The Laboratoire Régional des Ponts et Chaussées d'Angers - LRPC of Angers is currently studying the feasability
of applying an optical technique based on the principle of the laser optical feedback to long distance fog vision.
Optical feedback set up allows the creation of images on roadsigns. To create artificial fog conditions we used a
vibrating cell that produces a micro-spray of water according to the principle of acoustic cavitation. To scale the
sensitivity of the system under duplicatible conditions we also used optical densities linked to first-sight visibility
distances. The current system produces, in a few seconds, 200 × 200 pixel images of a roadsign seen through
dense artificial fog.
Vision through diuse media (fog, rain, smoke, snow, etc) is a large problem due to interactions between light and
particles composing the medium. In this paper, one focuses particulary on scattering media as fog. Therefore,
an analytical model for the determination of backscattered luminance induced by fog is described here. The
model is based on the Mie's theory and takes the optical device geometry into account. An analysis of its resulst
leads to several conclusions. The most notable and obvious one is that eliminate backscattering light is necessary
to have good-contrasted images. Starting from this premise, one presents here a range-gated active imaging
system enable to perform a temporal selection between backscattering pollution and photons holding optical