JPS618687A - Image display method of scanning sonar - Google Patents

Abstract

PURPOSE:To prevent the influence of a fish school from being eliminated even in case of a change in the running direction of a shipe by shifting the readout position of a memory device in proportion to the change in the running direction. CONSTITUTION:A preset type up counter 11 is added between a scanning signal generating circuit 2 and a low-order address counter 6, which is started with the signal output p1 of the circuit 2 through the up counter 11. Further, a compass 12 and a converter 13 which converts an output proportional to the quantity of the azimuth change (angle) are provided. The readout position of the past signa of a memory device 8 is shifted forcibly to the generation position of a current signal in proportion to the change quantity of the azimuth detected by th compass 12, which making the on start position of an analog switch 5 which applied an input to a cathode-ray tube receive 3 coincident with the current position of a received signal. Consequently, an image is prevented securely from disappearing even when the ship changes its running direction.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a scanning sonar for detecting objects such as schools of fish.

(Prior art) In scanning sonar, a transducer attached to the bottom of a ship rotates and scans the transmitted and received signals, and the reflected signals from fish schools and the like obtained thereby are spiral-swept in synchronization with the above-mentioned circular scan. In addition to cathode ray tube display devices, for example, as shown in FIG. 1, reflected signals from a school of fish F are displayed as images. However, in this case, the image of the school of fish is often disturbed by the image of the noise signal n and becomes unclear. Therefore, it is being considered to apply a method of reducing the level of the noise signal by applying so-called surface correlation or surface averaging.

In this method, the time interval between the emission of one sound wave and the emission of the next sound wave is short compared to the movement of a school of fish or the movement of a ship, so within the time period of emitting several sound waves, the school of fish hardly moves. The reflected signals from the fish schools also occur at the same location. On the other hand, noise signals are generally generated randomly and do not occur at the same location.
In short, by correlating and averaging the current reflected signal and past total reflected signals from one or more cylinders, the aim is to eliminate noise signals and reduce their levels to obtain clear detection images. .

For example, when using the surface correlation method, the output signal p of the clock pulse generation circuit (1) as shown in FIG. As a synchronization signal, the scanning signal p generated by the scanning signal generating circuit (2) is as shown in FIG. A scanning signal p is applied to a cathode ray tube display device (3) which is spirally scanned from the center toward the outer periphery as shown in FIG.
Figure 3(b) from the transceiver (4) controlled by the
A reflected signal p2 (p is transmission number 4) shown in is applied via an analog switch (5). Note that (4a) is a transducer.

On the other hand, the clock signal p is controlled by the output signal p□ of the scanning signal generation circuit (2). An address is specified by the output p3 of the lower address counter (6) that counts the clock signal p, and writing is started, and the lower address counter (6) receives the clock signal p. A memory device having a storage capacity for one screen whose writing and reading are controlled by the output p5 of the upper address counter (7) which sends out a read signal p5 when counting a signal p4 which is sent out every time a certain number of are counted. (8),
In other words, divide 3601' into n parts and use them as lower addresses in the memory, and change the upper addresses for each spiral scan to make N upper addresses in one detection time T. A memory device (8) with a memory capacity of nXN is provided. The output shaped by the waveform shaping circuit (9) is sent to the memory device (8) by the transmitter/receiver (4).
) is added and stored, and when the next transmitted fish school reflection signal p2', that is, the current signal, is received, the memory contents (i.e., the contents of the previous screen) are read out and outputted. p7 and the current reflected signal p6 whose waveform has been shaped
' is added to the AND circuit αa, and its output p8 controls the analog switch (5). and memory device (8
) when the position of the signal one screen before and the signal currently being received match, the analog ball inch (5)
is turned on so that only the reflection signal pJ of the current school of fish is input to the cathode ray tube display device (3). That is, as described above, the detection signal of a school of fish is almost the same as that of one screen ago, but the noise is random and therefore not displayed, and blurring of the image due to the noise is prevented.

In the case of area averaging, for example, the received signal No. 4 weighted by an analog-to-digital converter is stored in the memory device (8), and this is averaged with the weighted current received signal. In other words, the level of signals that appear at almost the same location, such as a school of fish, does not change even when averaged, but since interference and noise from other ships are random, the level is compressed by taking the average.

(Problems with the prior art) However, these surface correlation and averaging methods have the following drawback: When a ship that has been traveling in a fixed direction and continues its detection work changes its traveling direction, the reflected signal of a school of fish may not be displayed as an image on the cathode ray tube display screen, which has the disadvantage that it is difficult to apply it to scanning sonar.

For example, when the ship S was traveling in the N direction in Figure 5(a), a school of fish F was detected in the same direction in front of the ship S, and to make the explanation easier to understand, the center line of the ship S and the transmitting and receiving waves. It is assumed that the scanning start points of the instruments are positioned so that they coincide.

So now, if you change the direction of travel by turning right in the direction of N, the reception direction of the transducer will also shift from point H to point H, but the position of the school of fish F will be the same as in the direction of N. It's in the same position and doesn't change. The direction in which the fruit is currently being received,
Since the directions of the signals read from the memory device (8) do not match even if the same school of fish is detected, the image of the school of fish disappears when the above-mentioned surface correlation is taken. That is, the scanning signal p□ of the transceiver (4) of the younger brother 2 is as shown in FIG. 6 (al
(t in the figure is the time required for one scan)
, when the ship S turns to the right by 45 degrees, the reflected signal p2 (current signal) of the school of fish is the reflected signal p2 (one screen before signal) appears at time t at point NW in FIG. 5(a) with respect to the scanning start point P as shown in FIG. 6(e).However, this point appears at point NW in FIG. ), the analog switch circuit (5) is not turned on, and the image of the school of fish F is not displayed on the cathode ray tube display (3).

The present invention provides a scanning sonar image display method that does not erase the image of a school of fish even when the ship's direction changes, and provides a scanning sonar image display method that eliminates noise and level compression using surface correlation and surface averaging. It is designed to be applicable to

[Structure of the invention]

(Means and effects for solving the problem) The present invention is characterized by using an output signal proportional to the amount of change in the compass direction that indicates the true direction of the ship to change the reading position of the memory device to the ship's direction. By changing it in proportion to the amount of change in the running direction, the current reflected signal matches the readout position of the reflected signal one screen before stored in the memory device, and the cathode ray tube display is always displayed when the analog switch is on. The point is that it can be added to the device to prevent missing images of fish schools when changing the direction of travel. FIG. 7 is a circuit diagram of an embodiment of the present invention (same symbols as those in FIG. 2 indicate equivalent parts). A preset up counter αυ is provided between the circuit (2) and the lower address counter (6), and the lower address counter (6) receives the output signal p□ of the scanning signal generation circuit (2) via the up counter aυ. Form to be started. In addition, output proportional to compass ti2 and the amount of change (angle) in its direction is output as a bit output (for example, 8
In this case, the up counter αυ is also 8 bits)
A circuit (13) is installed to convert the ship S into
When the vehicle is traveling in the N direction, the data output of the conversion circuit α is set to be 64 in the O and N directions, 128 in the S direction, and 192 in the W direction. The conversion circuit output data proportional to the change angle with reference to the N direction is set in a preset up counter αυ, and the lower address counter (6) is started from the end point.

With this arrangement, when the ship S is moving in the direction N in FIG. 5, the set value of the up counter αυ based on the data from the conversion circuit a3 is ◯. Therefore, by the lower address counter (6) started by this signal p,
The address of the memory device (8) becomes the ○ address in the N direction, and the same operation as described above with reference to FIG. 6 is performed.

However, for example, as shown in Figure 5(b), the ship is 45km from the N direction.
When the vehicle turns to the right, the number of data output cylinders of the conversion circuit θ■ becomes 32 according to the azimuth instruction of the compass 02, so 32 is loaded into the up counter αυ. Therefore, the lower up counter (6) is cleared (synchronized) by the signal p of the up counter 0υ, so
The address O of the memory device (8) is 32 from the N direction.
The position NW of the cathode ray tube display device shown in FIG. 5(a) (-45 direction with reference to the N direction) becomes the O address. As a result, the upper address counter (7
), the reflection signal p7 of the fish school read out from the memory device (8) moves from the position shown in FIG. 8(c) to the point shown in FIG. Figure 8(a)
Figure 8 (
It temporally coincides with the current fish school reflection signal p2 shown in d).

Therefore, the analog switch (5) is also turned on at this point, and the fish school reaction is displayed on the cathode ray tube display (3) at the NW position of ta+ in FIG.

(Effects of the Invention) As described above, in the present invention, the reading position of the past signal in the memory device is forcibly shifted to the current signal generation position in proportion to the amount of azimuth change detected by the compass. The start of turning on the analog switch that adds input to the signal matches the current position of receiver No. 4. Therefore, it is possible to reliably prevent the image from disappearing even if there is a change in the running direction of the ship.

Similarly, according to the present invention, even when the surface averaging method is adopted, the image of the school of fish on the cathode ray tube display becomes faint or a virtual image appears, making it difficult to identify the school of fish when the boat changes direction. can be prevented.

[Brief explanation of drawings]

Figure 1 is an image display diagram by scanning sonar, Figure 2
The figure is a noise cancellation circuit diagram using the surface correlation method in scanning sonar, and Figures 3 (a) and (b) are explanatory diagrams of scanning signals.
Fig. 4 is a spiral scanning diagram, Fig. 5 is an explanatory diagram of the running direction of the ship, Fig. 6 is a waveform diagram for explaining operation, Fig. 7 is a circuit diagram of an embodiment of the present invention, and Fig. 8 is an illustration of the ship's running direction. FIG. 3 is a waveform diagram illustrating operation. (1)...Clock signal generation circuit, (2)...
Scanning signal generation circuit, (3)...Cathode-ray tube display device, (4)...
Transmitter/receiver, (5)...analog switch, (6)...lower address counter, (7)...
Upper address counter, (8)...memory device,
(9)... Waveform shaping circuit, αG... AND circuit, αB... Preset type up counter, α2III
I...Compass, al...Circuit that converts compass output into bit output.

Claims (1)

[Claims] The past reflected signals stored in the memory device are read out in synchronization with the current reflected signals, and subjected to face-to-face and face-to-face averaging processing.
In a scanning sonar image display method for removing blurring of a displayed image caused by noise, the reading position of the memory device is determined in accordance with the amount of azimuth change from a compass that generates a ship's true azimuth signal when the ship's traveling direction changes. Correct the
A scanning sonar image display method characterized by preventing display image omissions and generation of virtual images.