Laser Speckle Reduction Using a Motionless Despeckle Element Based on Random Mie Scattering

A motionless despeckle element based on Mie scattering and Brownian motion of suspended particles is proposed, which is achieved by filling a light pipe with diluted milk in laser projection systems. The Brownian motion of the milk fat particles leads to the superposition of the intensity of the instantaneous scattered light within the integration time of the human eye, which causes a reduction in laser speckle contrast because of temporal averaging intensity. Experimental results show that the speckle contrast mainly depends on the concentration of the suspended fat particles, and can be reduced down to 3.94% at the fat particle concentration of approximately 7.0 ×10^-4 μm^-3.