Patent ID: 6927401

Claim:
A method for characterizing fluorescent molecules or other particles in samples comprising the steps of a) monitoring fluctuating intensity of fluorescence emitted by the molecules or other particles in at least one measurement volume of a non-uniform spatial brightness profile by measuring numbers of photon counts in primary time intervals by a single or more photon detectors, b) determining at least one distribution function of numbers of photon counts, P(n), from the measured numbers of photon counts, c) determining physical quantities characteristic to said particles by fitting the experimentally determined distribution function of numbers of photon counts, wherein the fitting involves calculation of a theoretical distribution function of the number of photon counts P(n) through its generating function, defined as G ⁡ ( ξ → ) = ∑ n ⁢ ξ → n ⁢ P ⁡ ( n ) wherein step c) when calculating the theoretical distribution P(n), the spatial brightness profile is modeled by the expression: ⅆ V ⅆ x = A 0 ⁢ x ⁡ ( l + a 1 ⁢ x + a 2 ⁢ x 2 ) where dV denotes a volume element, x denotes logarithm of the relative spatial brightness, A 0 is a constant selecting the unit of volume, and a 1 and a 2 are empirically estimated parameters.