Optical fields carry vital diagnostic information, such as amplitude, phase, polarization, spectral, angular and correlation characteristics. The metrology of random optical fields plays an important role in optical diagnostics and optical recognition studies, with applications ranging from astronomy to industrial quality control. This monograph examines the possibilities for diagnostics of light-scattering objects and media by utilizing the properties of coherent optical radiation. Special emphasis is placed on diagnostics of rough surfaces. Ideas formulated in classical work on statistical radiophysics and optics have been adapted to diagnostic application. The text includes techniques and unconventional methods aimed at obtaining the maximum information available.