A fast automatic exposure adjustment method based on gray and information entropy for space camera

Abstract

With the development of space technology, spacecraft are serving more and more exploration missions. The cameras on spacecraft become an important data source for monitoring the space motion status of spacecraft, as well as the landing and takeoff processes at extraterrestrial bodies. However, space cameras are less sensitive to rapid changes in the external light environment and cannot quickly adapt to rapidly changing light scenes, resulting in slightly poorer imaging quality at default camera parameter settings. In order to obtain a better on-star imaging effect, space camera automatic exposure technology has become an important part of the on-star intelligent image processing algorithm, which provides important support for safe and stable spacecraft landing and status monitoring. Therefore, this paper proposes a fast automatic exposure algorithm for space cameras based on grayscale and information entropy, which can adjust the exposure time in real time according to the scene brightness and deliver the exposure time to the next image frame to effectively improve the quality of on-star space camera imaging. The algorithm contains three modules, which are grayscale threshold setting, image grayscale adjustment, and optimal exposure time selection and exposure time delivery. Image grayscale adjustment is achieved by high magnification for fast exposure time adjustment, and the optimal exposure time is selected according to the information entropy. The analysis of the camera images collected in the laboratory and the data acquired by the satellite shows that this algorithm can better adjust the exposure time and obtain high-quality and high-resolution remote sensing images.