Abstract

A $256\times256$ single-photon avalanche diode image sensor operating at 100 kfps with fill factor of 61% and pixel pitch of $16~\mu \text{m}$ is reported. An all-nMOS 7T pixel allows gated operation down to 4 ns and ~600-ps fall time with on-chip delay generation. The sensor operates with 0.996 temporal aperture ratio in rolling shutter. Gating and cooling allow the suppression of dark noise, which, in combination with the high fill factor, enables competitive low-light performance with electron multiplying charge-coupled devices while offering time-resolved imaging modes.

Highlights

  • S INGLE-PHOTON avalanche diode(SPAD) image sensors offer photon shot noise limited performance with picosecond timing resolution for applications in fluorescence lifetime imaging microscopy (FLIM), time-of-flight (ToF) 3-D imaging, and spectroscopy [1]

  • For single-photon avalanche diode (SPAD), external quantum efficiency (EQE) can be considered as the number of SPAD firings to incident photons, and has been historically limited by the low fill factor and large pixel pitches required by the complex digital pixel electronics necessary to Manuscript received June 21, 2017; revised September 10, 2017 and November 20, 2017; accepted November 29, 2017

  • The results indicate an optimized time gate that is comparable to other SPAD image sensors [16], and is ideal for selectively time gating the common fluorophores used in microscopy, which typically have a fluorescent lifetime between 0.5 and 4 ns [17]

Read more

Summary

INTRODUCTION

S INGLE-PHOTON avalanche diode(SPAD) image sensors offer photon shot noise limited performance with picosecond timing resolution for applications in fluorescence lifetime imaging microscopy (FLIM), time-of-flight (ToF) 3-D imaging, and spectroscopy [1]. For SPADs, EQE can be considered as the number of SPAD firings to incident photons, and has been historically limited by the low fill factor and large pixel pitches required by the complex digital pixel electronics necessary to Manuscript received June 21, 2017; revised September 10, 2017 and November 20, 2017; accepted November 29, 2017. Further improvements in sensitivity are required to match EMCCD or sCMOS performance in low-light imaging applications, such as single molecule localization microscopy, and to attain faster FLIM and ToF acquisition than is possible with existing SPAD sensors. In the device presented in this paper, the fill factor is enhanced by the optimization of the detector and pixel circuit. A consequence of having a large detector active area is increased dark count noise, compared to moving to a smaller pixel pitch and recovering fill factor using microlenses. The frame rate of 100 kfps ensures that there is practically no readout pile-up, and no loss of photons, in typical microscopy usage scenarios of around 10-k photons/s/pixel at output aggregate video rates of 10 frames/s

SENSOR ARCHITECTURE
PIXEL OPERATION AND GATING
NOISE AND NONUNIFORMITIES
Fluorescence Lifetime Imaging
Bead Tracking
SNR COMPARISON
CONCLUSION
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call