本方法主要针对定位容易出现错误的外边界，利用虹膜的结构特征和数学手段，对得到的虹膜外边界点进行验证，必要时通过计算得到准确的外边界点。

To the iris' outer boundary, we use the feature of the iris' structure and mathematical means to verify whether the iris outer boundary points are correct, and calculate the correct ones if necessary.

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