Since this book was first published in 1977, the major advances in optics have been the maturing of optical communications and the development of in­ tegrated optics. When I was offered the opportunity to prepare a revised edi­ tion, I decided to add chapters on these disciplines to the original work. This book, which was begun long before I joined the National Bureau of Stand­ ards, remains a private venture, written, so to speak, in my basement; there is no official connection with the National Bureau of Standards. I have also taken the opportunity to make some corrections and to add several short sections within the body of the earlier text. The most important of these changes include a discussion of group velocity, phase velocity and group index of refraction to anticipate the need for these concepts in Chap. 9; revision of the section on coherent-optical processing, including what is essen­ tially an optical derivation of the Fourier series; addition of the converging­ beam optical processor; and addition of a section on laser safety. The bulk of the new material comprises three chapters. The first is Chap. 9, "Optical Waveguides". In this chapter, I develop optical waveguide theory primarily on the basis of ray optics and interference in planar waveguides.