Image Focusing Using Gauss-Laguerre Circular Harmonic Filters

This paper presents a novel technique to measure the focus accuracy of an imaging system, by maximizing the energy captured by a bank of Gauss-Laguerre Circular Harmonic Filters (GL-CHFs). These indeed, provide a powerful tool to select and track a set of Focus Control Points (FCPs), over which a robust measure of the overall focus quality of the image can be computed. We will provide an experimental evidence that the proposed focus measure is monotonic and unimodal with respect to image blur and will present a comparative analysis against the most common algorithms available at the state of the art. The obtained results will show that the proposed technique is able to cope with highly noisy sensors, providing a valuable solution for the real time passive calibration of the optical payloads of Earth Observation systems.