Target detection device and target detection method

Abstract

To provide a target object detection device and a target object detection method capable of more accurately grasping a target object existing in water.SOLUTION: A target object detection device 10 includes: a transducer 2 that transmits ultrasonic waves in water and receives its reflected waves; a reception processing unit 14 that generates echo data according to strength of the reflected wave from a signal output from the transducer 2; an image generation unit 11a that generates a first image for display showing strength distribution of the reflected wave from the echo data; a region extraction unit 11b that extracts a latent region of a target object that is not displayed in the first image from the echo data; and a display processing unit 11c that superimposes the latent region on the first image and causes a display unit 16 to display it.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a target detection device and a target detection method for detecting an underwater target. [Background technology]

[0002] Conventionally, target detection devices for detecting underwater targets have been known. In this type of target detection device, ultrasonic waves are emitted into the water and the reflected waves are received. Echo data is generated according to the intensity of the received reflected waves. Based on the generated echo data, the intensity distribution of the reflected waves at each water depth is displayed using a corresponding color gradation. A fish finder with such a configuration is described in Patent Document 1 below. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-281736 Summary of the Invention [Problem to be solved by the invention]

[0004] In target detection devices such as those described above, the intensity range for setting the display gradation is often set relatively high. This makes the intensity distribution of the reflected wave easier to see, making it easier to identify targets in the water. However, with this method, if the intensity of the reflected wave from a target is lower than the intensity range, the intensity distribution based on the target will not be displayed in the image. On the other hand, if the intensity range is lowered, noise other than the target will be displayed, making it difficult to identify the distribution of targets in the water.

[0005] In view of the above problem, an object of the present invention is to provide a target detection device and a target detection method that can more accurately detect targets present in water. [Means for solving the problem]

[0006] A first aspect of the present invention relates to a target detection device, which includes a transducer that transmits ultrasonic waves into water and receives the reflected waves, a reception processing unit that generates echo data corresponding to the intensity of the reflected waves from signals output from the transducer, an image generation unit that generates a first image for display showing the intensity distribution of the reflected waves from the echo data, a region extraction unit that extracts, from the echo data, a potential region of a target that is not displayed in the first image, and a display processing unit that displays the first image on a display unit by superimposing the potential region on the first image. The area extraction unit generates a second image from the echo data for extracting the latent area, extracts an area of ​​a group of pixels in the second image where the intensity of the reflected wave is equal to or greater than a threshold and where there is continuity in the intensity of the reflected wave between adjacent pixels, and extracts the extracted area as the latent area based on the fact that there is no cluster of the intensity of the reflected wave corresponding to the target in the area on the first image corresponding to the extracted area.

[0007] According to the target detection device of this aspect, a latent area of ​​a target that is not displayed in the first image is displayed superimposed on the first image. This allows the user to identify the target from the intensity distribution of the reflected wave displayed in the first image, and also to identify targets with low reflected wave intensity from the latent area superimposed on the first image. This allows the user to more accurately identify targets present in the water from the displayed image.

[0008] A second aspect of the present invention relates to a target detection method, which includes generating echo data by receiving reflected waves of ultrasonic waves transmitted into water, generating an image for display showing an intensity distribution of the reflected waves from the echo data, extracting a potential area of ​​a target that is not displayed in the image from the echo data, and displaying the potential area superimposed on the image. In extracting the latent area, a second image for extracting the latent area is generated from the echo data, and in the second image, a region of a group of pixels where the intensity of the reflected wave is above a threshold and there is continuity in the intensity of the reflected wave between adjacent pixels is extracted, and the extracted region is extracted as the latent area based on the fact that there is no cluster of the intensity of the reflected wave corresponding to the target in the region on the first image corresponding to the extracted region.

[0009] According to the target detection method of this aspect, the same effects as those of the first aspect are achieved. [Effects of the Invention]

[0010] As described above, the present invention can provide a target detection device and a target detection method that can more accurately detect targets present in water.

[0011] The effects and significance of the present invention will become more apparent from the following description of the embodiments, however, the embodiments shown below are merely examples of how the present invention can be implemented, and the present invention is not limited to the embodiments described below. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram showing a usage form of a target detection device according to an embodiment. [Figure 2] FIG. 2 is a block diagram showing the configuration of a target detection device according to an embodiment. [Figure 3] 3A and 3B are diagrams each showing a schematic diagram of a setting state of a gradation setting range according to an embodiment. [Figure 4] 4(a) and 4(b) are diagrams showing specific examples of echo images when the gradation setting range is set relatively high and low, respectively, according to an embodiment. [Figure 5] FIG. 5 is a flowchart showing the processing of the target detection device according to the embodiment. [Figure 6] 6(a) is a diagram showing an extraction image according to an embodiment, and FIG. 6(b) is a diagram showing an echo image and a latent area superimposed on the echo image according to an embodiment. [Figure 7] FIG. 7 is a flowchart showing the latent area extraction process according to the embodiment. [Figure 8] 8(a) to 8(c) are schematic diagrams illustrating the process of extracting regions forming clumps according to the embodiment. [Figure 9] 9(a) to 9(c) are diagrams each showing a schematic diagram of a region forming a mass in an extraction image, a region forming a mass superimposed on an echo image, and an extracted latent region, according to an embodiment. [Figure 10]Fig. 10(a) is a flowchart showing the process of accepting the designation of a latent area and displaying the intensity distribution according to Modification Example 1. Fig. 10(b) is a diagram showing an echo image according to Modification Example 1 in which the designated latent area is displayed in a predetermined gradation. [Figure 11] FIG. 11 is a flowchart showing the process of accepting the latent area and the scale of the gradation display and displaying the intensity distribution according to the second modification. [Figure 12] Fig. 12(a) is a diagram showing an echo image in a state where a slider is displayed according to Modification Example 2. Fig. 12(b) is a diagram showing an echo image in a state where a designated latent area is displayed on a designated gradation display scale according to Modification Example 2. [Figure 13] Fig. 13(a) shows an echo image according to another modification in which all latent areas are displayed in a predetermined gradation, and Fig. 13(b) shows an echo image according to another modification in which all latent areas are switched to a state in which only the outlines are displayed. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, an example in which the present invention is applied to a target detection device installed on the hull of a fishing boat or the like is shown. However, the following embodiments are merely one embodiment of the present invention, and the present invention is not limited to the following embodiments.

[0014] FIG. 1 is a diagram showing a usage form of the target detection device.

[0015] In this embodiment, a transducer 2 is installed on the bottom of a ship 1, and an ultrasonic transmission beam 3 is transmitted from the transducer 2 into the water. The transmission beam 3 is a cone with a small apex angle, and is transmitted in pulses in the vertically downward direction. The transmission beam 3 is reflected by the water bottom 4 and a school of fish 5, and the reflected waves (echoes) are received by the transducer 2. The received signals of the reflected waves based on a single transmission of the transmission beam 3 generate echo data that shows the distribution of the signal strength of the received signal within the detection range in the water depth direction.

[0016] By accumulating the history of echo data, an echo image showing the distribution of signal strength in the water depth direction is generated. The echo image includes the intensity distribution of the target. The generated underwater echo image is displayed on a display unit installed in the wheelhouse of the ship 1, etc. This allows the user to confirm the location of targets (such as the bottom 4 or a school of fish 5) present in the water.

[0017] FIG. 2 is a block diagram showing the configuration of the target detection device 10. As shown in FIG.

[0018] The target object detection device 10 of this embodiment is a so-called fish finder and includes a control unit 11, a storage unit 12, a transmission processing unit 13, a reception processing unit 14, an input unit 15, a display unit 16, and the transducer 2 shown in FIG.

[0019] The control unit 11, memory unit 12, transmission processing unit 13, reception processing unit 14, input unit 15, and display unit 16 are installed in the wheelhouse or the like of the ship 1. The components excluding the transducer 2 may be unitized into a single housing, or some of the components such as the display unit 16 may be separate. The transmission processing unit 13 and reception processing unit 14 are each connected to the transducer 2 by a signal cable so as to be able to communicate with each other.

[0020] The transducer 2 comprises a transmitter used to transmit ultrasonic waves and a receiver used to receive ultrasonic waves. The transmitter and receiver of the transducer 2 are, for example, ultrasonic vibrators. The transmission processing unit 13 outputs a transmission signal to the transmitter of the transducer 2 under the control of the control unit 11. The transmitter of the transducer 2 transmits ultrasonic waves into the water based on the transmission signal. The receiver of the transducer 2 receives reflected waves of the transmitted ultrasonic waves and outputs a reception signal of a magnitude corresponding to the intensity of the reflected waves to the reception processing unit 14.

[0021] The reception processing unit 14 generates data (hereinafter referred to as "echo data") that associates the elapsed time from the timing at which the transmission beam 3 was transmitted with the intensity of the reflected wave based on the received signal from the receiver of the transducer 2, and outputs the generated echo data to the control unit 11. Note that the elapsed time from the timing at which the transmission beam 3 was transmitted corresponds to the distance to the target, and the intensity of the reflected wave attenuates as the distance to the target increases. Therefore, the reception processing unit 14 corrects the intensity of the reflected wave, which attenuates according to the elapsed time, and outputs the intensity-corrected echo data to the control unit 11.

[0022] The control unit 11 is composed of an arithmetic processing circuit such as a CPU, and an integrated circuit such as an FPGA. The storage unit 12 is composed of a ROM, a RAM, a hard disk, etc. Various programs are stored in the storage unit 12. The control unit 11 controls each unit according to the programs stored in the storage unit 12. The control unit 11 also executes the functions of an image generation unit 11a, an area extraction unit 11b, and a display processing unit 11c according to the programs stored in the storage unit 12. The control unit 11 in FIG. 2 shows functional blocks that the control unit 11 executes based on the programs. The processing contents of each functional block will be described later with reference to FIGS. 5 to 9(c).

[0023] The input unit 15 is configured with input means such as a mouse and a keyboard, and receives input from a user. The input unit 15 may be a touch panel integrated with the display unit 16. The display unit 16 is configured with a display device such as a CRT monitor or a liquid crystal panel, and displays an image generated by the control unit 11. As will be described later, the display unit 16 displays an echo image generated based on echo data.

[0024] The control unit 11 acquires echo data that associates elapsed time (distance) with the strength of the received signal for each transmission timing of the transmission beam 3. The control unit 11 generates an echo image based on one frame of continuously acquired echo data and displays it on the display unit 16. The echo image is sometimes called an echo diagram. The echo image is generated using two axes: water depth and time. In the echo image, each pixel is colored or shaded in a gradation that corresponds to the signal strength of the reflected wave.

[0025] In the target detection device 10 configured as described above, the intensity range for setting the display gradation (hereinafter referred to as the "gradation setting range") is often set relatively high. This makes the intensity distribution of the reflected wave easier to see, making it easier to identify targets in the water. However, with this method, if the intensity of the reflected wave from a target is lower than the gradation setting range, the intensity distribution based on this target will not be displayed in the echo image. On the other hand, if the predetermined level is lowered, noise other than the target will be displayed in the image, making it difficult to see the distribution of targets in the water.

[0026] With reference to FIGS. 3(a) to 4(b), an echo image when the gradation setting range is set high and an echo image when the gradation setting range is set low will be described.

[0027] 3(a) and 3(b) are diagrams each showing a schematic diagram of the setting state of the gradation setting range.

[0028] 3(a) and (b) show examples of echo data acquired at a predetermined transmission timing of the transmission beam 3. The vertical axis indicates the depth direction, and the horizontal axis indicates the intensity of the echo data. As shown in FIGS. 3(a) and (b), when targets T1 and T2 exist in the depth direction, the intensity of the echo data varies depending on the sizes of the targets T1 and T2. In this case, since the target T1 is larger than the target T2, the intensity of the echo data based on the target T1 is larger than the intensity of the echo data based on the target T2.

[0029] As shown in FIG. 3(a), when the gradation setting range is set high (when the sensitivity is set low), the lower limit intensity SV11 is higher than the highest intensity of the target T2, and the upper limit intensity SV12 is lower than the highest intensity of the target T1. In this case, echo data with intensities equal to or greater than SV11 and equal to or less than SV12 are displayed in gradations. That is, intensity SV11 is set to the lowest gradation, and intensity SV12 is set to the highest gradation. Echo data with intensities higher than the gradation setting range are all set to the highest gradation, and echo data with intensities lower than the gradation setting range are all set to the lowest gradation.

[0030] Therefore, in this case, when an echo image is generated using echo data acquired at each of the transmission timings for one frame that are consecutive in time, the generated echo image displays the area of ​​target T1 at a predetermined gradation, but displays all of the areas of target T2 at the lowest gradation, making it impossible to identify the area of ​​target T2 on the echo image.

[0031] On the other hand, as shown in Figure 3(b), when the gradation setting range is set low (when the sensitivity is set high), the lower limit intensity SV21 is lower than the highest intensity of target T2, and the upper limit intensity SV22 is lower than the highest intensity of target T1.

[0032] Therefore, in this case, when an echo image is generated from echo data acquired at each of the transmission timings for one frame that are consecutive in time, both the target regions T1 and T2 are displayed in a predetermined gradation in the generated echo image. However, in this case, noise other than the target is displayed in the echo image, making it difficult to see the distribution of the target in the water.

[0033] FIG. 4(a) is a diagram showing a specific example of an echo image 110 when the gradation setting range is set relatively high as in FIG. 3(a), and FIG. 4(b) is a diagram showing a specific example of an echo image 111 when the gradation setting range is set relatively low as in FIG. 3(b).

[0034] In Figures 4(a) and (b), the vertical axis represents depth and the horizontal axis represents time. Along the vertical axis, depth increases as one moves downward. Along the horizontal axis, the rightmost side corresponds to the most recent echo data, and the leftmost side corresponds to the oldest echo data. Both the echo image 110 in Figure 4(a) and the echo image 111 in Figure 4(b) are generated based on the same frame of echo data.

[0035] As shown in FIG. 4(a), the echo image 110 is generated with a high gradation setting range, allowing targets near region R1 to be identified with little noise. However, targets that would normally be present near region R2 cannot be identified in the echo image 110. On the other hand, as shown in FIG. 4(b), the echo image 111 is generated with a low gradation setting range, allowing targets near region R1 as well as regions R2 to be identified. However, in the case of the echo image 111, the range of high gradations is significantly expanded, and the distribution of noise other than targets becomes significantly larger, making it difficult to discern the distribution of objects in the water.

[0036] To solve this problem, in this embodiment, an echo image 110 with a high gradation setting range as shown in Fig. 4(a) is generated based on the echo data so that targets present in the water can be more accurately identified. Then, in relation to the gradation setting range, the echo image 110 is displayed on the display unit 16 with a distribution area of ​​potential targets that is not displayed on the echo image 110 superimposed on the echo image 110. This processing will be described below.

[0037] FIG. 5 is a flowchart showing the processing of the target detection device 10.

[0038] When the control unit 11 receives echo data at a predetermined timing from the reception processing unit 14 (S11: YES), the image generation unit 11a uses the echo data to generate an echo image 110 for display, which indicates the intensity distribution of the reflected wave (S12). The echo data used in this case is one frame of echo data including the echo data received in step S11 and echo data received within a predetermined period going back from the present. The echo image 110 is generated by displaying the echo data in gradations within a high gradation setting range, as described with reference to FIG. 3(a). As a result, an echo image 110 like that shown in FIG. 4(a) is generated.

[0039] Next, the control unit 11 performs extraction processing of a latent area using the function of the area extraction unit 11b (S13). The latent area is a distribution area of ​​targets not displayed in the echo image 110, and is extracted based on the extraction image 120 as shown in FIG. 6(a).

[0040] FIG. 6(a) is a diagram schematically illustrating extraction image 120. As shown in FIG. 6(a), extraction image 120 includes multiple echo data E1 arranged horizontally (in the time direction). Extraction image 120 is not an image based on a gradation setting range like echo image 110, but is an image based on echo data when a gradation setting range is not set. The pixel values ​​of each pixel arranged vertically and horizontally in extraction image 120 are values ​​that express the intensity of the reflected wave in gradation. In step S13, for example, as shown in FIG. 6(a), latent areas R11 to R15 are extracted from extraction image 120. The latent area extraction process will be described later with reference to FIGS. 7 to 9(c).

[0041] Next, the control unit 11 uses the function of the display processing unit 11c to superimpose the contours of the latent areas on the echo image 110 and display them on the display unit 16 (S14). As a result, for example, as shown in FIG. 6(b), the echo image 110 with the contours of the latent areas R11 to R15 superimposed on it is displayed on the display unit 16.

[0042] FIG. 7 is a flowchart showing the latent area extraction process.

[0043] The control unit 11 generates an extraction image 120 for extracting a latent area from the echo data (S21). The echo data used in this case is one frame of echo data including the echo data received in step S11 of Fig. 5 and echo data received within a predetermined period going back from the present, as in the generation of the echo image 110. Furthermore, in step S21, if a high-intensity area is found to be spreading over a wide area on the extraction image 120, the control unit 11 determines that this area corresponds to the seabed.

[0044] Note that "generation of extraction image 120" does not mean that extraction image 120 is generated for the purpose of display, but rather that extraction image 120 is generated for the purpose of data processing. In other words, in this embodiment, extraction image 120 is generated for the purpose of latent area extraction processing, and does not need to be generated as an image file, and does not need to be displayed on display unit 16.

[0045] Next, the control unit 11 performs a labeling process (S22) to extract regions in the extraction image 120 where the intensity is equal to or greater than a predetermined level and where clumps are formed. In other words, the control unit 11 extracts regions in the extraction image 120 of pixel groups where the intensity of the reflected wave is equal to or greater than a threshold and where there is continuity in the intensity of the reflected wave between adjacent pixels (S22).

[0046] 8(a) to 8(c) are schematic diagrams for explaining the process of extracting regions forming clusters in step S22. Part of extraction image 120 is shown in Figs. 8(a) to 8(c).

[0047] Extraction image 120 is generated by assigning the intensity of each pixel position in the echo data to that pixel. In step S22, control unit 11 shifts the pixel to be determined in extraction image 120 and, for each pixel to be determined, determines whether the intensity (pixel value) of the pixel to be determined is equal to or greater than a threshold (first determination), and determines whether there is continuity in intensity between the pixel to be determined and its four neighboring pixels (second determination). If both the first determination and the second determination are satisfied, control unit 11 includes the pixel to be determined and the pixel determined to have continuity in a group of pixels having continuity.

[0048] 8(a), the second pixel P1 from the left in the middle row is the pixel to be determined. In the following, as an example, in the first determination, it is determined whether the intensity of the pixel to be determined is equal to or greater than a threshold value Vs (=10), and in the second determination, it is determined whether the intensity of the adjacent pixel is equal to or greater than a ratio Vr (=50%) of the intensity of the pixel to be determined and whether the intensity of the adjacent pixel is equal to or greater than the threshold value Vs (=10).

[0049] The threshold value Vs used in the first determination is set to be smaller than the maximum intensity of pixels corresponding to targets that cannot be confirmed in the echo image 110. Specifically, the threshold value Vs used in the first determination is set to a value that is larger than the maximum intensity level of noise in the echo data by a predetermined value Va. If noise has been removed from the echo data in advance, the threshold value Vs used in the first determination is set to the predetermined value Va.

[0050] As shown in Fig. 8(a), the intensity of pixel P1 is equal to or greater than threshold value Vs (=10). Of the pixels above, below, left, and right of pixel P1, the only pixel whose intensity ratio to pixel P1 is equal to or greater than Vr (=50%) is pixel P2 to the right of pixel P1, and the intensity of pixel P2 is equal to or greater than threshold value Vs (=10). Therefore, as shown in Fig. 8(b), control unit 11 includes pixels P1 and P2 in pixel group G.

[0051] Next, the control unit 11 moves the pixel to be determined from pixel P1 to pixel P2 and performs a similar determination. As shown in FIG. 8(b), the intensity of pixel P2 is equal to or greater than threshold value Vs (=10). Furthermore, among the pixels above, below, left, and right of pixel P2, the pixels that have an intensity ratio Vr (=50%) of pixel P2 or greater are pixel P1 to the left of pixel P2, pixel P3 below pixel P2, and pixel P4 to the right of pixel P2, and the intensities of pixels P1, P3, and P4 are all equal to or greater than threshold value Vs (=10). Therefore, as shown in FIG. 8(c), the control unit 11 includes pixels P1, P2, P3, and P4 in pixel group G.

[0052] The control unit 11 performs the above-described determination for all pixels in the extraction image 120 while shifting the pixel to be determined. Note that if the pixel to be determined corresponds to a seabed area, the control unit 11 does not perform the above-described determination for the pixel to be determined, but shifts the pixel to be determined. This allows the control unit 11 to quickly perform the area extraction process. In this way, as illustrated in FIG. 9(a), areas R11 to R20 of pixel groups where the reflected wave intensity is equal to or greater than a threshold and where there is continuity in the reflected wave intensity between adjacent pixels are extracted in the extraction image 120.

[0053] The method for setting the pixel group area is not limited to the above. For example, in the second determination, control unit 11 may determine that there is continuity if the value obtained by subtracting the intensity of the pixel being determined from the intensity of the adjacent pixel is equal to or greater than a predetermined value. Furthermore, the threshold value Vs for the first determination and the ratio Vr for the second determination are not limited to the values ​​described above.

[0054] Returning to FIG. 7, the control unit 11 sequentially performs the processes of steps S23 to S26 on the regions extracted in step S22 (for example, regions R11 to R20 in FIG. 9(a)).

[0055] The control unit 11 determines the size of one of the regions extracted in step S22 (S23), and determines whether the size of the one region is equal to or greater than a predetermined size (S24). Specifically, the control unit 11 determines whether the one region continues for a predetermined value or more in the depth direction (vertical axis direction in FIG. 9(a)), whether the one region continues for a predetermined value or more in the time direction (horizontal axis direction in FIG. 9(a)), and whether the area of ​​the one region is equal to or greater than a predetermined value. If these three conditions are met, the control unit 11 determines that the size of the one region is equal to or greater than the predetermined size. For example, in the example shown in FIG. 9(a), the size of regions R11 to R15 and R17 to R20 is determined to be equal to or greater than the predetermined size, and the size of region R16 is determined to be less than the predetermined size.

[0056] The determination of the width in step S22 is not limited to the above determination, and may be based only on the width in the depth direction and the width in the time direction, or may be based only on the area.

[0057] If the size of the one region is equal to or larger than a predetermined size (S24: YES), the control unit 11 determines whether or not a target corresponding to the one region is present in the echo image 110 (S25). Specifically, the control unit 11 determines whether or not a cluster of reflected wave intensity corresponding to the target exists in the region on the echo image 110 corresponding to the one region. The determination of the presence or absence of a cluster is made, for example, by determining that a cluster of targets exists in the region on the echo image 110 corresponding to the one region when the proportion of pixels with a predetermined gradation or less is less than a predetermined value, and by determining that a cluster of targets does not exist in the region on the echo image 110 when the proportion of pixels with a predetermined gradation or less is equal to or larger than a predetermined value.

[0058] In the example shown in Fig. 9(b), it is determined that a cluster of reflected wave intensity corresponding to a target (the hatched portion in Fig. 9(b)) exists in the region on the echo image 110 corresponding to the regions R17 to R20. On the other hand, it is determined that a cluster of reflected wave intensity corresponding to a target does not exist in the region on the echo image 110 corresponding to the regions R11 to R16.

[0059] If there is no target corresponding to the one region in the echo image 110 (S25: NO), the control unit 11 extracts the one region as a latent region (S26). If the size of the one region is less than a predetermined size (S24: NO) or if there is a target corresponding to the one region in the echo image 110 (S25: YES), the processing of step S26 is skipped.

[0060] The control unit 11 determines whether or not the processing of steps S23 to S26 has been performed for all regions extracted in step S22 (S27). If processing has not been completed for all regions (S27: NO), the control unit 11 changes the region to be processed, returns the processing to step S23, and performs the processing of steps S23 to S26 for the regions that have not yet been processed. On the other hand, if processing has been completed for all regions (S27: YES), the latent region extraction process ends. As a result, for example, regions R11 to R15 are extracted as latent regions, as shown in FIG. 9(c).

[0061] <Effects of the embodiment> According to the embodiment, the following effects are achieved.

[0062] The latent areas of the target that are not displayed in the first image (echo image 110) (for example, latent areas R11 to R15 in FIG. 6(b)) are displayed superimposed on the first image. This allows the user to identify the target from the intensity distribution of the reflected wave displayed in the first image, and also allows the user to identify targets with low reflected wave intensity from the latent areas superimposed on the first image. This allows the user to more accurately identify targets present in the water from the displayed image.

[0063] Furthermore, the echo image 110 is a low-noise image because it is generated from echo data in a high intensity range (for example, the gradation setting range in FIG. 3(a)). On the other hand, the latent area may contain noise because it is extracted from the extraction image 120 generated from echo data without setting an intensity range. However, as described above, the echo image 110 based on the low-noise image only partially overlaps the latent area of ​​a target that is not displayed in the echo image 110. Therefore, the user can simultaneously identify targets in the water with low noise while simultaneously identifying targets with low intensity.

[0064] The control unit 11, using the function of the region extraction unit 11b, extracts a region of a pixel group in the second image (extraction image 120) where the reflected wave intensity is equal to or greater than a threshold and where there is continuity in the reflected wave intensity between adjacent pixels (S22 in FIG. 7). The control unit 11 extracts the extracted region (e.g., regions R11 to R20 in FIG. 9(a)) as a latent region (e.g., regions R11 to R15 in FIG. 9(c)) based on the absence of a cluster of reflected wave intensity corresponding to a target (S25: NO in FIG. 7) in the region on the first image (echo image 110) corresponding to the extracted region (e.g., regions R11 to R15 in FIG. 9(c)) (S26 in FIG. 7). This configuration allows for smooth and appropriate setting of latent regions.

[0065] The control unit 11, using the function of the region extraction unit 11b, extracts a region (for example, regions R11 to R20 in FIG. 9(a)) extracted from the second image (extraction image 120) as a latent region (for example, regions R11 to R15 in FIG. 9(c)) (S26 in FIG. 7) based on the fact that the size of the region (for example, regions R11 to R20 in FIG. 9(a)) is equal to or larger than a predetermined threshold (S24: YES in FIG. 7). With this configuration, if the size of the region extracted from the second image is small, the region is excluded from the latent region to be displayed, as it is determined to be a region caused by factors other than the target to be detected, such as noise or minute floating objects. This makes it possible to more accurately display the region of a latent target that is not displayed in the image.

[0066] The control unit 11, using the function of the display processing unit 11c, causes the display unit 16 to display the outline of the latent area (for example, areas R11 to R15 in FIG. 6(b)) superimposed on the first image (echo image 110) (S14 in FIG. 5). With this configuration, the user can grasp the area of ​​the target that is not displayed in the display format of the first image by the outline superimposed on the first image.

[0067] <Change example 1> In the above embodiment, only the outline of the latent area is superimposed on the echo image 110, but in addition to the outline of the latent area, the intensity distribution of the reflected waves within the specified latent area may also be superimposed.

[0068] FIG. 10(a) is a flowchart showing the processing for accepting the designation of a latent area and displaying the intensity distribution according to the first modification.

[0069] The control unit 11, using the function of the display processing unit 11c, begins accepting the designation of a latent area and determines whether the designation of a latent area has been accepted (S101). The user selects a latent area by performing an operation such as clicking or tapping on one of the latent areas on the echo image 110 displayed on the display unit 16 via the input unit 15. When the control unit 11 accepts the designation of a latent area (S101: YES), the control unit 11 uses the function of the display processing unit 11c to display the latent area accepted in step S101 in a predetermined gradation display based on the echo data (S102). The gradation display in this case is, for example, a gradation display based on an intensity range lower than the intensity range used to generate the echo image 110 (for example, the gradation setting range of FIG. 3(b)).

[0070] FIG. 10(b) is a diagram showing an echo image 110 in which the designated latent area is displayed in a predetermined gradation.

[0071] 10(b) shows a state in which latent area R11 is designated among latent areas R11 to R15. In this case, the intensity distribution within latent area R11 is displayed in a predetermined gradation.

[0072] According to Modification 1, control unit 11 receives the designation of a latent area using the function of display processing unit 11c, and causes the intensity distribution of reflected waves within the received latent area to be displayed in a predetermined gradation on display unit 16. With this configuration, the intensity distribution of reflected waves within any latent area is displayed in a predetermined gradation, allowing the user to grasp the type of target within any latent area, etc.

[0073] <Change example 2> In the above modification example 1, the designated latent area is displayed in a predetermined gradation, but the scale of the gradation display may be specified by the user.

[0074] Fig. 11 is a flowchart showing the process of accepting the latent area and the scale of the gradation display and displaying the intensity distribution according to Modification Example 2. In Fig. 11, steps S111 and S112 are added instead of step S102, as compared to Fig. 10(a).

[0075] When the control unit 11 receives the designation of the latent area (S101: YES), it starts receiving the scale of the gradation display using the function of the display processing unit 11c, and determines whether or not the scale of the gradation display has been received (S111). The user inputs the scale of the gradation display by moving the slider 130 (see FIG. 12(a)) displayed on the display unit 16 via the input unit 15. When the control unit 11 receives the scale of the gradation display (S111: YES), it uses the function of the display processing unit 11c to display the latent area received in step S101 using the scale of the gradation display received in step S111 based on the echo data (S112).

[0076] Fig. 12(a) is a diagram showing the echo image 110 in a state where the slider 130 is displayed. Fig. 12(b) is a diagram showing the echo image 110 in a state where the designated latent area is displayed on a designated gradation display scale.

[0077] FIG. 12(a) shows a state in which latent area R11 has been designated among latent areas R11 to R15. In this case, a slider 130 is displayed for the designated latent area R11. The user sets the scale of the gradation display within the designated latent area R11 by moving the slider 130. For example, when the slider 130 is moved to the left, the gradation setting range becomes lower while maintaining a predetermined width, and when the slider 130 is moved to the right, the gradation setting range becomes higher while maintaining a predetermined width. In this case, the settable gradation setting range is provided in several stages, and FIG. 12(a) shows that the gradation setting range has been set to the eighth stage from the bottom.

[0078] 12(b), the designated latent area R11 is displayed on the designated gradation scale. That is, within the designated latent area R11, the echo data is displayed in gradation within the gradation setting range designated by the slider 130.

[0079] According to the second modification, the control unit 11 receives a setting for a gradation display scale for the intensity of the reflected wave within the latent area using the function of the display processing unit 11c, and displays the intensity distribution of the reflected wave within the latent area in gradations using the received scale. With this configuration, the intensity of the reflected wave within the latent area can be displayed in gradations using any scale. This allows the user to more easily grasp the type of target in the latent area.

[0080] <Other change examples> The present invention is not limited to the above-described embodiment, and various modifications to the embodiment of the present invention are possible in addition to the above-described configuration.

[0081] For example, in the above embodiment, the image generating unit 11a, the area extracting unit 11b, and the display processing unit 11c are provided as functions of the control unit 11, but they may be provided as hardware in the target detection device 10. Furthermore, the image generating unit 11a, the area extracting unit 11b, and the display processing unit 11c do not necessarily have to be provided in one control unit 11, but may be provided in two or more control units.

[0082] 6(b), the contours of the latent regions R11 to R15 are superimposed on the echo image 110 with thin black solid lines, but they may be superimposed with thick solid lines, contours of other colors, dashed or dotted lines, or contours with a predetermined transparency. The manner in which these contours are displayed may be selected arbitrarily by the user.

[0083] Furthermore, in the above embodiment and modified examples 1 and 2, the latent region is always superimposed on the echo image 110, but the latent region may be superimposed in response to a predetermined operation from the user.

[0084] Furthermore, in the above modification example 1, the latent area specified by the user was displayed in a predetermined gradation, but as shown in FIG. 13(a), all latent areas may be displayed in a predetermined gradation without the user specifying a latent area. In this case, when an operation such as a click is performed on any of the latent areas R11-R15, as in the above embodiment, only the outlines of all latent areas R11-R15 are displayed, as shown in FIG. 13(b). Furthermore, when an operation such as a click is performed on any of the latent areas R11-R15 in the state shown in FIG. 13(b), the state switches to one in which all latent areas R11-R15 are displayed in a predetermined gradation, as shown in FIG. 13(a).

[0085] 13(a) and 13(b), the control unit 11 uses the function of the display processing unit 11c to display the intensity distribution of the reflected wave within the latent area in a predetermined gradation on the display unit 16. With this configuration, as in the first and second modifications, the intensity distribution of the reflected wave within the latent area is displayed in gradation, allowing the user to grasp the type of target in the latent area, etc.

[0086] Furthermore, in the above modification example 1 and the modification examples shown in Figures 13(a) and (b), the intensity distribution within the latent area is displayed using a predetermined gradation display, but this is not limited to this, and the gradation display within the latent area may be automatically and appropriately set.

[0087] In this case, for example, the control unit 11 may automatically set the scale of the gradation display within the latent area so that the average value of the gradation of the area corresponding to the target in the echo image 110 is equal to the average value of the gradation within the latent area superimposed on the echo image 110. The control unit 11 may also set a gradation setting range with a predetermined width for the echo data within the latent area, and gradate the intensity distribution within the latent area by adjusting the lower limit of the gradation setting range to the minimum intensity within the latent area. The control unit 11 may also set a gradation setting range for the echo data within the latent area, and gradate the intensity distribution within the latent area by adjusting the lower limit of the gradation setting range to the minimum intensity within the latent area and the upper limit of the gradation setting range to the maximum intensity within the latent area.

[0088] 12(a) and 12(b), the slider 130 is used to shift the gradation setting range of a predetermined width in the higher and lower directions. However, this is not limiting, and a slider for shifting the lower limit of the gradation setting range in the higher and lower directions, and a slider for shifting the upper limit of the gradation setting range in the higher and lower directions may be provided.

[0089] 1, the transmission beam 3 is transmitted in the vertically downward direction, but may be transmitted in a direction at an angle relative to the vertically downward direction. In this case, the up-down direction in the echo image 110 and the extraction image 120 corresponds to the transmission direction of the transmission beam 3, not the depth direction.

[0090] Furthermore, in the above embodiment, the target detection device 10 is a fish finder that detects directly below the ship 1, but it may also be a sonar that detects the periphery of the ship 1. In this case, the reception processing unit 14 performs beamforming processing on the reception signals output by the receiver of the transducer 2 to generate reception signals for each direction and generate echo data for each direction. Then, an echo image and an extraction image are generated based on the echo data for each direction, and a latent area extracted from the corresponding extraction image is superimposed on the echo image for each direction.

[0091] In addition, the embodiments of the present invention can be modified in various ways as appropriate within the scope of the claims. [Explanation of symbols]

[0092] 2 Transmitter / Receiver 10 Target detection device 11a Image generation section 11b Region extraction part 11c Display processing section 14 Receiving processing section 16 Display 110 Echo image (first image) 120 Extraction image (second image) R11~R20 area R11~R15 Potential area

Claims

1. a transducer that transmits ultrasonic waves into water and receives the reflected waves; a reception processing unit that generates echo data according to the intensity of the reflected wave from the signal output from the transducer; an image generating unit that generates a first image for display showing an intensity distribution of the reflected wave from the echo data; an area extraction unit that extracts a potential area of ​​a target that is not displayed in the first image from the echo data; a display processing unit that displays the latent area on the first image on a display unit, The region extraction unit generating a second image from the echo data for extracting the latent region; extracting, from the second image, a region of a pixel group where the intensity of the reflected wave is equal to or greater than a threshold and where there is continuity in the intensity of the reflected wave between adjacent pixels; extracting the extracted region as the latent region based on the absence of a cluster of the intensity of the reflected wave corresponding to a target in the region on the first image corresponding to the extracted region; A target detection device characterized by:

2. The target detection device according to claim 1, The region extraction unit further extracts the extracted region from the second image as the latent region based on the size of the extracted region being equal to or larger than a predetermined threshold. A target detection device characterized by:

3. 3. The target detection device according to claim 1, the display processing unit causes the display unit to display the outline of the latent area superimposed on the first image; A target detection device characterized by:

4. The target detection device according to any one of claims 1 to 3, the display processing unit displays the intensity distribution of the reflected wave within the latent area on the display unit in a predetermined gradation display; A target detection device characterized by:

5. The target detection device according to claim 4, the display processing unit receives the designation of the latent area and displays the intensity distribution of the reflected wave within the received latent area on the display unit in a predetermined gradation display; A target detection device characterized by:

6. 6. The target detection device according to claim 4, the display processing unit receives a setting of a scale for the gradation display relative to the intensity of the reflected wave within the latent area, and performs a gradation display of the intensity distribution of the reflected wave within the latent area using the received scale. A target detection device characterized by:

7. The reflected waves of the ultrasonic waves sent into the water are received to generate echo data. generating a display image showing an intensity distribution of the reflected wave from the echo data; extracting a potential area of ​​a target not displayed in the image from the echo data; Displaying the latent area superimposed on the image; In the extraction of the latent region, generating a second image from the echo data for extracting the latent region; extracting, from the second image, a region of a pixel group where the intensity of the reflected wave is equal to or greater than a threshold and where there is continuity in the intensity of the reflected wave between adjacent pixels; extracting the extracted region as the latent region based on the absence of a cluster of the intensity of the reflected wave corresponding to a target in the region on the first image corresponding to the extracted region; A target detection method characterized by:

Images