A High Dynamic Range 128 × 120 3-D Stacked CMOS SPAD Image Sensor SoC for Fluorescence Microendoscopy
Ahmet T. Erdogan, Tarek Al Abbas, Neil Finlayson, Charlotte Hopkinson, István Gyöngy, Oscar Almer, Neale A. W. Dutton, Robert Henderson
Abstract
A miniaturized 1.4 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times \,\, 1.4$ </tex-math></inline-formula> mm, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$128\times120$ </tex-math></inline-formula> single-photon avalanche diode (SPAD) image sensor with a five-wire interface is designed for time-resolved fluorescence microendoscopy. This is the first endoscopic chip-on-tip sensor capable of fluorescence lifetime imaging microscopy (FLIM). The sensor provides a novel, compact means to extend the photon counting dynamic range (DR) by partitioning the required bit depth between in-pixel counters and off-pixel noiseless frame summation. The sensor is implemented in STMicroelectronics 40-/90-nm 3-D-stacked backside-illuminated (BSI) CMOS process with 8- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> pixels and 45% fill factor. The sensor capabilities are demonstrated through FLIM examples, including <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ex vivo</i> human lung tissue, obtained at video rate.