ABSTRACT

This chapter explores a tool for the analysis of interferograms. Moiré methods are useful tools to detect aberrations in interferograms as well as for teaching demonstrations of the effect of tilts and defocusing on interferograms. If the wavefront under consideration is equal to the reference wavefront, we obtain a pattern of straight, parallel, equidistant lines; if the linear carriers of both interferograms are different, the result is like that found in any null test. When a ruling with a linear carrier is used as a reference, the magnification change can be a useful tool to visually remove the linear carrier or to change its magnitude. If the wavefront that produced the interferogram to be evaluated is nearly spherical, the reference interferogram must have a spherical wavefront with defocusing, similar to a Fresnel zone plate or Gabor plate. The holographic approach to studying interferograms can also be applied to interpreting the moiré patterns of interferograms.