IMAGING PERIODIC SURFACE-RELIEF STRUCTURES

Because of shadowing, multiple scatter and polarization effects, the interpretation of images of gratings with fine periods, isolated deep structures, and multiple scattering volume objects is seriously complicated. In this paper a review of the methods used to model such effects is presented. Periodic surface relief gratings are of particular current importance because of the possibility of producing calibration samples using them. Several examples which illustrate electromagnetic volume effects are examined, General trends which help in validating the use of Fourier-transform-based scalar transmittance theory are then indicated, The angular spectrum approach, which can be used, together with a scatter function generated using the rigorous electromagnetic theory, to calculate coherent, partially coherent and confocal images of volume objects, is also discussed.