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An 'eyeball camera' for cell phone -- with zoom

Image: Robotic eye
A newly developed robotic eye capable of zooming could find its way into commercial digital cameras someday. But there are still some engineering issues to address.John Rogers
/ Source: TechNewsDaily

A new camera modeled after the human eye, but with zoom capability, could let you take professional-quality pictures with your cell phone.

The size of a nickel, the “eyeball camera” uses curved photodetectors, which mimic the curved structure of the eye’s retina, on a rubber-like material that can be zoomed in and out with on-board hydraulics.

A camera based on the human eye was developed in 2008, but this is the first time this type of camera has been combined with zoom capability — a function that surpasses what the human eye can do.

The researchers have tested the prototype camera with different images and zoom levels. While conceptually it should work in any digital camera, there are still engineering issues to address. So far, the camera only processes a few hundred pixels, while today’s digital cameras offer images with millions of pixels. The camera will need to be scaled down in size as well.

Human eyeballs

The human eye has “an interesting design because the photodetector surface — the retina — has a hemispherically curved shape and that’s a lot different from a commercial digital camera, which uses a flat detector chip,” said study co-author John Rogers, a professor of materials science and engineering at the University of Illinois, Urbana-Champaign.

This curvature is important because the image that’s formed when light passes through a simple lens is curved, and in order to make a picture from this image the geometry of the image and the photodetector surface must be identical. (It’s sort of analogous to trying to wrap a piece of cement around a 3-D globe.)

“As a result, commercial cameras use multiple lenses to flatten that image so that it has the same geometry as the chip,” Rogers said.

A camera with a curved photodetector surface, on the other hand, needs simple optics, and therefore can be small, lightweight and inexpensive, Rogers said. This design also offers “an extremely wide-angle field of view with very low aberrations,” he said.

Eyeball cameras

The researchers built a prototype camera based on a curved photodetector. But to add zoom capability to the camera, they had to develop a tunable photodetector material, in which the curvature of the material could be adjusted to account for the zoom.

“When the magnification changes, then the curvature of the image that forms also changes,” Rogers said. “If you don’t have an ability to change the curvature of your photodetector array, then you lose all of the benefits of this curved geometry as the zoom magnification changes and the image surface curvature no longer matches the curvature of the photodetector array to begin with,” Rogers said.

The tunable photodetector array is “a very thin sheet of rubber, almost like a thin sheet of latex (that’s) stretched out like a drum head on an opening in a flat plate,” Rogers said. “Then we use hydraulics to pull it into a hemispherical shape with whatever radius of curvature we want,” he said.

Potential applications for the eyeball camera include night-vision and surveillance cameras, cell-phone cameras and cameras used in medical procedures such as endoscopic imaging.

Rogers and his colleagues detailed their findings online Jan. 17 in the Proceedings of the National Academy of Sciences.