Acousto-optic spectrum frequency detection method based on Lorentz linear function

Abstract

The invention relates to an acousto-optic spectrum frequency detection method based on a Lorentz linear function, and the method comprises the steps: providing a quartz crystal resonator which is provided with a first pin and a second pin, the first pin is used for signal input, and the second pin is used for signal output; the first pin inputs a sine wave signal, the frequency f of the sine wave signal is adjustable, and the amplitude A is constant; acquiring a second pin output signal, and detecting the amplitude; the amplitude of the sinusoidal signal is kept unchanged, the frequency delta f of the input sinusoidal signal is continuously increased or decreased until the amplitude of the signal output by the second pin reaches Amax, and the resonant frequency is obtained; the current resonant frequency is recorded as fPrevious; generating and superposing a plurality of groups of sine wave signals to obtain a frequency mixing signal; inputting the frequency mixing signal to a first pin; an output signal of the second pin is obtained, and through conditioning and collection of the output signal, a frequency spectrum is analyzed and a Lorentz line type is fitted so as to obtain a resonant frequency f0; and obtaining a final resonant frequency based on the fPrevious and the f0.

Description

Technical Field

[0001] The present application relates to the field of acousto-optic spectroscopy, and in particular to an acousto-optic spectroscopy frequency detection method based on a Lorentzian linear function. Background Art

[0002] Photoacoustic spectroscopy is an absorption spectroscopy technique based on the photoacoustic effect. It uses the light energy absorbed by the target gas sample to detect the presence and concentration of the gas. This technology has the characteristics of high sensitivity, small size, good long-term stability and excellent linearity, so it has been widely used in many fields such as environmental testing, industrial control, and medical diagnosis.

[0003] In the prior art, tunable semiconductor lasers are one of the key components in photoacoustic spectroscopy. By applying low-frequency scanning signals and high-frequency modulation signals to the laser injection current, the output wavelength and modulation frequency of the laser can be controlled. Among them, the frequency of the high-frequency modulation signal is set to half the resonance frequency of the quartz crystal resonator. When the laser beam passes through the target gas, it is focused on the quartz crystal resonator. If the absorption band of the target gas molecules is within the tuning range of the laser, the quartz crystal resonator will generate a resonance signal. As a high-precision frequency control element, it plays a key role in photoacoustic spectroscopy. The accuracy and stability of its resonance frequency directly affect the measurement accuracy and reliability of photoacoustic spectroscopy. However, the resonance frequency of the quartz crystal resonator is easily affected by many factors, such as changes in external conditions such as ambient temperature, air pressure, humidity, and changes in internal factors such as the material and structure of the quartz crystal resonator itself. These factors may cause the resonance frequency of the quartz crystal resonator to drift, thereby affecting its application effect in photoacoustic spectroscopy.

[0004] Therefore, in order to ensure the accuracy and reliability of photoacoustic spectroscopy, it is essential to calibrate the quartz crystal resonator regularly or in real time. Through calibration, the accurate resonance frequency of the quartz crystal resonator can be obtained in real time, thereby eliminating or reducing the influence of external factors on the measurement results. At the same time, calibration also helps to timely discover the performance changes of the quartz crystal resonator so that it can be adjusted or replaced in time to ensure the long-term stability of photoacoustic spectroscopy. Through precise calibration, the accuracy and stability of the quartz crystal resonator in photoacoustic spectroscopy can be ensured, providing reliable technical support for applications in environmental detection, industrial control, medical diagnosis and other fields.

[0005] Therefore, the technical problem of the prior art is that it is urgent to propose a frequency detection method of a quartz crystal resonator in photoacoustic spectroscopy technology. Summary of the invention

[0006] The present application provides an acoustic-optical spectrum frequency detection method based on the Lorentzian linear function, which adopts the following technical solution:

[0007] A method for detecting frequency of an acoustic-optical spectrum based on a Lorentzian linear function, comprising:

[0008] Preliminary detection: providing a quartz crystal resonator, the quartz crystal resonator having a first pin and a second pin, the first pin is used for signal input, and the second pin is used for signal output;

[0009] The first pin inputs a sine wave signal, the frequency f of the sine wave signal is adjustable, and the amplitude A is constant; the second pin outputs a signal, and the amplitude is detected; the amplitude of the sine signal is kept constant, and the resonant frequency is obtained by continuously increasing or decreasing the frequency Δf of the input sine signal until the amplitude of the output signal of the second pin reaches Amax; and the current resonant frequency is recorded as fPrevious;

[0010] Repeat the above-mentioned actions to adjust the frequency f of the sine wave signal. When the frequency f of the sine wave signal is close to the resonant frequency fPrevious, the increment or decrement of Δf is reduced; and when it is far from the resonant frequency, the increment or decrement of Δf is increased;

[0011] Re-detection: Generate several groups of sine wave signals and superimpose them to obtain a mixed signal;

[0012] Inputting the mixed signal to the first pin;

[0013] Obtain the output signal of the second pin, and obtain the resonance frequency f0 by conditioning and collecting the output signal, analyzing the spectrum and fitting the Lorentz line shape;

[0014] The final resonant frequency is obtained based on fPrevious and f0.

[0015] Preferably, the "conditioning and acquisition of the output signal" includes: amplifying, filtering and calibrating the signal to improve the quality of the signal, increase the signal-to-noise ratio, and adapt it to subsequent data acquisition and processing systems.

[0016] Preferably, the "analyzing spectrum" means: converting the output signal into a frequency domain representation, observing the amplitude, power or phase of the signal at different frequencies, and performing Fourier transform on the signal to obtain a graph with amplitude and phase as the vertical axis and frequency as the horizontal axis.

[0017] Preferably, the spectrum intensity An at each frequency point (f+n·Δf) is recorded, wherein f is the frequency of the sinusoidal signal, Δf is the amount of increase or decrease in frequency, and n is an integer.

[0018] Preferably, the “fitting the Lorentz line shape to obtain the resonance frequency” includes: performing Lorentz line shape fitting on the spectrum intensity An, and determining the peak value f0 of the Lorentz line shape fitting curve.

[0019] Preferably, the method further includes: replacing the frequency f of the sinusoidal signal with the frequency f0 corresponding to the peak value of the fitting curve obtained in the previous test, and reducing the frequency increase or decrease Δf to 1 / 10 of that in the previous test, reacquiring the second pin output signal, and analyzing the spectrum and fitting the Lorentz line shape to obtain the resonant frequency through conditioning and collection of the output signal.

[0020] Preferably, the method further includes: replacing the frequency f of the sinusoidal signal with the frequency f0 corresponding to the peak value of the fitting curve obtained in the previous test, and reducing the frequency increase or decrease Δf to 1 / 20 of that in the previous test, reacquiring the second pin output signal, and analyzing the spectrum and fitting the Lorentz line shape to obtain the resonant frequency through conditioning and collection of the output signal.

[0021] Preferably, the "generating several groups of sinusoidal wave signals" includes: defining 10 groups of sinusoidal signals: sin(2πf1t+φ1), sin(2πf2t+φ2), ..., sin(2πf10t+φ10).

[0022] Preferably, the “adding sine wave signals and superimposing them to obtain a mixed signal” includes: adding 10 groups of independent sine wave signals to obtain a mixed signal: Σsin(2πfit+φi), wherein Σ represents the sum of i from 1 to 10.

[0023] In summary, the present application includes at least one of the following beneficial technical effects:

[0024] 1. While keeping the amplitude of the sine wave signal unchanged, start to continuously increase or decrease the frequency Δf of the input sine signal. The purpose of this step is to find the frequency point where the amplitude of the output signal of the second pin reaches the maximum (i.e., Amax), which is the resonant frequency of the quartz crystal resonator. Once the resonant frequency is found, it is recorded as fPrevious for subsequent use. In order to further improve the accuracy and efficiency of frequency detection, the above actions are repeated, but this time an intelligent strategy is adopted when adjusting the frequency f of the sine wave signal. Specifically, when the frequency f of the sine wave signal is close to the previously recorded resonant frequency fPrevious, the increase or decrease of Δf is reduced to search for the resonant point more carefully. When the frequency f is far away from the resonant frequency, the increase or decrease of Δf is increased to speed up the search. In this way, the efficiency of frequency detection can be improved while ensuring accuracy, thereby realizing fast and accurate detection of the resonant frequency of the quartz crystal resonator. This detection method has broad application prospects in acousto-optic spectroscopy technology, especially in situations where precise frequency control is required.

[0025] 2. This method can accurately determine the resonance point of the quartz crystal resonator by analyzing the spectrum and fitting the Lorentz line shape to obtain the resonant frequency. The Lorentz line shape is a mathematical model that describes the resonance phenomenon. By fitting the spectrum data of the output signal, the frequency point that best matches the Lorentz line shape can be found, which is the resonant frequency. This method has high accuracy and reliability and can accurately reflect the performance characteristics of the quartz crystal resonator. By introducing mixing signals and sophisticated signal processing and analysis methods, this detection method can more comprehensively evaluate the performance of the quartz crystal resonator, improve test efficiency, and accurately obtain the resonant frequency. This is of great significance for frequency control in acousto-optic spectroscopy technology and the application of quartz crystal resonators. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the detection method described in this application;

[0027] Figure 2 It is the Lorentz linear function fitting diagram of the detection method described in this application. DETAILED DESCRIPTION

[0028] The serial numbers assigned to the components herein, such as "first", "second", etc., are only used to distinguish the objects described and do not have any order or technical meaning. The "connection" and "coupling" mentioned in this application, unless otherwise specified, include direct and indirect connections (couplings). In the description of this application, it should be understood that the orientation or position relationship indicated by the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc. are based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to this application.

[0029] In the present application, unless otherwise clearly specified and limited, a first feature being “above” or “below” a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being “above”, “above”, and “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “below”, “below”, and “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0030] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods. It should be understood that the specific embodiments described here are only used to explain the present application and are not used to limit the present application.

[0031] Photoacoustic spectroscopy is an absorption spectroscopy technique based on the photoacoustic effect. It uses the light energy absorbed by the target gas sample to detect the presence and concentration of the gas. This technology has the characteristics of high sensitivity, small size, good long-term stability and excellent linearity, so it has been widely used in many fields such as environmental testing, industrial control, and medical diagnosis.

[0032] In photoacoustic spectroscopy, tunable semiconductor lasers are one of the key components. Tunable semiconductor lasers are laser devices whose gain medium is based on semiconductor materials and whose operating wavelength can be changed within a certain wavelength range. The characteristics of this laser make it widely used in many fields, such as optical communications, sensing, and precision measurement. The tunability of tunable semiconductor lasers is mainly based on specific control mechanisms, such as mechanisms based on current control technology. By changing the current of the fiber grating and phase control parts at different positions in the laser, the relative refractive index of the fiber grating can be changed, thereby generating different spectra. By superimposing the spectra generated by fiber gratings in different regions, lasers with specific wavelengths can be selected for output. In addition, there are many types of tunable semiconductor lasers, such as SGDBR (sampled grating distributed Bragg reflector) type semiconductor lasers and tunable external cavity semiconductor lasers (ECDL). SGDBR lasers have a wide wavelength tuning range and a fast wavelength switching speed. They are easy to integrate with other optoelectronic devices and are one of the ideal light sources for future dynamic intelligent optical networks. ECDL introduces optical feedback elements, such as diffraction gratings, to screen the output frequency of the laser and narrow the line width, which can be used in the field of quantum optics for precise frequency stabilization control, such as cold atom interference experiments. Due to its unique tunable characteristics, tunable semiconductor lasers have important applications in many fields and provide strong support for the development of modern optical technology.

[0033] By applying a low-frequency scanning signal and a high-frequency modulation signal to the laser injection current, the output wavelength and modulation frequency of the laser can be controlled. Among them, the frequency of the high-frequency modulation signal is set to half the resonance frequency of the quartz crystal resonator. When the laser beam passes through the target gas and is focused on the quartz crystal resonator, if the absorption band of the target gas molecules is within the tuning range of the laser, the quartz crystal resonator will generate a resonance signal.

[0034] Quartz crystal resonators play an important role in signal detection in photoacoustic spectroscopy. However, their resonant frequency is affected by parameters such as ambient temperature, air pressure, and humidity, so their resonant frequency needs to be calibrated frequently during the measurement process. The traditional frequency calibration method is to input a sinusoidal input signal with a frequency of f into one pin of the quartz crystal resonator and measure the output signal from another pin. While keeping the amplitude of the sinusoidal signal unchanged, the frequency of the input sinusoidal signal is continuously changed so that it continuously increases or decreases by a fixed frequency interval Δf, and the amplitude of the output sinusoidal signal is recorded at the same time. When the amplitude of the output sinusoidal signal reaches a maximum at a certain frequency, this frequency is considered to be the resonant frequency of the quartz crystal resonator.

[0035] This traditional frequency calibration method, while effective, may have certain limitations. For example, it may take a long time to scan the entire frequency range and find the resonant frequency, especially when the frequency interval Δf is large. In addition, changes in environmental factors may cause the resonant frequency to drift, so regular recalibration is required.

[0036] In order to improve the calibration efficiency and accuracy, more advanced calibration methods can be considered. For example, automated control systems and algorithms can be used to quickly scan the frequency range and find the resonant frequency. In addition, the influence of environmental factors on the resonant frequency can also be studied to make more accurate compensation and correction during the calibration process.

[0037] The present application provides an acoustic-optical spectrum frequency detection method based on a Lorentzian linear function, which is used for frequency calibration of a quartz crystal resonator; this acoustic-optical spectrum frequency detection method based on a Lorentzian linear function is a technology for accurately measuring the resonant frequency of a quartz crystal resonator. A quartz crystal resonator is a commonly used electronic component, and its resonant frequency has a high degree of stability and accuracy, so it has a wide range of applications in the fields of communications, electronic measurement, etc.

[0038] like Figure 1 As shown, the method includes: providing a quartz crystal resonator: the quartz crystal resonator has two pins, namely a first pin and a second pin. The first pin is used for inputting a signal, and the second pin is used for outputting a signal.

[0039] Input a sine wave signal and detect the output: Input a sine wave signal to the quartz crystal resonator through the first pin. The frequency of this sine wave signal can be adjusted, but its amplitude remains constant. At the same time, obtain the output signal from the second pin and detect its amplitude.

[0040] Find the resonant frequency: While keeping the amplitude of the sine wave signal unchanged, gradually adjust its frequency. This adjustment is achieved by continuously increasing or decreasing a small frequency value Δf. When the amplitude of the output signal of the second pin reaches the maximum value Amax, the frequency of the input sine wave signal at this time is the resonant frequency of the quartz crystal resonator. After finding the resonant frequency, record this value as the reference frequency fPrevious for the next search.

[0041] Fine-tune the frequency search interval: In order to find the resonant frequency more accurately, the method adopts a variable interval search strategy. When the frequency of the input sine wave signal is close to the last found resonant frequency fPrevious, the frequency adjustment interval Δf is reduced. This is done to perform a more precise search close to the resonance point to avoid missing the true resonant frequency. On the contrary, when the frequency of the input sine wave signal is far away from the resonant frequency, the frequency adjustment interval Δf is increased. This can speed up the search and quickly locate the approximate range of the resonant frequency.

[0042] The advantage of the present application is that it combines the strategies of coarse adjustment and fine adjustment, which can not only quickly locate the approximate position of the resonant frequency within a wide frequency range, but also make fine adjustments close to the resonance point, thereby ensuring that the accurate resonant frequency is found. In addition, due to the use of a quartz crystal resonator, this method also has the characteristics of high stability and high precision. The resonant frequency of a quartz crystal resonator is less affected by environmental factors such as temperature and pressure, so its measurement results have high reliability and repeatability. The acousto-optic spectroscopy frequency detection method based on the Lorentz linear function is an efficient, accurate and reliable method for measuring the resonant frequency of a quartz crystal resonator, which is of great significance for applications requiring high-precision frequency measurement.

[0043] Furthermore, the present application further optimizes and expands the above detection method, introduces the concept of mixed frequency signal, and realizes more accurate measurement of the resonant frequency of the quartz crystal resonator by fine processing and analysis of the output signal. This acousto-optic spectrum frequency detection method based on the Lorentz linear function realizes more accurate measurement of the resonant frequency of the quartz crystal resonator by introducing mixed frequency signal and fine signal processing and analysis method. It improves the efficiency and accuracy of the test, which is of great significance for applications requiring high-precision frequency measurement.

[0044] In this embodiment, Figure 1 As shown in the figure, the acousto-optic spectrum frequency detection method based on the Lorentz linear function achieves a more accurate measurement of the resonant frequency of the quartz crystal resonator by introducing the concept of mixing signals. First, several groups of sine wave signals are generated and superimposed to obtain a mixing signal. The mixing signal is composed of multiple sine wave signals of different frequencies, and it contains multiple frequency components. The purpose of this is to more comprehensively stimulate the resonance characteristics of the quartz crystal resonator, thereby obtaining richer frequency response data.

[0045] The mixing signal is input to the first pin of the quartz crystal resonator. Since the mixing signal contains multiple frequency components, it can excite the vibration of the quartz crystal resonator at different frequencies. The output signal is obtained from the second pin of the quartz crystal resonator. This output signal is the response of the quartz crystal resonator to the mixing signal, which contains information about the resonant frequency.

[0046] In one embodiment, 10 groups of sinusoidal signals are defined: sin(2πf1t+φ1), sin(2πf2t+φ2), ..., sin(2πf10t+φ10); the 10 groups of independent sinusoidal signals are superimposed, and the obtained mixed signal is: Σsin(2πfit+φi), where Σ represents the sum of i from 1 to 10.

[0047] In order to extract useful information from the output signal, the output signal needs to be conditioned and collected. The conditioning process includes amplification, filtering and calibration of the signal to improve the quality of the signal and increase the signal-to-noise ratio. The acquisition process converts the conditioned signal into a digital signal for subsequent data processing and analysis.

[0048] After obtaining the output signal after conditioning and acquisition, the next step is spectrum analysis. Spectrum analysis is the process of converting the signal from the time domain to the frequency domain. Through methods such as Fourier transform, the amplitude, power or phase of the signal at different frequencies can be obtained. The distribution of the signal in the frequency domain can be observed, so as to analyze the position of the resonant frequency. This step includes amplification, filtering, and calibration of the signal, aiming to improve the quality of the signal, increase the signal-to-noise ratio, and adapt it to the subsequent data acquisition and processing system. Amplification of the signal: Since the signal output by the quartz crystal resonator may be very weak, the signal must first be amplified to a level that can be processed by the subsequent processing circuit. The selection of the amplifier should be based on the characteristics of the signal and the noise level to ensure that too much noise is not introduced while amplifying the signal. Filtering of the signal: The filtering operation is to remove the noise and interference components in the signal and make the useful signal components more prominent. The filter can be designed according to the frequency characteristics of the signal, selectively retaining the signal within the target frequency range and suppressing the noise of other frequencies. Calibration of the signal: The calibration process is to eliminate the offset and distortion in the signal and ensure the accuracy of the signal. This includes operations such as signal baseline adjustment and amplitude correction so that the processed signal can truly reflect the response of the quartz crystal resonator.

[0049] After the above conditioning steps, the signal quality has been significantly improved, and the signal-to-noise ratio has also been improved. Such a signal is more suitable for subsequent data acquisition and processing systems. The data acquisition system can convert the conditioned signal into a digital format to facilitate subsequent digital signal processing and analysis. By amplifying, filtering, and calibrating the output signal, the signal quality can be effectively improved, the signal-to-noise ratio can be increased, and high-quality signals can be provided for subsequent data acquisition and processing. This is crucial for accurately measuring the resonant frequency of the quartz crystal resonator, and helps to improve the accuracy and reliability of the measurement.

[0050] Analyzing the spectrum is a core step in this method. Figure 2 As shown in the figure, the main purpose of analyzing the spectrum is to convert the output signal from the time domain to the frequency domain in order to observe the characteristics of the signal at different frequencies and determine the resonant frequency. First, the output signal is converted to a frequency domain representation. This is achieved through Fourier transform. Fourier transform is a method of converting a time domain function into a frequency domain function, which can decompose a complex signal into a combination of a series of sine waves and cosine waves. Through Fourier transform, the distribution of the signal in the frequency domain can be obtained. In the frequency domain representation, the amplitude, power or phase of the signal at different frequencies can be observed. This information is crucial for analyzing the frequency characteristics of the signal. The amplitude represents the strength of the signal at different frequencies, the power reflects the energy distribution of the signal at different frequencies, and the phase describes the relative position of the signal at different frequencies. By Fourier transforming the signal, a graph with amplitude and phase as the vertical axis and frequency as the horizontal axis can be obtained, which is called a spectrum graph. This graph intuitively shows the distribution of the signal in the frequency domain, so that the characteristics of the signal at different frequencies can be clearly seen. In the spectrum graph, the peaks and valleys of the signal can be observed, which correspond to the resonant frequencies and non-resonant frequencies in the signal. By identifying and analyzing these peaks and valleys, the resonant frequency of the quartz crystal resonator can be determined.

[0051] like Figure 2 As shown, the spectrum intensity An at each frequency point (f+n·Δf) is recorded, where f is the frequency of the sinusoidal signal, Δf is the increase or decrease in frequency, and n is an integer. After obtaining the spectrum diagram of the signal, it is necessary to further analyze these data to find the resonant frequency. To this end, the spectrum intensity An at each frequency point (f+n·Δf) is recorded. Here f is the initial sinusoidal signal frequency, Δf is the increase or decrease in frequency, and n is an integer representing the number of steps taken when gradually increasing or decreasing the frequency at intervals of Δf starting from the initial frequency. By recording the spectrum intensity at these frequency points, a data set of frequency and spectrum intensity can be obtained. This data set will be used for subsequent Lorentz line shape fitting to help determine the resonant frequency more accurately.

[0052] Finally, the resonant frequency is accurately determined by using Lorentz line shape fitting. The Lorentz line shape is a mathematical model that describes the shape of the spectrum line of the resonance phenomenon. By fitting the spectrum intensity data of the output signal, the peak value of the Lorentz line shape fitting curve can be determined, and the frequency corresponding to the peak value is the resonant frequency.

[0053] Specifically, after obtaining the spectrum intensity An at each frequency point, the next step is to perform Lorentz line fitting. The Lorentz line shape is a mathematical model that describes the shape of the spectrum line of the resonance phenomenon, which can well describe the spectrum characteristics of the quartz crystal resonator when it resonates. By performing Lorentz line fitting on the spectrum intensity An, a fitting curve can be obtained. This fitting curve will be as close as possible to the actual spectrum intensity distribution. The peak value f0 of the fitting curve is the resonance frequency to be found. Determining the peak value of the Lorentz line fitting curve is a mathematical optimization problem, which can be achieved by mathematical methods such as the least squares method. Once the peak value f0 of the fitting curve is found, it can be considered that this frequency is the resonance frequency of the quartz crystal resonator.

[0054] Furthermore, the Lorentzian lineshape is used to describe the shape of the spectrum in the resonance phenomenon, especially when considering the damping or linewidth effect. In the frequency detection of the acoustic-optical spectrum, after the spectrum analysis of the response signal of the quartz tuning fork, the spectrum intensity data obtained can be fitted with the Lorentzian lineshape to extract the resonance frequency.

[0055] The specific steps are as follows:

[0056] Spectrum intensity data acquisition: First, the spectrum intensity An corresponding to different frequency components is obtained by performing spectrum analysis on the output signal of the quartz tuning fork. These intensity data are measured at a series of discrete frequency points.

[0057] Lorentz line shape formula: The Lorentz line shape can be expressed in the following form:

[0058]

[0059] Where I(f) is the intensity at frequency (f), I0 is the maximum intensity, f0 is the resonant frequency (i.e., the peak of the Lorentzian line shape), and γ is the damping coefficient related to the line width. In acousto-optic spectroscopy frequency detection, it is necessary to measure the spectrum intensity An at a series of frequency points, where (n) is the index of the frequency point. These data are then fitted using the Lorentzian line shape function to find the optimal (I0), (f0), and (γ) values.

[0060] Fitting process: Use mathematical tools (such as the SciPy library in Python) to perform Lorentzian line fitting on the acquired spectrum intensity data An. This involves adjusting the three parameters I0, f0 and γ to minimize the error (such as mean square error) between the fitting curve and the original data. Determine the peak value of the Lorentzian line fitting curve: After the fitting is completed, the frequency f0 corresponding to the peak value of the Lorentzian line curve is the desired resonance frequency. This peak value can be obtained by directly reading the fitting parameters or by finding the maximum value point on the fitting curve.

[0061] Furthermore, the acoustic-optical spectrum frequency detection method based on the Lorentz linear function can be further optimized, which adopts the idea of ​​iteration to more accurately determine the resonant frequency: first, the frequency f of the sinusoidal signal is replaced by the frequency f0 corresponding to the peak of the fitting curve obtained in the last test. This means that it no longer starts from the initial sinusoidal signal frequency, but from the approximate value of the resonant frequency obtained in the last test. Doing so can narrow the search range and converge to the true resonant frequency more quickly. Secondly, the frequency increase or decrease amount Δf is reduced to 1 / 10 of the last test. By reducing Δf, the spectrum near the resonant frequency can be searched more carefully, thereby obtaining more accurate results. Then, the output signal of the second pin is reacquired, and the spectrum is analyzed by conditioning and collecting the output signal. This step is similar to the previous step, but because a more accurate starting frequency and a smaller frequency interval are used, the spectrum data obtained will be more accurate. Finally, the new spectrum data is fitted with a Lorentz linear shape to determine a more accurate resonant frequency. By iterating this process multiple times, the true resonant frequency can be gradually approached. The benefit of this iterative approach is that it can use the results of the previous test to optimize the parameters of the next test in each iteration, thereby quickly converging to the precise resonant frequency.

[0062] Furthermore, the frequency f of the sine signal is replaced with the frequency f0 corresponding to the peak of the fitting curve obtained in the previous test to narrow the search range. Then, the frequency increment or decrement Δf is reduced to 1 / 20 of the previous test. Compared with 1 / 10, a smaller interval is used here. This can further increase the precision of the search. Next, the output signal of the second pin is acquired again, and the spectrum is analyzed by conditioning and collecting the output signal. This step is the same as the previous step, but because a smaller Δf is used, the spectrum data obtained will be more precise. Finally, the new spectrum data is fitted with a Lorentz line shape to determine a more accurate resonant frequency. By iterating this process multiple times, the true resonant frequency can be gradually approached.

[0063] In summary, based on fPrevious obtained by the preliminary detection and f0 obtained by the re-detection, the final resonance frequency is obtained. In one embodiment, the average of fPrevious and f0 may be taken.

[0064] Beneficial effects:

[0065] 1. While keeping the amplitude of the sine wave signal unchanged, start to continuously increase or decrease the frequency Δf of the input sine signal. The purpose of this step is to find the frequency point where the amplitude of the output signal of the second pin reaches the maximum (i.e., Amax), which is the resonant frequency of the quartz crystal resonator. Once the resonant frequency is found, it is recorded as fPrevious for subsequent use. In order to further improve the accuracy and efficiency of frequency detection, the above actions are repeated, but this time an intelligent strategy is adopted when adjusting the frequency f of the sine wave signal. Specifically, when the frequency f of the sine wave signal is close to the previously recorded resonant frequency fPrevious, the increase or decrease of Δf is reduced to search for the resonant point more carefully. When the frequency f is far away from the resonant frequency, the increase or decrease of Δf is increased to speed up the search. In this way, the efficiency of frequency detection can be improved while ensuring accuracy, thereby realizing fast and accurate detection of the resonant frequency of the quartz crystal resonator. This detection method has broad application prospects in acousto-optic spectroscopy technology, especially in situations where precise frequency control is required.

[0066] 2. This method can accurately determine the resonance point of the quartz crystal resonator by analyzing the spectrum and fitting the Lorentz line shape to obtain the resonant frequency. The Lorentz line shape is a mathematical model that describes the resonance phenomenon. By fitting the spectrum data of the output signal, the frequency point that best matches the Lorentz line shape can be found, which is the resonant frequency. This method has high accuracy and reliability and can accurately reflect the performance characteristics of the quartz crystal resonator. By introducing mixing signals and sophisticated signal processing and analysis methods, this detection method can more comprehensively evaluate the performance of the quartz crystal resonator, improve test efficiency, and accurately obtain the resonant frequency. This is of great significance for frequency control in acousto-optic spectroscopy technology and the application of quartz crystal resonators.

[0067] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0068] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A method for detecting frequency of an acoustic-optic spectrum based on a Lorentzian linear function, characterized in that: include: Preliminary detection: providing a quartz crystal resonator, the quartz crystal resonator having a first pin and a second pin, the first pin is used for signal input, and the second pin is used for signal output; The first pin inputs a sine wave signal, the frequency f of the sine wave signal is adjustable, and the amplitude A is constant; the second pin outputs a signal, and the amplitude is detected; the amplitude of the sine signal is kept constant, and the resonant frequency is obtained by continuously increasing or decreasing the frequency Δf of the input sine signal until the amplitude of the output signal of the second pin reaches Amax; and the current resonant frequency is recorded as fPrevious; Repeat the above-mentioned actions to adjust the frequency f of the sine wave signal. When the frequency f of the sine wave signal is close to the resonant frequency fPrevious, the increment or decrement of Δf is reduced; and when it is far from the resonant frequency, the increment or decrement of Δf is increased; Re-detection: Generate several groups of sine wave signals and superimpose them to obtain a mixed signal; Inputting the mixed signal to the first pin; Obtain the output signal of the second pin, and obtain the resonance frequency f0 by conditioning and collecting the output signal, analyzing the spectrum and fitting the Lorentz line shape; The final resonant frequency is obtained based on fPrevious and f0.

2. The method for detecting frequency of an acoustic-optic spectrum based on a Lorentzian linear function according to claim 1, characterized in that: The "conditioning and acquisition of the output signal" includes: amplifying, filtering, and calibrating the signal to improve the quality of the signal, increase the signal-to-noise ratio, and make it suitable for subsequent data acquisition and processing systems.

3. The method for detecting frequency of an acoustic-optic spectrum based on a Lorentzian linear function according to claim 1, characterized in that: The "analyzing spectrum" means: converting the output signal into a frequency domain representation, observing the amplitude, power or phase of the signal at different frequencies, and performing Fourier transform on the signal to obtain a graph with amplitude and phase as the vertical axis and frequency as the horizontal axis.

4. The method for detecting frequency of an acoustic-optic spectrum based on a Lorentzian linear function according to claim 3, characterized in that: The spectrum intensity An at each frequency point (f+n·Δf) is recorded, where f is the frequency of the sinusoidal signal, Δf is the amount of increase or decrease in frequency, and n is an integer.

5. The method for detecting frequency of an acoustic-optic spectrum based on a Lorentzian linear function according to claim 4, characterized in that: The “fitting the Lorentz line shape to obtain the resonance frequency” includes: performing Lorentz line shape fitting on the spectrum intensity An, and determining the peak value f0 of the Lorentz line shape fitting curve.

6. The method for detecting frequency of an acoustic-optic spectrum based on a Lorentzian linear function according to claim 5, characterized in that: Also includes: The frequency f of the sinusoidal signal is replaced with the frequency f0 corresponding to the peak value of the fitting curve obtained in the previous test, and the frequency increase or decrease Δf is reduced to 1 / 10 of that in the previous test, and the second pin output signal is obtained again. By conditioning and collecting the output signal, the spectrum is analyzed and the Lorentz line shape is fitted to obtain the resonant frequency.

7. The method for detecting frequency of an acoustic-optic spectrum based on a Lorentzian linear function according to claim 5, characterized in that: Also includes: The frequency f of the sinusoidal signal is replaced with the frequency f0 corresponding to the peak value of the fitting curve obtained in the previous test, and the frequency increase or decrease Δf is reduced to 1 / 20 of that in the previous test, and the second pin output signal is obtained again. By conditioning and collecting the output signal, the spectrum is analyzed and the Lorentz line shape is fitted to obtain the resonant frequency.

8. The method for detecting frequency of an acoustic-optic spectrum based on a Lorentzian linear function according to claim 1, characterized in that: The “generating several groups of sinusoidal wave signals” includes: defining 10 groups of sinusoidal signals: sin(2πf1t+φ1), sin(2πf2t+φ2), ..., sin(2πf10t+φ10).

9. The method for detecting frequency of an acoustic-optic spectrum based on a Lorentzian linear function according to claim 8, characterized in that: The “adding sine wave signals and obtaining a mixed signal” includes: adding 10 groups of independent sine wave signals, and obtaining a mixed signal: Σsin(2πfit+φi), wherein Σ represents the sum of i from 1 to 10.

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