JPS6322275B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION An object of the present invention is to illustrate the scattering intensity of a school of fish based on reflected waves returned from a reflector such as a school of fish.

Conventionally, as this type of device, for example, the
As seen in Publication No. 26299, there is a technology for digitally displaying the density of a school of fish and the total amount of fish based on the intensity of reflected waves, the cruising distance of a ship, and the orientation angle of a transducer. However, since this device displays calculation results numerically, it is difficult to use it intuitively as statistical data.

The present invention provides an apparatus that can quickly analyze the density of reflectors and their depth distribution.

Specifically, it is intended to graphically display the integration results of reflected waves for each minute depth range corresponding to each depth.

A case will be described below in which the present invention is applied to the analysis of waves reflected by a school of fish.

Principle of the Invention By emitting ultrasonic waves from a boat toward a school of fish and analyzing the reflected waves, information relating to the amount of fish can be obtained in some form. In particular, the level of reflected waves has important information representing the density of fish schools. However, the reflected wave level varies greatly depending on the distance from the sound source to the reflecting object. For this reason, it is first necessary to correct the attenuation of the reflected waves. Conventionally, this attenuation correction method simply uses an amplifier whose gain is controlled by a function generator whose output voltage changes exponentially, but this is insufficient for quantitatively measuring fish density. It is.

Generally, the attenuation characteristic TL of ultrasonic waves in water is TL=20log r+α/1000r...(1) is given by

Here, r: distance from the sound source, r=Δr×in α: absorption/attenuation coefficient, which has frequency dependence, and the following experimental formula has been obtained.

α=43.5 ² /7000+ ² +0.00033 ² (dB/Km)...
(2): Frequency (kHz) In equation (1), the first term indicates attenuation due to diffusion, and the second term indicates attenuation due to absorption. Normally, correction for the diffusion attenuation in the first term is performed using a charge or discharge curve function generator using a time constant.
No strict correction is made to the absorption attenuation in the second term.

One object of the present invention is to perform strict correction according to the attenuation characteristic shown in equation (1).

Measurement of fish school density Now consider a scattering layer F in which fish with a reflection coefficient of TS are distributed at a density of n fish per unit volume, as shown in Figure 1. Also, let the scattering intensity of this scatterer be SV. Generally, the intensity I _i of a sound wave at a point at a distance r from the sound source is I _i = I ₀ b (θ, φ) 1/r ² e ^- 〓 ^r ……(3) Reflection intensity I from a scatterer with a minute unit volume ΔV _r is I _r = I _i svΔV = I _i tsnΔV ... (4) The reflection intensity at the sound source is ΔI = I _r b (θ, φ) 1/r ² e ^- 〓 ^r ... (5) = I ₀ b ² (θ, φ)1/r ⁴ e ^-2 〓 ^r svΔv ……(6) where I ₀ : Intensity b at a point at unit distance from the sound source: Directional strength β : α/1000r=10log _e βr ……( 6A) Let ΔΩ be the solid angle at which the minute volume ΔV is viewed from the sound source,
Assuming sound speed C and pulse width τ, ΔV=r ² ΔΩcτ/2 ...(7) From equation (6), ΔI=I ₀ b ² (θ, φ)1/r ² e ^-2 〓 ^r svcτ/2ΔΩ...
…(8) Therefore, the reflection intensity from the scatterer included within the directivity angle of the oscillator is I=∫I ₀ b ² (θ, φ)1/r ^2-2 〓 ^r svcτ/2dΩ…
…(9) =I ₀ 1/r ² e ^-2 〓 ^r svcτ/2 ⁴ 〓 ₀ ∫b ² (θ, φ
)dΩ ……(10) =I ₀ 1/r ² e ^-2 〓 ^r svcτ/2ψ ……(11) =I ₀ 1/r ² e ^-2 〓 ^r ntscτ/2ψ ……(12) Here ψ is the beam width and the directivity constant.

10logI = 10logI ₀ - (20logr + 2αr / 1000) + 10log sv + 10log (cτ / 2ψ) ... (13) On the other hand, the transmission strength SL of the sound source is defined as follows.

SL=10logI ₀ /Iref ……(14) Here, Iref: If the reference intensity received echo level is EL=10log1/Iref, EL=SL−(20logr+2α/1000r)+sv +10log(cτ/2ψ) ……(15) = SL−(20logr+2α/1000r)+TS+10logn+10log(cτ/2ψ)……(16) Fish school density When the transducer receiving sensitivity is ER=20logEr, find the output V ₀ at the transducer end.

The sound pressure P at the receiving point is The output voltage V of the vibrator is proportional to the sound pressure P of the incident sound wave, Here, P ₀ = sound source voltage Pref = reference sound pressure (1 μbar) Equations (18) and (19) include sv or nts as information regarding the amount of fish. Also, in logarithmic expression, it can be expressed as 20logV=SL+ER−(20logr+2α/1000r) +10log(cτ/2ψ)+sv (20).

As shown in equation (18), the received output voltage of the fish school echo is proportional to √ of the scattering intensity sv.

Also, the relationship between the scattering intensity sv and the fish density n is sv=nts=nσ/4π...(21) Therefore, if the reflection coefficient ts or scattering cross section σ per fish is known, the fish school can be determined from the output voltage V. Density n can be found.

In equation (18) or (20), P ₀ /Pref (SL), Er (ER), c, τ, and ψ are all known system constants. Therefore, by correcting the term related to the propagation attenuation of sound waves, 1/re ^- 〓 ^r , by estimating the output voltage V, sv
can be found. .

The correction of 1/re ^- 〓 ^r is generally called TVG (TIME VARIED GAIN) and is performed by a variable gain amplifier that corresponds to the distance and has a gain characteristic of ``re〓 ^r .

If the characteristics of the TVG amplifier are Eg re〓 ^r , the output voltage V ₀ of the amplifier is Therefore, SV=V ₀ ² / (Eg・Er・Po/Pref)cτ/2ψ ……(23) =V ₀ ² /10{ ^{(EG+ER+SL)/10} }・cτ/2ψ ……(24 ) Also, the fish school density n (tails/m ³ ) is n=V ₀ ² /10{ ^{(EG+ER+SL+TS)/10} }・cτ/2ψ...(25) EG=receiver amplifier gain dB ER=receiver Wave sensitivity dB SL = Source level dB TS = Target strength dB τ = Pulse width sec c = Sound speed m/sec ψ = Directivity constant EG = 20logEg 0dB = 1V/1μBar 0dB = 1μBar/1m For example, EG: 0dB ER: - Assume that 75dB SL: 120dB τ: 3msec ψ: 0.062 c: 1500m/sec, and an output of V=1Vrms is obtained as a fish school echo.

If the reflection coefficient T s of a single fish constituting this school of fish is -45 dB, the scattering intensity and density of this school of fish are calculated from equations (23) and (25) as SV = -36.5 dB n = 7.2 fish/m ² It will be done.

When actually measuring the amount of fish, there are variations in the data for each firing pulse, so the average value is calculated every few miles. If the range of integration is horizontal direction (travel section) l and vertical direction (depth section) R ₁ to R ₂ , then
The average scattering intensity in that section is = [∫ ^L ₀ (∫ ^r2 _r1 sv(r,x)dr)dx]/L(r _2
-r1 )
...(26) = 10log ...(27)

The purpose of the present invention is to graph the calculation results of equation (27), and this will be explained below using examples.

In FIG. 2, 1 is a transmitter that periodically generates pulse waves in the ultrasonic band, 2 is a transmission controller that sets the pulse wave period and pulse width τ, 3 is a transmission/reception switch,
4 is an ultrasonic transducer, 5 is an attenuator, and 6 is an amplifier 7.
This is a TVG voltage generator that generates a control voltage that increases the gain of the TVG linearly with distance. Reference numeral 8 denotes a seabed detector that separates seabed reflected waves from the received signal in the amplifier 9, and controls gate means 12, which will be described later, to block the received signal data from being processed after the arrival of the seafloor wave. . 10 is an AD converter that digitizes the input analog signal including its level information. Reference numeral 11 denotes a storage device for storing output data of the AD converter, and reference numeral 13 denotes a saturation detection means for sending an output and lighting an indicator lamp 14 when the input is a saturation signal exceeding a preset level. Reference numeral 15 denotes a slicing means for excluding signals below the level set by the level setter 16.

Reference numeral 17 is an attenuation correction means for correcting the term 1/re ^{- 〓r} explained in the second half of page 8. 18 is a square circuit which produces an output corresponding to the numerator of equation (24) for calculating the fish school density.

Reference numeral 19 denotes a means for adding data received each time a school of fish is searched.

Next, 20 is a ship speed signal generator, for example, one that utilizes the Doppler effect using ultrasonic waves may be used. 21 is a periodic signal generator that generates a signal from the transmitter 1 according to the emission period. 22 is means for multiplying the ship speed signal and the periodic signal, and 23 is means for setting the search distance range L of the ship, which is expressed in miles. Reference numeral 24 denotes a comparison means that sends an output when the calculation result of the multiplication means 22 reaches the set value of the setting means 23. 25
is a latch means that latches the output of the addition means 19 when the output of the comparison means 24 is generated.

26 is a τ signal generation means for creating a pulse width signal from the output of the transmission controller 2, 27 is a constant signal setting means for setting the system constants EG, ER, and SL in equation (24), and 28 is a directivity constant ψ 29 is a setting means for the sound velocity signal C. 30
is a K calculation means that calculates the denominator K of equation (24) K=10{ ^{(EG+ER+SL)/10} }·cτ/2ψ (28) from these predetermined constants.

In this embodiment, the attenuation coefficient G is input from the attenuator 5 to the K calculation means 30. Therefore, we finally obtain K=10{ ^{(EG+ER+SL+G)/10} }・cτ/2ψ...(29).

31 is a division means for dividing the output of the latch means 25 by K, 32 is a division means for further dividing the output by the search range L to calculate the average scattering intensity, and 33 is a logarithm calculation means for taking the logarithm of the division output. be.

The output of the logarithm calculation means 33 is supplied to the recording block comparison means 34 shown on the right side. The level signal generator 3 is connected to the other input terminal of the comparing means 34.
The output voltage from 5 is supplied. The level signal generator 35 generates a DC signal whose level increases by one step each time the level counter 36 outputs. The level counter 36 is reset to 0 by the output of the comparing means 24, and is counted up every time a key pulse of a recorder 37, which will be described later, arrives from the line A, and supplies an output to the level signal generator every predetermined number of inputs. .

38 is an address counter, and recording paper 3
The depth section address for the effective paper width of 9 is specified. Therefore, the counter 38 is
It is reset by the keying pulse generated when the recording pen reaches the beginning of the recording paper 39, and the output of the clock pulse generator 41 generated as the recording pen advances is counted.

The output of the address counter 38 specifies the address of the upper left storage means 11.

Reference numeral 37 is a recorder, which includes a recording paper 39 that moves at low speed in the direction of the arrow, an endless belt 42 that runs across the recording paper, and a recording pen 4 attached to this belt.
It has 0. 43 is an energized rail that gives a signal to the recording pen; 44 and 45 are pulleys for driving the belt; 46 is a magnet provided on the belt to generate a pulse when the recording pen 40 reaches the starting edge of the recording paper 39; This is a reed switch for signal generation. 48 is a timer which sends out a recording signal every minute and supplies the signal to the recording contact piece 49.
41 is a clock pulse generator and a recording pen 4.
A pulse is generated in synchronization with the running of 0 to drive the address counter 38.

Attenuation correction means Attenuation correction is diffusion attenuation (20logr) as mentioned above.
It can be roughly divided into correction of absorption attenuation (α/1000r) and correction of absorption attenuation (α/1000r).

Conventional correction using TVG voltage mainly corrects diffusion attenuation, but in terms of depth, it
The maximum distance was about 300m. In the embodiment of the present invention, in addition to this conventional TVG technology, calculations are performed using an electronic computer, making it possible to perform precise correction at depths of 300 m or more. This will be explained next.

Referring again to FIG. 2, reference numeral 50 denotes correction limit setting means for setting the correction depth coefficient in of the TVG voltage generator 6 and its limit value ii. On the other hand, a frequency setting means 51 is separately provided, and based on the output thereof, α is calculated by an α calculation means 52 using equation (2). 53 is a calculation means that further calculates e〓 ^r using equation (6A). 54 supplies the output of the calculation means 53 as is to the attenuation correction means 17 when the measured depth is within the TVG effective range (r≦Δrii);
If the TVG effective range is exceeded (r>Δrii),
The attenuation correction means 1 drives the deep TVG voltage generation means 56 and calculates the product of its output and the output of the calculation means 53.
7. 56 is for deep depth
It is a TVG voltage generating means and generates a correction coefficient signal of in/ii (30) for depth in.

Here, ii: Correction depth limit value In the attenuation correction means 17, the product output VEge of the signal that changes depending on the distance, which is the output of the slicing means 15, and the output of the determination means 54 or the deep TVG voltage generation means 56. 〓 Send ^r r.

Operation of the Apparatus In the apparatus as described above, let us consider a case where the ship SP searches the sea area of section L in the direction of the arrow at speed U, as shown in FIG. The ship emits ultrasonic pulses of frequency F with a period τ of 1, 2, 3... m toward the ocean floor, receives the reflected waves, and processes the signals. In this case, the basic signal processing of the present invention is to divide the depth r direction into sections of Δr, consider a large number of transverse layers, and integrate the reflected signal in the traveling direction for each transverse layer.

In FIG. 2, when the transmitter 1 generates a high-frequency pulse, this pulse excites the ultrasonic transducer 4 via the transmitter/receiver switch 3, and emits an ultrasonic pulse having a pulse width τ and a directivity angle θ into the water. Reflected waves from schools of fish scattered at each depth return sequentially from those at shallower depths, pass through the ultrasonic transducer 4 and the transceiver switch 3, and reach the attenuator 5. The level of the signal is adjusted in the attenuator 5 so that the signal does not become saturated in the subsequent amplifier. The signal is further amplified by the amplifier 7, but the degree of amplification of this amplifier is
The voltage applied from the TVG voltage generator 6 is set to increase over time. Therefore, the attenuation of (20log r) shown in the first term of equation (1) is corrected. This correction depth limit is TVG
Determined by the maximum voltage value, the normal depth is approximately 300m.
That's about it. The signal then reaches an amplifier 9, where a submarine signal is detected on line B by a well-known submarine sorting circuit 8 that utilizes a level difference. Next, the signal is converted into a digital signal by an AD converter 10 and stored in a memory 11 for each Δr interval. The write address signal is input from address counter 38.

Now, the subsequent data processing is performed by the central processing unit (hereinafter abbreviated as CPU), and the procedure will be explained.

In the recorder 37 shown in FIG. 2, the address counter 38 is driven by a pulse generated by the read switch 47 when the recording pen 40 reaches the starting edge of the recording paper 39. The data in the memory 11 is read out in response to this counter read command. Among these data, the reflected waves after the seabed reflected waves are removed by the gate means 12. Furthermore, if the signal exceeds a predetermined level and becomes saturated, correct information processing cannot be performed, so this is detected by the saturation detection means 13 and notified by the display lamp 14. Low level signals are removed by the slicing means 15 so as not to be processed. These signals are subjected to attenuation correction means 17 in which the propagation attenuation component of the ultrasonic wave is corrected as described above. At this point (22)
This means that an output representative of the formula has been obtained. In other words, correct fish school information for the Δr depth section at depth i and the j-th pulse period has been obtained.

Further, this data is squared by a squaring means 18. As a result, a molecule of formula (23) or (24) was obtained.

The above calculations are repeated in the ship's traveling direction for each depth section Δr. This is displayed on 39.

Needless to say, the writing of new data to the memory and the reading from this memory do not need to be processed synchronously and are not directly related. Therefore, the above calculation operation does not need to be performed every time an ultrasonic wave is emitted from the ship.

Now, regarding the determination of the range in the sailing direction of the iterative calculation, in this embodiment, when the product of the total number of search pulses and the ship speed reaches a predetermined value L, the comparison means 2
4 activates the latch means to stop the repeated calculation. This means that, for example, even if the ship speed changes by half, the number of search pulses within range L will double, and the product will eventually remain constant. In other words, this is to enable range measurement without being affected by ship speed.

On the other hand, the raw fish school signal is read out from the storage circuit 11, converted into D/A, and then given to the recording pen 40, where the normal fish finder recording is performed as shown on the recording paper as F1 and F2.

The output of the comparison means 24 causes the level counter 36 to be reset. Then, a level signal whose value increases by one stage each time a subsequent pulse generated by the reed switch 47 is calculated is sent from the level signal generator 35 to the comparison means 34.

On the other hand, the calculation means obtains the denominator of equation (24) from the K calculation means 30, and the division means 31 calculates the output of the latch means.
Divide V ₀ ² . Therefore, the output of the dividing means 31 ends up representing the scattering intensity sv of equation (24). Further, the dividing means 32 divides sv by L to obtain the average scattering intensity of equation (26). Furthermore, the logarithm calculation means 33
Take the logarithm of sv to obtain equation (27). This output is supplied to comparison means 34.

In the end, the comparison means 34 compares the average scattering intensity reference level that increases leftward in the figure with each pen scan with the recording position (straight line P) immediately after passing through the integration range L as a reference line and the depth section corresponding to the pen existing position. The results of the logarithmic calculation of Δr are compared in synchronization with the pen scanning. Then, when both inputs match, an output is sent to the recording pen 40. Therefore, recording paper 3
9, the average scattering intensity sv is displayed for each depth section as a leftward deviation graph Q with the straight line P as the reference line.

In addition, there are minute and hour marks M, M in the blank space above the recording paper.
... is displayed, and if the chart paper feed speed is set to correspond to the ship's speed, changes in ship speed can be identified on the chart paper. This is useful in knowing the coarse density of search pulses in the travel direction.

As explained above, according to the present invention, it is possible to intuitively observe the average reflection intensity in the detection sea area, including the distribution in the depth direction, and it is possible to conveniently grasp the amount of fish resources in the sea area.

In the above embodiment, recording paper was used as the display device and a single pen was used as the display means.
As this display means, a multi-pen, which is commonly used for this type of recording paper, can be used. In this case, it is convenient to use the number of multi-pens as the number of depth division sections.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram for explaining the principle of the present invention, FIG. 2 is a block diagram showing an embodiment of the present invention,
FIG. 3 is an explanatory diagram for explaining the operation of the present invention.

Claims (1)

[Claims] 1. In a device that emits a search wave and displays its reflected wave on a display having a time axis versus a distance axis (depth axis), the intensity of the reflected wave is expressed as an attenuation function due to the propagation of the search wave. Accordingly, a correction means for correcting, a means for dividing the distance axis into a plurality of time intervals, an arithmetic means for integrating the reflected wave a predetermined number of times for each time interval, and a computation means provided in the display and for dividing the distance axis into a plurality of time intervals; a main display stage that performs main scanning at a predetermined speed; a sub-scanning means that sub-scans the display result of the display in the time axis direction; A reflection information display device comprising: means for converting into a deviation signal in the time axis direction based on the main scanning portion of the image; and means for supplying the deviation symbol to the display means. . 2 The above correction means corrects the diffusion attenuation.
2. The reflection information display device according to claim 1, comprising TVG voltage generation means, calculation means for correcting absorption and attenuation components, and means for summing both means. 3 The above calculation means has a squaring means for squaring the output of the ultrasonic propagation attenuation correction means and a means for dividing the value by 10{ ^{(EG+ER+SL)/10} }・Cτ/2ψ. The reflection information display device according to claim 1, characterized in that: 4. According to claim 1, wherein the display device comprises a recording paper that performs sub-scanning in a certain direction, and the display means comprises needle-shaped recording pens arranged so as to cross the recording paper. display device. 5. The display device according to claim 1, wherein the display device is a cathode ray tube display, and the display means is an electron beam sweeping the surface of the cathode ray tube.