IMAGING PERIODIC SURFACE-RELIEF STRUCTURES

Because of shadowing, multiple scatter and polarization effects, the i nterpretation of images of gratings with fine periods, isolated deep s tructures, and multiple scattering volume objects is seriously complic ated. In this paper a review of the methods used to model such effects is presented. Periodic surface relief gratings are of particular curr ent importance because of the possibility of producing calibration sam ples using them. Several examples which illustrate electromagnetic vol ume effects are examined, General trends which help in validating the use of Fourier-transform-based scalar transmittance theory are then in dicated, The angular spectrum approach, which can be used, together wi th a scatter function generated using the rigorous electromagnetic the ory, to calculate coherent, partially coherent and confocal images of volume objects, is also discussed.