Do we need large lenses for large lcd?

[exipnos]

Hi guys,

Sorry for the long post but I am still in the planning stages of building my projector and I have some unclear points regarding what necessary.

I am thinking of going the high resolution route using the laptop lcd as discussed in the LCD panel thread. This would probably mean that the lcd size would be large maybe even up to 14"-15".

If I wanted to use such a large lcd would I then need large lenses?

I guess that my projector lens could be normal size but will I need a large lens positioned after the lcd that gathers all the light and sends it to the projector lens.

Am I right in assuming that I could use a normal size lens but by position it far away from the lcd then it will still work. (but my picture will be less bright?). This will also mean that the projector will be very large.

Is it possible to find large lenses (10" or even 15") that could be used for gathering the picture and sending it to the projector lens? Are souch large lenses to expensive to even consider for my purpose?

I guess my setup will be as follows (in the order of positioning)

1. MH bulb with some reflector (probably 1000w)
2. Heat protection glass if needed
3. Fresnel lens to make light parallel
(4. Fresnel lens to send light to point behing lcd, positioned very close to lcd so that light is still as parallel as possible (do I need this?)
5. 14"-15"Lcd panel (1600*1200) (driven with controller cards found in lcd thread).
6. large lens (bigger then lcd that gathers the projection and sends it to the projector lens.
7. projector lens
8. projection screen

Last question. By using second fresnel lens in point 4 above would I remove the need for the large lens after the lcd?

Thanks for any help in clearing up my confusion above.

Cheers,

Exipnos...

 

[Tall Shadow]

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[Lifter]

Is it possible to find large lenses (10" or even 15") that could be used for gathering the picture and sending it to the projector lens? Are souch large lenses to expensive to even consider for my purpose?

Your project sounds a lot like mine. You just use a 15" fresnel. There are links to them. It works just like an overhead. However, that does mean that the projector will be big. Someone here also told me that the pixels will be spread apart from having the projector lens far away. I'm not sure that that's true, but if it is, it's a concern.

As to your question, I don't know what the alternative is. I thought of finding a 15" condenser lens or something and then you could have the projector lens closer, but nobody has really answered my question yet (see Lens FAQ thread).