Determine the Surface Tension and Contact Angle of Drop by Image Processing Method

The liquid experiment in space needs intelligence to deal with the surveillance image right away to obtain the goal parameters. A method is investigated to analyze the physical feature of a drop, such as surface tension, contact angle and volume through fitting contour of the drop picture. From the grey picture, generally contour of a drop is obtained by edge detection and segmentation algorithms. Constructed the Laplace equation of the drop, made contour approach process through comparing and using Newton-Raphson method, Runge-Kutta method and coordinate optimizing method. With the help of contour approach, physical feature of the drop is obtained. A new algorithm which nests Newton-Raphson method with One-dimensional optimization is presented. Compared with the original algorithm raised by Ref.\,[1], the new one reached convergence quickly with high accuracy. It is a key technique of the space experimental system for liquid experiment. The method is especially applicable for unmanned environment as well as non-contact measurement in the experiments.