Depth sensors like the ones used in Microsoft’s Kinect system perform well in a dark living room, which makes them ideal for gaming. They project a grid of infrared light points onto a scene and then measure the time it takes the signals to bounce back. However, any ambient infrared light gets mixed in with the reflected signals, which confuses the Kinect, so the technology doesn’t work outdoors. Alternatively, laser-based LIDAR systems work well even when surrounded by light, but they require hardware that is complicated and expensive. Engineers at MIT have come up with an economical, simple solution that leverages the sophisticated hardware that so many of us already carry in our pockets: smartphones. Li-Shiuan Peh and Jason Gao describe their invention in a research paper that they will present at the IEEE International Conference on Robotics and Automation (ICRA) in May.
By utilizing the processing power of the phone, we can perform more intensive image processing to identify the laser illumination and reject ambient light, improving performance for outdoor use.
By adding just $50 of hardware to an Android smartphone, Peh’s group built a laser distance sensor that works outdoors. Since the phone already has a camera, processor, an input/output, the engineers only had to incorporate a simple laser, control electronics, a 3D-printed mount, and a bandpass filter. The system uses a technique called active triangulation. It records video of a scene and then subtracts ambient light from the measurements, thus eliminating the background noise that limits Kinect’s depth sensor.
“My group has been strongly pushing for a device-centric approach to smarter cities, versus today’s largely vehicle-centric or infrastructure-centric approach,” explains Peh. “This is because phones have a more rapid upgrade-and-replacement cycle than vehicles. Cars are replaced in the timeframe of a decade, while phones are replaced every one or two years. This has led to drivers just using phone GPS today, as it works well, is pervasive, and stays up-to-date. I believe the device industry will increasingly drive the future of transportation.”