Archived posting to the Leica Users Group, 2006/02/11

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Subject: [Leica] Need HELP with ID of LF lens
From: douglas.sharp at gmx.de (Douglas Sharp)
Date: Sat Feb 11 15:47:34 2006
References: <C013BF53.83879%mak@teleport.com>

Mark, if it is for what I think it's for, analytic chemists, 
metallurgists, physicists, toxicologists.........
Fiffraction Interferometry can be used for  finding out the atomic 
structures of incandescent gases, wavelengths of light and general 
chemical analysis based on the light given off when something glows. 
They use something similar for working out what's inside stars making 
them tick. What puts me off a bit is the aperture construction. How big 
is the lens? And does it have any marks on the barrel showing where and 
how it might have been clamped into a test rig? If it's for a job like 
this it probably wouldn't be coated either.
If it was used with x-rays it would have extremely high diffraction/low 
absorption glass elements too, high resolution is the point (exact back 
focus value!), low contrast just wouldn't be much of an issue in this 
case. But it does make it a very elaborate and expensive piece of work , 
and unfortunately, probably pretty useless piece of equipment for 
anything but what it was planned to be used for.
The absolutely exact EFL must be to do with getting an exact focus on a 
target by measurement without any kind of focussing equipment (you 
didn't mention whether it was focussable)

I'm trying very hard to remember the set-up we used in my last years at 
school in the UK - I can remember a lens and a mask with very fine slits 
on a stand between the test object and the lens, then something about 
Fraunhofer lines which told you what elements were represented by which 
colours of the spectrum, I think Sodium was orange, but this is getting 
on for 35years ago so I'm a little
dusty on the theory. Let's hope someone who's used a similar set-up can 
tell us more. But I still think the accuracy to 3 dp's makes it part of 
a lab tool. The conversion of the inches to cm/mm is interesting too, is 
it a US or UK lens that has been used in metric labs, or the other way 
about? Somebody thought it was important enough to convert the values 
very accurately, and only lab people took the bother of making pretty 
cases for  things like that.
cheers
Douglas
BTW, are you anywhere near the Lawrence Berkeley National Labs in 
California, that's the kind of place it would come from

Mark Kronquist wrote:

>So who would have used such a beast 
>
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In reply to: Message from mak at teleport.com (Mark Kronquist) ([Leica] Need HELP with ID of LF lens)