Re: Koehler illumination in conoscopic observation

Dear Kevin,

Thank you for your helpful reply. There is only
one easy way to insert a diffuser and that is in a pre-
mounted swing-out filter holder between the field lens
and the condenser. Any other approach would require
mechanical modifications to the scope.

A diffuser in the filter holder would work fine, provided
it is fine grained and does not rob too much light. The
filter holder accepts round glass 33mm in diameter.
Do you have any idea where to get a suitable diffuser
with this dimension?

Thank you again
GR.

"Kevin Cunningham" <smskjc@xxxxxxxxxxxxxx> wrote in message
news:19dbf726-22d6-46da-8579-7d96fac082e3@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Nov 27, 4:50 pm, "NoSpam" <NoS...@xxxxxxxxxxxxxxxx> wrote:
Hello,

On a Nikon scope of type L-Ke the illumination
is truly of the Koehler type. The filament of the
tungsten light is imaged onto the diaphragm of
the condenser lens and is centered and clearly
visible at the back focal plane of the objective
when viewed through a Barlow lens.

Koehler illumination is considered to be an ad-
vantage for most types of observation. It is of
apparent disadvantage when one wishes to ob-
serve the interference figures formed by bire-
fringent crystals using the conoscopic form of
observation in polarization microscopy. In that
case the interference pattern formed by the
crystal is superimposed upon the image of the
lamp's filament causing difficulty in clearly seeing
it..

Does anybody know of a way to get around this
problem? One might think of a diffusing filter
someplace in the path of illumination. If this is
a feasible approach where would one place this
filter and what kind should one use?

Thanks for any suggestions
GR.

use conoscopic observation of the
interference figures formed by birefrigent crystals in the
manner

In the good ole days, Kohler illumination was done with a lamp who's
filament was about as wide as your finger. However your just not
going to find any of those lamps.

A ground glass filter should be used, I'll bet there is a place for
one. Other wise I'd put it close to the lamp, if possible directly in
front of the lamp. Then, technically, your using critical
illumination, not Kohler but who cares?

Thanks,

Kevin Cunningham
SMS


.

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