Receiving and transmitting combined synthetic aperture sonar distance stack imaging method, system and device

Abstract

The invention discloses a receiving and transmitting combined synthetic aperture sonar distance stack imaging method, system and device, and relates to the technical field of image processing, and the distance stack imaging method comprises the steps: calculating a two-way slant range course for a reference point target in an imaging region; calculating a reference echo signal of a reference point target based on the two-way slant range course and the parameters of the transmitted signal, and performing two-dimensional frequency domain transformation to obtain a reference frequency spectrum; two-dimensional frequency domain transformation is carried out on an original actually-measured echo signal of the receiving and transmitting combined synthetic aperture sonar to obtain an echo frequency spectrum, and conjugate multiplication is carried out on the echo frequency spectrum and a reference frequency spectrum in a two-dimensional frequency domain; coherent accumulation is carried out in a range direction frequency domain according to a conjugate multiplication result, and inverse Fourier transform is carried out in an azimuth direction; and processing the pixels at other distances in the imaging area according to the steps to obtain processing results of all the pixels in the whole imaging area, and carrying out carrier frequency removal on the basis to obtain an imaging result of the whole imaging area.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of image processing, in particular to a transmit-receive collocated synthetic aperture sonar range stack imaging method, system and device. BACKGROUND

[0002] The transmit-receive collocated synthetic aperture sonar virtually synthesizes a large aperture array based on a small aperture array moving at a constant speed in a straight line, thereby obtaining constant azimuth resolution independent of detection range and operating frequency. In order to simplify imaging processing, the traditional imaging algorithm generally makes an approximation that the transmit-receive collocated synthetic aperture sonar is stationary during signal transmission and echo reception, which is the so-called "stop-go-stop" approximation. In fact, the sonar cannot remain stationary during signal transmission and echo reception when it is working, but continuously moves at a constant speed in the azimuth direction. That is, the position of the sonar in the azimuth direction when receiving echoes is not the same as when transmitting signals. This position difference will cause changes in the Doppler and range migration of the echoes. If the traditional imaging algorithm based on the "stop-go-stop" approximation model is directly used for imaging processing, the Doppler and range migration errors caused by the position difference of the transmit-receive signal array elements are not compensated for, and when the imaging distance is far, the imaging result is not accurate enough, and even the imaging result may be distorted. SUMMARY

[0003] In view of the above technical problems, the present application provides a transmit-receive collocated synthetic aperture sonar range stack imaging method for imaging the echoes of a transmit-receive collocated synthetic aperture sonar, which comprises the following steps: S1, for a reference point target in the calculation imaging area with a distance coordinate of and an azimuth coordinate of 0, accurately calculating the two-way slant range history; S2, based on the accurately calculated two-way slant range history and the parameters of the transmitted signal, calculating the reference echo signal of the reference point target in step S1, and performing two-dimensional frequency domain transformation on the reference echo signal to obtain a reference spectrum; S3, performing two-dimensional frequency domain transformation on the original measured echo signal of the transmit-receive collocated synthetic aperture sonar to obtain an echo spectrum, and performing a conjugate multiplication operation on the echo spectrum and the reference spectrum in two-dimensional frequency domain; S4, for the conjugate multiplication result in step S3, performing a coherent accumulation operation in the range domain and an inverse Fourier transform operation in the azimuth direction; S5, for the pixels at other distances in the imaging area, processing according to the processing steps of steps S1, S2, S3 and S4, so as to obtain the processing results of all pixels in the entire imaging area, and then performing a de-chirp operation to obtain the imaging result of the entire imaging area.

[0004] Preferably, in step S1, it is assumed that the slow time of the transceiver combined synthetic aperture sonar in the azimuth direction is... The coordinates of any pixel in the imaging region in the distance direction are With the azimuth coordinate at 0, the tow velocity of the combined transceiver synthetic aperture sonar is... The coordinates of the combined transceiver synthetic aperture sonar in the azimuth direction are: The precise propagation time of the combined transmit and receive synthetic aperture sonar signal from transmission to reception is... During this time period, the distance the synthetic aperture sonar travels along the azimuth direction is... Calculate the distance between the transceiver synthetic aperture sonar at the moment of signal transmission and this pixel in the imaging region. The expression is Based on the precise propagation time of the synthetic aperture sonar signal from transmission to reception. Calculate the distance between the transceiver synthetic aperture sonar and this pixel in the imaging region at the moment of signal reception. The expression is This allows for the calculation of the precise two-way slant distance history. The expression is .

[0005] Preferably, in step S2, it is assumed that the transmitted signal is ,in For distance-to-time, precise two-way slant distance history. The corresponding latency is ,in Representing the speed of sound in water, the distance coordinate is... Echo signal of the reference point target with azimuth coordinate 0 It can be represented as: .

[0006] Preferably, in step S3, it is assumed that the original measured echo signal of the combined transceiver synthetic aperture sonar is The echo spectrum is obtained after performing a two-dimensional frequency domain transformation. , , Let represent the instantaneous frequency in the range direction and the Doppler frequency in the azimuth direction, respectively. The echo spectrum and the reference spectrum are multiplied by their conjugates in the two-dimensional frequency domain, and the expression is: Here, * indicates the reference spectrum in step S2. Perform the conjugate operation.

[0007] Preferably, in step S4, a coherent accumulation operation is performed in the range-direction frequency domain on the conjugate multiplication result from step S3, and the result after coherent accumulation... The expression is: Regarding the results after coherent accumulation Performing an inverse Fourier transform in the azimuth direction yields the range coordinates. Processing results of different pixels Its expression is: ,in, Indicates the target's coordinates in the azimuth direction. It represents the imaginary unit.

[0008] Preferably, in step S5, the processes of steps S1, S2, S3, and S4 are repeated, and in steps S1, S2, S3, and S4, the coordinates of the reference target in the imaging area in the range direction are updated to the corresponding coordinate values. To obtain the corresponding distance coordinate values The processing results By iteratively calculating the coordinate values ​​corresponding to all sampling gates along the distance direction according to the processing methods in steps S1, S2, S3, and S4, the processing result corresponding to the entire imaging area is obtained. Based on this result, carrier frequency removal processing is performed to obtain the final imaging result of the entire imaging area. Its expression is: , Indicates the carrier frequency.

[0009] According to another aspect of the present invention, the present invention provides a transceiver combined synthetic aperture sonar range stack imaging system for imaging the echoes of transceiver combined synthetic aperture sonar, the range stack imaging system comprising: A first calculation unit, wherein the first calculation unit is used to calculate the range coordinates of the imaging region. For a reference point target with an azimuth coordinate of 0, accurately calculate the two-way slant distance journey; A second calculation unit, wherein the second calculation unit is used to calculate the reference echo signal of the reference point target based on the accurately calculated two-way slant range history and the parameters of the transmitted signal; A first transformation unit, wherein the first transformation unit is used to perform a two-dimensional frequency domain transformation on the reference echo signal to obtain a reference spectrum; A second transformation unit, wherein the second transformation unit is used to perform two-dimensional frequency domain transformation on the original measured echo signal of the transceiver combined synthetic aperture sonar to obtain the echo spectrum; A conjugate multiplication unit, wherein the conjugate multiplication unit is used to perform a conjugate multiplication operation between the echo spectrum and the reference spectrum in the two-dimensional frequency domain, and obtain the conjugate multiplication result; a conjugate multiplication processing unit, wherein the conjugate multiplication processing unit is configured to perform a coherent accumulation operation on the conjugate multiplication result in the range frequency domain and an inverse Fourier transform operation in the azimuth direction; an imaging unit, wherein the imaging unit is configured to repeat the first calculation unit, the second calculation unit, the first transform unit, the second transform unit, the conjugate multiplication unit, and the conjugate multiplication result processing unit for pixels at other ranges in the imaging region to obtain processing results of all pixels in the imaging region, and perform a de-chirp operation based on the processing results to obtain an imaging result of the imaging region.

[0010] According to another aspect of the present application, the present application further provides a computing device comprising a processor and a memory, wherein computer program instructions are stored in the memory, and the computer program instructions, when executed in the processor, cause the processor to perform the following transceiver-compensated synthetic aperture sonar range stack imaging method: S1, for a reference point target in a calculation imaging region with a range coordinate of and an azimuth coordinate of 0, accurately calculating a two-way slant range history; S2, based on the accurately calculated two-way slant range history and parameters of a transmitted signal, calculating a reference echo signal of the reference point target in step S1, and performing a two-dimensional frequency domain transform on the reference echo signal to obtain a reference spectrum; S3, performing a two-dimensional frequency domain transform on an original measured echo signal of the transceiver-compensated synthetic aperture sonar to obtain an echo spectrum, and performing a conjugate multiplication operation on the echo spectrum and the reference spectrum in the two-dimensional frequency domain; S4, for the conjugate multiplication result in step S3, performing a coherent accumulation operation in the range frequency domain and an inverse Fourier transform operation in the azimuth direction; S5, for pixels at other ranges in the imaging region, performing processing according to the processing steps of steps S1, S2, S3, and S4 to obtain processing results of all pixels in the imaging region, and performing a de-chirp operation based on the processing results to obtain an imaging result of the imaging region.

[0011] Compared with the prior art, the present application has at least the following beneficial effects: compared with the traditional transceiver-compensated synthetic aperture sonar imaging method, the range stack imaging method of the present application compensates for the movement of the transceiver-compensated synthetic aperture sonar along the azimuth direction during transmission and reception of signals, so that targets in the entire imaging region can be completely focused, and the range stack imaging method of the present application can greatly improve the imaging efficiency of the transceiver-compensated synthetic aperture sonar. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1A flowchart of a range stacking imaging method of a transceiver collocated synthetic aperture sonar according to a preferred embodiment of the present application.

[0013] Figure 2 A spatial geometry between a transceiver collocated synthetic aperture sonar and a target in the range stacking imaging method according to the preferred embodiment of the present application.

[0014] Figure 3 An azimuth profile of imaging results of the range stacking imaging method according to the present application and a conventional range stacking imaging method.

[0015] Figure 4 A main lobe local enlarged view of the azimuth profile of imaging results of the range stacking imaging method according to the present application and a conventional range stacking imaging method.

[0016] Figure 5 A block diagram of a range stacking imaging system of a transceiver collocated synthetic aperture sonar according to a preferred embodiment of the present application.

[0017] Figure 6 A block diagram of a computing device according to a preferred embodiment of the present application.

[0018] In the drawings: 800, range stacking imaging system; 810, first computing unit; 820, second computing unit; 830, first transform unit; 840, second transform unit; 850, conjugate multiplication unit; 860, conjugate multiplication result processing unit; 870, imaging unit; 900, computing device; 910, processor; 920, memory; 930, input device; 940, output device. DETAILED DESCRIPTION

[0019] Before any embodiments of the application are explained in detail, it is to be understood that the application is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The application is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," or "having" and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms "mounted," "connected," "supported," and "coupled" and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, "connected" and "coupled" are not restricted to physical or mechanical connections or couplings.

[0020] And, in the disclosure of the application, the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, which are only for the convenience of describing the application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore the above terms cannot be understood as a limitation of the application; secondly, the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of one element can be one, and in another embodiment, the number of the element can be multiple, the term "one" cannot be understood as a limitation of the number.

[0021] Reference is made to the drawings accompanying the specification of the application Figure 1 A distance stack imaging method of a transceiver collocated synthetic aperture sonar according to a preferred embodiment of the application will be disclosed and described in the following description, which specifically includes the following steps: S1, accurately calculating the two-way slant range history for a reference point target in the calculation imaging area with a distance coordinate of 0 and a bearing coordinate of 0; S2, calculating the reference echo signal of the reference point target in step S1 based on the accurately calculated two-way slant range history and the parameters of the transmitted signal, and performing two-dimensional frequency domain transformation on the reference echo signal to obtain a reference spectrum; S3, performing two-dimensional frequency domain transformation on the original measured echo signal of the transceiver collocated synthetic aperture sonar to obtain an echo spectrum, and performing conjugate multiplication operation on the echo spectrum and the reference spectrum in two-dimensional frequency domain; S4, performing coherent accumulation operation in the distance domain and inverse Fourier transform operation in the bearing direction for the conjugate multiplication result in step S3; S5, processing the pixels at other distances in the imaging area according to the processing steps of steps S1, S2, S3 and S4, so as to obtain the processing results of all pixels in the entire imaging area, and then performing de-chirp operation to obtain the imaging results of the entire imaging area. The distance stack imaging method compensates for the movement along the bearing direction during the transmission and reception of the transceiver collocated synthetic aperture sonar, so that the targets in the entire imaging area can be completely focused. Moreover, the distance stack imaging method can greatly improve the imaging efficiency of the transceiver collocated synthetic aperture sonar.

[0022] Figure 2 The spatial geometry between the transceiver collocated synthetic aperture sonar and the target in the distance stack imaging method of the application, the axis is the distance direction, the axis is the bearing direction, and the black filled hexagonal star is a certain pixel in the imaging area along the distance direction, with a bearing coordinate of 0 and a distance coordinate of When the combined transceiver and synthetic aperture sonar is not in operation, its azimuth coordinate is 0, and its velocity... sports After a certain period of time, the azimuth coordinates of the combined transceiver synthetic aperture sonar are: The precise propagation time of the combined transmit and receive synthetic aperture sonar signal from transmission to reception is... During this time period, the distance traveled by the combined transceiver synthetic aperture sonar along the azimuth direction is... .

[0023] In step S1, for the distance coordinates in the calculated imaging region, In the section "Accurately Calculating the Two-Way Slant Range History for a Reference Point Target with Azimuth Coordinate of 0," it is assumed that the slow time of the combined transceiver synthetic aperture sonar in the azimuth direction is... The coordinates of any pixel in the imaging region in the distance direction are If the azimuth coordinate is 0, then calculate the distance between the transceiver synthetic aperture sonar at the moment of signal transmission and this pixel in the imaging region. The expression is Based on the precise propagation time of the signal from transmission to reception Calculate the distance between the transceiver synthetic aperture sonar and this pixel in the imaging region at the moment of signal reception. The expression is This allows for the calculation of the precise two-way slant distance history. The expression is .

[0024] In step S2, "Based on the precisely calculated two-way slant range history and the parameters of the transmitted signal, calculate the reference echo signal of the reference point target in step S1, and perform a two-dimensional frequency domain transformation on the reference echo signal to obtain the reference spectrum," it is assumed that the transmitted signal is... ,in, To determine the distance travel time, the accurate two-way slant distance history is obtained according to step S1. The corresponding latency is ,in, Representing the speed of sound in water, the distance coordinate is... Echo signal of the reference point target with azimuth coordinate 0 It can be represented as: Among them, the slow time for the azimuth direction is .right Perform a two-dimensional frequency domain transformation to obtain the reference spectrum. , , These represent the instantaneous frequency in the range direction and the Doppler frequency in the azimuth direction, respectively.

[0025] In step S3, the two-dimensional frequency domain transformation is performed on the raw measured echo signal of the transceiver collocated synthetic aperture sonar to obtain an echo spectrum, and the echo spectrum is conjugate multiplied with the reference spectrum in the two-dimensional frequency domain. After the two-dimensional frequency domain transformation, the echo spectrum is obtained , respectively represent the distance direction instantaneous frequency and the azimuth direction Doppler frequency, and the echo spectrum is conjugate multiplied with the reference spectrum in the two-dimensional frequency domain, and the expression is where * represents the conjugate operation on the reference spectrum in step S2.

[0026] In step S4, the coherent accumulation operation is performed on the conjugate multiplication result in step S3 in the distance direction frequency domain, and the inverse Fourier transform operation is performed in the azimuth direction, and the expression of the coherent accumulation result is wherein, is the coordinate of the target in the distance direction defined in step 1, , respectively represent the distance direction instantaneous frequency and the azimuth direction Doppler frequency.

[0027] The inverse Fourier transform is performed on the coherent accumulation result in the azimuth direction, and the processing result of different pixels with the distance direction coordinate value is obtained, and the expression is wherein, represents the coordinate of the target in the azimuth direction, represents the towing speed of the transceiver collocated synthetic aperture sonar, represents the imaginary unit.

[0028] In step S5, the processing steps of step S1, step S2, step S3, and step S4 are performed for the pixels at other distances in the imaging area, and the processing result of all pixels in the entire imaging area is obtained, and the de-chirp operation is performed on the basis of the imaging result of the entire imaging area. Repeating steps S1, S2, S3, and S4, and updating the coordinate of the reference target in the distance direction in the imaging area to the corresponding coordinate value in the processing of steps S1, S2, S3, and S4, to obtain the processing result on the corresponding distance coordinate value ​​​​​By iteratively calculating the coordinate values ​​corresponding to all sampling gates along the distance according to steps S1, S2, S3, and S4, the processing result corresponding to the entire imaging area is obtained. Based on this result, carrier frequency removal processing is performed to obtain the final imaging result of the entire imaging area. Its expression is: ,in, Indicates distance to fast time. Indicates the carrier frequency.

[0029] Assuming the tow speed of the combined transceiver synthetic aperture sonar (SAPS) is 0.125 m / s, the aperture of its array elements in the azimuth direction is 0.08 m, the center frequency of the transmitted linear frequency modulated (LFM) signal is 150 kHz, the bandwidth is 10 kHz, and the pulse repetition frequency is 6.25 Hz, and assuming an ideal point target exists in the scene with an azimuth aperture coordinate of 10 m and a range spatial coordinate of 111 m, the influence of the SAPS's azimuth motion during signal transmission and reception on the echo is considered. Echo simulation is performed, and based on this, both the traditional range stack imaging method (which does not consider the azimuth motion of the SAPS during signal transmission and reception) and the range stack imaging method described in this invention are used to image the simulated echo. Figure 3 An azimuth profile image obtained by imaging processing using a conventional range stacking method and the range stacking imaging method of the present invention, which do not consider the azimuth movement of the combined transceiver synthetic aperture sonar during signal transmission and reception. Figure 4 for Figure 3 A magnified view of a portion of the main lobe. From Figure 4 It can be clearly seen that the imaging results of traditional imaging methods have a small offset in the azimuth direction. This means that traditional imaging methods cannot accurately image the target, resulting in distortion of the focusing result. However, the distance stacking imaging method of the present invention can image the target more accurately without causing distortion of the focusing result, thus verifying that the distance stacking imaging method of the present invention can accurately focus the target within the imaging area.

[0030] Furthermore, comparing the range stack imaging method described in this invention with another transceiver combined synthetic aperture sonar time-domain point-by-point imaging method with better imaging effect, for 800 sampling points in the azimuth direction and 512 sampling points in the range direction, the range stack imaging method of this invention can obtain the imaging result in only 54s, while the time-domain point-by-point imaging method requires 46875s to obtain the imaging result. The range stack imaging method of this invention is about 868 times more efficient than the time-domain point-by-point imaging method, further verifying the high efficiency of the range stack imaging method of this invention.

[0031] Reference Appendix Figure 5 According to another aspect of the present invention, the present invention further provides a range stack imaging method system 800 for transceiver synthetic aperture sonar, used to image the echo of transceiver synthetic aperture sonar. The range stack imaging method system 800 includes a first calculation unit 810, a second calculation unit 820, a first transformation unit 830, a second transformation unit 840, a conjugate multiplication unit 850, a conjugate multiplication result processing unit 860, and an imaging unit 870. The first calculation unit 810, the second calculation unit 820, the first transformation unit 830, the second transformation unit 840, the conjugate multiplication unit 850, the conjugate multiplication result processing unit 860, and the imaging unit 870 cooperate with each other to compensate for the azimuthal motion of the transceiver synthetic aperture sonar during signal transmission and reception, thereby enabling the target within the entire imaging area to be fully focused.

[0032] Specifically, the first calculation unit 810 is used to calculate the range coordinates in the imaging region. The first calculation unit 820 is used to accurately calculate the two-way slant range history of a reference point target with an azimuth coordinate of 0. The second calculation unit 820 is used to calculate the reference echo signal of the reference point target based on the accurately calculated two-way slant range history and the parameters of the transmitted signal. The first transformation unit 830 is used to perform a two-dimensional frequency domain transformation on the reference echo signal to obtain a reference spectrum. The second transformation unit 840 is used to perform a two-dimensional frequency domain transformation on the original measured echo signal of the transceiver synthetic aperture sonar to obtain an echo spectrum. The conjugate multiplication unit 850 is used to perform a conjugate multiplication operation on the echo spectrum and the reference spectrum in the two-dimensional frequency domain to obtain the conjugate multiplication result. The conjugate multiplication result processing unit 860 is used to perform a coherent accumulation operation on the conjugate multiplication result in the range direction frequency domain and an inverse Fourier transform operation in the azimuth direction. The imaging unit 870 is used to repeatedly execute the first calculation unit 810, the second calculation unit 820, the first transformation unit 830, the second transformation unit 840, the conjugate multiplication unit 850, and the conjugate multiplication result processing unit 860 for pixels at other distances in the imaging area, so as to obtain the processing results of all pixels in the entire imaging area, and perform a carrier frequency removal operation on this basis to obtain the imaging result of the entire imaging area.

[0033] The first calculation unit 810 calculates the distance coordinate in the imaging region as follows: When accurately calculating the two-way slant range history for a reference point target with an azimuth coordinate of 0, it is assumed that the slow time of the combined transceiver synthetic aperture sonar in the azimuth direction is... The coordinates of any pixel in the imaging region in the distance direction are If the azimuth coordinate is 0, then calculate the distance between the transceiver synthetic aperture sonar at the moment of signal transmission and this pixel in the imaging region. The expression is Based on the precise propagation time of the signal from transmission to reception Calculate the distance between the transceiver synthetic aperture sonar and this pixel in the imaging region at the moment of signal reception. The expression is Therefore, the accurate two-way slant distance history can be calculated. The expression is .

[0034] When the second calculation unit 820 calculates the reference echo signal of the reference point target based on the accurately calculated two-way slant range history and the parameters of the transmitted signal, it assumes that the transmitted signal is... ,in For distance-to-time, precise two-way slant distance history. The corresponding latency is ,in To represent the speed of sound in water, the distance coordinate is... Echo signal of the reference point target with azimuth coordinate 0 It can be represented as: Among them, the slow time for the azimuth direction is .

[0035] When the first transformation unit 830 performs a two-dimensional frequency domain transformation on the reference echo signal to obtain the reference spectrum, the range coordinate is... Echo signal of the reference point target with azimuth coordinate 0 Perform a two-dimensional frequency domain transformation to obtain the reference spectrum. , , These represent the instantaneous frequency in the range direction and the Doppler frequency in the azimuth direction, respectively.

[0036] When the second transformation unit 840 performs a two-dimensional frequency domain transformation on the original measured echo signal of the transceiver synthetic aperture sonar to obtain the echo spectrum, it assumes that the original measured echo signal of the transceiver synthetic aperture sonar is... The echo spectrum is obtained after performing a two-dimensional frequency domain transformation. , , These represent the instantaneous frequency in the range direction and the Doppler frequency in the azimuth direction, respectively.

[0037] When the conjugate multiplication unit 850 performs a conjugate multiplication operation between the echo spectrum and the reference spectrum in the two-dimensional frequency domain, it performs a conjugate multiplication operation between the echo spectrum obtained by the second transformation unit 840 and the reference spectrum obtained by the first transformation unit 830 in the two-dimensional frequency domain to obtain the conjugate multiplication result, the expression of which is as follows: Here, * indicates the reference spectrum in step S2. Perform the conjugate operation.

[0038] When the conjugate multiplication result processing unit 860 performs a coherent accumulation operation in the range frequency domain and an inverse Fourier transform operation in the azimuth domain on the conjugate multiplication result, the result after coherent accumulation is... The expression is: ,in, The coordinates of any pixel in the imaging region defined by the first calculation unit 810 in the range direction, i.e., the coordinates of the target in the range direction. , These represent the instantaneous frequency in the range direction and the Doppler frequency in the azimuth direction, respectively.

[0039] The conjugate multiplication result processing unit 860 processes the result after coherent accumulation. Performing an inverse Fourier transform in the azimuth direction yields the range coordinates. Processing results of different pixels Its expression is: ,in, Indicates the target's coordinates in the azimuth direction. This indicates the tow velocity of the combined transmitting and receiving synthetic aperture sonar. It represents the imaginary unit.

[0040] When the imaging unit 870 "repeatedly executes the first calculation unit 810, the second calculation unit 820, the first transformation unit 830, the second transformation unit 840, the conjugate multiplication unit 850, and the conjugate multiplication result processing unit 860 for pixels at other distances in the imaging area to obtain the processing results of all pixels in the entire imaging area, and performs a carrier frequency removal operation on this basis to obtain the imaging result of the entire imaging area," the imaging unit 870 updates the coordinates of the reference target in the range direction in the imaging area to the corresponding coordinate values ​​for each processing step executed by the first calculation unit 810, the second calculation unit 820, the first transformation unit 830, the second transformation unit 840, the conjugate multiplication unit 850, and the conjugate multiplication result processing unit 860. To obtain the corresponding distance coordinate values The processing results For the coordinate values ​​corresponding to all sampling gates along the distance, iterative calculations are performed according to the processing steps of the first calculation unit 810, the second calculation unit 820, the first transformation unit 830, the second transformation unit 840, the conjugate multiplication unit 850, and the conjugate multiplication result processing unit 860 to obtain the processing result corresponding to the entire imaging area. Furthermore, based on this result, the imaging unit 870 performs carrier frequency removal processing to obtain the final imaging result of the entire imaging area. Its expression is: ,in, Indicates distance to fast time. Indicates the carrier frequency.

[0041] Reference Appendix Figure 6 According to another aspect of the present invention, the present invention further provides a computing device 900, wherein the computing device 900 includes a processor 910 and a memory 920, wherein computer program instructions are stored in the memory 920, and the computer program instructions, when executed in the processor 910, cause the processor 910 to execute a distance stack imaging method, wherein the distance stack imaging method includes the step: S1, calculating the distance coordinates in the imaging region as... S1. For the reference point target with azimuth coordinate 0, accurately calculate the two-way slant range history; S2. Based on the accurately calculated two-way slant range history and the parameters of the transmitted signal, calculate the reference echo signal of the reference point target in step S1, and perform a two-dimensional frequency domain transformation on the reference echo signal to obtain the reference spectrum; S3. Perform a two-dimensional frequency domain transformation on the original measured echo signal of the transceiver synthetic aperture sonar to obtain the echo spectrum, and perform a conjugate multiplication operation on the echo spectrum and the reference spectrum in the two-dimensional frequency domain; S4. For the conjugate multiplication result in step S3, perform a coherent accumulation operation in the range frequency domain, and perform an inverse Fourier transform operation in the azimuth direction; S5. For the pixels at other distances in the imaging area, process them according to the processing steps of steps S1, S2, S3, and S4 to obtain the processing results of all pixels in the entire imaging area. On this basis, perform a carrier frequency removal operation to obtain the imaging result of the entire imaging area. The range stack imaging method compensates for azimuthal motion during the transmission and reception of synthetic aperture sonar signals, thereby enabling the target to be fully focused throughout the imaging area.

[0042] In one embodiment of the computing device 900 of the present invention, the memory 920 may include one or more computer program products, which may include various forms of computer-readable storage media, such as volatile memory and / or non-volatile memory. The volatile memory may, for example, include random access memory (RAM) and / or cache memory. The non-volatile memory may, for example, include read-only memory (ROM), hard disk, flash memory, etc. One or more computer program instructions may be stored on the computer-readable storage medium, and the processor 910 may execute the program instructions to implement the function of the distance stack imaging method of the present invention described above.

[0043] In one embodiment of the computing device 900 of the present invention, the processor 910 may be a central processing unit (CPU) or other form of processing unit with data processing capability and / or instruction execution capability, which can run the program instructions stored on the computer-readable storage medium to realize the function of the distance stack imaging method of the present invention described above.

[0044] In one embodiment of the computing device 900 of the present invention, the computing device 900 may further include an input device 930 and an output device 940. The input device 930 may be, but is not limited to, a keyboard or a mouse, and the output device 940 may be, but is not limited to, a display, a speaker or a printer. The input device 930 and the output device 940 may be connected to the processor 910 via a bus system.

[0045] Those skilled in the art should understand that the embodiments described above and illustrated in the figures are merely illustrative of the invention and not intended to limit it. All equivalent implementations, modifications, and improvements within the spirit of this invention should be included within the scope of protection of this invention.

Claims

1. A range stack imaging method for transceiver synthetic aperture sonar, used for imaging the echoes of transceiver synthetic aperture sonar, characterized in that, The distance stack imaging method includes the following steps: S1, for calculating the range coordinates in the imaging region, For a reference point target with an azimuth coordinate of 0, accurately calculate the two-way slant distance journey; S2, based on the accurately calculated two-way slant range history and the parameters of the transmitted signal, calculate the reference echo signal of the reference point target in step S1, and perform a two-dimensional frequency domain transformation on the reference echo signal to obtain the reference spectrum. S3, perform a two-dimensional frequency domain transformation on the original measured echo signal of the transceiver synthetic aperture sonar to obtain the echo spectrum, and perform a conjugate multiplication operation between the echo spectrum and the reference spectrum in the two-dimensional frequency domain. S4. For the conjugate multiplication result in step S3, perform coherent accumulation in the frequency domain of the range direction and inverse Fourier transform in the azimuth direction. S5. For pixels at other distances in the imaging area, process them according to the processing steps of S1, S2, S3 and S4 to obtain the processing results of all pixels in the entire imaging area. On this basis, perform carrier frequency removal operation to obtain the imaging result of the entire imaging area.

2. The transceiver combined synthetic aperture sonar range stack imaging method according to claim 1, characterized in that, In step S1, it is assumed that the slow time of the transceiver combined synthetic aperture sonar in the azimuth direction is... The coordinates of any pixel in the imaging region in the distance direction are With the azimuth coordinate at 0, the tow velocity of the combined transceiver synthetic aperture sonar is... The coordinates of the combined transceiver synthetic aperture sonar in the azimuth direction are: The precise propagation time of the combined transmit and receive synthetic aperture sonar signal from transmission to reception is... During this time period, the distance traveled by the combined transceiver synthetic aperture sonar along the azimuth direction is... Calculate the distance between the transceiver synthetic aperture sonar at the moment of signal transmission and this pixel in the imaging region. The expression is Based on the precise propagation time of the signal from transmission to reception Calculate the distance between the transceiver synthetic aperture sonar and this pixel in the imaging region at the moment of signal reception. The expression is This allows for the calculation of the precise two-way slant distance history. The expression is .

3. The transceiver combined synthetic aperture sonar range stack imaging method according to claim 2, characterized in that, In step S2, assume the transmitted signal is ,in For distance-to-time, precise two-way slant distance history. The corresponding latency is ,in To represent the speed of sound in water, the distance coordinate is... Echo signal of the reference point target with azimuth coordinate 0 Represented as: .

4. The transceiver combined synthetic aperture sonar range stack imaging method according to claim 3, characterized in that, In step S3, it is assumed that the original measured echo signal of the combined transceiver synthetic aperture sonar is The echo spectrum is obtained after performing a two-dimensional frequency domain transformation. , , Let represent the instantaneous frequency in the range direction and the Doppler frequency in the azimuth direction, respectively. The echo spectrum and the reference spectrum are multiplied by their conjugates in the two-dimensional frequency domain, and the expression is: Here, * indicates the reference spectrum. Perform the conjugate operation.

5. The transceiver combined synthetic aperture sonar range stack imaging method according to claim 4, characterized in that, In step S4, the conjugate multiplication result from step S3 is coherently accumulated in the range-direction frequency domain. The result after coherent accumulation... The expression is: Regarding the results after coherent accumulation Performing an inverse Fourier transform in the azimuth direction yields the range coordinates. Processing results of different pixels Its expression is: ,in, Indicates the target's coordinates in the azimuth direction. It represents the imaginary unit.

6. The transceiver combined synthetic aperture sonar range stack imaging method according to claim 5, characterized in that, In step S5, the processes of steps S1, S2, S3, and S4 are repeated, and in steps S1, S2, S3, and S4, the coordinates of the reference target in the imaging area in the range direction are updated to the corresponding coordinate values. To obtain the corresponding distance coordinate values The processing results By iteratively calculating the coordinate values ​​corresponding to all sampling gates along the distance according to steps S1, S2, S3, and S4, the processing result corresponding to the entire imaging area is obtained. Based on this result, carrier frequency removal processing is performed to obtain the final imaging result of the entire imaging area. Its expression is: , Indicates the carrier frequency.

7. A transceiver combined synthetic aperture sonar range stack imaging system, used for imaging the echoes of transceiver combined synthetic aperture sonar, characterized in that, include: A first calculation unit, wherein the first calculation unit is used to calculate the range coordinates of the imaging region. For a reference point target with an azimuth coordinate of 0, accurately calculate the two-way slant distance journey; A second calculation unit, wherein the second calculation unit is used to calculate the reference echo signal of the reference point target based on the accurately calculated two-way slant range history and the parameters of the transmitted signal; A first transformation unit, wherein the first transformation unit is used to perform a two-dimensional frequency domain transformation on the reference echo signal to obtain a reference spectrum; A second transformation unit, wherein the second transformation unit is used to perform two-dimensional frequency domain transformation on the original measured echo signal of the transceiver combined synthetic aperture sonar to obtain the echo spectrum; A conjugate multiplication unit, wherein the conjugate multiplication unit is used to perform a conjugate multiplication operation between the echo spectrum and the reference spectrum in the two-dimensional frequency domain, and obtain the conjugate multiplication result; A conjugate multiplication processing unit, wherein the conjugate multiplication processing unit is used to perform a coherent accumulation operation on the conjugate multiplication result in the range frequency domain and an inverse Fourier transform operation in the azimuth direction; An imaging unit is provided, wherein the imaging unit is used to repeatedly execute the first calculation unit, the second calculation unit, the first transformation unit, the second transformation unit, the conjugate multiplication unit, and the conjugate multiplication result processing unit for pixels at other distances in the imaging region, so as to obtain the processing results of all pixels in the entire imaging region, and perform a carrier frequency removal operation on this basis to obtain the imaging result of the entire imaging region.

8. The transceiver combined synthetic aperture sonar range stack imaging system according to claim 7, characterized in that, The first calculation unit calculates the range coordinates of the imaging region as follows: When accurately calculating the two-way slant range history for a reference point target with an azimuth coordinate of 0, it is assumed that the slow time of the combined transceiver synthetic aperture sonar in the azimuth direction is... The coordinates of any pixel in the imaging region in the distance direction are With the azimuth coordinate at 0, the tow velocity of the combined transceiver synthetic aperture sonar is... Calculate the distance between the transceiver synthetic aperture sonar at the moment of signal transmission and this pixel in the imaging region. The expression is Based on the precise propagation time of the signal from transmission to reception Calculate the distance between the transceiver synthetic aperture sonar and this pixel in the imaging region at the moment of signal reception. The expression is This allows for the calculation of the precise two-way slant distance history. The expression is .

9. The transceiver combined synthetic aperture sonar range stack imaging system according to claim 8, characterized in that, When the second calculation unit calculates the reference echo signal of the reference point target based on the accurately calculated two-way slant range history and the parameters of the transmitted signal, it assumes that the transmitted signal is... ,in, For distance-to-time, precise two-way slant distance history. The corresponding latency is ,in, Representing the speed of sound in water, the distance coordinate is... Echo signal of the reference point target with azimuth coordinate 0 Represented as: .

10. A computing device, characterized in that, It includes a processor and a memory, wherein computer program instructions are stored in the memory, and when the computer program instructions are executed in the processor, the processor causes the processor to perform the transceiver combined synthetic aperture sonar range stack imaging method as described in any one of claims 1 to 6.

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