With the recent great expansion in optics and laser applications, several new areas of research have emerged, among which are: the theory of coherence, photon statistics, speckle phenomenon, statistical optics, atmospheric propa gation, optical communications, and light-beating and photon-correlation spectroscopy. A factor common to these overlapping subjects is their basic dependence on the treatment of light as a randomly fluctuating excitation. Moreover, they all necessitate a thorough understanding of the phenomenon of light detection and the additional randomness it introduces. My...