Interferometric resolution examined by means of electromagnetic theory

Interferometric methods are widely used in surface metrology. A question that arises is how much information about the surface can be extracted from a given interferogram. For examination of the resolution limit of
interferometry with coherent monochromatic light, interferograms of several surface relief gratings calculated with the use of approximate and rigorous theories are presented. The limits of the usefulness of scalar theory based on the use of the Fourier transform are indicated. Interferograms of dielectric and metallic structures are examined, including simple lamellar gratings and gratings made up of trapezoidal steps with varying slopes and depths. In all cases TE illumination is assumed. The effects of changing numerical aperture and defocus on the interferograms are also examined.