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Discussion Starter · #1 ·
Hey! In my new apartment I have made a dedicated room for my

home cinema. the problem is that I don't have enought throwdistance for my dlp projector. It's a Davis dpx16 without zoom. I am short with aproc 30 cm to fill out my 240 cm screen. Then I got an idea in my head...

If I put the projector on the wall facing downwards and use a mirror 30 cm down the wall in a 45 deegree angle, reflecting the image towards the screen, would that make up the 30 cm I was short on the throwdistance?

Or is this just a stupid idea?

Have anybody tried this before?

brgds Jorn from Oslo Norway.
 

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That'll work, but you'll probably be really unhappy with the results from a normal mirror. You'll need a special mirror (first or primary surface, I forget which it's called). These aren't cheap, but sometimes you can get one from a dead RPTV for a few bucks. Call your local TV repair shop and ask if they've got any laying around.


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Darren Rogers
 

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Discussion Starter · #3 ·
thanks for the reply! "not cheap".. what kind of numbers are we talking? 100$- 200$?

brgds jorn
 

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They're called first surface mirrors. SLR cameras use them in the mirror box, which is how I know about them. There's another thing you need to know about first surface mirrors, which is that the surface is very delicate, and easily scratched, to the point that you cannot wipe dust off of it. If it gets dirty, the only thing you can do is use compressed air to blow dirt off, taking care that no liquid compressed air lands directly on the mirror, which can happen if you angle the compressed air bottle. The liquid will discolor the silvered surface.


Stephen
 

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Discussion Starter · #5 ·
Thanks for the reply.

It sounds like the best thing to do is to be happy with the 210 cm wide picture I get from the throwdistance I have room for. At least I get a dedicated room for my theatre..

Looking forward to try out ps2 with gran turismo3 in this theatre...

brgds jorn.
 

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Yes, I had looked into this a while ago, so I could put my projector in a room adjacent to my main room and use a mirror to reflect. Then I found out about the maintenance and cost of the first surface mirror, and, well, that idea droped, as you may well have decided.




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David Mendicino

Sharp xv-s55u (Don't laugh) :)
 

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I like luvmytivo's response. After clearing out the useless CRTs and miscellaneous, you'd even have a (BIG) hush box for the projector http://www.avsforum.com/ubb/wink.gif .


One especially nice feature of this approach is that the angle is fixed for you; just mount your projection lens where the middle CRT used to be. You could seal the front opening to keep dust out with a piece of optical glass cut to fit. Line the inside of the RPTV screen around the exit aperture with black velvet to minimize stray light. Might not even need a fan for the box if the original RPTV wattage is close to your projector's.


But it may not match your decor.


-yogaman


[This message has been edited by yogaman (edited 06-22-2001).]
 

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actually I do exactly that. (the down pointing projector mirror thing)

the idea was to keep my LP340

cool by using convection in addition to the fan. it also has

a lot more room 'behind' the projector now, plus it keeps the goofy light spill from the front of the projector off of the screen. Looks a bit like a sconce light now :)

you might get 30cm more in throw distance just by rotating

the projector. you will need a BIG mirror if you want to mount it 30 cm away. http://www.edmundoptics.com has a number of mirrors but their search function misses things.

search on L32-354 or L40-042 to get a couple of tables I am looking at in the paper catalog.

be careful to get a big enough mirror a 2" mirror is not adequate even right at the lens.

these are 'protected' mirrors some fraction of a wavelength

of some coating over the silver. not as delicate as regular but still delicate. I have actully managed to scratch mine with windex and paper towel, but I can't tell by looking at the screen.


[This message has been edited by mhench (edited 06-22-2001).]
 
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