In connection with laser cutting or welding, the focus is the
point which is the thinnest point of the laser beam. The focus
is a defined distance from the focus lens - also called the fo-
cal length. The focus diameter in a typical application, e.g. with
the laser robot ROBOCUT, has a diameter of 0.2 mm. With the
laser system FLACS.SCAN with higher focal lengths, the focus
diameter is typically 0.3 - 0.5 mm. Once the focus diameter has
reached its smallest point, it becomes larger again. In other
words, a divergence of the laser beam forms at the back, which
has positive implications for laser cutting in terms of device
stability.