为了更精确地进行离焦模糊图像检测，提出了一种针对一幅图的离焦模糊图像客观检测的新方法，其核心思想是由线扩展函数（LSF）得到离焦模糊图像的点扩展函数（PSF）。该方法首先假定图像中至少能检测到一条明显边缘，然后由此边缘构造LSF。由于作用于空间域，无需复杂的傅里叶变换或迭代运算，因此该方法速度很快。此外，为使检测方法更具普遍性，还提出了离焦模糊检测的一般准则，这种准则适用于所有图像而不依赖于图像的内容。实验结果验证了该方法的精确性和有效性。

This paper presents a new method for objective measurement of out-of-focus blurred images of one authentic image. The essential idea is to derive the point spread function(PSF) of an out-of-focus blur image from the line spread function(LSF). In this method, it is assumed that at least one sharp edge could be detected. The LSF is thercafter constructed from the edge(s). This approach has fast speed as it works in spatial domain with neither complex Fourier transform nor iterative computation. Moreover, a generic criterion for out-of-focus blur measurement is proposed and it can be applied to all images being independent of image contents. The experimental results validate the accuracy and efficiency of the proposed method.