Laser Speckle Noise

Abstract

Speckle is observed when coherent light is scattered from a rough surface or is transmitted through a diffuser. Suppression of speckle noise is one main issue of laser displays because it seriously degrades the image quality. There are several suppression methods. The most effective one reduces the coherence of the laser beam itself, for example, by wavelength and angle diversity. Another way is the temporal averaging of speckle. A speckle pattern is moved or deformed by a moving diffuser and averaged during the response time constant of the eye. In this method, the fluctuation of the phase on the screen should be averaged spatially over the eye's resolution element.