Patent Publication Number: US-2013234045-A1

Title: Correction method of fluorescence sensor and fluorescence sensor

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation application of PCT/JP2011/073558 filed on Oct. 13, 2011 and claims benefit of Japanese Application No. 2010-240019 filed in Japan on Oct. 26, 2010, the entire contents of which are incorporated herein by this reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a fluorescence sensor for measuring concentration of an analyte and a correction method of the fluorescence sensor, and more particularly, to a fluorescence sensor which is a micro-fluorescence spectrophotometer manufactured using a semiconductor manufacturing technique and an MEMS technique and a correction method of the fluorescence sensor. 
     2. Description of the Related Art 
     Various analyzers for checking presence of an analyte, i.e., a substance to be measured in liquid or measuring concentration of the analyte have been developed. For example, there is a known fluorescence spectrophotometer for injecting fluorescent pigment, which changes in characteristics because of presence of an analyte and generates fluorescent light, and a solution to be measured including the analyte into a transparent container having a fixed capacity and irradiating excitation light E to measure fluorescent light intensity from the fluorescent pigment to thereby measure the concentration of the analyte. 
     A small fluorescence spectrophotometer includes a photodetector and an indicator layer containing fluorescent pigment. When the excitation light E from a light source is irradiated on the indicator layer into which the analyte in the solution to be measured can penetrate, the fluorescent pigment in the indicator layer generates fluorescent light having a light amount corresponding to the analyte concentration in the solution to be measured. The photodetector receives the fluorescent light. The photodetector is a photoelectric conversion element. The photodetector outputs an electric signal corresponding to the light amount of the received fluorescent light. The analyte concentration in the solution to be measured is measured from the electric signal. 
     In recent years, in order to measure an analyte in a micro-volume sample, a micro-fluorescence spectrophotometer manufactured using the semiconductor manufacturing technique and the MEMS technique has been proposed. The micro-fluorescence spectrophotometer is hereinafter referred to as a “fluorescence sensor”. 
     For example, a fluorescence sensor  110  shown in  FIGS. 1 and 2  is disclosed in U.S. Pat. No. 5,039,490. The fluorescence sensor  110  is configured by a transparent supporting substrate  101  through which excitation light E can be transmitted, an optical tabular section  105  including a photoelectric conversion element  103  configured to convert fluorescent light into an electric signal and a light-condensing function section  105 A configured to condense the excitation light E, an indicator layer  106  configured to interact with an analyte  9  to thereby generate fluorescent light through incidence of the excitation light E, and a cover layer  109 . 
     The photoelectric conversion element  103  is, for example, a photoelectric conversion element formed on a substrate  103 A made of silicon. The substrate  103 A does not transmit the excitation light E. Therefore, the fluorescence sensor  110  includes, around the photoelectric conversion element  103 , an air gap region  120  through which the excitation light E can be transmitted. 
     That is, only the excitation light E transmitted through the air gap region  120  and made incident on the optical tabular section  105  is condensed in the vicinity of an upper part of the photoelectric conversion element  103  in the indicator layer  106  by action of the optical tabular section  105 . Fluorescent light F is generated by interaction of condensed excitation light E 2  and the analyte  9  penetrating into an inside of the indicator layer  106 . A part of the generated fluorescent light F is made incident on the photoelectric conversion element  103 . A signal of an electric current, a voltage, or the like proportional to fluorescent light intensity, i.e., the concentration of the analyte  9  is generated in the photoelectric conversion element  103 . Note that the excitation light E is not made incident on the photoelectric conversion element  103  by action of a filter (not shown in the figure) formed to cover the photoelectric conversion element  103 . 
     As explained above, in the fluorescence sensor  110 , on the transparent supporting substrate  101 , a photodiode, which is the photoelectric conversion element  103 , is formed on the substrate  103 A in which the air gap region  120 , which is a passage of the excitation light E, is secured. The optical tabular section  105  and the indicator layer  106  are laminated on the substrate  103 A. 
     SUMMARY OF THE INVENTION 
     A correction method of a fluorescence sensor according to an aspect of the present invention includes: a first detection signal acquiring step for acquiring, at a first temperature, a first detection signal using a fluorescence sensor including a light-emitting element configured to generate excitation light, an indicator layer configured to generate fluorescent light corresponding to the excitation light and an analyte amount, and a photoelectric conversion element configured to output a detection signal in which an excitation light detection signal due to the excitation light is superimposed on a fluorescent light detection signal due to the fluorescent light, the fluorescence sensor having a temperature detecting function for outputting a temperature detection signal and a temperature adjusting function; a second detection signal acquiring step for acquiring, at a second temperature, a second detection signal when the analyte amount is the same as the analyte amount in the first detection signal acquiring step; a correction coefficient calculating step for calculating, on the basis of the first detection signal and the second detection signal, a correction coefficient for correcting the fluorescent light detection signal; and a correcting step for correcting subsequent detection signals using the correction coefficient and the temperature detection signal. 
     A fluorescence sensor according to another aspect of the present invention includes: a light-emitting element configured to generate excitation light; an indicator layer configured to generate fluorescent light corresponding to the excitation light and an analyte amount; and a photoelectric conversion element configured to output a detection signal in which an excitation light detection signal due to the excitation light is superimposed on a fluorescent light detection signal due to the fluorescent light, in which the fluorescence sensor has a temperature detecting function for outputting a temperature detection signal and a temperature adjusting function. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an explanatory diagram showing a sectional structure of a publicly-known fluorescence sensor; 
         FIG. 2  is an exploded view for explaining a structure of the publicly-known fluorescence sensor; 
         FIG. 3  is an explanatory diagram showing a configuration of a sensor system according to an embodiment; 
         FIG. 4  is an explanatory diagram showing a sectional structure of a fluorescence sensor according to the embodiment; 
         FIG. 5  is an exploded view for explaining a structure of the fluorescence sensor according to the embodiment; 
         FIG. 6  is an explanatory diagram for explaining correction processing by the fluorescence sensor according to the embodiment; 
         FIG. 7  is a flowchart for explaining the correction processing by the fluorescence sensor according to the embodiment; and 
         FIG. 8  is a time chart for explaining the correction processing by a fluorescence sensor according to the embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     System Configuration 
     As shown in  FIG. 3 , a needle-type fluorescence sensor  4  including a fluorescence sensor  10  according to an embodiment of the present invention configures a sensor system  1  in conjunction with a main body section  2  and a receiver  3 . 
     That is, the sensor system  1  includes the needle-type fluorescence sensor  4 , the main body section  2 , and the receiver  3  that receives and stores a signal from the main body section  2 . Transmission and reception of a signal between the main body section  2  and the receiver  3  is performed by radio or by wire. 
     The needle-type fluorescence sensor  4  includes a needle section  7  including a needle distal end portion  5 , which includes the fluorescence sensor  10  as a main functional section, and an elongated needle main body portion  6 , and a connector section  8  integrated with a rear end portion of the needle main body portion  6 . The needle distal end portion  5 , the needle main body portion  6 , and the connector section  8  may be integrally formed by the same material. 
     The connector section  8  detachably fits with a fitting section  2 A of the main body section  2 . The connector section  8  mechanically fits with the fitting section  2 A of the main body section  2 , whereby a plurality of wires  60  extended from the fluorescence sensor  10  of the needle-type fluorescence sensor  4  are electrically connected to the main body section  2 . The connector section  8  includes an arithmetic section  70  configured to perform control and an arithmetic operation for subjecting a detection signal from the fluorescence sensor  10  to correction processing. 
     Although not shown in the figure, the main body section  2  includes a radio antenna for transmitting and receiving a radio signal between the main body section  2  and the receiver  3 , and a battery and the like. When wired transmission and reception is performed between the main body section  2  and the receiver  3 , the main body section  2  includes a signal line instead of the radio antenna. Note that the main body section  2  or the receiver  3  may include an arithmetic section. 
     The fluorescence sensor  10  is a disposable section that is discarded after use to prevent infection or the like. However, the main body section  2  and the receiver  3  are reusable sections that are repeatedly reused. Note that, when the main body section  2  includes a memory section having a necessary capacity, the receiver  3  is unnecessary. 
     In a state in which the needle-type fluorescence sensor  4  is fit with the main body section  2 , a subject himself/herself stabs the needle-type fluorescence sensor  4  from a body surface. The needle distal end portion  5  is retained in a body. For example, the needle-type fluorescence sensor  4  continuously measures glucose concentration in body fluid and stores the glucose concentration in a memory of the receiver  3 . That is, the fluorescence sensor  10  according to the present embodiment is a sensor of a short-term subcutaneous retaining type that is continuously used for about one week. 
     &lt;Fluorescence Sensor Structure&gt; 
     As shown in  FIGS. 4 and 5 , the fluorescence sensor  10 , which is a main functional section of the needle-type fluorescence sensor  4  according to the present invention, has a structure in which an N-type silicon substrate  11 , which is a base substrate, a photo diode (hereinafter also referred to as “PD”) element  13 , which is a photoelectric conversion element, a silicon oxide layer  17 , a filter  14 , a light emitting diode (hereinafter also referred to as “LED”) element  12 , which is a light-emitting element that transmits fluorescent light, a transparent resin layer  15 , an indicator layer  16 , and a light blocking layer  19  are laminated in order from the silicon substrate  11  side. 
     At least respective parts of the PD element  13 , the filter  14 , the LED element  12 , and the indicator layer  16  are formed in the same region on an upper side of the silicon substrate  11 . It is desirable that, in the fluorescence sensor  10 , respective centers of the PD element  13 , the filter  14 , the LED element  12 , and the indicator layer  16  are formed in the same region on the upper side of the silicon substrate  11 . 
     That is, in the fluorescence sensor  10 , the LED element  12 , which is the light-emitting element that transmits fluorescent light from the indicator layer  16 , is used, whereby a structure completely different from a publicly-known fluorescence sensor is realized. 
     As the photoelectric conversion element, various photoelectric conversion elements such as a photoconductor or a photo transistor (PT) can also be selected. 
     The silicon oxide layer  17  is a first protective layer. As the first protective layer having thickness of several tens to several hundreds of nanometers, a silicon nitride layer or a composite laminated layer including a silicon oxide layer and a silicon nitride layer may be used. 
     The filter  14  is, for example, an absorption-type filter that does not transmit excitation light E generated by the LED element  12  and transmits fluorescent light F having wavelength longer than wavelength of the excitation light E. The filter  14  may be a band-pass filter that allows only fluorescent light to pass. However, actually, a part of the excitation light E is transmitted through the filter  14  and made incident on the LED element  12 . Note that the filter  14  is not an essential constituent element for the fluorescence sensor  10  that performs correction processing as explained below. 
     The LED element  12  is a light-emitting element that emits excitation light and transmits fluorescent light. The transparent resin layer  15  is a second protective layer. As the second protective layer, for example, silicone resin or transparent amorphous fluorocarbon resin used in bonding the LED element  12  to the filter  14  can also be used. 
     As a characteristic of the second protective layer of the fluorescence sensor  10 , it is important that generation of fluorescent light is little in the layer even if excitation light is irradiated on the layer. It goes without saying that this characteristic that generation of fluorescent light is little is an important characteristic of all transparent materials of the fluorescence sensor  10  excluding the indicator layer  16 . 
     The indicator layer  16  generates fluorescent light according to an interaction with an analyte  9  penetrating into the indicator layer  16  and excitation light, i.e., generates fluorescent light having a light amount corresponding to concentration of the analyte  9 . Thickness of the indicator layer  16  is set to about several tens of micrometers. The indicator layer  16  is configured by a base material including fluorescent pigment that generates fluorescent light having intensity corresponding to an amount of the analyte  9 , i.e., analyte concentration in a specimen. Note that a base material of the indicator layer  16  desirably has transparency for allowing excitation light from the LED element  12  and fluorescent light from the fluorescent pigment to be satisfactorily transmitted through the indicator layer  16 . The fluorescent pigment may be the analyte  9  itself present in the specimen. 
     The fluorescent pigment is selected according to a type of the analyte  9 . Any fluorescent pigment can be used as long as a light amount of the fluorescent light emitted according to the amount of the analyte  9  reversibly changes. For example, when hydrogen ion concentration or carbon dioxide in a living organism is measured, a hydroxypyrene-tris sulfonic acid derivative can be used. A phenylboronic acid derivative having a fluorescence residue can be used when saccharides are measured. A crown ether derivative having a fluorescence residue can be used when a potassium ion is measured. 
     When saccharides such as glucose are measured, as the fluorescent pigment, a substance that reversibly couples with glucose such as a ruthenium organic complex, a phenylboronic acid derivative, or fluorescein coupled with protein can be used. 
     As explained above, the fluorescence sensor  10  according to the present invention is adapted to various uses such as an oxygen sensor, a glucose sensor, a pH sensor, an immunosensor, or a microbial sensor according to the selection of the fluorescent pigment. 
     The indicator layer  16  has, for example, an easily-hydrated hydrogel as a base material. In the hydrogel, the fluorescent pigment is contained or coupled. As a component of the hydrogel, for example, a polysaccharide such as methylcellulose or dextran can be used. 
     The indicator layer  16  is joined to the transparent resin layer  15  via a not-shown adhesive layer formed of a silane coupling agent or the like. Note that a structure in which the transparent resin layer  15  is not formed and the indicator layer  16  is directly joined to a surface of the LED element  12  may be adopted. 
     The light blocking layer  19  is a layer having thickness equal to or smaller than several tens of micrometers formed on an upper surface side of the indicator layer  16 . The light blocking layer  19  prevents excitation light and fluorescent light from leaking to an outside of the fluorescence sensor  10  and, at the same time, prevents external light from penetrating into an inside of the fluorescence sensor  10 . 
     The fluorescence sensor  10  further includes a temperature sensor  21  having a temperature detecting function and a heater  22  having a temperature adjusting function. 
     The temperature sensor  21  performs temperature measurement for a photodetection system  20  including the PD element  13 , the filter  14 , the LED element  12 , and the indicator layer  16  and outputs a temperature detection signal. A variety of devices such as a diode, a thermistor, and a thermocouple can be applied to the temperature sensor  21 . When a PD element is used as the photoelectric conversion element, the PD element can be formed on the substrate  11  simultaneously with formation of the PD element  13  by the same diode structure. The temperature sensor  21  is set near the photodetection system  20 . 
     Note that, in the fluorescence sensor  10  including the PD element  13  as the photoelectric conversion element, the PD element  13  can be used as the temperature sensor  21  as well. That is, the PD element  13  can be used as the temperature sensor  21  as well when a photoelectric conversion operation is not performed. In this case, it is unnecessary to dispose the temperature sensor  21  exclusive for temperature measurement. 
     An error between temperature detected by the temperature sensor  21  arranged near the silicon substrate  11  having high thermal conductivity and temperature of the photodetection system  20  is small. When a substrate is not a high-thermal conductivity material, it is desirable to dispose a high-thermal conductivity body around the photodetection system  20  and arrange the temperature sensor  21  in a position where the temperature sensor  21  is in contact with the high-thermal conductivity body. 
     The heater  22 , which is a temperature adjusting section having the temperature adjusting function, is a heat generating member for heating the photodetection system  20  to a predetermined temperature, for example, 40° C. The heater  22  is a resistance heating type heater formed of a metal wire of aluminum or gold, conductive ceramic, carbon, conductive resin, or the like. The resistance heating type heater can be formed of a single material. However, when the resistance heating type heater includes a low-resistance wire and a high-resistance wire, local heating is possible. The temperature of the photodetection system  20  may be equalized by configuring the temperature adjusting section with a heat generating section and a heat transfer section made of a high thermal conductivity material and disposing the heat transfer section around the photodetection system  20 . 
     Further, other constituent members of the fluorescence sensor  10  may have the temperature adjusting function. For example, the LED element  12  continuously emits light to thereby generate heat. When the photoelectric conversion element is a diode, if an electric current in a forward direction is fed to the diode, the diode generates heat. In this case, it is unnecessary to dispose a heat adjusting section exclusive for heating. 
     &lt;Basic Operation of the Fluorescence Sensor  10 &gt; 
     Next, a basic operation of the fluorescence sensor  10  is explained with reference to  FIGS. 4 and 5 . 
     The LED element  12  emits, in a pulse-like manner, the excitation light E having center wavelength of about 375 nm, for example, at an interval of once in thirty seconds. For example, a pulse current to the LED element  12  is 1 mA to 100 mA and pulse width of light emission is 10 ms to 100 ms. 
     Excitation light E 1  generated by the LED element  12  is made incident on the indicator layer  16 . The indicator layer  16  emits the fluorescent light F having intensity corresponding to an amount of the analyte  9 . The analyte  9  penetrates into the indicator layer  16  passing through the light blocking layer  19 . The fluorescent pigment of the indicator layer  16  generates the fluorescent light F having larger wavelength, for example, wavelength of 460 nm with respect to the excitation light E having wavelength of 375 nm. 
     In the fluorescence sensor  10 , the excitation light E generated by the LED element  12  is irradiated in upward and downward directions. The excitation light E 1  irradiated in the upward direction is irradiated on the fluorescent pigment in the indicator layer  16 . In the fluorescent light F generated by the fluorescent pigment, both of fluorescent light F 1  passing through the LED element  12  and the filter  14  and reaching the PD element  13  and fluorescent light F 2  passing through the filter  14  and reaching the PD element  13  are converted into an electric signal in the PD element  13 . In the following explanation, the electric signal due to the fluorescent lights F 1  and F 2  is referred to as fluorescent light detection signal V F . 
     On the other hand, excitation light E 2  radiated downward from the LED element  12  passes through the filter  14  and the like. A part of excitation light E 3  reaches the PD element  13 . The excitation light E 3  is noise light inevitably generated according to a characteristic of the filter  14  and a structure of the fluorescence sensor  10 . In the following explanation, an electric signal due to the excitation light E 3  is referred to as an excitation light detection signal V EX . 
     That is, in a detection signal V outputted by the PD element  13 , the excitation light detection signal V EX  is superimposed on the fluorescent light detection signal V F . Since intensity L EX  of excitation light and the excitation light detection signal V EX  are different for each fluorescence sensor, the intensity L EX  of excitation light and the excitation light detection signal V EX  are causes of deterioration in detection accuracy of the fluorescence sensor  10 . 
     &lt;Correction Processing&gt; 
     Next, correction processing by the fluorescence sensor  10  is explained with reference to  FIG. 6 . 
     The fluorescence sensor  10  performs, with an arithmetic operation, correction processing for removing the excitation light detection signal V EX  from the detection signal V and extracting only the fluorescent light detection signal V F . 
     That is, the fluorescence sensor  10  performs, using the heater  22  having the temperature adjusting function and the temperature sensor  21  having the temperature detecting function, correction processing for calculating a correction coefficient for calculating the fluorescent light detection signal V F  on the basis of a plurality of detection signals V at a plurality of different temperatures and corrects subsequent detection signals on the basis of a result of the correction processing. 
     In the following explanation, a detection signal measured at temperature T, i.e., a photoelectromotive force outputted by the PD element  13  is represented as V and, for example, a detection signal measured at temperature T 1  is represented as V 1 . The fluorescence sensor  10  is heated by the heater  22 . A detection signal at the time when the fluorescence sensor  10  is heated to temperature T 2  is represented as V 2 . Volume of the photodetection system  20  is about several mm 3 . Therefore, a temperature rise of several degrees Celsius to ten-odd degrees Celsius occurs in several seconds to several tens of seconds from start of the heating. The correction processing is performed at timing when a sudden change does not occur in analyte concentration. Therefore, an analyte concentration change in several seconds to several tens of seconds can be neglected. Therefore, analyte concentration C during the correction processing can be regarded as a constant C 0 . 
     As explained above, the detection signal V, which is a sensor output, is configured by the excitation light detection signal V EX  and the fluorescent light detection signal V F . Therefore, the detection signal is represented by (Equation 1). 
         V=V   EX   +V   F   (Equation 1)
 
     First, an expression representing temperature dependency of the excitation light detection signal V EX  is calculated. 
     An excitation light emission amount L EX  by the LED element  12  is represented by (Equation 2). 
         L   EX   =L   EX0   ·T   EX   (Equation 2)
 
     L EX0  represents a light emission amount at reference temperature T 0 . T EX  represents a temperature dependency coefficient with respect to the light emission amount. The light emission amount L EX0  indicates a different value for each LED element  12 . In some case, a difference exceeding a double is perceived between elements. The difference in the light emission amount L EX0  is due to a manufacturing process for the LED element  12  and does not depend on a structure of the fluorescence sensor  10 . The temperature dependency coefficient T EX  is a function with respect to temperature. The temperature dependency coefficient T EX  can be calculated by a theory or an experiment. T EX  may be a linear function or a nonlinear function depending on a type and a temperature range of the LED element  12 . 
     An excitation light amount IN EX  made incident on the PD element  13  is represented by (Equation 3). 
         IN   EX   =L   EX ·β EX =( L   EX0   ·T   EX )·β EX   (Equation 3)
 
     β EX  represents a coefficient representing light condensation efficiency on the PD element  13  of excitation light determined as a result of attenuation of the excitation light due to scattering, reflection, and absorption in the photodetection system  20 . 
     As a result, the excitation light detection signal V EX  is represented by (Equation 4). 
         V   EX   =IN   EX   ·S   EX   ·T   SEX =( L   EX0   ·T   EX ·β EX )· S   EX   ·T   SEX   (Equation 4)
 
     S EX  represents photoelectric conversion efficiency of the PD element  13  with respect to excitation light. T SEX  represents a temperature dependency coefficient of the photoelectric conversion efficiency. 
     Next, an expression representing temperature dependency of the fluorescent light detection signal V F  in the detection signal V is calculated. 
     A fluorescent light emission amount L F  of the indicator layer  16  is represented by (Equation 5). 
         L   F =α EX   ·L   EX   ·e·T   F   (Equation 5)
 
     α EX  represents a coefficient indicating a ratio of excitation light that reaches the indicator layer  16  and contributes to fluorescent light emission among excitation lights generated by the LED element  12  and e represents a conversion coefficient (fluorescence yield) from excitation light to fluorescent light at a reference temperature T 0  and represents a function that depends on analyte concentration. T F  represents a temperature dependency coefficient of a fluorescent light emission amount and represents a function with respect to temperature. The temperature dependency coefficient T F  can be calculated by an experiment. T F  is a linear function or a non-linear function depending on a temperature range. 
     If (Equation 2) is substituted in (Equation 5), (Equation 6) is obtained. 
         L   F =α EX ·( L   EX0   ·T   EX )· e·T   F   (Equation 6)
 
     Further, a fluorescent light amount I NF  made incident on the PD element  13  is represented by (Equation 7). 
         IN   F   =L   F ·β F (α EX   ·L   EX0   ·T   EX   ·e·T   F )·β F   (Equation 7)
 
     β F  Represents a coefficient representing light condensation efficiency of fluorescent light determined as a result of attenuation of the fluorescent light F due to scattering, reflection, and absorption in the photodetection system  20 . 
     As a result, the fluorescent light detection signal V F  is represented by (Equation 8). 
         V   F   =IN   F   ·S   F   ·T   SF =(α EX   ·L   EX0   ·T   EX   ·e·T   F ·β F )· S   F   ·T   SF   (Equation 8)
 
     where, S F  represents photoelectric conversion efficiency of the PD element  13  with respect to fluorescent light. T SF  is a temperature dependency coefficient of the photoelectric conversion efficiency. 
     That is, the detection signal V, which is a sensor output, is represented by (Equation 9). 
         V=V   EX   +V   F =( L   EX0   ·T   EX ·β EX   ·S   EX   ·T   SEX )+(α EX   ·L   EX0   ·T   EX   ·e·T   F ·β F   ·S   F   ·T   SF )= a·T   EX   ·T   SEX   +b·T   EX   ·T   F   ·T   SF   (Equation 9)
 
     where, a=L EX0 ·β EX ·S EX  (Equation 10) and b=α EX ·L EX0 ·e·β F ·S F (Equation 11). 
     Coefficients a and b do not have temperature dependency. When analyte concentration is fixed at C 0 , a conversion coefficient e for conversion from excitation light to fluorescent light is a constant e C0 . That is, during the correction processing, the constant a and the constant b can be regarded as constants. 
     (Equation 9) is a relational expression between two unknown numbers a and b and known functions T EX , T SEX , T F , and T SF  and the detection signal V at known analyte concentration. That is, (Equation 9) indicates that, if T EX , T SEX , T F , and T SF  at two temperatures and the detection signal V at the temperatures are calculated, a and b are calculated. 
     (Equation 9) is represented by (Equation 12) according to (Equation 1). 
         V   F   =V−V   EX   =V−a·T   EX   ·T   SEX   (Equation 12)
 
     Next, a procedure for measuring sensor outputs at two different temperatures and calculating a fluorescent component is explained. Note that it is possible to treat the PD element  13  neglecting temperature dependency thereof at least in a temperature range of about 30 to 50° C. Therefore, the temperature dependency is simplified and represented as T SEX =T SF =1. 
     First, (Equation 13) holds concerning temperature T 1 . 
         V   (1)   =a·T   EX(1)   +b·T   EX(1)   ·T   F(1)   (Equation 13)
 
     Next, (Equation 14) holds concerning temperature T 2 . 
         V   (2)   =a·T   EX(2)   +b·T   EX(2)   ·T   F(2)   (Equation 14)
 
     A temperature dependency coefficient with respect to a light emission amount of the LED element  12  at the temperature T 1  is represented as T EX(1) , a temperature dependency coefficient of a fluorescent light emission amount at the temperature T 1  is represented as T F(1) , a temperature dependency coefficient of the LED element  12  at the temperature T 2  is represented as T EX(2) , and a temperature dependency coefficient of a fluorescent light emission amount at the temperature T 2  is represented as T F(2) . From (Equation 13) and (Equation 14), the coefficient a is calculated by (Equation 15). 
     
       
         
           
             
               
                 
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     Correction arithmetic processing for removing the excitation light detection signal V EX  from the detection signal V ends. The coefficient a calculated above depends on neither temperature nor analyte concentration. Therefore, thereafter, it is possible to calculate, at arbitrary temperature T, the fluorescent light detection signal V F  on the basis of the detection signal V of the PD element  13  and the temperature dependency coefficient T EX  of a light emission amount at the temperature T. 
     Note that the temperatures T 1  and T 2  during correction, fluorescent light outputs V F(1)  and V F(2)  corresponding to the temperatures T 1  and T 2 , and the analyte concentration C 0  at this point are initial values in calculating the analyte concentration C at arbitrary temperature after the correction arithmetic processing. 
     When the analyte is glucose, the analyte concentration C 0  is calculated using self monitoring of blood glucose (SMBG). 
     Next, processing for converting the fluorescent light detection signal V F  into the analyte concentration C is explained. 
     The analyte concentration C is calculated from (Equation 17) using a function δ. 
         C =δ( T,V   F )  (Equation 17)
 
     T represents temperature and V F  represents a fluorescent light detection signal at the temperature T. (Equation 17) includes a temperature dependency correction coefficient ε for correcting temperature dependency of the fluorescent light detection signal V F  and a coefficient γ for adjusting an initial value of analyte concentration to C 0 . However, the temperature dependency correction coefficient ε can be calculated from an expression derived from an experiment or a theory or can be tabulated as a data group. The coefficient γ is determined using the initial value. The function δ is an expression derived from an experiment or a theory. However, the function δ may be a tabulated data group. If the temperature dependency correction coefficient ε and the coefficient γ are set in advance, the analyte concentration C can be calculated on the basis of the fluorescent light detection signal V F  and a temperature detection signal at arbitrary temperature T using (Equation 17). 
     &lt;Correction Processing Procedure&gt; 
     Next, a correction processing procedure of the fluorescence sensor  10  is explained on the basis of a flowchart of  FIG. 7  and a time chart of  FIG. 8 . 
     &lt;Step S 10 &gt; 
     At time T 0 , the needle distal end portion  5  of the needle-type fluorescence sensor  4  is stabbed and the fluorescence sensor  10  is set in a body. At this point, the excitation light E is not irradiated, the heater  22 , which is the temperature adjusting section, is off, temperature of the fluorescence sensor  10  is T 1 , and a detection signal (a photoelectromotive force) of the PD element  13  is V 0 . 
     &lt;Step S 11 &gt; First Detection Signal Acquiring Step 
     At Time T 1  to T 2 , the LED element  12  is lit (turned on) and the detection signal V 1  is detected. Temperature at this point is T 1 . That is, the first detection signal V 1  at the first temperature T 1  is acquired. 
     &lt;Steps S 12  and S 13 &gt; Heating Step 
     At time T 3  to T 4 , an electric current is applied to the heater  22  and the heater  22  has an output W 1 . The fluorescence sensor  10  is heated until temperature of the fluorescence sensor  10  reaches the temperature T 2  (step S 13 : YES). 
     &lt;Step S 14 &gt; 
     At time T 4  to T 7 , the heater has an output W 2  and the temperature of the fluorescence sensor  10  is retained at T 2 . 
     &lt;Step S 15 &gt; Second Detection Signal Acquiring Step 
     At time T 5  to T 6 , the LED element  12  is lit and the detection signal V 2  is detected. That is, the second detection signal V 2  at the second temperature T 2  is acquired. 
     &lt;Step S 16 &gt; Correction Coefficient Calculating Step 
     The constant a, which is a correction coefficient, is calculated from the detection signal V 1 , the detection signal V 2 , and (Equation 15). 
     &lt;Steps S 17  and S 18 &gt; Correction Processing Completion 
     At time T 7 , the heater  22  is turned off and naturally cooled. When the cooling is completed at time T 8  (S 18 : YES), constant calculation processing, i.e., correction processing is completed. 
     &lt;Step S 19 &gt; Measuring Step 
     At time T 9  to T 10 , the LED element  12  is lit. Temperature T N  and a detection signal V N  at that point are measured. 
     &lt;Step S 20 &gt; Calculating Step 
     The arithmetic section  70  calculates the fluorescent light detection signal V F  using the temperature T N , the detection signal V N , and the constant a and further calculates the analyte concentration C using (Equation 17). 
     &lt;Step S 21 &gt; 
     Thereafter, the irradiation of excitation light, the acquisition of a detection signal, and the measurement of temperature are repeated until an end (S 21 : YES) in a constant period, whereby continuous measurement of the analyte concentration C is performed. 
     In a correction method of the fluorescence sensor  10 , it is possible to obtain an accurate value of the fluorescent light detection signal V F  in the detection signal V from the detection signals V at different two temperatures using a temperature controlling function. That is, the fluorescence sensor  10  can purely obtain only the fluorescent light detection signal V F . Therefore, the fluorescence sensor  10  and the correction method of the fluorescence sensor  10  have high detection accuracy. 
     For example, when T 0  and T F(1)  are set as T 0 =32° C. and T F(1) =1, at T 1 =37° C., T EX(1) =0.94, T F(1) =0.78, and V (1) =261(−) and, at T 2 =42° C., T EX(2) =0.87, TF (2) =0.55, and V (2) =223(−). 
     Consequently, the correction coefficient a=205 and the fluorescent light detection signal V F(1) =56 are obtained. 
     The temperature adjusting function explained above is heating means for raising temperature through heating. However, the temperature adjusting function may be cooling means for lowering temperature through cooling. Further, the fluorescence sensor may include the heating means and the cooling means. 
     The correcting method for calculating the fluorescent light detection signal V F  on the basis of the two detection signals V at the two different temperatures is explained above. However, the correction may be performed on the basis of three or more detection signals at three or more different temperatures. In particular, when it is necessary to eliminate the influence of not only the excitation light E but also an external light detection signal, which is a detection signal of the PD element, due to external light from the outside of the fluorescence sensor  10 , it is necessary to perform correction for calculating the fluorescent light detection signal V F  on the basis of detection signals at three kinds of temperatures. 
     The present invention is not limited to the embodiments and the like explained above and combinations, various alterations, modifications, and the like of the embodiments and the like can be made without departing from the spirit of the invention.