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The present invention relates to a stacked probe capable of transmitting and receiving multiple
frequencies u. A probe has been developed which stacks different types of piezoelectric elements,
each operating at different frequencies, and transmits and receives ultrasonic waves in that
stacking direction. EJ, this type of probe is identical temporally and spatially and It has the
advantage of being able to transmit and receive all ultrasonic waves of different product
frequencies. In this type of probe, there is a type in which the first layer on the sample side is an
organic piezoelectric material PVDF, the second layer after that is an endless piezoelectric
material PZT, and the layer VC after that is a backing material. However, in general, the organic
piezoelectric material has lower electric-acoustic conversion efficiency, that is, sensitivity to
ultrasonic wave transmission and reception, as compared with the silent piezoelectric material. It
is an object of the present invention to obtain a multi-frequency, multi-layered ultrasonic probe
with inorganic piezoelectric materials having high sensitivity. That is, the ultrasonic probe which
transmits and / or receives multiple piezoelectric materials t j 141 q multiple piezoelectric
materials from each layer to a pair of Mi 廿 匝 異 な る different from each layer, the
piezoelectric materials are respectively acoustic What is an inorganic pressure 'turtle material
with different impedances, and is selected so that acoustic impedance becomes larger or smaller
sequentially from the archaeologist to the fractured side? Although it is characterized, it will be
described in detail with reference to the drawings. FIG. 1 shows an embodiment of the present
invention. In this figure, 12 is an inorganic piezoelectric element, the former being
lithium sulfate and the latter being PZT. tl to t3 are electrical terminals of the piezoelectric
element, 14 is a backing material (Eboxy with gold powder), and 16 is an acoustic matching layer
made of epoxy resin. These constants in the following table? Show. In this table, 2 is an acoustic
impedance, and a unit is 106I # / m′′a (hereinafter, unit frequency will be omitted), and fr is a
resonance frequency 11 frequency. λ / 2 resonance · · ·: The wave number is V / 2tT, where
the speed of sound is k V × thickness Vi-t. Pressure "ai! * Rumors, as shown in the figure of 10
children and 0 children, are subjecting to idiom dance conversion. The electrical impedance of
the element 10.12 of the constants of Table 1 is about 500 for the element 12 while the value of
the element 10 is 20 times or more of that. Therefore, as shown in FIG. 2 (b), the transformer 10
has a winding ratio of 1: 5 (totally added to the element 10, and is made to be similar to the
electrical impedance element 12). As a result, the same efficiency and bandwidth were obtained
for both elements 10.12. The ultrasonic wave transmission and reception characteristics of such
a probe 20 are shown in FIG. In FIG. 3, the horizontal axis is frequency (MHz) and the vertical
axis is gain (dB). A indicates the PZT EETit element 12, and B indicates the lithium sulfate
piezoelectric element 10.
As apparent from this graph, the element 10 operates near 3.5 MHz and the chord 12 operates
near 2.2 MHz, and since the valley frequency band is separated, the ultrasonic waves of the
frequency of the number of units are simultaneous. Send, receive aJ 岨, cough! -Agility i wave
search · + r f-is obtained, ::: · · · 1 In the case of the laminated probe m '-+, it is necessary to make
the acoustic impedance of the piezoelectric element different, and in the case of employment as
such, the vibration in which Takinoko is united is the main and can operate only at fist frequency.
In this respect, the acoustic impedance of the cord 10 of FIG. 1 is 11.2 and the element 12 has a
clear wrinkle at 32.0, and simultaneous operation at different frequencies is possible. In addition
to PZT, acoustic impedance 2 of about 50 is P CMlLi Nb 03 * BIL Tl 0m * PbT 10 B, etc., and 2 of
about 10 is K other than lithium sulfate and quartz is a probe. You may make a combination of
The arrangement order of the elements 10.12 is determined in accordance with the acoustic
impedance of the sample (target to be detected). That is, when the sample is a human body, the
acoustic impedance 2 is about 1.5, so as shown in FIG. When the order is accepted, a large
difference in acoustic impedance occurs between P Z T and the sample ln J, which causes J! Ii =
loss due to wave reflection is%. Contrary to FIG. 1, when the specimen has a large size of 2 as in
the case of flaw detection, etc., the surface side is made larger in size by 2 larger in size, and the
PZTX-extention of 2 is made smaller in lithium sulfate. In this way, there is no part where there is
a difference in Z K 4 L, and ultrasonic transmission and reception with small reflection loss
becomes possible. In the probe 20 of FIG. 1, 2 of the piezoelectric element on the surface side is
11.2, and when the sample is a human body, there is a slight difference with respect to 1.5. The
acoustic matching layer 16 compensates for this. With the zfiao of the matching layer 16, the
button can improve the alignment of the human body with 1 ° 5. Therefore, no further
reflection occurs. If ZK has a large difference and reflection occurs at the boundary, the reflection
is repeatedly generated at the boundary, and one ultrasonic wave also emerges as a plurality of
waves. This reduces the resolution and is not preferable for diagnosis and flaw detection. In
addition, although the thickness of the matching layer generally matches the λ / 4 resonant
frequency to the operating frequency, since different frequency ultrasonic waves come and go in
the laminated probe, there is a problem in which frequency the λ / 4 resonant frequency is
combined . FIG. 4 shows the experimental results obtained by determining the appropriate
thickness of the acoustic matching layer, the vertical axis represents the thickness represented
by λ / 4 resonance frequency, and the vertical axis represents the wave number up to 120 dB
Further, as shown in FIG. 4, the wave number is the wave number n of the ultrasonic wave until it
reaches 120 dB, that is, 1/10 of the amplitude after reaching the maximum amplitude at P, and
this is preferably as small as possible. The curve IIICF; j shows the characteristics when the PZT
element 12 is operated alone, and the curve shows the characteristics when the lithium sulfate
element 10ft is operated alone. From these, the thickness ranges from E1 λ / 4 resonance
frequency to five five It turns out that it is the best at -2.5 MHz. This frequency corresponds to an
intermediate frequency of 15 MHz and 2.2 MHz in this example. In the present example, the
matching layer 'tI layer is used, but it can be easily guessed that the same effect can be obtained
with two or more layers. As described above, according to the present invention, it is possible to
provide a multi-frequency, high sensitivity, laminated ultrasonic probe based on only the
inorganic piezoelectric material K, which is extremely effective.
Brief description of the drawings
FIG. 1 is an explanatory view of an ultrasonic probe according to the present invention, □, 'FIG. 2
is a circuit diagram of a part of a dry drier of the piezoelectric rope, and FIGS. 3 and 4 are
characteristic planes- FIG.
In the drawing, 10.12 is a pressing material, U8W is an ultrasonic wave, 20 is an ultrasonic
probe, and 16 is an acoustic matching layer. Applicant: Fujitsu Limited Attorney Attorney Akira
Akira Akira Procedure correction (voluntary) 1. Display of the case Patent application Patent
application No. 173189 2 name of the invention ultrasonic probe 3 relationship with the case to
make correction Patent applicants residence 1017 name Kamiedanaka Nakahara ward Nakazaki
Ward Kanagawa Prefecture (522) Fujitsu Takuya Yamamoto, a shareholder of the stock meeting,
agent T "101" Claims in page 1 line 5 to 19 are amended as follows. [(1) In an ultrasonic probe
which laminates a plurality of piezoelectric materials and transmits and / or receives ultrasonic
waves of different frequencies from each layer to an object, the piezoelectric materials are
inorganic piezoelectric materials having different acoustic impedances. An ultrasonic probe
characterized in that the array is selected such that the acoustic impedance becomes larger or
smaller sequentially from the object side. (2) At least one layer of the piezoelectric material
comprising the first piezoelectric material operating at the first frequency and the second
piezoelectric material operating at the second frequency, provided on the target object side of
these stacked piezoelectric materials The thickness according to λ / 4 resonance frequency of
the acoustic matching layer of the present invention is made to coincide with the frequency
between the first frequency and the second frequency. Sound wave probe. 」
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