The art of back-of-the-envelope paraxial raytracing

Paraxial raytracing is a valuable tool for making quick "back-of-the-envelope" calculations in optical system design. Its popularity has been highly diminished as a consequence of the growing sophistication of computer-aided raytracing and the availability of powerful computers. The availability of raytracing computer programs does not harm in itself the usefulness of graphical raytracing, but it makes people forget, or never learn the basics of graphical raytracing. In this paper, some of the basic concepts of graphical raytracing are presented, along with some examples that illustrate how it can be applied to multielement systems. The mastering of the methods presented in this paper constitute some of the fundamentals required in the use of any optical software. Such knowledge is absolutely necessary for the conception of novel optical systems.