Modulation-spectral method for analyzing the amplitude-phase structure of optical inhomogeneities of objects

An original solution to the phase problem in optics is considered as applie d to the problems of recording and analysis of the amplitude-phase structur e of optical fields used for studying fine structures and inhomogeneities i n steady-state objects producing effects to fractions of the wavelength per iod. The problem is solved by probing objects using radiation with a known structure. Intensity distributions of the probing field are detected at the exit from the object by using the modulation-spectral method directly for the spatial frequency spectrum and for the spatial frequency spectrum subje cted to additional modulation formed in a special way, which is realized in the plane under study and provides visualization of the phase information contained in the light field in some form. The intensity distributions obta ined make it possible to calculate the two-dimensional amplitude-phase stru cture of the field analyzed and, hence, the fine structure of the optical i nhomogeneities of the object analyzed for the chosen probing direction. For steady-state objects, probing in a number of directions is possible. Infor mation on the bulk structure of the inhomogeneities under study can be obta ined by using the information available on the symmetry of the object. Two variants of action of the medium on probing radiation are considered. In th e first one, the action is related to spatial field modulation (described b y the multiplication operation); in the second one, the action leads to red istribution of radiation in the plane studied (described by the convolution operation). (C) 2001 MAIK "Nauka/Interperiodica".