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Axio Imager 2
4.12
Illumination and contrast methods
4.12.1
Setting transmitted-light brightfield according to KÖHLER
(1)
Application
Transmitted-light brightfield microscopy is the most common of all optical microscopic techniques, as it
permits high-contrast or stained specimens (e.g. blood smears) to be viewed easily and quickly.
Beside the so-called direct bundles of rays, the indirect bundles (i.e. those diffracted and scattered by
specimen details) are also of major importance for providing true imaging of the object. The higher the
proportion of indirect bundles of rays (aperture), the more realistic the microscopic image according to
ABBE.
To fully exploit the optical performance of the microscope, particularly that of the objective, the
condenser, luminous-field diaphragm and aperture diaphragm should be set based on the rules of the
KÖHLER illumination principle. These fundamental rules of microscope adjustment are described in detail
below in Section 4.12.1 (3) "Transmitted-light brightfield according to KÖHLER" for the Axio Imager 2.
(2)
Instrument equipment
− All Axio Imager 2 microscopes and their equipment allow transmitted-light brightfield microscopy.
− For the use of the achromatic-aplanatic universal condenser 0.9 H/0.8-0.9 DF, refer to
Section 4.12.2 (4).
(3)
Setting transmitted-light brightfield according to KÖHLER
− The microscope should be set up correctly as described in Section 3.
− Switch on the microscope.
• Set the toggle switch for the halogen illuminators on the rear of the instrument to transmitted light.
• Turn voltage control (Fig. 191/2) on the microscope base to adjust the image brightness. If the
transmitted-light shutter is closed (indicator LED not lit), open it by means of button (Fig. 191/1).
• Place a high-contrast specimen on the mechanical stage.
• Swivel in the front lens of the condenser (for objectives ≥ 10x) and use the vertical control of the
condenser (Fig. 191/5 or Fig. 192/3) to move it up to the upper stop. The stop must have been set in
such a manner that the specimen is not touched by the condenser (for information on setting the stop
of the vertical condenser drive, refer to Section 4.12.1 (4)).
• Swivel in 10x objective (yellow ring, also refer to Section 2.5) on nosepiece (Fig. 191/7) and bring the
specimen into sharp focus using the focusing drive (Fig. 191/4).
• Close luminous-field diaphragm (Fig. 191/3) until it becomes visible (not necessarily in focus) in the
field of view (Fig. 191/A).
• Turn the vertical control of the condenser drive (Fig. 191/5 or Fig. 192/3) to lower the condenser until
the edge of the luminous-field diaphragm appears in focus (Fig. 191/B).
01/2016
OPERATION
Illumination and contrast methods
430000-7544-001
ZEISS
161
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