It is shown that, because of the effects of the turbulent atmosphere, the probability density function of the intensity for a monochromatic, fully developed speckle pattern changes from an exponential distribution at low turbulence levels to a K distribution as the turbulence level increases. A physical model that leads to the K distribution is proposed, and the parameters of the K distribution are derived in terms of the strength of turbulence, path length, wavelength, and beam size. The work is then extended to polychromatic and partially developed speckle patterns and to speckle with a coherent background. Good agreement is obtained between the theoretical predictions and experimental measurements.
© 1982 Optical Society of America
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