Underwater single‑photon depth imaging

It has been demonstrated that time-correlated single-photon counting (TCSPC) has the potential to be the preferred choice of detection for high resolution three-dimensional profiling in several challenging scenarios, for example through obscurants and complex multiple surface targets. Over the last few years, the TCSPC technique has been used in highly scattering underwater environments, demonstrating submillimeter resolution in turbid environments with over 8 attenuation lengths between transceiver and target due to its excellent surface to surface resolution and high optical sensitivity. This presentation will describe several transceiver systems for underwater imaging based on a range of silicon single photon avalanche diode (Si-SPAD) detectors, either fabricated in custom planar fabrication technology and in complementary metal-oxide semiconductor (CMOS) technology. Laboratory based experiments and field trials were conducted in several scattering underwater environments, demonstrating imaging up to 9.2 attenuation lengths and ranging up to 14 attenuation lengths when using average optical power up to 50 mW.