A non Cartesian FFT approach to image alignment

The estimation of large motions without prior knowledge is an important problem in image registration. In this paper we present the angular difference function (ADF) and demonstrate its applicability to rotation estimation. The ADF of two functions is defined as the integral of their spectral difference along the radial direction. It is efficiently computed using the pseudo-polar Fourier transform, which computes the discrete Fourier transform of an image on a near spherical grid. Unlike other Fourier based registration schemes, the suggested approach does not require any interpolation. Thus, it is more accurate and significantly faster.