JP4936655B2 - Scanning sonar - Google Patents

Description

  The present invention relates to a scanning sonar, and more particularly to a scanning sonar characterized by control of a received beam.

  Scanning sonar is widely used in fishing rods because it can detect the size and location of a wide range of fish schools. FIG. 11 is a diagram illustrating an example in which the surroundings of a ship are detected by scanning sonar. T is a cylindrical transducer attached to the bottom of the ship, and a large number of transducers are attached along the circumferential and vertical directions of the cylinder. TB is an umbrella-shaped transmission beam, and RB is a pencil-shaped reception beam. The reception beam RB is formed with, for example, 64 resolutions in the azimuth direction. Then, the transmission beam TB is radiated in all directions from the transducer of the transmitter / receiver T, and the echo signals from the school of fish received by the reception beam RB in each direction are analyzed with a scanning sonar. Ask for data. On the other hand, for the distance direction, detection image data of each region P in the transmission beam TB is sequentially generated with a resolution corresponding to the sampling period on the time axis. Further, the detection range can be changed by changing the depression angle α of the transmission beam TB. A method for forming the transmission beam TB and the reception beam RB is described in Patent Document 4 described later.

In the above-described scanning sonar, in general, it is advantageous from the viewpoint of detection performance to increase the energy density of the reception beam RB in long-distance detection. Therefore, the reception beam RB having a narrow width (small spread angle) is used. It is done. It is also beneficial to reduce the width of the reception beam RB from the point of being less susceptible to reflections from the sea surface and the sea floor. On the other hand, in short-distance detection, if the width of the reception beam RB is narrowed, the range that can be covered by the reception beam RB becomes small, so a wide reception beam (with a wide spread angle) is used. For this reason, when a long-distance detection is performed using the narrow reception beam RB, a detection failure of a school of fish located at a short distance may occur. Therefore, when performing horizontal detection, by reducing the vertical divergence angle theta _V reception beam RB in accordance with the elapsed time from the transmission of the ultrasonic waves becomes longer (detection distance becomes longer), sea level Ya It has been proposed to enable detection over a wide range and a long distance without being affected by reflection from the seabed (for example, Patent Document 1). Further, by gradually decreasing the depression angle α and the vertical spread angle θ _{V of} the reception beam RB in conjunction with the increase in the elapsed time after transmitting the ultrasonic wave (the detection distance becomes longer), It has also been proposed to achieve the same object (for example, Patent Documents 2 and 3).

  FIG. 12 is a diagram illustrating an example in which vertical detection is performed using a scanning sonar, and illustrates a detection range in a vertical plane that forms a bearing angle β with respect to the heading indicated by an arrow. FIG. 12A shows an example in which the above-described cylindrical transducer T is used. FIG. 12B shows an example in which a spherical transducer Ta having a large number of transducers on the surface is used. In the figure, TB is a fan-shaped transmission beam, and RB is a pencil-shaped reception beam. In the detection in the vertical direction, a range extending in a fan shape in the vertical direction is detected. However, in the cylindrical transducer T, the transmission beam TB and the reception beam RB cannot be formed in the downward direction, so that the vicinity below the detection target is not detected. Also, the detection range in the vertical direction can be changed by changing the bearing angle β. The method for forming the above fan-shaped transmission beam TB is disclosed in Patent Document 4 described later.

  FIG. 13A is a diagram showing received beams in each direction in the above-described vertical detection, and FIG. 13B is a diagram showing a detection image displayed on the display unit of the scanning sonar. In the figure, 50 is the sea surface, 51 is the seabed, F1 and F2 are fish schools near the seabed 51, and P1 to P5 indicate the position of the seabed 51. P1 is a position vertically below the transducer Ta, and Q31 is a position where the distance from the transducer Ta is equal to P3. Further, since the reception beams RB12 and RB13 are symmetrical with respect to the reception beam RB11, the description of the reception beam RB13 is omitted. At the position P1, the image G0 of the seabed 51 is displayed on the display unit with a thickness corresponding to the difference between the distance from the transducer Ta to P2 and the distance to P1. An image G1 of the fish school F1 is also displayed above the image G0 of the seabed 51.

On the other hand, since the spread angles θ _V11 of the reception beams RB11 and RB12 are equal, in the reception beam RB12 in the direction where the angle formed by the vertically downward direction is large, the difference between the distance from the transducer Ta to P3 and the distance to P5 ( (Distance between Q31 and P5) increases. For this reason, the fish school F2 is located on the right side of the arc S31 having a radius between the transducers Ta and P3, and the echo signal from the fish school F2 is received during reception of the echo signal from the seabed 51. The Further, since the echo signal from the fish school F2 is generally lower in signal level than the echo signal from the seabed 51, it is buried in the echo signal from the seabed 51. Therefore, at the substantially intermediate position P4 between P3 and P5, only the image G0 of the seabed 51 is displayed on the display unit with a thickness corresponding to the distance between Q31 and P5.

JP-A-1-180484 (first page, right column, line 1 to page 2, upper right column, line 19) JP-A-9-15325 (Claim 1, paragraphs 0009 to 0017) JP-A-9-80147 (Claim 1, paragraphs 0009 to 0018) JP 2003-337171 (paragraphs 0020 to 0031, FIGS. 1 to 5)

  However, the above-mentioned Patent Documents 1 to 3 do not disclose any directional reception beam, control of the lateral spread angle of the reception beam, and the above-described vertical detection. For this reason, there is a problem that it cannot be applied to the scanning sonar, and a problem that the fish school F2 cannot be detected even though the fish schools F1 and F2 are equidistant from the seabed 51 (FIG. 13). Furthermore, in the above-mentioned Patent Documents 2 and 3, there is no mention of the depression angle at which the ultrasonic wave is transmitted, but when the detection distance is short, the depression angle of the reception beam is increased and the detection distance is long. Reduces the included angle of the receive beam. For this reason, a fish school may be detected based on a received beam formed in a direction in which no ultrasonic wave is transmitted, which causes a problem that it is impossible to detect a fish school that should be originally detected.

  The present invention solves the above-described problems, and an object of the present invention is to provide a scanning sonar that can detect a wide range by controlling the divergence angle of a received beam.

In the present invention, the “azimuth” is a concept including not only the angular position in the horizontal plane but also the position in the circumferential direction of the umbrella shown in FIG. 11 and the position in the circular arc shape shown in FIG. The “azimuth direction” refers to a direction in which the above azimuth changes .

In the first invention, a transducer having a plurality of transducers arranged in an azimuth direction and an orthogonal direction orthogonal to the azimuth direction, and a transmission beam of an ultrasonic wave having a predetermined depression angle by driving the plurality of transducers in the water Transmission control means for transmitting to each azimuth of the radiation surface, reception control means for synthesizing reception signals received by a plurality of transducers to form reception beam signals for each azimuth, and detection object based on the signals And a display control means for displaying the detection information on the display section, the reception control means , when the umbrella-shaped transmission beam is transmitted from the transducer at a predetermined depression angle, the depression angle of the reception beam follow the but controls to be equal to the depression angle of the transmit beam at a constant regardless of the detection distance of the transmitting direction of the transmission beam, detection range spread angle of the receive beam in a direction perpendicular to the radiation plane is longer Controlled so as to reduce Te is controlled to maintain the spread angle of the received beam in the radiation plane constant.

  By doing so, when the detection distance is short, the spread angle of the reception beam in the direction orthogonal to the radiation plane of the transmission beam (the spread angle in the vertical direction shown in the embodiment) is large, so that a wide range can be detected. It is possible to improve the efficiency of fish school detection. On the other hand, when the detection distance is long, the divergence angle is small, so that it is possible to prevent the echo signal of the fish school, that is, the energy density of the received beam signal, and detect the school of fish located at a long distance with high probability. it can. Further, as shown in Patent Documents 2 and 3, the reception beam is controlled so that the depression angle of the reception beam becomes equal to the depression angle of the transmission beam without changing the spread angle and the depression angle of the reception beam in conjunction with each other. A school of fish located in the direction in which the sound wave is transmitted can be reliably detected. Note that the spread angle of the received beam in the radiation plane of the transmission beam (the spread angle in the left-right direction shown in the embodiment) is kept constant because the reception beam for each direction is formed without a gap in the radiation plane of the transmission beam. Because it is done.

In the embodiment of the first invention, the reception control means controls the spread angle of the received beam in the direction so that the width of the received beam at each detection distance in the direction orthogonal to the radiation surface is constant. Can do. By doing so, the reception beam at each detection distance becomes a parallel beam of a certain width, so that the boundary of the detection range is clarified and the fish school in the boundary of the parallel beam can be detected reliably. it can. In addition, when changing the detection range by changing the depression angle, it is possible to easily determine a new detection range with no detection omission and little overlap of the detection ranges based on the depression angle before the change and the width of the parallel beam. As a result, the efficiency of fish detection can be improved.

In the embodiment of the first invention, the received signal to be synthesized is sampled at a predetermined period, and the reception control means controls the spread angle of the received beam in the direction orthogonal to the radiation surface for each sampled data. can do. In this way, an ideal reception beam corresponding to the detection distance can be finely formed.

In the embodiment of the first invention, the reception control means determines the number of reception signals of the transducers arranged in the orthogonal direction that contributes to the formation of the reception beam by the spread angle of the reception beam in the direction orthogonal to the radiation surface. It can be controlled by increasing or decreasing. In this way, the spread angle is controlled by increasing or decreasing the number of reception signals that contribute to the formation of the reception beam (increasing or decreasing the reception aperture), so that the amplitude of the reception signal of each transducer within the reception aperture is reduced. Compared with the amplitude control to be controlled, the spread angle can be changed with a high degree of freedom in a wide range without reducing the signal level of the received beam.

In the second invention, a transducer in which a plurality of transducers are arranged in an azimuth direction and an orthogonal direction orthogonal to the azimuth direction, and a plurality of transducers are driven to transmit an ultrasonic transmission beam to a vertical plane or a vertical plane. The transmission control means for transmitting to each azimuth of the underwater radiation surface, which is an inclined surface inclined at a predetermined angle, and the reception signals received by the plurality of transducers are combined to form reception beam signals for each azimuth. In a scanning sonar comprising a reception control means and a display control means for displaying detection information of a detection object on a display unit based on the signal, the reception control means transmits a fan-shaped transmission from the transducer to the radiation plane. When the beam is transmitted , control is performed so that the main axis of the reception beam coincides with the radiation surface, and the angle formed by the azimuth of the reception beam and the vertically downward direction is increased in the radiation surface. Follow Controlled to be small, controlled to maintain a constant spread angle of the reception beam in a direction perpendicular to the radiation surface.

  By doing in this way, in the azimuth where the angle between the azimuth of the received beam and the vertically downward direction is large, the spread angle of the received beam in the radiation plane of the transmitted beam is small. The range affected by this becomes narrower, and it becomes possible to detect fish schools near the seabed. That is, it is possible to detect a wide range. On the other hand, in the azimuth where the angle formed between the azimuth of the received beam and the vertically downward direction is small, the divergence angle is large, so that a wide range can be detected with a small number of received beams. Furthermore, since the main axis of the reception beam is controlled so as to coincide with the radiation surface, it is possible to reliably detect a school of fish located in the direction in which the ultrasonic waves are transmitted. The reason why the spread angle of the reception beam in the direction orthogonal to the radiation plane of the transmission beam is kept constant is that it is possible to detect a school of fish located in a predetermined range without variably controlling the spread angle. It is.

As a modification of the second aspect of the invention, the reception control means is configured to reduce the divergence angle as the detection distance becomes longer, instead of keeping the divergence angle of the received beam in a direction orthogonal to the radiation plane constant. You may control. By doing in this way, the effect similar to the said 1st invention is further acquired.

As a modification of the second invention, the reception control means, instead of holding the reception beam divergence angle in a direction orthogonal to the radiation plane constant, makes the divergence angle the vertical direction and the reception beam azimuth. You may control so that it may become small as an angle | corner becomes large. By doing this, the width of the received beam in the direction perpendicular to the radiation surface of the transmitted beam is larger in the direction with a large angle with the vertical downward direction where the detection range near the sea floor is often narrowed by the echo signal from the sea floor. Since it does not become wide, even when the radiation surface of the transmission beam is inclined with respect to the vertical plane, it becomes possible to more reliably detect a school of fish near the seabed.

In the embodiment of the second invention, the reception control means increases or decreases the number of reception signals of the transducers arranged in the azimuth direction that contributes to the formation of the reception beam by the spread angle of the reception beam in the radiation plane. Can be controlled by. In this way, the spread angle is controlled by increasing or decreasing the number of reception signals that contribute to the formation of the reception beam (increasing or decreasing the reception aperture), so that the amplitude of the reception signal of each transducer within the reception aperture is reduced. Compared with the amplitude control to be controlled, the spread angle can be changed with a high degree of freedom in a wide range without reducing the signal level of the received beam.

  According to the present invention, a wide range can be detected with a scanning sonar.

  Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a view showing the appearance of a spherical transducer. The transducer 1 is the same as the transducer Ta of FIG. 12B, and a large number of transducers (ultrasound transducers) 2 are provided on the surface of the spherical main body 1a. In order to make the arrangements uniform, for example, the vertex of a regular icosahedron (each surface is a regular triangle) inscribed in the spherical surface of the main body 1a or a point on a line obtained by projecting the side of the regular icosahedron onto the spherical surface, etc. Is arranged. Each transducer 2 is attached to the main body 1a so that the principal axis of the directivity characteristic with respect to the ultrasonic waves of the transducer 2 coincides with the normal line of the spherical surface of the main body 1a. Reference numeral 1b denotes a pipe for supporting the transducer 1 on the bottom of the ship, and the hollow portion of the pipe 1b accommodates wiring for connecting each vibrator 2 and the circuit portion of the scanning sonar. Further, the transducer 1 can be raised and lowered by a lifting mechanism (not shown). Although several tens of vibrators 2 are shown in the figure, generally several hundred vibrators 2 are attached to the transducer 1.

FIG. 2 is a diagram showing a transmission beam in the spherical transducer 1. In the following, the transducer 1 will be described as an example of the earth. In the figure, N represents a position on the transducer 1 corresponding to the north pole of the earth. In the vertical plane of the transducer 1, the opening angle (hereinafter, referred to as vertical aperture angle) opening to the phi _VT (hereinafter, referred to as vertical opening) analogy to the vibrator 2 (the earth contained in, for example, 45 degrees north latitude The transmission signal to be applied to the transducer 2) located in the range of 45 degrees south latitude is delayed by a time corresponding to the length of the arrow in the figure according to the position of the transducer 2 in the vertical direction. A transmission beam TB is formed on the entire circumference of the transducer 1 by matching the phase of the output ultrasonic wave. If the vertical opening is rotated downward by α degrees, an umbrella-shaped transmission beam TBa having a depression angle α is formed.

FIG. 3 is a diagram showing a reception beam in the spherical transducer 1. FIG. 3 (a), (b), the aperture angle in the horizontal plane (hereinafter, referred to as a horizontal aperture angle) opening (hereinafter, referred to as horizontal opening) to _H the phi vertical to the and vertical aperture angle phi _V range defined by the opening (hereinafter, the range of the receiving opening) thus to control the phase of the received signal, such as a transducer 2a included in, the receiving beam RB pencil is formed. Specifically, the phase of the received signal of each transducer 2a and the like is delayed by a time corresponding to the length of the arrow in FIG. 3A according to the position of the transducer 2a and the like in the reception aperture in the horizontal plane. At the same time, the phase of the received signal from each transducer 2p is delayed by a time corresponding to the length of the arrow in FIG. 3B in accordance with the position in the vertical direction of the transducer 2p in the reception aperture. Although the shape of the reception aperture is rectangular, the shape of the reception aperture may be elliptical.

FIG. 3C is a view of the reception beam RB as viewed from above. By changing the position of the horizontal opening in the horizontal plane, a reception beam of another direction, for example, the reception beam RBa can be formed. FIG. 3D is a view of the reception beam RB viewed from the side, and the reception beam RBb having a depression angle α can be formed by rotating the vertical opening downward by α degrees. The reception beam RB has a divergence angle in two directions (vertical direction and horizontal direction). θ _H is the spread angle in the left-right direction (in the horizontal plane), and θ _V is the spread angle in the vertical direction (in the vertical plane). Further, the two bisectors of the spread angles θ _H and θ _V are the main axes of the directivity of the reception beam RB. In the figure, the received beam RB is shown in a shape close to an isosceles triangle with the divergence angles θ _H and θ _V as apex angles, but the actual shape of the received beam is a more rounded shape. . The same applies to the following description.

The divergence angles θ _H and θ _V become predetermined angles by forming a pencil-type reception beam RB by controlling the phase of the reception signal. Furthermore, the magnitudes of the spread angles θ _H and θ _V can also be controlled by amplitude control for controlling the amplitude of the reception signal of each transducer 2 or reception aperture control for controlling the size of the reception aperture. Since the control method of the spread angles θ _H and θ _V is the same, the control of the spread angle θ _{H in} the left-right direction will be mainly described here.

First, the amplitude control disclosed in Patent Documents 2 and 3 will be described. In the amplitude control, the amplitude of the reception signal of each transducer 2a to 2e (FIG. 3A) contributing to the formation of the reception beam RB is controlled, and specifically, the weight to be multiplied with the reception signal is changed. Thus, the spread angle θ _H is controlled. For example, as shown in FIG. 3 (e), the weights multiplied by the reception signals of the respective vibrators 2a to 2e are reduced as the position of the vibrator 2 moves away from the center of the horizontal opening. Here, the transducer 2a, 2b, 2d, divergence angle theta _H by increasing the weight to be multiplied by the reception signal 2e is reduced, the spread angle theta _H by reducing the weight increases. Therefore, when the weights to be multiplied by the received signals of all transducers 2a~2e to 1, the spread angle theta _H is minimized. Similarly, the spread angle θ _V in the vertical direction is changed by changing the weight by which the reception signal of each transducer 2p, 2q, 2c, 2r, 2s (FIG. 3B) contributing to the formation of the reception beam RB is multiplied. To control.

Next, reception aperture control will be described. Receive aperture control is to enlarge or reduce the receive aperture defining a contributing vibrator 2 to form the receive beam RB, to control the size of the spread angle theta _H. That is, by increasing the horizontal opening, to reduce the spread angle theta _H. Moreover, by reducing the horizontal opening, increasing the spread angle theta _H. Similarly, by enlarging or reducing the vertical opening, for controlling the divergence angle theta _V in the vertical direction. In the reception aperture control, the size of the reception aperture can be freely enlarged or reduced. Therefore, compared to the amplitude control, the spread angles θ _H and θ _V are high in a wide range without reducing the signal level of the reception beam. It can be changed with a degree of freedom. The scanning sonar of the present invention includes a buffer memory 11a (FIG. 4) having a large storage capacity and can temporarily store the reception signals of a large number of transducers 2. Therefore, the scanning aperture control with high performance is adopted. Yes. This does not exclude the use of amplitude control or the combined use of reception aperture control and amplitude control.

  FIG. 4 is a block diagram showing a configuration of a scanning sonar (hereinafter also referred to as an apparatus) according to the present invention. The control unit 3 includes a CPU, a memory, and the like, and controls each unit of the apparatus based on data input from an operation unit (not shown) or data set in advance in the memory.

  The transmission beam forming unit 6 includes a transmission signal generation circuit 6b and a delay circuit 6a. The transmission signal generation circuit 6b generates a sine wave transmission signal having a predetermined frequency, for example, 40 kHz, and outputs it for about several milliseconds. That is, the transmission signal is generated in a pulse manner. As shown in FIG. 2, the delay circuit 6 a provided for each transducer 2 determines the position of the vertical opening based on the depression angle α of the transmission beam TB instructed from the control unit 20, and moves the transducer 2 in the vertical direction. The transmission signal is delayed by a time corresponding to the position. The transmission signal output from the delay circuit 6 a is amplified by the transmission amplifier 5 and drives the vibrator 2 of the transducer 1 through the transmission / reception switching circuit 4. As a result, ultrasonic waves are simultaneously transmitted from each transducer 2 into the water, and an umbrella-shaped transmission beam TB is formed around the transducer 1. In the following description, the transmission or reception system for each transducer 2 is called a channel.

Next, the receiving system will be described. The reception signal received by each transducer 2 is amplified by the reception amplifier 7 via the transmission / reception switching circuit 4 for each channel. The amplified received signal is converted into a digital signal by an A / D converter 9 after a signal component having a frequency other than a predetermined bandwidth including the frequency of the transmission signal is removed as noise by a BPF (band pass filter) 8. Is converted to The A / D converter 9 receives a first phase of an internal sine wave signal having the same frequency as the frequency of the transmission signal and a second phase that is 90 degrees apart from the first phase at a predetermined sampling period. The signal is sampled, and the sampled signal (sample data) is sequentially output. 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 reception beam signal described later, the phase of the reception signal is corrected by θ _C by multiplying the reception signal by exp (jθ _C ).

  The gain adjusting unit 10 is configured so that the amplitude of an echo signal from the same reflector in the water (for example, a fish school that is a detection target) 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 sample data of the received signal by an amplification factor corresponding to the elapsed time since the transmission beam was transmitted. The sample data of each channel output from the gain adjustment unit 10 is temporarily stored in the buffer memory 11 a of the reception beam forming unit 11.

The reception beam forming unit 11 includes a buffer memory 11a, a phase correction circuit 11b, a weight multiplication circuit 11c, an addition circuit 11d, a control circuit 11e, a coefficient memory 11f, and a DSP unit 11g including a DSP (digital signal processor) and a memory. Is done. First, an outline of the reception beam forming unit 11 will be described. The sample data of each channel stored in the buffer memory 11a is read by an address signal from the control circuit 11e. Phase correction (phase control) is performed on the sample data of each channel read from the buffer memory 11a by the phase correction amount θ _C for each channel output from the coefficient memory 11f by the phase correction circuit 11b. The weight multiplication circuit 11c multiplies the weight w (1 or 0) for each channel output from the coefficient memory 11f. Then, a reception beam signal is formed by adding the reception signals (sample data) of the respective channels by the adding circuit 11d.

Next, each part of the reception beam forming unit 11 will be described. FIG. 5 is a diagram illustrating an example of a coefficient table stored in the coefficient memory 11f, and FIG. 6 is a diagram illustrating an example of a spread angle table stored in the memory of the DSP unit 11g. The coefficient table 61 includes a phase correction amount θ _C (corresponding to the length of arrows in FIGS. 3A and 3B) and an A / D converter for each received beam signal for each direction. A weight w (1 or 0) for multiplying the received signal of each channel for each sample data sampled in 9 is stored. In FIG. 5, the first subscript of the phase correction amount θ _C indicates the number of the received beam signal, and the second subscript indicates the channel number. The first subscript of the weight w indicates the number of the received beam signal, the second subscript indicates the sample data number, and the third subscript indicates the channel number. The sample data # 1 weight is a weight for multiplying the sample data sampled first, and the sample data #j weight is a weight for multiplying the sample data sampled jth (last).

Next, the reason for storing the weight data for each sample data will be described. As will be described later, in the present invention, in the reception period for receiving an echo signal from a school of fish after transmitting an ultrasonic wave, the horizontal spread angle θ _H (FIG. 3C) of the received beam is kept constant. However, the vertical spread angle θ _V (FIG. 3D) is dynamically controlled according to the detection distance. Therefore, the control unit 3 determines the desired spread angle θ in the vertical direction of the received beam at each detection distance in the range from the shortest detection distance to the longest detection distance based on the detection distance data specified from the operation unit (not shown). _V is calculated. Since each detection distance and the number of sample data sequentially output from the A / D converter 9 have a correspondence relationship, the spread angle θ _V at each detection distance can be said to be the spread angle θ _V for each sample data. Calculated by the control unit 3, the data in the vertical divergence angle theta _V per sample data is written as a spread angle table 62 in the memory of the DSP portion 11g.

In the coefficient table 61, the weight w of the channel forming the reception beam, that is, the channel included in the reception aperture is set to 1, and the weight w of the channel not forming the reception beam is set to 0. Then, by setting the weight w of each channel to 1 or 0 for each sample data, the size of the above-described reception aperture is controlled, and the vertical spread angle θ _V of the reception beam is controlled for each sample data. Is done. The reason why the phase correction amount θ _C is not stored in the coefficient table 61 for each sample data is that the phase correction amount θ _C does not directly affect the dynamic control of the spread angle θ _V in the vertical direction. Because.

Next, generation of the coefficient table 61 will be described. In the memory of the DSP unit 11g, in addition to the divergence angle table 62, the position (coordinates) on the surface of the main body 1a of the transducer 1 received from the control unit 3, the depression angle of the received beam, and Data such as the direction of each reception beam is stored. The DSP unit 11g calculates the above-described phase correction amount θ _C based on the above data. Additionally, DSP unit 11g on the basis of the above data, such as the spread angle theta _V1 in the vertical direction of spread angle theta _V spread angle table 62 for each sampled data and equal, and the spread angle theta _H in the horizontal direction is constant The position and size of the reception aperture forming each reception beam is determined so as to be a value, the weight w of the channel included in the reception aperture is determined as 1, and the weight w of the other channels is determined as 0. Then, calculated the phase correction amount theta _C the determined weights w is DSP unit 11g by writing to the coefficient memory 11f, the coefficient table 61 is generated. Although the weight w is determined for each sample data here, the same weight w may be shared by a plurality of consecutive sample data in order to reduce the processing load of the DSP unit. The coefficient table 61 and the spread angle table 62 are generated when the detection conditions such as the detection distance and the depression angle of the transmission / reception beam are changed.

The control circuit 11e includes an oscillation circuit, a memory, a timing circuit, and the like. When receiving a notification that an ultrasonic wave has been transmitted from the transmission beam forming unit 6, the control circuit 11e starts counting pulses output from the oscillation circuit. Then, according to the count value (this count value indicates the elapsed time since the transmission of the ultrasonic wave), the control circuit 11e reads the sample data from the buffer memory 11a and the address signal for writing the sample data to the buffer memory 11a. An address signal for reading out, an address signal for reading out the phase correction amount θ _C and weight w in the coefficient table 61 used for the read sample data from the coefficient memory 11f, a control signal for reading and writing operations, etc. To do.

The sample data read from the buffer memory 11a is phase-corrected by the corresponding phase correction amount θ _C read from the coefficient table 61 by the phase correction circuit 11b, and further, the weight multiplication circuit 11c. The corresponding weight w read from the coefficient table 61 is multiplied. For example, when forming the reception beam signal of number 2 using the first sample data of the reception data of channel number 2, θ _C (2,2) (FIG. 5) is used as the phase correction amount θ _C. As the weight w, w (2,1,2) (this value is 1) is used. Furthermore, the reception signals of the respective channels subjected to the phase correction and the weight multiplication are added by the adder circuit 11d, so that the reception beam signals in the respective directions are generated and sequentially output from the adder circuit 11d. As described above, the phase control and the reception aperture control are performed on the reception signal of the channel forming the reception aperture, and the addition is performed, that is, by synthesizing the reception signal, the horizontal spread angle θ _H is constant. In addition, a reception beam in each direction in which the vertical spread angle θ _V dynamically changes according to the detection distance is formed.

  The detector 12 obtains the amplitude of the received beam signal in each direction, 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 each received beam signal. An envelope signal of the received beam signal (echo signal) is obtained. The magnitude of this signal is proportional to the size of the school of fish and the degree of density. The image processing unit 13 performs image processing on the signal output from the detection unit 12, thereby displaying an image of the fish school according to the size, density, orientation, and distance of the school of fish on the display unit 14.

  FIG. 7 is a diagram showing control of a received beam in fish school detection in shallow water. FIG. 7A is a view of a reception beam in one direction as viewed from the side, and FIG. 7B is a view of the reception beam as viewed from above. In the figure, 50 indicates the sea surface, 51 indicates the sea floor, and H indicates the distance between the transducer 1 and the sea floor 51. The distance H is obtained by transmitting an ultrasonic wave vertically downward from the transducer 1 and measuring the time taken to receive an echo signal from the seabed 51 or by using a depth meter. An arrow TB indicates an umbrella-shaped transmission beam transmitted from the transducer 1 at a depression angle α in one direction. Strictly speaking, a principal axis plane (also referred to as a radiation plane of the transmission beam TB) of the directivity characteristic of the transmission beam TB is shown.

RB1 to RB3 are reception beams in one azimuth, and indicate reception beams at detection distances D1 to D3, respectively. The spread angles θ _{V1 to} θ _{V3 in} the vertical direction of the reception beams RB1 to RB3 become smaller as the detection distances D1 to D3 become longer. Further, the vertical direction of the bisector of the spread angle theta _V received beams RB (i.e., the principal axis of the directivity of the receiving beam RB) is adapted to match the emission surface of the transmission beam TB. That is, the depression angle of the reception beam RB is equal to the depression angle α of the transmission beam TB. In the above description, the reception for each sample data beam is formed, i.e. in the vertical direction of the reception beam for each sample data is spread angle theta _V has to be controlled, wherein for convenience of illustration, the three The reception beams RB1 to RB3 for the detection distances D1 to D3, that is, for three sample data are shown.

Next, a description will be given of the control of the vertical divergence angle theta _V receive beam RB. Control unit 3, the reception beam RB at the time of the detection distance D is calculated by equation (1) the spread angle theta _V in the vertical direction affected by the reflection of the following at the seabed 51.
D · sin (α + θ _V / 2) = H (1)
Furthermore, the vertical spread angle θ _V of the reception beam RB is not limited to the effect of reflection on the seabed 51, but is also the energy density of the reception beam RB, the vertical spread angle of the transmission beam TB, and the reflection on the sea surface 50. It is determined in consideration of the influence.

For example, when a sufficient energy density cannot be obtained with the reception beam RB1 having the divergence angle θ _V1 (the level of the reception signal of the vibrator 2 is too small), the reception beam RB1a having a smaller vertical divergence angle θ _V1 is used. (Indicated by a broken line in FIG. 7A) may be formed. In consideration of the above, the control unit 3 calculates the vertical spread angle θ _V for each detection distance D, that is, for each sample data, as described above, and displays the calculation result as the spread angle table 62 (FIG. 6). ) To the memory of the DSP unit 11g. Further, as described above, the DSP unit 11g uses the data such as the spread angle table 62 and the position (coordinates) of the transducer 2 on the surface of the main body 1a of the transducer 1 to obtain the coefficient table 61 (FIG. 5). Generate.

On the other hand, the spread angle θ _H (FIG. 7B) in the left-right direction of the reception beams RB1 to RB3 is constant regardless of the detection distance D. Is the is constant regardless of the detection distance D in the lateral direction of the spread angle theta _H of the thus received beam RB, since no gap receiving beam RB are formed in all directions of the transducer 1, the divergence angle theta _H This is because there is no need to dynamically change. In FIG. 7B, the reception beams RB1 to RB3 and two adjacent reception beams are illustrated, but similar reception beams are formed in other directions.

Then, after the ultrasonic transmission beam TB of the depression angle α is radiated around the transducer 1, the fish detection is performed by analyzing the echo signal from the fish school received by the transducer 2. In the reception period, the reception signal received by each transducer 2 is sampled by the A / D converter 9 at a predetermined cycle. Then, the reception beam forming unit 11 forms reception beam signals at each detection distance D from the sample data sequentially output from the A / D converter 9 and sequentially outputs them. As described above, the received beam signal is formed by correcting the phase of the sample data of each channel with the phase correction amount θ _C stored in the coefficient table 61, multiplying the weight w, and then adding them. Is done. Here, since the coefficient table 61 stores weight w data for setting the vertical spread angles at the detection distances D1 to D3 to θ _V1 to θ _V3 , the reception beam RB1 shown in the figure is stored. ~ RB3 is formed.

As described above, as the spread angle theta _V in the vertical direction of the reception beam RB in accordance with detection distance D is longer decreases, the divergence angle theta _V is controlled. Further, when the control of the spread angle theta _V, such as the distance H from the transducer 1 to the seabed 51 are also contemplated. As a result, a wide range can be detected at a short distance, and a decrease in energy density of an echo signal can be prevented at a long distance detection. Further, detection can be performed without being affected by reflection from the sea surface 50 and the sea floor 51. Further, the vertical spread angle θ _V is dynamically controlled according to the detection distance D, but the depression angle of the reception beam RB is constant and is controlled to be equal to the depression angle α of the transmission beam TB. It is possible to reliably detect a school of fish located in the direction in which the ultrasonic waves are transmitted.

Further, the reception beam RB for each sample data outputted from the A / D converter 9 is formed, it is possible to control the divergence angle theta _V in the vertical direction finely, the reception beam RB of ideal shape Can be formed. When the common phase correction amount θ _C and weight w data are used for a plurality of continuous sample data as described above, for example, every time 50 msec elapses (if the sound speed in water is 1500 m / sec, each time the detection distance increases 75 m), spread angle theta _V in the vertical direction becomes smaller.

FIG. 8A is a diagram illustrating control of the reception beam when detecting a school of fish in a place where the sea floor is sufficiently deep. Here, there is no need to control the divergence angle theta _V in the vertical direction of the reception beam RB in consideration of the distance between the transducer 1 and the seabed. As in the case of FIG. 7, RB1 to RB3 are reception beams in one direction and indicate reception beams at detection distances D1 to D3, respectively. The spread angles θ _{V1 to} θ _{V3 in} the vertical direction of the reception beams RB1 to RB3 become smaller as the detection distances D1 to D3 become longer. Further, the bisector of the vertical divergence angle theta _V receive beam RB is made to match the emission surface of the transmission beam TB. That is, the depression angle of the reception beam RB is equal to the depression angle α of the transmission beam TB. Therefore, the same effect as in the case of FIG. 7 can be obtained.

In the above description, the reception for each sample data beam is formed, i.e. in the vertical direction of the reception beam for each sample data is spread angle theta _V has to be controlled, wherein for convenience of illustration, the three The reception beams RB1 to RB3 for the detection distances D1 to D3, that is, for three sample data are shown. Although not shown in the figure, the horizontal spread angle of the reception beam RB is kept constant regardless of the detection distance D.

FIG. 8B is a diagram showing the reception beams RB1 to RB3 that are controlled so that the vertical widths of the reception beams at the detection distances D1 to D3 are constant in the case of FIG. 8A. . Here, the vertical spread angle θ _V of the reception beam RB is controlled so that the vertical width L of the reception beam at each detection distance D is constant, that is, the following equation (2) is satisfied. .
D1 · tan (θ _V1 / 2) = D2 · tan (θ _V2 / 2) =
D3 · tan (θ _V3 / 2) = D · tan (θ _V / 2) = L / 2 (2)

By finely controlling the divergence angle theta _V of the vertical, specifically, by sequentially reducing the vertical divergence angle theta _V for each sample data, each detector further than detection distance D1 The width L in the vertical direction of the reception beam RB at the distance D is constant, and the parallel beam PB is formed. As a result, the boundary of the detection range becomes clear, and the fish school in the boundary of the parallel beam PB can be detected reliably. In addition, when changing the detection range by changing the depression angle, it is easy to create a new detection range with no detection omission and little overlapping of detection ranges based on the depression angle before the change and the width L of the parallel beam PB. Can be determined. Also in this case, the control unit 3 determines the width L of the parallel beam PB in consideration of the depression angle of the transmission beam TB, the distance between the transmitter / receiver 1 and the sea surface 50, and the like so as to realize the parallel beam PB having the width L. A divergence angle table 62 is generated. Furthermore, the DSP unit 11g generates a coefficient table 61 for realizing a parallel beam PB having a width L based on the divergence angle table 62 and the like. Then, based on the coefficient table 61, the spread angle theta _V in the vertical direction of the reception beam is controlled.

  A second embodiment of the present invention will be described. Also in this embodiment, the scanning sonar (FIG. 4) provided with the same spherical transducer 1 (FIG. 1) as the previous embodiment is used. In the previous embodiment, detection around the transmitter / receiver 1 was performed using the transmission beam TB of the predetermined depression angle α. In the present embodiment, detection in the vertical direction is performed as in FIG.

  FIG. 9A is a diagram showing the reception beams RB1 to RB5 in each direction in the vertical plane from which the transmission beam (not shown) is emitted. FIG. 9B is a diagram illustrating a detection image displayed on the display unit 14 of the scanning sonar. In the figure, 50 is the sea surface, 51 is the seabed, F1 and F2 are fish schools near the seabed 51, and P1 to P5 indicate the position of the seabed 51. P1 is a position below the transducer 1 in the vertical direction. Q3 and Q4 are positions where the distance from the transducer 1 is equal to P3 and P4, respectively. Further, the reception beams RB2 and RB3 and the reception beams RB4 and RB5 are bilaterally symmetric with respect to the reception beam RB1, and thus the description of the reception beams RB4 and RB5 is omitted. Next, the relationship between FIG. 9 and FIG. 13 will be described. The positions of the fish schools F1 and F2 are the same in both figures. The reception beam RB1 in FIG. 9 is the same as the reception beam RB11 in FIG. The reception beams RB2 and RB3 in FIG. 9 are obtained by dividing the reception beam RB12 in FIG. 13 into two.

Further, the relationship shown in the following formula (3) is established in the vertical spread angles θ _{V1 to} θ _V3 of the reception beams RB1 to RB3.
θ _V1 > θ _V2 > = θ _V3 (3)
theta _V2 that has a theta _V3 or more, the reception beam RB2, RB3 is a reception beam adjacent to each other, there is a case where both are equal on account of the control of the spread angle theta _V. Although not shown, in this embodiment as well, the horizontal spread angle θ _H of the reception beam RB is kept constant, and the main axis of the directivity of the reception beam RB exists in the radiation plane of the transmission beam. To do. In addition, the vertical spread angle θ _V and the horizontal spread angle θ _H in this embodiment can be expressed as a spread angle in the radiation plane of the transmission beam and a spread angle in a direction perpendicular to the radiation plane, respectively. On the other hand, the vertical spread angle θ _V and the horizontal spread angle θ _H in the previous embodiment can be expressed as a spread angle in a direction orthogonal to the radiation plane of the transmission beam and a spread angle in the radiation plane, respectively.

From the correspondence between FIG. 9 and FIG. 13, at the position P1, the image G0 of the seabed 51 and the image G1 of the fish school F1 are displayed on the display unit 14 as in FIG. On the other hand, since the spread angles θ _V2 and θ _V3 of the reception beams RB2 and RB3 are substantially half of the spread angle θ _V11 of the reception beam R12 in FIG. 13, the region affected by the echo signal from the seabed 51, that is, An echo signal from the seabed 51 in FIG. 13 is a portion on the right side of the arc S3 whose radius is the distance between the transducers 1 and P3 and a portion on the right side of the arc S4 whose radius is the distance between the transducers 1 and P4. Is smaller than the region affected by (the portion on the right side of the arc S31). As a result, the fish school F2 located in the region affected by the echo signal from the seabed 51 in FIG. 13 is located in the region not affected by the echo signal from the seabed 51 in FIG. The image G2 is displayed on the display unit 14. For the same reason, the thickness of the image G0 of the echo signal from the seabed 51 at the positions P3 to P5 is smaller than that in the case of FIG.

In the present embodiment, (according to the angle increases the azimuth and vertically below the receiving beam RB) orientation of the receive beam RB is the distance from the vertically downward, so that the vertical divergence angle theta _V reception beam RB is reduced I have to. As a result, even in the reception beams RB2 and RB3 with the azimuth away from vertically below, the area affected by the echo signal from the sea floor 51 is reduced, that is, the school of fish near the sea floor 51 is detected by the echo signal from the sea floor 51. The hindered range becomes narrow, and it becomes possible to detect a school of fish near the seabed 51 that could not be detected conventionally.

Next, a reception beam control method will be described. FIG. 10 is a diagram illustrating an example of the coefficient table and the spread angle table of the present embodiment. In the figure, the first subscript of the phase correction amount θ _C and the weight w indicates the number of the received beam signal, and the second subscript indicates the channel number. In the present embodiment, as shown in FIG. 9 (a), spread angle theta _V in the vertical direction of the reception beam RB for each orientation is constant regardless of the detection distance. Therefore, the coefficient table 61a stores, for each received beam signal, the phase correction amount θ _C of the received signal of each channel and the weight w by which the received signal of each channel is multiplied. The coefficient table 61 of the previous embodiment. As shown in FIG. 5, the weight w is not stored for each sample data.

On the other hand, as shown in FIG. 9A, the vertical spread angle θ _V of the reception beam RB in each direction varies depending on the direction of the reception beam RB. Therefore, the spread angle table 62a, to less than a predetermined size the area of influence of the echo signal from the seabed 51, the spread angle theta _V in the vertical direction is stored for each received beam signal. The divergence angle table 62a is generated by the control unit 3 and written in the memory of the DSP unit 11g of the reception beam forming unit 11 as in the previous embodiment. The coefficient table 61a is also generated by the DSP unit 11g and written to the coefficient memory 11f, as in the previous embodiment. Then, a reception beam signal is generated by the reception beam forming unit 11 using the coefficient table 61a, so that the reception beam RB shown in FIG. 9A is formed.

  In the embodiment described above, the scanning sonar using the spherical transducer 1 has been described. However, the scanning sonar including the cylindrical transducer T shown in FIGS. 11 and 12A is also applicable to the present invention. Can be implemented. However, in the cylindrical transducer T, a transmission beam and a reception beam cannot be formed in the downward direction. In the first embodiment, as shown in FIG. 7, the case where an umbrella-shaped transmission beam TB with a predetermined depression angle α is used has been described. However, the depression angle of the transmission beam is 0 degrees. Also, the present invention can be implemented.

Further, in the second embodiment, the horizontal spread angle θ _H of the reception beam RB is maintained at a constant angle. However, as the detection distance becomes longer as in the first embodiment, the spread angle is increased. You may make it make (theta) _H small. Furthermore, in the second embodiment, a case has been described in which the transmission beam formed in the vertical plane is used for detection in the vertical direction, but the transmission beam is inclined at a predetermined angle with respect to the vertical plane. Even in this case, the present invention can be applied. In that case, the reception beam is also formed on the inclined surface. Further, as the inclination angle increases, the reception beam RB increases as the angle between the azimuth of the reception beam RB and the vertically downward direction (in other words, the bisector of the central angle of the radiation surface of the transmission beam) increases. The difference in the timing of receiving echoes from the seabed between the left side and the right side of the seawater increases, causing a problem that it becomes impossible to detect a school of fish near the seabed. Therefore, in such a case, received according to the angle between the azimuth and vertically below the beam RB is large, the reception beam RB in the lateral direction of it is desirable to reduce the spread angle theta _H.

It is a figure which shows the external appearance of a spherical transducer. It is a figure which shows the transmission beam in a spherical transducer. It is a figure which shows the receiving beam in a spherical transducer. It is a block diagram which shows the structure of a scanning sonar. It is a figure which shows an example of a coefficient table. It is a figure which shows an example of a divergence angle table. It is a figure which shows the receiving beam in 1st Embodiment. It is a figure which shows the receiving beam in 1st Embodiment. It is a figure which shows the receiving beam and detection image in 2nd Embodiment. It is a figure which shows an example of the coefficient table in 2nd Embodiment, and a divergence angle table. It is a figure which shows the example which detects the circumference | surroundings of a ship with the scanning sonar. It is a figure which shows the example which performs the detection of a vertical direction with a scanning sonar. It is a figure which shows the conventional receiving beam and a detection image.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmitter / receiver 2 Oscillator 3 Control part 6 Transmission beam formation part 9 A / D converter 11 Reception beam formation part 13 Image processing part 14 Display part 61, 61a Coefficient table 62, 62a Spreading angle table

Claims (8)

A transmitter / receiver in which a plurality of transducers are arranged in an azimuth direction and an orthogonal direction orthogonal to the azimuth direction, and a plurality of transducers are driven to transmit an ultrasonic transmission beam having a predetermined depression angle to each azimuth of a radiation surface in water Transmission control means for transmitting, reception control means for synthesizing reception signals received by a plurality of transducers to form signals of reception beams according to orientations, and display unit for detecting detection information of a detection object based on the signals In a scanning sonar comprising display control means for displaying on
The reception control means is configured such that when an umbrella-shaped transmission beam is transmitted from the transducer at a predetermined depression angle, the depression angle of the reception beam is constant regardless of the detection distance in the transmission direction of the transmission beam. controls to be equal to the depression angle of the beam, the said detection range of the spread angle of the receive beam in a direction perpendicular to the radiation surface is controlled to be smaller as long, of the receive beam in the radiation plane A scanning sonar characterized by controlling the divergence angle to be kept constant. The scanning sonar of claim 1 ,
The scanning sonar characterized in that the reception control means controls a spread angle of the reception beam in the direction so that a width of the reception beam at each detection distance in a direction orthogonal to the radiation surface is constant. The scanning sonar according to claim 1 or 2 ,
The reception signal to be synthesized is sampled at a predetermined period, and the reception control means controls a spread angle of the reception beam in a direction orthogonal to the radiation surface for each sampled data. . The scanning sonar of claim 1 ,
The reception control means controls the spread angle of the reception beam in a direction orthogonal to the radiation surface by increasing or decreasing the number of reception signals of the transducers arranged in the orthogonal direction that contribute to the formation of the reception beam. Scanning sonar characterized by that. Transmitter / receiver in which a plurality of transducers are arranged in the azimuth direction and an orthogonal direction orthogonal to the azimuth direction, and the plurality of transducers are driven to tilt the ultrasonic transmission beam at a predetermined angle with respect to the vertical plane or the vertical plane Transmission control means for transmitting to each azimuth of the underwater radiation surface that is the inclined surface, reception control means for combining the reception signals received by the plurality of transducers to form reception beam signals for each azimuth, In a scanning sonar comprising display control means for displaying detection information of a detection object on a display unit based on a signal,
When the fan-shaped transmission beam is transmitted from the transducer to the radiation surface , the reception control means controls the main axis of the reception beam to coincide with the radiation surface, The divergence angle of the reception beam is controlled so as to decrease as the angle formed between the azimuth of the reception beam and the vertical downward direction increases, and the divergence angle of the reception beam in a direction orthogonal to the radiation surface is kept constant. Scanning sonar characterized by controlling to. The scanning sonar of claim 5 ,
The reception control means controls the divergence angle to become smaller as the detection distance becomes longer, instead of keeping the divergence angle of the reception beam in a direction orthogonal to the radiation plane constant. Scanning sonar. The scanning sonar of claim 5 ,
The reception control means replaces the divergence angle of the reception beam in a direction orthogonal to the radiation plane with a constant angle as the angle between the azimuth of the reception beam and the vertically downward direction increases. A scanning sonar that is controlled to be small. The scanning sonar of claim 5 ,
The reception control means controls the spread angle of the reception beam in the radiation plane by increasing or decreasing the number of reception signals of the transducers arranged in the azimuth direction that contribute to the formation of the reception beam. Scanning sonar.

Images