10.12.08

Projectors to use Laser beams!

AUTHOR: Inavate

Digital-cinema projectors that use lasers rather than traditional lamps could lead to richer colours on the silver screen, reports The Economist. Chinese researchers say that they have overcome one of the long standing barriers to the use of lasers as a projection light source thanks to a new technique.

Part of the pleasure of the cinema experience is enjoying films in a much richer environment than one can at home. A conventional flat panel TV you might find in your living room still only reproduces about 50% of the colours that our eyes are capable of detecting. 35mm film as used in analogue cinemas improves on this by delivering about 60% of the gamut. However as we know film degrades over time, reducing the quality. Digital cinema aims to get around this problem, but cinema-purists complain that this is again at the cost of some of the colour gamut.

However, researchers at the Chinese Academy of Sciences look to be about to change that with a new breed of digital cinema projectors that uses lasers as the light source. The researchers led by Bi Yong, are working in collaboration with a firm called Phoebus Vision Opto-Electronics Technology and say that the projector is capable of reproducing 80% of colours the human eye can see.

How is this achieved? Bi’s projector replaces the white light and colour filters used in today’s DLP digital projectrs, with several red, green and blue lasers. The lasers illuminate a digital micromirror device, a MEMS chip invented by Texas Instruments. The chip has an array of microscopic mirrors that each correspond to a pixel on the screen. The chip turns the pixels on or off by tilting the mirrors to direct light either towards or away from the screen.

Technologists have been looking at ways of replacing white light sources with coloured lasers for several years, but one of the things stopping them has always been a phenomenon called speckle. This is a form of interference particular to lasers which makes images shimmer and sparkle. It arises from the coherent (single wavelength) nature of laser light. Bi Yong’s team say that they have overcome this by using multiple lasers of slightly different wavelengths.

However, other manufacturers remain sceptical. Bob Rushby, Chief Technology Officer of Christie Digital said: “Speckle is an extremely challenging problem. The method helps, but it is not yet suitable for theatre going audiences.”

Another challenge is the cost of the units. Consultants have speculated that a laser lamp could cost between $10000 and $20000 as opposed to the couple of thousand for a xenon lamp.