R.M. Field, S. Realov, and K.L. Shepard A 100-fps, Time-Correlated Single-Photon-Counting-Based Fluorescence-Lifetime Imager in 130-nm CMOS, IEEE Journal of Solid-State Circuite, vol.49, no.4 (2014) advanced online version.

A fully-integrated single-photon avalanche diode (SPAD) and time-to-digital converter (TDC) array for high-speed fluorescence lifetime imaging microscopy (FLIM) in standard 130-nm CMOS is presented. This imager is comprised of an array of 64-by-64 SPADs each with an independent TDC for performing time-correlated single-photon counting (TCSPC) at each pixel. The TDCs use a delay-locked-loop-based architecture and achieve a 62.5-ps resolution with up to a 64-ns range. A data-compression datapath is designed to transfer TDC data to off-chip buffers, which can support a data rate of up to 42 Gbps. These features, combined with a system implementation that leverages a x4 PCIe-cabled interface, allow for demonstrated FLIM imaging rates at up to 100 frames per second.