Phone-based laser rangefinder works outdoors too

March 30, 2016 | 12:56
Credit: Christine Daniloff/MIT
Credit: Christine Daniloff/MIT
Sensors like the Microsoft Kinect, which use infrared light to gauge depth, are easily confused by ambient infrared light. Even indoors, they tend to require low-light conditions, and outdoors, they're hopeless. Researchers from MIT's Computer Science and Artificial Intelligence Laboratory (CSAIL) hope to overcome the problem with a new infrared depth-sensing system, built from a smartphone with a $10 laser attached to it, that works outdoors as well as in.

They 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.
The researchers prototyped the sensor using the camera in an ordinary cellphone and a commodity laser emitter that costs about $10.

In the proposed system, the outgoing light pulse thus has to last long enough that its reflection will register no matter which row it happens to strike. Future smartphone cameras, however, will have a "global shutter," meaning that they will read off measurements from all their photodetectors at once. That would enable the system to emit shorter light bursts, which could consequently have higher energies, increasing the effective range.
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