Fast zooming and focusing algorithm for real-time surveillance camera system

초록

To clearly identify the face given in a surveillance image, this paper proposes a new method that magnifies the face image large enough and brings the magnified face image in focus. For this purpose, the compound lens system consisted of the zooming and focusing lenses is analysed to derive the relationship between the positions of lenses and the image size. Once the face size in the surveillance image and the target face size to achieve are given, the positions of the lenses are determined by the derived relationship. To adjust the positions of the lenses to obtain the focused image, the four point measurement algorithm is proposed. It calculates the focus measures of at most 4 positions and estimates the position having the maximum focus measure. The algorithm has been implemented on the camera system whose lenses are controlled by fast motors. The experimental results have shown that the magnified and focused image can be obtained in 0.77 seconds on average.