Zeiss Standard 25 ICS, Руководство по эксплуатации

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Standard 25
ICS
3-8 B 40-029 e 01/98
3.4 Setting of transmitted-light darkfield
Darkfield is mainly used for small or minute objects such as treponema, spirochaeta, cilia and bacteria,
but also for emulsions or unstained objects in watery solutions.
The special benefit of the darkfield technique is its natural, true rendition of the original colors (color
fidelity).
The equipment required for darkfield always includes a condenser with central stop, the numerical
aperture of which exceeds that of the objective used. For further details please see the following table.
Condenser with illumination aperture suitable objective apertures
Ph condenser II Z 0.9 in position Ph 3 0.44
Ph condenser II Z 0.9 in position D 0.6/0.9)
0.4
0.4 -0.55
dry darkfield condenser 0.7 - 0.85
on condenser holder Z 0.4 - 0.6
dry darkfield condenser 0.8 - 0.95
on condenser holder Z 0.6 - 0.75
Ultracondenser 1.2 - 1.4
on condenser holder Z 0.75 - 1.0
Higher objective magnifications or apertures require objectives with an integrated iris aperture.
As described in chapter 2, the microscope is ready for operation and switched on according to section
3.1.
The microscope must be set for transmitted-light brightfield, as described in section 3.2.
Settings:
Correct condenser height until image background appears in optimum darkness.
Checking the objective pupil reveals whether it is dark indeed; for this purpose, remove the eyepiece
from the tube and view the objective exit pupil.
Setting of darkfield is made easier by performing precentration using an objective of a lower power.
Since the luminous field is visible only where particles light up, while the final specimen, however,
might be "empty" over large areas, we would recommend you to use a specimen for initial setting
which features a homogeneous distribution of details, e.g. a blood smear.
Darkfield microscopy requires specimens and optical surfaces to be extremely clean. Finger
prints and traces of grease in particular have negative effects, since they brighten the
background of the field of view.