JP4810810B2 - Sonar method and underwater image sonar - Google Patents

Description

  The present invention relates to an underwater image sonar, and more particularly to an underwater image sonar that obtains a front image of a target by frequency-separating reflected sound generated when a transmitted sound hits a target.

  This type of conventional underwater image sonar has M receiving waves that receive reflected sound reflected from an underwater target with respect to N linearly arranged transmitters that transmit the transmitted sound underwater. The transducers are arranged orthogonally so as to form a cross shape with the arrangement of the transmitters.

  In addition, this prior art operation linearly changes the frequency of the transmission sound over a predetermined time in a predetermined range, and also changes the direction of the transmission beam linearly in the predetermined range over the same predetermined time. I am going to do that. In other words, an acoustic signal (fan beam) that spreads a wide fan is sent from the top to the bottom while changing the direction of transmission, and the acoustic signal is transmitted, and the reflected sound from the target is converted into a number of vertical lines that are shifted in angle in the horizontal direction. Receive with a wide fan beam. The vertical direction is divided based on the difference in frequency, and the horizontal direction is divided based on the angle of the received beam, thereby producing a highly accurate image. (For example, refer to Patent Document 1).

  However, in order to obtain a clear image, it is necessary to increase the number of reception beams, so that the processing of the reception signal increases, and thus the CPU (DSP) processing time increases. There is also a problem that power consumption increases.

Japanese Patent Laid-Open No. 10-132930

  The conventional underwater image sonar described above has a drawback in that the number of received beams needs to be increased in order to obtain a clear image, so that processing of received signals increases and processing time increases.

  An object of the present invention is to remove such conventional drawbacks by transmitting signals with orthogonally arranged transmitters having different frequency bands, demapping the received frequencies for each frequency band in a matrix, and receiving beams. It is an object to provide an underwater image sonar capable of high-speed processing by reducing the number of received beams and reducing the amount of data processing.

  The sonar method of the present invention has a plurality of transmitters arranged linearly and orthogonally, assigns different frequency bands to each array, and performs acoustics at frequencies mapped in a matrix in synchronization with switching of the transmission beam direction. A signal is transmitted, the acoustic signal reflected from the target is received by a receiver corresponding to each frequency band, and a combination of the received frequencies is demapped to orthogonal coordinates based on each frequency band to receive a beam. It is characterized by recognizing directions.

  In addition, the sonar method of the present invention has a plurality of transmitters arranged linearly and orthogonally, assigns different frequency bands to each array, and maps frequencies in a matrix in synchronization with switching of the transmission beam direction. The acoustic signal is transmitted, the acoustic signal reflected from the target is received by a receiver corresponding to each frequency band, and the combination of the received frequencies is demapped to orthogonal coordinates based on each frequency band, The received frequency is multiplied between each frequency band, weighted based on the magnitude of the frequency component as a result of multiplication, and the target image is obtained from the received beam direction and weighted result by demapping. It is said.

  The plurality of transmitters may be of a cross fan beam system composed of one row in each horizontal / vertical direction.

  Moreover, the said receiver is comprised by two omnidirectional receivers corresponding to each frequency band, It is characterized by the above-mentioned.

  Further, the weighting is characterized by a single color shading or multicolor combination based on the size of the frequency component.

  The underwater image sonar according to the present invention scans a plurality of transmission means for radiating a transmission sound underwater, and a transmission beam direction of the transmission sound radiated from the plurality of transmission means, and is synchronized with the scanning. Control means for controlling the frequency of the transmitted sound gradually and continuously, two receiving means for receiving the reflected sound obtained by reflecting the transmitted sound by a target and converting it into an electrical signal, Multiplication means for multiplying the respective signals output from the two receiving means, frequency separation means for classifying the frequencies output from the multiplication means, and detecting the level for each classified frequency component, and each classification And a target detection processing unit that generates image data from the detected frequency and the detected level, and a display unit that displays the image data.

  Further, the wave transmitting means is composed of a plurality of wave transmitters arranged orthogonally in a straight line, and is characterized in that different frequency bands are assigned in the horizontal direction and the vertical direction.

  The transmission means transmits acoustic signals at frequencies mapped in a matrix in synchronization with switching of the transmission beam direction.

  Further, the wave receiving means is characterized by comprising two omnidirectional wave receivers corresponding to each frequency band.

  The image data may be obtained from a single color shading or a multicolor combination based on a level detected for each frequency component.

  According to the sonar method and the underwater image sonar of the present invention, signals are transmitted by transmitters of orthogonal arrangements having different frequency bands, and the received frequencies for each frequency band are demapped in a matrix form to obtain a reception beam direction. As a result, the number of received beams can be reduced and the amount of data processing can be reduced.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the underwater image sonar of the present invention. FIG. 1A shows a transmission unit, and FIG. 1B shows a reception unit.

  The underwater image sonar of the present embodiment shown in FIG. 1 includes a transmission unit including a transmission control unit 1, a beam shift 2, a power amplification unit 3, and a transmitter 4. The receiving unit includes a receiver 5, a preamplifier 6, a band limiter 7, an A / D converter 8, a multiplier 9, a band limiter 10, an FFT (Fast Fourier Transform) 11, and a target detector 12. It is configured to include.

  Next, the operation of the best mode for carrying out the present invention will be described with reference to the drawings. First, the transmission unit will be described.

  The transmission control unit 1 generates a frequency modulation signal 101 (excitation signal) in different frequency bands (F band, f band) and outputs it to the beam shift 2, and also controls the phase shift amount with respect to the beam shift 2. A control signal 102 is output. This phase shift amount is set so that the required transmission beam direction can be obtained together with the variable step of the transmission frequency every time the transmission beam direction is switched.

  In the beam shift 2, the excitation signal 101 and the phase control signal 102 are input from the transmission control unit 1, and each phase shifter (X direction x1 to xi, Y direction y1 to yj) corresponding to the number of transmitting elements is arranged. On the other hand, phase control for determining the transmission beam direction is performed, and each of the phase-controlled signals 201 is sent to the power amplifying unit 3.

  The power amplifying unit 3 amplifies each of the phase-controlled signals 201 to a predetermined level, and sends a transmission waveform 301 to each of the transmission elements constituting the transmitter 4.

  The transmitter 4 includes transmission elements (X direction x1 to xi, Y direction y1 to yj) arranged in the X (horizontal) direction and the Y (vertical) direction, and converts the transmission waveform 301 into an acoustic signal. Are supplied to the transmitting elements in the X direction array and the Y direction array. Each array element radiates transmission sound (acoustic signal) 401 into the water in the transmission beam direction based on a predetermined scanning procedure in a two-dimensional space by controlling the transmission beam direction in the X direction and the Y direction, respectively. That is, the plurality of transmitters are configured as a cross fan beam system composed of one row in each horizontal / vertical direction.

  Next, the receiving system will be described. The receiver 5 receives the reverberant sound reflected by the transmitted acoustic signal 401 from the target by the receiving elements 51 and 52 for reception in the F band and the f band, respectively, and receives the electric signal. Convert to 501.

  The preamplifier 6 outputs a waveform 601 obtained by amplifying each of the electric signals 501 to a predetermined level.

  The band limiting unit 7 extracts the respective signal bands of the input waveform 601 using the filters 71 and 72 for the F band or the f band, and sends them to the A / D conversion unit 8.

  The A / D conversion unit 8 converts the analog signal 701 into a digital signal 801.

  The multiplier 9 outputs a signal 901 obtained by multiplying the frequency signals of the F band and the f band.

  The band limiter 10 uses only a high-frequency signal 1001 using, for example, a high-pass filter from the high-frequency | F + f | band and the low-frequency | F−f | band included in the signal 901 output from the multiplier 9. Take out. Here, | F−f | indicates the absolute value of F−f, and in the case of the relationship of F <f, it becomes a low-frequency f−F band.

  The FFT 11 separates frequency components from the high frequency signal 1001 output from the band limiter 10.

  The target detection unit 12 weights the input data 1101 according to the level of each separated frequency component, and converts it into color or shade information. Further, an image is generated by arranging in a matrix based on whether each frequency component is a combination of the F band and the f band. The generated image is displayed by a display (display means) (not shown).

  With the above configuration, on the transmission side, the acoustic signals are transmitted by mapping the transmission beam direction and the set frequencies of two different frequency bands in a matrix using the transmitters arranged linearly and orthogonally. On the receiving side, the received beam direction is recognized by demapping the received frequencies for each frequency band in a matrix. Therefore, since it is not necessary to generate a plurality of reception beams on the reception side, the reception processing amount such as directivity synthesis of the reception beam and the FFT processing amount are reduced, and the load on the CPU (DSP) can be reduced.

  Next, the operation of the present embodiment will be specifically described. FIG. 2 is a schematic diagram showing an example of the arrangement of the transmitting elements and the receiving elements constituting the transmitter 4 and the receiver 5 shown in FIG. FIG. 3 is a diagram for explaining the scanning direction of the transmission beam.

  According to FIG. 2, on the transmission side, X (horizontal) direction transmitting elements (x1 to x8) and Y (vertical) direction transmitting elements (y1 to y9) are arranged. The transmission elements (x1 to x8) arranged in the X direction are phase-controlled by the beam shift 2 so that the transmission beam directions (ψ1 to ψn) are shifted in the horizontal direction, as shown in FIG. As shown in FIG. 3B, the phase of the transmitting elements (y1 to y9) arranged in the Y direction is similarly controlled by the beam shift 2 so that the transmitting beam direction (θ1 to θm) is shifted in the vertical direction. .

  In addition, the transmission elements (x1 to x8) arranged in the X direction are linearly switched within the f band range (f1 to fn) according to the horizontal direction (ψ1 to ψn), In the transmission elements (y1 to y9) arranged in the Y direction, the transmission frequency is linearly switched in the F band range (F1 to Fm) according to the vertical directions (θ1 to θm).

  Here, m and n correspond to the number of dots (resolution) when an image is displayed, and are arbitrarily set. Further, although the number of transmitting elements in the X direction and Y direction (X direction x1 to xi, Y direction y1 to yj) on the transmission side is set to x1 to x8 and y1 to y9, it is not particularly limited. The frequencies f1 to fn and F1 to Fm are selected so that the frequency components after the output of the multiplier 9 do not match.

  On the one receiving side, as shown in FIG. 2, receiving elements 51 and 52 for F band and f band are arranged. Since the wave receiving elements 51 and 52 are non-directional elements, an arrangement like a wave transmitting element is not required and the position is not limited.

  Next, a transmission procedure will be described. FIG. 4 is a time chart for explaining the transmission procedure. FIG. 5 is a diagram illustrating an irradiation image on the target. FIG. 6 is a diagram illustrating a spectrum of each frequency according to the reception level. FIG. 7 is a diagram showing a frequency array of the FFT processing result.

  According to FIG. 4, in the period t1 in the transmission period T1, first, the transmitting elements (y1 to y9) arranged in the Y direction are set in the transmission beam direction θ1 at the frequency F1. At this time, the transmitting elements (x1 to x8) arranged in the X direction are sequentially shifted from the transmission beam direction ψ1 to the transmission beam direction ψn at the timing of sequentially switching the frequency from f1 to fn.

  Next, in the period t2, the transmission elements (y1 to y9) arranged in the Y direction are set in the transmission beam direction θ2 at the frequency F2. During this period, the transmitting elements (x1 to x8) arranged in the X direction sequentially change the frequency from fn to f1 and in the opposite direction to the period t1, and sequentially from the transmission beam direction ψn to the transmission beam direction ψ1. Shifted.

  Thus, the transmission elements (y1 to y9) arranged in the Y direction are sequentially set from the transmission beam direction θ1 (frequency F1) to the transmission beam direction θm (frequency Fm) in the transmission period T1 (t1 to tm). Is done. During this time, the elements arranged in the X direction for each set direction in the Y direction are switched from the frequency f1 to the frequency fn and from the frequency fn to the frequency f1, and are switched at the timings. The signals are sequentially shifted from the transmission beam direction ψn to the transmission beam direction ψ1.

  As a result of the above operation, as shown in FIG. 5, the transmission sound in which the transmission beam direction is mapped in two frequency bands, that is, f1 to fn in the horizontal direction and F1 to Fm in the vertical direction is irradiated to the target.

  Next, in the reception period R1 shown in FIG. 4, the receiving-side receiving elements 51 and 52 randomly receive the reverberation sounds of the frequencies f1 to fn and F1 to Fm in the F band and the f band, respectively.

  The signal received by the receiver 5 is amplified by the preamplifier 6, and then only a necessary band (F band or f band) is taken out by the band limiter 7, and is converted into a digital signal by the A / D converter 8. Is converted to The A / D converted signal is input to the multiplier 9, and frequency components in the high frequency F + f band and the low frequency Ff band are generated by multiplying the F band signal and the f band signal. . Of these, for example, by extracting only the high band with the band limiter 10 and separating the predetermined frequency with the FFT 11, a spectrum of each frequency according to the reception level can be obtained as shown in FIG. At this time, the extracted high frequency (F + f band) is arranged as shown in FIG.

  Next, how an image is reproduced will be described. FIG. 8 is a diagram illustrating an image after the FFT processing.

  As shown in FIG. 5, the reflected sounds of the F-band transmitted sound and the f-band transmitted sound irradiated to the target are received. In FIG. 5, when the transmission sound having the frequency F4 on the Y axis reverberates to the target, if there is reverberation from the target even at f6, a strong reception level can be obtained by the combination of (F4, f6) on the matrix. Similarly, a strong reception level can be obtained with each combination if the echoes f3 to f8 at F5 and f3 to f8 at F6. By performing processing based on the reception level due to this echo, an image as shown in FIG. 8 can be obtained. Furthermore, if the weighting of the shade according to the reception level or the color (color classification) process is performed, a clearer (high accuracy) target image can be obtained.

  As described above, on the transmission side, the transmitter has transmitters arranged orthogonally in a straight line, two different frequency bands f1 to fn and F1 to Fm are assigned to each array, and the transmission beam direction and frequency are matrixed. The sound signal is transmitted by mapping in the shape.

  On the receiving side, the signals are received by two non-directional receiving elements corresponding to f1 to fn and F1 to Fm, and the target direction is identified using each frequency combination of the two frequency bands as information. Thus, the target direction (position) can be determined only from the reception frequency. Therefore, it is not necessary to generate a reception beam, the reception processing amount or the FFT processing amount is reduced, and the load on the CPU (DSP) can be reduced.

  Furthermore, by multiplying the frequency received between each frequency band and performing weighting or color (coloring) processing according to the magnitude of the frequency component resulting from the multiplication, a clearer (higher accuracy) target Images can be obtained.

  In the above description, a floating target is assumed. However, for example, when the target is the sea floor, transmission in the vertical (Y) direction can be omitted by substituting the time axis (distance). FIG. 9 is a block diagram showing a reception system when transmission in the vertical (Y) direction is omitted.

  According to FIG. 9, since reception is performed only in the f band, the configuration up to FFT 11 shown in FIG. 1B is simplified, and the number of reception system circuits can be further reduced.

  In the present embodiment shown in FIG. 1B, after multiplying two frequency bands, an HPF (high pass filter) is used to extract a high frequency after multiplication. It can also be realized by taking out a low frequency instead of.

It is a block diagram which shows one embodiment of the underwater image sonar of this invention. It is a schematic diagram which shows an example of the arrangement | sequence of the transmitting element and receiving element which comprise the transmitter 4 and the receiver 5 which are shown in FIG. It is a figure for demonstrating the scanning direction of a transmission beam. It is a time chart for demonstrating a transmission procedure. It is a figure which shows the irradiation image to a target. It is a figure which shows the spectrum of each frequency according to a reception level. It is a figure which shows the frequency arrangement | sequence of a FFT process result. It is a figure which shows the image after a FFT process. It is a block diagram which shows a receiving system when transmission in the vertical (Y) direction is omitted.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmission control part 2 Beam shift 3 Power amplifier 4 Transmitter 5 Receiver 6 Preamplifier 7 Band limiting part 8 A / D conversion part 9 Multiplier 10 Band limiter 11 FFT
12 Target detector

Claims (8)

Generating a frequency modulation signal of the first frequency band and the second frequency band;
Transmitting an acoustic signal of the same frequency in the first frequency band in the X (horizontal) direction;
Transmitting an acoustic signal of the same frequency in the second frequency band in the Y (vertical) direction;
The acoustic signal reflected from the target is received by a receiver corresponding to each frequency band,
Recognizing a received beam direction based on a combination of a frequency band of the received acoustic signal and a direction in which the acoustic signal is transmitted;
A sonar method characterized by that. Generating a frequency modulation signal of the first frequency band and the second frequency band;
Transmitting an acoustic signal of the same frequency in the first frequency band in the X (horizontal) direction;
Transmitting an acoustic signal of the same frequency in the second frequency band in the Y (vertical) direction;
The acoustic signal reflected from the target is received by the receiver corresponding to each frequency band,
Based on the combination of the received frequency band and the direction in which the acoustic signal was transmitted,
Characterized in that the reception was a frequency band multiplied respectively between each frequency band, it is weighted based on the size of the frequency component of the result of multiplying to obtain an image of more the target and the weighting result and the received beam direction And sonar method. 3. The sonar method according to claim 1, wherein the acoustic signal is transmitted by a cross fan beam system comprising one row in each of horizontal / vertical directions. The sonar method according to claim 1 or 2, wherein the receiver comprises two omnidirectional receivers corresponding to each frequency band. 3. The sonar method according to claim 2, wherein the weighting is a single color shading or multicolor combination based on the magnitude of the frequency component. It consists of a plurality of transmitters arranged in a straight line and orthogonally, and assigns different frequency bands and transmission beam directions in the horizontal direction and vertical direction to the transmitter, and radiates the transmission sound of the frequency bands in the beam direction. Transmission means,
Control means for scanning the direction of the transmission beam of the transmitted sound radiated from the plurality of transmission means, and controlling the frequency of the transmitted sound gradually and continuously in synchronization with the scanning;
Two receiving means for receiving the reflected sound obtained by reflecting the transmitted sound by the target and converting it into an electrical signal;
Multiplication means for multiplying the respective signals output from the two receiving means and outputting frequency components of the high frequency F + f band and the low frequency Ff band;
Frequency classification means for classifying frequency components output from the multiplication means and detecting a reception level for each of the classified frequency components;
Target detection processing means for generating image data from a single color shading or multicolor combination based on the classified frequency and the detected level; and display means for displaying the image data;
An underwater image sonar characterized by comprising: The underwater image sonar according to claim 6, wherein the plurality of transmission units transmit acoustic signals at frequencies mapped in a matrix in synchronization with switching of a transmission beam direction. The underwater image sonar according to claim 6, wherein the two wave receiving means are constituted by two omnidirectional wave receivers corresponding to each frequency band.

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