JPS61110051A - Ultrasonic probe - Google Patents

Abstract

PURPOSE:To enable a probe with a better transmitting/receiving sensitivity in an array type ultrasonic probe using a piezo-electric body, by sandwiching a plurality of split electrodes electrically drivable independently with planar piezo-electric bodies from both sides. CONSTITUTION:Split electrodes A1-A5 are sandwiched with planar piezo-electric bodies 1 from both sides so that the layer of the split electrodes A1-A5 will be positioned between the planar piezo-electric bodies 1. Adjacent ones of the split electrodes A1-A5 are driven by a transmission signal of opposite polarity to each other and received signals are amplified with amplifier opposite in the polarity thereto (the polarity of receiving amplifier RA2, RA4... is opposite to that of receiving amplifiers RA1, RA3...), delayed with delay circuit DL1, DL2... to form a received beam and added up with an addition circuit SIGMAto make an output signal RS of a receiving section. As in the sensitivity to the center frequency component of the probe thus arranged, the positions of the thickness-wise distortional vibration coincide, a probe with better transmitting sensitivity and receiving sensitivity is possible despite a structure requiring no cutting process.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an electronic scanning type or electronic focusing type arrayed ultrasonic probe used in an ultrasonic diagnostic device, an ultrasonic flaw detection device, an ultrasonic treatment device, etc. .

[Background of the invention]

Conventionally, this type of ultrasonic probe involves cutting a plate-shaped piezoelectric material uniformly polarized in the thickness direction into thin strips and attaching electrodes to the front and back surfaces of each piece. It has a structure that converts between ultrasound and electrical signals using thickness vibration.However, in recent years, the spatial resolution required in ultrasound diagnosis and measurement has progressed to higher levels, and the strip processing required for this has progressed. The technology is approaching its limits.In other words, in order to achieve high resolution, it is necessary to increase the ultrasonic frequency or increase the diameter of the aperture used for transmitting and receiving ultrasonic waves, but in either case, the above elements cannot be used. The width of the piece must be narrowed, which poses a major problem when cutting strips.

Attempts to provide an electronic scanning type or electronic focusing type array probe without a cutting process include JP-A-58-42968 and JP-A-58-15.
Van derp as described in Publication No. 6295
Probe structures having an auw type structure are already known. Of these, the latter (Reference I) has a plurality of divided electrodes A disposed on one surface of a piezoelectric plate so that they can be driven independently, and the polarities of the polarization directly under the adjacent divided electrodes A are opposite to each other. It has a polar structure and has a cross-sectional structure as schematically shown in FIG. 1, where the arrows in the figure indicate the lines of electric force during one polarization process. In addition, in detail, in the example of Reference I.

A uniform electrode C is added to the other surface of the piezoelectric plate.

However, a probe with this structure uses a back-loading material that has a lower acoustic impedance than the piezoelectric plate.

After all, when transmitting and receiving ultrasonic waves to a medium to be measured whose acoustic impedance is lower than that of a plate-shaped piezoelectric material, a problem may arise in the transmitting and receiving sensitivity.

In other words, if the X-axis is taken in the thickness direction as shown in Figure 1,
The magnitude of the X component of the polarization vector in the piezoelectric body decreases monotonically from X=O to x=x (here, the plate thickness is xo), and is driven by an electric field with the same polarity as during one polarization. When this happens, the magnitude of the X component of the electric field vector also monotonically decreases.

Therefore, the electro-mechanical result in the polarization axis direction (coupling coefficient lCa
The magnitude of the strain S in the thickness direction caused in the piezoelectric body by the bond originating from 5) also monotonically decreases from the same <, x=O to x=x, as shown in FIG. Here, in FIG. 2, due to simple ffff, X=X,
, S=O, and the distribution of S was approximated by a straight line.

Note that the dotted line in FIG. 5 is the strain distribution of the equivalent sound source when the acoustic impedance of the materials sandwiching the piezoelectric plate from both sides is small, taking into account the reflection of sound waves at the interface. Of this strain distribution, the center frequency component, that is, the vibration of the sinusoidal component I[
Ai is given by a linear expression.

A, =-.So... (1) π On the other hand, an electric field is applied in the thickness direction to drive the piezoelectric material which has been uniformly polarized in the thickness direction.

Regarding the type of probe that has been in practical use in the past, the distribution in the thickness direction of the magnitude of strain S in the thickness direction during driving is as shown in Fig. 4, and the amplitude A0 of the center frequency component is 1. It is given by the following formula.

A, =-.So (2) π Here, for simplicity, the maximum value of the strain S is set as So, which is the same as in the case of FIG.

Comparing equations (1) and (2), A, = - Ao ... (3), and the transmission sensitivity for the sine wave of the thickness resonance frequency of the probe with the structure shown in Figure 1. It can also be seen that the wave reception sensitivity is only about 50% of the conventional type of probe that has been put into practical use. Therefore, the probe having the structure shown in FIG. 1 has a problem in transmitting sensitivity or receiving sensitivity.

[Object of the Invention] The object of the present invention is to solve the above-mentioned problems of the prior art probe configuration as shown in FIG. - To provide an ultrasonic probe with good reception sensitivity.

[Summary of the invention]

For this purpose, the present invention adopts a structure in which a plurality of divided electrodes A are sandwiched between plate-shaped piezoelectric bodies from both sides so that they can be electrically driven independently.

The arrows in Figure 0, which proposes a probe structure having a cross-sectional shape as shown in Figure 5, indicate lines of electric force during one polarization process.

Furthermore, Figure 1 shows the case where the transmitting sensitivity and receiving sensitivity of the center frequency component are the highest, that is, when the layer of the single-segment electrode A is located approximately in the middle of both outer surfaces of the piezoelectric plate. be.

In a probe with such a structure, the distribution in the thickness direction of the magnitude S of the strain in the thickness direction during driving is as shown in Fig. 6, and the amplitude A3 of the sine wave component of the thickness resonance frequency is as shown in Fig. 6.
is given by a linear equation.

Therefore, the transmitting sensitivity or receiving sensitivity regarding the center frequency component of a probe with such a structure is the same as that of a conventionally used type of probe (a probe corresponding to the strain distribution shown in Figure 4). The sensitivity is about 82%, and it can be seen that the sensitivity is good because the positions of the strain vibrations in the thickness direction match. That is, it can be seen that the structure of the present invention realizes a probe that does not require a cutting process and yet has good wave transmitting sensitivity and wave receiving sensitivity.

[Embodiments of the invention]

Hereinafter, the present invention will be described in further detail with reference to Examples.

Using the probe shown in FIG. 5, electrodes adjacent to divided electrode A are driven by transmission signals of opposite polarity.

Moreover, an ultrasonic wave transmitting device and a wave receiving device can be configured by receiving received signals by amplifiers having opposite polarities. FIG. 7 shows an embodiment of the wave receiving device. Signals received by the 0-division iE poles A l , . . . are amplified by the RAI , .

For reception beam formation, the delays caused by the delay circuits DLI, . Here, RA2°RA4. ...
The polarity of RAI, RA3. RA5. ...and has the opposite polarity.

FIG. 8 is a cross-sectional structural diagram of a piezoelectric body shown in FIG. 5, with uniform ground electrodes C added to both outer surfaces of the piezoelectric body, as an embodiment of the present invention. A feature of this structure is that the piezoelectric body is prevented from disturbing the external electric field.

FIG. 9 shows, as still another example, a cross-sectional structure of a piezoelectric material having the electrode structure shown in FIG. The arrows in Figure 1 shown schematically represent the lines of electric force during one polarization process, as in the other figures. The feature of this structure is that the thickness distribution of the magnitude of strain S in the thickness direction during driving is closer to that shown in Figure 4 than the probes shown in Figures 5 and 8, and the transmission sensitivity is This will further improve reception sensitivity.

In FIG. 10, for comparison with the piezoelectric material having the structure shown in FIG. 9, a divided electrode A is shown on the first surface of the plate-shaped piezoelectric material.

1 shows a cross-sectional structure of a piezoelectric body having a structure having a ground electrode C on the second surface, and polarization treatment also applied between the one-segment electrode A and the ground electrode C, as in the case of FIG. 9. When the pitch P of the divided electrodes is relatively large with respect to the thickness xo of the piezoelectric body, in both the cases of Fig. 9 and Fig. 10, the contribution of the electric lines of force between AC to the sound source is dominant. However, when p is relatively small, the sensitivity in the case of FIG. 9 is about twice that of the case in FIG. 10.

In this respect, the probe of the present invention is advantageous. Also, when using a plate-shaped piezoelectric material as a probe without cutting it.

A mode propagating inside the plate in the longitudinal direction of the plate is generated, and unnecessary responses due to the waves leaking into the measured medium may become a problem, but this is also a problem.

The probe of FIG. 9 is advantageous. That is, in the piezoelectric body shown in FIG. 10, both the mode in which the antinode of strain vibration is at the center of the thickness of the plate and the mode in which the strain vibration is at the node are excited;
This is because in the piezoelectric material shown in FIG. 9, only a mode having an antinode at the center of the thickness of the plate is excited.

On the other hand, FIG. 11 shows a cross section of an embodiment of a probe having a structure in which a split electrode A and a ground electrode B having a shape that electrically separates A from each other are sandwiched between plate-shaped piezoelectric materials from both sides. Shown by structure. A probe with this structure.

Unlike the probe shown in Fig. 5, the polarization around each segmented electrode A is the same, so it is possible to use equivalent transmitter and receiver circuits for each segmented electrode. An example of this is shown in FIG. 12, which differs from the receiving circuit shown in FIG. 7.

RAI, RA2. . . . uses receiving amplifiers with the same polarity, and has the advantage that it is easier to match the characteristics of each receiving amplifier.

FIG. 13 shows a uniform grounding voltage piC electrically connected to electrode B on both outer sides of the piezoelectric body shown in FIG.
Also, like the piezoelectric body in FIG. 9, a divided electrode A is added.
The cross-sectional structure of a piezoelectric body in which polarization treatment is also applied between the ground electrode C and the ground electrode C is shown. A probe with this structure has the features of both the probe shown in FIG. 11 and the probe shown in FIG.

Furthermore, FIG. 14 shows an example of a method for manufacturing a probe according to the present invention. Since it is generally difficult to form electrodes in a piezoelectric material, the method shown in Figure 1 involves depositing an electrode on one side of a plate-shaped piezoelectric material of approximately equal thickness, bonding the two, and then subjecting it to polarization. Compared to when contact is made after treatment, the performance of the piezoelectric body is not affected by positional accuracy during bonding, but the dielectric strength of the adhesive layer must be able to withstand polarization treatment. The acoustic impedance of the material is comparable to that of the piezoelectric material, or if the difference is large, the thickness of the adhesive layer needs to be sufficiently thin.

As explained above, according to the present invention, it is possible to provide an array-type ultrasonic probe with high transmitting and receiving sensitivity without cutting, and the industrial significance of the present invention is extremely large. be.

In addition, in the above description, for convenience of explanation, an example of a linear one-dimensional array type probe has been mainly described.

The scope of application of the present invention is not limited to this, but also extends to convex type and concape type arrays as well as various two-dimensional arrays.

[Brief explanation of the drawing]

Fig. 1 shows the cross-sectional structure of a plate-shaped piezoelectric material for an ultrasonic probe according to the prior art closest to the present invention, and Fig. 2 shows the magnitude of the strain in the thickness direction that occurs in the piezoelectric material when the contactor of Fig. 1 is driven. The distribution of the thickness in the thickness direction. Figure 3 shows the distribution of the thickness resonance frequency component of the strain in the thickness direction of a plate-shaped piezoelectric material in the thickness direction. Figure 4 shows the distribution of the electric field in the thickness direction of a piezoelectric material that has been uniformly polarized in the thickness direction. The thickness direction distribution of the magnitude of thickness direction strain during driving for a type of probe that is driven by applying an electric current (a type of probe that has been in practical use in the past), Fig. 5 shows the ultrasonic probe according to the present invention. The cross-sectional structure of the child plate-shaped piezoelectric material, FIG. 6 shows the thickness distribution of the magnitude of the strain in the thickness direction that occurs in the piezoelectric material when the probe shown in FIG. 5 is driven,
Figure 7 is an example of a receiving circuit that forms a receiving beam based on the received signal from the probe in Figure 5, and Figure 8 shows a uniform grounding on both sides of the outside of the piezoelectric plate shown in Figure 5. An embodiment of the present invention in which electrodes are added, as shown in FIG. 9, is a plate piezoelectric material having the same electrode structure as in FIG. An embodiment of the present invention treated with
In Figure 10, the divided electrode A is held on one side of the piezoelectric plate, and the 9th
A piezoelectric body that has been polarized in the same way as in the case shown in the figure, Figure 11 has a structure in which a split electrode A and a ground electrode B, which has a shape that electrically isolates A from each other, are sandwiched between plate-shaped piezoelectric bodies from both sides. One embodiment of the present invention, FIG. 12 is an example of a receiving circuit that forms a receiving beam based on the received signal from the probe shown in FIG.
FIG. 3 shows an embodiment of the present invention in which a plate-shaped piezoelectric material having the electrode structure shown in FIG. 10 is subjected to polarization treatment similar to that of the piezoelectric material shown in FIG.
FIG. 14 is an example of a method for manufacturing a plate-shaped piezoelectric material for an ultrasonic probe according to the present invention. 1.2... Plate piezoelectric material, 3... Adhesive layer, X... Thickness direction coordinate, xo... Plate thickness, Al~A5... Divided so that it can be electrically driven independently. arrow in the piezoelectric body... lines of electric force in polarization process, S... strain in the thickness direction that occurs in the plate-shaped piezoelectric body during driving, So... S
Maximum value of RAI to RA5... receiving amplifier, I) Ll
~DL5...Delay circuit for receiving beam formation, Σ・
... Signal addition fi, Rs for receiving beam formation...
Receiver output signal, C...Grounding electrode on both outer sides of the piezoelectric plate, B...Grounding shaped to isolate the divided electrodes A from each other. Fig. 3S Fig. 4S. No. 9 No. 70 No. 11 No. ll No. 12 No. 73 No. 9

Claims (1)

[Claims] 1. In an array-type ultrasonic probe using plate-shaped piezoelectric bodies, the plate-shaped piezoelectric bodies sandwich electrode A, which is divided into a plurality of parts, from both sides so that it can be electrically driven independently. An ultrasonic probe characterized by having a structure. 2. The ultrasonic probe according to claim 1, wherein the layer of the divided electrode A is located approximately midway between the outer surfaces of the piezoelectric plate. 3. The probe according to claim 1 has a structure in which the divided electrode A and the electrode B having a shape that electrically isolates A from each other are sandwiched between plate-shaped piezoelectric bodies from both sides. Features of ultrasonic probe. 4. An ultrasonic probe according to claim 1, characterized in that uniform electrodes C are attached to both outer surfaces of the piezoelectric plate. 5. An ultrasonic probe according to claim 1, characterized in that the piezoelectric material is polarized by applying a potential difference between adjacent divided electrodes. 6. The ultrasonic probe according to claim 3, characterized in that the piezoelectric material is polarized by applying a potential difference between the divided electrode A and the adjacent electrode B. probe. 7. The probe according to claim 4, characterized in that the piezoelectric material is polarized by applying a potential difference between the divided electrode A and the outer uniform electrode C. Sonic probe.