Dept. of Applied Physics
Oregon Graduate Center
This study was concerned with the effects of atmospheric turbulence on propagating speckle fields. Measurements of normalized variance and covariance were made at two path lengths under various levels of turbulence strength. The results are compared to recently published theoretical formulations. The theory, developed by Lee, Holmes, and Kerr, contains general formulations for normalized variance and covariance of intensity for single frequency, single mode laser illumination of a diffuse target through turbulence. By assuming that phase perturbation is the dominant effect of turbulence and that the fields at the receiver are jointly Gaussian, simple closed form expressions are obtained. The covariance measurements described herein indicate that the additive amplitude perturbation terms in the general formulation may be very important in moderate to high turbulence conditions. It appears that the simple Gaussian assumption theory predicts accurate covariance scales only in low turbulence conditions (where Ï [subscript o] > âL/K). Due to inadequate temporal coherence of the illuminating laser, the measured normalized variance was lower than expected. As a result it was not possible to make detailed quantitative comparisons to either the general or simplified theory. However, the measurements do show a qualitative agreement with the general theory.
Fossey, Michael E., "Statistical measurements of speckle propagation through the turbulent atmosphere" (1976). Scholar Archive. 41.