Research Of Imaging Clearly And Area Constant Of Target In Motion In The Field Of View Of The Zoom Lens

Theodolite is one of the most important optical facilities, which is used tomeasure and track the path of the flying target and record flight attitude and events. Inorder to record and observe all kinds of parameters accurately, the image in thetheodolite has to be clear and steady, so it needs to change the focal length of the lensand focusing. Good performance optical systems is capable to response to the changeof target’s speed and distance quickly and guarantee the area of the image constant,the quality of the image clear.In the wake of the development of the science and technology, a lot of people andmoney had been put in the research of the system; of course, the performance of thezoom system is improved apparently. But compare to the foreign technique, domestictechnique of zoom system is behindhand, especially the system in the theodolite. Atpresent, although the system in the theodolite can realize the function of zoom theimage, it is a lot of difference before and after the operation, for example, the area ofthe image perhaps change suddenly which makes people feel uncomfortable. All ofabove are cause by the zoom system can not change the parameters according to thetarget’s status.By means of researching and studying the principle of the auto-focus andauto-zooming system existed in the theodolite, consider over the continuous increasing requirements of user in fact, the thesis put forward two academic means torealize the auto-zooming system. The first one is based on the distance of the target,according to the principle of projection lens，make use of the relationship of thedistance of object, the height of CCD and image, measure the distance of object tochange the focal length, after experimental verification, the method work well onregular shape object. The second one is based on the image information of the target,extract the image of target from the background, and make use of the ratio of pixels oftarget and background to change the focal length automatically. According to themeans mentioned above, system can realize the stable and continuous zoom.A better quality of image not only has a constant area of image, but also has aclear image and in a good condition of exposure, which needs to control the focusingand dimmer system. Solve the problem of auto-zooming system, at the same time,also analyze and design the auto-focusing and dimmer system. In the aspect ofauto-focusing, put forward a function of evaluation, compare to any other function,the algorithm has a small amount of calculation and more quickly, optimizedhill-climbing algorithm to avoid into local extreme. Adjust the exposure automaticallyby analysis the segment of the histogram.In the end of the thesis, test the strategy of auto-zooming、auto-focusing andauto-dimming on the experimental platform. It showed that in the observation of theflying target, the system with the strategy of auto-zooming complete the task ofchange the focal length in the pace with movement of target, furthermore, the qualityof the image keep clear and the exposure satisfied the requirement of the project.The proposed strategy of auto-zooming can realize the goal of measuring theflying target exactly，it has a reference value for further research. The improvedauto-focusing algorithm decrease the computing time，meet the real time requirementof theodolite.