Leica DM R Serie Mode D'emploi page 78

Make sure the specimen, the condenser lenses
and polarizers are clean, as this will affect the
accuracy of the setting.
A particularly accurate method of setting this
position is to use the built-in Bertrand lens (54.3
with 54.11) on the polarized light microscope as
follows:
Turn a high-magnification objective into the light
path (e.g. 40x, 50x, 63x).
Open the aperture diaphragm (54.9) (pos. PH).
Focus the Bertrand lens or auxiliary telescope
so that the slightly brighter circle in the centre of
the field of view is sharply defined. If you slightly
adjust the polarizer you will see 2 dark stripes
that close to form a cross when the polarizers
are exactly crossed (55a). If objectives and
condensers without the engraving "P" are used,
the cross usually does not completely close.
Fig. 55 Crossing the polarizers, viewing with a Bertrand lens and a high-aperture objective
a exactly crossed, b not exactly crossed
Pos. a cannot be set at all if there is strain in the condenser or objective
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Index adjustment on IC/P p olarizer
If the two index marks on the mount of the
polarizer (28.4) do not exactly coincide when the
polarizers have been crossed: alter the index
adjustment with the centering keys (28.3 or
54.17) until the index marks coincide. After this
adjustment the crossed position of the
polarizers can be set reproducibly or checked.
Examinations in polarized transmitted light
The following section is only intended as a
rough guide to the various examination
methods. Further details are to be found in the
Leica booklet "Polarized light microscopy",
code no. 923 009, and in many books on the
subject.
Examinations
Only one polarizer
If you want to examine specimens with other
transmitted light techniques such as brightfield,
phase contrast and darkfield instead of with
crossed polarizers, it is usually sufficient to dis-
engage either the analyser or the polarizer.
a
b