[MF3D.FORUM:940] Re: MF Projectors

[Tom Hubin <thubin@xxxxxxxxx>]

Dr. George A. Themelis wrote:
> 
> >Efficient use of light is paramount in stereo projection because of the
> >37.5% (3/8) transmission of typical projection polarizers and 75% (3/4)
> >transmission of the viewing glasses. That means that 9/32 of the light
> >gets to the eye compared to non stereo projection.
> 
> I would like to challenge these numbers :)  Where do they come
> from?  In particular, I question the 75% cutoff of the viewing
> glasses vs. only 37.5% of the projector polarizers.  It seems
> to me that the projector polarizers will cut off more light
> than the polarizing glasses for the simple reason that the
> light is already polarized when it gets through the glasses.
> Any thoughts on that?

You and I are both correct, George. But please read what I said again. I
use the term transmission and you use cutoff. 

But to clarify what we have said for those who are wondering about the
numbers: About 38% of randomly polarized light is transmitted by the
projector polarizers as polarized light to the screen. About 76% of the
already polarized light from the screen is transmitted by the viewer's
polarized eyewear. I rounded off 38% to 3/8 and 76% to 3/4 cuz it was
easier to do the math in my head. 

I use transmission to indicate the amount of light that passes through
the optics, not the amount rejected. I try to avoid using values for
losses as they are difficult to combine. Transmission factors multiply
nicely so are much easier to use.

Since I was winging it with the final factor of 7 comparing efficiency
of mono projectors to polarized stereo projectors I am interested in
finding out if that is consistant with experience or somebody else's
numbers.
 
Tom Hubin
thubin@xxxxxxxxx
AO Systems Design