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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.25
) 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.24
(a)
.
h. If the bright ring is still obscure as in
Fig.24
(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.24 (c)
, adjust the two centering screws on the
condenser ring plate till the two rings are coincided with
each other as shown in
Fig.24 (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.24
Fig.25
