Wednesday, August 10, 2016

Every Photon Counts

Sensors Journal publishes a paper "The Quanta Image Sensor: Every Photon Counts" by Eric Fossum, Jiaju Ma, Saleh Masoodian, Leo Anzagira and Rachel Zizza from Dartmouth College. "This paper reviews the QIS concept and its imaging characteristics. Recent progress towards realizing the QIS for commercial and scientific purposes is discussed. This includes implementation of a pump-gate jot device in a 65 nm CIS BSI process yielding read noise as low as 0.22 e− r.m.s. and conversion gain as high as 420 ┬ÁV/e−, power efficient readout electronics, currently as low as 0.4 pJ/b in the same process, creating high dynamic range images from jot data, and understanding the imaging characteristics of single-bit and multi-bit QIS devices. The QIS represents a possible major paradigm shift in image capture."

Illustration of photoelectron counting. The signal is the continuously sampled FD voltage from a TPG jot (with 0.28 e− r.m.s. read noise when operated in a CDS mode.) The FD voltage was changed by photoelectrons from SW (and possibly dark generated electrons.) Each single electron generates a fixed voltage jump on FD, and with deep sub-electron read noise, the electron quantization effect is visible.
Scatter plot of voltage read noise vs. CG for PG jots and TPG jots. The read noise in e− r.m.s. levels are shown with dashed lines.

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