Distortion operator kernel and accuracy of iterative image restoration

Variational functionals are commonly used for restoration of images distorted by a linear operator. In order to minimize a functional, the gradient descent method can be used. In this paper, we analyze the performance of the gradient descent method in the frequency domain and show that the method converges to the sum of the original undistorted function and the kernel function of a linear distortion operator. For uniform linear degradation, the kernel function is oscillating. It is shown that the use of metrical as well as topological characteristics can improve restoration quality. Computer simulation results are provided to illustrate the performance of the proposed algorithm.