JP2001311770A - Underwater acoustic image processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an underwater acoustic image processor receiving little influence by the changes of the states of waves on the sea surface and capable of sufficiently obtaining the effect of adding reception beams. SOLUTION: Vertical reception beams 8-1 through 8-m are concurrently formed at reception, the relative phase difference information among a plurality of vertical reception beams after a plurality of transmissions of acoustic waves is extracted from the information obtained by a plurality of vertical reception beams having little influence of waves near the sea surface, and the phase difference information is reflected on the process of horizontal reception beams. For the extraction of the phase difference information among a plurality of vertical reception beams, the correlation coefficient among the vertical reception beams is calculated based on the phasing output signal in the prescribed wave- form zone where the vertical reception beam includes the reflected signal of an object 6 or in the prescribed wave-form zone of a reception signal, and the phase difference giving the maximum value of the correlation coefficient is obtained. The influence by the changes of the state in the sea and on the sea surface is efficiently reduced, and reception beams by a plurality of transmissions and receptions can be added.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an underwater acoustic imaging device for visualizing underwater information by an acoustic method, such as a sonar device and a fish finder, and more particularly to a method for detecting a change in an image to be detected due to a change in underwater conditions. The present invention relates to an underwater acoustic imaging device to be reduced.

[0002]

2. Description of the Related Art Conventional sonar devices and the like are mainly mounted on ships, underwater vehicles, underwater vehicles, and underwater vehicles. Ships and crafts to be mounted are usually at sea level, underwater waves,
Or, it is affected by the sway caused by the cruising, and is operating in a state of always performing relative movement with respect to the absolute position coordinates on the earth.

On the other hand, for marine vessels, a Loran signal, which is generally known as a reference signal from a radio lighthouse,
In recent years, a Global Positioning System (GPS) that measures the absolute position based on radio waves from multiple satellites has been installed, along with the inertial navigation of the Doppler speedometer that uses the reflected signal of the sound wave transmitted to the sea floor. 2. Description of the Related Art Systems that can obtain sufficiently high-accuracy position information for navigation of ships in ports and the like have become widespread. The purpose of the sonar image is to grasp the information on the far-distance position sufficiently as much as possible in accordance with the propulsion speed of the marine vehicle such as a ship. In most cases, the distance to the underwater or underwater object to be imaged is very large compared to the wavelength of sound waves transmitted and received in water, and the speed of sound changes due to the vertical temperature distribution in the water, and the sound propagation path It is widely known that changes in the distance can cause significant deviations in the distance measurement to a target reflector at a long distance.

There is known an information processing method for processing an acoustic signal obtained by a plurality of transmissions and receptions of a sonar device to reduce the influence of changes in the state of the sea or the sea surface (JP-A-9-14).
No. 5840, JP-A-6-222142). In these processing methods, relatively suitable addition of received signals from a side scan sonar device or the like in the deep sea is performed.

[0005]

The prior art, such as the position information system, mainly gives the absolute position of the translatory motion of a marine vehicle such as a ship in the horizontal plane, but it is necessary to grasp the motion of the entire hull. However, there is a problem that the main focus is not placed on, and it is often not always possible to sufficiently detect the rolling and pitching fluctuations including the vertical motion element of the ship.

In the prior art, a method of estimating a sound ray path by measuring a vertical distribution of water temperature in the vicinity of a sonar device or the like has been adopted. There has been a problem that the accuracy of the absolute position of an image is usually significantly reduced as it gets farther.

[0007] Further, an acoustic beacon signal source or the like whose absolute position is calibrated is not installed in a specific port, a coast other than a route, a general marine environment, and the like. There is a practical limit to obtaining the absolute position of a ship from images and sonar information.

In the image processing method of the sonar device in the prior art, there is no disclosure of a method of measuring a signal in consideration of the influence of sea surface wind in a shallow sea area and a method of adding a received beam based on the method.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for efficiently reducing the influence of a change in the state of the sea and the sea surface and adding a plurality of reception beams by transmission / reception. It is another object of the present invention to provide an underwater acoustic imaging apparatus capable of sufficiently obtaining the effect of addition of reception beams.

[0010]

An underwater acoustic imaging apparatus according to the present invention comprises a vertical transducer having a plurality of vertical transducers arranged in a vertical direction, and a plurality of horizontal transducers arranged in a horizontal direction. And a horizontal detector having an element, and a desired detection range in the horizontal direction (region of interest) by a reception phasing circuit.
Form a plurality of reception beams and a plurality of reception beams in the vertical direction. The reception phasing circuit forms a plurality of reception beams in the vertical direction corresponding to the depth in water or the depression angle from the horizontal. The signal of the reception beam in the horizontal direction is stored in the horizontal reception beam memory, and the signal of the reception beam in the vertical direction is stored in the vertical reception beam memory. On the basis of the arithmetic processing result of the plurality of reception beams formed in the vertical direction, the addition of the plurality of reception beams in the desired region of interest in the horizontal direction over a plurality of times of transmission of sound waves is performed.

A correlation coefficient for a predetermined time section of a plurality of reception beams formed in the vertical direction is obtained over a plurality of transmissions of sound waves. From this correlation coefficient, a relative time difference between the start points of the predetermined time section in the waveforms of a plurality of reception beams over a plurality of transmissions of sound waves is detected. After giving this relative time difference to a plurality of reception beams in a desired region of interest in the horizontal direction, addition is performed over a plurality of transmissions of sound waves. A correlation coefficient for a predetermined time section of a plurality of reception beams formed in the vertical direction is obtained over a plurality of times of transmission of sound waves. The relative time difference when the correlation coefficient is the largest among the plurality of obtained correlation coefficients is determined. After giving this relative time difference to a plurality of reception beams in a desired region of interest in the horizontal direction, addition is performed over a plurality of transmissions of sound waves.

A plurality of receiving beams formed in the vertical direction corresponding to the depth in water or the depression angle from the horizontal are arranged in a part or all of them in the order of their depth in the water or the depression angle from the horizontal. To the exponent. These two-dimensional correlation coefficients relating to the exponent corresponding to the depth and time are obtained. That is, a two-dimensional correlation coefficient between a plurality of reception beams formed in the vertical direction with respect to the vertical (depth or depression angle) direction and the time direction is obtained. The multiple 2 sought
After obtaining a relative time difference when the two-dimensional correlation coefficient is the largest among the two-dimensional correlation coefficients, and applying the relative time difference to a plurality of reception beams in a desired region of interest in the horizontal direction,
The addition is performed over a plurality of transmissions of the sound wave.

According to the present invention, in an underwater acoustic imaging device such as a sonar device and a fish finder, the problem that the correlation of signals between reception beams in a long distance portion easily deteriorates due to wind waves is solved. it can.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a view for explaining an embodiment in which the present invention is applied to a ship sonar device. The sonar device (not shown in FIG. 1) mounted under the draft of the ship 1 is a probe sound (sound wave).
Has the detection range 2 determined by the transmission of Within the detection range 2, horizontal reception beams 3-1, 3-2,..., 3-t,. ing.

The horizontal reception beams 3-1 to 3-n are transmitted to the sea surface 4
In order to catch the object 6 floating between the sea and the seabed 5, a predetermined depression angle is formed from a horizontal plane as a reference, and useful information such as a sonar image is formed based on an acoustic reflection signal from within the fan-shaped detection range 2.

According to the present invention, the vertical reception beam 8-1 extends along the vertical line 7 in the vertical direction of the horizontal reception beam 3-t in the portion where the object 6 exists or where the object 6 is suspected to exist.
~ 8-m is newly formed. In addition, the horizontal receive beam 3-
The vertical receiving beam 8-1 to 8-1 in that t also follows the vertical line 7.
8-m.

Although the vertical receiving beams 8-1 to 8 -m may not accurately follow the vertical direction due to the motion of the ship 1 at sea, the effect of the deflection motion such as rolling and pitching of the ship 1 is not practical. Above small.

FIG. 2 is a view for explaining the principle of the ship sonar apparatus according to the embodiment of the present invention. A search sound is emitted from a sonar device 9 mounted on the ship 1, and the sound ray paths 10-1, 1
It reaches the object 6 via 0-2, 10-3, 10-4 and the like. Also, it is considered that the path of the reflected signal also goes through a similar path. At the transmission time t1 of the search sound, the state of the sea surface is state 11
At the transmission time t2 of the probe sound, the state of the sea surface is state 11
-2.

At the transmission time t1 of the search sound, the sound ray path 10-
1, but at the transmission time t2 of the search sound, the sound ray path 10-
1 changes to form a sound ray path 10-2. On the other hand, in the sound ray path 10-3 that directly reaches the object 6 and the sound ray path 10-4 that reflects off the sea floor 5, the sound ray paths 10-1 and 10-2
The fluctuation of the sound ray path of the search sound is small as shown in Fig. 7, and the sound ray path of the search sound is stable.

In the formation of the horizontal reception beam 3-t shown in FIG. 1, the reception phasing is performed in a state where all of the sound ray path groups are added, so that the reflection signal from the object 6 and the phasing output are obtained. Is usually accompanied by reverberation from these multiple ray paths.

When the object 6 is floating near the sea surface or the like, the detection range 2, which is the formation range of the horizontal reception beam, must be formed with a small depression angle with respect to the horizontal plane. Of energy, sound ray path 10-
As shown in 1,10-2, the ratio of the energy reflected by receiving multiple reflections on the sea surface in the reciprocating path increases, and therefore, unless the wind wave class is particularly low, the state change of the sea surface 4 causes A horizontal reception beam is formed by a reflected signal having reverberation that is significantly different for each transmission, and an object 6 based on various acoustic information is formed.
Making it difficult to detect.

On the other hand, since the sea surface due to wind waves can be applied to a predetermined statistical model, it is assumed that the fluctuation of the round-trip path of the sound ray path of the search sound follows the statistics, and the reception obtained by transmitting the search sound a plurality of times. Statistical processing of the phasing output as it is is widely used, but it is not always advantageous in situations where the effects of wind waves are large and the correlation of the received waveforms obtained by multiple transmissions of the probe sound is significantly lost. No result.

In the present invention, attention is paid to the fact that the sound ray path near the sea surface is greatly affected by wind waves, and the vertical reception beams 8-1 to 8 -m are simultaneously formed at the time of reception, so that the influence of wind waves near the sea surface is reduced. It is characterized in that relative phase difference information among a plurality of vertical reception beams is extracted from information obtained by a small number of vertical reception beams, and this phase difference information is reflected in processing of a horizontal reception beam.

The extraction of the phase (time) difference information of the plurality of vertical reception beams obtained by transmitting the plurality of search sounds over the plurality of transmissions of the search sound is performed by extracting the reflection signal of the object 6 from the vertical reception beam. A correlation coefficient between vertical reception beams is calculated based on a phasing output signal of a predetermined waveform section including or a predetermined waveform section of a reception signal, and a phase difference that gives a maximum value of the correlation coefficient can be obtained. it can. Hereinafter, this processing will be specifically described.

First, the operator adds to the phasing output waveform of the horizontal reception beam 3-t obtained by the transmission of the i-th probe sound a time section of length tp including the estimated detection time tix of the object 6, ｛ tia, tib｝ (tia ≦ tix ≦ ti
b, tp = tib-tia) is set. Time section of phasing output waveform of vertical receiving beams 8-1 to 8-m, Δti
a, tib}, the waveform cut out from ui (t,
1) to ui (t, m). Similarly, the phasing output waveform of the horizontal reception beam 3-t obtained by the transmission of the j-th search sound indicates the detection estimated time tj of the object 6 by the operator.
a time interval of the same length tp including x, {tja, tjb}
(Tja ≦ tjx ≦ tjb, tp = tjb−tja) is set. Time sections of the phasing output waveforms of the vertical reception beams 8-1 to 8-m, and waveforms cut out from the {tja, tjb} portion are referred to as uj (t, 1) to uj (t, m).

The waveform of the k-th (k = 1 to m) vertical reception beam obtained by the transmission of the i-th and j-th search tones, ui (t, k) and uj (t, k) Correlation coefficient ρ between
ij (t, k) is calculated from (Equation 1) to (Equation 4). In (Equation 1) to (Equation 3), the integral ∫dτ is given by τ =
It is performed between 0 and τ = tp.

[0028]

## EQU1 ## Cii (t, k) = ∫ui (τ, k) ui (t−τ, k) dτ (Equation 1)

[0029]

Cjj (t, k) = ∫uj (τ, k) uj (t−τ, k) dτ (Equation 2)

[0030]

## EQU3 ## Cij (t, k) = ∫ui (τ, k) uj (t−τ, k) dτ (Equation 3)

[0031]

Ρij (t, k) = Cij (t, k) /） (Cii (0, k) Cjj (0, k)) (Equation 4) Time section set by operator, {ts, te} The maximum value mxk of the correlation coefficient ρij (t, k) in (k = 1 to
m) is obtained for all k.

Further, k which gives the maximum value among mxk (k = 1 to m) is determined. The time at which the maximum value mxk of the correlation coefficient ρij (t, k) is given for k at which the maximum value is given is t
mx (ts ≦ tmx ≦ te), i-th and j-th
The processing of the horizontal reception beam obtained by the transmission of the second search sound is performed with reference to tmx.

When m has a certain size,
Instead of calculating the one-dimensional correlation coefficients of (Equation 1) to (Equation 4), the following two-dimensional correlation coefficients of (Equation 5) to (Equation 8) may be used. In (Equation 5) to (Equation 7), the integral ∫dτ
Is performed between τ = 0 and τ = tp, and the addition Σ is k =
This is performed for 1 to k = m.

[0034]

C′ii (t, z) = Σ∫ui (τ, k) ui (t−τ, k−z) dτ (Equation 5)

[0035]

C′jj (t, z) = Σ∫uj (τ, k) uj (t−τ, k−z) dτ (Equation 6)

[0036]

C′ij (t, z) = Σ∫ui (τ, k) uj (t−τ, k−z) dτ (Expression 7)

[0037]

Ρ′ij (t, k) = C′ij (t, k) /） (C′ii (0, k) C′jj (0, k)) (Expression 8) (Expression 8) Defines a two-dimensional correlation coefficient ρ ′ ij (t, k) according to, a section of time, {ts, te}, and a section of z (index indicating the depth in water or the depression angle from the horizontal) set by the operator. , {Zs, ze}, the maximum value mx ′ of ρ′ij (t, k) in the area of the two-dimensional section is determined, and the time when the maximum value mx ′ is given is tmx (ts ≦ tm
x ≦ te). The calculation of the above correlation coefficient may be multiplied by a window function.

The processing of the phasing output waveform of the horizontal reception beam using the value of tmx can be realized by the processing described below.

The waveform y of the phasing addition output of the horizontal reception beams 3-1 to 3-n obtained by transmitting the i-th search sound
waveforms of phasing addition output of i (t, 1) to yi (t, n) and horizontal reception beams 3-1 to 3-n obtained by transmission of the jth search sound, yj (t, 1) ) To yj (t, n) when performing the processing of adding yj (t, 1) to yj (t, n).
n) from the time section {tja, tjb} by tmx.

If the ship 1 is traveling during transmission of each search sound, tmx includes a time difference determined by the transmission sound transmission cycle and the traveling speed. The value of tmx is a time interval,
Since it is a local thing determined only with respect to {tia, tib}, {tja, tjb}, the estimation accuracy of tmx deteriorates when it is applied to all points in the exhaustion area in the detection range. , Time interval, {tia, tib},
It is desirable to provide a plurality of time sections corresponding to {tja, tjb} and obtain tmx individually for each time interval.

FIG. 3 is a diagram for explaining an example of the arrangement of horizontal and vertical transducer elements according to the embodiment of the present invention. As shown in FIG. 1, since it is necessary to form the horizontal reception beams 3-1 to 3-n and the vertical reception beams 8-1 to 8-m, the transducer elements arranged in the horizontal direction and the vertical direction are required. Become.

In FIG. 3, the horizontal transducer 12 corresponds to FIG.
Horizontal transmitting / receiving elements 13-1, 13-2, 13-3 to 13-p electrically connected to the transmitting / receiving circuit 16 shown in FIG.
Is provided. The horizontal transducer 12 is arranged such that the arrangement direction of the horizontal transducers 13-1 to 13 -p is horizontal with respect to the body (not shown in FIG. 3) of a ship or a cruising body that is stationary in still water. Controlled.

The vertical transducer 14 is a vertical transducer 1 electrically connected to the transmission / reception circuit 16 shown in FIG.
5-1, 15-2, 15-3 to 15-q. The vertical transducer 14 is used for the vertical transducer element 1 (not shown in FIG. 3) of a ship or a cruising body (not shown in FIG. 3) which is stopped by still water.
Control is performed so that the arrangement directions of 5-1 to 15-q are included in a plane including a predetermined vertical line.

The horizontal transducer 12 and the vertical transducer 14 are
It may be fixed to the body of the ship or the cruising body by a sway stabilizing mechanism that cancels the sway of the ship. In addition, since it is only necessary to form a plurality of beams in the vertical and horizontal directions, the horizontal transmitting and receiving elements 13-1 to 13-
p, a vertical transducer element 15 that constitutes the vertical transducer 14-
It is not essential that 1 to 15-q be linearly arranged one-dimensionally as in the example shown in FIG.

For example, the sound transmitting and receiving surfaces of the transmitting and receiving elements may be arranged two-dimensionally on a predetermined plane or curved surface in a vertical or horizontal manner, or may be two-dimensionally arranged so as to be unequally distributed in a vertical or horizontal direction. Needless to say, it is good.

FIG. 4 is a diagram for explaining a configuration example of a sonar device according to an embodiment of the present invention. Horizontal transducer 1 shown in FIG.
2. The vertical transducer 14 is connected to the transmission / reception circuit 16. The transmission / reception circuit 16 drives a plurality of transmission / reception elements constituting the horizontal transducer 12 and the vertical transducer 14 to emit a sound wave (probing sound) into water (not shown in FIG. 4). And a receiving circuit (not shown in FIG. 4) for receiving a signal generated by the transmitting / receiving element in response to a reflected sound from underwater by a plurality of transmitting / receiving elements constituting the horizontal transducer 12 and the vertical transducer 14 respectively. ).

The transmission circuit (not shown in FIG. 4) of the transmission / reception circuit 16 drives the transmission / reception elements of the horizontal and vertical transducers 12 and 14 according to the command of the transmission phasing circuit 17. The reception phasing circuit 18 receives a signal received by a reception circuit (not shown in FIG. 4) of the transmission / reception circuit 16, and performs phasing and addition processing for controlling at least a phase or a delay time to perform vertical reception shown in FIG. Beams 8-1 to 8 -m are formed, and the results are stored in the vertical reception beam memory 19.
1 to 3 -n are formed and the result is stored in the horizontal reception beam memory 20.

The correlation operation device 21 includes an operation device constituted by a microprocessor or the like, and performs an operation of a correlation coefficient represented by (Equation 1) to (Equation 8) and an operation of detecting a time difference tmx.

The arithmetic processing unit 22 receives the time difference tmx from the correlation arithmetic unit 21 and inputs the time difference tmx to the horizontal reception beam memory 20.
, The waveform of the time section to which the time difference tmx is applied is read out from the waveform of the reception beam, and the addition with the time shifted between the reception beam waveforms obtained by transmitting the search sound is repeated. The addition result is visualized by the display device 23. The correlation calculation device 21 may be omitted, and the calculation processing device 22 may execute a calculation process to be performed by the correlation calculation device 21.

The operation of all the components except for the horizontal transducer 12 and the vertical transducer 14 shown in FIG. 4 is controlled by a control device (not shown in FIG. 4) which regulates the operation of the entire apparatus. Further, the arithmetic processing device 22 may be configured to perform control to be executed by the control device.

[0051]

According to the present invention, it is possible to efficiently reduce the influence of changes in the state of the sea and the sea surface, to add the received beams by a plurality of transmissions and receptions, and to reduce the influence of the change in the sea surface wind conditions. It is possible to provide an underwater acoustic imaging apparatus capable of sufficiently obtaining the effect of adding the reception beams.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an embodiment in which the present invention is applied to a ship sonar device.

FIG. 2 is a diagram illustrating the principle of a ship sonar device according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating an example of the arrangement of horizontal and vertical transducer elements according to an embodiment of the present invention.

FIG. 4 is a diagram illustrating a configuration example of a sonar device according to an embodiment of the present invention.

[Explanation of symbols]

1 ship, 2 detection range, 3-1 to 3-n horizontal reception beam, 4 sea surface, 5 sea floor, 6 object, 7 vertical line, 8-
1 to 8-m: vertical receiving beam, 9: sonar device, 10
-1 to 10-4: sound ray path, 11-1, 11-2: state of the sea surface, 12: horizontal transducer, 13-1 to 13-p: horizontal transducer, 14: vertical transducer, 15-1 to 15-
q: vertical transmission / reception element, 16: transmission / reception circuit, 17: transmission phasing circuit, 18: reception phasing circuit, 19: vertical reception beam memory, 20: horizontal reception beam memory, 21: correlation operation device, 22: arithmetic processing Device, 23 ... Display device.

Claims (4)

[Claims] 1. A horizontal transducer comprising a transmitting / receiving element arranged in a horizontal direction, a vertical transducer comprising a transmitting / receiving element arranged in a vertical direction, and the horizontal and vertical transducers. A transmission / reception circuit for driving the transmission / reception element to transmit a sound wave and receive a reflected sound; and a plurality of reception signals in the horizontal and vertical directions from signals received by the transmission / reception elements of the horizontal and vertical transducers. Receiving phasing circuit for forming a beam, storage means for storing the output of the receiving phasing circuit over a plurality of transmissions of sound waves, and processing the waveforms of the plurality of reception beams read from the storage means An arithmetic processing unit for performing the processing in the horizontal direction based on the result of the arithmetic processing of the signals related to the plurality of reception beams formed in the vertical direction over a plurality of transmissions of the sound waves. The plurality of receiving Underwater Acoustic imaging apparatus characterized by a plurality of times summation over the transmission of sound waves of the beam. 2. The underwater acoustic imaging apparatus according to claim 1,
The arithmetic processing unit obtains a correlation coefficient for a predetermined time section between the plurality of reception beams formed in the vertical direction over a plurality of transmissions of sound waves, and is formed in the vertical direction from the correlation coefficient. Detecting a relative time difference between the plurality of receiving beams over a plurality of transmissions of the sound waves,
An acoustic imaging apparatus, wherein the relative time difference is given to the plurality of reception beams formed in the horizontal direction, and addition is performed over a plurality of transmissions of sound waves. 3. The underwater acoustic imaging apparatus according to claim 2,
The wave receiving phasing circuit forms the reception beam with respect to the plurality of depression angles in the vertical direction, and the arithmetic processing unit performs a predetermined operation on each of the reception beams with respect to the plurality of depression angles formed in the vertical direction. A correlation coefficient for a time section is determined over a plurality of transmissions of sound waves, and a relative time difference is determined from the correlation coefficient of the reception beam having the maximum value among the plurality of correlation coefficients. An acoustic imaging apparatus, wherein the addition is performed over a plurality of times of transmission of a sound wave by giving to the plurality of reception beams in the horizontal direction. 4. The underwater acoustic imaging apparatus according to claim 2,
The wave receiving phasing circuit forms the reception beam for the plurality of vertical depression angles, and the arithmetic processing unit causes the plurality of reception beams formed in the vertical direction to correspond to an index with respect to the depression angle, A two-dimensional correlation coefficient relating to the index and the time corresponding to the depression angle is obtained between the plurality of reception beams formed in the vertical direction, and the two-dimensional correlation coefficient among the plurality of two-dimensional correlation coefficients is determined. An acoustic imaging apparatus characterized in that a relative time difference in the case of the largest is obtained, the relative time difference is applied to the plurality of reception beams in the horizontal direction, and addition is performed over a plurality of transmissions of sound waves.