An incredibly fast camera that can see objects around corners has great potential for use in search and rescue operations and for use in cars to detect hidden oncoming traffic, says a team of scientists from Heriot-Watt University in Edinburgh, Scotland.
The ultra fast camera that uses laser beams can literally see moving objects around corners, even when they are completely hidden from view, the researchers explained in the academic journal Nature Photonics.
According to team leader, Professor Daniele Faccio, who works at the University’s School of Engineering & Physical Sciences; Photonics & Quantum Sciences, the camera can log the position of a photon in a 32 by 32 grid at 20 billion frames per second. A photon is a particle representing a quantum of light, i.e. the basic unit that makes up all light.
“We can now track hidden objects in real time, and can picture them in considerable detail,” said Prof. Daniele Faccio. (Image: hw.ac.uk)
The same team had previously used this precision to create a slow-motion film of a laser beam in flight. This time, they have adapted it to detect moving objects that are obscured from view.
Camera uses photon ‘echoes’ to detect objects
In the experiment, a scientist shot a laser beam at the floor close to the corner they wanted the camera to see around. When the light hits the ground, photons bounce off and produce a spherical ‘echo’ containing a few photons. Most cameras would never be able to see them, but this incredibly-sensitive one can.
As the spherical photon echo expands, some of it travels around the corner and hits the hidden object. When the photons hit the hidden object, another spherical echo is produced, which expands outwards, with some of the photons appearing in the camera’s field of vision.
For this study, the researchers used a 30-centimetre-high foam model that looks like a small human, nicknamed ‘Terry’. The camera sees ‘Terry’ when the second spherical echo of photons expands beyond the corner.
No matter where ‘Terry’ hides, the camera will see him.
The camera cannot locate objects by capturing just a single echo, because the photons also bounce off several non-moving objects, such as the wall. Sixty-seven million laser pulses per second are sent out to account for this.
As their target object moves, each echo’s signal is changed. By keeping track of their differences, the camera can work out the object’s exact position.
Study was carried out in the dark
Genevieve Gariepy, one of the study co-authors, explained:
“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.”
As soon as the photons in the second spherical echo, the one expanding around the hidden object, come into the field of view of the camera, it will detect it. (Image: Extreme Light Heriot-Watt University)
Everything was done in the dark in this latest study. However, the scientists say that the system would work in normal light if an infrared laser and filter were used.
It only takes about one second for the special camera to record all this information. That means if there is an object that is moving, it is possible to follow it.
This technology could also work on a human scale, in real-life applications. For example, it could be used in rescue missions, when the terrain is dangerous, or when you don’t want humans entering a room unless they have to. It could also be installed in cars and used to avoid accidents by detecting incoming vehicles from around the corner.
Reference: “Detection and tracking of moving objects hidden from view,” Robert Henderson, Genevieve Gariepy, Francesco Tonolini, Jonathan Leach & Daniele Faccio. Nature Photonics. 7th December, 2015. DOI: 10.1038/nphoton.2015.23.
Video – Seeing hidden objects around corners using lasers
