JPS58159735A - Ultrasonic probe - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic probe used in an ultrasonic pulse echo system.

Most conventional ultrasonic probes use a transducer formed from a standard square bar array that utilizes 35-mode thickness vibration, but they generally have the following drawbacks: .

(1) Since it is based on the technical concept of Q-dumping or multimodal processing based on resonance, it is essentially difficult to widen the band.

(2) Since the direction of wave transmission and reception and the direction of applying the electric field are the same, it is necessary to take out the lead wires from both the front and back sides of the original plate-shaped vibrator that forms the square rod array, and there are complications such as wrap-around electrodes. A method is required.

(5) When PZT is used as the vibrator material, it is necessary to deeply cut a large number of grooves to suppress coupling in the lateral direction. In the case of normal switched array linear scanning, the appropriate table required for the scanning procedure is NILEMEN F width X IE
% 3-3 minute elements with widths of 1/3 to 115 times
It is necessary to make a large number of grooves so that five pieces can be made in parallel and used as each element.

In view of these points, it is an object of the present invention to provide an ultrasonic probe having a simple structure, easy to manufacture, and applicable to wideband 7-ray sector scanning. be.

The present invention was developed by Van der Hoop (Van der P.
A plurality of stripe-like electrodes or island-like electrodes are formed on the surface of a piezoelectric material so as to form a auw type resonator, and the piezoelectric material is polarized using these electrodes to form a resonator array. It is something to do.

The present invention will be described in detail below using the drawings. First, we will explain the van der Hoop type transducer's W and fill. FIG. 1 is a diagram showing its basic configuration. A normal vibrator has electrodes on both sides of a piezoelectric plate and applies an electric field to the entire volume of the ink to access it from only one side of the ink. 1lrK is formed by disposing striped electrodes 1□, 2□ to 1n, - at equal intervals, and connecting every other electrode in common to apply a voltage.

Since the distribution of the applied signal voltage and the polarization of the piezoelectric material 5 are the same in all parts, the electrical and acoustic couplings are all in the same direction, and the ultrasonic pulse is directed in the direction perpendicular to this electrode group. (in the direction of the arrow in the figure) wavefronts are exchanged. In the case of surface waves (SAWs), the polarization is constant everywhere, and the transmitted and received electric fields are reversed for each stripe gap, so the traveling wave coupling that stays in the plane is the strongest, and the bulk in the direction perpendicular to the plane Waves are, at least in principle, completely opposite to non-occurrence.Therefore, SA
W) In the case of a transducer, coupling occurs primarily in the gaps between the stripes, whereas in the van der Hoop transducer, coupling occurs directly beneath the electrode stripes, resulting in only unidirectional coupling between the stripes and the stripes. Stop. In addition, if the d31 of the material is too strong even directly under the main stripe, lateral coupling becomes noticeable, impairing the fundamental impulse response, and may also cause resonance due to the lateral length of the entire bulk. So I don't like it.

Therefore, rather than the size of d33 itself, the d3 of '31
Materials with a lower ratio of P to 3, specifically P than PZT.
Much more preferred are bTiO3 and the like.

The most noteworthy feature of the Van Bleuhope transducer is its excellent impulse response. Although the bidirectional operation loss is somewhat inferior, the waveform generated in response to the step excitation becomes almost impulse-like even if it passes through the two transmitting and receiving locations. At DC and sufficiently high frequencies, the response converges to zero, so it exhibits a very wide bandpass characteristic.
The same is true for a fully backing bulk plate transducer.

In addition, the pitch between the electrodes may not be constant, but may be non-uniform (such a distribution is very effective in suppressing unwanted modes other than Iwayu).

Note that the van der Hoop structure can be used not only for striped electrode groups but also for surface distribution electrodes. 4? Additionally, it is also possible to realize mosaic-like, independent stripe-like or independent island-like electrodes. And from the stripe group, Rini J
- A two-dimensional play can be formed from a mosaic electrode or from a mosaic electrode. Shown in Figure 2. That is, stripe electrodes 1□, 2
Of □ to 1n+□ and 2n, 1□ to 1n+1 are commonly grounded, and the electrodes of the other 2□ to can be individually applied with driving voltages. When the electrodes 21 to 2n are driven individually,
Since the electric field under each stripe has at most no lines of electric force extending to the ground stripes on both sides, each stripe operates sufficiently independently even in a planar structure. From an acoustic perspective, the area directly below each derived stripe and about half of the stripes on both sides of it are considered to contribute to wave transmission and reception as elements. f of the Van der Pove combination. In other words, if you want to make the polarization depth independent, as shown in Figure 5, several independent stripes should be
Just bundle them together as a set. As the number of bundled wires increases, the depth of polarization becomes shallower ((r(,) can be made higher ().

Further, in order to improve the ratio between the polarization depth and the element pitch without grounding the stripes, there is a method shown in FIG. 4. That is, the transformer converts the signals of several independent single-wire grounding lines of coaxial cables into signals of the differential pressure between the stripes. In this case, even if the signals of all elements are added together, if the in-phase component is not dominant, there is a much greater possibility that they will cancel each other out, and a pair of stripes will absorb the potential difference between them from the other elements on the left and right. Even though they are distributed across all stripes, they themselves effectively function as a single element. At this time, both the drive source and the receiver connected to the other end of each transformer have low impedance. FIG. 85 shows a switching linear scan type scanning device to which this concept is applied.

That is, each stripe is connected to a switch S1 individually.
~One transformer T via Sm+□. Connect K.

Odd-numbered switches and even-numbered switches are connected in common, and a plurality of adjacent switches (for example, 7 or 8 switches) are simultaneously driven and scanned one by one. In this case, the number of odd-numbered and even-numbered switches to be selectively connected at the same time must be approximately the same. If this is not followed, it will become vulnerable to common mode noise and will also have a negative effect on the degree of contribution of each element.

FIG. 6 shows a switch trilinear scan system having an electronic focus function.

Monoke shown in Figure 6, primary switch Sp shown in Figure 5
(81~Sm+1) KAdditional secondary switch (18x8 cross point switch is shown here)s
It is configured so that near scan can be performed by adding $ and using eight elements as aperture holes. The technique of appropriately selecting the target element using the primary switch and the secondary switch is well known.A delay-in group DL for applying electronic focus is connected to the eight signal lines of @Aperture Your. The trap is designed to apply a time delay to the transmitted and received signals. Nine polarity switching transformers T are connected in series to the pulsar PL or summing amplifier ASK to this delay line group DL, so that positive and negative voltages alternately act on the selected element arrangement. There is. Note that if the pulser PS gives bipolar pulses to each delay line and the receiving summing amplifier As has a differential input, use these functions to omit the polarity switching transformer. Can be done. Further, the polarity changing transformer may be inserted and connected between the delay line group and the secondary switch. Furthermore, phased
When applied to the case of array sector scan, the color is the seventh
As shown in the figure, each element has a polarity changing transformer T.
It is better to insert Each transformer T has a pair of pulsers PS
and amplified good people are connected. Each pulser pS is phase driven by a transmission delay line DL1, and each amplification i
The received signals of the s people are guided to the adder ASK via the receiving delay line DL2 whose delay time changes like the transmitting delay line DL□. Of course, pulser PS1 amplifier A
If s has the above-mentioned function, the transformer T can be omitted.

As explained above, according to the present invention, van der
By adopting a pove-type electrode structure, it is possible to realize a broadband ultrasonic probe with a simple structure and easy manufacturing.
It is possible to realize an ultrasonic probe that can be easily applied to sector scanning.

[Brief explanation of the drawing]

Figure 1 is a block diagram for explaining the principle of a van der Bove type transducer, Figure 2 is a block diagram of an embodiment of the ultrasonic probe of the present invention, and Figures 3 to 7 ( is!l is another embodiment diagram of the present invention. 11, 21~"n+1' 2m...stripe electrode,
3... Piezoelectric material, 81~Srn+1... Switch,
DL...Delay line p, PL...Pulsa, A8
...Summing amplifier, To...Transformer, T...Polarity conversion transformer.

Claims (1)

[Claims] (1) An ultrasonic probe in which a plurality of electrodes are formed on one surface of a plate-shaped piezoelectric material, and the polarities of polarization directly under adjacent electrodes are opposite to each other. . (2) The ultrasonic probe according to claim 1, wherein the electrode is a striped electrode or an island electrode. (5) Every other electrode is grounded as a common connection. The ultrasonic probe according to claim 1, characterized in that the remaining electrodes every other Ilm are independent electrodes. (4) A plurality of adjacent electrodes among the remaining every other electrode The ultrasonic probe according to claim 5, characterized in that the electrodes are commonly connected to form independent electrodes. (5) The ultrasonic probe according to claim 1, wherein all of the electrodes are formed as independent electrodes.