Multi-focus Fusion Research Articles

Enhancing Depth of Field in LCSEM Scenes by Sharpness Map Partitioning

Large scale scanning electron microscopes (LCSEM) suffer from the problem of limited depth of field (DOF) making it difficult to inspect and image a 3-dimensional microscopic scene. Multifocus fusion is the process of unifying focal information from a set of scanned input images into one image, as one acquired under an extended DOF. Each input image has certain regions of the scene in focus, and an image partition is a region or a set of regions in an input image that fall on the same focal plane. The crux of our method is to isolate and attribute such partitions to one particular input image. A sharpness map is calculated for every input image Ii(x,y), using { } 2 / 1 2yi 2xi i ) y , x ( I ) y , x ( I ) y , x ( S + = ,where Ixi(x,y) and Iyi(x,y) are horizontal and vertical gradient maps. When the sharpness image of input image Ii(x,y) is examined with its N-1 counterparts for regions of sharper focus, one image partition, Pi(x,y) is isolated by, ) y , x ( S ) y , x ( S ) y , x ( P } i k { i i ≠ > = , for all k≠i. The union of the partitions, Pi(x,y)’s, forms the fused image space and the intersection of the partitions is the null set, i.e. the blurred sections of all the input images. The image partitions are then seamlessly mosaiced to form the fused image, from