Speckle reduction mechanism in laser rear projection displays using a small moving diffuser

Recently, a practical method of speckle reduction in laser rear projection displays that uses an optical system with a small moving diffuser has attracted much attention. In this paper, a model of the speckle generation and reduction mechanism in the system is presented. We investigated the speckle, focusing on the physical aspects of its generation, rather than treating it statistically. We found that the granularity of the speckle patterns generated by the small diffuser corresponded to the size of the coherent regions on the projection screen. This determined the efficiency of the speckle reduction when the small diffuser was rotated.