Autofocus Method For Remote Sensing Cameras

Remote sensing cameras,as one of the important means of space-to-ground observation,play a significant role in military reconnaissance,geographical mapping and situational awareness,the increasingly complex international environment and the growing domestic economic and social environment.With the increase of demand,its application mode is becoming more and more colorful.As we all know,autofocus technology is an important technical guarantee for imaging quality of all imaging systems.For remote sensing camera,auto focus technology is the guarantee of the key technical indicators,such as resolution and transfer function,of remote sensing cameras.Compared with manual focusing,autofocus technology has the advantages of high speed and high accuracy.Therefore,researchers have paid much attention it.The automatic focusing method of several typical remote sensing camera(scanning remote sensing camera,geostationary orbit staring remote sensing camera and low orbit short staring imaging remote sensing camera)is studied in this paper1)For scanning remote sensing camera,the automatic focusing method of scanning remote sensing cameras based on overlap imaging is proposed in this paper.This method uses the general structure of the focal plane detector,and applies the traditional image sharpness estimation function system to the scanning remote sensing cameras,And the reliability improvement method is specially designed,which makes the success rate of autofocus is enhanced by 12% compared with the traditional method.In addition,an automatic focusing method based on area detector using digital TDI overlap imaging is proposed.The influence of image motion on auto focusing effect is analyzed,and a new image sharpness evaluation function based on wavelet decomposition directional parameter is proposed,which effectively eliminates the influence of image motion.2)For geostationary orbit staring remote sensing cameras,based on the analysis of the imaging characteristics,the traditional image clarity evaluation function system and their respective characteristics are introduced and analyzed in details.Through the simulation of remote sensing images,several typical image sharpness evaluation function characteristics are analyzed,and the evaluation function which is suitable for the relatively low resolution of the staring camera is also defined.In addition,in order to enhance the focusing efficiency,we put forward the evaluation window selection criterion based on contour information extraction.Further,we put forward a localization method based on the particle swarm search algorithm,which greatly improve the efficiency of automatic focusing.3)For low orbit staring remote sensing camera,based on the automatic focusing demand of video capture,a phase detection automatic focusing method based on dual lens two stage imaging is proposed,which realizes one step quick focusing.The mathematical relation between phase difference and defocusing quantity is derived.In addition,a phase detection automatic focusing method based on dual band imaging is proposed.The phase detection function is realized by using dual band filter and linear array detector.Finally,two automatic focusing methods based on micro lens array and detector are proposed to simplify the software and hardware for automatic phase detection,they are a method based on microlens and pixel occlusion and a method based on microlens and special pixel structure.The method of image phase detection based on correlation function is given,and simulation analysis is carried out.