Darkfield Obervation (Df) - Optika Italy M-1157 Serie Instruction Manual

6.2 Darkfield obervation (DF)
• Usable objectives with different inserts
Insert
DF
Top lens position
DF OIL
Top lens position
(*) For observation with a 100X objective in darkfield oil we recommend the use of a 100X oil objective
with iris.
• Remove all filters from the optical path.
1. Rotate the condenser turret to enter the "DF"
position.
2. Pull the lever of the polarizer ① to remove it from
the optical path. (Fig. 11)
3. Place a specimen on the stage and focus the
specimen.
4. Observing in the eyepieces, lower or raise the
condenser until a homogeneous illumination of
the sample is obtained and therefore an optimal
dark field effect is achieved.
5. Using the centering screws on the condenser ①
(Fig. 13) centre the dark field ring until the field of
view is evenly illuminated.
• Darkfield requires a huge amount of light.
Switching from darkfield to brightfield, one
could be dazzled. Do not keep your eyes on
the eyepieces when moving the condenser
turret from DF to BF.
• "Dry" darkfield observation, that is, without
the use of oil, is only possible with objectives
with N.A. lower than 0,7.
• Observing in darkfield, it may be necessary to
slightly raise the condenser from the normal
position to obtain a more homogeneous
illumination. This is not a defect.
Objective 4X
-
OUT
-
OUT
10X 20X
¡ ¡
IN
- -
-
Page 11
40X 60X
-
¡
-
-
¡
IN
①
100X
-
-
¡(*)
F ig. 13 F ig. 13