Phasor-based widefield FLIM using a gated 512×512 single-photon SPAD imager

Arin Can Ulku, Claudio Bruschini, Ivan Michel Antolovic, Shimon Weiss, Xavier Michalet, Edoardo Charbon

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

6 Scopus citations


Single-photon avalanche diode (SPAD) imagers can perform fast time-resolved imaging in a compact form factor, by exploiting the processing capability and speed of integrated CMOS electronics. Developments in SPAD imagers have recently made them compatible with widefield microscopy, thanks to array formats approaching one megapixel and sensitivity and noise levels approaching those of established technologies. In this paper, phasor-based FLIM is demonstrated with a gated binary 512×512 SPAD imager, which can operate with a gate length as short as 5.75 ns, a minimum gate step of 17.9 ps, and up to 98 kfps readout rate (1-bit frames). Lifetimes of ATTO 550 and Rhodamine 6G (R6G) solutions were measured across a 472×256 sub-array using phasor analysis, acquiring data by shifting a 13.1 ns gate window across the 50 ns laser period. The measurement accuracy obtained when employing such a scheme based on long, overlapping gates was validated by comparison with TCSPC measurements and fitting analysis results based on a standard Levenberg-Marquardt algorithm (<90% accuracy for the lifetime of R6G and ATTO 550). This demonstrates the ability of the proposed method to measure short lifetimes without minimum gate length requirements. The FLIM frame rate of the overall system can be increased up to a few fps for phasor-based widefield FLIM (moving closer to real-time operation) by FPGA-based parallel computation with continuous acquisition at the full speed of 98 kfps.

Original languageEnglish
Title of host publicationMultiphoton Microscopy in the Biomedical Sciences XIX
EditorsAmmasi Periasamy, Peter T. C. So, Karsten Konig
ISBN (Electronic)9781510624061
StatePublished - 2019
Externally publishedYes
EventMultiphoton Microscopy in the Biomedical Sciences XIX 2019 - San Francisco, United States
Duration: 3 Feb 20196 Feb 2019

Publication series

NameProgress in Biomedical Optics and Imaging - Proceedings of SPIE
ISSN (Print)1605-7422


ConferenceMultiphoton Microscopy in the Biomedical Sciences XIX 2019
Country/TerritoryUnited States
CitySan Francisco

Bibliographical note

Publisher Copyright:
© COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.


  • FLIM
  • Gated
  • Imaging
  • Phasor
  • SPAD
  • Sensor
  • Widefield


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