Gas absorption spectrometer, control program, and control method

Abstract

To block a laser beam output to a resonator while suppressing an influence on calculation of a ring-down time.SOLUTION: The gas absorption spectrometer is a gas absorption spectrometer for analyzing a sample. The gas absorption spectrometer includes a resonator, a light source that outputs laser light to the resonator, an acousto-optic element that is disposed in an optical path between the light source and the resonator and modulates a frequency of the laser light in accordance with a frequency of an input signal, a photodetector that detects light output from the resonator, and a controller. The controller changes the frequency of the input signal to bring the laser light in the resonator into a non-resonant state, and measures the target component in the sample using the signal detected by the photodetector in a state in which the laser light in the resonator is in the non-resonant state.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a gas absorption spectroscopic device, a control program, and a control method. [Background technology]

[0002] As shown in Non-Patent Document 1, cavity ring down spectroscopy (CRDS) is known as one of the gas absorption spectroscopies. CRDS is a spectroscopic technique that uses a resonator (cavity) to increase the effective optical path length, thereby determining the concentration of a target component contained in a gas inside the resonator with high sensitivity.

[0003] In CRDS, laser light is input from a light source into a resonator. The laser light input into the resonator is accumulated in the resonator. After the laser light has been sufficiently accumulated in the resonator, the input of the laser light to the resonator is blocked. The attenuation of the light leaking out of the resonator is then measured. The gas absorption spectroscopy device acquires the output signal of the photodetector as a "ring-down signal." The gas absorption spectroscopy device measures the concentration of the target component contained in the gas inside the resonator by calculating the decay time constant of the light (ring-down time) using the acquired ring-down signal.

[0004] Such gas absorption spectroscopy devices may include an AOM (Acousto-Optic Modulator) between the resonator and the light source to block the input of laser light to the resonator. When an RF signal of an appropriate frequency is input to the AOM, diffracted light is generated. By stopping the input of the RF signal to the AOM, the laser path is switched and the laser light to the resonator is blocked. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Kazune Mano, "Development of a cavity ring-down spectrometer for radioactive carbon isotopes (14C)," Shimadzu Review, Vol. 78, pp. 255-264 (2021) Summary of the Invention [Problem to be solved by the invention]

[0006] However, even when the input of an RF signal to the AOM is stopped, a small amount of diffracted light can occur, causing part of the laser light to pass through the AOM, making it impossible to accurately calculate the ring-down time. For this reason, in order to more reliably block the laser light with the AOM, gas absorption analyzers are sometimes equipped with multiple AOMs or with an optical path in which the laser light passes through one AOM multiple times, which can make the circuit configuration of the gas absorption analyzer more complex.

[0007] The present disclosure has been made to solve the above-mentioned problems, and its purpose is to provide a technology that can block laser light output to a resonator while suppressing the effect on calculation of ring-down time. [Means for solving the problem]

[0008] A gas absorption spectroscopy apparatus according to one aspect of the present disclosure is a gas absorption spectroscopy apparatus for analyzing a sample, comprising: a resonator for storing the sample; a light source for outputting laser light to the resonator; an acousto-optic element disposed in an optical path between the light source and the resonator and for modulating the frequency of the laser light in accordance with the frequency of an input signal; a photodetector for detecting the light output from the resonator; and a controller for controlling the acousto-optic element. The controller changes the frequency of the input signal to bring the laser light in the resonator into a non-resonant state, and measures a target component in the sample using a signal detected by the photodetector while the laser light in the resonator is in the non-resonant state.

[0009] According to an aspect of the present disclosure, there is provided a control program for use in a gas absorption spectroscopy apparatus for analyzing a sample. The gas absorption spectroscopy apparatus includes a resonator for storing a sample, a light source for outputting laser light to the resonator, an acousto-optic element disposed in an optical path between the light source and the resonator and for modulating the frequency of the laser light in accordance with the frequency of an input signal, and a photodetector for detecting the light output from the resonator. The control program causes a computer to execute the steps of: changing the frequency of the input signal to bring the laser light in the resonator into a non-resonant state; and measuring a target component in the sample using a signal detected by the photodetector while the laser light in the resonator is in the non-resonant state.

[0010] A control method according to an aspect of the present disclosure is a control method used in a gas absorption spectroscopy apparatus for analyzing a sample. The gas absorption spectroscopy apparatus includes a resonator that stores a sample, a light source that outputs laser light to the resonator, an acousto-optic element that is arranged in an optical path between the light source and the resonator and that modulates the frequency of the laser light in accordance with the frequency of an input signal, and a photodetector that detects the light output from the resonator. The control method includes, as processing executed by a computer, the steps of changing the frequency of the input signal to bring the laser light in the resonator into a non-resonant state, and measuring a target component in the sample using a signal detected by the photodetector while the laser light in the resonator is in the non-resonant state. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to block the laser light output to the resonator while suppressing the effect on the calculation of the ring-down time. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram schematically illustrating the configuration of a gas absorption spectroscopy apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a conceptual diagram for explaining mode frequencies. [Figure 3] FIG. 1 is a diagram showing the relationship between the transmission intensity of a CRDS resonator and the laser frequency. [Figure 4]1 is a functional block diagram of a gas absorption spectroscopy apparatus according to an embodiment of the present invention. [Figure 5] 10 is a flowchart showing a process of blocking laser light output to a CRDS resonator in order to acquire a ring-down signal in the present embodiment. [Figure 6] FIG. 10 is a functional block diagram of a gas absorption spectroscopic device in a comparative example. [Figure 7] 10 is a flowchart showing a process of blocking laser light output to a CRDS resonator in order to acquire a ring-down signal in a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present embodiment will now be described in detail with reference to the drawings, in which the same or corresponding parts in the drawings are designated by the same reference numerals and description thereof will not be repeated.

[0014] <Configuration of gas absorption spectroscopy equipment> 1 is a diagram schematically illustrating the configuration of a gas absorption spectroscopy apparatus 1 according to this embodiment. The gas absorption spectroscopy apparatus 1 includes a laser light source 10, an AOM (Acousto-Optic Modulator) 20, a CRDS resonator 40, a photodetector (PD) 60, and a controller 70.

[0015] The laser light source 10 includes a measurement QCL (Quantum Cascade Laser) 11 and a laser driver 12. The measurement QCL 11 outputs laser light to a resonator 40. The measurement QCL 11 is configured to vary the oscillation frequency of the laser light based on a current applied from the laser driver 12. Specifically, the measurement QCL 11 is a distributed feedback quantum cascade laser (QCL). The measurement QCL 11 is an example of a "light source" in this disclosure.

[0016] The AOM 20 is provided in the optical path between the measurement QCL 11 and the CRDS resonator 40. The AOM 20 is an example of an “acousto-optic element” in this disclosure. The AOM 20 can quickly switch between outputting and blocking laser light from the measurement QCL 11 to the CRDS resonator 40.

[0017] When an RF (Radio Frequency) signal having a predetermined frequency is applied from the controller 70, the AOM 20 is put into an ON state in which it outputs laser light from the measurement QCL 11 to the CRDS resonator 40. When the application of the RF signal from the controller 70 is stopped, the AOM 20 is put into an OFF state in which it does not output laser light from the measurement QCL 11 to the CRDS resonator 40.

[0018] Furthermore, the AOM 20 in this embodiment modulates the frequency of the laser light. The AOM 20 changes the frequency of the laser light output from the AOM 20 to the CRDS resonator 40 in accordance with the frequency of the RF signal. More specifically, the frequency of the laser light modulated by the AOM 20 is a value obtained by adding the frequency of the RF signal to the frequency of the laser light output from the measurement QCL 11.

[0019] The CRDS resonator 40 is provided in the optical path between the AOM 20 and the photodetector 60. The CRDS resonator 40 is an example of a "resonator" in the present disclosure. The CRDS resonator 40 includes a container (cell) capable of storing a sample gas, and has an inlet pipe 44 for introducing the sample gas into the resonator before starting measurement and an outlet pipe 45 for discharging the sample gas to the outside after measurement is completed. The inlet pipe 44 is provided with an inlet valve 46. The outlet pipe 45 is provided with an outlet valve 47. The controller 70 controls the opening and closing of the inlet valve 46 and the outlet valve 47.

[0020] A pair of mirrors 41 and 42 are provided inside the CRDS resonator 40. The mirrors 41 and 42 are arranged facing each other so that light is reflected between them inside the CRDS resonator 40. The mirrors 41 and 42 are concave so that the stability conditions of the CRDS resonator 40 can be easily satisfied. The mirrors 41 and 42 have a high reflectivity (for example, about 99.9%) so that light leaking out of the CRDS resonator 40 is extremely weak. The number of mirrors arranged inside the CRDS resonator 40 is not limited to two, and may be three or more. In other words, the resonator may be one in which the mirrors are arranged so that light is reflected between them, or one in which the mirrors are arranged in a ring shape so that light is reflected in one direction.

[0021] A piezo element (piezoelectric element) 43 is disposed on the mirror 42. The piezo element 43 drives the mirror 42 constituting the CRDS resonator 40 in accordance with a command from the controller 70, thereby displacing the mirror 42 in the optical axis direction. This changes the resonator length of the CRDS resonator 40. Note that the piezo element may be disposed on the mirror 41 instead of the mirror 42, or piezo elements may be disposed on both the mirror 41 and the mirror 42.

[0022] The photodetector 60 is, for example, a photodiode. The photodetector 60 detects the weak light extracted from the mirror 42 of the CRDS resonator 40 as output light of the CRDS resonator 40, and outputs a detection signal to the controller 70. The photodetector 60 can be, for example, a liquid nitrogen-cooled InSb (indium antimony) detector.

[0023] The controller 70 includes a processor 71 such as a CPU (Central Processing Unit) or FPGA (Field-Programmable Gate Array), a memory 72 such as a ROM (Read Only Memory) and RAM (Random Access Memory), a storage device 78, and an input / output port (not shown).

[0024] The storage device 78 stores various programs executed by the processor 71, various data, etc. The storage device 78 may be one or more non-transitory computer-readable media, or one or more computer-readable storage media. Examples of the storage device 78 include flash memory, a hard disk drive (HDD), and a solid state drive (SSD).

[0025] The storage device 78 according to the first embodiment stores a control program 79. The control program 79 is a program for controlling the AOM 20, which will be described later, to perform light blocking.

[0026] The controller 70 controls each device constituting the gas absorption spectroscopy apparatus 1. Specifically, the controller 70 outputs a command to the laser driver 12 to scan the oscillation frequency of the laser light, and outputs the above-mentioned RF signal to the AOM 20. The controller 70 also outputs a command to the inlet valve 46 to introduce the sample gas into the CRDS resonator 40, and outputs a command to the outlet valve 47 to exhaust the sample gas to the outside of the CRDS resonator 40.

[0027] The controller 70 applies a voltage to the piezoelectric element 43 to displace the mirror 42. The controller 70 executes various data processing operations, including calculating the concentration (absolute concentration) of the target component contained in the sample gas based on the detection signal from the photodetector 60.

[0028] The controller 70 may be configured by dividing it into two or more units for each function. For example, the controller 70 may be divided into a unit that controls each device and a unit that executes various data processing.

[0029] <Measurement principle using cavity ring-down spectroscopy (CRDS)> The measurement principle of cavity ring-down absorption spectroscopy in the gas absorption spectroscopy device 1 will be described. Generally, when the frequency of light irradiated onto a resonator is a specific frequency, resonance occurs in the resonator. Hereinafter, the frequency of the laser light input to the CRDS resonator 40 will be referred to as the "laser frequency," and the frequency of light that can cause resonance by the CRDS resonator 40 will be referred to as the "mode frequency."

[0030] Fig. 2 is a conceptual diagram for explaining mode frequencies. As shown in Fig. 2, there are a plurality of mode frequencies at a predetermined frequency interval. Hereinafter, the interval between two adjacent mode frequencies among the plurality of mode frequencies will be referred to as the "free spectral range" (FSR).

[0031] When the laser frequency does not match any of the mode frequencies, no optical power is stored in the CRDS resonator 40. On the other hand, when the laser frequency matches any of the mode frequencies, optical power is stored in the CRDS resonator 40.

[0032] The controller 70 determines whether or not a sufficient amount of laser light power has accumulated in the CRDS resonator 40 based on the output signal from the photodetector 60. When the controller 70 determines that a sufficient amount of laser light power has accumulated in the CRDS resonator 40, the controller 70 controls the AOM 20 to cut off the output of laser light to the CRDS resonator 40. A method for controlling the AOM 20 will be described later.

[0033] As a result, the light stored in the CRDS resonator 40 travels back and forth between the mirrors 41 and 42 many times (usually thousands to tens of thousands of times). As this light travels back and forth between the mirrors 41 and 42, it gradually attenuates due to loss caused by reflection leakage at the mirrors 41 and 42 and absorption by the target component in the sample gas. Therefore, the output light of the CRDS resonator 40 that leaks from the mirror 42 gradually attenuates. In CRDS, by using the CRDS resonator 40 to lengthen the distance (effective optical path length) that the light travels through the sample gas, it is possible to detect even very slight light absorption by the target component.

[0034] The controller 70 acquires, as a "ring-down signal," a signal detected by the photodetector 60 while blocking the light input to the CRDS resonator 40. The controller 70 calculates the decay time constant of the acquired ring-down signal as a "ring-down time." The controller 70 calculates the concentration of the target component contained in the sample gas from the calculated ring-down time.

[0035] <Transmission intensity> Fig. 3 is a diagram showing the relationship between the transmission intensity and the laser frequency of the CRDS resonator 40. Fig. 3 shows a line Ln1 that indicates the transmission intensity of the CRDS resonator 40 when a specific resonant frequency is used as a reference.

[0036] The vertical axis represents the transmission intensity of the CRDS resonator 40. The transmission intensity is an index that indicates the degree to which the laser light output from the AOM 20 is transmitted through the CRDS resonator 40 to the photodetector 60. When the transmission intensity is high, the intensity of the laser light detected by the photodetector 60 increases, and when the transmission intensity is low, the intensity of the laser light detected by the photodetector 60 decreases.

[0037] The horizontal axis indicates the frequency of the laser light input to the CRDS resonator 40. More specifically, the horizontal axis indicates the frequency normalized by setting the resonant frequency of the CRDS resonator 40 to "0". In other words, the horizontal axis indicates how far the laser frequency output to the CRDS resonator 40 is from a specific resonant frequency. The frequency Δf is a value indicating the difference from the specific resonant frequency. When the frequency Δf is "0 MHz", the frequency of the laser frequency output to the CRDS resonator 40 is the resonant frequency.

[0038] 3, when the laser frequency of the laser light input to the CRDS resonator 40 is the resonance frequency, the transmission intensity of the CRDS resonator 40 is the highest. On the other hand, as the difference between the laser frequency of the laser light input to the CRDS resonator 40 and the resonance frequency increases, the transmission intensity of the CRDS resonator 40 decreases.

[0039] <Overall configuration functional block diagram> 4 is a functional block diagram of the gas absorption spectroscopy apparatus 1 according to this embodiment. As shown in FIG. 4, a beam splitter 15 is disposed between the measurement QCL 11 and the AOM 20. The laser light output from the measurement QCL 11 is split by the beam splitter 15 into two beams, one directed toward the AOM 20 and the other directed toward the wavelength stabilization controller 14.

[0040] Wavelength stabilization controller 14 detects the laser light output from measurement QCL 11 and sends a signal to adder 13 based on the detected laser light. Adder 13 uses the signal received from wavelength stabilization controller 14 to adjust the frequency of the laser light output from measurement QCL 11. This maintains the frequency of the laser light output from measurement QCL 11 at the desired frequency.

[0041] 4, the output signal of the photodetector 60 is output to a comparator 73. The comparator 73 is a comparator for comparing whether or not the power of the laser light in the CRDS resonator 40 is in a state where it has been sufficiently accumulated. The comparator 73 outputs a result indicating whether or not the power of the laser light in the CRDS resonator 40 is in a state where it has been sufficiently accumulated to an adder 74.

[0042] A constant voltage source 80 supplies a voltage for generating an RF signal to be output to the AOM 20. An adder 74 controls a voltage-controlled oscillator 75 based on the output result from the comparator 73. The voltage-controlled oscillator 75 adjusts the frequency of the RF signal. That is, the value of the frequency Δf in FIG. 3 is adjusted by the voltage-controlled oscillator 75. An amplifier 76 amplifies the RF signal whose frequency has been adjusted by the voltage-controlled oscillator 75.

[0043] In this embodiment, when the adder 74 receives from the comparator 73 a result indicating that the power of the laser light in the CRDS resonator 40 is sufficiently accumulated, the adder 74 changes the frequency of the RF signal adjusted by the voltage-controlled oscillator 75. The controller 70 in FIG. 1 may include at least one of the adder 74, the comparator 73, and the voltage-controlled oscillator 75 in FIG. 4. Each of the adder 74, the comparator 73, and the voltage-controlled oscillator 75 may be realized by the processor 71 performing processing.

[0044] 5 is a flowchart showing a process for blocking the laser light output to the CRDS resonator 40 in order to acquire a ring-down signal in this embodiment. The flowchart shown in FIG. 5 is realized by the processor 71 executing the control program 79.

[0045] The processor 71 determines whether or not a cutoff command has been received (step S101). In this embodiment, the cutoff command is a command requesting that the output of laser light to the CRDS resonator 40 be cut off, and is output based on the indication that the power of the laser light in the CRDS resonator 40 is sufficiently accumulated. In step S101, laser light having a resonance frequency is output from the AOM 20 to the CRDS resonator 40. That is, using the example of FIG. 3, the frequency Δf of the laser light input to the CRDS resonator 40 in step S101 is "0 MHz."

[0046] If the processor 71 does not receive a cutoff command (NO in step S101), it ends the process. If the processor 71 receives a cutoff command (YES in step S101), it changes the frequency of the RF signal applied to the AOM 20 from the resonant frequency to a predetermined frequency (step S102). For example, the processor 71 adjusts the absolute value of the frequency Δf to be 5 or greater. As a result, the transmission intensity of the CRDS resonator 40 decreases, as shown in FIG. 3 . That is, the output of the laser light to the CRDS resonator 40 is cut off. After the output of the laser light to the CRDS resonator 40 is cut off, the processor 71 calculates the concentration of the target component contained in the sample gas using the ring-down signal acquired by the photodetector 60 (step S103). Note that the amount of frequency shift changed in step S102 is not limited to 5 MHz and may be, for example, 2 MHz, 3 MHz, or 5 MHz or greater.

[0047] In this way, the gas absorption spectroscopy apparatus 1 in this embodiment reduces the transmission intensity of the CRDS resonator 40 by changing the frequency of the RF signal input to the AOM 20, and thereby blocks the output of laser light to the CRDS resonator 40.

[0048] A comparative example will be described below. Fig. 6 is a functional block diagram of a gas absorption spectroscopy apparatus 1Z in the comparative example. As shown in Fig. 6, comparator 73 outputs a result indicating whether or not the power of the laser light in CRDS resonator 40 is sufficiently accumulated to switch 74Z.

[0049] The RF signal oscillator 80Z generates an RF signal and supplies it to the AOM 20. When the switch 74Z is in an on state, it outputs the RF signal generated by the RF signal oscillator 80Z to the AOM 20 via the amplifier 76. When the switch 74Z is in an off state, it does not output the RF signal generated by the RF signal oscillator 80Z to the AOM 20 via the amplifier 76. The switch 74Z is configured to be turned off when it receives a result from the comparator 73 indicating that the power of the laser light in the CRDS resonator 40 is sufficiently accumulated.

[0050] When switch 74Z is turned off, no RF signal is output to AOM 20. As a result, the laser light output from measurement QCL 11 is output from AOM 20 along an optical path different from the optical path leading to CRDS resonator 40. In other words, the output of laser light to CRDS resonator 40 is blocked.

[0051] 7 is a flowchart showing a process for blocking the laser light output to the CRDS resonator 40 in order to acquire a ring-down signal in a comparative example. The process in the flowchart in FIG. 7 is the same as that in the flowchart in FIG. 5 except for step 102.

[0052] When the processor 71 receives a cutoff command (YES in step S101), it controls the state of the switch 74Z from the on state to the off state (step S102Z). As a result, the laser light output from the measurement QCL 11 is output from the AOM 20 along an optical path different from the optical path leading to the CRDS resonator 40. In other words, the output of the laser light to the CRDS resonator 40 is cut off. However, in the gas absorption spectroscopy apparatus 1Z of the comparative example, even when the input of the RF signal is stopped, a small amount of diffracted light occurs, causing part of the laser light to pass through the AOM, and it may not be possible to accurately calculate the ring-down time.

[0053] That is, in the gas absorption spectroscopy apparatus 1 of the comparative example, if the switch 74Z does not sufficiently block the RF signal, the laser light having the resonance frequency with the highest transmission intensity is output to the CRDS resonator 40. As a result, the photodetector 60 detects unintended laser light during the period in which the ring-down signal is acquired, and the ring-down time cannot be calculated accurately.

[0054] On the other hand, in the gas absorption spectroscopy apparatus 1 of the present embodiment, the output of laser light to the CRDS resonator 40 is blocked by changing the frequency of the RF signal input to the AOM 20. Therefore, even when laser light is output from the AOM 20 to the CRDS resonator 40, laser light having a lower transmission intensity compared to the resonance frequency is output to the CRDS resonator 40. As a result, in the present embodiment, laser light having a resonance frequency with the highest transmission intensity is not output to the photodetector 60 during the period in which the photodetector 60 acquires the ring-down signal. That is, in the present embodiment, it is possible to block the laser light output to the CRDS resonator 40 while suppressing the effect on the calculation of the ring-down time.

[0055] [Variations] In the gas absorption spectroscopy instrument 1 according to the first embodiment, an example has been described in which the processor 71 is an arithmetic processing unit such as a CPU. However, the processor 71 may be configured according to a hardware circuit dedicated to the gas absorption spectroscopy instrument 1. Furthermore, although the example in FIG. 1 illustrates a configuration in which there is a single processor, the gas absorption spectroscopy instrument 1 may have multiple processors.

[0056] The processor 71 is a computing entity (computer) that executes various processes according to various programs. The processor 71 may be configured, for example, with at least one of a CPU, an MPU, and a GPU (Graphics Processing Unit). The processor 71 has the function of executing various processes by executing programs, but some or all of these functions may be implemented as an application-specific integrated circuit such as an ASIC (Application Specific Integrated Circuit). The processor 71 may also be configured with an arithmetic circuit (processing circuitry).

[0057] In this disclosure, the term "processor" is not limited to a processor in the narrow sense that executes processing in a stored program manner, such as a CPU or MPU, but may also include hardwired circuits such as an ASIC or FPGA. Therefore, processor 71 can also be interpreted as a processing circuitry whose processing is defined in advance by computer-readable code and / or hardwired circuits.

[0058] The processor 71 may be configured as a single chip or multiple chips. Furthermore, the processor 71 and related processing circuits may be configured as multiple computers interconnected by wire or wirelessly via a local area network or a wireless network. The processor 71 and related processing circuits may be configured as a cloud computer that performs calculations remotely based on input data and outputs the calculation results to another device in a remote location.

[0059] Furthermore, in the above example, the storage device 78 is described as being an HD, SSD, or the like. However, the storage device 78 only needs to be in a format that can be read by the processor 71, which is a type of computer, and be capable of non-temporarily recording a program. For example, the storage device 78 may be any of a CD-ROM (Compact Disc - Read Only Memory), a DVD-ROM (Digital Versatile Disk - Read Only Memory), a USB (Universal Serial Bus) memory, a memory card, a FD (Flexible Disk), a hard disk, a magnetic tape, a cassette tape, an MO (Magnetic Optical Disc), an MD (Mini Disc), an IC (Integrated Circuit) card (excluding memory cards), an optical card, a mask ROM, and an EPROM.

[0060] [Aspect] It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0061] (Item 1) A gas absorption spectroscopy device according to one embodiment is a gas absorption spectroscopy device for analyzing a sample. The gas absorption spectroscopy device includes a resonator for storing the sample, a light source for outputting laser light to the resonator, an acousto-optic element disposed in an optical path between the light source and the resonator and for modulating the frequency of the laser light according to the frequency of an input signal, a photodetector for detecting the light output from the resonator, and a controller for controlling the acousto-optic element. The controller changes the frequency of the input signal to put the laser light in the resonator into a non-resonant state, and measures a target component in the sample using a signal detected by the photodetector while the laser light in the resonator is in the non-resonant state.

[0062] According to the gas absorption spectroscopic apparatus 1 described in paragraph 1, it is possible to block the laser light output to the CRDS resonator 40 while suppressing the influence on the calculation of the ring-down time.

[0063] (Item 2) In the gas absorption spectroscopic device described in Item 1, the resonator includes a plurality of mirrors and a piezoelectric element. The controller applies a voltage to the piezoelectric element to displace the positions of the plurality of mirrors.

[0064] According to the gas absorption spectroscopic device 1 described in the second aspect, the position of the mirror of the resonator can be adjusted using a piezoelectric element.

[0065] (Item 3) A control program according to one aspect is a control program used in a gas absorption spectroscopy apparatus for analyzing a sample. The gas absorption spectroscopy apparatus includes a resonator that stores a sample, a light source that outputs laser light to the resonator, an acousto-optic element that is disposed in an optical path between the light source and the resonator and that modulates the frequency of the laser light according to the frequency of an input signal, and a photodetector that detects the light output from the resonator. The control program causes a computer to execute the steps of: changing the frequency of the input signal to bring the laser light in the resonator into a non-resonant state; and measuring a target component in the sample using a signal detected by the photodetector while the laser light in the resonator is in the non-resonant state.

[0066] According to the control program described in paragraph 3, the laser light output to the CRDS resonator 40 can be blocked while suppressing the influence on the calculation of the ring-down time.

[0067] (Item 4) A control method according to one aspect is a control method used in a gas absorption spectroscopy apparatus for analyzing a sample. The gas absorption spectroscopy apparatus includes a resonator that stores a sample, a light source that outputs laser light to the resonator, an acousto-optic element that is disposed in an optical path between the light source and the resonator and that modulates the frequency of the laser light in accordance with the frequency of an input signal, and a photodetector that detects the light output from the resonator. The control method includes, as processing executed by a computer, a step of changing the frequency of the input signal to bring the laser light in the resonator into a non-resonant state, and a step of measuring a target component in the sample using a signal detected by the photodetector while the laser light in the resonator is in the non-resonant state.

[0068] According to the control method described in the fourth paragraph, it is possible to block the laser light output to the CRDS resonator 40 while suppressing the influence on the calculation of the ring-down time.

[0069] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. Unless there is a contradiction, at least two of the embodiments disclosed herein may be combined. The basic scope of the present disclosure is indicated by the scope of the utility model registration claims, rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the scope of the utility model registration claims. [Explanation of symbols]

[0070] 1 Gas absorption spectroscopy apparatus, 10 Laser light source, 12 Laser driver, 13, 74 Adder, 14 Wavelength stabilization controller, 15 Beam splitter, 40 CRDS resonator, 41, 42 Mirror, 43 Piezo element, 44 Inlet tube, 45 Outlet tube, 46 Inlet valve, 47 Outlet valve, 60 Photodetector, 70 Controller, 71 Processor, 72 Memory, 73 Comparator, 74Z Switch, 75 Voltage-controlled oscillator, 76 Amplifier, 78 Storage device, 79 Control program, 80 Constant voltage source, 80Z RF signal oscillator, Ln1 line, 11 Measurement QCL.

Claims

1. 1. A gas absorption spectroscopy apparatus for analyzing a sample, comprising: a resonator for storing the sample; a light source that outputs laser light to the resonator; an acousto-optic element disposed in an optical path between the light source and the resonator, for modulating the frequency of the laser light in accordance with the frequency of an input signal; a photodetector for detecting light output from the resonator; a controller for controlling the acousto-optic element; The controller changing the frequency of the input signal to bring the laser light in the resonator into a non-resonant state; a gas absorption spectrometer for measuring a target component in the sample using a signal detected by the photodetector while the laser light in the resonator is in a non-resonant state;

2. the resonator includes a plurality of mirrors and a piezoelectric element; The gas absorption spectroscopy apparatus according to claim 1 , wherein the controller applies a voltage to the piezoelectric element to displace the positions of the mirrors.

3. 1. A control program for use in a gas absorption spectrometer for analyzing a sample, comprising: The gas absorption spectroscopic device a resonator for storing the sample; a light source that outputs laser light to the resonator; an acousto-optic element disposed in an optical path between the light source and the resonator, for modulating the frequency of the laser light in accordance with the frequency of an input signal; a photodetector for detecting light output from the resonator; The control program is configured to changing the frequency of the input signal to bring the laser light into a non-resonant state in the resonator; and measuring a target component in the sample using a signal detected by the photodetector while the laser light in the resonator is in a non-resonant state.

4. 1. A control method for use in a gas absorption spectroscopy apparatus for analyzing a sample, comprising: The gas absorption spectroscopic device a resonator for storing the sample; a light source that outputs laser light to the resonator; an acousto-optic element disposed in an optical path between the light source and the resonator, for modulating the frequency of the laser light in accordance with the frequency of an input signal; a photodetector for detecting light output from the resonator; The control method includes the steps of: changing the frequency of the input signal to bring the laser light into a non-resonant state in the resonator; and measuring a target component in the sample using a signal detected by the photodetector while the laser light in the resonator is in a non-resonant state.

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