Researchers from Carnegie Mellon University have devised an experimental car headlight system of which the light is unaffected by falling rain or snow. The system calculates the trajectory of each snow flake or rain drop and then projects its light in such a way that the light rays pass between the drops and flakes. Such a system would make driving in rain or snow much safer and less tiring.
The system consists of a camera and a projector aimed at the road through a one-way mirror. The camera takes a picture of the falling rain from which the estimated trajectories of the drops at the top of the image are calculated. These trajectories are then used to construct a light image that excludes the paths of the drops. The delay between taking the picture and projecting the image is about 13 ms. The prototype built by the researchers managed an accuracy of 68.9% with rain drops falling at a speed of 25 mm/hour and a projection frequency of 120 Hz. With a frequency of 10 kHz the system scored an exemplary 100%.