A review of light sources used for laser speckle reduction in display and imaging applications

Laser speckle is greatly influenced by the chosen light source and how or if its emission is manipulated. A laser with intrinsically high coherence generates high speckle contrast (SC, a quantitative measure of speckle) leading to low image fidelity. However, by destroying the laser’s temporal or spatial coherence and/or applying beam diversity, SC can be reduced whilst retaining many of the benefits of low power laser illumination in holography, triangulation, cinematic projections, and in a variety of imaging applications. Thus, careful consideration of the choice of light source and SC reduction method is critical. This review summarizes the light sources commonly used by researchers in SC reduction applications. It was found that the output of laser didoes can be manipulated using the largest variety of techniques and, thus, offer the greatest flexibility in applying spectral, spatial, and/or angular diversity. This flexibility is found to be highly effective in reducing SC particularly when combining several techniques simultaneously.