Single lamp twin projetcor.

[T3D Prof. Lunazzi <lunazzi@xxxxxxxxxxxxxx>]

In Tech3D digest 200 P.J. Homer included interesting information, I will
try to summarize including my comments:

It seems that he states that there is no wavelength dependence on
dividing a beam by a prism polarizer.
I agree with that, because the angle of total reflection should have
enough tolerance as to include all visible wavelengths.  The paper
catalog of Newport Research Co. offers a Glan Prism acting from 320 -
2300nm wavelength.
But is expensive.  The internet catalog does not include the item yet
(<http://www.newport.com>).

The tolerance on the critical angle will allow not parallel light, but
it would be convenient to put the condenser before the prism.

Regarding the Anderton vs. an anaglyphic system, it is clear that the
anaglyphic is better in having only one projector and not needing metal
screen, but renders no colors.

Regarding my proposal of upgrading the Anderton system with a polarizing
sheet, the advantage remains in the calculation's result: less absorbed
energy and less parasitic image.  But I remain interested in the less
absorbed energy case. The critical angle for polarization (Brewster's)
has good tolerance to angle variation, considering the condenser before
the plates.  Fragility of glass plates would be a critical problem if
they must be thin in order to not include lateral displacement on the
reflections, it seems to me not important.

I prepared the calculations in English and other languages to put in my
internet catalog (WWW), but something is not working well when I try to
put it in the Geocities server.  It seems that the graphics (including
formulas) I made as .gif , were not accepted to enter into the server. 
The .htm and .jpg file are accepted.
Are any of you supplier of files to Geocities, do you think that it can
happen that way?. What is the difference between gif,  gif87a , gif89a ?.

I can send the calculations to who may be interested, about 30 kb, in
format HTML as a .zip file.

The problem of the parasitic image seems to me now less important
because of a report I received from Peter Abrahams. I understood that,
even if you polarize perfectly at the projection step (linear
polarization case), tilting of the observer's head introduces parasitic
(ghost) images.  

Is not possible that it is just because of the facility of mass
production of a single projector that Anderton's system is not made
anymore?.  Is there any Anderton's system available for testing? (it
would not be difficult to put a polarizer sheet inside). It seems that
Anderton, cited during the 1880s, died before Edwin Land (died 1992,
aprox.) presented available cheap polarizers.

Yours,
Jose' 

lunazzi@xxxxxxxxxxxx (Netscape 3.0, eternal address)
http://www.digicron.com/lunazzi         

http://www.aleph.com.br/kce   (sobre Esperanto/pri Esperanto)


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End of TECH-3D Digest 201
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