CN104035082B - A kind of diameter radar image detection method and device - Google Patents

A kind of diameter radar image detection method and device Download PDF

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CN104035082B
CN104035082B CN201410245802.9A CN201410245802A CN104035082B CN 104035082 B CN104035082 B CN 104035082B CN 201410245802 A CN201410245802 A CN 201410245802A CN 104035082 B CN104035082 B CN 104035082B
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sar image
sub
spectrum
pixel
coherence coefficient
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CN104035082A (en
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龚小冬
李飞
张志敏
王宇
邓云凯
刘亚波
李宁
许致火
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Institute of Electronics of CAS
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
    • G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
    • G01S13/9021—SAR image post-processing techniques
    • G01S13/9027—Pattern recognition for feature extraction
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/41—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
    • G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
    • G01S13/9021—SAR image post-processing techniques
    • G01S13/9029—SAR image post-processing techniques specially adapted for moving target detection within a single SAR image or within multiple SAR images taken at the same time

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  • Engineering & Computer Science (AREA)
  • Remote Sensing (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Physics & Mathematics (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Artificial Intelligence (AREA)
  • Computer Vision & Pattern Recognition (AREA)
  • Radar Systems Or Details Thereof (AREA)

Abstract

The invention discloses a kind of synthetic aperture radar (SAR) image detecting method, including：The initial range of SAR image is obtained to frequency spectrum；In SAR image each pixel corresponding coherence factor is determined to frequency spectrum according to the initial range；According to the corresponding coherence factor of described each pixel, all pixels in SAR image are carried out with topography's average coherence and is processed, obtain the destination object in SAR image.The present invention further simultaneously discloses a kind of SAR image detection means.

Description

Synthetic aperture radar image detection method and device
Technical Field
The present invention relates to Synthetic Aperture Radar (SAR) image detection technologies, and in particular, to a method and an apparatus for SAR image detection.
Background
The SAR is a high-resolution imaging sensor with all-weather and all-weather functions, combines the observation characteristics of multiband, multi-polarization and multi-angle, and is widely applied to the fields of agriculture, forestry, oceans, geology, environment, disasters, mapping, military affairs and the like. The high importance of marine remote sensing scientists who use SAR images for ship detection has become one of the important marine applications of SAR.
In the SAR image with medium and low resolution, the ship target generally consists of several to dozens of pixels, and the ship detection under the condition is typical point target detection and can be realized by using a traditional ship detection algorithm. However, for high resolution SAR images, the ship target is a target of a certain size and detail, which can reach several hundred pixels. Reflection information of different structures of a ship presented in a high-resolution SAR image is different, so that the intensity distribution of the whole ship target on the SAR image is uneven, such as: the parts of superstructure, mast and the like on the ship are mainly angular reflection or point reflection, and show a high-intensity part on the SAR image, while the part of the deck is mainly diffuse reflection, and shows a lower intensity on the image. Generally speaking, the main characteristics of the ship target in the high-resolution SAR image are that the intensity distribution is uneven, a strong target exists and more detailed information is presented.
Based on the characteristics, the complete ship target information is difficult to obtain from the high-resolution SAR image. In addition, in the high-resolution SAR image, the sea clutter shows strong brightness, and even the information of the ship target can be submerged in the sea clutter. For the situation, a traditional ship detection algorithm is adopted, and if the detection threshold value is lower, higher detection probability can be obtained, but certain false information can be introduced; if the detection threshold value is higher, the influence of sea clutter can be better inhibited, but the detection probability of the ship target can be reduced at the same time. Therefore, in the high-resolution SAR image, the sea clutter increases the difficulty of accurate detection of the ship target.
In conclusion, how to obtain accurate and complete ship target information in a high-resolution SAR image is an urgent problem to be solved.
Disclosure of Invention
In view of this, embodiments of the present invention are expected to provide an SAR image detection method and apparatus, which can obtain accurate and complete target object information.
In order to achieve the purpose, the technical scheme of the invention is realized as follows:
the embodiment of the invention provides an SAR image detection method, which comprises the following steps:
acquiring an original distance spectrum of the SAR image;
determining a coherence coefficient corresponding to each pixel in the SAR image according to the original distance direction frequency spectrum;
and according to the coherence coefficient corresponding to each pixel, carrying out local image average coherence processing on all pixels in the SAR image to obtain a target object in the SAR image.
In the above scheme, the obtaining of the original distance spectrum of the SAR image includes: carrying out range-direction fast Fourier transform on an original focused high-resolution SAR image to obtain a range-direction frequency spectrum of the SAR image; and removing a window function introduced in the imaging process of the SAR image to obtain an original distance spectrum of the SAR image.
In the foregoing scheme, the determining a coherence coefficient corresponding to each pixel in the SAR image according to the original distance direction spectrum includes: and carrying out segmentation, translation and windowing on the original distance direction frequency spectrum to obtain a distance direction sub-block frequency spectrum, and obtaining a coherence coefficient corresponding to each pixel in the SAR image according to the distance direction sub-block frequency spectrum.
In the foregoing scheme, the segmenting, translating, and windowing the original distance direction spectrum, and obtaining the distance direction sub-block spectrum includes: the method comprises the steps of carrying out center segmentation on an original distance direction frequency spectrum to obtain two sub-block frequency spectrums, respectively translating the two sub-block frequency spectrums to the same center frequency, and simultaneously respectively carrying out windowing processing on the sub-block frequency spectrums to obtain the distance direction sub-block frequency spectrums.
In the foregoing scheme, the obtaining a coherence coefficient corresponding to each pixel in the SAR image according to the distance sub-block spectrum includes: performing fast Fourier inverse transformation on the distance sub-block frequency spectrum to obtain a distance sub-view image pair according to the distance sub-block frequency spectrumCalculating a coherence coefficient between the sub-view image pairs to obtain a coherence coefficient corresponding to each pixel in the SAR image;
wherein gamma is a coherence coefficient, gamma is more than or equal to 0 and less than or equal to 1, and X1And X2Two sub-view images, a complex conjugate operation,<·>is a collective averaging operation.
In the above scheme, the method further comprises: setting a coherence coefficient threshold;
the step of performing local image average coherence processing on all the pixels according to the coherence coefficient corresponding to each pixel to obtain a target object in the SAR image includes:
selecting a sliding window, performing sliding window processing on the coherent coefficient corresponding to each pixel, and calculating the average coherent coefficient of all pixels in the sliding window; comparing the average coherence coefficient with a coherence coefficient threshold value, and determining logic values of all pixel points in the sliding window according to a comparison result; moving the sliding window, and repeating the operation until all pixels are processed, and obtaining logic data of all pixels; wherein, the processing result of the pixel of the overlapping part adopts logic OR processing; and multiplying the logic data by the original SAR image to obtain a target object in the SAR image.
The embodiment of the invention also provides an SAR image detection device, which comprises:
the acquisition module is used for acquiring an original distance spectrum of the SAR image;
the determining module is used for determining a coherence coefficient corresponding to each pixel in the SAR image according to the original distance direction spectrum;
and the processing module is used for carrying out local image average coherence processing on all pixels in the SAR image according to the coherence coefficient corresponding to each pixel to obtain a target object in the SAR image.
In the above scheme, the acquiring, by the acquiring module, the original distance spectrum of the SAR image includes: the acquisition module performs range-wise fast Fourier transform on an original focused high-resolution SAR image to acquire a range-wise spectrum of the SAR image; and removing a window function introduced in the imaging process of the SAR image to obtain an original distance spectrum of the SAR image.
In the above scheme, the determining, by the determining module, a coherence coefficient corresponding to each pixel in the SAR image according to the original distance direction spectrum includes: the determining module is used for carrying out segmentation, translation and windowing on the original distance direction frequency spectrum to obtain a distance direction sub-block frequency spectrum, and obtaining a coherence coefficient corresponding to each pixel in the SAR image according to the distance direction sub-block frequency spectrum.
In the foregoing solution, the determining module performs segmentation, translation, and windowing on the original distance direction spectrum, and obtaining the distance direction sub-block spectrum includes: the determining module performs center segmentation on the original distance direction frequency spectrum to obtain two sub-block frequency spectrums, the two sub-block frequency spectrums are respectively translated to the same center frequency, and meanwhile, the sub-block frequency spectrums are respectively subjected to windowing processing to obtain the distance direction sub-block frequency spectrums.
In the foregoing scheme, the obtaining, by the determining module, a coherence coefficient corresponding to each pixel in the SAR image according to the distance vector sub-block spectrum includes: the determining module performs inverse fast Fourier transform on the distance direction sub-block frequency spectrum to obtain a distance direction sub-view image pair according to the distance direction sub-block frequency spectrumCalculating a coherence coefficient between the sub-view image pairs to obtain a coherence coefficient corresponding to each pixel in the SAR image;
wherein gamma is a coherence coefficient, gamma is more than or equal to 0 and less than or equal to 1, and X1And X2Two sub-view images, a complex conjugate operation,<·>is a collective averaging operation.
In the above solution, the apparatus further includes a setting module, configured to set a coherence coefficient threshold;
the processing module performs local image average coherence processing on all pixels in the SAR image according to the coherence coefficient corresponding to each pixel, and the obtaining of the target object in the SAR image comprises the following steps:
the processing module selects a sliding window, performs sliding window processing on the coherent coefficient corresponding to each pixel, and calculates the average coherent coefficient of all pixels in the sliding window; comparing the average coherence coefficient with a coherence coefficient threshold value, and determining logic values of all pixel points in the sliding window according to a comparison result; moving the sliding window, and repeating the operation until all pixels are processed, and obtaining logic data of all pixels; wherein, the processing result of the pixel of the overlapping part adopts logic OR processing; and multiplying the logic data by the original SAR image to obtain a target object in the SAR image.
The SAR image detection method and device provided by the embodiment of the invention are used for acquiring the original distance spectrum of the SAR image; determining a coherence coefficient corresponding to each pixel in the SAR image according to the original distance direction frequency spectrum; and according to the coherence coefficient corresponding to each pixel, carrying out local image average coherence processing on all pixels in the SAR image to obtain a target object in the SAR image. Thus, accurate and complete target object information, such as ship target information, can be obtained in the high-resolution SAR image.
Drawings
Fig. 1 is a schematic flow chart of an SAR image detection method according to an embodiment of the present invention;
FIG. 2 is a schematic flow chart of a SAR image detection method according to an embodiment of the present invention;
FIG. 3 is an original high resolution SAR image of an embodiment of the present invention;
FIG. 4 is a graph of the coherence coefficient for each pixel obtained according to the embodiment of the present invention;
FIG. 5 is a diagram of a target object obtained by an embodiment of the present invention;
fig. 6 is a schematic structural diagram of a SAR image detection apparatus according to an embodiment of the present invention.
Detailed Description
In the embodiment of the invention, the original distance spectrum of the SAR image is obtained; determining a coherence coefficient corresponding to each pixel in the SAR image according to the original distance direction frequency spectrum; and according to the coherence coefficient corresponding to each pixel, carrying out local image average coherence processing on all pixels in the SAR image to obtain a target object in the SAR image.
Fig. 1 is a schematic flowchart of an SAR image detection method according to an embodiment of the present invention, and as shown in fig. 1, the SAR image detection method according to the embodiment of the present invention includes:
step 101: acquiring an original distance spectrum of the SAR image;
the method specifically comprises the following steps: the method comprises the steps of carrying out range-to-fast Fourier transform on an original focused high-resolution SAR image to obtain a range-to-spectrum of the SAR image, and removing a window function introduced into the SAR image in an imaging process to obtain the original range-to-spectrum of the SAR image because the range-to-spectrum is windowed in the SAR imaging process to suppress side lobes.
Step 102: determining a coherence coefficient corresponding to each pixel in the SAR image according to the original distance direction frequency spectrum;
the method specifically comprises the following steps: carrying out segmentation, translation and windowing on the original distance direction frequency spectrum to obtain a distance direction sub-block frequency spectrum, and obtaining a coherent coefficient corresponding to each pixel according to the distance direction sub-block frequency spectrum;
here, the segmenting, translating, and windowing the original distance direction spectrum, and obtaining the distance direction sub-block spectrum includes: performing center segmentation on an original distance direction frequency spectrum to obtain two sub-block frequency spectrums, respectively translating the two sub-block frequency spectrums onto the same center frequency to remove linear components possibly generated in subsequent processing, and simultaneously respectively performing windowing processing on the sub-block frequency spectrums to obtain distance direction sub-block frequency spectrums;
the obtaining of the coherence coefficient corresponding to each pixel in the SAR image according to the distance sub-block spectrum comprises: performing fast Fourier inverse transformation on the distance direction sub-block frequency spectrum to obtain a distance direction sub-view image pair, and calculating a coherent coefficient between the sub-view image pairs according to the following formula (1) to obtain a coherent coefficient corresponding to each pixel;
wherein gamma is a coherence coefficient, gamma is more than or equal to 0 and less than or equal to 1, and X1And X2Two sub-view images, a complex conjugate operation,<·>is a collective averaging operation.
Step 103: according to the corresponding coherence coefficient of each pixel, carrying out local image average coherence processing on all pixels in the SAR image to obtain a target object in the SAR image;
here, the target object may be a ship target;
prior to this step, the method further comprises: setting a coherence coefficient threshold gammath(ii) a Here, for the coherence coefficient threshold γthThe setting of the SAR image can be set according to the corresponding coherence coefficient of each pixel and the overall situation of the SAR image;
the step of performing local image average coherence processing on all pixels in the SAR image according to the coherence coefficient corresponding to each pixel to obtain the target object in the SAR image comprises the following steps:
selecting a sliding window, and performing sliding window processing on the coherent coefficient corresponding to each pixel to calculate the average coherent coefficient of all pixels in the sliding window; comparing the average coherence coefficient gamma with a coherence coefficient threshold gammathDetermining logic values of all pixel points in the sliding window according to the comparison result; moving the sliding window, and repeating the operation until all pixels in the SAR image are processed, so as to obtain logic data of all pixels in the SAR image; wherein, the processing result of the pixel of the overlapping part adopts logic OR processing; multiplying the logic data with the original SAR image to obtain a target object in the SAR image;
the window size of the sliding window can be determined according to the pixels of the target object, and the edge of the target object is covered as much as possible;
the determining the logic values of all the pixel points in the sliding window according to the comparison result comprises: determining that the average coherence coefficient gamma is greater than the coherence coefficient threshold gammathThe logic values of all pixel points in the sliding window are 1, and the average coherence coefficient gamma is determined to be less than or equal to the coherence coefficient threshold gammathThe logic values of all pixel points in the sliding window are 0;
the moving of the sliding window is specifically: moving the sliding windows to enable the adjacent windows to have an overlapping rate of 50% in the distance direction or the azimuth direction; wherein the adjacent windows are the ith sliding window and the (i-1) th sliding window, and i is a positive integer;
the logic or processing adopted by the processing result of the pixels of the overlapping part comprises: the logical value 1 exists at least once for the processing result of the pixel of the overlapping portion, and the logical value of the pixel is determined to be 1.
Fig. 2 is a schematic flow diagram of a SAR image detection method according to an embodiment of the present invention, and as shown in fig. 2, the SAR image detection method according to the embodiment of the present invention includes:
step 201: acquiring an original distance spectrum of the SAR image;
the method specifically comprises the following steps: performing range-oriented fast Fourier transform on an original focused high-resolution SAR image to obtain a range-oriented spectrum of the SAR image, wherein a window function introduced into the SAR image in an imaging process needs to be removed to obtain the original range-oriented spectrum of the SAR image because the range-oriented spectrum is windowed in the SAR imaging process to suppress side lobes; fig. 3 shows an original high resolution SAR map according to an embodiment of the present invention.
Step 202: obtaining a distance direction sub-block frequency spectrum according to the original distance direction frequency spectrum;
the method specifically comprises the following steps: the method comprises the steps of carrying out center segmentation on an original distance direction frequency spectrum to obtain two sub-block frequency spectrums, respectively translating the two sub-block frequency spectrums onto the same center frequency to remove linear components possibly generated in subsequent processing, and simultaneously respectively carrying out windowing processing on the sub-block frequency spectrums to obtain the distance direction sub-block frequency spectrums.
Step 203: determining a coherence coefficient corresponding to each pixel in the SAR image according to the distance vector sub-block frequency spectrum;
the method specifically comprises the following steps: performing fast Fourier inverse transformation on the distance direction sub-block frequency spectrum to obtain a distance direction sub-view image pair according to the distance direction sub-block frequency spectrumCalculating a coherence coefficient between the sub-view image pairs to obtain a coherence coefficient corresponding to each pixel;
wherein gamma is a coherence coefficient, gamma is more than or equal to 0 and less than or equal to 1, and X1And X2Two sub-view images, a complex conjugate operation,<·>an ensemble averaging operation; fig. 4 is a graph of the correlation coefficient corresponding to each pixel obtained by the embodiment of the invention.
Step 204: setting a coherence coefficient threshold gammath；
Here, for the coherence coefficient threshold γthThe setting of (3) can be set according to the coherence coefficient corresponding to each pixel and the overall situation of the SAR image.
Step 205: according to the corresponding coherence coefficient of each pixel, carrying out local image average coherence processing on all pixels in the SAR image to obtain a target object in the SAR image;
the method specifically comprises the following steps: selecting a sliding window, and performing sliding window processing on the coherent coefficient corresponding to each pixel to calculate the average coherent coefficient of all pixels in the sliding window; comparing the average coherence coefficient gamma with a coherence coefficient threshold gammathDetermining logic values of all pixel points in the sliding window according to the comparison result; moving the sliding window, and repeating the operation until all pixels are processed, and obtaining logic data of all pixels; wherein, the processing result of the pixel of the overlapping part adopts logic OR processing; multiplying the logic data with the original SAR image to obtain a target object in the SAR image; FIG. 5 is a diagram of a target object obtained by an embodiment of the present invention;
here, the window size of the sliding window may be determined according to the pixels of the target object, covering the edge of the target object as much as possible;
the determining the logic values of all the pixel points in the sliding window according to the comparison result comprises: determining the average coherence coefficient γGreater than the threshold value gamma of the coherence coefficientthThe logic values of all pixel points in the sliding window are 1, and the average coherence coefficient gamma is determined to be less than or equal to the coherence coefficient threshold gammathThe logic values of all pixel points in the sliding window are 0;
the moving of the sliding window is specifically: moving the sliding windows to enable the adjacent windows to have an overlapping rate of 50% in the distance direction or the azimuth direction; wherein the adjacent windows are the ith sliding window and the (i-1) th sliding window, and i is a positive integer;
the logic or processing adopted by the processing result of the pixels of the overlapping part comprises: the logical value 1 exists at least once for the processing result of the pixel of the overlapping portion, and the logical value of the pixel is determined to be 1.
Fig. 6 is a schematic structural diagram of a SAR image detection apparatus according to an embodiment of the present invention, and as shown in fig. 6, the SAR image detection apparatus according to the embodiment of the present invention includes: an acquisition module 61, a determination module 62 and a processing module 63; wherein,
the obtaining module 61 is configured to obtain an original range spectrum of the SAR image;
the determining module 62 is configured to determine a coherence coefficient corresponding to each pixel in the SAR image according to the original distance direction spectrum;
the processing module 63 is configured to perform local image average coherence processing on all pixels in the SAR image according to the coherence coefficient corresponding to each pixel, so as to obtain a target object in the SAR image;
here, the acquiring module 61 acquires the raw distance spectrum of the SAR image including: the acquisition module performs range-wise fast Fourier transform on an original focused high-resolution SAR image to obtain a range-wise spectrum of the SAR image, removes a window function introduced by the SAR image in an imaging process, and obtains the original range-wise spectrum of the SAR image;
the determining module 62 determines the coherence coefficient corresponding to each pixel in the SAR image according to the original distance direction spectrum, including: the determining module is used for carrying out segmentation, translation and windowing on the original distance direction frequency spectrum to obtain a distance direction sub-block frequency spectrum, and obtaining a coherence coefficient corresponding to each pixel in the SAR image according to the distance direction sub-block frequency spectrum.
Further, the determining module 62 performs segmentation, translation and windowing on the original distance direction spectrum, and obtaining the distance direction sub-block spectrum includes: the determining module performs center segmentation on an original distance direction frequency spectrum to obtain two sub-block frequency spectrums, respectively translates the two sub-block frequency spectrums to the same center frequency, and simultaneously performs windowing processing on the sub-block frequency spectrums to obtain distance direction sub-block frequency spectrums;
the determining module obtains a coherence coefficient corresponding to each pixel in the SAR image according to the distance sub-block spectrum, and the coherence coefficient comprises: the determining module performs inverse fast Fourier transform on the distance direction sub-block frequency spectrum to obtain a distance direction sub-view image pair according toCalculating a coherence coefficient between the sub-view image pairs to obtain a coherence coefficient corresponding to each pixel in the SAR image;
wherein gamma is a coherence coefficient, gamma is more than or equal to 0 and less than or equal to 1, and X1And X2Two sub-view images, a complex conjugate operation,<·>is a collective averaging operation.
Further, the apparatus further comprises a setting module 64 for setting a threshold value γ of the coherence coefficientth(ii) a Here, for the coherence coefficient threshold γthThe setting of (3) can be set according to the coherence coefficient corresponding to each pixel and the overall situation of the SAR image.
Further, the processing module 63 performs local image average coherence processing on all pixels according to a coherence coefficient corresponding to each pixel in the SAR image, and obtaining a target object in the SAR image includes:
the processing module 63 selects a sliding window, performs sliding window processing on the coherence coefficient corresponding to each pixel, and calculates an average coherence coefficient of all pixels in the sliding window; comparing the average coherence coefficient with a coherence coefficient threshold value, and determining logic values of all pixel points in the sliding window according to a comparison result; moving the sliding window, and repeating the operation until all pixels are processed, and obtaining logic data of all pixels; wherein, the processing result of the pixel of the overlapping part adopts logic OR processing; multiplying the logic data with the original SAR image to obtain a target object in the SAR image;
the window size of the sliding window can be determined according to the pixels of the target object, and the edge of the target object is covered as much as possible;
the determining the logic values of all the pixel points in the sliding window according to the comparison result comprises: determining that the average coherence coefficient gamma is greater than the coherence coefficient threshold gammathThe logic values of all pixel points in the sliding window are 1, and the average coherence coefficient gamma is determined to be less than or equal to the coherence coefficient threshold gammathThe logic values of all pixel points in the sliding window are 0;
the moving of the sliding window is specifically: moving the sliding windows to enable the adjacent windows to have an overlapping rate of 50% in the distance direction or the azimuth direction; wherein the adjacent windows are the ith sliding window and the (i-1) th sliding window, and i is a positive integer;
the logic or processing adopted by the processing result of the pixels of the overlapping part comprises: the logical value 1 exists at least once for the processing result of the pixel of the overlapping portion, and the logical value of the pixel is determined to be 1.
The obtaining module 61, the determining module 62, the Processing module 63 and the setting module 64 can be implemented by a Central Processing Unit (CPU) in a server, a Digital Signal Processor (DSP), or a Field Programmable Gate Array (FPGA).
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention.

Claims (10)

1. A Synthetic Aperture Radar (SAR) image detection method is characterized by comprising the following steps:
acquiring an original distance spectrum of the SAR image;
determining a coherence coefficient corresponding to each pixel in the SAR image according to the original distance direction frequency spectrum;
setting a coherence coefficient threshold;
selecting a sliding window, and repeatedly executing the following operations: performing sliding window processing on the coherent coefficient corresponding to each pixel, and calculating the average coherent coefficient of all pixels in the sliding window; comparing the average coherence coefficient with a coherence coefficient threshold value, and determining logic values of all pixel points in the sliding window according to a comparison result; moving the sliding window; until finishing processing all pixels, obtaining logic data of all pixels; wherein, the processing result of the pixel of the overlapping part adopts logic OR processing; and multiplying the logic data by the original SAR image to obtain a target object in the SAR image.
2. The method of claim 1, wherein obtaining the raw distance-wise spectrum of the SAR image comprises: carrying out range-direction fast Fourier transform on an original focused high-resolution SAR image to obtain a range-direction frequency spectrum of the SAR image; and removing a window function introduced in the imaging process of the SAR image to obtain an original distance spectrum of the SAR image.
3. The method of claim 1, wherein the determining the coherence coefficient corresponding to each pixel in the SAR image according to the original distance direction spectrum comprises: and carrying out segmentation, translation and windowing on the original distance direction frequency spectrum to obtain a distance direction sub-block frequency spectrum, and obtaining a coherence coefficient corresponding to each pixel in the SAR image according to the distance direction sub-block frequency spectrum.
4. The method of claim 3, wherein the segmenting, translating and windowing the original distance-oriented spectrum to obtain the distance-oriented sub-block spectrum comprises: the method comprises the steps of carrying out center segmentation on an original distance direction frequency spectrum to obtain two sub-block frequency spectrums, respectively translating the two sub-block frequency spectrums to the same center frequency, and simultaneously respectively carrying out windowing processing on the sub-block frequency spectrums to obtain the distance direction sub-block frequency spectrums.
5. The method of claim 3, wherein the obtaining a coherence coefficient corresponding to each pixel in the SAR image according to the distance vector sub-block spectrum comprises: performing the distance vector sub-block frequency spectrumInverse fast Fourier transform to obtain a pair of distance-wise sub-view images, based onCalculating a coherence coefficient between the sub-view image pairs to obtain a coherence coefficient corresponding to each pixel in the SAR image;
wherein gamma is a coherence coefficient, gamma is more than or equal to 0 and less than or equal to 1, and X1And X2Two sub-view images, a complex conjugate operation,<·>is a collective averaging operation.
6. An SAR image detection apparatus characterized by comprising:
the acquisition module is used for acquiring an original distance spectrum of the SAR image;
the determining module is used for determining a coherence coefficient corresponding to each pixel in the SAR image according to the original distance direction spectrum;
a setting module for setting a coherence coefficient threshold;
a processing module for selecting a sliding window and repeatedly performing the following operations: performing sliding window processing on the coherent coefficient corresponding to each pixel, and calculating the average coherent coefficient of all pixels in the sliding window; comparing the average coherence coefficient with a coherence coefficient threshold value, and determining logic values of all pixel points in the sliding window according to a comparison result; moving the sliding window; until finishing processing all pixels, obtaining logic data of all pixels; wherein, the processing result of the pixel of the overlapping part adopts logic OR processing; and multiplying the logic data by the original SAR image to obtain a target object in the SAR image.
7. The apparatus of claim 6, wherein the obtaining module obtains a raw range spectrum of the SAR image comprises: the acquisition module performs range-wise fast Fourier transform on an original focused high-resolution SAR image to acquire a range-wise spectrum of the SAR image; and removing a window function introduced in the imaging process of the SAR image to obtain an original distance spectrum of the SAR image.
8. The apparatus of claim 6, wherein the determining module determines the coherence coefficient corresponding to each pixel in the SAR image according to the raw distance direction spectrum comprises: the determining module is used for carrying out segmentation, translation and windowing on the original distance direction frequency spectrum to obtain a distance direction sub-block frequency spectrum, and obtaining a coherence coefficient corresponding to each pixel in the SAR image according to the distance direction sub-block frequency spectrum.
9. The apparatus of claim 8, wherein the determining module performs segmentation, translation, and windowing on the original distance-oriented spectrum, and obtaining the distance-oriented sub-block spectrum comprises: the determining module performs center segmentation on the original distance direction frequency spectrum to obtain two sub-block frequency spectrums, the two sub-block frequency spectrums are respectively translated to the same center frequency, and meanwhile, the sub-block frequency spectrums are respectively subjected to windowing processing to obtain the distance direction sub-block frequency spectrums.
10. The apparatus of claim 8, wherein the determining module obtains a coherence coefficient corresponding to each pixel in the SAR image according to the distance vector sub-block spectrum comprises: the determining module performs inverse fast Fourier transform on the distance direction sub-block frequency spectrum to obtain a distance direction sub-view image pair according to the distance direction sub-block frequency spectrumCalculating a coherence coefficient between the sub-view image pairs to obtain a coherence coefficient corresponding to each pixel in the SAR image;
wherein gamma is a coherence coefficient, gamma is more than or equal to 0 and less than or equal to 1, and X1And X2Two sub-view images, a complex conjugate operation,<·>is a collective averaging operation.
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