convert rear proj TV to front (and vice versa, and 3d hacks)

[hifidelitygaming]

I'm posting this here because even if the first step of the project will not be 3d just yet, the ultimate intent will be. Please let me know if it's more appropriate for a different forum, but I hoped there would be more tinkerers in this one who might have experience.


My goal is simple enough, a decent resolution multihead projection with 3d on a budget - spending hundreds instead of thousands. So this is part of exploring how to do this. This is requesting feedback on a couple possible ways to do so in particular involving parts from old projection TV's and such which often turn up cheap or free on craigslist.

As of right now CRT's are damn cheap right up to full HD resolution. They also can usually do 120hz though none I know can do both at the same time... yet 720p at 120hz is still good enough in my book. The main downsides are size not being big enough and bezel width. Big fresnels may be one way to fix this according to others but those are normally expensive - yet they seem to be what the screens are actually in old rear projection TV sets. Is there any reason I can't just collect some of the old 55's for instance and use the screens out of them to blow up a 22" computer monitor to about 55" with essentially no bezel between them? I'm aware light output will go down but in a dark adjusted room like a movie theater maybe it wont be such a problem. It's also possible resolution is an issue - I seem to remember reading somewhere that unless the fresnel is some very fine pitch, it will not resolve fine details, and most older projection TV's are made for SD res.

As to light issues i'm aware 55 inches will be darker if based off a 22" computer monitor, but if I adjust the viewing distance so that the same field of view (ie a 22" at 18 inches vs a 55" at more like 40 inches lets say) comes to my eye the light should be about the same, correct? Part of my reason for wanting fresnels is to get that "depth of field" effect where the picture seems even further away than the screen really is, along with eliminating bezels. Another possibility is just using the 55 or so inch fresnels with a larger CRT HDTV like the 36 inchers which are now comparatively cheap - I wouldn't have 120hz for 3d anymore, and the resolution closer to 540p, but I could at least eliminate bezels for an edge to edge display and hopefully still be immersive. But for obvious reason i'd rather use 120hz computer monitors so I can use shutter glasses.


The next things I was wondering is if anyone could provide references for either converting rear projection TV's to front projection (using the built in 3 CRT tube guns to project onto a larger, though admittedly darker then, screen) or the opposite - taking front projector type setups and projecting them onto an existing "rear projection set". Mostly i'm just curious what differences there are between them allowing hacking possibilities. For instance whether I could take a pair of homebrew LCD projectors, fit them with polarizing filters, and shoot that into the body of an old rear projection set for it's screen so I get a 3d display that is a little more tolerant of ambient light. (as RPTV's seem to work way better without total light control than FP setups) Or combine the innards of two RPTV's to add polarizing filters to the CRT's to shoot onto one screen. Or to strip innards of two RPTV's, add polarizing filters, and then use them as a cheap 3d front projection setup - to project onto a collimated display.

In short it's a few things - Where I am old RPTV's are thrown away, but front projector units never are... if I can convert the former to the latter it's worth experimenting with but i'm not sure where to begin such an exploration. Alternately RPTV's tolerate ambient light better and usually have displays right to the edge for mostly seamless multihead, so using the screens can have advantages were I do to things like those homebrew LCD projectors. (although 'real' HD projectors are as low as $350 now i'm aware, i'm used to $10 LCD monitors and $20 overhead projectors from thrift stores, plus I might need to run as many as six to get three heads with polarized light each way)

Can anyone provide leads of which of these designs might bear fruit, or where I could go to find others possibly experimenting with similar things?

[tritosine5G]

Recent DLP projectors will do a better job for 3D unless you can find one of these CRT-s (unlikely) :

http://www.cl.cam.ac.uk/research/rainbo ... tereo.html

oh and polarization preserving screens are a pain...