A multi-frequency ultrasonic transducer, an ultrasonic imaging system and method having the same

Abstract

The present invention provides a multi-frequency ultrasonic transducer, an ultrasonic imaging system and method having the same. The multi-frequency transducer includes a first transducer assembly and a second transducer assembly. The frequency of the second transducer assembly is lower than that of the first transducer assembly. Each first transducer assembly and each second transducer assembly include a backing layer, a piezoelectric layer and a matching layer which are stacked. The second transducer assemblies are arranged on both sides or around the first transducer assembly. It further includes an integral acoustic lens which is simultaneously stacked on the front side of the matching layer of the first transducer assembly and the front side of the matching layer of the second transducer assembly. It also includes a flexible circuit board which is electrically connected to the piezoelectric layer. The piezoelectric layer includes a ground electrode surface and a signal electrode surface. The ground electrode surface and the signal electrode surface respectively have electrodes, and the electrodes of the signal electrode surface are cut to form a plurality of piezoelectric array elements in the piezoelectric layer.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrasonic transducers, and in particular, to a multi-frequency ultrasonic transducer, an ultrasonic imaging system and method having the same. Background Art

[0002] Ultrasonic imaging is widely used in fields such as medical diagnosis and industrial inspection, and has advantages such as non-destructive, non-radiative, convenient, and low cost. An ultrasonic transducer is a device that can convert an electrical excitation signal into an ultrasonic signal and can also convert the reflected ultrasonic signal into an electrical signal, and is a key component of an ultrasonic imaging device. The performance of the ultrasonic transducer directly determines the quality of ultrasonic imaging. Ultrasonic transducers are mainly divided into single-element ultrasonic transducers and array ultrasonic transducers. Due to the convenience of imaging, currently, ultrasonic imaging devices in the medical and industrial fields mainly use array ultrasonic transducers.

[0003] In conventional ultrasonic imaging, an ultrasonic acoustic signal is directed to a detection area, and the corresponding reflected echo signal is detected. The characteristics of the echo signal, such as amplitude, phase shift, Doppler frequency shift, power, etc., are analyzed and quantified into pixel data, and these pixel data are used to create an image of the flow or represent the flow. Using conventional single-transducer ultrasonic imaging, the received ultrasonic echo signal is in the same frequency range as the transmitted ultrasonic signal.

[0004] Another method of performing ultrasonic imaging is to apply an ultrasonic signal at one frequency to an area of interest and capture and analyze the received echo signal at another frequency (such as one or more harmonics of the transmitted ultrasonic signal). Generally, the frequency of the harmonic is 3-5 times that of the transmitted signal. A specific use of harmonic imaging is to image tissues using a contrast agent. The contrast agent is usually a liquid or lipid-coated microbubble, the size of which can resonate at a specific transmitted ultrasonic frequency. Exposure of the body to ultrasonic waves at the resonance frequency of the microbubbles causes the bubbles to rupture and generate non-linear ultrasonic echo signals with much higher frequencies than the applied ultrasonic waves. For example, non-linear microbubbles can be designed to resonate at 1-6 MHz, but generate echo signals in the range of 10-30 MHz. The high-frequency echo signals allow the generation and study of detailed images of tissue structures, such as the microvascular system surrounding tumors in a clinical or preclinical setting.

[0005] The most conventional way to perform dual - frequency imaging is to use a mechanically scanned single - element transducer with confocal low - frequency and high - frequency transducer elements. Although such transducers work well, faster scans can be performed using transducer arrays that can be electronically controlled. Such transducers typically have a low - frequency transducer array and a high - frequency transducer array that are aligned with each other. One problem with dual - frequency transducers is aligning the low - frequency and high - frequency arrays. In a 30 - MHz high - frequency phased array, the element size (e.g., 1 / 2λ or less) is about 25 microns. At 50 MHz, the element size is about 15 microns. The process required to align the arrays usually involves making fine adjustments to the positions of the high - frequency and low - frequency transducers on a wet workbench and then gluing them together when the best match is found. This is both time - consuming and expensive. The technology discussed in this article relates to an improved dual - frequency transducer that is easier to manufacture and has a lower manufacturing cost.

[0006] Most of the existing manufacturing methods for multi - frequency ultrasonic transducers place the low - frequency transducer behind the high - frequency transducer to form a stacked structure. Due to the occlusion of the high - frequency transducer, the acoustic wave signals emitted by the low - frequency transducer at the rear are greatly interfered, affecting the output of the acoustic signals. For the high - frequency transducer at the front, since a backing layer cannot be added at the rear, the excess acoustic signals cannot be well absorbed, and the single - oscillation time of the piezoelectric layer cannot be shortened in time, resulting in a serious decrease in bandwidth, thus affecting the imaging resolution and bandwidth. For side - by - side multi - frequency ultrasonic transducers, either they have a complex mechanical structure, which leads to an increase in processing difficulty and a decrease in equipment reliability, or multiple transducers only have fixed angles, resulting in the need to manually move the position of the transducer to change the focus, with complex operation and low precision.

[0007] In summary, most of the existing multi - frequency ultrasonic transducers are dual - frequency confocal transducers with a fixed common focus. They can only change the common focus by manually moving the position of the transducer, with complex operation and low accuracy. When the high - frequency transducer is stacked in front of the low - frequency transducer, due to the occlusion of the high - frequency transducer, it will affect the propagation of the acoustic waves emitted by the low - frequency transducer and reduce the performance of the low - frequency transducer. In practical applications, it is often necessary to accurately control the focus of the ultrasonic transducer to meet the usage requirements. For example, in treatment processes such as tumor ablation and ultrasonic drug delivery, it is necessary to accurately control the common focus to avoid damaging healthy tissue cells and causing internal bleeding or other negative symptoms. Therefore, the existing ultrasonic transducers have great limitations in practical applications. Summary of the Invention

[0008] In view of this, in order to overcome the defects of the above - mentioned existing technologies, the present invention proposes a variable - focus multi - frequency ultrasonic transducer, an ultrasonic imaging system and method having the same.

[0009] Specifically, the multi-frequency ultrasonic transducer includes a first transducer component and a second transducer component. The frequency of the second transducer component is lower than that of the first transducer component. Each of the first transducer components and each of the second transducer components includes a backing layer, a piezoelectric layer, and a matching layer arranged in a stacked manner. The second transducer components are arranged on both sides or around the first transducer component. It further includes an integrated acoustic lens, which is simultaneously stacked on the front side of the matching layer of the first transducer component and the front side of the matching layer of the second transducer component. Multiple transducers are arranged in a side-by-side or surrounding pattern without an overlapping structure, eliminating the influence between the first transducer component and the second transducer component, and enabling multi-modal imaging modes such as high-quality ultrasonic imaging, superharmonic imaging, and elastography in multiple frequency bands simultaneously.

[0010] It further includes a flexible circuit board, which is electrically connected to the piezoelectric layer. The piezoelectric layer includes a ground electrode surface and a signal electrode surface, and the ground electrode surface and the signal electrode surface each have electrodes. Moreover, the electrodes of the signal electrode surface are cut to form multiple piezoelectric array elements in the piezoelectric layer. The integrated structural design of the acoustic lens simplifies the preparation process and difficulty of the device, and improves the integration and consistency of the device. The array design of the piezoelectric layer provides the transducer with the ability of electronic focusing, making the focal position of the transducer variable in two dimensions, and greatly improving the focusing efficiency and focusing range of the transducer.

[0011] Specifically, the array elements of the ground electrode surface are arranged in a one-dimensional linear array; or, the array elements of the ground electrode surface are arranged in a two-dimensional planar array.

[0012] The integrated acoustic lens has ultrasonic focusing characteristics and is used to focus ultrasonic waves of different frequencies emitted by the first transducer component and the second transducer component on a preset single target point or multiple preset target points along a first direction. Further, the physical parameters of the integrated acoustic lens are variable, and the integrated acoustic lenses with different physical parameters focus ultrasonic waves of different frequencies emitted by the first transducer component and the second transducer component at the same depth in the first direction; or, the integrated acoustic lenses with different physical parameters focus ultrasonic waves of different frequencies emitted by the first transducer component and the second transducer component at different depths in the first direction.

[0013] The shape of the integrated acoustic lens is concave or convex. The simultaneous presence of the array design of the piezoelectric layer and the integrated acoustic lens enables the first transducer component and the second transducer component to simultaneously achieve the focusing functions in two directions of variable electronic focusing and acoustic lens physical focusing, greatly improving the accuracy of the target position and the resolution of the image.

[0014] In some embodiments, the second transducer assembly is arranged on the left and right sides of the first transducer assembly, and the second transducer assembly emits ultrasonic waves to be focused along the first direction; the focused foci formed by the ultrasonic waves emitted by the second transducer assembly after passing through the integrated acoustic lens are on the center line of the first transducer assembly, or within the left and right regions of the ultrasonic waves of the first transducer assembly.

[0015] Alternatively, the second transducer assembly is arranged on the left and right sides of the first transducer assembly, and both the second transducer assembly and the first transducer assembly emit ultrasonic waves to be focused along the first direction; the focused foci formed by the ultrasonic waves emitted by the second transducer assembly and the ultrasonic waves emitted by the first transducer assembly after passing through the integrated acoustic lens coincide in the first direction, or are at different positions on the center line of the first transducer assembly.

[0016] The flexible circuit board covers the entire surface of the piezoelectric layer; or, additional connection regions are reserved on both sides of the piezoelectric layer, and the flexible circuit board covers the surfaces of the connection regions. Preferably, the flexible circuit board covers the surfaces of the connection regions, and the piezoelectric layer is in direct contact with the backing layer, which can achieve a better sound absorption effect. The flexible circuit board is connected to one or more sides of the piezoelectric layer.

[0017] The present invention also provides a method for manufacturing a multi-frequency ultrasonic transducer for manufacturing the above multi-frequency ultrasonic transducer, and the manufacturing of the multi-frequency ultrasonic transducer includes:

[0018] Manufacturing a piezoelectric layer, including: sputtering electrodes on the ground electrode surface of the piezoelectric layer and sputtering electrodes on the signal electrode surface;

[0019] Electrically connecting the piezoelectric layer to the flexible circuit board, stacking and manufacturing a matching layer on one side of the ground electrode surface of the piezoelectric layer, and stacking and manufacturing a backing layer on the side of the signal electrode surface;

[0020] Arranging and fixing the second transducer assembly on both sides or around the first transducer assembly, and simultaneously laminating an integrated acoustic lens in front of the matching layer of the first transducer assembly and in front of the matching layer of the second transducer assembly, and fitting and fixing the integrated acoustic lens to the matching layer of the first transducer assembly and the matching layer of the second transducer assembly.

[0021] Before the step of "sputtering electrodes on the ground electrode surface of the piezoelectric layer", it further includes: cutting on the ground electrode surface according to the preset number of array elements and the spacing of the array elements of the piezoelectric layer, and filling an acoustic decoupling material into the cut slits formed;

[0022] After "sputtering electrodes on the signal electrode surface", it further includes: cutting the electrodes on the signal electrode surface according to the gaps between the array elements of the ground electrode surface.

[0023] The present invention also provides an ultrasonic imaging system, and the ultrasonic imaging system includes the above multi-frequency ultrasonic transducer.

[0024] It further includes a control unit for generating a focusing adjustment signal for the first transducer assembly and the second transducer assembly along the second direction, so that the multi-frequency ultrasonic transducer can achieve variable focusing of the focal position along the second direction.

[0025] The integrated acoustic lens realizes focusing of the first transducer assembly and the second transducer assembly along the first direction.

[0026] Wherein, the first direction intersects or is perpendicular to the second direction.

[0027] Specifically, the control unit adjusts the electronic beam synthesis of the excitation system of the multi-frequency transducer.

[0028] An imaging method of the above ultrasonic imaging system includes:

[0029] By controlling the focal positions of the first transducer assembly and the second transducer assembly, and controlling the frequencies of the first transducer assembly and the second transducer assembly, at least one of the following imaging modes is achieved:

[0030] The first imaging mode: realizing focusing of the first transducer assembly and the second transducer assembly along the first direction on a preset single target point through the structural characteristics of the integrated acoustic lens, adjusting the focal positions of the first transducer assembly and the second transducer assembly along the second direction, so that the focal positions of the first transducer assembly and the second transducer assembly along the second direction are also the preset single target point, controlling the frequencies of the first transducer assembly and the second transducer assembly, and performing multi-frequency synchronous imaging on the single target point.

[0031] The second imaging mode: making the first transducer assembly and the second transducer assembly focus on multiple target points at different positions and depths on the same section or different sections through the structural characteristics of the integrated acoustic lens and controlling the frequencies of the first transducer assembly and the second transducer assembly, and performing synchronous imaging on each target point.

[0032] In summary, the multi-frequency ultrasonic transducer of the present invention has the following beneficial effects: Multiple transducers are arranged side by side or in a surrounding pattern, without an overlapping structure, eliminating the influence between the first transducer assembly and the second transducer assembly, enabling multi-modal imaging modes of high-quality ultrasonic imaging, superharmonic imaging, and elastography in multiple frequency bands simultaneously. The array design of the piezoelectric layer provides the transducer with the ability of electronic focusing, making the focal position of the transducer variable in two dimensions, greatly improving the focusing efficiency and focusing range of the transducer. Further, the simultaneous presence of the array design of the piezoelectric layer and the acoustic lens enables the first transducer assembly and the second transducer assembly to achieve electronic focusing and physical focusing simultaneously, greatly improving the accuracy of the target position and the resolution of the image. The multi-frequency ultrasonic transducer is applicable to array ultrasonic transducers in all working frequency ranges, without an internal mechanical structure, with simple technology, high reliability, strong operability, and the integrated structural design of the acoustic lens simplifies the equipment preparation process and difficulty, improving the equipment integration and consistency. The ultrasonic imaging system applying this multi-frequency transducer can achieve multiple imaging modes by controlling the first transducer assembly and the second transducer assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0034] Figure 1 Structural schematic diagram of the multi-frequency ultrasonic transducer of the present invention;

[0035] Figure 2 Overall structural schematic diagram of the multi-frequency ultrasonic transducer of the present invention;

[0036] Figure 3a Schematic diagram of longitudinal variable electronic focusing of the multi-frequency ultrasonic transducer of the present invention;

[0037] Figure 3b Schematic diagram of transverse physical focusing of the multi-frequency ultrasonic transducer of the present invention;

[0038] Figure 4a Schematic diagram of the multi-frequency synchronous imaging mode of the multi-frequency ultrasonic transducer of the present invention;

[0039] Figure 4b Schematic diagram of synchronous imaging of the multi-frequency ultrasonic transducer of the present invention for targets at different depths simultaneously;

[0040] Figure 5a Schematic diagram of the low-frequency excitation and high-frequency reception mode of the multi-frequency ultrasonic transducer of the present invention;

[0041] Figure 5b Schematic diagram of the multi - frequency ultrasonic transducer of the present invention for performing super - harmonic shaping and elastography on targets at different depths;

[0042] Figure 6 Another structural schematic diagram of the multi - frequency ultrasonic transducer of the present invention.

[0043] Reference numerals:

[0044] 1 - First transducer assembly; 2 - Second transducer assembly; 3 - Backing layer; 4 - Flexible circuit board; 5 - Piezoelectric layer; 6 - Matching layer; 7 - Integral acoustic lens. Detailed implementation manners

[0045] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0046] The present invention provides a variable - focus multi - frequency ultrasonic transducer and an ultrasonic imaging system and method having the same. The multi - frequency ultrasonic transducer of the present invention includes a first transducer assembly and a second transducer assembly. The second transducer assembly includes two or more transducers, and the specific number thereof may be two, three, four or more. The first transducer assembly is centered, and the second transducer assembly is arranged on both sides or around the first transducer assembly, specifically, the second transducer assembly is arranged on both sides or three sides of the first transducer assembly, or arranged around the first transducer assembly. Among them, the frequency of the second transducer assembly is lower than the frequency of the first transducer assembly. It may be that the frequency of the second transducer assembly is 1 - 5 MHz; the frequency of the first transducer assembly is 5 - 30 MHz. Therefore, in the present invention, the transducers of the first transducer assembly form a high - frequency unit with a relatively high frequency in the multi - frequency ultrasonic transducer, and the transducers of the second transducer assembly form a low - frequency unit with a relatively low frequency in the multi - frequency ultrasonic transducer.

[0047] Each first transducer assembly and each second transducer assembly include a backing layer, a piezoelectric layer, and a matching layer that are stacked. The multi - frequency ultrasonic transducer further includes an integral acoustic lens, and the integral acoustic lens is stacked on the front side of the matching layer of the first transducer assembly and the front side of the matching layer of the second transducer assembly at the same time. The second transducer assembly is used for outputting acoustic signals, and the first transducer assembly is used for receiving acoustic signals. The multiple transducers are integrated using a non - superimposed structure to avoid mutual interference between the transducers.

[0048] Embodiment 1

[0049] This embodiment provides a specific structure of a dual - frequency transducer. Refer to Figure 1 and Figure 2 , the first transducer assembly 1 of the dual - frequency transducer includes a high - frequency unit and the second transducer assembly 2 includes two low - frequency units; the type of the first transducer assembly 1 can be a linear array or a planar array transducer, and can be a phased array or a non - phased array transducer. Each transducer includes a backing layer 3, a flexible circuit board 4, a piezoelectric layer 5, and a matching layer 6. Among them, the backing layer 3, the piezoelectric layer 5, and the matching layer 6 are stacked in sequence. The two low - frequency units of the second transducer assembly 2 are arranged in parallel side by side on both sides close to the first transducer assembly 1. The matching layers 6 of the first transducer assembly 1 and the second transducer assembly 2 of the dual - frequency transducer are on the same plane. All transducers are connected by a monolithic acoustic lens 7, and the monolithic acoustic lens 7 is simultaneously stacked on the front side of the matching layer 6 of the first transducer assembly 1 and the front sides of the matching layers 6 of the two second transducer assemblies 2. The surface size of the monolithic acoustic lens 7 is the same as the size of the matching layer 6 formed after the dual - frequency transducer is arranged.

[0050] Define the direction perpendicular to the surface of the piezoelectric layer 5 as the first direction. The monolithic acoustic lens 7 has a focusing characteristic, which is used to focus ultrasonic waves of different frequencies emitted by the first transducer assembly 1 and the second transducer assembly 2 on a single target point or multiple preset target points along the first direction. The physical parameters of the monolithic acoustic lens 7 are variable. The monolithic acoustic lens 7 with different physical parameters enables the ultrasonic waves emitted by the multi - frequency transducer to be focused at the same depth in the first direction, or enables the ultrasonic waves emitted by the multi - frequency transducer to be focused at different depths in the first direction. Among them, the shape of the monolithic acoustic lens 7 can be concave or convex, the number of the matching layers 6 is one layer or multiple layers, and the preparation processes of the matching layer 6 and the backing layer 3 include methods such as direct bonding, casting, centrifugation, and vapor deposition. The integrated structural design of the acoustic lens simplifies the preparation process and difficulty of the device, and improves the integration and consistency of the device. Multiple transducers are arranged in a side - by - side or surrounding pattern, without an overlapping structure, eliminating the influence between the first transducer assembly 1 and the second transducer assembly 2.

[0051] Define the direction perpendicular to the cross - section of the multi - frequency ultrasonic transducer as shown in Figure 1 as the second direction. The first direction intersects or is perpendicular to the second direction, and the focal position of the multi - frequency transducer is variable in the second direction. Define the direction parallel to the surface of the piezoelectric layer 5 as the third direction. The variable physical parameters of the monolithic acoustic lens 7 can also enable the multi - frequency transducer to be focused at different positions in the third direction.

[0052] The piezoelectric layer 5 includes a ground electrode surface provided on one side surface and a signal electrode surface provided on the other side surface. The ground electrode surface and the signal electrode surface respectively have electrodes, and the electrode on the signal electrode surface is cut to form a plurality of piezoelectric array elements in the piezoelectric layer. Specifically, on the ground electrode surface, the array elements are arranged in an array structure, and the element gaps are filled with acoustic decoupling materials, which can specifically be a one-dimensional linear array or a two-dimensional planar array; the electrodes on the surface of the signal electrode surface are cut according to the element gaps of the ground electrode surface, so that the electrical signals between the elements are independent of each other. The array design of the piezoelectric layer 5 provides the transducer with the ability of electronic focusing, making the focal positions of the transducer variable in two dimensions, and greatly improving the focusing efficiency and focusing range of the transducer. Further, the coexistence of the array design of the piezoelectric layer 5 and the integrated acoustic lens 7 enables the first transducer assembly 1 and the second transducer assembly 2 to simultaneously achieve variable electronic focusing as shown in Figure 3a and acoustic lens physical focusing in two directions as shown in Figure 3b , greatly improving the accuracy of the target position and the resolution of the image. Optionally, the material of the piezoelectric layer 5 can be a traditional piezoelectric material, or a 1-3 composite piezoelectric material or a 2-2 composite piezoelectric material.

[0053] The flexible circuit board 4 is used to realize the electrical interconnection between the piezoelectric layer 5 and the external circuit, and includes a plurality of electrode leads and 2 ground wires. The wires in the flexible circuit board 4 are respectively and correspondingly attached to each element of the piezoelectric layer 5, and the width of each wire is less than the width of the element. When the elements of the piezoelectric layer 5 are in a one-dimensional array structure, the flexible circuit board 4 can lead out the element leads from one side, or lead out the element leads in an interpenetrating manner from both sides. The element pitch of the first transducer assembly 1 is too small and the lead density on one side is too large. Preferably, the interpenetrating lead method from both sides is adopted, specifically manifested as leading out the leads every other element on one side. The leads of two adjacent elements are respectively led out from both sides, and the two leads are at positions with a pitch of one element in the direction perpendicular to the element leads. If the elements of the piezoelectric layer 5 are in a two-dimensional array structure, the flexible circuit board 4 can lead out the element leads from one side or both sides or four sides.

[0054] When the flexible circuit board 4 is connected to the piezoelectric layer 5, it can directly cover the entire surface of the piezoelectric layer 5 and be located between the piezoelectric layer 5 and the backing layer 3; or small additional connection areas can be reserved on both sides of the element, and a hollowed-out area can be cut out on a flexible circuit board 4 for connecting the electrical signal of the element to the flexible circuit board 4, so that the flexible circuit board 4 only covers the surface of the connection area on the piezoelectric layer 5, and the piezoelectric layer 5 can directly contact the backing layer 3 to obtain a better sound absorption effect. In some embodiments, it can also be that multiple flexible circuit boards 4 are respectively used on both sides of the piezoelectric layer 5 to connect the flexible circuit board 4 to the electrical signal of the element through small additional connection areas reserved on both sides of the element, so that the piezoelectric layer 5 can directly contact the backing layer 3. Since the first transducer assembly 1 is sensitive to signal interference and attenuation, preferably, the form of hollowing out the middle of the flexible circuit board 4 or using two flexible circuit boards 4 to connect to the piezoelectric layer 5 is adopted to obtain a better sound absorption effect. In this embodiment, the flexible circuit board 4 covers the surface of the signal electrode surface and is bonded to the signal electrode surface with epoxy resin according to the one-to-one correspondence relationship between the wires and the elements.

[0055] There is a certain rule for arranging the second transducer assembly 2 at the positions of the focusing foci formed by the multi-frequency transducers on the left and right sides of the first transducer assembly 1:

[0056] As for the dual-frequency transducer described in this embodiment, the second transducer assemblies 2 on both sides of the first transducer assembly 1 are respectively the first low-frequency unit and the second low-frequency unit. The ultrasonic waves emitted by the first low-frequency unit and the second low-frequency unit are focused along the first direction through the integrated acoustic lens 7. The focusing foci formed by the ultrasonic waves emitted by the first low-frequency unit and the second low-frequency unit after passing through the integrated acoustic lens 7 are on the center line of the first transducer assembly 1, or within the ultrasonic wave action area of the first transducer assembly 1.

[0057] If the first low-frequency unit, the second low-frequency unit, and the first transducer assembly 1 all emit ultrasonic waves outward, the ultrasonic waves are focused along the first direction through the integrated acoustic lens 7. The focusing foci formed by the ultrasonic waves emitted by the first low-frequency unit, the second low-frequency unit, and the first transducer assembly 1 after passing through the integrated acoustic lens 7 coincide in the first direction, or are at different positions on the center line of the first transducer assembly 1 in the first direction.

[0058] The dual-frequency transducer of this embodiment has the characteristics of multi-modal imaging because the transducers do not affect each other and can simultaneously perform super-harmonic imaging and elastography modes of low-frequency excitation and high-frequency imaging, as well as a non-interfering synchronous high-quality ultrasonic imaging mode of multi-band transducers. For example, as Figure 4a shown, the multi-band transducers use confocal characteristics to perform multi-frequency synchronous imaging on a single target point to improve the imaging quality; as Figure 4bIt is shown that multi-frequency characteristics are used to synchronously image targets at different positions and depths on the same cross-section or different cross-sections, enhancing the imaging range and imaging efficiency of the transducer; such as Figure 5a It is shown that superharmonic imaging and elastography for low-frequency signal excitation and high-frequency signal reception at the same focused target position; such as Figure 5b It is shown that synchronous low-frequency excitation and high-frequency imaging are performed on target positions at different depths, or a pair of high-frequency units and low-frequency units are used to perform synchronous superharmonic imaging / elastography on the same target position and at the same time, another transducer is used for fundamental wave imaging or guidance.

[0059] The present invention is applicable to array ultrasonic transducers in all frequency ranges. This embodiment only provides a specific structure of a dual-frequency transducer. According to the principle of the present invention, those skilled in the art can combine multiple transducers into a multi-frequency ultrasonic transducer in the form of arranging the second transducer assembly 2 around the first transducer assembly 1 or arranging the second transducer assembly 2 side by side with the first transducer assembly 1. Among them, the number of the second transducer assemblies 2 is not limited.

[0060] Embodiment 2

[0061] This embodiment provides a manufacturing method of a dual-frequency ultrasonic transducer composed of a first transducer assembly 1 and second transducer assemblies 2 on both sides as shown in Figure 6 The specific steps are as follows:

[0062] Manufacture array elements in a one-dimensional linear array pattern on the ground electrode surface of the piezoelectric layer 5, and sputter the electrodes on the ground electrode surface:

[0063] Grind both sides of the piezoelectric wafer to be flat, and the thickness is greater than the first preset thickness. According to the preset number of array elements and element spacing, perform cutting in a one-dimensional direction on the ground electrode surface, and the cutting depth is greater than the final expected depth, but do not cut through the piezoelectric wafer. Fill the cut slit with insulating epoxy resin as an acoustic decoupling material. After the epoxy resin dries and cures, grind off the excess epoxy resin on the surface until the surface of the piezoelectric material is exposed, and then polish it to obtain a one-dimensional linear array piezoelectric layer 5. Sputter the upper electrode on the surface of the ground electrode surface and record the sample thickness. Specifically, the number of array elements and element spacing of the first transducer assembly 1 and the second transducer assembly 2 are different, and cutting is performed on the surface of the piezoelectric wafer according to the respective number of array elements and element spacing of different transducers. In this embodiment, the material of the piezoelectric layer 5 is ceramic.

[0064] Stack and manufacture a matching layer 6 on the ground electrode surface of the piezoelectric layer 5, and sputter the electrodes on the signal electrode surface:

[0065] Deposit a matching layer 6 with a modulated composition on the ground electrode surface by centrifugation. After drying and solidifying, grind its thickness to a second preset thickness, and record the total thickness of the laminated sample of the piezoelectric layer 5 and the first matching layer 6. Then, continue to deposit the second matching layer 6 on the first matching layer 6 by centrifugation. After drying and solidifying, grind the thickness of the second matching layer 6 to the second preset thickness. Turn the laminated sample over with the signal electrode surface facing up, grind the piezoelectric wafer to a first preset thickness and polish it. After sputtering the upper electrode on the surface of the signal electrode surface, gently cut the surface electrode along the slit of the one-dimensional linear array on the ground electrode surface of the piezoelectric layer 5, so that the electrical signals between the array elements are independent of each other.

[0066] The piezoelectric layer 5 is electrically connected to the flexible circuit board 4, and the circuit of the piezoelectric layer 5 is led out:

[0067] Customize the corresponding flexible circuit board 4 according to the different array element spacings and numbers of the second transducer assembly 2 and the first transducer assembly 1. According to the array element size, number, and arrangement method, design the circuit design diagram of the flexible circuit board 4. Among them, the flexible circuit board 4 includes several electrode leads and 2 ground wires, and the wires in the circuit board can be attached to each array element one by one, and the width of each wire is less than the width of the array element.

[0068] The flexible circuit board 4 covers the surface of the signal electrode surface to lead out the circuit of the piezoelectric layer 5. Specifically, the flexible circuit board leads out the array element leads of the second transducer assembly 2 from one side; since the array element spacing of the first transducer assembly 1 is too small and the density of the one-sided leads is too large, the two-sided interspersed leads are adopted, and on one side, the leads are made every other array element. The leads of two adjacent array elements are led out from both sides respectively, and the two leads are offset by an array element spacing in the direction perpendicular to the array element leads. In some embodiments, the flexible circuit board 4 of the second transducer assembly 2 directly covers the entire signal electrode surface; the flexible circuit board 4 of the first transducer assembly 1 is hollowed out in the middle, and the electrical signals of the array elements rely on the additional connection areas reserved on both sides of the array elements to be connected to the flexible circuit board 4. Bond the flexible circuit board 4 to the signal electrode surface according to the one-to-one correspondence between the wires and the array elements. Specifically, epoxy resin can be used for bonding.

[0069] Fabricate the backing layer 3:

[0070] Mix the materials of the backing layer 3 evenly according to a certain ratio relationship, centrifuge and cure them, and grind them flat to the required size. Use a fixture to paste the fabricated backing block to the flexible circuit board 4 with epoxy resin to form the backing layer 3. In some embodiments, the backing layer 4 is stacked on the signal electrode surface. When a small section of additional connection area is reserved on the piezoelectric layer 5 for connection with the flexible circuit board 4, the backing layer 4 is in direct contact with the signal electrode surface.

[0071] Fabricate an integrated acoustic lens 7 and integrate the dual-frequency transducer:

[0072] The preparation of the integrated acoustic lens 7 includes two methods: Method 1 is independent processing. Use TPX material or cure epoxy resin and then process it to the preset size and concave curvature of the lens. The thickness is processed to be slightly thicker than the third preset thickness, and the shape is a flat cuboid with one side being a plane and the other side being an inner arch. Place the arched side on a mold with the same curvature and size but being convex and fit and fix it completely. Grind the flat surface, and grind the integrated acoustic lens 7 to the third preset thickness. The surface size of the integrated acoustic lens 7 is the same as the size formed after the arrangement of the dual-frequency transducer. In this embodiment, the second transducer assembly 2 includes two low-frequency units, and the two low-frequency units are arranged in parallel side by side on both sides close to the first transducer assembly 1. Use an insulating adhesive to bond the dual-frequency transducer through the side of the transducer to ensure the flatness of one side of the matching layer 6 of the dual-frequency transducer. Then, bond the prepared acoustic lens to the matching layer 6 surface of the transducer with epoxy resin through a fixture.

[0073] The preparation method of Method 2 is casting. First, arrange and combine the transducers, and use an insulating adhesive to bond the transducers to ensure that the second matching layer 6 of the dual-frequency transducer is on the same plane. In this embodiment, the two low-frequency units of the second transducer assembly 2 are arranged in parallel side by side on both sides close to the first transducer assembly 1, and the dual-frequency transducer is bonded through the side of the transducer. Place the connected and fixed transducers into a specially customized mold, which has the same curvature as the required lens but is in a convex shape. After the transducers are placed, a gap is formed between the transducers and the mold, and the shape and size of this gap are the shape and thickness required for the lens. Then, pour the fluid epoxy resin into the gap and remove the excess burrs after curing.

[0074] Pack the above-made samples into an insulating housing for encapsulation, and connect the flexible circuit board 4 to the external circuit through a standard interface.

[0075] This embodiment provides a method for quickly manufacturing a transducer that meets the requirements of the present invention. Some steps can be adjusted. For example, first process the piezoelectric wafer, sputter electrodes on the ground electrode surface and the signal electrode surface respectively, then electrically connect the piezoelectric layer 5 to the flexible circuit board 4, and then stack and manufacture the matching layer 6 on the ground electrode surface.

[0076] In this embodiment, taking the manufacture of the dual-frequency transducer as an example, combining the structure of the multi-frequency ultrasonic transducer of the present invention and the process of this embodiment, those skilled in the art can manufacture more transducers to form a multi-frequency ultrasonic transducer.

[0077] Embodiment 3

[0078] This embodiment provides an ultrasonic imaging system, including the multi-frequency ultrasonic transducer described in Embodiment 1.

[0079] The integrated acoustic lens 7 can achieve focusing on the first transducer assembly 1 and the second transducer assembly 2 along the first direction. The change in the focusing positions of the ultrasonic waves with different frequencies emitted by the first transducer assembly 1 and the second transducer assembly 2 along the first direction can be achieved by adjusting the physical parameters of the integrated acoustic lens 7. The focusing positions are at different positions at the same depth in the first direction, or at different depths in the first direction. Adjusting the physical parameters of the integrated acoustic lens 7 can also focus the ultrasonic waves with different frequencies emitted by the first transducer assembly 1 and the second transducer assembly 2 at different positions in the third direction. The ultrasonic imaging system is also provided with a control unit for generating a focusing adjustment signal for the first transducer assembly 1 and the second transducer assembly 2 along the second direction, so that the multi-frequency ultrasonic transducer can achieve variable-focus focusing along the second direction. Specifically, the control unit adjusts the operation of the excitation system of the multi-frequency transducer, and can adjust the electronic beam synthesis. The change in the focusing position in the second direction is achieved by adjusting the electronic beam synthesis (i.e., the electronic phased array delay of the array).

[0080] The ultrasonic imaging system of this embodiment can achieve multiple imaging modes by controlling the focus positions of the first transducer assembly 1 and the second transducer assembly 2 and imaging through the control of the first transducer assembly 1 and the second transducer assembly 2. Specifically, it includes:

[0081] The first imaging mode: Achieve focusing on a preset single target point along the first direction of the first transducer assembly 1 and the second transducer assembly 2 through the structural characteristics of the integrated acoustic lens 7. Adjust the focus positions of the first transducer assembly and the second transducer assembly 2 along the second direction so that the focus positions of the first transducer assembly 1 and the second transducer assembly 2 along the second direction are also the above-mentioned preset single target point. Control the frequencies of the first transducer assembly 1 and the second transducer assembly 2 to perform multi-frequency synchronous imaging on the single target point.

[0082] The second imaging mode: Through the structural characteristics of the integrated acoustic lens 7 and controlling the frequencies of the first transducer assembly 1 and the second transducer assembly 2, make the first transducer assembly 1 and the second transducer assembly 2 focus on multiple target points at different positions and depths on the same cross-section or different cross-sections, and perform synchronous imaging on each target point.

[0083] In summary, the present invention provides a multi-frequency ultrasonic transducer in which a second transducer component is arranged around a first transducer component, and an integral acoustic lens is simultaneously laminated on the front side of the matching layer of the first transducer component for the second transducer component. This multi-frequency ultrasonic transducer has no superimposed structure, eliminating the influence between the first transducer component and the second transducer component. Since the transducers do not affect each other, multi-modal imaging modes such as high-quality ultrasonic imaging, superharmonic imaging, and elastography can be simultaneously performed in multiple frequency bands. The array design of the piezoelectric layer provides the transducer with the ability of electronic focusing, enabling the focal position of the transducer to be variable in two dimensions, greatly improving the focusing efficiency and focusing range of the transducer. Further, the simultaneous presence of the array design of the piezoelectric layer and the acoustic lens enables the first transducer component and the second transducer component to achieve electronic focusing and physical focusing simultaneously, greatly improving the accuracy of the target position and the resolution of the image. This multi-frequency ultrasonic transducer can be applied to array ultrasonic transducers in all working frequency ranges, has no built-in mechanical structure, simple process, high reliability, strong operability, and the integrated structural design of the acoustic lens simplifies the preparation process and difficulty of the device, improving the integration and consistency of the device. The ultrasonic imaging system applying this multi-frequency transducer can achieve multiple imaging modes by controlling the first transducer component and the second transducer component.

[0084] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. In addition to the above embodiments, there may be different variants. The technical features of the above embodiments can be combined with each other. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A multi-frequency ultrasonic transducer, characterized in that, it includes a first transducer component and a second transducer component, the frequency of the second transducer component is lower than that of the first transducer component, each of the first transducer components and each of the second transducer components includes a backing layer, a piezoelectric layer and a matching layer arranged in a stacked manner, and the second transducer components are arranged on both sides or around the first transducer component; it further includes an integral acoustic lens, and the integral acoustic lens is simultaneously stacked on the front side of the matching layer of the first transducer component and the front side of the matching layer of the second transducer component; it further includes a flexible circuit board, and the flexible circuit board is electrically connected to the piezoelectric layer; wherein, the flexible circuit board covers the entire surface of the piezoelectric layer; or, the flexible circuit board is connected to one side or multiple sides of the piezoelectric layer; or, additional connection areas are reserved on both sides of the piezoelectric layer, and the flexible circuit board covers the surface of the connection areas; the piezoelectric layer includes a ground electrode surface and a signal electrode surface, the ground electrode surface and the signal electrode surface respectively have electrodes, and the electrodes of the signal electrode surface are cut to form a plurality of piezoelectric array elements on the piezoelectric layer; the integral acoustic lens has an ultrasonic focusing characteristic, and is used to focus ultrasonic waves with different frequencies emitted by the first transducer component and the second transducer component on a preset single target point or multiple preset target points along a first direction; the physical parameters of the integral acoustic lens are variable, and the integral acoustic lens with different physical parameters focuses ultrasonic waves with different frequencies emitted by the first transducer component and the second transducer component at the same depth in the first direction; or, the integral acoustic lens with different physical parameters focuses ultrasonic waves with different frequencies emitted by the first transducer component and the second transducer component at different depths in the first direction.

2. The multi-frequency ultrasonic transducer according to claim 1, characterized in that, the second transducer components are arranged on the left and right sides of the first transducer component, and the ultrasonic waves emitted by the second transducer components are focused along the first direction; the focused focal points formed by the ultrasonic waves emitted by the second transducer components after passing through the integral acoustic lens are on the center line of the first transducer component, or, within the left and right ultrasonic regions of the first transducer component.

3. The multi-frequency ultrasonic transducer according to claim 1, characterized in that, the second transducer components are arranged on the left and right sides of the first transducer component, and both the second transducer components and the first transducer component emit ultrasonic waves and are focused along the first direction; the focused focal points formed by the ultrasonic waves emitted by the second transducer components and the ultrasonic waves emitted by the first transducer component after passing through the integral acoustic lens coincide in the first direction, or, are at different positions on the center line of the first transducer component.

4. A manufacturing method of a multi-frequency ultrasonic transducer, used to manufacture the multi-frequency ultrasonic transducer according to any one of claims 1-3, characterized in that, the manufacturing of the multi-frequency ultrasonic transducer includes: Fabricate a piezoelectric layer, including: sputtering electrodes on the ground electrode surface of the piezoelectric layer and sputtering electrodes on the signal electrode surface; Electrically connect the piezoelectric layer to a flexible circuit board, fabricate a matching layer on one side of the ground electrode surface of the piezoelectric layer, and fabricate a backing layer on one side of the signal electrode surface; Arrange and fix the second transducer assembly on both sides or around the first transducer assembly, stack an integral acoustic lens on the front side of the matching layer of the first transducer assembly and on the front side of the matching layer of the second transducer assembly at the same time, and bond and fix the integral acoustic lens to the matching layer of the first transducer assembly and the matching layer of the second transducer assembly.

5. The manufacturing method of the multi-frequency ultrasonic transducer according to claim 4, characterized in that, Before the step of sputtering electrodes on the ground electrode surface of the piezoelectric layer, it further includes cutting on the ground electrode surface according to the preset number of array elements and the spacing between array elements of the piezoelectric layer, and filling an acoustic decoupling material into the cut slits formed; After the step of sputtering electrodes on the signal electrode surface, it further includes cutting the electrodes on the signal electrode surface according to the gaps between the array elements on the ground electrode surface.

6. An ultrasonic imaging system, characterized in that, comprises the multi-frequency ultrasonic transducer according to any one of claims 1-3, further includes a control unit for generating a focusing adjustment signal along the second direction for the first transducer assembly and the second transducer assembly, so that the multi-frequency ultrasonic transducer can achieve variable focus position along the second direction; The integral acoustic lens realizes focusing along the first direction for the first transducer assembly and the second transducer assembly; wherein, the first direction intersects or is perpendicular to the second direction.

7. The ultrasonic imaging system according to claim 6, characterized in that, The control unit adjusts the electronic beam synthesis of the excitation system of the multi-frequency ultrasonic transducer.

8. An imaging method of the ultrasonic imaging system according to claim 6 or 7, characterized in that, By controlling the focus positions of the first transducer assembly and the second transducer assembly, and controlling the frequencies of the first transducer assembly and the second transducer assembly, at least one of the following imaging modes is realized: The first imaging mode: realizing focusing along the first direction for the first transducer assembly and the second transducer assembly on a preset single target point through the structural characteristics of the integral acoustic lens, adjusting the focus positions along the second direction of the first transducer assembly and the second transducer assembly, so that the focus positions along the second direction of the first transducer assembly and the second transducer assembly are also the preset single target point, controlling the frequencies of the first transducer assembly and the second transducer assembly, and performing multi-frequency synchronous imaging on the single target point; The second imaging mode: making the first transducer assembly and the second transducer assembly focus on multiple target points at different positions and depths on the same cross-section or different cross-sections through the structural characteristics of the integral acoustic lens and controlling the frequencies of the first transducer assembly and the second transducer assembly, and performing synchronous imaging on each target point.

Images