强散射体产生的像面散斑对比度与随机表面及成像系统关系的研究

Study on the dependence of the contrast of image speckles produced by strong scattering-object on random surface and imaging system

在对 4f光学成像系统中强散射体形成的像面散斑的统计特性的研究中 ,首先通过散斑场光波复振幅的一般形式和双重指数函数近似求出散斑光强的系综平均 ,然后利用散斑场光波复振幅的实部和虚部的旋转变换法求出散斑光强的方差 ,最后得出了散斑对比度与随机表面统计参量和系统参量的直接表达式 .本结果与现有文献中包含随机表面相关面积或散射粒子数目的隐含表达式相比具有明显的改进 ,并对标定随机表面的散斑对比度法具有重要意义 .

We study the statistical properties of the image speckles produced by strong-scattering objects in the 4f optical imaging system. Using the generic expression of the complex amplitude of speckles and the approximation of the double-exponential function, we first obtain the ensemble average of the speckle intensity. Then we derive the variance of the speckle intensity based on the rotational transformation of the real and imaginary parts of the complex amplitude of speckles. We finally obtain the expression for the contrast of the. speckles, which is explicitly related to the statistical parameters of random surface and to the parameters of the imaging system. Our results are an obvious improvement compared with those reported in the literature, where the relations including such implicit quantities as the average size of the scattering grains of the random surface and the number of scattering grains are usually used. The results of this paper would be helpful for the characterization of random surface by speckle contrast.