基于水平集的接触角算法及在RTV憎水性检测中的应用

Contact Angle Algorithm Based on Level Set and Its Application in RTV Silicone Rubber Hydrophobicity Detection

静态接触角是表征材料憎水性能的一个重要指标,但其难以自动准确获得。本文使用基于水平集的几何活动轮廓模型方法获得液滴的轮廓,该方法基于求解偏微分方程获得图像边缘,在边缘较清晰时能自动获得具有一定准确性的液滴轮廓。当试验液滴体积较小时,图像中液滴边缘为圆形的一部分,因此将所得边缘点按照一定准则分离为圆弧部分和水平线部分,考虑到它们满足相关方程的基础上采用最小二乘算法进行拟合获得了圆心、半径和水平线的纵坐标,据此即可获得静态接触角。针对仿真和实际拍摄的室温硫化硅橡胶涂层的液滴图像使用本文方法与基于手动获得液滴边缘然后拟合的算法进行比较,多幅图像的计算结果表明本文方法具有较高的准确性。该方法的提出为静态接触角的自动准确测量提供了一种思路。

Static contact angle is an important index of material hydrophobicity,but it is difficult to be obtained automatically and accurately.In this paper,droplet edge is obtained automatically by geometric active contour model based on the level set method after the droplet figure is obtained.The level set method obtains the droplet edge by solving partial differential equation,and if the droplet figure is relative clear,then the edge can be obtained relative accurately.If the volume of droplet is small,the edge of droplet figure is a part of circle.Then the obtained edge is divided into arc part and horizontal line part according to certain rule.The circle center,radius and vertical coordinates of horizontal line are obtained by least square fitting method according to coherent equation,and the static contact angle is calculated by circle parameters and intersection point of air,liquid and solid.The method is applied to simulated and real droplet figure of（room temperature vulcanization RTV） silicone rubber coating,and the result is compared to the method in which the edge is obtained manually,and the result indicates the proposed method has high accurate.The proposed method is helpful for study of automatic and accurate measurement of static contact angle.