Effect of fractal rough-surface Hurst exponent on speckle in imaging systems.

Speckle image contrasts from a fractal rough-surface object are investigated in simulation, where the image surface is conjugate to the object surface. It is observed that the Hurst exponent H of fractal roughness affects speckle contrast and statistics dramatically. For example, a strong rough surface (sigma(h)>lambda) exhibits Rayleigh statistics over increasing ranges of point spread function widths as H decreases. Conceptual explanations are also presented for effects of H and the coherence factor on speckle in imaging systems.