JPS61186850A - Acoustic wave probe - Google Patents

Abstract

PURPOSE:To prevent deterioration in SN ratio and to obtain a sharp image by forming an acoustic wave used for an ultrasonic microscope concavely, and making the edge of the spherical surface acute. CONSTITUTION:The acoustic lens 1 has a concave spherical part 8 formed at an end surface side facing a sample. The edge 16 between the spherical surface part 8 and a slanting part 17 which starts right at the spherical surface part is finished acutely. Then, a pulse is applied to the piezoelectric element 2 of the acoustic wave lens 1 to oscillate an ultrasonic wave, which is made incident on the sample from the concave surface part 8; and a reflected wave from the sample is received and made into an image by a receiver. In this case, the edge 16 of the spherical surface part 8 of the acoustic wave lens is made acute to prevent a converged ultrasonic beam from striking on the acoustic lens except at a lens aperture part. Thus, multiple reflection in the lens is prevented, so deterioration in SN ratio is prevented and the image is made sharp.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a sonic probe, and particularly to a sonic probe used in an ultrasound microscope.

[Background of the invention]

If the edge of the spherical part of the sonic lens of a sonic probe used in an ultrasound microscope is flat, ultrasound will leak into the medium from this part and be radiated, resulting in the signal of the focused ultrasound beam becoming effective. Since it is not used, the S/N deteriorates. Therefore, in order to prevent S/N deterioration, it has been devised to put a sound absorbing material on the edge of the spherical part of the sonic lens (Utility Model Publication No. 58-31200).
However, in reality, when using a sound wave lens with a high frequency and a short focal length, there is a problem that the sound absorbing material and the sample come into contact with each other.

[Purpose of the invention]

The purpose of the present invention is to prevent S/N deterioration and obtain a clear image without putting a sound absorbing material on the edge of the spherical part of the sonic lens, and to prevent unnecessary radiation of ultrasonic waves from other than the aperture of the sonic lens. It is an object of the present invention to provide a sonic probe that absorbs ultrasonic waves only from the hemispherical hole of the concave body without any hemispherical holes.

[Summary of the invention]

Since the sonic probe itself serves as a sound wave propagation medium, it is necessary to ensure that there are no internal or external defects, but also to pay close attention to the dimensions and finishing accuracy. is necessary. However, even if the edges of the spherical part of the concave body of a sound wave lens are finished at an acute angle through normal work, in reality, the edges are rounded or flat, and it is normal for 50 μm or more to remain. . By providing a sloped portion other than the lens opening, the focused ultrasonic beam is prevented from entering the medium and multiple reflections within the lens are alleviated, but as the frequency increases, the attenuation increases. In design, the radius of curvature of the spherical portion of the acoustic lens must be equal to or less than QJmm. However, it has been confirmed through experiments that if the proportion of the flat edge of the spherical part of the acoustic lens increases in relation to these minute dimensions, the S/N of the focused ultrasound beam deteriorates, making it impossible to obtain a clear image. are doing. The present invention aims to obtain clear images by further reducing the remaining edge of the spherical portion of the acoustic wave lens.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a diagram showing the main components of an ultrasound microscope. The focusing, transmission and reception of ultrasonic waves is carried out by a sonic lens 1, whose structure consists of optically polishing one side of a material made of cylindrical fused silica, etc., and placing a piezoelectric element (ZnO etc.) 2 on top of it.
A pulse 6 generated from a pulse oscillator 5 is applied to the piezoelectric element 2, which has a sandwich structure in which the piezoelectric element 2 is sandwiched between an upper electrode 3 and a lower electrode 4, to generate an ultrasonic wave 7. In addition, the diameter of the other end is 0.1 mmφ13,
A concave spherical part 8 of approximately Qmmφ is formed, and is filled with a medium (for example, water) 10 for propagating the light to the spherical part 8 and the sample 9.

The ultrasonic wave 7 generated by the piezoelectric element 2 propagates in the cylinder as a plane wave. When this plane wave reaches the spherical surface part 8, quartz (sound velocity 6ooom/s) and water (sound velocity 1500m/s
), a refraction effect occurs due to the difference in sound speed between the sample 9 and the sample 9, and the focused ultrasonic waves 7 can be irradiated onto the surface of the sample 9. On the contrary, sample 9
The ultrasonic waves reflected from the
It is converted into signal 11. This RF signal 11 is transmitted to the receiver 12
The video signal is received by a video signal 13, which is diode-detected and converted into a video signal 13, which is used as an input signal for a CRT display 14.

In the apparatus configured as described above, the sample 9 is scanned two-dimensionally within the X-Y plane by the sample stage drive power supply 15.The intensity of reflection from the sample surface as the sample is scanned is two-dimensionally reflected from the CRT surface. 14. An ultrasonic microscopic image can be obtained with the basic configuration described above. FIG. 4 is a sectional view of the acoustic lens of the present invention. The slope 17 starts immediately from the spherical part 8 of the concave body, the edge 16 is finished at an acute angle, and the radius of curvature of the spherical part 8 is 0.1. mm diameter, so the flat portion of the edge 16 is finished to have a dimension of 20 μm or less. The acoustic lens uses several different radii of curvatures of the spherical portion 8 depending on the frequency, and if the dimensions of the flat portion of the edge 16 differ, the S/N deterioration will naturally differ for each frequency. Therefore, in a sound wave lens having a frequency of 50 MH2 to IGH2, the flat portion of the edge 16 is formed at an acute angle so as to be limited to 50 μm to 20 μm. In this way, by finishing the edges of the spherical part of the sonic lens with an acute angle, there is no unnecessary radiation of ultrasonic waves from other than the lens opening, and the ultrasonic waves are emitted only from the spherical part of the concave body. By absorbing ultrasonic waves from only the ultrasonic beam, it is possible to prevent deterioration of the S/N of the focused ultrasonic beam. Therefore, since there is no need to apply sound absorbing material to the edge of the spherical portion of the acoustic wave lens, no particular problem occurs even when the frequency is high and the focal length is short.

〔Effect of the invention〕

As explained above, the present invention makes it possible to prevent the focused ultrasonic beam from entering the medium other than the lens opening by finishing the edge of the spherical part of the acoustic lens with an acute angle, and also to prevent multiple reflections within the lens. Therefore, it is possible to prevent deterioration of the S/N of the focused ultrasonic beam and obtain a clear image without applying a sound absorbing material to the edge of the spherical portion of the acoustic lens.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the sonic probe according to the present invention, and FIG. 2 is a block diagram of an ultrasound microscope using the sonic probe according to the present invention. FIG. 3 is a longitudinal cross-sectional view of a second acoustic lens.

Claims (1)

[Claims] 1. A sonic probe characterized in that it has a sonic lens formed into a concave spherical shape on one end surface of a sonic wave propagation medium, and the edge of the spherical portion of the sonic lens has an acute angle.