JPH11337639A - Synthetic aperture sonar - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a synthetic aperture sonar, in which an aperture is synthesized after a phasing beam is created and in which an image of high resolution is obtained by a method, wherein the aperture is synthesized by using information from a position detecting device in an echo video receiver. SOLUTION: An echo sounder receiver, a beam forming device, a device which detects the position of the echo sounder receiver, a device which synthesizes an aperture and a display device form a synthetic aperture sonar. A waveform at which waves are transmitted is generated by a waveform generation part, the transmitted waves are amplified by a power amplifying part, and the waves are transmitted by a wave transmitting array through a transmission-reception changeover part. A signal in which sound waves are received by a receiving array is passed through the transmission-reception changeover part, and it is then amplified by receiving, amplifying and filtering parts, and a phasing processing operation is performed by a phasing part. After that, the signal is processed by a signal-processing and image-reproducing part, and its result is displayed on a control and display part. In the case of a synthetic aperture sonar, an aperture synthesis part is installed between the signal-processing and image-reproducing part and the control and display part. An aperture is synthesized by the aperture synthesizing part. Its result is displayed with high resolution on the control and display part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an underwater sonar and, more particularly, to a synthetic aperture sonar for synthesizing received wave data obtained at an actual aperture to improve the azimuthal resolution higher than the resolution obtained at the actual aperture.

[0002]

2. Description of the Related Art The idea of a synthetic aperture sonar for synthesizing several actual apertures and obtaining a high azimuth resolution has existed for a long time. However, in order to combine the actual apertures, the actual apertures must be arranged on a straight line called the baseline, but since the marine vessel is shaken, the actual aperture mounted on the vessel is arranged on the baseline. It was difficult to do. For this reason, the practical use of the synthetic aperture sonar has been difficult.

[0003] In order to solve such a problem, there has been proposed a method of alleviating the sway of a sonar. For example, the method described in Japanese Patent No. 2609551 discloses a method in which a part of an actual aperture is overlapped to receive a wave, the sway is corrected based on information obtained in the overlapped part, and a new line is placed on a baseline. This is a method of obtaining high resolution by arranging information obtained from the actual aperture and synthesizing the actual aperture.

[0004]

The above-described method is a method in which a real aperture can be synthesized by overlapping a part of the real aperture. With this method, a high azimuth resolution can be obtained, but an output signal for each receiver is indispensable, and a synthetic aperture using a phasing beam cannot be obtained.

It is an object of the present invention to provide a high-resolution image by synthesizing an aperture after producing a phasing beam.

[0006]

In order to achieve the above object, a synthetic aperture sonar according to the present invention repeats transmission and reception at least twice or more, synthesizes the signals of the respective receptions, and executes the synthesis. In a sonar that obtains an image with a resolution higher than the resolution obtained at the aperture, a device that detects the position of the receiver, a beam forming device that processes the signal from the receiver to detect the direction of the sound wave, and the result of the beam forming It comprises a display device for displaying, and has a feature of synthesizing the aperture using information from the position detector of the receiver.

A sonar for transmitting and receiving waves at least twice or more, and synthesizing the signals of the respective received waves to obtain an image having a resolution higher than the resolution obtained by an actual aperture; Consists of a beamforming device that processes the signal from the receiver to detect the direction of the sound wave, and a display device that displays the result of the beamforming, performs beamforming while partially overlapping the receiver, The position of the receiver at the time of performing beam forming is detected from the detecting device, and the detected information is used to synthesize the aperture.

A sonar for detecting a position of a receiver in a sonar for repeating transmission and reception at least twice or more and synthesizing signals of each reception to obtain an image having a resolution higher than a resolution obtained by an actual aperture; A beamforming device that processes signals from a receiver to detect the direction of a sound wave, a device that synthesizes apertures by synthesizing the results of each beamforming, and a beamforming device or synthesizes apertures. It performs a beamforming of the received wave while overlapping a part of the receiver, detects the position of the receiver at the time of performing the beamforming from the detection device, and The method includes performing phase correction using information and performing aperture synthesis.

A sonar for detecting a position of a receiver in a sonar for performing transmission and reception at least twice or more and synthesizing signals of each reception to obtain an image having a resolution higher than the resolution obtained by an actual aperture; It consists of a beam forming device that processes the signal from the receiver to detect the direction of the sound wave, and a display device that displays the result of beam forming or the result of combining apertures. Perform beam forming while wrapping, detect the position of the receiver at the time of performing the beam forming from the detection device, and perform correction corresponding to the phase difference between the receivers using the position information of this receiver. , Combining apertures.

[0010]

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

FIG. 1 is a basic block diagram of the present invention. The present invention relates to a receiver, a beam forming device,
It consists of a device for detecting the position of the receiver, a device for synthesizing the aperture, and a display device.

FIG. 2 is an example of a diagram showing the entire configuration of the present invention. First, the procedure for transmitting waves will be described. A waveform to be transmitted is generated by the waveform generation unit, the transmission is amplified by the power amplification unit, and transmitted from the transmission array through the transmission / reception switching unit.
Next, the receiving procedure will be described. The signal that receives the sound wave in the wave receiving array passes through the transmission / reception switching unit, is amplified by the reception amplification / filtering unit, and is subjected to phasing processing by the phasing unit. After this, the signal processing / video playback section is usually performed, and then the control /
The result is displayed on the display unit. Here, in the case of the synthetic aperture sonar, an aperture synthesizing unit is provided between the signal processing / video reproduction unit and the control / display unit, where the apertures are synthesized, and the result is obtained by the control / display unit. High-resolution display is performed.

With such a hardware configuration, high azimuth resolution is realized by the following method.

First, when the receiver array can be moved on a straight line without fail, a high azimuth resolution can be realized by adding the results of beamforming obtained at each position as they are. However, the receiver cannot actually move on a straight line due to the influence of waves or the like.

The attitude of the receiver can be controlled by using an attitude control device. For this reason, as shown in FIG. 3, while receiving the attitude of the receiver, the reception is performed while partially overlapping the receiver. In this figure, first, the aperture is at the position A, and then a part of the aperture is overlapped and the wave is received at the position B, and the distance difference between A and B is δ. The portion of the receiver where the opening A overlaps is referred to as OA, and the overlapping portion of the opening B is referred to as OB. Receiving position A, B
After the phasing beams are created by the above, the addition of these beams is performed as shown in FIG.

Since the distance between the receiving positions A and B is δ,
A phase difference corresponding to this distance difference is obtained. Assuming that the phase difference is Φ and the wavelength used for transmission is λ, Φ can be obtained by the following equation.

[0017]

Φ = δ / λ (1) A product obtained by multiplying the phase difference obtained at the aperture position B by this phase difference is defined as FBΦ. The phasing beam FA obtained at the opening position A
If this FBΦ is added to this, the aperture can be synthesized.

Here, it is also possible to change the sign of the phase difference Φ, multiply the phasing beam obtained at the position of the aperture A, and add it to the phasing beam obtained at the aperture B. In this way, the aperture synthesis is performed on the extension of the aperture B. The result is displayed in the range of the azimuth corresponding to the synthetic aperture length. By performing such processing, a higher azimuth resolution can be obtained as compared with the actual aperture.

As described above, when the apertures are synthesized, the received signals received at the overlapping portion are added twice, but this is equivalent to shading, so that there is no need to add any signal. No problem.

If it is not desired to perform such shading, a value obtained by forming a beam at the overlapped portion may be subtracted from the result of beamforming of one of the reception positions A and B. It is assumed that the overlapping portion is obtained from the beam forming performed at the receiving position B and the aperture synthesis is performed.

Since the beam forming in the overlap portion V is considered to be a proportional distribution of the aperture length, if the result of the beam forming in this portion is OV, the OV can be expressed by the following equation.

[0022]

OVB = FBΦ × OB / L (2) In the above (2), L indicates the opening length. Value FB obtained by subtracting OV from beam forming result FB at opening position B
If the phase difference Φ between the opening positions AB is corrected to −OV and added to FA, it means that the apertures have been synthesized. The azimuth resolution at this time is in a range corresponding to the synthetic aperture length 2L-OV.

In this method, the data of the aperture received at the aperture position B is corrected to synthesize the apertures. Similarly, the data of the aperture received at the aperture position A is corrected. There is no problem.

There is also a method of correcting both data of the opening positions A and B. This method is a method of correcting an overlapping portion between the opening positions A and B, adding the corrected data, and synthesizing the opening. The correction value as a result of the beam forming of the overlapping portion can be obtained as follows. This method is shown in FIG.

First, the phase is corrected by multiplying the equation (2) by the phase difference Φ. The result of this phase correction is defined as FBΦ. The beam forming of the overlapping portion at the opening position A is obtained by the following equation when it is obtained in the same manner as the beam forming result of the overlapping portion obtained at the opening position B.

[0026]

OVA = FA × OA / L (3) The correction amount OV of the overlap portion is calculated from FBΦ and OVA by the following equation.

[0027]

OV = ４ (OVA + OVB) (4) Therefore, the result of the synthesis can be obtained by the following equation.

[0028]

## EQU5 ## FA + FBΦ-OV (5) In the above description, the base line for performing the synthetic opening is set on the extension of the opening position A, but the same applies when the base line is set on the extension of the opening position B. Discussion is possible. By performing the synthesis of the apertures a plurality of times in this manner, higher azimuth resolution can be realized.

The attitude control device can be realized using a GPS system, a gyroscope attached to a receiver, or the like.

[0030]

According to the present invention, an image having a high azimuth resolution can be provided by synthesizing apertures using phasing beams.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a synthetic aperture sonar according to an embodiment of the present invention.

FIG. 2 is a block diagram of the flow of the acoustic signal and the opening attitude information of FIG. 1;

FIG. 3 is a diagram showing the position of a conventional baseline.

FIG. 4 is a flowchart illustrating a method of aperture synthesis according to the present invention.

FIG. 5 is a flowchart illustrating a method of aperture synthesis according to the present invention.

[Explanation of symbols]

 100: actual aperture, δ: distance difference.

Claims (1)

[Claims] 1. A sonar for transmitting and receiving waves repeatedly at least twice or more, and for synthesizing signals of the respective received waves to obtain an image with a resolution higher than the resolution obtained by an actual aperture, detects a position of a receiver. A device, a beam forming device that processes the signal from the receiver to detect the direction of the sound wave, and a display device that displays the result of the beam forming, using information from the position detector of the receiver, Synthetic aperture sonar characterized by performing aperture synthesis.