By overcoming a major challenge in optics and image processing, the feat could usher in devices that can survey a scene beyond the line of sight. The technological trick might be used to spot people who are hidden from view, or inspect components concealed deep inside machines.
At the heart of the technique is the ability to build up images from light waves that are scattered off surfaces like walls in almost every direction.
As an illustration of how it works, below, imagine hiding an object around a corner in a mirrored corridor. It might still be visible because light bounces off the object and is reflected cleanly off the mirrored walls and towards the observer. But normal walls are not as shiny as mirrors. They scatter light diffusely, so any image is lost.
Ramesh Raska and colleagues overcame the problem by bouncing ultrafast pulses of laser light off walls towards a hidden object. Some of the laser light reached the object, was reflected back, scattered by the wall once more, and reached their camera.
The scientists recreated an image of the hidden object by recording the return time of the scattered light then changing where they fired the pulses of laser light.
Using a camera that takes a snapshot every two trillionths of a second, the MIT group reconstructed 3D images of hidden objects with one centimetre precision over a 40cm by 40cm hidden space.
Watch a video explaining how the technique works: