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JP2002044773

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DESCRIPTION JP2002044773
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
acoustic lens for emitting ultrasonic waves in a gas or a liquid, and more particularly to focusing
ultrasonic waves emitted from an ultrasonic radiation unit. The present invention relates to an
acoustic lens and an ultrasonic transducer.
[0002]
2. Description of the Related Art Ultrasonic waves are high in frequency and short in wavelength,
excellent in directivity, and easy to detect reflected waves. For this reason, ultrasonic waves are
widely used in nondestructive inspection devices and measurement of flow velocity and flow rate
of fluid. When ultrasonic waves are used, the ultrasonic waves are generally emitted into the air
or liquid, and the reflected waves from the object to be inspected and the ultrasonic waves
transmitted through the object to be inspected are detected. Also, although ultrasonic waves are
excellent in directivity, they are much easier to diffuse than light, so in the case of precise flaw
detection, etc., an ultrasonic wave transmission called an ultrasonic probe as shown in FIG. 3 is
carried out. A waver may be used to focus ultrasonic waves emitted into the air at one point and
irradiate the object under test.
[0003]
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In the conventional ultrasonic probe 10 shown in FIG. 3, an acoustic lens 14 is attached to an
ultrasonic transducer 12 serving as an ultrasonic wave radiating portion. The acoustic lens 14 is
formed of a material considered to reduce the difference in acoustic impedance between the
ultrasonic transducer 12 that generates ultrasonic waves and the air through which the
ultrasonic waves propagate, and the tip surface 16 has a concave curved surface. Then, the
ultrasonic waves 18 emitted from the tip end surface 16 of the acoustic lens 14 are focused at
the focal point O, and are irradiated to the inspection object (not shown). The position of the
focal point O of the ultrasonic wave 18 can be changed by changing the material of the acoustic
lens 14 or the curved surface shape (curvature) of the distal end surface 16 of the acoustic lens
14. In addition, in the case of focusing ultrasonic waves at one point, a method of installing a
reflecting plate having a concave surface in front of the ultrasonic wave generation unit and
reflecting and focusing the ultrasonic waves by the reflecting plate is also performed.
[0004]
However, in the ultrasonic probe 10 provided with the conventional acoustic lens 14, the
ultrasonic wave 18 emitted by the ultrasonic transducer 12 passes through the acoustic lens 14.
Therefore, the ultrasonic wave 18 is attenuated by the acoustic lens 14. For this reason, in order
to detect the reflected wave of the ultrasonic wave 18 or the ultrasonic wave transmitted through
the inspection object (not shown), it is necessary to generate the strong ultrasonic wave 18
having a large amplitude. Further, the acoustic lens 14 is formed so that the thickness t is thin at
the central portion and gradually thick toward the peripheral portion. Therefore, when the
ultrasonic wave 18 generated by the ultrasonic transducer 12 passes through the acoustic lens
14, the sound flux passing through the central portion of the acoustic lens 14 and the sound flux
passing through the peripheral portion of the acoustic lens 14 Have different propagation
distances, resulting in a phase shift in the ultrasound signal, which causes interference when
focused to the focal point O, causing a reduction in sensitivity at the focal point O, or a
disturbance or a reduction in frequency. .
[0005]
On the other hand, in the method in which the concave reflecting plate is installed in front of the
ultrasonic wave generator, the focal position is different from the traveling direction of the
ultrasonic wave emitted from the ultrasonic wave generator. For this reason, the structure of the
ultrasound probe becomes complicated or enlarged. Moreover, it becomes difficult to detect a
reflected wave.
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[0006]
The present invention has been made to solve the above-mentioned drawbacks of the prior art,
and aims at focusing ultrasonic waves with little attenuation. Another object of the present
invention is to focus ultrasonic waves in a state in which the broadband characteristics of the
ultrasonic transducer are maintained.
[0007]
SUMMARY OF THE INVENTION In order to achieve the above object, an acoustic lens according
to the present invention is disposed in front of an ultrasonic wave emitting portion to transmit
ultrasonic waves emitted from the ultrasonic wave emitting portion. A first reflector that reflects
laterally, and a second reflector that is provided on the side of the first reflector and that reflects
the ultrasonic wave reflected by the first reflector in a forward direction of the ultrasonic wave
radiation portion And is characterized in that
[0008]
Preferably, the first reflector and the second reflector are formed of a material having a large
acoustic impedance, such as metal or ceramic, so as to reflect ultrasonic waves well.
And a 1st reflector can form a reflective surface in a conical surface, and can make the vertex of
a conical surface be opposite to an ultrasonic wave radiation part. The angle of the apex of the
conical surface can be set arbitrarily. In addition, the second reflector is formed in a concave
curved surface that focuses the ultrasonic waves reflected by the first reflector at one point. By
changing the shape (curvature) of the curved surface of the second reflector, it is possible to
change the focus position (focus position) of the ultrasonic waves. Furthermore, the reflection
surface of the second reflector may reflect the ultrasonic wave reflected by the first reflector so
as to be parallel to the axis of the second reflector. And the ultrasonic wave transmitter
concerning this invention is characterized by having an ultrasonic wave radiation part provided
with the above-mentioned acoustic lens.
[0009]
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In the present invention configured as described above, the ultrasonic wave emitted from the
ultrasonic wave radiation unit is reflected and focused by the first reflector and the second
reflector, and the ultrasonic wave is acoustic. Since so-called total reflection and focusing are
performed without passing through the lens, it is possible to minimize ultrasonic attenuation.
Moreover, the propagation distance to the focal point of the sound flux of the ultrasonic wave
emitted from each position of the ultrasonic radiation unit can be made constant, and the
ultrasonic waves in phase can be focused on the focal point position, It is possible to prevent
interference of the ultrasonic waves caused and disturbance or lowering of the frequency. For
this reason, it is possible to focus the ultrasonic waves while maintaining the broadband
characteristics of the ultrasonic transducer.
[0010]
By making the reflecting surface of the first reflector a conical surface, the shape of the reflecting
surface of the second reflector for focusing the ultrasonic waves can be easily determined, and a
desired shape from the ultrasonic wave radiation portion can be obtained. Design of an acoustic
lens having a focus at distance can be facilitated.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of an acoustic lens
and an ultrasonic wave transmitter according to the present invention will be described in detail
with reference to the attached drawings.
FIG. 1 is a cross-sectional view schematically showing an ultrasonic wave transmitter according
to an embodiment of the present invention. In FIG. 1, the ultrasonic wave transmitter 20
comprises an ultrasonic wave radiation unit 22 and an acoustic lens 24. The ultrasonic radiation
unit 22 incorporates an ultrasonic transducer, and radiates (transmits) the ultrasonic wave 30
from the center on the right side of FIG. 1 which is the front side. In addition, the ultrasonic
radiation unit 22 applies a voltage to the ultrasonic transducer, and as described later, a terminal
unit (not shown) for taking out the ultrasonic wave received by the ultrasonic radiation unit 22
as an electric signal. Is provided on the rear side.
[0012]
The acoustic lens 24 comprises a first reflector 26 and a second reflector 28 disposed around the
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first reflector 26. In the case of the embodiment, the first reflector 26 and the second reflector
28 are formed of a metal having a large acoustic impedance such as aluminum or brass so that
the ultrasonic wave 30 can be substantially totally reflected. The reflecting surface 32 of the first
reflector 26 is formed in a conical surface, and the apex 34 faces the front surface of the
ultrasonic wave emitting unit 22. Further, in the case of the embodiment, the first reflector 26
has an angle θ of 90 degrees with the apex 34, and as shown in FIG. 1, the ultrasonic wave 30
emitted by the ultrasonic wave emitting unit 22 is an ultrasonic wave. As in 30a, the light is
reflected in the direction orthogonal to the axis 36.
[0013]
The second reflector 28 is disposed concentrically with the first reflector 26 and has an opening
37 at its central portion, and the ultrasonic wave 30 generated by the ultrasonic wave emitting
unit 22 is converted to an ultrasonic wave. It can radiate in front of the radiation part 22. In the
second reflector 28, the reflection surface 38 facing the first reflector 26 is a concave curved
surface, and the ultrasonic wave 30 a reflected by the first reflector 26 is further reflected by the
reflection surface 38 as the ultrasonic wave 30 b. As described above, the ultrasonic wave is
reflected in the forward direction of the ultrasonic radiation unit 22, and the ultrasonic wave 30
is focused on the focal point O. That is, the reflecting surface 38 is equally divided by an angle α
between the ultrasonic wave 30a reflected by the first reflector 26 whose normal surface 40 is
incident on the reflecting surface 38 and the ultrasonic wave 30b reflected by the second
reflector 28. It is a line.
[0014]
The details of the acoustic lens 24 are as shown in FIG. 2 in the case of the embodiment. That is,
in the first reflector 26 of the acoustic lens 24, the ring portion 44 is provided around the
reflecting main body 42 having the conical reflecting surface 32. The reflective main body 42 is
composed of a conical portion and a cylindrical portion, and the cylindrical portion is integrated
with the ring portion 44 by a plurality (three in the embodiment) of ribs 46. Then, in the ring
portion 44, a male screw portion is formed on the outer peripheral surface, and the male screw
portion is screwed with a female screw portion provided on the inner peripheral surface of the
distal end portion of the second reflector 28. It is screwed on 28 freely.
[0015]
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The second reflector 28 is provided with a mounting hole 48 on the rear end side, and can be
detachably attached to the ultrasonic wave emitting unit 22 through the mounting hole 48. The
second reflector 28 has an inward flange-like stopper portion 50 formed at the tip of the
mounting hole 48 so that the insertion amount of the ultrasonic wave radiation portion 22 can
be made constant. In addition, a holding member 52 formed of, for example, a rubber O-ring or
the like is disposed on the tip end side of the mounting hole 48, and the acoustic lens 24 is
attached to the ultrasonic wave radiation unit 22 via the second reflector 28. Sometimes, the
acoustic lens 24 is prevented from easily detaching from the ultrasonic radiation unit 22.
[0016]
In the ultrasonic wave transmitter 20 according to the embodiment formed as described above,
the case of transmitting ultrasonic waves is as follows. The ultrasonic wave transmitter 20
disposed in a gas such as in air has a reflection surface 32 of the first reflector 26 of the acoustic
lens 24 in which the ultrasonic wave 30 emitted from each position on the front surface of the
ultrasonic wave radiation unit 22. Incident to The reflecting surface 32 of the first reflector 26 is
a conical surface whose angle of the apex 34 is 90 degrees, and the reflecting surface 32 is
inclined 45 degrees with respect to the axis 36. Therefore, as shown by the ultrasonic wave 30a,
the ultrasonic wave 30 emitted by the ultrasonic wave emitting unit 22 is reflected by the
reflective surface 32 in a direction (side) orthogonal to the axis 36, and the reflection of the
second reflector 28 is It is incident on the surface 38. Then, the reflection surface 38 of the
second reflector 28 reflects the incident ultrasonic wave 30a in the forward direction of the
ultrasonic wave emitting unit 22 like the ultrasonic wave 30b and focuses it on the focal point O.
[0017]
As described above, in the acoustic lens 24 according to the embodiment, the ultrasonic wave 30
emitted by the ultrasonic radiation unit 22 is reflected by the first reflector 26 and the second
reflector 28 having large acoustic impedance. Since the focal point O is focused, the ultrasonic
wave 30 can be substantially totally reflected, and can be focused without attenuation. For this
reason, when transmitting the ultrasonic wave of the intensity | strength same as before, the
drive voltage given to the ultrasonic radiation part 22 can be reduced significantly compared
with the past. Moreover, it is possible to equalize the propagation distance to the focal point O of
the ultrasonic waves 30 emitted from each position of the ultrasonic radiation unit 22, and it is
possible to eliminate the phase shift of the sound flux of the focused ultrasonic waves 30; It is
possible to prevent phenomena such as interference of focused ultrasonic waves and disturbance
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or reduction of frequency. Therefore, the ultrasonic waves 30 can be focused while maintaining
the wide band characteristics of the ultrasonic radiation unit 22.
[0018]
In the embodiment described above, the acoustic lens 24 is attached to the ultrasonic wave
emitting unit 22 serving as the ultrasonic wave transmitting unit. However, the acoustic lens 24
may be attached to the ultrasonic wave receiving unit. And in the said embodiment, although the
ultrasonic wave transmitter 20 was demonstrated, as it is known, the ultrasonic wave transmitter
20 can be used as an ultrasonic wave receiver as it is. When the ultrasonic wave transmitter 20
according to the embodiment is used as an ultrasonic wave transmitter / receiver, and
nondestructive inspection is performed by ultrasonic waves as to whether or not pores or cracks
exist in the object to be inspected, as shown in FIG. As shown, the object 60 to be inspected is
placed at the focal point O of the acoustic lens 24.
[0019]
Thereafter, the ultrasonic wave transmitter 20 and the test object 60 are moved relative to each
other to scan the ultrasonic waves 30, and the pulse-like ultrasonic waves 30 generated by the
ultrasonic radiation unit 22 are subjected to the test object 60. And the reflected wave is received
(received) by the ultrasonic radiation unit 22. That is, the reflected wave from the object 60 to be
inspected propagates the propagation path of the ultrasonic wave 30 emitted by the ultrasonic
wave emitting unit 22 in the reverse direction, and is reflected by the second reflector 28 and the
first reflector 26 in order It reaches the surface of the radiation unit 22 and vibrates the
ultrasonic transducer contained in the ultrasonic radiation unit 22. The vibration of the
ultrasonic transducer is taken out as an electrical signal from a terminal provided on the rear
surface of the ultrasonic radiation unit 22.
[0020]
In the above embodiment, although the case where the angle θ of the apex 34 of the first
reflector 26 is 90 degrees has been described, the angle θ of the apex 34 can be formed
arbitrarily. In addition, by changing the shape (curvature) of the concave curved surface of the
reflection surface 38 of the second reflector 28, the distance L between the front surface of the
ultrasonic radiation unit 22 and the focal point O can be set arbitrarily. And although the case
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where the ultrasonic wave 30 is focused on the focal point O by the reflecting surface 38 of the
second radiator 28 has been described in the above embodiment, it may be reflected so as to be
parallel to the axis 36. Furthermore, although the case where the ultrasonic wave 30 is emitted
into the air has been described in the above embodiment, it may be emitted into a liquid such as
water. Moreover, in the said embodiment, although the case where the rib 46 of the 1st reflector
26 was three was demonstrated, the rib 46 should just be two or more. However, if the ribs 46
are too many or thick, the amount of the ultrasonic waves 30 reflected by the ribs 46 will be
large, and the amount of the ultrasonic waves 30 to be focused will be small. And although the
case where acoustic lens 24 was formed with metal was explained in the above-mentioned
embodiment, the material which forms acoustic lens may be other substances, such as ceramics,
if acoustic impedance is large. Moreover, in the said embodiment, although the case where the
1st reflector 26 and the 2nd reflector 28 were separately formed was demonstrated, you may
form these integrally.
[0021]
Further, in the above embodiment, the ultrasonic wave transmitter 20 is disposed on one side of
the object 60 to be inspected, and the reflected wave from the object 60 to be inspected is an
ultrasonic wave transmitted by the ultrasonic wave 30. Although the case where detection is
performed by the detector 20 has been described, a pair of ultrasonic wave transmitters 20 (20a,
20b) are disposed on both sides of the inspection target 60 in line symmetry with respect to the
focal point 30, and one ultrasonic wave transmission is performed. The ultrasonic wave 30 may
be emitted by the unit 20a and focused on the focal point O for irradiation, and the ultrasonic
wave transmitted through the object 60 to be inspected may be detected by the other ultrasonic
wave transmitter 20b.
[0022]
As described above, according to the present invention, the first and second reflectors reflect and
focus the ultrasonic wave emitted by the ultrasonic wave emitting unit. Since the ultrasonic
waves are focused by so-called total reflection without passing through the acoustic lens, it is
possible to minimize the attenuation of the ultrasonic waves.
Moreover, it is possible to make the propagation distance to the focal point of the sound flux
radiated from each position of the ultrasonic radiation unit constant, to be able to focus the
ultrasound waves in phase at the focal position, It can prevent interference or disturbance or
decrease in frequency. For this reason, it is possible to focus the ultrasonic waves while
maintaining the broadband characteristics of the ultrasonic transducer.
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[0023]
Further, according to the present invention, by making the reflecting surface of the first reflector
conical, the shape of the reflecting surface of the second reflector for focusing the ultrasonic
waves can be easily determined. It is easy to design an acoustic lens having a focal point at a
desired position from the radiation part.
[0024]
Brief description of the drawings
[0025]
1 is a cross-sectional view schematically showing an ultrasonic wave transmitter according to the
embodiment of the present invention.
[0026]
2 is a diagram showing the details of the acoustic lens according to the embodiment, (1) is a front
view, (2) is a cross-sectional view along the line AA of (1).
[0027]
3 is an explanatory view of a conventional ultrasonic wave transmitter.
[0028]
Explanation of sign
[0029]
20 ...... ultrasonic wave transmitter, 22 ...... ultrasonic wave emitting unit, 24 ...... acoustic lens, 26
...... first reflector, 28 ...... second reflector, 30, 30a, 30b ... ...... Ultrasonic waves 32, 38 ... ......
Reflective surface.
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