研究了三片式硅基液晶（LCOS）激光投影显示中散斑的成因、类型及其光学统计特性，并分析了激光散斑大小的测量方法。在此基础上，选用旋转散射片来减少三片式LCOS激光投影系统中产生的复合散斑，并通过一系列的仿真和实验，使得该激光投影机对比度C降到了人眼可接受的范围4.2%。证明了旋转散射片的方法能有效减少复合散斑，具有光学结构简单、实施性强等优点。

The factor, categorization and optical statistical characteristics of laser speckle shown in three-liquid crystal on silicon (LCOS) laser projection display system are studied, and a measuring method of laser speckle is analyzed. According to this, an optical method of rotating diffuser to reduce the composite speckle is applied. Through a series of simulations and experiments, the contrast of speckle patterns is reduced to 4.2%, which is acceptable to people′s eyes. So the method of rotating diffuser effectively suppresses laser speckle, which has simple optical structure and is easy to implement.