JPS59102156A - Ultrasonic microscope - Google Patents

Abstract

PURPOSE:To enable the display of an image at any position on the surface of and inside a sample by automatically extracting an envelope detection output with reflected ultrasonic waves from the focal position of an acoustic lens according to the position thereof. CONSTITUTION:An envelope detection output corresponding to reflected ultrasonic waves from a sample 8 via an acoustic lens 5, a circulator 2 and a gate 9 of an ultrasonic microscope is outputted from an amplification/detection output circuit 10' and held with a sample hole circuit 22 responding to a sensor 21 for outputting a time signal according to the position of a lens 4. This enables automatic extraction of the envelope detection output along with the reflected ultrasonic waves from the focal position of the lens 4 to control a CRT display 12 through a scan converter 11 thereby enable the display of an image at any position on the surface and inside a sample.

Description

DETAILED DESCRIPTION OF THE INVENTION Various types of ultrasonic microscopes have been proposed in the past, including one having the configuration shown in FIG. In this ultrasound microscope, an ultra-high frequency burst wave electric signal is generated by a high frequency pulse generator 1, and this lightning signal is supplied to a piezoelectric transducer 3 via a circulator 2.
Here, the lightning and air signals are converted into ultrasonic waves, and these ultrasonic waves are transmitted in the X-axis and Y-axis directions by a scanning controller 6 through an acoustic lens C (ultrasonic focusing lens) 4 and a liquid 5 as an ultrasonic transmission medium. A minute spot is projected onto a sample 8 placed on a sample stage 7 that moves two-dimensionally. Further, ultrasonic waves are reflected from the sample 8 according to its acoustic characteristics, and the reflected waves are collected by the acoustic lens 4 through the liquid 5 and converted into electrical signals by the piezoelectric transducer 3. This electrical signal is supplied to the gate circuit 9 via the circulator 2, where unnecessary signals other than sample information are removed.

The output signal of the gate circuit 9 is amplified by the amplification/detection circuit 10.
Detected, a detection signal corresponding to the intensity of the reflected wave from the sample is obtained, and this detection signal is synchronized with the scanning of the sample stage 7 by the scan control device 6 and sent to the scan converter 11 as a luminance signal at the corresponding position on the sample surface. The recorded luminance signal is displayed on the cathode ray tube 12 as an ultrasonic image. The operations of the high-frequency pulse generator], the scan control device 6, the gate, the circuit 9, and the scan converter] are controlled by a control circuit]3.

In the ultrasonic microscope described above, the ultrasonic waves emitted from the piezoelectric transducer 3 to the acoustic lens 4 undergo multiple reflections between the concave lens portion of the acoustic lens 4 and the piezoelectric transducer 3, and these reflected waves are generated by the piezoelectric Each is converted into an electrical signal by transducer 3 and sent to circulator 2.
The signal is supplied to the gate circuit 9 via.

FIG. 2A shows the signal input to the gate circuit 9 when the high frequency pulse generator 1 generates an extremely high frequency burst wave lightning signal for a short period of time under the control of the control circuit 3. Po represents the leakage signal that reaches the gate circuit 9 directly from the high-frequency pulse generator 1 through the circulator 2, and Pl, P2, and P8 represent the leakage signal between the piezoelectric transducer 3 and the lens part of the acoustic lens 4. represents the 1st degree second and eighth reflected wave signals at . Therefore, in this type of ultrasonic microscope, the acoustic lens 4 is designed so that the sample wave resistance signal S is located between the first reflected wave signal P0 and the second reflected wave signal P2, and the control circuit A gate control signal as shown in FIG. 2B is supplied from the gate circuit 13 to the gate circuit 9 so that only the sample reflected wave signal S is extracted as shown in FIG. 2C.

Now, focusing on the output signal of the gate circuit 9 (Fig. 2C), the reflected wave from the sample consists of the reflected wave from the surface and the internal reflected wave, and generally as shown in Fig. 3. When the reflected wave Sl from the sample surface is stronger than the reflected wave S2 from inside, the amplification/detection circuit]
Since the output signal is amplified, envelope detection is performed, and its peak is detected, the image displayed on the cathode ray tube is an ultrasonic image from the surface of the sample. In other words, in the case of a conventional ultrasound microscope, it is only possible to display an image of the position on the sample surface or inside where ultrasonic waves are most strongly reflected, and it is not possible to selectively display an image of an arbitrary position on the sample surface or inside. I couldn't do it.

SUMMARY OF THE INVENTION An object of the present invention is to provide an ultrasonic microscope capable of selectively displaying images of arbitrary positions on the surface and inside of a sample.

The ultrasonic microscope of the present invention includes means for changing the relative position between the focus of the acoustic lens and the sample in the ultrasonic generation direction, and moving the focus of the acoustic lens to a desired position on the surface of the sample or inside the sample; means for envelope-detecting an electrical signal corresponding to an ultrasonic wave reflected from the sample; and detecting only a portion corresponding to the sample information at the position where the focal point of the acoustic lens is located from the output signal of the envelope detection means. The method is characterized by comprising means for automatically extracting the information.

The invention will be explained below with reference to the drawings.

FIG. 3 shows an example of the ultrasonic microscope of the present invention. In FIG. 3, elements corresponding to those in FIG. 1 are given the same reference numerals, and detailed explanation thereof will be omitted.

According to the present invention, a mechanism (not shown) is provided for driving the acoustic lens 4 in the direction in which ultrasonic waves are emitted from the acoustic lens. The acoustic lens is moved so that the focal point is at a desired position inside the sample with reference to the position of the acoustic lens, and the distance traveled is detected by the sensor device 2. Generate output pulses at certain times.

As mentioned above, the signal generated from the gate circuit 9 is as shown in FIG. 3, and in the present invention, this signal is amplified and envelope-detected in the amplification/detection circuit 10'. The output waveform of this circuit 10' is shown in FIG. 5A! 'l Show f. According to the present invention, the sample internal reflection wave S2 of the output signal of this circuit 10' is sampled and held in the sample and hold circuit 22 using the output pulse of the sensor device 21 (FIG. 5B), and this sampled and held value is (Figure 5C)
is recorded as a luminance signal at a desired position within the sample in the scan converter], and this signal is displayed on the cathode ray tube 2 as described above.

The value obtained by sampling the signal generated from the amplification/detection circuit 10' (Fig. 5A) using the output pulse of the sensor device 21 (Fig. 5B) corresponds to information on the desired position (focal position) within the sample. Sensor device 2 for making
] will be explained below.

In FIG. 6A, the focal point of the acoustic lens 4 is located on the surface of the sample, and the ultrasonic wave generated from the piezoelectric transducer 3 passes through the acoustic lens 4 and the ultrasonic transmission medium 5, is reflected at the surface of the sample 8, and the ultrasonic wave is transmitted again. A case is shown in which the signal passes through a transmission medium 5 and an acoustic lens 4 and is converted into an electrical signal by a piezoelectric transducer 3. Here, l is the length of the acoustic lens, f is the focal length of the acoustic lens, C1 is the speed of sound within the acoustic lens, and C2 is the speed of sound within the ultrasonic transmission medium. In this case, the waveform of the signal supplied from the amplification/detection circuit 10' to the sample/hold circuit 22 is shown by a broken line in FIG. 6G.

In this FIG. 6C, 81' is information on the sample surface,
St is a start pulse generated from the control circuit 13,
This start pulse causes the high-frequency generator 1 to generate a high-frequency signal, and the time it takes for the surface information of the sensor material to reach the sample-hold circuit 22 (Fig. Since the transmission time is ignored, it can be regarded as the time from when the ultrasonic wave is generated from the piezoelectric transducer 3 until it enters the piezoelectric transducer again.Therefore, the following equation is satisfied.

In order to obtain information inside the sample, according to the present invention, the acoustic lens 4 is moved by a distance such that the generator point within the acoustic lens reaches a desired position X inside the sample as shown in FIG. 6B. let In this case, the waveform of the signal supplied to the sample-and-hold circuit 22 is shown by the solid line waveform in FIG. 6G. This sixth
In Figure C, So is information on the sample surface, and S2 is information on point X inside the sample. Therefore, the time t2 is equal to the time during which the ultrasonic wave passes through the ultrasonic transmission medium 5 by a distance of 2h, and the formula % (2) is satisfied. In addition, in FIG. 6B, from the time when the information on the surface of the sample 8 reaches the sample-and-hold circuit 22, the information on the point X in the sample reaches the sample-and-hold circuit 22.
The time it takes to reach , that is, the time t8 between the information S□ and 82 in Figure 6C, is the time from when the ultrasonic wave is incident on the surface of the sample until it is reflected at point X and emitted from this surface. If the sound velocity in the sample is 08, then the following equation holds true.

h t -□ ... (3) c8 As is clear from Fig. 6G, the time T from the instant the start pulse St is generated until the information S2 of the point X in the sample reaches the sample/hold circuit 22 is To T-t -t +t... (4)1
2 8 , and this equation (4) is replaced by equations (1), (2), and (3).
By substituting , the following equation (5) is obtained.

Since C□+02+Ca, l, and f in this equation (5) can be set in advance, if the moving distance of the acoustic lens 4 is measured using a known method using the sensor device 21, the equation The calculation in (5) can be easily accomplished by generating a sampling pulse as shown in FIG. 5B at this time T.

As is clear from the above, according to the present invention, by adjusting the focus position of the lever and acoustic lens 4 to a desired position within or on the sample, sample information at this desired position can be automatically displayed on the cathode ray tube. I can do it.

It goes without saying that the present invention is not limited to the above-mentioned example, and can be modified in many ways. For example, instead of moving the acoustic lens, the sample stage 7 can be moved in the same direction. In addition, the sensor device 21 does not detect the amount of movement of the acoustic lens, and the desired amount of movement is detected from the outside of this device 2].
It is also possible that the device 21 automatically performs only the arithmetic processing described above.

, 4. Brief explanation of the drawings Figure 1 is an explanatory diagram showing a conventional ultrasound microscope, Figure 2 is a waveform diagram to explain the operation of Figure 1, and Figure 8 is a waveform diagram of Figure 2G. A waveform diagram showing details, FIG. 4 is an explanatory diagram showing an example of the ultrasonic microscope of the present invention, FIG. 5 is a waveform diagram for explaining the operation of FIG. 4, and FIG. 6 is a detailed explanation of the present invention. This is a diagram for

]... High frequency pulse generator 2... Circulator 3... Piezoelectric transducer 4... Acoustic lens 5... Liquid (ultrasonic transmission medium) 6... Scanning control device 7... Sample stage 8 ...Sample 9...Gate circuit 10,]θ''...
・Amplification/detection circuit 1]...scan converter 12...cathode ray tube] 3
...Control circuit 21...Sensor device 22.
...Sample/hold circuit.

Figure 1 Figure 2 C-m-” to-m- Figure 3 Figure 4

Claims (1)

[Claims] L means for changing the relative position between the focus of the acoustic lens and the sample in the direction of ultrasonic generation, and moving the focus of the acoustic lens to a desired position on the surface of the sample or inside the sample; Means for envelope detection of an electric signal corresponding to an ultrasonic wave; and means for automatically extracting only a portion corresponding to sample information at a position where the focal point of the acoustic lens is located from the output signal of the envelope detection means. An ultrasonic microscope characterized by comprising: