Most driverless car systems (though notably not Tesla’s) use LIDAR (light detection and ranging) systems, which shoot pulses of infrared light and measure how long it takes to come back. “The immediately obvious application is self-driving cars, simply because this industry is already using similar hardware,” Satat says. They hope the system will one day have numerous real-world applications. They’re currently looking at making the system more photon efficient, which could allow it to see through denser fog to farther distances. Satat says it’s possible the system will work on other conditions such as rain and snow, but they haven’t tested them yet. Satat and his colleagues will present a paper about their system at the I nternational Conference on Computational Photography at Carnegie Mellon University in May. The results showed the system performed far better than human vision, in conditions far foggier than cars encounter on roads. They put small objects such as blocks and letter cards inside, to see how far and well the system could see. They eventually used a tank of water with a humidifier motor inside to create a fog chamber. They tried the kind of fog machine you can rent for parties, but the result was “way too intense” for their purposes, Satat says. To test the system, the team had to create fake fog. Then the system can eliminate the scattering and create a clear picture of what’s actually ahead. So the team developed a model for measuring how, exactly, fog droplets affect light’s return time. But fog causes light to scatter, making these measurements unreliable. In clear conditions, this time measurement could be used to gauge object distance. 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. The system uses ultrafast measurements and an algorithm to computationally remove fog and create a depth map of the objects in the vicinity.
“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.
If only we’d had a new imaging system developed by researchers at MIT, designed to see through fog and warn drivers of obstacles. So instead we’d inch along, squinting for the yellow glow of oncoming headlights through the fog. Oh, and did I mention many of the roads were one-way? If we’d pulled over, we could have been stuck for hours. Cinematic, enveloping white clouds, coming seemingly out of nowhere, making the boulder-strewn hills and craggy valleys disappear completely. When we weren’t working, we would drive through the Highlands on hiking and sightseeing trips.
Guy Satat, a graduate student in the MIT Media Lab, at the fog machineįive years ago, my husband and I spent the summer in Scotland.