JPH04320959A - Ultrasonic microscope - Google Patents

Abstract

PURPOSE:To enable a plurality of pieces of information which are in series in depth direction of an object to be measured to be taken out at one operation and an optimum gain for forming an image to be set to a signal-reception circuit for extracting each reflection component. CONSTITUTION:An ultrasonic microscope consists of a transmission portion 1 for generating a high-frequency transmission signal and an electrical - acoustic conversion portion 3 for changing a transmission signal into a supersonic wave, emitting it to the object to be measured, and then converting the reflection wave into a reflection signal, thus enabling a plurality of reflection wave components of the object to be measured to be extracted from the reflection signal and then an internal structure of the object to be measured to be formed as an image. A plurality of reception circuits 6 which are connected in parallel to an output terminal of the acoustic- electrical conversion portion 3, extracts mutually different reflection wave components from each input reflection signal from the electrical-acoustic conversion element 3, and at the same time sets a gain for each reflection component individually and a gain control means 7 which controls a gain of each reception circuit according to a signal strength of the reflection wave component to be extracted from each reception circuit are provided.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic microscope capable of imaging and observing the internal structure of an object to be measured using ultrasonic waves.

0002

[Prior Art] Conventionally, ultrasonic waves are applied to an object to be measured.
An ultrasonic microscope is known that converts the reflected wave into an electrical signal, extracts only a necessary portion containing internal information of the sample from the obtained reflected signal, and displays an image of the internal structure of the sample from the internal information.

In such an ultrasound microscope, a reflected signal is amplified by a predetermined amplification factor in an amplifier system, and then inputted to a gate circuit, and the timing of the gate signal applied to the gate circuit is adjusted to extract only the necessary portion of the reflected signal. . Furthermore, the extracted signal components are subjected to peak detection using a detection circuit, and the detected signal values are converted into images.

[0004] Since a series of reflected signals obtained from sample reflected waves contain information in the depth direction of the sample in a time-series manner, by sequentially applying a gate signal to these reflected signals, one Through this operation, it is possible to obtain multiple pieces of information that are continuous in the depth direction of the sample. For example, JP-A-2-8095
No. 4 describes an ultrasonic microscope that is equipped with multiple receiving circuits from amplification to detection in parallel and can perform parallel processing by sequentially applying a gate signal to the same reflected signal in each receiving circuit. ing.

[0005]

[Problems to be Solved by the Invention] Incidentally, in the ultrasonic microscope described in the above publication, the amplification factor of the amplifier of each receiving circuit is uniformly fixed to a predetermined value, and the reflected components from different locations inside the sample are were amplified at the same amplification rate.

However, the signal strength of the reflected signal from the sample varies greatly depending on the reflection position inside the sample, so even if the amplification factor of all receiving circuits is adjusted to match the signal strength of one reflected component, If the amplification factor is too large or too small for a component, there are problems such as the image in that part becomes blank or black.

Furthermore, as described in Japanese Patent Publication No. 2-29985, there is an ultrasonic microscope capable of adjusting the amplification factor of the amplifier so that the intensity of the reflected echo from the acoustic lens interface remains constant. However, even with this ultrasound microscope, it is not possible to set the optimal amplification factor for each of the reflected components with different signal intensities in a series of reflected signals, and it is not possible to obtain an optimal image without image deterioration. .

The present invention has been made in view of the above-mentioned circumstances, and when a plurality of pieces of information in the depth direction are extracted from a series of reflected signals of an object to be measured, all of the information extracted in one operation is It is an object of the present invention to provide an ultrasonic microscope that can adjust reflected components to the optimal signal strength for imaging and can obtain optimal images without image deterioration.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the present invention converts a high-frequency electric signal into an ultrasonic wave using an electro-acoustic conversion element, and converts the ultrasonic wave into a convergent spherical wave using an acoustic lens. The reflected wave from the object to be measured is received by the acoustic lens and converted into an electrical reflected signal by the electro-acoustic conversion element, and from this reflected signal, a plurality of reflected wave components of the object to be measured are detected. connected in parallel to the output terminal of the acousto-electric transducer in an ultrasonic microscope for imaging the internal structure of the object to be measured;
A plurality of receiving circuits in which mutually different reflected wave components are extracted from the reflected signals respectively inputted from the electro-acoustic transducer, and gains for each of these reflected wave components are individually set; and a gain of each of the receiving circuits. The configuration includes gain control means for controlling according to the signal strength of the reflected wave component to be extracted by each receiving circuit.

0010

[Operation] According to the present invention, the same reflected signal output from the electro-acoustic transducer is input to a plurality of receiving circuits, where each reflected component having information in the depth direction of the object to be measured is The signals are taken out in one operation, each adjusted with an individually set gain, and output. On the other hand, each receiving circuit is
Depending on the signal strength of each reflected component to be extracted, so that the signal strength of the output reflected component becomes an appropriate signal strength,
Each gain is controlled by gain control means. In this way, each receiving circuit is set to a gain that can form an appropriate image, and an optimal image without image deterioration can be obtained.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An ultrasonic microscope according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the basic functional blocks of an ultrasonic microscope according to this embodiment. As shown in the figure, a high frequency transmission signal generated at a predetermined timing from a transmission signal generating means 1 is transmitted through a circulator 2 to an electrical source.
The sound is supplied to the acoustic conversion element 3 and converted into ultrasonic waves. This ultrasonic wave is incident on the object to be measured S placed near the focal position of the acoustic lens 4. The reflected wave from the measurement object S received by the acoustic lens 4 is converted into an electrical reflected signal by the electro-acoustic conversion element 3 and input to the preamplifier 5. The circulator 2, the electro-acoustic conversion element 3, the acoustic lens 4, and the preamplifier 5 constitute an electro-acoustic conversion section.

[0013] A plurality of receiving circuits 6-1 and 6-2 are connected in parallel to this electro-acoustic converter. Each receiving circuit 6-1, 6-2 receives the measurement target S from the input reflected signal.
Each reflected component containing continuous information in the depth direction is extracted, and each reflected component is outputted at an arbitrary amplification factor.

The gain control means 7 controls each of these receiving circuits 6.
-1 and 6-2 are connected so that the amplification factors of 6-1 and 6-2 can be controlled separately, and the amplification factors of each receiving circuit 6-1 and 6-2 are set to a value corresponding to the signal strength of the reflected component to be extracted. .

A signal extraction means 8 is provided on the output side of the receiving circuits 6-1, 6-2, and the receiving circuits 6-1, 6-2 each have a signal extracting means 8.
Each of the reflected components extracted and amplified in step 6-2 is sequentially selected and taken out and outputted to the image display means 9 as a series of signals. The image display means 9 has a function of processing the signal string extracted by the signal extraction means 8 and displaying an image of the acoustic internal structure of the measurement object S. FIG. 2 is a diagram showing a more specific configuration of this embodiment.

The main control section 20 outputs timing signals such as a transmission trigger signal, a gate trigger signal, and a reset trigger signal to control the operation timing of the entire apparatus.

The transmission signal generation circuit 21 is a circuit that generates a high frequency transmission signal when receiving a transmission trigger signal from the main control section 20. The transmission means 1 is constituted by the transmission trigger signal generation function of the main control section 20 and the transmission signal generation circuit 21.

The electro-acoustic transducer includes an acoustic lens 4 coupled to an electro-acoustic transducer element 3 made of a piezoelectric material, etc., and an ultrasonic transmission medium between the acoustic lens 4 and the object S to be measured. An acoustic coupler 22 is interposed.

One of the receiving circuits 6-1 arranged in parallel is
Amplifier 23a, gate circuit 24a, variable amplifier 25a,
Detection circuit 26a, reset switch 27a, amplifier 28
a are connected in series. Similarly, the other receiving circuit 6-2 also includes an amplifier 23b, a gate circuit 24b, a variable amplifier 25b, a detection circuit 26b, and a reset switch 2.
7b and an amplifier 28b are connected in series.

The gate signal generation circuit 31 is a circuit for applying a gate signal to each gate circuit 24a, 24b at a predetermined timing. The gate signal generation timing is controlled by a gate trigger signal from the main control section 30.

The gain control means 7 includes variable amplifiers 25a,
This is for setting the amplification factors of 25b to arbitrary amplification factors. Each amplification factor set for each variable amplifier 25a, 25b is determined by the corresponding gate circuit 24a.
, 24b, an appropriate value suitable for imaging is selected depending on the signal strength of the reflected wave component cut out by .

The reset switches 27a and 27b are circuits for resetting the detection circuits 26a and 26b.
Opening and closing are controlled in response to a reset pulse signal from the reset pulse generation circuit 32. The output of the reset pulse signal is controlled by a reset trigger signal given from the main control section 30 to the reset pulse generation circuit 32.

The signal extraction means 8 is connected to the switching pulse generating circuit 33.
It is operated by the switching signal given from. That is, it operates so as to sequentially take in information appearing as a peak detection value at the output terminals of amplifiers 28a and 28b provided at the final stage of each receiving circuit 6-1 and 6-2.

The output side of the signal extraction means 8 is connected to an image display section 35 via an amplifier 34. Image display section 3
Reference numeral 5 is for displaying an ultrasonic image of the object S to be measured by converting the information taken in through the amplifier 34 under the operation control of the main control unit 30 into an image. The operation of this embodiment configured as above will be explained with reference to FIG.

A transmission trigger signal is applied from the main control section 20 to the transmission signal generation circuit 21, and a high frequency transmission signal is generated. The generated transmission signal is given to the electro-acoustic conversion element 3 via the circulator 2, where it is converted into an ultrasonic wave. This ultrasonic wave becomes a convergent spherical wave by the acoustic lens 4, propagates through the acoustic coupler 22, and is irradiated onto the object S to be measured.

On the other hand, the reflected waves reflected from the surface, inside, etc. of the object to be measured S are received by the acoustic lens 4 and converted into electric waves.
The acoustic conversion element 3 converts the signal into an electrical reflected signal. This reflected signal is input to the preamplifier 5 by the circulator 2. The reflected signals amplified by the preamplifier 5 are input to receiving circuits 6-1 and 6-2, respectively.

[0027] In the receiving circuits 6-1 and 6-2, respective reflected signals inputted and amplified by amplifiers 23a and 23b are inputted to gate circuits 24a and 24b. Gate circuit 24a,
The reflected signal input to 24b has a waveform as shown in FIG. 3(a), for example. The reflected component reflected from the surface of the measuring object S appears first, and the reflected component reflected inside the measuring object S appears later in time and with a smaller signal intensity. Therefore, by applying a gate to the reflected signal using the gate signals a and b having the timings shown in FIGS. 3(b) and 3(c), the surface reflected wave and the internal reflected wave are extracted by the gate circuits 24a and 24b, respectively. For example, by applying the gate signal a to the gate circuit 24a and the gate signal b to the gate circuit 24b, the gate circuit 24a extracts the surface reflected wave component, and the gate circuit 24b extracts the internal reflected wave component. Actually, while monitoring the reflected signal and the gate signal with an oscilloscope (not shown), the gate timing is adjusted so that the gate is applied at the timing shown in FIG.

The surface reflected wave component and internal reflected wave component, which are extracted in this way and have different signal intensities, are passed through variable amplifiers 25a and 25b, each of which is set to an appropriate amplification factor.
As shown in FIGS. 3(d) and 3(f), the signal is amplified to a signal strength suitable for imaging. variable amplifier 2
The signals amplified by 5a and 25b are sent to the corresponding detection circuit 26.
a, 26b, respectively, and the peak value is detected, and then the reset switches 27a, 27b are immediately turned on, and the detection circuits 26a, 26b have completed peak detection.
is reset. The peak detection values detected by the detection circuits 26a and 26b are transmitted to the corresponding amplifiers 28a and 2, respectively.
8b. Then, the output terminals of each amplifier 28a, 28b are sequentially switched by the signal extraction means 8 controlled by the switching pulse generation circuit 33, and the peak detection values are shown in FIGS. 3(e) and 3(g). 3(h), and the amplifier 34
The image is input to the image display unit 35 via. Image display section 35
Now we will convert this signal value into an image. Here, the variable amplifier 25
A method for setting the amplification factors of a and 25b will be explained.

As described above, when the surface reflected wave component is extracted by one receiving circuit 6-1, the switching pulse generating circuit 33 is controlled and the receiving circuit 6-1 side is connected to the image display unit 35. . Next, the acoustic lens 4 and the object to be scanned S are relatively moved by a scanning mechanism (not shown) to scan, for example, in the X direction, and the detected signal value for one scan is monitored. Then, the amplification factor of the variable amplifier 25a of the receiving circuit 6-1 is adjusted by the gain control means 7 according to this detected signal value, and the signal strength of the reflected component extracted by the gate circuit 24a is the optimal signal strength for imaging. Set the amplification factor.

Further, the signal extraction means 8 is connected to the receiving circuit 6-2.
For the other receiving circuit 6-2, the optimum amplification factor for the internal reflection component is set by the same operation as above.

After scolding, the measurement object S is scanned in X and Y,
Two-dimensional or three-dimensional image data is sampled and input to the image display section 35. The image display section 35 accurately reproduces an image of the internal structure of the measurement object S from the image data most suitable for imaging obtained as described above.

As described above, according to this embodiment, the object to be measured S
Receiving circuits 6-1 and 6-2 are provided in parallel on the output side of the electro-acoustic converter that converts reflected waves from the Since the configuration is such that the signal strength of the reflected components to be extracted can be set to be optimal for imaging, multiple receiving circuits connected in parallel can collect information in the depth direction of the measurement object S in a single operation. Even when extracting, the peak detection value of each extracted reflection component can be optimized for imaging.
Optimal images without image deterioration can be obtained. As a result, image deterioration that causes erroneous evaluation can be prevented, and reliability can be improved.

[0033] In the above embodiment, a case has been described in which the amplification factor is adjusted, but the same effect can be obtained by adjusting the attenuation factor of the amplified signal. This modification will be explained with reference to FIG. 4. For example, the receiving circuit 6
-1,6-2 variable amplifier with constant amplification factor 41
Attenuators 42a and 42b with variable attenuation rates are connected to the output terminals of the amplifiers 41a and 41b in place of the amplifiers 41a and 41b, and the gain control means 7 controls the attenuation rates of the attenuators 42a and 42b. The configuration of other parts is the same as that of the above embodiment. According to such a modification, the gains of each of the receiving circuits 6-1 and 6-2 can be adjusted to optimal gains for imaging.

Furthermore, in the above embodiment, the receiving circuit 6-1
．． Although we have shown an example in which 6-2 is installed in two stages, this is the minimum number of stages that can extract multiple pieces of information in the depth direction of the object to be measured in one operation. Of course, the number can be increased.

[0035]

[Effects of the Invention] As detailed above, according to the present invention, a plurality of pieces of information connected in the depth direction of the measurement object can be extracted from a series of reflected signals obtained from the reflected waves of the measurement object in a single operation. In such a case, the gain of each receiving circuit can be set to the optimum value for imaging, and an ultrasonic microscope that can obtain an optimum image without image deterioration can be provided.

[Brief explanation of drawings]

FIG. 1 is a functional block diagram for explaining the principle of an ultrasound microscope according to an embodiment of the present invention.

FIG. 2 is a detailed functional block diagram of an ultrasound microscope according to one embodiment.

FIG. 3 is an explanatory diagram of the operation of the ultrasound microscope according to one embodiment.

FIG. 4 is a diagram showing main parts of an ultrasound microscope according to a modification of the embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Transmission signal generation means, 2... Circulator, 3... Electric-acoustic conversion element, 4... Acoustic lens, 6... Receiving circuit, 7...
Gain control means, 8... Signal extraction means, 9... Image display means.

Claims (1)

[Claims] 1. A high-frequency electric signal is converted into an ultrasonic wave by an electro-acoustic conversion element, the ultrasonic wave is made incident on an object to be measured as a convergent spherical wave by an acoustic lens, and the reflected wave from the object is converted into an ultrasonic wave. The ultrasonic wave is received by a lens and converted into an electrical reflected signal by the electro-acoustic conversion element, and from this reflected signal, a plurality of reflected wave components of the object to be measured are extracted to image the internal structure of the object to be measured. In the sonic microscope, different reflected wave components are extracted from the reflected signals that are connected in parallel to the output terminals of the acoustic-to-electrical transducer and each input from the electro-acoustic transducer, and It is characterized by comprising a plurality of receiving circuits each having a gain set individually, and gain control means for controlling the gain of each of the receiving circuits according to the signal strength of the reflected wave component to be extracted by each receiving circuit. ultrasound microscope.