JP2000157543A - Ultrasonic wave probe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control a focus distance and to make a sensitivity excellent by adding mass to the end part of a piezoelectric element, suppressing a vibration and controlling the effective length of an ultrasonic wave exchange part in the piezoelectric element. SOLUTION: The both end parts of the piezoelectric element 1 are coated with solders 7a and 7b as mass, glass is stuck on a first layer 4a as an acoustic matching layer and a whole surface including the solders 7a and 7b is coated with a second-layer resin 4b. Then the second layer 4b is made to be flat together with the solders 7a and 7b after grinding the surface, the both first and second layers 4a and 4b are made to have the λ/4 thickness of an ultrasonic wave frequency, and the thickness of the solders 7a and 7b is made to be λ/2. By the configuration, the solders 7a and 7b are added at the both sides of the piezoelectric element 1 and the mass is increased compared with the center part where an acoustic matching layer 4 is formed. Therefore, a center part is dominative in the vibration area of the piezoelectric element 1 and the vibration is suppressed by a mass load at the both ends. Thus, the effective length of the ultrasonic wave exchange area in the element 1 becomes the center part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic probe in the industrial technical field, and more particularly to an ultrasonic probe in which the effective length of a piezoelectric element is controlled.

(Background of the Invention) An ultrasonic probe is widely used as a transmitting and receiving part of an ultrasonic wave in an ultrasonic diagnostic apparatus for medical use or the like. For example, the piezoelectric elements are linearly or sector-driven by arranging them in the width direction, or linearly driven by arranging them on a convex (convex curved surface). In these devices, the focal length of the ultrasonic wave is usually controlled by changing the length of the piezoelectric element and the curvature of the acoustic lens.

(Example of Prior Art) FIGS. 5 and 6 are views of an ultrasonic probe for explaining a conventional example, FIG. 5 is a front sectional view, and FIG. 6 is a side sectional view. The ultrasonic probe is formed by arranging a plurality of rectangular piezoelectric elements 1 on a backing material 2 in the width direction. The piezoelectric element 1 has electrodes 2 (ab) on both main surfaces. The transmitting / receiving wave surface (front surface) has, for example, an acoustic matching layer 4 having two layers, and an acoustic lens 5 is further covered. The acoustic lens 5 is in the length direction (short axis direction) of the piezoelectric element 1
And a convex surface. The electrode 2a is led out from the rear surface of the piezoelectric element 1 by a flexible substrate, and the electrode 2b is commonly connected to the ground by a common line and grounded to a ground potential (not shown).

In such a device, when the length of the piezoelectric element 1 is large, the focal length F at which the ultrasonic wave P converges is long, and when the length is short, the focal length F is short. Further, the focal length F is long when the curvature of the acoustic lens is large, and close when the curvature is small. Generally, these are appropriately selected in accordance with the specifications, and the focal length F is set. Then, a pulse voltage from a diagnostic device (not shown) is applied through a coaxial cable, and an ultrasonic wave and an electric signal due to the piezoelectric and inverse piezoelectric phenomena are transmitted / received to / from the object (living body). Thus, a diagnostic image near the focal length F is obtained.

[0005]

[Problems to be Solved by the Invention]
However, in the ultrasonic probe having the above configuration, a pulse voltage is applied via a coaxial cape. And, as shown in FIG. 7 (a), the coaxial cable 6 has a capacity (referred to as a line capacity) C1 between the core wire 6a and the ground wire 6b. On the other hand, a focal length (depth) F near the surface of the detection object
Is set, the acoustic lens 5 alone is not sufficient, and the length of the piezoelectric element 1 needs to be shortened.

However, when the length of the piezoelectric element 1 is reduced, the capacitance between the electrodes on both main surfaces (referred to as the interelectrode capacitance, FIG. 7B) C0 decreases. Then, as shown in FIG. 8, when the pulse voltage Ep is applied, the piezoelectric element 1 (interelectrode capacitance C0) and the line capacitance C1 of the coaxial cable 6 are connected in parallel. Therefore, when the interelectrode capacitance C0 of the piezoelectric element 1 decreases (increases in impedance), the coaxial cable 6
Current leakage due to the line capacitance C1 increases.

As a result, the driving power supplied to the piezoelectric element 1 by the pulse voltage Ep substantially decreases.
Therefore, the radiant energy of the ultrasonic wave from the piezoelectric element 1 also decreases due to the decrease in the driving power, and the level of the reflected wave also decreases accordingly.

Generally, as shown in FIG.
At the time of reception, the voltage Es between terminals of the piezoelectric element 3 generated by the reflected wave is detected by the load resistance RL. In this case, the piezoelectric element 3 sets the interelectrode capacitance C0 to an internal resistance (impedance).
The voltage source e becomes r. Therefore, when the inter-electrode capacitance C0 of the piezoelectric element 3 decreases, the internal impedance 1 / j
ωC increases, causing a loss in the terminal voltage Es.
For this reason, the reception voltage at the load resistance RL also decreases.

Therefore, in both transmission and reception, the inter-electrode capacitance C0 is reduced, which has an adverse effect, and reduces the reception voltage with respect to the pulse voltage Ep during transmission, resulting in a substantial decrease in sensitivity. There was a problem.

(Object of the Invention) It is an object of the present invention to provide an ultrasonic probe which controls the focal length and has good sensitivity.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a basic solution to controlling the effective length of an ultrasonic transmitting / receiving section in a piezoelectric element by adding a mass to an end of the piezoelectric element to suppress vibration. I do.

[0010]

According to the present invention, since the effective length of the piezoelectric element is controlled by the mass added to the end, the focal length can be controlled without changing the length of the piezoelectric element. Since the length of the piezoelectric element is fixed, the capacitance between the electrodes is not reduced. Hereinafter, an embodiment of the present invention will be described.

[0011]

1 and 2 are views of an ultrasonic probe for explaining an embodiment of the present invention. FIG. 1 is a plan view excluding an acoustic matching layer and an acoustic lens, and FIG. 2 is a sectional view. FIG. The same parts as those in the prior art are denoted by the same reference numerals, and the description thereof will be simplified or described. The ultrasonic probe is connected to the electrode 2 as described above.
A plurality of piezoelectric elements 1 having (ab) are arranged on a backing material 2, and an acoustic matching layer 4 and an acoustic lens 5 are provided on a wave transmitting / receiving surface (front surface).

In this embodiment, solder 7 (ab) as a mass is applied to both ends of the piezoelectric element 1. Then, the first layer 4a as the acoustic matching layer 4 is adhered to glass, and the second layer of resin 4b is applied entirely including the solder 7 (ab). Then, the surface is polished to flatten the second layer 4a together with the solder 7 (ab). Both the first layer 4a and the second layer 4b have a thickness of λ / 4 of the ultrasonic frequency, and the thickness of the solder 7 (ab) is λ / 2.

In such a structure, solder is added to both ends of the piezoelectric element 1, and the mass is larger than that of the central portion where the acoustic matching layer 4 is formed. Therefore, the center of the vibration region of the piezoelectric element 1 is dominant, and the vibration at both ends is suppressed by the mass load. As a result, the effective length of the ultrasonic wave transmission / reception area in the piezoelectric element 1 becomes the central portion.

This is equivalent to shortening the length of the piezoelectric element 1, and the focal length F along with the acoustic lens 5 is obtained.
Can be reduced. Further, since the length itself of the piezoelectric element 1 does not change, the inter-electrode capacitance C0 can be kept constant.
Therefore, a short-range tomographic image can be obtained and the sensitivity can be increased without causing a decrease in the pulse voltage during transmission and an increase in internal resistance during reception due to a decrease in the interelectrode capacitance C0.

[0015]

[Other Matters] In the above embodiment, the solder 7 (ab) is applied to both ends of the piezoelectric element 1, but it may be one end. However, in view of the symmetry of the ultrasonic probe, it is better to provide the ultrasonic probe uniformly on both ends. Also, mass beam solder 7 (ab)
However, the present invention is not limited to this, and any material having a specific gravity larger than that of the acoustic matching layer 4 may be basically used.

In the acoustic matching layer 4, the first layer 4a is bonded with glass and the second layer 4b is coated with resin.
For example, one layer or three or more layers by resin coating may be used. The first layer 4a is located between the solder 7 (ab).
May be provided to form the second layer 4b.

Although the acoustic lens 5 is provided on the acoustic matching layer 4, the application area of the solder 7 (ab) on both ends is enlarged to increase the effective length of the ultrasonic wave transmission / reception area of the piezoelectric element 3. The distance may be shortened to obtain a short-range sound field characteristic. In this case, the acoustic lens 5 can be removed.

Although described as ultrasonic probes, they may be flat or curved in shape.
The drive system may be a sector, a linear drive, or any other drive, and can be applied regardless of the shape and drive system.

In short, the present invention aims at suppressing at least one end of the piezoelectric element 1 by a mass load, substantially reducing the effective length of the ultrasonic wave transmitting / receiving area, and thereby maintaining the sensitivity. Such a concept basically belongs to the technical scope of the present invention.

[0019]

According to the present invention, the vibration is suppressed by adding mass to the end of the piezoelectric element, and the effective length of the ultrasonic wave transmitting / receiving section of the piezoelectric element is controlled. An excellent ultrasonic probe can be provided.

[Brief description of the drawings]

FIG. 1 is a plan view of an ultrasonic probe explaining one embodiment of the present invention.

FIG. 2 is a side sectional view of an ultrasonic probe explaining one embodiment of the present invention.

FIG. 3 is a side sectional view of an ultrasonic probe illustrating another embodiment of the present invention.

FIG. 4 is a side sectional view of an ultrasonic probe explaining still another embodiment of the present invention.

FIG. 5 is a front sectional view of an ultrasonic probe explaining a conventional example.

FIG. 6 is a side sectional view of an ultrasonic probe explaining a conventional example.

FIG. 7A is a view of a coaxial cable, and FIG. 7B is a cross-sectional view of a piezoelectric element.

FIG. 8 is a schematic circuit diagram illustrating a problem of the conventional example.

FIG. 9 is a schematic circuit diagram illustrating a problem of the conventional example.

[Explanation of symbols]

1 piezoelectric element, 2 backing material, 3 electrodes, 4 acoustic matching layer, 5 acoustic lens, 6 coaxial cable, 7 solder.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G047 BA03 BB01 BB04 CA01 EA05 GA00 GA02 GB00 GF18 4C301 EE06 GA03 GA20 HH13 HH27 HH60 5D019 AA00 AA21 BB18 EE05 FF04 GG02 GG03 GG05

Claims (1)

[Claims] 1. An ultrasonic probe wherein a vibration is suppressed by adding mass to an end of a piezoelectric element, and an effective length of an ultrasonic wave transmitting / receiving section in said piezoelectric element is controlled.