16 February 2011 A CMOS image sensor with draining only modulation pixels for fluorescence lifetime imaging
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Abstract
Fluorescence lifetime imaging is becoming a powerful tool in biology. A charge-domain CMOS Fluorescence Lifetime Imaging Microscopy (FLIM) chip using a pinned photo diode (PPD) and the pinned storage diode (PSD) with different depth of potential wells has been previously developed by the authors. However, a transfer gate between PPD and PSD causes charge transfer noise due to traps at the channel surface. This paper presents a time-resolved CMOS image sensor with draining only modulation pixels for fluorescence lifetime imaging, which removes the transfer gate between PPD and PSD. The time windowing is done by draining with a draining gate only, which is attached along the carrier path from PPD to PSD. This allows us to realize a trapping less charge transfer between PPD and PSD, leading to a very low-noise time-resolved signal detection. A video-rate CMOS FLIM chip has been fabricated using 0.18μm standard CMOS pinned diode image sensor process. The pixel consists of a PPD, a PSD, a charge draining gate (TD), a readout transfer gate (TX) between the PSD and the floating diffusion (FD), a reset transistor and a source follower amplifier transistor. The pixel array has 200(Row) x 256(Column) pixels and the pixel pitch is 7.5μm. Fundamental characteristics of the implemented CMOS FLIM chip are measured. The signal intensity of the PSD as a function of the TD gate voltage is also measured. The ratio of the signal for the TD off to the signal for the TD on is 212 : 1.
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Zhuo Li, Zhuo Li, Keita Yasutomi, Keita Yasutomi, Taishi Takasawa, Taishi Takasawa, Shinya Itoh, Shinya Itoh, Shoji Kawahito, Shoji Kawahito, } "A CMOS image sensor with draining only modulation pixels for fluorescence lifetime imaging", Proc. SPIE 7875, Sensors, Cameras, and Systems for Industrial, Scientific, and Consumer Applications XII, 78750D (16 February 2011); doi: 10.1117/12.877775; https://doi.org/10.1117/12.877775
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