Leica DM R Serie Mode D'emploi page 83

As these interference patterns occur in the pupil
they are not normally visible during normal
microscopic observation (orthoscopy). Their
observation can be improvised by removing one
of the eyepieces and looking into the tube with
one eye from a distance of a few centimetres.
Observation is better with the auxiliary
telescope for phase contrast (Fig. 51). Other
crystals in the field of view disturb the
interference patterns of a crystal in the centre,
so that this needs to be isolated. This can only
be done with the polarized light microscope
(tube optics HC P, with Bertrand lens and iris
diaphragm). This module also has a second tube
lens allowing additional magnification by a
factor of 1.6x.
Setting the microscope for conoscopy
The most suitable object areas for conoscopy
are those that show the lowest possible phase
differences (chart in Fig. 56).
Exact objective centration and exactly crossed
polarizers are essential for perfect conoscopical
observation. Turn an objective with as high an
aperture as possible (e.g. 40x, 50x or 63x) into
the light path. Open the aperture diaphragm
(54.9). Move the crystal you want to examine as
near to the centre of the field of view as
possible.
Turn in tube lens 1.6x.
Narrow the iris diaphragm (Fig. 58, pos. I) to match
the size of the crystal, stopping down the field
diaphragm (54.10) as well if necessary.
Push in the Bertrand lens (58B) and focus by
rotating the control until the interference image
or the circular bright-dark edge of the pupil is
focused. Centre the Bertrand lens if necessary.
This is done by inserting the hexagonal screw-
driver (1.1) into the two holes (54.1) in succession.
Align the right-hand eyepiece so that the
crosslines roughly correspond to the directions
of movement for the centration process.
Fig. 58 Functions of the der Pol tube optics HC P
Controls Orthoscopy 1x
Tube lense (54.11) 1x
Iris diaphragm doesn´t matter as matched of the field > object
Bertrand lens not in light path
(54.2)
Polarizers in or out
(54.3 and 54.16)
O/B
I
1x
Orthoscopy 1.6x Conoscopy
1.6x 1.6x
of view
out in
in or out crossed
(not for dichroism/
pleochroism)
O B
I I
1.6x 1.6x
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