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LEDs cut projector hassle

29 May 2003

Tiny image projectors that rely on LEDs and microdisplays were described at last week’s display show in Baltimore, US.

Equipping digital cameras and personal digital assistants (PDAs) with miniature image projectors may be a step closer thanks to US-Dutch research.

At the Society for Information Display's annual show (SID 2003) the latest prototype ultra-compact projectors were presented. Once commercialized the tiny projectors could mean an end to the hassle of connecting cameras and PDAs to laptop computers and shoebox-sized digital projectors to present images to an audience.

Philips CFT in Eindhoven, The Netherlands, is working with Lumileds Lighting, a Californian maker of high-brightness LEDs. To date, the collaboration has made an image projector that is hand-sized and consists of a single 5 W white LED, a collimator lens, a transmissive 0.7 inch diagonal LCD and a projection lens.

At a distance of 15 cm from the projector, the resulting image measures 5.5 inches in diagonal and has a flux of around 4 lm. A larger, more powerful system containing four white LEDs instead of just one delivered a brighter image with a flux of around 9 lm.

The team says that although the brightness of the projected images is low compared to conventional digital projectors used for business presentations it is quite acceptable for small screen sizes.

For example, it says that a 10 lm projector can create a display between 5 to 10 inches in size with a luminance of between 100 and 400 cd/m2 -- comparable to the brightness of a laptop screen.

Oliver Graydon is editor of Optics.org and Opto & Laser Europe magazine.

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