KR20240094368A - Method and device for laser absorption spectroscopy analysis - Google Patents

Abstract

The present invention is a method of analyzing a target gas existing in a measurement space using a laser absorption spectroscopic analysis device, comprising the steps of irradiating broadband light into the measurement space and obtaining an absorption spectrum for each wavelength of the broadband light that passed through the measurement space. It provides a laser absorption spectroscopy analysis method including calculating a temperature coefficient based on a reference wavelength of the absorption spectrum and estimating the temperature of the target gas by applying the temperature coefficient to a temperature table.

Description

Laser absorption spectroscopic analysis method and device {METHOD AND DEVICE FOR LASER ABSORPTION SPECTROSCOPY ANALYSIS}

The present invention relates to a laser absorption spectroscopy analysis method and device, and more specifically, to a laser absorption spectroscopy analysis method and device that can measure both the temperature and concentration of a gas using a broadband light source and an imaging spectrometer.

Tunable Diode Laser Absorption Spectroscopy (TDLAS) is a gas analysis technology that has recently received great attention in the energy and environmental fields. This type of analysis technology can measure the concentration of various types of gases using a light source containing light with an absorption wavelength determined depending on the type of gas to be analyzed, and can also be applied to large combustion systems in environments where measurement is difficult. It is applied in various forms.

The basic principle of gas concentration measurement in TDLAS comes from the light absorption characteristics of gas according to the Beer-Lambert law. Specifically, all gases absorb light of a certain set of wavelengths. As a representative example, light with a wavelength of 760 nm passes through other gas species, but oxygen (O ₂ ) absorbs it. In other words, if light with a wavelength around 760 nm is irradiated to a gas area containing oxygen and the light that passes through is analyzed using a photodetector, the light at that wavelength is not affected by other gas species but is only affected by oxygen. The principle is that the concentration of oxygen can be analyzed by analyzing the shape of the absorbed spectrum.

As environmental issues have emerged as a social issue around the world, efforts to reduce pollutants such as greenhouse gases and fine dust are being actively pursued, and research and efforts on this matter are continuing in Korea as well. In the case of industrial reactors used in power plants, steel mills, etc., many pollutants are generated during the combustion process, which requires efforts to optimize the air-fuel ratio. Optimizing the air-fuel ratio is possible by analyzing the concentration of oxygen present in the combustion process in real time, and interest in TDLAS as an analysis technology required in this process is increasing.

However, since TDLAS is basically a technology that analyzes gas by varying the very narrow wavelength of laser light as shown in Figure 1, a time delay occurs in the absorption spectrum for each wavelength, which has the disadvantage of lowering the accuracy of the analysis results. exist.

In addition, due to the harsh environment inside the measurement area, such as high temperature, gas flow, and vibration, thermal deformation (distortion), vibration, and dust (scattering) may occur, and as a result, the laser light passes through the measurement area and enters the photodetector. In the process, the size of the signal may become weak. As a result, when the laser light is received with the light receiver fixed, the optical axis of the laser light and the center of the light receiver are distorted, resulting in a weak signal, which makes it impossible to accurately analyze the gas.

In addition, since TDLAS is basically a technology that analyzes gas by varying the very narrow wavelength of laser light, it can only measure the concentration of the gas and cannot detect the temperature of the gas. Additionally, there is a problem in that another gas must be used to detect the temperature of the gas.

Registered Patent Publication No. 10-1767177

The purpose of the present invention is to provide a laser absorption spectroscopy analysis method and device that can accurately analyze both the concentration and temperature of a target gas in real time using a broadband light source and a spectrometer, as shown in FIG. 2.

In addition, the present invention provides a multi-channel laser absorption spectroscopy analysis method and device that can accurately analyze the target gas by configuring multiple laser beam paths even if the target gas is unevenly distributed in the measurement space by adding an imaging spectrometer. The purpose is to

In addition, the present invention provides a multi-channel laser absorption analysis method that can analyze multiple light emitting units, optical paths, and light receiving units using a single spectroscopic device even if the area to analyze gas is spatially separated by adding an imaging spectrometer, and The purpose is to provide a device.

The technical problems to be achieved in the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by those skilled in the art from the description below. There will be.

In order to solve this problem, the present invention is a method of analyzing a target gas existing in a measurement space using a laser absorption spectroscopic analysis device, comprising the steps of irradiating broadband light into the measurement space, and the wavelength of the broadband light passing through the measurement space. A laser absorption spectroscopy analysis method comprising the steps of acquiring a star absorption spectrum, calculating a temperature coefficient based on the reference wavelength of the absorption spectrum, and applying the temperature coefficient to a temperature table to estimate the temperature of the target gas. to provide.

Here, the step of calculating the temperature coefficient is the step of calculating the temperature coefficient based on the sum of the first absorption cross-section at the wavelengths located on one side and the sum of the second absorption cross-section at the wavelengths located on the other side with respect to the reference wavelength. You can.

More specifically, the step of calculating the temperature coefficient includes the difference between the sum of the first absorption cross-sections at the wavelengths located on one side and the second absorption cross-section at the wavelengths located on the other side with respect to the reference wavelength and the sum of the first absorption cross-sections. And it may be a step of calculating the temperature coefficient based on the ratio of the sum of the sum of the second absorption cross-sectional areas.

Additionally, the reference wavelength may vary depending on the type of target gas.

Additionally, the temperature table may be a table defining a temperature coefficient that changes linearly depending on the temperature of the target gas.

In addition, the laser absorption spectroscopic analysis method of the present invention may further include measuring the concentration of the target gas using the absorption cross-section of the absorption spectrum at the estimated temperature of the target gas.

In addition, a laser absorption spectroscopic analysis device is provided including an analysis unit that analyzes the target gas present in the measurement space by applying the above-described laser absorption spectroscopic analysis method.

Here, the laser absorption spectroscopic analysis device of the present invention includes a light source that irradiates broadband light, a first optical unit (light emitting unit) that condenses at least a portion of the broadband light and introduces it into the measurement space, and the broadband light that passes through the measurement space. It may further include a second optical unit (light receiver) that collects at least a portion of the light, a spectroscope that splits the broadband light collected by the second optical unit, and an image sensor that forms an image of the broadband light split by the spectrometer.

Additionally, the analysis unit may generate an absorption spectrum for each wavelength of the broadband light imaged on the image sensor.

In addition, the laser absorption spectroscopic analysis device of the present invention may further include an optical fiber block including at least one optical fiber that passes the broadband light collected by the second optical unit.

In addition, the laser absorption spectroscopic analysis device of the present invention is capable of simultaneously speculating and imaging broadband light transmitted through a plurality of optical fibers to an image sensor instead of a spectrometer that specifies and forms a single light collected by the second optical unit. It may further include an imaging spectrometer.

According to the present invention, there is an advantage in that both the concentration and temperature of the target gas can be quantified based on various absorption cross-sections in a wide wavelength range using a light source and a spectrometer that irradiates broadband light.

In addition, according to the present invention, since the type and concentration of the target gas is determined by analyzing the absorption cross-section for each wavelength at the same time after irradiating broadband light, there is no time delay in the absorption cross-section for each wavelength like in the conventional TDLAS, Because the absorption cross-sectional area over a wide wavelength range is analyzed, the target gas can be analyzed faster and more accurately than the existing laser absorption spectroscopy (TDLS).

Additionally, according to the present invention, by three-dimensionally analyzing broadband light that passes through a plurality of directions with respect to the measurement space, the target gas can be accurately analyzed even if the target gas is unevenly distributed within the measurement space.

In addition, according to the present invention, the type and concentration of the target gas can be accurately determined by detecting the spectrum of broadband light that does not pass through the measurement space, defining this spectrum as a reference spectrum, and comparing it with the spectrum of broadband light that passed through the measurement space. You can.

The effects that can be obtained from the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the description below. will be.

1 is a schematic diagram of a conventional laser absorption spectroscopy (TDLS).
Figure 2 is a schematic configuration diagram of a laser absorption spectroscopic analysis device according to an embodiment of the present invention.
Figure 3 is a detailed configuration diagram of an imaging spectrometer according to an embodiment of the present invention.
Figure 4 is a detailed configuration diagram of an optical fiber block according to an embodiment of the present invention.
Figure 5 is a diagram illustrating a process in which broadband light transmitted through a multi-channel (1,...n channel) optical fiber block is imaged on an image sensor.
Figure 6 shows the reference spectrum formed on the image sensor through the 1st channel of the imaging spectrometer after passing through the background space where oxygen does not exist, rather than the measurement space, and the image formed on the image sensor through the 12th channel of the imaging spectrometer without an optical path from a broadband light source. This is a diagram illustrating the corrected spectrum.
FIG. 7 is a diagram showing the spectrum for each wavelength and the light intensity for each wavelength detected on the image plane of the image sensor according to an embodiment of the present invention.
Figure 8 is a diagram illustrating a spectrum detected on the image plane of an image sensor using a 12-channel optical fiber block according to an embodiment of the present invention and a spectrum generated through simulation.
Figure 9 is a simplified diagram showing the absorption spectrum for each wavelength of broadband light generated by the analysis unit according to an embodiment of the present invention.
Figure 10 is a diagram showing the absorption spectrum of oxygen (O ₂ ) generated by the analysis unit according to an embodiment of the present invention by temperature.
Figure 11 is a graph showing the temperature coefficient that changes depending on the target gas temperature for each wavelength resolution of the imaging spectrometer according to an embodiment of the present invention.
Figure 12 is a diagram for explaining a method by which an analysis unit analyzes the concentration of a target gas according to an embodiment of the present invention.

Terms or words used in this specification and claims should not be construed as limited to their common or dictionary meanings, and the inventor may appropriately define the concept of terms in order to explain his or her invention in the best way. It must be interpreted with meaning and concept consistent with the technical idea of the present invention based on the principle that it is.

Therefore, the embodiments described in this specification and the configurations shown in the drawings are only the most preferred embodiments of the present invention and do not represent the entire technical idea of the present invention, so various equivalents can be substituted for them at the time of filing the present application. It should be understood that there may be variations.

Hereinafter, with reference to the attached drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention.

Figure 1 is a schematic diagram of a conventional laser absorption spectroscopic analysis device.

Referring to FIG. 1, in a conventional laser absorption spectroscopic analysis device, the light emitting part 10 is composed of a tunable diode laser, and the light receiving part is composed of a photo-detector.

Existing laser absorption spectroscopic analysis devices measure the absorption spectrum of a laser beam passing through a measurement space through an optical detector while changing the oscillation wavelength of a tunable laser over time. Here, the measured spectrum can be analyzed according to the Beer-Lambert law to estimate the concentration of the target gas.

Figure 2 is a schematic configuration diagram of a laser absorption spectroscopic analysis device according to an embodiment of the present invention, and Figure 3 is a detailed configuration diagram of a laser absorption spectroscopic analysis device according to an embodiment of the present invention.

Referring to FIGS. 1 and 2, the laser absorption spectroscopic analysis device according to an embodiment of the present invention, unlike the configuration of FIG. 1, has a broadband laser (super luminescent laser) that oscillates laser in a wide range as a light source 110. and an image spectrometer 170 is provided in the light receiving unit.

Referring to FIG. 3, the laser absorption spectroscopic analysis device according to an embodiment of the present invention is additionally provided with an optical fiber block 160 at the input end of the imaging spectrometer 170.

The laser absorption spectroscopic analysis device according to an embodiment of the present invention includes a light source 110, a first optical unit 120, and a first optical unit 120 to analyze the target gas present in the measurement space 11 inside the measurement cell 10. 2 It may be configured to include an optical unit 140, an optical fiber block 160, an imaging spectrometer 170, an image sensor 180, and an analysis unit 190.

The light source 110 may be a broadband laser that irradiates broadband light, but is not limited thereto. Here, the broadband laser can overcome the limitations of the limited wavelength band of existing monochromatic lasers or tunable lasers, and can be used in various fields such as bio imaging, inspection of semiconductor wafers and optoelectronic devices, and environmental monitoring.

The first optical unit 120 may include at least one lens and is disposed outside the measurement cell 10 to collect at least a portion of the broadband light irradiated from the light source 110 and store it inside the measurement cell 10. It can be introduced into the measurement space (11). Here, the light collected by the first optical unit 120 may be reflected by the first mirror 131 and enter the measurement space 11.

The second optical unit 140 may include at least one lens and is disposed outside the measurement cell 10 opposite the first optical unit 120 to select a portion of the broadband light passing through the measurement space 11. At least some of it can be concentrated. Here, the broadband light passing through the measurement space 11 may be reflected by the second mirror 132 and incident on the second optical unit 140. The light incident on the second optical unit 140 is input to one end of the plurality of optical fibers 161 and 163 present in the optical fiber block 160 and is transmitted to the imaging spectrometer 170.

Here, the optical fiber block 160 consists of a plurality of optical fibers 161 to 163, a V-grove array for optical fiber alignment, and a cover. Optical fibers 161 to 163 are a type of thin glass or plastic fiber that transmits light. The principle of optical fiber is that the inside and outside of the optical fiber are made of glass fibers with different densities and refractive indices, so that once incident light is inside the optical fiber. The goal is to minimize light loss by performing total reflection.

The plurality of optical fibers present in the optical fiber block 160 are divided into a correction optical fiber 163, a reference optical fiber 162, and a measurement optical fiber 161 according to the nature of the input light. The reference optical fiber 162 is connected to the light source 110 and can pass some of the broadband light emitted from the light source 110 without passing through the measurement space 11.

Although not shown in the drawing, the broadband light emitted from the light source 110 may be separated by a beam splitter. That is, some of the broadband light may be incident on the reference optical fiber 162 by the beam splitter, and the remainder may be incident on the first optical unit 120.

The image spectrometer 170 can split the broadband light that has passed through the measurement optical fiber 161, the reference optical fiber 163, and the correction optical fiber 163, respectively, and form an image on the image sensor 180. Here, the image spectrometer 170 is an optical device that specifies light using a dispersion element (eg, a diffraction grating) and forms an image on the image sensor 180, and can measure the intensity of light for each wavelength.

The image sensor 180 may detect the spectrum of broadband light split by the image spectrometer 170 as a binarized value. Here, the image sensor 180 may be a charge coupled device (CCD) camera or a complementary metal oxide semiconductor (CMOS) camera, but is not limited thereto.

The analysis unit 190 may estimate the temperature and concentration of the target gas by analyzing the spectrum data of the broadband light detected by the image sensor 180.

The laser absorption spectroscopy analysis method according to an embodiment of the present invention may be implemented in the form of an algorithm applied to the analysis unit 190.

Figure 4 is a detailed configuration diagram of an optical fiber block according to an embodiment of the present invention. Here, (a) is a diagram showing the side of the optical fiber block, and (b) is a diagram showing the front of the optical fiber block.

Referring to FIG. 4, the optical fiber block 160 may be configured to include n (where n is a natural number of 2 or more) measurement optical fibers 161_1 to 161_n. Correspondingly, the first optical unit 120 may be comprised of n first optical units 120_1 to 120_n, and the second optical unit 140 may be comprised of n second optical units 140_1 to 140_n. there is.

Here, n first optical units 120_1 to 120_n may be disposed in n different measurement cells located outside the measurement cell 10, and n second optical units 140_1 to 140_n may be disposed in n different measurement cells. 1 It may be disposed outside each measurement cell 10, opposite to the optical units 120_1 to 120_n.

Additionally, the n first optical units 120_1 to 120_n may each receive broadband light from n light sources 110, or may receive broadband light by branching one light source into n pieces.

The n measurement optical fibers 161_1 to 161_n transmit the broadband light collected by the n second optical units 140 to the optical fiber block 160 installed at the input terminal of the imaging spectrometer 170. That is, n measurement optical fibers 161_1 to 161_n can each receive broadband light that has passed through n different measurement spaces 11.

Although only one reference optical fiber 162 is shown in FIG. 4, the reference optical fibers 162 may be provided in the same number as a pair with the measurement optical fibers 161_1 to 161_n and have the same optical path.

Figure 5 is a diagram illustrating a process in which broadband light transmitted through a multi-channel (1,...n channel) optical fiber block is imaged on an image sensor.

Referring to FIG. 5, the imaging spectrometer 170 may be configured to include a slit 171 and a dispersion element 172.

The slit 171 has a line-shaped transmission area and is installed to match the end of the optical fiber block 160, so that the broadband light emitted from the n optical fibers 161_1 to 161_n is transmitted to the transmission area of the image spectrometer 170. It can be passed.

The dispersion element 172 can split the broadband light that has passed through the slit 171 by wavelength. Here, the dispersion element 172 may be a prism or a diffraction grating, but is not limited thereto.

In this way, the broadband light split by the image spectrometer 170 can be detected as a spectrum for each wavelength on the image plane of the image sensor 180.

Figure 6 shows the reference spectrum formed on the image sensor through the 1st channel of the imaging spectrometer after passing through the background space where oxygen does not exist, rather than the measurement space, and the image formed on the image sensor through the 12th channel of the imaging spectrometer without an optical path from a broadband light source. This is a diagram illustrating the corrected spectrum.

Referring to FIG. 6, the reference spectrum passing through the background space, which has the same optical path and environment as the measurement space and does not contain the gas to be analyzed, is the reference value ( ), and unlike a broadband light source, the correction spectrum obtained directly from a correction light source (Ar Lamp, etc.) through the correction optical fiber 163 is used at a correction wavelength (e.g., 772.38 nm, 763.52 nm) in the image sensor 180. , 750.39nm) can be used to calculate the exact wavelength range and wavelength value of the image spectrometer 170 by measuring the vertical position value and defining the main specifications of the image spectrometer 170, such as dispersion amount, half width, and wavelength resolution.

First, through image processing for the correction wavelength, the dispersion amount (d = 0.0152 nm/pixel) and the half width (w = 10 pixels) of the image spectrometer 170 are obtained, and from this, the wavelength resolution of the image spectrometer 170 ( r=d×w=0.152nm) can be calculated.

Also, by finding a straight line fit or parabolic equation using the three correction wavelengths, sampled wavelength values for all pixel positions can be obtained and the reference wavelength (762.04nm) for temperature analysis can be displayed.

Figure 7 is a diagram showing the spectrum (a) for each wavelength and the light intensity (b) for each wavelength detected on the image plane of the image sensor according to an embodiment of the present invention.

In FIG. 7, A is the absorption wavelength absorbed by the target gas, and A-W and A+W mean the full width at half maximum (FWHM) of broadband light.

Referring to FIG. 7 (a), broadband light emitted from n measurement optical fibers 161_1 to 161_n may pass through the image spectrometer 170 and be detected as a vertical line on the image plane of the image sensor 180. Specifically, n spectra corresponding to n measurement optical fibers 161_1 to 161_n may be detected as vertical lines at regular intervals in the horizontal direction.

Referring to FIG. 7 (b), the broadband light passing through the n-th measurement optical fiber 161_n strongly absorbs light of a specific wavelength (Wavelength) by the target gas while passing through the measurement space 11, and the remaining wavelengths are absorbed by the target gas. can weakly absorb light. Here, the greater the degree of absorption, the lower the light intensity. Using this principle, the analysis unit 190 can derive the type and concentration of the target gas present in the measurement space 11.

For example, if the target gas is oxygen (O ₂ ), oxygen mainly absorbs light with a wavelength of 760 nm and does not absorb light in the remaining wavelength ranges. Therefore, as shown in FIG. 7 (b), the analysis unit 190 confirms that the wavelength at which the light intensity decreases is 760 nm, and determines that the target gas present in the measurement space 11 is oxygen. You can. Additionally, the concentration of the target gas can be calculated according to the lowered light intensity.

As such, the laser absorption spectroscopic analysis device according to an embodiment of the present invention determines the type and concentration of the target gas by analyzing the absorption by wavelength at the same time after irradiating broadband light, so like the conventional TDLAS, There is no time delay in absorption, and thus the target gas can be accurately analyzed in real time.

Meanwhile, the target gas may be mostly unevenly distributed within the measurement space 11. Therefore, the target gas cannot be accurately analyzed only by analyzing the broadband light passing in one direction with respect to the measurement space 11.

Therefore, as described above, the laser absorption spectroscopic analysis device according to an embodiment of the present invention includes a light source 110, a first optical unit 120, a second optical unit 140, and a plurality of measurement optical fibers 161. By three-dimensionally analyzing the broadband light passing through the measurement space 11 in multiple directions, the target gas can be accurately analyzed even if the target gas is unevenly distributed within the measurement space 11.

In addition, as shown in FIGS. 3 and 5, the laser absorption spectroscopic analysis device according to an embodiment of the present invention includes only one relatively expensive image spectrometer 170, but one image spectrometer 170 is spatially Since all of the broadband light passing through the plurality of separated measurement spaces 11 is split and formed into an image on the image plane of the image sensor 180, there is an effect of reducing costs.

Meanwhile, in order to accurately determine the type and concentration of the target gas by analyzing the absorption by wavelength of the broadband light that passed through the measurement space 11, a judgment standard is necessary. In other words, it is necessary to check the spectrum of the broadband light emitted by the light source 11.

To this end, the analysis unit 190 may analyze the target gas by comparing the spectrum of the broadband light passing through the plurality of measurement optical fibers 161 and the spectrum of the broadband light passing through the reference optical fiber 162.

Specifically, as described above, the laser absorption spectroscopic analysis device according to an embodiment of the present invention passes at least a portion of the broadband light irradiated from the same light source 110 through the measurement space 11 and measures some of it. By providing a reference optical fiber 162 that passes through the space 11 without passing through it, the spectrum of broadband light passing through the reference optical fiber 162 can be detected. And, by comparing this spectrum with the spectrum of the broadband light that passed through the measurement optical fiber 161, the temperature and concentration of the target gas can be accurately determined.

Here, the image spectrometer 170 can split the broadband light that passed through the reference optical fiber 162, and the image sensor 180 can detect the spectrum of the broadband light split by the image spectrometer 170.

When there are a plurality of measurement optical fibers 161, the broadband light characteristics emitted by the plurality of light sources 110 may all be different, so the same number of reference optical fibers 162 are provided corresponding to these measurement optical fibers 161. desirable. Therefore, when analyzing the broadband light that has passed through the plurality of measurement spaces 11, it is possible to provide each judgment standard.

Figure 8 is a diagram showing a multi-channel spectral image acquired by an image sensor according to an embodiment of the present invention. While a typical spectrometer connected to a single optical fiber analyzes one analysis space, the configuration of FIG. 5 combining the optical fiber block 160 and the imaging spectrometer 170 can measure multiple different analysis spaces.

The analysis unit 190 may acquire the absorption spectrum of the target gas (eg, oxygen (O ₂ )) from the image sensor 180 in real time in a certain wavelength range (eg, 20 nm or more).

Figure 9 is a simplified diagram showing the absorption spectrum for each wavelength of broadband light generated by the analysis unit according to an embodiment of the present invention.

As shown in FIG. 9, the absorption spectrum generally appears in the form of two peaks, and the wavelength with the smallest absorption cross-section at the boundary of the two peaks can be defined as the reference wavelength.

Here, the reference wavelength has a constant value for the same target gas and varies depending on the type of target gas. Therefore, by identifying this reference wavelength, the type of target gas can be determined.

The analysis unit 190 can estimate the temperature of the target gas using the absorption cross-sectional area for each wavelength that changes depending on the gas temperature. A detailed explanation of this will be provided later.

Figure 10 is a diagram showing the absorption spectrum of oxygen (O ₂ ) generated by the analysis unit according to an embodiment of the present invention by temperature.

Here, (a) is the absorption spectrum when the gas temperature is 298K, (b) is the absorption spectrum when the gas temperature is 998K, and (c) is the absorption spectrum when the gas temperature is 1508K.

As shown in FIG. 8, since the target gas is the same as oxygen (O ₂ ), it can be confirmed that the reference wavelength (Q-branch, λ _q ) is the same at 762.04 nm even if the gas temperature is different.

However, when the gas temperature changes, the sum of the first absorption cross-sections (σ _L ) at wavelengths located on one side (e.g., left) and the wavelengths located on the other side (e.g., right) based on the reference wavelength (λ _q ). It can be confirmed that the second absorption cross-sectional area sum (σ _R ) of is different.

In this way, the analysis unit 190 can estimate the temperature of the target gas using the first absorption cross-sectional area sum (σ _L ) and the second absorption cross-sectional area sum (σ _R ) that vary depending on the gas temperature.

Specifically, the analysis unit 190 calculates the temperature coefficient (σ _C ) based on the reference wavelength (λ _q ) of the absorption spectrum, and applies the calculated temperature coefficient (σ _C ) to the temperature table to determine the temperature of the target gas. It can be estimated.

Here, the temperature coefficient (σ _C ) is the sum of the first absorption cross-sections (σ _L ) at wavelengths located on one side (e.g., left) and the wavelengths located on the other side (e.g., right) based on the reference wavelength (λ _q ). It can be calculated based on the second absorption cross-sectional area sum (σ _R ) in .

Specifically, the temperature coefficient (σ _C ) is the difference between the first absorption cross-sectional area sum (σ _L ) and the second absorption cross-sectional area sum (σ _R ) and the first absorption cross-sectional area sum (σ _L ) and the second absorption cross-sectional area sum (σ _R ) can be calculated by the ratio of the sum of the values.

Here, the first absorption cross-sectional area sum (σ _L ) and the second absorption cross-sectional area sum (σ _R ) may be defined by Equation 1 and Equation 2 below, respectively.

Additionally, the temperature coefficient (σ _C ) can be defined by Equation 3 below. And, by applying Equations 1 and 2 to Equation 3, the temperature coefficient (σ _C ) can be calculated.

[Equation 1]

[Equation 2]

[Equation 3]

Figure 11 is a graph showing the temperature coefficient that changes depending on the target gas temperature for each wavelength resolution of the imaging spectrometer according to an embodiment of the present invention.

As shown in FIG. 11, there are irregular sections in some sections, but overall, it can be seen that the temperature coefficient (σ _C ) changes (increases) linearly depending on the gas temperature.

The temperature table reflects the graph shown in FIG. 10 and can be set in advance using the temperature coefficient (σ _C ) calculated for each temperature of the target gas.

The analysis unit 190 may store a temperature table or function equation in memory and estimate the temperature of the target gas by applying the temperature coefficient of the target gas calculated using the absorption spectrum of the target gas to the stored temperature table. That is, the analysis unit 190 may estimate the gas temperature corresponding to the temperature coefficient of the target gas as the temperature of the target gas.

Additionally, the analysis unit 190 may measure the concentration of the target gas using the absorption cross-section of the absorption spectrum at the estimated temperature of the target gas.

Figure 12 is a diagram for explaining a method of analyzing the concentration of a target gas by an analysis unit according to an embodiment of the present invention.

As a basic analysis method for analyzing the concentration of a target gas (e.g., oxygen), the brightness distribution (I _o ) of the background light was considered constant without change depending on the wavelength, and the least squares method for the absorption spectrum was applied as shown in FIG. 12.

The molar concentration of the target gas is derived from a simultaneous equation consisting of the convolutional absorption cross-section (X _i ), absorption spectrum (Y _i ), column density (A), and natural logarithm of background light (B) at the temperature estimated through temperature analysis. (C) and background values can be calculated.

As such, the laser absorption spectroscopy analysis method and device according to an embodiment of the present invention uses a light source 110 and an imaging spectrometer 170 that irradiate broadband light to determine the concentration of the target gas based on various absorption areas in a multi-wavelength region. It has the advantage of being able to quantify both temperature and temperature, and there is no need to use other gases to estimate the temperature of the target gas as in the prior art.

The above detailed description is illustrative of the present invention. Additionally, the foregoing merely shows and describes preferred embodiments of the present invention, and the present invention can be used in various other combinations, modifications, and environments. That is, changes or modifications are possible within the scope of the inventive concept disclosed in this specification, the scope equivalent to the written disclosure, and/or the skill or knowledge in the art. The above-described embodiments are intended to explain the best state for carrying out the present invention, and are used in other states known in the art to use other inventions such as the present invention, and are required in the specific application field and use of the invention. Various changes are also possible. Accordingly, the detailed description of the invention above is not intended to limit the invention to the disclosed embodiments. Additionally, the appended claims should be construed to include other embodiments as well.

110: light source
120: first optical unit
140: second optical unit
160: optical fiber block
170: Imaging spectrometer
180: Image sensor
190: analysis department

Claims (7)

A method of analyzing a target gas existing in a measurement space using a laser absorption spectroscopic analysis device,
irradiating broadband light into the measurement space;
Obtaining an absorption spectrum for each wavelength of the broadband light passing through the measurement space;
calculating a temperature coefficient based on a reference wavelength of the absorption spectrum; and
Estimating the temperature of the target gas by applying the temperature coefficient to a temperature table
Laser absorption spectroscopic analysis method comprising.
According to claim 1,
The step of calculating the temperature coefficient is
The difference between the sum of the first absorption cross-sections at the wavelengths located on one side and the second absorption cross-section at the wavelengths located on the other side with respect to the reference wavelength and the sum of the first absorption cross-sections and the sum of the second absorption cross-sections The step of calculating the temperature coefficient by the ratio
Laser absorption spectroscopy method.
According to claim 1,
The reference wavelength is
Varies depending on the type of target gas
Laser absorption spectroscopy method.
According to claim 1,
The temperature table is
A table defined as a temperature coefficient value or function equation that changes linearly according to the temperature of the target gas for each wavelength resolution of the imaging spectrometer.
Laser absorption spectroscopy method.
According to claim 1,
Measuring the concentration of the target gas using the absorption cross-section of the absorption spectrum at the estimated temperature of the target gas.
A laser absorption spectroscopic analysis method further comprising:
A light source that irradiates broadband light;
a first optical unit that condenses at least a portion of the broadband light and introduces it into the measurement space;
a second optical unit that focuses at least a portion of the broadband light that has passed through the measurement space;
an optical fiber transmitting the broadband light collected by the second optical unit to an input terminal of a spectroscope;
a spectrometer that specifies the broadband light transmitted by the optical fiber and forms an image on an image sensor; and
An image sensor that converts the broadband light imaged by the spectrometer into spectral data
A laser absorption spectroscopic analysis device comprising a.
A light source that irradiates broadband light;
a first optical unit that condenses at least a portion of the broadband light and introduces it into the measurement space;
a second optical unit that focuses at least a portion of the broadband light that has passed through the measurement space;
an optical fiber block including at least one optical fiber that passes the broadband light condensed by the second optical unit;
an imaging spectrometer that specifies the broadband light transmitted by the optical fiber block and forms an image on an image sensor; and
An image sensor that converts the broadband light imaged by the imaging spectrometer into spectral data
A laser absorption spectroscopic analysis device comprising a.

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