WO2014112502A1 - Laser gas analysis device - Google Patents

Laser gas analysis device Download PDF

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Publication number
WO2014112502A1
WO2014112502A1 PCT/JP2014/050527 JP2014050527W WO2014112502A1 WO 2014112502 A1 WO2014112502 A1 WO 2014112502A1 JP 2014050527 W JP2014050527 W JP 2014050527W WO 2014112502 A1 WO2014112502 A1 WO 2014112502A1
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gas
wavelength
laser
absorption
light
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PCT/JP2014/050527
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French (fr)
Japanese (ja)
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康彦 光本
力 矢田部
平田　隆昭
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横河電機株式会社
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/39—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using tunable lasers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
    • G01N21/3504—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing gases, e.g. multi-gas analysis

Definitions

  • the present invention relates to a laser gas analyzer, and more particularly to a laser gas analyzer that can efficiently measure a hydrocarbon multicomponent mixed gas.
  • Laser gas analyzers using the TDLAS (Tunable Diode Laser Absorption Spectroscopy) method only irradiate light from a wavelength tunable semiconductor laser to the measurement target components such as high temperature and corrosive gas. Even in the case of a concentration of 1, there is an advantage that the component selectivity is high without being interfered by other components, and measurement can be performed in real time at high speed without contact.
  • TDLAS Tunable Diode Laser Absorption Spectroscopy
  • FIG. 7 is a block diagram showing an example of a conventional laser gas analyzer using the TDLAS method, in which a light source unit including a semiconductor laser that irradiates a measurement laser beam into a measurement gas atmosphere, and measurement of the measurement gas atmosphere It comprises a light receiving element that detects the measurement laser beam that has passed through the space, and a detection unit that includes an arithmetic processing unit that processes the output signal of this light receiving element.
  • a light source unit including a semiconductor laser that irradiates a measurement laser beam into a measurement gas atmosphere, and measurement of the measurement gas atmosphere It comprises a light receiving element that detects the measurement laser beam that has passed through the space, and a detection unit that includes an arithmetic processing unit that processes the output signal of this light receiving element.
  • the laser gas analyzer shown in FIG. 7 uses a semiconductor laser having a very narrow oscillation wavelength spectrum line width for the light absorption spectrum inherent to the molecule due to the vibration / rotational energy transition of the molecule to be measured existing in the infrared to near infrared region. To measure.
  • the absorption spectra unique to most molecules such as O 2 , NH 3 , H 2 O, CO, CO 2 are in the infrared to near-infrared region, and are measured by measuring the amount of light absorption (absorbance) at a specific wavelength. The concentration of the component can be calculated.
  • the semiconductor laser 11 provided in the light source unit 10 irradiates and outputs a measurement laser beam in the atmosphere of the measurement gas 20.
  • the laser light output from the semiconductor laser 11 has a very narrow oscillation wavelength spectrum line width, and the oscillation wavelength can be changed by changing the laser temperature or drive current. Therefore, only one of the absorption peaks of the absorption spectrum can be measured.
  • the absorption peak that is not affected by the interference gas can be selected, the wavelength selectivity is high, and it is not affected by other interference components. Therefore, the process gas is removed without removing the interference gas in the previous stage of measurement. Can be measured directly.
  • the spectrum shape includes the measurement gas temperature, the measurement gas pressure, It changes due to the broadening phenomenon of spectrum due to coexisting gas components. For this reason, the actual process measurement accompanied by these environmental variations requires correction.
  • the apparatus shown in FIG. 7 uses a spectrum area method in which the spectrum area is obtained by scanning the oscillation wavelength of the semiconductor laser 11 and measuring the absorption spectrum, and converting the spectrum area into the component concentration.
  • the peak height method for determining the measurement component from the peak height of the absorption spectrum or the wavelength scan signal is modulated and the PP (peak-to-peak) value of the frequency modulation waveform is double that frequency.
  • the 2f method for obtaining the concentration of the measured component from the above is used, but these are easily affected by fluctuations in temperature, pressure, coexisting gas components, and the like.
  • the spectrum area is not affected by changes due to the difference in the coexisting gas components in principle (the spectrum area is almost constant regardless of the coexisting gas components), and the spectrum area is also in principle against pressure fluctuations. Shows a linear change.
  • the above three fluctuation factors (temperature, pressure, coexisting gas components) all affect nonlinearly, and when these fluctuation factors coexist, correction is difficult.
  • the linear correction for the gas pressure fluctuation and the non-linear correction for the gas temperature fluctuation can be performed, and an accurate correction can be realized.
  • the measurement laser light that has passed through the atmosphere of the measurement gas 20 is received by the light receiving element 31 provided in the detection unit 30 and converted into an electrical signal.
  • the output signal of the light receiving element 31 is adjusted to an appropriate amplitude level via the variable gain amplifier 32, input to the A / D converter 33, and converted into a digital signal.
  • the integration is performed a predetermined number of times (for example, several hundred to several thousand times) between the integrator 34 and the memory 35, and the memory 35 is supplied. Is repeated, noise included in the measurement signal is removed and the data is smoothed, and then input to the CPU 36.
  • the CPU 36 performs arithmetic processing such as measurement gas concentration analysis based on the measurement signal from which noise has been removed, and an amplifier when the amplitude level of the output signal of the light receiving element 31 is not appropriate as the input level of the A / D converter 33. 32 gain adjustment is performed.
  • Non-Patent Document 1 describes the measurement principle, features, and specific measurement examples of a laser gas analyzer that applies wavelength-tunable semiconductor laser spectroscopy.
  • the laser gas analyzer configured as shown in FIG. 7 is limited to the measurement of a single component because the wavelength variable range of the semiconductor laser 11 is narrow.
  • hydrocarbons other than CH 4 when measuring a hydrocarbon multi-component gas mixture, hydrocarbons other than CH 4 have a complicated molecular structure and a large number of absorption lines overlap, so that broad absorption exists in the base other than sharp absorption lines. There is no wavelength. For this reason, it is impossible to correct the baseline fluctuation due to the change in the transmittance of the gas cell itself.
  • the spectrum width of aromatic hydrocarbon species having a large carbon number, alkylbenzene, etc. is several tens nm or more, whereas methane having a small carbon number has a narrow spectrum width of about 0.1 nm. Therefore, the spectrum broadening effect can be obtained by analyzing the concentration of mixed hydrocarbons of a gas with a narrow spectral width such as methane and a gas with a wide spectral width such as aromatic hydrocarbon species or alkylbenzene by the statistical method of the prior art.
  • the concentration error of a gas having no absorption peak increases due to the spectral error of a gas having a narrow spectral width due to a slight wavelength error.
  • a narrow gas spectrum such as a methane peak
  • the spectrum shape changes greatly due to the broadening effect, and the absorption error due to wavelength changes is large, so that the spectrum error due to wavelength errors is large.
  • the concentration of methane gas is sufficiently high compared to other gases
  • the spectral error due to such spectral shape change and wavelength error at the methane peak becomes so large that it cannot be ignored compared to other gas spectra. This is an error in measuring the concentration of gases other than methane.
  • the present invention solves these problems, and its purpose is to use a wavelength tunable laser having a wide wavelength tunable width as a laser light source, and remove a sharp peak portion of a mixed gas (for example, methane) for concentration detection.
  • a statistical method is used to realize a laser gas analyzer that can measure a hydrocarbon having a large spectral characteristic at the same time as a hydrocarbon having a small spectral characteristic with high accuracy. Even if the gas to be measured is a mixed gas of a gas having a small absorption spectrum characteristic and a gas having a large absorption spectrum characteristic, the concentration of the gas having a small absorption spectrum characteristic in the measurement gas can be accurately determined.
  • An object is to realize a laser gas analyzer capable of measuring.
  • a wavelength tunable laser having a wide wavelength tunable width a light irradiating means for irradiating the gas to be measured with the output light of the wavelength tunable laser as measurement light, and absorption related to the measurement light transmitted through the gas to be measured
  • a laser gas analyzer configured with a data processing unit for obtaining an absorption spectrum of the gas to be measured based on a signal and obtaining a concentration of each component based on a statistical method
  • the data processing unit determines the component concentration of a gas having no sharp absorption peak, and has a wavelength at which no sharp absorption peak of another gas component exists in an absorption spectrum obtained by sweeping a relatively wide wavelength range. The absorption spectrum of the region is used.
  • a wavelength tunable laser having a wide wavelength tunable width a light branching means for branching the output light of the wavelength tunable laser into measurement light and reference light, and irradiating the measurement light with the measurement light, and the reference light
  • a data processing unit for obtaining an absorption spectrum of the measurement gas based on the reference signal obtained and an absorption signal related to the measurement light transmitted through the measurement gas, and obtaining a concentration of each component based on a statistical method.
  • the data processing unit determines the component concentration of a gas having no sharp absorption peak, and has a wavelength at which no sharp absorption peak of another gas component exists in an absorption spectrum obtained by sweeping a relatively wide wavelength range. The absorption spectrum of the region is used.
  • the data processing unit An absorption line wavelength data storage unit for storing absorption line wavelength data of the measured gas;
  • the reference signal and the absorption signal are input and the absorption line wavelength data storage unit is connected, and wavelength calibration means for calibrating the wavelength of the absorption spectrum based on the absorption line wavelength data, the reference signal, and the absorption signal;
  • Wavelength region selection means for selecting a wavelength region of an optical signal used for measuring the concentration of the gas to be measured;
  • a concentration detecting means for determining the concentration of the gas to be measured based on a statistical model constructed in advance.
  • the wavelength calibration means compares the absorption line of the calibration gas with a known absorption line.
  • a laser gas analyzer for determining the concentration of a component contained in a gas to be measured which is a mixed gas
  • a tunable laser that sweeps a relatively wide wavelength range
  • An optical system that transmits at least part of the output light of the wavelength tunable laser as measurement light to the gas to be measured and guides the measurement light after transmission to the light receiving element
  • a data processing unit for obtaining an absorption spectrum of the gas to be measured based on the output of the light receiving element, and obtaining a concentration of each component based on a statistical method; With The data processing unit obtains an absorption spectrum in a wavelength region in which no sharp absorption peak exists in the absorption spectrum of the measurement gas when obtaining the concentration of a gas having a small absorption spectrum characteristic among the gases contained in the measurement gas. It is characterized by using.
  • the statistical method is characterized in that the concentration of each gas is obtained from the spectrum of the gas to be measured based on a statistical model in which the relationship between the spectrum and the concentration is preliminarily constructed based on a gas spectrum having a known concentration. .
  • the statistical model includes at least one of an outside air temperature, a gas temperature, and a gas pressure as a parameter.
  • the gas to be measured is a hydrocarbon mixed gas mixture
  • the gas having a large feature in the absorption spectrum is methane
  • the gas having a small characteristic in the absorption spectrum is a hydrocarbon other than methane.
  • An optical branching unit that divides at least a part of the light emitted from the wavelength tunable laser into two of measurement light and reference light; A gas cell into which the measurement gas is introduced and the measurement light is incident; A first light receiving element on which light emitted from the gas cell is incident; A second light receiving element on which the reference light is incident,
  • the distance from the light branching means to the incident end face of the gas cell is L1, the distance from the emission end face of the gas cell to the first light receiving element is L2, and the distance from the light branching means to the second light receiving element is L3.
  • concentration of each gas contained in a multicomponent mixed gas can be measured comparatively easily using a statistical method.
  • a wavelength variable laser having a wide wavelength variable width is used as a laser light source, and an absorption spectrum in a wavelength region where there is no sharp absorption peak of the gas to be measured is used, so that the gas to be measured has small absorption spectrum characteristics. Even if it is a mixed gas of a gas and a gas having a large absorption spectrum characteristic, it is possible to realize a laser gas analyzer that can accurately measure the concentration of a gas having a small absorption spectrum characteristic in the gas to be measured.
  • FIG. 2 is a differential spectrum diagram of 1% nC 4 H 10 spectrum and CH 4 having a concentration of 80%. It is a block diagram which shows the other Example of this invention. It is a block diagram which shows an example of the conventional laser gas analyzer.
  • FIG. 1 is a block diagram showing an embodiment of a laser gas analyzer according to the present invention.
  • a wavelength tunable laser 101 generates measurement light of an absorption spectrum of a gas to be measured, and is connected to an oscillation wavelength control circuit 102 that controls the oscillation wavelength.
  • the oscillation wavelength control circuit 102 sweeps the oscillation wavelength of the wavelength tunable laser 101 within a range of 1.67 to 1.72 ⁇ m, for example.
  • the light emitted from the wavelength tunable laser 101 is converted into parallel light by the lens 103, passes through the isolator 104, and is divided into two parallel light of measurement light and reference light by the beam splitter 105.
  • One of the parallel lights divided into two by the beam splitter 105 is incident on a gas cell 106 into which a gas to be measured is introduced as measurement light, collected by a lens 107, incident on a photodiode 108, and converted into an electrical signal. And input to one input terminal of the wavelength calibration means 111.
  • the other parallel light is condensed by the lens 109 and incident on the photodiode 110 as reference light, converted into an electric signal, and input to the other input terminal of the wavelength calibration means 111.
  • the absorption spectrum of the gas to be measured is obtained from the measurement signal based on the measurement light of the gas and the reference signal based on the reference light of the output intensity.
  • a wavelength region selection unit 112 is connected to the wavelength calibration unit 111, and a concentration detection unit 113 is connected to the wavelength region selection unit 112.
  • FIG. 2 is a block diagram showing a specific example of a laser gas analyzer based on the present invention for measuring hydrocarbon multicomponents, and the same reference numerals are given to the parts common to FIG.
  • an absorption line wavelength data storage unit 114 is connected to the wavelength calibration unit 111
  • a use wavelength data storage unit 115 is connected to the wavelength region selection unit 112
  • a statistical model storage unit 116 is connected to the concentration detection unit 113. It is connected.
  • MEMS-VCSEL is used as the wavelength tunable laser 101 (light source) and that the laser beam output from the wavelength tunable laser 101 is three beams by the beam splitter 117 after the isolator 104. And the third light is incident on the photodiode 120 through the wavelength calibration cell 118 and the lens 119 in which the reduced pressure CH 4 is enclosed. Note that the output signal of the photodiode 120 is also input to the wavelength calibration means 111.
  • FIG. 3 is a spectrum example of a chain saturated hydrocarbon to be measured in this example.
  • A is CH 4 (methane)
  • B is C 2 H 6 (ethane)
  • C is C 3 H 8 (propane)
  • D is iC 4 H 10 (isobutane)
  • E is nC 4 H 10 (normal butane)
  • F is iC 5 H 12 (isopentane)
  • G is C 5 H 12 (normal pentane).
  • CH 4 , C 2 H 6 , C 3 H 8 , and iC 4 H 10 have sharp peaks, but there are no sharp peaks in other gas spectra. Is small. In order to perform highly accurate concentration detection from a gas spectrum having a small feature, it is effective to perform statistical processing using an absorption spectrum obtained by sweeping a wide wavelength.
  • MEMS-VCSEL is a semiconductor laser and can be swept in a relatively wide wavelength range of about 50 nm, sufficient absorption spectrum information can be obtained, and highly accurate concentration detection can be performed by a statistical method.
  • FIG. 4 is a flowchart for explaining the flow of concentration measurement operation by the apparatus according to the present invention.
  • photodiode output data and database data are first read (step S1).
  • the wavelength calibration unit 111 calibrates the wavelength of the absorption spectrum of the gas to be measured based on the position of the absorption line of CH 4 in the calibration signal and the absorption line wavelength data stored in the absorption line wavelength data storage unit 114 (step S2).
  • the absorbance is proportional to the concentration (step S3).
  • I 0 is the incident intensity to the measurement gas cell
  • I is the transmitted light intensity from the measurement gas cell.
  • S1 is a reference signal
  • S2 is a measurement signal
  • T ( ⁇ ) is an apparatus function (transmittance of the gas cell 106 to be measured, wavelength dependence of the branching ratio of the beam splitter 117).
  • the constant term includes a term corresponding to the branching ratio of the beam splitter.
  • the concentration detection means 113 Statistical methods such as multivariate analysis are used as the concentration detection means 113 (step S4).
  • the statistical method means that a statistical model of the relationship between the spectrum and the concentration is built in advance based on the gas spectrum with a known concentration, and when the spectrum of the gas to be measured is acquired, the statistical model built in advance is used. Based on this, the concentration of each gas is obtained. For example, the PLS regression method is well known. In constructing a statistical model in advance, highly accurate concentration detection is possible by measuring as uniformly as possible within the measurement target concentration range.
  • the wavelength region selection unit 112 When concentration detection is performed from a gas spectrum, it is common to use a wavelength band having a large spectral feature such as a peak. However, it may be better not to use an absorption peak when the absorption by each gas is significantly different.
  • FIG. 5 shows a 1% nC 4 H 10 spectrum and a derivative spectrum of CH 4 at a concentration of 80%.
  • the differential spectrum indicates a difference from a spectrum having a wavelength different by 1 pm, and indicates a magnitude of a spectrum error caused by a wavelength error of 1 pm.
  • the influence of the CH 4 wavelength error is large, and when a 1 pm wavelength error occurs, a spectral error larger than the nC 4 H 10 spectrum occurs in the wavelength band where the CH 4 peak exists.
  • MEMS-VCSEL has sufficient reliability as an industrial instrument that combines a MEMS movable mirror without mechanical moving parts and a semiconductor laser that has been proven to be highly reliable in optical communications, and has a wide wavelength tunable range.
  • a wavelength tunable laser and performing wavelength sweeping within a wavelength range of 1.67 to 1.72 ⁇ m where absorption lines of various hydrocarbons exist, an absorption spectrum of a hydrocarbon multicomponent mixed gas can be measured.
  • An accurate absorption spectrum can be obtained by performing wavelength calibration of the absorption spectrum of the hydrocarbon multi-component mixed gas obtained using the CH 4 absorption line and wavelength table.
  • TDLAS that can be measured in real time has a narrow wavelength variable width of the light source, and is mainly limited to measurement of a single component.
  • the absorption spectrum of multi-component mixed gas is achieved by using MEMS-VCSEL, which has no mechanical moving parts and has high reliability required as an industrial instrument and can change the wavelength in a wide wavelength range as a light source.
  • Industrial TDLAS can be realized.
  • a TDLAS capable of analyzing a hydrocarbon multi-component gas mixture can be realized.
  • real-time measurement can be realized by using TDLAS.
  • the moisture spectrum in the air may become an obstacle to concentration detection, but by appropriately selecting the optical path lengths L1 to L3 of each part as shown in FIG. The influence of moisture in the air can be eliminated.
  • FIG. 6 is a block diagram showing another embodiment of the present invention, and the same reference numerals are given to portions common to FIG.
  • the distance from the center of the beam splitter 105 to the incident end face of the gas cell 106 is L1
  • the distance from the exit end face of the gas cell 106 to the incident face of the photodiode 108 is L2
  • the center of the beam splitter 105 is connected to the photodiode 110.
  • the distance to the incident surface is L3
  • the optical system as shown in FIG. 6 may be housed in the casing and purged with a gas that does not absorb in the infrared wavelength region such as nitrogen.
  • the light source a fiber output, it is possible to prevent the optical axis alignment from shifting due to the mounting or replacement of the wavelength tunable laser 101 which is the light source.
  • the CH 4 concentration is detected using the CH 4 peak, but the concentration detection method at this time is not limited to a statistical method, and an area method may be used.
  • a light branching means for branching the output light of the wavelength tunable laser into measurement light and reference light and irradiating the measurement gas with the measurement light, so that the data processing unit and reference signal related to the reference light
  • the reference signal is not used. Simple measurement is possible.
  • a tunable laser having a wide wavelength tunable width is used as a laser light source, and a statistical method is used for concentration detection by removing a sharp peak portion of a gas having a narrow spectral width such as methane. Therefore, it is possible to realize a laser gas analyzer that can measure hydrocarbons having large spectral characteristics and hydrocarbons having small spectral characteristics with high accuracy, and is effective for direct measurement of various process gases.

Abstract

The present invention implements a laser gas analysis device capable of measuring, with high accuracy, even hydrocarbon with a small spectral feature at the same time as hydrocarbon with a large spectral feature using a wavelength-variable laser with a wide wavelength-variable width as a laser light source and using a statistical method in which a sharp peak portion of methane is removed in concentration detection. A laser gas analysis device is configured from: a wavelength-variable laser which has a wide wavelength-variable width; a light irradiation means which irradiates gas to be measured with output light from the wavelength-variable laser as measurement light; and a data processing unit which, on the basis of an absorption signal related to the measurement light transmitted through the gas to be measured, finds the absorption spectrum of the gas to be measured and finds the concentration of each component by a statistical method. The laser gas analysis device is characterized in that the data processing unit uses, among absorption spectra obtained by sweeping a relatively wide wavelength range, an absorption spectrum in a wavelength region in which the sharp absorption peaks of other gas components are not present when a component concentration of gas that has no sharp absorption peak is found.

Description

レーザガス分析装置Laser gas analyzer
　本発明は、レーザガス分析装置に関し、詳しくは、炭化水素多成分混合ガスの測定が効率よく行えるレーザガス分析装置に関する。 The present invention relates to a laser gas analyzer, and more particularly to a laser gas analyzer that can efficiently measure a hydrocarbon multicomponent mixed gas.
　ＴＤＬＡＳ(Tunable Diode Laser Absorption Spectroscopy；波長可変半導体レーザ吸収分光)法を用いたレーザガス分析計は、測定対象に波長可変半導体レーザからの光を照射するだけで、高温や腐食性ガスなどの測定対象成分の濃度でも、他の成分の干渉を受けることなく成分選択性が高く、非接触で、高速にリアルタイムで測定できるという利点がある。 Laser gas analyzers using the TDLAS (Tunable Diode Laser Absorption Spectroscopy) method only irradiate light from a wavelength tunable semiconductor laser to the measurement target components such as high temperature and corrosive gas. Even in the case of a concentration of 1, there is an advantage that the component selectivity is high without being interfered by other components, and measurement can be performed in real time at high speed without contact.
　図７はＴＤＬＡＳ法を用いた従来のレーザガス分析装置の一例を示すブロック図であって、測定ガス雰囲気中に向けて測定用レーザ光を照射する半導体レーザを含む光源ユニットと、測定ガス雰囲気の測定空間を透過した測定用レーザ光を検出する受光素子およびこの受光素子の出力信号を処理する演算処理部を含む検出ユニットとで構成されている。 FIG. 7 is a block diagram showing an example of a conventional laser gas analyzer using the TDLAS method, in which a light source unit including a semiconductor laser that irradiates a measurement laser beam into a measurement gas atmosphere, and measurement of the measurement gas atmosphere It comprises a light receiving element that detects the measurement laser beam that has passed through the space, and a detection unit that includes an arithmetic processing unit that processes the output signal of this light receiving element.
　図７に示すレーザガス分析装置は、赤外から近赤外領域に存在する測定対象成分分子の振動・回転エネルギー遷移による分子固有の光吸収スペクトルを、極めて発振波長スペクトル線幅の狭い半導体レーザを用いて測定する。Ｏ２、ＮＨ３、Ｈ２Ｏ、ＣＯ、ＣＯ２など大半の分子の分子特有の吸収スペクトルは赤外～近赤外領域にあり、特定波長における光吸収量（吸光度）を測定することで対象成分の濃度を算出できる。 The laser gas analyzer shown in FIG. 7 uses a semiconductor laser having a very narrow oscillation wavelength spectrum line width for the light absorption spectrum inherent to the molecule due to the vibration / rotational energy transition of the molecule to be measured existing in the infrared to near infrared region. To measure. The absorption spectra unique to most molecules such as O 2 , NH 3 , H 2 O, CO, CO 2 are in the infrared to near-infrared region, and are measured by measuring the amount of light absorption (absorbance) at a specific wavelength. The concentration of the component can be calculated.
　図７において、光源ユニット１０に設けられている半導体レーザ１１は、測定用レーザ光を測定ガス２０の雰囲気中に照射出力する。この半導体レーザ１１が出力するレーザ光は、発振波長スペクトル線幅が極めて狭く、レーザ温度や駆動電流を変えることで発振波長を変更できるので、吸収スペクトルの各吸収ピークの１本のみを測定できる。 7, the semiconductor laser 11 provided in the light source unit 10 irradiates and outputs a measurement laser beam in the atmosphere of the measurement gas 20. The laser light output from the semiconductor laser 11 has a very narrow oscillation wavelength spectrum line width, and the oscillation wavelength can be changed by changing the laser temperature or drive current. Therefore, only one of the absorption peaks of the absorption spectrum can be measured.
　したがって、干渉ガスの影響を受けない吸収ピークを選定することができ、波長選択性が高く、他干渉成分の影響を受けることがないため、測定の前段階における干渉ガスを除去することなくプロセスガスを直接測定できる。 Therefore, the absorption peak that is not affected by the interference gas can be selected, the wavelength selectivity is high, and it is not affected by other interference components. Therefore, the process gas is removed without removing the interference gas in the previous stage of measurement. Can be measured directly.
　半導体レーザ１１の発振波長を測定成分の１本の吸収線の近傍でスキャンすることにより、干渉成分と重ならない正確なスペクトルの測定が行えるが、そのスペクトル形状は、測定ガス温度、測定ガス圧力、共存ガス成分などによるスペクトルのブロードニング（Broadening）現象により変化する。このため、これらの環境変動を伴う実プロセス測定では、その補正が必要になる。 By scanning the oscillation wavelength of the semiconductor laser 11 in the vicinity of one absorption line of the measurement component, an accurate spectrum that does not overlap with the interference component can be measured. The spectrum shape includes the measurement gas temperature, the measurement gas pressure, It changes due to the broadening phenomenon of spectrum due to coexisting gas components. For this reason, the actual process measurement accompanied by these environmental variations requires correction.
　そこで、図７の装置では、半導体レーザ１１の発振波長をスキャンして吸収スペクトルを測定することによりスペクトル面積を求め、そのスペクトル面積から成分濃度に変換するスペクトル面積法を用いている。 Therefore, the apparatus shown in FIG. 7 uses a spectrum area method in which the spectrum area is obtained by scanning the oscillation wavelength of the semiconductor laser 11 and measuring the absorption spectrum, and converting the spectrum area into the component concentration.
　他のレーザガス分析装置では、吸収スペクトルのピーク高さから測定成分を求めるピーク高さ法や波長スキャン信号を変調してその周波数の２倍周波数変調波形のＰ－Ｐ（ピーク・ツー・ピーク）値から測定成分の濃度を求める２ｆ法が使われているが、これらは、温度、圧力、共存ガス成分の変動などにより大きな影響を受けやすい。 In other laser gas analyzers, the peak height method for determining the measurement component from the peak height of the absorption spectrum or the wavelength scan signal is modulated and the PP (peak-to-peak) value of the frequency modulation waveform is double that frequency. The 2f method for obtaining the concentration of the measured component from the above is used, but these are easily affected by fluctuations in temperature, pressure, coexisting gas components, and the like.
　これに対し、スペクトル面積は原理的に共存ガス成分の違いによる変化の影響を受けることはなく（スペクトルの面積は共存ガス成分によらずほとんど一定）、圧力変動に対してもスペクトル面積は原理的に線形変化を示す。 On the other hand, the spectrum area is not affected by changes due to the difference in the coexisting gas components in principle (the spectrum area is almost constant regardless of the coexisting gas components), and the spectrum area is also in principle against pressure fluctuations. Shows a linear change.
　ピーク高さ法や２ｆ法では、上記３変動要因（温度、圧力、共存ガス成分）が全て非線形に影響し、これら変動要因が共存する場合は補正が困難であるが、スペクトル面積法によれば、ガス圧力変動に対する線形補正とガス温度変動に対する非線形補正を行うことができ、正確な補正を実現できる。 In the peak height method and the 2f method, the above three fluctuation factors (temperature, pressure, coexisting gas components) all affect nonlinearly, and when these fluctuation factors coexist, correction is difficult. The linear correction for the gas pressure fluctuation and the non-linear correction for the gas temperature fluctuation can be performed, and an accurate correction can be realized.
　測定ガス２０の雰囲気中を通過した測定用レーザ光は検出ユニット３０に設けられている受光素子３１で受光され、電気信号に変換される。 The measurement laser light that has passed through the atmosphere of the measurement gas 20 is received by the light receiving element 31 provided in the detection unit 30 and converted into an electrical signal.
　受光素子３１の出力信号はゲイン可変のアンプ３２を介して適切な振幅レベルに調整されてＡ／Ｄ変換器３３に入力され、デジタル信号に変換される。 The output signal of the light receiving element 31 is adjusted to an appropriate amplitude level via the variable gain amplifier 32, input to the A / D converter 33, and converted into a digital signal.
　Ａ／Ｄ変換器３３の出力データについて、半導体レーザ１１の波長のスキャンに同期して、積算器３４とメモリ３５との間で所定回数（たとえば数百～数千回）の積算とメモリ３５への格納が繰り返されて測定信号に含まれるノイズが除去されてデータが平滑化された後、ＣＰＵ３６に入力される。 With respect to the output data of the A / D converter 33, in synchronization with the wavelength scan of the semiconductor laser 11, the integration is performed a predetermined number of times (for example, several hundred to several thousand times) between the integrator 34 and the memory 35, and the memory 35 is supplied. Is repeated, noise included in the measurement signal is removed and the data is smoothed, and then input to the CPU 36.
　ＣＰＵ３６は、ノイズが除去された測定信号に基づき測定ガスの濃度解析などの演算処理を行うとともに、受光素子３１の出力信号の振幅レベルがＡ／Ｄ変換器３３の入力レベルとして適切でない場合にアンプ３２のゲイン調整を行う。 The CPU 36 performs arithmetic processing such as measurement gas concentration analysis based on the measurement signal from which noise has been removed, and an amplifier when the amplitude level of the output signal of the light receiving element 31 is not appropriate as the input level of the A / D converter 33. 32 gain adjustment is performed.
　非特許文献１には、波長可変半導体レーザ分光を応用したレーザガス分析計の測定原理とその特長および具体的な測定事例について記載されている。 Non-Patent Document 1 describes the measurement principle, features, and specific measurement examples of a laser gas analyzer that applies wavelength-tunable semiconductor laser spectroscopy.
　しかし、図７に示すような構成のレーザガス分析装置では、半導体レーザ１１の波長可変範囲が狭いことから、単一成分の測定に限られている。 However, the laser gas analyzer configured as shown in FIG. 7 is limited to the measurement of a single component because the wavelength variable range of the semiconductor laser 11 is narrow.
　たとえば炭化水素多成分混合ガスを測定する場合、ＣＨ４以外の炭化水素では分子構造が複雑で多数の吸収線が重なり合うことから、鋭い吸収線以外にブロードな吸収がベースに存在するため、吸収が無い波長は存在しない。このため、ガスセル自体の透過率の変化などによるベースライン変動を補正することができない。 For example, when measuring a hydrocarbon multi-component gas mixture, hydrocarbons other than CH 4 have a complicated molecular structure and a large number of absorption lines overlap, so that broad absorption exists in the base other than sharp absorption lines. There is no wavelength. For this reason, it is impossible to correct the baseline fluctuation due to the change in the transmittance of the gas cell itself.
　また、炭化水素多成分混合ガスを測定する場合には、ＣＨ４以外の炭化水素のブロードな吸収が重なり合った吸収スペクトルから各炭化水素の濃度（ガス分圧）を求める手法が必要となる。 Moreover, when measuring a hydrocarbon multicomponent mixed gas, a technique for obtaining the concentration (gas partial pressure) of each hydrocarbon from an absorption spectrum in which broad absorptions of hydrocarbons other than CH 4 overlap is necessary.
　このような手法として、従来から統計的手法（ケモメトリクス）が知られている。
　ところが、炭素数が大きい芳香族炭化水素種やアルキルベンゼンなどのスペクトル幅は数１０ｎｍ以上であるのに対し、炭素数が小さいメタンはスペクトル幅が０．１ｎｍ程度と狭い。そのため、メタンのようなスペクトル幅が狭いガスと芳香族炭化水素種やアルキルベンゼンなどのスペクトル幅が広いガスとの混合炭化水素の濃度分析を従来技術の統計的方法で行うと、スペクトルのブロードニング効果あるいはわずかな波長誤差によりスペクトル幅が狭いガスのスペクトル誤差により、吸収ピークを持たないガスの濃度誤差が大きくなる。
　メタンのピークのように幅が狭いガススペクトルでは、ブロードニング効果によるスペクトル形状の変化は大きく、また波長変化による吸収の変化が大きいことから波長誤差によるスペクトル誤差が大きい。特にメタンガスの濃度が他のガスに比べて十分に大きい場合、このようなメタンピーク部分でのスペクトル形状の変化や波長誤差によるスペクトル誤差が、他のガスのスペクトルと比較して無視できないほど大きくなり、メタン以外のガスの濃度測定誤差となる。 As such a method, a statistical method (chemometrics) has been conventionally known.
However, the spectrum width of aromatic hydrocarbon species having a large carbon number, alkylbenzene, etc. is several tens nm or more, whereas methane having a small carbon number has a narrow spectrum width of about 0.1 nm. Therefore, the spectrum broadening effect can be obtained by analyzing the concentration of mixed hydrocarbons of a gas with a narrow spectral width such as methane and a gas with a wide spectral width such as aromatic hydrocarbon species or alkylbenzene by the statistical method of the prior art. Alternatively, the concentration error of a gas having no absorption peak increases due to the spectral error of a gas having a narrow spectral width due to a slight wavelength error.
In a narrow gas spectrum such as a methane peak, the spectrum shape changes greatly due to the broadening effect, and the absorption error due to wavelength changes is large, so that the spectrum error due to wavelength errors is large. In particular, when the concentration of methane gas is sufficiently high compared to other gases, the spectral error due to such spectral shape change and wavelength error at the methane peak becomes so large that it cannot be ignored compared to other gas spectra. This is an error in measuring the concentration of gases other than methane.
　本発明は、これらの課題を解決するものであって、その目的は、レーザ光源として広い波長可変幅の波長可変レーザを用い、濃度検出にあたっては混合ガス（たとえばメタン）の鋭いピーク部分を外した統計的手法を用いてスペクトルの特徴が大きい炭化水素と同時にスペクトルの特徴が小さい炭化水素も高精度に測定できるレーザガス分析装置を実現することにある。
　本発明は、被測定ガスが吸収スペクトルの特徴が小さいガスと吸収スペクトルの特徴が大きなガスとの混合ガスであっても、被測定ガス中の吸収スペクトルの特徴が小さいガスの濃度を高精度に測定できるレーザガス分析装置を実現することを目的とする。 The present invention solves these problems, and its purpose is to use a wavelength tunable laser having a wide wavelength tunable width as a laser light source, and remove a sharp peak portion of a mixed gas (for example, methane) for concentration detection. A statistical method is used to realize a laser gas analyzer that can measure a hydrocarbon having a large spectral characteristic at the same time as a hydrocarbon having a small spectral characteristic with high accuracy.
Even if the gas to be measured is a mixed gas of a gas having a small absorption spectrum characteristic and a gas having a large absorption spectrum characteristic, the concentration of the gas having a small absorption spectrum characteristic in the measurement gas can be accurately determined. An object is to realize a laser gas analyzer capable of measuring.
　本発明の目的は、以下の構成によって達成される。
　（１）　広い波長可変幅を有する波長可変レーザと、前記波長可変レーザの出力光を測定光として被測定ガスに照射する光照射手段と、前記被測定ガスを透過した前記測定光に関連した吸収信号に基づいて前記被測定ガスの吸収スペクトルを求め、統計的手法に基づき各成分の濃度を求めるデータ処理部とで構成されたレーザガス分析装置において、
　前記データ処理部は、鋭い吸収ピークを持たないガスの成分濃度を求めるのにあたり、比較的広い波長範囲を掃引することにより得られる吸収スペクトルのうち、他のガス成分の鋭い吸収ピークが存在しない波長領域の吸収スペクトルを用いることを特徴とする。 The object of the present invention is achieved by the following configurations.
(1) A wavelength tunable laser having a wide wavelength tunable width, a light irradiating means for irradiating the gas to be measured with the output light of the wavelength tunable laser as measurement light, and absorption related to the measurement light transmitted through the gas to be measured In a laser gas analyzer configured with a data processing unit for obtaining an absorption spectrum of the gas to be measured based on a signal and obtaining a concentration of each component based on a statistical method,
The data processing unit determines the component concentration of a gas having no sharp absorption peak, and has a wavelength at which no sharp absorption peak of another gas component exists in an absorption spectrum obtained by sweeping a relatively wide wavelength range. The absorption spectrum of the region is used.
　（２）　広い波長可変幅を有する波長可変レーザと、前記波長可変レーザの出力光を測定光と参照光に分岐し前記測定光を被測定ガスに照射する光分岐手段と、前記参照光に関連した参照信号と前記被測定ガスを透過した前記測定光に関連した吸収信号に基づいて前記被測定ガスの吸収スペクトルを求め、統計的手法に基づき各成分の濃度を求めるデータ処理部とで構成されたレーザガス分析装置において、
　前記データ処理部は、鋭い吸収ピークを持たないガスの成分濃度を求めるのにあたり、比較的広い波長範囲を掃引することにより得られる吸収スペクトルのうち、他のガス成分の鋭い吸収ピークが存在しない波長領域の吸収スペクトルを用いることを特徴とする。 (2) A wavelength tunable laser having a wide wavelength tunable width, a light branching means for branching the output light of the wavelength tunable laser into measurement light and reference light, and irradiating the measurement light with the measurement light, and the reference light And a data processing unit for obtaining an absorption spectrum of the measurement gas based on the reference signal obtained and an absorption signal related to the measurement light transmitted through the measurement gas, and obtaining a concentration of each component based on a statistical method. In the laser gas analyzer
The data processing unit determines the component concentration of a gas having no sharp absorption peak, and has a wavelength at which no sharp absorption peak of another gas component exists in an absorption spectrum obtained by sweeping a relatively wide wavelength range. The absorption spectrum of the region is used.
　（３）　上記（２）に記載のレーザガス分析装置において、
　前記データ処理部は、
　前記被測定ガスの吸収線波長データを保存する吸収線波長データ格納部と、
　前記参照信号および吸収信号が入力されるとともに前記吸収線波長データ格納部が接続され、これら吸収線波長データと参照信号および吸収信号に基づき吸収スペクトルの波長を校正する波長校正手段と、
　前記被測定ガスの濃度測定に用いる光信号の波長領域を選択する波長領域選択手段と、
　事前に構築された統計モデルに基づき前記被測定ガスの濃度を求める濃度検出手段、とで構成されていることを特徴とする。 (3) In the laser gas analyzer described in (2) above,
The data processing unit
An absorption line wavelength data storage unit for storing absorption line wavelength data of the measured gas;
The reference signal and the absorption signal are input and the absorption line wavelength data storage unit is connected, and wavelength calibration means for calibrating the wavelength of the absorption spectrum based on the absorption line wavelength data, the reference signal, and the absorption signal;
Wavelength region selection means for selecting a wavelength region of an optical signal used for measuring the concentration of the gas to be measured;
And a concentration detecting means for determining the concentration of the gas to be measured based on a statistical model constructed in advance.
　（４）　上記（３）に記載のレーザガス分析装置において、
　前記波長校正手段は、校正用ガスの吸収線と既知の吸収線とを比較することを特徴とする。 (4) In the laser gas analyzer described in (3) above,
The wavelength calibration means compares the absorption line of the calibration gas with a known absorption line.
　（５）　混合ガスである被測定ガスに含まれる成分の濃度を求めるレーザガス分析装置において、
　比較的広い波長範囲を掃引する波長可変レーザと、
　前記波長可変レーザの出力光の少なくとも一部を測定光として前記被測定ガスに透過させ、透過後の測定光を受光素子に導く光学系と、
　前記受光素子の出力に基づいて前記被測定ガスの吸収スペクトルを求め、統計的手法に基づき各成分の濃度を求めるデータ処理部と、
　を備え、
　前記データ処理部は、前記被測定ガスに含まれるガスのうち吸収スペクトルの特徴の小さいガスの濃度を求めるにあたり、前記被測定ガスの吸収スペクトルのうち鋭い吸収ピークが存在しない波長領域の吸収スペクトルを用いることを特徴とする。 (5) In a laser gas analyzer for determining the concentration of a component contained in a gas to be measured which is a mixed gas,
A tunable laser that sweeps a relatively wide wavelength range;
An optical system that transmits at least part of the output light of the wavelength tunable laser as measurement light to the gas to be measured and guides the measurement light after transmission to the light receiving element;
A data processing unit for obtaining an absorption spectrum of the gas to be measured based on the output of the light receiving element, and obtaining a concentration of each component based on a statistical method;
With
The data processing unit obtains an absorption spectrum in a wavelength region in which no sharp absorption peak exists in the absorption spectrum of the measurement gas when obtaining the concentration of a gas having a small absorption spectrum characteristic among the gases contained in the measurement gas. It is characterized by using.
　（６）　上記（５）に記載のレーザガス分析装置において、
　前記統計的手法は、濃度既知のガススペクトルに基づいてスペクトルと濃度の関係をあらかじめ構築した統計モデルに基づいて、前記被測定ガスのスペクトルから各ガスの濃度を求めるものであることを特徴とする。 (6) In the laser gas analyzer described in (5) above,
The statistical method is characterized in that the concentration of each gas is obtained from the spectrum of the gas to be measured based on a statistical model in which the relationship between the spectrum and the concentration is preliminarily constructed based on a gas spectrum having a known concentration. .
　（７）　上記（６）に記載のレーザガス分析装置において、
　前記統計モデルは、吸収スペクトルのピーク部分を用いないで作成されたことを特徴とする。 (7) In the laser gas analyzer described in (6) above,
The statistical model is created without using a peak portion of an absorption spectrum.
　（８）　上記（６）または（７）に記載のレーザガス分析装置において、
　前記統計モデルは、パラメータに外気温、ガス温度、ガス圧力の少なくともいずれかを含むことを特徴とする。 (8) In the laser gas analyzer described in (6) or (7) above,
The statistical model includes at least one of an outside air temperature, a gas temperature, and a gas pressure as a parameter.
　（９）　上記（５）～（８）のいずれかに記載のレーザガス分析装置において、
　前記被測定ガスは炭化水素多成分の混合ガスであり、
　前記吸収スペクトルの特徴の大きいガスはメタンであり、
　前記吸収スペクトルの特徴の小さいガスはメタン以外の炭化水素であることを特徴とする。 (9) In the laser gas analyzer according to any one of (5) to (8),
The gas to be measured is a hydrocarbon mixed gas mixture,
The gas having a large feature in the absorption spectrum is methane,
The gas having a small characteristic in the absorption spectrum is a hydrocarbon other than methane.
　（１０）　上記（５）～（９）のいずれかに記載のレーザガス分析装置において、
　波長可変レーザからの出射光の少なくとも一部を測定光と参照光の２つに分ける光分岐手段と、
　前記被測定ガスが導入され、前記測定光が入射されるガスセルと、
　前記ガスセルからの出射光が入射される第１の受光素子と、
　前記参照光が入射される第２の受光素子と、を備え、
　前記光分岐手段から前記ガスセルの入射端面までの距離をＬ１、前記ガスセルの出射端面から前記第１の受光素子までの距離をＬ２、前記光分岐手段から前記第２の受光素子までの距離をＬ３としたときに
　Ｌ３＝Ｌ１＋Ｌ２
　としたことを特徴とする。 (10) In the laser gas analyzer according to any one of (5) to (9),
An optical branching unit that divides at least a part of the light emitted from the wavelength tunable laser into two of measurement light and reference light;
A gas cell into which the measurement gas is introduced and the measurement light is incident;
A first light receiving element on which light emitted from the gas cell is incident;
A second light receiving element on which the reference light is incident,
The distance from the light branching means to the incident end face of the gas cell is L1, the distance from the emission end face of the gas cell to the first light receiving element is L2, and the distance from the light branching means to the second light receiving element is L3. When L3 = L1 + L2
It is characterized by that.
　これらにより、多成分混合ガスに含まれる各ガスの濃度を統計的手法を用いて比較的簡単に測定できる。
　本発明によれば、レーザ光源として広い波長可変幅の波長可変レーザを用い、被測定ガスの鋭い吸収ピークが存在しない波長領域の吸収スペクトルを用いることにより、被測定ガスが吸収スペクトルの特徴が小さいガスと吸収スペクトルの特徴が大きなガスとの混合ガスであっても、被測定ガス中の吸収スペクトルの特徴が小さいガスの濃度を高精度に測定できるレーザガス分析装置を実現できる。 By these, the density | concentration of each gas contained in a multicomponent mixed gas can be measured comparatively easily using a statistical method.
According to the present invention, a wavelength variable laser having a wide wavelength variable width is used as a laser light source, and an absorption spectrum in a wavelength region where there is no sharp absorption peak of the gas to be measured is used, so that the gas to be measured has small absorption spectrum characteristics. Even if it is a mixed gas of a gas and a gas having a large absorption spectrum characteristic, it is possible to realize a laser gas analyzer that can accurately measure the concentration of a gas having a small absorption spectrum characteristic in the gas to be measured.
本発明の一実施例を示すブロック図である。It is a block diagram which shows one Example of this invention. 本発明に基づくレーザガス分析装置の具体例を示すブロック図である。It is a block diagram which shows the specific example of the laser gas analyzer based on this invention. 本発明に基づく装置が測定対象としている鎖状飽和炭化水素のスペクトル例図である。It is a spectrum example figure of the chain | strand-shaped saturated hydrocarbon which the apparatus based on this invention makes it a measuring object. 本発明に基づく装置による濃度測定動作の流れを説明するフローチャートである。It is a flowchart explaining the flow of the density | concentration measurement operation | movement by the apparatus based on this invention. １％のｎＣ４Ｈ１０スペクトルと、濃度８０％のＣＨ４の微分スペクトル図である。FIG. 2 is a differential spectrum diagram of 1% nC 4 H 10 spectrum and CH 4 having a concentration of 80%. 本願発明の他の実施例を示すブロック図である。It is a block diagram which shows the other Example of this invention. 従来のレーザガス分析装置の一例を示すブロック図である。It is a block diagram which shows an example of the conventional laser gas analyzer.
　以下、本発明の実施の形態について、図面を用いて詳細に説明する。図１は本発明に基づくレーザガス分析装置の一実施例を示すブロック図である。図１において、波長可変レーザ１０１は、被測定ガスの吸収スペクトルの測定光を発生するものであり、その発振波長を制御する発振波長制御回路１０２に接続されている。発振波長制御回路１０２は、波長可変レーザ１０１の発振波長を、たとえば１．６７～１．７２μｍの範囲内で掃引する。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a laser gas analyzer according to the present invention. In FIG. 1, a wavelength tunable laser 101 generates measurement light of an absorption spectrum of a gas to be measured, and is connected to an oscillation wavelength control circuit 102 that controls the oscillation wavelength. The oscillation wavelength control circuit 102 sweeps the oscillation wavelength of the wavelength tunable laser 101 within a range of 1.67 to 1.72 μm, for example.
　波長可変レーザ１０１の出射光はレンズ１０３で平行光となり、アイソレータ１０４を通り、ビームスプリッタ１０５により測定光と参照光の２つの平行光に分けられる。 The light emitted from the wavelength tunable laser 101 is converted into parallel light by the lens 103, passes through the isolator 104, and is divided into two parallel light of measurement light and reference light by the beam splitter 105.
　ビームスプリッタ１０５で２つに分けられた一方の平行光は測定光として被測定ガスが導入されているガスセル１０６に入射されてレンズ１０７により集光され、フォトダイオード１０８に入射されて電気信号に変換され、波長校正手段１１１の一方の入力端子に入力される。 One of the parallel lights divided into two by the beam splitter 105 is incident on a gas cell 106 into which a gas to be measured is introduced as measurement light, collected by a lens 107, incident on a photodiode 108, and converted into an electrical signal. And input to one input terminal of the wavelength calibration means 111.
　他方の平行光はレンズ１０９で集光されて参照光としてフォトダイオード１１０に入射され、電気信号に変換されて波長校正手段１１１の他方の入力端子に入力される。これらガスの測定光に基づく測定信号と出力強度の参照光に基づく参照信号から被測定ガス（炭化水素）の吸収スペクトルが求められる。 The other parallel light is condensed by the lens 109 and incident on the photodiode 110 as reference light, converted into an electric signal, and input to the other input terminal of the wavelength calibration means 111. The absorption spectrum of the gas to be measured (hydrocarbon) is obtained from the measurement signal based on the measurement light of the gas and the reference signal based on the reference light of the output intensity.
　波長校正手段１１１には波長領域選択手段１１２が接続され、波長領域選択手段１１２には濃度検出手段１１３が接続されている。 A wavelength region selection unit 112 is connected to the wavelength calibration unit 111, and a concentration detection unit 113 is connected to the wavelength region selection unit 112.
　図２は炭化水素多成分を測定する本発明に基づくレーザガス分析装置の具体例を示すブロック図であり、図１と共通する部分には同一の符号を付けている。図２において、波長校正手段１１１には吸収線波長データ格納部１１４が接続され、波長領域選択手段１１２には使用波長データ格納部１１５が接続され、濃度検出手段１１３には統計モデル格納部１１６が接続されている。 FIG. 2 is a block diagram showing a specific example of a laser gas analyzer based on the present invention for measuring hydrocarbon multicomponents, and the same reference numerals are given to the parts common to FIG. In FIG. 2, an absorption line wavelength data storage unit 114 is connected to the wavelength calibration unit 111, a use wavelength data storage unit 115 is connected to the wavelength region selection unit 112, and a statistical model storage unit 116 is connected to the concentration detection unit 113. It is connected.
　図２の図１からの変更点は、波長可変レーザ１０１（光源）としてMEMS-VCSELを用いている点と、波長可変レーザ１０１から出力されるレーザ光がアイソレータ１０４の後にビームスプリッタ１１７により３本の系統に分岐され、３本目の光が減圧されたＣＨ４が封入されている波長校正セル１１８およびレンズ１１９を通ってフォトダイオード１２０に入射されている点である。なお、フォトダイオード１２０の出力信号も波長校正手段１１１に入力されている。 2 differs from FIG. 1 in that MEMS-VCSEL is used as the wavelength tunable laser 101 (light source) and that the laser beam output from the wavelength tunable laser 101 is three beams by the beam splitter 117 after the isolator 104. And the third light is incident on the photodiode 120 through the wavelength calibration cell 118 and the lens 119 in which the reduced pressure CH 4 is enclosed. Note that the output signal of the photodiode 120 is also input to the wavelength calibration means 111.
　図３は本実施例が測定対象としている鎖状飽和炭化水素のスペクトル例図であり、（Ａ）はＣＨ４（メタン）、（Ｂ）はＣ２Ｈ６（エタン）、（Ｃ）はＣ３Ｈ８（プロパン）、（Ｄ）はｉＣ４Ｈ１０（イソブタン）、（Ｅ）はｎＣ４Ｈ１０（ノルマルブタン）、（Ｆ）はｉＣ５Ｈ１２（イソペンタン）、（Ｇ）はＣ５Ｈ１２（ノルマルペンタン）である。 FIG. 3 is a spectrum example of a chain saturated hydrocarbon to be measured in this example. (A) is CH 4 (methane), (B) is C 2 H 6 (ethane), and (C) is C 3 H 8 (propane), (D) is iC 4 H 10 (isobutane), (E) is nC 4 H 10 (normal butane), (F) is iC 5 H 12 (isopentane), (G) is C 5 H 12 (normal pentane).
　図３から明らかなように、ＣＨ４，Ｃ２Ｈ６，Ｃ３Ｈ８，ｉＣ４Ｈ１０は鋭いピークを持っているが、他のガススペクトルには鋭いピークは存在しておらず、特徴が小さい。これらの特徴の小さいガススペクトルから精度の高い濃度検出を行うためには、広く波長を掃引して得られた吸収スペクトルを用いて統計的に処理することが有効である。 As is clear from FIG. 3, CH 4 , C 2 H 6 , C 3 H 8 , and iC 4 H 10 have sharp peaks, but there are no sharp peaks in other gas spectra. Is small. In order to perform highly accurate concentration detection from a gas spectrum having a small feature, it is effective to perform statistical processing using an absorption spectrum obtained by sweeping a wide wavelength.
　既存の半導体レーザは数ｎｍ程度しか掃引できないため、統計的手法を用いても十分な効果はない。ところが、MEMS-VCSELは半導体レーザでありながら５０ｎｍ程度の比較的広い波長範囲で掃引できるため十分な吸収スペクトル情報を取得することができ、統計的手法によって精度の高い濃度検出が可能となる。 Since existing semiconductor lasers can only sweep a few nanometers, there is no sufficient effect even if statistical methods are used. However, since MEMS-VCSEL is a semiconductor laser and can be swept in a relatively wide wavelength range of about 50 nm, sufficient absorption spectrum information can be obtained, and highly accurate concentration detection can be performed by a statistical method.
　図４は、本発明に基づく装置による濃度測定動作の流れを説明するフローチャートである。一連の信号処理では、まずフォトダイオードの出力データとデータベースのデータを読み込む（ステップＳ１）。 FIG. 4 is a flowchart for explaining the flow of concentration measurement operation by the apparatus according to the present invention. In a series of signal processing, photodiode output data and database data are first read (step S1).
　波長校正手段１１１は、校正信号のＣＨ４の吸収線の位置と吸収線波長データ格納部１１４に保存された吸収線波長データに基づき被測定ガスの吸収スペクトルの波長を校正する（ステップＳ２）。 The wavelength calibration unit 111 calibrates the wavelength of the absorption spectrum of the gas to be measured based on the position of the absorption line of CH 4 in the calibration signal and the absorption line wavelength data stored in the absorption line wavelength data storage unit 114 (step S2).
　次に、濃度と比例する吸光度に変換する（ステップＳ３）。一般に波長λの吸光度は以下の方法で計算する。
　吸光度＝ｌｏｇ１０[Ｉ０(λ)／Ｉ(λ)］　　（１）
　ここでＩ０は測定ガスセルへの入射強度、Ｉは測定ガスセルからの透過光強度である。 Next, the absorbance is proportional to the concentration (step S3). In general, the absorbance at wavelength λ is calculated by the following method.
Absorbance = log 10 [I 0 (λ) / I (λ)] (1)
Here, I 0 is the incident intensity to the measurement gas cell, and I is the transmitted light intensity from the measurement gas cell.
　吸光度は、以下の式で求められる。
　吸光度＝ｌｏｇ１０[Ｓ１(λ)／Ｓ２(λ)・Ｔ(λ)］+ Constant　　（２）
　ここでＳ１は参照用信号, Ｓ２は測定用信号、Ｔ(λ)は装置関数（測定対象のガスセル１０６の透過率、ビームスプリッタ１１７の分岐比の波長依存性）である。なお、定数項にはビームスプリッタの分岐比に対応した項が入る。 Absorbance is determined by the following equation.
Absorbance = log 10 [S1 (λ) / S2 (λ) · T (λ)] + Constant (2)
Here, S1 is a reference signal, S2 is a measurement signal, and T (λ) is an apparatus function (transmittance of the gas cell 106 to be measured, wavelength dependence of the branching ratio of the beam splitter 117). The constant term includes a term corresponding to the branching ratio of the beam splitter.
　本発明では、
　吸光度＝ｌｏｇ１０[Ｓ１(λ)／Ｓ２(λ)] 　　（３）
として計算しているが、これは定数項を除去するアルゴリズムが導入されているためである。またＴ(λ)の波長依存性についても、測定用のガスセル１０６に吸収ガスを封入しないときの信号を差し引くことによって補正を行っている。 In the present invention,
Absorbance = log 10 [S1 (λ) / S2 (λ)] (3)
This is because an algorithm for removing a constant term has been introduced. The wavelength dependence of T (λ) is also corrected by subtracting the signal when the absorption gas is not sealed in the measurement gas cell 106.
　濃度検出手段１１３として多変量解析などの統計的手法を用いる（ステップＳ４）。ここで、統計的手法とは、濃度既知のガススペクトルに基づいてスペクトルと濃度の関係の統計モデルをあらかじめ構築しておき、被測定用ガスのスペクトルを取得したときは事前に構築した統計モデルに基づいて各ガスの濃度を求めるものであり、例えばＰＬＳ回帰法がよく知られている。事前に統計モデルを構築するのにあたり、測定目標濃度のレンジ内を可能な限り満遍なく測定することで、高い精度の濃度検出が可能となる。 Statistical methods such as multivariate analysis are used as the concentration detection means 113 (step S4). Here, the statistical method means that a statistical model of the relationship between the spectrum and the concentration is built in advance based on the gas spectrum with a known concentration, and when the spectrum of the gas to be measured is acquired, the statistical model built in advance is used. Based on this, the concentration of each gas is obtained. For example, the PLS regression method is well known. In constructing a statistical model in advance, highly accurate concentration detection is possible by measuring as uniformly as possible within the measurement target concentration range.
　次に、波長領域選択手段１１２について説明する。ガススペクトルから濃度検出を行う場合、ピークのようにスペクトルの特徴が大きい波長帯を使うことが一般的である。しかし、各ガスによる吸収度が大幅に異なる場合は、吸収ピークを使わない方がよい場合がある。 Next, the wavelength region selection unit 112 will be described. When concentration detection is performed from a gas spectrum, it is common to use a wavelength band having a large spectral feature such as a peak. However, it may be better not to use an absorption peak when the absorption by each gas is significantly different.
　例としてＣＨ４が８０％を占め、ｎＣ４Ｈ１０が１％のガスを測定することを考える。光源のレーザはスペクトル幅を持っていることや、波長校正に用いるＣＨ４ピークも幅を持っていることなどから、波長校正を行っても波長誤差は残る。 As an example, consider measuring CH 4 with 80% and nC 4 H 10 at 1%. Since the laser of the light source has a spectral width and the CH 4 peak used for wavelength calibration also has a width, the wavelength error remains even after wavelength calibration.
　図５に１％のｎＣ４Ｈ１０スペクトルと、濃度８０％のＣＨ４の微分スペクトルを示す。ここで微分スペクトルとは波長が１ｐｍ異なるスペクトルとの差を示しており、１ｐｍの波長誤差によって生じるスペクトル誤差の大きさを示している。図５から明らかなように、ＣＨ４の波長誤差による影響は大きく、１ｐｍの波長誤差が生じるとＣＨ４のピークがある波長帯ではｎＣ４Ｈ１０スペクトルよりも大きいスペクトル誤差が生じてしまう。 FIG. 5 shows a 1% nC 4 H 10 spectrum and a derivative spectrum of CH 4 at a concentration of 80%. Here, the differential spectrum indicates a difference from a spectrum having a wavelength different by 1 pm, and indicates a magnitude of a spectrum error caused by a wavelength error of 1 pm. As is clear from FIG. 5, the influence of the CH 4 wavelength error is large, and when a 1 pm wavelength error occurs, a spectral error larger than the nC 4 H 10 spectrum occurs in the wavelength band where the CH 4 peak exists.
　したがって、想定される波長誤差によるスペクトル誤差が被測定ガスに比べて大きくなるような吸収ピークを用いないで統計モデルを作成すれば、吸収強度の小さいガスについて精度の高い濃度検出ができる。 Therefore, if a statistical model is created without using an absorption peak in which a spectral error due to an assumed wavelength error is larger than that of the gas to be measured, a highly accurate concentration detection can be performed for a gas having a low absorption intensity.
　このように、機械的な可動部のないMEMS可動ミラーと光通信で高信頼性が実証されている半導体レーザを組み合わせた工業計器としての十分な信頼性を備えかつ波長可変範囲の広いMEMS-VCSEL波長可変レーザを用いて、種々の炭化水素の吸収線が存在する波長１．６７～１．７２μｍの範囲内で波長掃引することにより、炭化水素多成分混合ガスの吸収スペクトルが測定できる。 In this way, MEMS-VCSEL has sufficient reliability as an industrial instrument that combines a MEMS movable mirror without mechanical moving parts and a semiconductor laser that has been proven to be highly reliable in optical communications, and has a wide wavelength tunable range. By using a wavelength tunable laser and performing wavelength sweeping within a wavelength range of 1.67 to 1.72 μm where absorption lines of various hydrocarbons exist, an absorption spectrum of a hydrocarbon multicomponent mixed gas can be measured.
　ＣＨ４の吸収線と波長のテーブルを用いて得られた炭化水素多成分混合ガスの吸収スペクトルの波長校正を行うことにより、正確な吸収スペクトルが得られる。 An accurate absorption spectrum can be obtained by performing wavelength calibration of the absorption spectrum of the hydrocarbon multi-component mixed gas obtained using the CH 4 absorption line and wavelength table.
　統計的手法を用いることにより、スペクトルの特徴が大きいガスと同時にスペクトルの特徴の小さいガスの濃度も求めることができる。 By using a statistical method, it is possible to obtain the concentration of a gas having a small spectral characteristic as well as a gas having a large spectral characteristic.
　スペクトルのピーク部分を用いないで統計モデルを作成することにより、吸収スペクトルに特徴が小さい炭化水素ガスも高い精度で検出できる。 By creating a statistical model without using the peak portion of the spectrum, it is possible to detect hydrocarbon gas having a small feature in the absorption spectrum with high accuracy.
　これまで炭化水素多成分系の分析は、その成分分離能力の高さから主にガスクロが用いられてきたが、測定時間が長く測定値を直接制御に用いることはできなかった。一方、リアルタイムで測定可能なＴＤＬＡＳは、光源の波長可変幅が狭く、主に単成分の測定に限られていた。 So far, analysis of hydrocarbon multi-component systems has mainly used gas chromatography because of its high component separation ability, but the measurement time was long and the measured values could not be used for direct control. On the other hand, TDLAS that can be measured in real time has a narrow wavelength variable width of the light source, and is mainly limited to measurement of a single component.
　これらに対し、機械的な可動部が無くて工業計器として要求される高い信頼性を持ち、かつ広い波長範囲で波長変更可能なMEMS-VCSELを光源に用いることにより、多成分混合ガスの吸収スペクトルを測定可能な工業用ＴＤＬＡＳを実現できる。 On the other hand, the absorption spectrum of multi-component mixed gas is achieved by using MEMS-VCSEL, which has no mechanical moving parts and has high reliability required as an industrial instrument and can change the wavelength in a wide wavelength range as a light source. Industrial TDLAS can be realized.
　１．６７～１．７２μｍの波長範囲で発振するMEMS-VCSELを光源として用いることにより、炭化水素多成分混合ガスの分析が可能なＴＤＬＡＳを実現できる。 By using MEMS-VCSEL oscillating in the wavelength range of 1.67 to 1.72 μm as a light source, a TDLAS capable of analyzing a hydrocarbon multi-component gas mixture can be realized.
　さらに、ＴＤＬＡＳを用いることにより、リアルタイム計測が実現できる。 Furthermore, real-time measurement can be realized by using TDLAS.
　ところで、１７００ｎｍ（１．７μｍ）帯では、空気中の水分のスペクトルが濃度検出の障害となることがあるが、図６に示すように各部の光路長Ｌ１～Ｌ３を適切に選定することで、空気中の水分の影響を排除できる。 By the way, in the 1700 nm (1.7 μm) band, the moisture spectrum in the air may become an obstacle to concentration detection, but by appropriately selecting the optical path lengths L1 to L3 of each part as shown in FIG. The influence of moisture in the air can be eliminated.
　図６は本願発明の他の実施例を示すブロック図であり、図１と共通する部分には同一の符号を付けている。図６において、ビームスプリッタ１０５の中心からガスセル１０６の入射端面までの距離をＬ１とし、ガスセル１０６の出射端面からフォトダイオード１０８の入射面までの距離をＬ２とし、ビームスプリッタ１０５の中心からフォトダイオード１１０の入射面までの距離をＬ３とすると、各距離の関係は、Ｌ３＝Ｌ１＋Ｌ２になるように設定されている。 FIG. 6 is a block diagram showing another embodiment of the present invention, and the same reference numerals are given to portions common to FIG. In FIG. 6, the distance from the center of the beam splitter 105 to the incident end face of the gas cell 106 is L1, the distance from the exit end face of the gas cell 106 to the incident face of the photodiode 108 is L2, and the center of the beam splitter 105 is connected to the photodiode 110. Assuming that the distance to the incident surface is L3, the relationship between the distances is set so that L3 = L1 + L2.
　さらに、空気中の水分の影響を小さくするためには、図６のような光学系を筐体内に収めるとともに、窒素のような赤外波長領域において吸収を持たないガスでパージすればよい。 Furthermore, in order to reduce the influence of moisture in the air, the optical system as shown in FIG. 6 may be housed in the casing and purged with a gas that does not absorb in the infrared wavelength region such as nitrogen.
　また、光源をファイバ出力にすることによって、光源である波長可変レーザ１０１の取り付けや取り換えによる光軸アラインメントのずれを防止できる。 Also, by making the light source a fiber output, it is possible to prevent the optical axis alignment from shifting due to the mounting or replacement of the wavelength tunable laser 101 which is the light source.
　また、ＣＨ４の濃度はＣＨ４ピークを用いて検出するが、この際の濃度検出方法は統計的方法に限らず、面積法を用いてもよい。 Further, the CH 4 concentration is detected using the CH 4 peak, but the concentration detection method at this time is not limited to a statistical method, and an area method may be used.
　なお、ＣＨ４のピークは鋭いため、波長校正精度が悪いとスペクトル誤差が大きくなり、濃度誤差となる。この対策としては、スペクトル全体を平滑化によって鈍らせればよい。 Since the peak of CH 4 is sharp, if the wavelength calibration accuracy is poor, the spectrum error becomes large, resulting in a density error. As a countermeasure, the whole spectrum may be blunted by smoothing.
　また、測定濃度の精度を高める方法としては、以下のような方法を組み合わせるようにしてもよい。
　ａ）圧力を測定して圧力に起因する誤差を補償する
　ｂ）所望の測定精度が得られる状態が維持できるように圧力を制御する
　ｃ）ガスセル１０６の温度を制御する Further, the following methods may be combined as a method for increasing the accuracy of the measured concentration.
a) Measure pressure to compensate for errors due to pressure b) Control pressure to maintain desired measurement accuracy c) Control gas cell 106 temperature
　また、統計モデル作成時に外気温、ガス温度、圧力などのガス濃度以外をパラメータとしてモデルに導入することで、ガス濃度以外の要因によるスペクトル変化に対応できる。たとえばフォトダイオードや半導体レーザの窓による光干渉は外気温に依存するので、外気温をパラメータにすることで濃度誤差を小さくする効果が期待できる。 In addition, when a statistical model is created, other than gas concentrations such as outside air temperature, gas temperature, pressure, etc., are introduced into the model as parameters, so that it is possible to cope with spectrum changes due to factors other than gas concentration. For example, since light interference due to a window of a photodiode or a semiconductor laser depends on the outside air temperature, the effect of reducing the concentration error can be expected by using the outside air temperature as a parameter.
　また、上記実施例では、波長可変レーザの出力光を測定光と参照光に分岐し測定光を被測定ガスに照射する光分岐手段を設け、データ処理部が参照光に関連した参照信号と被測定ガスを透過した測定光に関連した吸収信号に基づいて被測定ガスの吸収スペクトルを求め、統計的手法に基づき各成分の濃度を求める例について説明したが、参照信号を用いない構成であっても簡易的な測定は行える。 Further, in the above embodiment, there is provided a light branching means for branching the output light of the wavelength tunable laser into measurement light and reference light and irradiating the measurement gas with the measurement light, so that the data processing unit and reference signal related to the reference light Although an example has been described in which the absorption spectrum of the gas to be measured is obtained based on the absorption signal related to the measurement light transmitted through the measurement gas, and the concentration of each component is obtained based on a statistical method, the reference signal is not used. Simple measurement is possible.
　以上説明したように、本発明によれば、レーザ光源として広い波長可変幅の波長可変レーザを用い、濃度検出にあたってはメタンなどのスペクトル幅が狭いガスの鋭いピーク部分を外した統計的手法を用いてスペクトルの特徴が大きい炭化水素と同時にスペクトルの特徴が小さい炭化水素も高精度に測定できるレーザガス分析装置を実現でき、各種プロセスガスの直接測定に有効である。 As described above, according to the present invention, a tunable laser having a wide wavelength tunable width is used as a laser light source, and a statistical method is used for concentration detection by removing a sharp peak portion of a gas having a narrow spectral width such as methane. Therefore, it is possible to realize a laser gas analyzer that can measure hydrocarbons having large spectral characteristics and hydrocarbons having small spectral characteristics with high accuracy, and is effective for direct measurement of various process gases.
　なお、以上の説明は、本発明の説明および例示を目的として特定の好適な実施例を示したに過ぎない。従って本発明は、上記実施例に限定されることなく、その本質から逸脱しない範囲で更に多くの変更、変形を含むものである。
　なお、本出願は、２０１３年１月１６日付で出願された日本特許出願（特願２０１３－００５３５７号）に基づいており、その全体が引用により援用される。また、ここに引用されるすべての参照は全体として取り込まれる。 The above description merely shows a specific preferred embodiment for the purpose of explanation and illustration of the present invention. Therefore, the present invention is not limited to the above-described embodiments, and includes many changes and modifications without departing from the essence thereof.
This application is based on a Japanese patent application (Japanese Patent Application No. 2013-005357) filed on Jan. 16, 2013, which is incorporated by reference in its entirety. Also, all references cited herein are incorporated as a whole.
　１０１　波長可変レーザ
　１０２　発振波長制御回路
　１０３、１０７、１０９　レンズ
　１０４　アイソレータ
　１０５　ビームスプリッタ
　１０６　ガスセル
　１０８、１１０　フォトダイオード
　１１１　波長校正手段
　１１２　波長領域選択手段
　１１３　濃度検出手段
　１１４　吸収線波長データ格納部
　１１５　使用波長データ格納部
　１１６　統計モデル格納部 DESCRIPTION OF SYMBOLS 101 Wavelength variable laser 102 Oscillation wavelength control circuit 103,107,109 Lens 104 Isolator 105 Beam splitter 106 Gas cell 108,110 Photodiode 111 Wavelength calibration means 112 Wavelength area selection means 113 Concentration detection means 114 Absorption line wavelength data storage part 115 Use wavelength Data storage unit 116 Statistical model storage unit

Claims (10)

  1. 　広い波長可変幅を有する波長可変レーザと、前記波長可変レーザの出力光を測定光として被測定ガスに照射する光照射手段と、前記被測定ガスを透過した前記測定光に関連した吸収信号に基づいて前記被測定ガスの吸収スペクトルを求め、統計的手法に基づき各成分の濃度を求めるデータ処理部とで構成されたレーザガス分析装置において、
    　前記データ処理部は、鋭い吸収ピークを持たないガスの成分濃度を求めるのにあたり、比較的広い波長範囲を掃引することにより得られる吸収スペクトルのうち、他のガス成分の鋭い吸収ピークが存在しない波長領域の吸収スペクトルを用いることを特徴とするレーザガス分析装置。     Based on a wavelength tunable laser having a wide wavelength tunable width, light irradiating means for irradiating the measurement gas with the output light of the wavelength tunable laser as measurement light, and an absorption signal related to the measurement light transmitted through the measurement gas In the laser gas analyzer configured with a data processing unit for obtaining the absorption spectrum of the gas to be measured and obtaining the concentration of each component based on a statistical method,
    The data processing unit determines the component concentration of a gas having no sharp absorption peak, and has a wavelength at which no sharp absorption peak of another gas component exists in an absorption spectrum obtained by sweeping a relatively wide wavelength range. A laser gas analyzer characterized by using an absorption spectrum in a region.
  2. 　広い波長可変幅を有する波長可変レーザと、前記波長可変レーザの出力光を測定光と参照光に分岐し前記測定光を被測定ガスに照射する光分岐手段と、前記参照光に関連した参照信号と前記被測定ガスを透過した前記測定光に関連した吸収信号に基づいて前記被測定ガスの吸収スペクトルを求め、統計的手法に基づき各成分の濃度を求めるデータ処理部とで構成されたレーザガス分析装置において、
    　前記データ処理部は、鋭い吸収ピークを持たないガスの成分濃度を求めるのにあたり、比較的広い波長範囲を掃引することにより得られる吸収スペクトルのうち、他のガス成分の鋭い吸収ピークが存在しない波長領域の吸収スペクトルを用いることを特徴とするレーザガス分析装置。     A wavelength tunable laser having a wide wavelength tunable width, light branching means for branching output light of the wavelength tunable laser into measurement light and reference light, and irradiating the measurement light with the measurement light, and a reference signal related to the reference light Gas analysis comprising: and a data processing unit for obtaining an absorption spectrum of the gas to be measured based on an absorption signal related to the measurement light transmitted through the gas to be measured, and obtaining a concentration of each component based on a statistical method In the device
    The data processing unit determines the component concentration of a gas having no sharp absorption peak, and has a wavelength at which no sharp absorption peak of another gas component exists in an absorption spectrum obtained by sweeping a relatively wide wavelength range. A laser gas analyzer characterized by using an absorption spectrum in a region.
  3. 　前記データ処理部は、
    　前記被測定ガスの吸収線波長データを保存する吸収線波長データ格納部と、
    　前記参照信号および吸収信号が入力されるとともに前記吸収線波長データ格納部が接続され、これら吸収線波長データと参照信号および吸収信号に基づき吸収スペクトルの波長を校正する波長校正手段と、
    　前記被測定ガスの濃度測定に用いる光信号の波長領域を選択する波長領域選択手段と、
    　事前に構築された統計モデルに基づき前記被測定ガスの濃度を求める濃度検出手段、とで構成されていることを特徴とする請求項２に記載のレーザガス分析装置。     The data processing unit
    An absorption line wavelength data storage unit for storing absorption line wavelength data of the measured gas;
    The reference signal and the absorption signal are input and the absorption line wavelength data storage unit is connected, and wavelength calibration means for calibrating the wavelength of the absorption spectrum based on the absorption line wavelength data, the reference signal, and the absorption signal;
    Wavelength region selection means for selecting a wavelength region of an optical signal used for measuring the concentration of the gas to be measured;
    The laser gas analyzer according to claim 2, comprising: a concentration detection unit that obtains the concentration of the gas to be measured based on a statistical model constructed in advance.
  4. 　前記波長校正手段は、校正用ガスの吸収線と既知の吸収線とを比較することを特徴とする請求項３に記載のレーザガス分析装置。 4. The laser gas analyzer according to claim 3, wherein the wavelength calibration means compares an absorption line of a calibration gas with a known absorption line.
  5. 　混合ガスである被測定ガスに含まれる成分の濃度を求めるレーザガス分析装置において、
    　比較的広い波長範囲を掃引する波長可変レーザと、
    　前記波長可変レーザの出力光の少なくとも一部を測定光として前記被測定ガスに透過させ、透過後の測定光を受光素子に導く光学系と、
    　前記受光素子の出力に基づいて前記被測定ガスの吸収スペクトルを求め、統計的手法に基づき各成分の濃度を求めるデータ処理部と、
    　を備え、
    　前記データ処理部は、前記被測定ガスに含まれるガスのうち吸収スペクトルの特徴の小さいガスの濃度を求めるにあたり、前記被測定ガスの吸収スペクトルのうち鋭い吸収ピークが存在しない波長領域の吸収スペクトルを用いることを特徴とするレーザガス分析装置。     In a laser gas analyzer for determining the concentration of a component contained in a gas to be measured which is a mixed gas,
    A tunable laser that sweeps a relatively wide wavelength range;
    An optical system that transmits at least part of the output light of the wavelength tunable laser as measurement light to the gas to be measured and guides the measurement light after transmission to the light receiving element;
    A data processing unit for obtaining an absorption spectrum of the gas to be measured based on the output of the light receiving element, and obtaining a concentration of each component based on a statistical method;
    With
    The data processing unit obtains an absorption spectrum in a wavelength region in which no sharp absorption peak exists in the absorption spectrum of the measurement gas when obtaining the concentration of a gas having a small absorption spectrum characteristic among the gases contained in the measurement gas. A laser gas analyzer characterized by being used.
  6. 　前記統計的手法は、濃度既知のガススペクトルに基づいてスペクトルと濃度の関係をあらかじめ構築した統計モデルに基づいて、前記被測定ガスのスペクトルから各ガスの濃度を求めるものであることを特徴とする請求項５に記載のレーザガス分析装置。 The statistical method is characterized in that the concentration of each gas is obtained from the spectrum of the gas to be measured based on a statistical model in which the relationship between the spectrum and the concentration is preliminarily constructed based on a gas spectrum having a known concentration. The laser gas analyzer according to claim 5.
  7. 　前記統計モデルは、吸収スペクトルのピーク部分を用いないで作成されたことを特徴とする請求項６に記載のレーザガス分析装置。 The laser gas analyzer according to claim 6, wherein the statistical model is created without using a peak portion of an absorption spectrum.
  8. 　前記統計モデルは、パラメータに外気温、ガス温度、ガス圧力の少なくともいずれかを含むことを特徴とする請求項６または７に記載のレーザガス分析装置。 The laser gas analyzer according to claim 6 or 7, wherein the statistical model includes at least one of an outside air temperature, a gas temperature, and a gas pressure as a parameter.
  9. 　前記被測定ガスは炭化水素多成分の混合ガスであり、
    　前記吸収スペクトルの特徴の大きいガスはメタンであり、
    　前記吸収スペクトルの特徴の小さいガスはメタン以外の炭化水素であることを特徴とする請求項５～８のいずれかに記載のレーザガス分析装置。     The gas to be measured is a hydrocarbon mixed gas mixture,
    The gas having a large feature in the absorption spectrum is methane,
    The laser gas analyzer according to any one of claims 5 to 8, wherein the gas having a small characteristic in the absorption spectrum is a hydrocarbon other than methane.
  10. 　波長可変レーザからの出射光の少なくとも一部を測定光と参照光の２つに分ける光分岐手段と、
    　前記被測定ガスが導入され、前記測定光が入射されるガスセルと、
    　前記ガスセルからの出射光が入射される第１の受光素子と、
    　前記参照光が入射される第２の受光素子と、
    を備え、
    　前記光分岐手段から前記ガスセルの入射端面までの距離をＬ１、前記ガスセルの出射端面から前記第１の受光素子までの距離をＬ２、前記光分岐手段から前記第２の受光素子までの距離をＬ３としたときに
    　Ｌ３＝Ｌ１＋Ｌ２
    　としたことを特徴とする請求項５～９のいずれかに記載のレーザガス分析装置。     An optical branching unit that divides at least a part of the light emitted from the wavelength tunable laser into two of measurement light and reference light;
    A gas cell into which the measurement gas is introduced and the measurement light is incident;
    A first light receiving element on which light emitted from the gas cell is incident;
    A second light receiving element on which the reference light is incident;
    With
    The distance from the light branching means to the incident end face of the gas cell is L1, the distance from the emission end face of the gas cell to the first light receiving element is L2, and the distance from the light branching means to the second light receiving element is L3. When L3 = L1 + L2
    The laser gas analyzer according to any one of claims 5 to 9, wherein
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