Target detection device and detection image generation method

Abstract

To provide a target detection device and a detection image generation method that can remove a virtual image with simple constitution through simple processing.SOLUTION: A radar system acquires sweep image data x to x-4 from a first radar device, acquires sweep image data y to y-4 from a second radar device, and generates a detection image D of a target T by removing an image F, which is present in the sweep image data y-3 to y-1 acquired from the second radar device, but not present in the sweep image data x-3 to x-1 acquired from the first radar device, from the sweep image data y-3 to y-1 of the second radar device in such a case.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a target detection device and a detection image generating method for use in the target detection device. [Background technology]

[0002] Radar devices mounted on ships and other vessels transmit waves from an antenna that rotates in an azimuth direction, repeatedly perform a sweep process in which the transmitted waves reflected by targets are received, and the azimuth sweep image data generated based on the reflected waves is arranged based on the acquired azimuth, thereby generating a detection image in PPI (Plan Position Indicator) format (see, for example, Patent Document 1).

[0003] Such a radar device has a problem that a false image (an image that appears on the radar even though no target exists) is generated. In response to this problem, a signal processing device that can accurately determine whether an echo image is a desired one is known (see, for example, Patent Document 2). This device includes a backwash echo determination unit that receives position information of a first echo image and a second echo image included in an echo obtained from a reflected wave of a transmission wave transmitted from a predetermined transmission position and determines whether the first echo image is an echo image generated due to a backwash of a target having a different attribute from the second echo image. The backwash echo determination unit also includes a traveling direction calculation unit that calculates the traveling direction of the first echo image based on a change in the position of the second echo image, and an angle condition determination unit that performs a determination based on whether an angle formed between a straight line along the traveling direction of the second echo image and a straight line connecting the position of the second echo image and the position of the first echo image is included within a predetermined angle range. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-326493 [Patent Document 2] Patent No. 6732900 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the device described in Patent Document 2 requires positional information of the first echo image and the second echo image contained in the echo, and further requires calculating the traveling direction of the first echo image based on a change in the position of the second echo image, and determining whether or not the first echo image is an echo image generated due to the wake of a target having attributes different from those of the second echo image based on whether or not the angle between a straight line along the traveling direction of the second echo image and a straight line connecting the positions of the second echo image and the first echo image is within a predetermined angle range, resulting in complex processing and configuration.

[0006] Therefore, an object of the present invention is to provide a target detection device and a detection image generating method that are capable of removing virtual images with a simple configuration and processing. [Means for solving the problem]

[0007] In order to solve the above problem, the invention described in claim 1 includes a plurality of transmitting / receiving means for repeatedly performing a sweep process of transmitting a transmission wave and receiving a reflected wave of the transmission wave reflected by a target while rotating in an azimuth direction, and generating sweep image data in the azimuth direction from the reflected wave, and a detection image generating means for arranging the sweep image data based on the acquisition azimuth to generate a detection image, wherein the detection image generating means generates a detection image by arranging the sweep image data based on the acquisition azimuth, and ... This is a target detection device characterized in that, when there is an image that does not exist in the sweep image data acquired from the receiving means, the detected image is generated by excluding the image from the sweep image data of one of the transmitting / receiving means.

[0008] The invention described in claim 2 is a detection image generation method for a target detection device comprising a plurality of transmission / reception means that transmit a transmission wave, repeatedly perform a sweep process of receiving the reflected wave of the transmission wave reflected by a target while rotating in an azimuth direction, and generate sweep image data in the azimuth direction from the reflected wave, and a detection image generation means that arranges the sweep image data based on the acquisition azimuth to generate a detection image, characterized in that when there is an image that is present in the sweep image data acquired from one of the plurality of transmission / reception means but not present in the sweep image data acquired from another of the plurality of transmission / reception means, the detection image is generated by excluding the image from the sweep image data of the one transmission / reception means. Effect of the Invention

[0009] According to the inventions described in claims 1 and 2, when an image exists in the sweep image data of a certain transmitting / receiving means but does not exist in the sweep image data of another transmitting / receiving means, such an image is regarded as a virtual image, and a detection image is generated by excluding this image. In other words, it is possible to generate an appropriate detection image without a virtual image. Moreover, since a detection image is generated by simply excluding an image that exists in the sweep image data of a certain transmitting / receiving means but does not exist in the sweep image data of another transmitting / receiving means among a plurality of transmitting / receiving means, the configuration and processing are simplified. [Brief description of the drawings]

[0010] [Figure 1] 1 is a block diagram showing a schematic configuration of a radar system according to an embodiment of the present invention; [Diagram 2] 4 is a flowchart showing a procedure for generating a detection image by the radar system shown in FIG. 1. [Diagram 3] 3 is an explanatory diagram showing a procedure for generating the detection image shown in FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the present invention will be described based on the illustrated embodiment.

[0012] 1 is a block diagram showing a schematic configuration of a radar system 10 according to an embodiment of the present invention. The radar system 10 is mounted on, for example, a ship, and includes a first radar device 1 that detects targets and displays a detection image in PPI format, and a second radar device 2. Here, the two radar devices 1 and 2 are disposed, for example, on the bow side of the ship so as to detect the same direction and area.

[0013] The first radar device 1 includes a radar antenna 11, a transmission / reception unit 12, a sweep image data generation unit 13, a detection image generation unit (detection image generation means) 14, a signal processing unit 15, a display unit 16, and an operation unit 17.

[0014] The radar antenna 11 transmits pulsed transmission waves while rotating in an azimuth direction in a horizontal plane, and repeats a sweep process at a predetermined period in which it receives reflected waves (echoes) of the transmission waves reflected by targets. The transmission / reception unit 12 generates transmission waves to be transmitted from the radar antenna 11 and inputs them to the radar antenna 11. The transmission / reception unit 12 also detects and amplifies the echoes received by the radar antenna 11, and generates analog echo signals.

[0015] The sweep process is performed at a predetermined interval while the radar antenna 11 is rotating. There are azimuths for which sweep processing is not performed. In addition, since the radar antenna 11 is installed in a position with good visibility of the ship, it does not rotate at a constant speed due to the influence of wind and waves. Therefore, the azimuth in which the transmission wave is sent from the radar antenna 11 is not constant, and the sweep processing and the azimuth are not synchronized.

[0016] The sweep image data generating unit 13 generates digital sweep image data by A / D converting the echo signal output from the transmitting / receiving unit 12. The radar antenna 11, the transmitting / receiving unit 12, and the sweep image data generating unit 13 constitute the transmitting / receiving means of the present invention. The detection image generating unit 14 arranges the sweep image data based on the acquisition direction to generate a detection image.

[0017] The signal processing unit 15 performs signal processing on the detection image generated by the detection image generation unit 14, including removing unnecessary echoes (clutter) caused by sea surface reflection, land reflection, rain and snow reflection, etc. The display unit 16 is a monitor or the like on which the detection image that has been subjected to signal processing by the signal processing unit 15 is displayed. The operation unit 17 is an input device used to operate the first radar device 1.

[0018] The second radar device 2 includes a radar antenna 21, a transmitting / receiving unit 22, a sweep image data generating unit 23, a detection image generating unit (detection image generating means) 24, a signal processing unit 25, a display unit 26, and an operation unit 27. Note that each component of the second radar device 2 is similar to that of the first radar device 1, and therefore detailed description thereof will be omitted.

[0019] The first radar device 1 and the second radar device 2 each independently detect a target and display a detected image, and also have a function to remove a false image (an image that appears on the radar when no target exists). Furthermore, in this embodiment, they cooperate to detect a target and display a detected image in order to fill in a direction (missing direction) for which sweep image data could not be acquired. The first radar device 1 and the second radar device 2 are connected to each other so that they can communicate with each other in order to cooperate to detect a target, display a detected image, and remove a false image.

[0020] Fig. 2 is a flow chart showing a procedure in which the first radar device 1 detects targets and displays detected images, and the second radar device 2 performs interpolation of missing directions of the first radar device 1 and removes virtual images. Fig. 3 shows a procedure in which the first radar device 1 generates a detected image in cooperation with the second radar device 2 and removes virtual images.

[0021] First, the radar antenna 11 and the transmission / reception unit 12 of the first radar device 1 transmit pulsed transmission waves while rotating in an azimuth direction in a horizontal plane, and repeat a sweep process in which echoes of the transmission waves reflected by a target are received at a predetermined period (step S1).

[0022] Next, the sweep image data generating unit 13 of the first radar device 1 performs A / D conversion on the echo signal output from the transmission / reception unit 12 to generate digital sweep image data (step S2). Similarly, the second radar device 2 also performs sweep processing (step S1) and generates sweep image data (step S2).

[0023] Here, Fig. 3(a) shows a state where sweep processing is performed at a predetermined period while rotating the radar antenna 11 of the first radar device 1 in a clockwise direction. In this figure, a rectangle shown by a dashed line indicates the transmission wave and the reception wave transmitted and received by the radar antenna 11, i.e., one sweep processing. Furthermore, the symbol x indicates the xth sweep processing, and the symbols x-1 to x-4 indicate the sweep processing performed 1 to 4 times before the sweep processing of the symbol x. The symbol T indicates a target object.

[0024] Similarly, Fig. 3(b) shows a state in which sweep processing is performed at a predetermined period while rotating the radar antenna 21 of the second radar device 2 clockwise. In this figure, a rectangle indicated by a dashed line indicates the transmission wave and the reception wave transmitted and received by the radar antenna 21, i.e., one sweep processing. Furthermore, the symbol y indicates the yth sweep processing, and the symbols y-1 to y-4 indicate the sweep processing performed 1 to 4 times before the sweep processing of the symbol y. The symbol T indicates a target object.

[0025] Next, the detection image generating unit 14 of the first radar device 1 generates a detection image by arranging the sweep image data based on the acquisition direction. Here, in the first radar device 1, as shown in Fig. 3(c), the target T is detected by sweep processing x-3 to x-1, so the detection image generated by the sweep image data (using the same reference numbers as the sweep processing) x-3 to x-1 of the sweep processing x-3 to x-1 has gaps in the missing direction, and the original shape of the target T cannot be accurately determined.

[0026] Similarly, in the second radar device 2, as shown in Fig. 3(d), the target T is detected by sweep processing y-3 to y-1, so the detection image generated by the sweep image data (the same reference numbers as in the sweep processing) y-3 to y-1 of the sweep processing y-3 to y-1 has gaps in the missing azimuth portion, and the original shape of the target T cannot be accurately determined. For this reason, when generating the detection image, the detection image generating unit 14 determines and confirms whether or not the sweep image data of the missing azimuth of the first radar device 1 has been acquired by the second radar device 2 (step S3).

[0027] That is, the first radar device 1 and the second radar device 2 have different orientations in which the radar antennas 11 and 21 perform the sweep process because the rotations of the radar antennas 11 and 21 are not synchronized. Also, the rotation speeds of the radar antennas 11 and 21 change due to the influence of wind and waves, so the orientations in which the radar antennas 11 and 21 perform the sweep process temporarily synchronize and then deviate again. For this reason, the detection image generating unit 14 of the first radar device 1 determines and confirms whether the second radar device 2 is performing the sweep process in the missing orientation when generating a detection image.

[0028] As a result, if the second radar device 2 has acquired sweep image data of the missing direction from the first radar device 1 ("YES" in step S3), the detection image generation unit 14 acquires the sweep image data of the missing direction from the second radar device 2 and generates a detection image (step S4).

[0029] That is, as shown in Fig. 3(c) and (d), when the sweep process of the second radar device 2 is performed in the missing direction, the sweep image data of the first radar device 1 and the sweep image data of the second radar device 2 are synthesized (arranged based on the acquired direction) as shown in Fig. 3(e). As a result, a detection image D of the target T as shown in Fig. 3(f) is generated by the sweep image data x-3 to x-1 of the first radar device 1 and the sweep image data y-3 to y-1 of the second radar device 2.

[0030] On the other hand, if the second radar device 2 has not acquired sweep image data of the missing direction of the first radar device 1 (if "NO" in step S3), the detection image generation unit 14, like a conventional radar device, copies the sweep image data acquired immediately before to interpolate the missing direction and generate a detection image (step S5).

[0031] Next, it is determined whether or not there is a virtual image (step S6). Here, a virtual image is an image that appears on the radar even though there is no target, and it is considered that a virtual image does not appear on all of the multiple radar devices at the same time. For this reason, the detection image generating unit 14 When an image exists in one sweep image data of the radar device 2 but does not exist in the other sweep image data, this image is determined to be a virtual image.

[0032] Specifically, for example, as shown in Fig. 3(c), only the target T appears in the sweep image data of the first radar device 1, but as shown in Fig. 3(d), the target T and an image F appear in the sweep image data y-3 to y-1 of the second radar device 2. In this case, when the two sweep image data are superimposed and sweep-combined as described above (Fig. 3(e)), the image F that appears in the sweep image data y-3 to y-1 of the second radar device 2 but does not appear in the sweep image data x-3 to x-1 of the first radar device 1 is determined to be a virtual image. In other words, the image F that does not appear continuously in the direction of change in azimuth (direction of rotation) across the sweep image data of the adjacent first radar device 1 and the sweep image data of the second radar device 2 is determined to be a virtual image.

[0033] As a result, when it is determined that a virtual image exists (step S6: YES), the detection image generating unit 14 generates a detection image by excluding the virtual image, that is, by excluding the image F from the sweep image data of the second radar device 2 (step S7). As a result, as shown in FIG. 3(f), a detection image D of only the target T without the virtual image (image F) is generated.

[0034] Then, the detection image D generated by the detection image generating unit 14 of the first radar device 1 is subjected to signal processing by the signal processing unit 15 and is displayed on the display unit 16 (step S8).

[0035] According to such a radar system 10, when an image F exists in the sweep image data of one of the radar devices 1, 2 but does not exist in the sweep image data of the other radar device 1, 2, such an image F is regarded as a virtual image, and a detection image D is generated by excluding this image F. In other words, it is possible to generate an appropriate detection image D without a virtual image. Moreover, since the detection image D is generated only by excluding an image F that exists in the sweep image data of one of the multiple radar devices 1, 2 but does not exist in the sweep image data of the other radar device 1, 2, the configuration and processing are simplified.

[0036] Moreover, according to this radar system 10, sweep image data of the missing azimuth of the first radar device 1 is acquired from the second radar device 2, and the sweep image data of the first radar device 1 and the sweep image data of the second radar device 2 are arranged based on the acquisition azimuth to generate a detection image I. Therefore, it is possible to generate a detection image D in which no gaps are generated (less gaps) in the missing azimuth and the accurate shape and size of the target T can be grasped. In addition, since it is possible to display small targets that would otherwise be contained in the missing azimuth, it is possible to perform more accurate and highly precise target detection.

[0037] Although the embodiment of the present invention has been described above, the specific configuration is not limited to the above embodiment, and even if there are design changes and the like within the scope of the gist of the present invention, they are included in the present invention.

[0038] For example, in the above embodiment, the case has been described where the sweep image data of the second radar device 2 is superimposed to interpolate the missing azimuth of the sweep image data of the first radar device 1, but such a superimposing method (determination method) is not necessary as long as it is possible to determine an image F that exists in the sweep image data of one of the radar devices 1, 2 but does not exist in the sweep image data of the other radar device 1, 2. For example, even if the sweep image data of the first radar device 1 and the sweep image data of the second radar device 2 partially overlap, they may simply be superimposed based on their respective azimuths.

[0039] In the above embodiment, the missing azimuth of the first radar device 1 is calculated based on the missing azimuth of the second radar device 2. Although the sweep image data is used for interpolation, the missing azimuth of the second radar device 2 may be interpolated using the sweep image data of the first radar device 1. In addition, if the radar antenna 11 of the first radar device 1 and the radar antenna 21 of the second radar device 2 are installed at positions apart from each other, the sweep image data may be offset according to the distance between the radar antennas 11 and 21 when performing the interpolation.

[0040] In addition, in the above embodiment, the radar system 10 including two radar devices has been described as an example, but three or more radar devices may be combined to configure the radar system 10. Furthermore, although two radar devices are provided, the radar system 10 may be configured, for example, as one radar device including a plurality of transmitting / receiving means (radar antennas, transmitting / receiving units, sweep image data generating units) and one detection image generating means (detection image generating unit).

[0041] 10. Radar Systems 1. First radar device 11 Radar antenna (one transmitting / receiving means) 12 Transmitting / receiving unit (one transmitting / receiving means) 13 Sweep image data generating unit (one transmission / reception means) 14 Detection image generation unit (detection image generation means) 2. Second radar device 21 Radar antenna (other transmission and reception means) 22 Transmitting / receiving unit (other transmitting / receiving means) 23 Sweep image data generator (other transmission / reception means) 24 Detection image generation unit (detection image generation means) T target F Virtual image

Claims

1. a plurality of transmitting / receiving means for repeatedly performing a sweep process of transmitting a transmission wave and receiving a reflected wave of the transmission wave reflected by a target while rotating in an azimuth direction, and generating sweep image data in the azimuth direction from the reflected wave; and a detection image generating means for arranging the sweep image data based on the acquisition azimuth to generate a detection image, When an image exists in the sweep image data acquired from one of the plurality of transmitting / receiving means and does not exist in the sweep image data acquired from another of the plurality of transmitting / receiving means, the detection image generating means generates the detection image by removing the image from the sweep image data of the one of the transmitting / receiving means. A target detection device comprising:

2. A detection image generating method for a target detection device, comprising: a plurality of transmitting / receiving means for repeatedly performing a sweep process of transmitting a transmission wave and receiving a reflected wave of the transmission wave reflected by a target while rotating in an azimuth direction, and generating sweep image data in the azimuth direction from the reflected wave; and a detection image generating means for arranging the sweep image data based on an acquisition azimuth to generate a detection image, When an image exists in the sweep image data acquired from one of the plurality of transmitting / receiving means and does not exist in the sweep image data acquired from another of the plurality of transmitting / receiving means, the detection image is generated by removing the image from the sweep image data of the one of the transmitting / receiving means. A detection image generating method comprising the steps of:

Images