Detection of visibility conditions through use of onboard cameras

An atmospheric visibility measurement system capable of quantifying the most common operating range of onboard exteroceptive sensors is a key parameter in the creation of driving assistance systems. This information is then utilized to adapt sensor operations and processing or to alert the driver that the onboard assistance system is momentarily inoperative. Moreover, a system capable of either detecting the presence of fog or estimating visibility distances constitutes in itself a driving assistance. In this paper, we present a measurement framework of different visibility distances using onboard CCD cameras, that we beforehand defined: meteorological visibility, obstacle visibility, mobilized visibility. The methods to estimate these different visibility distances are detailed. Whereas the first one is based on a physical model of light diffusion by the atmosphere, the two other methods are based on the "v-disparity" approach and local contrasts computation. The methods are evaluated thanks to video sequences under sunny weather and foggy weather.