A weighted contrast enhancement autofocus algorithm

Motion errors are inevitably introduced when data are acquired and considerably degrade the image quality in terms of geometric resolution, radiometric accuracy and image contrast, especially in high resolution spotlight synthetic aperture radar (SAR) imagery. In this paper, we describe a weighted contrast enhancement autofocus algorithm that is based on spatially variant model and adopts a mean square error (MSE) phase estimator in which the weights are determined by their contrasts of corresponding sub-scenes. The presented algorithm is very robust to deal with substantial errors over a variety of scenes even in conditions of homogenous areas with no prominent point scatters and enables the utilization of fast Fourier transform (FFT). Experimental results obtained by the proposed methods confirm that the analysis extends well to realistic situations.