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Patent

Abstract 

A detection system for detecting fluorescence lifetime comprises an excitation light source configured for repeatedly generating pulsed excitation light, and a detector (600). The detector (600) comprises a single-photon detection circuit (150) for generating digital pulses upon detection of photons a pulse-inhibit circuit (165) for rejecting detected photons that occur outside each one of a series of measurement time windows, each subsequent measurement time window starting after a subsequent excitation light pulse has stopped, and stopping before a next excitation light pulse is generated, each measurement time window having a measurement window period and a switched-capacitor circuit (160) having an input terminal for receiving a voltage ramp signal that is restarted with each new measurement window period, the switched-capacitor circuit being configured for repetitively computing an average voltage, based on an exponential moving average function applied to sample voltages recorded over past measurement time windows and determined by the voltage ramp signal in response to detected and not rejected photons, following the principles of the center-of-mass method, wherein the switched-capacitor circuit has a node (172) for outputting the computed average voltage as a measure of the fluorescence lifetime.

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