Phase-unwrapping is a basic problem in many interferometry. The phase unwrapping algorithm using DCT method is one of specially effective and robust ones. However

it is only suitable for rectangle fields. In this paper

it is effectively used for circle fields by introducing weighted and iterative methods. The computer simulation shows that the accuracy can reach to 10

-7

rad and important improvement is made. A sample of multiline is measured using phase-stepping interferometry in DOP-2000 digital optical profiler developed by us. Further experimental results indicate that the method is very effective and practical.