Study On Key Techniques Of Autofocusing For Long-focus Camera

Long focus cameras have been widely used in military and civil fields because of its characteristics such as high resolution.Researching and designing of Autofocusing system becomes one of the key technologies to ensure the imaging quality due to its optical structure.According to the project requirements,taking a long-focus camera as the research object,key Techniques of Autofocusing were studied in this paper.The main works are listed as following:Firstly,this paper studies on the main reasons for off-focusing and analysis the defocusing amount caused by environmental and height changes based on software simulation,then puts forward the suitable auto-focusing scheme.Secondly,this paper mainly studies on the key problems to construct the Clarity-Evaluation-Function: studies on the fuzzy principal of the image,and contrasts different Clarity-Evaluation-Function,then improve its performance.The Focusing window and search strategy also are studied in this part.Thirdly,this paper designs two kind of focusing mechanism.One of them is adjusting the mirror by ball screw assembly;another is moving the image plane by cam and gear.The principle of auto focusing,system composition,selection of key parts and the focal precision also were analyzed in this part.Lastly,this paper does the experiments.The results indicate that the designed auto focusing system meet the requirements of focusing accuracy.In the end of the paper,a conclusion has been drawn and some advices have been suggested.