Wednesday, August 6, 2008
New Light Sensor Mimicks Eye for Superior Camera Performance
Filed under: GI
, Ophthalmology
One of the disadvantages of modern photo cameras is the flat image sensor that converts light into electric signals. Because of its shape, optics must make up for various aberrations that come to light (excuse the pun). 
Now scientists at Northwestern University and University of Illinois at Urbana-Champaign have developed technology that allows for building curved sensors and accompanying electronics. The technology one day might come in handy for developing artificial retinas or next generation endoscopic devices.
From a NSF press release:
The technology breakthrough is a novel approach that bypasses a traditional planar sensor of adjacent pixels and instead relies upon an array of pixels interconnected by small wires. Using a flexible, temporary backing, the researchers can form the array into a curved shape and then transfer the array to its permanent location affixed to a glass lens.Over the last 20 years, many researchers have tried to manufacture such electronic eye systems, but until now, none were able to create a working camera.
"This strategy opens up exciting, new engineering design possibilities by eliminating the two dimensional, planar constraints of conventional, semiconductor wafer-based optoelectronics," said John Rogers, Flory-Founder Chair Professor of Materials Science and Engineering at University of Illinois at Urbana/Champaign.While a flat, planar sensor cannot flex without damaging its light-sensitive pixels, the new technology puts the strain on the wires, each flexing as much as 40 percent. Since the wires absorb the strain, the pixels are barely stressed, even when affixed to the retina-shaped housing of the new experimental camera.
Conventional digital cameras use planar chips based on rigid, brittle semiconductor wafer substrates that fracture at strains of less than 1 percent.
"Mechanics helps to reduce the stresses and strain in components, and guide and optimize the system design," said Yonggang Huang, Joseph Cummings Professor of Civil and Environmental Engineering and Mechanical Engineering, Northwestern University, who worked with his team to model the mechanical properties of the design so that it could be manufactured.
The current sensor array includes only 256 pixels, but because the technology is based on established materials and manufacturing processes, the researchers ultimately expect more sophisticated sensors in higher density arrays. The same approaches can be used for nearly any class of semiconductor electronic device for a range of functions such as sensing, actuating and computing.
Videos of John Rogers of the University of Illinois at Urbana-Champaign and Yonggang Huang of Northwestern University describing the workings of the camera...
Abstract in Nature...
Images: Top: Image of the newly developed camera. Side 1: This high magnification scanning electron micrograph shows a small cluster of silicon photodetector pixels and electronics interconnected by arc-shaped ribbons, all on a hemispherical substrate. These interconnects bow upward to accommodate the large mechanical strains needed to transform the planar layouts in which the systems are initially fabricated to the hemispherical geometries needed for implementation in the electronic eye. The image is colorized: pixel elements and interconnects appear gold; the substrate appears light blue. Side 2: Photo of an eye taken using the camera.
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