JPS5841346A - Bubble detector for acoustic lens used for ultrasonic microscope - Google Patents

Abstract

PURPOSE:To detect automatically the existence of bubble that is developed in an acoustic lens by detecting selectively the detection signal issued by the reflection wave from an acoustic lens and comparing the detection value with a specific threshhold value. CONSTITUTION:A detection signal issued by the reflection wave from a spherical concave surface lens 2 of an acoustic lens 3 is selectively detected by sample holding. This detected voltage is compared in a comparator 17 with a reference voltage Vr1 of a threshold value. In other words, when the detection output voltage VB1 by the first reflection wave is larger than Vr, the comparator is made to develop ON output. Therefore, if a bubble is in the concave surface lens 2, the detection output VB1 becomes larger than Vr, making the comparator 17 develop ON output, and by this the existence of bubble is immediately detected. With this arrangement the existence of bubble that is produced in the spherical concave lens 2 of the acoustic lens 3 can be automatically detected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an acoustic lens bubble detector for detecting the presence or absence of bubbles generated in a spherical concave lens portion of an acoustic lens in an ultrasonic microscope.

I! Figure 1 shows the acoustic lens of the ultrasound microscope facing the sample. 1 is a piezoelectric transducer that converts a burst wave electrical signal supplied from a high-frequency pulse generator (not shown) into ultrasonic waves;
The ultrasonic pressure (IIE) from the transducer is applied to the sample through the acoustic lens 3 having a tightly formed spherical concave lens part and the liquid J interposed between the spherical concave lens part λ and the sample. The sound waves are projected in a spot shape.Here, 6 is liquid! The figure shows an air bubble in the spherical concave lens part that fills the area.

The lens part formed at the end of the acoustic lens 3 facing the sample has a spherical concave surface, and the space between the spherical concave lens and the sample 1 is filled with liquid J, so that Air bubbles often occur in the spherical concave lens portion.

As is well known, ultrasonic waves are
Since the attenuation is much greater when passing through gas, if air bubbles are generated in the spherical concave lens part of the acoustic lens J as shown in the figure, the ultrasonic waves will not be transmitted to the liquid J1, so the sample da Since no information can be obtained, this bubble 6 must be removed.

Conventionally, when observing a sample using an ultrasonic microscope, in order to extract the reflected ultrasonic wave from one sample, an acoustic lens J is brought close to the sample, and the sample is positioned near the focal point of the acoustic lens 3. The focus joint is moved until the focal point is detected and monitored, and the position where the highest intensity of reflected waves is obtained is selected. In this case, when there is a bubble t in the spherical concave lens part, the reflected wave of the ultrasonic wave from the sample cannot be detected, so focal joint is impossible, but the observer does not notice this. There are many cases in which the acoustic lens 3 is brought too close to the sample DA and the two come into contact, resulting in damage to the sample 4It or the acoustic lens J.

SUMMARY OF THE INVENTION An object of the present invention is to provide an acoustic lens bubble detector that automatically detects the presence or absence of bubbles generated in the spherical concave lens portion of a concave lens in an ultrasonic microscope, in order to prevent the above-mentioned accidents. .

That is, the present invention converts an electric signal from a high-frequency pulse generator into an ultrasonic wave using a piezoelectric transducer, projects it onto a sample through an acoustic lens, and receives the reflected wave using the piezoelectric transducer to obtain a detected signal. In the ultrasonic microscope, a detection signal caused by a reflected wave from the spherical concave lens portion of the acoustic lens is selectively held and detected by a pulse signal having a predetermined timing synchronized with the electric signal. The present invention is characterized in that the presence or absence of air bubbles in the spherical concave lens portion is detected by comparing the detected value with a predetermined threshold value.

Hereinafter, the present invention will be explained based on illustrated embodiments.

Figure 1 shows the configuration of an embodiment in which the acoustic lens bubble detector of the present invention is applied to an ultrasonic microscope having a typical configuration, and the same parts as in Figure 1 are given the same reference numerals. In the figure, the high-frequency pulse generator 1 is controlled to start and stop by a control pulse signal from the control pulse generator 7, and a burst wave of high-frequency pulses is generated.

The high-frequency pulse signal is supplied to a piezoelectric transducer L via a circulator, where it is converted from an electric signal to an ultrasonic wave.The ultrasonic wave passes through an acoustic lens J and is then passed through a spherical four-sided lens formed at the other end. , is projected in the form of a spot by the scanning control device 10 via the liquid j onto a sample placed on a sample stage 11 that moves co-dimensionally in the X and Y directions.

The reflected wave of the projected ultrasonic wave from the sample is collected by the spherical concave lens part 1, enters the piezoelectric transducer 1, and is converted into an electric signal there.

This electrical signal is led to the amplification/detection circuit/2 via the circulator 9, where it is high-frequency amplified and detected to obtain a detected signal. The scan converter 1 converts this detected signal into a luminance signal.
3, it is converted into a video signal synchronized with the scanning of the sample stage // by the scanning MJll device 10, and the ultrasonic image is displayed on an image display device, for example, a cathode ray tube /l. In addition, the acoustic lens J is movable in two directions perpendicular to the sample stage. The acoustic lens is focused on the plane.

In an ultrasonic microscope having the above-described configuration, for example, a control pulse signal from the control pulse generator 7 is guided to a delayed pulse generator /j to generate a delayed pulse signal delayed by n7 hours with respect to the side split pulse signal. to occur.

Here, n is any integer greater than or equal to 1, and in this embodiment, l is selected. Further, τ is the time it takes for the ultrasonic wave to propagate through the acoustic lens 3, reflect at the spherical concave lens portion, return inside the acoustic lens J, and be converted into an electrical signal by the piezoelectric transducer l, and It is determined by the frequency, the structure of the acoustic lens, etc. /4 is a sample/hold device, which converts the delayed pulse signal from the delayed pulse generator /j into a sampling pulse and outputs it from the amplification and detection circuit /2. The configuration is such that the obtained detection signal is sampled, held, and output. Further, 17 is a comparator, and the threshold reference voltage vr set by the threshold reference voltage setter /I,
The output voltage vB of the sample-and-hold device 16 is compared, and the output is made when vB>vr, and the threshold reference voltage vr is set in the output of the sample-and-hold device/4. The desired output voltage is set to a value suitable for separating the desired output voltage from low-level voltages or noise components below the output voltage to prevent recreational operations.

The output of the comparator/7 is applied to the acoustic lens 3 as described later.
This occurs only when there is a bubble 6 near the spherical concave lens part 6, so the output activates the instruction @1/9 to notify the observer of the presence of the bubble to display an alarm, or at the same time, for example, The focus adjustment mechanism may be locked so that the scanning control device 10 stops the scanning operation and the acoustic lens 1 or the acoustic lens 3 cannot be brought any closer to the sample.

The operation of the configuration of the embodiment of the present invention as described above will be explained with reference to the timing chart shown in FIG.

The part of the spherical concave lens part between the acoustic lens 3 and the liquid j that faces the liquid is usually coated with an anti-reflection film to prevent reflection of ultrasonic waves at that part due to differences in acoustic impedance. There is. Therefore, when the spherical concave lens portion of the acoustic lens 3 is completely filled with the liquid j, there is almost no reflected wave, but when a bubble ≦ enters as shown in FIG. 1, a large reflected wave is generated.

Figure 3 shows the detection output of the amplification/detection circuit/2, and the leftmost waveform P represents the leaked transmitted wave detection output corresponding to the high frequency pulse signal from the high frequency pulse generator leaked from the circulator 9. ing. In the waveform indicated by the dotted line in the center, the high-frequency pulse signal corresponding to the leaky transmitted wave detection output at the left end is converted into an ultrasonic wave by the piezoelectric transducer L, propagates through the acoustic lens J, and the spherical concave surface at the tip thereof is converted into an ultrasonic wave by the piezoelectric transducer L. This is the detection output of the first reflected wave that is reflected by the lens part A, returns inside the acoustic lens 3, and is converted into an electrical signal by the piezoelectric transducer I, and is separated by a delay time τ from the leakage transmitted wave detection output P. 0, which is the detected signal obtained in , and the lI! The first reflected wave is reflected by the piezoelectric transducer/, propagates through the acoustic lens J, is reflected again by the spherical concave lens part, returns inside the acoustic lens 3, is converted into an electric signal by the piezoelectric transducer L, and is converted into an electrical signal by the piezoelectric transducer L.
At a time that is further delayed by 1 min than the reflected wave detection output R,
The detection signal hole of the first reflected wave is obtained. The detected signal R2 of this @2 reflected wave is shown by a dotted line at the right end. In this way, the reflected waves repeat many times and attenuate.

Therefore, in this actual 1sH, the detection signal from the amplification/detection circuit 12 is converted into a sampling pulse that is a pulse signal delayed by 7 hours from the leaky transmission wave detection output shown by P in the m7 diagram A above. 16, and the detected output of the II/reflected wave is taken out as a hold voltage.

That is, since the leaky transmitted wave detection output r is controlled by the high-dust control pulse signal, the control pulse signal from the control pulse generator 7 is guided to the delay pulse generator /j, and the output r is controlled for 7 hours. If a delayed pulse signal is generated, the timing of the delayed pulse signal matches the timing of the detection signal of the first reflected wave obtained from the amplification/detection circuit/2. As a sampling pulse in the hold device 14,
By using the delayed pulse signal, the detection signal of the @1 reflected wave can be reliably sampled and held.

The output voltage of the sample-and-hold device /4 thus obtained is compared with the threshold reference voltage vr set by the threshold reference voltage setter /l in the comparator /7. The threshold reference voltage vr is the detection output voltage corresponding to the #I1 reflected wave generated due to the bubble existing near the spherical concave lens part of the acoustic lens 3, as shown in Figure fM3. The detection output voltage vB of the first reflected wave is lower than vB
It is set to a value higher than the detection output voltage or other noise signal corresponding to low-level reflected waves that occur even when there are no air bubbles near the E or IIEU surface lens.

Also, the output of the sample-and-hold device 14 is given to the input terminal of the comparator n, and the threshold reference voltage vr from the threshold reference voltage setter II is given to the input terminal of the comparator n. device n is sample/hold device 1
1 output voltage vB1, that is, the first output voltage vB1 indicated by R in FIG.
It operates to output an ON output when the detected output voltage VB due to the reflected wave becomes vE,>vr.

Therefore, when there is no bubble 6 in the spherical concave lens portion of the acoustic lens 3, the detection output voltage corresponding to the first reflected wave is lower than the threshold reference voltage vr, so the comparator has an OFF output. However, if there is a bubble t in the spherical concave lens part, the detection output VB becomes VB>vr, so the comparator 17 becomes an ON output, which makes it possible to immediately detect the presence of a bubble. . Note that lq is a response device that is activated when the comparator 17 becomes an ON output. However, the response device/9 is not limited to an indicating device; for example, the presence of air bubbles in an acoustic lens may cause an observation or safety problem. There is no problem even if it is a control device for fixing the operation of a functional part of a sonic microscope, such as an XtY two-dimensional scanning control device or a focus adjustment mechanism of an acoustic lens, and the control lid and the indicating device are operated at the same time. You can do it like this.

Furthermore, if the anti-reflection film coating the spherical concave lens portion 2 of the acoustic lens 3 is incomplete or missing, the reflected waves from the spherical concave lens portion will increase, so the amplification/detection circuit The first reflected wave by the spherical concave lens portion obtained from /2 and the detection output corresponding to the first reflected wave are the third
As shown in Figure B with solid lines labeled R1' and R2', relatively large values V□ and vA2 are taken, but the detection outputs R and R2 corresponding to the waves reflected by the bubble A are: In such a case, the threshold reference voltage vr of the comparator 17 is set to the first reflected wave due to the bubble and the detection output R0/corresponding to the first reflected wave, as shown in the figure. , let the values of R21 be vB and vI32
In this case, the threshold value may be set using the threshold reference voltage setter/I so that VB□>vr>7 people.

In the above embodiment, only the detection signal resulting from the first reflected wave of the reflected waves reflected from the spherical concave lens portion of the N acoustic lens J is detected, but the present invention is not limited to this. , but the second one after the @ko reflected wave.
Any reflected waves including reflected waves may be detected. In that case, if a detection signal based on the n-th reflected wave is detected, the delay time for the pulse signal from the control pulse generator 7 of the delayed pulse signal shown by the delayed pulse generator 7 shown in FIG. needs to be set to n.

As is clear from the above description of the embodiments, according to the present invention, the presence or absence of bubbles generated in the spherical concave lens portion of the acoustic lens can be detected with a relatively simple configuration. Therefore, if the detection results are displayed on a display device, etc., when the observer observes the ultrasonic image of the sample by filling the space between the acoustic lens and the sample, it is possible to avoid any interference in obtaining the ultrasonic image. Since the presence or absence of air bubbles can be known in advance, damage accidents caused by contact between the acoustic lens and the sample, which often occur due to the failure to detect ultrasound images due to the presence of air bubbles, can be avoided during focusing. It is extremely effective in preventing

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the acoustic lens structure and its vicinity showing a state in which air bubbles are contained in the spherical concave lens portion. FIG. FIG. 3 is a timing chart for explaining the operation. L...Piezoelectric transducer, K...Spherical concave lens portion, 3...Acoustic lens, D...Sample, j...Liquid, B...Bubble, 7...Control pulse generator, l...
High frequency pulse generator, 9... Circulator, 10.
...Scan control device, ll...sample stage, /2...amplification/detection circuit, lJ...scan converter, /ri...
・Cathode ray tube, /j...delay pulse generator, /6...
Sample fist holder, n...Comparator, /l...Threshold reference voltage setter, n...Indication device〇Patent applicant Olympus Optical Industry Co., Ltd. Figure 2 Figure 3

Claims (1)

[Claims] L An ultrasonic wave that converts an electric signal from a high-frequency pulse generator into an ultrasonic wave using a piezoelectric transducer, projects it onto the sample through an acoustic lens, and receives the reflected wave by the piezoelectric transducer to obtain its detection signal. In the microscope, a pulse signal having a predetermined timing synchronized with the electric signal is used to selectively sample the detected signal due to the reflected wave from the spherical concave lens portion of the acoustic lens.
An acoustic lens bubble detector for an ultrasonic microscope, characterized in that the presence or absence of bubbles in the spherical concave lens portion is detected by holding and detecting the bubbles and comparing the detected value with a predetermined threshold value.