The visual measurement techniques play an important role in underwater three-dimensional (3D) topography reconstruction. Line structured light measurement are widely used in visual 3D information acquisition. Aiming at the refractive nonlinear imaging effects and image degradation problems in underwater measurements, this paper proposes a physical enhancement-based underwater nonlinear refraction measurement model (peUNR). First, the underwater images are corrected by physical enhancement based on scattering imaging theory to improve the image recognition. Second, a refraction relationship for underwater visual measurements is developed by ray tracing. In this model, the light plane is unchanged before and after reaching the surface of the underwater target. As a result, the system parameters can be calibrated in air, allowing high-precision 3D reconstruction underwater without the need for underwater calibration. At last, in order to reduce the dependence of structured light stripe extraction on image quality, a multiline rotating structured light projection mode is designed by using binary coding, which fulfils the need for fast and portable measurements and improves the measurement efficiency and resolution simultaneously. The experimental results of underwater measurement indicate that the residual error of the fitted plane obtained by the peUNR model is 1.81 mm in turbid water with a sand content of 125 g/m3, which satisfy the requirements of underwater 3D high-precision measurement.
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