Four components are required for fluorescent detection: 1) An excitation source 2) A fluorophore 3) A filter to isolate emission photons from excitation photons 4) A detector
Photobleaching describes irreversible damage to a fluorophore caused by excitation. The processes underlying photobleaching are complex and depend on the fluorophore used, its environment and the excitation source.
Several strategies can be used to attempt to reduce photobleaching of samples: 1) Use low light detection devices like CCD cameras 2) High numerical aperature objectives 3) Wide bandwidth emission filters 4) Use flurophores less prone to bleaching