Phase Contrast on the Olympus BH-2 Microscopes
Revision 1
Page 5 of 6
Center the Selected Phase Annulus
Per the following procedure, carefully adjust the two
orthogonal, spring-loaded centering thumbscrews on
the rear of the phase contrast condenser (see
in order to center the bright image of the phase annulus
within the dark image of the phase ring in the objective
(see
Figure 6
–
Centering screws of BH2-PC/PCD condenser
Figure 7
–
The phase ring and phase annulus images
To adjust the position of the phase annulus, carefully
depress
both
of
the
spring-loaded
centering
thumbscrews on the rear of the phase contrast
condenser (see
) until the thumbscrews engage
with the internal centering screws for the selected
phase annulus. Then, while watching through the
phase-centering telescope, adjust the thumbscrews to
get a feel for how the centering adjustments work and
how the two thumbscrews interact with each other.
Once you have gained a feel for it, use the thumbscrews
to adjust the position of the selected phase annulus so
that its image (the bright ring) falls within the image of
the phase ring in the objective (the dark ring) as shown
in
Figure 8
–
The phase annulus properly centered
After the selected phase annulus has been properly
centered, release the two centering thumbscrews and
allow them to disengage from the internal centering
screws for the phase annulus.
Caution
: Never turn the thumbscrews counterclockwise
beyond the point where the phase annulus ceases to
move in the field of view, or clockwise beyond the point
where their rotation begins to feel firm, and do not
rotate the selector dial on the phase contrast condenser
while one or both centering thumbscrews are engaged
with the internal centering screws, otherwise damage
to the phase contrast condenser may result
.
Center the Remaining Phase Annuli
Repeat the centering procedure described above to
center the phase annuli in the condenser for the
remaining phase contrast objectives on the microscope.
Replace Centering Telescope with the Eyepiece
Once the various phase annuli have been properly
centered, remove the phase-centering telescope from
the right-hand ocular tube and replace it with the
eyepiece.
Place Green/Yellow Filter into Filter Receptacle
Carefully place the green/yellow phase contrast filter
(the IF-550 interference filter provides the best results,
but lacking this, the 45G533 absorptive filter may be
used instead) into the 45mm filter receptacle beneath
the stage (see
).
