Roland Piquepaille's Technology Trends
How new technologies are modifying our way of life

samedi 3 juillet 2004

Video projectors able to project high-quality images will be embedded in your cellphones and laptops within two years. This is the promise of a new technology developed at Cambridge University. These pocket projectors will have no lenses and no light bulbs. Instead, these future battery-powered tiny projectors will rely on holographic technology and special algorithms. In "Holograms enable pocket projectors," Technology Research News explains that a 2D hologram will be created on a microdisplay and projected by using a laser beam. This has been possible because the researchers have written special algorithms which generates the holograms a million times faster than standard ones.

Here is a description of the concept.

Key to the device's diminutive size is the lack of lenses and high-power light bulbs. Conventional digital video projectors form images by generating a small picture on a transparent microdisplay inside the projector, then shining a high-power light through the microdisplay to a large magnifying lens.
In the researchers' design, a two-dimensional hologram is shown on the microdisplay rather than an image, and the projected image is formed by shining a laser beam through the microdisplay, which scatters the light into a particular pattern. "No lenses are required -- the projected image is formed entirely by diffraction," said Adrian Cable, a researcher at the University of Cambridge in England.

Another enabling technology is the use of special algorithms for a fast generation of the holograms.

The researchers' algorithm solves the problem, said Cable. The key was studying how noise, or the distortion of an image, affects people's perception of video. The researchers showed test subjects 300 pairs of video images and asked them to rate which, if either, was higher quality. The images were the same but contained different levels of noise. The researchers found that variation in noise levels affected people's perception of video quality more than the actual level of the noise.
The researchers' algorithm generates holograms about one million times faster than the standard direct binary search algorithm running on a 2 gigahertz Athlon personal computer, according to Cable.

"The figure below shows a horse-faced cheat being attacked by a crazed half-man-half-beast (left) and the same image (right), but reconstructed from a computer-generated hologram. The hologram took a few seconds to generate using the OSPR algorithm on a 2 GHz PC, representing an orders of magnitude improvement in both execution time and image quality over conventional hologram generation algorithms." (Credit for images and legend: Edward Buckley, Cable's professor at the Cambridge University Engineering Department (CUED)).

Buckley's original picture Buckley's computer-generated hologram

When will be be able to use our cellphones as projectors?

The researchers' prototype is black and white. They are working on configuring two or more of the devices in parallel to generate full-color video.
The researchers aim to produce practical pocket-sized video projectors in two to five years, said Cable.

Sources: Eric Smalley, Technology Research News, June 30/July 7, 2004; Edward Buckley, Cambridge University Engineering Department

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