基于拟合的接触角算法在硅橡胶憎水性检测中的应用

Application of Fitting Based Contact Angle Algorithm in Silicone Rubber Hydrophobicity Detection

准确获得水珠的接触角对硅橡胶憎水性的研究具有重要意义。在手动获得水珠边缘点的基础上,根据水珠体积很小时其所拍得图像中的水珠边缘成圆形的原理运用最小二乘算法拟合水珠边缘,根据圆方程计算获得接触角,结果表明,本文方法的精确度远高于常用的量角器方法。通过实验分析了多种因素对计算所得接触角精确度和实时性的影响。实验结果表明:拟合点数选择3个即可,点数的增加对精确度提高作用不大但会增加计算时间;选择的拟合点应在水珠边缘圆弧上均匀分布;接触角的真实值对拟合精度影响不大,但会影响最小乘法的最佳拟合次数,从而影响计算时间;噪声的存在使误差增大,此时选择3个边缘点对多次选择边缘点的计算结果求平均可很大程度减少误差;放大倍数和图像倾斜程度对精确度和实时性影响都很小。所得结论有利于该方法更准、更快获得接触角。

It is obviously that accurate measurement of contact angle is important to the study of the hydrophobicity of silicone rubber.After obtaining the globule edge point manually,least square algorithm is used to fitting the globule edge according to the rule of globule edge is round if the globule volume is small.Then the contact angle is calculated based on circle equation.The influence of various factors on the accuracy and real-time performance of contact angle calculation is analyzed by experiment.Those experiments and analysis indicate that three fitting points is enough,and the increase of fitting point number will has little influence on accuracy but will increase the calculation time;the selected points should distributed in globule edge uniform;the best fitting number and calculation time of the least square algorithm is affected by real value of contact angle,but which has little influence on accuracy;the error of measurement will increase with the increase of noise,then the three edge points should be selected,and the mean value of multiple calculation can be used to decrease error;the figure magnification times and inclination degree has little influence on accuracy and real-time performance.Those conclusions are beneficial to calculate contact angle more accurate and fast by the fitting method.