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Tony

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Posted on Friday, February 24, 2006 - 12:20 am:   Edit PostDelete PostView Post/Check IPPrint Post

Hi folks,

Today i viewed a passive stereo setup and was blown away, i have a 60hz LCD 1280x720p projector and was thinking of buying another one and then hooking them up in passive mode.

has anyone done this?

Also has anyone tried it with the sanyo plv-z2 this is my projector. I don't want to buy another projector to find that it doesn't work.

my projector has a svideo and dvi connection, would it still work if i get a dvi to vga adapter.

any help much appreciated


many thanks
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Alatar

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Posted on Friday, February 24, 2006 - 2:08 am:   Edit PostDelete PostView Post/Check IPPrint Post

Hard to do with LCD projectors, as the light from the projector is prepolarized, and in many cases the green is polarized perpendicularly to the red and blue.

Barco used to make a matched set, where one projector had the polarizations set to be 90 degrees offset from the other, but if you use two commercial projectors they will both have the same (pre)polarization.

This is why DLP projectors are so much better for passive systems.
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Tony

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Posted on Friday, February 24, 2006 - 2:52 pm:   Edit PostDelete PostView Post/Check IPPrint Post

'This is why DLP projectors are so much better for passive systems'

That is not necassarily true, i saw this pasive stereo setup done on two lcd projectors which had i think a resolution of 1080x900 per projector and they were using circular polariazed glasses and it really blew me away, there was huge depth and also the images flew right of the screen just like in imax theatres. the cost of both projectors were about 18,000 dollars which is not what i can afford.

So how come this projection setup was so amazing and you say dlp is better?
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Scott Warren

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Posted on Friday, February 24, 2006 - 2:53 pm:   Edit PostDelete PostView Post/Check IPPrint Post

Actually, thanks to Peter Wimmer, not so hard to do.

In Stereoscopic Player, use the "DualScreen Output|StereoBright" view method. This swaps the Green signals between screens. (You have to have a computer with dual video output, of course)
Then you just need a pair of Wave Retarder filters to rotate the polarization angle. Assuming the projectors are identical, if for example Green is vertically polarized and Red and Blue are horizontally polarized, get a 45° filter and a 135° filter. Now you're in business!
Very little additional loss of light through the filters, either.

Scott
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Tony

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Posted on Friday, February 24, 2006 - 3:05 pm:   Edit PostDelete PostView Post/Check IPPrint Post

Hi Scott,

What if i want to play PC games using two LCD projectors will it still be possible, as those settings in peter wimmers stereoscopic player can only be used for movies, so how do i get it to work for games?

Also with this dual lcd setup i would need a silver screen, do you know if i can make a DIY silver screen and how do i do it?

sorry for all the questions but do you also know if my projector will defintely work as if i go ahead i will need to buy another LCD projector identical to my one for it to work and i don't want to find after i buy it that it does not work.

i have only a dvi in, on my projector would i need to use a vga adapter?

do you know of any more sites that go into detail about passive lcd projector setups?

With passive lcd projection, do you use linear or circular polarized glasses or both?

Is there a large amount of 3d films on the market that has the correct format for passive lcd projection? I heard it's in the hundreds is that true?

Okay sorry last question with passive lcd projection can you play frame sequential 3d movies, page flipped, over and under, side by side, sync doubled, like all of the formats out there?

sorry for all the questions but am really intrigued by all this stereoscopic 3d goodness and would love to have all my questions answered as i am really looking to buy into another projector or even get a second hand one.

any help much appreciated


many many thanks
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Alatar

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Posted on Friday, February 24, 2006 - 3:24 pm:   Edit PostDelete PostView Post/Check IPPrint Post

I didn't mention the wave retarders as this feel under my definition of "hard to do". Also, all the experiments we have done with them result in at least some artifacts in the form of magenta and/or green tinting in the corners, although admittedly our tests did not involve perfect mounting of the filters.

You can test this with your existing single projector using Saran-wrap (which is a surprisingly good 1/4-wave retarder) and polarized glasses; if you can get it so that holding the glasses in a normal orientation one eye is completely blocked and the other completely transparent (all colours) then it should work. Double check by rotating the glasses 90 degrees, then the other eye should be visible instead.

The above is for linear polarization only, circular is for a different kettle of fish.

Your point about games and green is correct; one way to fix this would be custom dual VGA-cable with crossed green cables (provided of course the outputs were gen-locked).

DVI vs VGA cables isn't an issue as they carry the same wires, you can use converters to switch back and forth as neccessary.
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Alatar

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Posted on Friday, February 24, 2006 - 3:28 pm:   Edit PostDelete PostView Post/Check IPPrint Post

Added: sorry, "fell", not "feel" and re. the VGA vs. DVI, the DVI cable carries additional wires which will allow your projector to sync better to the signal; your best choice would be to get a video card with dual DVI outputs and use exclusively DVI cables.
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David6768

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Posted on Friday, March 10, 2006 - 3:56 am:   Edit PostDelete PostView Post/Check IPPrint Post

I would say if you get a second LCD projector you had better get the exact same make and model as the one you have or I could see you having a heck of a time aligning the two if you could at all. I think this might be obvious but you mentioned getting one second hand so I wanted to make sure you were talking about the exact same model as the one you have. I'm pretty new to this stuff but it would seem to me different throw distances and different lens manufactures would make it impossible to align the two images up well enough to get a good stereoscopic image. Any 3D guru out there correct me if I am wrong.
David
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Hornet

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Posted on Friday, March 10, 2006 - 11:25 am:   Edit PostDelete PostView Post/Check IPPrint Post

I thing with LCD projectors and linear polfilters are associated some color changes problems (the LCD projectors are internal polarised).From 3 colors the 1 had different polarisation, and this can by problematic for passive projection.
For passive is better DLP and for active setup too. I think good active setup for home use is more more cheaper and ev. better.

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