A fast auto focusing method for digital still camera

The focusing system is an important factor to determine the imaging quality of a digital still camera. And the image sharpness evaluation algorithm is a key aspect in implementing the focusing system. Now, different auto focusing methods exist for many digital still cameras, and various evaluation algorithms have been present, but there are some deficiencies for implementing the software auto focusing system. While not ignoring commercially available methods requiring specialized hardware, in this paper, a new evaluation method based on the image absolute central moment is presented. It is more efficient, reliable and accurate than others. On this basic, a focal plane searching algorithm and a focusing window select method are proposed, and an efficient, reliable and robust auto focusing system is implemented.