JPH056144B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention includes a sample stage on which a sample to be observed is placed, an ultrasonic beam directed at the sample placed on the sample stage, and an ultrasonic wave reflected from the sample. an acoustic lens that generates waves, a piezoelectric transducer attached to the acoustic lens, a scanning mechanism that moves the sample stage in a plane parallel to a scanning plane perpendicular to the axis of the ultrasound beam, and a scanning mechanism that moves the sample stage in a plane parallel to a scanning plane perpendicular to the axis of the ultrasonic beam. The present invention relates to a method for adjusting the inclination of a sample stage in an ultrasonic microscope, comprising a tilt adjustment mechanism for adjusting the inclination of the sample, and scanning the sample on the sample stand with an ultrasonic beam to obtain an ultrasonic image of the sample.

An ultrasound microscope is a device that uses ultrasound instead of light to observe the microscopic structure of objects. The principle is to scan the sample surface with a narrowly focused ultrasonic beam spot, receive the reflected ultrasonic waves that reflect according to differences in the acoustic properties of the sample surface or inside the sample, and convert them into electrical signals. This is processed into a brightness signal of a television signal and displayed as an image on a television image monitor for observation.The image is enlarged by raster scanning on the television image monitor. This is done by making the width larger than the scanning width of the ultrasonic beam at the sample surface.

FIG. 1 is a block diagram showing the general basic configuration of an ultrasound microscope based on the above principle.

The high-frequency burst signal from the high-frequency pulse generator 2, which generates an ultra-high frequency burst wave high-frequency signal at a period synchronized with the control signal from the control unit 1, passes through the circulator 3 to a piezoelectric generator that reversibly converts an electric signal and an ultrasonic signal. It is applied to the transducer 4 and converted into ultrasonic waves. This ultrasonic wave is transmitted through the acoustic lens 5
The beam is focused by the ultrasonic wave transmission medium 6, such as water, and is irradiated onto the surface of the sample 7 as a minute spot. The irradiated ultrasonic waves are reflected according to the acoustic characteristics of the sample 7, collected by the acoustic lens 5, received by the piezoelectric transducer 4, converted into an electrical signal, and then transmitted again via the circulator 3. The signal is guided to the receiving section 8. The electrical signal guided to the receiving section 8 is gated by a gate signal from the control section 1 to remove unnecessary signals, and is then amplified and detected to determine the intensity of the reflection from the sample 7. This becomes the detection output signal. The detection output signal obtained in this way is
The direction and Y direction information signals are guided to the scan converter 11, where they are recorded as luminance signals, and then converted into television signals and read out. Display the image as an image. The X direction scanning section 9 and the Y direction scanning section 10 are each driven by a control signal from the control section 1, and the acoustic lens 5 is excited in the X direction at high speed by the X direction scanning section 9. The sample table 13 is configured to move at a low speed in the Y direction by the Y direction scanning section 10.

When observing the sample 7 using the ultrasonic microscope configured as described above, in order to obtain a high-resolution ultrasonic microscope image, the sample 7 must be positioned at a focusing spot where the ultrasonic beam is minimized. need to be placed. In other words, the sample 7 must be placed on the sample stage 13 so that the scanning plane formed by the focused spot of the ultrasonic beam and the surface of the sample 7 to be observed are aligned or parallel. .
For this purpose, a goniometer that can adjust the parallelism of the plane in two directions has been used as the sample stage 13. In order to make the adjustment parallel to the scanning plane formed by the focused spot of the ultrasonic beam and the surface of the sample 7, scanning is repeated many times to make the image displayed on the display section 12. While observing, it is a hassle to have to adjust the goniometer many times to reduce the interference fringes that appear when the images are not parallel.
Therefore, most of the observation time is spent on adjustment, etc.
This is also a cause of inefficiency in the use of ultrasound microscopes.

An object of the present invention is to eliminate the trouble of adjusting the parallelism between the surface of a sample and the scanning plane formed by the focusing spot of the ultrasonic beam in the conventional ultrasound microscope as described above. It is an object of the present invention to provide a method for adjusting the tilt of a sample stage of an ultrasonic microscope that is easy and can be automatically adjusted.

The present invention provides a sample stand on which a sample to be observed is placed, an acoustic lens that irradiates the sample placed on the sample stand with an ultrasonic beam and receives the ultrasonic waves reflected from the sample, and an acoustic lens that receives ultrasonic waves reflected from the sample. A piezoelectric transducer attached to an acoustic lens, a scanning device that moves the sample stage in a plane parallel to a scanning plane perpendicular to the axis of the ultrasound beam, and a tilt adjustment mechanism that tilts the sample stage. In the tilt adjustment method for an ultrasonic microscope, the method includes: irradiating the sample with an ultrasonic beam from the acoustic lens at at least two locations on the sample surface, receiving the ultrasonic waves reflected from the sample, and adjusting the ultrasonic waves reflected from the sample from a reference time. The distance between the acoustic lens and at least two points on the sample surface is determined by measuring the time until the reception time of the ultrasonic wave, and the tilt adjustment mechanism is adjusted so that these distances are equal. The feature is that the sample surface and the scanning plane are made parallel by adjustment.

Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 2 shows how the acoustic lens 5, which includes the tilted sample 7 integrated with the piezoelectric transducer 4, scans the sample 7 in the X direction. As shown in the figure, the state where the acoustic lens 5 is on the leftmost side of the surface of the sample 7, for example, is L, and the state where it is on the rightmost side is R. Let L be the distance between the acoustic lens 5 and the sample 7 in _{the L} state, and _R be the distance in the R state. In the illustrated example, the state is _L / _R . As shown in FIGS. 3a and 3b, in both of these states, a burst wave high frequency pulse signal _P1 is generated from the high frequency pulse generator 2, and a burst wave high frequency pulse signal P1 is generated from the sample 7 corresponding to the ultrasonic wave caused by the burst wave high frequency pulse signal. Let t _L and t _R be the time it takes to obtain the received signals P ₂ and _{P 2 '} of the reflected waves of Distances _L and _R between the surfaces of the acoustic lens 5 and the sample 7 at each position of the lens 5 with respect to the sample 7
This is caused by the difference in Δt=2( _R
− _L )/C (C is the sound speed in water when the ultrasonic transmission medium is water).

Therefore, the received signal P ₂ obtained when the acoustic lens 5 is in state L at the left end facing position with respect to the sample 7 in linear reciprocating motion, and the state R at the right end facing position.
For example, by finding the time difference Δt=t _L − t _R between the respective times t L and _{t R} from the emitted ultrasonic wave P ₁ , the reference time until the received signal R ₂ ' obtained at , the state of inclination of the sample 7 can be detected.

Based on this principle, the present invention detects the signals corresponding to t _L and t _R and sets Δt = t _L - t _R = O, so the inclination of the sample stage is adjusted so that these detection signals become equal. The adjustment makes the sample surface parallel to the scanning plane formed by the focal spot of the ultrasound beam.

FIG. 4 is a block diagram showing an example of the configuration of an embodiment of the present invention, and the same parts as in FIG. 1 are designated with the same reference numerals.

In the figure, a control section 1 generates a constant period pulse signal shown in FIG. 5a, which is the basis of the operation of each section in this embodiment. The output of the high-frequency pulse generator 2 controlled by this pulse signal passes through the circulator 3 and is applied to the piezoelectric transducer 4 as explained in FIG. This received detection signal is guided to a circuit (see FIG. 1) for forming an ultrasonic microscope image, which includes a scan converter 11, a television image monitor 12, etc. (not shown), and the like.
In this embodiment, the pulse signal (FIG. 5a) from the control section 1 is guided to the integrator 21 and set and reset, thereby obtaining the sawtooth wave signal shown in FIG. 5B. The sample and hold circuits 22 and 23 shown in FIG.

On the other hand, the received signal due to the reflected wave from sample 7 is
The signal is amplified and detected in the receiving section 8, and then passed through the acoustic lens 5.
Unnecessary signals due to internal reflection etc. are removed,
As shown in FIG. 5c, the pulse signal for driving the high-frequency pulse generator 2, that is, for each ultrasonic beam irradiated on the sample 7, is based on the timing of the pulse signal in FIG. 5a, as explained earlier. time t _L , t _R corresponding to the distance between the acoustic lens 5 and the sample 7 surface.
The detected output signal is extracted as a delayed detection output signal.
Among these detection output signals, the detection output signals D _L and D _R at both ends of the X-direction scanning of the acoustic lens 5 are
If we compare the times t _L and t _R from the reference time, that is, the time of the pulse signal in Figure 5a, to the time of each detection output signal, we can calculate the time difference by Δt, which is the inclination of the surface of the sample 7 in the X direction. It will show the degree. Therefore, in this embodiment, the detection output signal from the receiving section 8 is guided to the L/R pulse generator 24, where it is set to exceed a predetermined reference voltage _Vp in order to avoid sounds such as noise, and the X-direction scanning section Only the detection output signals D _L and D _R during the period of each gate pulse having the timing at both ends of the X direction scan, which are generated in synchronization with the X direction scan by 9, are taken out and are shown in Fig. 5 d and e. As shown, sampling pulses _SL and _SR having the timings of the detection output signals _DL and _DR are obtained. These sampling pulses S _L and S _R are separately sent to the sample hold circuit 2.
2 and 23, the voltages V _L and _VR are sampled and held, respectively, from the sawtooth wave signal output from the integrator 21 shown in FIG. 5b. The levels V _L and V _R of the sample-and-hold signals shown in _{FIG .}
This corresponds to the time t _L and t _R from the reference time (the time of the pulse signal shown in a of FIG. 5) until the detection output signals D _L and D _R are obtained. These sample and hold signals are led to the gate section 25, where they are simultaneously gated by the gate signal G having the timing shown in _{FIG .} The corresponding slope information signals I _L and _IR are obtained simultaneously. The gate signal G _shown in FIG. By adding this, the sampling pulse S _R is generated at a timing slightly delayed by a time t _D . The tilt information signals I _L and _IR thus detected are supplied to the differential amplifier 27, and the tilt adjustment mechanism 28 is automatically controlled by an output signal corresponding to the amplitude difference between the tilt information signals I _L and _IR . Then, the inclination of the sample stage 13 in the X direction is adjusted so that the output of the differential amplifier 27 shows a zero value. After that, while maintaining the inclination in the X direction,
If the sample stage 13 is rotated 90 degrees by manual operation,
This means that the tilt of the sample 7 on the sample stage 13 in the Y direction has been eliminated. If the inclination of the sample stage 13 is adjusted again in the X direction in this state, the inclination will be adjusted in the X direction and the Y direction.
The surface of the sample 7 is adjusted to be perfectly parallel to the scanning plane formed by the focal spot of the ultrasonic beam by the acoustic lens 5.

In the above embodiment, an example was shown in which the drive source of the tilt adjustment mechanism 28 was automatically controlled by the output of the differential amplifier 27. Of course, the signals of and j may be displayed and the tilt adjustment mechanism 28 may be manually adjusted so that these two signals become equal. In addition, the sample 7 was scanned two-dimensionally in X-Y with an ultrasonic beam,
The X direction and the Y direction passing through approximately the center of the surface of the sample 7
For the reception detection output signals obtained from four locations near each scanning end in the direction, each slope information signal corresponding to the time from the reference time to reception is detected, and the slope information obtained from both ends in the X direction is detected. It can also be configured to automatically control the tilt of the sample stage in the X and Y directions so that the difference signal between the signals and the difference signal between the tilt information signals obtained from both ends in the Y direction are both zero. .

As is clear from the above description of the embodiments, according to the present invention, the focusing spot of the ultrasonic beam can easily and easily scan the sample plane with respect to the scanning plane formed by two-dimensionally scanning the sample plane. It has the effect of being able to parallelize quickly and with high precision. Therefore, in the ultrasonic microscope implementing the present invention,
As in the conventional method, the sample must be repeatedly scanned by an ultrasonic beam over and over again while observing the ultrasonic microscope on a television image monitor, and the inclination of the sample stage must be adjusted to avoid interference fringes. It is possible to eliminate a lot of complicated work,
This is extremely effective in terms of the efficiency of using an ultrasound microscope.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the basic configuration of an ultrasonic microscope. FIG. Similarly, FIG. 3 is a waveform diagram showing the timing relationship of the received signals in the state of FIG. 2, FIG. 4 is a block diagram showing an example of the configuration of the embodiment of the present invention, and FIG. FIG. 3 is a waveform diagram for explaining the operation of the embodiment shown in FIG. 1...Control unit, 2...High frequency pulse generator, 3
...Circulator, 4...Piezoelectric transducer, 5...Acoustic lens, 8...Receiving section, 9...X
Directional scanning unit, 13... sample stage, 21... integrator,
22, 23...sample hold circuit, 24...
L/R pulse generator, 25...gate section, 26...
...Delayed pulse generator, 27...Differential amplifier, 28
...Tilt adjustment mechanism.

Claims (1)

[Claims] 1. A sample stage on which a sample to be observed is placed, and an acoustic lens that irradiates the sample placed on the sample stage with an ultrasonic beam and receives the ultrasonic waves reflected from the sample. a piezoelectric transducer attached to the acoustic lens; a scanning device that moves the sample stage in a plane parallel to a scanning plane perpendicular to the axis of the ultrasonic beam; and a tilt adjustment mechanism that tilts the sample stage. A method for adjusting the tilt of a sample stage in an ultrasonic microscope, comprising: scanning the sample on the sample stage with an ultrasonic beam to obtain an ultrasonic image of the sample; irradiate the sample with an ultrasonic beam at two locations, receive the ultrasonic waves reflected from the sample, determine the distance between the acoustic lens and the at least two locations on the sample surface, and determine whether these distances are equal. A method for adjusting the inclination of a sample stage of an ultrasonic microscope, characterized in that the sample surface and the scanning plane are made parallel by adjusting the inclination adjustment mechanism so that the inclination adjustment mechanism becomes parallel.