Patent ID: 6809816
Filing Date: 2004-10-26
Classification: G01N

Abstract:
A method of measuring a fluorescence decay time, comprising the steps of:providing a sample medium containing at least one fluorescence molecule; directing a sequence of pulses of excitation radiation into the sample medium, the sample medium being transparent to the excitation radiation, the at least one fluorescence molecule being responsive to absorption of such excitation radiation to emit a fluorescence photon, and the sample medium being transparent to such a fluorescence photon; detecting fluorescence photons emitted from the sample medium in response to the sequence of pulses of excitation radiation; measuring time intervals each defined by a starting time at which one pulse of the excitation radiation is directed into the sample medium and an end time at which a fluorescence photon is emitted from the sample medium before the occurrence of a next pulse of the excitation radiation in succession in the said sequence; and determining a fluorescence decay time from a plurality of the measured time intervals, characterised by the steps of triggering occurrence of the said next pulse of the excitation radiation in response to detection of the said fluorescence photon which determines the said end time, and limiting the duration of the time between two successive pulses of excitation radiation in the said sequence to a predetermined maximum value.