# White Leds in Home Theater Projectors?

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Hi,

Does someone know why they don't start using white leds in those projectors?

You need only about half the energy and what is much more important the lifespan is about 50000 hours.

For most projector lamps that is more than a factor 10 longer.

So what is stopping them to use LEDs?

some info

Lamps:

Current home theater projectors are all working with a lamp

example of a projector:

http://www.projectorcentral.com/projectiondesign-F3_SXGA+.htm

Here you get 4000Lumen for an 250W lamp (16 lm/watt), lifespan 8000hours

LEDs:

White LEDs have in best case 80lm/watt

http://www.lrc.rpi.edu/resources/news/enews/Apr05/general251.html

(available now between 25 and 35lm/watt)

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The lamps have a MUCH higher power density.

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The lamps have a MUCH higher power density.

You mean using leds would mean they wouldn't have a 'point' light source.

I don't think that's a problem.

I just found these mini versions. (not much data though)

http://www.techtree.com/techtree/jsp/article.jsp?article_id=67373&cat_id=581

and

http://www.akihabaranews.com/en/news_9790.html

Some power LED info:

http://www.theledlight.com/LuxeonLEDs.html

price 16dollar/3W LED or 25*16=400dollar that is also the price of current lamps.

25LEDs*45lm/W*3W=3375lm

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just a thought, but could it Marketing?

they can make cars that dont Rust, but wont, simply because it doesnt pay to in the long term, if they made these LED light sources so good, who would buy spare bulbs?

the same reason ordinary Zinc Carbon batteries can be charged a good 20+ times, yet those sold here quite clearly state "Do Not Recharge, observe correct polarity and do not dispose of in fire" yet the ones we Export say all that EXCEPT for the "Do not recharge" bit

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No, Lance is right. LED's have less power density compared to those bulbs. Eventually they will be comparable. That'll be around the time LED illumination to light houses and stuff will begin. But for now, LED's just don't cut it for lighting a large area such as a wall for projection purposes.

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they can make cars that dont Rust' date=' but wont, simply because it doesnt pay to in the long term, ![/quote']Yeah YT, Back in the '70's, they specifically designed cars to rust shortly after the warranty expired.

I never knew that zinc carbon batteries could be recharged.

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just a thought, but could it Marketing?

I don't think that's the case because there is no monopoly.

The only reason I think is that they just need time to develope the new technology it's not like they just have to replace the lamp with the leds and done. They will probably use three different colour led's this way skipping the filtering of white light in to colours.

The mini version are just there to show that it can be done they 'just' need to put more leds in it to have a more mature led based projector

I would be surprised if there is no 2000lumen or more LED based projector on the market nex year. And I'm going to buy one

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No, Lance is right. LED's have less power density compared to those bulbs. Eventually they will be comparable. That'll be around the time LED illumination to light houses and stuff will begin. But for now, LED's just don't cut it for lighting a large area such as a wall for projection purposes.

Give me numbers....

look at this:http://www.luxeon.com/pdfs/DS45.PDF

Keep in mind that no one says that you only can use ONE LED like it is with lamps

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I'm not sure you have seen the size of projector bulbs. They have an extremely high power density. If you took 5W luxeon stars and lined them up in the same amount of space you wouldn't get anywhere near the required output requirement. Luxeon stars are not cheap either. If somebody can prove me wrong then they stand to gain a large sum of money assuming they know anything about marketing.

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Maybe another factor is that extrememly bright LED's dont have that "natural light" look that incandescent bulbs have.

An LED source: besthongkong.com

I would probaly consider buying a projecter as oppesed to a monitor if they were olny about 400 bucks and the bulbs didnt cost hundreds of dollars ( i think there that expensive).

Another thing, maybe there just simply not bright enough.

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I'm not sure you have seen the size of projector bulbs. They have an extremely high power density. If you took 5W luxeon stars and lined them up in the same amount of space you wouldn't get anywhere near the required output requirement. Luxeon stars are not cheap either. If somebody can prove me wrong then they stand to gain a large sum of money assuming they know anything about marketing.

The first thing they do is split the white light in to 3 colours, that isn't needed with led since they start with the three colours. hence they can be located at a different position so you already have a factor 3 of lm/mm² less to get the same effect.

Secondly I don't think that having a bigger surface that generates the needed light is a disadvantage, maybe it's an advantage since they can modify the shape of that surface. In worste case they need an extra lens.

A surface of 3cm*3cm (or 16/9 ratio) per colour should be more than enough to have enough lumen for your projector.

Generating the natural colours is probably not a problem since they said this about those mini projectors:

Koichi Kubota, general manager - projector marketing, Epson, said, "Projectors using 3LCD technology already have advantages in terms of bright, natural images that are easy on the eyes."

LED light sources provide several advantages over conventional lamps including immediate projection readiness, a long running time, and swift switch-off. The use of an LED light source in a projector is a first for 3LCD.

edit: some simplified math (http://www.luxeon.com/products/family.cfm?familyId=7)

2000lumen/3colours = 667lumen/colour

red 667lm/140lm/led=5Leds price: 5*6.5dollar=32.5

blue 667lm/30lm/led=22Leds price 22*8.5dollar=187

green 667lm/80lm/red=8leds Price: 8*8.5dollar=68

Led price for about 2000lumen=287.5dollar so not more expensive than a lamp

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