A fully digital auto-focusing system based on image restoration

In order to increase the accuracy in estimating the point spread function (PSF) of out-of-focus blur, we subdivided the input image and then averaged the PSFs from each subimage. The PSF of each subimage is estimated by differentiating the step response along the appropriately estimated edge direction under the assumption that an image usually has a piecewise linear boundary between an object and the background. Once the averaged PSF is obtained we can use any kind of image restoration filter according to specific application requirements, such as computational complexity or processing time.