A double-sided probe based on active backing structure

Abstract

The present invention discloses a double-sided probe based on an active backing structure, comprising two piezoelectric parts bonded together, wherein the outer end surfaces of the two piezoelectric parts are respectively provided with matching layers, and the two piezoelectric parts are both two piezoelectric sheets, and the voltage application surface is between the two piezoelectric sheets in the piezoelectric part, and the surface of the two piezoelectric sheets in the piezoelectric part away from each other is a grounding surface, and the surface between the piezoelectric sheets close to each other in the two piezoelectric parts is a grounding surface for both to be grounded together, and when voltage is applied to the two piezoelectric parts, ultrasonic signals are respectively generated, and the ultrasonic signals of the two piezoelectric parts facing each other attenuate and cancel each other, and the ultrasonic signal of one of the piezoelectric parts can be used for detection in different frequency bands; the present invention realizes the miniaturization of the ultrasonic probe by using the active backing structure; by the mutual substitution of the functions played by the two piezoelectric parts, the working surface and the working frequency band of the probe are increased, and the applicable scenarios of the probe are expanded in specific applications.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrasonic detection, and in particular to a double-sided probe based on an active backing structure. Background Art

[0002] With the continuous emergence of new technologies and the continuous upgrading of equipment, the application of ultrasonic probes in non-destructive testing, medical imaging and other fields has become more and more extensive. Traditional piezoelectric ultrasonic probes generally include an acoustic lens, a matching layer, a piezoelectric part, an FPC circuit board, a backing layer and other structures.

[0003] When a piezoelectric element is excited, it generates both forward and backward ultrasonic signals. The backward ultrasonic signal is generally unnecessary noise. Furthermore, for an ultrasonic probe with a given center frequency, the larger the bandwidth, the smaller the longitudinal resolution and the higher the imaging quality. To quickly absorb and attenuate the backward-transmitted noise to ensure forward transmission of the ultrasonic signal and to increase the probe's operating bandwidth, an acoustic material called a backing layer is typically applied to the back of the piezoelectric element. However, this backing layer occupies a large portion of the probe's volume, hindering its miniaturization.

[0004] In view of the above-mentioned defects, the inventors of the present invention finally obtained the present invention after a long period of research and practice. Summary of the Invention

[0005] The purpose of the present invention is to provide a double-sided probe based on an active backing structure, which solves the problem that the backing layer of a traditional ultrasonic probe occupies most of the volume of the probe, hindering the miniaturization of the probe, and on this basis expands the applicable scenarios of the probe.

[0006] The present invention solves the above-mentioned technical problems through the following technical solutions: the present invention includes two piezoelectric parts bonded together, and matching layers are respectively provided on the outer end surfaces of the two piezoelectric parts. The two piezoelectric parts are each two piezoelectric sheets, and the voltage application surface is between the two piezoelectric sheets in the piezoelectric part, and the surface of the two piezoelectric sheets in the piezoelectric part away from each other is the grounding surface, and the surface between the piezoelectric sheets close to each other in the two piezoelectric parts is the grounding surface for both to be grounded. When voltage is applied to the two piezoelectric parts, ultrasonic signals are respectively generated, and the ultrasonic signals of the two piezoelectric parts facing each other attenuate and cancel each other out. The ultrasonic signal of one of the piezoelectric parts can be used for detection in different frequency bands.

[0007] Preferably, the polarization directions of the two piezoelectric sheets in the piezoelectric portion are both with the voltage applied surface facing the ground plane.

[0008] Preferably, the cross-sectional shapes and sizes of the two piezoelectric parts and the matching layer are consistent.

[0009] Preferably, the two piezoelectric parts and the matching layer are integrated in a housing.

[0010] Preferably, the thicknesses of the two piezoelectric portions are equal, and the thickness t of the piezoelectric portion is:

[0011] t=N / f

[0012] Where f is the center frequency of the ultrasonic probe and N is the frequency constant.

[0013] Preferably, the thickness ratio of the two piezoelectric parts is 1:0.414.

[0014] Preferably, the piezoelectric sheet is made of piezoelectric material.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] 1. By using an active backing structure, the traditional backing layer structure is replaced, the volume of the ultrasound probe is reduced, and the miniaturization of the ultrasound probe is achieved.

[0017] 2. By replacing the functions of the two piezoelectric parts, the working surface and working frequency band of the probe are increased, and the applicable scenarios of the probe are expanded in specific applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of a piezoelectric element according to an embodiment;

[0019] Figure 2 is a curve showing the ratio of the lower end displacement of the fourth piezoelectric sheet to the upper end displacement of the first piezoelectric sheet in the embodiment;

[0020] Figure 3 ] is a ratio curve of the lower end displacement of the fourth piezoelectric sheet to the upper end displacement of the first piezoelectric sheet and a ratio curve of the upper end displacement of the first piezoelectric sheet to the lower end displacement of the fourth piezoelectric sheet in the embodiment. DETAILED DESCRIPTION

[0021] The above and other technical features and advantages of the present invention are described in more detail below with reference to the accompanying drawings.

[0022] This embodiment provides a technical solution: a double-sided probe based on an active backing structure, such as Figure 1 As shown, it includes two piezoelectric parts. The two piezoelectric parts can be divided into two parts, a piezoelectric emission layer and an active backing layer, according to their different functions. The two parts can replace each other in different frequency bands. The piezoelectric part is made of piezoelectric materials, such as PZT series piezoelectric ceramics, quartz, PVDF, etc. The probe contains two matching layer structures, which are located at the ends of the two piezoelectric parts, namely the upper matching layer 1 and the lower matching layer 2. There is no traditional backing layer structure. The two piezoelectric parts and the matching layer are integrated into a shell, and the piezoelectric part includes at least one piezoelectric sheet with two working surfaces, which can operate in multiple frequency bands, including:

[0023] The piezoelectric emission layer is used to generate ultrasonic signals for detection when the probe is working;

[0024] The active backing layer acts as the passive backing layer in a traditional ultrasonic probe. The ultrasonic signal it generates is in the opposite direction to the backscatter generated by the piezoelectric transmitting layer, thus attenuating and canceling the backscatter and achieving forward transmission of the ultrasonic signal.

[0025] The matching layer structure is a structure that all traditional ultrasonic probes have. This structure alleviates the huge impedance mismatch between the piezoelectric element and the transmission medium, reduces or eliminates the acoustic mismatch, and achieves effective energy transfer.

[0026] The thickness of the two piezoelectric parts can be determined based on theoretical formulas and actual application scenarios. The thickness of the two piezoelectric parts can be equal, the thickness ratio of the two piezoelectric parts can be 1:0.414, or other dimensions, that is:

[0027] When the thickness of the two piezoelectric parts is equal, the theoretical formula is used for calculation. For example, for a piezoelectric piece with a center frequency of 2 MHz, the thickness expansion mode is selected, and the corresponding frequency constant is 2000. According to the theoretical formula: t = N / f, where t is the thickness of the piezoelectric piece; N is the frequency constant corresponding to different modes of the piezoelectric material; and f is the center frequency, the thickness of the piezoelectric part is approximately t = 2000 / 2 MHz = 1 mm. The cross-sectional shape and area are determined according to the actual application scenario.

[0028] When the thickness ratio of the two piezoelectric parts is 1:0.414, if the thicker piezoelectric part is the piezoelectric emitter layer, the thickness ratio of the piezoelectric emitter layer to the active backing layer is 1:0.414; when the thinner piezoelectric part is the piezoelectric emitter layer, the thickness ratio of the piezoelectric emitter layer to the active backing layer is 1:2.4. Compared with the traditional backing layer, which is generally three times or more thicker than the piezoelectric material, the use of the active backing structure significantly reduces the overall volume of the probe.

[0029] Theoretically, based on the inverse piezoelectric effect, the thickness of the piezoelectric part serving as the active backing layer can take any value. The main purpose of adopting the active backing structure is to achieve the miniaturization of the ultrasonic probe. Therefore, the thickness of the piezoelectric part serving as the active backing layer will not be particularly large. Under the optimal conditions without considering other factors, the thickness of the piezoelectric part serving as the active backing layer can be 0.414 times the thickness of the piezoelectric part serving as the piezoelectric emitting layer. At the same time, the specific thickness can resonate and enhance the ultrasonic signal of the corresponding center frequency, so that the transducer has the best sound wave energy transmission efficiency.

[0030] The two piezoelectric parts respectively have two piezoelectric sheets, and the piezoelectric sheets of the two piezoelectric parts are respectively the first piezoelectric sheet 13, the second piezoelectric sheet 14, the third piezoelectric sheet 15 and the fourth piezoelectric sheet 16; different piezoelectric sheets can adopt different parameters, such as: different thicknesses, different densities, different center frequencies, different frequency constants, etc., without special restrictions, and are selected according to actual work needs; in order to make the solution more intuitive and convenient to explain the working principle, in this embodiment, the four layers of piezoelectric sheets adopt the same parameters.

[0031] The first piezoelectric sheet 13 and the second piezoelectric sheet 14 form a voltage unit, the third piezoelectric sheet 15 and the fourth piezoelectric sheet 16 form a voltage unit, and the polarization directions of the multiple piezoelectric sheets are opposite in sequence (the arrows in the figure represent the polarization directions of each layer).

[0032] The sides of the first piezoelectric sheet 13 and the second piezoelectric sheet 14 away from each other, and the sides of the third piezoelectric sheet 15 and the fourth piezoelectric sheet 16 away from each other are both grounding surfaces, and the second piezoelectric sheet 14 and the third piezoelectric sheet 15 have a common grounding surface 19 between them. The upper side of the first piezoelectric sheet 13 and the lower side of the fourth piezoelectric sheet 16 are respectively a first single grounding surface 17 and a second single grounding surface 111. The first piezoelectric sheet 13 and the second piezoelectric sheet 14, and the third piezoelectric sheet 15 and the fourth piezoelectric sheet 16 have respectively a first voltage application surface 18 and a second voltage application surface 110.

[0033] In this embodiment, a positive voltage (+150V) is applied to the first voltage application surface 18, and a negative voltage (-59V) is applied to the second voltage application surface 110. Based on the inverse piezoelectric effect, the mechanical vibration directions of the first and second piezoelectric sheets 13 and 14 are always opposite to those of the third and fourth piezoelectric sheets 15 and 16, meaning that the generated ultrasonic signals are always directed in opposite directions. This structure ensures that the ultrasonic waves generated by the active backing layer attenuate and offset the backscatter generated by the piezoelectric emitting layer, achieving forward transmission of the ultrasonic signal and fulfilling the role of a traditional backing layer. Therefore, it is referred to as an active backing structure.

[0034] Figure 2 Given in Figure 1 Under the above parameters, in the range of 0-2700kHz, the ratio curve of the lower end displacement of the fourth piezoelectric sheet 16 to the upper end displacement of the first piezoelectric sheet 13 (hereinafter referred to as the lower end displacement and the upper end displacement). If the third piezoelectric sheet 15 and the fourth piezoelectric sheet 16 are used as the active backing layer, and the first piezoelectric sheet 13 and the second piezoelectric sheet 14 are used as the piezoelectric emission layer, the smaller the displacement ratio, the better in order to reduce the influence of noise. If the maximum value of this displacement ratio is limited to 0.5 when the piezoelectric element is working, Figure 2As can be seen in the figure, within the 0-1298kHz range (thick solid line), the displacement ratio is less than 0.5, meeting operational requirements. However, within the 1298-2700kHz range (thin solid line), the displacement ratio is greater than 0.5, exceeding the maximum limit and failing to meet operational requirements. At this point, within the 0-2700kHz range, the probe's operational frequency band is limited to 0-1298kHz.

[0035] Figure 3 Given in Figure 1 Under the above parameters, in the range of 1000-2700kHz, the ratio curve of the lower end displacement to the upper end displacement and the ratio curve of the upper end displacement to the lower end displacement are reciprocal to each other. When the ratio of the lower end displacement to the upper end displacement is greater than 2, the ratio of the upper end displacement to the lower end displacement is less than 0.5. The maximum value of the displacement ratio is limited to 0.5 and remains unchanged. At this time, if the first piezoelectric sheet 13 and the second piezoelectric sheet 14 are used as active backing layers, and the third piezoelectric sheet 15 and the fourth piezoelectric sheet 16 are used as piezoelectric emission layers, Figure 3 As can be seen in the figure, within the 1618-2043kHz range (thick dashed line), the ratio of upper to lower displacement is less than 0.5, meeting operational requirements. However, within the 1000-1618kHz and 2043-2700kHz ranges (thin dashed lines), the ratio is greater than 0.5, exceeding the specified maximum and failing to meet operational requirements. Therefore, within the 1000-2700kHz range, the probe's operational frequency band is limited to 1618-2043kHz.

[0036] It can be concluded that when the probe needs to operate in the 0-1298 kHz range, the third piezoelectric sheet 15 and the fourth piezoelectric sheet 16 are used as active backing layers, the first piezoelectric sheet 13 and the second piezoelectric sheet 14 are used as piezoelectric emitting layers, and the side of the upper matching layer 1 is in the detection direction. The displacement ratio of the lower end of the fourth piezoelectric sheet 16 to the upper end of the first piezoelectric sheet 13 is less than 0.5. That is, the clutter signal generated by the piezoelectric portion of the fourth piezoelectric sheet 16 that acts as the active backing layer is much smaller than the working ultrasonic signal generated by the piezoelectric portion of the first piezoelectric sheet 13 that acts as the piezoelectric emitting layer, and will not affect the detection operation of the piezoelectric portion of the piezoelectric emitting layer. When the probe needs to operate in the 1618-2043kHz range, the first piezoelectric sheet 13 and the second piezoelectric sheet 14 are used as active backing layers, the third piezoelectric sheet 15 and the fourth piezoelectric sheet 16 are used as piezoelectric emission layers, and the side of the lower matching layer 2 is the detection direction. The displacement ratio of the upper end displacement of the first piezoelectric sheet 13 to the lower end displacement of the fourth piezoelectric sheet 16 is less than 0.5. That is, the clutter signal generated by the piezoelectric portion of the first piezoelectric sheet 13 that acts as the active backing layer is much smaller than the working ultrasonic signal generated by the piezoelectric portion of the fourth piezoelectric sheet 16 that acts as the piezoelectric emission layer, and will not affect the detection operation of the piezoelectric portion of the piezoelectric emission layer. In this way, the probe can meet the working requirements in both frequency bands. This is a reasonable embodiment of increasing the working frequency band and working surface of the probe by using the mutual substitution of the functions of the two voltage portions, demonstrating the superiority of the multi-layer double-sided ultrasonic probe based on the active backing structure.

[0037] In summary, the two working surfaces are located at either end of the ultrasound probe. When the probe operates in different frequency bands, different piezoelectric components act as the piezoelectric emitter, corresponding to different matching layers, and detecting in different directions, thus using different working surfaces. Due to the limited frequency range selected in this embodiment, the two working surfaces each only display a detectable frequency band. Therefore, by utilizing an active backing structure and allowing the two piezoelectric components to perform alternate functions at different frequency bands, not only does this increase the probe's operating frequency band, but it also increases the number of working surfaces, greatly expanding the probe's applicable scenarios.

[0038] The above description is merely a preferred embodiment of the present invention and is intended to be illustrative rather than restrictive of the present invention. Those skilled in the art will appreciate that many changes, modifications, and even equivalents may be made to the present invention within the spirit and scope of the claims, all of which fall within the scope of protection of the present invention.

Claims

1. A double-sided probe based on an active backing structure, characterized in that: It includes two piezoelectric parts bonded together, and matching layers are respectively provided on the outer end surfaces of the two piezoelectric parts. The two piezoelectric parts are both two piezoelectric sheets. The voltage application surface is between the two piezoelectric sheets in the piezoelectric part, the surface of the two piezoelectric sheets in the piezoelectric part away from each other is the grounding surface, and the surface between the piezoelectric sheets close to each other in the two piezoelectric parts is the grounding surface for both to be grounded. When voltage is applied to the two piezoelectric parts, ultrasonic signals are generated respectively. The ultrasonic signals of the two piezoelectric parts facing each other attenuate and cancel each other out, and the ultrasonic signal of one of the piezoelectric parts can be used for detection in different frequency bands.

2. A double-sided probe based on an active backing structure according to claim 1, characterized in that: The polarization directions of the two piezoelectric sheets in the piezoelectric portion are both directed toward the ground plane when the voltage is applied.

3. The double-sided probe based on an active backing structure according to claim 1, characterized in that: The cross-sectional shapes and sizes of the two piezoelectric parts and the matching layer are consistent.

4. The double-sided probe based on an active backing structure according to claim 1, characterized in that: The two piezoelectric parts and the matching layer are integrated in a shell.

5. The double-sided probe based on an active backing structure according to claim 1, characterized in that: The thickness of the two piezoelectric parts is equal, and the thickness t of the piezoelectric part is: t=N / f Where f is the center frequency of the ultrasonic probe and N is the frequency constant.

6. The double-sided probe based on an active backing structure according to claim 1, characterized in that: The thickness ratio of the two piezoelectric portions is 1:0.

414.

7. The double-sided probe based on an active backing structure according to claim 1, characterized in that: The piezoelectric sheet is made of piezoelectric material.

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