INV-101
WORLD PRECISION INSTRUMENTS
17
Phase Contrast Alignment
There are two phase contrast objectives included with the INV-101 microscope, the 10X
and the 20X. On a simplified level, phase contrast imaging occurs by the interference of
light that is created by special masks in the light path. There are two masks, each located
in a different part of the light path, which must be positioned correctly relative to each
another to create the phase contrast effect.
The annular ring (condenser annulus) is located in
the phase aperture frame, and it has a light masking
pattern that looks similar to
Fig. 60
. The phase ring
is the conjugate of the condenser annulus, and its
pattern is a ring that is the same size as the white
area in the condenser annulus pattern. The phase
ring pattern is located in the objective and cannot
be adjusted by the user.
The condenser annulus is adjustable by the user, and it is located in the phase aperture
frame. The user adjusts the position of the condenser annulus to establish the proper
relationship between the two masks to optimize the phase contrast effect.
Notice that there are two condenser annulus masks on the phase aperture frame. (See
Fig. 26
, page 9.) One is for use with the 10X and 20X phase contrast objectives,
and the larger one is for a 40X phase contrast objective (not included). Adjust the phase
aperture frame so that the correct mask is in the light path corresponding with the objective
to be used.
Adjusting the Phase Contrast Alignment
1. Adjust the phase aperture frame so that the open filter hole is in the light path of the
condenser head. With the open filter hole in this position, the only mask in the light
path is the phase ring in the phase contrast objective.
2. Select a phase contrast objective. In this case, it will be either the 10X or the 20X.
3. Replace one of the eyepieces with the phase telescope (
Fig. 61
).
Fig. 61
–Phase telescope in eyepiece
Fig. 60
–Two Annuli
Condenser Annulus
Phase Ring
