GB2554813A

GB2554813A - Underwater detection circuitry, underwater detection device and method of processing underwater detection signal

Info

Publication number: GB2554813A
Application number: GB1715230.7A
Authority: GB
Inventors: Hiraoka Yasushi
Original assignee: Furuno Electric Co Ltd
Current assignee: Furuno Electric Co Ltd
Priority date: 2016-10-07
Filing date: 2017-09-21
Publication date: 2018-04-11
Anticipated expiration: 2037-09-21
Also published as: JP2018059857A; GB2554813B; GB201715230D0; JP6811069B2

Abstract

An underwater detection circuit 10 comprises a memory 22 configured to store echo signals from reflections of ultrasonic waves successively transmitted. An image generating module 32 generates an interpolated image from the stored echo signals obtained from two or more successive transmissions and by increasing a weight coefficient with time of a latest echo signal from the stored echo signals. A display controlling module 33 then outputs the generated interpolated image. For a distance up to an intermediate distance of a maximum detection distance, the image module may set a weight coefficient of an echo signal N to be larger than a weight coefficient of an echo signal N-1. For a distance beyond the intermediate distance the weight coefficient of echo N-1 may be set to larger than a weight coefficient of echo signal N-2.

Description

(54) Title of the Invention: Underwater detection circuitry, underwater detection device and method of processing underwater detection signal

Abstract Title: Underwater detection circuitry configured to generate interpolated image (57) An underwater detection circuit 10 comprises a memory 22 configured to store echo signals from reflections of ultrasonic waves successively transmitted. An image generating module 32 generates an interpolated image from the stored echo signals obtained from two or more successive transmissions and by increasing a weight coefficient with time of a latest echo signal from the stored echo signals. A display controlling module 33 then outputs the generated interpolated image. For a distance up to an intermediate distance of a maximum detection distance, the image module may set a weight coefficient of an echo signal N to be larger than a weight coefficient of an echo signal N-1. For a distance beyond the intermediate distance the weight coefficient of echo N-1 may be set to larger than a weight coefficient of echo signal N-2.

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UNDERWATER DETECTION CIRCUITRY, UNDERWATER DETECTION DEVICE

AND METHOD OF PROCESSING UNDERWATER DETECTION SIGNAL

Technical Field [0001] The present disclosure relates to an underwater detection circuitry, which performs an underwater detection therearound to generate an underwater detection image.

Background of the Invention [0002] Conventional underwater detection devices perform an underwater detection by transmitting ultrasonic waves underwater and analyzing echo signals which are reflections of the ultrasonic waves. Such underwater detection devices are known to have a configuration in which a detection is performed around a ship concerned by setting an angle of the transmission direction of ultrasonic waves with respect to a water surface (depression angle) and transmitting the ultrasonic waves to a given range. JP4179699B discloses this kind of underwater detection device.

[0003] The underwater detection device of JP4179699B sets a depression angle, omnidirectionally transmits ultrasonic waves underwater, and receives echo signals. The underwater detection device determines echo intensities to be displayed in the current operation by using a given criteria based on latest and previously-obtained echoes, so that an interference wave (spurious wave) caused by an ultrasonic wave transmitted from an underwater detection device of another ship is removed.

[0004] Here, with the underwater detection device, a time required from the transmission to reception of the echo signal becomes longer as the reflected position of the transmission signal is farther from the device. Therefore, an update of an underwater detection image is performed such that a new underwater detection image spreads radially according to a timing when the echo signal is obtained. As a result, a boundary showing the positional change between the previous and new underwater detection images is displayed during the update. Since a user of the underwater detection device confirms an object on which the - 1 echo reflected by checking the size, shape etc. of the echo obtained by the underwater detection, the boundary described above may make it difficult to check the size and shape of the echo.

Summary of the Invention [0005] The purpose of this disclosure relates to providing an underwater detection circuitry, which solves the difficulty in confirming an echo due to a boundary between underwater detection images of before and after an update of the image.

[0006] According to a first aspect of this disclosure, an underwater detection circuitry having the following configuration may be provided. That is, the underwater detection circuitry may include a memory, an image generating module, and a display controlling module. The memory may store echo signals that are reflections of ultrasonic waves successively transmitted underwater. The image generating module may generate an interpolated image from the stored echo signals obtained from two or more successive transmissions and by increasing a weight coefficient with time of a latest echo signal from the stored echo signals. The display controlling module may output the generated interpolated image.

[0007] When an echo signal [N], obtained from an N-th transmission, is obtained up to an intermediate distance from a maximum detection distance, for a distance up to the intermediate distance, the image generating module may generate the interpolated image by setting a weight coefficient of the echo signal [N] to be larger than a weight coefficient of an echo signal [N-l] as the distance is shorter, the echo signal [N-l] being obtained from an (N-l)-th transmission, and for a distance beyond the intermediate distance, the image generating module may generate the interpolated image by setting the weight coefficient of the echo signal [N-l] to be larger than a weight coefficient of an echo signal [N-2] as the distance is shorter, the echo signal [N-2] being obtained from an (N-2)-th transmission. [0008] For a distance up to the intermediate distance, the image generating module may generate the interpolated image by using the echo signals obtained only at the N-th and

-2(N-l)-th transmissions, and for a distance beyond the intermediate distance, the image generating module may generate the interpolated image by using the echo signals obtained only at the (N-l)-th and (N-2)-th transmissions.

[0009] According to a second aspect of this disclosure, an underwater detection device having the following configuration may be provided. That is, the underwater detection device may include the underwater detection circuitry of any one of the above underwater detection circuitry. The underwater detection device may also include a transducer configured to transmit underwater the ultrasonic waves, receive reflections of the ultrasonic waves, and output the reflections to the underwater detection circuitry. The underwater detection device may also include a display unit configured to display the interpolated image outputted by the underwater detection circuitry.

[0010] According to a third aspect of this disclosure, the following method of processing an underwater detection signal may be provided. That is, the method may include successively transmitting underwater ultrasonic waves and storing echo signals that are reflections of the ultrasonic waves. The method may also include generating an interpolated image from the stored echo signals obtained from two or more successive transmissions and by increasing a weight coefficient with time of a latest echo signal from the stored echo signals. The method may also include outputting the generated interpolated image.

Effect(s) of the Invention [0011] Thus, by using an interpolated image, an underwater detection image may smoothly be switched. Therefore, a boundary showing a positional change of the image may not be or hardly be displayed, which may make it easier to confirm the underwater detection image. As a result, it may become easy to confirm a shape and size of an observed echo.

Brief Description of the Drawings [0012] The present disclosure is illustrated by way of example and not by way of limitation -3in the figures of the accompanying drawings, in which the like reference numerals indicate like elements and in which:

Fig. 1 is a block diagram illustrating a configuration of an underwater detection device according to one embodiment of the present disclosure.

Fig. 2 is a view illustrating a state where the underwater detection device performs an underwater detection.

Fig. 3 is a view illustrating an underwater detection image generated by an image generating module.

Fig. 4 is a chart illustrating generation of an interpolated image during acquisition of an echo signal [N] at a given azimuth.

Fig. 5 is a chart illustrating generation of an interpolated image during acquisition of an echo signal [N+l] at the given azimuth.

Fig. 6 is a view illustrating switching of an echo image performed by a conventional underwater detection device.

Fig. 7 is a view illustrating switching of the interpolated image performed by the underwater detection device of this embodiment.

Detailed Description of the Invention [0013] Hereinafter, one embodiment of the present disclosure is described with reference to the accompanying drawings. In the following embodiment, an example is illustrated in which this disclosure is applied to a ship. However, the present disclosure may be applied to any kinds of vehicles having a rudder or a similar steering device, such as other watercrafts including boats, vessels, and submarines. Fig. 1 is a block diagram illustrating a configuration of an underwater detection device 10. Fig. 2 is a view illustrating a state where the underwater detection device 10 performs an underwater detection. Fig. 3 is a view illustrating an underwater detection image generated by an image generating module 32.

[0014] The underwater detection device 10 may transmit ultrasonic waves to a given range -4(in this embodiment, 360° in azimuth) underwater and receive echo signal(s) which are reflections of the ultrasonic waves. The underwater detection device 10 may generate, based on the echo signal(s), an underwater detection image showing a school of fish, a waterbed etc., and display it. Hereinafter, the underwater detection device 10 is described in detail.

[0015] As illustrated in Fig. 1, the underwater detection device 10 may include an underwater detection circuitry 11, a transmission circuit 12, a transmission/reception switch 13, a transducer 14, a reception circuit 15, an A/D converter 16, a display unit 17, and a user-interface 18.

[0016] The underwater detection circuitry 11 may include an signal processing unit 21 and a memory 22. Further, the signal processing unit 21 may have a transmission controlling module 31, the image generating module 32, and a display controlling module 33.

[0017] The signal processing unit 21 may be achieved by an processing device, such as an FPGA, an ASIC, a CPU, etc. The signal processing unit 21 may execute various processings regarding the underwater detection device 10 by executing program(s) created beforehand. Although a transmission control, image generation, and image displaying are described in detail as processings executed by the signal processing unit 21, the signal processing unit 21 may execute other processings (e.g., switching of range, menu display, etc.).

[0018] The memory 22 may be achieved by a volatile memory, such as a RAM. The memory 22 may store echo signals obtained from two or more successive transmissions. [0019] The transmission controlling module 31 may control the transmission of the ultrasonic wave. For example, the transmission controlling module 31 may generate signals indicating a timing to generate the ultrasonic wave, an amplitude of the ultrasonic wave, a depression angle at which the ultrasonic wave is transmitted (an angle of the transmission direction of the ultrasonic wave with respect to a water surface, i.e., tilt angle), etc., and output them to the transmission circuit 12. The transmission circuit 12 may generate a pulse signal based on a signal received from the transmission controlling module

-531, and output it to the transducer 14 via the transmission/reception switch 13.

[0020] The transducer 14 may be an oscillator which is attached to a bottom of a ship to which the underwater detection device 10 is mounted, and transmit the ultrasonic wave underwater based on the signal received from the transmission circuit 12. The transducer 14 may include a substantially cylindrical housing and a plurality of oscillators. The plurality of oscillators may be attached to an outer circumferential surface of the housing. With this configuration, ultrasonic waves may be transmitted over a given azimuth range simultaneously. In this embodiment, the transducer 14 may transmit the ultrasonic waves omnidirectionally (360°, to all azimuths) at a depression angle instructed by the transmission controlling module 31 (see Fig. 2). The ultrasonic waves transmitted by the transducer 14 may travel in a ring shape in a plan view while spreading radially. Further, each oscillator of the transducer 14 may receive a reflection of the ultrasonic wave from an object, such as fish or a waterbed as an echo signal.

[0021] In the case of transmitting the ultrasonic waves omnidirectionally as in this embodiment, a single detection may be defined as a detection around the device, performed by transmitting the ultrasonic waves omnidirectionally and receiving echo signals omnidirectionally. Further, the underwater detection device 10 may successively perform the detection only for a set azimuth range (e.g., 180° on the front side), without limiting to omnidirection. In this case, a single detection may be defined as a detection performed by transmitting ultrasonic waves to a given azimuth range where the detection is requested to be performed, and receiving echo signals therefrom. Moreover, the underwater detection device 10 may transmit the ultrasonic waves to the azimuth range by dividing them into a plurality of transmissions instead of transmitting them at once. For example, when detecting all the azimuths, the ultrasonic waves may be divided into four transmissions, for an azimuth range of 90° at a time. In this case, a single detection may be defined as a detection performed by transmitting and receiving ultrasonic waves to and from the entire azimuth range where the detection is requested to be performed. Therefore, when transmitting the ultrasonic waves to the azimuth range of 90°, a single detection may be -6achieved by performing the transmission and reception of the ultrasonic waves four times. Further, the underwater detection device 10 may have a configuration in which a detection for a given azimuth range is performed by transmitting an ultrasonic wave to a single direction at a time instead of over a given azimuth range at once, and gradually changing the transmission azimuth (e.g., PPI sonar, search light sonar).

[0022] The transducer 14 may output each received echo signal to the reception circuit 15 via the transmission/reception switch 13. The transmission/reception switch 13 may output the signal outputted by the transmission circuit 12 to the transducer 14 and output the echo signal obtained by the transducer 14 to the reception circuit 15.

[0023] The reception circuit 15 may amplify etc. the received echo signal and output it to the A/D converter 16. The A/D converter 16 may convert the inputted echo signal from analog to digital and output it to the underwater detection circuitry 11. The A/D-converted echo signal may be stored in the memory 22. Note that, other processing(s) may follow the A/D conversion before the memory 22 stores the echo signal.

[0024] The image generating module 32 of the underwater detection circuitry 11 may process the echo signal received from the A/D converter 16 or stored in the memory 22. For example, the image generating module 32 may acquire a distance from the ship based on a time length from the transmission to reception of the ultrasonic wave, and acquire intensity of the echo signal corresponding to the amplitude (signal level). This process may be performed omnidirectionally (detection azimuths).

[0025] In the following, an image generated using the echo signal obtained from a single detection and without using other echo signals except for noise removal etc., may be referred to as an echo image. While the conventional underwater detection device only displays this echo image, the image generating module 32 of the underwater detection device 10 of this embodiment may generate and display an interpolated image instead of the echo image. The interpolated image may be an image which interpolates two consecutive echo images. In other words, the interpolated image may be an image showing a detection result which interpolates between a detection result obtained from a certain echo signal and -7a detection result obtained from another echo signal continuous to the certain echo signal. Note that, an echo image displayed on the conventional underwater detection device or an image showing an echo obtained as a result of the underwater detection, such as the interpolated image displayed on the underwater detection device 10 of this embodiment, may be referred to as the underwater detection image. The interpolated image generated by the image generating module 32 may be displayed on the display unit 17.

[0026] Fig. 3 shows one example of the underwater detection image (particularly, the interpolated image) displayed on the display unit 17. The underwater detection image may be a plan view illustrating information acquired by the underwater detection. Therefore, in the underwater detection image, the distance from the ship to the echo is longer (the water depth also becomes deeper) as the displayed position of the echo is farther from the center. At the center of the underwater detection image, a triangular ship mark 51 indicating the position and orientation of the ship may be displayed. In addition, when detecting all azimuths as in this embodiment, a ring-shaped echo 52 indicating the waterbed may be displayed. Moreover, an echo 53 indicating a school of fish may also be displayed in the underwater detection image of Fig. 3.

[0027] The underwater detection device 10 may perform the detection by transmitting the ultrasonic waves at a given transmission cycle. Therefore, the underwater detection device 10 may sequentially acquire new echo signals. The image generating module 32 may generate the interpolated image based on a new (latest) echo signal and the previously-obtained echo signal (described later in detail). The interpolated image thus generated may be displayed on the display unit 17, while being switched at a given timing by the display controlling module 33. When referring to the echo image, the interpolated image, or the underwater detection image, it may comprehensively mean an omnidirectional image or only an image of a given area or azimuth.

[0028] The user-interface 18 may have a given physical key and be capable of accepting an operation from a user. The content of the operation performed on the user-interface 18 by the user may be outputted to the underwater detection circuitry 11 etc. so that the user’s -8instruction may be reflected. The user may control the user-interface 18 to instruct, for example, switching of range, whether to display the interpolated image, the displayed number of interpolated images per unit time, etc. Note that the user-interface 18 may be attached to a housing of the display unit 17 or be a separate body from the display unit 17. Moreover, a touch panel display may be adopted so that the display unit 17 and the user-interface 18 may be configured integrally.

[0029] Next, a method of generating the interpolated image is described with reference to Figs. 4 and 5. In the following, an echo signal obtained in an N-th transmission may be referred to as an echo signal [N]. Fig. 4 is a chart illustrating the generation of the interpolated image during acquisition of an echo signal [N] at a given azimuth. Fig. 5 is a chart illustrating the generation of the interpolated image during acquisition of an echo signal [N+1] at the given azimuth.

[0030] Generally, the time length from a transmission of an ultrasonic wave to a reception of an echo signal may be dependent on the distance from the ship (more specifically, the transducer 14 of the underwater detection device 10, same for below) to the object. Therefore, in a case of generating an underwater detection image of an N-th transmission based on the echo signals [N] after the echo signal from the farthest position returns, a time length from the detection to drawing becomes long and real-time performance degrades. Therefore, in this embodiment, the generation of the interpolated image using the echo signals [N] of the N-th transmission may be started from an area where the echo signal [N] is already obtained (that is, from the area close to the ship). By varying the timing of using the echo signal [N] according to the distance from the device as described above, the echo signal [N] may be used early, and the real-time performance may be improved.

[0031] Further, the image generating module 32 of this embodiment may generate the interpolated image based on the echo signals obtained from two consecutive transmissions. For example, the interpolated image may be generated by applying a weight coefficient to each of the echo signals obtained from the two consecutive transmissions to acquire a linear sum. In Figs. 4 and 5, the echo signals obtained at a given azimuth may be listed vertically. -9The echo signal may be listed higher as the obtained timing of the echo signal is later. Moreover, the horizontal axis indicates distance from the ship which ascends to the right side. At the timing illustrated in Fig. 4, in terms of an echo signal [N-2] and an echo signal [N-l], all echo signals in a set distance R are obtained, whereas, in terms of the echo signal [N], echo signals are obtained to a distance XI. As illustrated in Fig. 4, the area where the echo signal [N] is obtained may be referred to as “echo obtained area,” and the area where the echo signal [N] is not obtained yet (the area where the distance from the ship is farther than the echo obtained area) may be referred to as an echo unobtained area. Therefore, in the example of Fig. 4, the distance range from a distance 0 to the distance XI may correspond to the echo obtained area, and the distance range from the distance XI to the distance R may correspond to the echo unobtained area.

[0032] The image generating module 32 may start the generation of the interpolated image using the echo signal [N], from the echo obtained area as described above. Therefore, in the echo obtained area, the interpolated image may be generated using the echo signals [N] and [N-l]. Further in the echo unobtained area, the interpolated image may be generated using the echo signals [N-l] and [N-2], [0033] The image generating module 32 may generate the interpolated image using data obtained by the convex combination of the echo signals obtained from the two consecutive transmissions. For example, as illustrated in Fig. 4, the data of the echo signals obtained from the N-th transmission (more specifically, array data indicating a change in amplitude according to the distance) may be referred to as Data[N]. In addition, the data which is the basis of the interpolated image for the echo obtained area may be referred to as DisplayDatal, for example. As illustrated in Fig. 4, DisplayDatal= a*Data[N]+P*Data [N-l] may be established. Here, a and β may be weight coefficients for convex combination of the data of the two echo signals. In this embodiment, a and β may be array data of which values change in the distance direction, and the values may change with time. [0034] A weight coefficient determining line illustrated in Fig. 4 may be a straight line used for obtaining a and β. The weight coefficient determining line may decline (to the older

- 10echo signal) as it extends rightward (to the side farther from the ship). Here, at a distance A in the echo obtained area, “the distance from the weight coefficient determining line to the echo signal [N-l]” : “the distance from the weight coefficient determining line to the echo signal [N]” may be L1:L2. In this case, a and β may be determined so that a:P=Ll:L2. For example, since α+β=1, a=Ll/(Ll+L2) and β=Ε2/(ΙΗ+Ε2) are established. In this manner, the weight coefficients a and β may be obtained.

[0035] Thus, the echo signal closer to the weight coefficient determining line may be used with higher priority (with a larger weight coefficient). Therefore, considering the inclination of the weight coefficient determining line, the newer echo signal (echo signal [N] in Fig. 4) may preferentially be used to generate the interpolated image as the distance from the ship becomes shorter. This may be similar for a and β in the echo unobtained area, except that the echo signals here may be older by one detection.

[0036] As time passes from the state illustrated in Fig. 4, the arrow of the echo signal [N] may extend further rightward, and the weight coefficient determination line may shift upward. Then, when all the echo signals [N] in the set distance R are obtained, the ultrasonic waves for the next detection may be transmitted and an echo signal [N+l] may start to be obtained. Fig. 5 illustrates a state after the echo signal [N+l] is obtained. As illustrated in Fig. 5, by starting to obtain the next echo signal [N+l], echo signals used for calculating DisplayDatal and DisplayData2 may be renewed one by one.

[0037] As described above, in this embodiment, immediately after a new echo signal is obtained from a given location, the weight of the echo signal may be 0 and the weight of the previous echo signal may be 1. That is, only one of the two echo signals may be used at this location. Note that, even at this location, using one of the echo signals may be a result of adjusting the weights of the two echo signals, and at a location slightly away from this given location, both of the two echo signals may be used. Accordingly, even if the location where only one of the two echo signals is used is included as described above, it is treated as a generation target of the interpolated image. Therefore, at this location, the weight of the new echo signal changes from 0 to 1 (at the same time, the weight of the previous echo - 11 signal changes from 1 to 0) over one period time of a transmission cycle of the ultrasonic wave).

[0038] As described above, the image generating module 32 may calculate data which is the basis of the interpolated image, for each of the echo obtained area and the echo unobtained area. The data calculated here may be data indicating a change in the amplitude according to the distance in a given direction. Moreover, the image generating module 32 may perform this processing of data calculation for all detected azimuths, and calculate the data as the basis of the interpolated image for each azimuth. As a result, the data may be calculated for all the detected areas. In other words, the DisplayData and Data described above may be variables of a two-dimensional array. Further, the image generating module 32 may be capable of generating the interpolated image by assigning a parameter, such as drawing color or brightness, according to the amplitude of this data. The image generating module 32 may generate the interpolated image a plurality of times by using the echo signals obtained from a single transmission. Although the generation frequency of the interpolated image may arbitrarily be set, since the underwater detection image changes smoothly as the generation frequency of the interpolated image becomes higher, the interpolated image may be generated particularly from 10 to 30 times per second. [0039] Next, the display of the generated interpolated image is described in comparison with a conventional example. In the following, in a case where an echo indicating a school of fish contained in the underwater detection image is moving, changes in the underwater detection image in the conventional example and this embodiment, are described in comparison with each other. Further in the following, an echo image showing a detection result obtained from the echo signal [N] may be referred to as the echo image [N], and an interpolated image for interpolating two detection results obtained from the echo signal [N-l] and the echo signal [N] may be referred to as the interpolated image [N-l, N].

[0040] Fig. 6 illustrates a change in the echo indicating the school of fish displayed on a display unit in the conventional example. A case where a school of fish (school-of-fish echo) moves leftward as illustrated in the upper left part of Fig. 6 may be considered. In

- 12the conventional example, only the echo image [N-l] and the echo image [N] are generated and no interpolated image is generated. Further, as the echo signal is obtained from the N-th transmission, the echo image [N-l] is switched to the echo image [N] progressively from the side closer to the ship (from the lower side in Fig. 6). Thus, the underwater detection image has a boundary showing a positional change of the image as illustrated in Fig. 6 and it may be difficult to check the size and shape of the echo. Further, the change in the boundary may catch attention of the user, causing a difficulty for the user to concentrate on confirming the echo.

[0041] Fig. 7 shows a change in the echo indicating the school of fish displayed on the display unit 17 in this embodiment. The movement of the school of fish (school-of-fish echo) may be the same as in Fig. 6. Note that in Fig. 7, the amplitude of the echo may be represented by the density of dots (the density of the dots is higher as amplitude is higher). [0042] In this embodiment, the image generating module 32 may generate the interpolated image [N-l, N] for interpolating the echo image [N-l] and the echo image [N]. Further, the interpolated image may be switched by the display controlling module 33. For example, for an area where the echo signal of the N-th transmission is not obtained yet, the image generating module 32 may generate an interpolated image [N-2, N-l] for interpolating the echo image [N-2] and the echo image [N-l]. Further, for an area where the echo signal of the N-th transmission is obtained, the image generating module 32 may generate the interpolated image [N-l, N] for interpolating the echo image [N-l] and the echo image [N]. As described with reference to Figs. 4 and 5, the interpolated image may be generated by preferentially using the newer echo signal (that is, by increasing the weight coefficient) over time. Therefore, also in Fig. 7, the interpolated image [N-2, N-l] may be changed so as to approach the amplitude of the echo signal [N-l] from the amplitude of the echo signal [N- 2] over time. In addition, the interpolated image [N-l, N] may be changed so as to approach the amplitude of the echo signal [N] from the amplitude of the echo signal [N-l] over time. Moreover, the interpolated image may be switched progressively from the side closer to the ship as described above. Therefore, also in Fig. 7, the interpolated

- 13image may be switched from the interpolated image [N-2, N-l] to the interpolated image [N-l, N] progressively from the lower side.

[0043] As illustrated in Fig. 7, in this embodiment, the underwater detection image may smoothly be switched. Therefore, a boundary showing a positional change of the image may not be or hardly be displayed, which may make it easier to confirm the underwater detection image. As a result, it may become easy to confirm the shape and size of the observed echo. Also, since the boundary may hardly be displayed, the user can concentrate on confirming the echo. Note that, although a large movement of the echo which indicates the school of fish is illustrated in Fig. 7 in order to facilitate the description of the image change, in reality, the echo indicating the school of fish may not move much in one period of the transmission cycle. In such a situation, the echo indicating the school of fish may move while maintaining the echo shape.

[0044] As described above, the underwater detection circuitry 11 of this embodiment may include the memory 22, the image generating module 32, and the display controlling module 33. The memory 22 may store the echo signals which are reflections of the ultrasonic waves successively transmitted to a given range underwater. The image generating module 32 may generate the interpolated image by reading from the memory 22 the echo signals obtained from two or more consecutive transmissions, and increasing the weight coefficient of the new echo signal with time by using the echo signals obtained from the two or more consecutive transmissions. The display controlling module 33 may execute the control for displaying the interpolated image generated by the image generating module 32.

[0045] Thus, the underwater detection image may be switched smoothly by using the interpolated image. Therefore, a boundary showing a positional change of the image may not be or hardly be displayed, which may make it easier to confirm the underwater detection image. As a result, it may become easy to check the shape and size of the observed echo. [0046] Further, with the underwater detection circuitry 11 of this embodiment, when the echo signal [N] is obtained to an intermediate position within the detection distance in the

- 14N-th transmission, for the distance range where the echo signal [N] is obtained (echo obtained area), the interpolated image may be generated by increasing the weight coefficient of the echo signal [N] to be larger than that of the echo signal [N-l] as the distance from the processor becomes shorter. For the distance range where the echo signal [N] is not obtained yet (echo unobtained area), the interpolated image may be generated by increasing the weight coefficient of the echo signal [N-l] to be larger than that of the echo signal [N-2] as the distance from the processor becomes shorter.

[0047] Generally, the time length from a transmission of an ultrasonic wave to a reception of an echo signal may be dependent on the distance from the ship to the object. By varying the timing of using the N-th echo according to the distance from the device as described above, the N-th echo may be used earlier.

[0048] Further, in the underwater detection circuitry 11 of this embodiment, the interpolated image may be generated by only using the echo signal [N-l] and the echo signal [N] for the area where the echo signal [N] is obtained. For the distance range where the echo signal [N] is not obtained yet, the interpolated image may be generated by only using the echo signal [N-2] and the echo signal [N-l].

[0049] By generating the interpolated image based only on two echo signals as described above, the generation process of the interpolated image may be simplified compared with a configuration using three or more echo signals.

[0050] Although the suitable embodiment of the present disclosure is described above, the above configuration may be modified as follows, for example.

[0051] Although movement and turning of the ship are not mentioned in the above embodiment, the underwater detection image (echo image, interpolated image) may be generated in consideration of the movement and turning. For example, when the ship moves before the echo signal is obtained, a correction may be performed by the moved amount. Further, when the ship turns before the echo signal is obtained, the turning angle of the ship may be acquired with an azimuth sensor etc. and the echo signal to be referred to may be extracted according to the turning angle.

- 15[0052] Although the interpolated image may be generated by using the echo signals obtained from two consecutive transmissions in the above embodiment, the interpolated image may be generated by using echo signals obtained from a large number of (e.g., three or four consecutive) transmissions.

[0053] Although in the above embodiment the data as the basis of the interpolated image may be calculated based on the echo signals obtained from two or more consecutive transmissions by using convex combination, the data as the basis of the interpolated image may be calculated based on the echo signals obtained from a plurality of consecutive transmissions by using a method other than convex combination. Moreover, the convex combination may be achieved by, for example, filtering which uses a digital filter of FIR. Further, the data calculation based on the previously-obtained echo signal by the method other than the convex combination, may be achieved by using, for example, an HR filter. [0054] Although in the above embodiment the weight coefficient determining line may be the straight line, at least a part thereof may be a curve. By adjusting the weight coefficient determining line in this way, the coefficient (weight) of the convex combination may be changed according to the situation and request so that a desired interpolated image may be generated.

[0055] Although the transducer 14 has the cylindrical casing in the above embodiment, it may have a different shape (e.g., spherical body). Moreover, although the oscillators of the transducer 14 may perform both the transmission and reception of the ultrasonic waves, different transducers may be used for transmission and reception, respectively. In this case, a device including a transmission oscillator and a reception oscillator may correspond to the transducer (the transmission oscillator and the reception oscillator may be disposed at separate positions).

[0056] In the above embodiment, the image generated by using the echo signal obtained from a single transmission and without using other echo signals except for noise removal etc. may be referred to as the echo image, and the image for interpolating the echo images by using the echo signals from a plurality of transmissions may be referred to as the - 16interpolated image. Further, the interpolated image may be displayed between two adjacent echo images. Alternatively, instead of displaying the echo images, it may be such that only the interpolated image is continuously displayed (that is, the weight coefficient may be changed so that the weight coefficient does not become zero).

[0057] In the above embodiment, as illustrated in Fig. 4, the data as the basis of the interpolated image may be calculated for the entire echo obtained area by using the echo signal [N] and the echo signal [N-l]. Instead of this configuration, in consideration of processing delay or other situations, the data as the basis of the interpolated image may be calculated by using the echo signal [N-l] and the echo signal [N-2] for a part of the echo obtained area.

[0058] In the above embodiment, in the N-th transmission, the generation of the interpolated image using the echo signal [N] may be started from the echo obtained area. In other words, the underwater detection image may be switched progressively from the side closer to the ship. Alternative to this configuration, the underwater detection image may entirely be switched at once regardless of the distance from the ship. In this case, the interpolated image [N-l, N] may be generated based on the echo image [N-l] and the echo image [N] after completion of the N-th detection (after obtaining all the echo signals [N]), which may result in smooth switching of the underwater detection image even though real-time performance degrades.

[0059] Although in the above embodiment the detection may be performed at a fixed elevation/depression angle within the given range in the azimuth direction, the detection may be performed at a fixed azimuth within a given range in the elevation/depression direction (e.g., from the port and starboard sides to below of the ship).

Claims

1. An underwater detection circuitry (11), comprising:

a memory (22) configured to store echo signals that are reflections of ultrasonic waves successively transmitted underwater;

an image generating module (32) configured to generate an interpolated image from the stored echo signals obtained from two or more successive transmissions and by increasing a weight coefficient with time of a latest echo signal from the stored echo signals; and a display controlling module (33) configured to output the generated interpolated image.

2. The circuitry (11) of claim 1, wherein, when an echo signal [N], obtained from an N-th transmission, is obtained up to an intermediate distance from a maximum detection distance, for a distance up to the intermediate distance, the image generating module (32) generates the interpolated image by setting a weight coefficient of the echo signal [N] to be larger than a weight coefficient of an echo signal [N-l] as the distance is shorter, the echo signal [N-l] being obtained from an (N-l)-th transmission, and for a distance beyond the intermediate distance, the image generating module (32) generates the interpolated image by setting the weight coefficient of the echo signal [N-l] to be larger than a weight coefficient of an echo signal [N-2] as the distance is shorter, the echo signal [N-2] being obtained from an (N-2)-th transmission.

3. The circuitry (11) of claim 2, wherein, for a distance up to the intermediate distance, the image generating module (32) generates the interpolated image by using the echo signals obtained only at the N-th and (N-l)-th transmissions, and

- 18for a distance beyond the intermediate distance, the image generating module (32) generates the interpolated image by using the echo signals obtained only at the (N-l)-th and (N-2)-th transmissions.

4. An underwater detection device (10), comprising:

the underwater detection circuitry (11) of any one of claims 1 to 3; a transducer (14) configured to transmit underwater the ultrasonic waves, receive reflections of the ultrasonic waves, and output the reflections to the underwater detection circuitry (11); and a display unit (17) configured to display the interpolated image outputted by the underwater detection circuitry (11).

5. A method of processing an underwater detection signal, comprising: successively transmitting underwater ultrasonic waves and storing echo signals that are reflections of the ultrasonic waves;

generating an interpolated image from the stored echo signals obtained from two or more successive transmissions and by increasing a weight coefficient with time of a latest echo signal from the stored echo signals; and outputting the generated interpolated image.

6. An underwater detection circuitry (11) substantially as described herein with reference to and as illustrated in the accompanying drawings.

7. An underwater detection device (10) substantially as described herein with reference to and as illustrated in the accompanying drawings.

8. A method of processing an underwater detection signal substantially as described herein with reference to and as illustrated in the accompanying drawings.

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Intellectual

Property

Office

Application No: GB1715230.7 Examiner: Mr Henry Nevell