Cameras: lensless and smaller than ever
26 June 2017
Engineers have developed a new camera design that replaces lenses with an ultra-thin optical phased array (OPA).
Even cameras in the thinnest of cell phones cannot be truly flat due to their lenses requiring a certain shape and size. The OPA achieves – computationally – what lenses do when they use 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.
Said Ali Hajimiri, Bren Professor of Electrical Engineering and Medical Engineering: “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 femtosecond –quadrillionth of a second precision.”
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 canceling it out elsewhere. Therefore, 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.
A similar principle is used in reverse in an optical phased array receiver, which is the basis for the new camera. Light waves that are received by each element across the array cancel each other out from all directions, except for one. In that direction, the waves amplify each other to create a focused ‘gaze’ that can be electronically controlled.
"The applications are endless," says graduate student Behrooz Abiri and coauthor of the OSA paper. "Even in today's smartphones, the camera is the component that limits how thin your phone can get. Once scaled up, this technology can make lenses and thick cameras obsolete. It may even have implications for astronomy by enabling ultra-light, ultra-thin enormous flat telescopes on the ground or in space."
Research: California Institute of Technology
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