128  ×  128-Pixel Current-Assisted Photonic Sampler Image Sensor and Camera System for Macroscale Fluorescence Lifetime Imaging With Multiexposure for Extended Dynamic Range
 
128  ×  128-Pixel Current-Assisted Photonic Sampler Image Sensor and Camera System for Macroscale Fluorescence Lifetime Imaging With Multiexposure for Extended Dynamic Range 
 
 
Abstract 

A 128×128-pixel current-assisted photonic sampler (CAPS) image sensor is designed for macroscale fluorescence lifetime imaging (MFLI). Current assistance is used for swift detection and time gating of the photogenerated carriers within the whole substrate. The sensor is fabricated in a commercial 350-nm CMOS process on a 15- μ m epilayer, with 19- μ m pixels and a 62\% FF. The pixel features gating widths below 1 ns subject to a 42-ps standard deviation on the gate width uniformity and a 27-ps standard deviation on its temporal position. The pixel has a quantum efficiency (QE) above 40\% for near-infrared (NIR) wavelengths, whereas the peak QE is 60\% at 675 nm. The gate{\textquoteright}s intrinsic decay is observed to be 280 ps, which allows for the MFLI of subnanosecond lifetime dyes. A multiexposure method has been implemented, where the pixel is nondestructively read-out multiple times—with different exposure times—after each reset. This allows for imaging with an extended dynamic range (DR) and is validated on commercial fluorescence phantoms. The MFLI capabilities are further demonstrated in a preclinical experiment.