UK prof pioneers new LCD screen system

Promises significantly cheaper flat displays

A Cambridge UK academic has come up with a completely new flat TV concept that relies on total internal reflection in a wedge shaped piece of clear plastic, fed by the same LCD video projectors that drive rear-projection televisions. The technique promises to cost about a fiftieth of the price of current plasma screens and yet deliver a similar quality picture.

The system works by introducing light at the bottom edge of the wedge, which bounces across and back again up the length of the wedge until it reaches the critical angle at which it escapes and leaves the face of the screen as light. A precise mathematical formula ensures that light for the correct pixel exits the screen at just the right distance up the wedge.

Dr Adrian Travis of Flat Projection Displays, a spin-off from Cambridge University's Department of Engineering, is negotiating for the concept to emerge onto the market in early 2007 and has it working perfectly on a 15-inch screen and shortly expects to have it ready to go on a 50-inch display.

"We have a 15-inch demo and a 50-inch demo, and have achieved 600 candelas per square meter generating 1 millimetre sized pixels. This is about the same as top-end plasma screens that appear in televisions costing $10,000 today," said Travis. "We have to play around with the image to make sure that the pixels don't bunch up, and that's part of our intellectual property which we have patented. If you don't do that the image can appear a little like an image reflected off water," he added.

Travis and his team of optical engineers have been working on the system for the past three or so years and have now done a deal with a local technical consultancy and in turn with a household name TV maker (which they cannot yet reveal) and will take the device to be manufactured in the Far East

"The manufacturing costs are so low because this falls within the scope of existing injection-moulding techniques. We are told that it will take about $500,000 to make a mould and that a dedicated machine to make these would cost around $6m. This compares with the $2.8bn that Samsung needs to spend every time it builds a new plant for Transflective LCD screens," explained Travis.

Making big TFT screens is inordinately complex, with glass being chemically cleaned, and various layers of chemicals laid evenly on it followed by 6 or 7 masks used to etch an amorphous silicon layer, more layers of chemicals and then a second glass screen being glued to the first. Reductions in this complexity are made inch by inch every year, and most of the patents for improving this process are held by a handful of mostly Japanese and Korean consumer electronics companies.

All the promising approaches to building cheap flat screens have rested on some form of rear projection system such as market leader Texas Instruments Digital Light Processing or Philips Liquid Crystal on Silicon technology, or the Sony-owned Grating Light Valve. Basically the approach is to manipulate a miniature mirror using semiconductor technology to make it either reflect a red, green or blue beam of light to the screen or away from the screen.

The Texas chips use up to 1.3m hinge-mounted microscopic mirrors. The chip manufacturing processes are more or less available to Moores Law, which is that they can be made smaller at a rate of double the density every 18 months or cheaper at the same rate.

Sony is also working on something called the Field Emission Display which is based on a similar concept to the cathode ray tube, with a ray exciting a phosphor coating, but using matrix addressing to trigger millions of electron emitting cathodes, which sit just a few millimetres behind the screen's surface.

None of these technologies promise anything beyond total internal reflection and with LCD projectors falling in prices at a rate of 3 per cent to 4 per cent a month, according to Travis, the total price of his system is likely to fall in line with rear projection screens and start much cheaper.

Flat Projection Displays will eventually also target cheap laptop displays using the clear wedge approach, but this will only be practical once a matchbox or smaller sized projector becomes available, which Travis says is certainly on the way.

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