Autofocus Of Remote Sensing Camera Based On Image Registration

With the development of imaging technique and peoples'aspiration for obtaining the information of Earth, the remote sensing imaging technique gradually has become the research hot spot. It will be used widely in environmental monitoring, resource survey, atmospheric and oceanographic observations, astronomical observations, military observations aspects and so on. With the concept of the Agile Earth Observation Satellite proposed, space camera technique referred to a new level. This paper is mainly about how to realize auto-focusing in real time when the object moves in a high speed.The picture captured by the remote sensing camera would be degenerated since the camera constantly rotates around the earth. The degenerated image may decrease the focusing accuracy. In order to solve this problem, the paper researched four image motion compensation methods and proposed a method which is based on the TDI pattern of interline transfer progressive scan CCD. Experiment chooses the interline transfer progressive scan CCD KAI-1003 as the imaging device, and uses PLD to control the driving timing signal for the sake of matching the velocity between CCD and object. In this way, the motion blur could be eliminated. The experiment results show that the imaging system not only eliminates the motion blur but also increases the SNR of the image. After removing the motion blur, an auto-focusing method of remote sensing camera is also proposed, with the feature that the images have overlapped regions captured in a short time. Firstly, calculate the displacement and the overlapped regions of two adjacent images in the image sequences using the image registration algorithm. Secondly, obtain a sequence of focusing accuracy values through performing a sharpness evaluation function on the overlapped region of each image. Finally, according to the transfer characteristic, unify the evaluation values in a same merit evaluation system and find the accurate focus position. The experiment results indicate:the imaging system works pretty well in auto-focusing when the object moves in a high speed. This paper has two main innovations. First, a real-time auto-focusing method of remote sensing camera is proposed with the feature that the images have overlapped regions captured in a short time. Second, in order to remove the motion blur, we provide a method based on the TDI pattern of interline transfer progressive scan CCD.