Instrument description
Axiostar
plus
Objectives
Carl Zeiss
40-815 e 12/01
1-7
1.4
Objectives
The objectives are the optical centerpiece of
the microscope.
The following is an example of how objectives
can be labeled:
CP-ACHROMAT 10
×
/0.25
∞
/-.
where:
10
×
= objective magnification, with a defined
color ring on the objective
allocated to each magnification step
(Carl Zeiss color code)
0.25 = numerical aperture
∞
= infinite tube length
−
= can be used with cover slip thickness
D = 0 or 0.17 mm
or
0.17 = can be used with cover slip thickness
D = 0.17 mm
and
Oil =
oil immersion objective
Ph 2 = phase contrast objective with green
objective labeling and annular
diaphragm Ph 2
The objective magnification multiplied by the
eyepiece magnification (usually 10
×
) results in
the visual overall magnification:
e. g. 10
×
10 = 100
×
.
The numerical aperture
×
1000,
e. g. 0.25
×
1000 = 250
×
, is the highest
useful magnification, i.e. no further details are
resolved above that limit.
☞
The objective labeling "
∞
" indicates that these
objectives may only be used with microscopes
featuring infinite optics (ICS) and not with
instruments whose objectives are marked with
"160" as their mechanical tube length (in
mm).
The exact observance of the cover slip thickness
of 0.17 mm is all the more necessary the
higher the numerical aperture of the
objective. Therefore, so-called "Corr"
objectives can be set for different cover slip
thickness via a correction ring. For this, a
specimen area is searched, and the position of
the correction ring where optimum focus and
image contrast are obtained is determined
(refocusing is always required).
Immersion objectives are always insensitive to
differences in cover slip thickness.
When immersion objectives are used, the air
between the cover slip and the objective is
replaced with a liquid, which is immersion oil
in most cases. The plastic oiler containing
20
ml of 581
N Immersol is particularly
suitable for this purpose.
Due to their short working distance, objectives
25
×
and higher feature resilient mounts
(specimen protection).
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