合成孔径激光成像雷达（SAIL）中的散斑效应严重影响成像质量。建立了远距离SAIL系统下激光散斑理论模型，分析了产生时空散斑效应的原因并推导了时空散斑效应的数学表达式。给出了由单个目标分辨单元粗糙表面引起的光学天线接收面上的散斑花样，通过具体实例分析了散斑的统计性质。模拟结果表明，散斑平均宽度与合成孔径中的光学足趾尺度相当；一次脉冲啁啾时间内散斑花样在距离向移动的距离等于散斑的平均宽度。通过大口径SAIL演示样机实验，验证了时空散斑效应的距离向波长特性，从而直接认识了SAIL中的散斑效应。模拟结果为实际SAIL系统中利用多口径接收装置抑制散斑效应提供了一定的参考。

In synthetic aperture imaging ladar (SAIL), the image quality is seriously degraded by the laser speckle effect. Based on the SAIL system in far-field diffraction region, the physical models of laser speckle effect are established, and the expressions for the intensity of speckles are derived. The reasons of space-time speckle effect are analyzed, and the specific speckle patterns are obtained. Research results indicate the statistical properties by simulating the phase and amplitude distribution of typical space-time speckle patterns. Simulation results show that the average width of speckle pattern equals the scale of footprint in SAIL system. The moving distance of speckle pattern along the range direction during a period of pulse time and the average speckle scale are roughly equivalent. Experiments are conducted on big aperture SAIL. Experimental results confirms the prediction. The vivid space-time speckle effect is firstly demonstrated. Simulation results provide a certain reference to the speckle reduction by using multi-channel transmitter/receiver.