JPH0581872B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a device for detecting buried abnormal objects such as mines and bombs buried on the seabed surface or under the seafloor, and in particular uses monopulse ultrasonic waves and a concave surface arrangement cross-array transmission/reception method. The transducer is mechanically scanned two-dimensionally to acquire reflection data, and the receiving system is equipped with an image processing circuit to improve image fidelity. The present invention relates to a device that can display a two-dimensional image and accurately explore the shape of an object.

Currently, there are areas where sea mines remain in the coastal waters of Japan, and it is estimated that a large number of mines still remain in these areas.

When carrying out underwater civil engineering works in these sea areas,
To ensure construction safety, a mine search will be conducted to confirm that no mines exist before construction begins. Traditionally, magnetic surveying has been used as a method of searching for mines buried under the seabed, but although this method can determine the presence or absence of submarine magnetic abnormalities, it cannot determine whether they are mines or other metal objects. , submerged explorations are being carried out by divers, and further confirmation is being carried out through magnetic testing. However, the strength of the magnetic field caused by mines varies greatly in relation to the earth's magnetism. Underwater exploration is conducted to detect even the smallest magnetic response as a potential mine. As a result, the time and costs required for these works have become enormous, and this has had the effect of delaying the construction work. As ports become deeper, the content and amount of work performed by divers will be severely restricted, and the current exploration methods will not be able to ensure sufficient safety, and will also become inefficient and uneconomical. Therefore, there is a need to develop and put into practical use devices that can automate and abbreviate remote exploration from the sea as an alternative to underwater exploration.

The present invention was invented in order to meet the strong demands of such port and marine construction workers.

FIG. 1 shows an example of an electric circuit diagram showing the configuration of the present invention, in which 1 indicates an electromagnetic induction transmitter array 2.
The transmitter array 2 is an electroacoustic transducer that has the function of converting this monopulse driving current into monopulse ultrasonic waves. Reference numeral 3 denotes a receiver array that converts monopulse ultrasonic waves from the transmitter array 2 reflected from objects on the seabed and returned to electrical signals. Since the output of the receiver array 3 is a weak electrical signal, it is amplified by the high frequency amplifier 4 and sent to the detector 5.
After detection, STC (Sensitivity Time
(Control) circuit 6 to compensate for diffusion attenuation due to increase in ultrasonic transmission distance. The signal passing through the STC circuit 6 is logarithmically compressed by the logarithmic amplifier 7.
Furthermore, the STC circuit 8 compensates for attenuation loss of ultrasonic waves in seabed sediment. The analog signals processed by the above amplifiers 4 to STC circuits 8 are converted into digital signals by an A/D converter 9 and stored in a digital memory (RAM) 10.

On the other hand, 11 is a position detector, which is a horizontal position detector.
The XY address and the Z address of the depth direction position are detected and inputted to the control device 12 to control the output data of the A/D converter 9 to be written to the corresponding address on the memory 10. Further, 13 is a reference plane level set to an arbitrary value, and the dividing circuit 14
By dividing the data read from the memory 10 by the reference surface level 13, level changes are emphasized and the level of the object is made noticeable. The data resulting from this division is stored in the digital memory 15, and the read data is compared with a predetermined level by a comparator circuit 16, and quantized as 1-bit data by comparison with the level. This clarifies the boundary line of the image of the object. The data quantized by the comparator 16 is stored in the digital memory 17, and the read data is added to the data of 27 addresses above, below, to the left, to the right, and to the left and right of the measurement address by the integrating circuit 18, and the data is added to the data located near the object. Removes isolated noise components such as pebbles. The data subjected to quantum averaging processing by the integration circuit 18 is stored in the digital memory 1.
9, each memory 10, 15, 17, 19
The data stored in the image processing display device can be arbitrarily switched by the switch 20.
The data is read out to the CRT device 21. The CRT device 21 displays X-Y, X-Z, and Y-Z tomographic images of the object in color.

Fig. 2 is a diagram comparing the monopulse ultrasonic waves generated from the high-voltage power supply 1 in Fig. 1 with conventional tone burst ultrasonic waves. This is the oscilloscope waveform. In figure a, Ta is the pulse width 22, which is a single waveform, that is, a pulse width of only one wavelength. On the other hand, in figure b, the pulse width Tb23 is due to the relationship of driving the vibrator.
Ten wavelengths or more are required, and the pulse width Tb23 is ten times or more compared to the monopulse pulse width Ta22. Therefore, the monopulse method shown in Fig. a can have a shorter pulse width than the conventional ultrasonic emission method shown in Fig. b, and the vertical resolution ability can be improved.

FIG. 3 shows a structural diagram of the transducer arrays 2 and 3 shown in FIG. There is. A plurality of receivers 3a are also attached to the fixed plate 24 in a row to form a receiver array 3. As shown in the figure, the transmitter array 2 and the receiver array 3 are arranged in a cross shape so as to be perpendicular to each other, and are transmitted so that their ultrasonic beams are focused on the object. The wave device 2a and the wave receiver 3a are attached to the fixed plate 24 so that the heights of the wave device 2a and the wave receiver 3a are respectively concave.

FIG. 4 is a diagram illustrating exploration and image display according to the present invention, in which the ultrasound beams 25 from the transducer arrays 2 and 3 are focused on an object 26 in FIG. The transducer arrays 2 and 3 can mechanically scan the XY horizontal plane so that the object 26 can be searched two-dimensionally. That is, for the transducer arrays 2 and 3, for example, the ultrasonic beam is swept in the positive and negative directions in the X direction, and the arrays 2 and 3 are mechanically moved in the positive and negative directions in the Y direction. Then, the reflection data from the object 26 in the Z direction is processed. To further explain FIG. 4 d, for example, when an ultrasonic beam is sent out from the array directly above the object 26 and the reflected wave is received, the image d of the XZ plane at that position is the data to be displayed, that is, the XZ One image of the surface is obtained. Therefore, the image on the XZ plane is a rectangle whose width is the width of the object and whose height is narrow in the direction in front of the object 26. As it approaches the center of the object, the vertical width gradually increases and becomes the largest at the center of the object. After that, it gradually becomes narrower. Note that 27 is the searchable depth, 28 is the XY plane, 29 is the XZ plane, and 30 is the YZ plane. Also, figures b, c, d, and e are of figure 1.
The method of displaying an image on the CRT device 21 is shown in Figure b, which shows a YZ tomographic image obtained by cutting the YZ plane in the X-axis direction.
Display. Figure c is the XY plane cut in the Z-axis direction.
Shows XY tomographic image, arbitrary XY image 3 on Z axis
Display 2. Figure d shows an XZ tomographic image obtained by cutting the XZ plane in the Y-axis direction.
Display image 33. Figure e is an XYZ three-dimensional image 3 that can be obtained by performing image processing on each of the two-dimensional three-directional tomographic image data b, c, and d.
3', but this is not the object of the present invention. Therefore, three-directional tomographic images at arbitrary positions of the object can be displayed using the CRT device from figures b, c, and d. Next, the laboratory experiments conducted so far have demonstrated that the device of the present invention is more effective than conventional devices for searching for abnormal objects buried in the seabed, and an overview thereof will be given below. The experimental equipment used was 100mm in diameter.
Six electromagnetic induction type transmitters were used as receivers, and 16 disk transducers with a diameter of 40 mm were installed in a cross shape, so that the ultrasonic beam was focused in a concave shape at a position of 2.5 m. It has been placed. As a result of preliminary experiments, the transmitted sound pressure was 90 db-m-1500 V, the pulse width was 40 μs, the dominant frequency was 25 kHz, the directivity of the ultrasound beam was approximately 3 degrees, and the underwater resolution width was 25 cm at a focal length of 2.5 m. As image processing, data with level changes emphasized is stored in the memory 15, data with clarified boundaries is stored in the memory 17, data with noise removed is stored in the memory 19, and further data processing is performed. Since raw data that cannot be displayed is stored in the memory 10, it is only necessary to select and retrieve data that can be clearly displayed from each memory. and
The image display by the CRT device 21 has, for example, 30 pixels.
Each element has a resolution of 5 cm with 30 x 30 pieces.
Using this device, a drum can (600φ x 900mm) was suspended underwater as a simulated mine in an experimental water tank, and a transducer was installed so that the object was at a focal length of 2.5m, and an exploration experiment was conducted. The experiment was conducted with the object horizontal, tilted at 7 degrees, 20 degrees, and 35 degrees.
Three-way tomographic images of the YZ plane were obtained. the result,
It was found that the three-directional tomographic image almost visualized the shape of the actual object. What is particularly remarkable is that even objects tilted at an angle of 10 degrees or more, which cannot be detected using conventional technology, are faithfully imaged. Also,
It is possible to observe images viewed from the YZ direction as well as XY, XZ, which is something that cannot be seen with conventional sonic exploration, and can be said to be a groundbreaking result.

Furthermore, as a simulation experiment of searching for mines buried under the seabed, sand was placed under the water tank and a drum was buried 25 cm from the sand surface. As a result, we were able to obtain three-directional tomographic images through image processing, despite exploration in sand with a large ultrasonic attenuation constant. In addition, with conventional technology, objects buried up to 50 cm below the seafloor are
When using ultrasonic waves with a pulsed waveform like the one shown in Figure 1, the reflected images from the seabed and the sunken objects overlapped, making it impossible to clearly detect images of only the sunken objects. According to the present invention, as a result of experiments, 25 cm below the seafloor
It was found that objects buried in the ground can be clearly detected.

As a result of the above experiments, it was found that inclined objects and objects buried shallowly on the seabed can be accurately detected.
The device of the present invention has unprecedented performance, such as being able to contribute to improving the efficiency of exploration work for abnormal objects buried on the seabed, and has been proven to be a device with great practical effects.

Fig. 5 is a diagram showing an embodiment in which the device of the present invention is used to search for abnormal objects buried under the seabed, such as mines and artillery bombs; This shows a case in which a ship is equipped with a device and performs sonic exploration while cruising. Figure b shows the case where the water is deep and the transducer cannot be suspended on the bottom of the ship.
This figure shows a case in which a transducer is installed on a pedestal, and the pedestal is lowered onto the ocean floor for exploration.

In Figure a, transducer arrays 2 and 3 are attached to the deck of the exploration vessel 34. The ultrasonic beam 36 emitted from the transmitter array 2 is reflected by an abnormal object 38 buried in the seabed 37, and the receiver array 3 receives this reflected beam and displays it on a CRT using the main body 35. Conduct exploration. In Figure b, the pedestal 40 is installed on the seabed 37 so as to be located above the abnormal object 38. The transducer arrays 2 and 3 are attached to the pedestal 40 so as to be movable in the X and Y directions, and are connected to the main body 35 by a cable 39 for transmitting signals and power source for the driving device. .

The image displayed on the CRT device 21 according to the present invention is a three-directional tomographic image, but if viewed with a device that displays three screens simultaneously, it can be judged as a three-dimensional stereoscopic image. Alternatively, if a personal computer is used to perform image processing using software, it is possible to display a three-dimensional stereoscopic image.

As explained above, if the device of the present invention is used in conjunction with conventional magnetic surveying methods, it is possible to accurately identify the shape of submerged abnormal objects such as mines and artillery bombs in three directions, which was impossible with magnetic surveying. can be displayed in the image,
Confirmation exploration by divers is no longer necessary, which improves the efficiency of exploration work and is advantageous in terms of safety measures. This is because the ultrasonic wave of the present invention is of a monopulse type, and the ultrasonic transducer array is of a concave type and orthogonal type, so that the received wave image can be processed with high resolution. This device is used not only to search for abnormal objects buried on the seabed such as mines and gun bombs, but also to search for shipwrecks, sunken trees, and other sunken objects, as well as the shapes of objects buried in earth and sand during underwater civil engineering works in rivers, lakes, and other areas. It can be used as a management system.

[Brief explanation of drawings]

The drawings show embodiments of the present invention; FIG. 1 is an electric circuit diagram of the present invention, FIG. 2 is a diagram comparing the characteristics of monopulse ultrasound according to the present invention with conventional tone burst ultrasound, and FIG. is a structural diagram of a transducer array according to the present invention, Fig. 4 is a diagram showing sonic exploration and image display method using the device of the present invention, and Fig. 5 is a diagram showing an abnormal object buried under the seabed using the device of the present invention. This shows an example of how to do this. 1... High voltage power supply device, 2... Transmitter array, 3
... Receiver array, 4 ... Amplifier, 5 ... Detector, 6, 8 ... STC circuit, 7 ... Logarithmic amplifier,
9...A/D converter, 10, 15, 17, 19...
...Digital memory, 11...Position detector, 12
...Control device, 13...Reference plane level, 14...
Division circuit, 16... Comparison circuit, 18... Integration circuit, 20... Switch, 21... CRT device, 22
...Pulse width Ta, 23...Pulse width Tb, 24...
... Fixed plate, 25 ... Ultrasonic beam, 26 ... Target object, 27 ... Searchable depth, 28 ... XY plane, 2
9...XZ plane, 30...YZ plane, 31...YZ image,
32...XY image, 33...XZ image, 33'...
XYZ image, 34...Exploration ship, 35...Main body, 3
6... Ultrasonic beam, 37... Seabed, 38... Submerged abnormal object on the seabed, 39... Cable, 40... Mount.

Claims (1)

[Claims] 1. A transmitter array in which a plurality of electromagnetic induction transmitter groups are arranged in a concave shape to transmit monopulse ultrasonic waves with a short pulse width, and a transmitter array that receives ultrasonic waves from the transmitter group. a receiver array in which a plurality of receivers for converting into wave electric signals are arranged in a concave shape and orthogonal to the transmitter array; a reflection data output means for scanning a two-dimensional plane, transmitting monopulse ultrasonic waves from a transmitter array to a target object, receiving the reflected waves at a receiver array to obtain reflection data; and using the reflection data as a reference. A device that emphasizes reflection data by dividing by the surface level to emphasize level changes so that the level of the object becomes noticeable;
A device that enhances the outline of the object by comparing the reflection data with a predetermined level using a comparison circuit and quantizing it as 1-bit data, and quantum averaging processing of the reflection data using an integration circuit. a reflection data processing means including a device for removing noise components by removing noise components; a plurality of storage means for storing data of the reflection data output means and the reflection data processing means; and a switch for converting two-dimensional data from each storage means. Object display means for arbitrarily switching the reflection data processing output according to the method, inputting it to a CRT device which is an image processing display device, and displaying a two-dimensional tomographic image of the object on the CRT device. An ultrasonic underwater abnormality detection device.