KR20190093739A - Method and apparatus for tracking target based on phase gradient autofocus - Google Patents

Abstract

A method for generating an image for target detection based on the PGA according to the present invention can comprise: a step of acquiring a synthetic aperture radar (SAR) image with respect to the ground surface of an object to be detected; a step of extracting a pixel which exceeds a predetermined pixel value from the SAR image to generate a reconstituted image; a step of performing pixel selection in a range direction and an azimuth direction with respect to each pixel of the reconstituted image; a step of selecting an effective distance index based on the result of the pixel selection; a step of comparing the number of the selected effective distance indexes and the predetermined reference number thereof; a step of, when the number of the effective distance indexes is greater than the predetermined reference number thereof, determining the selected effective distance indexes as a first distance index for autofocus; a step of, when the number of the effective distance indexes is smaller than the predetermined reference number thereof, determining a second distance index for autofocus based on a line in the azimuth direction of the reconstituted image; and a step of generating the image for target detection by performing a phase gradient autofocus based on the determined first distance index or second distance index.

Description

PGA-based image detection method and apparatus therefor {METHOD AND APPARATUS FOR TRACKING TARGET BASED ON PHASE GRADIENT AUTOFOCUS}

The present invention relates to a technique for generating a target detection image using a Synthetic Aperture Radar (SAR) equipment, and more particularly, based on Phase Gradient Autofocus (PGA). The present invention relates to a PGA-based target detection image generation method and apparatus for generating a target detection image.

As is well known, synthetic aperture radar (SAR) equipment is a technique that can be used for terrain observation and geodetic as active transmission and reception equipment using electromagnetic waves.

The characteristic of the synthetic aperture radar equipment is that it is possible to shoot 24 hours without affecting the weather environment, and because the target is measured (tracked) using electromagnetic waves, it is possible to easily observe the characteristics of the terrain or the electromagnetic wave of the target.

Therefore, synthetic aperture radar equipment is used as a military surveillance / reconnaissance equipment, etc., civilian is mainly used for geodetic geodetic and terrain information acquisition.

In general, the azimuth resolution of the radar is proportional to the beam width and the observation distance in the azimuth direction, and the synthesized aperture radar can arbitrarily adjust the azimuth direction of the synthesized antenna by the signal processing.

That is, a technique for obtaining a constant azimuth resolution regardless of the viewing distance is a synthetic aperture radar, for which the synthetic aperture radar is mounted on a moving payload (eg, an aircraft, a satellite, etc.).

Synthetic aperture radars generally assume an environment that moves in a straight line at a constant altitude, while satellites can operate relatively stable orbits, whereas for aircrafts it is practically impossible to maintain a straight trajectory in view of the operating environment. There is a problem.

Therefore, a technique for tracking and compensating the trajectory of an aircraft using a navigation system or the like is an essential technique in an aircraft mounted synthetic aperture radar. However, since the accuracy of the navigation apparatus does not meet the accuracy required by the synthetic aperture radar, an autofocus technique is used as a means to compensate for this.

Autofocus is a method of searching for a target that is expected to be a target and correcting the phase change at the azimuth frequency of the target. The key of the autofocus method is to find a target that has a good performance indicator in the image.

On the other hand, SAR images, unlike optical images, have a side lobe, so that a target with a relatively large electromagnetic wave reflection characteristic may cover a relatively small target.At present, there is a way to cope with this problem. Is also not shown.

In addition, since the conventional autofocus method performs autofocus on the entire SAR image, there is a problem in that the larger the image, the larger the data, and the excessive time for performing the autofocus.

Korea Patent Registration No. 10-1733039 (Notice date: May 08, 2017)

The present invention proposes a PGA-based target tracking method and apparatus for real-time searching for a point target isolated in both a distance direction and an azimuth direction through pixel selection in a distance direction and an azimuth direction.

The problem to be solved by the present invention is not limited to the above-mentioned, another problem to be solved is not mentioned can be clearly understood by those skilled in the art from the following description. will be.

According to an aspect of the present invention, there is provided a method for acquiring a SAR (Synthetic Aperture Radar) image of a target surface to be detected, extracting a pixel having a predetermined predetermined pixel value from the SAR image, and generating a reconstructed image; Performing pixel selection in a distance direction and azimuth direction for each pixel of the reconstructed image, selecting an effective distance index based on a result of the pixel selection, and selecting the number of the selected effective distance indexes Comparing a preset reference number, determining the selected effective distance index as a first distance index for autofocus when the number of the effective distance indexes is greater than the predetermined reference number, and the effective distance When the number of indexes is less than the preset reference number, autofocus is performed based on the azimuth line of the reconstructed image. And determining a second distance index for the target and generating a target detection image by performing phase gradient autofocus based on the determined first distance index or the second distance index. It is possible to provide a method for generating an image based on target detection.

In the generating of the reconstructed image of the present invention, the reconstructed image may be generated such that the extracted pixel has a predetermined value and the remaining pixels have a pixel value of “0”.

The performing of the pixel sorting of the present invention may include determining a distance direction line of a removal target through pixel selection in a distance direction with respect to each pixel of the reconstructed image, and including the determined distance direction line of the removal target. Converting the pixel value of the removed pixel to a predetermined predetermined size; and selecting the azimuth in the azimuth direction with respect to each pixel of the reconstructed image in which the pixel value of the distance direction line of the removal target is converted. Determining the line.

The determining of the distance direction line of the object to be removed may include determining the distance direction line of the object to be removed when the number of the pixels included in the distance direction line is equal to or greater than a first threshold. Determined by distance direction lines.

The determining of the azimuth line of the object to be removed may include determining the azimuth line of the object to be removed when the pixel in which the pixel value is converted to the predetermined size exists in a predetermined azimuth line. Can be determined.

Determining an azimuth line of the object to be removed of the present invention may include the number of pixels that are not adjacent to other extracted pixels among the extracted pixels included in the predetermined azimuth line and the predetermined azimuth line. When the sum of the number of the pixel groups is greater than or equal to a second predetermined threshold, the predetermined azimuth line may be determined as an azimuth line of the object to be removed.

In the determining of the second distance index of the present invention, a distance index including at least one pixel having a predetermined predetermined pixel value or more may be determined as the second distance index.

The target detection image of the present invention may be an image including isolated point targets in both a distance direction and an azimuth direction.

According to another aspect, the present invention provides a computer program stored in a computer-readable recording medium to enable a processor to perform the PGA-based target detection image generation method according to any one of claims 1 to 8. Can be.

According to another aspect of the present invention, an image receiver for acquiring a Synthetic Aperture Radar (SAR) image of a target surface to be detected, and an image for generating a reconstructed image by extracting pixels having a predetermined predetermined pixel value from the SAR image A reconstruction unit, an effective discrimination unit that performs pixel selection in a distance direction and an azimuth direction for each pixel of the reconstruction image, a line selection unit which selects an effective distance index based on a result of the pixel selection, and A first index determiner configured to determine the selected effective distance index as a first distance index for autofocus when the number of effective distance indexes is greater than a predetermined reference number, and the number of the effective distance indexes is the preset reference When less than the number, determining a second distance index for autofocus based on the azimuth line of the reconstructed image A PGA based autofocus performer including a second index determiner and an autofocus performer configured to generate a target detection image by performing phase gradient autofocus based on the determined first distance index or the second distance index An image generating apparatus for detecting a target may be provided.

The image reconstruction unit of the present invention may generate the reconstructed image such that the extracted pixel has a predetermined value and the remaining pixels have a pixel value of "0".

The validity determining unit of the present invention may include a distance direction search unit for determining a removal target distance direction line by selecting pixels in a distance direction with respect to each pixel of the reconstructed image, and pixels included in the determined distance direction line. A pixel converting unit for converting a pixel value of the pixel to a predetermined size; It may include an azimuth searcher to determine the line.

The distance direction search unit of the present invention may determine the predetermined distance direction line as the distance direction line to be removed when the number of the extracted pixels included in the predetermined distance direction line is equal to or greater than a first threshold. .

The azimuth direction determining unit of the present invention may determine the predetermined azimuth line as the azimuth direction line to be removed when a pixel whose pixel value is converted to the predetermined size exists in a predetermined azimuth line.

The azimuth direction determining unit of the present invention includes a sum of a number of pixels that are not adjacent to other extracted pixels among the extracted pixels included in the predetermined azimuth line and a number of pixel groups included in the predetermined azimuth line. When the predetermined second threshold value is greater than or equal to, the predetermined azimuth line may be determined as the azimuth line of the removal target.

The second index determiner of the present invention may determine a distance index including at least one pixel of a predetermined pixel value or more as the second distance index.

According to an embodiment of the present invention, by selecting pixels in the distance direction and azimuth direction, it is possible to detect the point targets isolated in both the distance direction and the azimuth direction with high definition, thereby realizing high definition of the target detection image. You can.

According to an embodiment of the present invention, by detecting the point target based on the pixel selection in the distance direction and the azimuth direction or the selection according to the pixel size, it is possible to effectively reduce the time required to perform the autofocus.

1 is a block diagram of a PGA-based target detection image generating device according to an embodiment of the present invention.
2 is a flowchart illustrating a main process of generating a target detection image based on PGA according to an embodiment of the present invention.
3 is an exemplary diagram of a reconstructed image obtained by extracting and reconstructing a pixel having a predetermined pixel value or more according to an embodiment of the present invention.
4 is an exemplary view illustrating a result of selecting pixels in a distance direction according to an exemplary embodiment of the present invention.
5 is an exemplary view illustrating a result of applying a distance index to be used for pixel selection of an azimuth line according to an exemplary embodiment of the present invention.
FIG. 6 is an exemplary view showing a result of performance comparison using a corner reflector for performance of a conventional PGA and performance of a PGA according to an embodiment of the present invention.
7 to 9 are diagrams illustrating images to which the conventional method and the method of the present invention are applied before performing the PGA for each image.
Figure 10a is a comparison table of the processing time according to the conventional method and the processing time according to the present invention for the entire image.
10B is a comparison table of processing time according to the conventional method and processing time according to the present invention with respect to an image using the size of a pixel value.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various forms, only the embodiments are to make the disclosure of the present invention complete, and those skilled in the art to which the present invention pertains. It is provided to fully inform the scope of the invention, and the scope of the invention is defined only by the claims.

In describing the embodiments of the present invention, detailed descriptions of well-known functions or configurations will be omitted unless they are actually necessary in describing the embodiments of the present invention. In addition, terms to be described below are terms defined in consideration of functions in the embodiments of the present invention, which may vary according to intentions or customs of users and operators. Therefore, the definition should be made based on the contents throughout the description of the present invention.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

In general, a synthetic aperture radar (SAR) image, unlike an optical image, has a side lobe, so that a target having a large electromagnetic wave reflection characteristic may cover a small target nearby. In order to solve the problem, the present invention considers both directions (distance direction and azimuth direction) to select a point target that is isolated in both the distance direction and the direction direction.

1 is a block diagram of a PGA-based target detection image generating apparatus according to an exemplary embodiment of the present invention. The target tracking apparatus includes an image receiver 102, an image reconstructor 104, an effective discriminator 106, The line selector 108, the first index determiner 110, the second index determiner 112, and the autofocus performer 114 may be included.

Referring to FIG. 1, the image receiving unit 102 acquires a SAR image obtained through a non-illustrated aircraft-mounted SAR equipment (or a SAR sensor), that is, a SAR image of a detection target (tracking target) and an image reconstruction unit 104. In this case, the SAR image obtained here may include, for example, a plurality of dot targets (pixels) that may be expressed as brightness values of gray scale.

Next, the image reconstruction unit 104 generates a reconstruction image by extracting a pixel having a predetermined predetermined pixel value or more from the SAR image transmitted from the image receiving unit 102, that is, generating a reconstruction image under the condition of Equation 1 below. can do.

[Equation 1]

은 복소(complex) SAR 영상을, m은 방위 방향 인덱스를, n은 거리 방향 인덱스를, M_t는 픽셀값의 크기를 선별하기 위한 임계값을 각각 나타내는 것으로, 소정 픽셀값 이상의 픽셀을 추출하여 재구성할 경우, 일례로서 도 3에 도시된 바와 같은 재구성 영상을 얻을 수 있다.In the above formula 1,

Represents a complex SAR image, m denotes an azimuth index, n denotes a distance index, and M _t denotes a threshold value for selecting the size of the pixel value. In this case, a reconstructed image as shown in FIG. 3 may be obtained as an example.

That is, the image reconstructing unit 104 compares each pixel value in the azimuth direction and the distance direction with a preset threshold value so that all of the pixels have a value of "0" when the pixel size is less than or equal to the threshold value, and the pixel value is greater than or equal to the threshold value. In this case, the image may be reconstructed to have a predetermined pixel value.

The validity determining unit 106 performs pixel selection in the distance direction and the azimuth direction for each pixel of the reconstructed image generated by the image reconstruction unit 104, and uses the effective distance index based on the result of the pixel selection. The effective determination unit 106 may include a distance direction search unit 1062, a pixel converter 1064, and an azimuth direction search unit 1066.

First, the distance direction search unit 1062 determines the distance direction line to be removed by selecting pixels in the distance direction for each pixel of the reconstructed image, that is, the number of extracted pixels included in the predetermined distance direction line. When the distance is equal to or greater than the first threshold, the predetermined distance direction line may be determined as the distance direction line to be removed.

In addition, the pixel converter 1064 may set a pixel value of each pixel included in the distance direction line to be removed determined by the distance direction search unit 1062 to a predetermined size (eg, “3” or “4”). Etc.) can be provided.

That is, the pixel selection in the distance direction line may be regarded as a process of masking whether m can be assumed to be a dot target when m is a constant value, which can be expressed as Equation 2 below.

[Equation 2]

는 자연수로 거리 방향 라인에서 제거될(걸러낼) 픽셀값을 조정(기 설정된 소정 크기로 변환)하여 방위 방향 라인의 픽셀 선별 시에 이용하기 위한 스케일 변수이다.In the above formula 2,

Is a scale variable for adjusting the pixel value to be removed (filtered out) from the distance direction line by a natural number (converting to a predetermined predetermined size) to use when selecting pixels of the azimuth line.

는 아래의 두 가지를 판단하기 위해서 계산하는 값인 것으로, 아래의 수식 3과 같이 계산될 수 있다.From here,

Is a value calculated to determine the following two things, and may be calculated as in Equation 3 below.

[Equation 3]

은 크기 선별된 픽셀값이 연속으로 존재할 경우, 몇 개의 거리 픽셀에 걸쳐 붙어 있는지를 판단하기 위한 값이다. 둘째,

은 하나의 방위 방향 인덱스에 몇 개의 점표적이 존재하는지를 계산하기 위한 값이다.first,

Is a value for determining how many distance pixels are attached when the size-selected pixel values are continuously present. second,

Is a value for calculating how many point targets exist in one azimuth index.

을 계산하면 언제나 음의 값이 나오기 때문에

을 판단하는 기준값으로 음의 값인

을 이용할 수 있다.From here,

Is always negative,

Is the reference value to determine the negative value

Can be used.

4 is an exemplary view illustrating a result of selecting pixels in a distance direction according to an exemplary embodiment of the present invention.

이

보다 작은 값을 가지는 픽셀로

값(소정 크기로 변환된 픽셀값)을 가지며, 옅은 파란색 픽셀은 값이 1인 픽셀이다.That is, FIG. 4 is a result of applying Equation 2 to the image of FIG.

this

Pixels with smaller values

It has a value (a pixel value converted to a predetermined size), and a light blue pixel is a pixel of value 1.

In addition, the azimuth direction searcher 1066 determines a direction line of the removal target by selecting pixels in the azimuth direction for each pixel of the reconstructed image in which the pixel value of the distance direction line of the removal target is converted. Can provide.

That is, the azimuth direction searcher 1066 can determine the azimuth direction line to be removed from two viewpoints. First, if a pixel whose pixel value is converted to a predetermined size exists in a predetermined azimuth direction line, the azimuth direction line is determined. May be determined as the azimuth line to be removed, and the number of pixels that are not adjacent to other extracted pixels among the extracted pixels included in the predetermined azimuth line and the group of pixels included in the predetermined azimuth line (or When the sum of the number of clustered pixel groups) is equal to or greater than the second threshold value, the predetermined direction line may be determined as the direction line of the object to be removed.

For example, the pixel selection in the azimuth direction may be regarded as a process of masking whether n can be assumed to be a dot target when n is a constant value, which can be performed using Equations 4 and 5 below.

[Equation 4]

[Equation 5]

That is, the pixel sorting in the azimuth direction may be performed in consideration of the case where the pixels excluded from the distance sorting (pixels converted to a predetermined size) are included and how many targets remain in the image size sorting.

5 is an exemplary view illustrating a result of applying a distance index to be used for pixel selection in a direction according to an embodiment of the present invention.

Next, the line selector 108 may provide a function such as determining an effective distance index based on a result of pixel selection, that is, a search result of the distance direction line to be removed and the azimuth line to be removed.

)와 기 설정된 기준 개수(

)를 비교하고, 그 비교 결과를 제 1 인덱스 결정부(110) 또는 제 2 인덱스 결정부(112)로 선택 제공하는 등의 기능을 제공할 수 있다.In addition, the line selecting unit 108 performs the number of effective distance indices finally obtained after the pixel selection in the distance direction and the pixel selection in the azimuth direction (

) And the preset number of criteria (

) And provide the comparison result to the first index determination unit 110 or the second index determination unit 112.

이

보다 많은 것으로 통지될 때, 라인 선정부(108)를 통해 선정된 유효 거리 인덱스를 자동초점을 위한 제 1 거리 인덱스로 결정하는 등의 기능을 제공할 수 있다.The first index determination unit 110 then moves from the line selection unit 108.

this

When notified of more, it is possible to provide a function such as determining the effective distance index selected through the line selecting unit 108 as the first distance index for autofocus.

For example, when the pixels are added in the distance direction, the first index determiner 110 may determine the first distance index by searching for a distance index whose sum is not “0”.

이

보다 적은 것으로 통지될 때, 영상 재구성부(104)를 통해 생성된 재구성 영상의 방위 방향 라인에 의거하여 자동초점을 위한 제 2 거리 인덱스를 결정하는 등의 기능을 제공할 수 있다.In addition, the second index determination unit 112 is provided from the line selecting unit 108.

this

When notified as less, it may provide a function such as determining a second distance index for autofocus based on the azimuth line of the reconstructed image generated by the image reconstruction unit 104.

For example, the second index determiner 112 may determine the second distance index by searching for a distance index including at least one pixel of a predetermined pixel value or more.

Here, using the reconstructed image generated based on the size of the pixel value when the number of effective distance indices is smaller than the preset reference number results in phase estimation when the autofocus is performed using only a certain number of distances or less. Because it may not. That is, if the number of effective distance indices does not exceed the preset reference number, autofocus is performed using the azimuth line of the reconstructed image generated based on the size of the pixel value.

Finally, the autofocus performer 114 automatically performs phase gradient using either the first distance index determined by the first index determiner 110 or the second distance index determined by the second index determiner 112. A function such as generating a target detection image by performing focus gradient autofocus may be provided.

Next, a series of processes for generating a target detection image based on PGA according to an embodiment of the present invention using the target tracking device of the present embodiment having the above-described configuration will be described in detail.

2 is a flowchart illustrating a main process of generating a target detection image based on PGA according to an embodiment of the present invention.

Referring to FIG. 2, the image receiving unit 102 acquires a SAR image obtained through a SAR device (or a SAR sensor) mounted on a vehicle, and transmits the SAR image to the image reconstructing unit 104 (step 202). The SAR image obtained here is obtained. For example, a plurality of dot targets (pixels), which may be represented by brightness values of gray scale, may be included.

The image reconstruction unit 104 generates a reconstruction image by extracting a pixel having a predetermined predetermined pixel value or more from the SAR image transmitted from the image receiving unit 102, that is, each pixel according to the azimuth direction and the distance direction and the preset threshold value. In operation 204, the image is reconstructed so as to have a value of "0" when the pixel size is less than or equal to the threshold value and the pixel value is greater than or equal to the threshold value (step 204).

Next, the distance direction searching unit 1062 performs pixel selection in the distance direction on each pixel of the reconstructed image to determine the distance direction line to be removed (step 206). For example, when the number of extracted pixels included in the predetermined distance direction line is equal to or greater than the first threshold value, the predetermined distance direction line is determined as the distance direction line to be removed.

In addition, the pixel converter 1064 converts (switches) the value of each pixel included in the distance line to be removed to a predetermined size (eg, a size of “3” or “4”) (step 208). . Herein, the value of the pixel is converted into a predetermined predetermined size so that the azimuth line including the pixel is removed in the subsequent pixel selection in the azimuth direction.

Subsequently, the azimuth direction searcher 1066 determines the azimuth direction line of the removal target by selecting pixels in the azimuth direction for each pixel of the reconstructed image whose pixel value of the distance direction line to be removed is converted (step 210). .

For example, in the azimuth direction search unit 1066, if a pixel whose pixel value is converted to a predetermined size exists in a first azimuth direction line, the azimuth direction line is determined as an azimuth line to be removed, and a second predetermined line is determined. The sum of the number of pixels which are not adjacent to other extracted pixels among the extracted pixels included in the azimuth line and the number of pixel groups (or clustered pixel groups) included in the predetermined azimuth line is equal to or greater than a second preset threshold. In this case, the predetermined azimuth line is determined as the azimuth line as a removal target.

Next, the line selecting unit 108 determines the effective distance index based on the pixel selection result, that is, the search result of the distance direction line to be removed and the azimuth line to be removed (step 212).

)와 기 설정된 기준 개수(

)를 비교한다(단계 214).Again, the line selector 108 selects the number of effective distance indices finally obtained through pixel selection in the distance direction and pixel selection in the azimuth direction (

) And the preset number of criteria (

) Are compared (step 214).

이

보다 많으면, 제 1 인덱스 결정부(110)에서는 라인 선정부(108)를 통해 선정된 유효 거리 인덱스를 자동초점을 위한 제 1 거리 인덱스로 결정한다(단계 216). 예컨대, 제 1 인덱스 결정부(110)에서는 거리 방향으로 픽셀을 가산할 때 그 합이“0”이 아닌 거리 인덱스를 탐색하는 방식으로 제 1 거리 인덱스를 결정할 수 있다.As a result of the comparison in step 214,

this

If more, the first index determiner 110 determines the effective distance index selected by the line selector 108 as the first distance index for autofocus (step 216). For example, when the pixels are added in the distance direction, the first index determiner 110 may determine the first distance index by searching for a distance index whose sum is not “0”.

이

보다 적으면, 제 2 인덱스 결정부(112)에서는 영상 재구성부(104)를 통해 생성된 재구성 영상의 방위 방향 라인에 의거하여 자동초점을 위한 제 2 거리 인덱스를 결정한다(단계 218). 예컨대, 제 2 인덱스 결정부(112)에서는 기 설정된 소정 픽셀값 이상의 픽셀을 적어도 하나 이상 포함하는 거리 인덱스를 탐색하는 방식으로 제 2 거리 인덱스를 결정할 수 있다.As a result of the comparison in step 214,

this

If less, the second index determiner 112 determines a second distance index for autofocus based on the azimuth line of the reconstructed image generated by the image reconstructor 104 (step 218). For example, the second index determiner 112 may determine the second distance index by searching for a distance index including at least one pixel of a predetermined pixel value or more.

Here, using the reconstructed image generated based on the size of the pixel value when the number of effective distance indices is smaller than the preset reference number results in phase estimation when the autofocus is performed using only a certain number of distances or less. Because it may not.

In operation 220, the autofocus performer 114 generates a target detection image by performing a phase gradient autofocus using either the first distance index or the second distance index.

The inventors of the present invention, in order to verify the effect of the present invention, the target detection image generation method according to the present invention was applied to the flight test results, the results are as shown in Figs.

FIG. 6 is an exemplary view showing a result of performance comparison using a corner reflector for performing a conventional PGA and performing a PGA according to an embodiment of the present invention.

Referring to FIG. 6, when the PGA is applied using only the distance index selected according to the embodiment of the present invention, since the autofocus improves the azimuth performance without affecting the distance direction, the result of the distance direction is Similar, however, the performance in the azimuth direction can be seen to greatly improve the method of the present invention. In Fig. 6, the solid line represents the result according to the present invention, and the dotted line represents the result according to the conventional method, respectively.

7 to 9 are diagrams illustrating images to which the conventional method and the method of the present invention are applied before performing the PGA for each image.

7 to 9, each left image of each figure is an image before performing PGA, each center image of each figure is an image to which PGA is applied according to a conventional method, and each right image of each figure is a method of the present invention. PGA is applied to the video.

As is apparent from FIG. 7 to FIG. 9, when applying the PGA in the method according to the present invention, it can be seen that the lubricous line of the building (object to be detected) is relatively clear compared to the conventional method. It is evident that the performance is also improved at.

FIG. 10A is a comparison table of processing time according to the conventional method and processing time according to the present invention for an entire image, and FIG. 10B is processing time according to the conventional method and processing time according to the present invention, for an image using the size of a pixel value. This is a comparison table.

10A and 10B, the PGA processing time according to the present invention takes relatively less than the PGA processing time according to the conventional method, regardless of the entire image or the image using the size of the pixel value (performance in terms of PGA processing time). Improvement).

On the other hand, the combination of each block in the accompanying block diagram and each step in the flowchart may be performed by computer program instructions. These computer program instructions may be mounted on a processor of a general purpose computer, special purpose computer, or other programmable data processing equipment such that instructions executed through the processor of the computer or other programmable data processing equipment may not be included in each block or flowchart of the block diagram. It will create means for performing the functions described in each step.

These computer program instructions may be stored on a computer usable or computer readable recording medium that can be directed to a computer or other programmable data processing equipment to implement functionality in a particular manner, so that the computer program instructions are computer readable or computer readable. Instructions stored on the recording medium may produce an article of manufacture containing instruction means for performing the functions described in each block of the block diagram or in each step of the flowchart.

In addition, computer program instructions may be mounted on a computer or other programmable data processing equipment, such that a series of operating steps may be performed on the computer or other programmable data processing equipment to create a computer-implemented process to generate a computer or other program. Instructions for performing possible data processing equipment may also provide steps for performing the functions described in each block of the block diagram and in each step of the flowchart.

In addition, each block or step may represent a portion of a module, segment, or code that includes at least one or more executable instructions for executing a specified logical function (s). It should also be noted that in some alternative embodiments, the functions noted in the blocks or steps may occur out of order. For example, the two blocks or steps shown in succession may in fact be executed substantially concurrently or the blocks or steps may sometimes be performed in the reverse order, depending on the functionality involved.

The above description is merely illustrative of the technical spirit of the present invention, and those skilled in the art to which the present invention pertains have various substitutions, modifications, changes, etc. without departing from the essential characteristics of the present invention. You will easily see this possible. That is, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments.

Therefore, the protection scope of the present invention should be interpreted by the claims to be described later, and all technical ideas within the equivalent scope will be construed as being included in the scope of the present invention.

102: image receiving unit 104: image reconstruction unit
106: validity discrimination unit 108: line selection unit
110: first index determiner 112: second index determiner
114: autofocus performing unit 1062: distance direction search unit
1064: pixel conversion unit 1066: azimuth search unit

Claims (16)

Obtaining a SAR (Synthetic Aperture Radar) image of the surface to be detected;
Generating a reconstructed image by extracting a pixel having a predetermined predetermined pixel value or more from the SAR image;
Performing pixel selection in a distance direction and an azimuth direction for each pixel of the reconstructed image;
Selecting an effective distance index based on a result of the pixel selection;
Comparing the number of the selected effective distance index with a preset reference number;
Determining the selected effective distance index as the first distance index for autofocus when the number of the effective distance indexes is greater than the predetermined reference number;
Determining a second distance index for autofocus based on an azimuth line of the reconstructed image when the number of the effective distance indexes is less than the preset reference number;
Generating a target detection image by performing phase gradient autofocus based on the determined first distance index or the second distance index
PGA-based target detection image generation method comprising a. The method of claim 1,
Generating the reconstructed image,
The reconstructed image is generated such that the extracted pixel has a predetermined value and the remaining pixels have a pixel value of "0".
PGA based image detection method for target detection. The method of claim 1,
Performing the pixel sorting,
Determining a distance direction line to be removed by selecting pixels in a distance direction for each pixel of the reconstructed image;
Converting pixel values of pixels included in the determined distance direction line to a predetermined size;
Determining an azimuthal direction line of the elimination object by selecting a pixel in an azimuth direction with respect to each pixel of the reconstructed image in which the pixel value of the distance direction line of the elimination object is converted;
PGA-based target detection image generation method comprising a. The method of claim 3, wherein
Determining the distance direction line of the object to be removed,
When the number of the extracted pixels included in a predetermined distance direction line is equal to or greater than a first predetermined threshold, the predetermined distance direction line is determined as the distance direction line to be removed.
PGA based image detection method for target detection. The method of claim 3, wherein
The determining of the azimuth line of the object to be removed may include:
If a pixel whose pixel value is converted to the predetermined size exists in a predetermined azimuth line, the predetermined azimuth line is determined as an azimuth line of the object to be removed.
PGA based image detection method for target detection. The method of claim 5,
The determining of the azimuth line of the object to be removed may include:
When the sum of the number of pixels which are not adjacent to other extracted pixels among the extracted pixels included in the predetermined azimuth line and the number of pixel groups included in the predetermined azimuth line is equal to or greater than a second preset threshold, The predetermined azimuth line is determined as an azimuth line of the object to be removed.
PGA based image detection method for target detection. The method of claim 1,
The determining of the second distance index may include:
Determining a distance index including at least one pixel greater than or equal to a predetermined predetermined pixel value as the second distance index
PGA based image detection method for target detection. The method of claim 1,
The target detection image,
Image that contains isolated point targets in both the street and azimuth directions
PGA based image detection method for target detection. A computer program stored in a computer-readable recording medium for allowing a processor to perform the PGA-based target detection image generation method according to any one of claims 1 to 8. An image receiver for acquiring a synthetic aperture radar (SAR) image of the surface to be detected;
An image reconstruction unit configured to generate a reconstructed image by extracting a pixel having a predetermined predetermined pixel value from the SAR image;
An effective discriminating unit which performs pixel selection in a distance direction and an azimuth direction for each pixel of the reconstructed image;
A line selecting unit that selects an effective distance index based on the pixel selection result;
A first index determiner configured to determine the selected effective distance index as a first distance index for autofocus when the number of the effective distance indexes is greater than a preset reference number;
A second index determiner configured to determine a second distance index for autofocus based on an azimuth line of the reconstructed image when the number of the effective distance indexes is less than the preset reference number;
An autofocus execution unit generating a target detection image by performing phase gradient autofocus based on the determined first distance index or the second distance index.
PGA-based target detection image generating device comprising a. The method of claim 10,
The image reconstruction unit,
The reconstructed image is generated such that the extracted pixel has a predetermined value and the remaining pixels have a pixel value of "0".
PGA based image detection device for target detection. The method of claim 10,
The validity determining unit,
A distance direction search unit for determining a distance direction line to be removed by selecting pixels in a distance direction for each pixel of the reconstructed image;
A pixel converter configured to convert pixel values of pixels included in the determined distance direction line to a predetermined size;
An azimuth direction searcher which determines an azimuth line of an object to be removed by selecting pixels in an azimuth direction with respect to each pixel of the reconstructed image in which the pixel value of the distance direction line of the object to be removed is converted.
PGA-based target detection image generating device comprising a. The method of claim 12,
The distance direction search unit,
When the number of the extracted pixels included in a predetermined distance direction line is equal to or greater than a first predetermined threshold, the predetermined distance direction line is determined as the distance direction line to be removed.
PGA based image detection device for target detection. The method of claim 12,
The azimuth direction determining unit,
If a pixel whose pixel value is converted to the predetermined size exists in a predetermined azimuth line, the predetermined azimuth line is determined as an azimuth line of the object to be removed.
PGA based image detection device for target detection. The method of claim 14,
The azimuth direction determining unit,
When the sum of the number of pixels which are not adjacent to other extracted pixels among the extracted pixels included in the predetermined azimuth line and the number of pixel groups included in the predetermined azimuth line is equal to or greater than a second preset threshold, The predetermined azimuth line is determined as an azimuth line of the object to be removed.
PGA based image detection device for target detection. The method of claim 10,
The second index determination unit,
Determining a distance index including at least one pixel greater than or equal to a predetermined predetermined pixel value as the second distance index
PGA based image detection device for target detection.

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