Fluorescent and Phase Contrast Light Path Combined
There may be times when it is useful to locate and view a specimen using phase contrast and then add fluorescence illumination to view an organelle or the location of a particular molecule in the cell. Once the specimen, say a cell, is located under phase contrast, the light intensity knob is used to turn down the halogen lamp and the fluorescence shutter is set to the "on" position. The correct filter cube is placed in the light path and the intensity of the halogen lamp is adjusted so that the cell can be seen (with phase) and the fluorescing structure(s) is/are visible (see the figure below).
A
cell viewed by phase contrast with a blue
fluorescent nucleus stained with DAPI
(courtesy Olympus Microscope Co.)