ABSTRACT
As we pointed out in Chap. 7, light may be considered in a first approximation as a bundle of rays, but the real nature is that of a wave. Frequently, the geometrical optics approximation is not accurate enough to describe and explain some phenomena or image structures. Then, it is necessary to use diffraction theory. In this chapter we will briefly describe this theory with a special emphasis on its applications to the study of images. This subject has been treated in many books and journal publications; see e.g., Born and Wolf (1964) and Malacara (1988).
