Wow. Now that appears to have some serious potential. If they can do 30,000 lumens on a 5" square, certainly they could do 1k-2k on something small enough to fit into a projector.

RG

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Only 25 lumens per led though. Unfortunately there's some reason you can't use led arrays with projectors, something to do with you need a single bright source or strange things happen (can't remember exactly what it was)

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inky blacks

· #5 · Mar 3, 2005

You would want a 200 watt panel, which would put out only 4,000 lumens at 20 lumens per watt. Would that be enough? Lumens inside the projector are not the same as lumens going to the screen.

IB

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RTFM

Discussion Starter · #6 · Mar 3, 2005

Quote:

Originally posted by sisaacs
Only 25 lumens per led though. Unfortunately there's some reason you can't use led arrays with projectors, something to do with you need a single bright source or strange things happen (can't remember exactly what it was)

Lots of fixed panel projectors use a "Fly Eye Lens" which turns the point source of an arc lamp into a diffuse light source so I can't think why a panel of LEDs shouldn't do the trick. But then, what do I know ?

Jeff

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AnthonyP

· #7 · Mar 3, 2005

you do realize this is 5" square

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rogo

· #8 · Mar 3, 2005

Quote:

Originally posted by RTFM
Lots of fixed panel projectors use a "Fly Eye Lens" which turns the point source of an arc lamp into a diffuse light source so I can't think why a panel of LEDs shouldn't do the trick. But then, what do I know ?

"Focusing" of light is hard to do. Look up etendue for more information.

If the array is small enough, the problem is no worse than the UHP and Xenon lamps used today. If the array is 5", forget it.

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AnthonyP

· #9 · Mar 3, 2005

Quote:

Wow. Now that appears to have some serious potential. If they can do 30,000 lumens on a 5" square, certainly they could do 1k-2k on something small enough to fit into a projector.

just saw that you already mentioned it.

on the other hand

1) you will need a lot more then 1-2k lumens. going through all the optics and stuff reduces light by a lot. For instance assuming a color wheel means 2/3 of the light is wasted just there , an LCD with 50% AR means that 50% of the light hitts the pixel borders and so cannot be transmitted through (and that does not even take into consideration all the stuff that hits the LCD part needs to go through and how much is lost.

2) it is not 6500K temperature but 5500k, that means the colour balance is not right and a extra

I don't know if 28k lumens is enough, but you cannot start with 1-2k lumens.

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AnthonyP

· #10 · Mar 3, 2005

Rogo, do you know where there is a place that discusses actual lumen output of the lamps in comparison to projector output? I think this would be interesting to know how many real lumens are needed

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sisaacs

· #11 · Mar 3, 2005

Would make a nifty flashlight though mmmm 28k lumen flashlight... the etendue thing is what I was remembering.

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car_rod

· #12 · Mar 3, 2005

Hey!

About LED, DLP, and projectors.

Shouldn't those tiny pjs presented at CES start to be on boutiques anytime soon?

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AnthonyP

· #13 · Mar 4, 2005

Andrikos

1)2) where did you get
Quote:

In a 3-chip configuration (DLP is the most efficient) you can achieve efficiencies of 36%.

just curious is it from the big DLPs or the mini ones

2) these are white LEDs, so you would need a color wheel, if you look at the BL-3000 (one of their other arrays) http://www.laminaceramics.com/products/bl3000.aspx

R=2045, B=162, g=570, w=567 w=3.5*B so the same array with blue LEDs (if possible and the relationship is the same) will only produce 8k lumens

3) like Rogo said the problem with LED arrays is etendue, the bigger the array the harder and less efficient it is to turn it into a beam needed for use in a projector.

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AnthonyP

· #14 · Mar 4, 2005

Quote:

Colorwheel on a 3-chip? Surely you jest

my point was not that it should, but that colour matters like in the BL-300, there is a big difference between the colours and even though we need a bit less blue, it will need to be the biggest array

I agree if it is a single LED no problem, but that is not what this article is talking about. And there is no LEDs remotely close to what is needed. In the short term (and possibly ever) the answer will have to be an array. The question is can there be an array small and bright enough?

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sisaacs

· #15 · Mar 4, 2005

I wonder how small and how bright an array would need to be to overcome the etendue problem. Is there a simple function you can stick those values into and get a rough estimation?

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sisaacs

· #16 · Mar 4, 2005

I wonder if aiming a buncha low power lasers at a piece of fiber optic cable would work, I wouldn't think the etendue problem would be a problem for lasers.

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rogo

· #17 · Mar 4, 2005

No lasers would be plenty "point source" enough for use. I believe there are issues of cost for enough light and color spectrum.

WRT to the above comments, I'm not convinced you'd need a single LED for R, G, and B, but I'm convinced you'd need a very small array to achieve what everyone is after.

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AnthonyP

· #18 · Mar 7, 2005

sisaacs: no idea, and would guess that it will depend on the efficiency of the arrey

Quote:

I'm not convinced you'd need a single LED for R, G, and B, but I'm convinced you'd need a very small array to achieve what everyone is after.

agree, I would guess smaller then the display chip/panel. And most probably a fraction of it.

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drpp

· #19 · Mar 7, 2005

The following *'.pdf presentation from Lumiled answers some of the questions related to etendue and LED usage in projection systems.

http://www.lumileds.com/solutions/LC...arbers_ppt.pdf

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rogo

· #20 · Mar 7, 2005

Any idea the date on the Lumileds Powerpoint? For whatever it's worth, they have always been behind on the roadmap, so I'd take the 5-year number much more seriously than the 2-year one for RPTV. And I'd note that the first pocket projectors are not -- according to those that saw them and other sources -- anywhere near the 70-lumen level.

If the presentation is recent, it seems like FP is out for this decade.

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