A filter-switching auto-focus framework for consumer camera imaging systems

Auto-focus (AF) has become a standard feature in consumer level cameras. The most common AF approach analyzes a captured image with a digital band-pass filter applied to a focus region producing a focus value, which is then used by a search algorithm to locate the peak value position. The existing literature does not adequately address how to set the AF parameters such as the filter pass-band and the step-size magnitude. In this paper, a framework is presented to derive the AF parameters automatically based on camera specifications. Also, a new AF search algorithm named Filter-Switching Search is introduced which takes advantage of the derived AF parameters. The effectiveness is demonstrated via real-time implementation on three different camera platforms. Results indicate that the developed solution is portable across different platforms and outperforms the existing approaches without the need for extensive parameter tuning.