Atmospheric Effects upon Laser Eye Safety. Part 1
STANFORD RESEARCH INST MENLO PARK CA
Pagination or Media Count:
The results of two laser scintillation experiments in the atmosphere are presented, as is a revised laser eye-hazard evaluation procedure incorporating these results. The objective of the research is to determine the influence of atmospheric thermal turbulence on laser eye safety. The experimental work on a 3.5-km near-ground horizontal propagation path was designed to determine the effect of range upon laser scintillation magnitude, represented by the log intensity standard deviation sigma. It was found that for very short ranges and low thermal turbulence, the measured values sigma sub m agree well with theory sigma sub t. However, for longer ranges and higher thermal turbulence, the values of sigma sub m reached a maximum value of approximately 1.25 at sigma sub t 2.50, and then decreased beyond, fitting the empirical function sigma sub m sigma sub t1 0.16sigma subtsquared fairly well. This supersaturation effect is quite significant in reducing eye- damage probabilities for typical ranges and thermal turbulence conditions. The second experiment was an attempt to confirm that scintillation saturation occurs on a slant path between a bround-based laser and a receiver on an orbiting aircraft. Some evidence of saturation was found, but the effect was not clearly established because of the limited ranges necessitated by the laser used. The eye-hazard evaluation procedure is quite generally applicable, and requires only readily available input data. The method covers propagation on a slant path with either a ground-based or airborne laser, as well as near-ground horizontal propagation.
- Lasers and Masers