JP2602896B2 - Focus transducer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus probe in which a point focus type probe is combined with a case in which a liquid containing the probe is housed. More particularly, the present invention relates to a focus probe suitable for focusing an ultrasonic beam emitted from the bottom of a case into a parallel beam having substantially the same diameter as the beam diameter at the focal point of a point focus type probe in the case.

[Conventional technology]

Conventionally, focus probes have been used mainly for point-focus type probes to detect minute defects in the subject by the water immersion method. The focused ultrasound beam is focused at one point and focused within the subject,
This is because an increase in sound pressure at the focal point has the property of increasing the flaw detection sensitivity and improving the ability to detect fine defects. An example of using a conventional focus probe will be described with reference to FIGS. 4 and 5. FIG. In the drawing, reference numeral 1 denotes a point-focus type probe (hereinafter, simply referred to as a probe), which is opposed to the subject 2.
Together with water 3. The inspection target is
For example, in the state of adhesion of a contact surface (hereinafter referred to as an interface) 2b between a thin member A and a member B constituting an object 2 such as an electronic component, the entire surface of the interface 2b is flaw-detected because it directly affects performance and life. Subject to. At the time of flaw detection, first, the probe 1 is focused on the surface 2a of the subject 2, and the known member A
Object 2 or probe 1 by a distance corresponding to the thickness dimension of
Is moved to focus on the interface 2b. Usually, whether or not the interface 2b is focused is determined by detecting the maximum level of the echo of the reflected wave from the interface 2b on an oscilloscope (not shown). However, at the end of the interface 2b, as shown in FIG. 5, the energy amount of the ultrasonic beam reaching the interface 2b via the member A is changed from the point of incidence of the beam on the surface 2a of the subject 2 by the member A. The distance D to the end face (substantially coincident with the center of the probe 1) is less than about 1/2 of the total beam, and the echo level sharply decreases. Has become a problem. The aperture D increases as the focal length decreases to reduce the size of the ultrasonic beam at the focal point of the probe 1.
As the material is faster in sound velocity, such as ceramics, the refraction angle becomes larger and the distance D is enlarged, and the range where the beam energy at the end of the interface 2b is reduced is enlarged. On the other hand, when scanning the interface 2b,
Scanning is normally started from the end of the interface 2b, and the focal position is moved to the left and right, and is sequentially moved at a predetermined pitch in the direction perpendicular to the left and right, but the beam energy at the end of the interface 2b is changed. Due to the decrease in the amount, the flaw detection accuracy in the peripheral portion was significantly reduced compared to the central portion of the interface 2b.

[Problems to be solved by the invention]

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a focus probe capable of detecting flaws in the vicinity of an edge of an interface with the same precision as the center.

[Means for solving the problem]

In order to achieve the above object, a focus probe according to the present invention is provided with a spherical shape inward at the center of the bottom surface of a cylindrical case in which a liquid is injected at one end and has a bottom surface at the other end. A swelled acoustic lens is formed, and a point focus type probe immersed in a liquid in the case is placed in the case at a position where the focal length of the probe matches the surface of the acoustic lens. It is characterized in that it is provided internally so as to be adjustable in position.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an overall sectional view of the probe, FIG. 2 is a detailed view of a portion "a" of FIG. 1, and FIG. 3 is a sectional view taken along line III-III of FIG. In the figures, the same reference numerals as those in FIGS. 4 and 5 indicate the same parts.
In the figure, reference numeral 4 denotes a probe having the same focal length as the conventional probe shown in FIG. 4, and a screw 4a is cut on the outer periphery. 5
Is a cylindrical case, one end of which is open and the other end has a bottom surface 5b.
Screw 5a screwed with 4a is cut. On the other hand, an acoustic lens 6 bulging spherically inward of the case is provided at the center of the bottom surface 5b. Water 7 is injected into the case 5, and the probe 4 is screwed in a state of being immersed in the water 7. At this time, a position where the focal length of the probe 4 matches the surface 6 a of the acoustic lens 6. Is fine-tuned for positioning. The case 5 and the acoustic lens 6 are made of uniform quartz glass, acrylic resin, aluminum alloy, or the like, and are manufactured to have a small thickness (for example, 1 mm to 3 mm) in consideration of strength, workability, acoustic characteristics, and the like. .
Further, the case 5 and the acoustic lens 6 may be integrated, or only the acoustic lens 6 may be made of another material in consideration of workability and the like. On the other hand, the curvature forming the surface 6a of the acoustic lens 6 is
Determined by the sound velocity ratio between the acoustic lens 6 and the water 7, the surface 6a
The ultrasonic beam focused at is refracted at the surface 6a,
The curvature is selected so as to be emitted by a parallel beam focused approximately the same diameter as the focal point. Reference numeral 8 denotes a slit provided so that the water 7 can move freely in the case 5 when the probe 4 is moved along the screws 4a and 5a in the case 5.

In the probe in which the probe 4 and the case 5 are combined, the acoustic lens 6 of the ultrasonic beam emitted from the probe 4
The size of the focal point on the surface 6a is actually a small finite size due to the wave nature of a sound wave, not a point. Second
In the figure, the size of the focal point is shown in an enlarged scale for the sake of explanation. The size d of the focal point is calculated based on the transducer diameter of the probe 4, the focal length, and the wavelength determined by the operating frequency. Value. However, as shown in FIG.
The emitted ultrasonic beam is refracted on the surface 6a under the influence of the acoustic lens 6, and is emitted from the acoustic lens 6 as a focused parallel beam having the same diameter as the focal point size d, and passes through the water 3. Incident on the subject 2 and reaches the interface 2b. For this reason, the distance D at which the energy amount of the conventional ultrasonic beam shown in FIG. 5 is reduced to half or less is almost equal to the focal spot size d, and is a small value substantially close to zero. Therefore the interface
Even at the end of 2b, the energy of the ultrasonic beam is incident with almost no decrease, and the interface 2b is located at the center,
Since the flaw detection can be performed without distinguishing the end portions, the whole surface of the interface 2b can be accurately flaw-detected.

In the above embodiment, the case 5 has a cylindrical shape,
A screw 5a is provided on the inner periphery of the open side, and an outer screw 4a of the probe 4 is provided.
However, the case 5 may be formed in a rectangular cylindrical shape, and the screw 4a, 5a may not be provided, and the outer periphery of the probe 4 may slide slightly on the inner periphery of the case. Good.

〔The invention's effect〕

As described above, the focus probe according to the present invention is a sound probe in which a cylindrical case having a bottom surface at one end side is spherically inwardly inflated at the center of the bottom surface of the cylindrical case. A point-focus type probe formed with a lens and immersed in the liquid in the case is adjusted in the case so that the focal length of the probe matches the surface of the acoustic lens. Because of the configuration, it is possible to focus the ultrasonic beam emitted from the bottom of the case into a parallel beam having substantially the same diameter as the beam diameter at the focal point of the probe in the case,
There is a practical effect that the flaw detection around the edge of the interface can be performed with the same precision as the center.

[Brief description of the drawings]

FIG. 1 is an overall sectional view of a focus probe showing one embodiment of the present invention, FIG. 2 is a detailed view of a portion "a" of FIG. 1, and FIG. 3 is a sectional view taken along line III-III of FIG. is there. FIG. 4 is an explanatory view of an example of use of a conventional focus probe, in which the focus is on the surface of the subject, and FIG. 5 is the same as FIG.
FIG. 4 is a diagram in which a focus is set on an interface of a subject.

Claims (2)

(57) [Claims] 1. An acoustic lens bulged spherically inward of a case is formed at a central portion of the bottom surface of a cylindrical case into which a liquid having one end open and a bottom surface is injected. A point-focus type probe immersed in a liquid in the case is provided in the case so as to be position-adjustable at a position where the focal length of the probe matches the surface of the acoustic lens. Focus probe characterized by the following. 2. An ultrasonic wave emitted from a probe in the case and focused on the surface of the acoustic lens is refracted at the surface of the acoustic lens, and has a diameter substantially equal to the size of the focal point from the bottom surface of the case. 2. The focus probe according to claim 1, wherein the focus probe is formed to have a curvature emitted by the focused parallel beam.