Measurement of hydrophilic angle on surface of insulator based on charge coupled device

The automatic measuring of hydrophilic angle on the surface of composite insulator is studied by charge coupled device(CCD).The devices and methods to acquire the image of the drip are described.And the process of the image manipulation is also described in brief,including the image pre-processing,the filtering,the binarization,the detection and refinement of the edge,and the filtering of the edge curve etc.The fitting of the edge curve is expounded emphatically.The two kinds of methods between polynomial fitting and orthogonal polynomials fitting are compared.Finally,the images of the fitting curve,the calculation of the tangent angles of two end points,as well as the analysis of the errors during acquisition of the hydrophilic angle are given.