H. P. Baltes We begin the introductory chapter with a general definition of the inverse optical problem. Next, we discuss the role of prior knowledge and the questions of uniqueness and stability. We then review the various specific inverse problems in optics as well as the contents of Chapters 2 to 6. Finally, we summarize the notation in co herence theory. 1. 1 Direct and Inverse Problems in Optical Physics The "direct" or "normal" problem in optical physics is to: Jredict the emission or propagation of radiation on the basis of a known constitution of sources or scat terers. The "inverse"...