New ultra-thin camera creates images without lenses

Los Angeles: Scientists have developed a new camera design that substitutes an array of light receivers for a lens, making cameras thin, light, cheap and flexible.

Traditional cameras - even those on the thinnest of cell phones - cannot be truly flat due to their optics: lenses that require a certain shape and size in order to function.

The ultra-thin optical phased array (OPA) does computationally what lenses do using large pieces of glass: it manipulates incoming light to capture an image.

Lenses have a curve that bends the path of incoming light and focuses it onto a piece of film or, in the case of digital cameras, an image sensor.

The OPA has a large array of light receivers, each of which can individually add a tightly controlled time delay (or phase shift) to the light it receives, enabling the camera to selectively look in different directions and focus on different things.

"Here, like most other things in life, timing is everything. With our new system, you can selectively look in a desired direction and at a very small part of the picture in front of you at any given time, by controlling the timing with femto-second - quadrillionth of a second - precision," said Ali Hajimiri, Professor at California Institute of Technology (Caltech) in the US.

"We have 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," Hajimiri said.

Phased arrays, which are used in wireless communication and radar, are collections of individual transmitters, all sending out the same signal as waves.

These waves interfere with each other constructively and destructively, amplifying the signal in one direction while cancelling it out elsewhere.

Thus, an array can create a tightly focused beam of signal, which can be steered in different directions by staggering the timing of transmissions made at various points across the array.