Circular fringe center location based on local gradient direction estimation

A method based on the local gradient direction information is proposed to locate the center of circular fringe. The new method is developed which based on the idea that the normal directions of any point on the circular fringe are always pointing towards the center. Besides, the local gradient direction of fringe is related to the normal line of fringe. We deduce theoretically the principle of local gradient direction estimation. Then a new circular fringe center location algorithm is developed with the help of digital image processing technology and statistical ideas. The simulation results show that new method can locate accurately the center of different types of circular fringes with less or without filtering. It also holds good robustness and can meet the requirements of actual engineering application.