WO2024103638A1 - 光声光谱相位锁定方法、装置和系统 - Google Patents

光声光谱相位锁定方法、装置和系统 Download PDF

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Publication number
WO2024103638A1
WO2024103638A1 PCT/CN2023/090960 CN2023090960W WO2024103638A1 WO 2024103638 A1 WO2024103638 A1 WO 2024103638A1 CN 2023090960 W CN2023090960 W CN 2023090960W WO 2024103638 A1 WO2024103638 A1 WO 2024103638A1
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Prior art keywords
phase
signal
laser
photoacoustic spectroscopy
photoacoustic
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PCT/CN2023/090960
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English (en)
French (fr)
Inventor
尹永刚
任丹阳
王钰琪
施钧辉
金涌涌
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之江实验室
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Priority to US18/225,694 priority Critical patent/US20240167940A1/en
Publication of WO2024103638A1 publication Critical patent/WO2024103638A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/1702—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/01—Arrangements or apparatus for facilitating the optical investigation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/1702—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids
    • G01N2021/1704—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids in gases

Definitions

  • the present application relates to the field of photoacoustic spectroscopy, and in particular to a photoacoustic spectroscopy phase locking method, device and system.
  • Photoacoustic spectroscopy is a laser absorption spectroscopy technology based on the photoacoustic effect. After gas molecules absorb modulated laser energy or pulsed laser energy, they will produce periodic thermal expansion, thereby exciting sound waves. The frequency of the sound waves depends on the modulation frequency of the laser. The strength of the sound waves reflects the concentration of the gas to be measured.
  • photoacoustic spectroscopy converts light energy into sound wave energy and is completely unaffected by background light; through the resonant design of acoustic resonators or mechanical resonators, the detection signal-to-noise ratio of sound wave signals can be further improved.
  • the photoacoustic spectroscopy gas detection system is increasingly affected by environmental factors, and the natural frequency of the resonant system will change with temperature, air pressure, etc.
  • the laser modulation frequency is generally fixed, which will cause the system to not always remain in a resonant state, and the output amplitude will drift with environmental influences, and the higher the system Q value, the greater the drift coefficient.
  • Traditional photoacoustic spectroscopy technology cannot track the resonant frequency of the system in real time, and can only calibrate the system frequency by periodic frequency sweeps.
  • a photoacoustic spectroscopy phase locking method, device and system are provided.
  • a photoacoustic spectroscopy phase locking method is provided, which is applied to a photoacoustic spectroscopy system, including: obtaining a mapping relationship between an output amplitude and an output phase of the photoacoustic spectroscopy system; determining a reference phase of the photoacoustic spectroscopy system according to the mapping relationship; and adjusting a scanning parameter of a laser in the photoacoustic spectroscopy system according to the reference phase so that the output phase of the photoacoustic spectroscopy system in a current preset period is equal to the reference phase.
  • the mapping relationship between the output amplitude and the output phase of the photoacoustic spectroscopy system is obtained by: obtaining a frequency sweep signal, wherein the frequency sweep signal includes a plurality of modulation signals of different frequencies; The laser is controlled to scan the inspected object to obtain the output amplitude and the output phase of the photoacoustic spectroscopy system.
  • acquiring the frequency sweep signal includes: acquiring a plurality of reference signals, the frequency ranges corresponding to the plurality of reference signals include the resonant frequency of the photoacoustic spectroscopy system; and frequency modulating the plurality of reference signals to obtain the frequency sweep signal.
  • determining the reference phase of the photoacoustic spectroscopy system according to the mapping relationship includes: determining a resonance peak according to the output amplitude; and using the output phase corresponding to the resonance peak as a reference phase according to the mapping relationship.
  • adjusting the scanning parameters of a laser in a photoacoustic spectroscopy system according to a reference phase includes: obtaining an output phase corresponding to a laser modulation signal of a previous preset period; adjusting the laser modulation signal of the previous preset period according to the output phase, reference phase and discrete PID (proportional-integral-derivative) control algorithm of the previous preset period to obtain a target modulation signal of a current preset period; and adjusting the scanning parameters of the laser in the photoacoustic spectroscopy system according to the target modulation signal.
  • PID proportional-integral-derivative
  • a photoacoustic spectroscopy phase locking device comprising:
  • An acquisition module used to acquire a mapping relationship between an output amplitude and an output phase of a photoacoustic spectroscopy system
  • a processing module used for determining a reference phase of a photoacoustic spectroscopy system according to a mapping relationship
  • the phase-locking module is used to adjust the scanning parameters of the laser in the photoacoustic spectroscopy system according to the reference phase, so that the output phase of the photoacoustic spectroscopy system output in each preset cycle is equal to the reference phase.
  • a photoacoustic spectroscopy system comprising: a first control device, a detection device and a second control device; wherein the first control device is connected to the detection device and the second control device respectively; the first control device is used to configure scanning parameters of the detection device; the detection device is used to emit a laser to a target under inspection according to the scanning parameters to generate a signal to be measured; and the second control device is used to execute the photoacoustic spectroscopy phase locking method of the first aspect mentioned above.
  • the detection device includes a laser, a photoacoustic cell and an acoustic sensor
  • the laser is connected to the first control device and the photoacoustic cell respectively
  • the photoacoustic cell is connected to the acoustic sensor
  • the acoustic sensor is connected to the second control device
  • the laser is used to emit laser to the photoacoustic cell according to scanning parameters
  • the photoacoustic cell is used to contain the gas to be measured so that the gas to be measured generates an acoustic wave signal under laser irradiation
  • the acoustic sensor is used to receive and enhance the acoustic wave signal, generate an electrical signal or a digital signal according to the enhanced acoustic wave signal and send it to the second control device.
  • the photoacoustic cell and/or the acoustic sensor are in resonance.
  • the first control device includes a signal generator and a laser controller
  • the second control device includes a phase-locked amplifier and a closed-loop controller.
  • the signal generator is connected to the closed-loop controller and the laser controller respectively, and the laser controller is connected to the laser;
  • the phase-locked amplifier is connected to the acoustic sensor and the closed-loop controller respectively;
  • the signal generator is used to generate a modulation signal and send it to the laser controller;
  • the laser controller is used to configure scanning parameters for the laser according to the modulation signal;
  • the phase-locked amplifier is used to generate an output amplitude and an output phase according to a reference signal and a signal to be measured;
  • the closed-loop controller is used to determine the reference phase according to the output amplitude and the output phase, generate a main control signal according to the reference phase and send it to the signal generator, so that the signal generator adjusts the scanning parameters of the laser in the photoacoustic spectroscopy system according to the main control signal, so that the output phase of the
  • FIG1 is a block diagram of the hardware structure of a terminal of the photoacoustic spectroscopy phase locking method according to the present embodiment.
  • FIG. 2 is a schematic diagram of the structure of a photoacoustic spectroscopy system according to an embodiment of the present application.
  • FIG. 3 is a schematic diagram of a detection device of a photoacoustic spectroscopy system according to an embodiment of the present application.
  • FIG. 4 is a schematic diagram of a first control device of a photoacoustic spectroscopy system according to an embodiment of the present application.
  • FIG. 5 is a schematic diagram of a second control device of a photoacoustic spectroscopy system according to an embodiment of the present application.
  • FIG. 6 is a schematic diagram of the structure of a photoacoustic spectroscopy system according to an optional embodiment of the present application.
  • FIG. 7 is a schematic diagram showing the mapping relationship between the output amplitude and the laser modulation frequency of a photoacoustic spectroscopy gas detection system at different temperatures according to the related art.
  • FIG8 is a schematic diagram of the mapping relationship between the output phase and the laser modulation frequency of a photoacoustic spectroscopy gas detection system at different temperatures according to the related art.
  • FIG. 9 is a diagram showing a mapping relationship between an output amplitude and an output phase of a photoacoustic spectroscopy system according to the related art.
  • FIG. 10 is a flow chart of the photoacoustic spectroscopy phase locking method of this embodiment.
  • FIG. 11 is a schematic diagram of the optimization effect of the photoacoustic spectroscopy phase locking method according to an embodiment of the present application.
  • FIG12 is a structural block diagram of the photoacoustic spectroscopy phase locking device of this embodiment.
  • connection is not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect.
  • the “multiple” involved in this application refers to two or more.
  • “And/or” describes the association relationship of associated objects, indicating that there can be three relationships, for example, "A and/or B” can mean: A exists alone, A and B exist at the same time, and B exists alone.
  • the character “/” indicates that the objects associated with each other are in an "or” relationship.
  • first, “second”, “third”, etc. involved in this application are only used to distinguish similar objects and do not represent a specific ordering of the objects.
  • FIG1 is a hardware structure block diagram of a terminal of the photoacoustic spectroscopy phase locking method of this embodiment.
  • the terminal may include one or more (only one is shown in FIG1 ) processors 102 and a memory 104 for storing data, wherein the processor 102 may include but is not limited to a processing device such as a microprocessor MCU or a programmable logic device FPGA.
  • the above-mentioned terminal may also include a transmission device 106 and an input and output device 108 for communication functions.
  • FIG1 is only for illustration and does not limit the structure of the above-mentioned terminal.
  • the terminal may also include more or fewer components than those shown in FIG1 , or have a different configuration than that shown in FIG1 .
  • the memory 104 can be used to store computer programs, for example, software programs and modules of application software, such as the computer program corresponding to the photoacoustic spectroscopy phase locking method in this embodiment.
  • the processor 102 executes various functional applications and data processing by running the computer program stored in the memory 104, that is, to implement the above method.
  • the memory 104 may include a high-speed random access memory, and may also include a non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory.
  • the memory 104 may further include a memory remotely arranged relative to the processor 102, and these remote memories may be connected to the terminal via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.
  • the transmission device 106 is used to receive or send data via a network.
  • the above network includes a wireless network provided by a communication provider of the terminal.
  • the transmission device 106 includes a network adapter (Network Interface Controller, referred to as NIC), which can be connected to other network devices through a base station so as to communicate with the Internet.
  • the transmission device 106 may be a radio frequency (RF) module, which is used to communicate with the Internet wirelessly.
  • RF radio frequency
  • a beam of monochromatic light with modulated intensity or wavelength is irradiated onto a sample sealed in a photoacoustic cell.
  • the sample absorbs light energy and de-excites by releasing heat energy.
  • the released heat energy causes the sample and the surrounding medium to be heated periodically according to the modulation frequency of the light, thereby causing periodic pressure fluctuations in the medium.
  • This pressure fluctuation can be detected by a sensitive microphone or piezoelectric ceramic microphone, and a photoacoustic signal can be obtained by amplification. This is the photoacoustic effect.
  • the wavelength of the incident monochromatic light is variable, a photoacoustic signal spectrum that varies with the wavelength can be measured. This is the photoacoustic spectrum.
  • Photoacoustic spectroscopy is a spectral technique based on the photoacoustic effect.
  • photoacoustic spectroscopy is different from traditional spectroscopy in that it detects not the light signal fed back after the interaction between light and matter, but the sound signal fed back after the interaction between light and matter, thus overcoming many difficulties existing in traditional spectroscopy in sample analysis.
  • traditional spectroscopy the scattering and reflection of light are the biggest interferences, because the amount of light energy absorbed by the sample is determined by measuring the intensity of the transmitted light, based on the difference obtained by subtracting the intensity of the transmitted light from the intensity of the incident light.
  • sample detection such as transparent or opaque solids, liquids, gases, powders, colloids, crystals or amorphous substances, etc., which essentially solves the problem of traditional spectroscopy in detecting samples with weak absorption, strong scattering, opacity, etc.
  • the photoacoustic spectroscopy system relies on the design of the resonant system, which is also called resonance.
  • the frequency of the external force is the same as or very close to the natural oscillation frequency of the system under the action of periodic external force, the phenomenon of a sharp increase in amplitude is called resonance, and the frequency when resonance occurs is called the resonant frequency.
  • the Q value is usually used to describe the resonant ability of the resonant system.
  • the photoacoustic spectroscopy gas detection system is increasingly affected by environmental factors, and the natural frequency of the resonant system will change with temperature, air pressure, etc.
  • the laser modulation frequency is generally fixed, which will cause the system to not always remain in a resonant state, and the output amplitude will drift with the influence of the environment, and the higher the system Q value, the greater the drift coefficient.
  • Traditional photoacoustic spectroscopy technology cannot track the resonant frequency of the system in real time, and can only calibrate the system frequency by periodic frequency sweeping. Therefore, it is urgent to improve the anti-interference performance of the photoacoustic spectroscopy system.
  • FIG2 is a schematic diagram of the structure of the photoacoustic spectroscopy system according to an embodiment of the present application.
  • the system includes a first control device 21, a detection device 22, and a second control device 23; wherein the first control device 21 is connected to the detection device 22 and the second control device 23 respectively; the first control device The device 21 is used to configure the scanning parameters of the detection device 22; the detection device 22 is used to emit a laser to the target to be detected according to the scanning parameters to generate a signal to be measured; the second control device 23 is used to obtain the mapping relationship between the output amplitude and the output phase of the current photoacoustic spectroscopy system, and determine the reference phase of the photoacoustic spectroscopy system according to the mapping relationship; the scanning parameters of the laser in the photoacoustic spectroscopy system are adjusted according to the reference phase, so that the output phase of the current preset period of the photoacoustic spect
  • the detection device is a device for performing photoacoustic spectroscopy detection, including a laser, a photoacoustic cell, and an acoustic sensor.
  • the inspected target includes, but is not limited to, transparent or opaque solids, liquids, gases, powders, colloids, crystals, or amorphous solids.
  • the first control device is used to perform signal modulation according to the control instructions issued by the user, and to configure the frequency, intensity, waveform, scanning time, etc. of the laser by adjusting the scanning parameters of the laser.
  • the second control device is used to facilitate the user to issue control instructions and obtain and analyze the detection signal generated by the detection device.
  • the second control device can select a reference phase according to the mapping relationship between the output amplitude and the output phase of the photoacoustic spectroscopy system, and send a main control signal to the first control device based on the phase, and make the output phase of the system equal to the reference phase by adjusting the scanning parameters of the laser in the photoacoustic spectroscopy system. Since the reference phase is the position corresponding to the peak value of the output amplitude, the reference phase will not drift due to changes in environmental factors such as temperature.
  • the phase of the control signal can be locked at the reference phase to ensure that the signal amplitude of the system output is at a peak value, thereby ensuring the resonance performance of the photoacoustic spectroscopy system and improving the anti-interference ability of the system.
  • the photoacoustic spectroscopy system of this embodiment adopts a phase closed-loop locking control method.
  • the reference phase By configuring the reference phase, the output phase of the system is always locked at the reference phase. Since the reference phase is located at a position corresponding to the resonant peak of the output amplitude under the resonant state of the photoacoustic spectroscopy system, the mapping relationship does not change with the change of the operating temperature of the system.
  • the output phase of the system is locked at the reference phase, so that the photoacoustic spectroscopy system is always kept in a resonant state, and the resonant frequency of the system can be locked in real time without regular frequency sweep calibration, which solves the problem that the system cannot cope with the change of the resonant frequency due to environmental factors, reduces the drift coefficient of the system, expands the operating temperature range of the system, and improves the stability of the system.
  • Figure 3 is a schematic diagram of a detection device of a photoacoustic spectroscopy system according to an embodiment of the present application.
  • the detection device includes a laser 31, a photoacoustic cell 32 and an acoustic sensor 33.
  • the laser 31 is connected to a first control device and a photoacoustic cell 32, respectively.
  • the photoacoustic cell 32 is connected to the acoustic sensor 33, and the acoustic sensor 33 is connected to a second control device.
  • the laser 31 is used to emit a laser to the photoacoustic cell 32 according to scanning parameters.
  • the photoacoustic cell 32 is used to accommodate a gas to be measured so that the gas to be measured generates an acoustic wave signal under laser irradiation.
  • the acoustic sensor 33 is used to receive and enhance the acoustic wave signal, generate an electrical signal or a digital signal according to the enhanced acoustic wave signal, and send it to the second control device.
  • the laser is used to emit laser light.
  • the laser can generally be a quantum cascade laser (QCL) with adjustable wavelength, a distributed feedback laser (DFB) or a Feed Back), Optical Parametric Oscillator (OPO), Interband Cascade Lasers (ICL), etc.
  • the laser emitted by the laser can be continuous light or pulsed light.
  • the photoacoustic cell is used to contain the gas to be measured. When the laser emitted by the laser passes through the photoacoustic cell, the gas molecules absorb the modulated laser energy and produce periodic thermal expansion, which in turn excites sound waves. This is the photoacoustic effect.
  • the sound wave signal is received by the acoustic sensor and converted into an electrical signal or a digital signal.
  • the photoacoustic cell and/or the acoustic sensor are in resonance.
  • a slender cylindrical photoacoustic cell is generally selected to form an acoustic resonant cavity, and the acoustic wave signal is enhanced by using standing waves.
  • a mechanical cantilever beam or a quartz tuning fork is generally selected as the acoustic sensor, and the acoustic wave signal is enhanced by using mechanical resonance, and a microphone with a flat frequency response cannot be selected as the acoustic sensor.
  • the output amplitude of the system can reach tens or even hundreds of times that of the non-resonant state. Therefore, in the photoacoustic spectroscopy system in this embodiment, it is necessary to ensure that at least one of the photoacoustic cell and the acoustic sensor is in a resonant state.
  • FIG. 4 is a schematic diagram of a first control device of a photoacoustic spectroscopy system according to an embodiment of the present application
  • FIG. 5 is a schematic diagram of a second control device of a photoacoustic spectroscopy system according to an embodiment of the present application.
  • the first control device includes a signal generator 41 and a laser controller 42
  • the second control device includes a lock-in amplifier 51 and a closed-loop controller 52.
  • the signal generator 41 is connected to the closed-loop controller 52 and the laser controller 42, respectively, and the laser controller 42 is connected to the laser; the lock-in amplifier 51 is connected to the acoustic sensor and the closed-loop controller 52, respectively; the signal generator 41 is used to Generate a modulation signal and send it to the laser controller 42; the laser controller 42 is used to configure scanning parameters for the laser according to the modulation signal; a phase-locked amplifier 51 is used to generate an output amplitude and an output phase according to a reference signal and a signal to be measured, and the output phase is the phase difference between the reference signal and the signal to be measured; a closed-loop controller 52 is used to determine a reference phase according to the output amplitude and the output phase, generate a master control signal according to the reference phase and send it to the signal generator 41, so that the signal generator 41 adjusts the scanning parameters of the laser in the photoacoustic spectroscopy system according to the master control signal, so that the output phase of the current preset cycle of the photoacous
  • the signal generator is used to generate a modulation signal, which modulates the current of the laser and then modulates the wavelength of the laser 31.
  • the modulation signal is generally a low-frequency sawtooth wave superimposed on a high-frequency sine wave.
  • the low-frequency sawtooth wave is used to determine the wavelength scanning range, and its frequency is generally 0.1Hz-10Hz.
  • the high-frequency sine wave is used to modulate the acoustic signal, and the modulation methods are mainly divided into first harmonic modulation and second harmonic modulation.
  • the frequency of the sine wave is equal to the frequency f of the acoustic signal to be measured.
  • the frequency of the sine wave is equal to half the frequency of the acoustic signal to be measured, that is, f/2.
  • Second harmonic modulation is the mainstream wavelength modulation method in the current photoacoustic spectroscopy system.
  • the frequency of the acoustic signal is modulated to the resonant frequency of the resonant system.
  • the resonant frequency is generally at the kHz level, and the resonance characteristics can be used to amplify and enhance the acoustic wave.
  • the signal generator can be controlled by a second control device, and the user
  • the second control device may send control instructions to cause the signal generator to change parameters such as the frequency and amplitude of its output waveform.
  • the second control device may be a computer device.
  • the laser controller can control the current and temperature of the laser, and thus the emission wavelength of the laser. Temperature control is to maintain the temperature characteristics of the laser so that its wavelength is fixed near the absorption peak of the gas to be measured. Current control is to scan the wavelength of the laser within a certain range to obtain the photoacoustic spectrum of the gas to be measured.
  • the function of a phase-locked amplifier is to extract the signal amplitude in a specific frequency range to suppress the noise in other frequency bands and improve the signal-to-noise ratio.
  • the phase-locked amplifier has two input terminals, one is the signal to be measured, that is, the output signal of the acoustic sensor, and the other is the reference signal, that is, the sine wave signal provided by the internal oscillator of the computer.
  • the frequency of the reference signal is equal to the frequency of the signal to be measured.
  • the phase-locked amplifier has two output terminals, one is the amplitude R, and the other is the phase ⁇ .
  • the amplitude is the signal strength of the signal to be measured near the frequency f, which is the final output of the system and reflects the properties of the sample. For example, in gas detection, the amplitude reflects the concentration of the gas.
  • the phase is the phase difference between the signal to be measured and the reference signal.
  • the phase in the i-th measurement cycle is recorded as ⁇ i .
  • the phase-locked amplifier uses a dual-phase demodulation method to calculate the amplitude and phase of the signal to be measured.
  • the computer uses an internal oscillator to generate two sinusoidal signals, signal A and signal B, the phase difference between signal A and signal B is 90°, the amplitude of signal A and signal B is 1, and the frequency is equal to the frequency f of the signal to be measured.
  • the signal to be measured, signal A and signal B can be expressed as:
  • the function of the closed-loop controller is to adjust the sine wave frequency of the signal generator so that the system phase is stable at the reference phase.
  • the reference phase is the phase difference between the measured signal preset by the system and the reference signal, which is denoted as ⁇ 0.
  • the closed-loop controller can be a PID controller, that is, a proportional-integral-differential controller. Using a discrete PID control algorithm, ⁇ i can be closed-loop controlled to keep ⁇ i - ⁇ 0 at 0.
  • the output of the closed-loop controller is a sine wave frequency, that is, the laser modulation frequency.
  • the frequency is f/2, that is, the sinusoidal wave component output by the signal generator can be expressed as sin( ⁇ ft).
  • Signal A is the reference signal of the phase-locked amplifier, and its frequency is also controlled by the closed-loop controller, which is the laser modulation frequency.
  • the frequency is twice the rate, which is equal to the frequency of the signal to be measured.
  • FIG6 is a schematic diagram of the structure of the photoacoustic spectroscopy system according to an optional embodiment of the present application.
  • the system includes: a laser 31, a photoacoustic cell 32, an acoustic sensor 33, a computer, a signal generator 41, and a laser controller 42, wherein a phase-locked amplifier 51 and a closed-loop controller 52 are located in the computer device 61.
  • the oscillator inside the computer device 61 provides a sinusoidal wave signal, which is sent to the signal generator 41.
  • the signal generator 41 receives the main control instruction of the computer, generates a modulation signal to modulate the current of the laser controller 42, and then modulates the wavelength of the laser 31.
  • the laser 31 emits a laser of a preset wavelength to irradiate the sample in the photoacoustic cell 32.
  • the photoacoustic cell 32 contains the gas to be detected.
  • an acoustic wave signal is generated.
  • the acoustic wave signal is received by the acoustic sensor 33 and converted into an electrical signal or a digital signal.
  • the function of the phase-locked amplifier 51 is to extract the signal amplitude in a specific frequency range to suppress the noise in other frequency bands and improve the signal-to-noise ratio of the signal.
  • the phase-locked amplifier 51 has two input terminals, one is the signal to be measured, that is, the output signal of the acoustic sensor 33, and the other is the reference signal, that is, the sine wave signal provided by the internal oscillator of the computer, which is equal to the frequency of the signal to be measured.
  • the phase-locked amplifier 51 has two output terminals, one is the amplitude and the other is the phase.
  • the function of the closed-loop controller 52 is to adjust the sine wave frequency of the signal generator 41 so that the system phase is stabilized at the reference phase, and the reference phase is the phase difference between the signal to be measured and the reference signal preset by the system.
  • phase difference between the system output and the laser modulation signal.
  • This difference is mainly determined by the processes of light-to-acoustic conversion, acoustic resonance or mechanical resonance, and sound-to-electric conversion, and each process will have a phase difference.
  • the phase difference between the output of the system and the modulation signal is measured as a reference phase, and then the laser modulation frequency is changed through a closed loop so that the system phase difference is always equal to the reference phase. Even if environmental factors such as temperature change, causing the system resonant frequency to change, the system will always remain in a resonant state.
  • the photoacoustic spectroscopy system of this embodiment controls the phase closed-loop lock.
  • the laser modulation frequency will automatically lock at half of the system resonant frequency, and the frequency of the sound wave to be measured is always equal to the resonant frequency.
  • the photoacoustic spectroscopy system always remains in a resonant state, which solves the problem that the photoacoustic spectroscopy system cannot cope with the change of the resonant frequency with environmental factors, and reduces the drift coefficient of the system.
  • the laser modulation frequency is generally fixed, but it is affected by environmental factors. For example, when the temperature changes, the resonant frequency of the system will drift.
  • the system uses a cylindrical acoustic resonant cavity as the photoacoustic cell with a diameter of 5mm and a length of 50mm.
  • the acoustic sensor uses a microphone with a flat frequency response.
  • the gas to be measured is carbon dioxide in pure nitrogen.
  • the laser is a mid-infrared quantum cascade laser with a wavelength of 4.3 ⁇ m.
  • the photoacoustic spectroscopy measurement is performed using the second harmonic modulation method.
  • Figure 7 is a schematic diagram of the mapping relationship between the output amplitude and the laser modulation frequency at different temperatures of the photoacoustic spectroscopy gas detection system according to the related art.
  • the resonance peak refers to the maximum value of the system output amplitude.
  • the resonance peak decreases from 0.6168V to 0.4566V, and the corresponding modulation frequency increases from 1680Hz to 1700Hz. It can be seen that with the change of the operating temperature of the photoacoustic spectroscopy system, the use of fixed frequency laser scanning will lead to a deterioration in the detection effect of the system.
  • Figure 8 is a schematic diagram of the mapping relationship between the output phase and the laser modulation frequency at different temperatures of the photoacoustic spectroscopy gas detection system according to the related art. As shown in Figure 8, as the temperature rises, the phase-frequency curve shifts to the right. Although the laser modulation frequency corresponding to the resonance peak increases with the increase in temperature, the output phase remains basically unchanged.
  • Figure 9 is a diagram of the mapping relationship between the output amplitude and the output phase of the photoacoustic spectroscopy system according to the related art. As shown in Figure 9, in this system, when the operating temperature of the system changes, the phase corresponding to the resonance peak is at 4.78V, and the phase remains unchanged. Therefore, when the output phase is guaranteed to be at this phase, it is guaranteed that the laser modulation frequency of the current system is at the resonance frequency, and the system is in a resonant state.
  • FIG. 10 is a flow chart of the photoacoustic spectroscopy phase locking method of this embodiment. As shown in FIG. 10 , the process includes the following steps:
  • Step S1001 obtaining a mapping relationship between an output amplitude and an output phase of a photoacoustic spectroscopy system.
  • a frequency sweep test is performed on the photoacoustic spectroscopy system to obtain the amplitude-frequency response curve and phase-frequency response curve of the system.
  • Step S1002 determining a reference phase of the photoacoustic spectroscopy system according to the mapping relationship.
  • the maximum value of the system output amplitude is the resonance peak value, and its frequency is the resonance frequency.
  • the phase difference between the system output and the input modulation signal at the resonance frequency is taken as the reference phase ⁇ 0 .
  • Step S1003 adjusting the scanning parameters of the laser in the photoacoustic spectroscopy system according to the reference phase, so that the output phase of the photoacoustic spectroscopy system in the current preset period is equal to the reference phase.
  • phase difference between the system output and the laser modulation signal.
  • This difference is mainly determined by the processes of light-to-acoustic conversion, acoustic resonance or mechanical resonance, and acoustic-to-electric conversion. Each process will have a phase difference.
  • the phase difference between the output of the measurement system and the modulation signal in the resonant state is used as the reference phase ⁇ 0 .
  • the laser modulation frequency is changed through a closed loop so that the system phase difference is always equal to the reference phase. Even if the environmental factors such as temperature change, causing the system resonant frequency to change, the system will always remain in a resonant state.
  • the phase closed-loop locking method provided in the embodiment of the present application can keep the photoacoustic spectroscopy system in a resonant state at all times, solve the problem that the system cannot cope with the change of the resonant frequency with the environment, and reduce the drift coefficient of the system.
  • the mapping relationship between the output amplitude and the output phase of the photoacoustic spectroscopy system is obtained by: obtaining a frequency sweep signal, wherein the frequency sweep signal includes a plurality of modulation signals of different frequencies;
  • the laser is controlled to scan the inspected target to obtain the output amplitude and the output phase of the photoacoustic spectroscopy system.
  • the frequency of the sine wave in the laser modulation signal is changed, and the photoacoustic spectroscopy system is subjected to a frequency scanning test to obtain the amplitude-frequency response curve and the phase-frequency response curve of the system.
  • the acquisition of the frequency sweep signal includes: acquiring multiple reference signals, the frequency range corresponding to the multiple reference signals includes the resonant frequency of the photoacoustic spectroscopy system, and frequency modulating the multiple reference signals to obtain the frequency sweep signal.
  • multiple reference signals are acquired, and the signal frequency range of the reference signals should cover the resonant frequency of the photoacoustic spectroscopy system.
  • the signal frequency range of the reference signal is between 1650Hz and 1750Hz.
  • the reference signal of the specified frequency is frequency modulated to obtain a frequency sweep signal, and the laser is controlled to scan the inspected target according to the frequency sweep signal; the output amplitude and output phase of the photoacoustic spectroscopy system in this preset cycle are determined according to the signal to be measured and the reference signal.
  • the frequency of the reference signal is changed to perform the above detection process. According to the output amplitude and output phase of multiple preset cycles, a relationship curve between the amplitude, phase and reference signal frequency is obtained.
  • determining the reference phase of the photoacoustic spectroscopy system according to the mapping relationship includes: determining the resonance peak according to the output amplitude; and taking the output phase corresponding to the resonance peak as the reference phase according to the mapping relationship. Specifically, according to the amplitude-frequency response curve and the phase-frequency response curve of the system obtained by performing a frequency sweep test on the photoacoustic spectroscopy system, the phase difference between the system output signal and the modulation signal at the resonance frequency is taken as the reference phase.
  • adjusting the scanning parameters of a laser in a photoacoustic spectroscopy system according to a reference phase includes: obtaining an output phase corresponding to a laser modulation signal of a previous preset period; adjusting the laser modulation signal of the previous preset period according to the output phase, reference phase and discrete PID control algorithm of the previous preset period to obtain a target modulation signal of a current preset period; and adjusting the scanning parameters of the laser in the photoacoustic spectroscopy system according to the target modulation signal.
  • the output phase of the previous cycle will be referenced, and the oscillation signal output by the second control device will be adjusted based on the output phase of the previous cycle and the reference phase.
  • a PID controller is used as a closed-loop controller to adjust the sine wave frequency of a signal generator so that the system phase is stabilized at a reference phase, where the reference phase is the phase difference between the measured signal and the reference signal preset by the system, denoted as ⁇ 0 .
  • the PID controller is composed of a proportional unit P, an integral unit I and a differential unit D, which are set by three parameters Kp, Ki and Kd.
  • the PID controller is mainly suitable for systems that are basically linear and whose dynamic characteristics do not change over time.
  • the PID controller is a common feedback loop component in industrial control applications.
  • This controller compares the collected data with a reference value, and then uses the difference to calculate a new input value, the purpose of which is to allow the system data to reach or remain at the reference value.
  • the PID controller can adjust the input value based on historical data and the occurrence rate of the difference, which can make the system more accurate and more stable.
  • the consistency of the output phase with the reference phase can be ensured.
  • the signal is modulated by second harmonic modulation.
  • Second harmonic modulation can avoid first harmonic interference caused by the absorption of stray laser energy by the inner wall of the photoacoustic cell, the optical window, etc.
  • the laser modulation frequency is automatically locked at half of the resonant frequency, so that the measured sound wave frequency f is always equal to the system resonant frequency f 0 , thereby achieving the locking of the resonant frequency.
  • FIG. 11 is a schematic diagram of the optimization effect of the photoacoustic spectroscopy phase locking method according to the embodiment of the present application.
  • the drift coefficient of the photoacoustic spectroscopy system before and after the phase closure is shown in FIG. 11.
  • the conventional photoacoustic spectroscopy gas detection system is used, and the laser modulation frequency is fixed to 1680 Hz.
  • the amplitude drift coefficient is about -0.028 V/°C.
  • the laser modulation frequency always locks the resonant frequency of the system, and its amplitude drift coefficient is about -0.016 V/°C. Therefore, the amplitude drift coefficient after the phase closure is reduced to 57% of the original.
  • the conventional photoacoustic spectroscopy system will be further away from the resonant frequency, causing the output signal of the system to be submerged in the noise and unable to work normally; while the photoacoustic spectroscopy system with the phase closure of the embodiment of the present application, combined with the photoacoustic spectroscopy phase locking method of the embodiment of the present application, the photoacoustic spectroscopy system can always remain in a resonant state. Although there is still a certain drift in the amplitude, it can be compensated in real time through modeling, which greatly expands the operating temperature range of the system.
  • a photoacoustic spectroscopy phase locking device is also provided, which is used to implement the above-mentioned embodiments and optional implementation modes, and the descriptions that have been made will not be repeated.
  • the terms “module”, “unit”, “subunit” and the like used below can implement a combination of software and/or hardware of a predetermined function.
  • the devices described in the following embodiments are preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceivable.
  • FIG12 is a block diagram of the photoacoustic spectroscopy phase locking device of this embodiment. As shown in FIG12 , the device includes:
  • An acquisition module 121 is used to acquire a mapping relationship between an output amplitude and an output phase of a photoacoustic spectroscopy system
  • a processing module 122 used to determine a reference phase of the photoacoustic spectroscopy system according to the mapping relationship
  • the phase locking module 123 is used to adjust the scanning parameters of the laser in the photoacoustic spectroscopy system according to the reference phase, so that the output phase of the photoacoustic spectroscopy system output in each preset cycle is equal to the reference phase.
  • the acquisition module 121 is also used to acquire a frequency sweep signal, which includes a plurality of modulation signals of different frequencies; and control the laser to scan the inspected target according to the frequency sweep signal to obtain the output amplitude and the output phase of the photoacoustic spectroscopy system.
  • the acquisition module 121 is further used to acquire multiple reference signals, the frequency range corresponding to the multiple reference signals includes the resonant frequency of the photoacoustic spectrum; and perform frequency modulation on the multiple reference signals to obtain the swept frequency signal.
  • the processing module 122 is further configured to determine a resonance peak value according to the output amplitude; and use the output phase corresponding to the resonance peak value as a reference phase according to the mapping relationship.
  • the phase-locking module 123 is also used to obtain the output phase corresponding to the laser modulation signal of the previous preset cycle;
  • the output phase of the preset period, the reference phase and the discrete PID control algorithm are used to adjust the laser modulation signal of the previous preset period to obtain the target modulation signal of the current preset period; and the scanning parameters of the laser in the photoacoustic spectroscopy system are adjusted according to the target modulation signal.
  • This embodiment also provides an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor is configured to run the computer program to execute the steps in any one of the above method embodiments.
  • the electronic device may further include a transmission device and an input/output device, wherein the transmission device is connected to the processor, and the input/output device is connected to the processor.
  • the processor may be configured to perform the following steps through a computer program:
  • a storage medium can also be provided in this embodiment to implement the method.
  • the storage medium stores a computer program; when the computer program is executed by a processor, any photoacoustic spectroscopy phase locking method in the above embodiments is implemented.

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Abstract

一种光声光谱相位锁定方法、装置和系统，其中，光声光谱相位锁定方法包括：获取光声光谱系统的输出幅值与输出相位之间的映射关系（S1001）；根据映射关系确定光声光谱系统的参考相位（S1002）；根据参考相位调节光声光谱系统中激光器的扫描参数，使光声光谱系统当前预设周期的输出相位与参考相位相等（S1003）。

Description

光声光谱相位锁定方法、装置和系统
相关申请
本申请要求2022年11月17日申请的，申请号为202211463444.X，名称为“光声光谱相位锁定方法、装置和系统”的中国专利申请的优先权，在此将其全文引入作为参考。
技术领域
本申请涉及光声光谱领域，特别是涉及一种光声光谱相位锁定方法、装置和系统。
背景技术
基于光声光谱的痕量、微量气体检测技术近年来广泛应用于环境保护、工业检测和医疗监控等领域。光声光谱技术是一种基于光声效应的激光吸收光谱技术，气体分子吸收调制激光能量或脉冲激光能量后，会产生周期性的热膨胀，进而激发出声波，声波频率取决于激光的调制频率，声波的强弱即反映了待测气体的浓度等信息。相比于传统的直接吸收光谱技术，光声光谱技术将光能转化为声波能量，完全不受背景光的影响；通过声学谐振腔或机械谐振器的谐振设计，可以进一步提升声波信号的检测信噪比。
然而，随着谐振系统的Q值不断提升，光声光谱气体检测系统受到环境因素的影响也越来越大，谐振系统的固有频率会随着温度、气压等发生改变。在目前的光声光谱气体检测技术中，激光调制频率一般固定不变，这将导致系统不能时刻保持在谐振状态，输出幅值会随着环境影响而产生漂移，而且系统Q值越高，该漂移系数越大。传统的光声光谱技术无法实时跟踪系统的谐振频率，只能通过定期扫频对系统频率进行校准。
针对相关技术中存在光声光谱系统的谐振频率受环境因素干扰较大的问题，目前还没有提出有效的解决方案。
发明内容
根据本申请的各种实施例，提供一种光声光谱相位锁定方法、装置和系统。
第一个方面，提供一种光声光谱相位锁定方法，应用于光声光谱系统，包括：获取光声光谱系统的输出幅值与输出相位之间的映射关系；根据映射关系确定光声光谱系统的参考相位；根据参考相位调节光声光谱系统中激光器的扫描参数，使光声光谱系统当前预设周期的输出相位与参考相位相等。
在其中的一个实施例中，所述获取光声光谱系统的输出幅值与输出相位之间的映射关系包括：获取扫频信号，所述扫频信号包括多个不同频率的调制信号；根据所述扫频信号 控制所述激光器扫描受检目标，得到光声光谱系统的所述输出幅值和所述输出相位。
在其中的一个实施例中，所述获取扫频信号包括：获取多个参考信号，所述多个参考信号对应的频率范围包括所述光声光谱系统的谐振频率；对所述多个参考信号进行频率调制，得到所述扫频信号。
在其中的一个实施例中，根据映射关系确定光声光谱系统的参考相位包括：根据输出幅值确定谐振峰值；根据映射关系将谐振峰值对应的输出相位作为参考相位。
在其中的一个实施例中，根据参考相位调节光声光谱系统中激光器的扫描参数包括：获取上一预设周期的激光调制信号对应的输出相位；根据上一预设周期的输出相位、参考相位和离散PID(proportional-integral-derivative)控制算法对上一预设周期的激光调制信号进行调整，得到当前预设周期的目标调制信号；根据目标调制信号调节光声光谱系统中激光器的扫描参数。
第二个方面，提供一种光声光谱相位锁定装置，包括：
获取模块，用于获取光声光谱系统的输出幅值与输出相位之间的映射关系；
处理模块，用于根据映射关系确定光声光谱系统的参考相位；
锁相模块，用于根据参考相位调节光声光谱系统中激光器的扫描参数，使光声光谱系统每一预设周期输出的输出相位与参考相位相等。
第三个方面，提供一种光声光谱系统，包括：第一控制设备、检测设备以及第二控制设备；其中，第一控制设备分别和检测设备以及第二控制设备连接；第一控制设备，用于配置检测设备的扫描参数；检测设备，用于根据扫描参数对受检目标发射激光，生成待测信号；第二控制设备用于执行上述第一个方面的光声光谱相位锁定方法。
在其中的一个实施例中，检测设备包括激光器、光声池和声学传感器，激光器分别与第一控制设备和光声池连接，光声池与声学传感器连接，声学传感器与第二控制设备连接；激光器，用于根据扫描参数向光声池发射激光；光声池，用于容纳待测气体，使待测气体在激光照射下生成声波信号；声学传感器，用于接收并增强声波信号，根据增强的声波信号生成电信号或数字信号并发送至第二控制设备。
在其中的一个实施例中，光声池和/或声学传感器处于谐振状态。
在其中的一个实施例中，第一控制设备包括信号发生器和激光器控制器，第二控制设备包括锁相放大器和闭环控制器，信号发生器分别与闭环控制器以及激光器控制器连接，激光器控制器与激光器连接；锁相放大器分别与声学传感器以及闭环控制器连接；信号发生器，用于生成调制信号并发送至激光器控制器；激光器控制器，用于根据调制信号为激光器配置扫描参数；锁相放大器，用于根据参考信号和待测信号生成输出幅值和输出相位； 闭环控制器，用于根据输出幅值和输出相位确定参考相位，根据参考相位生成主控信号并发送至信号发生器，使信号发生器根据主控信号调节光声光谱系统中激光器的扫描参数，使光声光谱系统当前预设周期的输出相位与参考相位相等。
本申请的一个或多个实施例的细节在以下附图和描述中提出，以使本申请的其他特征、目的和优点更加简明易懂。
附图说明
为了更清楚地说明本申请实施例或传统技术中的技术方案，下面将对实施例或传统技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据公开的附图获得其他的附图。
图1是本实施例的光声光谱相位锁定方法的终端的硬件结构框图。
图2是根据本申请实施例的光声光谱系统的结构示意图。
图3是根据本申请实施例的光声光谱系统的检测设备示意图。
图4是根据本申请实施例的光声光谱系统的第一控制设备示意图。
图5是根据本申请实施例的光声光谱系统的第二控制设备示意图。
图6是根据本申请可选实施例的光声光谱系统的结构示意图。
图7是根据相关技术的光声光谱气体检测系统在不同温度下的输出幅值与激光调制频率之间的映射关系示意图。
图8是根据相关技术的光声光谱气体检测系统在不同温度下的输出相位与激光调制频率之间的映射关系示意图。
图9是根据相关技术的光声光谱系统的输出幅值与输出相位之间的映射关系图。
图10是本实施例的光声光谱相位锁定方法的流程图。
图11是根据本申请实施例的光声光谱相位锁定方法的优化效果示意图。
图12是本实施例的光声光谱相位锁定装置的结构框图。
具体实施方式
下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
除另作定义外，本申请所涉及的技术术语或者科学术语应具有本申请所属技术领域具备一般技能的人所理解的一般含义。在本申请中的“一”、“一个”、“一种”、“该”、“这些”等类似的词并不表示数量上的限制，它们可以是单数或者复数。在本申请中所涉及的术语“包括”、“包含”、“具有”及其任何变体，其目的是涵盖不排他的包含；例如，包含一系列步骤或模块(单元)的过程、方法和系统、产品或设备并未限定于列出的步骤或模块(单元)，而可包括未列出的步骤或模块(单元)，或者可包括这些过程、方法、产品或设备固有的其他步骤或模块(单元)。在本申请中所涉及的“连接”、“相连”、“耦接”等类似的词语并不限定于物理的或机械连接，而可以包括电气连接，无论是直接连接还是间接连接。在本申请中所涉及的“多个”是指两个或两个以上。“和/或”描述关联对象的关联关系，表示可以存在三种关系，例如，“A和/或B”可以表示：单独存在A，同时存在A和B，单独存在B这三种情况。通常情况下，字符“/”表示前后关联的对象是一种“或”的关系。在本申请中所涉及的术语“第一”、“第二”、“第三”等，只是对相似对象进行区分，并不代表针对对象的特定排序。
在本实施例中提供的方法实施例可以在终端、计算机或者类似的运算装置中执行。比如在终端上运行，图1是本实施例的光声光谱相位锁定方法的终端的硬件结构框图。如图1所示，终端可以包括一个或多个(图1中仅示出一个)处理器102和用于存储数据的存储器104，其中，处理器102可以包括但不限于微处理器MCU或可编程逻辑器件FPGA等的处理装置。上述终端还可以包括用于通信功能的传输设备106以及输入输出设备108。本领域普通技术人员可以理解，图1所示的结构仅为示意，其并不对上述终端的结构造成限制。例如，终端还可包括比图1中所示更多或者更少的组件，或者具有与图1所示出的不同配置。
存储器104可用于存储计算机程序，例如，应用软件的软件程序以及模块，如在本实施例中的光声光谱相位锁定方法对应的计算机程序，处理器102通过运行存储在存储器104内的计算机程序，从而执行各种功能应用以及数据处理，即实现上述的方法。存储器104可包括高速随机存储器，还可包括非易失性存储器，如一个或者多个磁性存储装置、闪存、或者其他非易失性固态存储器。在一些实例中，存储器104可进一步包括相对于处理器102远程设置的存储器，这些远程存储器可以通过网络连接至终端。上述网络的实例包括但不限于互联网、企业内部网、局域网、移动通信网及其组合。
传输设备106用于经由一个网络接收或者发送数据。上述的网络包括终端的通信供应商提供的无线网络。在一个实例中，传输设备106包括一个网络适配器(Network Interface Controller，简称为NIC)，其可通过基站与其他网络设备相连从而可与互联网进行通讯。 在一个实例中，传输设备106可以为射频(Radio Frequency，简称为RF)模块，其用于通过无线方式与互联网进行通讯。
用一束强度或波长可调制的单色光照射到密封于光声池中的样品上，样品吸收光能，并以释放热能的方式退激，释放的热能使样品和周围介质按光的调制频率产生周期性加热，从而导致介质产生周期性压力波动，这种压力波动可用灵敏的微音器或压电陶瓷传声器检测，并通过放大得到光声信号，这就是光声效应。若入射单色光波长可变，则可测到随波长而变的光声信号图谱，这就是光声光谱。
光声光谱技术是基于光声效应的一种光谱技术。光声光谱技术作为光谱学的一个重要分支，与传统光谱学的不同之处在于，该技术探测的不是光与物质相互作用后反馈的光信号，而是探测光与物质相互作用后反馈的声信号，从而克服了传统光谱法在样品分析中存在的诸多困难。传统的光谱法中，光的散射、反射是最大的干扰，因为样品吸收光能量的大小是通过测量透射光强度的方式，依据从入射光强度中减去透射光强度得到的差额来确定，然而，光与物质相互作用的过程必然伴随着一定的反射、散射和其他的光损失，这将导致入射光强度的降低。此外，传统光谱法探测的是光与物质相互作用后的透射光信号，因此样品就必须具有一定的透光性。与之相比，光声光谱技术所检测的是因物质吸收光能而产生的声波信号，这种声波信号的强弱直接反映了物质吸收光能量的大小。从而避免了因样品中光的反射、散射等引起的信号干扰；同时，还可针对弱吸收样品适当增大入射光的辐照功率来提高信噪比。因此，它被广泛应用于各种试样检测，如透明的或不透明的固体、液体、气体、粉末、胶体、晶体或非晶体等，从本质上解决了传统光谱法对弱吸收、强散射、不透明等样品检测的难题。
光声光谱系统依赖于谐振系统的设计，谐振又称共振。振荡系统在周期性外力作用下，当外力作用频率与系统固有振荡频率相同或很接近时，振幅急剧增大的现象称为谐振，产生谐振时的频率称为谐振频率。通常用Q值描述谐振系统的谐振能力。随着谐振系统的Q值不断提升，光声光谱气体检测系统受到环境因素的影响也越来越大，谐振系统的固有频率会随着温度、气压等发生改变。在目前的光声光谱气体检测技术中，激光调制频率一般固定不变，这将导致系统不能时刻保持在谐振状态，输出幅值会随着环境影响而产生漂移，而且系统Q值越高，该漂移系数越大。传统的光声光谱技术无法实时跟踪系统的谐振频率，只能通过定期扫频对系统频率进行校准。因此，亟需提高光声光谱系统的抗干扰性能。
在本实施例中提供了一种光声光谱系统，图2是根据本申请实施例的光声光谱系统的结构示意图，如图2所示，该系统包括第一控制设备21、检测设备22以及第二控制设备23；其中，第一控制设备21分别和检测设备22以及第二控制设备23连接；第一控制设 备21，用于配置检测设备22的扫描参数；检测设备22，用于根据扫描参数对受检目标发射激光，生成待测信号；第二控制设备23用于获取当前光声光谱系统的输出幅值与输出相位的映射关系，根据映射关系确定光声光谱系统的参考相位；根据参考相位调节光声光谱系统中激光器的扫描参数，使光声光谱系统当前预设周期的输出相位与参考相位相等。
具体地，检测设备是用于进行光声光谱检测的设备，包括激光器、光声池和声学传感器等。受检目标包括但不限于透明或不透明的固体、液体、气体、粉末、胶体、晶体或非晶体等。第一控制设备用于根据用户下达的控制指令，进行信号调制，通过调整激光器的扫描参数，配置激光的频率、强度、波形、扫描时间等。第二控制设备，用于方便用户下达控制指令并获取和分析检测设备生成的检测信号。通过本实施例的光声光谱系统，第二控制设备可以根据光声光谱系统的输出幅值和输出相位的映射关系，选定参考相位，并基于该相位下发主控信号至第一控制设备，通过调节光声光谱系统中激光器的扫描参数，使系统的输出相位与参考相位相等。由于参考相位是输出幅值的峰值对应的位置，参考相位不会因温度等环境因素的变化而产生漂移，因此，可以通过控制信号的相位锁定在参考相位，保证系统的输出的信号幅值处于峰值，从而保证光声光谱系统的谐振性能，提升系统的抗干扰能力。
相较于相关技术中通过采用固定频率运行激光器的光声光谱系统，本实施例的光声光谱系统采取了一种相位闭环锁定的控制方式。通过配置参考相位，使系统的输出相位始终锁定在参考相位，由于参考相位位于光声光谱系统谐振状态下，与输出幅值的谐振峰值对应的位置，该映射关系不随系统的工作温度的改变而改变，因此，通过相位闭环锁定的方法，使系统的输出相位锁定在参考相位，从而使光声光谱系统始终保持在谐振状态，不需要定期扫频校准即可实现实时锁定系统的谐振频率，解决了系统无法应对谐振频率随环境因素改变的问题，降低了系统的漂移系数，扩展了系统的工作温度范围，提升了系统的稳定性。
在其中的一个实施例中，图3是根据本申请实施例的光声光谱系统的检测设备示意图，如图3所示，检测设备包括激光器31、光声池32和声学传感器33，激光器31分别与第一控制设备和光声池32连接，光声池32与声学传感器33连接，声学传感器33与第二控制设备连接；激光器31，用于根据扫描参数向光声池32发射激光；光声池32，用于容纳待测气体，使待测气体在激光照射下生成声波信号；声学传感器33，用于接收并增强声波信号，根据增强的声波信号生成电信号或数字信号并发送至第二控制设备。
具体地，激光器用于发射激光，在光声光谱系统中，激光器一般可以选择波长可以调节的量子级联激光器QCL(Quantum Cascade Laser)，分布式反馈激光器DFB(Distributed  Feed Back)，光学参量振荡器激光器OPO(Optical Parametric Oscillator)，带间级联激光器ICL(Interband Cascade Lasers)等，激光器发射的激光可以为连续光或脉冲光。光声池用于容纳待测气体，当激光器发射的激光穿过光声池时，气体分子吸收调制激光能量后，会产生周期性的热膨胀，进而激发出声波，这就是光声效应。声波信号被声学传感器接收转换为电信号或数字信号。
在其中的一个实施例中，光声池和/或声学传感器处于谐振状态。
具体地，若光声池工作在谐振状态，则一般选择细长圆柱状的光声池，形成声学谐振腔，利用驻波对声波信号进行增强。若声学传感器工作在谐振状态，则一般选择机械悬臂梁或石英音叉作为声学传感器，利用机械共振对声波信号进行增强，而不能选择平坦频率响应的麦克风作为声学传感器。谐振状态下，系统的输出幅值可以达到非谐振状态的数十甚至数百倍，因此，在本实施例中的光声光谱系统中，需要保证光声池和声学传感器中的至少一个处于谐振状态。
在其中的一个实施例中，图4是根据本申请实施例的光声光谱系统的第一控制设备示意图，图5是根据本申请实施例的光声光谱系统的第二控制设备示意图，如图4和图5所示，第一控制设备包括信号发生器41和激光控制器42，第二控制设备包括锁相放大器51和闭环控制器52，信号发生器41分别与闭环控制器52以及激光控制器42连接，激光控制器42与激光器连接；锁相放大器51分别与声学传感器以及闭环控制器52连接；信号发生器41，用于生成调制信号并发送至激光控制器42；激光控制器42，用于根据调制信号为激光器配置扫描参数；锁相放大器51，用于根据参考信号和待测信号生成输出幅值和输出相位，输出相位是参考信号和待测信号的相位差；闭环控制器52，用于根据输出幅值和输出相位确定参考相位，根据参考相位生成主控信号并发送至信号发生器41，使信号发生器41根据主控信号调节光声光谱系统中激光器的扫描参数，使光声光谱系统当前预设周期的输出相位与参考相位相等。
具体地，信号发生器用于产生调制信号，通过调制信号对激光器的电流进行调制，进而对激光器31的波长进行调制，在光声光谱检测系统中，调制信号一般为低频的锯齿波叠加高频的正弦波。低频锯齿波是用来确定波长扫描范围，其频率一般为0.1Hz-10Hz。高频正弦波用来对声波信号进行调制，调制方法主要分为一次谐波调制和二次谐波调制。在一次谐波调制中，正弦波的频率等于待测声信号的频率f，在二次谐波调制中，正弦波的频率等于待测声信号频率的一半，即f/2，二次谐波调制是目前光声光谱系统中的主流波长调制方法。同时，将声波信号频率调制到谐振系统的谐振频率，该谐振频率一般为kHz级别，可以利用谐振特性对声波进行放大增强。信号发生器可以受第二控制设备控制，用户 可通过第二控制设备下发控制指令，使信号发生器改变其输出波形的频率、幅值等参数，在其中的一个具体的实施例中，第二控制设备可以是计算机设备。
激光控制器可以控制激光器的电流和温度，进而控制激光器的发射波长。温度控制是为了保持激光器温度的特性，使其波长固定在待测气体的吸收峰附近。电流控制是为了激光器的波长在一定范围内扫描，得到待测气体的光声光谱。
锁相放大器的作用是提取特定频率范围的信号幅值，以抑制其他频段的噪声，提升信号的信噪比。锁相放大器有两个输入端，一个是待测信号，即声学传感器的输出信号，另一个是参考信号，即计算机内部振荡器提供的正弦波信号，参考信号的频率与待测信号的频率相等。锁相放大器有两个输出端，一个是幅值R，另一个是相位θ。该幅值是待测信号在频率f附近的信号强度，是系统的最终输出，反映了样品的性质，例如在气体检测中，幅值反映了气体的浓度。相位是待测信号与参考信号之间的相位差，在第i个测量周期的相位记为θi。
在其中的一个实施例中，锁相放大器采用双相位解调的方法计算待测信号的幅值和相位。具体地，计算机采用内部振荡器产生两个正弦信号，信号A和信号B，信号A和信号B的相位相差90°，信号A和信号B的幅值为1，频率等于待测信号的频率f。在t时刻，待测信号、信号A和B可以分别表示为：
待测信号：R×sin(2πft+θ)
信号A：sin(2πft)
信号B：sin(2πft+90°)
将待测信号分别与信号A和信号B相乘，即进行混频操作，再通过低通滤波去除高频分量，分别得到待测信号在同相和正交分量上的投影，记为X和Y，公式为：最终可以计算出待测信号的幅值和相位：幅值相位θ＝tan-1(Y/X)。
闭环控制器的作用是调节信号发生器的正弦波频率，使系统相位稳定在参考相位，参考相位是系统预设的待测信号与参考信号之间的相位差，记为θ0。在其中的一个具体的实施例中，闭环控制器可以为PID控制器，即比例-积分-微分控制器，采用离散PID控制算法，可以对θi进行闭环控制，使θi-θ0保持为0。闭环控制器的输出是正弦波频率，即激光调制频率，在二次谐波调制时频率为f/2，即信号发生器输出的正弦波分量可以表示为sin(πft)。信号A即为锁相放大器的参考信号，其频率也受闭环控制器控制，为激光调制频 率的2倍，等于待测信号的频率。
在本实施例中提供了一种具体的光声光谱系统，图6是根据本申请可选实施例的光声光谱系统的结构示意图，如图6所示，包括：激光器31，光声池32，声学传感器33，计算机，信号发生器41，激光控制器42，其中，锁相放大器51和闭环控制器52位于计算机设备61内。计算机设备61内部的振荡器提供正弦波信号，将该正弦波信号发送至信号发生器41，信号发生器41接收计算机的主控指令，产生调制信号对激光控制器42的电流进行调制，进而对激光器31的波长进行调制。激光器31发出预设波长的激光照射光声池32中的样品，当光声光谱系统用于检测气体时，光声池32内容纳待测气体，当激光器31发射的激光穿过光声池32时，会产生声波信号，声波信号被声学传感器33接收，转换为电信号或数字信号。锁相放大器51的作用是提取特定频率范围的信号幅值，以抑制其他频段的噪声，提升信号的信噪比。锁相放大器51有两个输入端，一个是待测信号，即声学传感器33的输出信号，另一个是参考信号，即计算机内部振荡器提供的正弦波信号，与待测信号频率相等。锁相放大器51有两个输出端，一个是幅值，另一个是相位。闭环控制器52的作用是调节信号发生器41的正弦波频率，使系统相位稳定在参考相位，参考相位是系统预设的待测信号与参考信号之间的相位差。
光声光谱气体系统在谐振状态下，系统的输出与激光调制信号之间的相位存在一个固定的差值。该差值主要受光-声转换、声学谐振或机械谐振、声-电转换这几个过程决定，每个过程都会有一个相位差。在谐振状态下测量系统的输出与调制信号之间的相位差，作为参考相位，再通过闭环改变激光调制频率，使系统相位差始终等于参考相位，那么即使温度等环境因素改变，导致系统谐振频率改变，系统也始终会保持谐振状态。本实施例的光声光谱系统，通过控制相位闭环锁定，在二次谐波调制模式下，激光调制频率会自动锁定在系统谐振频率的一半，待测声波频率始终等于谐振频率。光声光谱系统始终保持在谐振状态，解决了光声光谱系统无法应对谐振频率随环境因素改变的问题，降低了系统的漂移系数。
相关技术中的光声光谱气体检测方案中，激光调制频率一般固定不变，但是受到环境因素的影响，例如当温度发生变化时，系统的谐振频率会发生漂移。以一个具体的光声光谱气体检测系统为例，该系统采用圆柱形声学谐振腔作为光声池，直径为5mm，长度为50mm，声学传感器采用平坦频率响应的麦克风，待测气体为纯氮气中的二氧化碳，激光器为波长4.3μm的中红外量子级联激光器，采用二次谐波调制的方法进行光声光谱测量。图7是根据相关技术的光声光谱气体检测系统在不同温度下的输出幅值与激光调制频率之间的映射关系示意图，如图7所示，随着温度从40℃变化至50℃，系统的幅值和谐振频 率均发生了改变，谐振峰值是指系统输出幅值的极大值，谐振峰值降低，从0.6168V变化至0.4566V，对应的调制频率升高，从1680Hz变化至1700Hz。由此可见，随着光声光谱系统工作温度的变化，采用固定频率进行激光扫描，会导致系统的检测效果变差。
图8是根据相关技术的光声光谱气体检测系统在不同温度下的输出相位与激光调制频率之间的映射关系示意图，如图8所示，随着温度上升，相位-频率曲线向右平移。虽然随着温度的增加，与谐振峰值对应的激光调制频率增加，但是输出相位基本保持不变。图9是根据相关技术的光声光谱系统的输出幅值与输出相位之间的映射关系图，如图9所示，在该系统中，当系统的工作温度发生变化时，谐振峰值对应的相位处于4.78V，相位保持不变。因此，当保证输出相位处于该相位时，即保证了当前系统的激光调制频率处于谐振频率，系统处于谐振状态。
在本实施例中提供了一种光声光谱相位锁定方法，应用于改进后的光声光谱系统，图10是本实施例的光声光谱相位锁定方法的流程图，如图10所示，该流程包括如下步骤：
步骤S1001，获取光声光谱系统的输出幅值与输出相位之间的映射关系。
具体地，在系统初始状态下，对光声光谱系统进行频率扫描测试，得到系统的幅值-频率响应曲线和相位-频率响应曲线。
步骤S1002，根据映射关系确定光声光谱系统的参考相位。
具体地，系统输出幅值最大值即为谐振峰值，其频率为谐振频率，取谐振频率处系统输出与输入调制信号的相位差作为参考相位θ0。
步骤S1003，根据参考相位调节光声光谱系统中激光器的扫描参数，使光声光谱系统当前预设周期的输出相位与参考相位相等。
具体地，光声光谱气体检测系统在谐振状态下，系统的输出与激光调制信号之间的相位存在一个固定的差值，该差值主要受光-声转换、声学谐振或机械谐振、声-电转换这几个过程决定，每个过程都会有一个相位差。将谐振状态下测量系统的输出与调制信号之间的相位差，作为参考相位θ0。再通过闭环改变激光调制频率，使系统相位差始终等于参考相位，那么即使温度等环境因素改变，导致系统谐振频率改变，系统也始终会保持谐振状态。
通过上述步骤，本申请实施例提供的相位闭环锁定的方法，能够使光声光谱系统始终保持在谐振状态，解决了系统无法应对谐振频率随环境改变的问题，降低了系统的漂移系数。
在其中的一个实施例中，所述获取光声光谱系统的输出幅值与输出相位之间的映射关系包括：获取扫频信号，所述扫频信号包括多个不同频率的调制信号；根据所述扫频信号 控制所述激光器扫描受检目标，得到光声光谱系统的所述输出幅值和所述输出相位。具体地，在光声光谱系统的初始状态下，改变激光调制信号中正弦波的频率，对光声光谱系统进行频率扫描测试，得到系统的幅值-频率响应曲线和相位-频率响应曲线。
在其中的一个实施例中，所述获取扫频信号包括：获取多个参考信号，所述多个参考信号对应的频率范围包括所述光声光谱系统的谐振频率，对所述多个参考信号进行频率调制，得到所述扫频信号。具体地，获取多个参考信号，参考信号的信号频率范围应覆盖光声光谱系统的谐振频率。可选的，参考信号的信号频率范围为1650Hz至1750Hz之间。在单个预设周期中，对指定频率的参考信号进行频率调制，得到扫频信号，根据扫频信号控制激光器扫描受检目标；根据待测信号和参考信号确定本预设周期光声光谱系统的输出幅值和输出相位。改变参考信号的频率执行上述检测过程。根据多个预设周期的输出幅值与输出相位，得到幅值、相位与参考信号频率之间的关系曲线。
在其中的一个实施例中，根据映射关系确定光声光谱系统的参考相位包括：根据输出幅值确定谐振峰值；根据映射关系将谐振峰值对应的输出相位作为参考相位。具体地，根据对光声光谱系统进行频率扫描测试得到的系统的幅值-频率响应曲线和相位-频率响应曲线，取谐振频率处系统输出信号与调制信号的相位差作为参考相位。
在其中的一个实施例中，根据参考相位调节光声光谱系统中激光器的扫描参数包括：获取上一预设周期的激光调制信号对应的输出相位；根据上一预设周期的输出相位、参考相位和离散PID控制算法对上一预设周期的激光调制信号进行调整，得到当前预设周期的目标调制信号；根据目标调制信号调节光声光谱系统中激光器的扫描参数。
具体地，设置了参考相位后，在光声光谱系统的运行过程中，会参考上一周期的输出相位，基于上一周期的输出相位和参考相位对第二控制设备输出的振荡信号进行调节。
在其中的一个实施例中，将PID控制器作为闭环控制器调节信号发生器的正弦波频率，使系统相位稳定在参考相位，参考相位是系统预设的待测信号与参考信号之间的相位差，记为θ0。PID控制器，由比例单元P、积分单元I和微分单元D组成，通过Kp，Ki和Kd三个参数进行设定。PID控制器主要适用于基本上线性，且动态特性不随时间变化的系统。PID控制器是一个在工业控制应用中常见的反馈回路部件。这个控制器把收集到的数据和一个参考值进行比较，然后把这个差别用于计算新的输入值，这个新的输入值的目的是可以让系统的数据达到或保持在参考值。与其他简单的控制运算不同，PID控制器可以根据历史数据和差别的出现率来调整输入值，这样可以使系统更加准确，更加稳定。在本实施例中，通过预设参考相位并借助PID控制器的控制功能，即可保证输出相位与参考相位的一致性。
在其中的一个实施例中，采用二次谐波调制的方式进行信号调制。二次谐波调制可以避免光声池内壁、光学窗口等吸收杂散激光能量导致的一次谐波干扰。在本实施例中，光声光谱系统在二次谐波调制模式下，激光调制频率会自动锁定在谐振频率的一半，能够使待测声波频率f始终等于系统谐振频率f0，实现谐振频率的锁定。
在其中的一个实施例中，图11是根据本申请实施例的光声光谱相位锁定方法的优化效果示意图，光声光谱系统在相位闭环前后的漂移系数如图11所示，在相位闭环前，采用传统的光声光谱气体检测系统，激光调制频率固定为1680Hz，在40-50℃温度范围内，幅值漂移系数约为-0.028V/℃。在相位闭环后，即选用本申请实施例的光声光谱系统以及光声光谱相位锁定方法后，激光调制频率始终锁定系统的谐振频率，其幅值漂移系数约为-0.016V/℃。因此，相位闭环后幅值漂移系数降低为原来的57％。随着温度变化范围的增大，传统光声光谱系统会进一步远离谐振频率，导致系统的输出信号淹没在噪声之中，无法正常工作；而采用本申请实施例的相位闭环的光声光谱系统，结合本申请实施例的光声光谱相位锁定方法，光声光谱系统可以始终保持在谐振状态，虽然幅值依然存在一定的漂移，但可以通过建模进行实时补偿，大大扩展了系统的工作温度范围。
在本实施例中还提供了一种光声光谱相位锁定装置，该装置用于实现上述实施例及可选实施方式，已经进行过说明的不再赘述。以下所使用的术语“模块”、“单元”、“子单元”等可以实现预定功能的软件和/或硬件的组合。尽管在以下实施例中所描述的装置较佳地以软件来实现，但是硬件，或者软件和硬件的组合的实现也是可能并被构想的。
图12是本实施例的光声光谱相位锁定装置的结构框图，如图12所示，该装置包括：
获取模块121，用于获取光声光谱系统的输出幅值与输出相位之间的映射关系；
处理模块122，用于根据映射关系确定光声光谱系统的参考相位；
锁相模块123，用于根据参考相位调节光声光谱系统中激光器的扫描参数，使光声光谱系统每一预设周期输出的输出相位与参考相位相等。
获取模块121，还用于获取扫频信号，所述扫频信号包括多个不同频率的调制信号；根据所述扫频信号控制所述激光器扫描受检目标，得到光声光谱系统的所述输出幅值和所述输出相位。
所述获取模块121，还用于获取多个参考信号，所述多个参考信号对应的频率范围包括所述光声光谱的谐振频率；对所述多个参考信号进行频率调制，得到所述扫频信号。
处理模块122，还用于根据输出幅值确定谐振峰值；根据映射关系将谐振峰值对应的输出相位作为参考相位。
锁相模块123，还用于获取上一预设周期的激光调制信号对应的输出相位；根据上一 预设周期的输出相位、参考相位和离散PID控制算法对上一预设周期的激光调制信号进行调整，得到当前预设周期的目标调制信号；根据目标调制信号调节光声光谱系统中激光器的扫描参数。
在本实施例中还提供了一种电子装置，包括存储器和处理器，该存储器中存储有计算机程序，该处理器被设置为运行计算机程序以执行上述任一项方法实施例中的步骤。
可选地，上述电子装置还可以包括传输设备以及输入输出设备，其中，该传输设备和上述处理器连接，该输入输出设备和上述处理器连接。
可选地，在本实施例中，上述处理器可以被设置为通过计算机程序执行以下步骤：
S1，获取光声光谱系统的输出幅值与输出相位之间的映射关系。
S2，根据映射关系确定光声光谱系统的参考相位。
S3，根据参考相位调节光声光谱系统中激光器的扫描参数，使光声光谱系统当前预设周期的输出相位与参考相位相等。
需要说明的是，在本实施例中的具体示例可以参考上述实施例及可选实施方式中所描述的示例，在本实施例中不再赘述。
此外，结合上述实施例中提供的光声光谱相位锁定方法，在本实施例中还可以提供一种存储介质来实现。该存储介质上存储有计算机程序；该计算机程序被处理器执行时实现上述实施例中的任意一种光声光谱相位锁定方法。
应该明白的是，这里描述的具体实施例只是用来解释这个应用，而不是用来对它进行限定。根据本申请提供的实施例，本领域普通技术人员在不进行创造性劳动的情况下得到的所有其它实施例，均属本申请保护范围。
显然，附图只是本申请的一些例子或实施例，对本领域的普通技术人员来说，也可以根据这些附图将本申请适用于其他类似情况，但无需付出创造性劳动。另外，可以理解的是，尽管在此开发过程中所做的工作可能是复杂和漫长的，但是，对于本领域的普通技术人员来说，根据本申请披露的技术内容进行的某些设计、制造或生产等更改仅是常规的技术手段，不应被视为本申请公开的内容不足。
“实施例”一词在本申请中指的是结合实施例描述的具体特征、结构或特性可以包括在本申请的至少一个实施例中。该短语出现在说明书中的各个位置并不一定意味着相同的实施例，也不意味着与其它实施例相互排斥而具有独立性或可供选择。本领域的普通技术人员能够清楚或隐含地理解的是，本申请中描述的实施例在没有冲突的情况下，可以与其它实施例结合。
以上实施例仅表达了本申请的几种实施方式，其描述较为具体和详细，但并不能因此 而理解为对专利保护范围的限制。应当指出的是，对于本领域的普通技术人员来说，在不脱离本申请构思的前提下，还可以做出若干变形和改进，这些都属于本申请的保护范围。因此，本申请的保护范围应以所附权利要求为准。

Claims (10)

  1. 一种光声光谱相位锁定方法，其特征在于，包括：
    获取光声光谱系统的输出幅值与输出相位之间的映射关系；
    根据所述映射关系确定所述光声光谱系统的参考相位；
    根据所述参考相位调节所述光声光谱系统中激光器的扫描参数，使所述光声光谱系统当前预设周期的输出相位与所述参考相位相等。
  2. 根据权利要求1所述的光声光谱相位锁定方法，其中，所述获取光声光谱系统的输出幅值与输出相位之间的映射关系包括：
    获取扫频信号，所述扫频信号包括多个不同频率的调制信号；
    根据所述扫频信号控制所述激光器扫描受检目标，得到光声光谱系统的所述输出幅值和所述输出相位。
  3. 根据权利要求2所述的光声光谱相位锁定方法，其中，所述获取扫频信号包括：
    获取多个参考信号，所述多个参考信号对应的频率范围包括所述光声光谱系统的谐振频率；
    对所述多个参考信号进行频率调制，得到所述扫频信号。
  4. 根据权利要求1所述的光声光谱相位锁定方法，其中，所述根据所述映射关系确定所述光声光谱系统的参考相位包括：
    根据所述输出幅值确定谐振峰值；
    根据所述映射关系将所述谐振峰值对应的所述输出相位作为所述参考相位。
  5. 根据权利要求1所述的光声光谱相位锁定方法，其中，所述根据所述参考相位调节所述光声光谱系统中激光器的扫描参数包括：
    获取上一预设周期的激光调制信号对应的所述输出相位；
    根据上一预设周期的所述输出相位、所述参考相位和离散PID控制算法对上一预设周期的所述激光调制信号进行调整，得到当前预设周期的目标调制信号；
    根据所述目标调制信号调节所述光声光谱系统中所述激光器的扫描参数。
  6. 一种光声光谱相位锁定装置，其特征在于，包括：
    获取模块，用于获取光声光谱系统的输出幅值与输出相位之间的映射关系；
    处理模块，用于根据所述映射关系确定所述光声光谱系统的参考相位；
    锁相模块，用于根据所述参考相位调节所述光声光谱系统中激光器的扫描参数，使所述光声光谱系统每一预设周期输出的输出相位与所述参考相位相等。
  7. 一种光声光谱系统，其特征在于，包括：第一控制设备、检测设备以及第二控制设 备；其中，所述第一控制设备分别和所述检测设备以及所述第二控制设备连接；
    所述第一控制设备，用于配置所述检测设备的扫描参数；
    所述检测设备，用于根据所述扫描参数对受检目标发射激光，生成待测信号；
    所述第二控制设备用于执行权利要求1至权利要求5中任一项所述的光声光谱相位锁定方法。
  8. 根据权利要求7所述的光声光谱系统，其中，所述检测设备包括激光器、光声池和声学传感器，所述激光器分别与所述第一控制设备和所述光声池连接，所述光声池与所述声学传感器连接，所述声学传感器与所述第二控制设备连接；
    所述激光器，用于根据所述扫描参数向所述光声池发射激光；
    所述光声池，用于容纳待测气体，使所述待测气体在激光照射下生成声波信号；
    所述声学传感器，用于接收并增强所述声波信号，根据增强的所述声波信号生成电信号或数字信号并发送至所述第二控制设备。
  9. 根据权利要求8所述的光声光谱系统，其中，所述光声池和/或所述声学传感器处于谐振状态。
  10. 根据权利要求8所述的光声光谱系统，其中，所述第一控制设备包括信号发生器和激光器控制器，所述第二控制设备包括锁相放大器和闭环控制器，所述信号发生器分别与所述闭环控制器以及激光器控制器连接，所述激光器控制器与所述激光器连接；所述锁相放大器分别与所述声学传感器以及闭环控制器连接；
    所述信号发生器，用于生成调制信号并发送至所述激光器控制器；
    所述激光器控制器，用于根据所述调制信号为所述激光器配置扫描参数；
    所述锁相放大器，用于根据参考信号和所述待测信号生成输出幅值和输出相位；
    所述闭环控制器，用于根据所述输出幅值和所述输出相位确定参考相位，根据所述参考相位生成主控信号并发送至所述信号发生器，使所述信号发生器根据所述主控信号调节所述光声光谱系统中激光器的扫描参数，使所述光声光谱系统当前预设周期的输出相位与所述参考相位相等。
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