Focus-based depth estimation in the SEM

Depth estimation in the scanning electron microscope (SEM) is an important topic especially for automation purposes. The SEM only delivers two-dimensional (2D) images, which makes manipulation processes difficult. In spite of the high depth of focus in the SEM, it is still possible to use depth from focus as a depth estimation technique for nanomanipulation applications. This article deals with the extraction of depth information from SEM images using focus-based methods, and possibilities to improve the performance of these algorithms. A new approach is presented, combining 2D object tracking with focus-based depth estimation methods in order to obtain a possibility for limited three-dimensional tracking.