36
4.1 Coaxial coarse and fine focusing
The coarse drive (53.1) and the fine drive (53.2)
act on the objective nosepiece and the objec-
tives.
The sample is focused by raising or lowering the
objective nosepiece and the objective that is cur-
rently in the light path.
The position of the stage remains unchanged,
making it extremely stable and suitable for heavy
samples.
The total vertical travel of the coarse and fine
focusing is 7 mm, from 2 mm below to 5 mm above
the stage surface.
One drum interval of the fine focus corresponds
to a vertical movement of approx. 2 mm of the
objective nosepiece (53.2).
When focusing the specimens and altering the
x/y position, please take extra care when using
high-magnification objectives!
When objectives with high magnifications and
short working distances (from 50 x upwards) are
used, the specimen and the stage insert may
easily be raised and tilted.
When the specimen is scanned, the front lens of
the objective may then knock against the edge of
the stage insert.
4 Start-up
and operation
n.b.!
Before rotating the nosepiece and changing
objectives of 50 x–250 x magnification, lower the
coarse and fine focus drive if possible, to avoid
contact between the front lens and the stage in-
sert.
n.b.!
Caution with special objectives PL FLUOTAR 100 x
OIL, PL APO 100 x, 150 x, 250 x!
With these objectives, the front lens and the
stage insert come into contact as soon as the
objective is moved over the edge of the inner hole
of the stage insert (Fig. 54.1).
n.b.!
Caution with stage insert with 40 mm inner hole!
When using high-magnification darkfield objec-
tives above 50 x, only about 38 mm of the inner
hole can be used as the annular mirror lifts the
stage insert at the edge.