JP4963482B2 - Component concentration measuring apparatus and component concentration measuring method - Google Patents

Description

  The present invention relates to a component concentration measuring apparatus and a component concentration measuring method for a target component using a photoacoustic method, and more particularly to a non-invasive component concentration measuring apparatus and a component concentration measuring method in which a measurement object is a human or an animal.

  With the aging of society, dealing with adult diseases is becoming a major issue. In blood glucose level and other tests, blood collection is necessary, which places a heavy burden on the patient. Therefore, a non-invasive component concentration measurement apparatus that does not collect blood has attracted attention.

  A photoacoustic method has been proposed as a noninvasive component concentration measuring apparatus. The photoacoustic method irradiates the skin with electromagnetic waves, causes the blood component to be measured, for example, glucose molecules to absorb the electromagnetic waves, and causes local thermal expansion due to the radiation of heat from the glucose molecules, resulting in thermal expansion. Observe sound waves generated from the body. However, the interaction between glucose and electromagnetic waves is small, and there is a limit to the intensity of electromagnetic waves that can be safely irradiated to a living body.

  4 and 5 are configuration examples showing a conventional component concentration measuring apparatus using a photoacoustic method. The concentration of the target component in the solution in which the background component and the target component are mixed is measured.

  The first conventional example shown in FIG. 4 attempts to increase accuracy by using two light sources having different wavelengths and continuously modulating the intensity. Light sources having different wavelengths, that is, a first light source 201 and a second light source 202 are driven by a driving power source 203 and a driving power source 204, respectively, and output continuous light.

  The light output from the first light source 201 and the second light source 202 is intermittently driven by a chopper plate 213 that is driven by a motor 214 and rotates at a constant rotational speed. Here, the chopper plate 213 is formed of an opaque material, and a relatively small number of openings are formed on the circumference through which the light of the first light source 201 and the second light source 202 passes with the axis of the motor 214 as the center. Is formed.

  With the above-described configuration, the light output from each of the first light source 201 and the second light source 202 is intensity-modulated with the prime modulation frequency f1 and the modulation frequency f2, and then multiplexed by the multiplexer 211. The object to be measured 101 is irradiated as a light beam.

  Inside the DUT 101, a photoacoustic signal having a modulation frequency f1 is generated by the light from the first light source 201, and a photoacoustic signal having a modulation frequency f2 is generated by the light from the second light source 202. The acoustic signal is detected by the acoustic sensor 212 and converted into an electrical signal proportional to the sound pressure, and the frequency spectrum is observed by the frequency analyzer 215.

  The wavelengths of the two light sources are all set to the absorption wavelength of glucose, and the intensity of the photoacoustic signal corresponding to each wavelength is measured as an electrical signal corresponding to the amount of glucose contained in the blood. The relationship between the intensity of the measured value of the photoacoustic signal and the value obtained by measuring the glucose concentration by separately collected blood is stored in advance, and the amount of glucose is measured from the measured value of the photoacoustic signal.

The second conventional example shown in FIG. 5 also uses a light source that is continuously intensity modulated. The first light source 110 generates the measuring light having a wavelength of lambda _1. The second light source 111 generates a reference wavelength lambda _2. The oscillator 114 outputs a modulation signal for intensity-modulating light output from the first light source 110 and the second light source 111. The 180 ° phase shifter 113 inverts one of the modulation signals from the oscillator 114 and outputs the result. The drive circuit 112a drives the first light source 110. The drive circuit 112b drives the second light source 111 based on the modulation signal inverted by the 180 ° phase shifter 113. The first light source 110 modulates the intensity of the measurement light having the wavelength λ _{1 with} the signal from the drive circuit 112 a and outputs the measurement light. The second light source 111 modulates the intensity of the reference light having the wavelength λ ₂ by the signal from the drive circuit 112b and outputs the reference light. Thereby, each of the different two wavelengths λ ₁ and λ _{2 is} electrically intensity-modulated with a signal of the opposite phase at the same frequency and output.

Here, the two wavelengths λ ₁ and λ ₂ are wavelengths in which the difference in absorption exhibited by the target component is larger than the difference in absorption exhibited by the background component. The wavelength λ ₁ is set to a wavelength at which the target component exhibits characteristic absorption. The wavelengths λ ₁ and λ ₂ may be two wavelengths in which the difference in absorption exhibited by the target component is greater than the difference in absorption exhibited by the other components. Thereby, the influence of absorption by components other than water and the component to be measured can be reduced, and the measurement accuracy of the component concentration measuring apparatus can be improved.

By modulating the modulation frequency for electrically intensity-modulating each of the _two wavelengths λ ₁ and λ _{2 at} the same frequency as the resonance frequency related to the detection of the sound wave generated in the object to be measured, Measures sound waves for light of two wavelengths selected in consideration of the nonlinearity related to the absorption coefficient, and eliminates the influence of many parameters that cannot be kept constant from these measured values. Sound waves generated inside can be detected.

The photoacoustic signals are generated inside the device under test 101 by the light of the _two wavelengths λ ₁ and λ ₂ , and these photoacoustic signals are detected by the acoustic sensor 117 and converted into electrical signals proportional to the sound pressure. Observed by the phase detection amplifier 119. The difference in the intensity of the photoacoustic signal corresponding to the two wavelengths is measured as an electrical signal corresponding to the amount of glucose contained in the blood.
JP-A-10-189 JP 2007-89662 A

  As described above, the conventional component concentration measuring apparatus needs to perform intensity modulation at a certain modulation frequency. When a general DFB (Distributed Feedback) laser is used as a light source for the photoacoustic method, the laser intensity stability is about 0.1% / h in the continuous light mode. In the prior art, the DFB laser needs to be electrically modulated with a drive current at a certain frequency, and the intensity stability is reduced to about 0.1% / h. For this reason, there are cases where it cannot be used in a mode in which stable driving is possible.

  Also, the 180 ° phase shifter that sets the two light sources in opposite phases has a delay stability of about several ns, and the differential signal of the photoacoustic signal may drift. For this reason, due to the delay of the 180 ° phase shifter 113 set to the opposite phase, the photoacoustic signal generated from the background component may not be differentially removed.

  Therefore, an object of the present invention is to enable use in a stable drive mode and to eliminate a difference in photoacoustic signals generated from background components without using a 180 ° phase shifter.

In order to solve the above-mentioned problem, a component concentration measuring apparatus according to the present invention has two light sources that output continuous light having different wavelengths and continuous light from the two light sources alternately determined in advance. An optical switch that outputs from the same output terminal at a constant frequency, and a sound wave detector that detects a sound wave for measurement generated from the object to be measured by the light from the two light sources output from the optical switch. It is characterized by.

  Since each light source outputs continuous light, it can be used in a stable drive mode. In addition, the optical switch alternately outputs continuous light from each light source at a constant frequency, so that the combined light for measurement, which is composed of two continuous wavelengths of light with the same frequency and opposite phase, is output from the same output terminal. can do. Thereby, the photoacoustic signal generated from the background component can be removed from the measurement sound wave detected by the sound wave detection unit without using a 180 ° phase shifter.

In the component concentration measuring apparatus according to the present invention, it is preferable that the plurality of light sources output different wavelengths having the same absorption of the background component in a solution in which the background component and the target component are mixed.
Since the absorption of the background component is the same, the differential photoacoustic signal (s ₁ -s ₂ ) obtained by differentially removing the photoacoustic signal generated from the background component from the measurement sound wave generated from the measurement object by the synthetic light for measurement is obtained. Obtainable.

In the component concentration measurement apparatus according to the present invention, it is preferable that at least one of the plurality of light sources has a wavelength that maximizes the absorption of the target component in a solution in which the background component and the target component are mixed.
Since the absorption exhibited by the target component is maximal, the measurement efficiency of sound waves generated from the target component can be increased.

In the component concentration measuring apparatus according to the present invention, there is further provided phase-synchronizing detection means for detecting the measurement sound wave detected by the sound wave detection unit so as to be synchronized with the phase of the integral multiple of the constant frequency output from the optical switch. It is preferable to provide.
Noise other than the measurement sound wave can be eliminated by detecting the measurement sound wave in phase synchronization with a constant frequency in the optical switch.

In the component concentration measuring apparatus according to the present invention, it is preferable that the apparatus further includes a temperature detecting unit that detects the temperature of the object to be measured.
From the temperature of the object to be measured, the absorbance of the background component and the target component at that temperature can be used. Thereby, the density | concentration of the target component which excluded the influence of the temperature dependence of a light absorbency can be measured.

The component concentration measuring apparatus according to the present invention preferably further includes a temperature correction unit that corrects the amplitude of the measurement sound wave detected by the sound wave detection unit based on the temperature detected by the temperature detection unit.
By further including the temperature correction unit, it is possible to remove the influence of the temperature of the measurement object on the measurement sound wave.

In order to solve the above problems, the component concentration measurement method according to the present invention includes a light output step in which two light sources output continuous light having different wavelengths, and a continuous light output in the light output step by an optical switch. Alternately , an optical switch step for outputting from the same output terminal at a predetermined constant frequency, and a sound wave detection unit from the object to be measured by the light from the two light sources output in the optical switch step. And a sound wave detecting step for detecting generated sound waves for measurement in order.

  In the light output step, since each light source outputs continuous light, it can be used in a stable drive mode. Moreover, in the optical switch step, the optical switch alternately outputs continuous light from each light source at a constant frequency, so that the combined light for measurement obtained by combining the light of two consecutive wavelengths with the same frequency and opposite phase is the same. Can be output from the output terminal. As a result, the photoacoustic signal generated from the background component can be removed from the measurement sound wave detected in the sound wave detection step without using a 180 ° phase shifter.

In the component concentration measurement method according to the present invention, it is preferable that the temperature detection unit further includes a temperature detection step of detecting the temperature of the object to be measured before or after the sound wave detection step or simultaneously with the sound wave detection step.
By further including a temperature detection step, the absorbance of the background component and the target component at that temperature can be used from the temperature of the object to be measured. Thereby, the density | concentration of the target component which excluded the influence of the temperature dependence of a light absorbency can be measured.

In the component concentration measurement method according to the present invention, a temperature detection step for detecting the temperature of the object to be measured before or after the sound wave detection step or simultaneously with the sound wave detection step, and after the sound wave detection step, the sound wave detection step It is preferable to further include a temperature correction step of correcting the amplitude of the measurement sound wave detected in the step based on the temperature of the object to be measured.
By further including the temperature correction step, it is possible to remove the influence of the temperature of the measurement object on the measurement sound wave. Thereby, a differential photoacoustic signal that is not affected by the temperature of the object to be measured can be obtained.

  According to the present invention, the component concentration measuring apparatus and the component concentration measuring method according to the present invention enable use in the stable drive mode, and the difference between the photoacoustic signals generated from the background components without using the 180 ° phase shifter. Can be removed.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiment described below is an example of the configuration of the present invention, and the present invention is not limited to the following embodiment.

  FIG. 1 is a schematic configuration diagram of a component concentration measuring apparatus according to the present embodiment. The component concentration measuring device 91 includes a configuration for measuring the concentration of the target component in a solution in which the background component and the target component are mixed using the photoacoustic method. For example, the component concentration measuring device 91 includes a first light source 10, a second light source 11, a drive circuit 12a for the first light source 10, a drive circuit 12b for the second light source 11, and drive circuits 12a and 12b. A constant voltage current source 13 for supplying a voltage to the optical switch 15, an optical switch 15, an oscillator 14 for inputting a clock signal having a constant frequency to the optical switch 15, and output light from the optical switch 15 to the object under test 101. The light emitting unit 16, the sound wave detection unit 17 that detects sound waves generated from the DUT 101, the preamplifier 18 that amplifies the sound waves detected by the sound wave detection unit 17, and the phase of the amplified sound waves of the preamplifier 18 A phase detection amplifier 19 for detection and a photoacoustic signal output terminal 20 for outputting a photoacoustic signal detected by the phase detection amplifier 19 are provided.

  The first light source 10 and the second light source 11 output continuous light having different wavelengths. By outputting continuous light, the first light source 10 and the second light source 11 can be used in the stable drive mode. The light source that outputs continuous light is, for example, a laser light source such as a dye laser, a titanium sapphire laser, or an Er-doped fiber laser, or a white light source. In order to stabilize the light intensity of the continuous light, it is preferable to provide a photodetector (not shown) that receives part of the light generated by the first light source 10 and the second light source 11. By feeding back the intensity of light received by a photodetector (not shown) to the constant voltage current source 13 and the drive circuits 12a and 12b, the light intensity can be stabilized.

Wavelength lambda ₂ of the light output of the wavelength lambda ₁ and the second light source 11 of the light output of the first light source 10 is a different wavelength absorption are equal presented by the background component. For example, if the DUT 101 is a living body and the target component is glucose in blood, the absorption exhibited by the background component can be the absorption exhibited by water.

And it is preferable that at least one of the first light source 10 and the second light source 11 has a wavelength that maximizes the absorption exhibited by the target component. For example, if the DUT 101 is a living body and the target component is glucose in blood, the first light source 10 preferably has a wavelength of 1600 nm or 2100 nm, which is a wavelength at which absorption exhibited by glucose is maximized. In this case, the output continuous light of the first light source 10 becomes a wavelength lambda ₁ of the measuring light, the output continuous light of the second light source 11 becomes a wavelength lambda ₂ of the reference beam.

  In order to set the wavelength of the continuous light output from the first light source 10 and the second light source 11 to the above wavelength, if it is a laser light source, a laser medium that generates light of a specific wavelength, temperature, or driving current is selected. If the light source is a light source with a wide wavelength band, such as a white light source, the output light is filtered using a wavelength tunable filter such as a bandpass filter.

  The oscillator 14 has a function of generating a pulse train having an arbitrary frequency, and outputs a clock signal having a constant frequency. The optical switch 15 is driven by a clock signal, and switches the first light source 10 and the second light source 11 at a constant frequency from the oscillator 14.

The optical switch 15 sequentially outputs continuous light from the first light source 10 and the second light source 11 from the same output terminal at a predetermined constant frequency. Here, the constant frequency is input from the oscillator 14. For example, the optical switch 15 includes two input terminals and one output terminal, and the measurement light having the wavelength λ ₁ from the first light source 10 and the reference light having the wavelength λ ₂ from the second light source 11 are It is input via an optical fiber which is a light transmission means. Then, the connection of the input terminals is switched according to the clock signal from the oscillator 14 using an acousto-optic modulator (AOM) or an electro-optic modulator (EOM). By doing so, it is possible to output from the output terminal measurement combined light in which the measurement light and the reference light are mixed at a constant frequency and in reverse phase. Thereby, the difference of the photoacoustic signal generated from the background component can be removed without using a 180 ° phase shifter. As the optical switch 15, a waveguide type or a bulk crystal type can be used among AOM and EOM. In addition to the AOM or EOM, a fiber type, a micro electro mechanical system (MEMS), a Mach-Zehnder type, or a TO (Thermo-Optec) type can also be used as the optical switch 15.

FIG. 2 is an explanatory diagram showing an example of the relationship between an optical switch and a photoacoustic signal, where (a) is a clock signal from an oscillator, (b) is measurement light from the first light source 10 and its photoacoustic signal, (C) shows the reference light from the second light source 11 and its photoacoustic signal. In FIG. 2 (b), the broken line measurement light, a solid line represents a photoacoustic signal s ₁ which is generated by the measurement light. In FIG. 2 (c), the dashed line reference light, a solid line represents a photoacoustic signal s ₂ generated by the reference beam. The measurement light and the reference light output from the optical switch according to the clock signal are measurement combined light having the same frequency and opposite phase. For this reason, the differential photoacoustic signal (s ₁ -s ₂ ) obtained by removing the difference of the photoacoustic signal generated by the background component is measured by irradiating the object to be measured with the synthetic light for measurement obtained by combining the measurement light and the reference light. can do.

  The combined light for measurement output from the output terminal of the optical switch 15 shown in FIG. 1 is input to the light emitting unit 16 through an optical fiber that is a light transmission means. The light emitting unit 16 emits the light output from the optical switch 15 toward the device under test 101. A right-angle prism, fiber collimator, or filler may be bonded to the tip of the optical fiber in accordance with the shape of the device under test 16. For example, when the temperature conduction window 21 is a support that is curved along the shape of the DUT 101, the shape of the right-angle prism is matched to the curved shape.

The sound wave detection unit 17 illustrated in FIG. 1 detects sound waves generated from the object to be measured 101 by light from the first light source 10 and the second light source 11. When the constant voltage current source 13 supplies a voltage to the drive circuits 12a and 12b, the measurement composite light is irradiated onto the device under test 101. Therefore, the difference light is detected by detecting the measurement sound wave generated by the measurement composite light. An acoustic signal (s ₁ -s ₂ ) can be measured. When the constant voltage current source 13 does not supply a voltage to the drive circuit 12a and the constant voltage current source 13 supplies a voltage only to the drive circuit 12b, the reference light is applied to the device under test 101, and thus generated by the reference light. It can be measured photoacoustic signal s ₂ by detecting the normalized wave for.

  The phase detection amplifier 19 has a function as a phase synchronous detection means. For example, the phase detection amplifier 19 receives a clock signal having a constant frequency from the oscillator 14 and detects the sound wave detected by the sound wave detection unit 17 so as to be synchronized with the phase of the clock signal. Since the measurement sound wave is generated at a frequency half that of the switching frequency of the optical switch 15, noise other than the measurement sound wave can be eliminated by synchronizing with the switching frequency of the optical switch 15 and the phase of the common clock signal. Can do.

  It is preferable that the component concentration measuring device 91 further detects the temperature of the object 101 to be measured. The temperature shift amount of the absorbance of the background component and the target component can be estimated from the temperature of the DUT 101. In this case, a temperature conduction window 21 that conducts the temperature of the DUT 101, a temperature detection unit 22 that detects the temperature of the temperature conduction window 21, and a temperature signal output terminal 23 that outputs the temperature detected by the temperature detection unit 22. Is provided. Then, the temperature of the DUT 101 detected by the temperature detector 22 through the temperature conduction window 21 is output from the temperature signal output terminal 23.

  The component concentration measuring device 91 preferably further corrects the concentration of the target component based on the temperature of the DUT 101. The influence of the temperature shift of the absorbance at the measured concentration of the target component can be eliminated. In this case, a temperature correction unit (not shown) is provided after the sound wave detection unit 17, for example, after the phase detection amplifier 19. A temperature correction unit (not shown) stores in advance a correction curve for a background component and a target component corresponding to the temperature, and a background component and a target component corresponding to the temperature of the DUT 101 output from the temperature signal output terminal 23. Read the correction value. Then, the measurement sound wave output from the phase detection amplifier 19 is corrected using the read correction value. Thereby, the differential photoacoustic signal which excluded the influence by the temperature shift of the light absorbency in the measurement density | concentration of an object component can be output from the photoacoustic signal output terminal 20. FIG. The above correction may be performed by a temperature correction unit (not shown) or by a person.

  The component concentration measurement method according to this embodiment will be described with reference to FIG. The component concentration measurement method according to this embodiment includes a light output step, an optical switch step, and a sound wave detection step in order. Preferably, the component concentration measurement method further includes a temperature detection step and a temperature correction step. The temperature detection step is performed before or after the sound wave detection step or simultaneously with the sound wave detection step. The temperature correction step is performed after the sound wave detection step and the temperature detection step.

In the light output step, the first light source 10 and the second light source 11 output continuous light having different wavelengths. For example, the first light source 10 outputs a measurement light having a wavelength lambda _1. The second light source 11 outputs the reference light wavelength lambda _2. The measurement light and the reference light are input to the input terminal of the optical switch 15 through an optical fiber.

  In the optical switch step, the optical switch 15 sequentially outputs the continuous light output in the optical output step from the same output terminal at a predetermined constant frequency. For example, the oscillator 14 inputs a predetermined constant frequency clock signal to the optical switch 15. The optical switch 15 switches the connection with the input terminal according to the clock signal. The output terminal of the optical switch 15 alternately outputs measurement light and reference light at a constant frequency. As a result, the measurement combined light in which the measurement light and the reference light are mixed at a constant frequency and in reverse phase is output from the optical switch 15.

  The synthetic light for measurement from the optical switch 15 is transmitted to the light emitting part 16 to the object to be measured 101 by an optical fiber which is a light transmission means. The light from the light emitting part 16 reaches the device under test 101 through the temperature conduction window 21. The synthetic light for measurement is absorbed by the background component and the target component contained in the solution present in the DUT 101. When the background component and the target component absorb the synthetic light for measurement, a sound wave for measurement is generated by the photoacoustic effect.

In the sound wave detection step, the sound wave detection unit 17 detects the measurement sound wave generated from the measurement object 101 by the light from the first light source 10 and the second light source 11 output in the optical switch step. The sound wave signal converted into the electric signal by the sound wave detection unit 17 is amplified by the preamplifier 18 and input to the phase detection amplifier 19. The phase detection amplifier 19 extracts the amplitude and phase so as to be synchronized with the phase of the clock signal from the oscillator 14, and outputs the differential photoacoustic signal (s ₁ -s ₂ ) to the photoacoustic signal output terminal 20.

Through the above operation, the measurement combined light is generated using the measurement light having the wavelength λ ₁ output from the first light source 10 and the reference light having the wavelength λ ₂ output from the second light source 11. The differential photoacoustic signal (s ₁ -s ₂ ) can be measured from the measurement sound wave generated on the measurement object 101 by irradiating the measurement object 101 and the synthetic light for measurement.

Further, if the power supply to the first light source 10 is stopped and only the second light source 11 is driven, only the reference light output from the second light source 11 is applied to the device under test 101 for normalization. Sound waves are detected by the sound wave measuring unit 17. Then, the photoacoustic signal s ₂ obtained from the normalization sound wave is output to the photoacoustic signal output terminal 20. At this time, the optical switch 15 can measure the standardized sound wave having the same frequency as the measurement sound wave if the output light is switched by a clock signal having the same constant frequency as that of the measurement sound wave.

By using the differential photoacoustic signal (s ₁ -s ₂ ) and the photoacoustic signal s ₂ output from the photoacoustic signal output terminal 20, a target component with high measurement accuracy can be obtained by removing the difference from the photoacoustic signal generated from the background component. Concentration can be measured.

When the component concentration measurement method according to the present embodiment further includes a temperature detection step, in the temperature detection step, the temperature detection unit 22 detects the temperature of the measurement object 101. For example, the heat generated by the photothermal conversion in the DUT 101 is conducted through the temperature conduction window 21 and the temperature is detected by the temperature detection unit 22. Then, the temperature detected by the temperature detector 22 is output to the temperature signal output terminal 23. The temperature shift of the differential photoacoustic signal (s ₁ -s ₂ ) and the photoacoustic signal s ₂ generated from the measurement light and the reference light is corrected using the temperature of the DUT 101 output from the temperature signal output terminal 23. be able to. The correction is performed using a temperature correction unit (not shown) and other arithmetic devices. The arithmetic device may be outside the component concentration measuring device 91.

When the component concentration measurement method according to this embodiment further includes a temperature correction step, in the temperature correction step, the temperature correction unit (not shown) uses the amplitude of the measurement sound wave detected in the sound wave detection step to Correct based on temperature. For example, the background component corresponding to the temperature and the correction curve of the target component are stored in advance before the light output step. In the temperature correction step, the measurement sound wave output from the sound wave detection unit 17 in the sound wave detection step and the temperature of the measurement object 101 output from the temperature signal output terminal 23 in the temperature detection step are acquired. The amplitude of the sound wave for measurement is corrected from the acquired temperature of the measured object 101. The temperature correction step is preferably performed not only for the measurement sound wave but also for the normalization sound wave generated by the reference light. By performing the temperature correction step, the photoacoustic signal output terminal 20 outputs the differential photoacoustic signal (s ₁ -s ₂ ) and the photoacoustic signal s ₂ excluding the influence of the temperature shift of the absorbance at the measured concentration of the target component. be able to. The temperature correction step may be performed not only by a temperature correction unit (not shown) but also by a person.

  In addition, although this embodiment demonstrated the case where the several light source was two, three or more may be sufficient. For example, when there are three light sources, a plurality of types of differential photoacoustic signals obtained by combining the wavelengths can be measured if the absorption of the background component is equivalent at the output wavelength of each light source. By setting the number of the plurality of light sources to three or more, it is possible to measure the absorbance of the target component and the background component at more wavelengths, and to increase the measurement accuracy of the target component. Further, when there are four or more light sources, a plurality of types of differential photoacoustic signals having different absorbances can be measured.

Next, a setting example of the wavelength λ ₁ output from the first light source 10 and the wavelength λ ₂ output from the second light source 11 in this embodiment will be described with reference to FIG. FIG. 3 is an example of the absorbance of the solution, (a) shows the absorbance and absorption coefficient of the glucose aqueous solution, and (b) shows the absorbance difference and specific absorbance of glucose with respect to water. Hereinafter, the wavelength setting when quantitatively analyzing the glucose concentration in the aqueous glucose solution using the solution as the glucose aqueous solution and the target component as glucose will be exemplified.

First, from the difference spectrum obtained by subtracting water from the glucose aqueous solution shown in FIG. 3B, the wavelength at which the absorption of glucose as the target component is maximized is the wavelength λ ₁ of the first light source. In the aqueous solution, the main background absorption component is water. Therefore, in order to remove the sound wave generated from the background absorption by subtracting the wavelength λ ₂ of the second light source, the water shown in FIG. A wavelength exhibiting an absorbance equal to the wavelength λ ₁ from the absorption spectrum may be used.

ここで、Ｃは、変化し制御又は予想が困難な係数である。例えば、図１における、音響結合、音波検出部１７の感度、光出射部１６と被測定物１０１の間の距離（以下ｒと定義する）、被測定物１０１の比熱、被測定物１０１の熱膨張係数、被測定物１０１での音速、発振器１４の発振周波数、さらに、吸収係数に依存する未知数である。 Next, a method for measuring the concentration M of glucose as the target component using the differential photoacoustic signal (s ₁ -s ₂ ) and the photoacoustic signal s ₂ output from the photoacoustic signal output terminal 20 shown in FIG. Will be described.
To know the absorption coefficients α ₁ ^(b) and α ₂ ^{(b) of} the background component and the molar absorption coefficients α ₁ ⁽⁰⁾ and α ₂ ⁽⁰⁾ of the target component for each of the wavelength λ ₁ and the wavelength λ ₂ , simultaneous equations including the photoacoustic signal s ₂ in the photoacoustic signal s ₁ and the wavelength lambda ₂ at a wavelength lambda ₁ is represented by equation (1).

Here, C is a coefficient that changes and is difficult to control or predict. For example, in FIG. 1, acoustic coupling, sensitivity of the sound wave detection unit 17, distance between the light emitting unit 16 and the object to be measured 101 (hereinafter, defined as r), specific heat of the object to be measured 101, heat of the object to be measured 101. It is an unknown that depends on the expansion coefficient, the speed of sound at the DUT 101, the oscillation frequency of the oscillator 14, and the absorption coefficient.

ここで、数式（２）の後段の変形にはｓ_１≒ｓ_２という性質を用いている。 When the coefficient C is deleted from the mathematical formula (1), it is expressed as the following mathematical formula (2), and the photoacoustic signals s ₁ and s ₂ , the molar absorption coefficients α ₁ ⁽⁰⁾ , α ₂ ^{(0) of} the target component, and The concentration M of the target component can be obtained from the absorption coefficient α ₁ ^{(b) of the} background component.

Here, the property of s ₁ ≈s ₂ is used for the subsequent deformation of Equation (2).

From the above, since the molar absorption coefficients α ₁ ⁽⁰⁾ and α ₂ ⁽⁰⁾ of the target component are known, the differential photoacoustic signal (s ₁ -s ₂ ) and light output from the photoacoustic signal output terminal 20 by measuring the acoustic signal s _2, it is possible to measure the concentration M of glucose is the target component. In the present embodiment, since the first light source 10 and the second light source 11 output continuous light, the stability of the output intensity can be maintained. Further, by reducing the measurement time difference between the differential photoacoustic signal (s ₁ -s ₂ ) and the photoacoustic signal s ₂ , the calculation error of the concentration M based on the formula (2) can be further reduced.

  The present invention relates to a noninvasive component concentration measuring device for a solution existing in a human or an animal, and a component concentration measuring device for a solution collected from a human or an animal.

1 is a schematic configuration diagram of a component concentration measuring apparatus according to the present embodiment. It is explanatory drawing which shows an example of the relationship between an optical switch and a photoacoustic signal, (a) is the clock signal from an oscillator, (b) is the measurement light and its photoacoustic signal from a 1st light source, (c) is the 1st. The reference light from 2 light sources and its photoacoustic signal are shown. It is an example of the light absorbency of a solution, (a) shows the light absorbency and absorption coefficient of glucose aqueous solution, (b) shows the light absorbency difference and specific light absorbency of glucose with respect to water. It is a structural example which shows the 1st component density | concentration measuring apparatus by the conventional photoacoustic method. It is a structural example which shows the 2nd component density | concentration measuring apparatus by the conventional photoacoustic method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 1st light source 11 2nd light source 12a, 12b Drive circuit 13 Constant voltage current source 14 Oscillator 15 Optical switch 16 Light-emitting part 17 Sound wave detection part 18 Preamplifier 19 Phase detection amplifier 20 Photoacoustic signal output terminal 21 Temperature conduction Window 22 Temperature detection unit 23 Temperature signal output terminal 91 Component concentration measurement device 101 Device under test 110 First light source 111 Second light source 112a, 112b Drive circuit 113 180 ° phase shifter 114 Oscillator 115 Optical branch 117 Acoustic sensor 119 Phase Detection amplifier 201 First light source 202 Second light source 203, 204 Drive power supply 211 Multiplexer 212 Acoustic sensor 213 Chopper plate 214 Motor 215 Frequency analyzer

Claims (9)

Two light sources that output continuous light of different wavelengths;
An optical switch that outputs continuous light from the two light sources alternately from the same output terminal at a predetermined constant frequency; and
A sound wave detection unit that detects sound waves for measurement generated from the object to be measured by the light from the two light sources output from the optical switch;
A component concentration measuring apparatus comprising:   The component concentration measuring apparatus according to claim 1, wherein the plurality of light sources output different wavelengths having the same absorption of the background component in a solution in which the background component and the target component are mixed.   3. The component concentration according to claim 1, wherein at least one of the plurality of light sources has a wavelength that maximizes absorption exhibited by the target component in a solution in which a background component and the target component are mixed. measuring device.   2. A phase-locked detection unit that detects a measurement sound wave detected by the sound wave detection unit so as to be synchronized with a phase of an integral multiple component of the constant frequency output from the optical switch. 4. The component concentration measuring apparatus according to any one of 3 above.   The component concentration measuring apparatus according to claim 1, further comprising a temperature detecting unit that detects a temperature of the object to be measured.   6. The component concentration measuring apparatus according to 5, further comprising a temperature correction unit that corrects the amplitude of the measurement sound wave detected by the sound wave detection unit based on the temperature detected by the temperature detection unit. A light output step in which two light sources output continuous light having different wavelengths; and
An optical switch step in which the continuous light output in the optical output step is alternately output from the same output terminal at a predetermined constant frequency; and
A sound wave detecting step in which a sound wave detecting unit detects a sound wave for measurement generated from the object to be measured by light from the two light sources output in the optical switch step;
A component concentration measurement method comprising:   The component concentration measurement according to claim 7, wherein the temperature detection unit further includes a temperature detection step of detecting a temperature of the object to be measured before or after the sound wave detection step or simultaneously with the sound wave detection step. Method.   After the sound wave detection step and the temperature detection step, the temperature correction unit further includes a temperature correction step of correcting the amplitude of the measurement sound wave detected in the sound wave detection step based on the temperature of the object to be measured. The component concentration measuring method according to claim 8, wherein the component concentration is measured.

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