JPH06102260A - Confocal ultrasonic microscope - Google Patents

Abstract

PURPOSE:To obtain a confocal ultrasonic microscope which can be adjusted easily and can produce an image of same quality as that of transmission ultrasonic microscope with high resolution. CONSTITUTION:The confocal ultrasonic microscope comprises a transmission means 21, an electroacoustic conversion means 23, an acoustic lens 24, and a concave reflector 26 having spherical or cylindrical reflection face 26a focal point thereof being matched with that of the acoustic lens 24. Acoustic wave transmitted through a sample is reflected on the concave reflector 26 and impinges again on the acoustic lens 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type ultrasonic microscope which receives a transmitted sound wave transmitted through a sample into an acoustic lens again and captures it as image information.

[0002]

2. Description of the Related Art Conventionally, as an ultrasonic microscope, FIG.
The transmissive type shown in FIG. 3A and the reflective type shown in FIG. 3B are known. In the transmission type ultrasonic microscope shown in FIG. 5A, the transmission signal generated by the transmitter 1 is converted into ultrasonic waves by the transducer 2, and the ultrasonic waves are converged by the acoustic lens 3. The sample 5 held by the sample holder 4 is arranged at the focal position of the acoustic lens 3 which is the convergence point of ultrasonic waves, and the transmitted wave transmitted through the sample 5 is received by another acoustic lens 6. The transmitted wave received by the acoustic lens 6 is converted into an electric signal by the transducer 7 and further input into the receiver 8 to be converted into image information of one point of the sample 5.
An image of the sample 5 is obtained by repeating the above operation while two-dimensionally scanning the sample 5 with the sample holder 4.

By the way, in the above transmission type ultrasonic microscope, the acoustic lenses 3 and 6 are provided in order to efficiently receive the transmitted wave.
It is necessary to arrange them in a confocal state as shown in FIG. For confocal arrangement, the inter-lens distance is adjusted to a confocal position (Z-axis adjustment), the axes of the two acoustic lenses 3 and 6 are made parallel (tilt adjustment), and the axes of the two lenses are matched. Will be adjusted accordingly. Thus, the transmission ultrasonic microscope requires complicated adjustment.

On the other hand, in the reflection type ultrasonic microscope shown in FIG. 5B, the transmission signal output from the transmitter 9 is applied to the transducer 11 via the circulator 10, and the ultrasonic wave generated by the transducer 11 is transmitted to the acoustic lens. Converged by 12. The sample 14 placed on the stage 13 is arranged at the focal position of the acoustic lens 12.

In the reflection type ultrasonic microscope, the ultrasonic wave incident on one point of the sample 14 is reflected and again reflected by the acoustic lens 12.
Is input to the receiver 15 and is converted into an electric signal by the transducer 11 and then input to the receiver 15 via the circulator 10.

In this reflection type ultrasonic microscope, as shown in FIG.
As shown in, the focal length of the acoustic lens 12 and the distance between the lens and the sample are matched, and the sample surface is adjusted to be perpendicular to the lens axis. This adjustment is simpler than the adjustment required for the transmission ultrasonic microscope described above.

However, unlike the transmission type ultrasonic microscope, the reflection type ultrasonic microscope described above has an image based on the absorption amount,
It is not suitable for obtaining an internal image that is not affected by the sample surface. Therefore, recently, an ultrasonic microscope which can obtain the same type of image as the transmission ultrasonic microscope and has the same operability as that of the reflection ultrasonic microscope has been considered.

The structure of such an ultrasonic microscope is shown in FIG. In this ultrasonic microscope, the flat detector 17 is opposed to the acoustic lens 16, and the acoustic lens 16 and the flat detector 17 are arranged as shown in FIG. 7B. Then, the ultrasonic wave reflected by the flat surface of the flat detector 17 is converged on the sample, and the transmitted wave is reflected by the wave receiving surface of the acoustic lens 16 and is made incident vertically on the flat detector 17 as parallel light. Flat detector 17
An ultrasonic wave that is vertically incident on is converted into an electric signal by the transducer 18 and input to the receiver 19.

In this ultrasonic microscope, in order to obtain a transmitted wave, the acoustic lens 16 is adjusted to a distance that becomes a parallel acoustic wave when the acoustic wave that has passed through the focus once is reflected by the acoustic lens 16 (Z-axis adjustment). It is necessary to adjust the tilt so that the lens axis and the flat detector 17 are vertical. Such an adjustment is almost the same as the adjustment required for the above-mentioned reflection type ultrasonic microscope and can be easily performed.

[0010]

However, in the ultrasonic microscope shown in FIG. 7, the spherical wave emitted from the acoustic lens 16 is once reflected by the plane of the flat detector 17, and then the sample placed at the focal position is measured. Illuminate and acoustic lens 1
Since it is reflected by the spherical portion of 6 and converted into a plane wave, there is a drawback that the aberration is large and the vertical resolution is lowered.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a confocal ultrasonic microscope which can realize a high resolution by using a transmitted wave and can be easily adjusted.

[0012]

In order to achieve the above object, a confocal ultrasonic microscope of the present invention comprises transmitting means for generating a transmission signal which is converted into ultrasonic waves, and conversion of the transmission signals into ultrasonic waves. An electric / acoustic conversion means for converting an ultrasonic wave given together into an electric signal, and an acoustic lens for converging the ultrasonic wave generated by the electric / acoustic conversion means to a focal position,
A concave reflector having a spherical reflective concave surface or a cylindrical reflective concave surface and having the focal position of the reflective concave surface aligned with the focal position of the acoustic lens; and a combination of the acoustic lens and the concave reflector. Sample holding means for holding a sample at a focus position, and a transmitted acoustic wave transmitted through the sample is processed by an electric signal output from the electric / acoustic conversion means by being reflected by the concave reflector and incident on the acoustic lens. And a signal processing unit for converting into image information.

[0013]

In the confocal ultrasonic microscope of the present invention, the transmission signal generated by the transmitting means is input to the electric / acoustic converting means to generate ultrasonic waves. The ultrasonic wave is converged on the sample by the acoustic lens. The transmitted sound wave that has passed through the sample is reflected by the concave reflector, converges again at the same point on the sample, and then enters the acoustic lens.

Here, since the concave reflector has a spherical or cylindrical reflective concave surface, the aberration at the time of reflection is much smaller than that of the flat detector. Further, since the ultrasonic wave converges twice at the same point on the sample, it is affected twice by the amount of absorption at that point, so that an image with good contrast can be obtained. In the case of a cylindrical concave reflector, only the transmitted sound waves that have entered the concave reflector perpendicularly to the longitudinal direction of the reflecting concave surface return to the acoustic lens, so a contrast image due to the anisotropy of the sample can be obtained. .
The transmitted wave received by the acoustic lens is converted into an electric signal by the electric / acoustic conversion means, and then input to the signal processing unit and converted into image information.

[0015]

EXAMPLES Examples of the present invention will be described below. FIG. 1 shows the configuration of a confocal ultrasonic microscope according to an embodiment of the present invention.

The confocal ultrasonic microscope of this embodiment is equipped with a transmitter 21 for generating a high frequency burst wave of 100 to 1000 MHz at a cycle of 20 to 100 Hz as a transmission signal for generating ultrasonic waves. The high frequency burst wave sent from the transmitter 21 passes through the circulator 22 and is applied to the transducer 23 as an electric / acoustic conversion means to be converted into ultrasonic waves. Transducer 23
Is provided on one end surface of the acoustic lens 24, and a lens surface 24a for converging the ultrasonic waves generated by the transducer 23 to a predetermined position is formed on the other end surface of the acoustic lens 24. At the convergence point (focus) of the ultrasonic wave by the acoustic lens 24, the thin film sample S as a transmission sample is held by the sample holder 25.

A reflector 26 is installed at a position facing the acoustic lens 24 with the thin film sample S interposed therebetween. The reflector 26 has a reflecting concave surface 26 a formed of a spherical concave surface on the surface facing the acoustic lens 24.

Here, when the curvature of the lens surface 24a formed on the acoustic lens 24 is R0, the focal length of the acoustic lens 24 becomes substantially equal to the curvature R0. In addition, the reflector 26
Assuming that the curvature of the reflecting concave surface 26a formed in 1 is R1, the focal length of the reflecting concave surface 26a is substantially equal to the curvature R1.

In this embodiment, the distance (R) is provided between the lens surface 24a of the acoustic lens 24 and the reflective concave surface 26a of the reflector 26.
0 + R1) apart so that both focal points of the lens surface 24a and the reflective concave surface 26a coincide on the thin film sample S,
The acoustic lens 24 and the reflector 26 are arranged.

That is, as shown in FIG. 2, the acoustic lens 2
All the ultrasonic waves emitted from the lens surface 24a of No. 4 converge at one point of the sample, the transmitted wave is reflected by the reflection concave surface 26a of the reflector 26 and converges again at the same point of the sample, Both of them are arranged so that the sound wave that has passed twice is re-incident on the acoustic lens 24.

The acoustic lens 24 is used in the Z stage 2
It is supported by 7 so as to be movable in a direction parallel to the lens axis. The reflector 26 is fixed on an XY stage 28 and can be moved in a plane perpendicular to the Z direction in the X and Y directions orthogonal to each other in a plane perpendicular to the Z direction. Further, the sample holder 25 is supported by a scanning mechanism (not shown) for scanning the thin film sample S in each of the X, Y and Z directions. A space between the lens surface 24a of the acoustic lens 24 and the reflection concave surface 26a of the reflector 26 is filled with a coupler liquid 29 for propagating ultrasonic waves.

The circulator 22 sends a transmission signal input from the transmitter 21 to the first input terminal to the transducer 23 side from the first output terminal, and a reception signal input from the transducer 23 to the second input terminal. It is configured to output from the second output terminal. The receiver 31 is connected to the second output terminal of the circulator 22.

The receiver 31 has a function to gate the received signal input from the circulator 22 to extract only the reflected wave component from the sample S and hold the peak value of the extracted reflected wave component. The peak hold value of the reflected wave component is used as image information in the digital memory 32.
Stored in the digital memory 32, and the data stored in the digital memory 32 is C
Images can be displayed on the RT33.

The operation of the entire apparatus is controlled by the controller 34. The controller 34 stores a sequence program for realizing the following operation functions. That is, the transmitter 21 is provided with a transmission timing and the receiver 31 is provided with a gate timing to capture image data, and the Z stage drive unit 35 is also provided.
And a control signal to the XY stage drive unit 36 to control the Z stage 27 and the XY stage 28 so that the acoustic lens 24 and the reflector 26 have the above-mentioned positional relationship, and further scan in accordance with the transmission timing. A control signal is given to the mechanism drive unit 37 to scan the thin film sample S. Next, the operation of this embodiment configured as described above will be described.

First, the acoustic lens 24 and the reflective concave surface 26a of the reflector 26 are adjusted so as to be confocal. For example,
As shown in FIG. 3A, it is assumed that the focus P of the acoustic lens 24 and the focus Q of the reflective concave surface 26a are deviated.

In such a positional relationship, the acoustic lens 24 is moved in the Z direction by the Z stage 27,
As shown in FIG. 3B, the focus P of the acoustic lens 24 is adjusted to the same height as the focus Q of the reflective concave surface 26a (adjustment in the Z direction). Next, the reflector 26 is moved by the XY stage 28 to X,
The focus is moved in the Y direction so that the focus Q coincides with the focus P as shown in FIG. As a result, the radial direction of the spherical portion of the reflective concave surface 26a formed on the reflector 26 and the lens axis coincide, so that the sound wave reflected by the reflective concave surface 26a is accurately returned to the acoustic lens 24.

When the above adjustment is completed, the controller 3
A control signal is given from 4 to the scan mechanism drive unit 37, and the sample holder 25 is moved so that the scan start point of the thin film sump S is on the lens axis. Next, a transmission timing is given from the controller 34 to the transmitter 21, and the high frequency burst wave is output from the transmitter 21 at the above-described cycle.

The high frequency burst wave is applied to the transducer 23 via the circulator 22, and is converted into ultrasonic waves there. The ultrasonic wave propagates through the acoustic lens 24, is refracted at the lens surface 24a, and converges at one point of the thin film sample S. When the ultrasonic wave passes through one point of the thin film sump S, the ultrasonic wave is affected by absorption and the like from the converged portion. Then, the transmitted sound wave that has passed through the thin film sample S spreads again and becomes a spherical wave and is incident on the reflection concave surface 26 a of the reflector 26.

Since the focal point of the reflecting concave surface 26a of the reflector coincides with the lens axis, the sound wave reflected by the reflecting concave surface 26a converges at the same point of the thin film sample S, and then the lens surface of the acoustic lens 24. It is incident on 24a and returned to a parallel wave.

The transmitted wave received by the acoustic lens 24 is converted into an electric received signal by the transducer 23. This received signal is input to the receiver 31 via the circulator 22, where it is converted into image data by the processing described above, and the image data is stored in the digital memory 32.

By the above operation, the image data of one point of the thin film sample S is taken in. Therefore, two-dimensional image data of the thin film sample S can be obtained by repeating the above operation while raster-scanning the thin film sample S by the scanning mechanism driving unit 37.

As described above, according to this embodiment, the reflecting concave surface 26
Since the reflector 26 having a is arranged so as to face the confocal position with the acoustic lens 24 with the thin film sample S interposed therebetween, an image of the same quality as the transmission ultrasonic microscope and high resolution can be obtained from the transmission ultrasonic microscope. Can be obtained by simple adjustment, and the structure can be further simplified.

That is, since the ultrasonic wave is converged on the sample S and the transmitted sound wave is reflected by the reflection concave surface 26a and passed through the same portion of the sample S again, an image due to absorption or an internal image not affected by the surface is obtained. Related data can be obtained, and the information such as the absorption amount is included twice in the received signal, so that an image with good contrast can be obtained. Further, in the present embodiment, since the adjustment in the XY directions is performed by the XY stage 28, the structure becomes simpler than that of the conventional rotating mechanism. In particular, in a cryogenic ultrasonic microscope in which a measuring mechanism is provided in a closed container, the adjusting mechanism can be easily replaced by the parallel moving means instead of the complicated rotating mechanism, so that the effect is great. Also, like the conventional transmission ultrasonic microscope, in the rotating mechanism, if the center of rotation does not match the focus, the height changes during rotation, so Z
The stage has to be readjusted, but in the present embodiment, such readjustment is not necessary and the adjustment is easy.

In the above embodiment, the reflector 26 having the spherical reflection concave surface 26a is used as the reflector.
Instead of this, the cylindrical reflecting concave surface 3 shown in FIG.
It is also possible to use a reflector 30 with 0a.

The reflector 30 shown in the figure has a reflecting concave surface 30a.
The height corresponding to the curvature of the
Line focus). For example, if the line focus direction is the X direction, the reflector 30 does not exhibit a converging action in the X direction. Therefore, when the reflector 30 having such a shape is used, the sound wave in the X direction has an inclination with respect to the lens axis when returning to the transducer 23 via the acoustic lens 24 and is not received by the transducer. Therefore, only the sound wave in the YZ plane is received by the transducer, and the anisotropic information of the sample can be obtained. The present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention.

[0036]

As described above in detail, according to the present invention, since the concave reflector having the spherical reflective concave surface or the cylindrical reflective concave surface is confocally arranged with respect to the acoustic lens, the acoustic lens and the reflector are provided. It becomes easy to adjust with
It is possible to obtain an image of the same quality as that of the transmission type acoustic microscope, and to obtain an image with good contrast.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an ultrasonic microscope according to an embodiment of the present invention.

FIG. 2 is a diagram showing a positional relationship between an acoustic lens and a reflector provided in the ultrasonic microscope shown in FIG.

FIG. 3 is a diagram for explaining an adjustment work of an acoustic lens and a reflector in the ultrasonic microscope shown in FIG.

FIG. 4 is a perspective view of a reflector according to a modification.

FIG. 5 is a diagram showing a configuration of a conventional transmission ultrasonic microscope and a conventional reflection ultrasonic microscope.

FIG. 6 is a diagram showing a positional relationship between acoustic lenses of the transmission ultrasonic microscope shown in FIG. 5A and a positional relationship between the acoustic lens and the stage of the reflection ultrasonic microscope shown in FIG. is there.

FIG. 7 is a diagram showing a configuration of an ultrasonic microscope including an acoustic lens and a flat detector, and a positional relationship between the acoustic lens and the flat detector.

[Explanation of symbols]

21 ... Transmitter, 23 ... Transducer, 24 ... Acoustic lens, 25 ... Sample holder, 26, 30 ... Reflector,
26a ... Spherical reflective concave surface, 30a ... Cylindrical reflective concave surface.

Claims (1)

[Claims] 1. A transmission means for generating a transmission signal converted into an ultrasonic wave, an electric / acoustic conversion means for converting the transmission signal into an ultrasonic wave, and an electric / acoustic conversion means for converting the supplied ultrasonic wave into an electric signal, An acoustic lens for converging the ultrasonic waves generated by the acoustic converting means to a focal position, and a spherical reflective concave surface or a cylindrical reflective concave surface are arranged so that the focal position of the reflective concave surface coincides with the focal position of the acoustic lens. A concave reflector, a sample holding means for holding a sample at a confocal position between the acoustic lens and the concave reflector, and a transmitted sound wave transmitted through the sample is reflected by the concave reflector to the acoustic lens. A confocal ultrasonic microscope, comprising: a signal processing unit that processes an electric signal output from the electric / acoustic conversion means by being incident and converts the electric signal into image information.