Hi, i just drawed one schematics, how to build projector with LEDs,.. my friend from Latvia have tested LEDs without fresnel matrix, and he got some grid on output image... so that is the drawing do - describes how to correctly setup LEDs



The only problem is - WHERE to get this FresnelMatrix ? maybe there is some company we can order special size frsnel matrix to build !?

the only i have found is from 3Dlens.com - http://www.3dlens.com/media/fresnel_408(large).jpg


Thanks

PS: your ideas ??

the fresnell at 3dlens, is a negative one, it will not work, you need positive focal fresnell matrix.

the light is paralell so just a small amount will hit the projection lens... hot spot.

and the worst part in my opinion; know what leds would you use? total price?

I think MH are the cheapest and best choice for us yet. But I believe someday a ultra bright led will be available for us.

20kMCD (~220lum) is so bad for LED? also available 35kMCD...
as i sad, LED source have been tested...

220 lum? any link to it?

one candlepower (1 cd) equivalent equals 12.57 lumens
1 milicandle is 1/1000 candelpower (logical )

so, 1000 mcd = 12.57 Lum

In the www.led1.de e-shop we can get 10000mcd(126Lum), 20000mcd(~250Lum), 35000mcd (440Lum) LEDs

this LEDs are about 5mm, so on 300x200 mm panel we should have ~925 LEDs (3mm gap)... basicly it is about 1200 LEDs for 15" LCD

100pcs of LEDs are about 50Eur (20000mcd), so it is aprox 600Eur (pretty expensive ) for 1200 LEDs. Light power is - 300.000 Lum !!!!

The gap should be minimal for not to gettong grid on final image on screen (as i sad my friend have tested such LED panel with 10000mcd 10x10cm LED panel, and got some grid )


Resources:
LEDs - http://www.led1.de/shop/product_info.php?products_id=328
cd to Lum - google.com

I read the first line on your post and didn´t need to continue .

this is wrong statement, check it.

OK, thanks, i think i am wrong... usong this http://led.linear1.org/lumen.wiz

20000mcd (20degrees) is only ~2 Lum. 1200 LEDs will produce 2400 Lum only... seems not so good as it should be :/

Can i calculate like this:

If MH lamp produce light source on all 360 degrees, but projector uses only ~45 degrees of light,... so koef = 360/45 = 8.

and lamp intensity is ~20000 Lum, so it is a ~2500 Lum used for our DIY projectors?
if we use reflector, logicly, it is about 2x bigger amount of ligth is getting - ~5000 Lum

Correct me, please.

If it is correct, so LEDs light power with 2400Lum is pretty usable

you can´t consider "360 degrees" since it is not in plane but in 3D. This is called stereoradian, "r^2" and it is for meassuring solid angles (like a cone aperture). The candelas unit is based on howmany lumenes are there in one stereoradian.

if you can direct 2400 lumens from leds to the rear fresnell (as it would come from its focal) then yes, this would work fine.

we can nothing is imposible. but how much it will cost - this is an another Q

What about this LED bulb? Usable?
http://www.megain.net/english/feature/feature7.html

As it boasts a long life of >50000 hours, it is economic even if expensive (in China I don't think it will be too expensive). Only wonder whether it can suits in the projector box...

nope, LED source should be like LCD panel size. or 1-point light-source, which is impossible with current LEDs of cause

LED panel + fresnel matrix is that one i suitable for LCD projector. LED panel can be done, but fresnel matrix does not exist at all :/

If you're interested in trying this, the C. Crane company has an LED spotlight. They advertise 120 Lumens.

you mean we should discart our current 32000 lumens (400W MH) and try with those 120 lumens? then see what is better?

I like sarcasm.

Na I'm not saying that. I'm just saying, here is somthing to experiment with if you feel like it.