Measurement device, measurement method, and program

Abstract

To provide a measurement device capable of accurately measuring the state of a gas to be measured by reducing the influence of interference gases.SOLUTION: A measurement device 1 according to the present disclosure comprises an irradiation unit 10 that irradiates irradiation light L, a light receiving unit 20 that receives light to be measured ML based on the irradiation light L irradiated onto a measured region R by the irradiation unit 10, and a control unit 90 that calculates the state of a gas to be measured G1 contained in the measured region R based on first reference information of the gas to be measured G1 acquired at a first central wavelength λ1 of the gas to be measured G1, second reference information of an interference gas G2 acquired at a second central wavelength λ2 and a first central wavelength λ1 of the interference gas G2, and a received signal at the first central wavelength λ1 and the second central wavelength λ2 of the light to be measured ML received by the light receiving unit 20.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a measurement device, a measurement method, and a program. [Background technology]

[0002] Conventionally, there are known techniques for measuring the state of a measurement gas, including the concentration of the measurement gas, etc. For example, Patent Document 1 discloses a laser gas analyzer that can accurately calculate the concentration by adding a simple analysis logic to eliminate the influence of interference. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-191246 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the conventional technique described in Patent Document 1 leaves room for improvement in reducing the influence of interference gases on the measurement of the state of the gas to be measured.

[0005] An object of the present disclosure is to provide a measurement device, a measurement method, and a program that can reduce the influence of interference gases and accurately measure the state of a gas to be measured. [Means for solving the problem]

[0006] In some embodiments, the measuring device comprises an irradiation unit that irradiates irradiation light, a light receiving unit that receives measured light based on the irradiation light irradiated onto the measured area by the irradiation unit, and a control unit that calculates the state of the measured gas contained in the measured area based on first reference information of the measured gas obtained at a first central wavelength of the measured gas, second reference information of the interfering gas obtained at a second central wavelength of the interfering gas and the first central wavelength, and received signals at the first central wavelength and the second central wavelength of the measured light received by the light receiving unit.

[0007] This allows the measurement device to reduce the influence of interference gases and accurately measure the state of the measurement gas.The measurement device can correct errors caused by interference gases using reference information including second reference information for the interference gas, thereby accurately measuring the state of the measurement gas.For example, the measurement device acquires and corrects information about the interference gas contained in the measurement region during the measurement process, so even if the distance to the scatterer or the concentration of the interference gas changes, it can correct the measurement value based on the received light signal in accordance with the changes.For example, when measuring the state of the measurement gas using WMS (Wavelength Modulation Spectroscopy) measurement, the measurement device can easily obtain measurement values ​​with reduced errors caused by interference gases.As an example, the measurement device can estimate the column concentration caused only by NH3 as the measurement gas.

[0008] In one embodiment, the control unit may modulate the wavelength of the irradiated light at a modulation frequency, and the first reference information may include, as first correlation data, a first calibration curve that correlates the concentration of the measurement gas with the intensity of the light-receiving signal at a frequency component twice the modulation frequency. This allows the measurement device to compare the magnitude of the 2f component obtained from the light-receiving signal at a first center wavelength with the first calibration curve obtained in advance, and accurately calculate the corresponding concentration.

[0009] In one embodiment of the measurement device, the first reference information may include a first phase of the light-receiving signal of the measurement gas. This allows the measurement device to set a criterion for determining whether to use a first calculation formula or a second calculation formula to calculate the magnitude of the 2f component for the measurement gas at a first center wavelength, as shown in FIG. 5 . For example, the measurement device can set the relationship between the phase and the first phase as the criterion. The measurement device can select an appropriate calculation formula depending on the relationship.

[0010] In one embodiment, the second reference information may include, as second correlation data, a second calibration curve that correlates the concentration of the interference gas with the intensity of the received light signal at a frequency component twice the modulation frequency, thereby enabling the measurement device to compare the magnitude of the 2f component obtained from the received light signal at the second center wavelength with the previously acquired second calibration curve and accurately calculate the corresponding concentration.

[0011] In one embodiment, the second calibration curve may include both a calibration curve at the first center wavelength and a calibration curve at the second center wavelength. This allows the measurement device to compare the magnitude of the 2f component obtained from the received light signal at the second center wavelength with a previously acquired calibration curve at the second center wavelength, thereby accurately calculating the corresponding concentration. The measurement device then compares the calculated concentration with the previously acquired calibration curve at the first center wavelength, thereby accurately calculating the magnitude of the corresponding 2f component.

[0012] In one embodiment, the control unit may calculate the concentration of the interference gas by comparing a first intensity of the light-receiving signal at the frequency component acquired at the second center wavelength with the second calibration curve at the second center wavelength. This allows the measurement device to easily obtain correction information for reducing errors due to the interference gas in the measurement value when measuring the state of the measurement target gas by WMS measurement.

[0013] In one embodiment, the control unit may calculate a second intensity of the received light signal at the frequency component for the interference gas at the first center wavelength by comparing the calculated concentration of the interference gas with the second calibration curve at the first center wavelength, thereby enabling the measurement device to accurately obtain the magnitude of the 2f component as the correction information.

[0014] In one embodiment, the control unit may calculate a fourth intensity of the light-receiving signal at the frequency component for the measurement target gas at the first center wavelength by canceling out the contribution of the second intensity in a third intensity of the light-receiving signal at the frequency component acquired at the first center wavelength. This allows the measurement device to reduce errors caused by interference gases in the measurement value when measuring the state of the measurement target gas by, for example, WMS measurement.

[0015] In one embodiment, the control unit may change a calculation formula for the fourth intensity depending on whether the phase of the light-receiving signal related to the third intensity coincides with or does not coincide with the first phase. This allows the measurement device to calculate the fourth intensity using a more appropriate calculation formula depending on the relationship between the phase and the first phase. Therefore, the measurement device can reduce the influence of interference gas and accurately measure the state of the measurement target gas.

[0016] In one embodiment of the measurement device, the control unit may calculate the concentration of the measurement gas as the state of the measurement gas by comparing the calculated fourth intensity with the first calibration curve. This allows the measurement device to compare the magnitude of the 2f component obtained from the light-receiving signal at the first center wavelength with the first calibration curve acquired in advance, thereby accurately calculating the corresponding concentration. The measurement device can accurately measure the state of the measurement gas by reducing the influence of interference gas. For example, the measurement device acquires the concentration of interference gas contained in the measurement region and corrects the measurement value. Therefore, even if the distance to the scatterer or the concentration of the interference gas changes, the measurement value can be corrected in accordance with the change.

[0017] A measurement method according to some embodiments includes irradiating irradiation light, receiving measured light based on the irradiation light irradiated onto a measurement area, and calculating the state of the measured gas contained in the measurement area based on first reference information of the measured gas obtained at a first central wavelength of the measured gas, second reference information of the interference gas obtained at a second central wavelength of the interference gas and the first central wavelength, and received signals of the measured light at the first central wavelength and the second central wavelength.

[0018] This allows the measurement device executing the measurement method to reduce the influence of interference gases and accurately measure the state of the measurement gas. The measurement device can correct errors caused by interference gases using reference information including second reference information for the interference gas, thereby accurately measuring the state of the measurement gas. For example, the measurement device acquires and corrects information about the interference gas contained in the measurement region during the measurement process. Therefore, even if the distance to the scatterer or the concentration of the interference gas changes, the measurement value based on the received light signal can be corrected in accordance with the changes. For example, when measuring the state of the measurement gas using WMS measurement, the measurement device can easily obtain measurement values ​​with reduced errors caused by interference gases. For example, the measurement device can estimate the column concentration caused only by NH3 as the measurement gas.

[0019] A program according to some embodiments causes a measurement device to perform operations including irradiating irradiation light, receiving measured light based on the irradiation light irradiated onto a measured area, and calculating the state of the measured gas contained in the measured area based on first reference information of the measured gas obtained at a first central wavelength of the measured gas, second reference information of the interference gas obtained at a second central wavelength of the interference gas and the first central wavelength, and a received signal of the received measured light at the first central wavelength and the second central wavelength.

[0020] This allows the measurement device to reduce the influence of interference gases and accurately measure the state of the measurement gas. The measurement device can correct errors caused by interference gases using reference information including second reference information for the interference gas, thereby accurately measuring the state of the measurement gas. For example, the measurement device acquires and corrects information about the interference gas contained in the measurement region during the measurement process. Therefore, even if the distance to the scatterer or the concentration of the interference gas changes, the measurement value based on the received light signal can be corrected in accordance with the changes. For example, when measuring the state of the measurement gas using WMS measurement, the measurement device can easily obtain measurement values ​​with reduced errors caused by interference gases. As an example, the measurement device can estimate the column concentration caused only by NH3 as the measurement gas. [Effects of the Invention]

[0021] According to the present disclosure, it is possible to provide a measurement device, a measurement method, and a program that can reduce the influence of interference gases and accurately measure the state of a gas to be measured. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a block diagram illustrating an example of a configuration of a measurement device according to an embodiment of the present disclosure. [Figure 2] FIG. 10 is a first diagram for explaining an example of the operation of the measurement device of FIG. [Figure 3] FIG. 2 is a second diagram for explaining an example of the operation of the measurement device of FIG. [Figure 4] FIG. 3 is a third diagram for explaining an example of the operation of the measurement device of FIG. [Figure 5] 2 is a flowchart illustrating an example of a measurement method executed by the measurement device of FIG. [Figure 6] FIG. 1 is a graph illustrating a problem with the conventional technology. DETAILED DESCRIPTION OF THE INVENTION

[0023] The background and problems of the prior art will now be described in more detail.

[0024] Spectroscopic gas detectors using a laser as a light source have been widely known. Conventional spectroscopic gas detectors irradiate a space with wavelength-modulated laser light as illumination light, and receive the return light reflected or scattered by objects located in the background of an area where the measured gas may be present as the measured light. Conventional spectroscopic gas detectors detect the measured gas based on changes in the light reception signal output by a photodetector when the measured light is received. For example, conventional spectroscopic gas detectors detect the target measured gas based on the measured light, utilizing the light absorption characteristics unique to the measured gas.

[0025] Figure 6 is a graph illustrating the problems of the prior art. In Figure 6, the solid line graph shows the wavelength dependence of the absorbance of ammonia (hereinafter referred to as "NH") as the gas to be measured. The dashed line graph shows the wavelength dependence of the absorbance of water (hereinafter referred to as "H2O") as the interference gas.

[0026] When measuring the state of NH3 using light, light sources with wavelengths in the near-infrared region are widely used. For example, wavelength modulation spectroscopy (WMS) is known to be capable of achieving highly sensitive measurements and is widely used. When measuring NH3 as the measured gas in the near-infrared region using WMS, the wavelength of the light used as the light source is mainly limited to the 1.5 μm band due to the wavelength dependence of the absorption spectrum of the measured gas.

[0027] The wavelength of the light used in the light source is adjusted to a predetermined absorption peak among the many absorption peaks of the gas to be measured. The predetermined absorption peak is, for example, an absorption peak with high sensitivity and high absorbance, and also includes an absorption peak that does not overlap with the absorption of other interfering gases due to gas selectivity. In order to detect NH3 leaked into the atmosphere, it is necessary to select an absorption peak that does not interfere with the absorption of atmospheric gases.

[0028] However, for example, absorption by H2O is prevalent in the 1.5 μm band. Therefore, it is not easy to select an absorption peak for NH3 that does not interfere completely with H2O. Therefore, even if the wavelength of light is set to the wavelength of a certain absorption peak in NH3, the measured value of the state of the measured gas will contain errors due to H2O. In addition, because H2O is contained throughout the atmosphere, its concentration changes depending on the distance to the background. This is because the concentration signal value obtained by a WMS is an integrated value of the concentration over the optical path length. This type of concentration is specifically called column concentration and is expressed in units of ppm·m.

[0029] In order to solve the above problems, the present disclosure aims to provide a measurement device, a measurement method, and a program that can reduce the influence of interference gases and accurately measure the state of a measurement gas. For example, the present disclosure aims to provide a measurement device, a measurement method, and a program that can correct errors caused by interference gases such as HO from a measurement value based on a light-receiving signal for a measurement gas such as NH.

[0030] An embodiment of the present disclosure will be mainly described below with reference to the accompanying drawings. The following description also applies to a measurement method and a program executed by a measurement device 1 to which the present disclosure is applied.

[0031] 1 is a block diagram showing an example of the configuration of a measurement device 1 according to an embodiment of the present disclosure. An example of the configuration and functions of the measurement device 1 according to an embodiment of the present disclosure will be mainly described with reference to FIG.

[0032] The measurement device 1 has an irradiation unit 10, a light receiving unit 20, a driving unit 30, an extraction unit 40, a modulation unit 50, a storage unit 60, an input unit 70, an output unit 80, and a control unit 90.

[0033] The irradiation unit 10 has a light source 11 and an irradiation optical system 12. The light source 11 includes a laser such as a semiconductor laser. The irradiation optical system 12 includes optical elements such as lenses and mirrors that optically act on the irradiation light L emitted from the light source 11. The irradiation unit 10 guides the irradiation light L emitted from the light source 11 to the outside of the measurement device 1 via the irradiation optical system 12. The irradiation unit 10 irradiates the irradiation light L toward a measurement region R where a measurement gas G1 may be present. In addition to the measurement gas G1 that may be additionally present due to leakage, the measurement region R also contains an interference gas G2 such as H2O that is normally contained in the atmosphere.

[0034] In the present disclosure, the "measurement gas G1" includes, for example, any gas that is the target of detection and measurement using the measurement device 1. For example, the measurement gas G1 may include NH3. The "interference gas G2" includes, for example, any gas whose absorption interferes with the first central wavelength of the absorption peak of the measurement gas G1. For example, the interference gas G2 may include H2O. The irradiation unit 10 irradiates the irradiation light L toward the measurement region R where the measurement gas G1 may be present in addition to the interference gas G2. The measurement region R exists, for example, in the space between the scatterer W and the irradiation unit 10. The scatterer W includes background objects such as walls and piping.

[0035] The wavelength of the irradiation light L irradiated by the irradiation unit 10 is included in the optical absorption band of the measurement gas G1. That is, the wavelength of the irradiation light L is included in one of the first optical absorption wavelength bands of the measurement gas G1. Similarly, the wavelength of the irradiation light L is included in the optical absorption band of the interference gas G2. That is, the wavelength of the irradiation light L is included in one of the second optical absorption wavelength bands of the interference gas G2. Each of the first optical absorption wavelength band and the second optical absorption wavelength band is included in a wavelength range such as the visible range and the infrared range.

[0036] The light receiving unit 20 has a photodetector 21 and a light receiving optical system 22. The photodetector 21 includes a light receiving element such as a photodiode (PD) and an IV conversion circuit. The light receiving optical system 22 includes optical elements such as lenses and mirrors that optically act on light such as the measured light ML that has entered the light receiving unit 20. The light receiving unit 20 guides light such as the measured light ML that has entered the light receiving unit 20 to the photodetector 21 via the light receiving optical system 22. The light receiving unit 20 receives the measured light ML that is based on the irradiation light L that has been irradiated onto the measurement region R by the irradiating unit 10.

[0037] In the present disclosure, the "measurement light ML" is, for example, scattered light or reflected light from the scatterer W based on the irradiation light L irradiated from the irradiation unit 10, and includes light absorbed by gases present in the measurement region R, such as the measurement gas G1 and interference gas G2. The light receiving unit 20 receives the measurement light ML that has passed through the gases present in the measurement region R between the scatterer W and the light receiving unit 20. At least a part of the wavelength band that can be received by the light receiving unit 20 is included in the light absorption band of the gas. The photodetector 21 of the light receiving unit 20 has detection sensitivity at the wavelength of the measurement light ML.

[0038] The light-receiving unit 20 is arranged on the same side as the irradiation unit 10. More specifically, the irradiation unit 10 is arranged on the opposite side of the scattering medium W with respect to the measurement region R so that the measurement region R is located between the scattering medium W and the irradiation unit 10. Similarly, the light-receiving unit 20 is arranged on the opposite side of the scattering medium W with respect to the measurement region R so that the measurement region R is located between the scattering medium W and the light-receiving unit 20.

[0039] The photodetector 21 further includes the above-mentioned IV conversion circuit that converts the current-based light-receiving signal, which is output when the PD detects the light to be measured ML, into a voltage. When the photodetector 21 detects the light to be measured ML, it converts the current-based light-receiving signal into a voltage-based light-receiving signal and outputs it to the extraction unit 40.

[0040] The driving unit 30 includes a driving module for driving the light source 11 of the irradiation unit 10. The driving module includes, for example, a laser driver for driving a laser such as a semiconductor laser.

[0041] The extraction unit 40 includes any circuit module that extracts a predetermined frequency component from the voltage-based light-receiving signal output from the photodetector 21 of the light-receiving unit 20. The circuit module includes, for example, a lock-in amplifier. The lock-in amplifier receives a voltage signal that indicates a signal waveform, such as a sine wave, that fluctuates at a predetermined frequency and is output from the modulation unit 50, and multiplies the voltage-based light-receiving signal with the voltage-based light-receiving signal, thereby extracting the predetermined frequency component from the light-receiving signal.

[0042] The modulation unit 50 includes any circuit module that outputs a voltage signal exhibiting a predetermined signal waveform. The circuit module includes, for example, a function generator (FG). The FG outputs a voltage signal to the drive unit 30 as a modulation signal for modulating the wavelength of the irradiation light L emitted from the irradiation unit 10 at a modulation frequency f. The FG outputs a voltage signal to the extraction unit 40 as a reference signal for extracting a predetermined frequency component from the voltage-based light receiving signal in the extraction unit 40.

[0043] The storage unit 60 includes storage modules such as a hard disk drive (HDD), a solid state drive (SSD), an electrically erasable programmable read-only memory (EEPROM), a read-only memory (ROM), and a random access memory (RAM). The storage unit 60 stores information necessary to realize the operation of the measuring device 1. The storage unit 60 stores information obtained by the operation of the measuring device 1. For example, the storage unit 60 stores system programs, application programs, and various data acquired by any means such as communication.

[0044] The storage unit 60 may function as a main storage module, an auxiliary storage module, or a cache memory. The storage unit 60 is not limited to being built into the measuring device 1, and may include an external storage module connected via a digital input / output port such as a USB (Universal Serial Bus).

[0045] The input unit 70 includes one or more input interfaces that detect user input and acquire input information based on the user's operation. The input interfaces include physical keys, capacitive keys, a touch screen integrated with the display of the output unit 80, an imaging module such as a camera, and a microphone that accepts audio input.

[0046] The output unit 80 includes one or more output interfaces that output information to notify the user. The output interfaces include a display that outputs information as an image, a speaker that outputs information as sound, and a vibrator that outputs information as vibration. The displays include LCD (Liquid Crystal Display) and organic EL (Electro Luminescence) displays.

[0047] The control unit 90 includes one or more processors. In this disclosure, a "processor" refers to, but is not limited to, a general-purpose processor or a dedicated processor specialized for a specific process. The control unit 90 includes, for example, a CPU (Central Processing Unit). The control unit 90 is communicably connected to each component of the measurement device 1 and controls the operation of the measurement device 1 as a whole.

[0048] The measurement device 1 may be configured as a single device in which the memory unit 60, input unit 70, output unit 80, and control unit 90 are integrated with the other components, or as a separate device in which they are arranged separately from the other components. When the measurement device 1 is configured as a separate device, the memory unit 60, input unit 70, output unit 80, and control unit 90 may be included in any general-purpose electronic device capable of realizing their functions, such as a personal computer (PC), tablet PC, smartphone, or wearable device such as a smartwatch. The measurement device 1 may be controlled by such a general-purpose electronic device and cooperate with the electronic device to perform various processes related to the measurement method described below.

[0049] The measuring device 1 operates as, for example, a spectroscopic gas detector using a light source 11. To detect the surrounding measurement gas G1, the measuring device 1 irradiates a measurement region R with laser light as irradiation light L from the light source 11 of the irradiation unit 10. The measuring device 1 receives, using the light receiving unit 20, the measurement light ML that is scattered or reflected back by a scatterer W located in the background of the measurement region R where the measurement gas G1 may be present.

[0050] The measuring device 1 detects the measurement gas G1 by utilizing the optical absorption characteristics determined by the type of measurement gas G1. The measuring device 1 operates by WMS, a type of laser spectroscopy. WMS is a method for acquiring the state of the measurement gas G1 on the optical path by modulating the wavelength of a laser beam and measuring changes in the received light signal of the modulated measurement light ML.

[0051] In this disclosure, the "state of the measurement gas G1" includes, for example, the concentration of the measurement gas G1. The concentration of the measurement gas G1 includes, for example, the column concentration of the measurement gas G1. The column concentration is given by the product of the optical path length when light passes through the measurement gas G1 and the concentration of the measurement gas G1. The unit of the column concentration is expressed in ppm m, as described above.

[0052] The following mainly describes the contents of basic processing by the control unit 90 when the measurement device 1 operates according to the WMS.

[0053] The control unit 90 controls, for example, a laser driver included in the drive unit 30. As a result, the control unit 90 sets the center wavelength λc of the laser light output from the light source 11 to a desired first center wavelength at the absorption peak of the measurement gas G1.

[0054] The control unit 90 controls the FG included in the modulation unit 50 to input a voltage signal that fluctuates at a modulation frequency f as a modulation signal from the modulation unit 50 to a laser driver included in the drive unit 30. The control unit 90 inputs the modulation signal from the FG to the drive unit 30, thereby modulating the wavelength of the irradiation light L emitted from the irradiation unit 10 at the modulation frequency f. The control unit 90 controls the FG so that the wavelength of the laser light as the irradiation light L is modulated at a constant modulation frequency f and modulation width ΔλL around a center wavelength λc. For example, the control unit 90 modulates the wavelength of the laser light at a modulation frequency f and modulation width ΔλL around the center wavelength λc. The modulation width ΔλL is, for example, expressed in units of wavelength rather than frequency.

[0055] The control unit 90 causes the light source 11 and the irradiation optical system 12 of the irradiation unit 10 to irradiate the wavelength-modulated laser light as irradiation light L toward the measurement region R. The measured light ML scattered or reflected by the scatterer W is detected by the photodetector 21 via the light-receiving optical system 22 of the light-receiving unit 20. The measured light ML is converted into a photocurrent by the PD of the photodetector 21, and then converted into a voltage signal by the IV conversion circuit of the photodetector 21. The light-receiving unit 20 outputs such a voltage signal to the extraction unit 40 as a light-receiving signal.

[0056] The control unit 90 measures the state of the measurement gas G1 based on the light-receiving signal from the light-receiving unit 20. The control unit 90 extracts a frequency component that is twice the modulation frequency f, i.e., a 2f component, from the light-receiving signal, and calculates the state of the measurement gas G1 based on the extracted frequency component.

[0057] For example, when a desired measurement gas G1 is present in the optical path of the irradiation light L, a new frequency component twice the modulation frequency f is generated in the measurement light ML that passes through the measurement gas G1. The magnitude of the 2f component in the received light signal is proportional to the column concentration of the measurement gas G1. Therefore, the control unit 90 extracts the 2f component from the received light signal based on phase-sensitive detection using a lock-in amplifier in the extraction unit 40, thereby obtaining a voltage signal proportional to the column concentration of the measurement gas G1. The control unit 90 calculates the column concentration of the measurement gas G1 by measuring the magnitude of the 2f component.

[0058] In this case, the 2f component is proportional not only to the column concentration of the measurement gas G1 but also to the received light power of the measurement light ML. In this disclosure, "received light power" refers to the received light power of the measurement light ML at the light receiving unit 20. The received light power varies depending on the distance from the scattering medium W to the measurement device 1, the surface condition of the scattering medium W, and other factors. Therefore, the control unit 90 needs to remove the fluctuations contained in the received light power from the 2f component in order to calculate the column concentration of the measurement gas G1.

[0059] Therefore, the control unit 90 uses the frequency component identical to the modulation frequency f, i.e., the 1f component. The control unit 90 acquires the magnitude of the 1f component as well as the 2f component using a lock-in amplifier. The magnitude of the 1f component contained in the received light signal is proportional to the received light power. Therefore, the control unit 90 divides the 2f component by the 1f component, i.e., calculates the 2f component / 1f component, thereby canceling out fluctuations in the received light power and acquiring a value proportional to the column concentration of the measured gas G1.

[0060] As described above, the control unit 90 measures the state of the measurement gas G1 based on the absorption characteristics of the measurement gas G1 with respect to the irradiated light L. The control unit 90 measures the state of the measurement gas G1 from the 1f signal and 2f signal obtained by the lock-in amplifier of the extraction unit 40 based on the light-receiving signal from the light-receiving unit 20. The control unit 90 calculates, for example, the column concentration of the measurement gas G1 from the 1f signal and 2f signal obtained from the light-receiving signal from the light-receiving unit 20.

[0061] In addition to the above, the control unit 90 also performs other calculations related to measuring the state of the measurement gas G1. For example, as shown in FIG. 6, if the interference gas G2 has a predetermined absorbance at the first center wavelength λ1 of the measurement gas G1, the basic calculation method described above will result in an error in the calculated measurement value due to the interference gas G2. Below, the operation of the measurement device 1 to solve this problem will be mainly described using NH3 as the measurement gas G1 and H2O as the interference gas G2 as an example. However, the present disclosure is equally applicable to gases other than these.

[0062] FIG. 6 shows that the absorption peak of NH3, which also includes interference from HO, is located at a first central wavelength λ1 in the near-infrared region. As an example, the first central wavelength λ1 is approximately 1512.2 nm. The absorption waveform of HO is superimposed on the absorption waveform of NH3 at the first central wavelength λ1. In other words, interference occurs. As described above, in WMS measurements, the column concentration of NH3 is proportional to the magnitude of the 2f component contained in the measured light ML. In actual measurements, the 1f component is also acquired to cancel fluctuations in the received light power, and the 2f component / 1f component is calculated. This allows for the acquisition of a received light signal that is independent of changes in the received light power and is proportional to the column concentration.

[0063] This is an advantage of WMS, but since the 1f component is unrelated to absorption and is not included in the essence of this disclosure, the following explanation will focus mainly on the 2f component. As shown in Figure 6, when interference due to H2O occurs, such as in the absorption peak at the first central wavelength λ1, the 2f component of the received light signal contains an error due to H2O.

[0064] In both the calibration process and the measurement process described below, phase-sensitive detection is performed using a lock-in amplifier in the extraction unit 40 to measure minute signals. The received light signal based on the phase-sensitive detection is acquired as a vector. Typically, the magnitude of the vector of the received light signal is a 2f component proportional to the concentration. In this case, errors due to gases other than the measurement gas G1 to be measured appear as a vector sum.

[0065] According to a simulation using a database at the first center wavelength λ1, the phase of the light-receiving signal due to the "skirt" of the superimposed absorption spectrum of HO differs by 180° from the phase of the light-receiving signal due to NH3. This causes the light-receiving signals to cancel each other out. Therefore, by considering not only the magnitude of the light-receiving signal as a vector including NH3 and HO but also its phase, the measuring device 1 can estimate the light-receiving signal due to NH3 alone, with the influence of HO corrected. The measuring device 1 calculates the column concentration of NH3 by using a calibration curve previously acquired for the light-receiving signal. Note that the calibration curve is basically generated for the magnitude of the light-receiving signal and does not include phase information.

[0066] The measurement device 1 needs to acquire information about the column concentration of HO in a preliminary calibration process. To avoid the influence of absorption by NH3, the measurement device 1 acquires this information in a band other than the first center wavelength λ1. For example, the absorption peak of only HO at the second center wavelength λ2 shown in FIG. 6 is used. As an example, the second center wavelength λ2 is approximately 1511.8 nm. By using the absorption peak of HO at the second center wavelength λ2, the influence of absorption by NH3 is reduced, and HO becomes dominant.

[0067] If the measurement device 1 previously acquires a calibration curve containing information on the column concentration of HO at the second center wavelength λ2 through a calibration process, the measurement device 1 can acquire the column concentration of HO through WMS measurement at the second center wavelength λ2 in the measurement process. By previously acquiring a calibration curve for HO at the first center wavelength λ1 through a calibration process, the measurement device 1 can acquire the magnitude of the 2f component due to HO at the first center wavelength λ1 based on the column concentration of HO acquired at the second center wavelength λ2. By performing WMS measurement at the first center wavelength λ1 and using information on the 2f component due to HO, the measurement device 1 can extract the received light signal attributable only to NH3 from the magnitude and phase of the received light signal. As described above, even if the measurement value at the first center wavelength λ1 includes contributions from both HO and NH3, the measurement device 1 can reproduce the 2f component of NH3 alone by acquiring the column concentration of HO based on the measurement results at the second center wavelength λ2.

[0068] The operation of the measuring device 1 outlined above will be described in more detail below with reference to the drawings.

[0069] FIG. 2 is a first diagram for explaining an example of the operation of the measurement apparatus 1 of FIG. 1. FIG. 2 conceptually illustrates the configuration of a calibration process executed by the measurement apparatus 1 before measuring the state of the measurement gas G1. FIG. 3 is a second diagram for explaining an example of the operation of the measurement apparatus 1 of FIG. 1. FIG. 4 is a third diagram for explaining an example of the operation of the measurement apparatus 1 of FIG. 1. FIGS. 3 and 4 conceptually illustrate the configuration of a measurement process when the measurement apparatus 1 actually measures the state of the measurement gas G1. FIG. 5 is a flowchart for explaining an example of a measurement method executed by the measurement apparatus 1 of FIG. 1.

[0070] In step S101, the control unit 90 of the measurement device 1 acquires reference information. In the present disclosure, "reference information" includes, for example, first reference information and second reference information. Step S101 corresponds to a calibration process performed by the measurement device 1 before measuring the state of the measurement gas G1. As shown in FIG. 2, in step S101, for example, when only one of the measurement gas G1 and the interference gas G2 is present alone in the measurement region R, first reference information and second reference information are acquired for each of these gases. The present invention is not limited to the above configuration, and the reference information may be acquired in advance at a location different from the measurement region R.

[0071] The first reference information is, for example, reference information for the measurement gas G1 acquired at a first center wavelength λ1 of the measurement gas G1. The first reference information includes, as first correlation data, a first calibration curve La1 that correlates the concentration Ca of the measurement gas G1 with the intensity of the received light signal at a frequency component twice the modulation frequency f, i.e., the magnitude Sa of the 2f component. The concentration Ca may be, for example, a column concentration (ppm m). The first reference information also includes a first phase θ1 of the received light signal obtained by WMS measurement of the measurement gas G1.

[0072] The second reference information is, for example, reference information of the interference gas G2 acquired at the second center wavelength λ2 and the first center wavelength λ1 of the interference gas G2. The second reference information includes, as second correlation data, a second calibration curve Lw that correlates the concentration Cw of the interference gas G2 with the intensity of the received light signal at a frequency component twice the modulation frequency f, i.e., the magnitude Sw of the 2f component. The concentration Cw may be, for example, a column concentration (ppm m). The second calibration curve Lw includes both a calibration curve Lw1 at the first center wavelength λ1 and a calibration curve Lw2 at the second center wavelength λ2.

[0073] The control unit 90 of the measurement device 1 stores the acquired reference information in the storage unit 60.

[0074] The process from step S102 onwards corresponds to the measurement process when the measurement device 1 actually measures the state of the measurement gas G1. As shown in Figures 3 and 4, from step S102 onwards, it is assumed that both the measurement gas G1 and the interference gas G2 are present in the measurement region R.

[0075] In step S102, the control unit 90 of the measurement device 1 performs WMS measurement at the second center wavelength λ2. The control unit 90 acquires the magnitude S2 of the 2f component and the second phase θ2 as the measurement results of the WMS measurement. At this time, as shown in FIG. 3, the measurement gas G1 and the interference gas G2 are present in the measurement region R, but the interference gas G2 is dominant in terms of light absorption.

[0076] In step S103, the control unit 90 of the measurement device 1 calculates the concentration Cw of the interference gas G2 by comparing the first intensity of the light receiving signal at the frequency component twice the modulation frequency f, acquired at the second center wavelength λ2, with the second calibration curve Lw2 at the second center wavelength λ2. For example, the control unit 90 calculates the concentration Cw of the interference gas G2 from the second calibration curve Lw2 acquired in step S101, using the magnitude S2 of the 2f component acquired in step S102 as the first intensity.

[0077] In step S104, the control unit 90 of the measurement device 1 compares the concentration Cw of the interference gas G2 calculated in step S103 with the second calibration curve Lw1 at the first center wavelength λ1 to calculate a second intensity of the received light signal at a frequency component twice the modulation frequency f for the interference gas G2 at the first center wavelength λ1. For example, the control unit 90 calculates the magnitude Sw of the 2f component as the second intensity for the interference gas G2 at the first center wavelength λ1.

[0078] In step S105, the control unit 90 of the measurement device 1 performs WMS measurement at the first center wavelength λ1. The control unit 90 acquires the magnitude S and phase θ of the 2f component as the measurement results of the WMS measurement. At this time, as shown in FIG. 4, the measurement gas G1 and the interference gas G2 are present in the measurement region R, and the light absorption is affected by both the measurement gas G1 and the interference gas G2. Therefore, the magnitude S of the 2f component includes information on both the measurement gas G1 and the interference gas G2.

[0079] In step S106, the control unit 90 of the measurement device 1 determines whether the phase θ acquired in step S105 and the first phase θ1 acquired in step S101 are the same. If the control unit 90 determines that the phase θ and the first phase θ1 are the same, it executes the process of step S107. If the control unit 90 determines that the phase θ and the first phase θ1 are different, it executes the process of step S108.

[0080] In steps S107 and S108, the control unit 90 of the measurement apparatus 1 calculates a fourth intensity of the received light signal at the frequency component twice the modulation frequency f, acquired at the first center wavelength λ1, for the measured gas G1 by canceling out the contribution of the second intensity to the third intensity of the received light signal at that frequency component. For example, the control unit 90 calculates a fourth intensity of the received light signal at the first center wavelength λ1 for the measured gas G1 using the magnitude S of the 2f component acquired in step S105 as the third intensity, the magnitude Sw of the 2f component acquired in step S104 as the second intensity, and the magnitude Sa of the 2f component as the fourth intensity. At this time, the control unit 90 changes the calculation formula for the fourth intensity depending on whether the phase θ of the received light signal related to the third intensity matches or does not match the first phase θ1.

[0081] For example, in step S107, if the control unit 90 of the measurement device 1 determines in step S106 that the phase θ and the first phase θ1 match each other, the control unit 90 calculates the magnitude Sa of the 2f component using a first calculation formula. The first calculation formula includes, for example, the formula Sa = S + Sw.

[0082] For example, in step S108, if the control unit 90 of the measurement device 1 determines in step S106 that the phase θ and the first phase θ1 do not match each other, the control unit 90 calculates the magnitude Sa of the 2f component using a second calculation formula. The second calculation formula includes, for example, the formula Sa = |S - Sw|. An example of θ ≠ θ1 is the relationship θ = θ1 + π.

[0083] In step S109, the control unit 90 of the measuring device 1 calculates the concentration Ca of the measured gas G1 as the state of the measured gas G1 by comparing the magnitude Sa of the 2f component as the fourth intensity calculated in step S107 or step S108 with the first calibration curve La1 obtained in step S101.

[0084] As described above, the control unit 90 of the measurement device 1 calculates the state of the measurement gas G1 contained in the measurement region R based on the reference information acquired by the calibration process and the light-receiving signals at the first central wavelength λ1 and the second central wavelength λ2 of the measurement light ML received by the light-receiving unit 20. The control unit 90 may display the calculated state of the measurement gas G1 on a display of the output unit 80, for example.

[0085] In step S110, the control unit 90 of the measurement device 1 determines whether the measurement has ended. If the control unit 90 determines that the measurement has ended, the process ends. If the control unit 90 determines that the measurement has not ended, the process returns to step S102 and repeats the process from step S102 onwards.

[0086] The measurement device 1 according to the embodiment described above can reduce the influence of the interference gas G2 and accurately measure the state of the measurement gas G1. The measurement device 1 calculates the state of the measurement gas G1 contained in the measurement region R based on previously acquired reference information and the light-receiving signals at the first central wavelength λ1 and the second central wavelength λ2. The reference information includes first reference information of the measurement gas G1 acquired at the first central wavelength λ1 of the measurement gas G1 and second reference information of the interference gas G2 acquired at the second central wavelength λ2 of the interference gas G2 and the first central wavelength λ1.

[0087] As a result, the measurement device 1 can correct errors caused by the interference gas G2 using reference information including the second reference information for the interference gas G2, and accurately measure the state of the measurement gas G1. For example, the measurement device 1 acquires and corrects information about the interference gas G2 contained in the measurement region R during the measurement process. Therefore, even if the distance to the scatterer W or the concentration Cw of the interference gas G2 changes, the measurement value based on the received light signal can be corrected in accordance with these changes. For example, when measuring the state of the measurement gas G1 using WMS measurement, the measurement device 1 can easily obtain a measurement value with reduced errors caused by the interference gas G2. As an example, the measurement device 1 can estimate the column concentration Ca caused only by NH3 as the measurement gas G1.

[0088] The first reference information includes, as first correlation data, a first calibration curve La1 that correlates the concentration Ca of the measurement gas G1 with the intensity Sa of the light-receiving signal at a frequency component twice the modulation frequency f. This enables the measurement device 1 to compare the magnitude Sa of the 2f component obtained from the light-receiving signal at the first center wavelength λ1 with the previously acquired first calibration curve La1, and accurately calculate the corresponding concentration Ca.

[0089] The first reference information includes a first phase θ1 of the light-receiving signal of the measurement gas G1. This allows the measurement device 1 to set a criterion for determining whether to use the first calculation formula or the second calculation formula to calculate the magnitude Sa of the 2f component for the measurement gas G1 at the first center wavelength λ1, as shown in Fig. 5. For example, the measurement device 1 can set the relationship between the phase θ and the first phase θ1 as the criterion. The measurement device 1 can select an appropriate calculation formula depending on the relationship.

[0090] The second reference information includes, as second correlation data, a second calibration curve Lw that correlates the concentration Cw of the interference gas G2 with the intensity of the received light signal at a frequency component twice the modulation frequency f. This allows the measurement device 1 to compare the magnitude S2 of the 2f component obtained from the received light signal at the second center wavelength λ2 with the previously acquired second calibration curve Lw, and accurately calculate the corresponding concentration Cw.

[0091] The second calibration curve Lw includes both the calibration curve Lw1 at the first center wavelength λ1 and the calibration curve Lw2 at the second center wavelength λ2. This allows the measurement device 1 to compare the magnitude S2 of the 2f component obtained from the light-receiving signal at the second center wavelength λ2 with the previously acquired calibration curve Lw2, thereby accurately calculating the corresponding concentration Cw. Subsequently, the measurement device 1 compares the calculated concentration Cw with the previously acquired calibration curve Lw1, thereby accurately calculating the magnitude Sw of the corresponding 2f component.

[0092] The measuring device 1 calculates the concentration Cw of the interference gas G2 by comparing the first intensity S2 of the light receiving signal at the frequency component twice the modulation frequency f, acquired at the second center wavelength λ2, with the second calibration curve Lw2 at the second center wavelength λ2. This allows the measuring device 1 to easily obtain correction information for reducing errors in the measured value due to the interference gas G2 when measuring the state of the measurement target gas G1 by WMS measurement.

[0093] The measurement device 1 compares the calculated concentration Cw of the interference gas G2 with the second calibration curve Lw1 at the first center wavelength λ1 to calculate a second intensity Sw of the received light signal at a frequency component twice the modulation frequency f for the interference gas G2 at the first center wavelength λ1. This allows the measurement device 1 to accurately obtain the magnitude Sw of the 2f component as the above-mentioned correction information.

[0094] The measuring device 1 calculates a fourth intensity Sa of the received light signal at the frequency component twice the modulation frequency f at the first central wavelength λ1 by canceling out the contribution of the second intensity Sw in the third intensity S of the received light signal at the first central wavelength λ1. This allows the measuring device 1 to reduce errors of the interference gas G2 in the measured value when measuring the state of the measured gas G1 by, for example, WMS measurement.

[0095] The measurement device 1 changes the calculation formula for the fourth intensity Sa depending on whether the phase θ of the received light signal related to the third intensity S matches or does not match the first phase θ1. This allows the measurement device 1 to calculate the fourth intensity Sa using a more appropriate calculation formula depending on the relationship between the phase θ and the first phase θ1. Therefore, the measurement device 1 can reduce the influence of the interference gas G2 and accurately measure the state of the measurement gas G1.

[0096] The measuring device 1 compares the calculated fourth intensity Sa with the first calibration curve La1 to calculate the concentration Ca of the measured gas G1 as the state of the measured gas G1. This allows the measuring device 1 to compare the magnitude Sa of the 2f component obtained from the light-receiving signal at the first center wavelength λ1 with the previously acquired first calibration curve La1, thereby accurately calculating the corresponding concentration Ca. The measuring device 1 can accurately measure the state of the measured gas G1 by reducing the influence of the interference gas G2. For example, the measuring device 1 obtains the concentration Cw of the interference gas G2 contained in the measurement region R to correct the measured value. Therefore, even if the distance to the scatterer W changes or the concentration Cw of the interference gas G2 changes, the measured value can be corrected in accordance with the change.

[0097] Although the present disclosure has been described based on the drawings and examples, it should be noted that those skilled in the art can make various modifications and alterations based on the present disclosure. Therefore, it should be noted that these modifications and alterations are included in the scope of the present disclosure. For example, the functions included in each configuration or step can be rearranged so as not to be logically inconsistent, and multiple configurations or steps can be combined or divided into one.

[0098] For example, a general-purpose electronic device such as a smartphone or computer can be configured to function as part of the measuring device 1 according to the embodiment described above. Specifically, a program describing the processing content for realizing each function of the control unit 90 of the measuring device 1 according to the embodiment is stored in the memory of the electronic device, and the program is read and executed by a processor of the electronic device. Therefore, the present disclosure can also be realized as a program executable by a processor.

[0099] Alternatively, the present disclosure may be realized as a non-transitory computer-readable medium storing a program that can be executed by one or more processors to cause the measurement device 1 according to one embodiment to perform each function. It should be understood that these are also included within the scope of the present disclosure.

[0100] For example, the shape, pattern, size, arrangement, orientation, type, and number of each of the above-mentioned components are not limited to those shown in the above description and drawings. The shape, pattern, size, arrangement, orientation, type, and number of each component may be configured arbitrarily as long as the function can be realized. Each component of the illustrated measuring device 1 is a functional concept, and the specific form of each component is not limited to that shown.

[0101] In the above embodiment, the first reference information is described as including the first correlation data, which is the first calibration curve La1 that correlates the concentration Ca of the measurement gas G1 with the intensity Sa of the light-receiving signal at a frequency component twice the modulation frequency f. However, the first reference information is not limited to this. Instead of or in addition to the first correlation data, the first reference information may include any other information that can be used to calculate the state of the measurement gas G1.

[0102] In the above embodiment, the first reference information includes the first phase θ1 of the light-receiving signal of the measurement gas G1, but is not limited to this. Instead of or in addition to the first phase θ1, the first reference information may include any other information that can be used to calculate the state of the measurement gas G1. For example, the first reference information may include the second phase θ2 included in the measurement result when WMS measurement is performed at the second center wavelength λ2.

[0103] In the above embodiment, the second reference information is described as including the second correlation data, which is the second calibration curve Lw that correlates the concentration Cw of the interference gas G2 with the intensity of the light-receiving signal at a frequency component twice the modulation frequency f. However, the second reference information may include any other information that can be used to calculate the state of the measurement gas G1 instead of or in addition to the second correlation data.

[0104] In the above embodiment, the second calibration curve Lw includes both the calibration curve Lw1 at the first center wavelength λ1 and the calibration curve Lw2 at the second center wavelength λ2, but is not limited to this. The second calibration curve Lw may include only one of the calibration curves Lw1 and Lw2 as long as the measurement device 1 can calculate the state of the measurement gas G1.

[0105] In the above embodiment, the measurement device 1 calculates the concentration Cw of the interference gas G2 by comparing the first intensity S2 of the light-receiving signal at the frequency component twice the modulation frequency f, acquired at the second center wavelength λ2, with the second calibration curve Lw2 at the second center wavelength λ2. However, the present invention is not limited to this. The measurement device 1 may calculate the concentration Cw by any other method using the reference information and the light-receiving signal at the second center wavelength λ2. Alternatively, the measurement device 1 may not need to calculate the concentration Cw during the measurement process as long as the state of the measurement gas G1 can be calculated using the reference information and the light-receiving signal at the second center wavelength λ2.

[0106] In the above embodiment, the measurement device 1 calculates the second intensity Sw of the light receiving signal at the frequency component twice the modulation frequency f for the interference gas G2 at the first central wavelength λ1 by comparing the calculated concentration Cw of the interference gas G2 with the second calibration curve Lw1 at the first central wavelength λ1. However, the measurement device 1 may calculate the second intensity Sw by any other method using the reference information and the light receiving signal at the second central wavelength λ2.

[0107] In the above embodiment, the measurement device 1 calculates the fourth intensity Sa of the light-receiving signal at the first central wavelength λ1 for the measurement gas G1 by canceling out the contribution of the second intensity Sw in the third intensity S of the light-receiving signal at the frequency component twice the modulation frequency f, which is acquired at the first central wavelength λ1. However, the measurement device 1 may calculate the fourth intensity Sa by any other method using the reference information and the light-receiving signals at the first central wavelength λ1 and the second central wavelength λ2.

[0108] In the above embodiment, the measurement device 1 changes the calculation formula for the fourth intensity Sa depending on whether the phase θ of the received light signal related to the third intensity S matches or does not match the first phase θ1. However, this is not limiting. The measurement device 1 may use any other criteria as a criterion for selecting a calculation formula, instead of or in addition to the relationship between the phase θ and the first phase θ1.

[0109] In the above embodiment, the measurement device 1 is described as calculating the concentration Ca of the measurement gas G1 as the state of the measurement gas G1 by comparing the calculated fourth intensity Sa with the first calibration curve La1, but this is not limited to this. The measurement device 1 may calculate the concentration Ca by any other method using the reference information and the light-receiving signals at the first central wavelength λ1 and the second central wavelength λ2.

[0110] In the above embodiment, the measurement device 1 calculates the state of the measurement gas G1 at one first central wavelength λ1 for one type of measurement gas G1, but this is not limiting. The measurement device 1 may calculate the state of the measurement gas G1 for multiple types of measurement gas G1, or may calculate the state of the measurement gas G1 when the first central wavelength λ1 includes multiple wavelengths.

[0111] In the above embodiment, the measurement device 1 calculates the state of the measurement gas G1 based on one second central wavelength λ2 for one type of interference gas G2, but this is not limiting. The measurement device 1 may calculate the state of the measurement gas G1 for multiple types of interference gas G2, or may calculate the state of the measurement gas G1 when the second central wavelength λ2 includes multiple wavelengths.

[0112] For example, in the above embodiment, the measurement device 1 has the irradiation unit 10 and the drive unit 30 as separate components, but this is not limited to this. The measurement device 1 may also have the irradiation unit 10 and the drive unit 30 integrated into a single component. For example, the measurement device 1 may be configured such that the driver function is integrated into the irradiation unit 10, or the drive unit 30 may integrate the function of the light source 11, and irradiate the irradiation light L to the outside via an irradiation optical system 12 including a light-guiding member such as an optical fiber, a lens, etc.

[0113] In the above embodiment, the measurement device 1 has the light receiving unit 20 and the extraction unit 40 as different components, but this is not limited to this. The measurement device 1 may also have the light receiving unit 20 and the extraction unit 40 integrated into one component.

[0114] In the above embodiment, the measurement device 1 extracts the frequency component twice the modulation frequency f from the received light signal and calculates the state of the measurement gas G1 based on the extracted frequency component. However, this is not limited to this. The measurement device 1 may calculate the state of the measurement gas G1 using any other method. For example, the measurement device 1 may calculate the state of the measurement gas G1 using another method that does not rely on the WMS.

[0115] In the above embodiment, the measurement device 1 calculates the 2f component / 1f component to cancel fluctuations in the light-receiving power and obtain a value proportional to the concentration Ca of the measurement gas G1 as a state of the measurement gas G1. However, the present invention is not limited to this. The measurement device 1 may calculate the state of the measurement gas G1 using any other arithmetic expression based on the 2f component extracted from the light-receiving signal.

[0116] In the above embodiment, the measurement device 1 has been described as having a lock-in amplifier as the extraction unit 40, but this is not limited to this. Instead of or in addition to the lock-in amplifier, the measurement device 1 may use software executed by the CPU of the control unit 90 or the like to achieve the same function as the lock-in amplifier of the extraction unit 40. In this case, the measurement device 1 may use a Fourier transform.

[0117] In the above embodiment, the measurement device 1 is described as measuring the state of the measurement gas G1 based on the absorption characteristics of the measurement gas G1 with respect to the irradiated light L, but the present invention is not limited to this. The measurement device 1 may also measure the state of the measurement gas G1 based on the scattering characteristics and reflection characteristics of the measurement gas G1 with respect to the irradiated light L.

[0118] In the above embodiment, the light receiving unit 20 is arranged on the same side as the irradiating unit 10 and receives the measured light ML scattered or reflected by the scatterers W located behind the measurement gas G1, but this is not limiting. The light receiving unit 20 may be arranged to face the irradiating unit 10 across the measurement region R. In this case, the light receiving unit 20 may receive the measured light ML obtained when the irradiation light L irradiated from the irradiating unit 10 passes through the measurement region R.

[0119] In the above embodiment, the scatterer W is described as including background objects such as walls and pipes, but is not limited thereto. The scatterer W may be any object other than walls and pipes.

[0120] In the above embodiment, the state of the measurement gas G1 is described as including the concentration of the measurement gas G1, but is not limited to this. The state of the measurement gas G1 may also include the presence or absence of the measurement gas G1.

[0121] Some embodiments of the present disclosure will be described below as examples, however, it should be noted that the embodiments of the present disclosure are not limited to these examples. [Appendix 1] an irradiation unit that irradiates irradiation light; a light receiving unit that receives light to be measured based on the irradiated light irradiated onto the measurement area by the irradiating unit; a control unit that calculates a state of the measurement target gas contained in the measurement region based on first reference information of the measurement target gas acquired at a first central wavelength of the measurement target gas, second reference information of the interference gas acquired at a second central wavelength of the interference gas and the first central wavelength, and light receiving signals of the measurement target light received by the light receiving unit at the first central wavelength and the second central wavelength; Equipped with Measuring device. [Appendix 2] 10. The measurement device of claim 1, the control unit modulates the wavelength of the irradiated light at a modulation frequency; the first reference information includes, as first correlation data, a first calibration curve in which the concentration of the measurement target gas and the intensity of the light-receiving signal at a frequency component twice the modulation frequency are correlated with each other; Measuring device. [Appendix 3] 10. The measurement device of claim 2, the first reference information includes a first phase of the light receiving signal of the measurement target gas; Measuring device. [Appendix 4] 4. The measurement device according to claim 2 or 3, the second reference information includes, as second correlation data, a second calibration curve in which the concentration of the interference gas and the intensity of the received light signal at a frequency component twice the modulation frequency are correlated with each other; Measuring device. [Appendix 5] 5. The measurement device of claim 4, the second calibration curve includes both a calibration curve at the first central wavelength and a calibration curve at the second central wavelength; Measuring device. [Appendix 6] 6. The measurement device according to claim 4 or 5, the control unit calculates the concentration of the interference gas by comparing a first intensity of the light receiving signal at the frequency component acquired at the second center wavelength with the second calibration curve at the second center wavelength. Measuring device. [Appendix 7] 7. The measurement device of claim 6, the control unit calculates a second intensity of the light receiving signal at the frequency component for the interference gas at the first center wavelength by comparing the calculated concentration of the interference gas with the second calibration curve at the first center wavelength; Measuring device. [Appendix 8] 8. The measurement device of claim 7, the control unit calculates a fourth intensity of the light receiving signal at the frequency component for the measurement gas at the first center wavelength by canceling out a contribution of the second intensity in a third intensity of the light receiving signal at the frequency component acquired at the first center wavelength. Measuring device. [Appendix 9] 9. The measurement device of claim 8, the control unit changes a calculation formula for the fourth intensity depending on whether a phase of the light receiving signal related to the third intensity matches or does not match the first phase. Measuring device. [Appendix 10] 10. The measurement device according to claim 8 or 9, the control unit calculates the concentration of the measurement gas as the state of the measurement gas by comparing the calculated fourth intensity with the first calibration curve. Measuring device. [Appendix 11] Irradiating with irradiation light; receiving light to be measured based on the irradiated light irradiated onto a measurement area; calculating a state of the measurement target gas contained in the measurement region based on first reference information of the measurement target gas acquired at a first central wavelength of the measurement target gas, second reference information of the interference gas acquired at a second central wavelength of the interference gas and the first central wavelength, and light receiving signals of the received measurement target light at the first central wavelength and the second central wavelength; Including, Measurement method. [Appendix 12] The measuring device Irradiating with irradiation light; receiving light to be measured based on the irradiated light irradiated onto a measurement area; calculating a state of the measurement target gas contained in the measurement region based on first reference information of the measurement target gas acquired at a first central wavelength of the measurement target gas, second reference information of the interference gas acquired at a second central wavelength of the interference gas and the first central wavelength, and light receiving signals of the received measurement target light at the first central wavelength and the second central wavelength; causing an action including program. [Explanation of symbols]

[0122] 1. Measuring equipment 10 Irradiation unit 11 Light source 12 Irradiation optical system 20 Light receiving section 21 Photodetector 22 Light receiving optical system 30 Drive unit 40 Extraction part 50 Modulation section 60 Storage section 70 Input section 80 Output section 90 Control Unit f modulation frequency Ca concentration Cw concentration G1 Measurement gas G2 Interfering Gas L irradiation light La1 1st calibration curve Lw 2nd calibration curve Lw1 calibration curve Lw2 calibration curve ML Measured light R Measurement area S 2f component magnitude (third intensity) S2 2f component magnitude (first intensity) Sa 2f component magnitude (fourth intensity) Sw 2f component magnitude (second intensity) W scatterer λ1 1st center wavelength λ2 2nd center wavelength θ phase θ1 1st phase θ2 Second phase

Claims

1. an irradiation unit that irradiates irradiation light; a light receiving unit that receives light to be measured based on the irradiated light irradiated onto the measurement area by the irradiating unit; a control unit that calculates a state of the measurement target gas contained in the measurement region based on first reference information of the measurement target gas acquired at a first central wavelength of the measurement target gas, second reference information of the interference gas acquired at a second central wavelength of the interference gas and the first central wavelength, and light receiving signals of the measurement target light received by the light receiving unit at the first central wavelength and the second central wavelength; Equipped with Measuring equipment.

2. 2. The measuring device according to claim 1, the control unit modulates the wavelength of the irradiated light at a modulation frequency; the first reference information includes, as first correlation data, a first calibration curve in which the concentration of the measurement gas and the intensity of the light-receiving signal at a frequency component twice the modulation frequency are correlated with each other; Measuring equipment.

3. 3. The measuring device according to claim 2, the first reference information includes a first phase of the light receiving signal of the measurement target gas; Measuring equipment.

4. 4. The measuring device according to claim 3, the second reference information includes, as second correlation data, a second calibration curve in which the concentration of the interference gas and the intensity of the received light signal at a frequency component twice the modulation frequency are correlated with each other; Measuring equipment.

5. 5. The measuring device according to claim 4, the second calibration curve includes both a calibration curve at the first central wavelength and a calibration curve at the second central wavelength. Measuring equipment.

6. 5. The measuring device according to claim 4, the control unit calculates the concentration of the interference gas by comparing a first intensity of the light receiving signal at the frequency component acquired at the second center wavelength with the second calibration curve at the second center wavelength. Measuring equipment.

7. 7. The measuring device according to claim 6, the control unit calculates a second intensity of the light receiving signal at the frequency component for the interference gas at the first center wavelength by comparing the calculated concentration of the interference gas with the second calibration curve at the first center wavelength. Measuring equipment.

8. 8. The measuring device according to claim 7, the control unit calculates a fourth intensity of the light receiving signal at the frequency component for the measurement gas at the first center wavelength by canceling out a contribution of the second intensity in a third intensity of the light receiving signal at the frequency component acquired at the first center wavelength. Measuring equipment.

9. 9. The measuring device according to claim 8, the control unit changes a calculation formula for the fourth intensity depending on whether a phase of the light receiving signal related to the third intensity matches or does not match the first phase. Measuring equipment.

10. 9. The measuring device according to claim 8, the control unit compares the calculated fourth intensity with the first calibration curve to calculate the concentration of the measurement gas as the state of the measurement gas. Measuring equipment.

11. Irradiating with irradiation light; receiving light to be measured based on the irradiated light irradiated onto a measurement area; calculating a state of the measurement target gas contained in the measurement region based on first reference information of the measurement target gas acquired at a first central wavelength of the measurement target gas, second reference information of the interference gas acquired at a second central wavelength of the interference gas and the first central wavelength, and light receiving signals of the received measurement target light at the first central wavelength and the second central wavelength; Including, Measurement method.

12. The measuring device Irradiating with irradiation light; receiving light to be measured based on the irradiated light irradiated onto a measurement area; calculating a state of the measurement target gas contained in the measurement region based on first reference information of the measurement target gas acquired at a first central wavelength of the measurement target gas, second reference information of the interference gas acquired at a second central wavelength of the interference gas and the first central wavelength, and light receiving signals of the received measurement target light at the first central wavelength and the second central wavelength; performing an action including program.

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