Abstract
It is important that the accurate measurement of strain and stress in the tooth for the reliable evaluation of strength or life of gear. In this paper, the method which is based on the image processing is applied in order to measure the strain near the fillet. The displacement of the point in the tooth flank is tracked, and then, the strain is calculated. The interrogation window size of cross-correlation method affect the accuracy and the resolution. In case of complicated profile such as fillet, the small size of the window is suitable.