Underwater detection apparatus and underwater detection method

An underwater detection apparatus is provided. The apparatus may include a transmission transducer, a reception transducer, and processing circuitry. The transmission transducer may transmit a transmission wave. The reception transducer may include a plurality of reception elements that generate a reception signal based on a reflection wave including a reflection of the transmission wave on an underwater target. The processing circuitry may generate a 3D image data that represents an echo intensity of the underwater target based at least in part on the reception signal generated by each reception element, and may set a depth marking on the 3D image data for which a depth is equal to a given depth, by changing an echo intensity color that represents the echo intensity of the 3D image data into a depth color that represents a depth of the 3D image data, the depth color being different from the echo intensity color.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2018-192382, which was filed on Oct. 11, 2018, the entire disclosure of which is hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to an underwater detection apparatus and an underwater detection method, which detect an underwater object.

BACKGROUND

Three-dimensional (3D) sonar is known as an underwater detection apparatus, for example, as disclosed in “ECHO PILOT FLS 3D FORWARD LOOKING SONAR PRODUCT Brochure,” Page 2, [online], ECHO PILOT, [searched on Apr. 20, 2018], Internet <URL: https://echopilot.com/wp-content/uploads/2017/10/Brochure_FLS_3D_FLS3D-B01Issue01_D0561_18102017.pdf>. The 3D sonar transmits a beam from a transmitter element and receives an echo by a receiver element. By processing the reception signal acquired by receiving the echo, 3D image data indicative of an echo intensity of an underwater target object is generated, and a 3D echo image is displayed on a display screen based on the 3D image data. Note that, the 3D sonar indicates grid lines indicative of a depth of a seabed in the 3D echo image.

However, in the above configuration, the grid lines in the 3D echo image only indicates water depths. Therefore, in the 3D echo image, it is difficult to visually grasp a water depth of the underwater target object, such as a school of fish. For example, by a user performing a mouse operation to rotate the 3D echo image in a display screen, it may become easier to visually recognize the water depth of the underwater target object. However, since the user's operation of rotating the 3D echo image is troublesome for the user, it is difficult to expect the user to perform frequent image rotating operations.

SUMMARY

The present disclosure is made in view of solving the above problem, and it is to provide an underwater detection apparatus and an underwater detection method which enable a user to visually grasp a water depth of an underwater target object more easily in a 3D echo image.

In order to solve the problem described above, an underwater detection apparatus according to one aspect of the present disclosure may include a transmission transducer, a reception transducer, and processing circuitry. The transmission transducer may transmit a transmission wave. The reception transducer may include a plurality of reception elements that generate a reception signal based on a reflection wave including a reflection of the transmission wave on an underwater target. The processing circuitry may generate a 3 dimensional image data that represents an echo intensity of the underwater target based at least in part on the reception signal generated by each reception element, and may set a depth marking on the 3 dimensional image data for which a depth is equal to a given depth, by changing an echo intensity color that represents the echo intensity of the 3 dimensional image data into a depth color that represents a depth of the 3 dimensional image data, the depth color being different from the echo intensity color.

The processing circuitry may generate the 3 dimensional image data by performing isosurface processing, may set the marking on the 3 dimensional image data when the echo intensity of the 3 dimensional image data is a given echo intensity, less than a maximum echo intensity of the 3 dimensional image data, and when the 3 dimensional image data includes a plurality of different echo intensity parts, the processing circuitry may set the marking on only one echo intensity part of the plurality of different echo intensity parts.

In order to solve the problem described above, an underwater detection method according to one aspect of the present disclosure may include transmitting a transmission wave, generating a reception signal based on a reflection wave including a reflection of the transmission wave on an underwater target, by using a plurality of reception elements, generating a 3 dimensional image data that represents an echo intensity of the underwater target based at least in part on the reception signal generated by each reception element, and setting a depth marking on the 3 dimensional image data for which a depth is equal to a given depth, by changing an echo intensity color that represents the echo intensity of the 3 dimensional image data into a depth color that represents a depth of the 3 dimensional image data, the depth color being different from the echo intensity color.

According to the present disclosure, a user can visually grasp the water depth of an underwater target object more easily in a 3D echo image.

DETAILED DESCRIPTION

Hereinafter, an underwater detection apparatus1and an underwater detection method according to one embodiment of the present disclosure will be described with reference to the accompanying drawings.

[Configuration of Underwater Detection Apparatus]

FIG. 1is a block diagram illustrating a configuration of an underwater detection apparatus1according to one embodiment of the present disclosure.FIG. 2is a view schematically illustrating a transmitting range of a transmission wave transmitted from a transducer2. Referring toFIGS. 1 and 2, the underwater detection apparatus1of this embodiment is mounted on a ship S, such as a fishing boat, for example. Below, the ship S provided with the underwater detection apparatus1may be referred to as “the ship S” in order to distinguish from other ships. Note that, inFIG. 1, only some of components provided to a receiver8are illustrated.

The underwater detection apparatus1according to this embodiment may be a scanning sonar. The underwater detection apparatus1according to this embodiment may generate an image on which an underwater target object included in a three-dimensional (3D) area Z1is projected, the three-dimensional (3D) area Z1being a 3D transmission wave area near the ship S. The underwater detection apparatus1may generate the 3D image and its side image on which the underwater target object included in the 3D area Z1near the ship S may be projected by performing operation which will be described below.

The underwater detection apparatus1may include the transducer2(which may also be referred to as a “transmission transducer” or a “reception transducer”), a transmission and reception device3(which may also be referred to as a “transmission and reception circuit”), a display unit4, and a user interface5.

The transducer2may have a function to transmit and receive an ultrasonic wave, and may be attached to the bottom of the ship. The transducer2may have a substantially cylindrical shape, and may be disposed so that its axial direction is oriented along the up-and-down direction and its radial direction is oriented along the horizontal direction.

In detail, the transducer2may have a substantially cylindrical casing, and ultrasonic transducers as a plurality of transceiver elements2a(which may also be referred to as transmission elements and/or reception elements) attached to an outer circumferential surface of the casing. The ultrasonic transducers may transmit an ultrasonic wave underwater, receive an echo, convert the echo into an electrical signal (reception signal), and output it to the receiver8. Note that, in this embodiment, although the transducer2has the cylindrical shape, the shape may not be particularly limited to this shape and may be other shapes such as a spherical shape.

InFIG. 2, a transmitting range of the transmission wave transmitted from the transducer2mounted on the ship S is schematically illustrated by a dot-hatched part.

In this embodiment, the transmission wave as illustrated inFIG. 2may be transmitted from the transducer2. The transducer2may transmit the transmission wave to all the horizontal directions centering on the ship S. A beam width θ2of the transmission wave is, for example, several tens of degrees.

The transducer2may be driven by the transmission and reception device3to transmit the transmission wave, and may generate a reception signal based on a reflection wave including a reflection of the transmission wave from the underwater target object, such as a school of fish T1or a seabed T2.

The transmission and reception device3may include a transmission-and-reception switching part3a, a transmitter7, and the receiver8(which may also be referred to as “processing circuitry”).

FIG. 3is a block diagram illustrating a configuration of the receiver8. Referring toFIGS. 1 to 3, the transmission and reception device3may be comprised of devices, such as a hardware processor9(for example, a CPU, a FPGA, etc.), an analog circuitry, and a nonvolatile memory. The hardware processor9may function as a controller7bdescribed in detail below, a quadrature detecting module13, a beam forming module14, a filtering module15, an image data generation module16, an acquiring module17, a boundary setting module18, and a depth indicating processing module19. For example, by the CPU reading a program from the nonvolatile memory and executing the program, the hardware processor9functions as the controller7b, the quadrature detecting module13, the beam forming module14, the filtering module15, the image data generation module16, the acquiring module17, the boundary setting module18, and the depth indicating processing module19. The controller7b, the quadrature detecting module13, the beam forming module14, the filtering module15, the image data generation module16, the acquiring module17, the boundary setting module18, and the depth indicating processing module19may be included in the signal processor20.

The transmission-and-reception switching part3amay switch the transmission and the reception of a signal to/from the transducer2. In detail, when transmitting to the transducer2a drive signal for causing the transducer2to be driven, the transmission-and-reception switching part3amay output to the transducer2the drive signal outputted from the transmitter7. On the other hand, when receiving the reception signal from the transducer2, the transmission-and-reception switching part3amay output the reception signal received by the transducer2to the receiver8.

The transmitter7may generate a drive signal used as the basis of the transmission wave to be transmitted from the transducer2. The transmitter7may include a transmission circuit7aand the controller7b.

The transmission circuit7amay generate a drive signal under the control of the controller7b. In detail, the transmission circuit7amay have a transmission circuit (not illustrated) provided corresponding to each ultrasonic transducer2a, and each transmission circuit may generate the drive signal by being suitably controlled by the controller7b. The drive signal may be a signal used as the basis of the transmission wave to be transmitted from the transducer2.

The controller7bmay cause the transmission circuit7ato generate the drive signal by suitably controlling each of the plurality of transmission circuits provided to the transmission circuit7a. For example, if the shape of the transducer2is the cylindrical shape, the controller7bcontrols the amplitude and the phase of the drive signal so that a function of a shading coefficient in the up-and-down direction becomes a sinc function.

The receiver8may include an analog part11, an A/D converter12, the quadrature detecting module13, the beam forming module14, the filtering module15, the image data generation module16, the acquiring module17, the boundary setting module18, and the depth indicating processing module19. The analog part11and the A/D converter12may be provided as a reception circuit which processes the reception signal generated based on the reflection wave of the transmission wave.

The analog part11may amplify the reception signal as the electrical signal from the transducer2and remove an unnecessary frequency component by limiting its frequency band. The analog part11may process the reception signal as the electrical signal generated from the reflection wave of the transmission wave.

The A/D converter12may convert the reception signal as the electrical signal processed by the analog part11into a reception signal as a digital signal. That is, the A/D converter12may process the reception signal as the electrical signal generated based on the reflection wave of the transmission wave to convert it into the reception signal as the digital signal.

The quadrature detecting module13may apply a quadrature detection to the reception signal which is generated by each ultrasonic transducer2aand processed by the analog part11and the A/D converter12to generate an I-signal and a Q-signal. These signals may be processed as a complex signal which uses the I-signal as a real part and uses the Q-signal as an imaginary part. The quadrature detecting module13may output the generated complex signal to the beam forming module14.

The complex signal from the quadrature detecting module13of the receiver8may be inputted into the beam forming module14. The beam forming module14may perform a beam forming (in detail, summing phase shifted signals or adaptive beam forming) to the complex signal obtained from particular transducers among the plurality of ultrasonic transducers2a(at least some of the ultrasonic transducers2a). Therefore, the beam forming module14may generate a reception beam signal which is a signal equivalent to what is obtained by a single ultrasonic transducer having a sharp directivity in a particular direction. In this embodiment, an area in which the beam signal is formed may be referred to as a “reception beam area.” The beam forming module14may generate a large number of reception beam signals having directivities in all directions by repeating the processes, while changing a combination of the ultrasonic transducers2aused for the beam forming. The beam forming module14may scan the range to which the transmission waves are transmitted by generating the reception beam signal having a beam width narrower than a beam width θ2of the transmission wave, and gradually changing its tilt angle. Note that positional information on each 3D data (will be described later in detail) generated based on these reception beam signals may be calculated based on a distance from the transducer2to a reflection target which can be obtained based on a period of time from the transmission to the reception of the transmission wave, and a direction of the reception beam signal.

The filtering module15may perform a bandlimiting filtering or a pulse compression filtering to the reception beam signal formed by the beam forming module14. The reception beam signal processed by the filtering module15may be a signal acquired from each position included in a 3D area Z1, and may have a 3D position from which each signal is acquired, and an echo intensity of the signal, as echo image information.

The image data generation module16may generate the 3D data indicative of a distribution of underwater target objects around the ship based on the amplitude of the reception beam signal filtered by the filtering module15(in detail, an absolute value of the complex signal). In detail, the image data generation module16may generate the 3D data based on the signal acquired from the 3D area Z1. Then, the image data generation module16may generate 3D (i.e., 3 dimensional) image data D3which specifies a 3D image IM3and a side image IM4of the echo by projecting the 3D data on a two-dimensional (2D) plane.

As described above, the image data generation module16may generate the 3D image data D3which expresses the position and the echo intensity of the underwater target object as the echo image, and may contain color information based on at least the reception signal generated by each ultrasonic transducer (each receiving element)2a. Moreover, in order to generate the 3D image data D3, the image data generation module16expresses, for example, a set of echoes at which the echo intensity is the same, by an isosurface. That is, in the example of this embodiment, the image data generation module16may generate the 3D image data D3by performing isosurface processing. Moreover, the image data generation module16may generate the 3D image data D3based on the result of the beam forming performed by the beam forming module14to the reception signal generated by each ultrasonic transducer2a.

FIG. 4Ais a view schematically illustrating the 3D image IM3of the echo specified by the 3D image data D3generated by the image data generation module16, where a state before a boundary processing is performed is illustrated.FIG. 4Bis a side image IM4which is an image of the 3D image IM3of the echo, seen horizontally from one side, where a state before the boundary processing is performed is illustrated. Referring toFIGS. 1 to 4, the 3D image data D3generated by the image data generation module16may be outputted to the display unit4. The display unit4may display an image specified by the given 3D image data D3on a screen of the display unit4.

For example, the 3D image IM3and the side image IM4of the 3D image IM3may suitably be displayed on the display unit4. The 3D image IM3and the side image IM4may be alternatively or selectively displayed, or may be displayed simultaneously. For example, when the 3D image IM3and the side image IM4are displayed simultaneously, the side image IM4is displayed above the 3D image IM3. For example, when a user operates a mouse of the user interface5to instruct a drag of the 3D image IM3, the image data generation module16rotates the 3D image IM3on the screen of the display unit4.

The 3D image IM3may express, as an image, a 3D space which spreads in the horizontal direction and the water depth direction from a ship position marker IM30. In the 3D image IM3, x-axis and y-axis extend in the horizontal direction, and z-axis extends in the water depth direction.

For sake of convenience of description, in the 3D image IM3, the echo image may be given two levels of darkness according to the echo intensity. In this embodiment, the echo image with the highest echo intensity is indicated by an oblique hatching, and the echo image with the second highest echo intensity is indicated by a dot hatching. Below, the echo image to which the oblique hatching is given may be referred to as a “high intensity echo image IM37,” and the echo to which the dot hatching is given may be referred to as a “moderate intensity echo image IM38.” Note that, in the actual display unit4, the high intensity echo image IM37is indicated in deep red, and the moderate intensity echo image IM38is indicated in a transparent light blue (however, they may also be indicated in other colors).

In the 3D image IM3, the high intensity echo images IM37and the moderate intensity echo images IM38surrounding the perimeter of the high intensity echo images IM37may exist in each of shallow areas IM35corresponding to a comparatively shallow water depth WD and seabed depth areas IM36corresponding to a seabed depth WD1. Thus, the moderate intensity echo images IM38may exist outside the high intensity echo images IM37, and the moderate intensity echo images IM38may be located so as to surround the high intensity echo images IM37. In the 3D image IM3illustrated as one example inFIG. 4, a case where there are a larger number of high intensity echo images IM37in the seabed depth area IM36is illustrated, compared with the number of high intensity echo images IM37in the shallow area IM35. In this embodiment, the high intensity echo image IM37and the moderate intensity echo image IM38in the shallow area IM35may be school-of-fish echo images IM31indicative of schools of fish T1, and the high intensity echo image IM37and the moderate intensity echo image IM38in the seabed depth area IM36may be seabed echo images IM32indicative of the seabed T2.

Similarly to the 3D image IM3, in the side image IM4, the high intensity echo images IM47and the moderate intensity echo images IM48surrounding the perimeter of the high intensity echo images IM47may exist in each of shallow areas IM45corresponding to the comparatively shallow water depth WD and the seabed depth areas IM46corresponding to the seabed depth WD1. Thus, the moderate intensity echo images IM48may exist outside the high intensity echo images IM47, and the moderate intensity echo images IM48may be located so as to surround the high intensity echo images IM47. In the side image IM4illustrated as one example inFIG. 4, there may be more high intensity echo images IM47in the seabed depth area IM46than the high intensity echo images IM47in the shallow area IM45. In this embodiment, the high intensity echo image IM47and the moderate intensity echo image IM48in the shallow area IM45may be school-of-fish echo images IM41, and the high intensity echo image IM47and the moderate intensity echo image IM48in the seabed depth area IM46may be seabed echo images IM42.

In the 3D image IM3, the high intensity echo image IM37and the moderate intensity echo image IM38in the shallow area IM35, and the high intensity echo image IM37and the moderate intensity echo image IM38in the seabed depth area IM36are indicated by similar echo intensities, and therefore, it may be difficult to distinguish one from another. Similarly, in the side image IM4, the high intensity echo image IM47and the moderate intensity echo image IM48in the shallow area IM45, and the high intensity echo image IM47and the moderate intensity echo image IM48in the seabed depth area IM46are indicated by similar echo intensities, and therefore, it may be difficult to distinguish one from another. Therefore, in this embodiment, in order to facilitate the visual identification between the high intensity echo image IM37and the moderate intensity echo image IM38in the seabed depth area IM36, and the high intensity echo image IM37and the moderate intensity echo image IM38in an area other than the seabed depth area IM36, a boundary processing may be performed. This boundary processing may also include processing for facilitating the visual identification between the high intensity echo image IM47and the moderate intensity echo image IM48in the seabed depth area IM46, and the high intensity echo image IM47and the moderate intensity echo image IM48in the area other than the seabed depth area IM46.

FIG. 5Ais a view schematically illustrating the 3D image IM3, where a state after the boundary processing is performed is illustrated, andFIG. 5Bis the side image IM4, where a state after the boundary processing is performed is illustrated.

Referring toFIGS. 1 to 5, next, the boundary processing is described concretely. In this embodiment, the acquiring module17of the receiver8may be configured to acquire the seabed depth WD1directly under the ship S (i.e., water depth data). Moreover, the boundary setting module18may set a boundary B1which passes through a reference point P1having a water depth WD substantially equal to the acquired seabed depth WD1, and form a given angle θB1with the horizontal direction.

Next, the image data generation module16may process the 3D image data D3so that the color information in the 3D image IM3and the side image IM4which are specified by the 3D image data D3is at least based on positions of the underwater target objects T1and T2with respect to the boundary B1.

The seabed depth WD1may refer to a distance between the surface (seabed surface) of the seabed T2at the position directly under the ship S, and the ship S (sea surface). Strictly, since the transducer2is located at a given depth below the sea surface, a value obtained by subtracting the given depth from the seabed depth obtained from the fishfinder31which will be described later may be used as the seabed depth WD1. However, in this embodiment, in order to simplify the description, the seabed depth WD1obtained from the fishfinder31may be used as the seabed depth WD1in the underwater detection apparatus1. In this embodiment, the acquiring module17may obtain the seabed depth WD1from the fishfinder31as an external source of information, which is different from the reception signal from the transducer2, or obtain the same by a manual input by the user operating the user interface5.

For example, the user can look at the side image IM4displayed on the display unit4, and input the seabed depth WD1through the user interface5. When the acquiring module17obtains the seabed depth WD1in response to the manual input by the user operating the user interface5, the seabed depth WD1directly under the ship S may be given from the user interface5to the image data generation module16.

Next, a configuration of the image data generation module16obtaining the seabed depth WD1from the fishfinder31is described.

FIG. 6is a view schematically illustrating a transmission wave US transmitted from the transducer32of the fishfinder31. Referring toFIG. 6, the fishfinder31may have a transducer32and a signal processor (not illustrated).

The transducer32may convert the electrical signal into the transmission wave US as the ultrasonic wave and transmit the transmission wave US underwater for every given timing (i.e., a given cycle), and convert the received ultrasonic wave into the electrical signal. The transducer32may transmit the ultrasonic wave directly below the ship S. For example, the ultrasonic wave is transmitted in the shape of a conical area.

The signal processor of the fishfinder31may process the reception wave received by the transducer32after the transmission of the transmission wave US to calculate the seabed depth WD1. For example, the signal processor may calculate a distance from a location where the echo intensity above a given value spreads uniformly in the horizontal direction to the ship S (transducer32) as the seabed depth WD1. The signal processor of the fishfinder31may output the seabed depth WD1to the boundary setting module18.

Referring toFIGS. 1 to 5, the image data generation module16may perform the boundary processing when receiving an instruction for setting the color information based on the position of the underwater target object with respect to the boundary B1from the user interface5by the user operating the user interface5.

In the boundary processing, the boundary setting module18may first set the boundary B1. The boundary B1may be a conical surface and may be a shape including a straight line.

The boundary B1may form a given angle θB1with the horizontal direction. This angle θB1may be an oblique angle. The reason why the angle θB1is set as described above is as follows. Even if the actual seabed T2is flat, due to the resolution of the underwater detection apparatus1, upper end positions of the seabed echo images IM32and IM42may be located upward the further the seabed T2is positioned away from the position of the seabed T2directly under the ship S.

As illustrated inFIG. 5, a reference point image P3corresponding to the reference point P1may be displayed on the 3D image IM3and the side image IM4, and a boundary image B3corresponding to the boundary B1may be displayed. The boundary image B3may be a boundary set in the 3D image IM3and the side image IM4, may be displayed as the conical surface in the 3D image IM3, and may be displayed as a substantially V-shape including the straight line in the side image IM4. In the 3D image IM3and the side image IM4, the boundary image B3may form the given angle θB1with the horizontal direction. Note that the boundary image B3may not be displayed in the 3D image IM3and the side image IM4.

The boundary setting module18may set the angle θB1so that the boundary image B3extends along the upper end position of the seabed echo image IM42. The boundary setting module18may set the angle θB1based on a width of a reception beam formed in order to generate the reception signal of the reception wave corresponding to the transmission wave.

Note that the angle θB1may be finely set or tuned by a manual input of an instruction by the user operating the user interface5. When the angle θB1is set by the user's manual input, it may be set by the user operating numerical key(s) of the user interface5. Alternatively, the seabed depth WD1may be tuned by a drag-and-drop operation of the reference point image P3by a user's mouse operation, and the angle θB1may be set by a drag-and-drop operation of the boundary image B3. Alternatively, a touch-panel function may be provided to the display unit4, and the angle θB1may be set by a user's finger operation while using the touch panel as the user interface5. A change operation of the angle θB1can be immediately reflected to the display contents of the display unit4by any of the input method according to the numerical key operation, the input method according to the drag-and-drop operation, and the input method of the touch panel type, thereby facilitating the adjustment work. Note that, also when the seabed depth WD1is inputted by the user's manual input, the input using the touch-panel operation described above may also be performed.

The image data generation module16may set the color information of the seabed T2as the underwater target object located at a depth deeper than the water depth WD of the boundary B1independently from the color information of the school-of-fish T1as the underwater target object located at the water depth WD shallower than the water depth WD of the boundary B1. Moreover, the image data generation module16may set the color information of the seabed T2as the underwater target object which is located at a depth deeper than the water depth WD of the boundary B1and of which the signal level of the reception signal is above a given threshold (for example, above the signal level of the moderate intensity echo image) independently from the signal level of the reception signal.

In this embodiment, the image data generation module16may set, in the 3D image IM3and the side image IM4, the color of the echo images IM37, IM38, IM47, and IM48located below the boundary image B3(seabed echo images IM32and IM42) as a different color from the color of the echo images IM37, IM38, IM47, and IM48located above the boundary image B3(school-of-fish echo images IM31and IM41). For example, the image data generation module16may set the color of the echo images IM37, IM38, IM47, and IM48located below the boundary image B3(seabed echo images IM32and IM42) as a monotone color, such as light gray.FIG. 5illustrates, for convenience, that the image data generation module16changed the echo image IM37, IM38, IM47, and IM48located below the boundary image B3(seabed echo images IM32and IM42) from the indication with hatching to the indication without hatching. Note that the seabed echo images IM32and IM42located below the boundary image B3may be indicated with gradation.

The image data generation module16, the acquiring module17, and the boundary setting module18may perform the processing described above as the boundary processing, when the instruction for performing the boundary processing is received from the user interface5. Then, the image data generation module16may generate boundary image data indicative of the position of the boundary image B3, and add this boundary image data to the 3D image data D3. At this time, the 3D image data D3may include data indicative of the boundary image B3in addition to the 3D image IM3and the side image IM4.

Moreover, in this embodiment, the image data generation module16may generate the 3D image data D3so that the 3D image IM3and the side image IM4are displayed in parallel to each other on the display unit4. Note that the image data generation module16may generate the 3D image data D3so that the 3D image IM3and the side image IM4are alternatively or selectively displayed on the display unit4.

As well illustrated inFIG. 5, the 3D image IM3and the side image IM4to which boundary processing is performed make it easy to distinguish the school-of-fish echo images IM31and IM41from the corresponding seabed echo images IM32and IM42. However, it may be desirable to enable the user to visually recognize more easily the water depth WD of the school-of-fish echo images IM31and IM41, and a relative spatial relationship between the plurality of school-of-fish echo images IM31and IM41.

Thus, in this embodiment, equi-depth contours (which may also be referred to as isodepth or isobath lines) L3and L4indicative of the water depth WD may be displayed on at least one of the 3D image IM3and the side image IM4before the boundary processing illustrated inFIG. 4, and the 3D image IM3and the side image IM4after the boundary processing illustrated inFIG. 5. The configuration for displaying the equi-depth contours L3and L4is described below. Below, although the indication of the equi-depth contours L3and L4in the 3D image IM3and the side image IM4after the boundary processing illustrated inFIG. 5is described, the indication of the equi-depth contours L3and L4in the 3D image IM3and the side image IM4before the boundary processing illustrated inFIG. 4may be similar.

FIG. 7Ais a view schematically illustrating the 3D image IM3after the boundary processing is performed, where the equi-depth contour L3is further displayed, andFIG. 7Bis the side image IM4after the boundary processing is performed, where the equi-depth contour L4is further displayed.

Referring toFIGS. 2, 3, and 7, the depth indicating processing module19may add data to the 3D image data D3for displaying the one or more equi-depth contours L3(which may also be referred to as “marking” or “depth marking”) on the 3D image IM3, and for displaying one or more equi-depth contours L4(which may also be referred to as “marking” or “depth marking”) on the side image IM4. That is, in this embodiment, the depth indicating processing module19may add the data of the equi-depth contours L3and L4to the 3D image data D3, as the markings indicative of the water depth WD.

In more detail, in this embodiment, the depth indicating processing module19may add the data of the equi-depth contours L3and L4as the marking indicative of the water depth WD to the 3D image data D3, by changing an echo intensity color CL1indicative of the echo intensity of the 3D image data D3, of which the echo intensity indicated in the 3D image data D3is above a given threshold Th, and of which the water depth WD indicated in the 3D image data D3is equal to a given water depth WDx (x is a variable) into a depth color CL2, which is indicative of the water depth WD of the 3D image data D3and which is a different color from the color of the echo intensity color CL1. By adding the markings to the 3D image data D3, the equi-depth contours L3and L4may be displayed in the 3D image IM3and the side image IM4of the 3D image IM3specified by the 3D image data D3to which markings are added. Note that, for example, the threshold Th used for the depth indicating processing module19may be a certain level of the reception signal received by the ultrasonic transducer2a(e.g., a level of the echo intensity of the moderate intensity echo image IM38).

The depth indicating processing module19may receive an equi-depth contour display instruction which is, for example, given by the user operating the mouse provided to the user interface5. For example, the equi-depth contour display instruction includes (a) an instruction of ON/OFF of the equi-depth contours L3and L4in the 3D image IM3and the side image IM4, (b) an instruction of the numbers of equi-depth contours L3and L4, (c) an instruction of the water depth positions of the equi-depth contours L3and L4, (d) an instruction of an interval of the equi-depth contours L3and an interval of the equi-depth contours L4, (e) an instruction of ON/OFF of an equi-depth plane indication in the 3D image IM3, and (f) an instruction of the water depth position of the equi-depth plane F3. As described above, the underwater detection apparatus1may be provided with the user interface5where the user performs operation for causing the depth indicating processing module19to receive the equi-depth contour display instruction. Thus, the underwater detection apparatus1may be provided with the user interface5which sets the given water depth WDx.

The ON/OFF instruction of the above (a) is given, for example, by the user pressing a given key of the keyboard provided to the user interface5. The depth indicating processing module19which received the ON instruction from the user interface5may add the data of the equi-depth contours L3and L4as the markings indicative of the water depth WDx to the 3D image data D3. Thus, the depth indicating processing module19may process the 3D image data D3so that, in the 3D image IM3and the side image IM4, the state where the equi-depth contours L3and L4are not displayed is changed to the state where the equi-depth contours L3and L4are displayed. On the other hand, the depth indicating processing module19which received the OFF instruction from the user interface5may delete the data of the equi-depth contours L3and L4as the marking indicative of the water depth WDx from the 3D image data D3. Thus, the depth indicating processing module19may process the 3D image data D3so that, in the 3D image IM3and the side image IM4, the equi-depth contours L3and L4get deleted from the state where the equi-depth contours L3and L4are displayed.

The instruction of each of the numbers of the equi-depth contours L3and L4of the above (b) is given, for example, by the user pressing given key(s) in the keyboard of the user interface5. The depth indicating processing module19which received the instruction of the numbers of equi-depth contours L3and L4from the user interface5may set the number of equi-depth contours L3to be displayed on the 3D image IM3, and the number of equi-depth contours L4to be displayed on the side image IM4. InFIGS. 7A and 7B, for example, the three equi-depth contours L3(L31, L32, and L33) and the three equi-depth contours L4(L41, L42, and L43) are displayed at equal intervals in the water depth direction (in the up-and-down direction in the 3D image IM3and the side image IM4).

The instruction of the water depth positions of the equi-depth contours L3and L4of the above (c) is given, for example, by the user dragging and dropping one of the equi-depth contours L4of the side image IM4by using the mouse of the user interface5. The depth indicating processing module19which received the drag-and-drop operation instruction from the user interface5may process the 3D image data D3so that the water depth position(s) of only the equi-depth contours L4for which the drag-and-drop operation is carried out, or all the equi-depth contours L4is changed in real time. At this time, the depth indicating processing module19may process the 3D image data D3so that the equi-depth contour L3corresponding to the equi-depth contour L4for which the drag-and-drop operation is carried out or all the equi-depth contours L3is/are changed in the water depth position.

Note that the water depth positions of the equi-depth contours L3and L4may be set by the depth indicating processing module19so that they become positions passing through the centers of the shapes of the school-of-fish echo images IM31and IM41.

The instruction of the interval of the equi-depth contours L3and the interval of the equi-depth contours L4of the above (d) is given, for example, by the user pressing the given key(s) in the keyboard of the user interface5. The depth indicating processing module19which received the interval instruction from the user interface5may set an interval of the equi-depth contours L3adjacent to each other in the water depth direction, and an interval of the equi-depth contours L4adjacent to each other in the water depth direction.

Note that, when displaying each of the equi-depth contours L3and L4only at a single water depth WDx, the functions of the above (b) and (d) may be omitted.

The depth indicating processing module19may add the data of the equi-depth contours L3and L4(markings) to the 3D image data D3so that the equi-depth contours L3and L4according to the equi-depth contour display instruction described above are displayed on the corresponding 3D image IM3and side image IM4. The depth indicating processing module19may add the data of the equi-depth contours L3and L4(markings) indicative of the water depths WDx to the 3D image data D3so that, among the school-of-fish echo image IM31and IM41which are located above the boundary image B3and of which the echo intensities are above the echo intensities of the moderate intensity echo images IM38and IM48, the equi-depth contours L3and L4indicative of the water depths WDx are displayed at locations equal to the water depths WDx given by the instruction of the above (c).

The depth indicating processing module19may add the data of equi-depth contours L3and L4to the 3D image data D3so that, among the high intensity echo images IM37and IM47and the moderate intensity echo images IM38and IM48of the school-of-fish echo images IM31and IM41which are specified by the 3D image data D3, the equi-depth contours L3and L4are generated for the moderate intensity echo images IM38and IM48having the given echo intensities. That is, the depth indicating processing module19may add the data of the equi-depth contours L3and L4to the 3D image data D3as the markings when the echo intensity of the 3D image data D3is the given echo intensity. Then, the depth indicating processing module19may add the data of the equi-depth contours L3and L4to the 3D image data D3so that the equi-depth contours L3and L4are displayed for the moderate intensity echo images IM38and IM48having the echo intensities below the maximum echo intensities of the school-of-fish echo images IM31and IM41. That is, the given echo intensity may be below the maximum echo intensity in the 3D image data D3. Note that, on the other hand, the depth indicating processing module19may not display the equi-depth contours L3and L4for the high intensity echo images IM37and IM47of the school-of-fish echo images IM31and IM41.

In other words, the depth indicating processing module19may add the data of the equi-depth contour L3to the 3D image data D3so that, among the plurality of echo intensity portions IM37and IM38of a set of school-of-fish echo images IM31specified by the 3D image data D3, the equi-depth contour L3is generated for one echo intensity portion IM38. Further, the depth indicating processing module19may add the data of the equi-depth contour L4to the 3D image data D3so that, among the plurality of echo intensity portions IM47and IM48of a set of school-of-fish echo images IM41specified by the 3D image data D3, the equi-depth contour L4is generated for one echo intensity portion IM48. As described above, when there are a plurality of different echo intensity portions in the 3D image data D3, the depth indicating processing module19may add the data of the equi-depth contours L3and L4to only one of the plurality of different echo intensity portions, as the markings.

As illustrated inFIG. 8, if equi-depth contours L3′ and L3at the same water depth WD are added to the high intensity echo image IM37and the moderate intensity echo image IM38, respectively, as a plurality of echo intensity portions of a set of school-of-fish echo images IM31specified by the 3D image data D3, since the equi-depth contours L3′ and L3are adjacent to each other in the 3D image IM3, the equi-depth contours L3′ and L3may be displayed so as to be overlapped with each other, and therefore, it may turn out to be more difficult for the user to visually grasp the water depth WD of the school-of-fish echo image IM31.FIG. 8is a view illustrating one example of the 3D image IM3, where the equi-depth contours L3′ and L3are added to the high intensity echo image IM37and the moderate intensity echo image IM38, respectively.

Referring again toFIGS. 2, 3, and 7, in this embodiment, the data of equi-depth contours L3and L4may be added to the 3D image data D3as the markings so that the equi-depth contours L3and L4are displayed at the outermost circumferential surfaces of the moderate intensity echo images IM38and IM48of the school-of-fish echo image IM31and IM41specified by the 3D image data D3.

The depth indicating processing module19may change an echo intensity color CL1indicating the echo intensity of the 3D image data D3and used for indicating the echo intensity value of the moderate intensity echo images IM38and IM48to a depth color CL2indicating the water depth WD of the 3D image data D3, used for indicating the water depth WD of the school-of-fish echo images IM31and IM41, and different from the echo intensity color CL1to add the data of the equi-depth contours L3and L4to the 3D image data D3as the markings so that the equi-depth contours L3and L4are displayed for the moderate intensity echo images IM38and IM48of the school-of-fish echo images IM31and IM41.

In this embodiment, the depth indicating processing module19may set the depth color CL2according to the water depth WD of the 3D image data D3. In more detail, the depth indicating processing module19may set the depth color CL2so as to be changed continuously or in a stepped fashion according to the water depth WD of the 3D image data D3indicative of the water depth WD of the school-of-fish echo images IM31and IM41. Moreover, in this embodiment, the depth indicating processing module19may add the data of the equi-depth contours L3and L4to the 3D image data D3as the markings at a plurality of given water depths WDx (three water depths WDx in the example illustrated inFIG. 7). Therefore, at the plurality of given water depths WDx, the equi-depth contours L3and L4may be displayed for the moderate intensity echo images IM38and IM48of the school-of-fish echo images IM31and IM41.

As described above, the echo intensity color CL1of the moderate intensity echo images IM38and IM48may be translucent light blue, and is indicated by the dot hatching in the figure. On the other hand, the depth color CL2of the plurality of equi-depth contours L3and L4in the 3D image IM3and the side image IM4are indicated, for example by, as a different color from the echo intensity color CL1, a depth color CL21in orange (indicated by a thin dotted line inFIG. 7, which indicates the color of the equi-depth contours L31and L41), a depth color CL22in green (indicated by a thick dotted line inFIG. 7, which indicates the color of the equi-depth contours L32and L42), and a depth color CL23in blue (indicated by a thick solid line inFIG. 7, which indicates the color of the equi-depth contours L33and L43), in this order. Note that, the colors illustrated above are only examples, and the depth color CL2may be other colors, or an arbitrary combination of colors may be set by the user operating the user interface5. The echo intensity color CL1may similarly be other colors.

The depth indicating processing module19may add data of an indicator IG to the 3D image data D3so that the indicator IG indicative of a relation between the color of the equi-depth contours L3and L4and the water depth WD is displayed in the 3D image IM3. The indicator IG may indicate that the water depth WD is deeper as it goes downward from the top.

As apparent from the above configuration, the depth indicating processing module19may add the data of the equi-depth contours L3and L4to the 3D image data D3so that the equi-depth contours L3and L4are displayed for the school-of-fish echo images IM31and IM41at the water depth WDx. Therefore, in the 3D image IM3and the side image IM4, the equi-depth contours L3and L4may not be displayed at a location where the echo image does not exist at the water depth WDx where the equi-depth contours L3and L4are displayed for the school-of-fish echo images IM31and IM41.

The above is a description about the equi-depth contours L3and L4. Next, the equi-depth plane F3(which may also be referred to as isodepth or isobath plane) is described.FIG. 9is a view illustrating a state where the equi-depth plane F3is added to the 3D image IM3illustrated inFIG. 7.

Referring toFIGS. 3 and 9, the instruction of ON/OFF of the equi-depth plane indication in the 3D image IM3of the above (e) is given, for example, by the user pressing the given key of the keyboard provided to the user interface5. The depth indicating processing module19which received the ON instruction from the user interface5may add the equi-depth plane F3as the markings (in detail, data of the equi-depth plane F3for displaying the equi-depth plane F3on the 3D image IM3) to the 3D image data D3so that the equi-depth plane F3is displayed in the 3D image IM3from the state where the equi-depth plane F3is not displayed. That is, in the state where the 3D image IM3is displayed based on the 3D image data D3to which the data of the equi-depth plane F3is not added, the equi-depth plane F3may not be displayed in the 3D image IM3, as illustrated inFIG. 7. From this state, when the depth indicating processing module19receives the ON instruction, the data of the equi-depth plane F3may be added as the marking to the 3D image data D3. Then, the 3D image IM3may be displayed based on the 3D image data D3to which the data of the equi-depth plane F3is added, and the equi-depth plane F3may be displayed in the 3D image IM3, as illustrated inFIG. 9. On the other hand, the depth indicating processing module19which received the OFF instruction from the user interface5may delete the data of the equi-depth plane F3from the 3D image data D3in the 3D image IM3so that the state where the equi-depth plane F3is displayed becomes the state where the equi-depth plane F3is not displayed. That is, in the state where the 3D image IM3is displayed based on the 3D image data D3to which the data of the equi-depth plane F3is added, the equi-depth plane F3may be displayed in the 3D image IM3, as illustrated inFIG. 9. From this state, when the depth indicating processing module19receives the OFF instruction, the data of the equi-depth plane F3may be deleted from the 3D image data D3. Then, the 3D image IM3may be displayed based on the 3D image data D3to which the data of the equi-depth plane F3is not added, and the equi-depth plane F3may not be displayed in the 3D image IM3, as illustrated inFIG. 7.

The instruction of the water depth position of the equi-depth plane F3of the above (f) is given, for example, by the user dragging and dropping the equi-depth plane F3of the 3D image IM3by using the mouse of the user interface5. The depth indicating processing module19which received the drag-and-drop operation instruction from the user interface5may add the data of the equi-depth plane F3(marking) to the 3D image data D3so that the water depth position of the equi-depth plane F3for which the drag-and-drop operation is carried out is changed in real time.

Thus, the depth indicating processing module19may add the data of the equi-depth plane F3to the 3D image data D3as the marking so that the equi-depth plane F3is displayed at the water depth WDx specified in the 3D image IM3in response to the reception of the ON instruction of the display of the equi-depth plane F3from the user interface5. The equi-depth plane F3may be displayed as a translucent plane of an arbitrary color, such as blue. In the 3D image IM3ofFIG. 9, the equi-depth plane F3is indicated by cross-hatching. InFIG. 9, the equi-depth plane F3is displayed above the equi-depth contour L3(L32) at the second water depth position. The school-of-fish echo image IM31at the water depth WD shallower than the water depth WDx of the equi-depth plane F3is displayed above the equi-depth plane F3. InFIG. 9, the school-of-fish echo image IM31at the water depth WD shallower than the water depth WDx of the equi-depth plane F3is displayed so as not to overlap with the cross-hatching. On the other hand, the school-of-fish echo image IM31at the water depth WD deeper than the water depth WDx of the equi-depth plane F3is displayed below the equi-depth plane F3. InFIG. 9, the school-of-fish echo image IM31at the water depth WD deeper than the water depth WDx of the equi-depth plane F3is displayed so as to overlap with the cross-hatching.

As apparent from the above configuration, the depth indicating processing module19may add the data of the equi-depth plane F3to the 3D image data D3as the marking indicative of the water depth WDx by changing the echo intensity color indicative of the echo intensity of the 3D image data D3of which the water depth WD is equal to the given water depth WDx to the depth color which is a depth color indicative of the water depth WD of the 3D image data D3and is different from this echo intensity color.

[Operation of Underwater Detection Apparatus]

FIG. 10is a flowchart illustrating one example operation of the underwater detection apparatus1. InFIG. 10, the following operation is illustrated. The transmission wave may be transmitted underwater from the transducer2, and the reception signal may be generated based on the reflection wave including the reflection of the transmission wave from the underwater target object. Further, the processing described above may be performed by the underwater detection apparatus1, and the 3D image IM3and its side image IM4may be displayed on the display unit4. After the 3D image IM3and the side image IM4are displayed on the display unit4, the operation illustrated in the flowchart ofFIG. 10may again be performed when the transmission wave is transmitted underwater from the transducer2. Note that, as illustrated inFIG. 10, the underwater detection method of this embodiment may be implemented by the operation of the underwater detection apparatus1being performed.

In the operation of the underwater detection apparatus1, the transducer2may first transmit the transmission wave underwater (Step S101). The transmission wave transmitted underwater may be reflected on the underwater target object and may be received by the transducer2. The transducer2may receive the reflection wave including the reflection of the transmission wave from the underwater target object by using the plurality of ultrasonic elements (receiving elements)2a, and generate the reception signal based on the received reflection wave (Step S102).

When the reception signal is generated, the transducer2may output the generated reception signal to the receiver8of the transmission and reception device3. The receiver may perform the processings described above by the analog part11, the A/D converter12, and the quadrature detecting module13to the reception signal, and may perform the beam forming by the beam forming module14to form the reception beam signal. Further, the receiver8may perform the processing described above by the filtering module15to the reception beam signal, and generate the 3D image data D3based on the reception beam signal by the image data generation module16, as described above (Step S103). That is, the image data generation module16may generate the 3D image data D3indicating the position and the echo intensity of the underwater target object as the echo image, based on the reception signal generated at least by each ultrasonic transducer (each receiving element)2a.

Moreover, in the receiver8, when the processing to generate the 3D image data D3by the image data generation module16is finished, the depth indicating processing module19may then perform the addition of the marking indicative of the water depth WDx to the 3D image data D3, as described above (Step S104). That is, the depth indicating processing module19may add the data of the equi-depth contours L3and L4to the 3D image data D3as the markings indicative of the water depth WDx by changing the echo intensity color CL1indicative of the echo intensity of the 3D image data D3of which the water depth WD is equal to the given water depth WDx to the depth color CL2which indicates the water depth WD of the 3D image data D3and is different from the echo intensity color CL1.

When the depth indicating processing module19adds the markings to the 3D image data D3generated by the image data generation module16, the 3D image data D3to which the markings are added may be outputted to the display unit4(Step S105). As illustrated inFIG. 7orFIG. 9, the images, such as the 3D image IM3and its side image IM4, specified by the 3D image data D3may be displayed on the screen of the display unit4based on the inputted 3D image data D3. Therefore, in the screen of the display unit4, the equi-depth contours L3and L4may be displayed, in addition to the school-of-fish echo images IM31and IM41. When the image, such as the 3D image IM3, specified by the 3D image data D3is displayed on the display unit4, the operation of the underwater detection apparatus1illustrated inFIG. 10may once be finished. Once the operation of the underwater detection apparatus1illustrated inFIG. 10is finished, the transmission wave may again be transmitted underwater from the transducer2to again start the operation illustrated inFIG. 10.

As described above, according to the underwater detection apparatus1and the underwater detection method of this embodiment, the depth indicating processing module19may add the data of the equi-depth contours L3and L4to the 3D image data D3as the markings indicative of the water depth WDx by changing the echo intensity color CL1indicative of the echo intensity of the 3D image data D3of which the water depth WD is equal to the specified water depth WDx to the depth color CL2which indicates the water depth WD of the 3D image data D3and is different from the echo intensity color CL1. According to this configuration, in the 3D image IM3and the side image IM4of the echo which are specified by the 3D image data D3, the equi-depth contours L3and L4may be displayed at the locations where the school-of-fish echo images IM31and IM41indicative of the school of fish T1as the underwater target object are located. Therefore, the user can visually grasp more easily the water depth WD of the school of fish T1(underwater target object) indicated by the school-of-fish echo images IM31and IM41in the 3D image IM3and the side image IM4of the echo. As a result, the user's burden for rotating the 3D image IM3on the screen of the display unit4in order to confirm the water depth WD of the school of fish T1can be reduced. Therefore, according to this embodiment, it is possible to realize the underwater detection apparatus1and the underwater detection method suitable for the fishing boat which performs fishing by particularly referring to the 3D image IM3. Moreover, according to this embodiment, the equi-depth contours L3and L4can be displayed on the 3D image IM3and the side image IM4by the simple processing of changing a part of the color data of the school-of-fish echo images IM31and IM41.

Moreover, according to the underwater detection apparatus1, the depth indicating processing module19may add the data of the equi-depth contours L3and L4(markings) to the 3D image data D3so that the equi-depth contours L3and L4are displayed for the moderate intensity echo images IM38and IM48of which the echo intensities are relatively low among the school-of-fish echo images IM31and IM41specified by the 3D image data D3. According to this configuration, since the equi-depth contours L3and L4are displayed in the outward areas of the school-of-fish echo images IM31and IM41, the user can visually recognize the equi-depth contours L3and L4more clearly. Moreover, the equi-depth contours L3and L4may be displayed only for the moderate intensity echo images IM38and IM48among the moderate intensity echo images IM38and IM48and the high intensity echo images IM37and IM47of the school-of-fish echo images IM31and IM41. Therefore, the 3D image IM3and the side image IM4of the echo can be displayed, while hardly hiding the echo information, such as the echo intensities of the school-of-fish echo images IM31and IM41.

Moreover, according to the underwater detection apparatus1, the water depth WDx of the equi-depth contours L3and L4may be adjusted by the user operating the user interface5. According to this configuration, for indicating the water depth WD of the school-of-fish echo images IM31and IM41of the user's interest, the equi-depth contours L3and L4can be set at any water depth position.

Moreover, according to the underwater detection apparatus1, the depth indicating processing module19may set the depth color CL2according to the water depth WD of the 3D image data D3indicative of the water depth WD of the school-of-fish echo images IM31and IM41. According to this configuration, the user can visually grasp the water depth WD of the school-of-fish echo images IM31and IM41more easily.

Moreover, according to the underwater detection apparatus1, the depth indicating processing module19may add the data of the equi-depth contours L3and L4(markings) to the 3D image data D3at a plurality of given water depths WDx. According to this configuration, the user can visually recognize the height of the school-of-fish echo images IM31and IM41in the water depth direction more clearly. Moreover, the user can grasp the relative position of the plurality of schools of fish T1indicated by the plurality of school-of-fish echo images IM31and IM41more accurately.

Moreover, according to the underwater detection apparatus1, the depth indicating processing module19may add the data of the equi-depth plane F3to the 3D image data D3, and therefore, the equi-depth plane F3is displayed in the 3D image IM3. According to this configuration, in the 3D image IM3, the user can visually recognize more easily whether the plurality of school-of-fish echo images IM31is above or below the equi-depth plane F3.

The present disclosure is not limited to the above embodiment, and various changes are possible within the scope of the appended claims. For example, the following configurations may be adopted.

(1) In the above embodiment, the equi-depth contours L3and L4are not displayed for the seabed echo images IM32and IM42below the boundary image B3. However, it may be configured in a different way. As illustrated inFIG. 11which illustrates a modification of the 3D image IM3and the side image IM4after the boundary processing, the equi-depth contours L3(L34, L35, and L36) and L4(L44, L45, and L46) may be displayed for the seabed echo images IM32and IM42as the echo images located below the boundary image B3. In this case, it may be desirable that the color of the equi-depth contours L3and L4added to the seabed echo images IM32and IM42below the boundary image B3is set differently from the color of the equi-depth contours L3and L4of the school-of-fish echo images IM31and IM41above the boundary image B3.

(2) Moreover, in the above embodiment, the equi-depth plane F3is displayed in the horizontal coordinates of the 3D image IM3. However, it may be configured in a different way. For example, the depth indicating processing module19may add data of a vertical plane to the 3D image data D3so that the vertical plane extending in the water depth direction is displayed in the 3D image IM3. In this case, the vertical plane may become a plane extending in an azimuth direction R1(illustrated inFIG. 2) from the ship position. Both the vertical plane and the equi-depth plane F3may be displayed in the 3D image IM3, or one of them may be displayed selectively.

(3) Moreover, in the above embodiment, the data of the equi-depth contours L3and L4and the data of the equi-depth plane F3are described as the examples of the marking. However, it may be configured in a different way. Instead of the data of the equi-depth contours L3and L4and the data of the equi-depth plane F3, data of images having given shapes may be used as the markings.

(4) Moreover, in the above embodiment, the image data generation module16generates the 3D image data D3by performing the isosurface processing. However, it may be configured in a different way. The image data generation module16may generate the 3D image data D3by performing volume rendering processing, instead of the isosurface processing. When generating the 3D image data D3by the volume rendering processing, the image data generation module16may use all the echo intensities and adjust the opacity according to echo intensities to generate the 3D data. Then, the image data generation module16may generate the 3D image data D3which specifies the 3D image IM3and the side image IM4of the echo by projecting the 3D data of which the opacity is adjusted according to the echo intensities on the 2D plane. Thus, in the image data generation module16, the volume rendering processing may be used instead of the isosurface processing.

(5) Moreover, in the above embodiment and modifications, when performing the boundary processing, the seabed echo images IM32and IM42below the boundary image B3may be set as a color other than gray, or may be deleted from the corresponding 3D image IM3and side image IM4.

(6) Moreover, in the above embodiment and modifications, the acquiring module17obtains the seabed depth WD1from the fishfinder31or the user of the underwater detection apparatus1. However, it may be configured in a different way. For example, instead of the transducer2, a transducer2A illustrated inFIG. 12Amay be used, or a transducer2B illustrated inFIG. 12Bmay be used, or a transducer2C illustrated inFIG. 12Cmay be used.

The transducer2A may have a casing which is formed in a substantially cylindrical shape and a lower part thereof is formed in a hemispherical shape. A plurality of ultrasonic transducers2amay be attached to an outer circumferential surface and a hemispherical surface of the casing. The transducer2B may have a casing formed in a hemispherical shape which is directed downwardly. The plurality of ultrasonic transducers2amay be attached to a hemispherical surface of the casing. The transducer2C may have a spherical casing. The plurality of ultrasonic transducers2amay be attached to the entire surface of the casing. With such configurations, each of the transducers2A-2C can output the transmission wave directly under the ship S. Therefore, the acquiring module17can measure the seabed depth WD1based on the reception signal.

(7) Moreover, in the above embodiment and modifications, the scanning sonar in which the transducer2transmits and receives the signal in the stationary state with respect to the ship S is illustrated. However, it may be configured in a different way. For example, a movable transducer2D illustrated inFIG. 13may be used as the transducer.

The transducer2D may include wave transmitting part41(which may also be referred to as a “transmission transducer”), a wave receiving part42(which may also be referred to as a “reception transducer”), a motor43which rotates the wave transmitting part41and the wave receiving part42as a rotary driving part, and a rotational angle detecting part44.

FIG. 14is a view schematically illustrating a transmission beam formed by the wave transmitting part41, and a reception beam received by the wave receiving part42. Referring toFIGS. 13 and 14, the wave transmitting part41may be provided in order to transmit the transmission wave underwater. The wave transmitting part41may have a configuration in which one or more wave transmitting elements41aare attached to a casing as the ultrasonic transducer. In this embodiment, a plurality of wave transmitting elements41amay be disposed linearly. That is, the wave transmitting part41may be a linear array.

The wave receiving part42may have a configuration in which one or more wave receiving elements (receiving elements)42aare attached to the casing as the ultrasonic transducer. The wave receiving part42may receive the reflection wave of each transmission pulse wave which is an ultrasonic wave transmitted from the wave transmitting part41as the reception wave, and convert it into the echo signal as the electrical signal. In this embodiment, a plurality of wave receiving elements42amay be disposed linearly. That is, the wave receiving part42may be a linear array.

The wave transmitting part41and the wave receiving part42may be integrally rotated by the motor43. In this modification, the motor43may rotate the wave transmitting part41and the wave receiving part42in the azimuth direction R1centering on a center axis extending in the up-and-down direction as a rotation axis.

The rotational angle detecting part44may be attached to the motor43. In this modification, an angle position of the wave transmitting part41and the wave receiving part42may be calculated based on the rotational angle of the motor43detected by the rotational angle detecting part44.

The wave transmitting part41may form a transmission fan-shaped area TT1which is an area to which a 3D transmission beam is outputted, as illustrated inFIG. 14. The transmission fan-shape area TT1may be a substantially fan-shaped, fan beam area.

The wave receiving part42may be configured to receive a signal of a reception fan-shaped area RT1as a 3D reception beam area, as illustrated inFIG. 14. The Reception fan-shaped area RT1may be substantially a fan shape.

The motor43may rotate the transmission fan-shaped area TT1and the reception fan-shaped area RT1on the rotation axis of the motor43. In detail, the motor43may rotate the wave transmitting part41and the wave receiving part42by rotating the transmission fan-shaped area TT1and the reception fan-shaped area RT1.

By rotating the wave transmitting part41and the wave receiving part42all around the rotation axis of the motor43, i.e., by forming the transmission fan-shaped area TT1and performing the signal reception operation in the reception fan-shaped area RT1, the reception signal required for the image data generation module16generating the 3D image data D3may be acquired. That is, the transducer 2D may generate the reception signal required for generating the 3D image data D3by the plurality of wave receiving elements (receiving elements)42a. Then, the beam forming may be carried out to the acquired reception signal, and the image data generation module16may generate the 3D image data D3based on the result of the beam forming.

The present disclosure is widely applicable to underwater detection apparatuses and underwater detection methods.

Terminology

Unless otherwise explicitly stated, articles such as “a” or “an” should generally be interpreted to include one or more described items. Accordingly, phrases such as “a device configured to” are intended to include one or more recited devices. Such one or more recited devices can also be collectively configured to carry out the stated recitations. For example, “a processor configured to carry out recitations A, B and C” can include a first processor configured to carry out recitation A working in conjunction with a second processor configured to carry out recitations B and C. The same holds true for the use of definite articles used to introduce embodiment recitations. In addition, even if a specific number of an introduced embodiment recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations).

It will be understood by those within the art that, in general, terms used herein, are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.).

As used herein, the terms “attached,” “connected,” “mated,” and other such relational terms should be construed, unless otherwise noted, to include removable, moveable, fixed, adjustable, and/or releasable connections or attachments. The connections/attachments can include direct connections and/or connections having intermediate structure between the two components discussed.

Numbers preceded by a term such as “approximately,” “about,” and “substantially” as used herein include the recited numbers, and also represent an amount close to the stated amount that still performs a desired function or achieves a desired result. For example, the terms “approximately,” “about,” and “substantially” may refer to an amount that is within less than 10% of the stated amount. Features of embodiments disclosed herein are preceded by a term such as “approximately,” “about,” and “substantially” as used herein represent the feature with some variability that still performs a desired function or achieves a desired result for that feature.