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  • Tiny camera takes a wide view

Photonics Spectra
Dec 2013
SAN DIEGO – A new imager achieves the optical performance of a traditional wide-angle or fish-eye lens – and in high resolution – but in a device less than one-tenth the volume. Such a system could enable high-resolution imaging in unmanned aerial microvehicles, or smartphone photos more comparable to those from a full-size single-lens reflex camera, its developers say.

wide-angle lens
These insets show the resolution of a conventional wide-angle lens (left) compared with that of the new fiber-coupled monocentric lens system (right), where both images were captured with identical 5-MP focal planes.


The imager, created at the University of California, San Diego, has a 100× range of focus – meaning it can image anything between half a meter and 500 m away – and 0.2-mrad resolution, equivalent to 20/10 human vision.

“The major commercial application may be compact wide-angle imagers with so much resolution that they’ll provide wide-field pan and ‘zoom’ imaging with no moving parts,” said project leader Joseph Ford, a professor in the Jacobs School of Engineering at UCSD.

To engineer the new system, researchers turned to monocentric lenses made of concentric glass shells, which are perfectly round, like glass marbles. Their symmetry allows them to produce wide-angle images with high resolution and hardly any of the geometrical distortions common to fish-eye lenses.

When such lenses have been tried for high-res, wide-angle viewing, two main problems they had were with trouble conveying the rich information collected by the lens to electronic sensors that could record the image, and with focusing.

fiber-coupled monocentric lens camera
The new fiber-coupled monocentric lens camera, next to the much larger Canon EOS 5D Mark III DSLR, used for conventional wide-angle imaging. Photo courtesy of UCSD Jacobs School of Engineering.


Ford’s team addressed the first problem using a dense array of glass optical fiber bundles polished to a concave curve on one side so that they perfectly aligned with the surface of the lens. The researchers had expected that the fibers would have to move in and out to focus to different distances, or else the lens would provide perfect focus for only a single direction. But the group showed that the changes in axial distance between fibers and lens did not distort the image.

Ford and colleagues at UCSD and Distant Focus Corp. are currently assembling a 30-MP prototype and plan to go even bigger in the future. “Next year, we’ll build an 85-megapixel imager with a 120-degree field of view, more than a dozen sensors and an f/2 lens – all in a volume ‘roughly the size of a walnut,’ ” he said.

The project is part of the DARPA-funded SCENICC (Soldier Centric Imaging via Computational Cameras) program.


GLOSSARY
optical fiber
A thin filament of drawn or extruded glass or plastic having a central core and a cladding of lower index material to promote total internal reflection (TIR). It may be used singly to transmit pulsed optical signals (communications fiber) or in bundles to transmit light or images.  
zoom
To control, by magnifying or reducing, the size of a televised image, either electronically or optically.
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