Ultrathin Camera Creates Images Without Lenses

A novel camera uses an ultrathin optical phased array (OPA) in place of lenses to enable a thin, light, flexible design. The OPA manipulates light through a large array of light receivers. Each receiver can add a tightly controlled phase shift to the light it receives, enabling the camera to selectively look in different directions and focus on different things.

At Caltech, engineers have developed a new camera design that replaces the lenses with an ultrathin optical phased array (OPA). Courtesy of Caltech.

The 2D lensless camera has an array composed of 64 light receivers in an 8 × 8 grid. The 8 × 8 OPA receiver operates using a heterodyne architecture on a thin silicon-photonics integrated silicon-on-insulator (SOI) substrate. It has a receiving beam width of 0.75° and beam steering range of 8°.

The camera, which is capable of creating a full image, was built by a team from the California Institute of Technology (Caltech). The resulting images have low resolution, but according to the team, the system represents a proof of concept for a fundamental rethinking of camera technology.

“The ability to control all the optical properties of a camera electronically using a paper-thin layer of low-cost silicon photonics without any mechanical movement, lenses or mirrors opens a new world of imagers that could look like wallpaper, blinds or even wearable fabric," said professor Ali Hajimiri.

Last year, the team introduced a one-dimensional version of the camera that was capable of detecting images in a line, similar to a lensless barcode reader but with no mechanically moving parts.

“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,” said Hajimiri .

The OPA chip placed on a penny for scale. Courtesy of Caltech/Hajimiri Lab.

Light waves that are received by each element of the camera across the array cancel each other from all directions except one. In that one direction, the waves amplify each other to create a focused “gaze” that can be electronically controlled.

“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,” said Caltech researcher Reza Fatemi.

“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,” Hajimiri said.

Next, the team will work on scaling up the camera by designing chips that enable much larger receivers with higher resolution and sensitivity.

“The applications are endless,” said researcher Behrooz Abiri. “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 ultralight, ultrathin enormous flat telescopes on the ground or in space.”

The research was published in OSA Technical Digest, a publication of OSA, the Optical Society of America (doi: 10.1364/CLEO_AT.2017.JW2A.9).

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At Caltech, engineers have developed a new camera design that replaces the lenses with an ultrathin optical phased array (OPA). The OPA does computationally what lenses do using large pieces of glass: It manipulates incoming light to capture an image. Courtesy of Caltech.