Analysis system

Abstract

To specify a concentration of an observation object gas with high accuracy and in a simple manner.SOLUTION: An analysis system for analyzing a concentration of an observation object gas in a measurement space is equipped with: a light-emitting element for emitting detection light; a pressure acquisition part 62 for acquiring a pressure P of an observation object gas; an amplitude setting part 63 for setting a modulation amplitude according to the pressure P; a wavelength control part for sweeping in a sweep range including a light absorption wavelength of the observation object gas, while fluctuating a wavelength of the detection light using the modulation amplitude; a light-receiving element for generating a light-receiving signal by receiving the detection light transmitted through the measurement space; a signal detection part for acquiring a detection waveform D by lock-in detection with respect to the light-receiving signal; and an analysis processing part 61 for specifying a concentration C of the observation object gas from the detection waveform D.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present disclosure relates to a technique for identifying the concentration of a specific gas. [Background technology]

[0002] Techniques for determining the concentration of a specific gas (hereinafter referred to as "target gas") by irradiating it with laser light have been proposed. The linewidth of the absorption line spectrum of the target gas depends on the pressure of the target gas. Therefore, for example, Patent Document 1 discloses a technique for minimizing the effect of pressure on the target gas concentration. The technique of Patent Document 1 corrects the target gas concentration by using pre-registered correction information and the amplitudes of detection waveforms corresponding to different modulation amplitudes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-106742 Summary of the Invention [Problem to be solved by the invention]

[0004] According to the configuration of Patent Document 1, it is possible to calculate an appropriate concentration by correcting the pressure dependence of the concentration. However, there is a demand for a technology that can analyze the concentration of the target gas with higher accuracy and ease. In consideration of the above circumstances, one aspect of the present disclosure aims to determine the concentration of the target gas with higher accuracy and ease. [Means for solving the problem]

[0005] In order to solve the above problems, an analysis system according to one aspect of the present disclosure is an analysis system for analyzing the concentration of a target gas in a measurement space, and includes: a light-emitting element that emits detection light; a pressure acquisition unit that acquires the pressure of the target gas; an amplitude setting unit that sets a modulation amplitude according to the pressure; a wavelength control unit that sweeps the wavelength of the detection light within a sweep range that includes the absorption wavelength of the target gas while varying the modulation amplitude; a light-receiving element that generates a received light signal by receiving the detection light that has passed through the measurement space; a signal detection unit that acquires a detection waveform by lock-in detection of the received light signal; and an analysis processing unit that identifies the concentration of the target gas from the detection waveform. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a configuration diagram of an analysis system according to a first embodiment. [Figure 2] 1 is a graph showing the absorption characteristics of an observation target gas. [Figure 3] FIG. 10 is an explanatory diagram relating to the sweeping of the wavelength of the detection light. [Figure 4] FIG. 10 is a waveform diagram of a detected waveform. [Figure 5] 10 is a graph showing the relationship between the pressure of the gas to be observed and the amplitude of the detected waveform. [Figure 6] 10 is a graph showing the relationship between pressure and modulation amplitude for setting the amplitude of the detected waveform to a predetermined value. [Figure 7] FIG. 1 is a block diagram illustrating a configuration of an information processing device. [Figure 8] FIG. 2 is a block diagram illustrating a functional configuration of an information processing device. [Figure 9] FIG. 2 is a schematic diagram of a look-up table. [Figure 10] 10 is a flowchart of an analysis process. [Figure 11] FIG. 10 is an explanatory diagram of a detection peak interval in the second embodiment. [Figure 12] 10 is a graph showing the relationship between the pressure of the gas to be observed and the interval between detected peaks. [Figure 13]FIG. 10 is a block diagram illustrating the configuration of a pressure acquisition unit in a second embodiment. [Figure 14] FIG. 10 is a schematic diagram of a look-up table in the second embodiment. [Figure 15] 10 is a flowchart of a pressure acquisition process in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The following description of an embodiment of the present disclosure will be given with reference to the accompanying drawings. Note that the embodiment described below is an exemplary embodiment that may be envisioned when implementing the present disclosure. Therefore, the scope of the present disclosure is not limited to the embodiment exemplified below.

[0008] A: First embodiment 1 is a configuration diagram of an analysis system 100 according to a first embodiment. The analysis system 100 is a concentration measurement system for analyzing the concentration C of a gas to be observed (hereinafter referred to as "observation target gas"). The analysis system 100 of the first embodiment analyzes the concentration C of the observation target gas by wavelength modulation optical spectroscopy.

[0009] The gas to be observed is a gas that flows through the space inside the flow path 10 (hereinafter referred to as the "measurement space 15"). The flow path 10 is a flue through which the gas to be observed, generated in, for example, an industrial process or a chemical process, flows, and includes a first wall 11 and a second wall 12 that face each other. The measurement space 15 is the space between the first wall 11 and the second wall 12. An opening 111 is formed in the first wall 11, and an opening 121 is formed in the second wall 12.

[0010] The absorption line spectrum of the target gas is shown in Figure 2. As shown in Figure 2, the absorption intensity (absorption cross section) of the target gas is maximized at an absorption wavelength λ0 specific to the type of target gas.

[0011] Figure 2 shows absorption line spectra for a plurality of cases where the pressure P of the gas to be observed is varied (P = PL, PM, PH). The pressure PL is lower than the pressure PM, and the pressure PH is higher than the pressure PM (PL < PM < PH). As understood from Figure 2, the shape of the absorption line spectrum depends on the pressure P of the gas to be observed. Specifically, there is a relationship (pressure broadening) in which the line width of the absorption line spectrum increases as the pressure P increases.

[0012] As illustrated in Figure 1, the analysis system 100 of the first embodiment includes a pressure sensor 13, a light emitting unit 20, a light receiving unit 30, and a communication line 40. The pressure sensor 13 is a sensor that measures the pressure P of the gas to be observed within the measurement space 15. For example, various sensors such as a piezoelectric pressure sensor, a strain gauge pressure sensor, a mechanical pressure sensor, a capacitive pressure sensor, or an optical pressure sensor are used as the pressure sensor 13.

[0013] The light emitting unit 20 is installed outside the first wall portion 11 via a tubular connection portion 42. The light receiving unit 30 is installed outside the second wall portion 12 via a tubular connection portion 43. That is, the measurement space 15 is located between the light emitting unit 20 and the light receiving unit 30. The communication line 40 is used for signal transmission between the light emitting unit 20 and the light receiving unit 30. In a form where the light emitting unit 20 and the light receiving unit 30 communicate wirelessly, the communication line 40 may be omitted.

[0014] The light emitting unit 20 is an optical unit that emits detection light L. The detection light L is a laser beam containing a component of the absorption wavelength λ0 of the gas to be observed. The detection light L emitted from the light emitting unit 20 passes through the opening 111 of the first wall portion 11 and enters the measurement space 15. A part of the detection light L that has entered the measurement space 15 is absorbed by the gas to be observed, and the remaining component that is not absorbed by the gas to be observed passes through the opening 121 of the second wall portion 12 and reaches the light receiving unit 30. The light receiving unit 30 is an optical unit that receives the detection light L that has passed through the measurement space 15.

[0015] 1 , the light-emitting unit 20 includes a first housing 21, a light-emitting element 22, an optical element 23, and a wavelength control unit 24. The first housing 21 is a hollow structure having an exit port 211 formed therein through which the detection light L passes. The light-emitting element 22, the optical element 23, and the wavelength control unit 24 are housed in and supported by the first housing 21.

[0016] The light-emitting element 22 emits detection light L. Specifically, the light-emitting element 22 is a wavelength-tunable laser element that emits laser light as the detection light L. For example, various light source devices such as a distributed feedback (DFB) laser device, a vertical cavity surface-emitting laser (VCSEL) device, or a distributed Bragg reflector (DBR) laser device are used as the light-emitting unit 20.

[0017] The optical element 23 is a collimating lens that converts the detection light L emitted by the light emitting element 22 into parallel light, and is installed at the light exit 211 of the first housing 21. Note that other elements such as a parabolic mirror may also be used as the optical element 23.

[0018] The wavelength control unit 24 controls the wavelength λ of the detection light L. Specifically, the wavelength control unit 24 controls the wavelength λ of the detection light L by supplying a drive current to the light emitting element 22. FIG. 3 is an explanatory diagram of the wavelength λ of the detection light L emitted by the light emitting element 22 under the control of the wavelength control unit 24. As illustrated in FIG. 3, the wavelength control unit 24 sweeps the wavelength λ of the detection light L within a sweep range R that includes the absorption wavelength λ0 of the target gas.

[0019] 3 is a wavelength range with a width of 2W centered around the absorption wavelength λ0. Specifically, the sweep range R has a lower limit of a wavelength (λ0-W) that is shorter than the absorption wavelength λ0 by a predetermined wavelength W, and an upper limit of a wavelength (λ0+W) that is longer than the absorption wavelength λ0 by the wavelength W.

[0020] 3, the wavelength λ of the detection light L is swept while periodically fluctuating according to the fluctuation width of the modulation amplitude M so that the center wavelength changes over time from the lower limit (λ0-W) to the upper limit (λ0+W) of the sweep range R. The frequency at which the wavelength λ of the detection light L fluctuates (the modulation frequency) is, for example, about 50 kHz. As described above, the wavelength control unit 24 of FIG. 1 sweeps the wavelength λ of the detection light L within the sweep range R while fluctuating it with the modulation amplitude M. Specifically, the wavelength control unit 24 generates a drive current by superimposing a modulation signal (e.g., a sine wave) of the modulation frequency on a sweep signal for sweeping the wavelength λ within the sweep range R, and supplies the drive current to the light emitting element 22.

[0021] The wavelength control unit 24 of the first embodiment can control the modulation amplitude M. Specifically, the wavelength control unit 24 sets the modulation amplitude M to a numerical value instructed by the information processing device 50, which will be described later. For example, the oscillation wavelength of the light-emitting element 22 depends on the current supplied to the light-emitting element 22. Therefore, the wavelength control unit 24 controls the modulation amplitude M of the detection light L by controlling the current value of the drive current supplied to the light-emitting element 22. Specifically, in terms of a coefficient Z relating to the dependency between the emission wavelength and the drive current, the wavelength control unit 24 supplies to the light-emitting element 22 a drive current whose current value I [mA] is a numerical value (M / Z) obtained by dividing the modulation amplitude M [nm] by the coefficient Z [nm / mA].

[0022] 1 , the light receiving unit 30 includes a second housing 31, an optical element 32, a light receiving element 33, a signal detection unit 34, and an information processing device 50. The second housing 31 is a hollow structure having an entrance 311 through which the detection light L that has passed through the measurement space 15 enters. The optical element 32, the light receiving element 33, the signal detection unit 34, and the information processing device 50 are housed in and supported by the second housing 31.

[0023] The light receiving element 33 generates a light receiving signal X by receiving the detection light L that has passed through the measurement space 15. Specifically, the light receiving element 33 is a photodiode that generates the light receiving signal X as a voltage corresponding to the intensity of the detection light L. The light receiving sensitivity of the light receiving element 33 is distributed over the entire sweep range R of the detection light L.

[0024] The optical element 32 is a condenser lens that condenses the detection light L onto the light receiving surface of the light receiving element 33, and is installed at the light entrance 311 of the second housing 31. Note that other elements such as a parabolic mirror, a tablet lens, or a diffractive lens may also be used as the optical element 32.

[0025] The signal detection unit 34 is a detection circuit that acquires a detection waveform D by lock-in detection of the received light signal X supplied from the light receiving element 33. The detection waveform D is a time series of the signal intensity of the detection signal generated by lock-in detection of the received light signal X. For example, the signal detection unit 34 performs lock-in detection using a frequency that is a multiple (e.g., double) of the modulation frequency applied to the sweep of the detection light L.

[0026] The information processing device 50 is a computer system that analyzes the concentration C of the target gas in the measurement space 15 by analyzing the detection waveform D generated by the signal detection unit 34. The information processing device 50 may be installed outside the second housing 31. In other words, the information processing device 50 may be installed as an element separate from the light receiving unit 30.

[0027] Fig. 4 is a schematic diagram of the detection waveform D. As illustrated in Fig. 4, the signal intensity (i.e., the detection output) in the detection waveform D roughly reaches a minimum at time t0 when the wavelength λ of the detection light L matches the absorption wavelength λ0 of the target gas, and reaches a maximum around time t0.

[0028] Figure 4 also shows the detected waveform D for several cases (P = PL, PM, PH) in which the pressure P is changed while the concentration C of the target gas is kept constant. As mentioned above, the shape of the absorption line spectrum of the target gas depends on the pressure P of the target gas. Therefore, the amplitude A of the detected waveform D depends not only on the concentration C of the target gas, but also on the pressure P of the target gas, as shown in the example of Figure 4. Specifically, there is a relationship in which the amplitude A of the detected waveform D decreases as the pressure P increases. The amplitude A of the detected waveform D is the difference (peak-to-peak value) between the maximum and minimum values ​​of the signal strength in the detected waveform D.

[0029] FIG. 5 is a graph showing the relationship between the pressure P of the gas being observed and the amplitude A of the detection waveform D. FIG. 5 also shows the relationship between the pressure P and the amplitude A for each of several cases (M = M1, M2, M3, M4) in which the modulation amplitude M of the detection light L is changed while the concentration C of the gas being observed is kept constant. The numerical value Mk (k = 1, 2, 3, 4) of the modulation amplitude M is calculated by adding the product of a predetermined change amount Δ and a coefficient (k-1) to the reference value M0 of the modulation amplitude M (Mk = M0 + (k-1)Δ). As can be seen from FIG. 5, the relationship between the pressure P of the gas being observed and the amplitude A of the detection waveform D depends on the modulation amplitude M.

[0030] FIG. 5 illustrates a predetermined value (hereinafter referred to as the "predetermined value A0") for the amplitude A of the detection waveform D. As can be seen from FIG. 5, the modulation amplitude M when the amplitude A of the detection waveform D becomes the predetermined value A0 depends on the pressure P of the gas being observed. In other words, by setting the modulation amplitude M to a value corresponding to the pressure P, it is possible to adjust the amplitude A of the detection waveform D to the predetermined value A0. For example, if the pressure P of the gas being observed is a value P1, setting the modulation amplitude M to a value M1 will make the amplitude A of the detection waveform D become the predetermined value A0. On the other hand, if the pressure P of the gas being observed is a value P2, setting the modulation amplitude M to a value M2 will make the amplitude A of the detection waveform D become the predetermined value A0. The values ​​M1 and M2 of the modulation amplitude M are different values.

[0031] FIG. 6 is a graph showing the relationship between the pressure P and modulation amplitude M for maintaining the amplitude A of the detection waveform D at a predetermined value A0. As shown in FIG. 6, the modulation amplitude M for maintaining the amplitude A of the detection waveform D at a predetermined value A0 depends on the pressure P of the gas being observed. Specifically, the modulation amplitude M increases substantially linearly with an increase in the pressure P. In other words, the modulation amplitude M for maintaining the amplitude A of the detection waveform D at a predetermined value A0 is approximately expressed by the following equation (1), which uses the pressure P as a variable. M=α·P+β …(1) The coefficient α in the formula (1) is the gradient of the modulation amplitude M with respect to the pressure P. On the other hand, the coefficient β in the formula (1) is a predetermined value (intercept) corresponding to the case where the pressure P is zero.

[0032] As explained above, by applying the modulation amplitude M that satisfies the condition of Equation (1) with respect to the pressure P of the gas to be observed to the control of the detection light L, the influence of the pressure P on the amplitude A of the detection waveform D is reduced (ideally eliminated). In other words, the amplitude A of the detection waveform D is a value that does not depend on the pressure P of the gas to be observed, but depends only on the concentration C of the gas to be observed. The information processing device 50 of the first embodiment sets the modulation amplitude M of the detection light L using the relationship explained above. In other words, as mentioned above, the information processing device 50 not only analyzes the concentration C of the gas to be observed in the measurement space 15 by analyzing the detection waveform D, but also sets the modulation amplitude M of the detection light L in accordance with the pressure P measured by the pressure sensor 13.

[0033] 7 is a block diagram illustrating an example of the configuration of an information processing device 50. As illustrated in FIG. 7, the information processing device 50 includes a control device 51, a storage device 52, an operation device 53, and an output device 54. The information processing device 50 may be realized as a single device, or may be realized as a plurality of devices (systems) configured separately from each other. The wavelength control unit 24 or the signal detection unit 34 may be mounted on the information processing device 50.

[0034] The control device 51 is composed of one or more processors that control each element of the information processing device 50. For example, the control device 51 is composed of one or more types of processors such as a central processing unit (CPU), a graphics processing unit (GPU), a sound processing unit (SPU), a digital signal processor (DSP), a field programmable gate array (FPGA), or an application specific integrated circuit (ASIC).

[0035] The storage device 52 is one or more memories that store programs executed by the control device 51 and various data used by the control device 51. The storage device 52 is configured with a known storage medium such as a magnetic storage medium or a semiconductor storage medium. The storage device 52 may be configured with a combination of multiple types of storage medium. Also, a portable storage medium that can be attached to and detached from the information processing device 50 may be used as the storage device 52.

[0036] The operation device 53 is an input device that receives instructions from a user of the analysis system 100. For example, a user-operable control is used as the operation device 53. The output device 54 outputs the results of the analysis of the target gas to be observed. For example, the output device 54 is exemplified by a display device that displays the analysis results, or a sound emitting device (e.g., a speaker) that plays back the sound of the analysis results.

[0037] 8 is a block diagram illustrating an example of the functional configuration of the information processing device 50. The control device 51 executes a program stored in the storage device 52 to realize a plurality of functions (an analysis processing unit 61, a pressure acquisition unit 62, and an amplitude setting unit 63) for analyzing the target gas to be observed.

[0038] The analysis processing unit 61 identifies the concentration C of the target gas from the detection waveform D generated by the signal detection unit 34. As described above, the amplitude A of the detection waveform D correlates with the concentration C of the target gas. Taking the above correlation into consideration, the analysis processing unit 61 identifies the concentration C of the target gas according to the amplitude A of the detection waveform D. Specifically, the analysis processing unit 61 identifies the concentration C corresponding to the amplitude A as the measurement result based on a predetermined correlation. The analysis processing unit 61 also outputs the measurement result via the output device 54.

[0039] The pressure acquiring unit 62 acquires the pressure P of the gas to be observed. The pressure acquiring unit 62 of the first embodiment receives the pressure P measured by the pressure sensor 13. The amplitude setting unit 63 sets the modulation amplitude M in accordance with the pressure P acquired by the pressure acquiring unit 62. Specifically, the amplitude setting unit 63 sets the modulation amplitude M using a reference table B1 stored in the storage device 52.

[0040] Fig. 9 is a schematic diagram of reference table B1. As illustrated in Fig. 9, reference table B1 is a data table in which a modulation amplitude M (M1, M2, ...) is associated with each of a plurality of different pressures P (P1, P2, ...). For each of the plurality of pressures P, a modulation amplitude M is set that has the relationship shown in Fig. 6 (Equation (1)) with respect to the pressure P. In other words, reference table B1 defines the relationship between pressure P and modulation amplitude M.

[0041] The amplitude setting unit 63 identifies the modulation amplitude M corresponding to the pressure P acquired by the pressure acquisition unit 62 from among the multiple modulation amplitudes M registered in the reference table B1. That is, the amplitude setting unit 63 sets the modulation amplitude M so that the modulation amplitude M increases as the pressure P increases. Specifically, the amplitude setting unit 63 sets the modulation amplitude M so that the amplitude A of the detection waveform D becomes a predetermined value A0.

[0042] The modulation amplitude M set by the amplitude setting unit 63 is notified to the wavelength control unit 24 via the communication line 40. The wavelength control unit 24 sweeps the wavelength λ of the detection light L within the sweep range R while varying the wavelength λ by the modulation amplitude M notified from the information processing device 50 (amplitude setting unit 63).

[0043] 10 is a flowchart of a process (hereinafter referred to as "analysis process") executed by the control device 51 for analyzing the gas to be observed. For example, the analysis process is started in response to an instruction from the user via the operation device 53.

[0044] When the analysis process starts, the control device 51 (pressure acquisition unit 62) acquires the pressure P of the gas to be observed (S1). The control device 51 (amplitude setting unit 63) identifies the modulation amplitude M corresponding to the pressure P by referring to reference table B1 (S2). The control device 51 (amplitude setting unit 63) instructs the wavelength control unit 24 about the modulation amplitude M (S3). The wavelength control unit 24 controls the light emission of the light emitting element 22 so that the wavelength λ of the detection light L varies at the modulation amplitude M instructed by the control device 51. That is, the wavelength λ of the detection light L is swept within the sweep range R while varying at the modulation amplitude M set in accordance with the pressure P of the gas to be observed.

[0045] The signal detection unit 34 acquires a detection waveform D by lock-in detection of the light receiving signal X supplied from the light receiving element 33. The control device 51 (analysis processing unit 61) identifies the concentration C of the gas to be observed from the detection waveform D (S4). The control device 51 (analysis processing unit 61) also outputs the identified concentration C of the gas to be observed from the output device 54 (S5).

[0046] The control device 51 determines whether a predetermined termination condition is met (S6). The termination condition is, for example, an instruction to terminate the analysis process being issued by operating the operation device 53. If the termination condition is not met (S6: NO), the control device 51 transitions the process to step S1. That is, the control of the modulation amplitude M according to the pressure P of the gas to be observed (S1 to S3) and the determination and output of the concentration C of the gas to be observed using the detection waveform D (S4, S5) are repeated until the termination condition is met. If the termination condition is met (S6: YES), the control device 51 terminates the analysis process.

[0047] As described above, in the first embodiment, the modulation amplitude M is set in accordance with the pressure P of the gas to be observed, and therefore the influence of the pressure P on the amplitude A of the detection waveform D is (ideally eliminated) compared to a configuration in which the modulation amplitude M does not depend on the pressure P. In other words, according to the first embodiment, the concentration C of the gas to be observed can be determined with high accuracy using a simple configuration in which the modulation amplitude M is set in accordance with the pressure P.

[0048] In particular, in the first embodiment, the modulation amplitude M is set so that it increases as the pressure P of the gas to be observed increases. Therefore, under the relationship shown in FIG. 6 , in which the modulation amplitude M for maintaining the amplitude A of the detection waveform D at a predetermined value A0 increases as the pressure P of the gas to be observed increases, the concentration C of the gas to be observed can be determined with high accuracy. Also, in the first embodiment, the modulation amplitude M is set so that the amplitude A of the detection waveform D becomes the predetermined value A0. Therefore, fluctuations in the amplitude A of the detection waveform D according to the pressure P of the gas to be observed are reduced, and as a result, the concentration C of the gas to be observed can be determined with high accuracy.

[0049] B: Second embodiment A second embodiment will be described. Note that, for elements in the following exemplary aspects that have the same functions as those in the first embodiment, the same reference numerals as those in the first embodiment will be used, and detailed descriptions of each will be omitted as appropriate.

[0050] In the first embodiment, the pressure P measured by the pressure sensor 13 in Fig. 1 is received by the pressure acquisition unit 62. In the second embodiment, the method by which the pressure acquisition unit 62 acquires the pressure P of the gas to be observed differs from that in the first embodiment. Specifically, the pressure acquisition unit 62 in the second embodiment identifies the pressure P of the gas to be observed by analyzing the detection waveform D generated by the signal detection unit 34. As described above, in the second embodiment, the pressure P is identified from the detection waveform D, so the pressure sensor 13 in Fig. 1 that measures the pressure P may be omitted.

[0051] Fig. 11 is a schematic diagram of the detected waveform D. As in Fig. 4, Fig. 11 also shows the detected waveform D for each of a number of cases where the pressure P of the gas to be observed is different (P = PL, PM, PH).

[0052] 11, the detection waveform D has a first peak Q1 and a second peak Q2. The first peak Q1 is a time point in the detection waveform D where the signal intensity is maximized before time t0, which corresponds to the absorption wavelength λ0 of the target gas. On the other hand, the second peak Q2 is a time point in the detection waveform D where the signal intensity is maximized after time t0, which corresponds to the absorption wavelength λ0 of the target gas. In other words, the first peak Q1 and the second peak Q2 sandwich time t0, which corresponds to the absorption wavelength λ0, on the time axis.

[0053] 11 shows the interval between the first peak Q1 and the second peak Q2 on the time axis (hereinafter referred to as "detection peak interval T"). The detection peak interval T is the time difference between the first peak Q1 and the second peak Q2 on the time axis. As can be seen from FIG. 11, the detection peak interval T depends on the pressure P of the gas being observed.

[0054] 12 is a graph showing the relationship between the pressure P of the gas to be observed and the detection peak interval T. As shown in FIG. 12, there is a relationship in which the detection peak interval T increases as the pressure P increases. The pressure acquisition unit 62 of the second embodiment identifies the pressure P from the detection peak interval T in the detection waveform D by utilizing the relationship exemplified above.

[0055] 13 is a block diagram illustrating the configuration of the pressure acquisition unit 62 in the second embodiment. The pressure acquisition unit 62 in the second embodiment includes an interval determination unit 621 and a pressure determination unit 622.

[0056] The interval specifying unit 621 specifies the detected peak interval T from the detected waveform D generated by the signal detection unit 34. Specifically, the interval specifying unit 621 detects a first peak Q1 and a second peak Q2 from the detected waveform D, and specifies the time difference between the first peak Q1 and the second peak Q2 as the detected peak interval T. Note that the interval specifying unit 621 may specify the detected peak interval T after suppressing high frequency components of the detected waveform D by, for example, low-pass filtering.

[0057] The pressure identifying unit 622 identifies the pressure P of the gas to be observed according to the detection peak interval T. Specifically, the pressure identifying unit 622 identifies the pressure P by using a reference table B2 stored in the storage device 52.

[0058] Fig. 14 is a schematic diagram of reference table B2. As illustrated in Fig. 14, reference table B2 is a data table in which a pressure P (P1, P2, ...) is associated with each of a plurality of different detection peak intervals T (T1, T2, ...). For each of the plurality of detection peak intervals T, a pressure P is set that has the relationship shown in Fig. 12 with respect to the detection peak interval T. In other words, reference table B2 defines the relationship between the detection peak interval T and the pressure P.

[0059] The pressure specifying unit 622 specifies, from among the multiple pressures P registered in the reference table B2, a pressure P that corresponds to the detected peak interval T specified by the interval specifying unit 621. In other words, the pressure specifying unit 622 specifies the pressure P such that the pressure P increases as the detected peak interval T increases.

[0060] In the second embodiment, the process of Fig. 15 (hereinafter referred to as "pressure acquisition process") is executed in step S1 of the analysis process described above with reference to Fig. 10. When the pressure acquisition process starts, the control device 51 (interval determination unit 621) determines the detected peak interval T from the detected waveform D (S11). The control device 51 (pressure determination unit 622) determines the pressure P corresponding to the detected peak interval T by referring to reference table B2 (S12).

[0061] The operations other than the pressure acquisition process (S1) are the same as those in the first embodiment. That is, the control of the modulation amplitude M according to the pressure P of the gas to be observed (S2, S3) and the determination and output of the concentration C of the gas to be observed using the detected waveform D (S4, S5) are repeated. Therefore, the second embodiment also achieves the same effects as the first embodiment.

[0062] Furthermore, in the second embodiment, the pressure P of the target gas is determined according to the detection peak interval T in the detection waveform D, so no special equipment (e.g., pressure sensor 13 in FIG. 1) is required to measure the target gas pressure P. This simplifies the configuration for determining the target gas concentration C. The detection waveform D is also used to determine the target gas concentration C and the pressure P used to set the modulation amplitude M. This simplifies the configuration for determining the target gas concentration C compared to a configuration in which separate pieces of information are used to determine the target gas concentration C and the pressure P.

[0063] In particular, in the second embodiment, the pressure P is determined so that the pressure P increases as the detection peak interval T increases. Therefore, based on the relationship in Fig. 12 in which the detection peak interval T increases as the pressure P of the gas to be observed increases, the pressure P of the gas to be observed can be determined with high accuracy.

[0064] C: Modified Example Specific modified embodiments that can be added to each of the embodiments exemplified above are exemplified below. Two or more embodiments arbitrarily selected from the following examples may be combined as appropriate within the scope of not being mutually contradictory.

[0065] (1) In the second embodiment, the pressure P determined by the pressure acquisition unit 62 is used to set the modulation amplitude M, but the method of using the pressure P determined from the detection peak interval T is not limited to the above example. For example, as illustrated below, the pressure P may be used to correct the concentration C of the gas to be observed.

[0066] For example, as described above with reference to FIG. 4, in a configuration in which the modulation amplitude M is fixed to a predetermined value, the amplitude A of the detection waveform D depends on the pressure P of the gas to be observed. Therefore, the control device 51 (analysis processing unit 61) may correct the amplitude A of the detection waveform D in accordance with the pressure P determined from the detection peak interval T. For example, the control device 51 corrects the amplitude A so that the amplitude A increases as the pressure P of the gas to be observed increases. The control device 51 (analysis processing unit 61) may also correct the concentration C determined from the amplitude A of the detection waveform D in accordance with the pressure P determined from the detection peak interval T. For example, the control device 51 corrects the concentration C so that the concentration C increases as the pressure P of the gas to be observed increases. Even in the configuration exemplified above, the influence of the pressure P on the amplitude A of the detection waveform D is reduced (ideally eliminated), and as a result, the concentration C can be determined with high accuracy.

[0067] (2) In the first embodiment, a configuration (hereinafter referred to as "Configuration 1") is exemplified in which the modulation amplitude M is set according to the pressure P of the gas to be observed, and in the second embodiment, a configuration (hereinafter referred to as "Configuration 2") is exemplified in which the pressure P is determined according to the detection peak interval T of the detection waveform D. Configuration 1 is not essential for Configuration 2, and Configuration 2 alone can be established independently.

[0068] For example, the analysis system 100 having the configuration 2 is used to determine the pressure P of the gas to be observed. In the analysis system 100 that determines the pressure P using the configuration 2, the configuration 1 that sets the modulation amplitude M according to the pressure P and the configuration that determines the concentration C of the gas to be observed may be omitted.

[0069] (3) In each of the above-described embodiments, the amplitude setting unit 63 sets the modulation amplitude M using the reference table B1, but the configuration and method for setting the modulation amplitude M according to the pressure P of the gas to be observed are not limited to the above examples. For example, the amplitude setting unit 63 may calculate the modulation amplitude M by a calculation that applies the pressure P. Specifically, the amplitude setting unit 63 calculates the modulation amplitude M by applying the pressure P to the above-described formula (1). As described above, the use of the reference table B1 may be omitted.

[0070] Furthermore, in a configuration in which reference table B1 is used to set the modulation amplitude M, for example, if the pressure P acquired by the pressure acquisition unit 62 is not registered in reference table B1, the amplitude setting unit 63 may calculate the modulation amplitude M by interpolating multiple numerical values ​​registered in reference table B1. For example, the amplitude setting unit 63 identifies two pressures P that sandwich the pressure P acquired by the pressure acquisition unit 62 from reference table B1, and calculates the final modulation amplitude M by interpolating the modulation amplitude M corresponding to each of the two pressures P. As can be understood from the above example, even in a configuration in which reference table B1 is used, the modulation amplitude M set by the amplitude setting unit 63 does not have to be the numerical value itself registered in reference table B1.

[0071] (4) In the above-described embodiments, the pressure determination unit 622 determines the pressure P using the reference table B2. However, the configuration and method for determining the pressure P according to the detected peak interval T are not limited to the above examples. For example, the pressure determination unit 622 may calculate the pressure P by applying the detected peak interval T to a predetermined arithmetic expression. The arithmetic expression is a mathematical expression that approximates the relationship between the detected peak interval T and the pressure P (the relationship illustrated in FIG. 12). As described above, the use of the reference table B2 may be omitted.

[0072] Furthermore, in a configuration in which reference table B2 is used to identify the pressure P, for example, if the detection peak interval T identified by the interval identification unit 621 is not registered in reference table B2, the pressure identification unit 622 may calculate the pressure P by interpolating multiple numerical values ​​registered in reference table B2. For example, the pressure identification unit 622 identifies two detection peak intervals T that sandwich the detection peak interval T identified by the interval identification unit 621 from reference table B2, and calculates the final pressure P by interpolating the pressure P corresponding to each of the two detection peak intervals T. As can be understood from the above example, even in a configuration in which reference table B2 is used, the pressure P identified by the pressure identification unit 622 does not have to be the numerical value itself registered in reference table B2.

[0073] (5) In the first embodiment, an example is given in which the pressure acquisition unit 62 receives the pressure P from the pressure sensor 13, and in the second embodiment, an example is given in which the pressure acquisition unit 62 identifies the pressure P from the detection peak interval T. As can be understood from the above examples, the "acquisition" of the pressure P encompasses both the process of receiving the pressure P from an external device such as the pressure sensor 13 and the process of identifying the pressure P by itself from information such as the detection peak interval T.

[0074] (6) According to the second embodiment, the pressure P is determined according to the detected peak interval T, and therefore the pressure sensor 13 is not required in principle. However, a configuration including both a configuration for determining the pressure P according to the detected peak interval T (the interval determination unit 621 and the pressure determination unit 622) and the pressure sensor 13 is also conceivable. That is, the pressure acquisition unit 62 may have both the function of determining the pressure P according to the detected peak interval T and the function of receiving the pressure P from the pressure sensor 13. For example, the pressure acquisition unit 62 calculates the final pressure P by using one of the pressure P determined according to the detected peak interval T and the pressure P received from the pressure sensor 13 to correct the other.

[0075] (7) In the above-described embodiments, the information processing device 50 instructs the wavelength control device 24 about the modulation amplitude M (S3), but the content of the instruction from the information processing device 50 to the wavelength control device 24 is not limited to the above examples. For example, the information processing device 50 may instruct the wavelength control device 24 about a current value I (I=M / Z) for varying the wavelength λ of the detection light L with the modulation amplitude M.

[0076] (8) In the above-described embodiments, one type of target gas is present in the measurement space 15, but multiple types of target gases may be present in the measurement space 15. The absorption wavelength λ0 differs for each type of target gas. Therefore, the analysis process illustrated in the above-described embodiments is performed sequentially or in parallel for each of the multiple target gases. Note that the relationship between pressure P and modulation amplitude M (reference table B1) illustrated in FIG. 6 differs for each type of target gas. Furthermore, the relationship between detection peak interval T and pressure P (reference table B2) illustrated in FIG. 12 also differs for each type of target gas.

[0077] In a configuration in which pressure sensor 13 is used, when multiple types of target gases are present in measurement space 15, pressure sensor 13 identifies the partial pressure of each target gas as the pressure P of that target gas. In a configuration in which the partial pressure of the target gas correlates with the total pressure in measurement space 15, the total pressure in measurement space 15 may be used as the target gas pressure P. Note that in the second embodiment, the pressure P identified from the detection peak interval T corresponds to the partial pressure of one type of target gas.

[0078] (9) In the above-described embodiments, the concentration C of the target gas to be observed is specified, but the target of analysis by the analysis processing unit 61 is not limited to the above examples. For example, the analysis processing unit 61 may determine the presence or absence of the target gas to be observed in the measurement space 15 based on whether or not the amplitude A of the detection waveform D exceeds a predetermined threshold. In the present disclosure, the "concentration of the target gas to be observed" encompasses not only the numerical value of the concentration of the target gas to be observed, but also the presence or absence of the target gas to be observed in the measurement space 15 (or a determination of high or low concentration).

[0079] (10) In the above-described embodiments, the output device 54 outputs the concentration C of the target gas, but the target of output by the output device 54 can be changed as desired. For example, the output device 54 may output the presence or absence of the target gas in the measurement space 15 as an image or sound. Also, a configuration in which the output device 54 displays or sounds a warning when the concentration of the target gas exceeds a threshold is also conceivable.

[0080] D: Notes From the above-described exemplary embodiments, the following configurations can be understood, for example.

[0081] [Aspect A] According to the configuration of Patent Document 1, it is possible to calculate an appropriate concentration by correcting the pressure dependence of the concentration. However, there is a demand for a technology that can analyze the concentration of the target gas with even higher accuracy and ease. In consideration of the above circumstances, one aspect (Aspect A) of the present disclosure aims to determine the concentration of the target gas with high accuracy and ease.

[0082] In order to solve the above problems, an analysis system according to one aspect (aspect A1) of the present disclosure is an analysis system for analyzing the concentration of a target gas in a measurement space, and includes: a light-emitting element that emits detection light; a pressure acquisition unit that acquires the pressure of the target gas; an amplitude setting unit that sets a modulation amplitude according to the pressure; a wavelength control unit that sweeps the wavelength of the detection light within a sweep range that includes the absorption wavelength of the target gas while varying the modulation amplitude; a light-receiving element that generates a received light signal by receiving the detection light that has passed through the measurement space; a signal detection unit that acquires a detection waveform by lock-in detection of the received light signal; and an analysis processing unit that identifies the concentration of the target gas from the detection waveform.

[0083] The modulation amplitude for maintaining the amplitude of the detection waveform after detection of the received light signal at an appropriate value varies depending on the pressure of the target gas. Therefore, a configuration in which the modulation amplitude is set depending on the pressure of the target gas reduces the influence of the target gas compared to a configuration in which the modulation amplitude does not depend on the pressure. In other words, according to the above-mentioned aspect, the concentration of the target gas can be determined with high accuracy using a simple configuration in which the modulation amplitude is set depending on the pressure.

[0084] In a specific example (Aspect A2) of Aspect A1, the amplitude setting unit sets the modulation amplitude so that the modulation amplitude increases as the pressure increases. As the pressure of the gas to be observed increases, the modulation amplitude for maintaining the amplitude of the detection waveform at an appropriate value also increases. Therefore, by setting the modulation amplitude so that the modulation amplitude increases as the pressure increases, the concentration of the gas to be observed can be determined with high accuracy.

[0085] In a specific example (Aspect A3) of Aspect A1 or A2, the amplitude setting unit sets the modulation amplitude so that the amplitude of the detection waveform is a predetermined value. In the above aspects, the modulation amplitude is set so that the amplitude of the detection waveform is a predetermined value. Therefore, fluctuations in the amplitude of the detection waveform according to the pressure of the target gas are reduced, and as a result, the concentration of the target gas can be determined with high accuracy.

[0086] In a specific example (Aspect A4) of any of Aspects A1 to A3, the pressure acquisition unit includes an interval determination unit that determines a detection peak interval, which is the interval between a first peak and a second peak of the detection waveform that sandwich a time point corresponding to the absorption wavelength, and a pressure determination unit that determines the pressure according to the detection peak interval. In the above aspects, the pressure of the target gas is determined according to the detection peak interval, which is the time difference between the first peak and the second peak. Therefore, no special equipment is required to measure the pressure of the target gas. This simplifies the configuration for determining the concentration of the target gas. Furthermore, the detection waveform is shared for determining the concentration of the target gas and for determining the pressure used to set the modulation amplitude. Therefore, the configuration for determining the concentration of the target gas can be simplified compared to an aspect in which separate information is used for determining the concentration and the pressure of the target gas.

[0087] In a specific example (Aspect A5) of Aspect A4, the pressure determination unit determines the pressure such that the pressure increases as the detection peak interval increases. As the pressure of the gas to be observed increases, the time difference between the first peak and the second peak in the detected waveform (detection peak interval) increases. Therefore, according to the embodiment in which the pressure is determined such that the pressure increases as the detection peak interval increases, the pressure of the gas to be observed can be determined with high accuracy.

[0088] [Aspect B] The pressure of the gas to be observed is measured, for example, using a pressure sensor. However, in a configuration in which a special mechanism for measuring the pressure of the gas to be observed is necessary, there is a problem that the configuration of the analysis system becomes complicated. In consideration of the above circumstances, one aspect (Aspect B) of the present disclosure aims to simplify the configuration for identifying the pressure of the gas to be observed.

[0089] To solve the above problems, an analysis system according to one aspect (Aspect B1) of the present disclosure is an analysis system for analyzing the pressure of a target gas in a measurement space, and includes: a light-emitting element that emits detection light; a wavelength control unit that sweeps the wavelength of the detection light within a sweep range that includes the absorption wavelength of the target gas; a light-receiving element that generates a received light signal by receiving the detection light that has passed through the measurement space; a signal detection unit that acquires a detection waveform by lock-in detection of the received light signal; an interval determination unit that determines a detection peak interval, which is the time difference between a first peak and a second peak in the detection waveform that sandwich a time point corresponding to the absorption wavelength; and a pressure determination unit that determines the pressure according to the detection peak interval. In the above aspect, the pressure of the target gas is determined according to the detection peak interval, which is the time difference between the first peak and the second peak. Therefore, no special equipment is required to measure the pressure of the target gas. This simplifies the configuration for determining the pressure of the target gas.

[0090] In a specific example (Aspect B2) of Aspect B1, the pressure determination unit determines the pressure such that the pressure increases as the detection peak interval increases. As the pressure of the gas to be observed increases, the time difference between the first peak and the second peak in the detected waveform (detection peak interval) increases. Therefore, according to the embodiment in which the pressure is determined such that the pressure increases as the detection peak interval increases, the pressure of the gas to be observed can be determined with high accuracy. [Explanation of symbols]

[0091] 100...analysis system, 10...flow path, 11...first wall portion, 12...second wall portion, 13...pressure sensor, 15...measurement space, 20...light emitting portion, 21...first housing, 22...light emitting element, 23...optical element, 24...wavelength control portion, 30...light receiving portion, 31...second housing, 32...optical element, 33...light receiving element, 34...signal detection portion, 40...communication line, 42...connection portion, 43...connection portion, 50...information processing device, 51...control device, 52...storage device, 53...operation device, 54...output device, 61...analysis processing portion, 62...pressure acquisition portion, 621...interval determination portion, 622...pressure determination portion, 63...amplitude setting portion.

Claims

1. An analysis system for analyzing a concentration of a target gas in a measurement space, comprising: a light emitting element that emits detection light; a pressure acquisition unit that acquires the pressure of the observation target gas; an amplitude setting unit that sets a modulation amplitude in accordance with the pressure; a wavelength control unit that sweeps the wavelength of the detection light within a sweep range that includes the absorption wavelength of the target gas while varying the wavelength of the detection light with the modulation amplitude; a light-receiving element that generates a light-receiving signal by receiving the detection light that has passed through the measurement space; a signal detection unit that acquires a detection waveform by lock-in detection of the received light signal; an analysis processing unit that identifies the concentration of the target gas from the detected waveform; An analysis system comprising:

2. The amplitude setting unit sets the modulation amplitude so that the modulation amplitude increases as the pressure increases. The analytical system of claim 1.

3. The amplitude setting unit sets the modulation amplitude so that the amplitude of the detection waveform becomes a predetermined value. The analytical system of claim 1.

4. The pressure acquisition unit an interval specifying unit that specifies a detection peak interval, which is an interval between a first peak and a second peak of the detection waveform that sandwich a time point corresponding to the absorption wavelength; a pressure specifying unit that specifies the pressure according to the detection peak interval. The analytical system of claim 1.

5. The pressure specifying unit The pressure is determined so that the pressure increases as the detection peak interval increases. The analysis system of claim 4.

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