A three-dimensional high-resolution underwater acoustic imaging system

Abstract

This invention discloses a three-dimensional high-resolution underwater acoustic imaging system, comprising: a watertight electronics chamber and an array transducer deployed beneath the watertight electronics chamber, and a host computer. The array transducer includes a receiving array and a transmitting array. Eight Archimedean spirals are drawn with the acoustic center as the reference point. Eight elements closest to the array elements on each spiral are selected as optimized receiving array elements to determine the receiving array. The arc between two adjacent elements on the outermost periphery of the receiving array is divided into five equal parts. Transmitting array elements are designed at the division points, and the receiving array elements are simultaneously used as transmitting array elements to determine the transmitting array. The watertight electronics chamber includes a signal processing board. Through signal processing of the received signals from the receiving array, a single transmitter drives the transmission of planar acoustic waves. Each received snapshot data is subjected to vortex phase modulation to obtain the topological charge number. l The system obtains snapshot data with vortex phase modulation; the host computer processes each snapshot data based on the underwater acoustic correlation imaging algorithm to achieve three-dimensional high-resolution underwater acoustic imaging.

Description

Technical Field

[0001] This invention belongs to the field of underwater acoustic engineering, and in particular relates to a three-dimensional high-resolution underwater acoustic imaging system. Background Technology

[0002] With the implementation of the national marine development strategy, the acquisition of marine information has become increasingly important. Sound waves are, to date, the only means discovered that can propagate over long distances in water. Underwater acoustic imaging technology, as an important aspect of acquiring underwater information, has advantages such as intuitiveness and visualization, and has already been widely applied. Compared to commonly used two-dimensional underwater acoustic imaging technology, the development of three-dimensional underwater acoustic imaging has been relatively slow. The main reason for this is that the receiving transducer in a three-dimensional underwater acoustic imaging system is a two-dimensional array, making the hardware system very complex, requiring thousands of transducer elements with strict consistency and signal conditioning and processing circuits. On the other hand, the angular resolution of traditional three-dimensional underwater acoustic imaging systems is limited by the aperture of the receiving transducer array. Large-aperture two-dimensional arrays typically include tens of thousands or even hundreds of thousands of elements, making the implementation of so many receiving and processing channels extremely difficult.

[0003] When divers are working underwater, they are usually operating directly below the work vessel. The command personnel on the work vessel need to keep abreast of the water and seabed conditions below, which urgently requires a three-dimensional high-resolution underwater acoustic imaging system to observe and command the divers' operations.

[0004] Underwater safety is of great importance. When ships are anchored, they need to monitor the water and seabed in real time to prevent attacks from underwater divers or autonomous underwater vehicles. Therefore, when ships are anchored, a three-dimensional high-resolution underwater acoustic imaging system needs to be suspended on the ship's side to observe the water and seabed and ensure the safety of the ship itself.

[0005] In summary, real-world underwater information is three-dimensional, thus necessitating the development of three-dimensional high-resolution underwater acoustic imaging technology. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and to propose a three-dimensional high-resolution underwater acoustic imaging system.

[0007] In view of this, the present invention proposes a three-dimensional high-resolution underwater acoustic imaging system, comprising: a watertight electronic chamber and an array transducer deployed under the watertight electronic chamber, and a host computer.

[0008] The array transducer includes a receiving array and a transmitting array. Through optimized array layout technology, eight Archimedean spirals are drawn with the sound center as the base point. Eight elements are selected from each Archimedean spiral. The nearest array element is used as the optimized receiving array element to determine the receiving array; the arc between two adjacent elements on the outermost edge of the receiving array is divided into 5 equal parts, and transmitting array elements are designed at the division points. The receiving array elements are also used as transmitting array elements to determine the transmitting array.

[0009] The watertight electronics compartment includes a signal processing board that processes the signals received by the receiving array to enable a transmitter to drive the transmission of planar acoustic waves. It also performs vortex phase modulation on each received snapshot data to obtain the topological charge number. l Snapshot data of vortex phase modulation;

[0010] The host computer processes each snapshot data based on the underwater acoustic correlation imaging algorithm to achieve three-dimensional high-resolution underwater acoustic imaging.

[0011] As an improvement to the above system, the center frequency of the area array transducer is 100kHz, corresponding to a half wavelength of 7.5mm, the transmit beam opening angle is 100°, and the receive beam is distributed in a conical imaging region with a 90° opening angle.

[0012] As an improvement to the above system, the determination of the receiving array includes:

[0013] exist Based on the positions of the array receiver transducer elements, draw eight Archimedean spirals with the acoustic center as the reference point. On each Archimedean spiral, select eight elements that are connected to the transducer elements. The nearest element of the array is used as the optimized receiving element, resulting in 64 elements as the elements of the receiving array.

[0014] The coordinates of the eight elements on the first spiral are: a(1)=(11.25, 3.75), a(2)=(18.75, 26.25), a(3)=(11.25, 48.75), a(4)=(-26.25, 63.75), a(5)=(-63.75, 56.25), a(6)=(-93.75, 33.75), a(7)=(-108.75, 3.75), a(8)=(-116.25, -33.75), in mm;

[0015] The coordinates of the eight elements on the second spiral are as follows: b(1)=(3.75, 11.25), b(2)=(-3.75, 33.75), b(3)=(-33.75, 41.25), b(4)=(-63.75, 26.25), b(5)=(-86.25, -3.75), b(6)=(-86.25, -41.25), b(7)=(-78.75, -78.75), b(8)=(-56.25, -108.75), in mm;

[0016] The coordinates of the eight elements on the third spiral are: c(1)=(-3.75, 11.25), c(2)=(-18.75, 18.75), c(3)=(-48.75, 3.75), c(4)=(-63.75, -18.75), c(5)=(-56.25, -56.25), c(6)=(-41.25, -86.25), c(7)=(-11.25, -108.75), c(8)=(33.75, -116.25), in mm;

[0017] The coordinates of the eight elements on the fourth spiral are: d(1)=(-11.25, 3.75), d(2)=(-33.75, -3.75), d(3)=(-41.25, -33.75), d(4)=(-26.25, -63.75), d(5)=(3.75, -86.25), d(6)=(41.25, -86.25), d(7)=(78.75, -78.75), d(8)=(108.75, -56.25), in mm;

[0018] The coordinates of the eight elements on the fifth spiral are: e(1)=(-11.25,-3.75), e(2)=(-18.75, -26.25), e(3)=(-3.75, -56.25), e(4)=(26.25, -63.75), e(5)=(63.75, -56.25), e(6)=(93.75, -33.75), e(7)=(108.75, -3.75), e(8)=(116.25, 33.75), in mm;

[0019] The coordinates of the eight array elements on the sixth spiral are: f(1)=(-3.75, -11.25), f(2)=(3.75, -33.75), f(3)=(33.75, -41.25), f(4)=(71.25, -18.75), f(5)=(86.25, 11.25), f(6)=(86.25, 48.75), f(7)=(78.75, 78.75), f(8)=(56.25, 108.75), in mm;

[0020] The coordinates of the eight elements on the seventh spiral are as follows: g(1)=(3.75, -11.25), g(2)=(26.25, -18.75), g(3)=(48.75, -3.75), g(4)=(63.75, 18.75), g(5)=(56.25, 56.25), g(6)=(41.25, 86.25), g(7)=(3.75, 108.75), g(8)=(-33.75, 116.25), in mm;

[0021] The coordinates of the eight elements on the eighth spiral are: h(1)=(11.25, -3.75), h(2)=(33.75, 3.75), h(3)=(41.25, 26.25), h(4)=(33.75, 56.25), h(5)=(11.25, 78.75), h(6)=(-26.25, 93.75), h(7)=(-63.75, 86.25), h(8)=(-101.25, 63.75), in mm.

[0022] As an improvement to the above system, the determination of the transmitting array includes:

[0023] A combined transmit and receive circuit is used to connect the 64 elements of the receiving array in parallel and use them as transmitting elements simultaneously.

[0024] Divide the arc between two adjacent elements on the outermost perimeter of the receiving array into 5 equal parts. Connect the 4 elements corresponding to each arc in parallel to form the transmitting array elements, as follows:

[0025] The coordinates of the four array elements corresponding to the first arc are: A(1)=(-109.90, -52.38), A(2)=(-100.00, -69.43), A(3)=(-87.48, -84.67), A(4)=(-72.66, -97.68), in mm;

[0026] The coordinates of the four array elements corresponding to the second arc are: B(1)=(-38.92, -115.36), B(2)=(-21.00, -119.92), B(3)=(-2.61, -121.72), B(4)=(15.85, -120.71), in mm;

[0027] The coordinates of the four array elements corresponding to the third arc are: C(1)=(52.38, -109.90), C(2)=(69.43, -100.00), C(3)=(84.67, -87.48), C(4)=(97.68, -72.66), in mm;

[0028] The coordinates of the four array elements corresponding to the fourth arc are: D(1)=(115.36, -38.92), D(2)=(119.92, -21.00), D(3)=(121.72, -2.61), D(4)=(120.71, 15.85), in mm;

[0029] The coordinates of the four array elements corresponding to the fifth arc are: E(1)=(109.90, 52.38), E(2)=(100.00, 69.43), E(3)=(87.48, 84.67), E(4)=(72.66, 97.68), in mm;

[0030] The coordinates of the four array elements corresponding to the sixth arc are: F(1)=(38.87, 115.37), F(2)=(20.91, 119.93), F(3)=(2.47, 121.72), F(4)=(-16.03, 120.68), in mm;

[0031] The coordinates of the four array elements corresponding to the seventh arc are: G(1)=(-50.51, 110.77), G(2)=(-66.01, 102.29), G(3)=(-80.12, 91.66), G(4)=(-92.55, 79.10), in mm;

[0032] The coordinates of the four array elements corresponding to the eighth arc are: H(1)=(-112.46, 46.63), H(2)=(-118.70, 27.06), H(3)=(-121.56, 6.72), H(4)=(-120.96, -13.81), in mm.

[0033] This led to the determination of a surface array transmitting element comprising 96 array elements.

[0034] As an improvement to the above system, the 96 elements of the transmitting array are connected in parallel through a transceiver conversion circuit and driven by a high-power transmitter with an instantaneous power of 2000-3000W to transmit uniform 100kHz plane sound waves.

[0035] As an improvement to the above system, the watertight electronic cabin also includes: a transmitter board, a power supply and energy storage board, a receiver board, and a transceiver conversion board.

[0036] As an improvement to the above system, the signal processing board's processing procedure includes:

[0037] The control receiver board performs time gain conditioning on the 64 channels of received signals from the input receiver array;

[0038] The digital signal of each channel is acquired by 64-channel AD. The digital signal of each channel is quadrature demodulated and digitally downconverted by sine and cosine signals with a local oscillator frequency of 100kHz to obtain the baseband signal. The I and Q data of the baseband signal are reduced to 10kHz after data rate reduction.

[0039] After being filtered by a low-pass filter with a bandwidth of 2kHz, the I and Q data of the output baseband signal are combined to form the complex signal data of the baseband.

[0040] After filtering by 360 angular bandpass filters, each output is respectively compared with... Multiply, then perform linear superposition, and output. This represents the baseband signal of a snapshot array element field data of the transmitted plane wave echo incident on the output of the receiving array, after passing through a topological charge of... The output after vortex phase modulation, where, , Indicates the corresponding number The angle of incidence of a plane wave at the center of the angular passband of a angular domain bandpass filter. Represents the imaginary part of a complex signal. .

[0041] As an improvement to the above system, the underwater acoustic correlation imaging algorithm includes:

[0042] The following processing is performed on each snapshot data:

[0043] When the observation time is u Time k The complex signal of the radiation field intensity of each pixel is t ( u , k Then the reference recording matrix in underwater acoustic correlation imaging for:

[0044]

[0045] Wherein, the first in the matrix u The row indicates the number of topological loads in use. u When observing vortex phase modulation, all p The complex signal of the radiation field intensity of the nth pixel, the nth k The column represents the first observation when using different vortex phase OAM modes. k The complex signal of radiation field intensity of each pixel;

[0046] The backscattering coefficient of a pixel in the imaging region is expressed as: The superscript T indicates transpose; (Note: The last part is a typo and can be left as is.) ,in yes Figure 7 Topological charge number is u The first vortex phase modulation v The output of each array element The topological charge number is u The first vortex phase modulation v The phase of each array element, The topological charge number is u Given the sum of signals received by all array elements, we have:

[0047]

[0048] Right now:

[0049]

[0050] Underwater acoustic correlation imaging processing was performed to obtain :

[0051]

[0052] in, F For the correlation processing algorithm, the least squares method is selected for the correlation processing of vortex-phase spiral waves, with the error square function... e ( S )for:

[0053]

[0054] right e ( S Take the minimum value and perform differentiation:

[0055]

[0056] if If not singular, then There is a unique solution that satisfies the following equation:

[0057]

[0058] That is, to obtain the backscattering coefficients of each pixel in the target imaging region. .

[0059] As an improvement to the above system, the host computer includes a memory, a processor, and a computer program stored in the memory, characterized in that the processor executes the computer program to implement an underwater acoustic correlation imaging algorithm.

[0060] As an improvement to the above system, the signal processing board communicates with the host computer via a network port.

[0061] Compared with the prior art, the advantages of the present invention are:

[0062] 1. By optimizing the position of transducer array elements, this invention only requires a few dozen receiving array elements to perform three-dimensional high-resolution underwater acoustic imaging, while existing three-dimensional high-resolution underwater acoustic imaging array transducers using half-wavelength arrays require tens of thousands of array elements. This invention has significant advantages in reducing the number of transducer array elements, receiving signal conditioning, and signal processing channels.

[0063] 2. Existing technology generates vortex-phase helical sound waves through phased control of multiple emitting sound sources, which is suitable for generating topological charge numbers of... l The vortex phase spiral wave requires at least The invention generates vortex phase modulation at the receiving end through signal processing. The sound source is connected in parallel with the array elements of the traditional three-dimensional underwater acoustic imaging, and only one transmitter is needed to drive the array elements to emit sound waves.

[0064] 3. The order of the vortex-phase spiral signal generated by this invention is much higher than that of the vortex-phase spiral acoustic wave generated by the prior art. As a result, the incident signal plane wave has a larger phase difference in the azimuth direction, which is beneficial for obtaining higher acoustic map angular resolution in three-dimensional underwater acoustic imaging.

[0065] 4. Compared with existing technologies that can only perform staring imaging of stationary targets by transmitting vortex-phase helical acoustic waves with different topological charge numbers, this invention obtains the phase difference of incident plane waves in different directions by using a snap at the receiving end to modulate the vortex phase with different topological charge numbers. This allows for not only staring imaging of stationary targets but also real-time underwater acoustic imaging of moving targets. Attached Figure Description

[0066] Figure 1 This is an overall diagram of an embodiment of the present invention;

[0067] Figure 2 This is a mechanical diagram of the wet end of the present invention;

[0068] Figure 3-1 This is a conventional half-wavelength pitch array involved in the embodiments of the present invention;

[0069] Figure 3-2 The embodiments of this invention involve conventional half-wavelength pitch arrays and Archimedean spirals.

[0070] Figure 3-3 This is the optimized coordinate diagram of the receiving transducer array element used in this invention;

[0071] Figure 3-4 This is the optimized coordinate diagram of the transmitting transducer array element used in this invention;

[0072] Figure 4-1 These are simulation curves of the array element transmit voltage response according to an embodiment of the present invention;

[0073] Figure 4-2 This is a simulation curve of the array element receiving voltage sensitivity according to an embodiment of the present invention;

[0074] Figure 5-1 This is a simulation diagram of the array element directivity of the present invention;

[0075] Figure 5-2 This is a simulation diagram of the beam directivity of the area array transmission of the present invention;

[0076] Figure 6-1 This is a simulation diagram of the directivity of the center beam of the receiving array of the present invention;

[0077] Figure 6-2 This is a simulation diagram of the directivity of a beam next to the receiving array of the present invention;

[0078] Figure 7 This is a flowchart of the vortex phase modulation signal processing at the receiving end of the present invention;

[0079] Figure 8 This is a schematic diagram of the host computer structure of the imaging device involved in the embodiment of the present invention.

[0080] Figure Labels

[0081] 1. Cylinder 2. End cap 3. Spring washer 4. Hex nut

[0082] 5. Flat washer 6. Lifting ring 7. Area array transducer 8. Area array transducer base Detailed Implementation

[0083] Figure 1This is an overall diagram of an embodiment of the present invention. During operation, the surface array transducer at the bottom of the watertight electronic compartment emits sound waves with a certain beamwidth downwards. Then, the surface array receiving transducer receives the scattered echoes from the water and seabed. If the surface array receiving transducer uses a traditional equidistant half-wavelength array, then tens of thousands of receiving array elements are required. The present invention overcomes this drawback by optimizing the traditional half-wavelength surface array receiving scheme, controlling the number of array elements of the receiving transducer to within a few dozen elements. At the same time, when the optimized few dozen array elements perform conventional beamforming, the beam performance, such as the main lobe width and main-side lobe ratio, is the same as that of the traditional half-wavelength equidistant surface array receiving transducer, and there are no grating lobes. The sound wave beam emitted by the surface array transmitting transducer must cover the beam of the optimized surface array receiving transducer, and the sound wave intensity distribution within the illumination surface of the transmitting beam must be uniform. The present invention specifically designs a surface array transmitting transducer scheme after optimizing the surface array receiving transducer.

[0084] Traditional 3D underwater acoustic imaging uses wavefronts with equiphase surfaces, resulting in a uniform wavefront that makes it difficult to form an uncorrelated radiation field. To improve the angular resolution of 3D underwater acoustic imaging by creating an uncorrelated radiation field, existing techniques involve multiple transmissions of helical sound waves with different topological charges and vortex phases. These orthogonal vortex sound fields with different topological charges are used to achieve staring imaging of stationary targets. This invention, like traditional 3D underwater acoustic imaging, transmits sound waves with equiphase wavefronts, ensuring uniformity. The received traditional echo signal is modulated onto helical wave signals with different topological charges and vortex phase structures. The modulated wavefronts exhibit uncorrelated spatial differential distributions, allowing for different weights in different regions of the radiation field. By modulating the echo electrical signal onto vortex acoustic field electrical signals with different topological charge numbers, and simultaneously making the orbital angular momentum (OAM) modes of different vortex acoustic field electrical signals mutually orthogonal, it is possible to overcome the limitation of sonar beam angular resolution by aperture and thus realize three-dimensional high-resolution underwater acoustic imaging. It can not only perform staring imaging of stationary targets, but also perform real-time imaging of moving targets, and the underwater acoustic imaging speed is fast.

[0085] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0086] Example 1

[0087] As attached Figure 1 As shown, the watertight electronics compartment contains circuit boards such as transceiver boards, receiver boards, signal processing boards, power supply and energy storage boards, and transmitter boards. Figure 2This is a mechanical diagram of the wet end of a three-dimensional high-resolution underwater acoustic imaging system. In the diagram, 1 is a cylinder, 2 is an end cap, 3 is a spring washer, 4 is a hexagonal nut, 5 is a flat washer, 6 is a lifting ring, 7 is a transducer array, and 8 is a transducer array mount. The transducer array 7 is divided into a transmitting transducer and a receiving transducer. The transducer of this invention operates at a center frequency of 100kHz, corresponding to a half-wavelength of 7.5mm. To prevent grating lobes, the element spacing of traditional receiving transducer arrays is generally 7.5mm (half-wavelength). Figure 3-1 The image shown is the traditional one. A 100kHz area array transducer with a single array element requires 1024 channels of receiving signal conditioning, acquisition, and signal processing circuitry. This not only results in high hardware costs but also a large size and weight, and low system reliability. To improve resolution, the number of array elements needs to be increased to enlarge the aperture of the receiving transducer; for example, doubling the beam angle resolution requires… A 100kHz area array transducer with one array element requires 4096 channels of receiving signal conditioning, acquisition, and signal processing circuitry, which is obviously very costly.

[0088] This invention employs optimized array technology, in Figure 3-1 shown Based on the positions of the array receiver transducer elements, draw eight Archimedean spirals with the acoustic center as the reference point, and obtain the following: Figure 3-2 The tradition shown Coordinate diagram of the coexistence of half-wavelength pitched receiving array and Archimedean spiral, where the red spiral is the Archimedean spiral, and 8 points are taken from each Archimedean spiral. The nearest element to the array element is used as the optimized receiving element, resulting in the following: Figure 3-3 The 64 array elements shown are the array elements of the optimized receiving array of the present invention.

[0089] Figure 3-3 Each spiral is labeled a, b, c, d, e, f, g, and h. The array elements on the spirals are numbered sequentially from the inside out. The rectangular coordinates of each array element on the spiral (indicated by...) Figure 3-3 The two perpendicular red lines in the image are used as a reference (unit: mm), as follows:

[0090] 1. α-helix:

[0091] a(1)=(11.25, 3.75), a(2)=(18.75, 26.25), a(3)=(11.25, 48.75),

[0092] a(4)=(-26.25, 63.75), a(5)=(-63.75, 56.25), a(6)=(-93.75, 33.75),

[0093] a(7)=(-108.75, 3.75), a(8)=(-116.25, -33.75);

[0094] 2. b-helix:

[0095] b(1)=(3.75, 11.25), b(2)=(-3.75, 33.75), b(3)=(-33.75, 41.25),

[0096] b(4)=(-63.75, 26.25), b(5)=(-86.25, -3.75), b(6)=(-86.25, -41.25),

[0097] b(7)=(-78.75, -78.75), b(8)=(-56.25, -108.75);

[0098] 3. c-helix:

[0099] c(1)=(-3.75, 11.25),c(2)=(-18.75, 18.75),c(3)=(-48.75, 3.75),

[0100] c(4)=(-63.75, -18.75), c(5)=(-56.25, -56.25), c(6)=(-41.25, -86.25),

[0101] c(7)=(-11.25, -108.75), c(8)=(33.75, -116.25);

[0102] 4. d-helix:

[0103] d(1)=(-11.25, 3.75), d(2)=(-33.75, -3.75), d(3)=(-41.25, -33.75),

[0104] d(4)=(-26.25, -63.75), d(5)=(3.75, -86.25), d(6)=(41.25, -86.25),

[0105] d(7)=(78.75, -78.75), d(8)=(108.75, -56.25);

[0106] 5. e-helix:

[0107] e(1) = (-11.25, -3.75), e(2) = (-18.75, -26.25), e(3) = (-3.75, -56.25),

[0108] e(4) = (26.25, -63.75), e(5) = (63.75, -56.25), e(6) = (93.75, -33.75),

[0109] e(7) = (108.75, -3.75), e(8) = (116.25, 33.75);

[0110] 6. f spiral:

[0111] f(1) = (-3.75, -11.25), f(2) = (3.75, -33.75), f(3) = (33.75, -41.25),

[0112] f(4) = (71.25, -18.75), f(5) = (86.25, 11.25), f(6) = (86.25, 48.75),

[0113] f(7) = (78.75, 78.75), f(8) = (56.25, 108.75);

[0114] 7. g spiral:

[0115] g(1) = (3.75, -11.25), g(2) = (26.25, -18.75), g(3) = (48.75, -3.75),

[0116] g(4) = (63.75, 18.75), g(5) = (56.25, 56.25), g(6) = (41.25, 86.25),

[0117] g(7) = (3.75, 108.75), g(8) = (-33.75, 116.25);

[0118] 8. h spiral:

[0119] h(1) = (11.25, -3.75), h(2) = (33.75, 3.75), h(3) = (41.25, 26.25),

[0120] h(4) = (33.75, 56.25), h(5) = (11.25, 78.75), h(6) = (-26.25, 93.75),

[0121] h(7)=(-63.75, 86.25), h(8)=(-101.25, 63.75).

[0122] The above 64 array elements are transceiver array elements. Through the transceiver array circuit, these array elements serve as receiving array elements to output the received echo signals, and are also connected in parallel through the transceiver array circuit to be driven by a transmitter to transmit signals and produce sound.

[0123] If only the above 64 array elements are connected in parallel to emit sound waves, the beam opening angle of the emitted sound waves will not meet the requirements of this invention, which requires the receiving beam to be distributed in a conical imaging region with a 90° opening angle, due to the relatively sparse outer array elements. To improve the beam opening angle, this invention divides the arc between the two outermost adjacent array elements into 5 equal parts, and designs the transmitting array elements at the division points. The rectangular coordinates of the array elements on the transmitting arcs A, B, C, D, E, F, G, and H (as shown in the figure) are... Figure 3-4 The two perpendicular red lines in the image are used as a reference (unit: mm), as follows:

[0124] 9. A transmitting element (numbered sequentially from nearest to farthest from spiral a; 4 elements connected in parallel are used only as transmitting elements):

[0125] A(1)=(-109.90, -52.38), A(2)=(-100.00, -69.43),

[0126] A(3)=(-87.48, -84.67), A(4)=(-72.66, -97.68);

[0127] 10. B transmitting elements (numbered sequentially from nearest to farthest from the b spiral; 4 elements connected in parallel are used only as transmitting elements):

[0128] B(1)=(-38.92, -115.36), B(2)=(-21.00, -119.92),

[0129] B(3)=(-2.61, -121.72), B(4)=(15.85, -120.71);

[0130] 11. C-type transmitting elements (numbered sequentially from closest to furthest from the c-helix; 4 elements connected in parallel are used only as transmitting elements):

[0131] C(1)=(52.38, -109.90), C(2)=(69.43, -100.00),

[0132] C(3)=(84.67, -87.48),C(4)=(97.68, -72.66);

[0133] 12. D-type transmitting elements (numbered sequentially from closest to furthest from the d-helix; 4 elements connected in parallel are used only as transmitting elements):

[0134] D(1)=(115.36, -38.92), D(2)=(119.92, -21.00),

[0135] D(3)=(121.72, -2.61),D(4)=(120.71, 15.85);

[0136] 13. E-transmitting array elements (numbered sequentially from nearest to farthest from the e-spiral; 4 elements connected in parallel are used only as transmitting array elements):

[0137] E(1)=(109.90, 52.38),E(2)=(100.00, 69.43),

[0138] E(3)=(87.48, 84.67),E(4)=(72.66, 97.68);

[0139] 14. F-type transmitting elements (numbered sequentially from closest to furthest from the f-spiral; 4 elements connected in parallel are used only as transmitting elements):

[0140] F(1)=(38.87, 115.37),F(2)=(20.91, 119.93),

[0141] F(3)=(2.47, 121.72),F(4)=(-16.03, 120.68);

[0142] 15. G-type transmitting elements (numbered sequentially from closest to furthest from the g-spiral; 4 elements connected in parallel are used only as transmitting elements):

[0143] G(1)=(-50.51, 110.77), G(2)=(-66.01, 102.29),

[0144] G(3)=(-80.12, 91.66),G(4)=(-92.55, 79.10);

[0145] 16. H-type transmitting elements (numbered sequentially from closest to furthest from the h-spiral; 4 elements connected in parallel are used only as transmitting elements):

[0146] H(1)=(-112.46, 46.63), H(2)=(-118.70, 27.06),

[0147] H(3)=(-121.56, 6.72), H(4)=(-120.96, -13.81).

[0148] The transmitting transducer consists of 32 transmitting array elements connected in parallel and 64 array elements on the Archimedes spiral connected in parallel through a transceiver conversion circuit, all driven by a single transmitter to produce sound. The transmitting transducer has a total of 96 array elements emitting sound signals.

[0149] The simulation curves of the array element transmit voltage response of this invention are as follows: Figure 4-1 The directional simulation diagram of the array elements is as follows: Figure 5-1 The simulation diagram of the directivity of the transmitted beam of the array is shown below, based on the positions of the aforementioned transmitting elements. Figure 5-2 The transmit beam has an opening angle of 100°, covering 90° of the imaging airspace of the receive beam.

[0150] The simulation curves of the array element receiving voltage sensitivity in this embodiment of the invention are as follows: Figure 4-2 The directivity simulation diagram of the center beam of the receiving array formed by conventional beamforming is shown below. Figure 6-1 As can be seen, the main lobe of the beam is at the center of the array, there is no grating lobe, and the main-to-side lobe ratio is 13dB, which is the same as the beam performance of a traditional half-wavelength pitch array. A simulation diagram of the directivity of a beam next to a conventional beamforming receiving array is shown below. Figure 6-2 It can be seen that the main lobe of the beam points to the side of the array, there is no grating lobe, and the main-side lobe ratio is 13dB, which is the same as the beam performance of a traditional half-wavelength pitch array.

[0151] Similar to traditional 3D underwater acoustic imaging systems, Figure 3-4 The 96 array elements are connected in parallel via a transceiver circuit and driven by a high-power transmitter to emit uniform 100kHz plane acoustic waves. The echoes from the water and seabed are transmitted by... Figure 3-3 The 64 array elements on the 8 Archimedean spirals shown are input to a 64-channel receiver via a transceiver conversion circuit. The signal processing board controls the receiver to condition the 64 input signals. The conditioned 64-channel receiver output signal is acquired by 64 AD converters on the signal processing board. The digital signal of each channel is down-converted to a baseband signal after quadrature demodulation of sine and cosine signals with a local oscillator frequency of 100kHz. The I and Q data of the baseband signal are down-processed to a data rate of 10kHz, and then filtered by a 2kHz low-pass filter to output the required I and Q data of the baseband signal. The I and Q data form the complex baseband signal data, which is then input to... Figure 7 The 360 ​​angular bandpass filters shown have outputs that are respectively... Multiply and then linearly superimpose to output The baseband signal of a snapshot array element field data output by the transmitted plane wave echo incident on the receiving array passes through a topological charge of... The output after vortex phase modulation, where, , This represents the plane wave incident angle corresponding to the center of the angular passband of the nth angular domain bandpass filter. j Represents the imaginary part of a complex signal. .pass Figure 7 The signal processing in the process twists the in-phase plane wave incident on the 360° imaging plane of each snapshot into a vortex-phase spiral wave, thereby realizing vortex phase modulation of the incident plane wave at the receiving end.

[0152] go through Figure 7 After signal processing, high-resolution underwater acoustic imaging can be performed using an underwater acoustic correlation imaging algorithm. The reference record matrix in underwater acoustic correlation imaging can be described by equation (1). When the observation time is... u Time k The complex signal of the radiation field intensity of each pixel can be written as: t ( u , k ). No. u The row indicates the number of topological loads in use. u When observing vortex phase modulation, all p The complex signal of the radiation field intensity of each pixel. k The column represents the first observation when using different vortex phase OAM modes. k The complex signal of radiation field intensity of each pixel.

[0153] (1)

[0154] The backscattering coefficient of a pixel in the imaging region is expressed as: .remember ,in S ( u , v )yes Figure 7 Topological charge number is u The first vortex phase modulation v The output of each array element The topological charge number is u The first vortex phase modulation v The phase of each array element, The topological charge number is u Given the sum of signals received by all array elements, we have:

[0155] (2)

[0156] Equation (2) can be written as Equation (3):

[0157]

[0158] After the planar sound field is modulated into a vortex sound field, its amplitude takes the form of a Bessel function of the first kind, generating a non-uniform radiation field in the imaging region. Furthermore, each imaging observation utilizes an OAM mode with a different topological charge number, and these modes are mutually orthogonal, which is beneficial for... The matrix is ​​full rank, allowing for the independent extraction of different pixel information to achieve super-resolution sonar imaging. Equation (2) is processed using underwater acoustic correlation imaging to obtain... S p×1 .

[0159] (4)

[0160] in F This is the correlation processing algorithm. If the least squares method is used for the correlation processing of vortex-phase spiral waves, let the error square function be denoted as... e ( S Equation (5) is given by:

[0161] (5)

[0162] right e ( S Taking the minimum value and differentiating it, we get:

[0163] (6)

[0164] if If not singular, then There is a unique solution, as shown in equation (7), from which the backscattering coefficients of each pixel in the target imaging region can be obtained:

[0165] (7)

[0166] This invention conducts in-depth research on correlation processing algorithms to reduce errors and improves the backscattering coefficient of pixels in the imaging region through optimization. The accuracy.

[0167] Each snapshot data point undergoes the same processing described above to obtain a high-resolution three-dimensional underwater acoustic image.

[0168] Figure 1 The signal processing board inside the watertight electronic compartment communicates with the host computer via a network port. The host computer for the imaging equipment includes at least one processor, a memory, and an imaging program stored in the memory and executable on the processor. The imaging program is configured to implement the steps of the imaging method described in the above embodiments.

[0169] The processor may include a main processor and a coprocessor. The main processor, also known as a CPU (Central Processing Unit), is used to process data in the wake-up state. The coprocessor is a low-power processor used to process data in the standby state. The memory may include one or more computer-readable storage media, which may be non-transitory. The memory may also include high-speed random access memory and non-volatile memory. The non-transitory computer-readable storage media in the memory is used to store at least one instruction, which is executed by the processor to implement the steps corresponding to the three-dimensional high-resolution underwater acoustic imaging method of the present invention.

[0170] The host computer imaging device may also optionally include: a communication interface and at least one peripheral device. The processor, memory, and communication interface can be interconnected via a bus. Each peripheral device can be connected to the communication interface via a bus, signal line, or circuit board. Specifically, the peripheral device includes at least one of a display screen and a power supply. The communication interface can be used to connect at least one I / O (Input / Output) related peripheral device to the processor and memory. The display screen is used to display the UI (User Interface). The UI can include graphics, text, icons, video, and any combination thereof. The power supply is used to power the various components in the electronic device. The power supply can be AC ​​power, DC power, a disposable battery, or a rechargeable battery. Figure 8 The structure shown does not constitute a limitation on the imaging device and may include more components than illustrated, or combine certain components, or have different component arrangements. It is worth noting that in the embodiments of the above system, the various modules are divided according to functional logic, but are not limited to the above division, as long as the corresponding functions can be achieved; furthermore, the specific names of each functional module are only for easy distinction and are not intended to limit the scope of protection of this invention.

[0171] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A three-dimensional high-resolution underwater acoustic imaging system comprising: The water-tight electronic cabin, the planar array transducer arranged under the water-tight electronic cabin and the upper computer are characterized in that The surface array transducer comprises a receiving surface array and a transmitting surface array, 8 Archimedes spirals are drawn based on the sound center by optimizing the array technology, 8 points are taken on each Archimedes spiral, and the points are used as The nearest array element of the surface array element is used as an optimized receiving array element to determine the receiving surface array; a circular arc between the two adjacent array elements on the outermost periphery of the receiving surface array is equally divided into 5 parts, a transmitting array element is designed on the equally divided point, and the receiving array element is used as the transmitting array element at the same time to determine the transmitting surface array; The watertight electronic cabin comprises a signal processing board, which realizes driving the emission of plane acoustic waves by one transmitter through processing the signals received by the receiving surface array, and vortex phase modulation of each snapshot data received, to obtain vortex phase modulated snapshot data with a topological charge number of l ​ The upper computer processes each snapshot data based on a water acoustic correlation imaging algorithm to realize three-dimensional high-resolution water acoustic imaging. The water-tight electronic cabin further comprises a transmitter board, a power supply and energy storage board, a receiver board and a transceiver conversion board. The processing procedure of the signal processing board comprises: The receiver board controls time gain conditioning of 64-channel receiving signals of the input receiving planar array; Through 64-channel AD acquisition, the digital quantity of each channel is subjected to orthogonal demodulation and digital down-conversion by the cosine and sine signals with a local oscillation frequency of 100 kHz to obtain a baseband signal, and the I and Q data of the baseband signal are subjected to speed reduction data processing to reduce the speed to 10 kHz; After being filtered by a low-pass filter with a bandwidth of 2 kHz, the I and Q data of the baseband signal are output, and the I and Q data constitute complex signal data of the baseband. After 360 angular domain band-pass filter filtering, each output is multiplied with , and then linearly superimposed, output . The baseband signal representing the output of one snapshot element domain data of the receiving plane array when the plane wave echo is incident is output after the vortex phase modulation with the topological charge , wherein, , , wherein, , represents the plane wave incident angle corresponding to the center of the angular passband of the th angular domain band-pass filter, , represents the imaginary part of the complex signal.

2. The three-dimensional high-resolution underwater acoustic imaging system of claim 1, wherein, The center frequency of the planar array transducer is 100 kHz, the corresponding half wavelength is 7.5 mm, the transmission beam opening angle is 100°, and the receiving beams are distributed in a conical imaging area with an opening angle of 90°.

3. The three-dimensional high-resolution underwater acoustic imaging system of claim 1, wherein, The determination of the receiving planar array comprises: In Based on the position of the array elements of the surface array receiving transducer, 8 Archimedes spirals are drawn with the acoustic center as the base point, and 8 points are taken on each Archimedes spiral, which are 8 points on the Archimedes spiral closest to the acoustic center. The nearest array element of the surface array element is taken as the optimized receiving array element, and 64 array elements are obtained as the array elements of the receiving surface array. The coordinates of the 8 array elements on the first spiral are a(1)=(11.25, 3.75), a(2)=(18.75, 26.25), a(3)=(11.25, 48.75), a(4)=(-26.25, 63.75), a(5)=(-63.75, 56.25), a(6)=(-93.75, 33.75), a(7)=(-108.75, 3.75), a(8)=(-116.25, -33.75), in units of mm; The coordinates of the 8 array elements on the second spiral are b(1)=(3.75, 11.25), b(2)=(-3.75, 33.75), b(3)=(-33.75, 41.25), b(4)=(-63.75, 26.25), b(5)=(-86.25, -3.75), b(6)=(-86.25, -41.25), b(7)=(-78.75, -78.75), b(8)=(-56.25, -108.75), in units of mm; The coordinates of the 8 array elements on the third spiral are c(1)=(-3.75, 11.25), c(2)=(-18.75, 18.75), c(3)=(-48.75, 3.75), c(4)=(-63.75, -18.75), c(5)=(-56.25, -56.25), c(6)=(-41.25, -86.25), c(7)=(-11.25, -108.75), c(8)=(33.75, -116.25), in units of mm; The coordinates of the eight array elements on the fourth spiral are: d(1)=(-11.25, 3.75), d(2)=(-33.75, -3.75), d(3)=(-41.25, -33.75), d(4)=(-26.25, -63.75), d(5)=(3.75, -86.25), d(6)=(41.25, -86.25), d(7)=(78.75, -78.75), d(8)=(108.75, -56.25), in units of mm; The coordinates of the eight array elements on the fifth spiral are: e(1)=(-11.25, -3.75), e(2)=(-18.75, -26.25), e(3)=(-3.75, -56.25), e(4)=(26.25, -63.75), e(5)=(63.75, -56.25), e(6)=(93.75, -33.75), e(7)=(108.75, -3.75), e(8)=(116.25, 33.75), in units of mm; The coordinates of the eight array elements on the sixth spiral are: f(1)=(-3.75, -11.25), f(2)=(3.75, -33.75), f(3)=(33.75, -41.25), f(4)=(71.25, -18.75), f(5)=(86.25, 11.25), f(6)=(86.25, 48.75), f(7)=(78.75, 78.75), f(8)=(56.25, 108.75), in units of mm; The coordinates of the eight array elements on the seventh spiral are: g(1)=(3.75, -11.25), g(2)=(26.25, -18.75), g(3)=(48.75, -3.75), g(4)=(63.75, 18.75), g(5)=(56.25, 56.25), g(6)=(41.25, 86.25), g(7)=(3.75, 108.75), g(8)=(-33.75, 116.25), in units of mm; The coordinates of the eight array elements on the eighth spiral are: h(1)=(11.25, -3.75), h(2)=(33.75, 3.75), h(3)=(41.25, 26.25), h(4)=(33.75, 56.25), h(5)=(11.25, 78.75), h(6)=(-26.25, 93.75), h(7)=(-63.75, 86.25), h(8)=(-101.25, 63.75), in units of mm.

4. The three-dimensional high-resolution underwater acoustic imaging system of claim 3, wherein, The determination of the transmitting surface array comprises: parallelly connecting the 64 array elements of the receiving surface array to simultaneously serve as transmitting array elements by using a transceiving integrated circuit; The arc between the adjacent two outermost elements of the receiving surface array is divided into five equal parts, and the four elements corresponding to each arc are connected in parallel to form a transmitting element, respectively: The coordinates of the four elements corresponding to the first arc are A(1)=(-109.90, -52.38), A(2)=(-100.00, -69.43), A(3)=(-87.48, -84.67), and A(4)=(-72.66, -97.68), unit: mm; The coordinates of the four elements corresponding to the second arc are B(1)=(-38.92, -115.36), B(2)=(-21.00, -119.92), B(3)=(-2.61, -121.72), and B(4)=(15.85, -120.71), unit: mm; The coordinates of the four elements corresponding to the third arc are C(1)=(52.38, -109.90), C(2)=(69.43, -100.00), C(3)=(84.67, -87.48), and C(4)=(97.68, -72.66), unit: mm; The coordinates of the four elements corresponding to the fourth arc are D(1)=(115.36, -38.92), D(2)=(119.92, -21.00), D(3)=(121.72, -2.61), and D(4)=(120.71, 15.85), unit: mm; The coordinates of the four elements corresponding to the fifth arc are E(1)=(109.90, 52.38), E(2)=(100.00, 69.43), E(3)=(87.48, 84.67), and E(4)=(72.66, 97.68), unit: mm; The coordinates of the four elements corresponding to the sixth arc are F(1)=(38.87, 115.37), F(2)=(20.91, 119.93), F(3)=(2.47, 121.72), and F(4)=(-16.03, 120.68), unit: mm; The coordinates of the four elements corresponding to the seventh arc are G(1)=(-50.51, 110.77), G(2)=(-66.01, 102.29), G(3)=(-80.12, 91.66), and G(4)=(-92.55, 79.10), unit: mm; The coordinates of the four elements corresponding to the eighth arc are H(1)=(-112.46, 46.63), H(2)=(-118.70, 27.06), H(3)=(-121.56, 6.72), and H(4)=(-120.96, -13.81), unit: mm; And further determine the surface array transmitting element including 96 elements.

5. The three-dimensional high-resolution underwater acoustic imaging system of claim 4, wherein, The 96 array elements of the transmitting surface array are connected in parallel through a transceiving conversion circuit and are driven by a high-power transmitter with an instantaneous power of 2000-3000W to emit uniform 100kHz plane sound waves.

6. The three-dimensional high-resolution underwater acoustic imaging system of claim 1, wherein, The underwater acoustic correlation imaging algorithm comprises the following steps: The following processing is performed on each snapshot data: When the observation time is u , the radiation field intensity complex signal of the k th pixel is t ( u , k ), the reference record matrix in underwater acoustic correlation imaging is: ​ ； wherein the first column of the matrix represents the complex signal of the radiation field intensity of all the N pixels when observed with a vortex phase modulation with topological charge u OAMn= 1 u ; the first row represents the complex signal of the radiation field intensity of all the N pixels when observed with a vortex phase modulation with OAM mode p OAMm= 1 k ; the first element of the list represents the complex signal of the radiation field intensity of the first pixel when observed with a vortex phase modulation with OAM mode k OAMk= 1 ; and the last element of the list represents the complex signal of the radiation field intensity of the Nthpixel when observed with a vortex phase modulation with OAM mode The backscattering coefficient of a pixel in the imaging region is expressed as: The superscript T indicates transpose; (Note: The last part is a typo and can be left as is.) ,in The topological charge number is u The first vortex phase modulation v The output of each array element The topological charge number is u The first vortex phase modulation v The phase of each array element, The topological charge number is u When the vortex phase modulation is applied, the sum of the signals received by all array elements is given by: ； That is, ； The water acoustic correlation imaging processing is performed to obtain : ； wherein, F For the correlation processing algorithm, the least square method is selected to process the correlation algorithm of the vortex phase spiral wave, and the error square function e ( S ) is: ； To e ( S ) take the minimum and differentiate: ； If Non-singular, then Has a unique solution, satisfying the following equation: ； The backscattering coefficient of each pixel point in the target imaging region is obtained .

7. The three-dimensional high-resolution underwater acoustic imaging system of claim 6, wherein, The host computer comprises a memory, a processor and a computer program stored in the memory, and the processor executes the computer program to implement the underwater acoustic correlation imaging algorithm.

8. The three-dimensional high-resolution underwater acoustic imaging system of claim 1, wherein, The signal processing board communicates with the host computer through a network port.

Images