基于广义惠更斯菲涅耳原理分析了高斯谢尔光束通过湍流大气漫射目标的散射统计特性。假定相位结构函数起主导作用, 根据高斯谢尔光束的交叉密度函数, 推导了散斑场的互相干函数表达式, 进而得出接收面处的散斑尺寸大小和强湍流起伏的时延协方差函数表达式。数值分析了源相干长度、波长、湍流强度对互相干函数的影响。对理想漫射目标, 接收面的散斑尺寸大小由束腰宽度、源相干长度和湍流强度确定, 随着湍流强度的增加, 散斑尺寸变小; 在弱湍流区, 散斑尺寸由源相干长度决定, 当湍流增强时, 散斑尺寸大小逐渐趋于一致。

We utilize the extended Huygens-Fresnel principle to make an analysis of the scattering of a Gaussian Schell-model beam from a diffuse target in a turbulent atmosphere. It is assumed that the wave structure function is dominated by the phase structure function. Using the cross-spectral density function of the GSM beam, the analytical expressions are developed for the mutual coherence function (MCF) of the speckle field at the receiver, and then time-delayed variance of the scattering intensity in strong turbulence is derived. From the normalized MCF, estimates are given for the speckle size at receiver. We also analyze the influences of the coherence length of the source, wavelength, and turbulence strength on the mutual coherence function. For a diffuse target, the speckle size is only determined by the waist width, the coherence length of the source and the turbulence strength. With the turbulence strength increasing, the speckle radius will decrease at the receiver. In weak turbulence, speckle radius is dominated by the value of source coherence.