A method for calculating wave tangent plane angle and sea wave height equation by measuring laser spot jitter position

Abstract

The application discloses a method for calculating wave tangent plane angle and sea wave height equation by measuring laser spot jitter position, and belongs to the technical field of ocean monitoring. The method comprises the following steps: emitting laser to the water-air interface through an underwater laser, and detecting the position coordinates of the laser spot after being refracted by the interface above the wave; calculating the angle between the wave tangent plane and the horizontal plane according to the geometric optical refraction principle based on the position coordinates of the spot; constructing a sea wave height equation by using a directional spectrum model according to the angle between the wave tangent plane and the horizontal plane; and calculating the normal vector of the wave surface based on the sea wave height equation. The application inverses the wave shape through the spot position, solves the stability problem of the optical link in a dynamic environment, and realizes real-time and accurate measurement of the dynamic wave tangent plane angle.

Description

Technical Field

[0001] This invention relates to the field of marine monitoring technology, specifically to a method for calculating the wave tangent plane angle and wave height equation by measuring the position of laser spot jitter. Background Technology

[0002] Cross-domain laser communication systems are a key technology for achieving high-speed data transmission between underwater equipment and aerial platforms, operating in environments encompassing air, underwater, and wave interfaces. During laser link establishment, the optical communication terminal needs to achieve initial alignment by aiming and capturing the optical signal, subsequently transitioning to a tracking phase to maintain link stability. However, the random undulations of ocean waves cause continuous changes in the geometry of the water-air interface, significantly interfering with laser cross-medium propagation.

[0003] Specifically, the dynamic tilt of the wave shear plane alters the refraction angle of the laser beam, causing it to deflect, spread, or split as it crosses the interface, resulting in random jitter in the receiver's spot position. This effect severely limits the acquisition efficiency and tracking accuracy of the optical signal, especially in harsh sea conditions. Traditional compensation methods based on fixed refraction models struggle to adapt to real-time wave surface changes, leading to link interruptions or degraded communication performance. Existing technologies have attempted to address the impact of waves through simple logic control or active scanning mechanisms, but limitations in sensor accuracy and computational efficiency make it difficult to achieve high-precision inversion of dynamic wave surfaces in complex marine environments.

[0004] Therefore, existing technologies lack the ability to accurately measure the angle between the dynamic wave tangent plane in real time, resulting in an inability to effectively compensate for changes in the laser refraction angle caused by ocean waves. This severely affects the stability of spot acquisition and tracking in cross-domain laser communication. An innovative solution is urgently needed to address these issues. Summary of the Invention

[0005] The purpose of this invention is to provide a method for calculating the wave tangent plane angle and wave height equation by measuring the position of laser spot jitter. By inverting the wave morphology through the position of the laser spot, the stability problem of the optical link in dynamic environment is solved, and the real-time accurate measurement of the dynamic wave tangent plane angle is achieved.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for calculating the wave tangent plane angle and wave height equation by measuring the position of laser spot jitter includes the following steps: S1: Emit a laser to the water-air interface using an underwater laser, and detect the position coordinates of the laser spot after refraction at the interface above the wave; S2: Based on the position coordinates of the light spot, calculate the angle between the wave tangent plane and the horizontal plane according to the principle of geometric optics refraction; S3: Based on the angle between the wave tangent plane and the horizontal plane, the wave height equation is constructed using the directional spectrum model; S4: Based on the wave height equation, the normal vector of the wave surface is calculated.

[0007] Further, S2 includes: Calculate the measurement angle θ0 based on the coordinates of the light spot position; Based on Snell's law of refraction and the geometric relationship between the angle of refraction and the angle of incidence, the angle of incidence θ1 is obtained by combining the equations. The incident angle θ1 is defined as the angle α between the wave tangent plane and the horizontal plane.

[0008] Furthermore, the expression for the wave height equation described in S3 is: ; in, is the wave height at point (x, y) at time t; m is the division of the angular frequency range; n is the division of the direction angle range; The amplitude of the component wave; The component wave angular frequency; The wave number corresponding to the component wave; The component wave direction angle; The component wave is given a random initial phase.

[0009] Furthermore, the directional spectrum model described in S3 uses the PM wave spectrum to calculate the amplitude of each component wave.

[0010] Further, S4 includes: calculating the partial derivatives of the wave height equation in two directions on the horizontal plane, and synthesizing the normal vector of the wave surface based on the partial derivatives.

[0011] Another object of the present invention is to provide a system for calculating the wave tangent plane angle and wave height equation by measuring the position of laser spot jitter. When executed, this system implements the method for calculating the wave tangent plane angle and wave height equation by measuring the position of laser spot jitter, comprising a laser emitting unit, a spot detection unit, a data processing unit, and a synchronization control unit, wherein: The laser emitting unit is fixedly installed by an underwater mechanical support, with its optical axis vertically aligned with the water-air interface. The spot detection unit is mounted above the wave via an aerial support structure, forming an optical alignment with the laser emission unit; The synchronization control unit is electrically connected to the laser emitting unit and the spot detection unit respectively, providing a unified time synchronization signal; The data processing unit is connected to the spot detection unit and receives and processes the spot position coordinate information.

[0012] Furthermore, the spot detection unit includes an optical filter module, which is installed at the front end of the detector's optical path via a detachable interface, and its center wavelength is matched with the laser wavelength.

[0013] Furthermore, the data processing unit integrates a wave parameter inversion algorithm module, which includes and is sequentially connected to a spot coordinate preprocessing submodule, a wave tangent plane calculation submodule, and a wave height equation construction submodule.

[0014] Furthermore, the system also includes an environmental sensing unit that communicates with the data processing unit to provide real-time parameters such as water temperature, salinity, and wind speed.

[0015] This invention provides a method for calculating the wave tangent plane angle and wave height equation by measuring the position of laser spot jitter. Through the innovative method of inverting the wave tangent plane angle by changing the laser spot position, it achieves real-time and accurate measurement of dynamic wave morphology, laying a key technological foundation for the engineering application of cross-medium laser communication. Compared with existing technologies, it achieves the following significant advantages: 1. High measurement accuracy. Based on the analytical model of the light spot position according to the law of refraction, the measurement error of the angle between the wave tangent planes can be controlled within a very small range, providing a reliable data basis for light spot jitter compensation.

[0016] 2. High real-time performance. Through direct mathematical mapping between light spot coordinates and wave parameters, no complex iterative calculations are required, enabling millisecond-level dynamic response and effectively adapting to the rapid changing characteristics of ocean waves.

[0017] 3. Good compatibility. This invention can be directly integrated into existing optical communication terminals. Wave parameter sensing can be achieved by adding a detector without modifying the core optical path structure, significantly reducing implementation costs.

[0018] 4. Improved communication stability. By using precise wave height equations and surface normal vector calculations, forward-looking compensation parameters are provided for the tracking system, greatly improving the acquisition success rate and tracking stability of cross-domain laser links. Attached Figure Description

[0019] Figure 1 This is a flowchart of the method of the present invention; Figure 2 This is a schematic diagram of a laser beam emitted from underwater across waves. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0021] This embodiment provides a method for calculating the wave tangent plane angle and wave height equation by measuring the position of laser spot jitter. Figure 1 As shown, the process includes: emitting a laser beam towards the water-air interface using an underwater laser, and detecting the position coordinates of the laser spot after refraction at the interface above the wave; calculating the angle between the wave tangent plane and the horizontal plane based on the position coordinates of the laser spot and the principle of geometrical optics refraction; constructing a wave height equation using a directional spectrum model based on the angle between the wave tangent plane and the horizontal plane; and calculating the normal vector of the wave surface based on the wave height equation. The following is a detailed description with reference to specific embodiments.

[0022] The method described in this embodiment requires the following hardware components: a laser emitting unit employing a 532 nm Nd:YAG frequency-doubled laser; a spot detection unit employing a high-precision position detector, such as a CCD or CMOS detector; a data processing unit containing a high-performance processor and memory for executing subsequent algorithm flows; and a support and auxiliary unit including a mechanical support structure for fixing the laser and detector, resistant to water flow and wave impact, a synchronization triggering device (such as a GPS- or fiber-optic synchronizer), and environmental parameter sensors (for measuring water temperature, salinity, wind speed, etc.). The laser should be installed at a predetermined depth underwater (e.g., 1-3 meters below the surface), ensuring the laser beam is perpendicular to the water-air interface. The detector should be positioned appropriately above the waves (e.g., 5-20 meters above the surface) to ensure its field of view effectively captures the refracted laser spot.

[0023] First, an underwater laser is emitted towards the water-air interface, and the coordinates of the laser spot position after refraction through the interface are detected above the wave. The water-air interface described in this invention, particularly in a marine environment, is a dynamic wave interface.

[0024] A Nd:YAG frequency-doubled laser is fixed at a designated underwater location, emitting a 532nm wavelength laser beam towards the water-air interface. The laser power is adjusted according to the actual detection distance, typically ranging from 100-500mW. The detector performs a small-range scan above the waves, acquiring the coordinates of the laser spot position formed after passing through the wave interface. The sampling frequency should be significantly higher than the wave variation frequency, typically set to no less than 100 Hz, to ensure the capture of the dynamic changes in the waves. During the acquisition process, high-precision time synchronization technology (such as GPS synchronization or fiber optic synchronization) should be used to ensure that the timestamp synchronization accuracy between the laser and the detector reaches the microsecond level, guaranteeing a strict correspondence between the position data and the timestamp. To effectively suppress ambient light interference, a narrowband filter with a center wavelength of 532 nm should be installed in front of the detector's optical path, with its bandwidth preferably controlled within ±5 nm. The acquired raw spot coordinates need to be preprocessed, including: removing outliers (e.g., using the 3σ criterion), performing smoothing filtering (e.g., using a moving average filtering algorithm with a window size of 10-20 sampling points), and performing coordinate system-wide correction.

[0025] Then, based on the position coordinates of the light spot, the angle between the wave tangent plane and the horizontal plane is calculated according to the principle of geometric optics refraction. This process includes: calculating the measurement angle θ0 based on the position coordinates of the light spot; obtaining the incident angle θ1 based on Snell's law of refraction and the geometric relationship between the angle of refraction and the angle of incidence; and determining the incident angle θ1 as the angle α between the wave tangent plane and the horizontal plane.

[0026] Using the acquired laser spot position coordinates, according to Figure 2 As shown, calculate the angle of the wave's tangent plane (the angle α between the wave's tangent plane and the horizontal plane). This tangent plane is the interface where the laser light refracts, and its direction is determined by the normal at that point (the tangent plane and the normal are perpendicular to each other). The calculated angle α is the angle between this tangent plane and the horizontal plane. Figure 2 As shown, since the Nd:YAG frequency-doubled laser is fixedly installed and configured to emit laser light perpendicularly to the water-air interface, the direction of the incident light is parallel to the vertical. According to the definition of geometric optics, the incident angle θ1 is the angle between the incident light and the interface normal. Simultaneously, the angle α between the wave-cutting plane and the horizontal plane is numerically equal to the angle between the normal at that point and the vertical. Therefore, in a preferred embodiment of the present invention, the angle α between the wave-cutting plane and the horizontal plane is equal to the incident angle θ1.

[0027] Based on the principle of geometric optics refraction, a mathematical model is established to represent the angle between the light spot position and the wave's tangent plane. The fundamental equations are established according to Snell's law of refraction. (1) in: The refractive index of seawater is 1.34. The refractive index of air is 1.0. Angle of incidence; The angle of refraction. The refractive index of seawater. It changes with temperature and salinity; real-time temperature and salinity data can be used to... The value is corrected.

[0028] Next, the geometric relationship is established, and the relationship between the position coordinates and angle of the light spot is expressed as follows: (2) Define the measurement angle, let From equation (2), we can see that: .

[0029] The derivation of the angle between the wave tangent plane and the horizontal line is obtained by solving a series of equations: (3) Substituting into (1), we get: (4) Solving the above equation using trigonometric identities, we obtain the final expression for the angle α between the wave tangent plane and the horizontal plane: (5) Next, based on the angle between the wave tangent plane and the horizontal plane, the wave height equation is constructed using a directional spectrum model. The expression for the directional spectrum model is: (6) Substituting equation (5) into the above equation, we obtain the real-time wave height equation, which is the spatiotemporal model describing the change in sea surface height. Its expression is: (7) in The wave height is represented at time t (x, y); m is the division of the angular frequency range; n is the division of the direction angle range. For component waves, Its amplitude, Its angular frequency, For the corresponding wave number, Its direction angle, For random initial phase (0≤ ≤2π). Wave number and angular frequency It satisfies the linear wave dispersion relation, and its expression is: (8) The amplitude was calculated using the PM (Pierson-Moskowitz) wave spectrum model. It can be obtained through equations (9) and (10). : (9) (10) Where ω is the angular frequency of the wave, g is the gravitational acceleration, and u is the wind speed at 19.8 meters above sea level.

[0030] To accurately simulate real ocean waves, the frequency sampling range must cover the main regions of wave energy distribution, with particular attention needed to the vicinity of the spectral peaks where energy is most concentrated. The spectral peak frequencies are represented as... And described as (11): (11) frequency sequence Should be With the core as the center, the waves are distributed reasonably before and after it to ensure that the shape of the waves can be accurately reproduced.

[0031] In practical applications, model parameters need to be adjusted according to specific marine environmental conditions. For different sea states, the following parameter settings are preferred: In calm sea states (wind speed u < 5 m / s), the angular frequency division m can be 10-15, and the azimuth angle division n can be 8-12; in moderate sea states (5 m / s ≤ u < 10 m / s), m can be 15-20, and n can be 12-16; in severe sea states (u ≥ 10 m / s), m can be 20-25, and n can be 16-20. Such parameter settings ensure a balance between computational accuracy and efficiency.

[0032] Finally, based on the wave height equation, the normal vector of the wave surface is calculated. To further improve the spot tracking accuracy, the wave surface normal vector is calculated based on the obtained wave height equation and used for spot jitter compensation. The normal vector at a point on the wave surface (x,y,z=H(x,y,t)) is... The calculation formula is: (12) in, These represent the partial derivatives of the wave height in the x and y directions, respectively.

[0033] When calculating partial derivatives, the central difference method is used to improve calculation accuracy:

[0034]

[0035] in, and The spatial step size is 1 / 100 to 1 / 50 of the wave characteristic length.

[0036] Through the above process, this invention achieves real-time, non-contact, and precise measurement of the angle between the tangent planes of dynamic waves. Furthermore, it constructs a high-precision wave height equation and surface normal vector model, providing crucial wave disturbance information for cross-domain laser communication systems. This directly serves beam jitter compensation and significantly improves the acquisition and tracking capabilities of optical links in dynamic environments.

[0037] This embodiment also provides a system for calculating the wave tangent plane angle and wave height equation by measuring the position of laser spot jitter. When executed, this system implements the method for calculating the wave tangent plane angle and wave height equation by measuring the position of laser spot jitter. The system includes a laser emitting unit, a spot detection unit, a data processing unit, and a synchronization control unit. Specifically: the laser emitting unit is fixedly installed via an underwater mechanical support, with its optical axis vertically aligned with the water-air interface; the spot detection unit is arranged above the wave via an aerial support, forming optical alignment with the laser emitting unit; the synchronization control unit is electrically connected to both the laser emitting unit and the spot detection unit, providing a unified time synchronization signal; and the data processing unit is data-connected to the spot detection unit, receiving and processing the spot position coordinate information.

[0038] The spot detection unit includes an optical filter module, which is installed at the front end of the detector's optical path via a detachable interface, and its center wavelength is matched to the laser wavelength. The data processing unit integrates a wave parameter inversion algorithm module, which includes and is sequentially connected to a spot coordinate preprocessing submodule, a wave tangent plane calculation submodule, and a wave height equation construction submodule. Additionally, the system includes an environmental sensing unit, which is communicatively connected to the data processing unit to provide real-time water temperature, salinity, and wind speed parameters.

[0039] Embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0040] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0041] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0042] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0043] Contents not described in detail in this specification are prior art known to those skilled in the art. It is hereby indicated that the above description is intended to help those skilled in the art understand this invention, but does not limit the scope of protection of this invention. Any equivalent substitutions, modifications, improvements, or simplifications of the above descriptions that do not depart from the essential content of this invention fall within the scope of protection of this invention.

Claims

1. A method for calculating the wave tangent plane angle and wave height equation by measuring the position of laser spot jitter, characterized in that, Includes the following steps: S1: Emit a laser to the water-air interface using an underwater laser, and detect the position coordinates of the laser spot after refraction at the water-air interface above the wave; S2: Based on the position coordinates of the laser spot, calculate the angle between the wave tangent plane and the horizontal plane according to the principle of geometric optics refraction; including: Calculate the measurement angle based on the laser spot position coordinates. ; Based on Snell's law of refraction and the geometric relationship between the angle of refraction and the angle of incidence, the angle of incidence can be obtained by combining the equations. ; The angle of incidence The angle α between the wave tangent plane and the horizontal plane is determined. S3: Based on the angle between the wave tangent plane and the horizontal plane, a wave height equation is constructed using a directional spectrum model; the expression for the wave height equation is: ； in, is the wave height at point (x, y) at time t; m is the division of the angular frequency range; n is the division of the direction angle range; The amplitude of the component wave; The component wave angular frequency; The wave number corresponding to the component wave; The component wave direction angle; The component wave is randomly initialized with a phase; S4: Based on the wave height equation, the normal vector of the wave surface is calculated.

2. The method for calculating the wave tangent plane angle and wave height equation by measuring the position of laser spot jitter according to claim 1, characterized in that, The directional spectrum model described in S3 uses the PM wave spectrum to calculate the amplitude of each component wave.

3. The method for calculating the wave tangent plane angle and wave height equation by measuring the position of laser spot jitter, as described in claim 1, is characterized in that... S4 includes: calculating the partial derivatives of the wave height equation in two directions on the horizontal plane, and synthesizing the normal vector of the wave surface based on the partial derivatives.

4. A system for calculating the wave tangent plane angle and wave height equation by measuring the position of laser spot jitter, characterized in that, When executed, this system implements the method described in any one of claims 1-3 for calculating the wave tangent plane angle and wave height equation by measuring the position of laser spot jitter, comprising a laser emitting unit, a spot detection unit, a data processing unit, and a synchronization control unit, wherein: The laser emitting unit is fixedly installed by an underwater mechanical support, with its optical axis vertically aligned with the water-air interface. The spot detection unit is mounted above the wave via an aerial support structure, forming an optical alignment with the laser emission unit; The synchronization control unit is electrically connected to the laser emitting unit and the spot detection unit respectively, providing a unified time synchronization signal; The data processing unit is connected to the spot detection unit to receive and process the laser spot position coordinate information.

5. The system for calculating the wave tangent plane angle and wave height equation by measuring the position of laser spot jitter according to claim 4, characterized in that, The spot detection unit includes an optical filter module, which is installed at the front end of the optical path of the spot detection unit through a detachable interface, and its center wavelength is matched with the laser wavelength.

6. The system for calculating the wave tangent plane angle and wave height equation by measuring the position of laser spot jitter according to claim 5, characterized in that: The data processing unit integrates a wave parameter inversion algorithm module, which includes and is sequentially connected to a laser spot coordinate preprocessing submodule, a wave tangent plane calculation submodule, and a wave height equation construction submodule.

7. The system for calculating the wave tangent plane angle and wave height equation by measuring the position of laser spot jitter according to claim 6, characterized in that: The system also includes an environmental sensing unit, which is connected to the data processing unit to provide real-time parameters such as water temperature, salinity, and wind speed.

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