JPS59202059A - Probe for ultrasonic tomographic apparatus - Google Patents

Abstract

PURPOSE:To easily fabricate a probe for an ultrasonic tomographic apparatus without generating the deterioration of capacity and without requiring multiple concentric circle processing, by forming a circular and a ring shaped electrodes so as to cover a large number of vibrators which are provided to a disc shaped piezoelectric material and by forming straight grooves to said piezoelectric material in a crossing state. CONSTITUTION:Crossing straight grooves are provessed to disc shaped piezoelectric ceramic 12 to form vibrator parts 14 in a mozaic pattern. A disc shaped electrode 17a and ring shaped electrodes 17b, 17c, ... concentric to said electrode 17a are provided to the surface of said ceramic 12 to which the grooves are not formed to be adhered to a sound absorbing material 6 while a common earthing electrode 15 is provided to the other surface of the ceramic 12 to form a probe. By this constitution, the probe for an ultrasonic tomographic apparatus which is prevented from the deterioration of capacity and focuses ultrasonic beam to the central point thereof is obtained without subjecting the piezoelectric material to multiple concentric circle processing.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a probe for an ultrasonic tomography apparatus in which a vibrator or its electrode is divided into concentric circles (rings).

Conventional probes of this type (annual array probes) are
As shown in FIG. 1, vibrators 1 to 5 made of a piezoelectric ceramic made of PZT or the like, having a central disc shape and a plurality of annular shapes concentrically arranged around its outer circumference, are electrically connected to each other. They are completely mechanically separated and placed on the sound absorbing material 6 (see FIG. 2).

Ultrasonic tomographic image formation using this type of probe will be explained with reference to FIG. 2. In FIG. 2, 1 to 5 are transducers, 6 is a sound absorbing material, and P+-Ps is the center point in the radial direction of the transducers of electrodes attached to the front and back surfaces of the transducers 1 to 5, respectively.

Here, the electrodes on the front surface (lower surface in the figure) of vibrators 1 to 5 are commonly connected and grounded as ground electrodes, and the electrodes on the back surface (upper surface in the figure)
The electrodes are electrically separated and connected to the output terminal of the pulse voltage generator 7 and the input terminal of the delay circuit 8, respectively, as vibrator selection drive electrodes. 9 is a timing circuit, 10 is a control circuit, and 11 is an adder.

In such an ultrasonic tomography device, a point O in front of the probe
The operation when focusing the ultrasonic beam on is explained below. Now, draw an arc with the point O as the center and the distance connecting this point O and the center point P5 of the outermost annular vibrator 5 as a radius, and draw a straight line passing through the center points P1 to P4 of each of the vibrators 1 to 4. O
P'+ r P'2 H\
Let s + P'a.

Under the above premise, PI PS+ P2 P4. Ps
P≦, P4 If each transducer 1 to 5 is driven with a delay corresponding to the time that the ultrasonic wave propagates between each PI3, the ultrasonic wave transmitted from the transducers 1 to 5 will be at point O. will arrive and converge at the same point in time. Here, the timing circuit 9 controlled by the control circuit 10 generates a timing signal corresponding to the above-described time delay, and drives the pulse voltage generator 7 to perform the above-described focusing operation.

On the other hand, in order to focus on point O and receive the echo signal, each transducer 1 to
After applying it to the signal from 5, it can be added. That is,
If the signals from point O are added in the adder 11 in the same phase, the echo signal reflected from point O will have the maximum sensitivity. The delay circuit 8 performs the delay at this time.
This delay circuit 8 is designed so that the position of the point O (focal point) can be moved arbitrarily, so that its delay time can be changed as appropriate by a signal from the control circuit 10.

Through the operations described above, the cyanular array probe has the advantage of being able to move its focal point to an arbitrary point, and can form a clear ultrasonic tomographic image over a wide field of view. In addition, this type of probe has an axis that passes through its center.
Since the ultrasonic waves are focused axially symmetrically, there is an advantage that artifacts are less likely to occur.

As mentioned above, the ultrasonic tomography apparatus using the above-mentioned probe has excellent performance (advantages), but the above-mentioned probe has a single disk-shaped structure as shown in Figs. It requires a vibrator 1 and a large number of annular vibrators 2 to 5. However, these vibrators 1 to 5 are difficult to process because they usually use piezoelectric ceramics.

In particular, processing becomes extremely difficult when increasing the number of annular oscillators to improve performance, or when making the width between each oscillator minute to manufacture small diameter probes for high frequency applications. Ta. In other words, the ultrasonic machining method is usually considered to be the most practical for the above-mentioned machining, but even with this machining method, the machining speed is slow, the machining cost is high, and the cutting between each vibrator is difficult. The groove width could not be made narrow enough, making mass production difficult.

Further, when PZT is used as a vibrator, depending on the setting of the radial width of the annular vibrator, unnecessary vibration in the radial direction may occur in addition to vibration in the thickness direction of the vibrator. Therefore, in order to suppress the unnecessary vibrations, it is necessary to divide more annular transducers, regardless of improving the performance of the probe, which further increases the manufacturing cost and reduces mass production. became difficult.

The present invention has been made in view of the above-mentioned circumstances, and aims to provide a probe for an ultrasonic tomography device that can be easily mass-produced without deteriorating performance and that can significantly reduce manufacturing costs. purpose.

The present invention will be described in detail below with reference to FIGS. 3 to 6. FIG. 3 is a sectional view showing a main part of an embodiment of a probe for an ultrasonic tomography apparatus according to the present invention, and FIG.
■ Line sectional view, Figure 5 is the ■ - V line sectional view in Figure 6, 1
In each figure, 6 indicates a sound absorbing material as in Fig. 2. 12 is a disk-shaped piezoelectric ceramic made of PZT, lead titanate ceramic, etc. Third
A large number of transducer sections 14 are formed in a mosaic pattern by providing a large number of linear grooves 16 intersecting each other on the lower surface in the figure. Here, as shown in FIG.
A large number of square-shaped vibrators 14 are provided parallel to each other at regular intervals in the vertical and horizontal directions in the figure, that is, in the shape of a base grid.
is formed. In this case, the valley grooves 13 are formed at such a depth that the piezoelectric ceramic 12 is not separated by the grooves 16, as shown in an enlarged view in FIG. In this way, even if each vibrator part 14 is not completely separated mechanically by the groove 16, the thickness vibration of one vibrator part 14 will be affected by the thickness vibration of the other adjacent vibrator part 14, as in the case of complete separation. It is known that there is little chance of propagation and influence on
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A thin common electrode 15 is formed to cover the plurality of vibrator sections 14, and is used as a ground electrode. Reference numeral 16 denotes an electrode that is uniformly deposited on the piezoelectric ceramic 12 before it is processed as described below.

Reference numeral 17 denotes a vibrator selection drive electrode, which connects the piezoelectric ceramic 12
A circular electrode 17a is formed covering the center of the other side surface (upper surface in FIG. 3) of the circular electrode 17a, and a circular electrode 17a is attached to the outer circumferential side of the circular electrode 17a, concentrically therewith and spaced apart from each other by an appropriate amount. It consists of a plurality of annular electrodes 17b to 17e, here four. The mutual spacing between the electrodes 17a to 17e is arbitrarily set within a range that does not interfere with electrical isolation between the electrodes.

Reference numeral 18 denotes lead wires led out from the electrodes 17a to 17e.

In the probe of the present invention having the above-mentioned structure, a circular or annular sound source (vibrator) that is almost equivalent to the disk-shaped piezoelectric ceramic is not cut into many concentric circles as in conventional probes. Can be configured. That is, there is one group of vibrator parts corresponding to each position of the circular and annular electrodes 17a to 17e.
For example, when a voltage is applied to the electrode 17e, the vibrator group in the area indicated by a notch in FIG. 5 is excited. in this case,
As the number of grooves 13 in each direction increases and the vibrator portion 14 is formed finely, a circular or annular sound source that is close to a perfect circle is formed, and the sound source is approximated to a circular or annular vibrator. Usually, a dicing saw used for industrial purposes is used to form the grooves at a frequency of 4.3.5 MHz to 5.0 MHz.
The piezoelectric ceramic disk that becomes the PZT vibrator of z is 0.2
It is not difficult to process a large amount of grooves with a pitch of mm to 0.3 mm and a minimum button width of microns. Therefore, according to the present invention, a probe very similar to an annular array probe consisting of one disc-shaped vibrator and multiple annular vibrators can be obtained industrially easily and at low cost. Become.

An example of a method for manufacturing the above-mentioned probe of the present invention will be described below.

First, a disk-shaped piezoelectric ceramic made of PzT or lead titanate ceramic is prepared. Silver electrodes (16, 17) are baked on both sides of this piezoelectric ceramic, and by mechanically cutting the silver electrodes (17) on either side, an electrode 17a as shown in FIG. 4 is formed. ~1
Form 7e. This cutting of the electrode may be performed by a photoetching method. In addition, the formation of the electrodes 17a to 17e involves applying a fourth ink containing silver to one side of the piezoelectric ceramic.
This may be done by screen printing the shape shown in the figure and then baking it. It is also possible to use a vapor deposition method using an electrode-shaped mask.

Next, the sound absorbing material 6 is bonded to the surface of the piezoelectric ceramic on which the electrodes 17a to 17e are formed by the method described above. The sound absorbing material B is bonded to the piezoelectric ceramic electrodes 17a to 17 using a mold made of epoxy resin or silicone rubber mixed with metal powder.
e It may be carried out by pouring it onto the forming surface, and
Alternatively, a pre-formed silicone rubber containing metal powder may be adhered onto the surfaces of the piezoelectric ceramics on which the electrodes 17a to 17e are formed.

In any case, the lead wires 18 can be led out from each electrode 17a to 17e.

In the next step, the piezoelectric ceramic having the sound absorbing material 6 bonded to the back surface thereof is cut into grooves 1 in the shape of the base grain, as shown in FIG. 5, for example. The depth is set to such an extent that the piezoelectric ceramic is not mechanically separated by cutting the groove, as shown in FIG.

A large number of vibrator parts 14 are formed in sections by the above-mentioned groove cutting, and then a single sheet is cut on the whole vibrator part 14, more specifically, on the silver electrode 16 on the front surface of the vibrator part 14. A conductive plastic thin plate is joined to form a common electrode (ground electrode) 15.

In addition, as shown in FIG. 6, inside the groove 13, a soft material,
For example, if the surface of the piezoelectric ceramic 12 on the side where the vibrator portion 14 is formed by filling it with silicone rubber 19 is made substantially flat,
The common electrode 15 can be easily formed by applying a conductive paint on the plane.

In the above-mentioned embodiment, the base material is cut by first cutting a large number of straight grooves in parallel at equal intervals in one direction, and then cutting a large number of linear grooves at equal intervals in a direction perpendicular to the first direction. Although one vibrator part 14 is formed into a square shape except for the outermost circumferential side, it is not limited to this, and other shapes such as rectangular cedar, triangle, or rhombus, etc.
It may be formed into various shapes. Regardless of the shape, the same effects as in the above-mentioned embodiments can be obtained.

As described above, the present invention does not require any separation process such as cutting to draw multiple concentric circles on the piezoelectric material, but only requires the process of forming linear grooves, making it easy to mass-produce. This has the effect that the manufacturing cost can be reduced to within a certain range. Moreover, in this case, the performance of the probe can be made almost the same as that of the conventional probe, as described above.

[Brief explanation of drawings]

Fig. 1 is a front view of the main parts of a conventional probe, Fig. 2 is a circuit diagram of an ultrasonic tomography apparatus in which the same probe is used, and Fig. 6 is a diagram of a probe for an ultrasonic tomography apparatus according to the present invention. 4 is a sectional view taken along the line IV-IV in FIG. 6, FIG. 5 is a sectional view taken along the ■-V line in FIG. 6, and FIG. FIG. 7 is an enlarged cross-sectional view of a main part of another embodiment of the feeler. 6...Sound absorbing material, 12...Piezoelectric ceramic, 16...
・Groove, 14... Vibrator part, 15... Common electrode, 17
．． 17a-17e... Vibrator selection drive electrode, 18...
·Lead. Patent applicant Hitachi Medical Co., Ltd. Agent Patent attorney Tadashi Akimoto Figure 6

Claims (1)

[Claims] A disc-shaped piezoelectric material in which a large number of vibrator sections are segmented by providing a large number of intersecting linear grooves on one surface, and a piezoelectric material formed on one surface of the piezoelectric material. A common electrode formed to cover a large number of vibrator parts, a circular electrode formed to cover the center of the other side of the piezoelectric material, and an outer peripheral side of the circular electrode arranged concentrically with the common electrode. 1. A probe for an ultrasonic tomography apparatus, comprising a plurality of annular electrodes, and a transducer selection driving electrode in which the electrodes are electrically separated.