New Philips LCOS with Color Prism(Wheel?) - AVS Forum
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post #1 of 12 Old 04-20-2001, 10:59 AM - Thread Starter
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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.

Barry Fox

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post #2 of 12 Old 04-20-2001, 11:06 AM
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Hi Barry,

Great find. I think that it was mentioned once before here, but always good to hear the latest news.

I sure hope that they do it in an FP model as well!

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post #3 of 12 Old 04-20-2001, 11:40 AM
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"He says 1-meter diagonal displays will be ready by 2003 and cost under $3000."
----------

I think the tiny one meter size is a big mistake. That is too small to make an impression. For a 9:16 ratio screen, I feel you need a minimum of 62" diagonal to obtain sufficient screen height. A one meter screen is so small that it will lack impact, no matter how good the colors or how high the definition of detail. Make it bigger or just use it for a computer display, not for movies.

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post #4 of 12 Old 04-20-2001, 12:06 PM
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One question is what the prism, like a color wheel, will do to brightness.
That probably gets down to heating. I assume that if the prism is used prior to the chip, heating will be minimal.

Also, will it produce artifacts?
The LCOS supposedly has higher bandwidth than conventional LCDs. If it has much higher bandwidth than DMDs, the color wheel artifacts could be history.

It could have better contrast than conventional DILAs since there would be fewer reflecting surfaces and it should be easier to control polarization.

Sounds good for HT if anyone gets to making a 2500 lumen 16:9 panel with it. Maybe JVC is being quiet for a reason?....

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post #5 of 12 Old 04-20-2001, 03:54 PM
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The post does say give 200 Hz as the "scroll" rate of the prism, if one cycle is for a flash of all three colours it should be more than fast enough to eliminate the rainbow effect.

Regards,

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post #6 of 12 Old 04-20-2001, 08:29 PM
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A refresh rate of 200Hz would mean the response time of the LCOS pixels is under 5ms.

DILA panels are LCOS aren't they ? Yet the JVC panels are much slower than this. I remember this was the limiting factor when I wondered why JVC couldn't make a DILA projector using the single chip and color-wheel method that DLP employs.

I am still not clear on how they will manage to get the correct saturation of each color, though. They must be able to turn off the LCOS pixels partway through their cycle -- so they only reach a partially open state.

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post #7 of 12 Old 04-20-2001, 08:35 PM
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I just stumbled on this interesting link related to this...

http://www.mdreport.com/summaries/june00.html

Interestingly, there is a D-ILA headline below the LCOS headline as well.

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post #8 of 12 Old 04-21-2001, 11:58 AM
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Very interesting....

Note that this was from last June.

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post #9 of 12 Old 04-21-2001, 10:40 PM
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What makes this especially frustrating is that DILA seems to be an obvious choice for best HT and JVC doesn't seem to know what to do with it.

I expect would expect some new models announced based on this new technology at Infocomm.

That means at least a year before we see it on the street.

I don't know if I can wait.

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post #10 of 12 Old 04-22-2001, 12:59 PM
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I think this product is slated for lower end use than what we are currently using. I think it is aimed at replacing the direct view 36" CRT. But for $3000 2 years from now I think you will get a very good deal on a 36' 16:9 direct view CRT with a reference quality image. I think that will be hard to beat for a new technology.

This is very similar to a 1-chip DLP. And as many of you have mentioned, the reason that a 1-chip d-ila isn't possible is because the reponse time of the panel isn't fast enough.

Well, If they can get a stunning contrast ratio out the device, I think they will be on to something but otherwise they have a steap hill to climb when going up against any 1-chip DLP product 2 years from now.

I am putting this in the cool but not a contender file for right now.

Thanks for the info.

-Mr. Wigggles

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post #11 of 12 Old 04-22-2001, 03:32 PM
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Perhaps there has been a technical breakthrough with LCOS technology response time. Either better liquid crystals, and/or faster drivers.

Since inexpensive SXGA DLPs aren't right around the corner, the one-chip LCOS may be the best short term alternative right around the corner.

It seems more realistic than the Silicon Light Machines approach.

Also, high brightness and contrast should be feasible at least in principle. My guess is that one could get a great projector with 1.5 to 2K lumens with a 350W bulb. One nice thing about a prism is that it doesn't absorb light, it refracts it. It won't heat up like a color wheel.

Also, perfect convergence could be obtained.

The cost savings could be applied to use better or multiple polarizers to improve contrast.

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post #12 of 12 Old 04-23-2001, 06:37 AM
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This was discussed in: http://www.avsforum.com/ubb/Forum10/HTML/005417.html

and yes I do know more but am not allowed to disclose, sorry.

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Closed Thread Digital Hi-End Projectors - $3,000+ USD MSRP

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