49
Focus the specimen. It may be easier to focus a
stained specimen first or the edge of the
coverglass. Set Koehler illumination exactly (
→
p. 37), then find an empty area of the specimen
or remove the specimen.
Engage the polarizer (34.9 or 33.5a) and turn it
round the zero position until the optimum
extinction position is observed through the
eyepiece. This setting can be found particularly
accurately with a high magnification objective
(40x or 63x) as follows:
Open the aperture diaphragm (34.3) as far as the
stop, swing in the condenser top (10.1; 10.4).
Using the auxiliary telescope in place of an
eyepiece, focus by moving the front piece (30.2)
fix with (30.3) or just remove an eyepiece and
observe without an eyepiece. The polarizers are
exactly crossed when the two branches of the
hyperbola are as near to each other as possible
(35b) or form a blurred cross (35a).
Fix this crossed position with the clamp screw
(34.8).
Adjustment of the condenser prisms
If the equipment was delivered together, the
condenser prisms will already have been
adjusted at the factory, but it advisable to check
the adjustment from time to time, especially
after transport:
Pull out the objective-side prism slide (34.6; 32.8)
fully or partway.
Swing in the condenser top (10.4 or 10.1). Use
the auxiliary telescope (30.1) in place of an
eyepiece.
Engage the condenser-side prisms (34.2; 11.5)
one after the other and focus (30.2 and 30.3) the
auxiliary telescope on the dark diagonal
compensation stripe (Fig. 36). The compensator
must be inactive, i.e. the engraving
λ
must be on
the lower side of the analyser (34.1) or the
λ
and
λ
/4 plate (32.4) must be removed.
Fig. 36
Objective pupil with correctly centered compensation
stripe
Fig. 35a, b
Crossing the polarizers when observing through
an auxiliary telescope or Bertrand lens, high-aperture Pol
objective
a
exactly crossed,
b
not exactly crossed
Pos. a cannot be set if there is strain in the condenser or
objective, Pos. b is adequate for ICT and polarization contrast
a
b
Summary of Contents for DM L
Page 1: ...Leica DM L Instructions...
