JPH0130433B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an underwater detection and display device suitable for use in determining bottom sediments on the seabed.

The main purpose of underwater detection and display devices is to detect schools of fish and the seabed, but the bottom sediment of the seabed is equally important as it is an element of searching for schools of fish. In general, seabed reflected waves have an extremely high level compared to fish school signals, etc., and even when displayed on recording paper or a black and white cathode ray tube with a small dynamic range, they immediately become saturated, making it extremely difficult to judge the bottom quality. For this reason, it is conceivable to prevent the saturation by suppressing the gain in the entire received signal or in the vicinity of the depth where the seabed appears.

However, if the seabed signal is suppressed as a whole as described above, it becomes difficult to identify the fish school signal due to the decrease in the fish signal level. Suppression of the rising level of the signal makes it unclear whether the bottom layer of the seafloor surface layer is distinguished. This is especially clear when considering the presence of bottom-dwelling fish.

The present invention has been made in view of the above, and provides an underwater detection and display device that saturates the rising part of the seabed as it is, and immediately after that saturates the gain, which makes it possible to discriminate the bottom sediment. .

The description will be given below based on the drawings.

FIG. 1 is a circuit diagram showing an embodiment of the present invention.
In the figure, 1 is a transmission trigger generation circuit that sends out trigger pulses at a constant cycle (Figure 2a), and 2 is a transmission trigger generation circuit that sends ultrasonic pulses into the water based on the trigger pulses, and returns them from various targets. This is a transducer (Fig. 2a) that receives reflected waves. Reference numeral 3 denotes an amplification and detection circuit for amplifying and detecting the signal received by the transducer 2, and its amplification degree is controlled by an output signal from a DA conversion circuit 4, which will be described later. Reference numeral 5 denotes a slice circuit that extracts seafloor signals by determining a certain level by focusing on the level difference between, for example, the fish school signal (Fig. 2b, F ₁ , F ₂ ) and the seafloor reflected wave _B1 . A pulse-shaped pulse signal is sent out from the circuit 5 (FIG. 2C). Reference numeral 6 denotes a pulse generating circuit that sends out a relatively high-frequency pulse train e, which is guided to an AND circuit 7 together with the output pulse C from the slice circuit 5. That is, the pulse train e passes through the AND circuit 7 only during the high level period of the output pulse C. 8 is a counter that subtracts and counts, for example, the output pulse from the AND circuit 7, and the count value is the trigger pulse a.
It is reset to the initial value at the rising time (transmission time) of the pulse d of a predetermined width generated by the pulse generating circuit 9 based on the above. Further, the counting operation is stopped during the high level period of the pulse d. The high level period of the pulse d is normally set to several ms in order to prevent malfunctions caused by strong reflected signals in a short distance area, such as reflected waves R ₁ and signals F ₁ based on transmitted waves. The D-A conversion circuit 4 sends voltage (or current) signals V ₁ , V _{2 ,} etc. (FIG. 2 f) according to the output count value of the counter 8, and the amplification/detection circuit 3 performs amplification based on the signal level. degree is controlled. Regarding the relationship between the signal level and the amplification degree, it is assumed that, for example, when the signal level is high, the amplification degree is high.

Next, regarding the above circuit, the second
This will be explained with reference to the figures.

Immediately after transmission, the signal b received by the transducer 2 passes through the amplification and detection circuit 3, and is sent to a recorder, etc. (not shown).
and is also guided to the slice circuit 5.
As mentioned above, pulse d based on trigger pulse a
Since the counter 8 is set to the initial value and maintained at the initial value without performing a counting operation, the counter 8 continues to send out the initial value as is until the submarine pulse is received. Then, a voltage signal of _V1 level corresponding to this initial value is sent out from the DA conversion circuit 4, whereby the received signal is amplified at a high amplification degree.

When the submarine signal B ₁ is received, the slice circuit 5
sends out a pulse C ₁ (however, the falling time t ₁ of the pulse C ₁ will be described later), and the count value of the counter 8 is sequentially subtracted from the initial value based on the pulse train e from the low level state of the pulse d. Ru. And D
-A conversion circuit 4 gradually lowers the voltage signal level from _V1 and sequentially decreases the corresponding amplification degree. Therefore, the received signal B ₁ is subject to the above-mentioned amplification limit, and the signal level is rapidly suppressed by the amplification which gradually decreases in proportion to time from the reception time t ₀ (Fig. 2 g), and reaches the signal level at the time t ₁ . becomes below the slice level. Therefore, the output pulse _C1 from the slice circuit 5 falls to a low level, and at the same time the counting operation of the counter 8 also stops. Therefore, since the amplification/detection circuit 3 amplifies the submarine signal while maintaining a low amplification degree corresponding to the voltage signal level V ₂ at time t ₁ , the submarine signal changes below the slice level as shown by the waveform G ₁ . As a result, as a record of submarine signals, first t ₀
A dark line with a width corresponding to the period from t ₁ appears,
Immediately after that, a signal waveform containing sediment information appears in dark and light colors.

As described above, according to the present invention, it is possible to display the bottom sediment status at the same time while making use of conventional features such as clarifying the point at which the seabed rises.

In this embodiment, the amplification degree control is performed by the amplification detection circuit 3.
However, after the received signal is amplified and detected in the first stage, the amplification level of the amplified and detected signal may be controlled in the next stage amplifier circuit.

Furthermore, although it is not an essential requirement of the present invention, since the pulse d exists for only a few milliseconds in the pulse generation circuit 9, which is provided from the viewpoint of operational stability, the slice level v will change between then and when the submarine signal is generated.
For example, when a strong signal is generated, the same amplification control as described above is performed for that signal as well. However, due to the short width of such signals, the seafloor waveform
It has little effect on the formation of _G1 .

Furthermore, although the voltage output of the DA converter circuit 4 appears in a stepwise manner, the change can be made smooth by, for example, energizing a smoothing circuit.

Finally, in the present invention, the basic amplification control signal is formed by a pulse and a counter, but the pulse generation circuit 6 is used as a constant current source, and the counter 8 and D-
By combining the A converters into an integrating circuit and replacing the AND circuit 7 with a gate, it is also possible to form an amplification control signal whose integration is controlled by the slice output C.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention. FIG. 2 is a waveform diagram for explaining the operation of the circuit diagram.

Claims (1)

[Claims] 1. An underwater detection display device that transmits ultrasonic pulses underwater, receives the return reflected waves from a target object, amplifies and detects them, and then displays them on a display device, which an amplifier circuit that is amplified by the amplification degree; a submarine signal extraction circuit that extracts only a submarine signal from the output signal of the amplifier circuit by using the level difference between each received signal; and an extraction output of the submarine signal extraction circuit that is transmitted. While the extraction output is being transmitted, the amplification degree of the amplifier is suppressed over time, and after the extraction output is stopped, the amplification degree is suppressed so that the amplification degree at the time of stopping is maintained for a specific period of time. An underwater detection display device comprising an amplification control circuit for controlling.