A High SNR Multi-Tap Lock-In Pixel Image Sensors

抄録

A programmable sub-nanosecond time-gated 4-tap CMOS lock-in pixel image sensor using in-pixel pulse-generator (PG) is developed for time-resolved (TR) biomedical imaging system such as a fluorescence lifetime imaging microscopy (FLIM), and demonstrated by simulations and measurements. Using in-pixel PG circuits, very narrow time-window (TW) of 0.8ns for charge modulation is achieved. Because of fast time-gating, intensely weak signals from living cells can be successfully captured with high signal-to-noise ratio (SNR) by the developed TR CMOS image sensor (CIS). The developed CIS achieves very quick intrinsic response of 170ps at 472nm, and very low temporal random noise of 0.85e-rms at 45fps with true correlated double sampling (CDS) operation using 2-stage charge transfer. The multiple output ports (＞4) of lock-in pixel make possible to realize a real-time fluorescence lifetime (FLT) measurement system, even though a fluorescent sample has multi-FLT components (more than two).