预处理过程中对虹膜的精确定位，使定位后的虹膜图像具有平移、尺度和旋转的不变性。

Precision locating for iris in the process of preprocessing makes iris image have invariance in translation, size and rotation.

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因此，本文实现虹膜旋转不变性的方法不会增加虹膜识别系统的计算复杂度，同时实现了优秀的旋转不变性。

So, in our methods, the complexity of the methods are not increased, and the error rates of the methods may never increase, no matter how much the iris rotate.

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