Using non-uniform sampling to make automatic focusing result correct

In automatic focusing system, the focusing window directly affects the speed and veracity of auto focusing. If focusing window is too big or too small, there will be incorrect focus result because of background in the window or object out of the window. A practical real-time auto-focus algorithm for digital camera is presented, and it improves the reliability and speed of auto focusing process. The proposed algorithm adopts non-uniform sampling and threshold gradient in order to get higher resolution in image central part and wider view field. Experimental results demonstrate that the proposed algorithm can be an effective alternative to most of the images, especially to the images in which the objects are out of focusing window or the objects don´t content intensity changes in focusing window. In addition, the speed and veracity of focus are improved and the data of image is reduced.