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Join Date: Apr 1999
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This article was in today's Tech Notes. I don't remember seeing it discussed here before. Isn't RCA coming out with something similar to this?
Subject: Sharp shooter Jumbo-sized televisions needn't weigh a ton or cost a small fortune
From: Barry Fox
"A REVOLUTIONARY display technology finally promises to make high-resolution, widescreen televisions more affordable. The display, developed at Philips's research lab in Eindhoven, the Netherlands, uses a rotating prism to create a large, full-colour image from a single, cheap liquid-crystal display chip. The new screen costs about half as much as a conventional LCD or plasma screen, and consumes much
less power than a bulky cathode-ray tube.
Display designers have to find their way through a maze of compromises. The size of CRT screens is limited by the weight of the glass needed to make sure that the evacuated tube doesn't implode under atmospheric pressure, and its electron guns waste energy as heat. But making large LCD panels is tricky because a single faulty cell creates a permanent blip on the screen. Plasma panel TVs are bulky, gobble power and cost over $10,000.
One way around these problems has been to use a back-projection TV that beams pictures onto a translucent screen. In some projectors, red, green and blue light passes through separate small LCD panels,
which act as "light valves". These three images are projected onto the screen, where they are superimposed. But it's difficult to keep the colours perfectly aligned, and you have to pay for three LCDs. In addition, the layer of transistors which control the LCD's cells block some of the light, reducing brightness.
Philips's answer is to use a new kind of LCD panel made by depositing a liquid-crystal array directly onto a transparent silicon chip. It places a transparent electrode sheet on top of the LCD and a reflective layer underneath. Light shines through the top sheet and then through the LCD, before being reflected by the backing layer into a projection lens system. The projected image is very bright because there are no transistors to obstruct the light. The resolution of Philips's "liquid crystal on silicon" (LCOS) panel is high because the LCD cells can be very small - just 2 micrometres apart.
To cut the cost of flat-screen/widescreen TV - and its complexity - the researchers have devised a clever way to squeeze full-colour video from a single LCOS chip. White light from an arc lamp is split into red, green and blue beams, which pass through a rapidly rotating prism. This continuously scrolls red, green and blue horizontal strips of light down the LCOS panel, so the cells in the LCOS panel reflect the three colours in sequence. The video signal is split into red, green and blue frames and fed to the panel in synchrony with the
corresponding light beams. So when the LCD cells are bathed in red light they display only the red content of the picture, when bathed in blue light they display only the blue content, and so on. The prism scrolls at 200 hertz - fast enough to fool the eye into seeing full colour without flicker.
Project leader Ad de Vaan will demonstrate the new screen at the Society for Information Display annual conference in San Jose, California, on 3 June. He says 1-metre diagonal displays will be ready by 2003 and cost under $3000.