T3D Rear Projection Stereo

[Bill Davis <bd3d@xxxxxxxxxxxxx>]

> I'm sure this has come up before, but I just can't remember.  Is it
> possible to maintain polarization using a rear-projection screen?
>
> -Jim C.


Most rear-projection materials for flatties are flexible vinyl.  They
depolarize lots. 

Previous Photo-3D postings have mentioned a Depthography in NYC that has a
functional r.p. setup.  I never got a reply to my query to them, so I don't
know what they are using.

Stereo World did an article a few years back about the Norwegian Forestry
Museum in Elverum that has a r.p. stereo theater.  Very limited info on the
material used for the screen, though.  No manufacturer listed, just a
description of the screen as a polymetamethyl acrylate material. Spent a
lot of time searching the net for this one, to no avail.

The Black Screen from QD Technologies is probably the best, but it ain't
cheap.  According to Brad Nelson of QD, a 4x6 ft. screen is in the $4000
range, less a bit without the frame.  Since I *am* cheap, I didn't pursue
this one.  Might be feasible for someone with corporate backing, though.

The two materials I have tested successfully are both from Da-Lite.  One, a
material they call Poly-Lens is a three-part composite with a rear fresnel,
center glass diffuser and front lenticulated panel.  Works great, with
about the same corduroy appearance as a lenticular silver screen.  A bit
annoying for something like a Project-or-View, but unnoticeable at further
distances.  Don't know about price.

The other product is a new addition to their line called Dai-Nippon Wide
Angle.  See the website http://www.da-lite.com/Hotspot/dainippo.htm  

This material is similar to the Poly-Lens, in that it has a fresnel rear
surface and   lenticular front, but it is all one sheet of acrylic.  The
fresnel and lenticles are so fine that this material looks frosted.  This
seems at least as good as my Da-Lite silver screen in initial tests.  

I've put my testing on hold for a bit, awaiting samples of polarizing
material from Polaroid and the arrival of a 2D Project-or-View from a
recent eBay auction.  This will allow me to test the materials a bit more
easily, I think.

If anyone is interested, Polaroid has a tech page for their linear
polarizing materials at   
http://www.polaroid.com/products/oem/polarizers/products/lin-polar.html


Will let you know what I find.
Best regards,
Bill Davis
mailto:bd3d@xxxxxxxxxxxxx



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