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Axioskop 40
OPERATION
Axioskop 40 FL
Illumination and contrast procedures
Carl Zeiss
B 40-810 e 12/01
3-27
3.5.4
Setting transmitted-light dark field
(1)
General principle
Due to their transparency, unstained biological specimens, such as bacteria or living cell cultures, are
often barely or not at all visible in transmitted-light bright field. This changes markedly if such specimens
are viewed in transmitted-light dark field, where the specimen is illuminated using an aperture that is
larger than that of the objective used.
In dark field, only the diffracted and scattered light components, which are important for imaging, reach
the objective, while the direct unchanged light bundles are directed past the objective. This is one of the
reasons why even fine structures can be resolved, although they are sometimes below the resolving
power of the light microscope and appear very bright on a dark background.
(2)
Transmitted-light dark field configuration for the Axioskop 40 and Axioskop 40 FL
−
Universal condenser with dark field stop in position D and 0.76 to 0.90 aperture on the illumination
side
−
Use of ICS objectives up to the maximum aperture of 0.65. Objectives with a higher aperture can only
be used in conjunction with the above universal condenser if they feature an integrated aperture iris
stop.
☞
The Ph 3 stop of the PH, H and Var slider can be used with the 0.9/1.25 H condenser and
objectives < 40x as a dark field stop.
(3)
Setting transmitted-light dark field on the Axioskop 40 and Axioskop 40 FL
•
Setting KÖHLER illumination is identical to transmitted-light brightfield, except that the highest
aperture objective (not oil immersion) must be used instead of the 10x objective.
•
Turn the turret disk of the universal condenser to position D and switch in condenser front lens.
•
Remove the eyepiece from the tube (replace it with the auxiliary microscope) and check the centering
of the dark field stop in the objective exit pupil. If the central dark field stop D in the universal
condenser is outside or out of the center of the objective exit pupil, and if the exit pupil is not
homogeneously dark, the dark field stop must be recentered.
•
To center the dark field stop, use the two SW 1.5 Allen screwdrivers (3-23/
1
and
4
) and adjust the
two centering screws (3-23/
2
and
3
) until the objective exit pupil is homogeneously dark. After
centering, remove both SW 1.5 screwdrivers from the condenser.
☞
Since the apertures of objectives with an integrated aperture iris stop are too high for
transmitted-light dark field, the aperture iris stop must be closed to the limit aperture of 0.65.
As dark a background of the field of view as possible is always the performance criterion for the dark
field technique.
Summary of Contents for Axioskop 40
Page 1: ...Operating Manual Axioskop 40 Axioskop 40 FL Routine microscope...
Page 14: ...INTRODUCTION Axioskop 40 Carl Zeiss Axioskop 40 FL 0 14 B 40 810 e 12 01...
Page 30: ...INSTRUMENT DESCRIPTION Axioskop 40 Carl Zeiss Axioskop 40 FL 1 16 B 40 810 e 12 01...
Page 77: ...Axioskop 40 OPERATION Axioskop 40 FL Carl Zeiss B 40 810 e 12 01 3 3...
Page 128: ...OPERATION Axioskop 40 Carl Zeiss Axioskop 40 FL 3 54 B 40 810 e 12 01...
Page 146: ...APPENDIX Axioskop 40 Carl Zeiss Axioskop 40 FL A 8 B 40 810 e 12 01...