A combined method for obtaining fringe orientations of ESPI

Fringe orientation can direct the processing of fringe patterns and provide basic information for understanding the fringe patterns. The gradient method is popularly used for its convenience but it is easily affected by noise. The plane-fit method is capable of obtaining precise local fringe orientation despite the high speckle noise but it is strict with the calculating window size. In this paper, a combined method is proposed. This method uses the plane-fit algorithm to get local gradients and uses the gradient method to get the orientation results from these gradients. It can be seen that this new method can get more accurate orientations for ESPI than both the gradient method and the plane-fit method.