An introduction to the theory of interferometry

An understanding of some of the physical bases of interferometric imaging can be helpful both in designing and understanding interferometric telescope arrays and in planning, executing and interpreting astronomical interferometric observations. This paper presents a brief introduction to some of these key principles at a level suitable for those who are new to interferometry, and with particular emphasis on four key areas: classical imaging theory, coherence functions, interferometric observables, and interferometric imaging. These topics underpin the practice of much of interferometric astronomy (at optical as well as other wavelengths), and provide a valuable basis from which to develop a better understanding of the operation of the VLTI in later chapters.