Re: ghosting

[T3D Prof. Lunazzi <lunazzi@xxxxxxxxxxxxxx>]

John Vala wrote:

>    The output of these polarizers is linear (as opposed to circular)
> so they will work with your typical polarizing glasses.  I'm not sure
> how they will take the heat (how much heat will there be? We don't know),
> but to quote the catalog "Our polarizers are made of a Dichroic Polarizing
> Sheet sandwiched between selected strain-free glass plates.  Because
> dichroic materials function by selective absorption, they cannot be used in
> high power laser beams"......  Well, we're not using high power lasers but
> you get the idea about heat. I wouldn't think they'd get a whole lot warmer
> than lower quality polarizers placed over the outside of a projector lens
> where outside ambient air is continuously circulating over it.

I agree, although I do not have figures (values, numbers) with me now,
polarizers absorb *almost* 50% of the intensity due to its basic principle.  
The difference between 50% and the real value is negligible when calculating
energy.

There is another absorbtion, natural and independent of polarization,
much greater than this and that should be indicated also.

Usually, polarizers with high extinction ratio also have high absorbtion
(appear darker).

Because in Brazil we have much Calcite (birefringent crystal) I thought
many years ago about making an illuminator for projectors which divides 
the original beam into two with opposite polarizations, absorbing no (or
almost) no energy.  It would be a double projector, using one lamp and a
long crystal, about 30 cm long, 80 mm x 40 mm wide.
I do not know if such a long crystal can be found, somebody talked me
about needing to assemble two or three.

It could have been a task for some student of physics here, but the
person did not finally come to work.

There could be other ways of dividing polarization between the lamp and
the photographs, did you hear of something similar?.

Yours,
Jose'

lunazzi@xxxxxxxxxxxx (Netscape 3.0, eternal address)
http://www.digicron.com/lunazzi    
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End of TECH-3D Digest 196
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