but selectively blocks other light. A spectral layer  31  is installed over the light-shielding layer  28 . The spectral devices  26  are arrayed in a grid in the spectral layer  31 . The spectral devices  26 , also called etalons, are devices that selectively pass near-infrared rays of predetermined wavelengths. The spectral devices  26  in response to an input instruction signal pass reflected light  30  of the wavelength specified by the instruction signal. The spectral devices  26  include a pair of oppositely disposed mirrors, and an electrostatic actuator is installed that adjusts the distance between the mirrors. The passage of reflected light  30  of predetermined wavelengths is permitted by the electrostatic actuator adjusting the distance between the mirrors. 
     Glucose has peak wavelengths of 1200 nm, 1600 nm, and 2000 nm. Blood sugar level can be measured by detecting transmittance at these three wavelengths. The wavelengths of the reflected light  30  passed by the spectral devices  26  are not particularly limited. In the present embodiment, the spectral devices  26 , for glucose detection, pass light of, for example, 1500 nm to 1700 nm wavelengths centered at 1600 nm. 
     A light-receiving layer  32  is installed over the spectral layer  31 . The light-receiving layer  32  has a grid-like two-dimensional array of light-receiving devices  33 . The light-receiving devices  33  are arrayed in the same pattern as the spectral devices  26 . The light-receiving devices  33  overlie the spectral devices  26  as viewed in the direction of travel of the reflected light  30 . 
     The light-receiving devices  33  output electrical signals according to the quantity of the reflected light  30  they receive. The light-receiving devices  33  may use, for example, imaging devices such as CCD (Charge Coupled Device Image Sensor), and CMOS (Complementary Metal Oxide Semiconductor Image Sensor), as long as light intensity can be converted into electrical signals. The light-receiving devices  33  each may have a configuration that includes a plurality of devices for receiving wavelength components necessary for calibration. The sensor module  10  has its front surface on the side of the light-emitting layer  27 , and is installed on the back surface  5   b  of the first exterior portion  5  in such an orientation that the front surface side faces the skin surface of the subject  4 . 
     The light-emitting devices  25  and the light-receiving devices  33  have optical axes in the same direction. The light-emitting devices  25  emit the measurement light  29  in a predetermined directional characteristic. The direction with the highest light quantity in the directional characteristic of the measurement light  29  represents the optical axis of the light-emitting device. The detection sensitivity of the light-receiving devices  33  for the reflected light  30  has a predetermined directional characteristic. The direction with the highest sensitivity in the sensitivity directional characteristic represents the optical axis of the light-receiving devices  33 . In the sensor module  10 , the direction with a high emission quantity and the direction with the highest photoreception sensitivity are the same. Specifically, the measurement light  29  and the light-receiving devices  33  have optical axes in the same direction. Accordingly, the sensor module  10  can receive the reflected light  30  with good sensitivity with a measured portion  4   a  placed on the optical axes of the light-emitting devices  25  and the light-receiving devices  33 . 
     As illustrated in  FIG. 3C , all the imaging light-emitting devices  25   a  in the sensor module  10  simultaneously emit light in capturing the location of a blood vessel  34 . The location opposite the sensor module  10  represents the measured portion  4   a . The measurement light  29  is applied over the whole region of the measured portion  4   a  of the subject  4 . The measurement light  29  is reflected at the measured portion  4   a , and becomes the reflected light  30 . The reflected light  30  is received by all the light-receiving devices  33 , and a biological image is acquired. For the measurement of blood components, only the specified devices in the measurement light-emitting devices  25   b  emit light, and the reflected light  30  is received by the specified devices in the light-receiving devices  33 . 
       FIG. 4A  is a schematic perspective view representing the structure of the second unit.  FIG. 4B  is a schematic plan view representing the contacting structure of the first unit and the second unit.  FIG. 4C  is a schematic side view representing a structure in which the first unit and the second unit are in contact with each other. As illustrated in  FIG. 4A , the second unit  3  has a plate-shaped second exterior portion  35 . The second exterior portion  35  has a thickness direction along Z direction. The second exterior portion  35  is rectangular in outer shape when viewed in Z direction. The longitudinal direction of the second exterior portion  35  as viewed in Z direction is along X direction, and the direction orthogonal to this longitudinal direction is Y direction. 
     The second exterior portion  35  has a surface  35   a  on −Z direction side. The surface  35   a  is a surface that contacts the first unit  2 . A calibration plate  36  is installed as a calibrator on X direction side of the surface  35   a . The calibration plate  36  has a shape of a quadrangular plate, and the sides of the quadrangle are longer than the sides of the sensor module  10 . The material of the calibration plate  36  is not particularly limited, as long as it can stably reflect infrared light over extended time periods. Materials such as polytetrafluoroethylene, and metals may be used. Polytetrafluoroethylene is also called Teflon®. In the present embodiment, for example, the calibration plate  36  is a plate produced by compacting and sintering polytetrafluoroethylene particles. The plate has a high reflectance of about 98% or more in a 1500 nm to 1700 nm wavelength region. The calibration plate  36  can thus efficiently output the reflected light  30  to the light-emitting devices  25 . 
     A communication socket  37  and a power socket  38  are installed on −X direction side of the calibration plate  36 . The communication socket  37  is a connection for the communication connector  11 , and the first unit  2  and the second unit  3  communicate with each other via the communication connector  11  and the communication socket  37 . The power socket  38  is a connection for the power connector  12 , and the second unit  3  supplies power to the first unit  2  via the power connector  12  and the power socket  38 . 
     Four locating projections  41  are installed as locating sections around the calibration plate  36 , the communication socket  37 , and the power socket  38 . The first unit  2  is installed in contact with the second unit  3  in such a manner that the exterior of the first unit  2  contacts the locating projections  41 . In this way, the locating projections  41  locate the first unit  2 . A second display section  42  is installed on −X direction side of the communication socket  37  and the power socket  38 . The second display section  42  is where the results of computations performed by the second unit  3 , or text guidance to an operator are displayed. Operation switches  43  are installed on −X direction side of the second display section  42 . Operation switches  43  are switches an operator presses to operate the second unit  3 . An operator checking the second display section  42  can send instructions to the second unit  3  by operating the operation switches  43 . 
     A communication outlet  44  and a power cable  45  are installed on the side surface of the second exterior portion  35  on −X direction side. The communication outlet  44  is a connection used to install a communication cable when communicating with external devices. The power cable  45  is an external power input cable, and has a power plug  46  at the end. 
     As illustrated in  FIG. 4B , the first unit  2  is installed on the surface  35   a  of the second unit  3 . Here, the first exterior portion  5  is installed along the locating projections  41 . The first exterior portion  5  has locating receptacles  5   c  as locating sections that contact the locating projections  41 . The locating receptacles  5   c  are shaped to fit the locating projections  41 . This makes it possible to install the first unit  2  and the second unit  3  relative to each other with good repeatability. 
     As illustrated in  FIG. 4C , the sensor module  10  and the calibration plate  36  are disposed face to face with the locating projections  41 . This ensures that the light-receiving devices  33  receive the reflected light  30  in response to the light-emitting devices  25  outputting the measurement light  29 . 
       FIG. 5  is a block diagram representing the electrical control of the first unit. Referring to  FIG. 5 , the first unit  2  includes a first controller  47  that controls the operation of the first unit  2 . The first controller  47  includes a first CPU  48  (Central Processing Unit) as a processor that performs various arithmetic processes, and first memory  49  that stores a variety of information. A sensor drive circuit  50 , the operation input section  24 , the first display section  23 , the operation switches  7 , the speaker  9 , the vibrator  16 , the first communication section  51  (sending section), and the rechargeable battery  22  are connected to the first CPU  48  via an input/output interface  52  and a data bus  53 . 
     The sensor drive circuit  50  is a circuit that drives the sensor module  10 . The sensor drive circuit  50  drives the light-emitting devices  25 , the spectral devices  26 , and the light-receiving devices  33  constituting the sensor module  10 . The light-emitting devices  25 , the spectral devices  26 , and the light-receiving devices  33  are two-dimensionally arrayed in a grid in the sensor module  10 . The sensor drive circuit  50  turns on and off the light-emitting devices  25  according to instruction signals from the first CPU  48 . The sensor drive circuit  50  sets a wavelength for passage of reflected light  30  through the spectral devices  26 , using an instruction signal from the first CPU  48 . The sensor drive circuit  50  amplifies the light intensity signal of the light received by the light-receiving devices  33 , and sends the signal to the first CPU  48  after converting it into a digital signal. 
     The first display section  23  displays predetermined information according to instructions from the first CPU  48 . An operator operates the operation input section  24  according to the displayed content, and enters instruction content. The instruction content is sent to the first CPU  48 . 
     The speaker  9  is an audio output unit, and makes various audio outputs according to instructions from the first CPU  48 . The speaker  9  outputs notification sounds indicative of information such as the start and the end of a glucose level measurement, and occurrence of an error. 
     The vibrator  16  is a device that vibrates the first exterior portion  5 . Because the first exterior portion  5  is in contact with the subject  4 , the first unit  2  can caution the subject  4  by vibrating the first exterior portion  5 . The subject  4  can be cautioned using the vibrator  16  when the use environment of the component measurement apparatus  1  does not permit making sound from the speaker  9 . 
     The first communication section  51  is configured from circuits such as a wired communication circuit, and a communication control circuit. The communication connector  11  performs communications with the second unit  3 . The first communication section  51  may be used as a wireless communication circuit to perform wireless communications with the second unit  3 . 
     The rechargeable battery  22  supplies power for driving the first unit  2 . The rechargeable battery  22  outputs data indicative of a charge level to the first CPU  48 . The first CPU  48  is adapted to detect the power charged in the rechargeable battery  22 . The rechargeable battery  22  is connected to the power connector  12 , and charged by the second unit  3 . 
     The first memory  49  is a concept that includes semiconductor memories such as RAM and ROM, and external memory devices such as a hard disc, and a DVD-ROM. Functionally, the first memory  49  has a storage region set therein to store a system program  54  that describes control procedures for the operation of the component measurement apparatus  1 , and a storage region set therein to store a blood component measurement program  55  that describes arithmetic procedures for estimating blood components. The first memory  49  also has a storage region set therein to store a light-emitting device list  56  that represents data indicative of the locations of the light-emitting devices  25 . 
     The first memory  49  also has a storage region set therein to store a light-receiving device list  57  that represents data indicative of the locations of the light-receiving devices  33 . The first memory  49  also has a storage region set therein to store biological image data  58  obtained by capturing the location of the blood vessel  34  under the light emitted by all the light-emitting devices  25 . The first memory  49  also has a storage region set therein to store calibration related data  61  used to calibrate light intensity. The first memory  49  also has a storage region set therein to store blood vessel location data  62  indicative of the location of the blood vessel  34  computed from the biological image data  58 . The first memory  49  also has a storage region set therein to store measurement location data  63  indicative of the location of the blood vessel  34  being measured. 
     The first memory  49  also has a storage region set therein to store absorption spectrum data  64  that represents the optical transmittance of the measured blood. The first memory  49  also has a storage region set therein to store blood component value data  65  indicative of the blood concentrations of the measured blood components. The first memory  49  also has various other storage regions set therein to serve different purposes, including a storage region that serves as a work area for the first CPU  48 , and a storage region that serves as temporary files. 
     The first CPU  48  controls the measurement of blood glucose concentration according to the system program  54  and the blood component measurement program  55  stored in the first memory  49 . Specifically, the first CPU  48  has an emission control section  66  to realize its functions. The emission control section  66  controls the switching that selectively turns on and off the light-emitting devices  25 . The first CPU also has a photoreception control section  67 . The photoreception control section  67  controls the acquisition of digital data of the light quantity received by the light-receiving devices  33 . The first CPU  48  also has a filter control section  68 . The filter control section  68  controls the sensor drive circuit  50  to switch the wavelength that can pass through the spectral devices  26 . 
     The first CPU  48  also has a biological image acquisition section  69 . The biological image acquisition section  69  acquires a biological image of a portion of body directly below the sensor module  10 . The acquisition of a biological image is made possible by the appropriate use of biological image capturing techniques, such as a known vein authentication technique. Specifically, all the light-receiving devices  33  are used to capture an image under the light emitted by all the imaging light-emitting devices  25   a  of the sensor module  10 . The captured image generates a biological image. The biological image acquired by the biological image acquisition section  69  is stored as the biological image data  58  in the first memory  49 . 
     The first CPU  48  also has a measurement location arithmetic section  70 . The measurement location arithmetic section  70  performs a predetermined image process on the biological image, and acquires blood vessel location data. Specifically, a vein pattern is identified from the biological image using a known image processing technique. For example, the biological image is subjected to pixel-wise binarization or filtering relative to a reference luminance. In the processed biological image, pixels with luminance values below the reference luminance indicate blood vessels, and pixels with luminance values equal to or greater than the reference luminance indicate a non-blood vessel region. The blood vessel location data acquired by the measurement location arithmetic section  70  is stored as blood vessel location data  62  in the first memory  49 . 
     The measurement location arithmetic section  70  selects a measurement target by selecting a location of blood vessel  34  satisfying predetermined selection conditions. The location selected as the measurement target may be a single blood vessel  34 , or more than one blood vessel  34 . The data of the blood vessel  34  at the selected measurement target location is stored as the measurement location data  63  in the first memory  49 . 
     The measurement location arithmetic section  70  selects a measurement light-emitting device  25   b  and a light-receiving device  33  that are to be driven for the blood vessel  34  at each measurement location. Specifically, the measurement location arithmetic section  70  selects a light-emitting device  25  and a light-receiving device  33  that lie on a straight line orthogonal to the center line of the blood vessel  34  at the measurement location. Here, the measurement light-emitting device  25   b  and the light-receiving device  33  are selected in such a manner that the distance between the measurement location and the light-emitting device  25 , and the distance between the measurement location and the light-receiving device  33  take values close to the optimum distance. The measurement light-emitting device  25   b  so selected is stored as the light-emitting device list  56  in the first memory  49 . The light-receiving device  33  so selected is stored as the light-receiving device list  57  in the first memory  49 . 
     The first CPU  48  also has a measurement control section  71 . The measurement control section  71  makes the sensor drive circuit  50  turn on the measurement light-emitting device  25   b . The measurement control section  71  causes the sensor drive circuit  50  to drive the light-receiving device  33  for detection of the light intensity of the reflected light  30 . Here, the light intensity is the light intensity of the light that has passed through the blood vessel  34 . 
     The first CPU  48  also has an absorption spectrum calculating section  72 . The absorption spectrum calculating section  72  generates an absorption spectrum of the measured blood vessel  34 . Specifically, the absorption spectrum calculating section  72  calculates the transmittance T of the blood vessel  34  using the light intensity of the light received by the light-receiving device  33 , and generates an absorption spectrum. The absorption spectrum so calculated is stored as the absorption spectrum data  64  in the first memory  49 . The measurement may be made at one or more wavelengths λ. The wavelength λ varies with the measured blood component. 
     The first CPU  48  also has a component value calculating section  73  as a glucose level arithmetic section. The component value calculating section  73  calculates a glucose concentration using the absorption spectrum. The calculation of absorption spectrum may use analysis techniques such as multiple linear regression analysis, main component regression analysis, PLS regression analysis, and independent component analysis. When there is more than one blood vessel  34  at the measurement location, a glucose concentration is calculated from the average absorption spectrum of different blood vessels  34 . The calculated value is stored as the blood component value data  65  in the first memory  49 . 
     The first CPU  48  also has an abnormal state determining section  74  as a determining section. The abnormal state determining section  74  compares the glucose concentration calculated by the component value calculating section  73  with a determination value to make a determination. When there is abnormality in the glucose concentration, the abnormal state determining section  74  warns the subject  4  using the first display section  23 , the speaker  9 , and the vibrator  16 . 
       FIG. 6  is a block diagram representing the electrical control of the second unit. Referring to  FIG. 6 , the second unit  3  includes a second controller  75  that controls the operation of the second unit  3 . The second controller  75  includes a second CPU  76  as a processor that performs various arithmetic processes, and second memory  77  that stores a variety of information. The second display section  42 , the operation switches  43 , a second communication section  78  (receiving section), and a charge circuit  79  are connected to the second CPU  76  via an input/output interface  81 , and a data bus  82 . 
     The second display section  42  displays predetermined information according to instructions from the second CPU  76 . An operator operates the operation switches  43  according to the displayed content, and enters instruction content. The instruction content is sent to the second CPU  76 . 
     The second communication section  78  is configured from circuits such as a wired communication circuit, and a communication control circuit. The second communication section  78  communicates with the first unit  2  via the communication socket  37 . When the communication outlet  44  is connected to an external device (not illustrated), the second communication section  78  communicates with the external device via the communication outlet  44 . The second communication section  78  may be used as a wireless communication circuit to perform wireless communications with the first unit  2  and external devices. 
     The charge circuit  79  is connected to the power socket  38 , and charges the rechargeable battery  22  of the first unit  2  via the power socket  38 . The charge circuit  79  can detect the start and the end of charging by detecting the current passing the power socket  38 . The charge circuit  79  outputs to the second CPU  76  information concerning whether charging is in progress. 
     The second memory  77  is a concept that includes semiconductor memories such as RAM and ROM, and external memory devices such as a hard disc, and a DVD-ROM. Functionally, the second memory  77  has a storage region set therein to store a system program  83  that describes control procedures for the operation of the second unit  3 , and a storage region set therein to store a light-emitting device list  84  that represents data indicative of the locations of the light-emitting devices  25 . 
     The second memory  77  also has a storage region set therein to store a light-receiving device list  85  that represents data indicative of the locations of the light-receiving devices  33 . The second memory  77  also has a storage region set therein to store calibration related data  86  used to calibrate light intensity with a calibration plate  36 . The second memory  77  also has a storage region set therein to store blood component value data  87  as glucose level information indicative of the blood concentration of the measured blood component. The second memory  77  also has a storage region set therein to store determination reference data  88  as reference data used to determine the blood component value data  87 . The second memory  77  also has a storage region set therein to store countermeasure data  89  indicative of how to deal with abnormality when the result of the determination of the blood component value data  87  is abnormal. The second memory  77  also has various other storage regions set therein to serve different purposes, including a storage region that serves as a work area for the second CPU  76 , and a storage region that serves as temporary files. 
     The second CPU  76  computes data used for calibration, or performs an arithmetic analysis of changes in blood glucose concentration, according to the system program  83  stored in the second memory  77 . Specifically, the second CPU  76  has a calibration measurement control section  90  to realize this function. The calibration measurement control section  90  cooperates with the emission control section  66 , the photoreception control section  67 , and the filter control section  68  of the first CPU  48  to control the reflectance measurement of the calibration plate  36 . The second CPU  76  also has a calibration data arithmetic section  91 . The calibration data arithmetic section  91  uses the measured reflectance of the calibration plate  36  to check the performance of the light-emitting layer  27  and the light-receiving devices  33 , and compute data for calibrating the output of the light-emitting layer  27  and the light-receiving devices  33 . The second CPU  76  also has an analysis arithmetic section  92 . The analysis arithmetic section  92  computes patterns in which the blood component value data  87  are changing. The second CPU  76  also has a countermeasure selecting section  93 . When the changing patterns of the blood component value data  87  are not desirable for the subject  4 , a countermeasure that is suited for the subject  4  is selected by the countermeasure selecting section  93  from the countermeasures stored in the countermeasure data  89 , and the countermeasure selecting section  93  displays the selected countermeasure in the second display section  42 . 
     The present embodiment has been described through the case where the functions of the first unit  2  are achieved by program software using the first CPU  48 . However, these functions may be achieved with the use of an electronic circuit, when an electronic circuit (hardware) alone is sufficient to achieve the foregoing functions without using the first CPU  48 . Similarly, the functions of the second unit  3 , achieved by program software using the second CPU  76  in the foregoing embodiment, may be achieved with the use of an electronic circuit when an electronic circuit (hardware) alone is sufficient to achieve the foregoing functions without using the second CPU  76 . 
     The following describes an information acquisition method that uses the component measurement apparatus  1  described above, with reference to  FIG. 7  to  FIG. 14D . FIG.  7  is a flowchart representing the information acquisition method. In the flowchart of  FIG. 7 , step S 1  corresponds to a maintenance step, in which the charge circuit  79  charges the rechargeable battery  22  of the first unit  2 . In step S 1 , the light-emitting devices  25  apply the measurement light  29  to the calibration plate  36 , and the light-receiving devices  33  detect the reflected light  30 . Step S 1  is also a step in which the calibration data arithmetic section  91  calculates a calibration coefficient. The sequence then goes to step S 2 . Step S 2  corresponds to a unit mounting step. In this step, an operator installs the first unit  2  on the subject  4 . Step S 3  is an object measurement step. In this step, the measurement light  29  is applied to the measured portion  4   a , and the light-receiving devices  33  detect the reflected light  30 . Blood glucose is measured in this step. The sequence then goes to step S 4 . Step S 4  is a warning determination step in which the abnormal state determining section  74  determines whether to warn the subject  4 . When warning the subject  4 , the sequence goes to step S 5 . The sequence goes to step S 6  when not warning the subject  4 . 
     Step S 5  is a warning step. This step warns the subject  4  that an abnormal event has occurred. The sequence then goes to step S 6 . Step S 6  is a maintenance determination step of determining whether to perform maintenance. When maintenance is performed, the sequence goes to step S 1 . The sequence goes to step S 7  when not performing maintenance. Step S 7  is an end determining step, which determines whether to continue or end the measurement. When continuing the measurement, the sequence goes to step S 3 . The sequence goes to step S 8  when ending the measurement. Step S 8  is a maintenance step. Step S 8  is the same as step S 1 . This completes the information acquisition process. 
       FIG. 8  is a flowchart representing the maintenance step (step S 1 ) in detail. In the flowchart of  FIG. 8 , steps S 11  to S 17  and step S 18  are performed in parallel. Step S 11  corresponds to a unit contacting step. In this step, the first unit  2  is brought into contact with the second unit  3  by installing the first unit  2  on the second unit  3 . The sequence then goes to step S 12 . Step S 12  is a calibration data acquisition step. In this step, the measurement light  29  is applied to the calibration plate  36 , and the reflected light  30  from the calibration plate  36  is detected. The sequence then goes to step S 13 . 
     Step S 13  is a calibration coefficient computation step. In this step, the light intensity of the reflected light  30  is used to compute the calibration coefficient used in the object measurement step (step S 3 ). Step S 13  is also a step in which calibration coefficient data is transferred from the second unit  3  to the first unit  2 . The sequence then goes to step S 14 . Step S 14  is a measurement data transfer step. In this step, the blood component value data  65  is transferred from the first memory  49  of the first unit  2  to the second memory  77  of the second unit  3 . 
     Step S 15  is a measurement data analyzing step. In this step, the analysis arithmetic section  92  analyzes the blood component value data  65  to analyze the patterns in which the blood glucose concentration is changing. The sequence then goes to step S 16 . Step S 16  is a countermeasure selecting step. In this step, a countermeasure to be performed by the subject  4  is selected from the countermeasure data  89  when the blood glucose concentration is showing an increasing pattern. The sequence then goes to step S 17 . Step S 17  is a countermeasure display step. In this step, the countermeasure selected in step S 16  is displayed. Step S 18  is a charging step. In this step, the second unit  3  sends power to the first unit  2 , and the rechargeable battery  22  is charged. This completes the maintenance step (step S 1 ). 
       FIG. 9  is a flowchart representing the object measurement step (step S 3 ) in detail. In the flowchart of  FIG. 9 , step S 21  corresponds to an image acquisition step. In this step, the biological image acquisition section  69  simultaneously turns on all the imaging light-emitting devices  25   a , and the light-receiving devices  33  of the light-receiving layer  32  capture an image of the blood vessel  34 . The sequence then goes to step S 22 . Step S 22  is a blood vessel location acquisition step. In this step, the image captured by the measurement location arithmetic section  70  is used to acquire the location of the blood vessel  34 . The sequence then goes to step S 23 . 
     Step S 23  is a measurement target selecting step. In this step, a location suited for measurement is selected from the blood vessel  34  in the measurement portion  4   a  by the measurement location arithmetic section  70 . The measurement location arithmetic section  70  also selects a reference measurement location. The sequence then goes to step S 24 . Step S 24  is a light-emitting and light-receiving device selecting step. In this step, the measurement location arithmetic section  70  selects a measurement light-emitting device  25   b  and a light-receiving device  33  that are to be driven for the measurement. The measurement location arithmetic section  70  also selects a measurement light-emitting device  25   b  and a light-receiving device  33  that are to be driven for the acquisition of reference data. The sequence then goes to step S 25 . 
     Step S 25  is a measurement step. In this step, the measurement light-emitting device  25   b  applies the measurement light  29  to the measured portion  4   a , and the light intensity of the reflected light  30  received by the light-receiving device  33  is measured. The sequence then goes to step S 26 . Step S 26  is a calibration step. In this step, the light intensity measured by the calibration data arithmetic section  91  is multiplied by the calibration coefficient. The sequence then goes to step S 27 . Step S 27  is an absorption spectrum computation step. In this step, the absorption spectrum calculating section  72  computes the blood transmittance using the measurement result data. The sequence then goes to step S 28 . Step S 28  is an average absorption spectrum computation step, in which the blood transmittances at different measurement locations are used to compute the mean transmittance value. The sequence then goes to step S 29 . Step S 29  is a blood component concentration computation step. This step computes blood glucose concentration. This completes the object measurement step (step S 3 ). 
       FIG. 10A  to  FIG. 14D  are schematic views explaining the biological information acquisition method. Referring to  FIG. 10A  to  FIG. 14D , the biological information acquisition method is described below in detail, along with the corresponding steps described in  FIGS. 7 to 9 . The sequence begins with the unit contacting step (step S 11 ) in the maintenance step (step S 1 ).  FIG. 10A  is a diagram corresponding to the unit contacting step (step S 11 ). As represented in  FIG. 10A , an operator in step S 11  installs the first unit  2  on the second unit  3 . The first unit  2  is installed using the locating projections  41  of the second unit  3  as a guide. This installs the sensor module  10  at a location opposite the calibration plate  36 . The power connector  12  contacts the power socket  38 . The communication connector  11  contacts the communication socket  37 . 
     The operator operates the operation switches  43  to start the maintenance procedure. This starts the charging step (step S 18 ). The second unit  3  supplies power to the first unit  2 . In response, the rechargeable battery  22  starts charging in the first unit  2 . In the second unit  3 , the charge circuit  79  detects the charge state, and displays in the second display section  42  whether charging is in progress. 
       FIGS. 10B and 10C  are diagrams corresponding to the calibration data acquisition step (step S 12 ). As illustrated in  FIG. 10B , in step S 12 , one of the measurement light-emitting devices  25   b  is turned on to irradiate the calibration plate  36 . The measurement light  29  from the measurement light-emitting device  25   b  is reflected at the calibration plate  36 , and becomes the second reflected light  30   a . The second reflected light  30   a  off the calibration plate  36  irradiates the sensor module  10 . The light-receiving devices  33  near the measurement light-emitting device  25   b  that has emitted light receive the second reflected light  30   a , and detect its light intensity. Upon the light-receiving devices  33  detecting the light intensity, the measurement light-emitting device  25   b  is turned off, and another measurement light-emitting device  25   b  is turned on. In this manner, photodetection sensitivity data can be acquired for the combination of the activated measurement light-emitting device  25   b  and the light-receiving device  33 . 
     The measurement light-emitting devices  25   b  are switched, and turned on one after another. The light-receiving devices  33  near the measurement light-emitting device  25   b  that has emitted light receive the second reflected light  30   a , and detect its light intensity. In this manner, photodetection sensitivity data is acquired for all the measurement light-emitting devices  25   b . In  FIG. 10C , the vertical axis represents the light intensity detected by the light-receiving devices  33 . The horizontal axis represents device number. The device number is a combination of numbers for the measurement light-emitting devices  25   b  and the light-receiving devices  33 . 
     The measurement light-emitting devices  25   b  and the light-receiving devices  33  each have designated numbers. For example, the device number (2,5) is assigned to data detected by the fifth light-receiving device  33  from the light emitted by the second measurement light-emitting device  25   b . A sensitivity data line  94  represents an example of light intensities for different device number combinations. As represented by the sensitivity data line  94 , light intensities corresponding to combinations of measurement light-emitting devices  25   b  and light-receiving devices  33  are measured, and the measured data are stored as the calibration related data  86  in the second memory  77 . The sensitivity data line  94 , shown as a line chart, may be stored in a tabular form by tabulating device number and light intensity. 
     In the calibration coefficient computation step (step S 13 ), the calibration data arithmetic section  91  computes the calibration coefficient. Prior to computation, a reference value of light intensity is set. Preferably, a reference value of light intensity is set using the light intensity received by a light-receiving device  33  of known performance under the measurement light  29  emitted by a measurement light-emitting device  25   b  of known performance. 
     The calibration data arithmetic section  91  then divides the reference value by the light intensity of each device number to calculate the calibration coefficient. The calibration coefficient is 1 when the reference value and the detected light intensity have the same value. The calibration coefficient becomes smaller than 1 when the detected light intensity is larger than the reference value. The calibration coefficient becomes larger than 1 when the detected light intensity is smaller than the reference value. 
       FIG. 10D  is a diagram corresponding to the calibration coefficient computation step (step S 13 ). In  FIG. 10D , the vertical axis represents calibration coefficient. The horizontal axis represents device number. A calibration coefficient line  95  represents an example of calibration coefficients for different device number combinations. As represented by the calibration coefficient line  95 , calibration coefficients corresponding to combinations of measurement light-emitting devices  25   b  and light-receiving devices  33  are computed, and the computed result is stored as the calibration related data  61  in the first memory  49 . The calibration coefficient line  95 , shown as a line chart, may be stored in a tabular form by tabulating device number and calibration coefficient. 
     In the measurement data transfer step (step S 14 ), the first unit  2  transfers blood glucose concentration data to the second unit  3 . Blood glucose concentration data are accumulated as the blood component value data  65  in the first memory  49  of the first unit  2 . Blood glucose concentration data are data that have been measured in the object measurement step (step S 3 ). Blood glucose concentration data are accumulated as the blood component value data  87  in the second memory  77  of the second unit  3 . The blood glucose concentration data are transferred from the first memory  49  to the second memory  77 . The amount of data in the first memory  49  decreases after the transfer, and the first memory  49  can be prevented from being overloaded. Blood glucose concentration data are accumulated in the second memory  77  every time the maintenance step (step S 1 ) is performed. The second memory  77  can thus accumulate blood glucose concentration data over extended time periods. 
       FIGS. 11A and 11B  are diagrams corresponding to the measurement data analyzing step (step S 15 ). As represented in  FIG. 11A , blood glucose concentration changes are analyzed in step S 15 . In the figures, the vertical axis represents glucose level. The glucose level is higher from the bottom to top of the diagram. Glucose level is also referred to as blood glucose concentration. The horizontal axis represents measurement time. The direction of the passage of time is from right to left. A glucose level measurement line  96  represents an example of glucose level changes in the subject  4 . The analysis arithmetic section  92  calculates a glucose level approximate line  96   a  from the glucose level measurement line  96  using the least squares approximation method. Whether the glucose level is rising or falling can be clearly found from the slope of the glucose level approximate line  96   a . A rate of change also can be clearly found from the slope of the glucose level approximate line  96   a.    
     The analysis arithmetic section  92  compares the glucose level approximate line  96   a  with an upper-limit determination value  97  and a lower-limit determination value  98 . The glucose level is determined as normal when the glucose level approximate line  96   a  is at or below the upper-limit determination value  97 , and is at or above the lower-limit determination value  98 . The glucose level is determined as high when the glucose level approximate line  96   a  tends to be above the upper-limit determination value  97 . The glucose level is determined as low when the glucose level approximate line  96   a  tends to be below the lower-limit determination value  98 . In the example represented by the glucose level measurement line  96 , it can be seen that the subject  4  has high glucose levels. The method used to determine glucose levels is not limited to this, and various other methods may be used. 
       FIG. 11B  represents another example of glucose level changes in the subject  4 . A glucose level measurement line  101  represents an example of glucose level changes in the subject  4 . A glucose level approximate line  101   a  is an approximate line for the glucose level measurement line  101 . As can be seen in the figure, the glucose level is normal because the glucose level approximate line  101   a , initially above the upper-limit determination value  97 , falls below the upper-limit determination value  97  and remains above the lower-limit determination value  98 . 
     In the countermeasure selecting step (step S 16 ), whether the glucose level is above or below the upper-limit determination value  97  and the lower-limit determination value  98  is determined by referring to the slope of the glucose level approximate line. How to deal with high sugar levels and low sugar levels is stored in the countermeasure data  89  of the second memory  77 . From the countermeasure list in the countermeasure data  89 , the countermeasure selecting section  93  selects a countermeasure that is considered to be most appropriate. 
     The countermeasures in the countermeasure data  89  are indexed, and are prepared according to the extent of high and low sugar levels. This enables the countermeasure selecting section  93  to easily select a countermeasure using the slope of the glucose level approximate line of the subject  4 , and the results of comparisons with the upper-limit determination value  97  and the lower-limit determination value  98 . 
       FIG. 11C  is a diagram corresponding to the countermeasure display step (step S 17 ). As represented in  FIG. 11C , in step S 17 , the countermeasure selecting section  93  displays the glucose level status of the subject  4 , and the selected countermeasure in the second display section  42 . This completes the maintenance step (step S 1 ), and the sequence goes to the unit mounting step (step S 2 ). 
       FIG. 12A  is a diagram corresponding to the unit mounting step (step S 2 ). As illustrated in  FIG. 12A , the operator in step S 2  installs the first unit  2  on the subject  4 . The first unit  2  is installed in such a manner that the back surface  5   b  contacts the subject  4 . Here, the first unit  2  is installed in such an orientation that the touch panel  8  can be seen. The operator presses the operation switches  7  to start a measurement, and the sequence goes to step S 3 . 
     The object measurement step (step S 3 ) begins with step S 21 .  FIGS. 12B and 12C  are diagrams corresponding to the image acquisition step (step S 21 ). As illustrated in  FIG. 12B , in step S 21 , an image of the measured portion  4   a  is captured. The biological image acquisition section  69  outputs to the emission control section  66  an instruction signal for turning on the imaging light-emitting devices  25   a . The emission control section  66  outputs to the sensor drive circuit  50  the instruction signal for turning on the imaging light-emitting devices  25   a . The sensor drive circuit  50  drives and turns on the imaging light-emitting devices  25   a . The measurement light  29  emitted by the imaging light-emitting devices  25   a  irradiates the measured portion  4   a . The measurement light  29  is reflected at the measured portion  4   a , and becomes first reflected light  30   b . The reflected light  30  off the measured portion  4   a  is referred to as first reflected light  30   b.    
     The biological image acquisition section  69  outputs to the filter control section  68  an instruction signal for instructing the spectral devices  26  to pass light of 800 nm wavelength. The filter control section  68  outputs to the sensor drive circuit  50  an instruction signal for varying the wavelength characteristics of the spectral devices  26 . The sensor drive circuit  50  drives the spectral devices  26 , and sets an 800 nm wavelength for passage of light through the spectral devices  26 . In this way, the first reflected light  30   b  of a wavelength that is easily absorbable by the blood vessel  34  passes through the spectral device  26 , and it becomes easier to capture an image of the blood vessel  34 . 
     The biological image acquisition section  69  outputs to the photoreception control section  67  an imaging instruction signal. The photoreception control section  67  outputs to the sensor drive circuit  50  an instruction signal for driving the light-receiving devices  33 . The sensor drive circuit  50  drives the light-receiving devices  33 , and outputs the light intensity of the input light to the photoreception control section  67  after converting the light intensity into photoreception data. By being arrayed in a grid, the light-receiving devices  33  function as an image capturing camera. The photoreception data forms a biological image  102  representing the captured shape of the blood vessel  34 , as shown in  FIG. 12C . The photoreception control section  67  stores the biological image  102  as the biological image data  58  in the first memory  49 . 
       FIG. 12C  is a diagram corresponding to the image acquisition step (step S 21 ) and the blood vessel location acquisition step (step S 22 ). The biological image  102  shown in  FIG. 12C  is an output image of the measured portion  4   a  from the sensor module  10 . The biological image  102  is obtained as a two-dimensional image with pixels corresponding to the array of the light-receiving devices  33  in the sensor module  10 . The blood vessel  34  more easily absorbs near-infrared rays than the non-blood vessel portion. Accordingly, the blood vessel image  102   a , an image of the blood vessel  34 , has lower luminance, and appears darker than the non-blood vessel image  102   b  of the non-blood vessel portion in the biological image  102 . A blood vessel pattern can thus be extracted by extracting the lower luminance portion in the biological image  102  in step S 22 . Specifically, the presence or absence of the blood vessel directly below the light-receiving device  33  can be determined by determining whether the luminance of the corresponding pixel constituting the biological image  102  has a value that is equal to or less than a predetermined threshold value. This makes it possible to detect the location of the blood vessel  34 . 
       FIG. 12D  is a diagram corresponding to the measurement target selecting step (step S 23 ), schematically representing blood vessel location information obtained from the biological image  102 . The blood vessel location information is information indicative of whether the location corresponding to each pixel of the biological image  102  is the blood vessel  34  or the non-blood vessel portion  105 . In step S 23 , the measurement location arithmetic section  70  selects a measurement site  106 , a measurement location of the blood vessel  34 . The measurement location arithmetic section  70  selects the measurement site  106  by satisfying the following selection conditions. The measurement site  106  satisfies the selection conditions when it is not a branching or a merging portion of the blood vessel, or an end portion of the image, and has a predetermined length and width. 
     At branching and merging portions  34   a  of the blood vessel, the reflected light  30  has the possibility of mixing with light that has passed through a blood vessel  34  that is not a measurement target. The light that has passed through a blood vessel  34  that is not a measurement target has the possibility of affecting the absorption spectrum of the measurement site  106  selected as the measurement target. This may result in poor measurement accuracy. The measurement site  106  is thus selected from portions other than the branching and merging portions  34   a  of the blood vessel  34 . 
     At end portions  34   b  of the blood vessel  34  in the biological image  102 , there is no information about the blood vessel structure in the vicinity of the outer side of the image, whether the blood vessel is branched or merging. For the same reason described above, the measurement site  106  is thus selected from portions of blood vessel  34  other than the end portions  34   b  of the biological image  102  to avoid the possibility of lowering measurement accuracy. 
       FIG. 13A  is a diagram corresponding to the light-emitting and light-receiving device selecting step (step S 24 ). As illustrated in  FIG. 13A , the measurement location arithmetic section  70  in step S 24  selects a measurement light-emitting device  25   b  and a light-receiving device  33  that are to be driven for measurement. Here, a measurement light-emitting device  25   b  and a light-receiving device  33  are selected so that the measurement site  106  is between the measurement light-emitting device  25   b  and the light-receiving device  33 . The light-receiving device  33  detects light that has passed through the measurement site  106 . 
     The measurement location arithmetic section  70  also selects a measurement light-emitting device  25   b  and a light-receiving device  33  that are to be driven for reference measurement. Here, a measurement light-emitting device  25   b  and a light-receiving device  33  are selected so that the measurement site  106  is not between the measurement light-emitting device  25   b  and the light-receiving device  33 . The light-receiving device  33  detects light that did not pass through the measurement site  106 . This measurement will be referred to as reference measurement. In the present embodiment, the same device is set for the measurement light-emitting device  25   b  and the reference measurement light-emitting device  25  at the same location. 
     Assume here that the measurement light-emitting device  25   b  at the irradiation position is a light-emitting device  25   c , and the light-receiving device  33  at the reception position for measurement is a measurement light-receiving device  33   a . The measurement location arithmetic section  70  sets locations for the light-emitting device  25   c  and the measurement light-receiving device  33   a  so that the measurement site  106  is centered between the light-emitting device  25   c  and the measurement light-receiving device  33   a . The measurement location arithmetic section  70  also sets locations for the light-emitting device  25   c  and the measurement light-receiving device  33   a  so that the distance between the light-emitting device  25   c  and the measurement light-receiving device  33   a  becomes a predetermined optimum distance  107 . 
     Assume here that the light-receiving device  33  at the reference reception position for reference measurement is a reference light-receiving device  33   b . The light-emitting device  25  at the irradiation position for reference measurement is the light-emitting device  25   c . The location for the reference light-receiving device  33   b  is set so that the blood vessel  34  does not exist between the light-emitting device  25   c  and the reference light-receiving device  33   b . The measurement location arithmetic section  70  sets the locations for the light-emitting device  25   c  and the reference light-receiving device  33   b  so that the distance between the light-emitting device  25   c  and the reference light-receiving device  33   b  becomes the predetermined optimum distance  107 . 
       FIGS. 13B and 13C  are diagrams corresponding to the measurement step (step S 25 ). These are schematic cross sectional views taken in depth direction, explaining propagation of light inside the body tissue. Hatching is omitted for viewability. As illustrated in  FIG. 13B , the light-emitting device  25   c  in step S 25  emits measurement light in a predetermined directional characteristic. The cellular tissue surrounding the blood vessel  34  in the subject  4  represents a common tissue  4   d . The common tissue  4   d  is a cellular tissue including, for example, skin tissue, adipose tissue, and muscle tissue, surrounding the blood vessel  34  being measured. Some of the measurement light  29  passes through the blood vessel  34  through the common tissue  4   d . Some of the measurement light  29  passes through the blood vessel  34  after being scattered by the common tissue  4   d . Some of the measurement light  29  passes through the blood vessel  34 , and enter the measurement light-receiving device  33   a  as first reflected light  30   b . Some of the measurement light  29  enters the measurement light-receiving device  33   a  and the reference light-receiving device  33   b  as first reflected light  30   b , without passing through the blood vessel  34 . 
       FIG. 13C  is a diagram simulating the paths of light rays emitted by the light-emitting device  25  and entering the light-receiving devices  33 , using a ray tracing method. As illustrated in  FIG. 13C , the measurement light  29  radiating from the light-emitting device  25   c  undergoes diffuse reflection inside the body tissue, and some of the radiating light reaches the light-receiving devices  33 . The light paths of the propagating light travel through banana-shaped regions confined between two arcs. The light path is widest along the depth direction near substantially the center between the light-emitting device  25  and the light-receiving device  33 . The light path is also deepest in this part of the tissue. The reachable light depth increases as the distance between the light-emitting device  25  and the light-receiving device  33  increases. 
     For improved measurement accuracy, it is desirable that the light-receiving device  33  receives more transmitted light from the blood vessel  34 . For this reason, it is desirable to locate the measurement target, or the measurement site  106 , at substantially the center between the light-emitting device  25  and the light-receiving device  33 . The optimum distance  107  is specified according to the supposed depth of the measurement site  106 . The optimum distance  107  representing the optimum interval between the light-emitting devices  25  and the light-receiving devices  33  is about two times the depth of the blood vessel  34  from skin surface. For example, the optimum distance  107  is about 5 to 6 mm for a depth of about 3 mm. 
     The wavelength of the measurement light  29  emitted by the light-emitting device  25   c  is such that the absorbance varies with blood glucose levels. Some of the reflected light  30  detected by the measurement light-receiving device  33   a  passes through the blood vessel  34 , and some of the first reflected light  30   b  is absorbed by blood in the blood vessel  34 . Accordingly, the output data from the measurement light-receiving device  33   a  contains information about the blood absorbance and the absorbance of the non-blood vessel portion  105 . On the other hand, the reflected light  30  detected by the reference light-receiving device  33   b  does not pass through the blood vessel  34 , and is not absorbed by blood in the blood vessel  34 . Accordingly, the output data from the reference light-receiving device  33   b  contains information about the absorbance of the non-blood vessel portion  105 . 
       FIGS. 14A and 14B  are diagrams corresponding to the calibration step (step S 26 ). In  FIG. 14A , the vertical axis represents measured value, specifically the light intensity value detected by the light-receiving device  33 . The light intensity on vertical axis becomes higher from the bottom to top. The horizontal axis depicts the measurement light-receiving device  33   a  and the reference light-receiving device  33   b . The measured values by the measurement light-receiving device  33   a  and the reference light-receiving device  33   b  are presented as a bar chart. The measured values detected by the measurement light-receiving device  33   a  and the reference light-receiving device  33   b  are given as blood measurement value  108   a  and reference measurement value  108   b , respectively. 
     The calibration data arithmetic section  91  multiplies the measured value by the calibration coefficient. The calibration coefficient is the coefficient calculated by the calibration data arithmetic section  91  in step S 1 . The calibration coefficient is set for each combination of the light-emitting device  25  and the light-receiving device  33 . In  FIG. 14B , the vertical axis represents measured value after calibration, specifically value after the calibration of the light intensity value detected by the light-receiving device  33 . The light intensity on vertical axis becomes higher from the bottom to top. The horizontal axis depicts the measurement light-receiving device  33   a  and the reference light-receiving device  33   b . The calibrated blood measurement value  109   a  and the calibrated reference measurement value  109   b  are presented as a bar chart. 
     In this step, the blood measurement value  108   a  is multiplied by the calibration coefficient corresponding to the combination of the light-emitting device  25   c  and the measurement light-receiving device  33   a  to calculate the calibrated blood measurement value  109   a . The calibrated reference measurement value  109   b  is calculated by multiplying the reference measurement value  108   b  by the calibration coefficient corresponding to the combination of the light-emitting device  25   c  and the reference light-receiving device  33   b.    
     The light-emitting devices  25  and the light-receiving devices  33  have performance variance attributed to production. There is also a performance change due to changes with time. In step S 1 , the calibration coefficient is set with the use of the calibration plate  36  having a reflectance that is uniform throughout the plane and that does not easily undergo changes with time. In step S 26 , the measured values are calibrated with the calibration coefficient. The calibrated blood measurement value  109   a  and the calibrated reference measurement value  109   b  obtained in step S 26  are thus unlikely to be affected by changes occurring in the light-emitting devices  25  and the light-receiving devices  33  over time, or by the production variance of the light-emitting devices  25  and the light-receiving devices  33 . 
     In the absorption spectrum computation step (step S 27 ), the transmittance through the blood vessel  34  is computed with the calibrated blood measurement value  109   a  and the calibrated reference measurement value  109   b . The transmittance may be calculated through four arithmetic operations of the calibrated blood measurement value  109   a  and the calibrated reference measurement value  109   b . In a simpler operation, the calibrated blood measurement value  109   a  may be divided by the calibrated reference measurement value  109   b  to obtain a transmittance. The operation of the calibrated blood measurement value  109   a  may take into account the proportion of the first reflected light  30   b  that passed through the blood vessel  34 . The proportion of the first reflected light  30   b  that passed through the blood vessel  34  may be calculated using methods such as a phantom method, and a Monte Carlo simulation method. 
     In the average absorption spectrum computation step (step S 28 ), the mean value is computed using a plurality of transmittance values. Step S 25  has been described through the case of a measurement at a single measurement location. The mean value is computed in step S 28  when there is more than one measurement location. The moving average may be computed when performing measurements at predetermined time intervals. Step S 28  may be omitted when the mean is not computed. 
       FIG. 14C  is a diagram corresponding to the blood component concentration computation step (step S 29 ). In step S 29 , the calculated transmittance is used to compute blood glucose concentration. In  FIG. 14C , the vertical axis represents blood glucose concentration. The concentration is higher from the bottom to top of the diagram. The horizontal axis represents transmittance, representing the blood transmittance rate of light of the same wavelength as the wavelength of the measurement light  29 . In the diagram, the transmittance increases from the left to right. A correlation curve  110  represents the relationship between blood transmittance and blood glucose concentration. Absorption of light increases with increase of blood glucose concentration, and the transmittance decreases. When the mean value calculated in the step S 28  is a calculated transmittance value  111 , the correlation curve  110  is used to calculate an arithmetic concentration value  112  representing blood glucose concentration. The correlation curve  110  may be represented as a function, or as a correlation table in a tabular form. The arithmetic concentration value  112  can be calculated from the calculated transmittance value  111  also in these cases. This completes the object measurement step (step S 3 ), and the sequence goes to step S 4 . 
     In the warning determination step (step S 4 ), the arithmetic concentration value  112  is compared to determination values. The determination values include an upper determination value and a lower determination value. The current state is determined as normal, and not in need of a warning when the arithmetic concentration value  112  is at or below the upper determination value, and at or above the lower determination value. The current state is determined as abnormal when the arithmetic concentration value  112  is higher than the upper determination value. The current state is also determined as abnormal when the arithmetic concentration value  112  is below the lower determination value. In an abnormal state, it is determined to give a warning, and the sequence goes to step S 5 . 
       FIG. 14D  is a diagram corresponding to the warning step (step S 5 ). As illustrated in  FIG. 14D , the subject  4  is warned in step S 5 . The touch panel  8  displays a warning text  8   a . The warning text  8   a  contains a statement explaining that the subject  4  is at risk. The subject  4  reading the statement can easily understand his or her status. The speaker  9  produces a warning sound. Warning sound data are prestored in the first memory  49 , and the first CPU  48  outputs to the speaker  9  a voltage waveform based on the warning sound data. The speaker  9  outputs sound after converting the voltage waveform into a sound wave. The subject  4  also can be brought to attention even when he or she is not looking at the touch panel  8 . The first CPU  48  vibrates the first exterior portion  5  by driving the vibrator  16 . Because the first exterior portion  5  is in contact with the subject  4 , the vibration is transmitted to the subject  4 . The subject  4  can then be brought to attention that he or she is in an abnormal state. 
     The maintenance determination step (step S 6 ) determines whether to maintain the first unit  2 . It is determined to maintain the first unit  2  when the accumulated power in the rechargeable battery  22  is below a determination value. This step also determines to perform maintenance when the stored data in the first memory  49  is approaching the allowable volume. It is also determined to perform maintenance when a predetermined time period has elapsed from the last time the maintenance step (step S 1 ) was performed. The maintenance determination step determines not to perform maintenance when these conditions are not met. When it is determined to perform maintenance, the first unit  2  is removed from the subject  4 , and the sequence goes to step S 1 . The sequence goes to step S 7  when it is determined not to perform maintenance. 
     In the end determining step (step S 7 ), it is determined whether to end the acquisition of blood glucose concentration information. It is determined to end the acquisition upon the operator operating the operation switches  7 , the operation input section  24 , or the operation switches  43 , and giving an instruction to end the acquisition of blood glucose concentration information. It is determined to continue the process, and steps S 3  to S 7  are repeated when the operator does not give an instruction to end the acquisition. The object measurement step (step S 3 ) is thus repeatedly performed with the first unit  2  installed on the subject  4 . Blood glucose concentration changes in the subject  4  can be detected even when the subject  4  is moving. 
     When it is determined in step S 7  to end the process, the first unit  2  is removed from the subject  4 , and the sequence goes to step S 8 . The content of the maintenance step (step S 8 ) is the same as that of step S 1 . As such, the rechargeable battery  22  is charged, and calibration data is computed. The blood component value data  65  in the first memory  49  are transferred to the second memory  77 , and information of blood glucose concentration is analyzed. This completes the acquisition of glucose concentration information from the subject  4 . 
     As described above, the present embodiment has the following effects. 
     (1) According to the present embodiment, the light-receiving devices  33  upon receiving the first reflected light  30   b  output a signal corresponding to the light intensity of the first reflected light  30   b  reflected at the measured portion  4   a . Upon reflecting light, the measured portion  4   a  absorbs light of a specific wavelength that varies with the blood glucose concentration. Blood glucose concentration can thus be measured by analyzing the output light intensity of the first reflected light  30   b  from the light-receiving devices  33 . 
     (2) According to the present embodiment, the component measurement apparatus  1  includes the first unit  2  and the second unit  3 . The first unit  2  and the second unit  3  are separable from each other. This enables saving the weight of the first unit  2 . The first unit  2  is used by being mounted on the subject  4 . With the lightness of the unit mounted on the subject  4 , the component measurement apparatus  1  can measure glucose levels with good portability. 
     (3) According to the present embodiment, the second unit  3  includes the calibration plate  36  with which the second reflected light  30   a  for comparing the light intensity of the first reflected light  30   b  is output to the light-receiving devices  33 . Upon receiving the second reflected light  30   a , the light-receiving devices  33  output a signal corresponding to the light intensity of the second reflected light  30   a  at the calibration plate  36 . The performance of the light-emitting devices  25  that apply light to the calibration plate  36  and the measured portion  4   a  changes over time. The rate at which the light-receiving devices  33  convert the reflected light  30  into a signal also changes with time. On the other hand, the reflectance of the calibration plate  36  remains stable for extended time periods. Changes in the detected light intensity of the second reflected light  30   a  at the calibration plate  36  have a correlation with the effects of changes occurring in the performance of the light-emitting devices  25  and the light-receiving devices  33 . Changes in the detected light intensity of the second reflected light  30   a  at the calibration plate  36 , and the detected light intensity of the first reflected light  30   b  at the measured portion  4   a  can thus be used to accurately detect the characteristics of the first reflected light  30   b  at the measured portion  4   a.    
     (4) According to the present embodiment, the first unit  2  has the locating receptacles  5   c  in the first exterior portion  5 , and the second unit  3  has the locating projections  41 . The sensor module  10  and the calibration plate  36  are oriented face to face with the locating receptacles  5   c  and the locating projections  41 . This ensures that the light-receiving devices  33  receive the second reflected light  30   a  reflected at the calibration plate  36  upon application of the light by the light-emitting devices  25 . 
     (5) According to the present embodiment, the light-emitting devices  25  and the light-receiving devices  33  have optical axes in the same direction. In the sensor module  10 , the direction with a high emission quantity and the direction with the highest photoreception sensitivity are the same. The sensor module  10  can thus receive the second reflected light  30   a  with good sensitivity with the calibration plate  36  installed in the direction of the optical axes of the light-emitting devices  25  and the light-receiving devices  33 . Likewise, the sensor module  10  can receive the first reflected light  30   b  with good sensitivity with the measured portion  4   a  placed in the direction of the optical axes of the light-emitting devices  25  and the light-receiving devices  33 . 
     (6) According to the present embodiment, the calibration plate  36  contains polytetrafluoroethylene. Polytetrafluoroethylene reflects near-infrared light without absorbing it. This makes it possible to efficiently obtain the second reflected light  30   a  used for calibration. 
     (7) According to the present embodiment, the component measurement apparatus  1  includes the component value calculating section  73 , the abnormal state determining section  74 , and the speaker  9 . The component value calculating section computes a glucose level using an output signal corresponding to the light intensity of the first reflected light  30   b  from the photoreceiver. The determining section compares the glucose level with a determination value to determine whether the object is in an abnormal state. The speaker  9  gives a warning when it is determined that the subject  4  is in an abnormal state. This makes it possible to immediately notify the subject  4  of an abnormal state when the subject  4  is in an abnormal state. 
     (8) According to the present embodiment, the first unit  2  includes the first communication section  51 , and the second unit  3  includes the second communication section  78 . The first unit  2  sends glucose level information to the second unit  3 . The second unit  3  includes the second memory  77 , and the blood component value data  87  are stored in the second memory  77 . The second memory  77  can store long-term information concerning the blood component value data  87 . This makes it possible to analyze information of changing glucose levels over extended time periods. 
     (9) According to the present embodiment, the analysis arithmetic section  92  analyzes information of the blood component value data  87 . The second memory  77  of the second unit  3  stores long-term information of glucose levels. The analysis arithmetic section  92  can thus analyze long-term patterns of glucose levels, and long periodic changes of glucose levels. 
     (10) According to the present embodiment, the analysis arithmetic section  92  selects a countermeasure for the subject  4  from the countermeasure data  89 . The second display section  42  displays the countermeasure. The subject  4  can thus recognize ways to maintain normal glucose levels. 
     (11) According to the present embodiment, the light intensity detection of the first reflected light  30   b , and the computation of blood glucose concentration are repeated with the component measurement apparatus  1  installed on the subject  4 . Blood glucose concentration changes in the subject  4  can thus be detected even when the subject  4  is moving. 
     Second Embodiment 
     An embodiment of the component measurement apparatus is described below with reference to  FIGS. 15A and 15B , and  FIG. 16 .  FIG. 15A  is a block diagram representing a relevant portion of a sensor drive circuit according to Second Embodiment, and  FIG. 15B  is a flowchart representing a maintenance step (step S 1 ) in detail.  FIG. 16  is a flowchart representing an object measurement step (step S 3 ) in detail. The present embodiment differs from First Embodiment in that the value measured with the calibration plate  36  is used to adjust the output of the light-emitting device  25 . The same features already described in First Embodiment will not be described further. 
     Specifically, in the present embodiment, a sensor drive circuit  116  connected to the first controller  47  is installed in a component measurement apparatus  115  (information acquisition apparatus), as shown in  FIG. 15A . The sensor drive circuit  116  drives the light-emitting devices  25 , the spectral devices  26 , and the light-receiving devices  33 . The first controller  47  has an emission control section  66 , and a photoreception control section  67  to realize its functions. The first controller  47  also has a region in first memory  49  where calibration related data  61  are stored. 
     The second controller  75  has a calibration measurement control section  90  and a calibration data arithmetic section  91  to realize its functions. The second controller  75  also has a region in second memory  77  where calibration related data  86  are stored. The first controller  47  and the second controller  75  communicate with each other via the first communication section  51  and the second communication section  78 . 
     The sensor drive circuit  116  includes a first D/A (Digital/Analog) converter  117 , a first amplifier  118 , and a switch section  121 . The first controller  47  and the first D/A converter  117  are connected to each other, and the first D/A converter  117 , the first amplifier  118 , and the switch section  121  are connected in this order. The switch section  121  is connected to the light-emitting device  25 . The first D/A converter  117 , the first amplifier  118 , and the switch section  121  are provided in the same number as the number of light-emitting devices  25 . A different applied voltage may be set for each different light-emitting device  25 . The sensor drive circuit  116  also includes a second amplifier  122 , and an A/D (Analog/Digital) converter  123 . The light-receiving devices  33 , the second amplifier  122 , the A/D converter  123 , and the first controller  47  are connected in this order. 
     The calibration related data  61  includes drive voltage data for driving the light-emitting devices  25 . The calibration measurement control section  90  outputs light-emitting and light-receiving instruction signals to the emission control section  66  and the photoreception control section  67 . The emission control section  66  receives drive voltage data for the light-emitting device  25  from the calibration related data  61 , and outputs the data to the first D/A converter  117 . The first D/A converter  117  converts the voltage data into a voltage signal, and outputs the signal to the first amplifier  118 . The first amplifier  118  receives the voltage data, and outputs it to the switch section  121  after amplifying the power. The switch section  121  receives the instruction signal from the emission control section  66 , and the power amplified voltage signal. The switch section  121  then outputs to the light-emitting device  25  a voltage waveform corresponding to the instruction signal. This drives the light-emitting device  25  according to the voltage instructed by the emission control section  66 . The light-emitting device  25  emits the measurement light  29 . The measurement light  29  is applied to the calibration plate  36 . 
     The second reflected light  30   a  reflected at the calibration plate  36  enters the light-receiving device  33 . The light-receiving device  33  converts the light intensity of the second reflected light  30   a  into voltage, and outputs the voltage signal to the second amplifier  122 . The second amplifier  122  amplifies the input voltage signal, and outputs it to the A/D converter  123 . The A/D converter  123  converts the voltage signal into voltage data, and outputs it to the first controller  47 . In the first controller  47 , the first CPU  48  sends the corresponding voltage data of the second reflected light  30   a  to the second controller  75 , and the data are stored in the second memory  77 . 
     In  FIG. 15B , steps S 11  and S 12  are the same as in First Embodiment, and will not be described. The sequence goes to step S 31  after step S 12 . In the drive voltage computation step (step S 31 ), the calibration data arithmetic section  91  computes a drive voltage for the light-emitting device  25 . Prior to computation, a reference value is set for the voltage corresponding to the light intensity received by the light-receiving device  33 . The reference value includes an upper-limit reference value corresponding to the upper-limit light intensity, and a lower-limit reference value corresponding to the lower-limit light intensity. The calibration data arithmetic section  91  receives from the second memory  77  the voltage data corresponding to the second reflected light  30   a  detected in step S 12 . 
     The calibration data arithmetic section  91  then compares the corresponding voltage data of the second reflected light  30   a  with the reference value. The drive voltage data driving the light-emitting device  25  is decreased when the voltage data exceeds the upper-limit reference value. The drive voltage data driving the light-emitting device  25  is increased when the voltage data is below the lower-limit reference value. The drive voltage data is varied over a range that is proportional to the difference between the voltage data and the reference value. The calibration data arithmetic section  91  compares the corresponding voltage data of the second reflected light  30   a  with the reference value for all the light-emitting devices  25 , and varies the drive voltage data when the voltage data is larger than the upper-limit reference value and when the voltage data is smaller than the lower-limit reference value. The varied data is stored in the calibration related data  86  in the second memory  77 . The sequence then goes to step S 32 . 
     In the drive voltage varying step (step S 32 ), the drive voltage data varied in step S 31  is transferred from the second memory  77  to the first memory  49 . This varies the drive voltage data stored in the first memory  49 . The sequence then goes to step S 14 . Steps S 14  to S 17  are the same as in First Embodiment, and will not be described. The following describes the object measurement step (step S 3 ). 
     In  FIG. 16 , steps S 21  to S 25  are the same as in First Embodiment, and will not be described. The sequence goes to step S 27  (absorption spectrum computation step) after step S 25 . The calibration step (step S 26 ) is omitted. Step S 26  can be omitted because the drive voltage for the light-emitting device  25  is varied in steps S 31  and S 32 . Steps S 27  to S 29  are the same as in First Embodiment, and will not be described. 
     As described above, the present embodiment has the following effects. 
     (1) According to the present embodiment, the voltage driving the light-emitting device  25  is calibrated when there is a performance change in the light-emitting devices  25  and the light-receiving devices  33 . The output voltage data from the sensor drive circuit  116  to the first controller  47  can thus accurately reflect the state of the measured portion  4   a.    
     (2) According to the present embodiment, the voltage driving the light-emitting device  25  is increased when there is a performance drop in the light-emitting devices  25  and the light-receiving devices  33 . This increases the light intensity of the measurement light  29 , and can suppress decrease of the SN ratio (Signal Noise) in the output voltage data to the first controller  47 . 
     Third Embodiment 
     An embodiment of the component measurement apparatus is described below with reference to  FIGS. 17A and 17B .  FIG. 17A  is a block diagram representing a relevant portion of a sensor drive circuit.  FIG. 17B  is a flowchart representing a maintenance step (step S 1 ) in detail. The present embodiment differs from Second Embodiment in that the value measured with the calibration plate  36  is used to adjust the amplification gain for the output of the light-receiving device  33 . The same features already described in First and Second Embodiments will not be described further. 
     Specifically, in the present embodiment, a sensor drive circuit  127  connected to the first controller  47  is installed in a component measurement apparatus  126  (information acquisition apparatus), as shown in  FIG. 17A . The sensor drive circuit  127  drives the light-emitting devices  25 , the spectral devices  26 , and the light-receiving devices  33 . The first controller  47  has an emission control section  66 , and a photoreception control section  67  to realize its functions. The first controller  47  also has a region in first memory  49  where calibration related data  61  are stored. 
     The second controller  75  has a calibration measurement control section  90 , and a calibration data arithmetic section  91  to realize its functions. The second controller  75  also has a region in second memory  77  where calibration related data  86  are stored. The first controller  47  and the second controller  75  communicate with each other via the first communication section  51  and the second communication section  78 . 
     The sensor drive circuit  127  includes a first D/A converter  117 , a first amplifier  118 , and a switch section  121 . The first controller  47  and the first D/A converter  117  are connected to each other, and the first D/A converter  117 , the first amplifier  118 , and the switch section  121  are connected in this order. The switch section  121  is connected to the light-emitting device  25 . The first D/A converter  117 , the first amplifier  118 , and the switch section  121  are provided in the same number as the number of light-emitting devices  25 . A different applied voltage may be set for each different light-emitting device  25 . The sensor drive circuit  127  also includes a second amplifier  128 , a second D/A converter  129 , and an A/D converter  123 . The light-receiving device  33 , the second amplifier  128 , the A/D converter  123 , and the first controller  47  are connected in this order. The second amplifier  128  has a variable gain, and is connected to the first controller  47  via the second D/A converter  129 . 
     The light-emitting devices  25  apply the measurement light  29  to the calibration plate  36 . The second reflected light  30   a  reflected at the calibration plate  36  enters the light-receiving device  33 . The light-receiving device  33  converts the light intensity of the second reflected light  30   a  into voltage, and outputs the voltage signal to the second amplifier  128 . The second amplifier  128  amplifies the input voltage signal, and outputs it to the A/D converter  123 . The A/D converter  123  converts the voltage signal into voltage data, and outputs it to the first controller  47 . In the first controller  47 , the first CPU  48  sends the corresponding voltage data of the second reflected light  30   a  to the second controller  75 , and the data are stored in the second memory  77 . 
     The calibration related data  61  includes gain data for the second amplifier  128 . The photoreception control section  67  outputs the gain data to the second D/A converter  129 . The second D/A converter  129  converts the gain data into a voltage signal indicative of a gain, and outputs it to the second amplifier  128 . The second amplifier  128  receives the voltage signal indicative of a gain, and amplifies the corresponding voltage signal of the second reflected light  30   a  with the instructed gain. The second amplifier  128  amplifies the input voltage signal, and outputs it to the A/D converter  123 . 
     In  FIG. 17B , steps S 11  and S 12  are the same as in First Embodiment, and will not be described. The sequence goes to step S 41  after step S 12 . In the gain computation step (step S 41 ), the calibration data arithmetic section  91  computes a gain of the second amplifier  128 . Prior to computation, a reference value is set for the voltage corresponding to the light intensity received by the light-receiving device  33 . The reference value includes an upper-limit reference value corresponding to the upper-limit light intensity, and a lower-limit reference value corresponding to the lower-limit light intensity. The calibration data arithmetic section  91  receives from the first memory  49  the voltage data corresponding to the second reflected light  30   a  detected in step S 12 . 
     The calibration data arithmetic section  91  then compares the corresponding voltage data of the second reflected light  30   a  with the reference value. The gain data indicative of the gain of the second amplifier  128  is decreased when the voltage data exceeds the upper-limit reference value. The gain data is increased when the voltage data is below the lower-limit reference value. The gain data is varied over a range that is proportional to the difference between the voltage data and the reference value. As a result, the voltage data corresponding to the second reflected light  30   a  takes a value between the upper-limit reference value and the lower-limit reference value. The calibration data arithmetic section  91  compares the corresponding voltage data of the second reflected light  30   a  with the reference value for all the light-receiving devices  33 , and varies the gain data when the voltage data is larger than the upper-limit reference value and when the voltage data is smaller than the lower-limit reference value. In this manner, the gain data is varied so that the voltage data corresponding to the second reflected light  30   a  takes the same value as the reference value in all the light-receiving devices  33 . The sequence then goes to step S 42 . 
     In the gain varying step (step S 42 ), the gain data varied in step S 41  is transferred in the first memory  49 . This varies the gain data stored in the first memory  49 . The sequence then goes to step S 14 . Steps S 14  to S 17  are the same as in First Embodiment, and will not be described. In the object measurement step (step S 3 ), the calibration step (step S 26 ) is omitted, as in Second Embodiment. 
     As described above, the present embodiment has the following effect. 
     (1) According to the present embodiment, the gain of the second amplifier  128  is varied when there is a performance change in the light-emitting devices  25  and the light-receiving devices  33 . The output voltage data from the sensor drive circuit  127  to the first controller  47  can thus accurately reflect the state of the measured portion  4   a.    
     The present embodiment is not limited to the description of the embodiments above, but may be altered or modified in many ways by a person with ordinary skill in the art within the technical idea of the invention. Variations are described below. 
     Variation 1 
     In the foregoing First Embodiment, the computed blood component is glucose concentration. However, this should not be construed as a limitation, and blood oxygen concentration may be measured using the transmittance of hemoglobin. Hemoglobin can be detected with measurement light  29  of about 650 nm wavelength. A wavelength of about 650 nm is thus set for passage of reflected light  30  through the spectral devices  26 . The transmittance can then be computed to measure blood oxygen concentration. Aside from blood oxygen concentration, the concentration of other components such as lipids may be computed. The blood vessels are not a limitation, and the concentration of the lymph fluid component in a lymph duct may be measured and computed. It is also possible to measure and compute the concentration of the cerebrospinal fluid component. The component measurement apparatus  1  also may be used to test animals other than humans. Aside from animals, the component measurement apparatus  1  also may be used for the measurement of the liquid components or concentrations in plants such as fruits. 
     Variation 2 
     In the foregoing First Embodiment, the light-emitting devices  25  are installed in the sensor module  10 . However, the light-emitting devices  25  may be excluded from the sensor module  10 , and the measurement light  29  may be applied to the measured portion  4   a  from a light source different from the light-emitting devices  25 . Because the light-emitting devices  25  are absent, the sensor module  10  can be produced with improved productivity. 
     Variation 3 
     In the foregoing First Embodiment, the second unit  3  performs the functions of the calibration measurement control section  90  and the calibration data arithmetic section  91 . However, the functions of the calibration measurement control section  90  and the calibration data arithmetic section  91  may be performed by the first unit  2 . In this way, the communication volume between the first unit  2  and the second unit  3  can be reduced. This makes it possible to reduce the time required for the maintenance step (step S 1 ). 
     Variation 4 
     In the foregoing Second Embodiment, the input voltage signal to the first amplifier  118  from the first D/A converter  117  is varied. However, it is also possible to vary the gain of the first amplifier  118 , as in Third Embodiment. The light intensity of the measurement light  29  can also be varied in this manner. 
     Variation 5 
     In the foregoing Second Embodiment, the applied voltage to the light-emitting devices  25  is varied. In the foregoing Third Embodiment, the gain of the second amplifier  128  is varied. However, it is also possible to vary both the applied voltage to the light-emitting devices  25 , and the gain of the second amplifier  128 . With a wider variable range, the device life can be extended when changes occur over time. 
     The entire disclosure of Japanese Patent Application No. 2015-033759 filed Feb. 24, 2015 is hereby incorporated herein by reference.