关键词: 散焦模糊, 点扩展函数, 线扩展函数, 图像模糊度, 模板匹配

Abstract: This paper proposes a new method to estimate the parameter of Point Spread Function（PSF） for out-of-focus Image.At first，the out-of-focus blurring is modeled as Gaussian blurring.Then，analyze the differential features of several types of image edges and extract Gaussian Line Spread Function（LSF） from image edges using these differential features.Since matching filtering has the advantage of maximizing the output signal-to-noise ratio，based on this philosophy this paper applies template matching method to the evaluation of LSF standard deviation（STDEV）.The STDEV of Gaussian PSF can be easily calculated from the STDEV of LSF by the symmetric property of PSF.The result shows that the proposed method can accurately evaluate the STDEV of out-of-focus image PSF.Finally，this paper takes the STDEV of PSF as an objective metric of image blurriness.The testing result shows that this objective metric correlates well with the judgment of human observers.Therefore，the STDEV of PSF is an excellent quality metric for out-of-focus blur images.

Key words: out-of-focus blur, point spread function, line spread function, image blurriness, template matching