Camera with no Lens

Rajesh Menon has discovered a way to create an optics-less camera in which a regular pane of glass or any see-through window can become the lens. (Source: D. Hixson, Univ. of Utah)

In the future, your car wind­shield could become a giant camera sensing objects on the road. Or each window in a home could be turned into a security camera. Univer­sity of Utah electrical and computer engi­neers have discovered a way to create an optics-less camera in which a regular pane of glass or any see-through window can become the lens.

University of Utah elec­trical and computer engi­neering associate professor Rajesh Menon argues that all cameras were developed with the idea that humans look at and decipher the pictures. But what if, he asked, you could develop a camera that can be inter­preted by a computer running an algo­rithm “Why don’t we think from the ground up to design cameras that are opti­mized for machines and not humans. That’s my philosophical point,” he says. If a normal digital camera sensor such as one for a mobile phone or an SLR camera is pointed at an object without a lens, it results in an image that looks like a pixelated blob. But within that blob is still enough digital infor­mation to detect the object if a computer program is properly trained to identify it. You simply create an algo­rithm to decode the image.

Through a series of experi­ments, Menon and his team of researchers took a picture of the University of Utah’s “U” logo as well as video of an animated stick figure, both displayed on an LED light board. An inex­pensive, off-the-shelf camera sensor was connected to the side of a plexiglass window, but pointed into the window while the light board was posi­tioned in front of the pane at a 90-degree angle from the front of the sensor. The resulting image from the camera sensor, with help from a computer processor running the algorithm, is a low-reso­lution picture but defi­nitely recog­nizable. The method also can produce full-motion video as well as color images, Menon says.

The process involves wrapping reflec­tive tape around the edge of the window. Most of the light coming from the object in the picture passes through the glass, but just enough – about 1 percent – scatters through the window and into the camera sensor for the computer algorithm to decode the image. While the resulting photo is not enough to win a Pulitzer Prize, it would be good enough for appli­cations such as obstacle-avoi­dance sensors for auto­nomous cars. But Menon says more powerful camera sensors can produce higher-reso­lution images.

Appli­cations for a lensless camera can be almost unlimited. Security cameras could be built into a home during con­struction by using the windows as lenses. It could be used in augmented-reality goggles to reduce their bulk. With current AR glasses, cameras have to be pointed at the user’s eyes in order to track their positions, but with this technology they could be posi­tioned on the sides of the lens to reduce size. A car windshield could have multiple cameras along the edges to capture more infor­mation. And the technology also could be used in retina or other biometric scanners, which typi­cally have cameras pointed at the eye.

“It’s not a one-size-fits-all solution, but it opens up an interes­ting way to think about imaging systems,” Menon says. From here, Menon and his team will further develop the system, including 3-D images, higher color resolution and photo­graphing objects in regular household light. His current experi­ments involved taking pictures of self-illu­minated images from the light board. (Source: U. Utah)

Reference: G. Kim & R. Menon: Computational imaging enables a “see-through” lens-less camera, Opt. Exp. 26, 22826 (2018); DOI: 10.1364/OE.26.022826

Link: Laboratory for Optical Nanotechnology, University of Utah, Salt Lake City, USA

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