
566 Handbook of Biomedical Optics
eld aperture plane is at its focal point. For a telecentric micro-
scope, this arrangement ensures that angular scanning of the
excitation light is converted to linear translation of the objective
focal point. A tube lens is positioned to recollimate the exci-
tation light directed towards the innity-corrected objective
via a dichroic mirror. e scan lens and the tube lens function
together as a beam expander that overlls the back aperture
of the objective lens to ensure excitation light is diraction-
limited. Typically high NA objectives are used to maximize
excitation eciency. An objective posit ...