Thin film thickness measuring method, device and equipment based on ultrasonic time domain signal

Abstract

The invention discloses a thin film thickness measurement method, device and equipment based on an ultrasonic time domain signal, and relates to the technical field of liquid film thickness ultrasonic measurement. The method comprises the following steps: interpolating an obtained solid-liquid-air three-layer medium interlayer film echo signal, and recording an intersection position of a threshold voltage and the interpolated solid-liquid echo signal; moving the interpolated solid-liquid-air echo signal by taking the interpolated solid-liquid echo signal as a reference, so that the two echo signals are aligned; subtracting the solid-liquid echo signal after interpolation from the solid-liquid-air echo signal after alignment to obtain a liquid-air echo signal; and performing cross-correlation operation on the interpolated solid-liquid echo signal and the interpolated liquid-air echo signal to determine the thickness of the thin film. The problem that the reference signal and the echo signal are difficult to synchronize can be solved, and the thickness of the ultra-thin liquid film in the industry can be measured.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrasonic measurement of liquid film thickness, and in particular to a method, device and equipment for measuring film thickness based on ultrasonic time domain signals. Background Art

[0002] Thin film thickness measurement technology has important applications in many fields. For example, in the microelectronics manufacturing industry, thin films are widely used in integrated circuits, display devices, and sensors. Measuring the thickness of thin films is crucial to ensuring the stability and reliability of device performance. In the field of optical coatings, thin films are widely used in optical components, automobiles, aerospace, and construction. The thickness of thin film coatings directly affects the corrosion resistance, aesthetics, and functional performance of the coatings. Thin film thickness measurement technology can ensure the quality and performance of the coatings. In materials science research, thin films are often used to prepare functional materials and study the properties of new materials. Measuring film thickness is one of the important means to understand and optimize material properties. In surface engineering and nano-processing, precise thickness control of thin films is the key to achieving specific surface properties and functions. Thin film thickness measurement technology plays an important role in achieving fine control of surface properties. In the field of multiphase flow fluid detection research, liquid film thickness is one of the important parameters of flowing fluids. Its accurate measurement is of great significance for studying its cross-sectional content and pressure drop, as well as flow mechanism and development evolution law.

[0003] The measurement methods of liquid film thickness include optical method, electrical method, radiation method and ultrasonic method. Compared with many measurement methods, the ultrasonic measurement method has the advantages of strong penetration, long propagation distance, and small propagation energy loss, and can be applied to many industrial measurement scenarios. At present, the commonly used ultrasonic thickness measurement methods are ultrasonic pulse echo method, ultrasonic thin film resonance method and ultrasonic thin film resonance main frequency method. Among them, the ultrasonic pulse echo method is suitable for the measurement of thicker liquid film thickness. The ultrasonic thin film resonance method and ultrasonic thin film resonance main frequency method are affected by the center frequency and bandwidth range of the ultrasonic transducer, which limits their measurement lower limit. For micron-level film thickness, the existing ultrasonic methods cannot meet its measurement accuracy. In addition, when ultrasonically measuring the thickness of thin liquid films, the echo signals on both sides of the liquid film will be superimposed. Researchers usually use reference signals to obtain the film thickness, but are limited by the clock and sampling frequency performance of the acquisition device. Under normal circumstances, it is difficult for the reference signal and the echo signal to achieve synchronization, resulting in large errors in the liquid film thickness results. Summary of the invention

[0004] The purpose of the present invention is to provide a thin film thickness measurement method, device and equipment based on ultrasonic time domain signals, which can solve the problem of difficulty in synchronizing the reference signal and the echo signal and realize the measurement of the thickness of extremely thin liquid films in industry.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A film thickness measurement method based on ultrasonic time domain signals, comprising:

[0007] The film echo signal is obtained by using the constructed experimental device; the film echo signal includes a solid-liquid echo signal and a solid-liquid-air echo signal; the experimental device includes a solid medium, an ultrasonic transducer, a transceiver circuit, a data acquisition module and a computer connected in sequence; a liquid medium is also attached to the solid medium, and an air medium is also attached to the liquid medium;

[0008] interpolating the film echo signal, comparing the interpolated film echo signal with a preset threshold voltage, and recording an intersection position of the threshold voltage and the interpolated solid-liquid echo signal;

[0009] Taking the interpolated solid-liquid echo signal as a reference, moving the interpolated solid-liquid-air echo signal according to the intersection position, calculating the phase difference data points of the two echo signals after the movement, and aligning the two echo signals according to the phase difference data points;

[0010] Subtracting the interpolated solid-liquid echo signal from the aligned solid-liquid-air echo signal to obtain a liquid-air echo signal;

[0011] The interpolated solid-liquid echo signal and liquid-air echo signal are cross-correlated to determine the film thickness.

[0012] Optionally, the step of obtaining the film echo signal by using the constructed experimental device specifically includes:

[0013] The transceiver circuit is used to simultaneously transmit an excitation signal and a trigger signal; the excitation signal is used to excite the ultrasonic transducer to work; the trigger signal is used to trigger the data acquisition module to work;

[0014] The ultrasonic transducer is used to perform acquisition work to obtain an original echo signal, and the original echo signal is converted into an electrical signal by the transceiver circuit, and then a thin film echo signal is obtained after amplification and filtering, and the thin film echo signal is transmitted to the data acquisition module and the computer in sequence.

[0015] Optionally, interpolating the film echo signal, comparing the interpolated film echo signal with a preset threshold voltage, and recording an intersection position of the threshold voltage and the interpolated solid-liquid echo signal specifically includes:

[0016] Set the solid-liquid echo signal before interpolation to R0(n), the solid-liquid-air echo signal before interpolation to E0(n), and the threshold voltage volt;

[0017] Using the cubic spline interpolation method, x data points are inserted between every two points of the two echo signals to obtain the interpolated solid-liquid echo signal and the interpolated solid-liquid-air echo signal, which are recorded as R1(n) and E1(n) respectively;

[0018] The position where the threshold voltage volt and the interpolated solid-liquid echo signal R1(n) intersect is recorded as M.

[0019] Optionally, the process of aligning the two echo signals is specifically as follows:

[0020] Taking the interpolated solid-liquid echo signal R1(n) as the reference, the interpolated solid-liquid-air echo signal E1(n) is moved forward and backward by 10x data points respectively. When one data point is moved, the first M data sequences of R1(n) and E1(n) are subtracted, the absolute values ​​are taken and summed, and the values ​​are stored in the sum array. After the movement is completed, there are (20x+1) values ​​in the sum array. The position corresponding to the minimum value in the sum array is determined to obtain the data point I of the difference between R1(n) and E1(n), and E1(n) is moved again by I data points to align with R1(n). The aligned E1(n) is recorded as E2(n).

[0021] Optionally, performing a cross-correlation operation on the interpolated solid-liquid echo signal and the liquid-air echo signal to determine the film thickness specifically includes:

[0022] The interpolated solid-liquid echo signal R1(n) and the liquid-air echo signal D(n) obtained by subtraction operation are cross-correlated to obtain a cross-correlation sequence. When the cross-correlation sequence reaches a maximum value, the correlation between the interpolated solid-liquid echo signal R1(n) and the liquid-air echo signal D(n) is the largest. The film thickness is determined according to the moving step size and thickness calculation formula at this time; the thickness calculation formula is:

[0023]

[0024] Among them, h is the film thickness, c is the ultrasonic propagation velocity in the liquid, f is the sampling frequency of the data acquisition module, and l0 is the moving step size.

[0025] The present invention also provides a film thickness measuring device based on ultrasonic time domain signals, comprising: a solid medium, an ultrasonic transducer, a transceiver circuit, a data acquisition module and a computer connected in sequence; a liquid medium is also attached to the solid medium, and there is an air medium outside the liquid medium.

[0026] The present invention also provides an electronic device, including a memory and a processor, wherein the memory is used to store a computer program, and the processor runs the computer program to enable the electronic device to perform the above-mentioned film thickness measurement method based on ultrasonic time domain signals.

[0027] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0028] The present invention discloses a film thickness measurement method, device and equipment based on ultrasonic time domain signals, the method comprising obtaining a film echo signal by using a constructed experimental device; interpolating the film echo signal, and comparing the interpolated film echo signal with a preset threshold voltage, recording the intersection position of the threshold voltage and the interpolated solid-liquid echo signal; taking the interpolated solid-liquid echo signal as a reference, moving the interpolated solid-liquid-air echo signal according to the intersection position, calculating the phase difference data points of the two echo signals after the movement, and aligning the two echo signals according to the phase difference data points; subtracting the interpolated solid-liquid echo signal from the aligned solid-liquid-air echo signal to obtain a liquid-air echo signal; performing cross-correlation operation on the interpolated solid-liquid echo signal and the liquid-air echo signal to determine the film thickness. The present invention can solve the problem that the reference signal and the echo signal are difficult to synchronize, and realize the measurement of the thickness of extremely thin liquid films in industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0030] Figure 1 It is a schematic flow chart of a method for measuring film thickness based on ultrasonic time domain signals of the present invention;

[0031] Figure 2 FIG. 1 is a diagram of an experimental device in this embodiment;

[0032] Figure 3 The original solid-liquid and solid-liquid-air echo signal diagrams of this embodiment;

[0033] Figure 4 Schematic diagram of the interpolated solid-liquid echo signal and the interpolated and aligned solid-liquid-air echo signal in this embodiment;

[0034] Figure 5 Schematic diagram of solid-liquid echo signal and liquid-air echo signal after interpolation in this embodiment;

[0035] Figure 6 : is the cross-correlation diagram of the solid-liquid echo signal and the liquid-air echo signal after interpolation in this embodiment. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] The purpose of the present invention is to provide a thin film thickness measurement method, device and equipment based on ultrasonic time domain signals, which can solve the problem of difficulty in synchronizing the reference signal and the echo signal and realize the measurement of the thickness of extremely thin liquid films in industry.

[0038] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] like Figure 1-Figure 2 As shown, the present invention provides a film thickness measurement method based on ultrasonic time domain signals, comprising:

[0040] Step 100: Obtain a thin film echo signal using the constructed experimental device; the thin film echo signal includes a solid-liquid echo signal and a solid-liquid-air echo signal; the experimental device includes a solid medium, an ultrasonic transducer, a transceiver circuit, a data acquisition module and a computer connected in sequence; a liquid medium is also attached to the solid medium, and there is an air medium outside the liquid medium.

[0041] Step 200: interpolating the film echo signal, comparing the interpolated film echo signal with a preset threshold voltage, and recording the intersection position of the threshold voltage and the interpolated solid-liquid echo signal.

[0042] Step 300: Taking the interpolated solid-liquid echo signal as a reference, the interpolated solid-liquid-air echo signal is moved according to the intersection position, the phase difference data points of the two echo signals after the movement are calculated, and the two echo signals are aligned according to the phase difference data points.

[0043] Step 400: subtract the interpolated solid-liquid echo signal from the aligned solid-liquid-air echo signal to obtain a liquid-air echo signal.

[0044] Step 500: performing cross-correlation operation on the interpolated solid-liquid echo signal and the liquid-air echo signal to determine the film thickness.

[0045] As a specific implementation method, the above steps are described in more detail.

[0046] Step 100: Build an experimental device, including an ultrasonic transducer, a solid, a liquid attached to the solid, surrounding air, a transceiver circuit, a data acquisition module, and a computer. The solid is the first layer of medium, the liquid attached to the solid is the second layer of medium, and the air above the liquid is the third layer of medium. The ultrasonic transducer is tightly attached to the bottom of the solid through a coupling agent, and the transceiver circuit is connected to the ultrasonic transducer and the data acquisition module, which simultaneously transmits an excitation signal and a trigger signal. The excitation signal is used to excite the ultrasonic transducer to work, and the trigger signal is used to trigger the data acquisition module to start data acquisition. The ultrasonic transducer experimental sampling obtains the original solid-liquid echo signal R0(n) and the original solid-liquid-air echo signal E0(n), which are converted into electrical signals by the transceiver circuit and transmitted to the data acquisition module after amplification and filtering, and finally saved to the computer for data processing.

[0047] Step 200: For the original solid-liquid echo signal R0(n) and the original solid-liquid-air echo signal E0(n) obtained in step 100, use the cubic spline interpolation method to insert x data points between every two points of the two echo signals to obtain the interpolated solid-liquid echo signal and solid-liquid-air echo signal, which are respectively recorded as R1(n) and E1(n). Set a threshold voltage volt to determine whether the echo signal has been reached, and the position where the threshold voltage volt intersects with the interpolated solid-liquid echo signal R1(n) is recorded as M.

[0048] Step 300: Further, based on R1(n), E1(n) is moved forward and backward by 10x data points respectively. Each time a data point is moved, the first M data sequences of R1(n) and E1(n) are subtracted and the absolute values ​​are taken and the sum is stored in the sum array (as shown in formula (1)). After the movement, there are (20x+1) values ​​in sum. The position corresponding to the minimum value in the sum array is determined, and the position is the data point I where R1(n) and E1(n) differ. E1(n) is moved by I data points to align with R1(n), and the aligned E1(n) is recorded as E2(n).

[0049]

[0050] Step 400: Subtract R1(n) and E2(n) obtained in step 300 to obtain a liquid-air echo signal, i.e., a subtraction signal D(n), as shown in formula (2).

[0051] D(n)=E2(n)-R1(n) (2)

[0052] Step 500: Further, the interpolated solid-liquid echo signal R1(n) and the liquid-air echo signal D(n) are cross-correlated, as shown in equation (3).

[0053]

[0054] In the formula, C DR (l) represents the cross-correlation sequence, N is the sequence length, and l represents the moving step size.

[0055] When C DR When (l) reaches the maximum value, the correlation between R1(n) and D(n) is the largest, and the moving step at this time is recorded as l0. Then the film thickness of the liquid layer is shown in formula (4).

[0056]

[0057] Where c is the ultrasonic propagation velocity in the liquid, and f is the sampling frequency of the data acquisition module.

[0058] The measurement lower limit of the ultrasonic echo signal alignment subtraction method is shown in formula (5).

[0059]

[0060] Based on the above specific processing process, the following embodiment is provided.

[0061] like Figure 1 , build an experimental device, including an ultrasonic transducer, a solid, a liquid attached to the solid, the surrounding air, a transceiver circuit, a data acquisition module, and a computer. In the experiment, the solid is a round tube made of organic glass with a thickness of 10mm and an inner diameter of 50mm. An ultrasonic transducer is arranged on the top of the round tube. The ultrasonic transducer uses an ultrasonic piezoelectric transducer with a center frequency of 5MHz and a chip size of 6mm to transmit and receive signals. The transceiver circuit simultaneously transmits an excitation signal and a trigger signal. The excitation signal is used to stimulate the ultrasonic transducer to work, and the trigger signal is used to trigger the data acquisition module to start data acquisition. The ultrasonic transducer experimental sampling obtains the original solid-liquid echo signal R0(n) and the solid-liquid-air echo signal E0(n), which are converted into electrical signals by the transceiver circuit and transmitted to the data acquisition module after amplification and filtering, and finally saved on the computer for data processing. The sampling frequency f of the data acquisition module is set to 80MHz, and the sampling time is 60s. The specific experimental measurement process is as follows:

[0062] (1) Measuring the original solid-liquid echo signal R0(n): Fill the circular tube with water and use Figure 2The experimental setup shown collects one original solid-liquid echo signal R0(n).

[0063] (2) Measuring the original solid-liquid-air echo signal E0(n): Based on the capabilities of the laboratory gas-liquid two-phase flow experimental device and the measurement range of film thickness, the gas phase apparent velocity at the gas-liquid two-phase flow operating point is set to 15m / s, 20m / s, 25m / s, and 30m / s, the liquid phase apparent velocity is set to 0.015m / s, 0.035m / s, 0.06m / s, 0.1m / s, and 0.2m / s, and the system pressure is set to 0.1MPa, 0.3MPa, 0.5MPa, and 0.7MPa. The repetition frequency of the excitation signal and trigger signal of the transceiver circuit is set to 100Hz, the acquisition time of the data acquisition module is 60s, and a total of 6000 original solid-liquid-air echo signals E0(n) are collected.

[0064] The following takes an original solid-liquid echo signal R0(n) and an original solid-liquid-air echo signal E0(n) as an example (e.g. Figure 3 As shown), the method is introduced. As can be seen from the figure, although the excitation signal and the trigger signal are generated at the same time, due to the high center frequency of the ultrasonic transducer and the limited sampling frequency of the data acquisition module, the two signals R0(n) and E0(n) are not completely aligned at the start-up time. Before aligning the two signals, the cubic spline interpolation method is first used to insert x=10 data points between every two points of the two signals to obtain the interpolated solid-liquid echo signal R1(n) and the solid-liquid-air echo signal E1(n). On this basis, the threshold voltage volt=50mV is set to determine whether the echo signal has arrived, that is, the ultrasonic transducer start-up time. The position where the threshold voltage volt and the interpolated solid-liquid echo signal R1(n) intersect is recorded as M.

[0065] Furthermore, taking R1(n) as the reference, E1(n) is moved forward and backward by (10x=100) data points respectively. Each time a data point is moved, the first M data sequences of R1(n) and E1(n) are subtracted and the absolute values ​​are taken and the sum is stored in the sum array (as shown in formula (1)). After the movement, there are (20x+1=201) values ​​in sum. Determine the position corresponding to the minimum value in the sum array, which is the data point I where R1(n) and E1(n) differ. Move E1(n) by I data points to align it with R1(n). The aligned E1(n) is recorded as E2(n), as shown in Figure 4 shown.

[0066] Step 4: Subtract R1(n) and E2(n) obtained in step 3 (as shown in formula (2)) to obtain the liquid-air echo signal, i.e., the subtraction signal D(n), as shown in Figure 5shown.

[0067] Step 5: Further, the interpolated solid-liquid echo signal R1(n) and the liquid-air echo signal D(n) are cross-correlated, as shown in formula (3). The cross-correlation result is as follows: Figure 6 shown.

[0068] When C DR When (l) reaches the maximum value, the correlation between R1(n) and D(n) is the largest, and the moving step at this time is recorded as l0. Then the film thickness of the liquid layer is shown in formula (4).

[0069] The data acquisition module collects 60 seconds of data, and collects 6000 original solid-liquid-air echo signals E0(n). Then the liquid film thickness at the top of the gas-liquid two-phase flow pipeline is the average value of the liquid film thickness obtained by the 6000 original solid-liquid-air echo signals E0(n). The lower limit of the measurement of the ultrasonic echo signal alignment subtraction method is shown in formula (5).

[0070] The sampling frequency of this experiment is f=80MHz. The propagation speed of ultrasound in water at normal temperature and pressure is 1480m / s, and the lower limit of the measurable film thickness is 9.25μm.

[0071] As an evaluation of the effect of the method in this embodiment, in order to verify the accuracy and reliability of the ultrasonic echo signal alignment subtraction method provided by the present invention in measuring the film thickness, a dynamic measurement experiment of the top liquid film thickness of a horizontal gas-liquid two-phase flow was carried out. The pipe is made of plexiglass, the liquid is water, and the gas is air. Affected by gravity, the top liquid film thickness in the horizontal pipe gas-liquid two-phase flow is the thinnest, so the ultrasonic transducer is installed on the top of the pipe. Experimental gas phase apparent velocity u sg The liquid surface velocity u is 15m / s, 20m / s, 25m / s, 30m / s sl The pressures P are 0.1MPa, 0.3MPa, 0.5MPa and 0.7MPa. As shown in Table 1, some experimental results of measuring the top film thickness h of horizontal gas-liquid two-phase flow by ultrasonic echo signal alignment subtraction method are given.

[0072] Table 1 Partial measurement results of liquid film thickness at the top of horizontal tube

[0073]

[0074] The lower limit of the film thickness measurement of this method is related to the sampling frequency of the data acquisition module. The sampling frequency of this experiment is f = 80MHz. The propagation speed of ultrasound in water at normal temperature and pressure is 1480m / s, and the lower limit of the film thickness that can be measured is 9.25μm. When the sampling frequency f is greater than 80MHz, the lower limit of the film thickness that can be measured will be smaller.

[0075] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0076] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A film thickness measurement method based on ultrasonic time domain signals, characterized in that: include: The film echo signal is obtained by using the constructed experimental device; the film echo signal includes a solid-liquid echo signal and a solid-liquid-air echo signal; the experimental device includes a solid medium, an ultrasonic transducer, a transceiver circuit, a data acquisition module and a computer connected in sequence; a liquid medium is also attached to the solid medium, and an air medium is also attached to the liquid medium; interpolating the film echo signal, comparing the interpolated film echo signal with a preset threshold voltage, and recording an intersection position of the threshold voltage and the interpolated solid-liquid echo signal; Taking the interpolated solid-liquid echo signal as a reference, moving the interpolated solid-liquid-air echo signal according to the intersection position, calculating the phase difference data points of the two echo signals after the movement, and aligning the two echo signals according to the phase difference data points; Subtracting the interpolated solid-liquid echo signal from the aligned solid-liquid-air echo signal to obtain a liquid-air echo signal; The interpolated solid-liquid echo signal and liquid-air echo signal are cross-correlated to determine the film thickness.

2. The film thickness measurement method based on ultrasonic time domain signal according to claim 1 is characterized in that: The method of obtaining the film echo signal by using the constructed experimental device specifically includes: The transceiver circuit is used to simultaneously transmit an excitation signal and a trigger signal; the excitation signal is used to excite the ultrasonic transducer to work; the trigger signal is used to trigger the data acquisition module to work; The ultrasonic transducer is used to perform acquisition work to obtain an original echo signal, and the original echo signal is converted into an electrical signal by the transceiver circuit, and then a thin film echo signal is obtained after amplification and filtering, and the thin film echo signal is transmitted to the data acquisition module and the computer in sequence.

3. The film thickness measurement method based on ultrasonic time domain signal according to claim 1 is characterized in that: The interpolating the film echo signal, comparing the interpolated film echo signal with a preset threshold voltage, and recording the intersection position of the threshold voltage and the interpolated solid-liquid echo signal specifically includes: Set the solid-liquid echo signal before interpolation to R0(n), the solid-liquid-air echo signal before interpolation to E0(n), and the threshold voltage volt; Using the cubic spline interpolation method, x data points are inserted between every two points of the two echo signals to obtain the interpolated solid-liquid echo signal and the interpolated solid-liquid-air echo signal, which are recorded as R1(n) and E1(n) respectively; The position where the threshold voltage volt and the interpolated solid-liquid echo signal R1(n) intersect is recorded as M.

4. The film thickness measurement method based on ultrasonic time domain signal according to claim 3 is characterized in that: The process of aligning the two echo signals is specifically as follows: Taking the interpolated solid-liquid echo signal R1(n) as the reference, the interpolated solid-liquid-air echo signal E1(n) is moved forward and backward by 10x data points respectively. When one data point is moved, the first M data sequences of R1(n) and E1(n) are subtracted, the absolute values ​​are taken and summed, and the values ​​are stored in the sum array. After the movement is completed, there are (20x+1) values ​​in the sum array. The position corresponding to the minimum value in the sum array is determined to obtain the data point I of the difference between R1(n) and E1(n), and E1(n) is moved again by I data points to align with R1(n). The aligned E1(n) is recorded as E2(n).

5. The method for measuring film thickness based on ultrasonic time domain signals according to claim 4, characterized in that: The interpolated solid-liquid echo signal and liquid-air echo signal are cross-correlated to determine the film thickness, specifically including: The interpolated solid-liquid echo signal R1(n) and the liquid-air echo signal D(n) obtained by subtraction operation are cross-correlated to obtain a cross-correlation sequence. When the cross-correlation sequence reaches a maximum value, the correlation between the interpolated solid-liquid echo signal R1(n) and the liquid-air echo signal D(n) is the largest. The film thickness is determined according to the moving step size and thickness calculation formula at this time; the thickness calculation formula is: Among them, h is the film thickness, c is the ultrasonic propagation velocity in the liquid, f is the sampling frequency of the data acquisition module, and l0 is the moving step size.

6. A film thickness measuring device based on ultrasonic time domain signals, characterized in that: include: A solid medium, an ultrasonic transducer, a transceiver circuit, a data acquisition module and a computer connected in sequence; The solid medium is also attached with a liquid medium, and outside the liquid medium there is an air medium.

7. An electronic device, characterized in that: The device comprises a memory and a processor, wherein the memory is used to store a computer program, and the processor runs the computer program to enable the electronic device to perform the thin film thickness measurement method based on ultrasonic time domain signals according to any one of claims 1 to 5.

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