Ultrasonic transducer
View Patent ↗An ultrasonic transducer includes: a piezoelectric transducer ( 1 ) emitting ultrasonic waves; and a backing layer ( 4 ) provided in contact with a back side of the piezoelectric transducer ( 1 ) and attenuating ultrasonic waves that are emitted toward the back side of the piezoelectric transducer ( 1 ) and have an opposite phase to the phase of ultrasonic waves emitted toward a front side of the piezoelectric transducer ( 1 ). The acoustic tubes ( 5 ) are disposed in the backing layer ( 4 ) such that a longitudinal direction of each acoustic tube ( 5 ) is in line with a traveling direction of the ultrasonic waves emitted by the piezoelectric transducer ( 1 ) toward the front and the back side. The acoustic tubes ( 5 ) have mutually different lengths on the basis of a principle of an acoustic wave synthesis, and attenuate in whole or in part the ultrasonic waves emitted by the piezoelectric transducer ( 1 ) toward the backing layer ( 4 ).
1. An ultrasonic transducer comprising:
a vibrating element which emits ultrasonic waves; and
a backing material which is provided in contact with a back side of said vibrating element and which attenuates ultrasonic waves that are emitted toward the back side of said vibrating element and have an opposite phase to a phase of ultrasonic waves emitted toward a front side of said vibrating element,
wherein acoustic tubes are disposed in said backing material such that a longitudinal direction of each of said acoustic tubes is in line with a traveling direction of the ultrasonic waves which are emitted by said vibrating element and travel toward the front side and the back side, said acoustic tubes having mutually different lengths on the basis of a principle of an acoustic wave synthesis, and
said acoustic tubes attenuate in whole or in part the ultrasonic waves emitted by said vibrating element toward said backing material.
2. The ultrasonic transducer according to claim 1 ,
wherein said backing material includes, instead of said acoustic tubes, reflectors equivalent to said acoustic tubes.
3. The ultrasonic transducer according to claim 1 ,
wherein said acoustic tubes are aligned in an order of integer n in a linear direction on a plane where said backing material contacts an other layer, and
said acoustic tubes are disposed such that a length Ln of said each acoustic tube satisfies Equation 2 where c denotes a speed of sound, N denotes a prime number, n denotes an integer which varies in a range of 0 to (N−1), and wr denotes any design frequency:
[
Math
.
1
]
Ln
=
c
·
n
2
(
mod
N
)
2
N
ω
r
(
Equation
2
)
4. The ultrasonic transducer according to claim 1 ,
wherein said acoustic tubes are aligned in an order of integer n in a linear direction on a plane where said backing material contacts an other layer, and
said acoustic tubes are disposed such that a length Ln of said each acoustic tube satisfies Equation 3 where c denotes a speed of sound, N denotes a prime number, n denotes an integer which varies in a range of 0 to (N−1), r denotes a primitive root of N, and wr denotes any design frequency:
[
Math
.
2
]
Ln
=
c
·
r
n
(
mod
N
)
2
(
N
-
1
)
ω
r
(
Equation
3
)
5. The ultrasonic transducer according to claim 1 ,
wherein said backing material includes microcapsules and curable polymeric resin, and
reflectors equivalent to said acoustic tubes are said microcapsules which are distributed in said polymeric resin.
6. The ultrasonic transducer according to claim 5 ,
wherein each of said microcapsules is of a spherical or cylindrical shape obtained by providing an outer shell to a base material through sol-gel reaction, the base material being made of a monofilament fiber of predetermined length.
7. The ultrasonic transducer according to claim 5 ,
wherein each of said microcapsules is of a cylindrical shape, and
the reflectors equivalent to said acoustic tubes are said cylindrical microcapsules which are disposed such that said cylindrical microcapsules are aligned lengthwise.
8. An ultrasonic diagnostic apparatus comprising the ultrasonic transducer according to claim 1 .
9. A method of forming a backing material used in an ultrasonic transducer,
the ultrasonic transducer comprising:
a vibrating element which emits ultrasonic waves; and
the backing material which is provided in contact with a back side of the vibrating element and which attenuates ultrasonic waves that are emitted toward the back side of the vibrating element and have an opposite phase to a phase of ultrasonic waves emitted toward a front side of the vibrating element,
wherein acoustic tubes are disposed in the backing material such that a longitudinal direction of each of the acoustic tubes is in line with a traveling direction of the ultrasonic waves which are emitted by the vibrating element and travel toward the front side and the back side, the acoustic tubes having mutually different lengths on the basis of a principle of an acoustic wave synthesis, and
the acoustic tubes attenuate in whole or in part the ultrasonic waves emitted by the vibrating element toward the backing material,
said method comprising:
preparing mixtures of microcapsules and curable polymeric resin, each of the mixtures having a different microcapsule inclusion ratio; and
forming the backing material by stacking resin layers formed from the mixtures each having the different microcapsule inclusion ratio, and by subsequently curing and molding the stacked resin layers into a predetermined shape.
10. The method of forming a backing material according to claim 9 ,
wherein each of the microcapsules is formed to have a spherical or cylindrical shape by providing an outer shell to a base material through sol-gel reaction, the base material being made of a monofilament fiber of predetermined length.
11. A method of forming a backing material used in an ultrasonic transducer,
the ultrasonic transducer comprising:
a vibrating element which emits ultrasonic waves; and
the backing material which is provided in contact with a back side of the vibrating element and which attenuates ultrasonic waves that are emitted toward the back side of the vibrating element and have an opposite phase to a phase of ultrasonic waves emitted toward a front side of the vibrating element,
wherein acoustic tubes are disposed in the backing material such that a longitudinal direction of each of the acoustic tubes is in line with a traveling direction of the ultrasonic waves which are emitted by the vibrating element and travel toward the front side and the back side, the acoustic tubes having mutually different lengths on the basis of a principle of an acoustic wave synthesis, and
the acoustic tubes attenuate in whole or in part the ultrasonic waves emitted by the vibrating element toward the backing material,
said method comprising:
preparing a mixture of microcapsules and curable polymeric resin; and
forming the backing material by performing extrusion molding on the mixture to cause the microcapsules to be aligned lengthwise in the mixture and curing the mixture.
12. The method of forming a backing material according to claim 11 ,
wherein each of the microcapsules is formed as a material of a cylindrical shape by providing an outer shell to a base material through sol-gel reaction, the base material being made of a monofilament fiber of predetermined length.
13. The method of forming a backing material according to claim 12 , wherein there are two or more lengths in a longitudinal direction for the microcapsules.