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DESCRIPTION JPH04128499

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DESCRIPTION JPH04128499
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
ultrasonic probe used in the medical field, fish school detection field, etc., and more particularly
to the improvement of the transducer structure.
[0002]
2. Description of the Related Art Conventionally, ultrasonic probes have been used in medical
devices, fish finders and the like. In the medical field, in order to transmit ultrasonic waves into
the living body and receive reflected waves from cancer cells etc. to acquire information
necessary for treatment etc. In order to transmit waves and receive a reflected wave from a
school of fish and the like to extract information such as the size and distance of the school of
fish, an ultrasonic probe is essential.
[0003]
In an ultrasound probe used for such an application, it is necessary to focus ultrasound on a
predetermined distance. For this reason, for example, an ultrasound probe provided with an
acoustic lens is conventionally known.
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[0004]
FIG. 3 shows the structure of an ultrasonic probe according to one prior art example. The
ultrasound probe shown in this figure is an ultrasound probe provided with an acoustic lens.
That is, for example, a vibrator 14 made of a piezoelectric material such as PZT is formed by
depositing electrodes 10 and 12 made of silver on the surface, and a back load 16 is observed on
the electrode 12 side as viewed from the ultrasonic vibrator 14. An acoustic lens 18 is provided
on the electrode 10 side. The acoustic lens 18 is a member formed of, for example, resin, glass or
the like, and applies an electric voltage between the electrodes 10 and 12 to cause an ultrasonic
wave generated in the ultrasonic transducer 14 to focus on a predetermined focal point 100. It is
a structure. For this reason, the acoustic lens 18 has a convex lens shape.
[0005]
By forming the focal point 100 by the action of the acoustic lens 18 as described above,
diagnosis and the like can be performed. In the living body, there is a portion having a different
acoustic impedance from blood which is a propagation medium of ultrasonic waves, such as
bones, cancer cells, etc. The ultrasonic waves reflected by the bones, cancer cells etc. By being
received by the vibrator 14 through the information, information concerning bone, cancer cells
and the like can be obtained. That is, the size and position of the reflector can be known.
[0006]
In the ultrasonic probe having such a configuration, the position of the focal point 100 depends
on the shape of the surface of the acoustic lens 18. Therefore, it is difficult to change the position
of the focal point 100. For this reason, an ultrasonic probe capable of forming the focal point
100 with variable position has been conventionally studied and put into practical use. FIGS. 4
and 5 show an example configuration of such an ultrasonic probe.
[0007]
In the prior art, a plurality of ring-shaped ultrasonic transducers 14 are used as the ultrasonic
transducers 14. As shown in FIG. 5, the ultrasonic transducers 14 are concentrically arranged on
the back load 16. The ultrasonic transducers 14 arranged in this manner are all driven by the
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transceiver 20. In this driving, voltages are supplied via a plurality of delay circuits 22 each
having a different delay amount.
[0008]
That is, the vibrators 14 in this conventional example are driven by signals different in
application time. That is, the signal applied to each transducer 14 is delayed by a time τi = li / v
(v: sound velocity) corresponding to the distance indicated by li in the figure. The distance li is set
to be longer at the central portion 14 than at the peripheral portion 14, and setting of the
distance li brings the focal point 100 to a predetermined position. Therefore, if the delay time of
the delay circuit 22 is set appropriately, the position of the focal point 100 can be changed.
[0009]
However, in the ultrasonic probe capable of changing the focal length as described above, the
processing difficulty, the precise assembly difficulty, and the transmission sensitivity are low.
There are problems with That is, although a piezoelectric ceramic material such as PZT is
conventionally known as a material for forming the vibrator, it is very difficult to arrange the
shape of the vibrator formed from ceramics into a ring shape. For example, even if it is processed
into a ring shape by means of ultrasonic processing or the like in the state of a relatively soft
green sheet, the shape after firing is not limited, and therefore, processing difficulty, precise
assembly difficulty, etc. Will occur. Alternatively, there is also a method of providing grooves in
plate-like ceramics, but this is also difficult to process.
[0010]
As means for avoiding such difficulties, it is also conceivable to use a vibrator formed of an
organic piezoelectric material such as PVDF or a composite piezoelectric material instead of a
piezoelectric ceramic such as PZT. Here, the composite piezoelectric material is a material formed
by mixing a piezoelectric ceramic powder in a rubber such as epoxy, chloroprene, urethane and
the like. In such materials, the g constant representing the amount of charge generated per 1N is
large, so the reception sensitivity is high, and since the acoustic impedance Z is low, the
compatibility with ultrasonic wave propagation media such as seawater and blood is high. You
can get an advantage. However, when such a material is used, for example, even when the same
power as that of a vibrator formed of PZT is injected, the transmission pulse becomes small, and
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as a result, the transmission sensitivity becomes low. The present invention has been made to
solve such problems, and aims to realize an ultrasonic probe in which transmission sensitivity is
ensured while realizing ease of processing and assembly. I assume.
[0011]
SUMMARY OF THE INVENTION In order to achieve the above object, the ultrasonic probe of the
present invention is formed in a ring shape with a first piezoelectric vibrator formed in a plate
shape. And a plurality of second piezoelectric vibrators arranged concentrically on the first
piezoelectric vibrator, wherein the second piezoelectric vibrator is formed of an organic
piezoelectric material It is characterized by
[0012]
According to a second aspect of the present invention, the second piezoelectric vibrator is formed
of a composite piezoelectric material produced by mixing a piezoelectric ceramic powder and a
rubber.
[0013]
Furthermore, according to a third aspect of the present invention, the first piezoelectric vibrator
is supplied with a voltage to transmit ultrasonic waves, and the second piezoelectric vibrator is
used to delay a signal related to the ultrasonic waves received. And means for forming a focus.
[0014]
The first piezoelectric vibrator is formed of any one of Pb (Zr, Ti) O3: lead zirconate titanate
(PZT), BaTiO3: barium titanate or PbTiO3: lead titanate. It is characterized by
[0015]
A fifth piezoelectric vibrator according to the present invention is a second piezoelectric vibrator
comprising PVDF: polyvinylidene fluoride, PVDF copolymer, P (VDCN / VAc): copolymer of
vinylidene cyanide and vinyl acetate, or P (VDF / TrFE). It is characterized in that it is formed
from any of a copolymer of vinylidene fluoride and trifluoroethylene.
[0016]
According to a sixth aspect of the present invention, of the materials forming the second
piezoelectric vibrator, NBR: copolymer of butadiene and acrylonitrile, SBR: radical copolymer of
butadiene and styrene or urethane rubber It is characterized by being either.
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[0017]
In the first aspect of the present invention, the second piezoelectric vibrator is formed of an
organic piezoelectric material.
The organic piezoelectric material is easier to process than a piezoelectric ceramic material such
as PZT, and can be in the form of, for example, a film.
As a result, an ultrasonic probe that is easier to process and assemble can be obtained.
[0018]
In the second aspect, the second vibrator is formed of a so-called composite piezoelectric
material.
Since this composite piezoelectric material is also formed of rubber as a base, it exhibits the
effect of facilitating processing and assembly in the same manner as the organic piezoelectric
material in the first aspect.
[0019]
In the third aspect, the first piezoelectric vibrator is used for transmitting ultrasonic waves, and
the second piezoelectric vibrator is used for receiving ultrasonic waves.
The signal obtained by receiving is delayed to form a focal point.
As described above, since focus formation is performed on the reception side by delaying the
signal, focus setting can be performed by setting the delay amount.
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[0020]
In the fourth aspect, the first piezoelectric vibrator is formed of a piezoelectric ceramic material
such as PZT.
Piezoelectric ceramic materials such as PZT are materials having high transmission sensitivity,
and as a result, it is possible to ensure good transmission sensitivity as well as ease of processing
and assembly obtained in claim 1 or 2.
[0021]
In the fifth aspect, the second piezoelectric vibrator is formed of an organic piezoelectric material
such as PVDF. The organic piezoelectric material has the property that the acoustic impedance is
closer to an ultrasonic wave propagation medium such as blood or seawater as compared with a
piezoelectric ceramic material such as PZT, and the g constant is larger. Therefore, an ultrasonic
probe with high integrity of the ultrasonic wave propagation medium and high reception
sensitivity can be obtained.
[0022]
According to the sixth aspect of the present invention, the second piezoelectric vibrator is formed
of a mixed material such as piezoelectric ceramic powder and NBR. This material is a material
close to the ultrasonic wave propagation medium of acoustic impedance and has a large g
constant as in the case of PVDF and the like, and hence the same effect as in claim 5 can be
obtained.
[0023]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the
present invention will be described below based on the drawings. The same reference numerals
as in the conventional example shown in FIGS. 3 to 5 denote the same parts in FIG.
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[0024]
FIG. 1 shows a circuit configuration of an ultrasonic probe according to an embodiment of the
present invention. FIG. 2 also shows the focus formation principle of this embodiment.
[0025]
As in the prior art shown in FIG. 5, the embodiment shown in these figures has a configuration
using a ring-shaped vibrator. That is, the vibrator 14-2 has a ring shape and is arranged
concentrically. However, these transducers 14-2 are disposed not on the back load 16 but on the
ultrasonic transducers 14-1 having a thickness of about 400 to 500 μm, for example.
[0026]
The ultrasonic transducer 14-1 is formed of PZT in this embodiment. An electrode 12-1 made of
silver or the like is provided on the lower surface of the plate-like ultrasonic transducer 14-1, and
an electrode 10-1 is provided on the upper surface. Although not shown, a rear load is disposed
below the electrode 14-1, and an ultrasonic transducer 14-2 is bonded to the electrode 10-1 by a
conductive adhesive 24. The ultrasonic transducer 14-2 is concentrically arranged on the
ultrasonic transducer 14-1. An electrode 12-2 is provided on the lower surface of the ultrasonic
transducer 14-2, and an electrode 10-2 is provided on the upper surface.
[0027]
In this embodiment, the ultrasonic transducer 14-2 is a transducer formed of PVDF having a
thickness of about 300 μm, for example, when vibrating at 3 to 5 MHz. Therefore, the
processability is excellent as compared with the case of forming from PZT. For example, the ringshaped ultrasonic transducer 14-2 can be easily obtained by punching a film-like PVDF material.
The vibrator 14-2 thus obtained can be bonded onto the ultrasonic vibrator 14-1 by the
conductive adhesive 24 made of epoxy resin or the like. The width of the vibrator 14-2 is about
0.5 to 1 mm, and the distance between the vibrators 14-2 is about 0.1 to 0.3 mm.
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[0028]
As a result of bonding the vibrators 14-1 and 14-2 with the adhesive 24, the electrodes 10-1 and
12-2 are brought into conduction. Therefore, the electrodes 10-1 and 12-2 can be handled as a
common electrode. In this embodiment, a voltage is applied from the transmitter 26 between the
common electrode and the electrode 12-1, and a signal appearing between the common
electrode and the electrode 10-2 is transmitted to the delay circuit 22 and the signal combining
circuit 28. It is made to take in to receiver 30 via.
[0029]
That is, in this embodiment, the ultrasonic transducer 14-1 formed of PZT is used exclusively for
transmission. As a result, a decrease in transmission sensitivity is prevented. That is, PZT is a
material having high transmission sensitivity, and is strong against mechanical distortion, and
can make large injection power. As a result, the transmission sensitivity of the ultrasonic probe is
secured and transmission becomes possible. On the other hand, in this embodiment, the
ultrasonic transducer 14-2 formed of PVDF is used exclusively for reception. The acoustic
impedance of PVDF is, for example, about 3 to 5 × 10 6 kg / m 2 s, which is close to the acoustic
impedance of blood and seawater 1.5 × 10 6 kg / m 2 s. This is much closer to blood or the like
than the acoustic impedance 35 × 10 6 kg / m 2 s of PZT.
[0030]
Therefore, in this embodiment, the transmission sensitivity is secured, and the acoustic
consistency with the ultrasonic wave propagation medium is improved. Furthermore, PVDF has a
larger g constant than PZT, and therefore, the reception sensitivity is high.
[0031]
As in the prior art, the delay circuit 22 is a circuit for delaying the signal relating to the vibrator
14-2 by a time .tau.i corresponding to the distance li shown in FIG. However, in this embodiment,
unlike the prior art, a delay is provided on the receiving side. Accordingly, as shown by the
arrows in FIG. 2, in the case of transmission, ultrasonic waves are emitted to the front, and the
focal point 100 is formed on the receiving side. The signal combining circuit 28 is a circuit that
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combines the signals obtained from the plurality of delay circuits 22 and supplies the combined
signal to the receiver 30.
[0032]
Therefore, in this embodiment, the action of variable focus in the conventional example can be
secured. As a result, a highly usable ultrasound probe can be realized.
[0033]
In the above description, PZT is assumed as the material of the vibrator 14-1, and PVDF is
assumed as the material of the vibrator 10-2. However, the present invention is limited to these
materials. It is not a thing. For example, a piezoelectric ceramic material such as BaTiO 3 or
PbTiO 3 may be used as a material for forming the vibrator 14-1, and as a material for forming
the second piezoelectric vibrator 14-2, a PVDF copolymer, P (VDCN / P An organic piezoelectric
material such as VAc) or P (VDF / TrFE), or a composite piezoelectric material in which a
piezoelectric ceramic powder is mixed in NBR, SBR, urethane rubber or the like may be used.
[0034]
As described above, according to claim 1 of the present invention, since the second piezoelectric
vibrator is formed of an organic piezoelectric material, ultrasonic wave detection and processing
are easy. You can get a feeler.
[0035]
In the second aspect of the invention, since the second piezoelectric transducer is formed of a socalled composite piezoelectric material, it is possible to obtain an ultrasonic probe which is easy
to process and assemble as in the first aspect of the invention. it can.
[0036]
According to the third aspect of the invention, since the signal is delayed on the receiving side to
form the focal point, the focal point can be set by setting the delay amount.
[0037]
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According to the fourth aspect of the invention, since the first piezoelectric vibrator is formed of
a piezoelectric ceramic material such as PZT, an ultrasonic probe with high transmission
sensitivity can be obtained.
[0038]
According to the fifth aspect of the invention, since the second piezoelectric transducer is formed
of an organic piezoelectric material such as PVDF, an ultrasonic probe with high reception
sensitivity and high acoustic consistency can be obtained.
[0039]
According to the sixth aspect of the invention, the second piezoelectric vibrator is formed of a
mixed material of the piezoelectric ceramic main body and the NBR, so that the same effect as the
fifth aspect can be obtained.
[0040]
Brief description of the drawings
[0041]
1 is a diagram showing a circuit configuration of an ultrasonic probe according to an
embodiment of the present invention.
[0042]
2 is a diagram showing the principle of focus formation in this embodiment.
[0043]
3 is a diagram showing an ultrasound probe according to the first prior art example.
[0044]
4 is a diagram showing the configuration of an ultrasound probe according to the second
conventional example.
[0045]
5 is a perspective view showing the structure of an ultrasonic probe according to this
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conventional example.
[0046]
Explanation of sign
[0047]
10-1, 10-2, 12-1, 12-2 electrode 14-1, 14-2 ultrasonic transducer 22 delay circuit 26 transmitter
30 receiver 100 focus
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