Ultra-Thin Optical Phased Array
Cameras, those on the traditional side inclusive of the thinnest ones on cell phones cannot be really flat owing to their optics and lenses tend to need a definite shape and size for functioning. Engineers at Caltech have established a latest strategy Camera with out lens which tends to substitute the lenses with an ultra-thin optical phased array – OPA. The OPA is said to computationally do what lenses tend to do utilising huge pieces of glass, manipulating incoming light in order to capture an image. Lenses are said to have a curve which is inclined to bend the path of incoming light focusing it onto a piece of film or an image sensor in the case of digital cameras. The OPA tends to have a huge array of light receivers and each tend to individually add a tightly controlled time delay or phase shift to the light it seems to receive, thus permitting the camera to selectively view in various directions as well as focus on various things. Ali Hajimiri, Bren professor of Electrical Engineering and medical Engineering in the Division of Engineering and Applied Science at Caltech and the principal investigator of a paper defining the new camera had commented that like most of the other thing in life here, timing is everything.
Fish-Eye to Telephoto Lens
With the new system one can selectively view in a desired direction and at very small part of the image before you at any given point of time by controlling the timing with femto-second, quadrillionth of a second, precision. The paper had been presented at the Optical Society of America’s – OSA Conference on Lasers and Electro-Optics – CLEO which had been published online in March 2017 by the OSA in the OSA Technical Digest.
Hajimiri had stated that they had generated a single thin layer of assimilated silicon photonics which tends to follow the lens and sensor of a digital camera thereby reducing the thickness as well as the cost of digital cameras. It tends to imitate a regular lens though can switch from a fish-eye to a telephoto lens promptly with only a simple alteration in the way the array tends to receive light. Phased arrays utilised in wireless communications and radar are said to be an assembly of distinct transmitters which all seem to send out same signal as waves.
These waves interfere with each other constructively and destructively, amplifying the signal in one direction though cancels it out elsewhere. Consequently an array can develop a firmly engrossed beam of signal that can be directed in various directions by staggering the timing of transmission that has developed at various points all over the array.
One-Dimensional Version of Camera
An identical source had been used in reverse, in optical phased array receiver that is the basis for the new camera. The light waves which are received by individual element all over the array, cancel each other from every direction with the exception of one.
The waves amplify each other in that direction in order to create a directed `gaze’ which can be electronically organized. Graduate student Reza Fatemi lead author of the OSA paper commented that what the camera does is same as looking through a thin straw and scanning it across the field of view. An image can be formed at an extremely quick speed on controlling the light rather than moving a mechanical object.
The team of Hajimiri had rolled out a one-dimensional version of the camera, last year which had the potential of detecting images in a line such as it acted like a lensless barcode reader though with no mechanically moving parts. The progress this year was to build the first two dimensional array with the proficiency of creating a full image.
The first 2D lensless camera tends to have an array composed of only 64 light receivers in a 8 x 8 grid and the resulting image is said to have low resolution. However this system has a tendency of representing a proof of concept for fundamental rethinking of camera technology according to Hajimiri and his colleagues.
Designing Chips – Higher Resolution/Sensitivity
Graduate student Behrooz Abiri, co-author of the OSA paper had stated that the application seems endless and even in present days’ smartphones, the camera is said to be the component which limits how thin ones’ phone could get.
This technology, once scaled could make lenses and thick cameras out-dated. It could also have consequences of astronomy by permitting ultra-light, ultra-thin massive flat telescopes on ground as well as in space.
Hajimiri informed that the ability in controlling all the optical properties of a camera electronically utilising a paper-thin layer of low-cost silicon photonic without the need of any mechanical movement, lenses or mirrors gives way to a new world of imagers which could look like wallpaper, blind or also wearable fabric. The team would work next on topping up the camera by designing chips which would enable much bigger receivers with higher resolution and sensitivity.
