Dual-side snapshot light field imaging for accurate 3D volumetry of opaque and drifting underwater particles

Accurate in-situ volume measurement of small (1mm–10 cm) drifting underwater particles is critical for marine ecology and pollutant monitoring, yet it demands snapshot 3D imaging to avoid motion artifacts. Existing imaging techniques—including digital holography and conventional light field imaging—face a fundamental limitation in recovering the complete surface geometry of opaque and semi-transparent particles due to optical occlusion and limited perspective sampling. We overcome this challenge with a face-to-face dual light field camera (F2F-DLFC) system, which simultaneously captures both sides of a target under incoherent dark-field illumination. This dual-side snapshot strategy enables full 3D reconstruction of opaque particles, with experimental results showing volume errors below 6% for targets such as live fish and irregular pellets. While semi-transparent objects still present reconstruction challenges, this work establishes a foundational methodology for in-situ volumetric instrument development, providing a viable approach for accurate volumetry of a wide range of underwater particles.