Telescopes make bug-eye optics

By Eric Smalley, Technology Research News

The latest wave of miniaturization -- optics -- has brought the world the cell phone camera, but such small camera lenses produce relatively low quality images.

Researchers working to overcome this physical limitation are following nature's lead by developing arrays of tiny lenses that work like insects' compound eyes. Arrays of microlenses are a route to smaller and cheaper optics because they can be made in bulk using chipmaking techniques.

Researchers at the Fraunhofer Institute for Applied Optics and Precision Engineering in Germany, SUSS MicroOptics SA and the University of Neuchâtel in Switzerland have developed a prototype artificial compound eye made from three stacked sets of microlenses that form an array of tiny telescopes.

The microtelescope array magnifies relatively distant objects within a wide field of view, said Jacques Duparré, a physicist at the Fraunhofer Institute. Each telescope captures a portion of the field of view and the array is aligned to combine these elemental images to form a single complete image.

The artificial compound eye could be used for camera phones, infrared vision systems and optical sensors, said Duparré. "Compact vision is needed everywhere," he said.

The approach could make optics as inexpensive and compact as electronics, said Duparré. "Cameras in toys are in sight."

The researchers made the microtelescope array by etching the lenses from fused silica. The researchers' 2-millimeter thick prototype consists of 21 microtelescopes that each contain three lenses. The array has a 70- by 10-degree field of view and produces a 4.5- by 0.5-millimeter image. Individual lenses range from 8 to 20.2 microns thick and from 73.2-micron disks to ellipses 311.2 microns long. A micron is one thousandth of a millimeter.

The lenses in the top array of focusing lenses are elliptical. The middle, or field, lenses are circular and aligned with square openings in a mask. The bottom, relay lenses are circular and are aligned with circular, offset openings in another mask.

Ideally, the lens alignments and mask opening configurations seamlessly combine the elemental images. The researchers' prototype, however, has gaps in some places and overlaps in others. Sixteen of the 21 microtelescopes in a prototype worked, yielding a 63-degree field of view, said Duparré. The researchers plan to iteratively improve the alignments to correct these problems, he said.

The next step is to arrange microlenses in a circular array that mimics an ordinary single lens to produce a square image, said Duparré.

The artificial compound eye could be ready for practical application in five years, said Duparré.

Duparré's research colleagues were Peter Schreiber, André Matthes, Ekatrina Pshenay-Severin, Andreas Bräuer and Andreas Tünnermann of the Fraunhofer Institute for Applied Optics and Precision Engineering in Germany, Reinhard Völkel and Martin Eisner of SUSS MicroOptics SA, and Toralf Scharf of the University of Neuchâtel in Switzerland. They published the research in the February 7, 2005 issue of Optics Express. The research was funded by the Fraunhofer Institute.

Timeline:   5 years
Funding:   Private
TRN Categories:  Optical Computing, Optoelectronics and Photonics
Story Type:   News
Related Elements:  Technical paper, "Microoptical telescope compound eye," Optics Express, February 7, 2005


April 20/27, 2005

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