ABSTRACT
The subject of this chapter is free-space optics, that is the optical means and devices which transfer and transform the radiation output from a laser to a workpiece in such a way that it activates the desired processes. Thus it entails both radiation beam transport (relaying) and beam manipulation. The latter is mostly in the form of focusing to a spot of some desired size and shape but an application may also require a radiation beam transformation, which produces a homogeneous irradiation over a certain area of the workpiece. The optical methods and devices for achieving these goals vary considerably with the type of laser used and, more specifically its wavelength, mainly due to restrictions set by wavelength-dependent material properties.
