Incoherent Superposition of Multiple Self-imaging Lau Effect and Moiré Fringe Explanation

Characteristics of the diffraction field of two spatially separated linear diffraction gratings under incoherent illumination are studied. The analytical model is based on the spatial superposition of many mutually incoherent Talbot (self-imaging) effects. It permits a simple explanation of the basic parameters of the ‘incoherent’ diffraction images: axial localization, spatial period and lateral displacement. The moiré fringe formation in space, the imaging of a grating by a second grating, and the Lau effect are considered; the results are compared with the former studies in the literature.