Since 2004, SPIE Field Guides have provided information at your fingertips, giving you the key definitions, equations, illustrations, application examples, design considerations, methods, and tips that you need in the lab and in the field. Now as an app, use your fingertips to interact with Field Guides like never before.* Full-text search* Bookmarking* Note taking* Hyperlinked terms* History logging* Interactive equations* Interactive figuresThis Field Guide app derives from the treatment of geometrical optics that has evolved from both the undergraduate and graduate programs at the Optical Sciences Center at the University of Arizona. This app covers Gaussian imagery, paraxial optics, first-order optical system design, system examples, illumination, chromatic effects, and an introduction to aberrations. The appendices provide supplemental material on radiometry and photometry, the human eye, and several other topics.