In order to study the effect of laser speckle on target detection, according to the extended Huygens-Fresnel principle, statistical properties of the speckle scattered from the rough surfaces in the far field were analyzed in double transmission. Analytical expressions for the correlation function and covariance of the speckle intensity were derived under the illumination of focused beam and collimated beam. The results indicate that under the illumination of focused beam, the speckle intensity correlation function of the receiver surface is decreased fast with the laser beam waist and transmission distance decreasing. However, under the illumination of collimated beam, the speckle intensity correlation function of the receiver surface is decreased fast with the laser beam waist and transmission distance increasing. In the whole, it decreased fast under the collimated illumination than focused illumination. The change rule of intensity covariance is identical with the speckle intensity correlation function.%为了研究激光散斑对目标探测的影响,采用广义惠更斯-菲涅耳原理,进行了双程传输中激光束照射远场目标时在接收平面上散斑的统计特性的理论分析,导出了汇聚光束及准直光束照射情况下散斑场的互相关函数、平均散射强度以及强度协方差的表达式.结果表明,随着波束特征半径以及传输距离的减小,会聚波束照射时接收平面上散斑场的互相关函数下降迅速,而准直波束正好相反,总体上准直波束比会聚波束下降要快得多;强度协方差函数的变化规律与互相关函数的变化规律基本一致.
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