JPS60149963A - Ultrasonic microscope - Google Patents

Abstract

PURPOSE:To make it possible to stably hold a liquid medium to the leading end part of a sound wave lens, by enlarging the solid angle of a spherical surface forming the transmitting receiving surface of the sound wave lens to at least 180 deg. or more. CONSTITUTION:In the case of the drawing (b), a concaved surface part having a spherical surface of which the solid angle is slightly larger than 180 deg. is formed to the transmitting receiving surface of a lens 1. This lens 1 having such shape can be easily obtained by a method wherein a spherical air bubble remaining in a lens material such as quartz is utilized and the lens material is ground to the vicinity of the equator surface of the air bubble to expose a spherical surface. The drawing (c) shows such a state that the spherical lens of the drawing (b) is used in an ultrasonic microscope and, when a liquid metal 14 is inserted into the concaved surface hole as shown by the drawing, said liquid metal 14 is sufficiently held in the concaved surface hole and, therefore, stably held between the spherical lens 1 and a specimen 7 without receiving the influence of external shock.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an ultrasound microscope, and more particularly to an ultrasound microscope equipped with means for photographing a specimen.

In recent years, it has become possible to generate and detect ultra-high frequency sound waves of up to 1 GHz, making it possible to realize sound wavelengths of approximately 1 μm underwater, and as a result, it has become possible to obtain high-resolution sonic imaging devices. That is, a concave lens is used to create a focused sound wave beam, achieving a high resolution of 1 μm.

Insert a sample into the above beam and detect the reflected ultrasonic waves from the sample to elucidate the elastic properties of minute regions of the sample.
Alternatively, if the sample is mechanically scanned in two dimensions and the intensity of this signal is displayed as a brightness signal on a cathode ray tube, the fine structure of the sample can be enlarged.

FIG. 1 is a diagram showing a schematic configuration of such an ultrasound microscope. Ultrasonic waves are focused, transmitted and received by a sonic lens l, whose structure consists of optically polishing one side of a material made of old columnar fused silica, etc., and then applying a piezoelectric thin film (for example, Z
A pulse oscillator 4 is connected to the piezoelectric thin film 2 which has a sandwich structure in which n0) 2 is sandwiched between the upper and lower electrodes 3.
The ultrasonic wave 6 is generated by applying the pulse 5 generated from the ultrasonic wave 6. In addition, a concave hole with a diameter of about 0.1 to 1.0 mm is formed at the other end, and between this hole and the sample,
Medium for propagating the ultrasonic waves 6 to the sample 7 (e.g. water)
8 is fulfilled.

The ultrasonic waves 6 generated by the piezoelectric thin film 2 propagate in the cylinder as open-plane waves. When this plane wave reaches the hole, the quartz (
A refraction effect occurs due to the difference in sound speed between water (sound speed 6000 m/s) and water (sound speed 1500 m/s), and focused ultrasonic waves 6 can be irradiated onto the surface of the sample 7. Conversely, the ultrasonic waves reflected from the sample 7 are collected and phased by a spherical lens.
It becomes a plane wave and reaches the piezoelectric thin film 2, where the RF signal 9
is converted to This RF signal 9 is received by a receiver 10,
Here, the diode is detected and the video signal is converted into 11 parts.
It is used as a CRT display 120 input signal.

In the apparatus configured in this way, the sample 7 is placed on the sample stage 7'.
When the drive power source 13 is used to scan two-dimensionally within the x-y plane, the strength of reflection from the sample surface as the sample is scanned is
It is displayed on the CRT surface 12 dimensionally.

The above explanation describes a method in which the spherical lens 1 is fixed and the sample facing it is scanned two-dimensionally within the x-y plane. scan,
The same effect as the above-mentioned method can be obtained by fixing the sample 7.

Ultrasonic microscopes are characterized by the fact that ultrasonic waves can pass through optically opaque objects, making it possible to observe the internal structure of materials and to obtain information reflecting changes in mechanical properties such as elasticity, density, and viscosity of materials. As a result, even unstained biological tissues and cells can be observed as a contrast.

When trying to observe a sample using a device with these characteristics, especially when trying to observe the inside of the sample,
The medium 8 is selected so that the sound wave propagates inside the sample as much as possible, and the acoustic impedance of the sample (2=ρ・V, ρ:
It is desirable to use a material having a value close to the density (v: sound velocity) for the medium 8. This is because two substances with different acoustic impedances2. ．． This is because the reflection of the & wave at the interface of 22 is proportional to (Zz 'l* / (Zl +22), and is reflected by 1 mte. As an example, when the substance to be observed is a metal material , whose almost acoustic impedance Z s = 20~50 X I O
' Since it has the value of M K S, water (
Z w ~1.5 X 10' MKS),
Most of the sound waves are reflected at the interface and return to the sound source (and cannot propagate inside the sample), making it impossible to observe the inside of the sample. I end up.

For this reason, liquid metals such as Hg+In and Ga are used as suitable media when observing substances with large acoustic impedance values such as metal materials. For example, Hg is Z=~], 9X10'MK
Since it is S, the value is almost the same as AQ's 2=~18X10'MKS.The reflection at the ground and interface is,
This becomes a negligible value, allowing most of the sound waves to propagate inside the sample, making it possible to observe the interior of the sample.

However, when Hg is used as the medium 8, Hg cannot be applied to the sample surface, and the sample surface becomes spherical and scatters, so it must be held between the spherical lens 1 and the sample 7 as a stable medium. This poses a problem in practical use because it is difficult to store.

[Purpose of the invention]

In view of the above-mentioned problems, the present invention makes it possible to stably maintain the liquid medium filling the space between the sample and the sonic lens, thereby efficiently cleaning the sample. The purpose is to provide an ultrasonic microscope that can perform a single observation.

[Summary of the invention]

The present invention improves the solid angle of the spherical surface formed on the wave transmitting/receiving surface of the sonic lens (the solid angle 9 seen from the center of the spherical surface by at least 180
This makes it possible to stably hold the liquid medium at the tip of the sonic lens.

[Embodiments of the invention]

Examples are shown below using figures. Figure 2 (,)
1 is a diagram showing the shape of a conventional acoustic lens, where ■ is a spherical lens, 7 is a sample, and 14 is a liquid metal medium. The F number, which represents the brightness of the lens, is F = 1/ [2sin (a/Rf) Co - - = -
(L), which is determined by the aperture diameter a and focal length Rf of the lens.

In the case of a lens with a radius of curvature R of a hemispherical hole, if the sound speed of the lens material is VB, Vv, then the refractive index of the lens is n.

is ne=yW/ye·=---=(2), and the focal length Rf is given by Rf=R/(1-ne) (3).

The lens materials used by the authors include sapphire and quartz, but when such lens materials are used, the solid angle θ seen from the center of the spherical surface of the lens is 120
°, achieving an F number of 0.7.

On the other hand, due to the nature of sound waves, in order for the sound waves to propagate inside the sample, the irradiation angle to the sample must be the critical angle θC of the sample (for most materials, the critical angle is around 10 to 15 inches). ) must be irradiated at a smaller angle,
Therefore, as a spherical lens primarily used for internal observation of samples, no matter how large the aperture angle is made and the F number is increased, no improvement in resolution can be expected.

In other words, if only the internal observation of a sample is concerned, a solid angle of 15 degrees or more of the spherical surface of a spherical lens has no bearing on the resolution.

For this reason, the purpose of the present invention is to increase the solid angle of the spherical surface of the lens to at least exceed 130°.

An example thereof is shown in FIG. 2(b). That is, a concave portion having a spherical surface with a solid angle slightly larger than 180° is formed on the wave transmitting/receiving surface of the lens 1.

A lens of this shape can be easily obtained by utilizing spherical bubbles remaining in a lens material such as quartz, and by polishing the lens material close to the equatorial plane of the bubble to expose the spherical surface. Furthermore, the lens material can be heated to near its melting point in a container with a minute depression on the bottom, or the lens material can be heated in a container in which a minute gas generating object is placed. It is also possible to use a lens material in which bubbles are formed. A method for forming a spherical lens using these bubbles is described in Japanese Patent Application Laid-Open No. 55-149.
It is described in detail in Publication No. 98.

FIG. 2(c) describes the state in which the spherical lens ultrasonic microscope of FIG. 2(b) is used.
When inserted into the concave hole, the liquid metal 14 is sufficiently held by the concave hole and is not affected by external impact.

It is stably held between the spherical lens 1 and the sample 7.

〔Effect of the invention〕

As described above, according to the present invention, even when a liquid metal is used as a sound wave propagation medium between a lens and a sample, the medium can be stably maintained, thereby enabling efficient observation of the sample using ultrasonic waves. You can get a microscope.

[Brief explanation of the drawing]

Figure 1 is a block diagram of an ultrasound microscope, Figure 2 (a) is a diagram showing the main parts of a conventional ultrasound microscope, Figures 2 (b) and (C)
1 is a diagram showing main parts of an embodiment of the present invention. ■... Spherical lens, 7... Sample, 14... Liquid medium. /3 12

Claims (1)

[Claims] In an ultrasonic microscope that has a sonic lens formed in a concave shape so that a sound wave transmission/reception surface forms a part of a spherical surface, and that photographs a sample using the disturbed sound waves emitted from the sample located near the focal point of the sonic lens, An ultrasonic microscope characterized in that the acoustic lens has a concave surface with a solid angle of 180° or more when viewed from the center of the spherical surface.