The traditional knife-edge method has the limitation that the chosen edge must be approximately perpendicular or parallel to the sampling direction （ideal edge）

which leads to difficulties of choosing usable knife-edge.Focusing on the issue

a new model of calculating PSF based on knife-edges with any slant angles is proposed in this paper.The proposed method is not only equivalent to the traditional one with the ideal edge

but also better than the traditional method with a slant edge in the PSNR （Peak Signal to Noise Ratio）

MSE （Mean Square Error） and SNR （Signal to Noise Ratio） of the restored image by the extracted PSF.The proposed method is robust to extract PSFs from knife-edges of any slant angles for image restoration

which extends its application.The validity of the proposed method has been reasoned both theoretically and practically

and tested with simulated data andADS40 data.