JPH06125894A - Ultrasonic probe - Google Patents

Abstract

PURPOSE:To provide the ultrasonic diagnostic device which is improved in ultrasonic waves over a wide range and has a high resolution by providing a piezoelectric vibrator which has a front surface electrode and rear surface electrode transmitting and receiving ultrasonic waves and a backing which changes the acoustic impedance coupled to the piezoelectric vibrator as a function of the spreading position of the rear surface electrode. CONSTITUTION:The backing 501 which changes the acoustic impedance in such a manner that the acoustic impedance is small in the central part of the piezoelectric vibrator 101 having the front surface electrode 101a and the rear surface electrode 101b and is gradually larger toward the end with respect to the directions X and Y parallel with the rear surface electrode is coupled to the above-mentioned piezoelectric vibrator 101. The backing 501 is formed of resins, such as epoxy, urethane and silicone, mixed with metallic powders, such as iron oxide and tungsten powder. The packing amt. of the metallic powders is changed from the central part to the end of the piezoelectric vibrator 101.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic probe which converts an input electric signal into an ultrasonic wave and transmits the ultrasonic wave and converts the received ultrasonic wave into an electric signal and outputs the electric signal.

[0002]

2. Description of the Related Art An ultrasonic wave is transmitted to a subject, especially a human body, an ultrasonic wave reflected by a tissue in the human body is returned to obtain a reception signal, and an image inside the human body based on the reception signal is obtained. An ultrasonic diagnostic apparatus that facilitates diagnosis of diseases such as internal organs of the human body by displaying has been conventionally used.
In this ultrasonic diagnostic apparatus, an ultrasonic probe is used as a transducer that converts an electric signal into an ultrasonic wave and transmits the ultrasonic wave into the subject and receives an ultrasonic wave reflected in the subject and converts it into an electric signal. ing.

FIG. 27 is a perspective view schematically showing an example of a conventional ultrasonic probe, and FIG. 28 is a block diagram showing a circuit connected to the ultrasonic probe. In the lateral direction (x direction) of FIG. 27, for example, piezoelectric ceramics (PZT)
A large number of piezoelectric vibrators 1 consisting of are arranged in a strip shape, and a common front electrode 1a electrically connected to each other is formed on the front surface side thereof and is grounded. Further, back electrodes 1b that are independent of each other are formed on the back side of each piezoelectric vibrator 1, and each lead wire 2 is connected to each back electrode 1b. Also, in the lower part of the figure of each piezoelectric vibrator 1,
A matching layer 3 made of epoxy resin or the like corresponding to each of the piezoelectric vibrators 1 is formed, and further below the matching layer 3 in the y direction perpendicular to the arrangement direction (x direction) of the piezoelectric vibrators 1. An acoustic lens 4 made of silicone rubber or the like is attached to converge the ultrasonic waves transmitted from the acoustic probe. Further, above the piezoelectric vibrator 1 in the figure, the backing 5 sandwiches the back electrode 1b for the purpose of shortening the waveform duration of the ultrasonic wave and absorbing the ultrasonic wave transmitted to the back surface side. Is bound to.

To transmit an ultrasonic wave into a subject (not shown) such as a human body using the ultrasonic probe configured as described above, each piezoelectric vibrator is transmitted from the transmission circuit 6 shown in FIG. Each pulse signal is transmitted toward 1, so that ultrasonic waves are transmitted in pulses from each piezoelectric vibrator 1. Here, the transmission timing of each pulse signal transmitted from the transmission circuit 6 is controlled so that the ultrasonic wave transmitted from each piezoelectric vibrator 1 is focused at a predetermined depth in the subject.

Further, the ultrasonic waves transmitted from this ultrasonic probe and reflected in the subject are received by the respective piezoelectric vibrators 1 and converted into respective received signals. Each received signal is appropriately amplified by each amplifier 7 and then input to the delay adder circuit 8 where the focus is focused on a fixed or sequentially changed depth position in the subject. Delay addition is performed so that they are connected.

The reception signal delayed and added by the delay and addition circuit 8 is input to a signal processing circuit (not shown), and an image signal representing an image inside the subject by ultrasonic waves is generated based on the reception signal. An image is displayed on, for example, a CRT display device based on this image signal. FIG. 29
30 is a diagram showing a schematic structure of the ultrasonic probe and a sound pressure distribution of ultrasonic waves emitted from the ultrasonic probe, FIG.
FIG. 30 is a diagram showing the intensity distribution (A) and the beam diameter (B) in the cross-sectional direction of the ultrasonic beam in the case of the radiated sound pressure distribution shown in FIG. 29.

As shown in FIG. 29, when an ultrasonic wave having a uniform radiated sound pressure is transmitted to both the central portion and the end portion of the piezoelectric vibrator, FIG.
As shown in (1), a large side lobe is generated in the ultrasonic beam inside the subject, and therefore the ultrasonic beam cannot be narrowed down, and the beam diameter becomes considerably wide as a whole.
FIG. 31 is a diagram showing a schematic structure of the ultrasonic probe and another example of the radiation sound pressure distribution, and FIG. 32 is a cross-sectional intensity of the ultrasonic beam in the case of the radiation sound pressure distribution shown in FIG. It is a figure showing distribution (A) and beam diameter (B).

As shown in FIG. 31, there is known a method of transmitting an ultrasonic wave in which the radiated sound pressure is greatly increased in the central portion of the piezoelectric vibrator 1 and is decreased toward the end portions. As shown by 32, the side lobe can be suppressed small, and therefore the beam diameter can be narrowed down as a whole.

[0009]

FIG. 33 is a schematic diagram showing a conventional amplitude weighting method. A plurality of piezoelectric vibrators 1 are arranged in the X direction, and when the ultrasonic waves are received by these piezoelectric vibrators 1, the gain of the amplifier 7 connected to the central piezoelectric vibrator 1 is large and the end side The gain of the amplifier 7 in contact with the piezoelectric vibrator 1 is reduced. Thereby, on the receiving side, the piezoelectric vibrator 1
A process equivalent to the radiated sound pressure shown in the drawing is performed in the X direction in which the lines are lined up. However, in order to obtain the radiated sound pressure distribution on the transmission side, it is necessary to change the size of the voltage pulse applied to each piezoelectric vibrator, and attempting to achieve this will increase the circuit scale and cost. Has not reached.

Further, the arrangement direction of the plurality of piezoelectric vibrators 1 (X
Direction), the amplitude weighting in the minor axis direction (Y direction) orthogonal to
The technology described in Japanese Patent No. 24480 is known.
34 and 35 are schematic diagrams for explaining the techniques described in Japanese Patent Publication No. 1-24479 and Japanese Patent Publication No. 24480, respectively.

As shown in FIG. 34, the technique disclosed in Japanese Patent Publication No. 24479/1989 discloses a short-axis direction (Y direction) of an array type ultrasonic probe in which a plurality of piezoelectric vibrators 1 are arranged. The amplitude weighting is performed by increasing the polarization intensity at the central portion of the piezoelectric vibrator 1 and decreasing it toward the ends. However, the polarization intensity of the piezoelectric vibrator is greatly influenced by the polarization voltage, polarization temperature, polarization time, etc. during polarization, and it is difficult to obtain a desired polarization intensity distribution.

Further, as shown in FIG. 35, the technique disclosed in Japanese Examined Patent Publication No. 1-24480 discloses a shape of each piezoelectric vibrator 1 in the minor axis direction (Y direction) of an array type ultrasonic probe. By devising the above, the amplitude of the piezoelectric vibrator 1 is widened in the center and narrowed toward both ends to perform amplitude weighting. However, the piezoelectric vibrator 1 processed in this way has a problem that cracks and chips easily occur because both ends are thin. Another problem is that when the piezoelectric vibrator is processed using a dicing saw, the piezoelectric vibrator can be cut only linearly, and thus the shape of the piezoelectric vibrator is limited to a rhombus or a triangle.

In view of the above circumstances, the present invention does not require the piezoelectric vibrator itself to be processed to have a polarization distribution or cut into rhombuses, and does not need to have a special large-scale circuit. The purpose is to realize amplitude weighting in the X direction, the Y direction, or both of them, and for both transmission and reception, thereby suppressing the side lobe level.

[0014]

A first ultrasonic probe of the present invention that achieves the above object converts an input electric signal into an ultrasonic wave and transmits the ultrasonic wave, and at the same time, converts the received ultrasonic wave into an electric signal. In an ultrasonic probe for converting and outputting, at least one piezoelectric vibrator having a front electrode and a back electrode on a front surface for transmitting and receiving ultrasonic waves and a back surface facing the front surface, and a piezoelectric vibration with the back electrode interposed therebetween. A backing coupled to the child, the acoustic impedance of which changes as a function of the position of the back electrode in the one-dimensional or two-dimensional direction in which it spreads.

Here, it is preferable that the backing is one whose acoustic impedance is one-dimensionally or two-dimensionally changed such that the acoustic impedance gradually increases from the central portion toward the end portion. As the shape of this change, the acoustic impedance is one-dimensionally or two-dimensionally, for example, a triangle, a trapezoid, a step shape that descends from the central portion toward the end, a Gaussian function type, a raised cosine function type, a Hamming function type. A shape or the like obtained by inverting any one shape selected from the above is selected.

The acoustic impedance of this backing is
For example, it can be changed by changing the mixing ratio of the metal powder to the resin. The acoustic impedance of this backing is 2 × 10 ⁶ kg / mm ² / se.
It is preferable that the backing spreads from c or less to 10 × 10 ⁶ kg / mm ² / sec or more.

When a plurality of piezoelectric vibrators are arranged one-dimensionally in a predetermined direction, the direction in which the acoustic impedance of the backing changes is the predetermined direction in which the piezoelectric vibrators are arranged according to the purpose. , One of the directions intersecting with the predetermined direction is selected, or both directions are selected. The same applies when a plurality of piezoelectric vibrators are arranged in a two-dimensional matrix or concentric circles.

Further, the second ultrasonic probe of the present invention which achieves the above object, converts an inputted electric signal into an ultrasonic wave and transmits the same, and at the same time, converts a received ultrasonic wave into an electric signal and outputs the electric signal. In the ultrasonic probe, at least one piezoelectric vibrator having a front electrode and a back electrode on a front surface for transmitting and receiving ultrasonic waves and on a back surface facing the front surface, respectively,
The first material and the second material having a smaller acoustic impedance than the first material, which are coupled to the piezoelectric vibrator with the back electrode sandwiched therebetween, are the second material with respect to the first material. The backing electrode is characterized in that the backing electrode is combined with a backing which has a shape in which the area ratio in contact with the back electrode changes as a function of the position of the back electrode spreading in one-dimensional or two-dimensional directions.

Here, it is preferable that the backing is a backing in which the area ratio is one-dimensionally or two-dimensionally changed so as to become gradually smaller from the central portion toward the end portion. As the shape of this change, the area ratio is one-dimensionally or two-dimensionally, for example, a triangle, a trapezoid, a step shape rising from the central part toward the end, a Gaussian function type, a raised cosine function type, a Hamming function type. Any one of these shapes is selected.

As the first material and the second material forming the backing, for example, resins having different metal powder mixing ratios can be used. At this time, the acoustic impedance of the first material is 10 × 10 ⁶ kg.
/ Mm ² / sec or more, and the second material preferably has an acoustic impedance of 2 × 10 ⁶ kg / mm ² / sec or less.

When a plurality of piezoelectric vibrators are arranged one-dimensionally in a predetermined direction, the direction of change of the area ratio of the second material to the first material of the backing is piezoelectric vibration according to the purpose. Either one of a predetermined direction in which the children are arranged and a direction intersecting with the predetermined direction is selected, or both directions are selected. The same applies when a plurality of piezoelectric vibrators are arranged in a two-dimensional matrix or concentric circles.

Furthermore, the third aspect of the present invention that achieves the above object.
The ultrasonic probe of No. 2 does not use the second material in the second ultrasonic probe, but hollows out a portion corresponding to the second material. The backing in the ultrasonic probe is not the area ratio of the first material and the second material, but the area of the first material in contact with the back electrode is one-dimensional or two-dimensional. The backing is a shape that changes as a function of position in the dimensional direction. Each aspect of the third ultrasonic probe is the same as each aspect of the second ultrasonic probe when the second material in the second ultrasonic probe is replaced with a cavity. Is.

[0023]

OPERATION FIG. 1 is an explanatory view showing the operation of the backing. FIG. 1A shows that when the acoustic impedance of the backing is close to the acoustic impedance of the piezoelectric vibrator,
FIG. 1B shows a case where the acoustic impedance of the backing is different from the acoustic impedance of the piezoelectric vibrator.

As shown in FIG. 1A, when a backing 5A having an acoustic impedance similar to that of the piezoelectric vibrator 1 is coupled to the back side of the piezoelectric vibrator 1, a voltage is applied to the piezoelectric vibrator 1. By applying the pulse, the ultrasonic wave generated by the piezoelectric vibrator 1 is strongly transmitted to the backing 5A side, and therefore the amplitude of the ultrasonic wave transmitted to the front surface side becomes small.

On the other hand, when a backing 5B having an acoustic impedance different from the acoustic impedance of the piezoelectric vibrator 1 is coupled to the back side of the piezoelectric vibrator 1 as shown in FIG. The generated ultrasonic waves do not enter the backing 5B so much, and the amplitude of the ultrasonic waves transmitted to the front side increases. The present invention has been completed paying attention to this point.

The piezoelectric vibrator 1 usually has a considerably high acoustic impedance, and the backing part also has the purpose of attenuating the ultrasonic waves that have entered the backing. The material is selected on the side where the acoustic impedance is smaller than 1.
Therefore, the acoustic impedance of the backing 5A is large in the case of FIG. 1A, and the acoustic impedance of the backing 5B is small in the case of FIG. 1B.

In the first ultrasonic probe of the present invention, paying attention to the above points, the piezoelectric backing which causes the acoustic impedance to change as a function of the position of the back electrode in the one-dimensional or two-dimensional direction in which it spreads. It is bound to the child. Here, when a material whose acoustic impedance is smaller than that of the piezoelectric vibrator is selected as the material for the backing, as in the case of doing so, the acoustic impedance is one-dimensionally or two-dimensionally, from the central portion to the end portion. The backing is changed so that it becomes larger toward the back. As a result, the central part emits ultrasonic waves with a large amplitude toward the front side and weakens the amplitude of the ultrasonic waves emitted toward the end side, thus reducing the side lobes of the ultrasonic beam and realizing a narrow beam diameter. Therefore, an ultrasonic image with high resolution can be obtained.

Although the case of transmitting ultrasonic waves has been described here, when an ultrasonic probe having the above-mentioned backing is used, the same thing occurs at the time of reception, and high sensitivity is achieved in the central portion. , The signal is received with a lower sensitivity toward the end side, which further reduces the side lobes and realizes a narrow beam diameter. This backing is made by changing its acoustic impedance to a large extent, i.e.
10 ⁶ kg / mm ² / sec or less, 1 in large areas
The side lobe can be more effectively reduced by setting the pressure to 0 × 10 ⁶ kg / mm ² / sec or more.

The side lobes of the ultrasonic beam are reduced in the direction in which the acoustic impedance of the backing changes, and when a plurality of piezoelectric vibrators are arranged one-dimensionally in a predetermined direction, or When a plurality of piezoelectric vibrators are arranged in a two-dimensional matrix or concentric circles, the direction of change in the acoustic impedance of the backing can be arbitrarily selected according to the purpose.

In the second ultrasonic probe of the present invention, instead of the first ultrasonic probe which employs a backing whose acoustic impedance is sequentially changed,
This is a backing in which a first material and a second material having different acoustic impedances are combined with each other, and the area ratio is changed from the central portion toward the end portion. That is,
In the second ultrasonic probe of the present invention, the first material and the second material having a smaller acoustic impedance than the first material are:
A backing having a shape in which a ratio of an area of the second material in contact with the back electrode to the first material changes as a function of a position of the back electrode in a one-dimensional or two-dimensional direction in which the back electrode spreads Therefore, as in the case of the first ultrasonic probe described above, ultrasonic waves are transmitted with a large amplitude at the center and a smaller amplitude toward the ends, reducing side lobes and achieving a narrow beam diameter. To be done.

Further, the third ultrasonic probe of the present invention is
A portion corresponding to the second material having a small acoustic impedance in the second ultrasonic probe is a cavity (acoustic impedance is extremely small), and this cavity is in the second ultrasonic probe. The same effect as the second material is achieved, and similarly, the side lobe is reduced and the narrow beam diameter is realized.

[0032]

EXAMPLES Examples of the present invention will be described below. Figure 2
Is a diagram showing a first embodiment of the first ultrasonic probe of the present invention, FIG. 3 is a diagram showing changes in acoustic impedance in the embodiment shown in FIG. 2, and FIG. 4 is an acoustic impedance. FIG. 6 is a diagram showing various functional forms of

The first embodiment shown in FIG. 2 is the front electrode 101.
a piezoelectric vibrator 10 having a and a back electrode 101b
1, the acoustic impedance is parallel to the back electrode in the X direction
The central part of the piezoelectric vibrator 101 in both the Y direction and the Y direction.
Change to become smaller as it goes to the end.
The backing 501 is attached (see FIG. 3).
This ultrasonic probe has only one piezoelectric vibrator 101.
The ultrasonic probe is used to
To scan with a wave beam, the orientation of this ultrasonic probe itself
Is mechanically deflected. Backing acoustic impedan
Change from the center to the end of the piezoelectric vibrator.
Numbers include triangles, trapezoids, and centers as shown in Fig. 4.
Gauss (Gaus)
s) functional form, raised cosine
ine) function type, Hamming function type
I would like a functional form with one of them inverted.
Yes. Backing to change the acoustic impedance
Iron oxide powder on resin such as epoxy, urethane, silicone,
It is made of a mixture of metal powder such as tungsten powder.
The metal powder filling amount from the center to the end of the piezoelectric vibrator.
It can be realized by changing. Also the sound of the backing
As for the acoustic impedance, the place where the impedance is small
Then 2 × 10⁶ kg / mm² / Sec or less, big place
10 × 10 ⁶ kg / mm² / Sec or more
And is desirable.

FIG. 5 is a diagram showing a second embodiment of the first ultrasonic probe of the present invention, and FIG. 6 is a diagram showing changes in acoustic impedance in the embodiment shown in FIG. .
The second embodiment shown in FIG. 5 is an electronic linear type ultrasonic probe or electronic sector type ultrasonic probe in which piezoelectric vibrators 102 are arranged in an array for the purpose of obtaining a two-dimensional ultrasonic tomographic image. The acoustic impedance of the backing 502 is changed in the length direction (Y-axis direction) of the piezoelectric vibrator 102 as shown in FIG. As a result, the side lobe level in the ultrasonic radiation pattern of the electronic linear ultrasonic probe or the electronic sector ultrasonic probe in the Y-axis direction is suppressed, and a thin ultrasonic beam can be realized in the Y-axis direction.

FIG. 7 is a diagram showing a third embodiment of the first ultrasonic probe of the present invention, and FIG. 8 is a diagram showing changes in acoustic impedance in the embodiment shown in FIG. .
The third embodiment shown in FIG. 7 is an electronic sector type ultrasonic probe in which piezoelectric vibrators 103 are arranged in an array for the purpose of obtaining a two-dimensional ultrasonic tomographic image, and a backing 503.
The acoustic impedance of is changed in the scanning direction (X-axis direction). As a result, the side lobe level in the ultrasonic radiation pattern in the X-axis direction of the electronic sector ultrasonic probe is suppressed, and a thin ultrasonic beam can be realized in the X-axis direction.

FIG. 9 is a diagram showing a fourth embodiment of the first ultrasonic probe of the present invention, and FIG. 10 is a diagram showing changes in acoustic impedance in the embodiment shown in FIG. . The fourth embodiment shown in FIG. 8 is an electronic sector ultrasonic probe in which piezoelectric vibrators 104 are arranged in an array for the purpose of obtaining a two-dimensional ultrasonic tomographic image.
The acoustic impedance of No. 04 is changed in both the scanning direction (X-axis direction) and the short axis direction (Y-axis direction) of the piezoelectric vibrator. As a result, the side lobe level in the ultrasonic radiation pattern in the X-axis direction and the Y-axis direction of the electronic sector ultrasonic probe is suppressed, and a thin ultrasonic beam can be realized in both the X-axis direction and the Y-axis direction. .

FIG. 11 is a diagram showing a fifth embodiment of the first ultrasonic probe of the present invention. The fifth embodiment shown in FIG. 11 is an example in which the piezoelectric vibrators 105 are arranged in a two-dimensional matrix, and the backing 505 changes the acoustic impedance in the Y-axis direction. For observation of a short-distance region with a small depth inside the subject, only the piezoelectric vibrators 105 arranged in the central row among the three rows of piezoelectric vibrators 105 arranged in the Y-axis direction are used to transmit and receive ultrasonic waves with a small opening. 3 in the Y-axis direction in a long-distance region with a deep depth inside the subject.
Ultrasonic waves are transmitted and received through a large opening using all of the piezoelectric vibrators 105 arranged in a row. As a result, it is possible to realize a thinner ultrasonic beam over a wide range of regions from the short range to the long range.

FIG. 12 is a diagram showing a sixth embodiment of the first ultrasonic probe of the present invention. In the sixth embodiment shown in FIG. 12, the piezoelectric vibrators 106 are arranged concentrically,
The backing 506 is one in which the acoustic impedance is changed concentrically. The sixth embodiment is an example of an ultrasonic probe which performs scanning by mechanically deflecting it.
For observation of a short-distance region, ultrasonic waves are transmitted and received with a small aperture using the central piezoelectric vibrator 106, and for observation of a long-distance region, the central and end piezoelectric vibrators 106 are simultaneously used for a large aperture. To send and receive ultrasonic waves. As a result, as in the case of the fifth embodiment, it is possible to realize a thinner ultrasonic beam over a wide area from the short distance area to the long distance area.

FIG. 13 is a diagram showing the first embodiment of the second ultrasonic probe of the present invention, and FIG. 14 is for the first material having a large acoustic impedance in the embodiment shown in FIG. FIG. 15 is a diagram showing the area ratio of the second material having a small acoustic impedance.
6 is a diagram showing various functional forms of the area ratio of the material of FIG.

The first embodiment shown in FIG. 13 is the front electrode 11
One piezoelectric vibrator 1 having 1a and a back electrode 111b
11, the second area ratio of the small acoustic impedance to the first material of the large acoustic impedance is large in the central portion of the piezoelectric vibrator 111 in the plane parallel to the back electrode surface in both the X direction and the Y direction, and the end portion is large. The backing 511, which is changed so as to become smaller as it goes to the right (see FIG. 13), is connected. This ultrasonic probe is provided with only one piezoelectric vibrator 111. To scan the inside of a subject with an ultrasonic beam using this ultrasonic probe, the ultrasonic probe itself is used. Is mechanically deflected.

First material 5 having high acoustic impedance
As a function of the position of changing the area ratio of the second material 511b having a small acoustic impedance with respect to 11a in contact with the back electrode 111b from the central portion to the end portion of the piezoelectric vibrator 111, a triangle as shown in FIG. Trapezoid, stepped shape from the center to the end, Gaus
s) functional form, raised cosine
Ine function form, Hamming function form and the like are desirable. The acoustic impedance of the first material 511a having a large acoustic impedance is 10
^{× 10 6 kg / mm 2 /} sec or more of, a relatively small second material 511b acoustic impedance, it is desirable that the acoustic impedance to adopt the following ^{2 × 10 6 kg / mm 2} / sec.

In the first embodiment shown in FIG. 13, the acoustic impedance is small in the central portion, and the area ratio of the second material 511b which is separated from the acoustic impedance of the piezoelectric vibrator 111 is large. Therefore, ultrasonic waves are large on the front side. Emitted in amplitude. Further, the area ratio of the second material 511b decreases and the area ratio of the first material 511a having a large acoustic impedance increases toward the end portions in both the X and Y directions, so that the ultrasonic wave is absorbed on the backing side. Is transmitted and is emitted with a small amplitude from the front side. As a result, the side lobes of the ultrasonic beam are reduced and a narrow beam diameter is realized.

FIG. 16 is a diagram showing a second embodiment of the second ultrasonic probe of the present invention. The second shown in FIG.
The second embodiment 5 has a low acoustic impedance.
12b is a first material 51 having a large acoustic impedance.
The backing 512, which is fitted as a set of a plurality of segments so that the density increases toward the central portion in 2a, is connected to the back surface of the piezoelectric vibrator 112, as shown in FIG.
The same operation as that of the first embodiment shown in FIG.

FIG. 17 is a diagram showing a third embodiment of the second ultrasonic probe of the present invention. The third shown in FIG.
In the example of FIG.
13a is a second material 513 having a low acoustic impedance
A backing 513 fitted as a set of a plurality of segments in b is connected to the back surface of the piezoelectric vibrator 113. In this case, the first material 513 divided into a plurality of segments is fitted so that the density becomes higher on the end side than on the central part.

FIG. 18 is a diagram showing a fourth embodiment of the second ultrasonic probe of the present invention, and FIG. 19 is an area of the second material with respect to the first material in the embodiment shown in FIG. It is a figure showing the ratio. A fourth embodiment shown in FIG. 18 is a piezoelectric vibrator 11 for the purpose of obtaining a two-dimensional ultrasonic tomographic image.
4 is an electronic linear type ultrasonic probe or an electronic sector type ultrasonic wave in which 4 are arranged in an array.
The area ratio of the second material to the first material is changed in the length direction (Y-axis direction) of the piezoelectric vibrator 114 as shown in FIG. As a result, the side lobe level in the ultrasonic radiation pattern in the Y-axis direction of the electronic linear ultrasonic probe or the electronic sector ultrasonic probe is suppressed, and a thin ultrasonic beam can be realized in the Y-axis direction.

FIG. 20 is a diagram showing a fifth embodiment of the second ultrasonic probe of the present invention, and FIG. 21 is an area of the second material with respect to the first material in the embodiment shown in FIG. It is a figure showing change of a ratio. The fifth embodiment shown in FIG. 20 is an electronic sector ultrasonic probe in which piezoelectric vibrators 115 are arranged in an array for the purpose of obtaining a two-dimensional ultrasonic tomographic image, and the area ratio of the backing 515 is the same. In the scanning direction (X-axis direction). As a result, the side lobe level in the ultrasonic radiation pattern in the X-axis direction of the electronic sector ultrasonic probe is suppressed, and an ultrasonic beam narrow in the X-axis direction can be realized.

FIG. 22 is a diagram showing a sixth embodiment of the second ultrasonic probe of the present invention, and FIG. 23 is an area of the second material with respect to the first material in the embodiment shown in FIG. It is a figure showing the ratio. The sixth embodiment shown in FIG. 22 is a piezoelectric vibrator 11 for the purpose of obtaining a two-dimensional ultrasonic tomographic image.
6 is an electronic sector type ultrasonic probe in which 6 are arranged in an array, and the acoustic impedance of the backing 516 is set in the scanning direction (X-axis direction) and in the short axis direction of the piezoelectric vibrator (Y-axis direction).
It was changed in both directions. As a result, the side lobe level in the ultrasonic radiation pattern in the X-axis direction and the Y-axis direction of the electronic sector ultrasonic probe is suppressed, and a thin ultrasonic beam can be realized in both the X-axis direction and the Y-axis direction. .

FIG. 24 is a diagram showing a seventh embodiment of the second ultrasonic probe of the present invention. The seventh shown in FIG.
In this example, the piezoelectric vibrators 117 are arranged in a two-dimensional matrix, and the backing 517 changes the area ratio of the second material to the first material in the Y-axis direction. For observation of a short-distance region with a small depth inside the subject, only the piezoelectric vibrators 117 arranged in the central row among the three rows of piezoelectric vibrators 117 arranged in the Y-axis direction are used to transmit and receive ultrasonic waves with a small opening. In a long-distance region where the depth is deep inside the subject, ultrasonic waves are transmitted and received with a large opening by using all of the piezoelectric vibrators 117 arranged in three rows in the Y-axis direction. As a result, it is possible to realize a thinner ultrasonic beam over a wide range of regions from the short range to the long range.

FIG. 25 is a diagram showing an eighth embodiment of the second ultrasonic probe of the present invention. In the eighth embodiment shown in FIG. 25, the piezoelectric vibrators 118 are arranged concentrically,
The backing 518 is formed by concentrically changing the area ratio of the second material to the first material. The eighth embodiment is an example of an ultrasonic probe that performs scanning by mechanically deflecting it, and for observation of a short-distance region, a piezoelectric vibrator 118 in the center portion is used to generate an ultrasonic wave with a small opening. Transmission / reception is performed, and for observation of a long-distance region, ultrasonic waves are transmitted / received through a large opening by using the piezoelectric vibrators 118 at the central portion and the end portions simultaneously. Thereby, as in the case of the seventh embodiment,
It is possible to realize a narrower ultrasonic beam over a wide range from a short range area to a long range area.

FIG. 26 is a diagram showing a first embodiment of the third ultrasonic probe of the present invention. In the first embodiment shown in FIG. 26, a backing 521 having a cavity 521b is coupled to one piezoelectric vibrator 121 having a front electrode 121a and a back electrode 121b. Due to the presence of the hollow portion 521b, the area of the backing 521 in contact with the back electrode 121b is smaller in the central portion and larger in the end portion side. This embodiment is the second embodiment shown in FIG.
Second material 51 of the first embodiment of the ultrasonic probe of
The region 1b is replaced with a cavity 521b.
The cavity portion 521b corresponds to a material having an extremely low acoustic impedance, and therefore has the same function as that of the first embodiment of the second ultrasonic probe shown in FIG.

Also for the third ultrasonic probe of the present invention which requires that the backing has a hollow portion,
Although there are many examples other than the above examples, the second to eighth examples (third example) of the above-described second ultrasonic probe of the present invention can be cited. The third material of the present invention is obtained by replacing the second material in (excluding) with a cavity.
The ultrasonic probe corresponds to each embodiment of the present invention, and its operation is also the same, and therefore, illustration and description thereof are omitted here.

Here, when an acoustic lens (see FIG. 27) is provided in each of the various embodiments of the above-mentioned first, second, and third ultrasonic probes, the focus of the acoustic lens is set to these ultrasonic probes. 2 / of the maximum diagnosis depth of the ultrasonic diagnostic equipment to which the child is connected
It is desirable to set the depth to 3 or more. It should be noted that the various embodiments of the first, second, and third ultrasonic probes illustrated here are merely examples, and the present invention includes various aspects other than those illustrated here. It goes without saying that this is something that is done.

[0053]

As described above, according to the ultrasonic probe of the present invention, the backing whose acoustic impedance is changed depending on the position and the materials having different acoustic impedances are changed in the area ratio of those materials depending on the position. Since the backing is combined, or a backing having a cavity so that the area in contact with the piezoelectric vibrator changes depending on the position, the ultrasonic wave transmitted or received by the ultrasonic probe is used. Amplitude weighting is applied to sound waves,
As a result, the ultrasonic beam is improved over a wide range from a short distance to a long distance, which contributes to the realization of a high resolution ultrasonic diagnostic apparatus.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the action of a backing.

FIG. 2 is a diagram showing a first embodiment of the first ultrasonic probe of the present invention.

FIG. 3 is a diagram showing changes in acoustic impedance in the embodiment shown in FIG.

FIG. 4 is a diagram showing various functional forms of acoustic impedance.

FIG. 5 is a diagram showing a second embodiment of the first ultrasonic probe of the present invention.

6 is a diagram showing changes in acoustic impedance in the embodiment shown in FIG.

FIG. 7 is a diagram showing a third embodiment of the first ultrasonic probe of the present invention.

8 is a diagram showing changes in acoustic impedance in the embodiment shown in FIG.

FIG. 9 is a diagram showing a fourth example of the first ultrasonic probe of the present invention.

10 is a diagram showing changes in acoustic impedance in the embodiment shown in FIG.

FIG. 11 is a diagram showing a fifth example of the first ultrasonic probe of the present invention.

FIG. 12 is a diagram showing a sixth embodiment of the first ultrasonic probe of the present invention.

FIG. 13 is a diagram showing a first example of a second ultrasonic probe of the present invention.

14 is a diagram showing the area ratio of the second material to the first material in the example shown in FIG.

FIG. 15 is a diagram showing various functional forms of the area ratio of the second material to the first material.

FIG. 16 is a diagram showing a second embodiment of the second ultrasonic probe of the present invention.

FIG. 17 is a diagram showing a third example of the second ultrasonic probe of the present invention.

FIG. 18 is a diagram showing a fourth example of the second ultrasonic probe of the present invention.

19 is a diagram showing the area ratio of the second material to the first material in the example shown in FIG.

FIG. 20 is a diagram showing a fifth example of the second ultrasonic probe of the present invention.

21 is a diagram showing changes in the area ratio of the second material to the first material in the example shown in FIG.

FIG. 22 is a diagram showing a sixth example of the second ultrasonic probe of the present invention.

23 is a diagram showing the area ratio of the second material to the first material in the example shown in FIG. 22. FIG.

FIG. 24 is a diagram showing a seventh embodiment of the second ultrasonic probe of the present invention.

FIG. 25 is a view showing an eighth embodiment of the second ultrasonic probe of the present invention.

FIG. 26 is a diagram showing a first example of a third ultrasonic probe of the present invention.

FIG. 27 is a perspective view schematically showing an example of a conventional ultrasonic probe.

FIG. 28 is a block diagram showing a circuit connected to the ultrasonic probe shown in FIG. 27.

FIG. 29 is a diagram showing a schematic structure of an ultrasonic probe and a radiated sound pressure distribution at each position of ultrasonic waves radiated from the ultrasonic probe.

30 is a diagram showing the intensity distribution (A) and the beam diameter (B) in the cross-sectional direction of the ultrasonic beam in the case of the radiated sound pressure distribution shown in FIG. 29.

FIG. 31 is a diagram showing a schematic structure of an ultrasonic probe and another example of radiated sound pressure distribution.

32 is a diagram showing the intensity distribution (A) and the beam diameter (B) in the cross-sectional direction of the ultrasonic beam in the case of the radiated sound pressure distribution shown in FIG.

FIG. 33 is a schematic diagram showing a conventional amplitude weighting method.

FIG. 34 is an explanatory diagram of an example of a conventional radiation sound pressure distribution forming method.

FIG. 35 is an explanatory diagram of another example of the conventional radiation sound pressure distribution forming method.

[Explanation of symbols]

101, 102, ..., 106; 111, 112, ..., 1
18; 121 Piezoelectric vibrator 101a, 102a, ..., 106a, 111a; 112
a, ..., 118a; 121a Front electrodes 101b, 102b, ..., 106b, 111b; 112
b, ..., 118b; 121b Back electrodes 501, 502, ..., 506; 511, 512 ,.
18; 521 Backing 511a, 512a, ..., 518a First material 511b, 512b, ..., 518b Second material 521b Cavity

Claims (15)

[Claims] 1. An ultrasonic probe for converting an input electric signal into an ultrasonic wave and transmitting the ultrasonic wave and converting a received ultrasonic wave into an electric signal for output, and a front surface for transmitting and receiving ultrasonic waves and a front surface for transmitting and receiving the ultrasonic wave. At least one having a front electrode and a back electrode on opposite back surfaces, respectively
Two piezoelectric vibrators, and a backing coupled to the piezoelectric vibrators with the back electrode sandwiched therebetween, the acoustic impedance changing as a function of the position of the back electrode spreading in one-dimensional or two-dimensional directions. An ultrasonic probe characterized in that. 2. The backing according to claim 1, wherein the backing has a one-dimensional or two-dimensional change in acoustic impedance such that the acoustic impedance gradually increases from the center toward the end. Ultrasonic probe. 3. The backing has one-dimensional or two-dimensional acoustic impedance of a triangular shape, a trapezoidal shape, a step shape descending from a central portion toward an end portion, a Gaussian function type, a raised cosine function type, and a Hamming function type. The ultrasonic probe according to claim 2, wherein the ultrasonic probe is a backing that changes one of the shapes selected from the above into an inverted shape. 4. The backing is formed of a resin in which a mixing ratio of metal powder is one-dimensionally or two-dimensionally changed sequentially from a central portion toward an end portion. The ultrasonic probe according to 2 or 3. 5. The backing has an acoustic impedance of 2 × 10 ⁶ kg / mm ² / sec or less to 10 × 10.
5. The backing which spreads to ⁶ kg / mm ² / sec or more, any one of claims 2 to 4.
The ultrasonic probe described in the item. 6. A backing comprising a plurality of the piezoelectric vibrators arranged one-dimensionally in a predetermined direction, wherein the backing has an acoustic impedance changed in the predetermined direction and / or in a direction intersecting with the predetermined direction. The ultrasonic probe according to any one of claims 1 to 5, wherein 7. A plurality of the piezoelectric vibrators arranged in a two-dimensional matrix or concentric circles, wherein the acoustic impedance of the backing changes in one-dimensional direction or two-dimensional direction in which the piezoelectric vibrators are arranged. It is a backing, The ultrasonic probe of any one of Claim 1 to 5 characterized by the above-mentioned. 8. An ultrasonic probe for converting an input electric signal into an ultrasonic wave and transmitting the ultrasonic wave and converting a received ultrasonic wave into an electric signal for output, and a front surface for transmitting and receiving ultrasonic waves and a front surface for transmitting and receiving the ultrasonic wave. At least one having a front electrode and a back electrode on opposite back surfaces, respectively
Two piezoelectric vibrators, and a first material and a second material having an acoustic impedance smaller than that of the first material, which is coupled to the piezoelectric vibrators with the back electrode sandwiched therebetween, with respect to the first material. A backing formed in combination with a shape in which an area ratio of the second material in contact with the back electrode changes as a function of a position of the back electrode in a one-dimensional or two-dimensional direction in which the back electrode extends. Sonic probe. 9. The backing according to claim 8, wherein the area ratio is one-dimensionally or two-dimensionally changed so that the area ratio is gradually reduced from the central portion toward the end portion side. Ultrasonic probe. 10. The backing has an area ratio of 1
Dimensionally or two-dimensionally changes to any one shape selected from a triangle, a trapezoid, a step shape that goes down from the central part toward the end, a Gaussian function shape, a raised cosine function shape, and a Hamming function shape. The ultrasonic probe according to claim 9, wherein the ultrasonic probe is a backing. 11. The first backing material and the second backing material, wherein the backing is made of resins having different metal powder mixing ratios.
The ultrasonic probe according to claim 8, 9 or 10, wherein the ultrasonic probe is a backing in which the above material is combined. 12. The first backing having an acoustic impedance of 10 × 10 ⁶ kg / mm ² / sec or more.
The ultrasonic probe according to any one of claims 9 to 11, which is a backing in which the above material and the second material having a weight of 2 × 10 ⁶ kg / mm ² / sec or less are combined. Child. 13. A plurality of the piezoelectric vibrators, which are arranged one-dimensionally in a predetermined direction, wherein the backing has the area ratio changed in the predetermined direction and / or in a direction intersecting with the predetermined direction. The ultrasonic probe according to any one of claims 8 to 12, which is a backing. 14. A plurality of the piezoelectric vibrators arranged in a two-dimensional matrix or concentric circles, wherein the backing changes the area ratio in one-dimensional direction or two-dimensional direction in which the piezoelectric vibrators are arranged. The ultrasonic probe according to claim 8, wherein the ultrasonic probe is a backing. 15. A one-dimensional or two-dimensional area in which the back electrode has an area in which the back electrode has a hollow portion instead of the second material, and the back electrode of the first material is in contact with the back electrode instead of the backing. The ultrasonic probe according to any one of claims 8 to 14, comprising a backing that changes as a function of position in different directions.