Correction method for segmenting valid measuring region of interference fringe patterns

Segmenting the valid measuring region from an interferogram is an important step in the grazing incidence interferometry, which is related to the accuracy of the measurement result. For the spurious fringes which are generated by the diffuse reflection of the chamfering in the edge of the object surface, we propose a method-spin segment to correct the result of the image segment. First, a phase schematic diagram whose stripe feature is clearer than the original interference fringe patterns is generated. Next, the difference of the gray gradient between the fringe's local normal direction and local tangent direction is calculated to judge the valid measurement region. The principles of selecting some parameters are summarized and the calculation steps are shown. To examine the correction method, the results of an experimental application of spin segment are given to verify the feasibility and accuracy.