JP4953566B2 - Underwater detection device and underwater detection method - Google Patents

Description

  The present invention relates to an underwater detection apparatus and an underwater detection method for detecting underwater information such as an underwater fish school by transmitting and receiving ultrasonic waves.

  FIG. 8 is a diagram showing an aspect of detecting underwater information such as a school of fish using a scanning sonar that is one of the underwater detection devices. In the figure, 80 is a scanning sonar mounted on a ship 81, 1 is a transmitter / receiver for transmitting and receiving ultrasonic waves provided in the scanning sonar 80, and 82 is a water surface. Bt is a transmission beam radiated from the transmitter / receiver 1, Br is a reception beam for receiving an echo signal that is reflected by the transmission beam Bt reflected by a fish school underwater, and α is a depression angle of the transmission beam Bt. The transmission beam Bt is radiated all at once in all directions in the water to form an umbrella-shaped beam. On the other hand, the reception beam Br is a pencil-shaped beam with sharp directivity formed by the transducer 1 being electrically scanned in the circumferential direction. Then, by analyzing the echo signal received by the reception beam Br, underwater information relating to the school of fish of each cross section P is obtained, and this is displayed on the display unit of the scanning sonar 80 as a detection image.

  As shown in FIG. 9, a large number of transducers 2 are arranged in, for example, 60 rows in the circumferential direction and 5 levels in the vertical direction on the surface of the cylindrical main body 1a of the transducer 1 described above. . Further, as shown in FIG. 10, a transmission beam Bt that extends in a fan shape along a vertical plane that forms a predetermined angle β with respect to the traveling direction of the ship is formed, and the depression angle of the pencil-shaped reception beam Br is formed along the fan shape. It is also possible to detect underwater information by sequentially changing α, that is, by electrically scanning the reception beam Br. Patent Document 4 to be described later shows a method of forming an umbrella-shaped transmission beam, a pencil-shaped reception beam, and the like.

  When a plurality of ships equipped with such a scanning sonar 80 are operating in one place, a situation occurs in which the transducer 1 receives an ultrasonic wave transmitted from another ship. Hereinafter, this is referred to as “interference occurs”. A signal generated by the interference is referred to as an “interference signal”. In this case, if there is a sufficient difference between the frequency of the ultrasonic wave transmitted from another ship and the frequency of the ultrasonic wave used by itself, another bandpass filter or the like provided in the receiving unit of the scanning sonar 80 may be used. Ultrasonic waves (interference signals) from the ship can be removed as noise. However, if it cannot be removed as noise, the echo signal from the school of fish and the interference signal cannot be identified. For this reason, the false image by interference will be displayed on a display part. A false image is an image displayed on the display unit by a signal other than an echo signal (such as an interference signal).

  FIG. 11 is a diagram illustrating a screen of the display unit on which the false image 111 due to interference is displayed. The center of the figure is the position of the ship 81 (transmitter / receiver 1), and the upper part of the figure is the bow direction (the traveling direction of the ship). “R: 400 m” indicates that the detection distance is 400 m, and “T: 0 °” indicates that the depression angle α of the umbrella-shaped transmission beam is 0 degree. The false image 111 appears strongly in the direction DD where the other ship is located due to the directivity characteristics of the transducer 2 of the transducer 1 and becomes weak as the direction is shifted, but when the distance to the other ship is short, etc. May appear over a wide range. Further, the position of the false image 111 in the perspective direction is determined by the distance from the other ship, the time difference between the time when the ultrasonic wave is transmitted from the other ship and the time when the ultrasonic wave is transmitted by itself. When the false image 111 due to interference is displayed in this way, there is a possibility that the false image 111 is erroneously determined as an image of a school of fish.

  Therefore, taking advantage of the fact that ultrasonic waves from other ships are generally not received at the same timing every time, the reception signal of the previous time, etc. is stored in the memory two times in advance to receive this time. The signal and the received signal of the previous time, the previous time, etc. are sequentially compared along the time axis of the received signal, and the received signal of the lowest level or the intermediate level is sequentially extracted from the plurality of received signals. It has been proposed to display an image on a display unit (for example, Patent Document 1). By doing so, the interference signal is removed and the false image is not displayed. Note that the update period of the display screen of the scanning sonar 80 is sufficiently fast, so that the fish image will not disappear from the display unit by the above processing (hereinafter referred to as image correlation processing).

  In addition, the azimuth detection circuit provided in the ship obtains the absolute azimuth (east, west, north, south, etc.) of the ship's traveling direction, transmits ultrasonic waves with different frequencies for each absolute azimuth, and receives echo signals from each absolute azimuth It has also been proposed that a false image due to interference is not displayed by allowing only a signal having a frequency in the absolute direction to pass through a band-pass filter provided in the section (for example, Patent Document 2).

  Although it does not prevent the false image due to the interference from being displayed, Patent Documents 3 and 4 do not display the false image due to the side lobe or the grating lobe of the reception signal of the transducer on the display unit. It is shown that ultrasonic waves are transmitted and received as follows. Within one detection cycle, ultrasonic waves with different frequencies are transmitted simultaneously for each direction of the transmitter / receiver, or the transmission apertures of the transmitter / receiver are sequentially moved in the azimuth direction, and ultrasonic waves with different frequencies for each position of the transmission apertures. Send. The receiving unit selects a frequency for each direction so as to obtain a reception signal in a predetermined direction. Patent Document 5 discloses that the center frequency of the received signal for each direction is obtained by the complex autocorrelation method using the received signal for each direction. Non-Patent Literature 1 describes other underwater detection devices such as searchlight sonar, sector scanning sonar, and Doppler tide meter.

JP 2000-304861 A (Abstract, paragraphs 0001-0006) JP-A-3-282390 (first page, right column, first line to third page, lower left column, seventh line) JP-A-1-185471 (first page, left column, line 15 to second page, upper right column, line 10) JP 2003-337171 A (Claims 1-4, paragraphs 0020-0031) JP 2003-84060 A (paragraphs 0026 to 0027) The Ocean Acoustics Society edited and published “Ocean Acoustic Terminology”, published in May 1999

  However, in the case shown in Patent Document 1, when the time difference between the time when ultrasonic waves are transmitted from another ship and the time when ultrasonic waves are transmitted by itself is constant (the transmission timing is synchronized). The interference signal is generated at the same position in the received signal every time. For this reason, an interference signal cannot be removed by the above image correlation processing, and a false image is displayed. In what is shown in Patent Document 2, it is assumed that all ships are equipped with scanning sonar of the same specification, and for ultrasonic waves emitted from ships equipped with scanning sonar of different specifications, Not considered. For example, when the frequency of the ultrasonic wave transmitted from the scanning sonar of Patent Document 2 in the north direction is f1, and another ship located in the north direction transmits the ultrasonic wave of the frequency f1 in all directions, the north direction A false image due to interference is displayed on the screen. Thus, since the false image due to the interference is displayed, there is a problem that the false image is erroneously determined to be an image of a school of fish and the like, and the working efficiency of the fishery is lowered.

  The present invention solves the above-described problems, and an object of the present invention is to provide an underwater detection device and an underwater detection method that can reduce the adverse effects of ultrasonic waves transmitted from other ships. It is in.

In the present invention, a transducer having a plurality of transducers arranged in the azimuth direction, transmission control means for driving the plurality of transducers to transmit ultrasonic waves into water, and reception received by the plurality of transducers Reception control means for combining signals to form a reception beam signal; and display control means for displaying information on the detection target object on a display unit based on an echo signal from the detection target object included in the reception beam signal. In the underwater detection apparatus provided, the transmission control means drives each transducer so as to transmit ultrasonic waves having different frequencies or frequency bands depending on the direction, and transmits the ultrasonic wave to each direction every one or a plurality of detection cycles. Each transducer is driven so that the frequency or frequency band of the sound wave changes. The reception control means selects a frequency for each azimuth every one or a plurality of detection cycles to form a reception beam signal for each azimuth. Here, the “azimuth” is a concept including not only the angular position in the horizontal plane but also the position of the umbrella-shaped transmission beam in the circumferential direction and the position of the fan-shaped transmission beam in the arc direction. “Frequency selection” is a concept including not only a single frequency but also a predetermined frequency band. The transmission control means corresponds to the transmission beam forming unit, the control unit, and the like described in the embodiment. The reception control means corresponds to the reception beam forming unit, the second BPF, the control unit, and the like described in the embodiment.

  In this way, ultrasonic waves having different frequencies or frequency bands are transmitted for each direction, and the frequency is selected for each direction to form a reception beam signal for each direction. As a result, even if a false image (due to interference) due to reception of an ultrasonic wave transmitted from another ship is displayed, the false image is displayed only in a narrow limited range in the azimuth direction. Missing display of detection information such as school of fish is prevented. In addition, since the frequency or frequency band of the ultrasonic wave transmitted in each direction is changed every one or a plurality of detection cycles, the ultrasonic wave transmission timing is synchronized with the ultrasonic wave transmission timing of other ships. Even if it exists, a false image is not continuously displayed on the same position of a display part like patent document 1, but the display state of a false image (it is displayed / not displayed, a display position moves). It changes with every detection cycle. This makes it easy to distinguish between images of fish, etc. that are displayed at substantially the same position even if the detection cycle changes, and false images due to interference. It is possible to prevent a decrease in fishing work efficiency.

  In the embodiment of the present invention, a storage unit that stores the reception beam signal of one or more past detection cycles is provided, and the display control means receives the reception beam signal of the current detection cycle and the reception unit stored in the storage unit. It is possible to generate a display signal from the beam signal and display information on the detection target object on the display unit based on the display signal. Here, the received beam signal stored in the storage unit may be either a received beam signal after detection or a received beam signal before detection. The display signal is generated by, for example, sequentially comparing the received beam signal of the current detection cycle with the received beam signal stored in the storage unit along the time axis, and receiving or storing the received beam signal of the current detection cycle. This is performed by sequentially extracting received beam signals at levels other than the highest level among the received beam signals. By doing so, even if the transmission timing of the ultrasonic wave is synchronized with the transmission timing of the ultrasonic wave of another ship, a false image due to interference is not displayed. This eliminates the need for the operator of the underwater detection device to determine whether the image is a false image due to interference or an image of a school of fish from the change in the display state of the image, thereby reducing human error of the operator. be able to.

Further, in the embodiment of the present invention, it includes a random number generator for generating a random number, the transmission control means based on the value of the random number generator is generated, by changing the timing of transmitting ultrasonic waves, or, Based on the value of the random number generated by the random number generator, the relationship between each azimuth and the frequency or frequency band assigned to each azimuth can be changed for different frequencies or frequency bands depending on the azimuth. By doing in this way, even when other ships are using the underwater detection device of the present invention and the transmission timing of the ultrasonic wave is synchronized with the transmission timing of the ultrasonic wave of the other ship, The transmission timing is not synchronized, or the relative positional relationship of the frequency or frequency band for each direction assigned to each direction between the two underwater detection devices is shifted for each detection cycle. As a result, the false image due to the interference is not displayed, or the display state of the false image is changed every detection cycle, so that it is possible to prevent the false image from being mistaken for an image such as a school of fish.

  Furthermore, in the embodiment of the present invention, a detection unit that detects the center frequency of the reception beam signal is provided, and the detection unit detects the center frequency for each direction from the reception beam signal of each direction before transmitting the ultrasonic wave. The transmission control means transmits ultrasonic waves having a frequency different from the center frequency for each direction detected by the detection unit, or ultrasonic waves having a frequency band having a frequency different from the center frequency to each direction. Each vibrator can be driven. By doing in this way, the center frequency of the interference signal by receiving the ultrasonic wave from other ships which arrives from each azimuth | direction can be detected. When an interference signal is detected, an ultrasonic wave having a frequency different from the center frequency for each direction detected by the detection unit, or an ultrasonic wave in a frequency band having a frequency different from the center frequency as the center frequency is detected. Transmitted in each direction, the interference signal is removed by the reception control means. Thereby, it is possible to prevent a false image due to interference from being displayed on the display unit.

Furthermore, the present invention is an underwater detection method in an underwater detection device that transmits ultrasonic waves from a transducer into water, detects underwater information based on a received signal received by the transducer, and displays a detection result on a display unit. Then, in the first detection cycle, underwater information of each direction based on a signal generated by transmitting ultrasonic waves of different frequencies or frequency bands to each direction and selecting a received signal of each direction by frequency for each direction in the first detection cycle. was detected, in the second detection cycle, the different frequencies or frequency bands in azimuth by an ultrasonic, ultrasonic waves of different frequencies or frequency bands from the first detection cycle to send to each orientation, for each orientation based on the signals generated by selecting a frequency of the received signal by orientation detect the water information of each orientation. Here, the “azimuth” is a concept including not only the angular position in the horizontal plane but also the position of the umbrella-shaped transmission beam in the circumferential direction and the position of the fan-shaped transmission beam in the arc direction. “Frequency selection” is a concept including not only a single frequency but also a predetermined frequency band. Also, it may not take place immediately the second detection cycle after the first detection cycle only once, for example, after the first detection cycle twice, so as to perform the second detection cycle Also good.

In this way, ultrasonic waves having different frequencies or frequency bands are transmitted for each direction, and the frequency of the received signal in each direction is selected for each direction. As a result, even if a false image (due to interference) due to reception of an ultrasonic wave transmitted from another ship is displayed, the false image is displayed only in a narrow limited range in the azimuth direction. Missing display of detection information such as school of fish is prevented. Also, since the frequency or frequency band of the ultrasonic waves transmitted in each direction is different between the first detection cycle and the second detection cycle , the ultrasonic transmission timing is synchronized with the ultrasonic transmission timing of other ships. Even in this case, the false image is not continuously displayed at the same position of the display unit as in Patent Document 1, and the display state of the false image changes between detection cycles . This makes it easy to distinguish between images of fish, etc. that are displayed at substantially the same position even if the detection cycle changes, and false images due to interference. It is possible to prevent a decrease in fishing work efficiency.

  ADVANTAGE OF THE INVENTION According to this invention, the influence of the ultrasonic wave transmitted from another ship can be reduced. That is, even if the vibrator receives ultrasonic waves from another ship, the false image due to interference is displayed so that it can be identified from the image of the school of fish, etc. The image is not mistaken for an image of a school of fish and the like, and it is possible to prevent a decrease in fishing work efficiency.

  FIG. 1 is a cross-sectional view of the transducer 1 at the center stage shown in FIG. The upper part of the figure is the bow direction. In the figure, the transducers 2 (ultrasonic transducers) included in the regions A1 to A12 are not shown, but five transducers 2 are arranged in the circumferential direction of the transducer 1 in each region A1 to A12. It is arranged at equal intervals along. FIG. 1A shows the frequency according to the direction in a certain detection cycle. FIG. 1B shows the frequency for each direction in the next detection cycle.

First, an outline of the transmission beam and the reception beam will be described with reference to FIG. The transducer 1 is divided into 12 regions (also referred to as transmission apertures) A1 to A12 having a central angle (aperture angle) of 30 degrees. The vibrators 2 in the regions A1 to A12 are driven by signals having frequencies f1 to f12, respectively. As a result, ultrasonic waves having frequencies f1 to f12 are simultaneously transmitted (radiated) to the respective directions D1 to D12, and an umbrella-shaped transmission beam is formed around the transducer 1. Here, the frequencies f1 to f12 are determined so that the relationship of f1 <f2 <... <F11 <f12 is established. For example, f1 is 24 kHz, f12 is 26 kHz, and between f1 to f12. The frequency difference is substantially the same. Further, to the highest frequency f12 to the maximum frequency _{f H,} the lowest frequency f1 the lowest frequency _{f L,} the frequency f6 or f7 medium called a medium frequency _{f M.}

  When receiving an ultrasonic wave, a reception beam signal is formed from a reception signal of the transducer 2 included in a reception opening at a predetermined angle, for example, 90 degrees. For example, the reception beam signal B1 of the reception beam B1 having the directional main axis in the direction D1 (the direction of the bisector of the central angle of the area A1) is formed from the reception signals of the transducers 2 in the three areas A12 to A2. . Hereinafter, the same code is used for the received beam and the received beam signal. By rotating the reception aperture counterclockwise by 30 degrees (moving in the azimuth direction), reception beam signals B2 to B12 in the azimuth directions D2 to D12 are also formed. By repeatedly forming the received beam signals B1 to B12 in one detection cycle and analyzing the echo signals included in the received beam signals B1 to B12, it is possible to create a school of fish from short to long distances in all directions. Detect.

  In the next detection cycle, as shown in FIG. 1B, the azimuth-specific frequencies f1 to f12 are assigned to the regions A1 to A12 in a manner different from that shown in FIG. In the present invention, by changing the direction-specific frequencies f1 to f12 for each detection cycle, when interference occurs due to ultrasonic waves transmitted from other ships, it is possible to identify a false image due to the interference and an image such as a school of fish. Or prevent false images due to interference from being displayed. Details of this point will be described later. Further, since the frequency of the signal for driving each transducer 2 is changed every detection cycle, a broadband transducer having uniform transmission and reception characteristics over a certain frequency band is used as the transducer 2.

  FIG. 2 is a block diagram showing a configuration of a scanning sonar (hereinafter also referred to as an apparatus) which is one of the underwater detection apparatuses according to the present invention. The control unit 20 includes a CPU, a memory, and the like, and controls each unit of the device based on data input from an operation unit (not shown), data set in advance in the memory, data received from each unit of the device, and the like. To do. In addition, the control unit 20 includes a function (random number generator 20a) that generates a random number when the CPU executes a random number generation program stored in the memory.

  The transmission beam forming unit 5 includes a transmission signal generation circuit 5b and a phase adjustment circuit 5a. The transmission signal generation circuit 5b generates a plurality of sine waves having different frequencies, that is, sine waves having frequencies f1 to f12. The phase adjustment circuit 5a provided for each transducer 2 has the above sine wave according to the position of the transducer 2 in the step direction so that the depression angle of the umbrella-shaped transmission beam becomes an angle instructed by the control unit 20. Adjust the phase. The phase-adjusted transmission signal is amplified by the transmission amplifier 4 and drives the vibrator 2 of the transducer 1 via the transmission / reception switching circuit 3. As a result, ultrasonic waves having frequencies f1 to f12 are simultaneously transmitted from the transducers 2 into the water, and a transmission beam is formed around the transducer 1. In the following description, the transmission or reception system for each transducer 2 is called a channel, and the reception signal before the reception beam signal is formed is called a channel signal.

Next, the receiving system will be described. The reception signal (channel signal) received by each transducer 2 is amplified by the reception amplifier 6 via the transmission / reception switching circuit 3 for each channel. The amplified received signal is subjected to A / D conversion after the first BPF 7 (band pass filter) removes signal components of frequencies other than the predetermined bandwidth including the above-mentioned minimum frequency f _L to maximum frequency f _H as noise. The digital signal (time series data) is converted by the device 8.

In A / D converter 8 at a predetermined timing, for example, a first phase of the internal sinusoidal signal of medium frequency f _M of the above, the first phase and 90 degree phase by different second phase The received signal is sampled every cycle. A signal sampled in the first phase is called an I signal, a signal sampled in the second phase is called a Q signal, and I + jQ (j is an imaginary unit) is called an IQ signal. Various operations are performed on the received signal represented by the I signal and the Q signal in a subsequent circuit. For example, at the time of forming a received beam signal, which will be described later, the phase of the received signal is corrected by θ by multiplying the received signal by exp (jθ).

  The gain adjusting unit 9 is configured so that the amplitude of the echo signal from the same reflector in the water (for example, a school of fish to be detected) is constant without depending on the distance between the transducer 1 and the reflector. Adjust the gain of the received signal. That is, the amplitude of the received signal is adjusted by multiplying each time-series data of the received signal by an amplification factor corresponding to the elapsed time since the transmission beam was transmitted. The time series data of each channel output from the gain adjusting unit 9 is temporarily stored in the buffer memory 10 for each channel.

  The reception beam forming unit 11 includes a phase correction circuit 11a and an addition circuit 11b, and forms a reception beam signal from a channel signal stored in the buffer memory 10 by a known method. First, the phase correction circuits 11a provided as many as the number of transducers 2 included in the reception aperture for forming a reception beam are used to transmit and receive the transducers 2 of each channel so that the phases of the channel signals match. The phase of each channel signal is corrected by a correction amount corresponding to the position in the stage direction and the position in the circumferential direction in the device 1. The adder circuit 11b forms a reception beam signal by adding the phase-corrected channel signals.

  The second BPF 12 (band pass filter) takes into account the frequency variation of the received signal due to the Doppler effect of vessel navigation, and selects the selected frequency (for example, any one of the frequencies f1 to f12) from the received beam signal. ) Only. As the selection frequency, the azimuth-specific frequencies f1 to f12 of the ultrasonic waves transmitted in the same directions D1 to D12 as the reception beams B1 to B12 are designated. For example, when the received beam signal B1 is filtered, the control unit 20 sets data such as the selection frequency f1, the position of the region A1 in the bow direction, and the navigation speed in the second BPF 12.

  A DSP (digital signal processor) (not shown) of the second BPF 12 calculates a center frequency f1 + Δf (Δf is a frequency fluctuation amount due to the Doppler effect) from the set data, and the second BPF 12 having a predetermined bandwidth with respect to the center frequency f1 + Δf. The filter coefficient of is obtained. The second BPF 12 set to this filter coefficient passes only a signal having a frequency component having a predetermined bandwidth with respect to the center frequency f1 + Δf. That is, the second BPF 12 selects a frequency for each direction and forms a reception beam signal in each direction. The center frequency detector 13 to which the received beam signal is input will be described later.

  The detector 14 obtains the amplitude of the output signal of the second BPF 12, that is, the square root of the sum of the square of the real component (I signal) and the square of the imaginary component (Q signal) of the output signal. Echo signal) envelope is obtained. The magnitude of this amplitude is proportional to the degree of density of the school of fish. The detection signal output from the detection unit 14 is sent to the past data storage unit 15 and the image processing unit 16. The past data storage unit 15 stores detection signals of one or a plurality of detection cycles. The image processing unit 16 performs predetermined image processing on the detection signal from the detection unit 14 to display an image of the fish school on the display unit 17 according to the density, direction, and distance of the fish school. Alternatively, the image processing unit 16 generates a display signal from the detection signal from the detection unit 14 and the detection signal stored in the past data storage unit 15, and a predetermined image is generated with respect to the display signal. By performing the processing, an image of the school of fish can be displayed on the display unit 17. The detection signal stored in the past data storage unit 15 is used to prevent a false image due to interference from being displayed. Details will be described later.

  Next, the operation of the scanning sonar according to the present invention will be described. First, as shown in FIG. 1 (a), a method of assigning the orientation-specific frequencies f1 to f12 to the regions A1 to A12 of the transducer 1 will be described. In the memory of the control unit 20, a direction-specific frequency allocation table 31a shown in FIG. This directional frequency allocation table 31a defines the relationship between the areas A1 to A12 (directions D1 to D12) of the transmitter / receiver 1 and the frequencies f1 to f12 of the transmission signals allocated to the areas A1 to A12. The number in the leftmost column indicates the number of the frequency allocation pattern by direction. FIG. 1 (a) shows the frequency allocation pattern classified by azimuth number 1, and FIG. 1 (b) shows the frequency allocation pattern classified by azimuth number 2.

  When transmitting an ultrasonic wave in a certain detection cycle, the control unit 20 takes out a frequency allocation pattern with any number from the memory and sends it to the transmission beam forming unit 5. The transmission signal generation circuit 5b of the transmission beam forming unit 5 generates a sine wave transmission signal having a frequency included in the directional frequency allocation pattern, and transmits the transmission signal of each frequency for each transducer 2 in the corresponding region A1 to A12. This is sent to the phase adjustment circuit 5a. As a result, for example, when the frequency allocation pattern classified by number 1 is used, as shown in FIG. 1A, the vibrators 2 in the regions A1 to A12 are driven by sine waves having the frequencies f1 to f12, respectively. Then, ultrasonic waves having frequencies f1 to f12 are transmitted to the directions D1 to D12, respectively. When the frequency allocation pattern classified by direction 2 is used, as shown in FIG. 1B, the vibrators 2 in the regions A1 to A12 are driven by sine waves of frequencies f10 to f9, respectively, and the directions D1 to D1 are used. Ultrasonic waves having frequencies f10 to f9 are transmitted to D12.

  FIG. 4 is a time chart showing transmission and reception of ultrasonic waves. First, in the first detection cycle DC1, ultrasonic waves are transmitted for a predetermined time using the frequency allocation pattern classified by direction No. 1 in the frequency allocation table 31a classified by orientation. At this time, the transmission beam forming unit 5 adjusts the phase of the transmission signal of each channel so that the depression angle of the transmission beam becomes the depression angle designated by the control unit 20. As a result, as shown in FIG. 1A, ultrasonic waves having frequencies f1 to f12 are transmitted in the directions D1 to D12, respectively, and an umbrella-shaped transmission beam having a predetermined depression angle is transmitted in all directions.

  In the reception period after transmitting the ultrasonic wave, the reception signal received by each transducer 2 is amplified by the reception amplifier 6, the noise component is removed by the first BPF 7, and predetermined sampling is performed by the A / D converter 8. It is converted into a digital signal with a period. As shown in FIG. 4, the reception beam forming unit 11 repeatedly forms and outputs reception beam signals B1 to B12 in the directions D1 to D12 in order from the channel signal until the reception period ends. For example, the reception beam signal B1 of the reception beam B1 having the directional main axis direction in the direction D1 is formed from the channel signals of the vibrator 2 included in the three regions A12 to A2. In this way, the received beam signals B1 to B12 of each cross section from the short distance to the long distance in all directions D1 to D12 of the transducer 1 are output.

  In the second BPF 12, the selection frequencies f1 to f12 are set by the control unit 20 in accordance with the reception beam signals B1 to B12 sequentially output from the reception beam forming unit 11. For example, the selection frequency f1 is set when the reception beam signal B1 is output, and the selection frequency f2 is set when the reception beam signal B2 is output. Therefore, the signals arriving from the directions D1 to D12, that is, the signals arriving from the directional main axis directions of the reception beams B1 to B12 are extracted from the reception beam signals B1 to B12, respectively. The detector 14 detects the received beam signals B1 to B12 that are sequentially output from the second BPF 12. Based on the detection signal output from the detection unit 14, the image processing unit 16 draws an image of a fish school or the like spirally from the center of the display unit 17 toward the outside.

  Assume that in the first detection cycle DC1, a school of fish is located in the azimuth D9, and an ultrasonic wave having a frequency f1 is transmitted from all other ships located in the azimuth D1 in all directions, and this ultrasonic wave is received. . In this detection cycle DC1, since the selected frequency f1 is set to the second BPF 12 for the received beam signal B1 in the direction D1, the second BPF 12 removes interference signals due to ultrasonic waves of the frequency f1 from other ships. I can't. For this reason, as shown in FIG. 5A, a false image 52 due to interference is displayed in the direction D1. A fish school image 51 is displayed in the direction D9. In the figure, “R = 400 m” indicates that the detection distance is 400 m, and “T = 0 °” indicates that the depression angle of the transmission beam is 0 degree. In addition, it is assumed that the position of the fish school, the position of the other ship, and the frequency of the ultrasonic wave transmitted by the other ship are the same in the subsequent detection cycles DC2 to DC5.

  In the next detection cycle DC2, ultrasonic waves are transmitted for a predetermined time by using the frequency allocation pattern by direction of number 2 in the frequency allocation table 31a by direction. As a result, as shown in FIG. 1B, the direction in which the ultrasonic waves having the frequencies f1 to f12 are transmitted rotates by 90 degrees counterclockwise as compared with FIG. In the detection cycle DC2, the direction-specific frequency f10 of the direction D1 is set in the second BPF 12 as the selected frequency for the received beam signal B1 of the direction D1 where the other ship is located. The interference signal due to the ultrasonic wave can be removed by the second BPF 12. As a result, as shown in FIG. 5B, only the fish school image 51 is displayed in the direction D9, and the false image 52 due to interference is not displayed.

  In the next detection cycles DC3 and DC4, the frequency allocation patterns by direction 3 and 4 of the frequency allocation table 31a by direction are used, and the selected frequencies f7 and f4 are set to the second BPF 12, respectively. The second BPF 12 can remove the interference signal due to the ultrasonic wave having the frequency f1, and only the fish school image 51 is displayed in the direction D9 as shown in FIG. 5B. In the next detection cycle DC5, the direction-specific frequency assignment pattern of number 1 in the direction-specific frequency assignment table 31a is used again, so that a false image 52 due to interference is displayed in the direction D1, as shown in FIG. An image 51 of the fish school is displayed in the direction D9.

  As described above, ultrasonic waves of different frequencies f1 to f12 are transmitted for each of the directions D1 to D12, and only the signal components of the frequencies f1 to f12 of the corresponding directions D1 to D12 are received by the second BPF 12 for the received beam signals B1 to B12. As shown in FIG. 5 (a), a false image 52 due to interference is displayed only in the direction D1 where the other ship is located, and a false image due to interference is displayed in the adjacent directions D2, D12, etc. The image is not displayed. As a result, the number of cases where the false image 52 due to interference covers and hides the image 51 such as a school of fish is reduced. That is, lack of detection information such as a school of fish is prevented.

  Moreover, since the frequencies f1 to f12 of the ultrasonic waves transmitted to the respective directions D1 to D12 are changed for each detection cycle, the ultrasonic transmission timing is synchronized with the ultrasonic transmission timings of other ships. However, the false image 52 due to interference is not continuously displayed at the same position as in Patent Document 1, and is displayed or disappears as described above. The display position of the false image 52 due to interference may move for each detection cycle depending on the position of another ship, the content of the frequency pattern for each direction to be used, and the like. In any case, the display state of the false image 52 due to interference changes every detection cycle. On the other hand, images of fish schools and the like are displayed at substantially the same position even if the detection cycle changes. Thereby, the operator of the scanning sonar can easily identify the false image 52 due to the interference and the image 51 such as the school of fish, and can definitely recognize the image of the school of fish.

  Next, a method for preventing the false image 52 due to interference from being displayed on the display unit 17 using the detection signal stored in the past data storage unit 15 will be described. The detection signal 61 of the above-described detection cycle DC4 includes only a fish school signal 61a as shown in FIG. The detection signal 62 of the detection cycle DC5 includes a fish school signal 62a and an interference signal 62b as shown in FIG. Here, the horizontal axis (not shown) is a time axis, and the generation times of the fish signals 61a and 62a are substantially the same. In the detection cycle DC4, the detection signal 61 output from the detection unit 14 is sequentially written in the past data storage unit 15.

  In the detection cycle DC5, the detection signal 62 output from the detection unit 14 is sequentially written in the past data storage unit 15. At this time, the image processing unit 16 sequentially reads the detection signal 61 of the detection cycle DC4 stored in the past data storage unit 15, sequentially compares both detection signals 61 and 62 along the time axis, and the one with the smaller level , That is, a signal that is not at the maximum level is sequentially extracted, and the extracted signal is used as a display signal 63 (FIG. 6C), and an image is drawn on the display unit 17 based on the display signal 63. Here, the level of the fish school signal 62a is smaller than the level of the fish school signal 61a, and the detection signal 61 is in a no-signal state at the time of the interference signal 62b. Therefore, the display signal 63 that does not include the interference signal 62b is extracted. . As a result, the false image 52 due to interference is not displayed even in the detection cycle DC5. This also applies to the other detection cycles DC1 to DC4. The process of generating the display signal 63 by comparing the detection signal 62 of the current detection cycle DC5 and the detection signal 61 of the previous detection cycle DC4 as described above is called image correlation processing.

  As described above, even when the ultrasonic transmission timing is synchronized with the ultrasonic transmission timing of other ships, the false image 52 due to interference is not displayed. It is not necessary to determine from the change in the display state whether the image is a false image 52 due to interference or an image 51 such as a school of fish. Thereby, it is possible to reduce an artificial mistake that the false image 52 due to interference is mistaken for the image 51 such as a school of fish.

  In the above description, the case where the display signal 63 is generated from the detection signals 61 and 62 of the two detection cycles DC4 and DC5 has been described. However, as disclosed in Patent Document 1, the detection signals of the previous and previous detection cycles are described. Are stored in the past data storage unit 15 and the detection signals of the previous, previous, and current detection cycles are sequentially compared along the time axis, and the intermediate level signal among the three detection signals, that is, not the maximum level. The signal may be extracted, and the extracted signal may be used as a display signal.

  Next, consider a situation different from the situation described above. In the previous situation, a case has been described in which ultrasonic waves of frequency f1 are transmitted in all directions from another ship located in the direction D1. Here, it is assumed that another ship equipped with the same device as the device of the present invention is located in the direction D1. The state of the transmitter / receiver 1 is assumed to be the state shown in FIG. 1A (the direction-specific frequency assignment pattern number 1 in the direction-specific frequency assignment table 31a is used). It is assumed that the other ships transmit ultrasonic waves having the frequency f1 in the direction D7 (the frequency allocation pattern by direction of number 3 in the frequency allocation table by direction 31a is used). Then, interference of the received signal occurs in the direction D1, and both frequencies are f1, so the second BPF 12 cannot remove the interference signal, and as shown in FIG. A false image 52 is displayed.

  Since the own ship and the other ship's devices are controlled by the same program, in the next detection cycle, the respective frequency assignment patterns of No. 2 and No. 4 in the direction-specific frequency assignment table 31a are used, and the own ship's direction D1. Is assigned the frequency f10 and the direction f7 of the other ship is also assigned the frequency f10. Therefore, when the transmission timings of the ultrasonic waves of the own ship and the other ship are synchronized (for example, detection of the own ship and the other ship). When both distances are 400 m), a false image 52 due to interference is displayed at the same distance position in the direction D1 in the next detection cycle. Further, in the subsequent detection cycle, the false image 52 due to interference is continuously displayed at the same distance position in the direction D1. For this reason, the operator determines that the displayed false image 52 is the fish school image 51. Further, since the false image 52 is continuously displayed at the same position, the false image 52 due to interference cannot be removed by the above-described image correlation processing.

  Therefore, the above problem is solved as follows. First, the control unit 20 multiplies the random number value generated by the random number generator 20a by a predetermined coefficient to generate a delay time of about 0 to 0.2 seconds, for example. Then, immediately after the end of a certain detection cycle, transmission of ultrasonic waves of the next detection cycle is not started, and transmission of ultrasonic waves of the next detection cycle is started after the delay time has elapsed. By doing so, the transmission timings of the ultrasonic waves of the ship and the other ship are not synchronized, and even if interference occurs, the display state of the false image 52 due to the interference changes every detection cycle. Therefore, the operator can determine that the displayed false image 52 is a false image 52 due to interference. Further, the false image 52 due to interference can be removed by the image correlation method.

  In this embodiment, the direction-specific frequency assignment pattern of the direction-specific frequency assignment table 31a is switched in order of number for each detection cycle. However, the random number generated by the random number generator 20a is based on the value based on the value. It is also possible to determine the number of the separate frequency allocation table 31a and use the directional frequency allocation pattern of that number. By doing in this way, even if it is a case where the transmission timing of the ultrasonic wave of own ship and another ship is synchronizing, it is the frequency f1-f12 classified by direction allocated to each direction D1-D12 between two ships. Since the relative positional relationship is shifted for each detection cycle, even if interference occurs, the display state of the false image 52 due to interference changes for each detection cycle. As a result, the same effect as that obtained when the delay time is used can be obtained. In addition, in the frequency allocation table 31a by direction with a small number of frequency allocation patterns by direction, the effect of using random numbers cannot be sufficiently obtained. Therefore, as shown in FIG. It is desirable to use another frequency allocation table 31b.

  A second embodiment of the present invention will be described. In the previous embodiment, when interference occurs, a method that allows an operator of the apparatus to determine whether the displayed image is a false image 52 due to interference or an image 51 such as a school of fish, and due to interference Although the method for preventing the false image 52 from being displayed has been described, the present embodiment prevents the false image 52 from being displayed due to interference in advance. The scanning sonar shown in FIG. 2 is also used in this embodiment. FIG. 7 is a time chart illustrating transmission / reception of ultrasonic waves according to the second embodiment. Each detection cycle DC1, DC2 differs from that shown in FIG. 4 in that an interference check is performed to check the presence and frequency of ultrasonic waves from other ships before transmitting ultrasonic waves.

  The interference check is performed as follows. The reception amplifier 6, the first BPF 7, the A / D converter 8, and the buffer memory 10 operate in the same manner as in the reception period. The gain adjusting unit 9 operates so as to amplify the received signal at a constant amplification factor according to an instruction from the control unit 20. Since ultrasonic waves from other ships mainly come from the horizontal direction, the reception beam forming unit 11 receives a transmission beam having a relatively small depression angle (for example, 0 degrees) according to an instruction from the control unit 20. Operate to form a shaped receive beam signal. The reception beam forming unit 11 sequentially outputs the reception beam signals B1 to B12 of the respective directions D1 to D12. When receiving ultrasonic waves from other ships, the received beam signals B1 to B12 include interference signals. The center frequency detector 13 detects the center frequencies of the interference signals coming from the respective directions D1 to D12 by detecting the center frequencies of the reception beam signals B1 to B12. There are several methods for detecting the center frequency in real time. In this embodiment, the complex autocorrelation method disclosed in Patent Document 5 is used.

According to the complex autocorrelation method, the center frequency f _C of the received beam signal Z (t) represented in the complex form of the following equation (1) is calculated from the following equation (2).
Z (t) = I (t) + j · Q (t) (1)
f _C = (1 / 2πT) tan ⁻¹ {R i (t) / R r (t)} (2)
Here, T is the sampling period of the A / D converter 8. Rr (t) and Ri (t) are the real part and imaginary part of the autocorrelation function R (t) = Rr (t) + j · Ri (t), and are expressed by the following equations (3) and (4). expressed.
Rr (t) = I (t) .I (t-1) + Q (t) .Q (t-1) (3)
Ri (t) = I (t-1) .Q (t) -I (t) .Q (t-1) (4)
The center frequency detector 13 performs the calculation of the above equation (2) for the received beam signals B1 to B12 of the respective directions D1 to D12, and the center frequency for each direction D1 to D12, that is, an ultrasonic wave transmitted from another ship. Is determined in real time. At this time, if the signal levels of the reception beam signals B1 to B12 are equal to or lower than a predetermined value, the center frequency is treated as zero.

  Then, the detected center frequencies of the respective directions D1 to D12 are sent to the control unit 20. When the center frequencies of all the directions D1 to D12 are 0, the control unit 20 uses the frequency allocation pattern classified by direction of the next number in the frequency allocation table 31a classified by orientation in the same manner as in the previous embodiment, and the like Detecting. On the other hand, when the center frequency of any azimuth is not 0, the directional frequency assignment pattern is selected so that the same frequency as the center frequency detected in the azimuth or an approximate frequency is not assigned. For example, when the center frequency of the direction D5 is f2, the direction-specific frequency assignment pattern other than the number 2 in the direction-specific frequency assignment table 31a is used.

  For example, when the frequency allocation pattern by direction of number 4 is used, even if an ultrasonic wave having the frequency f2 of another ship arrives from the direction D5 during the reception period, the received beam signal B5 of the direction D5 Since the selection frequency f8 is set to the second BPF 12, the interference signal of the frequency f2 is removed, and the false image 52 due to the interference is not displayed on the display unit 17. As described above, the interference check is performed before transmitting the ultrasonic wave, and when the ultrasonic wave from another ship is detected, the frequency according to the direction is assigned to each direction D1 to D12 so that the interference signal can be removed by the second BPF 12. Since f1 to f12 are assigned, it is possible to prevent the false image 52 due to interference from being displayed on the display unit 17 in advance.

In addition, when the interference check is performed, ultrasonic waves are not transmitted from other ships, but ultrasonic waves may be transmitted from other ships after entering the reception period. Even in this case, by switching the orientation-specific frequency f1~f12 each detection cycle, as shown in the previous embodiment, it is possible to identify the false image 52 and fish image 51 due to interference. Furthermore, it is possible to prevent the false image 52 due to interference from being displayed on the display unit 17 by using the image correlation processing shown in the previous embodiment.

  In the above embodiment, the direction-specific frequencies f1 to f12 are switched for each detection cycle. However, even if the direction-specific frequencies f1 to f12 are switched for a plurality of detection cycles, the direction-specific frequencies f1 to f12 are switched for each detection cycle. The same effect as when switching is obtained.

  Moreover, in the said embodiment, although the transmitter / receiver 1 was divided | segmented into 12 area | regions A1-A12 and different frequency f1-f12 was allocated to each area | region A1-A12, the number of area | regions A1-A12 is from 12. More or less. Further, it is not necessary that the frequencies assigned to the respective regions are different from each other. For example, as shown in the number 1 of the directional frequency assignment table 31c in FIG. The present invention can also be implemented by assigning the same frequency-specific frequency (for example, frequency f3) to.

  Further, in the above-described embodiment, the reception aperture angle for forming the reception beams B1 to B12 is 90 degrees, and when the reception beams B1 to B12 of each direction are formed, the reception aperture is rotated by 30 degrees for each of the 12 reception beams B1. However, the reception aperture angle is not limited to 90 degrees, and the rotation angle of the reception aperture may be reduced to form a larger number of reception beams. Furthermore, in the above-described embodiment, the case where a single-frequency ultrasonic wave is transmitted from each transducer 2 has been described. However, an ultrasonic wave having a predetermined frequency band, for example, the center frequency is f and the frequency is f−Δf ( Alternatively, the present invention can also be applied when transmitting FM-modulated ultrasonic waves that continuously change from f + Δf) to f + Δf (or f−Δf).

  Furthermore, although the case where the umbrella-shaped transmission beam is used has been described in the above embodiment, the present invention can be implemented even when the fan-shaped transmission beam Bt shown in FIG. 10 is used. In this case, the direction of the present invention is the direction in the vertical plane of the fan-shaped transmission beam Bt. Furthermore, in the above-described embodiment, the case where the cylindrical transducer 1 is used has been described. However, a transducer having another shape, for example, a transducer in which a large number of vibrators are provided on the surface of a spherical main body is provided. Even if it uses, this invention can be implemented. Furthermore, in the above-described embodiment, the effects of ship rolling and pitching due to waves and the like have not been described, but in order to cancel these effects, the amount of phase adjustment at the time of transmission beam formation based on the rolling angle and pitching angle In addition, the phase correction amount at the time of receiving beam formation is appropriately corrected.

  In the embodiments described above, the case where the underwater detection device is a scanning sonar has been described. However, the present invention is also implemented in an underwater detection device such as a sector scanning sonar, a searchlight sonar, and a Doppler tide meter (hereinafter referred to as a tide meter). can do. First, the operation of the present invention in the sector scanning sonar will be described. In the scanning sonar, as shown in FIG. 8, an umbrella-shaped transmission beam Bt is formed on the entire circumference of the transducer 1, but in the sector scanning sonar, a predetermined central angle (here, A fan-shaped transmission beam having a central angle of 90 degrees and a depression angle is formed. Then, the underwater information in each direction in the transmission beam is detected by scanning the fan-shaped transmission beam with a pencil-shaped reception beam. In addition, since only the fan-shaped range can be detected by one transmission of ultrasonic waves, the entire circumference is detected by mechanically rotating the transducer. Also, the depression angle of the transmission beam is mechanically performed.

  First, the first detection cycle (first detection process) will be described. In the first detection cycle, for example, detection of underwater information is performed using the frequency for each direction shown in FIG. 1A, and first, a fan-shaped transmission beam in a range of 90 degrees centered on the direction D2. Is formed. And underwater information of each direction D1-D3 is detected using receiving beam B1-B3 of direction D1-D3. At this time, in the same manner as in the case of the scanning sonar, the reception beams B1 to B3 are frequency-selected by the direction-specific frequencies f1 to f3 by the band pass filters, respectively. Furthermore, by detecting the underwater information of the azimuths D4 to D6, the azimuths D7 to D9, and the azimuths D10 to D12 by continuously rotating the transducer by 90 degrees and changing the transmission direction of the transmission beam, One detection cycle ends. In the second detection cycle (second detection step), for example, the underwater information of each azimuth D1 to D12 is used in the same manner as in the first detection cycle using the directional frequency of each azimuth shown in FIG. Is detected. Further, the third, fourth,... Detection cycles are continuously executed.

  Next, the operation of the present invention in searchlight sonar will be described. In searchlight sonar, a pencil-shaped ultrasonic wave is transmitted from a transducer of a transducer at a predetermined depression angle in one direction. Based on the received signal received by the transducer, detection of underwater information in the direction is performed. Since only a narrow pencil-shaped area can be detected by one transmission of ultrasonic waves, the entire circumference is detected by mechanically rotating the transducer. Further, the depression angle at which the ultrasonic wave is transmitted is also mechanically performed.

  First, the first detection cycle will be described. In the first detection cycle, for example, first, an ultrasonic wave having a frequency f1 is transmitted to the azimuth D1 using the directional frequency of each azimuth shown in FIG. 1A, and an echo signal returned from the azimuth is transmitted to the transducer. The underwater information in the direction D1 is detected based on a signal selected from the received signal at the frequency f1 by direction. Similarly, by detecting the underwater information in the directions D2 to D12 by mechanically rotating the transmitter / receiver by 30 degrees to change the ultrasonic wave transmission direction, the first detection cycle is completed. In the second detection cycle, for example, the underwater information in each direction D1 to D12 is detected in the same manner as in the first detection cycle, using the direction-specific frequency shown in FIG. 1B. Further, the third, fourth,... Detection cycles are continuously executed.

  As described above, ultrasonic waves having different frequencies f1 to f12 are transmitted for the respective directions D1 to D12, and the reception signals of the respective directions are frequency-selected at the respective directional frequencies f1 to f12 of the corresponding directions D1 to D12. The direction in which the false image is displayed is limited, and the number of cases where the false image due to interference covers an image of a school of fish is reduced. Moreover, since the frequency f1-f12 of the ultrasonic wave transmitted to each direction D1-D12 is changed for every detection cycle (detection process), the transmission timing of the ultrasonic wave is synchronized with the transmission timing of the ultrasonic wave of another ship. Even in such a case, the display state of the false image due to the interference changes every detection cycle. On the other hand, fish and other images are displayed at approximately the same position even if the detection cycle changes, so operators of sector scanning sonar and searchlight sonar can easily identify false images from interference and images of fish. And can definitely recognize images of fish schools.

  Next, the operation of the present invention in the tide meter will be described. The tide meter transmits ultrasonic waves with a predetermined depression angle to the front, rear, left, and right directions of the ship, and detects scattered signals in seawater and echo signals from the seabed, that is, underwater information, included in the received signals of each direction. By doing so, the speed and direction of the tidal current are obtained, and these are displayed on the display unit. In the first detection cycle, ultrasonic waves having different frequencies f1 to f4 are transmitted in four directions from the transducer of the transducer, and echo signals coming from each direction are received by the transducer. Underwater information in each azimuth is detected based on signals that have been frequency-selected at azimuth-specific frequencies f1 to f4. In the second detection cycle, for example, by transmitting ultrasonic waves of the azimuth-specific frequencies f3, f4, f1, and f2 to the above four azimuths so that the azimuth-specific frequencies are different from those of the first detection cycle, Underwater information of direction is detected.

  Here, when interference of reception signals occurs due to ultrasonic waves transmitted from other ships, the underwater information in one azimuth is greatly increased in the first detection cycle and the second detection cycle among the underwater information in each direction. Is different. When such a difference in underwater information is detected, the first and second detection cycles are performed again to determine whether there is a difference in the underwater information. On the other hand, if the difference in the underwater information is not detected, the speed and direction of the tidal current are obtained from the underwater information in the four directions obtained in the first or second detection cycle. As described above, since different azimuth-specific frequencies are used in the first and second detection cycles, it is possible to detect the occurrence of interference due to ultrasonic waves transmitted from other ships, It is possible to prevent the direction from being required. It should be noted that the speed and direction of the tidal current can be obtained in the same manner with a tide meter that transmits ultrasonic waves in three azimuths separated by 120 degrees instead of the four azimuths on the front, rear, left and right sides of the ship.

It is a figure which shows the frequency according to the direction of a transducer. It is a block diagram which shows the structure of a scanning sonar. It is a figure which shows the frequency allocation table according to direction. It is a time chart which shows transmission / reception of an ultrasonic wave. It is a figure which shows the screen of the display part on which the false image by interference was displayed. It is a figure for demonstrating an image correlation process. It is a time chart which shows transmission / reception of the ultrasonic wave of 2nd Embodiment. It is a figure which shows the aspect which detects underwater information with a scanning sonar. It is a figure which shows a transducer. It is a figure which shows the fan-shaped transmission beam transmitted from a transducer. It is a figure which shows the screen of the display part on which the false image by the conventional interference was displayed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmitter / receiver 2 Vibrator 5 Transmit beam forming part 11 Receive beam forming part 12 2nd BPF
13 Center frequency detection unit 15 Past data storage unit 16 Image processing unit 17 Display unit 20 Control unit 20a Random number generators 31a to 31c Directional frequency allocation table A1 to A12 Transmitter and receiver regions B1 to B12 Received beam, received beam signal D1 ~ D12 Direction f1 to f12 Directional frequency

Claims (6)

A transmitter / receiver in which a plurality of transducers are arranged in the azimuth direction, transmission control means for driving the plurality of transducers to transmit ultrasonic waves into water, and a reception signal received by the plurality of transducers are synthesized. Underwater detection comprising: reception control means for forming a reception beam signal; and display control means for displaying information on the detection target object on a display unit based on an echo signal from the detection object included in the reception beam signal. In the device
The transmission control means drives each transducer so as to transmit ultrasonic waves having different frequencies or frequency bands according to directions, and transmits the ultrasonic frequencies or frequencies transmitted to the respective directions every one or a plurality of detection cycles. Drive each transducer so that the band changes,
The underwater detection apparatus, wherein the reception control means selects a frequency for each direction for each one or a plurality of detection cycles to form a reception beam signal in each direction. The underwater detection device according to claim 1,
A storage unit for storing received beam signals of one or more past detection cycles;
The display control means generates a display signal from the received beam signal of the current detection cycle and the received beam signal stored in the storage unit, and based on the display signal, information on the detection target is displayed on the display unit. An underwater detection device characterized by being displayed on the screen. In the underwater detection device according to claim 1 or 2,
A random number generator for generating random numbers,
The transmission control means changes the timing of transmitting an ultrasonic wave based on the random number value generated by the random number generator , or varies depending on the direction based on the random number value generated by the random number generator. An underwater detection apparatus characterized by changing the relationship between each direction and the frequency or frequency band assigned to each direction with respect to the frequency or frequency band. The underwater detection device according to any one of claims 1 to 3,
A detector for detecting a center frequency of the received beam signal;
The detection unit detects a center frequency for each direction from the reception beam signal of each direction before transmitting an ultrasonic wave,
The transmission control unit transmits, in each direction, an ultrasonic wave having a frequency different from the central frequency for each direction detected by the detection unit, or an ultrasonic wave in a frequency band having a frequency different from the central frequency as the central frequency. As described above, an underwater detection apparatus that drives each of the vibrators as described above. The underwater detection device according to any one of claims 1 to 4,
A frequency allocation table for each direction that defines the relationship between each direction and the frequency of the ultrasonic wave allocated to each direction is provided.
The direction-specific frequency allocation table includes a plurality of allocation patterns,
The underwater detection apparatus, wherein the transmission control means transmits an ultrasonic wave to each direction using different allocation patterns in the frequency allocation table for each direction for every one or a plurality of detection cycles. An underwater detection method in an underwater detection device that transmits ultrasonic waves from a transducer into water, detects underwater information based on a received signal received by the transducer, and displays a detection result on a display unit,
In the first detection cycle, ultrasonic waves having different frequencies or frequency bands are transmitted to each direction in each direction, and underwater information in each direction is obtained based on a signal generated by selecting the frequency of the received signal in each direction according to the direction. detection and,
In the second detection cycle, ultrasonic waves having different frequencies or frequency bands depending on the direction, and ultrasonic waves having different frequencies or frequency bands from the first detection cycle are transmitted to each direction. underwater detection wherein the benzalkonium to detect the water information of each orientation on the basis of the signal generated by the frequency selected by the azimuth.

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