Fraunhofer's Micro Nano Array Projectors


Nanoworld in color

Microscopically small nanostructured arrays of lenses that can record or project amazingly sharp images in brilliant colors are being demonstrated by Fraunhofer research scientists at the nano tech 2011 trade show in Tokyo from February 16 to 18.

The image illuminating the wall of the Fraunhofer exhibition stand at nano tech 2011 will be produced by a luminous cube. The prototype of the new projector consists of an optical system just eleven millimeters square and three millimeters thick through which a powerful LED lamp shines. The images are amazingly sharp, the colors brilliant – all thanks to micro and nanotechnology. "The special thing about the new projection technology is that the image is already integrated in the microoptics. The pixels measuring just a hundred nanometers or so are stored in a chromium layer under the lens array. Such a microarray has around 250 microlenses, and under each lens there is a microimage. When all of them are projected onto the wall together, a high-quality complete image is produced from an extremely small projector," explains Marcel Sieler, physicist at the Fraunhofer Institute for Applied Optics and Precision Engineering IOF in Jena.

Mini-projectors – maximum performance


In all current systems of pocket projectors, a single imaging channel is used. This means a minimal size for the projector is a given – and smaller will not work. Except for Marcel Sieler: His construction method relies on a number of regularly ordered micro-lenses – an array – as the projection lens. Thanks to the many channels, the construction length of the entire system can be clearly reduced, without impeding luminosity. A high-performance LED is used as the light source.

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The technology was inspired by a device known as a fly’s eye condenser used to smooth out beams of light from LEDs. The Fraunhofer team had to design a very precisely arranged array of aspheric lenses designed with a specific shape.

The array is created from a glass wafer with moulded micro-optics on either side. ‘You put a liquid monomer layer on top of the glass and press a negative tool into it and it’s polymerised to get the perfect shape for the microlenses,’ said Sieler.

As well as the basic proof-of-concept model, the team have also used the technology to create prototypes of a larger projector for advertising and illumination, a video graphics array (VGA) camera, and a video projector that takes images from a micro-LCD display.

The team is now seeking industrial partners to help commercialise the devices and Sieler estimates that it is likely to be five years before they are available to buy.