Zeiss Axiostar plus - Using transmitted-light darkfield technique

Operation
Carl Zeiss Transmitted-light darkfield Axiostar plus
3-8 B 40-81 e 12/01
3.4 Using the transmitted-light
darkfield technique
3.4.1 General principle
Darkfield is mainly used for small or minute
objects such as bacteria, but also for emulsions
or unstained objects in watery solutions.
In transmitted-light brightfield, unstained
biological specimens, such as bacteria or living
cell cultures, are often barely identifiable – if at
all – on account of their light transmission. The
situation changes significantly if such specimens
are viewed in transmitted-light darkfield. In
principle, the specimen is illuminated with an
illumination aperture which is larger than that
of the objective used.
Only the diffracted and scattered light
components which are so important for image
production reach the objective, while the
directly reflecting light bundles are guided past
the objective.
This is one of the reasons why even fine
structures can be resolved and appear bright on
a dark background although they partially lie
below the resolving power of the light
microscope.
3.4.2 Transmitted-light darkfield
configuration
– Condenser with slider for darkfield.
– When using the Abbe condenser with
5-position turret, set the darkfield position
(DF, 0.65 / 0.9) via the turret disk.
– ICS objectives with a numerical aperture
smaller than that of the used darkfield stop
can be used.
– For further details, please see the following
table:
Condenser with slider for contrasting techniques Suitable objectives
Slider for darkfield 0.25/0.9 (DF 10) CP-Achromat 5x/0.12
DF setting on condenser revolver (0.65/0.9) CP-Achromat 10x/0.25
A-Plan 5x/0.12
A-Plan 10x/0.25
Achroplan 4x/0.10
Plan-Neofluar 2.5x/0.075
Slider for darkfield 0 .65/0.9 (DF 40) CP-Achromat 10x/0.25
DF setting on condenser revolver (0.65/0.9) CP-Achromat 40x/0.65
A-Plan 10x/0.25
A-Plan 20x/0.45
Achroplan 10x/0.25
Achroplan 20x/0.45
Achroplan 40x/0.65
Slider for phase contrast Ph 1 All engraved Ph 1
Slider for phase contrast Ph 2 All engraved Ph 2
Slider for phase contrast Ph 3 All engraved Ph 3
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