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Measurement and Analysis of Turbulence Degradation in Underwater Laser Imaging Using the Particle Image Velocimetry (PIV) Method
Y.Z. Chen, Y.W. Guo, Y.N. Pan, Z. Li and W.L. Yang

The turbulence which exists in natural water such as river and lake is a serious impact factor in underwater laser imaging detection. In order to improve the visual quality by reducing the degradation caused by turbulence, the properties of the turbulent flow are studied in this paper. The turbulent velocity field of river water is measured using a particle image velocimetry (PIV) method in which small bubbles are seeded into the water as nonpolluting tracing particles. Using the velocity field as prior knowledge for image restoration and reconstruction in an underwater laser imaging exploration system, experimental results prove that the proposed method can effectively measure the properties of the turbulent flow and improve the resolution and quality for imaging in turbid ocean water. This presented effort shows potential of improving image quality for detecting objects embedded or geological exploration in media with turbulence, such as lake water, river water, and sea water in various applications.

Keywords: Diode laser, underwater, particle image velocimetry (PIV), velocity field, image restoration, point spread function (PSF), prior knowledge

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