Dept. of Applied Physics
Oregon Graduate Center
Speckle-turbulence interaction has the potential for allowing single ended remote sensing of the path averaged strength of turbulence (structure constant) along the limit of sight to a remote object. Unfortunately, the fluctuations in received intensity due to speckle and those due to the turbulence cannot be directly separated. It was therefore proposed that by utilizing optical spatial filtering (OSF) before measuring the received intensity, that the effects of speckle and turbulence could be separated. Consequently, the research for this dissertation was directly toward a better understanding of laser and laser generated speckle propagation through turbulence, the effect of optical spatial filtering on the received intensity and its application to optical remote sensing of the strength of turbulence. The work involved both analysis of the statistics for the received intensity after OSF and experimental work to verify the analysis. The mean and the variance of the received intensity after OSF both for the line of sight case and the single ended case were analyzed and the results studied. These results indicated that the OSF mean intensity in both cases could be used very effectively to remote sense the strength of turbulence, but that the variance was not useful for that purpose. Experimental work was conducted for both the line of sight and single ended cases in the atmosphere and also utilizing the OGC turbulence simulation tank. The results agree with the theoretical predictions and demonstrate that OSF can be used in both the line of sight case and the single ended case for optically remote sensing the strength of turbulence. The technique should be useful for turbulence levels from around 10 [superscript -16] to 10 [superscript -12] m [superscript -2/3] by choosing appropriate laser wavelengths and the high-pass spatial filter sizes.
Sun, Libo, "The effect of optical spatial filtering on the statistics of laser radiation propagating through the turbulent atmosphere" (1988). Scholar Archive. 275.