Ok, so, I really really want to wipe the smirk off the "MH ownzers LED" people's face. Not that I am qualified to do that, but there are so many people saying that LEDs just cannot make a projector work, its so tempting!
This question will boil down to:
"How much lumens need to hit a square inch of the LCD panel to get a good picture?"
I realize that question relies a lot on how big the LCD is, and how big the projected image is.
Because I understand that LEDs are expensive, I am going to aim for a small projector as a proof of concept.
The primary thing I want to do with this proof of concept is play dvds. So, to that end, I think I will start off with a Toshiba SD-P2700 with the 1024x600 resolution ploysilicon screen. This means I have to light up a modest 8.9 inches diagonal. (ps, anyone with sizing information on the screen itself, please send it to me, would be appreciated!)
I have been playing with hexagon layouts in cad, to determine just how many Luxeon III Stars I can fit behind that 8.9" diagonal.
I think the best layout I have got right now, is placing the stars at 35mm centers, and then topping them off with L2 15degree lenses. Each star would then have a dedicated collimator fresnel (laser cut hexagons out of the 3dlens business card magnifiers.)
The light path would look like this then:
Luxeon Star -> L2 15degree -> .7mm lexan -> dedicated hexagon collimators -> .7mm lexan -> collector fresnel -> lcd -> projection lens. (the lexan is sandwiching the loose hexagon collimators)
With the 35mm spacing, I can fit 36 stars, giving me an affective panel coverage of 201mm x 121mm.
With 36 luxeon stars, each producing 80 lumens of 5500K light, brings total light emitted to 2880 lumens at 1A. (or you can overdrive the LEDs at 1.4A, and get 5040 lumens, at the cost of longevity)
Figuring an average light waste at the optics of 10%, and a light waste at the LCD of 90% (is that a realistic number?), then I should get:
2880 * .9^6 * .1 =~ 153 lumens at the end of the projector.
So, back to my original question, is 153 lumens enough to light up a 50-60" screen comfortably?
Of course, Luxeon released yet another product, the K2. The K2 can produce 120 lumens of 6500K light. Now, do to the different optics manufactured for the K2, I would be forced to space them a little closer. At 30mm centers, I fit 50 K2s behind an effective panel of 217mm x 116mm. With the K2s, I would expect closer to 318 lumens out of the projector. Is that enough to light up a screen?
Thanks to everyone who read this long winded post, and double thanks to those that can provide insight.