JPH0965488A - Ultrasonic transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic transducer with a small size, high resolution and wide observation range at a low cost. SOLUTION: An acoustic matching layer 3, a piezoelectric element 2 and a rear side damping member 1 are integrated. The matching layer 3 is integrated with a matching part 4 in which the absolute value of an acoustic impedance is matched with respect to that of the piezoelectric element 2 and an ultrasonic wave medium and an unmatching part 5 in which the absolute value of an acoustic impedance is not matched with respect to that of the piezoelectric element 2 and the ultrasonic wave medium. Then ultrasonic wave intensity distribution oscillated from the matching part 4 and the unmatching part 5 is properly controlled to form a sound field with a wide observation range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic transducer used in a medical or nondestructive ultrasonic diagnostic apparatus.

[0002]

2. Description of the Related Art As a structure of a conventional ultrasonic transducer, as shown in FIG. 9, a piezoelectric element 52 made of a PZT piezoelectric ceramics plate having electrodes formed on both sides of a back braking material 51 with an insulating layer interposed is bonded. In addition, the acoustic matching layer 53
And the one to which the acoustic lens 54 is adhered is known ("Medical Ultrasonic Equipment Handbook", Corona Publishing Co., P18).
6, issued April 20, 1985).

In order to drive such an ultrasonic transducer, a pulsar (not shown) is attached to the piezoelectric element 52.
By applying a driving pulse of about 100 to several hundreds of volts, the piezoelectric element 52 is rapidly deformed by the inverse piezoelectric effect, and the ultrasonic pulse excited by this is passed through the acoustic matching layer 53 and the acoustic lens 54. This is done by oscillating.

Further, the oscillated ultrasonic pulse is reflected at the interface between tissues in the body for medical use, and after being reflected from a discontinuous portion such as a scratch in the object to be measured for nondestructive inspection, and then the acoustic wave is emitted. It re-enters the piezoelectric element 52 through the lens 53 and the acoustic matching layer 54 to vibrate the piezoelectric element 52. The mechanical vibration of the piezoelectric element 52 is converted into an electric signal by the piezoelectric action, and is imaged by an observation device (not shown).

The ultrasonic pulse oscillated as described above is focused by the acoustic lens 54 and shaped into a narrow beam, and high resolution in the scanning direction can be obtained.

In recent years, in the field of optics, the intensity distribution in the direction orthogonal to the wave propagation direction is represented by the 0th-order Bessel.
It is reported that a distribution similar to the l) function can propagate a beam that does not diffract in the wave and does not spread over a long distance.

Attempts have also been made to apply a similar method to the propagation of ultrasonic waves. For example, "Utra
sonic Nondiffracting Transducer for Medical Imagin
g ”, by JIAN-YU and JAMES F. GREENLEAF, IEEE Tans
actions on Ultrasonice, Ferroelectrics, and Freque
As shown in ncy Control Vol.37, No.5, Spt. 1990, P418-447, the method of weighted driving array transducers, which are divided into many concentric circles, is used. It has been reported that a non-diffracted beam can be obtained.

[0008]

As described above, in order to sharpen the ultrasonic beam oscillated from the ultrasonic oscillator and obtain a good observation image with high resolution and S / N ratio, the ultrasonic oscillator is used. It is performed to bond an acoustic lens to the. However, in this method, since the ultrasonic beam only focuses on one point, the optimum observation range, which is a high-resolution observation range defined by the depth of focus, which is the length of the narrow portion of the ultrasonic beam, narrow.

Further, the short-distance sound field before being focused by the acoustic lens has a large side lobe, while the ultrasonic beam is diffused after the focused portion, resulting in a decrease in resolution.

Further, the applicant of the present invention filed an application first, and disclosed in
-250799 discloses an ultrasonic wave having a structure in which the acoustic impedance distribution in the back damping material is made smaller in the central portion and becomes larger toward the edges and approaches the acoustic impedance of the piezoelectric element. According to the transducer, although the near-field sound field is significantly improved among the above, as for the far-field sound field, the ultrasonic beam is diffused as in the case already described, and the resolution is apt to decrease. I couldn't deny it.

On the other hand, according to the method using the above-mentioned non-diffracted ultrasonic beam, the above diffusion does not occur,
The optimal observation range can be widened. However, as described above, it is necessary to use an array type transducer that is divided into a large number of concentric circles and weight-drive each transducer. This complicates the structure of the transducer, the driving circuit, and the driving method. For this reason, it is very difficult to miniaturize the transducer, and at the same time, the cost of the transducer and the drive circuit becomes very high, and the industrial profitability becomes poor.

The present invention has been made in view of the above circumstances, and provides an ultrasonic transducer having a high resolution and a wide optimum observation range which can be reduced in size and cost.

[0013]

According to the first aspect of the present invention,
In an ultrasonic transducer formed by integrating an acoustic matching layer, a piezoelectric element, and a back damping material, the acoustic matching layer is
An integral structure of a matching portion whose absolute value of acoustic impedance is matched with respect to the piezoelectric element and the ultrasonic medium and a mismatched portion whose absolute value of acoustic impedance is not matched with respect to the piezoelectric element and the ultrasonic medium It is characterized by consisting of.

According to a second aspect of the present invention, in an ultrasonic transducer in which an acoustic matching layer, a piezoelectric element and a back damping material are integrated, the acoustic matching layer has a small attenuation of ultrasonic waves in the acoustic matching layer. It is characterized in that it is formed integrally with a portion and a portion with large attenuation.

According to a third aspect of the present invention, in an ultrasonic transducer in which an acoustic matching layer, a piezoelectric element and a back damping material are integrated, the thickness of the acoustic matching layer is the center of the oscillation frequency of the ultrasonic transducer. It is characterized in that it is formed acoustically non-uniform with respect to the frequency Fr, and the oscillated ultrasonic waves have a mixture of components with inverted phases.

According to a fourth aspect of the present invention, the acoustic matching layer in the ultrasonic transducer according to the third aspect is composed of a plurality of types of materials having different ultrasonic sound velocities, and the acoustic matching layer has a high sound velocity region. And a low region are formed, and the difference in sound velocity between both regions is set to be an even multiple of the sound velocity of the ultrasonic medium.

According to a fifth aspect of the present invention, the acoustic matching layer in the ultrasonic transducer according to the third aspect is composed of a plurality of kinds of materials having different ultrasonic sound speeds, and the acoustic matching layer has a high sound speed region. And a low region, the acoustic thickness of both regions is set to an odd multiple of ¼ wavelength with respect to the center frequency Fr, and at the same time, the difference in mechanical thickness between the two regions is set to the center of the ultrasonic medium. It is characterized in that it is an odd multiple of 1/2 wavelength which is the acoustic thickness of the frequency Fr.

According to a sixth aspect of the invention, in the ultrasonic transducer according to the third aspect, the center frequency Fr is provided at the boundary of each component of the acoustic matching layer composed of a plurality of components.
Is provided with a portion having an acoustic thickness of ½ wavelength.

According to a seventh aspect of the invention, in the ultrasonic transducer according to the first to sixth aspects, a portion where the acoustic matching layer is not formed is provided at the boundary of each component of the acoustic matching layer composed of a plurality of components. It is characterized by.

The operation of each invention described above will be described in detail below.

According to the ultrasonic transducer of the first aspect of the present invention, the acoustic matching layer includes a matching portion in which the absolute value of the acoustic impedance is matched with respect to the piezoelectric element and the ultrasonic medium, and the acoustic impedance. Since the absolute value of the piezoelectric element and the mismatched portion that is not matched with respect to the ultrasonic medium are integrally formed, the overall structure can be downsized and the cost can be reduced. By appropriately controlling the intensity distribution of the ultrasonic waves oscillated by the matching portion, it is possible to form a sound field with a wide optimum observation range.

According to the ultrasonic transducer of the second aspect of the present invention, the overall structure can be downsized and the cost can be reduced, and the acoustic matching layer is a portion where the attenuation of ultrasonic waves in the acoustic matching layer is small. Since it is integrally configured with a portion having a large attenuation, the sound intensity in the acoustic matching layer is made non-uniform and the intensity distribution of the oscillated ultrasonic wave is appropriately controlled to produce a sound with a wide optimum observation range. A field can be formed.

According to the ultrasonic transducer of the third aspect of the present invention, the overall structure can be downsized and the cost can be reduced, and the thickness of the acoustic matching layer can be set to the center frequency of the oscillation frequency of the ultrasonic transducer. Since Fr is formed acoustically non-uniformly, and the oscillated ultrasonic wave has a mixed component of which the phase is inverted, the phase distribution of the oscillated ultrasonic wave is appropriately controlled and the optimum observation range is wide. A sound field can be formed.

According to the ultrasonic transducer of the fourth aspect of the invention, a region having a high sound velocity and a region having a low sound velocity are formed in the acoustic matching layer in the ultrasonic transducer of the third aspect, and the sound velocity of both regions is increased. Since the difference is set to be an even multiple of the sound velocity of the ultrasonic medium, the boundary region of the acoustic matching layer where the phase of the ultrasonic wave is inverted can be made to have a structure in which the ultrasonic wave does not easily oscillate. It is possible to more appropriately control the phase distribution of the ultrasonic waves to form a sound field with a wide optimum observation range.

According to the ultrasonic transducer of the fifth aspect of the invention, the acoustic matching layer in the ultrasonic transducer of the third aspect is composed of a plurality of materials having different ultrasonic sound speeds. A region having a high sound velocity and a region having a low sound velocity are formed therein, and the acoustic thickness of both regions is set to an odd multiple of ¼ wavelength with respect to the center frequency Fr, and at the same time, the difference in mechanical thickness of both regions is 1/2 of the acoustic thickness of the ultrasonic medium with respect to the center frequency Fr
Since it is an odd multiple of the wavelength, as in the case of the ultrasonic transducer according to claim 3, it is possible to make the boundary region of the acoustic matching layer where the phase of the ultrasonic wave is inverted a structure in which the ultrasonic wave hardly oscillates. It is possible to more appropriately control the phase distribution of the oscillated ultrasonic waves to form a sound field with a wide optimum observation range.

According to the ultrasonic transducer of the sixth aspect of the invention, the acoustic thickness relating to the center frequency Fr is 1 at the boundary of each component of the acoustic matching layer in the ultrasonic transducer of the third aspect. Since the part having a wavelength of / 2 is provided, it is possible to give components having different intensities and phases to the oscillated ultrasonic waves, and to optimally control the intensity distribution and phase distribution of the oscillated ultrasonic waves. A sound field with a wide observation range can be formed.

According to the ultrasonic transducer of the seventh aspect, in the ultrasonic transducers of the first to third aspects, a portion where the acoustic matching layer is not formed is provided at the boundary between the constituent elements of the acoustic matching layer. Therefore, the oscillated ultrasonic waves can have components with different intensities and phases, and the intensity distribution and the phase distribution of the oscillated ultrasonic waves are appropriately controlled to form a sound field with a wide optimum observation range. be able to.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an ultrasonic transducer according to the present invention will be described below with reference to the accompanying drawings.

[First Embodiment] First, a first embodiment of the present invention will be described with reference to FIGS.

The ultrasonic transducer 10 shown in FIG.
Is formed by joining the acoustic matching layer 3 and the back braking material 1 to the piezoelectric element 2. This ultrasonic transducer 10
Is mounted in a case (not shown) and is also immersed in an ultrasonic medium (not shown) such as water while being connected to a pulsar (not shown) and an image processing device, so that ultrasonic waves can be transmitted and received. Has become.

The acoustic matching layer 3 is a concentric unitary structure of a matching portion 4 that is acoustically matched and a mismatching portion 5 that is not acoustically matched with respect to the piezoelectric element 2 and the ultrasonic medium. Has become. Here, the matching portion 4
A low density resin is used as a matrix, and a small amount of high density powder as a filler is dispersed in this matrix area. Here, alumina ceramic powder and tungsten particles were used as the powder, and epoxy thermosetting resin was used as the matrix-shaped region. The acoustic characteristics were a sound velocity of 2800 m / s and an acoustic impedance of 4.2 Ns / m3.

Of the matching portion 4, the portion corresponding to the central portion of the ultrasonic transducer 10 is
An epoxy resin material with high hardness and low attenuation was used, and alumina ceramic fine powder with a small particle size was used as a filler. The other parts were made of a soft and highly damped epoxy resin material, and tungsten particles having a larger particle size were used.

The mismatched portion 5 was formed by cutting a plate material of alumina ceramics by YAG laser processing. The acoustic characteristics were a sound velocity of 8400 m / s and an acoustic impedance of 33 Ns / m3.

The matching portion 4 and the non-matching portion 5 of the acoustic matching layer 3 are concentric in shape, and the distribution of the concentric circles is from the portion close to the central portion to the peripheral portion as shown in FIG. It is set so as to alternately repeat alignment → mismatch → alignment → mismatch → alignment in the order of. Here, since the ultrasonic medium is water having an acoustic impedance of 1.5 Ns / m3 and is the lowest, the lower part is represented as the matching part 4 in FIG.

When the thickness of each member is normalized by the wavelength λr of the ultrasonic wave in each member related to the resonance frequency of the piezoelectric element 2, the piezoelectric element 2 is 1 / 2λr and the matching portion 4 is 3 /.
4λr, and the mismatched portion was ¼λr. At the same time, the thicknesses of the matching portion 3 and the mismatching portion 4 are set to be the same because of the difference in sound velocity.

According to the ultrasonic transducer 10 described above, since the acoustic impedance distribution in the acoustic matching layer 3 is non-uniform, the ultrasonic transmission loss is larger in the unmatched portion 5 than in the matched portion 4. As a result, of the ultrasonic waves oscillated from the ultrasonic transducer 10, the component oscillated from the mismatched portion 5 becomes relatively weak.

Also in the matching portion 4, the portions other than the center of the ultrasonic transducer 10 are attenuated by the soft epoxy resin which is the matrix-like region, and the tungsten particles as the filler and the soft epoxy resin are used. Due to the large scattering of the acoustic impedance between the ultrasonic wave and the ultrasonic wave, the intensity of the ultrasonic wave is relatively attenuated compared to the central portion made of the fine powder of hard resin and alumina ceramics.

At the same time, since the acoustic thickness difference between the matching portion 4 and the mismatching portion 5 is ½ wavelength, the intensity of the ultrasonic wave oscillated from the mismatching portion 5 is weak. At the same time, the phase shifts by half a cycle.

The ultrasonic beam 7 oscillated from the ultrasonic transducer 10 has the strongest on the central axis as shown in FIG. 2, and becomes stronger → 0 → weak → 0 as the distance from the center increases.
→ Weak → 0 ... At the same time, the phase of the ultrasonic beam is + 1/4 cycle difference → 0 → -1 / 4 cycle, where the phase at the boundary between the matching portion 4 and the mismatching portion 5 where the intensity becomes 0 is 0 as a convenient reference. Difference → 0 → + 1/4 cycle difference → 0.

Due to these interactions, the ultrasonic beam 7 oscillated as shown in FIG. 2 exhibits a 0th-order Bessel function-like intensity and phase distribution. Therefore, the oscillated ultrasonic beam 7 becomes a non-diffracted beam 8b as conceptually shown in FIG. 3 and is transmitted with a narrow width over a long distance, so that it is converged by using an acoustic lens or the like. Compared with the ultrasonic beam 8a (acoustic lens: concave surface) of the conventional example, the optimum observation distance is greatly expanded. In FIG. 2, 6 indicates the distribution of acoustic impedance in the acoustic matching layer 3, and 9
Indicates an acoustic emission surface.

According to the ultrasonic transducer 10 having the above-described structure, a high-performance ultrasonic transducer capable of obtaining an observation image with high resolution and high sensitivity without degrading the S / N ratio is provided. realizable.

As the acoustic impedance distribution pattern described above, a stepwise distribution, a sawtooth distribution, or the like can be used. As for the distribution pattern, in addition to repeating from the center to the outside as shown in this example, matching → mismatching → matching → ..., repeating from the center to the outside → matching → mismatching → ... A quadratic Bessel function-like distribution is possible.

Regarding the acoustic impedance distribution shape, in addition to the concentric annular pattern described above, a simple modification of this is an ellipse, a non-concentric annular pattern, a pattern composed of a combination of polygons, etc. Is also possible. Moreover, it is of course possible to distribute not only the symmetrical shape but also the straight line. When distributed on a straight line, it is particularly suitable for application to various array type ultrasonic transducers such as linear, convex and radial.

Further, although the shape of the piezoelectric element 2 is not specified in the above-mentioned embodiment, a flat plate typified by a rectangular plate, a circular plate or the like, a part of a conical or spherical shell, or these. A combination of the above can be used.

In the first embodiment, the number of the acoustic matching layers 3 is shown and described as one layer for convenience of explanation, but two or more layers which are generally used for the purpose of widening the band are provided. It is also possible to adopt multi-layer matching, and apply the structure shown in the first embodiment to any one or more of the layers.

Regarding the material of the acoustic matching layer 3, in the case of the one-layer matching as shown in the first embodiment, the matching portion 4 is made of a thermosetting resin such as epoxy type, phenol type, polyimide type, or the like. Thermoplastic resins such as ABS (acrylonitrile butadiene styrene), polyethylene and PMMA (polymethylmethacrylate) can be used. Regarding the mismatched portion 5, glass, machinable ceramics, ceramics such as alumina, stainless steel, etc. Metal etc. can be used.

However, in these cases, as shown in the first embodiment, the matching portion 4 and the mismatching portion 5 are tripled or three times.
It is necessary to have a sound velocity difference of about double. As for the part where the phase is inverted, as shown in FIG. 4, by selecting a material that becomes the acoustic matching layer 11 having a thickness of ½ wavelength, the intensity of the ultrasonic wave oscillated from the part is selected. It is also possible to reduce as much as possible or to provide the portion 12 where the acoustic matching layer 11 is not formed as shown in FIG. As a result, the intensity distribution of the oscillated ultrasonic waves can be controlled more strictly, and more accurate sound field control can be performed.

[Second Embodiment] Next, referring to FIG.
Embodiment 2 of the present invention will be described. In the description of the second embodiment, the same elements as those in the first embodiment described above are designated by the same reference numerals, and duplicated description will be omitted.

Ultrasonic Transducer 1 of Embodiment 2
At 0A, as shown in FIG. 6, a portion of the acoustic matching layer 3 corresponding to the unmatched portion 5 shown in the first embodiment is made of tungsten powder in a weight ratio of 90.
% Or more of the high-attenuation portion 13 (sonic velocity 180
0m / s, acoustic impedance 16Ns / m3, thickness 3
/ 4λr). Further, the matching portion 4 shown in the first embodiment is made of machinable ceramics (sound velocity 54
00 m / s, an acoustic impedance of 16 Ns / m 3, and a thickness of 1/4 λr). The other structure is the same as that of the ultrasonic transducer 10 according to the second embodiment.

Further, in the second embodiment, the acoustic matching layer 3 is the first layer of the multi-layer matching type acoustic matching layer consisting of three layers, and although not shown on the acoustic matching layer 3, high hardness,
A structure in which a second layer made of a low-damping epoxy resin and a third layer made of polyethylene or silicone rubber on the second layer are integrated is adopted.

Ultrasonic Transducer 1 of Embodiment 2
According to 0A, since the acoustic damping layer 3 is provided with the high attenuation portion 13 having a large attenuation of the ultrasonic wave intensity in the portion corresponding to the mismatched portion 5 shown in the first embodiment, the high attenuation portion 13 is provided. In this case, the ultrasonic waves are greatly attenuated as compared with the matching section 4, and as a result, in addition to the mismatch of the acoustic impedance in the case of the ultrasonic transducer 10 according to the first embodiment, the non-uniformity of the strength of the ultrasonic waves. Occurs,
The intensity distribution of the oscillated ultrasonic waves can be controlled in a larger range, and thus the effect of the sound field control becomes greater.

The ultrasonic transducer 1 shown in FIG.
Among various materials of the acoustic matching layer 3 in 0A, as a material for forming a matrix-shaped region, epoxy-based, phenol-based thermosetting resin, ABS, polyethylene, PMMA or other thermoplastic resin, silicone rubber, Rubber such as butyl rubber can be used.

As the filler, in addition to tungsten, metals such as stainless steel, silver and copper and oxides thereof, ceramic powder such as alumina and zirconia, Ba-ferrite, samarium cobalt (SmCo5, Sm2Co1) are used.
Magnetic particles such as 7) or the above-mentioned inorganic particles coated with a magnetic material can be used. Further, as described above, the low acoustic impedance portion may be a portion having a small amount of filler, and the filler may be omitted altogether. Also,
It is of course possible to mix two or more kinds of the above powders.

[Third Embodiment] A third embodiment will be described with reference to FIGS. In the description of the third embodiment, the same elements as those in the first embodiment described above are designated by the same reference numerals, and the duplicated description will be omitted.

Ultrasonic Transducer 1 of Embodiment 3
In 0B, as shown in FIG. 7, in the acoustic matching layer 3, a portion corresponding to the unmatched portion 5 shown in the first embodiment is made of glass (sound velocity 5800 m / s, acoustic impedance 16 Ns / m 3, thickness Height 1 / 4λr), and a portion corresponding to the matching portion 4 shown in the first embodiment is a high hardness and low attenuation epoxy resin (sonic velocity 2800 m / s, acoustic impedance 4.
2 Ns / m3, thickness 1/4 λr) low sound velocity part 14
The feature is that

The materials forming the high sonic velocity portion 15 and the low sonic velocity portion 14 have different ultrasonic sound velocities, and therefore have different lengths of one wavelength for the same frequency. Accordingly, the wavelength λ at the resonance frequency of the piezoelectric element 2 in each member
Normalized by r, the acoustic thickness is the same (1/4 λr)
The mechanical thicknesses of the high sound velocity portion 15 and the low sound velocity portion 14 determined to be different from each other are different, and the surface of the acoustic matching layer 3 has irregularities as shown in FIGS. 7 and 8.

The uneven portion due to the difference in thickness between the high sonic velocity portion 15 and the low sonic velocity portion 14 is filled with an ultrasonic medium (not shown) in which the ultrasonic transducer 10B is immersed during its operation. The ultrasonic medium in this portion is virtually used as the ultrasonic medium layer 16 (material water, sound velocity 1500 m / s).

In the ultrasonic transducer 10B described above, regarding the sound velocity of each member, the ultrasonic medium layer 1 is used.
The acoustic thickness of 6 is selected to be 1/2 λr, and the sound velocity of the material of the high sound velocity portion 15 which is the mismatched portion is V
mu, the sound velocity of the material of the low sound velocity portion 14 which is the matching portion
mm, when the sound velocity of the ultrasonic medium layer 16 is Vm, Vm
u-Vmm = 2nVm is established. Here, n is a natural number and n = 1 in the third embodiment.

According to the ultrasonic transducer 10B of the third embodiment, as shown in FIG. 8, when the surface of the thicker high sound velocity portion 15 is the virtual acoustic radiation surface 17, oscillation occurs from the low sound velocity portion 14. The generated ultrasonic waves are transmitted through the ultrasonic medium layer 16 by ½λr before reaching the virtual acoustic radiation surface 17.
Is transmitted by the acoustic length of. Therefore, on the virtual acoustic emission surface 17, a phase difference is generated between the ultrasonic wave oscillated from the high sound velocity portion 15 and the ultrasonic wave oscillated from the low sound velocity portion 14 by a half cycle.

The ultrasonic transducer 10B according to the third embodiment has basically the same effect as that of the ultrasonic transducer 10 according to the first embodiment, but the acoustic thickness of the acoustic matching layer 3 itself is increased. Since the length is equivalent to a quarter wavelength, the pulse width of the oscillating ultrasonic wave is unlikely to be elongated due to multiple reflections in the acoustic matching layer 3. Therefore, it is possible to obtain the ultrasonic transducer 10B having excellent resolution in the depth direction of the single pulse width.

The material of the acoustic matching layer 3 is not limited to that described above, but the material of the low sound velocity portion 14 is the same as in the first embodiment.
The low acoustic impedance member shown in 1 above and the high acoustic impedance member shown in the first embodiment can be similarly applied as the material of the high sound velocity portion 15. However, even in this case, it is essential that each member is a combination that establishes the relationship of acoustic characteristics as shown in the third embodiment.

When the thickness of each layer is increased in order to avoid damage or the like during handling of the member, the acoustic matching layer 3 has an acoustic thickness of an odd multiple of 1/4 wavelength. Is desirable in order to reduce the transmission / reception loss of ultrasonic waves.

[0063]

According to the first aspect of the present invention, the entire structure can be downsized and the cost can be reduced, and the intensity distribution of the ultrasonic waves oscillated by the matching portion and the mismatching portion of the acoustic matching layer can be appropriately adjusted. It is possible to provide an ultrasonic transducer capable of forming a sound field having a wide optimum observation range by controlling the above.

According to the second aspect of the present invention, the entire structure can be downsized and the cost can be reduced, and the intensity distribution of the ultrasonic waves oscillated by making the attenuation of the ultrasonic waves in the acoustic matching layer non-uniform is appropriate. It is possible to provide an ultrasonic transducer capable of forming a sound field having a wide optimum observation range by controlling the above.

According to the third aspect of the present invention, the overall structure can be downsized, the cost can be reduced, and the oscillated ultrasonic wave contains the phase-inverted components. It is possible to provide an ultrasonic transducer capable of forming a sound field having a wide optimum observation range by appropriately controlling.

According to the fourth aspect of the present invention, the boundary region of the acoustic matching layer in which the phase of the ultrasonic wave is inverted can be made to have a structure in which the ultrasonic wave hardly oscillates. It is possible to provide an ultrasonic transducer capable of controlling the distribution more appropriately and forming a sound field having a wide optimum observation range.

According to the fifth aspect of the invention, as in the case of the ultrasonic transducer of the third aspect, the boundary region of the acoustic matching layer in which the phase of the ultrasonic wave is inverted has a structure in which the ultrasonic wave hardly oscillates. Accordingly, it is possible to provide an ultrasonic transducer capable of more appropriately controlling the phase distribution of the oscillated ultrasonic waves and forming a sound field with a wide optimum observation range.

According to the sixth aspect of the present invention, the oscillated ultrasonic waves can have components having different intensities and phases, and the intensity distribution and the phase distribution of the oscillated ultrasonic waves can be controlled appropriately. It is possible to provide an ultrasonic transducer capable of forming a sound field having a wide optimum observation range.

According to the invention described in claim 7, as in the invention described in claim 6, the oscillated ultrasonic wave can have components having different intensities and phases, and the intensity distribution of the oscillated ultrasonic wave. Also, it is possible to provide an ultrasonic transducer capable of appropriately controlling the phase distribution and forming a sound field having a wide optimum observation range.

[Brief description of drawings]

FIG. 1 is a perspective view showing an ultrasonic transducer according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a distribution of a matching portion and a mismatching portion and an ultrasonic beam intensity distribution of the ultrasonic transducer according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram showing the shapes of an ultrasonic transducer of the first embodiment and an ultrasonic beam of a conventional example with respect to an acoustic radiation surface.

FIG. 4 is a perspective view showing another example of the acoustic matching layer of the ultrasonic transducer of the first embodiment.

FIG. 5 is a perspective view showing still another example of the acoustic matching layer of the ultrasonic transducer of the first embodiment.

FIG. 6 is a perspective view showing an ultrasonic transducer according to a second embodiment of the present invention.

FIG. 7 is a perspective view showing an ultrasonic transducer according to a third embodiment of the present invention.

FIG. 8 is an explanatory diagram showing a distribution of an acoustic matching layer and an ultrasonic beam intensity distribution of the ultrasonic transducer of the third embodiment.

FIG. 9 is a front view showing a conventional ultrasonic transducer.

[Explanation of symbols]

 1 Back Damping Material 2 Piezoelectric Element 3 Acoustic Matching Layer 4 Matching Part 5 Mismatching Part 7 Ultrasonic Beam 10 Ultrasonic Transducer 10A Ultrasonic Transducer 10B Ultrasonic Transducer 11 Acoustic Matching Layer 13 High Attenuation Part 14 Low Sound Speed Part 15 High Sound Speed Part 16 Ultrasonic medium layer 17 Acoustic reflection surface

Claims (7)

[Claims] 1. An ultrasonic transducer in which an acoustic matching layer, a piezoelectric element, and a back damping material are integrated with each other, wherein the acoustic matching layer has an absolute acoustic impedance matching with respect to the piezoelectric element and the ultrasonic medium. An ultrasonic transducer, comprising: a matching portion that is matched with the piezoelectric element and a mismatched portion where the absolute value of the acoustic impedance is not matched with respect to the ultrasonic medium. 2. An ultrasonic transducer in which an acoustic matching layer, a piezoelectric element, and a backside damping material are integrated with each other, wherein the acoustic matching layer has a large attenuation and a large attenuation of ultrasonic waves in the acoustic matching layer. An ultrasonic transducer characterized by being configured integrally with a part. 3. An ultrasonic transducer in which an acoustic matching layer, a piezoelectric element and a backside damping material are integrated, wherein the thickness of the acoustic matching layer is acoustically related to a center frequency Fr of an oscillation frequency of the ultrasonic transducer. An ultrasonic transducer characterized in that non-uniformly formed and oscillated ultrasonic waves have a mixture of components with inverted phases. 4. The acoustic matching layer is made of a plurality of kinds of materials having different sound velocities of ultrasonic waves, and a region having a high sound velocity and a region having a low sound velocity are formed in the acoustic matching layer, and a difference in sound velocity between the two regions. 4. The ultrasonic transducer according to claim 3, wherein is set to be an even multiple of the speed of sound of the ultrasonic medium. 5. The acoustic matching layer is made of plural kinds of materials having different sound velocities of ultrasonic waves, and a region having a high sound velocity and a region having a low sound velocity are formed in the acoustic matching layer, and acoustic thicknesses of both regions are formed. Is an odd multiple of 1/4 wavelength with respect to the center frequency Fr, and at the same time, the difference between the mechanical thicknesses of both regions is an odd number of 1/2 wavelength which is the acoustic thickness of the ultrasonic medium with respect to the center frequency Fr. The ultrasonic transducer according to claim 3, wherein the ultrasonic transducer is doubled. 6. The acoustic matching layer composed of a plurality of constituent elements is provided with a portion having an acoustic thickness of ½ wavelength with respect to the center frequency Fr at a boundary between the constituent elements. The ultrasonic transducer described. 7. The ultrasonic transducer according to claim 1, wherein a portion where an acoustic matching layer is not formed is provided at the boundary of each constituent element of the acoustic matching layer composed of a plurality of constituent elements.