CN110907938B - Near-field rapid downward-looking synthetic aperture three-dimensional imaging method - Google Patents

Near-field rapid downward-looking synthetic aperture three-dimensional imaging method Download PDF

Info

Publication number
CN110907938B
CN110907938B CN201811087621.2A CN201811087621A CN110907938B CN 110907938 B CN110907938 B CN 110907938B CN 201811087621 A CN201811087621 A CN 201811087621A CN 110907938 B CN110907938 B CN 110907938B
Authority
CN
China
Prior art keywords
course
distance
imaging
signal
synthetic aperture
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN201811087621.2A
Other languages
Chinese (zh)
Other versions
CN110907938A (en
Inventor
王朋
秦留洋
张羽
刘纪元
黄海宁
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Institute of Acoustics CAS
Original Assignee
Institute of Acoustics CAS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Institute of Acoustics CAS filed Critical Institute of Acoustics CAS
Priority to CN201811087621.2A priority Critical patent/CN110907938B/en
Publication of CN110907938A publication Critical patent/CN110907938A/en
Application granted granted Critical
Publication of CN110907938B publication Critical patent/CN110907938B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • 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
    • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/88—Sonar systems specially adapted for specific applications
    • G01S15/89—Sonar systems specially adapted for specific applications for mapping or imaging
    • G01S15/8906—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques
    • G01S15/8997—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques using synthetic aperture techniques
    • 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
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/539—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section

Abstract

The invention discloses a near-field rapid downward-looking synthetic aperture three-dimensional imaging method, which comprises the following steps: step 1) calculating sonar echo digital signals according to working parameters of a sonar system, and performing depth-wise pulse compression processing on the sonar echo digital signals to obtain depth-wise compressed signals under a cylindrical coordinate system; step 2) performing course-crossing distance migration correction on the deeply compressed signal, performing data blocking according to the skew distance, and performing course-crossing distance correction on each data block to obtain a course-crossing compressed signal; and 3) carrying out migration correction along the course distance on the signal after the cross-course compression, thereby completing the imaging processing along the course synthetic aperture and forming a final three-dimensional image. The rapid imaging method provided by the invention can be decomposed into imaging processing in three directions of an oblique distance direction, a track direction and a pitching direction respectively, compared with an accurate time delay imaging algorithm, the calculation amount is reduced to a great extent, and the method can be effectively applied to a downward-looking synthetic aperture imaging sonar system.

Description

Near-field rapid downward-looking synthetic aperture three-dimensional imaging method
Technical Field
The invention relates to the field of imaging sonar systems, in particular to a near-field rapid downward-looking synthetic aperture three-dimensional imaging method.
Background
The downward-looking synthetic aperture three-dimensional imaging technology is a new three-dimensional imaging system based on the synthetic aperture technology, and the technology not only has high azimuth resolution compared with the traditional side-looking synthetic aperture imaging sonar, but also has the capability of measuring the depth of a target. The imaging system can obtain high-resolution imaging in the sound wave propagation direction (depth direction) and the azimuth direction (along the course) through pulse compression and synthetic aperture technology, but the cross-course resolution capability is limited by the length of a receiving array, the cross-course resolution can be effectively improved by increasing the length of the cross-course receiving array, and the difficulty, complexity and cost of system implementation are sharply increased. An effective method for solving the problem comprises the step of realizing the course-crossing high-resolution imaging by adopting a multi-input multi-output (MIMO) structure and a high-resolution imaging method (MVDR, MUSIC and the like) in the course crossing process, but because the working characteristics of a downward-looking three-dimensional imaging system mainly adopt a near field, under the condition of the near field, the downward-looking synthetic aperture imaging algorithm has large calculation amount and is difficult to realize quickly in real time.
Disclosure of Invention
The invention aims to: the invention provides a near-field rapid downward-looking synthetic aperture three-dimensional imaging method, aiming at a series of problems that downward-looking synthetic aperture three-dimensional imaging sonar mainly uses near-field work, has large imaging calculation amount, high requirement on a system calculation platform, is difficult to realize a real-time system and the like.
In order to achieve the above object, the present invention provides a near-field fast downward-looking synthetic aperture three-dimensional imaging method, which comprises:
step 1) calculating sonar echo digital signals according to working parameters of a sonar system, and performing depth-wise pulse compression processing on the sonar echo digital signals to obtain depth-wise compressed signals under a cylindrical coordinate system;
step 2) performing course-crossing distance migration correction on the deeply compressed signal, performing data blocking according to the skew distance, and performing course-crossing distance correction on each data block to obtain a course-crossing compressed signal;
and 3) carrying out migration correction along the course distance on the signal after the cross-course compression, thereby completing the imaging processing along the course synthetic aperture and forming a final three-dimensional image.
As an improvement of the above method, the step 1) specifically includes:
step 1-1), enabling the transmitting and receiving array to have a height H from the seabed, and enabling the downward looking synthetic aperture sonar to sail linearly at a constant speed v along the y direction, wherein the total number of receiving array elements is M; the position coordinate of the target is (x)0,y0,z0) Position of the mth receiving array element (x)m,yR,0)：
Figure BDA0001803544970000021
Wherein, L represents the aperture of the receiving array, and y represents the coordinate value on the y axis of the receiving array; using equivalent phase centres (X)mY,0) denotes the position of the mth array element of the equivalent receiving array:
Figure BDA0001803544970000022
wherein t2r represents the distance between the transmitting array and the xOz where the receiving array is located;
step 1-2) calculating an equivalent phase center (X)mY,0) and target point T ═ x in underwater three-dimensional scene0,y0,z0) The distance R of (2) is:
Figure BDA0001803544970000023
thus, the time delay tau of each receiving array element of the look-down synthetic aperture sonar is 2R/c, and c is the sound velocity;
step 1-3) sonar emission signals adopting linear frequency modulation signals are as follows:
Figure BDA0001803544970000024
wherein f is0Representing the carrier frequency, KrRepresenting the frequency, T, of a chirp signalrFor the pulse width, the echo signal reflected by the target is demodulated and expressed as:
Figure BDA0001803544970000025
where σ represents the echo signal amplitude and t represents time, the distance between the receiving array and the target point can also be represented as:
Figure BDA0001803544970000026
wherein v ═ xm,yR0); obtaining a distance R0The unit vector expression of the target beam direction is u ═ x0,y0,z0)/R0，
Figure BDA0001803544970000027
The Fresnel approximation of R is:
Figure BDA0001803544970000031
step 1-4) under a cylindrical coordinate system, the Fresnel approximate expression of R is as follows:
Figure BDA0001803544970000032
wherein the content of the first and second substances,
Figure BDA0001803544970000033
step 1-5) echo signals under a cylindrical coordinate system are as follows:
Figure BDA0001803544970000034
wherein, the signal wavelength is c/f0；
Step 1-6) performing depth direction pulse compression processing on the echo signal under the cylindrical coordinate system to obtain a depth direction compressed signal Sr(t,y)：
Sr(t,y)＝ArCyCxsinc[B(t-2r0/c)] (16)
Wherein A isrRepresenting the amplitude of the signal after pulse compression, and B is the bandwidth of the signal;
Figure BDA0001803544970000035
representing a range migration expression related to the heading;
Figure BDA0001803544970000036
and representing a range migration expression related to the cross-heading.
As an improvement of the above method, the step 2) specifically includes:
step 2-1) for the slant distance r0Performing data blocking on the signals subjected to depth direction compression, dividing the signals into Nr block data according to different skew distances, and assuming the skew distance r0The number of sampling points is Ns, the number of the points of each block in the slope direction is Ns
Figure BDA0001803544970000037
Step 2-2) correcting the cross-course distance migration of each block data:
S(t,y)＝Sr(t,y)Hercmc＝ArCysinc[B(t-2r0/c)]psinc(sinθ0)
wherein the content of the first and second substances,
Figure BDA0001803544970000041
representing cross-headingA reference function for correcting range migration is set,
Figure BDA0001803544970000042
Figure BDA0001803544970000043
and expressing the result of the compressed signal after the cross-heading distance migration correction, wherein theta represents a cross-heading scanning angle, and d represents an array element interval.
As an improvement of the above method, the step 3) specifically includes:
step 3-1) S (t, y) correction of migration along the course distance is as follows:
Sa(t,Y)＝S(t,Y)＝AaArsinc[B(t-2R0/C)]psinc(sinθ0)sinc[Ba(Y-y0)] (20)
wherein the content of the first and second substances,
Figure BDA0001803544970000044
representing a migration-correcting reference function along the course distance,
Figure BDA0001803544970000045
B a2 α/λ denotes the signal bandwidth along the heading, α is the heading opening angle, AaRepresenting the amplitude of the corrected signal after migration along the course distance;
the three-dimensional imaging result obtained at the end of the step 3-2) is expressed as:
Image_3D＝Asinc[B(t-2R0/C)]psinc(sinθ0)sinc[Ba(Y-y0)] (21)
wherein a represents a signal amplitude value after three-dimensional imaging processing.
The invention has the advantages that:
1. the method of the invention provides a near-field rapid imaging method on the basis of a downward-looking synthetic aperture three-dimensional imaging sonar echo model, and the method is rapid imaging realized under a cylindrical coordinate system, can effectively perform underwater target three-dimensional imaging, and effectively improves imaging efficiency;
2. the rapid imaging method provided by the invention can be decomposed into imaging processing in three directions of an oblique distance direction, a track direction and a pitching direction respectively, compared with an accurate time delay imaging algorithm, the calculation amount is reduced to a great extent, and the method can be effectively applied to a downward-looking synthetic aperture imaging sonar system.
Drawings
FIG. 1 is a schematic diagram of a geometrical model of a down-looking synthetic aperture three-dimensional imaging sonar echo signal of the present invention;
FIG. 2 is a schematic diagram of a combination relationship between a rectangular coordinate system and a cylindrical coordinate transformation;
FIG. 3 is a schematic diagram of a three-dimensional imaging simulation result (3 target points) of the three-dimensional imaging method of the present invention;
FIG. 4(a) is a two-dimensional cross-sectional view along the course-across the course of the present invention;
FIG. 4(b) is a cross-directional-depth two-dimensional cross-sectional view of the present invention;
FIG. 4(c) is a two-dimensional cross-sectional view along the course-depth direction of the present invention;
FIG. 5(a) is a comparison of the cross-course imaging results of target 1 for the method of the present invention and the precision time delay method;
FIG. 5(b) is a comparison of the cross-course imaging results of target 2 for the method of the present invention and the precision time delay method;
FIG. 5(c) is a comparison of the cross-course imaging results of the target 3 of the method of the present invention and the precision time delay method;
FIG. 6(a) is a comparison of the course-along imaging results of target 1 for the method of the present invention and the precision time-delay method;
FIG. 6(b) is a comparison of the course-along imaging results of the target 2 of the method of the present invention and the precision time-delay method;
FIG. 6(c) is a comparison of the course-along imaging results of the target 3 of the method of the present invention and the precision time-delay method;
FIG. 7(a) is a comparison of the depth imaging results of target 1 for the method of the present invention and the precision time delay method;
FIG. 7(b) is a comparison of the depth imaging results of the target 2 of the method of the present invention and the precision time delay method;
FIG. 7(c) is a comparison of the depth imaging results of the target 3 of the method of the present invention and the precision time delay method;
FIG. 8(a) is a cross-course-along-course two-dimensional plot of a tubing target;
FIG. 8(b) is a two-dimensional plot of the target of the tubing along the course-depth direction;
FIG. 8(c) is a cross-course-depth two-dimensional map of the tubing target;
FIG. 9 is a schematic diagram showing the results of three-dimensional imaging of a petroleum pipeline in an offshore test by the method of the present invention.
Detailed Description
The invention will now be further described with reference to the accompanying drawings.
The method is realized by dividing the down-view synthetic aperture imaging sonar imaging into three relatively independent parts of depth direction imaging, cross course imaging and course synthetic aperture processing, greatly reducing the system calculation amount, improving the calculation efficiency and realizing the rapid three-dimensional imaging. This will be described in detail below.
The invention provides a near-field rapid look-down synthetic aperture three-dimensional imaging method, which comprises the following steps:
step 1) calculating sonar echo digital signals according to working parameters of a sonar system, and performing depth-to-pulse compression processing on the digital signals;
step 2) according to a near-field echo signal model under a cylindrical coordinate system, performing course-crossing distance migration correction on a depth-direction pulse compressed signal, performing data blocking according to the skew distance, and performing course-crossing distance correction on each data module to obtain a course-crossing signal compression stroke image;
and 3) carrying out migration correction along the course distance on the depth direction and cross-course compressed signals obtained in the step 2) to finish the imaging processing along the course synthetic aperture and a three-dimensional image at the end of the travel.
The geometrical model of echo signals of downward-looking synthetic aperture sonar is shown in figure 1, and the transmitting and receiving array is high from the sea bottomAnd the degree is H, and the downward-looking synthetic aperture sonar travels at a constant speed v in a straight line along the y direction. Wherein, the circle represents a receiving array, the square represents a transmitting array, and the total number of M receiving array elements. According to the echo model of the downward-looking synthetic aperture sonar target in FIG. 1, the position coordinate of the target is (x)0,y0,z0) Obtaining the distance R0The unit vector expression of the target beam direction is u ═ u (u)x,uy,uz)＝(x0,y0,z0)/R0Wherein
Figure BDA0001803544970000061
The position of the transmitting array element is (0, y)T0), the position of the receiving array element is v ═ xm,yR0), the corresponding geometric position relation with that in fig. 1 can represent the receiving array element as
Figure BDA0001803544970000062
Wherein L represents the aperture of the receiving array and the transmitting array element is represented as yT＝yR+ t2r, where t2r denotes the distance between the transmitting array and the xOz where the receiving array is located, and for simplicity of the model, the position of the transducer array is described by the equivalent phase center of the present invention as:
Figure BDA0001803544970000063
calculating the equivalent receiving unit and a target point T (x) in the underwater three-dimensional scene by using the assumption of the equivalent phase center0,y0,z0) The distance of (a) is:
Figure BDA0001803544970000064
therefore, the time delay expression of each receiving unit of the downward-looking synthetic aperture sonar can be expressed as tau-2R/c, and the sonar transmitting signal adopts a chirp signal as follows:
Figure BDA0001803544970000065
wherein f is0Representing the carrier frequency, KrRepresenting the frequency, T, of a chirp signalrFor the pulse width, the echo signal reflected by the target is demodulated and expressed as:
Figure BDA0001803544970000071
the distance expression of the receiving array from the target point can be expressed as
Figure BDA0001803544970000072
Wherein v ═ xm,yR0) indicating the coordinate position of the m-th array element in the plane of the receiving array in the nth echo. It is assumed that,
Figure BDA0001803544970000073
therefore, the Taylor series expansion of the formula is expressed as
Figure BDA0001803544970000074
The delay parameter is simplified, the last two terms in the above formula can be ignored, and the following approximation is obtained
Figure BDA0001803544970000075
The approximate Fresnel expression obtained by the above formula is
Figure BDA0001803544970000076
According to the transformation definition from the rectangular coordinate system to the cylindrical coordinate system in fig. 2, the target position T ═ x0,y0,z0) From rectangular to cylindrical coordinates (theta)0,y0,r0) Is expressed as follows
Figure BDA0001803544970000077
So that the distance R is obtained in a cylindrical coordinate system0The unit vector expression of the target beam direction is as follows:
Figure BDA0001803544970000078
substituting the expression into a Fresnel approximate distance expression to obtain
Figure BDA0001803544970000079
Assuming that the beam opening angle along the heading is small, an approximate distance formula can be obtained:
Figure BDA0001803544970000081
combining with a downward-looking synthetic aperture three-dimensional imaging sonar signal echo model, obtaining an echo signal model under a cylindrical coordinate system, wherein the echo signal model is expressed as follows:
Figure BDA0001803544970000082
wherein λ ═ C/f0The first phase item contains the information of the slant direction (sound wave propagation direction), the second phase item contains the information of the track direction (synthetic aperture direction), and the third phase item contains the information of the pitch direction (cross heading direction). Therefore, the downward-looking synthetic aperture three-dimensional imaging near-field rapid algorithm provided by the invention can be decomposedAnd the imaging processing is carried out in three directions of the oblique distance direction, the track direction and the pitching direction respectively, and compared with an accurate time delay imaging algorithm, the calculation amount is reduced.
According to the near-field approximate echo signal model obtained by derivation, near-field approximate rapid three-dimensional imaging is carried out, depth direction pulse compression processing is firstly carried out, and depth direction imaging is obtained, and the method specifically comprises the following operations:
Figure BDA0001803544970000086
wherein FFT (-) represents a fast Fourier transform; IFFT (·) represents an inverse fourier transform;
Figure BDA0001803544970000083
representing a depth-wise matched filter reference function;
Figure BDA0001803544970000084
representing a range migration expression related to the heading;
Figure BDA0001803544970000085
and representing a range migration expression related to the cross-heading.
The step 2) cross-course processing method is one of the key parts of the invention, and the method is used for correcting the distance migration of the cross-course to obtain a cross-course imaging result. The calculation method of the step 2) is as follows:
the cross-heading distance correction term is expressed as:
Figure BDA0001803544970000091
the cross-course distance migration term and the slant distance r can be seen from the distance correction expression0And a cross-heading pitch angle theta0In relation to the skew distance r0Performing data blocking, and performing course-crossing distance migration correction on each block of data at the slant distance, wherein the distance migration correction expression is
Figure BDA0001803544970000092
Wherein
Figure BDA0001803544970000093
Representing a cross-course distance migration correction reference function, and realizing cross-course distance migration correction through the reference function;
Figure BDA0001803544970000094
representing a range migration expression related to the heading;
Figure BDA0001803544970000095
and representing the result of the compressed signal after the course-crossing distance migration correction.
The method for processing the synthetic aperture along the course in the step 3) is one of the key parts of the invention, and performs range migration correction on the course to obtain an imaging result along the course. The calculation method of the step 3) is as follows:
the cross-heading distance correction term is expressed as:
Figure BDA0001803544970000096
the cross-course distance migration term and the slant distance r can be seen from the distance correction expression0And a distance y along the course0Related, the correction expression of migration along course distance is
Sa(t,Y)＝S(t,Y)
＝Ar sinc[B(t-2R0/C)]p sinc(sinθ0)Cy×Ha (20)
＝AaAr sinc[B(t-2R0/C)]p sinc(sinθ0)sinc[Ba(Y-y0)]
Wherein
Figure BDA0001803544970000097
Indicating a correction reference for migration along a course distanceA function, which is used for realizing correction of migration along the course distance through the reference function; b isa2 α/λ represents the signal bandwidth along the heading, determined by the angle of opening α along the heading and the signal wavelength; a. theaRepresenting the amplitude of the corrected signal moving along the course distance.
The final three-dimensional imaging result can be expressed as:
Image_3D＝Asinc[B(t-2R0/C)]psinc(sinθ0)sinc[Ba(Y-y0)] (21)
the basic simulation parameters adopted by the method are shown in table 1, the imaging result is shown in figure 3, and the three-dimensional imaging result of three point targets is larger than-21 dB, so that the three-dimensional imaging of the point targets can be effectively carried out by the near-field rapid imaging method provided by the invention as can be seen from figure 3. FIG. 4(a), FIG. 4(b) and FIG. 4(c) show the imaging results of the two-dimensional cross-section along the course-along the course, along the course-depth direction and along the course-depth direction, respectively, and the imaging results show that the rapid imaging algorithm provided by the invention can accurately realize the target three-dimensional imaging.
TABLE 1
Figure BDA0001803544970000101
In order to further analyze the effectiveness of the algorithm, the invention carries out the contrast analysis of the imaging result of the rapid imaging algorithm and the accurate time domain algorithm. The cross-heading imaging result comparison conditions of the three targets are respectively shown in fig. 5(a), fig. 5(b) and fig. 5(c), and it can be seen that compared with an accurate time domain imaging method, the cross-heading imaging result of the approximate imaging method of the invention has reduced imaging resolution along with the increase of the cross-heading pitch angle. And 6(a), 6(b) and 6(c) respectively show the comparison of the imaging results of the three targets along the course, and it can be seen that compared with the accurate time domain imaging method, the imaging result along the course of the approximate imaging method is equivalent to the accurate imaging result, and the effectiveness of the approximate method is verified. Fig. 7(a), 7(b) and 7(c) respectively show the comparison of the depth-direction imaging results of three targets, and it can be seen that, compared with the accurate time-domain imaging method, the depth-direction imaging result of the approximate imaging method of the present invention is equivalent to the accurate time-delay method, which further verifies the effectiveness of the method of the present invention, and at the same time, it can be found that the imaging resolution of the depth direction decreases with the increase of the cross-heading pitch angle, and the spatial domain variation characteristic of the depth-direction resolution appears.
The downward-looking synthetic aperture rapid three-dimensional imaging algorithm provided by the invention is verified through an offshore test, and the offshore test selects a semi-buried oil pipeline target for three-dimensional imaging. Typical oil pipe target imaging results are shown in fig. 8(a), fig. 8(b) and fig. 8(c), fig. 8(a) is a cross-course-along-course two-dimensional graph of an oil pipe target, fig. 8(b) is a along-course-depth direction two-dimensional graph of the oil pipe target, and fig. 8(c) is a cross-course-depth direction two-dimensional graph of the oil pipe target, and as can be seen from fig. 8, the rapid imaging algorithm can accurately perform three-dimensional imaging on the oil pipe target, and further verifies the effectiveness of the algorithm.
The calculation efficiency of the near-field time domain rapid imaging method provided by the invention is demonstrated by comparing the method with the accurate time domain imaging hair. Supposing that M frame signals are provided, the number of array elements is N, three-dimensional imaging processing is carried out to obtain a three-dimensional image with Along _ N Along course pixel points, Across _ N cross course pixel points and Depth _ N Depth pixel points, the calculated amount of an imaging algorithm is measured by using floating point operation times, and the calculated amount of an accurate time domain imaging method is CRDM(8 × M × N-2) × Along _ N × Across _ N × Depth _ N; the calculation amount of the rapid method is as follows:
CROA＝((8×M-2)×N×Across_N+(8×N-2)×Along_N×Across_N)×Depth_N。
assuming that the number of receiving array elements N is 12, the number of signal frames M is 160, the number of Depth pixels Depth _ N is 512, and the number of cross-heading pixels Across _ N is 128, the comparison of floating point operands in the two methods is shown in fig. 9. It can be seen from fig. 9 that the fast imaging method of the present invention has significant advantages in terms of computation.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and are not limited. Although the present invention has been described in detail with reference to the embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (3)

1. A method for near-field fast look-down synthetic aperture three-dimensional imaging, the method comprising:
step 1) calculating sonar echo digital signals according to working parameters of a sonar system, and performing depth-wise pulse compression processing on the sonar echo digital signals to obtain depth-wise compressed signals under a cylindrical coordinate system;
specifically, the step 1) specifically includes:
step 1-1), enabling the transmitting and receiving array to have a height H from the seabed, and enabling the downward looking synthetic aperture sonar to sail linearly at a constant speed v along the y direction, wherein the total number of receiving array elements is M; the position coordinate of the target is (x)0,y0,z0) Position of the mth receiving array element (x)m,yR,0)：
Figure FDA0003268406550000011
Wherein, L represents the aperture of the receiving array, and y represents the coordinate value on the y axis of the receiving array; using equivalent phase centres (X)mY,0) represents the position of the mth array element of the equivalent receiving array: d is array element interval;
Figure FDA0003268406550000012
wherein t2r represents the distance between the transmitting array and the xOz where the receiving array is located;
step 1-2) calculating an equivalent phase center (X)mY,0) and target point T ═ x in underwater three-dimensional scene0,y0,z0) The distance R of (2) is:
Figure FDA0003268406550000013
thus, the time delay tau of each receiving array element of the look-down synthetic aperture sonar is 2R/c, and c is the sound velocity;
step 1-3) sonar emission signals adopting linear frequency modulation signals are as follows:
Figure FDA0003268406550000014
wherein f is0Representing the carrier frequency, KrRepresenting the frequency, T, of a chirp signalrFor the pulse width, the echo signal reflected by the target is demodulated and expressed as:
Figure FDA0003268406550000015
where σ represents the echo signal amplitude and t represents time, the distance between the receiving array and the target point can also be represented as:
Figure FDA0003268406550000021
wherein v ═ xm,yR0); obtaining a distance R0The unit vector expression of the target beam direction is u ═ x0,y0,z0)/R0，
Figure FDA0003268406550000022
The Fresnel approximation of R is:
Figure FDA0003268406550000023
step 1-4) under a cylindrical coordinate system, the Fresnel approximate expression of R is as follows:
Figure FDA0003268406550000024
wherein the content of the first and second substances,
Figure FDA0003268406550000025
step 1-5) echo signals under a cylindrical coordinate system are as follows:
Figure FDA0003268406550000026
wherein, the signal wavelength is c/f0；
Step 1-6) performing depth direction pulse compression processing on the echo signal under the cylindrical coordinate system to obtain a depth direction compressed signal Sr(t,y)：
Sr(t,y)＝ArCyCxsinc[B(t-2r0/c)] (16)
Wherein r is0Is the slant pitch; a. therRepresenting the amplitude of the signal after pulse compression, and B is the bandwidth of the signal;
Figure FDA0003268406550000027
representing a range migration expression related to the heading;
Figure FDA0003268406550000028
representing a range migration expression related to a cross-heading;
step 2) performing course-crossing distance migration correction on the deeply compressed signal, performing data blocking according to the skew distance, and performing course-crossing distance migration correction on each block data after the data is blocked to obtain a course-crossing compressed signal;
and 3) carrying out migration correction along the course distance on the signal after the cross-course compression, thereby completing the imaging processing along the course synthetic aperture and forming a final three-dimensional image.
2. The method for fast look-down synthetic aperture three dimensional imaging of the near field according to claim 1, wherein said step 2) comprises in particular:
step 2-1) for the slant distance r0Performing data blocking on the signals subjected to depth direction compression, dividing the signals into Nr block data according to different skew distances, and assuming the skew distance r0The number of sampling points is Ns, the number of the points of each block in the slope direction is Ns
Figure FDA0003268406550000031
Step 2-2) correcting the cross-course distance migration of each block data:
S(t,y)＝Sr(t,y)Hercmc＝ArCysinc[B(t-2r0/c)]psinc(sinθ0)
wherein the content of the first and second substances,
Figure FDA0003268406550000032
representing a cross-heading distance migration-correcting reference function,
Figure FDA0003268406550000033
Figure FDA0003268406550000034
and expressing the result of the compressed signal after the cross-heading distance migration correction, wherein theta represents a cross-heading scanning angle, and d represents an array element interval.
3. The method for fast look-down synthetic aperture three dimensional imaging of the near field according to claim 1, wherein said step 3) comprises in particular:
step 3-1) S (t, y) correction of migration along the course distance is as follows:
Sa(t,Y)＝S(t,Y)＝AaArsinc[B(t-2r0/c)]psinc(sinθ0)sinc[Ba(Y-y0)] (20)
wherein the content of the first and second substances,
Figure FDA0003268406550000035
representing a migration-correcting reference function along the course distance,
Figure FDA0003268406550000036
Ba2 α/λ denotes the signal bandwidth along the heading, α is the heading opening angle, AaRepresenting the amplitude of the corrected signal after migration along the course distance;
the three-dimensional imaging result obtained at the end of the step 3-2) is expressed as:
Image_3D＝Asinc[B(t-2r0/c)]psinc(sinθ0)sinc[Ba(Y-y0)] (21)
wherein a represents a signal amplitude value after three-dimensional imaging processing.
CN201811087621.2A 2018-09-18 2018-09-18 Near-field rapid downward-looking synthetic aperture three-dimensional imaging method Active CN110907938B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN201811087621.2A CN110907938B (en) 2018-09-18 2018-09-18 Near-field rapid downward-looking synthetic aperture three-dimensional imaging method

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201811087621.2A CN110907938B (en) 2018-09-18 2018-09-18 Near-field rapid downward-looking synthetic aperture three-dimensional imaging method

Publications (2)

Publication Number Publication Date
CN110907938A CN110907938A (en) 2020-03-24
CN110907938B true CN110907938B (en) 2021-12-07

Family

ID=69812747

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201811087621.2A Active CN110907938B (en) 2018-09-18 2018-09-18 Near-field rapid downward-looking synthetic aperture three-dimensional imaging method

Country Status (1)

Country Link
CN (1) CN110907938B (en)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111487628B (en) * 2020-05-19 2022-05-03 中国科学院声学研究所 'zero degree' interference suppression method for downward-looking multi-beam synthetic aperture imaging sonar
CN113608225B (en) * 2021-08-05 2024-02-13 苏州桑泰海洋仪器研发有限责任公司 Method for calculating depth of buried water bottom target based on synthetic aperture sonar
CN116893411B (en) * 2023-09-11 2023-12-08 西安电子科技大学 Near-field multidimensional matching method based on FD-LFM time domain bandwidth synthesis

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105891827A (en) * 2015-10-30 2016-08-24 中国人民解放军空军工程大学 Machine-mounted MIMO-SAR downward-looking three dimensional sparse imaging method
CN107064911A (en) * 2017-04-20 2017-08-18 中国人民解放军91388部队 A kind of multiple submatrixes synthetic aperture sonar kinematic error compensation method
CN108008387A (en) * 2017-11-23 2018-05-08 内蒙古工业大学 Three-D imaging method is regarded under a kind of airborne array antenna
CN108132466A (en) * 2017-12-22 2018-06-08 内蒙古工业大学 Three-D imaging method and system are regarded under a kind of airborne array antenna

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6801474B2 (en) * 2002-05-31 2004-10-05 Quester Tangent Corporation Resampling sonar echo time series primarily for seabed sediment classification
US10031216B2 (en) * 2015-03-11 2018-07-24 Raytheon Company Synthetic aperture sonar system for inspecting underwater surfaces

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105891827A (en) * 2015-10-30 2016-08-24 中国人民解放军空军工程大学 Machine-mounted MIMO-SAR downward-looking three dimensional sparse imaging method
CN107064911A (en) * 2017-04-20 2017-08-18 中国人民解放军91388部队 A kind of multiple submatrixes synthetic aperture sonar kinematic error compensation method
CN108008387A (en) * 2017-11-23 2018-05-08 内蒙古工业大学 Three-D imaging method is regarded under a kind of airborne array antenna
CN108132466A (en) * 2017-12-22 2018-06-08 内蒙古工业大学 Three-D imaging method and system are regarded under a kind of airborne array antenna

Non-Patent Citations (5)

* Cited by examiner, † Cited by third party
Title
MIMO antenna array design for airborne down-looking 3D imaging SAR;Xie Wencheng et.al.;《2010 2nd International Conference on Signal Processing Systems》;20100823;第452—456页 *
合成孔径声呐成像算法研究及MATLAB仿真;陈丽;《中国优秀硕士学位论文全文数据库 工程科技Ⅱ辑》;20170415(第4期);正文第20—22页 *
基于俯仰角压缩的阵列天线合成孔径雷达三维成像算法研究;杜磊等;《中国科学院研究生院学报》;20110309;第27卷(第6期);第800—808页 *
多波束合成孔径声呐成像技术研究;姚永红;《中国优秀硕士学位论文全文数据库 工程科技Ⅱ辑》;20120515(第5期);正文第8—39页 *
近场目标三维SAR成像技术;徐秀丽等;《制导与引信》;20100930;第31卷(第3期);第41—44页、第57页 *

Also Published As

Publication number Publication date
CN110907938A (en) 2020-03-24

Similar Documents

Publication Publication Date Title
CN107229048B (en) High-resolution wide-range SAR moving target speed estimation and imaging method
CN110907938B (en) Near-field rapid downward-looking synthetic aperture three-dimensional imaging method
CN112505710B (en) Multi-beam synthetic aperture sonar three-dimensional imaging algorithm
CN110412587B (en) Deconvolution-based downward-looking synthetic aperture three-dimensional imaging method and system
CN112269164A (en) Weak target positioning method based on interference structure matching processing under deep sea reliable acoustic path
CN110346798B (en) Bistatic synthetic aperture radar wavenumber domain efficient imaging processing method
CN115856854B (en) Radar detection method and system driven by model and data in hybrid mode
CN112505666B (en) Two-dimensional multi-beam synthetic aperture sonar target echo simulation method
CN105260524B (en) Ship-navigation radar two dimension echo sequence is as emulation mode under a kind of scanning mode
CN114910915A (en) Multi-mode imaging method for underwater target of side scan sonar
CN111580079B (en) Underwater moving target nearest distance estimation method based on single-vector hydrophone
CN110879391B (en) Radar image data set manufacturing method based on electromagnetic simulation and missile-borne echo simulation
CN114114260A (en) Maneuvering target ISAR self-focusing imaging method based on deep learning
CN105259557A (en) Multi-frequency emission beam formation method and application
CN109375227A (en) A kind of deconvolution Wave beam forming three-dimensional acoustic imaging method
CN106886025A (en) The fast time-domain imaging method of bistatic multi-beam synthetic aperture sonar in the same direction
CN113156444B (en) Multi-beam sonar high-precision imaging method based on motion compensation
CN110412585B (en) Downward-looking synthetic aperture three-dimensional imaging method and system based on MVDR
CN206546434U (en) A kind of multidimensional acoustic imaging system under water
CN111983599A (en) Target two-dimensional DOA estimation method based on azimuth-pitch dictionary
CN111487628A (en) 'zero degree' interference suppression method for downward-looking multi-beam synthetic aperture imaging sonar
CN116794643A (en) Back projection method based on acoustic reflection tomography imaging
CN114780911A (en) Ocean wide swath distance ambiguity solving method based on deep learning
CN113075633A (en) Target positioning method based on distance-pitching joint dictionary
CN110736988B (en) Bistatic PFA moving object parameter estimation and imaging method

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant