Geometrical optics assumes that light travels in straight lines and is concerned with the laws controlling the reflection and refraction of rays of light. This up-to-date introduction to the subject gives a comprehensive coverage to many aspects of this topic, using terminology that leads naturally towards the modern practices of computer-aided optical design. Special attention is paid to Gaussain optics, first-order layout and design. There are complete examples of third-order design together with software tools that will allow the reader to follow examples in details, or develop other examples independently. Problems at the end of each chapter make it ideal for students who wish to practice and extend the concepts taught.