A multi-receiving array synthetic aperture sonar imaging method and system

Abstract

The present invention provides a multi-receiving array synthetic aperture sonar imaging method and system, relating to the field of image processing technology. The method comprises: establishing a multi-receiving array synthetic aperture sonar platform, using a receiving array with a zero baseline length in the platform as a reference array, and calculating a reference range history of the reference array; using a first range migration curve of a receiving array with a non-zero baseline length in the platform as a translation of the reference range history in a two-dimensional plane, and using the geometric relationship and series inversion of the first range migration curve to constrain and solve the unknown variables in the first range migration curve to obtain a second range migration curve for any receiving array in the platform; obtaining a two-dimensional spectrum analytical expression based on the second range migration curve, and imaging each array element individually, and obtaining an imaging result after coherent superposition. The present invention can simultaneously account for range history errors at both short and long distances, thereby meeting high-resolution imaging requirements throughout the entire survey swath.

Description

Technical Field

[0001] The present invention relates to the technical field of image processing, and in particular to a multi-receiving array synthetic aperture sonar imaging method and system based on improved series inversion. Background Art

[0002] The basic principle of synthetic aperture sonar (SAS) is to use a small-sized array to move at a uniform speed in a straight line in space to simulate a large-aperture array, transmit and receive echo signals at sequential positions along the motion trajectory, and perform coherent superposition processing on the echo signals at different positions based on the spatial position and phase relationship, thereby forming an equivalent large aperture and obtaining high resolution along the direction of motion (azimuth).

[0003] The sound waves emitted by synthetic aperture sonar have a certain ability to penetrate seafloor sediments. While this property can be used to detect buried objects underwater, its penetration is limited. For targets at the same depth beneath the sediment, the greater the angle of incidence, the thicker the sediment layer the sound waves must penetrate, resulting in greater attenuation. This means that the angle of incidence of the sound waves hitting the sediment layer cannot be too large. Because this limited angle of incidence means that the working distance for buried object detection is usually very close.

[0004] Traditional methods based on phase center approximation typically use the distance from the equivalent phase center of the transmit / receive array pair to the beam center as the range history. However, at close ranges, the phase center approximation causes a sharp increase in range history error; at long ranges, the beam center approximation causes the range history error to increase with increasing distance and beam width. Therefore, imaging performance will be significantly degraded at both close and long ranges, failing to meet the requirements of high-resolution imaging. Furthermore, while the range history error of series inversion methods is minimal at close ranges, the use of the beam center approximation increases the range history error at long ranges.

[0005] Therefore, it is urgent to find a method that can simultaneously solve the problem that the distance history error increases sharply at both close and long distances. Summary of the Invention

[0006] Based on this, it is necessary to provide a multi-receiving array synthetic aperture sonar imaging method and system based on improved series inversion to address the above technical problems, which solves the problem that the distance history error increases sharply at close or long distances, thereby leading to a decrease in imaging performance.

[0007] In one aspect, the present invention provides a multi-receiving array synthetic aperture sonar imaging method, the method comprising:

[0008] A multi-receiving array synthetic aperture sonar platform is established, and the receiving array with zero baseline length in the platform is used as the reference array. The reference distance history of the reference array is calculated.

[0009] A first range migration curve of a receiving array with a non-zero baseline length in the platform is used as a translation of the reference range history in a two-dimensional plane, and unknown variables in the first range migration curve are constrained and solved using geometric relationships and series inversion to obtain a second range migration curve for any receiving array in the platform.

[0010] A two-dimensional spectrum analytical expression is obtained based on the second range migration curve, and each array element is imaged separately, and an imaging result is obtained after coherent superposition.

[0011] Furthermore, the multi-receiving array synthetic aperture sonar platform includes a transmitting array and a plurality of evenly arranged receiving arrays.

[0012] Furthermore, the method for obtaining the first distance migration curve includes: obtaining it based on the reference distance history and the translation amount.

[0013] Furthermore, the solution includes: listing a set of equations with the same number as the unknown variables; obtaining analytical expressions of the unknown variables through the set of equations, and then obtaining the second distance migration curve.

[0014] Furthermore, the series inversion includes: fitting the second range migration curve using a set of basis functions; wherein the basis functions are derived from the reference range history of the reference array.

[0015] Furthermore, the expression of the second distance migration curve R m (t; r) is:

[0016]

[0017] Among them, m , γ m ,η m All represent the unknown variables, which are obtained through the constraint relationship; v represents the platform movement speed; t represents the azimuth time; d m represents the baseline length from the mth receiving array to the transmitting array; r represents the vertical distance between the target and the track; c represents the speed of sound in water.

[0018] Furthermore, the constraint relationship includes: the values ​​of the derivatives of each order of the second range migration curve and the derivatives of each order of the precise range history of the receiving array relative to the target at t=0 are equal.

[0019] Furthermore, the unknown variable ζ m , γ m,η m They are:

[0020]

[0021] Among them, d m represents the baseline length from the mth receiving array to the transmitting array; r represents the vertical distance between the target and the track; c represents the speed of sound in water; v represents the platform movement speed.

[0022] Furthermore, each array element is imaged individually, and the imaging results obtained after coherent superposition include:

[0023] Treating multiple receiving array synthetic aperture sonars as multiple transmitting and receiving array pairs, performing a bistatic imaging algorithm on each transmitting and receiving array pair, performing Taylor expansion of the two-dimensional spectrum analytical expression with respect to range frequency and retaining it to the third order, and obtaining the imaging result of a single array element;

[0024] The azimuth aliasing is removed by superposition in the range Doppler domain or spatial domain to obtain the imaging result.

[0025] On the other hand, the present invention also proposes a multi-receiving array synthetic aperture sonar imaging system, comprising a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of any one of the above methods.

[0026] In general, the present invention provides a multi-receiver array synthetic aperture sonar imaging method and system based on improved series inversion, which can achieve the following beneficial effects compared with the existing technology:

[0027] This method uses the first range migration curve of a receiving array with a non-zero baseline length in the platform as a reference for the translation of the range history in a two-dimensional plane. The geometric relationships and series inversion of the first range migration curve are then used to constrain and solve for unknown variables. This results in a second range migration curve for any receiving array in the platform. Based on the second range migration curve, a two-dimensional spectrum analytical expression is then derived to produce the imaging result. This method can simultaneously account for range history errors at both short and long distances, ensuring high-resolution imaging throughout the entire survey swath. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 This is a schematic diagram of a method flow of a multi-receiving array synthetic aperture sonar imaging method and system provided by the present invention;

[0030] Figure 2 This is a schematic diagram of the positional relationship between the transmitting array and the receiving array in a multi-receiving array synthetic aperture sonar platform of a multi-receiving array synthetic aperture sonar imaging method and system provided by the present invention;

[0031] Figure 3 It is a comparative schematic diagram of a reference range history, a first range migration curve, and a second range migration curve of a multi-receiving array synthetic aperture sonar imaging method and system provided by the present invention;

[0032] Figure 4 This is a schematic diagram of the imaging algorithm flow of a multi-receiving array synthetic aperture sonar imaging method and system provided by the present invention;

[0033] Figure 5 This is a schematic diagram of the close-range target focused imaging results of a multi-receiving array synthetic aperture sonar imaging method and system provided by the present invention;

[0034] Figure 6 The present invention provides a multi-receiving array synthetic aperture sonar imaging method and system for focusing imaging results of a long-distance target. DETAILED DESCRIPTION

[0035] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0036] It should be noted that, in the description of the embodiments of the present invention, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a method, step, or system comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such method, step, or system. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the method, step, or system comprising the element.

[0037] like Figure 1 As shown, the present invention provides a multi-receiver array synthetic aperture sonar imaging method, including solving the reference range history, solving the second range migration curve based on improved series inversion, and solving the two-dimensional spectrum and imaging algorithm. More specifically, the method includes:

[0038] Step 101: Establish a multi-receiving array synthetic aperture sonar platform, use a receiving array with a zero baseline length in the platform as a reference array, and calculate a reference distance history of the reference array.

[0039] The baseline length is the distance from the receiving array to the transmitting array. Taking the receiving array with a zero baseline length in the platform as the reference array, its corresponding range history is the reference array range history of the reference array. The reference array range history is the basis for solving the subsequent second range migration curve.

[0040] The multi-receiver array synthetic aperture sonar platform consists of a transmitting array and multiple evenly arranged receiving arrays.

[0041] As a specific embodiment, Figure 2 As shown in the figure, a multi-receiver array synthetic aperture sonar platform (SAS platform) operates in the front-side view mode, consisting of one transmitting array and m evenly spaced receiving arrays. The receiving array positions are indicated in yellow, and m is the receiving array number, ranging from -M1, -M1+1, ..., 0, ..., M2. The transmitting array positions are indicated in red.

[0042] The x-axis, along the track, is called the azimuth, also known as the along-track direction. The r-axis, perpendicular to the track, is called the range, also known as the vertical-track direction. The SAS platform moves uniformly along the azimuth at a speed v to detect the ideal scattering point P(r, 0).

[0043] It should be noted that the precise distance history of the receiving array m relative to the target P(0, r) can be obtained based on the non-stop-and-go assumption without any approximation.

[0044] As an example, the expression of the exact distance history is:

[0045]

[0046] Where A = c 2 -v 2 ; C=d m 2 +2vtd m ; c is the speed of sound in water; v is the platform speed; t is the azimuth time; d m represents the baseline length from the mth receiving array to the transmitting array; r represents the vertical distance between the target and the track.

[0047] The receiving array with a baseline length of zero from the receiving array to the transmitting array in the platform is used as the reference array, that is, d m = 0 is used as the reference array. That is, the reference distance history of the reference array can be obtained based on the precise distance history.

[0048] Specifically, directly convert d m=0 is substituted into the expression of the precise distance history, and the reference distance history of the reference array can be obtained. like Figure 3 The red curve in .

[0049] As an example, the reference distance history The expression can be:

[0050]

[0051] Where γ0=c 2 / (c 2 -v 2 ), η0=v 2 / (c 2 -v 2 ), c represents the speed of sound in water, v represents the platform speed, t represents the azimuth time, and r represents the vertical distance between the target and the track.

[0052] In addition, the first beam center crossing time can be obtained based on the reference distance history. Specifically, let That is, the first beam center crossing time can be obtained.

[0053] As an embodiment, the first beam center passes through time t c,0 The expression can be:

[0054]

[0055] Where r is the vertical distance between the target and the track; c is the speed of sound in water; and v is the platform speed.

[0056] Because no approximations are made in this step, the resulting reference distance history is precise. Without the approximations made by phase center approximation and series inversion methods, all subsequent work is based on this precise reference distance history. Compared to existing technologies, the resulting distance history error does not increase dramatically at both close and long distances, resulting in more accurate imaging results.

[0057] Step 102: The first range migration curve of the receiving array with a non-zero baseline length in the platform is used as the translation of the reference range history in the two-dimensional plane, and the geometric relationship and series inversion of the first range migration curve are used to constrain and solve the unknown variables in the first range migration curve to obtain the second range migration curve of any receiving array in the platform.

[0058] If we ignore the curvature of the range migration curves of different receiving arrays and the differences in the reference array, we can directly use the translation of the reference range history within the two-dimensional plane as the first range migration curve of receiving array m. In other words, we use the first range migration curve of the receiving array with a non-zero baseline length in the platform as the translation of the reference range history within the two-dimensional plane.

[0059] As an embodiment, the first distance migration curve can be obtained based on the reference distance history and the translation amount. More specifically, the translation amounts of the reference distance history on the t-axis and the r-axis are d m / (2v) and ζ m , then the expression of the first distance migration curve can be: like Figure 3 The green curve in .

[0060] The beam center transit time of the first range migration curve may be obtained by adjusting the pulse repetition period and the platform movement speed, and obtaining the second beam center transit time based on the first beam center transit time.

[0061] Since the SAS platform is generally sampled uniformly along the azimuth direction, that is, the appropriate pulse repetition period and platform movement speed are adjusted so that the sampling interval between the receiving array m and the reference array is d m / (2v), that is, the second beam center crossing time of the receiving array m can be obtained.

[0062] As an embodiment, the second beam center passes through time t c,m The expression can be:

[0063] t c,m =t c,0 -d m / (2v);

[0064] Among them, t c,0 represents the first beam center crossing time; d m represents the baseline length from the mth receiving array to the transmitting array; v represents the platform movement speed.

[0065] It should be noted that a two-dimensional spectrum analytical expression can be directly obtained according to the first range migration curve, and then the imaging result can be obtained.

[0066] However, in actual SAS platforms, different receiving arrays have different squint angles for the echoes received from the same target. Even at the same azimuth interval, a receiving array with a larger squint angle will have a larger variation in range history. The variation in range history relative to azimuth time represents the slope of the range migration curve, or the degree of curvature. Therefore, in addition to using the first range migration curve of receiving array m as a reference for the two-dimensional translation of the array, the differences in the curvature of the first range migration curve should also be considered.

[0067] Since the degree of curvature is mainly determined by the square root term, the present invention modifies the first distance migration curve by introducing η m To change the curvature of the first distance migration curve, and then obtain the second distance migration curve; Figure 3 The blue curve in .

[0068] More specifically, the correction method includes: using the geometric relationship of the first range migration curve and series inversion to constrain and solve the unknown variables in the first range migration curve to obtain the second range migration curve of any receiving array in the platform.

[0069] The solution includes: listing a set of equations with the same number as the unknown variables; obtaining analytical expressions of the unknown variables through the set of equations, and then obtaining the second range migration curve.

[0070] As an embodiment, the expression R of the second range migration curve is m (t; r) is:

[0071]

[0072] Among them, m , γ m ,η m All represent unknown variables, which are obtained through constraint relationships; v represents the platform movement speed; t represents the orientation time; d m represents the baseline length from the mth receiving array to the transmitting array; r represents the vertical distance between the target and the track; c represents the speed of sound in water.

[0073] It should be noted that the unknown variable is the coefficient of the azimuth-time term in the first range migration curve, which is used to determine the translation of the first range migration curve in azimuth and range directions relative to the reference range history, as well as the degree of curvature relative to the reference range history.

[0074] From the expression of the second range migration curve R m (t; r) It can be seen that R m (t; r) contains only constant terms, square root terms with respect to t, and linear terms with respect to t, facilitating the subsequent azimuth FFT to obtain an analytical azimuth spectrum. Therefore, the constraint relationship can include that the derivatives of the second range migration curve and the derivatives of the precise range history of the receiving array relative to the target are equal at t = 0. In other words, for the precise range history and the second range migration curve containing unknown variables, the derivatives of both at the beam center are equal. The order of the expansion is determined by the number of unknown variables.

[0075] That is:

[0076] According to the constraint relationship, we can get the unknown variable ζ m , γ m ,η m .

[0077] More specifically, the unknown variable ζ m , γ m ,η m They are:

[0078]

[0079] Among them, d m represents the baseline length from the mth receiving array to the transmitting array; r represents the vertical distance between the target and the track; c represents the speed of sound in water; v represents the platform movement speed.

[0080] Series inversion includes fitting the second range migration curve using a set of basis functions.

[0081] It should be noted that the basis function can be {1,t,t 2 ,t 3 ,t 4}.

[0082] Since the second range migration curve is similar in form to the curve of the reference array distance history, preferably, the basis function is derived from the reference distance history of the reference array, which is Compared with the traditional basis function {1,t,t 2 ,t 3 ,t 4}, the improved one has better fitting effect.

[0083] Step 103: Obtain a two-dimensional spectrum analytical expression based on the second range migration curve, perform imaging on each array element individually, and obtain an imaging result after coherent superposition.

[0084] It should be noted that the derivation of the two-dimensional spectrum analytical expression is based on the second range migration curve, using the phase dwell principle and azimuth spectrum replication operation.

[0085] The spectrum replication operation is to complete the azimuth data to all sampling points to facilitate subsequent imaging processing of a single array element.

[0086] As an example, the two-dimensional spectrum analytical expression SS m (f r ,f a ; r) can be:

[0087]

[0088] Among them, W r(·) represents the spectrum envelope of the transmitted signal; f r Indicates the distance frequency; f a represents the Doppler frequency; f c represents the center frequency of the signal; v represents the platform movement speed; D T Indicates the size of the transmitting array; D R represents the receiving array size; c represents the speed of sound in water; j represents an imaginary number; r represents the vertical distance between the target and the track; represents the distance migration factor; d m represents the baseline length from the mth receiving array to the transmitting array; K r Indicates the frequency modulation slope.

[0089] Methods for obtaining the analytical expression of the two-dimensional spectrum include:

[0090] S111: Acquire the echo signal of the target P received by the mth receiving array, and obtain the phase of the two-dimensional spectrum based on the echo signal.

[0091] Among them, the baseband form of the echo signal of target P received by the mth receiving array can be expressed as:

[0092]

[0093] Among them, A0 represents the coefficient; w r (·) represents the envelope of the transmitted signal; τ represents the fast-changing time; R m (t; r) represents the second range migration curve; c represents the speed of sound in water; w a (·) represents the azimuth spectrum envelope; j represents an imaginary number; f c Indicates the signal center frequency; K r Indicates the frequency modulation slope.

[0094] In order to obtain the phase of the two-dimensional spectrum of the echo signal, a range-direction Fast Fourier Transform (FFT) is performed on the baseband form of the echo signal to obtain a range-frequency domain signal.

[0095] Range frequency domain signal Ss m (f r ,t;r) can be expressed as:

[0096]

[0097] Phase in the integral expression of the distance frequency domain signal for:

[0098]

[0099] According to the phase dwell principle, Then the range phase dwell time can be obtained.

[0100] Range phase dwell time τ PSP,m (f r ,t;r) can be expressed as:

[0101]

[0102] Based on the range-oriented phase dwell time τ PSP,m (f r ,t;r) and the phase in the integral expression of the range frequency domain signal The distance frequency domain signal Ss can be obtained m (f r ,t;r).

[0103] More specifically, τ PSP,m (f r ,t;r)Substitute In the equation, we get:

[0104]

[0105] Then further, the distance frequency domain signal Ss m (f r ,t;r) can be written as:

[0106]

[0107] Among them, W r (f r )=w r (f r / K r );w r (·) represents the envelope of the transmitted signal; f r Indicates the distance frequency; K r Indicates the frequency modulation slope.

[0108] In actual processing, SAS data is arranged in order of pulses. The number of pulses is Npulse. Each pulse is arranged in the order of array element numbers. The total number of azimuth sampling points is N. pulse ×(M1+M2+1), the number of opposite points is N pulse The azimuth FFT of the receiving array m data is obtained:

[0109]

[0110] Where, t = i·PRI; i = 1, 2, ..., N pulse , the echo signal of each receiving array is sampled at PRF, the azimuth sampling frequency

[0111] Due to PRF a ,so The two-dimensional spectrum of a single array element shown in is undersampled in azimuth, and the true azimuth frequency is aliased. Directly applying the imaging algorithm to it will seriously affect the imaging quality due to spectrum aliasing.

[0112] Therefore, the present invention will undersample The cycle is extended to the total number of sampling points Npulse×(M1+M2+1) to obtain the two-dimensional spectrum of the receiving array m. This is achieved by copying the data in azimuth. The specific expression is:

[0113]

[0114] Among them, f a ∈[-(M1+M2+1)·PRF / 2,(M1+M2+1)·PRF / 2]; REP(·) represents the azimuth matrix replication function, M1+M2+1 is the total number of receiving arrays, and represents the number of replications.

[0115] After this operation, the number of sampling points and the Doppler sampling frequency become M1+M2+1 times the original, and (M1+M2+1)×PRF≥B a Spectral aliasing can be removed by applying an imaging algorithm to the replicated two-dimensional spectra and then performing coherent superposition.

[0116] S112: Based on the second distance migration curve R m (t; r), distance frequency domain signal Ss m (f r ,t;r) and the number of opposite points is N pulse The expression for the azimuth FFT of the receiving array m data is Get the phase expression θ in the integral expression m (f r ,f a ; r, t).

[0117] The phase expression in the integral expression can be:

[0118] S113: Based on the phase dwell principle, let Get the phase dwell time t PSP,m ; and substitute the phase dwell time into the phase expression θ m (f r ,f a ; r, t), the two-dimensional spectrum analytical expression is obtained.

[0119] Wherein, the phase dwell time t PSP,m The expression can be ​

[0120] Since no approximations are made during the solution process, the two-dimensional spectrum is completely analytical and the most accurate. The range migration factor is element-dependent, so each element must be imaged separately and finally coherently superimposed to obtain the imaging result.

[0121] As an example, Figure 4 As shown in the figure, FFT stands for Fast Fourier Transform, and IFFT stands for Inverse Fast Fourier Transform. The imaging algorithm process includes 4 (M1+M2+1) Fourier transform / inverse transform operations and (M1+M2+1) interpolation operations.

[0122] Since the range migration factor is related to the array element, the array element number m and the azimuth frequency f a They are coupled, so single-station conversion cannot be performed to remove the element-dependent phase term.

[0123] Therefore, as an embodiment of the present invention, imaging is performed on each array element individually, and an imaging result is obtained after coherent superposition, including:

[0124] Multiple receiving array synthetic aperture sonars are regarded as multiple transmitting and receiving array pairs. A bistatic imaging algorithm is performed on each transmitting and receiving array pair. The two-dimensional spectrum analytical expression is Taylor expanded with respect to the range frequency and retained to the third order to obtain the imaging result of a single array element. The imaging result is obtained by superposition in the range Doppler domain or spatial domain to remove azimuth aliasing.

[0125] The two-dimensional spectrum analytical expression is Taylor expanded to the distance frequency and retained to the third order:

[0126]

[0127] The process of obtaining the imaging result of a single array element includes:

[0128] First, distance compression, quadratic distance compression term, and cubic term compensation are performed in the two-dimensional frequency domain.

[0129] The compensation filter can be:

[0130]

[0131] Among them, r ref The reference distance is usually the center of the surveying zone.

[0132] The signal expression after compensation can be:

[0133]

[0134] Then, the range is transformed into the range time domain through IFFT, and the linear phase of the range frequency is corrected using Singer interpolation.

[0135] The signal expression after interpolation can be:

[0136]

[0137] Finally, the azimuth compression filter is passed. The azimuth compression filter expression can be:

[0138]

[0139] Since the imaging results of a single sub-array are under-sampled in azimuth, it is also necessary to remove the azimuth aliasing of the focusing results in the range Doppler domain or spatial domain, such as Figure 5 and Figure 6 As shown, the final high-resolution imaging result is obtained.

[0140] On the other hand, the present invention provides a multi-receiving array synthetic aperture sonar imaging system, comprising a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of any one of the above methods.

[0141] The technical solution of the system is consistent with the technical solution of the method and will not be described in detail here.

[0142] It should be noted that for the aforementioned embodiments, for the sake of simplicity, they are all expressed as a series of action combinations, but those skilled in the art should be aware that this application is not limited to the order of the actions described. According to this application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in this specification are all preferred embodiments, and the actions and modules involved are not necessarily required by this application.

[0143] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, please refer to the relevant description of other embodiments. In the several embodiments provided in this application, it should be understood that the disclosed method or system can be implemented in other ways. For example, the embodiments described above are merely schematic. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed.

[0144] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0145] In addition, the functional units in the various embodiments of the present application may be integrated into a single processing unit, or each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0146] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable memory. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, which is stored in a memory and includes a number of instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application.

[0147] Those skilled in the art will appreciate that all or part of the various circuits in the above embodiments may be implemented by instructing related hardware through a program, and the program may be stored in a computer-readable memory, which may include a flash drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0148] The above is only an exemplary embodiment of the present disclosure and cannot be used to limit the scope of the present disclosure. That is, any equivalent changes and modifications made according to the teachings of the present disclosure are still within the scope of the present disclosure. After considering the specification and practicing the disclosure herein, those skilled in the art will easily think of the implementation scheme of the present disclosure. This application is intended to cover any variation, use or adaptation of the present disclosure, which follows the general principles of the present disclosure and includes common knowledge or customary technical means in the art that are not recorded in the present disclosure. The description and examples are to be regarded as exemplary only, and the scope and spirit of the present disclosure are defined by the claims.

[0149] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. As long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0150] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A multi-receiver array synthetic aperture sonar imaging method, characterized in that: The method comprises: A multi-receiving array synthetic aperture sonar platform is established, and the receiving array with zero baseline length in the platform is used as the reference array. The reference distance history of the reference array is calculated. A first range migration curve of a receiving array with a non-zero baseline length in the platform is used as a translation of the reference range history in a two-dimensional plane, and unknown variables in the first range migration curve are constrained and solved using geometric relationships and series inversion to obtain a second range migration curve for any receiving array in the platform. The expression of the second distance migration curve is for: ； in, 、 、 All represent unknown variables, and the unknown variables are obtained through constraint relationships; Indicates the platform movement speed; Indicates direction and time; Indicates the The baseline length from the receiving array to the transmitting array; Indicates the vertical distance between the target and the track; represents the speed of sound in water; A two-dimensional spectrum analytical expression is obtained based on the second range migration curve, and each array element is imaged separately, and an imaging result is obtained after coherent superposition; including: Treating multiple receiving array synthetic aperture sonars as multiple transmitting and receiving array pairs, performing a bistatic imaging algorithm on each transmitting and receiving array pair, performing Taylor expansion of the two-dimensional spectrum analytical expression with respect to range frequency and retaining it to the third order, and obtaining the imaging result of a single array element; The azimuth aliasing is removed by superposition in the range Doppler domain or spatial domain to obtain the imaging result.

2. The multi-receive array synthetic aperture sonar imaging method according to claim 1, characterized in that: The multi-receiving array synthetic aperture sonar platform includes a transmitting array and a plurality of evenly arranged receiving arrays.

3. The multi-receive array synthetic aperture sonar imaging method according to claim 1, characterized in that: The method for obtaining the first distance migration curve includes: obtaining the first distance migration curve based on the reference distance history and the translation amount.

4. The multi-receive array synthetic aperture sonar imaging method according to claim 1, characterized in that: The solution includes: listing a set of equations with the same number as the unknown variables; obtaining analytical expressions of the unknown variables through the set of equations, and then obtaining the second distance migration curve.

5. The multi-receive array synthetic aperture sonar imaging method according to claim 3, wherein: The series inversion includes: fitting the second range migration curve using a set of basis functions; wherein the basis functions are derived from the reference range history of the reference array.

6. The multi-receive array synthetic aperture sonar imaging method according to claim 1, wherein: The constraint relationship includes: the derivatives of each order of the second range migration curve and the derivatives of each order of the precise range history of the receiving array relative to the target, The values ​​at are equal.

7. The multi-receive array synthetic aperture sonar imaging method according to claim 6, characterized in that: The unknown variable 、 、 They are: ； in, Indicates the The baseline length from the receiving array to the transmitting array; Indicates the vertical distance between the target and the track; represents the speed of sound in water; Indicates the platform movement speed.

8. A multi-receiver array synthetic aperture sonar imaging system, comprising a memory, a processor, and a computer program stored in the memory, characterized in that: The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 7.

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