Laser Ranging System Tracks Movement of Hidden Objects in Real Time

A single-photon avalanche diode camera system has been used to image objects located out of the camera's line of sight and track their movements with centimeter precision.

A laser ranging system can see around walls and locate hidden objects with centimeter precision and then track their movements. Courtesy of Heriot-Watt University.

Previous methods for detecting and tracking objects hidden beyond corners or walls have successfully reconstructed the shape of an object, but haven't enabled real-time movement tracking. Now researchers at Heriot-Watt University have done just that with a compact, non-line-of-sight laser ranging technology that holds promise for defense and security and search and rescue applications.

The system sends light around obstacles using a scattering floor and detects the return signal from a hidden object within only a few seconds of acquisition time.

"By measuring the time it takes to return to the camera, we know how far away the object is," said Ph.D. researcher Genevieve Gariepy. "By recording the shape of the laser ‘echo’, we know what direction it's coming from. It takes only a second for the camera to record all of this: So if the object is moving, we can follow it."

"The ability to detect the 3D shape of static, hidden objects has been demonstrated before, but the long acquisition time required by existing methods meant locating and monitoring the objects was a major challenge," said professor Daniele Faccio. "We can now track hidden objects in real time and we’re still making discoveries about how the light identifies the objects, and can picture them in considerable detail."

The research team has already increased the distance from which the camera system will work to several meters. They are also exploring methods for 3D reconstruction of the objects captured by the camera.

The research was published in Nature Photonics (doi: 10.1038/nphoton.2015.234).