JP2019004946A - Component concentration measuring device and measuring method - Google Patents

Abstract

To provide a component concentration measuring device and measuring method in which highly precise measurement is possible even if the irradiation light intensity to a sample to be measured by the OPBS method fluctuates in terms of time.SOLUTION: Light sources 101-106 are optically connected to the optical path switching unit 107. The optical path switching unit 107 is configured such that a period drive circuit 108 controls the optical path switching unit 107 in a preset period time, and thereby the optical path switching is made and the light source of the light for applying light irradiation to a workpiece is selected. An optical path opening/closing time of an ON/OFF switch 112 is controlled so that light irradiation may be made only as for the irradiation time calculated so as to become a preset time summation light intensity W. The light irradiation to the workpiece is subjected to ON/OFF control, and the light of the preset time summation light intensity Wradiates the workpiece in the workpiece cell 113. The sound wave produced by the light irradiation is detected, and the photoacoustic signal intensity to each time summation light intensity of each light source is detected, and thereby the specific component concentration of the workpiece can be measured.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a component concentration measuring apparatus and a measuring method for measuring the concentration of a dispersed or dissolved component in a medium in which light and an acoustic signal propagate together, such as water.

  In order to prevent diabetes, it is important to continuously monitor the blood glucose level of diabetic patients. In monitoring blood glucose levels, it is necessary to accurately measure the glucose concentration present in blood. As a measuring method, there is a photoacoustic method. According to the measurement by the photoacoustic method, it is possible to continuously monitor the glucose concentration in the blood. In addition, the photoacoustic measurement is painless for diabetic patients, does not require a blood sample, and does not cause discomfort to the diabetic patient. Also, in the photoacoustic method measurement, compared to other optical measurement methods, efficiency is not deteriorated due to the scattering media, and high sensitivity characteristics can be obtained by combining optics and acoustics.

  There are two photoacoustic methods, a pulse method and a continuous-wave (CW) method. However, in the conventional pulse method and CW method, during the measurement of the glucose concentration in plasma several times, there is a high possibility that other plasma parameters other than the glucose concentration (for example, body temperature, concentration of other components, etc.) will also change. Therefore, there is a problem that the glucose selectivity is poor and it is difficult to obtain an accurate glucose concentration.

  Therefore, an optical power balance shift (OPPBS) method has been developed in which component concentration is measured by a continuous rectangular wave having a phase difference of π (180 °) between two wavelengths (Patent Documents 1-5). reference).

  Specifically, intensity-modulated light having a phase difference of two π of wavelengths λ1 and λ2 is combined and emitted to the object to be measured. Then, a sound wave generated by being absorbed by the component of the object to be measured is detected, and the concentration of the measurement target component in the object to be measured is measured from the magnitude of the sound wave.

Here, for example, the wavelength λ _A and the wavelength λ _B are set so that the absorbance by water, which is the background component in the object to be measured, is equal to each other. The wavelength λ _A is set so that the absorbance due to glucose, which is a measurement target component in the object to be measured, is maximized.

When light of such two different wavelengths is emitted, the light of wavelength λ _A is absorbed by both glucose and water, and the sound wave generated from the object to be measured and the light of wavelength λ _B are absorbed by water. Since the sound wave generated from the measurement object has the same frequency and opposite phase, it is superimposed inside the measurement object, and only the magnitude of the sound wave generated from the measurement object as glucose is absorbed as glucose difference. Will remain.

That is, the size S of the detected acoustic wave is equivalent to the difference between the magnitude of the acoustic wave was measured using only the light of the size and the wavelength lambda _B of the waves measured by using only the light of wavelength lambda _A, to be measured The size is based only on the absorption of a specific component (here, glucose) in the object.

[OPBS measurement method]
Here, the measurement principle of the conventional OPBS method will be briefly described. In the conventional OPBS method, in order to search for a point where no ultrasonic wave is generated from the object to be measured, that is, a point where the intensity S of the photoacoustic signal is 0, the power of the two wavelengths of light is adjusted.

For example, even if the intensity S of the photoacoustic signal is not 0 but is a constant S ₀ , there is no problem as long as it is a known constant. However, for the sake of simplification of explanation, it is assumed that the constant S ₀ is 0.

When the intensity S of the photoacoustic signal is S = 0, the following theoretical formula is established.
α _A P _A −α _B P _B = 0 (1)

Here, P _A and P _B are the powers of the two wavelengths of light A and B, and α _A and α _B are the light absorption coefficients of the object to be measured for the light powers of P _A and P _B , respectively.

At this time, since the sound waves generated from the two wavelengths of light have the same frequency and opposite phases, the intensity S = 0 of the photoacoustic signal cancels inside the object to be measured (or the minimum value: S ₀ ). It can be. In other words, at this time, it can be said that the intensity balance of the sound waves of the light of two wavelengths is balanced.

Here, when the concentration of the component to be measured changes, for example, it is assumed that the glucose concentration has changed by Cg as the component of the object to be measured. When the light absorption coefficients α _A and α _B change by δα _A and δα _B , respectively, due to this change in concentration, the state changes from the state in which equation (1) holds to the state in equation (2).
(Α _A + δα _A C _g ) P _A − (α _B + δα _B C _g ) P _B ≠ 0 (2)

Here, the light absorption coefficient change rates δα _A and δα _B are light absorption coefficients per unit concentration at the light wavelengths λ _A and λ _B of light A and B relating to glucose as a component of the object to be measured. It is a value that can be separately detected by light absorption spectrum measurement using a single reagent solution.

In order to return to the state of S = 0, for example, when the light intensity PA of the light _A is changed, the following equation is established.
(Α _A + δα _A C _g ) (P _A + δP _A ) − (α _B + δα _B C _g ) P _B = 0 (3)

Subsequently, when the light intensity P _B of the other light B is changed at the same time, the following equation is established as in the equation (3).
(Α _A + δα _A Cg) (P _A + δP _A ) − (α _B + δα _B Cg) (P _B + δP _B ) = 0 (4)

In formulas (3) and (4), δP _A and δP _B are the amounts of change in the light intensities P _A and P _B of the light _A and _B , respectively.

  At this time, the following equation is obtained from equation (4).

From formulas (1), (3), and (4), unknown light absorption coefficients α _A and α _B are obtained, and it can be seen from formula (5) that the glucose concentration C _g can be measured.

  Subsequently, the measurement procedure of the OPBS method will be specifically described with reference to a chart.

In the OPBS method disclosed in Patent Documents 1-5, as shown in FIG. 1, two rectangular continuous waveforms of light A and light B having different light wavelengths and having a phase difference of π are identical to the object to be measured. Irradiate from the light output port. At this time, the photoacoustic wave signal S generated from the object to be measured is represented by the following equation where the light absorption coefficient of the object to be measured is α and the light intensity of a certain intensity is P, and the time of each irradiation light in FIG. It becomes the area of a rectangular continuous waveform that is a change.
S = α × P (6)

The OPBS method searches for an inflection point of the phase where the amplitude of the photoacoustic signal is minimum while increasing or decreasing the light intensities P _A and P _B of these two wavelengths of light A and B. This is a method for obtaining the concentration of a dissolved object to be measured.

More specifically, as shown in FIGS. 2A to 2C, first, the light intensity P _B of one of the two lights A and B having different wavelengths is made constant, and the other continue to measure the photoacoustic signal intensity S while changing the light intensity P _a light a. At this time, a curve change in which the photoacoustic signal intensity S takes a minimum value as shown in FIG. In particular, at the position shown in FIG. 2B, the photoacoustic signal intensity S shows a minimum value. This is a state in which the intensity balance of sound waves caused by the two wavelengths of light A and B is balanced. It is a state that holds.

Thereafter, when the light absorption coefficient α _B caused by the increase or decrease in the concentration of a specific component (for example, glucose) in the object to be measured changes, the curve of the photoacoustic signal intensity S shifts as indicated by the broken line in FIG. When the photoacoustic signal intensity takes the minimum value at the same position as in FIG. 2B, the state of Expression (3) is obtained, and the light intensity PA of the light _A also changes (broken line in FIG. 2D). Furthermore, since the state of the equation (4) can be reproduced by changing the light intensity P B of the light _{B in the} same manner, from the equations (1) and (3) to (5), allows evaluation of the concentration C _g of the specific component (e.g. glucose).

However, in practice, the light wavelength of one light _A can be selected so that the light absorption coefficient change rate δα _A of a specific component (for example, glucose) in the object to be measured is so small that it can be ignored (δα _A ≈0). Yes, since the measurement can be evaluated by the change in the light intensity of only the light A and the expressions (1) and (3), that is, by changing only the light intensity P _{B at} which the photoacoustic signal intensity is minimum, It is possible to accurately measure the concentration of a specific component (for example, glucose).

That is, the concentration C = C intensity P _B (C ₀₎ of light B which takes a minimum value of the solid line shown in FIG. 2 (d) when the ₀ in the formula (1) of a specific component in the measuring object (e.g. glucose), Further, the intensity P _{B of the} light B taking the minimum value of the broken line in FIG. 2D when the concentration C ₁ = C ₀ + ΔC when the concentration of the specific component (for example, glucose) in the object to be measured is increased by ΔC. From (C ₁ = C ₀ + ΔC) and equation (3), a concentration increase ΔC of a specific component (for example, glucose) in the object to be measured is obtained.

Japanese Patent Laid-Open No. 2006-154585 JP2015-31670A JP 2014-50563 A JP 2013-106874 A JP 2012-179212 A

In the conventional OPBS method, the optical powers P _A and P _B change even when the driving current of the laser diode is constant, due to the case where the output stability of the light source is not good or the environmental temperature varies. For example, in the formula (1), the optical power P _A is changed by epsilon, expressed by the following equation.
α _A (P _A + ε) −α _B P _B ≠ 0 (7)

In the state of Expression (7), even if the glucose concentration is constant, one of the light intensities (for example, P _A ) must be adjusted in order to make S = 0.
α _A ((P _A + δP _A ) + ε) −α _B P _B = 0 (8)

Therefore, the effect of changes in impact and glucose concentration change in the output of the light source has on the intensity of the photoacoustic signal S is supplied to the intensity S of photoacoustic signal is the same, to distinguish these changes from [delta] P _A measurement result Therefore, it is difficult to accurately measure the glucose concentration when there is a change in the output of the light source. That is, in the conventional OPBS method, it is necessary to always measure the output power of the light source and keep the output of the light source constant.

That is, in the conventional OPBS method, in order to search for the point where the intensity of the photoacoustic signal is the lowest, the intensity of the photoacoustic signal is measured while finely changing the power P _B while keeping the light intensity P _A constant. There is a need to do.

Therefore, the laser diode light intensity, P _A , and P _B stability are required, and long-term stability for short-term stability and measurement reproducibility within one cycle of measurement time for obtaining the minimum value of the photoacoustic signal. Both sexes are required.

  However, in practice, even if injection current control with a feedback circuit is performed, the temporal change stability of the light intensity of LD (laser diode) light is not so high. Intensity fluctuations will occur. Therefore, when the above measurement is actually performed, there is a problem that light intensity noise of several percent is included in the time for measuring the minimum value, which causes a measurement error of the OPBS method that is difficult to improve.

  The present invention has been made in order to solve the above-described problems, and a component concentration measuring apparatus capable of measuring with high accuracy even when the intensity of light irradiated to a sample to be measured varies with time during measurement by the OPBS method. And it aims at providing a measuring method.

  In order to solve the above-described problems, the present invention provides a component concentration measuring apparatus, which is a light source that irradiates a plurality of lights having different wavelengths, and a rectangular continuous waveform having a phase that differs by π among the plurality of lights having different wavelengths. Optical path switching means for switching the light sources of the first and second lights, light intensity measuring means for measuring the light intensity of each of the first and second lights, and the light of the first and second lights Opening / closing means for controlling ON / OFF of irradiation intermittently to control the irradiation time of the first and second lights, and an object to be measured by light irradiation of the first and second lights from the opening / closing means A photoacoustic signal detecting means for detecting a photoacoustic wave generated from the light and outputting a photoacoustic signal intensity; and a time integrated light intensity of the first and second lights calculated from the light intensity and the irradiation time , By controlling the irradiation time The first and second light when the time integrated light intensity of one of the second light and the second light is constant and the other time integrated light intensity is changed so that the photoacoustic signal intensity becomes a minimum value. A concentration deriving means for deriving a concentration of a component to be measured included in the object to be measured, based on each of the time integrated light intensity, a change amount of the time integrated light intensity, a light absorption coefficient, and a light absorption coefficient change rate; It is provided with.

  The invention according to claim 2 is the component concentration measuring apparatus according to claim 1, further comprising a light branching means installed between the optical path switching means and the opening and closing means, the light intensity measuring means, The light intensity of the light branched by the light branching means is measured.

  The invention according to claim 3 is a component concentration measuring apparatus, comprising: a light source that irradiates a plurality of light beams having different wavelengths; and a first rectangular continuous waveform having a phase different by π among the plurality of light beams having different wavelengths. An optical switch that switches the light source of the second light between the first and second optical paths and controls the irradiation time of the first and second lights to the first optical path; A light intensity measuring means for measuring the light intensity of each of the two lights, and a photoacoustic wave generated from the object to be measured by the light irradiation of the first and second lights from the first optical path of the optical switch. And controlling the irradiation time for the photoacoustic signal detection means for outputting the photoacoustic signal intensity and the time-integrated light intensity of the first and second lights calculated from the light intensity and the irradiation time. The time of one of the first and second lights by The time-integrated light intensity of each of the first and second lights when the other time-integrated light intensity is changed so that the calculated light intensity is constant and the photoacoustic signal intensity becomes a minimum value, the time And a concentration deriving unit for deriving the concentration of the component to be measured included in the object to be measured based on the change amount of the integrated light intensity, the light absorption coefficient, and the light absorption coefficient change rate.

  According to a fourth aspect of the present invention, in the component concentration measuring apparatus according to the third aspect, the optical switch is connected to the first optical switch connected to the light source and the first and second optical paths. A second optical switch, and further comprising an optical branching unit disposed between the first optical switch and the second optical switch, wherein the optical intensity measuring unit is branched by the optical branching unit. The light intensity of the emitted light is measured.

  The invention according to claim 5 is a component concentration analysis method, comprising: irradiating a plurality of lights having different wavelengths; and first and second rectangular continuous waveforms having a phase different by π among the plurality of lights having different wavelengths. Switching the connection of the second light between the first and second optical paths and controlling the irradiation time of the first and second lights on the first optical path; and A step of measuring each light intensity of light, and detecting a photoacoustic wave generated from the object to be measured by light irradiation of the first and second light from the first optical path and outputting a photoacoustic signal intensity The time integrated light intensity of the first and second lights calculated from the light intensity and the irradiation time, and controlling one of the first and second lights by controlling the irradiation time. The time integrated light intensity is constant, and the photoacoustic The time integrated light intensity of each of the first and second lights, the amount of change in the time integrated light intensity, and the light absorption coefficient when the other time integrated light intensity is changed so that the signal intensity becomes a minimum value. And a step of deriving the concentration of the component to be measured included in the object to be measured based on the change rate of the light absorption coefficient.

  According to a sixth aspect of the present invention, in the component concentration analysis method according to the fifth aspect, in the step of deriving the concentration of the component to be measured, the concentration of the component to be measured and the light absorption coefficient of the solvent are known. Deriving the rate of change of the light absorption coefficient of the first and second lights using a standard sample.

  According to a seventh aspect of the present invention, in the component concentration analysis method according to the fifth or sixth aspect, the step of deriving the concentration of the component to be measured includes the time period so that the photoacoustic signal intensity becomes a minimum value. After adjusting the integrated light intensity, the concentration of the component to be measured is increased or decreased, and the amount of change in the time integrated light intensity at which the photoacoustic signal intensity becomes a minimum value after the increase or decrease in the concentration of the component to be measured, light absorption The method includes the step of measuring a coefficient change rate.

  According to the present invention, the concentration of a dissolved component in a light-transmitting solution can be detected using a photoacoustic signal, and can be applied to a solution analysis technique. In particular, by using it for analysis of blood and body fluids, it is possible to monitor the concentration of components such as blood glucose and albumin, which can be introduced into various medical analysis techniques.

It is a figure which shows the time change of the light intensity at the time of irradiating light A and B by the conventional OPBS method alternately. (A)-(c) is a figure which shows the time change of the light intensity at the time of irradiating light A and B alternately, (d) is light intensity dependence of the photoacoustic signal intensity S in the conventional OPBS method. It is a figure which shows sex. (A) is a figure which shows the time change of the light intensity change at the time of intermittently irradiating light A and B with time intermittently, (b) is a figure which shows the time change of a time integration light intensity change. It is a figure which shows the time integration light intensity change with respect to each irradiation time of light A and B. FIG. It is a figure which shows the division | segmentation dependence of each irradiation time of the time integration light intensity of light A and B. FIG. It is a block diagram of the component concentration measuring apparatus which concerns on the 1st Embodiment of this invention. It is a block diagram of the component concentration measuring apparatus which concerns on the 2nd Embodiment of this invention. It is a flowchart of the component concentration analysis method which concerns on the 3rd Embodiment of this invention. Time integrated light intensity P _A of the light A and light B of the present invention, is a flow diagram of a light irradiation method of P _B. It is a block diagram of the component concentration measuring apparatus which concerns on the 3rd Embodiment of this invention.

In conventional OPBS method, for the intensity of the photoacoustic signal is to search the lowest point (minimum value), constantly measures the one of the light intensity P _A, while maintaining a constant intensity, while finely changing the power P _B and measured the intensity of the photoacoustic signal, the power P _a is always the assumption is that is kept constant, the power variation width [Delta] P _a in the case of fluctuations in measurement, the intensity of the photoacoustic signal Was the cause of error in finding the lowest point (minimum value).

Therefore, the component concentration measuring apparatus of the present invention measures the measured optical power in order to search for the point where the intensity of the photoacoustic signal is the lowest as in the conventional OPBS method, and applies the same time per unit time to the sample to be measured. By adjusting the irradiation time intermittently ON / OFF to adjust the integrated light intensity W, the same photoacoustic signal intensity can be stably maintained even if the irradiation light power varies. It is characterized by that. In the present invention therefore, as in the prior art, always measured one light intensity P _A, while maintaining a constant intensity, there is no need to perform intensity measurements of the photoacoustic signal while finely changing the power P _B.

That is, instead of the power P _A constant, by the time integration light intensity W per unit measurement time for obtaining a measurement point of one point constant, those to be obtained the same photoacoustic signal It is.

  The time-integrated light intensity W is expressed by the following equation using the time change of the measured light intensity.

  At this time, if the temporal change of the light intensity generated within the time for intermittent ON / OFF control is sufficiently small, the time integrated light intensity W is discretized as a set of rectangular waves as in the following equation. be able to.

In particular, when the temporal change in the light intensity that occurs within one period of measurement using light of a plurality of wavelengths is sufficiently small, the time integrated light intensity W is the light intensity of P _S , one period of light irradiation. If the total time is T _S , it can be expressed as a simple product as shown in the following equation.
W = P _S × T _S (11)

At this time, light absorption occurs in the sample to be measured, local thermal expansion occurs due to thermal conversion or thermal radiation, and light irradiation is performed within the conversion time until the photoacoustic wave generated from the living body is generated due to the thermal expansion. Since it is desirable to adjust the integrated amount by intermittently measuring the time, the intermittent time is desirably 10 milliseconds or less. Furthermore, in order to make it difficult for the acoustic microphone to detect noise, a frequency operation of 20 kHz or more is desirable, and the intermittent time is desirably 5 × 10 ⁻⁵ seconds or less.

FIGS. 3A and 3B are diagrams for explaining the principle of keeping the time integrated light intensity W constant even when the light intensity fluctuates over time. 3 (a) shows relative time change, the wavelength lambda _A and lambda _B of light A, the example of light intensity change at the time of intermittently irradiating time alternately B. The light intensity P _A of the light _A does not change over time, but the light intensity P B of the light _B changes over time. The broken line connects the light intensity of the light A, and the one-dot broken line connects the light intensity of the light B. Like the light A, in order to maintain the light intensity P _A constant, it is necessary to control the measured light intensity P _A constantly light intensity P _A. However, when the time integrated light intensity W is calculated using the equations (9) to (11), the irradiation time is controlled without always controlling the light intensity like the light B in FIG. As shown in FIG. 3B, the light B can keep the time-integrated light intensity W constant as in the case of the light A.

  Further, in the conventional OPBS method, the intensity of the photoacoustic signal is measured while finely changing at least one of a plurality of optical powers having different wavelengths, but high-precision feedback control of the optical power is required. Due to problems such as temperature and current stability of the LD power supply, optical power fluctuations of about several percent occur.

  Therefore, in the present invention, the intensity of the photoacoustic signal is measured by adjusting the irradiation time to vary the optical time integrated intensity, and the amount of change in the time integrated intensity at which the photoacoustic signal intensity is minimum is measured. The concentration of a specific component (for example, glucose) in the object to be measured is accurately measured.

FIG. 4 illustrates the principle of changing the time integrated light intensity W. When the light beams A and B having the wavelengths λ _A and λ _B are alternately irradiated with a period of 2π, the time integrated light intensity W _B of the light _B is changed while keeping the time integrated light intensity W _A of the light _A constant. The case is illustrated.

For the sake of brevity, assuming that the light beams A and B having the wavelengths λ _A and λ _B always have a constant light intensity, for example, time T = π × 2n to π × (2n + 1) ( n: an integer greater than or equal to 0), the light irradiation time of light A in each cycle is constant, so that the time-integrated light intensity WA of light _A is always constant as shown by the broken line of light A in FIG. be able to. On the other hand, when it is desired to increase the time integrated light intensity W as in the light B, the time T = π × (2m + 1) to π × (2m + 2) (m is an integer equal to or greater than 0) as in the light B in FIG. irradiation time of the light B in each cycle of), for example long as T = π~2π, it is sufficient to increase the time integration light intensity W _B. That is, in particular, when the time-integrated light intensity WB of the light _B is changed as shown by the one-dot broken line in FIG. 4, the irradiation time may be increased or decreased as the light B shown in FIG.

Furthermore, as a method of irradiating the same time-integrated light intensity W, the total irradiation time may be a constant value, and in principle, it does not depend on the number of divisions or the interval. More specifically, for the case of irradiating wavelengths period as 2 [pi lambda _A and lambda _B of light A, B alternately, will be exemplified in FIG. (For the sake of brevity, it is assumed that the light beams A and B having the wavelengths λ _A and λ _B always have a constant light intensity.) For example, as a method of irradiating the same time-integrated light intensity W ₀ , FIG. It is possible to irradiate light continuously in time like light B at time T = π to 2π in FIG. 5, but time as light A in time T = 0 to π in FIG. It is also possible to divide and irradiate light. At this time, the length of time division may be unequal intervals like the light A at time T = 2π to 3π in FIG. Rather, when the influence of the high frequency component of the generated sound wave due to the time division of light irradiation appears, it is desirable to irradiate the light by dividing the time into unequal intervals.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 6 is a block diagram showing the configuration of the component concentration measuring apparatus according to the first embodiment of the present invention. In the block diagram, solid lines connecting the blocks indicate light irradiation, and double lines connecting the blocks indicate electrical signal connections.

  In the component concentration measuring apparatus according to the first embodiment, light sources 101 to 106 having different wavelengths of light to be emitted are optically connected to the optical path switch 107 and are measured via the optical branch 109 and the ON / OFF switch 112. It is selectively connected to the optical path leading to the measured object cell 114 containing the object.

  At this time, various light sources such as a normal lamp, a fluorescent tube, an LED (light emitting diode), and a gas laser can be used as the light sources 101 to 106, but the light intensity is large, the light intensity stability of the irradiated light is relatively high, and the output A distributed feedback semiconductor laser (DFB-LD) is desirable because it is desirable that the optical spectrum line width of the emitted light wavelength is a narrow band.

  Further, it is desirable that the light sources 101 to 106 are stable with high accuracy in the injection current to the light source, the environmental temperature, and the like so that a constant light intensity can be stably output for an arbitrary time.

  Further, FIG. 6 shows the case of the light sources 101 to 106, but only six light sources are shown for convenience of explanation, and it is sufficient that the number of light sources is two or more. If more than one light wavelength is required, seven or more light sources may be provided.

  On the other hand, instead of using a plurality of light sources, the light sources 101 to 106 may be replaced with one wavelength tunable laser to vary the light wavelength. At this time, there are a method of changing the oscillation frequency by temperature adjustment, a method of using an external resonator, and the like. In addition, a solid-state laser can also be used, and a predetermined wavelength may be extracted using a dispersion element such as a prism or a diffraction grating.

  Furthermore, as shown in FIG. 6, the optical path switching unit 107 has a function of switching the light source with respect to the measurement time. The optical path switching unit 107 uses a MEMS driving light mirror, a mechanical driving mirror, a prism, or the like. Is possible.

  The optical path switch 107 is switched by the periodic drive circuit 108 controlling the optical path switch 107 in a preset cycle time, and the light source for irradiating the object to be measured is selected.

  A part of the light output from the optical path switcher 107 is branched to the light intensity measuring device 110 at the light branch 109, and the light intensity measured by the light intensity measuring device 110 and the branching ratio of the light branch 109 are passed to the object to be measured. The intensity of the irradiated light is measured.

  At this time, the light branch 109 only needs to have a constant light branch ratio in the light wavelength band of each light source to be used, and a mirror having a small refractive index dispersion in the light wavelength band of each light source can be used. The light intensity measuring device 110 also has a function of monitoring each light intensity of each of the light sources 101 to 106.

From the light intensity obtained by the light intensity measuring device 110, the irradiation time is calculated by the control computer 117 so that the preset time integrated light intensity W ₀ is obtained, and the light is irradiated for the calculated irradiation time. Further, the optical path opening / closing time of the ON / OFF switch 112 is controlled by using the integration driving circuit 111. Thereby, the integrated light is irradiated by the ON / OFF switch 112 that controls ON / OFF of the light output from the optical path switch 107 to the object to be measured, and the light having the preset time integrated light intensity W ₀ is obtained. Is irradiated to the object to be measured in the object cell 113.

  The sound wave generated by irradiating the object to be measured is detected by the sonic / electrical conversion element 114, amplified by the amplifier 115, and synchronized with the periodic signal supplied to the periodic drive circuit 108. 116 is selectively amplified.

  At this time, the sonic electric conversion element 114 may be a piezoelectric element using a dielectric crystal or the like, or a microphone using a magnet and a coil, and is a highly sensitive and broadband sonic electric conversion element capable of detecting photoacoustic waves as precisely as possible. Is desirable.

  By detecting a photoacoustic signal with respect to each time integrated light intensity W of each light source obtained as described above, and recording and analyzing it in the control computer 117, it is possible to measure the concentration of a specific component of the object to be measured.

(Second Embodiment)
FIG. 7 is a block diagram showing a configuration of a component concentration measuring apparatus according to the second embodiment of the present invention. In the block diagram, solid lines connecting the blocks indicate light irradiation, and double lines connecting the blocks indicate electrical signal connections.

In the component concentration measurement apparatus according to the second embodiment, first, a first LD (laser diode) 201 having a light wavelength λ _{A and} a second LD having a light wavelength λ _B , each having a different light wavelength, emit a 2 × 1 branch optical path. Optically connected to the changeover switch 203. At this time, the first LD 201 and the second LD 202 are preferably DFB-LD.

  The two first LD 201 and the second LD 202 may be replaced with one wavelength tunable laser to vary the optical wavelength. At this time, there are a method of changing the oscillation frequency by temperature adjustment, a method of using an external resonator, and the like. In addition, a gas laser or a solid-state laser can also be used, and a predetermined wavelength may be extracted using a dispersion element such as a prism or a diffraction grating.

  In addition, as an optical connection method of the second embodiment, a light beam may be directly propagated through the space in the atmosphere. However, in order to be affected by temperature and fluctuations in the atmosphere, light in the light wavelength band to be used is used. An optical connection using an optical fiber that can transmit stably with low loss and low dispersion is desirable.

  The first optical path switching switch 203 selects a light source that irradiates the object to be measured after the optical path is switched by the periodic drive circuit 204 in a preset periodic time, and is switched through the optical branch 205 and the second optical path switching switch 208. It is selectively connected to the optical path to the device cell 210 to be measured containing the object to be measured.

  A part of the light output from the first optical path switching switch 203 is branched to the light intensity measuring device 206 by the light branching 205, and the light intensity is measured from the light intensity measured by the light intensity measuring device 206 and the branching ratio of the light branching 205. The light intensity irradiated to the measurement object is measured.

  At this time, as the optical branching 205, an optical splitter using an optical waveguide or an optical fiber having a certain branching ratio in the optical wavelength band to be used can be used.

The irradiation time is calculated by the control computer 214 from the light intensity obtained by the light intensity measuring device 206 so as to be a preset time integrated light intensity W _0, and light is irradiated for the calculated irradiation time. In addition, the second optical path changeover switch 208 is controlled by the integration driving circuit 207. In order to prevent stray light, the optical terminator 209 is switched outside the irradiation time, so that the optical connection is switched between the optical terminator 209 and the measured object cell 210 by the second optical path switching switch 208.

As a result, the light output from the first optical path selector switch 203 is irradiated with integrated light by switching the second optical path selector switch 208, and light having a preset time integrated light intensity W ₀ is applied to the object cell 210 to be measured. Irradiate the measurement object with light.

At this time, the optical path change-over switches 203 and 208 are preferably high-speed, wide-band, and high extinction ratio optical switches. Thermo-optic effect switches using MEMS drive optical mirrors or Mach-Zehnder interferometers having an optical waveguide structure, InP optical switches A phase modulation optical switch such as a waveguide switch or a LiNbO ₃ optical waveguide, an optical waveguide surface acoustic wave (SAW) switch using a dielectric crystal, or the like can be used.

  The sound wave generated by irradiating the object to be measured is detected by the sonic electric conversion element 211, amplified by the amplifier 212, and supplied to the periodic drive circuit 204, as in the first embodiment. The signal is selectively amplified by the lock-in amplifier 213 by synchronizing with the periodic signal.

  By detecting the photoacoustic signal intensity with respect to each time integrated light intensity of each light source obtained as described above, and recording and analyzing it in the control computer, it is possible to measure the concentration of the specific component of the object to be measured.

  The component concentration analysis procedure according to the second embodiment will be described below with reference to FIG.

First, the light absorption coefficient change rate δWα of a specific component in the object to be measured with respect to the time-integrated light intensity change of the light wavelengths λ _A and λ _B having different light wavelengths is measured. First, in order to obtain the light absorption coefficient change rate δWα _A of the specific component in the measured object with respect to the time-integrated light intensity change of the light _A , prepare a standard sample whose concentration of the specific component and the light absorption coefficient of the solvent are known, Irradiate light A (step S101). The time integrated light intensity WA of the light _A is swept, and the time integrated light intensity dependency of the photoacoustic signal _SAG of the specific component of the light A is measured (step S102). The measurement result to calculate the optical absorption coefficient change rate Derutadaburyuarufa _A light A from the photoacoustic signal S _AG of the specific component of the light A from (step S103).

Subsequently, in order to obtain the light absorption coefficient change rate δWα _B of the specific component in the measured object with respect to the time-integrated light intensity change of the light _B , a standard sample whose concentration of the specific component and the light absorption coefficient of the solvent are known is prepared. The light B is irradiated (step S104). The time integrated light intensity WB of the light _B is swept, and the time integrated light intensity dependency of the photoacoustic signal _SBG of the specific component of the light B is measured (step S105). The measurement result to calculate the optical absorption coefficient change rate Derutadaburyuarufa _B light B from the photoacoustic signal S _BG of the specific component of the light B from (step S106).

  Subsequently, the process proceeds to measurement of an object to be measured. For example, using a component concentration measuring apparatus as shown in FIG. 7, the light to be measured is irradiated alternately with two light A and light B having a different π phase at the frequency f (step S107).

  At this time, since the frequency f is the frequency of the photoacoustic signal S, it is desirable that the frequency f be a frequency band that can be detected by the sonic electric transducer 211 such as a microphone or a piezoelectric element. Specifically, it is desirable that it is 20 KHz or less.

First, while adjusting one light B to have a constant time integrated light intensity W _B , the time integrated light intensity W _A of the other light _A is swept, and the time of the photoacoustic signal S _A of the object to be measured is swept. The integrated light intensity dependency is measured (step S108). From this measurement result, it is searching for a minimum value from time integration light intensity variation of the photoacoustic signal S _A, and obtains the time integrated light intensity W _A of the light A when the (step S109).

Subsequently, the measurement is returned to the initial state, and the two light A and the light B are combined and irradiated onto the object to be measured (step S110). The time-integrated light intensity of light _B is increased to W _B ′ = W _B + δW _B , and the time-integrated light intensity WA of light _A is swept while adjusting so as to obtain a constant light intensity. The dependence of the signal S _A 'on the time integrated light intensity is measured (step S111). From this measurement result, the minimum value is searched from the change in the time integrated light intensity of the photoacoustic signal S _A ′, and the time integrated light intensity W _A ′ = W _A + δW _A of the light _A is obtained at that time (step S112).

Finally, using the values of the parameters δWα _A , δWα _B , W _A , W _B , δW _A , and δW _B obtained in the previous measurement, the concentration of the specific component in the object to be measured is derived (step S112). ). From the above procedure, the concentration of the specific component in the object to be measured can be derived.

Further, an irradiation procedure for one cycle when the light A and B in steps S105 and S108 are set to specific time-integrated light intensities W _A and W _B will be described with reference to FIG.

First, a cycle time for alternately irradiating light A and light B is set (step S201), and a time integrated light intensity WA of the light _A and an intermittent time pattern are set (step S202). Next, time measurement of the light A is started (step S203), and the light A is irradiated to the object to be measured in accordance with the set time intermittent pattern (step S204). At this time, the time-intermittent pattern on the time axis may be equal intervals or unequal intervals, but unequal intervals are desirable because harmonics of sound waves are less likely to occur.

Thereafter, it is checked whether or not the time integrated light intensity WA of the light _A has reached a preset time integrated light intensity _WA0 (step S205), and if it has reached the set time integrated light intensity _WA0. If not, the irradiation of the light A in the set time intermittent pattern is continued.

If the time integrated light intensity WA of the light _A has reached the preset time integrated light intensity _WA0 , it is checked whether or not a predetermined period of time given to the light A has passed (step S206). If the predetermined cycle time has not been reached, the light B is not irradiated until the set cycle time (step S207). If the elapse of a predetermined period time, then proceeds to the irradiation of light B, to set the light B time integrated light intensity W _B and rest time pattern (step S208). Subsequently, time measurement of the light B is started (step S209), and the light B is irradiated to the object to be measured in accordance with the set time intermittent pattern (step S210). At this time, the time-intermittent pattern on the time axis may be equal intervals or unequal intervals, but unequal intervals are desirable because harmonics of sound waves are less likely to occur.

Then, time integrated light intensity W _B light B performs a check whether the reached accumulated light intensity W _B0 preset time (step S211), if not reach the time set integrated light intensity W _B0 If not, the irradiation of the light B in the set time intermittent pattern is continued.

If the time integrated light intensity W _B of the light B has reached a preset time integrated light intensity W _B0 , it is checked whether or not a predetermined period of time given to the light B has elapsed (step S212). If the predetermined cycle time has not been reached, the light A is not irradiated until the set cycle time (step S213), but if it has elapsed, the one cycle operation of the light irradiation is completed.

(Third embodiment)
FIG. 10 is a block diagram showing a configuration of a component concentration measuring apparatus according to the third embodiment of the present invention. In the block diagram, solid lines connecting the blocks indicate light irradiation, and double lines connecting the blocks indicate electrical signal connections.

  The basic component concentration measurement flow is the same as in the first and second embodiments. However, in the component concentration measurement apparatus according to the third embodiment, first, the first LD 301 and the second LD 302 having different light wavelengths are emitted. Are driven by the first LD driving circuit 303 and the second LD driving circuit 304, respectively. Further, the first LD 301 and the second LD 302 measure the light intensity in order to realize a stable light output, and the light intensity is corrected by the internal feedback circuit.

  At this time, the first LD 301 and the second LD 302, and the first LD driving circuit 303 and the second LD driving circuit 304 can output the light intensity values as electric signals. By using these light intensity values, the light of the light source A configuration for detecting branching and light intensity is not required. Therefore, it is possible to configure a component concentration measuring device with only one 2 × 2 light changeover switch 305.

  The light change-over switch 305 periodically switches between the first LD 301 and the second LD 302 based on the signal from the periodic drive circuit 308, and controls the light irradiation time by the integrating drive circuit 306 to enter the object to be measured. The measured object cell 309 is irradiated with light.

  As in the first and second embodiments, the sound wave generated by irradiating the object to be measured is detected by the sonic electric conversion element 310, amplified by the amplifier 311, and sent to the periodic drive circuit 308. The signal is selectively amplified by a lock-in amplifier 312 by synchronizing with a given periodic signal.

  It is possible to measure the concentration of the specific component of the object to be measured by detecting a photoacoustic signal for each time integrated light intensity of each light source obtained as described above, and recording and analyzing it in a control computer. .

101 to 106 Light source 107 Optical path switch 108, 204, 307 Periodic drive circuit 109, 205 Optical branch 110, 206 Light intensity measuring device 111, 207, 306 Accumulated drive circuit 112 ON / OFF switch 113, 210, 309 Device under test Cell 114, 211, 310 Sonic transducer 115, 212, 311 Amplifier 116, 213, 312 Lock-in amplifier 117, 214, 313 Control computer 201, 202, 301, 302 LD
203, 208, 305 Optical switch 209, 307 Optical terminator 303, 304 LD drive circuit

Claims (7)

A light source that emits a plurality of lights having different wavelengths;
Optical path switching means for switching the light sources of the first and second rectangular continuous waveforms having a phase different by π among the plurality of lights having different wavelengths;
Light intensity measuring means for measuring the light intensity of each of the first and second lights;
An opening / closing means for intermittently turning on / off the light irradiation of the first and second lights to control the irradiation time of the first and second lights;
Photoacoustic signal detection means for detecting a photoacoustic wave generated from the object to be measured by light irradiation of the first and second lights from the opening / closing means and outputting a photoacoustic signal intensity;
For the time integrated light intensity of the first and second lights calculated from the light intensity and the irradiation time, the time integrated light of one of the first and second lights is controlled by controlling the irradiation time. The time integrated light intensity and the time integrated light of each of the first and second lights when the other time integrated light intensity is changed so that the intensity is constant and the photoacoustic signal intensity becomes a minimum value. A concentration deriving means for deriving the concentration of the component to be measured included in the object to be measured based on the intensity change amount, the light absorption coefficient, and the light absorption coefficient change rate;
A component concentration measuring apparatus comprising: Further comprising an optical branching means installed between the optical path switching means and the opening and closing means,
2. The component concentration measuring apparatus according to claim 1, wherein the light intensity measuring unit measures the light intensity of the light branched by the light branching unit. A light source that emits a plurality of lights having different wavelengths;
The light sources of the first and second rectangular continuous waveforms having a phase different by π among the plurality of lights having different wavelengths are switched between the first and second optical paths, and the first light path to the first optical path is switched. An optical switch for controlling the irradiation time of the first and second lights;
Light intensity measuring means for measuring the light intensity of each of the first and second lights;
Photoacoustic signal detection means for detecting a photoacoustic wave generated from the object to be measured by light irradiation of the first and second lights from the first optical path of the optical switch and outputting a photoacoustic signal intensity;
For the time integrated light intensity of the first and second lights calculated from the light intensity and the irradiation time, the time integrated light of one of the first and second lights is controlled by controlling the irradiation time. The time integrated light intensity and the time integrated light of each of the first and second lights when the other time integrated light intensity is changed so that the intensity is constant and the photoacoustic signal intensity becomes a minimum value. A concentration deriving means for deriving the concentration of the component to be measured included in the object to be measured based on the intensity change amount, the light absorption coefficient, and the light absorption coefficient change rate;
A component concentration measuring apparatus comprising: The optical switch includes a first optical switch connected to the light source, and a second optical switch connected to the first and second optical paths,
An optical branching unit disposed between the first optical switch and the second optical switch;
4. The component concentration measuring apparatus according to claim 3, wherein the light intensity measuring unit measures the light intensity of the light branched by the light branching unit. Irradiating a plurality of lights having different wavelengths;
Among the plurality of lights having different wavelengths, the connection of the first and second light having a rectangular continuous waveform having a phase different by π is switched between the first and second optical paths, and the first to the first optical path is switched. And controlling the irradiation time of the second light,
Measuring the light intensity of each of the first and second lights;
Detecting a photoacoustic wave generated from the object to be measured by light irradiation of the first and second lights from the first optical path and outputting a photoacoustic signal intensity;
For the time integrated light intensity of the first and second lights calculated from the light intensity and the irradiation time, the time integrated light of one of the first and second lights is controlled by controlling the irradiation time. The time integrated light intensity and the time integrated light of each of the first and second lights when the other time integrated light intensity is changed so that the intensity is constant and the photoacoustic signal intensity becomes a minimum value. Deriving the concentration of the component to be measured included in the object to be measured based on the intensity change amount, the light absorption coefficient, and the light absorption coefficient change rate;
A component concentration measurement method comprising:   The step of deriving the concentration of the component to be measured uses the standard sample whose concentration of the component to be measured and the light absorption coefficient of the solvent are known to determine the rate of change of the light absorption coefficient of the first and second lights. The component concentration measuring method according to claim 5, further comprising a deriving step.   The step of deriving the concentration of the component to be measured adjusts the time integrated light intensity so that the photoacoustic signal intensity becomes a minimum value, and then increases or decreases the concentration of the component to be measured. 7. The component according to claim 5, further comprising a step of measuring a change amount of the time-integrated light intensity and a light absorption coefficient change rate at which the photoacoustic signal intensity becomes a minimum value after increase / decrease of the concentration of the component. Concentration measurement method.