“We want to see through the fog as if the fog was not there,” says Guy Satat, a PhD candidate at MIT Media Lab who led the research.
The system uses ultrafast measurements and an algorithm to computationally remove fog and create a depth map of the objects in the vicinity. It uses a SPAD (single photon avalanche diode) camera that shoots pulses of laser light and measures how long it takes for the reflections to return. In clear conditions, this time measurement could be used to gauge object distance. But fog causes light to scatter, making these measurements unreliable. So the team developed a model for measuring how, exactly, fog droplets affect light’s return time. Then the system can eliminate the scattering and create a clear picture of what’s actually ahead.