JP2017188822A - Supersonic wave irradiation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a supersonic wave irradiation device capable of radiating a longitudinal wave to an object at high efficiency without interposing a liquid like water.SOLUTION: If an input electric signal is applied to an interdigital electrode 2, a lamb wave mode is efficiently excited to a piezoelectric substrate. The lamb wave mode is leaked to a solid medium 3 as a longitudinal wave in a case where a longitudinal speed in the solid medium 3 is equal to a phase speed of the lamb wave mode or is lower than that. The longitudinal wave in the solid medium 3 is bent in a boundary surface of the solid medium 3 and an object 4, and is transmitted into the object 4. Thus, the longitudinal wave can be radiated to the object 4 without using a liquid as a medium.SELECTED DRAWING: Figure 1

Description

The present invention relates to an ultrasonic irradiation apparatus that irradiates an object with ultrasonic waves without using a liquid as a medium.

In order to irradiate an object with ultrasonic waves, a piezoelectric transducer in a thickness vibration mode in which the driving frequency depends on the thickness of the piezoelectric substrate, or a leaky surface acoustic wave transducer in which interdigital electrodes are provided on the piezoelectric substrate is used. It is widely used. These conventional transducers have a problem that not only the irradiation angle is limited, but also high frequency driving is difficult. In addition, in the case of a leaky surface acoustic wave transducer, it is necessary to provide a liquid layer between the surface of the piezoelectric substrate on which the interdigital electrode is provided and the object, which causes difficulties in device fabrication.

In order to solve the above problem, an ultrasonic sound pressure sensor (Patent Document 1) is disclosed. This includes a piezoelectric substrate 1, an interdigital transducer 2, an elastic membrane 5 and a storage chamber 6. During driving, the leakage component of the elastic wave excited by the piezoelectric substrate 1 is irradiated as a longitudinal wave to the elastic film 5 using the liquid in the storage chamber 6 as a medium. Such a conventional device requires liquid intervention in order to irradiate the elastic film 5 with longitudinal waves.

Moreover, an ultrasonic irradiation device (Patent Document 2) is disclosed. This includes a polymer film 8 made of silicon rubber in addition to the piezoelectric substrate 1 and the second input interdigital electrode 3. During driving, the leakage component of the elastic wave excited by the piezoelectric substrate 1 is irradiated as a longitudinal wave through a polymer film 8 into a substance such as cytoplasm. In such a conventional device, the longitudinal wave may attenuate or disappear in the polymer film 8 depending on the material and thickness of the polymer film 8. Furthermore, the invention of Patent Document 2 does not disclose that the polymer film 8 contributes to longitudinal wave irradiation into a metal or other hard substance.

In this way, it is difficult to manufacture a device with the conventional technique of irradiating the object with ultrasonic waves through the liquid, and with the conventional technique of irradiating the object with ultrasonic waves through the polymer film, Irradiation is impossible depending on the material and thickness of the molecular film.

JP 2001-304952 A JP 2001-309596 A

The problem to be solved is that it is difficult to manufacture a device and the conditions for the polymer film are unclear in the conventional technology in which an object is irradiated with ultrasonic waves via a liquid or a polymer film. Therefore, it is unclear whether or not the irradiation function can be exhibited, and has a problem of lack of practicality.

An object of this invention is to provide the ultrasonic irradiation apparatus which can irradiate an ultrasonic wave in a target object irrespective of whether a target object is a liquid, sol, gel, or solid.

Another object of the present invention is to provide an ultrasonic irradiation apparatus that does not require a liquid as a medium to irradiate an object with ultrasonic waves.

Moreover, an object of this invention is to provide the ultrasonic irradiation apparatus which can irradiate a target object with an ultrasonic wave over a wide angle.

Moreover, an object of this invention is to provide the ultrasonic irradiation apparatus which can irradiate an ultrasonic wave efficiently in a target object.

Another object of the present invention is to provide an ultrasonic irradiation apparatus excellent in low voltage and low power consumption driving.

Another object of the present invention is to provide an ultrasonic irradiation apparatus that has a simple structure, is light in weight, is easy to manufacture, has a good yield, and has excellent durability.

It is another object of the present invention to provide an ultrasonic irradiation apparatus that can be easily attached to a small object.

Another object of the present invention is to provide an ultrasonic irradiation apparatus that can be easily supported by a mechanical scanning system or the like.

Moreover, an object of this invention is to provide the ultrasonic irradiation apparatus suitable also for a disposable usage form.

Another object of the present invention is to provide an ultrasonic irradiation apparatus applicable to a nondestructive inspection technique for detecting an internal defect of an object.

Moreover, an object of this invention is to provide the ultrasonic irradiation apparatus applicable to the ultrasonic diagnostic technique which detects a cancer cell etc., for example.

It is another object of the present invention to provide an ultrasonic irradiation apparatus applicable to a drug delivery system and, for example, an ultrasonic therapy technique for attacking cancer cells.

In order to achieve the above object, an ultrasonic irradiation apparatus of the present invention includes a piezoelectric substrate, at least one interdigital electrode provided on the piezoelectric substrate, and a solid medium provided under the piezoelectric substrate. It is what you have.

With this configuration, the interdigital electrode has a function of exciting a Lamb wave to the piezoelectric substrate by applying an input electric signal and irradiating the object through the solid medium as a longitudinal wave. Have.

Moreover, the ultrasonic irradiation apparatus of the present invention has a configuration including two or more interdigital electrodes each having a different electrode period length.

By comprising in this way, compared with the case where two or more interdigital electrodes which have the same electrode period length are used, longitudinal wave irradiation to a solid medium in multiple directions is attained.

In addition, the ultrasonic irradiation apparatus of the present invention includes two or more interdigital electrodes each having a different electrode cycle length, and has a configuration in which the piezoelectric substrate is arranged in order from a smaller electrode cycle length to a larger one. .

By comprising in this way, the exact longitudinal wave irradiation to multiple directions with respect to a solid medium is attained.

Moreover, the ultrasonic irradiation apparatus of the present invention can be configured to include four transducer groups. Each transducer group includes at least one interdigital electrode.

By comprising in this way, longitudinal wave irradiation to a multi-directional with respect to a solid medium is attained.

Further, the ultrasonic irradiation apparatus of the present invention has a configuration in which the directions of the two electrode fingers are parallel to each other and orthogonal to the directions of the other two electrode fingers in a configuration including four transducer groups. .

By comprising in this way, the exact longitudinal wave irradiation to a multi-directional with respect to a solid medium is attained.

The ultrasonic irradiation apparatus of the present invention has a configuration in which the longitudinal wave velocity in the solid medium is equal to or lower than the phase velocity of the Lamb wave in the piezoelectric substrate.

With this configuration, the Lamb wave excited on the piezoelectric substrate efficiently leaks into the solid medium as a longitudinal wave.

The ultrasonic irradiation apparatus of the present invention has a layered structure in which the solid medium is composed of at least two layers, and the longitudinal wave velocity propagating through the uppermost layer portion of the layered structure is equal to the phase velocity of the Lamb wave in the piezoelectric substrate. It has the structure of being equal or lower than that.

With this configuration, the Lamb wave excited on the piezoelectric substrate efficiently leaks into the solid medium as a longitudinal wave.

The ultrasonic irradiation apparatus of the present invention has a configuration in which the thickness of the solid medium is sufficient to reinforce the piezoelectric substrate and does not exceed the necessary thickness.

With this configuration, the Lamb wave excited on the piezoelectric substrate efficiently leaks into the object as a longitudinal wave through the solid medium.

Further, in the ultrasonic irradiation apparatus of the present invention, the attenuation constant of the solid medium does not exceed a value such that the propagation of the longitudinal wave to the object no longer occurs.

With this configuration, the Lamb wave excited on the piezoelectric substrate efficiently leaks into the object as a longitudinal wave through the solid medium.

In the ultrasonic irradiation apparatus of the present invention, the piezoelectric substrate is made of piezoelectric ceramic, and the direction of the polarization axis of the piezoelectric ceramic is parallel to the thickness direction.

With this configuration, Lamb waves are efficiently excited on the piezoelectric substrate.

In the ultrasonic irradiation apparatus of the present invention, the piezoelectric substrate is made of a single crystal having piezoelectricity or a piezoelectric polymer film.

With this configuration, Lamb waves are efficiently excited on the piezoelectric substrate.

Further, in the ultrasonic irradiation apparatus of the present invention, the interdigital electrode has an electrode cycle length that is equal to or greater than the thickness of the piezoelectric substrate.

With this configuration, Lamb waves are efficiently excited on the piezoelectric substrate.

In addition, the ultrasonic irradiation apparatus of the present invention has a distributed electrode structure in which the interdigital electrode has at least two electrode period lengths.

By configuring in this way, longitudinal wave irradiation in more directions is possible.

In the ultrasonic irradiation apparatus of the present invention, the interdigital electrode has an arc-shaped electrode pattern.

With this configuration, local irradiation of a longitudinal wave is possible.

In addition, the ultrasonic irradiation apparatus of the present invention has a distributed electrode structure in which the interdigital electrode has an arc-shaped electrode pattern and has at least two electrode periodic lengths.

By configuring in this way, it is possible to perform local irradiation of longitudinal waves in more directions.

ADVANTAGE OF THE INVENTION According to this invention, a longitudinal wave can be efficiently irradiated in a target object, without utilizing a liquid as a medium.

It is the schematic which shows the 1st Example of the ultrasonic irradiation apparatus of this invention. Example 1 It is a top view when the ultrasonic irradiation apparatus of FIG. 1 is viewed from above. It is another top view when the ultrasonic irradiation apparatus of FIG. 1 is seen from upper direction. FIG. 6 is a characteristic diagram showing the ft dependence of the phase velocity (V _Lami ) of each Lamb wave mode excited by a piezoelectric substrate 1 and a two-layer body made of a solid medium 3. It is a characteristic diagram showing the ft dependence of electromechanical coupling factor k ^2. It is a characteristic view which shows the relationship between the insertion loss of the Lamb wave mode in the above-mentioned two-layer body, and the frequency (f _i ) of the input electric signal. FIG. 4 shows a characteristic diagram similar to FIG. 4 except that the piezoelectric ceramic described in FIG. 4 is replaced with a lithium niobate single crystal having piezoelectricity. FIG. 6 is a plan view of the interdigital electrode 6. It is a top view when the 2nd Example of the ultrasonic irradiation apparatus of this invention is seen from upper direction. (Example 2) 4 is a plan view of the interdigital electrode 8. FIG. It is the schematic which shows the 3rd Example of the ultrasonic irradiation apparatus of this invention. (Example 3) It is a top view when the 4th example of the ultrasonic irradiation apparatus of the present invention is seen from the upper part. Example 4 It is a top view when the 5th example of the ultrasonic irradiation apparatus of the present invention is seen from the upper part. (Example 5) It is a side view of the ultrasonic irradiation apparatus of FIG. It is the schematic which shows the 6th Example of the ultrasonic irradiation apparatus of this invention. (Example 6)

The object of easy production and efficient irradiation of longitudinal waves into the object has been achieved by using a solid medium instead of a liquid.

FIG. 1 is a schematic view showing a first embodiment of the ultrasonic irradiation apparatus of the present invention. In this embodiment, the piezoelectric substrate 1, the interdigital electrode 2, and the solid medium 3 are used. The piezoelectric substrate 1 is made of, for example, a piezoelectric ceramic having a thickness (t) of 230 μm, and the direction of the polarization axis is parallel to the direction perpendicular to both end faces, that is, the thickness (t) direction. At this time, it is also possible to use a piezoelectric member such as a single crystal having piezoelectricity or a piezoelectric polymer film as the piezoelectric substrate 1. The interdigital electrode 2 is made of, for example, an aluminum thin film, and is provided on the upper end surface of the piezoelectric substrate 1. The piezoelectric substrate 1 is provided on the solid medium 3. The solid medium 3 is made of acrylic resin or the like, has a low attenuation constant, and has a thickness of 1 mm, for example. This thickness is sufficient to allow the solid medium 3 to reinforce the piezoelectric substrate 1. Thus, since the ultrasonic irradiation apparatus of FIG. 1 is small and light and has a simple structure, it can be easily attached to a small object and is suitable for a disposable form of use. Further, it is easy to manufacture, has a good yield, and is excellent in durability. When the object is irradiated with ultrasonic waves using the ultrasonic irradiation apparatus of FIG. 1, it is necessary to bring the object 4 into contact with the lower end surface of the solid medium 3. The object 4 includes a target 5, for example. The arrows drawn in the piezoelectric substrate 1, the solid medium 3 and the object 4 in FIG. 1 indicate the directions of waves propagating through them during driving.

FIG. 2 is a plan view of the ultrasonic irradiation apparatus of FIG. 1 as viewed from above. The interdigital electrode 2 has an electrode period length (p) that is equal to or greater than the thickness (t) of the piezoelectric substrate 1. The arrows in FIG. 2 indicate the direction of waves propagating through the piezoelectric substrate 1 during driving.

In the ultrasonic irradiation apparatus of FIG. 1, if an input electric signal having a frequency f _i (i = 1, 2,..., Or n) is applied to the interdigital electrode 2, the electrode period length (p) is substantially reduced. A Lamb wave mode having a corresponding wavelength and a phase velocity V _Lami (i = 1, 2,..., Or n) is efficiently excited in the piezoelectric substrate 1. This is because the piezoelectric substrate 1 is made of piezoelectric ceramic, and the direction of the polarization axis is parallel to the thickness (t) direction. Thus, the device of FIG. 1 is excellent in low voltage and low power consumption driving.

The Lamb wave mode excited by the piezoelectric substrate 1 is effectively applied to the solid medium 3 as a longitudinal wave when the longitudinal wave velocity V _Me in the solid medium 3 is equal to or lower than the phase velocity V _Lami of the Lamb wave mode. Leak. In other words, under the condition of V _Me ≦ V _Lami , mode conversion from a leaky Lamb wave to a longitudinal wave occurs at the interface between the piezoelectric substrate 1 and the solid medium 3. Since the Lamb wave mode is a wave propagating in the piezoelectric substrate 1 along a direction parallel to both end faces thereof, the angle θ _Lam at which the Lamb wave mode propagates in the piezoelectric substrate 1 is θ _Lam = π / The relationship 2 is established. Therefore, regarding the irradiation angle θ _Mei (i = 1, 2,..., Or n) of the leaky Lamb wave to the solid medium 3, sin θ _Lam / sin θ _Mei = V _Lami / V _Me , that is, θ _Mei = sin ^−1. The relationship (V _Me / V _Lami ) is established.

The thickness of the solid medium 3 should minimize the attenuation of longitudinal waves in the solid medium 3. Therefore, it is required that the thickness of the piezoelectric substrate 1 is not too thick as necessary to reinforce the strength of the piezoelectric substrate 1. In order for the propagation of the longitudinal wave to the object 4 to occur efficiently, it is desirable that the attenuation constant of the solid medium 3 is as low as possible. At least it should not be so high that the propagation of longitudinal waves to the object 4 no longer takes place.

The longitudinal wave in the solid medium 3 is refracted at the interface between the solid medium 3 and the object 4 and propagates into the object 4. Regarding the refraction angle θ _Obi (i = 1, 2,..., Or n) and the longitudinal wave velocity V _Ob in the object 4 at this time, a relationship of sin θ _Mei / sin θ _Obi = V _Me / V _Ob is established. FIG. 1 shows that θ _Mei is greater than θ _Obi when V _Me is higher than V _Ob . The device of FIG. 1 makes it possible to irradiate the object 4 with longitudinal waves without using a liquid as the solid medium 3. In order to transmit the message to the object 4, an amplitude modulation signal, a frequency modulation signal, a phase modulation signal, or the like can be used as an input electric signal.

By changing the frequency f _i of the input electrical signal, V _Lami also changes accordingly. This means that the Lamb wave mode can be changed by changing f _i . That is, the diversity of the frequency of the input electric signal leads to the diversity of the refraction angle into the object 4 of the longitudinal wave. In this way, the all-solid device as shown in FIG. 1 is effective for irradiating longitudinal waves over a wide angle into various types and types of objects 4. It does not matter whether the object 4 is a liquid, sol, gel or solid, for example water, solution, cytoplasm, cement, glass, metal, alloy, concrete, stone or the like.

When the target 5 is included in the object 4, at least one of longitudinal waves hits the target 5 regardless of the size and position of the target 5. Therefore, the device of FIG. 1 can change f _i during driving, and thus is effective for irradiating a longitudinal wave over a wide angle in various types, types and sizes of targets 5. Examples of the target 5 include blood vessels under the skin, cancer cells, and parts having different densities in the metal.

FIG. 3 is another plan view when the ultrasonic irradiation apparatus of FIG. 1 is viewed from above, and is a diagram in the case of being driven using a mechanical scanning system. The mechanical scanning system is not depicted in FIG. 3, but consists of, for example, two rails that are orthogonal to each other and moves the device of FIG. 1 along the two rails. At this time, the device of FIG. 1 needs to be easily supported. In this way, the device can scan the entire surface of the object 4. The arrows in FIG. 3 indicate the operation direction of the device. Of course, it is also possible to manually move the device in all directions. By scanning the surface of the object 4, it becomes easier to irradiate longitudinal waves into the target 5.

FIG. 4 is a characteristic diagram showing the ft dependence of the phase velocity (V _Lami ) of each Lamb wave mode excited by the piezoelectric substrate 1 and the two-layered body made of the solid medium 3. The piezoelectric substrate 1 is a piezoelectric ceramic. The solid medium 3 is made of an acrylic resin. The ft value represents the product of the frequency (f _i ) of the input electrical signal and the thickness (t) of the piezoelectric substrate 1. A velocity dispersion curve and a black circle indicate a calculated value and an actually measured value, respectively. All values are obtained when the upper end surface of the piezoelectric substrate 1 and the lower end surface of the solid medium 3 are electrically short-circuited and opened, respectively. The velocity dispersion curve showed almost no difference from the case of the piezoelectric substrate 1 alone or the case of the two-layered body made of water instead of the solid medium 3. The numbers on the side of the velocity dispersion curve are the serial numbers of the individual Lamb wave modes. The three slanted straight dashed lines represent operating characteristics (operating straight lines) when the interdigital electrode 2 has three electrode period lengths (p) of 400 μm, 500 μm, and 600 μm, respectively. The intersection between the oblique line and the velocity dispersion curve corresponds to the optimum operating condition when the interdigital electrode 2 has each electrode period length (p). Two horizontal straight dashed L _a and L _w are the locus of the longitudinal wave velocity propagating through each solid medium 3 alone and water alone in. Water is generally used widely as a substance that mediates between a piezoelectric substrate and an object. For example, when an input electrical signal of 14.2 MHz (f _i ) is applied to the interdigital electrode 2 having an electrode period length (p) of 400 μm, a second phase velocity of about 5.7 km / s (V _Lami ) is obtained. Only the fifth-order Lamb wave is excited by the piezoelectric substrate 1 having a thickness (t) of 230 μm. Since V _Me = 2.7 km / s, according to the equation θ _Mei = sin ⁻¹ (V _Me / V _Lami ), the fifth-order Lamb wave has an irradiation angle (θ _Mei of about 29 degrees). ) To leak into the solid medium 3. FIG. 4 shows which mode of Lamb wave leaks into the solid medium 3 under the condition that the thickness (t) of the piezoelectric substrate 1 and the electrode periodic length (p) of the interdigital electrode 2 are unchanged. , Depending on the frequency f _i of the input electrical signal.

Figure 5 is a characteristic diagram showing the ft dependence of electromechanical coupling factor k ^2. The k ² value is in a short circuit state with V _{Lami in} Lamb wave mode when the upper end surface of the piezoelectric substrate 1 is in an electrically open state when the lower end surface of the solid medium 3 is in an electrically open state. Calculated from the difference from the time V _Lami . The numbers on the side of the velocity dispersion curve are the serial numbers of the individual Lamb wave modes. FIG. 5 shows that, for example, when the ft value is 1.2 MHz · mm, the maximum value of k ² of the first-order Lamb wave is 12.5%. In other words, the first-order Lamb wave is excited to the piezoelectric substrate 1 most efficiently when the ft value is 1.2 MHz · mm. The k ² value in FIG. 5 is almost the same as the value for the piezoelectric substrate 1 alone. This means that the conversion efficiency from the input electric signal to the Lamb wave mode is almost the same as that of the piezoelectric substrate 1 alone even in the two-layer body composed of the piezoelectric substrate 1 and the solid medium 3.

FIG. 6 is a characteristic diagram showing the relationship between the insertion loss in the Lamb wave mode and the frequency (f _i ) of the input electrical signal in the two-layer body. However, it is a characteristic diagram when the solid medium 3 has a thickness of 1 mm and the interdigital electrode 2 has an electrode period length (p) of 600 μm. The minimum value of the insertion loss is -33.1 dB in the first order mode, f _i value at this time is 5.56 MHz. The value of this insertion loss is considerably larger than that of the piezoelectric substrate 1 alone. This indicates that driving at 5.56 MHz is suitable for irradiating the solid medium 3 and then the object 4 with longitudinal waves.

FIG. 7 shows a characteristic diagram similar to FIG. 4, but for a two-layer body in which the piezoelectric ceramic described in FIG. 4 is replaced with a lithium niobate single crystal having piezoelectricity. In this two-layer body, the upper end surface of the piezoelectric substrate 1 and the lower end surface of the solid medium 3 are both electrically open. The diagonal straight broken line represents the operating characteristic when the interdigital electrode 2 has an electrode period length (p) of 300 μm (operating line). For example, when an input electrical signal of 20.3 MHz (f _i ) is applied to the interdigital electrode 2 having an electrode period length (p) of 300 μm, a first phase having a phase velocity of about 6.1 km / s (V _Lami ) is obtained. Only the secondary mode Lamb waves are excited by the piezoelectric substrate 1 having a thickness (t) of 230 μm. Since V _Me = 2.7 km / s, it can be seen that the second-order Lamb wave leaks into the solid medium 3 at an irradiation angle (θ _Mei ) of about 26 degrees. FIG. 7 shows that not only acrylic resin and other polymer materials, but also metals, alloys, and other materials are effective as the solid medium 3 as long as the relationship of V _Me ≦ V _Lami is established. In other words, in the ultrasonic irradiation apparatus of the present invention, not only the low-order mode but also the high-order mode Lamb wave can be leaked into the solid medium 3 depending on the material of the solid medium 3. Indicates.

FIG. 8 is a plan view of the interdigital electrode 6. The interdigital electrode 6 is used in place of the interdigital electrode 2 in FIG. 2, and is the same as the interdigital electrode 2 except that the configuration of the electrode fingers is a dispersion type having an electrode period length of 2 or more. It has a structure. Specifically, the interdigital electrode 6 has a gradually increasing electrode period length p _i (i = 1, 2,..., And n). In this way, the interdigital electrode 6 has a series of electrode period lengths from p ₁ (400 μm) to _pn (600 μm).

A series of input electrical signals having a frequency corresponding to the electrode period length p _i (i = 1, 2,..., N) is an interdigital electrode 6 provided in place of the interdigital electrode 2 in the device of FIG. Is applied to the piezoelectric substrate 1, a series of multi-mode Lamb waves having a wavelength substantially corresponding to an electrode period length p _i of 400 μm to 600 μm is excited. A series of multi-mode Lamb waves efficiently leak into the solid medium 3 as a series of longitudinal waves when the longitudinal wave velocity in the solid medium 3 is substantially equal to or lower than the phase velocity of the Lamb wave mode. By using the interdigital electrode 6, it becomes possible to irradiate longitudinal waves in more directions than in the case where the interdigital electrode 2 is used. That is, the interdigital electrode 6 enables reliable longitudinal wave irradiation to the target 5 regardless of the size and position of the target 5. FIG. 4 shows that the velocity dispersion curve in the region sandwiched between two oblique broken lines corresponding to the interdigital electrode 2 having an electrode period length (p) of 400 μm and 600 μm is the optimum of the interdigital electrode 6. It shows that it corresponds to a driving condition.

FIG. 9 is a plan view when the second embodiment of the ultrasonic irradiation apparatus of the present invention is viewed from above. This embodiment has the same structure as that of FIG. 1 except that the interdigital electrode 7 is used instead of the interdigital electrode 2. The solid medium 3, the object 4 and the target 5 are not drawn in FIG. The interdigital electrode 7 has an arc-shaped electrode pattern with an opening angle of 60 degrees and an electrode cycle length (p) of 300 μm. The arrows in FIG. 9 indicate the directions of waves that propagate through the piezoelectric substrate 1 during driving.

In the ultrasonic irradiation apparatus of FIG. 9, the Lamb wave mode is excited in the piezoelectric substrate 1 in the same manner as in FIG. 1, and the Lamb wave mode is efficiently converted into a longitudinal wave in the solid medium 3 and subsequently in the object 4. Well irradiated. By comprehensively adjusting the electrode period length (p) of the interdigital electrode 7, the thickness (t) of the piezoelectric substrate 1, and the thickness of the solid medium 3, the interdigital electrode 7 can be used only for the target 5. Allows longitudinal energy to be concentrated at a single point. In this way, the interdigital electrode 7 enables local irradiation of longitudinal waves to the target 5 regardless of the size and position of the target 5.

FIG. 10 is a plan view of the interdigital electrode 8. The interdigital electrode 8 is used in place of the interdigital electrode 7 of FIG. 9 and is the same as the interdigital electrode 7 except that the configuration of the electrode fingers is a dispersed type having two or more electrode period lengths. It has a structure. Specifically, the interdigital electrode 8 has a gradually increasing electrode period length p _i (i = 1, 2,..., And n). In this way, the interdigital electrode 8 has a series of electrode period lengths from p ₁ (400 μm) to _pn (600 μm).

By using the interdigital electrode 8, a series of multi-mode Lamb waves having a wavelength substantially corresponding to the electrode period length p _i is excited on the piezoelectric substrate 1. A series of multi-mode Lamb waves are efficiently irradiated as a series of longitudinal waves onto the solid medium 3 and subsequently into the object 4. The interdigital electrode 8 enables further longitudinal wave irradiation in more directions than the interdigital electrode 7. By adjusting the electrode periodic length (p _i ) of the interdigital transducer 8, the thickness (t) of the piezoelectric substrate 1, and the optimum thickness of the solid medium 3, the interdigital transducer 8 can be used as a target 4. Alternatively, it is possible to concentrate the energy of the longitudinal wave at a single point of the target 5. In this way, the interdigital electrode 8 enables reliable and local irradiation of longitudinal waves to the target 5 regardless of the size and position of the target 5.

FIG. 11 is a schematic view showing a third embodiment of the ultrasonic irradiation apparatus of the present invention. The present embodiment includes a piezoelectric substrate 1, three interdigital electrodes 2 provided on the upper end surface of the piezoelectric substrate 1, and a solid medium 3. The object 4 is not drawn in FIG. The arrows in FIG. 11 indicate the directions of waves that propagate during driving.

In the ultrasonic irradiation apparatus of FIG. 11, each interdigital electrode 2 performs the same function as the interdigital electrode 2 in FIG. By using at least two interdigital electrodes 2, it is possible to irradiate longitudinal waves in multiple directions in the solid medium 3 than when using one. That is, effective longitudinal wave irradiation can be performed in the Z-axis direction and the X-axis direction. FIG. 11 shows that θ _Mei is smaller than θ _Obi when V _Me is lower than V _Ob . The device of FIG. 11 can consist of at least two interdigital electrodes 6, at least two interdigital electrodes 7, or at least two interdigital electrodes 8, respectively, instead of at least two interdigital electrodes 2.

FIG. 12 is a plan view when the fourth embodiment of the ultrasonic irradiation apparatus of the present invention is viewed from above. This embodiment has the same structure as that of FIG. 11 except that interdigital electrodes 21, 22, and 23 are used in place of the three interdigital electrodes 2, respectively. Solid medium 9, object 4 and target 5 are not depicted in FIG. The interdigital electrodes 21, 22, and 23 have different electrode cycle lengths, and are arranged in order from the smallest electrode cycle length to the largest. By using the interdigital electrodes 21, 22, and 23, it becomes possible to irradiate the solid medium 9 with longitudinal waves in more directions than in the case of using the three interdigital electrodes 2, and in addition, the target object 4 and target 5 can be accurately irradiated with longitudinal waves. The interdigital electrodes 21, 22, and 23 can have an arc-shaped electrode pattern similar to the interdigital electrode 7 or a distributed electrode structure such as the interdigital electrodes 6 and 8. When the interdigital electrodes 21, 22, and 23 have a dispersive electrode structure, they are arranged in order from the smallest electrode periodic length region to the largest.

FIG. 13 is a plan view of the fifth embodiment of the ultrasonic irradiation apparatus of the present invention as viewed from above. In this embodiment, the piezoelectric substrate 9, the solid medium 10, and four transducer groups are included. The solid medium 10 is made of the same material as the solid medium 3. Each transducer group consists of interdigital electrodes 24, 25, 26. Each interdigital electrode has the same structure as the interdigital electrode 2 except for the length of the electrode fingers. The solid medium 10 is not depicted in FIG. The four transducer groups are arranged on the piezoelectric substrate 9 so that the directions of two of the four electrode fingers are parallel to each other and orthogonal to the directions of the other two groups of electrode fingers. Has been.

FIG. 14 is a side view of the ultrasonic irradiation apparatus of FIG. The piezoelectric substrate 9 is made of a piezoelectric ceramic having a thickness (t) of 230 μm, and the direction of its polarization axis is parallel to the thickness (t) direction.

In the ultrasonic irradiation apparatus of FIG. 13, an input electric signal is applied to each interdigital electrode of the four transducer groups. By using four transducer groups, it is possible to irradiate longitudinal waves in more directions than in the case of using one transducer group. That is, more effective longitudinal wave irradiation in the Z-axis, X-axis, and Y-axis directions is possible.

The interdigital electrodes 21, 22, 23 can be used in place of the interdigital electrodes 24, 25, 26. By using the interdigital electrodes 21, 22, and 23, it becomes possible to irradiate longitudinal waves in more directions than in the case of using the interdigital electrodes 24, 25, and 26.

FIG. 15 is a schematic view showing a sixth embodiment of the ultrasonic irradiation apparatus of the present invention. This embodiment has the same structure as that of FIG. 1 except that solid media 11 and 12 are used instead of the solid media 3. Target 5 is not depicted in FIG. The solid medium 11 is made of the same material as the solid medium 3, and the solid medium 12 is made of a material different from the solid medium 11. Solid media 11 and 12 form a layered structure. During driving, the solid medium 11 corresponding to the upper layer portion of the layered structure is in contact with the piezoelectric substrate 1, and the lower end surface of the solid medium 12 is placed on the object 13. The object 13 includes the target 5, for example.

In the ultrasonic irradiation apparatus of FIG. 15, when the relationship of V ₁₁ ≦ V _Lami is established with respect to the longitudinal wave velocity V ₁₁ and the phase velocity V _Lami of the leaky Lamb wave in the solid medium 11, the piezoelectric substrate 1 and the solid medium 11 Mode conversion from a leaky Lamb wave to a longitudinal wave occurs at the interface. The longitudinal wave is refracted at the interface between the solid mediums 11 and 12 and then refracted again at the interface between the solid medium 12 and the object 13 and propagates into the object 13.

Longitudinal wave irradiation angle θ ₁₁ on solid medium 11, longitudinal wave refraction angle θ ₁₂ at the interface between solid medium 11 and 12, longitudinal wave refraction angle θ 13 at the interface between solid medium 12 and object ₁₃ , the longitudinal wave velocity V ₁₁ of the solid-state medium 11, for longitudinal wave velocity V ₁₂ of the solid-state medium ^{_{12, θ 11 = sin -1 (}} V 11 / V Lam), sinθ 11 / sinθ 12 = V 11 / V 12, sinθ The relationship ₁₂ / sinθ ₁₃ = V ₁₂ / V ₁₃ is established. 15, when V ₁₁ is higher than V _12, the theta ₁₁ indicates that greater than theta _12, when V ₁₂ is higher than V ₁₃ indicates theta ₁₂ is greater than theta _13. That is, selecting materials having different longitudinal wave propagation velocities as the materials of the solid media 11 and 12 leads to diversification of the irradiation direction of the longitudinal waves into the object 13. The device of FIG. 15 can use the interdigital electrode 6, 7 or 8 instead of the interdigital electrode 2 as an input transducer. Further, the layered medium composed of the solid mediums 11 and 12 in FIG. 15 can be used instead of the single-layer medium such as the solid medium 3 or 10.

DESCRIPTION OF SYMBOLS 1 Piezoelectric substrate 2 Interdigital electrode 3 Solid medium 4 Target 5 Target 6 Interdigital electrode 7 Interdigital electrode 8 Interdigital electrode 9 Piezoelectric substrate 10 Solid medium 11 Solid medium 12 Solid medium 13 Target 21 Interdigital electrode 22 Interdigital electrode 23 Interdigital electrode 24 Interdigital electrode 25 Interdigital electrode 26 Interdigital electrode

Claims (15)

A piezoelectric substrate; at least one interdigital electrode; and a solid medium. The at least one interdigital electrode excites a Lamb wave to the piezoelectric substrate by applying an input electric signal to the Lamb wave. An ultrasonic irradiation apparatus having a function of irradiating an object as a longitudinal wave through the solid medium. A piezoelectric substrate; at least two interdigital electrodes each having a different electrode period length; and a solid medium. Each interdigital electrode transmits a Lamb wave to the piezoelectric substrate by applying an input electric signal. An ultrasonic irradiation apparatus having a function of exciting and irradiating an object as a longitudinal wave through the solid medium. 3. The ultrasonic irradiation apparatus according to claim 2, wherein the at least two interdigital electrodes are arranged in order from the smallest electrode period length to the largest electrode period in the piezoelectric substrate. A piezoelectric substrate, four transducer groups, and a solid medium, each of the four transducer groups including at least one interdigital electrode, the at least one interdigital electrode being applied with an input electrical signal Accordingly, an ultrasonic irradiation apparatus having a function of exciting a Lamb wave to the piezoelectric substrate and irradiating the object through the solid medium as the Lamb wave as a longitudinal wave. The ultrasonic irradiation apparatus according to claim 4, wherein directions of two electrode fingers of the four transducer groups are parallel to each other and orthogonal to directions of other two electrode fingers. The ultrasonic wave irradiation apparatus according to any one of claims 1 to 5, wherein a longitudinal wave velocity in the solid medium is equal to or lower than a phase velocity of the Lamb wave. The ultrasonic wave according to any one of claims 1 to 5, wherein the solid medium has a layered structure, and a longitudinal wave velocity propagating in an upper layer portion of the layered structure is equal to or lower than a phase velocity of the Lamb wave. Irradiation device. The ultrasonic irradiation apparatus according to claim 1, wherein a thickness of the solid medium is sufficient to reinforce the piezoelectric substrate and does not exceed a necessary thickness. The ultrasonic irradiation apparatus according to claim 1, wherein an attenuation constant of the solid medium does not exceed a value at which propagation of the longitudinal wave to the object no longer occurs. The ultrasonic irradiation apparatus according to claim 1, wherein the piezoelectric substrate is made of piezoelectric ceramic, and a direction of a polarization axis of the piezoelectric ceramic is parallel to a thickness direction. The ultrasonic irradiation apparatus according to claim 1, wherein the piezoelectric substrate is made of a single crystal having piezoelectricity. The ultrasonic irradiation apparatus according to claim 1, wherein the piezoelectric substrate is made of a piezoelectric polymer film. The ultrasonic irradiation apparatus according to claim 1, wherein the interdigital electrode has an electrode period length that is equal to or greater than a thickness of the piezoelectric substrate. The ultrasonic irradiation apparatus according to claim 1, wherein the interdigital electrode has a distributed electrode structure having at least two electrode periodic lengths. The ultrasonic irradiation apparatus according to claim 1, wherein the interdigital electrode has an arc-shaped electrode pattern.