Measuring device, measurement method, and program

Abstract

To provide a measuring device capable of easily constituting an entire device.SOLUTION: A measuring device 1 comprises: an irradiation section 10 for applying irradiation light L; a light reception section 20 for receiving measured light ML based on the irradiation light L applied to a measured area R2 that is at least one portion of an irradiation area R1 of the irradiation light L by the irradiation section 10; and a control section 90 for executing calibration processing for calibrating a wavelength λc of the irradiation light L by acquiring reference information of a measured gas G1 included in the irradiation area R1 on the basis of a light reception signal from the light reception section 20 and measurement processing for calculating a state of a measured gas G2 included in a measured area R2 by using the irradiation light L with a calibration wavelength λ obtained by the calibration processing.SELECTED DRAWING: Figure 1

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 uses a tunable laser with a wide wavelength tunable range as a laser light source, and that can measure hydrocarbons with small spectral features as well as hydrocarbons with large spectral features with high accuracy by using a statistical method that excludes the sharp peak of methane when detecting the concentration. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-035385 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional technology described in Patent Document 1, it is necessary to arrange a wavelength calibration means separately from the measurement optical system used to measure the gas to be measured, and sufficient consideration has not been given to simplifying the configuration of the entire device.

[0005] An object of the present disclosure is to provide a measurement device, a measurement method, and a program that allow the entire device to be configured simply. [Means for solving the problem]

[0006] In some embodiments, the measurement device includes an irradiation unit that irradiates irradiation light, a light receiving unit that receives measured light based on the irradiation light irradiated onto a measured area, which is at least a part of the irradiation area of ​​the irradiation light by the irradiation unit, and a control unit that performs a calibration process that acquires reference information of the measured gas contained in the irradiation area based on the received light signal from the light receiving unit and calibrates the wavelength of the irradiation light, and a measurement process that calculates the state of the measured gas contained in the measured area using the irradiation light of the calibrated wavelength obtained in the calibration process.

[0007] This allows the entire measurement device to be configured simply. The measurement device can perform wavelength calibration using a measurement gas present in an irradiation area including a measurement area. For example, the measurement device can perform wavelength calibration as a methane gas detector using methane present in the atmosphere of the irradiation area. As a result, the measurement device can be configured simply without the need to install a wavelength calibration means such as a gas cell. Because the measurement device does not need to hold a wavelength calibration means within the device, the device configuration can be simplified, and it can be made lighter, smaller, and less expensive.

[0008] In one embodiment, the control unit modulates the wavelength at a modulation frequency, and the reference information includes data indicating that the intensity of the received light signal at a frequency twice the modulation frequency varies depending on the wavelength. This enables the measurement device to accurately calibrate the wavelength of the irradiated light based on, for example, the absorption spectrum of a measurement gas normally contained in the atmosphere in the irradiated region.

[0009] In one embodiment of the measuring device, the control unit may control the irradiating unit to sweep the wavelength in a wavelength band in which the intensity varies depending on the wavelength during the calibration process. This allows the measuring device to accurately acquire the absorption spectrum of the measured gas in a wavelength band including, for example, a peak wavelength corresponding to the calibration wavelength. As a result, the measuring device can accurately calibrate the wavelength of the irradiating light based on the absorption spectrum of the measured gas.

[0010] In one embodiment, the measurement device may further include an input unit that accepts input operations from a user, and the control unit may set the wavelength band based on input information entered by the user using the input unit, thereby enabling the measurement device to set the wavelength band within an optimal range for calibration processing based on the input information from the user.

[0011] In one embodiment, the input information may include setting information about the wavelength input by the user through the input unit so as to set the wavelength to the calibration wavelength in the calibration process. This enables the measurement device to set a wavelength band within an optimal range for the calibration process, for example, by using setting information about the wavelength when it was accurately set to the calibration wavelength in a previous calibration process.

[0012] In one embodiment of the measurement device, the control unit may set the wavelength band based on a predetermined time that has elapsed since the start of the measurement process. This allows the measurement device to set the wavelength band in a range that is optimal for the calibration process based on the predetermined time. For example, if the predetermined time is relatively short and it is estimated that the drift of a wavelength once calibrated to a calibration wavelength is small, the measurement device can set the wavelength band relatively narrow. This allows the measurement device to shorten the processing time required for the calibration process. On the other hand, for example, if the predetermined time is relatively long and it is estimated that the drift of a wavelength once calibrated to a calibration wavelength is large, the measurement device can set the wavelength band relatively wide. This allows the measurement device to easily search for the absorption peak of the gas to be measured.

[0013] In one embodiment, the control unit may set the wavelength at which the intensity is maximized as a peak wavelength in the spectrum of the measurement gas, and calibrate the wavelength to the peak wavelength. This allows the measurement device to accurately align the wavelength of the irradiated light with, for example, an absorption peak in the absorption spectrum of the measurement gas during calibration.

[0014] In one embodiment, the control unit may execute the calibration process again when it determines that a predetermined time has elapsed since the start of the measurement process. This allows the measurement device to periodically execute the calibration process based on the predetermined time. Therefore, even if the wavelength of the irradiated light deviates from the calibration wavelength due to drift caused by temperature change or the like, the measurement device can easily correct the wavelength deviation.

[0015] A measurement method according to some embodiments includes irradiating irradiation light, receiving measured light based on the irradiation light irradiated onto a measurement area that is a part of the irradiation area of ​​the irradiation light, performing a calibration process to acquire reference information of the measurement gas contained in the irradiation area based on the received light signal and calibrate the wavelength of the irradiation light, and performing a measurement process to calculate the state of the measurement gas contained in the measurement area using the irradiation light of the calibrated wavelength obtained in the calibration process.

[0016] As a result, the measurement device that performs the measurement method can be configured simply as a whole. The measurement device can perform wavelength calibration using the measurement gas present in the irradiation area including the measurement area. For example, the measurement device can perform wavelength calibration as a methane gas detector using methane present in the atmosphere in the irradiation area. As a result, the measurement device can be configured simply without the need to install a wavelength calibration means such as a gas cell. Because the measurement device does not need to hold a wavelength calibration means within the device, the device configuration can be simplified, and it can be made lighter, smaller, and less expensive.

[0017] 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 measurement area that is a part of the irradiation area of ​​the irradiation light, a calibration process for acquiring reference information of the measurement gas contained in the irradiation area based on the received light signal and calibrating the wavelength of the irradiation light, and a measurement process for calculating the state of the measurement gas contained in the measurement area using the irradiation light of the calibrated wavelength obtained in the calibration process.

[0018] This allows the entire measurement device to be configured simply. The measurement device can perform wavelength calibration using a measurement gas present in an irradiation area including a measurement area. For example, the measurement device can perform wavelength calibration as a methane gas detector using methane present in the atmosphere of the irradiation area. As a result, the measurement device can be configured simply without the need to install a wavelength calibration means such as a gas cell. Because the measurement device does not need to hold a wavelength calibration means within the device, the device configuration can be simplified, and it can be made lighter, smaller, and less expensive. [Effects of the Invention]

[0019] According to the present disclosure, it is possible to provide a measurement device, a measurement method, and a program that allow the entire device to be configured simply. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a block diagram showing a first example of the configuration of a measurement device according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a block diagram showing a second example of the configuration of a measurement device according to an embodiment of the present disclosure. [Figure 3] FIG. 3 is a graph illustrating an example of the operation of the measurement device of FIGS. [Figure 4] 3 is a flowchart illustrating an example of a measurement method executed by the measurement device of FIGS. DETAILED DESCRIPTION OF THE INVENTION

[0021] The background and problems of the prior art will now be described in more detail.

[0022] 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 irradiation light, and receive, as measured light, return light reflected or scattered by objects located in the background of an area where a measured gas may exist. Conventional spectroscopic gas detectors detect a measured gas based on changes in a light-receiving signal output by a photodetector upon receiving the measured light. For example, conventional spectroscopic gas detectors detect a target measured gas based on the measured light by utilizing the optical absorption characteristics unique to the measured gas. Conventional spectroscopic gas detectors such as those described above generally additionally include a gas cell for calibrating the wavelength of the irradiation light and a light-receiving system for wavelength calibration.

[0023] Light sources with wavelengths in the near-infrared region are widely used to measure the state of a gas to be measured in space with high sensitivity using light. For example, wavelength modulation spectroscopy (WMS) is known to be capable of achieving high-sensitivity measurements and is widely used.

[0024] Generally, to stably measure the state of a measurement gas with an optimal signal-to-noise (S / N) ratio using a WMS, the wavelength of the laser light source must match the absorption wavelength of the measurement gas. Therefore, the laser wavelength must be calibrated. As in the prior art described in Patent Document 1, a method is known in which a gas cell containing a reference gas identical to the measurement gas to be measured is mounted on a measurement device, and the laser wavelength is feedback-controlled to match the absorption wavelength of the measurement gas using light absorption by the reference gas. Alternatively, a method is known in which a reference gas in the atmosphere is introduced into a housing located at a different position from the measurement optical system and used for analysis in the calibration process.

[0025] However, the above-described methods based on the conventional techniques tend to increase the number of components and size of the measuring device, which tends to complicate the configuration of the measuring device.

[0026] In order to solve the above problems, the present disclosure aims to provide a measurement device, a measurement method, and a program that can easily configure the entire device. For example, the present disclosure provides a measurement device, a measurement method, and a program that can achieve wavelength calibration for methane present in the atmosphere without using a wavelength calibration means such as a gas cell.

[0027] 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.

[0028] FIG. 1 is a block diagram showing a first example of the configuration of a measurement device 1 according to an embodiment of the present disclosure. FIG. 1 shows a state when a calibration process, which will be described later, is performed by the measurement device 1. FIG. 2 is a block diagram showing a second example of the configuration of the measurement device 1 according to an embodiment of the present disclosure. FIG. 2 shows a state when a measurement process, which will be described later, is performed by the measurement device 1. 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 FIGS. 1 and 2.

[0029] 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.

[0030] 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 R2 where a measurement gas G2 may be present.

[0031] The measurement region R2 is at least a part of the irradiation region R1 of the irradiation light L from the irradiation unit 10. Both the irradiation region R1 and the measurement region R2 exist, for example, in the space between the scatterer W and the irradiation unit 10. Both the irradiation region R1 and the measurement region R2 are included in the atmospheric region located between the measurement device 1 and the scatterer W. The scatterer W includes background objects such as walls and piping. In addition to the measurement gas G1 normally contained in the atmosphere in the irradiation region R1, the measurement region R2 may additionally contain a measurement gas G2 due to leakage, etc. For the purpose of simplifying the illustration, the measurement gas G1 normally contained in the atmosphere shown in FIG. 1 is omitted in FIG. 2.

[0032] In the present disclosure, "measurement gas G2" includes, for example, any gas that is the target of detection and measurement using the measurement device 1. For example, the measurement gas G2 may contain methane. "Measurement gas G1" is, for example, the same gas as the measurement gas G2. When the measurement device 1 detects and measures methane as the measurement gas G2 due to a leak or the like, the measurement gas G1 may contain methane that is normally contained in the atmosphere. Hereinafter, when descriptions that apply commonly to both the measurement gas G1 and the measurement gas G2 are used, the measurement gas G1 and the measurement gas G2 will be collectively referred to as "measurement gas G" for convenience.

[0033] The wavelength of the irradiation light L irradiated by the irradiation unit 10 is included in the optical absorption band of the measurement gas G. For example, the wavelength of the irradiation light L is included in one of the optical absorption bands of the measurement gas G. The optical absorption band is included in a wavelength range such as the infrared range and the visible range.

[0034] 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 a measurement region R2, which is at least a part of the irradiation region R1 of the irradiation light L from the irradiating unit 10.

[0035] In the present disclosure, the "measurement light ML" is, for example, scattered light or reflected light from the scattering medium W based on the irradiation light L irradiated from the irradiation unit 10, and includes light absorbed by a gas present in the measurement region R2, such as the measurement gas G2. The light receiving unit 20 receives the measurement light ML that has passed through the gas present in the measurement region R2 between the scattering medium 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 included in the light receiving unit 20 has detection sensitivity at the wavelength of the measurement light ML.

[0036] 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 irradiation region R1 so that the irradiation region R1 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 irradiation region R1 so that the irradiation region R1 is located between the scattering medium W and the light receiving unit 20.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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, but may also include an external storage module connected via a digital input / output port such as a USB (Universal Serial Bus).

[0043] 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. The input unit 70 accepts the user's input operation.

[0044] 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.

[0045] The control unit 90 includes one or more processors. The processors may be, but are not limited to, general-purpose processors or dedicated processors specialized for specific processing. 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.

[0046] 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.

[0047] The measuring device 1 operates as, for example, a spectroscopic gas detector using a light source 11. To detect the surrounding measurement gas G2, the measuring device 1 irradiates a measurement region R2 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 and returned by scatterers W located in the background of the measurement region R2 where the measurement gas G2 may be present.

[0048] The measuring device 1 detects the measurement gas G2 by utilizing the optical absorption characteristics determined by the type of measurement gas G2. The measuring device 1 operates by WMS, a type of laser spectroscopy. WMS is a method for acquiring the state of the measurement gas G2 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.

[0049] In this disclosure, the "state of the measurement gas G2" includes, for example, the concentration of the measurement gas G2. The concentration of the measurement gas G2 includes, for example, the column concentration of the measurement gas G2. The column concentration is given by the product of the optical path length when light passes through the measurement gas G2 and the concentration of the measurement gas G2. The unit of the column concentration is expressed in ppm m.

[0050] The following mainly describes the contents of basic processing by the control unit 90 when the measurement device 1 operates according to the WMS.

[0051] 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 wavelength λc of the laser light output from the light source 11 to a desired calibration wavelength λ corresponding to the absorption peak of the measurement gas G2, which is obtained by a calibration process described later.

[0052] 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 λc 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 around the wavelength λc at a constant modulation frequency f and modulation width ΔλL. For example, the control unit 90 modulates the wavelength of the laser light around the wavelength λc at the modulation frequency f and modulation width ΔλL. The modulation width ΔλL is, for example, expressed in units of wavelength rather than frequency.

[0053] 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 R2. 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 this voltage signal to the extraction unit 40 as a light-receiving signal.

[0054] The control unit 90 measures the state of the measurement gas G2 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 G2 based on the extracted frequency component.

[0055] For example, when the measurement gas G2 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 has passed through the measurement gas G2. The magnitude of the 2f component in the received light signal is proportional to the column concentration of the measurement gas G2. 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 G2. The control unit 90 calculates the column concentration of the measurement gas G2 by measuring the magnitude of the 2f component.

[0056] In this case, the 2f component is proportional not only to the column concentration of the measurement gas G2 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 G2.

[0057] 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 G2.

[0058] As described above, the control unit 90 measures the state of the measurement gas G2 based on the absorption characteristics of the measurement gas G2 with respect to the irradiated light L. The control unit 90 measures the state of the measurement gas G2 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 G2 from the 1f signal and 2f signal obtained from the light-receiving signal from the light-receiving unit 20.

[0059] In addition to the above, the control unit 90 also performs other calculation processes related to the measurement of the state of the measurement target gas G2, etc. In the following, an example of another operation of the measurement device 1 will be mainly described.

[0060] 1 and 2. Fig. 3 shows an example of the absorption spectrum of methane as the measurement gas G. In the following, the measurement gas G will be mainly described using methane as an example, but the measurement gas G that is the target of the measurement apparatus 1 is not limited to methane.

[0061] FIG. 3 shows the methane absorption peak at a peak wavelength λ in the near-infrared region. As an example, the peak wavelength λ is slightly smaller than 1651 nm. As described above, in WMS measurements, the methane column concentration 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 proportional to the column concentration. While this is an advantage of WMS, the 1f component is unrelated to absorption and is not included in the essence of this disclosure. Therefore, the following description will focus primarily on the 2f component.

[0062] In this disclosure, the measurement device 1 is used as an example of a methane gas detector, and wavelength calibration is performed using methane present in the atmosphere. Remote gas detection using light produces a received light signal proportional not only to the gas concentration but also to the distance the light travels through the gas. Therefore, the unit of the received light signal is expressed as ppm·m, which is the product of concentration and distance. Parameters expressed in such units are called column concentration or integrated concentration.

[0063] Assuming that methane is uniformly present in the atmosphere, light continues to be absorbed by methane on the way to the background object, which is the scatterer W. For example, if the distance from the irradiation position of the irradiation unit 10 to the scatterer W is 20 m, and the concentration of methane normally contained in the atmosphere is 1.8 ppm, the product of these will give a received light signal with a column concentration of 36 ppm m. Lasers are widely used as the light source 11 in optical gas detection, and this column concentration is at a level that can be measured with such a gas detector.

[0064] Because gas absorption signals appear as minute changes in signal value, the WMS described above is commonly used. In WMS, gases are detected by detecting the 2f component, which is a frequency component twice the modulation frequency f, when the target gas is present. If the laser wavelength deviates from the absorption wavelength of the target gas for some reason, the magnitude of the 2f component decreases in WMS. Specifically, the measurement device 1 acquires a received signal indicating the atmospheric methane concentration while sweeping the laser wavelength λc across the methane peak wavelength λ. This allows for the calibration wavelength λ, which gives the maximum value of the 2f component. While Figure 3 shows the peak wavelength λ as the calibration wavelength, the wavelength used for wavelength calibration is not limited to the peak wavelength λ and may be any other wavelength in the methane absorption spectrum.

[0065] The measurement device 1 can perform methane measurement processing with an optimal signal-to-noise ratio by matching the laser wavelength λc to the calibration wavelength λ. Using this measurement method eliminates the need for additional components such as a gas cell for wavelength calibration.

[0066] 4 is a flowchart illustrating an example of a measurement method executed by the measurement apparatus 1 shown in FIGS. 1 and 2. In FIG. 4, steps S101 to S103 show the flow of a calibration process executed by the measurement apparatus 1. The control unit 90 of the measurement apparatus 1 acquires reference information for the measurement gas G1 contained in the irradiation region R1 shown in FIG. 1 based on a light-receiving signal from the light-receiving unit 20, and executes a calibration process to calibrate the wavelength λc of the irradiation light L. Steps S104 to S106 show the flow of a measurement process executed by the measurement apparatus 1. The control unit 90 of the measurement apparatus 1 executes a measurement process to calculate the state of the measurement gas G2 contained in the measurement region R2 shown in FIG. 2, using the irradiation light L with the calibration wavelength λ obtained in the calibration process.

[0067] In step S101, the control unit 90 of the measurement device 1 acquires a light reception signal by the WMS from the light receiving unit 20 for the measurement gas G1 contained in the irradiation region R1 based on the configuration shown in FIG.

[0068] In step S102, the control unit 90 of the measuring device 1 acquires reference information for the measurement gas G1 contained in the irradiation region R1 based on the light-receiving signal from the light-receiving unit 20 acquired in step S101. In the present disclosure, the "reference information" includes, for example, data indicating that the intensity of the light-receiving signal at a frequency component twice the modulation frequency f varies depending on the wavelength λc of the irradiation light L. That is, the reference information includes, for example, absorption spectrum data of the measurement gas G1 typically contained in the atmosphere in the irradiation region R1, as shown in FIG. 3 . The control unit 90 of the measuring device 1 stores the acquired reference information in the memory unit 60.

[0069] In step S102 of the calibration process, the control unit 90 of the measurement device 1 controls the irradiation unit 10 to sweep the wavelength λc in a wavelength band in which the intensity of the received light signal at a frequency component twice the modulation frequency f varies depending on the wavelength λc. This wavelength band includes, for example, the region from the lower limit value of 1650 nm to the upper limit value of 1652 nm of the wavelength λc shown in FIG.

[0070] The control unit 90 of the measurement device 1 sets the wavelength band based on, for example, input information input by a user using the input unit 70. In the present disclosure, "input information" includes, for example, setting information regarding wavelength λc input by a user via the input unit 70 to set wavelength λc to the calibration wavelength λ in a past calibration process. "Setting information" includes, for example, parameter values ​​for driving the laser included in the light source 11 of the irradiation unit 10 when wavelength λc matches the calibration wavelength λ. "Parameters" include current, temperature, and the like. The control unit 90 sets the wavelength band by, for example, changing the parameter values ​​within a predetermined range centered on the parameter values ​​when wavelength λc matches the calibration wavelength λ.

[0071] In step S103, the control unit 90 of the measurement device 1 sets the wavelength λc at which the intensity of the received light signal in the frequency component twice the modulation frequency f is maximized as the peak wavelength λ in the optical spectrum, for example, the absorption spectrum, of the measurement target gas G1, and calibrates the wavelength λc to the peak wavelength λ.

[0072] In step S104, the control unit 90 of the measurement device 1 performs WMS measurement using the irradiated light L with the calibration wavelength λ obtained in the calibration process of step S103. Based on the results of the WMS measurement, the control unit 90 calculates the state of the measurement gas G2 contained in the measurement region R2.

[0073] In step S105, the control unit 90 of the measurement device 1 determines whether a predetermined time has elapsed since the start of the measurement process in step S104. If the control unit 90 determines that the predetermined time has elapsed, it executes the calibration process again. If the control unit 90 determines that the predetermined time has elapsed, it executes the process again from step S101. If the control unit 90 determines that the predetermined time has not elapsed, it executes the process of step S106.

[0074] In step S106, 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 of step S104 is executed again.

[0075] According to the measuring device 1 of the embodiment described above, the entire device can be configured simply. The measuring device 1 performs a calibration process to acquire reference information for the measurement gas G1 contained in the irradiation region R1 based on the light-receiving signal from the light-receiving unit 20 and calibrate the wavelength λc of the irradiation light L, and a measurement process to calculate the state of the measurement gas G2 contained in the measurement region R2. The measuring device 1 can perform wavelength calibration using the measurement gas G1 present in the irradiation region R1, including the measurement region R2. For example, the measuring device 1 can perform wavelength calibration using methane present in the atmosphere in the irradiation region R1 as a methane gas detector. As described above, the measuring device 1 can be configured simply without the need for a wavelength calibration means such as a gas cell. Because the measuring device 1 does not require a wavelength calibration means to be held within the device, the device configuration can be simplified, and lighter, smaller, and less expensive.

[0076] The reference information includes data indicating that the intensity of the received light signal at a frequency component twice the modulation frequency f varies depending on the wavelength λc. This allows the measurement device 1 to accurately calibrate the wavelength λc of the irradiated light L based on, for example, the absorption spectrum of the measurement gas G1 that is normally contained in the atmosphere in the irradiation region R1.

[0077] In the calibration process, the measurement device 1 controls the irradiating unit 10 to sweep the wavelength λc in a wavelength band in which the intensity of the received light signal at a frequency component twice the modulation frequency f varies depending on the wavelength λc. This allows the measurement device 1 to accurately acquire the absorption spectrum of the measurement target gas G1 in a wavelength band including, for example, the peak wavelength λ corresponding to the calibration wavelength. As a result, the measurement device 1 can accurately calibrate the wavelength λc of the irradiated light L based on the absorption spectrum of the measurement target gas G1.

[0078] The measurement device 1 sets the wavelength band based on input information input by the user using the input unit 70. This allows the measurement device 1 to set the wavelength band within an optimal range for the calibration process based on the input information from the user.

[0079] The input information includes setting information related to wavelength λc that is input by the user via the input unit 70 so as to set wavelength λc to the calibration wavelength λ in the calibration process. This enables the measurement device 1 to set the wavelength band within an optimal range for the calibration process, for example, by using setting information related to wavelength λc when it was accurately set to the calibration wavelength λ in a past calibration process.

[0080] The measuring device 1 sets the wavelength λc at which the intensity of the received light signal in the frequency component twice the modulation frequency f is maximized as the peak wavelength λ in the optical spectrum of the measured gas G1, and calibrates the wavelength λc to the peak wavelength λ. This allows the measuring device 1 to accurately align the wavelength λc of the irradiated light L with, for example, an absorption peak in the absorption spectrum of the measured gas G1 during the calibration process.

[0081] When the measurement device 1 determines that a predetermined time has elapsed since the start of the measurement process, it performs the calibration process again. This allows the measurement device 1 to perform the calibration process periodically based on the predetermined time. Therefore, even if the wavelength λc of the irradiated light L deviates from the calibration wavelength λ due to drift caused by temperature changes or the like, the measurement device 1 can easily correct the deviation of the wavelength λc.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] In the above embodiment, the measurement device 1 is described as modulating the wavelength λc of the irradiated light L at the modulation frequency f, but this is not limited to this. The measurement device 1 may perform the calibration process and the measurement process by any other method other than WMS. The reference information is described as including data indicating that the intensity of the received light signal at a frequency component twice the modulation frequency f varies depending on the wavelength λc, but this is not limited to this. The reference information may include any other information that can be used by the measurement device 1 to perform the calibration process, instead of or in addition to this data. For example, the reference information may include data on the intensity of the received light signal acquired only at multiple points discretely positioned on the horizontal axis of the wavelength λc, instead of or in addition to the absorption spectrum data of the measurement gas G1.

[0087] In the above embodiment, the measurement device 1 controls the irradiation unit 10 in the calibration process to sweep the wavelength λc in a wavelength band in which the intensity of the received light signal at a frequency component twice the modulation frequency f varies depending on the wavelength λc, but this is not limiting. The measurement device 1 may also control the irradiation unit 10 to discretely change the wavelength λc instead of continuously sweeping.

[0088] In the above embodiment, the measurement device 1 is described as further including an input unit 70 that accepts input operations from the user, but is not limited to this. The measurement device 1 does not have to include the input unit 70. The measurement device 1 is described as setting the wavelength band based on input information entered by the user using the input unit 70, but is not limited to this. The measurement device 1 may automatically set the wavelength band itself, for example, based on information about the calibration wavelength λ used in a past calibration process or measurement process.

[0089] Alternatively, the measurement apparatus 1 may set the wavelength band based on a predetermined time that has elapsed since the start of the measurement process. This allows the measurement apparatus 1 to set the wavelength band in a range that is optimal for the calibration process based on the predetermined time. For example, if the predetermined time is relatively short and it is estimated that the drift of the wavelength λc once calibrated to the calibration wavelength λ is small, the measurement apparatus 1 can set the wavelength band relatively narrow. This allows the measurement apparatus 1 to shorten the processing time required for the calibration process. On the other hand, for example, if the predetermined time is relatively long and it is estimated that the drift of the wavelength λc once calibrated to the calibration wavelength λ is large, the measurement apparatus 1 can set the wavelength band relatively wide. This allows the measurement apparatus 1 to easily search for the absorption peak of the measurement gas G1.

[0090] In the above embodiment, the input information has been described as including setting information related to the wavelength λc input by the user from the input unit 70 so as to set the wavelength λc to the calibration wavelength λ in the calibration process, but is not limited to this. The input information may include any other information that can be used to set the wavelength band instead of or in addition to the setting information. For example, the input information may include information that is more directly related to setting the wavelength band, such as the bandwidth and center wavelength of the wavelength band desired by the user.

[0091] In the above embodiment, the measurement device 1 sets the wavelength λc at which the intensity of the received light signal in the frequency component twice the modulation frequency f is maximized as the peak wavelength λ in the spectrum of the measured gas G1, and calibrates the wavelength λc to the peak wavelength λ, but this is not limiting. The measurement device 1 may also calibrate the wavelength λc to any other calibration wavelength different from the peak wavelength λ, at which the intensity of the received light signal in the frequency component twice the modulation frequency f is shifted from the maximum value.

[0092] In the above embodiment, the measurement device 1 executes the calibration process again when it determines that a predetermined time has elapsed since the start of the measurement process, but this is not limiting. The measurement device 1 does not have to execute such repeated processing.

[0093] In the above embodiment, the measurement gas G is described as containing methane, but is not limited to this. The measurement gas G that is the target of the calibration process and measurement process by the measurement device 1 may contain any other gas. For example, the measurement device 1 may perform the above-described calibration process and measurement process on another gas that has absorption at a wavelength close to the absorption peak of methane.

[0094] In addition to the configuration of the above embodiment, the measurement device 1 may further include an acquisition unit capable of acquiring the optical path length of the optical path passing through the measurement region R2 from the irradiation unit 10 to the light receiving unit 20. The acquisition unit may include, for example, a ranging module such as a LiDAR (Light Detection and Ranging) capable of measuring the distance between the measurement device 1 and the scatterer W. The measurement device 1 may acquire information on the concentration of the measurement gas G1 normally contained in the atmosphere based on user input via the input unit 70, and calculate the column concentration of the measurement gas G1 normally contained in the atmosphere based on the optical path length and the concentration acquired by the acquisition unit.

[0095] The measurement device 1 may evaluate the validity of the peak wavelength λ in the calibration process using the calculated column concentration as a criterion. For example, in data in which the intensity of the received light signal at a frequency component twice the modulation frequency f varies depending on the wavelength λc, if the maximum value of the intensity of the received light signal at a frequency component twice the modulation frequency f is approximately the same as the intensity value corresponding to the calculated column concentration, the measurement device 1 can reliably set the wavelength λc corresponding to this maximum value as the peak wavelength λ. Similarly, the measurement device 1 may evaluate the validity of the state of the measurement gas G2 in the measurement process using the calculated column concentration as a criterion. If the state of the measurement gas G2 calculated in the measurement process, for example, the column concentration of the measurement gas G2, is clearly greater than the column concentration calculated using the acquisition unit capable of acquiring the optical path length, the measurement device 1 can reliably determine that the measurement gas G2 is indeed leaking.

[0096] 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 so 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 and a lens.

[0097] 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.

[0098] 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 G2 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 G2 using any other method. For example, the measurement device 1 may calculate the state of the measurement gas G2 using another method that does not rely on the WMS.

[0099] 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 of the measurement gas G2 as a state of the measurement gas G2. However, the present invention is not limited to this. The measurement device 1 may calculate the state of the measurement gas G2 using any other arithmetic expression based on the 2f component extracted from the light-receiving signal.

[0100] 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.

[0101] In the above embodiment, the measurement device 1 is described as measuring the state of the measurement gas G2 based on the absorption characteristics of the measurement gas G2 with respect to the irradiated light L, but is not limited to this. The measurement device 1 may also measure the state of the measurement gas G2 based on the scattering characteristics and reflection characteristics of the measurement gas G2 with respect to the irradiated light L.

[0102] In the above embodiment, the light receiving unit 20 is described as being arranged on the same side as the irradiating unit 10 and receiving the measured light ML scattered or reflected by the scatterers W located behind the measurement gas G2, but this is not limited to this. The light receiving unit 20 may be arranged to face the irradiating unit 10 across the measurement region R2. 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 R2.

[0103] In the above embodiment, the scatterer W includes background objects such as walls and pipes, but is not limited to this. The scatterer W may be any object other than walls and pipes.

[0104] In the above embodiment, the state of the measurement target gas G2 is described as including the concentration of the measurement target gas G2, but is not limited to this. The state of the measurement target gas G2 may also include the presence or absence of the measurement target gas G2.

[0105] 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. [Appendix 1] an irradiation unit that irradiates irradiation light; a light receiving unit that receives light to be measured based on the irradiation light irradiated onto a measurement area, which is at least a part of an irradiation area of ​​the irradiation light from the irradiation unit; a control unit that executes a calibration process of acquiring reference information of the measurement gas contained in the irradiation area based on the light receiving signal from the light receiving unit and calibrating the wavelength of the irradiation light, and a measurement process of calculating the state of the measurement gas contained in the measurement area using the irradiation light of the calibrated wavelength obtained in the calibration process; Equipped with Measuring equipment. [Appendix 2] 10. The measurement device of claim 1, The control unit modulates the wavelength at a modulation frequency, the reference information includes data indicating that the intensity of the received light signal at a frequency component twice the modulation frequency varies depending on the wavelength. Measuring equipment. [Appendix 3] 10. The measurement device of claim 2, the control unit controls the irradiation unit in the calibration process to sweep the wavelength in a wavelength band in which the intensity changes depending on the wavelength. Measuring equipment. [Appendix 4] 4. The measurement device of claim 3, further comprising an input unit that accepts an input operation by a user; the control unit sets the wavelength band based on input information input by the user using the input unit. Measuring equipment. [Appendix 5] 5. The measurement device of claim 4, the input information includes setting information regarding the wavelength input by the user from the input unit so as to set the wavelength to the calibration wavelength in the calibration process. Measuring equipment. [Appendix 6] 6. The measurement device according to any one of claims 3 to 5, the control unit sets the wavelength band based on a predetermined time that has elapsed since the start of the measurement process. Measuring equipment. [Appendix 7] 7. The measurement device according to any one of claims 2 to 6, the control unit sets the wavelength at which the intensity is maximum as a peak wavelength in the spectrum of the measurement gas, and calibrates the wavelength to the peak wavelength. Measuring equipment. [Appendix 8] 8. The measurement device according to any one of claims 1 to 7, When the control unit determines that a predetermined time has elapsed since the start of the measurement process, the control unit executes the calibration process again. Measuring equipment. [Appendix 9] Irradiating with irradiation light; receiving light to be measured based on the irradiation light irradiated onto a measurement area that is a part of an irradiation area of ​​the irradiation light; a calibration process for calibrating the wavelength of the irradiated light by acquiring reference information of the measurement target gas contained in the irradiation area based on the light receiving signal; and a measurement process for calculating the state of the measurement target gas contained in the measurement area using the irradiated light of the calibrated wavelength obtained in the calibration process; Including, Measurement method. [Appendix 10] The measuring device Irradiating with irradiation light; receiving light to be measured based on the irradiation light irradiated onto a measurement area that is a part of an irradiation area of ​​the irradiation light; a calibration process for calibrating the wavelength of the irradiated light by acquiring reference information of the measurement target gas contained in the irradiation area based on the light receiving signal; and a measurement process for calculating the state of the measurement target gas contained in the measurement area using the irradiated light of the calibrated wavelength obtained in the calibration process; performing an action including program. [Explanation of symbols]

[0106] 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 G Measured gas G1 Measurement gas G2 Measurement gas L irradiation light ML Measured light R1 irradiation area R2 Measured area W scatterer λc wavelength λ Peak wavelength (calibration wavelength)

Claims

1. an irradiation unit that irradiates irradiation light; a light receiving unit that receives light to be measured based on the irradiation light irradiated onto a measurement area, which is at least a part of an irradiation area of ​​the irradiation light from the irradiation unit; a control unit that executes a calibration process of acquiring reference information of the measurement gas contained in the irradiation area based on the light receiving signal from the light receiving unit and calibrating the wavelength of the irradiation light, and a measurement process of calculating the state of the measurement gas contained in the measurement area using the irradiation light of the calibrated wavelength obtained in the calibration process; Equipped with Measuring equipment.

2. 2. The measuring device according to claim 1, The control unit modulates the wavelength at a modulation frequency, the reference information includes data indicating that the intensity of the received light signal at a frequency component twice the modulation frequency varies depending on the wavelength. Measuring equipment.

3. 3. The measuring device according to claim 2, the control unit controls the irradiation unit in the calibration process to sweep the wavelength in a wavelength band in which the intensity changes depending on the wavelength. Measuring equipment.

4. 4. The measuring device according to claim 3, further comprising an input unit that accepts an input operation by a user; the control unit sets the wavelength band based on input information input by the user using the input unit. Measuring equipment.

5. 5. The measuring device according to claim 4, the input information includes setting information regarding the wavelength input by the user from the input unit so as to set the wavelength to the calibration wavelength in the calibration process. Measuring equipment.

6. 6. The measuring device according to claim 3, the control unit sets the wavelength band based on a predetermined time that has elapsed since the start of the measurement process. Measuring equipment.

7. 6. The measuring device according to claim 2, wherein the control unit sets the wavelength at which the intensity is maximum as a peak wavelength in the spectrum of the measurement gas, and calibrates the wavelength to the peak wavelength. Measuring equipment.

8. 6. The measuring device according to claim 1, When the control unit determines that a predetermined time has elapsed since the start of the measurement process, the control unit executes the calibration process again. Measuring equipment.

9. Irradiating with irradiation light; receiving light to be measured based on the irradiation light irradiated onto a measurement area that is a part of an irradiation area of ​​the irradiation light; a calibration process for calibrating the wavelength of the irradiated light by acquiring reference information of the measurement target gas contained in the irradiation area based on the light receiving signal; and a measurement process for calculating the state of the measurement target gas contained in the measurement area using the irradiated light of the calibrated wavelength obtained in the calibration process; Including, Measurement method.

10. The measuring device Irradiating with irradiation light; receiving light to be measured based on the irradiation light irradiated onto a measurement area that is a part of an irradiation area of ​​the irradiation light; a calibration process for calibrating the wavelength of the irradiated light by acquiring reference information of the measurement target gas contained in the irradiation area based on the light receiving signal; and a measurement process for calculating the state of the measurement target gas contained in the measurement area using the irradiated light of the calibrated wavelength obtained in the calibration process; performing an action including program.

Images