GB2553404A - Underwater detection system - Google Patents

Abstract

A transducer array is driven to generate a first transmission wave of narrow beam width and a second wave of wider beamwidth. A reception circuit receives reflected waves corresponding to each of the first and second transmission waves, and generates respective reception signals. First and second image generators process those signals to generate images based, respectively, on reflections corresponding to the first and second transmission waves. The first and second images may respectively be 2D or 3D images, where the 3 dimensional image may be a projection of three dimensional data onto a plane (horizontal, vertical, or otherwise inclined) such as top and bottom views representing projections upwards or downwards from the data. The 3D image may include several projections. Processing apparatus 5 may be remote from the sensor array, and data transfer and processing operations of that apparatus may take place in parallel with generation of the first image.

Description

(56) Documents Cited:

GB 2426337 A US 20140269192 A1 US 20060236770 A1

US 20150369908 A1 US 20110013484 A1 (71) Applicant(s):

Furuno Electric Company Limited (Incorporated in Japan)

9-52 Ashihara-cho, Nishinomiya City, Hyogo 662-8580, Japan (72) Inventor(s):

Akira Okunishi Sanae Nagai Yoshihiro Kamiyama

Humminbird, 2013, Operations Summary Guide, [online], Available from: https:// www.humminbird.com/WorkArea/

DownloadAsset.aspx?id=3023 [Accessed 15 November 2017] (58) Field of Search:

INT CL G01S Other: WPI, EPODOC (74) Agent and/or Address for Service:

CSY London

Fetter Lane, London, EC4A 1BR, United Kingdom (54) Title of the Invention: Underwater detection system

Abstract Title: An underwater detection system which generates images using reflection waves from transmitted waves of wide and narrow beam width (57) A transducer array is driven to generate a first transmission wave of narrow beam width and a second wave of wider beamwidth. A reception circuit receives reflected waves corresponding to each of the first and second transmission waves, and generates respective reception signals. First and second image generators process those signals to generate images based, respectively, on reflections corresponding to the first and second transmission waves. The first and second images may respectively be 2D or 3D images, where the 3 dimensional image may be a projection of three dimensional data onto a plane (horizontal, vertical, or otherwise inclined) such as top and bottom views representing projections upwards or downwards from the data. The 3D image may include several projections. Processing apparatus 5 may be remote from the sensor array, and data transfer and processing operations of that apparatus may take place in parallel with generation of the first image.

TRANSDUCER E

FIRST DISPLAY UNIT

9

FIG. 1

1/26

FIG. 1

2/26

FIG. 2

3/26

FIG. 3

4/26

Ο

cc

5/26 s

FIG. 5

6/26

LO

σ ο

oc

CD

7/26

H2u

FIG. 7

8/26

L

FIG. 8

9/26

FIG. 9

10/26

FRONT <

> REAR

DOWN

^:W^:

FIG. 10

11/26

PROCESSING APPARATUS

SCANNING SONAR

FIG. 11

12/26

FIG. 12

13/26 (0

10a

CQ

14/26

/

Bv, CS1

FIG. 14Α

FIG. 14B

15/26

H2u

Βν, CS1

FIG. 15

16/26

V2b, V2

FIG. 16A

V2l, V2 /

FIG. 16B

17/26

V2b, V2

FIG. 17

18/26

FIG. 18

19/26

FIG. 19

20/26

FIG. 20

21/26

V2b, V2

FIG. 21A

V2l, V2

FIG. 21B

22/26

FIG. 22

23/26

V2b, V2

k Bv, CS2

FIG. 23A

FIG. 23B

24/26

H2l

' Bv, CS4

FIG. 24

25/26

V2b, V2

FIG. 25A

V2l, V2

FIG. 25B

26/26

PROCESSING APPARATUS

SCANNING SONAR

FIG. 26

UNDERWATER DETECTION SYSTEM

Technical Field [0001] This disclosure relates to an underwater detection system, which detects a target object.

Background of the Invention [0002] For example, JP5089319B discloses an underwater detection device (sonar) which may transmit an ultrasonic beam underwater to scan a 3-dimensional area, and display underwater information (e.g., school of fish) in the scanned area as a 3-dimensional image based on received echoes. This sonar may form an omnidirectional transmission beam in a given 3-dimensional area. In reception mode, the sonar may form a pencil beam as a reception beam which has a narrow beam width, and scan the reception beam in the 3-dimensional area. JP1985-078372A and JP2885989B disclose similar sonars which also form a transmission beam having a wide beam width and a reception beam having a narrow beam width.

[0003] A general scanning sonar transmits transmission waves having a narrow beam width in the vertical plane, to all azimuths around a ship simultaneously, and then forms reception beams also having a narrow beam width in the vertical plane while changing the azimuth around the ship. Thus, a school of fish in or near an area at a desired tilt angle of the sonar with respect to the ship on which the sonar is mounted can be detected.

[0004] Also, a known scanning sonar displays a top view horizontal image illustrating image signals which are generated based on reception signals obtained from a detection area.

[0005] To detect a school of fish in a 3-dimensional area by using the general scanning sonar, the 3-dimensional area may be scanned while gradually changing the tilt angle of the beam. However, such method requires extremely large computation load compared with a normal scanning sonar, which leads to a size increase of the device and a higher cost of - 1 manufacturing. Although there may be a manner to perform the above scanning without increasing the size of the device, since an update cycle of the image is long in such a manner there is a problem that real-time information is difficult to obtain.

[0006] Further, by only using the top view horizontal image illustrating image signals as in the known scanning sonar, if positions of a plurality of schools of fish vertically overlap, the school of fish located below the other may be overlooked.

Summary of the Invention [0007] The purpose of this disclosure relates to providing a convenient underwater detection system, which is reduced in cost as a whole.

[0008] The purpose of this disclosure also relates to providing an underwater detection system, which is capable of preventing a detection miss of a school of fish.

[0009] (1) In order to solve the above problems, according to one aspect of this disclosure, an underwater detection system is provided. The underwater detection system includes a transducer, a transmission circuit, a reception circuit, a first controller, a first image generator, a second controller and a second image generator. The transducer includes a plurality of transducer elements. The transmission circuit drives the plurality of transducer elements to transmit a first transmission wave and a second transmission wave, the second transmission wave having a beam width wider than that of the first transmission wave. The reception circuit generates a first reception signal based on a reflection wave of the first transmission wave and generates a second reception signal based on a reflection wave of the second transmission wave. The first controller causes the transmission circuit to generate a first drive signal, the first drive signal being the basis of the first transmission wave. The first image generator generates a first image based at least in part on the first reception signal outputted by the reception circuit. The second controller causes the transmission circuit to generate a second drive signal, the second drive signal being the basis of the second transmission wave. The second image generator generates a second image based at least in part on the second reception signal outputted by the reception circuit.

-2[0010] (2) The beam width of the first transmission wave in the vertical plane may be less than 20 degrees. The beam width of the second transmission wave in the vertical plane may be 20 degrees or more.

[0011] (3) The underwater detection system may further include a scanning sonar and a processing apparatus. The scanning sonar may include the transmission circuit, the reception circuit, the first controller and the first image generator. The processing apparatus may include the second controller and the second image generator. The processing apparatus may be provided separately from the scanning sonar.

[0012] (4) At least a part of a data transfer of the second reception signal to the processing apparatus may be performed at the same time as at least a part of the generation of the first image.

[0013] (5) The scanning sonar may further include a first display apparatus to display the first image. The underwater detection system may further include a second display apparatus to display the second image.

[0014] (6) The processing apparatus may be a personal computer.

[0015] (7) At least a part of the generation of the first image may be performed at the same time as at least a part of the generation of the second image.

[0016] (8) A frequency of occurrence at which the second transmission wave is transmitted may be less than that of the first transmission wave.

[0017] (9) The first image may be a 2-dimensional image generated based on the first reception signal obtained from an area in which the first transmission wave is transmitted. The second image may be a 3-dimensional image generated based on the second reception signal obtained from a 3-dimensional volume in which the second transmission wave is transmitted.

[0018] (10) The 3-dimensional image may be at least one of a vertical image and a horizontal image, the vertical image being a projection on a vertical plane of 3-dimensional data including 3-dimensional position information and echo intensity information obtained from the second reception signal for each position within the 3-dimensional volume, and the -3horizontal image being a projection on a horizontal plane of said 3-dimensional data.

[0019] (11) The 3-dimensional image may contain a top view horizontal image and a bottom view horizontal image, the top view horizontal image being the horizontal image resulting from a projection of the 3-dimensional data on an upper side horizontal plane positioned above the 3-dimensional data, and the bottom view horizontal image being the horizontal image resulting from a projection of the 3-dimensional data on a lower side horizontal plane positioned below the 3-dimensional data.

[0020] (12) The bottom view horizontal image may be obtained by reflection over an axis of reflection of the horizontal image obtained by projection of the 3-dimensional data on the lower side horizontal plane, the axis of reflection being within the lower side horizontal plane.

[0021] (13) The 3-dimensional image may contain at least two of the vertical image, the horizontal image and a perspective image, the perspective image being a projection of the 3-dimensional data on an inclined plane intersecting both the vertical plane and the horizontal plane.

[0022] (14) As a result of a user selecting a given position on one of the vertical image, the horizontal image and the perspective image as a selected image, a first mark may be displayed at said given position on the selected image and a second mark may be displayed at a position corresponding to said given position on at least one of the vertical image, the horizontal image and the perspective image not displaying the first mark.

[0023] (15) The second transmission wave has a beam width wider than that of the first transmission wave at least in the vertical plane.

[0024] (16) In addition, in order to solve the above problems, according to another aspect of this disclosure, an underwater detection system is provided. The underwater detection system includes a transducer, a transmission circuit, a reception circuit, a 3-dimensional data generator, and an image generator. The transducer includes a plurality of transducer elements. The transmission circuit drives the plurality of transducer elements to transmit a transmission wave that allows 3-dimensional data to be generated, the transmission wave -4being transmitted toward a 3-dimensional volume. The reception circuit generates a reception signal based on a reflection wave of the transmission wave. The 3-dimensional data generator generates the 3-dimensional data from the reception signal, the 3-dimensional data including 3-dimensional position information and echo intensity information for each position within the 3-dimensional volume. The image generator generates a top view horizontal image and a bottom view horizontal image, the top view horizontal image resulting from a projection of the 3-dimensional data on an upper side horizontal plane positioned above the 3-dimensional data, and the bottom view horizontal image resulting from a projection of the 3-dimensional data on a lower side horizontal plane positioned below the 3-dimensional data.

[0025] (17) The bottom view horizontal image may be obtained by reflection over an axis of reflection of an image obtained by projection of the 3-dimensional data on the lower side horizontal plane, the axis of reflection being within the lower side horizontal plane.

[0026] (18) The image generator may further generate at least one of a vertical image and a perspective image, the vertical image being obtained by projection of the 3-dimensional data on a vertical plane, and the perspective image being obtained by projection of the 3-dimensional data on an inclined plane intersecting the upper side horizontal plane, the lower side horizontal plane and the vertical plane.

[0027] (19) As a result of a user selecting a given position on one of the top view horizontal image, the bottom view horizontal image, the vertical image and the perspective image as a selected image, a first mark may be displayed at said given position on the selected image and a second mark may be displayed at a position corresponding to said given position on at least one of the top view horizontal image, the bottom view horizontal image, the vertical image and the perspective image not displaying the first mark.

[0028] (20) The underwater detection system may further include a display apparatus to display the top view horizontal image and the bottom view horizontal image.

Effects of the Invention

-5[0029] According to this disclosure, the underwater detection system being convenient and having a cost held down may be provided. In addition, the underwater detection system capable of preventing a detection miss of a school of fish may be provided.

Brief Description of the Drawings [0030] The present disclosure is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings, in which the like reference numerals indicate like elements and in which:

Fig. 1 is a block diagram illustrating a configuration of an underwater detection system according to one embodiment of this disclosure;

Fig. 2 is a view schematically illustrating a transmission range of a first transmission wave transmitted from a transducer;

Fig. 3 is a view schematically illustrating a transmission range of a second transmission wave transmitted from the transducer;

Fig. 4 is a block diagram illustrating a configuration of a receiver;

Fig. 5 is a view schematically illustrating one example of a display screen of a first display unit;

Fig. 6 is a block diagram illustrating a configuration of a processing apparatus;

Fig. 7 is a view schematically illustrating one example of a top view horizontal image;

Fig. 8 is a view schematically illustrating a first bottom view horizontal image generated in the process of generating a second bottom view horizontal image;

Fig. 9 is a view schematically illustrating one example of the second bottom view horizontal image;

Fig. 10 is a view schematically illustrating a generation process of the top view horizontal image and the second bottom view horizontal image generated by a second image generating module;

Fig. 11 is a flowchart illustrating operation of the underwater detection system;

-6Fig. 12 is a view illustrating one example of the 3-dimensional image displayed on a second display unit of the underwater detection system according to one modification;

Fig. 13 is a block diagram illustrating a configuration of an underwater detection system according to another modification;

Figs. 14A and 14B are views illustrating one example of two 3-dimensional images displayed on a second display unit of an underwater detection system according to another modification, in which Fig. 14A is a view illustrating a top view horizontal image and Fig. 14B is a view illustrating a vertical image;

Fig. 15 is a view illustrating one example of a top view horizontal image displayed on a second display unit of an underwater detection system according to another modification;

Figs. 16A and 16B illustrate vertical images corresponding to the top view horizontal image illustrated in Fig. 15, in which Fig. 16A illustrates a rear view vertical image, and Fig. 16B illustrates a left view vertical image;

Fig. 17 is a view illustrating one example of a rear view vertical image displayed on a second display unit of an underwater detection system according to another modification;

Fig. 18 illustrates a top view horizontal image corresponding to the rear view vertical image illustrated in Fig. 17;

Fig. 19 illustrates a second bottom view horizontal image corresponding to the rear view vertical image illustrated in Fig. 17;

Fig. 20 is a view illustrating one example of a top view horizontal image displayed on a second display unit of an underwater detection system according to another modification;

Figs. 21A and 21B illustrate vertical images corresponding to the top view horizontal image illustrated in Fig. 20, in which Fig. 21A illustrates a rear view vertical image, and Fig. 21B illustrates a left view vertical image;

Fig. 22 is a view illustrating one example of a top view horizontal image H2u displayed on a second display unit of an underwater detection system according to another

-7modification;

Figs. 23A and 23B illustrate vertical images corresponding to the top view horizontal image illustrated in Fig. 22, in which Fig. 23A illustrates a rear view vertical image, and Fig. 23B illustrates a left view vertical image;

Fig. 24 is a view illustrating one example of a second bottom view horizontal image displayed on a second display unit of an underwater detection system according to this modification;

Figs. 25A and 25B illustrate vertical images corresponding to the second bottom view horizontal image illustrated in Fig. 24, in which Fig. 25A illustrates a rear view vertical image, and Fig. 25B illustrates a left view vertical image; and

Fig. 26 is a flowchart illustrating another operation example of the underwater detection system according to the embodiment.

Detailed Description of the Invention [0031] Hereinafter, an underwater detection system 1 according to one embodiment of this disclosure is described with reference to the accompanying drawings. In the following embodiment, an example is illustrated in which this disclosure is applied to a ship. However, the present disclosure may be applied to any kinds of vehicles having a rudder or a similar steering device, such as other watercrafts including boats (fishing boats), vessels, and submarines.

[Configuration of Underwater Detection System] [0032] Fig. 1 is a block diagram illustrating a configuration of the underwater detection system 1 of the embodiment of this disclosure. Below, a ship equipped with the underwater detection system 1 may be referred to as “the ship.” Note that Fig. 1 only illustrates some of components constituting a receiver 8 and a processing apparatus 5.

[0033] As illustrated in Fig. 1, the underwater detection system 1 of this embodiment may include a scanning sonar 10, the processing apparatus 5, and a second display unit 6 (which

-8may also be referred to as a second display apparatus or a display apparatus). The scanning sonar 10 may be a general scanning sonar, and the underwater detection system 1 may be configured by externally attaching the processing apparatus 5 and the second display unit 6 to the scanning sonar 10.

[0034] The scanning sonar 10 may include a transducer 2, a transmitting-and-receiving device 3, and a first display unit 4 (which may also be referred to as a first display apparatus).

[0035] The transducer 2 may have a function to transmit and receive ultrasonic waves and be attached to a bottom of the ship. For example, the transducer 2 may have a substantially cylindrical shape and be arranged so that its axial direction is in the vertical plane and its radial direction is parallel to the horizontal direction.

[0036] For example, the transducer 2 may include a substantially cylindrical casing and ultrasonic transducers (not illustrated) as a plurality of transducer elements attached to an outer circumferential surface of the casing. Each ultrasonic transducer may transmit an ultrasonic wave underwater, receive an echo, convert the echo into an electric signal, and output it to the receiver 8. Note that, although in this embodiment the casing of the transducer 2 has the cylindrical shape, without particularly limiting to this, other shapes may also be adopted, for example, a spherical shape.

[0037] Fig. 2 is a view schematically illustrating a transmission range of a first transmission wave which is transmitted from the transducer 2. Fig. 3 is a view schematically illustrating a transmission range of a second transmission wave transmitted from the transducer 2. In Figs. 2 and 3, the transmission range of the transmission wave which is transmitted from the transducer 2 mounted on the ship S is schematically illustrated as the stippled section.

[0038] In this embodiment, the transducer 2 may transmit two kinds of transmission waves, specifically, the first transmission wave illustrated in Fig. 2 and the second transmission wave illustrated in Fig. 3. The transducer 2 may transmit the transmission waves in all horizontal directions from the ship.

-9[0039] The first transmission wave may be a transmission wave having a comparatively narrow beam width θι in the vertical plane. For example, the beam width θι of the first transmission wave may be about 8 degrees, but not limited to this as long as it is less than 20 degrees. Hereinafter, an area to which the first transmission wave is transmitted may be referred to as a 2-dimensional area Zl. Here, the beam width Oj of the first transmission wave in the vertical plane may be a minimum vertical beam width which the transducer 2 can achieve, or may be a value close to the minimum vertical beam width, which makes the area to which the first transmission wave is transmitted, comparatively narrow. Therefore, this area may be referred to as the 2-dimensional area Zl in this specification.

[0040] The second transmission wave may be a transmission wave having a wider beam width 0₂ in the vertical plane than the first transmission wave. The beam width 0₂ of the second transmission wave may be, for example, about 30 degrees, but not limited to this as long as it is 20 degrees or more. Hereinafter, an area to which the second transmission wave is transmitted may be referred to as a 3-dimensional area Z2 (which may also be referred to as a 3-dimensional volume). Here, while the beam width θι in the vertical plane of the first transmission wave is comparatively narrow as described above, the second transmission wave having the beam width θ₂ of 20 degrees or more may be said to have a sufficiently wide beam width, wider than the first transmission wave. Therefore, the area which has comparatively large 3-dimensional expansion and to which the second transmission wave having such a sufficient beam width is transmitted may be referred to as the 3-dimensional area Z2 in this specification.

[0041] For example, after the transducer 2 performs a set of transmission of the first transmission waves and reception of reflection waves caused by the transmitted first transmission waves a plurality of times, the transducer 2 may perform a set of transmission of the second transmission wave and reception of reflection wave caused by the transmitted second transmission wave once. In other words, in this embodiment, the frequency of occurrence at which the second transmission wave is transmitted may be less than that of the first transmission wave.

- 10[0042] The transmitting-and-receiving device 3 may include a transmission/reception switch 3a, a transmitter 7, and the receiver 8. The transmitting-and-receiving device 3 may be comprised of devices, such as a hardware processor 9 (CPU, FPGA, etc.), an analog circuit, and a nonvolatile memory. The hardware processor 9 may function as a first controlling module 7b (which may also be referred to as a first controller), a quadrature detection module 13, a first beam forming module 14, a filtering module 15, and a first image generating module 16 (which may also be referred to as a first image generator), which are described later in detail. The hardware processor 9 may perform the function of these modules, for example, by causing the CPU to read and execute program(s) from the nonvolatile memory.

[0043] The transmission/reception switch 3a may switch the signal transmission and reception status with respect to the transducer 2. For example, in order to drive the transducer 2 to output the transmission waves, the transmission/reception switch 3a may transmit a drive signal outputted from the transmitter 7 to the transducer 2. On the other hand, when receiving the reception signal from the transducer 2, the transmission/reception switch 3a may output the reception signal received by the transducer 2 to the receiver 8. [0044] The transmitter 7 may generate the drive signal being the basis of the transducer 2 to transmit the transmission wave. The transmitter 7 may include a transmission circuit part 7a (which may also be referred to as a transmission circuit) and the first controlling module 7b.

[0045] The transmission circuit part 7a may be controlled by the first controlling module 7b and a second controlling module 20 (which may also be referred to as a second controller) (described later in detail) of the processing apparatus 5 to generate the drive signal. For example, the transmission circuit part 7a may have transmission circuits (not illustrated), each being provided corresponding to each ultrasonic transducer. The transmission circuit may suitably be controlled by the first controlling module 7b to generate a first drive signal. The first drive signal may be a signal being the basis of the first transmission wave (the transmission wave having the beam width of about 8 degrees in - 11 the vertical plane) transmitted from the transducer 2. Moreover, each transmission circuit of the transmission circuit part 7a may be controlled by the second controlling module 20 to generate a second drive signal. The second drive signal may be a signal being the basis of the second transmission wave (the transmission wave having the beam width of about 30 degrees in the vertical plane) transmitted from the transducer 2.

[0046] The first controlling module 7b may suitably control each of the plurality of transmission circuits to generate the first drive signals.

[0047] Fig. 4 is a block diagram illustrating a configuration of the receiver 8. The receiver 8 may include an analog unit 11, an A/D converter 12, the quadrature detection module 13, the first beam forming module 14, the filtering module 15, and the first image generating module 16. The analog unit 11 and the A/D converter 12 may be provided as a reception circuit which generates a reception signal based on a reflection wave of a transmission wave.

[0048] The analog unit 11 may amplify an electric signal outputted from the transducer 2 and limit its bandwidth, so as to remove an unnecessary frequency component. The analog unit 11 may process both of the electric signal obtained from the reflection wave of the first transmission wave and the electric signal obtained from the reflection wave of the second transmission wave.

[0049] The A/D converter 12 may convert the electric signal generated by the analog unit 11 into a digital reception signal. The A/D converter 12 may process the electric signal obtained from the reflection wave of the first transmission wave to generate a first reception signal, and process the electric signal obtained from the reflection wave of the second reception wave to generate a second reception signal.

[0050] The quadrature detection module 13 may apply quadrature detection processing on the first reception signal and the second reception signal obtained from each ultrasonic transducer, to generate an I signal and a Q signal. These signals may be processed as a complex signal of which the real part is the I signal and the imaginary part is the Q signal. When the reception signals outputted from the A/D converter 12 are the first reception - 12signals, the quadrature detection module 13 may output the generated complex signals to the first beam forming module 14 as first complex signals. On the other hand, when the reception signals outputted from the A/D converter 12 are the second reception signals, the quadrature detection module 13 may output the generated complex signals to the processing apparatus 5 as second complex signals. Note that the output of the second complex signals from the quadrature detection module 13 to the processing apparatus 5 may be performed after these second complex signals are temporarily stored in a memory (not illustrated) of the transmitting-and-receiving device 3.

[0051] Note that the example in which the quadrature detection module 13 generates the second complex signals and then outputs them to the processing apparatus 5 is described here; however, this disclosure is not limited to this. For example, the quadrature detection processing may be performed in the processing apparatus 5 by outputting the second reception signals generated by the A/D converter 12 directly to the processing apparatus 5. [0052] The first beam forming module 14 may perform beamforming (specifically, summing phase shifted signals) on the first complex signals obtained from specific two or more ultrasonic transducers to obtain a first beam signal equivalent to a signal obtained from a single ultrasonic transducer having sharp directivity in a specific direction. The first beam forming module 14 may form a large number of first beam signals having directivity in every azimuth by repeating this process while changing the combination of the ultrasonic transducers subjected to the beamforming. As illustrated in Fig. 2, thus formed first beam signals may have a comparatively narrow beam width θι in the vertical plane (e.g., about 8 degrees).

[0053] The filtering module 15 may generate 2-dimensional image signals for generating first images (2-dimensional images) which are described later, by applying band limiting filter or pulse compression filter on the first beam signals formed by the first beam forming module 14.

[0054] The first image generating module 16 may generate the 2-dimensional image illustrating distribution of target objects (e.g., school of fish) around the ship based on - 13amplitudes of the 2-dimensional image signals (specifically, absolute values of the complex signals) generated by the filtering module 15. For example, the first image generating module 16 may generate a top view image illustrating the distribution on a conical surface taking the vertex at a position of the transducer 2 of the ship (hereinafter, may be referred to as “the horizontal mode image Hl”), or an image illustrating the distribution in a vertical plane which includes the transducer 2 (hereinafter, may be referred to as “the vertical mode image Vl”). Note that the image generated by the first image generating module 16 may be generated based on signals resulted from the first transmission waves having the comparatively narrow beam width, and obtained from a 2-dimensional area. Note that the area where the horizontal mode image Hl is obtained is the stippled section in Fig. 2.

[0055] Fig. 5 is a view schematically illustrating one example of a display screen 4a of the first display unit 4. The display screen 4a of the first display unit 4 may display the horizontal mode image Hl and the vertical mode image Vl generated by the first image generating module 16. For example, a user may suitably operate a user-interface (not illustrated), such as a keyboard, of the underwater detection system 1 to display the horizontal mode image Hl and the vertical mode image Vl selectively in a switchable manner or simultaneously on the first display unit 4. Fig. 5 illustrates an example in which a school of fish is located in the 2 o'clock direction from the ship S.

[0056] The first display unit 4 may stipple with high density an area where signals with high echo intensities are obtained, stipple with medium density an area where signals with medium echo intensities are obtained, and stipple with low density an area where signals with low echo intensities are obtained. Hereinafter, the area stippled with high density may be referred to the high echo intensity area, the area stippled with medium density may be referred to as the medium echo intensity area, and the area stippled with low density may be referred to as the low echo intensity area. Note that the first display unit 4 may actually illustrate the high echo intensity area in red, the medium echo intensity area in green, and the low echo intensity area in blue.

[0057] The processing apparatus 5 may be a device connected to the - 14transmitting-and-receiving device 3 of the scanning sonar 10 by a cable etc., and be configured by, for example, a PC (personal computer). Although described later in detail, the processing apparatus 5 may process portion of the reception signals processed by the transmitting-and-receiving device 3.

[0058] Incidentally, the underwater detection system 1 of this embodiment, not only is capable of causing the scanning sonar 10 to generate the projection images of the target object within the 2-dimensional area Z1 near the ship (specifically, the horizontal mode image Hl and the vertical mode image VI), but is also capable of causing the processing apparatus 5 (described later in detail) to generate projection images of target objects within the 3-dimensional area Z2 near the ship (see Fig. 3). Until the underwater detection system 1 is not inputted with a given instruction from the user via the user-interface, the scanning sonar 10 may generate the projection images of the target object within the

2- dimensional area Zl. On the other hand, when the underwater detection system 1 receives the given instruction from the user via the user-interface, the processing apparatus 5, the scanning sonar 10, etc. may perform the operations described below, to generate the projection images of the target object within the 3-dimensional area Z2 illustrated by stippling in Fig. 3. Hereinafter, this given instruction may be referred to as the

3- dimensional image generation instruction.

[0059] Fig. 6 is a block diagram illustrating a configuration of the processing apparatus 5. The processing apparatus 5 may include the second controlling module 20, a second beam forming module 21, a filtering module 22 (which may also be referred to as a 3-dimensional data generator), and a second image generating module 23 (which may also be referred to as a second image generator or an image generator).

[0060] Upon the 3-dimensional image generation instruction by the user, the second controlling module 20 may suitably control each of the transmission circuits of the transmission circuit part 7a to generate the second drive signal. For example, when the transducer 2 has a cylindrical shape, the second controlling module 20 may control the amplitude and phase of the drive signal so that the function of the shading coefficient in the - 15vertical plane becomes a sine function.

[0061] The second beam forming module 21 may receive the second complex signals from the quadrature detection module 13. The second beam forming module 21 may perform beamforming (specifically, summing phase shifted signals) on the second complex signals obtained from specific two or more of the ultrasonic transducers to obtain a single beam signal equivalent to a signal obtained from a single ultrasonic transducer having sharp directivity in a specific direction. The second beam forming module 21 may generate a large number of second beam signals having directivity in every azimuth by repeating this process while changing the combination of the ultrasonic transducers subjected to the beamforming. The generated second beam signals may have a narrower beams width than the beam width θ₂ of the second transmission wave, and the second beam forming module 21 may scan the range where the second transmission waves are transmitted, by gradually changing a tilt angle of the signal. Note that positional information of each 3-dimensional image data (described later in detail) generated based on each beam signal may be calculated based on a distance from the transducer 2 to an object on which the second transmission wave is reflected, and an orientation of the second beam signal. The distance may be obtained based on the time length from the transmission to reception of the second transmission wave.

[0062] The filtering module 22 may generate 3-dimensional image data for generating second images (3-dimensional images) which is described later, by applying band limiting filter or pulse compression filter on the second beam signals formed by the second beam forming module 21. The 3-dimensional image data may be a signal obtained from each position within the 3-dimensional area Z2, and have information of a 3-dimensional position at which each signal is obtained, and an echo intensity.

[0063] The second image generating module 23 may generate the image illustrating distribution of the target objects around the ship based on amplitudes of 3-dimensional image data (specifically, absolute values of the complex signals) generated by the filtering module 22. For example, the second image generating module 23 may generate the - 163-dimensional images, which are the second images, based on the signals obtained from the 3-dimensional area Z2 (see Fig. 3).

[0064] Fig. 7 is a view schematically illustrating one example of a top view horizontal image H2u. Fig. 8 is a view schematically illustrating a first bottom view horizontal image H2_l’ generated in the process of generating a second bottom view horizontal image H2_L. Fig. 9 is a view schematically illustrating one example of the second bottom view horizontal image H2_L. In this embodiment, the second image generating module 23 may generate, as the 3-dimensional images, the top view horizontal image H2u of which example is illustrated in Fig. 7 and the second bottom view horizontal image H2_L of which example is illustrated in Fig. 9. The second bottom view horizontal image H2_L may also be referred to as bottom view horizontal image.

[0065] Fig. 10 is a view schematically illustrating a generation process of the top view horizontal image H2u and the second bottom view horizontal image H2_L generated by the second image generating module 23. Fig. 10 illustrates a given plane (specifically, a vertical plane extending in front-rear direction) of 3-dimensional image data Sg plotted in a 3-dimensional rectangular coordinate system. The 3-dimensional image data Sg illustrated in Fig. 10 may be comprised of a high echo intensity area S_H illustrated in red (stippled with high density in Fig. 10), a medium echo intensity area S_M illustrated in green (stippled with medium density in Fig. 10), and a low echo intensity area S_L illustrated in blue (stippled with low density in Fig. 10). Note that, the 3-dimensional rectangular coordinate system on which the 3-dimensional image data Sg is plotted may be defined by x-, y- and z-axes which are parallel to left-right (port-starboard) direction, front-rear (bow-stern) direction, and up-down (top-bottom) direction of the ship, respectively.

[0066] The top view horizontal image H2u may result from a projection of the 3-dimensional image data Sg on an upper side horizontal plane P_Hu positioned above the 3-dimensional image data Sg. On the other hand, the second bottom view horizontal image H2_L may result from a projection of the 3-dimensional image data Sg on a lower side horizontal plane P_Hl positioned below the 3-dimensional image data Sg.

- 17[0067] The second image generating module 23 may generate the top view horizontal image H2u in the following manner. That is, as illustrated in Fig. 10, the second image generating module 23 may generate the top view horizontal image H2u by assigning the color at the uppermost side of the 3-dimensional image data Sg to the upper side horizontal plane P_Hu- Note that, in this embodiment, by setting suitable transparency for the areas S_M and S_L indicated by green and blue, the green area S_M covered with blue on the upper side may be projected on the upper side horizontal plane P_Hu, and the red area S_H covered with at least one of blue and green on the upper side may be projected on the upper side horizontal plane P_Hu- Here, the red area S_H covered by at least one of blue and green on the upper side may be displayed in a color other than red (e.g., ocher color). Thus, the top view horizontal image H2u as illustrated in Fig. 7 may be generated.

[0068] Moreover, the second image generating module 23 may generate the second bottom view horizontal image H2_L in the following manner. First, the second image generating module 23 may generate the first bottom view horizontal image H2_L’ being the basis of the second bottom view horizontal image H2_L.

[0069] For example, as illustrated in Fig. 10, the second image generating module 23 may generate the first bottom view horizontal image H2_L’ by assigning the color at the lowermost side of the 3-dimensional image data Sg (in the specific example depicted in Fig. 10: blue) to the lower side horizontal plane P_Hl- Note that, in this embodiment, by setting suitable transparency for the areas S_M and S_L indicated by green and blue, the green area S_M covered with blue on the lower side may be projected on the lower side horizontal plane Phl and the red area S_H covered with at least one of blue and green on the lower side may be projected on the lower side horizontal plane Phl· Here, the red area S_H covered by at least one of blue and green on the lower side may be displayed in a color other than red (e.g., ocher color). Thus, the second bottom view horizontal image H2_L’ as illustrated in Fig. 8 may be generated.

[0070] Further, the second image generating module 23 may generate the second bottom view horizontal image H2_L based on the first bottom view horizontal image H2_L’. For - 18example, the second image generating module 23 may perform a reflection of the first bottom view horizontal image H2_L’ over a front-rear axis L passing through the position corresponding to the ship S in the first bottom view horizontal image H2_L’ as illustrated in Fig. 8. Thus, the second bottom view horizontal image H2_L may be generated.

[0071] The second display unit 6 may display the 3-dimensional images generated by the second image generating module 23. In this embodiment, the second display unit 6 may display the top view horizontal image H2u and the second bottom view horizontal image H2_l.

[Operation of Underwater Detection System] [0072] Fig. 11 is a flowchart illustrating operation of the underwater detection system 1. Hereinafter, operations of the scanning sonar 10 and the processing apparatus 5 provided to the underwater detection system 1 are described with reference to Fig. 11.

[0073] First, once the underwater detection system 1 is activated, the scanning sonar 10 may start a normal operation (SI). The normal operation of the scanning sonar 10 may be the following series of operations. That is, in the normal operation, the transducer 2 may first transmit the first transmission waves having the narrow beam width 0| and receive the reflection waves caused thereby. The received reflection waves may be processed by the respective components of the receiver 8 to generate the horizontal mode image Hl and the vertical mode image VI. As illustrated in Fig. 5, the first display unit 4 may display the horizontal mode image Hl and the vertical mode image VI. Note that, the transmission waves transmitted so as to generate the vertical mode image V1 may have a comparatively wide beam width in the vertical plane.

[0074] If the instruction to generate the 3-dimensional image from the user is not issued during the normal operation (NO at S3), the scanning sonar 10 may repeat the normal operation. On the other hand, if the 3-dimensional image generation instruction is issued by the user (YES at S3), the underwater detection system 1 may execute the following S4 to S6. That is, when the 3-dimensional image generation instruction is issued at S2, the - 19second controlling module 20 may control the transmission circuit part 7a to generate the second drive signals. Then at S4, the transducer 2 may transmit the second transmission wave based on the second drive signals. The reflection wave of the second transmission wave may be received by the transducer 2 and then processed by the analog unit 11, the A/D converter 12, and the quadrature detection module 13 to generate the second complex signals (S5). Each second complex signal may be transferred to the second beam forming module 21 of the processing apparatus 5 upon generation or after being stored temporarily in the memory (not illustrated) as a bulk (S6).

[0075] Note that, at S6, at least a part of the transfer of the second complex signals to the processing apparatus 5 may be performed at the same time as at least a part of the generation of the first images during the normal operation. In this embodiment, the transfer of the second complex signals and the normal operation may be performed in parallel. Since the scanning sonar 10 may perform the normal operation while performing the transfer of the second complex signals, the data transfer in order to generate the 3-dimensional image can be performed substantially without lowering update rates of the images (i.e., the horizontal mode image Hl and the vertical mode image VI) generated during the normal operation.

[0076] At S7, the processing apparatus 5, after receiving the second complex signals, may process the second complex signals. For example, at S7, the second beam forming module 21 may generate the second beam signals from the second complex signals, and the filtering module 22 may filter the second beam signals to generate the 3-dimensional image data Sg. The top view horizontal image Η2_υ and the second bottom view horizontal image H2_L may be generated based on the 3-dimensional image data Sg. Thus generated top view horizontal image H2u and second bottom view horizontal image H2_L may be displayed on the second display unit 6 (S8). Then, if an instruction to stop generating the 3-dimensional image is not issued by the user (NO at S9), the generation of the 3-dimensional image may continue. On the other hand, if the instruction to stop generating the 3-dimensional image is issued by the user (YES at S9), the generation of the 3-dimensional image may be -20stopped. Note that at least a part of the generation of the second images (top view horizontal image Η2_υ and second bottom view horizontal image H2_L) may be performed at the same time as at least a part of the generation of the first images during the normal operation. Since these images can be generated in parallel, decrease in the update rate of each image can be prevented.

[0077] Conventionally, underwater detection devices (e.g., sonars) which transmit an ultrasonic beam underwater to scan a 3-dimensional area, and display underwater information (e.g., school of fish) in the scan area as a 3-dimensional image based on received echoes are disclosed. The sonar disclosed in JP5089319B may form an omnidirectional transmission beam in a given 3-dimensional area. In reception mode, the sonar may form a pencil beam as a reception beam having a narrow beam width and scan the reception beam in the 3-dimensional area.

[0078] A general scanning sonar transmits transmission waves having a narrow beam width in the vertical plane, to all azimuths around a ship at once, and then form reception beams also having a narrow beam width in the vertical plane while changing the azimuth. Thus, a school of fish in or near an area at a desired tilt angle of the beam with respect to the ship on which the sonar is mounted can be detected.

[0079] To detect a school of fish in a 3-dimensional area by using the general scanning sonar, the 3-dimensional area may be scanned while gradually changing the tilt angle of the beam. However, such method requires extremely large computation load compared with a normal scanning sonar, which leads to a size increase of the device and a higher cost of manufacturing. Although there may be a manner to perform the above scanning without increasing the size of the device, since an update cycle of the image is long in such a manner there is a problem that real-time information is difficult to obtain.

[Effects] [0080] In this regard, the underwater detection system 1 of this embodiment may generate the horizontal mode image Hl and the vertical mode image VI at substantially the same - 21 update rates as the conventional scanning sonar, on the basis of the first reception signals obtained based on the reflection waves of the first transmission waves having the comparatively narrow beam width θι in the vertical plane. Moreover, the underwater detection system 1 may also obtain the images Η2_υ and H2_L of the target objects located within the 3-dimensional area Z2, on the basis of the second reception signals obtained based on the reflection waves of the second transmission waves having the wider beam width θ₂ than the beam width Θ, of the first transmission waves. Thus, while obtaining the horizontal mode image Hl and the vertical mode image VI at substantially the same update rates as the conventional art, the distribution of the target objects located within the 3-dimensional area Z2 may also be grasped.

[0081] Therefore, according to the underwater detection system 1, a convenient underwater detection system which is reduced in cost as a whole may be provided.

[0082] According to the underwater detection system 1, the 2-dimensional images (in this embodiment, the horizontal and vertical mode images Hl and VI) may be generated on the basis of the first reception signals obtained based on the reflection waves of the first transmission waves. Additionally, the 3-dimensional images (in this embodiment, the top view horizontal image Η2_υ and second bottom view horizontal image H2_L) may be generated on the basis of the second reception signals obtained based on the reflection waves of the second transmission waves having the different beam width from that of the first transmission waves.

[0083] In the underwater detection system, since the area in which the target objects are detectable depends on the beam width of the transmission wave, by performing the target detection using the transmission wave having a wide beam width as in the underwater detection system 1, target objects located within 3-dimensional space may be detected. Moreover, the target objects detected in the 3-dimensional space may be projected on the 3-dimensional image. Therefore, according to the underwater detection system 1, the echo images having different characteristics may be generated based on the reception signals corresponding to the transmission waves having different beam widths from each other. - 22For example, according to the 2-dimensional images obtained based on the first transmission waves having the narrow beam width 0_b the target objects may be detected from the 2-dimensional area (in this embodiment, the 2-dimensional area Zl). Thus, the positions of the target objects may be accurately grasped. On the other hand, according to the 3-dimensional images obtained based on the second transmission waves having the wide beam width θ₂, the target objects may be detected from the 3-dimensional area (in this embodiment, the 3-dimensional area Z2). Thus, the target objects may be detected from large space. That is, according to the underwater detection system 1, it becomes possible for the user to, for example, roughly grasp the position of a desired school of fish from the 3-dimensional images and then grasp a more accurate position of the school of fish from the

2-dimensional images. Thus, a convenient underwater detection system may be provided. [0084] According to the underwater detection system 1, the beam width of the first transmission wave may be set to less than 20 degrees (specifically, about 8 degrees), while the beam width of the second transmission wave may be set to 20 degrees or more (specifically, about 30 degrees). Thus, the 2-dimensional area where the detection is performed with the first transmission wave and the 3-dimensional area where the detection is performed with the second transmission wave may be set.

[0085] According to the underwater detection system 1, by connecting the processing apparatus 5 comprised of the PC to the conventionally known scanning sonar 10, it becomes possible to easily generate images based on signals obtained from the 3-dimensional area (3-dimensional images). In other words, according to the underwater detection system 1, an underwater detection system capable of generating 3-dimensional images may be provided at low cost and without significant change of equipment.

[0086] In the underwater detection system 1, the scanning sonar 10 may perform the normal operation while the reception signal is transferred from the scanning sonar 10 to the processing apparatus 5. Thus, the data transfer in order to generate the 3-dimensional images may be performed without substantially lowering the update rate of the 2-dimensional images generated during the normal operation.

-23[0087] In the underwater detection system 1, the first display unit 4 may display the

2- dimensional images based on the echo signals obtained from the 2-dimensional area ZI, and the second display unit 6 may display the 3-dimensional images. As a result, the user can visually confirm the images obtained from both the areas ZI and Z2.

[0088] In the underwater detection system 1, the processing apparatus 5 may be comprised of the PC. Thus, the processing apparatus 5 may be constructed at a relatively low cost. [0089] In the underwater detection system 1, the frequency of occurrence at which the second transmission wave is transmitted may be lower than that of the first transmission wave. Thus, the 3-dimensional images may be generated without greatly lowering the update rate of the scanning sonar 10.

[0090] In the underwater detection system 1, the first images may be obtained based on the echoes of the target objects located within the 2-dimensional area ZI to which the first transmission wave is transmitted, and the second images may be obtained based on the echoes of the target objects located within the 3-dimensional area Z2 to which the second transmission wave is transmitted. Thus, in the underwater detection system 1, the first images based on the echoes obtained from the 2-dimensional area ZI with a small

3- dimensional volume may be obtained and the second images based on the echoes obtained from the 3-dimensional area Z2 may be obtained. Thus, a convenient underwater detection system may be provided.

[0091] Incidentally, a display unit of the conventional underwater detection system displays a top view image illustrating image signals generated based on reception signals obtained from a detection area. In this case, if positions of a plurality of schools of fish vertically overlap, there is a possibility that the school of fish located below the other is overlooked. [0092] In this regard, with the underwater detection system 1, even if schools of fish vertically overlap, the position of the school of fish located above the other may be grasped from the top view horizontal image H2u, and the position of the school of fish located below may be grasped from the second bottom view horizontal image H2_L. For example, with reference to Figs. 7 and 9, both of an echo image A in Fig. 7 and an echo image C in Fig. 9

- 24may be echoes from schools of fish. By displaying the top view horizontal image Η2_Π and the second bottom view horizontal image H2_L on the display units as in the underwater detection system 1, two vertically overlapping schools of fish may be grasped. In other words, according to the underwater detection system 1, detection miss of a school of fish may be prevented. Note that an echo image B in Fig. 7 may be an echo image illustrating a trail of the ship.

[0093] In the first bottom view horizontal image H2_L’ which is simply the bottom view of the 3-dimensional image data Sg, a school of fish located on the starboard side of the ship may be displayed at the left side on the display screen and a school of fish located at the port side of the ship may be displayed at the right side on the display screen. In this manner, it may be difficult for the user to intuitively grasp the positions of the schools of fish from this image. For example, an echo image C which indicates a school of fish in Fig. 8 illustrating the first bottom view horizontal image H2_L’ may be located on the right side, although the school of fish is actually located on the port side of the ship.

[0094] In this regard, in the underwater detection system 1, the second bottom view horizontal image H2_L may be generated by reflection of the first bottom view horizontal image H2_L’ as described above. In this manner, a school of fish on the starboard side of the ship may be displayed at the right side of the display screen, and a school of fish on the port side of the ship may be displayed at the left side on the display screen, which makes it easier for the user to intuitively grasp the positions of the schools of fish.

[Modifications] [0095] Although the embodiment of this disclosure is described above, this disclosure is not limited to this, and various modifications are possible without departing from the scope of this disclosure.

[0096] (1) Fig. 12 is a view illustrating one example of the 3-dimensional image displayed on the second display unit of the underwater detection system according to one modification. In the above embodiment, both of the top view horizontal image H2u and the second bottom -25view horizontal image H2_L may be displayed on the second display unit 6 as 3-dimensional images; however, without limiting to this, the second display unit 6 may display only one of the top view horizontal image H2u and the second bottom view horizontal image H2_L. Alternatively, a perspective image H2_T as illustrated in Fig. 12 may be displayed as the 3-dimensional image. The perspective image H2_T may be a projection of the 3-dimensional image data Sg on an inclined plane intersecting both a vertical plane and a horizontal plane. In other words, the perspective image H2_T may be an image of the 3-dimensional image data Sg seen in an oblique direction (i.e., a direction different from a direction perpendicular to a vertical plane and a horizontal plane). By displaying the perspective image H2_T on the second display unit 6, the position of the school of fish can be grasped more intuitively. Note that the perspective image H2_T may illustrate a top perspective view of the 3-dimensional image data Sg, or a bottom perspective view of the 3-dimensional image data Sg.

[0097] (2) Fig. 13 is a block diagram illustrating a configuration of an underwater detection system la according to another modification. In the above embodiment, the example in which the underwater detection system 1 is configured by connecting the processing apparatus 5, which is comprised of the PC and provided separately from the conventional scanning sonar 10, to the scanning sonar 10 is described; however, this disclosure is not limited to this. For example, as illustrated in Fig. 13, the components of the processing apparatus 5 described in the underwater detection system 1 of the above embodiment may be incorporated in a scanning sonar 10a. A transmitting-and-receiving device 3b illustrated in Fig. 13 may include a transmitter 7c incorporated with the second controlling module 20, and a receiver 8a incorporated with the second image generating module 23. Note that, although not illustrated in Fig. 13, the second beam forming module 21 and the filtering module 22 of the above embodiment may be incorporated in the receiver 8a. In the underwater detection system la, the 2-dimensional images and the 3-dimensional images may be displayed on the first display unit 4.

[0098] As described above, according to the underwater detection system la of this -26modification, the processing apparatus 5 of the underwater detection system 1 of the above embodiment, may become unnecessary, and the components of this processing apparatus 5 may be incorporated in the components of the scanning sonar 10a. Thus, the size of the underwater detection system may be reduced.

[0099] (3) Figs. 14A and 14B are views illustrating one example of two 3-dimensional images displayed on a second display unit of an underwater detection system according to another modification, in which Fig. 14A is a view illustrating a top view horizontal image H2u and Fig. 14B is a view illustrating a vertical plane image V2.

[0100] The second display unit of this modification may display the top view horizontal image H2u and a rear view vertical image V2_B. The rear view vertical image V2_B may result from a projection of 3-dimensional image data Sg on a vertical plane positioned rearward of the 3-dimensional image data Sg and extending in the left- right direction.

[0101] Further, in the underwater detection system of this modification, with reference to Fig. 14A, when the user selects via a user-interface (e.g., mouse) an arbitrary point (e.g., a point Pl in Fig. 14A) in the top view horizontal image H2u displayed on the second display unit, cursors may be displayed on both images H2u and V2_B. For example, an upper side horizontal cross cursor CS1 (which may also be referred to as a first mark) passing through the point Pl selected by the user may be displayed on the top view horizontal image H2u. Moreover, a vertical cursor CS_BH (which may also be referred to as a second mark) passing through a position corresponding to the point Pl may be displayed on the rear view vertical image V2_B to extend in an up-down direction of the display screen. The upper side horizontal cross cursor CS1 may be formed by a vertical bar Bv extending in the up-down direction of the display screen, and a horizontal bar Bh extending in a left-right direction of the display screen.

[0102] As described above, according to this modification, since the top view horizontal image H2u and the vertical image V2 may be generated based on the 3-dimensional image data Sg, by visually associating the top view horizontal image H2u and the vertical image V2 with each other, the position of a desired school of fish in water may be grasped.

-27[0103] Further, according to this modification, the cross cursor CS1 passing through the point Pl selected by the user may be displayed on the top view horizontal image Η2_υ and the vertical cursor CS_BH passing through the position corresponding to the point Pl may be displayed on the rear view vertical image V2_B. Therefore, with reference to these cursors, the position of the school of fish may accurately be grasped.

[0104] (4) Fig. 15 is a view illustrating one example of a top view horizontal image H2u displayed on a second display unit of an underwater detection system according to another modification. Figs. 16A and 16B illustrate vertical images V2 corresponding to the top view horizontal image H2u illustrated in Fig. 15, in which Fig. 16A illustrates a rear view vertical image V2_B, and Fig. 16B illustrates a left view vertical image V2_L.

[0105] The second display unit of this modification may display the top view horizontal image H2u, the rear view vertical image V2_B, and the left view vertical image V2_L. The left view vertical image V2_L may result from a projection of 3-dimensional image data Sg on a vertical plane positioned leftward (port side) of the 3-dimensional image data Sg and extending in the front-rear direction.

[0106] In the underwater detection system of this modification, with reference to Fig. 15, when the user selects via a user-interface (e.g., mouse) an arbitrary point (e.g., a point P2 in Fig. 15) in the top view horizontal image H2u displayed on the second display unit, cursors may be displayed on all of the three images H2u, V2_B and V2_L. For example, an upper side horizontal cross cursor CS1 (first mark) passing through the point P2 selected by the user may be displayed on the top view horizontal image H2u. Vertical cursors CS_BH and CS_LH (second marks) passing through positions corresponding to the point P2 and extending in the up-down direction of the display screen may be displayed on the rear view vertical image V2_B and the left view vertical image V2_L, respectively.

[0107] As described above, according to this modification, the top view horizontal image H2u, the rear view vertical image V2_B, and the left view vertical image V2_L may be generated based on the 3-dimenisonal image data Sg. Therefore, by visually associating these images with each other, the position of a school of fish in water may be grasped more -28accurately.

[0108] Further, according to this modification, the cross cursor CS1 passing through the point P2 selected by the user may be displayed on the top view horizontal image H2u, and the vertical cursors CS_BH and CS_LH passing through the positions corresponding to the point P2 may be displayed on the rear view vertical image V2_B and the left view vertical image V2_l, respectively. Therefore, with reference to these cursors, the position of the school of fish may accurately be grasped.

[0109] (5) Fig. 17 is a view illustrating one example of a rear view vertical image V2_B displayed on a second display unit of an underwater detection system according to another modification. Fig. 18 illustrates a top view horizontal image Η2_υ corresponding to the rear view vertical image V2_B illustrated in Fig. 17. Fig. 19 illustrates a second bottom view horizontal image H2_L corresponding to the rear view vertical image V2_B illustrated in Fig. 17.

[0110] In this modification, when the user inputs a desired depth range within which the user wants to detect a school of fish, a depth range scale R indicating the desired depth range may be displayed on the rear view vertical image V2_B. As for the top view horizontal image H2u and the second bottom view horizontal image H2_L, only echo images located within the depth range may be displayed. In this manner, schools of fish located outside the desired detection depth range by the user, or unnecessary echo images (e.g., the echo image B caused by the ship trail in Fig. 7) may be removed from the display screen, thus, echo images which are not required to be displayed may be eliminated from the display screen while certainly displaying echo images of the desired school of fish.

[0111] (6) Fig. 20 is a view illustrating one example of a top view horizontal image H2u displayed on a second display unit of an underwater detection system according to another modification. Figs. 21A and 21B illustrate vertical images V2 corresponding to the top view horizontal image H2u illustrated in Fig. 20, in which Fig. 21A illustrates a rear view vertical image V2_B, and Fig. 21B illustrates a left view vertical image V2_L.

[0112] In this modification, when the user inputs a desired azimuth range within which the -29user wants to detect a school of fish, a line LI and a line L2 indicating the desired azimuth range may be displayed on the top view horizontal image H2u. For the rear view vertical image V2_B and the left view vertical image V2_L, only echo images located within the azimuth range may be displayed. In this manner, schools of fish located outside the desired detection azimuth range by the user may be removed from the display screen, thus, echo images which are not required to be displayed may be eliminated from the display screen while certainly displaying echo images of the desired school of fish.

[0113] (7) In the above embodiment, the example of displaying the echo images located within a given distance range from the ship is described; however, this disclosure is not limited to this. For example, an underwater detection system may be configured such that, when the user inputs a desired distance range within which the user wants to detect a school of fish, only echo images located within the distance range may be included in each 3-dimensional image.

[0114] (8) In the above embodiment and modifications, each image is displayed in a color corresponding to the echo intensity; however this disclosure is not limited to this. For example, although not illustrated, the color of each image may correspond to depth. In this manner, for example, by displaying the horizontal image and the perspective image, the depth of each school of fish may be easily grasped.

[0115] (9) In the above embodiment, the example in which all reception signals located within the given distance range from the ship are subjected to signal processing; however, this disclosure is not limited to this. For example, the user may input two or more of a distance range, an azimuth range, and a depth range within which the user wants to detect a school of fish, so that only echo signals located within these ranges are subjected to signal processing. In this manner, the processing of the echo signals obtained outside the desired ranges inputted by the user may be omitted, which may reduce the computation load of the transmitting-and-receiving device.

[0116] (10) Fig. 22 is a view illustrating one example of a top view horizontal image H2u displayed on a second display unit of an underwater detection system according to another -30modification. Figs. 23A and 23B illustrate vertical images V2 corresponding to the top view horizontal image H2u illustrated in Fig. 22, in which Fig. 23A illustrates a rear view vertical image V2_B, and Fig. 23B illustrates a left view vertical image V2_L. Further, Fig. 24 is a view illustrating one example of a second bottom view horizontal image H2_L displayed on the second display unit of the underwater detection system according to this modification. Figs. 25A and 25B illustrate vertical images V2 corresponding to the second bottom view horizontal image H2_L illustrated in Fig. 24, in which Fig. 25A illustrates a rear view vertical image V2_B, and Fig. 25B illustrates a left view vertical image V2_L.

[0117] In this modification, when a user clicks with a mouse cursor etc. on an echo image of a school of fish on one of the 3-dimensional images to identify the position thereof, the position may be displayed on another one of the 3-dimensional images. For example, as illustrated in Figs. 22 and 23, when the user clicks on the position of a point P3 in the top view horizontal image H2u illustrated in Fig. 22, a top view horizontal cross cursor CS1 (first mark) having the crossing point at the point P3 of the top view horizontal image H2u may be displayed. The top view horizontal cross cursor CS1 may be formed by a vertical bar Bv extending in the up-down direction of the display screen, and a horizontal bar Bh extending in the left-right direction of the display screen. Here, a rear view vertical cross cursor CS2 (second mark) having the crossing point at a coordinate position corresponding to the point P3 in the rear view vertical image V2_B illustrated in Fig. 23A may be displayed. Moreover, a left view vertical cross cursor CS3 (second mark) having the crossing point at a coordinate position corresponding to the point P3 in the left view vertical image V2_L illustrated in Fig. 23B may be displayed. Thus, the correspondence of the school of fish displayed in the 3-dimensional images may be grasped more easily. Note that, as the depth position of the point P3, the shallowest position within an echo intensity range which includes the selected point P3 (in the example of Fig. 22, the cross-hatched echo intensity range) may be selected to be the depth position of the point P3.

[0118] Similarly, as illustrated in Figs. 24 and 25, when the user clicks on the position of a point P4 in the second bottom view horizontal image H2_L illustrated in Fig. 24, a lower side -31 horizontal cross cursor CS4 (first mark) having the crossing point at the point P4 in the second bottom view horizontal image H2_L may be displayed. Here, a rear view vertical cross cursor CS2 (second mark) having the crossing point at a coordinate position corresponding to the point P4 in the rear view vertical image V2_B illustrated in Fig. 25A may be displayed. Moreover, a left view vertical cross cursor CS3 (second mark) having the crossing point at a coordinate position corresponding to the point P4 in the left view vertical image V2_L illustrated in Fig. 25B may be displayed. Note that, as the depth position of the point P4, the deepest position within an echo intensity range which includes the selected point P4 (in the example of Fig. 24, the cross-hatched echo intensity range) may be selected to be the depth position of the point 4.

[0119] Although in this example, when a certain position in the top view horizontal image H2u or the second bottom view horizontal image H2_L is selected, the cross cursors CS2 and CS3 may be displayed at the positions corresponding to the selected position in the rear view vertical image V2_B and the left view vertical image V2_L, this disclosure is not limited to this. For example, when a certain position in one of a plurality of 3-dimensional images is selected, second cross cursors may be displayed at positions corresponding to the selected position in another 3-dimensional image.

[0120] Moreover, although in this example the first mark and the second mark may be cross cursors, this disclosure is not limited to this. For example, the first and second marks may be “o” mark or “x” mark.

[0121] (11) Fig. 26 is a flowchart illustrating another operation example of the underwater detection system 1 of the above embodiment. In the above embodiment, the example in which the 3-dimensional images may continuously be generated until the user issues the instruction to stop the generation of the 3-dimensional image is described with reference to Fig. 11; however, this disclosure is not limited to this. For example, as illustrated in the flowchart of Fig. 26, after the 3-dimensional images are generated, they may not be updated until the next 3-dimensional image generation instruction is issued by the user. Alternatively, the update cycle of the 3-dimensional images may be specified by the user.

-32[0122] (12) Sensors capable of detecting a roll angle and a pitch angle of the ship may be provided in the underwater detection system 1 of the above embodiment, and the processing apparatus 5 may display 3-dimensional images at coordinates subjected to coordinate transformation based on the roll angle and the pitch angle detected by the sensors. Thus, a spatial distribution of schools of fish may accurately be grasped without being influenced by swaying motion of the ship.

[0123] (13) In the underwater detection system 1 of the above embodiment, the transmission wave having the comparatively wide beam width in the vertical plane may be used as the transmission wave to generate the vertical mode image VI; however, without transmitting this transmission wave, the second transmission wave which is transmitted to generate the 3-dimensional images may be used to generate the vertical mode image VI. Since the second transmission wave may have a comparatively wide beam width in the vertical plane, it may also be used to generate the vertical mode image VI. By using the second transmission wave, which is for generating the 3-dimensional images, to generate the vertical mode image, it becomes unnecessary to transmit a transmission wave specifically to generate the vertical mode image VI. Asa result, the 3-dimensional images may be displayed while preventing lowering of the update rate of the image during the normal operation of the scanning sonar.

[0124] This disclosure may broadly be applied as an underwater detection system which detects a target object.

Claims (20)

1. An underwater detection system (1, la), comprising:

a transducer (2) comprising a plurality of transducer elements; a transmission circuit (7a) configured to drive the plurality of transducer elements to transmit a first transmission wave and a second transmission wave, the second transmission wave having a beam width wider than that of the first transmission wave;

a reception circuit (11, 12) configured to generate a first reception signal based on a reflection wave of the first transmission wave and to generate a second reception signal based on a reflection wave of the second transmission wave;

a first controller (7b) configured to cause the transmission circuit (7a) to generate a first drive signal, the first drive signal being the basis of the first transmission wave;

a first image generator (16) configured to generate a first image based at least in part on the first reception signal outputted by the reception circuit (11, 12);

a second controller (20) configured to cause the transmission circuit (7a) to generate a second drive signal, the second drive signal being the basis of the second transmission wave; and a second image generator (23) configured to generate a second image based at least in part on the second reception signal outputted by the reception circuit (11, 12).

2. The underwater detection system of claim 1, wherein the beam width of the first transmission wave in the vertical plane is less than 20 degrees; and the beam width of the second transmission wave in the vertical plane is 20 degrees or more.

3. The underwater detection system of claim 1 or claim 2, further comprising: a scanning sonar (10) including the transmission circuit (7a), the reception circuit

-34(11, 12), the first controller (7b) and the first image generator (16); and a processing apparatus (5) including the second controller (20) and the second image generator (23); wherein the processing apparatus (5) is provided separately from the scanning sonar (10).

4. The underwater detection system of claim 3, wherein at least a part of a data transfer of the second reception signal to the processing apparatus (5) is performed at the same time as at least a part of the generation of the first image.

5. The underwater detection system of claim 3 or claim 4, wherein the scanning sonar (10) further includes a first display apparatus (4) configured to display the first image; and the underwater detection system further comprises a second display apparatus (6) configured to display the second image.

6. The underwater detection system of any one of claims 3 to 5, wherein the processing apparatus (5) is a personal computer.

7. The underwater detection system of any of the preceding claims, wherein at least a part of the generation of the first image is performed at the same time as at least a part of the generation of the second image.

8. The underwater detection system of any of the preceding claims, wherein a frequency of occurrence at which the second transmission wave is transmitted is less than that of the first transmission wave.

9. The underwater detection system of any of the preceding claims, wherein

-35the first image is a 2-dimensional image generated based on the first reception signal obtained from an area in which the first transmission wave is transmitted; and the second image is a 3-dimensional image generated based on the second reception signal obtained from a 3-dimensional volume in which the second transmission wave is transmitted.

10. The underwater detection system of claim 9, wherein the 3-dimensional image is at least one of a vertical image and a horizontal image, the vertical image being a projection on a vertical plane of 3-dimensional data including 3-dimensional position information and echo intensity information obtained from the second reception signal for each position within the 3-dimensional volume, and the horizontal image being a projection on a horizontal plane of said 3-dimensional data.

11. The underwater detection system of claim 10, wherein the 3-dimensional image contains a top view horizontal image and a bottom view horizontal image, the top view horizontal image being the horizontal image resulting from a projection of the 3-dimensional data on an upper side horizontal plane positioned above the 3-dimensional data, and the bottom view horizontal image being the horizontal image resulting from a projection of the 3-dimensional data on a lower side horizontal plane positioned below the 3-dimensional data.

12. The underwater detection system of claim 11, wherein the bottom view horizontal image is obtained by reflection over an axis of reflection of the horizontal image obtained by projection of the 3-dimensional data on the lower side horizontal plane, the axis of reflection being within the lower side horizontal plane.

-3613. The underwater detection system of claim 10, wherein the 3-dimensional image contains at least two of the vertical image, the horizontal image and a perspective image, the perspective image being a projection of the 3-dimensional data on an inclined plane intersecting both the vertical plane and the horizontal plane.

14. The underwater detection system of claim 13, wherein as a result of a user selecting a given position on one of the vertical image, the horizontal image and the perspective image as a selected image, a first mark is displayed at said given position on the selected image and a second mark is displayed at a position corresponding to said given position on at least one of the vertical image, the horizontal image and the perspective image not displaying the first mark.

15. The underwater detection system of any of the preceding claims, wherein the second transmission wave has a beam width wider than that of the first transmission wave at least in the vertical plane.

16. An underwater detection system, comprising:

a transducer (2) comprising a plurality of transducer elements; a transmission circuit (7a) configured to drive the plurality of transducer elements to transmit a transmission wave that allows 3-dimensional data to be generated, the transmission wave being transmitted toward a 3-dimensional volume;

a reception circuit (11, 12) configured to generate a reception signal based on a reflection wave of the transmission wave;

a 3-dimensional data generator (22) configured to generate the 3-dimensional data from the reception signal, the 3-dimensional data including 3-dimensional position information and echo intensity information for each position within the 3-dimensional volume; and

-37an image generator (23) configured to generate a top view horizontal image and a bottom view horizontal image, the top view horizontal image resulting from a projection of the 3-dimensional data on an upper side horizontal plane positioned above the 3-dimensional data, and the bottom view horizontal image resulting from a projection of the 3-dimensional data on a lower side horizontal plane positioned below the 3-dimensional data.

17. The underwater detection system of claim 16, wherein the bottom view horizontal image is obtained by reflection over an axis of reflection of an image obtained by projection of the 3-dimensional data on the lower side horizontal plane, the axis of reflection being within the lower side horizontal plane.

18. The underwater detection system of claim 16 or claim 17, wherein the image generator (23) further generates at least one of a vertical image and a perspective image, the vertical image being obtained by projection of the 3-dimensional data on a vertical plane, and the perspective image being obtained by projection of the 3-dimensional data on an inclined plane intersecting the upper side horizontal plane, the lower side horizontal plane and the vertical plane.

19. The underwater detection system of claim 18, wherein as a result of a user selecting a given position on one of the top view horizontal image, the bottom view horizontal image, the vertical image and the perspective image as a selected image, a first mark is displayed at said given position on the selected image and a second mark is displayed at a position corresponding to said given position on at least one of the top view horizontal image, the bottom view horizontal image, the vertical image and the perspective image not displaying the first mark.

-3820. The underwater detection system of any one of claims 16 to 19, further comprising:

a display apparatus (6) configured to display the top view horizontal image and the bottom view horizontal image.

21. An underwater detection system or method substantially as described herein with reference to and as illustrated in the accompanying drawings.

-3940

Intellectual

Property

Office

Dr Maurice Blount

22 November 2017