A multi-refraction-based 3D reconstruction method for underwater measurement with rotating scanning.

This paper presents a novel reconstruction method based on multi-refraction to remedy the non-linear refraction, which recovers 3D geometry from 2D images. To simplify calibration, this paper prove that air calibration can replace underwater calibration. Finally, a multi-line rotating structured is designed to improve the measurement efficiency without additional equipment. The results of the clean water experiment show that the measurement accuracy is 1.91 mm within the 1000–2000 mm depth of field. The qualitative analysis demonstrates our method can reconstruct the surface topography of underwater U and N letter boards. In different Nephelometric Turbidity Unit (NTU) (as NTU = 0.156 mg/ml) environment, a circular plate with a diameter of 220 mm is measured, the shape reconstruction error (whether the reconstructed shape is a circular, square, or other) is 1.74 mm; the diameter measurement result is 218 mm, so the size error of the circular plate is 2 mm. [ABSTRACT FROM AUTHOR]