JPS6053626B2 - Ultrasonic inspection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic inspection apparatus that uses ultrasonic pulses to observe the inside of an object, and more specifically to a medical ultrasonic inspection apparatus in which a variable delay circuit has a completely new configuration. This provides a more compact and high-performance ultrasonic inspection device.

Among ultrasonic inspection devices, fan-shaped scanning ultrasonic inspection devices are
The area of the ultrasonic transmitter is small, and the area to be examined can be widened by scanning ultrasonic waves in a fan shape, so this device is particularly effective for diagnosing the circulatory system, such as the heart and abdomen of the human body.

Conventionally, this sector scanning method has two types: mechanical scanning and electronic scanning.
There is a way. Although mechanical scanning devices have advantages such as simple construction and low cost, they also have the following disadvantages. 1. The transducer in the diagnostic section is movable and has a built-in driver, which causes vibration and noise.

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

On the other hand, an electronic scanning type device is an improved version of the mechanical scanning type device, and an example of its configuration is shown in FIG.

In the figure, 101 is a subject such as a human body, 102 is a transducer array consisting of a plurality of piezoelectric vibrators, and 10
3 is a transmission circuit for supplying high frequency pulses to the transducer array 102; 104 is a variable delay circuit; 105
106 is a receiving circuit, 106 is a display, and 107 is a control circuit for controlling each of the above-mentioned parts. The operation of this device will be explained based on FIG.

A plurality of high-frequency pulse signals generated by the transmitting circuit 103 are supplied to the transducer array 102 via a plurality of signal lines 108, and the ultrasonic signals 1 are transmitted into the subject.
It works to send 09. The plurality of pulse signals generated by the transmitting circuit 103 each have a certain delay relationship, and as a result, the high-frequency pulse signal is allowed to travel only in a certain 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 traveling direction of the ultrasonic pulse signal, and this value θ is related to the delay time and can be adjusted by controlling the delay time. angle 0 can be controlled. This principle is shown in detail in, for example, Japanese Patent Laid-Open 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 and subjected to addition. Thereafter, the received signal is subjected to appropriate signal processing by the receiving circuit 105 and 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 purpose is to change the directivity of the echo to match the directivity of the transmitted ultrasonic pulse signal to efficiently receive the signal.

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

The biggest problem with the ultrasonic inspection apparatus having such a configuration is the variable delay circuit 104.

That is, most of the variable delay circuits used in the present device are so-called low temperature delay circuits, which have an inductor and a capacitor as main components as delay elements, but such delay circuits are large in size.

2 Variable type with tap is expensive. can be,
It also has large losses and poor frequency characteristics.

A large number of 3-compensation amplifiers and the like are required.

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

5. There are many errors in the amount of delay.

6. Adjustment is difficult.

It had many problems such as.

The present invention eliminates the drawbacks seen in the above-mentioned conventional examples, and by creating a completely new configuration of the variable delay circuit and the signal addition section by utilizing the optical diffraction phenomenon caused by ultrasonic waves,
This provides an ultrasonic inspection device that can be made smaller and have higher performance.

An embodiment of the present invention will be described in detail below based on the drawings.
FIG. 2 shows the main parts of the configuration of an ultrasonic inspection apparatus according to the present invention in which the variable delay circuit and the adder are replaced by using the light diffraction phenomenon caused by ultrasonic waves, and FIG. 2A is an external view of the same. , FIG. 2B is a cross-sectional view taken along the line a-a'' of FIG.
After being modulated with high frequency, the signals from the ultrasonic waves are radiated back into the acoustic wave propagation medium 201 as ultrasound signals by the second transducer array 202 . The incident angle of the laser beam 204 is set to the flag angle at which the acousto-optic light diffraction effect of the acoustic wave propagation medium 2 no. 01 is maximized, and the incident light 204
4 is an ultrasonic train 203 radiated into the sound wave propagation medium 201;
and is separated into diffracted light 205 and undiffracted light 206.

The intensity 11 of the diffracted light is the intensity I of the incident light.

It is determined by the intensity Pa of the ultrasonic wave and is expressed by the following equation. Further, since the sound waves 203 from each transducer 202 are delayed, they are also delayed within the sound wave propagation medium 201. In other words, the difference in delay time between both ends of the transducer array is τ, and the sound velocity of the sound wave propagation medium is V1.
When the distance between both ends of the transducer array 202 is L, the sound wave train 203 in the sound wave propagation medium 201 is inclined in the direction shown by .

Therefore, as shown in FIG. 2A, the laser beam 204 emitted from the light source is shaped into a rectangle using a shaper, etc.
If the rotation angle of the rectangular laser beam 204 is controlled to match the inclination angle θ of the sound wave train 203 as shown in FIG. By converting this into an electrical signal using a suitable converter, a signal equivalent to the signal passed through a variable delay line and an adder in a conventional device can be obtained.

FIG. 3 shows an ultrasonic inspection apparatus according to an embodiment of the present invention using the configuration shown in FIG. The first transducer array 302 in contact with the specimen 301 results in an ultrasound train 310 and an arrow 309
fired in the direction. The manner in which the light is reflected within the subject 301 and received again by the first transducer array 302 is similar to that of a conventional electronic scanning device. The received signal is then sent through a receive amplifier bank 304 to an amplitude modulator bank 305 .

In this modulator array 305, a high frequency oscillator 31 is used as a carrier wave.
Signals from 8 are input and each is modulated by the received signal. This modulated signal is again amplified by a power amplifier bank 306 and applied to a second transducer array 307 mounted on an acoustic wave propagation medium 308 . As a sound wave propagation medium, for example, 0 Applied Physics J42 Volume 11
No., page 1055, Table 2 (b), acousto-optic elements such as tellurium dioxide crystals and glasses can be used. In particular, when using tellurium dioxide crystals, longitudinal waves propagating in the C-axis direction of the crystals can be used. The effect is great when you use it. Next, the sound wave train advances in the direction shown by the arrow 319, but as shown in FIG.
It is tilted by an angle 02 corresponding to a deflection angle θ1 of 10.

A laser beam is emitted from a light source 311 and sent to a beam expander 3.
12 expands the light beam into a light beam with a diameter of L or more.

The light beam shaper 313 is, for example, a rotary disk with a thin rectangular slit at the center thereof, the length of which is longer than L, and whose rotation angle is controlled by a control signal from the control device 320.
It is always set to match the sound wave inclination angle θ2. After this rectangular light beam 314 is diffracted by the sound wave train in the sound wave propagation medium 308 as described above, only the diffracted light is selected by a light separation device 315 such as a slit and sent to a photodetector 316. After being converted into an electrical signal, it is displayed on the display 321 via the receiving circuit 317. Here, the width of the rectangular light beam irradiated onto the sound wave propagation medium 308 is:
It is determined as a value that defines the radial resolution in sector scanning.

For example, if the width of the light beam is 1TnIn, the light beam transit time will be 0.24μSec when using the C-axis propagation sound wave of a tellurium dioxide crystal, which is equivalent to about 0.35Trn in the sound wave propagation distance in the human body, which is sufficient. It has a distance resolution. Next, as another embodiment of the present invention, a case where a surface acoustic wave element is used as the sound wave propagation medium will be described with reference to FIG. 4. For example, a Y plate of lithium niobate crystal is used as the surface wave propagation medium 401, and a comb-shaped electrode array 402 is provided on the surface of the crystal.

When a modulation signal from an amplifier 306 in FIG. 3 is applied to the comb-shaped electrodes, a surface wave train 403 travels on the crystal surface as an ultrasonic signal. When laser light 404 is irradiated onto this surface wave train at a flag angle, diffracted light 405 and undiffracted light 406 are generated, similar to an acousto-optic element. This diffracted light 405 may be detected, converted into an electrical signal, and displayed in the same manner as in FIG. 3. The present invention further improves the quality of the displayed image by changing the intensity of the diffracted light from each transducer element by making the slit shape of the light beam shaper 313 into a diamond shape or a convex lens shape instead of a rectangular shape. It is also possible to

This has the same effect as the conventional method of changing the excitation distribution of the transmitting transducer and using it for sidelobe suppression. Furthermore, when the delay time between each transducer row is not constant in order to converge the ultrasonic waves, the convergence effect can be exerted by making the shape of the laser beam arcuate. In this case, the receiving section 30 in FIG.
A correction delay circuit can also be inserted between the modulation section 305 and the amplification section 306. In addition, regarding the reception sensitivity and dynamic range of the entire device, the dynamic range of the acousto-optic element and surface acoustic wave element is sufficient at 70 to 80 dB.
In addition, when a photomultiplier tube is used as a photodetector, the dynamic range of an acousto-optic device or a surface acoustic wave device can be used with almost no reduction.

Similarly, the rotating part of the light beam shaping unit can be considered as a part that regulates the lifespan of the entire device, but unlike in conventional mechanical scanning devices, this part is built into the main device, and its dimensions are also limited. Since there is a margin, there is no particular life limit, and there is no need to increase the size of the diagnostic probe or generate noise.

Although the method using the diffracted light of the laser by the ultrasonic train has been described above, the undiffracted light shown in FIG. 2 or 4 can also be used instead of the diffracted light. This is because the undiffracted light is subjected to intensity modulation opposite to that of the diffracted light. As explained above, the present invention provides a completely new method of replacing the variable delay circuit and adder of conventional ultrasonic inspection equipment with a sound wave propagation medium having an optical diffraction phenomenon, such as an acousto-optic element or a surface acoustic wave element. It has many effects as shown below.

1. Acousto-optic elements and surface acoustic wave elements are small in size (less than a few dozen), and small and inexpensive He-N can be used as a laser light source.
If an e-laser or a semiconductor laser is used, a small, low-cost device can be obtained.

2 Compared to conventional mechanical scanning devices, it produces lower noise and has a longer lifespan.

3. Superior reception sensitivity and dynamic range compared to conventional equipment.

By using 42 light beams, UCG and tomographic images can be obtained simultaneously in cardiac diagnosis.

It can produce a convergence effect of 5 sound waves and improve resolution.

6. The basic principle of the present invention can also be applied to a linear electronic scanning ultrasonic inspection device, which enables high-speed scanning.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional fan-shaped electronic scanning ultrasonic inspection device, FIG. 2A is a perspective view showing the structure of an acousto-optic element used in the main part of the present invention, and FIG. , 3rd
FIG. 4 is a block diagram showing the overall configuration of an ultrasonic inspection apparatus according to an embodiment of the present invention, and FIG. 4 is a perspective view showing the structure of a surface acoustic wave element used in another embodiment of the present invention. 201...Sound wave propagation medium, 202...Transducer array, 203...Sound wave train, 204...Incoming light, 205...Diffracted light, 206...Non-diffracted light, 301
...Object, 302...Transducer array,
303... Transmission circuit, 304... Receiving amplifier array, 3
05... Modulator row, 306... Power amplifier row, 30
7... second transducer array, 308...
Sound wave propagation medium, 309... Sound wave traveling direction, 310...
- Acoustic wave front, 311... Loser light source, 312... Zehm expander, 313... Beam shaper, 314... Light beam, 315... Light separation device, 316... Photodetector, 317... ...Reception circuit, 318...High frequency oscillator,
319... Sound wave traveling direction, 320... Control circuit, 3
21... Display, 401... Surface acoustic wave element, 402... Beam-shaped electrode, 403... Surface wave array, 40
4... Incident light, 405... Diffracted light, 406... Non-diffracted light.

Claims (1)

[Claims] 1. A modulator array that amplitude-modulates a high-frequency signal using signals from a plurality of piezoelectric vibrators arranged in an array, a high-frequency signal generator that generates the high-frequency signal, and a high-frequency signal generator that generates the amplitude-modulated high-frequency signal. a plurality of transducers for supplying ultrasonic signals to the surface or inside of a sound wave propagation medium; means for irradiating a laser beam at a Bragg angle to the ultrasonic train propagating on the surface or inside of the sound wave propagation medium; means for rotating the laser beam in accordance with the wavefront formed by the ultrasonic train; and means for detecting at least one of diffracted light or non-diffracted light of the laser beam Bragg-diffracted by the ultrasound train, and generating an electrical signal. An ultrasonic inspection device characterized by comprising means for taking out the ultrasonic test device.