High-precision time-to-digital converters (TDC) are simply scientific stopwatches capable of providing a timing resolution much less than 50ps. TDCs are widely used for time-of-flight applications, such as ranging [1], space sciences [2], particle detection [3], time-resolved spectroscopy and imaging [4, 5], quantum communications [6], and medical diagnosis and tomography [7, 8]. They are one of the most important timing components (along with oscillators) that interpret fast physical phenomena into human readable formats. Scientific standard TDCs, however, are not cheap, especially when we need to develop multi-channel acquisition systems.

With radical progresses in semiconductor manufacturing, new FPGA chips have allowed TDCs to provide a resolution much lower than 50ps [9]. This allows wider scientific communities to develop cheaper and more flexible acquisition front-ends. In this project, we will implement a brandnew TDC architecture with Xilinx FGPAs to develop a high-linearity multi-channel 8ps TDC with smart on-the-fly calibrations to be used for ranging and fluorescence lifetime imaging applications [1, 4, 5, 10]. The developed TDC systems are likely to bring immediate impact in time-of-arrival (including sensing and imaging) communities. 

1. G. Gariepy, F. Tonolini, R. Henderson, J. Leach, and D. Faccio, "Detection and tracking of moving objects hidden from view," Nature Photonics, 2015.

2. G. A. Neumann, J. F. Cavanaugh, X. Sun, E. M. Mazarico, D. E. Smith, M. T. Zuber, et al., "Bright and dark polar deposits on Mercury: Evidence for surface volatiles," Science, vol. 339, pp. 296-300, 2013.

3. J. S. Karp, S. Surti, M. E. Daube-Witherspoon, and G. Muehllehner, "Benefit of time-of-flight in PET: experimental and clinical results," J. Nucl. Med., vol. 49, pp. 462-70, 2008.

4. D. Li, J. Arlt, D. Tyndall, R. Walker, J. Richardson, D. Stoppa, E. Charbon, R. K. Henderson, "Video-rate fluorescence lifetime imaging camera with CMOS single-photon avalanche diode arrays and high-speed imaging algorithm," J. Biomed. Opt. 16(9), 096012, 2011.

5. S. P. Poland, N. Krstajić, J. Monypenny, S. Coelho, D. Tyndall, R. J. Walker, et al., "A high speed multifocal multiphoton fluorescence lifetime imaging microscope for live-cell FRET imaging," Biomed. Opt. Express, vol. 6, pp. 277-296, 2015.

6. M. Förtsch, J. U. Fürst, C. Wittmann, D. Strekalov, A. Aiello, M. V. Chekhova, et al., "A versatile source of single photons for quantum information processing," Nature Communications, vol. 4, p. 1818, 2013.

7. L. H. Braga, L. Gasparini, L. Grant, R. K. Henderson, N. Massari, M. Perenzoni, et al., "A fully digital 8 16 SiPM array for PET applications with per-pixel TDCs and real-time energy output," IEEE J. Solid-State Circuits., vol. 49, pp. 301-314, 2014.

8. Z. Cheng, M. J. Deen, and H. Peng, "A low-power gateable vernier ring oscillator time-to-digital converter for biomedical imaging applications," IEEE Trans. Biomed. Circuits Syst., vol. 10, pp. 445-454, 2016.

9. J. Y. Won and J. S. Lee, "Time-to-Digital Converter Using a Tuned-Delay Line Evaluated in 28-, 40-, and 45-nm FPGAs," IEEE Trans. Instrum. Meas., vol. 65, pp. 1678-1689, 2016.

10. T. Laviv, B.B. Kim, J. Chu, A.J. Lam, M.Z. Lin, and R. Yasuda, "Simultaneous dual-color fluorescence lifetime imaging with novel red-shifted fluorescent proteins," Nature Methods 13, 989-992, 2016.