The FIDSAM method analyses the number of different molecules contributing to a measured fluorescence signal.
Assuming a pure fluorescent dye solution in an isotropic surrounding, the individual emitters are indistinguishable.
Accordingly, the time evolution samples a summation of numerous individual decay statistics and can be written as: The FIDSAM technique bases on a time correlated single photon counting (TCSPC) measurement and analyses the degree of deviation of a recorded fluorescence decay from a monoexponential behavior.
This way, fluorescence signal, which originates from autofluorescence background and therefore exhibits increased error-values, is divided by a relatively large number, whereas fluorescence signal from target molecules exhibits small error-values around unity is divided by a small number and remains largely unaffected.
Whereas the measurement protocol equals fluorescence lifetime imaging microscopy (FLIM), the read-out parameter is different.