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Discussion Starter · #1 ·
I got one of the Dell LT150's, and intend to use it with an ISCOII in a rear projection installation. The combined throw ratio is 1.22:1.


At some point I expect to move to a 16:9 projector without the anamorphic lens (too hard to move back and forth inside the projection booth), and will be constrained to about the same throw distance by the size of the mirrors and booth. I don't want to spend a thousand or two extra dollars for an optional or aftermarket short throw lens.


There must be thousands of lenses in CRT graveyards. Is there any reason I couldn't adapt one to the DLP? I have a lathe and milling machine and can make any necessary adapters.


Does anyone happen to know which CRT projectors have throw ratios in the 1.2:1 range?


Thanks very much.


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Noah


[This message has been edited by noah katz (edited 08-29-2001).]
 

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OK I was just trawling ebay and 'ISCO' turned up a LCD wide angle lens at $9.99 I nearly had a fit as I was assuming it was an ISCO 1 but no, it is a wide angle lens that I think would give you short throw...


It has a threaded end but does have a 75mm diameter so a bit of DIY ?!?... Of course it may be useless for your purposes but at least you can email and try...


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Discussion Starter · #3 ·
PP,


I searched on ebay using short throw, but hadn't thought to use wide angle. I'll take a look.


Thanks


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Noah
 

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So does anyone know if a CRT lens(es) can be used on a DLP? I don't mind losing zoom, but of course I need to keep the ability to focus.


Thanks


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Noah
 

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Hi Ken,


"Loose the two end lenses,and you can make a mount out of what's left"


Do you mean loosen them, or get rid of them?


Do you know until about what year they used glass, and which brands?


Thanks a lot.


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Noah
 

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Almost all of the newer units (RPTV's) are using cheap silvered (polished) metal mirrirs. anythig older than about 5 years or so is virtually guaranteed to have a high quality glass first-surface mirror in it.


Loose, or.. get rid of the two end lenses. heck, all they will be,is in your way.


The entire CRT/lens assembly comes out in one big chunk in most of thse things. The lens is DESIGNED to have perfect focus in the corners, on that PJ, with the tube face a specific point away from the surface of the lens...and with the screen a specific distance away.(no edge focus capacity)



The lens off of a CRT FP PJ might be the only way out.. (inner/outer focus)something like a HD-6ML (a very nice lens).


Here's where you MIGHT have a problem.. the DMD or LCD or whatever, might not be at the right point to focus the thing properly... on the surface of the RP screen.


Calling all optics experts!!?! what the heck will happen here? anyone know? Or am I just being stupid about the optical situation?


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Ken Hotte

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[This message has been edited by KBK (edited 09-06-2001).]
 

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Discussion Starter · #7 ·
Yes, there's the potentially different distances between the CRT lens and the phosphors, and between the DLP lens and the chip; and also the fact that the former is expanding a raster size that's much larger than the DLP chip.


Re removing the end lenses, is it two lenses from one end or one lend from each end? And why remove them; what do they do in a CRT system that doesn't need to be done in a DLP?


Re focus, CRT lens sets have mechanical focus adjustmemt (at least my Toshiba RPTV does), and both CRT and DLP focus to a flat image plane, so it seems like that aspect wouldn't be a problem. Unless the phosphor imaging area isn't flat; is it?


Thanks


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Go to a place that services CRT RPTV's. They will surely have enough chassis that they want to get rid of. The entire assembly will be ther for you to fool with. Loose the two end lenses,and you can make a mount out of what's left (with a bit of thought) for your DLP. the lens will definitely be short enough throw. Re-positioning is possible (for edge fill) as the DLP is small enough. the chassis has more than enough room for you to fool with the positioning, and the mirror will be big enough. If you run an ad in the local paper, I can virtually guarantee that you will run into a 60-70" unit that you can haul away for nothing.. and use as the chassis of the beast that you are trying to create. If you strictly want the lenses, you will probably still have to take the whle thing. The great part is that you will definitely find high grade first-surface mirrros in these older units.


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Ken Hotte

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No.. but you could mount 3 LT-150's on their sides, and do a triple run, for a rez of 3072x2304. Mess with the lens mount angles, run a image scaling device, and presto. The ultimate HD workstation monitor. Might be decent for HT as well. Hey, ya never know. Some might lke it.



A rez to die for. Of course, you probably won't be able to do it, unless it was DVI in nature...


The 3 channel DVI converter. the PJ's, and the PJ box.. a bit of fiddling. It might be possible to do it for under $10K. Damn. I wish I had cash some times. I could build that in a week.


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Ken Hotte

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