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.