23
7.2.2 Centering Diaphragm
（
Fig.35
）
Generally do not need to center. If
necessary, please adjust the diaphragm
according to the following steps:
1. Place the specimen on the stage and focus
it.
2. Take out a eyepiece and replace it with the
centering telescope(CT).
3. Make sure the matched phase contrast
objective and diaphragm ( in the phase
contrast slider) have been in the light path.
4. Observe the image of bright ring
⑤
on the
slider and dark ring
⑥
on the objective with
the CT. If the bright ring’s image is not clear,
shift the CT’s ocular until the image of the
bright ring
⑤
is clear.
5. Adjust the centering screw
④
on the left side
of phase contrast slider with screwdriver
until the center of bright ring and the dark
ring are coincided.
6. The 10×,the 20×and 40×phase contrast
objective use the same diaphragm on the
phase contrast slider. the center of the bright
ring and the dark ring should coincide when
changing the objective. If having deviation,
you ought to center again.
★
If the diaphragm is centering incorrectly,
the best viewing effect of the phase
contrast microscopy will not be
obtained.
★
After removing or replacing a thick
specimen, the bright ring and the dark
ring are likely to deviate each other,
which will result in a decline of the image
contrast. So if happened, please repeat
the steps as above.
★
If the specimen is not flat, it maybe need
to repeat the centering steps for
obtaining greater effect. Use the phase
contrast
objective
to
center
the
diaphragm , according to the sequence
of low to high magnification.
图
26
Fig.35
⑥
⑤
