CN112630306B - An autofocus method and system based on an ultrasonic microscope point focus transducer - Google Patents

Abstract

The embodiment of the present application discloses an autofocus method and system based on an ultrasonic microscope point focus transducer, wherein the method includes: obtaining an A-scan signal image on the surface of the specimen; setting focusing parameters; The speed of sound in the center is corrected, and the position of the autofocus on the upper surface is calculated by the focal length and delay of the acoustic lens of the point-focusing transducer; the A-scan signal is analyzed by discrete wavelet decomposition and Wiener deconvolution to obtain the Layering information; select the target to focus on the reflection signal of the middle layer according to the layering information of the specimen; move the transducer to find the approximate position coordinates of the maximum reflection signal of the middle layer; move the focus transducer back to the point coordinates of the maximum position A coordinate point; move the point to focus on the transducer, and find the precise point coordinates of the maximum value of the reflected signal to complete autofocus. Effectively improve the focusing speed and precision of the ultrasonic microscope point focusing transducer during use.

Description

An autofocus method and system based on an ultrasonic microscope point focus transducer

technical field

The embodiment of the present application relates to the field of acoustic technology and non-destructive testing technology, and specifically relates to an autofocus method and system based on an ultrasonic microscope point focusing transducer.

Background technique

Ultrasonic microscopes are non-destructive testing and microscopic imaging equipment widely used in high-tech manufacturing industries such as chip manufacturing, biomedicine, and material science. Ultrasonic microscopes (as shown in the schematic diagram of the ultrasonic microscope in Figure 1) generally use liquid-immersion point-focused ultrasonic transducers (as shown in the schematic diagram of the point-focused ultrasonic transducer in Figure 2), which can converge the sound beam at one point , so that the energy in the converging area is concentrated and strengthened, and the width of the sound beam becomes smaller, which can meet the detection requirements of high sensitivity and high resolution.

At present, ultrasonic microscopes generally adopt the manual focusing method, which is not only low in precision but also inefficient, especially in the face of highly integrated IC chips, multi-layer thin film materials, etc., manual focusing has greatly reduced the detection efficiency, and it is possible Affect the detection effect. In the process of scanning imaging and non-destructive testing of complex multi-layer structure specimens, especially chips, by using point-focusing transducers, the focusing process of the middle layer requires the operator to have rich working experience and comparative experience. long operating time. This also largely limits the wide application of ultrasound microscopy.

At present, due to the continuous improvement of the manufacturing process, the layered structure and process of many tested parts have reached the sub-micron level. However, the depth of field of the point focus transducer above 50MHZ is lower than 10 microns, and the vertical position of the transducer needs to be adjusted repeatedly during scanning to match the focal plane and the target layer. Especially when using a high-frequency ultrasonic transducer, its depth of field work is smaller, requiring higher focusing accuracy.

Contents of the invention

To this end, an embodiment of the present application provides an autofocus method and system based on an ultrasonic microscope point focusing transducer, which can realize fast autofocus on the surface and the middle layer. Effectively improve the focusing speed and accuracy of the ultrasonic microscope point-focusing transducer during use, greatly reduce the randomness and uncertainty caused by manual operation in the focusing process, and reduce the dependence on the operator's technical level and work experience , Reduce operational complexity and improve work efficiency.

In order to achieve the above purpose, the embodiment of the present application provides the following technical solutions:

According to the first aspect of the embodiments of the present application, there is provided an autofocus method based on an ultrasonic microscope point focusing transducer, the method comprising:

Obtain the A-scan signal image of the surface of the test piece;

Setting focus parameters, the focus parameters include delay parameters of point focus transducers, focal length parameters and intermediary fluid temperature parameters;

The speed of sound in the intermediary liquid is corrected according to the temperature of the intermediary liquid, and the autofocus position on the upper surface is calculated by the focal length and delay parameters of the acoustic lens of the point-focus transducer to move the point-focus transducer to the position to complete the upper surface surface autofocus;

The A-scan signal is analyzed by discrete wavelet decomposition and Wiener deconvolution to obtain the layered information of the specimen;

According to the stratification information of the specimen, the target is selected to focus on the reflection signal of the middle layer;

Move the transducer to find the approximate point coordinates of the maximum reflected signal in the middle layer;

Move the point focus transducer back to the last coordinate point of the maximum position point coordinates;

Move the spot focusing transducer to find the precise point coordinates of the maximum value of the reflected signal to complete autofocus.

Optionally, the focal length parameter of the point focusing transducer is calculated according to the following formula:

F _L =R/(1-c ₀ /c ₁ )

Among them, R is the radius of curvature of the acoustic lens, c ₀ represents the speed of sound in the intermediary liquid, and c ₁ represents the speed of sound in the lens.

Optionally, the A-scan signal is composed of complex reflected waves of the inner M-layer structure of the detected part, and the model of the A-scan signal is:

Among them, n(t) is the noise function, * means convolution, and x(t) is the incident signal function; if noise is not considered, y(t) is the convolution of x(t) and r(t).

Optionally, the moving transducer finds the coordinates of the point where the reflection signal of the middle layer is the largest, including:

Control the transducer to move vertically to the upper surface of the specimen in the step of the set distance in the Z-axis direction, analyze the sampled A-scan signal, and obtain the reflection signal of the middle layer; judge whether the reflection signal of the middle layer is gradually enhanced or weakened , if it gradually weakens, the maximum value of the layered reflection signal appears between the last two set distance step coordinate points.

Optionally, the moving point focusing transducer to find the precise position of the maximum value of the reflected signal, so as to complete autofocus, includes:

In the process of moving the point-focusing transducer each time, the A-scan signal is collected to analyze the signal, and it is judged whether the reflection signal of the middle layer is gradually enhanced or weakened. If it is gradually weakened, the maximum value of the reflection signal of the layer and its corresponding value are determined. Z-axis coordinates, move the ultrasonic transducer to the coordinates to complete the autofocus of the middle layer.

According to the second aspect of the embodiment of the present application, there is provided an autofocus system based on an ultrasonic microscope point focusing transducer, the system comprising:

The initial signal acquisition module is used to obtain the A-scan signal image of the surface of the test piece;

A focus parameter calculation module is used to set the focus parameters, the focus parameters include the delay parameter of the point focus transducer, the focal length parameter and the temperature parameter of the intermediary fluid;

The upper surface autofocus module is used to correct the speed of sound in the intermediary fluid according to the temperature of the intermediary fluid, and calculate the position of the upper surface autofocus through the focal length and delay parameters of the acoustic lens of the point focus transducer, so as to move the point focus transducer the sensor to the position to complete the autofocus on the upper surface;

The layered information calculation module is used to analyze the A-scan signal through discrete wavelet decomposition and Wiener deconvolution to obtain the layered information of the specimen;

The target focusing intermediate layer reflection signal determination module is used to select the target focusing intermediate layer reflection signal according to the layering information of the test piece;

The point coordinate determination module of the maximum reflected signal is used to move the transducer to find the approximate point coordinates of the maximum reflected signal in the middle layer;

The rough focus module in the middle layer is used to move the point focus transducer back to the last coordinate point of the maximum position point coordinates;

The autofocus module is used to move the spot focusing transducer to find the exact point coordinates of the maximum value of the reflected signal to complete autofocus.

Optionally, in the focusing parameter calculation module, the focal length parameter of the point focusing transducer is calculated according to the following formula:

F _L =R/(1-c ₀ /c ₁ )

Among them, R is the radius of curvature of the acoustic lens, c ₀ represents the speed of sound in the intermediary liquid, and c ₁ represents the speed of sound in the lens.

Optionally, the A-scan signal is composed of complex reflected waves of the inner M-layer structure of the detected part, and the model of the A-scan signal is:

Among them, n(t) is the noise function, * means convolution, and x(t) is the incident signal function; if noise is not considered, y(t) is the convolution of x(t) and r(t).

Optionally, the coordinate determination module of the position point with the largest reflected signal is specifically used for:

Control the transducer to move vertically to the upper surface of the specimen in the step of the set distance in the Z-axis direction, analyze the sampled A-scan signal, and obtain the reflection signal of the middle layer; judge whether the reflection signal of the middle layer is gradually enhanced or weakened , if it gradually weakens, the maximum value of the layered reflection signal appears between the last two set distance step coordinate points.

Optionally, the autofocus module is specifically used for:

In the process of moving the point-focusing transducer each time, the A-scan signal is collected to analyze the signal, and it is judged whether the reflection signal of the middle layer is gradually enhanced or weakened. If it is gradually weakened, the maximum value of the reflection signal of the layer and its corresponding value are determined. Z-axis coordinates, move the ultrasonic transducer to the coordinates to complete the autofocus of the middle layer.

In summary, the embodiment of the present application provides an autofocus method and system based on an ultrasonic microscope point focus transducer, by obtaining the A-scan signal image on the surface of the test piece; setting focus parameters, the focus parameters include point focus Transducer delay parameters, focal length parameters and intermediary fluid temperature parameters; correct the sound velocity in the intermediary fluid according to the intermediary fluid temperature, and calculate the autofocus position on the upper surface through the focal length and delay parameters of the acoustic lens of the point-focusing transducer , to move the point focus transducer to the position to complete the upper surface autofocus; analyze the A-scan signal by discrete wavelet decomposition and Wiener deconvolution to obtain the layered information of the specimen; according to the analysis of the specimen Layer information selects the target to focus on the reflected signal of the middle layer; moves the transducer to find the approximate position point coordinates of the maximum reflected signal in the middle layer; moves the focus transducer to return to the previous coordinate point of the maximum position point coordinate; moves the point to focus on the transducer Find the precise point coordinates of the maximum value of the reflected signal to complete autofocus. Effectively improve the focusing speed and accuracy of the ultrasonic microscope point-focusing transducer during use, greatly reduce the randomness and uncertainty caused by manual operation in the focusing process, and reduce the dependence on the operator's technical level and work experience , Reduce operational complexity and improve work efficiency.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the accompanying drawings that are required in the description of the embodiments or the prior art. Apparently, the drawings in the following description are only exemplary, and those skilled in the art can also obtain other implementation drawings according to the provided drawings without creative work.

The structures, proportions, sizes, etc. shown in this manual are only used to cooperate with the content disclosed in the manual, so that people familiar with this technology can understand and read, and are not used to limit the conditions for the implementation of the present invention, so there is no technical In the substantive meaning above, any modification of structure, change of proportional relationship or adjustment of size should still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and goals that can be achieved by the present invention. within the scope covered.

Fig. 1 is the principle diagram of the ultrasonic microscope provided by the embodiment of the present application;

FIG. 2 is a schematic diagram of the focusing principle of the point-focused ultrasonic transducer provided by the embodiment of the present application;

FIG. 3 is a schematic flow chart of an autofocus method based on an ultrasonic microscope point-focusing transducer provided in an embodiment of the present application;

FIG. 4 is a logic flow chart of the middle layer auto-focus method provided by the embodiment of the present application;

Fig. 5 is the A-scan echo signal of the flip chip provided by the embodiment of the present application;

FIG. 6 is a schematic diagram of analyzing layered information of plastic-encapsulated chips provided by the embodiment of the present application;

FIG. 7 is a schematic diagram of flip chip layering information analysis provided by the embodiment of the present application;

FIG. 8 is a schematic diagram of a reflection signal focusing curve provided by an embodiment of the present application;

FIG. 9 is a block diagram of an autofocus system based on an ultrasonic microscope point focusing transducer provided in an embodiment of the present application.

Detailed ways

The implementation mode of the present invention is illustrated by specific specific examples below, and those who are familiar with this technology can easily understand other advantages and effects of the present invention from the contents disclosed in this description. Obviously, the described embodiments are a part of the present invention. , but not all examples. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

In view of the above problems, the embodiment of the present application provides an autofocus technology based on the point-focusing transducer of the ultrasonic microscope, which can effectively solve the problems of slow focusing speed and low precision of the point-focusing transducer of the ultrasonic microscope, and improve the performance of the ultrasonic microscope. Imaging quality and NDT efficiency. As shown in Figure 3, the method includes the following steps:

Step 301: Obtain an A-scan signal image of the surface of the test piece.

Step 302: Setting focus parameters, the focus parameters include delay parameters, focal length parameters and intermediary fluid temperature parameters of the point focus transducer.

Step 303: Correct the speed of sound in the intermediary fluid according to the temperature of the intermediary fluid, and calculate the auto-focus position on the upper surface through the focal length and delay parameters of the acoustic lens of the point-focus transducer, so as to move the point-focus transducer to the The position completes the upper surface autofocus.

Step 304: Analyzing the A-scan signal through discrete wavelet decomposition and Wiener deconvolution to obtain layered information of the specimen.

Step 305: Select a target to focus on the reflection signal of the middle layer according to the layering information of the specimen.

Step 306: Move the transducer to find the approximate point coordinates of the maximum reflected signal in the middle layer.

Step 307: Move the spot focusing transducer back to the last coordinate point of the maximum position point coordinate.

Step 308: Move the spot focusing transducer to find the precise point coordinates of the maximum value of the reflected signal, so as to complete autofocus.

In a possible implementation manner, in step 302, the focal length parameter of the point focusing transducer is calculated according to the following formula (1):

F _L =R/(1-c ₀ /c ₁ )...Formula (1)

Among them, R is the radius of curvature of the acoustic lens, c ₀ represents the speed of sound in the intermediary liquid, and c ₁ represents the speed of sound in the lens.

In a possible implementation manner, the A-scan signal is composed of complex reflected waves of the inner M-layer structure of the detected part, and the model of the A-scan signal is shown in formula (2):

Among them, n(t) is the noise function, * means convolution, and x(t) is the incident signal function; if noise is not considered, y(t) is the convolution of x(t) and r(t).

In a possible implementation manner, in step 306, the moving transducer to find the coordinates of the point where the reflected signal of the middle layer is the largest includes: controlling the transducer to move forward with a set distance in the direction of the Z axis. The upper surface of the part moves vertically, analyzes the sampled A-scan signal, and obtains the reflection signal of the middle layer; judges whether the reflection signal of the middle layer is gradually strengthened or weakened, and if it is gradually weakened, the maximum value of the reflection signal of the layer appears in the last two layers. A set distance between stepping coordinate points.

In a possible implementation manner, in step 308, the moving point focusing transducer to find the precise position of the maximum value of the reflected signal, so as to complete the automatic focusing, includes: the process of moving the point focusing transducer each time In this method, the A-scan signal is collected to analyze the signal, and it is judged whether the reflected signal of the middle layer is gradually enhanced or weakened. If it is gradually weakened, the maximum value of the layered reflected signal and its corresponding Z-axis coordinate are determined, and the ultrasonic transducer is moved to On the coordinates, the intermediate layer auto-focus is completed.

In order to make the auto-focusing method for the middle layer of the test piece provided by the embodiment of the present application facing the ultrasonic microscope point-focusing transducer clearer, the embodiment of the present application will be further described in detail in conjunction with FIG. 4:

In step (1), the initial A-scan echo signal image of the sample surface is obtained.

In step (2), relevant parameters are set, including: the time delay of the ultrasonic transducer, the focal length, and the temperature of the intermediary fluid (generally water).

In step (3), the program accurately corrects the speed of sound in the water according to the water temperature, accurately calculates the precise position of the upper surface autofocus through the focal length and time delay of the acoustic lens of the transducer, and moves the point focus transducer to this position to complete the upper surface. Surface autofocus.

Fig. 2 shows a schematic diagram of the focusing principle of a point-focused ultrasonic transducer, wherein the focal length calculation formula of the point-focused transducer can be calculated according to formula (3):

F _L =R/(1-c ₀ /c ₁ )...Formula (3)

Among them, R is the radius of curvature of the acoustic lens, c ₀ represents the speed of sound in water, c ₁ represents the speed of sound in the lens, let t be the time for the sound wave to reach the plane T of the transducer, then there is formula (4):

t＝2L/c ₀ +2H/c ₁ ......Formula (4)

Wherein, 2H/c ₁ is the delay time t _d of the ultrasonic transducer.

In order to calculate the focus position more accurately, the embodiment of the present application considers the influence of temperature on the speed of sound in water, and corrects the speed of sound at different temperatures, as shown in formula (5):

c ₀ ＝1452(1+2.9376×10 ^-5 temp+1.90574×10 ^-6 temp ² )...Formula (5)

The ultrasonic scanning microscope uses the sound path time t to represent the coordinate position of the Z axis. It can be seen from formula (8-9) that when t=2F _L /c ₀ +t _d , the sound path time t is the coordinate position of the Z axis, and the parameters F _L , c ₀ , t _d are all known, so the automatic up The surface is in focus.

In step (4), the A-scan signal is analyzed to obtain the stratification information of the specimen.

The A-scan signal is composed of complex reflected waves of the multi-layer structure inside the tested part. The reflectivity r(t) of the ultrasonic signal is the impulse response function of the ultrasonic scanning microscope, x(t) is the incident signal function, and y(t ) is the observed A-scan signal. The reflectivity r(t) of the ultrasonic signal is calculated according to formula (6):

Z ₁ and Z ₂ are the acoustic impedances of the water and the specimen, respectively. Here, the reflection signal of the flip chip is used for illustration, as shown in Figure 5(a), and the Z-axis coordinate position after the upper surface is focused is the coordinate origin.

Assuming that the detected part has M layers in total, the model of the A-scan signal can be expressed as formula (7):

In the formula, n(t) is noise; * means convolution, and x(t) is the incident signal. If noise is not considered, y(t) can be regarded as the convolution of x(t) and r(t).

When performing scanning imaging and non-destructive testing on complex multi-layer structure specimens, especially complex multi-layer structures such as chips, due to the advanced specimen manufacturing process, the thickness of the layered structure is often lower than the wavelength of the acoustic signal of the point-focused transducer , so in many cases there will be superposition of signals. For example, in the soldering layer of a flip chip as shown in Figure 5, s(t ₁ ), s(t ₂ ), and s(t ₃ ) are the upper surface layer, soldering layer, For the echo signal of the substrate layer, when the thickness of the solder layer is greater than the wavelength of the point-focused transducer, the echo signals s(t ₂ ) and s(t ₃ ) have a better separation, and when the thickness of the solder layer is smaller than the point focus transducer When focusing on the wavelength of the transducer, the echo signals s(t ₂ ) and s(t ₃ ) are superimposed on each other. At this time, the echo signals of the soldering layer and the substrate layer cannot be found, so the intermediate layer cannot be automatically focused.

The embodiment of the present application adopts discrete wavelet decomposition to perform multi-scale analysis on ultrasonic signals. Discrete wavelet transform can use sub-band filtering to decompose the signal into different frequency bands; combining wavelet analysis with deconvolution realizes the sub-band analysis of ultrasonic echo signals. with decomposition. According to the Mallat algorithm, the signal can be decomposed into the following two parts in the expression as in formula (8):

In the formula, is a discrete approximation, /> is the discrete details, h ₀ and h ₁ are the factorized low-pass and high-pass filter coefficients, respectively. In order to reduce non-zero coefficients, this embodiment selects wavelet basis functions such as daubechies and Coiflet whose shape is similar to that of the ultrasonic signal waveform as the mother wavelet. It can decompose the signal N times, and 2 ^N is the length of the signal to be decomposed. The scale to be decomposed is determined according to the actual situation such as the number of sampling points and the size of the noise. If the decomposition scale is too high, the time domain resolution will be reduced, and if the scale is too low, the noise will not be effectively suppressed. In the embodiment of the present application, the decomposition coefficient is set to 2-3. The signal in the low-frequency band preserves a large amount of information of the useful signal, so the same mother wavelet function is selected, for /> Perform single-branch reconstruction to obtain the reconstructed signal as the input signal for subsequent processing.

After wavelet decomposition, Wiener deconvolution filtering (Wiener) is used to continue to process the signal in the ground frequency band. Wiener deconvolution is a deconvolution method widely used in signal and image processing. The Wiener deconvolution filter can be expressed as formula (9):

where R(ω) and Y(ω) are the Fourier transforms of r(t) and y(t), respectively, X(ω) is the energy density spectrum of the incident signal x(t), and Q is the noise block factor, the value of Q in the embodiment of the present application is set to 1% of the maximum value of |X(ω)| ² . Traditional Wiener deconvolution assumes that the frequency of the incident signal remains constant during propagation. However, the A-scan signal has relatively large waveform distortion during propagation. The frequency and amplitude will continue to decrease, and the traditional Wiener deconvolution is not suitable for processing the echo signal of the ultrasonic scanning microscope. Therefore, firstly, the discrete wavelet preprocesses the ultrasonic signal to eliminate the signal distortion in the transmission process, which can improve the poor filtering effect of Wiener deconvolution. As shown in Figure 6 and Figure 7, the echo information that was originally superimposed together can be Better for separation.

In step (5), the reflection signal of the middle layer that needs to be focused is selected.

After the layered signal is analyzed by discrete wavelet and Wiener deconvolution, the overlapping signal is separated, and the separated intermediate layer reflection signal can be accurately found, and the intermediate layer that needs to be focused can be selected.

In step (6), move the transducer to find the coordinates of the maximum value of the reflected signal. The program controls the vertical movement of the spot-focusing transducer toward the specimen in 10-micron steps along the Z-axis. Every time a step is moved, the A-scan signal is collected to analyze the signal, and the coordinates of the point where the reflected signal of the middle layer is the largest are recorded and searched.

After the general focusing process starts, control the transducer to move vertically to the upper surface of the specimen with a step of 10 microns in the Z-axis direction, analyze the sampled A-scan signal, and obtain the reflection signal of the middle layer. At this time, the reflection signal of the middle layer It will gradually increase, and if the reflection signal is found to be weakened, it means that the maximum value of the layered reflection signal appears between the last two 10 micron step coordinate points. If the intensity of the reflected signal during this process is taken as the ordinate, and the Z-axis displacement is taken as the abscissa, the reflected signal focus curve in Figure 8 can be obtained.

Step (7), move the transducer back to the previous node of the maximum value. Move the ultrasonic transducer to the last step coordinate point of this position to complete the rough focusing of the middle layer.

In Fig. 8, after finding the approximate maximum reflection position of the curve, move the ultrasonic transducer to the previous step coordinates of this position, and prepare to start the precise focusing process.

Step (8), accurately find the largest reflective surface. Continue to move the point-focusing transducer along the Z-axis of the specimen with a step of 1 micron, find the precise position of the maximum value of the reflected signal, and complete auto-focusing.

In the process of each movement, the A-scan signal is collected to analyze the signal. At this time, the reflection signal of the middle layer will gradually increase. If the reflection signal is found to be weakened, the maximum value of the reflection signal of the layer and its corresponding Z-axis coordinate can be obtained. , move the ultrasonic transducer to this coordinate, that is to complete the precise focusing of the middle layer. Figure 6 and Figure 7 are the renderings of focusing and scanning imaging using this device, respectively focusing on the middle layer of the reflection signal S2 and focusing on the middle layer of the reflection signal S3.

Compared with the manual focusing technology commonly used now, the autofocus technology of the ultrasonic microscope point-focusing transducer provided in the embodiment of the present application can effectively improve the focusing speed and accuracy of the ultrasonic microscope point-focusing transducer during use. Greatly reduce the randomness and uncertainty brought by human operation in the focusing process, reduce the dependence on the operator's technical level and work experience, reduce the complexity of operation, and improve work efficiency.

The embodiment of the present application discloses an autofocus technology for point-focus transducers of ultrasonic microscopes, including collecting designed A-scan signals, setting point-focus transducer parameters and temperature parameters, automatically completing the upper surface focus, and performing signal processing. Analyze to find the middle reflective layer, move the point-focusing transducer to find the maximum position of the signal amplitude in the range of the middle layer, and complete the auto-focusing of the middle layer. The upper autofocus process accurately corrects the speed of sound in water according to the water temperature. In the process of analyzing the reflection signal, the discrete wavelet and Wiener deconvolution filter are used to separate the overlapping signals, and the reflection signal in the middle layer can be clearly located. It can effectively solve the problems of slow focusing speed and low precision of the ultrasonic microscope point-focusing transducer, and improve the imaging quality and non-destructive testing efficiency of the ultrasonic microscope.

In summary, the embodiment of the present application provides an autofocus method and system based on an ultrasonic microscope point focus transducer, by obtaining the A-scan signal image on the surface of the test piece; setting focus parameters, the focus parameters include point focus Transducer delay parameters, focal length parameters and intermediary fluid temperature parameters; correct the sound velocity in the intermediary fluid according to the intermediary fluid temperature, and calculate the autofocus position on the upper surface through the focal length and delay parameters of the acoustic lens of the point-focusing transducer , to move the point focus transducer to the position to complete the upper surface autofocus; analyze the A-scan signal by discrete wavelet decomposition and Wiener deconvolution to obtain the layered information of the specimen; according to the analysis of the specimen Layer information selects the target to focus on the reflected signal of the middle layer; moves the transducer to find the approximate position point coordinates of the maximum reflected signal in the middle layer; moves the focus transducer to return to the previous coordinate point of the maximum position point coordinate; moves the point to focus on the transducer Find the precise point coordinates of the maximum value of the reflected signal to complete autofocus. Effectively improve the focusing speed and accuracy of the ultrasonic microscope point-focusing transducer during use, greatly reduce the randomness and uncertainty caused by manual operation in the focusing process, and reduce the dependence on the operator's technical level and work experience , Reduce operational complexity and improve work efficiency.

Based on the same technical concept, the embodiment of the present application also provides an autofocus system based on an ultrasonic microscope point focusing transducer, as shown in Figure 9, the system includes:

The initial signal acquisition module 901 is used to acquire the A-scan signal image of the surface of the test piece.

The focus parameter calculation module 902 is used to set the focus parameters, the focus parameters include the time delay parameter of the point focus transducer, the focal length parameter and the temperature parameter of the intermediary fluid.

The upper surface autofocus module 903 is used to correct the speed of sound in the intermediary fluid according to the temperature of the intermediary fluid, and calculate the position of the upper surface autofocus through the focal length and delay parameters of the acoustic lens of the point focus transducer to move the point focus Transducer to the position to complete the upper surface autofocus.

The hierarchical information calculation module 904 is used to analyze the A-scan signal through discrete wavelet decomposition and Wiener deconvolution to obtain the hierarchical information of the specimen.

The target focusing intermediate layer reflection signal determination module 905 is configured to select the target focusing intermediate layer reflection signal according to the stratification information of the specimen.

The point coordinate determining module 906 of the maximum reflected signal is used to move the transducer to find the point coordinates of the maximum reflected signal in the middle layer.

The rough focusing module 907 in the middle layer is used to move the point focusing transducer back to the last coordinate point of the maximum rough position point coordinates.

The auto-focus module 908 is used to move the point-focusing transducer to find the precise point coordinates of the maximum value of the reflected signal, so as to complete auto-focus.

Optionally, in the focusing parameter calculation module 902, the focal length parameter of the point focusing transducer is calculated according to the following formula (1).

In a possible implementation manner, the A-scan signal is composed of complex reflected waves of the M-layer structure inside the detected part, and the model of the A-scan signal is shown in formula (2).

In a possible implementation manner, the position coordinate determination module 906 of the maximum reflected signal is specifically used to: control the transducer to move vertically to the upper surface of the test piece in a step of a set distance in the Z-axis direction, and to The sampled A-scan signal is analyzed to obtain the reflection signal of the middle layer; it is judged whether the reflection signal of the middle layer is gradually enhanced or weakened, and if it is gradually weakened, the maximum value of the layered reflection signal appears at the last two set distance step coordinates between points.

Optionally, the auto-focus module 908 is specifically configured to collect A-scan signals and analyze the signals during each movement of the point-focus transducer, and determine whether the reflection signal of the middle layer is gradually enhanced or weakened, if Gradually weaken, determine the maximum value of the layered reflection signal and its corresponding Z-axis coordinate, move the ultrasonic transducer to the coordinate, and complete the middle layer autofocus.

Based on the same technical concept, the embodiment of the present application also provides a device, which includes: a data collection device, a processor and a memory; the data collection device is used to collect data; the memory is used to store one or more a program instruction; the processor is configured to execute one or more program instructions to perform the method.

Based on the same technical concept, the embodiment of the present application also provides a computer-readable storage medium, the computer storage medium contains one or more program instructions, and the one or more program instructions are used to execute the method .

Each embodiment of the above-mentioned method in this specification is described in a progressive manner, the same and similar parts of each embodiment can be referred to each other, and each embodiment focuses on the differences from other embodiments. For related information, please refer to the description of the method embodiments.

It should be noted that although the operations of the method of the present invention are described in a specific order in the accompanying drawings, this does not require or imply that these operations must be performed in this specific order, or that all shown operations must be performed to achieve the desired result. result. Additionally or alternatively, certain steps may be omitted, multiple steps may be combined into one step for execution, and/or one step may be decomposed into multiple steps for execution.

Although the present application provides method operation steps such as embodiments or flowcharts, more or less operation steps may be included based on conventional or non-inventive means. The sequence of steps enumerated in the embodiments is only one of the execution sequences of many steps, and does not represent the only execution sequence. When executed by an actual device or client product, the methods shown in the embodiments or drawings can be executed sequentially or in parallel (such as a parallel processor or multi-thread processing environment, or even a distributed data processing environment). The term "comprising", "comprising" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, product, or apparatus comprising a set of elements includes not only those elements, but also other elements not expressly listed elements, or also elements inherent in such a process, method, product, or apparatus. Without further limitations, it is not excluded that there are additional identical or equivalent elements in a process, method, product or device comprising said elements.

The units, devices, or modules described in the above embodiments may be specifically implemented by computer chips or entities, or by products with certain functions. For the convenience of description, when describing the above devices, functions are divided into various modules and described separately. Of course, when implementing the present application, the functions of each module can be implemented in the same or multiple software and/or hardware, and modules that implement the same function can also be implemented by a combination of multiple sub-modules or sub-units. The device embodiments described above are only illustrative. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated. to another system, or some features may be ignored, or not implemented. In another point, the mutual coupling or direct coupling or communication connection shown or discussed may be through some interfaces, and the indirect coupling or communication connection of devices or units may be in electrical, mechanical or other forms.

Those skilled in the art also know that, in addition to realizing the controller in a purely computer-readable program code mode, it is entirely possible to make the controller use logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded The same function can be realized in the form of a microcontroller or the like. Therefore, this kind of controller can be regarded as a hardware component, and the devices included in it for realizing various functions can also be regarded as the structure in the hardware component. Or even, means for realizing various functions can be regarded as a structure within both a software module realizing a method and a hardware component.

This application may be described in the general context of computer-executable instructions, such as program modules, being executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, classes, etc. that perform particular tasks or implement particular abstract data types. The application may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote computer storage media including storage devices.

It can be known from the above description of the implementation manners that those skilled in the art can clearly understand that the present application can be implemented by means of software plus a necessary general-purpose hardware platform. Based on this understanding, the essence of the technical solution of this application or the part that contributes to the prior art can be embodied in the form of software products, and the computer software products can be stored in storage media, such as ROM/RAM, disk , optical disc, etc., including several instructions to enable a computer device (which may be a personal computer, a mobile terminal, a server, or a network device, etc.) to execute the methods described in various embodiments or some parts of the embodiments of the present application.

Each embodiment in this specification is described in a progressive manner, and the same or similar parts of each embodiment can be referred to each other, and each embodiment focuses on the difference from other embodiments. The application can be used in numerous general purpose or special purpose computer system environments or configurations. Examples: personal computers, server computers, handheld or portable devices, tablet-type devices, multiprocessor systems, microprocessor-based systems, set-top boxes, programmable electronic devices, network PCs, minicomputers, mainframe computers, including the above A distributed computing environment for any system or device, and more.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the application in detail. It should be understood that the above descriptions are only specific embodiments of the application and are not intended to limit the scope of the application. Scope of protection: All modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application shall be included within the scope of protection of this application.

Claims (10)

1. an autofocus method based on ultrasonic microscope point focus transducer, it is characterized in that, described method comprises: Obtain the A-scan signal image of the surface of the test piece; Setting focus parameters, the focus parameters include delay parameters of point focus transducers, focal length parameters and intermediary fluid temperature parameters; The speed of sound in the intermediary liquid is corrected according to the temperature of the intermediary liquid, and the autofocus position on the upper surface is calculated by the focal length and delay parameters of the acoustic lens of the point-focus transducer to move the point-focus transducer to the position to complete the upper surface surface autofocus; The A-scan signal is analyzed by discrete wavelet decomposition and Wiener deconvolution to obtain the layered information of the specimen; According to the stratification information of the specimen, the target is selected to focus on the reflection signal of the middle layer; Move the transducer to find the approximate point coordinates of the maximum reflected signal in the middle layer; Move the point focus transducer back to the last coordinate point of the maximum position point coordinates; Move the spot focusing transducer to find the precise point coordinates of the maximum value of the reflected signal to complete autofocus. 2. The method according to claim 1, wherein the focal length parameter of the point focus transducer is calculated according to the following formula: F _L =R/(1-c ₀ /c ₁ ) Among them, R is the radius of curvature of the acoustic lens, c ₀ represents the speed of sound in the intermediary liquid, and c ₁ represents the speed of sound in the lens. 3. method as claimed in claim 1, is characterized in that, described A scanning signal is made up of the complex reflected wave of inner M layer structure of detected part, and the model of described A scanning signal is: Among them, n(t) is the noise function, * means convolution, and x(t) is the incident signal function; if noise is not considered, y(t) is the convolution of x(t) and r(t). 4. The method according to claim 1, wherein the moving transducer finds the maximum position point coordinates of the intermediate layer reflection signal, comprising: Control the transducer to move vertically to the upper surface of the specimen in the step of the set distance in the Z-axis direction, analyze the sampled A-scan signal, and obtain the reflection signal of the middle layer; judge whether the reflection signal of the middle layer is gradually enhanced or weakened , if weakened, the maximum value of the layered reflection signal appears between the last two set distance step coordinate points. 5. The method according to claim 1, wherein the moving point focusing transducer to find the precise position of the maximum value of the reflected signal to complete autofocus includes: In the process of moving the point-focusing transducer each time, the A-scan signal is collected to analyze the signal, and it is judged whether the reflection signal of the middle layer is gradually strengthened or weakened. If it is weakened, the maximum value of the reflection signal of the layer and its corresponding Z Axis coordinates, move the ultrasonic transducer to the coordinates, and complete the middle layer autofocus. 6. An autofocus system based on an ultrasonic microscope point focus transducer, characterized in that the system comprises: The initial signal acquisition module is used to obtain the A-scan signal image of the surface of the test piece; A focus parameter calculation module is used to set the focus parameters, the focus parameters include the delay parameter of the point focus transducer, the focal length parameter and the temperature parameter of the intermediary fluid; The upper surface autofocus module is used to correct the speed of sound in the intermediary fluid according to the temperature of the intermediary fluid, and calculate the position of the upper surface autofocus through the focal length and delay parameters of the acoustic lens of the point focus transducer, so as to move the point focus transducer the sensor to the position to complete the autofocus on the upper surface; The layered information calculation module is used to analyze the A-scan signal through discrete wavelet decomposition and Wiener deconvolution to obtain the layered information of the specimen; The target focusing intermediate layer reflection signal determination module is used to select the target focusing intermediate layer reflection signal according to the layering information of the test piece; The point coordinate determination module of the maximum reflection signal is used to move the transducer to find the point coordinates of the maximum reflection signal in the middle layer; The rough focus module in the middle layer is used to move the point focus transducer back to the previous coordinate point of the maximum position point coordinate; The auto-focus module is used to move the point-focus transducer to find the precise position of the maximum value of the reflected signal to complete auto-focus. 7. The system according to claim 6, wherein, in the focus parameter calculation module, the focal length parameter of the point focus transducer is calculated according to the following formula: F _L =R/(1-c ₀ /c ₁ ) Among them, R is the radius of curvature of the acoustic lens, c ₀ represents the speed of sound in the intermediary liquid, and c ₁ represents the speed of sound in the lens. 8. The system according to claim 6, wherein the A-scan signal is composed of complex reflected waves of the internal M-layer structure of the detected part, and the model of the A-scan signal is: Among them, n(t) is the noise function, * means convolution, and x(t) is the incident signal function; if noise is not considered, y(t) is the convolution of x(t) and r(t). 9. The system according to claim 6, wherein the coordinate determination module of the maximum position point of the reflected signal is specifically used for: Control the transducer to move vertically to the upper surface of the specimen in the step of the set distance in the Z-axis direction, analyze the sampled A-scan signal, and obtain the reflection signal of the middle layer; judge whether the reflection signal of the middle layer is gradually enhanced or weakened , if it gradually weakens, the maximum value of the layered reflection signal appears between the last two set distance step coordinate points. 10. The system according to claim 6, wherein the autofocus module is specifically used for: In the process of moving the point-focusing transducer each time, the A-scan signal is collected to analyze the signal, and it is judged whether the reflection signal of the middle layer is gradually enhanced or weakened. If it is gradually weakened, the maximum value of the reflection signal of the layer and its corresponding value are determined. Z-axis coordinates, move the ultrasonic transducer to the coordinates to complete the autofocus of the middle layer.