A method, device and equipment for measuring the thickness of a thin film based on ultrasonic time-domain signals

Abstract

The present invention discloses a method, device and equipment for measuring the thickness of a thin film based on ultrasonic time-domain signals, relating to the technical field of ultrasonic measurement of liquid film thickness. The method includes: interpolating the echo signal of the middle-layer thin film in the solid-liquid-air three-layer medium obtained, and 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 to align the two echo signals; subtracting the interpolated solid-liquid echo signal from the aligned solid-liquid-air echo signal to obtain the liquid-air echo signal; performing a cross-correlation operation on the interpolated solid-liquid echo signal and the liquid-air echo signal to determine the thin film thickness. The present invention can solve the problem that it is difficult to synchronize the reference signal and the echo signal, and realize the measurement of the thickness of extremely thin liquid films in industry.

Description

Technical Field

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

[0002] The 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, sensors, etc. Measuring the thickness of the thin film is crucial for ensuring the stability and reliability of device performance. In the field of optical coatings, thin films are widely used in optical components, automobiles, aerospace, construction and other fields. The thickness of the thin film coating directly affects the anti-corrosion, aesthetics and functional performance of the coating. The thin film thickness measurement technology can ensure the quality and performance of the coating. In materials science research, thin films are usually used to prepare functional materials and study the properties of new materials. Measuring the thin film thickness is one of the important means to understand and optimize the material properties. In surface engineering and nanomanufacturing, precise thickness control of thin films is the key to achieving specific surface properties and functions. The thin film thickness measurement technology plays an important role in realizing the fine regulation of surface properties. In the field of multiphase flow fluid detection research, the liquid film thickness, as one of the important parameters of flowing fluids, its accurate measurement is of great significance for studying its cross-sectional holdup, pressure drop, flow mechanism and development and 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, small propagation energy loss, etc., and can be applied to many industrial measurement scenarios. Currently, 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 measuring the thickness of thicker liquid films. The ultrasonic thin film resonance method and the 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 the thickness of micron-level thin films, the existing ultrasonic methods cannot meet the measurement accuracy. In addition, when measuring the thickness of a relatively thin liquid film by ultrasound, the echo signals on both sides of the liquid film will appear superimposed. Researchers usually rely on a reference signal to obtain the film thickness. However, due to the performance of the clock and sampling frequency of the acquisition device, generally, it is difficult for the reference signal and the echo signal to reach synchronization, resulting in a large error in the liquid film thickness result. Summary of the Invention

[0004] The purpose of the present invention is to provide a method, device and equipment for measuring the thickness of a thin film based on ultrasonic time-domain signals, which can solve the problem that it is difficult for the reference signal and the echo signal to be synchronized, 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 method for measuring the thickness of a thin film based on ultrasonic time-domain signals, comprising:

[0007] Obtaining the thin film echo signal by using the built 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; the solid medium is also attached with a liquid medium, and there is also an air medium outside the liquid medium;

[0008] Interpolating the thin film echo signal, comparing the interpolated thin film echo signal with a preset threshold voltage, and recording the 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 difference data points of the two echo signals after the movement is completed, and aligning the two echo signals according to the 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] Performing a cross-correlation operation on the interpolated solid-liquid echo signal and the liquid-air echo signal to determine the thin film thickness.

[0012] Optionally, the obtaining the thin film echo signal by using the built experimental device specifically includes:

[0013] Simultaneously transmitting an excitation signal and a trigger signal by using the transceiver circuit; 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] Using the ultrasonic transducer to perform acquisition work to obtain an original echo signal, converting the original echo signal into an electrical signal by using the transceiver circuit, and then obtaining a thin film echo signal after amplification and filtering processing, and sequentially transmitting the thin film echo signal to the data acquisition module and the computer.

[0015] Optionally, the interpolating the thin film echo signal, comparing the interpolated thin 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:

[0016] Setting the solid-liquid echo signal before interpolation as R0(n), the solid-liquid-air echo signal before interpolation as E0(n), and the threshold voltage as 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 respectively denoted as R1(n) and E1(n);

[0018] The position where the threshold voltage volt intersects with the interpolated solid-liquid echo signal R1(n) is denoted 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 a reference, the interpolated solid-liquid-air echo signal E1(n) is moved forward and backward by 10x data points respectively. When moving each data point, the absolute value of the subtraction of the first M data sequences of R1(n) and E1(n) is taken and summed, and 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 judged to obtain the data point I by which R1(n) and E1(n) differ, and E1(n) is moved again by I data points to be aligned with R1(n), and the aligned E1(n) is denoted as E2(n).

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

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

[0023]

[0024] where h is the film thickness, c is the ultrasonic propagation speed 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 measurement device based on an ultrasonic time-domain signal, including: 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 also an air medium outside the liquid medium.

[0026] The present invention also provides an electronic device, including a memory and a processor. The memory is used to store a computer program, and the processor runs the computer program to enable the electronic device to execute the thin film thickness measurement method based on the ultrasonic time domain signal as described above.

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

[0028] The present invention discloses a thin film thickness measurement method, device and equipment based on ultrasonic time domain signals. The method includes obtaining a thin film echo signal by using a built experimental device; interpolating the thin film echo signal, comparing the interpolated thin film echo signal with a preset threshold voltage, and 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 difference data points of the two echo signals after the movement, and aligning the two echo signals according to the 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 a cross-correlation operation on the interpolated solid-liquid echo signal and the liquid-air echo signal to determine the thin film thickness. The present invention can solve the problem that it is difficult to synchronize the reference signal and the echo signal, and realize the measurement of the thickness of an extremely thin liquid film in industry. Description of the Drawings

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0030] Figure 1 It is a schematic flowchart of the thin film thickness measurement method based on ultrasonic time domain signals of the present invention;

[0031] Figure 2 It is a diagram of the experimental device in this embodiment;

[0032] Figure 3 It is a diagram of the original solid-liquid and solid-liquid-air echo signals in this embodiment;

[0033] Figure 4 It is a 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 It is a schematic diagram of the interpolated solid-liquid echo signal and the liquid-air echo signal in this embodiment;

[0035] Figure 6 This is the cross-correlation diagram of the interpolated solid-liquid echo signal and the liquid-air echo signal in this embodiment. Specific implementation manner

[0036] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0037] The object of the present invention is to provide a method, device and equipment for measuring the thickness of a thin film based on an ultrasonic time-domain signal, which can solve the problem that it is difficult to synchronize the reference signal and the echo signal, and realize the measurement of the thickness of an extremely thin liquid film in industry.

[0038] In order to make the above objects, features and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0039] As Figure 1 - Figure 2 shown, the present invention provides a method for measuring the thickness of a thin film based on an ultrasonic time-domain signal, including:

[0040] Step 100: Obtain a thin film echo signal by using the built 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 attached to the solid medium, and there is also an air medium outside the liquid medium.

[0041] Step 200: Interpolate the thin film echo signal, compare the interpolated thin film echo signal with a preset threshold voltage, and record 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, move the interpolated solid-liquid-air echo signal according to the intersection position, calculate the difference data points of the two echo signals after the movement is completed, and align the two echo signals according to the 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: Perform 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, each of the above steps is described in more detail.

[0046] Step 100: Set up 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. The solid serves as the first layer of medium, the liquid attached above the solid is the second layer of medium, and the air above the liquid is the third layer of medium. The ultrasonic transducer is closely attached to the bottom of the solid through a coupling agent. The transceiver circuit is connected to the ultrasonic transducer and the data acquisition module, and it simultaneously emits an excitation signal and a trigger signal. The excitation signal is used to drive the ultrasonic transducer to work, and the trigger signal is used to trigger the data acquisition module to start data acquisition. The ultrasonic transducer experimentally samples the original solid-liquid echo signal R0(n) and the original solid-liquid-air echo signal E0(n), converts them into electrical signals through the transceiver circuit, and after amplification and filtering, transmits them to the data acquisition module, and finally stores them on 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 the solid-liquid-air echo signal, denoted as R1(n) and E1(n) respectively. Set a threshold voltage volt to determine whether the echo signal reaches it. The position where the threshold voltage volt intersects with the interpolated solid-liquid echo signal R1(n) is denoted as M.

[0048] Step 300: Further, taking R1(n) as a reference, move E1(n) forward and backward by 10x data points respectively. When moving each data point, subtract the first M data sequences of R1(n) and E1(n), take the absolute value, and sum them and store them in the sum array (as shown in Equation (1)). After moving, there are (20x + 1) values in sum. Determine the position corresponding to the minimum value in the sum array, and this position is the data point I by which R1(n) and E1(n) differ. Move E1(n) by I data points to align it with R1(n), and the aligned E1(n) is denoted as E2(n).

[0049]

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

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

[0052] Step 500: Further, perform cross-correlation on the interpolated solid-liquid echo signal R1(n) and the liquid-air echo signal D(n), 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 (l) reaches the maximum value, the correlation between R1(n) and D(n) is the largest, and the moving step size at this time is denoted as l0. Then the film thickness of the liquid layer is as shown in Equation (4).

[0056]

[0057] In the formula, c is the ultrasonic propagation speed 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 as shown in Equation (5).

[0059]

[0060] Based on the above specific processing process, the following embodiments are provided.

[0061] As Figure 1 , set up 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 circular tube made of plexiglass, with a thickness of 10 mm and an inner diameter of 50 mm. An ultrasonic transducer is arranged at the top of the circular tube. The ultrasonic transducer is an ultrasonic piezoelectric transducer with a center frequency of 5 MHz and a wafer size of 6 mm to emit and receive signals. The transceiver circuit simultaneously emits 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 experimentally samples the original solid-liquid echo signal R0(n) and the solid-liquid-air echo signal E0(n), converts them into electrical signals through the transceiver circuit, and after amplification and filtering, transmits them to the data acquisition module, and finally stores them on the computer for data processing. The sampling frequency f of the data acquisition module is set to 80 MHz, and the sampling time is 60 s. The specific experimental measurement process is as follows:

[0062] (1) Measure the original solid-liquid echo signal R0(n): Fill the circular tube with water, and use as Figure 2The experimental device shown collects the original solid-liquid echo signal R0(n) once.

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

[0064] Taking one original solid-liquid echo signal R0(n) and one original solid-liquid-air echo signal E0(n) as examples (as Figure 3 shown), the method is introduced. It can be seen from the figure that although the excitation signal and the trigger signal are generated simultaneously, due to the relatively 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 starting moment of vibration. Before aligning the two signals, first use the cubic spline interpolation method to insert x = 10 data points between every two points of the two signals respectively, and obtain the interpolated solid-liquid echo signal R1(n) and the solid-liquid-air echo signal E1(n). On this basis, set the threshold voltage volt = 50 mV to judge whether the echo signal arrives, that is, the starting moment of the ultrasonic transducer. The position where the threshold voltage volt intersects with the interpolated solid-liquid echo signal R1(n) is denoted as M.

[0065] Furthermore, taking R1(n) as a reference, move E1(n) forward and backward by (10x = 100) data points respectively. When moving each data point, subtract the first M data sequences of R1(n) and E1(n) and take the absolute value and sum them and store them in the sum array (as shown in Equation (1)). After moving, there are (20x + 1 = 201) values in sum. Judge the position corresponding to the minimum value in the sum array, and this position is the number of data points I by which R1(n) and E1(n) differ. Move E1(n) by I data points to align it with R1(n), and the aligned E1(n) is denoted as E2(n), as Figure 4 shown.

[0066] Step 4: Subtract the R1(n) and E2(n) obtained in Step 3 (as shown in Equation (2)) to get the liquid-air echo signal, that is, the subtraction signal D(n), as Figure 5as shown

[0067] Step 5: Further, perform cross-correlation on the interpolated solid-liquid echo signal R1(n) and the liquid-air echo signal D(n), as shown in Equation (3), and the cross-correlation result is as Figure 6 shown

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

[0069] The data acquisition module collects data for 60 s, and a total of 6000 original solid-liquid-air echo signals E0(n) are collected. 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 from these 6000 original solid-liquid-air echo signals E0(n). The measurement lower limit of the ultrasonic echo signal alignment subtraction method is as shown in Equation (5).

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

[0071] As the effect evaluation of the method in this embodiment, to verify the accuracy and reliability of the ultrasonic echo signal alignment subtraction method provided by the present invention when measuring the film thickness, a dynamic measurement experiment on the liquid film thickness at the top of the horizontal gas-liquid two-phase flow was carried out. The pipeline is made of plexiglass, the liquid is water, and the gas is air. Affected by gravity, the liquid film thickness at the top of the horizontal pipe gas-liquid two-phase flow is the thinnest, so the ultrasonic transducer is installed at the top of the pipeline. The superficial gas velocity u sg is 15 m / s, 20 m / s, 25 m / s, 30 m / s, the superficial liquid velocity u sl is 0.015 m / s, 0.035 m / s, 0.06 m / s, 0.1 m / s, and the pressure P is 0.1 MPa, 0.3 MPa, 0.5 MPa, 0.7 MPa. As shown in Table 1, some experimental results of measuring the top film thickness h of the horizontal gas-liquid two-phase flow by the ultrasonic echo signal alignment subtraction method are given.

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

[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 = 80 MHz. The propagation speed of ultrasonic waves in water at normal temperature and pressure is 1480 m / s, and the lower limit of the film thickness that can be measured is 9.25 μm. When the sampling frequency f is greater than 80 MHz, 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. Each embodiment focuses on the differences from other embodiments. For the same and similar parts between the various embodiments, reference can be made to each other.

[0076] Specific examples are used in this article to elaborate on the principles and implementation manners of the present invention. The description of the above embodiments is only used to help understand the core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A method for measuring the thickness of a thin film based on ultrasonic time-domain signals, characterized in that, Including: Obtaining thin-film echo signals by using the established experimental device; the thin-film echo signals include solid-liquid echo signals and solid-liquid-air echo signals; 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 also an air medium outside the liquid medium; Interpolate the thin film echo signal, compare the interpolated thin film echo signal with a preset threshold voltage, and record the intersection position of the threshold voltage and the interpolated solid-liquid echo signal M ; 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 difference data points of the two echo signals after the movement is completed, and aligning the two echo signals according to the difference data points; the specific process of aligning the two echo signals is as follows: The interpolated solid-liquid echo signal R 1( n ) as the reference, and the interpolated solid-liquid-air echo signal E 1( n ) Move forward and backward 10 x data points, and each time you move a data point R 1( n )and E 1( n ) M The data sequence is subtracted, the absolute value is taken and summed, and stored in sum In the array, after the move is completed sum The array contains (20 x +1) value; judgement sum The position corresponding to the minimum value in the array is obtained R 1( n )and E 1( n ) The difference in data points I , and E 1( n )Move again I Data points and R 1( n ) and align the aligned E 1( n ) is recorded as E 2( n ); Subtracting the interpolated solid-liquid echo signal from the aligned solid-liquid-air echo signal to obtain the liquid-air echo signal; Performing a cross-correlation operation on the interpolated solid-liquid echo signal and the liquid-air echo signal to determine the thin-film thickness.

2. The method for measuring the thickness of a thin film based on an ultrasonic time-domain signal according to claim 1, wherein The obtaining of the thin-film echo signals by using the established experimental device specifically includes: Simultaneously transmitting an excitation signal and a trigger signal by using the transceiver circuit; 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; Performing acquisition work by using the ultrasonic transducer to obtain the original echo signal, converting the original echo signal into an electrical signal through the transceiver circuit, and then obtaining the thin-film echo signal after amplification and filtering processing, and sequentially transmitting the thin-film echo signal to the data acquisition module and the computer.

3. The method for measuring the thickness of a thin film based on ultrasonic time-domain signals according to claim 1, wherein, The interpolation of the thin-film echo signal and the comparison of the interpolated thin-film echo signal with a preset threshold voltage, and the recording of the intersection position of the threshold voltage and the interpolated solid-liquid echo signal specifically include: Set the solid-liquid echo signal before interpolation as R 0 ( n ), the solid-liquid-air echo signal before interpolation is E 0 ( n ), and the threshold voltage volt ; 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 the interpolated solid-liquid-air echo signal, and denote them as R 1( n ) and E 1( n ), respectively; Take the threshold voltage volt and the interpolated solid-liquid echo signal R 1( n ) and mark the intersection position as M .

4. The method for measuring the thickness of a thin film based on an ultrasonic time-domain signal according to claim 1, wherein, The performing of the cross-correlation operation on the interpolated solid-liquid echo signal and the liquid-air echo signal to determine the thin-film thickness specifically includes: The interpolated solid-liquid echo signal R 1( n ) and the liquid-air echo signal obtained by subtraction operation D ( n ) are subjected to cross-correlation operation to obtain a cross-correlation sequence. When the cross-correlation sequence reaches the maximum value, the interpolated solid-liquid echo signal R 1( n ) and the liquid-air echo signal D ( n ) have the maximum correlation. 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, l 0 is the moving step size.

5. An electronic device, characterized in that, Including a memory and a processor, the memory is used to store a computer program, and the processor runs the computer program to enable the electronic device to execute the thin-film thickness measurement method based on ultrasonic time-domain signals according to any one of claims 1-4.

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