JP2013104839A - Device and method for detecting quantitative biological information - Google Patents

Abstract

PROBLEM TO BE SOLVED: To rapidly detect highly accurate quantitative biological information free of dark current influence while conserving power consumption.SOLUTION: Provided is a quantitative biological information detector 1 which includes: a PD (photo diode) 15 for detecting quantitative biological information comprising an analog signal which includes a dark current component and the dark current component comprising an analog signal; an integrator circuit 23 for converting the quantitative biological information detected by the PD 15 to a first pulse width and the dark current component detected by the PD 15 to a second pulse width; a counter for counting the first pulse width converted by the integrator circuit 23 using a reference clock to produce a first counter value and for counting the second pulse width converted by the integrator circuit 23 using the reference clock to produce a second counter value; and an arithmetic unit for obtaining the quantitative biological information from the difference between the first counter value and the second counter value produced by the counter.

Description

  The present invention relates to a biological information amount detection apparatus and a biological information amount detection method.

Conventionally, a biological information amount detection device such as a glucose monitor is known (for example, see Patent Document 1).
In addition to the biological information amount, a dark current generated in the sensor is superimposed on the output signal from the sensor that measures the biological information amount, which causes a measurement error. The biological information amount detection device described in Patent Literature 1 subtracts the current value of a sensor that measures dark current while the LED is turned off from the current value of the sensor that measures biological information while the LED is turned on. Thus, the influence of the dark current generated in the sensor is canceled.
Similarly, there is an apparatus that uses an LED and a sensor to measure a pulse wave and a blood oxygen concentration as biological information other than glucose.

JP-A-2-278142

  However, the biological information amount detection device described in Patent Document 1 is based on the current value of the analog signal from the sensor that measured the biological information amount with the LED turned on and the sensor that measured the dark current with the LED turned off. Since the current value of the analog signal is converted to the current value of the digital signal and the difference between the two is obtained, the processing takes time and the power consumption increases as much as each signal is converted. is there.

  The present invention has been made in view of the above-described circumstances, and is a biological information amount detection apparatus and biological information capable of detecting a highly accurate biological information amount from which the influence of dark current has been removed quickly and with low power consumption. It aims to provide a quantity detection method.

In order to achieve the above object, the present invention provides the following means.
The present invention is a sensor for detecting a biological information amount including an analog signal including a dark current component and a dark current component including an analog signal, and converting the biological information amount detected by the sensor into a first pulse width, A conversion circuit for converting the dark current component detected by the sensor into a second pulse width; and generating a first counter value by counting the first pulse width converted by the conversion circuit with a reference clock; A counter that counts the second pulse width converted by the conversion circuit with a reference clock to generate a second counter value, and a difference between the first counter value generated by the counter and the second counter value There is provided a biological information amount detection device including a calculation unit for obtaining a biological information amount.

  According to the present invention, the calculation unit detects a highly accurate biological information amount in which the dark current component composed of the analog signal is removed from the biological information amount composed of the analog signal including the dark current component detected by the sensor. The dark current refers to a discharge current that flows even in a non-operating state in the sensor.

  In this case, each analog signal is converted into the first pulse width and the second pulse width by the conversion circuit, respectively, and each pulse width is converted to the first counter value and the second counter value counted by the reference clock by the counter, By calculating the amount of biological information from these differences by the calculation unit, the processing time can be shortened and the power consumption can be reduced as compared with the case where each analog signal is converted into a digital signal for calculation processing. Therefore, a highly accurate amount of biological information from which the influence of dark current has been removed can be detected quickly and with low power consumption.

In the above invention, the arithmetic unit may convert the analog signal of the biological information amount obtained by the difference between the first counter value and the second counter value into a digital signal.
With this configuration, the amount of biological information can be efficiently recorded, stored, compressed, transmitted, and the like.

Moreover, in the said invention, the said sensor is good also as performing the detection of the biometric information amount which consists of an analog signal containing a dark current component, and the detection of the dark current component which consists of an analog signal alternately.
This configuration reduces the detection time difference between the amount of biological information consisting of analog signals containing dark current components and the dark current component consisting of analog signals, and the influence of dark current and circuit temperature characteristics from the amount of biological information. It can be removed with high accuracy.

  In the above invention, the conversion circuit converts the current signal of the biological information amount detected by the sensor and the current signal of the dark current component, and outputs a voltage signal that satisfies the first reference potential. And an integration unit that integrates each voltage signal converted by the conversion unit and outputs a pulse width satisfying a second reference potential different from the first reference potential.

  By configuring in this way, even if the output change due to the temperature characteristic generated in the conversion part and the integration part changes in the negative direction, that is, in the decreasing direction of the current signal of the sensor, the change amount is extracted, and the influence of the temperature characteristic is Can be removed.

In the above invention, the conversion circuit may be a double integration method.
With this configuration, conversion of an analog signal into a pulse width can be easily performed. Therefore, it is possible to averagely remove noise with a short period and detect the amount of biological information with high accuracy.

  In addition, the present invention provides a detection step of detecting a biological information amount including an analog signal including a dark current component and the dark current component including an analog signal, and the biological information amount detected by the detection step is set to a first pulse width. And converting the dark current component detected in the detection step into a second pulse width, and counting the first pulse width converted in the conversion step with a reference clock to obtain a first counter value And generating a second counter value by counting the second pulse width converted by the conversion step with a reference clock, the first counter value generated by the counting step, and the second counter value There is provided a biological information amount detection method including a calculation step of obtaining the biological information amount based on a difference from a counter value.

According to the present invention, a highly accurate biological information amount in which the dark current component of the analog signal is removed from the biological information amount of the analog signal including the dark current component detected by the detection step is detected by the calculation step.
In this case, each analog signal is converted into a pulse width by the conversion process, and the biological information amount is obtained from the difference by the calculation process in a state where each pulse width is counted by the reference clock by the counting process. Therefore, it is possible to quickly detect a highly accurate amount of biological information from which the influence of dark current is removed with low power consumption.

In the above invention, the calculation step may convert the analog signal of the biological information amount obtained by the difference between the first counter value and the second counter value into a digital signal.
With this configuration, the amount of biological information can be efficiently recorded, stored, compressed, transmitted, and the like.

Moreover, in the said invention, the said detection process is good also as performing the detection of the biometric information amount which consists of an analog signal containing a dark current component, and the detection of the dark current component which consists of an analog signal alternately.
By configuring in this way, the detection time difference between the biological information amount of the analog signal including the dark current component and the dark current component of the analog signal is reduced, and the influence of the dark current and the temperature characteristic of the circuit is accurately determined from the biological information amount. Can be removed.

Moreover, in the said invention, the said conversion process converts the current signal of the said biometric information amount detected by the said detection process, and outputs the voltage signal which satisfy | fills the 1st reference potential by converting the current signal of the said dark current component, Each voltage signal may be integrated to output a pulse width that satisfies a second reference potential different from the first reference potential.
With this configuration, even if the output change due to the temperature characteristic occurring in the circuit changes in the decreasing direction of the current signal of the sensor, the change amount can be extracted and the influence of the temperature characteristic can be removed.

In the above invention, the conversion step may be performed by a double integration method.
With this configuration, it is possible to easily convert the analog signal into a pulse width, average out noise with a short period, and accurately detect the amount of biological information.

  According to the present invention, there is an effect that a highly accurate amount of biological information from which the influence of dark current is removed can be detected quickly and with low power consumption.

It is a block diagram which shows the biometric information amount detection apparatus which concerns on 1st Embodiment of this invention. It is a block diagram which shows the periphery of the counter of the control circuit of the biological information amount detection apparatus of FIG. It is a timing chart which shows the relationship of the signal of each part by the processing circuit and control circuit of the biological information amount detection apparatus of FIG. It is a flowchart explaining the biometric information amount detection method which concerns on 1st Embodiment of this invention. It is a timing chart explaining the biometric information detection apparatus and biometric information detection method which concern on 1st Embodiment of this invention. It is a block diagram which shows the biometric information amount detection apparatus which concerns on 2nd Embodiment of this invention. It is a timing chart which shows the relationship of the signal of each part by the processing circuit and control circuit of the biometric information detection apparatus of FIG. It is a timing chart explaining the biometric information amount detection apparatus and biometric information amount detection method which concern on 2nd Embodiment of this invention.

[First Embodiment]
A biological information amount detection apparatus and a biological information amount detection method according to a first embodiment of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, the biological information amount detection apparatus 1 according to the present embodiment controls a signal detection unit 3, a processing circuit 5 that processes a signal detected by the signal detection unit 3, and the processing circuit 5. In addition, a control circuit (MCU: microcontroller) 7 that calculates the amount of biological information based on the signal processed by the processing circuit 5 is provided.

  The signal detection unit 3 emits light F such as fluorescence or reflected light emitted from the biological reaction member 13 by being irradiated with the light source 11 such as an LED (Light-Emitting Diode) and the light E emitted from the light source 11. A PD (photodiode: sensor) 15 for detection is provided.

As the biological reaction member 13, for example, a member whose fluorescence or reflectance changes according to the amount of the living body when light from the light source 11 is irradiated is used. Moreover, when the light from the light source 11 changes according to the amount of biological information, the biological reaction member 13 may be a simple reflector. Examples of the biological information amount include a pulse wave, a blood oxygen saturation concentration, and a glucose concentration.
The PD 15 outputs a current signal Iout having a magnitude corresponding to the detected intensity of the light F.

  The processing circuit 5 includes an IV conversion circuit 21 that converts the current signal Iout output from the PD 15 into a voltage signal IVout, and an integration that converts the voltage signal IVout output from the IV conversion circuit 21 into a pulse width proportional to the current of the PD 15. Circuit (conversion circuit) 23.

The IV conversion circuit 21 includes an operational amplifier 21a and a conversion resistor 21b that connects a negative input terminal and an output terminal of the operational amplifier 21a.
The first reference potential V _ref1 generated by the reference potential generation IC 18 is input to the positive input terminal of the operational amplifier 21a. The first reference potential V _ref1 is, for example, a potential of 1.25V.

Integrator circuit 23 compares the integral unit 25 that outputs a voltage signal INTEG_out by integrating the voltage signal IVout, voltage signal INTEG_out output from the integrating section 25 and the first reference potential _{V ref1,} the voltage signal INTEG_out first And a comparison unit 27 that outputs a signal that is in a low state when it falls below one reference potential V _ref1 .

The integrating unit 25 is input from the operational amplifier 25a, the capacitor 25b that connects the negative input terminal and the output terminal of the operational amplifier 25a, the switch 25c that short-circuits or cuts off both ends of the capacitor 25b, the input resistor 25d, and the IV conversion circuit 21. A switch 25e for switching the input / output of the voltage signal IVout to the resistor 25d and a switch 25f for switching the input / output of the third reference potential _Vref3 to the input resistor 25d are provided.

The third reference potential V _ref3 is generated by the reference potential generation IC 19 and is, for example, a potential of 3.0V.
The positive input terminal of the operational amplifier 25a, similar to the operational amplifier 21a, the first reference potential _{V ref1} of 1.25V potential generated by reference potential generating IC18 is adapted to be input.

The comparison unit 27 includes a comparator 27a and a NOT gate 27b that outputs a signal COMP_out opposite to the output of the comparator 27a.
The pulse width of the signal COMP_out output from the NOT gate 27b is proportional to the current signal Iout output from the PD 15.

Similar to the operational amplifiers 21a and 25a, the first reference potential V _{ref1 of} 1.25 V generated by the reference potential generation IC 18 is input to the positive input terminal of the comparator 27a.
Reference numerals R1 and R2 indicate resistors, respectively, and reference numeral 29 indicates an AND gate.

  The control circuit 7 includes a reset terminal 7a that outputs a reset signal NX, a charge terminal 7b that outputs a charge signal N1 (N1 pulse) for charging a capacitor 25b provided in the integrating circuit 23, and a capacitor 25b. And a discharge terminal 7c for outputting a discharge signal N3 for discharging the charged electric charge.

  The reset signal NX output from the reset terminal 7a is input to the switch 25c, the charge signal N1 output from the charge terminal 7b is input to the switch 25e, and the discharge signal N3 output from the discharge terminal 7c is input to the switch 25f. It has become so.

  The discharge signal N3 output from the discharge terminal 7c and the signal COMP_out output from the NOT gate 27b of the processing circuit 5 are logically operated by the AND gate 29. The logical product N2 (N2 pulse: first pulse, second pulse) obtained by the AND gate 29 is input to the control circuit 7.

  Further, as shown in FIG. 2, the control circuit 7 includes an oscillator 7d that oscillates a reference clock (clock period T [sec]; hereinafter referred to as a reference clock T) and a reference clock T that is oscillated from the oscillator 7d. , A counter 7e for counting a charge signal N1 (N1 pulse) from the charge terminal 7b and a logical product N2 (N2 pulse) from the AND gate 29, and a counter value (first counter value, second count) counted by the counter 7e, respectively. And an arithmetic unit (arithmetic unit) 7g for calculating the amount of biological information based on the counter value.

As shown in FIG. 3, the control circuit 7 switches signals output from the terminals 7a, 7b, and 7c as follows.
The charge signal N1 output from the charge terminal 7b is switched between the Hi state and the Low state in synchronization with the irradiation timing of the light E from the light source 11. Specifically, when the light E from the light source 11 is irradiated, the charge signal N1 is switched to the Hi state, and when the irradiation with the light E is stopped, the charge signal N1 is switched to the Low state.

  Further, when the charge signal N1 from the charge terminal 7b is switched to the Hi state, the reset signal NX output from the reset terminal 7a is switched to the Low state, and when the charge signal N1 from the charge terminal 7b is switched to the Low state. The discharge signal N3 output from the discharge terminal 7c is switched to the Hi state. When the discharge signal N3 from the discharge terminal 7c is switched to the Low state, the reset signal NX from the reset terminal 7a is switched to the Hi state.

When the reset signal NX is in the Hi state, the switch 25c is closed and both ends of the capacitor 25b are short-circuited. As a result, the voltage of the integrating circuit 23 is reset to the first reference potential V _ref1 . On the other hand, when the reset signal NX is in the low state, the switch 25c of the integration circuit 23 is opened, and the integration operation by the integration circuit 23 is enabled.

  When the charge signal N1 is switched to the Hi state, the switch 25e is closed and the reset signal NX is switched to the LOW state, whereby the integration by the integration circuit 23 of the voltage signal IVout output from the IV conversion circuit 21 is started. The capacitor 25b is charged up. The counter 7e starts counting the charge signal N1 (N1 pulse).

When the discharge signal N3 from the discharge terminal 7c is in the Hi state, the switch 25f is closed and the charge signal N1 is switched to the Low state, so that the switch 25e is opened. As a result, the third reference potential V _ref3 larger than the first reference potential V _ref1 is input to the negative input terminal of the operational amplifier 25a, and the capacitor 25b is discharged. The counter 7e starts counting the logical product N2.

In the circuit configuration of the biological information detecting device 1 according to the present embodiment, the output (voltage signal IVout) of the conversion circuit 15 is calculated by the following equation (1).
IVout = V _ref1 −Iout × Riv (1)
Riv indicates the resistance value of the conversion resistor 21b.

Further, the voltage Vc of the voltage signal INTEG_out at the time of charging is calculated by the following equation (2).
Vc = V _ref1 + {1 / (Rint × Cint)} × ∫ (V _ref1 −IVout) dt
= V _ref1 + {1 / (Rint × Cint)} × N1 × T × (V _ref1 −IVout) (2)
Rint represents the voltage value of the input resistor 25d, Cint represents the voltage value of the capacitor 25b, and N1 represents the counter value of the charge signal N1 by the counter 7e.

Further, the voltage Vc of the voltage signal INTEG_out at the time of discharge is calculated by the following equation (3).
Vc = V _ref1 + (1 / Rint × Cint) × ∫ (V _ref3 −V _ref1 ) dt
= V _ref1 + (1 / Rint × Cint) × N2 × T × (V _ref3 −V _ref1 ) (3)
N2 indicates the counter value of the logical product N2 by the counter 7e.

From the expressions (1), (2), and (3), the current signal Iout output from the PD 15 is calculated by the following expression (4).
Iout = (N2 / N1) × (V _ref3 −V _ref1 ) / Riv (4)

  Here, the current signal Iout as the amount of biological information detected by the PD 15 tends to cause a measurement error due to the influence of the dark current generated in the PD 15. The dark current refers to a discharge current that flows even in the non-operating state in the PD 15. Note that the dark current of the PD 15 varies with temperature.

  As shown in the flowchart of FIG. 4, the biological information amount detection method according to this embodiment includes a biological information amount current signal Iout composed of an analog signal including a dark current component and a dark current component current signal Iout composed of an analog signal. The detection step S1 to detect, the current signal Iout of the amount of biological information detected by the detection step S1 is converted into a pulse signal COMP_out (first pulse width), and the dark current component is converted into a pulse signal COMP_out (second pulse width) And a logical value N2 based on the first pulse width signal COMP_out converted by the conversion step S2 is counted by the reference clock T to generate a counter value (first counter value), The counter value (second counter value) is generated by counting the logical product N2 based on the signal COMP_out with the reference clock T. A count process S3 that, and a calculating step S4 for obtaining the biometric information amount Ib by the difference of the first counter value generated by the counting step S3 and the second counter value.

In the detection step S1, the PD 15 detects a biological information amount current signal Iout composed of an analog signal including a dark current component when the light source 11 is turned on, and the dark current component composed of an analog signal when the light source 11 is turned off. The current signal Iout is detected. In the detection step S1, the current signal Iout when the light source 11 is turned on and the current signal Iout when the light source 11 is turned off are alternately and continuously detected.
In the calculation step S4, the biological information amount Ib from which the influence of the dark current is removed is obtained from the difference between the counter values of the pulse widths of the analog signals by the calculator 7g.

The biological information amount Ib obtained by the calculator 7g is calculated by the following equation (5).
Ib = Is−Id (5)
Is indicates the current signal Iout of the PD 15 when the light source 11 is turned on, and Id indicates the current signal Iout of the PD 15 when the light source 11 is turned off.

From the formula (5), Id and Is are calculated by the following formulas (6) and (7).
Id = (N2d / N1) × (V _ref3 −V _ref1 ) / Riv (6)
Is = (N2s / N1) × (V _ref3 −V _ref1 ) / Riv (7)
N2d represents the N2 count number when the light source 11 is turned off, and N2s represents the N2 count number when the light source 11 is turned on.

Expressions (6) and (7) replace expression (5) with the following expression (8).
Ib = [{(N2s-N2d ) / N1} × (V ref3 -V ref1)] / Riv ·· (8)

The operation of the biological information amount detection apparatus 1 and the biological information amount detection method according to this embodiment configured as described above will be described below with reference to the timing chart of FIG.
In order to detect the amount of biological information using the biological information amount detection device 1 according to the present embodiment, first, the PD 15 detects the current signal Iout of the dark current component composed of an analog signal when the light source 11 is turned off, and the pulse A counter value (second counter value) of the width (second pulse width) is acquired.

By the operation of the control unit 14, the reset signal NX in the Hi state is output from the reset terminal 16c with the light source 11 turned off, the switch 25c is closed, and the voltage of the integrating circuit 23 is reset to the first reference potential _Vref1. . From this state, the reset signal NX is switched to the Low state, and at the same time, the charge signal N1 from the charge terminal 7b is switched to the Hi state.

  When the charge signal N1 is switched to the Hi state, the switch 25e is closed, and the current signal Iout of the dark current component of the PD 15 is detected (detection step S1). Is started (conversion step S2). A period during which the capacitor 25b is charged is an N1 period. The counter 7e counts the charge signal N1 from the charge terminal 7b in the N1 period with the reference clock T.

If the charge of the capacitor 25b is started, so is higher than the potential of the first reference potential _{V ref1} to the potential of the voltage signal INTEG_out supplied to the negative input terminal of the comparator 27a is input to the positive input terminal, the comparator 27a The output voltage signal INTEG_out is in a Low state, and a Hi state signal COMP_out is output by the NOT gate 27b. However, since the discharge signal N3 is in the low state and the logical product N2 output from the AND gate 29 is maintained in the low state, the counting of the logical product N2 by the counter 7e is not started.

Next, the charge signal N1 is switched to the low state, the switch 25e is opened, and the input of the voltage signal IVout from the IV conversion circuit 21 to the integration circuit 23 is cut off. At the same time, the discharge signal N3 from the discharge terminal 7c is switched to the Hi state, the switch 25f is closed, the third reference potential _Vref3 is input to the negative input terminal of the operational amplifier 25a, and the capacitor 25b is discharged.

By the capacitor 25b is discharged, a change in the value of the voltage signal INTEG_out output from integrator 25 is compared with a first reference potential _{V ref1} by the comparator 27a. The period during which the value of the voltage signal INTEG_out exceeds than the first reference potential _{V ref1} to N2 periods.

Since the signal COMP_out output from the NOT gate 27b is maintained in the Hi state during the N1 period when the capacitor 25b is charged, when the discharge of the capacitor 25b is started, the logical product N2 output from the AND gate 29 is In the Hi state, the counter 7e starts counting the logical product N2 (counting step S3).
Since the voltage value of the capacitor 25b is proportional to the intensity of light detected by the PD 15 at the start of discharge, the time required for discharge is also proportional to the intensity of light.

The discharge of the capacitor 25b proceeds, the processing circuit 5 to the voltage signal INTEG_out output falls below the first reference potential _{V ref1} from the integrating portion 25, the output of the comparator 27a is in Hi state, the output of the NOT gate 27b is Low The state is switched, the output of the AND gate 29 becomes the Low state, and the counting by the counter 7e is stopped. Thereby, the N2 counter value N2d when the light source 11 is turned off is obtained.

  Next, the PD 15 detects a biological information amount current signal Iout composed of an analog signal including a dark current component when the light source 11 is turned on, and calculates a counter value (first counter value) of the pulse width (first pulse width). get.

  When the lighting of the light source 11 is started, the operation of the control unit 14 causes the charge signal N1 from the charge terminal 7b of the control circuit 7 to be switched to the Hi state in synchronization with this, and at the same time, the reset signal NX from the reset terminal 7a becomes Low. Switch to state. Thus, in the same manner as when the light source 11 is turned off, the voltage signal IVout corresponding to the current signal Iout including the dark current component of the PD 15 detected by the detection step S1 is input to the integration circuit 23 by the conversion step S2 and the capacitor 25b (N1 period). Further, the counter 7e counts the charge signal N1 in the N1 period with the reference clock T.

  By activating the light source 11 until the counter value by the counter 14d becomes N1, when the counter value counted by the counter 14d becomes N1, the charge signal N1 is switched to the low state and the switch 25e is switched. Simultaneously with the opening, the discharge signal N3 is switched to the Hi state, and the input of the voltage signal IVout from the IV conversion circuit 21 to the integration circuit 23 is cut off.

At the same time, the discharge signal N3 from the discharge terminal 7c is switched to the Hi state, the switch 25f is closed, the third reference potential _Vref3 is input to the negative input terminal of the operational amplifier 25a, and the capacitor 25b is discharged. Then, a change in the value of the voltage signal INTEG_out output from the integrating unit 25 is compared with the first reference potential V _ref1 by the comparator 27a, and the value of the voltage signal INTEG_out is higher than the first reference potential V _{ref1 in the} N2 period. The logical product N2 output from the AND gate 29 is counted by the counter 7e. Thereby, the N2 count number N2s when the light source 11 is turned on is obtained.

Thereafter, the biological information amount Ib is calculated by the calculator 7g from the difference between the count number N2d when the light source 11 is turned off and the count number N2s when the light source 11 is turned on based on the equation (8) (calculation step S4).
As a result, a highly accurate biological information amount Ib obtained by removing the dark current component of the analog signal from the biological information amount of the analog signal including the dark current component detected by the PD 15 is detected.

  In this case, each analog signal is converted into a first pulse width and a second pulse width by the IV conversion circuit 21 and each pulse width is counted by the reference clock T by the counter 14d. In this state, the calculation unit 14e obtains the amount of biological information from these differences, whereby each analog signal is converted into a digital signal for calculation processing, that is, the current signal of the PD 15 from the N2 counter values N2s and N2d, respectively. Compared to the case where Iout (Is, Id) is obtained and the difference is taken, the processing time can be shortened and the power consumption can be reduced. Further, the influence of the positive direction of the temperature characteristics (increase direction of the current signal IVout of the PD 15) generated in the IV conversion circuit 21 and the integration circuit 23 can be canceled.

  Therefore, according to the biological information amount detection apparatus 1 according to the present embodiment, a highly accurate biological information amount in which the influence of the dark current generated in the PD 15 and the influence of the positive direction of the temperature characteristic of the circuit is removed can be quickly and with low power consumption. Can be detected.

[Second Embodiment]
Next, a biological information amount detection apparatus and a biological information amount detection method according to a second embodiment of the present invention will be described.
The biological information amount detection apparatus 101 according to this embodiment is different from the first embodiment in that the reference potential input to the operational amplifier 21a of the IV conversion circuit 21 is different from the reference potential input to the operational amplifier 25a and the comparator 27a of the integration circuit 23. .
In the following, parts having the same configuration as those of the biological information amount detection device 1 and the biological information amount detection method according to the first embodiment are denoted by the same reference numerals and description thereof is omitted.

As illustrated in FIG. 6, the biological information amount detection apparatus 101 according to the present embodiment inputs the first reference potential V _ref1 generated by the first reference potential generation IC 18 only to the operational amplifier 21 a of the IV conversion circuit 21. The second reference potential generation IC 118 for inputting the second reference potential V _ref2 different from the first reference potential V _ref1 to the operational amplifier 25a and the comparator 27a of the integration circuit 23 is provided.
For example, the second reference potential generation IC 118 outputs a second reference potential V _ref2 of 2.048V.

In the biological information amount detection method according to the present embodiment, the conversion step SA2 converts the biological information amount current signal Iout detected in the detection step SA1 and outputs a voltage signal IVout that satisfies the first reference potential V _ref1. , and outputs a voltage signal IVout satisfying a second reference potential _{V ref2} converts the current signal Iout of the dark current component, the pulse width (first pulse width that satisfies the second reference potential _{V ref2} by integrating the voltage signal IVout , Second pulse width) voltage signal INTE_Gout and signal COMP_out are output.

In the circuit configuration of a biological information amount detecting device 101 according to this embodiment, as shown in FIG. 7, the voltage of the potential difference Vsigvoltage the voltage signal IVout and the second reference potential _{V ref2,} which is calculated by the following equation (9) The capacitor 25b of the integrating unit 25 is charged.
IVout = V _ref1 −Iout × Riv (1)
Vsigvoltage = V _ref2 −IVout (9)

Further, the voltage Vc of the voltage signal INTEG_out at the time of charging is calculated by the following equation (10).
Vc = V _ref2 + (1 / Rint × Cint) × ∫ (Vsigvoltage) dt
= V _ref2 + (1 / Rint × Cint) × N1 × T × Vsigvoltage (10)

Further, the voltage Vc of the voltage signal INTEG_out at the time of discharge is calculated by the following equation (11).
Vc = V _ref2 + (1 / Rint × Cint) × ∫ (V _ref3 −V _ref2 ) dt
= V _ref2 + (1 / Rint × Cint) × N2 × T × (V _ref3 −V _ref2 ) (11)

From the equations (10) and (11), the equation (9) is replaced by the following equation (12).
Vsigvoltage = (N2 / N1) × (V _ref3 −V _ref2 ) / Riv (12)

From the equations (1), (9), and (12), the current signal Iout output from the PD 15 is calculated by the following equation (13).
Iout = {(N2 / N1) × (V _ref3 −V _ref2 ) − (V _ref2 −V _ref1 )} / Riv (13)

The operation of the biological information amount detection apparatus 101 and the biological information amount detection method according to the present embodiment configured as described above will be described with reference to the timing chart of FIG.
In order to detect the amount of biological information using the biological information amount detection device 1 according to the present embodiment, the current signal Iout of the dark current component made up of an analog signal when the light source 11 is turned off by the PD 15 as in the first embodiment. Subsequently, a current signal Iout having a biological information amount made up of an analog signal including a dark current component when the light source 11 is turned on is detected, and the difference between the counter values of the pulse widths of the respective analog signals is detected by the calculator 7g. Thus, the biological information amount Ib from which the influence of the dark current is removed is obtained.

The biological information amount Ib obtained by the calculator 7g is calculated by the following equation (14).
Ib = (Vsigvoltage_s−Vsigvoltage_a) / Riv (14)
Vsigvoltage_a indicates the voltage signal IVout output from the IV conversion circuit 21 when the light source 11 is turned off, and Vsigvoltage_s indicates the voltage signal IVout output from the IV conversion circuit 21 when the light source 11 is turned on.

Vsigvoltage_a and Vsigvoltage_s are calculated by the following equations (15) and (16) according to the equation (12).
Vsigvoltage_a = (N2a / N1) × (V ref3 -V ref2) / Riv ·· (15)
Vsigvoltage_s = (N2s / N1) × (V ref3 -V ref1) / Riv ·· (16)
N2a indicates the N2 counter value when the light source 11 is turned off.

Expressions (15) and (16) replace expression (14) with the following expression (17).
Ib = [{(N2s-N2a ) / N1} × (V ref3 -V ref2)] / Riv ·· (17)

In the timing chart of FIG. 8, the flow for obtaining the N2 counter value N2a when the light source 11 is turned off and the N2 counter value N2 when the light source 11 is turned on is the same as in the first embodiment, and thus description thereof is omitted.
According to the biological information amount detection apparatus 101 and the biological information amount detection method according to the present embodiment, the influence of the dark current of the PD 15 and the influence of the negative direction of the circuit temperature characteristic (the decreasing direction of the current signal IVout of the PD 15) are not included. The biological information Ib can be obtained from the difference between the N2 counter value N2a and the counter value of N2s. Even if the output change due to the temperature characteristic generated in the IV conversion circuit 21 and the integration circuit 23 is in the negative direction, the change amount can be extracted and the influence of the temperature characteristic can be canceled. Therefore, it is possible to detect a highly accurate biological information amount from which the influence of the dark current and the negative influence of the temperature characteristic of the circuit are removed, quickly and with low power consumption.

In the present modification, the first reference potential V _ref1 <the second reference potential V _ref2 , but this is due to the circuit configuration in which the voltage signal IVout decreases as the current signal Iout of the PD 15 increases. In a circuit configuration in which the voltage signal IVout increases as the PD current signal Iout increases, it is desirable that the first reference potential V _ref1 > the second reference potential V _ref2 .

  In the first embodiment and the second embodiment, detection of biological information amount including an analog signal including a dark current component when the light source 11 is turned on, and detection of a dark current component including an analog signal when the light source 11 is turned off. It is desirable to carry out alternately and continuously. By doing this, the detection time difference between the amount of biological information consisting of an analog signal containing a dark current component and the dark current component consisting of an analog signal is reduced, and the dark current and circuit temperature characteristics at the time of measuring the amount of biological information Can be canceled with high accuracy.

  In each of the above embodiments, the current amount corresponding to the biological information amount Ib is digitized from the difference between the counter values, and the current amount and biological information amount (for example, glucose value mg / dl) measured in advance are calculated. The biological information amount Ib may be determined based on the relationship between the counter values, or the biological information amount Ib may be directly determined from the counter value difference based on the relationship between the counter value difference measured in advance and the biological information amount. May be.

  As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the specific structure is not restricted to this embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included. For example, the present invention is not limited to those applied to the above-described embodiments and modifications, but may be applied to embodiments in which these embodiments and modifications are appropriately combined, and is not particularly limited. Absent.

7e Counter 7g Calculator (Calculator)
15 PD (sensor)
23 Integration circuit (conversion circuit)
25 Integration Unit 27 Comparison Unit T Reference Clock V _ref1 First Reference Potential V _ref2 Second Reference Potential S1 Detection Step S2 Conversion Step S3 Counting Step S4 Calculation Step

Claims (10)

A sensor for detecting the amount of biological information composed of an analog signal including a dark current component and the dark current component composed of an analog signal;
A conversion circuit that converts the amount of biological information detected by the sensor into a first pulse width, and converts the dark current component detected by the sensor into a second pulse width;
The first pulse width converted by the conversion circuit is counted with a reference clock to generate a first counter value, and the second pulse width converted by the conversion circuit is counted with a reference clock to calculate a second counter value. A counter that generates
A biological information amount detection apparatus comprising: an arithmetic unit that obtains the biological information amount based on a difference between the first counter value and the second counter value generated by the counter.   The biological information amount detection apparatus according to claim 1, wherein the calculation unit converts an analog signal of the biological information amount obtained by a difference between the first counter value and the second counter value into a digital signal.   The biological information amount detection according to claim 1 or 2, wherein the sensor continuously and alternately performs detection of a biological information amount including an analog signal including a dark current component and detection of a dark current component including an analog signal. apparatus.   The conversion circuit converts the current signal of the biological information amount detected by the sensor and the current signal of the dark current component, and outputs a voltage signal satisfying the first reference potential, and the conversion unit converts the current signal The biological information amount detection according to any one of claims 1 to 3, further comprising: an integration unit that integrates each of the voltage signals thus output and outputs a pulse width that satisfies a second reference potential different from the first reference potential. apparatus.   The biological information detection device according to any one of claims 1 to 4, wherein the conversion circuit is a double integration method. A detection step for detecting a biological information amount including an analog signal including a dark current component and the dark current component including an analog signal;
A conversion step of converting the biological information amount detected by the detection step into a first pulse width, and converting the dark current component detected by the detection step into a second pulse width;
The first pulse width converted by the conversion step is counted with a reference clock to generate a first counter value, and the second pulse width converted by the conversion step is counted with a reference clock to calculate a second counter value. A counting process to generate
A biological information amount detection method comprising: a calculation step of obtaining the biological information amount based on a difference between the first counter value and the second counter value generated by the counting step.   The biological information amount detection method according to claim 6, wherein the calculating step converts an analog signal of the biological information amount obtained from a difference between the first counter value and the second counter value into a digital signal.   The biological information amount according to claim 6 or 7, wherein the detection step alternately and continuously performs detection of a biological information amount including an analog signal including a dark current component and detection of a dark current component including an analog signal. Detection method.   The conversion step converts the current signal of the biological information amount detected by the detection step and the current signal of the dark current component, outputs a voltage signal satisfying the first reference potential, and integrates each voltage signal The biological information detection method according to any one of claims 6 to 8, wherein a pulse width satisfying a second reference potential different from the first reference potential is output.   The biological information amount detection method according to claim 6, wherein the conversion step is performed by a double integration method.

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