JPS5993495A - Acoustic spherical lens - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an acoustic spherical lens, particularly to an acoustic spherical lens suitable for use in an ultrasound microscope that utilizes high-frequency sound energy.

[Prior art]

In recent years, it has become possible to generate and detect high-frequency sound waves up to IQ)IZ, resulting in a sound wave wavelength of about 1 micron underwater, and therefore, a microscope using sound wave energy has been considered.

The key to such a device is how to create a narrow focused acoustic beam, and a conventional example will be explained with reference to FIG. That is, the cylindrical crystal 2, such as sapphire, has one end surface optically polished and laid flat, and the other end surface has a concave hole. Piezoelectric element 11 created on a flat plate surface? :RF
An electrical signal is applied to radiate plane wave RF sound waves into the crystal 2. This planar preposition is the crystal formed in the concave hole.
It is focused by a positive lens formed at the interface of the medium 3 to its fixed focal point. As is well known, if the ratio of the focal length to the aperture, ie, the F-number of the lens, is sufficiently small, this configuration can produce a very narrow acoustic beam. When a sample is placed near the focal point, this focused sound wave is subject to disturbances such as reflection, scattering, and transmission attenuation. Therefore, by detecting the energy of such disturbed sound waves, it is possible to generate an electrical signal that reflects the elastic properties of the sample. It is possible to get a signal. For detection of sound wave energy, the above-mentioned crystal system may be used again, or a similar crystal system may be placed opposite the confocal area.

As is clear from the above description, the conventional example uses a positive spherical lens as its focusing principle, which utilizes the sound speed difference between the crystal and the medium. Therefore, it is necessary to form a hemispherical concave hole in the crystal, but since the sound wave attenuation of the medium (usually water) from the lens surface to the focal point is extremely large, it is difficult to make a lens with a low F number, e.g. It is necessary to create a microspherical hole such as 0.2- and reduce the distance from the lens surface to the focal point to avoid sound wave attenuation. Moreover, in order for the spherical surface to function as a lens, it must not have any irregularities of at least 1/1O wavelength of the acoustic wave length. This is on the order of 0.1 μm for the IGH2 sound wave.

Conventionally, such lenses are processed by polishing, which is an extremely difficult process and can only produce lenses with a diameter of 0.5 mm.

[Purpose of the invention]

The present invention has been made in view of the above points, and its object is to provide a spherical lens with a minute aperture and a mirror surface.

[Summary of the invention]

It is well known in the industry that when creating glasses such as quartz glass, or when using natural quartz, crystal, etc., bubbles due to residual gas etc. exist or are generated inside the glass, and how to remove these bubbles. It is widely known that this determines the quality of such materials. By the way, for example, when we carefully observed the bubbles in quartz, we found that the bubbles had extremely good sphericity, and their interfaces had mirror surfaces that were impossible to achieve using polishing methods. In fact, as shown in Fig. 2, we cut out the bubble part 6 from a quartz plate 5 containing busy bubbles, attached a piezoelectric element 1 to the other side, and conducted an IGHz sound wave focusing experiment, and found that the focusing was extremely good. It was confirmed that the lens was excellent as a spherical lens for focusing high-frequency sound waves.1 The bubbles scattered in the quartz plate were spherical in size, ranging from 0.5 μm to 10 μm. Because of its existence, it is possible to obtain a spherical lens with a minute aperture, specularity, and sphericity that are impossible with polishing methods. However, when creating an acoustic lens using air bubbles that naturally occur in lens materials, the bubbles have various sizes and shapes, so it is difficult to create an acoustic lens with the same performance, that is, the same aperture. However, it is difficult to manufacture acoustic lenses in large quantities.

In order to eliminate this drawback, the present invention is characterized by using an acoustic lens in which a concave surface is formed using microspheres.

[Embodiments of the invention]

FIG. 3 is a diagram for explaining the acoustic lens according to the present invention, in which a cylindrical lot 7 as shown in FIG.
A conical concave surface 7 having a size d at the axial center of the tip of the
'make. Of course, the size d of this concave surface 7' can be selected depending on the spherical lens to be manufactured.

Next, as shown in Fig. 3('b), an adhesive such as epoxy resin 8 is applied to this concave portion, and the above-mentioned sphere 9 is placed as shown in Fig. 3(e)K, and the resin 8 is hardened. let The sphere 9 may be a completely hollow glass sphere sold by Airson & Riki Mink Co., Ltd.
]) uke 5 scientific('orporat
We use spheres sold by ion. Thereafter, only the sphere 9 is removed by melting or peeling off, to complete a lot 7 having a concave hole 9' of a predetermined size at the tip, as shown in FIG. Using this lot 7 as a template, a method for creating spherical lenses of the same shape from this will be described below.

After hardening the periphery of the lot 7 with plaster 10 as shown in FIG. 5(a), the lot 7 is taken out to complete a female mold 11 as shown in FIG. 5(b). This female shape 11 is shown in Figure 5 (C
), its properties are different from ordinary graphite, and rather it is a carbon material similar to glass and has the characteristic of not exhibiting any anisotropy.

It is effective to use furfural (CiHsCh ) and virol (04HsN) as organic substances. It was found that when 4 parts of furfural and 6 parts of pyrrole were selected, it had an appropriate viscosity and also had a good carbon yield in the firing carbonization step described below.As a catalyst for 0 polymerization, 4 to 5 times diluted hydrochloric acid (f! s degree 3.6%) to 1 to 3% of the above organic matter.
When added and stirred while heating to 50-80C, 2-
It polymerizes in 8 minutes and becomes a viscous liquid.

Heat this in air from room temperature to 80C at a rate of O, SC/C/lower to complete preheating.In this state, female type 11
The glassy carbon was peeled off from the glass, so the glassy carbon was taken out and heated at 1300t:'~25cm in vacuum.
When heated at 00tl:'t, a concave lens completely converted to glassy carbon can be made.

The glassy carbon thus prepared is ~10-1Ω
・It has σ electrical conductivity, its mechanical properties are similar to glass, Young's modulus ~3 x 10''N/m', density 1.
It was found that it has almost the same properties as Nokuirex glass, with a speed of 5X10"/ms and a sound speed of ~4600m/s. After sintering, the glassy X12 can be easily ejected from the female mold. As a result, a spherical lens is completed.

〔Effect of the invention〕

As described above, according to the present invention, since a hollow glass bulb is used, an acoustic spherical lens having the same diameter and high sphericity can be obtained.

[Brief explanation of the drawing]

1 and 2 are diagrams for explaining a conventional acoustic spherical lens, and FIGS. 3, 4, and 5 are diagrams for explaining an acoustic spherical lens according to the present invention. Agent Patent Attorney Toshiyuki Usuda 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. An acoustic spherical lens characterized by having a concave hole formed by transferring the spherical surface of a completely hollow glass sphere to one end surface of a sound wave propagation medium. 2. The acoustic spherical lens according to claim 1, wherein the sound wave propagation medium is glassy carbon.