I am looking to build a gaming table for roleplaying and miniature wargames, where the projector is built into the base of the table and is shot up to the tabletop from beneath. I have a couple of commercial projectors, and random bits and eces from a DIY project which I could use as the basis - so this could be a DIY projector, or it could just use a commercial unit. I am leaning to the DIY for the cost and maintenance, but...?

Anyway, the main question I wish to ask; projecting from within the table's pedestal base, I need to figure out how to make a screen sized roughly 3' by 4' (assuming 4:3 screen ratio). I would like the table itself to be close to standard height, so about 36" tall give or take a couple inches, and about 10" to 12" all around the screen for player space - making it about 5' by 7' in overall dimensions. Assuming the projector is mounted horizontally at the base of one end of the table, and assuming that we push the pedestal base all the way out (inconvenient for seating, but if necessary I will do it), I have a box of 3' by 5' by 7' to play around in and bounce the image off of mirrors and whatnot, to end up with the image projected up to the center(ish) of the table and be 3' by 4' in size.

I have no idea how to calculate that kind of thing out - so I thought I would post here and ask...

It doesn't need to be high definition, but I would want it to be a clear image and preferably at least an 800x600 resolution (so not 480i/480p), no screendoor effect, and fairly good contrast/color balance.

I plan on using a sheet of translucent white plexiglass as the projection surface, mounted in the wooden frame of the table. I will add any cooling necessary to keep the inside of the pedestal base cool while the projector is running.

Any suggestions on how I can figure this out?

As always, two things.

First, this might help you figure out the distance you will need. THE FOCAL DISTANCE CALCULATOR

Second, since you are going to need to fold the design somehow I would try out Google Sketchup to model it in 3d before you start building. Its really easy, and there are many models of PJs up already.

Start there, and also look through the PLOG section for the folded builds. They will give you an idea of what you will need. Oh, and I am just gonna guess that you are going to need a short throw triplet.

I have been thinking about this thread more and more over the last day or so.

What about just getting a RPTV and gutting it and moding it into a table? Just sorta lay it flat? More Ideas on the way. I am working on a Sketchup model of what I am thinking. I am gonna see if it could be done using a standard build and then just folding it after the triplet.

Thanks for the earlier advice and the subsequent thoughts on it, lol...

I think the focal distance calculator is a bit beyond me at the moment; one of the reasons I posted in the beginner's forum - I have never yet made a DIY projector, and am not 100% on everything involved.

As to a RPTV, I thought of that first, but all the RPTVs I have seen had too much of a screen door effect, and weren't capable of accepting computer input - I want to display image maps from the web, photoshopped images, maybe even use it as a second monitor using one of the several decent 'virtual game tables' out there, like OpenRPG or other similar setups.

I'm toying with ideas and just trying to learn enough that the calculator makes sense to me, lol. Until I get to that point, I still welcome any thoughts you may have!

You said you had a few projectors laying around right? Set one up and figure out how far it needs to be away from the wall to get the size image you need. Then you will know how long of a light path you need to have. Then with a series of mirros you can fold the light path to make it fit into a table. Simple right. LOL Really it is not that hard of a thing to do. The hard part is figuring out the folds and getting it to all line up right.