A scanning depth imaging system is used for the investigation of three-dimensional image reconstruction and classification of targets in underwater environments. The system uses the Time-Correlated Single-Photon Counting (TCSPC) technique to measure single-photon time-of-flight. In this paper, we use both single and multiple wavelengths to interrogate underwater targets. This presentation will show laboratory measurements on several target scenarios, including targets in clutter. We demonstrate high resolution depth and intensity image reconstruction in highly scattering underwater scenarios, and show image reconstruction at up to nine attenuation lengths between transceiver and target. The system comprised a scanning transceiver unit, fiber coupled to a silicon single-photon avalanche diode (Si SPAD) and a supercontinuum laser system operating at the repetition rate of 19.5 MHz. An acousto-optic tunable filter (AOTF) is used to select an individual operational wavelength in the range 500 nm to 725 nm. The measurements used a range of system configurations, including both single wavelength and multiple wavelength measurements. Generally, the measurements used sub-milliwatt average optical power levels. Bespoke algorithms were developed to identify man-made objects hidden by marine vegetation in the scanned scene. Advanced statistical image processing methods were used to improve target discrimination and to reconstruct the target under different conditions, including reduced number of wavelengths and number of pixels, and reduced acquisition time. Particular attention will be given to the photon starved regime, which will be typical of data acquired at long distances in open ocean waters or in highly scattering environments.

© 2018 COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Aurora Maccarone, Aongus McCarthy, Abderrahim Halimi, Julian Tachella, Puneet S. Chhabra, Yoann Altmann, Andrew M. Wallace, Stephen MaLaughlin, Yvan R. Petillot, and Gerald S. Buller, "Time-correlated single-photon counting for single and multiple wavelength underwater depth imaging (Conference Presentation)," Proc. SPIE 10659, Advanced Photon Counting Techniques XII, 106590R (Presented at SPIE Commercial + Scientific Sensing and Imaging: April 19, 2018; Published: 14 May 2018); https://doi.org/10.1117/12.2304937.5783307451001.