T3D Re: T3D Re rear projection polarisation

[bercov@xxxxxxxxxxx (John Bercovitz)]

P.J.Homer writes:

> I understood that it is possible to do polarised rear projection and i have
> made some tentative experiments myself. Although I dont understand how it
> can work as they seem more equivalent to ordinary screens than to silver
> ones .

I dunno.  The ordinary screen is beaded or white paint.  Beaded has multiple
screwy reflections which depolarize.  Not sure how white paint does it but
white paint is TiO2 crystals, clear, very fine.  However, if a rear-screen
has only a flat front surface and many facets on the back surface, it seems
like the facets would just change the direction of the light following Snell's
law and not have any other effect.  Of course the front surface has to be
good so that you don't have it reflecting light back into the screen mat'l.
That would give you multiple reflections and I think that's where the danger
lies.

John B


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