Surface area-based focus criterion for multi-focus image fusion

Nowadays image processing and machine vision fields have become important research topics due to numerous applications in almost every field of science. Performance in these fields is critically dependent to the quality of input images. In most of the imaging devices, optical lenses are used to capture images from a particular scene. But due to the limited depth of field of optical lenses, objects in different distances from focal point will be captured with different sharpness and details. Thus, important details of the scene might be lost in some regions. Multi-focus image fusion is an effective technique to cope with this problem. The main challenge in multi-focus fusion is the selection of an appropriate focus measure. In this paper, we propose a novel focus measure based on the surface area of regions surrounded by intersection points of input source images. The potential of this measure to distinguish focused regions from the blurred ones is proved. In our fusion algorithm, intersection points of input images are calculated and then input images are segmented using these intersection points. After that, the surface area of each segment is considered as a measure to determine focused regions. Using this measure we obtain an initial selection map of fusion which is then refined by morphological modifications. To demonstrate the performance of the proposed method, we compare its results with several competing methods. The results show the effectiveness of our proposed method.