JPS5837503B2 - sonic probe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sonic probe, particularly a sonic probe suitable for use in a microscope that utilizes high frequency wave energy.

In recent years, it has become possible to generate and detect high-frequency sound waves up to IGHz, resulting in a sound wave wavelength of approximately 1 micron underwater, and therefore, a microscope that utilizes sound wave energy has been considered.

In such devices, it is important to create a narrow and focused acoustic beam, and it is strongly desired to improve the performance of the acoustic probe.

First, a conventional sonic probe will be explained with reference to FIG.

That is, the sonic probe has one end surface polished to a flat surface, and the other end surface has a cylindrical crystal 1 made of a sound propagation medium such as sapphire with a concave hole cut out, and this crystal 1 is polished to a flat surface. A lower electrode 2 made of titanium, gold, chrome, aluminum, etc. is provided on the end face by vapor deposition or the like, a piezoelectric material 3 such as zinc oxide is provided on it by sputtering or the like, and an upper electrode 4 is further provided thereon by vapor deposition or the like. It consists of a piezoelectric element.

When an RF electric signal is applied between the upper electrode 4 and the lower electrode 2 of such a probe, the piezoelectric material 3 emits a plane wave RF sound wave into the crystal 1.

This plane wave is focused at a predetermined focal point S by a positive lens formed at the interface between the crystal 1 and the medium 5 formed in the concave portion.As is well known, the ratio of the focal length to the aperture is determined by the lens If the F-number of is sufficiently small, a significantly narrower acoustic beam can be created with the above-described configuration.

The focused sound wave is transmitted to the sample 6 placed near its focal point.
As a result, the sample undergoes disturbances such as reflection, scattering, and transmission attenuation, and by detecting this disturbed sound wave energy, it is possible to obtain an electrical signal that reflects the elastic properties of the sample.

Note that the above-mentioned sound wave energy detection may be performed by using the above-mentioned sonic probe again, or by using a round-shaped sonic probe placed opposite the confocal point.

As is clear from the above, the conventional example uses a positive spherical lens as its focusing principle, which utilizes the difference in sound speed between the crystal and the medium.

Therefore, in order to form a spherical lens with good focusing properties, it is important to form a concave hole with excellent specularity and sphericity in the crystal.

Moreover, since the attenuation of sound waves in the medium from the lens surface to the focal point S is extremely large, it is possible to create a lens with a low F number by forming a concave hole with a minute diameter of, for example, 0.2 mm. However, it is necessary to reduce the distance from the lens surface to the focal point 1 to avoid sound wave attenuation.

On the other hand, as the spherical surface of the lens becomes smaller, it is desirable that the area of the piezoelectric element portion that emits RF sound waves becomes smaller.

That is, as shown in FIG. 1, it is desirable that the diameter d of the concave hole and the diameter D of the upper electrode 4 be equal.

This is due to the following reasons.

That is, for example, as shown in FIG. 2, under the condition of d<D, R
When the F signal is radiated, plane waves propagate within the crystal along the path shown by the dotted line.

Therefore, the plane wave transmitted to the outside of the concave hole is diffusely reflected within the crystal and enters the piezoelectric material 3, causing unnecessary signals (noise).

Moreover, in contrast to the above-mentioned condition, when d>D, the F number of the lens becomes large, resulting in poor focusing performance and high resolution cannot be obtained.

Here, the relationship between the F number of the lens and the resolution will be described based on FIG. 3.

In the figure, the wavelength of the Hiranami wave is λ, and the F number of the lens is S.
When inθm, the resolution lρ is calculated by the following equation.

Here, θm is the opening angle of the sound wave beam.

Therefore, the resolution Aρ is better as the aperture angle θm of the acoustic beam becomes larger.

As explained above, in order to obtain high-resolution images using a microscope device that uses sound wave energy, it is necessary to reduce the lens diameter of the focusing spherical lens in the sound wave probe and to It is also necessary to reduce the area of the radiating piezoelectric element.

The present inventors have discovered that air bubbles that exist or occur inside glass such as quartz glass, or when natural quartz, crystal, etc. are used, are extremely useful as spherical lenses. It has now become possible to form a spherical lens with a micro aperture (0.2 mm), specularity, and sphericity that is impossible with conventional polishing methods.

However, as mentioned above, the diameter of the concave hole is 0. 2
When the diameter becomes as small as urn, it is extremely difficult to attach an upper electrode having the same diameter on the axis of the concave hole by vapor deposition or the like as in the past.

Furthermore, it was extremely difficult to connect a lead wire for applying an RF electric signal to this upper electrode.

The present invention has been made in view of the above points, and uses a conductive material, which is a flat part whose one end is rotatably supported and whose other end is in contact with a piezoelectric material with a predetermined cross-sectional area, as an upper electrode. The present invention provides a sonic probe that

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 4 is a diagram showing an embodiment of the present invention.

In the figure, the crystal 1 is supported by the case 7 and a predetermined gap is maintained between it and the sample 6.

A connector 8 for connecting to an RF oscillator is attached to the upper part of the case 7.

The octopus connector 8 can be moved on the XY plane using four knobs 9.

A flexible bellows 10 is attached to the tip of the connector 8, and a ball (metal ball) 1 is attached to the ball receiver 11 with a diameter.
2 transmits an RF signal to the piezoelectric material 3.

Therefore, under normal setting conditions, the ball 12 can be moved on the central axis of the lens ball hole by adjusting the knob (acoustic), and since the bellows 10 is flexible, the ball 12 can be moved on the surface of the piezoelectric material 3. is extremely light and makes reliable electrical contact.

As a result, the upper surface of the piezoelectric material 3 is not damaged.

FIG. 5 is an enlarged view of the vicinity of the ball receiver 11.

The upper part of the ball 12 is rotatably supported by a ball receiver 11 having a concave hole that substantially matches the spherical surface of the ball.

Also, the lower part of the ball 12 is a concave hole of the crystal 1 (lens spherical surface)
It is polished to a flat surface to have a diameter D equal to the diameter d of.

When assembling the device, even if the upper surface of the piezoelectric material 3 and the flat polished portion of the lower part of the ball 12 are supported at an angle θ such that they are not completely parallel to each other as shown in FIG. gradually approach the ball 12 until a portion of the piezoelectric material 3
(FIG. 6b), the ball 12 rotates and the notch of the ball completely contacts the surface of the piezoelectric material 3 (FIG. 6C).

Here, as shown in FIG. 7, the length L of the notch of the ball 12
If the diameter D of the cutout part of the ball 12 is made equal to the concave hole d of the crystal 1, it will fit the crystal 1 with any concave hole installed in the case 7. By simply replacing the piezoelectric material 3 with a new ball 12, a plane wave can be emitted from the piezoelectric material 3 into the crystal 1 while satisfying the condition d=D.

The above has been described with regard to electrically contacting the piezoelectric material 3 with the ball 12 having a notch, but instead of the ball 12, a liquid metal with a high surface tension (for example, mercury, etc.) is used in the ball receiver 11. When the liquid metal reaches the concave surface of the ball 12, it becomes spherical, but the contact area of the liquid metal can be changed by adjusting the gap with the piezoelectric material.
It is also clear that the same effect can be obtained.

Furthermore, as shown in Figure 8, the apex portion of the cone has a length L.
A similar effect can be obtained by cutting the hole so that the diameter D in the cutting direction is equal to the concave hole d.

However, in this case, the support of the cone should not be flexible, and if the parallelism with the top surface of the piezoelectric material 3 is not maintained as shown in FIG. contact, and complete contact is impossible.

In the above embodiment, a sonic probe having two electrodes was described, but the sonic propagation medium may be a material having electrical conductivity (for example, glassy carbon such as glassy carbon).
It goes without saying that the present invention can also be applied to a sonic probe in which the sonic wave propagation medium itself serves as the lower electrode.

As described above, according to the present invention, it is possible to omit the upper electrode deposition process and the lead wire connection process, which were extremely difficult in the past, and at the same time, it is possible to easily equalize the area of the sound wave focusing part and the area of the sound wave emission part. It has the great advantage of being able to do a lot of things, and can be expected to have great effects when creating devices that use high-frequency focused sound waves, such as sonic microscopes, microscopic non-abrasive inspections, and ultrasonic spectroscopy.

[Brief explanation of the drawing]

Figure 1 is a diagram to explain the structure of a conventional sonic probe, Figure 2 is a diagram to explain the drawbacks of a conventional sonic probe, and Figure 3 is a diagram to explain the relationship between the F number of the lens and the resolution. Figure 4 is a diagram for explaining the configuration of an embodiment of the present invention, Figure 5 is a diagram showing the configuration of an embodiment of the present invention.
The figures are shown in FIG. 4 - A diagram showing the configuration of the main parts of the embodiment, and FIG. 6 is a diagram illustrating the state of contact between the upper electrode and the piezoelectric material for the embodiment shown in FIG. 4. , FIG. 7 is a diagram showing the above-mentioned upper electrode, and FIG. 8 is a diagram showing an upper electrode of another embodiment of the present invention.

Claims (1)

[Claims] 1. A sound wave propagation medium having a concave hole formed at one end, a first electrode, a piezoelectric material, and a second electrode formed at the other end of the sound wave propagation medium in this order. A sonic probe consisting of a piezoelectric element, which is provided with means for rotatably supporting one end of the second electrode, and the other end of the second electrode is connected to the piezoelectric material in a predetermined cross-sectional area. A sonic probe characterized by having a flat part that makes contact. 2. In the sonic probe according to claim 1,
A sonic probe characterized in that the second electrode is a metal ball whose flattened portion is a cutout portion with a predetermined cross-sectional area.