Microscope objectives for single molecule fluorescence detection

6 Microscope objectives for single molecule fluorescence detection 

The numerical aperture (NA) of an objective describes the solid angle over which light is collected by the lens. The NA is given by, 

The NA can have a large effect on the collection efficiency of the objective. For example, NAs of 1.45,1.3, and 0.95 correspond to 40%, 26%, and 10% of the total possible sphere of collection around an object. Thus small improvements in NA can result in significantly more photons at the detector. 

Crucial in the design of the instrument is the focusing control for the microscope objective. For TIRF applications it is necessary to place the centre of the depth of focus of the objective (the objective focal plane) near the glass water interface. For diffusion confocal and two-photon designs it is desirable to always 

MP multi-photon TIRF total internal reflection fluorescence. 

---