Date: Fri, 08 Jun 2001 09:56:22 -0400

Author: Gerald Zani

Subject: Re: 3D video by polarised light



I have not tried the 3D video method you describe. I saw a 3D method
in 1996 at Notre Dame U. that uses two cross polarized slide projectors,
a silver screen, and polarized viewing glasses.

Have you tried this before trying the video method?

I did not know that RGB video is polarized. You might try it first without
the RGB depolarizer? If you need to depolarize the RGB components I
believe you can
use either a 1/4 wave plate or a circular polarizer, which contains a 1/4
wave plate.

Here is some info on 3D:

BTW I think that one of my faculty, Hank Gerritsen, will be visiting your
department? Jerry

At 12:17 PM 6/8/2001 +1200, you wrote:
>Dear Tappers
>I have been asked by a person here in Christchurch, New Zealand, about
>projecting 2 cross polarised video pictures in order to allow 3D viewing. He
>proposes to do the following:-
>1) Attach a mirror arrangement to the front of a video camera to record a
>picture split horizontally so as to get two 8:3 aspect ratio pictures
>instead of
>the usual single 4:3 ratio picture.
>2) Back project the resulting two frames (superimposed) by using the same
>device on a video projector and with crossed polaroid filters at 45 degrees
>(each way) to the vertical in each beam.
>3) Equip the viewers with crossed polaroid spectacles.
>4) Voila! 3D movies
>Assuming all this is possible, the problem he approached me with is that he
>finds that the individual RGB components from the video projector are already
>polarised independently of one another. He wants to unpolarise (depolarise?,
>randomize?) these three components and believes there is such a thing as a
>"homogeniser" which will do this. The back projection material will apparently
>retain polarisation but rotates it by 90 degrees in transmission.
>Has anyone out there tried anything like this? Did it prove feasible? Do
>Homogenisers exist? If so, where can they be obtained? Are they made of
>expensive unobtainium?
>Your comments would be appreciated.
>Alistair Lightfoot
> Alistair Lightfoot, Teaching Support Technician,
> Physics & Astronomy, Teaching and Computer Support,
> University of Canterbury, Phone : +64 3 364-2987 ext. 7611
> Private Bag 4800, Fax : +64 3 364-2469
> Christchurch 8020, mailto:
> New
> Zealand.

Gerald Zani
Manager of demonstrations
Department of Physics
Brown University
Box 1843
Providence, RI 02912

Do a little more of that work which you have confessed to be good,
which you feel that society and your most Just Judge rightly demand of you.
Cultivate the tree which you have found to bear fruit in your soil.
If you have any experiments you would like to try, try them.
Now's your chance.
Henry David Thoreau, Journal entry, 1850.