laser speckle reduction using a passive diffuser . a diffuser for reducing laser speckle is disclosed comprising a diffuser having a colloid configured for placement in a light path of a coherent light source . the colloid exhibits brownian motion . the diffuser can be formed of transparent plates containing the colloid . in a system for illumination , a coherent source of light outputting a light beam along a light path is provided ; and a diffuser for reducing laser speckle effects is placed in the light path , the diffuser comprising a colloid disposed in a container that is transparent to the light beam output by the coherent source . a method includes illuminating a photosensitive sensor , comprising transmitting a coherent light from a light source through a diffuser comprising a colloid and directing the light from the diffuser onto the photosensitive sensor . additional embodiments are disclosed .