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 theOcean, and Sargasso Sea) are presented. These measurements are used to validate extensive laboratorymeasurements [S. Q. Duntley, “Underwater Lighting by Submerged Lasers and Incandescent Sources,” SIORef. 71-1, Scripps Institution of Oceanography, U. California, San Diego (1971)]. In all three locations asimple exponential expression describes the angular variation of the PSF in the 4-100-mrad range. Theexponent in this relationship has a simple location specific dependence on attenuation length and the ratio ofthe absorption to beam attenuation coefficient. These relationships can be used to predict the PSF for anarbitrary path length.