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JPH0458150

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DESCRIPTION JPH0458150
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
ultrasonic probe used in an ultrasonic flaw detector and an ultrasonic microscope. [Prior Art] An
ultrasonic flaw detector is an apparatus for inspecting the presence or absence of a defect in an
object and the state of an object surface using an ultrasonic wave, and an ultrasonic microscope
is an apparatus for mainly analyzing physical properties of an object surface. . In any of the
devices, an ultrasound probe is used to transmit and receive ultrasound. Such an ultrasonic probe
will be described with reference to FIG. FIG. 6 is a side view of a conventional ultrasonic probe. In
the figure, 1 shows an ultrasound probe. An acoustic lens 2 has a concave lens surface 2a and a
flat surface 2b opposed thereto. Reference numeral 3 denotes a conversion element, which
comprises a piezoelectric element 3a, a lower electrode 3b and an upper electrode 3c. 3 d shows
the lead wire connected to each electrode. The conversion element 3 is fixed to the flat surface 2
b of the acoustic lens 2. Reference numeral 4 denotes an object to be inspected (object to be
inspected), and reference numeral 5 denotes a medium (usually water) to be interposed between
the lens concave surface 2a and the object 4 to be inspected. In the ultrasonic probe 1, when a
predetermined voltage (usually a burst wave) is applied to the electrodes 3b and 3c through the
lead wire 3d, the piezoelectric element 3a is excited to generate an ultrasonic wave. This
ultrasonic wave passes through the acoustic lens 2 as shown by a broken line in the figure, and is
focused on the focal point F at the lens concave surface 2a. In the figure, the case where the
surface of the subject 4 and the focal point F coincide with each other is shown. If the radiation
angle e (one-half of the aperture angle) of the ultrasound from the lens concave surface 2a is
smaller than the predetermined critical angle determined by the inspection object 4, the
ultrasound is emitted toward the focal point F and When a reflective surface exists halfway, the
surface reflected wave reflected by the reflective surface, the reflected wave near the focal point
of the ultrasonic wave propagated inside, etc. return to the same path as the radiation path and
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are converted to the conversion element 3a. It reaches and excites the piezoelectric element 3a.
As a result, an electric signal proportional to the size of the returned ultrasonic wave is output
from the piezoelectric element 3a, and defect information and the like of the reflective surface
and the inside can be obtained based on this electric signal (ultrasonic flaw detector). On the
other hand, when the radiation angle e of the ultrasonic wave from the lens concave surface 2a is
equal to or more than the critical angle, the ultrasonic wave incident on the inspection object 4 at
the critical angle propagates as a surface acoustic wave on the surface of the inspection object 4,
Of the surface acoustic waves, an ultrasonic wave emitted to a path symmetrical to the radiation
path reaches the conversion element 3. The ultrasonic waves are emitted from the vicinity of the
central axis and reflected on the surface of the inspection object 40 and interfere with the
ultrasonic waves returned from the radiation path, and the interference waves excite the
piezoelectric element 3a to output an electric signal.
From the state of FIG. 6, while moving the ultrasonic probe 1 toward the test object 4 (in the -Z
direction), the electric signal of the interference wave is collected and plotted to obtain a constant
period. You can get the curve that you have. This curve is the so-called V (Z) curve, which is
shown in FIG. 7 (ultrasound microscope). FIG. 7 is a waveform diagram showing a V (Z) curve, in
which the abscissa represents the position of the probe 1 and the ordinate represents the
received signal level of the interference wave. As shown, the V (Z) curve has a constant period
?2. The period ?Z has a predetermined relationship with the propagation velocity of the
surface acoustic wave of the inspection object 4, and the propagation velocity can be understood
by measuring the period ?Z, and the physical properties of the inspection object can be
evaluated by knowing the propagation velocity. be able to. [Problems to be Solved by the
Invention] In the above-mentioned ultrasonic flaw detector, it may be necessary to narrow the
ultrasonic beam outputted from the acoustic lens depending on the type of the inspection object
4 or the inspection mode. In this case, an ultrasound probe with an opening angle adapted to the
purpose has to be replaced with the currently mounted ultrasound probe. On the other hand, in
the case of an ultrasonic microscope, the surface acoustic wave velocity is different depending on
the type of the object to be inspected, and the critical angle is usually different accordingly. Also,
when the inspection object 4 is a thin film, there are cases where a plurality of surface acoustic
waves are generated, and in this case, a probe having an opening angle suitable for each surface
acoustic wave must be replaced and used. . The replacement of these ultrasound probes is not
only extremely troublesome for the user, but it is also necessary to stock many ultrasound
probes, they have to be stored, and extra time in terms of storage management. I needed it. An
object of the present invention is an ultrasonic probe which solves the problems in the abovementioned prior art, can arbitrarily change the opening angle, and can accurately collect a
required signal by changing the opening angle. To provide [Means for Solving the Problems] In
order to achieve the above object, according to the present invention, there is provided an
acoustic lens having a lens concave surface formed at any end, and fixed on the acoustic lens at a
position facing the lens concave surface. A shield for shielding the ultrasonic wave from the
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concave surface of the lens, in an ultrasonic probe comprising: an ultrasonic probe which
generates an ultrasonic wave by voltage application and converts the received ultrasonic wave
into an electric signal proportional to the ultrasonic wave; A shield driving means for driving the
shield to change the shield head surface, forming a surface of the shield opposite to the concave
surface of the lens as a scattering surface, and The surface on the concave side of the lens is
covered with a member that suppresses the reflection of ultrasonic waves.
[Operation] When the shield driving means is operated, the shield is driven at the lower part of
the concave surface of the lens, and the shield area is changed to change the opening angle.
Thereby, the opening angle can be arbitrarily changed, and one ultrasonic probe can handle
various test objects, various inspection modes, and various critical angles. Also, the reflection of
the ultrasonic wave incident on the shield is suppressed, and the ultrasonic wave transmitted
through the shield is scattered on the scattering surface. As a result, the ultrasonic waves emitted
by the lens concave surface or ? and blocked by the shield never reach the conversion element,
and have no adverse effect on the electric signal output from the conversion element, and an
accurate signal is collected. be able to. The present invention will be described below based on
the illustrated embodiments. FIG. 1 is a side view of an ultrasonic probe according to an
embodiment of the present invention, and FIG. 2 is a perspective view of a shielding plate shown
in FIG. In FIG. 1, the same parts as those shown in FIG. Denoted at 10a and 1ob are shielding
plates extending in the same direction at the lower part of the lens concave surface 2a, and at lla
and llb are arms supporting the shielding plates lOa and 10b at the lower part and having a
twisting hole at the upper part. The shields 10a and IOb will be described in more detail below
with reference to FIG. Reference numerals 12a and 12b denote supports fixed on opposite side
surfaces of the acoustic lens 2, and project toward the front in the figure. The reference numeral
13 denotes a hinged rod which is screwed into the arms 11a, Ilb and the supports 12a, 12b. The
shielding plates 10a and 10b are supported by the supports 12a and 12b via the wing 13 and
the arms 11a and 11b. Reference numeral 14 denotes a knob for rotating the butterfly rod 13.
The screws of the wing 13 are cut in the opposite direction, and the arms 11a, 11b and the
support holes of the supports 12a, 12b are also formed in the corresponding support holes.
Reference numeral 15 denotes the ultrasonic probe of this embodiment. The shielding plate 10a
is configured as shown in FIG. That is, 10a is a shielding plate main body, which is made of, for
example, sapphire. 10a = is an acoustic matching layer applied to the upper surface (lens concave
surface 2a side) of the shielding plate body 10a1, and a member having an acoustic impedance
intermediate between the acoustic impedance of the medium 5 and the acoustic impedance of
the shielding plate body 10a, eg, It is configured by applying silicon dioxide at a thickness of 1?4
or 3?4 of the wavelength of ultrasonic waves. Reference numeral 10a denotes a scattering
surface formed on the lower surface (opposite to the lens concave surface 2a) of the shielding
plate main body 10al, which is composed of a large number of asperities.
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The configuration of the shielding plate 10b is also the same as the configuration of the shielding
plate 10a, so the description thereof will be omitted. Next, the operation of this embodiment will
be described with reference to FIGS. 3 and 4. FIG. 3 is a side view of the vicinity of the concave
surface 2a of the lens. In the figure, the same parts as those shown in FIG. 1 are given the same
reference numerals. When the thumb 14 is rotated, the butterfly rod 13 is also rotated, and in
response to this rotation, the arms 11a and Ilb move. For example, when the thumb 14 is rotated
to the right, the arm 11a moves to the left and the arm 11b moves to the right. As a result, the
distance t (FIG. 3) between the shielding plates 10a and 10b is expanded, and the opening angle
? is increased. Conversely, when the thumb 14 is turned to the left, the arm 11a moves to the
right and the arm 11b moves to the left. As a result, the interval t (FIG. 3) between the shielding
plates 10a and 10b is sandwiched, and the opening angle ? decreases. Now, when the inspection
object is replaced from one inspection object to another, if the opening angle suitable for the
inspection object is smaller than the opening angle used in the inspection object of the foremost,
the inspector will turn the knob 14 to the left Then, the shield plates 10a and 10b are brought
close to each other, the interval t is narrowed, and the opening angle ? is changed to an
appropriate angle. Conversely, if a larger opening angle is required, the mass 14 is rotated in the
reverse direction to increase the distance t and change the front opening angle to an appropriate
angle. FIG. 4 is a side view of the vicinity of one shielding tri 10 a. In this figure, Bo, Bet, B (12, B,
all indicate ultrasonic waves. The ultrasonic wave B + output from the conversion element 3 is
emitted to the inspection object 4 without being shielded by the shielding plate 10a. However,
the ultrasonic wave emitted from the acoustic lens 2 at an angle larger than the ultrasonic wave
B1 is shielded by the shielding plate 10a. In FIG. 4 the BO is shown shielded ultrasound. The
ultrasonic wave B0 emitted from the acoustic lens 2 is incident on the acoustic matching layer
10a2 of the shielding plate 10a, but most of the incident ultrasonic wave B0 passes through the
shielding plate body 10a1 because of the above configuration of the acoustic matching layer
10a2. Little part scratching B. Only I is reflected from the acoustic matching layer 10a2 and
returns to the acoustic lens 2. However, the ultrasonic wave BOI hardly reaches the conversion
element 3 because of the return angle and the small amount of return. On the other hand, among
the ultrasonic waves B0 incident on the acoustic matching layer 10a2, the ultrasonic waves that
have passed through the shielding plate main body 10a + by i3 reach the scattering surface 10as
and are scattered outside at various angles. One of them is indicated by the symbol BOW.
Because of this scattering, among the ultrasonic waves transmitted through the shielding plate
10a, there are hardly any ultrasonic waves that are reflected by the inspection object 4 and
returned to the conversion element 3.
From the above, even if the shielding plates 10a and 10b are provided, the signal output from the
conversion element 3 is not adversely affected. FIG. 5 is a plan view of another specific example
of the shielding plate. In the figure, 20 is a shielding plate of this embodiment, and 20S + to 20Sfi
are plates constituting the shielding plate 20. Each plate 20S, -20. . Are arranged in a rectangular
shape as shown in FIG. Since such a shutter structure and its drive device are well known,
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detailed illustration and description will be omitted. By operating the drive device, the size of the
central circular opening can be freely selected, whereby the size of the opening angle can be
arbitrarily selected. Although not shown, each of the plates 20S1 to 20S is provided with an
acoustic matching layer and a scattering surface as in the case of the shield plate 10a and Job of
the above specific example, so as to achieve the same function. It has become. As described
above, in the present embodiment, since the shielding plate is selectively displaced, the opening
angle can be arbitrarily changed, and ultrasonic probe can be performed every time the
inspection object, inspection mode, and critical angle are different. There is no need to replace
the child, which makes handling easier. In addition, it is possible to eliminate the need for having
a large number of ultrasonic probes, thereby saving the storage management time and reducing
the cost for the ultrasonic probes. Furthermore, since each shield plate or plate is provided with
the acoustic matching layer and the scattering surface, the adverse effect of the ultrasonic waves
shielded by the shield can be almost completely eliminated. It is apparent that the present
invention is also applicable to a lens (line focus lens) in which a lens concave surface is formed in
a semi-cylindrical surface as an acoustic lens. [Effects of the Invention] As described above,
according to the present invention, since the displaceable shield is provided under the concave
surface of the acoustic lens, the opening angle of the lens surface can be arbitrarily selected. It is
not necessary to replace the ultrasonic probe every time the inspection object, inspection mode
and critical angle are different, and the handling can be facilitated. In addition, it is possible to
eliminate the need for having a large number of ultrasonic probes, thereby saving the storage
management time and reducing the cost for the ultrasonic probes. Furthermore, since each shield
plate or plate is provided with the acoustic matching layer and the scattering surface, the adverse
effect of the ultrasonic waves shielded by the shield can be almost completely eliminated.
[0002]
Brief description of the drawings
[0003]
1 is a side view of an ultrasonic probe according to an embodiment of the present invention, FIG.
2 is a perspective view of a shielding plate shown in FIG. 1, FIG. 3 is a side view in the vicinity of
a lens surface, and FIG. 5 is a plan view of another specific example of the shielding plate, FIG. 6
is a side view of a conventional ultrasonic probe, and FIG. 7 is a waveform of a V (Z) curve FIG.
2 ииииииииииииии Acoustic lens, 3 ииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииии Shielding plate, 10
a, 10 b и и и Shielding plate body, 10az, 10bz иии и и и Acoustic matching layer, 10as, 10bi и и и и и
Scattering surface, 11a, llb и и и и и и и и и и и и и и 12a, 12b и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и
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ииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииии???
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