Abstract
Three-dimensional imaging in underwater environments was investigated using a picosecond resolution silicon single-photon avalanche diode (SPAD) detector array fabricated in complementary metal-oxide semiconductor (CMOS) technology. Each detector in the 192 × 128 SPAD array had an individual time-to-digital converter allowing rapid, simultaneous acquisition of data for the entire array using the time-correlated single-photon counting approach. A picosecond pulsed laser diode source operating at a wavelength of 670 nm was used to illuminate the underwater scenes, emitting an average optical power up to 8 mW. Both stationary and moving targets were imaged under a variety of underwater scattering conditions. The acquisition of depth and intensity videos of moving targets was demonstrated in dark laboratory conditions through scattering water, equivalent to having up to 6.7 attenuation lengths between the transceiver and target. Data were analyzed using a pixel-wise approach, as well as an image processing algorithm based on a median filter and polynomial approximation.
Highlights
High resolution optical imaging in turbid underwater scenarios remains a major challenge for the photonics community
This paper describes an investigation of the potential of single-photon avalanche diode (SPAD) detector arrays, operating at frame rates approaching 1 kHz, for single-photon depth imaging of stationary and moving targets in an underwater environment
This work presents the first depth and intensity profiles obtained in highly scattering underwater environments using a SPAD detector array
Summary
High resolution optical imaging in turbid underwater scenarios remains a major challenge for the photonics community. Underwater moving target data are acquired in two dimensions using complementary metal oxide semiconductor (CMOS) [6] or Si-based electron-multiplying charge coupled device (EMCCD) [7] based sensors, which are able to detect low light levels with a high pixel resolution (≥ 1024 × 1024) These cameras, are not equipped with picosecond timing electronics, and full depth information needs to be obtained with alternative techniques. The CMOS based system described in [6] uses a Q-switched laser emitting a 3.5 W average optical power beam at the wavelength 532 nm and obtained depth information with a range gated sweeping technique, which allows three dimensional imaging at up to 4.5 AL at 8 meters and a depth resolution of a few centimeters, depending on water turbidity
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