Patent ID: 7507582

Claim:
A method of fluorescence measurement on analytes in a sample, wherein the sample contains at least two analytes marked with different fluorescent markers or wherein the sample contains at least one analyte marked with at least two different fluorescent markers, the fluorescent markers having spectrally different fluorescence emissions, said method comprising: (a) illumination of the sample in the measurement volume using only a single pulse laser emitting a single laser line to excite the fluorescence emission of each of the different fluorescent markers by 2-photon absorptions, said illumination of the sample in the measurement volume being performed with said single pulse laser using a single laser line and wherein said single pulse laser has an excitation intensity sufficiently high that the different fluorescent markers are jointly excited through said 2-photon absorptions; (b) detection of the fluorescence emission using at least two detector devices which are adapted for light detection in different spectral ranges in accordance with the spectral fluorescence properties of the different fluorescent markers, and (c) performance of one or both of a cross-correlation and coincidence analysis of detector signals of the detector devices.