JP2553480B2 - Single fish discrimination circuit for fish finder - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a fish finder,
The present invention relates to a discrimination circuit for discriminating a reflection signal or noise from a school of fish or the sea bottom and a reflection signal from one fish (single fish).

[0002]

2. Description of the Related Art In utilizing fishery resources, it is extremely important to measure fish bodies in order to control the distribution of fish schools, manage resources, and improve fishing efficiency. Measurement of fish bodies has been conventionally performed using a fish finder for measurement. First, the principle of the conventional weighing fish finder will be described. The acoustic properties of fish species are well studied. The intensity of the sound waves transmitted by the transducers reflected by the fish body varies somewhat depending on the fish species, but generally large fish return a large reflected intensity signal and small fish return a small reflected intensity signal. Similarly, a signal with a large reflection intensity comes from a school of fish with a high density, and a signal with a low reflection intensity comes from a school of fish with a high density.

On the other hand, the intensity of the returning reflected wave is large at a point close to a fish body or a school of fish, and small at a point far from it.
Therefore, when measuring the amount of fish or school of fish, make sure that the intensity of the reflected waves returning from the fish or school of fish depends only on the size of the fish or the density of the school of fish, regardless of the distance from the transducer to the fish or school of fish. If corrected, the fish body or school of fish can be measured.

Therefore, as described above, in order to obtain a signal which does not depend on the water depth or distance and changes only depending on the size of the fish or the density of the school of fish, the receiver gain is changed with a predetermined characteristic depending on the propagation time. A reception amplifier with TVG (Time Varied Gain) capable of time correction or distance correction is used. That is, if the receiving amplifier with TVG is used, it is possible to obtain information based only on the density of the fish or the school of fish, regardless of the distance. The conventional fish finder for measurement uses the above principle, and is performed by the system shown in the block diagram of the conventional fish finder for measurement of FIG.

In FIG. 3, reference numeral 1 is a transmission unit for generating a transmission signal. Reference numeral 2 denotes a wave transmitter / receiver that converts a transmission signal received from the transmission unit into a sound wave, transmits the sound wave to a predetermined sea area, receives a reflected wave that is reflected and returned, and converts the reflected wave into an electric signal. Reference numeral 3 denotes a TVG-equipped receiving and amplifying unit for a single fish whose amplification factor is controlled by the propagation time. Reference numeral 4 denotes a TVG-equipped receiving / amplifying unit for a fish school whose amplification factor is controlled by the propagation time. Reference numeral 5'denotes a transmission controller for controlling the pulse width of transmission. Transmission controller 5 '
The transmission unit 1 generates a transmission signal in response to the transmission pulse signal from and transmits the transmission signal to the transceiver 2.

When the fish is to be weighed, the transmitter 1 generates a transmission signal during the pulse width generated by the transmission controller 5'and inputs the transmission signal into the transducer 2. The transmitter / receiver 2 receives the transmission signal from the transmission unit 1, transmits a sound wave to the survey area, receives the returned reflected wave, converts it into an electric signal, and converts the electric signal into the TVG-equipped reception amplification unit 3 and Tell 4 The TVG-equipped receiving / amplifying unit 3 performs TVG amplification for correcting the distance attenuation of the return signal due to the sound wave reflection of a single fish, and the amplifying unit 4 corrects the distance attenuation of the return signal for the school of fish.
Performed G amplification and knew the reflection intensity of the fish body from the voltage value of the output level of the TVG-equipped reception / amplification unit 3 for the fish body, or displayed it on a color CRT that converts the voltage to a color or a recorder that converts the voltage to shades. I knew the reflection intensity of the fish.

[0007]

However, in the conventional fish finder for weighing as described above, the output signal of the TVG-equipped receiving / amplifying unit 3 is not limited to the reflection signal from one fish body, but a plurality of signals. The echoes are combined because the fish are close to each other, and the signal as the fish school echo, the echo of the seabed,
Furthermore, it includes noise that is not an echo. For this reason, conventionally, in order to identify only the single echoes from one fish body from among them, the echoes are recorded by displaying them on a recorder or a CRT screen, and the shape of the image is judged and identified.

FIG. 4 shows the situation. Figure (a) shows a situation where a fish finder catches a single fish, figure (b) shows a situation where a fish school is caught, and figure (c) shows an image that appears on the display, and 12 indicates A single fish echo is shown, and 13 is a fish school echo. Reference numeral 14 shows an interference image from another fish finder. However, such a judgment with images requires experience, and it takes time to make a judgment based on echo recording or the continuity of images, and also has a drawback that a display device is necessary. .

In order to solve the above-mentioned problems of the prior art, the object of the present invention is to be limited to the echo from a single fish when the pulse width of the transmission and the pulse width of the reflected wave are substantially equal. Focusing on (1), it is to provide a single fish discrimination circuit for discriminating fish echoes, seabed echoes, other interferences and noises from single fish echoes.

[0010]

The present invention has the following means for achieving the above object. That is, in the single fish discrimination circuit of the fish finder of the present invention, the pulse width τ
A transmission control unit for transmitting the ultrasonic transmission pulse of _{1 and} the ultrasonic transmission pulse of pulse width τ _{2 at} a constant transmission repetition period, alternately or in another predetermined order; A waveform shaping circuit that shapes a rectangular wave; the transmission pulse width is τ ₁
A first storage circuit for storing the waveform-shaped signal of the received signal at the time; and a second storage circuit for storing the waveform-shaped signal of the received signal when the transmission pulse width is τ _2. stored in the circuit signal and of the second storage circuit stores the signal read out a leading edge time position corresponding square wave between the second
Is it the first memory circuit for the time width of the signal from the memory circuit?
The ratio of the time widths of these signals is calculated, and the ratio is (τ ₁ / τ
₂ ) ± It is within the allowable range by comparing whether it is within the allowable range
Only when the received signal is a judgment circuit for outputting a judgment signal for judging that the received signal is from a single fish, it is characterized by being provided.

[0011]

The operation of the fish finder single fish discriminating circuit having the above means will be described below. In fish finder, ultrasonic waves with a predetermined pulse width are periodically transmitted into water from a transducer.
Now, let this transmission pulse width be τ. When the reflector has no depth, that is, thickness in the traveling direction of the ultrasonic wave, the pulse width of the received pulse reflected and returned is also τ. Now 1
If the depth of one fish is 1, the pulse width τ _R of the reflected received pulse is

[0012]

[Formula 1] τ _R = τ + (2l / C) where C is the speed of sound of ultrasonic waves in water

[0013] And usually (2l / C) << τ

[0014]

[Formula 2] τ _R ≈ τ

[0015] On the other hand, when r is the distance between two single fish in the direction of travel of ultrasonic waves, r> (Cτ / 2)
In that case, the reflected waves from the two single fishes are separated in time and received, and their pulse widths are τ. On the other hand, when r ≦ (Cτ / 2), the reflected waves from the two single fish are temporally adhered and received, and the received pulse width τ
_R is

[0016]

(3) τ _R = τ + (2r / C)

Further, the received pulse width τ _R when a plurality of single fish are present at intervals r ₁ , r ₂ , r ₃ , ..., R _N of _C τ / 2 or less in the traveling direction of ultrasonic waves. Is

[0018]

[Equation 4]

It is represented by The received pulse reflected from the school of fish is thus wide. As described above, the received pulse width differs between the reflected wave from the single fish and the reflected wave from the school of fish, but it is difficult to distinguish between the single fish and the school of fish based only on this pulse width. This is because it is difficult to accurately extract the pulse width of the received pulse because the received waveform is not an ideal rectangular wave, the received level is different, and the receiver gain is different depending on the distance depending on the TVG. . In the present invention, the transmission pulse width is set to two types, long and short, and the ratio of the pulse widths of the reflected and received signals when the long pulse is transmitted and the reflected and received signals when the short pulse is transmitted from the same target is calculated. By observing it, it is discriminated whether it is a reflected wave received signal from a single fish, a reflected wave received signal from a school of fish or other seabed reflected signals, noise and interference signals.

Now, assume that the long pulse width of the transmission pulse width is τ ₁ , the short pulse width is τ ₂ , and the ratio thereof is τ ₁ / τ ₂ = m. As mentioned above, even if it is not possible to know the absolute value of the pulse width accurately depending on the conditions of the reception level and reception gain, the reflected wave from the same target is received in the same situation except that the pulse width is changed. However, the ratio of the received pulse width is maintained even if reception processing such as amplification and waveform shaping is performed. Since the reflected pulse width from a single fish is almost equal to the transmitted pulse width, the received pulse width for long pulse width transmission is τ ₁ , and the received pulse width for short pulse width transmission is τ ₂ . Therefore, the pulse width ratio after reception processing is m. On the other hand, in the case of a school of fish, the received pulse width during long pulse width transmission is

[0021]

[Equation 5] τ ₁ + (2R / C)

Therefore, the received pulse width at the time of short pulse width transmission is the same as Equation 4

[0023]

[Equation 6] τ ₂ + (2R / C)

[Mathematical formula-see original document] Thus, the ratio of equation 5 and equation 6 is

[0025]

## EQU7 ## {τ ₁ + (2R / C)} / {τ ₂ + (2R / C)} ≠ m

It does not become m like. Similarly, the reflection of the seabed is reflected not only from the surface of the seabed but also from within the formation, so that the reflection pulse width becomes wider than the transmission pulse width, and the ratio of the reflection pulse widths is not m. Further, since noise is completely random, it does not maintain a ratio value, and interference does not maintain a ratio value because it is independent of the pulse width of its own transmission.

Therefore, if the pulse width ratio after reception processing when transmitting with a short pulse width is m ± permissible range, the received signal is due to a reflected wave from a single fish. When it shows a certain value other than m, it means that it is a reflected wave from a school of fish. The operation will be described below in line with the above-mentioned means configuration.

In the present invention, the transmission controller causes the transmitter to transmit the pulse width τ ₁ and the pulse width τ _{2 in} the designated order. In either case, the received signal is shaped into a rectangular wave by the waveform shaping circuit. The shaped signal is stored in the first storage circuit when the transmission pulse width is τ ₁ , and is stored in the second storage circuit when the transmission pulse width is τ ₂ . The determination circuit reads the signals from both storage circuits, calculates the ratio of the pulse widths of the reflected and received signals from the same target, and the value is (τ ₁ / τ ₂ ) ±
It is determined whether or not it is within the allowable range, and a determination signal is output. Thus, it is possible to more reliably discriminate the single fish from the school of fish, the seabed signal, etc., as compared with the conventional technique.

[0029]

Embodiments of the circuit of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration block diagram of an embodiment of the circuit of the present invention. 1 is a transmitter that generates a transmission signal, 2 is a transmitter / receiver that receives and transmits a sound wave into the sea, and 3 makes the reception signal the reflection intensity from one fish (single fish) independent of distance The TVG receiving / amplifying section for fish 5 is a transmission control section for switching the transmission pulse width to an arbitrary reference τ and an arbitrary multiple m · τ thereof alternately for each transmission, and 6 is a T control section.
An A / D converter that digitizes the reception output signal voltage of the VG-equipped reception amplification unit 3 by converting it into a DC signal. Reference numeral 7 indicates whether or not the A / D-converted receiver output signal voltage is equal to or higher than an arbitrarily set threshold level value. Threshold section for judging and discarding the following as noise and discarding the above as pulse width of echo, 8 is a switching section composed of switches that switch according to transmission pulse width τ and m · τ of transmission control section 5, and 9 is switching A memory for storing a reception echo having a transmission pulse width of τ selected by switching the section 8; a memory for storing a reception echo having a transmission pulse width of m · τ; 11 a memory 9 and a memory 10; This is a single echo determination unit that continuously compares the pulse widths of the memory contents for each same water depth and determines only echoes that approximate a pulse ratio of 1: m as single echoes.

The transmission control unit 5 sends the pulse time width τ for transmission to the transmission unit 1 at a certain cycle, similar to the general fish finder and the fish finder for measurement. However, in this embodiment, the pulse width is alternately transmitted by τ and m · τ for each transmission. However, the order of transmission is not limited to alternating. As shown in FIG. 2, the reception signal output from the transmitter / receiver 2 by this control has a change in pulse width with respect to the fish body, the school of fish, and noise. The feature here is that the fish body 1 is proportional to the transmission pulse width.
It is a reflected signal from only the tail. This signal is passed through the TVG reception / amplification unit 3 and the A / D converter 6, and the threshold unit 7
By outputting the pulse width of the reflected wave (including noise)
To detect. In the present embodiment, the threshold level is provided to shape the waveform, but other waveform shaping circuits in which pulse width information remains may be used.

The switching unit 8 inputs the received echo when the transmission control unit 5 outputs the pulse width of τ into the memory 9, and m · τ
The received echo having the pulse width of is input to the memory 10.
Also, these memories are always rewritten with new inputs. The two memories are compared in the depth direction with a time width (Δr) sufficiently shorter than the pulse width from the time of sound wave emission. A single echo is extracted by extracting a pulse whose comparison value is close to 1: m.

FIG. 2 shows the outline of the above description. In the case where fish are distributed as in the condition (a), the pulse width τ and 2τ, where m is 2 in the above description, are alternately transmitted. (B) is a reflected wave with a pulse width τ, (C) is a reflected wave with 2τ, and (D) is an output of the A / D converter 6 with a pulse width τ (digital is analogized for description. And (e) are outputs with a pulse width of 2τ, and arbitrary threshold levels are also shown by chain lines. (F) is the output of the threshold unit 7 with the pulse width τ, and (G) is the output with the pulse width 2τ, which are the contents of the memory 9 and the memory 10, respectively.

When the pulse widths of both data are judged by the single echo judgment unit 11, as is apparent from FIG. 2, the ratio of the pulse widths due to the rising from the same water depth is 1: 2, that is, the ratio of the transmission pulse widths. Is only a single echo. Noise pulses are also shown in (f) and (g) in the figure. This too is obviously unrelated to the transmitted pulse width and is discarded by the decision.

In the actual deviceization, τ and m · τ
In the judgment of the ratio of 1: m, that is, 1: m, an appropriate allowable range is provided in the single echo extraction so as to prevent an erroneous measurement in which the single echo is judged to be a non-single echo due to the fluctuation of the echo. There is.

[0035]

As described above, the single fish discriminating circuit of the present invention, when transmitted with two types of pulse widths, long and short, has a pulse width ratio in the received signal which is a reflected received signal from a single fish. The transmission pulse width ratio becomes, and the point that the transmission pulse width ratio does not become in the reflected wave reception signal from the school of fish or the sea bottom,
Judge whether the pulse width ratio between the reflected received signal at the time of long pulse width transmission and the reflected signal at the same target of the received signal at the time of short pulse width transmission is within the transmission pulse width ratio ± allowable range Since this is done, there is an advantage that the reflected wave reception signal from a single fish can be discriminated and extracted more reliably than in the past, regardless of the wave reception level, the reception gain, and the distance to the target.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of an embodiment of the present invention.

FIG. 2 is a waveform diagram for explaining the operation in the embodiment of the present invention.

FIG. 3 is a block diagram of a conventional weighing fish finder.

FIG. 4 is an explanatory view of a determination situation of a single fish and a school of fish by a display image in a conventional device.

[Explanation of symbols]

 1 Transmitter 2 Transducer 3 Reception unit with TVG for fish body 4 Reception amplification unit with TVG for fish school 5,5 'Transmission control unit 6 A / D converter 7 Threshold unit 8 Switching unit 9,10 Memory 11 Single echo judgment Part 12 Single fish echo 13 Fish school echo 14 Interference noise

Claims (1)

(57) [Claims] _1. An ultrasonic wave transmission pulse having a pulse width τ _{1 and} an ultrasonic wave transmission pulse having a pulse width τ ₂ are transmitted to a transmitting section at a constant transmission repetition rate.
Ri In return period, and a transmission control unit for transmitting alternately or in another defined et al in the order; and the waveform shaping circuit for shaping the received signal into a rectangular wave; transmission pulse width is received signals when the tau ₁ A first memory circuit for storing the waveform shaping signal; a second memory circuit for storing the waveform shaping signal of the received signal when the transmission pulse width is τ ₂ ; and a signal stored in the first memory circuit At the leading edge of reading the signal stored in the second memory circuit
Signals from the second memory circuit are transmitted between the rectangular waves corresponding to the inter-position.
Of the signal from the first memory circuit with respect to the time width of the signal
The ratio is calculated, and the ratio is compared with (τ ₁ / τ ₂ ) ± permissible range. Only when the ratio is within the range, the received signal is received.
And a determination circuit that outputs a determination signal for determining that the number is from a single fish. The single fish determination circuit of the fish finder according to claim 1.