Tiny Camera Takes a Wide View
SAN DIEGO, Oct. 2, 2013 — 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 (SLR) camera, its developers say.
Researchers at the University of California, San Diego, created the
imager, which has a 100X 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.
The new fiber-coupled monocentric lens camera (left), next to the much larger Canon EOS 5D Mark III DSLR, used for conventional wide-angle imaging. Photos courtesy of UCSD Jacobs School of Engineering.
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.
Such lenses have been tried for high-res wide-angle viewing, but the main problems were that they had trouble conveying the rich information collected by the lens to electronic sensors that could record the image, and with focusing.
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.
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 lens' surface. To address issues with focusing, the researchers had expected that the fibers would have to move in and out to focus to different distances, or 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.
Advantages of a monocentric lens. Top: This image was captured with a conventional wide-angle lens, a Canon EOS 5D Mark III DSLR with a 12-mm focal length. Middle: An inset of the image above. A close-up (right) of the man holding the board shows that this picture, taken with a conventional wide-angle camera with 12-mm focal length, does not have very high resolution. Bottom: An image taken with a monocentric lens relayed onto a high-magnification digital microscope. This system did not include the fiber coupling developed by the researchers for their prototype camera, but the clarity of the detail shows the potential of using monocentric lenses to take images with both high resolution and a wide field of view.
The project is part of the DARPA-funded "SCENICC" (Soldier Centric Imaging via Computational Cameras) program.
Ford will present a talk on the work at The Optical Society's (OSA) annual meeting, Frontiers in Optics (FiO) 2013, which will take place Oct. 6-10 in Orlando, Fla. His presentation, "System Optimization of Compact Monocentric Lens Imagers," will be held Monday, Oct. 7, at 4:45 p.m. in the Bonnet Creek Ballroom, Salon X at the Hilton Bonnet Creek.
For more information, visit: www.jacobsschool.ucsd.edu
- 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.
- To control, by magnifying or reducing, the size of a televised image, either electronically or optically.
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