An automatic measurement system for micro electro mechanical element with optical interferometric microscope is presented in the paper. The system introduces a novel method to calculate the central dark fringe (intensity minimum) and central bright fringe (intensity maximum) in the image. The changing of height in asymmetric micro-structure, based on the phase definition of interference fringe can be calculated. Interferometric image information is derived through image processing method, and

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... novated contour line algorithm is used to build up micro-structure 3D profile. In the experiments, the total processing time for five parts of element could be reduced to less than 5 s and the system error is less than 0.02 m.