JP6954866B2 - Acoustic matching device and acoustic probe system using it - Google Patents

Description

The present invention relates to an acoustic matching device capable of obtaining wide-band acoustic matching characteristics between a wide range of dissimilar materials having various specific acoustic impedances, and an acoustic probe system using the same.

An ultrasonic transducer is used as a means for transmitting and receiving ultrasonic waves having a frequency (about 20,000 Hz or more) beyond the human audible range. For example, in medical ultrasonic equipment, non-destructive inspection, and marine sonar, this ultrasonic transducer is brought into contact with various materials that transmit ultrasonic waves (water, human body, semiconductor wafer, metal, ceramic, concrete, plastic, etc.). Ultrasonic waves are input and output.

Acoustic impedance, which is one of the physical characteristics of materials, is important as a cause of hindering the efficient propagation of sound waves. Sound does not propagate efficiently between materials with different acoustic impedances due to sound reflection. In order to solve this, it is common to insert an acoustic matching layer between the ultrasonic transducer and the material in which the ultrasonic waves are to be propagated.

The acoustic matching layer efficiently propagates sound waves from a sound source into a target medium, efficiently propagates sound waves from different media to a medium, and efficiently receives sound waves propagating through a certain medium. It is a structure for squeezing.

The acoustic impedance of the acoustic matching layer takes an intermediate value of the acoustic impedance of each of the two media in which the sound wave is desired to be propagated, and is usually a thickness of 1/4 wavelength of the frequency in which the thickness of the acoustic matching layer is desired to be propagated. Let's say. In order to propagate sound waves more efficiently, the acoustic matching layer may be composed of two or more layers instead of one layer (Non-Patent Document 1).

In addition, as a method for performing acoustic matching over a wider band, a tapered columnar structure whose cross-sectional area gradually changes with a material having a specific acoustic impedance close to that of a vibrator is created so that the acoustic impedance gradually changes. There is known a plate-shaped acoustic matcher that fills the gaps of the tapered columnar structure with a material having a specific acoustic impedance close to that of the material on the acoustic radiation surface side of the above (Patent Document 1).

Japanese Patent No. 3964508

Transaction on Sonics and Ultrasonics, Vol. SU-13, No.1 (March, 1996)

Among the above-mentioned prior arts, in the case of the method of producing an acoustic matching layer having a thickness of 1/4 wavelength (Non-Patent Document 1), in principle, it is efficient only in a certain frequency and a limited frequency range around it. There is a problem that sound waves cannot be propagated.

In the case of the other conventional method of filling the tapered columnar structure with another material (Patent Document 1), the specific acoustic impedance of the tapered columnar structure vibrates in order to obtain sufficient sound wave propagation efficiency. There are restrictions that it is close to the specific acoustic impedance of the child and that the specific acoustic impedance of the filling material must be close to the specific acoustic impedance of the material on the acoustic radiation surface. Therefore, in order to apply it to a material having various specific acoustic impedances, it is necessary to select or develop an optimum material as a tapered columnar structure or a filling material, and there is a problem that it is difficult to apply it to a wide range of fields.

Therefore, if it is possible to change the propagation cross-sectional area of a sound wave without being limited to the material and in such a way that the sound wave is not reflected, efficient sound wave propagation will be possible in a wider range of fields.

The above and other objects and novel features of the present invention will become apparent from the description and accompanying drawings herein.

A brief overview of typical embodiments disclosed in the present application is as follows.

The acoustic matching device according to a typical embodiment is composed of a first membrane structure portion, a second membrane structure portion, and a wall structure portion that supports them, and the first membrane structure portion is a first film structure portion. The second membrane structure portion is joined to the second acoustic medium having a specific acoustic impedance different from that of the first acoustic medium. The contact area between each film structure and the wall structure is the ratio of the specific acoustic impedance of the material constituting the acoustic matching device to the contact area between each film structure and the wall structure of each acoustic medium. It is adjusted to match the specific acoustic impedance.

According to the present invention, it is possible to realize an acoustic matching device having a wide band acoustic matching characteristic for a wide range of acoustic propagation materials.

It is a figure explaining the idea which is the basis of this invention. It is a figure explaining the basic principle of the acoustic matching device of this invention. It is a figure explaining the basic structure of the acoustic matching device of this invention. It is a figure which shows another example of the acoustic matching device of this invention. It is a figure which shows another example of the acoustic matching device of this invention. It is a figure which shows another example of the acoustic matching device of this invention. (A) to (e) are plan views showing the shape of the contact surface between the film structure portion and the wall structure portion in the acoustic matching device of the present invention. It is a graph which shows the acoustic matching performance of the acoustic matching device of this invention in comparison with the prior art. It is a figure which shows another example of the acoustic matching device of this invention. (A) and (b) are plan views which show the shape example of the contact surface of the film structure part and the wall structure part in the acoustic matching device of FIG. (A) and (b) are plan views which show the shape example of the contact surface of the film structure part and the wall structure part in the acoustic matching device of FIG. It is a top view which shows the shape example of the contact surface of the film structure part and the wall structure part in the acoustic matching device of FIG. It is a figure which shows another example of the acoustic matching device of this invention. It is a figure which shows another example of the acoustic matching device of this invention. It is a perspective view of the acoustic probe system to which the membrane structure type acoustic matching device of this invention is applied. It is a perspective view of another example of the acoustic probe system to which the membrane structure type acoustic matching device of this invention is applied.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In all the drawings for explaining the embodiment, the members having the same function are designated by the same reference numerals, and the repeated description thereof will be omitted. Further, in the drawings for explaining the embodiment, in order to make the configuration easy to understand, hatching may be added even in the plan view, or hatching may be omitted even in the cross-sectional view.

(Embodiment 1)
First, the basic idea of the present invention will be described with reference to FIG. Sound waves propagating through an elastic body are usually reflected at the interface between different materials. This is because the acoustic impedance between different materials is different. The material-specific specific acoustic impedance z is represented by the product of the sound wave propagation velocity (sound velocity) c and the density ρ, and the acoustic impedance Z is obtained by multiplying this by the cross-sectional area A through which the sound wave propagates. Therefore, when the cross-sectional area through which the sound wave propagates is constant, the difference in the specific acoustic impedance z becomes the difference in the acoustic impedance Z as it is.

Conventionally, as one of the methods for matching acoustic impedance, there is a method in which a sheet-like structure called an acoustic matching layer is inserted between an ultrasonic transducer and a material for propagating ultrasonic waves (Non-Patent Document 1). ). However, since this acoustic matching layer is effective only in a specific frequency and a frequency range in the vicinity thereof, wideband acoustic matching is impossible.

Further, as another method for matching the acoustic impedance, a method of matching the acoustic impedance between the materials by adjusting the propagation cross-sectional area of the sound wave between different materials can be considered. However, in an elastic body, a sudden change in the cross-sectional area through which a sound wave propagates in a section shorter than the wavelength of the sound wave usually results in a sudden change in acoustic impedance when viewed from the sound wave. Therefore, at this time, a large reflected wave is generated at the boundary between different materials, so that the sound wave cannot be propagated efficiently.

As a countermeasure, there is also a method of solving this problem by gradually changing the cross-sectional area of the material along the propagation direction of the sound wave as in Patent Document 1. However, the method of Patent Document 1 has a problem that the materials capable of acoustic matching are limited.

Next, the principle of the present invention will be described with reference to FIGS. 2 (a) and 2 (b). In FIG. 2, _{the first acoustic medium 5 having the specific acoustic impedance z 1} and the first film structure portion 2 are joined, and the specific acoustic impedance z _{0 is applied} to the left and right ends of the first film structure portion 2, respectively. It is a film structure in which the wall structure 3 made of the material to be provided is in contact with each other. Although the actual structure has a three-dimensional structure, it is considered here in a two-dimensional plane for convenience of explanation.

The bonding area between the first acoustic medium 5 and the first film structure portion 2 corresponds to the width L in the two-dimensional plane. Further, the contact area between the first film structure portion 2 and the wall structure portion 3 corresponds to the _{width w 1/2 in the two-dimensional plane.} In FIG. 2, since there are two contact points between the film structure portion 2 and the wall structure portion 3, the total contact area is twice as large as _{w 1/2 as a whole.} Further, the thickness d ₁ of the first film structure portion 2 is made sufficiently smaller than the wavelength of the assumed frequency band inside the material constituting the first film structure portion 2.

When the membrane structure including the first membrane structure portion 2 and the wall structure portion 3 is in contact with the acoustic medium, sound waves (coarse and dense waves) propagate in the first acoustic medium 5 in the x direction. Think about it. When the coarse state of the sound wave reaches the boundary of the first film structure portion 2, as shown in FIG. 2A, the central portion of the first film structure portion 2 instantly moves in the positive direction of x (lower part of the figure). ) Transforms. At this time, the force received by the entire first film structure portion 2 is transmitted to both ends of the first film structure portion 2 which is an elastic body, and a bending moment is generated. Due to this bending moment, a force that pushes the wall structure portion 3 in the positive direction of x is generated at the boundary between the first film structure portion 2 and the wall structure portion 3. On the other hand, when the dense state of the coarse wave reaches the boundary of the first film structure portion 2, the central portion of the first film structure portion 2 is instantly deformed in the negative direction of x as shown in FIG. 2 (b). do. At this time, contrary to the case of FIG. 2A, a force for pulling the wall structure portion 3 in the negative direction of x is generated at the boundary between the first film structure portion 2 and the wall structure portion 3. In this way, when viewed from the sound wave, the sound wave is instantly transmitted to the wall structure portion 3 through the bending force of the first film structure portion 2.

Using the principles described above, as described in FIG. 1, in accordance with the theory of acoustic propagation, as follows, the width L and the width w ₁ be designed such acoustic impedance matching, to a specific frequency and material It is possible to acoustically match the first acoustic medium 5 without limitation. That is,
_{L × z 1 = (2 ×} w 1/2) × z 0 (1)
w ₁ = L (z ₁ / z ₀ ) (2)
_{W 1} may be set so as to be.

FIG. 3 shows a form of the acoustic matching device 1 according to the present invention. The first acoustic medium 5 and the second acoustic medium 6 are _{elastic bodies having different specific acoustic impedances z 1} and z ₂ , respectively, and between them are composed of a material having a _{specific acoustic impedance z 0.} This is the acoustic matching device 1 of the present invention.

At the boundary between the acoustic matching device 1 and the first acoustic medium 5, there is a _{first film structure portion 2 having a certain width L and a thickness d 1} , and the acoustic matching device 1 and the second acoustic medium 6 At the boundary of, there is a second membrane structure 4 having _{a width L and a certain thickness d 2.} The left and right ends of each of the first film structure portion 2 and the second film structure portion 4 are connected via a wall structure portion 3 having a length h.

Further, the acoustic matching device 1 of FIG. 3 has a length D in the depth direction, and has a rectangular structure having an area S = length D × width L when viewed from above. Here, in order to realize acoustic matching, the dimensions of each structure are defined as follows in the present invention.

As shown in FIG. 3 (a) and (b), the bonding surfaces of the two portions of the first film structure 2 and the wall structure 3 has a width each w _1/2, the junction area is the s _1/2 do. Here, the relationship between the area S where the first acoustic medium 5 and the first film structure portion 2 come into contact with each other and the bonding area s _1/2 is set to be as follows.

_{S / (2 × s 1/} 2) = z 1 / z 0 (3)
That is,
s ₁ = S (z ₁ / z ₀ ) (4)
or,
s ₁ / S = z ₁ / z ₀ (5)
Will be. Here, in the first embodiment, since S = D × L and s ₁ = D × w ₁ , these can be substituted into the equation (4).
w ₁ = L (z ₁ / z ₀ ) (6)
The relationship holds.

Similarly, as shown in FIG. 3 (a) and (c), the bonding surfaces of the two portions of the second film structure 4 and the wall structure 3, a width w _2/2, respectively, the junction area s _2/2 . Here, the relationship between the area S and the bonding area s _2/2 where the second acoustic medium 6 and the second film structure 4 is in contact so as to be less.

_{S / (2 × s 2/} 2) = z 2 / z 0 (7)
That is,
s ₂ = S (z ₂ / z ₀ ) (8)
or,
s ₂ / S = z ₂ / z ₀ (9)
Will be. Here, in the first embodiment, since S = D × L and s ₂ = D × w ₂ , these can be substituted into the equation (8).
w ₂ = L (z ₂ / z ₀ ) (10)
The relationship holds.

Since the object of the present invention is matching between materials having different specific acoustic impedances, _{it is assumed that z 1} and z ₂ have different values from each other. For convenience, _{when the relationship of z 1} <z ₂ is satisfied, the relationship of _{s 1} <s ₂ and w ₁ <w ₂ is established from the equations (4), (6), (8), and (10).

Further, in order to realize more efficient acoustic propagation, it is advisable to set the dimensions of the structure as follows. That is, it is desirable that the thicknesses d ₁ and d ₂ are smaller than the wavelength of the desired frequency band inside the material constituting the acoustic matching device 1. Furthermore, if the whole of the acoustic matching device 1 is composed of a homogeneous material with the same Young's modulus, and thickness d ₁ is smaller than the width w _1/2, the stiffness of the first film structure 2 is wall structure The rigidity is relatively smaller than the rigidity for deforming the portion 3, and the deflection of the first film structure portion 2 becomes large.

In this case, the sound wave propagating in the first acoustic medium 5 consumes a large amount of energy for the first film structure portion 2 to bend, which causes a loss for the energy propagation to the wall structure portion 3. .. Therefore, more efficient sound wave propagation can be realized by setting _{d 1} > w _1/2. For the same _reason, it is desirable that the d _{2> w} 2/2. However, this does not apply when the materials of the first film structure portion 2 and the second film structure portion 4 and the material of the wall structure portion 3 are different from each other and have different Young's modulus.

Furthermore, the film structure supported at both ends resonates at a certain frequency. At the resonance frequency, the vibration energy is easily confined inside the film structure, and the energy is difficult to propagate to the wall structure portion 3. Therefore, it is desirable to set the _{width L, the thickness d 1} and d ₂ so that the resonance frequency of the structure is out of the desired frequency band.

On the other hand, it is desirable that the length h of the wall structure portion 3 in the acoustic propagation direction is larger than the wavelength of the desired frequency band. _{It is desirable that the wall structure portion 3 smoothly and continuously changes from w 1} to w ₂ , but if the scale is smaller than the wavelength of the desired frequency band, the wall structure portion 3 has a stepped structure as shown in FIG. May be. Alternatively, as shown in FIG. 5, in order to reinforce the wall structure portion 3, the wall structure portions 3 may be joined to each other by the reinforcing member 7. _{It is desirable that the thickness d 3} of the reinforcing member at this time is smaller than the wavelength of the desired frequency band.

The gap of the wall structure portion 3 may have a hollow structure, but has a specific acoustic impedance sufficiently different from the specific acoustic impedance of the wall structure portion 3, the first film structure portion 2 and the second film structure portion 4. As long as it is a material to have, as shown in FIG. 6, the filler 8 may be filled in the gap of the wall structure portion 3. This is because if the filler 8 has sufficiently different specific acoustic impedances, the presence of the filler 8 can be almost ignored from the sound waves once transmitted to the wall structure portion 3 and the membrane structure portions 2 and 4.

Next, the shape of the contact surface between the film structure (first film structure 2 and the second film structure 4) and the wall structure 3 in the present invention will be described. In FIG. 3, contact surfaces between the film structure portion and the wall structure portion were formed on both sides of the rectangular structure. However, this shape is only one aspect, and various shapes can be considered.

FIG. 7 is a top view showing various shapes of the contact surface between the first film structure portion 2 (or the second film structure portion 4) and the wall structure portion 3. As shown in FIG. 7A, it is also possible to form the contact surface 10 so as to cover the periphery of the rectangular film structure portion. At this time, as long as the contact area and s ₁ satisfy the equation (4), there is no difference in the effect in the present invention. Other examples of the contact surface 10 may be a triangle, a circle, a regular hexagon, or the like, as shown in FIGS. 7B, 7C, and 7D. Alternatively, as shown in FIG. 7 (e), the circular contact surface 10 may be provided inside the hexagonal contact surface 10. As described above, in the present invention, the shape of the film structure portion and the shape of the contact surface between the film structure portion and the wall structure portion can be any shape such as a circular shape, a polygonal shape, or a combination thereof, and are limited. It's not a thing.

Next, a method for manufacturing the acoustic matching device 1 of the present invention will be described. In the present invention, any material may satisfy the relationships shown in the above formulas (1) to (10). Therefore, the film structure and the wall structure can be obtained by casting metal or plastic, machining, 3D printer, or the like. May be integrally molded, or the film structure part and the wall structure part may be manufactured separately and then welded, bonded, or joined by bolts or screws. In the ultrasonic region, an extremely fine size may be required. In such a case, a film structure can be formed by using a semiconductor process, or a hollow structure can be formed by etching. When the length of the wall structure in the x direction is large and it is difficult to manufacture with one semiconductor wafer, a plurality of processed wafers may be bonded together. The material of the structure of the present invention is not particularly limited to materials such as wood, metal, resin, glass, silicon (Si) and silicon-based materials used in semiconductor processes, metals, and plastics.

The film structure and wall structure actually manufactured as described above are not completely flat or smooth as shown in FIG. 3, and may have some irregularities or differences in shape. It does not impair the effect of the invention.

Next, the acoustic matching ability in the specific design of the acoustic matching device 1 according to the present invention is calculated, and the effect is shown. As the structure, the basic structure of FIG. 3 is assumed. Water is assumed as the material of the first acoustic medium 5, and its specific acoustic impedance is 1.5M Rayl. The material of the membrane structure type acoustic matching device 1 is silicon (Si) used in a semiconductor device or the like, and its specific acoustic impedance is 20.2M Rayl. The second acoustic medium 6 is assumed to be PZT widely used as an ultrasonic transducer, and its specific acoustic impedance is set to 20M Rayl. Since the first acoustic medium 5 and the acoustic matching device 1 have significantly different specific acoustic impedances, w ₁ is 1.5 / 20.2 = 0.074 with respect to the width L. On the other hand, since the second acoustic medium 6 and the film structure type acoustic matching device 1 have specific acoustic impedances close to each other, w ₂ has a value considerably close to the film structure width L. Further, d ₁ > w ₁ and d ₂ > w ₂ . Here, the desired frequency band is set to around 10 MHz. If d ₁ and d ₂ are set to 5 μm, which can be sufficiently manufactured by the semiconductor manufacturing process, and L is designed to be sufficiently small (for example, 10 μm), the resonance frequency becomes about 100 MHz, which can be sufficiently deviated from the desired frequency band. be.

For comparison, based on the conventional 1/4 wavelength matching theory, the specific acoustic impedance between the first acoustic medium 5 and the second acoustic medium 6 and the thickness of 1/4 wavelength of 10 MHz are obtained. The calculation is performed assuming that the member to be held is inserted. FIG. 8 shows the acoustic transmittance according to the prior art and the present invention. The vertical axis represents the ratio of sound waves reaching from the first acoustic medium 5 to the second acoustic medium 6 (1 is total transmission), and the horizontal axis is frequency. As can be seen from FIG. 8, the present invention enables a very wide band and highly efficient propagation characteristics as compared with the prior art.

In the above description, the target frequency is the ultrasonic region, but the present invention is not limited to the ultrasonic region and is also effective in the audible region.

(Embodiment 2)
The basic structure of the acoustic matching device 1 of the present invention shown in the first embodiment can have various widths L. On the other hand, when considering the application, it is necessary to assume an acoustic propagation surface having various width L and depth length D. Alternatively, in the case of a structure as shown in FIG. 3 in order to obtain a processing problem or an efficient acoustic propagation characteristic in a desired frequency band, there is a limitation in the width L that can be actually taken.

On the other hand, as shown in FIG. 9, the above problem can be solved by a composite structure in which the basic structures shown in FIG. 3 are arranged in an array on the yz plane. Since the composite structure shown in FIG. 9 is simply a regular arrangement of the basic structures shown in FIG. 3, there is no difference in the characteristics as an acoustic matching layer. In terms of workability, it can be produced by machining or processing using a semiconductor process, as in the case of the first embodiment.

10 to 12 show the shape of the contact surface between the first film structure portion 2 and the second film structure portion 4 and the wall structure portion 3 in the same manner as that shown in FIG. 7 of the first embodiment. Shown. 10 (a) shows the yz plane of FIG. 9, and FIGS. 10 (b), 11 (a), 11 (c), and 12 show an array structure of a quadrangle, a triangle, a circle, and a hexagon, respectively. ing. As in the case of the basic structure of FIG. 7, it is difficult to uniquely define the width of the wall structure with respect to the thickness of the film structure, but the essence of the present invention is the area of the film structure to be joined to the acoustic medium. Since the ratio of the contact area between the film structure portion and the wall structure portion satisfies the equations (4) and (8), it is not always necessary to specify the width as shown in FIGS. 3 and 9.

Further, in the case of a composite structure in which the basic structures are arranged in an array, a relatively large contact area may be formed between the basic structure and the basic structure, particularly like a circular structure. Alternatively, although not shown, there may be an array in which the shape and size of the basic structure are random. In such a case, it is difficult to specify the area of the membrane structure portion and the contact area between the membrane structure portion and the wall structure portion in the basic structural unit. In this case, the entire array in the present invention, the total area S _all regions membrane structure portion is joined to the acoustic medium (specific acoustic impedance z _1), film structure and the wall structure (specific acoustic impedance lens z The total area s _{1_all of the region in contact with 0} ) may satisfy the following equation.

s _{1_all} = s _all (z ₁ / z ₀ ) (11)
(Embodiment 3)
In the first embodiment and the second embodiment, it has been shown that the membrane structure type acoustic matching device 1 of the present invention enables acoustic matching between a specific material and the material. In the third embodiment, even if the specific acoustic impedance of the first acoustic medium 5 changes, the same film structure type acoustic matching device 1 can handle the change.

The membrane structure type acoustic matching device 1 shown in FIG. 13A has an upper membrane structure portion 13 supported by a post 12 above the first membrane structure portion 2 in the structure of FIG. , Electrodes 14 are provided inside the first film structure portion 2 and inside the upper film structure portion 13, respectively. Further, an intermediate wall structure portion 15 is added between the wall structure portions 3 as a member for connecting the first film structure portion 2 and the second film structure portion 4.

In this structure, when a voltage is applied between the electrode 14 of the first membrane structure portion 2 and the electrode 14 of the upper membrane structure portion 13, an electrostatic force is generated between the two electrodes 14, and FIG. 13 (b) shows. As shown, when the upper membrane structure portion 13 and the first membrane structure portion 2 attract each other and the voltage reaches a certain level or higher, a part of the upper membrane structure portion 13 finally becomes the first membrane structure portion 2. Come into contact with. In such a state, when the sound wave propagating from the first acoustic medium 5 reaches the upper film structure portion 13, the sound wave propagates not only in the conventional wall structure portion 3 but also in the intermediate wall structure portion 15. That is, the acoustic propagation area of the membrane structure type acoustic matching device 1 is increased, and the acoustic impedance is increased. This makes it possible to change the specific acoustic impedance of the first acoustic medium 5 before and after applying the voltage.

As described above, by adopting the structure of the third embodiment shown in FIG. 13, it is possible to realize a variable acoustic matching device instead of a specific specific acoustic impedance. The amount of acoustic impedance to be changed can be controlled by the contact area between the upper film structure portion 13 and the first film structure portion 2. As a specific method, it is possible by changing the voltage applied to the electrode 14. As the voltage applied to the electrode 14 is increased, the upper film structure portion 13 can be brought into strong contact with the first film structure portion 2, so that not only the center of the upper film structure portion 13 but also the periphery of the upper film structure portion 13 has a film structure. It comes into contact with the part 2 over a wide area.

In the example shown in FIG. 13, the upper film structure portion 13 is provided on the first acoustic medium 5 side, but when a similar structure is provided on the second acoustic medium 6 side, the specific acoustic impedance to be matched is set. It is possible to change on both sides.

The width of the intermediate wall structure portion 15 does not need to be a specific value because the design value changes depending on the acoustic medium to be matched. Further, the distance between the upper film structure portion 13 and the support column 12 and the thickness of the upper film structure portion 13 can be freely designed according to the purpose.

The upper film structure portion 13 was present in the above-mentioned film structure type acoustic matching device 1, but as shown in FIG. 14, if the electrode 14 is embedded inside the intermediate wall structure portion 15, the upper film structure portion is not necessarily present. 13 is not needed.

(Embodiment 4)
FIG. 15 shows a case where the membrane structure type acoustic matching device 1 of the present invention is used for the acoustic probe system 20.

By joining the membrane structure type acoustic matching device 1 of the present invention to the electroacoustic vibration device 21 and incorporating it into the housing, efficient sound wave transmission / reception is possible in various applications. It is also possible to combine the protective material 22 depending on the application.

For example, by combining the acoustic probe system 20 with a main body control device 24 including a transmission / reception circuit and a display via a cable 23, it can be used as a medical ultrasonic system, a non-destructive inspection device, a marine sonar, and an acoustic camera.

In the audible range, a high sound absorption effect can be obtained by incorporating it into an acoustic microphone or a speaker system, or by joining the sound wave attenuation material 25 and the acoustic matching device 1 of the present invention as shown in FIG.

Although the invention made by the present inventor has been specifically described above based on the embodiment thereof, the present invention is not limited to the embodiment and various modifications can be made without departing from the gist thereof. Is.

1 Membrane structure type acoustic matching device 2 1st film structure 3 Wall structure 4 2nd film structure 5 1st acoustic medium 6 2nd acoustic medium 7 Reinforcing member 8 Filling material 10 1st film structure Joint cross section between the wall structure and the wall structure 11 Joint cross section between the second membrane structure and the wall structure 12 Strut 13 Upper membrane structure 14 Electrode 15 Intermediate wall structure 20 Acoustic probe system 21 Electroacoustic vibration device 22 Protective material 23 Cable 24 Main body control device 25 Sound damping material

Claims (12)

An acoustic matching device that propagates sound waves by joining to a first medium and a second medium having different specific acoustic impedances.
Contact with the first membrane structure portion to be bonded to the first medium, the second membrane structure portion to be bonded to the second medium, the first membrane structure portion and the second membrane structure portion, respectively. With a wall structure
An acoustic matching device that satisfies the following equations 1 and 2.
s ₁ / S = z ₁ / z ₀ ... Equation 1
s ₂ / S = z ₂ / z ₀ ... Equation 2
(In the equation, z ₁ is the specific acoustic impedance of the first medium, z ₂ is the specific acoustic impedance of the second medium, z ₀ is the specific acoustic impedance of the material constituting the acoustic matching device, and S is the first. The area of the region where the medium 1 and the first film structure or the second medium and the second film structure are joined, and s ₁ is the area where the first medium and the wall structure are joined. The area of the region, s ₂ represents the area of the region where the second medium and the wall structure are joined). In the acoustic matching device according to claim 1,
An acoustic matching device in which the thickness of the first film structure portion and the thickness of the second film structure portion are thinner than the wavelength of the sound wave to be matched in the acoustic matching device. In the acoustic matching device according to claim 1,
The thickness of the first film structure portion is thicker than the width of the wall structure portion in contact with the first film structure portion.
An acoustic matching device in which the thickness of the second membrane structure portion is thicker than the width of the wall structure in contact with the second membrane structure. In the acoustic matching device according to claim 1,
An acoustic matching device in which the resonance frequency of the first membrane structure portion and the resonance frequency of the second membrane structure portion are higher than the frequency of the sound wave to be matched. In the acoustic matching device according to claim 1,
The length of the wall structure in contact with the first membrane structure and the length of the wall structure in contact with the second membrane structure are wavelengths in the acoustic matching device of the frequency of the sound wave to be matched. Longer, acoustic matching device. In the acoustic matching device according to claim 1,
Further having a reinforcing member for joining the wall structural parts to each other,
An acoustic matching device in which the thickness of the reinforcing member is thinner than the wavelength in the acoustic matching device of the frequency of the sound wave to be matched. In the acoustic matching device according to claim 1,
The width of the wall structure portion changes stepwise from one of the first membrane structure portion and the second membrane structure portion toward the other.
An acoustic matching device in which the height of the staircase is lower than the wavelength in the acoustic matching device of the frequency of the sound wave to be matched. In the acoustic matching device according to claim 1,
An acoustic matching device in which a filler is filled in the gap of the wall structure portion. A composite acoustic matching device in which a plurality of acoustic matching devices according to any one of claims 1 to 8 are arranged in an array. In the composite acoustic matching device according to claim 9.
Throughout the array, the total area S _all of the region where the film structure is bonded to the first and second medium, wherein the film structure and the wall structure (specific acoustic impedance lens z ₀₎ and is in contact The total area s _{1_all of the} region is the following equation 3
s _{1_all} = s _all (z ₁ / z ₀ ) ... Equation 3
A composite acoustic matching device that meets the requirements. An acoustic probe system using the acoustic matching device according to any one of claims 1 to 8. An acoustic probe system using the composite acoustic matching device according to claim 9.

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