Archived posting to the Leica Users Group, 2006/02/11
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]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 > > >_______________________________________________ >Leica Users Group. >See http://leica-users.org/mailman/listinfo/lug for more information > > > >