改进的基于光学成像模型的逆合成孔径激光雷达成像算法  

Modified Imaging Algorithm for Inverse Synthetic Aperture LiDAR Based on Optical Imaging Model

作　　者：徐晨 宋岸鹏 晋凯 魏凯[1,2] Xu Chen;Song Anpeng;Jin Kai;Wei Kai(Key Laboratory on Adaptive Optics,Chinese Academy of Sciences,Chengdu 610209,Sichuan,China;Institute of Optics and Electronics,Chinese Academy of Sciences,Chengdu 610209,Sichuan,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院自适应光学重点实验室,四川成都610209 [2]中国科学院光电技术研究所,四川成都610209 [3]中国科学院大学,北京100049

出　　处：《激光与光电子学进展》2023年第12期367-373,共7页Laser & Optoelectronics Progress

摘　　要：逆合成孔径激光雷达(ISAL)是一种相干成像系统,其图像具有明显的散斑,影响目标识别和判断。为解决该问题,近年来有学者提出一种基于模型的迭代重构(MBIR)算法。该算法直接重构目标反射率而非复反射系数(传统重构方法普遍采用的),所重构图像质量更接近光学图像。然而,该算法存在优化模型较复杂、采用的无梯度线搜索算法求解效率较低且不易收敛的问题。针对以上问题,进行两点改进。首先从信息传递的角度得到复反射系数分布、反射率分布和测量信号之间的马尔可夫关系,据此将复反射系数假设为反射率估计的完整数据集,简化了优化模型。其次,针对模型求解,应用更容易求解梯度的先验模型替代函数,并结合对数变换,将原问题转换为含梯度的无约束问题,进行高效求解。最后通过仿真数据和7 km外场实验数据验证了所提改进方法的有效性和效率。结果表明,对于高中低具有不同载噪比(5 dB、0 dB、-5 dB)的回波数据,所提改进方法在5次迭代之内即可得到较优质量的图像。Inverse synthetic aperture LiDAR(ISAL)is a kind of coherent imaging system.It acquires images with speckles that affect target recognition and judgment.In recent years,some scholars proposes a model-based iterative reconstruction(MBIR)algorithm to solve the problem.The algorithm directly estimates the real valued reflectance instead of the complex valued one commonly used by traditional reconstruction methods,making the reconstructed image closer to the optical image.However,the MBIR algorithm faces the problems of complex optimization model,low efficiency,and difficult convergence when the gradient-free line search version is used.To address these problems,this study presents two proposals.First,the Markov relation between the distributions of the complex reflectance and reflectivity,and the measurement signal is obtained from the viewpoint of information transfer.The complex reflectance is assumed as a complete dataset of the reflectivity estimation that simplifies the optimization.Second,the surrogate function of a prior model,whose gradient is easier to obtain,and the logarithm transformation are used to improve the algorithm efficiency in which the original problem is transformed into an unconstrained problem with gradient.The effectiveness and efficiency of the proposed method are verified by simulation and outdoor experimental data from a target 7 km away.The results show that the proposed method can obtain better images within five iterations for echo data with carrier-to-noise ratio of 5 dB,0 dB,and−5 dB.

关 键 词：合成孔径激光雷达 计算成像 贝叶斯估计 图像重构 

分 类 号：TN958[电子电信—信号与信息处理]