INSTRUMENT
DECRIPTION
Carl Zeiss
Objectives
Axio Imager
26
430000-7344-001
M70-2-0020 e 06/2009
2.5
Objectives
The objectives are the optical heart of the microscope. The
following is an example of how objectives can be labeled:
N-ACHROPLAN 10x/0.25
∞
/0,17.
where
10x : Objective magnification, with a defined color ring
on the objective being allocated to each
magnification step
(Zeiss color code)
0.25 : Numerical aperture
∞
: Infinite image distance: These objectives can only be
used with ICS microscopes from Carl Zeiss.
0.17
:
Can only be used with cover slip thickness
D = 0.17 mm.
or
−
: Can be used with cover slip thickness D = 0 or
0.17 mm.
Other labels:
Oil : Oil immersion objective
Ph 2 : Phase-contrast objective with green inscription and
phase stop Ph 2
The color of the inscription denotes the contrasting method
the objective is designed for:
Black:
Standard
Green:
Phase contrast
Red:
Strain-free for polarization (Pol); low-strain for differential interference contrast (DIC)
The color rings indicate the magnification of the objective (color code):
Color ring on
objective
Black Brown
Red Orange
Yellow
Green Light
blue
Dark
blue
White
Magnification
factor
1x; 1.25x 2.5x
4x; 5x
6.3x
10x
16x; 20x;
25x; 32x
40x; 50x 63x
100x;
150x
Objective magnification multiplied by eyepiece magnification (usually 10x) results in overall visual
magnification: e.g. 10 x 10 = 100x.
When working with the microscopes, total magnification should not drop below or exceed the range of
useful magnification. The range of useful magnification was defined by Ernst ABBE as 500 to 1,000 times
the numerical aperture of the objective used. There is no resolution for further details above that limit.
Accordingly, the range of useful magnification for an objective with a numerical aperture of 0.3 is
between 150x and 300x.
Exact observance of the cover slip thickness of 0.17 mm is all the more necessary the higher the
numerical aperture of the objective. For this reason, certain objectives are equipped with a correction
mount providing adjustment to different cover slip thicknesses. To this end, a specimen area is searched
for, and the position of the correction ring where optimum focus and image contrast are obtained is
determined (refocusing is invariably required).
Fig. 2-1
Objective
