Method for sensing direction of water sound wave vector and water sound sensing system

Abstract

The application provides a method for sensing a direction of a water acoustic wave vector and a water acoustic sensing system. The method comprises the following steps: acquiring a two-dimensional displacement signal of a light spot formed by at least two detection lasers passing through a to-be-detected sound field of an underwater sound source; determining two-dimensional trajectory information of the light spot formed by each detection laser passing through the to-be-detected sound field within a preset time window; determining a two-dimensional trajectory matrix corresponding to the two-dimensional trajectory information, performing eigenvalue decomposition on a covariance matrix of the two-dimensional trajectory matrix, and determining a unit eigenvector corresponding to a maximum eigenvalue in the eigenvalue decomposition as a target two-dimensional displacement signal of the light spot; and processing the target two-dimensional displacement signal of the light spot to obtain three-dimensional wave vector information of the to-be-detected sound field. The application fuses and solves the wave vector projection direction of the to-be-detected sound field in multiple two-dimensional planes, so as to obtain the three-dimensional wave vector information of the to-be-detected sound field, without the need to construct a complex multi-beam array structure, and the number of light beams and channels can be effectively reduced.

Description

Technical Field

[0001] This application relates to the field of underwater acoustic sensing technology, specifically to an underwater acoustic wave vector direction sensing method and an underwater acoustic sensing system. Background Technology

[0002] Traditional vector hydrophones typically obtain sound field direction information by measuring sound pressure and particle velocity, or through pressure gradient structures; their directivity... Figure 1 They are generally shaped like an "8" and have limited directional selectivity. However, with the development of technology, the acoustic-optical deflection effect is increasingly being used for underwater acoustic sensing.

[0003] However, acousto-optic deflection direction finding typically employs a beam array structure, then calculates the direction of the incoming underwater acoustic wave based on the phase difference, time difference, and amplitude difference between the received signals from different beams. In other words, the main direction finding logic of related acousto-optic deflection direction finding technologies still relies on the relative information between multiple beams and channels. Essentially, it is close to constructing an optical array sensing structure from multiple laser beams, which presents problems such as complex system structure, limited array aperture, high requirements for channel consistency, and difficulties in installation and calibration. In some small underwater platforms, compact sonar nodes, or distributed underwater acoustic sensing terminals, limitations in size and packaging space make it difficult to deploy large-aperture arrays and ensure long-term consistency among multiple array elements, affecting the underwater acoustic monitoring effect. Summary of the Invention

[0004] Therefore, it is necessary to provide a method for sensing the direction of underwater acoustic wave vectors and an underwater acoustic sensing system to address the above-mentioned technical problems, so as to at least partially solve the technical problems of complex system structure and limited array aperture in the related acousto-optic deflection direction finding technology.

[0005] In a first aspect, this application provides a method for sensing the direction of underwater acoustic wave vectors, the method comprising: Two-dimensional displacement signals of light spots formed by at least two probe lasers passing through the underwater sound source in the test sound field are obtained, wherein the at least two probe lasers include a first probe laser and a second probe laser that are orthogonal to each other, and the two-dimensional displacement signal of each light spot is used to indicate the wave vector projection direction of the test sound field in a two-dimensional plane perpendicular to each of the probe lasers. Determine the two-dimensional trajectory information of the light spot formed by each of the probe lasers passing through the acoustic field to be tested within a preset time window. The two-dimensional trajectory information of the light spot includes the two-dimensional displacement signal of the light spot formed by the probe lasers passing through the acoustic field to be tested at multiple different time points. The two-dimensional trajectory matrix corresponding to the two-dimensional trajectory information of the light spot is determined, and the covariance matrix of the two-dimensional trajectory matrix is ​​decomposed into eigenvalues. The unit eigenvector corresponding to the largest eigenvalue in the eigenvalue decomposition is determined as the two-dimensional displacement signal of the target light spot. The two-dimensional displacement signal of the target light spot is processed to obtain the three-dimensional wave vector information of the sound field to be measured.

[0006] In one embodiment of this application, determining the two-dimensional trajectory matrix corresponding to the two-dimensional trajectory information of the light spot includes: For each probe laser-formed spot's two-dimensional trajectory information, the two-dimensional trajectory information is fitted with its principal axis to obtain the two-dimensional trajectory matrix. In one embodiment of this application, the process of fitting the two-dimensional trajectory information with its principal axis to obtain the two-dimensional trajectory matrix includes: The zero-point offset is subtracted from the two-dimensional displacement signal of each spot in the two-dimensional trajectory information of the spot to obtain the corrected two-dimensional trajectory matrix. The zero-point offset is determined by the background output corresponding to the laser detection in the silent field state, or by the low-frequency drift within the preset time window.

[0007] In one embodiment of this application, processing the two-dimensional displacement signal of the target light spot to obtain the three-dimensional wave vector information of the sound field to be measured includes: Linear constraint processing is performed on multiple sets of two-dimensional displacement signals of the target light spot to eliminate error interference in the multiple sets of two-dimensional displacement signals of the target light spot, thereby obtaining the three-dimensional wave vector information of the sound field to be measured.

[0008] In one embodiment of this application, the step of performing linear constraint processing on multiple sets of two-dimensional displacement signals of the target light spots to eliminate error interference present in the multiple sets of two-dimensional displacement signals of the target light spots, and obtaining the three-dimensional wave vector information of the sound field to be measured, includes: The linear constraint matrix of the three-dimensional wave vector information is determined based on multiple sets of two-dimensional displacement signals of the target light spot. Under the constraint that the three-dimensional wave vector information is a unit direction vector, the covariance matrix of the linear constraint matrix is ​​decomposed into eigenvalues, and the unit eigenvector corresponding to the minimum eigenvalue is taken as the three-dimensional wave vector information of the sound field to be measured.

[0009] In one embodiment of this application, the method further includes: The positive and negative polarities of each wave vector direction in the three-dimensional wave vector information of the sound field to be measured are determined, wherein the positive and negative polarities of the wave vector directions are determined by at least one of the following information: The incident direction of the detection laser and the relative position information of the underwater sound source.

[0010] In one embodiment of this application, determining the two-dimensional trajectory information of the light spots formed by each of the probe lasers passing through the acoustic field to be tested within a preset time window includes: The two-dimensional displacement signal of the light spot is preprocessed to obtain a preprocessed two-dimensional displacement signal of the light spot. The preprocessing includes at least one of amplification, filtering, DC removal, background subtraction, normalization, channel gain correction, envelope extraction or frequency component extraction. Based on the preprocessed two-dimensional displacement signal of the light spot, the two-dimensional trajectory information of the light spot formed by each of the probe lasers passing through the acoustic field to be tested within a preset time window is determined.

[0011] Secondly, this application provides an underwater acoustic sensing system, including a laser transceiver module and a processor; The laser transceiver module is used to emit at least two probe lasers into the sound field to be tested formed by the underwater target sound source, and to receive the two-dimensional displacement signal of the light spot formed by each probe laser passing through the sound field to be tested. The at least two probe lasers include a first probe laser and a second probe laser that are orthogonal to each other. The two-dimensional displacement signal of each light spot is used to indicate the wave vector projection direction of the sound field to be tested in a two-dimensional plane perpendicular to each probe laser. The processor is used to determine the two-dimensional trajectory information of the light spot formed by each of the probe lasers passing through the acoustic field to be tested within a preset time window. The two-dimensional trajectory information of the light spot includes the two-dimensional displacement signal of the light spot formed by the probe lasers passing through the acoustic field to be tested at multiple different time points. The two-dimensional trajectory matrix corresponding to the two-dimensional trajectory information of the light spot is determined, and the covariance matrix of the two-dimensional trajectory matrix is ​​decomposed into eigenvalues. The unit eigenvector corresponding to the largest eigenvalue in the eigenvalue decomposition is then determined as the two-dimensional displacement signal of the target light spot. The two-dimensional displacement signal of the target light spot is processed to obtain the three-dimensional wave vector information of the sound field to be measured.

[0012] In one embodiment of this application, the laser transceiver module includes at least a first position detector and a second position detector. The first position detector is used to receive a two-dimensional displacement signal of a first spot formed by the first probe laser as it passes through the sound field to be measured. The second position detector is used to receive a two-dimensional displacement signal of a second spot formed by the second probe laser as it passes through the sound field to be measured.

[0013] In one embodiment of this application, the laser transceiver module includes a first laser sensing unit and a second laser sensing unit, wherein the first laser sensing unit is used to emit the first detection laser, and the second laser sensing unit is used to emit the second detection laser; or The laser transceiver module includes a third laser sensing unit and a beam splitting component. The third laser sensing unit is used to emit the first detection laser, and the first detection laser is split into a second detection laser orthogonal to the first detection laser after passing through the beam splitting component.

[0014] The underwater acoustic wave vector direction sensing method provided in this application acquires two-dimensional displacement signals of light spots formed by at least two orthogonal probe lasers passing through the underwater sound source at the test acoustic field. Each light spot two-dimensional displacement signal can be used to indicate the wave vector projection direction of the test acoustic field in a two-dimensional plane perpendicular to each probe laser. Furthermore, it determines the two-dimensional trajectory information of the light spots formed by each probe laser passing through the test acoustic field within a preset time window. The light spot two-dimensional trajectory information includes the light spot two-dimensional displacement signals formed by the probe lasers passing through the test acoustic field at multiple different time points. The two-dimensional trajectory matrix corresponding to the light spot two-dimensional trajectory information is used to perform eigenvalue decomposition, and the unit eigenvector corresponding to the largest eigenvalue is determined as the target light spot two-dimensional displacement signal. This allows the wave vector projection direction of the test acoustic field in a two-dimensional plane perpendicular to each probe laser after eliminating background interference. Thus, the three-dimensional wave vector information of the test acoustic field is further determined through the target light spot two-dimensional displacement signal. This application treats the two-dimensional spot trajectories formed by at least two orthogonal laser beams in their respective detector planes as a whole, thereby improving the accuracy of the subsequent calculation of the three-dimensional wave vector information. In addition, compared with related technologies that rely on the phase difference between multiple laser beams as the core direction finding basis, it does not require the construction of a complex multi-beam array structure, which can effectively reduce the number of beams and channels, and reduce the complexity of optical path layout, device adjustment and signal calculation. It has better application effects in small underwater platforms, compact sonar nodes or distributed underwater acoustic sensing terminals. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This application provides a schematic flowchart of a method for sensing the direction of underwater acoustic wave vectors. Figure 2 A schematic diagram illustrating the deflection principle of a single-beam detection laser provided in an embodiment of this application; Figure 3 A schematic diagram of a structure for spatial acoustic vector sensing using transverse and longitudinal dual-beams is provided in an embodiment of this application; Figure 4 This application provides a schematic flowchart of a step for linearly constraining a two-dimensional displacement signal of a target light spot, as shown in the embodiments of this application. Figure 5 A flowchart illustrating the steps for processing light spot information provided in this application embodiment; Figure 6 A complete flowchart of an underwater acoustic wave vector direction sensing method provided in this application embodiment; Figure 7 This is a schematic diagram of the structure of an underwater acoustic sensing system provided in an embodiment of this application; Detailed Implementation

[0017] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0018] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0019] In the description of this application, the word "for example" is used to mean "used as an example, illustration, or description." Any embodiment described as "for example" in this application is not necessarily to be construed as being more preferred or advantageous than other embodiments. The following description is provided to enable any person skilled in the art to make and use the invention. Details are set forth in the following description for purposes of explanation. It should be understood that those skilled in the art will recognize that the invention can be made without using these specific details. In other instances, well-known structures and processes will not be described in detail to avoid obscuring the description of the invention with unnecessary detail. Therefore, the invention is not intended to be limited to the embodiments shown, but is consistent with the broadest scope of the principles and features disclosed in this application.

[0020] To clearly understand the underwater acoustic wave vector direction sensing method and underwater acoustic sensing system provided in this application, the relevant application scenarios of the underwater acoustic wave vector direction sensing method provided in this application will be described below. Specifically, the underwater acoustic wave vector direction sensing method is typically used in hydrophones and can be applied in various underwater acoustic wave detection fields. For example, in one possible implementation scenario, the underwater acoustic monitoring method based on the acousto-optic deflection effect provided in this application can be applied to mobile platforms such as AUVs (Autonomous Underwater Vehicles), UUVs (Unmanned Underwater Vehicles), underwater gliders, and underwater robots to sense the direction of external sound sources, the direction of vehicle noise, the direction of arrival of acoustic beacons, or the direction of target echoes. The obtained spatial acoustic vector information can provide input for underwater navigation, target avoidance, acoustic communication alignment, and environmental situational awareness. Alternatively, in another possible implementation scenario, it can be used for receiver direction sensing in underwater acoustic communication systems to assist in determining the direction of arrival of communication sound sources or acoustic beacons. In underwater communication, response positioning, acoustic navigation, and cooperative formation scenarios, sound source direction information is provided for link acquisition, receiver pointing adjustment, sound source tracking, and spatial interference suppression. Alternatively, in another possible implementation scenario, it can be used in passive acoustic sensing systems in ports, nearshore areas, submarine pipelines, submarine cables, marine ranches, and key waterways. By acquiring sound source direction information, the direction of approach of ships, submersibles, mechanical equipment, biological sound sources, or abnormal sound sources can be determined, providing support for underwater target detection, acoustic early warning, and regional security monitoring. Of course, in addition to the aforementioned implementation scenarios, the underwater acoustic wave vector direction sensing method provided in this application can be applied to any field of sound source sensing and monitoring of underwater target sound sources, achieving the sensing of the underwater sound source sound field by constructing an acousto-optic vector hydrophone.

[0021] Traditional vector hydrophones typically obtain sound field direction information by measuring sound pressure and particle velocity, or through pressure gradient structures; their directivity... Figure 1 Generally shaped like an "8", sonar arrays have limited directional selectivity. However, with technological advancements, the acousto-optic deflection effect is increasingly being used for underwater acoustic sensing. Currently, acoustic field direction finding based on the acousto-optic effect largely relies on beam array structures. It calculates the direction of incoming underwater acoustic waves by utilizing the phase difference, time difference, and amplitude difference between signals received by different beams. In other words, the main measurement logic depends on the relative information between multiple beams and channels, which is akin to constructing an optical array sensing structure from multiple laser beams. This presents problems such as complex system structure. Consequently, in some small underwater platforms, compact sonar nodes, or distributed underwater acoustic sensing terminals, the size and packaging space limitations make it difficult to deploy large-aperture arrays, thus affecting the underwater acoustic monitoring effect.

[0022] To at least partially address the aforementioned technical problems, this application provides a method for sensing the direction of underwater acoustic wave vectors. This method uses a single-beam probe laser as an acousto-optic vector sensing unit with planar direction sensing capabilities. By combining at least two probe lasers horizontally and vertically, acoustic vector information in three-dimensional space is obtained. This avoids the problems of complex optical paths, numerous devices, and high underwater sealing difficulty caused by over-reliance on multi-beam laser phase differences or multi-channel spatial differences to calculate the direction of incoming waves. Specifically, for ease of understanding, the following description will be provided in conjunction with specific related embodiments.

[0023] For details, please refer to Figure 1 , Figure 1 This application provides a flowchart illustrating the steps of an underwater acoustic wave vector direction sensing method, specifically including steps S110-S140: S110, acquire the two-dimensional displacement signal of the light spot formed by at least two probe lasers passing through the underwater sound source at the test sound field.

[0024] In one embodiment of this application, the detection laser can be emitted by a laser emitting device in an underwater acoustic monitoring system. Specifically, at least two detection laser beams can be emitted by the same laser emitting device via a beam splitter, or they can be emitted separately by different laser emitting devices. This application does not limit the emission process of the detection laser. Furthermore, when the detection laser passes through the sound field to be measured formed by the underwater sound source, the modulation effect of the underwater acoustic field on the refractive index of the medium causes the laser beam to deflect as it passes through the acousto-optic interaction region. This allows the two-dimensional displacement signal of the spot formed by the detection laser in the sound field to be measured through the underwater sound source to be captured by various position detectors in the underwater acoustic monitoring system, such as position-sensitive detectors, four-quadrant detectors, or other two-dimensional spot detectors. Specifically, this application also does not limit the reception of the two-dimensional displacement signal of the spot formed by the detection laser in the underwater acoustic monitoring system. Specific details will be provided in subsequent embodiments of the underwater acoustic monitoring system based on the acousto-optic deflection effect.

[0025] Furthermore, in one embodiment of this application, it can be understood that the two-dimensional displacement signal of each spot can be used to indicate the wave vector projection direction of the sound field under test in a two-dimensional plane perpendicular to each of the probe lasers. The following will explain this in conjunction with specific related principles.

[0026] Please see Figure 2 , Figure 2 A schematic diagram illustrating the deflection principle of a single-beam detection laser provided in an embodiment of this application is described in detail below.

[0027] For ease of understanding, the embodiments of this application will be described using a single-beam probe laser propagating along the x-axis as an example. Assume the probe laser propagates along the x-axis, and the detector plane is the yOz plane. Specifically, as follows... Figure 2 As shown.

[0028] When the sound field under test acts on the water medium, it causes local changes in sound pressure, density, and refractive index. Under small perturbation linear conditions, the refractive index of the medium can be expressed as: ; In the above formula, The refractive index of the medium under the influence of the sound field, and its relationship with spatial position. And related to time t, The static refractive index, For pressure-optical coefficients, Let be the sound pressure. This relationship shows that, under fixed temperature and fixed probe laser wavelength conditions, the sound pressure perturbation can be approximately linearly mapped to the refractive index perturbation.

[0029] When the probe laser passes through a non-uniform refractive index medium modulated by an underwater acoustic field, the direction of light propagation changes. Under geometrical optics, weak perturbation, paraxial small angle, and quasi-static approximation conditions, only the component of the refractive index gradient perpendicular to the laser principal axis will cause beam deflection. For example, please refer to [link to relevant documentation]. Figure 2 In other words, the propagation direction of the laser light returns to its original straight line, meaning the reference optical path, which was not deflected, is adjusted to the actual optical path after deflection. Let the effective acousto-optic interaction length of the probe laser be L, and its exit deflection angle be... It can be written as: ; In the above formula, To detect the unit vector along the x-axis of the laser principal axis, Let be the integral variable along the optical path. The above expression illustrates the deflection angle of the probe laser. The intensity of the acoustic pressure gradient along the optical path is determined by the integral of the acoustic pressure gradient perpendicular to the laser principal axis. Therefore, a single-beam probe laser is sensitive to spatial gradient information related to the direction of acoustic wave propagation.

[0030] Based on the above, we can further assume that the sound field to be measured can be approximated as a far-field simple harmonic plane wave within the acousto-optic interaction region, and its sound pressure expression is: ; In the formula, The sound pressure level is the amplitude. The angular frequency of the sound wave Let be the acoustic wave vector. Then, for the probe laser propagating along the x-axis in the diagram, the acoustic wave vector can be defined as: ; in, For sound wave number, The speed of sound in water, The angle between the acoustic wave vector and the principal optical axis (x-axis) of the probe laser is given. Let be the projection direction angle of the sound wave vector in the yOz plane.

[0031] Substituting the plane wave expression above into the beam deflection integral relationship, we can obtain the deflection angle vector of the probe laser: ; The sinc() function is defined as follows: . and These are the unit vectors of the probe laser on the corresponding y-axis and z-axis, respectively.

[0032] It can be understood that this equation shows that the deflection vector of the single-beam probe laser lies in the probe plane perpendicular to its principal optical axis, i.e., in the yOz plane, and the direction of the deflection vector is determined by... The direction of the deflection vector is determined by the projection of the sound wave vector onto the detection plane. The magnitude of the deflection vector is determined by the sound pressure amplitude, the sound wave number, the acousto-optic interaction length, the incident angle, and the finite optical path integral term.

[0033] Therefore, a single-beam probe laser can be used as a planar acousto-optic vector sensing unit to sense the projection direction of the acoustic wave vector in a plane perpendicular to the principal optical axis of the laser beam.

[0034] Building upon the aforementioned foundation, the probe laser, propagating along the x-axis, continues its propagation to the position detector after leaving the acousto-optic interaction region. Let the distance between the position detector and the acousto-optic interaction region be... Under the small-angle approximation, the displacements of the center of mass of the light spot in two directions within the detector plane satisfy the following: ; ; in, and These represent the components of the beam deflection angle along the y-axis and z-axis, respectively. Let be the vertical distance between the centroid of the light spot and the y-axis of the yOz plane, and Let be the vertical distance between the centroid of the light spot and the z-axis of the yOz plane. This represents the vertical distance between the centroid of the light spot and the y-axis of the yOz plane. As time t changes, This represents the vertical distance between the centroid of the light spot and the z-axis of the yOz plane. The change over time t.

[0035] When a four-quadrant detector is used for the position detector, the output photocurrents of the four quadrants, namely Q1 in the first quadrant, Q2 in the second quadrant, Q3 in the third quadrant, and Q4 in the fourth quadrant, are respectively... Then, the position outputs in two orthogonal directions can be obtained through difference normalization: ; ; Within the small displacement linear operating region, the normalized output is approximately proportional to the displacement of the spot centroid: ; ; In the formula, Let be the equivalent position-to-electrical signal conversion coefficient for the detector and its subsequent circuitry. Substituting the aforementioned beam deflection angle, we obtain: ; ; in, The definitions of other parameters in the formula have been explained above and will not be repeated here.

[0036] The above two equations give the relationship between the acoustic pressure field after acoustic refractive index modulation, beam deflection, free propagation and photoelectric conversion, and finally mapped to the two orthogonal output signals of the detector.

[0037] because and Having the same time term, sound pressure amplitude term, acousto-optic interaction length term, and sinc(·) modulation term, their ratio can eliminate common factors, resulting in: ; Right now ; To avoid the uncertainty of the ordinary arctangent function in quadrant determination, a two-parameter arctangent function can be used as follows: ; Therefore, the direction of the two-dimensional spot trajectory formed by a single-beam probe laser on the position detector can be used to characterize the projection direction of the acoustic wave vector in a plane perpendicular to the principal optical axis of the laser beam.

[0038] It should be noted that the single-beam probe laser does not provide the complete azimuth or elevation angle of the sound wave in three-dimensional space, but rather the two-dimensional wave vector projection angle of the sound wave vector within the detector plane at the corresponding position of the laser beam. Therefore, in one embodiment of this application, projection information on at least two non-parallel planes is obtained by utilizing at least two non-parallel probe lasers, specifically by using a first and second probe laser that are orthogonal to each other, thereby further fusing and calculating to obtain the final complete three-dimensional wave vector information, i.e., the angle information in three dimensions.

[0039] Specifically, the two-dimensional displacement signal of the first spot formed by the first probe laser and the two-dimensional displacement signal of the second spot formed by the second probe laser can be used to indicate the wave vector projection direction of the sound field under test in two mutually orthogonal two-dimensional planes. By using mutually orthogonal probe lasers, it is much more convenient to subsequently fuse and solve multiple sets of two-dimensional displacement signals of the spot, that is, the wave vector projection direction of the sound field under test in two mutually orthogonal two-dimensional planes. The specific implementation scheme will be described in the relevant embodiments of the fusion processing of multiple sets of two-dimensional displacement signals of the spot in the following sections.

[0040] Specifically, it should be noted that, based on the different definitions of the actual origin and coordinate axis directions in three-dimensional space, the detection laser provided in this application can also propagate in any direction. However, for ease of understanding and calculation, in the subsequent related embodiments of this application, the wave vector projection direction of the sound field to be measured in the yOz plane will be obtained through the detector by the detection laser propagating along the x-axis, and the wave vector projection direction of the sound field to be measured in the xOy plane will be obtained through the detector by the detection laser propagating along the z-axis. This should not be construed as a limitation on the technical solution of this application.

[0041] Building upon the aforementioned foundation, for a probe laser propagating along the z-axis, its detector output can be expressed as a planar vector form: ; Substituting the above output expression, we get: ; If the direction of the normalized acoustic wave vector is denoted as: ; in: ; The above single-beam laser output can then be written as: ; This equation shows that the two-dimensional output vector of a single-beam probe laser propagating along the x-axis is consistent with the projection direction of the acoustic wave vector onto the yOz plane. In other words: ; Therefore, the transverse probe laser can obtain the projection direction of the acoustic wave vector in the yOz plane, and its output ratio satisfies: ; Similarly, a transverse probe laser is used to obtain the two-dimensional wave vector projection trajectory of the acoustic wave vector in the yOz plane; a longitudinal probe laser is used to obtain the two-dimensional wave vector projection trajectory of the acoustic wave vector in the xOy plane. To make the subsequent three-dimensional solution relationship more direct, the longitudinal probe laser is set to propagate along the z-axis, and its position detector surface is the xOy plane; the transverse probe laser propagates along the x-axis, and its position detector surface is the yOz plane.

[0042] For a longitudinal probe laser propagating along the z-axis, its position detector plane is the xOy plane. Let the two outputs of the position detector corresponding to the longitudinal probe laser be... and Then we have: ; ; in, The common amplitude factor of the longitudinally probed laser channels cannot be used to directly inversely deduce the angle because it includes factors such as source level, sound pressure amplitude, propagation loss, source power, acousto-optic interaction length, finite optical path integral term, and detector gain. However, since the two channels have the same common amplitude factor, the directions of the two-dimensional spot trajectories formed by them in the xOy plane satisfy: ; Similarly, for a transverse probe laser propagating along the x-axis, its position detector plane is the yOz plane. Let the two outputs of the position detector corresponding to the transverse probe laser be... and Then we have: ; ; in, The common amplitude factor of the transversely probed laser channels cannot be used to directly infer the angle. Since the two channels have the same common amplitude factor, the directions of the two-dimensional spot trajectories formed by them in the yOz plane satisfy: ; Therefore, the longitudinal probe laser obtains the two-dimensional wave vector projection direction in the xOy plane, while the transverse probe laser obtains the two-dimensional wave vector projection direction in the yOz plane. Thus, the final complete three-dimensional wave vector requires at least the fusion calculation of these two two-dimensional projection trajectories.

[0043] S120, determine the two-dimensional trajectory information of the light spots formed by each of the probe lasers passing through the acoustic field to be tested within a preset time window.

[0044] Building upon the aforementioned foundation, and based on the wave vector projection directions of the measured sound field in different two-dimensional planes, particularly in two orthogonal two-dimensional planes, under ideal conditions, there exists a fundamental geometric correspondence between the two two-dimensional wave vector projection angles and the three-dimensional wave vector direction. The processing module can obtain an initial estimate of the three-dimensional wave vector from this relationship. For a more detailed understanding of the above, please refer to [link to relevant documentation]. Figure 3 , Figure 3 A schematic diagram of a structure for spatial acoustic vector sensing using transverse and longitudinal dual-beams is provided in this application embodiment, and is described in detail below.

[0045] Spatial acoustic vector sensing is achieved by combining transverse and longitudinal probe lasers. Assume the transverse probe laser propagates along the x-axis and the longitudinal probe laser propagates along the z-axis. The two probe lasers form non-parallel acousto-optic paths within the acousto-optic interaction region, such as orthogonal acousto-optic paths.

[0046] At this point, establish a fixed coordinate system Oxyz for the sensor, and let the direction of the unit wave vector of the sound wave to be measured be: ; in, , , Let be the direction cosines of the sound wave vector along the x-axis, y-axis, and z-axis, respectively, and satisfy the following: ; The longitudinal probe laser propagates along the z-axis, and its position detector surface is the xOy plane. The longitudinal probe laser has two output channels. and This is used to obtain the two-dimensional projection trajectory of the acoustic wave vector in the xOy plane, where the two-dimensional projection direction satisfies: ; The transverse probe laser propagates along the x-axis, and its position detector surface is the yOz plane. The transverse probe laser has two output channels. and This is used to obtain the two-dimensional projection trajectory of the acoustic wave vector in the yOz plane, where the two-dimensional projection direction satisfies: ; Under ideal conditions, the initial estimate of the three-dimensional wave vector can be calculated by matching the observation results with the proportions of the cosines in each direction, and ensuring that the sum of the squares of the cosines in each direction is 1. However, due to channel noise, background light bias, zero-point drift, and angle singularities in actual measurements, the initial estimate has certain errors. To further improve the accuracy of calculating the direction of the three-dimensional wave vector, subsequent embodiments of this application will propose a scheme that can accurately fuse and process multiple sets of two-dimensional displacement signals of light spots to obtain more accurate three-dimensional wave vector information. Specifically, the following will describe this in conjunction with specific embodiments.

[0047] In one embodiment of this application, the two-dimensional trajectory information of the light spot includes the two-dimensional displacement signal of the light spot formed by the probe laser passing through the acoustic field to be tested at multiple different time points.

[0048] Specifically, in actual underwater acoustic measurements, if a single sampling point is used to calculate the two-dimensional projection angle, the instantaneous ratio will fluctuate significantly when the acoustic signal is at a zero-crossing point, the amplitude of a certain channel is small, background light bias exists, or noise is strong. To improve the stability of the three-dimensional wave vector angle information calculation, in this embodiment, the two-dimensional light spot trajectories formed by the two laser beams in their respective positions within the detector plane are treated as a whole. The two-dimensional wave vector projection direction is extracted by fitting the principal axis of the trajectory, thereby improving the accuracy of the subsequently calculated three-dimensional wave vector information. That is, for each probe laser beam, the two-dimensional trajectory information of the light spot formed by the probe laser as it passes through the acoustic field under test will be collected within a preset time window. This two-dimensional trajectory information includes the two-dimensional displacement signal of the light spot formed by the probe laser as it passes through the acoustic field under test at multiple different time points.

[0049] S130, determine the two-dimensional trajectory matrix corresponding to the two-dimensional trajectory information of the light spot, perform eigenvalue decomposition on the covariance matrix of the two-dimensional trajectory matrix, and determine the unit eigenvector corresponding to the largest eigenvalue in the eigenvalue decomposition as the two-dimensional displacement signal of the target light spot.

[0050] In one embodiment of this application, considering that background interference such as changes in sound source level, propagation loss, and fluctuations in light source power mainly change the length of the two-dimensional light spot trajectory formed on the plane, but do not change the trajectory principal axis direction for the two-dimensional light spot trajectory information formed for each probe laser, by fitting the trajectory principal axis of the two-dimensional light spot trajectory information, that is, the two-dimensional light spot displacement signal formed at multiple different time points, can be obtained in the wave vector projection direction of the target light spot in the two-dimensional plane perpendicular to each probe laser after the background interference is eliminated.

[0051] Specifically, for ease of understanding of the above content, in one embodiment of this application, determining the two-dimensional trajectory matrix corresponding to the two-dimensional trajectory information of the light spot includes: For each probe laser spot's two-dimensional trajectory information, the trajectory principal axis is fitted to the two-dimensional trajectory information to obtain the two-dimensional trajectory matrix.

[0052] Specifically, within a certain time window, the N sets of outputs from the detector at the corresponding position of the transverse detection laser are collected. Taking N light spot two-dimensional displacement signals as an example, the N light spot two-dimensional displacement signals can form a two-dimensional trajectory matrix.

[0053] Specifically, in one embodiment of this application, the two-dimensional trajectory matrix composed of the N spot two-dimensional displacement signals can also be a corrected two-dimensional trajectory matrix obtained by subtracting the zero-point offset. That is, the process of fitting the two-dimensional trajectory information of the spot to the principal axis to obtain the two-dimensional trajectory matrix includes: The zero-point offset is subtracted from the two-dimensional displacement signal of each spot in the two-dimensional trajectory information of the spot to obtain the corrected two-dimensional trajectory matrix. The zero-point offset is determined by the background output corresponding to the laser detection in the silent field state, or by the low-frequency drift within the preset time window.

[0054] Specifically, taking the aforementioned N sets of outputs For example, take the two-dimensional displacement signal of N light spots.

[0055] After subtracting the zero-point offset, the corrected two-dimensional displacement signal of the back spot can be obtained: ; ; in, and The zero-point offset is typically determined by the background output of the detector at the corresponding position of the transverse detection laser in a silent field, or estimated by the low-frequency drift within the preset time window. This application does not limit the zero-point offset used in its embodiments.

[0056] Based on the above, the corrected two-dimensional trajectory matrix can be constructed: ; The two-dimensional trajectory matrix filters out relevant background components to a certain extent. Of course, it is also feasible to directly use the N sets of outputs without deducting the zero-point offset, that is, to directly construct the two-dimensional trajectory matrix corresponding to the two-dimensional trajectory information of the light spot, and this application does not impose any restrictions on this.

[0057] Building upon the aforementioned foundation, by further constructing the covariance matrix of the two-dimensional trajectory matrix, that is... ; Then the matrix Perform eigenvalue decomposition and extract the unit eigenvector corresponding to the largest eigenvalue: ; This eigenvector represents the principal axis direction of the transverse probe laser spot trajectory in the yOz plane, and therefore satisfies: ; That is: ; Of course, similarly to the above method, the process of extracting the principal axis of the longitudinal probe laser trajectory in the xOy plane can be obtained, as follows.

[0058] Within the same preset time window, N sets of outputs are collected from the detectors at the corresponding positions of the longitudinal detection laser. ; The zero-point offset is subtracted in a similar way, that is: ; ; in, and The background output of the detector at the corresponding position of the longitudinal detection laser in the silent field state, or the zero bias estimated by the low-frequency drift within the time window.

[0059] Construct the two-dimensional trajectory matrix of the longitudinally probing laser: ; Reconstruct the covariance matrix: ; right Perform eigenvalue decomposition and extract the unit eigenvector corresponding to the largest eigenvalue: ; This eigenvector represents the principal axis direction of the longitudinal probe laser spot trajectory in the xOy plane, and therefore satisfies: ; That is: ; It is understandable that changes in sound source level, propagation loss, and fluctuations in light source power primarily alter the length of the two-dimensional light spot trajectory, without changing the direction of the trajectory's principal axis. Therefore, the method provided in this application, which does not rely on acoustic amplitude to infer angles, treats the two-dimensional light spot trajectories formed by two laser beams (horizontal and vertical) within their respective detector planes as a single object. By fitting the principal axis of the trajectory to extract the wave vector projection direction in the two-dimensional plane perpendicular to each detector laser after eliminating background interference, the stability of the three-dimensional wave vector angle information calculation can be further improved.

[0060] S140, the two-dimensional displacement signal of the target light spot is processed to obtain the three-dimensional wave vector information of the sound field to be measured.

[0061] Based on the above, by obtaining the wave vector projection direction to eliminate interference through the aforementioned method, and processing the two-dimensional displacement signal of the target spot, the three-dimensional wave vector information of the sound field to be measured can be obtained.

[0062] For example, in one possible implementation, the principal axis direction obtained from the longitudinally probed laser can be known as follows: ; Two parallel two-dimensional vectors mean that their two-dimensional cross product is zero, therefore: ; The principal axis direction obtained from the transverse detection laser indicates that: ; Similarly, we can conclude that: ; Therefore, the direction of the three-dimensional wave vector The following linear constraints should be satisfied: ; Among them, record A The linear constraint matrix related to the two-dimensional displacement signals of multiple target light spots, i.e. ; Then we have: ; Simultaneously, the three-dimensional wave vector direction Since it is a unit direction vector, it satisfies: .

[0063] It should be noted that, under ideal noise-free conditions, the direction of the three-dimensional wave vector... The null space direction of matrix A. However, in actual measurements, due to background light, noise, assembly errors, and position detector channel gain errors, there may be slight deviations between the two two-dimensional principal axis directions. Therefore, in one embodiment of this application, in order to further improve the fusion and solution of three-dimensional wave vector information, a method of linear constraint is proposed to eliminate the error interference existing in multiple sets of target spot two-dimensional displacement signals to obtain the final three-dimensional wave vector information. That is, the processing of multiple sets of target spot two-dimensional displacement signals to obtain the three-dimensional wave vector information of the sound field to be measured includes: Linear constraint processing is performed on multiple sets of two-dimensional displacement signals of the target light spot to eliminate error interference in the multiple sets of two-dimensional displacement signals of the target light spot, thereby obtaining the three-dimensional wave vector information of the sound field to be measured.

[0064] For details, please refer to Figure 4 , Figure 4 This application provides a flowchart illustrating the steps for linearly constraining a two-dimensional displacement signal of a target light spot, specifically including steps S410-S420: S410, determine the linear constraint matrix of the three-dimensional wave vector information based on the multiple sets of two-dimensional displacement signals of the target light spots.

[0065] S420, under the constraint that the three-dimensional wave vector information is a unit direction vector, the covariance matrix of the linear constraint matrix is ​​decomposed into eigenvalues, and the unit eigenvector corresponding to the minimum eigenvalue is used as the three-dimensional wave vector information of the sound field to be measured.

[0066] Specifically, for ease of understanding, the following will be explained in conjunction with specific embodiments.

[0067] In one embodiment of this application, the three-dimensional wave vector direction is solved using position-constrained least squares as an example, that is, the objective function is as follows: ; When expanded, ; make ; The above problem then becomes: ; According to the Rayleigh quotient property, the solution to this problem is a matrix. The unit eigenvector corresponding to the smallest eigenvalue. That is, to find: .

[0068] in, For matrix The smallest eigenvalue, This is the corresponding unit eigenvector. This unit eigenvector is a candidate solution for the direction of the three-dimensional wave vector. Based on this, according to the pre-defined front-back direction and the installation coordinate system, the candidate unit wave vectors obtained by unit constraint least squares are normalized in direction, thereby selecting the direction that satisfies the forward incident constraint as the final three-dimensional wave vector output.

[0069] Furthermore, in one embodiment of this application, for the determined three-dimensional wave vector information, it is usually still necessary to further determine the positive and negative polarities of the wave vector directions in each sound field to be measured, wherein the positive and negative polarities of the wave vector directions are determined by at least one of the following information: The incident direction of the detection laser and the relative position information of the underwater sound source.

[0070] For example, in one possible implementation, the sign of the wave vector direction can usually be determined based on the sensor's installation orientation, such as the incident direction of the detection laser or the half-space where the underwater sound source is located. Of course, in some embodiments, the sign of the wave vector direction can also be determined by the active sound source emission reference, the polarity of the detector channel, or the continuity of historical directions, thereby obtaining the final three-dimensional unit wave vector.

[0071] The application provided by this application The scheme for obtaining the three-dimensional wave vector direction using the minimum eigenvector does not require explicit calculation. This avoids numerical divergence when the two-dimensional projection angle is close to 90°, and can directly use the main axis direction of the light spot trajectory in the plane of the two position detectors for fusion, making it suitable for stable calculations in the presence of noise and channel errors.

[0072] Of course, besides the unit-constrained least-squares solution for the three-dimensional wave vector direction provided above, in some embodiments, for the basic structure of two orthogonal laser beams, the above least-squares solution can also be written in an equivalent closed-form form. (From:) ; as well as: ; A vector parallel to the three-dimensional wave vector can be constructed: ; Therefore, under conditions of no singularities and low noise (or without considering noise interference), the direction of the three-dimensional wave vector can also be written as: ; in, That is, the magnitude of the vector.

[0073] Building upon the foregoing, after obtaining the three-dimensional wave vector information of the sound field to be measured, in some embodiments of this application, spatial angle information can be further output. For example, in one possible implementation, after obtaining the three-dimensional unit wave vector... Then, if azimuth angle is defined Let be the angle between the projection of the sound wave vector onto the xOy plane and the x-axis, then: ; If the pitch angle is defined Let be the angle between the sound wave vector and the xOy plane, then: ; exist Under the given conditions, it can also be written as: ; Therefore, the underwater acoustic wave vector direction sensing method provided in this application can further output parameter values ​​including three-dimensional unit wave vector, azimuth angle, pitch angle or other equivalent spatial angles according to the needs of actual application scenarios. Of course, the embodiments of this application do not limit this.

[0074] Of course, in the above process, in order to further improve the underwater acoustic sensing effect, during the process of capturing the two-dimensional displacement signal of the light spot by the detector, relevant signal preprocessing methods can be used to preprocess the signal to ensure the accuracy of subsequent processing. Please see Figure 5 , Figure 5 A flowchart illustrating the steps for processing light spot information provided in this application embodiment specifically includes: S510, the two-dimensional displacement signal of the light spot is preprocessed to obtain a preprocessed two-dimensional displacement signal of the light spot, wherein the preprocessing includes at least one of amplification, filtering, DC removal, background subtraction, normalization, channel gain correction, envelope extraction or frequency component extraction.

[0075] S520, based on the preprocessed two-dimensional displacement signal of the light spot, determine the two-dimensional trajectory information of the light spot formed by each of the probe lasers passing through the acoustic field to be tested within a preset time window.

[0076] For example, in one possible implementation, taking frequency component extraction as an example, for narrowband acoustic signals, the effective output at the target frequency can be extracted; for broadband acoustic signals, the vector output corresponding to each frequency component can be extracted by frequency band. Of course, in addition to the above-mentioned solutions, the embodiments of this application do not limit the preprocessing of signals such as amplification, filtering, noise reduction, and correction based on actual needs.

[0077] It should be noted that in some embodiments of this application, the single-beam probe laser not only provides the projection direction within the probe plane, but its total output amplitude also exhibits a spatial response related to the direction of arrival. Taking a probe laser propagating along the x-axis as an example, its total spot displacement or total output amplitude within the detector plane can be written as: ; or: ; Substituting the aforementioned relationship, we can obtain its direction-dependent magnitude term: ; After removing the time and gain terms, the directional response function of a single-beam probe laser can be defined as: ; in, The term originates from the projection of the sound pressure gradient onto the direction perpendicular to the laser principal axis. The term originates from the continuous integral effect within a finite acousto-optic interaction length. This directional response differs from the simple figure-eight-shaped dipole directivity in traditional vector hydrophones; instead, it is spatial selectivity formed by superimposing a finite optical path continuous integral on the acoustic pressure gradient projection.

[0078] Therefore, the underwater acoustic wave vector direction sensing method provided in this application can not only obtain the spatial acoustic vector direction, but also form a more concentrated directional response feature by utilizing the continuous acoustic-optical interaction path.

[0079] It is understandable that the total output amplitude mentioned above can be used to evaluate the signal strength and channel operating status of a single-beam probe laser. However, since it is affected by factors such as sound source level, propagation loss, light source power, channel gain, and background light, this application does not directly infer the incoming wave angle from the total output amplitude. Instead, it fuses the principal axis directions of the two-dimensional spot trajectories in the planes of the two position detectors to obtain the fusion calculation. The two-dimensional wave vector projection direction is extracted by fitting the principal axis of the trajectory, and linear constraints, such as unit constraint least squares, are suitable for stable calculation under the presence of noise and channel errors, ensuring the accurate output of the three-dimensional wave vector information or other equivalent spatial angles of the sound field.

[0080] To clearly understand the complete underwater acoustic wave vector direction sensing method provided in this application's embodiments, the following detailed explanation will be provided in conjunction with specific related embodiments. Please refer to... Figure 6 , Figure 6 A complete flowchart of an underwater acoustic wave vector direction sensing method provided in this application embodiment is shown, specifically including the following steps: Step S1: Activate the lateral laser sensing unit and the longitudinal laser sensing unit, so that the lateral detection laser and the longitudinal detection laser pass through the acousto-optic interaction area and are incident on the corresponding position detectors respectively.

[0081] In step S2, the underwater acoustic signal to be measured enters the acousto-optic interaction region, causing a change in the refractive index distribution of the medium and forming a refractive index gradient field related to the spatial gradient of the sound field.

[0082] In step S3, the transverse and longitudinal probe lasers are modulated by the refractive index gradient during propagation, resulting in a slight deflection related to the direction of the acoustic wave vector.

[0083] Step S4: The first position detector acquires the two-dimensional spot displacement of the transverse detection laser and outputs... and The second position detector acquires the two-dimensional spot displacement of the longitudinal probe laser and outputs... and .

[0084] Step S5 involves preprocessing the signals from each channel. Preprocessing includes amplification, filtering, DC removal, background subtraction, normalization, channel gain correction, and envelope extraction or frequency component extraction. For narrowband acoustic signals, the effective output at the target frequency can be extracted; for wideband acoustic signals, the vector output corresponding to each frequency component can be extracted by frequency band.

[0085] Step S6: Within a preset time window, the processing module constructs a two-dimensional spot trajectory matrix of the longitudinal probe laser in the xOy plane and a two-dimensional spot trajectory matrix of the transverse probe laser in the yOz plane, and extracts the principal axis directions of the two two-dimensional trajectories by eigenvalue decomposition of the covariance matrix.

[0086] Step S7: The processing module determines the main axis direction of the longitudinal detection laser. and the principal axis direction of the transverse detection laser .

[0087] Step S8: Construct the linear constraint matrix for the three-dimensional wave vector direction: ; Step S9, the processing module solves the unit-constrained least squares problem: ; And The unit eigenvector corresponding to the smallest eigenvalue is used as a candidate solution for the three-dimensional wave vector direction.

[0088] Furthermore, depending on the requirements, the processing module can further determine the positive and negative polarities of the three-dimensional wave vector direction based on the sensor installation direction, the half-space where the sound source is located, the active sound source emission reference, the detector channel polarity, or the continuity of historical directions, to obtain the final three-dimensional unit wave vector. .

[0089] In step S10, the processing module converts the three-dimensional unit wave vector into azimuth, pitch, or other equivalent spatial angle parameters, and outputs the direction perception results of the acousto-optic vector hydrophone.

[0090] The underwater acoustic wave vector direction sensing method provided in this application utilizes the acousto-optic deflection effect to generate a deflection signal related to the sound pressure gradient when the probe laser passes through the underwater acoustic field. For a single probe laser, its two-dimensional spot displacement output can characterize the projection direction of the acoustic wave vector in a plane perpendicular to the principal optical axis of the laser beam; the transverse and longitudinal probe lasers respectively provide acoustic vector projection information in two orthogonal planes; the processing module calculates the spatial acoustic wave vector direction based on the projection relationship between the two planes, thereby realizing the function of an acousto-optic vector hydrophone.

[0091] Furthermore, this application extracts the principal axis directions of the two-dimensional spot trajectories of the transverse and longitudinal probe lasers within their respective detector planes within a preset time window, constructs a linear constraint matrix for the three-dimensional wave vector from the two principal axis directions, and then solves for the three-dimensional wave vector direction using the unit constraint least squares method. This processing method avoids the numerical singularity and noise sensitivity problems caused by directly using instantaneous ratios and tan relationships, making the calculation of the three-dimensional wave vector angle information more stable.

[0092] This scheme treats each probe laser beam as an acousto-optic vector sensing unit with planar directional response, rather than as a conventional receiving channel in multi-beam phase difference direction finding. Therefore, this application can achieve spatial acoustic vector sensing in a transverse and longitudinal dual-beam structure, and form acousto-optic directional response characteristics different from those of traditional figure-eight vector hydrophones.

[0093] Meanwhile, this application concretizes the information fusion process of the horizontal and vertical dual beams into a complete algorithm flow of "two-dimensional wave vector projection trajectory acquisition - trajectory principal axis fitting - linear constraint matrix construction - unit constraint least squares solution - spatial azimuth and elevation angle output", so that the three-dimensional wave vector angle solution of the acousto-optic vector hydrophone is no longer a simple coordinate component splicing, but a fusion solution method with clear mathematical constraints and engineering stability.

[0094] By acquiring two-dimensional displacement signals of light spots formed by at least two orthogonal probe lasers passing through the underwater sound source at the test acoustic field, each light spot two-dimensional displacement signal can be used to indicate the wave vector projection direction of the test acoustic field in a two-dimensional plane perpendicular to each probe laser. Furthermore, the two-dimensional trajectory information of light spots formed by each probe laser passing through the test acoustic field within a preset time window is determined. The light spot two-dimensional trajectory information includes the light spot two-dimensional displacement signals formed by the probe lasers passing through the test acoustic field at multiple different time points. The two-dimensional trajectory matrix corresponding to the light spot two-dimensional trajectory information is used for eigenvalue decomposition, and the unit eigenvector corresponding to the largest eigenvalue is determined as the target light spot two-dimensional displacement signal. This allows the wave vector projection direction of the test acoustic field in a two-dimensional plane perpendicular to each probe laser after eliminating background interference to be obtained. Thus, the three-dimensional wave vector information of the test acoustic field is further determined through the target light spot two-dimensional displacement signal. This application treats the two-dimensional spot trajectories formed by at least two orthogonal laser beams in their respective detector planes as a whole, thereby improving the accuracy of the subsequent calculation of the three-dimensional wave vector information. In addition, compared with related technologies that rely on the phase difference between multiple laser beams as the core direction finding basis, it does not require the construction of a complex multi-beam array structure, which can effectively reduce the number of beams and channels, and reduce the complexity of optical path layout, device adjustment and signal calculation. It has better application effects in small underwater platforms, compact sonar nodes or distributed underwater acoustic sensing terminals.

[0095] The underwater acoustic wave vector direction sensing method provided in this application typically operates in underwater acoustic sensing systems, such as common hydrophones. This method is configured to run as a computer program within the processor of the underwater acoustic sensor system. The underwater acoustic sensing system usually also includes other components for data collection; for details, please refer to [link to relevant documentation]. Figure 7 , Figure 7 This is a schematic diagram of the structure of an underwater acoustic sensing system provided in an embodiment of this application, which can also be understood as a schematic diagram of an application scenario for underwater acoustic sensing. Details are as follows.

[0096] Specifically, in one embodiment of this application, the underwater acoustic sensing system includes a laser transceiver module and a processor. The laser transceiver module is used to emit at least two probe lasers into the sound field to be measured formed by the underwater target sound source, and to receive a two-dimensional displacement signal of the light spot formed by each probe laser passing through the sound field to be measured. The at least two probe lasers include a first probe laser and a second probe laser that are orthogonal to each other. The two-dimensional displacement signal of each light spot is used to indicate the wave vector projection direction of the sound field to be measured in a two-dimensional plane perpendicular to each of the probe lasers. The processor is used to determine the two-dimensional trajectory information of the light spot formed by each of the probe lasers passing through the acoustic field to be tested within a preset time window. The two-dimensional trajectory information of the light spot includes the two-dimensional displacement signal of the light spot formed by the probe lasers passing through the acoustic field to be tested at multiple different time points. The two-dimensional trajectory matrix corresponding to the two-dimensional trajectory information of the light spot is determined, and the covariance matrix of the two-dimensional trajectory matrix is ​​decomposed into eigenvalues. The unit eigenvector corresponding to the largest eigenvalue in the eigenvalue decomposition is then determined as the two-dimensional displacement signal of the target light spot. The two-dimensional displacement signal of the target light spot is processed to obtain the three-dimensional wave vector information of the sound field to be measured.

[0097] For example, in one possible implementation, the laser transceiver module may include laser sensing units, such as a lateral laser sensing unit and a longitudinal laser sensing unit, as well as position detectors, such as a first position detector and a second position detector.

[0098] The signals collected by these detectors are processed by the signal acquisition module. The signal acquisition module amplifies, filters, samples, and normalizes the electrical signals output by the first and second position detectors before transmitting them to the processor, i.e., the processing module in the figure, to execute the underwater acoustic wave vector direction sensing method mentioned in any of the embodiments, including those described above. For each probe laser's two-dimensional trajectory information of the spot, the two-dimensional trajectory information of the spot is fitted with the principal axis to obtain the target spot two-dimensional displacement signal. The target spot two-dimensional displacement signal is used to indicate the wave vector projection direction of the sound field under test in the two-dimensional plane perpendicular to each probe laser after background interference is eliminated. For each probe laser spot's two-dimensional trajectory information, the trajectory principal axis is fitted to the two-dimensional trajectory information to obtain the two-dimensional trajectory matrix.

[0099] Alternatively, the zero-point offset can be subtracted from the two-dimensional displacement signal of each spot in the two-dimensional trajectory information of the spot to obtain the corrected two-dimensional trajectory matrix. The zero-point offset is determined by the background output corresponding to the laser detection in the silent field state, or by the low-frequency drift within the preset time window.

[0100] Alternatively, linear constraint processing can be performed on multiple sets of two-dimensional displacement signals of the target light spots to eliminate error interference in the multiple sets of two-dimensional displacement signals of the target light spots, thereby obtaining the three-dimensional wave vector information of the sound field to be measured.

[0101] Alternatively, the linear constraint matrix of the three-dimensional wave vector information can be determined based on multiple sets of two-dimensional displacement signals of the target light spot; Under the constraint that the three-dimensional wave vector information is a unit direction vector, the covariance matrix of the linear constraint matrix is ​​decomposed into eigenvalues, and the unit eigenvector corresponding to the minimum eigenvalue is taken as the three-dimensional wave vector information of the sound field to be measured.

[0102] Of course, in addition to the steps mentioned above, the processing module can also perform more steps related to the underwater acoustic wave vector direction sensing method mentioned above, based on actual needs. This application embodiment does not limit this, and you can refer to the foregoing description of the relevant embodiments of the underwater acoustic wave vector direction sensing method.

[0103] Based on the foregoing, please refer to Figure 7 The laser transceiver module includes at least a first position detector and a second position detector. The first position detector is used to receive a two-dimensional displacement signal of a first spot formed by the first probe laser as it passes through the sound field to be measured. The second position detector is used to receive a two-dimensional displacement signal of a second spot formed by the second probe laser as it passes through the sound field to be measured.

[0104] Furthermore, the laser transceiver module includes a first laser sensing unit (such as...). Figure 7 The lateral laser sensing unit in the middle) and the second laser sensing unit (such as Figure 7 (The longitudinal laser sensing unit in the middle), the first laser sensing unit is used to emit the first detection laser, and the second laser sensing unit is used to emit the second detection laser; or The laser transceiver module includes a third laser sensing unit and a beam splitting component. The third laser sensing unit is used to emit the first detection laser, and the first detection laser is split into a second detection laser orthogonal to the first detection laser after passing through the beam splitting component.

[0105] In one embodiment of this application, a first laser sensing unit is used to generate a transverse detection laser. This transverse detection laser passes through the acousto-optic interaction region along a first direction and is incident on a first position detector. The detection plane of the first position detector is perpendicular to the principal optical axis of the transverse detection laser and is used to detect the spot displacement of the transverse detection laser in two orthogonal directions within the detection plane. A second laser sensing unit is used to generate a longitudinal detection laser. This longitudinal detection laser passes through the acousto-optic interaction region along a second direction and is incident on a second position detector. The second direction is not parallel to the first direction; preferably, the second direction is orthogonal to the first direction. The detection plane of the second position detector is perpendicular to the principal optical axis of the longitudinal detection laser and is used to detect the spot displacement of the longitudinal detection laser in two orthogonal directions within its detection plane. Specifically, the first and second laser sensing units include a collimating lens group, a reflector, and an optical window.

[0106] Furthermore, in another embodiment of this application, the transverse and longitudinal probe lasers are generated from the same laser via a beam splitter. This approach reduces the number of light sources, improves system compactness, and helps maintain the frequency and power stability of the two laser beams. Specifically, the transverse and longitudinal probe lasers are formed from the same laser via a beam splitter, and then formed into two mutually orthogonal probe beams through reflection, deflection, or light guiding structures. Since the two probe beams originate from the same light source, their center wavelength, power drift characteristics, and beam quality are consistent, which helps reduce the impact of wavelength differences, power drift differences, and beam quality differences between different light sources on the dual-plane wave vector projection fusion. In this case, the processing module can normalize and correct the outputs of the two position detectors based on the common intensity fluctuation characteristics of the beams from the same source, thereby reducing the impact of light source power drift on the dual-beam projection fusion.

[0107] Of course, in addition to the modules mentioned above, more components can be added to the underwater acoustic sensing system as needed. For example, in some possible implementations, the system can also include a housing or reference frame for fixing the laser, collimation assembly, reflection assembly, optical window, position detector, signal acquisition circuit, and processing circuit. The housing is equipped with a sound-transmitting structure, acoustic channel, or acoustic window to allow external underwater acoustic signals to enter the acousto-optic interaction region. The acousto-optic interaction region is the area where the probe laser interacts with the underwater acoustic field. When the acoustic field to be measured enters this region, it causes a change in the refractive index distribution of the medium, thereby deflecting the laser passing through the region. Furthermore, to reduce the influence of scattered background light on the position detector output, a field-limiting aperture, spatial filter structure, or narrowband filter element can be placed in front of each position detector, and an extinction structure or light-absorbing layer can be placed on the inner wall of the housing or in the non-working optical path area. The processing module can record the background output in the absence of a sound field and subtract the background from the position detector output during actual measurement.

[0108] The underwater acoustic sensing system provided in this application has good scalability and engineering adaptability. The two detection laser beams, one horizontal and one vertical, can be generated by two independent lasers, or by the same laser through beam splitting, reflection, or folding. Furthermore, the position detector can be a four-quadrant detector, a position-sensitive detector, or other two-dimensional spot detector. The processing module can obtain the spatial acoustic vector direction using methods such as analytical calculation, projection fusion, least squares, lookup table calibration, or model matching. Therefore, the underwater acoustic sensing system provided in this application is easy to design structurally according to different hydrophone sizes, packaging forms, and application scenarios.

[0109] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the methods described above. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, or optical storage, etc. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc.

[0110] The technical features of the above embodiments can be combined in any way. For the sake of brevity, 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, they should be considered to be within the scope of this specification.

[0111] The above provides a detailed description of a method and system for sensing underwater acoustic wave vector direction provided by the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for sensing the direction of underwater acoustic wave vectors, characterized in that, include: Two-dimensional displacement signals of light spots formed by at least two probe lasers passing through the underwater sound source in the test sound field are obtained, wherein the at least two probe lasers include a first probe laser and a second probe laser that are orthogonal to each other, and the two-dimensional displacement signal of each light spot is used to indicate the wave vector projection direction of the test sound field in a two-dimensional plane perpendicular to each of the probe lasers. Determine the two-dimensional trajectory information of the light spot formed by each of the probe lasers passing through the sound field to be tested within a preset time window, wherein the two-dimensional trajectory information of the light spot includes the two-dimensional displacement signal of the light spot formed by the probe lasers passing through the sound field to be tested at multiple different time points; The two-dimensional trajectory matrix corresponding to the two-dimensional trajectory information of the light spot is determined, and the covariance matrix of the two-dimensional trajectory matrix is ​​decomposed into eigenvalues. The unit eigenvector corresponding to the largest eigenvalue in the eigenvalue decomposition is determined as the two-dimensional displacement signal of the target light spot. The two-dimensional displacement signal of the target light spot is processed to obtain the three-dimensional wave vector information of the sound field to be measured; The process of processing the two-dimensional displacement signal of the target light spot to obtain the three-dimensional wave vector information of the sound field under test includes: The linear constraint matrix of the three-dimensional wave vector information is determined based on multiple sets of two-dimensional displacement signals of the target light spot. Under the constraint that the three-dimensional wave vector information is a unit direction vector, the covariance matrix of the linear constraint matrix is ​​decomposed into eigenvalues, and the unit eigenvector corresponding to the minimum eigenvalue is taken as the three-dimensional wave vector information of the sound field to be measured.

2. The method according to claim 1, characterized in that, Determining the two-dimensional trajectory matrix corresponding to the two-dimensional trajectory information of the light spot includes: For each probe laser spot's two-dimensional trajectory information, the trajectory principal axis is fitted to the two-dimensional trajectory information to obtain the two-dimensional trajectory matrix.

3. The method according to claim 2, characterized in that, The step of fitting the principal axis of the two-dimensional trajectory information of the light spot to obtain the two-dimensional trajectory matrix includes: The zero-point offset is subtracted from the two-dimensional displacement signal of each spot in the two-dimensional trajectory information of the spot to obtain the corrected two-dimensional trajectory matrix. The zero-point offset is determined by the background output corresponding to the laser detection in the silent field state, or by the low-frequency drift within the preset time window.

4. The method according to claim 1, characterized in that, The method further includes: The positive and negative polarities of each wave vector direction in the three-dimensional wave vector information of the sound field to be measured are determined, wherein the positive and negative polarities of the wave vector directions are determined by at least one of the following information: The incident direction of the detection laser and the relative position information of the underwater sound source.

5. The method according to any one of claims 1 to 4, characterized in that, The determination of the two-dimensional trajectory information of the light spots formed by each of the probe lasers passing through the acoustic field to be tested within a preset time window includes: The two-dimensional displacement signal of the light spot is preprocessed to obtain a preprocessed two-dimensional displacement signal of the light spot. The preprocessing includes at least one of amplification, filtering, DC removal, background subtraction, normalization, channel gain correction, envelope extraction or frequency component extraction. Based on the preprocessed two-dimensional displacement signal of the light spot, the two-dimensional trajectory information of the light spot formed by each of the probe lasers passing through the acoustic field to be tested within a preset time window is determined.

6. An underwater acoustic sensing system, characterized in that, Includes a laser transceiver module and a processor; The laser transceiver module is used to emit at least two probe lasers into the sound field to be tested formed by the underwater target sound source, and to receive the two-dimensional displacement signal of the light spot formed by each probe laser passing through the sound field to be tested. The at least two probe lasers include a first probe laser and a second probe laser that are orthogonal to each other. The two-dimensional displacement signal of each light spot is used to indicate the wave vector projection direction of the sound field to be tested in a two-dimensional plane perpendicular to each probe laser. The processor is used to determine the two-dimensional trajectory information of the light spot formed by each of the probe lasers passing through the acoustic field to be tested within a preset time window. The two-dimensional trajectory information of the light spot includes the two-dimensional displacement signal of the light spot formed by the probe lasers passing through the acoustic field to be tested at multiple different time points. The two-dimensional trajectory matrix corresponding to the two-dimensional trajectory information of the light spot is determined, and the covariance matrix of the two-dimensional trajectory matrix is ​​decomposed into eigenvalues. The unit eigenvector corresponding to the largest eigenvalue in the eigenvalue decomposition is then determined as the two-dimensional displacement signal of the target light spot. The two-dimensional displacement signal of the target light spot is processed to obtain the three-dimensional wave vector information of the sound field to be measured; The process of processing the two-dimensional displacement signal of the target light spot to obtain the three-dimensional wave vector information of the sound field under test includes: The linear constraint matrix of the three-dimensional wave vector information is determined based on multiple sets of two-dimensional displacement signals of the target light spot. Under the constraint that the three-dimensional wave vector information is a unit direction vector, the covariance matrix of the linear constraint matrix is ​​decomposed into eigenvalues, and the unit eigenvector corresponding to the minimum eigenvalue is taken as the three-dimensional wave vector information of the sound field to be measured.

7. The system according to claim 6, characterized in that, The laser transceiver module includes at least a first position detector and a second position detector. The first position detector is used to receive a two-dimensional displacement signal of a first spot formed by the first probe laser as it passes through the sound field to be measured. The second position detector is used to receive a two-dimensional displacement signal of a second spot formed by the second probe laser as it passes through the sound field to be measured.

8. The system according to claim 7, characterized in that, The laser transceiver module includes a first laser sensing unit and a second laser sensing unit, wherein the first laser sensing unit is used to emit the first detection laser, and the second laser sensing unit is used to emit the second detection laser; or The laser transceiver module includes a third laser sensing unit and a beam splitting component. The third laser sensing unit is used to emit the first detection laser, and the first detection laser is split into a second detection laser orthogonal to the first detection laser after passing through the beam splitting component.

Images