JP5621154B1 - Absorption spectrum analyzer, absorption spectrum baseline setting method, and computer program - Google Patents

Abstract

An absorption spectrum analyzer capable of setting a baseline of an absorption spectrum without using a calibration curve, a method for setting a baseline of an absorption spectrum of a substance, and a computer program are provided. A wave number at a plurality of peaks of an actual measurement value of an absorption spectrum measured by infrared spectroscopy using the sun as a light source is specified, and a theoretical value of an absorption spectrum corresponding to each of the specified plurality of wave numbers is obtained. The transmittance is specified, and each specified transmittance is interpolated to generate a theoretical value interpolation line. In addition, the wave number at a plurality of peaks of the theoretical value of the absorption spectrum is specified, the transmittance of the measured value of the absorption spectrum corresponding to each of the specified plurality of wave numbers is specified, and each specified transmittance is interpolated. An actual measurement value interpolation line is generated. A line obtained by averaging the theoretical value interpolation line and the actual measurement value interpolation line for each wave number is set as the base line. [Selection] Figure 6

Description

  The present invention relates to an absorption spectrum analyzer for setting a baseline of an absorption spectrum of a substance, a method for setting a baseline of an absorption spectrum of a substance, and a computer program.

  In order to detect the concentration of a specific substance in a gas (for example, the atmosphere), it is known to optically measure the gas to obtain an absorption spectrum of the specific substance.

  For example, Patent Literature 1 discloses a gas analyzer using Fourier transform infrared spectroscopy (FT-IR method). In the gas analyzer described in Patent Document 1, it is determined whether or not the peak value specific to the measurement component found in the predetermined wavenumber region is found in the absorption spectrum data obtained by the measurement in the calibration curve. As a result of the determination, if there is no peak value in the predetermined wavenumber region, the baseline is corrected using the absorption spectrum data, assuming that the measurement target gas does not contain a predetermined measurement component such as ethanol.

JP 2010-151624 A

  In order to accurately measure the concentration of a substance using spectroscopy, it is essential to set an accurate baseline. However, the gas analyzer disclosed in Patent Document 1 requires a calibration curve for correcting the baseline. In order to create a calibration curve, an absorption spectrum must be measured using a standard substance, which is a heavy burden on the operator.

  The present invention has been made in view of such circumstances, and its main purpose is an absorption spectrum analyzer capable of setting a baseline of an absorption spectrum without using a calibration curve, and a baseline of an absorption spectrum of a substance. A setting method and a computer program are provided.

In order to solve the above-described problem, an absorption spectrum analyzer according to one embodiment of the present invention includes an actual measurement value of an absorption spectrum indicating a relationship between a wavelength or wave number and the absorbance or transmittance of a specific substance, and the wavelength or wave number. An absorption spectrum analyzer that sets a baseline of an absorption spectrum of the specific substance based on a theoretical value of an absorption spectrum indicating a relationship with the absorbance or transmittance of the specific substance, the measured value acquisition means for acquiring measurement data on the absorption spectrum, the and the theoretical value obtaining means for obtaining a theoretical value of the absorption spectrum of a specific substance, based on the measurement data acquired by the measured value acquisition means, the absorbance Alternatively, the first wavelength / wave number specifying means for specifying the wavelengths or wave numbers at a plurality of peaks of the measured transmittance value and the first wavelength / wave number specifying means A theoretical value specifying means for specifying the absorbance or transmittance of the theoretical value of the absorption spectrum at a plurality of wavelengths or wave numbers, and based on the theoretical value of the absorption spectrum acquired by the theoretical value acquisition means, the absorbance or transmission Second wavelength / wave number specifying means for specifying wavelengths or wave numbers at a plurality of peaks of the theoretical value of the rate, and absorbance of the measured value of the absorption spectrum at a plurality of wavelengths or wave numbers specified by the second wavelength / wave number specifying means Alternatively, actual measurement value specifying means for specifying transmittance, first interpolation line generating means for generating a theoretical value interpolation line by interpolating a plurality of theoretical values specified by the theoretical value specifying means, and the actual measurement value specifying means Interpolating a plurality of actual measurement values specified by the second interpolation line generation means for generating an actual measurement value interpolation line, and the first interpolation line generation means Therefore, the result of averaging the theoretical value interpolation line generated by the second interpolation line generation means and the actual value interpolation line generated by the second interpolation line generation unit for each wavelength or wave number is the baseline of the absorption spectrum of the specific substance. And baseline setting means for setting as follows.

  In this aspect, the first interpolation line generation unit is configured to generate a theoretical value interpolation line by linearly interpolating a plurality of theoretical values specified by the theoretical value specifying unit, and the second interpolation line The line generation means may be configured to generate an actual measurement value interpolation line by linearly interpolating a plurality of actual measurement values specified by the actual measurement value specifying means.

  In the above aspect, the actual measurement value acquisition unit corrects the actual measurement value of the absorption spectrum with respect to the wavelength or wave number based on the wavelength or wave number at a plurality of peaks of the theoretical value of absorbance or transmittance of the specific substance. And an actual measurement value of the absorption spectrum corrected by the correction means may be acquired as the measurement data.

  In the above aspect, the theoretical value acquisition unit acquires a theoretical value of an absorption spectrum of the specific substance at the position, temperature, and pressure at which the measurement data acquired by the actual measurement value acquisition unit is measured. It may be configured.

  In the above aspect, the theoretical value acquisition unit is configured to acquire a theoretical value of an absorption spectrum of the specific substance in a wavelength or wave number range in the measurement data acquired by the actual measurement value acquisition unit. Also good.

  In the above aspect, the first wavelength / wave number identification unit divides the measurement data acquired by the actual measurement value acquisition unit into a plurality of sections with respect to wavelength or wave number, and absorbs or transmits light in each of the divided sections. It is configured to specify one peak of the measured value of the rate, and to specify the wavelength or wave number at each peak, and the second wavelength / wave number specifying means is the measurement data by the first wavelength / wave number specifying means. May be configured to identify one peak of the theoretical value of absorbance or transmittance and to identify the wavelength or wave number at each peak in each of the plurality of sections for the wavelength or wave number into which.

  In addition, the method for setting the baseline of the absorption spectrum according to another aspect of the present invention includes an actual measurement value of an absorption spectrum indicating a relationship between the wavelength or wave number and the absorbance or transmittance of a specific substance, the wavelength or wave number, and the specific A method for setting a baseline of an absorption spectrum of the specific substance based on a theoretical value of an absorption spectrum indicating a relationship with the absorbance or transmittance of the substance, wherein the measurement data of the absorption spectrum of the specific substance is A step of acquiring, a step of acquiring a theoretical value of an absorption spectrum of the specific substance, and a step of specifying wavelengths or wave numbers at a plurality of peaks of the measured values of absorbance or transmittance based on the acquired measurement data Identifying the theoretical absorbance or transmittance of the absorption spectrum at the specified wavelengths or wavenumbers; Based on the theoretical value of the absorption spectrum, identifying the wavelength or wave number at a plurality of peaks of the theoretical value of absorbance or transmittance, and the absorbance or transmittance of the measured value of the absorption spectrum at the identified plurality of wavelengths or wave numbers Interpolating a plurality of specified theoretical values to generate a theoretical value interpolation line, interpolating a plurality of specified actual values, and generating an actual value interpolation line; Setting the result of averaging the generated theoretical value interpolation line and the generated actual measurement value interpolation line for each wavelength or wave number as a baseline of the absorption spectrum of the specific substance.

Further, the computer program according to another aspect of the present invention includes an actual measurement value of an absorption spectrum indicating a relationship between a wavelength or wave number and the absorbance or transmittance of a specific substance, and the absorbance or transmittance of the specific substance. A computer program for causing a computer to set a baseline of an absorption spectrum of the specific substance based on a theoretical value of an absorption spectrum indicating a relationship with Based on the measurement data acquired by the actual measurement value acquisition means, the theoretical value acquisition means for acquiring the theoretical value of the absorption spectrum of the specific substance, and the actual measurement value acquisition means . First wavelength / wave number specifying means for specifying wavelengths or wave numbers at a plurality of peaks, and specified by the first wavelength / wave number specifying means A theoretical value specifying means for specifying the absorbance or transmittance of the theoretical value of the absorption spectrum at a plurality of wavelengths or wave numbers, and based on the theoretical value of the absorption spectrum acquired by the theoretical value acquiring means, the absorbance or transmission Second wavelength / wave number specifying means for specifying wavelengths or wave numbers at a plurality of peaks of the theoretical value of the rate, and absorbance of the measured value of the absorption spectrum at a plurality of wavelengths or wave numbers specified by the second wavelength / wave number specifying means Alternatively, actual measurement value specifying means for specifying transmittance, first interpolation line generating means for generating a theoretical value interpolation line by interpolating a plurality of theoretical values specified by the theoretical value specifying means, and the actual measurement value specifying means Interpolating a plurality of actual measurement values specified by the second interpolation line generation means for generating an actual measurement value interpolation line, and the first interpolation line generation means The result of averaging the theoretical value interpolation line generated by the second interpolation line generation unit and the actual value interpolation line generated by the second interpolation line generation unit for each wavelength or wave number is used as the base of the absorption spectrum of the specific substance. The computer is caused to function as baseline setting means for setting as a line.

  According to the absorption spectrum analyzer, the absorption spectrum baseline setting method, and the computer program according to the present invention, it is possible to set the absorption spectrum baseline without using a calibration curve.

The schematic diagram which shows the structure of the absorption spectrum measuring system which concerns on embodiment. The schematic diagram which shows the structure of an optical measurement unit. The block diagram which shows the structure of an absorption spectrum analyzer. The flowchart which shows the procedure of the measurement data analysis process by an absorption spectrum analyzer. The figure explaining the wave number shift of an observation spectrum. The flowchart which shows the procedure of a baseline setting process. The figure for demonstrating the content of the baseline setting process.

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

[Configuration of absorption spectrum measurement system]
FIG. 1 is a schematic diagram showing a configuration of an absorption spectrum measurement system according to the present embodiment. The absorption spectrum measurement system measures the absorption spectrum of a specific substance (for example, carbon dioxide) by measuring sunlight and analyzes it to detect the concentration of the substance. Such an absorption spectrum measurement system 100 is mainly configured by an optical measurement unit 1 and an absorption spectrum analyzer 2.

  <Configuration of optical measurement unit 1>

  FIG. 2 is a schematic diagram showing the configuration of the optical measurement unit 1. The optical measurement unit 1 includes a short wavelength cut filter 11, a collimator 12, an interference filter 13, an etalon 14, a condenser lens 15, a detection element 16, and a signal processing circuit 17.

  The measurement wavelength of the optical measurement unit 1 is a region having a half width of 2 nm centered on 1572 nm, and ultraviolet and visible light are out of the measurement range. For this reason, the short wavelength cut filter 11 is configured to block a short wavelength region of 1.3 μm or less.

  The collimator 12 combines two convex lenses and an aperture to match the sun's viewing angle of 0.5 degrees, thereby preventing extra light from entering from a cloud or the like. The collimator 12 is configured to obtain high-quality parallel light for the interference filter 13 and the etalon 14.

  The interference filter 13 has a structure in which the mounting angle can be changed in order to finely adjust the center wavelength. The wavelength can be adjusted in the range of 1569 nm to 1574 nm by changing the mounting angle in the range of 0 degree to 8 degrees. In the measurement of carbon dioxide, the wavelength is adjusted to 1572 nm by setting the mounting angle to 5.5 degrees.

  The etalon 14 is provided with a temperature adjusting unit 14a having a Peltier element, and has a structure capable of controlling the temperature. A temperature control unit 14b is connected to the temperature adjustment unit 14a. The temperature control unit 14b can change the temperature of the etalon 14 within a temperature range of about 10 ° C. The measurement of carbon dioxide is performed while repeatedly raising and lowering the temperature of the etalon 14 by about 10 ° C. The carbon dioxide concentration is measured once in one up / down cycle. The temperature adjustment unit 14a includes a thermistor (not shown), and the temperature control unit 14b is configured to control the temperature of the etalon 14 by PI control using the temperature detected by the thermistor.

  The light emitted from the etalon 14 is collected by the condenser lens 15. The light emitted from the condenser lens 15 is detected by the detection element 16.

  The detection element 16 is an InGaAs photodiode, and can detect light in the near infrared region of 800 nm to 1700 nm.

  The signal processing circuit 17 receives the detection signal output from the detection element 16 and performs various signal processing. The detection signal output from the detection element 16 is converted from an analog signal to a digital signal by the signal processing circuit 17 and output from the signal processing circuit 17 as measurement data indicating the received light intensity for each wavelength.

<Configuration of absorption spectrum analyzer 2>
Next, the configuration of the absorption spectrum analyzer 2 will be described. The absorption spectrum analyzer 2 is configured by a computer. FIG. 3 is a block diagram showing the configuration of the absorption spectrum analyzer 2. The absorption spectrum analyzer 2 is realized by the computer 20. As shown in FIG. 3, the computer 20 includes a main body 21, a display unit 22, and an input unit 23. The main body 21 includes a CPU 21a, ROM 21b, RAM 21c, hard disk 21d, reading device 21e, input / output interface 21f, and image output interface 21h. The CPU 21a, ROM 21b, RAM 21c, hard disk 21d, reading device 21e, input / output interface 21f, The image output interface 21h is connected by a bus 21j.

  The CPU 21a can execute a computer program loaded in the RAM 21c. The computer 21 functions as the absorption spectrum analyzer 2 by the CPU 21a executing the computer program 24a for absorption spectrum analysis.

  The ROM 21b is configured by a mask ROM, PROM, EPROM, EEPROM, or the like, and stores a computer program executed by the CPU 21a, data used for the same, and the like.

  The RAM 21c is configured by SRAM, DRAM, or the like. The RAM 21c is used for reading the computer program 24a recorded on the hard disk 21d. Further, when the CPU 21a executes a computer program, it is used as a work area for the CPU 21a.

  The hard disk 21d is installed with various computer programs to be executed by the CPU 21a, such as an operating system and application programs, and data used for executing the computer programs. A server computer program 24a is also installed in the hard disk 21d.

  The reading device 21e is configured by a flexible disk drive, a CD-ROM drive, a DVD-ROM drive, or the like, and can read a computer program or data recorded on the portable recording medium 24. The portable recording medium 24 stores a computer program 24a for causing the computer to function as the absorption spectrum analyzer 2. The computer 2a reads the computer program 24a from the portable recording medium 24, and the computer program 24a can be installed in the hard disk 21d.

  The computer program 24a is not only provided by the portable recording medium 24, but also from an external device that is communicably connected to the computer 2a via an electric communication line (whether wired or wireless). It is also possible to provide through. For example, the computer program 24a is stored in the hard disk of a server computer on the Internet. The computer 2a can access the server computer, download the computer program, and install it on the hard disk 21d. is there.

  For example, an operating system such as Windows (registered trademark) manufactured and sold by Microsoft Corporation is installed in the hard disk 21d. In the following description, it is assumed that the computer program 24a according to the present embodiment operates on the operating system.

  The input / output interface 21f is, for example, a serial interface such as USB, IEEE1394, or RS-232C, a parallel interface such as SCSI, IDE, or IEEE1284, and an analog interface including a D / A converter, an A / D converter, and the like. It is configured. An input unit 23 composed of a keyboard and a mouse is connected to the input / output interface 21f, and the user can input data to the computer 2a by using the input unit 23.

  Further, the above-described optical measurement unit 1 is connected to the input / output interface 21f. The measurement data output from the optical measurement unit 1 is given to the input / output interface 21f.

  The image output interface 21h is connected to a display unit 22 composed of an LCD, a CRT, or the like, and outputs a video signal corresponding to image data given from the CPU 21a to the display unit 22. The display unit 22 displays an image (screen) according to the input video signal.

[Operation of absorption spectrum measurement system]
Next, the absorption spectrum measurement operation by the absorption spectrum measurement system 100 according to the present embodiment will be described.

  First, the user determines a substance to be measured and measures sunlight with the optical measurement unit 1. At this time, necessary settings are made according to the substance to be measured, such as adjusting the mounting angle of the interference filter 13. In the present embodiment, the operation of the absorption spectrum measurement system when carbon dioxide is the measurement target will be described.

  Data measured by the optical measurement unit 1 is given to the absorption spectrum analyzer 2 and analyzed by the absorption spectrum analyzer 2.

  FIG. 4 is a flowchart showing a procedure of measurement data analysis processing by the absorption spectrum analyzer 2.

  The measurement data output from the optical measurement unit 1 is received by the input / output interface 21f of the absorption spectrum analyzer 2 (step S1). Measurement data (observation spectrum) is information indicating received light intensity for each wavelength. The CPU 21a converts the information indicating the received light intensity for each wavelength into information indicating the transmittance for each wave number (step S2).

  Further, the CPU 21a shifts the wave number of the observation spectrum after conversion (step S3). FIG. 5 is a diagram for explaining the wave number shift of the observed spectrum. As shown in the figure, the observed spectrum has a plurality of minimum values (peaks of valleys) with respect to the transmittance. The wave numbers of these peaks are specific to the object to be measured and are theoretically known. In the observed spectrum, the wave number at each peak includes an error, and in many cases deviates from the theoretical value. The process of step S3 is for correcting such an error. Specifically, the observed spectrum is wavenumber shifted so that the difference between each wavenumber at each peak and each corresponding theoretical value is minimized. The wavenumber-shifted observation spectrum data is stored in the RAM 21c or the hard disk 21d.

  Next, the CPU 21a applies a device function specific to the optical measurement unit 1 to the calculated spectrum of the black body radiation, and the observation spectrum when the black body radiation is virtually observed by the optical measurement unit 1 (hereinafter, referred to as “black body radiation”). (Referred to as “virtual solar spectrum”) (step S4). The theoretical value of the spectrum of blackbody radiation does not include variations in optical measurements. On the other hand, when the spectrum of blackbody radiation is actually measured, variation occurs depending on the state of the apparatus that performs the optical measurement. The process of step S4 is for reproducing the spectrum of the black body radiation actually observed by the optical measurement unit 1 by calculation.

  Next, the CPU 21a acquires the wave number range of the observation spectrum stored in the RAM 21c or the hard disk 21d, and extracts data within the wave number range from the data included in the virtual solar spectrum (step S5). Hereinafter, this extracted data is referred to as an extracted solar spectrum.

  In addition, the CPU 21a displays an input screen for inputting the observation position (altitude), temperature, and atmospheric pressure on the ground surface on the display unit 22, and receives the input of the observation position, temperature, and atmospheric pressure from the user (step S6). The user operates the input unit 23 to input the observation position, the temperature, and the atmospheric pressure to the absorption spectrum analyzer 2.

  Next, the CPU 21a executes an absorption spectrum theoretical value calculation process (step S7). In this absorption spectrum theoretical value calculation process, an absorption spectrum when the carbon dioxide concentration is set to a predetermined value (385 ppm) is calculated based on the extracted solar spectrum and the input observation position, temperature, and atmospheric pressure.

  Here, the absorption spectrum theoretical value calculation processing will be described in more detail. In the absorption spectrum theoretical value calculation process, the linearity (absorption line) of the absorption spectrum of the substance is expressed by an approximate expression.

ただし、τ（ν）は光学的厚みである。簡単のために吸収する成分が１種類だけとすると、光学的厚みτ（ν）は、次式で表される。

ただし、（２）式において、σ（ｚ，ν）は吸収係数を、ｑ（ｚ）は吸収成分の高度ｚにおける数密度を、ｄｕは光路に沿った積分を示す。また、光路は大陽天頂角によって定まる。 Assuming that the sunlight intensity at the upper end of the atmosphere is I ₀ (ν), the observed light intensity I (ν) is expressed by the following equation.

Where τ (ν) is the optical thickness. Assuming that only one type of component is absorbed for simplicity, the optical thickness τ (ν) is expressed by the following equation.

In equation (2), σ (z, ν) is an absorption coefficient, q (z) is a number density of the absorption component at an altitude z, and du is an integration along the optical path. The optical path is determined by the Taiyo zenith angle.

ただし、Ｓ（Ｔ）は線強度を、ｆ（ν，Ｐ，Ｔ）は吸収線形関数（吸収線形の近似式）を示す。 The absorption coefficient σ (z, ν) is determined from the intensity of absorption and its spread, and is given by the following equation.

Here, S (T) represents the line intensity, and f (ν, P, T) represents an absorption linear function (an approximate expression of absorption linear).

ただし、Ｓ_０、Ｅ"、ν_０、ν_Ｌ０、ｎのそれぞれは定数である。また、Ｐは圧力を、Ｔは温度を示し、Ｔ_０＝２９６Ｋ、Ｐ_０＝１０１３．２５ｈＰａである。 The absorption line shape is a superposition of the spread due to the Doppler width and the Lorentz width, and is generally approximated by a function called a Vogt function.

However, S ₀ , E ″, ν ₀ , ν _L0 , and n are constants. P represents pressure, T represents temperature, and T ₀ = 296K and P ₀ = 1013.25 hPa.

  The absorption spectrum can be calculated by preparing the necessary q (z), T (z), and P (z) as inputs using the above formula. In the absorption spectrum theoretical value calculation process, the concentration of carbon dioxide, which is a measurement target component, is set to 385 ppm, and the absorption spectrum is obtained using the input observation position, temperature, and atmospheric pressure.

  After executing the absorption spectrum theoretical value calculation process as described above, the CPU 21a calculates the absorption spectrum actual data obtained after the wave number shift stored in the RAM 21c or the hard disk 21d and the absorption spectrum theoretical value calculation process. Baseline setting processing is executed using the theoretical data (step S8).

  FIG. 6 is a flowchart showing the procedure of the baseline setting process, and FIG. 7 is a diagram for explaining the contents of the baseline setting process. In the baseline setting process, first, the CPU 21a divides the measured value of the absorption spectrum after the wave number shift into a plurality of sections (step S801). In this process, as shown in FIG. 7, the wave number corresponding to the lower peak value is obtained, and the sections are divided using each wave number as a boundary. In FIG. 7, the measured value of the absorption spectrum is indicated by a solid curve, and the theoretical value of the absorption spectrum is indicated by a broken curve. In addition, the boundary of the section is indicated by a solid line (thin line).

  Next, the CPU 21a detects a maximum value (peak of a mountain) in each section of the actually measured value of the absorption spectrum, and specifies the wave number corresponding to each maximum value (step S802). In FIG. 7, the maximum value of the actually measured value of the absorption spectrum is indicated by a black circle.

  Next, the CPU 21a specifies the theoretical value of the absorption spectrum corresponding to the wave number specified in step S802 (step S803). In FIG. 7, the theoretical value corresponding to the maximum value of the actually measured value of the absorption spectrum is indicated by a black square mark.

  Next, the CPU 21a linearly interpolates adjacent theoretical values specified in step S803 (step S804). Hereinafter, the line obtained by interpolating the theoretical value in step S804 is referred to as “theoretical value interpolation line”. In FIG. 7, the theoretical value interpolation line is indicated by a broken line.

  Next, the CPU 21a detects a maximum value (peak of a mountain) in each section of the theoretical value of the absorption spectrum, and specifies a wave number corresponding to each maximum value (step S805). The section at this time is the same as the section set in step S801. In FIG. 7, the maximum value of the theoretical value of the absorption spectrum is indicated by white circles.

  Next, the CPU 21a specifies an actual measurement value of the absorption spectrum corresponding to the wave number specified in step S805 (step S806). In FIG. 7, the actual measurement value corresponding to the maximum value of the theoretical value of the absorption spectrum is indicated by a white square mark.

  Next, the CPU 21a linearly interpolates adjacent measured values specified in step S806 (step S807). Hereinafter, the line obtained by interpolating the actual measurement values in step S807 is referred to as “actual measurement value interpolation line”. In FIG. 7, the actually measured value interpolation line is indicated by a broken line.

  Next, the CPU 21a averages the theoretical value interpolation line and the actual measurement value interpolation line for each identical wave number, and sets the obtained average line as a base line (step S808). In FIG. 7, the base line is indicated by a solid line. When the process of step S808 ends, the CPU 21a returns the process to the main routine.

  After completing the baseline setting process as described above, the CPU 21a calculates the concentration of carbon dioxide by fitting a forked function to the measured value of the absorption spectrum for which the baseline has been set (step S9).

  In step S9, the concentration of carbon dioxide is calculated as follows.

波長方向のデータ数がＭ個あるとすると、σ_ｉ，ｊは次のような行列となる。

To actually solve the equation (2), if the atmosphere is divided into N layers and rewritten as the sum of absorption in each layer, the following equation is obtained.

Assuming that the number of data in the wavelength direction is M, σ _{i, j} is a matrix as follows.

これにより、（３）式は、次式のようになる。

あとは、

とおいて、Ｒｅｓが最小になるように、

を解く。 If the inverse matrix of σ is calculated, q (z) can be obtained from the observed value τ, but the calculation of the inverse matrix is not easy. Here, in the present embodiment, the total amount of the air column (the number of molecules of the measurement target component contained in the air column from the ground having a unit cross-sectional area to the upper end of the atmosphere) is obtained. When only the total amount of air column is calculated, the variable can be reduced to one.

As a result, Equation (3) becomes as follows.

later,

In order to minimize Res,

Solve.

  When the carbon dioxide concentration is calculated by spectrum fitting as described above, the CPU 21a displays the calculated concentration of carbon dioxide on the display unit 22 (step S10), and the process ends.

  By configuring as described above, in the absorption spectrum analysis system 100 according to the present embodiment, it is possible to set a baseline and to obtain the concentration of the substance to be measured with high accuracy. In addition, no calibration curve is required to set the baseline. This eliminates the need for a standard substance necessary for preparing a calibration curve, and eliminates the need to measure the standard substance. In addition, in the infrared spectroscopy from the ground using the sun as a light source, as in the absorption spectrum analysis system 100 according to the present embodiment, the calibration is performed by setting a device function corresponding to the resolution of the optical measurement unit 1. Absorption spectra are measured without using lines. Therefore, a baseline setting method that does not require a calibration curve is particularly useful in infrared spectroscopy using such Taiyo as a light source.

(Other embodiments)
In the above embodiment, the absorption spectrum indicates the relationship between the wave number and the transmittance. However, the present invention is not limited to this. It is also possible to use an absorption spectrum showing the relationship between wavelength and absorbance.

  In the above embodiment, the configuration for analyzing the absorption spectrum of carbon dioxide by infrared spectroscopy from the ground using Taiyo as the light source has been described, but the present invention is not limited to this. In infrared spectroscopy using an infrared laser, it is also possible to adopt a configuration in which a baseline is set based on the measured value of the absorption spectrum of the substance to be measured and the theoretical value of the absorption spectrum of the substance to be measured. .

  Moreover, in said embodiment, although the absorption spectrum analyzer 2 was comprised by the computer 20, it is not limited to this. It is also possible to configure hardware that can perform the same processing as the absorption spectrum analyzer 2 by using an application specific integrated circuit (ASIC) or a field-programmable gate array (FPGA). Further, in the present embodiment, the optical measurement unit 1 and the absorption spectrum analyzer 2 are configured as separate units. However, one device in which the function of the optical measurement unit 1 and the function of the absorption spectrum analyzer 2 are mounted. It is also possible.

  Absorption spectrum analyzer, substance absorption spectrum baseline setting method, and computer program according to the present invention include an absorption spectrum analyzer for setting a substance absorption spectrum baseline, and a substance absorption spectrum baseline setting method And as a computer program.

DESCRIPTION OF SYMBOLS 1 Optical measurement unit 11 Short wavelength cut filter 12 Collimator 13 Interference filter 14 Etalon 15 Condensing lens 16 Detection element 17 Signal processing circuit 2 Absorption spectrum analyzer 20 Computer 21 Main body 21a CPU
21c RAM
21d Hard disk 22 Display unit 23 Input unit 24 Portable recording medium 24a Computer program

Claims (8)

Based on the measured value of the absorption spectrum indicating the relationship between the wavelength or wave number and the absorbance or transmittance of the specific substance, and the theoretical value of the absorption spectrum indicating the relationship between the wavelength or wave number and the absorbance or transmittance of the specific substance An absorption spectrum analyzer for setting a baseline of an absorption spectrum of the specific substance,
Actual value acquisition means for acquiring measurement data of the absorption spectrum of the specific substance;
A theoretical value acquisition means for acquiring a theoretical value of an absorption spectrum of the specific substance;
Based on the measurement data acquired by the actual measurement value acquisition unit , a first wavelength / wave number identification unit that identifies wavelengths or wave numbers at a plurality of peaks of the actual measurement value of absorbance or transmittance;
Theoretical value specifying means for specifying the absorbance or transmittance of the theoretical value of the absorption spectrum at a plurality of wavelengths or wave numbers specified by the first wavelength / wave number specifying means;
Based on the theoretical value of the absorption spectrum acquired by the theoretical value acquiring means, second wavelength / wave number specifying means for specifying wavelengths or wave numbers at a plurality of peaks of the theoretical value of absorbance or transmittance;
Actual value specifying means for specifying the absorbance or transmittance of the actual measurement values of the absorption spectrum at a plurality of wavelengths or wave numbers specified by the second wavelength / wave number specifying means;
First interpolation line generation means for generating a theoretical value interpolation line by interpolating a plurality of theoretical values specified by the theoretical value specifying means;
Second interpolation line generation means for interpolating a plurality of actual measurement values specified by the actual measurement value specifying means to generate an actual measurement value interpolation line;
A result obtained by averaging the theoretical value interpolation line generated by the first interpolation line generation unit and the actual measurement value interpolation line generated by the second interpolation line generation unit for each wavelength or wave number is obtained as the specific value. A baseline setting means for setting as a baseline of the absorption spectrum of the substance;
Comprising
Absorption spectrum analyzer. The first interpolation line generation means is configured to linearly interpolate a plurality of theoretical values specified by the theoretical value specifying means to generate a theoretical value interpolation line,
The second interpolation line generation unit is configured to linearly interpolate a plurality of actual measurement values specified by the actual measurement value specifying unit to generate an actual measurement value interpolation line.
The absorption spectrum analyzer according to claim 1. The actual measurement value acquisition means comprises correction means for correcting the actual measurement value of the absorption spectrum with respect to the wavelength or wave number based on the wavelength or wave number at a plurality of peaks of the theoretical value of absorbance or transmittance of the specific substance, The actual value of the absorption spectrum corrected by the correcting means is configured to obtain as the measurement data,
The absorption spectrum analyzer according to claim 1 or 2. The theoretical value acquisition means is configured to acquire a theoretical value of an absorption spectrum of the specific substance at a position where the measurement data acquired by the actual measurement value acquisition means is measured, temperature, and atmospheric pressure.
The absorption spectrum analyzer according to any one of claims 1 to 3. The theoretical value acquisition unit is configured to acquire a theoretical value of an absorption spectrum of the specific substance in a wavelength or wave number range in the measurement data acquired by the actual measurement value acquisition unit.
The absorption spectrum analyzer according to any one of claims 1 to 4. The first wavelength / wave number identification unit divides the measurement data acquired by the actual measurement value acquisition unit into a plurality of sections with respect to wavelength or wave number, and in each of the divided sections, the measured values of absorbance or transmittance are measured. It is configured to identify one peak and identify the wavelength or wave number at each peak,
The second wavelength / wave number specifying means obtains one peak of a theoretical value of absorbance or transmittance in each of a plurality of sections for the wavelength or wave number obtained by dividing the measurement data by the first wavelength / wave number specifying means. Is configured to identify and identify the wavelength or wave number at each peak,
The absorption spectrum analyzer according to any one of claims 1 to 5. Based on the measured value of the absorption spectrum indicating the relationship between the wavelength or wave number and the absorbance or transmittance of the specific substance, and the theoretical value of the absorption spectrum indicating the relationship between the wavelength or wave number and the absorbance or transmittance of the specific substance A method for setting a baseline of an absorption spectrum of the specific substance,
Obtaining measurement data of an absorption spectrum of the specific substance;
Obtaining a theoretical value of an absorption spectrum of the specific substance;
Identifying the wavelength or wave number at a plurality of peaks of the measured value of absorbance or transmittance based on the acquired measurement data; and
Identifying the absorbance or transmittance of the theoretical value of the absorption spectrum at the specified wavelengths or wave numbers;
Identifying the wavelength or wave number at a plurality of peaks of the theoretical value of absorbance or transmittance based on the obtained theoretical value of the absorption spectrum;
Identifying the absorbance or transmittance of the measured value of the absorption spectrum at the specified wavelengths or wave numbers;
Interpolating a plurality of identified theoretical values to generate a theoretical value interpolation line;
Interpolating a plurality of identified actual measurement values to generate an actual measurement value interpolation line;
Setting the result of averaging the generated theoretical value interpolation line and the generated actual measurement value interpolation line for each wavelength or wave number as a baseline of the absorption spectrum of the specific substance;
Having
How to set the baseline of absorption spectrum. Based on the measured value of the absorption spectrum indicating the relationship between the wavelength or wave number and the absorbance or transmittance of the specific substance, and the theoretical value of the absorption spectrum indicating the relationship between the wavelength or wave number and the absorbance or transmittance of the specific substance A computer program for causing a computer to set a baseline of the absorption spectrum of the specific substance,
Actual value acquisition means for acquiring measurement data of the absorption spectrum of the specific substance;
A theoretical value acquisition means for acquiring a theoretical value of an absorption spectrum of the specific substance;
Based on the measurement data acquired by the actual measurement value acquisition unit , a first wavelength / wave number identification unit that identifies wavelengths or wave numbers at a plurality of peaks of the actual measurement value of absorbance or transmittance;
Theoretical value specifying means for specifying the absorbance or transmittance of the theoretical value of the absorption spectrum at a plurality of wavelengths or wave numbers specified by the first wavelength / wave number specifying means;
Based on the theoretical value of the absorption spectrum acquired by the theoretical value acquiring means, second wavelength / wave number specifying means for specifying wavelengths or wave numbers at a plurality of peaks of the theoretical value of absorbance or transmittance;
Actual value specifying means for specifying the absorbance or transmittance of the actual measurement values of the absorption spectrum at a plurality of wavelengths or wave numbers specified by the second wavelength / wave number specifying means;
First interpolation line generation means for generating a theoretical value interpolation line by interpolating a plurality of theoretical values specified by the theoretical value specifying means;
Second interpolation line generation means for interpolating a plurality of actual measurement values specified by the actual measurement value specifying means to generate an actual measurement value interpolation line;
A result obtained by averaging the theoretical value interpolation line generated by the first interpolation line generation unit and the actual measurement value interpolation line generated by the second interpolation line generation unit for each wavelength or wave number is obtained as the specific value. As a baseline setting means to set as the baseline of the absorption spectrum of a substance,
Causing the computer to function;
Computer program.

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