Laser system can see round corners

A new laser system captures the behavior of individual photons and uses advanced optics to deduce what’s around the corner.

Developed by researchers from MIT, Harvard, the University of Wisconsin, and Rice University, it could be used in disaster recovery situations, as well as in noninvasive biomedical imaging applications.

“Imagine photons as particles bouncing right off the walls and down a corridor and around a corner – the ones that hit an object are reflected back,” says MIT graduate student Otkrist Gupta.

“When this happens, we can use the data about the time they take to move around and bounce back to get information about geometry.”

Using an ultrafast laser and a 2D streak camera, both of which run at trillions of cycles per second, the team captured billions of images per second and was able to analyze the light moving around a corner or through a water bottle.

The image formed is determined by the time profile of the incoming photons.

“This type of imaging provides us with a very good idea of how long each of the photons takes to bounce and come back. If there’s something around the corner, the photons come back sooner and arrive earlier in time,” says Gupta.

“We’re actually capturing and counting photons. Each image we shoot has three or fewer photons in it. And we take lots of images very quickly to create ‘streak’ images, which help us determine the distance traveled by the photons in centimeters. Once we collect that data, we can infer the basic geometry of the hidden objects and a 3D picture emerges.”