Auto focusing under microscopic views by integrating multiple measures

Auto focusing has been implemented in many applications for decades. However, challenges still exist in design of high speed and reliability of a focusing algorithm under a variety of microscopic views. The clarity of images measured by a method is generally varying in hill-shaped manner with respect to lens positions at a focus region, but the signal-to-noise ratio of the measure is low at a far-off focused. This will limit the working range of focusing. This paper proposes a new method by integrating multiple measures for near and far-off focused. Monotonous variation of individual measures is integrated and used for expanding the working range of focusing control with adaptation of step size. Views for focusing under x50 microscopic lens using the proposed method are illustrated in this study. The working range is expanded to be 50 times of depth of field from focused. Feasibility of the proposed method is investigated on a practical PC-based system. Two case studies are provided to demonstrate the feasibility.