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Problem
The periphery of the viewfield is bright on one side only.
Solution
Check the nosepiece to ensure the objective is correctly positioned in the optical axis of
the microscope. There is a detent stop that should produce a positive “click” when the
objective is properly positioned.
Problem
Images of the specimen are not clear and lacking in sufficient contrast and detail.
Solution
The specimen might not be suitable for darkfield microscopy. Many stained specimens do
not scatter enough light to be clearly imaged under darkfield conditions.
Specimen thickness may also be a problem, because very thin specimens are often not
imaged well with the oblique light rays emitted from darkfield condensers. Change to bri
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ghtfield or phase contrast to determine if this improves specimen contrast.
Problem
Bright areas that are out of focus obstruct viewing and/or photomicrography of darkfield
specimens.
Solution
This is probably due to dust, hair, fibers, and/or dirt contamination of an optical surface
somewhere above the condenser. Thoroughly clean the specimen slide with optical-grade
tissue or cotton. Occasionally, this problem arises due to contamination on the objective
front lens. Carefully loosen the objective from its seat in the nosepiece and slowly turn
while observing the specimen through the eyepieces. If the obstruction rotates along with
the objective, then it is probably due to dust on the front lens. Remove the objective and
moisten the front lens by gently exhaling on it, then clean with lens tissue or a cotton swab
wrapped on a long wooden rod.
Replace the objective and check to make certain the obstruction has been completely
removed.
Problem
The image of the lamp condenser partially fills the viewfield, obscuring details of the spe
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cimen.
Solution
The slide may be too thin or the condenser may be adjusted too high. Measure the thi
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ckness of the microscope slide and check to make certain the oil contact is not broken. If
difficulty is encountered keeping the bottom of the slide oiled, try using a thicker slide.
4.1 TROUBLESHOOTING
