WO2017031679A1 - 超声换能器 - Google Patents

超声换能器 Download PDF

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Publication number
WO2017031679A1
WO2017031679A1 PCT/CN2015/087981 CN2015087981W WO2017031679A1 WO 2017031679 A1 WO2017031679 A1 WO 2017031679A1 CN 2015087981 W CN2015087981 W CN 2015087981W WO 2017031679 A1 WO2017031679 A1 WO 2017031679A1
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WO
WIPO (PCT)
Prior art keywords
backing layer
ultrasonic transducer
impedance
thickness
piezoelectric wafer
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PCT/CN2015/087981
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English (en)
French (fr)
Inventor
司康
吴飞
陈振宇
Original Assignee
深圳迈瑞生物医疗电子股份有限公司
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Application filed by 深圳迈瑞生物医疗电子股份有限公司 filed Critical 深圳迈瑞生物医疗电子股份有限公司
Priority to PCT/CN2015/087981 priority Critical patent/WO2017031679A1/zh
Priority to CN201580008885.2A priority patent/CN106413563B/zh
Publication of WO2017031679A1 publication Critical patent/WO2017031679A1/zh
Priority to US15/890,744 priority patent/US10575820B2/en

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
    • A61B8/44—Constructional features of the ultrasonic, sonic or infrasonic diagnostic device
    • A61B8/4483—Constructional features of the ultrasonic, sonic or infrasonic diagnostic device characterised by features of the ultrasound transducer
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
    • A61B8/42—Details of probe positioning or probe attachment to the patient
    • A61B8/4272—Details of probe positioning or probe attachment to the patient involving the acoustic interface between the transducer and the tissue
    • A61B8/4281—Details of probe positioning or probe attachment to the patient involving the acoustic interface between the transducer and the tissue characterised by sound-transmitting media or devices for coupling the transducer to the tissue
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
    • A61B8/44—Constructional features of the ultrasonic, sonic or infrasonic diagnostic device
    • A61B8/4444—Constructional features of the ultrasonic, sonic or infrasonic diagnostic device related to the probe
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
    • A61B8/44—Constructional features of the ultrasonic, sonic or infrasonic diagnostic device
    • A61B8/4483—Constructional features of the ultrasonic, sonic or infrasonic diagnostic device characterised by features of the ultrasound transducer
    • A61B8/4494—Constructional features of the ultrasonic, sonic or infrasonic diagnostic device characterised by features of the ultrasound transducer characterised by the arrangement of the transducer elements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/06—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction
    • B06B1/0607—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using multiple elements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/06—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction
    • B06B1/0607—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using multiple elements
    • B06B1/0622—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using multiple elements on one surface

Definitions

  • the present invention relates to an ultrasonic transducer.
  • Ultrasonic diagnostic equipment mainly relies on ultrasonic transmission of information
  • ultrasonic transducers also known as ultrasonic probes
  • the ultrasonic transducer can convert the electrical signal into an ultrasonic signal for propagation in human tissue, and can convert the ultrasonic signal reflected from the human tissue into an electrical signal, and after processing, display the image on the monitor in the form of an image. For the doctor to analyze and diagnose the disease.
  • the broadband ultrasonic transducer can send and receive ultrasonic waves of different frequencies to meet the needs of the diagnostic equipment to use different operating frequencies in the near field and the far field.
  • the broadband ultrasonic transducer is also applied to harmonic imaging technology, and the wide frequency band can receive multiple harmonics generated by sound waves in human tissues, thereby improving the axial resolution and sensitivity of the image.
  • a wideband ultrasonic transducer is shown in Fig. 1.
  • the lower operating frequency of the corresponding transducer is adjusted by adjusting the maximum thickness LMAX and the minimum thickness LMIN of the piezoelectric wafer.
  • the energy of the device has good sensitivity from low frequency to high frequency, and the effect of widening the bandwidth is achieved; however, the range of bandwidth expansion of the technical solution has certain limitations, and is limited by the manufacturing process, usually LMAX/LMIN ⁇ 140%, if this The value is too large and the piezoelectric wafer is easily broken when the transducer is fabricated.
  • FIG. 2 Another wideband ultrasonic transducer is shown in Fig. 2, in which the concave surface of the piezoelectric wafer 42 is connected to the backing 40, which can reduce the possibility of chipping of the piezoelectric wafer during bonding and pressurization.
  • other solutions include transducers of two layers of variable thickness piezoelectric wafers 42, 44, as shown in FIG. 3; and transducers including three layers of variable thickness piezoelectric wafers 24, 26, 28, as shown in FIG. Show.
  • the scheme of the multi-layer variable thickness piezoelectric wafer can reduce the curvature of the upper and lower sides while ensuring the total equivalent curvature, thereby reducing the possibility of chipping of the piezoelectric wafer; however, these technical solutions are all easy.
  • the broken piezoelectric wafer is made into a concave thickness, which increases the difficulty of the manufacturing process, so that the piezoelectric wafer has the risk of chipping; and, since the piezoelectric wafer is concave, the coverage is increased on it.
  • the difficulty of the electrode is made into a concave thickness, which increases the difficulty of the manufacturing process, so that the piezoelectric wafer has the risk of chipping; and, since the piezoelectric wafer is concave, the coverage is increased on it. The difficulty of the electrode.
  • the present invention provides a new ultrasonic transducer.
  • the present invention provides an ultrasonic transducer comprising a piezoelectric wafer and a backing, the backing comprising
  • a high-resistance backing layer and a low-impedance backing layer a rear surface of the piezoelectric wafer being coupled to a front surface of the high-impedance backing layer, a rear surface of the high-impedance backing layer and the low-impedance backing The front surface of the layer is joined and the high-impedance backing layer is thickened.
  • the piezoelectric wafer is of a thickness.
  • the high-resistance backing layer has a thickness that is small in the middle and small on both sides.
  • the back surface of the high-impedance backing layer is a curved concave surface, a wedge concave surface, or a trapezoidal concave surface.
  • the piezoelectric wafer and the high-impedance backing layer are both thickened.
  • the thickness of the piezoelectric wafer is small on both sides, and the thickness of the high-resistance backing layer is small on both sides.
  • the front surface of the piezoelectric wafer is concave
  • the rear surface of the piezoelectric wafer is planar
  • the front surface of the high-impedance backing layer is planar
  • the rear surface of the high-impedance backing layer It is a curved concave surface, a wedge concave surface or a trapezoidal concave surface.
  • the piezoelectric wafer has a thickness such that the thickness of the high-resistance backing layer is small on both sides and the rear surface is concave; the thickness of the low-resistance backing layer is small in the middle and small on both sides, and the front surface thereof Is a convex surface; a rear surface of the high-resistance backing layer conforms to a front surface of the low-impedance backing layer.
  • the ultrasonic transducer further includes a matching layer, a rear surface of the matching layer being coupled to a front surface of the piezoelectric wafer.
  • the matching layer can be thickened or equal in thickness.
  • a component such as a matching layer, a piezoelectric wafer, a high-impedance backing layer, or a low-impedance backing layer
  • a component such as a matching layer, a piezoelectric wafer, a high-impedance backing layer, or a low-impedance backing layer
  • it has a maximum thickness and a minimum thickness.
  • the thickness of the element or the like may mean that the maximum thickness and the minimum thickness are equal.
  • the variable thickness of the component may mean that the maximum thickness and the minimum thickness are not equal.
  • An ultrasonic diagnostic apparatus includes the ultrasonic transducer.
  • the backing includes a high-impedance backing layer and a low-impedance backing layer, which produces strong reflections at the junction of the two. More acoustic waves are reflected back to the piezoelectric wafer, thereby increasing the sensitivity of the ultrasonic transducer.
  • FIG. 1 is a schematic structural view of a first prior art ultrasonic transducer
  • FIG. 2 is a schematic structural view of a second prior art ultrasonic transducer
  • FIG. 3 is a schematic structural view of a third conventional ultrasonic transducer
  • FIG. 4 is a schematic structural view of a fourth conventional ultrasonic transducer
  • Figure 5 is a schematic structural view of a first embodiment of an ultrasonic transducer
  • FIG. 6 is a schematic diagram of a high-impedance backing and an equal-thickness piezoelectric wafer equivalent to a variable thickness piezoelectric wafer;
  • FIG. 7 is a schematic structural view of a second embodiment of an ultrasonic transducer
  • FIG. 8 is a schematic structural view of a third embodiment of an ultrasonic transducer
  • FIG. 9 is a schematic structural view of a fourth embodiment of an ultrasonic transducer
  • Figure 10 is a schematic structural view of a fifth embodiment of the ultrasonic transducer.
  • Figure 11 is a schematic structural view of a sixth embodiment of the ultrasonic transducer.
  • FIG. 12 is a schematic structural view of a seventh embodiment of an ultrasonic transducer
  • Figure 13 is a schematic structural view of an eighth embodiment of the ultrasonic transducer.
  • Figure 14 is a schematic perspective view of the ultrasonic transducer.
  • an ultrasonic transducer includes a matching layer 3, a piezoelectric wafer 1, a high-impedance backing layer 2a, and a low-impedance backing layer 2b, the matching layer, a piezoelectric wafer, and a high-impedance backing layer. And the low-impedance backing layer is stacked in order from top to bottom.
  • the piezoelectric wafer is an equal thickness piezoelectric wafer
  • the high-impedance backing layer is a variable thickness high-resistance backing layer
  • the rear surface of the piezoelectric wafer is connected with the front surface of the high-impedance backing layer to form an equivalent piezoelectric wafer.
  • a piezoelectric wafer can be equivalent to a variable thickness piezoelectric wafer.
  • a "high-impedance backing layer” may refer to a backing layer having a relatively high acoustic impedance (eg, relative to a low-impedance backing layer), for example, which may be relatively acoustically impedanced (eg, relative to a low impedance) Backing layer Material) Made of a higher backing material.
  • the "low-impedance backing layer” may refer to a lower backing layer having a relatively lower acoustic impedance (eg, relative to a high-impedance backing layer), for example, which may be relatively acoustically impedance (eg, relative to high impedance)
  • the material of the backing layer is made of a lower backing material.
  • 1 is a piezoelectric wafer
  • 2a is a high-impedance backing layer
  • 2b is a low-impedance backing layer.
  • the piezoelectric wafer 1 operates and emits ultrasonic waves
  • the ultrasonic waves propagating backward thereof mostly enter the high-resistance backing layer 2a and form a strong interface at the interface between the high-resistance backing layer 2a and the low-impedance backing layer 2b.
  • the reflected, reflected back ultrasonic waves pass through the piezoelectric wafer 1 and are emitted forward.
  • the piezoelectric wafer 1 and the high-impedance backing layer 2a constitute an equivalent vibrator (i.e., an equivalent piezoelectric wafer), and the resonant frequency of the equivalent vibrator is inversely proportional to the thickness of the high-impedance backing layer 2a. Therefore, by changing the thickness of the high-impedance backing layer 2a, the vibration frequency of the equivalent vibrator can be changed, that is, the operating frequency of the equivalent vibrator can be changed, thereby expanding the bandwidth of the ultrasonic transducer.
  • a single component such as a matching layer, a piezoelectric wafer, a high-impedance backing layer, or a low-impedance backing layer, it has a maximum thickness and a minimum thickness.
  • a single element “equal thickness” may mean that its maximum thickness and minimum thickness are equal.
  • a single element “variable thickness” may mean that its maximum thickness and minimum thickness are not equal.
  • the ultrasonic transducer includes a matching layer 3, a piezoelectric wafer 1, a high-impedance backing layer 2a, and a low-impedance backing layer 2b.
  • the rear surface 302 of the matching layer 3 is connected to the front surface 101 of the piezoelectric wafer 1, and the piezoelectric wafer 1
  • the rear surface 102 is connected to the front surface 201 of the high-impedance backing layer 2a, and the rear surface 202 of the high-resistance backing layer 2a is connected to the front surface 203 of the low-impedance backing layer 2b.
  • the piezoelectric wafer 1 is equal in thickness t, and its front surface 101 and rear surface 102 are both planar.
  • the high-impedance backing layer 2a has a reduced thickness (for example, the thickness in the Z direction is variable along the X direction in FIG. 5, rather than constant), and the thickness is small in the middle and the front surface 201 is a flat surface.
  • the rear surface 202 is a curved concave surface.
  • the low-resistance backing layer 2b has a thickness which is small in the middle and large on both sides, and the front surface 203 is an arcuate convex surface which coincides with the rear surface of the high-resistance backing layer.
  • the matching layer 3 has a reduced thickness, and its front surface 301 may be a concave surface, and its rear surface 302 may be a flat surface.
  • the rear surface 204 of the low impedance backing layer 2b can be planar.
  • the front surface 301 of the matching layer is connected to the acoustic lens 5.
  • the left and right direction X and the front and rear direction Z are perpendicular, and the thickness may be It refers to the Z coordinate difference between the front surface and the back surface having the same X coordinate value for a single component such as a matching layer, a piezoelectric wafer, a high-impedance backing layer or a low-impedance backing layer.
  • the middle and both sides may refer to the middle and both sides in the left and right direction X.
  • FIG. 7 which is a second embodiment of the ultrasonic transducer
  • the main difference between this embodiment and the first embodiment is that the rear surface of the high-resistance backing layer 2a is a wedge-shaped concave surface, and the wedge-shaped concave wedge The tip is oriented toward the piezoelectric wafer, and correspondingly, the front surface of the low-impedance backing layer 2b is a wedge-shaped convex surface.
  • FIG. 8 which is a third embodiment of the ultrasonic transducer
  • the main difference between this embodiment and the first embodiment is that the rear surface of the high-resistance backing layer 2a is a trapezoidal concave surface, correspondingly, low impedance.
  • the front surface of the backing layer 2b is a trapezoidal convex surface.
  • the main difference between this embodiment and the first embodiment is that the thickness of the matching layer 3 is equal to that of the front surface and the rear surface;
  • the rear surface of the backing layer 2a is a wedge-shaped concave surface whose tip is oriented toward the piezoelectric wafer, and correspondingly, the front surface of the low-impedance backing layer 2b is a wedge-shaped convex surface.
  • the main difference of the embodiment in the first embodiment is that the thickness of the matching layer 3 is equal to that of the front surface and the rear surface;
  • the rear surface of the backing layer 2a is a trapezoidal concave surface, and correspondingly, the front surface of the low-resistance backing layer 2b is a trapezoidal convex surface.
  • the ultrasonic transducer includes a matching layer 3, a piezoelectric wafer 1, a high-impedance backing layer 2a, and a low-impedance backing layer 2b which are sequentially stacked from top to bottom.
  • the thickness of the matching layer 3 is such that the front surface is an arcuate concave surface and the rear surface thereof is an arcuate convex surface.
  • the piezoelectric wafer 1 has a thickness which is large in the middle and small in both sides, and its front surface is a curved concave surface, and its rear surface is a flat surface.
  • the high-resistance backing layer 2a has a thickness which is large in the middle and small in both sides, and its front surface is a flat surface, and its rear surface is a curved concave surface.
  • the low-resistance backing layer 2b has a thickness which is small in the middle and small on both sides, and the front surface thereof is a curved convex surface.
  • FIG. 12 which is a seventh embodiment of the ultrasonic transducer
  • the main difference between this embodiment and the sixth embodiment is that the rear surface of the high-resistance backing layer 2a is a wedge-shaped concave surface, and the wedge tip is oriented toward the pressure. Electric wafer.
  • the main difference between this embodiment and the sixth embodiment is that the rear surface of the high-resistance backing layer 2a is a trapezoidal concave surface, correspondingly, low impedance.
  • the front surface of the backing layer 2b is a trapezoidal convex surface.
  • an ultrasonic transducer For an ultrasonic transducer, it includes a matching layer, a piezoelectric wafer, a high impedance backing layer, and a low impedance backing layer.
  • the matching layer enables impedance matching between human tissue and the piezoelectric wafer.
  • a piezoelectric wafer is an element having a piezoelectric effect.
  • Both the high-impedance backing layer and the low-impedance backing layer absorb sound waves and provide damping, and increase the bandwidth of the ultrasonic transducer. The greater the impedance, the greater the damping and the wider the bandwidth.
  • the matching layer may be of equal thickness or variable thickness.
  • the piezoelectric wafer and the high-impedance backing layer are joined to form an equivalent piezoelectric crystal, and the equivalent piezoelectric crystal has a thickness which is small in the middle and small on both sides.
  • the low-impedance backing layer has a thickness that is small in the middle and large on both sides.
  • the acoustic impedance of the high-impedance backing layer can be greater than that of the piezoelectric wafer, and the acoustic impedance of the low-impedance backing layer can be smaller than that of the piezoelectric wafer.
  • the difference between the high and low acoustic impedances may be appropriately increased.
  • the acoustic impedance of the high-impedance backing layer may be n times the acoustic impedance of the piezoelectric wafer, and the acoustic impedance of the piezoelectric wafer may be low.
  • the impedance of the impedance backing layer is m times, and both n and m may be greater than one.
  • the acoustic impedance of the high-impedance backing layer may be three times that of the piezoelectric wafer, and the acoustic impedance of the low-impedance backing layer may be 1/10 of the acoustic impedance of the piezoelectric wafer.
  • the high-impedance backing layer and the low-impedance backing layer have a strong reflection coefficient at the junction of the high-impedance backing layer, which can generate strong reflected waves, enabling high-impedance backing layers of variable thickness and piezoelectric wafers of equal thickness.
  • the equivalent replacement of the variable thickness piezoelectric wafer greatly reduces the difficulty in manufacturing the piezoelectric wafer; and the fragile piezoelectric wafer is of equal thickness, so the ordinary process can ensure the safety of the wafer.
  • the maximum thickness/minimum thickness of the variable thickness high-resistance backing layer can be made relatively large, that is, the equivalent maximum thickness/minimum thickness ratio of the piezoelectric wafer is larger, as the value can be ⁇ 200%, so the ultrasonic transducer The bandwidth can be made wider.
  • the maximum thickness of the high-impedance backing layer the low-frequency portion of the ultrasonic transducer can be adjusted; by adjusting the minimum thickness of the high-impedance backing layer, the high-frequency portion of the ultrasonic transducer can be adjusted.

Abstract

一种超声换能器包括压电晶片（1）及背衬层，背衬层包括高阻抗背衬层（2a）和低阻抗背衬层（2b）。压电晶片的后表面与高阻抗背衬层的前表面连接，高阻抗背衬层的后表面与低阻抗背衬层的前表面连接。高阻抗背衬层和低阻抗背衬层的交界处会产生强反射，因而较多声波反射回压电晶片，提高了超声换能器的灵敏度。

Description

超声换能器 技术领域
本发明是关于一种超声换能器。
背景技术
超声诊断设备主要依靠超声波传递信息，超声换能器(又称为超声探头)就是实现信息传递的特殊功能器件。超声换能器既可以将电信号转换成超声波信号，以便在人体组织中传播；又可以将人体组织内反射回来的超声波信号转换成电信号，经过处理后以图像的形式显示在监视器上，供医生分析和诊断疾病。
带宽是衡量超声换能器好坏的一个重要特性。宽频带超声换能器可以收发不同频率的超声波，满足诊断设备在近场、远场使用不同工作频率的需求。同时，宽频带超声换能器也应用于谐波成像技术，宽频带能接受声波在人体组织中产生的多次谐波，从而提高图像的轴向分辨力和灵敏度。
一种宽频带超声换能器如图1所示，其中压电晶片11厚度越厚的位置，对应的换能器工作频率越低，通过调整压电晶片最大厚度LMAX和最小厚度LMIN，使换能器从低频到高频都有较好的灵敏度，达到拓宽带宽的效果；但是该种技术方案拓宽带宽的范围有一定的限制，受制作工艺的限制，通常LMAX/LMIN≤140％，如果此值太大，在制作换能器时压电晶片容易碎裂。
另一种宽频带超声换能器如图2所示，其中压电晶片42凹面和背衬40连接，这样可以在粘接加压过程中减小压电晶片碎裂的可能。此外，另一些方案包括两层变厚度压电晶片42、44的换能器，如图3所示；以及包括三层变厚度压电晶片24、26、28的换能器，如图4所示。该等多层变厚度压电晶片的方案可以在保证总等效弧度的情况下，减小上下面的弧度，从而减小压电晶片碎裂的可能性；但是，这些技术方案都是将易碎的压电晶片做成变厚度凹形的，都增加了制作工艺的难度，从而使压电晶片存在碎裂的风险；并且，由于压电晶片是凹面的，增大了在其上制作覆盖电极的难度。
发明内容
本发明提供一种新的超声换能器。
本发明提供一种超声换能器，包括压电晶片及背衬，所述背衬包括
高阻抗背衬层和低阻抗背衬层，所述压电晶片的后表面与所述高阻抗背衬层的前表面连接，所述高阻抗背衬层的后表面与所述低阻抗背衬层的前表面连接，并且所述高阻抗背衬层变厚度。
一些实施例中，所述压电晶片等厚度。
一些实施例中，所述高阻抗背衬层的厚度中间小两边大。
一些实施例中，所述高阻抗背衬层的后表面是弧形凹面、楔形凹面或梯形凹面。
一些实施例中，所述压电晶片和高阻抗背衬层均变厚度。
一些实施例中，所述压电晶片的厚度中间小两边大，所述高阻抗背衬层的厚度中间小两边大。
一些实施例中，所述压电晶片的前表面是凹面，所述压电晶片的后表面是平面，所述高阻抗背衬层的前表面是平面，所述高阻抗背衬层的后表面是弧形凹面、楔形凹面或梯形凹面。
一些实施例中，所述压电晶片等厚度，所述高阻抗背衬层的厚度中间小两边大，其后表面是凹面；所述低阻抗背衬层的厚度中间大两边小，其前表面是凸面；所述高阻抗背衬层的后表面和所述低阻抗背衬层的前表面吻合。
一些实施例中，所述的超声换能器，还包括匹配层，所述匹配层的后表面与所述压电晶片的前表面连接。匹配层可以变厚度或等厚度。
对于某个元件，如匹配层、压电晶片、高阻抗背衬层或低阻抗背衬层，其具有最大厚度和最小厚度。本文中，元件等厚度可以是指最大厚度和最小厚度相等。元件变厚度可以是指最大厚度和最小厚度不相等。
一种超声诊断设备，包括所述超声换能器。
本发明的有益效果是：
1)背衬包括高阻抗背衬层和低阻抗背衬层，在两者的交界处会产生强反射，进 而较多声波反射回压电晶片，从而提高了超声换能器的灵敏度。
2)利用等厚度压电晶片和变厚度高阻抗背衬层替代变厚度压电晶片，降低了压电晶片的制造工艺难度，有效减小压电晶片破裂的风险。
附图说明
图1是第一种现有超声换能器的结构示意图；
图2是第二种现有超声换能器的结构示意图；
图3是第三种现有超声换能器的结构示意图；
图4是第四种现有超声换能器的结构示意图；
图5是超声换能器第一具体实施方式的结构示意图；
图6是高阻抗背衬与等厚度压电晶片等效为变厚度压电晶片的原理图；
图7是超声换能器第二具体实施方式的结构示意图；
图8是超声换能器第三具体实施方式的结构示意图；
图9是超声换能器第四具体实施方式的结构示意图；
图10是超声换能器第五具体实施方式的结构示意图；
图11是超声换能器第六具体实施方式的结构示意图；
图12是超声换能器第七具体实施方式的结构示意图；
图13是超声换能器第八具体实施方式的结构示意图；
图14是超声换能器的立体结构示意图。
具体实施方式
如图5所示，一种超声换能器，包括匹配层3、压电晶片1、高阻抗背衬层2a和低阻抗背衬层2b，该匹配层、压电晶片、高阻抗背衬层及低阻抗背衬层由上至下依次层叠设置。压电晶片是等厚度压电晶片，高阻抗背衬层是变厚度高阻抗背衬层，压电晶片的后表面和高阻抗背衬层的前表面连接而构成等效压电晶片，该等效压电晶片能够等效于变厚度压电晶片。
本文中，所说的“高阻抗背衬层”可以是指声阻抗相对(例如相对于低阻抗背衬层)较高的背衬层，例如，其可以由声阻抗相对(例如相对于低阻抗背衬层的 材料)较高的背衬材料制成。类似地，所说的“低阻抗背衬层”可以是指声阻抗相对(例如相对于高阻抗背衬层)较低的背衬层，例如，其可以由声阻抗相对(例如相对于高阻抗背衬层的材料)较低的背衬材料制成。
该等效压电晶片的原理如下文简述。
如图6所示，其中1为压电晶片，2a为高阻抗背衬层，2b为低阻抗背衬层。当压电晶片1工作并发射超声波时，其向后传播的超声波大部分进入高阻抗背衬层2a并在高阻抗背衬层2a与低阻抗背衬层2b之间的界面处形成较强的反射，反射回来的超声波又经过到压电晶片1并向前发出。这样，压电晶片1和高阻抗背衬层2a构成了等效振子(即等效的压电晶片)，并且该等效振子的谐振频率与高阻抗背衬层2a的厚度成反比。因此，通过改变高阻抗背衬层2a的厚度，即可改变该等效振子的振动频率，也即改变该等效振子的工作频率，从而扩展超声换能器的带宽。
本文中，对于单一元件，如匹配层、压电晶片、高阻抗背衬层或低阻抗背衬层，其具有最大厚度和最小厚度。本发明的一些实施例中，单一元件“等厚度”可以是指其最大厚度和最小厚度相等。单一元件“变厚度”可以是指其最大厚度和最小厚度不相等。
如图5及图14所示，其为超声换能器的第一具体实施方式。超声换能器包括匹配层3、压电晶片1、高阻抗背衬层2a及低阻抗背衬层2b，匹配层3的后表面302与压电晶片1的前表面101连接，压电晶片1的后表面102与高阻抗背衬层2a的前表面201连接，高阻抗背衬层2a的后表面202与低阻抗背衬层2b的前表面203连接。压电晶片1等厚度t，其前表面101和后表面102均是平面。高阻抗背衬层2a变厚度(例如，沿着图5中X方向，在Z方向上的厚度是变化的，而不是恒定的)，其厚度中间小两边大，其前表面201是平面，其后表面202是弧形凹面。低阻抗背衬层2b变厚度，其厚度中间大两边小，其前表面203是与高阻抗背衬层的后表面吻合的弧形凸面。匹配层3变厚度，其前表面301可以是凹面，其后表面302可以是平面。低阻抗背衬层2b的后表面204可以是平面。匹配层的前表面301与声透镜5连接。
如图5所示，本发明的一些实施例中，左右方向X和前后方向Z垂直，厚度可以 是指对于单一元件(如匹配层、压电晶片、高阻抗背衬层或低阻抗背衬层)、具有相同X坐标值的前表面和后表面的Z坐标差值。中间和两边可以是指在左右方向X上的中间和两边。
如图7所示，其为超声换能器的第二具体实施方式，该实施方式与第一实施方式的主要区别在于：高阻抗背衬层2a的后表面是楔形凹面，该楔形凹面的楔尖朝向压电晶片，对应的，低阻抗背衬层2b的前表面是楔形凸面。
如图8所示，其为超声换能器的第三具体实施方式，该实施方式与第一实施方式的主要区别在于：高阻抗背衬层2a的后表面是梯形凹面，对应的，低阻抗背衬层2b的前表面是梯形凸面。
如图9所示，其为超声换能器的第四具体实施方式，该实施方式与第一实施方式的主要区别在于：匹配层3等厚度，其前表面和后表面均是平面；高阻抗背衬层2a的后表面是楔形凹面，其楔尖朝向压电晶片，对应的，低阻抗背衬层2b的前表面是楔形凸面。
如图10所示，其为超声换能器的第五具体实施方式，该实施方式于第一实施方式的主要区别在于：匹配层3等厚度，其前表面和后表面均是平面；高阻抗背衬层2a的后表面是梯形凹面，对应的，低阻抗背衬层2b的前表面是梯形凸面。
如图11所示，其为超声换能器的第六具体实施方式。超声换能器包括由上至下依次层叠的匹配层3、压电晶片1、高阻抗背衬层2a及低阻抗背衬层2b。匹配层3等厚度，其前表面是弧形凹面，其后表面是弧形凸面。压电晶片1变厚度，其厚度中间小两边大，其前表面是弧形凹面，其后表面是平面。高阻抗背衬层2a变厚度，其厚度中间小两边大，其前表面是平面，其后表面是弧形凹面。低阻抗背衬层2b变厚度，其厚度中间大两边小，其前表面是弧形凸面。
如图12所示，其为超声换能器的第七具体实施方式，该实施方式与第六实施方式的主要区别在于：高阻抗背衬层2a的后表面是楔形凹面，其楔尖朝向压电晶片。
如图13所示，其为超声换能器的第八具体实施方式，该实施方式与第六实施方式的主要区别在于：高阻抗背衬层2a的后表面是梯形凹面，对应的，低阻抗背衬层2b的前表面是梯形凸面。
对于超声换能器，其包括匹配层、压电晶片、高阻抗背衬层和低阻抗背衬层。匹配层能够实现人体组织和压电晶片之间的阻抗匹配。压电晶片是具有压电效应的元件。高阻抗背衬层和低阻抗背衬层均能够吸收声波和起到阻尼作用，并能够增加超声换能器的带宽，且阻抗越大，阻尼作用越大，带宽也变宽。匹配层可以是等厚度，也可以是变厚度。压电晶片和高阻抗背衬层连接而形成等效压电晶体，该等效压电晶体变厚度，其厚度中间小两边大。低阻抗背衬层变厚度，其厚度中间大两边小。
高阻抗背衬层的声阻抗可以大于压电晶片，低阻抗背衬层的声阻抗可以小于压电晶片。为了提升超声换能器的灵敏度，可以适当拉大高低声阻抗的差值，如高阻抗背衬层的声阻抗可以是压电晶片的声阻抗的n倍，压电晶片的声阻抗可以是低阻抗背衬层的声阻抗的m倍，该n和m可以均大于1。在一种可行的方案中，高阻抗背衬层的声阻抗可以是压电晶片的声阻抗的3倍，低阻抗背衬层的声阻抗可以为压电晶片的声阻抗的1/10。压电晶片向后传播的声波大部分进入高阻抗背衬层，然后在高阻抗背衬层和低阻抗背衬层的交界处形成强反射，进而几乎全部反射回压电晶片，这样可以大大提高超声换能器的灵敏度。
对于超声换能器，高阻抗背衬层和低阻抗背衬层的交界处有较强的反射系数，能够产生强反射波，使变厚度的高阻抗背衬层和等厚度的压电晶片能够等效替代变厚度压电晶片，大大降低了压电晶片的制造难度；并且易碎的压电晶片是等厚度的，所以普通的工艺就能够保证该晶片的安全。同时，变厚度高阻抗背衬层的最大厚度/最小厚度能够做的比较大，即等效的压电晶片最大厚度/最小厚度比更大，如该值可以≥200％，因此超声换能器的带宽可以做到更宽。通过调整高阻抗背衬层的最大厚度，可以调整超声换能器的低频部分；通过调整高阻抗背衬层的最小厚度，可以调整超声换能器的高频部分。
以上内容是结合具体的实施方式对本发明所作的进一步详细说明，不能认定本发明的具体实施只局限于这些说明。对于本发明所属技术领域的普通技术人员来说，在不脱离本发明构思的前提下，还可以做出若干简单推演或替换。
技术问题
问题的解决方案
发明的有益效果

Claims (14)

  1. 一种超声换能器，包括压电晶片及背衬，其特征在于，所述背衬包括高阻抗背衬层和低阻抗背衬层，所述压电晶片的后表面与所述高阻抗背衬层的前表面连接，所述高阻抗背衬层的后表面与所述低阻抗背衬层的前表面连接，其中，所述高阻抗背衬层变厚度。
  2. 如权利要求1所述的超声换能器，其特征在于，所述压电晶片等厚度。
  3. 如权利要求1所述的超声换能器，其特征在于，所述高阻抗背衬层的厚度中间小两边大。
  4. 如权利要求3所述的超声换能器，其特征在于，所述高阻抗背衬层的后表面是弧形凹面、楔形凹面或梯形凹面。
  5. 如权利要求3所述的超声换能器，其特征在于，所述高阻抗背衬层的前表面是平面。
  6. 如权利要求2所述的超声换能器，其特征在于，所述压电晶片的前表面和后表面均是平面。
  7. 如权利要求1所述的超声换能器，其特征在于，所述压电晶片和高阻抗背衬层均变厚度。
  8. 如权利要求7所述的超声换能器，其特征在于，所述压电晶片的厚度中间小两边大，所述高阻抗背衬层的厚度中间小两边大。
  9. 如权利要8所述的超声换能器，其特征在于，所述压电晶片的前表面是凹面，所述压电晶片的后表面是平面，所述高阻抗背衬层的前表面是平面，所述高阻抗背衬层的后表面是弧形凹面、楔形凹面或梯形凹面。
  10. 如权利要求1所述的超声换能器，其特征在于，所述压电晶片等厚度，所述高阻抗背衬层的厚度中间小两边大，其后表面是凹面；所述低阻抗背衬层的厚度中间大两边小，其前表面是凸面；所述高阻抗背衬层的后表面和所述低阻抗背衬层的前表面吻合。
  11. 如权利要求1-10中任意一项所述的超声换能器，其特征在于，还包括匹配层，所述匹配层的后表面与所述压电晶片的前表面连接。
  12. 如权利要求11所述的超声换能器，其特征在于，所述匹配层变厚度，且其厚度中间小两边大。
  13. 如权利要求11所述超声换能器，其特征在于，所述匹配层等厚度。
  14. 一种具有权利要求1-13中任意一项所述的超声换能器的超声诊断设备。
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