Précis: This book is intended to convey an overall understanding of opti cal pathways. It sheds light on the background of light parti cles (electromagneti c waves, photons), from their origin, their path to the opti cs, their conditi oning by the opti cs, up to a sensor system. One focus is on the transiti on to opti cally refracti ve material. It conveys an understanding what exactly is happening as refracti on, diff racti on, polarizati on, refl ecti on, and absorpti on. Easily comprehensible opti cal path calculati ons and the esti mati on of image quality follow. Moreover, opti cal coati ngs and their eff ects are discussed. Various opti cal systems, their functi oning, and how they can be modifi ed and combined to achieve specifi c customer soluti ons are introduced. Catalogue opti cs occupies an important part of the book. It shows how to select opti cal systems and how to build them with prefabricated elements. This aspect is important, because catalogue opti cs is relati vely economical and in general quickly available. Many applicati ons can be implemented this way without the need for expensive, custom-made opti cs. This book is writt en primarily for mechanical engineers, electrical engineers, and similar professional groups. It is intended to assist the engineer or technician who is involved in some way with opti cs, but defi nitely also the interested craft sman who simply wants to skip the formulas someti mes and deepen his understanding of optics.