In physics, the focus describes the point in an optical system where the light rays intersect after passing through the optics. At this point, therefore, the information that previously ran parallel is centered and thus fully captured. Most often, the term focus is used to mean that something is displayed in optimum sharpness. Depending on the device and the system, the determination of the focus is done selectively, centrally or point by point.

In our systems, the focus is determined over the entire scan area by means of a contrast measurement. Where the contrast is highest is the optimum sharpness plane, i.e. the focus. By looking at the entire scan area, it is ensured that the edge areas are also optimally sharp and not just the center of the original.