Gas analyzing device

Abstract

The present invention is provided with: a multi-reflection cell 30 into which sample gas comprising a plurality of components is introduced; a first analyzing mechanism 10 that causes first light to enter the multi-reflection cell 30, that detects the first light passed through the multi-reflection cell 30, and that analyzes the components of the sample gas according to a first principle; and a second analyzing mechanism 20 that causes second light to enter the multi-reflection cell 30, that detects the second light passed through the multi-reflection cell, and that analyzes the components of the sample gas according to a second principle, which is different from the first principle.

Description

Gas analyzers

[0001] The present invention relates to a gas analyzer using a multi-reflection cell.

[0002] Conventionally, gas analyzers for analyzing components contained in sample gases use multi-reflection cells such as White cells and Herriott cells. Various multi-reflection cells are used depending on the principle of application. For example, a White cell is used when analyzing multiple components in a sample gas by Fourier transform infrared spectroscopy (FTIR) (see Patent Document 1). Furthermore, a Herriott cell is used when analyzing components in a sample gas by laser absorption spectroscopy (LAS).

[0003] While FTIR is capable of broad spectrum measurement and allows for simultaneous analysis of a large number of components, it is inferior in performance, for example, in terms of sensitivity, compared to laser absorption spectroscopy. On the other hand, laser absorption spectroscopy allows for fast and highly sensitive component analysis, but because it uses laser light, component analysis is limited to a limited wavenumber range compared to FTIR, and the number of components that can be simultaneously analyzed is reduced. In other words, each principle has different strengths and weaknesses in performance areas. Therefore, in order to compensate for the shortcomings of each principle, it is possible to use two gas analyzers: one for FTIR and one for laser absorption spectroscopy.

[0004] However, simply using two gas analyzers, each with a different principle, not only increases costs but also causes problems with the analysis results of each gas analyzer. Specifically, if the multiple analysis cells of each gas analyzer are connected in series, there will be a time lag between the analysis results, and if the multiple analysis cells of each analyzer are connected in parallel, the same sample will not be measured.

[0005] Japanese Patent Application Publication No. 2020-094990

[0006] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a gas analyzer that can minimize the time difference between analysis results using multiple different principles and that can also analyze the same sample.

[0007] That is, the gas analysis apparatus of the present invention is characterized by comprising a multi-reflection cell into which a sample gas consisting of multiple components is introduced, a first analysis mechanism that causes a first light to be incident into the multi-reflection cell, detects the first light that has passed through the multi-reflection cell, and analyzes the components of the sample gas according to a first principle, and a second analysis mechanism that causes a second light to be incident into the multi-reflection cell, detects the second light that has passed through the multi-reflection cell, and analyzes the components of the sample gas according to a second principle that is different from the first principle.

[0008] In this way, first and second light beams can be introduced into a single multi-reflection cell, and components can be analyzed using different principles with the first and second light beams that have passed through the multi-reflection cell. This makes it possible to virtually eliminate the time difference between the analyses using each principle and to analyze the same sample. Furthermore, since there is no need to prepare separate gas analyzers for the first and second principles, it is easy to configure an integrated operating system as a system, and operability can be improved. Additionally, since the multi-reflection cell is shared between the two principles, costs can be reduced compared to simply preparing two gas analyzers.

[0009] In order to simultaneously measure multiple components and to measure a specific component of interest at high speed and with high sensitivity, the first principle should be Fourier transform infrared spectroscopy and the second principle should be laser absorption spectroscopy. In this case, multiple components can be analyzed by Fourier transform infrared spectroscopy (FTIR) and then components of particular interest can be analyzed by laser absorption spectroscopy (LAS), enabling high-speed, high-sensitivity analysis. Furthermore, since FTIR can also analyze components other than those targeted by LAS, it is possible to correct the coexistence or interference effects of other components in the analysis results of a specific component obtained by LAS, thereby obtaining more accurate analysis results.

[0010] In order to be able to perform analyses, for example, by FTIR and LAS, using one multi-reflection cell, the multi-reflection cell must comprise a cell body into whose internal space the sample gas is introduced, and a multi-reflection mechanism that is provided in the internal space and that multiple-reflects the incident light before emitting it to the outside, and the cell body must be formed with a light introduction window through which first light is introduced into the cell body, and a light outlet window through which the first light that has passed through the multiple reflection mechanism is output to the outside of the cell body, and the multi-reflection mechanism must comprise a field mirror, a first objective mirror that faces the field mirror and is provided on the light entrance side of the multi-reflection mechanism, and a second objective mirror that faces the field mirror and is provided on the light exit side of the multi-reflection mechanism.

[0011] In order to simultaneously introduce the first light and the second light into the multi-reflection cell and analyze each component of the sample gas without causing a time difference between the first principle and the second principle, the first analysis mechanism may include a first light source that emits the first light, which is continuous light including light of multiple wave numbers, and a first photodetector that detects the first light that has passed through the multi-reflection cell, and the second analysis mechanism may include a second light source that emits the second light, which is laser light, and a second photodetector that detects the second light that has passed through the multi-reflection cell.

[0012] In order to minimize the time difference in analysis by making the first light and the second light pass through the same point at the same time within the multi-reflection cell, the second analysis mechanism may be configured so that the second light emitted from the second light source is introduced into the cell body through the light introduction window, and the second light emitted from the light extraction window is detected by the second photodetector.

[0013] In order to prevent the first light from entering the second photodetector, to prevent the analysis results based on the second principle from being affected by the first light, and to improve the accuracy of the analysis based on the second principle, the second analysis mechanism may be configured so that the second light emitted from the second light source is introduced into the cell body through the light outlet window, and the second photodetector detects the second light emitted from the light introduction window.

[0014] A specific optical path configuration for simultaneously introducing the first light and the second light into the multi-reflection cell is one in which the first analysis mechanism further includes an interferometer into which the light emitted from the first light source is incident, an incident side mirror that reflects the first light that has passed through the interferometer and makes it incident into the light introduction window, and an exit side mirror that reflects the first light emitted from the light extraction window and makes it incident into the first photodetector, and the incident side mirror and the exit side mirror have light passage holes formed therein to allow the second light to pass through.

[0015] In order to reduce the number of detectors required for performing analyses based on the first principle and the second principle and thereby further reduce the cost of the gas analyzer, the first analysis mechanism may include a first light source that emits a first light, which is continuous light including light of multiple wave numbers, and an interferometer into which the light emitted from the first light source is incident, and the second analysis mechanism may include a second light source that emits a second light, which is laser light, and may be configured so that the first light or the second light that has passed through the multi-reflection cell is detected by a single common photodetector.

[0016] In order to enable accurate analysis based on each principle using only one photodetector, the interferometer may further include a concentration calculation unit that calculates the concentration of a component in the sample gas based on the output of the common photodetector, and the concentration calculation unit may be configured to calculate the concentration of one or more components in the sample gas using Fourier transform infrared spectroscopy (FTIR) while the movable mirror of the interferometer is moving, and to calculate the concentration of one or more components in the sample gas using laser absorption spectroscopy (LAS) while the movable mirror is stationary.

[0017] If the concentration calculation unit further includes a pressure control mechanism that controls the pressure of the sample gas in the multi-reflection cell according to the principle used, the pressure can be adjusted to suit each principle, improving the analytical accuracy.

[0018] A preferred mode of pressure control is one in which the pressure control mechanism is configured to lower the pressure of the sample gas while the movable mirror is stopped compared to when the movable mirror is moving.

[0019] In order to use the interferometer to perform wavelength calibration of the second light, which is laser light emitted from the second light source, and to facilitate improving analytical accuracy, it is sufficient to further include an optical path switching mechanism that switches the optical path between a measurement optical path in which the second light emitted from the second light source bypasses the interferometer and enters the multi-reflection cell, and an adjustment optical path in which the second light emitted from the second light source enters the interferometer.

[0020] In order to be able to individually set optical path lengths suitable for the first principle and the second principle within the multi-reflection cell and further improve the analytical accuracy using each principle, the multi-reflection cell may further include a pair of reflecting mirrors provided separately from the multi-reflection mechanism within the cell body, and may be configured so that the second light emitted from the second light source is multiply reflected by the pair of reflecting mirrors before being emitted to the outside from the multi-reflection cell.

[0021] For example, to enable analysis based on another principle, such as NDIR, to be performed simultaneously, thereby making it easier to correct for coexistence effects or interference effects, the apparatus may further include a third light source that emits a third light so that it passes through the multi-reflection cell without being reflected therein, and a third photodetector that detects the third light that has passed through the multi-reflection cell. This makes it possible to correct for interference effects that cause errors in the calculated concentrations when the absorption wavelength bands of the components to be analyzed overlap, and coexistence effects that cause errors in the calculated concentrations simply because the components are present, even when the absorption wavelength bands of the components to be analyzed do not overlap.

[0022] As described above, the gas analyzer according to the present invention can introduce first and second light beams into the multi-reflection cell, and analyze components using different principles with the first and second light beams that pass through the multi-reflection cell. In other words, since there is no need to prepare separate multi-reflection cells for each principle, it is possible to virtually eliminate the time difference between analyses using each principle and to analyze the same sample. Furthermore, since only one multi-reflection cell is required, costs can be reduced compared to preparing two gas analyzers for analyses using each principle, and it is easy to integrate interfaces and other components into the analytical system.

[0023] 1 is a schematic diagram showing a gas analyzer according to a first embodiment of the present invention; 2 is a schematic diagram showing the structure of a multi-reflection cell according to the first embodiment; 3 is a schematic diagram showing a method for modulating a laser oscillation wavelength according to the first embodiment; 4 is a schematic diagram showing the oscillation wavelength, light intensity I(t), logarithmic intensity L(t), and characteristic signal F according to the first embodiment; ｉ (t), correlation value S ｉ1 is a time series graph showing an example of a time series graph of a concentration or partial pressure calculated using a single correlation value and a sample correlation value according to the same embodiment. FIG. 2 is a schematic diagram showing a modified example of a gas analyzer according to a first embodiment of the present invention. FIG. 3 is a schematic diagram showing a gas analyzer according to a second embodiment of the present invention. FIG. 4 is a timing chart showing that analyses based on each principle in the second embodiment are performed alternately. FIG. 5 is a timing chart showing a batch measurement mode in a modified example of the second embodiment. FIG. 6 is a schematic diagram showing the configuration of a gas analyzer according to another modified example of the second embodiment. FIG. 7 is a schematic diagram showing a state in which a gas analyzer according to a third embodiment of the present invention is switched to the measurement optical path. FIG. 8 is a schematic diagram showing a state in which a gas analyzer according to the third embodiment is switched to the adjustment optical path. FIG. 9 is a schematic diagram showing a gas analyzer according to a fourth embodiment of the present invention. FIG. 10 is a schematic diagram showing a gas analyzer according to a fifth embodiment of the present invention. FIG. 11 is a schematic diagram showing the configuration of a multi-reflection cell according to the fifth embodiment of the present invention and its periphery. FIG. 12 is a schematic diagram showing the configuration of a multi-reflection cell according to another embodiment of the present invention.

[0024] A gas analyzer 100 according to a first embodiment of the present invention will be described with reference to Figs. 1 to 5. The gas analyzer 100 according to the first embodiment analyzes target components (here, for example, CO, CO) contained in a sample gas such as exhaust gas from an internal combustion engine. ２ , N ２ O, NO, NO ２ , H ２ O, SO ２ , C.H. ４ , N.H. ３ This gas analyzer 100 is configured to be able to measure the concentration of a target component based on two different principles by introducing two types of light into a single multi-reflection cell 30 into which a sample gas is introduced.

[0025] Here, "principle" refers to the analytical principle for, for example, qualitatively determining the components to be analyzed in a sample gas, quantifying the components to be analyzed, detecting the presence or absence of the components to be analyzed, or measuring the temperature of the components to be analyzed or the sample gas.

[0026] Specifically, as shown in FIG. 1 , the gas analyzer 100 includes a multi-reflection cell 30, a first analysis mechanism 10 for performing gas analysis by Fourier transform infrared spectroscopy (hereinafter also referred to as FTIR), a second analysis mechanism 20 for performing gas analysis by infrared laser absorption modulation (hereinafter also referred to as IRLAM), which is a type of laser absorption spectroscopy (hereinafter also referred to as LAS), and an information processing device COM for performing calculations related to the analysis of sample gas and controlling each device. The first analysis mechanism 10 and the second analysis mechanism 20 are configured to introduce first light and second light, respectively, into the multi-reflection cell 30 and individually detect the first light and second light that pass through the multi-reflection cell 30. Furthermore, the first analysis mechanism 10 and the second analysis mechanism 20 share an optical path at least within the multi-reflection cell 30.

[0027] Here, in the second principle, infrared laser absorption modulation (IRLAM) (see Japanese Patent No. 6886507), a feature quantity is extracted from a light intensity signal obtained by irradiating a sample gas with a laser beam, and the feature quantity is used to perform a least squares calculation to calculate the concentration of a target component in the sample gas.

[0028] As shown in Figure 2, the multi-reflection cell 30 is a so-called White cell, and includes a cell body 31 into whose internal space a sample gas is introduced, and a multi-reflection mechanism 32 that is provided in the internal space and that multiple-reflects incident light and then emits it to the outside.

[0029] The cell body 31 has a generally hollow cylindrical shape, and is provided on one end face thereof with a light introduction window 36 through which the first light is introduced into the cell body 31 and a light outlet window 37 through which the first light having passed through the multiple reflection mechanism 32 is led out of the cell body 31. The cell body 31 is also provided with a gas introduction hole and a gas outlet hole (neither of which are shown) for introducing and guiding the sample gas. A pressure gauge (not shown) for measuring the pressure of the sample gas in the cell body 31 is provided in the cell body or in an inlet or outlet path communicating with the cell body.

[0030] The multiple reflection mechanism 32 is composed of three spherical mirrors and includes a field mirror 33 arranged on the end face of the cell body 31 where the light introduction window 36 and the light outlet window 37 are formed, a first objective mirror 34 facing the field mirror 33 and provided on the light entrance side of the multiple reflection mechanism 32, and a second objective mirror 35 facing the field mirror 33 and provided on the light exit side of the multiple reflection mechanism 32. The first objective mirror 34 and the second objective mirror 35 are arranged on the end face of the cell body 31 opposite the end face where the light introduction window 36 and the light outlet window 37 are formed. The number of light reflections between each mirror can be changed by adjusting the angle of the first objective mirror 34 or the second objective mirror 35 relative to the field mirror 33. In the first embodiment, light entering through the light introduction window 36 first enters the first objective mirror 34 and is finally reflected by the second objective mirror 35 to reach the light outlet window 37. Alternatively, the configuration may be such that the light incident through the light introduction window 36 first enters the second objective mirror 35 , is finally reflected by the first objective mirror 34 , and reaches the light outlet window 37 .

[0031] Here, the multi-reflection cell 30 has a configuration suitable for performing analysis by, for example, FTIR, but it is also possible to perform analysis by IRLAM using laser light.

[0032] As shown in FIG. 1, the first analyzing mechanism 10 includes a first light source 11, an interferometer IF, and a first photodetector 18.

[0033] The first light source 11 emits light having a broad spectrum (continuous light including light of many wavenumbers) as the first light, and may be, for example, a tungsten-iodine lamp or a high-intensity ceramic light source. A light-guiding mirror 12 is provided between the first light source 11 and the interferometer IF to reflect the first light emitted from the first light source 11 and cause it to enter the interferometer IF. In the first embodiment, the light-guiding mirror 12 is, for example, a parabolic mirror provided to bend the optical axis of the first light emitted from the first light source 11 by 90 degrees.

[0034] The interferometer IF utilizes a so-called Michelson interferometer equipped with a single half mirror 13 (beam splitter), a fixed mirror 14, and a movable mirror 15. The first light from the first light source 11 incident on the interferometer IF is split by the half mirror 13 into a reflected light and a transmitted light. One light is reflected by the fixed mirror 14, and the other is reflected by the movable mirror 15, returning to the half mirror 13, where it is combined and emitted from the interferometer IF. An incident-side mirror 16 is provided between the exit of the interferometer IF and the multi-reflection cell 30, and guides the first light that has passed through the interferometer IF to the light introduction window 36 of the multi-reflection cell 30. The incident-side mirror 16 is, for example, a parabolic mirror, and reflects the first light once so that the optical axis of the first light is incident at a predetermined angle obliquely with respect to the light introduction window 36.

[0035] The first photodetector 18 detects the first light output from the multi-reflection cell 30 and is a photodetector whose output value is linear with respect to the incident light intensity within a predetermined range and nonlinear with respect to other ranges, such as an MCT photodetector. Based on the spectrum of the first light detected by the first photodetector 18, the concentrations of multiple components in the sample gas are calculated by FTIR.

[0036] An exit-side mirror 17 is provided between the multi-reflection cell 30 and the first photodetector 18 to guide the first light that has passed through the multi-reflection cell 30 to the first photodetector 18. The exit-side mirror 17 is a parabolic mirror configured to reflect the first light that has been guided out from the light guide window 37 twice so that its optical axis is crank-shaped, and guide it to the first photodetector 18.

[0037] The second analysis mechanism 20 includes a second light source 21 that emits second light, which is laser light, and a second photodetector 22 that detects the second light that has passed through the multi-reflection cell 30 .

[0038] The second light source 21 is a quantum cascade laser (QCL) that emits mid-infrared (4 μm to 10 μm) laser light. The second light source 21 is capable of modulating (changing) the oscillation wavelength by applying a current (or voltage). Note that other types of lasers may be used as long as the oscillation wavelength is variable, and the oscillation wavelength may be changed by changing the temperature, for example.

[0039] The second light source 21 is arranged so as to sandwich the aforementioned incident side mirror 16 between it and the light introduction window 36 of the multi-reflection cell 30, and the second light emitted from the second light source 21 is configured to pass through a light passing hole 2H formed in the incident side mirror 16 and enter the light introduction window 36 of the multi-reflection cell 30.

[0040] The second photodetector 22 is a thermal type such as a relatively inexpensive thermopile, but other types, such as quantum photoelectric elements with good responsiveness, made of HgCdTe, InGaAs, InAsSb, PbSe, etc., may also be used. The second photodetector 22 is provided so as to sandwich the aforementioned exit-side mirror 17 between itself and the light-outlet window 37 of the multi-reflection cell 30, and the second light emitted from the light-outlet window 37 reaches the second detector through a light passing hole 2H formed in the exit-side mirror 17.

[0041] By forming the optical paths of the first light and the second light in this manner, the first light and the second light can travel simultaneously within the multi-reflection cell 30, and their respective intensities can be measured almost simultaneously by the first photodetector 18 and the second photodetector 22, respectively.

[0042] The information processing device COM is equipped with analog electrical circuits consisting of buffers, amplifiers, etc., digital electrical circuits consisting of a CPU, memory, etc., and A / D converters, D / A converters, etc. that mediate between these analog and digital electrical circuits, and the CPU and its peripheral devices work together in accordance with a predetermined program stored in a predetermined area of ​​the memory, thereby fulfilling the functions of a concentration calculation unit 40 and a light source control unit 43 as shown in FIG. 1.

[0043] The concentration calculation unit 40 includes at least an FTIR unit 41 that calculates the concentration of each component of the sample gas using FTIR based on the absorbance of the first light, and an IRLAM unit 42 that calculates the concentration of at least one component of the sample gas using IRLAM based on the absorbance of the second light.

[0044] The FTIR unit 41 calculates the spectrum of light that has passed through the sample gas from the output value indicated by the detection signal of the first photodetector 18, and also obtains the absorbance of light at each wavenumber from this optical spectrum to analyze the sample gas. The FTIR unit 41 calculates the optical spectrum as follows.

[0045] When the movable mirror 15 is moved back and forth and the light intensity of the first light that has passed through the sample gas is observed with the position of the movable mirror 15 on the horizontal axis, the light intensity draws a sine curve due to interference in the case of light with a single wavenumber. On the other hand, the first light that has passed through the sample gas is light with many wavenumbers, and the sine curve differs for each wavenumber, so the actual light intensity is a superposition of the sine curves drawn by each wavenumber, and the interference pattern (interferogram) takes the form of a wave packet.

[0046] The FTIR unit 41 determines the position of the movable mirror 15 using a rangefinder (not shown) such as a HeNe laser, and determines the light intensity of the first light at each position of the movable mirror 15 from the output of the first photodetector 18. The interference pattern obtained from these is then subjected to a fast Fourier transform (FFT) to convert it into an optical spectrum with each wavenumber component on the horizontal axis and the light intensity signal on the vertical axis. Finally, the FTIR unit 41 calculates the concentration of each component corresponding to each wavenumber based on the obtained optical spectrum.

[0047] Next, the IRLAM unit 42 and the light source control unit 43 will be described.

[0048] The light source control unit 43 controls at least the current source (or voltage source) of the second light source 21 by outputting a current (or voltage) control signal. Specifically, the light source control unit 43 changes the drive current (or drive voltage) of the second light source 21 at a predetermined frequency, and modulates the oscillation wavelength of the laser light output from the second light source 21 at the predetermined frequency with respect to the center wavelength (see FIG. 3 ). As a result, the second light source 21 emits modulated light modulated at the predetermined modulation frequency.

[0049] In this embodiment, the light source control unit 43 changes the drive current to a triangular waveform and modulates the oscillation frequency to a triangular waveform (see "Oscillation Wavelength" in FIG. 4). In practice, the drive current is modulated using a different function so that the oscillation frequency becomes a triangular waveform. Furthermore, as shown in FIG. 3, the oscillation wavelength of the laser light is modulated with the peak of the optical absorption spectrum of the component to be measured as the center wavelength. Alternatively, the light source control unit 43 may change the drive current to a sine wave, a sawtooth wave, or any other function, and modulate the oscillation frequency to a sine wave, a sawtooth wave, or any other function.

[0050] The IRLAM section 42 comprises a logarithmic calculation section 42a, a correlation value calculation section 42b, a storage section 42c, a density output section 42d, and the like.

[0051] The logarithmic calculation unit 42a performs logarithmic calculation on the light intensity signal, which is the detection signal of the photodetector 23. A function I(t) showing the time-series change of the light intensity signal obtained by the photodetector 23 is shown as "light intensity I(t)" in Fig. 4, and by performing logarithmic calculation, it becomes shown as "logarithmic intensity L(t)" in Fig. 4.

[0052] The correlation value calculation unit 42b calculates correlation values ​​between an intensity-related signal related to the intensity of sample light obtained when measuring the sample gas and a plurality of predetermined feature signals. The feature signal is a signal for extracting waveform features of the intensity-related signal by correlating it with the intensity-related signal. The feature signal can be, for example, a sinusoidal signal or any other signal that matches the waveform feature to be extracted from the intensity-related signal. Here, the correlation value calculation unit 42b uses a logarithmically calculated light intensity signal (logarithmic intensity L(t)) as the intensity-related signal.

[0053] Furthermore, the correlation value calculation unit 42b calculates a number of feature signals F that is greater than the total number of types of measurement target components (reaction products in this embodiment) and the number of types of interference components. ｉ (t) (i=1, 2, . . . , n), a plurality of sample correlation values ​​S, which are correlation values ​​between the intensity-related signal of the sample light and each of the plurality of feature signals, are calculated by the following equation (1): ｉ where T in Equation 1 is the modulation period.

[0054]

[0055] When calculating the sample correlation value, the correlation value calculation unit 42b calculates the sample correlation value by using the intensity-related signal L(t) of the sample light and the plurality of characteristic signals F as shown in Equation 1. ｉ (t) and the correlation value S ｉ to the reference light intensity related signal L ０ (t) and a plurality of feature signals F ｉ (t) is the correlation value with the reference correlation value R ｉ The corrected sample correlation value S ｉ It is desirable to calculate '. This removes the offset contained in the sample correlation value, resulting in a correlation value proportional to the concentrations of the measurement target component and the interfering component, thereby reducing measurement errors. Note that a configuration may be adopted in which the reference correlation value is not subtracted.

[0056] Here, the timing of acquiring the reference light may be simultaneous with the timing of acquiring the sample light, before or after measurement, or at any other timing. The intensity-related signal or reference correlation value of the reference light may be acquired in advance and stored in the storage unit 42 c. Alternatively, a method of simultaneously acquiring the reference light may be, for example, to provide two second photodetectors 22, split the modulated light from the second light source 21 using a beam splitter or the like, and use one for measuring the sample light and the other for measuring the reference light.

[0057] In this embodiment, the correlation value calculation unit 42b calculates the correlation value based on a plurality of feature signals F ｉ For (t), a function that can more easily capture the waveform characteristics of the logarithmic intensity L(t) than a sine function is used. In the case of a sample gas containing a measurement target component and one interference component, two or more characteristic signals F １ (t), F２ (t) and two feature signals F １ (t), F ２ For example, a function based on a Lorentzian function that approximates the shape of the absorption spectrum and a differential function of the Lorentzian function can be used as (t). Furthermore, instead of a function based on a Lorentzian function, a function based on a Voigt function or a Gaussian function can also be used as the feature signal. By using such a function as the feature signal, a larger correlation value can be obtained than when a sine function is used, thereby improving measurement accuracy.

[0058] Here, it is desirable to remove the DC component from the feature signal, i.e., to adjust the offset so that it becomes zero when integrated over the modulation period. This makes it possible to eliminate the effect of an offset on the intensity-related signal due to fluctuations in light intensity. Note that instead of removing the DC component from the feature signal, the DC component may be removed from the intensity-related signal, or the DC components may be removed from both the feature signal and the intensity-related signal. Alternatively, the feature signal may be a sample value of the absorption signal of the measurement target component and / or interference component, or a value simulating these.

[0059] In addition, two feature signals F １ (t), F ２ By setting (t) to a sequence of orthogonal functions or a sequence of functions close to a sequence of orthogonal functions, the characteristics of the logarithmic intensity L(t) can be extracted more efficiently, and the concentration obtained by the simultaneous equations described below can be more accurately obtained.

[0060] The storage unit 42c stores the intensity-related signals and the plurality of characteristic signals F when the measurement target component and each interference component are present alone. ｉ The single correlation value, which is the correlation value per unit concentration of the measurement target component and each interfering component calculated from (t), is stored. ｉ (t) is a plurality of feature signals F used in the correlation value calculation unit 42b ｉ It is the same as (t).

[0061] Here, when storing the single correlation value, the storage unit 42c desirably subtracts the reference correlation value from the correlation value when the measurement target component and each interfering component are present alone, and then stores the corrected single correlation value converted to a value per unit concentration. This removes the offset contained in the single correlation value, resulting in a correlation value proportional to the concentrations of the measurement target component and each interfering component, thereby reducing measurement errors. Note that a configuration in which the reference correlation value is not subtracted may also be used.

[0062] The single correlation value of the interfering component stored in storage unit 42c may be a value calculated based on the concentration of the interfering component measured by FTIR by first analysis mechanism 10. By doing so, it is possible to further improve the accuracy of the measurement of the concentration of the target component by IRLAM by second analysis mechanism 20 by utilizing the measurement results of the concentration of the interfering component by first analysis mechanism 10.

[0063] The concentration output section 42d calculates the concentration of the measurement target component using the plurality of sample correlation values ​​obtained by the correlation value calculation section 42b.

[0064] Specifically, the concentration output unit 42d calculates the concentration of the component to be measured based on the plurality of sample correlation values ​​obtained by the correlation value calculation unit 42b and the plurality of single correlation values ​​stored in the storage unit 42c. More specifically, the concentration output unit 42d calculates the concentration of the component to be measured by solving simultaneous equations consisting of the plurality of sample correlation values ​​obtained by the correlation value calculation unit 42b, the plurality of single correlation values ​​stored in the storage unit 42c, and the concentrations of the component to be measured and each interfering component. Note that Fig. 5 shows a conceptual diagram of concentration or partial pressure calculation using the single correlation value and sample correlation value in the concentration output unit 42d.

[0065] When the sample gas contains one measurement target component and one interference component, the concentration output unit 42d outputs the sample correlation value S calculated by the correlation value calculation unit 42b. １ ', S ２ ' and the single correlation value s １ｔ , s ２ｔ , s １ｉ , s ２ｉand the concentration C of the component to be measured and each interfering component. ｔａｒ , C ｉｎｔ The following simultaneous equations with two unknowns are solved: １ｔ is the single correlation value of the measurement target component in the first feature signal, s ２ｔ is the single correlation value of the measurement target component in the second feature signal, s １ｉ is the single correlation value of the interference component in the first feature signal, s ２ｉ is the single correlation value of the interference component in the second feature signal.

[0066]

[0067] As a result, the concentration C of the component to be measured, from which the influence of interference has been removed, can be obtained by a simple and reliable calculation of solving the simultaneous equations in the above formula (Formula 2). ｔａｒ can be determined.

[0068] Even when it is assumed that two or more interfering components are present, the concentration of the component to be measured, from which the effects of interference have been removed, can be determined by adding a single correlation value equal to the number of interfering components and solving a system of simultaneous equations with the same number of elements as the number of component types.

[0069] According to the gas analyzer 100 of the first embodiment configured in this manner, the optical paths of the first analysis mechanism 10 for performing analysis by FTIR and the second analysis mechanism 20 for performing analysis by IRLAM are shared by a single multi-reflection cell 30, so that analysis of a sample gas by FTIR and analysis of the same sample gas by IRLAM can be performed simultaneously without any time lag.

[0070] Furthermore, while FTIR can measure the concentrations of many components in a sample gas, IRLAM can achieve high-speed, high-sensitivity concentration measurement of a component of interest. In other words, the performance weaknesses of FTIR and IRLAM can be complemented, allowing for both multi-component concentration measurement and high-sensitivity measurement.

[0071] Furthermore, since FTIR analysis and IRLAM analysis can be performed using a single multi-reflection cell 30, the entire gas analyzer 100 can be made more compact, reducing its introduction cost. In addition, since measurements based on each principle can be performed using a single CPU, it is easy to integrate the user interface, etc., making it possible to achieve multi-functional analysis while also improving ease of use.

[0072] Next, a modification of the first embodiment will be described with reference to FIG.

[0073] In the first embodiment, the laser light, which is the second light emitted from the second light source 21, travels in the same direction as the first light, enters the multi-reflection cell 30 through the light introduction window 36, and is emitted to the outside through the light outlet window 37. However, the second light may be configured to travel in the opposite direction to the first light, as shown in Fig. 6. That is, the second light emitted from the second light source 21 may be configured to enter the interior of the multi-reflection cell 30 through the light outlet window 37, be multiply reflected by the multi-reflection mechanism 32, and then be emitted to the outside through the light introduction window 36 and detected by the second photodetector 22.

[0074] With the gas analyzer 100 configured in this manner, the first light is less likely to be incident on the second photodetector 22, and the output of the second photodetector 22 is derived solely from the second light. Therefore, the influence of the first light can be largely eliminated, and the accuracy of analysis by IRLAM can be further improved.

[0075] Next, a gas analyzer 100 according to a second embodiment of the present invention will be described with reference to FIGS.

[0076] 7 , the gas analyzer 100 according to the second embodiment differs from the gas analyzer 100 according to the first embodiment in that the first analysis mechanism 10 and the second analysis mechanism 20 do not have individual photodetectors but share a single photodetector. Specifically, the first photodetector 18 in the first embodiment is used as the shared photodetector CD in the second embodiment, and in the second embodiment, a light passing hole 2H is formed only in the entrance-side mirror 16 to pass the laser light, which is the second light emitted from the second light source 21. Therefore, in the second embodiment, not only the first light but also the second light is reflected by the exit-side mirror 17 and detected by the shared photodetector CD.

[0077] Furthermore, while in the first embodiment the FTIR unit 41 and the IRLAM unit 42 always output the concentrations of components simultaneously, in the second embodiment the FTIR unit 41 and the IRLAM unit 42 are configured to alternately output the concentrations. That is, in the concentration calculation unit 40 of the second embodiment, only one of the FTIR unit 41 or the IRLAM unit 42 outputs the concentration depending on the movement of the movable mirror 15, as shown in the timing chart of FIG. 8 . More specifically, the concentration calculation unit 40 stops the movable mirror 15 at the closest point or the farthest point from the half mirror 13 for a predetermined time to perform the IRLAM analysis, and after the IRLAM analysis is completed, moves the movable mirror 15 at a constant speed to perform the FTIR analysis. That is, the concentration calculation unit 40 is configured to change the position of the movable mirror 15 over time so that it becomes approximately trapezoidal, and to alternate between the FTIR analysis and the IRLAM analysis.

[0078] The gas analyzer 100 of the second embodiment configured as described above can perform FTIR analysis and IRLAM analysis on the same sample at approximately the same time using only one shared photodetector CD and one multi-reflection cell 30. Therefore, it is possible to reduce the number of components of the gas analyzer 100 and thereby reduce costs, while achieving analysis that is approximately the same as that of the first embodiment.

[0079] Next, a modified batch measurement of the second embodiment will be described with reference to FIG. 9 . In this modified example, FTIR analysis is performed while the movable mirror 15 moves back and forth multiple times. After the FTIR analysis is completed, the movable mirror 15 is stopped for a predetermined period of time and then the IRLAM analysis is performed. This modified example also includes a pressure control mechanism (not shown) that controls the pressure of the sample gas in the multi-reflection cell 30, and is configured to change the pressure depending on the analysis principle. The pressure control mechanism includes, for example, the pressure gauge described above, a control valve (not shown) provided in either or both of the sample gas inlet and outlet paths connected to the cell body, and a pressure controller (not shown) that performs pressure feedback control of the control valve opening so that the measured pressure measured by the pressure gauge matches the set pressure. Specifically, the pressure control mechanism controls the sample gas pressure so that the sample gas pressure during the IRLAM analysis is lower than the sample gas pressure during the FTIR analysis. Therefore, as shown in FIG. 9 , the sample gas pressure is configured to periodically increase and decrease.

[0080] With this arrangement, analysis can be performed under conditions where the sample gas pressure is adjusted to an optimum level for each analysis principle, thereby further improving the accuracy of analysis for each analysis principle.

[0081] Next, a modified example of the optical system of the second embodiment will be described with reference to Fig. 10. In this modified example, the incident-side mirror 16 does not have a light passing hole 2H for passing the second light, i.e., laser light, but a small reflecting mirror 23 is disposed on the optical path of the first light, and the second light emitted from the second light source 21 is reflected by the incident-side mirror 16 and enters the light introducing window 36.

[0082] Even with such a structure, if the area of ​​the small reflecting mirror 23 that blocks the first light is made small enough, it will be possible to perform analysis by IRLAM while having almost no effect on analysis by FTIR.

[0083] Next, a gas analyzer 100 according to a third embodiment of the present invention will be described with reference to FIGS. 11 and 12 . The gas analyzer 100 according to the third embodiment is configured to calibrate the second light emitted from the second light source 21 using the interferometer IF of the first analysis mechanism 10. That is, the gas analyzer 100 according to the third embodiment includes an optical path switching mechanism 50 that switches an optical path between a measurement optical path L1 shown in FIG. 11 , in which the second light emitted from the second light source 21 bypasses the interferometer IF and enters the multi-reflection cell 30, and an adjustment optical path L2 shown in FIG. 12 , in which the second light emitted from the second light source 21 enters the interferometer IF. The optical path switching mechanism 50 includes a movable switching unit 51 that includes a pair of mirrors 52 and 53. When the mirrors 52 and 53 of the switching unit 51 are positioned on the optical axis of the second light emitted from the second light source 21 and on the optical axis of the first light at the output side of the interferometer IF, respectively, the measurement optical path L1 is selected, and the second light bypasses the interferometer IF and enters the multi-reflection cell 30 directly. On the other hand, when the switching unit 51 is moved so that the mirrors 52 and 53 are not on the optical axes of the respective lights, the adjustment optical path L2 is selected, and the second light enters the adjustment fixed mirror 54 fixed near the light-guiding mirror 12, passes through a light-guiding hole formed in the light-guiding mirror 12, and enters the interferometer IF. By moving the movable mirror 15 in this state, the interference state of the laser light can be confirmed at the shared photodetector CD, and the oscillation wavelength can be calibrated.

[0084] Next, a gas analyzer 100 according to a fourth embodiment of the present invention will be described with reference to FIG. 13 . In the gas analyzer 100 according to the fourth embodiment, the first and second light beams do not share a common optical path within the multi-reflection cell 30, but are configured to achieve optical path lengths suited to their respective principles. That is, the multi-reflection cell 30 includes both a White cell reflection mechanism and a Herriott cell reflection mechanism within the cell body 31. Specifically, the multi-reflection cell 30 further includes a pair of reflection mirrors 38 provided separately from the multi-reflection mechanism 32 within the cell body 31, such that the second light beam emitted from the second light source 21 is multiply reflected by the pair of reflection mirrors 38 before being emitted to the outside from the multi-reflection cell 30. In the fourth embodiment, the opposing direction of the field mirror 33, the first objective mirror 34, and the second objective mirror 35 is configured to be approximately perpendicular to the opposing direction of the pair of reflection mirrors 38. The second light source 21 emits second light from the side surface of the cell body 31, and the second light is introduced between the pair of reflecting mirrors 38 through a port P formed in the center of the reflecting mirrors. After multiple reflections, the second light is again guided outside the cell body 31. The second light that has passed through the multi-reflection cell 30 is then guided by the external mirror 24 to the shared photodetector CD.

[0085] According to the gas analyzer 100 of the fourth embodiment, it is possible to realize optical path lengths within the multi-reflection cell 30 that are suitable for FTIR and IRLAM, respectively, and to optimize the analytical accuracy of each principle.

[0086] Next, a gas analyzer 100 according to a fifth embodiment of the present invention will be described with reference to FIG. 14 . In the fifth embodiment, a single multi-reflection cell 30 is configured to simultaneously perform not only FTIR analysis and IRLAM analysis, but also NDIR analysis. That is, the gas analyzer 100 further includes a third light source unit 61 that emits infrared light of a predetermined wavelength, which is a third light, so that the third light passes through the multi-reflection cell 30 without being reflected therein, and a third light detection unit 62 that detects the third light that has passed through the multi-reflection cell 30. The third light source unit 61 and the third light detection unit 62 are arranged so as to sandwich the side surfaces of the cell body 31, and measure the absorbance of the third light independently of the first analysis mechanism 10 and the second analysis mechanism 20.

[0087] 15 , on both side surfaces of the cell body 31 on which the reflecting mirrors 33, 34, and 35 are not formed, there are formed a second light introduction window 613 that introduces the third light emitted from the third light source unit, and a second light outlet window 623 that outputs the third light that has passed through the cell body 31 to the outside of the cell body 31. The pair of second light introduction window 613 and second light outlet window 623 are formed in positions facing each other. In this embodiment, the third light source unit 61 and the third light detection unit 62 are each configured to form a light-collecting optical system.

[0088] Specifically, the third light source unit 61 includes a third light source 611, such as a thermal light source, an infrared LED, or an infrared laser, that emits infrared light, and a parabolic mirror 612 that is positioned forward in the light emission direction of the third light source 611 and facing the second light introduction window 612. The light emitted from the third light source 611 is reflected by the reflective surface of the parabolic mirror 612 and condensed into approximately parallel light, which is then guided to the second light introduction window 612. On the other hand, the third light detection unit 62 includes a parabolic mirror 622 that is positioned facing the second light guide window 623, and a third light detector 621 that detects infrared light. The light guided from the second light guide window 623 is reflected by the reflective surface of the parabolic mirror 622 and condensed on the detection surface of the third light detector 621. The third light detector 621 is preferably, for example, a four-element pyro detector. In this way, it becomes possible to measure up to three components with one third photodetector 621 .

[0089] 16, multiple pairs of third light source units 61 and third light detection units 62 may be provided. In this case, multiple pairs (two pairs in this case) of second light introduction windows 613 and second light extraction windows 623 may be formed on both side surfaces of the cell body 31 on which the reflecting mirrors 33, 34, and 35 are not formed. In this way, if a four-element pyro detector, for example, is used as the third light detector 621, it becomes possible to measure up to six or more components in NDIR analysis.

[0090] Such a device would enable the concentration of even more components to be measured, and would make it possible to, for example, perform interference correction based on the results of each measurement, or to examine the validity of the measurement.

[0091] Other embodiments will be described.

[0092] Although a shared photodetector is used in the third to fifth embodiments, it is also possible to provide a first photodetector and a second photodetector so as to individually detect the first light and the second light, as in the first embodiment.

[0093] The first and second principles are not limited to FTIR and IRLAM, but may be other combinations. For example, the first principle may be NDIR and the second principle may be IRLAM. Furthermore, the second principle is not limited to IRLAM, which is a type of LAS, but may be another LAS, such as TDLAS (Tunable Diode Laser Absorption Spectroscopy). In short, it is sufficient that each principle is different. Examples of principles using continuous light containing light of multiple wavenumbers that can be applied to the first or second principle of the present invention include ultraviolet / visible spectrophotometry, infrared spectrophotometry, Fourier transform infrared spectroscopy (FTIR), non-dispersive infrared spectroscopy (NDIR), and near-infrared spectroscopy (NIR). In addition to LAS, other principles using laser light that can be applied to the first or second principle include cavity ring-down spectroscopy (CRDS) and cavity-enhanced absorption spectroscopy (CEAS). Additionally, the first or second principle is not limited to measuring the intensity of light passing through a cell, but may also be, for example, photoacoustic spectroscopy (PAS), which detects an acoustic signal (pressure fluctuations of the sample gas) generated by irradiating the sample gas with light whose wavelength periodically changes, thereby analyzing the sample gas. More specifically, the principles may be combined, such as using FTIR or LAS as the first principle and PAS as the second principle.

[0094] The multi-reflection cell is not limited to those described in the respective embodiments and may have other configurations. For example, the multi-reflection cell may not only have a multi-reflection mechanism as a White cell, but may also have a multi-reflection mechanism as a Herriott cell. Furthermore, the pressure control mechanism for controlling the pressure of the sample gas in the cell body is not limited to the second embodiment and may also be provided in other embodiments. For example, when sample gas is simultaneously analyzed using the first and second principles, the pressure control mechanism may be configured to control the sample gas pressure to a pressure suitable for simultaneous analysis using each principle. For example, if optimal first and second pressures are set for each analysis using the first and second principles, respectively, the pressure control mechanism may control the sample gas pressure to a weighted average pressure of the first and second pressures. The weighting coefficient may be appropriately set so that each analysis can be performed with a predetermined accuracy, or it may simply be the average pressure of the first and second pressures.

[0095] The information processing device may be configured to calculate the instantaneous mass of each target component and the total amount of each target component emitted during the analysis period based on the concentration of each target component in the sample gas calculated by the concentration calculation unit of the gas analyzer and the flow rate of the sample gas or the target component.

[0096] In addition, various modifications of the embodiments and combinations of parts of the embodiments may be made as long as they do not go against the spirit of the present invention.

[0097] A gas analyzer is provided that can minimize the time difference in analysis results using a plurality of different principles and also enables analysis of the same sample.

[0098] 100: Gas analyzer 10: First analysis mechanism 11: First light source IF: Interferometer 12: Light-guiding mirror 13: Half mirror 14: Fixed mirror 15: Movable mirror 16: Incident side mirror 17: Exit side mirror 18: First photodetector 20: Second analysis mechanism 21: Second light source 22: Second photodetector 2H: Light passing hole 23: Small reflecting mirror 24: External mirror CD: Shared photodetector 30: Multiple reflection cell 31: Cell body 32: Multiple reflection mechanism 33: Field mirror 34: First objective mirror 35: Second objective mirror 36: Light introduction window 37: Light introduction window 38: Pair of reflecting mirrors P: Port COM: Information processing device 40: Concentration calculation unit 41 : FTIR section 42 : IRLAM section 50 : Optical path switching mechanism L1 : Measurement optical path L2 : Adjustment optical path 51 : Switching section 52, 53 : Mirror 54 : Adjustment fixed mirror 61 : Third light source 62 : Third photodetector

Claims

1. a multi-reflection cell into which a sample gas consisting of a plurality of components is introduced; a first analysis mechanism that causes a first light to enter the multi-reflection cell, detects the first light that has passed through the multi-reflection cell, and analyzes components of the sample gas according to a first principle; a second analysis mechanism that causes a second light to be incident into the multi-reflection cell, detects the second light that has passed through the multi-reflection cell, and analyzes the components of the sample gas according to a second principle different from the first principle.

2. 2. The gas analyzer of claim 1, wherein said first principle is Fourier transform infrared spectroscopy and said second principle is laser absorption spectroscopy.

3. The multi-reflection cell includes a cell body into whose internal space the sample gas is introduced, and a multi-reflection mechanism that is provided in the internal space and that multiple-reflects incident light and then emits the light to the outside, a light introduction window through which the first light is introduced into the cell body, and a light exit window through which the first light having passed through the multiple reflection mechanism is exited to the outside of the cell body are formed in the cell body; The multiple reflection mechanism is Field mirror and a first objective mirror disposed opposite the field mirror and on the light incident side of the multiple reflection mechanism; 3. A gas analyzer according to claim 1, further comprising: a second objective mirror disposed opposite said field mirror and on the light exit side of said multiple reflection mechanism.

4. The first analysis mechanism is A first light source that emits a first light that is a continuous light including light of a plurality of wave numbers; a first photodetector for detecting a first light passing through the multi-reflection cell; The second analysis mechanism is a second light source that emits a second light, which is a laser beam; 4. A gas analyzer as claimed in claim 3, further comprising a second photodetector for detecting a second light beam passing through said multi-reflection cell.

5. 5. The gas analyzer according to claim 4, wherein the second analysis mechanism is configured such that the second light emitted from the second light source is introduced into the cell body through the light introducing window, and the second light emitted from the light exit window is detected by the second photodetector.

6. 5. The gas analyzer according to claim 4, wherein the second analysis mechanism is configured such that the second light emitted from the second light source is introduced into the cell body through the light outlet window, and the second light emitted from the light outlet window is detected by the second photodetector.

7. The first analytical mechanism, an interferometer into which the light emitted from the first light source is incident; an incident side mirror that reflects the first light that has passed through the interferometer and causes the first light to enter the light introducing window; an exit side mirror that reflects the first light emitted from the light guide window to cause the first light to be incident on the first photodetector, 5. The gas analyzer according to claim 4, wherein the entrance side mirror and the exit side mirror are formed with light passing holes for passing the second light.

8. The first analysis mechanism is A first light source that emits a first light that is a continuous light including light of a plurality of wave numbers; an interferometer into which the light emitted from the first light source is incident, The second analysis mechanism is a second light source that emits a second light that is a laser beam; 4. The gas analyzer according to claim 3, wherein the first light or the second light having passed through the multi-reflection cell is detected by a single common photodetector.

9. a concentration calculation unit that calculates a concentration of a component in the sample gas based on an output of the common photodetector, the concentration calculation unit calculates the concentration of one or more components in the sample gas by Fourier transform infrared spectroscopy while the movable mirror of the interferometer is moving; 9. The gas analyzer of claim 8, further configured to calculate the concentration of one or more components in the sample gas by laser absorption spectroscopy while the moving mirror is stationary.

10. 10. The gas analyzer according to claim 9, further comprising a pressure control mechanism for controlling the pressure of the sample gas in the multi-reflection cell in accordance with a principle used in the concentration calculation section.

11. 11. The gas analyzer according to claim 10, wherein the pressure control mechanism is configured to lower the pressure of the sample gas while the movable mirror is stationary compared to when the movable mirror is moving.

12. 8. The gas analyzer according to claim 7, further comprising an optical path switching mechanism that switches an optical path between a measurement optical path in which the second light emitted from the second light source bypasses the interferometer and enters the multi-reflection cell, and an adjustment optical path in which the second light emitted from the second light source enters the interferometer.

13. The multi-reflection cell is a pair of reflecting mirrors provided separately from the multiple reflecting mechanism within the cell body; 5. The gas analyzer according to claim 4, wherein the second light emitted from the second light source is multiply reflected by the pair of reflecting mirrors and then emitted to the outside from the multi-reflection cell.

14. a third light source that emits a third light so as to pass through the multi-reflection cell without being reflected in the multi-reflection cell; 5. The gas analyzer according to claim 4, further comprising a third photodetector for detecting a third light beam that has passed through the multi-reflection cell.