Pulse echo performance characterization method, system and equipment of ultrasonic transducer

Abstract

The invention relates to the technical field of ultrasonic transducer performance testing, and discloses a pulse echo performance characterization method, system and equipment of an ultrasonic transducer, and the method comprises the steps: separating waveforms with different frequencies in a pulse echo signal reflected by a target piece to obtain harmonic signals with different frequencies; mapping on the surface of the excitation array element to obtain mapping distribution of the surface of the excitation array element; calculating a point spread function of an imaging system formed by the excitation array element and the target piece in a preset propagation medium according to a sound field of array element radiation in the preset medium; and carrying out deconvolution iteration processing on the mapping distribution based on a point spread function to obtain echo signal distribution equivalent to an infinite receiving surface, and then carrying out inverse Fourier transform to obtain a corrected pulse echo signal to represent the pulse echo performance of the ultrasonic transducer. According to the method, the problem of vibration signal loss caused by sound wave diffusion can be corrected, so that the performance characterization precision of the ultrasonic transducer is improved, the calculated amount is small, and the processing speed is high.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrasonic transducer performance testing, and in particular to a method, system and equipment for characterizing the pulse echo performance of an ultrasonic transducer. Background Art

[0002] Ultrasonic transducers can realize the mutual conversion between electrical signals and vibration signals, and are the key components for realizing medical ultrasonic imaging technology. With the development of the domestic medical device industry, the demand for technical research on high-performance medical ultrasonic transducers has increased dramatically. Performance characterization can evaluate the performance of the transducer and guide the subsequent optimization direction during the development process. For the detection of the most basic parameters of ultrasonic transducers such as sensitivity, bandwidth, center frequency, wavelength, etc., the most commonly used and effective method is the pulse echo method. Ultrasonic waves rely on pulse echo signals to obtain information about the structure of human tissues. The advantage of this method is that it can simultaneously obtain the location of the target tissue and acoustic information, so as to fully understand the special structures that may exist in the tissue. The pulse echo method is used to obtain the pulse echo signal of the transducer in a single homogeneous medium to determine whether the performance of the pulse wave excited by the transducer meets the use standard.

[0003] The performance of ultrasonic transducers is characterized based on the pulse echo method. Usually, a certain array element in the array transducer is excited. The echo generated by the target is received by the surface of the array element, and then transmitted to the oscilloscope through the amplification circuit. After calculation using the oscilloscope's FFT function, the oscilloscope will display the pulse echo signal and its Fourier transform curve. Assuming that the excited array element and the target are regarded as an ideal imaging system, when the sound wave generated by the vibration of the piezoelectric chip propagates to the surface of the array element through various matching layers, the sound wave should be a spherical wave with a certain range. In the ideal imaging system of the above spherical wave, the energy radiated from the point source on the target surface where the inhomogeneous medium is located will be concentrated in a certain range in the plane of the array element, which is an "ideal sphere" without energy diffusion.

[0004] In actual situations, when an ultrasonic probe is used to image the medium being tested in pulse-echo mode, the propagation of sound waves in the medium will produce a certain diffusion phenomenon, which will cause the "ideal sphere" to be magnified. If the receiving surface is an infinitely large plane, all vibration signals can be received without energy loss regardless of how the sound waves diffuse. In actual situations, the area of ​​the transceiver array element used for receiving is small, and the diffusion range of the sound wave will exceed the surface area of ​​the receiving array element, thereby losing some vibration signals that should have been collected. Without considering the electrical crosstalk between the array elements, the surface of the excitation array element cannot fully receive the vibration signal of the pulse echo, thereby losing the amplitude information at certain frequencies, which in turn affects the subsequent processing and performance characterization accuracy. Summary of the invention

[0005] In view of this, the present invention provides a method, system and device for characterizing the pulse echo performance of an ultrasonic transducer to solve the problem of how to improve the accuracy of characterizing the performance of an ultrasonic transducer.

[0006] In a first aspect, the present invention provides a method for characterizing the pulse echo performance of an ultrasonic transducer, the method comprising:

[0007] Acquire a pulse echo signal reflected by the target after the ultrasonic transducer is pulse-excited, and separate waveforms of different frequencies in the pulse echo signal to obtain harmonic signals of different frequencies;

[0008] Based on the wavefront propagation law of spherical waves, the separated harmonic signals are distributed on the surface of the excitation array element, and the mapping distribution of the pulse echo signal on the surface of the excitation array element is obtained;

[0009] Calculate the point spread function of the imaging system composed of the excitation array element and the target in the preset propagation medium according to the acoustic field radiated by the array element in the preset medium;

[0010] Performing deconvolution iterative processing on the mapping distribution of the pulse echo signal on the surface of the excitation array element based on the point spread function to obtain an echo signal distribution equivalent to an infinite receiving surface;

[0011] The echo signal distribution equivalent to the infinite receiving surface is subjected to inverse Fourier transformation to obtain a corrected pulse echo signal to characterize the pulse echo performance of the ultrasonic transducer.

[0012] The pulse echo performance characterization method of the ultrasonic transducer provided in this embodiment combines the diffusion phenomenon of sound waves in the medium and the convolution characteristics of the linear ultrasonic imaging system to analyze the relationship between the echo signal actually received by the excitation array element and the echo signal received by the infinite plane in the pulse echo test of the array ultrasonic transducer, and uses the deconvolution technology to correct the vibration information collected in the pulse echo test, thereby improving the performance characterization accuracy of the ultrasonic transducer, with small calculation amount and fast processing speed.

[0013] In an optional implementation, the method of distributing the separated harmonic signals on the surface of the excitation array element based on the wavefront propagation law of the spherical wave includes:

[0014] Dividing the excitation element surface of the ultrasonic transducer into sub-arrays having the same number as the harmonic signals;

[0015] A two-dimensional coordinate system is established on the surface of the excitation array element. According to the rule that the high-frequency harmonic signal corresponds to the sub-array in the preset central area of ​​the excitation array element surface, and the low-frequency harmonic signal corresponds to the sub-array in the preset edge area of ​​the excitation array element surface, the separated harmonic signal is evenly mapped on the surface of the excitation array element according to the frequency, wherein the high-frequency harmonic signal and the low-frequency harmonic signal are determined according to the central frequency of the surface of the excitation array element.

[0016] The embodiment of the present invention distributes harmonic signals of different frequencies to different sub-arrays based on the wavefront propagation law of spherical waves, so that the separated harmonic signals are evenly mapped on the array element surface according to the frequency, for subsequent deconvolution processing.

[0017] In an optional implementation, the mapping distribution s(x, y) of the pulse echo signal on the surface of the excitation array element is expressed by the following formula:

[0018]

[0019] Where x, y represent the coordinates of the signal mapping on the surface of the excitation array element, g(x, y) represents the point spread function of the imaging system, represents a two-dimensional convolution operator, and f(x,y) represents the echo signal distribution based on an infinite receiving surface.

[0020] The embodiment of the present invention establishes a convolution expression of pulse echo imaging to represent the relationship between finite and infinite receiving surface signals for subsequent processing.

[0021] In an optional implementation, the step of calculating the point spread function of an imaging system composed of an excitation array element and a target in a preset propagation medium according to the acoustic field radiated by the array element in the preset medium includes:

[0022] Using the preset boundary conditions of the rectangular array element in the liquid medium, the relationship between the point spread function and the sound field is derived;

[0023] Calculate the three-dimensional sound field distribution of a single rectangular array element in a uniform medium based on the multivariate Gaussian beam model;

[0024] The relationship between the point spread function and the sound field is combined with the three-dimensional sound field distribution to obtain the point spread function of the imaging system of the excitation array element in the liquid medium.

[0025] The embodiment of the present invention combines the diffusion phenomenon of sound waves in the medium and the convolution characteristics of the linear ultrasonic imaging system, analyzes the relationship between the echo signal actually received by the array element and the echo signal received by the infinite plane in the pulse echo test of the array transducer, and derives the relationship between the point spread function and the sound field by using the boundary conditions of the rectangular array element in the liquid medium. Then, combined with the steady-state sound field calculation method based on the multivariate Gaussian beam model, the point spread function of the exciting array element in the underwater imaging system is obtained.

[0026] In an optional implementation, the relationship between the point spread function and the sound field is expressed as:

[0027]

[0028] Among them, v0 represents the velocity amplitude of the ultrasonic transducer surface, ω represents the central frequency of the excitation element surface, ρ represents the density of the liquid medium, i represents the imaginary part, and H(x, y, z) represents the three-dimensional sound field distribution, which is expressed as:

[0029]

[0030] Where k represents the wave number, c represents the speed of sound in the liquid medium, a represents the length of the array element in the x-axis direction, b represents the length of the array element in the y-axis direction, f represents the center frequency of the array element, z represents the length of the z-axis in the three-dimensional space coordinates, and A l (n),B l (n) represents 25 sets of complex-valued coefficients.

[0031] In an optional implementation, the Richardson-Lucy algorithm is used based on the point spread function, and a preset iterative convergence condition is set to perform deconvolution iterative calculation on the mapping distribution of the pulse echo signal on the surface of the excitation array element to obtain the optimal echo signal distribution equivalent to an infinite receiving surface.

[0032] In the embodiment of the present invention, the Richardson-Lucy algorithm is used to perform deconvolution iterative calculation on s(x, y). This method has a fast processing speed, can ensure the efficiency of pulse echo testing of ultrasonic transducers, and is more in line with practical applications in the industry.

[0033] In a second aspect, the present invention provides a pulse echo performance characterization system for an ultrasonic transducer, the system comprising:

[0034] A harmonic signal acquisition module is used to acquire a pulse echo signal reflected by the target after the ultrasonic transducer is pulse-excited, and to separate waveforms of different frequencies in the pulse echo signal to obtain harmonic signals of different frequencies;

[0035] A pulse echo signal mapping module is used to distribute the separated harmonic signal on the surface of the excitation array element based on the wavefront propagation law of the spherical wave, so as to obtain the mapping distribution of the pulse echo signal on the surface of the excitation array element;

[0036] A point spread function calculation module, used to calculate the point spread function of an imaging system composed of an excitation array element and a target in a preset propagation medium according to the sound field radiated by the array element in the preset medium;

[0037] A deconvolution iterative processing module, used for performing deconvolution iterative processing on the mapping distribution of the pulse echo signal on the surface of the excitation array element based on the point spread function, so as to obtain an echo signal distribution equivalent to an infinite receiving surface;

[0038] The pulse echo performance characterization module is used to perform inverse Fourier transform on the echo signal distribution equivalent to the infinite receiving surface to obtain a corrected pulse echo signal to characterize the pulse echo performance of the ultrasonic transducer.

[0039] In a third aspect, the present invention provides a device for characterizing the pulse echo performance of an ultrasonic transducer, comprising: a memory and a processor, the memory and the processor being communicatively connected to each other, the memory storing computer instructions, and the processor executing the computer instructions to execute the method for characterizing the pulse echo performance of an ultrasonic transducer of the first aspect or any corresponding embodiment thereof.

[0040] In a fourth aspect, the present invention provides a computer-readable storage medium having computer instructions stored thereon, the computer instructions being used to enable a computer to execute the method for characterizing the pulse echo performance of an ultrasonic transducer according to the first aspect or any corresponding embodiment thereof.

[0041] In a fifth aspect, the present invention provides a computer program product, comprising computer instructions for causing a computer to execute the method for characterizing the pulse echo performance of an ultrasonic transducer according to the first aspect or any corresponding embodiment thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0043] Figure 1 is a flow chart of a method for characterizing the pulse echo performance of an ultrasonic transducer according to an embodiment of the present invention;

[0044] Figure 2It is a schematic diagram of establishing a two-dimensional coordinate system on the surface of an excitation array element according to an embodiment of the present invention and distributing harmonic signals of different frequencies to different sub-arrays;

[0045] Figure 3 is a flow chart of another method for characterizing the pulse echo performance of an ultrasonic transducer according to an embodiment of the present invention;

[0046] Figure 4 is a schematic diagram of the relative positions of the array element surface and the target surface according to an embodiment of the present invention;

[0047] Figure 5 is an example of 25 sets of complex-valued coefficients according to an embodiment of the present invention;

[0048] Figure 6 is a structural block diagram of a pulse echo performance characterization system for an ultrasonic transducer according to an embodiment of the present invention;

[0049] Figure 7 is a structural block diagram of a pulse echo performance characterization system of another ultrasonic transducer according to an embodiment of the present invention;

[0050] Figure 8 It is a schematic diagram of the hardware structure of a computer device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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 those skilled in the art without creative work are within the scope of protection of the present invention.

[0052] In actual situations, the area of ​​the receiving and transmitting elements of the ultrasonic transducer is relatively small, and the diffusion range of the sound waves will exceed the surface area of ​​the receiving elements, thereby losing some vibration signals that should have been collected. Without considering the electrical crosstalk between the elements, the surface of the excitation element cannot completely receive the vibration signal of the pulse echo, thereby losing the amplitude information at certain frequencies, which in turn affects the subsequent processing and performance characterization accuracy. How to overcome the information loss caused by the diffusion of sound waves on the small receiving surface of the existing pulse echo method, make up for the loss of pulse echo frequency and insufficient performance test accuracy of the existing method in a single imaging medium, and improve the accuracy of ultrasonic transducer performance characterization while ensuring detection efficiency, is a technical problem that needs to be solved at present.

[0053] According to an embodiment of the present invention, an embodiment of a method for characterizing the pulse echo performance of an ultrasonic transducer is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in an order different from that shown here.

[0054] In this embodiment, a pulse echo performance characterization method of an ultrasonic transducer is provided, which can be applied to array ultrasonic transducers in the medical device industry. Figure 1 is a flow chart of a method for characterizing the pulse echo performance of an ultrasonic transducer according to an embodiment of the present invention. Figure 1 As shown, the process includes the following steps:

[0055] Step S101, obtaining a pulse echo signal reflected by a target after pulse excitation of an ultrasonic transducer, and separating waveforms of different frequencies in the pulse echo signal to obtain harmonic signals of different frequencies.

[0056] Specifically, the constructed pulse echo test platform is used to pulse excite the ultrasonic transducer to be detected, the pulse echo signal reflected by the steel target is collected, the waveforms of different frequencies in the pulse signal are separated, and the harmonic signals of different frequencies in the pulse echo are obtained: v1(t), v2(t), ..., v n (t), n is the number of harmonic signals.

[0057] Step S102 : Distribute the separated harmonic signals on the surface of the excitation array element based on the wavefront propagation law of the spherical wave, and obtain the mapping distribution of the pulse echo signal on the surface of the excitation array element.

[0058] Specifically, Figure 2 As shown, the excitation element surface of the ultrasonic transducer is divided into sub-arrays with the same number as the harmonic signals; a two-dimensional coordinate system xy is established on the excitation element surface, and the high-frequency harmonic signal corresponds to the sub-array in the center area of ​​the element surface, and the low-frequency harmonic signal corresponds to the sub-array in the edge area of ​​the element surface, so as to realize the separation of the harmonic signals v1(t), v2(t), ..., v n (t) is evenly mapped on the surface of the excitation array element according to the frequency. The coordinates of the signal mapped on the surface of the array element can be recorded as (x, y), x = 1, 2, ..., i; y = 1, 2, ..., j; i × j = n. Among them, the high-frequency harmonic signal and the low-frequency harmonic signal are determined according to the center frequency of the excitation array element surface. The signal lower than the center frequency of the pulse echo is regarded as the low-frequency harmonic signal, and the signal higher than the center frequency of the pulse echo is regarded as the high-frequency harmonic signal.

[0059] Step S103, calculating the point spread function of the imaging system composed of the excitation array elements and the target in the preset propagation medium according to the acoustic field radiated by the array elements in the preset medium.

[0060] In the embodiment of the present invention, the imaging system formed by the excited array elements and the target in the water medium is regarded as a linear input-output system, and the point spread function of the imaging system is calculated according to the acoustic field radiated by the array elements in the liquid medium.

[0061] Step S104: performing deconvolution iterative processing on the mapping distribution of the pulse echo signal on the surface of the excitation array element based on the point spread function to obtain an echo signal distribution equivalent to an infinite receiving surface.

[0062] The embodiment of the present invention is based on the diffusion phenomenon of sound waves in the medium and the convolution characteristics of the linear ultrasonic imaging system. By analyzing the relationship between the echo signal actually received by the array element and the echo signal received by the infinite plane, the deconvolution technology is used to correct the vibration information collected in the pulse echo test based on the point spread function of the imaging system, and the echo signal distribution equivalent to the infinite receiving surface is obtained.

[0063] Step S105 , performing inverse Fourier transform on the echo signal distribution equivalent to the infinite receiving surface to obtain a corrected pulse echo signal to characterize the pulse echo performance of the ultrasonic transducer.

[0064] Specifically, by performing inverse Fourier transform on the echo signal distribution of the infinite receiving surface, a time domain signal is obtained to characterize the pulse echo performance.

[0065] The pulse echo performance characterization method of the ultrasonic transducer provided in the embodiment of the present invention combines the diffusion phenomenon of sound waves in the medium and the convolution characteristics of the linear ultrasonic imaging system, analyzes the relationship between the echo signal actually received by the excitation array element and the echo signal received by the infinite plane in the pulse echo test of the array ultrasonic transducer, and uses the deconvolution technology to correct the vibration information collected in the pulse echo test, thereby improving the performance characterization accuracy of the ultrasonic transducer, with small calculation amount and fast processing speed.

[0066] This embodiment also provides a method for characterizing the pulse echo performance of an ultrasonic transducer. Figure 3 is a flow chart of a method for characterizing the pulse echo performance of an ultrasonic transducer according to an embodiment of the present invention. Figure 3 As shown, the process includes the following steps:

[0067] Step S301, obtain the pulse echo signal reflected by the target after the ultrasonic transducer is pulse-excited, and separate the waveforms of different frequencies in the pulse echo signal to obtain harmonic signals of different frequencies. For details, please refer to Figure 1Step S101 of the illustrated embodiment will not be described in detail here.

[0068] Step S302: distribute the separated harmonic signals on the surface of the excitation array element based on the wavefront propagation law of the spherical wave, and obtain the mapping distribution of the pulse echo signal on the surface of the excitation array element. Figure 1 Step S102 of the illustrated embodiment will not be described in detail here.

[0069] Step S303, calculating the point spread function of the imaging system composed of the excitation array element and the target in the preset propagation medium according to the acoustic field radiated by the array element in the preset medium. Specifically, step S303 includes:

[0070] Step S3031, using the preset boundary conditions of the rectangular array element in the liquid medium, deriving the relationship between the point spread function and the sound field;

[0071] Step S3032, calculating the three-dimensional sound field distribution of a single rectangular array element in a uniform medium based on a multivariate Gaussian acoustic beam model;

[0072] Step S3033: combining the relationship between the point spread function and the sound field with the three-dimensional sound field distribution to obtain the point spread function of the imaging system of the excitation array element in the liquid medium.

[0073] Specifically, in the pulse echo mode, the echo signal distribution based on the infinite receiving surface is f(x, y), where x and y are coordinate points on the surface of the excitation array element. The mapping distribution of the harmonic signals of different frequencies on the surface of the excitation array element is s(x, y), which can be expressed as the convolution of f(x, y) and the point spread function of the imaging system. The mapping distribution s(x, y) of the pulse echo signal on the surface of the excitation array element is expressed by the following formula:

[0074]

[0075] Where g(x,y) is the point spread function of the imaging system, is a two-dimensional convolution operator. Equation (1) is the convolution expression of pulse echo imaging, which expresses the relationship between finite and infinite receiving surface signals.

[0076] like Figure 4 As shown in the figure, if the area of ​​the excitation array element is A(x, y), the plane where the target surface is located is the pulse reflection plane, and the reflection plane is assumed to be at a distance z=z0 and parallel to the array element surface. The pulse echo amplitude f(x, y) reflected on the target plane can be reconstructed based on the signal received on the array element surface. If the signal function on the excitation array element surface is S(t, x, y), then the signal function is expressed as:

[0077]

[0078] Where x′, y′ are the coordinates on the target surface, p(t, x′, y′, z) is the acoustic pressure field on the array element surface, and t is a variable in the time domain. The acoustic pressure field is given by the following wave equation:

[0079]

[0080] Where c is the sound velocity of the medium around the array element. The surface of the solid immersed in the liquid in contact with the liquid is a rigid interface. In the case of a hard boundary in the liquid medium, the particle velocity perpendicular to the boundary surface is zero. Figure 4 In the example, the boundary is perpendicular to the z-axis because the boundary condition specifies that the velocity in the z-axis is v. z (x, y, z). For a medium with a density of ρ, the relationship between its pressure p and velocity v is expressed as:

[0081]

[0082] The Rayleigh integral solution of the acoustic field is given under the Direk boundary condition, but the diffraction problem of the acoustic wave in the medium will lead to the generation of mixed boundary conditions. The approximate solution for the reflecting object of arbitrary shape can be obtained by Kirchhoff approximation correction. In this case, equation (2) can be written as the convolution form of the pulse echo amplitude f(x′, y′) at the plane x′-y′ and the point spread function of the imaging system:

[0083]

[0084] Based on Kirchhoff's approximation, the point spread function can be obtained, that is, the relationship between the point spread function g(x, y) and the three-dimensional sound field distribution H(x, y, z) can be expressed as:

[0085]

[0086] Where v0 represents the velocity amplitude of the ultrasonic transducer surface, ω represents the central frequency of the excitation element surface, ρ represents the density of the liquid medium, i represents the imaginary part, and H(x, y, z) represents the three-dimensional sound field distribution. Equation (6) shows the relationship between the point spread function g(x, y) and the sound field distribution H(x, y, z) at the target plane (z = z0).

[0087] In order to obtain the acoustic field distribution function of the array element excited at the target surface, the embodiment of the present invention calculates the three-dimensional acoustic pressure field of a single rectangular array element in a uniform medium based on a multivariate Gaussian acoustic beam model, thereby deriving the required point spread function. Among them, the steady-state acoustic field excited by the rectangular array element in water can be expressed as:

[0088]

[0089] Where k represents the wave number, c represents the speed of sound in the liquid medium, a represents the length of the array element in the x-axis direction, b represents the length of the array element in the y-axis direction, f represents the center frequency of the array element, z represents the length of the z-axis in the three-dimensional space coordinates, and A l (n),B l (n) represents 25 sets of complex-valued coefficients, such as Figure 5 shown.

[0090] Substituting equations (7) and (8) into equation (6) can obtain the point spread function. It should be noted that the steady-state sound field distribution of the above-mentioned excitation array element on the target plane can be calculated by other analytical methods or finite element methods, and the above is only used as an example.

[0091] Step S304: performing deconvolution iterative processing on the mapping distribution of the pulse echo signal on the surface of the excitation array element based on the point spread function to obtain an echo signal distribution equivalent to an infinite receiving surface.

[0092] In the embodiment of the present invention, the Richardson-Lucy algorithm is used to perform deconvolution iterative calculation on s(x, y). This method has a fast processing speed, can ensure the efficiency of pulse echo testing of ultrasonic transducers, and is more in line with practical applications in the industry.

[0093] The mapping distribution s(x, y) of the pulse echo signal received on the surface of a finite-sized array element is obtained by convolution of f(x, y) and g(x, y). The probability density function of the distribution of pulse signals of different frequencies on the surface of the array element can be expressed as:

[0094]

[0095] There are n pulse harmonic signals distributed on the surface of the array element, then the likelihood function L is:

[0096]

[0097] In the Richardson-Lucy iterative algorithm, when the partial derivatives of the likelihood function L with respect to f(x, y) are all zero, the probability density function has a maximum likelihood solution, so the iterative formula for the amplitude of the reflected echo f(x, y) on the target plane is:

[0098]

[0099] in, is the complex conjugate function of the point spread function g(x,y), and e in this formula represents the number of iterations required for deconvolution correction. e With f e-1 The difference between is used to judge whether the iteration has completed convergence. The specific iteration convergence criteria are as follows:

[0100]

[0101] In one embodiment, the minimum threshold value can be set to 0.5%, which is only an example and is not limited thereto. When the iteration meets the above judgment condition, the iteration is exited, and the corresponding number of iterations is the optimal number of iterations, and the optimal echo signal distribution f(x, y) based on the infinite receiving surface is obtained.

[0102] Step S305, perform inverse Fourier transform on the echo signal distribution equivalent to the infinite receiving surface to obtain a corrected pulse echo signal to characterize the pulse echo performance of the ultrasonic transducer. Figure 1 Step S105 of the illustrated embodiment will not be described in detail here.

[0103] The pulse echo performance characterization method of the ultrasonic transducer provided in this embodiment combines the diffusion phenomenon of sound waves in the medium and the convolution characteristics of the linear ultrasonic imaging system, analyzes the relationship between the echo signal actually received by the array element and the echo signal received by the infinite plane in the pulse echo test of the array transducer, and uses the boundary conditions of the rectangular array element in the liquid medium to derive the relationship between the point spread function and the sound field, and then combines it with the steady-state sound field calculation method based on the multivariate Gaussian beam model to obtain the point spread function of the exciting array element in the underwater imaging system, and finally uses the Richardson-Lucy algorithm to obtain the echo signal distribution equivalent to the infinite receiving surface. The method provided by the present invention can correct the problem of vibration signal loss caused by sound wave diffusion to a certain extent, and has a small amount of calculation, fast processing speed, and improves the test accuracy of pulse echo.

[0104] In this embodiment, a pulse echo performance characterization system for an ultrasonic transducer is also provided, and the system is used to implement the above-mentioned embodiments and preferred implementation modes, and the descriptions that have been made are not repeated here. As used below, the term "module" can implement a combination of software and / or hardware for a predetermined function. Although the system described in the following embodiments is preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceivable.

[0105] The embodiment of the present invention provides a pulse echo performance characterization system of an ultrasonic transducer, such as Figure 6 As shown, including:

[0106] The harmonic signal acquisition module 601 is used to acquire the pulse echo signal reflected by the target after the ultrasonic transducer is pulse-excited, and separate the waveforms of different frequencies in the pulse echo signal to obtain harmonic signals of different frequencies;

[0107] The pulse echo signal mapping module 602 is used to distribute the separated harmonic signal on the surface of the excitation array element based on the wavefront propagation law of the spherical wave, so as to obtain the mapping distribution of the pulse echo signal on the surface of the excitation array element;

[0108] A point spread function calculation module 603 is used to calculate the point spread function of the imaging system composed of the excitation array element and the target in the preset propagation medium according to the sound field radiated by the array element in the preset medium;

[0109] A deconvolution iterative processing module 604 is used to perform deconvolution iterative processing on the mapping distribution of the pulse echo signal on the surface of the excitation array element based on the point spread function to obtain an echo signal distribution equivalent to an infinite receiving surface;

[0110] The pulse echo performance characterization module 605 is used to perform an inverse Fourier transform on the echo signal distribution equivalent to an infinite receiving surface to obtain a corrected pulse echo signal to characterize the pulse echo performance of the ultrasonic transducer.

[0111] In some optional embodiments, such as Figure 7 As shown, the pulse echo signal mapping module 602 includes:

[0112] A subarray division unit 6021 is used to divide the excitation element surface of the ultrasonic transducer into subarrays with the same number as the harmonic signal;

[0113] The signal mapping unit 6022 is used to establish a two-dimensional coordinate system on the surface of the excitation array element, correspond the high-frequency harmonic signal to the preset central area of ​​the surface of the excitation array element, correspond the low-frequency harmonic signal to the preset edge area of ​​the surface of the excitation array element, and evenly map the separated harmonic signal on the surface of the excitation array element according to the frequency, wherein the high-frequency harmonic signal and the low-frequency harmonic signal are determined according to the center frequency of the surface of the excitation array element.

[0114] In some optional implementations, the mapping distribution s(x, y) of the pulse echo signal obtained in the signal mapping unit on the surface of the excitation array element is expressed by the following formula:

[0115]

[0116] Where x, y represent the coordinates of the signal mapping on the surface of the excitation array element, g(x, y) represents the point spread function of the imaging system, represents a two-dimensional convolution operator, and f(x,y) represents the echo signal distribution based on an infinite receiving surface.

[0117] In some optional embodiments, such as Figure 7 As shown, the point spread function calculation module 603 includes:

[0118] A point spread function and sound field relationship analysis unit 6031, used to derive a relationship between the point spread function and the sound field using preset boundary conditions of the rectangular array element in the liquid medium;

[0119] A three-dimensional sound field distribution calculation unit 6032 is used to calculate the three-dimensional sound field distribution of a single rectangular array element in a uniform medium based on a multivariate Gaussian acoustic beam model;

[0120] The point spread function calculation unit 6033 is used to combine the relationship between the point spread function and the sound field with the three-dimensional sound field distribution to obtain the point spread function of the imaging system of the excitation array element in the liquid medium.

[0121] In some optional implementations, the relationship between the point spread function and the sound field is expressed as:

[0122]

[0123] Among them, v0 represents the velocity amplitude of the ultrasonic transducer surface, ω represents the central frequency of the excitation element surface, ρ represents the density of the liquid medium, i represents the imaginary part, and H(x, y, z) represents the three-dimensional sound field distribution, which is expressed as:

[0124]

[0125]

[0126] Where k represents the wave number, c represents the speed of sound in the liquid medium, a represents the length of the array element in the x-axis direction, b represents the length of the array element in the y-axis direction, f represents the center frequency of the array element, z represents the length of the z-axis in the three-dimensional space coordinates, and A l (n),B l (n) represents 25 sets of complex-valued coefficients.

[0127] In some optional implementations, the deconvolution iterative processing module 604 uses the Richardson-Lucy algorithm based on the point spread function, sets a preset iterative convergence condition, and performs deconvolution iterative calculation on the mapping distribution of the pulse echo signal on the surface of the excitation array element to obtain the optimal echo signal distribution equivalent to an infinite receiving surface.

[0128] The further functional description of each of the above modules and units is the same as that of the above corresponding embodiments and will not be repeated here.

[0129] The pulse echo performance characterization system of the ultrasonic transducer in this embodiment is presented in the form of a functional unit, where the unit refers to an ASIC (Application Specific Integrated Circuit) circuit, a processor and memory that executes one or more software or fixed programs, and / or other devices that can provide the above functions.

[0130] The embodiment of the present invention also provides a computer device having the above Figure 6 or Figure 7 The pulse-echo performance characterization system of the ultrasonic transducer is shown.

[0131] See also Figure 8 , Figure 8 is a schematic diagram of the structure of a computer device provided by an optional embodiment of the present invention, such as Figure 8 As shown, the computer device includes: one or more processors 10, a memory 20, and interfaces for connecting various components, including high-speed interfaces and low-speed interfaces. Various components are connected to each other using different buses for communication, and can be installed on a common mainboard or installed in other ways as needed. The processor can process the instructions executed in the computer device, including instructions stored in or on the memory to display the graphical information of the GUI on an external input / output device (such as, a display device coupled to the interface). In some optional embodiments, if necessary, multiple processors and / or multiple buses can be used together with multiple memories and multiple memories. Similarly, multiple computer devices can be connected, and each device provides some necessary operations (for example, as a server array, a group of blade servers, or a multi-processor system). Figure 8 A processor 10 is taken as an example.

[0132] The processor 10 may be a central processing unit, a network processor or a combination thereof. The processor 10 may further include a hardware chip. The hardware chip may be a dedicated integrated circuit, a programmable logic device or a combination thereof. The programmable logic device may be a complex programmable logic device, a field programmable gate array, a general purpose array logic or any combination thereof.

[0133] The memory 20 stores instructions executable by at least one processor 10, so that at least one processor 10 executes the method shown in the above embodiment.

[0134] The memory 20 may include a program storage area and a data storage area, wherein the program storage area may store an operating system, an application required for at least one function; the data storage area may store data created according to the use of the computer device, etc. In addition, the memory 20 may include a high-speed random access memory, and may also include a non-transient memory, such as at least one disk storage device, a flash memory device, or other non-transient solid-state storage device. In some optional embodiments, the memory 20 may optionally include a memory remotely arranged relative to the processor 10, and these remote memories may be connected to the computer device via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0135] The memory 20 may include a volatile memory, such as a random access memory; the memory may also include a non-volatile memory, such as a flash memory, a hard disk or a solid state drive; the memory 20 may also include a combination of the above types of memory.

[0136] The computer device further comprises a communication interface 30 for the computer device to communicate with other devices or a communication network.

[0137] The embodiment of the present invention also provides a computer-readable storage medium. The method according to the embodiment of the present invention can be implemented in hardware, firmware, or can be implemented as a computer code that can be recorded in a storage medium, or can be implemented as a computer code that is originally stored in a remote storage medium or a non-temporary machine-readable storage medium and will be stored in a local storage medium through a network download, so that the method described herein can be stored in such software processing on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. Among them, the storage medium can be a magnetic disk, an optical disk, a read-only storage memory, a random access memory, a flash memory, a hard disk or a solid-state hard disk, etc.; further, the storage medium can also include a combination of the above types of memories. It can be understood that a computer, a processor, a microprocessor controller, or programmable hardware includes a storage component that can store or receive software or computer code. When the software or computer code is accessed and executed by a computer, a processor, or hardware, the method shown in the above embodiment is implemented.

[0138] A part of the present invention may be applied as a computer program product, such as a computer program instruction, which, when executed by a computer, can call or provide the method and / or technical solution according to the present invention through the operation of the computer. Those skilled in the art should understand that the existence of the computer program instruction in a computer-readable medium includes, but is not limited to, a source file, an executable file, an installation package file, etc., and accordingly, the way in which the computer program instruction is executed by the computer includes, but is not limited to: the computer directly executes the instruction, or the computer compiles the instruction and then executes the corresponding compiled program, or the computer reads and executes the instruction, or the computer reads and installs the instruction and then executes the corresponding installed program. Here, the computer-readable medium may be any available computer-readable storage medium or communication medium accessible to the computer.

[0139] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A method for characterizing the pulse echo performance of an ultrasonic transducer, characterized in that: The method comprises: Acquire a pulse echo signal reflected by the target after the ultrasonic transducer is pulse-excited, and separate waveforms of different frequencies in the pulse echo signal to obtain harmonic signals of different frequencies; Based on the wavefront propagation law of spherical waves, the separated harmonic signals are distributed on the surface of the excitation array element to obtain the mapping distribution of the pulse echo signal on the surface of the excitation array element; the point spread function of the imaging system composed of the excitation array element and the target in the preset propagation medium is calculated according to the acoustic field radiated by the array element in the preset medium; Performing deconvolution iterative processing on the mapping distribution of the pulse echo signal on the surface of the excitation array element based on the point spread function to obtain an echo signal distribution equivalent to an infinite receiving surface; The echo signal distribution equivalent to the infinite receiving surface is subjected to inverse Fourier transformation to obtain a corrected pulse echo signal to characterize the pulse echo performance of the ultrasonic transducer.

2. The method according to claim 1, characterized in that The method of distributing the separated harmonic signals on the surface of the excitation array element based on the wavefront propagation law of the spherical wave includes: Dividing the excitation element surface of the ultrasonic transducer into sub-arrays having the same number as the harmonic signals; A two-dimensional coordinate system is established on the surface of the excitation array element. According to the rule that the high-frequency harmonic signal corresponds to the sub-array in the preset central area of ​​the excitation array element surface, and the low-frequency harmonic signal corresponds to the sub-array in the preset edge area of ​​the excitation array element surface, the separated harmonic signal is evenly mapped on the surface of the excitation array element according to the frequency, wherein the high-frequency harmonic signal and the low-frequency harmonic signal are determined according to the central frequency of the surface of the excitation array element.

3. The method according to claim 1 or 2, characterized in that: The mapping distribution s(x, y) of the pulse echo signal on the surface of the excitation array element is expressed by the following formula: Where x, y represent the coordinates of the signal mapping on the surface of the excitation array element, g(x, y) represents the point spread function of the imaging system, represents a two-dimensional convolution operator, and f(x,y) represents the echo signal distribution based on an infinite receiving surface.

4. The method according to claim 3, characterized in that The step of calculating the point spread function of the imaging system composed of the excitation array element and the target in the preset propagation medium according to the acoustic field radiated by the array element in the preset medium includes: Using the preset boundary conditions of the rectangular array element in the liquid medium, the relationship between the point spread function and the sound field is derived; Calculate the three-dimensional sound field distribution of a single rectangular array element in a uniform medium based on the multivariate Gaussian beam model; The relationship between the point spread function and the sound field is combined with the three-dimensional sound field distribution to obtain the point spread function of the imaging system of the excitation array element in the liquid medium.

5. The method according to claim 4, characterized in that The relationship between the point spread function and the sound field is expressed as: Among them, v0 represents the velocity amplitude of the ultrasonic transducer surface, ω represents the central frequency of the excitation element surface, ρ represents the density of the liquid medium, i represents the imaginary part, and H(x, y, z) represents the three-dimensional sound field distribution, which is expressed as: Where k represents the wave number, c represents the speed of sound in the liquid medium, a represents the length of the array element in the x-axis direction, b represents the length of the array element in the y-axis direction, f represents the center frequency of the array element, z represents the length of the z-axis in the three-dimensional space coordinates, and A l (n),B l (n) represents 25 sets of complex-valued coefficients.

6. The method according to claim 1, characterized in that The step of performing deconvolution iterative processing on the mapping distribution of the pulse echo signal on the surface of the excitation array element based on the point spread function to obtain an echo signal distribution equivalent to an infinite receiving surface includes: Based on the point spread function, the Richardson-Lucy algorithm is used to perform deconvolution iterative calculation on the mapping distribution of the pulse echo signal on the surface of the excitation array element by setting the preset iterative convergence condition, and the optimal echo signal distribution equivalent to an infinite receiving surface is obtained.

7. A pulse echo performance characterization system for an ultrasonic transducer, characterized in that: The system comprises: A harmonic signal acquisition module is used to acquire a pulse echo signal reflected by the target after the ultrasonic transducer is pulse-excited, and to separate waveforms of different frequencies in the pulse echo signal to obtain harmonic signals of different frequencies; A pulse echo signal mapping module is used to distribute the separated harmonic signal on the surface of the excitation array element based on the wavefront propagation law of the spherical wave, so as to obtain the mapping distribution of the pulse echo signal on the surface of the excitation array element; A point spread function calculation module, used to calculate the point spread function of an imaging system composed of an excitation array element and a target in a preset propagation medium according to the sound field radiated by the array element in the preset medium; A deconvolution iterative processing module, used for performing deconvolution iterative processing on the mapping distribution of the pulse echo signal on the surface of the excitation array element based on the point spread function, so as to obtain an echo signal distribution equivalent to an infinite receiving surface; The pulse echo performance characterization module is used to perform inverse Fourier transform on the echo signal distribution equivalent to the infinite receiving surface to obtain a corrected pulse echo signal to characterize the pulse echo performance of the ultrasonic transducer.

8. A computer device, characterized in that: include: A memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the pulse echo performance characterization method of the ultrasonic transducer according to any one of claims 1 to 6 by executing the computer instructions.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer instructions, and the computer instructions are used to enable a computer to execute the pulse-echo performance characterization method of an ultrasonic transducer according to any one of claims 1 to 6.

10. A computer program product, characterized in that The method comprises computer instructions for causing a computer to execute the pulse-echo performance characterization method of an ultrasonic transducer according to any one of claims 1 to 6.

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