KR101058773B1 - Image Processing Method and System of Synthetic Open Surface Radar - Google Patents

Abstract

The present invention divides the area of the raw data obtained through SAR capable of detecting all-weather targets regardless of day or night or bad weather into a plurality of bursts, binds a certain number of bursts into sub data, and divides the geometric model. The present invention relates to a method and a system for SAR, wherein the Doppler parameter information is calculated for each burst using the Doppler parameter information of the corresponding burst in the processing result region.
The SAR image processing system according to the present invention divides raw data into bursts by dividing the raw data at regular intervals in the direction of the radar payload (Azimuth), bundles a predetermined number of bursts to determine a sub data group, and determines the temporal data of the raw data. An image processing controller which corresponds to a position and a visual position on the processing result image, assigns a corresponding burst to the processing result area, and controls to generate a processing result image using the Doppler parameter information in the burst; A parameter calculator configured to calculate a Doppler parameter for each burst, calculate a center time of the processed result image, calculate a size of the processed result image, and calculate a pixel resolution of the processed result image; An image processor which processes the raw data using Doppler information and a focusing algorithm; A file manager which reads or stores image data into block files during an image processing process to process a large amount of the raw data; And a parallel processor configured to simultaneously process Azimuth Lines or Range Lines for the processing result image by the number of setting threads.
According to the present invention, the speed of file access in a video radar can be improved. In addition, by applying a BIP (Band Interleaved by Pixel) structure to each image to perform parallel processing for each burst (burst) to improve the system speed. In addition, a large amount of image data can be processed at high speed, and a block file processing method can be used for the entire processed image, thereby enabling stable and fast operation.

Description

System and method for processing a picture image about synthetic aperture radar

The present invention relates to an image processing method and system of a synthetic aperture radar (SAR) for generating an image such as a photograph taken with a camera by detecting a target on the ground using electromagnetic waves. Regardless of bad weather or bad weather, the area of raw data acquired through SAR that can detect all-weather targets is divided into a number of bursts, a certain number of bursts are divided into subapertures, and each burst by geometric model is used. The present invention relates to an image processing method and system for a SAR, wherein the Doppler parameter information is calculated and a Doppler parameter information of a corresponding burst is applied to a processing result region to generate a processing result image.

SAR (Synthetic Aperture Radar) signal processing technology has been introduced since the 1960s and has been changing a lot. Early SAR algorithms, called unfocused SARs, mapped the data received by the antenna to a two-dimensional image plane without any special signal processing. After that, it has been developed to obtain high resolution video images through focused SAR signal processing that changes the phase of the received signal.

However, due to the enormous amount of data, optical processing has been relied on rather than processing by a digital computer. Therefore, only a method of continuously obtaining a strip image of a terrain located vertically in the direction of the radar movement called stripmap mode SAR has been used.

On the other hand, as the computer's processing speed increases, even if the SAR data are processed digitally, real-time processing is possible according to the amount of data. More importantly, the image position is easily compensated for by the received signal regardless of the direction of the radar movement. It became possible to get Therefore, research on various signal processing algorithms and various applications that are made possible by digitally processing SAR data is emerging as a very important field of radar signal processing.

Representative SAR image processing algorithms include range doppler algorithm (RDA), chirp scaling algorithm (CSA), and frequency scaling algorithm (FSA). They describe how to accurately handle the target in the center of the image. Therefore, if these algorithms are used as they are, there is a problem that the quality is lowered away from the center of the processed image.

SUMMARY OF THE INVENTION An object of the present invention for solving the above-described problems is to divide an area of raw data into a plurality of bursts at regular intervals in the SAR payload progression direction, and in each area, perpendicular to the SAR payload travel direction. A certain number of bursts that are uniformly aligned in the direction are grouped and divided into sub data, and the Doppler parameter information is calculated for each burst using a geometric model, and a processing result image is generated using the Doppler parameter information of the corresponding burst in the processing result area. The present invention provides a method and system for image processing of SAR.

In the SAR image processing system according to the present invention for achieving the above object, the raw data is divided into bursts by dividing the raw data at regular intervals in the direction of the radar payload (Azimuth), and grouping the bursts by a predetermined number to determine the sub data group. An image processing control unit which corresponds to a temporal position of the raw data and a visual position on a processing result image, and allocates a corresponding burst to a processing result region and controls to generate a processing result image using the Doppler parameter information corresponding to the burst; A parameter calculator configured to calculate a Doppler parameter for each burst, calculate a center time of the processed result image, calculate a size of the processed result image, and calculate a pixel resolution of the processed result image; An image processor which processes the raw data using Doppler information and a focusing algorithm; A file manager which reads or stores image data into block files during an image processing process to process a large amount of the raw data; And a parallel processor configured to simultaneously process Azimuth Lines or Range Lines for the processing result image by the number of setting threads.

The image processing control unit may use Doppler parameter information corresponding to the center for each sub data group in the radar payload range direction processing on the raw data, and correspond to each burst in the radar payload travel direction processing. The processing result image is generated using the Doppler parameter information.

The image processing controller may upload and process the entire data in a memory when the size of the raw data is small, and use a block file input / output method when the size of the raw data is large.

The image processing controller divides the raw data into block files, performs Azimuth Processing one line from the first column line, and repeats each column line by the number of threads.

On the other hand, the SAR image processing method according to the present invention for achieving the above object is a SAR image processing method for obtaining the raw data of the image from the moving radar payload, (a) proceeding the radar payload (b) dividing the bursts at equal intervals according to the azimuth direction of the radar payload as bursts of the same size according to a range direction, and grouping the bursts by a predetermined number to determine a sub data group; (b) calculating Doppler parameter information for each burst by using a geometric model for each sub data group, and setting pixel positions on the processed image corresponding to each burst; (c) calculating a temporal position of the processing result image at the temporal position of the raw data, and allocating corresponding bursts by dividing the temporal region of the processing result image; And (d) generating a processing result image by using Doppler parameter information of the corresponding burst in the processing result region.

Further, the step (d) may use Doppler parameter information corresponding to the center for each sub data group in the radar payload range direction processing on the raw data, and correspond to each burst in the radar payload direction processing. The processing result image is generated by using Doppler parameter information.

In the step (d), the Azimuth Lines or Range Lines for the processing result image are simultaneously processed by the number of setting threads.

In the step (d), the raw data is divided into block files, Azimuth Processing is performed one line from the first column line, and each column line is grouped by the number of threads and repeated.

According to the present invention, the speed of file access in a video radar can be improved.

In addition, by applying a BIP (Band Interleaved by Pixel) structure to each image to perform parallel processing for each burst (burst) to improve the system speed.

In addition, a large amount of image data can be processed at high speed, and a block file processing method can be used for the entire processed image, thereby enabling stable and fast operation.

1 is a block diagram schematically illustrating a functional block of an image processing system of a SAR according to an embodiment of the present invention.
2 is a flowchart illustrating an image processing method of a SAR according to an exemplary embodiment of the present invention.
3 is a diagram illustrating a process of obtaining SAR raw data from a radar payload according to an embodiment of the present invention.
4 is a diagram illustrating raw data and a processing result image according to an exemplary embodiment of the present invention.
5A to 5E illustrate data sizes of an image based on a pixel unit according to an exemplary embodiment of the present invention.
6 is a diagram illustrating a parallel processing thread used in the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram schematically illustrating a functional block of an image processing system of a SAR according to an embodiment of the present invention.

Referring to FIG. 1, the image processing system 100 of the SAR according to the present invention includes an image processing controller 110, a parameter calculator 120, an image processor 130, a file manager 140, and a parallel processor 150. It includes.

The image processing control unit 110 divides the raw data into bursts by dividing the raw data at regular intervals in the direction of the radar payload (Azimuth), bundles a predetermined number of bursts to determine a sub data group, and determines the temporal position and processing result of the raw data. Corresponding to the visual position on the image, and assigns a corresponding burst to the processing result region and controls to generate a processing result image using the Doppler parameter information in the burst.

To this end, the image processing controller 110 sets burst numbers corresponding to a start and an end at a temporal position of the processing result image. That is, the image processing controller 110 maps the temporal position of the raw data and the visual position on the processing result image, and allocates the corresponding burst to the processing result region, thereby calculating the corresponding burst number for any temporal position of the processing result image. Can be.

Here, the burst refers to a change region of the Doppler signal (pulse) for recognizing the target or the reflection signal of the ground surface from the radar signal.

The parameter calculator 120 calculates Doppler parameters for each burst, calculates a center time of the processed result image, calculates a size of the processed result image, and calculates a pixel resolution of the processed result image.

The image processor 130 processes raw data using Doppler information and a focusing algorithm. At this time, the image processor 130 operates by an EFSA (Extended FSA) algorithm that accurately and stably handles the Azimuth Spectrum signal by adding an Azimuth Spectral Length Extension process to the Frequency Scaling Algorithm (FSA).

The file manager 140 divides the image data into block files and reads or stores them during the image processing process in order to process a large amount of raw data stably and quickly.

The parallel processor 150 simultaneously processes as many image data lines as the number of setting threads in order to maximize the processing speed.

Here, the parallel processing is not to perform Azimuth blocks in parallel, but to simultaneously process Azimuth Lines or Range Lines of the image data by the number of threads as shown in FIG. 6. 6 is a diagram illustrating a parallel processing thread used in the present invention.

The SAR image processing system 100 according to the present invention uses a block file processing method to stably and quickly process a large amount of data.

The image processing control unit 110 uses the Doppler parameter information corresponding to the center for each sub-data group in the radar payload range direction processing on the raw data, and the Doppler parameter information corresponding to each burst in the radar payload progress direction processing. To generate the processing result image.

2 is a flowchart illustrating an image processing method of a SAR according to an exemplary embodiment of the present invention.

In general, a SAR image processing system receives raw data from a radar payload such as a radar-mounted satellite or a flying vehicle through a beam every time the raw data is moved in a sliding spotlight step steering mode. Acquire. 3 is a diagram illustrating a process of obtaining SAR raw data from a radar payload.

Subsequently, the image processing system 100 of the SAR according to the present invention divides the raw data into bursts having the same size according to the vertical direction of the radar payload traveling direction as shown in FIG. In operation S210, the burst data is divided into a predetermined number according to the azimuth direction of the radar payload, and the bursts are grouped by a predetermined number (S210).

Subsequently, the SAR image processing system 100 calculates Doppler parameter information for each burst by using a geometric model for each sub data group, and sets pixel positions on the corresponding processed image for each burst (S220).

In this case, the SAR image processing system 100 may store and store the calculated Doppler parameter information or the set pixel position.

Subsequently, the SAR image processing system 100 calculates the temporal position of the processing result image at the temporal position of the raw data, and allocates corresponding bursts by dividing the temporal region of the processing result image (S230).

Here, if the SAR image processing system 100 is small when the size of the SAR raw data is small, it is quick to upload and process the entire data in memory, and if the size of the raw data is large and large Since you can't upload everything to memory, you need to access and read data directly from mass storage media such as hard disks. In this case, the image processing system 100 of the SAR uses a block file input / output method in order to process stably and quickly because the processing time becomes considerably longer.

5A to 5E illustrate data sizes of an image based on a pixel unit according to an exemplary embodiment of the present invention. One pixel is represented by two real numbers representing the I and Q channel values listed in the range direction on the file or in memory. In FIG. 5A, three memories to be used for file input / output are prepared as shown in (a). (b) shows raw data. FIG. 5B is a diagram of dividing the raw data (a) of FIG. 5A into checkered block files according to a block file processing method. 5C is a diagram illustrating a process of reading Azimuth block files in a first column into memory considering data size after Azimuth Processing. FIG. 5D illustrates a process of performing Azimuth Processing one line from the first column line on the read memory and storing it in the memory. As shown in (e) of FIG. 5D, multi-threads may be applied by repeatedly performing column lines by repeating the number of threads. FIG. 5D is a diagram illustrating a process of dividing the processed memory into block files in the Azimuth direction again. FIG. 5E shows a block file resulting from processing all the column block files of the raw data block file as described above.

In addition, the SAR image processing system 100 determines the block area in the Azimuth direction with respect to the raw data to perform parallel processing. That is, each Azimuth block is processed in parallel through each thread as shown in FIG. As shown in FIG. 6, the SAR algorithm generates as many threads as commanded threads to process the parallel processing interval. Each created thread executes parallel processing section of SAR algorithm level through thread management. 6 is a diagram illustrating a parallel processing thread used in the present invention.

Multi Core is based on the premise of speed improvement obtained by Parallel Computing using Multi Thread. But not all tasks can be parallelized. Therefore, the speed improvement obtained when using Multi Core depends on how much parallelism the program can be made. The commonly used law is Amdahl's law as shown in Equation 1 below.

Where N is a number of processors or cores, and F represents a sequential fraction.

Approximately 20% of all programs can be executed in parallel and run concurrently. If the program is run on a CPU with four cores, the F value, which is executed sequentially, is 1-0.2 = 0.8, which is 1.176 times compared to that performed by a single core. There is only a performance improvement. Even if the number of cores is increased to infinity, the performance can be improved by 1.25 times. Therefore, the number of cores is also important, but how much can be executed in parallel is very important. For example, in the case of 100% parallelism, the performance can be improved in multiples of the number of cores. In other words, four cores can expect 4x better performance.

Therefore, the thread generation of the SAR image processing algorithm is created and managed according to the CPU and the core of the system environment. If the number of threads created exceeds the allowable range of CPU and Core, performance degradation may occur. In order to provide optimal performance, the thread generation of the SAR image processing algorithm is limited to the number of CPU (or core) * 2 because file I / O operations are mixed.

Subsequently, the SAR image processing system 100 processes the above-described process using the Doppler parameter information of the corresponding burst in the processing result region and then displays the processing result image as shown in (b) of FIG. 4. ) Is generated (S240).

Here, as shown in (b) of FIG. 4, the dark colored region indicates a temporal position where the resultant image appears when the entire raw data is processed. Divide this region into several smaller regions and map each region to its corresponding burst and subaperture. 4 is a diagram illustrating raw data and a processing result image according to an exemplary embodiment of the present invention.

In this case, the SAR image processing system 100 uses Doppler parameter information corresponding to the center for each sub data group in the vertical direction processing of the radar payload advancing direction with respect to the raw data, and in the radar payload advancing direction processing. A processing result image is generated by using Doppler parameter information corresponding to each burst.

Most SLC (Single Look Complex) data is stored in the form of Band Interleaved by Pixel (BIP), Band Interleaved by Line (BIL), and Band Sequential (BSQ). The same data format is used when processing data in a program. Receives data from SAR-equipped satellites and aircraft, and stores observation data in two channels, I (In Phase) and Q (Quadrature Phase). Since both channels form one sample of data, the BIP format is convenient for handling the data.

As described above, according to the present invention, a predetermined number of regions of the raw data are divided into a plurality of bursts at regular intervals in the radar payload advancing direction, and a predetermined number is uniformly adjusted in the vertical direction in the radar payload advancing direction in each area. The bursts of SAR are divided into sub data, the Doppler parameter information is calculated for each burst using a geometric model, and the resultant image can be generated using the Doppler parameter information of the corresponding burst in the processing result area. Image processing methods and systems can be realized.

As those skilled in the art to which the present invention pertains may implement the present invention in other specific forms without changing the technical spirit or essential features, the embodiments described above are intended to be illustrative in all respects and should not be considered as limiting. Should be. The scope of the present invention is shown by the following claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included in the scope of the present invention. do.

The present invention can be applied to an image radar device that generates an image such as taking a photograph by a camera by detecting a target on the ground using electromagnetic waves.

In addition, the scattering characteristics of the object displayed in the image radar may be modeled and applied to an algorithm for extracting physical factors.

The present invention can also be applied to radar payloads such as satellites equipped with SAR, aircraft, and ground vehicles.

In addition, the operation mode can be digitally processed to increase the sampling rate in terms of time and radar position, and can be applied to spotlight imaging radar devices or systems that need to process large amounts of data at high speed.

100: SAR image processing system 110: image processing control unit
120: parameter calculation unit 130: image processing unit
140: file management unit 150: parallel processing unit

Claims (8)

Divide the raw data into bursts by dividing the raw data at regular intervals in the direction of the radar payload (Azimuth), determine the number of bursts as a sub data group (Subaperture), and match the temporal position of the raw data with the visual position on the processing result image. An image processing controller configured to allocate a corresponding burst to the processing result region and to generate a processing result image using the Doppler parameter information corresponding to the burst;
A parameter calculator configured to calculate a Doppler parameter for each burst, calculate a center time of the processed result image, calculate a size of the processed result image, and calculate a pixel resolution of the processed result image;
An image processor which processes the raw data using Doppler information and a focusing algorithm;
A file manager which reads or stores image data into block files during an image processing process to process a large amount of the raw data; And
A parallel processor for simultaneously processing Azimuth Lines or Range Lines for the processing result image by the number of setting threads;
SAR image processing system comprising a.
The method of claim 1,
The image processing control unit uses Doppler parameter information corresponding to the center for each sub data group in the vertical direction processing of the radar payload traveling direction with respect to the raw data, and for each burst during the radar payload traveling direction processing. And a processing result image is generated using corresponding Doppler parameter information.
The method of claim 1,
If the size of the raw data is small, the image processing controller uploads the entire data into a memory and processes the data. If the size of the raw data is large, the SAR image processing system comprises a block file input / output method. .
The method of claim 1,
The image processing controller divides the raw data into block files, performs Azimuth Processing one line from the first column line, and repeats each of the column lines by the number of threads. Image processing system.
An image processing method of SAR for obtaining raw data of an image from a radar payload,
(a) The raw data is divided into regular bursts according to the azimuth direction of the radar payload as bursts having the same size according to the vertical direction of the travel direction of the radar payload, and the bursts are bundled by a predetermined number. Determining a sub data group;
(b) calculating Doppler parameter information for each burst by using a geometric model for each sub data group, and setting pixel positions on the processed image corresponding to each burst;
(c) calculating a temporal position of the processing result image at the temporal position of the raw data, and allocating corresponding bursts by dividing the temporal region of the processing result image; And
(d) generating a processing result image by using Doppler parameter information of the corresponding burst in the processing result area;
SAR image processing method comprising a.
The method of claim 5, wherein
In the step (d), the Doppler parameter information corresponding to the center of each sub data group is used in the vertical direction processing of the radar payload advancing direction with respect to the raw data, and the radar payload advancing direction is processed. And the processing result image is generated by using Doppler parameter information corresponding to each burst.
The method of claim 5, wherein
In the step (d), the Azimuth Lines or Range Lines for the processing result image are simultaneously processed by the number of setting threads.
The method of claim 5, wherein
In step (d), the raw data is divided into block files, Azimuth Processing is performed one line from the first column line, and each column line is grouped by the number of threads and repeated. SAR image processing method.

Images