JPS5831200Y2 - ultrasonic focusing lens - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to the structure of an ultrasonic focusing lens used in an ultrasonic microscope.

The idea of using ultrasound instead of light to observe the microscopic structure of objects has been around for a long time, and recently mechanical scanning ultrasound microscopes have been developed.

In principle, this ultrasound microscope mechanically scans the sample surface with a narrowly focused ultrahigh-frequency ultrasound beam, collects the scattered ultrasound waves, converts them into electrical signals, and sends them to the surface of a cathode ray tube. It displays it dimensionally and obtains a microscopic image.

The configuration depends on how the ultrasonic waves are detected; in other words, the ultrasonic waves that have passed through the sample while being scattered or attenuated are detected, and the ultrasonic waves that have been reflected due to differences in the acoustic properties within the sample are detected. They are divided into transmissive type and reflective type.

FIG. 1 is a block diagram showing the basic configuration of a transmission type ultrasound microscope, in which 1 is a high-frequency oscillator, 2 is a transmitting-side ultrasound focusing lens made of an ultrasound propagation medium material such as sapphire, and - A wave transmitting transducer 2a is attached to the surface,
The other surface has a spherical lens portion 2b hollowed out into a spherical shape.

Reference numeral 3 denotes an ultrasonic focusing lens on the delivery side, which is also made of an ultrasonic propagation medium material such as a sapphire plate, and has a delivery transducer 3a attached to the negative side and a spherical lens portion 3b hollowed out into a spherical shape on the other side. .

A pair of such ultrasonic focusing lenses are arranged in a confocal configuration with their spherical lens portions facing each other with water 4 serving as a sound field medium interposed therebetween.

Reference numeral 5 denotes a sample holding frame on which a mylar film 6 is stretched, and a sample 7 serving as an object to be inspected is attached to the mylar film 6.

8 is a scanning device that moves the sample holding frame 5 in the X and Y directions, 9 is a scanning circuit that controls the scanning device 8, 10 is a receiving circuit that receives the output of the delivery-side ultrasonic focusing lens 3, and 11 is a display device. It is.

In the ultrasonic microscope as described above, first, plane ultrasonic waves emitted by the transmitting transducer 2a are focused by the spherical lens portion 2b and focused into water.

The ultrasonic waves gathered at this focal point are collected by the spherical lens portion 3b of the delivery-side ultrasonic focusing lens 3 arranged confocally and become horizontal plane ultrasound waves, which are transmitted to the delivery transducer 3.
is converted into an electrical signal by a.

Therefore, by moving the sample holding frame 5 little by little in the Y direction instead of vibrating it in the X direction while keeping the inspection surface of the sample 7 at the focal point, the ultrasonic beam can relatively scan the sample surface. become.

When the ultrasonic beam passes through the sample 7, it undergoes changes in amplitude and phase.
By sweeping the electron beam and subjecting it to 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 shown in detail in FIG. 2a, the above-mentioned ultrasound microscope has peripheral parts 2C and spherical lens parts 2b and 3b of the transmitting-side ultrasound focusing lens 2 and the receiving-side ultrasound focusing lens 3, respectively. In many cases, 3C is used with a flat shape.

However, when continuous waves are used in a lens system with this type of shape, standing waves are generated within the ultrasonic propagation medium, and ultrasonic waves leak and radiate into the water from the flat peripheral area 2C of the lens surface. , the signal of the focused ultrasound beam is masked to reduce the S/N
deteriorates.

In addition, in order to prevent deterioration of the S/N ratio, as shown in Figure 2, there is a sound absorbing material 12 attached to the flat peripheral parts 2C and 3C, but the frequency of the ultrasonic waves becomes high and the focus If it becomes too short, the sound absorbing material 12 will come into contact with the sample, which is extremely inconvenient.

The present invention is a new invention that improves the above-mentioned conventional drawbacks, and its purpose is to emit ultrasound only from the spherical lens part without unnecessary radiation of ultrasound from parts other than the spherical lens part in an ultrasound microscope. Another object of the present invention is to provide an ultrasonic focusing lens that absorbs ultrasonic waves only from the spherical lens portion.

Next, one embodiment of the present invention will be described in detail with reference to the drawings.

In the embodiment of the present invention, sapphire is used as the ultrasonic propagation medium material, and it is Z-cut to form a sapphire rod with a diameter d of 4 mmφ and a length l of 4 mm, as shown in FIGS. 3 and 4. do.

A flat surface 14 is provided at one end, and a lens portion 15 is formed at the other end.

The diameter and radius of curvature of this lens portion 15 are each 2 mm.
Therefore, the F number of the lens is approximately 1.1.

An inclined surface 16 is formed at the end where the lens portion 15 is provided,
The surfaces of the inclined surface 16 and side surface 17 are roughened.

An l-transducer 18 is attached to the center of the flat surface 14.

This transducer 18 is a 140 MHz zinc oxide (ZnO) piezoelectric film transducer formed by sputtering.

Note that the diameter of this transducer is 1.6 mmφ.

In order to investigate the transmission characteristics of the entire ultrasonic focusing lens system having the above configuration, we measured the frequency characteristics of the insertion loss between the input and output quadrangle juicers in a 50Ω system when two ultrasonic focusing lenses were placed in a confocal arrangement. However, the results shown in FIG. 5 were obtained.

In addition, in FIG. 5, the solid line shows the case of continuous wave measurement, and the broken line shows the case of measurement with high frequency pulse (pulse width about 0.6 μ5 ec).

The ripples observed in the case of continuous waves are due to standing waves within the sapphire rod, and the ripples are larger than those previously measured by the inventors using the conventional lens shown in Figure 1. It has decreased by more than ten dB.

The insertion loss is approximately 52 dB near 140 MH2, but if we estimate the propagation loss in water to be 16 dB and the transmission loss at the boundary between sapphire and water to be approximately 20 dB for transmission and reception, the conversion loss of only the transducer is Approximately 8
dB.

Next, in order to understand the focusing status of the lenses, we observed changes in the output of the receiving transducer while moving a copper wire with a diameter of 30 μm in the direction perpendicular to the Z-axis on the confocal plane of the two ultrasonic focusing lenses.

The results are shown in FIG.

In FIG. 6, the solid line shows the result when the ultrasonic focusing lens according to the present invention is used, and the broken line shows the result when the conventional ultrasonic lens shown in FIG. 2a is used.

We also observed changes in the received wave output when the two ultrasonic focusing lenses were shifted from their confocal positions.

FIG. 7 shows the characteristics when both lenses are shifted along the Z axis.

Further, FIGS. 8a and 8l) show the characteristics in the X direction and the Y direction, respectively, when shifted in the direction perpendicular to the Z axis.

The width of the 3 dB reduction is approximately 80 μm in the Z direction and approximately 11 μm in the X and Y directions.

In addition, although the above-mentioned example is a case where the ultrasonic focusing lens according to the present invention is applied to a transmission type ultrasound microscope, it goes without saying that this can also be applied to a reflection type ultrasound microscope.

In addition to sapphire, the ultrasonic propagation medium materials include crystal,
Materials such as ruby, diamond, and Pyrex glass can also be used.

As explained in detail above, the present invention provides an inclined surface at the end of the ultrasonic propagation medium, which is the base of the ultrasonic focusing lens, at which the lens portion is provided, and forms the inclined surface and the side wall surface into rough surfaces. Therefore, the standing number generated in the ultrasonic medium material is much smaller than that of the conventional one.

Therefore, when an ultrasonic focusing lens is used for transmitting waves, there is very little leakage of ultrasonic waves from areas other than the lens, and when it is used for receiving waves, there is almost no sound absorption from areas other than the lens. Therefore, the S/N ratio of the ultrasonic microscope has improved compared to the conventional method.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a transmission ultrasound microscope, FIGS. 2a and 2b are side views of a conventional ultrasound focusing lens, and FIGS. 3 and 4 are perspective views showing an embodiment of the present invention. The sectional views, FIGS. 5, 6, 7, and 8 a and b are characteristic curve diagrams of an embodiment of the present invention. In the figure, 1 is a high-frequency oscillator, 2 is an ultrasonic focusing lens on the transmitting side, 3 is an ultrasonic focusing lens on the delivery side, 4 is ice, 5 is a sample holding frame, 6 is a mylar film, 7 is a sample, and 8 is a scanning 1 is a device, 9 is a scanning circuit, 10 is a receiving circuit, 11 is a display device, 14 is a flat surface, 15 is a lens portion, 16 is an inclined surface, 17 is a side surface, 1
8 is a 1-transducer.

Claims (1)

[Scope of utility model registration request] In an ultrasonic focusing lens in which a transducer is provided at one end of a rod-shaped ultrasonic propagation medium material and a lens portion is provided at the other end,
An ultrasonic focusing lens characterized in that an inclined surface is provided at an end portion where a lens portion is provided, and the inclined surface and side surfaces are formed into rough surfaces.