JP5530832B2 - Blood component analyzer and light receiving circuit for blood component analyzer - Google Patents

Description

  The present invention relates to a blood component analyzer and a light receiving circuit for the blood component analyzer.

  In recent years, with the reduction in size and weight of blood component analyzers such as blood glucose measuring devices, opportunities for component analysis outdoors have increased. However, in an optical blood component analyzer, component analysis outdoors may be affected by ambient light. Taking a blood glucose measurement device that measures blood glucose optically as an example, when measuring blood glucose outdoors, measurement errors may occur due to the influence of ambient light such as sunlight. As a technique for reducing a measurement error due to disturbance light, an optical measurement device disclosed in Patent Document 1 is known. In the optical measurement device of Patent Document 1, in the stage of calculating the blood sugar level, the measurement error due to the influence of disturbance light is reduced by subtracting the received light amount when the light emitting element is turned off from the received light amount when the light emitting element is turned on. Yes.

JP 2008-232626 A

  However, if the ambient light is strong, the electrical signal is already detected when the electrical signal corresponding to the received light amount is amplified before subtracting the received light amount when the light emitting element is turned off from the received light amount when the light emitting element is turned on. There is a risk of saturation to the limit voltage. In this way, when the electrical signal is saturated, blood glucose is accurately measured by simply subtracting the received light amount when the light emitting element is turned off from the received light amount when the light emitting element is turned on as in the above prior art. It is difficult.

  The present invention has been made to solve the above-described problems. Accordingly, an object of the present invention is to provide a blood component analyzer that prevents an electric signal corresponding to the amount of received light from being saturated to a detection limit voltage even when disturbance light is strong.

  Another object of the present invention is to provide a light receiving circuit for the blood component analyzer.

  The above object of the present invention is achieved by the following means.

The blood component analyzer of the present invention is a blood component analyzer that analyzes the component based on a change in the color of a reagent that has reacted with a component contained in blood, and that emits pulsed light toward the test piece to which the blood has adhered. Light-emitting means for emitting light, light-receiving means for receiving the reflected light reflected by the test piece and converting it into an electric signal, and filtering the electric signal to suppress the AC component of the electric signal. Filtering means for generating an electrical signal after filtering, calculation means for calculating the amount of the component based on the signal level of the output signal during extinction and emission of the pulsed light, and before filtering by the filtering means Differential amplification means for differentially amplifying an electrical signal and the filtered electrical signal to obtain an output signal , wherein the differential amplification means is a first buffer into which the electrical signal before filtering is input Part A second buffer unit for the signal after the filtering is input,
A first input terminal to which an output terminal of the first buffer unit is electrically connected; and a second input terminal to which an output terminal of the second buffer unit is electrically connected. A third amplifier unit that differentially amplifies a signal between the first input terminal and the second input terminal to obtain the output signal in which the influence of ambient light is reduced; and the first input terminal of the third amplifier unit or the first input terminal And a digital-to-analog converting means connected to the two input terminals for applying an adjustment voltage .

The light-receiving circuit of the present invention is a light-receiving circuit for a blood component analyzer, and receives a pulsed light and converts it into an electric signal, and suppresses the AC component of the electric signal by filtering the electric signal. Filtering means for generating an electrical signal after filtering, and differential amplification means for differentially amplifying the electrical signal before filtering by the filtering means and the electrical signal after filtering to obtain an output signal , The differential amplifying means includes a first buffer unit to which an electric signal before the filtering is input, a second buffer unit to which the signal after the filtering is input, and an output terminal of the first buffer unit electrically A first input terminal to be connected and a second input terminal to which an output terminal of the second buffer unit is electrically connected; and a signal between the first input terminal and the second input terminal. Before reducing the effect of ambient light by differential amplification A third amplifier unit to obtain an output signal, is connected to the first input or the second input terminal of said third amplifier portion, and wherein a, a digital-to-analog conversion means for applying an adjustment voltage To do.

  According to the present invention, even when the disturbance light is strong, the electric signal corresponding to the amount of received light is prevented from being saturated to the detection limit voltage, so that the influence of the disturbance light can be reduced, and a bright place such as under sunlight. The component analysis is also possible.

It is a block diagram for demonstrating the blood component analyzer in one embodiment of this invention. It is a block diagram for demonstrating the light reception processing circuit shown in FIG. It is a figure which shows an example of the circuit of the light reception process part 160 shown by FIG. It is a wave form diagram for demonstrating operation | movement of the light reception process part shown in FIG. 2 and FIG. It is a figure which shows the comparative example with respect to the light reception process part shown in FIG. It is a figure which shows the other example of the circuit of the light reception process part shown by FIG.

  Embodiments of a blood component analyzer and a light receiving circuit thereof according to the present invention will be described below with reference to the accompanying drawings. In the drawings, the same reference numerals are used for the same members.

(Embodiment)
FIG. 1 is a block diagram for explaining a blood component analyzer according to an embodiment of the present invention. The blood component analyzer of the present embodiment extracts a voltage increase due to disturbance light by filtering an electrical signal corresponding to the amount of received light with a low-pass filter. Then, differential amplification is performed so that the voltage increase is subtracted from the electric signal, thereby preventing the electric signal from being saturated to the detection limit voltage. In the following, the main part of the blood component analyzer of the present embodiment will be described, and description of the same parts as those of the conventional blood component analyzer will be omitted.

  In the present embodiment, a colorimetric blood glucose measurement device that measures a blood glucose level based on a change in the color of a reagent that has reacted with glucose contained in blood will be described as an example. In the colorimetric blood glucose measurement device, light is applied to a test paper (test piece) to which blood adheres, and the reflected light from the test paper is received to be contained in blood based on the color change of the reagent that has reacted with blood. Analyze ingredients. The test paper contains a reagent that develops color in response to glucose in the blood. The higher the glucose concentration, the darker the color of the test paper. The blood glucose level is measured by utilizing the change in the amount of received light due to the difference in color density.

  As shown in FIG. 1, a blood component analyzer (colorimetric blood glucose measuring device) 100 according to the present embodiment includes an arithmetic control unit 110, a mounting unit 120, a light emitting element 130, a light emitting driving unit 140, a light receiving element 150, a light receiving process. A unit 160, an operation unit 180, and a display unit 190. The light receiving element 150 and the light receiving processing unit 160 are combined to constitute a light receiving circuit 170. Hereafter, each component shown in FIG. 1 is demonstrated in order.

  The arithmetic control unit 110 executes overall control of the blood component analyzer 100 and calculation of a blood sugar level. More specifically, the arithmetic control unit 110 includes peripheral circuits including, for example, a CPU, a memory, a communication circuit, and the like, and is electrically connected to the operation unit 180, the light emission drive unit 140, the light reception processing unit 160, and the display unit 190. It is connected to the. The arithmetic control unit 110 activates the blood component analyzer 100 in accordance with an instruction from the operator input via the operation unit 180, and executes measurement processing according to a predetermined procedure.

  The startup procedure and measurement processing procedure of blood component analyzer 100 are stored in advance in a nonvolatile memory such as a ROM as a program, and the CPU executes the program sequentially. After starting the blood component analyzer 100, the arithmetic control unit 110 instructs the light emission drive unit 140 to output a predetermined pulse signal, and the signal processed by the light reception processing unit 160 is used as light reception amount data. Instructs to store in volatile memory such as RAM.

  A signal processed and output by the light receiving processing unit 160 (hereinafter referred to as “output signal”) is sampled at a predetermined timing by a sample hold circuit (not shown) provided in the arithmetic control unit 110, for example, and A / It is converted into received light amount data of a digital value via a D converter and stored in a memory. Then, the arithmetic control unit 110 calculates a blood glucose level based on the stored received light amount data and outputs it to the display unit 190.

  The timing of sampling the output signal is controlled by the arithmetic control unit 110. Specifically, the sampling timing is determined in association with the timing at which the light emitting element 130 emits light. More specifically, the arithmetic control unit 110 samples the output signal at a first timing immediately before the light emitting element 130 emits pulsed light and a second timing during which pulsed light is emitted. The second timing can also be set after a predetermined time has elapsed from the first timing. Then, the arithmetic control unit 110 stores the difference between the signal level of the output signal at the second timing and the signal level of the output signal at the first timing as received light amount data, and uses it for calculating the blood component amount. That is, it can be said that the blood component amount is calculated based on the signal level of the output signal during the extinction of the pulsed light and during the light emission. More specifically, the arithmetic control unit 110 calculates the blood sugar level based on a value obtained by subtracting the signal level of the output signal at the first timing from the signal level of the output signal at the second timing.

  In the present embodiment, the blood glucose level is calculated based on the absorbance of the test paper 121 before and after blood is adhered to the test paper 121. Since the test paper 121 before the blood is attached is a color close to white, the absorbance is small. On the other hand, the test paper 121 after the blood is attached has a reaction as the reaction between the blood component and the reagent proceeds. Color develops and absorbance increases. For this reason, as the absorbance after blood is adhered, it is desirable to adopt the absorbance when the rate of increase in absorbance is within a predetermined value as the reaction between the blood component and the reagent is completed. The calculation control unit 110 calculates the absorbance of the test paper 121 before and after attaching blood to the test paper 121 using the received light amount data stored in the memory as a calculation means, and then the correspondence relationship between the absorbance and the glucose concentration. To calculate the blood sugar level. The correspondence between the absorbance and the glucose concentration is stored in advance in a nonvolatile memory such as a ROM as a lookup table, or is calculated from the relational expression between the absorbance and the glucose concentration.

  The test paper 121 is held by the mounting unit 120. For example, the mounting unit 120 is attached to a housing (not shown) of the blood component analyzer 100. Thereby, the positional relationship between the test paper 121 and the light emitting element 130 and the light receiving element 150 is determined.

  The light emitting element 130 is an element that emits pulsed light toward the test paper 121 at a predetermined interval. The light emitting element 130 is attached to the housing of the blood component analyzer 100 such that the light emitting surface faces the direction of the test paper 121. Irradiation light from the light emitting element 130 is collected in a spot shape by a lens (not shown) and irradiates the test paper 121. The light emitting element 130 is, for example, a light emitting diode (LED) that emits light within a wavelength range of about 500 to 720 nm.

  The light emission driver 140 is a drive circuit that supplies a pulse signal to the light emitting element 130. More specifically, the light emission driving unit 140 supplies a pulse signal having a predetermined pulse width, intensity, and period to the light emitting element 130 based on an instruction from the arithmetic control unit 110. The light emitting element 130 is turned on for a period of this pulse width in accordance with the supplied pulse signal, and is repeatedly turned off until the next rising edge of the pulse signal. The pulse width is approximately in the range of 10 to 1000 μs, preferably about 100 μs. The period is about 1 ms to 10 ms, and preferably about 2 ms. The pulse width, intensity, and period can be changed as appropriate according to the design conditions of other components.

  The light receiving element 150 is an element that receives reflected light obtained by reflecting the pulsed light from the test paper 121 and converts it into a current signal (photocurrent) as light receiving means. The light receiving element 150 is attached to the housing of the blood component analyzer 100 so that the light receiving surface thereof faces the test paper 121. The light receiving element 150 is, for example, a photodiode (PD). When the blood component analyzer is operated outdoors, disturbance light such as sunlight may be incident on the light receiving element 150 in addition to the reflected light of the pulsed light reflected by the test paper 121. In general, disturbance light such as sunlight is steady light with little temporal variation, and is low-frequency disturbance light of 100 Hz or less. In particular, sunlight is light with little temporal variation, and the frequency of the amount of received light is approximately 0 Hz. Therefore, the light receiving element 150 generates a current signal in which the component of the reflected light obtained by reflecting the pulsed light by the test paper 121 is biased by the direct current component due to the disturbance light.

  The light receiving processing unit 160 is a circuit that performs signal processing on the electrical signal converted by the light receiving element 150. More specifically, the light reception processing unit 160 passes the electrical signal converted by the light receiving element 150 through a low-pass filter, and generates a signal in which the AC component is suppressed. Here, the signal in which the AC component is suppressed is extracted as a voltage increase due to disturbance light such as sunlight. Next, an output signal is obtained by differentially amplifying the voltage increase from the electrical signal. Details of the light reception processing unit 160 will be described later. The light receiving element 150 and the light receiving processing unit 160 are combined to constitute a light receiving circuit 170.

  The operation unit 180 transmits an instruction from the operator to the arithmetic control unit 110. The operation unit 180 has a push button switch, for example, and is attached to the housing of the blood component analyzer 100. The operator gives instructions for starting / stopping the blood component analyzer 100 and displaying the measurement results via the operation unit 180.

  The display unit 190 displays the blood sugar level calculated by the calculation control unit 110. The display unit 190 has a liquid crystal display panel, for example, and is attached to the housing of the blood component analyzer 100.

  In the blood component analyzing apparatus configured as described above, the light emitting element 130 emits pulsed light toward the test paper to which blood adheres, and the light receiving element 150 receives the reflected light reflected by the test paper 121. To convert it into an electrical signal. The light reception processing unit 160 generates a filtered electrical signal that suppresses an AC component of the electrical signal by filtering (filtering) the electrical signal. Then, the light receiving processing unit 160 differentially amplifies the electric signal before filtering by the filtering unit and the electric signal after filtering to obtain an output signal. Next, the arithmetic control unit 110 calculates the blood component amount based on the signal level of the output signal when the pulsed light is turned off and during light emission.

  Next, the light receiving processing unit shown in FIG. 1 will be described in more detail. FIG. 2 is a block diagram illustrating the configuration of the light receiving processing unit shown in FIG.

  As shown in FIG. 2, the light receiving processing unit 160 of the blood component analyzer 100 in the present embodiment includes an I / V conversion circuit (current / voltage conversion circuit) 161, a low-pass filter circuit 162, and a differential amplifier circuit 163. Hereinafter, the components of the light receiving processing unit 160 illustrated in FIG. 2 will be described in order.

  The I / V conversion circuit 161 converts a current signal (photocurrent) generated by the light receiving element 150 according to the amount of received light into a voltage signal by converting the current signal into a voltage signal. This voltage signal becomes an electric signal processed by the low-pass filter circuit 162 and the differential amplifier circuit 163. When the light receiving element 150 is a voltage output type element that outputs a photovoltage instead of a photocurrent according to the amount of received light, the I / V conversion circuit 161 can be omitted.

  The low-pass filter circuit 162 is a filtering unit that generates the filtered electric signal that suppresses the AC component of the electric signal by filtering the electric signal (the voltage signal from the I / V conversion circuit 161). The input terminal of the low-pass filter circuit 162 is connected to the output terminal of the I / V conversion circuit 161. Here, the filtered electrical signal corresponds to a voltage increase due to direct current or low frequency disturbance light. That is, the low-pass filter circuit 162 extracts a voltage increase due to disturbance light. The frequency band cut off by the low pass filter circuit 162 is determined by the high cut off frequency of the low pass filter. A signal component higher than the high-frequency cutoff frequency is significantly suppressed by the low-pass filter circuit 162, and a low-frequency component lower than the high-frequency cutoff frequency, preferably a DC component, is output from the low-pass filter circuit 162. The high-frequency cutoff frequency of the low-pass filter circuit 162 can be set between a few Hz to 1 kHz, more preferably 300 Hz or less, and even more preferably 100 Hz or less, depending on the design conditions of other components. Is done.

  The differential amplifier circuit 163 is a differential amplifier that differentially amplifies the electric signal before filtering by the low-pass filter circuit 162 and the electric signal after filtering by the circuit 162 to obtain an output signal. In other words, the electrical signal is prevented from being saturated to the detection limit voltage by differential amplification so as to subtract the voltage increase due to direct current or low frequency disturbance light from the electrical signal. The output terminal of the IV conversion circuit 161 is electrically connected to the first input terminal of the differential amplifier circuit 163, and the output terminal of the low-pass filter circuit 162 is electrically connected to the second input terminal. Has been. The differential amplifier circuit 163 outputs an output voltage obtained by amplifying the difference between the voltages applied to the first and second input terminals at a predetermined amplification factor to the output terminal.

  FIG. 3 shows an example of a circuit of the light receiving processing unit 160 shown in FIG.

  The I / V conversion circuit 161 includes an operational amplifier OP1 and a feedback resistor R1. The feedback resistor R1 is connected between the first input terminal and the output terminal of the operational amplifier OP1. The second input terminal of the operational amplifier OP1 is connected to ground or the like. One end of a photodiode that is the light receiving element 150 is connected to a first input terminal of the operational amplifier OP1.

  The low-pass filter circuit 162 includes a resistor R2 and a capacitor C1 that are electrically connected to each other. Of the two ends of the resistor R2, the end on the side not connected to the capacitor C1 is the input end of the low-pass filter circuit 162, and the end on the side connected to the capacitor C1 is the output end of the low-pass filter circuit 162. Become. Note that the end of the capacitor C1 that is not connected to the resistor R2 is connected to ground or the like.

  The differential amplifier circuit 163 includes an operational amplifier OP2 and resistors R3, R4, R5, and R6. The feedback resistor R3 is electrically connected between the first input terminal and the output terminal of the operational amplifier OP2. The resistors R4 and R6 are input resistors connected to the first input terminal and the second input terminal of the operational amplifier OP2, respectively. Each end of the resistor R4 and the resistor R6 becomes a first input terminal and a second input terminal of the differential amplifier circuit 163. Note that the second input terminal of the operational amplifier OP2 is connected to the ground or the like via a resistor R5.

  The output terminal of the operational amplifier OP1, which is the output terminal of the I / V conversion circuit 161, is electrically connected to the resistor R4, which is the first input terminal of the differential amplifier circuit 163. On the other hand, the output terminal of the low-pass filter circuit 162 is electrically connected to the resistor R6 which is the second input terminal of the differential amplifier circuit 163. That is, the electric signal Vin1 before filtering by the low-pass filter circuit (filtering means) 162 is input to the first input terminal, and the electric signal Vin2 after filtering is input to the second input terminal. Here, when the voltages at the input terminals of the operational amplifier are V (−) and V (+) and the voltage at the output terminal is Vout, the following relationship is derived.

V (+) = (R5 / (R6 + R5)) * Vin2
V (−) = (R3 / (R3 + R4)) * (Vout−Vin1) + Vin1
Here, the amplification factor of the differential amplifier circuit 163 is obtained from V (+) = V (−). If R3 = R5 and R4 = R6, Vout = (R3 / R4) (Vin1-Vin2).

  Therefore, the low-pass filter circuit 162 extracts the filtered electric signal Vin2 corresponding to the voltage increase due to disturbance light, and the differential amplifier circuit 163 subtracts the electric signal Vin2 from the pre-filtered electric signal Vin1. Differential amplification is performed at a predetermined amplification factor.

  The operation of the light receiving processing unit 160 configured as described above will be described. FIG. 4 is a waveform diagram for explaining the operation of the light receiving processing unit shown in FIGS. Further, in order to explain in detail the effect of suppressing the direct current component by the light receiving processing unit of the present embodiment, a description will be given while comparing with a comparative example. FIG. 5A is a block diagram illustrating a configuration of a light reception processing unit as a comparative example with respect to the light reception processing unit illustrated in FIG. 2. FIG. 5B is a waveform diagram of an output signal of the amplifier circuit in FIG.

  As shown in FIG. 4A, at the output end of the I / V conversion circuit 161 shown in FIG. 2 and FIG. A voltage biased from the reference voltage by the low frequency component is output. The reference voltage is an output voltage of the I / V conversion circuit 161 when the light receiving element 150 is not irradiated with light.

  The low-pass filter circuit 162 receives an electric signal that is an output voltage of the I / V conversion circuit 161. The low-pass filter circuit 162 filters the electrical signal to generate a filtered electrical signal that suppresses the AC component of the electrical signal. Specifically, the filtered electric signal corresponds to a voltage increase (corresponding to a bias) due to DC or low-frequency disturbance light. In general, disturbance light such as sunlight is steady light with little temporal variation, and is low-frequency disturbance light of 100 Hz or less. In particular, sunlight is light with little temporal variation, and the frequency of the amount of received light is approximately 0 Hz. Therefore, as shown in FIG. 3, the low-pass filter circuit 162 removes an AC component from the output signal of the I / V conversion circuit 161 and outputs a signal obtained by extracting a DC component, that is, a bias component due to disturbance light (FIG. 3). 4 (B)).

  Next, the differential amplifier circuit 163 differentially amplifies the electric signal before filtering by the low-pass filter circuit 162 and the electric signal after filtering by the circuit 162. That is, an output signal (FIG. 4C) is generated by subtracting the signal of FIG. 4B from the signal of FIG. As described above, according to the differential amplification, the signal shown in FIG. 4A is subtracted from the signal shown in FIG. 4A and then amplified, so that an output signal with reduced influence of disturbance light can be obtained. . As a result, the signal is prevented from being saturated to the detection limit voltage when amplified.

  As described above, in the present embodiment, as a result, the signal is prevented from being saturated to the detection limit voltage when amplified, but the light receiving processing unit 160 ′ as a comparative example to the present embodiment is It is difficult to prevent saturation. That is, the light receiving processing unit 160 ′ as a comparative example includes an I / V conversion circuit 161 ′ and an amplification circuit 163 ′ as shown in FIG. 5A, and the I / V conversion circuit 161 ′ is an amplification circuit. 163 ′ is directly connected. Since the light reception processing circuit 160 ′ amplifies the electrical signal of the I / V conversion circuit 161 ′ without performing differential amplification with the electrical signal of the I / V conversion circuit 161 ′, the output signal of the amplification circuit 163 ′ is In some cases, the detection limit voltage is saturated. For example, as shown in FIG. 5B, when the bias voltage due to disturbance light is vb1, the output signal of the amplifier circuit 163 'is not saturated. However, in the case of vb2 where the bias voltage due to disturbance light is high, the output signal of the amplifier circuit 163 'is saturated up to the detection limit voltage, and thus the signal indicated by the broken line is not reproduced.

  Therefore, in the case of the comparative example, as shown in FIG. 5B, there is a portion where the signal is not reproduced, and thus it is difficult to accurately measure the blood glucose level. On the other hand, in the present embodiment, as shown in FIG. 4D, the pulse signal is turned off (sampling timing T1) and light is emitted (sampling timing T2) with respect to the output signal from the differential amplifier circuit 163. The blood glucose level can be accurately measured based on the difference between the output signals sampled and sampled while the pulsed light is turned off and emitted.

  In the present embodiment, the voltage increase (corresponding to the bias) due to the disturbance light of the substantially DC component is calculated using the low-pass filter circuit 162, while the electric signal of the I / V conversion circuit 161 is used as it is. Since the voltage increase is subtracted from the electrical signal of the I / V conversion circuit 161 by the dynamic amplifier circuit 163, waveform distortion caused by high-frequency components of the pulse waveform occurs compared to the case of using a band-pass filter or a high-pass filter. Hateful. Thus, since the waveform resulting from the high frequency component of the pulse waveform is not distorted, sampling is easy. In other words, if the waveform is distorted and the waveform is pointed, it is difficult to capture the peak, and the measured value greatly fluctuates when the sampling timing T2 changes due to circuit variations or the like. In order to prevent this, a peak hold circuit or the like is required, but according to the present embodiment, a peak hold circuit or the like is not necessary. In particular, since a diode necessary for the peak hold circuit can be omitted, it is possible to simplify the circuit and to make it one chip.

  As described above, the described blood component analyzer and the light receiving circuit thereof according to the present embodiment have the following effects.

  According to the blood component analyzer of the present embodiment, the voltage increase due to low-frequency or direct-current disturbance light is extracted by the low-pass filter circuit, and this voltage increase is differentially amplified so as to be subtracted from the electrical signal. It is possible to prevent the electric signal from being saturated to the detection limit voltage due to a bias caused by disturbance light such as sunlight.

  According to the blood component analyzer of the present embodiment, a voltage increase due to low-frequency or direct-current disturbance light can be output and subtracted from the electrical signal using a low-pass filter circuit, so that the output of the I / V conversion circuit Compared to a process that takes in the analog digital converter (AD converter), calculates the voltage rise due to low frequency or DC disturbance light by the processor, outputs it from the DA converter, and subtracts it from the electrical signal. Can be

  By using a differential amplifier circuit, the difference calculation process and the amplification process can be performed in an integrated manner, so that the circuit arrangement space can be omitted.

  In addition, although the blood component analyzer of this Embodiment was demonstrated as mentioned above, the blood component analyzer of this invention is not restricted to this case.

(Modification)
FIG. 6 shows a modification of the light receiving processing unit in the blood component analyzer of the present embodiment. In this modification, the light receiving processing unit 160 is configured as a single-chip IC that is the same as the multiplexer 111, the A / D converter 112, and the arithmetic control unit 110. That is, it is configured as a custom IC having a mixed digital / analog circuit. As shown in FIG. 6, the one-chip IC 200 has a plurality of operational amplifiers OP1, OP2-1, OP2-2, and OP2-3 while mounting an arithmetic control unit (CPU or the like) 110. The I / V conversion circuit 161 and the low-pass filter circuit 162 can be configured by connecting capacitors C1 and C2, resistors R1 and R2, and the like. In the present embodiment, waveform distortion is unlikely to occur as described above, and a peak hold circuit including a diode is not necessary, so that it is easy to make one chip.

  In addition, the I / V conversion circuit 161 according to this modification has a capacitor C2 connected in parallel with the feedback resistor R1 to form a kind of filter circuit. Therefore, the I / V conversion circuit 161 converts the current signal (photocurrent) generated by the light receiving element 150 according to the amount of received light into a voltage signal by current-voltage conversion, and has other AC components such as a fluorescent lamp. Suppresses noise. Therefore, the AC component noise is suppressed by the I / V conversion circuit 161, and the low-pass filter circuit unit 162 and the differential amplifier circuit 163 further reduce the influence of disturbance light of low frequency or DC components such as sunlight. can do.

  Further, the differential amplifier circuit 163 of the present modification includes a differential amplifier (instrumentation amplifier) having three amplifiers: a first buffer amplifier OP2-1, a second buffer amplifier OP2-2, and a third amplifier OP2-3. It has become. In this modification, the first input terminal (+ terminal) of the first buffer amplifier OP2-1 and the first input terminal (+ terminal) of the second buffer amplifier OP2-2 are the first input terminals of the differential amplifier circuit 163. And the second input terminal.

  The second input terminal (− terminal) of the first buffer amplifier OP2-1 and the second input terminal (− terminal) of the second buffer amplifier OP2-2 are electrically connected via a resistor R9. . A feedback resistor R7 is connected between the output terminal and the second input terminal of the first buffer amplifier OP2-1. Similarly, a feedback resistor R8 is connected between the output terminal and the second input terminal of the second buffer amplifier OP2-2. The third amplifier OP2-3 is the same as the operational amplifier OP2 of FIG. 3, and the first buffer amplifier OP2- is connected to two input terminals of the third amplifier OP2-3 via a resistor R4 and a resistor R6, respectively. 1 and the output terminal of the second buffer amplifier OP2-2 are electrically connected to each other. Note that the resistor R5 of this modification is connected to a D / A converter that supplies the adjustment voltage Vref. The adjustment voltage Vref can be controlled by the arithmetic control unit 110.

  Such an instrumentation amplifier can also be used as the differential amplifier circuit 163. In this case, assuming that R7 = R8, R4 = R6, and R3 = R5, assuming that the voltage at the output terminal is Vout, Relationships are guided.

  Vout = − (R3 / R4) (1 + 2 · R7 / R9) (Vin1−Vin2) + Vref.

  Therefore, the low-pass filter circuit 162 extracts the filtered electric signal Vin2 corresponding to the voltage increase due to disturbance light, and the differential amplifier circuit 163 subtracts the electric signal Vin2 from the pre-filtered electric signal Vin1. Differential amplification is performed at a predetermined amplification factor. Further, by adjusting the adjustment voltage Vref, it is possible to reduce the influence caused by the variation of components.

  In this modification, not only the output terminal of the differential amplifier circuit 163 but also the output terminal of the I / V conversion circuit 161 is connected to the input side of the multiplexer 111 via a sample hold circuit (not shown), for example. The output side of the multiplexer 111 is connected to the analog-digital converter 112, and the digitized output signal of the differential amplifier circuit 163 and the output signal of the I / V conversion circuit 161 are not shown as received light amount data. Stored in memory. The output signal of the digitized differential amplifier circuit 163 is used to calculate the blood glucose level. The output signal of the I / V conversion circuit 161 can be used for various controls.

  The modification shown in FIG. 6 can provide the same effects as those shown in FIG. 4 and, in addition, the following effects.

  Since a peak hold circuit that requires a diode is unnecessary, it is easy to make a custom IC with a mixture of analog and digital.

  While the AC component noise is reduced by the I / V conversion circuit 161 having a filter function, the low-pass filter circuit unit 162 and the differential amplifier circuit 163 affect the influence of low-frequency or direct-current disturbance light such as sunlight. Can be reduced.

  The differential amplification circuit 163 cancels the equivalent of the bias by subtracting the voltage increase due to the disturbance light from the electrical signal to prevent saturation, and further controls the adjustment voltage Vref for changes due to component variations and the like. Can be adjusted.

  As described above, the blood component analyzer and the light receiving circuit for the blood component analyzer of the present invention have been described in the embodiment and the modification. However, it goes without saying that the present invention can be appropriately added, modified, and omitted by those skilled in the art within the scope of the technical idea.

  For example, in the present embodiment, the calculation control unit has described the method for calculating the blood sugar level based on the difference between the signal levels of the output signal at each time point when the pulsed light is turned off and during the light emission. However, the method by which the arithmetic control unit calculates the blood glucose level is not limited to the above method. For example, the arithmetic control unit can calculate the blood glucose level by calculating the difference after multiplying the output signal at each time point when the pulse light is turned off and during the light emission by a predetermined correction coefficient.

  Further, in the present embodiment, the case where the sample hold circuit is built in the arithmetic control unit has been described. However, as described in the modification, the sample hold circuit may be incorporated in the light receiving processing unit.

  In addition, the present invention can be suitably used for calculating blood sugar levels, but it can be widely used in the field of performing blood component analysis by quantitatively measuring the amount of transmitted light or reflected light of a pulse wave. Of course.

100 blood component analyzer,
110 arithmetic control unit (calculation means),
120 mounting part,
121 Test paper (test piece)
130 light emitting element (light emitting means),
140 light emission drive unit,
150 light receiving element (light receiving means),
160 light reception processing unit (filtering means, differential amplification means),
161 I / V conversion circuit,
162 low-pass filter circuit,
163 differential amplifier circuit,
170 light receiving circuit,
180 operation unit,
190 Display section.

Claims (6)

A blood component analyzer that analyzes the component based on a change in the color of a reagent that has reacted with a component contained in blood,
A light emitting means for emitting pulsed light toward the test piece to which the blood has adhered;
A light receiving means for receiving the reflected light reflected by the test piece and converting it into an electrical signal;
Filtering means for generating an electric signal after filtering by suppressing the AC component of the electric signal by filtering the electric signal;
Calculating means for calculating the amount of the component based on the signal level of the output signal during extinction and emission of the pulsed light;
Differential amplification means for differentially amplifying the electric signal before filtering by the filtering means and the electric signal after filtering to obtain an output signal ;
The differential amplification means includes
A first buffer unit to which an electric signal before filtering is input;
A second buffer unit to which the filtered signal is input;
A first input terminal to which an output terminal of the first buffer unit is electrically connected; and a second input terminal to which an output terminal of the second buffer unit is electrically connected. A third amplifier unit that differentially amplifies a signal between the first input terminal and the second input terminal to obtain the output signal in which the influence of disturbance light is reduced;
A digital-to-analog converter connected to the first input terminal or the second input terminal of the third amplifier section and applying an adjustment voltage;
A blood component analyzer characterized by comprising:   The blood component analyzer according to claim 1, wherein the filtering unit includes a low-pass filter.   The blood component analyzer according to claim 1 or 2, wherein the filtered signal corresponds to a voltage increase due to reception of sunlight.   The calculation means calculates the amount of the component based on a difference between a signal level of the output signal when the pulsed light is extinguished and a signal level of the output signal when the pulsed light is emitted. The blood component analyzer according to any one of claims 1 to 3. The light receiving means includes a light receiving element that receives pulsed light and generates a photocurrent,
The blood component analyzer further comprises:
The blood component analyzer according to any one of claims 1 to 4, further comprising current-voltage conversion means for converting the photocurrent generated by the light receiving element into current-voltage to generate the electrical signal. A light receiving means for receiving pulsed light and converting it into an electrical signal;
Filtering means for generating an electric signal after filtering by suppressing the AC component of the electric signal by filtering the electric signal;
Differential amplification means for differentially amplifying the electric signal before filtering by the filtering means and the electric signal after filtering to obtain an output signal ;
The differential amplification means includes
A first buffer unit to which an electric signal before filtering is input;
A second buffer unit to which the filtered signal is input;
A first input terminal to which an output terminal of the first buffer unit is electrically connected; and a second input terminal to which an output terminal of the second buffer unit is electrically connected. A third amplifier unit that differentially amplifies a signal between the first input terminal and the second input terminal to obtain the output signal in which the influence of disturbance light is reduced;
A digital-to-analog converter connected to the first input terminal or the second input terminal of the third amplifier section and applying an adjustment voltage;
A light receiving circuit for a blood component analyzer, characterized by comprising:

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