Acoustic imaging system and method for underwater target

Abstract

The invention provides an acoustic imaging system and method for an underwater target, and the system comprises a transducer which is used for transmitting a first sound wave signal to an underwater target object, so that the first sound wave signal is reflected at a first position, and an echo signal is formed; the laser sensing device is used for emitting a laser beam and determining echo wave vector information of an echo signal based on first phase information of the laser beam under the influence of the echo signal; and determining normal information at the first position according to the first sound wave vector information and the echo vector information of the first sound wave signal so as to form acoustic imaging of the underwater target object. Vector information of the normal vector is fused into acoustic imaging, high-quality imaging is achieved, the precision of the wave vector information of the echo signal also meets the requirement of high-resolution acoustic imaging, and the acoustic imaging effect can be effectively achieved especially in underwater long-distance and small-target imaging detection scenes.

Description

Technical Field

[0001] This application relates to the field of acoustic imaging technology, and particularly to an acoustic imaging system and method for underwater targets. Background Art

[0002] Underwater target imaging is an important development direction of underwater information technology and also an important development technology for underwater national defense security. The target characteristics (underwater acoustic and the interaction process of the target) relied on by underwater target imaging in related technologies are the reflection or scattering intensity information of the target. Then, the sound pressure (intensity) distribution on the target surface is inversely calculated using the received sound pressure distribution for target imaging.

[0003] However, there are theoretical limitations in improving the resolution in this way. Limited by the wavelength and receiving aperture, the resolution will significantly decrease in the imaging detection scenarios of long - distance and small targets underwater. Summary of the Invention

[0004] Based on this, it is necessary to provide an acoustic imaging system and method for underwater targets in view of the above - mentioned technical problems, aiming to solve the technical problem that the imaging effect of acoustic imaging in related technologies is not ideal enough.

[0005] In a first aspect, this application provides an acoustic imaging system for underwater targets, including a transducer, a laser sensing device, and a processor; The transducer is configured to emit at least one first acoustic wave signal towards an underwater target object, so as to reflect at a first position on the underwater target object and form an echo signal corresponding to the first acoustic wave signal; The laser sensing device is arranged on the propagation path of the echo signal, and is configured to emit at least two mutually orthogonal laser beams, and determine the echo wave vector information of the echo signal based on the first phase information of the laser beams affected by the echo signal; The processor is configured to determine the normal information at the first position on the underwater target object according to the first acoustic wave vector information of the first acoustic wave signal and the echo wave vector information, so as to form the acoustic imaging of the underwater target object based on the normal information at multiple positions of the underwater target object; Among them, determining the echo wave vector information of the echo signal based on the first phase information of the laser beams affected by the echo signal includes: Performing Fourier transform on the laser signals of at least two laser beams affected by the echo signal in the target orthogonal direction to obtain the phase spectrum of the laser beams; Based on the frequency of the echo signal, determine the phase difference of at least two laser beams at the frequency from the phase spectra of the at least two laser beams, so as to determine the echo wave vector information of the echo signal in the target orthogonal direction based on the phase difference and the distance between the at least two laser beams; The echo wave vector information of the echo signal in the target orthogonal direction is calculated by the following formula: ; where, is the echo angle in the echo wave vector information of the echo signal in the target orthogonal direction, represents a function, d is the distance between the laser beams, n is the cycle ambiguity number, is the phase difference of the first phase information of multiple laser beams under the influence of the echo signal, is the wavelength of the echo signal, is the frequency of the echo signal, is the sound speed of the echo signal.

[0006] In an embodiment of the present application, the echo wave vector information of the echo signal includes at least wave vector information in two orthogonal directions, and the laser beams emitted by the laser sensing device include at least a first laser beam and a second laser beam in the two orthogonal directions. Among them, the first laser beam includes at least two parallel laser beams in the first orthogonal direction, and the second laser beam includes at least two parallel laser beams in the second orthogonal direction.

[0007] In an embodiment of the present application, the laser sensing device includes at least two layers of laser arrays, and each layer of laser array is used to emit at least two mutually orthogonal laser beams; The laser sensing device is further configured to determine the echo wave vector information of the echo signal based on the phase information of the laser beams in each layer of laser array under the influence of the echo signal, and the response time difference of at least two layers of laser arrays under the influence of the echo signal.

[0008] In an embodiment of the present application, the laser sensing device is further configured to determine the sound speed information of the echo signal based on the phase information of the laser beams in each layer of laser array under the influence of the echo signal, and the response time difference of at least two layers of laser arrays under the influence of the echo signal, where the sound speed information is used to assist in realizing the acoustic imaging of the underwater target object.

[0009] In an embodiment of the present application, the transducer is further configured to emit at least one second acoustic signal to the laser sensing device; The laser sensing device is further configured to determine second acoustic wave vector information of the second acoustic wave signal based on second phase information of the laser beam under the influence of the second acoustic wave signal; The laser sensing device is further configured to determine a first propagation time for the first acoustic wave signal to reach the laser sensing device after being reflected by the underwater target object, and a second propagation time for the second acoustic wave signal to reach the laser sensing device; The processor is configured to determine positioning information at the first position based on the first propagation time, the second propagation time, the first acoustic wave vector information, the second acoustic wave vector information, and the echo wave vector information, so as to obtain a tangent plane at the first position according to the positioning information and the normal information, and thus the tangent planes at multiple positions of the underwater target object form an acoustic imaging of the underwater target object.

[0010] In one embodiment of the present application, when the underwater target object is an arc-shaped structure object in a moving state, the transducer is further configured to emit at least one beam of first acoustic wave signals to the underwater target object at multiple moments, and collect echo signals corresponding to the multiple moments; The processor is further configured to determine echo wave vector information corresponding to the echo signal based on the Doppler frequency of the echo signals corresponding to the multiple moments, or based on the echo signals corresponding to the multiple moments and the moving speed of the underwater target object.

[0011] In one embodiment of the present application, the transducer is disposed on a moving mechanism, and the moving mechanism is configured to control the movement of the transducer so that the transducer emits first acoustic wave signals to the underwater target object at multiple different positions to form multiple echo signals corresponding to the multiple first acoustic wave signals; The laser sensing device is further configured to determine echo wave vector information of the multiple echo signals; The processor is further configured to determine normal information at a first position on the underwater target object based on the displacement information of the transducer and the echo wave vector information of the multiple echo signals.

[0012] In one embodiment of the present application, the transducer is composed of multiple array element sound sources, and the multiple array element sound sources are controlled to emit sound through a phased array model to emit at least one beam of first acoustic wave signals to the underwater target object, where the first acoustic wave signal is a plane wave signal.

[0013] In a second aspect, the present application provides an acoustic imaging method for an underwater target, which is applied to the acoustic imaging system for an underwater target as described in any one of the above, and the method includes: Transmit at least one first acoustic wave signal to an underwater target object through a transducer, so as to reflect at a first position on the underwater target object and form an echo signal corresponding to the first acoustic wave signal; Transmit at least two mutually orthogonal laser beams through a laser sensing device arranged on the propagation path of the echo signal, and determine the echo wave vector information of the echo signal based on the first phase information of the laser beams under the influence of the echo signal; According to the first acoustic wave vector information of the first acoustic wave signal and the echo wave vector information, determine the normal information at the first position on the underwater target object, so as to form the acoustic imaging of the underwater target object based on the normal information at multiple positions of the underwater target object; Among them, determining the echo wave vector information of the echo signal based on the first phase information of the laser beams under the influence of the echo signal includes: For a target orthogonal direction, perform Fourier transform on the laser signals of at least two laser beams affected by the echo signal in the target orthogonal direction to obtain the phase spectrum of the laser beams; Based on the frequency of the echo signal, determine the phase difference of the at least two laser beams at the frequency from the phase spectra of the at least two laser beams, so as to determine the echo wave vector information of the echo signal in the target orthogonal direction based on the phase difference and the distance between the at least two laser beams; The echo wave vector information of the echo signal in the target orthogonal direction is calculated by the following formula: ; Among them, is the echo angle in the echo wave vector information of the echo signal in the target orthogonal direction, represents a function, d is the distance between the laser beams, n is the integer ambiguity number, is the phase difference of the first phase information of multiple laser beams under the influence of the echo signal, is the wavelength of the echo signal, is the frequency of the echo signal, is the sound speed of the echo signal.

[0014] An acoustic imaging system for underwater targets provided by an embodiment of the present application transmits at least one first acoustic wave signal to an underwater target object through a transducer, so as to reflect at a first position on the underwater target object and form an echo signal corresponding to the first acoustic wave signal, and uses a laser sensing device to emit a laser beam to accurately obtain the wave vector information of the echo signal by using the acousto-optic effect, thereby detecting the normal vector at the first position on the underwater target object by combining the wave vector information of the first acoustic wave signal, and integrating the vector information into the acoustic imaging process of the underwater target object, realizing high-quality imaging of the underwater target object, and the accuracy of the wave vector information of the echo signal determined by the above method also meets the requirements of high-resolution acoustic imaging. Especially in the imaging detection scenario of underwater long-distance and small targets, the effect of acoustic imaging can be effectively satisfied. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those skilled in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0016] Figure 1 It is a schematic structural diagram of an acoustic imaging system for underwater targets provided by an embodiment of the present application; Figure 2a It is a schematic diagram of the effect of a process of generating an echo on a target object provided by an embodiment of the present application; Figure 2b It is a schematic diagram of the effect of multiple laser beams in the orthogonal direction being affected by an acoustic wave signal provided by an embodiment of the present application; Figure 2c It is a schematic diagram of the effect of multiple laser beams of a multi-layer laser array in the orthogonal direction being affected by an acoustic wave signal provided by an embodiment of the present application; Figure 3 It is a schematic diagram of the effect of an imaging model of an underwater target object provided by an embodiment of the present application; Figure 4 It is a schematic diagram of an application scenario of an acoustic imaging system for underwater targets provided by an embodiment of the present application; Figure 5 It is a schematic diagram of the step flow of an acoustic imaging method for underwater targets provided by an embodiment of the present application; Figure 6 It is a schematic structural diagram of an electronic device provided by an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application.

[0018] In the description of the present application, the terms "first" and "second" are only used for descriptive purposes, and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of the described features. In the description of the present application, "a plurality" means two or more, unless otherwise specifically defined.

[0019] In the description of the present application, the term "for example" is used to mean "serving as an example, illustration, or explanation". Any embodiment described as "for example" in the present application is not necessarily construed as being more preferred or having more advantages than other embodiments. In order to enable any person skilled in the art to implement and use the present invention, the following description is given. In the following description, details are set forth for the purpose of explanation. It should be understood that those of ordinary skill in the art can recognize that the present invention can be implemented without using these specific details. In other instances, well-known structures and processes are not described in detail to avoid unnecessary details from obscuring the description of the present invention. Therefore, the present invention is not intended to be limited to the embodiments shown, but is consistent with the broadest scope that conforms to the principles and features disclosed in the present application.

[0020] To facilitate the understanding of the underwater target acoustic imaging system and method provided in the embodiments of the present application, the application scenarios of the underwater target acoustic imaging provided by the present application will be described below. Specifically, underwater target imaging is an important development direction of underwater information technology and also an important development technology for underwater national defense security. Currently, acoustic imaging usually relies on the reflection or scattering intensity information of underwater acoustic waves (underwater sound waves) and the target object, and then uses the received sound pressure distribution to inversely calculate the sound pressure (intensity) distribution on the target surface for target imaging. However, the target imaging obtained in this way has theoretical limitations, that is, it depends on the wavelength and receiving aperture, resulting in a significant decrease in resolution in some underwater long-distance and small-target imaging detection scenarios, affecting the imaging effect.

[0021] To solve the above problems, the present application provides an acoustic imaging system based on vector information. By detecting the wave vector information of sound waves before and after reflection at a target object, the normal information at a specific position is determined, and then the normal information is integrated into the acoustic imaging process to achieve high-precision acoustic imaging. In addition, through the acousto-optic effect, the interaction between the laser beam and the acoustic wave signal can be used to determine high-precision wave vector information, thereby effectively improving the resolution of acoustic imaging. It is particularly suitable for imaging detection scenarios of long-distance and small targets underwater, and can effectively improve the effect of acoustic imaging. Specifically, the acoustic imaging system for underwater targets will be described in detail below.

[0022] Specifically, please refer to Figure 1 , Figure 1 which is a schematic structural diagram of an acoustic imaging system for underwater targets provided by an embodiment of the present application. Specifically, it includes a transducer 110, a laser sensing device 120, and a processor 130.

[0023] Among them, the transducer 110 is used to emit at least one first acoustic wave signal towards an underwater target object, so as to reflect at a first position on the underwater target object and form an echo signal corresponding to the first acoustic wave signal.

[0024] The laser sensing device 120 is arranged on the propagation path of the echo signal, and is used to emit at least two mutually orthogonal laser beams, and determine the echo wave vector information of the echo signal based on the first phase information of the laser beams under the influence of the echo signal; The processor 130 is used to determine the normal information at the first position on the underwater target object according to the first acoustic wave vector information of the first acoustic wave signal and the echo wave vector information, so as to form the acoustic imaging of the underwater target object based on the normal information at multiple positions of the underwater target object.

[0025] The specific structure and related principles of each component in the system will be described in detail below in combination with the foregoing content.

[0026] In one embodiment, the transducer 110 is usually an underwater acoustic transducer and can be controlled to form a specific acoustic wave signal. For example, the transducer can be controlled to emit an acoustic wave signal with specific wave vector information towards an underwater target object, or the transducer can also be controlled to emit a specific acoustic wave signal towards other targets, such as the laser sensing device. The present application does not limit the function of the transducer in this embodiment.

[0027] On the basis of the foregoing, in order to further improve the subsequent acoustic imaging effect, in one embodiment of the present application, the transducer 110 is usually used to emit an acoustic wave signal approximating a plane wave to maintain the consistency of wave vector information. Specifically, the wave vector information of the plane wavek is a constant vector, and the direction of the wave vector is always consistent with the propagation direction of the wave and does not change with spatial position in a homogeneous medium, thus effectively simplifying subsequent calculations. Specifically, the wave vector information usually includes the direction of wave propagation and the spatial frequency of the wave. In the embodiments of the present application, mainly based on the direction of wave propagation, that is, the wave vector direction, the calculation of the normal information on the underwater target object is realized. Specifically, in three-dimensional space, the wave vector direction can usually be described by the direction cosine wherein, can be regarded as the angles between the unit vector and the x, y, and z axes in three-dimensional space. Also, since it satisfies condition, therefore, usually in the detection process, only two of its components need to be considered. For example, considering the component , for convenience of description, can be slightly transformed as follows: ; It can be understood that since has symmetric properties, similarly, also has symmetric properties. Therefore, in the subsequent embodiments of the present application, one of the components, for example, the angular component relative to the x-axis (positive direction), will be taken as an example for illustration. For the other component, such as the angular component relative to the z-axis, reference can be made to the description of the angular component , and the embodiments of the present application will not repeat the description here.

[0028] Of course, in order to enable the transducer to emit an acoustic wave signal approximating a plane wave, in one embodiment, the transducer may be configured to be composed of a plurality of array element sound sources. Among them, the plurality of array element sound sources are controlled by a phased array model to form a specific sound generation function under the phased array model, so as to be controlled to emit an acoustic wave signal approximating a plane wave, that is, the first acoustic wave signal, to the underwater target object.

[0029] Of course, in addition to the foregoing solutions provided, implementation solutions for enabling the transducer to emit at least one beam of the first acoustic wave signal to the underwater target object through other forms are also feasible, and the embodiments of the present application will not elaborate here.

[0030] It can be understood that when the first acoustic wave signal emitted by the transducer reaches the first position on the underwater target object, it will be reflected and form an echo signal corresponding to the first acoustic wave signal. Based on the wave vector information of the first acoustic wave signal, if the wave vector information of the echo signal can be accurately determined, the normal information at the specific first position can be obtained, and thus the normal information is introduced in the subsequent acoustic imaging process to improve the imaging quality. Specifically, for easy understanding, please refer to Figure 2a ,Figure 2a This is a schematic diagram of the effect of a process that generates echoes on a target object provided by an embodiment of the present application, which is described in detail below.

[0031] Specifically, please refer to Figure 2a , this schematic diagram of the effect projects the entire process onto the xoy plane, that is, regards the angular component relative to the z-axis as 0 (perpendicular to the z-axis). At this time, the angle between the wave vector direction of the emitted plane wave and the x-axis is , and the wave vector direction of the echo vector is . Since the propagation medium of the sound wave is water and the target object is a solid with an impedance greater than that of water, only the case where the acoustic boundary is a hard boundary is considered. In this case, the action process conforms to Snell's acoustic reflection law. Therefore , , The magnitude relationship of is: ; Similarly, for the angle between the wave vector direction of the emitted plane wave and the z-axis, that is, when it is the other angular component (perpendicular to the x-axis, regarding as 0), the relationship of can also be obtained , , : ; Therefore, under ideal conditions, such as when synchronization is well done, by emitting a series of plane waves with modulated acoustic wave vectors and recording their corresponding parameters . Then, by collecting the angle of arrival of the high-precision echo signal and obtaining its corresponding wave vector information , the normal vector of the tangent plane at the target action point can be obtained.

[0032] It can be understood that the accuracy of the wave vector information of the echo signal affects the acoustic imaging effect to a certain extent, that is, the higher the accuracy of the wave vector information, the higher the acoustic imaging effect, such as improving the resolution of the acoustic imaging. Therefore, in the embodiment of the present application, an implementation scheme based on the acousto-optic effect principle to accurately determine the echo wave vector information of the echo signal is also provided. Specifically as follows.

[0033] In the embodiment of the present application, the calculation of the echo wave vector information of the echo signal is realized based on the laser sensor device. Specifically, for ease of understanding, the laser sensor device can be configured to be composed of a laser emitting unit and a laser receiving unit. Under normal circumstances, when there is no external environmental interference, the laser beam emitted by the laser emitting unit will propagate in a straight line and be received by the laser receiving unit. When there is external environmental interference, the laser beam emitted by the laser emitting unit will be interfered by the acoustic signal based on the acoustic-optical interference effect and deflected to a certain extent, thereby affecting the laser signal received by the laser receiving unit. Therefore, in some embodiments, the echo wave vector information of the echo signal, that is, the echo direction, can be determined based on the characteristic information of the received laser signal. For example, in the embodiment of the present application, the echo wave vector information of the echo signal can be determined based on the first phase information of the laser beam under the influence of the echo signal. Of course, combined with the above-mentioned related description, it can be known that since it is usually necessary to determine the echo wave vector information of the echo signal in multiple directions, in some embodiments, the laser sensor device is used to emit at least two mutually orthogonal laser beams to more accurately determine the echo wave vector information of the echo signal. For example, in one embodiment, the laser sensor device may adopt a structure approximately in a circle, and a laser emitting unit and a laser receiving unit are respectively arranged on opposite sides of the circular structure. Since the echo wave vector information of the echo signal includes at least wave vector information in two orthogonal directions, that is, for example, the angle component provided above , . Therefore, correspondingly, the laser beam generated by the laser sensor device also includes at least the first laser beam and the second laser beam in the two orthogonal directions, wherein the first laser beam includes at least two parallel laser beams in the first orthogonal direction, and the second laser beam includes at least two parallel laser beams in the second orthogonal direction, that is, at least two parallel laser beams are included in each orthogonal direction, so that the echo wave vector information in the corresponding orthogonal direction is realized based on the laser signals of the at least two laser beams, which can be understood as the angle between the wave arrival direction and the corresponding orthogonal direction, that is, a grid-like laser beam will be formed on the inner side of the circular structure of the laser sensor device to realize the measurement of the echo wave vector information. That is to say, in one embodiment, the step of determining the echo wave vector information of the echo signal based on the first phase information of the laser beam under the influence of the echo signal in the laser sensor device includes: For a target orthogonal direction, receiving laser signals of at least two laser beams in the target orthogonal direction affected by the echo signal, and performing Fourier transform on the laser signals to obtain a phase spectrum of the laser beam; Based on the frequency of the echo signal, determine the phase difference between at least two laser beams at the frequency from the phase spectra of the at least two laser beams, so as to determine the echo wave vector information of the echo signal in the target orthogonal direction based on the phase difference and the distance between the at least two laser beams.

[0034] Specifically, for ease of understanding the above content, please refer to Figure 2b , Figure 2b which is a schematic diagram of the effect of acoustic signals on multiple laser beams in the orthogonal direction provided by an embodiment of the present application. Details are as follows.

[0035] In the embodiment of the present application, it can be understood that due to the symmetry of the laser beam, that is, the signal processing methods in multiple orthogonal directions are the same. Therefore, the data processing process of the laser array in one of the orthogonal directions is taken as an example for illustration in the embodiment of the present application. Among them, the wave vector direction angle is , the wavelength of the echo signal is , and the distance between two laser beams is d. Among them, similar to the traditional two-dimensional plane double array element, the wave vector direction angle satisfies the following formula: ; Therefore, the average value of the spot offset angles of at least two laser beams can be used as a rough estimate of the wave vector direction angle and substituted into the left side of the equation to determine the value of the integer ambiguity number n. Then, perform Fourier transform on the laser signals of the two received laser beams to obtain the phase spectrum, take the phases at the corresponding acoustic frequency points and make a difference, and the fractional part of the phase difference can be obtained . At this time, by eliminating spatial aliasing through the rough estimate and the phase difference, the angle of arrival can be accurately estimated. That is to say, in one embodiment, the echo angle in the echo wave vector information in the target orthogonal direction can be obtained, that is, the angle of arrival direction in the target orthogonal direction. The specific calculation formula is: ; Among them, is the echo angle in the echo wave vector information in the target orthogonal direction of the echo signal, representing the function, d is the distance between the laser beams, n is the integer ambiguity number, is the phase difference of the first phase information of multiple laser beams under the influence of the echo signal, is the wavelength of the echo signal, is the frequency of the echo signal, is the sound speed of the echo signal, which can be a preset value or determined by other means.

[0036] Furthermore, based on the above-provided solution, due to the complex and variable underwater environment, seawater is not a uniform medium with fixed properties, which results in the sound speed not being a constant. In the above solution, since it is impossible to avoid the error caused by the difference between the actual sound speed and the substituted theoretical sound speed, a method is needed to reduce or even eliminate the influence of the sound speed on the angle of arrival.

[0037] Considering that the sound field information within the measurement area will not change due to the laser measurement, therefore, based on the above-provided laser sensing device, the present application also provides a multi-layer laser array to improve the angle of arrival, that is, a solution for realizing the accuracy of the echo wave vector information of the echo signal. Specifically, the laser sensing device includes at least two layers of laser arrays, where each layer of laser array is used to emit at least two mutually orthogonal laser beams. At this time, please refer to Figure 2c , Figure 2c which is a schematic diagram of the effect of multiple laser beams of the multi-layer laser array in the orthogonal direction being affected by the acoustic signal provided by the embodiment of the present application.

[0038] In the embodiment of the present application, compared with Figure 2b the shown schematic diagram of the effect, an additional layer of laser array is provided below most of the laser beams of the first layer of laser array, and the distance between the laser beams in this laser array and the corresponding laser beams in the first layer of laser array is h. Among them, the layout of the second layer of laser array can not only increase a series of laser detection points, but also increase the equivalent aperture of the array, where the increased equivalent aperture is . In addition, more importantly, it can assist in eliminating the influence of the sound speed c on the measurement of the angle of arrival. Specifically as follows.

[0039] Similar to the formula provided above, the angle of arrival of each layer of laser array satisfies the following formula: ; At the same time, if the second layer of laser is aligned with the first layer of laser and the distance between the corresponding two laser beams is , then the angle of arrival and the sound speed also satisfy: ; where is the time difference between the responses of the corresponding two laser beams in the first layer of laser and the second layer of laser to the acoustic signal, that is, the response time difference of at least two layers of laser arrays affected by the echo signal.

[0040] Therefore, in combination with the relationships provided above, the direction-of-arrival angle can be determined based on the phase information and the response time difference. That is, in one embodiment, the laser sensing device is further configured to determine the echo wave vector information of the echo signal based on the phase information of the laser beams in each layer of the laser array under the influence of the echo signal, and the response time difference between at least two layers of the laser array under the influence of the echo signal. At this time, the specific calculation formula for the finally obtained direction-of-arrival angle is as follows: ; Among them, the definitions of the parameters in the above formula have been described above, and the embodiments of the present application will not be elaborated here.

[0041] It should be noted that the influence of the sound speed c on the direction-of-arrival angle measurement is eliminated in the above process. Of course, in one embodiment, the above solution can also be used to determine the sound speed information of the echo signal, and this sound speed information can be used to assist in realizing the acoustic imaging of the underwater target object. That is, in one embodiment, the laser sensing device is further configured to determine the sound speed information of the echo signal based on the phase information of the laser beams in each layer of the laser array under the influence of the echo signal, and the response time difference between at least two layers of the laser array under the influence of the echo signal, where the sound speed information is used to assist in realizing the acoustic imaging of the underwater target object.

[0042] Specifically, the specific calculation formula for the sound speed information c of the echo signal is: ; By performing error analysis on the above two solutions, such as comparing the error terms in the calculation formulas of the two solutions, it can be found that there are period number errors in the angle error terms of both solutions , adjacent laser spacing errors in the same layer , and frequency errors . And these three error terms in the formula of the multi-layer laser array are all smaller than those of the single-layer laser array. In addition, the unique sound speed error term in the single-layer laser array is greater than the sum of the errors of the distance between two layers of lasers and the time difference of the responses of two layers of lasers in the multi-layer laser array. Therefore, by arranging a multi-layer laser array and using the distance between two layers of lasers, the influence of the sound speed on the direction-of-arrival angle measurement can be eliminated, thereby further improving the measurement accuracy.

[0043] In addition, in complex waters such as the ocean, the speed of sound changes with time and spatial position. The laser sensing device with a single-layer laser array cannot avoid the influence of the speed of sound on the measurement results, resulting in poor anti-interference ability. Once the speed of sound changes significantly, there will be a large deviation in the measurement results. The laser sensing device with a multi-layer laser array introduces a new dimension and belongs to a multi-dimensional acousto-optic sensing model. Since its measurement results are not affected by the speed of sound, changes in the external environment will not seriously affect the measurement results of this model, that is, the laser sensing device with a multi-layer laser array has strong anti-interference ability.

[0044] After determining the echo wave vector information of the echo signal by the method provided in any of the foregoing embodiments, the normal vector information at the first position on the underwater target object can be determined based on the first acoustic wave vector information of the first acoustic wave signal and the echo wave vector information. It can be understood that since the normal vector information at the first position on the underwater target object can describe the curvature change of the underwater target object (especially the circular arc target) at the local position, therefore, in one embodiment, the acoustic imaging of the underwater target object can be formed based on the normal vector information at multiple positions of the underwater target object.

[0045] Specifically, for the convenience of understanding the above content, a small period of time The parameters emitted within (i.e., the acoustic wave vector information) are The plane waves are recorded as a group, and the time interval between adjacent two groups of acoustic waves is set to And Assume a stationary state in this small period of time: Taking a 75 kHz acoustic signal as an example, the period is about 13.33, so within 0.2 ms, at most about 15 plane waves with different wave vectors can be emitted. Substituting the normal speed of a certain submersible of 38 knots (about 19.55 m / s), the underwater target only displaces about 4 mm; and the minimum angular deflection within a group of emitted acoustic waves is 0.02°, and the action point will deviate about 35 mm after 100 m. Assuming that the speed of the imaginary detection target is less than this speed, therefore, it can be assumed that the target object is in a stationary state within this small period of time.

[0046] Record a certain moment Start emitting the first group of acoustic waves, The wave vectors within are: ; Among them, Is To The wave vector of the last plane wave emitted within the time period of, and .

[0047] At this time, it can be discussed in several cases according to whether the object is flat, that is, whether the normal vectors of the tangent planes at each point on the surface of the target object are the same, and the motion state of the object: (1) When the target object is flat and stationary: The emitted wave vector is The echo wave vector obtained by interacting with the target is , because the target object is stationary and flat, the normal vectors of the tangent planes at each point on the surface are equal, and the target object is stationary. Therefore, in an ideal situation, the result of the normal vector calculation .

[0048] (2) When the target object is non-flat (such as arc-shaped) and stationary: The emitted wave vector is The echo wave vector obtained by interacting with the target is . The result of the normal vector calculation: ; Among them, because the target is not flat, the normal vectors of the tangent planes at each point on the surface are not equal, The elements of each row vector will not be equal even in an ideal situation. And because the target object is stationary, is independent of time, so the elements of its column vectors should be equal in an ideal calculation situation. That is can be simplified to: ; (3) When the target object is flat and moving in a straight line: Under this condition, the calculation result will be the same as that in condition (1), but due to the movement of the target, the distance between the transmitting end and the target object will change, and the flight time of the sound wave will also become larger or smaller. At the same time, after synchronizing the time between the receiving end and the transmitting end, the distance to the target object can be calculated through the flight time, and then combined with the angle of arrival information detected by the laser underwater acoustic sensing array, the preliminary positioning of the target object can be completed.

[0049] (4) When the target object is flat and rotating: The emitted wave vector is The echo wave vector obtained by interacting with the target is , the result of the normal vector calculation: ; Because the target object is flat, the normal vectors of the tangent planes at each point on the surface are equal. Therefore, in an ideal situation, the elements of each row vector are equal; but due to the rotation of the target object, the normal vectors of the tangent planes at each point on its surface will change with time. That is can be simplified to: ; (5) When the target object is non-planar and moving: The emitted wave vector is The echo wave vector obtained by interacting with the target is , and the result of the normal vector calculation: ; The normal vector of the tangent plane of the action point on the target surface at the corresponding moment of the row vector in the matrix can be obtained, and then the shape information of the target in the detection area at this moment can be obtained. By comparing the "overlap" of the elements in different row vectors, the surface shape of the target can be further drawn and used to preliminarily judge the motion state of the target: For example, if the following situation occurs, it can be preliminarily judged that the target surfaces corresponding to these three vectors are in the same area: ; Then on the one hand, the second and third row vectors of the matrix can be used to supplement and expand the information of the first row vector to obtain more information about the target object surface, thereby expanding the imaging range. At the same time, on the other hand, it also proves that the target object has at least two motion states within the time, and the motion state of the target object can be preliminarily obtained based on factors such as time difference, echo direction, and sound speed.

[0050] In addition, in order to more accurately implement acoustic imaging of an underwater target object, in one embodiment, the transducer is further configured to emit at least one beam of second acoustic wave signals to the laser sensing device; The laser sensing device is further configured to determine the second acoustic wave vector information of the second acoustic wave signal based on the second phase information of the laser beam under the influence of the second acoustic wave signal; The laser sensing device is further configured to determine the first propagation time for the first acoustic wave signal to reach the laser sensing device after being reflected by the underwater target object, and the second propagation time for the second acoustic wave signal to reach the laser sensing device; The processor is configured to determine the positioning information at the first position based on the first propagation time, the second propagation time, the first acoustic wave vector information, the second acoustic wave vector information, and the echo wave vector information, so as to obtain the tangent plane at the first position according to the positioning information and the normal information, and thus the tangent planes at multiple positions of the underwater target object form the acoustic imaging of the underwater target object.

[0051] Specifically, for ease of understanding the above content, please refer to Figure 3 , Figure 3 which is a schematic diagram of the effect of an imaging model of an underwater target object provided by an embodiment of the present application, and is described in detail as follows.

[0052] Among them, S represents the sound source, that is, the transducer, T represents the action point of the sound wave on the target object, that is, the first position, and O represents the laser sensing device, that is, the laser array. represents the angle between the tangent line of the target object at the action point and the x-axis, and is also equal to the angle between the normal vector of the target at the action point and the y-axis. is the angle between the direct signal wave vector at the laser array and the y-axis, that is, the second sound wave vector information of the second sound wave signal. is the angle between the echo signal wave vector at the laser array and the y-axis, that is, the echo wave vector information. represents the angle formed by connecting the head and tail of the sound wave vector emitted at the target action point and the echo wave vector.

[0053] In addition, the distance between the sound source (S) and the laser array (O) can be obtained according to the time difference between the second sound wave signals; on the other hand, the laser array will also receive the echo signal reflected by the target object, and then calculate the angle and the sum of the distances between the sound source (S) and the target object (T), and between the target object (T) and the laser array (O).

[0054] Then, by solving the triangle (triangle STO) formed by the sound source (S), the action point of the sound wave on the target object (T), and the laser array (O), the three-side information and three-angle information of this triangle can be obtained, and : ; ; ; ; ; ; ; Among them, is the sound speed information, which can be specifically determined by combining the multi-layer laser array provided above. represents the time taken for the sound to propagate directly from the sound source to the laser array. represents the time taken for the sound wave to be emitted from the sound source, reflected by the target object, and then propagated to the laser array.

[0055] Next, vector imaging of the target is performed: After obtaining the three side lengths and three angles of the triangle STO, the coordinates of the target action point in the coordinate system can be obtained to complete the positioning of the target action point. . At the same time, combining the angle between the normal vector of the target at the action point and the y-axis , complete imaging: At the coordinates in the two-dimensional xoy coordinate system according to the first set of data make a line segment with an angle of with the x-axis; expand this line segment into a sub-plane passing through this line segment and perpendicular to the xoy plane in the space coordinate system; perform the same processing on each set of data to obtain several sub-planes, and combine these sub-planes to obtain a preliminary vector imaging result, that is, the acoustic imaging of the target object.

[0056] In addition, it should be noted that the acoustic imaging system for underwater targets provided by this application can be particularly applicable to the acoustic imaging of arc-shaped structure objects in a moving state underwater. For example, it is applicable to the detection of underwater vehicles. This is mainly because the movement of the arc-shaped structure target itself in a moving state can also modulate the echo vector of the sound field, that is, change the characteristics of the echo signal (such as frequency, phase, or direction). Therefore, when there is a priori estimation of the moving speed of the target, the echo vector can be predicted and corrected based on the speed, or alternatively, the Doppler frequency shift (Doppler frequency shift) of the echo signal can be analyzed through the Doppler effect to calculate the echo vector. That is to say, in one embodiment, when the underwater target object is an arc-shaped structure object in a moving state, the transducer is further configured to transmit at least one beam of first acoustic wave signals to the underwater target object at multiple moments and collect the corresponding echo signals at multiple moments; The processor is further configured to determine the echo wave vector information corresponding to the echo signal based on the Doppler frequency offset of the echo signals corresponding to the multiple moments, or based on the echo signals corresponding to the multiple moments and the moving speed of the underwater target object.

[0057] It can be understood that the above-provided solution can be used to calculate the echo wave vector information. Of course, the calculated echo wave vector information can also be used to correct the echo wave vector information collected by the laser sensing device. For example, based on the echo wave vector information determined by the laser sensing device, combined with the correction amount of the echo wave vector information determined by the Doppler frequency offset or the moving speed, a more accurate echo wave vector information can be further obtained.

[0058] Of course, the above-provided solution relies on the movement of the underwater target. In fact, in one embodiment, it is only necessary to control the relative movement between the acoustic imaging system provided in this application and the underwater target object. That is to say, the solution provided in this application can also be used for target imaging of a target object in a stationary state. For example, in one embodiment of this application, the transducer is disposed on a moving mechanism, and the moving mechanism is used to control the movement of the transducer so that the transducer emits a first acoustic wave signal to the underwater target object at multiple different positions to form a plurality of echo signals corresponding to the plurality of first acoustic wave signals; The laser sensing device is further configured to determine the echo wave vector information of the plurality of echo signals; The processor is further configured to determine the normal information at a first position on the underwater target object based on the displacement information of the transducer and the echo wave vector information of the plurality of echo signals.

[0059] Among them, determining the normal information at a first position on the underwater target object based on the displacement information of the transducer and the echo wave vector information of the plurality of echo signals will not be elaborated in this embodiment of the application. Specifically, it can be based on the acoustic wave information with different incident angles emitted by the transducers at different positions and the reflection angles of the corresponding echo signals to determine different normal information, and based on the statistics of these normal information to obtain more accurate normal information. This will not be specifically elaborated in this embodiment of the application.

[0060] Specifically, for a clear understanding of the acoustic imaging system of the underwater target provided in this embodiment of the application, please refer to Figure 4 , Figure 4 which is a schematic diagram of an application scenario of an acoustic imaging system for an underwater target provided in an embodiment of the application. Among them, the information of each device in this scenario schematic diagram can refer to the relevant descriptions provided in the foregoing embodiments. In addition, for other auxiliary acoustic imaging devices such as the power amplifier, signal generator, computer measurement and control system, and anechoic structure (anechoic wedge) in the scenario schematic diagram, this embodiment of the application does not make any restrictions.

[0061] An acoustic imaging system for underwater targets provided by an embodiment of the present application emits at least one first acoustic wave signal towards an underwater target object through a transducer, so as to reflect at a first position on the underwater target object and form an echo signal corresponding to the first acoustic wave signal, and uses a laser sensing device to emit a laser beam to accurately obtain the wave vector information of the echo signal by using the acousto-optic effect, thereby detecting the normal vector at the first position on the underwater target object by combining the wave vector information of the first acoustic wave signal, and fusing the vector information into the acoustic imaging process of the underwater target object, achieving high-quality imaging of the underwater target object, and the accuracy of the wave vector information of the echo signal determined by the above method also meets the requirements of high-resolution acoustic imaging. Especially in the imaging detection scenario of long-distance and small targets underwater, it can effectively meet the effect of acoustic imaging.

[0062] Based on the above-provided solution, the present application further provides an acoustic imaging method applied to the above acoustic imaging system for underwater targets. Specifically, please refer to Figure 5 , Figure 5 which is a schematic flowchart of the steps of an acoustic imaging method for underwater targets provided by an embodiment of the present application. Specifically, it includes steps S510 to S530: S510, emit at least one first acoustic wave signal towards an underwater target object through a transducer, so as to reflect at a first position on the underwater target object and form an echo signal corresponding to the first acoustic wave signal.

[0063] S520, emit at least two mutually orthogonal laser beams through a laser sensing device arranged on the propagation path of the echo signal, and determine the echo wave vector information of the echo signal based on the first phase information of the laser beam under the influence of the echo signal.

[0064] S530, determine the normal information at the first position on the underwater target object according to the first acoustic wave vector information of the first acoustic wave signal and the echo wave vector information, so as to form the acoustic imaging of the underwater target object based on the normal information at multiple positions on the underwater target object.

[0065] In an embodiment of the present application, the specific implementation process of each step in the acoustic imaging method can refer to the relevant description of the above acoustic imaging system for underwater targets, and the embodiments of the present application will not be elaborated here.

[0066] Specifically, in one embodiment, the determining the echo wave vector information of the echo signal based on the first phase information of the laser beam under the influence of the echo signal includes: For a target orthogonal direction, receive laser signals of at least two laser beams affected by the echo signal in the target orthogonal direction, and perform Fourier transform on the laser signals to obtain the phase spectra of the laser beams; Based on the frequency of the echo signal, determine the phase differences of the at least two laser beams at the frequency from the phase spectra of the at least two laser beams, so as to determine the echo wave vector information of the echo signal in the target orthogonal direction based on the phase differences and the distances between the at least two laser beams.

[0067] Specifically, in one embodiment, the echo angle of the echo wave vector information is calculated by the following formula: ; wherein, is the echo angle in the echo wave vector information of the echo signal in the target orthogonal direction, represents a function, is the distance between the laser beams, is the cycle ambiguity number, is the phase difference of the first phase information of the multiple laser beams affected by the echo signal, is the wavelength of the echo signal, is the frequency of the echo signal, is the sound speed of the echo signal.

[0068] Specifically, in one embodiment, the method further includes: determining the echo wave vector information of the echo signal based on the phase information of the laser beams in each layer of the laser array affected by the echo signal and the response time difference between at least two layers of the laser array affected by the echo signal.

[0069] Specifically, in one embodiment, the method further includes: determining the sound speed information of the echo signal based on the phase information of the laser beams in each layer of the laser array affected by the echo signal and the response time difference between at least two layers of the laser array affected by the echo signal, wherein the sound speed information is used to assist in realizing the acoustic imaging of the underwater target object.

[0070] Specifically, in one embodiment, the method further includes: determining the second acoustic wave vector information of the second acoustic wave signal based on the second phase information of the laser beam affected by the second acoustic wave signal; determining the first propagation time when the first acoustic wave signal reaches the laser sensing device after being reflected by the underwater target object and the second propagation time when the second acoustic wave signal reaches the laser sensing device; Determine the positioning information at the first position based on the first propagation time, the second propagation time, the first acoustic wave vector information, the second acoustic wave vector information, and the echo wave vector information, so as to obtain the tangent plane at the first position according to the positioning information and the normal information, thereby forming the acoustic imaging of the underwater target object with the tangent planes at multiple positions of the underwater target object.

[0071] Specifically, in one embodiment, the method further includes: transmitting a first acoustic wave signal to the underwater target object at multiple different positions to form multiple echo signals corresponding to the multiple first acoustic wave signals; Determine the echo wave vector information of the multiple echo signals; Based on the displacement information of the transducer and the echo wave vector information of the multiple echo signals, determine the normal information at the first position on the underwater target object.

[0072] An acoustic imaging method for an underwater target provided by an embodiment of the present application transmits at least one beam of first acoustic wave signals to the underwater target object through a transducer, so as to reflect at the first position on the underwater target object and form an echo signal corresponding to the first acoustic wave signal, and uses a laser sensing device to emit a laser beam to accurately obtain the wave vector information of the echo signal by means of the acousto-optic effect, thereby detecting the normal vector at the first position on the underwater target object in combination with the wave vector information of the first acoustic wave signal, and fusing the vector information into the acoustic imaging process of the underwater target object, realizing high-quality imaging of the underwater target object, and the accuracy of the wave vector information of the echo signal determined by the above method also meets the requirements of high-resolution acoustic imaging. Especially in the imaging detection scenario of long distance and small target underwater, it can effectively meet the effect of acoustic imaging.

[0073] In one embodiment, the present application also provides an electronic device, and the electronic device interacts with the acoustic imaging system of the underwater target to realize imaging of the underwater target object. Taking the electronic device as a terminal device as an example, its internal structure diagram can be as Figure 6 shown. The electronic device 600 may include: a processor, a memory. The electronic device may further include one or more of a multimedia component, an input / output (I / O) component, and a communication component. In this embodiment, the electronic device may be a processing device in the acoustic imaging system of the underwater target provided in this embodiment.

[0074] Among them, the processor is used to control the overall operation of the electronic device to complete all or part of the steps in the above-mentioned acoustic imaging method for underwater targets. The memory is used to store various types of data to support the operation of the auxiliary electronic device. These data may include, for example, instructions for any application or method operating on the auxiliary electronic device, as well as application-related data, such as contact data, received and sent messages, pictures, audio, video, and so on. The memory can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as Static Random Access Memory (SRAM), Electrically Erasable Programmable Read Only Memory (EEPROM), Erasable Programmable Read Only Memory (EPROM), Programmable Read Only Memory (PROM), Read Only Memory (ROM), magnetic memory, flash memory, magnetic disk or optical disk. The multimedia component may include a screen and an audio component. The screen can be, for example, a touch screen, and the audio component is used to output and / or input audio signals. For example, the audio component may include a microphone for receiving external audio signals. The received audio signal can be further stored in the memory or sent through the communication component. The audio component also includes at least one speaker for outputting audio signals. The I / O component provides an interface between the processor and other interface modules, and the other interface modules mentioned above can be a keyboard, a mouse, buttons, etc. These buttons can be virtual buttons or physical buttons. The communication component is used for the electronic device to communicate with other devices, such as a target imaging device that fuses acoustic field gradient information, through wired or wireless communication. Wireless communication, such as Wi-Fi, Bluetooth, Near Field Communication (NFC), 2G, 3G, 4G, Narrow Band Internet of Things (NBIoT), Enhanced Machine Type Communication (eMTC), or other 5G, etc., or a combination of one or several of them, is not limited here. Therefore, the corresponding communication component may include: a Wi-Fi module, a Bluetooth module, an NFC module, and so on.

[0075] In an exemplary embodiment, an electronic device may be implemented by one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), controllers, microcontrollers, microprocessors, or other electronic components, and is used to execute the acoustic imaging method for underwater targets provided in any of the above embodiments. For example: Transmit at least one first acoustic wave signal to an underwater target object through a transducer, so as to reflect at a first position on the underwater target object and form an echo signal corresponding to the first acoustic wave signal; Transmit at least two mutually orthogonal laser beams through a laser sensing device arranged on the propagation path of the echo signal, and determine the echo wave vector information of the echo signal based on the first phase information of the laser beams under the influence of the echo signal; According to the first acoustic wave vector information of the first acoustic wave signal and the echo wave vector information, determine the normal information at the first position on the underwater target object, so as to form the acoustic imaging of the underwater target object based on the normal information at multiple positions of the underwater target object.

[0076] In another exemplary embodiment, a computer-readable storage medium including program instructions is further provided. When the program instructions are executed by a processor, the steps of the above-mentioned target imaging method for fusing sound field gradient information are implemented. For example, the computer-readable storage medium may be the above-mentioned memory including program instructions, and the above-mentioned program instructions may be executed by the processor of the electronic device to implement or execute the various methods, steps, and logic block diagrams disclosed in the embodiments of the present application; Or, when the instructions are executed by a computer, the various methods, steps, and logic block diagrams disclosed in the embodiments of the present application are implemented or executed. For example, the following steps are executed: Transmit at least one first acoustic wave signal to an underwater target object through a transducer, so as to reflect at a first position on the underwater target object and form an echo signal corresponding to the first acoustic wave signal; Transmit at least two mutually orthogonal laser beams through a laser sensing device arranged on the propagation path of the echo signal, and determine the echo wave vector information of the echo signal based on the first phase information of the laser beams under the influence of the echo signal; Determine the normal information at the first position on the underwater target object according to the first acoustic wave vector information of the first acoustic wave signal and the echo wave vector information, so as to form the acoustic imaging of the underwater target object based on the normal information at multiple positions of the underwater target object.

[0077] It should be understood that although the steps in the flowcharts involved in the above-described embodiments are sequentially shown according to the indications of the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless there is a clear description in this article, there is no strict order limit for the execution of these steps, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above-described embodiments may include multiple steps or multiple stages. These steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be executed alternately or alternately with at least a part of other steps or steps or stages in other steps.

[0078] Those of ordinary skill in the art can understand that all or part of the processes of implementing the methods in the above embodiments can be completed by instructing relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above methods.

[0079] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0080] The above-described embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. An acoustic imaging system for underwater targets, characterized in that, It includes a transducer, a laser sensing device, and a processor; The transducer is configured to emit at least one first acoustic wave signal towards an underwater target object, so as to reflect at a first position on the underwater target object and form an echo signal corresponding to the first acoustic wave signal; The laser sensing device is arranged on the propagation path of the echo signal, and is configured to emit at least two orthogonally polarized laser beams, and determine the echo wave vector information of the echo signal based on the first phase information of the laser beams under the influence of the echo signal; The processor is configured to determine the normal information at the first position on the underwater target object according to the first acoustic wave vector information of the first acoustic wave signal and the echo wave vector information, so as to form the acoustic imaging of the underwater target object based on the normal information at multiple positions of the underwater target object; Wherein, determining the echo wave vector information of the echo signal based on the first phase information of the laser beams under the influence of the echo signal includes: Performing Fourier transform on the laser signals of at least two laser beams in the target orthogonal direction affected by the echo signal in the target orthogonal direction to obtain the phase spectrum of the laser beams; Based on the frequency of the echo signal, determining the phase difference of the at least two laser beams at the frequency from the phase spectra of the at least two laser beams, so as to determine the echo wave vector information of the echo signal in the target orthogonal direction based on the phase difference and the distance between the at least two laser beams; The echo wave vector information of the echo signal in the target orthogonal direction is calculated by the following formula: ； Among them, is the echo angle in the echo wave vector information in the target orthogonal direction of the echo signal, represents a function, d is the distance between the laser beams, n is the integer ambiguity number, is the phase difference of the first phase information of multiple laser beams under the influence of the echo signal, is the echo signal wavelength, is the echo signal frequency, is the echo signal sound speed.

2. The system according to claim 1, wherein The echo wave vector information of the echo signal includes at least the wave vector information in two orthogonal directions. The laser beams emitted by the laser sensing device include at least a first laser beam and a second laser beam in the two orthogonal directions. Among them, the first laser beam includes at least two parallel laser beams in a first orthogonal direction, and the second laser beam includes at least two parallel laser beams in a second orthogonal direction.

3. The system according to claim 1, wherein The laser sensing device includes at least two layers of laser arrays, wherein each layer of laser array is configured to emit at least two orthogonally polarized laser beams; The laser sensing device is further configured to determine the echo wave vector information of the echo signal based on the phase information of the laser beams in each layer of laser array under the influence of the echo signal, and the response time difference of the at least two layers of laser arrays affected by the echo signal.

4. The system according to claim 3, wherein The laser sensing device is further configured to determine the sound speed information of the echo signal based on the phase information of the laser beams in each layer of laser array under the influence of the echo signal, and the response time difference of the at least two layers of laser arrays affected by the echo signal, wherein the sound speed information is used to assist in realizing the acoustic imaging of the underwater target object.

5. The system according to claim 1, wherein The transducer is further configured to emit at least one second acoustic wave signal towards the laser sensing device; The laser sensing device is further configured to determine the second acoustic wave vector information of the second acoustic wave signal based on the second phase information of the laser beams under the influence of the second acoustic wave signal; The laser sensing device is further configured to determine a first propagation time for the first acoustic wave signal to reach the laser sensing device after being reflected by the underwater target object, and a second propagation time for the second acoustic wave signal to reach the laser sensing device; The processor is configured to determine positioning information at the first position based on the first propagation time, the second propagation time, the first acoustic wave vector information, the second acoustic wave vector information, and the echo wave vector information, so as to obtain a tangent plane at the first position according to the positioning information and the normal information, and thus the tangent planes at multiple positions of the underwater target object form an acoustic image of the underwater target object.

6. The system according to claim 1, wherein When the underwater target object is an arc-shaped structure object in a moving state, the transducer is further configured to transmit at least one beam of first acoustic wave signals to the underwater target object at multiple moments, and collect echo signals corresponding to the multiple moments; The processor is further configured to determine echo wave vector information corresponding to the echo signals based on the Doppler frequency shift of the echo signals corresponding to the multiple moments, or based on the echo signals corresponding to the multiple moments and the moving speed of the underwater target object.

7. The system according to claim 1, characterized in that, The transducer is disposed on a moving mechanism, and the moving mechanism is configured to control the movement of the transducer so that the transducer transmits first acoustic wave signals to the underwater target object at multiple different positions to form multiple echo signals corresponding to the multiple first acoustic wave signals; The laser sensing device is further configured to determine echo wave vector information of the multiple echo signals; The processor is further configured to determine normal information at a first position on the underwater target object based on the displacement information of the transducer and the echo wave vector information of the multiple echo signals.

8. The system according to claim 1, characterized in that The transducer is composed of multiple array element sound sources, and the multiple array element sound sources are controlled to emit sound through a phased array model to transmit at least one beam of first acoustic wave signals to the underwater target object, where the first acoustic wave signal is a plane wave signal.

9. An acoustic imaging method for underwater targets, characterized in that, Applied to the acoustic imaging system of the underwater target according to any one of claims 1 to 8, the method includes: Transmitting at least one beam of first acoustic wave signals to the underwater target object through a transducer, so as to reflect at a first position on the underwater target object and form an echo signal corresponding to the first acoustic wave signal; Transmitting at least two mutually orthogonal laser beams through a laser sensing device disposed on the propagation path of the echo signal, and determining echo wave vector information of the echo signal based on first phase information of the laser beams affected by the echo signal; Determining normal information at a first position on the underwater target object according to the first acoustic wave vector information of the first acoustic wave signal and the echo wave vector information, so as to form an acoustic image of the underwater target object based on the normal information at multiple positions of the underwater target object; Wherein, determining the echo wave vector information of the echo signal based on the first phase information of the laser beams affected by the echo signal includes: For a target orthogonal direction, perform Fourier transform on the laser signals of at least two laser beams affected by the echo signal in the target orthogonal direction to obtain the phase spectrum of the laser beams; Based on the frequency of the echo signal, determine the phase difference of the at least two laser beams at the frequency from the phase spectra of the at least two laser beams, so as to determine the echo wave vector information of the echo signal in the target orthogonal direction based on the phase difference and the distance between the at least two laser beams; The echo wave vector information of the echo signal in the target orthogonal direction is calculated by the following formula: ； Among them, is the echo angle in the echo wave vector information in the orthogonal direction of the target for the echo signal, represents a function, d is the distance between the laser beams, n is the integer ambiguity number, is the phase difference of the first phase information of multiple laser beams under the influence of the echo signal, is the echo signal wavelength, is the echo signal frequency, is the echo signal sound velocity.

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