JPH0115830B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In a scanning sonar, the presence or absence of an object to be detected underwater is displayed on a display cathode ray tube.
This relates to a detection and display method that displays a planar image (PPI display) at a certain depth.

When a fishing boat discovers a school of fish using sonar and casts a net to capture this school of fish, the most important information it wants to know is the horizontal distance from its boat to the school of fish and the depth of the school of fish, as well as the elapsed time. This is an actual picture of the swimming state, showing how the spread and movement of the fish school changes over time.

The following technology has already been proposed as a method to meet this demand to a certain extent (Japanese Patent Application Laid-Open No. 1983-1999).
22980).

In other words, when displaying received echoes from a school of fish on a cathode ray tube, we use a so-called PPI display that shows the direction and horizontal distance of the school of fish in a two-dimensional manner.
Another idea is to take the sea surface as the X-axis and the depth as the Z-axis, and create a scale for each to show the horizontal distance to the school of fish and the depth of the school of fish, and set another scale as appropriate, such as above or below the PPI display surface. It also displays the trajectory of fish school behavior over time as a vertical cross-sectional view somewhat similar to a general fish finder, providing three-dimensional information as a whole. be.

FIG. 1 shows an example of the display portion. In the figure, the circular part indicated by 1 is the PPI display part, and the part indicated by 2 is the part that displays the vertical cross section. PPI display section 1
The 0 above indicates the bow direction, and the 3 indicates the fish shadow that appears on the PPI display when scanning at a certain depression angle.
θ indicates the horizontal azimuth of the fish shadow with respect to the bow direction, and the distance from the center of the PPI display to fish shadow 3 represents the horizontal distance from the own boat to the school of fish.

In the cross-section display section 2, a point S indicates the position of the own ship on the sea surface, and corresponds to the sea surface. This is now the X-axis. indicates the vertical axis from own ship. This is now the Z axis. The cathode ray tube beam of the cross section display section 2 is scanned radially like a line representing an angle φ with the point S as the center. Since the scanning speed is constant, the scanned length is proportional to time. Furthermore, the scanning angle is made to match the tilt angle of the transmitted and received waves. Therefore, if a school of fish is detected in the direction of θ when scanning at an angle of depression φ, a fish shadow 3 will appear on the PPI display section 1, a fish shadow 3' will appear on the cross-section display section 2, and so on.
In the figure, the length of the diagonal straight line connecting point S and fish shadow 3' indicates the actual distance from the own boat to the school of fish. The projection onto the X-axis indicates the horizontal distance, and the projection onto the Z-axis indicates the depth.

Once a school of fish has been detected in this way, it is important to know how the school of fish is moving and its swimming condition. For this reason, the swimming state is grasped by changing the angle of depression little by little every cycle of the waves transmitted from the transducer and observing the movements of the fish 3 and 3'. Also, by doing this, you can find out what kind of school a school of fish forms in the depth direction.

As described above, in order to know the swimming state of a school of fish whose bearing is in the θ direction, the display on the cross-section display section 2 is such that when the scanning beam of transmitted and received waves comes within a certain range of angles centered on the bearing θ, It is starting to be displayed.

By doing this, you will definitely get 3 fish shadows.
It can be said that the fish shadow in the cross-sectional representation of the school of fish shown by is 3'.

The above description has been made regarding the case where only one school of fish has been detected, but in reality, as shown in 4, 5, and 6, several schools of fish may be detected and captured at the same time. In such a case, the method described above requires as many cross-section display sections as the number of schools of fish whose swimming status is to be ascertained at the same time, and furthermore, if the angle of depression of the transmitted and received waves is changed for each of the cross-section display sections, It is necessary to track the image of

However, it is practically difficult to track the shadows of several schools of fish by changing the angle of depression in this way, considering the swimming speed of the schools of fish.

As described above, the conventional method has the disadvantage that when there are multiple schools of fish to be detected, the number of cross-section display sections must be increased, making it extremely difficult to perform operations to track the swimming of each school of fish. Ta.

In addition, when a school of fish distributed in a planar shape (for example, circularly) with a wider spread than the cross-sectional beam layer of the cone-shaped beam is detected in the middle layer under the water surface by applying an angle of depression, the image of the school of fish displayed on the PPI display unit 1 is detected. appears in an arc shape as shown in fish shadows 3, 4, 5, and 6. This means that the fish shadow indicated by 32 in the plan view of Fig. 1b and the cross-sectional view of Fig. 1c is
When irradiating with a sound wave having a cone-shaped transmission beam 33 having a cone-shaped transmission beam 33, only the hatched areas in FIGS. b and c are actually irradiated in the fish school 32. Therefore, as can be seen from Figure b, this can be called PPI
This is because the fish shadow when represented on the screen appears as a part of a donut-shaped circle 34 when the beam 33 is irradiated onto a plane at the depth of the school of fish. This has the disadvantage that the fish shadows shown on the PPI display look different from the actual spread of the school of fish.

An object of the present invention is to provide a scanning sonar detection and display method that allows the spread and swimming status of a plurality of schools of fish to be grasped moment by moment without such operational difficulties.

The present invention has the following configuration to achieve the above object. In other words, transmission from the transducer is performed with a wide beam width that includes all of the beam widths of all reception tilt angles φ ₁ to φ _o , and reception is performed for each reception tilt angle φ ₁ to _{φ o} . From the position information of the received signal passed through the reception system for each tilt angle φ ₁ to φ _o and obtained from the polar coordinate information of the azimuth θ, depression angle φ _n , and distance r, x=r _cps θ・cosφ _n y=r _sio θ・Calculate cosφ _n z=r _sio φ _n , and set x and y to the X axis and Y axis in the horizontal plane.
The data is converted into position data on three-dimensional orthogonal coordinates, with z being position data on the vertical Z-axis representing depth, and stored in a three-dimensional storage circuit.

When reading the data stored in the above manner, the depth is used as a parameter, and the received signal on the plane at each depth is projected as a PPI image on the cathode ray tube. There are various possible display methods, such as displaying a plurality of images for each depth simultaneously in parallel, or switching the display along with the depth display at regular intervals, but by applying the method described above, Since it is possible to observe flat images at each depth using depth as a parameter, even if there are multiple schools of fish within the search range, it is possible to easily understand the spread and swimming state of each school of fish.

Embodiments of the present invention will be described below based on the drawings. FIG. 2b is a diagram showing the state of transmitting and receiving beams in the transducer when the present invention is applied. As an example, the case where the receiving beam has four directions of depression angle (also referred to as tilt angle) is shown. It shows. That is, 7, 8, 9, and 10 indicate receiving beams with tilt angles of φ ₁ , φ ₂ , φ ₃ , and φ ₄ , respectively, and 1
1 is a transmitting beam, and receiving beams 7, 8,
The waves are transmitted with a wide beam width that encompasses all of 9 and 10.

For example, if the current receive beam width is about 10 degrees, the transmit beam width will be about 40 degrees, which is about four times that.

In this way, waves are transmitted with a wide beam angle, and waves are received with a plurality of narrow beams divided toward each tilt angle to receive echoes from each tilt direction.

Figure 2a shows, for reference, the PPI display in the conventional technology in which azimuth scanning is performed while transmitting and receiving waves at each tilt angle.
3' shows an image of fish schools 12 and 13 projected onto a horizontal plane.

FIG. 3 is a block diagram showing the configuration of an embodiment of the present invention. First, the time base generator 14 generates a timing signal that is the basis of the periodic operation of the scanning sonar. A scanning signal generator 15 generates an orientation signal θ based on the timing signal. The distance signal generator 16 generates a distance signal R based on the number of repetitions of this direction signal. Then, the distance signal generator 16 generates a certain signal every time the maximum detection distance set for the sonar is reached, and sends it to the transmitter 17.

On the other hand, the transmission tilt signal generator 24 also supplies a transmission tilt signal to the transmitter 17, which determines the tilt angle of the transmission beam, based on the signal from the tilt signal generator 23. The transmitter 17 transmits with a constant pulse width based on these two signals, and the transmitted signal is applied to the transducer 19 via the transmitter/receiver switching circuit 18 and has a determined beam width (see FIG. 2b). 11) and a determined tilt angle, the waves are transmitted into the water as sound waves.

As soon as the above-mentioned wave transmission ends, wave reception begins. That is, the reflected wave from the object within the range of the transmitted beam width is received by the transducer 19. The received signal converted into an electric signal by the transducer 19 is guided to the receiving system via the transmitter/receiver switch 18. This receiving system is, for example, b7, 8 in Fig. 2,
It has a receiving system for each receiving beam indicated by 9 and 10, and the reflected signal from the object within each beam is processed by the receiving system corresponding to that beam.

In other words, the received signals from all the transducers (for example, 432 transducers in the case of 36 transducers all around the azimuth stacked in 12 stages) that make up the transducer 19 pass through the transducer switch 18, and then the number of receiving beams is changed. All signals are sent to phase shift receivers 20, 20, 20, 20, which are provided in the same number as . On the other hand, a reception tilt signal is applied to each phase shift receiver 20 from a reception tilt signal generator 25 .
This received tilt signal is based on the signal from the tilt signal generator 23. Then, only the received signals from the tilt angle direction designated by the received tilt signal are phase-combined and amplified and appear at the output of each phase shift receiver 20. For example, in Fig. 3, the tilt angles of the received series are φ ₁ , φ ₂ , φ 3 , φ ₃ ,
A reflected signal from the direction of _φ4 will be received.
The signals thus obtained are applied to each series of scanning circuits 21, where the reception direction is scanned by the signal from the scanning signal generator 15. The output signal of the scanning circuit 21 for each tilt angle is converted into a digital signal by an analog-to-digital converter 22, and then sent to a storage circuit 27.

On the other hand, to the write address circuit 26, the scanning signal generator 15 sends an ever-changing azimuth scanning signal θ, the distance signal generator 16 sends a constantly changing distance information signal r, and the reception tilt The signal generator 25 adds tilt angle information φ ₁ , φ ₂ , φ ₃ , φ ₄ for each receiving beam. Here, the underwater position information represented by these three pieces of information is expressed as position information x on a three-dimensional rectangular coordinate consisting of the X axis representing the horizontal plane, the Y axis perpendicular coordinate, and the Z axis representing depth, Convert to y and z.

The position information (address data) on the rectangular coordinates thus obtained is supplied to the storage circuit 27 and indicates the address to be stored.

By doing so, the received signal from the analog-to-digital converter 22 is stored at the position (address) on the rectangular coordinates designated at the time of reception.

The received signal thus stored is read out as follows. First, from the time base generator 14, the read address circuit 28 and the raster scan circuit 30
Tohe sends a signal that is the basis of timing. The read address circuit 28 instructs the address of data to be read from the storage circuit 27 in accordance with the timing of the storage operation and in accordance with the two-dimensional address of the raster scanning circuit 30. In this readout, data of a plane at a constant depth is read out using the depth, that is, z, as a parameter. The data thus read out is converted into analog data by the digital-to-analog converter 29 and applied to the cathode ray tube display 31 as a brightness modulation signal of the cathode ray tube. On the other hand, since a raster scanning signal synchronized with the readout timing is applied to the cathode ray tube display from the raster scanning circuit 30, the situation on a plane at a certain depth is displayed on the cathode ray tube display 31.

Although one embodiment of the present invention has been described above, the following various examples are also conceivable.

First, regarding the transmission method, in the explanation of Fig. 3, the entire reception area (the corner that includes all of φ ₁ to _{φ 4} )
Although an example was given in which the signals are transmitted simultaneously, it is also possible to use a beam with a narrow beam width in the tilt direction and transmit at each tilt angle while changing the tilt angle to cover the entire area. This method has the advantage that, compared to the case where waves are transmitted to the entire area at the same time, the momentary transmission output can be made smaller by the amount of division, and cavitation can be avoided. In this case, a slight time lag occurs in the transmission of waves for each tilt angle, but the effect on distance accuracy is negligible and does not pose a problem.

Second, regarding the reception method, in the explanation of Fig. 3, a case where a reception system is provided for each reception tilt angle is shown, but the reception system and reception beam are set as one channel, and the reception system is set between φ ₁ and _{φ 4} for each transmission. may be sequentially searched and the received signals at each tilt angle may be sequentially written into the three-dimensional storage circuit described above, and then displayed by depth. Alternatively, instead of arranging the tilt angles φ ₁ to φ _o continuously, a method may be adopted in which they are divided as appropriate and transmitted and received, respectively, as shown in FIG.

Thirdly, regarding the display method, first, the images for each depth are sequentially switched and observed over time, and the second is the method for displaying the images for each depth in parallel as shown in Figure 5 (d ₁ to _d4 indicate depth), and further,
As shown in Fig. 6, there is a method in which the image of the next depth layer is sequentially rewritten from the center of the displayed image at regular intervals like a general scanning sonar;
As shown in the figure, a so-called scrolling display method may be used in which the planar image of the next depth layer is sequentially rewritten from bottom to top along the horizontal axis at regular intervals.

As explained above, if the present invention is applied to scanning sonar, it is possible to observe the in-plane situation at each depth below the sea surface simultaneously or sequentially over a certain period of time. Even if there are schools of fish at different depths at the same time, it is possible to easily understand the spread and swimming status of each school of fish. Since it is extracted as a flat image with depth as a parameter, the fish shadows do not have an arc shape as shown in Figure 1a, and the shape of the actual spread of the school of fish can be displayed as it is, which is a leap forward from the conventional method. This method has the advantage of being able to cast nets in a more rational manner and shorten operating time.

[Brief explanation of drawings]

FIG. 1a is a diagram showing an example of a conventional three-dimensional display system, FIGS. 1b and c are diagrams showing that a fish shadow appears in an arc shape, and FIG. FIG. 3 is a block diagram showing the configuration of one embodiment of the present invention.
Figure 4 shows the case where transmission and reception are performed by dividing the tilt angle appropriately, Figure 5 shows the parallel display of images for each depth, and Figure 6 shows the distance from the center of the displayed image to the next depth. A diagram showing the display method of rewriting the video,
FIG. 7 is a diagram showing a scroll display method for each depth. 1...PPI display section, 2...Vertical section display section,
3, 3', 4, 5, 6...fish shadow, 7, 8, 9, 1
0... Reception beam, 11... Transmission beam, 12,
13...School of fish, 12', 13'...Shadow of fish, 14...
time base generator, 15...scanning signal generator,
16... Distance signal generator, 17... Transmitter, 18
... Transmission/reception switching circuit, 19... Transducer/receiver, 20...
Phase shift receiver, 21...Scanning circuit, 22...Analog-to-digital converter, 23...Tilt signal generator,
24... Transmission tilt signal generator, 25... Reception tilt signal generator, 26... Write address circuit, 2
7... Memory circuit, 28... Read address circuit, 2
9...Digital analog converter, 30...Raster scanning circuit, 31...Cathode ray tube display, 32...
...School of fish, 33...Cone-shaped transmission beam, 34...
...The irradiation surface of a cone-shaped transmission beam of a flat plane with a constant depth.

Claims (1)

[Claims] 1 In scanning sonar, the search range is divided into multiple sections in the direction of depression angle, and the reflected signals for each of the divisions are received, while the write address circuit writes azimuth information, depression angle information, and direct distance information. Converting the underwater position information thus expressed into position information on three-dimensional rectangular coordinates including a vertical axis corresponding to depth, and expressing the received signal in the three-dimensional rectangular coordinates based on the position information. A readout address circuit reads a signal in an underwater plane with a constant depth from the memory circuit, and displays a planar image with depth as a parameter on a cathode ray tube display. A scanning sonar detection and display method that is characterized by: