Turbulence disturbance resistant vortex light detection method on aviation platform

Abstract

The invention discloses a vortex light detection method for resisting turbulence disturbance on an aviation platform. The method comprises a tracking system, a spiral scanning module, a self-adaptive optical unit and an interferometer device. The invention provides an anti-turbulence vortex light interference detection method for an aviation platform. According to the system, rapid capturing and accurate positioning of a dynamic target are realized through a high-precision tracking system and a spiral scanning positioning module, and accurate projection of a coding light beam is ensured; afterwards, the system emits the composite vortex light bearing information to an aviation platform, wavefront distortion caused by atmospheric turbulence and platform vibration is corrected in real time through a built-in adaptive optical unit, and the stability of a transmission link is remarkably improved. And at a receiving end, a self-reference interference device is adopted to perform interference detection on the vortex light, and reliable decoding of modal phase encoding information is realized in combination with an advanced phase resolving algorithm.

Description

Technical Field

[0001] This invention relates to a vortex light detection method for resisting turbulent disturbances on an aviation platform, belonging to the field of laser interferometry technology. Background Technology

[0002] A vortex interferometry method is employed to detect the phase information carried by composite vortex beams. This method utilizes the interference of a known reference plane beam with the vortex beam under test, and inverts its phase information by decoding the resulting interference pattern. When the two beams interfere, their unique helical phase structures interact, forming a complex pattern containing specific forked gratings or helical fringes. The distribution, curvature, bifurcation, and the number and position of phase singularities in this pattern directly encode key information such as the topological charge, phase singularity distribution, and wavefront distortion of the beam under test. By analyzing these characteristics, especially the differences from the interference pattern under ideal conditions, qualitative discrimination and quantitative reconstruction of the phase information carried by the vortex beam can be achieved.

[0003] To overcome the technical bottlenecks of traditional vortex interferometry detection technology, such as unstable interferograms and poor decoding reliability caused by atmospheric turbulence and platform vibrations in dynamic environments, this solution innovatively integrates a high-performance adaptive optics system at the front end of the interferometric optical path. This system uses a Shaker-Hartmann wavefront sensor to detect the dynamic distortion of the incident light wavefront in real time and employs a high-speed control algorithm to drive a deformable mirror to generate conjugate phase compensation, achieving active optical correction for atmospheric turbulence and mechanical vibrations. This forward-thinking design allows the system to eliminate most wavefront errors at the physical level before interference occurs, ensuring that the output interferogram maintains high contrast and high stability. This breakthrough not only significantly improves the demodulation accuracy of vortex light mode phase information but also provides reliable technical support for next-generation airborne optical detection and communication systems, opening up new technical pathways for the precise manipulation and application of structured light fields in complex environments. Summary of the Invention

[0004] To address the shortcomings of traditional interferometry methods, such as lack of modal selectivity for composite vortex light, inability to decode high-dimensional optical fields composed of multiple helical phase structures, and beam drift in turbulent environments, this invention proposes an automatically corrected vortex light interferometric detection method for use on an airborne platform, resistant to turbulence disturbances. This method combines an interferometric system with an automatic correction system to detect the encoded composite vortex light beam after it has been subjected to turbulence disturbances. The detection results are processed to obtain the bit error rate of the beam signal at the receiving end. Based on the bit error rate, the optical path of the interferometric system and noise generated by air vibrations are corrected, thereby obtaining a stable interferogram and ensuring the accuracy of the original information of the composite vortex light.

[0005] The technical solution of this invention to solve the technical problem is as follows: An automatic correction vortex interferometry detection method for turbulence-resistant applications on aircraft platforms, characterized by the following steps: Step 1: After the aerial platform arrives at the mission airspace, it activates the tracking camera to conduct a wide-area search for the ground target board. Step two: Activate a fundamental mode Gaussian beam from the reference laser emitter to illuminate the target plate. Adjust the optical path to ensure the laser spot illuminates the crosshair center as much as possible. Activate the laser energy probe and, based on the position of the tracking camera's field of view center, drive the tracking turntable using a helical scanning method covering 1 / 2 or 2 / 3 of the tracking camera's field of view. During the scan, simultaneously record the turntable's azimuth and elevation angles, as well as the laser energy probe readings at each moment. After the scan is complete, determine the maximum laser energy value and its corresponding angle value, and calculate the deviations ΔX and ΔY from the initial locking angle. Adjust the tracking system's field of view based on these deviations, using the point of maximum energy as the new reference aiming point, and stably track at this point.

[0006] Step 3: Gaussian light is converted into composite vortex light for detection using a liquid crystal spatial light modulator. A waveform generator is activated to generate a known, ideal composite vortex light beam as the detection signal. During the vortex light phase modulation stage, the activated waveform generator is essentially a high-precision arbitrary waveform generator. This device generates a corresponding analog voltage waveform based on a preset communication encoding sequence (such as a binary data stream "1011001"). The preset vortex light phase θ=0 corresponds to binary "0", and θ=π corresponds to binary "1". This voltage waveform is input to the electrodes of the electro-optic phase modulator via an RF cable, forming a time-varying electric field in its lithium niobate waveguide. When the prepared basic vortex light field is transmitted through the modulator, its optical phase will strictly follow the amplitude change law of the applied voltage—each voltage amplitude corresponds to a specific phase offset, such as 0V corresponding to 0 radians and 5V corresponding to π radians. By carefully designing the correspondence between voltage waveform and phase change (such as NRZ encoding), digital information can be precisely loaded onto the phase parameters of the vortex light. This achieves an encoding process that modulates the phase without changing the topological charge of the vortex light, generating a composite modulated light field that carries both orbital angular momentum and digital information, preparing for subsequent free-space transmission and demodulation. Simultaneously, the adaptive optics unit is activated, and the Shaker-Hartmann wavefront sensor begins receiving beacon light returning from the target, measuring in real time the wavefront distortion caused by atmospheric turbulence and platform vibration. The real-time controller rapidly calculates the compensation signal based on the wavefront sensor data. The controller drives the deformable mirror to change its surface shape, generating a corrected wavefront with the opposite phase to the distorted wavefront. The system enters a high-frequency closed-loop control state, dynamically maintaining the diffraction-limited quality of the optical link to ensure the stable shape and concentrated energy of the vortex light spot emitted onto the target.

[0007] Step four: On a stable optical link, to perform specific detection tasks, a precisely designed computational hologram needs to be dynamically loaded onto the liquid crystal spatial light modulator via a computer control system. These holograms are generated in real time based on different detection purposes: for micro-deformation detection, a dynamic vortex light field sequence containing continuous phase gradient changes is generated, and nanometer-level displacement measurement is achieved by analyzing wavefront distortion; for multi-parameter synchronous sensing, a composite vortex light field carrying different combinations of topological charges is created, and spatial multiplexing is achieved by utilizing the orthogonality of orbital angular momentum modes. Each hologram is generated by a Fourier transform algorithm, which includes both the helical phase structure of the target vortex light field and embedded reference fringes for calibration, and zero-order diffraction and modal crosstalk are suppressed by an optimization algorithm. During loading, the system continuously switches hologram modes at a refresh rate of 200Hz, while simultaneously monitoring diffraction efficiency and modal purity in real time, ensuring that the generated composite vortex light accurately carries the encoded information required for detection while maintaining phase correlation, providing an optimized structured light field for subsequent high-precision interferometric demodulation. Step five: The reflected light carrying the target information encoding is captured by the receiving telescope. This light field is first purified in real-time by an adaptive optics unit, which achieves real-time purification of the light wave through closed-loop control: First, the wavefront sensor detects the phase distortion of the incident light field at a rate of over a thousand frames per second, transmitting the acquired wavefront slope data to the real-time controller; the controller generates a digital model of the distorted wavefront using a reconstruction algorithm and calculates a conjugate correction signal; this signal drives the deformable mirror surface to produce a corresponding nanoscale deformation, implanting a compensation wavefront with the opposite phase to the distorted wavefront in the optical path. When the distorted light field is reflected through the deformable mirror, the two superimpose, canceling out the wavefront error and outputting a flat wavefront close to the diffraction limit. The entire correction process is completed within milliseconds, effectively suppressing aberrations caused by atmospheric turbulence and wavefront jitter caused by platform vibration, achieving light field purification in dynamic environments. The correction also addresses turbulence disturbances reintroduced during transmission. The purified light field enters the interferometer, which converts the invisible phase information into visible interference fringe patterns. The phase resolution algorithm is run to identify the vortex light state corresponding to the interference pattern in the interferogram, and the codebook is queried to demodulate the original binary data stream.

[0008] Step six: The system continues to run steps three through five, forming an automated closed loop of "calibration-emission-detection-demodulation". Throughout the mission, the tracking system maintains precise lock-on to the target, the adaptive optics system continuously combats turbulence, and the interferometric detection system continuously acquires high-precision detection data or communication information. After the mission is completed, each subsystem is shut down sequentially.

[0009] The beneficial effects of this invention are: This invention does not require an extremely stable flight platform or an absolutely silent environment; it does not rely on post-processing software algorithms to repair turbulence effects; and this method can achieve high-precision optical axis alignment without complex mechanical structure adjustments.

[0010] This invention improves the optical detection accuracy and communication stability of aviation platforms under strong turbulent disturbances, and solves the technical problems of unstable interferometric patterns and poor decoding reliability caused by atmospheric turbulence and platform vibration in traditional interferometry methods.

[0011] This invention integrates adaptive optics as a pre-processing "cleanup" unit with interferometric complex amplitude demodulation technology, forming a complete anti-interference optical information processing architecture. This solution effectively addresses key technical challenges faced by traditional optical detection in dynamic environments, such as signal distortion and decoding difficulties, providing an innovative solution for achieving high-reliability optical communication and information processing based on modal phase coding over long distances and in atmospheric channels. Through the orthogonal characteristics of multimodal vortex light, the system maintains its ability to extract high-dimensional information hidden in the phase of the optical field even under complex physical environments, laying a solid technical foundation for the development of next-generation airborne optical detection and communication systems. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of a vortex optical detection method for resisting turbulent disturbances on an aviation platform according to the present invention; Figure 2 This is a schematic diagram of a tracking camera tracking a target range; Figure 3 The deviation between the tracking camera's line of sight and the laser energy probe's line of sight is determined by using a spiral scanning method. Figure 4 This is a schematic diagram of the adaptive optics unit used in this invention; Figure 5 This is a schematic diagram of the interference device used in this invention; Figure 6 This is a flowchart of the phase calculation algorithm for identifying the vortex light state corresponding to the interference pattern from the interference pattern. Detailed Implementation

[0013] The present invention will now be described in detail with reference to the accompanying drawings.

[0014] A method for detecting vortex light in the context of turbulent conditions on an airborne platform includes the following steps: Step 1, as follows Figure 2 As shown, a tracking camera is used to search, capture, lock onto, and track the target plate, ensuring that the target plate is at the center of the tracking camera's field of view. A spiral scan is employed during the tracking process, as illustrated in the diagram below. Figure 3 As shown.

[0015] Step two: After completing system self-test and optical path calibration, the laser energy probe is activated. Based on the position of the tracking camera's line-of-sight center, the tracking turntable is driven using a helical scanning method, covering 1 / 2 or 2 / 3 of the tracking camera's field of view. During the scan, the azimuth and elevation angles of the turntable, as well as the laser energy probe readings, are recorded simultaneously at each moment. After scanning, the maximum laser energy value and its corresponding angle value are determined, and the deviations ΔX and ΔY from the initial locking angle are calculated. The line-of-sight of the tracking system is adjusted based on these deviations, and the point of maximum energy is used as the new reference aiming point, with stable tracking at this point. Then, the operator executes the laser emitter startup procedure sequentially through the main control console: first, the closed-loop water cooling system is activated to stabilize the operating temperature at 20±0.5℃; then, the power controller is turned on to complete a 120-second preheating; after the status indicator light turns to ready, an enable command is sent through the control software, gradually increasing the erbium-doped fiber amplifier pump current above the threshold, ultimately outputting a continuous laser with a wavelength of 1550nm and a power of 500mW. The laser beam is expanded and collimated into a parallel beam with a diameter of 8 mm. Through closed-loop control of a high-precision two-dimensional turntable (resolution 0.5 μrad), the center of the beam is precisely positioned at the crosshair of the target plate 500 meters away, forming an illumination spot with a power density of 3.2 W / cm² on the target surface. The system uses a 1 kHz sinusoidal modulation frequency for carrier encoding, with a single illumination duration set to 3 seconds. During this time, the output is dynamically adjusted by real-time monitoring of the reflected light intensity to ensure that the illuminance fluctuation in the target area does not exceed ±2%, establishing a reference light field that conforms to the human eye safety standard (IEC 60825-1) for subsequent vortex interferometry detection.

[0016] Step 3: Gaussian light is converted into composite vortex light for detection using a liquid crystal spatial light modulator. A waveform generator is activated to generate a known, ideal composite vortex light beam as the detection signal. During the vortex light phase modulation stage, the activated waveform generator is essentially a high-precision arbitrary waveform generator. This device generates a corresponding analog voltage waveform based on a preset communication encoding sequence (such as a binary data stream "1011001"). The preset vortex light phase θ=0 corresponds to binary "0", and θ=π corresponds to binary "1". This voltage waveform is input to the electrodes of the electro-optic phase modulator via an RF cable, forming a time-varying electric field in its lithium niobate waveguide. When the prepared basic vortex light field is transmitted through the modulator, its optical phase will strictly follow the amplitude change law of the applied voltage—each voltage amplitude corresponds to a specific phase offset, such as 0V corresponding to 0 radians and 5V corresponding to π radians. By carefully designing the correspondence between voltage waveforms and phase changes (such as NRZ encoding), digital information can be precisely loaded onto the phase parameters of the vortex light. This achieves an encoding process that modulates the phase without changing the topological charge of the vortex light, generating a composite modulated optical field that carries both orbital angular momentum and digital information, preparing for subsequent free-space transmission and demodulation. Simultaneously, the adaptive optics unit is activated, such as... Figure 4 As shown, the Shaker-Hartmann wavefront sensor begins receiving beacon light returning from the target, measuring in real time the wavefront distortion caused by atmospheric turbulence and platform vibration. The real-time controller rapidly calculates a compensation signal based on the wavefront sensor data. The controller drives a deformable mirror to change its shape, generating a corrected wavefront with the opposite phase to the distorted wavefront. The system then enters a high-frequency closed-loop control state, dynamically maintaining the diffraction-limited quality of the optical link to ensure a stable shape and concentrated energy of the vortex beam emitted onto the target.

[0017] Step four: On a stable optical link, to perform specific detection tasks, a precisely designed computational hologram needs to be dynamically loaded onto the liquid crystal spatial light modulator via a computer control system. These holograms are generated in real time based on different detection objectives: for micro-deformation detection, a dynamic vortex light field sequence containing continuous phase gradient changes is generated, and nanometer-level displacement measurement is achieved by analyzing wavefront distortion; for multi-parameter synchronous sensing, a composite vortex light field carrying different combinations of topological charges is created, and spatial multiplexing is achieved by utilizing the orthogonality of orbital angular momentum modes. Each hologram is generated by a Fourier transform algorithm, containing both the helical phase structure of the target vortex light field and embedded reference fringes for calibration, and zero-order diffraction and modal crosstalk are suppressed through optimization algorithms. During loading, the system continuously switches hologram modes at a 200Hz refresh rate, while simultaneously monitoring diffraction efficiency and modal purity in real time, ensuring that the generated composite vortex light accurately carries the encoded information required for detection while maintaining phase correlation, providing an optimized structured light field for subsequent high-precision interferometric demodulation. Step 5: The reflected light, carrying the target information encoding, is captured by the receiving telescope. This light field is first purified in real-time by an adaptive optics unit. The adaptive optics unit achieves real-time purification of the light wave through closed-loop control: First, the wavefront sensor detects the phase distortion of the incident light field at a rate of over a thousand frames per second, transmitting the acquired wavefront slope data to the real-time controller. The controller generates a digital model of the distorted wavefront using a reconstruction algorithm and calculates a conjugate correction signal. This signal drives the deformable mirror surface to produce a corresponding nanoscale deformation, implanting a compensation wavefront with the opposite phase to the distorted wavefront in the optical path. When the distorted light field is reflected through the deformable mirror, the two superimpose, canceling out the wavefront error and outputting a flat wavefront close to the diffraction limit. The entire correction process is completed within milliseconds, effectively suppressing aberrations caused by atmospheric turbulence and wavefront jitter caused by platform vibration, achieving light field purification in dynamic environments. The correction also addresses turbulence disturbances reintroduced during transmission. The purified light field then enters the interferometer, as shown in the diagram. Figure 5 As shown, after interference by this device, the resulting fringes exhibit a spiral distribution. The number of spirals indicates the topological charge of the vortex beam. The direction of the spiral (clockwise or counterclockwise) determines the sign of the topological charge. Using this information, the basic information of the complete vortex beam can be obtained, thus enabling decoding. The interferometer converts invisible phase information into visible interference fringe patterns. A phase resolution algorithm is then run to identify the vortex beam state corresponding to the interference pattern. The flowchart of the phase resolution algorithm is shown below. Figure 6 As shown, the codebook is then consulted to demodulate the original binary data stream; Step six: The system continues to run steps three through five, forming an automated closed loop of "calibration-emission-detection-demodulation". Throughout the mission, the tracking system maintains precise lock-on to the target, the adaptive optics system continuously combats turbulence, and the interferometric detection system continuously acquires high-precision detection data or communication information. After the mission is completed, each subsystem is shut down sequentially.

Claims

1. A vortex optical detection method for resisting turbulent disturbances on an aircraft platform, characterized in that, include: Step 1: After the aerial platform arrives at the mission airspace, it activates the tracking camera to conduct a wide-area search for the ground target board. Step 2: Activate a fundamental mode Gaussian beam from the reference laser emitter to irradiate the target plate; Step 3: Switch the laser source to a vortex light for detection; Step four: On a stable optical link, a programmable vortex light generator dynamically loads different computational holograms according to the detection objective; Step 5: The reflected light carrying the target information code is captured by the receiving telescope; Step six: The system continues to run steps three through five, forming an automated closed loop of "calibration-transmission-detection-demodulation".

2. The vortex optical detection method for resisting turbulent disturbances on an aircraft platform according to claim 1, characterized in that, Step two includes: adjusting the optical path so that the laser spot illuminates the crosshair target center; starting the laser energy probe and driving the tracking turntable in a spiral scanning manner according to the position of the tracking camera's line of sight center and within 1 / 2 or 2 / 3 of the tracking camera's field of view.

3. The vortex optical detection method for resisting turbulent disturbances on an aircraft platform according to claim 2, characterized in that, During the scanning process, the azimuth angle, elevation angle, and laser energy probe readings of the turntable are recorded simultaneously at each moment. After the scanning is completed, the maximum laser energy value and its corresponding angle value are determined, and the deviations ΔX and ΔY from the initial locking angle are calculated. The line of sight of the tracking system is adjusted according to the deviation, and the point with the maximum energy is used as the new reference aiming point, and the system is stably tracked at this point.

4. The vortex optical detection method for resisting turbulent disturbances on an aircraft platform according to claim 1, characterized in that, Step three involves activating a programmable vortex light generator to produce a known, ideal composite vortex light beam as a detection signal. Simultaneously, the adaptive optics unit is activated, and the Shak-Hartmann wavefront sensor begins receiving beacon / signal light returning from the target, measuring in real-time wavefront distortion caused by atmospheric turbulence and platform vibration.

5. The vortex optical detection method for resisting turbulent disturbances on an aircraft platform according to claim 4, characterized in that, Step three also includes the real-time controller quickly calculating the compensation signal based on the wavefront sensor data; the controller drives the deformable mirror to change its surface shape, generating a corrected wavefront with the opposite phase to the distorted wavefront; the system enters a high-frequency closed-loop control state, dynamically maintaining the diffraction-limited quality of the optical link, ensuring that the vortex spot emitted onto the target has a stable shape and concentrated energy.

6. The vortex optical detection method for resisting turbulent disturbances on an aircraft platform according to claim 1, characterized in that, Step five includes: the light field is first purified in real time by an adaptive optics unit to correct turbulence disturbances introduced again during transmission; the purified light field enters the interferometer, which converts the invisible phase information into visible interference fringe patterns.

7. The vortex optical detection method for resisting turbulent disturbances on an aircraft platform according to claim 6, characterized in that, The phase resolution algorithm is run to identify the vortex light state corresponding to the interference pattern in the interferogram, and the codebook is queried to demodulate the original binary data stream.

8. The vortex optical detection method for resisting turbulent disturbances on an aircraft platform according to claim 1, characterized in that, Step six includes: throughout the mission, the tracking system maintains a precise lock on the target, the adaptive optics system continuously combats turbulence, and the interferometric detection system continuously acquires high-precision detection data or communication information; after the mission is completed, each subsystem is shut down in sequence.

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