I'm wondering out loud here about the feasibility of using a stripped out 22" widescreen LCD as an image source for a DIY projector.

I won't go into the reasons I'm considering using such a large LCD here, except to say: I have my reasons for wondering if it's possible.

Assume, for the moment, we are talking about a "split fresnel" design.

First off, and based on my current level of understanding, one obvious problem would be to light such a large LCD relatively evenly. Two solutions come to mind: 1) Use some sort of LCD lightsource placed evenly behind the surface area of the entire LCD; or

2) use what's known here at LL as a "frankenfresnel." A dual bulb, short focus-dual fresnel design to (theoretically, and thus relatively evenly) illuminate the backside of the entire area of this very large LCD.

For discussion purposes, let's imagine I'm using an evenly matched pair of 400w bulbs, each illuminating half the LCD via a pair of (side by side) 220mm FL fresnels.

Is there an obvious reason (which I have overlooked) that I cannot at least do THIS much?

Thanks for any replies.


k

Do you have a front fresnel that is wide enough in mind ?

I measure my desktop 22 diag LCD monitor at 18.5" x 11.5" (470mm x 290mm)
The LL Pro fresnels are 17" x 16" (431mm x 406mm)
http://lumenlab.com/estore/product.php?pro...=253&page=1
And 3dlens . com large fresnels are 15.25" x 15.25" (387mm x 387mm)
Both of these are too narrow to cover my 22" screen.

First you won't find a fresnel large enough.

Second you won't find a triplet with a wide enough fov, even the Pro triplet probably wouldn't work.

Third there are much better and smaller solutions.

The importance of using a 22" WS LCD is that there will shortly be at least two monitors of this size on the market sporting a 120Hz refresh rate (from Samsung and ViewSonic)...which, and assuming either or both are strippable, might make them suitable for use with the new Nvidia stereo drivers and shutterglasses if used in a DIY projector.

While I'm sure that as time goes on, 120Hz LCD's will gradually replace 60-81Hz refresh LCD's even in the smaller sizes...and even for laptop sized LCD's like the WUXGA 15.4" LCD sometimes used in DIY projectors here at LL... that's still off in the future.

For right now, and assuming a 22" projector could be engineered at anything like a reasonable cost, this presents a possible alternative to using dual-LCD passive projectors (or dual commercial projectors) like that DIY project pioneered here at LL by "relieve3D."

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The primary purpose (for me) would be for use in simulations (gaming). Hopefully using a relatively short throw of 3'-5' or so (projecting from near the centerpoint of a sphere out onto the inside of a dome, with the viewer sitting just below the lens, in order to minimize distortion).

I had thought it might be possible using part of either a large "solar furnace" type fresnel (typical FL's seem to be 800-1000mm) on the triplet side, or perhaps using a portion of a cannibalized rear-projection screen TV fresnel (FL to be determined).

So there's the reason I'm thinking 22." I hadn't really thought it important to bring it up at first...at least as far as feasibility of the projector itself is concerned...but I suppose it really is after all if anyone is to take the idea of building such a large format projector seriously.

Please note: It's certainly not a case of "my projector is bigger than yours." Not at all.

The idea of using stereo (shutterglasses) with the projected image is the real purpose.

So...can it be done?


k

No, it can not be done!. It is impossible.














I just said that to properly motivate you!.
edit:
My reason for a large LCD would be to be able to use more LEDs and have a better brightness compared to a smaller LCD. The fresnel and lens are probably difficult to source, but who knows. I'll be on the lookout for those too and if i find something i will put it up here.

Here is one thats 28.5" x 35.5" with a 24" focal point.

http://cgi.ebay.com/45-Fresnel-lens-framed...1QQcmdZViewItem

Wow!!!
Ok...So my first thought was that'd be a huge projector...lol!
But then I watched the demonstration with that thing.....and it got me to wonder about a projector with a sun powered light source...Just because of how much light that thing culminates....which led to my searching on the topic again....
Another big Fresnel lens with 40" focal...
more sun talk...
anyhoo...didn't mean to stray off topic too much...

No worries. You never know when a random comment might spark a brilliant idea, so I say: keep 'em coming.

These 24" FL fresnels look promising for my (short throw) purposes. Good find, rengate, and thx.

They would require a triplet with a large field angle (I think of this as a "capture angle"). Perhaps something like a copy lens?

Assuming these fresnels worked...and assuming a suitable lens could be found...this might lower the overall length of "throw" from LCD to screen to perhaps 6', instead of 8'. Making the image inside the dome that much brighter.

That would be very important for a "shutterglasses"-type projector, because the overall level of brightness is effectively cut in half when using the glasses (each eye is alternately blanked out, so each eye sees only half the level of projected light).


k