JP2529444B2 - Ultrasonic probe - Google Patents

Description

TECHNICAL FIELD The present invention relates to an ultrasonic probe used in an ultrasonic flaw detector or an ultrasonic microscope.

[Conventional technology]

The ultrasonic flaw detector is a device that inspects the presence or absence of defects inside the object and the state of the object surface using ultrasonic waves, and the ultrasonic microscope is a device that mainly analyzes the physical properties of the surface layer of the object. An ultrasonic probe is used to transmit and receive ultrasonic waves in both devices. 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,
Reference numeral 1 denotes an ultrasonic probe. An acoustic lens 2 has a lens concave surface 2a and a flat surface 2b facing the concave surface 2a. Reference numeral 3 denotes a conversion element, which is a piezoelectric element 3a, a lower electrode 3b, and an upper electrode.
Composed of 3c. 3d shows the lead wire connected to each electrode. The conversion element 3 is fixed to the flat surface 2b of the acoustic lens 2. Reference numeral 4 is an object to be inspected (inspection object), and 5 is a medium (usually water is used) interposed between the concave surface 2a of the lens and the inspection object 4.

In the ultrasonic probe 1, when a predetermined voltage (normal burst wave) is applied to each of the electrodes 3b and 3c via the lead wire 3d, the piezoelectric element 3a is excited and an ultrasonic wave is generated. This ultrasonic wave passes through the acoustic lens 2 as shown by the wavy line in the figure, and is focused on the focal point F at the lens concave surface 2a. The figure shows a case where the surface of the object 4 to be inspected and the focal point F coincide with each other.

Radiation angle Θ of ultrasonic wave from lens concave surface 2a (1 / the aperture angle)
2) is smaller than a predetermined critical angle determined by the object 4 to be inspected, the ultrasonic wave is radiated toward the focal point F, and if there is a reflecting surface in the middle, the ultrasonic wave is reflected by the reflecting surface. The reflected surface reflected wave and the reflected wave near the focal point of the ultrasonic wave propagating inside return to the same path as the radiation path, and the conversion element 3a
And the piezoelectric element 3a is excited. As a result, an electric signal proportional to the magnitude of the returned ultrasonic wave is output from the piezoelectric element 3a, and defect information on the reflecting surface or inside is obtained based on this electric signal (ultrasonic flaw detector).

On the other hand, when the radiation angle Θ 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 on the surface of the inspection object 4 as a surface acoustic wave, Among the surface acoustic waves, ultrasonic waves radiated in a path symmetrical to the radiation path reach the conversion element 3. This ultrasonic wave interferes with the ultrasonic wave that is radiated from the vicinity of the central axis and is reflected on the surface of the inspection object 4 and returned along the radiation path, and this interference wave is generated by the piezoelectric element.
3a is excited to output an electric signal. From the state shown in FIG. 6, the ultrasonic probe 1 is directed toward the DUT 4 (in the -Z direction).
By collecting the electric signal of the interference wave while moving and plotting this, a curve having a constant period can be obtained. This curve is the so-called V (Z) curve and is shown in FIG. 7 (acoustic microscope).

FIG. 7 is a waveform diagram showing a V (Z) curve, where the horizontal axis represents the position of the probe 1 and the vertical axis represents the received signal level of the interference wave. As shown, the V (Z) curve has a certain period ΔZ. The period ΔZ has a predetermined relationship with the propagation velocity of the surface acoustic wave of the inspected body 4, and the propagation velocity can be known by measuring the period ΔZ, and the physical properties of the inspected body can be evaluated by knowing the propagation velocity. be able to.

[Problems to be Solved by the Invention]

In the ultrasonic flaw detector, it may be necessary to narrow down the ultrasonic beam output from the acoustic lens depending on the type of the inspection object 4 or the inspection mode. In this case, the ultrasonic probe having an opening angle suitable for the purpose must be replaced with the currently installed ultrasonic probe.

On the other hand, in the 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. When the object 4 to be inspected is a thin film, 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. .

Replacing these ultrasonic probes is not only extremely troublesome for the user, but also many ultrasonic probes must be prepared and stored, which requires extra labor from the viewpoint of storage management. I needed it.

An object of the present invention is to solve the above-mentioned problems in the prior art, to change the aperture angle arbitrarily, and to obtain a desired signal accurately by changing the aperture angle. To provide a child.

[Means for solving the problem]

In order to achieve the above object, the present invention is an acoustic lens having a lens concave surface formed at one end, and is fixed at a position facing the lens concave surface on the acoustic lens and generates ultrasonic waves by applying a voltage. In an ultrasonic probe provided with a conversion element for converting the received ultrasonic wave into an electric signal proportional thereto, and a shield for shielding the ultrasonic wave from the concave surface of the lens, by driving the shield. It is characterized in that a shield driving means for changing the shield region is provided.

[Action]

When the shield driving means is operated, the shield is driven in the lower part of the concave surface of the lens to change the shield region and change the aperture angle. Thereby, the opening angle can be arbitrarily changed, and one ultrasonic probe can cope with various kinds of objects to be inspected, various kinds of inspection modes, and various kinds of critical angles.
Further, the reflection of the ultrasonic waves that have entered the shield is suppressed, and the ultrasonic waves that have passed through the shield are scattered by the scattering surface. As a result, the ultrasonic waves emitted from the concave surface of the lens and shielded by the shield do not reach the conversion element and do not have any adverse effect on the electric signal output from the conversion element.
Accurate signals can be collected.

〔Example〕

 Hereinafter, the present invention will be described 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 the shield plate shown in FIG. First
In the figure, the same parts as those shown in FIG. 6 are designated by the same reference numerals and the description thereof will be omitted. 10a and 10b are shielding plates extending in the same direction at the bottom of the concave lens surface 2a, and 11a and 11b are shielding plates at the bottom.
It is an arm that supports 10a and 10b and has a screw hole at the top. The shield plates 10a and 10b will be described in more detail later with reference to FIG. Reference numerals 12a and 12b denote supports fixed to opposite side surfaces of the acoustic lens 2 and project toward the front in the figure. Reference numeral 13 is a spiral rod screwed into the arms 11a and 11b and the supports 12a and 12b. The shield plates 10a and 10b are the spiral rod 13 and the arm.
It is supported by supports 12a and 12b via 11a and 11b. Reference numeral 14 is a knob for rotating the spiral rod 13. The screw of the spiral rod 13 is cut left and right, and the arms 11a and 11b and the supports 12a and 12b are cut.
The screw holes of are also formed in corresponding screw holes. Reference numeral 15 denotes the ultrasonic probe of this embodiment.

The shielding plate 10a is constructed as shown in FIG. That is, 10a ₁ is a shield plate body, and is made of, for example, sapphire. 10a ₂ is the acoustic matching layer applied on the upper surface of the shielding plate body 10a ₁ (lens concave surface 2a side), member having an intermediate acoustic impedance between the acoustic impedance of the acoustic impedance shield body 10a ₁ of the medium 5, For example, silicon dioxide is applied at a thickness of 1/4 or 3/4 of the wavelength of ultrasonic waves. 10a ₃ A scattering surface formed on the lower surface of the shielding plate body 10a ₁ (on the side opposite to the lens concave surface 2a), and is composed of a large number of irregularities. The configuration of the shielding plate 10b is also the shielding plate 10a.
Since the configuration is the same as that of 1, 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 near the lens concave surface 2a. In the figure, the same parts as those shown in FIG. 1 are designated by the same reference numerals. When the knob 14 is rotated, the spiral rod 13 is also rotated, and the arms 11a and 11b move according to this rotation. For example,
When the knob 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 Θ _A is increased. Conversely, when the knob 14 is rotated to the left, the arm 11a moves to the right and the arm 11b moves to the left. As a result, the distance t (FIG. 3) between the shielding plates 10a and 10b is narrowed and the opening angle Θ _A is reduced.
Now, when the inspection object is changed from one inspection object to another, and the opening angle suitable for the inspection object is smaller than the opening angle used for the previous inspection object, the inspector moves knob 14 to the left. Then, the shield plates 10a and 10b are moved closer to each other, the gap t is narrowed, and the opening angle Θ _A is set and changed to an appropriate angle. On the contrary, when a larger opening angle is required, the knob 14 is rotated in the opposite direction to increase the interval t and change the opening angle to an appropriate angle.

FIG. 4 is a side view in the vicinity of one shield plate 10a. In this figure, B ₀ , B ₀₁ , B ₀₂ and B ₁ all represent ultrasonic waves. The ultrasonic wave B ₁ output from the conversion element 3 is radiated to the device under test 4 without being shielded by the shield plate 10a. However, the ultrasonic wave emitted from the acoustic lens 2 at an angle larger than the ultrasonic wave B ₁ is shielded by the shield plate 10a. In FIG. 4, B ₀ shows the shielded ultrasonic wave. Ultrasonic waves emitted from the acoustic lens 2
B ₀ is incident on the acoustic matching layer 10a ₂ of the shielding plate 10a, but due to the above-described configuration of the acoustic matching layer 10a ₂ , most of the incident ultrasonic wave B ₀ passes through the shielding plate main body 10a ₁ and is extremely small. only B ₀₁ reflected from the acoustic matching layer 10a ₂ returns to the acoustic lens 2. However, this ultrasonic wave B ₀₁ hardly reaches the conversion element 3 because of its return angle and a minute return amount. On the other hand, among the ultrasonic waves B ₀ that have entered the acoustic matching layer 10a ₂ , the ultrasonic waves that have passed through the shielding plate body 10a ₁ reach the scattering surface 10a ₃ and are scattered to the outside at various angles. One of them is labeled B ₀₂ . Due to this scattering, of the ultrasonic waves that have passed through the shield plate 10a, there is almost no ultrasonic wave that is reflected by the device under test 4 and returns to the conversion element 3. From the above, the shielding plates 10a, 10b
Even if the above is provided, no adverse effect is exerted on the signal output from the conversion element 3.

FIG. 5 is a plan view of another specific example of the shielding plate. In the figure,
Reference numeral 20 is a shield plate of this specific example, and 20S _{1 to} 20S _n are plate bodies constituting the shield plate 20. Each plate member 20S ₁ to 20 _n are configured as shown in a rectangular shape, are arranged sequentially stacked, a so-called shutter structure. Since such a shutter structure and its drive device are well known, detailed illustration and description thereof will be omitted. The size of the central circular opening can be freely selected by operating the driving device, and thus the size of the opening angle can be arbitrarily selected. Although not shown, each of the plate bodies 20S _{1 to} 20S _n includes
Similar to the shielding plates 10a and 10b in the specific example described above, an acoustic matching layer and a scattering surface are provided so as to achieve the same function.

As described above, in this embodiment, since the shield plate is selectively displaced, the opening angle can be arbitrarily changed, and the ultrasonic probe can be used for each of the object to be inspected, the inspection mode, and the critical angle. There is no need to replace the child, and handling is easy. Also,
It is possible to eliminate the need to provide a large number of ultrasonic probes, which can save the labor of storage management and reduce the cost for the ultrasonic probes. Furthermore, since the acoustic matching layer and the scattering surface are provided on each shielding plate or plate, it is possible to almost completely eliminate the adverse effect of the ultrasonic waves shielded by the shielding plate.

It is obvious that the present invention can be applied to a lens (line focus lens) in which a concave lens surface is formed as a semi-cylindrical surface as an acoustic lens.

〔The invention's effect〕

As described above, according to the present invention, since the displaceable shield is provided below the concave surface of the lens of the acoustic lens, the aperture angle of the lens surface can be arbitrarily selected. It is not necessary to replace the ultrasonic probe each time the mode and the critical angle are different, and the handling can be facilitated.
In addition, it is possible to eliminate the need to have a large number of ultrasonic probes, which saves the trouble of storage management.
In addition, the cost for the ultrasonic probe can be reduced.

[Brief description of drawings]

FIG. 1 is a side view of an ultrasonic probe according to an embodiment of the present invention,
2 is a perspective view of the shield plate shown in FIG. 1, FIG. 3 is a side view near the lens surface, and FIG. 4 is a side view near one shield plate.
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 diagram of a V (Z) curve. 2 ... Acoustic lens, 3 ... Conversion element, 4 ... Inspected object,
10a, 10b ... shield plate, 10a, 10b ₁ ... shield plate body, 10
a ₂ , 10b ₂ ... acoustic matching layer, 10a ₃ , 10b ₃ ... scattering surface, 11
a, 11b ... arms, 12a, 12b ... supports, 13 ... spirals, 14 ...
… Knob, 15… Ultrasonic probe

Claims (3)

(57) [Claims] 1. An acoustic lens having a lens concave surface formed at one end, and an acoustic lens which is fixed at a position facing the lens concave surface on the acoustic lens, generates ultrasonic waves by applying a voltage, and receives ultrasonic waves. In an ultrasonic probe provided with a conversion element for converting into an electric signal proportional to, and a shield for shielding the ultrasonic wave from the concave surface of the lens, a shield for driving the shield to change the shield area. An ultrasonic probe having a driving means. 2. The ultrasonic probe according to claim 1, wherein the shield has a surface opposite to the concave surface of the lens as a scattering surface. 3. The shield according to claim 1 or 2, characterized in that the concave surface of the lens is covered with a member that suppresses reflection of ultrasonic waves. And ultrasonic probe.