Polarization single lamp twin projector.

[T3D Prof. Lunazzi <lunazzi@xxxxxxxxxxxxxx>]

P.J.Homer wrote:

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

> Maybe the "pile of plates polariser" mentioned above could be used.  
> Anderton used the transmitted light but the reflected light is also 
> polarised at right angles to the transmitted . There used to be a device in 
> Anderton's time called an "Elbow polariscope" which used light reflected 
> from a pile of glass plates for the polariser and a Nicol in the small 
> objective lens as an analyser for projecting images of microscopic 
> birefringent specimens.  The deviation of the transmitted beam by 
> refraction would probably not be as much as that by reflection so there 
> could be path length problems as with one of the types of prism.

Yes!, I agree. I was thinking on the subject yesterday and thought on
the plate polarizers, then came the information on Anderton's system.

A single glass plate polarizes 100% the 28% of reflected light, remaining 
not entirely polarized 72% of transmitted light (I can make the
calculation available to whom wants it, since it is one excercise of my
optics course, already typed). Reflectivity is 15% at the external
surface and same at internal surface, so that transmission of the
unpolarized part is 28 % (not 22,5 %).

It would be interesting to know why the Anderton system was not kept
nowadays, because if some residual of unpolarized light remains after the
plates, this could be eliminated by a polarizer sheet.

Just using the previous values I calculated that 6 plates allows for 10%
of unpolarized light (20% of one polarization) and proportion between
both polarized beams would be 1/0.8 .
The angle between both beams would be 66 degrees, a mirror at the
reflected beam could make them parallel.  Aluminum reflective coating,
f.ex., absorbs 18% of the light and balance between intensities would be
equal. Total absortion: 20% , distributed within the mirror and the
polarizer sheet.  The ghost image would be 5 times less than with the
ordinary system.

If someone is interested in the calculations, they are simple, and I
would be glad to interact in order that he could also certify my
results.

Thanks P.J. Homer for the information.

Jose'
<lunazzi@xxxxxxxxxxxx>
<http://www.digicron.com/lunazzi


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End of TECH-3D Digest 198
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