JPH0659028A - Underwater detector - Google Patents

Abstract

PURPOSE:To make it possible to obtain three-dimensional underwater detection information in a short period of time by means of an underwater detector and prevent lack of image and occurrence of false image. CONSTITUTION:An underwater detector is provided with a transmitted beam forming means 18 which forms transmitted beams which have wide and flat directivity characteristics over the whole periphery centered on ultrasonic wave send and receive point and with the predetermined tilt angle, a received beam forming means 17 which forms received beams which have sharper directivity characteristics than the transmitted beams, and a directivity direction control means 33 which repeats the operation which changes tilt angle after scanning the wave receive beams in the horizontal direction a plural number of times while rotating in the scope of the transmitted beams in the emission cycle of the transmitted beams.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an underwater detecting apparatus capable of detecting a three-dimensional distribution of fish schools in water.

[0002]

2. Description of the Related Art In an underwater detection device for obtaining underwater information in a wide range, for example, a scanning sonar, a large number of vibrators are stacked to form one vibrator block, and the vibrator blocks are arranged in an annular shape. It has a full-circulation type transducer, which drives the transducers at the same time to emit an ultrasonic beam in the entire circumferential direction of the water, while the reflected wave has a sharp directivity. Underwater detection is performed by swirling and scanning the received beam.

In this case, as shown in FIG. 7, the tilt angle θ is set in order to scan the received beam Br with a predetermined angle from the horizontal plane. In the conventional apparatus, the tilt angle θ remains fixed during one ultrasonic wave transmission / reception, and is not changed midway. Therefore,
The detection range when the received beam Br is rotated once is a range corresponding to the conical surface with the ultrasonic wave transmitting / receiving point p as the apex.
Therefore, the detection information when the fish school a ₀ exists is, as shown in FIG. 8, the cut a ₁ cut by the conical surface on which the received beam Br is scanned. This is also the case when transmitting an ultrasonic beam having a wide directional characteristic in which the signal strength is constant in a wide azimuth range.

With such detection information a ₁ in a plane limited range, it is not possible to sufficiently grasp the three-dimensional distribution of the school of fish a ₀ .

Further, a school of fish b _{0 and the} like located outside the conical surface on which the received beam Br is scanned cannot be detected.

Therefore, in order to improve the above inconvenience,
In the conventional technique, ultrasonic waves are transmitted and received a plurality of times, and three-dimensional detection information is obtained by gradually changing the tilt angle θ each time one ultrasonic wave is transmitted and received. A device has been proposed.

However, in order to obtain three-dimensional detection information in the conventional device, it is necessary to repeat the transmission and reception of ultrasonic waves many times, and it takes a long time to collect information. For example, when the tilt angle is changed in the range of 0 ° to 40 ° in steps of 5 °, it is necessary to transmit and receive ultrasonic waves 9 times.

Then, as shown in FIG. 7, a fish c ₀ or the like moving at a high speed in the water moves far away from the detection range while repeating transmission and reception of ultrasonic waves, and the movement of these fish schools. Cannot be captured.

On the other hand, if the ultrasonic beam has a wide directional characteristic in both transmission and reception, each fish a _{0 to} c ₀ in FIG. 7 can be captured.

However, if the ultrasonic beam has a wide directional characteristic in both transmission and reception, the seabed echo having a greater intensity than the echoes from the fish school is also received at a certain distance or more, and as a result, the seabed. The echo of the school of fish is masked, and the school of fish cannot be captured.

In order to solve the above-mentioned inconvenience, the present applicant transmits an ultrasonic beam having a wide directional characteristic and receives the reflected wave as disclosed in Japanese Patent Application No. 3-49459. When waving, the tilt angle of the received beam having a narrow directional characteristic and the swivel scanning are alternately switched in a time division manner, so that three-dimensional underwater detection information can be obtained within a short time. Provided a detection device.

That is, in this device, a transmission beam having a flat directivity characteristic in the vertical direction is emitted at a predetermined cycle tr over the entire circumference around the ultrasonic wave transmission / reception point. Then, as shown in FIG. 9, within the emission period tr of the transmitted beam, the tilt angle θ is sequentially switched in a stepwise manner in accordance with the number R of times of swivel scanning of the received beam. For example, when the number of times of turning scans is Ri, θi is selected as the tilt angle, and when the number of times of turning scans Ri ₊₁ is next, θi ₊₁ is selected as the tilt angle.

[0013]

As described above, Japanese Patent Application No.
The underwater detection device disclosed in Japanese Patent No. 49494/1989 has an advantage that three-dimensional detection information in water can be obtained within a short time, as compared with the conventional device. Upon examination, it was found that the following problems remained.

That is, in this underwater detecting apparatus, the tilt angle is changed every time the received beam is swiveled once, but in reality, the tilt angle cannot be changed instantaneously. It changes gradually with a time constant. Therefore, when an underwater situation is displayed as an image based on the received beam, a false image may occur.

Explaining this concretely, changing the tilt angle is a phase correction signal to be added to a received signal from each transducer arrayed in the vertical direction when phase combination is performed. This means changing the phase shift amount of the (carrier signal), but it takes some time to stabilize the output after phase combination after changing the phase shift amount of this phase correction signal (carrier signal). It takes. And, even during the period until this stabilization, as shown in FIG. 10, the tilt angle continuously changes (x ₁ in the figure,
x _2, ... range of), the exact orientation of the receive beam is not found. For example, as shown in FIG. 11, when the points at straight line distances r ₁ and r ₂ from the transducer are A and B, the vertical depths h ₁ and h ₂ from the water surface are h ₁ = r ₁ sin θ ₁ (1) h ₂ = r ₂ sin θ ₂ (2) Now, when the tilt angle is switched from θ ₁ to θ ₂ , A
If the transition from point B to point B is made and the elapsed time is ignored, r ₁
It can be thought of as ≈r ₂ . Therefore, h ₂ = r ₂ sin θ ₂ = r ₁ sin θ ₂ (3) Here, since θ ₁ and θ ₂ may be considered in the range of 0 to π / 2, θ ₁ <θ ₁ + Δθ <θ ₂ (however, , Δθ is the tilt angle that changed within a minute time Δt)
Therefore, sin θ ₁ <sin (θ ₁ + Δθ) <sin θ ₂ Therefore, the following equation holds.

R ₁ sin θ ₁ <r ₁ sin (θ ₁ + Δθ) <r ₁ sin θ ₂ (4) Substituting the relationships of the expressions (1) and (3) into the expression (4), h ₁ <sin (θ ₁ + Δθ) <h ₂ (5) In other words, when switching the tilt angle from θ ₁ to θ ₂ , the value of θ ₂ is used in the calculation as if it was switched instantaneously, but in reality the tilt angle is , The true tilt angle is θ ₁ + Δθ (<θ ₂ ), so
The calculated depth h ₂ is calculated deeper than the true depth sin (θ ₁ + Δθ). Conversely, when switching the tilt angle from θ ₂ to θ ₁ , the calculated depth h ₁ is the true depth sin (θ
It is calculated shallower than ₁ + Δθ). As a result, when the received signal data obtained by the transmitter / receiver is coordinate-converted from the first polar coordinate system to the orthogonal coordinate system for image display, the depth direction distance becomes uncertain, which causes a false image.

On the other hand, if the received signal data obtained in such a state where the tilt angle is uncertain is omitted, the occurrence of the false image disappears, but due to the lack of the data, the image display can be performed for the specific azimuth associated with the change of the tilt angle. It causes troubles such as not being present.

[0018]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and obtains three-dimensional underwater detection information within a short period of time and at the same time generates a false image or an image. It is possible to effectively prevent the occurrence of omission.

Therefore, according to the present invention, a transmitting beam forming means for forming a transmitting beam having a wide and flat directional characteristic around the entire circumference of the ultrasonic transmitting / receiving point and centering on a predetermined tilt angle. And a receiving beam forming means for forming a receiving beam having a sharper directivity than this transmitting beam,
Within the emission cycle of the transmitted beam, the pointing direction control means for repeating the operation of rotating the received beam in the horizontal direction a plurality of times within the range of the transmitted beam and then changing the tilt angle in the vertical direction, I have it.

[0020]

The transmitting beam forming means forms a transmitting beam having a wide and flat directional characteristic around the entire circumference around the ultrasonic wave transmitting / receiving point and around a predetermined tilt angle. The beam is transmitted into the water.

The receiving beam forming means forms a receiving beam having a directivity sharper than that of the transmitting beam, and the pointing direction control means within the range of the transmitting beam within the emission cycle of the transmitting beam. The operation of changing the tilt angle is repeated after the received beam is rotated and scanned in the horizontal direction a plurality of times.

As a result, the swivel scanning of the received beam and the change of the tilt angle are performed within the emission period of the transmitted beam, and three-dimensional detection information can be obtained within a short time.
Moreover, since the tilt angle is changed after the received beam is swirled in the horizontal direction a plurality of times, even if the received signal data obtained when the tilt angle is changed is invalid,
Since the data in the same direction is collected in the state where the tilt angle is determined by the revolving scanning again, the loss of an image and the occurrence of a false image are avoided.

[0023]

1 is a block diagram showing the configuration of an underwater detection apparatus according to an embodiment of the present invention.

In the figure, reference numeral 1 denotes the whole underwater detection apparatus, and 2 is a vibrator. These vibrators 2 are stacked in multiple stages to form one vibrator block 4a to 4n. 4a to 4n are arranged in an annular shape to form a single all-round swivel type transducer 3.
Is attached to the bottom of the ship.

6a to 6n are oscillator blocks 4a to 4n, respectively.
Is a vertical phase synthesizing circuit for aligning the phases of the received signals obtained by the respective transducers 2 included in
4n are individually provided. Each of the vertical phase synthesizing circuits 6a to 6n has the same configuration. For example, when focusing on one vertical phase synthesizing circuit 6a, as shown in FIG. The pre-amplifiers 8 individually connected to the
The received signal output from the
A phase shifter 10 for mixing the phase shift correction signals from 0 so that each received signal has the same phase, and these phase shifters 1
It is composed of an adder 12 that adds each reception signal phase-shifted by 0.

Reference numeral 14 is a switching circuit which is switched and scanned in order to select one group (m pieces in this example) of received signals to be subjected to phase combination in the horizontal direction, and 16 is one group selected by the switching circuit 14. It is a horizontal phase synthesizing circuit for aligning the horizontal phases of (m) received signals to form a received beam.

Then, the above vertical phase synthesizing circuits 6a-6
The n, the switching circuit 14 and the horizontal phase synthesizing circuit 16 constitute the received beam forming means 17 in the claims.

Reference numeral 18 denotes sinx / x (where x = x) along the arrangement direction of the transducers 2 forming the transducer blocks 4a to 4n.
(π ・ sin θ _BW / 2λ) ・ d ・ N, λ is the wavelength of the carrier frequency signal, θ _BW is the beam width of the directional characteristic, d is the array pitch of the transducers, and N is the amplitude distribution determined by the transducer position. It is a transmission unit that outputs a drive signal for ultrasonic transmission that has been weighted to have. That is, the transmitting unit 18 functions as a transmitting beam forming unit in the claims,
In this example, as shown in FIG. 3, a trigger signal output from the control unit 32, which will be described later, for determining the timing of ultrasonic wave emission.
A signal generator 20 for generating a pulse signal having a predetermined carrier frequency (for example, 200 kHz) in response to the (keying pulse) T, a phase shifter 22 for shifting the pulse signal from the signal generator 20, and each shifter. An amplifier 24 with an adjustable gain for amplifying the output of the phaser 22. And each phase shifter 2
2, as shown in FIG. 4, the firing direction alpha _0/2 of the ultrasonic wave from each transducer block 4a to 4n (alpha ₀ is ultrasound transmit beam width) the amount of phase shift so that the It is set in advance. As a result, the acoustic energy is small in unnecessary directions such as the sea surface of the ultrasonic waves emitted from the transducer 3, and large in the necessary directions. Also, each amplifier 2
The amplification factor of 4 is weighted and adjusted so that each of the transducer blocks 4a to 4n has an amplitude distribution determined by sinx / x along the arrangement direction of the transducer 2, and thus the transducer From 3 onward, an ultrasonic wave having a flat directional characteristic is emitted in a certain angle range in the vertical direction (see Japanese Patent Laid-Open No. 61-22398).

Reference numeral 26 denotes a distance counter for inputting and counting the above-mentioned trigger signal T as a reset signal, and also for inputting and counting the turning scanning end signal S output from the control section 32 each time one turning scanning of the receiving beam is finished. Is. That is, the distance counter 26 counts up each time the turning scanning end signal S is applied, but the count value R
Corresponds to the straight line distance to the detection point of the received beam Br.

Further, 28 is a tilt angle corresponding to the count value R output from the distance counter 26, which sequentially outputs setting data of the tilt angle θ preset according to the distance to the detection point of the received beam. This is a setting data generator. That is, the tilt angle setting data generation unit 28
Is composed of, for example, a ROM, and as shown in FIG. 5, data of the tilt angle θ is stored in association with the address position designated by the count value R output from the distance counter 26. In this case, as the count value R linearly increases, the tilt angle θ increases and decreases stepwise, and the tilt angle value changes only after the count value increases by two. ing.

Reference numeral 30 denotes a phase correction for aligning the vertical phase of the received signal with respect to the vertical phase synthesizing circuits 6a to 6n based on the setting data of the tilt angle θ read from the tilt angle setting data generator 28. It is a phase correction signal generator that outputs a signal (carrier signal) φ.

32 outputs the above-mentioned trigger signal KP, and sets the phase shift amount of the horizontal phase synthesizing circuit 16 within the output period tr of the trigger signal T, and then repeats the switching scanning of the switching circuit 14 repeatedly. The control unit is configured to rotate the received beam Br in a swivel scan and output a swirl scan end signal S each time the swirl scan is completed.

The distance counter 26, the tilt angle setting data generator 28, the phase correction signal generator 30,
Further, the control unit 32 constitutes the pointing direction control means 33 in the claims.

Next, the operation of transmitting and receiving ultrasonic waves in the underwater detecting apparatus having the above configuration will be described.

At the time of transmitting the ultrasonic wave, a trigger signal T is output from the control unit 32, and this trigger signal T is transmitted by the transmission unit 1.
8 and the distance counter 26, respectively.

In response to the trigger signal T, the signal generator 20 of the transmitter 18 outputs a pulse signal having a predetermined carrier frequency (for example, 200 KHz) as a drive signal, which is sent to each phase shifter 22. A predetermined amount of phase shift is given respectively, and each pulse signal is amplified by the amplifier 8 by a predetermined amplification degree and then added to all the vibrators 2.

As a result, the ultrasonic transmission beam Bt of the ultrasonic waves emitted is, as shown in FIG.
For each n, have the alpha _0/2 of the tilt angle, and a wide ultrasonic beam width alpha _0, in the range of the beam width alpha ₀ has a flat directional characteristics, and the ultrasonic transmitter point p The beam is formed so as to cover the entire circumference around the center.

Then, the receiving operation described below is performed within the emission period tr of the ultrasonic transmission beam Bt.

The ultrasonic echo in the water is received by each transducer block 4a-4n of the wave transmitter / receiver 3, and accordingly,
Received signals are output from the oscillators 2 forming the oscillator blocks 4a to 4n, and these received signals are input to the vertical phase synthesis circuits 6a to 6n in the next stage. At this time, as will be described later, from the phase correction signal generation unit 30 to each of the vertical phase synthesis circuits 6a to 6n, under a certain tilt angle θi,
Phase correction signal to align the vertical phase of the received signal
Since (carrier signal) φ is given, the phases of the received signals in the vertical direction are aligned and combined. Further, the control section 32 switches and scans the switching circuit 14 so that one group (m) of received signals among the outputs of the vertical phase synthesizing circuits 4a to 4n are selected by the switching circuit 14 and these received signals are selected. Is input to the horizontal phase synthesizing circuit 16 and the phases in the horizontal direction are aligned and synthesized.

As a result, under a certain tilt angle θ, a received beam Br having a narrow width in each of the vertical direction and the horizontal direction is formed and is swirled and scanned.

Next, the directional control in the case of changing the tilt angle θ while rotating and scanning the received beam Br will be described.

First, the distance counter 26 is reset by the trigger signal T from the control unit 32. Further, the control unit 32 outputs the turning scan end signal S to the distance counter 26 every time the turning scan of the received beam Br is completed once. Therefore, the distance counter 26 counts the number of turning scans. Therefore, the count value R of the distance counter 26 is sequentially incremented each time the received beam Br is scanned once. Then, the count value R is added to the tilt angle setting data generator 28 of the next stage as a read address of the data of the tilt angle θ. As a result, the tilt angle setting data generator 28 reads the data of the tilt angle θ as shown in FIG. The tilt angle θ data read here increases and decreases stepwise as the count value R increases, and the tilt angle data changes only after the count value increases by two. For example, when the count value of the distance counter 26 indicates Ri, the tilt angle is θi.
Is output, and even if the count value becomes Ri ₊₁ , the same tilt angle data of θi is output. Then, only when the count value becomes Ri ₊₂ , the tilt angle is changed to become θi ₊₁ .

Since the data of the tilt angle θ read in this way is added to the phase shift correction signal generator 30 in the next stage, the phase shift correction signal generator 30 receives the data of the tilt angle θ. According to the vertical phase synthesizing circuit 6a-
The phase correction signal φ for aligning the vertical phase of the received signal with respect to 6n is output. As a result, the received beam B
While r is rotated and scanned twice, vertical phase synthesizing circuits 6a-6
At n, the tilt angle θ is fixed to a predetermined value, and the phases of the received signals in the vertical direction are aligned and combined.

In this way, the rotational scanning of the received beam Br and the change of the tilt angle are performed within the emission period tr of the transmitted beam Bt, so that three-dimensional detection information can be obtained within a short time. . Moreover, as shown in FIG. 6, after the receiving beam is turning scanned twice in the horizontal direction under a certain tilt angle .theta.i, tilt angle is changed to .theta.i _+1, under this tilt angle .theta.i ₊₁ Since the operation of changing the tilt angle θ after rotating the received beam twice is repeated as in the case where the received beam is swung twice again, the received signal obtained when the tilt angle is switched. data
Even if the azimuth of (x ₁ , x ₂ , ... in Fig. 6) is unclear, the data of the same azimuth is collected in the state where the tilt angle is fixed by the second swivel scan. If it is used, underwater detection information without missing of images or generation of false images can be obtained.

In this embodiment, the tilt angle θ is changed each time the received beam Br is swung twice, but the invention is not limited to this.
Even if the tilt angle θ is changed after the orbiting scanning is performed more than once, the same effect can be obtained.

[0046]

According to the present invention, unlike the prior art, it is not necessary to transmit and receive ultrasonic waves a plurality of times, and the ultrasonic waves are swirled and tilted and tilted within the emission period of the transmitted beam. 3D detection information can be obtained within a short period of time since the change is performed.

Moreover, since the operation of changing the tilt angle is repeated after the receive beam is swirled and scanned in the horizontal direction a plurality of times within the range of the transmit beam, the received signal data obtained when the tilt angle is changed is invalid. However, since the data in the same direction is collected in the state where the tilt angle has been determined by the revolving scanning again, it is possible to obtain underwater detection information without image loss or false image generation, which is an excellent effect. Play.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an underwater detection device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing details of a vertical phase synthesizing circuit of the apparatus shown in FIG.

3 is a block diagram showing details of a transmission unit of the apparatus of FIG.

FIG. 4 is an explanatory diagram showing directional characteristics of an ultrasonic transmission beam.

FIG. 5 is an explanatory diagram showing tilt angle data read from a tilt angle setting data generator based on a count value of a distance counter.

FIG. 6 is an explanatory diagram stereoscopically showing the mutual relationship between the change of the tilt angle of the received beam and the swivel scanning.

FIG. 7 is an explanatory diagram showing a range of detection information obtained by conventional swivel scanning of a received beam.

FIG. 8 is an explanatory diagram of a case where underwater detection information is displayed as an image.

FIG. 9 is a diagram for explaining a mutual relationship between conventional tilt angle change and swivel scanning.

FIG. 10 is an explanatory diagram stereoscopically showing the relationship between the conventional swivel scanning of the received beam and the change of the tilt angle.

FIG. 11 is an explanatory diagram showing a relationship between a true depth during a tilt angle transition and a calculated depth when the tilt angle is changed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Underwater detection device, 2 ... Oscillator, 4a-4n ... Oscillator block, 6a-6n ... Vertical phase synthetic | combination circuit, 16 ... Horizontal phase synthetic | combination circuit, 17 ... Receiving beam forming means, 18 ... Transmitter (transmission) Beam forming means), 26 ... Distance counter, 28 ... Tilt angle setting data generator, 30 ... Phase correction signal generator,
32 ... Control unit, 33 ... Directional direction control means.

Claims (1)

[Claims] 1. A transmission beam forming means for forming a transmission beam having a wide flat directional characteristic around an ultrasonic wave transmitting / receiving point and a predetermined tilt angle, and the transmitting beam forming means. A receiving beam forming means for forming a receiving beam having a sharper directional characteristic than that of the wave beam; and within the emission cycle of the transmitting beam, the receiving beam is horizontally swirled a plurality of times within the range of the transmitting beam. An underwater detecting apparatus comprising: a pointing control unit that repeats an operation of changing a tilt angle after scanning.