Forty years ago this month Max Born and I dispatched to the publishers the Preface to the first edition of Principles of Optics. Since that time the book has been published in six editions and has been reprinted seventeen times (not counting unauthorized editions and several translations), usually with only a small number of corrections. A recent change to a new publisher, who expressed willingness to reset the whole text, has given me the opportunity to make more substantial changes.

The first edition was published a year before the invention of the laser, an event which triggered an explosion of activities in optics and soon led to the creation of entirely new fields, such as non-linear optics, fiber optics and opto-electronics. Numerous applications followed, in medicine, in optical data storage, in information transfer and in many other areas. On a more fundamental level, quantum optics emerged as a vibrant and rapidly expanding field, which has provided new ways of testing some basic assumptions of quantum physics relating, for example, to localization and indistinguishability. The progress made in these fields has been rapid and broad and some of the newer areas have themselves become the subjects of books.

It is clear that a fully updated new edition of Principles of Optics would require that it be expanded into several volumes. Consequently, in order to preserve a singlevolume, only a few new topics have been added; they were selected to some extent so as not to necessitate major revisions of the original text.