目的 多聚焦图像融合技术一个关键问题是如何准确地判断待融合图像的清晰度。提出了基于归一化结构极值点数目的清晰度判断准则。方法 基于图像的局部极值点特性，定义了归一化结构极值点数目这个指标作为清晰度判断准则，同时还给出了利用该准则和融合决策矩阵快速估计技术的多聚焦图像快速融合方法。结果 利用提出的清晰度判断准则和融合方法，实验结果表明上述问题得到了很好的解决。结论 提出了一个新的图像清晰度判断准则，该准则判断准确率高，且对脉冲噪声有好的鲁棒性。通过与传统融合方法对两组实验图像融合结果的主客观比较表明，该方法的融合速度和效果比现有多聚焦图像融合方法有明显提高。

Objective A key question of multi-focus image fusion is how to decide the clarity of the source images. To solve this problem, a new focus measure is proposed. Method The new focus measure based on properties of local extrema is proposed, namely, the normalized structure extrema. We propose a fast image fusion method based on the new focus measure and a quick estimation of the fusion decision matrix. Result With the new criterion of image clarity and the fusion method introduced in the paper, multi-focus image fusion yield superior performance than the conventional approaches in terms of the test results. Conclusion Normalized structure extrema number is a new focus measure that can judge the clarity of a region effectively and more robustly against pulse noise. Compared with some traditional methods of multi-focus image fusion on both the subjective visual effect and objective evaluation, it indicates that the presented method improves the fused results and efficiency saliently.