A incredible camera that sees around corners, detecting moving objects even when they are completely obscured from view, has been created by a team of Scottish scientists, who say it has great potential for use in vehicles to detect oncoming cars, or for search-and-rescue operations.
Team leader, Professor Daniele Faccio, from the School of Engineering & Physical Sciences; Photonics & Quantum Sciences, at Heriot-Watt University in Edinburgh, and colleagues wrote about their creation in the academic journal Nature Photonics.
The device can log the position of a photon (a particle representing a quantum of light) in a 32 x 32 grid at the equivalent of 20 billion frames a second. The researchers had previously used this precision to make a slow-motion movie of a laser beam in flight. Now, however, they have developed a way to detect moving objects that are hidden from view.
Imagine the things you could do if you could locate and track objects that are moving, yet hidden away from view. This camera can! (Image: Extreme Light Heriot-Watt University)
Device uses expanding spherical echoes of photons
The scientists shoot a laser at the floor close to the corner they want to see around. The light hits the ground, bounces off it and produces a spherical ‘echo’ consisting of a few photons. Most devices would never be able to see them, except for this super-sensitive camera, which can.
The echo of photons expands, and some of them travel around the corner and hit the hidden object.
For their experiment, the team members used ‘Terry’, a 30-centimetre-high foam human model. The photons formed the expanding echo bounced off Terry, which immediately created another echo, which also expanded with parts entering the field of view of the camera, which sits next to the laser.
By capturing just a single echo the camera is not able to locate the object, because the photons also bounce off the wall and other unmoving background objects. The team sends out 67 million laser pulses per second to account for this. As their target object moves, the signal of each echo is changed. By monitoring their differences, the device can work out its position.
A laser sends sharp pulses of light to the floor. When the light hits the floor it bounces off in every direction, like an expanding echo sphere, which travels behind the wall to reach the hidden object, where a second expanding echo forms, sending light back to where it came from. (Image: Extreme Light Heriot-Watt University)
Experiment was done in the dark
Co-author, Genevieve Gariepy, said:
“Most people were trying to reconstruct in 3D, but we were trying to track. We developed new algorithms to be able to achieve this, and achieve it fast.”
In this latest experiment, everything was done in the dark. However, the authors say that the system should work in normal light if an infrared laser and filter is used.
Citation: “Detection and tracking of moving objects hidden from view,” Genevieve Gariepy, Francesco Tonolini, Robert Henderson, Jonathan Leach & Daniele Faccio. Nature Photonics. 07 December, 2015. DOI: 10.1038/nphoton.2015.23.
Video – Seeing around corners using lasers