zGman
Joined: 22 May 2006
Posts: 599
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| Posted: Wed Oct 03, 2007 8:56 pm Post subject: refractive index! |
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Nothing gets by Ile is right!
The mismatch of refractive index (RI) causes internal reflections, thus lowering light output and contrast ratio.
The transition from air (RI~1.0) to glass(RI~1.5) and vice versa causes approximately 3.8% reflection,
so about 8% total light lost just going through a window.
The glycol matches closely the tube glass (around 1.5) and the acrylic c-element (around 1.424),
which will substantially decrease reflection at those two interfaces. The other lens elements have
all got thin film anti-reflective coatings, which is one very good reason you don't want scratched
lenses, and be darn careful cleaning, as the coatings on acrylic lenses are soft, because
they can't be done(vacuum deposition) at high temps like the ones on glass. The glass elements
are internal to the projection lenses, the parts you can touch are always acrylic (AFAIK)
As far as heat output, the housings themselves may not get very warm, but I definitely noticed
that the middle of the c-elements were quite warm, when I was swapping lenses on the 9500
during some lens testing and the PJ was still running continously.
Cheers,
Galen
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