ATM [Hist.][Long] Schmidt corrector plates in old televisions/Slumping Schmidt correctors

["Matt Considine" <matt@considine.net>]

Hi,

I came across a reference that mentioned Polaroid Corp. making 
Schmidt corrector plates for television sets in the post-WWII years.

Does anyone know anything about this?  I'm curious about how 
they made them (perhaps the profile did not need to be that 
accurate) and whether or not one could be used for ATMing.  

The diagram I saw seemed to indicate that the image was project 
from the RoC of a spherical mirror back to the mirror, from which it 
was reflected through the plate to the screen.  I assumed that this 
involved both a relatively small plate diameter as well as a short 
focal length mirror.  Yet the sizes might be useful for an ATMer.

Also, in poking around for non-vacuum methods for figuring a 
Schmidt profile, I came across a discussion of the work of a 
gentleman named Edgar Derry Tillyer at
http://www.geocities.com/Heartland/Flats/3808/page5.html

Quoting in full from that page :
"Doc worked on a lens system that was part of a secret military 
optical device during the War. These secret devices required one 
of the "Schmidt Corrective Plates." The plate was to be used with a 
circular lens with multiple curves used in high speed astronomical 
photography209 and for night viewing instruments. Wider angles 
than any others in use at that time were required.210 Before World 
War II there was less that 50 such corrective plates in the world. 
During the war, there became a very real need for many more. 

The methods to produce the corrector plates, however, were 
slow, exacting and difficult. It was a tedious hand process that 
took weeks and even months for a skilled operator to grind and 
polish one of these plates. 

The United States government requested that the AO assign Doc to 
the problem. Doc was asked to find a method to mass produce 
something that defied mass production. The war effort depended 
on it. The plate was discovered in Germany, one of the greatest 
optical centers of the world, and they were rushing to find a 
solution to this problem at that very time. They were actually 
working on it on a twenty-four-hour basis. 

Doc studied the difficulty with the Schmidt Corrective Plate 
production methods. He soon saw through the problem and 
developed a process, called the Green Block process, to produce 
the corrective plates in a few hours instead of days as before. He 
did it by heating sheets of ground, polished optical glass until it 
dropped or "sagged" onto a refractory mold that had been 
previously ground to the desired shape. This allowed the
circular, wavelike Schmidt curves to be imparted to one side of the 
lens. This mold had a surface that could only be expressed by a 
very complicated mathematical equation. The other side was later 
reground in the traditional manner and polished. 

The Germans were right on Doc's tail but could not get past the 
hurdle of distortion and sticking. Doc solved this problem by putting 
a kyanite 211 clay and other ingredients against each other in 
molds.212 

Louis ROWE was the chief mathematician at the Research 
Laboratory. He had become associated with Doc during the 
development of the "Green Block" process and said that he was 
amazed at Doc's grasp of these mathematical concepts and 
equations and his practical, simple methods to perform complex 
tasks.213 

It was called the Green Block because it was a green colored 
mold.214 "

Later on that page :

"Once the war was over, it became apparent that the discoveries 
made during the war, could be used to better civilian life. Doc's 
revolutionary Green Block heat molding process used for the 
Schmidt plate molding was used in the postwar period for the 
manufacture of telescopes and large television sets. It was also 
used in a device which was used to detect stomach cancers.218 
The telescope at Palomar Observatory, in San Diego County, 
California, has a mirror 72 inches in diameter with a 48-inch 
diameter corrector plate made using Doc's Green Block process 
and was designed by Dr. GLANCY.219 220 "

(The numbers are bibliographic references)

Anyway, has anyone tried slumping a complex profile such as 
this?  I would think it would be a bear to get control of ...

Regards,
Matt Considine