Light-induced thermoelastic spectrum gas concentration detection device and method based on annular absorption cell

Abstract

The invention relates to the technical field of gas sensing, and discloses a photoinduced thermoelastic spectrum gas concentration detection device and method based on an annular absorption cell, and the device comprises a light source system which is used for generating and outputting a wavelength-modulatable laser beam; the laser absorption system comprises an integrated annular absorption cell, an optical fiber collimator and an optical convergence lens, a laser window is arranged on the side wall of the integrated annular absorption cell, and after being input into the optical fiber collimator, a laser beam enters the integrated annular absorption cell through the laser window; after being reflected for multiple times, the light is emitted from the laser window and then enters the optical converging lens; the signal detection system is used for detecting the intensity of the emergent light focused by the optical converging lens and converting the intensity into an electric signal; and the data processing system is used for demodulating the electric signal generated by the signal detection system and inverting the concentration of the gas to be detected. The method corresponds to the device. According to the invention, the detection stability and the detection sensitivity are improved.

Description

Technical Field

[0001] The present application relates to the field of gas sensing technology, and in particular to a device and method for detecting gas concentration using photothermoelastic spectroscopy based on an annular absorption cell. Background Art

[0002] Trace gas detection technology plays a vital role in environmental, industrial, aerospace, and medical fields. Recently, photothermoelastic spectroscopy (LITES), a non-contact detection technique, has emerged. It uses a small, low-cost, and wide-wavelength-response tuning-fork quartz crystal oscillator (QI) to replace traditional photodetectors to detect changes in light absorption intensity. In LITES, an absorption cell is placed within a test gas environment to enable interaction between laser light and the gas being measured. Laser light emitted from the absorption cell illuminates the surface of the tuning-fork quartz crystal oscillator. The heat energy generated by the light absorption is converted into mechanical vibrations of the oscillator's arms through the photothermoelastic effect. When the light intensity is modulated at the resonant frequency of the crystal oscillator, the mechanical vibrations of the crystal arms are amplified and converted into an electrical signal proportional to the absorbed light intensity through the piezoelectric effect. The tuning-fork quartz crystal oscillator is placed outside the absorption cell and signals are acquired by detecting the intensity of the light emitted from the cell. This separates the laser action area from the detection area, reducing the risk of detector corrosion from corrosive gases and improving the system's long-range detection capabilities.

[0003] In photothermoelastic spectroscopy (PTES), to improve the absorption path of lasers, some teams have used absorption cells that enable multiple reflections of the laser, providing an interaction path of tens of meters. However, traditional absorption cells typically consist of two or more spherical mirrors, which have poor mechanical stability between the spherical mirror groups. This requires more optical components for optical path alignment, increasing system complexity. Therefore, how to achieve a highly stable and compact PTS gas concentration detection device remains a pressing challenge for both industry and academia. Summary of the Invention

[0004] The purpose of the present application is to provide a device and method for detecting gas concentration by photothermoelastic spectroscopy based on an annular absorption cell, so as to solve the problems of low sensitivity and poor system stability in the prior art mentioned in the above background technology.

[0005] To achieve the above objectives, this application discloses the following technical solutions: In a first aspect, the present application discloses a photothermoelastic spectroscopy gas concentration detection device based on an annular absorption cell, comprising: A light source system for generating and outputting a wavelength-modulatable laser beam; The laser absorption system includes an integrated annular absorption cell, a fiber collimator, and an optical converging lens. The side wall of the integrated annular absorption cell is provided with a laser window. After the laser beam is input into the fiber collimator, it is incident on the integrated annular absorption cell through the laser window. After multiple reflections, it is emitted from the laser window and incident on the optical converging lens. A signal detection system, used to detect the intensity of the light emitted after being focused by the optical converging lens and convert it into an electrical signal; The data processing system is used to demodulate the electrical signal generated by the signal detection system and invert the concentration of the gas to be measured.

[0006] Preferably, the light source system comprises: a laser light source, a first function generator, a second function generator, a signal adder and a light source control module; The output terminals of the first function generator and the second function generator are respectively connected to the input terminals of the signal adder; The output end of the signal adder is connected to the input end of the light source control module, the output end of the light source control module is connected to the laser light source, and the laser light source outputs a wavelength-modulated laser beam under the action of the light source control module; The output end of the laser light source is connected to the input end of the optical fiber collimator.

[0007] Preferably, the laser light source is an infrared laser light source or a terahertz laser light source.

[0008] Preferably, the integrated annular absorption cell, the optical fiber collimator and the optical converging lens are coaxially arranged, and the horizontal angle between the axis of the laser beam output by the optical fiber collimator and the laser window is 10° to 85°.

[0009] Preferably, the signal detection system includes a tuning fork quartz crystal oscillator and a preamplifier circuit module, the two signal input ports of the preamplifier circuit module are connected to the two electrodes of the tuning fork quartz crystal oscillator, and one of the signal input ends of the preamplifier circuit module is connected to the electrode output end of the tuning fork quartz crystal oscillator and then grounded; the outgoing light focused by the optical converging lens is irradiated on the surface of the vibration arm base of the tuning fork quartz crystal oscillator.

[0010] Preferably, the vibration arm of the tuning fork quartz crystal oscillator is a segmented variable-section cantilever beam structure.

[0011] Preferably, the resonance frequency of the tuning fork quartz crystal oscillator is 12 kHz.

[0012] Preferably, the data processing system includes a lock-in amplifier module and a computer, the signal output end of the preamplifier circuit module is connected to the signal input end of the lock-in amplifier module, and the signal output end of the lock-in amplifier module is connected to the computer.

[0013] Preferably, the inner wall of the integrated annular absorption cell is plated with a silver film with a reflectivity of 98%, and the bottom of the integrated annular absorption cell is sealed by laser welding, and a symmetrical dual gas path interface is provided on the top.

[0014] In a second aspect, the present application discloses a method for detecting gas concentration by photothermoelastic spectroscopy based on an annular absorption cell, which is applied to the above-mentioned device for detecting gas concentration by photothermoelastic spectroscopy based on an annular absorption cell. The method comprises the following steps: The S1-laser light source outputs a laser beam under the action of the light source control module; the first function generator outputs a triangular wave signal, and the output wavelength of the laser light source is scanned by adjusting its voltage amplitude; the second function generator outputs a sine wave signal, and the output wavelength of the laser light source is modulated by adjusting its modulation frequency; S2-The laser beam is collimated by a fiber collimator and then incident on the integrated annular absorption cell, and forms an annular optical path through multiple reflections on the inner wall of the integrated annular absorption cell; S3-After multiple reflections, the outgoing light beam is focused by a converging lens onto the surface of the vibrating arm base of the tuning fork quartz crystal oscillator, generating mechanical vibration through the photothermoelastic effect; S4-collect the electrical signal generated by the tuning fork quartz crystal oscillator, demodulate it through the lock-in amplifier module and invert the concentration of the gas to be measured Compared with the prior art, the photothermoelastic spectroscopy gas concentration detection device and method based on the annular absorption cell of the present application has the following beneficial effects: 1. Compared with the traditional absorption cell composed of two or more spherical mirrors, the present application adopts an integrated annular absorption cell. The laser beam realizes multiple reflections on the integrated annular absorption cell, which solves the problem of poor mechanical stability of the traditional absorption cell. At the same time, the integrated annular absorption cell can achieve a high number of reflections in a very small size, significantly increasing the effective interaction path length and improving the detection sensitivity of the photothermoelastic spectroscopic sensor. 2. This application uses a tuning fork quartz crystal oscillator with a segmented variable-section cantilever beam structure. By reducing the mass at the bottom of the oscillator arm, the quality factor of the quartz crystal oscillator is increased, thereby improving the light-to-heat conversion capability of the oscillator. At the same time, the resonant frequency of the tuning fork quartz crystal oscillator is set to 12 kHz, which increases the energy accumulation time of the laser in the oscillator arm, further improving the detection sensitivity of the sensor. 3. The detection object of this application is an optical signal, and the gas to be detected is isolated from the tuning fork quartz crystal oscillator. Therefore, it is suitable for long-distance non-contact detection of corrosive gases. It not only does not need to consider the interference of environmental noise during long-distance transmission, but also solves the problem of detection in a small space. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0016] Figure 1 A schematic diagram of the structure of a photothermoelastic spectroscopy gas concentration detection device based on an annular absorption cell provided in an embodiment of the present application; Figure 2 A schematic structural diagram of an integrated annular absorption tank provided in an embodiment of the present application; Figure 3 A diagram showing the optical path distribution within the integrated annular absorption cell provided in an embodiment of the present application; Figure 4 A schematic diagram comparing the detection results provided in the embodiments of the present application.

[0017] Figure numerals: 1. laser light source; 2. first function generator; 3. second function generator; 4. signal adder; 5. light source control module; 6. laser absorption system; 61. integrated annular absorption cell; 62. optical fiber collimator; 63. optical converging lens; 7. tuning fork quartz crystal oscillator; 8. preamplifier circuit module; 9. phase-locked amplifier module; 10. computer. DETAILED DESCRIPTION

[0018] The following is a clear and complete description of the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0019] In this document, the term "comprising" is intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising..." does not preclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0020] In a first aspect, this embodiment provides a Figure 1 The photothermoelastic spectroscopy gas concentration detection device based on an annular absorption cell shown includes: A light source system for generating and outputting a wavelength-modulatable laser beam; The laser absorption system 6 is used to achieve high-precision, long-distance interaction between the laser beam and the gas to be measured. It includes an integrated annular absorption cell 61, a fiber collimator 62, and an optical converging lens 63. The side wall of the integrated annular absorption cell 61 is provided with a laser window. After the laser beam enters the fiber collimator 62, it passes through the laser window and enters the integrated annular absorption cell 61. After multiple reflections, it is emitted from the laser window and incident on the optical converging lens 63. A signal detection system for detecting the intensity of the light emitted after focusing from the optical converging lens 63 and converting it into an electrical signal; The data processing system is used to demodulate the electrical signal generated by the signal detection system and invert the concentration of the gas to be measured.

[0021] In one embodiment, the light source system includes: a laser light source 1, a first function generator 2, a second function generator 3, a signal adder 4, and a light source control module 5. The light source control module 5 is used to control the light source temperature and current of the laser light source. The outputs of the first and second function generators 2 and 3 are respectively connected to the inputs of the signal adder 4. Specifically, the first function generator 2 is connected to input terminal 1 of the signal adder 4, and the output of the second function generator 3 is connected to input terminal 2 of the signal adder 4. The voltage amplitude of the first function generator 2 is adjusted so that the wavelength of the output laser continuously scans near the selected absorption line of the gas to be measured. The scanning rate is set to 50 mHz to ensure that the output laser wavelength slowly passes through the target absorption line of the gas to be measured. The output frequency of the second function generator 3 is set to half the resonant frequency of the tuning fork quartz crystal oscillator 7 described below. The output of the signal adder 4 is connected to the input of the light source control module 5, and the output of the light source control module 5 is connected to the laser light source 1. Under the control of the light source control module 5, the laser light source 1 outputs a wavelength-modulated laser beam. The output end of the laser light source 1 is connected to the input end of the optical fiber collimator 62 .

[0022] It is feasible that the laser light source is an infrared laser light source or a terahertz laser light source.

[0023] In one embodiment, the integrated annular absorption pool 61, the optical fiber collimator 62 and the optical converging lens 63 are coaxially arranged (i.e., all three are located on the same optical path), and the horizontal angle between the axis of the laser beam output by the optical fiber collimator 62 and the laser window is 10° to 85°. By rotating the angle between the annular optical path pool mirror and the laser beam, adjusting the height, and observing the number of light spots in the cavity, the number of reflections and the optical path are determined. Figure 2 As shown, in this embodiment, the main structure of the integrated annular absorption pool 61 is a hollow cylindrical chamber design with an inner diameter of 20 cm and a height of 8 cm. A circular through hole with a diameter of 2.5 cm is provided on the side wall of the integrated annular absorption pool 61 for installing a laser window. After the laser beam is incident from the laser window on the side wall, it is reflected multiple times by the inner wall to form an annular light path, which significantly increases the effective optical path.

[0024] like Figure 3 As shown in the figure, the propagation path of the laser beam in the annular optical path cell under different incident angles is simulated using TracePro simulation software. The incident light enters the annular absorption cell at a specific angle and then cyclically reflects along the inner wall of the annular cell. The propagation pattern formed by the cyclic reflection of the light on the inner wall is called a star polygon. Figure 3 The simulation results are shown in Figure 1, when the horizontal angles between the axis of the incident laser beam and the laser window are 48° and 70°, respectively, and the number of reflections is 5 and 13.

[0025] Furthermore, the optical path distribution in the integrated annular absorption cell 61 adopts an annular optical path layout. When the horizontal angle between the axis of the laser beam output by the optical fiber collimator 62 and the laser window is 81.43°, a maximum of 26 reflections can be achieved, corresponding to an equivalent absorption path length of 5.2 m.

[0026] Furthermore, the side walls of the integrated annular absorption pool 61 are integrally formed using stainless steel material, and the laser beam is reflected multiple times on the inner wall surface of the integrated annular absorption pool 61, thereby improving the mechanical stability of the absorption pool; the inner surface of the integrated annular absorption pool 61 is polished with high precision and coated with a silver film with a reflectivity of 98%, thereby reducing the loss of optical power; the bottom of the integrated annular absorption pool 61 is laser welded to achieve a fully enclosed structure, and dual gas path interfaces are symmetrically arranged on the top as the inlet and outlet of the gas to be measured.

[0027] In one embodiment, the signal detection system includes a tuning fork quartz crystal oscillator 7 and a preamplifier circuit module 8, wherein the two signal input ports of the preamplifier circuit module 8 are connected to the two electrodes of the tuning fork quartz crystal oscillator 7, and one of the signal input ends of the preamplifier circuit module 8 is connected to the electrode output end of the tuning fork quartz crystal oscillator 7 and then grounded; the outgoing light focused by the optical converging lens 63 is irradiated on the surface of the vibration arm base of the tuning fork quartz crystal oscillator 7.

[0028] Furthermore, the arm of the tuning fork quartz crystal oscillator 7 is a segmented, variable-section cantilever beam structure. The total height of the quartz crystal oscillator arm is 10 mm, with a lateral width of 2 mm at the top and a length of 3 mm, and a lateral width of 1.5 mm at the bottom and a length of 7 mm. The thickness of the quartz crystal oscillator arm is 0.3 mm, and the gap between the two arms is 1 mm. The outgoing laser beam is focused by a converging lens and irradiated onto the surface of the arm base of the tuning fork quartz crystal oscillator 7 at a distance of 1.2 mm to 2.5 mm from the bottom of the arm.

[0029] Furthermore, the resonance frequency of the tuning fork quartz crystal oscillator 7 is 12 kHz, the frequency of the sinusoidal signal generated by the second function generator 3 is 6 kHz, and the demodulation mode of the lock-in amplifier module 9 is the second harmonic demodulation mode.

[0030] In one embodiment, the data processing system includes a lock-in amplifier module 9 and a computer 10. The signal output of the preamplifier circuit module 8 is connected to the signal input of the lock-in amplifier module 9, which is in turn connected to the computer 10. The reference signal output of the second function generator 3 is connected to the reference signal input of the lock-in amplifier module 9. During the demodulation process, the time constant and filter slope of the lock-in amplifier module 9 are set to 1 s and 12 dB / oct.

[0031] In a second aspect, this embodiment provides a method for detecting gas concentration by photothermoelastic spectroscopy based on an annular absorption cell, which is applied to the above-mentioned device for detecting gas concentration by photothermoelastic spectroscopy based on an annular absorption cell. The method comprises the following steps: S1- The laser light source 1 outputs a laser beam under the action of the light source control module 5; the first function generator 2 outputs a triangular wave signal, and scans the output wavelength of the laser light source 1 by adjusting its voltage amplitude, that is, by controlling the voltage amplitude of the triangular wave signal, the output wavelength of the laser light source is scanned within a certain range; the second function generator 3 outputs a sine signal, and modulates the output wavelength of the laser light source 1 by adjusting its modulation frequency; The S2-laser beam is collimated by the fiber collimator 62 and then incident on the integrated annular absorption cell 61, and forms an annular optical path through multiple reflections on the inner wall of the integrated annular absorption cell 61; S3-The outgoing light beam after multiple reflections is focused by a converging lens and then irradiated onto the surface of the vibrating arm base of the tuning fork quartz crystal oscillator 7. The tuning fork quartz crystal oscillator 7 generates mechanical vibrations through the photothermoelastic effect; S4-collect the electrical signal generated by the tuning fork quartz crystal oscillator 7, demodulate it through the lock-in amplifier module 9 and then invert the concentration of the gas to be measured.

[0032] It should be noted that the photothermoelastic spectroscopy gas concentration detection method based on annular absorption cell provided in this embodiment corresponds to the aforementioned photothermoelastic spectroscopy gas concentration detection device based on annular absorption cell. Therefore, the parts that are not specifically described in the photothermoelastic spectroscopy gas concentration detection method based on annular absorption cell (including but not limited to specific structure / function limitations, parameter limitations, technical effects, etc.) can be correspondingly referred to the description of the aforementioned photothermoelastic spectroscopy gas concentration detection device based on annular absorption cell, and will not be repeated here.

[0033] Based on the above, if Figure 4 As shown in the figure, the measurement results of acetylene concentration using the photothermoelastic spectroscopic gas concentration detection device based on the annular absorption cell provided in this embodiment and the trace gas concentration detection device based on the traditional absorption cell are respectively used. The solid line is the signal detected by the photothermoelastic spectroscopic gas concentration detection device based on the annular absorption cell of this embodiment, wherein the excitation light beam is reflected 26 times in the absorption cell, corresponding to an equivalent absorption path length of 5.2 m. The dotted line is the signal detected by the trace gas concentration detection device based on the traditional absorption cell, corresponding to an equivalent absorption path length of 0.6 m. Figure 4 It can be seen that under the same experimental conditions, the signal detected by the photothermoelastic spectroscopy gas concentration detection device based on the annular absorption cell of this embodiment is about 8 times higher than the signal detected by the trace gas concentration detection device using the traditional absorption cell.

[0034] In summary, the annular absorption cell-based photothermoelastic spectroscopy gas concentration detection device and method of this embodiment employs an integrated annular absorption cell 61. Multiple reflections of the laser beam on the integrated annular absorption cell 61 address the poor mechanical stability of conventional absorption cells. Furthermore, the integrated annular absorption cell 61 achieves a high number of reflections despite its compact size, significantly increasing the effective interaction path length and enhancing the detection sensitivity of the photothermoelastic spectroscopy sensor. A tuning fork-type quartz crystal oscillator 7 with a segmented, variable-section cantilever beam structure is employed. By reducing the mass at the bottom of the oscillator arm, the quality factor of the quartz crystal oscillator is increased, improving the oscillator's photothermal conversion capability. Furthermore, the resonant frequency of the tuning fork-type quartz crystal oscillator 7 is set to 12 kHz, increasing the energy accumulation time of the laser within the oscillator arm and further enhancing the sensor's detection sensitivity. The detection target is an optical signal, and the gas to be detected is isolated from the tuning fork-type quartz crystal oscillator 7. Therefore, the device is suitable for long-distance, non-contact detection of corrosive gases. This eliminates the need to consider interference from ambient noise during long-distance transmission and addresses the challenge of detection in confined spaces.

[0035] In the embodiments provided herein, it should be understood that the embodiments described herein can be implemented using hardware, software, firmware, middleware, code, or any appropriate combination thereof. For hardware implementation, the processor may be implemented in one or more of the following: an application-specific integrated circuit (ASIC), a digital signal processor (DSP), a digital signal processing device (DSPD), a programmable logic device (PLD), a field-programmable gate array (FPGA), a processor, a controller, a microcontroller, a microprocessor, or other electronic units designed to implement the functionality described herein, or any combination thereof. For software implementation, some or all of the processes of the embodiments may be performed by a computer program instructing the relevant hardware. During implementation, the program may be stored in a computer-readable storage medium or transmitted as one or more instructions or codes on a computer-readable storage medium. Computer-readable storage media include computer storage media and communication media, wherein communication media includes any medium that facilitates the transmission of a computer program from one location to another. The storage medium may be any available medium that can be accessed by a computer. Computer-readable storage media may include, but are not limited to, RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage media or other magnetic storage devices, or any other medium capable of carrying or storing the desired program code in the form of instructions or data structures and accessible by a computer.

[0036] Finally, it should be noted that the above is only a preferred embodiment of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent replacements for some of the technical features therein. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A photothermoelastic spectroscopy gas concentration detection device based on an annular absorption cell, characterized in that: include: A light source system for generating and outputting a wavelength-modulatable laser beam; The laser absorption system includes an integrated annular absorption cell, a fiber collimator, and an optical converging lens. The side wall of the integrated annular absorption cell is provided with a laser window. After the laser beam is input into the fiber collimator, it is incident on the integrated annular absorption cell through the laser window. After multiple reflections, it is emitted from the laser window and incident on the optical converging lens. A signal detection system, used to detect the intensity of the light emitted after being focused by the optical converging lens and convert it into an electrical signal; The data processing system is used to demodulate the electrical signal generated by the signal detection system and invert the concentration of the gas to be measured.

2. The photothermoelastic spectroscopy gas concentration detection device based on an annular absorption cell according to claim 1 is characterized in that: The light source system includes: a laser light source, a first function generator, a second function generator, a signal adder and a light source control module; The output terminals of the first function generator and the second function generator are respectively connected to the input terminals of the signal adder; The output end of the signal adder is connected to the input end of the light source control module, the output end of the light source control module is connected to the laser light source, and the laser light source outputs a wavelength-modulated laser beam under the action of the light source control module; The output end of the laser light source is connected to the input end of the optical fiber collimator.

3. The photothermoelastic spectroscopy gas concentration detection device based on an annular absorption cell according to claim 2 is characterized in that: The laser light source is an infrared laser light source or a terahertz laser light source.

4. The photothermoelastic spectroscopy gas concentration detection device based on an annular absorption cell according to claim 1 is characterized in that: The integrated annular absorption pool, the optical fiber collimator and the optical converging lens are coaxially arranged, and the horizontal angle between the axis of the laser beam output by the optical fiber collimator and the laser window is 10° to 85°.

5. The photothermoelastic spectroscopy gas concentration detection device based on an annular absorption cell according to claim 1 is characterized in that: The signal detection system includes a tuning fork quartz crystal oscillator and a preamplifier circuit module, wherein the two signal input ports of the preamplifier circuit module are connected to the two electrodes of the tuning fork quartz crystal oscillator, and one of the signal input ends of the preamplifier circuit module is connected to the electrode output end of the tuning fork quartz crystal oscillator and then grounded; the outgoing light focused by the optical converging lens is irradiated on the surface of the vibration arm base of the tuning fork quartz crystal oscillator.

6. The photothermoelastic spectroscopy gas concentration detection device based on an annular absorption cell according to claim 5 is characterized in that: The vibration arm of the tuning fork quartz crystal oscillator is a segmented variable-section cantilever beam structure.

7. The photothermoelastic spectroscopy gas concentration detection device based on an annular absorption cell according to claim 5 or 6, characterized in that: The resonance frequency of the tuning fork quartz crystal oscillator is 12 kHz.

8. The photothermoelastic spectroscopy gas concentration detection device based on an annular absorption cell according to claim 5 is characterized in that: The data processing system includes a lock-in amplifier module and a computer. The signal output end of the preamplifier circuit module is connected to the signal input end of the lock-in amplifier module, and the signal output end of the lock-in amplifier module is connected to the computer.

9. The photothermoelastic spectroscopy gas concentration detection device based on an annular absorption cell according to claim 1 is characterized in that: The inner wall of the integrated annular absorption cell is plated with a silver film with a reflectivity of 98%, and the bottom of the integrated annular absorption cell is sealed by laser welding, and a symmetrical double gas path interface is provided on the top.

10. A method for detecting gas concentration by photothermoelastic spectroscopy based on an annular absorption cell, applied to the device for detecting gas concentration by photothermoelastic spectroscopy based on an annular absorption cell according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: The S1-laser light source outputs a laser beam under the action of the light source control module; the first function generator outputs a triangular wave signal, and the output wavelength of the laser light source is scanned by adjusting its voltage amplitude; the second function generator outputs a sine wave signal, and the output wavelength of the laser light source is modulated by adjusting its modulation frequency; S2-The laser beam is collimated by a fiber collimator and then incident on the integrated annular absorption cell, and forms an annular optical path through multiple reflections on the inner wall of the integrated annular absorption cell; S3-After multiple reflections, the outgoing light beam is focused by a converging lens onto the surface of the vibrating arm base of the tuning fork quartz crystal oscillator, generating mechanical vibration through the photothermoelastic effect; S4-collecting the electrical signal generated by the tuning fork quartz crystal oscillator, demodulating it through a lock-in amplifier module, and then inverting the concentration of the gas to be measured.

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