A system for the optical analysis of a sample. An illumination source illuminates the sample, exciting fluorescence. The fluorescence is collected by an objective lens, which transmits the collected illumination light onto an imaging lens, which focuses the collected light onto an area array detector. Collected light rays between the objective lens and the imaging lens are parallel and pass through an emission filter. Both the objective lens and the imaging lens are positioned on a mount that allows an alternative objective or imaging lens to be positioned to collect or image the emitted light. Any objective lens/imaging lens pair is optically symmetrical, greatly reducing the optically degrading effects.