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Microscopes, Course/Fine vs "Coaxial" Focus
(Dave) wrote in message om...
henning wrote in message ...
I believe the illumination scheme from a condenser under a slide stage
is the main thing defining a "biological" scope. If the illumination
is from above I believe this is considered metalurgical. Not sure if
this is the complete story. Many low power scopes can use either
illumination mode.
Not always in either case. I have a 1940's vintage AO that has
illumination either from the top or the bottom, as well as polaroid
filtering. Came out of a lab at the university, botany, IIRC. I
quite often use the Eppe illumination for examining algae, and have
been known to use the polarizing filters to check out crystals growing
as the solution on the slide dries. Transmitted illumination doesn't
do a lot of good for metalurgy, that's almost always reflected, and at
one time I had a 40's vintage metalurgical that used a carbon arc lamp
for the illumination. B&L had a scheme, the lenses themselves were
mounted in a lucite sleeve, and there was a coaxial tube in the barrel
of the microscope. The outer portion contained a light, and the inner
sleeve kept this out of the light path to the eyepiece. 40X is about
the highest magnification objective I've seen with this, but most
metalurgical stuff isn't high power anyhow. (40 X would yield 400X
when using 10X eyepieces, anything stronger than that in an eyepiece
and you're pushing things beyond what they were designed to do.
Standard design eyepiece for most scopes is 5X.)
Another common confusion is between binocular and stereo scopes. Both
have two eyepieces, but the binocular only has one objective, and is
NOT stereo. I have some 30's vintage AO's that have binocular heads
on them, but stereo wasn't a consideration and is not included in
them. One that I'm glad I did pick up, came from an electron
microscope. 7X, but 9" working distance. Best "sliver finder" I've
ever had. Also very good for finding that "click" in the rack of a
dial caliper.
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