CN219016067U - Feedback type photoacoustic spectrum gas detection device - Google Patents
Feedback type photoacoustic spectrum gas detection device Download PDFInfo
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- CN219016067U CN219016067U CN202222711003.9U CN202222711003U CN219016067U CN 219016067 U CN219016067 U CN 219016067U CN 202222711003 U CN202222711003 U CN 202222711003U CN 219016067 U CN219016067 U CN 219016067U
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Abstract
The utility model relates to the technical field of gas detection, in particular to a feedback type photoacoustic spectrum gas detection device; wherein: the sawtooth wave generator is connected with the light source and the first feedback controller; the phase-locked amplifier is respectively connected with the light source, the photoelectric detector, the first feedback controller, the second feedback controller and the sawtooth wave amplifier; the piezoelectric control platform is respectively connected with the piezoelectric controller and the second feedback controller; the emergent opening of the light source is provided with a beam splitter, and the beam splitter is spaced from the emergent opening by a preset distance; a piezoelectric controller is also arranged on the extension line of the light source and the beam splitter, and an incident light port of the piezoelectric controller is arranged corresponding to the beam splitter; a photoelectric detector is arranged on a reflection angle of a light path formed from the light ray along the piezoelectric controller to the beam splitter; the light-emitting port of the piezoelectric controller is sequentially provided with a photoacoustic cavity and a reflecting mirror in the light path direction. According to the utility model, the feedback loop is arranged to perform feedback adjustment on the frequency and the light wave, so that the detection precision is effectively improved.
Description
Technical Field
The utility model relates to the technical field of gas detection, in particular to a feedback type photoacoustic spectrum gas detection device.
Background
The photoacoustic spectroscopy technology is a spectroscopic analysis technology based on the photoacoustic effect, and is widely used in the field of gas analysis and detection because the technology can effectively relate gas concentration information to a spectroscopic image.
During gas detection, the gas molecules absorb incident light generated by the laser and then are excited to a high-energy state, the molecules in the high-energy state collide with each other to enable part of the excited molecules to return to a ground state through non-radiative relaxation, and then the light energy absorbed by the molecules is changed into heat energy; at this time, if the gas is in a closed photoacoustic cavity, the photoacoustic cavity will generate sound waves due to thermal expansion of the gas; if the amplitude of the acoustic wave is measured by a microphone or the like, the concentration information of the gas to be measured can be correspondingly obtained, which is a photoacoustic spectroscopy technique.
At present, two methods for improving the detection precision of the photoacoustic spectrum exist, one is to adjust the wavelength of the light wave to enable the light wave to be in the position of gas absorption so as to improve the detection precision; the other is to adjust the laser frequency to keep the same with the frequency of the photoacoustic cell, so as to reduce noise and improve detection precision. The existing device for measuring the gas concentration based on the photoacoustic spectroscopy technology generally compares the known gas absorption peak position with the obtained photoacoustic spectroscopy absorption peak position, and adjusts the wavelength of the light wave through a computer; the phase of the detection signal and the modulation signal is identified by a phase discriminator, and the output signal of the phase discriminator is used as error signal feedback to adjust the laser frequency; however, the above-mentioned methods are all used for adjusting the wavelength or the frequency singly, the detection accuracy is still low, and if the frequency adjustment is directly combined with the wavelength tuning, the problems of large volume, high cost and the like are caused.
Disclosure of Invention
The utility model provides a feedback type photoacoustic spectrum gas detection device, which is provided with a feedback detection loop, so that the information to be corrected of the light wave and the frequency of the incident light in a photoacoustic cavity is obtained at the same time, and the frequency and the light wave are subjected to feedback adjustment, so that the detection precision is effectively improved.
The technical scheme provided by the utility model is as follows: a feedback photoacoustic spectroscopy gas detection apparatus comprising: sawtooth wave generator, lock-in amplifier, photoelectric detector, first feedback controller, second feedback controller, light source, beam splitter, piezoelectric controller, piezoelectric control platform, photoacoustic cavity, microphone, speculum, wherein:
the sawtooth wave generator is connected with the light source and the first feedback controller;
the phase-locked amplifier is respectively connected with the light source, the photoelectric detector, the first feedback controller, the second feedback controller and the sawtooth wave amplifier;
the piezoelectric control platform is respectively connected with the piezoelectric controller and the second feedback controller;
the light source comprises a light source body, wherein an emergent opening of the light source body is provided with a beam splitter, and the beam splitter is spaced from the emergent opening by a preset distance;
the piezoelectric controller is further arranged on an extension line of the light source and the beam splitter, and an incident light port of the piezoelectric controller is arranged corresponding to the beam splitter;
the photoelectric detector is arranged on a reflection angle of a light path formed by the light ray from the piezoelectric controller to the beam splitter;
the photoacoustic cavity and the reflecting mirror are sequentially arranged in the light path direction of the emergent light port of the piezoelectric controller;
the microphone is arranged on the side wall of the photoacoustic cavity.
Specifically, the sawtooth wave generator is used for providing sawtooth wave signals for the light source;
the lock-in amplifier is used for providing a sine wave signal for the light source;
the light source is used for emitting light beams with corresponding frequencies and wavelengths according to the sawtooth wave signals and the sine wave signals.
Specifically, the photoacoustic cavity is used for storing gas to be detected and exciting the gas to be detected to generate an acoustic wave signal through the incident light beam;
the microphone is used for acquiring the sound wave signal, converting the sound wave signal into an electric signal and transmitting the electric signal to the lock-in amplifier;
the photoelectric detector is used for receiving the optical signal and converting the optical signal into an electric signal;
the phase-locked amplifier is used for generating a frequency correction signal and a wavelength correction signal according to the electric signal provided by the photoelectric detector, and transmitting the generated frequency correction signal to the first feedback controller and the generated wavelength correction signal to the second feedback controller; and demodulating the electrical signal transmitted by the microphone into a secondary photoacoustic signal related to the concentration of the gas;
the first feedback controller is used for correcting sine wave frequency generated by the lock-in amplifier and sawtooth wave frequency generated by the sawtooth wave generator according to the received frequency correction signal;
the second feedback controller is used for sending a wavelength correction signal to the piezoelectric control platform according to the received wavelength correction signal;
the piezoelectric control platform is used for controlling the piezoelectric controller to act and correcting the wavelength of light.
Specifically, the light source includes: laser driving and lasers;
the laser driver is connected with the sawtooth wave generator and the first feedback controller;
the first feedback controller is used for driving the laser to emit light according to the sawtooth wave generated by the sawtooth wave generator and the sine wave transmitted by the first feedback controller;
the laser is in driving connection with the laser and is used for emitting laser beams with specific frequencies according to signals of the laser driving.
Specifically, optical filters are arranged on two sides of the photoacoustic cavity, and are used for injecting light beams from one side of the optical filters and injecting light beams from the other side of the optical filters.
Specifically, an air inlet valve and an air outlet valve are further arranged in the cavity of the photoacoustic cavity and are used for filling and discharging sample gas.
Specifically, the microphone is closely attached to one side of the photoacoustic cavity, which is not in or out of the light beam.
Specifically, a multi-surface piezoelectric reflector for adjusting the emergent light path is arranged inside the piezoelectric controller.
Specifically, the photoacoustic cavity is in a sealed state when the valve is closed.
Specifically, the multi-surface piezoelectric reflector is at least two surfaces.
According to the technical scheme, the beneficial effects of the utility model are as follows: the utility model provides a feedback type photoacoustic spectrum gas detection device, which comprises: sawtooth wave generator, lock-in amplifier, photoelectric detector, first feedback controller, second feedback controller, light source, beam splitter, piezoelectric controller, piezoelectric control platform, photoacoustic cavity, microphone, speculum, wherein: the sawtooth wave generator is connected with the light source and the first feedback controller; the phase-locked amplifier is respectively connected with the light source, the photoelectric detector, the first feedback controller, the second feedback controller and the sawtooth wave amplifier; the piezoelectric control platform is respectively connected with the piezoelectric controller and the second feedback controller; a beam splitter is arranged at a certain distance from the emergent opening of the light source; a piezoelectric controller is further arranged on the extension line of the light source and the beam splitter at a certain distance, and an incident light port of the piezoelectric controller is opposite to the beam splitter; a photoelectric detector is arranged on a reflection angle of a light path formed from the light ray along the piezoelectric controller to the beam splitter; an optical-acoustic cavity is arranged at a position extending a certain distance in the direction of an emergent light port of the piezoelectric controller, and a reflecting mirror is arranged on an extension line of the piezoelectric controller and the optical-acoustic cavity at a certain distance; the microphone is arranged on the side wall of the photoacoustic cavity; based on the connection relation, the photoelectric detector can effectively detect the attenuation condition of the optical power in the photoacoustic cavity through the incident light of the beam splitter, convert the attenuation condition into an electric signal and transmit the electric signal to the lock-in amplifier, the lock-in amplifier can generate a wavelength and frequency correction signal according to the electric signal, the frequency of the incident light is changed through the first feedback controller to enable the frequency of the incident light to resonate with the frequency of the photoacoustic cavity, the second feedback controller tunes the optical wave, the wavelength of the optical wave is changed, and the optical wave is located at the absorption peak position of the sample gas, so that noise is reduced, and the detection precision is further improved; and the reflecting mirror is arranged to reflect the light beam, so that the light power entering the photoacoustic cavity is improved, the requirement on a light source is reduced, and the cost is saved.
Drawings
In order to more clearly illustrate the embodiments of the utility model or the technical solutions of the prior art, the drawings which are used in the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the description below are only some embodiments of the utility model, and that other drawings can be obtained according to these drawings without inventive faculty for a person skilled in the art.
FIG. 1 is a schematic diagram of a feedback photoacoustic spectroscopy gas detection apparatus;
in the figure: 1-a sawtooth generator; a 2-lock-in amplifier; 3-a first feedback controller; 4-a second feedback controller; 5-a piezoelectric control platform; 6, a photoelectric detector; 7-a light source; 8-beam splitters; 9-a piezoelectric controller; 10-an photoacoustic cavity; 11-a microphone; 12-mirror.
Detailed Description
Other advantages and effects of the present utility model will become apparent to those skilled in the art from the following disclosure, which is to be read in light of the specific examples.
The structures, proportions, sizes, etc. shown in the drawings are used for matching with the disclosure of the present utility model, and are not intended to limit the applicable limitation of the present utility model, and any structural modification, change of proportion or adjustment of size should fall within the scope of the disclosure of the present utility model without affecting the efficacy of the present utility model.
The structure of the feedback type photoacoustic spectrum gas detection device provided by the utility model is shown in fig. 1, and the feedback type photoacoustic spectrum gas detection device comprises: the device comprises a sawtooth wave generator 1, a phase-locked amplifier 2, a first feedback controller 3, a second feedback controller 4, a piezoelectric control platform 5, a photoelectric detector 6, a light source 7, a beam splitter 8, a piezoelectric controller 9, a photoacoustic cavity 10, a microphone 11 and a reflecting mirror 12;
the light source 7 is respectively connected with the sawtooth wave generator 1 and the lock-in amplifier 2 and is used for driving the sawtooth wave signal generated by the sawtooth wave generator 1 and the sine wave signal generated by the lock-in amplifier 2 to emit light beams;
the beam splitter 8 is arranged at a certain distance from the emergent opening of the light source 7, and the beam splitter 8 is used for transmitting light passing through one side surface and reflecting light passing through the other side surface;
a piezoelectric controller 9 is further arranged on the extension line of the light source 7 and the beam splitter 8 at a certain distance, and an incident light port of the piezoelectric controller 9 is opposite to the beam splitter 8;
at a certain distance from the emergent light port of the piezoelectric controller 9, a photoacoustic cavity 10 is arranged for filling the sample gas to be tested, and the sample gas to be tested can be expanded in a beam irradiation mode, so that the photoacoustic cavity 10 emits sound waves;
a microphone 11 is arranged on the side wall surface of the photoacoustic cavity 10, and the microphone 11 is also connected with the phase-locked amplifier 2 and is used for detecting a photoacoustic signal and converting the photoacoustic signal into an electric signal to be input into the phase-locked amplifier 2, and the electric signal is demodulated into a second harmonic photoacoustic signal with related gas concentration through the phase-locked amplifier 2;
a reflecting mirror 12 is further arranged on the extension line of the emergent light port of the piezoelectric controller 9 and the photoacoustic cavity 10 and is used for reflecting the light beam so that the light beam can enter the photoacoustic cavity 10 for the second time, and the light power of the light beam in the photoacoustic cavity 10 is doubled;
a photoelectric detector 6 is arranged on a reflection angle of a light path formed by the light rays along the piezoelectric controller 9 to the beam splitter 8, and is connected with the lock-in amplifier 2 and used for detecting the attenuation condition of the light power of the incident light, converting the attenuation condition into an electric signal and transmitting the electric signal to the lock-in amplifier 2;
the lock-in amplifier 2 is further connected to the first feedback controller 3, the second feedback controller 4, and the sawtooth wave generator 1, and is configured to obtain, according to an electrical signal generated by the photodetector 6, wavelength and frequency information of the light source 7 to be corrected, adjust, according to the frequency information to be corrected, a sine wave signal frequency provided by the lock-in amplifier 2 and a sawtooth wave signal frequency provided by the sawtooth wave generator 1 through the first feedback controller 3, and control, according to the wavelength information to be corrected, the piezoelectric control platform 5 to form a wavelength tuning signal through the second feedback controller 4.
It will be appreciated that by controlling the sine wave and saw tooth frequency, frequency pulsing of the optical signal is achieved.
In the specific implementation process, the gas to be detected is filled in the photoacoustic cavity 10, the sawtooth wave generator 1 is controlled to emit sawtooth waves, and the lock-in amplifier 2 is controlled to emit sine waves; the light source 7 emits light beams under the common drive of the sawtooth wave signals and the sine wave signals, and the light beams enter the piezoelectric controller 9 after passing through the beam splitter 8; after refraction in the piezoelectric controller 9, the light is emitted, then passes through the photoacoustic cavity 10 to reach the reflecting mirror 12, and enters the photoacoustic cavity 10 for the second time through reflection of the reflecting mirror 12; the gas in the photoacoustic cavity 10 expands due to the absorption of the light energy, thereby causing the photoacoustic cavity 10 to generate sound waves; at this time, a microphone 11 is provided on the side wall of the photoacoustic cavity 10, and the microphone 11 converts the acoustic wave signal into an electric signal after acquiring it and transmits it to the lock-in amplifier 2, and the electric signal is demodulated into a second harmonic photoacoustic signal concerning the gas concentration in the lock-in amplifier 2.
Meanwhile, when the light beam passes through the photoacoustic cavity 10, the light beam returns to the beam splitter 8 along the original light path, and enters the photoelectric detector 6 after being refracted by the beam splitter 8, the photoelectric detector 6 detects the attenuation condition of the light power and converts the light signal into an electric signal to be input to the lock-in amplifier 2; in the conventional experiment, it was found that when the attenuation of the optical power reaches the peak value, the absorption of the gas to be measured to light is the greatest, the frequency is also called as the resonance frequency, and when the frequency of the light beam resonates with the photoacoustic cell, the frequency noise is the least, and the detection accuracy is the highest; therefore, the lock-in amplifier 2 obtains the frequency signal to be adjusted accordingly, and controls the sine wave signal output by the lock-in amplifier 2 to the light source 7 and the sawtooth wave signal output by the sawtooth wave generator 1 to the light source 7 through the first feedback controller 3, and finally realizes frequency adjustment on the emergent light beam of the light source 7 until reaching the resonance frequency.
Under the condition that the first feedback is locked to the frequency, the phase-locked amplifier 2 obtains the wavelength to be tuned according to the electric signal detected by the photoelectric detector 6; according to the gas absorption principle, the laser has the strongest absorption peak at a certain wavelength, and the absorption effect of the laser on the light is strongest at the wavelength, so that the detection accuracy of the gas can be improved to a certain extent; therefore, the lock-in amplifier 2 sends a control signal to the second feedback control according to the wavelength to be tuned, the second feedback controller 4 controls the piezoelectric control platform 5 according to the wavelength to be tuned, and then the piezoelectric control platform 5 controls the action amplitude of the piezoelectric controller 9 to realize wavelength tuning until the wavelength is at the gas absorption peak position, so that the detection precision is further improved.
In another specific embodiment of the present utility model, the light source 7 includes: laser driving and lasers;
the laser driver is connected with the sawtooth wave generator 1 and the first feedback controller 3 and is used for driving the laser to emit light according to sawtooth waves generated by the sawtooth wave generator 1 and sine waves transmitted by the first feedback controller 3;
the laser is connected with the laser driver and is used for emitting laser beams with specific frequencies according to signals of the laser driver.
In another embodiment of the utility model, the photoacoustic cavity 10 is provided with filters on both sides for taking in and emitting light from one side filter to the other.
In another specific embodiment of the present utility model, an air inlet valve and an air outlet valve are further arranged in the cavity of the photoacoustic cavity 10, and are used for filling and discharging sample gas.
In another embodiment of the present utility model, microphone 11 is placed in close proximity to the side of photoacoustic cavity 10 that does not enter or exit the beam.
In another specific embodiment of the present utility model, a multi-faceted piezoelectric mirror for adjusting the outgoing light path is provided inside the piezoelectric controller 9.
In another embodiment of the present utility model, the photoacoustic cavity 10 is closed when the valve is closed.
In another more specific embodiment of the utility model, the number of piezoelectric mirrors within the piezoelectric controller 9 is at least two.
Claims (10)
1. A feedback photoacoustic spectroscopy gas detection apparatus, comprising: sawtooth wave generator, lock-in amplifier, photoelectric detector, first feedback controller, second feedback controller, light source, beam splitter, piezoelectric controller, piezoelectric control platform, photoacoustic cavity, microphone, speculum, wherein:
the sawtooth wave generator is connected with the light source and the first feedback controller;
the phase-locked amplifier is respectively connected with the light source, the photoelectric detector, the first feedback controller, the second feedback controller and the sawtooth wave amplifier;
the piezoelectric control platform is respectively connected with the piezoelectric controller and the second feedback controller;
the light source comprises a light source body, wherein an emergent opening of the light source body is provided with a beam splitter, and the beam splitter is spaced from the emergent opening by a preset distance;
the piezoelectric controller is further arranged on an extension line of the light source and the beam splitter, and an incident light port of the piezoelectric controller is arranged corresponding to the beam splitter;
the photoelectric detector is arranged on a reflection angle of a light path formed by the light ray from the piezoelectric controller to the beam splitter;
the photoacoustic cavity and the reflecting mirror are sequentially arranged in the light path direction of the emergent light port of the piezoelectric controller;
the microphone is arranged on the side wall of the photoacoustic cavity.
2. The feedback photoacoustic spectroscopy gas detection apparatus of claim 1, wherein the sawtooth generator is configured to provide a sawtooth signal for the light source;
the lock-in amplifier is used for providing a sine wave signal for the light source;
the light source is used for emitting light beams with corresponding frequencies and wavelengths according to the sawtooth wave signals and the sine wave signals.
3. The feedback photoacoustic spectroscopy gas detection apparatus of claim 1, wherein the photoacoustic cavity is configured to store a gas to be measured and to excite the gas to be measured by an incident beam to generate an acoustic signal;
the microphone is used for acquiring the sound wave signal, converting the sound wave signal into an electric signal and transmitting the electric signal to the lock-in amplifier;
the photoelectric detector is used for receiving the optical signal and converting the optical signal into an electric signal;
the phase-locked amplifier is used for generating a frequency correction signal and a wavelength correction signal according to the electric signal provided by the photoelectric detector, and transmitting the generated frequency correction signal to the first feedback controller and the generated wavelength correction signal to the second feedback controller; and demodulating the electrical signal transmitted by the microphone into a secondary photoacoustic signal related to the concentration of the gas;
the first feedback controller is used for correcting sine wave frequency generated by the lock-in amplifier and sawtooth wave frequency generated by the sawtooth wave generator according to the received frequency correction signal;
the second feedback controller is used for sending a wavelength correction signal to the piezoelectric control platform according to the received wavelength correction signal;
the piezoelectric control platform is used for controlling the piezoelectric controller to act and correcting the wavelength of light.
4. The feedback photoacoustic spectroscopy gas detection apparatus of claim 1, wherein the light source comprises: laser driving and lasers;
the laser driver is connected with the sawtooth wave generator and the first feedback controller;
the first feedback controller is used for driving the laser to emit light according to the sawtooth wave generated by the sawtooth wave generator and the sine wave transmitted by the first feedback controller;
the laser is in driving connection with the laser and is used for emitting laser beams with frequencies corresponding to the driving signals according to the signals of the laser driving.
5. The feedback photoacoustic spectroscopy gas detection apparatus of claim 1 wherein filters are provided on both sides of the photoacoustic cavity for injecting a beam of light from one side filter and from the other side filter.
6. The feedback photoacoustic spectroscopy gas detection apparatus of claim 1, wherein an air inlet valve and an air outlet valve are further disposed inside the photoacoustic cavity for filling and discharging the sample gas.
7. The feedback photoacoustic spectroscopy gas detection apparatus of claim 1 wherein the microphone is positioned in close proximity to a side of the photoacoustic cavity that is not in or out of the beam.
8. The feedback photoacoustic spectroscopy gas detection apparatus of claim 1, wherein a multi-faceted piezoelectric mirror for adjusting the outgoing light path is provided inside the piezoelectric controller.
9. The feedback photoacoustic spectroscopy gas detection apparatus of claim 6 wherein the photoacoustic cavity is sealed when the valve is closed.
10. The feedback photoacoustic spectroscopy gas detection apparatus of claim 8 wherein the multi-faceted piezoelectric mirror is at least two-sided.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202222711003.9U CN219016067U (en) | 2022-10-14 | 2022-10-14 | Feedback type photoacoustic spectrum gas detection device |
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| CN202222711003.9U CN219016067U (en) | 2022-10-14 | 2022-10-14 | Feedback type photoacoustic spectrum gas detection device |
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| CN219016067U true CN219016067U (en) | 2023-05-12 |
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| CN202222711003.9U Active CN219016067U (en) | 2022-10-14 | 2022-10-14 | Feedback type photoacoustic spectrum gas detection device |
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