湍流大气中微运动粗糙目标散斑场高阶矩和动态特性研究

The micro-motion detection of a spatial object is an important application of laser speckle measurement technolog, which is widely used in many areas, such as, remote sensing, space detection, ballistic missile defense, air defense operation and monitoring. However, because of the existance of the atmoshperic turbulence, the temporal and spatial characteristics of the speckle field may be greatly disturbed, which will introduce a large error to the measurement. Therefore, it is necessary to research the characteristics of the speckle field from a rough object in micro-motion in turbulence. The Huygens-Fresnel integral expression of the speckle field are established by introducing reasonable approximations on the base of the Kirchhoff theory about electromagnetic scattering from a rough target. The temporal-spatial correlation function of the intensity of the speckle field in turbulence are derived by combining the Rytov theory and the Extended Huygens-Fresnel principle. The effect of atmospheric turbulence on the correlation length, the correlation time and the normalized variance of the intensity of the speckle field are numerically analyzed. Finally the Slip-Step Method is extented to the simulation of the speckle field from a rough object in mico-motion in turbulence, the correlation length and correlation time are statistically calculated and compared with the theoretical results. The results of the research will provide a theoretical basis and technical supporta for the application of laser speckle measurement technolog in atmospheric turbulence.

空间目标微运动测量是激光散斑测量技术的一项重要应用，广泛用于遥感、空间探测、弹道导弹防御、防空作战和监视等领域。但是由于湍流大气的干扰，激光散斑的时间-空间分布特性都会发生明显的变化，从而给测量结果造成较大误差。为了对测量结果进行修正，有必要对湍流大气影响下的微运动粗糙目标散斑时-空特性进行研究。本项目在粗糙目标散射场基尔霍夫理论的基础上进行合理近似，建立粗糙目标散斑场的惠更斯－菲涅耳积分表达式。结合Rytov理论和广义惠更斯-菲涅耳原理，建立湍流大气中微运动粗糙目标回波强度起伏时间-空间相关函数表达式，数值分析湍流大气对微运动粗糙目标散斑场相干长度、相关时间和归一化强度方差的影响。最后把分步傅立叶算法推广到微运动粗糙目标和动态湍流条件下，数值仿真湍流大气中的动态散斑场，统计分析散斑相干长度和相关时间，对理论结果进行了对比验证。本项目的研究可为湍流大气中散斑测量技术提供理论依据和技术支撑。

本项目实验测量了旋转粗糙目标的时间相关函数，基于基尔霍夫近似理论建立了粗糙目标散斑时－空相关函数简化模型；利用理论分析和数值计算两种方法研究了光学表面与离散粒子复合目标的散射场特性；基于广义惠更斯－菲涅耳原理和Stokes参数法研究分别研究了部分相干平顶电磁光束和部分相干椭圆偏振平顶波束在湍流大气中斜程传输的偏振特性；利用非相干叠加的方法，建立了湍流大气中随机离散目标的回波强度起伏模型，数值分析了归一化强度起伏方差随着散射点个数及其离散程度的变化。利用类似的方法，针对三维分布的大量的离散颗粒，建立湍流大气中粒子群目标的回波强度起伏模型，建立了强度相关函数及归一化强度起伏方差模型。利用广义惠更斯-菲涅尔原理建立了湍流大气中硬边平面粗糙目标和无限大平面目标的回波强度起伏模型。考虑了后向增强效应的影响，理论推导和计算了回波归一化强度协方差和方差函数。对分步傅立叶算法进行了改进，拓宽了分步算法的使用范围。利用分步傅立叶算法研究了艾里波束在湍流大气中沿斜程传输的情况，分析了倾斜角度、传播距离、波束宽度以及湍流强度对波束传输过程中自修复和无衍射特性的影响。仿真研究了涡旋波束在湍流大气中传输时，其平均强度、相位、轨道角动量的变化。仿真研究了环状艾里高斯涡旋波束在湍流大气中传输时平均强度的变化规律。其研究成果对湍流大气中激光雷达信息提取以及散斑测量技术有重要的理论意义和应用价值。