Leica DM L, Инструкция по эксплуатации

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42
Immersion condensers
The condensers CL/PH 0.90/1.25 OIL and UCL
0.90/1.25 OIL (Fig. 7) are usually used dry. The
maximum illumination aperture is then 0.90. Both
condensers can also be used with immersion oil
(30.4). 1 – 3 drops of immersion oil are applied to
the front lens, the specimen is put on the stage,
avoiding air bubbles, and Koehler illumination is
set as usual,
→
p. 37. The optical coupling
medium then allows apertures of up to max. 1.25,
i.e. an improvement of the resolving power of
high-aperture oil objectives (e.g. 100x/1.25
OIL ),
although only for brightfield. See p. 62 on how to
remove the oil.
You can also use glycerine instead of oil. The Pol
condensers CL P/PH 0.85 and UCL P 0.85 can
only be used dry.
The condenser top P 1.40 OIL S1 (Fig. 12) can
also be used on the UCA/P condenser (Fig. 10)
for enhancing resolution for objectives with
apertures from about 1.0.
Brightfield
Illumination techniques which display the empty
areas of the specimen as the brightest parts of
the image are called brightfield. Light-absorbing
object structures are required for this type of
imaging, i.e. it usually makes sense to stain the
specimen first. Optical contrasting techniques
offer an alternative (PH, DF, POL etc.).
Operation of phase contrast
Possible errors
Wrong coverglass thickness (
→
p. 27) or wrong
objective. Specimen has been placed on stage
with coverglass downwards instead of upwards.
Aperture diaphragm (28.14) opened too wide or
closed. Condenser at wrong height or wrongly
centered. Light ring engaged by mistake (28.15;
7.2; 7.7).
Lamp not inserted straight (
→
p. 21). Dirty
optics.
2.5x lens not centered.
Phase contrast
Similar to transmitted light darkfield (
→
p. 44),
phase contrast is used to form high contrast
images of unstained specimens.
Turn the phase contrast objective (engraving
PH, Fig. 25) with the lowest magnification
(usually 10x) into the light path and focus the
specimen. If you have difficulty in finding the
object plane: Temporarily narrow the aperture
diaphragm (28.14) or use a stained specimen.
Set the condenser disc in the
BF position (28.15)
or pull out the light ring slide (7.7).
Set Koehler illumination (
→
p. 37): Focus the
field diaphragm together with the object by x, y
and z adjustment of the condenser.