LAND's filters

[P3D Paul S. Boyer <boyer@xxxxxxxxxxxxx>]

It is true that Edwin Land did not discovery polarization, or
polarizers.  As a geologist, I remeber well that polization by
minerals was known well back in the last century.  When Henry Clifton
Sorby invented the thin-section (about 1857), he also developed the
techniques of optical mineralogy, the way of identifying minute
mineral grains in thin-section by purely optical methods.
Polarization is a major part of the technique, which is so complex
that it requires a two-semester graduate course.  Sorby figured it
out in about one year.
Anyway, the usual method of making a polarizer was to cut a precisely
oriented piece of calcite crystal.  It was bulky, and the crystals
were limited in size.  People had the idea of using numerous small
xtals instead of single, large ones, but the trick was to get the
small xtals aligned.  As I recall, Land did this by imbedding the
elongate xtals in a plastic sheet, and then stretching the sheet of
soft (warm?) plastic, causing the minute xtals to become aligned.
This produced a cheap, thin, light polarizing sheet, and made
polarizing material available and practical for numerous uses, among
them projection stereo, filters for photography, and sunglasses which
selectively cut reflections from horizontal surfaces.
His success gave him the capital to develope the instant camera.  He
continued experimenting even while administering a wonderfully
successful business.  I once met Dr. Land, and found him to be a
person of great cleverness, curiosity, and enthusiasm.
I am not surprised to hear that the theory of projection stereo was
already figured out in the last century.  The more I read of 19th
Century science and technology, the more impressed I am.  As Barrie
once said, "Always, always rememeber to denigrate the Victorians.
There will be time enough for humility when we try to equal them."
--Paul S. Boyer   <boyer@xxxxxxxxxxxxx>


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