为研究高速摄影中激光相干噪声的影响因素,降低激光照明中散斑噪声对高速摄影成像质量的影响,对激光照射表面的粗糙程度与形成的散斑场统计特性之间的关系进行了研究。基于菲涅尔-基尔霍夫衍射原理,分析了高斯光束入射在随机粗糙表面上经反射形成的散斑图样,通过对大量散斑图样的数据统计,得出了激光散斑的信噪比、自相关函数、概率密度函数与入射表面粗糙度之间的变化关系。计算结果表明: 粗糙度的增大使散斑场信噪比降低、相干程度减小、概率密度降低,即表面越粗糙散斑噪声越严重。

In order to research the influence factors of laser coherent noise in high speed photography, and reduce the impact brought by speckle noise on the quality of high-speed photography imaging, the relationship between the roughness of the surface irradiated by the laser and the statistical properties of the laser speckle was studied. Based on the principle of Fresnel-Kirchhoff diffraction theory, the laser speckle patterns by reflection on random surface by Gaussian beam incident was analyzed, and the relationship between the SNR and autocorrelation and probability density function and the roughness of the incident surface was obtained through the statistics of a large amount of data of laser speckles. The results show that bigger roughness lead to smaller SNR of speckle field, degree of coherence and probability density, that is to say, the noise of the speckle increases with the increase of the roughness of the surface.