Laser scanning imaging system for underwater robotics vehicle

Abstract

Optical vision has great advantages for its intuitive representation and high resolution. However, optical image quality is severely degraded due to the absorption and scattering of light in turbid water environments. An illumination model is developed to analyze the relationship between light flux, illumination volume, and water turbidity. It focuses on highly turbid water condition, and assumes that forward and backward scattered fluxes uniformly fill all forward and backward directions. When a light beam is being expanded, the total flux received by a camera increases, and backscattered component increases faster than the correctly transmitted (or desired) component. The model is verified with experimental measurements in a 0.6 meter long water tank. Various illumination volume settings of a laser beam are tested and their output images are evaluated by the MTF (modulation transfer function) assessment. The model is applied to a prototype of laser scanning imaging system on a small underwater robotics vehicle to optimize the illumination volume, scanning speed, and image quality.