Analysis device, program for analysis device, and analysis method

Abstract

The present invention provides an analysis device 100 that analyzes a measured component included in a sample, the analysis device correcting a change in the light absorption spectrum of a measured component, said change occurring due to a resonance effect caused by a resonant component or due to deviation in the wavelength of reference light, and highly precisely measuring the concentration of the measured component, wherein the analysis device 100 comprises: a light source 2 that emits reference light toward the sample; a light detector 3 that detects the intensity of sample light, which is produced upon the reference light having passed through the sample; parameter determination units 64, 66 that determine parameters representing changes in the light absorption spectrum of the measured component or an interference component, said changes occurring due to a resonance effect caused by a resonant component included in the sample or due to deviation in the wavelength of the reference light; and a concentration calculation unit 65 that uses the parameters representing the changes in the light absorption spectrum to calculate a corrected concentration of the measured component from an intensity-related signal related to the intensity of the sample light.

Description

Technical Field

[0001] The present invention relates to an analyzer or the like used for, for example, component analysis of gas and the like.

Background Art

[0002] Conventionally, as shown in Patent Document 1, there is an analysis method (TDLAS: Tunable Diode Laser Absorption Spectroscopy) in which the injection current of a semiconductor laser is modulated to sweep the oscillation wavelength, and the absorption spectrum of a gas to be measured is obtained to perform concentration quantification.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in absorption spectroscopy using a laser such as TDLAS, not only the influence of interfering components (interference influence) having an absorption spectrum overlapping with the light absorption spectrum of the component to be measured, but also the change in the concentration of co-existing components co-existing at a high concentration (about several % to several tens %) affects the shape and causes it to change (co-existing influence). Specifically, the width of the light absorption spectrum becomes wider and the absorption peak becomes lower (broadening). As a result, a measurement error occurs in the concentration of the component to be measured. When the component to be measured itself is at a high concentration, the component to be measured itself becomes a co-existing component, and a co-existing influence occurs due to the change in the concentration of the component to be measured itself (self-broadening). That is, a co-existing component is a component that gives a broadening effect to itself or other components. Also, in absorption spectroscopy using a laser such as TDLAS, a measurement error occurs in the concentration of the component to be measured due to the wavelength shift of the light emitted from the laser due to ambient temperature changes or the like. That is, in any case, the light absorption spectrum of the component to be measured has changed, and a measurement error has occurred in the concentration of the component to be measured.

[0005] The present invention has been made in view of the above-described problems, and in an analyzer using light absorption, it is a main object thereof to correct a change in the light absorption spectrum caused by co-existing influence due to co-existing components or wavelength shift, and accurately measure the concentration of the component to be measured.

[0006] As shown in Fig. 10(A), it is known that the light absorption spectrum broadened by the influence of co-existing components has a spectrum width that widens and the height of the absorption peak decreases according to the concentration of the co-existing components, but the overall area hardly changes. On the other hand, when the pressure fluctuates, as shown in Fig. 10(B), the width of the light absorption spectrum widens, but the height of the absorption peak hardly changes.

[0007] Therefore, the inventor of the present application focused on the differences and similarities in the changes in the light absorption spectrum due to co-existing influence and pressure fluctuation, and the broadening factor F indicating the change rate of the light absorption spectrum of the component to be measured caused by the co-existing components contained in the sample BWhen newly introduced and the absorbance signal at a certain pressure P is denoted as A(t, P), the broadening factor F due to coexistence effects B It has been found that the absorbance signal A'(t, P) when broadening of occurs is approximately expressed by the following equation.

[0008]

Equation

[0009] That is, the spectral change due to coexistence effects is almost the same as the spectral change when the pressure becomes F B times and the absorbance becomes 1 / F B times. The present invention is based on the basic concept of converting the broadening due to coexistence effects into a pressure change using this fact and performing coexistence effect correction simultaneously with pressure correction.

[0010] Also, since the light absorption spectrum changes due to a shift in the wavelength of the light source caused by a change in the ambient temperature or the like, it is necessary to detect and correct this change.

Means for Solving the Problem

[0011] That is, the analyzer according to the present invention is an analyzer for analyzing a measurement target component contained in a sample, and includes a light source that irradiates the sample with reference light, a photodetector that detects the intensity of sample light that has passed through the sample, a parameter determination unit that determines a parameter representing a change in the light absorption spectrum of the measurement target component or interference component caused by a coexisting component contained in the sample or a wavelength shift of the reference light, and a concentration calculation unit that calculates the concentration of the measurement target component corrected using the parameter representing the change in the light absorption spectrum from an intensity-related signal related to the intensity of the sample light.

[0012] With such a configuration, the concentration of the component to be measured is calculated using a parameter that represents the change in the light absorption spectrum of the component to be measured or the interference component caused by the coexisting components contained in the sample or the wavelength shift of the reference light. Therefore, it is possible to correct the coexistence influence caused by the coexisting components or the change in the light absorption spectrum caused by the wavelength shift, and accurately measure the concentration of the component to be measured.

[0013] Examples of the parameter representing the change in the light absorption spectrum include a broadening factor indicating the change rate of the light absorption spectrum of the component to be measured or the interference component caused by the coexisting components contained in the sample, or the amount of wavelength shift of the reference light.

[0014] Thereby, the concentration calculation unit calculates the concentration of the component to be measured with the coexistence influence caused by the coexisting components or the wavelength shift of the reference light corrected, using the intensity-related signal related to the intensity of the sample light and the broadening factor or the amount of wavelength shift.

[0015] The parameter determination unit may determine the broadening factor by fitting reference data related to the light absorption signals of the component to be measured and the interference component with a known broadening factor or pressure, and sample data related to the light absorption signal obtained from the intensity of the sample light. Here, fitting means comparing and collating the reference data and the sample data. In addition, when comparing and collating, the reference data is converted and used using the pressure value of the sample and the relationship of the above-described formula (Equation 1). Specific examples of the method of comparison and collation include, for example, a non-linear least squares method involving iterative calculations using the steepest descent method, the Gauss-Newton method, the Levenberg-Marquardt method, and the like.

[0016] Further, the parameter determination unit may determine the broadening factor using relationship data indicating the relationship between the concentration of the coexisting component and the broadening factor and the measured concentration of the coexisting component.

[0017] The parameter determination unit may determine the wavelength shift amount by fitting reference data related to the optical absorption signals of the component to be measured and the interference component, whose wavelength shift amounts are known, and sample data related to the optical absorption signal obtained from the intensity of the sample light.

[0018] Also, the parameter determination unit may determine the wavelength shift amount of the reference light by using relationship data indicating the relationship between the ambient temperature and the wavelength shift amount and the measured ambient temperature.

[0019] The analyzer further includes a correlation value calculation unit that calculates a correlation value between an intensity-related signal related to the intensity of the sample light and a predetermined characteristic signal. The concentration calculation unit preferably calculates the concentration of the component to be measured with the coexistence influence by the coexisting component or the wavelength shift of the reference light corrected by using the correlation value and a parameter representing a change in the optical absorption spectrum of the component to be measured or the interference component. With this configuration, the correlation value between the intensity-related signal related to the intensity of the sample light and the characteristic signal is calculated, and the concentration of the component to be measured is calculated using the calculated correlation value. Therefore, without converting the absorption signal into an absorption spectrum, the characteristics of the absorption signal can be captured with a dramatically small number of variables, and the concentration of the component to be measured can be measured by a simple calculation without performing complex spectral calculation processing. For example, hundreds of data points are required for general spectral fitting, but in the present invention, the concentration can be calculated with the same accuracy using at most several to several tens of correlation values. As a result, the load of the calculation processing can be dramatically reduced, an advanced calculation processing device is not required, the cost of the analyzer can be reduced, and miniaturization is possible.

[0020] The analyzer of the present invention is an analyzer for analyzing a component to be measured in a sample containing interference components from which one or more interference effects should be removed. The correlation value calculation unit calculates a plurality of correlation values using a number of characteristic signals equal to or greater than the sum of the number of types of the component to be measured and the number of types of the interference components. The concentration calculation unit preferably calculates the concentration of the component to be measured using the plurality of correlation values and a parameter representing a change in the light absorption spectrum of the component to be measured or the interference component.

[0021] The analyzer of the present invention further includes a storage unit that stores single correlation values, which are correlation values per unit concentration of the component to be measured and each interference component, obtained from the intensity-related signals of the component to be measured and each interference component when they exist alone and the plurality of characteristic signals. The concentration calculation unit preferably calculates the concentration of the component to be measured using the plurality of correlation values obtained by the correlation value calculation unit, the plurality of single correlation values, and a parameter representing a change in the light absorption spectrum of the component to be measured or the interference component.

[0022] Specifically, it is desirable that the concentration calculation unit corrects the plurality of single correlation values using a parameter representing a change in the light absorption spectrum of the component to be measured or the interference component, and calculates the concentration of the component to be measured using the corrected plurality of single correlation values and the plurality of correlation values obtained by the correlation value calculation unit. With this configuration, the concentration of the component to be measured from which the interference effect, the coexistence effect due to coexisting components, or the effect of the wavelength shift of the reference light has been removed can be determined by a simple and reliable calculation of solving at most several to several tens of simultaneous equations with the original number.

[0023] More specifically, it is desirable that the concentration calculation unit calculates the concentration of the component to be measured by solving a system of simultaneous equations including the plurality of correlation values obtained by the correlation value calculation unit, the corrected plurality of single correlation values, and the concentrations of the component to be measured and each interference component.

[0024] Here, in order to correct the single correlation value, it is desirable to previously store in the storage unit the single correlation values of each component obtained at a plurality of known pressures or wavelength shifts of the reference light. By doing so, the single correlation value can be corrected using the broadening factor or the wavelength shift amount determined by the parameter determination unit. Note that the single correlation value previously stored in the storage unit may be the one obtained at a known broadening factor instead of the one obtained at a known pressure. However, since it is not easy to create the state of a known broadening factor, it is more desirable to use the single correlation value obtained at a known pressure.

[0025] Also, when the pressure of the sample fluctuates during measurement, it is desirable to monitor the pressure of the sample with a pressure sensor or the like and use the pressure value to correct the single correlation value. By doing so, the coexistence influence by the coexisting components and the influence by the pressure fluctuation can be corrected simultaneously.

[0026] At this time, the concentration calculation unit can correct the single correlation value using the relationship of the following formula (Equation 2) with the single correlation value of each component obtained for each of the plurality of known pressures of the sample, the plurality of correlation values obtained by the correlation value calculation unit, the pressure value in the cell, and

[0027]

Equation

[0028] Here, p is the pressure of the sample measured by the pressure sensor, F B is the broadening factor determined by the broadening factor determination unit, s ij is the single correlation value at each pressure stored in the storage unit, and s′ ij is the corrected single correlation value. Note that the above formula (Equation 2) is for the single correlation value s ij (p) at the pressure p of the sample during sample measurement, and the single correlation value at the pressure multiplied by the pressure by F B times is 1 / F BBy multiplying, the corrected single correlation value s′ ij is shown to be obtained. In addition, when the interference component is also affected by broadening due to the coexisting component, the broadening factor of the interference component may be separately determined to correct the single correlation value of the interference component. Thereby, the measurement accuracy can be further improved.

[0029] The program for an analyzer according to the present invention is a program applied to an analyzer including a light source that irradiates a sample with reference light and a photodetector that detects sample light transmitted through the sample, and is a parameter for determining a parameter representing a change in the light absorption spectrum of the measurement target component or the interference component caused by a coexisting component contained in the sample or a wavelength shift of the reference light. A parameter determination unit, and a concentration calculation unit that calculates the concentration of the measurement target component corrected using the parameter representing the change in the light absorption spectrum from an intensity-related signal related to the intensity of the sample light, and causes the analyzer to exhibit a function as such. It is characterized by that.

[0030] Furthermore, the analysis method according to the present invention is an analysis method for analyzing a measurement target component contained in a sample using a light source that irradiates the sample with reference light and a photodetector that detects sample light transmitted through the sample, and is a coexisting component contained in the sample, or A parameter representing a change in the light absorption spectrum of the measurement target component or the interference component caused by a wavelength shift of the reference light is determined, and the concentration of the measurement target component corrected using the parameter representing the change in the light absorption spectrum is calculated from an intensity-related signal related to the intensity of the sample light. It is characterized by that.

Advantages of the Invention

[0031] According to the present invention described above, in an analyzer using light absorption, the change in the light absorption spectrum caused by the coexistence effect of the coexisting component or the wavelength shift of the reference light can be corrected, and the concentration of the measurement target component can be accurately measured.

Brief Description of the Drawings

[0032]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Explanation of Reference Numerals

[0033] 100 ··· Analyzer 1 ··· Cell 2 ··· Light source (semiconductor laser) 3 ··· Photodetector 4 ··· Signal processing device 61 ··· Logarithmic operation unit 62 ··· Correlation value calculation unit 63 ··· Storage unit 64 ··· Broadening factor determination unit 65 ··· Concentration calculation unit 66 ··· Wavelength shift determination unit 7 ··· Pressure sensor

Embodiments for Carrying Out the Invention

[0034] <First Embodiment (Coexistence Influence Correction Function)> The analyzer 100 of this embodiment is a concentration measurement device that measures the concentration of a measurement target component (here, for example, CO, CO2, etc.) contained in a sample gas such as exhaust gas. As shown in FIG. 1, it includes a cell 1 into which the sample gas is introduced, a semiconductor laser 2 as a light source that irradiates the cell 1 with modulated laser light, a photodetector 3 provided on the optical path of the sample light, which is the laser light transmitted through the cell 1, for receiving the sample light, a signal processing device 4 that receives the output signal of the photodetector 3 and calculates the concentration of the measurement target component based on the value, and a pressure sensor 7 that monitors the pressure inside the cell 1.

[0035] Note that an introduction flow path for introducing sampling gas into the analyzer 100 is connected to the analyzer 100 of this embodiment, and an exhaust flow path through which the gas analyzed by the analyzer 100 is discharged is also connected. A pump for introducing sampling gas into the analyzer 100 is provided in the introduction flow path or the exhaust flow path. Further, the introduction flow path may be configured to directly sample exhaust gas from an exhaust pipe or the like, may be configured to introduce exhaust gas from a bag in which the exhaust gas is collected, or may be configured to introduce exhaust gas diluted by a dilution device such as a CVS (Constant Volume Sampler).

[0036] Each part will be described. The cell 1 is made of a transparent material such as quartz, calcium fluoride, or barium fluoride that has almost no light absorption in the absorption wavelength band of the measurement target component, and has an optical inlet and an optical outlet formed therein. Although not shown, the cell 1 is provided with an inlet port for introducing gas into the interior and an outlet port for discharging the internal gas, and the sample gas is introduced into the cell 1 through this inlet port and sealed.

[0037] The semiconductor laser 2 is here a quantum cascade laser (QCL), which is a type of semiconductor laser 2, and emits mid-infrared (4 - 12 μm) laser light. This semiconductor laser 2 can modulate (change) the oscillation wavelength by a given current (or voltage). Note that as long as the oscillation wavelength is variable, other types of lasers can be used, and the temperature can be changed etc. to change the oscillation wavelength.

[0038] The photodetector 3 uses a thermal type such as a relatively inexpensive thermopile here, but other types, for example, quantum type photoelectric elements such as HgCdTe, InGaAs, InAsSb, PbSe with good responsiveness can also be used.

[0039] The signal processing device 4 includes an analog electric circuit composed of a buffer, an amplifier, etc., a digital electric circuit composed of a CPU, a memory, etc., and an AD converter, a DA converter, etc. that mediate between these analog / digital electric circuits. According to a predetermined program stored in a predetermined area of the memory, the CPU and its peripheral devices cooperate to function as a light source control unit 5 that controls the output of the semiconductor laser 2 as shown in Figure 2, and a signal processing unit 6 that receives the output signal from the photodetector 3, performs arithmetic processing on its value, and calculates the concentration of the component to be measured.

[0040] The pressure sensor 7 monitors the pressure of the sample. Here, it measures the absolute pressure inside the cell 1, and a silicon piezoresistive absolute pressure sensor is used here. Although not shown in the figure, the pressure inside the cell during measurement is adjusted to be about 20 - 30 kPa using a pump and a pressure regulator.

[0041] Each part will be described in detail below. The light source control unit 5 controls the current source (or voltage source) of the semiconductor laser 2 by outputting a current (or voltage) control signal. Specifically, the light source control unit 5 changes the drive current (or drive voltage) of the semiconductor laser 2 at a predetermined frequency, and modulates the oscillation wavelength of the laser light output from the semiconductor laser 2 at a predetermined frequency with respect to the center wavelength. As a result, the semiconductor laser 2 emits modulated light modulated at a predetermined modulation frequency.

[0042] In this embodiment, the light source control unit 5 changes the drive current in a triangular wave shape and modulates the oscillation frequency in a triangular wave shape (see "oscillation wavelength" in FIG. 4). Actually, the modulation of the drive current is performed by another function so that the oscillation frequency becomes triangular. Further, as shown in FIG. 3, the oscillation wavelength of the laser light is modulated with the peak of the light absorption spectrum of the component to be measured as the center wavelength. In addition, the light source control unit 5 may change the drive current in a sine wave shape, a sawtooth wave shape, or an arbitrary function shape, and modulate the oscillation frequency in a sine wave shape, a sawtooth wave shape, or an arbitrary function shape.

[0043] The signal processing unit 6 includes a logarithmic operation unit 61, a correlation value calculation unit 62, a storage unit 63, a broadening factor determination unit 64 which is a parameter determination unit, a concentration calculation unit 65, and the like.

[0044] The logarithmic operation unit 61 performs a logarithmic operation on the light intensity signal which is the output signal of the photodetector 3. The function I(t) indicating the temporal change of the light intensity signal obtained by the photodetector 3 is as shown in "light intensity I(t)" in FIG. 4, and by performing a logarithmic operation, it becomes as shown in "logarithmic intensity L(t)" in FIG. 4.

[0045] The correlation value calculation unit 62 calculates the respective correlation values between the intensity-related signal related to the intensity of the sample light and a plurality of predetermined characteristic signals. The characteristic signal is a signal for extracting the waveform characteristics of the intensity-related signal by taking the correlation with the intensity-related signal. As the characteristic signal, for example, a sine wave signal or various signals adapted to the waveform characteristics to be extracted from other intensity-related signals can be used.

[0046] Hereinafter, an example in the case of using a signal other than a sine wave signal as the characteristic signal will be described. The correlation value calculation unit 62 calculates the respective correlation values between the intensity-related signal related to the intensity of the sample light and a plurality of characteristic signals that have a correlation different from that of a sine wave signal (sine function) with respect to the intensity-related signal. Here, the correlation value calculation unit 62 uses the logarithmically calculated optical intensity signal (logarithmic intensity L(t)) as the intensity-related signal.

[0047] Further, the correlation value calculation unit 62 uses a number of characteristic signals F i (t) (i = 1, 2, ···, n) that is equal to or more than the total number of types of components to be measured and the number of types of interference components to be removed, and according to the following formula (Equation 3), a plurality of sample correlation values S i that are the respective correlation values between the intensity-related signal of the sample light and the plurality of characteristic signals are calculated. Note that T in the following formula (Equation 3) is the modulation period.

[0048]

Equation

[0049] When calculating the sample correlation value, the correlation value calculation unit 62, as in formula (Equation 3), subtracts the reference correlation value R i which is the correlation value between the intensity-related signal L0(t) of the reference light and the plurality of characteristic signals F i from the correlation value S i which is the correlation value between the intensity-related signal L(t) of the sample light and the plurality of characteristic signals F i to correct and calculate the sample correlation value S′ i This can remove the offset included in the sample correlation value, resulting in a correlation value proportional to the concentrations of the component to be measured and the interference component, and can reduce the measurement error. Note that a configuration that does not subtract the reference correlation value may also be used.

[0050] Here, the acquisition timing of the reference light is the same as that of the sample light, before and after the measurement, or at any timing. The intensity-related signal or reference correlation value of the reference light may be acquired in advance and stored in the storage unit 63. Further, as a method of simultaneously acquiring the reference light, for example, two photodetectors 3 are provided, and the modulated light from the semiconductor laser 2 is branched by a beam splitter or the like, and one is used for sample light measurement and the other is used for reference light measurement.

[0051] In the present embodiment, the correlation value calculation unit 62 uses, as a plurality of characteristic signals F i (t), a function that can more easily capture the waveform characteristics of the logarithmic intensity L(t) than the sine function. When it is desired to correct the coexistence influence by the coexisting component of the measurement target component in the sample gas including the measurement target component and one interference component, it is conceivable to use three characteristic signals F1(t), F2(t), and F3(t). As these three characteristic signals, for example, a function based on a Lorentz function close to the form of the absorption spectrum shown in the following formula (Equation 4) and a partial derivative function regarding the Lorentz width of the function based on the Lorentz function are considered. Note that w in the formula (Equation 4) is the Lorentz width, s is the deviation from the reference time position of the absorption peak due to the wavelength shift, A is an arbitrary constant, and A1, A2, and A3 are offsets adjusted so as to be zero when integrating F1(t), F2(t), and F3(t) over the modulation period. By using such a function as the characteristic signal, the spectral change due to the coexistence influence can be captured more sensitively, and the coexistence influence correction can be performed more accurately. Further, as the characteristic signal, instead of the function based on the Lorentz function, a function based on a Voigt function, a function based on a Gaussian function, or the like can also be used. By using such a function as the characteristic signal, a larger correlation value can be obtained than when using the sine function, and the measurement accuracy can be improved.

[0052]

Equation

[0053] Here, it is desirable to adjust the offset of the characteristic signal so that the direct current component is removed, that is, it becomes zero when integrated over the modulation period. By doing so, it is possible to remove the influence when an offset is superimposed on the intensity-related signal due to fluctuations in the light intensity. Note that instead of removing the direct current component of the characteristic signal, the direct current component of the intensity-related signal may be removed, or the direct current components of both the characteristic signal and the intensity-related signal may be removed. In addition, as the characteristic signal, the actually measured value of the absorption signal of the component to be measured and / or the interference component, or something simulating them may be used respectively.

[0054] Note that by using three characteristic signals F1(t), F2(t), and F3(t) as an orthogonal function sequence orthogonal to each other or a function sequence close to an orthogonal function sequence, the characteristics of the logarithmic intensity L(t) can be extracted more efficiently, and the concentration obtained by the simultaneous equations described later can be made more accurate.

[0055] The storage unit 63 stores the single correlation value, which is the correlation value per unit concentration of the component to be measured and each interference component obtained from the respective intensity-related signals when the component to be measured and each interference component exist alone at the pressure in a known cell and the plurality of characteristic signals F i (t). The plurality of characteristic signals F i (t) used to obtain this single correlation value is the same as the plurality of characteristic signals F i (t) used in the correlation value calculation unit 62. In this way, the storage unit 63 stores the single correlation values for each pressure in various cells.

[0056] Here, when storing the single correlation value, it is desirable for the storage unit 63 to store the single correlation value obtained by subtracting the reference correlation value from the correlation value when the component to be measured and each interference component exist alone and then performing correction to convert it per unit concentration. Thereby, the offset included in the single correlation value is removed, and the correlation value is proportional to the concentrations of the component to be measured and the interference component, and the measurement error can be reduced. Note that a configuration in which the reference correlation value is not subtracted may also be used.

[0057] The broadening factor 64 indicates the broadening factor F of the change rate of the light absorption spectra of the component to be measured and the interference component caused by the coexisting components contained in the sample. B When the coexistence effect of the coexisting components on the interference component should also be considered, the broadening factor F B is added and determined for each component.

[0058] As a method for determining the broadening factor F B , for example, the following procedures (a) or (b) can be considered.

[0059] (a) For each pressure p k (k = 1, 2, ···, l) in the cell, each individual correlation value s i corresponding to each characteristic signal F itar (t) of the component to be measured and the interference component is obtained in advance, and the sample correlation value obtained during measurement is compared and collated with the individual correlation value to determine the broadening factor F k . When comparing and collating, the individual correlation value is converted and used by using the pressure value in the cell and the relationship of the above formula (Equation 2). In the case of this method, the number of necessary characteristic signals is equal to or more than the sum of the number of types of components to be measured, the number of types of interference components, and the number of types of broadening factors. iint (p k ) to determine the broadening factor F B . When comparing and collating, the individual correlation value is converted and used by using the pressure value in the cell and the relationship of the above formula (Equation 2). In the case of this method, the number of necessary characteristic signals is equal to or more than the sum of the number of types of components to be measured, the number of types of interference components, and the number of types of broadening factors.

[0060] (b) Using the relationship data showing the relationship between the concentration of the coexisting component and the broadening factor F B and the measured concentration of the coexisting component, the broadening factor F B is determined. At this time, the relationship data is generated in advance by obtaining the broadening factor F B for each concentration of the coexisting component by experiment or calculation. The measured concentration of the coexisting component may be measured by the analyzer 100 of the present embodiment before coexistence effect correction, or may be measured using another analyzer.

[0061] The concentration calculation unit 65 calculates the concentration of the component to be measured using a plurality of sample correlation values obtained by the correlation value calculation unit 62.

[0062] Specifically, the concentration calculation unit 65 calculates the concentration of the component to be measured based on a plurality of sample correlation values obtained by the correlation value calculation unit 62, a broadening factor F determined by the broadening factor determination unit 64, B and a plurality of individual correlation values stored in the storage unit 63. More specifically, the concentration calculation unit 65 corrects and obtains a plurality of individual correlation values stored in the storage unit 63 from the broadening factor F B determined by the broadening factor determination unit 64. Then, the concentration calculation unit 65 solves a system of simultaneous equations consisting of a plurality of sample correlation values obtained by the correlation value calculation unit 62, a plurality of corrected individual correlation values corresponding to the determined broadening factor F B and the concentrations of the component to be measured and each interfering component, thereby calculating the concentration of the component to be measured.

[0063] Next, an example of the operation of this analyzer 100 will be described while also providing a detailed explanation of each part. Hereinafter, it is assumed that the sample gas contains one component to be measured and one interfering component.

[0064] <Reference measurement> First, the light source control unit 5 controls the semiconductor laser 2 to modulate the wavelength of the laser light at a predetermined modulation frequency and modulation depth and centered on the peak of the absorption spectrum of the component to be measured. Note that before the reference measurement using the span gas, a reference measurement using the zero gas may be performed to measure the reference correlation value.

[0065] Next, the span gas (a gas with a known component concentration) is introduced into the cell 1 by the operator or automatically, and the reference measurement is performed. This reference measurement is performed for each of the span gas in which the component to be measured exists alone and the span gas in which the interfering component exists alone.

[0066] Specifically, in the reference measurement, the logarithmic operation unit 61 receives each output signal of the photodetector 3 at the pressure in each cell and calculates the logarithmic intensity L(t). Then, the correlation value calculation unit 62 calculates the correlation values between the logarithmic intensity L(t) and the three characteristic signals F1(t), F2(t), and F3(t), and divides the result obtained by subtracting the reference correlation value from the correlation values by the concentration of the span gas to calculate the individual correlation values, which are the correlation values of each span gas per unit concentration. Instead of calculating the individual correlation values per unit concentration, the span gas concentration and the individual correlation values of the span gas may be stored.

[0067] Specifically, it is as follows. Adjust the pressure in the cell to p k and introduce the span gas in which the component to be measured exists alone into cell 1, whereby the correlation value calculation unit 62 calculates the correlation values S 1tar (p k ), S 2tar (p k ), S 3tar (p k ). Here, S 1tar (p k ) is the correlation value with the first characteristic signal, S 2tar (p k ) is the correlation value with the second characteristic signal, and S 3tar (p k ) is the correlation value with the third characteristic signal. Then, the correlation value calculation unit 62 subtracts the reference correlation value R i from those correlation values S 1tar (p k ), S 2tar (p k ), S 3tar (p k ) and divides the result by the span gas concentration c i of the component to be measured to obtain the individual correlation values s tar (p 1tar ), s k (p 2tar ), s k ), s 3tar (p kCalculate it. By means such as adjusting a pressure regulator that adjusts the pressure in the cell, while sequentially changing the pressure in the cell (for example, from 20 to 40 kPa at intervals of 1 kPa), perform this at each pressure, and store the relationship between the individual correlation value at each obtained pressure and that pressure. Note that the span gas concentration c of the component to be measured tar is input to the signal processing unit 6 in advance by the user or the like.

[0068] Also, introduce a span gas in which the interference component exists alone into the cell 1 whose pressure value in the cell is adjusted to p k so that the correlation value calculation unit 62 calculates the correlation values S 1int (p k ), S 2int (p k ), S 3int (p k ). Here, S 1int (p k ) is the correlation value with the first characteristic signal, S 2int (p k ) is the correlation value with the second characteristic signal, and S 3int (p k ) is the correlation value with the third characteristic signal. Then, the correlation value calculation unit 62 subtracts the reference correlation value R 1int (p k ) from those correlation values S 2int (p k ), S 3int (p k ), S i and divides the result by the span gas concentration c int of the interference component to calculate the individual correlation values s 1int (p k ), s 2int (p k ), s 3int (p k ). By performing this procedure while sequentially changing the pressure in the cell (for example, from 20 to 40 kPa at intervals of 1 kPa), perform this at each pressure, and store the relationship between the individual correlation value at each obtained pressure and that pressure. Note that the span gas concentration c of the interference component int is input to the signal processing unit 6 in advance by the user or the like.

[0069] The pressure p in each cell calculated as described above k The single correlation value s 1tar (p k ), s 2tar (p k ), s 3tar (p k ), s 1int (p k ), s 2int (p k ), s 3int (p k ) are stored in the storage unit 63. Note that this reference measurement may be performed before product shipment or may be performed periodically.

[0070] <Sample measurement> The light source control unit 5 controls the semiconductor laser 2 and modulates the wavelength of the laser light at a predetermined modulation frequency and modulation depth around the peak of the absorption spectrum of the component to be measured.

[0071] Next, a sample gas is introduced into the cell 1 by the operator or automatically, and a sample measurement is performed.

[0072] Specifically, in the sample measurement, the logarithmic operation unit 61 receives the output signal of the photodetector 3 and calculates the logarithmic intensity L(t). Then, the correlation value calculation unit 62 calculates the sample correlation values S1, S2, S3 between the logarithmic intensity L(t) and the plurality of characteristic signals F1(t), F2(t), F3(t), and calculates the sample correlation values S'1, S'2, S'3 obtained by subtracting the reference correlation value R i from the correlation values.

[0073] Also, the broadening factor determination unit 64 determines the broadening factor F B by the method (a) or (b) described above.

[0074] The concentration calculation unit 65 calculates the single correlation value of the pressure p in each cell stored in the storage unit 63 k with the pressure value p in the cell measured by the pressure sensor 7 and the broadening factor F determined by the broadening factor determination unit 64B Using the above formula (Equation 2), the single correlation value s′ of the component to be measured corrected by both the pressure in the cell and the broadening factor 1tar , s′ 2tar and the single correlation value s′ of the interference component corrected only by the pressure in the cell (the broadening factor is set to 1) 1int , s′ 2int are determined. As a method of determination, for example, methods using linear interpolation, quadratic interpolation, spline interpolation, etc. can be considered.

[0075] Then, the concentration calculation unit 65 corrects the sample correlation values S′1, S′ calculated by the correlation value calculation unit 62 with the reference correlation value 2、 and the corrected single correlation value s′ 1tar , s′ 2tar , s′ 1int , s′ 2int and the concentrations C tar , C int of the component to be measured and the interference component respectively, and solves the following system of binary simultaneous equations (see Fig. 5).

[0076]

Equation

[0077] Thus, by a simple and reliable operation of solving the system of equations of the above formula (Equation 5), the concentration C of the component to be measured from which the interference effect and the coexistence effect are removed tar can be determined.

[0078] Even when it is assumed that there are two or more interference components from which the interference effect should be removed, by adding the single correlation values by the number of interference components and solving a system of simultaneous equations with the same number of equations as the number of component species, the concentration of the component to be measured from which the interference effect and the coexistence effect are removed can be similarly determined.

[0079] That is, generally, when there are n types of gases including the component to be measured and the interference components, the corrected single correlation value of the j-th gas species in the i-th characteristic signal is s′ ij , and the concentration of the j-th gas species is C j, the i-th characteristic signal F i The sample correlation value in (t) is S i Then, the following equation (Equation 6) holds.

[0080]

Equation

[0081] By solving the n - variable simultaneous equations represented by this Equation (Equation 6), it is possible to determine the concentrations in which the interference effects and co - existence effects of each gas of the component to be measured and the interference component are corrected. Even when the sample does not contain an interference component, by solving the above n - variable simultaneous equations, it is possible to determine the concentrations in which the co - existence effects of each gas of the component to be measured and the co - existing component are corrected.

[0082] According to the analyzer 100 of the present embodiment configured as described above, the broadening factor F B indicating the change rate of the light absorption spectrum of the component to be measured caused by the co - existing component is determined, and using the determined broadening factor F B the concentration of the component to be measured with the co - existence effect by the co - existing component corrected is calculated. Thus, the change in the light absorption spectrum of the component to be measured caused by the co - existence effect by the co - existing component is corrected, and the concentration of the component to be measured can be accurately measured.

[0083] Also, according to the analyzer 100 of the present embodiment, the logarithmic intensity L(t), which is an intensity - related signal related to the intensity of the sample light, and a plurality of characteristic signals F i (t) are calculated for each correlation value S i between them, and the plurality of calculated correlation values S iSince the concentration of the component to be measured is calculated using [it], the characteristics of the absorption signal can be captured with a dramatically smaller number of variables without converting the absorption signal into an absorption spectrum, and the concentration of the component to be measured can be measured by a simple calculation without performing complex spectral arithmetic processing. For example, hundreds of data points are required for general spectral fitting, but in the present invention, the concentration can be calculated with the same accuracy using at most several to several tens of correlation values. As a result, the load of arithmetic processing can be dramatically reduced, an advanced arithmetic processing device is not required, the cost of the analyzer 100 can be reduced, and miniaturization is possible. Here, since a plurality of characteristic signals use signals having a correlation different from that of a sine wave signal, the concentration of the component to be measured can be obtained with the same or higher accuracy as that of an analyzer that performs concentration calculation by a conventional method using lock-in detection.

[0084] <Second Embodiment (Wavelength Shift Correction Function)> The analyzer 100 of the present embodiment is a concentration measuring device that measures the concentration of a component to be measured (here, for example, CO, CO2, etc.) contained in a sample gas such as exhaust gas. As shown in FIG. 6, a cell 1 into which the sample gas is introduced, a semiconductor laser 2 as a light source that irradiates the cell 1 with modulated laser light, and a sample light that is laser light transmitted through the cell 1. It includes a photodetector 3 that is provided on the optical path of the sample light and receives the sample light, and a signal processing device 4 that receives the output signal of the photodetector 3 and calculates the concentration of the component to be measured based on the value. In the second embodiment, the functions of the components denoted by the same reference numerals as those in the first embodiment are basically the same as those in the first embodiment, and the description thereof is omitted. In the following, differences from the first embodiment will be described.

[0085] As shown in FIG. 7, the signal processing unit 6 includes a logarithmic operation unit 61, a correlation value calculation unit 62, a storage unit 63, a concentration calculation unit 65, a wavelength shift detection unit 66 that is a parameter determination unit, and the like.

[0086] In the present embodiment, the correlation value calculation unit 62 has a plurality of characteristic signals F iAs (t), a function that can more easily capture the waveform characteristics of the logarithmic intensity L(t) than the sine function is used. When it is desired to correct the influence of the wavelength shift of the reference light in a sample gas containing the component to be measured and one interference component, it is conceivable to use three characteristic signals F1(t), F2(t), and F3(t). As these three characteristic signals, for example, a function based on a Lorentz function similar to the shape of the absorption spectrum shown in the following formula (Equation 7) and a partial derivative function of the deviation from the reference time position of the function based on the Lorentz function can be considered. In Equation (Equation 7), w is the Lorentz width, s is the deviation from the reference time position of the absorption peak due to the wavelength shift, A is an arbitrary constant, and A1, A2, and A3 are offsets adjusted so as to become zero when integrated over the modulation period of F1(t), F2(t), and F3(t), respectively. When such a function is used as the characteristic signal, spectral changes due to the influence of the wavelength shift of the reference light can be captured more sensitively, and the correction of the influence of the wavelength shift of the reference light can be performed more accurately. Also, as the characteristic signal, instead of the function based on the Lorentz function, a function based on a Voigt function, a function based on a Gaussian function, or the like can also be used. By using such a function as the characteristic signal, a larger correlation value can be obtained than when using the sine function, and the measurement accuracy can be improved.

[0087]

Equation

[0088] The storage unit 63 stores each intensity-related signal when the component to be measured and each interference component exist alone at the wavelength shift amount of the known reference light, and the single-correlation value that is the correlation value per unit concentration of each of the component to be measured and each interference component obtained from the plurality of characteristic signals F i (t). The plurality of characteristic signals F i (t) used to obtain this single-correlation value is the same as the plurality of characteristic signals F i (t) used by the correlation value calculation unit 62. In this way, the storage unit 63 stores the single-correlation values for each wavelength shift of various reference lights.

[0089] Here, when the storage unit 63 stores the single correlation value, it is desirable to store the single correlation value that has been corrected to be per unit concentration after subtracting the reference correlation value from the correlation value when the component to be measured and each interference component exist alone. This removes the offset included in the single correlation value, resulting in a correlation value proportional to the concentrations of the component to be measured and the interference components, and can reduce the measurement error. Note that a configuration that does not subtract the reference correlation value may also be used.

[0090] The wavelength shift determination unit 66 determines the wavelength shift amount W of the reference light from the light intensity signal that is the output signal of the photodetector 3.

[0091] As a method for determining the wavelength shift amount W, for example, the following procedures (a) or (b) can be considered.

[0092] (a) For each wavelength shift W k (k = 1, 2, ···, l) of the reference lights, each characteristic signal F i (t) of the component to be measured and the interference components, the corresponding single correlation values s itar (W k ) and s iint (W k ) are acquired in advance, and the sample correlation value obtained during measurement is compared and collated with the single correlation value to determine the wavelength shift W of the reference light. In the case of this method, the number of necessary characteristic signals is equal to or more than the number obtained by adding 1 to the sum of the number of types of the component to be measured and the number of types of the interference components. The reason for adding 1 is to correspond to the wavelength shift amount, which is a parameter common to the light absorption spectra of each component.

[0093] (b) Using the relationship data indicating the relationship between the ambient temperature and the wavelength shift amount W and the measured ambient temperature, the wavelength shift amount W of the reference light is determined. At this time, the relationship data is generated in advance by experimentally or computationally obtaining the wavelength shift W of the reference light for each ambient temperature of the light source 2.

[0094] The concentration calculation unit 65 calculates the concentration of the component to be measured using the plurality of sample correlation values obtained by the correlation value calculation unit 62.

[0095] Specifically, the concentration calculation unit 65 calculates the concentration of the component to be measured based on the plurality of sample correlation values obtained by the correlation value calculation unit 62, the wavelength shift amount W determined by the wavelength shift determination unit 66, and the plurality of single correlation values stored in the storage unit 63. More specifically, the concentration calculation unit 65 corrects and acquires the plurality of single correlation values stored in the storage unit 63 from the wavelength shift amount W obtained by the wavelength shift determination unit 66. Then, the concentration calculation unit 65 solves a system of simultaneous equations composed of the plurality of sample correlation values obtained by the correlation value calculation unit 62, the corrected plurality of single correlation values corresponding to the determined wavelength shift amount W, and the concentrations of the component to be measured and each interference component, thereby calculating the concentration of the component to be measured (see FIG. 5).

[0096] Next, an example of the operation of this analyzer 100 will be described, also serving as a detailed explanation of each part above. Hereinafter, it is assumed that the sample gas contains one component to be measured and one interference component.

[0097] <Reference measurement> First, the light source control unit 5 controls the semiconductor laser 2 to modulate the wavelength of the laser light at a predetermined modulation frequency and modulation depth and centered on the peak of the absorption spectrum of the component to be measured. Note that before performing the reference measurement using the span gas, a reference measurement using the zero gas may be performed to measure the reference correlation value.

[0098] Next, the span gas (gas with known component concentration) is introduced into the cell 1 by the operator or automatically, and the reference measurement is performed. This reference measurement is performed for each of the span gas in which the component to be measured exists alone and the span gas in which the interference component exists alone.

[0099] Specifically, in the reference measurement, the logarithmic operation unit 61 receives each output signal of the photodetector 3 at each wavelength shift amount of the reference light and calculates the logarithmic intensity L(t). Then, the correlation value calculation unit 62 calculates the correlation values between the logarithmic intensity L(t) and the three characteristic signals F1(t), F2(t), and F3(t), and divides the result obtained by subtracting the reference correlation value from the correlation values by the concentration of the span gas to calculate the individual correlation values, which are the correlation values of each span gas per unit concentration. Instead of calculating the individual correlation values, the relationship between the span gas concentration and the correlation value of the span gas may be memorized.

[0100] Specifically, it is as follows. Adjust the wavelength shift amount of the reference light to w k and introduce the span gas in which the component to be measured exists alone into the cell 1, whereby the correlation value calculation unit 62 calculates the correlation values S 1tar (w k ), S 2tar (w k ), S 3tar (w k ). Here, S 1tar (w k ) is the correlation value with the first characteristic signal, S 2tar (w k ) is the correlation value with the second characteristic signal, and S 3tar (w k ) is the correlation value with the third characteristic signal. Then, the correlation value calculation unit 62 subtracts the reference correlation value R i tar from these correlation values S 1tar (w k ), S 2tar (w k ), S 3tar (w k ) and divides the result by the span gas concentration c tar of the component to be measured to obtain the individual correlation values s 1tar (w k ), s 2tar (w k ), s 3tar (w k) is calculated. By means such as changing the set temperature of the semiconductor laser 2, while sequentially changing the wavelength shift amount of the reference light (for example, from -0.01 cm -1 to +0.01 cm -1 in steps of 0.001 cm -1 ), this is performed at each wavelength shift amount, and the relationship between the autocorrelation value at each obtained wavelength shift amount and its wavelength shift is memorized. Note that the span gas concentration c tar of the component to be measured is input to the signal processing unit 6 in advance by the user or the like.

[0101] Also, by adjusting the wavelength shift amount of the reference light to w k and introducing the span gas in which the interference component exists alone into the cell 1, the correlation value S 1int (w k ), S 2int (w k ), S 3int (w k ) of the interference component is calculated. Here, S 1int (w k ) is the correlation value with the first characteristic signal, S 2int (w k ) is the correlation value with the second characteristic signal, and S 3int (w k ) is the correlation value with the third characteristic signal. Then, the correlation value calculation unit 62 divides the result of subtracting the reference correlation value R 1int (w k ) from those correlation values S 2int (w k ), S 3int (w k ) by the span gas concentration c i of the interference component to calculate the autocorrelation values s int (w 1int ), s k (w 2int ), s k (w 3int ). By means such as changing the set temperature of the semiconductor laser 2, while sequentially changing the wavelength shift amount of the reference light (for example, from -0.01 cm k to +0.01 cm -1 in steps of 0.001 cm -1 ), this is performed at each wavelength shift amount, and the relationship between the autocorrelation value at each obtained wavelength shift amount and its wavelength shift is memorized.-1 Perform this operation for each wavelength shift amount, and memorize the relationship between the individual correlation value at each obtained wavelength shift amount and the wavelength shift amount. Note that the spangas concentration c of the interference component int is input to the signal processing unit 6 in advance by the user or the like.

[0102] The wavelength shift amount w of each reference light calculated as described above k at the individual correlation value s 1tar (w k ), s 2tar (w k ), s 3tar (w k ), s 1int (w k ), s 2int (w k ), s 3int (w k ) are stored in the storage unit 63. Note that this reference measurement may be performed before product shipment or may be performed periodically.

[0103] <Sample Measurement> The light source control unit 5 controls the semiconductor laser 2 and modulates the wavelength of the laser light at a predetermined modulation frequency and modulation depth and centered on the peak of the absorption spectrum of the component to be measured.

[0104] Next, a sample gas is introduced into the cell 1 by the operator or automatically, and a sample measurement is performed.

[0105] Specifically, in the sample measurement, the logarithmic operation unit 61 receives the output signal of the photodetector 3 and calculates the logarithmic intensity L(t). Then, the correlation value calculation unit 62 calculates the sample correlation values S1, S2, S3 between the logarithmic intensity L(t) and the plurality of characteristic signals F1(t), F2(t), F3(t), and calculates the sample correlation values S'1, S'2 obtained by subtracting the reference correlation value R i from the correlation values.

[0106] Also, the wavelength shift determination unit 66 determines the wavelength shift amount W by the method described above.

[0107] The concentration calculation unit 65 uses the individual correlation value of the wavelength shift amount w of each reference light stored in the storage unit 63 and the wavelength shift amount W determined by the wavelength shift determination unit 64 to obtain the individual correlation values s' of the measurement target component and the interference component corrected by the wavelength shift amount W k and determines s' 1tar of s' 2tar of s' 1int of s' 2int and s'. As the determination method, for example, methods using linear interpolation, quadratic interpolation, spline interpolation, etc. can be considered

[0108] Then, in the same manner as in the first embodiment, the concentration calculation unit 65 corrects the sample correlation values S'1 and S'2 calculated by the correlation value calculation unit 62 with the reference correlation value, and the corrected individual correlation values s' 1tar of s' 2tar of s' 1int of s' 2int and s', and the concentrations C tar of C int of C and the following simultaneous binary equations consisting of the concentration C of each of the measurement target component and each interference component are solved

[0109]

Equation

[0110] When there are n kinds of gases including the measurement target component and the interference component, the concentration calculation unit 65 solves an n - variable simultaneous equation such as the above - mentioned formula (Equation 6) in the same manner as in the first embodiment

[0111] According to the analyzer 100 of the present embodiment configured as described above, the wavelength shift amount W of the reference light is determined, and using the determined wavelength shift amount W, the concentration of the measurement target component with the influence of the wavelength shift of the reference light corrected is calculated. Therefore, the change in the light absorption spectrum of the measurement target component caused by the wavelength shift of the reference light can be corrected, and the concentration of the measurement target component can be accurately measured

[0112] <Other Embodiments> For example, an analyzer that performs both coexistence influence correction and wavelength shift correction by combining the configurations of the first embodiment and the second embodiment may be configured. Specifically, the analyzer 100 has the broadening factor determination unit 64 of the first embodiment and the wavelength shift determination unit 66 of the second embodiment, and the storage unit 63 stores the pressure p in various cells as in the first embodiment and the second embodiment k and the wavelength shift w of the reference light k for each individual correlation value s ij (p k , w k ) is stored. In this analyzer 100, the concentration calculation unit 65 uses the pressure value p in the cell measured by the pressure sensor 7, the broadening factor F determined by the broadening factor determination unit 64 and the wavelength shift determination unit 66 B and the wavelength shift amount W to determine the individual correlation values of the measurement target component and the interference component corrected by the pressure in the cell, the broadening factor, and the wavelength shift amount according to the following formula (Equation 9). Then, the concentration calculation unit 65 calculates the concentration of the measurement target component using the corrected individual correlation value and the above-mentioned (Equation 6).

[0113]

Equation

[0114] The logarithmic operation unit 61 of each of the above embodiments performs a logarithmic operation on the light intensity signal of the photodetector 3, but it may calculate the logarithm of the ratio of the intensity of the sample light to the intensity of the modulated light that is the reference light (so-called absorbance) using the light intensity signal of the photodetector 3. At this time, the logarithmic operation unit 61 may calculate the absorbance by calculating the logarithm of the intensity of the sample light, calculating the logarithm of the intensity of the reference light, and then subtracting them, or by calculating the ratio of the intensity of the sample light to the intensity of the reference light and then taking the logarithm of the ratio.

[0115] Also, although the correlation value calculation unit 62 in each of the above embodiments calculates the correlation value between the intensity-related signal and the characteristic signal, it may calculate the inner product value between the intensity-related signal and the characteristic signal.

[0116] Also, in each of the above embodiments, the storage unit 63 stores the single correlation value corrected using the reference correlation value. However, the storage unit 63 may store the single correlation value before correction, and the concentration calculation unit 63 may subtract the reference correlation value from the single correlation value before correction and then perform correction to convert it into a single correlation value per unit concentration.

[0117] The plurality of characteristic signals are not limited to the above embodiments, and may be different functions from each other. Further, as the characteristic signal, for example, a function indicating the waveform (sample spectrum) of the light intensity, logarithmic intensity, or absorbance obtained by flowing span gas with a known concentration may be used. Also, when measuring the concentration of one measurement target component, at least one characteristic signal is sufficient.

[0118] Furthermore, when there are n types of gases including the measurement target component and the interference component, characteristic signals of more than n types may be used to obtain a number of single correlation values and sample correlation values greater than the number of gas types, create a system of simultaneous equations with a number of elements greater than the number of gas types, and determine each component concentration by the least squares method. By doing so, it becomes possible to determine the concentration with less error even for measurement noise.

[0119] In the first embodiment, during reference measurement, the single correlation value at the pressure in each cell is stored in the storage unit 63 and converted into the single correlation value at each broadening factor using the relationship of Equation (2). However, the single correlation value at each broadening factor may be directly measured during reference measurement and stored in the storage unit 63.

[0120] The light source control unit 5 in each of the above embodiments continuously oscillated (CW) the semiconductor laser. However, as shown in FIG. 8, it may perform pseudo-continuous oscillation (pseudo-CW). In this case, the light source control unit 5 controls the current source (or voltage source) of each semiconductor laser 2 by outputting a current (or voltage) control signal, and sets the drive current (drive voltage) of the current source (or voltage source) to be equal to or higher than a predetermined threshold value for pulse oscillation. Specifically, the light source control unit 5 performs pseudo-continuous oscillation by pulse oscillation with a predetermined pulse width (for example, 10 to 50 ns, Duty ratio 5%) repeated at a predetermined period (for example, 1 to 5 MHz). Then, the light source control unit 5 changes the drive current (drive voltage) of the current source (or voltage source) at a predetermined frequency with a value for wavelength sweeping that is less than the threshold value for the pulse oscillation, thereby generating a temperature change and performing sweeping of the oscillation wavelength of the laser light. The modulation signal for modulating the drive current changes in a triangular wave shape, sawtooth wave shape, or sine wave shape, and its frequency is, for example, 1 to 100 Hz.

[0121] In this way, when the semiconductor laser is pseudo-continuously oscillated, the light intensity signal obtained by the photodetector is as shown in FIG. 9. In this way, the absorption spectrum can be obtained for the entire pulse train. Pseudo-continuous oscillation has a lower power consumption of the light source and easier heat exhaust treatment compared to continuous oscillation, and furthermore, the light source can have a longer lifespan.

[0122] Also, the sample gas may be not only exhaust gas but also air, etc., or may be a liquid or a solid. In that sense, the measurement target component can be not only a gas but also a liquid or a solid to which the present invention is applicable. Also, it can be used not only for calculating the absorbance of light transmitted through the measurement target but also for calculating the absorbance by reflection.

[0123] The light source may also be a laser of another type regardless of the semiconductor laser, or a single-wavelength light source having a half-value width sufficient to ensure measurement accuracy, and any light source may be used as long as it can be wavelength-modulated.

[0124] In addition, various modifications and combinations of embodiments may be made as long as they do not contravene the spirit of the present invention.

Industrial Applicability

[0125] According to the present invention, it is possible to accurately measure the concentration of a component to be measured by correcting a change in the light absorption spectrum of the component to be measured caused by the coexistence effect of coexisting components or the wavelength shift of reference light.

Claims

1. An analyzer for analyzing a component to be measured contained in a sample, comprising: a light source that irradiates the sample with reference light; a photodetector that detects the intensity of sample light transmitted through the sample by the reference light; a parameter determination unit that determines a parameter representing a change in the light absorption spectrum of the component to be measured or an interference component caused by a coexisting component contained in the sample or a wavelength shift of the reference light; a correlation value calculation unit that calculates a correlation value between an intensity-related signal related to the intensity of the sample light and a predetermined characteristic signal; a concentration calculation unit that calculates the concentration of the component to be measured with the coexistence influence of the coexisting component or the wavelength shift of the reference light corrected using the correlation value and the parameter representing the change in the light absorption spectrum of the component to be measured or the interference component.

2. The analyzer according to claim 1, wherein the parameter representing the change in the light absorption spectrum is a broadening factor indicating a change rate of the light absorption spectrum of the component to be measured or the interference component caused by a coexisting component contained in the sample, or a wavelength shift amount of the reference light.

3. The analyzer according to claim 2, wherein the concentration calculation unit calculates the concentration of the component to be measured with the coexistence influence of the coexisting component or the wavelength shift of the reference light corrected using the intensity-related signal related to the intensity of the sample light and the broadening factor or the wavelength shift amount.

4. The analyzer according to claim 2 or 3, wherein the parameter determination unit determines the broadening factor by fitting reference data related to the light absorption signals of the component to be measured and the interference component with a known broadening factor or pressure and sample data related to the light absorption signal obtained from the intensity of the sample light.

5. The analyzer according to claim 2 or 3, wherein the parameter determination unit determines the broadening factor using relationship data indicating the relationship between the concentration of the coexisting component and the broadening factor and the measured concentration of the coexisting component.

6. The analyzer according to claim 2 or 3, wherein the parameter determination unit determines the wavelength shift amount by fitting reference data related to the light absorption signals of the component to be measured and the interference component with a known wavelength shift amount and sample data related to the light absorption signal obtained from the intensity of the sample light.

7. The analysis apparatus according to claim 2 or 3, wherein the parameter determination unit determines the amount of wavelength shift of the reference light by using relationship data indicating the relationship between the ambient temperature and the amount of wavelength shift and the measured ambient temperature.

8. An analysis apparatus for analyzing a component to be measured in a sample containing one or more interference components to be removed, wherein the correlation value calculation unit calculates a plurality of correlation values by using a number of characteristic signals equal to or greater than the total number of types of the component to be measured and the types of interference components, The concentration calculation unit calculates the concentration of the component to be measured by using the plurality of correlation values and a parameter representing a change in the light absorption spectrum of the component to be measured or the interference component. The analysis apparatus according to any one of claims 1 to 7.

9. further comprising a storage unit that stores individual correlation values, which are correlation values per unit concentration of the component to be measured and each interference component, obtained from the intensity-related signals of the component to be measured and each interference component when they exist alone and the plurality of characteristic signals, The concentration calculation unit calculates the concentration of the component to be measured by using the plurality of correlation values obtained by the correlation value calculation unit, the plurality of individual correlation values, and a parameter representing a change in the light absorption spectrum of the component to be measured or the interference component. The analysis apparatus according to claim 8.

10. The concentration calculation unit corrects the plurality of individual correlation values by using a parameter representing a change in the light absorption spectrum of the component to be measured or the interference component, and calculates the concentration of the component to be measured by using the corrected plurality of individual correlation values and the plurality of correlation values obtained by the correlation value calculation unit. The analysis apparatus according to claim 9.

11. The concentration calculation unit calculates the concentration of the component to be measured by solving a system of simultaneous equations including the plurality of correlation values obtained by the correlation value calculation unit, the corrected plurality of individual correlation values, and the concentrations of the component to be measured and each interference component. The analysis apparatus according to claim 10.

12. further comprising a pressure sensor that monitors the pressure of the sample, The concentration calculation unit corrects the individual correlation values by using the pressure value obtained by the pressure sensor. The analysis apparatus according to any one of claims 9 to 11.

13. The parameter determination unit determines a broadening factor indicating a change rate of the optical absorption spectrum of the component to be measured or the interfering component caused by the coexisting components included in the sample, wherein the concentration calculation unit corrects the individual correlation values using the individual correlation values of each component acquired for each of a plurality of known pressures of the sample, the plurality of correlation values obtained by the correlation value calculation unit, the pressure value of the sample, and the relationship of the following formula (Equation 2). The analyzer according to claim 12. 【Number 2】 Here, p is the pressure of the sample measured by the pressure sensor, F Ｂ is the broadening factor determined by the parameter determination unit, s ｉｊ is the single correlation value at each pressure stored in the storage unit, and s' ｉｊ is the corrected single correlation value. Note that the above formula (Equation 2) represents the single correlation value s ｉｊ (p) at the pressure p of the sample during sample measurement, and the single correlation value at the pressure multiplied by F Ｂ is multiplied by 1 / F Ｂ times to obtain the corrected single correlation value s' ｉｊ .

14. An analyzer for analyzing a component to be measured included in a sample, a light source that irradiates the sample with reference light, a photodetector that detects the intensity of the sample light transmitted through the sample by the reference light, a parameter determination unit that determines a parameter representing a change in the optical absorption spectrum of the component to be measured or the interfering component caused by coexisting components included in the sample, and a concentration calculation unit that calculates the concentration of the component to be measured corrected using the parameter representing the change in the optical absorption spectrum from an intensity-related signal related to the intensity of the sample light. The parameter representing the change in the optical absorption spectrum is a broadening factor indicating a change rate of the optical absorption spectrum of the component to be measured or the interfering component caused by coexisting components included in the sample, The analyzer, wherein the parameter determination unit determines the broadening factor by fitting reference data related to the optical absorption signals of the component to be measured and the interfering component for which the broadening factor or pressure is known and sample data related to the optical absorption signal obtained from the intensity of the sample light.

15. An analyzer for analyzing a component to be measured included in a sample, a light source that irradiates the sample with reference light, a photodetector that detects the intensity of the sample light transmitted through the sample by the reference light, a parameter determination unit that determines a parameter representing a change in the optical absorption spectrum of the component to be measured or the interfering component caused by coexisting components included in the sample, and a concentration calculation unit that calculates the concentration of the component to be measured corrected using the parameter representing the change in the optical absorption spectrum from an intensity-related signal related to the intensity of the sample light. The parameter representing the change in the light absorption spectrum is a broadening factor indicating the rate of change in the light absorption spectrum of the component to be measured or the interfering component caused by the coexisting components contained in the sample, The parameter determination unit is an analyzer that determines the broadening factor using relationship data indicating the relationship between the concentration of the coexisting component and the broadening factor and the measured concentration of the coexisting component.

16. A program applied to an analyzer including a light source that irradiates a sample with reference light and a photodetector that detects the sample light transmitted through the sample, A function as a parameter determination unit that determines a parameter representing a change in the light absorption spectrum of the component to be measured or the interfering component caused by the coexisting components contained in the sample or a wavelength shift of the reference light, A function as a correlation value calculation unit that calculates a correlation value between an intensity-related signal related to the intensity of the sample light and a predetermined characteristic signal, A function as a concentration calculation unit that calculates the concentration of the component to be measured with the coexistence influence by the coexisting component or the wavelength shift of the reference light corrected using the correlation value and the parameter representing the change in the light absorption spectrum of the component to be measured or the interfering component, characterized in that the analyzer is caused to exhibit the function. A program for an analyzer.

17. An analysis method for analyzing a component to be measured contained in a sample using a light source that irradiates the sample with reference light and a photodetector that detects the sample light transmitted through the sample, Determine a parameter representing a change in the light absorption spectrum of the component to be measured or the interfering component caused by the coexisting components contained in the sample or a wavelength shift of the reference light, Calculate a correlation value between an intensity-related signal related to the intensity of the sample light and a predetermined characteristic signal, An analysis method for calculating the concentration of the component to be measured with the coexistence influence by the coexisting component or the wavelength shift of the reference light corrected using the correlation value and the parameter representing the change in the light absorption spectrum of the component to be measured or the interfering component.

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