This light excites fluorescence species in the sample, which then emit light of a longer wavelength. Collect the emitted fluorescence. This type of excitation-emission configuration, in which both the excitation and emission light travel through the objective, is called epifluorescence. In a fluorescence microscope, a dichroic mirror is used to separate the excitation and emission light paths. Within the objective, the excitation emission share the same optics.
Dichroic mirror separates excitation and emission light paths.
In this type of microscope, the sample is illuminated and imaged from below the stage. In a fluorescence microscope, the dichroic mirror separates the light paths. The excitation light reflects off the surface of the dichroic mirror into the objective. The fluorescence emission passes through the dichroic to the eyepiece or detection system. The dichroic mirror's special reflective properties allow it to separate the two light paths.