An On-Satellite Real Time Fusion Technology for HDR Images Acquired by Large Array CMOS Sensors

The high dynamic-range (HDR) imaging technology has become an important topic in remote sensing imagery in recent years as it can provide more meticulous information. However, real time HDR fusion on satellites is still an engineering knot, mainly for two reasons: first, the weakened timeliness of remote sensing images caused by the earthward image transmission as complex fusion algorithms are restricted on satellites with only limited hardware processing platforms available thereon; second, the possible smearing for moving objects caused by multiple exposures of on-satellite imaging may reduce the definition and usability of images acquired. The paper studies a HDR real time fusion system for a type of large area array CMOS sensors. With the system, a real time HDR fusion is achieved for two images of different brightness with high gain and low gain, respectively, output by CMOS image sensors through one exposure. The system can not only use the two images exposed at the same time point to avoid smearing caused by asynchronous imaging, but also abstain from complex fusion algorithms like image registration, greatly reducing the hardware requirements for on-satellite real time fusion of HDR images, and improving the equipment employment feasibility on satellites. First, the paper elaborates the fusion algorithm based on the working principle of CMOS sensors . Then, as general on-chip memories are unable to handle the large area array CMOS sensor’s massive pixels and data processing, the design in the paper combines off-chip large-capacity flash memories and DDR memories to meet the requirement of massive storage and achieve a rapid real time fusion. Finally, an imaging verification test is carried out. The results show that the designed HDR real time fusion system can meet the on-satellite use demands of large area array CMOS sensors.