Underwater 3D reconstruction using a photometric stereo with illuminance estimation.

Underwater image sensing is directly affected by the change in illuminance towards a camera caused by the refraction of light in different media. In this study, the convergence of a near-field point light source in water is analyzed using a light propagation model. The photometric stereo (PS) formula is determined based on an accurate estimation of the illuminance entering the camera. An underwater PS system is designed to verify the proposed method's feasibility. The experimental results demonstrate improved accuracy in normal calculation. This helps achieve accurate underwater 3D reconstruction of objects that is suitable for underwater surface microdefect detection.