Comparison of laser speckle suppression due to angle diversity

Angle variation formula of illumination, which is induced by moving lens, or moving retroreflecting right-angle prism, or rotating mirror, was derived according to imaging principle. The extent of the angle change of illumination depends on three parameters, such as focal length of the lens, object distance, and divergence angle of light source. The three methods introducing angle diversity were compared. The experimental results are consistent with the theoretical analysis. The results demonstrate that 20 m displacement for the retro-reflecting right-angle prism and 0.02 of rotating angle for the mirror can easily achieve two completely independent speckle patterns under the same conditions, which provides a basis to design a motion scheme introducing angle diversity to suppress laser speckle.