This book is intended to convey an overall understanding of optical pathways. It sheds light on the background of light particles (electromagnetic waves, photons), from their origin, their path to the optics, their conditi oning by the optics, up to a sensor system. One focus is on the transition to optically refractive material. It conveys an understanding what exactly is happening as refraction, diffraction, polarization, reflection, and absorption. Easily comprehensible optical path calculations and the estimation of image quality follow. Moreover, optical coatings and their effects are discussed. Various optical systems, their functioning, and how they can be modified and combined to achieve specific customer Solutions are introduced. Catalogue optics occupies an important part of the book. It shows how to select optical systems and how to build them with prefabricated elements. This aspect is important, because catalogue optics is relatively economical and in general quickly available. Many applicati ons can be implemented this way without the need for expensive, custom-made optics. This book is written 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 optics, but definitely also the interested craftsman who simply wants to skip the formulas sometimes and deepen his understanding of optics.