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In practical application of focusing inversion��there are two problems need to be solved in time: the skin effect of imaging and excessive convergency of anomalous source�� Skin effect problem can be solved by restraining focusing inversion using index depth weight function�� The results show that the depth weight method does well in limiting the convergency of too much anomalous sources in the surface�� In order to control the excessive convergency of the anomalous sources��the authors proposed the expansion of anomalous source method which makes the remnant anomalous sources expand out of the anomalous body iteratively�� The experimental results indicate that the imaging effect using expansion of anomalous source method was much better than that by using conventional chopping of anomalous sources��