介绍了接触角法测定表面洁净度的基本原理,并针对表面液滴图像的特点,采用图像处理技术测量表面接触角。首先利用中值滤波算法对图像进行预处理;然后利用边缘检测和轮廓跟踪等算法提取液滴的边界曲线;最后采用以多项式作为基函数的最小二乘拟合算法拟合液滴边界曲线,继而求导得到接触角。结果表明,当选用四阶或五阶多项式为拟合函数,拟合采样点选取在60～200个范围内时,该软件测量接触角的精度高于德国KRUSS光学接触角测量仪DSA100的测量精度,且与手动测量接触角的结果相比较,误差值均小于2°。

Basic principles of determining the surface cleanliness by the method of contact angle is described. Considering the characteristics of the surface droplet image, the surface′s contact angle is measured based on image processing techniques. Firstly, the median filter algorithm was deployed to preprocess the droplet images; secondly, in order to extract the boundary curve of the droplet, the edge detecting algorithm and the outline tracking algorithm were used; finally, the least squares fitting algorithm was deployed to fit the boundary curve of droplet, hence contact angles were calculated. Experiments show that the contact angle measurement′s accuracy was better than that of Germany KRUSS optical contact angle measuring instrument DSA100 when four or five order polynomial fitting function was selected and the fitting sampling points were selected in the range of 60 to 200. The difference between contact angle measurement results proposed and the results of the angle measured by MB-ruler software was less than 2°.