P3D Re: De-polarising filter?

[Tom Hubin <thubin@xxxxxxxxx>]

> 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