JPS5950936B2 - Ultrasonic microscope sample holding plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sample holding plate used in an ultrasonic microscope.

Ultrasonic microscopes have recently been developed as a new method of exploring the microscopic world of objects using sound waves instead of light.

Unlike an optical microscope that uses the refractive index of light, this system forms images based on physical characteristics, and it is possible to see parts hidden beneath the surface of an object. In principle, this ultrasonic microscope mechanically scans the sample surface using narrowly focused ultrasonic waves, collects the scattered ultrasonic waves, converts them into electrical signals, and generates a two-dimensional image on the surface of a cathode ray tube. The image is displayed on the screen and a microscopic image is obtained.

The resolution of this microscope is determined by how the ultrasonic waves irradiated onto the sample are propagated without loss and how the reflected sounds are collected.
This is the key to increasing clarity. A typical ultrasonic microscope is configured by two methods: one detects ultrasound that has passed through the sample while being scattered or attenuated, and the other detects ultrasound that is reflected due to differences in acoustic properties within the sample. They are divided into transmission type and reflection type, depending on the case in which the ultrasonic waves transmitted are detected.

FIG. 1 is a block diagram showing the basic configuration of a transmission type ultrasound microscope.

1 is a high frequency oscillator, 2 is a transmitting side ultrasonic focusing lens made of an ultrasonic propagation medium such as sapphire, 3 is a receiving side ultrasonic focusing lens and is made of an ultrasonic propagating medium such as sapphire, and 4 is a sound source such as water. field medium, 5 is a sample holding plate, 6 is a sample, 7 is a scanning device that moves the sample holding plate 5 in the x and Y directions, 8 is a scanning circuit that controls the scanning device 7, 9 is a receiving side ultrasonic focusing lens A receiving circuit receives the output from 3, and 10 is a display device.

In the ultrasonic microscope as described above, first, the plane ultrasonic wave emitted by the transmitting transducer 2a is focused by the spherical lens part 2b and focused in the sound field medium. It is located at a confocal position with the ultrasound focusing lens 3, and the ultrasound collected by the spherical part 3b of the ultrasound focusing lens 3 on the receiving side becomes a plane ultrasound and is converted into an electric wave by the receiving transducer 3a. converted into a signal.

Therefore, by vibrating the sample holding plate 5 in the X direction and moving it little by little in the Y direction while keeping the inspection surface of the sample at the focal point of the ultrasonic focusing lens, the ultrasonic beam will scan the sample surface relatively. I will do it.

When the ultrasonic beam passes through the sample 6, the amplitude and phase change, so the electron beam of the cathode ray tube (CRT) in the display device 10 is swept in correspondence with each point on the sample surface where the ultrasonic beam crosses. However, by applying brightness modulation according to the output signal of the receiving transducer 3a, a two-dimensional microscopic image can be obtained on the CRT surface. By the way, as mentioned above,
In ultrasonic microscopes, conventionally, resolution and clarity have been affected due to attenuation by the acoustic field medium that is the propagation medium of the ultrasonic beam, the sample holding plate, etc., or reflection at the interface between the acoustic field medium and the sample holding plate. I was not able to raise it sufficiently.

That is, conventionally, as the sample holding plate 5 used in an ultrasonic microscope, a Mylar plate with a thickness of 30 to 50 μm is used because it is relatively easy to obtain flatness and is easy to handle. Water or the like was used as the medium.

However, in a Mylar plate with a thickness of 30 to 50 μm, the loss in the Mylar plate is large, and as shown in the characteristic curve D in FIG. Indeed, it increases and reaches about 10 dB near the 300M ratio.

Therefore, when Mylar plate is used as the material for the sample holding plate 5, the practical limit is 100M ratio and the resolution is 15μ.
m was the limit. Also, Mylar board is not strong enough, so the thickness of the board cannot be made thinner. The drawback was that there was no. The present invention improves the conventional drawbacks as described above.
The purpose of this is to reduce the attenuation of the ultrasonic beam in the sample holding plate in the ultrasonic microscope, and to reduce reflections at the interface between the sample holding plate and the sound field medium, thereby producing images with high resolution and clarity. The purpose is to provide a sample holding plate that can obtain the following.

Next, embodiments of the present invention will be described in detail.

FIG. 2 shows an embodiment of the sample holding plate of the present invention, and the sample holding plate 11 shown in the same figure is made of sapphire and has a thickness that is an integral multiple of half the wavelength of the ultrasonic beam. It was formed in The thickness of the sample holding plate 11 is set to 1/2 of the wavelength.
Since the acoustic impedance as seen from the sound field medium is equivalent to the specific acoustic impedance of the sound field medium and is independent of the acoustic impedance of the sample holding plate 11, the reflection loss at the sample holding plate 11 is is approximately zero.

In addition, the material of the sample holding plate 11 was made of sapphire in the fifth model.
As shown in characteristic curve C in the figure, the propagation loss in the material at high frequencies is small compared to Mylar board, and there is almost no propagation loss even for frequencies over 300 M ratio, and at frequencies over several hundred M ratio. This is because ultrasonic beams can be used to improve resolution and clarity.

FIG. 3 shows another embodiment of the sample holding plate of the present invention, in which the upper and lower surfaces of the sample holding plate 11 made of sapphire whose thickness is an integral multiple of 1/2 the wavelength of the ultrasonic beam are shown. A silicon dioxide layer 12 having a thickness one-fourth of the wavelength of the ultrasonic beam is formed thereon.

The characteristic acoustic impedance of the silicon dioxide layer 12 formed on the upper and lower surfaces of the sample holding plate 11 configured as described above is approximately equivalent to the geometric mean value of the characteristic acoustic impedance of the sound field medium (water) and the characteristic acoustic impedance of Saphire. It is.

Since the thickness of the silicon dioxide layer 12 is set to one quarter of the wavelength of the ultrasonic beam, the acoustic impedance of the sample holding plate 11 when viewed from the sound field medium (water) is approximately The acoustic impedance becomes equivalent to the specific acoustic impedance of the field medium 4, and the acoustic impedance when the sound field medium 4 is viewed from the sample holding plate 11 becomes equivalent to the specific acoustic impedance of the sample holding plate 11. As a result, the ultrasonic beam is
- Transmits without being reflected at each interface between the silicon oxide layer 12 and the sound field medium 4.

Therefore, similarly to the embodiment shown in FIG. 2, it is possible to improve the resolution and sharpness and obtain a good image by using an ultrasonic beam of several hundred M or more.

In addition, as shown in Fig. 4, there is a sample holding plate 1 made only of sapphire.
1, when the plate thickness deviates from an integer multiple of half the wavelength, the transmittance sharply changes due to the reflection of the sound wave at the interface between the sound field medium 4 and the sample holding plate 11, as shown in characteristic curve A. However, four silicon dioxide layers 12 are placed on the top and bottom surfaces of the sample holding plate 11.
In the case of a sandwich type formed to a thickness of one-half wavelength, as shown in characteristic curve B, even if the thickness of the sample holding plate 11 slightly deviates from an integer multiple of one-half the wavelength, the silicon dioxide layer 12 acts as an acoustic impedance matching layer, reducing loss due to reflection, which has the advantage of providing images with high resolution and clarity. As explained in detail above, the sample holding plate of the present invention has little attenuation in the sample holding plate even for ultrasonic beams of several hundred MH7 seconds or more, and there is little reflection at the interface of the sample holding plate, so ultrasonic waves It is possible to obtain high-quality microscopic images with high resolution and clarity.

In addition, although sapphire was used as the sample holding plate in one example,
Other materials such as crystal and ruby can also be used.

[Brief explanation of drawings]

FIG. 1 is a plotter diagram of a transmission ultrasound microscope, FIG. 2 is a perspective view of a sample holding plate of one embodiment of the present invention, and FIG. 3 is a perspective view of another embodiment of the sample holding plate of the present invention. 4 and 5 are characteristic curve diagrams of an embodiment of the present invention. 1... High frequency oscillator, 2... Ultrasonic focusing lens on the transmitting side, 3... Ultrasonic focusing lens on the receiving side, 4... Sound field Medium, 5, 11...Sample holding plate, 6...Sample, 7...Scanning device, 8...Scanning circuit, 9... - Receiving circuit, 10...Display device, 12...Silicon dioxide layer.

Claims (1)

[Scope of Claims] 1. In an ultrasonic microscope that detects an ultrasonic beam transmitted through a sample and a sample holding plate that holds the sample, the sample holding plate is made of a material with low propagation loss of the ultrasonic beam, and The thickness of the plate is 1/2 of the wavelength of the ultrasonic beam.
A sample holding plate for an ultrasonic microscope, characterized in that the plate is an integral multiple of . 2. In an ultrasonic microscope that detects an ultrasonic beam transmitted through a sample and a sample holding plate that holds this sample, the sample holding plate is made of a material with low propagation loss of the ultrasonic beam, and the thickness of the plate is 1/2 of the wavelength of the beam
The upper and lower surfaces of the sample holding plate are made of a material such as silicon dioxide whose specific acoustic impedance approximates the geometric mean of the specific acoustic impedance of the sound field medium and the sample holding plate, which is a quarter of the wavelength of the ultrasonic wave. A sample holding plate for an ultrasonic microscope, characterized in that it is formed to have a thickness that is an odd number times as large as .