JP2007288397A - Ultrasonic probe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic probe, having an acoustic matching layer of a 2-layer structure that broadbands the frequency characteristics wider than that of prior art, by reexamining an ideal value of the acoustic impedance of respective acoustic matching layers. <P>SOLUTION: The ultrasonic probe includes a resonator with a piezoelectric body 11 formed by piezoelectric ceramics and electrodes 12, 13 formed at both ends of the piezoelectric body for transmitting ultrasonic waves, depending on an applied voltage and generating a voltage by receiving ultrasonic waves; a first acoustic matching layer 14 formed on a principal side of the resonator and with the acoustic impedance, the ratio of which to the acoustic impedance of the resonator is 0.265 to 0.294; and a second acoustic matching layer 15, formed on the first acoustic matching layer 14 and with the acoustic impedance, the ratio of which to the acoustic impedance of the resonator is 0.069 to 0.079. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ultrasonic probe used in a medical ultrasonic diagnostic apparatus or the like, which includes a piezoelectric vibrator that transmits and receives ultrasonic waves and an acoustic matching layer for matching acoustic impedance.

  Conventionally, in ultrasonic transducers used for transmitting and / or receiving ultrasonic waves, piezoelectric ceramics represented by PZT (lead zirconate titanate) and PVDF (polyvinyliden difluoride: polyvinylidene difluoride). In general, vibrators (piezoelectric vibrators) in which electrodes are formed on both ends of a piezoelectric body such as a polymer piezoelectric material represented by (1) have been used.

  When a voltage is applied to the electrodes of such a vibrator, the piezoelectric element expands and contracts due to the piezoelectric effect, and ultrasonic waves are generated. Furthermore, an ultrasonic beam can be formed in a desired direction by arranging a plurality of transducers in a one-dimensional or two-dimensional manner and driving with a plurality of drive signals given a predetermined delay. On the other hand, the vibrator expands and contracts by receiving propagating ultrasonic waves and generates an electrical signal. This electric signal is used as an ultrasonic reception signal.

  An ultrasound diagnostic apparatus transmits an ultrasonic wave to a subject, receives a reflected wave from the subject, and displays an image based on the received signal to inspect an internal organ or blood vessel. . However, when piezoelectric ceramic is used for the vibrator, there is a large gap between the acoustic impedance of the vibrator (expressed by the product of the acoustic medium density and the speed of sound) and the acoustic impedance of the subject (human body, etc.). There is a difference, and at the boundary surface where there is such a difference in acoustic impedance, reflection of ultrasonic waves occurs, resulting in propagation loss of ultrasonic waves.

The acoustic impedance is a material-specific constant represented by the product of the acoustic medium density and the speed of sound. The unit is generally MRayl (mega-rail), and 1 MRayl = 1 × 10 ⁶ kg · m ^{−. 2} · s ⁻¹ . A typical piezoelectric ceramic has an acoustic impedance of about 23 MRayl to about 35 MRayl, and a human body has an acoustic impedance of about 1.5 MRayl.

When the piezoelectric vibrator is brought into direct contact with the human body, most ultrasonic waves are reflected at the contact interface due to the difference in acoustic impedance between them. The acoustic impedance of the piezoelectric vibrator and Z _0, when the body of the acoustic impedance and Z _M, the reflectance R _P of ultrasonic wave in the contact interface is given by the following equation (1).
R _P = (Z ₀ −Z _M ) / (Z ₀ + Z _M ) (1)
In Equation (1), when Z ₀ = 35 MRayl and Z _M = 1.5 MRayl, R _P = 0.92, and it can be seen that ultrasonic waves do not propagate by 10%.

  In order to solve this problem, an acoustic matching layer is inserted between the transducer and the subject to achieve acoustic impedance matching. Furthermore, the propagation efficiency of ultrasonic waves is improved by making the acoustic matching layer have a multilayer structure. Here, in order to maximize the propagation efficiency of the ultrasonic wave, it is possible to theoretically obtain the ideal value of the acoustic impedance in each acoustic matching layer. Non-Patent Document 1 describes the optimum acoustic impedance obtained based on the energy transmission theory (see FIG. 7).

By providing the acoustic matching layer, the propagation efficiency of the ultrasonic wave is improved and the sensitivity is increased, but there is also a disadvantage that the oscillation frequency band is narrowed. Therefore, according to Non-Patent Document 1, the frequency bandwidth in an ultrasonic probe having two acoustic matching layers was calculated. Here, a general piezoelectric ceramic (Z ₀ = about 35 MRayl, electromechanical coupling constant K ₃₃ = about 0.7) and a general backing material (acoustic impedance is about 1.75 MRayl to 20.0 MRayl) are used. Shall.

  In general, a backing material with high acoustic impedance is produced by mixing a high-density powder with a resin having damping (braking) properties. However, in consideration of the balance with the sound attenuation capability, 20 MRayl is the upper limit of the acoustic impedance. Value. Further, from the viewpoint of holding the piezoelectric vibrator, 1.75 MRayl when produced by using a resin material such as epoxy / polystyrene resin is the lower limit value of the acoustic impedance.

  Non-Patent Document 2 discloses that the thickness of each acoustic matching layer is set to ¼ of the oscillation wavelength in view of the reflection of ultrasonic waves at the interface of the acoustic matching layer. The same conditions are used.

As a result, the frequency bandwidth f _BW (%) was about 60% to 65%. The frequency bandwidth f _BW (%) is expressed by the following equation (2).
f _BW (%) = 100 × (f _H −f _L ) / f _C (2)
Here, the frequencies f _H and f _L are two frequencies at which the sound pressure is attenuated by 6 dB from the peak value (f _L <f _H ), and the frequency f _C is a center frequency between the frequency f _H and the frequency f _L. .

  In general, since the ultrasonic wave in the low frequency region has a low attenuation factor, the image obtained thereby has a high brightness but is a coarse image, and the ultrasonic wave in the high frequency region has a large attenuation factor. Is a low but fine image. In order to make use of these characteristics, an ultrasonic probe is selectively used depending on the diagnosis target.

However, endoscope-type probes inserted into the digestive organs and catheter-type probes inserted into blood vessels are required to have a performance capable of covering a wide frequency band from a low frequency region to a high frequency region. ing. Thereby, the frequency | count of inserting a probe in a human body can be reduced. Thus, in the probe inserted into the human body, it is desirable that the frequency bandwidth f _BW (%) is about 65% or more. Further, even in a general ultrasonic probe, the image quality of an obtained ultrasonic image can be improved by realizing a wideband frequency characteristic.

  Due to such circumstances, when setting the acoustic impedance of the acoustic matching layer, the frequency characteristics obtained as a result should be taken into consideration. When the acoustic matching layer has a multilayer structure, the ideal value of the acoustic impedance in each acoustic matching layer is set so as to maximize the propagation efficiency of ultrasonic waves. However, the frequency band obtained as a result is not necessarily suitable for realizing a wide frequency characteristic.

  As a related technique, the following Patent Document 1 discloses an ultrasonic probe that has a plurality of passbands, and the sum of the plurality of passbands effectively realizes wideband characteristics and high sensitivity. ing. In this ultrasonic probe, two pass bands are realized by making the resonance frequencies of the two vibrators significantly different.

  Patent Documents 2 to 4 listed below disclose an ultrasonic probe having an acoustic matching layer having a three-layer structure and having an acoustic impedance in the acoustic matching layer in a specific range. According to this ultrasonic probe, it has low loss and low ripple, has a wider frequency band characteristic than an ultrasonic probe having a two-layer acoustic matching layer, and has excellent ultrasonic pulse response characteristics. Can be realized.

  Further, in Patent Document 5 below, an ultrasonic pulse having an appropriate pulse width and amplitude can be easily emitted by appropriately setting a combination of the acoustic impedance of the backing layer, the thickness of the acoustic matching layer, and the acoustic impedance. An ultrasonic probe is disclosed.

As described above, various techniques have been developed in order to realize a broadband frequency characteristic in an ultrasonic probe. However, in response to recent high demands, it is required to further broaden the frequency characteristics of the ultrasonic probe.
JP 60-113599 A (page 4, FIG. 7) JP-A-60-113600 (5th page, FIG. 7) JP-A-60-185499 (7th page, FIG. 70) JP-A-60-223299 (7th page, FIG. 70, FIG. 71) JP-A-6-30933 (page 5, FIG. 3) “Ultrasonic Handbook”, Maruzen, p. 116 Masayasu Ito, Tsuyoshi Mochizuki “Ultrasound Diagnostic Device”, Corona, p. 30

  Accordingly, in view of the above points, the present invention provides an ultrasonic probe having an acoustic matching layer having a two-layer structure. The purpose is to widen the bandwidth.

  In order to solve the above problems, an ultrasonic probe according to a first aspect of the present invention includes a piezoelectric body formed of piezoelectric ceramic and electrodes formed at both ends of the piezoelectric body, and is applied. A transducer that transmits ultrasonic waves according to a voltage and receives ultrasonic waves to generate a voltage, and an acoustic wave that is formed on the main surface of the transducer and has a ratio of 0.265 to 0.294 with respect to the acoustic impedance of the transducer A first acoustic matching layer having impedance, and a second acoustic matching layer formed on the first acoustic matching layer and having an acoustic impedance having a ratio of 0.069 to 0.079 with respect to the acoustic impedance of the vibrator; It comprises.

  The ultrasonic probe according to the second aspect of the present invention includes a piezoelectric body formed of piezoelectric ceramic and electrodes formed at both ends of the piezoelectric body, and generates ultrasonic waves according to an applied voltage. A transducer that transmits and receives ultrasonic waves to generate a voltage, and a first transducer that is formed on the main surface of the transducer and has an acoustic impedance that has a ratio to the acoustic impedance of the transducer of 0.309 to 0.338. And a second acoustic matching layer formed on the first acoustic matching layer and having an acoustic impedance with a ratio of 0.062 to 0.088 to the acoustic impedance of the vibrator.

  Furthermore, the ultrasonic probe according to the third aspect of the present invention includes a piezoelectric body formed of piezoelectric ceramic and electrodes formed at both ends of the piezoelectric body, and transmits ultrasonic waves according to an applied voltage. A transducer that transmits and receives ultrasonic waves to generate a voltage, and a first transducer that is formed on the main surface of the transducer and has an acoustic impedance that has a ratio to the acoustic impedance of the transducer of 0.353 to 0.456. And a second acoustic matching layer formed on the first acoustic matching layer and having an acoustic impedance with a ratio of 0.062 to 0.106 with respect to the acoustic impedance of the vibrator.

  According to the present invention, since the range of the acoustic impedance of the first and second acoustic matching layers suitable for broadening the frequency characteristic of the ultrasonic probe is newly specified, the frequency characteristic is more than conventional. Can be broadened.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. The same constituent elements are denoted by the same reference numerals, and the description thereof is omitted.
FIG. 1 is a perspective view showing the internal structure of an ultrasonic probe according to an embodiment of the present invention. As shown in FIG. 1, an ultrasonic probe 1 includes a piezoelectric body 11 that expands and contracts due to a piezoelectric effect and generates an ultrasonic wave, and an electrode 12 to which a voltage for causing the piezoelectric body 11 to generate a piezoelectric effect is applied. And 13, and a piezoelectric vibrator constituted by the piezoelectric body 11 and the electrodes 12 and 13, and a first acoustic matching that increases the propagation efficiency of ultrasonic waves by matching the acoustic impedance between a subject such as a human body The layer 14 and the second acoustic matching layer 15, and a backing layer 16 that attenuates unnecessary ultrasonic waves generated from the piezoelectric body 11 are included.

  Furthermore, the ultrasonic probe 1 reduces interference between a plurality of piezoelectric vibrators, suppresses the lateral vibration of the piezoelectric vibrators, and causes the piezoelectric vibrators to vibrate only in the vertical direction. The filler 17 may be included. Further, the ultrasonic probe 1 may include an acoustic lens 18 for converging the ultrasonic wave, but a case where the acoustic lens 18 is not provided will be described below.

In the present embodiment, a piezoelectric ceramic is used as the material of the piezoelectric body 11. Piezoelectric ceramics have a high electrical / mechanical energy conversion capability, so that they can generate powerful ultrasonic waves that can reach deep inside the body and have high reception sensitivity. Specific materials include PZT (lead zirconate titanate: Pb (Ti, Zr) O ₃ ), a metamorphic material having a similar perovskite crystal structure, and a material generally called a relaxor material Etc. can be used.

  When a piezoelectric ceramic is used as the material of the piezoelectric body 11, there is a large difference between the acoustic impedance of the piezoelectric vibrator and the acoustic impedance of the subject (human body, etc.), so that there is a difference between the piezoelectric vibrator and the human body. By providing an acoustic matching layer having an acoustic impedance between them, it is necessary to match the acoustic impedance and increase the propagation efficiency of ultrasonic waves. Here, as the acoustic matching layer has a multilayer structure, the propagation efficiency of ultrasonic waves is improved. However, from the viewpoint of manufacturing, a two-layer structure or a three-layer structure is often used. In the present invention, the material of the piezoelectric body is not limited to piezoelectric ceramic. For example, the present invention is also applied to the case where a material having a small difference between the acoustic impedance of the piezoelectric vibrator and the acoustic impedance of a subject (such as a human body) is used.

  In the present embodiment, as the material of the first acoustic matching layer 14, for example, quartz glass or a material powder (tungsten, an organic material (epoxy resin, urethane resin, silicon resin, acrylic resin, etc.)) having high acoustic impedance. A material mixed with ferrite powder or the like can be used. As a material of the second acoustic matching layer 15, for example, an organic material (epoxy resin, urethane resin, silicon resin, acrylic resin, or the like) can be used. Further, as the material of the backing layer 16, epoxy resin, rubber, or the like, which is a material having a large acoustic attenuation, can be used.

  When setting the number of acoustic matching layers and acoustic impedance, the frequency band characteristics obtained as a result are also important. Therefore, in order to broaden the frequency characteristics, the following design is used in this embodiment. The method is used.

  First, a method for calculating the frequency characteristics of the ultrasonic probe will be described. By replacing each component included in the ultrasonic probe with an equivalent four-terminal circuit, the ultrasonic transmission system can be divided into four layers in which a backing layer, a piezoelectric vibrator, and an acoustic matching layer are connected in series. Think of it as a terminal network. Each component has a specific acoustic impedance, and a specific frequency characteristic is generated when transmitting or receiving an ultrasonic wave via an ultrasonic transmission system. Therefore, by inputting a voltage to one end of this four-terminal network and terminating the other end by an equivalent circuit of the subject, the oscillation performance of the ultrasonic probe can be changed to a transmission / reception characteristic VTG (Voltage Transfer Gain). Can be calculated and predicted.

ここで、

とする。また、Ｋは電気機械結合定数を表し、Ｚ_０は圧電振動子の音響インピーダンスを表し、Ｚ_Ａは音響整合層の音響インピーダンスを表し、Ｚ_Ｂはバッキング層の音響インピーダンスを表している。また、ｍ_Ａは、前記Ｚ_ＡとＺ_０との比を表し、ｍ_Ｂは、前記Ｚ_ＢとＺ_０との比を表している。ｆ_０は設計上の中心周波数（圧電振動子の機械共振周波数）を表し、Ｃ_０は容量値を表している。角周波数ω_０は、周波数ｆ_０を用いて、２πｆ_０と表される。また、γは伝送位相を表し、ｖ_Ｌは圧電振動子内部における縦波の音速を表し、ｄは圧電振動子の厚さを表している。 The input impedance Z of the transmission system is expressed as (3) below, and the transmission / reception characteristic VTG is calculated based on the input impedance Z.

here,

And K represents the electromechanical coupling constant, Z ₀ represents the acoustic impedance of the piezoelectric vibrator, Z _A represents the acoustic impedance of the acoustic matching layer, and Z _B represents the acoustic impedance of the backing layer. _{M A} represents the ratio of Z _A and Z _0, and m _B represents the ratio of Z _B and Z ₀ . f ₀ represents a design center frequency (mechanical resonance frequency of the piezoelectric vibrator), and C ₀ represents a capacitance value. The angular frequency ω ₀ is expressed as 2πf ₀ using the frequency f ₀ . Further, γ represents the transmission phase, v _L represents the acoustic velocity of the longitudinal wave inside the piezoelectric vibrator, and d represents the thickness of the piezoelectric vibrator.

  Furthermore, in order to perform a simulation in which this equivalent circuit is applied to an acoustic matching layer having a two-layer structure, an ultrasonic transmission system includes a backing layer, a piezoelectric vibrator, a first acoustic matching layer, and a second acoustic matching layer. Consider a four-terminal network connected in series. In this transmission model, assuming that the transmission sound pressure is equal to the reception sound pressure, the signal transfer function T is obtained based on the input impedance of the transmission system and the constants of the four-terminal network. By calculating 20 · log (T) at each frequency with respect to this signal transfer function T, the transmission / reception characteristic VTG is obtained.

  FIG. 2 shows the calculation conditions in the simulation of the transmission / reception characteristics in comparison with the conventional example. In this embodiment, since an acoustic matching layer having a two-layer structure is used, the acoustic impedance of the first acoustic matching layer, the acoustic impedance of the second acoustic matching layer, the acoustic impedance of the piezoelectric vibrator, and the electromechanical coupling constant The acoustic impedance of the backing layer and the design center frequency of the piezoelectric vibrator are shown.

In the conventional example, the first acoustic impedance is 8.92 MRayl and the second acoustic impedance is 2.34 MRayl (same as FIG. 7). On the other hand, in this embodiment, the first acoustic impedance is 12 MRayl and the second acoustic impedance is 2.7 MRayl. Other calculation conditions are the same. That is, the acoustic impedance Z ₀ of the piezoelectric ceramic is 34 MRayl, the electromechanical coupling constant K ₃₃ is 0.65, and the acoustic impedance of the backing layer is 5.5 MRayl.

  In FIG. 3, the simulation result of the transmission / reception characteristic in this embodiment is shown in comparison with the conventional example. In FIG. 3, the horizontal axis represents frequency (MHz) and the vertical axis represents transmission / reception wave characteristics VTG (dB). Moreover, the solid line has shown the calculation result in this embodiment, and the broken line has shown the calculation result in a prior art example.

In FIG. 3, when the frequency bandwidth f _BW (%) is obtained using Equation (2) based on two frequencies f _H and f _L at which the sound pressure attenuates 6 dB from the peak value, _H = 8.6 MHz, f _L = 4.5 MHz, f _C = 6.55 MHz, and the frequency bandwidth f _BW (%) is 63%. On the other hand, in the present embodiment, since f _H = 8.6 MHz, f _L = 4.1 MHz, and f ₀ = 6.35 MHz, the frequency bandwidth f _BW (%) is 71%. As described above, by changing the acoustic impedance values of the first and second acoustic matching layers, which have been optimized in the past, the frequency bandwidth can be improved over the conventional design conditions.

  Ultrasound has the property that the higher the frequency, the greater the attenuation in the body and water. Therefore, in the ultrasonic probe created by the conventional design guidelines, the calculated value does not take attenuation into account. In comparison, the high frequency component is low, and the frequency bandwidth is often narrow. On the other hand, according to the present embodiment, in addition to the expansion of the frequency bandwidth, the VTG characteristic can be designed high in the high frequency region, and the attenuation of the high frequency component can be compensated.

  Next, a description will be given of an embodiment that is experimentally manufactured based on the above calculation result. In this embodiment, PZT is used as the piezoelectric body 11 shown in FIG. 1, quartz glass is used as the first acoustic matching layer 14, a polyimide sheet is used as the second acoustic matching layer 15, and ferrite is contained as the backing layer 16. Rubber material is used.

  Here, the acoustic impedance of the piezoelectric body 11 is about 34 MRayl, the acoustic impedance of the first acoustic matching layer 14 is 12 MRayl, the acoustic impedance of the second acoustic matching layer 15 is 2.7 MRayl, and the backing layer The acoustic impedance of 16 is about 5.5 MRayl. Therefore, each acoustic impedance is under the same conditions as in the simulation shown in FIG. The design center frequency is 6.5 MHz, and the ultrasonic wavelength is determined based on this. Here, the thickness of the piezoelectric body is set to ½ of the ultrasonic wavelength, and the thickness of each acoustic matching layer is set to ¼ of the ultrasonic wavelength in view of the reflection of the ultrasonic wave at the interface of the acoustic matching layer. Set to.

  FIG. 4 shows the actual measurement results of the transmission / reception characteristics in this embodiment. In FIG. 4, the horizontal axis represents frequency (MHz), and the vertical axis represents transmission / reception wave characteristics VTG (dB). The actual measurement result of the transmission / reception characteristics shown in FIG. 4 is a curve close to the simulation result of the transmission / reception characteristics shown by the solid line in FIG. Therefore, it was proved that the above simulation is valid.

  5 and 6 are diagrams showing frequency bandwidths when the acoustic impedances of the first and second acoustic matching layers are changed in the above simulation. In the horizontal direction, the acoustic impedance ratio of the first acoustic matching layer relative to the vibrator is changed, and in the vertical direction, the acoustic impedance ratio of the second acoustic matching layer relative to the vibrator is changed.

For example, in FIG. 5, when the acoustic impedance ratio of the first acoustic matching layer to the vibrator is 0.262 and the acoustic impedance ratio of the second acoustic matching layer to the vibrator is 0.069, The frequency bandwidth f _BW (%) of the ultrasonic probe is 63.16%.

  Here, assuming that the acoustic impedance of the vibrator is 34 MRayl, the ratio of the acoustic impedance of the first acoustic matching layer to the vibrator is 0.262 means that the acoustic impedance of the first acoustic matching layer is 8. It means 91 MRayl. In addition, the acoustic impedance ratio of the second acoustic matching layer to the vibrator being 0.069 means that the acoustic impedance of the second acoustic matching layer is 2.35 MRayl. That is, this condition is almost the same as the condition of the conventional example shown in FIG. 3, and the value of the frequency bandwidth is also almost the same.

  In FIG. 5 and FIG. 6, when the condition for the frequency bandwidth value to be relatively large exceeding 63.16% in the conventional example is selected, the frequency bandwidth is generally represented by a region surrounded by a thick line. Is done. That is, in FIG. 5, the acoustic impedance ratio of the first acoustic matching layer to the vibrator is 0.265 to 0.294, and the acoustic impedance ratio of the second acoustic matching layer to the vibrator is 0.069. A combination of ~ 0.079 is applicable.

  In FIG. 6, the acoustic impedance ratio of the first acoustic matching layer to the vibrator is 0.309 to 0.338, and the acoustic impedance ratio of the second acoustic matching layer to the vibrator is 0.062. The acoustic impedance ratio of the first acoustic matching layer relative to the vibrator is 0.353 to 0.456, and the acoustic impedance ratio of the second acoustic matching layer relative to the vibrator is 0. A combination of .062 to 0.106 is applicable. In the case where the acoustic impedance of the backing layer is in the range of about 1.75 MRayl to 20.0 MRayl, substantially the same result is obtained. In practice, the acoustic impedance of the backing layer is in the range of 1.75 MRayl to 6.0 MRayl, and more preferably in the range of 3.5 MRayl to 6.0 MRayl.

  Thus, according to the present invention, when the acoustic matching layer has a two-layer structure, by selecting a combination of the acoustic impedance of the first acoustic matching layer and the acoustic impedance of the second acoustic matching layer, The frequency bandwidth of the ultrasonic probe can be widened. The present invention can be applied to an ultrasonic probe having any shape such as a sector type, a linear type, a convex type, and a radial type.

  The present invention has a piezoelectric vibrator that transmits and receives ultrasonic waves and an acoustic matching layer for matching acoustic impedance, and is used in an ultrasonic probe used in a medical ultrasonic diagnostic apparatus and the like. It is possible.

It is a perspective view which shows the internal structure of the probe for ultrasonic waves which concerns on one Embodiment of this invention. It is a figure which shows the calculation conditions in simulation of a transmission / reception wave characteristic compared with a prior art example. It is a figure which shows the simulation result of the transmission / reception wave characteristic in one Embodiment of this invention compared with a prior art example. It is a figure which shows the actual measurement result of the transmission / reception wave characteristic in one Example of this invention. It is a figure which shows the frequency bandwidth at the time of changing the acoustic impedance of the 1st and 2nd acoustic matching layer. It is a figure which shows the frequency bandwidth at the time of changing the acoustic impedance of the 1st and 2nd acoustic matching layer. It is a figure which shows the conventional optimal acoustic impedance calculated | required based on energy transmission theory.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Probe for ultrasonic waves 11 Piezoelectric body 12, 13 Electrode 14 1st acoustic matching layer 15 2nd acoustic matching layer 16 Backing layer 17 Filler 18 Acoustic lens

Claims (4)

A vibrator that transmits an ultrasonic wave according to an applied voltage and receives the ultrasonic wave to generate a voltage;
A first acoustic matching layer formed on a main surface of the vibrator and having an acoustic impedance of a ratio of 0.265 to 0.294 with respect to the acoustic impedance of the vibrator;
A second acoustic matching layer formed on the first acoustic matching layer and having an acoustic impedance with a ratio of 0.069 to 0.079 to the acoustic impedance of the vibrator;
An ultrasonic probe comprising: A vibrator that transmits an ultrasonic wave according to an applied voltage and receives the ultrasonic wave to generate a voltage;
A first acoustic matching layer formed on a main surface of the vibrator and having an acoustic impedance of a ratio of 0.309 to 0.338 with respect to the acoustic impedance of the vibrator;
A second acoustic matching layer formed on the first acoustic matching layer and having an acoustic impedance with a ratio of 0.062 to 0.088 to the acoustic impedance of the vibrator;
An ultrasonic probe comprising: A vibrator that transmits an ultrasonic wave according to an applied voltage and receives the ultrasonic wave to generate a voltage;
A first acoustic matching layer formed on a main surface of the vibrator and having an acoustic impedance with a ratio of 0.353 to 0.456 to the acoustic impedance of the vibrator;
A second acoustic matching layer formed on the first acoustic matching layer and having an acoustic impedance of a ratio of 0.062 to 0.106 with respect to the acoustic impedance of the vibrator;
An ultrasonic probe comprising: 4. The method according to claim 1, further comprising a backing layer formed on a surface opposite to the main surface of the vibrator and having an acoustic impedance ratio of 0.05 to 0.59. The ultrasonic probe according to item 1.

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