Fluorescence microscopes

Fluorescence microscopes produce widefield images. This is the basis of what happens in a fluorescence microscope:

  • The fluorescence source (from the arc lamp) produces bright white light which is passed through a coloured filter to produce the specific excitation light, in this case blue for GFP
  • This is reflected by the dichroic mirror, goes through the objective and to the sample
  • The sample (hopefully!) fluoresces as described above and some of the emission light goes back through the objective
  • This is the important bit: the dichroic mirror transmits the longer wavelength light so the very bright excitation and the relatively weak fluorescence are separated.
  • The emission is normally passed through another filter and then can be either seen with the naked eye or captured with a camera
duke lmcf principle fluorescence microscope

This is what an upright fluorescence scope typically looks like. Notice the fluorescence light path is only above the stage (this is called epi-illumination and the objective is both the condenser and the imaging lens). The transmitted light path features a condenser on one side of the sample and the objective on the other.

duke lmcf typical upright fluorescence scope