Leica DM R Serie Mode D'emploi page 48

achieve the full performance of the objective.
We recommend coverglasses no. 1 H (high
performance, 0.17
– 0.02
DIN 58878/ISO 8255/1. The thickness of the
embedding medium layer between the specimen
and the coverglass should be as thin as
possible. However, if you have a high dry
aperture and a non-standard coverglass
thickness, the aperture can be reduced by
integrating an iris diaphragm (41.7) to make
deviating coverglass thicknesses uncritical.
Alternatively, an objective with correction
mount (CORR) can be used.
0
Coverglass thickness 0, i.e. specimens must not
be covered with a coverglass. These objectives
are primarily designed for reflected light
specimens, but can also be used to great
advantage with transmitted light specimens
without a coverglass, e.g. blood smear
specimens.
–
The specimen can either be covered or not. A
maximum aperture of about 0.25 is considered
the threshold value for dry objectives for univer-
sal use with or without a coverglass; for oil
immersions this upper threshold is 1.25.
48
0
mm) which comply with
A, B, C, D, E
Pupil position in the objective: the exit pupil of
most Leica microscope objectives has 4
standard positions A, B, C and D, the so-called
pupil blocks. When using the ICT and ICR
interference contrast devices make sure that
the IC prism (25.3 and 60.7) used above the
objective has the same letter, see "Optics" data
sheet.
The most important performance criteria of
microscope objectives (apart from aperture and
magnification, see below) are field performance
and chromatic correction. Field performance is
understood as the diameter of the focused
intermediate image formed in the eyepiece (cf
page 43). As regards chromatic correction,
there are three main types: achromats,
semiapochromats
chromats.
C PLAN
Achromatic objectives with a field performance
up to 20 mm (eyepiece fov max. 20).
N PLAN, PLAN
Planachromatic objectives with a field per-
formance of at least 20 – 22 mm. For visual
observation eyepieces with a field performance
of 20 or 22 mm are recommended, e.g. HC PLAN
10x/20. However, eyepieces up to 25 field of view
can be used if you are prepared to accept
slightly blurred edge definition.
(or fluorites) and apo-