Average speckle size as a function of intensity threshold level: comparisonof experimental measurements with theory.

Speckle phenomena result whenever spatially coherent radiation is reflected from a rough surface or propagated through a random medium such as atmospheric turbulence. Speckle characteristics are therefore a major concern in many laser-imaging or wave-propagation applications. We present the results of experimental measurements of target-induced speckle patterns produced in the laboratory from a variety of targets and illumination conditions. We then compare these experimental measurements with a theoretical model for the average speckle size as a function of intensity threshold level. Excellent agreement is obtained for intensity threshold levels greater than approximately twice the mean intensity level.