P3D Re: De-polarising filter?

["gl@xxxxxxxx" <gl@xxxxxxxxxxxxxx>]

Hmm... from Peter Homer's post (and what I'm seeing) it looks like the
different primary colours aren't all polarised in the same direction, so I'm
guessing this approach wouldn't work?  Unless I misunderstand the effect a
half-wave retarder would have (wouldn't surprise me ;).
--
gl

----- Original Message -----
From: "Tom Hubin" <thubin@xxxxxxxxx>
To: "Multiple recipients of list PHOTO-3D" <photo-3d@xxxxxxxxxxxxxxxxx>
Sent: Friday, January 21, 2000 11:19 AM
Subject: P3D Re: De-polarising filter?


> > The idea is to insert this between the projector lens and the polarising
> > filter, to get the max lightoutput before the intended polarisation
occurs.
> > So, do they exist, how about in convenient filter form, do they have an
> > adverse effect on image quality, and, most importantly, where could I
source
> > such a thing (in the UK)?
> > --
> > gl
>
> Hello gl,
>
> There is a better solution. If the LCD output is linearly polarized.
> Circular and elliptical polarization is also possible but not common.
> You can use a half wave retarder to rotate the polarization without
> loosing any light. This is even better than using a polarizer which
> absorbs much of the light.
>
> You can get broad band visible half wave retarder sheets from American
> Polarizers in PA. I found them on the web once. Spoke to somebody who
> sent me a 2 inch square sample. Used it on an LCD display that I could
> not see with polarized sunglasses. Rotated the display polarization so
> that it was compatible with the sunglasses.
>
> Maybe Edmunds Scientific has the stuff. The sheets are easily cut with a
> blade or scissors. Nearly transparent so very little light is lost.
>
> Place the sheet between the projector and the screen. Then rotate the
> sheet. The polarized light will rotate twice as much. So rotate the
> sheet until the light at the screen is polarized whatever way suits you.
>
> Tom Hubin
> thubin@xxxxxxxxx