Re: polarizing filters

[P3D Alexander Klein <klein@xxxxxxxxxxxxxxxxx>]

P3D  <s.spicer@xxxxxxxxx> writes regarding henry chung  <magicmtp@xxxxxxxxxx>

> >I would like to ask if any one knows where I could buy a pair of high
> >optical quality heat resistant polarizing filters. I am building a pair
> >of 35-mm film projectors for 3-d projection. They have lamp houses of
> >5,000w  xenon arc.
> >I had tried Hoya polarizing filters, they lasted 5 seconds and the
> >centre part turns yellow and becomes transparent.
> 
> The first thing that came to mind was where are you putting the polarising
> filters? In a conventional projector there are generally three choices:

[... stuff deleted ...]

> 3. On the outside of the projector in front of the projection lens:
> This is where I ended up putting my polarisers. They have worked fine here
> for over 10 years. I don't like it as the polarisers are exposed to knocks.
> I used standard camera polarisers (that rotate for adjustment), and clamped
> them down with a bracket once set. The heat here is quite minimal. It could
> be that if you haven't tried putting your polarisers here, it may be worth
> trying. I like knowing that the light leaving the projector is as well
> polarised as it can be, and this position is best for this.

IMAX 3D (polarized) has large polarizing filters mounted approximately
40 cm in front of the projection lenses - and they use even brighter
projectors.

By the way: will your projection be installed at any public place? I 
suppose it's not for home-projection :-))

alex


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