 
Summary: Enhancing Depth of Field in LCSEM Scenes by Sharpness Map Partitioning
H. Hariharan*, A. Koschan*, B. Abidi*, D. Page*, M. Abidi*, J. Frafjord** and S. Dekanich**
*IRIS Laboratory, ECE Dept, University of Tennessee, 1508, Middle Dr, Knoxville, TN 37996
**Y12 National Security Complex, Bear Creek Rd, Oak Ridge, TN 37831
Large scale scanning electron microscopes (LCSEM) suffer from the problem of limited depth of
field (DOF) making it difficult to inspect and image a 3dimensional 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
{ } 2/12
yi
2
xii )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 N1 counterparts for
regions of sharper focus, one image partition, Pi(x,y) is isolated by,
)y,x(S)y,x(S)y,x(P }ik{ii
>= , for all ki. 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
