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中国物理学会期刊

基于深度卷积神经网络的大气湍流相位提取

CSTR: 32037.14.aps.69.20190982

Extracting atmospheric turbulence phase using deep convolutional neural network

CSTR: 32037.14.aps.69.20190982
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  • 光束在自由空间中传播时容易受到大气湍流的影响, 其对传输光束的影响相当于附加一个随机噪声相位, 导致传输光束质量下降. 本文提出了一种基于深度卷积神经网络(convolutional neural network, CNN)的湍流相位信息提取方法, 该方法采用受湍流影响的光强图为特征提取对象, 经过对海量样本进行自主学习后, CNN的损失函数值收敛到0.02左右, 其在测试集上的平均损失函数值低于0.03. 训练好的CNN模型具有很好的泛化能力, 可以直接根据输入的光强图准确提取出湍流相位. 利用I5-8500 CPU, 预测C_\rmn^2 = 1 \times 10^ - 14\;\rmm^ - 2/3 , C_\rmn^2 = 5 \times 10^ - 14\;\rmm^ - 2/3C_\rmn^2 = 1 \times 10^ - 13\;\rmm^ - 2/3三种湍流强度的湍流相位所需要的平均时间低至5 \times 10^ - 3\;\rms. 此外, CNN的湍流相位提取能力可以通过提高计算能力或者优化模型结构来进一步提升. 这些结果表明, 基于CNN的湍流相位提取方法能够有效的提取湍流相位, 在湍流补偿、大气湍流特性研究和图像重构等方面具有重要的应用价值.

     

    When a light beam transmits in free space, it is easily affected by atmospheric turbulence. The effect on transmitted light is equivalent to adding a random noise phase to it, which leads its transmission quality to deteriorate. The method of improving the quality of transmitted beams is usually to compensate for the phase distortion at the receiver by adding reverse turbulence phase, and the premise of this method is to obtain the turbulence phase carried by the distorted beam. The adaptive optics system is the most common way to extract the phase information. However, it is inefficient to be applied to varying turbulence environments due to the fact that a wave-front sensor and complex optical system are usually contained. Deep convolutional neural network (CNN) that can directly capture feature information from images is widely used in computer vision, language processing, optical information processing, etc. Therefore, in this paper proposed is a turbulence phase information extraction scheme based on the CNN, which can quickly and accurately extract the turbulence phase from the intensity patterns affected by atmosphere turbulence. The CNN model in this paper consists of 17 layers, including convolutional layers, pooling layers and deconvolutional layers. The convolutional layers and pooling layers are used to extract the turbulent phase from the feature image, which is the core structure of the network. The function of the deconvolutional layers is to visualize the extracted turbulence information and output the final predicted turbulence phase. After learning a huge number of samples, the loss function value of CNN converges to about 0.02, and the average loss function value on the test set is lower than 0.03. The trained CNN model has a good generalization capability and can directly extract the turbulent phase according to the input light intensity pattern. Using an I5-8500 CPU, the average time to predict the turbulent phase is as low as s under the condition of C_n^2 = 1 \times 10^ - 14\;\rmm^ - 2/3, 5 \times 10^ - 14\;\rmm^ - 2/3, and 1 \times 10^ - 13\;\rmm^ - 2/3. In addition, the turbulence phase extraction capability of CNN can be further enhanced by improving computing power or optimizing model structure. These results indicate that the CNN-based turbulence phase extraction method can effectively extract the turbulence phase, which has important application value in turbulence compensation, atmospheric turbulence characteristics research and image reconstruction.

     

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