Troubleshooting - OPTIKA MICROSCOPES B-500DK Manual De Instrucciones

4.1 TROUBLESHOOTING

There are numerous common problems associated with darkfield microscopy and photomicrography.
These range from insufficient illumination and condenser misalignment to using a field stop of incor-
rect size. Most darkfield illumination problems are associated with the substage condenser, and this
should be the first suspect when things do not work properly.
The following problems and solutions should be used as a guide when imaging specimens using
this technique.
Problem There is insufficient illumination to make the specimen visible, or the specimen is visible
but very faint.
Solution Check the substage condenser to ensure that it is positioned correctly. Also, check the li-
ght path for color and/or neutral density filters, polarizers, retardation plates, or any other
components that might reduce illumination intensity.
Check to make certain that the condenser top lens is correctly oiled to the bottom of the
microscope slide. If the immersion contact has been broken, re-apply the oil and rack
up the condenser until the top lens is completely immersed in oil and in contact with the
bottom of the slide.
Problem The viewfield has a dark spot in the center reducing illumination intensity, but objects in the
periphery are well-illuminated and appear normal.
Solution The substage condenser is incorrectly positioned. Carefully rack the condenser up and
down while observing the specimen in the viewfield. Check to make certain that both the
condenser aperture and field diaphragms are set to the wide open position.
Occasionally this problem arises when microscope slides of excessive thickness (greater
than the standard one millimeter) are used. Use a micrometer or a set of dial calipers to
determine the thickness of the slide and the slide/coverslip combination.
Problem The image has a brightfield periphery with or without dark regions in the center.
Solution This problem is typical when the substage condenser is incorrectly centered.
Revert to brightfield and re-establish the conditions of Köhler illumination, then repeat the
darkfield procedure, making sure the condenser is centered.
If there is an internal iris diaphragm in the objective, reduce the iris opening size to deter-
mine if too much oblique illumination is entering the front lens of the objective.
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