JPS58118959A - Ultrasonic microscope - Google Patents

Abstract

PURPOSE:To measure and display the magnitude of reflection intensity from a sample, which is not varied by the magnitude E of an RF signal to be applied, the transmitting and receiving sensitivity T of a transducer, and the amplification degree G of a receiver, by using the magnitude of reflection intensity from the surface of a lens and a medium, as a reference signal. CONSTITUTION:A signal from an RF continuous generator 300 is converted to an RF pulse signal by an analog switch 310, is applied to a transducer system 330 through a directional coupler 320, its reflection detecting signal is outputted as a reflecting signal from a sample, from a sampling circuit 380 through a directional coupler 320, an AGC receiving amplifier 350, an RF variable amplifier 360, and a diode detector 370, also an output of the AGC receiving amplifier 350 is passed through a sampling circuit 400, a reflecting signal is detected from the lens surface, and by comparing it with reference voltage, the gain of the AGC receiver 350 is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photographing device using ultrasonic energy, particularly an ultrasonic microscope.

In recent years, it has become possible to generate and detect ultra-high frequency sound waves up to IGH2, making it possible to realize sound wavelengths of about 1 μm underwater, and as a result, it has become possible to obtain high-resolution sound wave Wjif & devices. That is, a concave lens is used to create a focused sound wave beam, achieving a high resolution of 1 μm. (R, A.

Mr. Lemon, C, F, and Mr. Fates' AScanning A
IE entitled Coustic Microscope
EE Cat.

No, 73CH148298UpI) 423-426.
Paper published in 1973).

Then, a sample is placed in the beam, and the reflected sound waves from the sample are detected to obtain information reflecting the elastic properties of the sample, or information reflecting the elastic properties of the sample is obtained, or information is created by mechanically scanning the sample.

A conventional example of obtaining such a sound wave image is shown in 1. This will be explained using FIG.

FIG. 1 is a diagram showing a schematic configuration of a ninth probe thread for obtaining a reflected signal from a sample. In the figure, 20 tons of sound wave propagation medium (for example, cylindrical crystal such as sapphire or quartz glass)
One end surface I'i is optically polished and is a plane, and the other end surface has a concave spherical hole 30 formed therein. An RF pulsed electrical signal applied to the piezoelectric thin film 10 causes a plane wave RF pulsed sound wave to be emitted within the crystal 20 . This plane sound wave is transmitted to the sample placed at a predetermined focus by a positive lens formed at the interface between the spherical hole 30 and the medium (generally water) 40 (in other words, the spherical hole has an aperture of The sound waves reflected by the sample 50 are collected by the same lens, converted into plane waves, propagated through the crystal 20, and finally converted into electrical signals by the piezoelectric thin film 1oVC.This situation When viewed in the video domain, it becomes as shown in Fig. 2. Here, the horizontal axis represents the signal intensity with the time axis perpendicular to the axis. Al1 launch echo (echo) t, B are echoes from the lens interface 3o (echO) 1. Also, C is the reflected echo from the sample (ec
ho). These have a repetition time of 1. is repeated. Since the reflected echo C changes depending on the acoustic properties of the sample and the scanning of the sample, this reflected echo C is repeated for a time of 1. If the sample is made into a sample with a machine and displayed in synchronization with the mechanical scanning, a sonic image can be obtained.

By the way, the magnitude of the reflected ultrasonic wave of the sample Rikishima et al. is determined by the acoustic impedance of the medium and the sample, and the reflectance R is as follows: ZI: Acoustic impedance of the sample Zw: A-quality sound impedance xs Mi ZII/Zw: The acoustic impedance of the sample normalized by the acoustic impedance of the medium (hereinafter referred to as relative impedance is proportional to Tsubobun. This situation indicates that the relative impedance of the sample itself can be determined by examining the magnitude of the reflected echo C. Therefore, for this purpose, it is necessary to express or display the magnitude of the reflected echo C using some absolute reference level as a reference. Conventionally, only the magnitude of the reflected echo C is used to calculate the reflectance R. In other words, as shown in Figure 3, the RF
The output pulse of the pulse oscillator 100 is transferred to the directional coupler 110.
and is applied to the transducer 130 via the matching box 120t. The RF electric signal including the reflected ultrasound signal passes through a matching box 120 and a directional coupler 110, is amplified by a fRF amplifier 140, and is diode-detected by a video detector 150 (the waveform shown in FIG. 2 above). corresponds to this output waveform)
, the magnitude of only the echo C is extracted by the sampling circuit 160 and used as the CRT luminance signal. As a result of studying this conventional circuit, the present inventors discovered that the conventional display n
The proportionality constant between the luminance signal and the reflectance R of the sample is:
We have found that this is mainly expressed by the product of the width E of the RF pulse applied to the transducer 130, the degree T of the transducer's transmission and reception, and the degree G of the receiving system including the video area.

Therefore, in order to quantitatively determine the reflectance of the sample itself using some method, it was necessary to skillfully control these three quantities. Conventionally, when the thickness Ee of the applied RF pulse is fixed and the reflected echo is adjusted to a predetermined size, the degree of enhancement is defined as the absolute value of the size of the reflected echo. However, if the ultrasonic frequency used or the sensor itself is changed, the transmitting and receiving sensitivity of the transducer itself changes, so in order to use the above amplification degree Gi as an absolute standard for the magnitude of the reflected echo, It is necessary to create a calibration table for each sensor and each ultrasonic frequency used, which is too complicated to be practical.

The present invention has been made in view of the above points, and provides an indication of the magnitude of a reflected echo that does not change depending on the thickness E of the RF pulse, the transmitting/receiving sensitivity T of the transducer, and the amplification degree G of the receiver. The purpose is to provide the necessary standard level.

That is, the present invention is characterized in that the echo B from the interface between the lens and the medium, which has heretofore been treated as rather useless, is used as a reference signal.

Of course, the size of the echo B from the lens interface itself is the same as the size of the echo C from the sample, and is also based on the three quantities mentioned above: the thickness of the applied RF flaw signal E, the transmitting and receiving sensitivity of the transducer Although it changes when the amplification degree G of the T1 reception amplifier is changed, the ratio between the two is not dependent on these quantities.

This situation will be quantitatively explained below using FIG. 4. In FIG. 4, the echo B from the lens interface is generated by the phenomenon that the ultrasonic pulse generated in the lens material 220 from the piezoelectric thin film 210 is reflected at the lens interface 230, so the thickness vl of the echo B is %ZL. : Given by the acoustic impedance of the lens material. (Zw −Zt, ) /
(ZW +ZL) is the reflectance of the lens interface itself.

On the other hand, the reflected echo C from the sample is reflected from the lens interface 2 above.
30, the ultrasonic pulse propagates through the medium 240 while being attenuated, is reflected by the sample 250, and is again collected by the lens, so the magnitude of the echo C, Vc, is: where αW: medium Attenuation rate d per unit propagation distance in the lens: given by the distance between the lens and the sample. 4 ZLZW/ (ZL+Zw)'' is the transmittance when passing through the lens interface t-2 degrees, and e
-2dw4 represents the attenuation rate of the wave removed as it travels back and forth in the medium over a distance of 2d.

Therefore, if we express the magnitude of the echo C reflected from the sample using the magnitude of the echo B from the lens interface as a standard, we get the following: (4) The above three amounts of change E, It is possible to set the absolute level of the reflected echo regardless of T or G.

Thus, in order to obtain the optimum picture quality, E, T.

Even if the setting of G is changed, the amount expressed by the size of the reflected echo C as the overall standard for the size of the echo B from the lens interface remains unchanged, so it can be measured independently of image observation.

As described above, according to the present invention, the thickness of the RF pulse E
%) It is possible to measure the magnitude of the reflected ultrasonic echo from the sample without depending on the transmitting/receiving sensitivity T of the transducer and the amplification degree G of the receiver. An example will be described below with reference to the drawings.

FIG. 5 is a diagram showing an embodiment of the present invention, in which RF continuous wave electrical damage signals (for example, IGH
11i with lt-analog switch 310 Duration 1. (for example, 10018) (control signal in FIG. 6(b)), the directional coupler 320
to the transducer system 330 via. After the reflected detection signal is amplified by the AGC reception amplifier 350 and the RF' variable amplifier 360 via the directional coupler 320t, the diode detector 370 converts it into a video signal (bandwidth ~10MH!).
), and the reflected signal C't from the sample, which is a desired signal, is sampled using the time gate sampling circuit 380t (control signal in FIG. 6(d)) and used as a signal for imaging. Furthermore, the output of the AGC receiving amplifier 360 (waveform in FIG. 6(a)) is converted in the video band by a diode detector 390, and then converted from the lens interface by a time gate sampling circuit 400 (control waveform in FIG. 6(c)). Detect the magnitude of echo B of
A comparator 410 detects the difference between this and a preset reference voltage, and the gain of the AGC receiver 360 is controlled so as to make the output of the comparator 410 zero. The control circuit 360a is a circuit that generates the control signals shown in FIG. 6 ft) l to (d) at a repetition period III.

According to this configuration, the width E of the applied RF pulse described above is
,) Regardless of the transducer's transmitting/receiving sensitivity T, the echo B from the lens interface always remains at the preset reference voltage value.
The gain of the AGC amplifier 350 is adjusted so that the magnitudes of the . Therefore, the reflected echo from the sample is also automatically 000.
Since the width is doubled, it is used as the amplification rate Gt1 of the variable amplifier 360, and V c ” Gt・v3 ・・・・・・・・・・・・・・・
Due to the relationship (5), the reflected echo Ct from the sample can always be displayed or measured based on the magnitude of the echo B from the lens interface.

FIG. 7 is a diagram showing another embodiment of the present invention, including an RF continuous wave oscillator 500, an analog switch 510, a directional coupler 520, a transducer 530, and a control circuit 540.
performs the same function as in the previous embodiment. The reflected detection signal is amplified by an RF variable amplifier 550 and then sent to a diode detector 56.
0 to the video band (waveform shown in FIG. 6(a)). This is branched into two systems and converted into two circuits 570 and 580.
Enter.

The interpolation circuit 570 detects the magnitude of the echo B from the lens interface using the gate waveform shown in FIG. 6(C), and the interpolation circuit 580 detects the magnitude of the echo C reflected from the sample using the gate waveform shown in FIG. 6(d). Detect roughness. In this example, these two
The output of the divider 590 which receives the two detected waveforms as input is used as a display or measurement signal.

The display signal clearly goes into Valsp=V (6
) It is clear that the effects of the present invention can be achieved.

Of course, the output of the seeding circuit 570? −? The above embodiment including an AGC circuit may be added to adjust the level.

In the embodiments described above, the former is the echo B from the lens interface.
By setting the size to a fixed level, the latter becomes an echo B.
By taking the ratio of the size of the echo C and the size of the echo C, the thickness of the reflected echo that does not change depending on the thickness E of the RF pulse, the transmitting/receiving sensitivity T of the transducer, and the amplification degree GK of the receiver, which is the object of the present invention, can be calculated. It goes without saying that the present invention is not limited to this, as long as it provides a display method and a reference level, and it embodies the spirit of the present invention.

In summary, according to the present invention, a means is provided for uniquely displaying the magnitude of the reflected echo C from the sample based on the magnitude of the echo B from the lens interface, regardless of other conditions, and the reflectance of the sample is It quantitatively provides sample-specific quantities, and its contribution to the ultrasonic microscopy industry is significant.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a schematic configuration of the main parts of a conventional ultrasonic microscope, Fig. 2 is a diagram illustrating its operation, and Fig. 3 is a block diagram of the conventional technology for obtaining a luminance signal. FIG. 4 is a diagram for explaining the present invention. FIG. 5 is a block diagram showing the configuration of an embodiment of the present invention. FIG. 6 is a waveform diagram for explaining the operation. FIG. 7 shows the structure of another embodiment of the present invention. Figure 3 Figure 4 m-:d-i Iris 5 Figure 6 Figure (d)
t Kojo Troll 347 Figure

Claims (1)

[Claims] 1. In ultrasonic microscopic ambiguity, the reflection intensity from the lens interface is thick -g? An ultrasonic microscope characterized by having a means for measuring the intensity of reflection from a sample as a reference.