Display device, display control method, and program for displaying echo image

Abstract

A fish finding ultraound system for a ship comprising a display device (30, fig 10) for an echo image, a display control method for the echo image, and a program displaying an echo image of fish group

Description

[0001] The present invention relates to a display device, display control method, and program for displaying an echo image obtained by transmitting and receiving ultrasonic waves.

[0002] Conventionally, an underwater detection device, as known as a sonar (SONAR = Sound Navigation and Ranging), for detecting underwater objects are known. This type of sonar transmits ultrasonic waves into the water, receives the reflected waves, calculates the echo intensity from each position in the water, and displays the echo image.

[0003] For example, the sonar transmits an umbrella-shaped transmission wave along a conical surface from a transducer having transducer elements (i.e., ultrasonic vibrator / wave transmitter), and receives the reflected waves by the transducer. From the electric signals output from each transducer element of the transducer due to the reception of the reflected waves, a plurality of reception beams arranged in the circumferential direction on the conical surface are formed by beamforming, and a reception signal is generated for each reception beam. From the thus generated reception signal, an echo image corresponding to the scanning range of the reception beam is generated and displayed.

[0004] In this type of sonar, each position on the conical surface is converted to a position of the latitude (L) / longitude (L) / depth (D) coordinate system consisting of latitude, longitude, and depth, and the echo intensity of each position after conversion is acquired as the echo intensity for a point on the latitude (L ) / longitude (L) coordinate plane overlapping each position in the depth direction, and the echo image in which these echo intensity are distributed in a two-dimensional manner is displayed.

[0005] Such the echo image may include noise images based on echoes from fish groups and floating objects in the water. As a method to suppress the noise image, there is a method to obtain the average value of the echo intensity at each point on the L / L coordinate plane and use the average value as the echo intensity at that point.

[0006] Namely, since the conical plane moves with the movement of a ship, the echo intensity for different depths is sequentially acquired at each point on the L / L coordinate plane for each ping (i.e., ultrasonic wave transmission and reception period). The series of echo intensity are averaged to obtain the above-mentioned average value. Here, since the depth range of floating objects is narrow, the number of pings for which the echo of floating objects may be obtained at each point is small. Therefore, the echo of floating objects hardly affects the average value at each point. Thus, noise images such as floating objects may be effectively suppressed from the echo image.

[0007] However, in this configuration, the echo intensity from the fish group as well as the echo intensity of noise are weakened by averaging at each point. Therefore, the echo of the fish group is difficult to be clearly captured in the echo image.

[0008] On the other hand, the following Patent Literature 1 describes an echo image display device which may more clearly display the echo image of the fish group. In this display device, a plurality of layers is set in the depth direction. The display device obtains the average value of the echo intensity for each layer for each point, and displays the echo image at the point based on the largest average value among these average values.

[0009] According to this method, the effect of noise may be suppressed by the averaging process. In addition, since the fish group tends to be distributed over a relatively wide range in any layer, the average value of the echo intensity in that layer may be increased according to the fish group. Therefore, by displaying the echo image at the point based on the largest average value among the averages obtained for each layer as described above, the echo image of the fish group may be displayed more clearly.

[0010] Patent Literature 1- Japan Patent No. 4781240

[0011] However, in the above method, when the fish group moves, the number of times that the echo intensity of the fish group is obtained at the point where the fish group moves directly under the fish group decreases, and then when the fish group moves away from the point directly under the fish group, the echo intensity close to the 0 level continues to be applied to the mean value at that point. Therefore, the maximum mean value at this point becomes smaller, and after the fish group moves away from the point directly under the fish group, the mean value gradually decreases. As a result, the image of the fish group on the echo image becomes blurred and fades over time.

[0012] In view of such problems, an object of the present invention is to provide a display device for an echo image, a display control method for an echo image, and a program which may clearly display an echo image of a fish group even when the fish group moves.

[0013] A first aspect of the present invention relates to a display device for displaying an echo image obtained by transmitting and receiving ultrasonic waves. The display device according to this aspect is provided with an echo intensity acquisition unit configured to acquire echo intensity for each point on a latitude / longitude plane overtime, a fish group echo estimation unit configured to estimate the echo intensity of a group of fish based on the echo intensity, an average value calculation unit configured to calculate an average value at each point by a weighted average process in which the weight of the echo intensity of the fish group is set larger than the weight of the other echo intensity and the respective weights are applied to the echo intensity, and an image generation unit configured to generate an echo image at each point based on the average value at each point, and the display device configured to display the echo image at each point while updating the echo image at each point as the ship moves.

[0014] According to the display device, according to this aspect, the influence of the echo intensity (i.e., sound wave intensity) of noise such as floating objects on the echo image may be suppressed by the weighted average processing. Furthermore, since the weight of the echo intensity of the fish group is increased compared with the weight of the echo intensity of the echo intensity other than the fish group, the average value may be increased at each point. Therefore, the echo image of the fish group may be displayed more clearly by generating the echo image at each point using the average value. Furthermore, at the point where the fish group exists directly under the fish group, the weight applied to the echo intensity is reduced after the fish group has passed, and therefore, the weighted average value hardly decreases with time. Therefore, even after the fish group has passed, the average value at the point is hardly decreased, and the echo image of the fish group is hardly faded. Therefore, the echo image of the fish group may be displayed clearly even when the fish group moves.

[0015] In the display device, according to the present embodiment, the echo intensity acquisition unit is further configured to acquire the echo intensity for each of a plurality of layers obtained by dividing a predetermined underwater area in the depth direction over time, the average value calculation unit id further configured to calculate an average value at each point for each layer, and the image generation unit is further configured to generate an echo image at point based on the maximum value of the average value at each point.

[0016] In this case, a range of each layer is set so as to partially overlap the range of the adjacent layers in the depth direction.

[0017] According to these configurations, the group of fish is easily included in any layer, and the average value at that layer may be increased. Therefore, the echo image of the group of fish may be clearly displayed by generating the echo image at the point from the maximum value of the average value acquired at each point.

[0018] A second aspect of the present invention relates to a display method (i.e., control method) for displaying an echo image obtained by transmitting and receiving ultrasonic waves. The display method includes, according to this aspect, acquiring, by an echo intensity acquisition unit, echo intensity for each point on a latitude / longitude plane over time, estimating, by a fish group echo estimation unit, the echo intensity of a group of fish based on the echo intensity, setting the weight of the echo intensity of the fish group larger than the weight of the other echo intensity, calculating, by an average value calculation unit, an average value at each point by a weighted average process in which the weight of the echo intensity of the fish group is set larger than the weight of the other echo intensity and the respective weights are applied to the echo intensity, generating, by an image generation unit, an echo image at each point based on the average value at each point, and displaying, by a display device, the echo image at each point while updating the echo image at each point as the ship moves .

[0019] According to the underwater detection method, according to this aspect, the same effect as that of the echo image display device according to the first aspect may be achieved.

[0020] A third aspect of the present invention relates to a program for causing a control unit of a device for displaying an echo image obtained by transmitting and receiving ultrasonic waves to execute a predetermined function. A program according to this aspect causes the control unit to execute a function of acquiring, by an echo intensity acquisition unit, echo intensity for each point on a latitude / longitude plane over time, a function of estimating, by a fish group echo estimation unit, the echo intensity of a group of fish based on the echo intensity, a function of calculating, by an average value calculation unit, an average value at each point by a weighted average processing in which the weight of the echo intensity of the fish group is set larger than the weight of the other echo intensity and the respective weights are applied to the echo intensity, a function of generating, by an image generation unit, an echo image at each point based on the average value of each point, and a function of displaying, by a display device, the echo image at each point while updating the echo image at each point as the ship moves. In short, the third aspect of the present invention relates to a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method described above.

[0021] According to the program, according to this embodiment, the same effect as that of the echo image display apparatus according to the first embodiment may be achieved. Advantageous Effects of Invention

[0022] As described above, according to the present invention, it is possible to provide an echo image display device, an echo image display control method, and a program capable of clearly displaying an image of a fish group even when the fish group moves.

[0023] The effect or significance of the present invention will become more apparent from the description of the following embodiments. However, the following embodiments are merely examples of the present invention, and the present invention is not limited in any way to those described in the following embodiments.

[0024] FIG. 1 is a diagram schematically showing an underwater search performed by an sonar according to an embodiment of the present invention. FIG. 2 is a diagram schematically showing an underwater search performed by an sonar according to an embodiment of the present invention. FIG. 3 is a block diagram showing a configuration of an sonar according to an embodiment of the present invention. FIG. 4 is a diagram showing a method for obtaining an average value of echo intensity for each layer according to an embodiment of the present invention. FIG. 5 is a diagram schematically showing the state of acquiring the echo intensity of a group of fish when the group of fish moves according to the embodiment of the present invention. FIG. 6 is a flowchart showing the processing of generating and displaying an echo image according to the embodiment of the present invention. FIG. 7 is a flowchart showing the processing of labeling each point (i.e., coordinate position) of the L / L / D coordinate system according to the embodiment as to whether it corresponds to a group of fish or not. FIG. 8 is a flowchart showing the processing of displaying an echo image according to the embodiment of the present invention. FIG. 9 (a) is a diagram showing an example of displaying an echo image according to the embodiment of the present invention. FIG. 9 (b) is a diagram showing an example of displaying an echo image according to the comparative example. FIG. 10 is a diagram showing the configuration of a system including a display device according to the modified example shown in FIG. 10.

[0025] Embodiments of the present invention will be described below with reference to the drawings. For convenience, XYZ axes orthogonal to each other are appropriately added to the drawings. The X-axis direction and the Y-axis direction are horizontal, and the Z-axis direction is vertical. The X-axis positive direction is the direction in which the ship is moving.

[0026] In the following embodiments, a sonar 10 (i.e., echo image display device) corresponds to an "echo image display device" described in the claims. However, the following embodiments are examples of embodiments of the present invention and do not limit the present invention in any way.

[0027] FIGS. 1 and 2 are a diagram schematically showing an underwater search performed by an sonar 10, according to an embodiment of the present invention.

[0028] In FIGS. 1 and 2, (p is an azimuth angle around a transducer 13 installed on a bottom of a ship SI, and 0 is a tilt angle of a scanning surface SP1 described later with respect to a horizontal plane (X-Y plane).

[0029] The sonar 10 includes the transducer 13 installed at the bottom of the ship SI such as a fishing boat. The sonar 10 transmits a pulse (i.e., transmission pulse) of sound waves from the transducer 13, and receives a sound wave (i.e., echo) reflected (i.e., backscattered) by an object such as a fish existing in the water by the same transducer 13. The sonar 10 detects an object existing in the water based on the sound wave received by the transducer 13.

[0030] The transducer 13 includes transducer elements (i.e., ultrasonic vibrator). Each ultrasonic transducer converts an input electrical signal into an acoustic wave and emits it during transmission, and converts an incident acoustic wave into an electrical signal and outputs it during reception. Typically, the transducer 13 has a cylindrical shape, and hundreds of ultrasonic transducers are regularly arranged on its side.

[0031] Here, the area to be detected by the sonar 10 is a conical surface. The axis of this conical surface is parallel to the vertical direction (i.e., Z-axis direction). The conical surface is referred to as the scanning surface SP1, and the apex and axis of the scanning surface SP1 are referred to as the origin and the scanning axis, respectively. The origin coincides with the position of the transducer 13, and the scanning axis extends from the origin in the direction just below the lead. Here, the scanning axis coincides with the Z-axis. The angle formed by the scanning surface SP1 with the horizontal plane (i.e., X-Y plane) is the tilt angle 9 described above.

[0032] As shown in FIG. 1, the sonar 10 transmits a transmission beam TB1 (i.e., ultrasonic wave) having the maximum intensity on the scanning surface SP1 over the entire circumference during transmission. The transmission beam TB1 has an axial intensity distribution with respect to the scanning axis (Z-axis in FIG. 1), and its vertical width is relatively narrow.

[0033] As shown in FIG. 2, the sonar 10 forms a large number of receiving beams (i.e., reception beams) RBI having maximum sensitivity on the scanning surface SP1 during reception. The receiving beams RB1 are formed by applying beamforming processing to electrical signals output from the transducer elements 13a arranged in the transducer 13.

[0034] Each receiving beam RBI is a pencil beam having a narrow width in both the vertical and horizontal directions and has the same directivity. A straight line passing through the origin and facing the direction in which the sensitivity of the receiving beam RBI is maximum is the beam axis of each receiving beam RBI. The receiving beams RB 1 are formed side by side at a fixed angular interval in the direction of azimuth angle (p over the entire circumference of the scanning surface SP1. The sonar 10 converts the intensity of sound waves received by each receiving beam RBI into colors and displays them as an echo image. The method of generating the echo image will be described later with reference to FIGS. 4 to 7.

[0035] FIG. 3 is a block diagram showing the configuration of the sonar 10, according to an embodiment of the present invention.

[0036] The sonar 10 includes a control unit 11, a storage unit 12, a transducer 13, a transmission processing unit 14, a reception processing unit 15, a transmission / reception switching unit 16, a display unit 17, a display processing unit 18, an input interface 19, and an input processing unit 20. The transducer 13 is installed on the bottom of the ship SI as described above, and other components such as the control unit 11 are installed in the wheelhouse or the like of the ship SI. The sonar 10 acquires the position and heading of the ship SI from a navigation device 100 having a GPS function or the like as needed.

[0037] The control unit 11 includes an arithmetic processing circuit such as a Central Processing Unit (CPU), and executes control processing described later by a program stored in the storage unit 12. The storage unit 12 includes a storage medium such as a Read Only Memory (ROM), a Random Access Memory (RAM), and a hard disk. The storage unit 12 stores a program for the control unit 11 to execute control processing.

[0038] The transducer 13 includes transducer elements 13a as described above. During each ping (i.e., transmission / reception period), the transducer 13 transmits an ultrasonic wave as the transmission beam TB1 shown in FIG. 1, and receives the reflected wave by each transducer element 13a.

[0039] The transmission processing unit 14 outputs a transmission signal for transmitting the ultrasonic wave to the transducer 13 via the transmission / reception switching unit 16 in response to the control from the control unit 11. As shown in FIG. 3, the transmission signal is a signal that oscillates with a predetermined amplitude for a fixed period. During one transmission of the transmission beam TB1, this transmission signal is supplied to each transducer element 13a of the transducer 13 via the transmission / reception switching unit 16. Thus, as shown in FIG. 3, the ultrasonic wave corresponding to the transmission signal is transmitted from each transducer element 13a. An ultrasonic pulse transmitted in one transmission is called a transmission pulse.

[0040] The reception processing unit 15 receives the electric signal outputted by each of transducer element 13a of the transducer 13 after receiving the reflected wave of the ultrasonic wave through the transmission / reception switching unit 16, and applies amplification and noise removal (i.e., bandpass filter) processing to the received electric signal. The reception processing unit 15 outputs the electric signal subjected to these processing to the control unit 11.

[0041] The transmission / reception switching unit 16 outputs the transmission signal outputted from the transmission processing unit 14 to the transducer 13 (transducer element 13a) during transmission of the transmission beam TB1, and outputs the electric signal outputted from the transducer 13 (transducer element 13a) to the reception processing unit 15 during a fixed period from the timing when transmission of the transmission beam TB1 is completed.

[0042] Although the transmission processing unit 14 and the reception processing unit 15 are illustrated one by one in FIG. 3, the above-described processing in the transmission processing unit 14 and the reception processing unit 15 is performed for each transducer element 13a arranged in the transducer 13. Therefore, the electric signal subjected to amplification and noise removal processing to the electric signal outputted from each transducer elements 13a is individually input to the control unit 11. When these electric signals are input to the control unit 11, they are converted into digital signals with a predetermined sampling period by an A / D converter.

[0043] The display unit 17 includes a display such as a liquid crystal display. The display processing unit 18 causes the display unit 17 to display a predetermined image in response to the control from the control unit 11. The input interface 19 includes input means such as an operation key and a mouse. The input processing unit 20 outputs a signal corresponding to the operation of the input interface 19 to the control unit 11 in response to the control from the control unit 11. The display unit 17 and the input interface 19 may be composed of a liquid crystal panel in which a touch panel is superimposed on a liquid crystal display.

[0044] In this embodiment, the functions of a received signal generation unit Ila (i.e., reception signal generation unit), an echo intensity acquisition unit 11b (i.e., echo intensity acquiring unit), a fish group echo estimation unit 11c (i.e., fish group echo estimating unit), an average value calculation unit lid, and an image generation unit lie (i.e., image generating unit) are given to the control unit 11 by the program stored in the storage unit 12.

[0045] The received signal generation unit Ila beamforms the electric signal (i.e., digital signal) output from each transducer element 13a to form the receiving beam RBI shown in FIG. 2, and generates the received signal corresponding to the sound wave incident on the transducer 13 from the beam axis direction (i.e., the direction of a predetermined azimuth angle (p and a tilt angle 0) of each receiving beam RBI. Furthermore, the received signal generation unit Ila applies the band limitation and envelope detection processes to the received signal in each beam axis direction to acquire the envelope signal in each beam axis direction.

[0046] Here, the band limitation process is a process for extracting the frequency component of the transmission signal output from the transmission processing unit 14. The process is performed when the transmission signal output from the transmission processing unit 14 is a constant frequency signal (i.e., CW signal).

[0047] On the other hand, if the transmission signal output from the transmission processing unit 14 is not a constant frequency signal (i.e., CW signal) but a frequency-modulated chirp signal (i.e., FM signal), the received signal generation unit Ila applies the matched filter process to the received signal in each beam axis direction instead of the band limitation process. Then, the received signal generation unit Ila applies the envelope detection process to the signal after the matched filter process, and acquires envelope signals in each beam axis direction.

[0048] The envelope signals thus acquired are signals indicating the echo intensity (i.e., sound wave intensity) that changes according to the elapsed time from the transmission timing of the transmission beam TB1. Here, the elapsed time from the transmission timing corresponds to the distance from the transducer 13 in each beam axis direction.

[0049] The echo intensity acquisition unit 11b acquires the echo intensity at each distance position in each beam axis direction from the envelope signal by associating the elapsed time from the transmission timing with the distance. The echo intensity is acquired with a predetermined distance resolution. Furthermore, the echo intensity acquisition unit 11b converts each distance position into a position of the latitude (L) / longitude (L) / Depth (D) coordinate system consisting of latitude, longitude, and depth, and acquires the echo intensity as an echo intensity for a point on the latitude (L) / longitude (L ) coordinate plane overlapping each position in the depth direction.

[0050] Then, the echo intensity acquisition unit 1 lb acquires the echo intensity for each point in time for each layer obtained by dividing the search range in the depth direction into the depth direction. This process will be described later with reference to FIG. 4.

[0051] The fish group echo estimation unit 11c estimates the echo intensity of the fish group based on the echo intensity acquired by the echo intensity acquisition unit 11b. More specifically, the fish group echo estimation unit 11c labels the positions corresponding to the fish group among the positions in the L / L / D coordinate system based on the echo intensity acquired for each ping. The labeling identifies whether the echo intensity of each position corresponds to the echo intensity of the fish group. The labeling process will be described later with reference to FIG. 7.

[0052] The average value calculation unit lid adds weight to the echo intensity and calculates the average value of the echo intensity at each point for each layer. More specifically, the average value calculation unit lid calculates the average value at each point for each layer by a weighted averaging process in which the weight of the echo intensity of the fish group is set higher than the weight of the other echo intensity and the respective weights are applied to the echo intensity. In this embodiment, the weighted average value is calculated as the average value. The average value calculation process will be described later with reference to FIG. 4.

[0053] The image generation unit lie generates the echo image at each point based on the maximum value of the average value of each layer for each point. The echo image generation process will be described later with reference to FIG. 8.

[0054] FIG. 4 is a diagram showing a method for obtaining the average value of the echo intensity for each layer LI, L2, and L3, according to an embodiment of the present invention.

[0055] FIG. 4 schematically shows the underwater state when viewed from the left side of the ship S1. Accordingly, FIG. 4 shows a cross section of the umbrella-shaped scanning surface SP1 that is cut in a plane including its apex (i.e., origin) and axis (i.e., Z axis) and the traveling direction of the ship SI. The front and rear two receiving beams RBI included in this cross section are shown. As the ship SI progresses, the two receiving beams RBI move together with the scanning surface SP1. In FIG. 4, the beam axis of the receiving beam RBI in the current ping is shown as a solid line, and the beam axis of the receiving beam RBI in the past several pings are shown as a short dashed line. The beam axis of the receiving beam RBI in the next ping is shown as a long dashed line.

[0056] In this embodiment, the underwater search range is divided in the depth direction, and a plurality of layers are set. Here, three layers LI to L3 are set. The search range is divided into four parts in the depth direction. Layer LI is formed by integrating the upper two divided ranges, layer L2 is formed by integrating the middle two divided ranges, and layer L3 is formed by integrating the lower two divided ranges. That is, the range of each layer partially overlaps the range of adjacent layers in the depth direction. Here, the adjacent layers overlap by half.

[0057] Fish group Fl exists near the center of the search range in the depth direction. Three floating objects N1 to N3 are present in the search range. For convenience, the fish group Fl and the floating objects N1 to N3 are shown by hatching showing the echo intensity. The higher the density of the hatching, the higher the echo intensity.

[0058] Pl to P4 are the points where part of the fish group Fl and floating objects N1 to N3 are present in the depth direction among the latitude (L ) / longitude (L) points included in the above cross section. Part of the fish group Fl is present in the direction directly under the lead of the point Pl, and floating objects N1 to N3 are present in the points P2 to P3, respectively.

[0059] For the point Pl, the echo intensity of the fish group Fl (indicated by a circle on the dash-dot line extending from the point Pl) is obtained by the receiving beam RBI of the current ping and several times in the past. For the points P2 to P3, the echo intensity of floating objects N1 to N3 (indicated by a circle on the dash-dot line extending from the points P2 to P3) is obtained by the receiving beam RB1 of the current ping only. On each dash-dot line, the pings for which the echo intensity near zero is obtained are not shown, but the echo intensity near zero is also present on these dash-dot lines.

[0060] The lower part of FIG. 4 schematically shows the echo images of the points (cross sections) in the case where the echo intensity of the points included in the cross sections are obtained by different methods. In these echo images, the echo intensity is also indicated by hatching. The higher the density of the hatch, the higher the echo intensity.

[0061] In the top-most method (i.e., peak hold), the maximum echo intensity among a series of echo intensity acquired at each point is retained. The maximum retained echo intensity is reflected in the echo image at each point. In this method, the echo image of the fish group Fl may be clearly displayed. However, on the other hand, since the echo intensity of the floating object N1 to N3 is retained as the maximum echo intensity, the echo image of the floating object N1 to N3 remains clearly in the echo image.

[0062] In the second step method from the top (i.e., average), the average value of a series of echo intensity acquired at each point is calculated. The calculated average value is reflected in the echo image of each point. In this method, the echo intensity of the floating object N1 to N3 is weakened by the averaging process, and the echo intensity of the floating object N1 to N3 does not substantially affect the echo image. However, on the other hand, the echo intensity of the fish group Fl is also weakened by the averaging process, and the echo image of the fish group Fl becomes unclear.

[0063] In the method of the third stage from the top (i.e., average peak L1 / L3), a series of echo intensity acquired at each point are averaged for each layer LI and L3, and the largest average value is set to the echo intensity of the corresponding point. The maximum set average value is reflected in the echo image at each point. In this method, the echo intensity of floating objects N1 to N3 is weakened by the averaging process, and the echo intensity of floating objects N1 to N3 does not affect the echo image. In addition, since the maximum echo intensity is set at each point, the echo image of fish group Fl becomes clearer than the average method in the second stage from the top. In this method, the echo image of fish group Fl becomes clearer by increasing the number of layers by increasing the number of divisions of the search range in the depth direction.

[0064] In the method in the fourth stage from the top (i.e., average peak L1-L3), a series of echo intensity obtained at each point are averaged for layers LI, L2, and L3, and the maximum average value is set to the echo intensity of the corresponding point. It differs from the average peak L1 / L3 method in the third stage from the top in that the layer L2 which overlaps with the adjacent layer is further set. The maximum set average value is reflected in the echo image of each point. Even in this method, the echo intensity of floating objects N1 to N3 is weakened by the averaging process, and the echo intensity of floating objects N1 to N3 does not affect the echo image. In addition, since the maximum echo intensity is set at each point, the echo image of fish group Fl becomes clearer than the average method in the second stage from the top. Furthermore, the addition of layer L2 makes it easier to include fish group Fl in any layer. Therefore, this method makes the echo image of the fish group Fl clearer than the average peak L1 / L3 method in the third stage from the top. In this method, the echo image of the fish group Fl is clearer by increasing the number of layers by increasing the number of divisions of the search range in the depth direction.

[0065] As described above, by using the average peak L1 / L3 method and the average peak L1-L3 method, the echo image of the fish group Fl may be clearly displayed while suppressing the noise image caused by floating objects N1 to N3. However, in these methods, as shown in FIG. 5, when the fish group Fl moves and moves away from the point Pl, the echo intensity close to the zero level is continuously applied to the average value at this point Pl. In the example shown in FIG. 5, the echo intensity of the fish group Fl is obtained only at the current and one previous ping. Therefore, the maximum average value at this point Pl is small, and the maximum average value gradually decreases by the averaging process for the subsequent ping. As a result, as shown in the lower echo image, the echo image of the fish group Fl becomes blurred, and then gradually fades with the passage of time (the progress of the ping).

[0066] Therefore, in this embodiment, a control is performed to enable the image of the fish group Fl to be displayed more clearly even when the fish group Fl moves. This control will be described below.

[0067] FIG. 6 is a flowchart showing the processing of generating and displaying the echo image, according to the embodiment of the present invention.

[0068] In this flowchart, the processing of steps S101, S106 and S107 is performed by the function of the average value calculating unit lid in FIG. 3, and the processing of steps SI02 to SI04 is performed by the function of the received signal generation unit Ila in FIG. 3. The processing of step SI05 is performed by the function of the echo intensity acquisition unit 11b in FIG. 3. The processing of steps SI08 and SI09 is performed by the function of the image generation unit lie in FIG. 3. The labeling in step SI06 is performed by the function of the fish group echo estimation unit 11c in FIG. 3 according to the processing in FIG. 7. In the following description, it is assumed that the control unit 11 executes the processing of the corresponding step by these functions.

[0069] When the display operation of the echo image starts, the control unit 11 initializes the calculation formula of the average value in step S107 (S101). The average value is calculated by the following formula. Here, the average value is obtained by the weighted 5 average.

[0070] Equation (1) LevelSum — LevelSum + Li xWi --(1)

[0071] Equation (2) Weight — Weight + Li x PKi -’(2) 10

[0072] Equation (3) Average — LevelSum / W eight --(3)

[0073] LevelSum is the sum of the echo intensity obtained for each of the layers LI, L2, and L3 shown in Fig. 5. Li is the echo intensity obtained for that point in the current ping, and Wi is the weight assigned to the echo intensity at that point in the current ping. 15 The weight is set to either the value when the echo intensity at that point corresponds to the fish group Fl (For example, 0.9) or the value when the echo intensity at that point does not correspond to the fish group Fl (For example, 0.1). Weight is the sum of the weighted average weights obtained for layers LI, L2, and L3. Average is the weighted average value obtained for layers LI, L2, and L3.

[0074] In equation (1), the Level Sum is updated by adding the value obtained by multiplying the echo intensity Li obtained by the current ping by the weighted Wi to the LevelSum calculated until the previous ping. In equation (2), the weight is updated by adding the value obtained by multiplying the echo intensity Li obtained by the current ping by the weighted Wi to the Weight calculated until the previous ping. In equation (3), the LevelSum calculated by equation (1) is multiplied by the Weight calculated by equation (2) to calculate the Average in the current ping.

[0075] In step S101 of FIG. 6, the control unit 11 resets the values of the parameters of equations (1) to (3) to 0 for all layers LI, L2, and L3 at all points (L / L coordinate points) included in the search range in a plane view. After that, when the echo intensity for 1 ping is obtained (S102: YES), the control unit 11 determines whether or not the level conversion processing is set (SI03).

[0076] The level conversion processing is a process of lowering the level of the echo signal from the bottom based on the bottom detection so as not to superimpose the bottom echo. In place of the level conversion processing, a filter processing for removing noise may be performed. Both the level conversion processing and the filter processing may be performed. The setting of these processes is performed by the user via the input interface 19. If the level conversion processing or the like has been set (step S103: YES), the control unit 11 performs the level conversion processing described above in step SI 04. If the level conversion processing or the like has not been set (step SI03: NO), the control unit 11 skips the processing in step SI04.

[0077] Next, the control unit 11 converts each position on the conical scanning surface SP1 into each coordinate position of the latitude (L) / longitude (L) / depth (D) coordinate system (i.e., three-dimensional coordinate system) (step S105). The control unit 11 sets weighted Wi based on the labeling of the presence or absence of fish groups Fl to each coordinate position after the conversion (step SI06). Using the set weighted Wi and the echo intensity Li of each coordinate position, the control unit 11 calculates an average value Average from the equations (1) to (3) for each layer LI, L2, and L3 of each point (L / L coordinate point) (step SI07).

[0078] The control unit 11 compares the average values of the layers LI, L2, and L3 for each point, and acquires the largest average value among them (SI08). The control unit 11 executes display processing of the echo image based on the largest average value acquired for each point (S109). If the display operation has not ended (SI 10: NO), the control unit 11 returns the processing to step S102 and performs the same processing. The control unit 11 repeats the processing of steps SI02 to SI09 until the display operation ends (SI 10: NO). Thus, the echo image is updated every ping. After that, when the display operation ends (S110: YES), the control unit 11 ends the processing of FIG. 6.

[0079] FIG. 7 is a flowchart showing the processing of labeling each point (i.e., coordinate position) of the L / L / D coordinate system, according to the embodiment as to whether it corresponds to a group of fish or not.

[0080] As described above, the labeling processing of FIG. 7 is performed by the control unit 11 in accordance with the function of the fish group echo estimation unit 11c of FIG. 3. The control unit 11 resets the echo intensity at each coordinate position of the L / L / D coordinate system to 0 and initializes the labeling processing (S201). When the echo intensity for 1 ping is obtained (S202: YES), the control unit 11 executes the level conversion processing (S204) or skips the level conversion processing according to whether or not the level conversion processing is set (S203). Subsequently, the control unit 11 binarizes the echo intensity of each position on the scanning surface SP1 by a threshold value (S205). Thus, 1 is set to the echo intensity of a strong echo generated from a fish group Fl or floating objects N1 to N3, and 0 is set to the echo intensity of other weak echoes.

[0081] Subsequently, the control unit 11 performs shrinkage and expansion processing on the echo intensity of each position after binarization (S206). By this processing, a value of 0 suddenly occurring in a group of 1 values is changed to a value of 1, and a value of 1 suddenly occurring in a group of 0 values is changed to a value of 0. Thus, the echo intensity of each position corresponding to the fish group Fl becomes a value of 1, and the echo intensity of a position corresponding to a floating object N1 to N3 is replaced with a value of 0.

[0082] The control unit 11 labels a position where a value of 1 is set as a position of the group of fish, and a position where a value of 0 is set as a position of a non-group of fish (S207). Then, the control unit 11 converts these positions after labeling into coordinate positions of the L / L / D coordinate system (S208). As a result, labeling is applied to these coordinate positions as to whether they correspond to the group of fish or not. In step S106 of FIG. 6, a weight is set to each coordinate position based on this labeling. For example, a weight of 0.9 is set to a coordinate position corresponding to the group of fish, and a weight of 0.1 is set to a coordinate position not corresponding to the group of fish. The control unit 11 executes the process shown in FIG. 7 for each ping to label each coordinate position of the L / L / D coordinate system.

[0083] FIG. 8 is a flowchart showing the processing of displaying (i.e., display process) an echo image executed in step SI 09 of FIG. 6, according to an embodiment of the present invention.

[0084] As described above, the display process shown in FIG. 8 is performed by the control unit 11 in accordance with the function of the image generation unit lie of FIG. 3.

[0085] When the control unit 11 obtains the maximum average value for each point in step SI08 of FIG. 6, it determines whether or not the setting to display a normal echo image is set (S302). Whether or not a normal echo image is displayed is set in advance by the input interface 19. The normal echo image is an echo image reflecting the echo intensity of each point (L / L coordinate point) obtained in the current ping. If the setting to display a normal echo image is set (S301: YES), the control unit 11 executes a process to display a normal echo image. On the other hand, if the setting to display a normal echo image is not set (S301: NO), the control unit 11 skips step S302.

[0086] Furthermore, the control unit 11 executes a process to display an echo image at each point in accordance with the maximum average value of each point obtained in step S108 of FIG. 6 (S303). At this time, if the normal echo image display process is executed in step S302, an echo image based on the maximum average value in step S303 is displayed superimposed on the normal echo image. Thus, the echo image becomes easier to see for the user who is familiar with the normal echo image. The control unit 11 further adds additional information such as a grid to the echo image (S304). Thus, the control unit 11 ends the process of FIG. 8.

[0087] FIG. 9 (a) is a diagram showing an example of displaying an echo image by the process of FIG. 6, according to an embodiment of the present invention. FIG. 9 (b) is a diagram showing an echo image when an echo image is generated by the average peak L1-L3 method (without weighting) shown in FIG. 4 using the same echo data as in FIG. 9 (a), according to the comparative example.

[0088] In FIG. 9 (a), a plurality of layers is set so that adjacent layers partially overlap, as in FIG. 5. The method of setting the layers in FIG. 9 (b) is the same as in FIG. 9 (b). In FIGS. 9 (a) and 9 (b), normal echo images are not superimposed. For convenience, in FIGS. 9 (a) and 9 (b), the echo images are shown in gray scale, and the closer to black, the higher the echo intensity.

[0089] As seen by comparing FIGS. 9 (a) and 9 (b), by changing the weighting according to the position corresponding to the fish group or not, the echo images Fil, F12, and F13 of the fish group may be displayed clearly and without fading over time by the processing in FIG. 6. Therefore, the user may more clearly grasp the position and size of the fish group from the echo image.

[0090] Effect of the Embodiment- According to the above embodiment, the following effects may be achieved.

[0091] As shown in FIGS. 3 and 4, the sonar 10 (i.e., echo image display device) is provided with an echo intensity acquisition unit 11b for acquiring echo intensity for each point on the latitude / longitude plane with time, with respect to each of a plurality of layers LI to L3 obtained by dividing a predetermined range in the water in the depth direction, a fish group echo estimation unit 11c for estimating the echo intensity of a fish group based on the acquired echo intensity, an average value calculation unit 1 Id for calculating the average values of each point for each layer by weighted average processing in which the weight of the echo intensity of the fish group is set larger than the weight of the other echo intensity and the respective weights are applied to the echo intensity, and an image generation unit lie for generating an echo image at the point based on the maximum value of the average values of each point. As shown in FIG. 6, the control unit 11 updates and displays the echo image at each point (SI03 to SI09) in accordance with the movement of the own vessel (S102: YES).

[0092] Further, as shown in FIGS. 6 and 7, the control method of the sonar 10 (i.e., echo image display device) acquires echo intensity for each point on the latitude and longitude plane with time for each of the plurality of layers LI to L3 obtained by dividing a predetermined range in the water in the depth direction (SI02 to SI06), estimates the echo intensity of the fish groups based on the echo intensity (steps S201 to S206), calculates the average values of each point for each layer by weighted average processing in which the weight of the echo intensity of the fish groups is set higher than the weight of the other echo intensity, and the respective weights are applied to each echo intensity (SI07), generates an echo image at the point based on the maximum value of the average values of each point (SI08, SI09), and displays the echo image at each point while updating it as the ship SI moves (SI09).

[0093] According to this configuration, the influence of the echo intensity of noise such as floating objects N1 to N3 on the echo image may be suppressed by the weighted average processing. In addition, since the weight for the echo intensity of the fish group is higher than that for the echo intensity other than the fish group, the average value of the layer including the fish group may be increased at each point. Therefore, by generating the echo image of each point using the maximum value of the average value, the echo image of the fish group may be displayed more clearly. Furthermore, at the point where the fish group exists directly under the fish group, since the weight applied to the echo intensity after the fish group passes through becomes smaller, the weighted average value of the layer including the fish group is less likely to decrease with time. Therefore, even after the fish group passes through, the maximum value of the average value at the point is less likely to decrease, and the echo image of the fish group is less likely to fade. Therefore, the echo image of the fish group may be clearly displayed even when the fish group moves.

[0094] As shown in FIG. 4, the ranges of the layers LI to L3 are set so as to partially overlap the ranges of adjacent layers in the depth direction.

[0095] According to this configuration, the fish group is easily included in one of the layers, so that the maximum value of the average value at the point where the fish group exists immediately below may be increased. Therefore, the echo image of the fish group may be clearly displayed.

[0096] In the above embodiment, the sonar 10 constitutes the display device, and the echo image using the average value is displayed on the display unit 17 of the sonar 10. However, this is not limited to this configuration, and the display device may be arranged separately from the sonar 10, and the echo data acquired by the sonar 10 may be provided to the display device, and the above-described processing may be performed in the display device.

[0097] For example, as shown in FIG. 10, a personal computer may be used as a display device 30 (i.e., personal computer) of the echo image, and the echo data may be transmitted from the sonar 10 to the display device 30 via an external communication network 40 such as the Internet. In this case, the display device 30 performs the same processing as in FIGS. 6 to 8 on the received echo data to display the echo image on a display unit 31. A wireless communication unit (i.e., wireless communication module) for connecting to the external communication network 40 is added to the sonar 10.

[0098] The control unit 11 (i.e., CPU) of the display device 30 performs the same functions as the received signal generation unit Ila, echo intensity acquisition unit 11b, fish group echo estimation unit 11c, average value calculation unit lid, and image generation unit lie by a program stored in the storage unit 12. Step S102 in FIG. 6 is replaced with a determination whether or not the echo intensity for 1 ping has been received from the sonar 10.

[0099] The display device 30 may be installed in the ship SI (i.e., wheelhouse). In this case, the display device 30 may be connected to the sonar 10 by a communication line. Alternatively, instead of the method of transmitting and receiving echo data online, the data collected by the sonar 10 may be recorded in a recording medium such as a USB memory, and the recording medium may be attached to the display device 30, so that the echo data is delivered to the display device 30. In this case, the display device 30 may sequentially execute the processes shown in FIGS. 6 to 8 for the echo data of each ping to display the echo image on the display unit 31.

[0100] In the display example shown in FIG. 9 (a), a method similar to the average peak LI to L3 method shown in FIG. 4 in which adjacent layers partially overlap is used as the layer setting method, but the method of setting layers to which the present invention may be applied is not limited to this method. For example, the process shown in FIG. 6 may be performed using a method similar to the average peak L1 / L3 method shown in FIG. 4 in which the boundaries of adjacent layers coincide. Even in this method, in the process shown in FIG. 6, the weighted average value is obtained by increasing the weight of the echo intensity from the fish group to the weight of the other echo intensity, so that the echo image of the fish group may be clearly displayed while suppressing noise images such as floating objects N1 to N3 on the echo image.

[0101] In addition, the above-described weighted averaging process may be applied to the average method shown in FIG. 4 to generate an echo image. In this case, in step SI07 of FIG. 6, the weighted average value is calculated for each point by the equations (1) to (3) described above for one layer including the search range. Step 108 of FIG. 6 is omitted. Then, in step 303 of FIG. 8, an echo image of each spot is generated and displayed based on the weighted average value calculated for each spot. Even in this process, since the weighted average value is obtained by increasing the weight of the echo intensity from the fish group to the weight of the other echo intensity, the echo image of the fish group may be clearly displayed on the echo image while suppressing noise images such as floating objects N1 to N3.

[0102] Further, the calculation formula of the weighted average value is not limited to the above equations (1) to (3), and for example, the equation (2) may be changed to the following equation (4).

[0103] Equation 4 Weight ~ Weight + W7 -(4) Even when this equation (4) is used, the echo image of the fish group Fl may be hardly faded with time, and a clear echo image of the fish group may be displayed.

[0104] In the above embodiment, the received signal generation unit Ila shown in FIG. 3 and the like are realized as functions by a program stored in the storage unit 12, but these functions may not necessarily be realized by a program stored in the storage unit 12. For example, one or more of these functions may be configured by an Field-Programmable Gate Array (FPGA) or hardware with integrated logic circuits.

[0105] Further, the processing for generating and displaying the echo image is not limited to the processing shown in FIG. 5, and may be changed accordingly. For example, the processing related to the level conversion processing in steps SI03 and SI04 may be omitted from the processing shown in FIG. 6, and the processing for superimposing a normal echo image may be omitted. Alternatively, the cutting process shown in Patent 28 Document 1 may be added to the process shown in FIG. 5. The method for estimating the echo intensity from the fish group is not limited to the above-described labeling method, but a well-known method for estimating the range of the fish group from the echo data may be used. 5

[0106] In the above embodiment, the sonar 10 for transmitting and receiving waves along the scanning surface SP1 of a cone is shown, but the present invention may be applied to the sonar 10 for transmitting and receiving waves in other ways. For example, the present invention may be applied to the sonar 10 for transmitting and receiving waves along the scanning surface SP1 of a semicircular or arc shape with a predetermined 10 depression angle, and an echo image of each point may be generated and displayed. In addition, the transmitter for transmitting waves and the receiver for receiving waves may be separately arranged.

[0107] In addition, the embodiment of the present invention may be modified as needed within the scope of the claims. 15

Claims

1. A display device (30) for displaying an echo image obtained by transmitting and receiving ultrasonic waves, comprising:an echo intensity acquisition unit (11b) configured to acquire echo intensity for each point on a latitude / longitude plane over time;a fish group echo estimation unit (11c) configured to estimate the echo intensity of a group of fish based on the echo intensity;an average value calculation unit (lid) configured to calculate an average value at each point by a weighted average process in which the weight of the echo intensity of the fish group (Fl) is set larger than the weight of the other echo intensity and the respective weights are applied to the echo intensity; andan image generation unit (lie) configured to generate an echo image at each point based on the average value at each point; andthe display device (30) configured to display the echo image at each point while updating the echo image at each point as the ship (SI) moves.

2. The display device (30) according to claim 1, whereinthe echo intensity acquisition unit (11b) is further configured to acquire the echo intensity for each of a plurality of layers (LI, L2, and L3) obtained by dividing a predetermined underwater area in the depth direction over time;the average value calculation unit (lid) is further configured to calculate an average value at each point for each layer; andthe image generation unit (lie) is further configured to generate an echo image at each point based on the maximum value of the average value at eachpoint.

3. The display device (30) according to claim 2, whereina range of each layer is set so as to partially overlap the range of the adjacent layers in the depth direction.

4. A display method for displaying an echo image obtained by transmitting and receiving ultrasonic waves, comprising:acquiring, by an echo intensity acquisition unit (11b), echo intensity for each point on a latitude / longitude plane over time;estimating, by a fish group echo estimation unit (11c), the echo intensity of a group of fish based on the echo intensity;calculating, by an average value calculation unit (lid), average value at each point by a weighted average process in which the weight of the echo intensity of the fish group (Fl) is set larger than the weight of the other echo intensity and the respective weights are applied to the echo intensity; andgenerating, by an image generation unit (lie), an echo image at each point based on the average value at each point; anddisplaying, by a display device (30), the echo image at each point while updating the echo image at each point as the ship (SI) moves.

5. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method of claim 4.

Images