How does MeX work?

The image formation process in the SEM is based on perspective projection. Similar to a conventional light microscope the three dimensional object is projected onto a two dimensional image plane and information about the third dimension is lost. Note, the large depth of focus in SEM provides full depth of focus images, but does not allow to measure depth. Only two dimensional measurements in the image plane are feasible.

An eucentric tilting of the stage, meaning that the intersection of the primary electron beam with the specimen define the centre of tilting, yield a second image of the specimen observed form a different viewpoint. A so called stereoscopic image is generated. Overlay techniques such as red-green coloring provide anaglyph viewing and thus depth perception but again no quantitative analysis. The leading technology of Alicona now automatically identifies points in each of the images that belong to the same point on the specimen. From theses so called homologous points the true three dimensional coordinates of the observed point can be recovered. This demanding task is robustly solved for each pixel in each of the images and thus a dense 3D model of the specimen is obtained. An additional third image captured from a third tilt position allows to automatically refine given calibration data. Thus traceable results are obtained.