Grey Wolf Optimizer-Based Automatic Focusing for High Magnification Systems

Abstract

High-quality astronomical images significantly affect the results of astronomical scientific research. Since the accurate focus is one of the principal factors that vary the observation quality, automatic focusing is essential. The automatic focusing finds the best position by measuring the images’ focus level at different positions and considering the best one. It applies a focus measure operator to evaluate the focus level. However, the astronomical images suffer from high blur due to the high magnification of the telescope. Thus, a proper focus measure is tricky due to a high blur. In this paper, we firstly investigate a focus operator based on fuzzy logic because of its ability to deal with imprecise data. We secondly optimized the parameters of the membership functions using the grey wolf optimizer (GWO). We acquired two data sets using the 74-inches telescope of the Kottamia astronomical observatory (KAO) at good seeing conditions and composed of in-focus and out-of-focus images. After that, we compare the measures using four criteria. The results show that the optimized one outperforms the other operators.