Simple empirical model of the oceanic point spread function.

The point spread function (PSF) is an important property for predicting beam propagation and imaging system performance. Measurements of the PSF in three different locations (Pacific Ocean, Tongue of the Ocean, and Sargasso Sea) are presented. These measurements are used to validate extensive laboratory measurements [S. Q. Duntley, "Underwater Lighting by Submerged Lasers and Incandescent Sources," SIO Ref. 71-1, Scripps Institution of Oceanography, U. California, San Diego (1971)]. In all three locations a simple exponential expression describes the angular variation of the PSF in the 4-100-mrad range. The exponent in this relationship has a simple location specific dependence on attenuation length and the ratio of the absorption to beam attenuation coefficient. These relationships can be used to predict the PSF for an arbitrary path length.