Lens-less camera sensor chip re-focuses on the fly

July 05, 2017 //By Julien Happich
Doing away with bulky lenses, researchers from the California Institute of Technology (Caltech) have managed to capture images purely by sequential reverse beam steering through the use of an 8x8 optical phased array (OPA) receiver. Designed as a proof-of-concept, the small optical phased array receiver was controlled through a heterodyne architecture built on a thin silicon-photonics integrated SOI substrate.

Using a principle similar to beam forming, but in reverse, the OPA device receives the incoming light from different directions but can focus in a particular direction through meticulous signal acquisition timing (setting femto-second delays across the different sensing elements of the array). That way, light waves that are received by each element across the array can cancel each other from all directions, except for one in which the waves amplify each other to create a focused "gaze", electronically controlled. 

This motion-less and lens-less light manipulation is akin to computational photography, removing the need for any optics and allowing for a simple array to sequentially look in different directions and focus on different things, selectively.

"We've created a single thin layer of integrated silicon photonics that emulates the lens and sensor of a digital camera, reducing the thickness and cost of digital cameras. It can mimic a regular lens, but can switch from a fish-eye to a telephoto lens instantaneously—with just a simple adjustment in the way the array receives light", explained Ali Hajimiri, Bren Professor of Electrical Engineering and Medical Engineering in the Division of Engineering and Applied Science at Caltech.

"What the camera does is similar to looking through a thin straw and scanning it across the field of view. We can form an image at an incredibly fast speed by manipulating the light instead of moving a mechanical object," explains graduate student Reza Fatemi, lead author of the paper "An 8X8 Heterodyne Lens-less OPA Camera" presented at the Optical Society of America's (OSA) Conference on Lasers and Electro-Optics (CLEO). 

The 64-element array is an improvement on the one-dimensional implementation previously designed at Caltech, which was only capable of detecting images in a line. Although only a low-resolution proof-of-concept, the OPA could be scaled up to large area sensors, which the researchers anticipate could make lenses and thick cameras obsolete in applications ranging from slimmer smartphones to ultra-thin