JPH04305181A - Removing apparatus for clutter of radar - Google Patents

Abstract

PURPOSE:To discriminate a video signal of an image other than a target to be detected by a radar, as clutter, and to remove it or to display another discrimination mark. CONSTITUTION:An image memory means 3 which stores video data on a pattern of a target detected by a radar, a clutter condition setting means which sets an upper limit value of the aspect ratio of the shape of the target pattern, and a target pattern detecting means 5 which detects the target pattern from the video data stored in the image memory means 3, are provided. Moreover, a clutter shape discriminating means 6 which compares the shape of the target pattern detected by the target pattern detecting means 5 with set conditions from the clutter condition setting means and thereby discriminates it as the shape of clutter, and a means 9 for update of video data and display control which executes erasure of the video data discriminated as the shape of the clutter or display of another discrimination mark or addition of the discrimination mark and makes updated video data displayed, are provided.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar clutter removal device that discriminates clutter from the pattern shape of a video signal detected by a radar and removes the determined clutter image.

0002

2. Description of the Related Art Conventionally, a display device (such as a PP
As a display device for I), a device that displays a two-dimensional target pattern obtained by performing binary quantization processing on a radar video signal for each direction and unit distance of the radar antenna has been used. Here, binary quantization processing refers to comparing the amplitude of the video signal with a predetermined reference level at each period of the sampling signal corresponding to the unit distance, and converting it into a valid signal or an invalid signal, that is, digital data of 1 or 0. Refers to the process of converting. In this way, the target object is identified based on the size (area) and shape of the target object pattern obtained by binary quantizing the video signal.

0003

[Problems to be Solved by the Invention] However, in the above-mentioned radar target object identification display device, when used as a radar for maritime surveillance, for example, it is difficult to detect objects other than maritime targets such as ships, which are the original detection targets. There is a problem in that two-dimensional clutter from the sea surface, land, etc., as well as three-dimensional clutter such as rain particles and sand storms are displayed at the same time.

[0004] The present invention has been made in order to solve this problem, and it is possible to distinguish a video signal other than a target object to be detected by a radar as clutter, and remove the video signal determined to be clutter. An object of the present invention is to obtain a radar clutter removal device that prevents radar clutter from being displayed.

[0005]

[Means for Solving the Problems] A radar clutter removal device according to the present invention provides a target object pattern in which a video signal from a target object detected by a radar is quantized for each detected direction and unit distance. an image memory means for storing video data for at least one screen of a display device, and a clutter shape that sets an upper limit value of an aspect ratio in which the length in the longitudinal direction of the shape of the target object pattern is set as a clutter shape condition. Condition setting means, target pattern detection means for detecting individual target patterns from video data stored in the image memory means, and shapes of the individual target patterns respectively detected by the target pattern detection means. clutter shape determining means for determining that the shape of the target pattern is a clutter shape when the target pattern exceeds the upper limit set by the clutter shape condition setting means; Either write data to erase the image data of the target pattern that has been determined as such, or write identification mark data in place of the image data, or add identification mark data near the image data. updating and displaying video data by updating the video data stored in the image memory means by writing data, and reading the updated video data from the image memory means and displaying it on a display device. and control means.

[0006]

[Operation] In the present invention, the image memory means quantizes the image signal from the target object detected by the radar for each detected direction and unit distance, and stores the image data of the target object pattern on at least the display device. One screen worth of is memorized. The clutter shape condition setting means sets, as a clutter shape condition, an upper limit value of an aspect ratio in which the length in the longitudinal direction of the shape of the target object pattern is taken as vertical. The target pattern detection means detects each target pattern from the video data stored in the image memory means. The clutter shape determining means determines the shape of each target pattern detected by the target pattern detecting means when the shape of each target pattern exceeds the upper limit set by the clutter shape condition setting means. It is determined that the shape is clutter. The video data update and display control means writes data for erasing the video data of the target pattern determined to have a clutter shape by the clutter shape determining means, or writes data of an identification mark in place of the video data. The video data stored in the image memory means is updated by writing data, either by writing data in the image memory means or by adding identification mark data near the video data, and updating the video data stored in the image memory means. is read out from the image memory means and displayed on the display.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a radar clutter removal device according to the present invention. In the figure, reference numeral 1 denotes an antenna that rotates continuously at a predetermined speed while the radar is in operation, and is a transmitting/receiving antenna. In addition to transmitting and receiving radio waves, the antenna 1 also outputs an antenna direction signal. Reference numeral 2 denotes a radar transmitting/receiving section, which includes both a transmitting section and a receiving section. This transmitter generates a pulse transmission radio wave at every predetermined repetition period and transmits it via the antenna 1. In addition, the receiving section amplifies and detects the received signal reflected from the target object and received via antenna 1 to obtain a video signal, and binary quantizes this video signal for each direction and unit distance of antenna 1. Outputs video data of a two-dimensional target pattern.

Reference numeral 3 in FIG. 1 is an image memory, which stores video data of a binary quantized target pattern inputted from the transmitter/receiver 2 for at least one screen of the display (usually one rotation of the antenna 1). minute) has a storage capacity. The stored video data is then sequentially read out, and if it is determined that it is clutter, the video data is updated. Accessing this image memory 3 involves writing new data,
Reading and updating of written data, as well as reading and displaying updated data, are performed very frequently. Therefore, normally, the image memory 3 has two built-in memories (a first image memory and a second image memory) capable of storing one screen worth of video data to be displayed on the display 4. One of the two memories is selected alternately, and image data for one rotation of the antenna obtained from the radar is written to the selected memory, and at the same time, one antenna rotation is written from the memory that is not currently being written. In many cases, the video data before rotation is read out, and this video data is rewritten, updated, and displayed. Note that it is theoretically possible to limit the memory capacity of the image memory 3 to one screen displayed on the display 4, but in this case, new data can be written, and written data can be read and updated. It is technically complex because it is necessary to separate each timing of display and avoid overlapping.

4 in FIG. 1 is a display device, for example, PPI (
Plan Position Indicator)
It is. The rewritten and updated video data read from the image memory 3 is then displayed. Reference numeral 5 denotes target pattern detection means, which sequentially reads out video data once stored in the image memory 3 and detects a target pattern. 6 is a clutter shape determining means, and a target pattern detecting means 5
It is determined whether the shape of the target pattern detected by the above matches the clutter shape condition stored in the clutter shape condition memory 7, which will be described later. be.

FIG. 2 is a diagram for explaining the clutter shape conditions according to the present invention. In the diagram, the direction and distance from the radar installation position K vary from (θ1, r1) to (θ2, r
An example is shown in which a continuous bar-shaped target pattern up to 2) is obtained, and the ratio of the length A in the longitudinal direction of this target pattern shape to the length B in the direction perpendicular to the longitudinal direction ( In other words, if the aspect ratio (in which the length in the longitudinal direction of the pattern shape is defined as height) exceeds a preset value (for example, 8), this target pattern is determined to be clutter. . Generally, the average value of the ratio of the total length to the width of a ship, which is a marine target, is approximately 6, so if this ratio exceeds a certain set value (for example, 8 above), it is considered to be clutter rather than a ship. It is considered to be a reasonable discrimination method.

Reference numeral 7 in FIG. 1 is a clutter shape condition memory, which stores clutter shape condition data set as the upper limit value of the aspect ratio (however, the longitudinal direction is the vertical direction) of the target pattern shape as explained in FIG. This condition data is stored in advance and supplied to the clutter shape determining means 6. Reference numeral 8 denotes a clutter shape condition input means, such as a keyboard, which is used to store clutter shape condition data in the clutter shape condition memory 7 via the clutter shape determining means 6. Reference numeral 9 denotes a video data update and display control means, which erases video data that is determined to be clutter by the clutter shape determination means 6 from among the video data stored in the image memory 3 and does not display the video data; Either the image data is deleted and an identification mark indicating clutter is displayed in its place, or the clutter video data is left and an identification mark indicating clutter is added and displayed in its vicinity. In this way, part of the video data stored in the image memory 3 is rewritten and updated, and display control is performed to read the updated video data from the image memory 3 and display it on the display 4.

FIG. 3 is a diagram illustrating updating of clutter video data in the image memory. (a) of the same figure shows an example of the display of the clutter image before updating, and (b) of the same figure shows an example of the display of the clutter image after the update. In Figure 3,
C is an image that has been determined to be clutter, and CM is a broken line of a clutter identification mark that erases the clutter image C and displays it instead. T indicates a target image determined not to be clutter, K indicates the installation position of the radar station, and L indicates the coastline.

The operation of FIG. 1 will be explained with reference to FIG. (1). First, as an initial setting operation for the clutter removal device of this radar, the operator operates the clutter shape condition input means 8 such as a keyboard, and inputs the aspect ratio of the target pattern shape, which is the clutter shape condition data (however, the longitudinal direction is ) is stored in the clutter condition memory 7. (2). Next, when the radar is activated, the video data for one rotation of the antenna (that is, one screen of the display) obtained from the radar is stored in one of the two memories built into the image memory 3.
stored in (3). The target pattern detection means 5 sequentially reads out the video data stored in the image memory 3 in which data writing has been completed starting from the initial direction of data reading (for example, due north direction) and detects each target pattern. do. Here, each target pattern must be detected as a two-dimensional pattern that extends in both the radar azimuth direction and the distance direction. Therefore, for each target pattern, we check how far the pattern is continuous in both the azimuth direction and the distance direction (in other words, the continuity of the pattern), and for example, the shape of the target pattern as shown in Fig. 2 is determined. It is something to detect. Furthermore, in radar, since a plurality of targets may exist at different distances in the same direction, the shape of each target pattern is detected for each target at each distance in this case as well.

(4). Next, the clutter shape determining means 6
Based on the condition data stored in the clutter shape condition memory 7 in section (1), it is determined whether the shape of each target pattern detected by the target pattern detection means 5 in section (2) conforms to the clutter condition. Determine whether or not. (5). If the determination result in section (4) is not clutter, the process immediately returns to section (3), and the target pattern detection means 5 moves the direction by a unit angle from the previous data read direction, and reads the data from the image memory 3 again. The detection operation for the next target pattern is continued based on the read video data.

(6). If the determination result in item (4) is clutter, the video data update and display control means 9 writes data to erase the video data of the target pattern determined to be clutter, or Updating the video data stored in the image memory 3 by writing either data of an identification mark instead of the video data, or adding data of an identification mark near the video data. Do the following. Returning to item (3), the target pattern detection means 5 moves the direction by a unit angle from the previous data reading direction, and performs the next target pattern detection operation based on the video data read out from the image memory 3 again. Continue.

(7). The video data update and display control means 9 detects each target pattern for all directions and distances for the video data stored in the memory that is currently reading and updating data in the image memory 3. , determines whether or not the detected target pattern is clutter, and determines whether updating processing of the video data in the case of clutter has been completed, and if the determination result is complete, the updated target pattern is determined. A display control operation is performed to read out the video data from the image memory 3 and display it on the display 4. (8). While the video data update and display control means 9 is updating and displaying data in one memory in the image memory 3, when the radar antenna rotates once, the data in the other memory in the image memory 3 is updated and displayed. Writing of new video data has been completed. Therefore, the present device performs the operations (3) to (7) again on the other memory in which the new video data is stored, and then repeats the above operations.

FIG. 4 is another block diagram of the radar clutter removal device according to the present invention, and 1 to 4 and 7 are the same as those in FIG.
This is the same device. 10 and 12 are input/output interfaces, 11 is a microprocessor (hereinafter referred to as CPU)
It includes a read-only memory (hereinafter referred to as ROM) containing a control program and a random access memory (hereinafter referred to as RAM) as a work area memory. 13 is a keyboard, which is a specific device of the clutter shape condition input means 8 shown in FIG. Further, the devices 10 to 12 and the devices including the clutter shape condition memory 7 can be configured by a commercially available personal computer or the like.

The CPU 11 in FIG. 4 performs video data reading and update writing operations for the image memory 3 via the input/output interface 10 and by using the work area memory RAM in accordance with the control program stored in the built-in ROM. , and write operation of clutter shape condition data input from the keyboard 13 via the input/output interface 12 into the clutter condition memory 7. Therefore, by storing in advance a control program that performs the same operation as the device shown in FIG.
Each operation of the target pattern detection means 5, the clutter shape discrimination means 6, and the video data updating and display control means 9 is controlled by the CP.
This can be done by controlling U11.

[0019]

As described above, according to the present invention, if the aspect ratio, in which the longitudinal length of the shape of the target pattern detected by the radar is taken as vertical, exceeds a preset upper limit, it is determined as clutter. The video data identified as clutter is erased, displayed in place of an identification mark, or displayed with an identification mark added to it to prevent confusion between the target object, which is the original detection target, and clutter. This also has the effect of making identification easier.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a radar clutter removal device according to the present invention.

FIG. 2 is a diagram illustrating clutter shape conditions according to the present invention.

FIG. 3 is a diagram illustrating updating of video data in an image memory.

FIG. 4 is another block diagram of the radar clutter removal device according to the present invention.

[Description of symbols] 1 antenna 2 transmitting/receiving section 3 image memory 4 display 5 target pattern detection means 6 clutter shape discrimination means 7 clutter shape condition memory 8 clutter shape condition input means 9 video data update and display control means 10, 12
Input/output interface 11 CPU 13 Keyboard

Claims (1)

[Claims] Claim 1: Image data of a target object pattern obtained by quantizing a video signal from a target object detected by a radar for each detected direction and unit distance is displayed on at least one display device.
an image memory means for storing information for a screen; a clutter shape condition setting means for setting an upper limit value of an aspect ratio in which the length in the longitudinal direction of the shape of the target object pattern is taken as a height as a clutter shape condition; target pattern detection means for detecting individual target patterns from stored video data; and shapes of the individual target patterns detected by the target pattern detection means are set by the clutter shape condition setting means. a clutter shape determining means for determining the shape of the target pattern to be a clutter shape when the upper limit value is exceeded; and video data of a target pattern determined to be a clutter shape by the clutter shape determining means. writing data to erase the video data, writing identification mark data in place of the video data, or adding and writing identification mark data near the video data. The image data updating and display control means updates the video data stored in the image memory means, reads the updated video data from the image memory means, and displays the updated video data on a display. radar clutter removal device.