Transmitted Light Cube for Ploem Fluorescence

This is a special cube used in the Ploem epi-fluorescence illuminators that accept the earlier filter cube systems. It is marked ‘TL’ and is intended for use when normal transmitted light is to be employed. The excitation filter port is blocked with a metal cover to prevent stray UV light from interfering with observations. Also installed are a pair of glass plates, one in the position normally occupied by the dichroic beam-splitter, and the other in the barrier filter position. The purpose of these plates is to maintain a parfocal system when switching between fluorescence cubes and the bright field position. The angled plate also displaces the image axially to the same extent the dichroics do so that image registration is more easily accomplished when comparing fluorescence and bright-field images.