A Fourier optics model of two-beam scanning laser interferometers

The article illustrates the use of Fourier optics to describe the operation of two-beam scanning laser interferometers. It deals with the effect of di ffraction on the spatial periodicity of a monochromatic and coherent beam. Particular attention is given to the analysis of systematic errors in high- accuracy laser metrology. The article reviews the special case of plane wav e and Gaussian illuminations, examines how beam truncation affects the peri od of traveling fringes and presents a general relation between the relativ e wavelength deviation and the impulse standard deviation of the photons.