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A new scheme for CMOS-based fluorescence lifetime imaging with hardware-level exponential-to-linear conversion is proposed. The exponential relationship between drain current and drain-to-source voltage in a subthreshold MOSFET is explored for linearisation of the photocurrent generated during a fluorescence decay. Simple measurement of the resulting slope, either through voltage or time measurement, provides lifetime information in a single excitation cycle. The scheme is less sensitive to time and voltage errors compared with charge modulation techniques and are suitable for applications, where high-frame rate and rapid extraction are desired.
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Exponential-to-linear conversion for fluorescence lifetime measurement