This text on optics for graduate students explains how to determine material properties and parameters for inaccessible substrates and unknown films as well as how to measure extremely thin films. Its 14 case studies illustrate concepts and reinforce applications of ellipsometry -- particularly in relation to the semiconductor industry and to studies involving corrosion and oxide growth. A User's Guide to Ellipsometry will enable readers to move beyond limited turn-key applications of ellipsometers. In addition to its comprehensive discussions of the measurement of film thickness and optical constants in film, it also considers the trajectories of the ellipsometric parameters Del and Psi and how changes in materials affect parameters. This volume also addresses the use of polysilicon, a material commonly employed in the microelectronics industry, and the effects of substrate roughness. Three appendices provide helpful references.