Photoacoustic spectrometry trace gas detection device and method with light-force synergistic effect

Abstract

The invention discloses a light-force synergistic photoacoustic spectrum trace gas detection device and method. The device comprises a signal generator, a tunable laser, a laser alignment system, a focusing lens, a gas chamber, a photoinduced shrinkage or elongation material, a quartz tuning fork, a signal amplifier, a data collector and a computer. Different from a traditional off-axis incidence mode, the design of in-plane incidence laser is innovatively adopted, and the laser penetrates through a tuning fork gap along the interdigital plane of the quartz tuning fork and accurately acts on the surface of a photoinduced shrinkage or elongation material at the bottom of the quartz tuning fork. According to the unique structural design and the laser incidence mode, the sound-force dual-mode synergistic effect is achieved. When laser interacts with gas molecules, sound waves can be generated, and meanwhile, the photoinduced shrinkage or elongation material is modulated by periodic laser to generate force with the same frequency as the sound waves. The sound wave and the force simultaneously act on the quartz tuning fork, so that the vibration amplitude of the quartz tuning fork is remarkably improved, and the detection sensitivity of the sensor is further improved.

Description

Technical Field

[0001] The present invention relates to a device and method for detecting trace gases using photoacoustic spectroscopy, and in particular to a device and method for detecting trace gases using photoacoustic spectroscopy with photo-mechanical synergy. Background Art

[0002] Quartz-enhanced photoacoustic spectroscopy (QEPAS) sensing technology uses a quartz tuning fork as a sensing element, combining acoustic resonance with the fork's high quality factor to effectively improve detection performance. This technology has been widely used due to its advantages, including fast response, good selectivity, and online monitoring capabilities. In a QEPAS sensing system, laser excitation of gas molecules generates acoustic waves, which act on a quartz tuning fork. Due to the piezoelectric effect, the fork vibrates under the excitation of the acoustic wave and converts it into an electrical signal. Analysis of this electrical signal enables gas concentration detection. Despite significant progress in QEPAS technology, the efficiency of coupling acoustic wave energy into the quartz tuning fork in traditional QEPAS is limited by several factors. For one thing, path loss during acoustic wave propagation weakens the acoustic wave energy reaching the fork. Furthermore, the mechanical response of the fork itself affects its efficiency in receiving and converting acoustic wave energy. These factors together restrict the ultimate sensitivity of quartz-enhanced photoacoustic spectroscopy in low-concentration gas detection, making the detection of extremely low-concentration gases still challenging in practical applications.

[0003] The working principle of traditional quartz enhanced photoacoustic spectroscopy sensing technology is to place a quartz tuning fork in an air chamber and contact it with the gas to be measured, and then use a tunable laser to shoot into the air chamber, and the incident laser passes through the two vibrating arms of the quartz tuning fork. After the gas molecules absorb the laser energy, they generate radiation transitions to the ground state, thereby generating sound waves. When the frequency of the generated sound waves is consistent with the resonant frequency of the quartz tuning fork, the quartz tuning fork resonates and the vibration amplitude increases significantly. Utilizing the piezoelectric effect of the quartz tuning fork, its elastic deformation will generate a current signal, and the current signal is demodulated to obtain gas concentration information. In terms of improving the performance of quartz enhanced photoacoustic spectroscopy technology, researchers have explored multiple directions, mainly including structural optimization, low-frequency quartz tuning fork design, and improving optical power. Among them:

[0004] In terms of structural optimization, acoustic microresonators enhance the intensity of sound waves through a special cavity design. The principle is to use the resonance characteristics of the cavity to make the sound waves reflect and superimpose multiple times in the cavity, thereby increasing the energy density of the sound waves and further enhancing the sound wave signal acting on the quartz tuning fork. Although acoustic microresonators can enhance the intensity of sound waves, they introduce additional assembly error risks. Due to the relatively complex cavity structure of the acoustic microresonator, during the assembly process, slight errors may cause the resonance characteristics of the cavity to change, affecting the enhancement effect of the sound waves and even causing the system performance to degrade. Moreover, the installation and debugging of acoustic microresonators require high technical requirements and professional equipment, which increases the complexity and cost of the system.

[0005] In terms of low-frequency quartz tuning fork design, the purpose of using low-frequency quartz tuning forks is to extend the energy accumulation time. Because low-frequency quartz tuning forks can accumulate more sound wave energy in the same amount of time, they can theoretically improve detection sensitivity. However, the manufacturing process of low-frequency quartz tuning forks is complex and costly, which makes them face significant obstacles in large-scale production and practical applications. The high cost limits their application in some cost-sensitive fields, such as portable gas detection equipment. In addition, the performance stability of low-frequency quartz tuning forks also needs to be further improved. Under different environmental conditions, their resonant frequency and quality factor may change, affecting the accuracy of the detection results.

[0006] Increasing laser power can increase optical power by allowing gas molecules to absorb more energy, generating a stronger acoustic signal, thereby linearly increasing the strength of the detection signal. While increasing laser power can improve signal strength, it also significantly increases system power consumption. High-power lasers require a larger power supply, which not only increases the size and weight of the equipment but also increases energy costs. Furthermore, increasing laser power significantly increases thermal noise, which interferes with the detection signal, reducing the system's signal-to-noise ratio and impacting detection accuracy and reliability. Summary of the Invention

[0007] In order to solve the above-mentioned problems existing in quartz enhanced photoacoustic spectroscopy sensing technology, the present invention provides a photoacoustic spectroscopy trace gas detection device and method with photo-mechanical synergy.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] A photoacoustic spectroscopy trace gas detection device with photo-mechanical synergy includes a signal generator, a tunable laser, a laser collimation system, a focusing lens, a gas chamber, a photostrictive material, a quartz tuning fork, a signal amplifier, a data collector, and a computer. The signal generator drives the tunable laser to output laser light, which is collimated by the laser collimation system and focused by the focusing lens before entering the gas chamber. The photostrictive material is disposed at the root of the quartz tuning fork, and the two are in close contact and fixed to a base. The laser light is incident on the surface of the photostrictive material along the front plane of the vibrating arm of the quartz tuning fork. The target gas interacts with the modulated laser light, generating acoustic waves that excite the quartz tuning fork to vibrate. Simultaneously, the photostrictive material disposed at the root of the quartz tuning fork is irradiated by the modulated laser light, generating periodic photostrictive forces on the root of the quartz tuning fork, enhancing the vibration amplitude of the quartz tuning fork. The piezoelectric signal generated by the forced vibration of the quartz tuning fork is output as a voltage signal by the signal amplifier. The data collector is then controlled by the computer to achieve signal acquisition and concentration inversion.

[0010] A method for detecting trace gases by photoacoustic spectroscopy using the above-mentioned device for photomechanical synergy comprises the following steps:

[0011] Step 1: Fix the photostrictive material to the root of the quartz tuning fork and ensure that the two are in close contact with no gap;

[0012] Step 2: Start the signal generator, set the output signal parameters, and drive the tunable laser to output laser light of a specific wavelength and power;

[0013] Step 3: After the laser is output from the tunable laser, it enters the laser collimation system for collimation processing;

[0014] Step 4: The collimated laser beam passes through a focusing lens and is precisely focused onto the surface of the photostrictive material in the gas chamber in an in-plane incident manner, while the target gas is introduced into the gas chamber.

[0015] Step 5: The target gas interacts with the modulated laser to generate acoustic waves. At the same time, the photostrictive material is periodically modulated by the laser, generating a photostrictive force at the same frequency as the acoustic wave. The acoustic wave and the photostrictive force act together on the quartz tuning fork, causing it to produce forced vibrations.

[0016] Step 6: The piezoelectric signal generated by the forced vibration of the quartz tuning fork is transmitted to the signal amplifier for amplification and output as a voltage signal;

[0017] Step 7: The computer controls the data collector to collect the amplified voltage signal according to the set sampling frequency and A / D conversion accuracy, and transmits the collected data to the computer;

[0018] Step 8: The computer uses the calibrated linear relationship to analyze and process the collected data, invert the concentration information of the target gas, and display and store it.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] The present invention fills the bottom of the quartz tuning fork with a specific photostrictive material and uses the pins of the quartz tuning fork to output the signal. Different from the traditional off-axis incident method, the present invention innovatively adopts the design of in-plane incident laser. The laser is incident on the surface of the photostrictive material along the front plane of the quartz tuning fork's vibrating arm, and acts precisely on the surface of the photostrictive material at the bottom of the quartz tuning fork. This unique structural design and laser incident method realizes the synergistic effect of sound and force dual modes. When the laser interacts with the gas molecules, sound waves are generated. At the same time, the photostrictive material is periodically modulated by the laser, generating a force with the same frequency as the sound waves. The sound waves and force act on the quartz tuning fork at the same time, which significantly increases the vibration amplitude of the quartz tuning fork, thereby improving the detection sensitivity of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the structure of the photoacoustic spectroscopy trace gas detection device with light-force synergy;

[0022] Figure 2 is a diagram showing the positional relationship between the photostrictive material and the quartz tuning fork;

[0023] Figure 3 for Figure 2 A top view of

[0024] Figure 4 for Figure 2 Stereoscopic image of

[0025] Figure 5 Comparison of the output signals of traditional photoacoustic spectroscopy and photomechanical synergy method. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described below with reference to the accompanying drawings, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention that does not depart from the spirit and scope of the technical solution of the present invention should be included in the scope of protection of the present invention.

[0027] The present invention provides a photoacoustic spectroscopy trace gas detection device with photomechanical synergy, such as Figure 1As shown, the device comprises a signal generator 1, a tunable laser 2, a laser alignment system 3, a focusing lens 4, a gas chamber 5, a photostrictive material 6, a quartz tuning fork 7, a signal amplifier 8, a data acquisition device 9, and a computer 10. The signal generator 1 drives the tunable laser 2 to output laser light, which is collimated by the laser alignment system 3 and then incident on the photostrictive material 6 within the gas chamber 5 through the focusing lens 4. The laser light is incident in-plane, i.e., incident from the front plane of the vibrating arm of the quartz tuning fork 7 onto the surface of the photostrictive material 6. The target gas interacts with the modulated laser light, generating acoustic waves that excite the quartz tuning fork 7 to vibrate. Simultaneously, the photostrictive material 6 at the base of the quartz tuning fork 7 is irradiated by the modulated laser light, generating a periodic photoforce acting on the base of the quartz tuning fork 7, increasing the vibration amplitude of the quartz tuning fork 7. The piezoelectric signal generated by the forced vibration of the quartz tuning fork 7 is output as a voltage signal by the signal amplifier 8. This signal signal can then be controlled by the computer 10 to control the data acquisition device 9, enabling signal acquisition and concentration inversion. The specific implementation process is as follows:

[0028] Step 1: Fix the photostrictive material 6 to the root of the quartz tuning fork 7 through a precision assembly process, and ensure that the contact between the two is tight and there is no gap.

[0029] Step 2: Start the signal generator 1, set the output signal parameters, and drive the tunable laser 2 to output laser light of a specific wavelength and power. The laser power must meet the requirements for effective excitation of the photostrictive material 6.

[0030] Step 3: After the laser is output from the tunable laser 2, it enters the laser collimation system 3 for collimation processing. The collimation accuracy is strictly controlled within the specified range to ensure that the laser beam is transmitted with high collimation.

[0031] Step 4: The collimated laser beam passes through the focusing lens 4 and is precisely focused onto the surface of the photostrictive material 6 in the gas chamber 5 in accordance with the in-plane incidence method, while the target gas is introduced into the gas chamber 5 at the same time.

[0032] Step 5: The target gas interacts with the modulated laser to generate acoustic waves. At the same time, the photostrictive material 6 is periodically modulated by the laser to generate a photostrictive force with the same frequency as the acoustic wave. The acoustic wave and the photostrictive force act together on the quartz tuning fork 7, causing it to generate forced vibration.

[0033] Step 6: The weak piezoelectric signal generated by the forced vibration of the quartz tuning fork 7 is transmitted to the signal amplifier 8. The amplification factor of the signal amplifier 8 is adjusted according to the signal strength to amplify the piezoelectric signal into a voltage signal of appropriate amplitude.

[0034] Step 7: The computer 10 controls the data collector 9 to collect the amplified voltage signal according to the set sampling frequency and A / D conversion accuracy, and transmits the collected data to the computer 10 .

[0035] Step 8: The computer 10 analyzes and processes the collected data using the calibrated linear relationship, inverts the concentration information of the target gas, and displays and stores it.

[0036] In the present invention, in order to ensure that the photostrictive material 6 can effectively respond to laser modulation and generate sufficient photostrictive force, the photostrictive coefficient of the selected photostrictive material 6 should be greater than 1.5×10 -6 , to ensure the coupling effect and mechanical stability with the quartz tuning fork 7.

[0037] In the present invention, in order to generate a larger acoustic wave signal and improve detection sensitivity, the laser power should be greater than 30 mW.

[0038] In the present invention, the collimation accuracy of the laser collimation system 3 needs to be below 0.1 mrad, so as to ensure that the divergence of the collimated laser beam during transmission is extremely small and can be accurately focused on the surface of the photostrictive material 6.

[0039] In the present invention, the interior of the air chamber 5 needs to be polished to a surface roughness of less than 0.1 μm to reduce the reflection loss of sound waves on the inner wall of the air chamber. At the same time, the sealing performance of the air chamber needs to ensure that the internal air pressure fluctuation is within the range of ±0.1 kPa.

[0040] In the present invention, in order for the quartz tuning fork 7 to receive sound waves and photostriction more effectively, the natural frequency of its vibrating arm must match the frequency of the sound waves generated by the target gas and the frequency of the photostriction generated by the photostrictive material.

[0041] In the present invention, the amplification factor of the signal amplifier 8 needs to be adjustable between 10 and 1000 times, and the noise introduced by itself needs to be less than 1 μV to meet the amplification requirements of signals of different intensities and ensure signal quality.

[0042] In the present invention, the sampling frequency of the data collector 9 needs to be greater than 2.5 times the highest frequency of the target signal to ensure the integrity and accuracy of the collected data, and its A / D conversion accuracy needs to reach more than 16 bits.

[0043] In the present invention, Figures 2 to 4 As shown, in a coordinate system established with the quartz tuning fork base as the xy plane and the z-axis as the interdigital direction, the photostrictive material 6 is affixed to the center of the base, perfectly aligned with the upper surface of the base (the z=0 plane). The polished contact surface is mechanically coupled via optical adhesive to minimize vibration energy loss. The geometric center of the photostrictive material is strictly aligned with the center of the base, ensuring that laser radiation covers the surface of the photostrictive material and avoids irradiating non-photostrictive areas of the base.

[0044] Example:

[0045] This embodiment uses a laser with a central wavelength of 450 nm and an output power of 40 mW to detect nitrogen dioxide. MAPbI3 is also used as the photostrictive material. A chopper is used to periodically change the intensity of the emitted laser, matching the resonant frequency of the quartz tuning fork and enhancing the signal detection effect. Using the photoacoustic spectroscopy trace gas detection method of the present invention, the signal collected by the data collector can be obtained, such as Figure 5 As shown. Figure 5 In the study, conventional photoacoustic spectroscopy and photomechanical synergy were used to detect trace gases. It was found that the signal amplitude was small when using conventional photoacoustic spectroscopy, while the signal amplitude was significantly larger when using photomechanical synergy, increasing by approximately 2.1 times. The comparison of conventional photoacoustic spectroscopy and photomechanical synergy in trace gas detection demonstrated the effectiveness of this method.

Claims

1. A photoacoustic spectroscopy trace gas detection device with photomechanical synergy, characterized in that The device includes a signal generator, a tunable laser, a laser collimation system, a focusing lens, an air chamber, a photostrictive material, a quartz tuning fork, a signal amplifier, a data acquisition device, and a computer. The signal generator drives the tunable laser to output laser light, which is collimated by the laser collimation system and focused by the focusing lens before entering the air chamber. The photostrictive material is disposed at the root of the quartz tuning fork, and the two are in close contact and fixed to a base. The laser light is incident on the surface of the photostrictive material along the front plane of the vibrating arm of the quartz tuning fork. The target gas interacts with the modulated laser light, generating acoustic waves that excite the quartz tuning fork to vibrate. Simultaneously, the photostrictive material disposed at the root of the quartz tuning fork is irradiated by the modulated laser light, generating periodic photostrictive force acting on the root of the quartz tuning fork, thereby enhancing the vibration amplitude of the quartz tuning fork. The piezoelectric signal generated by the forced vibration of the quartz tuning fork is output as a voltage signal by the signal amplifier. The data acquisition device is then controlled by the computer to achieve signal acquisition and concentration inversion.

2. The photoacoustic spectroscopy trace gas detection device based on photomechanical synergy according to claim 1 is characterized in that The photostrictive coefficient of the photostrictive material is greater than 1.5×10 -6 .

3. The photoacoustic spectroscopy trace gas detection device based on photomechanical synergy according to claim 1 is characterized in that The laser power is greater than 30 mW.

4. The photoacoustic spectroscopy trace gas detection device based on photomechanical synergy according to claim 1 is characterized in that The alignment accuracy of the laser alignment system 3 is less than 0.1 mrad.

5. The photoacoustic spectroscopy trace gas detection device based on photomechanical synergy according to claim 1 is characterized in that The interior of the air chamber is polished, with a surface roughness of less than 0.1 μm, and the internal air pressure fluctuation of the air chamber is within the range of ±0.1 kPa.

6. The photoacoustic spectroscopy trace gas detection device based on photomechanical synergy according to claim 1 is characterized in that The natural frequency of the quartz tuning fork vibrating arm matches the frequency of the sound waves generated by the target gas and the photostrictive frequency generated by the photostrictive material.

7. The photoacoustic spectroscopy trace gas detection device based on photomechanical synergy according to claim 1 is characterized in that The amplification factor of the signal amplifier is adjustable between 10 and 1000 times, and the noise introduced by the signal amplifier itself must be less than 1 μV.

8. The photoacoustic spectroscopy trace gas detection device based on photomechanical synergy according to claim 1 is characterized in that The sampling frequency of the data collector is greater than 2.5 times the highest frequency of the target signal, and its A / D conversion accuracy must reach more than 16 bits.

9. A method for detecting trace gases by photoacoustic spectroscopy using the device according to any one of claims 1 to 8 for photomechanical synergy, characterized in that The method comprises the following steps: Step 1: Fix the photostrictive material to the root of the quartz tuning fork and ensure that the two are in close contact with no gap; Step 2: Start the signal generator, set the output signal parameters, and drive the tunable laser to output laser light of a specific wavelength and power; Step 3: After the laser is output from the tunable laser, it enters the laser collimation system for collimation processing; Step 4: The collimated laser beam passes through a focusing lens and is precisely focused onto the surface of the photostrictive material in the gas chamber in an in-plane incident manner, while the target gas is introduced into the gas chamber. Step 5: The target gas interacts with the modulated laser to generate acoustic waves. At the same time, the photostrictive material is periodically modulated by the laser, generating a photostrictive force at the same frequency as the acoustic wave. The acoustic wave and the photostrictive force act together on the quartz tuning fork, causing it to produce forced vibrations. Step 6: The piezoelectric signal generated by the forced vibration of the quartz tuning fork is transmitted to the signal amplifier for amplification and output as a voltage signal; Step 7: The computer controls the data collector to collect the amplified voltage signal according to the set sampling frequency and A / D conversion accuracy, and transmits the collected data to the computer; Step 8: The computer uses the calibrated linear relationship to analyze and process the collected data, invert the concentration information of the target gas, and display and store it.

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