A CMOS Lock-In Pixel Image Sensor With Multisimultaneous Gate for Time-Resolved Near-Infrared Spectroscopy

This article proposes a CMOS lock-in pixel image sensor aiming for time-resolved near-infrared spectroscopy (TR-NIRS). The pixel employs lateral electric field charge modulation (LEFM) with an eight-tap multisimultaneous gate structure and negative substrate bias. The optimization of pixel structure creates a high potential slope with no barrier to facilitate the high-speed photo-generated charge transfer required in the time-resolved application. The sensor employs a two-stage charge transfer architecture with pinned storage diodes (SDs). The effectiveness of the sensor is demonstrated through simulations and experimental measurements. A prototype sensor with 70 (V) x 110 (H) effective pixels to characterize the multisimultaneous gate lock-in pixel is implemented in a 0.11-mu m 1-poly-4metal CMOS image sensor (CIS) technology. A fast intrinsic response of 240 ps is achieved using an 80-ps pulsewidth 780-nm laser diode by the characterization using two simul- taneous gates and a single time window of the lock-in pixel. Performance evaluation using silicon phantoms and further measurement with a rat demonstrates the feasibility of the proposed sensor and setup for TR-NIRS applications.