JPH08173423A - Ultrasonic probe - Google Patents

Abstract

PURPOSE: To provide an ultrasonic probe; which lessens the signal leakage by acoustic coupling between vibrator sections and improving a bearing resolution and sensitivity. CONSTITUTION: This ultrasonic probe 1 has arrangement type vibrators 3 formed by arranging the many vibrator sections 2 of a laminated structure at every specified spacing and consists of piezoelectric elements 4, acoustic matching layers 5 formed on the front surfaces on the ultrasonic radiation side of these piezoelectric elements 4 and backing materials 6 which are formed on the rear surface side of the arrangement type vibrators 3 and are bored in a part of each of the plural spacing. First packing layers 7a1 are formed in the spacings between the backing materials 6 adjacent to each other, second packing layers 7a2 in the spacings between the piezoelectric elements 4 adjacent to each other and third packing layers 7a3 in the spacings between the acoustic matching layers 5 adjacent to each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic probe provided with an array type vibrator formed by arranging a large number of vibrator parts, and more particularly to the size of a gap between adjacent vibrator parts and its size. The present invention relates to an ultrasonic probe having a characteristic acoustic impedance of a material filled in a gap.

[0002]

2. Description of the Related Art There is an ultrasonic diagnostic apparatus that electrically vibrates a piezoelectric element to scan an ultrasonic signal (ultrasonic beam) in a living body and display a tomographic image in the living body.

In this ultrasonic diagnostic apparatus, an ultrasonic probe is used to scan an ultrasonic signal in a living body. An example of this ultrasonic probe is shown in FIGS. In addition,
FIG. 5 is a perspective view showing a schematic configuration of a conventional ultrasonic probe, and FIG. 6 is a vertical cross-sectional view of the ultrasonic probe shown in FIG. 5 taken along the line BB in the stacking direction at a substantially central portion thereof. (Enlarged view).

The ultrasonic probe 11 has a vibrator portion 12 having a piezoelectric conversion function. This vibrator unit 12 is
The piezoelectric element 13, an acoustic matching layer 14 formed on the front surface of the piezoelectric element 13 on the ultrasonic signal emitting side, and a backing material 15 formed on the rear surface of the device facing the front surface of the piezoelectric element 13. , Has a laminated structure as a whole.

A large number of the vibrator portions 12 are arranged at regular intervals to form an array type vibrator 16.
Adjacent transducer units 12 in this array type transducer 16
The gap 17 is uniformly filled with a resin material z having an acoustic impedance of, for example, 3 Mrayl and excellent in dielectric strength for potting, molding, or bonding. Further, on the front surface of the acoustic matching layer 14,
The acoustic lens 18 is adhered.

In this ultrasonic probe 11, an oscillator unit 12 is independently driven by a transmitter / receiver unit (not shown) to perform electronic scanning such as linear scanning or sector scanning. Also,
By independently controlling the drive timing of each transducer unit 12 by the transmission / reception unit, the ultrasonic signal is focused (electronically focused) at a predetermined position to enhance the resolution in the scanning direction (hereinafter referred to as azimuth resolution).

[0007]

The prerequisites for electronically scanning and focusing an ultrasonic signal are:
This means that the drive of each transducer unit can be controlled independently. However, in reality, signals may leak from the driving element to the non-driving element due to various factors.

The signal leakage to the non-driving element causes an increase in the driving aperture width per element. In other words, the directivity (element factor) of one element was sharpened, and as a result, the width of the focused beam was increased. For example, if the center frequency is 10 MHz, the width of the focused beam is 130
Increased from μm to 180 μm, center frequency is 7.5 MHz
, The focused beam width is from 150 μm to 23 μm.
Increase to 0 μm.

This increase in beam width eventually causes deterioration of lateral resolution and deterioration of sensitivity, resulting in deterioration of diagnostic ability.

Factors of signal leakage that cause such a problem include electrical coupling and mechanical (acoustic) coupling of the driving element and the non-driving element. The former is due to the fact that the wiring portions are electrostatically and electromagnetically coupled via the impedance component such as the parasitic capacitance existing in the wiring portion of the transmission / reception circuit connected to each transducer.

On the other hand, the latter is because the adjacent transducer portions are acoustically coupled with each other through a gap. Due to this acoustic coupling, a signal leaked from the driving element through the gap in the direction of the adjacent element, in the front direction of the gap (direction of the acoustic lens), and in the back direction (direction of the device side).

In particular, with respect to the signal leakage due to the acoustic coupling between the adjacent vibrator portions, no specific solution has been taken at present.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an ultrasonic probe in which signal leakage due to acoustic coupling between transducers is reduced and lateral resolution and sensitivity are improved. .

[0014]

In order to achieve the above object, an ultrasonic probe according to a first aspect of the present invention is configured such that a large number of vibrator portions having a laminated structure including at least a piezoelectric element and an acoustic matching layer are arranged at regular intervals. Equipped with an array type vibrator formed by
In an ultrasonic probe capable of transmitting and receiving ultrasonic signals by driving the vibrator part, a plurality of filling layers having acoustic impedances different from those of the constituent elements of the vibrator part are formed in each of the gaps. There is.

Particularly, in the ultrasonic probe according to claim 2, the vibrator portion includes the piezoelectric element, and the acoustic matching layer formed on a front surface of the piezoelectric element on the ultrasonic wave emitting side.
The backing material is formed on the back surface side of the array type vibrator, and a part of each of the plurality of gaps is formed, and the filling layer corresponds to a gap between the backing materials adjacent to each other. The first filling layer, the second filling layer corresponding to the gap between the piezoelectric elements adjacent to each other, and the third filling layer corresponding to the gap between the acoustic matching layers adjacent to each other.

Further, in the ultrasonic probe according to the third aspect, when the wavelength corresponding to the center frequency of the ultrasonic signal in each layer of the plurality of filling layers is λ, the length w of the gap in the arrangement direction is w. _g ,

Equation 3] _{w g = 1/4 × λ} (2n-1) {n ≧ 1: INTEGER} is set to the value of the value or near determined by.

Further, in the ultrasonic probe according to the present invention, an acoustic lens is bonded to the front surface of the acoustic matching layer in the array type vibrator, and the ultrasonic probe corresponds to the center frequency of the ultrasonic signal in each layer of the filling layer. When the wavelength to be set is λ, the length l _t of each filling layer in the stacking direction is

[Mathematical formula-see original document] It is formed so as to have a value determined by l _t = 1/4 × λ (2n−1) {n ≧ 1: integer} or its vicinity, and the acoustic impedance of an arbitrary layer of the filling layer is It is set to a value different from the geometric mean value of the acoustic impedance of the adjacent layers or members in the laminating direction of the arbitrary layers.

Further, in the ultrasonic probe according to the fifth aspect, the acoustic impedance value of the acoustic lens and the acoustic impedance value of the second filling layer are matched. Furthermore, in the ultrasonic probe according to claim 6, the length l _{t of} the first filling layer in the stacking direction is:
It is formed to be longer than the wavelength corresponding to the center frequency of the ultrasonic signal in the filling layer, and the acoustic impedance of the first filling layer is set to be larger than the acoustic impedance of the backing material.

[0019]

The operation of the present invention will be described with reference to the drawings. In addition,
FIG. 1 is a perspective view showing a schematic configuration of an ultrasonic probe 1 according to the present invention, and FIG. 2 is a cross-sectional view of the ultrasonic probe 1 shown in FIG. 1 cut along the line AA in the stacking direction. It is a longitudinal cross-sectional view (enlarged view).

In the ultrasonic probe 1 of the present invention, an array type vibrator 3 is formed by arranging a large number of vibrator portions 2 having a laminated structure at regular intervals.

Each vibrator portion 2 has a piezoelectric element 4, an acoustic matching layer 5 formed on the front surface of the piezoelectric element 4 on the ultrasonic wave emitting side,
The backing material 6 is formed on the back side of the array type vibrator 3 and a part of each of the plurality of gaps is formed. In addition, the acoustic lens 8 is provided on the front surface of the acoustic matching layer 2.
Are glued together.

The gap of the vibrator portion 2 is formed by a filling layer having a laminated structure. That is, in the gap 6b between the backing materials 6 adjacent to each other, the first filling layer 7a ₁ having an acoustic impedance Z _Bg different from the acoustic impedance Z _{B of the} backing material 6 is formed,
A second filling layer 7a ₂ having an acoustic impedance Z _g different from the acoustic impedance Z _{e of the} piezoelectric element 4 is formed in the gap 4b between the piezoelectric elements 4 adjacent to each other. Furthermore, the acoustic matching layers 5 adjacent to each other
A third filling layer 7a ₃ having an acoustic impedance Z _mg different from the acoustic impedance Z _{m of the} acoustic matching layer 5 is formed in the gap 5b between them.

Now, let us consider the leakage of signals between the piezoelectric elements 4 which are adjacent to each other among the transducers 2 which are adjacent to each other.

Now, as shown in FIG. 2, assuming that the length (hereinafter referred to as width) of the gap 4b between the piezoelectric element 4 and the adjacent piezoelectric element 4'in the array direction is w _g , the piezoelectric element being driven. Consider the energy transmissivity of the ultrasonic signal transmitted from 4 to the adjacent piezoelectric element 4'through the gap 4b. Here, the following theory is generally known regarding transmission of longitudinal waves (reference: ultrasonic fundamental engineering, published by Nikkan Kogyo Shimbun;
Author, Yoshiaki Yamamoto).

[0025]

(Equation 5) Here, T is the transmittance of energy transmitted from the piezoelectric element 4 to the piezoelectric element 4'through the gap 4b, and θ ₂ is θ ₂ = 2.
πw _g / λ _g (λ _g is a wavelength corresponding to the center frequency of the ultrasonic signal traveling in the second filling layer 7a ₂ filled in the gap 4b; hereinafter, simply referred to as the wavelength of the gap 4b).

In the above equation (1), the transmittance T with Z _g as a variable is “Z _g = Z _e ”, that is, the acoustic impedance Z _e of the piezoelectric element 4 and the second filling layer 7a ₂ in the gap 4b. When the acoustic impedance Z _g is equal, T = 1 (maximum). In other words, at least the second inside the gap 4
Setting the acoustic impedance Z _g of the filling layer 7a ₂ of No. ₂ to a value different from the acoustic impedance Z _e of the adjacent piezoelectric element 4 (that is, a value for mismatching) is a prerequisite for reducing the transmittance T. is there.

Here, when the width w _g of the gap 4b is used as a variable, the piezoelectric element 4'through the gap 4b from the piezoelectric element 4.
FIG. 3 shows the calculation result of the energy transmission rate T that is transmitted to (the piezoelectric element and the piezoelectric element 4'have the same acoustic impedance) (see References). In addition, in FIG. 3, the width w _g of the gap 4b is normalized by the wavelength λ _g of the gap 4b, and w _g / λ.
_The horizontal axis is _g .

According to FIG. 3, w _g / λ _g is 0.25 or
In the vicinity of 0.75, that is, w _g is about “1/4 × λ
_{g (2n-1) {n} ≧ 1: INTEGER} determined by "value or its vicinity (for _{example,, 1/4 × λ g} (2n-1) ± 1 /
It can be seen that when the length is 8 (2n−1) {n ≧ 1: integer}, the transmittance T becomes almost minimum.

Therefore, the acoustic impedance Z _{g of the second} filling layer 7a ₂ filled in the gap 4b between the piezoelectric elements 4 is large.
_Is at least a value different from the acoustic impedance Z _e of the adjacent piezoelectric elements 4, and the width w _{g of the} gap 4 b is a length in the vicinity of “1/4 × λ _g (2n−1) {n ≧ 1: integer}”. By so doing, it is possible to reduce the ultrasonic signal transmitted from the piezoelectric element 4 which is a driving element to another adjacent piezoelectric element 4 ′ which is a non-driving element, and to reduce signal leakage.

The above-mentioned relationship is the same for the matching layer 5 and the gap 5b between the matching layers 5'adjacent to each other, and for the backing material 6 and the gap 6b between the backing materials 6'adjacent to each other. .

In other words, conventionally, the same material was filled in the gap between the vibrator portions adjacent to each other.
Since the inside of the gap is formed by a plurality of filling layers having acoustic impedance different from that of each constituent element (acoustic matching layer, piezoelectric element, backing material) of the adjacent vibrator parts, the adjacent vibrator parts are adjacent to each other. Between transducer parts (acoustic matching layer,
Signal leakage between the piezoelectric elements and between the backing materials) can be reduced.

Next, let us consider the leakage of signals from the gap between the adjacent transducer parts toward the front side. At this time, the length (hereinafter referred to as the thickness) of the first filling layer 7a _{1 in} the stacking direction is 1 _Bg , the thickness of the second filling layer 7a ₂ is 1 _g , and the thickness of the third filling layer 7a ₃ is 1 _mg. Based on the above, the concept of the transmittance between the adjacent transducer units described above is applied.

That is, as shown in FIG. 2, the acoustic impedance of the acoustic lens 8 is Z _L , and the wavelength corresponding to the center frequency of the ultrasonic signal traveling in the third filling layer 7a ₃ is λ.
Assuming that _mg and θ ₂ = 2πl _mg / λ _g , for example, the piezoelectric element 4
The energy transmissivity T'of the ultrasonic signal transmitted from the gap 4b to the acoustic lens 8 through the gap 5b of the matching layer 5 has a thickness of the gap 5b of "1/4 × λ _mg (2n-1) {n ≧ 1:
Value determined by "integer}" or its vicinity (for example, 1 /
4 × λ _mg (2n-1) ± 1/8 (2n-1) {n ≧ 1:
(Within the range of integer)),

(Equation 6) Given in.

According to the above equation (2), "Z _L × Z _g = Z
_mg ² , in other words Z _mg = (Z _L × Z _g / 2) ^1/2 ”,
That is, the acoustic impedance Z of the _third filling layer 7a _3
mg is the acoustic impedance Z _{g of the second} filling layer 7a ₂ which is an adjacent layer in the stacking direction of the third filling layer 7a ₃ , and
T = 1 (maximum) when it is equal to the geometric mean value ((Z _L × Z _g / 2) ^1/2 ) of the acoustic impedance Z _L of the adjacent acoustic lens 8. Therefore, the thickness l _mg of the _third filling layer 7a ₃ is set to “1/4 × λ _mg (2n-1)
{N ≧ 1: integer} ”and the length in the vicinity thereof, and the acoustic impedance Z _{mg of the third} filling layer 7a ₃
Is the acoustic impedance Z _{g of the second} filling layer 7a ₂ that is the adjacent layer in the stacking direction of the third filling layer 7a ₃ and the acoustic impedance Z of the acoustic lens 8 that is the adjacent member.
Geometric mean value between the _{L ((Z L × Z g} / 2) 1/2) and is set to a different value, the front of the gap 4b transmittance of the ultrasonic signal to be transmitted to the (acoustic lens 8 direction) T ' Can be reduced.

Particularly, the acoustic impedance of the adjacent layer (second filling layer 7a ₂ ) or the member (acoustic lens 8) in the stacking direction of the third filling layer 7a ₃ becomes equal (Z _L =
Z _g ), the relationship of FIG. 3 above can be applied,
The transmittance T'can be almost minimized.

Further, let us consider leakage of signals in the rear surface direction from the gap 4b between the piezoelectric elements 4 adjacent to each other. Here, the acoustic impedance Z _Bg of the first filling layer 7a ₁ filled in the gap 6b between the adjacent backing materials 6 is made larger than the acoustic impedance Z _B of the backing material 6 (hereinafter, referred to as the first condition. ), And its first packing layer 7
The thickness l _{Bg of} a ₁ is made longer than the wavelength based on the center frequency of the ultrasonic signal traveling in the first filling layer 7a ₁ (hereinafter referred to as the second condition) from the piezoelectric element 4 to the backing material. 6. Estimate the signal transfer characteristic A to be transferred to 6.

As an example, when the acoustic impedance of the backing material is increased about 3 times (corresponding to about 10 dB in ratio), the state of the transfer characteristic of the vibrator is calculated and shown in FIG.
Shown in

According to FIG. 4, the sensitivity of the transfer characteristic is reduced by about 10 dB in the vicinity of the center frequency f _{c as} compared with the normal characteristic, that is, when the first and second conditions are not set. . From this result, it is estimated that the sensitivity of the signal transmitted from the piezoelectric element 4 to the backing material 6 is reduced under the first and second conditions.

[0039]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described below with reference to the accompanying drawings.

The ultrasonic probe 1 of the present invention comprises an array type vibrator 3 in which a large number of vibrator portions 2 having a laminated structure are arranged at regular intervals. Each arrayed transducer unit 2 is shown in FIG.
As shown in FIG. 2, the piezoelectric element 4, the acoustic matching layer 5 on the front surface of the piezoelectric element 4 on the ultrasonic signal emission side, and the rear surface side of the array type vibrator 3 are formed, and one of each of the plurality of gaps is formed. The part is perforated.

In the array type vibrator 6, the acoustic impedance Z _B (for example, 6Mrayl) of the backing material 6 is provided in the gap 6b between the backing materials 6 adjacent to each other.
) Different acoustic impedance Z _Bg (eg 10 Mrayl
) Are filled with the first filling layer 7a _{1 and} the gap between the piezoelectric elements 4 adjacent to each other is set in the gap 4b.
The second filling layer 7a ₂ having an acoustic impedance Z _g (for example, 1 Mrayl) different from the acoustic impedance Z _e (for example, 30 Mrayl) of ₁ is formed. Further, in the gap 5b between the acoustic matching layers 5 adjacent to each other, the third filling layer 7a ₃ having an acoustic impedance Z _mg (for example, 3 Mrayl) different from the acoustic impedance Z _m (for example, 8 Mrayl) of the acoustic matching layer 5. Are formed.

Each of the filling layers 7a _{1 to} 7a ₃ is made of a resin material excellent in dielectric strength, for example, for potting, molding, or adhesion, and has a laminated structure as a whole.

On the front surface of the acoustic matching layer 2, an acoustic lens 8 (acoustic impedance Z _L : 1Mrayl) is adhered for focusing in the direction orthogonal to the electronic scanning direction.

By the way, such an arrayed array type vibrator 3 is desired for each constituent element of the vibrator part 2 while changing the thickness of the cutting blade as needed with a high precision cutter, for example. Grooves having a depth and an interval are formed according to the number of vibrator portions, and the filling layers 7a _{1 to} 7a ₃ are formed in the grooves.
Are filled and cured, and further, by repeating this process, the respective constituent elements of the vibrator part 2 are laminated.

Specifically, first, a kerf having a required depth and interval is formed in the backing material 6, and this groove (gap 6b) is formed.
Then, the filling layer 7a ₁ is formed into a layer and cured.

Then, the piezoelectric element 4 is formed on the backing material 6.
And then the gap 6b formed in the backing material 6
A kerf is formed from the surface of the piezoelectric element 4 to the surface of the filling layer 7a ₁ in the gap 6b in accordance with the position. Further, the filling layer 7a ₂ is formed in layers in this groove (hereinafter referred to as the gap 4b) and is cured.

Then, an acoustic matching layer 5 is laminated on the piezoelectric element 4, and a kerf (hereinafter referred to as a gap 5b) from the acoustic matching layer 5 to the surface of the filling layer 7a ₂ in the gap 4b is aligned with the position of the gap 4b. To form. After that, the filling layer 7a ₃ is formed into a layer and cured.

From the above steps, the acoustic impedance of the gap (5b, 4b, 6b) in each layer (acoustic matching layer 5, piezoelectric element 4, backing material 6) of the vibrator portion 5 having a laminated structure is different from that of each layer. It is possible to obtain the array type vibrator 6 formed of the filling layers 7a _{1 to} 7a ₃ having

Further, in the present embodiment, the length (hereinafter referred to as width) w of the gap 5b between the matching layers 5 adjacent to each other is w.
The _g1, is set to 1/4 (1 / 4λ _mg) of the filling in the gap 5b were traveling through the packed bed 7a ₃ (a lambda _mg) wavelength corresponding to the center frequency of the ultrasonic signal. In addition, the length l _mg (hereinafter, referred to as thickness) of the filling layer 7a _{3 in} the stacking direction is 3/4 times the wavelength (λ _mg ) (3 / 4λ).
_mg ).

Similarly, the width w _g2 of the gap 4b between the adjacent piezoelectric elements 4 is set to a wavelength (λ _g) corresponding to the center frequency of the ultrasonic signal traveling in the filling layer 7a ₂ filled in the gap 4b.
Set to 1/4 (1 / 4λ _g) of that), also the thickness l _g of this filling layer 7a _2, 7/4 of the wavelength (lambda _g)
It is set to double (7/4 λ _g ).

Further, the width w of the gap 6b of the backing material 6
The _g3, is set to 1/4 (1 / 4λ _Bg) of a wavelength based on the center frequency of the ultrasonic signal traveling through the packed bed 7a ₁ filled in the gap 6b (lambda and _Bg), also, this The thickness l _Bg of the filling layer 7a ₁ is set to 5/4 times the wavelength (λ _Bg ) (5 / 4λ _Bg ).

In this embodiment, the filling layers 7a ₁ and 7a are
₂ and 7a ₃ are made of materials having almost the same sound velocity, the widths (w _g1 , w _g2 ) of the gaps (2b to 4b) are
w _g3 ) is a common width w _g .

Further, the filling layer 7a ₂ in the gap 4b is filled so that the thickness l _g thereof becomes slightly thicker than the thickness of the laminated piezoelectric element 4 itself, and the filling layer 7a ₃ in the gap 5b. Is filled so that the thickness l _mg thereof is slightly smaller than the thickness of the laminated acoustic matching layer 5 itself. Further, the filling layer 7a ₁ in the gap 6b is filled so that the thickness l _Bg thereof is slightly thinner than the depth (thickness) of the first cut kerf. This is because it is most important to reduce the signal leakage from the piezoelectric element 4 to another adjacent piezoelectric element 4 '.

Here, when the leakage of the ultrasonic signal from the piezoelectric element 4 which is the driving element to the adjacent piezoelectric element 4'is estimated by the energy transmittance,

(Equation 7) Because

(Equation 8) Can be obtained by This can also be considered as follows. Now, the width w of the gap 4b between the piezoelectric elements 4
_{Since g} is “1 / 4λ _g ”, the acoustic impedance Z _e ′ when the adjacent non-driving piezoelectric element 4 ′ side including the filling layer 7a ₂ from the driving piezoelectric element 4 is viewed as “Z _e ′ = Z _g ²
/ Z _e ”, and the transmittance T is

[Equation 9] (This is the same result as the above equation (3)).

Using the above equation (3) or equation (4),
When the transmittance T of the energy transmitted from the most important piezoelectric element 4 to the non-driving piezoelectric element 4'through the gap constituent material 7a ₂ is calculated,

[Equation 10] It turns out that it is small enough.

Similarly, the transmittance T of the energy transmitted from the acoustic matching layer 5 to the acoustic matching layer 5'through the filling layer 7a ₃ is T.
Is “T = approximately 0.432 (43.2%)”, and the transmittance T of energy transmitted from the backing material 6 to the backing material 6 ′ through the filling layer 7a ₁ is “T = 0.778 (7
7.8%) ", which is sufficiently small.

The energy transmittance of ultrasonic waves from the gap 4b of the piezoelectric element 4 toward the front surface (the direction of the acoustic lens 8) can be obtained by the above equation (2). Even in this case, the same idea as the expression (3) can be applied. That is, now
Since the thickness 1 _{mg of the} gap 5b is ¼ λ _mg , the gap 4b
The gap constituent material 7a ₂ of the gap 5b to the gap constituent material 7a of the gap 5b
The acoustic impedance Z _L ′ when viewing the adjacent acoustic lens 8 side including ₃ can be set to “Z _L ′ = Z _mg ² / Z _L ² ”, and the transmittance T ′ is

[Equation 11] (This is the same result as the above equation (2)).

The relationship between the acoustic impedance Z _mg of the filling layer 7a _{3 in} the gap 5b and the acoustic impedances Z _L and Z _g of the adjacent layer 7a ₂ of the filling layer 7a ₃ and the adjacent member acoustic lens 8 is: , "Z _mg (3Mrayl) ≠ (Z _{L
(1Mrayl) × Z g (1Mrayl} ) / 2) are full ^1/2 ".

When the energy transmittance T'is obtained,

(Equation 12) It turns out that it becomes sufficiently small.

Further, the acoustic impedance Z _Bg (10 Mrayl) of the filling layer 7a ₁ adjacent to the backing material 6 is made larger than the acoustic impedance Z _B (6 Mrayl) of the backing material 6 and the filling layer 7a ₁ is laminated in the laminating direction. Since the thickness l _Bg is made longer than the wavelength λ _Bg based on the center frequency of the ultrasonic signal in the gap 6b (l _Bg = 5 / 4λ _Bg ), as shown in FIG. 5, in the vicinity of the center frequency f _c ,
The signal transfer characteristic from the vibrator 4 to the backing material 6 is deteriorated. Therefore, it can be inferred that the energy transmittance from the gap 4b of the vibrator 4 in the rear surface direction (apparatus side direction) decreases.

As described above in detail, according to the configuration of the present embodiment, the light is transmitted from the vibrator part to the adjacent vibrator part, the acoustic lens side (front side), and the device side (back side) via a gap. Since the transmittance of the generated energy is reduced, the amount of signal leaking from the driving element to the non-driving element or the like can be reduced.

As the resin material for forming the filling layer,
For example, when an epoxy resin is used, the acoustic impedance is about 3 mrayl, but it is also possible to change the acoustic impedance as a mixture by further filling various materials and selecting the filling density. . Further, the silicone rubber material has an acoustic impedance of about 1 Mrayl, and can be sufficiently used in this configuration.

Further, in this embodiment, each gap (5b,
4b, 6b) with a width of "w _g1 = 1/4 λ _mg , w _g2 = 1 /
4λ _g , w _g3 = 1 / 4λ _Bg (= about w _g (= 1/4)
λ _g )) ”, but the present invention is not limited to this, and w _g1 = 1/4 λ _mg (2n-1), respectively.
± 1/8 (2n-1) {n ≧ 1: n integer}, w _g2 = 1 /
4λ _g (2n-1) ± 1/8 (2n-1) {n ≧ 1: n
Integer}, w _g3 = 1 / 4λ _Bg (2n-1) ± 1/8 (2n
-1) It may be any appropriate value within the range of {n ≧ 1: n integer}.

Further, in this embodiment, the gaps (5b, 4
b, the thickness of the 6b), _{"l mg = 3 / 4λ mg,} l g = 7 /
4 λ _g , 1 _Bg = 3/4/4 _Bg ”, but the present invention is not limited to this, and 1 _mg = 1/4, respectively.
_{λ mg (2n-1) ±} 1/8 (2n-1) {n ≧ 1: n _{integer}, l g = 1 / 4λ} g (2n-1) ± 1/8 (2n-
1) {n ≧ 1: n integer}, l _Bg = 1 / 4λ _Bg (2n−
1) Any appropriate value within the range of ± 1/8 (2n-1) {n ≧ 1: n integer} may be used.

[0065]

As described above, according to the present invention, it is possible to reduce the ultrasonic signal leaking from the driving vibrator portion through the gap toward the adjacent vibrator portion, the front surface direction and the rear surface direction. Therefore, it is possible to increase the independence of control of driving each transducer unit, and to provide a high-performance ultrasonic probe with improved lateral resolution and sensitivity.

[Brief description of drawings]

FIG. 1 is a perspective view showing a schematic configuration of an ultrasonic probe according to an embodiment of the present invention.

FIG. 2 is a vertical sectional view of FIG.

FIG. 3 is a graph showing energy transmittance.

FIG. 4 is a graph showing transfer characteristics.

FIG. 5 is a perspective view showing a schematic configuration of a conventional ultrasonic probe.

6 is a vertical cross-sectional view of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Ultrasonic probe 2 Transducer section 3 Array type transducer section 4 Piezoelectric element 4b Piezoelectric element gap 5 Matching layer 5b Gap between matching layers 6 Backing material 6b Gap between backing materials 7a ₁ First filling layer 7a ₂ Second Filled layer 7a ₃ Third filled layer 8 Acoustic lens Z _L Acoustic impedance of acoustic lens Z _m Acoustic impedance of acoustic matching layer Z _e Acoustic impedance of piezoelectric element Z _B Acoustic impedance of backing material Z _{mg In} gap between acoustic matching layers Acoustic impedance of the filled layer to be filled Z _g Acoustic impedance of the filled layer filled in the gap between the piezoelectric elements Z _Bg Acoustic impedance of the filled layer filled in the gap between the backing materials w _g1 Width of the gap between acoustic matching layers w _g2 Width of gap between piezoelectric elements w _g3 Width of gap between backing materials w _g Width of transducer part l _mg Thickness of gap between acoustic matching layers _lg Piezoelectric element The thickness of the gap between the two l _Bg The thickness of the gap between the backing materials

Claims (6)

[Claims] 1. An array type vibrator is provided, which is formed by arranging a large number of vibrator portions having a laminated structure including at least a piezoelectric element and an acoustic matching layer at regular intervals, and an ultrasonic signal is generated by driving the vibrator portion. In the ultrasonic probe that can send and receive
An ultrasonic probe, wherein a plurality of filling layers having acoustic impedances different from those of the constituent elements of the transducer section are formed in each of the gaps. 2. The vibrator section is formed on the piezoelectric element, the acoustic matching layer formed on a front surface of the piezoelectric element on an ultrasonic wave emission side, and on the back side of the array type vibrator, and A backing material in which a part of each of a plurality of gaps is provided, and the filling layer is a first filling layer corresponding to a gap between the backing materials adjacent to each other, and a piezoelectric element adjacent to each other. 2. The ultrasonic probe according to claim 1, wherein the ultrasonic probe comprises a second filling layer corresponding to the gap of the above, and a third filling layer corresponding to the gap between the acoustic matching layers adjacent to each other. 3. When the wavelength corresponding to the center frequency of the ultrasonic signal in each layer of the plurality of filling layers is λ, the length w _g of the gap in the arrangement direction is expressed by the following _equation : w _g = 1 / 3. A value determined by 4 × λ (2n−1) {n ≧ 1: integer} or a value in the vicinity thereof.
The ultrasonic probe described. 4. When the acoustic lens is bonded to the front surface of the acoustic matching layer in the array type transducer and the wavelength corresponding to the center frequency of the ultrasonic signal in each layer of the filling layer is λ, each filling layer Is formed so that its length l _t in the stacking direction is a value determined by the following formula: l _t = 1/4 × λ (2n−1) {n ≧ 1: integer} 4. The ultrasonic probe according to claim 2, wherein the acoustic impedance of the arbitrary layer is set to a value different from the geometric mean value of the acoustic impedance of the adjacent layers or members in the laminating direction of the arbitrary layer. . 5. The ultrasonic probe according to claim 4, wherein the acoustic impedance value of the acoustic lens and the acoustic impedance value of the second filling layer are matched. 6. The length l _t of the first filling layer in the stacking direction is formed to be longer than the wavelength corresponding to the center frequency of the ultrasonic signal in the filling layer, and the first filling layer is formed. The acoustic impedance of the backing material is set to be larger than the acoustic impedance of the backing material.
The ultrasonic probe described.