Line-of-sight is very commonly used phrase used to reference things in the field of vision — whether of the human eye or a camera/ telescope/ etc — and it is commonly understood that sight and light are more or less linear. But scientists in China have developed a new technology that can help with non-line-of-sight (NLOS) imaging, i.e. identifying objects which aren’t in the line-of-sight of the device or even hidden behind a screen. In a video shared by South China Morning Post, the laser-device was able to track a person 1.43 kilometres away, at a diagonal, and hidden behind a screen.
Non-line-of-sight imaging isn’t new but its previous models have been able to work within a fixed range of few metres. The distance managed by the team from the University of Science and Technology of China is path-breaking. Their research has been published in Proceedings of the National Academy of Sciences.
“This range is about three orders of magnitude longer than previous experiments. The results will open avenues for the development of NLOS imaging techniques and relevant applications to real-world conditions,” the paper said.
The laser emitter was placed within the university campus in urban Shanghai whereas a mannequin was kept behind a screen in the balcony in an apartment building 1.43km away. The laser pulsed and bounced off of the apartment’s wall thrice in multiple directions. As the light scattered, some photons reflected off of the mannequin and some others travelled to a sensor located next to the laser emitter.
Then, a computer algorithm did the rest. Analysing the time of flight for the bounced-back light, and comparing it to the light bouncing between the wall, mannequin, and sensor, they were able to calculate precisely where the mannequin was hidden behind the wall. A fuzzy, 3D image was rendered by the computer simulation. As the speed of light is constant, the calculations were easily achieved by the simulator.
The technology could have widespread applications in defence, policing, tracking etc.