JPS6222616B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic inspection apparatus for observing the inside of an object using ultrasonic pulses.

Hereinafter, first, among conventional examples of ultrasonic inspection apparatuses, those related to the present invention will be explained. The ultrasonic testing apparatus shown in FIG. 1 is a so-called fan-type electronic scanning ultrasonic testing apparatus, and is primarily used for diagnosing the circulatory system of the human body.

In the figure, 101 is a subject such as a human body, 102
is a transducer array, which is generally composed of a plurality of piezoelectric vibrators. 103 is a transmitting circuit for supplying high frequency pulses to the transducer array 102, 104 is a variable delay circuit, 105 is a receiving circuit, 106 is a display,
Reference numeral 107 is a control signal generation circuit for controlling each of the above-mentioned parts. The operation of this device will be explained based on FIG. The plurality of high frequency pulse signals generated by the transmitting circuit 103 are transmitted to the plurality of signal lines 10.
8 and is supplied to a transducer array 102, which serves to send an ultrasound signal 109 into the subject. The plurality of pulse signals generated by the transmitting circuit 103 each have a fixed time difference, and as a result, the ultrasonic pulse signal is allowed to travel only in a fixed direction determined by the delay time.

The angle θ shown in FIG. 1 is the angle between the normal to the transducer array surface and the direction of the ultrasonic pulse signal, and this value θ is related to the delay time and can be used to control the delay time. angle θ by
can be controlled. This situation is detailed in, for example, Japanese Unexamined Patent Publication No. 52-20058, so it will be omitted here. On the other hand, the ultrasonic echo signal 110 reflected from inside the subject 101 is converted into an electrical signal by the transducer array 102 again, and is supplied to the variable delay circuit 104 via a plurality of signal lines 108, where it is added. After receiving the signal, it is subjected to appropriate signal processing by the receiving circuit 105,
The image is displayed on the display 106 as an image such as a tomographic image of the subject.

The role of the variable delay circuit 104 in FIG. 1 is to pass a plurality of electrical signals obtained from the plurality of echo signals through a delay line whose delay amount changes by a predetermined value, so that the electrical signals are received in the subject. The aim is to change the directivity of the echo and to efficiently receive it in accordance with the directivity of the transmitted ultrasonic pulse signal.

Note that the transmitting circuit 103, the variable delay circuit 104,
The receiving circuit 105 and the display 106 are
All are controlled by control signals issued from the control signal generation circuit 107.

The biggest problem with the ultrasonic inspection apparatus in this conventional example is the variable delay circuit 104. In other words, the variable delay circuit used in this device has, as a delay element,
Most of the circuits were so-called LC delay circuits that consisted of an inductor and a capacitor as the main components, but such LC delay circuits were: 1. Large.

2. A variable type with a tap is expensive, has large losses, and has poor frequency characteristics.

3. Many compensation amplifiers etc. are required.

4. It is difficult to control the amount of delay.

5 There are many errors in the amount of delay.

6 Difficult to adjust.

It had many problems such as.

Next, a second conventional example will be explained based on FIG. 2. In the figure, 201 is a subject, and 202 is a movable transducer, which is coupled to a transducer driver 203. 204 is a transmitting circuit, 205 is a receiving circuit, 206 is a display,
207 is a control circuit. The operation of this device will be explained based on FIG. The high frequency pulse emitted from the transmitting circuit 204 is transmitted to the movable transducer 20.
2, where it is converted into an ultrasonic pulse 208 and travels through the subject 201 as shown. The movable transducer 202 is moved in an oscillating motion by the transducer driver 203, and the sector angle θ changes with time. Therefore, the emission direction of the ultrasonic pulse 208 changes as the sector angle θ changes, and the ultrasound pulse 208 scans the object 201 in a sector shape. On the other hand, the echo signal 209 reflected from inside the object 201 is sent to the movable transducer 20 again.
2, the signal is converted into an electric pulse, subjected to signal processing in a receiving circuit 205, and then supplied to a display 206, where it is displayed as a tomographic image.

This device can be made smaller and has a simpler configuration than the first device. Although it has features such as being inexpensive, it also has the following drawbacks. That is, 1. The transducer 202 is a movable type and causes vibration and noise together with the driver 203.

2. The life of the movable transducer 202 is extremely short.

The present invention eliminates the drawbacks seen in the conventional examples described above, and provides an ultrasonic inspection device that can be made smaller and lower in price by using a completely new configuration for the variable delay circuit. . An embodiment of the present invention will be described in detail below based on the drawings.

FIG. 3 shows an embodiment of the present invention.
In the figure, 301 is a subject, and 302 is the same transducer array as shown in FIG. 303 is a transmitting circuit, 304 is a receiving amplifier circuit, and 305 is a variable delay element, which is composed of a transducer array 306 and an acoustic propagation medium 307. 308 is a light source, typically a laser. Reference numeral 309 denotes a light deflection element, such as an electro-optic light deflection element, an acousto-optic light deflection element, or a mechanical light deflection element. 310 is a driver for an optical deflection element, 311 is an analyzer composed of a polarizing plate, etc., 312 is a photodetector, 313 is a receiving circuit, 314 is a display, and 315 is a control signal generation circuit.

The operation of this device will be explained below based on the figures.

A plurality of high-frequency pulse signals emitted from the transmitting circuit 303 are sent to a plurality of signal lines 316 with appropriate delay times, as in the conventional example shown in FIG. Ultrasonic signal 31 is transmitted into the object 301 by 302.
Send 7. This operation is completely similar to the conventional example.
Echo signal 318 reflected from inside the object 301
returns to the transducer array 302, is detected there, is amplified through the receiving amplification circuit 304, and is supplied to the variable delay element 305. Transducer array 30 in variable delay element 305
6 has the same elements as the transducer array 302, but it may have more or less elements. The effects of transducer array 306 are received at transducer array 302;
The echo signal 318 transmitted to the transducer array 306 via the signal line 316 and the reception amplification circuit 304 is emitted again into the acoustic propagation medium 307 as an ultrasonic signal 319 for optical diffraction. Typical examples of the acoustic propagation medium 307 are given in, for example, "Applied Physics" Vol. 42, No. 11, page 1055, Table 2(b), and the one with a large optical diffraction figure of merit that indicates the performance of the optical diffraction effect is desirable. In this example, H ₂ O (water), which has a relatively large optical diffraction figure of merit, will be used. Since the propagation speed of the optical diffraction ultrasonic signal 319 traveling through the acoustic propagation medium 307 made of water is the same as the propagation speed in the human body, the deflection angle θ ₂
coincides with the deflection angle θ ₁ in the subject. On the other hand, the light beam 320 emitted from the light source 308 is deflected by the optical deflection element 309 and
7 and interacts with the ultrasonic signal 319 for optical diffraction.

The interaction between the incident light 321 in the acoustic propagation medium 307 and the ultrasonic signal 319 for optical diffraction is the so-called
This is due to the optical diffraction effect of Raman-Nath,
Incident light 321 is generated by ultrasonic signal 319 for optical diffraction.
The traveling direction of a portion of the light is bent as diffracted light. Let the intensity of the incident light 321 be _IOO , and the first
If the next diffraction ray intensity is I ₁ , then the diffraction efficiency I ₁ /
The value of I _OO means that the ultrasonic signal 319 is the incident light 3
When traveling in a direction perpendicular to the traveling direction of 21, it is supported by I ₁ /I _OO = J ₁ ² (η√ _s ). Here, P _s is the power of the ultrasonic signal 319 for optical diffraction, η is a constant value that is related to the optical diffraction figure of merit shown above and is not related to P _s , and J ₁ is the first-order Betzel function. It is.

What should be emphasized here is the value of the above-mentioned equation (1) and the relationship between the diffraction efficiency and the traveling direction of the incident light 321. That is, the diffraction efficiency is maximum when the traveling direction of the incident light 321 and the traveling direction of the ultrasonic signal 319 are substantially perpendicular to each other, but when the traveling direction deviates from this, the diffraction efficiency rapidly decreases. That is, the intensity of the diffracted light beam exhibits sharp sensitivity in the direction in which the ultrasonic signal 319 travels. For example, in the case of a fan-shaped scanning ultrasonic inspection device, the deflection angle of the optical deflection element 309 is varied in accordance with the deflection angle θ ₁ , so that the traveling direction of the incident light 321 is always almost the same as the traveling direction of the ultrasound signal 319. Holding the light at right angles means that the variable delay element 305 provides the maximum intensity of the diffracted light. In other words, the variable delay element 305 has sharp directivity with maximum sensitivity at a deflection angle θ ₂ corresponding to the deflection angle θ ₁ .

In this way, by making light incident in a direction perpendicular to the direction of travel of the ultrasonic signal 319 and causing interaction, signals with a phase difference obtained from the transducer array 302 can be calculated using a variable delay line. The result is The sensitivity of the diffracted light to the deflection angle θ ₂ is expressed as the angle Δθ〓 corresponding to the half-width of the diffracted light intensity I ₁ , which is Δθ〓αλ/L λ: Light wavelength L: Width of the light ray α: smaller than 1 If a He-Ne laser with a width of 1 mm is used as a light source given by a constant, Δθ〓0.03゜. For example, if the maximum value of the deflection angle _{θ 1 is} set to 36゜, then θ ₁ max / Δθ〓 > 1000. Become. This means that the variable delay element 3 based on the present invention
05 has a practically sufficient resolution. The diffracted light is separated from the non-diffracted portion of the incident light beam and other unnecessary light beams by an analyzer 311, and is supplied to a photodetector 312. The analyzer 311 may be something like a slit through which only the traveling direction of the diffracted light can pass through, or depending on the type of acoustic propagation medium, an analyzer such as a polarizing plate that rotates the plane of polarization of the diffracted light by 90 rotations. Can be used. Further, the photodetector 312 may be one, or may be a combination of a plurality of detectors and switches. Detector 31
The output from 2 is subjected to signal processing by a receiving circuit 313 in the same manner as in a conventional ultrasonic inspection apparatus, and is displayed as an appropriate image on a display 314. Note that the display 314, the receiving circuit 313, the optical deflector driver 310, and the transmitting circuit 303 are all controlled by a control signal generating circuit 315. Note that another example of the medium 307 is TeO ₂ crystal. As detailed in the August 25, 1975 issue of Nikkei Electronics, pages 76 to 96, this crystal has an extremely high acousto-optic figure of merit, which indicates good optical diffraction efficiency. Because the speed of sound is slow, the medium can be made smaller. Another example of the medium 307 is a caleghenite optical glass. As detailed in the Nippon Telegraph and Telephone Public Corporation version of "Research and Practical Application Report," Vol. 21, No. 7, page 1371, this material has high light deflection efficiency and low sound speed, making it convenient as a medium. be.

Next, in the above embodiment, the signal line 31
A case has been described in which only the receiving amplifier 304 is provided between the transducer array 306 and the transducer array 306.

In other embodiments of the invention, a delay circuit is included as part of receive amplifier 304. FIG. 4 is a block diagram of the receiving amplifier and delay circuit in this embodiment. This part can be considered to be replaced with the reception amplifier 304 in FIG. In the figure, 401 is a receiving amplifier, one signal line 403 is connected to a transducer array (302 in FIG. 3), and the other signal line 404 is connected to a delay circuit 402. Delay circuit 40
The other signal line 405 of 2 is connected to the transducer array (306 in FIG. 3). By controlling the delay time of this delay circuit 402, the azimuth resolution during reception can be improved.

This situation is similar to the measures taken to improve the azimuthal resolution in the conventional example. For example, in FIG. 1 showing a first conventional example, by slightly shifting the delay times of a plurality of delay elements of a variable delay circuit 104,
Measures have been taken to improve the so-called azimuth resolution by changing the reception sensitivity of the echo signal 110 in the receiver to realize focusing during reception, and similar measures can be applied to the present invention. is possible. That is, by slightly shifting the mutual delay times of the delay circuits 402 in FIG. 4 in the same manner as in the conventional example, the echo signal (301 in FIG. 3) in the subject (301 in FIG. 3) is adjusted. It is possible to focus the reception sensitivity for 318) and improve the azimuth resolution.

As explained above, the present invention has a completely new configuration for the variable delay section of a conventional ultrasonic inspection apparatus, and has many effects as shown below.

(1) Small size, low cost, and easy to use.

(2) Receiving sensitivity and dynamic range are superior to conventional equipment, and there are fewer spurious signals.

(3) Since so-called optical probing is used, there is no disturbance caused by detection.

(4) The deflection angles θ ₁ and θ ₂ can be set freely.
In the figure, if two or more incident lights are used, two or more lines can be scanned at the same time. This makes it possible to simultaneously display UCG and tomographic images, for example, in cardiac diagnosis.

(5) If the optical deflector is made into a solid state, the device can be operated purely electronically.

(6) The basic principle of the present invention can also be applied to a linear electronic scanning ultrasonic inspection device, etc., whereby radio waves can be emitted in a diagonal direction during linear electronic scanning.

(7) Only the transducer array comes into contact with the subject, making it easy to operate.

[Brief explanation of the drawing]

1 and 2 are block diagrams showing the configuration of a conventional fan-shaped electronic scanning type ultrasonic inspection device, FIG. 3 is a block diagram of an ultrasonic inspection device according to an embodiment of the present invention, and FIG. FIG. 4 is a block diagram showing an improved example of the width-enhancing portion of FIG. 3; 301... Subject, 302... First transducer array, 303... Transmission circuit, 304...
... Receiving amplifier circuit, 305 ... Variable delay element, 3
06...Second transducer array, 307
...Acoustic propagation medium, 308...Light source, 309...
Optical deflection element, 310... Optical deflection element driver, 31
1...Analyzer, 312...Photodetector, 313...
Receiving circuit, 314... Display, 315...
Control signal generation circuit, 401... Reception amplifier, 40
2...Delay line.

Claims (1)

[Claims] 1. A first transducer array having a plurality of piezoelectric vibrators arranged in an array and transmitting and receiving ultrasonic waves; A transmitting circuit that excites by giving time,
a second transducer array that converts the electrical signal received by the first transducer array into an ultrasonic signal for optical diffraction; the first transducer array and the second transducer array; a compensation delay line provided as necessary on each signal line connecting the second transducer array, a sonic propagation medium for propagating the optical diffraction ultrasonic signal from the second transducer array, and a light source for emitting light; a means for deflecting the light from the light source so that it passes approximately at right angles to the propagation direction of the ultrasonic signal for optical diffraction; means for removing undiffracted components; a photodetector for converting an optical signal subjected to the Raman-Nath optical diffraction effect by the ultrasonic signal for optical diffraction into an electrical signal; and signal processing of the output from the photodetector. 1. An ultrasonic inspection apparatus, comprising: means for displaying the information after the measurement is performed. 2. The ultrasonic testing device according to claim 1, characterized in that water is used as the sound wave propagation medium. 3. The ultrasonic inspection device according to claim 1, characterized in that a TeO ₂ single crystal is used as the sound wave propagation medium. 4. The ultrasonic inspection device according to claim 1, which uses chalcogenite optical glass as a sound wave propagation medium.