A new approach to the analysis of grating systems, based on an investigation of the changes of the Fourier spectrum during field propagation through the gratings, is applied to analyze the Fresnel field of an arbitrary system. Detailed considerations of Talbot and grating-shearing interferometers used in various metrological problems are presented. A qualitative analysis of the output fringe patterns is given. The application of the phase-stepping method with the phase shift introduced by lateral and longitudinal translations of gratings is discussed. These theoretical considerations are checked by experiment.