RE: ATM Anamorphic Lens (Slightly Off Topic)

[Anthony Stillman <atmer@flash.net>]

Mike,

In my response I neglected to note my sources.  My description was based an
anamorphic prism system invented by Brewster.  The compression ratio I
noted was lifted from a book by Daniel Malacara.  Like so much of his work,
there was no derivation and a good deal of assumption.  After reading your
response I too took out paper and pencil and like you came up with a
different answer.

Giving the top angle of the first prism as alpha (also the angle of
incidents of the wavefront as it exits the prism through the hypotenuse)
and the angle of refraction on exit as theta I arrived at a compression
factor of cos^2(theta)* cos^2(alpha) for a two prism system.  This differs
from you result.  In the limit of alpha going to zero the compression
factor becomes cos^2(theta).

I can only speculate about the physical constraints your projection system
imposes, however I will note that some anamorphs are placed before the
projection lens.

You mention a dearth of sources.  I noticed recently that Surplus Shed
http://www.surplusshed.com has two items which may interest you.  L1760 a
16.4mm dia. 1.55mm thick 0.08mm wedge and L2003D a 37.9mm by 22mm  30-60-90
Littrow dispersion prism.

Anthony