去斑后，采用基于阈值的直方图规定化方法，以弥补对比度可能降低情况。
After speckle reducing, a histogram defined method based on the threshold is employed to compensate for possible contrast reduction.
该方法不仅全自动提取变化信息，而且经过三次降斑去噪处理，因此检测精度较高。
The method not only can extract change information automatically, but also reduce spot noise three times, so it has high accuracy.
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