A multi-layer phase screen synthesis method for atmospheric turbulence simulation

Abstract

The present invention relates to the field of optical imaging technology, and in particular to a multi-layer phase screen synthesis method for atmospheric turbulence simulation, comprising: allocating memory in a computer and setting an initial light field in the memory; inputting set turbulence parameters into a parameter configuration module of the computer, generating a random phase screen sequence at the same time, and loading the turbulence parameters and the phase screen sequence into the memory; simulating the initial light field to propagate through each layer of phase screen in turn in free space to generate a target light field; using the target light field as the initial value for reverse propagation, reversely calculating and synthesizing an equivalent phase diagram through the modulation effect of each layer of phase screen and the diffraction effect of the propagation path; performing phase extraction on the phase diagram, adding a fill factor to compensate for amplitude attenuation, and mapping it to a single spatial light modulator; and realizing a multi-layer phase screen synthesis method for atmospheric turbulence simulation. The present invention can more accurately simulate the propagation of light waves in turbulent media and flexibly adapt to the simulation requirements of different scenarios.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical imaging, and in particular relates to a multi-layer phase screen synthesis method for atmospheric turbulence simulation. Background Art

[0002] Atmospheric turbulence simulation technology is a key experimental tool in fields such as optical imaging, free-space communications, and remote sensing. Its core goal is to reproduce the wavefront distortion effects of light waves propagating in random media through controllable phase modulation. Traditional methods rely primarily on a cascade system of multiple spatial light modulators (SLMs), simulating the layered perturbations of the light field in a turbulent path by connecting multiple phase screens in series. In this architecture, each level of the SLM corresponds to an independent phase screen. After the light wave is modulated through each layer in sequence, the detector collects the accumulated distorted light field information. This type of system designs the optical path based on Fresnel diffraction theory and uses geometric approximation to discretize the continuous turbulent medium into a finite number of phase perturbation units.

[0003] However, as application scenarios demand increased simulation accuracy and dynamic adaptability, traditional technologies have gradually exposed limitations such as complex hardware architecture, high cost, and difficult calibration. A cascaded system of multiple spatial light modulators requires a precise optical path consisting of splitting, combining, and relay imaging modules to maintain coaxiality and precise control of propagation distance between multiple devices. During the actual assembly process, with each additional phase screen stage, the alignment error of the optical components increases exponentially due to the multi-stage amplification effect, resulting in wavefront coplanarity deviations exceeding wavelength levels. Furthermore, the high cost of a single high-precision spatial light modulator, and the total cost of a multi-cascade system can reach millions of yuan, severely restricting its application. A multi-phase screen composite method can achieve the same effect using a single spatial light modulator. Existing composite methods typically use the principle of linear superposition to synthesize the modulation effect of multiple phase screens, directly adding the phase perturbations of each layer and applying them to the light field. This model ignores the cumulative impact of nonlinear effects such as diffraction and interference during light wave propagation, resulting in systematic deviations in the phase distribution of the reconstructed light field from the actual turbulent environment. Especially under strong turbulence conditions (e.g., atmospheric coherence length less than 0.01 meters), the far-field spot divergence angle error generated by traditional methods exceeds 50%, failing to meet the accuracy requirements for adaptive optics system correction or high-resolution imaging quality assessment. After the optical path of existing multi-spatial light modulator systems is established, the number of phase screen layers, spacing, and turbulence parameters are typically fixed, making them incapable of real-time adjustment to simulate dynamically changing turbulent environments. Furthermore, traditional methods struggle to flexibly generate paired original-degraded image datasets, limiting the training efficiency and generalization capabilities of data-driven image restoration algorithms. Summary of the Invention

[0004] In view of this, the present invention aims to provide a multi-layer phase screen synthesis method for atmospheric turbulence simulation to solve the problems of complex hardware architecture, high cost and difficult calibration in the prior art.

[0005] To achieve the above object, the technical solution created by the present invention is implemented as follows:

[0006] A multi-layer phase screen synthesis method for atmospheric turbulence simulation, the method comprising:

[0007] allocating memory in a computer and setting an initial light field in the memory;

[0008] Inputting set turbulence parameters into the parameter configuration module of the computer, generating a random phase screen sequence, and loading the turbulence parameters and the phase screen sequence into the memory;

[0009] Simulating the free-space propagation of the initial light field after it passes through each phase screen layer in a forward direction to generate a target light field;

[0010] The target light field is used as the initial value of reverse propagation, the modulation effect is stripped off through each layer of phase screen in reverse order, and an equivalent phase map is calculated and synthesized through free space propagation;

[0011] Phase extraction is performed on the phase image, a fill factor is added to compensate for amplitude attenuation, and the phase image is mapped to a single spatial light modulator to realize a multi-layer phase screen synthesis method for atmospheric turbulence simulation.

[0012] Furthermore, the turbulence parameters include: atmospheric coherence length, number of phase screen layers and inter-layer propagation distance sequence.

[0013] Furthermore, the performance parameters of this method are: phase image generation time t of 10-layer phase screen is less than 1s; dynamic parameter update delay T is less than 50ms.

[0014] Furthermore, the parameter range of this method is: atmospheric coherence length ,correspond ;Simulated target distance: 0.1~20km.

[0015] Furthermore, the initial light field Expressed in the form of a Gaussian beam:

[0016]

[0017] in is the amplitude, is the beam waist radius, and x and y represent the coordinates.

[0018] Furthermore, the extracted phase for:

[0019]

[0020] in is the light field during reverse propagation, represents the extracted phase, is the pixel spacing of the spatial light modulator, and the sinc function is used to correct the amplitude attenuation caused by discrete sampling. and are the spatial frequency coordinates respectively.

[0021] A system for synthesizing a multi-layer phase screen for simulating atmospheric turbulence, the system comprising: a silicon-based AMOLED microdisplay, a collimator, a polarizing filter, a spatial light modulator, an imaging component, and an image recording device; the image recording device reads and stores image data or video data of a real scene, loads and displays the data through the silicon-based AMOLED microdisplay, and simulates the optical properties of the image data or video data of the real scene; the collimator collimates divergent light emitted by the silicon-based AMOLED microdisplay, converting the divergent light into parallel light; the polarizing filter polarizes the parallel light to match the polarization properties of the spatial light modulator; the spatial light modulator modulates the phase of the polarized light wave to simulate the wavefront distortion effect caused by atmospheric turbulence and form a degraded image; the imaging component forms an image of the degraded image with the changed phase, and the image recording device stores the image.

[0022] Furthermore, the imaging component includes: a fixed-focus optical lens and an industrial camera; the fixed-focus optical lens and the industrial camera are integrated together to ensure optical stability and high-quality acquisition of the degraded image.

[0023] Furthermore, it also includes: a control computer; the control computer drives the spatial light modulator, dynamically loads phase screen data, and phase modulates the polarized light waves passing through its surface.

[0024] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0025] 1. This invention encodes the cumulative effect of multiple phase screens into a composite phase image loaded onto a single spatial light modulator, achieving "single-device equivalent of multiple cascades." This innovation significantly reduces hardware costs, simplifies the optical path structure, avoids coaxial errors associated with multi-stage calibration, and significantly improves optical path stability and experimental repeatability.

[0026] 2. Based on the rigorous light field propagation theory of the Helmholtz equation, this invention utilizes the angular spectrum method to accurately model the nonlinear propagation of light waves, and compensates for phase delay errors through an inverse iterative algorithm. This enables the present invention to more accurately simulate the propagation of light waves in turbulent media, with significant improvements in accuracy over long distances or under conditions of strong turbulence. Furthermore, it supports real-time adjustment of the number of phase screen layers, their spacing, and turbulence parameters, flexibly adapting to the simulation requirements of different scenarios.

[0027] 3. This invention designs a parameterized composite phase generation algorithm that supports dynamic adjustment of key parameters. This algorithm can rapidly generate multi-level degraded images covering all turbulence conditions, from weak to strong, providing high-precision benchmark data for wavefront correction and deformable mirror optimization in adaptive optics systems. Furthermore, it can generate paired datasets of original and degraded images, providing physically consistent training and validation data for deep learning-driven image restoration algorithms, thereby enhancing optical system performance and advancing intelligent image processing technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0029] Figure 1 This is a principle block diagram of the single spatial light modulator atmospheric turbulence simulation system described in an embodiment of the present invention.

[0030] Figure 2 This is a flow chart of a multi-layer phase screen synthesis method for atmospheric turbulence simulation described in an embodiment of the present invention.

[0031] Figure 3 The following are examples of the output effects of a multi-layer phase screen synthesis method for atmospheric turbulence simulation described in an embodiment of the present invention applied to a single spatial light modulator atmospheric turbulence simulation system. (a) represents the original image, (b) represents the phase screen when the atmospheric coherence length is 0.001m, (c) the output effect of the spatial light modulator loaded with (b), (d) the output effect of the spatial light modulator when two composite phase screens are loaded using this synthesis method, (e) the output effect of the spatial light modulator when four composite phase screens are loaded using this synthesis method, (f) the output effect of the spatial light modulator when six composite phase screens are loaded using this synthesis method, (g) the output effect of the spatial light modulator when eight composite phase screens are loaded using this synthesis method, and (h) the output effect of the spatial light modulator when ten composite phase screens are loaded using this synthesis method.

[0032] Description of reference numerals:

[0033] 1. Silicon-based AMOLED microdisplay; 2. Collimator; 3. Polarization filter; 4. Spatial light modulator; 5. Control computer; 6. Fixed-focus optical lens; 7. Industrial camera; 8. Image recording device. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation to the present invention. Similar elements in different embodiments use associated similar element numbers. In the following embodiments, many detailed descriptions are intended to enable the present invention to be better understood. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other elements, materials, or methods. In some cases, some operations related to the present invention are not shown or described in the specification. This is to avoid the core part of the present invention being overwhelmed by too much description. For those skilled in the art, it is not necessary to describe these related operations in detail. They can fully understand the related operations based on the description in the specification and the general technical knowledge in the art.

[0035] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other to form various implementation methods. At the same time, the steps or actions in the method description can also be interchanged or adjusted in a manner that is obvious to those skilled in the art. Therefore, the various orders in the description and the drawings are only for the purpose of clearly describing a certain embodiment and are not intended to be a required order, unless otherwise specified that a certain order must be followed.

[0036] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0037] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art can understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0038] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0039] like Figures 1 to 3 As shown, a multi-layer phase screen synthesis method for atmospheric turbulence simulation is described. The system used in this method includes: a silicon-based AMOLED microdisplay 1, a collimator 2, a polarizing filter 3, a spatial light modulator 4, a control computer 5, a fixed-focus optical lens 6, an industrial camera 7, and an image recording device 8. The image recording device 8 reads and stores picture data or video data of a real scene, loads and displays it through the silicon-based AMOLED microdisplay 1, simulating the optical characteristics of the real scene. The collimator 2 collimates the divergent light emitted by the silicon-based AMOLED microdisplay 1, converting the divergent light into parallel light. The polarizing filter 3 polarizes the parallel light to match the polarization characteristics of the spatial light modulator 4. The control computer 5 controls the spatial light modulator 4 to modulate the phase of the polarized light wave to simulate the wavefront distortion effect caused by atmospheric turbulence. The fixed-focus optical lens 6 and the industrial camera 7 capture the degraded image with the changed phase, which is then stored by the image recording device 8. The method includes:

[0040] Step 1: Allocate memory in the control computer 5 and set the initial light field in the memory ; Initial light field Expressed in the form of a Gaussian beam:

[0041]

[0042] in is the amplitude, is the beam waist radius, and x and y represent the coordinates.

[0043] Step 2: Load the set turbulence parameters into the parameter configuration module of the control computer 5, including: atmospheric coherence length , number of phase screen layers In this embodiment, Take 1-10, the corresponding propagation distance , Indicates the phase screen number; in this embodiment, Take 0.1-20km.

[0044] At the same time, a random phase screen sequence is generated according to the Kolmogorov spectrum. , its spatial power spectrum satisfies:

[0045]

[0046] in is the atmospheric coherence length, For spatial frequencies, turbulence parameters and phase screen sequences are loaded into memory.

[0047] Step 3: Simulate the current phase screen Loaded into the initial light field , and modulate the phase:

[0048]

[0049] in Represents the current light field, is a complex exponential function, which represents the phase modulation of the complex amplitude of the light field. j is an imaginary unit used to construct the phase modulation term in the form of a complex exponential.

[0050] The modulated current light field Simulate the free space propagation process; in this embodiment, the angular spectrum method is used to forward propagation distance .

[0051]

[0052]

[0053] in is the Fourier transform, stands for inverse Fourier transform, is the Fresnel transfer function, and are the spatial frequency coordinates, is the wavelength.

[0054] Step 4: After passing through each phase screen in the forward order and completing all phase screen and free space propagation processes, save the final light field as the initial value of the reverse iteration to generate the target light field :

[0055] .

[0056] Step 5: Target light field As the initial value of reverse propagation, the distance is reversed using the angular spectrum method ,

[0057]

[0058] in represents the reverse propagating light field, express Take conjugate;

[0059] Remove the influence of the current phase screen and output the complex amplitude distribution required by the 4-plane spatial light modulator:

[0060]

[0061] Pass through each phase screen in reverse order, remove the modulation effect in step 3, and reversely calculate and synthesize an equivalent phase map.

[0062] Step 6: Extract the phase of the phase image.

[0063]

[0064] Adding fill factor to compensate for amplitude attenuation,

[0065]

[0066] in is the extracted phase, For phase extraction, is the 4-pixel pitch of the spatial light modulator, is the filling factor, and the sinc function is used to correct the amplitude attenuation caused by discrete sampling. and are the spatial frequency coordinates respectively.

[0067] The phase is mapped to a single spatial light modulator 4 to realize a multi-layer phase screen synthesis method for atmospheric turbulence simulation.

[0068] The performance parameters of this method are: phase image generation time t<1s for 10-layer phase screen; dynamic parameter update delay T<50ms. Parameter range: atmospheric coherence length , corresponding to the refractive index structure constant ;Simulated target distance: 0.1~20km.

[0069] exist Figure 1 The effect of applying this method in the atmospheric turbulence simulation system of the single spatial light modulator 4 is shown in FIG. Figure 3 It can be seen that when the spatial light modulator 4 is loaded with a single turbulence phase screen, only low-order aberration simulation under weak phase disturbance can be achieved, showing a slight blurring effect, which cannot simulate the actual atmospheric turbulence effect. Therefore, a multi-layer phase screen synthesis method must be applied. Figure 3 (d) Figure 3 (e) Figure 3 (f) Figure 3 (g) Figure 3 (h) shows the output effects of spatial light modulator 4 using this synthesis method at different propagation distances when loaded with 2, 4, 6, 8, or 10 composite phase screens. It can be seen that the output effect can dynamically adapt to different turbulence intensities, number of phase screen layers, and propagation distances, thereby achieving the equivalent physical effect of a traditional multi-cascade system on a single spatial light modulator 4.

[0070] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in the present disclosure can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solutions disclosed in the present disclosure can be achieved. This is not limited herein.

[0071] The above specific embodiments do not limit the scope of protection of the present invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A multi-layer phase screen synthesis method for atmospheric turbulence simulation, characterized by: The method includes: allocating memory in a computer and setting an initial light field in the memory; Inputting set turbulence parameters into the parameter configuration module of the computer, generating a random phase screen sequence, and loading the turbulence parameters and the phase screen sequence into the memory; Simulating the free-space propagation of the initial light field after it passes through each phase screen layer in a forward direction to generate a target light field; The target light field is used as the initial value of reverse propagation, the modulation effect is stripped off through each layer of phase screen in reverse order, and an equivalent phase map is calculated and synthesized through free space propagation; Phase extraction is performed on the phase image, a fill factor is added to compensate for amplitude attenuation, and the phase image is mapped to a single spatial light modulator to realize a multi-layer phase screen synthesis method for atmospheric turbulence simulation.

2. A multi-layer phase screen synthesis method for atmospheric turbulence simulation according to claim 1, characterized in that: The turbulence parameters include: atmospheric coherence length, phase screen layer number and inter-layer propagation distance sequence.

3. The multi-layer phase screen synthesis method for atmospheric turbulence simulation according to claim 1, characterized in that: The performance parameters of this method are: phase image generation time t<1s for a 10-layer phase screen; dynamic parameter update delay T<50ms.

4. The multi-layer phase screen synthesis method for atmospheric turbulence simulation according to claim 1, characterized in that: The parameter range of this method is: atmospheric coherence length ,correspond ; Simulated target distance: 0.1~20km.

5. The multi-layer phase screen synthesis method for atmospheric turbulence simulation according to claim 1, characterized in that: The initial light field Expressed in the form of a Gaussian beam: in is the amplitude, is the beam waist radius, and x and y represent the coordinates.

6. The multi-layer phase screen synthesis method for atmospheric turbulence simulation according to claim 1, characterized in that: The extracted phase : in is the light field during reverse propagation, represents the extracted phase, is the pixel spacing of the spatial light modulator, and the sinc function is used to correct the amplitude attenuation caused by discrete sampling. and are the spatial frequency coordinates respectively.

7. A system for synthesizing multi-layer phase screens for atmospheric turbulence simulation, based on the method for synthesizing multi-layer phase screens for atmospheric turbulence simulation according to any one of claims 1 to 6, characterized in that: The system includes: a silicon-based AMOLED microdisplay, a collimator, a polarizing filter, a spatial light modulator, an imaging component, and an image recording device; the image recording device reads and stores image data or video data of a real scene, loads and displays the data through the silicon-based AMOLED microdisplay, and simulates the optical properties of the image data or video data of the real scene; the collimator collimates the divergent light emitted by the silicon-based AMOLED microdisplay and converts the divergent light into parallel light; the polarizing filter polarizes the parallel light to match the polarization properties of the spatial light modulator; the spatial light modulator modulates the phase of the polarized light wave to simulate the wavefront distortion effect caused by atmospheric turbulence and form a degraded image; the imaging component forms an image of the degraded image with the changed phase, and the image recording device stores the image.

8. The system for multi-layer phase screen synthesis for atmospheric turbulence simulation according to claim 7, characterized in that: The imaging component includes: a fixed-focus optical lens and an industrial camera; the fixed-focus optical lens and the industrial camera are integrated together to ensure optical stability and high-quality acquisition of the degraded image.

9. The system for multi-layer phase screen synthesis for atmospheric turbulence simulation according to claim 7, characterized in that: Also includes: A control computer; the control computer drives the spatial light modulator, dynamically loads phase screen data, and phase modulates the polarized light waves passing through its surface.

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