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Specification 1, Title of the Invention 2, 11% Claim (1) A piezoelectric material having an
interdigital electrode on the surface is placed such that the electrode is in contact with the liquid,
and AC signals and ultrasonic waves applied or induced to the electrodes The interdigital
transducer has a uniform electrode cycle, and alternating electrical signals are selectively applied
to the interdigital transducer, and the selected electrode fingers are sequentially arranged along
the arrangement of the electrode fingers. An ultrasonic conversion method characterized by
generating an ultrasonic beam emitted in a predetermined direction from an interdigital
transducer and displaced in time by moving it. -(2) The invention according to claim 1, wherein
the radiation direction of the ultrasonic beam is changed by changing the frequency of the
alternating current electrical signal.
Ultrasonic conversion method
3. Detailed Description of the Invention The present invention relates to a method and transducer
for generating or detecting ultrasound used in an ultrasonic apparatus, and more particularly to a
method and transducer for generating or detecting parallel beam ultrasound. Even in optically
opaque media, as long as they are acoustically transparent, observation of fluoroscopic images by
acoustic waves is possible as in fluoroscopy by X-rays. The ultrasound imaging of the optically
opaque body 5 can be applied to the fields of medical diagnosis, microscopy, nondestructive
inspection, observation of bottom pattern, and earthquake research. As conventional ultrasonic
transducers, one using an acoustic phase plate, one using an annular array, one using an 0
acoustic lens, one using a light-acoustic transducer, and the like have been proposed. However,
the fact is that there is still room for improvement in terms of the characteristics of the sound
wave necessary for ultrasonic imaging. Furthermore, although the conventional transducer is
premised on focusing the excited 15 ultrasonic beams, even non-convergent parallel beams can
be used for acoustic imaging by moving the beams. Conventional devices of this type add an
EndPage: 1 combination of a plurality of transducer elements with bulk oscillations (two parallel
beams to be emitted, and at the same time, the signal processing technique is used to move the
transducer to which the electrical signal is applied. By moving the parallel beam from the sound
source in the X-axis direction. However, in this conventional method, there is a problem in
manufacturing reproducibility because a technique of mechanically cutting and dividing one
piezoelectric material is used in producing a transducer consisting of a large number of elements.
The upper limit of the frequency used was limited. Accordingly, the present invention aims to
ameliorate the above-mentioned drawbacks of the prior art, wherein the% is arranged with a
piezoelectric material having uniformly spaced back electrodes on nine surfaces such that the
electrodes are in contact with the liquid Ultrasonic wave moved from the sound source in the Xaxis direction (arrangement direction of the electrode fingers) by selectively applying an
alternating electric signal to the interdigital electrodes and sequentially moving the selected
electrode fingers along the arrangement of the electrode fingers The generation method and the
ultrasonic detection method according to the same principle. This will be described in detail with
reference to the drawings. FIG. 1 is a structural example of a convergent ultrasonic transducer
according to the present invention, in which a liquid 2 is produced in a container 1 and a
piezoelectric substance 3 having an interdigital electrode 4 on the surface 9 is produced in the
liquid. . As a liquid. Water, ether, acetone, glycerin and the like are possible. The electrode 1 is a
single-phase electrode in which tooth-shaped electrodes of <Ls and <Ls are alternately
interdigitally arranged in FIG. 2 (A), and an alternating current signal is applied to the terminals
(C) and (αL) And, as shown in Fig. 2 (E), the interdigital electrodes are connected to every third
electrode, and a three-phase AC signal is applied from the terminals (α,,), Cbi,) and (C force). It is
possible to use three-phase electrodes that are connected together or multi-phase electrodes in
which n (B is a natural number of 4 or more) electrodes are connected to one another to mark an
n-phase AC signal.
In the case of a single-phase electrode, two ultrasonic beams are generated in both directions
(the solid line and the dotted line in FIG. 1), while in the case of a three-phase electrode, one
ultrasonic beam in a single 15 directions is obtained. . For example, a combination of Or and Au
as a material of the electrode is strong in water resistance and good. The electrodes may be
formed on the piezoelectric plate by photolithographic methods or may be deposited by
evaporation through a photolithographically formed mask. As the piezoelectric material, idL,
NbO, quartz, n 3112 G, 0.. . OTPZT-based porcelain (for example, 91A material manufactured by
Tokyo Electric Chemical Industry Co., Ltd. 0) can be used. The period of the electrode (the
relationship between J and the direction (θ) at which the ultrasonic beam is emitted in the
maximum direction) is determined by dSinθ = λr / li (λf is the wavelength of the sound wave
of frequency f in the liquid). From this equation, it can be understood that if the electrode period
('tt) is made uniform, a parallel ultrasonic beam with a force direction can be obtained from the
interdigital electrode. In addition, it is understood that the radiation direction θ is changed by
changing the periodic mantissa. Next, the experimental results of the beam radiation 24 ° θ for
each combination of piezoelectric material and liquid are shown in the following table. From this
table, in order to reduce the value of θ, a combination of a liquid having a slow sound velocity
and a piezoelectric having a high surface wave propagation velocity is combined. I understand
that it is good. FIG. 3 (A) shows the time relationship of the application of alternating current
signal to the electrodes in the case of the single-phase electrode of FIG. 2 (A), arranged in the X
axis 5 direction (direction of arrangement of electrode fingers 1j). Electrodes (a, α2.α5. An
alternating current signal is selectively applied sequentially to... As shown in FIG. 3 (A). Therefore,
the ultrasonic beam generated from NCi moves temporally in the X-axis direction. As a circuit of
10 for applying such an alternating current signal, for example, each tap of the delay line with a
tap is connected to one of (α1.α2.α3. The three-phase electrode (two applied voltages) of FIG.
3 (screaming FIG. 2 (t,)) which can correspond to... An alternating current signal of the same
frequency having a phase difference of 120 ° from each other is applied to the electrodes α, b,
C and 15 arranged at every third wire, as shown in FIG. At the moment when time passes, an
alternating voltage is applied to only three electrodes as indicated by hatching in the figure.
Although FIG. 2 (A) exemplifies a configuration in which three pairs of electrodes are added to
one section and EndPage: 2, the electrodes are not fixed sections (= connection terminals with
signal processing taps are 1: 1̶ If it is connected with, it is possible to shift the beam in the
more precise X-axis direction. As an experimental example of the present invention, the bundle
has an electrode period of 856 μm on the surface of a piezoelectric ceramic 91A material
(polarization perpendicular to the substrate surface, length 70 M1, width 20 mm, thickness 6
mm) manufactured by Electrochemical Chemical Co., Ltd. Make an interdigital electrode with a
width of 10 and a width of 10, and let water come in contact with the electrode as a liquid.
It was observed that a good collimated sound beam was emitted by applying a high frequency
pulsed electrical signal. At the same time, when the carrier frequency of the high frequency pulse
was changed, the direction θ of the sound beam from the transducer changed as shown in FIG.
Thus, by changing the frequency, the direction of the acoustic beam can be electrically changed.
As described above in detail in the embodiments, by applying a high frequency signal to the
interdigital electrodes of uniform period while switching the electrodes in order, it is possible to
generate an ultrasonic beam whose beam moves in parallel. Although the above embodiment has
mainly described generation of ultrasonic waves, ultrasonic waves can be detected by the same
structure to obtain corresponding AC signals.
4. Brief description of the drawings Fig. 1 shows an example of the structure of the ultrasonic
wave generation (detection) device 5 according to the present invention, Fig. 2 (A) and Fig. 2 (B)
(example of structure of interdigital transducer, Fig. 3 (A) and FIG. 3 (B) 1 / Ji The time
relationship lx of the alternating current signal applied to the interdigital electrode, FIG. 4 is a
graph showing the direction of the beam and the frequency applied to the two waves. 101;
container, 2; liquid. 3; Piezoelectric substance, '4; interdigital electrode. Patent applicant 15
Tokyo Electric Chemical Industry Co., Ltd. Door 1) Koji Patent application agent Patent attorney
Attorney Yamamoto-ka / 隼 2 "W tan Fig. 2 (B ') α t-→ to t (MHz) EndPage: 3
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