The Microsoft Kinect was a boon to robotics researchers. The cheap, off-the-shelf depth sensor allowed them to quickly and cost-effectively prototype innovative systems that enable robots to map, interpret, and navigate their environments.
The sensors like the Kinect use infrared light to gauge depth. So they are easily confused by ambient infrared light. Even indoors, they tend to require low-light conditions, and outdoors, they’re hopeless.
At the International Conference on Robotics and Automation in May, researchers from MIT’s Computer Science and Artificial Intelligence Laboratory will present a new infrared depth-sensing system, built from a smartphone with a $10 laser attached to it, that works outdoors as well as in.
The researchers envision that cellphones with cheap, built-in infrared lasers could be snapped into personal vehicles, such as golf carts or wheelchairs, to help render them autonomous. A version of the system could also be built into small autonomous robots, like the package-delivery drones proposed by Amazon, whose wide deployment in unpredictable environments would prohibit the use of expensive laser rangefinders.
Infrared depth sensors come in several varieties, but they all emit bursts of laser light into the environment and measure the reflections. Infrared light from the sun or man-made sources can swamp the reflected signal, rendering the measurements meaningless.
To compensate, commercial laser rangefinders use higher-energy bursts of light. But to limit the risk of eye damage, those bursts need to be extremely short. And detecting such short-lived reflections requires sophisticated hardware that pushes the devices’ cost into the thousands of dollars.
The MIT’s new system instead performs several measurements, timing them to the emission of low-energy light bursts. Essentially, it captures four frames of video, two of which record reflections of laser signals and two of which record only the ambient infrared light. It then simply subtracts the ambient light from its other measurements.
News Source: http://news.mit.edu/2016/phone-based-laser-rangefinder-works-outdoors-0325
