Time-domain point-by-point imaging method, system and apparatus for a transceiver integrated synthetic aperture sonar

Abstract

The application discloses a time-domain point-by-point imaging method, system and device of a transceiver combined synthetic aperture sonar, and the time-domain point-by-point imaging method comprises the following steps: for any pixel in an imaging area, calculating a synthetic aperture length and a synthetic aperture time; calculating a distance between a sonar at a signal transmitting time and the pixel, and calculating a distance between a sonar at a signal receiving time and the pixel to obtain an accurate two-way slant range history; according to the two-way slant range history and relevant parameters of the signal, calculating a reference echo signal corresponding to the pixel; performing distance domain transformation on a measured echo signal and a reference echo signal, and performing conjugate multiplication processing on the transformed results; coherently accumulating all the conjugate multiplication results as an imaging result of the pixel; and repeating the above steps for other pixels in the imaging area to obtain imaging results of all the pixels in the entire imaging area.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of image processing, in particular to a time-domain point-by-point imaging method, system and device for a transceiver collocated synthetic aperture sonar, wherein the method fully considers the influence of the motion along the azimuth direction during the transmission and reception of the transceiver collocated synthetic aperture sonar, can fully focus all pixels in the entire imaging area, and thus can improve the target focusing quality in the entire imaging area. BACKGROUND

[0002] The transceiver collocated synthetic aperture sonar uses one array element to simultaneously realize the transmission and reception of signals, has a relatively simple principle, and is an important tool for obtaining underwater information. The imaging algorithm is an important step of the transceiver collocated synthetic aperture sonar, mainly inverts the strength of the target reflection characteristics according to the received echo signal to realize imaging, and the time-domain point-by-point imaging method first simulates a reference echo signal for each pixel in the imaging area, and then obtains a focusing result according to a correlation processing method. In actual processing, the correlation processing can be realized by frequency domain conjugate multiplication, so that the correlation processing can be efficiently realized. The time-domain point-by-point imaging method does not sample any approximation and can obtain a relatively accurate imaging result, which can be used as an evaluation standard for other imaging methods. At the same time, since the time-domain point-by-point imaging method is realized in the azimuth direction, it can be conveniently combined with inertial navigation data to realize the compensation of motion errors, and is a very valuable method. However, the traditional time-domain point-by-point imaging method does not consider the influence of the motion along the azimuth direction during the transmission and reception of the transceiver collocated synthetic aperture sonar. Since the distance focusing step and the azimuth focusing of the time-domain point-by-point imaging method are completed at the same time, the problem of ignoring the motion along the azimuth direction during the transmission and reception of the transceiver collocated synthetic aperture sonar will affect the distance focusing and the azimuth focusing, and finally make the target completely defocused, thereby affecting the detection, classification and identification of the target, and being not conducive to the interpretation of the transceiver collocated synthetic aperture sonar image. SUMMARY

[0003] In view of the above technical problems, the present application provides a time-domain point-by-point imaging method for a transceiver collocated synthetic aperture sonar, which fully considers the influence of the motion along the azimuth direction during the transmission and reception of the transceiver collocated synthetic aperture sonar, and can accurately image the target, wherein the time-domain point-by-point imaging method comprises the following steps:

[0004] S1, for any pixel in the imaging area, calculating the synthetic aperture length and the synthetic aperture time according to the main lobe width of the transceiver collocated synthetic aperture sonar and the distance of the target;

[0005] S2, for any pixel in the imaging region assumed in step S1, within the beam illumination range at the time of transmitting the signal from the combined synthetic aperture sonar, calculate the distance between the combined synthetic aperture sonar and the pixel in the imaging region at the time of transmitting the signal. Within the beam illumination range at the time of receiving the signal, calculate the distance between the combined synthetic aperture sonar and the pixel in the imaging region at the time of receiving the signal based on the precise propagation time of the signal from transmission to reception, thereby obtaining the precise two-way slant range history.

[0006] S3. Based on the calculated accurate two-way slant range history and the relevant parameters of the transmitted signal, for any pixel in the imaging area assumed in step S1, within the beam illumination range at the time of transmitting the signal and the time of receiving the signal, calculate the reference echo signal corresponding to this pixel.

[0007] S4, perform range-to-frequency domain transformation on the acquired synthetic aperture sonar measured echo signal and perform range-to-frequency domain transformation on the simulated reference echo signal in step S3. Then, for any pixel in the imaging area assumed in step S1, within the beam illumination range at the time of transmitting and receiving signals, perform conjugate multiplication between the result of range-to-frequency domain transformation of the measured echo signal and the result of range-to-frequency domain transformation of the simulated reference echo signal.

[0008] S5, coherently accumulate the results of multiplying all conjugates within the beam illumination range at the time of transmitting and receiving signals, and use them as the imaging result of that pixel;

[0009] S5. For the other pixels in the imaging area, process them according to the processing steps of S1, S2, S3, S4 and S5 to obtain the imaging result of all pixels in the entire imaging area.

[0010] In step S1, for any pixel in the imaging area, the synthetic aperture length and synthetic aperture time are calculated based on the main lobe width of the transceiver synthetic aperture sonar and the distance to the target; assuming the target's distance in the range direction is... The main lobe width of the combined transceiver synthetic aperture sonar is Then the synthetic aperture length corresponding to the target The expression is Assuming the towing speed of the combined transceiver synthetic aperture sonar is... Then the corresponding synthesis aperture time The expression is: .

[0011] In step S2, for any pixel in the imaging region assumed in step S1, within the beam illumination range at the time of transmission of the combined transceiver synthetic aperture sonar, the distance between the combined transceiver synthetic aperture sonar and this pixel in the imaging region is calculated. Within the beam illumination range at the time of reception, based on the precise propagation time of the signal from transmission to reception, the distance between the combined transceiver synthetic aperture sonar and this pixel in the imaging region at the time of reception is calculated, thus obtaining the precise two-way slant range history; assuming the slow time of the combined transceiver synthetic aperture sonar in the azimuth direction is... Assume that the coordinates of any pixel in the imaging region in the distance direction are... The coordinates in the azimuth direction are Therefore, within the beam illumination range at the time of transmitting and receiving the combined synthetic aperture sonar signal, the azimuth coordinates of any pixel in the imaging region assumed in step S1 during the transmission and reception of the combined synthetic aperture sonar signal are... Combined with the time, azimuth, and coordinates of the transmitted signal of the synthetic aperture sonar Satisfying the relation Calculate the distance between the transceiver synthetic aperture sonar and this pixel in the imaging region at the moment of signal transmission. The expression is The azimuth coordinates of any pixel in the imaging region assumed in step S1 when the transceiver synthetic aperture sonar is within the beam illumination range at the time of signal reception. Azimuth coordinates of the transceiver combined synthetic aperture sonar at the time of signal reception Satisfying the relation 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 leads to the accurate two-way slant distance history. The expression is .

[0012] In step S3, based on the calculated precise two-way slant range history and the relevant parameters of the transmitted signal, for any pixel in the imaging region assumed in step S1, within the beam illumination range at the time of transmitting and receiving the signal, the reference echo signal corresponding to that pixel is calculated; within the beam illumination range at the time of transmitting and receiving the signal, the azimuth coordinates of any pixel in the imaging region assumed in step S1 and the azimuth coordinates of the transceiver synthetic aperture sonar simultaneously satisfy the following relationship: At that time, the expression for the reference echo signal corresponding to this pixel is:

[0013] ,

[0014] Here, denotes the logical AND, is the accurate two-way slant range history calculated in step S2, denotes the center frequency of the transmitted signal, denotes the range fast time, denotes the azimuth slow time, denotes the frequency modulation of the transmitted linear frequency modulation signal, denotes the sound speed in water, denotes the imaginary unit.

[0015] In the step S4, the collected transceiver array synthetic aperture sonar measured echo signal is subjected to range frequency domain transformation, and the step S3 reference echo signal is subjected to range frequency domain transformation, and then for any pixel in the imaging area assumed in the step S1, the conjugate multiplication processing is performed between the result of the range frequency domain transformation of the measured echo signal and the result of the range frequency domain transformation of the simulated reference echo signal in the beam illumination range at the transmission signal time and the reception signal time; the results of all the conjugate multiplications in the beam illumination range at the transmission signal time and the reception signal time are coherently accumulated as the imaging result of the pixel; assuming is the collected transceiver array synthetic aperture sonar measured echo signal, the result of the range frequency domain transformation is ; and the result of the range frequency domain transformation of the step S3 simulated reference echo signal is , so the result of the conjugate multiplication processing is , here denotes the conjugate operation on the result of the frequency domain transformation of the step S3 simulated reference echo signal.

[0016] In the step S5, when the azimuth coordinates of any pixel in the imaging area assumed in the step S1 and the azimuth coordinates of the transceiver array synthetic aperture sonar at the transmission signal time and the reception signal time simultaneously satisfy the relationship , the coherent accumulation of all the conjugate multiplications obtains the imaging result of the pixel, the expression is:

[0017] ,

[0018] Here, is the accumulation, denotes the azimuth slow time, denotes the range fast time.

[0019] In the step S6, for other pixels in the imaging region, the processing steps of the step S1, the step S2, the step S3, the step S4 and the step S5 are performed, and the imaging results of all pixels in the whole imaging region are obtained.

[0020] Preferably, for each processing step of the step S1, the step S2, the step S3, the step S4 and the step S5, the coordinates of the pixel in the imaging region in the range direction and the azimuth direction are updated to the corresponding coordinate values of the new pixel, so as to obtain the imaging result of the new pixel.

[0021] According to another aspect of the present application, the present application further provides a time-domain point-by-point imaging system of a transceiver combined synthetic aperture sonar, for imaging the echo of the transceiver combined synthetic aperture sonar, wherein the time-domain point-by-point imaging system comprises:

[0022] a first calculation unit, for calculating the synthetic aperture length and the synthetic aperture time according to the main lobe width of the transceiver combined synthetic aperture sonar and the distance of the target, for any pixel in the imaging region;

[0023] a second calculation unit, for calculating the distance between the transceiver combined synthetic aperture sonar and the pixel in the imaging region at the signal transmission time within the beam illumination range at the signal transmission time, and calculating the distance between the transceiver combined synthetic aperture sonar and the pixel in the imaging region at the signal receiving time according to the accurate propagation time of the signal from the transmission to the reception, at the signal receiving time within the beam illumination range, so as to obtain the accurate two-way slant range history, for any pixel in the assumed imaging region;

[0024] a simulation unit, for calculating the reference echo signal corresponding to the pixel at the signal transmission time and the signal receiving time within the beam illumination range, according to the accurate two-way slant range history calculated by the second calculation unit and the related parameters of the transmitted signal, for any pixel in the assumed imaging region;

[0025] a conjugate multiplication processing unit, for performing the distance direction frequency domain transformation on the collected actual echo signal of the transceiver combined synthetic aperture sonar and the reference echo signal simulated by the simulation unit, and then performing the conjugate multiplication processing on the result of the distance direction frequency domain transformation of the actual echo signal and the result of the distance direction frequency domain transformation of the simulated reference echo signal, for any pixel in the assumed imaging region at the signal transmission time and the signal receiving time within the beam illumination range;

[0026] a coherent accumulation unit, for coherently accumulating all the conjugate multiplication results at the signal transmission time and the signal receiving time within the beam illumination range, as the imaging result of the pixel;

[0027] An imaging unit is used to repeatedly execute the first calculation unit, the second calculation unit, the simulation unit, the conjugate multiplication processing unit, and the coherent accumulation unit for other pixels in the imaging region to obtain the imaging results of all pixels in the entire imaging region.

[0028] Preferably, it is assumed that the target's distance in the range direction is... The main lobe width of the combined transceiver synthetic aperture sonar is The synthetic aperture length corresponding to this target The expression is Assuming the towing speed of the combined transceiver synthetic aperture sonar is... The corresponding synthesis aperture time The expression is .

[0029] Preferably, it is assumed that the slow time of the combined transceiver synthetic aperture sonar in the azimuth direction is... Assume that the coordinates of any pixel in the imaging region in the distance direction are... The coordinates in the azimuth direction are Within the beam illumination range at the time of transmitting and receiving the combined synthetic aperture sonar signal, the azimuth coordinates of any pixel in the assumed imaging region during the transmission and reception of the combined synthetic aperture sonar signal are... Combined with the time, azimuth, and coordinates of the transmitted signal of the synthetic aperture sonar Satisfying the relation Calculate the distance between the transceiver synthetic aperture sonar and this pixel in the imaging region at the moment of signal transmission. The expression is The azimuth coordinates of any pixel in the assumed imaging region at the time of signal reception by the combined transceiver synthetic aperture sonar within the beam illumination range. Azimuth coordinates of the transceiver combined synthetic aperture sonar at the time of signal reception Satisfying the relation 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 To obtain the accurate two-way slant distance history The expression is .

[0030] 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 a time-domain point-by-point imaging method, wherein the time-domain point-by-point imaging method comprises the following steps:

[0031] S1, for any pixel in the imaging region, according to the main lobe width of the transceiver array synthetic aperture sonar, the distance of the target, the synthetic aperture length and the synthetic aperture time are calculated;

[0032] S2, for any pixel in the imaging region assumed in the step S1, in the beam illumination range at the signal transmission time of the transceiver array synthetic aperture sonar, the distance between the transceiver array synthetic aperture sonar and the pixel in the imaging region at the signal transmission time is calculated, and in the beam illumination range at the signal receiving time, according to the accurate propagation time of the signal from transmission to reception, the distance between the transceiver array synthetic aperture sonar and the pixel in the imaging region at the signal receiving time is calculated, and then the accurate two-way slant range history is obtained;

[0033] S3, according to the calculated accurate two-way slant range history and the related parameters of the transmitted signal, for any pixel in the imaging region assumed in the step S1, the reference echo signal corresponding to the pixel is calculated in the beam illumination range at the signal transmission time and the signal receiving time;

[0034] S4, the collected transceiver array synthetic aperture sonar measured echo signal is transformed into frequency domain in distance direction, and the reference echo signal simulated in the step S3 is transformed into frequency domain in distance direction, and then for any pixel in the imaging region assumed in the step S1, the conjugate multiplication processing is performed between the result of the distance direction frequency domain transformation of the measured echo signal and the result of the distance direction frequency domain transformation of the simulated reference echo signal in the beam illumination range at the signal transmission time and the signal receiving time;

[0035] S5, the results of all the conjugate multiplications in the beam illumination range at the signal transmission time and the signal receiving time are coherently accumulated as the imaging result of the pixel;

[0036] S6, for other pixels in the imaging region, the processing steps of the step S1, the step S2, the step S3, the step S4 and the step S5 are performed, and the imaging results of all the pixels in the entire imaging region are obtained.

[0037] Compared with the prior art, the application has at least the following beneficial effects: compared with the traditional transceiver collocation synthetic aperture sonar imaging method, the time domain point-by-point imaging method proposed by the application fully considers the influence of the motion along the azimuth direction during the transceiver signal transmission and reception of the transceiver collocation synthetic aperture sonar, can accurately image the target, and will not cause the problem of target defocusing. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 A flowchart of a time domain point-by-point imaging method of a transceiver collocation synthetic aperture sonar according to a preferred embodiment of the application.

[0039] Figure 2 A spatial geometry between the transceiver collocation synthetic aperture sonar and the target in the time domain point-by-point imaging method according to the preferred embodiment of the application.

[0040] Figure 3 An imaging result of a traditional time domain point-by-point imaging method.

[0041] Figure 4 An imaging result of the time domain point-by-point imaging method according to the preferred embodiment of the application.

[0042] Figure 5 An azimuth profile of the imaging results of the traditional time domain point-by-point imaging method and the time domain point-by-point imaging method according to the application.

[0043] Figure 6 A main lobe local enlarged view of Figure 5 .

[0044] Figure 7 A range profile of the imaging results of the traditional time domain point-by-point imaging method and the time domain point-by-point imaging method according to the application.

[0045] Figure 8 A block diagram of a time domain point-by-point imaging system of a transceiver collocation synthetic aperture sonar according to a preferred embodiment of the application.

[0046] Figure 9 A block diagram of a computing device according to a preferred embodiment of the application.

[0047] In the drawings:

[0048] 800, time domain point-by-point imaging system; 810, first computing unit; 820, second computing unit; 830, simulation unit; 840, conjugate multiplication processing unit; 850, coherent accumulation unit; 860, imaging unit;

[0049] 900, computing device; 910, processor; 920, memory; 930, input device; 940, output device. DETAILED DESCRIPTION

[0050] 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 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.

[0051] Also, in the disclosure of the present application, the terms "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, which are only for the convenience of describing the present 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, and therefore the above terms cannot be understood as limiting the present application. In the second aspect, 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, and the term "one" cannot be understood as limiting the number.

[0052] Reference is made to the accompanying drawings that form a part of this specification Figure 1A time-domain point-by-point imaging method of a transceiver combined synthetic aperture sonar according to a preferred embodiment of the present application will be disclosed and described in the following description, wherein the specific steps of the time-domain point-by-point imaging method include: S1, for any pixel in an imaging area, calculating a synthetic aperture length and a synthetic aperture time according to a main lobe width of the transceiver combined synthetic aperture sonar and a target distance; S2, for any pixel in the imaging area assumed in the step S1, calculating a distance between the transceiver combined synthetic aperture sonar and the pixel in the imaging area at a signal transmitting time within a beam illumination range at the signal transmitting time, and calculating a distance between the transceiver combined synthetic aperture sonar and the pixel in the imaging area at a signal receiving time within a beam illumination range at the signal receiving time according to an accurate signal propagation time from the signal transmitting to the signal receiving, and then obtaining an accurate two-way slant range history; S3, according to the calculated accurate two-way slant range history and related parameters of the transmitted signal, for any pixel in the imaging area assumed in the step S1, calculating a reference echo signal corresponding to the pixel at the signal transmitting time and the signal receiving time within the beam illumination range; S4, performing distance domain transformation on collected actual echo signals of the transceiver combined synthetic aperture sonar and on the reference echo signal simulated in the step S3, and then for any pixel in the imaging area assumed in the step S1, performing conjugate multiplication processing on the result of the distance domain transformation of the actual echo signal and the result of the distance domain transformation of the simulated reference echo signal at the signal transmitting time and the signal receiving time within the beam illumination range; S5, performing coherent accumulation on all conjugate multiplication results at the signal transmitting time and the signal receiving time within the beam illumination range as an imaging result of the pixel; S6, for other pixels in the imaging area, performing processing according to the processing steps of the step S1, the step S2, the step S3, the step S4 and the step S5, and then obtaining imaging results of all pixels in the entire imaging area. The time-domain point-by-point imaging method proposed in the present application fully considers the influence of the motion along the azimuth direction during the signal transmission and reception of the transceiver combined synthetic aperture sonar, can accurately image the target, and will not cause target defocusing problems.

[0053] Figure 2 The spatial geometry between the transceiver combined synthetic aperture sonar and the target in the time-domain point-by-point imaging method of the present application, wherein the axis is the distance direction, the axis is the azimuth direction, the black filled hexagonal star is a certain pixel in the imaging area, the coordinate of which in the azimuth direction is the coordinate of which in the distance direction is the coordinate of the transceiver combined synthetic aperture sonar in the azimuth direction is 0 when the transceiver combined synthetic aperture sonar is not working, and after time, the coordinate of the transceiver combined synthetic aperture sonar in the azimuth direction is The coordinates of the moving synthetic aperture sonar in the azimuth direction are: The precise propagation time of the signal from the transceiver combined synthetic aperture sonar from transmission to reception is... During this time period, the distance traveled by the combined transceiver synthetic aperture sonar along the azimuth direction is... .

[0054] In step S1, "For any pixel in the imaging region, calculate the synthetic aperture length and synthetic aperture time based on the main lobe width of the transceiver synthetic aperture sonar and the distance to the target," it is assumed that the target's distance in the range direction is... The main lobe width of the combined transceiver synthetic aperture sonar is Then the synthetic aperture length corresponding to the target The expression is Assuming the towing speed of the combined transceiver synthetic aperture sonar is... Then the corresponding synthesis aperture time The expression is: .

[0055] In step S2, "For any pixel in the imaging region assumed in step S1, within the beam illumination range at the time the combined transmit / receive synthetic aperture sonar transmits a signal, calculate the distance between the pixel in the imaging region and the time the combined transmit / receive synthetic aperture sonar transmits a signal; within the beam illumination range at the time the signal is received, calculate the distance between the combined transmit / receive synthetic aperture sonar and the pixel in the imaging region at the time the signal is received, based on the precise propagation time of the signal from transmission to reception, thereby obtaining the precise two-way slant range history," it is assumed that the slow time of the combined transmit / receive synthetic aperture sonar in the azimuth direction is... Assume that the coordinates of any pixel in the imaging region in the distance direction are... The coordinates in the azimuth direction are Therefore, within the beam illumination range at the moment of transmitting and receiving the combined synthetic aperture sonar signal, i.e., within the imaging region assumed in step S1 when transmitting and receiving the combined synthetic aperture sonar signal, the azimuth coordinates of any pixel are considered. Combined with the time, azimuth, and coordinates of the transmitted signal of the synthetic aperture sonar Satisfying the relation Calculate the distance between the transceiver synthetic aperture sonar and this pixel in the imaging region at the moment of signal transmission. The expression is The azimuth coordinates of any pixel in the imaging region assumed in step S1 when the transceiver synthetic aperture sonar is within the beam illumination range at the moment of signal reception. Azimuth coordinates of the transceiver combined synthetic aperture sonar at the time of signal reception Satisfying the relation the exact propagation time of the transmit-receive-aperture synthetic aperture sonar signal from transmission to reception the distance between the transmit-receive-aperture synthetic aperture sonar at the reception signal time and this pixel in the imaging region is calculated the expression of which is and the exact two-way slant range history is obtained the expression of which is .

[0056] In step S3 "for any pixel in the imaging region assumed in step S1, the reference echo signal corresponding to this pixel is calculated in the beam illumination range at the sonar transmission time and the reception time according to the calculated more accurate two-way slant range history and the relevant parameters of the sonar transmitted signal", when the azimuth direction coordinate of any pixel in the imaging region assumed in step S1 and the azimuth direction coordinate of the transmit-receive-aperture synthetic aperture sonar at the transmission signal time and the reception signal time satisfy the relationship at the same time, the expression of the reference echo signal corresponding to this pixel is: , here, represents the logical "and", is the exact two-way slant range history calculated in step S2, represents the center frequency of the transmitted signal, represents the range direction fast time, represents the azimuth direction slow time, represents the frequency modulation rate of the transmitted linear frequency modulation signal, represents the sound speed in water, represents the imaginary unit.

[0057] In step S4 "the range direction frequency domain transform is performed on the collected transmit-receive-aperture synthetic aperture sonar measured echo signal, and the range direction frequency domain transform is performed on the reference echo signal in step S3, and then for any pixel in the imaging region assumed in step S1, the conjugate multiplication processing is performed on the result of the range direction frequency domain transform of the measured echo signal and the result of the range direction frequency domain transform of the simulated reference echo signal in the beam illumination range at the sonar transmission time and the reception time", and step S5 "the coherent accumulation is performed on all the conjugate multiplication results in the beam illumination range at the sonar transmission time and the reception time as the imaging result of this pixel", it is assumed that is the collected transmit-receive-aperture synthetic aperture sonar measured echo signal, the result of the range direction frequency domain transform is , and the result of the range direction frequency domain transform of the simulated reference echo signal in step S3 is , so the result of the conjugate multiplication processing is , here represents a conjugate operation on the frequency domain transform result of the reference echo signal simulated in step S3, and when the relationship of the arbitrary pixel azimuth direction coordinate in the beam irradiation range at the transmitting signal moment, the receiving signal moment, i.e. the imaging area assumed in step S1, and the transceiver combined synthetic aperture sonar transceiver signal moment azimuth direction coordinate is satisfied simultaneously , the coherent accumulation result of all the conjugate multiplications is the imaging result of the pixel , the expression is: , here, is the accumulation, represents the azimuth direction slow time, represents the distance direction fast time.

[0058] In step S6, “for other pixels in the imaging area, the processing steps of steps S1, S2, S3, S4 and S5 are processed, and the imaging results of all pixels in the entire imaging area are obtained”, for each processing step of steps S1, S2, S3, S4 and S5, the coordinates of the pixels in the imaging area in the distance direction and the azimuth direction need to be updated to the corresponding coordinate values of the new pixels to obtain the imaging results of the new pixels.

[0059] In order to verify the effectiveness of the time domain point-by-point imaging method of the present application, it is assumed that the towing speed of the transceiver combined synthetic aperture sonar is 0.125 m / s, the azimuth direction aperture of the transceiver combined synthetic aperture sonar element is 0.08 m, the center frequency of the transmitted linear frequency modulation signal is 150 kHz, the bandwidth is 10 kHz, the pulse repetition frequency is 6.25 Hz, and there is an ideal point target in the scene, whose azimuth direction aperture coordinate is 8 m and whose distance direction spatial coordinate is 114 m. The echo signal is simulated based on the distance of the movement along the azimuth direction during the transceiver combined synthetic aperture sonar transceiver signal, and the simulated echo signal is processed by the traditional time domain point-by-point imaging method which does not consider the distance of the movement along the azimuth direction during the transceiver combined synthetic aperture sonar transceiver signal and the time domain point-by-point imaging method of the present application, Figure 3 is the imaging result of the traditional time domain point-by-point imaging method, Figure 4 is the imaging result of the time domain point-by-point imaging method of the present application, Figure 5 is the azimuth direction profile graph of the imaging results of the traditional time domain point-by-point imaging method and the time domain point-by-point imaging method of the present application, Figure 6 is Figure 5 the main lobe local enlarged view, Figure 7 is the distance direction profile graph of the imaging results of the traditional time domain point-by-point imaging method and the time domain point-by-point imaging method of the present application. Since the distance direction focusing and the azimuth direction focusing of the traditional time domain point-by-point imaging method are implemented synchronously, Figure 3It can be seen that the conventional time-domain point-by-point imaging method has poor imaging results because it ignores the distance along the azimuth direction during the transmission and reception of the synthetic aperture sonar. Figure 4 It can be seen that the time-domain point-by-point imaging method of the present application can accurately image the target because it takes into account the influence of the distance along the azimuth direction during the transmission and reception of the synthetic aperture sonar. The coordinates of the imaged target are completely consistent with the theoretical coordinates, verifying the effectiveness of the time-domain point-by-point imaging method of the present application. Figure 5 、 Figure 6 and Figure 7 The superiority of the time-domain point-by-point imaging method of the present application over the conventional time-domain point-by-point imaging method is further verified, further proving that the time-domain point-by-point imaging method of the present application can accurately image the target without causing the problem of target defocusing.

[0060] Reference is made to the accompanying drawings Figure 8 According to another aspect of the present application, the present application further provides a time-domain point-by-point imaging system 800 for a transceiver combined synthetic aperture sonar, which is used for imaging the echo of the transceiver combined synthetic aperture sonar. The time-domain point-by-point imaging system 800 comprises a first calculation unit 810, a second calculation unit 820, a simulation unit 830, a conjugate multiplication processing unit 840, a coherent accumulation unit 850 and an imaging unit 860. The first calculation unit 810, the second calculation unit 820, the simulation unit 830, the conjugate multiplication processing unit 840, the coherent accumulation unit 850 and the imaging unit 860 cooperate with each other to accurately image the target without causing the problem of target defocusing.

[0061] Specifically, the first calculation unit 810 is configured to calculate, for any pixel in the imaging region, a synthetic aperture length and a synthetic aperture time according to a main lobe width of the transceiver combined synthetic aperture sonar and a distance where a target is located; the second calculation unit 820 is configured to calculate, for any pixel in the assumed imaging region, a distance between the transceiver combined synthetic aperture sonar and the pixel in the imaging region at a signal transmission time within a beam illumination range of the transceiver combined synthetic aperture sonar when transmitting a signal, and a distance between the transceiver combined synthetic aperture sonar and the pixel in the imaging region at a signal receiving time within the beam illumination range according to an accurate propagation time of the signal from transmission to reception, and then obtain an accurate two-way slant range history; the simulation unit 830 is configured to calculate, for any pixel in the assumed imaging region, a reference echo signal corresponding to the pixel at the signal transmission time and the signal receiving time within the beam illumination range according to the accurate two-way slant range history calculated by the second calculation unit 820 and relevant parameters of the transmitted signal; the conjugate multiplication processing unit 840 is configured to perform distance-to-frequency domain transformation on an actual echo signal of the transceiver combined synthetic aperture sonar and on the reference echo signal simulated by the simulation unit, and then perform conjugate multiplication processing on the distance-to-frequency domain transformed result of the actual echo signal and the distance-to-frequency domain transformed result of the simulated reference echo signal for any pixel in the assumed imaging region at the signal transmission time and the signal receiving time within the beam illumination range; the coherent accumulation unit 850 is configured to coherently accumulate all conjugate multiplication results at the signal transmission time and the signal receiving time within the beam illumination range as an imaging result of the pixel; and the imaging unit 860 is configured to repeat the first calculation unit 810, the second calculation unit 820, the simulation unit 830, the conjugate multiplication processing unit 840 and the coherent accumulation unit 850 for other pixels in the imaging region to obtain imaging results of all pixels in the entire imaging region. The time domain point-by-point imaging system 800 fully considers the influence of the motion along the azimuth direction during the signal transmission and reception of the transceiver combined synthetic aperture sonar, and can accurately image the target without causing target defocusing problems.

[0062] When the first calculation unit 810 calculates, for any pixel in the imaging region, a synthetic aperture length and a synthetic aperture time according to a main lobe width of the transceiver combined synthetic aperture sonar and a distance where a target is located, it is assumed that the distance of the target in the distance direction is , the main lobe width of the transceiver combined synthetic aperture sonar is , and then the expression of the synthetic aperture length corresponding to the target is , and it is assumed that the towing speed of the transceiver combined synthetic aperture sonar is , and then the corresponding synthetic aperture time The expression of the distance between the transceiver-combined synthetic aperture sonar and the pixel in the imaging area at the time of receiving the signal is: .

[0063] When the second calculation unit 820 assumes that the slow time of the transceiver-combined synthetic aperture sonar in the azimuth direction is , assumes that the coordinate of any pixel in the imaging area in the distance direction is , and assumes that the coordinate of any pixel in the imaging area in the azimuth direction is , then, in the beam illumination range at the time of transmitting the signal by the transceiver-combined synthetic aperture sonar, that is, the azimuth coordinate of any pixel in the imaging area assumed in the step S1 at the time of transmitting the signal by the transceiver-combined synthetic aperture sonar and the azimuth coordinate of the transceiver-combined synthetic aperture sonar at the time of transmitting the signal satisfy the relationship , the distance between the transceiver-combined synthetic aperture sonar and the pixel in the imaging area at the time of transmitting the signal is calculated as The expression of the distance between the transceiver-combined synthetic aperture sonar and the pixel in the imaging area at the time of receiving the signal is: ; in the beam illumination range at the time of receiving the signal by the transceiver-combined synthetic aperture sonar, that is, the azimuth coordinate of any pixel in the imaging area assumed at the time of receiving the signal by the transceiver-combined synthetic aperture sonar and the azimuth coordinate of the transceiver-combined synthetic aperture sonar at the time of receiving the signal satisfy the relationship , the distance between the transceiver-combined synthetic aperture sonar and the pixel in the imaging area at the time of receiving the signal is calculated according to the accurate propagation time of the signal from transmission to reception The expression of the distance between the transceiver-combined synthetic aperture sonar and the pixel in the imaging area at the time of receiving the signal is: ; and the accurate two-way slant range history The expression of the accurate two-way slant range history is: . .

[0064] The simulation unit 830, when calculating the reference echo signal corresponding to any pixel in the assumed imaging area within the beam illumination range at the transmission signal time and the reception signal time according to the accurate two-way slant range history calculated by the second calculation unit 820 and the relevant parameters of the transmitted signal, assumes that the azimuth direction coordinate of the pixel and the azimuth direction coordinate of the transceiver array synthetic aperture sonar at the transmission signal time and the reception signal time satisfy the relationship formula at the same time. Herein, represents the logical "and", is the accurate two-way slant range history calculated in step S2, represents the center frequency of the transmitted signal, represents the distance direction fast time, represents the azimuth direction slow time, represents the frequency modulation rate of the transmitted linear frequency modulation signal, represents the sound speed in water, represents the imaginary unit.

[0065] The conjugate multiplication processing unit 840, when performing the conjugate multiplication processing on the distance direction frequency domain transformed results of the collected transceiver array synthetic aperture sonar measured echo signal and the distance direction frequency domain transformed results of the reference echo signal simulated by the simulation unit, assumes that is the collected transceiver array synthetic aperture sonar measured echo signal, and the distance direction frequency domain transformed result is , and the distance direction frequency domain transformed result of the reference echo signal simulated in step S3 is , so the conjugate multiplication processing result is Herein represents the conjugate operation on the frequency domain transformed result of the reference echo signal simulated by the simulation unit 830, and the azimuth direction coordinate of any pixel in the assumed imaging area and the azimuth direction coordinate of the transceiver array synthetic aperture sonar at the transmission signal time and the reception signal time satisfy the relationship formula at the same time. The coherent accumulation of all the conjugate multiplication results obtains the imaging result of the pixel Here, The table is accumulated, The slow time is represented in the azimuth direction, The fast time is represented in the range direction.

[0066] When the imaging unit 860 repeatedly performs the first calculation unit 810, the second calculation unit 820, the simulation unit 830, the conjugate multiplication processing unit 840 and the coherent accumulation unit 850 to obtain the imaging results of all pixels in the entire imaging area, for each processing step of the first calculation unit 810, the second calculation unit 820, the simulation unit 830, the conjugate multiplication processing unit 840 and the coherent accumulation unit 850, the coordinates of the pixels in the imaging area in the range direction and the azimuth direction need to be updated to the corresponding coordinate values of the new pixels to obtain the imaging results of the new pixels.

[0067] Reference is made to the accompanying drawings that show, by way of example, Figure 8According to another aspect of the present application, the present application further provides a computing device 900, wherein the computing device 900 comprises a processor 910 and a memory 920, and 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 perform a time-domain point-by-point imaging method, wherein the time-domain point-by-point imaging method comprises the following steps: S1, for any pixel in an imaging region, according to a main lobe width of a transceiver array synthetic aperture sonar, a target distance, a synthetic aperture length and a synthetic aperture time are calculated; S2, for any pixel in the imaging region assumed in the step S1, a distance between the transceiver array synthetic aperture sonar and the pixel in the imaging region at a signal transmission time is calculated within a beam illumination range at the signal transmission time, and a distance between the transceiver array synthetic aperture sonar and the pixel in the imaging region at a signal receiving time is calculated within a beam illumination range at the signal receiving time according to an accurate signal propagation time from the signal transmission to the signal receiving, and then an accurate two-way slant range history is obtained; S3, according to the calculated accurate two-way slant range history and related parameters of the transmitted signal, a reference echo signal corresponding to the pixel is calculated within the beam illumination range at the signal transmission time and the signal receiving time for any pixel in the imaging region assumed in the step S1; S4, a distance domain transformation is performed on an actual echo signal of the transceiver array synthetic aperture sonar, and a distance domain transformation is performed on the reference echo signal simulated in the step S3, and then for any pixel in the imaging region assumed in the step S1, a conjugate multiplication processing is performed between a result of the distance domain transformation of the actual echo signal and a result of the distance domain transformation of the simulated reference echo signal within the beam illumination range at the signal transmission time and the signal receiving time; S5, a coherent accumulation is performed on all the conjugate multiplication results within the beam illumination range at the signal transmission time and the signal receiving time, and the coherent accumulation is taken as an imaging result of the pixel; and S6, for other pixels in the imaging region, the processing steps of the step S1, the step S2, the step S3, the step S4 and the step S5 are performed, and then imaging results of all the pixels in the entire imaging region are obtained.

[0068] In one embodiment of the computing device 900 of the present application, the memory 920 can include one or more computer program products that can include various forms of computer-readable storage media, such as volatile and / or non-volatile memory. The volatile memory, for example, can include random access memory (RAM), and / or a cache, etc. The non-volatile memory, for example, can include read-only memory (ROM), hard disks, flash memory, etc. The computer-readable storage media can store one or more computer program instructions that the processor 910 can execute in order to implement the functionality of the time-domain point-by-point imaging method of the present application described above.

[0069] In one embodiment of the computing device 900 of the present application, the processor 910 can be a central processing unit (CPU) or other form of processing unit having data processing and / or instruction executing capabilities, which can execute the program instructions stored on the computer-readable storage media in order to implement the functionality of the time-domain point-by-point imaging method of the present application described above.

[0070] In one embodiment of the computing device 900 of the present application, the computing device 900 can further include an input device 930 and an output device 940. The input device 930 can be, but is not limited to, a keyboard, a mouse, etc. The output device 940 can be, but is not limited to, a display, a speaker, a printer, etc. The input device 930 and the output device 940 can be connected to the processor 910 through a bus system.

[0071] Those ordinarily skilled in the art should understand that the above-described embodiments and the drawings shown are only for illustratively explaining the present application, but not for limiting the present application. All equivalent embodiments, modifications and improvements within the spirit of the present application should be included in the protection scope of the present application.

Claims

1. A time-domain point-by-point imaging method for a transceiver array synthetic aperture sonar for imaging echoes of a transceiver array synthetic aperture sonar, characterized in that, The time-domain point-by-point imaging method comprises the following steps: S1, for any pixel in the imaging area, according to the main lobe width of the transceiver combination synthetic aperture sonar and the distance where the target is located, the synthetic aperture length and the synthetic aperture time are calculated; S2, for any pixel in the imaging area assumed in the step S1, in the beam illumination range at the signal transmission time of the transceiver combination synthetic aperture sonar, the distance between the transceiver combination synthetic aperture sonar and the pixel in the imaging area at the signal transmission time is calculated, and in the beam illumination range at the signal receiving time, according to the accurate propagation time of the signal from transmission to reception, the distance between the transceiver combination synthetic aperture sonar and the pixel in the imaging area at the signal receiving time is calculated, and then the accurate two-way slant range history is obtained; S3, according to the calculated accurate two-way slant range history and the related parameters of the transmitted signal, the related parameters including the center frequency of the transmitted signal, the distance fast time, the azimuth slow time and the frequency modulation rate of the transmitted linear frequency modulation signal, for any pixel in the imaging area assumed in the step S1, the reference echo signal corresponding to the pixel is calculated in the beam illumination range at the signal transmission time and the signal receiving time; S4, the collected transceiver combination synthetic aperture sonar measured echo signal is subjected to distance domain frequency domain transformation, and the reference echo signal simulated in the step S3 is subjected to distance domain frequency domain transformation, and then for any pixel in the imaging area assumed in the step S1, the conjugate multiplication processing is performed between the results of the distance domain frequency domain transformation of the measured echo signal and the results of the distance domain frequency domain transformation of the simulated reference echo signal in the beam illumination range at the signal transmission time and the signal receiving time; S5, the results of all the conjugate multiplications in the beam illumination range at the signal transmission time and the signal receiving time are coherently added as the imaging result of the pixel; S6, for other pixels in the imaging area, the processing steps of the step S1, the step S2, the step S3, the step S4 and the step S5 are processed, and the imaging results of all the pixels in the entire imaging area are obtained.

2. The time-domain point-by-point imaging method of a transceiver-hybrid synthetic aperture sonar according to claim 1, characterized in that, In the step S1, assuming that the target is at a distance of , the main lobe width of the transceiver synthetic aperture sonar is , the expression of the synthetic aperture length corresponding to the target is , assuming that the transceiver synthetic aperture sonar tow speed is , the expression of the corresponding synthetic aperture time is .

3. The time-domain point-by-point imaging method for a transceiver array synthetic aperture sonar according to claim 2, characterized in that, In the step S2, assuming that the transmit-receive combined synthetic aperture sonar is in the slow time of the azimuth direction , assuming that the coordinate of any pixel in the imaging area in the range direction is , the coordinate in the azimuth direction is , in the beam illumination range at the transmit signal time of the transmit-receive combined synthetic aperture sonar, the azimuth direction coordinate of any pixel in the imaging area assumed in the step S1 when the transmit-receive combined synthetic aperture sonar transmits a signal , and the azimuth direction coordinate at the transmit signal time of the transmit-receive combined synthetic aperture sonar , satisfy the relationship , the expression for calculating the distance between the transmit-receive combined synthetic aperture sonar and the pixel in the imaging area at the transmit signal time is ; The transceiver collocated synthetic aperture sonar receives a signal at a time instant when the beam is illuminating the area of the imaging region assumed in step S1 The transceiver collocated synthetic aperture sonar receives a signal at a time instant when the beam is illuminating the area of the imaging region assumed in step S1 The transceiver collocated synthetic aperture sonar receives a signal at a time instant when the beam is illuminating the area of the imaging region assumed in step S1 The transceiver collocated synthetic aperture sonar receives a signal at a time instant when the beam is illuminating the area of the imaging region assumed in step S1 The transceiver collocated synthetic aperture sonar receives a signal at a time instant when the beam is illuminating the area of the imaging region assumed in step S1 The transceiver collocated synthetic aperture sonar receives a signal at a time instant when the beam is illuminating the area of the imaging region assumed in step S1 The transceiver collocated synthetic aperture sonar receives a signal at a time instant when the beam is illuminating the area of the imaging region assumed in step S1 The transceiver collocated synthetic aperture sonar receives a signal at a time instant when the beam is illuminating the area of the imaging region assumed in step S1 The transceiver collocated synthetic aperture sonar receives a signal at a time instant when the beam is illuminating the area of the imaging region assumed in step S1 4. The time-domain point-by-point imaging method of a transceiver-hybrid synthetic aperture sonar according to claim 3, characterized in that, In the step S3, according to the calculated accurate two-way slant range history and the related parameters of the transmitted signal, the reference echo signal corresponding to any pixel in the imaging area assumed in the step S1 is calculated within the beam illumination range at the transmitting signal time and the receiving signal time; when the azimuth direction coordinate of any pixel in the imaging area assumed in the step S1 and the azimuth direction coordinate of the transmitting-receiving combined synthetic aperture sonar at the transmitting-receiving signal time satisfy the relationship formula simultaneously within the beam illumination range at the transmitting signal time and the receiving signal time The expression of the reference echo signal corresponding to this pixel is: ， wherein denotes a logical AND, is the exact two-way slant range history computed at step S2, denotes the center frequency of the transmitted signal, denotes the range fast time, denotes the azimuth slow time, denotes the frequency modulation of the transmitted linear frequency modulated signal, denotes the sound speed in water, denotes the imaginary unit.

5. The time-domain point-by-point imaging method of a transceiver-hybrid synthetic aperture sonar according to claim 4, characterized in that, In the step S4, it is assumed that The result of the frequency domain transform of the collected transceiver compounding synthetic aperture sonar measured echo signal in the range direction is The result of the frequency domain transform of the step S3 simulated reference echo signal in the range direction is The result of the conjugate multiplication processing is , wherein represents the conjugate operation on the frequency domain transform result of the step S3 simulated reference echo signal; in the step S5, when the arbitrary pixel azimuth direction coordinate in the imaging area assumed in the step S1 and the transceiver compounding synthetic aperture sonar azimuth direction coordinate at the transceiver signal time satisfy the relationship formula at the same time in the beam illumination range at the transmission signal time and the reception signal time, the coherent accumulation of all the conjugate multiplication results obtains the imaging result of the pixel , and the expression is: ， wherein, The table is cumulative, represents the azimuthal slow time, represents the range fast time.

6. The time-domain point-by-point imaging method of a transceiver-hybrid synthetic aperture sonar according to any one of claims 1 to 5, characterized in that, In the step S5, for each processing step of the step S1, the step S2, the step S3, the step S4 and the step S5, the coordinates of the pixels in the imaging area in the distance direction and the azimuth direction need to be updated to the corresponding coordinate values of the new pixels to obtain the imaging result of the new pixels.

7. A time-domain point-by-point imaging system for a transceiver array synthetic aperture sonar for imaging returns from a transceiver array synthetic aperture sonar, characterized by, Comprise: A first calculation unit is configured to calculate, for any pixel in the imaging area, the synthetic aperture length and the synthetic aperture time according to the main lobe width of the transceiver combination synthetic aperture sonar and the distance where the target is located; The second calculation unit is configured to, for any pixel in the assumed imaging area, calculate a distance between the transceiver-compound aperture sonar and the pixel in the imaging area at a transmission signal time when a beam illumination range is within a transmission signal time, and calculate a distance between the transceiver-compound aperture sonar and the pixel in the imaging area at a reception signal time according to an accurate propagation time of a signal from transmission to reception within a beam illumination range at the reception signal time, and further obtain an accurate two-way slant range history; The simulation unit is configured to, according to the accurate two-way slant range history calculated by the second calculation unit and relevant parameters of the transmitted signal, calculate a reference echo signal corresponding to any pixel in the assumed imaging area within the beam illumination range at the transmission signal time and the reception signal time, wherein the relevant parameters include a center frequency of the transmission signal, a distance direction fast time, a bearing direction slow time, and a frequency modulation rate of a transmission linear frequency modulation signal. The conjugate multiplication processing unit is configured to perform distance direction frequency domain transformation on the collected transceiver-compound aperture sonar measured echo signal and the reference echo signal simulated by the simulation unit, and then perform conjugate multiplication processing on the transceiver-compound aperture sonar measured echo signal and the reference echo signal simulated by the simulation unit within the beam illumination range at the transmission signal time and the reception signal time. The coherent accumulation unit is configured to coherently accumulate all conjugate multiplication results within the beam illumination range at the transmission signal time and the reception signal time as an imaging result of the pixel. The imaging unit is configured to repeat the first calculation unit, the second calculation unit, the simulation unit, the conjugate multiplication processing unit, and the coherent accumulation unit for other pixels in the imaging area to obtain imaging results of all pixels in the entire imaging area.

8. The time-domain point-by-point imaging system for a transceiver-housed synthetic aperture sonar of claim 7, wherein, Assuming the target is at a distance of , the main lobe width of the transceiver synthetic aperture sonar is , the expression of the synthetic aperture length corresponding to the target is , assuming the transceiver synthetic aperture sonar tow speed is , the expression of the corresponding synthetic aperture time is .

9. The time-domain point-by-point imaging system for a transceiver-housed synthetic aperture sonar of claim 8, wherein, Assume that the slow time of the transmit-receive combined synthetic aperture sonar in the azimuth direction is , assume that the coordinate of any pixel in the imaging area in the range direction is , the coordinate in the azimuth direction is , in the range of the beam illumination when the transmit-receive combined synthetic aperture sonar transmits a signal, the azimuth coordinate of any pixel in the assumed imaging area when the transmit-receive combined synthetic aperture sonar transmits a signal is , the azimuth coordinate at the time when the transmit-receive combined synthetic aperture sonar transmits a signal satisfies the relationship , the expression for calculating the distance between the transmit-receive combined synthetic aperture sonar at the time when a signal is transmitted and the pixel in the imaging area is ; The transceiver collocated synthetic aperture sonar receives signals at a time instant when the beam is illuminating a range in the assumed imaging area The transceiver collocated synthetic aperture sonar receives signals at a time instant when the beam is illuminating a range in the assumed imaging area The transceiver collocated synthetic aperture sonar receives signals at a time instant when the beam is illuminating a range in the assumed imaging area The transceiver collocated synthetic aperture sonar receives signals at a time instant when the beam is illuminating a range in the assumed imaging area The transceiver collocated synthetic aperture sonar receives signals at a time instant when the beam is illuminating a range in the assumed imaging area The transceiver collocated synthetic aperture sonar receives signals at a time instant when the beam is illuminating a range in the assumed imaging area The transceiver collocated synthetic aperture sonar receives signals at a time instant when the beam is illuminating a range in the assumed imaging area The transceiver collocated synthetic aperture sonar receives signals at a time instant when the beam is illuminating a range in the assumed imaging area The transceiver collocated synthetic aperture sonar receives signals at a time instant when the beam is illuminating a range in the assumed imaging area 10. A computing device, characterized by The processor and the memory, wherein computer program instructions are stored in the memory, and the computer program instructions make the processor execute the time domain point-by-point imaging method in any one of claims 1 to 6 when running in the processor.

Images