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.