激光束发散角的测量对于激光制导、激光测量有着重要的意义，激光束发散角是激光质量的一个重要参数。大发散角激光照明在大范围散斑干涉测量中也有着重要应用。基于散斑自相关的方法推导了椭圆高斯光束照明下的散斑二维尺寸与照明光束参数之间的关系，通过散斑自相关运算直接计算得出接收面上散斑二维尺寸从而测量出光束有效照明尺寸，根据不同距离的有效照明尺寸确定光束的发散角。采用激光散斑计量光束有效照明半径的方法有着大范围的光强适用性，无需考虑离轴误差影响。该方法结构简单，对环境光有一定的抑制作用。

Divergent angle of laser beam which used in laser guidance and measurement is an important parameter. Large area illumination of laser is also an important application in large-scale speckle interferometry. The relation between speckle size and elliptical Gaussian laser beam illumination parameter is derived by using speckle auto-correlation, and the effective two-dimensional lighting size at receiving plane is calculated, the divergence according to the lighting sizes at different distances futhermore determined. This device is simply constructed. Using laser speckle auto-correlation metrology methods the dynamic range of laser intensity is enlarged, ignoring the off-axis influence, and environmental light is suppressed.