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20
Note:
There are 3 phase contrast objectives: 10X, 40X and 100X, and there are 3
condenser ring plates: 10X, 40X and 100X. The corresponding objective and ring
plate must work together, i.e.
10X
phase contrast objective must work with
10X
condenser ring plate, and so on.
2) Centering the condenser ring plate
a. Connect the power cord to the microscope and insert the plug into a power outlet.
b. Turn the desired phase contrast objective into light path.
c. Choose the ring plate that corresponding to the phase contrast objective in light path
and screw it on the condenser.
d. Replace the bright field condenser with the phase contrast condenser with ring plate
on.
e. Remove one eyepiece from the microscope eyepiece
tube and insert the centering telescope.
f. Turn the light of microscope on and observe from the
telescope.
g. Turn the top of the telescope (
Fig.24
) until the dark ring
image is in focus. If the dark ring is hard to find, put a
normal white print paper on the stage and under the
objective then you will see the dark ring as shown in
Fig.23
(a)
.
h. If the bright ring is still obscure as in
Fig.23
(b)
, raise or
lower the condenser by adjusting the condenser
focusing knob (or the microscope focusing knob if
necessary) till the bright ring is in focus and the dark
ring is visible.
i. If the two ring images are not coincided as shown in
Fig.23 (c)
, adjust the two centering screws on the
condenser ring plate till the two rings are coincided with each
other as shown in
Fig.23 (d)
.
j. Remove the centering telescope and replace it with the
eyepiece.
3) Performing the phase contrast observation
After you center the ring plate, you can perform the phase
contrast observation the same way as a normal bright field
microscope.
Note:
When change to another phase contrast objective and
corresponding condenser ring plate, the focusing and
centering of bright ring and dark ring should be repeated
following the procedures from
2)-b to 2)-h
.
Tips:
Make the illumination as bright as possible.
The thinner the specimen, the better the image.
(a)
(b)
(d)
(c)
Fig.23
Fig.24
