The Development Of Video Autofocus Method

As a key technology in digital imaging system,autofocus plays an important role in terms of improving performace of digital imaging products.This paper presents an autofocus method of the camera with captured video sequence used in video conference . The proposed technique consists of two processing phases: automatic focus adjusting and monitoring phases. In the adjusting phase, mountain climbing algorithm is used to find the peek point of the focusing criteria function which reflects the definition of the images. To speed up searching processing and to keep good subjective quality of pictures, the concept of hyperfocal distance is utilized, and the searching step of the algorithm is adapted dynamically. Which searching processing, a return-examination method is used to exclude the affects of the varied shots on the focusing correctness. During monitoring phase, the variety of scenes is effectively detected and the condition under which automatic focus adjusting phase is restarted can be correctly determinded.The performance of the developed method has been successfully and effectively tested on 8020plus video conference terminal. Test results clearly show that the algorithm proposed achieves fast focus with less than 2 seconds and high precision. The technique also is robustness, and can be used in practical fields.