Ghearing.com - LED Projector Project

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Last update:
June 13. 2009 11:36:00

LED Projector Project

I've been playing with the idea of making a LCD projector with ultra-bright LEDs as the light source. What's cool about this is they don't produce any heat or IR light. The downside is they aren't that bright, so I'll need at least a hundred to get the same light you get from regular projector bulbs. With regular bulbs you have to screen out the IR rays and at best will last 2500 hours, LEDs can easily last 100,000 hours and will use far less power and all at about the same price.

I have a suitable LCD and some large fresnels to play with, all that's left is to buy the LEDs and rig it up. I'm trying to find an old cheap/free overhead projector for the project.

Update - Oct 8, 2003
Well, I bought 100 LEDs of 5000mC, and well, it isn't enough. I also found that you can easily damage white LEDs, If you put too much power through them they turn back into blue LEDs. White LEDs are made by putting a bit of sulfer on top of a blue LED which emits the other colors somehow using the blue lght. When you overpower them the sulfer starts desolving/oxidizing.

My little 100 LED array works to project an image, but I figure that you'll need more like 1000 LEDs of around 7000mC to get a really good projector running(like the really big ones that use lamps). Luckily around 1000 is perfect for the 14.1" LCD panels I have. I figure an array of LEDs in 36X27 spaced .3" apart would give a great backlight. Now to get a job again so I can afford to throw more money at this. I've seen 1000 LED packs on ebay for around $250.

Update Feb - 14, 2004
Nothing new here but I found a neat article about a commercial LED LCD Projector. They mentioned that they had filed pantents, that got me thinking about searching the US Pantent Database for how they did it, I couldn't find them but MAN are there a lot of patents that look identical for a LCD screen.

Links

Update July - 30,2004
Well, I've played a lot recently with my setup fine tuning stuff and decided it is too hard to get a clear image. I think the problem with colminating the light into a single cone of light will just get worse the more LEDs you add. I tried to take some pics of images from my setup but none really came out. I have to hold the lens perfectly to keep the image in focus and then try to take a shot. Anyway, here is a blurring projected image, I got it clear enough to read the text on the screen which was 14pt times new roman. Next time I attemp this I'll have someone help me so I can get a better pic.

This next pic is of my setup, I wrapped a sheet of paper around the LED array to minimize the amount of light that escaped into the room, and then used a large hand-held fresnel lens above to project the image onto the ceiling. The junk in the bottom of the box is just there for filler to hold the LEDs. The box edge is supprting the LCD screen and the board at the top is the LCD controller.

I also found another good article http://optics.org/articles/ole/8/7/3/1. It deals more with focusing the LED light and image than any other I've seen, but it's all about realllly small projectors.