Fourier transforms are eternal. They have not changed their nature since the last edition ten years ago: but the intervening time has allowed the author to correct errors in the text and to expand it slightly to cover some other interesting applications. The van Cittert–Zernike theorem makes a belated appearance, for example, and there are hints of some aspects of radio aerial design as interesting applications.

I also take the opportunity to thank many people who have offered criticism, often anonymously and therefore frankly, which has (usually) been acted upon and which, I hope, has improved the appeal both of the writing and of the contents.