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JPS61278297

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DESCRIPTION JPS61278297
[0001]
[Technical Field of the Invention] The present invention relates to improvement of an ultrasonic
probe for generating and detecting ultrasonic waves used for medical ultrasonic diagnosis,
nondestructive inspection and the like. [Technical Background of the Invention] Ultrasonic
probes using a piezoelectric imaging element are widely used in medical ultrasonic diagnostic
devices and nondestructive inspection devices. For example, an ultrasonic diagnostic apparatus
generates ultrasonic pulses in a living body, detects reflection echoes from the inside of the living
body, and obtains information from the inside of the living body. In these devices, ultrasonic
probes operating at different frequencies are used depending on the purpose. For example, in the
case of an ultrasonic diagnostic apparatus, an ultrasonic probe in the range of about 2 MH7 to
20 MHz is used as the frequency. In general, the higher the frequency of the used ultrasonic
wave, the higher the resolution, but the attenuation of the ultrasonic wave in the living tissue
becomes larger as the frequency becomes higher. Therefore, when it is desired to obtain
information from the deep part of a living body with large attenuation, a high frequency probe
can not obtain a sufficient reflected signal, so an ultrasonic probe with a low frequency is
required. In order to obtain information on a portion with low attenuation, it is necessary to use
an ultrasonic probe with a frequency as high as possible within the lead range which allows the
resolution (to give the resolution. [Problems of the Related Art] However, since the operating
frequency of the ultrasonic probe is generally determined by the thickness of the piezoelectric
transducer, one ultrasonic probe operates at only one center frequency. That is, ultrasonic probes
having different operating frequencies such as 2.5 MHz, 5 MHz, 7.5 MHz, etc. are prepared, and
they should be replaced according to the purpose, and a plurality of ultrasonic probes may be
used. In addition to the inconvenience of requiring an ultrasound probe, it has the problem of the
complexity of replacement work. The present invention has been made based on the abovementioned circumstances, and an object thereof is to provide an ultrasonic probe capable of
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transmitting and receiving ultrasonic waves of a plurality of frequencies. [Summary of the
invention] In order to achieve such an object, an ultrasonic probe according to the present
invention is disposed by laminating 2M or more composite piezoelectric materials on a backing
material substantially equal in effective acoustic impedance of the composite piezoelectric
materials. An electrode is derived from each layer of the composite piezoelectric body, and
ultrasonic transmission / reception at a plurality of frequencies can be performed without the
need for probe replacement. Embodiments of the present invention will be described with
reference to the drawings. In FIG. 1, reference numerals 11, 12 and 13 denote composite
piezoelectric members having electrodes on the upper and lower surfaces, respectively, and the
polarization directions are laminated in the same direction.
A backing material 14 is disposed by being stacked on the composite piezoelectric body 11 °
12.13. As the composite piezoelectric body 11.12.13, for example, one having a structure in
which a piezoelectric ceramic is cut into strips and the cut grooves are filled with a polymer
material is used. Such a composite piezoelectric body 11.12.13 has an effective acoustic
impedance of 5 to 10 × 10 6 phrases / 麓 · sec although it changes depending on the size ratio
of the ceramic part and the cut / filled part . On the other hand, as the packing material 14, one
having a rubber material mixed with ferrite powder, etc., which has a capacity of 5 × 10′Kg /
condition · sea, is put to practical use. That is, there is a piezoelectric material and a backing
material that are approximately equal in acoustic impedance. Next, the operation of the present
embodiment configured as described above will be described. Now, as a backing material, a
ferrite rubber with an acoustic impedance of about 5 × 10 BKg / ffl · SeC is used, and as a
piezoelectric material, a composite piezoelectric with an effective acoustic impedance of about 5
× 10′Kg / rd-sea is used. The effective sound velocity of the composite piezoelectric material is
σ G, and the thickness of each of the composite piezoelectric material 11 ° 12.13 is tl, t2. It is
t3. When the switch SW is joined to the contact point 21, as shown in FIG. 2, the composite
piezoelectric body 11 serves as a transducer having a thickness tl, and the composite
piezoelectric body 12.13 serves as a part of the backing material. The central frequency i in this
case is approximately f1 = σa / 2t1. Next, when the switch SW is joined to the contact point 22,
as shown in FIG. 3, the composite piezoelectric body 11.12 becomes a thick transducer (t1 + t2),
and the composite piezoelectric body 13 acts as a part of the backing material. The center
frequency bit 2 in this case is approximately 2 = σa / 2 (tl + t2). Similarly, when the switch SW is
joined to the contact 23, as shown in FIG. 4, the composite piezoelectric body 11.12.13 acts as a
thick t1 + t2 + t3) transducer, and the center frequency f3 is approximately f3-.sigma.Q / 2 (t1 +
t2 + t3) It becomes. That is, one ultrasonic probe of FIG. 1 operates as an ultrasonic probe of
three different center frequencies shown in FIG. 2, FIG. 3 and FIG. 4 only by switch switching.
Become. Of course, it is a matter of course that the ultrasonic transmitting and receiving
apparatus joined to this probe must be a system which switches to a frequency corresponding to
the center frequency and transmits and receives in accordance with the switch switching. As
described above, according to the present embodiment, it is possible to operate at a plurality of
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center frequencies with only one switching operation with one ultrasonic probe.
If this is applied to an ultrasonic diagnostic apparatus, ultrasonic diagnosis at different
frequencies becomes possible with switch operation alone without the distortion of ultrasonic
probe replacement, and its practical value is extremely high. In this example, a three-layered
composite piezoelectric material is described, but 3 m! Even if it is above, it is practicable. [Effects
of the Invention] As described above, according to the present embodiment, two or more layers
of composite piezoelectric materials are stacked and arranged on a backing material substantially
equal in effective acoustic impedance of the composite piezoelectric materials, and the above
composite By deriving the electrode from each layer of the piezoelectric body, it is possible to
provide an ultrasonic probe capable of transmitting and receiving ultrasonic waves of a plurality
of frequencies.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a block diagram showing an embodiment of an ultrasonic probe according to the
present invention, and FIGS. 2 to 4 are diagrams for explaining the operation of the embodiment.
11.12.13 ... composite piezoelectric body, 14 ... backing material. Applicant Agent Patent
Attorney Suzue No. 1 Fig. 21
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