<title>Quantitative image quality evaluations of enhanced images in turbid water medium</title>

In order to improve underwater visibility, general considerations are planned in two stages. There is hardware upgrading followed by system optimization stage. For the former, we choose to improve the underwater visibility with advanced techniques: range gated imaging system, and the optimization in terms of image processing techniques. Four selected image enhancement technique has been tested, namely Contrast Stretching, CLAHE, Illumination-reflectance Model and Homomorphic Filtering. Quantitative image quality measures are used to evaluate the enhanced imaging techniques. Three image assessment techniques are used to quantify image quality of the imaging system in increased turbidity condition, namely Modified Fidelity (MF), Modified Strehl Ratio (MSR2), and Contrast-to-Noise Ratio (CNR). In the first stage, the quantitative measures have shown at least 40% improvement from non-gated to gated images in increased turbidity. Finally, the enhancement techniques further improve the gated images with limited noise amplification issues.