50
PH 2
Phase contrast objective, with phase ring no. 2
built in. For phase contrast observation, the
corresponding light ring 2 in the condenser must
be selected, see page 72.
Phase contrast objectives all have green
engraving.
P
Extremely low-strain objective for polarized light
microscopy, with red engraving.
BD
Dry objective with M32 thread, for BF and DF
(incident light).
↑
Leica objectives with infinite tube length can be
used for both transmitted and incident light.
However, objectives corrected for coverglass
thickness 0.17 are only used in transmitted light,
as incident light specimens, of course, are never
covered (except for fluorescence specimens).
The upwards arrow
↑
indicates that this
objective for use with or without a coverglass
should only be used in transmitted light, as
disturbing reflections may occur in incident
light. This is indicated by the letter T instead
↑
of
arrow in the objective charts.
OIL
Oil immersion objective: it may only be used with
DIN/ISO standard optical immersion oil. For
apertures over 1.25 the engraving 0 or 0.17
shows whether the objective should be used
with or without a coverglass. The coverglass
thickness should be adhered to as exactly as
possible (
±
5
µ
m) for apertures larger than 1.32.
Immersion objectives with an aperture greater
than 1.35 should only be used in a temperature
range of 20 – 25
°
C. the refractive index of liquids
varies considerably at different temperatures,
the optical coordination between the objective
and the oil changes during major temperature
fluctuations. The quality of the image may suffer
in the same way as for the wrong coverglass
thickness. Also remember that if specimens are
stained in strong colours, the temperature of the
immersion oil may rise by a few degrees due to
the object absorption. The illuminated object
field should therefore be strictly limited to the
area observed (Koehler illumination, page 69)
and the illumination intensity reduced if
necessary using a neutral density filter or the
lamp supply.
The immersion oil is applied with the stage
lowered or the objective turned out of the light
path, taking care to avoid air bubbles. It is later
removed with a clean cloth and ethyl alcohol, cf
p. 111.
First read the safety data sheet (available on
request from your Leica agency).
