Abstract

Finite aerosol structures with Gaussian spatial number density distributions have been used to model localized obscurants and might be used as an extremely simple model of water clouds with fuzzy edges. A Monte Carlo method has been used to compute radiative transport of a laser beam through such structures. Coupled with the Monte Carlo program is an optics ray tracing program which was used to simulate the operation of a camera. The intensity of direct and scattered light was computed as a function of off-axis angle at the image plane of the camera and as a function of cloud size, optical depth, distance of cloud center from the camera, and width of an assumed Gaussian phase function. It was found that the intensity of the scattered light increases with decreasing width of the phase function, but that the angular width and shape of the beam aureole is independent of the width of the phase function. The angular size of the aureole depends primarily on the distance of cloud center from the camera. The intensity of scattered light drops off approximately as the inverse square of this distance. Thus, although scattered light may predominate close to the cloud, at large distances it may become insignificant relative to the directly transmitted light.

© 1985 Optical Society of America